Cellular telephone location system

Abstract

A cellular telephone location system for automatically recording the location of one or more mobile cellular telephones comprises three or more cell site systems 12. Each cell site system is located at a cell site of a cellular telephone system. Each cell site system includes an antenna that may be mounted on the same tower or building as the antenna employed by the cellular telephone system and equipment that may be housed in the equipment enclosure of the corresponding cell site. The cell site systems are coupled via T1 communication links 14 to a central site 16. The central site may be collocated with the cellular telephone system's MTSO. The central site 16 is further coupled to a database 20, which may be remotely located from the central site and made available to subscribers.

Claims

We claim: 1. A cellular telephone location system for determining the locations of multiple mobile cellular telephones each initiating periodic signal transmission over one of a prescribed set of reverse control channels, comprising: (a) at least three cell site systems, each cell site system comprising: an elevated ground-based antenna; a baseband convertor operatively coupled to said antenna for receiving cellular telephone signals transmitted over a reverse control channel by said cellular telephones and providing baseband signals derived from the cellular telephone signals; a timing signal receiver for receiving a timing signal common to all cell sites; and a sampling subsystem operatively coupled to said timing signal receiver and said baseband convertor for sampling said baseband signal at a prescribed sampling frequency and formatting the sample signal into frames of digital data, each frame comprising a prescribed number of data bits and time stamp bits, said time stamp bits representing the time at which said cellular telephone signals were received; and (b) a central site system operatively coupled to said cell site systems, comprising: means for processing said frames of data from said cell site systems to generate a table identifying individual cellular telephone signals and the differences in times of arrival of said cellular telephone signals among said cell site systems; and means for determining, on the basis of said times of arrival differences, the locations of the cellular telephones responsible for said cellular telephone signals. 2. A cellular telephone location system as recited in claim 1, wherein said timing signal receiver comprises a global positioning system (GPS) receiver. 3. A cellular telephone location system as recited in claim 1, wherein said central site system comprises a correlator for cross-correlating the data bits of a frame from one cell site system with corresponding data bits from each other cell site system. 4. A cellular telephone location system as recited in claim 3, wherein said central site system further comprises: a plurality of data inputs ports each connected to receive a signal from one of said cell site systems; interface/deformatting circuits for receiving the signals from said input ports and outputting data bits and a clock signal; a plurality of FIFO registers each coupled to an interface/deformatting circuit to receive the data bits and clock signal from that circuit; a switch comprising a plurality of input ports, each input port coupled to an output of one of said FIFO registers, and a first output port (A) and a second output port (B), said first output port coupled to an input port of said correlator; a computer operatively coupled to said switch to select two of the inputs to said switch to be output on the output ports of said switch; a RAM control circuit coupled to said computer and said FIFO registers; a sample read clock controlled by said computer and said RAM control to read sample bits from previously selected FIFO registers; and a quadrature channel generator comprising an input port coupled to said second output port of said switch and a first output port (B1) and a second output port (B2), and means for outputting an in-phase signal on said first output port (B1) and a quadrature signal on said second output port (B2); wherein said correlator calculates a first correlation coefficient for said DATA A and DATA B1 signals, and a second correlation coefficient for said DATA A and DATA B2 signals. 5. A cellular telephone location system as recited in claim 1, wherein said baseband convertors each comprise: a first mixer providing an intermediate frequency (IF) signal; a synthesizer providing a local oscillator (LO) signal; a single sideband mixer operatively coupled to said first mixer and said synthesizer for converting said IF signal to an upper sideband signal and a lower sideband signal; and means for filtering said upper sideband and lower sideband signals and providing said baseband signals on the basis of the filtered upper and lower sideband signals. 6. A cellular telephone location system as recited in claim 1, comprising: first receiver means at a first cell site for receiving a cellular telephone signal; demodulator means at said first cell site for demodulating the received cellular telephone signal at said first cell site to produce a demodulated digital bit stream; first modulator means at said first cell site for modulating the demodulated digital bit stream to reconstruct the cellular telephone signal as it was originally transmitted, whereby a first reconstructed cellular telephone signal is produced; first cross-correlator means at said first cell site for cross-correlating said reconstructed signal against the cellular telephone signal received at said first cell site to produce a first peak indicative of a time of arrival of the cellular telephone signal at the first cell site; means for determining the time of arrival of the cellular telephone signal at the first cell site on the basis of said first peak and producing first time of arrival data indicative thereof; means for sending the demodulated digital bit stream and first time of arrival data from the first cell site to the central site; means for distributing the demodulated digital bit stream and first time of arrival data to a second cell site; second modulator means at said second cell site for modulating the demodulated digital bit stream at the second cell site to reconstruct the cellular telephone signal as it was first transmitted by the cellular telephone, whereby a second reconstructed cellular telephone signal is produced; second receiver means at said second cell site for receiving said cellular telephone signal; second cross-correlator means at said second cell site for cross-correlating the second reconstructed signal against the cellular telephone signal received at the second cell site to produce a second peak indicative of a time of arrival of the cellular telephone signal at the second cell site; means for determining the time of arrival of the cellular telephone signal at the second cell site on the basis of said second peak and producing second time of arrival data indicative thereof; means for sending said second time of arrival data from the second cell site to the central site; and means at said central site for determining time difference of arrival data on the basis of said first and second time of arrival data. 7. A cellular telephone location system as recited in claim 1, comprising location estimation means for: (1) creating a grid of theoretical points covering a prescribed geographic area, said theoretical points being spaced at prescribed increments of latitude and longitude; (2) calculating theoretical values of time delay for a plurality of pairs of cell sites; (3) calculating a least squares difference (LSD) value based on the theoretical time delays and measured time delays for a plurality of pairs of cell sites; (4) searching the entire grid of theoretical points and determining the best theoretical latitude and longitude for which the value of LSD is minimized; and (5) starting at the best theoretical latitude and longitude, performing another linearized-weighted-least-squares iteration to resolve the actual latitude and longitude to within a prescribed number of degrees or fraction of a degree. 8. A cellular telephone location system as recited in claim 7, wherein said calculating step (2) comprises accounting for any known site biases caused by mechanical, electrical, or environmental factors, said site biases determined by periodically calculating the positions of reference cellular transmitters at known locations. 9. A cellular telephone location system as recited in claim 7, wherein said least squares difference is given by: LSD=[Q.sub.12 (Delay.sub.-- T.sub.12 -Delay.sub.-- O.sub.12).sup.2 +Q.sub.13 (Delay.sub.-- T.sub.13 -Delay.sub.-- O.sub.13).sup.2 +...Q.sub.xy (Delay.sub.-- T.sub.xy -Delay.sub.-- O.sub.xy).sup.2 ] where, Delay -- T xy represents the theoretical delay between cell sites x and y, x and y being indices representative of cell sites; Delay -- O xy represents the observed delay between cell sites x and y; Q xy is the quality factor the delay measurement cell sites x and y, said quality factor being an estimated measure of the degree to which multipath or other anomalies may have affected a particular delay measurement. 10. A cellular telephone location system as recited in claim 7, further comprising means for detecting a first leading edge of a cellular telephone signal and rejecting subsequent leading edges of said cellular telephone signal, whereby the effects of multipath may be reduced. 11. A cellular telephone location system as recited in claim 1, comprising velocity estimation means for: (1) creating a grid of theoretical points covering a prescribed range of velocities, said theoretical points being spaced at prescribed increments; (2) calculating theoretical values of frequency difference for a plurality of pairs of cell sites; (3) calculating a least squares difference (LSD) value based on the theoretical frequency differences and measured frequency differences for a plurality of pairs of cell sites; (4) searching the entire grid of theoretical points and determining the best theoretical velocity for which the value of LSD is minimized; and (5) starting at the best theoretical velocity, performing another linearized-weighted-least-squares iteration to resolve the actual velocity to within a prescribed tolerance. 12. A cellular telephone location system as recited in claim 1, further comprising a database for storing location data identifying the cellular telephones and their respective locations, and means for providing access to said database to subscribers at remote locations. 13. A cellular telephone location system as recited in claim 12, further comprising means for providing location data to a specific one of said cellular telephones upon request by the specific telephone. 14. A cellular telephone location system as recited in claim 12, further comprising means for merging said location data with billing data for said cellular telephones and generating modified billing data, wherein said billing data indicates the cost for each telephone call made by said cellular telephones within a certain time period, said cost being based upon one or more predetermined billing rates, and said modified billing data is based upon a different rate for calls made from one or more prescribed locations. 15. A cellular telephone location system as recited in claim 14, wherein the system applies a lower billing rate for telephone calls made from a user's home. 16. A cellular telephone location system as recited in claim 1, further comprising means for transmitting a signal to a selected cellular telephone to cause said selected telephone to transmit a signal over a control channel. 17. A cellular telephone location system as recited in claim 1, further comprising means for automatically sending location information to a prescribed receiving station in response to receiving a distress signal from a cellular telephone, whereby emergency assistance may be provided to a user in distress. 18. A cellular telephone location system as recited in claim 1, further comprising means for comparing the current location of a given telephone with a prescribed range of locations and indicating an alarm condition when said current location is not within said prescribed range. 19. A cellular telephone location system as recited in claim 1, further comprising means for detecting a lack of signal transmissions by a given telephone and in response thereto automatically paging said given telephone to cause said given telephone to initiate a signal transmission and means for indicating an alarm condition. 20. A cellular telephone location system as recited in claim 1, further comprising means for estimating a time of arrival of a given telephone at a prespecified location. 21. A cellular telephone location system as recited in claim 1, further comprising means for continuously tracking a given telephone by receiving voice signals transmitted by said given telephone over a voice channel and determining the location of said given telephone on the basis of said voice signals. 22. A ground-based cellular telephone system serving a plurality of subscribers possessing mobile cellular telephones, comprising: (a) at least three cell sites equipped to receive signals sent by multiple mobile cellular telephones each initiating periodic signal transmissions over one of a prescribed set of reverse control channels; (b) locating means for automatically determining the locations of said cellular telephones by receiving and processing signals emitted during said periodic reverse control channel transmissions; and (c) database means for storing location data identifying the cellular telephones and their respective locations, and for providing access to said database to subscribers at remote locations. 23. A ground-based cellular telephone system as recited in claim 22, further comprising means for providing location data to a specific one of said cellular telephones upon request by the specific telephone. 24. A ground-based cellular telephone system as recited in claim 22, further comprising means for merging said location data with billing data for said cellular telephones and generating modified billing data, wherein said billing data indicates the cost for each telephone call made by said cellular telephones within a certain time period, said cost being based upon one or more predetermined billing rates, and said modified billing data is based upon a different rate for calls made from one or more prescribed locations. 25. A ground-based cellular telephone system as recited in claim 22, further comprising means for transmitting a signal to a selected cellular telephone to cause said selected telephone to transmit a signal over a control channel. 26. A ground-based cellular telephone system as recited in claim 22, further comprising means for automatically sending location information to a prescribed receiving station in response to receiving a distress signal from a cellular telephone, whereby emergency assistance may be provided to a subscriber in distress. 27. A ground-based cellular telephone system as recited in claim 22, further comprising means for comparing the current location of a given telephone with a prescribed range of locations and indicating an alarm condition when said current location is not within said prescribed range. 28. A ground-based cellular telephone system as recited in claim 22, further comprising means for detecting a lack of signal transmissions by a given telephone and in response thereto automatically paging said given telephone to cause said given telephone to initiate a signal transmission. 29. A ground-based cellular telephone system as recited in claim 22, further comprising means for estimating a time of arrival of a given telephone at a prespecified location. 30. A ground-based cellular telephone system as recited in claim 22, further comprising means for continuously tracking a given telephone by receiving voice signals transmitted by said given telephone over a voice channel and determining the location of said given telephone on the basis of said voice signals. 31. A method for determining the location(s) of one or more mobile cellular telephones periodically transmitting signals over one of a prescribed set of reverse control channels, comprising the steps of: (a) receiving said reverse control channel signals at at least three geographically-separated cell sites; (b) processing said signals at each cell site to produce frames of data, each frame comprising a prescribed number of data bits and time stamp bits, said time stamp bits representing the time at which said frames were produced at each cell site; (c) processing said frames of data to identify individual cellular telephone signals and the differences in times of arrival of said cellular telephone signals among said cell sites; and (d) determining, on the basis of said times of arrival differences, the locations of the cellular telephones responsible for said cellular telephone signals. 32. A method as recited in claim 31, further comprising the steps of storing, in a database, location data identifying the cellular telephones and their respective locations, and providing access to said database to subscribers at remote locations. 33. A method as recited in claim 31, further comprising merging said location data with billing data for said cellular telephones and generating modified billing data, wherein said billing data indicates the cost for each telephone call made by said cellular telephones within a certain time period, said cost being based upon one or more predetermined billing rates, and said modified billing data is based upon a different rate for calls made from one or more prescribed locations. 34. A method as recited in claim 31, further comprising transmitting a signal to a selected cellular telephone to cause said selected telephone to transmit a signal over a control channel. 35. A method as recited in claim 31, further comprising automatically sending location information to a prescribed receiving station in response to receiving a distress signal from a cellular telephone, whereby emergency assistance may be provided to a subscriber in distress. 36. A method as recited in claim 31, further comprising comparing the current location of a given telephone with a prescribed range of locations and indicating an alarm condition when said current location is not within said prescribed range. 37. A method as recited in claim 31, further comprising detecting a lack of signal transmissions by a given telephone and in response thereto automatically paging said given telephone to cause said given telephone to initiate a signal transmission. 38. A method as recited in claim 31, further comprising estimating a time of arrival of a given telephone at a prespecified location. 39. A method as recited in claim 31, further comprising continuously tracking a given telephone by receiving voice signals transmitted by said given telephone over a voice channel and determining the location of said given telephone on the basis of said voice signals. 40. A method as recited in claim 31, comprising the steps of: receiving a cellular telephone signal at a first cell site; demodulating the received cellular telephone signal at said first cell site to produce a demodulated digital bit stream; modulating the demodulated digital bit stream to reconstruct the cellular telephone signal as it was originally transmitted, thereby producing a first reconstructed cellular telephone signal; cross-correlating said reconstructed signal against the cellular telephone signal received at said first cell site to produce a first peak indicative of a time of arrival of the cellular telephone signal at the first cell site; determining the time of arrival of the cellular telephone signal at the first cell site on the basis of said first peak and producing first time of arrival data indicative thereof; sending the demodulated digital bit stream and first time of arrival data from the first cell site to a central site; distributing the demodulated digital bit stream and first time of arrival data to a second cell site; modulating the demodulated digital bit stream at the second cell site to reconstruct the cellular telephone signal as it was first transmitted by the cellular telephone, thereby producing a second reconstructed cellular telephone signal; receiving said cellular telephone signal at said second cell site; cross-correlating the second reconstructed signal against the cellular telephone signal received at the second cell site to produce a second peak indicative of a time of arrival of the cellular telephone signal at the second cell site; determining the time of arrival of the cellular telephone signal at the second cell site on the basis of said second peak and producing second time of arrival data indicative thereof; sending said second time of arrival data from the second cell site to the central site; and determining time difference of arrival data on the basis of said first and second time of arrival data. 41. A method as recited in claim 31, comprising estimating the location of a cellular telephone by performing the following steps: (1) creating a grid of theoretical points covering a prescribed geographic area, said theoretical points being spaced at prescribed increments of latitude and longitude; (2) calculating theoretical values of time delay for a plurality of pairs of cell sites; (3) calculating a least squares difference (LSD) value based on the theoretical time delays and measured time delays for a plurality of pairs of cell sites; (4) searching the entire grid of theoretical points and determining the best theoretical latitude and longitude for which the value of LSD is minimized; and (5) starting at the best theoretical latitude and longitude, performing another linearized-weighted-least-squares iteration to resolve the actual latitude and longitude to within a prescribed number of degrees or fraction of a degree. 42. A method as recited in claim 41, wherein said calculating step (2) comprises accounting for any known site biases caused by mechanical, electrical, or environmental factors, said site biases determined by periodically calculating the positions of reference cellular transmitters at known locations. 43. A method as recited in claim 41, wherein said least squares difference is given by: LSD=[Q.sub.12 (Delay.sub.-- T.sub.12 -Delay.sub.-- O.sub.12).sup.2 +Q.sub.13 (Delay.sub.-- T.sub.13 -Delay.sub.-- O.sub.13).sup.2 +...Q.sub.xy (Delay.sub.-- T.sub.xy -Delay.sub.-- O.sub.xy).sup.2 ] where, Delay -- T xy represents the theoretical delay between cell sites x and y, x and y being indices representative of cell sites; Delay -- O xy is the observed delay between cell sites x and y; Q xy is the quality factor the delay measurement cell sites x and y, said quality factor being an estimated measure of the degree to which multipath or other anomalies may have affected a particular delay measurement. 44. A method as recited in claim 40, further comprising detecting a first leading edge of a cellular telephone signal and rejecting subsequent leading edges of said cellular telephone signal. 45. A method as recited in claim 31, comprising estimating the velocity of a cellular telephone by performing the following steps: (1) creating a grid of theoretical points covering a prescribed range of velocities, said theoretical points being spaced at prescribed increments; (2) calculating theoretical values of frequency difference for a plurality of pairs of cell sites; (3) calculating a least squares difference (LSD) value based on the theoretical frequency differences and measured frequency differences for a plurality of pairs of cell sites; (4) searching the entire grid of theoretical points and determining the best theoretical velocity for which the value of LSD is minimized; and (5) starting at the best theoretical velocity, performing another linearized-weighted-least-squares iteration to resolve the actual velocity to within a prescribed tolerance.
FIELD OF THE INVENTION The present invention relates generally to the field of mobile cellular telephone systems (including both analog and digital cellular systems) and more particularly relates to a system for automatically locating mobile cellular telephones operating within a prescribed geographic area. BACKGROUND OF THE INVENTION Prior to the invention disclosed herein, there has been no known system for automatically tracking mobile cellular telephones. Although related technologies (radio navigation systems such as direction finding and LORAN, emergency location devices for aircraft, satellite tracking and surveillance, and the like) have been extant for many years, none of these technologies has been applied to automatically locate cellular telephones as described herein. Accordingly, the background information most pertinent to gaining an understanding of the present invention relates to a cellular telephone system itself, as opposed to the peripherally related radio navigation and location technologies. The following discussion refers to FIGS. 1A-1C in providing an overview of a cellular telephone technology. In addition, it should be noted that the inventive concepts disclosed herein are applicable to both analog and digital (for example, TDMA) cellular systems that employ analog control channels. Cellular telephone systems typically include many cell sites and a centrally-located cellular switch, called a Mobile Telephone Switching Office (MTSO). There are typically sixty to one hundred cell sites in large cities and fifteen to thirty cell sites in smaller cities. Cell sites are usually spaced at distances of one-half to twenty miles. Each cell site generally comprises one or more antennas mounted on a triangular platform. The platform is placed on a tower or atop a tall building, preferably fifty to three hundred feet above the surrounding terrain. The fundamental idea behind a cellular system is frequency reuse. This concept of frequency reuse is implemented by employing a pattern of overlapping cells, with each cell conceptually viewed as a hexagon. This concept is illustrated in FIG. 1A, which depicts a layout for a cellular system employing seven distinct sets of frequencies. In this figure, each shading pattern represents a unique frequency set. FIG. 1C schematically depicts the main components and arrangement of cellular telephone system. As discussed above, frequency reuse allows the cellular system to employ a limited number of radio channels to serve many users. For example, FIG. 1A depicts an area served by 14 cells, divided into two clusters. Each cluster contains seven cells. A separate set of channels is assigned to each cell in a cluster. However, the sets used in one cluster are reassigned in the other cluster, thus reusing the available spectrum. The signals radiated from a cell in channels assigned to that cell are powerful enough to provide a usable signal to a mobile cellular telephone within that cell, but preferably not powerful enough to interfere with co-channel signals in distant cells. All cellular telephones can tune to any of the channels. The Federal Communications Commission (FCC) has allocated a 25 MHz spectrum for use by cellular systems. This spectrum is divided into two 12.5 MHz bands, one of which is available to wire line common carriers only and the other of which is available to non-wire line common carriers only. In any given system, the non-wire line service provider operates within the "A side" of the spectrum and the wire line provider operates within the "B side" of the spectrum Cellular channels are 30 KHz wide and include control channels and voice channels. In particular, the twenty-one control channels for "A" systems are numbered 313 through 333 and occupy a 30 KHz band of frequencies 834.390 MHz to 834.990 MHz. The control channels for "B" systems are numbered 334 through 354 and occupy 835.020 MHz to 835.620 MHz. Each cell site (or, where a cell site is "sectored" as described below, each sector of that cell site) uses only a single control channel. The control channel from a cell site to a mobile unit is called the "forward" control channel and the control channel from the cellular telephone to the cell site is called the "reverse" control channel. Signals are continuously broadcast over a forward control channel by each cell site. In contrast, signals are discontinuously (periodically) broadcast by the cellular telephones over a reverse control channel. If the cell sites are so close to one another that control channels using the same frequency interfere with each other, the control channel at each cell site is further qualified by a digital color code ranging from zero to three. This allows each cell site to be uniquely identified, for example, within a range of twenty to thirty miles. Directional cell site antennas may be used to reduce co-channel and adjacent-channel interference. FIG. 1B illustrates how sectored antennas may be used to reduce such interference. The circles represent cell sites and the broken lines represent the azimuthal edges of the front lobes of 120° directional antennas. The labels "A" , "B" , and "C" refer to channel sets, cells, and cell sites simultaneously. The labels "1" , "2" , and "3" refer to directional antennas and sectors of cells simultaneously. Thus, for example, if a particular channel is assigned to sector 1 of cell B and adjacent channels are assigned to cells A and C, these adjacent channels should be assigned to sector 1 in cells A and C. When a cellular telephone is first turned on, it scans all forward control channels, listening for the channel with the strongest signal. The telephone then selects the forward control channel with the strongest signal and listens for system overhead messages that are broadcast periodically, for example, every 0.8 seconds. These overhead messages contain information regarding the access parameters to the cellular system. One such access parameter is the frequency of registration, which refers to how often a given telephone must inform the system that the telephone is within the system's geographic confines. Registration frequencies typically range from once per minute to once per thirty minutes. The overhead messages also contain busy/idle bits that provide information about the current availability of the reverse control channel for that cell. When the reverse control channel becomes free, as indicated by the busy/idle bit, the cellular telephone attempts to register itself by seizing the reverse control channel. Cellular telephones re-register themselves at the rate determined by the cellular system. Registration parameter requirements are determined by each cellular system. For example, the options include (1) 7-digit NXX-XXXX, (2) 3-digit NPA, and (3) 32-bit electronic serial number. Each of these options constitutes a digital word. Because of sync bits and error correction techniques, each digital word is 240 bits long. With an initial 48-bit sync stream, each cellular telephone transmission is a minimum of 288 bits long, and as long as 1488 bits. Moreover, each discontinuous transmission by a cellular telephone includes a period of unmodulated carrier. Therefore, an average transmission on the reverse control channel lasts about 100 milliseconds. Cellular telephones also transmit in response to pages by the cellular system, as well as in response to user-initiated calls. The term "paging" is used to describe the process of determining a mobile telephone's availability to receive an incoming call. The complementary function of initiating a call by the mobile telephone is called "access." The paging and access functions occur on the control channels. When turned on but not in active use, a mobile cellular telephone periodically scans the control channels assigned to the system and marks for use the strongest carrier found. With the mobile receiver tuned to this strongest carrier, the cellular telephone continuously decodes a digital modulating data stream, looking for incoming calls. Any call to a mobile terminal is initiated like a normal telephone call. A seven- or ten-digit number is dialed and the telephone network routes the call to a central computer. The number is broadcast on the control channels of every cell in the system. When a called telephone detects its number in the incoming data stream, it sends its identification back to the system. The system uses a digital message on the control channel to designate a channel for the telephone to use. The telephone tunes to this channel and the user is then alerted to the incoming call. A similar sequence is involved when a cellular telephone user originates a call. The user dials the desired telephone number into a register in the telephone. This number is transmitted over the control channel to the nearest cell (i.e., the cell with the strongest carrier). The system computer then designates a channel for the call and the mobile unit is automatically tuned to that channel. The cellular telephone industry has enjoyed widespread success in its relatively brief lifetime. New subscribers, apparently recognizing the many advantages in being able to initiate and receive calls while away from home, are being enrolled in ever-increasing numbers. Indeed, in many cities, the competition between the A and B sides to enlist new subscribers is fierce. Accordingly, there is a great need for new services to offer current and potential subscribers. The present invention sprang from the recognition that mobility, the main advantage offered by a cellular system, is also a disadvantage in certain situations. For example, a lost or stolen cellular telephone is difficult to recover. Thus, a system that could automatically locate the telephone would be quite beneficial to users. In addition, if the cellular telephone were in an automobile and the automobile were stolen, a system that could locate the telephone would also be able to locate the automobile, thus providing a valuable service to users. Moreover, there are situations where the user of a cellular telephone may become lost. An example of such a situation is where the user is driving in an unknown area at night with his telephone in the car. Again, it would be a great advantage for the system to be able to automatically locate the telephone and, upon request, inform the user of his location. Similarly, a cellular telephone user experiencing a medical emergency who dials an emergency telephone number (for example, 911) may not be able to tell the dispatcher his location. Prior art systems are unable to trace a call from a cellular telephone. Therefore, a cellular telephone user in such a situation would be in a dire predicament. Once again, it would be highly advantageous for the system to be able to ascertain the user's location and provide this information to emergency medical personnel. There would be numerous other applications for a system that could automatically locate a cellular telephone. SUMMARY OF THE INVENTION The present invention provides a cellular telephone location system for determining the locations of multiple mobile cellular telephones each initiating periodic signal transmissions over one of a prescribed set of control channels. The invention may be embodied in a system that employs much of the existing infrastructure of a cellular system. For example, as described below in greater detail, a cellular telephone location system in accordance with the present invention may employ the cellular system's towers and cell site enclosures. In this sense, the cellular telephone location system may be overlaid on the cellular system. There are numerous advantages provided by monitoring control channels to track the locations of cellular telephones. First, a voice channel is an expensive and relatively scarce resource. Cellular systems typically require approximately six to eight seconds to allocate a voice channel to a specific telephone. If voice channels were employed for location tracking, the cellular telephone would have to be called and commanded to initiate a voice channel call every time a location sample were to be taken. This would be both expensive and time consuming. Thus, it would be extremely inefficient for a location system to require the telephone to initiate periodic voice channel transmissions. Second, each voice channel transmission adds a call record in an associated billing system. Therefore, a large burden would be placed on the billing system if the location system were to require periodic voice channel transmissions. In contrast, control channel transmissions already occur periodically in cellular systems. Thus, the present invention is compatible with existing cellular telephone protocols and would not require the cellular system or the individual cellular telephones to be modified. Third, since the frequency of control channel transmissions is software controllable, a location system in accordance with the present invention could control the frequency of control channel transmissions and offer different subscribers different location information update rates. Fourth, another advantage afforded by monitoring control channel transmissions is in connection with energy efficiency. Control channel transmissions are very short and require little power in comparison to voice channel transmissions. Accordingly, requiring periodic voice channel transmissions would cause a significant battery drain in the individual cellular telephones. This is avoided by monitoring control channels. Accordingly, there are significant advantages afforded by monitoring periodic control channel transmissions to automatically locate mobile cellular telephones. However, monitoring control channels requires detection of such weak, short duration signals that have travelled large distances (for example, twenty-five miles). The present inventors have developed highly sophisticated signal processing methods and apparatus to detect extremely brief, low power control channel signals. Both the concept of monitoring periodic control channel transmissions, as opposed to voice channel transmissions, and the particular way in which this function is carried out represent significant technological advancements. An exemplary embodiment of the present invention comprises at least three cell site systems and a central site system. Each cell site system comprises an elevated ground-based antenna; a baseband convertor for receiving cellular telephone signals transmitted by the cellular telephones and providing baseband signals derived from the cellular telephone signals; a timing signal receiver for receiving a timing signal common to all cell sites; and a sampling subsystem for sampling the baseband signal and formatting the sampled signal into frames of digital data. Each frame includes a prescribed number of data bits and time stamp bits, wherein the time stamp bits represent the time at which the cellular telephone signals were received. The central site system comprises means for processing the frames of data from the cell site systems to generate a table identifying individual cellular telephone signals and the differences in times of arrival of the cellular telephone signals among the cell site systems; and means for determining, on the basis of the times of arrival, the locations of the cellular telephones responsible for the cellular telephone signals. In one preferred embodiment of the invention, the central site system comprises a correlator for cross-correlating the data bits of each frame from one cell site with the corresponding data bits of each other cell site. In addition, this preferred embodiment comprises a database for storing location data identifying the cellular telephones and their respective locations, and means for providing access to the database to subscribers at remote locations. The system also comprises means for providing location data to a specific cellular telephone user upon request by using, for example, CPDP without setting up a voice call ("CPDP" represents the Cellular Packet Data Protocol, which involves sending data over voice channels when the voice channels would not otherwise be in use). The latter feature is especially useful in connection with laptop or handheld computers having cellular modems and mapping software. Embodiments of the invention may also advantageously include means for merging the location data with billing data for the cellular telephones and generating modified billing data. In this embodiment, the billing data indicates the cost for each telephone call made by the cellular telephones within a certain time period, the cost being based upon one or more predetermined billing rates, and the modified billing data is based upon a different rate for calls made from one or more prescribed locations. For example, the system may apply a lower billing rate for telephone calls made from a user's home or office or other geographic locale. Embodiments of the invention may also advantageously include means for transmitting a signal to a selected cellular telephone to cause the selected telephone to transmit a signal over a control channel. Such capability would allow the system to immediately locate that telephone without waiting for one of its periodic control channel transmissions. In addition, embodiments of the invention may comprise means for automatically sending location information to a prescribed receiving station in response to receiving a distress signal from a cellular telephone. With this capability, emergency assistance may be provided to a user in distress. For example, when a user dials "911" the system would automatically tell an emergency dispatcher the user's location. Another element of a preferred embodiment is a means for comparing the current location of a given telephone with a prescribed range of locations and indicating an alarm condition when the current location is not within the prescribed range. Such an element could be used, for example, to notify a parent when the child, who borrowed the parent's car and cellular telephone to "go to the mall," has in fact gone somewhere else. Of course, many other applications of such an alarm function are possible. Yet another element of a preferred embodiment is a means for detecting a lack of signal transmissions by a given telephone and in response thereto automatically paging the given telephone to cause it to initiate a signal transmission. This would allow the system to locate a telephone that has failed to register itself with the cellular system. Such a lack-of-signal-transmission detection feature could be used, for example, to generate an alarm for subscribers at remote locations. In addition, preferred embodiments may also include means for estimating a time of arrival of a given telephone at a prespecified location. This would be useful, for example, in connection with a public transportation system to provide quasi-continuous estimated times of arrival of busses along established routes. Of course, many other applications of this feature are also possible. Embodiments of the present invention may also comprise means for continuously tracking a given telephone by receiving voice signals transmitted by the given telephone over a voice channel and determining the location of the given telephone on the basis of the voice signals. This voice channel tracking could be used as an adjunct to control channel tracking. This feature would require the location system to track the channel assignment of each telephone whose location is to be determined. The tracking of channel assignments by the location system could employ the dynamic channel assignment protocol employed by the cellular system. The present invention also provides methods for determining the location of one or more mobile cellular telephones. Such methods comprise the steps of: (a) receiving the signals at at least three geographically-separated cell sites; (b) processing the signals at each cell site to produce frames of data, each frame comprising a prescribed number of data bits and time stamp bits, the time stamp bits representing the time at which the frames were produced at each cell site; (c) processing the frames of data to identify individual cellular telephone signals and the differences in times of arrival of the cellular telephone signals among the cell sites; and (d) determining, on the basis of the times of arrival, the locations of the cellular telephones responsible for the cellular telephone signals. One preferred embodiment of the inventive method comprises estimating the location of a cellular telephone by performing the following steps: (1) creating a grid of theoretical points covering a prescribed geographic area, the theoretical points being spaced at prescribed increments of latitude and longitude; (2) calculating theoretical values of time delay for a plurality of pairs of cell sites; (3) calculating a least squares difference (LSD) value based on the theoretical time delays and measured time delays for a plurality of pairs of cell sites; (4) searching the entire grid of theoretical points and determining the best theoretical latitude and longitude for which the value of LSD is minimized; and (5) starting at the best theoretical latitude and longitude, performing another linearized-weighted-least-squares iteration to resolve the actual latitude and longitude to within a prescribed number of degrees or fraction of a degree. Preferably, the calculating step (2) comprises accounting for any known site biases caused by mechanical, electrical, or environmental factors, the site biases determined by periodically calculating the positions of reference cellular transmitters at known locations. In addition, the least squares difference is preferably given by: LSD=[Q.sub.12 (Delay.sub.-- T.sub.12 -Delay.sub.-- O.sub.12).sup.2 +Q.sub.13 (Delay.sub.-- T.sub.13 -Delay .sub.-- O.sub.13).sup.2 +...Q.sub.xy (Delay.sub.-- T.sub.xy -Delaye.sub.-- O.sub.xy).sup.2 ] where, Delay -- T xy represents the theoretical delay between cell sites x and y, x and y being indices representative of cell sites; Delaye -- O xy represents the observed delay between cell sites x and y; Q xy represents a quality factor for the delay measurement between cell sites x and y, the quality factor being an estimated measure of the degree to which multipath or other anomalies may have affected a particular delay measurement. Further, the inventive method may advantageously include detecting a first leading edge of a cellular telephone signal and rejecting subsequent leading edges of the cellular telephone signal. This allows the system to reduce the effects of multipath. In addition, preferred embodiments include estimating the velocity (speed and direction) of a cellular telephone by performing steps similar to those performed for location estimation, including: (1) creating a grid of theoretical points covering a prescribed range of velocities, the theoretical points being spaced at prescribed increments; (2) calculating theoretical values of frequency difference for a plurality of pairs of cell sites; (3) calculating a least squares difference (LSD) value based on the theoretical frequency differences and measured frequency differences for a plurality of pairs of cell sites; (4) searching the entire grid of theoretical points and determining the best theoretical velocity for which the value of LSD is minimized; and (5) starting at the best theoretical velocity, performing another linearized-weighted-least-squares iteration to resolve the actual velocity to within a prescribed tolerance. Other features of the present invention are described below. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1A is a depiction of an exemplary frequency reuse pattern employed in a cellular telephone system. FIG. 1B is a schematic depiction of an exemplary channel assignment pattern where cell sectoring is employed. FIG. 1C is a schematic depiction of the basic components of a cellular telephone system. FIG. 2 is a schematic diagram of a cellular telephone location system in accordance with the present invention. FIG. 3 is a block diagram of one preferred embodiment of a cell site system 12. FIG. 4 is a block diagram of one preferred embodiment of a baseband converter 12-3. FIG. 5 is a schematic diagram of the data format provided by a format block 12-5. FIG. 6 is a block diagram of one preferred embodiment of a central site system 16. FIG. 6A is a block diagram of a correlator for use in the central site system 16. FIG. 7 is a simplified flowchart of a preferred operating sequence of the central site system. FIG. 7A is a block diagram depicting exemplary embodiments of cell site systems employed in a location system which performs cross-correlations at the cell sites. FIGS. 8A-8E are a flowchart of the operation of the cell site system 16 in obtaining correlation data, time delay and frequency difference (TDOA, FDOA) data, and calculating the location of a cellular telephone on the basis of such data. FIG. 9 is a schematic diagram of a process for generating a modified billing tape in accordance with the present invention. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Overview Preferred embodiments of the present invention comprise a network of receivers located at multiple cell sites in a cellular system. These receivers listen to the mobile control channel commands/responses normally occurring in the cellular system and estimate the physical location of each cellular telephone operating within the system. Based upon the known identity of each telephone, obtained from listening to the control channel, and the estimated physical location of the telephone, the system provides a continuous, real time data stream to a database. The database may be collocated with the cellular switch or may be in some other convenient location. The data stream provided to the database comprises a set of numbers, the first number being the telephone number of the telephone, the second number being the estimated latitude, longitude, and altitude of the transmitter, and the third number being the time stamp of the measurement. The database software that processes the data stream may be maintained by the operator of the location system rather than the operator of the cellular telephone system, if the two are not the same. The location system operates by using the frequencies assigned to the control channels of the cellular system. Cellular telephones use these control channels to maintain regular contact with the cellular system, with the time between each contact being typically no more than thirty minutes and generally about ten minutes. Each control channel comprises a 10 kbps Manchester encoded data stream. There is only one control channel used per cellular sector or omni cell site. The location system is capable of functioning by listening only to the control channel broadcasts of the cellular telephones; it does not depend on control channel broadcasts from the cell sites. The location system preferably comprises equipment that is located atop cellular towers (although the equipment may be located on other tall structures), in the equipment enclosure at cells sites, and at the central switch site(s). Referring now to FIG. 2, a cellular telephone location system in accordance with the present invention comprises at least three, and preferably more, cell site systems 12a, 12b, 12c, 12d. (It should be noted that this figure, as well as the other figures, is simplified in that some elements and interconnections have been omitted. However, the instant specification and attached drawings are sufficient to enable one skilled in the art to make and use the invention disclosed herein.) Each cell site system may be located at a cell site of the cellular telephone system; however, this is not required since additional antenna and receiving equipment could be deployed at locations not well covered by cell sites. FIG. 2 also shows a user with a cellular telephone 10a. As described below, each cell site system includes an antenna that may be mounted on the same tower or building as the antenna employed by the cellular telephone system. In addition, each cell site system includes equipment (described below) that may be housed in the equipment enclosure of the corresponding cell site. In this manner, the cellular telephone location system may be overlaid on the cellular telephone system and thus may be implemented inexpensively. The cell site systems 12a, 12b, 12c, 12d are coupled via communication links 14a, 14b, 14c, 14d (for example, T1 communication links) to a central site 16. The central site 16 may be collocated with the cellular telephone system's MTSO. The central site 16 may include a disk storage device 18. The central site 16 is further coupled to a database 20, which may be remotely located from the central site and made available to subscribers. For example, FIG. 2 depicts a first terminal 22 coupled via a modem (not shown) and telephone line to the database 20; a second terminal 24 in radio communication with the database 20; and a third, handheld terminal 26, which is carried by a user who also has a cellular telephone 10b, in radio communication with the database. The user with the cellular telephone 10b and handheld terminal 26 may determine his own location by accessing the database. The handheld terminal 26 may include special mapping software for displaying the user's location, for example, on a map, on the terminal 26. Moreover, the cellular telephone and handheld terminal could be combined into one unit. Cell Site Systems FIG. 3 is a block diagram of one presently preferred embodiment of a cell site system 12. Before discussing the exemplary cell site system depicted in this figure, it should be noted that there are two alternative preferred embodiments for the equipment at each cell site, with the particular embodiment for a particular cellular system dependent upon desired cost. The first embodiment is the most preferred embodiment, and comprises (1) an antenna suited for receiving signals in the cellular frequency band; (2) a low delay bandpass filter with a bandwidth of 630 KHz located within ten to fifteen feet of the cellular antenna for removing adjacent channel interference; (3) an amplifier of sufficient gain to compensate for cable loss in the distance from the amplifier to the next filter, which is typically the height of the antenna tower plus any horizontal distance over which the cable is routed; (4) a set of twenty-one individual low delay bandpass filters, each with a bandwidth of 30 KHz centered about one of the twenty-one control channels; and (5) a set of twenty-one automatic gain control circuits with a dynamic range of 70 dB (note that not all of these components are depicted in FIG. 3). This embodiment is preferred because of its superior interference discrimination and rejection. The second embodiment comprises (1) an antenna suited for receiving signals in the cellular frequency band; (2) a low delay bandpass filter of bandwidth 630 KHz located within ten to fifteen feet of the cellular antenna for removing adjacent channel interference; (3) an amplifier of sufficient gain to compensate for cable loss in the distance from the amplifier to the next filter, which is typically the height of the antenna tower plus any horizontal distances over which the cable is routed; (4) a second low delay bandpass filter of bandwidth 630 KHz; and (5) an automatic gain control circuit with a dynamic range of 70 dB. Referring now to FIG. 3, one exemplary embodiment of a cell site system 12 includes a first antenna 12-1 that is mounted at an elevated location, preferably on the same structure employed by the cellular telephone system to mount a cell site antenna. The first antenna 12-1 may be independent of the cellular system or may be the antenna employed by the cellular system; i.e., the location system may take a fraction of the signal from the cellular system's antenna. A filter/AGC element 12-12 could advantageously be located near the antenna 12-1. This would reduce cable losses caused by conducting the RF signal over coaxial cable from the antenna to the cell site receiving equipment. The cell site system 12 further includes an amplifier 12-2 (as discussed above, the amplifier 12-2 may advantageously include sets of filtering and AGC circuits, one for each control channel); a baseband converter 12-3; a sample block 12-4, which includes an upper sideband sampler and a lower sideband sampler; a format block 12-5 (which may be implemented in software); a second antenna 12-6, used to receive timing data, for example, from a global positioning system (GPS); an amplifier 12-7; a timing signal (for example, GPS) receiver 12-8; an automatic gain control (AGC)/control block 12-9; a 5 MHz oscillator 12-10; and a computer 12-11. The cell site system 12 is coupled to the central site 16 (FIG. 2) via a communications line 14. The cell site system 12 receives one or more cellular telephone signals transmitted over a control channel from one or more cellular telephones, converts these signals to baseband signals, samples the baseband signals (wherein the sampling frequency is determined by a clock signal provided by AGC/control block 12-9), and formats the sampled signals into frames of data of a prescribed format. The format of the data frames is described below with reference to FIG. 5. The data frames are processed at the central site as described below. The 5 MHz oscillator 12-10 provides a common reference frequency for all cell site equipment. Its frequency is controlled by the controller 12-9 based on measurements made by the controller of the time interval between reception of the one second mark signal from the timing signal receiver 12-8 and an internally generated one second mark signal. The computer 12-11 performs three distinct functions concurrently: (1) It reads the output of square law detectors 54 and 60 inside the baseband convertor 12-3 (see FIG. 4 and discussion below) and then calculates the proper control signals to be sent to filter boards 48 and 50 (FIG. 4) to adjust the gain and attenuation on these boards with the goal of maintaining their output power at a constant level. (2) It receives a signal at each occurrence of a one second mark signal from timing signal receiver 12-8. At this time, it reads from controller 12-9 the difference in times of arrival of the one second mark signal from the timing signal receiver 12-8 and a corresponding one second mark signal internal to controller 12-9. The one second mark signal internal to the controller 12-9 is generated from the 5 MHz oscillator 12-10. The computer then calculates a signal to be sent back to the 5 MHz oscillator to alter its frequency of oscillation with the goal of causing the timing receiver's one second mark signal and the internally generated one second mark signal to occur simultaneously. (3) It calculates the information to be encoded in the status bits (see FIG. 5) and sends that information to the controller 12-9. Referring to FIG. 4, one preferred embodiment of the baseband convertor 12-3 includes an RF input connector 30 to which the elevated ground-based antenna 12-1 (FIG. 3) is connected (via amplifier 12-2 and filter/AGC 12-12), followed by an attenuator 32 and bandpass filter 34, which sets the level and restricts the frequency response of the baseband convertor. The filter 34 is followed by a single sideband mixer 36 that mixes the RF frequency down to a first IF frequency by action of a local oscillator signal from buffer amplifier 38. The IF frequency in the preferred embodiment is in the vicinity of 10 MHz. The output of the buffer amplifier 38, in addition to being directed to mixer 36, is also directed to the divider 42, where it is compared with a 5 MHz reference frequency from the controller 12-9 (FIG. 3). The output of divider 42 is used to control the frequency of an oscillator 40 so that the collective action of oscillator 40, divider 42, and buffer amplifier 38 provides a local oscillator signal that is phase locked to the 5 MHz reference frequency from the controller 12-9. The signal at the first IF frequency is then directed to single sideband mixer 44, where it is mixed down to a baseband frequency by the action of a computer controlled synthesizer 46. Synthesizer 46 is also phase locked to the 5 MHz signal from the controller. The upper sideband (USB) output of mixer 44 is then directed to filter/automatic gain control (AGC) amplifier 48, where it is filtered and its power is continually adjusted to a nominal value. The lower sideband (LSB) output of mixer 44 is similarly acted upon by filter/AGC amplifier 50. The output of the filter/AGC amplifier 48 includes a 375 KHz signal at 0 dBm directed to the upper sideband sampler (which is part of sample block 12-4) on wire 52, a separate output at -22 dBm directed to a square law detector 54, and a separate output directed to a front panel monitor (not shown). The output of the filter/AGC amplifier 50 includes a 375 KHz signal at 0 dBm directed to the lower sideband sampler on wire 64, a separate output at -22 dBm directed to a square law detector 60, and a separate output directed to the front panel monitor. The baseband converter 12-3 also includes a power distribution board 57 that provides power to the filter/AGC circuits 48, 50. FIG. 5 depicts a presently preferred format of the data provided by the format block 12-5 to the central site 16 (FIG. 2) via the communications line 14. As shown, the format block 12-5 provides approximately 1.536 Mbps of data to the communications line. Each frame includes 64 sync bits, 48 status bits, 60 kb of sample data (1.5 Mbs divided by 25 frames per second), and approximately 3.6 kb of "filler" data. The 1.5 Mb of sample data represent the upper sideband and lower side signal samples. The status bits include a time stamp representing the exact time the frame of data was created (which is essentially the same as the time the RF signal was received at the cell site in question). Central Site System FIG. 6 is a block diagram of the central site system 16. In one preferred embodiment, the central site system includes sixteen data inputs each connected to a T1 channel from one of the cell sites. Each data input is connected to interface/deformatting circuitry 16-1 (for example, a T1 CSU) which receives the bipolar T1 signal and outputs data bits and a clock signal. The data bits from each channel are clocked into a FIFO 16-2 by the clock signal from that channel. A computer 16-8 selects two of the channel FIFOs through a "select 2 of N" switch 16-3. A sample read clock 16-4 is controlled by the computer 16-8 and a RAM control 16-5 to read sample bits from the previously selected FIFOs. The output of one selected channel FIFO is called "DATA A," and the output of the other selected channel FIFO is called "DATA B." For the DATA B samples, a quadrature channel is calculated by means of an approximate Hilbert transform in the quadrature channel generator 16-6, resulting in in-phase output B1 and quadrature phase output B2. A complex correlator 16-7 is then used to calculate the correlation coefficient of the DATA A and DATA B1 signals, and the DATA A and DATA B2 signals, as a function of the time delay introduced between the DATA A, DATA B1 and DATA A, DATA B2, respectively. The complex correlator may be implemented in hardware or software, or a combination of hardware and software, although hardware is presently preferred because it provides greater processing speed. (One exemplary embodiment of the complex correlator is described below with reference to FIG. 6A.) The computer 16-8 is used to read the resulting correlations periodically. The correlation process, comprising switching the select 2 of N switch, reading the FIFOs, generating quadrature samples, and correlation, is fast enough that a single complex correlator 16-7 can be used to sequentially process all pairs among the sixteen data input channels. Because cellular signals are generally weak (e.g., as weak as 6 mW at the cellular telephone), a reliable and accurate method is required to detect the signal at as many cell sites as possible, and then to accurately time the same edge of the received signal at each cell site. This ability to accurately time the arrival of the signal is critical to calculating the delays between pairs of cell sites, and therefore to calculate position. Referring now to FIG. 6A, the predetection cross-correlation method employed in preferred embodiments of the present invention involves inputting a sampled strong cellular signal from a first cell site to an input 72 and inputting a delayed sampled cellular signal from any of second, third, fourth, etc., cell sites to an input 70. The correlator may be embodied in either hardware or software, as economics dictate for a particular system. The correlator preferably includes sixteen channels of shift registers 74, two-bit multipliers 76, and counters 78. Multiple correlators may be used in series, With each correlator passing bits through its shift register to the next correlator, creating multiple delay channels. The sampled cellular signal from a second cell site is input to the chained shift registers 74. The outputs from the registers are then applied simultaneously to all two-bit multipliers. For each delay channel, the signal input at 70 delayed by a prescribed number of sample periods is applied to each multiplier along with the sampled cellular signal input at 72. The outputs of the multipliers 76 are input to summation circuitry, comprising twenty-four-bit counters 78. The output of each counter is proportional to the strength of the cross-correlation for a particular relative delay. By using a plurality of delays, or correlation channels, a large range of relative delays can be measured simultaneously. The number of "lags" required is based upon the geographic area to be searched, in terms of position determination, the speed of light, and the bandwidth of the received signal being applied to the correlator. For example, in the embodiment described above, the control channels are grouped into an upper and lower sideband, each with a bandwidth of 375 KHz. This signal must be sampled at the minimum Nyquist rate or greater, for example, 750 Kbps. If an area of 100 kilometers is to be searched, the number of lags required is ##EQU1## As discussed above, another embodiment employs individual receivers for each cellular control channel. If this signal were sampled at 71.428 KHz, the number of lags required would be: ##EQU2## Location System Operation 1. Overview FIG. 7 is a simplified flowchart of the processing performed by the central site system 16. (A detailed flowchart of the signal processing is provided by FIGS. 8A-8E.) First, this system receives a frame of data from each of the cell sites. Next, each frame from a given cell site (or the sampled signal portion of each frame) is cross-correlated with each corresponding frame (or the sample portion of each other frame) from the other cell sites. (The term "corresponding" refers to frames being associated with the same interval of time). Next, the system generates a table of data identifying the individual signals received by the cellular telephone location system during the interval of time represented by the frames of data currently being processed, the individual signals being represented by the letters "A" , "B" , "C" in FIG. 7. The table further identifies the times of arrival of the signals at each cell site. These times of arrival are represented by the subscripts "T1", "T2", "T3". The system therefore identifies the signals received from one or more cellular telephones during a certain interval of time, and further identifies the time that such signals arrived at the respective cell sites. This information is then used to calculate time difference of arrival (TDOA) and frequency difference of arrival (FDOA) data, the latter being employed to estimate velocity. This data is then filtered to remove points the system judges to be erroneous. Next, the filtered TDOA data is employed to calculate the location (for example, in terms of latitude and longitude) of the individual cellular telephone responsible for each signal A, B, C. Next, the system decodes the telephone number corresponding to each cellular telephone whose location has been determined. The decoding of the telephone number may be accomplished with software in computer 16-8 or in hardware (not shown) located at the cell sites. The system employs the strongest sample (highest power) of each signal to determine its telephone number. Thereafter, the location and telephone number data for each telephone is written to the database 20 or stored locally via the local disk storage device 18 (FIG. 2). Finally, the data may be provided to a user, dispatcher, or billing system. The fields (data) sent to the user, dispatcher, or billing system would preferably include the data bits representing the dialed digits, the status bits, and the message type from the standard cellular control channel message. The data bits could be used by the user or a dispatcher to send coded messages to a display terminal. Thus, in addition to the location services, the location system could provide a limited form of messaging at no incremental cost. It should be noted that the expression "time difference of arrival," or TDOA, may refer to the time of arrival of a cellular telephone signal at one cell site (for example, cell site A) as determined by a clock reading at that cell site minus the time of arrival of the same cellular telephone signal at a second cell site (cell site B) as determined by a clock reading at the second cell site. This analysis would be carried out for all pairs of cell sites A, B. However, the individual times of arrival need not be measured; only the difference between the signals, times of arrival at the cell sites of a given pair is required. In addition, frequency difference of arrival, or FDOA, refers to the frequency of the cellular signal at a first cell site (cell site A), measured by comparison (effectively) with the cell site's 5 MHz oscillator signal, minus the same quantity for another site (cell site B). The TDOA data may be used to estimate the latitude and longitude of the cellular telephone by calculating that latitude and longitude for which the sum of the squares of the difference between the observed TDOA and the TDOA calculated on the basis of the cell site geometry and the assumed cellular telephone location is an absolute minimum, where the search of trial latitudes and longitudes extends over the entire service area of the system. The FDOA data may be used to measure the velocity (speed and direction of motion) of the cellular telephone. The velocity estimation may be carried out in manner similar to the location estimation. 2. Control Channel Signal Detection The inventive method for detecting extremely weak control channel signals has two preferred embodiments, the selection of which is dependent on the desired capital and operating costs for implementing any particular system. Both methods compensate for the variability of a particular cellular signal. That is, a transmission on the control channel is comprised of multiple fields, such as the cellular telephone number, the electronic serial number, any dialed digits, the message type, and status and other bits, which make a cellular signal variable. Therefore, the signal cannot be compared against any stored signal because each transmission is potentially unique. In method one, the cell site systems are of higher capital cost, but the communication links are of lower speed, for example, 56 Kbps, and therefore lower operational cost. FIG. 7A schematically depicts this method by illustrating the functional components of the cell site systems. In this method, cross-correlations are performed at the cell sites in the following manner. For each "strong" signal (e.g., signal "A" ) received on a particular control channel at a particular first cell site (where "strong" is at least several dB above the noise level), that strong signal is first applied to a signal decoder, such as that used by the cellular system itself. This decoder demodulates the cellular signal to produce the original digital bit stream which had been modulated to produce the cellular signal. If the decoder cannot demodulate the digital stream within allowable error thresholds, this strong signal is rejected as a starting point for the remaining part of this process. This digital bit stream is then modulated by the cell site system to reconstruct the original signal waveform as it was first transmitted by the cellular telephone. This reconstructed signal waveform is cross-correlated against the received signal at the first cell site. The cross-correlation produces a peak from which an exact time of arrival can be calculated from a predetermined point on the peak. The first cell site system then sends the demodulated digital bit stream and the exact time of arrival to the central site over the communications line. The central site then distributes the demodulated digital bit stream and the exact time of arrival to other cell sites likely to have also received the cellular transmission. At each of these other second, third, fourth, etc., cell sites, the digital bit stream is modulated by the cell site system to reconstruct the original signal waveform as it was first transmitted by the cellular telephone. This reconstructed signal waveform is cross-correlated against the signal received at each cell site during the same time interval. In this case, the same time interval refers to a period spanning several hundred to several thousand microseconds of time in either direction from the time of arrival of the strong signal at the first cell site. The cross-correlation may or may not produce a peak; if a peak is produced, an exact time of arrival can be calculated from a predetermined point on the peak. This exact time of arrival is then sent via the communications line to the central site, from which a delay difference for a particular pair of cell sites can be calculated. This method permits the cell site systems to extract time of arrival information from an extremely weak signal reception, where the weak signal may be above or below the noise level. In addition, cross-correlating at cell sites enables the cell site systems to detect a first leading edge of a cellular telephone signal and to reject subsequent leading edges caused by multipath. The value of this technique for reducing the effects of multipath will be appreciated by those skilled in the art. This method is applied iteratively to sufficient pairs of cell sites for each strong signal received at each cell site for each sample period. For any given telephone transmission, this method is only applied once. The results of the delay pairs for each signal are then directed to the location calculation algorithm. In method two, the cell site systems are of relatively low cost, as they are primarily responsible for sampling each of the control channels and sending the sampled information back to the central site. However, because no correlation is performed at the cell site, all sampled data must be sent back to the central site. This requires a high speed communications line, for example, a T1 line. The central site receives data from all cell sites over identical communications lines, where the data has been sampled and time stamped using the same time reference (derived from timing receiver). This method is applied iteratively to sufficient pairs of cell sites for each strong signal received at each cell site for each sample period. This method is only applied once for any given telephone transmission. The results of the delay pairs for each signal are then directed to the location calculation algorithm described below. 3. Location Calculation A preferred algorithm used for calculating the location of a cellular telephone is an iterative process. The first step of the process involves creating a grid of theoretical points covering the geographic area of the cellular telephone system. These points may be, for example, at 1/2 minute increments or some other increment of latitude and longitude. From each of these theoretical points, the theoretical values of delay are calculated for each relevant pair of cell sites. In calculating the theoretical values of delay, any known site biases are incorporated into the calculation. Known site biases can be caused by any number of mechanical, electrical, or environment factors and may vary from time to time. The site biases are determined by periodically locating the positions of reference cellular transmitters. Since the reference transmitters are, by definition, at known locations, any variance in the calculated position of the transmitter from the known position is assumed to have been caused by permanent or temporary site biases. These site biases are assumed to also affect the measurements of the unknown positions of cellular telephones. Once the theoretical delays are calculated from each theoretical point on the grid, a least squares difference calculation is performed between the theoretical delays and the actual observed delays for each pair of cell sites for which delays could be determined by correlation. The least squares calculation takes into consideration a quality factor for each actual delay measurement. The quality factor is an estimated measure of the degree to which multipath or other anomalies may have affected that particular delay measurement. (This quality factor is described below.) Therefore, the least squares difference equation takes the form: LSD=[Q.sub.12 (Delay.sub.-- T.sub.12 -Delay.sub.-- O.sub.12).sup.2 +Q.sub.13 (Delay.sub.-- T.sub.13 -Delay.sub.-- O.sub.13).sup.2 +...Q.sub.xy (Delay.sub.-- T.sub.xy -Delay.sub.-- O.sub.xy).sup.2 ] where, Delay -- T xy is the theoretical between cell sites x and y; Delay -- O xy is the observed delay between cell sites x and y; Q xy is the quality factor the delay measurement cell sites x and y; and LSD is the least squares difference value that is absolutely minimized over the cellular system's geographic area. The algorithm searches the entire grid of theoretical points and determines the best theoretical point for which the value of LSD is minimized. Starting at this best theoretical latitude-longitude, the algorithm then performs another linearized-weighted-least-squares iteration similar to the above-described process to resolve the actual latitude-longitude to within 0.0001 degrees, or any other chosen resolution. By performing the calculation of latitude-longitude in two steps, the amount of processing required may be greatly reduced over other approaches. Those familiar with the art will note that this iterative method of determining position automatically incorporates geometric dilution of precision (GDOP) considerations into the calculation of the position of the cellular telephone. That is, no separate GDOP table is required since both iterations in the calculation of the grid of theoretical delay values also calculate error values. Cellular telephone signals are subject to multipath and other impairments in travelling from the cellular telephone to the various cell sites. Therefore, the methods described herein incorporate compensation for multipath. As described above, the symbol rate of the digital bit stream of the cellular control channel is 10 Kbps, which has a bit time of 100 microseconds. Published multipath studies have shown typical multipath delays of 5 to 25 microseconds in urban and suburban settings. The present inventors have discovered that the typical effect of multipath in this case would be to lengthen the bit times of the digital data streams and that the correlation algorithms described above can determine the degree to which a particular transmission has been impaired. As mentioned above, when a cross-correlation is performed, a quality factor Q xy may be calculated based upon the size of the peak generated by the cross-correlation and the width of the peak, where Q xy is the quality factor for a particular delay value measurement for a particular pair of cell sites. This quality factor is useful to weight the least squares calculation used in position determination and thereby mitigate the effects of multipath. FIGS. 8A-8E are, collectively, a flowchart of the signal processing employed by the location system to (1) obtain correlation data, (2) obtain time delay and frequency difference data, and (3) calculate location data. Referring now to FIG. 8A, which depicts the processing employed to obtain correlation data, the processing begins by making a determination whether the received power is above a prescribed threshold at any cell site. If so, the complex correlator inputs are set to process that cell site's data as an autocorrelation, i.e., with both inputs set to receive the data from the same cell site. The system then waits until the correlator is finished computing the autocorrelation data. Thereafter, the autocorrelation data is Fourier transformed to obtain power spectrum data. Next, the system determines which signal channels have transmissions and saves the results. Next, a time index is cleared, and then the system sets the correlator input "B" to receive data from another cell site, leaving the "A" input unchanged. The system then waits until the correlator is finished, and then saves the correlation results. Thereafter, the system makes a determination whether there is a "B" cell site that has not been processed yet. If so, the processing branches back as shown to process the data from that cell site. If not, the system determines whether power is still being received; if not, this part of the processing is finished; if so, the time index is incremented and the "B" channel cell site signals are processed again, as shown. The processing performed to obtain time delay and frequency difference data is depicted in FIG. 8B. The system first sets a first index to a site index for the site at which power was detected. Thereafter, a second index is set to another site. The time index is then set to a first time. The correlation data is then stored in a row of a two dimensional array, where the row number corresponds to the time index. Next, the system determines whether another time sample is to be processed; if so, the time index is incremented and the system branches back as shown. If not, the data in the two-dimensional array is Fourier transformed. The transformed data is then searched for the highest amplitude. An interpolation is then performed to estimate the peak of the transformed data. The time delay and frequency difference results are then saved. The system then determines whether the second index is to be incremented and, if so, branches back as shown. FIGS. 8C-8E depict the location estimation process. Referring to FIG. 8C, the system first retrieves the observed delays and frequencies. The corresponding telephone information is then retrieved. Thereafter, the latitude and longitude are set to starting latitude, longitude values. Given the starting values, the system then calculates theoretical values of delays, taking account of site biases, if any. The system then obtains the sum of squares of the observed delays minus the computed delays. This is denoted "X". The system then determines whether this is the smallest "X" obtained thus far. If not, the system branches forward as shown to increment the starting longitude value. If this is the smallest "X", the latitude is saved in "BEST -- LAT" and the longitude is saved in "BEST -- LON". The system then determines whether another longitude and latitude should be tested. If not, the system performs a linearized-weighted-least-squares iteration step, starting at BEST -- LAT and BEST -- LON, to determine correction values "LAT -- CORRECTION" and "LON -- CORRECTION". Referring now to FIG. 8D, the location determination process is continued by determining whether the magnitude of LAT -- CORRECTION is less than 0.0001 degrees. Similarly, the system determines whether LON -- CORRECTION is less than 0.0001 degree. If either of these tests yields a negative result, the value of LAT -- CORRECTION is added to BEST -- LAT and the value of LON CORRECTION is added to BEST -- LON , and the processing branches back to perform another linearized-weighted-least-squares iteration step (FIG. 8C). Once the magnitudes of LAT -- CORRECTION and LON -- CORRECTION are less than 0.0001, the system proceeds with the velocity calculation by setting a speed variable to zero and a direction variable to zero (i.e., North). Given these starting values of speed and direction, the system calculates theoretical values of frequencies, taking account of any site bias. The system then computes the sum of the squares of observed frequencies minus computed frequencies. This sum is denoted "Y". The system then determines whether this value of "Y" is the smallest obtained thus far. If so, the speed is saved in "BEST -- SPEED" and the direction is saved in "BEST -- DIRECTION". The system then determines whether another direction should be tested. If so, the direction is incremented and the processing branches back as shown. Similarly, the system determines Whether another speed should be tried and, if so, increments the speed and branches back as shown. If the system decides not to try another direction or speed, it performs a linearized-weighted-least-squares calculation, starting at BEST -- SPEED and BEST -- DIRECTION, to determine correction values "SPEED -- CORRECTION" and "DIRECTION -- CORRECTION". Thereafter, the system determines whether the magnitude of SPEED -- CORRECTION is less than a specified value, e.g., one mile per hour. If so, the system determines whether the magnitude of DIRECTION -- CORRECTION is less than 1°. If either of these tests results in an affirmative answer, the system adds SPEED -- CORRECTION to BEST -- SPEED and adds DIRECTION -- CORRECTION to BEST -- DIRECTION, and the processing branches back as shown to perform another linearized-weighted-least-squares calculation. If SPEED -- CORRECTION is less than 1 mile per hour and DIRECTION -- CORRECTION is less than 1°, the system outputs the telephone information, BEST -- LAT , BEST -- LON , BEST -- SPEED , and BEST -- DIRECTION. Applications There are a variety of commercially valuable applications of the inventive technology disclosed herein. For example, in addition to the basic function of tracking the location of a mobile cellular telephone, the present invention may be employed to offer subscribers billing rates that vary on the basis of the location from which a call was made. As depicted in FIG. 9, a location tape, containing a record over time of the locations of the subscribers' cellular telephones, may be merged with a billing tape to produce a modified billing tape. The billing tape contains data indicating the cost for each telephone call made by the cellular telephones within a certain time period. This cost is based upon one or more predetermined billing rates. The modified billing data is based upon a different rate for calls made from certain specified locations. For example, the system may apply a lower billing rate for telephone calls made from a user's home or office. The invention may also be employed to provide emergency assistance, for example, in response to a "911" call. In this application, the location system includes means for automatically sending location information to a specified receiving station in response to receiving a "911" signal from a cellular telephone. Further, the invention may be employed in connection with an alarm service. In this application, a means is provided for comparing the current location of a given telephone with a specified range of locations and indicating an alarm condition when the current location is not within the prescribed range. Yet another application involves detecting a lack of signal transmissions by a given telephone and in response thereto automatically paging the telephone to cause it to initiate a signal transmission. This allows the system to locate a telephone that has failed to register itself with the cellular system. Such a feature could be used, for example, to generate an alarm for subscribers at remote locations. Still another application involves estimating a time of arrival of a given telephone at a specified location. This application is useful, for example, in connection with a public transportation system to provide estimated times of arrival of busses along established routes. Many other applications of this feature are also possible. Conclusion Finally, the true scope the present invention is not limited to the presently preferred embodiments disclosed herein. For example, it is not necessary that all or even any of the "cell site systems" be collocated with actual cell sites of an associated cellular telephone system. Moreover, communication links other than T1 links may be employed to couple the cell site systems to the central site system. In addition, the timing signal receiver need not be a GPS receiver, as other means for providing a common timing signal to all cell site systems will be apparent to those skilled in the art. Furthermore, the present invention may be employed in connection with many applications not specifically mentioned above. These include stolen vehicle recovery, fleet management, cell system diagnostics, and highway management. Accordingly, except as they may be expressly so limited, the scope of protection of the following claims is not intended to be limited to the particularities described above.

Description

Topics

Download Full PDF Version (Non-Commercial Use)

Patent Citations (37)

    Publication numberPublication dateAssigneeTitle
    US-3384891-AMay 21, 1968Gen ElectricMethod and system for long distance navigation and communication
    US-3646580-AFebruary 29, 1972Raytheon CoSurface vehicle fleet command and control system
    US-3680121-AJuly 25, 1972Gen ElectricMobile locator system for metropolitan areas
    US-4177466-ADecember 04, 1979Lo-Jack CorporationAuto theft detection system
    US-4297701-AOctober 27, 1981John D. AnglemanRangefinder using expanded time delay
    US-4433335-AFebruary 21, 1984Her Majesty The Queen In Right Of Canada, As Represented By Minister Of National Defence Of Her Majesty's Canadian GovernmentLocating device
    US-4596988-AJune 24, 1986Wanka James TRemote controlled tracking transmitter and tracking support system
    US-4638321-AJanuary 20, 1987Eaton CorporationUnambiguous wide baseline interferometer
    US-4639733-AJanuary 27, 1987Racal Communications Equipment LimitedDirection finding
    US-4651156-AMarch 17, 1987Mcgraw-Edison Co.Integrated radio location and communication system
    US-4651157-AMarch 17, 1987Mets, Inc.Security monitoring and tracking system
    US-4728959-AMarch 01, 1988Ventana Sciences Inc.Direction finding localization system
    US-4740792-AApril 26, 1988Hughes Aircraft CompanyVehicle location system
    US-4742357-AMay 03, 1988Rackley Ernie CStolen object location system
    US-4791572-ADecember 13, 1988Mets, Inc.Method for accurately displaying positional information on a map
    US-4797679-AJanuary 10, 1989U. S. Philips CorporationRadio direction-finding using time of arrival measurements
    US-4818998-AApril 04, 1989Lo-Jack CorporationMethod of and system and apparatus for locating and/or tracking stolen or missing vehicles and the like
    US-4870422-ASeptember 26, 1989Western Atlas International, Inc.Method and system for determining position from signals from satellites
    US-4888593-ADecember 19, 1989Signal Science, Inc.Time difference of arrival geolocation method, etc.
    US-4891650-AJanuary 02, 1990Trackmobile Inc.Vehicle location system
    US-4908629-AMarch 13, 1990Lo-Jack CorporationApparatus for locating and/or tracking stolen or missing vehicles and the like
    US-4926161-AMay 15, 1990Cupp Ted WMethod of monitoring golf carts on a golf course
    US-4975710-ADecember 04, 1990Baghdady Elie JMethods and apparatus for direction of arrival measurement and radio navigation aids
    US-5003317-AMarch 26, 1991Mets, Inc.Stolen vehicle recovery system
    US-5008679-AApril 16, 1991Interferometrics IncorporatedMethod and system for locating an unknown transmitter
    US-5023809-AJune 11, 1991Precision Technology Inc.Target tracking device
    US-5023900-AJune 11, 1991Tayloe Daniel R, Bonta Jeffrey DCellular radiotelephone diagnostic system
    US-5055851-AOctober 08, 1991Trackmobile, Inc.Vehicle location system
    US-5095500-AMarch 10, 1992Motorola, Inc.Cellular radiotelephone diagnostic system
    US-5101501-AMarch 31, 1992Qualcomm IncorporatedMethod and system for providing a soft handoff in communications in a cdma cellular telephone system
    US-5126748-AJune 30, 1992Qualcomm IncorporatedDual satellite navigation system and method
    US-5128623-AJuly 07, 1992Qualcomm IncorporatedDirect digital synthesizer/direct analog synthesizer hybrid frequency synthesizer
    US-5153902-AOctober 06, 1992Telefonaktiebolaget L M EricssonMulti-exchange paging system for locating a mobile telephone in a wide area telephone network
    US-5166694-ANovember 24, 1992Hughes Aircraft CompanyVehicle location system having enhanced position location processing
    US-5208756-AMay 04, 1993Song Han LVehicle locating and navigating system
    US-5218618-AJune 08, 1993Hughes Aircraft CompanyCellular telephone service using spread spectrum transmission
    WO-9306685-A1April 01, 1993Qualcomm IncorporatedMethode d'enregistrement pour dispositif de radiocommunications mobile

NO-Patent Citations (1)

    Title
    Smith, William W., Passive Location of Mobile Cellular Telephone Terminals, IEEE, 1991, pp. 221 225.

Cited By (951)

    Publication numberPublication dateAssigneeTitle
    US-6601048-B1July 29, 2003Mci Communications CorporationSystem and method for detecting and managing fraud
    US-2010009654-A1January 14, 2010Fougnies Douglas V, Harned Dan BPrepaid security cellular telecommunications system
    US-7714778-B2May 11, 2010Tracbeam LlcWireless location gateway and applications therefor
    US-2006030334-A1February 09, 2006Fujitsu LimitedPosition information management system
    US-8331953-B2December 11, 2012Andrew LlcSystem and method for estimating the location of a mobile device
    US-2011171912-A1July 14, 2011Andrew, LlcSystem and Method for Mobile Location By Proximity Detection
    US-5854975-ADecember 29, 1998Freedom Wireless, Inc.Prepaid security cellular telecommunications system
    US-2008068170-A1March 20, 2008I.D. Systems, Inc.System and method for reading and verifying RFID tags
    US-7974633-B2July 05, 2011Andrew, LlcSystem and method for single sensor geolocation
    US-8208942-B2June 26, 2012Telefonaktiebolaget L M Ericsson (Publ)Extended clustering for improved positioning
    WO-0037961-A1June 29, 2000Telefonaktiebolaget Lm Ericsson (Publ)A self-calibrating reference terminal
    US-7783299-B2August 24, 2010Trueposition, Inc.Advanced triggers for location-based service applications in a wireless location system
    US-6064881-AMay 16, 2000Trw Inc.System and method for processing satellite based telephone usage data for billing service providers
    US-2009286551-A1November 19, 2009Kennedy Joseph P, Carlson John P, Martin Alles, Nicolas Graube, Robert RoweE-otd augmentation to u-tdoa location system
    US-2006237531-A1October 26, 2006Jacob Heffez, Guy Heffez, Christopher WoodMethod and system for monitoring electronic purchases and cash-withdrawals
    US-2010210264-A1August 19, 2010Eran Netanel, Alon SegalPortable cellular phone system having automatic initialization
    US-6748226-B1June 08, 2004Minorplanet Systems Usa, Inc.System and method for locating a mobile unit within the service area of a mobile communications network
    US-2008214205-A1September 04, 2008Commscope, Inc. Of North CarolinaSystem and method for generating a location estimate using a method of intersections
    US-6044261-AMarch 28, 2000Ericsson, Inc.Multiple home zone areas within a mobile telecommunications network
    US-2005197136-A1September 08, 2005Friday Robert J., Hills Alexander H.Selective termination of wireless connections to refresh signal information in wireless node location infrastructure
    US-8331956-B2December 11, 2012Andrew LlcSystem and method of UMTS UE location using uplink dedicated physical control channel and downlink synchronization channel
    US-7260408-B2August 21, 2007Airespace, Inc.Wireless node location mechanism using antenna pattern diversity to enhance accuracy of location estimates
    US-8428617-B2April 23, 2013Andrew LlcMethod and apparatus to select an optimum site and/or sector to provide geo-location data
    US-2008285530-A1November 20, 2008Cisco Systems, Inc.Wireless Node Location Mechanism Featuring Definition of Search Region to Optimize Location Computation
    US-6233459-B1May 15, 2001The Atlantis Company, Limited, JapanSystem for providing Geolocation of a mobile transceiver
    US-2008122626-A1May 29, 2008I.D. Systems, Inc.System and method for reading and verifying RFID tags
    US-5568153-AOctober 22, 1996Telefonaktiebolaget Lm EricssonIndividually defined personal home area for subscribers in a cellular telecommunications network
    US-2007049337-A1March 01, 2007Cingular Wireless Ii, LlcWireless communication device with call screening
    US-7286833-B2October 23, 2007Airespace, Inc.Selective termination of wireless connections to refresh signal information in wireless node location infrastructure
    US-6184829-B1February 06, 2001Trueposition, Inc.Calibration for wireless location system
    US-6175811-B1January 16, 2001Lucent Technologies Inc.Method for frequency environment modeling and characterization
    US-2009124266-A1May 14, 2009Andrew CorporationRanging in UMTS networks
    US-9531865-B2December 27, 2016Kristine A. Wilson, Kelce S. Wilson, Edward A. WilsonHacker-resistant denial of wireless device operation in restricted areas
    WO-2012149565-A2November 01, 2012Trekintelligence, Inc.Système et procédé de ciblage et de suivi de téléphone cellulaire
    US-7616555-B2November 10, 2009Cisco Technology, Inc.Minimum variance location estimation in wireless networks
    US-8229579-B2July 24, 2012Invensys Systems, Inc.Control systems and methods with versioning
    US-7986266-B2July 26, 2011Andrew, LlcMethod and system for selecting optimal satellites in view
    US-7683760-B2March 23, 2010I.D. Systems, Inc.Mobile portal for RFID applications
    US-5973643-AOctober 26, 1999Corsair Communications, Inc.Method and apparatus for mobile emitter location
    US-6922567-B1July 26, 2005Telefonaktiebolaget L.M. EricssonSystems, methods and computer program products for identifying items of interest that are geographically proximate to wireless communicator users
    US-9654921-B1May 16, 2017X One, Inc.Techniques for sharing position data between first and second devices
    US-2005075114-A1April 07, 2005Sycord Limited PartnershipCellular telephone system that uses position of a mobile unit to make call management decisions
    US-6400320-B1June 04, 2002Trueposition, Inc., Massachusetts Insitute Of TechnologyAntenna selection method for a wireless location system
    US-7023383-B2April 04, 2006Trueposition, Inc.Multiple pass location processor
    US-6239748-B1May 29, 2001Qualcomm IncorporatedMethod for use with analog FM cellular telephones
    US-6011973-AJanuary 04, 2000Ericsson Inc.Method and apparatus for restricting operation of cellular telephones to well delineated geographical areas
    US-2011230206-A1September 22, 2011Andrew, LlcSystem and method for single sensor geolocation
    US-6490454-B1December 03, 2002Telefonaktiebolaget Lm Ericsson (Publ)Downlink observed time difference measurements
    US-2007213074-A1September 13, 2007Openwave Systems, Inc.Interface for wireless location information
    US-2010130225-A1May 27, 2010Andrew LlcSystem and method for multiple range estimation location
    US-7707054-B2April 27, 2010I.D. Systems, Inc.System and method for remotely managing maintenance operations associated with an asset
    US-5930717-AJuly 27, 1999Ericsson IncSystem and method using elliptical search area coverage in determining the location of a mobile terminal
    US-8994591-B2March 31, 2015Tracbeam LlcLocating a mobile station and applications therefor
    US-9241040-B2January 19, 2016Telecommunication Systems, Inc.Mobile activity status tracker
    US-9372266-B2June 21, 2016Nextnav, LlcCell organization and transmission schemes in a wide area positioning system (WAPS)
    WO-9738538-A1October 16, 1997Motorola Inc.Appareil et procede de facturation dans un systeme de transmission sans fil
    US-9635540-B2April 25, 2017Jeffrey D. MullenSystems and methods for locating cellular phones and security measures for the same
    US-6518921-B1February 11, 2003Ericsson Inc.Cellular positioning system that compensates for received signal delays in positioning radio receivers
    US-6732082-B1May 04, 2004Worldcom, Inc.System, method and computer program product for processing event records
    US-8204512-B2June 19, 2012Cisco TechnologyWireless node location mechanism featuring definition of search region to optimize location computation
    US-6646604-B2November 11, 2003Trueposition, Inc.Automatic synchronous tuning of narrowband receivers of a wireless location system for voice/traffic channel tracking
    EP-0961937-A4July 16, 2003Motorola IncDetermination de l'angle d'arrivee d'un signal
    US-5596330-AJanuary 21, 1997Nexus Telecommunication Systems Ltd.Differential ranging for a frequency-hopped remote position determination system
    US-2005195109-A1September 08, 2005Davi Gregg S., Dietrich Paul F., Hills Alexander H.Wireless node location mechanism responsive to observed propagation characteristics of wireless network infrastructure signals
    EP-2642312-A1September 25, 2013Medav GmbHHardwarereduziertes System zur TDOA-Lokalisierung von Funkfrequenzemittern
    US-6006097-ADecember 21, 1999Telefonaktiebolaget L M Ericsson (Publ)Method for determining position of mobile communication terminals
    US-RE45808-ENovember 17, 2015Qualcomm IncorporatedMethod and apparatus for determining location of a base station using a plurality of mobile stations in a wireless mobile network
    US-7293088-B2November 06, 2007Cisco Technology, Inc.Tag location, client location, and coverage hole location in a wireless network
    US-8179316-B2May 15, 2012ThalesSet mode passive location in TOA/TDOA modes
    US-6724835-B1April 20, 2004Symmetricam, Inc.Carrier tracking method
    US-5873041-AFebruary 16, 1999Nec CorporationMobile telephone location system
    US-2008261611-A1October 23, 2008Mia Rashidus S, Ronald Lefever, Anderson Robert JSparsed U-TDOA Wireless Location Networks
    US-2008183522-A1July 31, 2008I.D. Systems, Inc.Mobile asset data management system
    US-2008248811-A1October 09, 2008Trueposition, Inc.TDOA/GPS Hybrid Wireless Location System
    US-6009334-ADecember 28, 1999Telefonaktiebolaget L M EricssonMethod and system for determining position of mobile radio terminals
    US-7990317-B2August 02, 2011At&T Mobility Ii LlcSignal path delay determination
    US-7107046-B1September 12, 2006France Telecom, S.A., Teldiffusion De France SaService transmission system related to relevant geographical zones and receiver designed to be used with said transmission system
    US-5732354-AMarch 24, 1998At&T Wireless Services, Inc.Method and apparatus for determining the location of a mobile telephone
    US-6522890-B2February 18, 2003Cambridge Positioning Systems, Ltd.Location and tracking system
    US-2011090122-A1April 21, 2011Andrew LlcLocation measurement acquisition adaptive optimization
    US-6477362-B1November 05, 2002Ericsson Inc.Systems and methods for providing information to emergency service centers
    US-2007161385-A1July 12, 2007Anderson Robert JGPS synchronization for wireless communications stations
    US-8217832-B2July 10, 2012Andrew, LlcEnhancing location accuracy using multiple satellite measurements based on environment
    US-8068855-B2November 29, 2011Polaris Wireless, Inc.Location determination using RF fingerprinting
    US-5799061-AAugust 25, 1998Greater Harris County 9-1-1 Emergency NetworkComputer integrated telephony system for the processing of 9-1-1 calls for service
    US-5963550-AOctober 05, 1999Ntt Mobile Communications Network, Inc.Packet transfer scheme and mobile communication system
    US-5838237-ANovember 17, 1998Revell; Graeme Charles, Revell; Ashley MarkPersonal alarm device
    US-6204812-B1March 20, 2001Cell-Loc Inc.Methods and apparatus to position a mobile receiver using downlink signals, part II
    US-6049720-AApril 11, 2000Transcrypt International / E.F. Johnson CompanyLink delay calculation and compensation system
    US-6266013-B1July 24, 2001Trueposition, Inc.Architecture for a signal collection system of a wireless location system
    US-8200242-B2June 12, 2012Cisco Technology, Inc.Enhanced wireless node location using differential signal strength metric
    US-9615204-B1April 04, 2017X One, Inc.Techniques for communication within closed groups of mobile devices
    US-8301160-B2October 30, 2012Andrew LlcSystem and method for SUPL roaming using a held client
    US-6996392-B2February 07, 2006Trueposition, Inc.E911 overlay solution for GSM, for use in a wireless location system
    US-7366492-B1April 29, 2008Verizon Corporate Services Group Inc., Bbn Technologies Corp.Method and system for mobile location detection using handoff information
    US-7853511-B2December 14, 2010Telecommunication Systems, Inc.Prepaid short messaging
    US-7750841-B2July 06, 2010Cambridge Consultants LimitedDetermining positional information
    US-2006003775-A1January 05, 2006Bull Jeffrey F, Czarnecki Paul M, Ginter Thomas S, Ward Matthew L, Anderson Robert JAdvanced triggers for location-based service applications in a wireless location system
    US-7962165-B2June 14, 2011Garmin Switzerland GmbhCombined global positioning system receiver and radio
    US-8738496-B2May 27, 2014Telecommunication Systems, Inc.Prepaid short messaging
    US-2006208891-A1September 21, 2006Ehrman Kenneth S, Ehrman Michael L, Jagid Jeffrey MMobile portal for rfid applications
    US-6317602-B1November 13, 2001Nokia Telecommunications OySignal processing system for locating a transmitter
    US-6330454-B1December 11, 2001Nortel Networks LimitedSystem and method for locating mobile units operating within a wireless communication system
    US-6349211-B2February 19, 2002Ace K Computer Co., Ltd.Position display system of mobile terminal
    WO-03009613-A1January 30, 2003Trueposition, Inc., Massachusetts Institute Of TechnologyImproved method for estimating tdoa and fdoa in a wireless location system
    US-6044265-AMarch 28, 2000Bellsouth CorporationMethods and apparatus for cellular set programming
    US-9277525-B2March 01, 2016Tracbeam, LlcWireless location using location estimators
    US-8204511-B2June 19, 2012Trueposition, Inc.Mid-call synchronization for U-TDOA and AOA location in UMTS
    US-7656271-B2February 02, 2010I.D. Systems, Inc.System and method for managing a remotely located asset
    US-6230018-B1May 08, 2001Nortel Networks LimitedDevices and processing in a mobile radio communication network having calibration terminals
    US-2010156713-A1June 24, 2010Andrew LlcSystem and method for determining a reference location of a mobile device
    US-6544171-B2April 08, 2003Biotronik Mess- Und Therapiegerate Gmbh & Co. Ingenieurburo BerlinSystem for patient monitoring
    US-8712453-B2April 29, 2014Telecommunication Systems, Inc.Login security with short messaging
    US-7142900-B1November 28, 2006Garmin Ltd.Combined global positioning system receiver and radio
    US-8116784-B2February 14, 2012Trueposition, Inc.Mid-call synchronization for U-TDOA and AoA location in UMTS
    US-8225271-B2July 17, 2012Invensys Systems, Inc.Apparatus for control systems with objects that are associated with live data
    US-6492944-B1December 10, 2002Trueposition, Inc.Internal calibration method for receiver system of a wireless location system
    US-8483717-B2July 09, 2013Qualcomm IncorporatedLocal area network assisted positioning
    US-7626546-B2December 01, 2009L-3 Communications Integrated Systems L.P.Methods and systems for detection and location of multiple emitters
    US-5987377-ANovember 16, 1999Highwaymaster Communications, Inc.Method and apparatus for determining expected time of arrival
    US-8918278-B2December 23, 2014Inrix Global Services LimitedMethod and system for modeling and processing vehicular traffic data and information and applying thereof
    US-6317604-B1November 13, 2001Trueposition, Inc.Centralized database system for a wireless location system
    EP-0961937-A1December 08, 1999Motorola, Inc.Bestimmung der einfallsrichtung eines signals
    US-8706078-B2April 22, 2014Enovsys LlcLocation reporting satellite paging system with privacy feature
    US-6185428-B1February 06, 2001Ericsson IncSystem and method for adaptively modifying base station transceiver resources for time of arrival measurements
    US-2010173609-A1July 08, 2010Eran Netanel, Lavine James FMethod and Apparatus for Secure Immediate Wireless Access in a Telecommunications Network
    US-6463290-B1October 08, 2002Trueposition, Inc., Massachusetts Institute Of TechnologyMobile-assisted network based techniques for improving accuracy of wireless location system
    US-7956803-B2June 07, 2011Andrew, LlcSystem and method for protecting against spoofed A-GNSS measurement data
    US-7899938-B1March 01, 2011Dennis S. FernandezIntegrated medical sensor and messaging system and method
    US-9408024-B2August 02, 2016Nextnav, LlcWide area positioning system
    US-6535163-B1March 18, 2003Enuvis, Inc.Determining location information using sampled data containing location-determining signals and noise
    US-6492941-B1December 10, 2002Garmin CorporationCombined global positioning system receiver and radio
    US-7925278-B2April 12, 2011Motorola Mobility, Inc.Method and system for locating a wireless device in a wireless communication network
    US-5974329-AOctober 26, 1999Rutgers UniversityMethod and system for mobile location estimation
    US-8290496-B2October 16, 2012Trueposition, Inc.Cooperating receiver selection for UMTS wireless location
    US-5842122-ANovember 24, 1998Motorola, Inc.Apparatus and method for alternative radiotelephone system selection
    US-2010227593-A1September 09, 2010Makor Issues And Rights Ltd.Traffic speed enforcement based on wireless phone network
    US-6658258-B1December 02, 2003Lucent Technologies Inc.Method and apparatus for estimating the location of a mobile terminal
    US-8135413-B2March 13, 2012Tracbeam LlcPlatform and applications for wireless location and other complex services
    US-6424840-B1July 23, 2002Signalsoft Corp.Method and system for dynamic location-based zone assignment for a wireless communication network
    US-6040800-AMarch 21, 2000Ericsson Inc.Systems and methods for locating remote terminals in radiocommunication systems
    US-8509728-B2August 13, 2013Qualcomm IncorporatedEmergency call handling in a wireless communication system
    US-9854402-B1December 26, 2017X One, Inc.Formation of wireless device location sharing group
    US-7899070-B2March 01, 2011Invensys Systems, Inc.Control system apparatus with change updates
    US-7944350-B2May 17, 2011Spectrum Tracking Systems, Inc.Method and system for providing tracking services to locate an asset
    US-7440762-B2October 21, 2008Trueposition, Inc.TDOA/GPS hybrid wireless location system
    US-9182474-B2November 10, 2015Stmicroelectronics S.A., Stmicroelectronics (Grenoble 2) SasMethod for localizing an object
    US-7024205-B1April 04, 2006Openwave Systems Inc.Subscriber delivered location-based services
    US-7946480-B2May 24, 2011Diebold Self-Service Systems, Division Of Diebold, IncorporatedTransaction dependent on ATM receiving user input of the security code sent during transaction to account'S designated mobile phone
    US-8195205-B2June 05, 2012Telecommunication Systems, Inc.Gateway application to support use of a single internet address domain for routing messages to multiple multimedia message service centers
    US-6334059-B1December 25, 2001Trueposition, Inc.Modified transmission method for improving accuracy for e-911 calls
    US-8904460-B2December 02, 2014Arcom Digital, LlcMethods and apparatus for locating leakage of digital signals
    US-9778372-B2October 03, 2017Qualcomm IncorporatedWireless network hybrid positioning
    US-7522927-B2April 21, 2009Openwave Systems Inc.Interface for wireless location information
    US-6111541-AAugust 29, 2000Sony Corporation, Sony Electronics, Inc.Positioning system using packet radio to provide differential global positioning satellite corrections and information relative to a position
    US-8059028-B2November 15, 2011Trueposition, Inc.Hybrid GNSS and TDOA wireless location system
    US-8517261-B2August 27, 2013Diebold Self-Service Systems Division Of Diebold, IncorporatedAutomated banking machine that outputs interference signals that jam reading ability of unauthorized card readers
    US-8479983-B1July 09, 2013Diebold Self-Service Systems Division Of Diebold, IncorporatedAutomated banking machine operation authorization based on user location verified by data read from data bearing records
    US-6259894-B1July 10, 2001Lucent Technologies Inc.Method for improved line-of-sight signal detection using RF model parameters
    US-7570212-B2August 04, 2009The Boeing CompanyReference beacon methods and apparatus for TDOA/FDOA geolocation
    US-5873040-AFebruary 16, 1999International Business Machines CorporationWireless 911 emergency location
    US-6026304-AFebruary 15, 2000U.S. Wireless CorporationRadio transmitter location finding for wireless communication network services and management
    US-6249252-B1June 19, 2001Tracbeam LlcWireless location using multiple location estimators
    US-8160609-B2April 17, 2012Andrew LlcSystem and method for multiple range estimation location
    US-2007229251-A1October 04, 2007Ehrman Kenneth S, Ehrman Michael L, Jagid Jeffrey M, Pinzon Joseph M, Yaron Hecker, Leonard PimentelMobile asset data management system
    WO-02078382-A1October 03, 2002Telia Ab (Publ)Dispositifs et procedes de positionnement d'unites de communication mobiles
    US-6266014-B1July 24, 2001Cell-Loc Inc.Methods and apparatus to position a mobile receiver using downlink signals part IV
    US-2011151839-A1June 23, 2011Trueposition, Inc.Location Intelligence Management System
    US-6519465-B2February 11, 2003Trueposition, Inc.Modified transmission method for improving accuracy for E-911 calls
    US-6122529-ASeptember 19, 2000Transcept, Inc.Simulcast with hierarchical cell structure overlay
    US-2011171961-A1July 14, 2011Itis Uk LimitedSystem and method for geographically locating a cellular phone
    US-8120467-B2February 21, 2012I.D. Systems, Inc.Mobile portal for RFID applications
    US-6286044-B1September 04, 2001Mitsubishi Denki Kabushiki KaishaNetwork-connected device management system
    US-8484045-B1July 09, 2013Dennis FernandezAdaptive direct transaction for network client group
    US-7304571-B2December 04, 2007Information Systems Laboratories, Inc.Firefighter locator with activator
    US-9503450-B2November 22, 2016Telecommunications Systems, Inc.Login security with short messaging
    US-6259404-B1July 10, 2001Signatron Technology CorporationPosition location system and method
    US-6353743-B1March 05, 2002Sony Corporation, Sony Electronics, Inc.Positioning system using packet radio to determine position and to obtain information relative to a position
    US-7916705-B2March 29, 2011Cisco Technology, Inc.Method, apparatus, and software product for detecting rogue access points in a wireless network
    US-2010273504-A1October 28, 2010Trueposition, Inc.Network Autonomous Wireless Location System
    US-2008293435-A1November 27, 2008George Maher, Ananth Kalenahalli, John CarlsonMethod and apparatus to select an optimum site and/or sector to provide geo-location data
    US-7764231-B1July 27, 2010Tracbeam LlcWireless location using multiple mobile station location techniques
    US-7548158-B2June 16, 2009Telecommunication Systems, Inc.First responder wireless emergency alerting with automatic callback and location triggering
    US-7657266-B2February 02, 2010Andrew LlcE-OTD augmentation to U-TDOA location system
    US-8436768-B2May 07, 2013Trueposition, Inc.Diversity time and frequency location receiver
    US-8112096-B2February 07, 2012Andrew, LlcSystem and method for locating an unknown base station
    US-8650605-B2February 11, 2014Arcom Digital, LlcLow-cost leakage detector for a digital HFC network
    US-6317081-B1November 13, 2001Trueposition, Inc.Internal calibration method for receiver system of a wireless location system
    US-6768909-B1July 27, 2004Ericsson, Inc.Handoff between external and internal positioning systems
    US-2010227626-A1September 09, 2010Polaris Wireless, Inc.Location Determination Using RF Fingerprinting
    US-9036792-B2May 19, 2015At&T Intellectual Property Ii, L.P.Method for confirming end point location of 911 calls
    US-7298327-B2November 20, 2007Tracbeam LlcGeographic location using multiple location estimators
    US-2009131075-A1May 21, 2009Commscope, Inc. Of North CarolinaSystem and method for locating an unknown base station
    US-6374098-B1April 16, 2002Ericsson Inc.Systems and methods for locating remote units operating in a radiocommunication system using an adjunct system
    US-9078101-B2July 07, 2015Dennis DuprayGeographically constrained network services
    US-8186578-B1May 29, 2012Diebold Self-Service Systems Division Of Diebold, IncorporatedATM transaction authorization based on user location verification
    US-8204503-B1June 19, 2012Sprint Communications Company L.P.Base station identification to indicate mobility of a wireless communication device
    US-6639552-B2October 28, 2003Northrop Grumman CorporationMethod of and apparatus for deriving a signal for enabling a radio wave source location to be derived
    US-2007155489-A1July 05, 2007Frederic Beckley, Ward Matthew LDevice and network enabled geo-fencing for area sensitive gaming enablement
    US-7430425-B2September 30, 2008Telecommunication Systems, Inc.Inter-carrier digital message with user data payload service providing phone number only experience
    US-6816733-B1November 09, 2004Rockwell Electronic Commerce Technologies LlcTracking agent call processing locations in connection with an automatic call distribution system
    US-2010194604-A1August 05, 2010I.D. Systems, Inc.Mobile portal for rfid applications
    US-6035202-AMarch 07, 2000Ericsson Inc.Method and apparatus for locating a mobile unit
    US-7974627-B2July 05, 2011Trueposition, Inc.Use of radio access technology diversity for location
    WO-9714257-A1April 17, 1997Accucom Wireless Services, Inc.Systeme et procede de localisation de telephones mobiles
    US-6275705-B1August 14, 2001Cambridge Positioning Systems Ltd.Location and tracking system
    US-7167713-B2January 23, 2007Trueposition, Inc.Monitoring of call information in a wireless location system
    US-6414635-B1July 02, 2002Wayport, Inc.Geographic-based communication service system with more precise determination of a user's known geographic location
    US-5987329-ANovember 16, 1999Ericsson IncSystem and method for mobile telephone location measurement using a hybrid technique
    US-7860857-B2December 28, 2010Invensys Systems, Inc.Digital data processing apparatus and methods for improving plant performance
    GB-2395080-BMarch 23, 2005Trueposition Inc, Massachusetts Inst TechnologyImproved method for estimating TDOA and FDOA in a wireless location system
    US-2009131073-A1May 21, 2009Andrew CorporationSystem and method for locating umts user equipment using measurement reports
    US-6266534-B1July 24, 2001Ericsson Inc.Systems and methods for locating remote terminals in radiocommunication systems
    US-6084546-AJuly 04, 2000Us Wireless CorporationLocation determination in wireless communication systems using velocity information
    US-5594425-AJanuary 14, 1997Peoplenet, Inc.Locator device
    US-6073005-AJune 06, 2000Ericsson Inc.Systems and methods for identifying emergency calls in radiocommunication systems
    US-2011170444-A1July 14, 2011Martin Alles, Khalid Al-Mufti, Ananth Kalenahalli, Gravely Thomas BSystem and method for multiple range estimation location
    US-2007111746-A1May 17, 2007Anderson Robert JTransmit-power control for wireless mobile services
    US-7529544-B1May 05, 2009Sprint Spectrum L.P.Method and system for initiating a communication with a network entity to communicate information regarding a fixed wireless device
    WO-0209059-A1January 31, 2002Telia Ab (Publ)Systeme de localisation et de surveillance interactives
    US-6091959-AJuly 18, 2000Motorola, Inc.Method and apparatus in a two-way wireless communication system for location-based message transmission
    US-2006250264-A1November 09, 2006Cutler Robert T, Mutsuya IiMethod and system for computing and displaying location information from cross-correlation data
    US-6300904-B1October 09, 2001Honeywell International Inc.Narrowband based navigation scheme
    US-8090384-B2January 03, 2012Andrew, LlcSystem and method for generating a location estimate using a method of intersections
    US-9173185-B1October 27, 2015Sprint Spectrum L.P.Methods and systems for managing registration signaling based on off-time duration
    WO-9602006-A1January 25, 1996Lockheed Sanders, Inc.Appareil et procede de localisation de telephones cellulaires et d'emetteurs similaires
    US-6166691-ADecember 26, 2000Telefonaktiebolaget Lm Ericsson (Publ)Self-calibrating reference terminal
    US-9798985-B2October 24, 2017Inrix Holdings LimitedApparatus and methods for providing journey information
    US-7949340-B2May 24, 2011Andrew, LlcMethod and system for applying wireless geolocation technology
    US-2010328148-A1December 30, 2010Andrew CorporationMethod and System for Providing Assistance Data for A-GPS Location of Handsets in Wireless Networks
    US-9191520-B2November 17, 2015Telecommunication Systems, Inc.Location services gateway server
    US-8447319-B2May 21, 2013Andrew LlcSystem and method for locating UMTS user equipment using measurement reports
    KR-100958465-B1May 17, 2010트루포지션, 인크.Automatic synchronous tuning of narrowband receivers of a wireless location system for voice/traffic channel tracking
    US-7869810-B2January 11, 2011Agilent Technologies, Inc.Method and system for computing and displaying location information from cross-correlation data
    US-8090452-B2January 03, 2012Invensys Systems, Inc.Methods and apparatus for control using control devices that provide a virtual machine environment and that communicate via an IP network
    US-8130141-B2March 06, 2012Commlabs, Inc.Wide area positioning system
    US-6830213-B1December 14, 2004Lucent Technologies Inc.Wireless guidance system
    US-6201499-B1March 13, 2001Consair CommunicationsTime difference of arrival measurement system
    US-5539665-AJuly 23, 1996Xerox CorporationRecording and retrieval of information relevant to the activities of a user
    US-9237543-B2January 12, 2016Tracbeam, LlcWireless location using signal fingerprinting and other location estimators
    US-RE45505-EMay 05, 2015Adc Telecommunications, Inc.Localization of a mobile device in distributed antenna communications system
    WO-0059256-A1October 05, 2000Qualcomm IncorporatedProcede et dispositif de determination de l'emplacement d'une station a distance dans un reseau de telecommunications amcr
    US-8374575-B2February 12, 2013Jeffrey D MullenSystems and methods for locating cellular phones and security measures for the same
    US-2005037775-A1February 17, 2005Mark Moeglein, Douglas Rowitch, Wyatt Riley, Deloach James Douglass, Leonid SheynblatMethod and apparatus for wireless network hybrid positioning
    US-8353450-B2January 15, 2013Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking system controlled responsive to data bearing recordings and user input of a phone received security code
    US-8204510-B2June 19, 2012Trueposition, Inc.Detection and selection of a reference signal for network-based wireless location
    US-2008166973-A1July 10, 2008Cisco Technology, Inc.Locally Adjusted Radio Frequency Coverage Maps in Wireless Networks
    US-8311018-B2November 13, 2012Andrew LlcSystem and method for optimizing location estimate of mobile unit
    US-7427952-B2September 23, 2008Trueposition, Inc.Augmentation of commercial wireless location system (WLS) with moving and/or airborne sensors for enhanced location accuracy and use of real-time overhead imagery for identification of wireless device locations
    US-8116275-B2February 14, 2012Trapeze Networks, Inc.System and network for wireless network monitoring
    US-7599995-B1October 06, 2009Fernandez Dennis S, Hu Irene YIntegrated vehicular sensor and messaging system and method
    CN-103329000-ASeptember 25, 2013真实定位公司无线地理定位网络中的对等感测站的网络定位以及同步
    US-6151505-ANovember 21, 2000Northern Telecom LimitedSystem and method for reporting the location of a mobile telecommunications unit to an authorized terminator telecommunications unit
    US-8643540-B2February 04, 2014Nextnav, LlcWide area positioning system
    US-2007300294-A1December 27, 2007Eran Netanel, Lavine James FMethod and Apparatus for Secure Immediate Wireless Access in a Telecommunications Network
    US-7117191-B2October 03, 2006Mci, Inc.System, method and computer program product for processing event records
    US-8028272-B2September 27, 2011Invensys Systems, Inc.Control system configurator and methods with edit selection
    US-2009102712-A1April 23, 2009Guy HeffezMethod and system for monitoring electronic purchases and cash-withdrawals
    US-5952969-ASeptember 14, 1999Telefonakiebolaget L M Ericsson (Publ)Method and system for determining the position of mobile radio terminals
    US-8019339-B2September 13, 2011Andrew LlcUsing serving area identification in a mixed access network environment
    US-8224348-B2July 17, 2012Trueposition, Inc.Location intelligence management system
    US-8049617-B2November 01, 2011Spectrum Tracking Systems, Inc.Method and system for providing tracking services to locate an asset
    US-2007040741-A1February 22, 2007Loomis Peter V WCellphone GPS positioning system
    US-6424837-B1July 23, 2002Christopher J. Hall, Clay S. Turner, Jimmy C. RayAutomated testing for cellular telephone system including emergency positioning
    US-2007155401-A1July 05, 2007Trueposition Inc.User plane uplink time difference of arrival (u-tdoa)
    US-8022874-B2September 20, 2011Elta Systems Ltd.Method and system for detecting signal sources in a surveillance space
    US-8199050-B2June 12, 2012Trueposition, Inc.Hybrid GNSS and TDOA wireless location system
    US-8127060-B2February 28, 2012Invensys Systems, IncMethods and apparatus for control configuration with control objects that are fieldbus protocol-aware
    US-7933615-B2April 26, 2011Telecommunication Systems, Inc.Mobile originated interactive menus via short messaging services method
    US-2008123608-A1May 29, 2008Qualcomm IncorporatedPositioning for WLANs and other wireless networks
    US-6031490-AFebruary 29, 2000Telefonaktiebolaget L M EricssonMethod and system for determining the position of mobile radio terminals
    WO-2008071777-A1June 19, 2008ThalesToa/tdoa mode global passive location
    WO-02091762-A1November 14, 2002Motorola, Inc.Method and apparatus in a wireless communication system for determining a location of a mobile station
    US-7330150-B1February 12, 2008Garmin CorporationCombined global positioning system receiver and radio
    US-8077079-B2December 13, 2011Cisco Technology, Inc.Radiolocation using path loss data
    US-8150357-B2April 03, 2012Trapeze Networks, Inc.Smoothing filter for irregular update intervals
    US-7739361-B2June 15, 2010Thibault Richard L, Canna Bruce S, Couper Gerald SMethods for remote process control with networked digital data processors and a virtual machine environment
    US-8917209-B2December 23, 2014Nextnav, LlcCoding in a wide area positioning system (WAPS)
    US-8138975-B2March 20, 2012Trueposition, Inc.Interference detection, characterization and location in a wireless communications or broadcast system
    US-7715828-B2May 11, 2010At&T Mobility Ii, LlcWireless communication device with call screening
    US-7205938-B2April 17, 2007Airespace, Inc.Wireless node location mechanism responsive to observed propagation characteristics of wireless network infrastructure signals
    US-8761808-B2June 24, 2014West CorporationApparatus and method for locating a mobile telecommunication device
    US-5583517-ADecember 10, 1996Nexus 1994 LimitedMulti-path resistant frequency-hopped spread spectrum mobile location system
    US-8938252-B2January 20, 2015Andrew LlcSystem and method to collect and modify calibration data
    US-6301240-B1October 09, 2001Transcept, Inc.Centrally located equipment for wireless telephone system
    US-6236365-B1May 22, 2001Tracbeam, LlcLocation of a mobile station using a plurality of commercial wireless infrastructures
    US-8810452-B2August 19, 2014Trueposition, Inc.Network location and synchronization of peer sensor stations in a wireless geolocation network
    EP-0705046-A3March 24, 1999US WEST Technologies, Inc.Système et méthode pour la mise à jour d'une base de données de localisation
    US-9191799-B2November 17, 2015Juniper Networks, Inc.Sharing data between wireless switches system and method
    US-2008140544-A1June 12, 2008I.D. Systems, Inc.Mobile asset data management system
    WO-2010123655-A1October 28, 2010Trueposition, Inc.Système de localisation sans fil indépendant du réseau
    US-RE42285-EApril 12, 2011Trueposition, Inc.Applications processor including a database system, for use in a wireless location system
    US-7933394-B2April 26, 2011At&T Intellectual Property I, L.P.Method and apparatus for routing calls based on the identification of the calling party or calling line
    US-9408047-B2August 02, 2016Telecommunication Systems, Inc.Read acknowledgement interoperability for text messaging and IP messaging
    US-9035829-B2May 19, 2015Nextnav, LlcWide area positioning systems and methods
    US-2009289851-A1November 26, 2009The Boeing CompanyReference beacon methods and apparatus for tdoa/fdoa geolocation
    US-2007233664-A1October 04, 2007Invensys Systems, Inc.Digital data processing apparatus and methods for improving plant performance
    US-8463964-B2June 11, 2013Invensys Systems, Inc.Methods and apparatus for control configuration with enhanced change-tracking
    US-8958754-B2February 17, 2015Andrew, LlcSystem and method for sub-coherent integration for geo-location using weak or intermittent signals
    US-6826394-B1November 30, 2004Ericsson Inc.Interaction between an adjunct positioning system and a radiocommunication system
    US-6876859-B2April 05, 2005Trueposition, Inc., Massachusetts Institute Of TechnologyMethod for estimating TDOA and FDOA in a wireless location system
    EP-1113688-A3July 31, 2002Rockwell Electronic Commerce CorporationTracking agent call processing locations in connection with an automatic call distribution system
    US-8694025-B2April 08, 2014Dennis DuprayGeographically constrained network services
    US-8897801-B2November 25, 2014Qualcomm IncorporatedTransmission of location information by a transmitter as an aid to location services
    WO-0119122-A1March 15, 2001Ericsson Inc.Procede et reseau de fourniture de donnees de positionnement du temps d'arrivee (tea)
    WO-9927738-A1June 03, 1999Telefonaktiebolaget Lm Ericsson (Publ)Procede et systeme pour determiner la position de terminaux de radiocommunications mobiles
    US-7861924-B1January 04, 2011Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking system controlled responsive to data bearing records
    US-7890127-B2February 15, 2011Telecommunication Systems, Inc.Inter-carrier messaging service providing phone number only experience
    US-8380222-B2February 19, 2013Andrew LlcSystem and method for multiple range estimation location
    CN-1731094-BMay 05, 2010倚天资讯股份有限公司具有地理信息的行动通讯方法与系统
    WO-0204975-A1January 17, 2002Sirf Technology IncLocal area beacon system for position determination
    US-6920329-B2July 19, 2005Allen TelecomMethod and system for applying wireless geolocation technology
    US-6018652-AJanuary 25, 2000Telefonaktiebolaget Lm Ericsson (Publ.)Cellular telephone system having mobile charging region and area based pricing method and apparatus
    US-5592180-AJanuary 07, 1997Nexus1994 LimitedDirection finding and mobile location system for trunked mobile radio systems
    US-8046581-B2October 25, 2011Telespree CommunicationsMethod and apparatus for secure immediate wireless access in a telecommunications network
    US-2010106774-A1April 29, 2010Andrew LlcSystem and method for providing location services for multiple access networks from a single location server
    US-5946611-AAugust 31, 1999Sycord Limited PartnershipCellular telephone system that uses position of a mobile unit to make call management decisions
    US-7502656-B2March 10, 2009Invensys Systems, Inc.Methods and apparatus for remote process control
    FR-2987136-A1August 23, 2013St Microelectronics Sa, St Microelectronics Grenoble 2Procede de localisation d'un objet
    US-7812766-B2October 12, 2010Tracbeam LlcLocating a mobile station and applications therefor
    US-8818322-B2August 26, 2014Trapeze Networks, Inc.Untethered access point mesh system and method
    US-9324232-B2April 26, 2016INRX Gloabal Services LimitedMethod and system for modeling and processing vehicular traffic data and information and applying thereof
    US-6388618-B1May 14, 2002Trueposition, Inc.Signal collection system for a wireless location system
    US-6438380-B1August 20, 2002Lucent Technologies Inc.System for robust location of a mobile-transmitter
    US-6847822-B1January 25, 2005Sycord Limited PartnershipCellular telephone system that uses position of a mobile unit to make call management decisions
    US-6061565-AMay 09, 2000Hewlett-Packard CompanyMobile radio systems
    US-9778371-B2October 03, 2017Commscope Technologies LlcAutonomous transmit chain delay measurements
    US-9121923-B2September 01, 2015Trueposition, Inc.Interference detection, characterization and location in a wireless communications or broadcast system
    US-6112095-AAugust 29, 2000Us Wireless CorporationSignature matching for location determination in wireless communication systems
    US-5537460-AJuly 16, 1996Holliday, Jr.; Robert O., Howe; Jerry W.Method and apparatus for determining the precise location of a modified cellular telephone using registration messages and reverse control channel transmission
    US-9814016-B2November 07, 2017Qualcomm IncorporatedLocal area network assisted positioning
    US-9858556-B2January 02, 2018Diebold Nixdorf, IncorporatedBanking system controlled responsive to data bearing records and user input of a phone received security code
    WO-0051391-A1August 31, 2000Telefonaktiebolaget Lm EricssonMethod and arrangement relating to mobile telephone communications network
    US-7984420-B2July 19, 2011Invensys Systems, Inc.Control systems and methods with composite blocks
    US-6154727-ANovember 28, 2000Cyberhealth, Inc.Visit verification
    US-2011183688-A1July 28, 2011Cisco Technology, Inc.Enhanced Wireless Node Location Using Differential Signal Strength Metric
    US-5883598-AMarch 16, 1999Signatron Technology CorporationPosition location system and method
    US-2010203849-A1August 12, 2010Garmin Ltd.Combined global positioning system receiver and radio
    US-6097336-AAugust 01, 2000Trueposition, Inc.Method for improving the accuracy of a wireless location system
    US-2010120435-A1May 13, 2010Trueposition, Inc.Use of Radio Access Technology Diversity for Location
    US-2011092226-A1April 21, 2011Andrew LlcMethod and Apparatus to Select an Optimum Site and/or Sector to Provide Geo-Location Data
    US-8629803-B2January 14, 2014Nextnav, LlcWide area positioning system
    US-2006111833-A1May 25, 2006Israel Feldman, Arie Trinker, Yochai Meltzer, Allon Eshpar, Amnon LotemMethod and system for modeling and processing vehicular traffic data and information and applying thereof
    US-2004203429-A1October 14, 2004Anderson Robert J., Sheehan Joseph W.E911 overlay solution for GSM, for use in a wireless location system
    US-6243588-B1June 05, 2001Ericsson Inc.Mobile positioning method for a portable communications device using shortened repetitive bursts
    US-5742509-AApril 21, 1998Trimble Navigation LimitedPersonal tracking system integrated with base station
    US-6529165-B1March 04, 2003Cambridge Positioning Systems, Ltd.Radio positioning systems
    US-7725111-B2May 25, 2010Polaris Wireless, Inc.Location determination using RF fingerprinting
    US-8866672-B2October 21, 2014L-3 Communications Integrated Systems LpCooperative systems and methods for TDOA-based emitter location
    US-8340683-B2December 25, 2012Andrew, LlcSystem and method for a high throughput GSM location solution
    US-7256737-B2August 14, 2007Hall Christopher J, Turner Clay S, Ray Jimmy CMethod and apparatus for geolocating a wireless communications device
    US-6414634-B1July 02, 2002Lucent Technologies Inc.Detecting the geographical location of wireless units
    US-6236851-B1May 22, 2001Freedom Wireless, Inc.Prepaid security cellular telecommunications system
    WO-9601531-A2January 18, 1996Karbasi, Amir, KiumarsSysteme de positionnement cellulaire
    US-5774802-AJune 30, 1998Motorola Inc.Apparatus and method for billing in a wireless communication system
    US-7299074-B2November 20, 2007At&T Bls Intellectual Property, Inc.Wireless communications methods and systems using a remote, self-contained communications antenna unit
    US-7286835-B1October 23, 2007Airespace, Inc.Enhanced wireless node location using differential signal strength metric
    US-8032149-B2October 04, 2011Andrew LlcTasking and reporting method and implementation for wireless appliance location systems
    US-2011165861-A1July 07, 2011Wilson Kristine A, Wilson Kelce S, Wilson Edward ACellular Device Identification and Location with Emergency Number Selectivity Enforcement (CILENSE)
    WO-9535636-A1December 28, 1995Gte Laboratories IncorporatedSysteme de reperage se basant sur un reseau cellulaire
    US-8384595-B2February 26, 2013Trueposition, Inc.Position estimation through iterative inclusion of measurement data
    WO-03084079-A3January 22, 2004Trueposition IncSyntonisation sequentielle automatique de recepteurs a bande etroite d'un systeme de positionnement hertzien pour suivi de canal vocal/trafic
    US-7882197-B2February 01, 2011Invensys Systems, Inc.Control system methods that transfer control apparatus information over IP networks in web page-less transfers
    US-9467844-B2October 11, 2016Telecommunication Systems, Inc.Mobile activity status tracker
    US-6281834-B1August 28, 2001Trueposition, Inc.Calibration for wireless location system
    US-2008125145-A1May 29, 2008Adc Technology Inc.Portable communicator
    US-2008095350-A1April 24, 2008At&T Delaware Intellectual Property, Inc., Formerly Known As Bellsouth Intl. Property Corp.Method and Apparatus for Routing Calls Based on the Identification of the Calling Party or Calling Line
    EP-2086271-A2August 05, 2009TruePosition, Inc.Différence d'heure d'arrivée en liaison montante de plan utilisateur
    CN-100499920-CJune 10, 2009重庆邮电大学Cdma移动目标的手持式探测设备及探测方法
    US-2006286989-A1December 21, 2006Illion Brian E BGeographical and calendar based advertising system and method
    US-2010039320-A1February 18, 2010Boyer Pete A, Ronald Lefever, Mia Rashidus S, Anderson Robert JHybrid GNSS and TDOA Wireless Location System
    US-8174446-B2May 08, 2012At&T Mobility Ii LlcSignal path delay determination
    US-8005050-B2August 23, 2011Lgc Wireless, Inc.Localization of a mobile device in distributed antenna communications system
    US-5898402-AApril 27, 1999Federal Communications Commission/Compliance And Information Bureau/Equipment Development GroupWide aperature radio frequency data acquisition system
    US-5519760-AMay 21, 1996Gte Laboratories IncorporatedCellular network-based location system
    US-8737452-B2May 27, 2014Trueposition, Inc.Identification and isolation of radio signals for a wireless location system
    US-7756527-B2July 13, 2010Fujitsu LimitedPosition information management system
    WO-9848588-A2October 29, 1998Ericsson Inc.Systemes et procedes permettant de localiser des unites distantes dans un systeme de radiocommunication au moyen d'un systeme assistant
    EP-1720033-A2November 08, 2006Agilent Technologies, Inc.Procédé et système d'affichage d'informations de lieu
    US-2008140440-A1June 12, 2008I.D. Systems, Inc.Mobile asset data management system
    US-2008084858-A1April 10, 2008Cisco Technology, Inc.Relative location of a wireless node in a wireless network
    US-2007121560-A1May 31, 2007Edge Stephen WPositioning for wlans and other wireless networks
    US-8874398-B2October 28, 2014Nextnav, LlcWide area positioning system
    US-9258702-B2February 09, 2016Trapeze Networks, Inc.AP-local dynamic switching
    US-8559942-B2October 15, 2013Mundi Fomukong, Denzil Willoughby ChesneyUpdating a mobile device's location
    US-9418545-B2August 16, 2016Inrix Holding LimitedMethod and system for collecting traffic data
    US-8638762-B2January 28, 2014Trapeze Networks, Inc.System and method for network integrity
    US-8261976-B1September 11, 2012Diebold Self-Service Systems Division Of Diebold, IncorporatedATM transaction authorization based on user location verification
    US-7200387-B1April 03, 2007Cellco PartnershipApplication invocation on a mobile station using messaging service
    US-5809424-ASeptember 15, 1998Daimler-Benz Aerospace AgProcess for locating mobile stations in a cellular mobile radio network and mobile radio network for carrying out the process
    US-6421009-B2July 16, 2002Peter SuprunovMobile station position tracking system for public safety
    US-5999124-ADecember 07, 1999Snaptrack, Inc,Satellite positioning system augmentation with wireless communication signals
    US-6714779-B2March 30, 2004Christopher J. Hall, Clay S. Turner, Jimmy C. RayAutomated testing for cellular telephone system including emergency positioning
    US-5570412-AOctober 29, 1996U.S. West Technologies, Inc.System and method for updating a location databank
    US-6172644-B1January 09, 2001Trueposition, Inc.Emergency location method for a wireless location system
    US-6347230-B2February 12, 2002Ace K Computer Co., Ltd.Position display system of mobile terminal
    US-6522887-B2February 18, 2003Telefonaktiebolaget Lm Ericsson (Publ)Identifying starting time for making time of arrival measurements
    US-2010227628-A1September 09, 2010Trueposition, Inc.Advanced Triggers for Location-Based Service Applications in a Wireless Location System
    US-2006259240-A1November 16, 2006Fujitsu LimitedPosition information management method and apparatus
    US-2005185618-A1August 25, 2005Friday Robert J., Dietrich Paul F.Wireless node location mechanism using antenna pattern diversity to enhance accuracy of location estimates
    US-7903029-B2March 08, 2011Tracbeam LlcWireless location routing applications and architecture therefor
    US-8175953-B1May 08, 2012Telecommunication Systems, Inc.Prepaid short messaging
    US-6331825-B1December 18, 2001Peoplenet, Inc.Mobile locator system
    WO-9848575-A2October 29, 1998Ericsson Inc.Systemes et procedes permettant de traiter les appels d'urgence dans les structures cellulaires hierarchisees
    US-8400358-B2March 19, 2013Andrew LlcMethod to modify calibration data used to locate a mobile unit
    US-2010127928-A1May 27, 2010Andrew LlcSystem and method for server side detection of falsified satellite measurements
    US-6574478-B1June 03, 2003Alcatel Usa Sourcing, L.P.System and method for locating mobile devices
    US-7720944-B2May 18, 2010Invensys Systems, Inc.Process control system with networked digital data processors and a virtual machine environment
    US-2006261940-A1November 23, 2006Pro Tech Monitoring, Inc.System, method and apparatus for locating and controlling objects
    WO-0069111-A3February 21, 2002Rienzo Andrew L DiAuthentification
    US-5854834-ADecember 29, 1998Mci Communications CorporationNetwork information concentrator
    US-7286515-B2October 23, 2007Cisco Technology, Inc.Method, apparatus, and software product for detecting rogue access points in a wireless network
    US-2011159875-A1June 30, 2011Itis Uk LimitedSystem and method for geographically locating a cellular phone
    US-7769620-B1August 03, 2010Dennis FernandezAdaptive direct transaction for networked client group
    US-7925320-B2April 12, 2011Garmin Switzerland GmbhElectronic device mount
    US-2008188242-A1August 07, 2008Andrew CorporationSystem and method for optimizing location estimate of mobile unit
    WO-9711384-A1March 27, 1997Cambridge Positioning Systems LimitedSysteme de localisation
    WO-9809467-A1March 05, 1998Nokia Telecommunications OyMethod for determination of subscribers position and zone dependent tariff
    WO-0027143-A1May 11, 2000Signalsoft CorporationGestion de plusieurs donnees d'entree pour des applications sans fil dependant de la localisation
    US-RE41006-ENovember 24, 2009Telecommunication Systems, Inc.Inter-carrier short messaging service providing phone number only experience
    US-2008161015-A1July 03, 2008Trueposition, Inc.Robust, Efficient, Localization System
    US-2010127923-A1May 27, 2010Andrew LlcSystem and method for determining falsified satellite measurements
    US-8978105-B2March 10, 2015Trapeze Networks, Inc.Affirming network relationships and resource access via related networks
    US-8725596-B2May 13, 2014I.D. Systems, Inc.Mobile asset data management system
    US-8838139-B2September 16, 2014Trueposition, Inc.Advanced triggers for location-based service applications in a wireless location system
    US-2008102784-A1May 01, 2008Vineet Mittal, Bhupesh Manoharlal UmattEmergency call handing in a wireless communication system
    US-2008068171-A1March 20, 2008I.D. Systems, Inc.Mobile portal for RFID luggage handling applications
    US-2006187119-A1August 24, 2006Hall Christopher J, Turner Clay S, Ray Jimmy CMethod and apparatus for geolocating a wireless communications device
    US-2012223133-A1September 06, 2012Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking System Controlled Responsive to Data Bearing Records and User Input of a Phone Received Security Code
    US-9749876-B2August 29, 2017Qualcomm IncorporatedLocal area network assisted positioning
    WO-9909778-A1February 25, 1999Telefonaktiebolaget Lm Ericsson (Publ)Procede et systeme d'evaluation de la position de terminaux du service radio mobile
    US-2010120436-A1May 13, 2010Itis Uk LimitedSystem and method for geographically locating a cellular phone
    US-8725120-B2May 13, 2014Crystal Development Consulting Services L.L.C.Internet system for connecting client-travelers with geographically-associated data
    US-9838942-B2December 05, 2017Trapeze Networks, Inc.AP-local dynamic switching
    US-6704563-B1March 09, 2004Boston Communications Group, Inc.Systems and methods for prerating costs for a communication event
    US-2007236389-A1October 11, 2007Lommen Layne D, Edewaard David O, Halladay Henry EReference beacon methods and apparatus for tdoa/fdoa geolocation
    US-6091957-AJuly 18, 2000Northern Telecom LimitedSystem and method for providing a geographic location of a mobile telecommunications unit
    US-6285321-B1September 04, 2001Trueposition, Inc., Massachusetts Institute Of TechnologyStation based processing method for a wireless location system
    WO-9624915-A1August 15, 1996Highwaymaster Communications, Inc.Procede et appareil pour determiner le temps d'arrivee prevu
    US-2008137524-A1June 12, 2008Trueposition, Inc.Location of Wideband OFDM Transmitters With Limited Receiver Bandwidth
    US-9001811-B2April 07, 2015Adc Telecommunications, Inc.Method of inserting CDMA beacon pilots in output of distributed remote antenna nodes
    US-RE35916-EOctober 06, 1998Dennison; Everett, Nass; Edwin L., Duffy; Timothy J., Pauley; Gregory T., Jones; Scott L., Shale; Deborah J.Cellular telephone system that uses position of a mobile unit to make call management decisions
    US-8509805-B2August 13, 2013Trueposition, Inc.Advanced triggers for location-based service applications in a wireless location system
    US-8892495-B2November 18, 2014Blanding Hovenweep, LlcAdaptive pattern recognition based controller apparatus and method and human-interface therefore
    US-9191912-B2November 17, 2015Adc Telecommunications, Inc.Systems and methods for location determination
    WO-2011027347-A3May 19, 2011Pin Nav LlcDispositif et procédé de calcul d'instant d'arrivée d'une trame dans un réseau sans fil
    US-2008081619-A1April 03, 2008Hideki Nagata, Hiroyuki Minakata, Takayuki Ide, Atsushi Kohashi, Minoru OmakiMobile device system and mobile device
    US-2006122846-A1June 08, 2006Jonathan Burr, Gary Gates, Slater Alan GApparatus and method for providing traffic information
    US-2008026740-A1January 31, 2008Eran NetanelMethod and apparatus for secure immediate wireless access in a telecommunications network
    US-9552725-B2January 24, 2017Inrix Global Services LimitedMethod and system for modeling and processing vehicular traffic data and information and applying thereof
    US-2010033379-A1February 11, 2010Lommen Layne DReference beacon identification using transmission sequence characteristics
    US-6115599-ASeptember 05, 2000Trueposition, Inc.Directed retry method for use in a wireless location system
    US-2007252758-A1November 01, 2007Loomis Peter V WRadio positioning system for providing position and time for assisting gps signal acquisition in mobile unit
    US-2010062790-A1March 11, 2010Telefonaktiebolaget Lm Ericsson (Publ)Extended clustering for improved positioning
    US-2007286143-A1December 13, 2007Olson Timothy S, Kaiser Daryl A, Roshan Pejman DMethod, apparatus, and software product for detecting rogue access points in a wireless network
    US-6483460-B2November 19, 2002Trueposition, Inc., Massachusetts Institute Of TechnologyBaseline selection method for use in a wireless location system
    US-8213957-B2July 03, 2012Trueposition, Inc.Network autonomous wireless location system
    US-7904072-B2March 08, 2011Telespree CommunicationsMethod and apparatus for secure immediate wireless access in a telecommunications network
    US-6167274-ADecember 26, 2000At&T Wireless Svcs. Inc.Method for locating a mobile station
    US-7548961-B1June 16, 2009Fernandez Dennis S, Hu Irene YIntegrated vehicular sensor and messaging system and method
    US-6965344-B1November 15, 2005Information Systems Laboratories, Inc.Firefighter locator
    US-6999779-B1February 14, 2006Fujitsu LimitedPosition information management system
    US-8315632-B2November 20, 2012Telefonaktiebolaget Lm Ericsson (Publ)Adaptive enhanced cell identity positioning
    US-8897813-B2November 25, 2014Andrew LlcLTE user equipment positioning system and method
    US-2005029872-A1February 10, 2005Ehrman Kenneth S., Jagid Jeffrey M., Ehrman Michael L., John OrrisUniversal power supply
    US-2010105353-A1April 29, 2010Christina Cacioppo, Gilboy Christopher P, Stephen ShinnersMethod for Confirming End Point Location of 911 Calls
    GB-2403862-BMarch 29, 2006Trueposition IncAutomatic sequential tuning of narrowband receivers of a wireless location system for voice/traffic channel tracking
    US-2010234022-A1September 16, 2010Andrew LlcSystem and method for supl roaming in wimax networks
    US-2006069496-A1March 30, 2006Israel Feldman, Arie Trinker, Yochai Meltzer, Allon Eshpar, Amnon LotemMethod and system for modeling and processing vehicular traffic data and information and applying thereof
    US-2005148346-A1July 07, 2005Maloney John E., Anderson Robert J.TDOA/GPS hybrid wireless location system
    WO-2008131122-A1October 30, 2008Trueposition, Inc.Réseaux de localisation sans fil u-tdoa éparpillés
    US-6873290-B2March 29, 2005Trueposition, Inc.Multiple pass location processor
    US-7057556-B2June 06, 2006Hall Christopher J, Turner Clay S, Ray Jimmy CMethod and apparatus for geolocating a wireless communications device
    US-6002342-ADecember 14, 1999Motorola, Inc.Communication system and device having unit locating feature
    US-7292189-B2November 06, 2007Worcester Polytechnic InstituteMethods and apparatus for high resolution positioning
    WO-2008131020-A1October 30, 2008Trueposition, Inc.Sparsed u-tdoa wireless location networks
    US-6256504-B1July 03, 2001Motorola, Inc.Apparatus and method for billing in a wireless communication system
    US-2010141529-A1June 10, 2010ThalesSet mode passive location in toa/tdoa modes
    US-2010311439-A1December 09, 2010Andrew, LlcSystem and method for supl roaming using a held client
    US-8838463-B2September 16, 2014Dennis S. Fernandez, Irene HuAdaptive direct transaction for network client group
    US-7424282-B2September 09, 2008Sprint Spectrum L.P.Method and system for delivering photos to called destinations
    US-2010049084-A1February 25, 2010Nock Andrew P, Ramon RamosBiopsy marker delivery device
    US-6104931-AAugust 15, 2000Ericsson Inc.System and method for defining location services
    US-5999131-ADecember 07, 1999Information Systems Laboratories, Inc.Wireless geolocation system
    US-2005075992-A1April 07, 2005Mci Worldcom, Inc.System, method and computer program product for processing event records
    US-8152055-B2April 10, 2012Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking system controlled responsive to data bearing records and user input of a phone received security code
    US-7933610-B2April 26, 2011Andrew LlcMethod and apparatus to select an optimum site and/or sector to provide geo-location data
    US-7558852-B2July 07, 2009Cisco Technology, Inc.Tag location, client location, and coverage hole location in a wireless network
    US-6088586-AJuly 11, 2000Codem Systems, Inc.System for signaling within a cellular telephone system
    US-2008261614-A1October 23, 2008Mia Rashidus S, Ronald Lefever, Anderson Robert JSparsed U-TDOA Wireless Location Networks
    US-2004230643-A1November 18, 2004Invensys Systems, Inc.Methods and apparatus for remote process control
    GB-2395080-AMay 12, 2004Trueposition Inc, Massachusetts Inst TechnologyImproved method for estimating TDOA and FDOA in a wireless location system
    US-8676670-B2March 18, 2014I.D. Systems, Inc.Mobile asset data management system
    US-5936571-AAugust 10, 1999Lockheed Martin CorporationIntegrated GPS/interference location system
    US-6456852-B2September 24, 2002Trafficmaster Usa, Inc., Motorola, Inc.Internet distributed real-time wireless location database
    EP-1118871-A3September 19, 2001Cambridge Positioning Systems LimitedMethod of estimating time offsets in a position determining system
    US-8849254-B2September 30, 2014Trueposition, Inc.Location intelligence management system
    US-9204283-B2December 01, 2015Jeffrey D MullenSystems and methods for locating cellular phones and security measures for the same
    US-2005164712-A1July 28, 2005Kennedy Joseph P.Jr., Gravely Thomas B., Carlson John P., Andrew BeckMethod and system for applying wireless geolocation technology
    US-7177631-B2February 13, 2007Cingular Wireless Ii, LlcWireless communication device with call screening
    US-8060222-B2November 15, 2011Invensys Systems, Inc.Control system configurator and methods with object characteristic swapping
    EP-0811296-A1December 10, 1997Highwaymaster Communications, Inc.Ortsbestimmungssystem und -verfahren unter verwendung eines mobilen kommunikationsnetzes
    US-6272350-B1August 07, 2001Lucent Technologies Inc.Method for improved line of sight signal detection using time/frequency analysis
    US-5815538-ASeptember 29, 1998Omniplex, Inc.Method and apparatus for determining location of a subscriber device in a wireless cellular communications system
    US-8150421-B2April 03, 2012Trueposition, Inc.User plane uplink time difference of arrival (U-TDOA)
    US-9038119-B2May 19, 2015Arcom Digital, LlcLow-cost leakage detector for a digital HFC network
    WO-2005081796-A3November 03, 2005Interdigital Tech Corp, Fatih OzluturkSupport sur la base de reseaux multiples pour services de localisation
    US-7668552-B2February 23, 2010Allen Telecom LlcMethod and system for applying wireless geolocation technology
    US-2009002153-A1January 01, 2009Viktors Berstis, Creighton Matthew HicksKey Fob and System for Indicating the Lock Status of a Door Lock
    US-8370268-B2February 05, 2013I.D. Systems, Inc.Systems and methods for remote vehicle rental with remote vehicle access
    US-5722067-AFebruary 24, 1998Freedom Wireless, Inc.Security cellular telecommunications system
    US-8380220-B2February 19, 2013Andrew LlcSystem and method for generating a location estimate using a method of intersections
    US-8670383-B2March 11, 2014Trapeze Networks, Inc.System and method for aggregation and queuing in a wireless network
    US-8032153-B2October 04, 2011Tracbeam LlcMultiple location estimators for wireless location
    EP-1137305-A1September 26, 2001Telefonaktiebolaget Lm EricssonVerfahren und System zur Erfassung der Position eines Mobilfunkendgerätes in einem Mobilfunknetz
    US-RE44378-EJuly 16, 2013Verizon Laboratories Inc.Cellular network-based location system
    US-6285885-B1September 04, 2001Matsushita Electric Industrial Co., Ltd.Mobile communication apparatus with distance measuring unit
    EP-1137301-A1September 26, 2001TELEFONAKTIEBOLAGET L M ERICSSON (publ)Méthode pour l'emplacement des stations mobiles dans un réseau mobile
    US-8045506-B2October 25, 2011Trueposition, Inc.Sparsed U-TDOA wireless location networks
    US-6236849-B1May 22, 2001Metawave Communications CorporationSystem and method of determining a mobile station's position using directable beams
    US-2007270168-A1November 22, 2007Qualcomm IncorporatedDynamic location almanac for wireless base stations
    US-8218449-B2July 10, 2012Trapeze Networks, Inc.System and method for remote monitoring in a wireless network
    US-2009224957-A1September 10, 2009Chung Hyo K, Le Phuong H, Parker John M, Reid David L, Robertson Mark AMethods and systems for detection and location of multiple emitters
    US-8035557-B2October 11, 2011Andrew, LlcSystem and method for server side detection of falsified satellite measurements
    US-6064339-AMay 16, 2000Us Wireless CorporationSubspace signature matching for location ambiguity resolution in wireless communication systems
    US-2005080552-A1April 14, 2005Trafficsoft, Inc. (Formerly Estimotion Inc.)Method and system for modeling and processing vehicular traffic data and information and applying thereof
    US-8463293-B2June 11, 2013Andrew LlcSystem and method for a high throughput GSM location solution
    US-2001041535-A1November 15, 2001Karmel Clayton R.Positioning system using packet radio to determine position and to obtain information relative to a position
    US-2008045235-A1February 21, 2008Kennedy Joseph P, John Peter CarlsonSystem and method for single sensor geolocation
    US-2007102626-A1May 10, 2007Halsey J DDisplacement and velocity sensor
    US-2014351125-A1November 27, 2014Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking system controlled responsive to data bearing records and user input of a phone received security code
    US-8463297-B2June 11, 2013Trueposition, Inc.Subscriber selective, area-based service control
    US-8922430-B2December 30, 2014Trueposition, Inc.Optimization of variable coherence integration for the location of weak signals
    WO-9602007-A1January 25, 1996Lockheed Sanders, Inc.Apparatus and method for locating cellular telephones and similar transmitters
    US-8044859-B2October 25, 2011The Boeing CompanyReference beacon methods and apparatus for TDOA/FDOA geolocation
    US-6891500-B2May 10, 2005Christopher J. Hall, Clay S. Turner, Jimmy C. RayMethod and apparatus for geolocating a wireless communications device
    US-8290510-B2October 16, 2012Andrew LlcSystem and method for SUPL held interworking
    US-8514827-B2August 20, 2013Trapeze Networks, Inc.System and network for wireless network monitoring
    US-9875492-B2January 23, 2018Dennis J. DuprayReal estate transaction system
    US-RE38267-EOctober 07, 2003Verizon Laboratories, Inc.Cellular network-based geographic coverage area reporting method and apparatus
    US-6208297-B1March 27, 2001Cell-Loc Inc.Methods and apparatus to position a mobile receiver using downlink signals, part I
    US-9155060-B2October 06, 2015INRX Global Services LimitedSystem and method for geographically locating a cellular phone
    US-8456530-B2June 04, 2013Arcom Digital, LlcMethods and apparatus for detecting and locating leakage of digital signals
    US-8254966-B2August 28, 2012Andrew, LlcSystem and method to modify wireless network calibration data
    US-6047183-AApril 04, 2000Ericsson Inc.Selection of positioning handover candidates based on angle
    US-7925274-B2April 12, 2011Trueposition, Inc.TDOA/GPS hybrid wireless location system
    US-9854394-B1December 26, 2017X One, Inc.Ad hoc location sharing group between first and second cellular wireless devices
    US-6321092-B1November 20, 2001Signal Soft CorporationMultiple input data management for wireless location-based applications
    US-6330452-B1December 11, 2001Cell-Loc Inc.Network-based wireless location system to position AMPs (FDMA) cellular telephones, part I
    US-6633754-B1October 14, 2003Ericsson Inc.Systems and methods for increasing emergency call access speed in radiocommunication systems
    GB-2341516-BJuly 03, 2002Inc EricssonSystems and methods for handling emergency calls in hierarchical cell structures
    US-6091362-AJuly 18, 2000Trueposition, Inc.Bandwidth synthesis for wireless location system
    US-9810761-B2November 07, 2017Qualcomm IncorporatedLocal area network assisted positioning
    US-5748084-AMay 05, 1998Isikoff; Jeremy M.Device security system
    US-2011043640-A1February 24, 2011Arcom Digital, LlcMethods and apparatus for detecting and locating leakage of digital signals
    US-2006208890-A1September 21, 2006Ehrman Kenneth S, Ehrman Michael L, Jagid Jeffrey MMobile portal for rfid applications
    US-7162252-B2January 09, 2007Andrew CorporationMethod and apparatus for supporting multiple wireless carrier mobile station location requirements with a common network overlay location system
    US-7356494-B2April 08, 2008I.D. Systems, Inc.Robust wireless communications system architecture and asset management applications performed thereon
    EP-1720033-A3December 27, 2006Agilent Technologies, Inc.Method and system for displaying location information
    US-7525484-B2April 28, 2009Tracbeam LlcGateway and hybrid solutions for wireless location
    US-7456784-B2November 25, 2008Garmin CorporationCombined global positioning system receiver and radio
    US-8744491-B2June 03, 2014Telecommunication Systems, Inc.Wireless network tour guide
    US-9134398-B2September 15, 2015Tracbeam LlcWireless location using network centric location estimators
    US-8635444-B2January 21, 2014Trapeze Networks, Inc.System and method for distributing keys in a wireless network
    US-9173060-B2October 27, 2015CommScope Technologies LLPSystem and method for mobile location by dynamic clustering
    GB-2322248-BOctober 17, 2001Fujitsu LtdPosition information management system
    US-5512908-AApril 30, 1996Lockheed Sanders, Inc.Apparatus and method for locating cellular telephones
    CN-100526909-CAugust 12, 2009真实定位公司Automatic sequential tuning of narrowband receivers of a wireless location system for voice/traffic channel tracking
    US-8369967-B2February 05, 2013Hoffberg Steven M, Hoffberg-Borghesani Linda IAlarm system controller and a method for controlling an alarm system
    US-8264402-B2September 11, 2012Cisco Technology, Inc.Radiolocation using path loss data
    US-2008057935-A1March 06, 2008Eran Netanel, Alon SegalPortable cellular phone system having automatic initialization
    US-2006075131-A1April 06, 2006Douglas Bretton L, Olson Timothy S, Halasz David E, Deng John Z, Bilstad Arnold M, Sheausong Yang, Rebo Richard D, Leary Jonathan S, Kaiser Daryl ATag location,client location, and coverage hole location in a wireless network
    US-2009025070-A1January 22, 2009Eran Netanel, Lavine James FSystem and method to enable subscriber self-activation of wireless data terminals
    US-2003100318-A1May 29, 2003Erik Larsson, Ari Kangas, Sven FischerIdentifying starting time for making time of arrival measurements
    US-7916071-B2March 29, 2011Andrew, LlcSystem and method for determining a reference location of a mobile device
    US-8462769-B2June 11, 2013Andrew LlcSystem and method for managing created location contexts in a location server
    US-7197320-B2March 27, 2007Joseph JosephSystem for managing traffic patterns using cellular telephones
    US-9026114-B2May 05, 2015INRX Global Services LimitedSystem and method for geographically locating a cellular phone
    US-8368640-B2February 05, 2013Invensys Systems, Inc.Process control configuration system with connection validation and configuration
    US-7844280-B2November 30, 2010Trueposition, Inc.Location of wideband OFDM transmitters with limited receiver bandwidth
    US-7801512-B1September 21, 2010Makor Issues And Rights Ltd.Traffic speed enforcement based on wireless phone network
    US-6393294-B1May 21, 2002Polaris Wireless, Inc.Location determination using RF fingerprinting
    US-8954028-B2February 10, 2015Telecommunication Systems, Inc.Geo-redundant and high reliability commercial mobile alert system (CMAS)
    US-8031851-B2October 04, 2011At&T Intellectual Property I, L.P.Method and apparatus for routing calls based on the identification of the calling party or calling line
    US-8331955-B2December 11, 2012Trueposition, Inc.Robust downlink frame synchronization schemes in CDMA wireless networks for geo-location
    US-2005181793-A1August 18, 2005Eran NetanelMethod and apparatus for secure immediate wireless access in a telecommunications network
    US-2006212146-A1September 21, 2006Invensys Systems, Inc.Methods and apparatus for control using control devices that provide a virtual machine environment and that communicate via an IP network
    US-2008232328-A1September 25, 2008Stefan Scheinert, Peter WaltherLocalization of a mobile device in distributed antenna communications system
    US-8103313-B2January 24, 2012Adc Technology Inc.Portable communicator
    US-6433740-B1August 13, 2002Qualcomm IncorporatedDetermination method for use with analog cellular system
    US-2005108089-A1May 19, 2005Ehrman Kenneth S., Jagid Jeffrey M., Loosmore Natthan H., Michael EhrmanFully automated vehicle rental system
    US-8413898-B2April 09, 2013Guy HeffezMethod and system for monitoring electronic purchases and cash-withdrawals
    US-2006252431-A1November 09, 2006Mullen Jeffrey DSystems and methods for locating cellular phones and security measures for the same
    US-8060429-B2November 15, 2011Telecommunication Systems, Inc.Prepaid short messaging
    WO-0135683-A1May 17, 2001Signalsoft Corp.Procede et systeme d'attribution dynamique de zone en fonction de l'emplacement destines a un reseau de communication sans fil
    US-7171381-B2January 30, 2007I.D. Systems, Inc.System architecture and communications for an asset management system
    US-2011148709-A1June 23, 2011At&T Mobility Ii LlcSignal path delay determination
    US-8188920-B2May 29, 2012Andrew, LlcLocation measurement acquisition optimization with Monte Carlo simulation
    US-6526283-B1February 25, 2003Samsung Electronics Co, LtdDevice and method for tracking location of mobile telephone in mobile telecommunication network
    US-7866544-B1January 11, 2011Diebold Self-Service Systems Division Of Diebold, IncorporatedCard reading automated banking machine authorization based on user location verification
    US-8073463-B2December 06, 2011Andrew, LlcSystem and method of UMTS UE location using uplink dedicated physical control channel and downlink synchronization channel
    US-8442538-B2May 14, 2013Trueposition, Inc.Cooperating receiver selection for UMTS wireless location
    US-7376584-B1May 20, 2008Verizon Corporate Services Group Inc.Systems and methods for fulfilling orders using location-based abbreviated dialing
    US-5787347-AJuly 28, 1998Gte Laboratories IncorporatedMethod and apparatus for selecting a cellular system for communication with a cellular telephone in a roaming area
    US-8170585-B2May 01, 2012Andrew, LlcRanging in UMTS networks
    US-9538495-B2January 03, 2017Commscope Technologies LlcSystem and method for hybrid location in an LTE network
    WO-9848588-A3April 01, 1999Ericsson Ge Mobile IncSystems and methods for locating remote units operating in a radiocommunication system using an adjunct system
    EP-1113688-A2July 04, 2001Rockwell Electronic Commerce CorporationTracking agent call processing locations in connection with an automatic call distribution system
    US-6603428-B2August 05, 2003Trueposition, Inc.Multiple pass location processing
    US-8532024-B2September 10, 2013Andrew LlcMethod and apparatus for determining coupled path loss
    US-8459546-B1June 11, 2013Diebold Self-Service Systems Division Of Diebold, IncorporatedATM transaction authorization based on user location verification
    US-7689240-B2March 30, 2010Trueposition, Inc.Transmit-power control for wireless mobile services
    US-7429914-B2September 30, 2008Andrew CorporationSystem and method for CDMA geolocation
    US-5991454-ANovember 23, 1999Lockheed Martin CoporationData compression for TDOA/DD location system
    US-8762519-B2June 24, 2014Andrew LlcSystem and method for providing location services for multiple access networks from a single location server
    WO-9800988-A2January 08, 1998Ericsson Inc.Procede et appareil permettant de communiquer des informations sur la position d'une station mobile dans un reseau de telephones cellulaires
    US-2006069526-A1March 30, 2006Kaiser Daryl A, Datla Kirshnam R VRadiolocation using path loss data
    US-7359718-B2April 15, 2008Hong Kong Applied Science And Technology Research Institute Co., Ltd.Location determination and location tracking in wireless networks
    US-8818380-B2August 26, 2014Israel Feldman, Yochay Meltzer, Uri Lavee, Allon EshparSystem and method for geographically locating a cellular phone
    US-6308067-B1October 23, 2001At&T Corp.Wireless communications system and method of operation for reducing fraud
    US-5726893-AMarch 10, 1998Stanford Telecommunications, Inc.Cellular telephone with voice-in-data modem
    US-7911320-B2March 22, 2011I.D. Systems, Inc.Mobile asset data management system
    US-2007049336-A1March 01, 2007Cingular Wireless Ii, LlcWireless communication device with call screening
    GB-2403862-AJanuary 12, 2005Trueposition IncAutomatic sequential tuning of narrowband receivers of a wireless location system for voice/traffic channel tracking
    US-6374124-B1April 16, 2002Transcept, Inc.Dynamic reallocation of transceivers used to interconnect wireless telephones to a broadband network
    US-9286490-B2March 15, 2016Nextnav, LlcSystems and methods for providing conditional access to transmitted information
    GB-2341516-AMarch 15, 2000Inc EricssonSystems and methods for handling emergency calls in hierarchical cell structures
    US-2003225707-A1December 04, 2003Ehrman Kenneth S., Ehrman Michael L., Jagid Jeffrey M., Pinzon Joseph M., Yaron Hecker, Leonard PimentelSystem and method for managing a remotely located asset
    US-8526968-B2September 03, 2013Andrew LlcSystem and method for mobile location by dynamic clustering
    US-7133685-B2November 07, 2006Openwave Systems Inc.Monitoring boundary crossings in a wireless network
    US-7992777-B1August 09, 2011Diebold Self-Service Systems Division Of Diebold, IncorporatedATM user authorization based on user location verification
    US-6845240-B2January 18, 2005Grayson WirelessSystem and method for analog cellular radio geolocation
    US-8682362-B2March 25, 2014Telecommunication Systems, Inc.Inter-carrier messaging service providing phone number only experience
    US-8320264-B2November 27, 2012Andrew LlcMethod and apparatus for determining path loss by active signal detection
    EP-1193990-A1April 03, 2002Lucent Technologies Inc.Procédé et dispositif d'estimation de la position d'un terminal mobile
    US-8391884-B2March 05, 2013Andrew LlcSystem and method for managing created location contexts in a location server
    US-6351235-B1February 26, 2002Trueposition, Inc.Method and system for synchronizing receiver systems of a wireless location system
    US-6563460-B2May 13, 2003Trueposition, Inc., Massachusetts Institute Of TechnologyCollision recovery in a wireless location system
    WO-9601531-A3February 29, 1996Karbasi Amir Kiumars, Behruz VazvanCellular positioning system (cps)
    US-6546256-B1April 08, 2003Ksi Inc.Robust, efficient, location-related measurement
    US-7503489-B2March 17, 2009Bpriv, LlcMethod and system for monitoring electronic purchases and cash-withdrawals
    US-7623872-B2November 24, 2009Andrew CorporationMethod for sparse network deployment accuracy enhancements
    US-8213955-B2July 03, 2012Andrew, LlcNetwork measurement report caching for location of mobile devices
    US-6661379-B2December 09, 2003Trueposition, Inc., Massachusetts Institute Of TechnologyAntenna selection method for a wireless location system
    US-6342854-B1January 29, 2002Cambridge Positioning Systems Ltd.Position determining system
    US-9042917-B2May 26, 2015Qualcomm IncorporatedPositioning for WLANS and other wireless networks
    WO-9800988-A3May 07, 1998Ericsson Ge Mobile IncProcede et appareil permettant de communiquer des informations sur la position d'une station mobile dans un reseau de telephones cellulaires
    US-8340110-B2December 25, 2012Trapeze Networks, Inc.Quality of service provisioning for wireless networks
    US-6014102-AJanuary 11, 2000Motorola, Inc.Method and apparatus for calibrating location finding equipment within a communication system
    US-7565142-B2July 21, 2009Telespree CommunicationsMethod and apparatus for secure immediate wireless access in a telecommunications network
    US-2010127920-A1May 27, 2010Andrew LlcSystem and method for determining falsified geographic location of a mobile device
    US-2010073229-A1March 25, 2010Ganesh Pattabiraman, Subramanian Meiyappan, Arun Raghupathy, Hari SankarWide Area Positioning System
    US-8457031-B2June 04, 2013Trapeze Networks, Inc.System and method for reliable multicast
    US-7107075-B2September 12, 2006Bellsouth Intellectual Property CorporationWireless communications methods and systems using a remote, self-contained communications antenna unit
    WO-2008073706-A1June 19, 2008Trueposition, Inc.Localisation d'émetteurs ofdm à large bande avec largeur de bande de récepteur limitée
    US-2010225472-A1September 09, 2010Culpepper Jerry W, Smith Lawrence M, Vancleave James PMethod and system for providing tracking services to locate an asset
    US-2008204322-A1August 28, 2008Gordon Kenneth Andrew Oswald, Alexandra Joanna Geoghegan, Charles Peter Bell, Nicholas Simon Russ, Mario Del Mistro, Michael Hugh Burchett, Desmond Keith Phillips, Vincent Arne UtsiDetermining Positional Information
    EP-0743802-A3May 19, 1999Alcatel N.V., Alcatel SEL AktiengesellschaftProzessorgesteuerte Vorrichtung zur Verfolgung einer Mobilstation in einem SDMA-Mobilfunksystem
    US-2010076878-A1March 25, 2010Itis Holdings PlcApparatus and method for implementing a road pricing scheme
    EP-0713344-A3May 06, 1999Nec CorporationMobiles Funkübertragungssystem
    US-2006262011-A1November 23, 2006Bull Jeffrey F, Anderson Robert J, Ginter Thomas S, Ward Matthew LAugmentation of commercial Wireless Location System (WLS) with moving and/or airborne sensors for enhanced location accuracy and use of real-time overhead imagery for identification of wireless device locations
    US-5724243-AMarch 03, 1998Highwaymaster Communications, Inc.Method and apparatus for determining expected time of arrival
    US-9060341-B2June 16, 2015Tracbeam, LlcSystem and method for hybriding wireless location techniques
    US-2010217630-A1August 26, 2010I.D. Systems, Inc.Systems and methods for remote vehicle rental
    US-7756529-B2July 13, 2010Fujitsu LimitedPosition information management method and apparatus
    US-7869800-B2January 11, 2011Telespree CommunicationsPortable cellular phone system having automatic initialization
    US-2004017312-A1January 29, 2004Anderson Robert J., Stilp Louis A., Ward Matthew L.Multiple pass location processor
    US-9584960-B1February 28, 2017X One, Inc.Rendez vous management using mobile phones or other mobile devices
    US-2008140483-A1June 12, 2008I.D. Systems, Inc.Mobile asset data management system
    US-2007060202-A1March 15, 2007Bellsouth Intellectual Property CorporationWireless communications methods and systems using a remote, self-contained communications antenna unit
    US-7711102-B2May 04, 2010At&T Intellectual Property I, L.P.Automatically sequentially ringing alternative telephone numbers
    US-8965341-B2February 24, 2015Kristine A. Wilson, Kelce S. Wilson, Edward A. WilsonCellular device identification and location with emergency number selectivity enforcement (CILENSE)
    US-2002094821-A1July 18, 2002Kennedy Joseph P.Pseudolite positioning system and method
    US-7835749-B1November 16, 2010Cisco Technology, Inc.Location inspector in wireless networks
    US-2006044407-A1March 02, 2006Sprint Spectrum L.P.Method and system for delivering photos to called destinations
    US-2007083539-A1April 12, 2007Glorikian Harry AInternet System for Connecting Client-Travelers with Geographically-Associated Data
    US-2010009659-A1January 14, 2010Eran Netanel, Lavine James FSystem and Method to Enable Subscriber Self-Activation of Wireless Data Terminals
    US-2009191900-A1July 30, 2009West CorporationApparatus and method for locating a mobile telecommunication device
    US-6347228-B1February 12, 2002Motorola, Inc.Location apparatus and method in a mobile telecommunications system
    US-8274432-B2September 25, 2012Elta Systems Ltd.Method and system for detecting signal sources in a surveillance space
    US-6201803-B1March 13, 2001British Telecommunications Public Limited CompanyCellular radio location system
    US-9247392-B2January 26, 2016Nextnav, LlcSystems and methods for location positioning of user device
    WO-0075681-A1December 14, 2000Honeywell Inc.Plan de navigation base sur des signaux a bande etroite
    US-7525578-B1April 28, 2009Sprint Spectrum L.P.Dual-location tagging of digital image files
    US-7761923-B2July 20, 2010Invensys Systems, Inc.Process control methods and apparatus for intrusion detection, protection and network hardening
    US-5844522-ADecember 01, 1998Trackmobile, Inc.Mobile telephone location system and method
    US-6765531-B2July 20, 2004Trueposition, Inc.System and method for interference cancellation in a location calculation, for use in a wireless location system
    FR-2910131-A1June 20, 2008Thales SaLocalisation passive ensembliste en modes toa/tdoa
    US-2011285589-A1November 24, 2011Trueposition, Inc.Network Location and Synchronization of Peer Sensor Stations in a Wireless Geolocation Network
    US-2010127874-A1May 27, 2010Curtis Guy PInformation locator
    US-8806653-B2August 12, 2014Andrew L. Di RienzoLocation based service
    US-2002002575-A1January 03, 2002Eisler Craig G., Roundtree Brian C.Hypertext concept notation for dynamically constructing a sentence to respond to a user request
    US-9226257-B2December 29, 2015Qualcomm IncorporatedPositioning for WLANs and other wireless networks
    EP-0832440-A4November 17, 1999Sanconix IncVerbesserte positionsberechnung
    WO-2012149565-A3February 07, 2013Trekintelligence, Inc.System and method for cell phone targeting and tracking
    GB-2356098-BOctober 03, 2001Fujitsu LtdPortable radio terminal
    US-8028275-B2September 27, 2011Invensys Systems, Inc.Control systems and methods with smart blocks
    US-2003013449-A1January 16, 2003Hose David A., Fitch James A.Monitoring boundary crossings in a wireless network
    US-2004203854-A1October 14, 2004Nowak Steven P.Formatting location information based on output device specifications
    US-2005090266-A1April 28, 2005Leonid SheynblatLocal area network assisted positioning
    US-9709621-B2July 18, 2017Arcom Digital, LlcLeakage detection of digital signals in an HFC network
    US-6952158-B2October 04, 2005Kennedy Jr Joseph PPseudolite positioning system and method
    US-5463672-AOctober 31, 1995Nec CorporationPersonal mobile communications system having central station for paging mobile users via base stations
    US-8902904-B2December 02, 2014Trapeze Networks, Inc.Network assignment based on priority
    US-9727867-B2August 08, 2017Guy Hefetz, Jacob Heffez, Christopher Donald WoodMethod for detecting misuse of identity in electronic transactions
    US-2003129996-A1July 10, 2003Ksi Inc.Robust, efficient, localization system
    US-6269246-B1July 31, 2001Ppm, Inc.Location determination using RF fingerprinting
    US-6434378-B1August 13, 2002Cellexis International, Inc.Pre-paid cellular telephone system
    US-9291712-B2March 22, 2016Nextnav, LlcCell organization and transmission schemes in a wide area positioning system (WAPS)
    GB-2316823-AMarch 04, 1998Motorola LtdLoxcating cellular radio transmitter
    EP-2642313-A1September 25, 2013Medav GmbHVerfahren und Vorrichtung zur TDOA-Lokalisierung mit reduzierten Datenraten
    US-6567671-B2May 20, 2003At&T Wireless Services, Inc.Wireless communication device with call screening
    WO-9642021-A1December 27, 1996Boshell & KnoxPersonal satellite link with user identifier
    US-6047192-AApril 04, 2000Ksi Inc.Robust, efficient, localization system
    US-6115596-ASeptember 05, 2000Ericsson Inc.Systems and methods for handling emergency calls in hierarchical cell structures
    US-7433696-B2October 07, 2008Cisco Systems, Inc.Wireless node location mechanism featuring definition of search region to optimize location computation
    CN-1629654-BMay 26, 2010O2控股有限公司Cellular radio location system
    US-9699609-B2July 04, 2017Dennis J. DuprayNetwork services dependent upon geographical constraints
    WO-9814018-A1April 02, 1998Rutgers UniversityProcede et systeme d'estimation de position de station mobile
    EP-0832440-A2April 01, 1998Sanconix, INC.Calcul de position ameliore
    US-6724340-B1April 20, 2004Information Systems LaboratoriesDetecting system having a coherent sparse aperture
    US-7966021-B2June 21, 2011Cisco Systems, Inc.Enhanced wireless node location using differential signal strength metric
    US-7898388-B2March 01, 2011I.D. Systems, Inc.Mobile asset data management system
    US-7924224-B2April 12, 2011Trueposition, Inc.Variable coherence integration for the location of weak signals
    US-7408660-B1August 05, 2008Sprint Spectrum L.P.Method and system for managing delivery of digital image files to image processing labs
    US-7940213-B2May 10, 2011Andrew, LlcSystem and method for determining falsified satellite measurements
    GB-2338374-ADecember 15, 1999Motorola LtdLocating a mobile telephone using time of arrival measurements
    US-2002025836-A1February 28, 2002Knight Clifford LeeWireless communications methods and systems using a remote, self-contained communications antenna unit
    US-2005090268-A1April 28, 2005Hitachi, Ltd.Base station for mobile terminal positioning system
    US-2007049290-A1March 01, 2007Mullen Jeffrey DSystems and methods for locating cellular phones and security measures for the same
    GB-2356098-AMay 09, 2001Fujitsu LtdPortable radio terminal for position information system
    US-7519373-B2April 14, 2009Andrew LlcSystem and method for geo-location of mobile appliances using diverse standard tasking and reporting
    US-2009117907-A1May 07, 2009Torbjorn WigrenAdaptive Enhanced Cell Identity Positioning
    US-7711359-B2May 04, 2010Telespree CommunicationsPortable cellular phone system having automatic initialization
    US-8082096-B2December 20, 2011Tracbeam LlcWireless location routing applications and architecture therefor
    US-2010316006-A1December 16, 2010Andrew LlcSystem and method for supl held interworking
    US-9176217-B2November 03, 2015Nextnav, LlcCell organization and transmission schemes in a wide area positioning system (WAPS)
    US-9788165-B2October 10, 2017Comcast Cable Communications, LlcLocation intelligence management system for border security
    US-8467805-B2June 18, 2013Andrew LlcSystem and method for determining a reference location using cell table data mining
    US-2004132466-A1July 08, 2004Kennedy Joseph P.Method and apparatus for supporting multiple wireless carrier mobile station location requirements with a common network overlay location system
    US-2008014965-A1January 17, 2008Emsat Advanced Geo-Location Technology, LlcCellular telephone system that uses position of a mobile unit to make call management decisions
    GB-2322248-AAugust 19, 1998Fujitsu LtdPosition determination, processing and display
    US-7800533-B2September 21, 2010Andrew, LlcSystem and method for determining falsified geographic location of a mobile device
    US-6871077-B2March 22, 2005Grayson WirelessSystem and method for geolocating a wireless mobile unit from a single base station using repeatable ambiguous measurements
    US-2011070892-A1March 24, 2011Andrew LlcSystem and method for a high throughput gsm location solution
    US-9883360-B1January 30, 2018X One, Inc.Rendez vous management using mobile phones or other mobile devices
    US-7131591-B1November 07, 2006Symbol Technologies, Inc.Link cost minimization for portable wireless terminal connectable to the internet
    US-8140092-B2March 20, 2012Trueposition, Inc.Sparsed U-TDOA wireless location networks
    US-7593738-B2September 22, 2009Trueposition, Inc.GPS synchronization for wireless communications stations
    US-5913170-AJune 15, 1999Highwaymaster Communications, Inc.Locating system and method using a mobile communications network
    US-7428510-B2September 23, 2008Telecommunication Systems, Inc.Prepaid short messaging
    GB-2341519-BJanuary 09, 2002Ericsson IncSystems and methods for locating remote units operating in a radiocommunication system using an adjunct system
    US-2010173615-A1July 08, 2010Harris Technology, LlcLocating Lost Cell Phones
    US-2011033002-A1February 10, 2011Trueposition, Inc.Location of Wideband OFDM Transmitters With Limited Receiver Bandwidth
    US-6157823-ADecember 05, 2000Freedom Wireless, Inc.Security cellular telecommunications system
    US-9331798-B2May 03, 2016Commscope Technologies LlcSystem and method for mobile location by proximity detection
    US-2006281469-A1December 14, 2006Gary Stoller, Stephen SilversteinEmployee tracking system with verification
    US-2006030333-A1February 09, 2006Ward Matthew L, Czarnecki Paul M, Anderson Robert JGeo-fencing in a wireless location system
    WO-03084079-A2October 09, 2003Trueposition, Inc.Syntonisation sequentielle automatique de recepteurs a bande etroite d'un systeme de positionnement hertzien pour suivi de canal vocal/trafic
    US-8041367-B2October 18, 2011Trueposition, Inc.Sparsed U-TDOA wireless location networks
    US-2011156901-A1June 30, 2011Culpepper Jerry W, Smith Lawrence M, Vancleave James PMethod and system for providing tracking services to locate an asset
    US-2005261004-A1November 24, 2005Dietrich Paul F, Davi Gregg S, Friday Robert JWireless node location mechanism featuring definition of search region to optimize location computation
    US-2004203923-A1October 14, 2004Mullen Jeffrey D.Systems and methods for locating cellular phones and security measures for the same
    US-7295156-B2November 13, 2007Trimble Navigation LimitedCellphone GPS positioning system
    US-7904092-B2March 08, 2011Cisco Technology, Inc.Locally adjusted radio frequency coverage maps in wireless networks
    US-8971913-B2March 03, 2015Qualcomm IncorporatedMethod and apparatus for wireless network hybrid positioning
    DE-19882332-B3March 01, 2012Ericsson Inc.Mobileinheit und Verfahren zum Handhaben von Notrufen in hierarchischen Zellenstrukturen
    US-7729684-B1June 01, 2010Garmin Ltd.Combined global positioning system receiver and radio
    US-7627333-B2December 01, 2009Andrew LlcE-OTD augmentation to U-TDOA location system
    US-9386421-B2July 05, 2016Trueposition, Inc.Location intelligence management system for border security
    US-6356763-B1March 12, 2002Telefonaktiebolaget Lm Ericsson (Publ)Downlink observed time difference measurements
    US-6246884-B1June 12, 2001Sigmaone Communications CorporationSystem and method for measuring and locating a mobile station signal in a wireless communication system
    US-2004232277-A1November 25, 2004Lucent Technologies Inc.Wireless guidance system
    US-7196718-B1March 27, 2007Sprint Spectrum L.P.Method and apparatus for transmission of digital image to destination associated with voice call participant
    US-2002094824-A1July 18, 2002Kennedy Joseph P., Gravely Thomas Booker, Carlson John Peter, Andrew BeckMethod and system for applying wireless geolocation technology
    US-7196659-B1March 27, 2007Garmin CorporationCombined global positioning system receiver and radio
    US-5950137-ASeptember 07, 1999Daewoo Telecom, Ltd.Method for supplying subscriber location information in a mobile communications system
    US-7205890-B2April 17, 2007Pro Tech Monitoring, Inc.System, method and apparatus for locating and controlling objects
    US-2008070633-A1March 20, 2008At&T Delaware Intellectual Property, Inc.,Formerly Known As Bellsouth Intellectual Property Corp.Wireless communications methods and systems using a remote, self-contained communications antenna unit
    US-9535563-B2January 03, 2017Blanding Hovenweep, LlcInternet appliance system and method
    US-7668123-B1February 23, 2010Nortel Networks LimitedNetwork access device location
    US-7894825-B2February 22, 2011Telecommunication Systems, Inc.Mobile activity status tracker
    US-2010123622-A1May 20, 2010Neil Harper, Martin DawsonSystem and method for determining the location of a mobile device
    US-9749790-B1August 29, 2017X One, Inc.Rendez vous management using mobile phones or other mobile devices
    US-2010285813-A1November 11, 2010Andrew LlcSystem and method for determining a reference location using cell table data mining
    US-7508344-B2March 24, 2009L-3 Communications Integrated Systems, LpSystems and methods for TDOA/FDOA location
    US-8489122-B2July 16, 2013Andrew LlcSystem and method for total flight time ratio pattern matching
    US-7626969-B2December 01, 2009Cisco Technology, Inc.Relative location of a wireless node in a wireless network
    US-2007202885-A1August 30, 2007Kennedy Joseph P Jr, Carlson John Peter, Martin AllesMethod For Sparse Network Deployment Accuracy Enhancements
    US-2005192026-A1September 01, 2005Carlson John P., Gravely Thomas B., Kennedy Joseph P.System and method for CDMA geolocation
    US-9625566-B2April 18, 2017Raytheon CompanyDirect geolocation from TDOA, FDOA and AGL
    US-7165040-B2January 16, 2007I.D. Systems, Inc.System and method for managing remotely and distantly located assets
    US-2005037776-A1February 17, 2005Polaris Wireless, Inc.Location determination using RF fingerprints
    WO-9907177-A1February 11, 1999Ericsson, Inc.System and method using elliptical search area coverage in determining the location of a mobile terminal
    US-2007225039-A1September 27, 2007Friday Robert J, Dletrich Paul FWireless Node Location Mechanism Using Antenna Pattern Diversity to Enhance Accuracy of Location Estimates
    US-9538493-B2January 03, 2017Finetrak, LlcLocating a mobile station and applications therefor
    US-2014145877-A1May 29, 2014Eutelsat S AMethod of geo localization of a terminal sending a single signal to a satellite system
    US-2011068977-A1March 24, 2011Andrew LlcEnhancing location accuracy using multiple satellite measurements based on environment
    US-2007077945-A1April 05, 2007Leonid SheynblatDynamic location almanac for wireless base stations
    US-6941553-B2September 06, 2005Action Engine CorporationHypertext concept notation for dynamically constructing a sentence to respond to a user request
    US-2007239292-A1October 11, 2007Ehrman Kenneth S, Ehrman Michael L, Jagid Jeffrey M, Pinzon Joseph M, Yaron Hecker, Leonard PimentelMobile asset data management system
    EP-1755356-A1February 21, 2007Telefonaktiebolaget LM Ericsson (publ)Verbesserungen des Durchführens der Ankunftszeitsmessung
    US-2010044096-A1February 25, 2010International Business Machines CorporationHorizontally Split Vias
    US-6108557-AAugust 22, 2000Us Wireless CorporationSignature matching for location determination in wireless communication systems
    US-2005206566-A1September 22, 2005True Position, Inc.Multiple pass location processor
    US-9119165-B2August 25, 2015Nextnav, LlcCoding in a wide area positioning system (WAPS)
    US-8320931-B2November 27, 2012Trueposition, Inc.Geo-fencing in a wireless location system
    US-8483729-B2July 09, 2013Telecommunication Systems, Inc.Inter-carrier messaging service providing phone number only experience
    EP-0811296-A4July 05, 2000Highwaymaster Comm IncOrtsbestimmungssystem und -verfahren unter verwendung eines mobilen kommunikationsnetzes
    US-5835530-ANovember 10, 1998Corsair Communications, Inc.Bit characteristics measurement system for digitally modulated signals
    US-9299088-B2March 29, 2016Cufer Asset Ltd. L.L.C.Internet system for connecting client-travelers with geographically-associated data
    US-7786844-B2August 31, 2010I.D. Systems, Inc.Mobile portal for RFID applications
    US-2001046869-A1November 29, 2001Mats Cedervall, Ari Kangas, Johan JoberMethod and system for locating mobile stations in a mobile communication network
    US-5890068-AMarch 30, 1999Cell-Loc Inc.Wireless location system
    US-6094168-AJuly 25, 2000Cambridge Positioning Systems Ltd.Position determining system
    US-7271765-B2September 18, 2007Trueposition, Inc.Applications processor including a database system, for use in a wireless location system
    US-7289763-B2October 30, 2007Emsat Advanced Geo-Location Technology, LlpCellular telephone system that uses position of a mobile unit to make call management decisions
    US-7593736-B1September 22, 2009Cambridge Positioning Systems Ltd.Positioning system for digital telephone networks
    US-5930713-AJuly 27, 1999Telefonaktiebolaget L M Ericsson (Publ)Proactive communication of mobile station position information following inter-exchange handoff
    US-6219556-B1April 17, 2001Samsung Electronics Co., Inc.Method for pursuing missing cellular telephone
    US-9335419-B2May 10, 2016Qualcomm IncorporatedWireless network hybrid positioning
    US-7876197-B2January 25, 2011I.D. Systems, Inc.Mobile asset data management system
    US-6064875-AMay 16, 2000Usa Telecommunications Services, Inc.Wireless communications system and method of operation for reducing fraud
    US-8320934-B2November 27, 2012Qualcomm IncorporatedDynamic location almanac for wireless base stations
    US-8125377-B2February 28, 2012Andrew LlcSystem and method for determining the location of a mobile device
    US-2008140482-A1June 12, 2008I.D. Systems, Inc.Mobile asset data management system
    WO-9848578-A3March 04, 1999Ericsson Ge Mobile IncSystemes et procedes de localisation de terminaux distants dans les systemes de radiocommunication
    US-7274332-B1September 25, 2007Tracbeam LlcMultiple evaluators for evaluation of a purality of conditions
    US-2006030332-A1February 09, 2006Carrott David T, Kessler Brian LMethod and system for geolocation of wireless transmissions using distributed processors in wireless receiver towers and a method for collecting a fee for processing geolocation requests
    US-2007293239-A1December 20, 2007Andrew CorporationOptimizing location services performance by combining user plane and control plane architectures
    US-2003176196-A1September 18, 2003Hall Christopher J., Turner Clay S., Ray Jimmy C.Method and apparatus for geolocating a wireless communications device
    US-7382742-B2June 03, 2008Allied Telesis K.K.Communication system, information collecting system and method therefor
    US-2009129573-A1May 21, 2009Mci Communications CorporationSystem and method for detecting and managing fraud
    US-2009201207-A1August 13, 2009Martin Alles, John Carlson, George Maher, Selcuk MazlumMethod to modify calibration data used to locate a mobile unit
    WO-2005081796-A2September 09, 2005Interdigital Technology CorporationSupport sur la base de reseaux multiples pour services de localisation
    US-8145238-B2March 27, 2012Trueposition, Inc.Location of wideband OFDM transmitters with limited receiver bandwidth
    US-7203503-B2April 10, 2007Telefonaktiebolaget Lm Ericsson (Publ)Method and system for locating mobile stations in a mobile communication network
    US-7853272-B2December 14, 2010Telecommunication Systems, Inc.Wireless network tour guide
    US-7043235-B2May 09, 2006Action Engine CorporationSecondary data encoded along with original data for generating responses to requests from wireless devices
    WO-0069111-A2November 16, 2000Rienzo Andrew L DiAuthentification
    US-8081584-B2December 20, 2011Invensys Systems, Inc.Control system apparatus and systems using value-based transfers
    US-8161278-B2April 17, 2012Trapeze Networks, Inc.System and method for distributing keys in a wireless network
    US-2011090121-A1April 21, 2011Andrew LlcLocation measurement acquisition optimization with monte carlo simulation
    WO-2011027347-A2March 10, 2011Pin Nav LlcDispositif et procédé de calcul d'instant d'arrivée d'une trame dans un réseau sans fil
    US-2008274750-A1November 06, 2008John Carlson, Martin AllesSystem and method for estimating the location of a mobile device
    US-8738010-B2May 27, 2014Trueposition, Inc.Cooperating receiver selection for UMTS wireless location
    US-8023500-B2September 20, 2011Invensys Systems, Inc.Methods for process control with change updates
    KR-100881946-B1February 06, 2009매사츄세츠 인스티튜트 오브 테크놀러지, 트루포지션, 인크.무선 로케이션 시스템의 tdoa 및 fdoa를 추정하기 위한 향상된 방법
    WO-9848575-A3March 25, 1999Ericsson Ge Mobile IncSystemes et procedes permettant de traiter les appels d'urgence dans les structures cellulaires hierarchisees
    US-5682142-AOctober 28, 1997Id Systems Inc.Electronic control system/network
    US-7283091-B1October 16, 2007Trimble Navigation LimitedRadio positioning system for providing position and time for assisting GPS signal acquisition in mobile unit
    US-7656273-B2February 02, 2010I.D. Systems, Inc.Mobile portal for RFID luggage handling applications
    US-2002004736-A1January 10, 2002Roundtree Brian C., Eisler Craig G.Assembling personal information of a target person based upon third-party
    US-7979488-B2July 12, 2011Invensys Systems, Inc.Control system methods using value-based transfers
    US-8242959-B2August 14, 2012Trueposition, Inc.Sparsed U-TDOA wireless location networks
    EP-2642311-A1September 25, 2013Medav GmbHMethod and apparatus for improving measurement precision in the area of travelling time differences of signals
    EP-0743802-A2November 20, 1996Alcatel SEL Aktiengesellschaft, Alcatel N.V.Prozessorgesteuerte Vorrichtung zur Verfolgung einer Mobilstation in einem SDMA-Mobilfunksystem
    US-8000701-B2August 16, 2011Andrew, LlcCorrelation mechanism to communicate in a dual-plane architecture
    GB-2460611-BDecember 07, 2011Trueposition IncSparsed u-tdoa wireless location networks
    US-6560205-B1May 06, 2003Emulex CorporationMethod and apparatus for control of soft handoff usage in radiocommunication
    EP-1118871-A2July 25, 2001Cambridge Positioning Systems LimitedMethod of estimating time offsets in a position determining system
    US-8594814-B2November 26, 2013Invensys Systems, Inc.Systems and methods for immersive interaction with actual and/or simulated facilities for process, environmental and industrial control
    US-2005136945-A1June 23, 2005Kennedy Joseph P., Carlson John P., Martin Alles, Nicolas Graube, Robert RoweE-OTD augmentation to U-TDOA location system
    US-7340259-B2March 04, 2008Ksi Inc.Robust, efficient, localization system
    US-2009149132-A1June 11, 2009Trueposition, Inc.Detection of Time of Arrival of CDMA Signals in a Wireless Location System
    US-2005171720-A1August 04, 2005Olson Timothy S., Kaiser Daryl A., Roshan Pejman D.Method, apparatus, and software product for detecting rogue access points in a wireless network
    US-2004198361-A1October 07, 2004At&T Wireless Services, Inc.Wireless communication device with call screening
    US-2005272443-A1December 08, 2005Openwave Systems Inc.Monitoring boundary crossings in a wireless network
    US-2004150560-A1August 05, 2004Jun Feng, Hill Edward L.Positioning system and method
    US-6782264-B2August 24, 2004Trueposition, Inc.Monitoring of call information in a wireless location system
    US-2009170528-A1July 02, 2009Trueposition, Inc.Subscriber Selective, Area-based Service Control
    US-8718673-B2May 06, 2014Maple Acquisition LlcSystem and method for location assurance of a mobile device
    US-2005268330-A1December 01, 2005Di Rienzo Andrew LAuthentication
    US-2009005061-A1January 01, 2009Trueposition, Inc.Location quality of service indicator
    US-2004015419-A1January 22, 2004I.D. Systems, Inc.System architecture and communications for an asset management system
    US-2005208952-A1September 22, 2005Dietrich Paul F, Davi Gregg S, Friday Robert JLocation of wireless nodes using signal strength weighting metric
    US-6836651-B2December 28, 2004Telespree CommunicationsPortable cellular phone system having remote voice recognition
    US-2005184907-A1August 25, 2005Hall Christopher J., Turner Clay S., Ray Jimmy C.Method and apparatus for geolocating a wireless communications device
    US-7667649-B2February 23, 2010Trueposition, Inc.Detection of time of arrival of CDMA signals in a wireless location system
    US-7433855-B2October 07, 2008Mci Communications CorporationSystem and method for detecting and managing fraud
    US-8289210-B2October 16, 2012Andrew LlcLocation measurement acquisition adaptive optimization
    EP-0814627-A3September 09, 1998Ace K Computer Co., Ltd.Position display system of mobile terminal
    US-9648460-B2May 09, 2017Telecommunication Systems, Inc.System and method for location assurance of a mobile device
    WO-0007404-A1February 10, 2000Telefonaktiebolaget Lm Ericsson (Publ)Improvements in making time of arrival measurements
    US-2008080429-A1April 03, 2008Cisco Technology, Inc.Minimum variance location estimation in wireless networks
    US-2004111305-A1June 10, 2004Worldcom, Inc.System and method for detecting and managing fraud
    CN-100397911-CJune 25, 2008真实定位公司;麻省理工学院在无线定位系统中估计tdoa和fdoa的改进方法
    US-8175620-B2May 08, 2012Andrew, LlcSystem and method for generating non-uniform grid points from calibration data
    US-7953440-B2May 31, 2011Olympus CorporationMobile device system and mobile device
    US-8660015-B2February 25, 2014Trueposition, Inc.Location of mobile devices served by a relay node
    US-9390279-B2July 12, 2016Nextnav, LlcSystems and methods for providing conditional access to transmitted information
    US-2005186967-A1August 25, 2005Interdigital Technology CorporationMulti-network location services support
    US-2008004042-A1January 03, 2008Dietrich Paul F, Davi Gregg SEnhanced Wireless Node Location using Differential Signal Strength Metric
    US-9736618-B1August 15, 2017X One, Inc.Techniques for sharing relative position between mobile devices
    US-2003216976-A1November 20, 2003I.D. Systems, Inc.System and method for remotely managing maintenance operations associated with an asset
    US-8362898-B2January 29, 2013International Business Machines CorporationKey fob and system for indicating the lock status of a door lock
    US-8462745-B2June 11, 2013Skyhook Wireless, Inc.Methods and systems for determining location using a cellular and WLAN positioning system by selecting the best WLAN PS solution
    US-8239483-B2August 07, 2012Andrew, LlcSystem and method for generic application of location determination for network attached devices
    US-2005176443-A1August 11, 2005J. Doss HalseyCellular phone geolocation system
    US-2004242234-A1December 02, 2004Gunther KlennerMethod and device for determining the position of a base station
    US-6952181-B2October 04, 2005Tracbeam, LlcLocating a mobile station using a plurality of wireless networks and applications therefor
    WO-2005091915-A3March 23, 2006Airespace IncLocalisation de noeuds sans fil par la mesure de ponderation d'intensite de signal
    US-7890927-B2February 15, 2011Invensys Systems, Inc.Apparatus and method for configuring and editing a control system with live data
    US-8966018-B2February 24, 2015Trapeze Networks, Inc.Automated network device configuration and network deployment
    US-2008261612-A1October 23, 2008Mia Rashidus S, Anderson Robert JSparsed U-TDOA Wireless Location Networks
    US-9615199-B1April 04, 2017X One, Inc.Methods for identifying location of individuals who are in proximity to a user of a network tracking system
    WO-03027705-A3August 21, 2003Guenther Klenner, Willtek Comm GmbhMethod and device for determining the position of a base station
    EP-0895600-A1February 10, 1999Motorola, Inc.Method and apparatus for covariance matrix estimation in a weighted least-squares location solution
    US-7640031-B2December 29, 2009Telecommunication Systems, Inc.Mobile originated interactive menus via short messaging services
    US-7424310-B1September 09, 2008Sprint Spectrum L.P.System, method, and apparatus for automatic transmission of recently captured images
    US-2008285505-A1November 20, 2008Andrew CorporationSystem and method for network timing recovery in communications networks
    US-7313401-B2December 25, 2007Sony Corporation, Sony Electronics, Inc.Positioning system using packet radio to determine position and to obtain information relative to a position
    CN-100454772-CJanuary 21, 2009真实定位公司;麻省理工学院用于提高无线定位系统精度的基于移动协助网络的技术
    EP-2078966-A1July 15, 2009Snaptrack IncorporatedSatellite positioning system augmentation with wireless communication signals
    GB-2341519-AMarch 15, 2000Ericsson IncSystems and methods for locating remote units operating in a radiocommunication system using an adjunct system
    US-7954703-B2June 07, 2011Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking system controlled responsive to data bearing records
    US-7116988-B2October 03, 2006Airespace, Inc.Location of wireless nodes using signal strength weighting metric
    US-2008261613-A1October 23, 2008Anderson Robert J, Ward Matthew LSparsed U-TDOA Wireless Location Networks
    US-2005009575-A1January 13, 2005Allied Telesis K.K.Communication system, information collecting system and method therefor
    US-9288628-B2March 15, 2016Trueposition, Inc.Advanced triggers for location-based service applications in a wireless location system
    US-2005003802-A1January 06, 2005Joseph JosephSystem for managing traffic patterns using cellular telephones
    US-8326317-B2December 04, 2012Andrew LlcSystem and method to obtain calibration data using estimation techniques
    US-9057606-B2June 16, 2015Nextnav, LlcWide area positioning system
    US-7463908-B2December 09, 2008At&T Intellectual Property I, L.P.Wireless communications methods and systems using a remote, self-contained communications antenna unit
    US-8249622-B2August 21, 2012Andrew, LlcSystem and method for multiple range estimation location
    US-2008136584-A1June 12, 2008I.D. Systems, Inc.Mobile asset data management system
    US-9060281-B2June 16, 2015Trueposition, Inc.Overlay network-based location of E-UTRAN devices
    US-8733635-B2May 27, 2014Diebold Self-Service Systems, division of Diebold IncorporatedBanking system controlled responsive to data bearing records and user input of a phone received security code
    US-2007120738-A1May 31, 2007Stroud Ken ASystems and methods for TDOA/FDOA location
    US-9390418-B2July 12, 2016Verizon Patent And Licensing Inc.System and method for detecting and managing fraud
    US-9715001-B2July 25, 2017Commscope Technologies LlcMobile location in a remote radio head environment
    US-9423508-B2August 23, 2016Commscope Technologies LlcAutonomous Transmit Chain Delay Measurements
    US-8638725-B2January 28, 2014Skyhook Wireless, Inc.Methods and systems for determining location using a cellular and WLAN positioning system by selecting the best WLAN PS solution
    US-8238942-B2August 07, 2012Trapeze Networks, Inc.Wireless station location detection
    FR-2902195-A1December 14, 2007Thales SaRadio frequency signal arrival time determining method for geographic localization of mobile telephone, involves crosscorrelating useful signals with reference signal, where arrival time is determined by summing time and time-based position
    US-9097784-B2August 04, 2015Commscope Technologies LlcSystem and method to collect and modify calibration data
    US-8000702-B2August 16, 2011Andrew, LlcOptimizing location services performance by combining user plane and control plane architectures
    US-7991411-B2August 02, 2011Telecommunication Systems, Inc.Method to qualify multimedia message content to enable use of a single internet address domain to send messages to both short message service centers and multimedia message service centers
    US-7667573-B2February 23, 2010I.D. Systems, Inc.Mobile portal for RFID applications
    KR-100847714-B1July 23, 2008스냅트랙 인코포레이티드Method and apparatus for signal processing in a satellite positioning system
    US-8380170-B2February 19, 2013Kristine A. Wilson, Kelce S. Wilson, Edward A. WilsonCellular device identification and location with emergency number selectivity enforcement (CILENSE)
    US-2011238574-A1September 29, 2011Diebold Self-Service Systems Division Of Diebold, IncorporatedBanking system controlled responsive to data bearing records and user input of a phone received security code
    US-2005246334-A1November 03, 2005Hong Kong Applied Science And Technology Research Institute Co., Ltd.Location determination and location tracking in wireless networks
    EP-0856746-A2August 05, 1998Matsushita Electric Industrial Co., Ltd.Method and system for locating a mobile station
    US-2006244661-A1November 02, 2006Worcester Polytechnic InstituteMethods and apparatus for high resolution positioning
    US-2003195825-A1October 16, 2003I.D. Systems, Inc.System and method for managing remotely and distantly located assets
    US-8964747-B2February 24, 2015Trapeze Networks, Inc.System and method for restricting network access using forwarding databases
    US-2005024265-A1February 03, 2005Trueposition, Inc.Multiple pass location processor