Systems and Methods for Providing Geolocation Using Wireless Signals

Abstract

A system and method for determining location of a wireless communications device using wireless signals. A radio signal is transmitted by each of multiple base stations and received by a wireless communications device. The wireless device captures the waveform of the received radio signal and stores the received radio signal with a time at which the signal was received. The signal is demodulated to a data stream and passed through a virtual transmitter module to recreate the transmitted signal. A time shift for the received signal is calculated, and a position of the wireless device relative to the base stations is determined based on the time shift. A location of the wireless device is determined based on a location of the base stations and the position of the device relative to the base stations.

We claim: 
     
         1 . A method, for locating a receiver device, comprising:
 receiving, by the receiver device, from a transmitter, a radio signal;   capturing, by the receiver device, the radio signal to yield a received signal waveform;   generating, by the receiver device, based on the received signal waveform, a virtual transmitted signal waveform; and   determining, by the receiver device, based upon the received signal waveform and the virtual transmitted signal waveform, a position of the receiver device relative to the transmitter.   
     
     
         2 . The method of  claim 1 , wherein determining the position of the receiver device relative to the transmitter is based also on transmission timing information relating to the transmitter. 
     
     
         3 . The method of  claim 1 , wherein generating the virtual transmitted signal waveform comprises:
 generating, by a virtual transmitter module of the receiver device, a data stream being substantially identical to a transmitted data stream relating to the radio signal received from the transmitter; and   transmitting virtually the data stream to obtain the virtual transmitted signal waveform.   
     
     
         4 . The method of  claim 1 , wherein:
 the method further comprises determining a time difference with respect to the signal;   determining the time difference comprises:
 comparing, by a time shift determiner associated with the receiver device, the virtual transmitted signal waveform and the received signal waveform; and 
 determining, by the time shift determiner, based on the comparing, the time difference being a time shift required to align the virtual transmitted signal waveform to the received signal waveform; and 
   determining the position of the receiver device relative to the transmitter is based also upon the time difference.   
     
     
         5 . The method of  claim 1 , wherein the method further comprises:
 obtaining transmitter location data corresponding to the transmitter; and   determining a location of the receiver device based upon the transmitter location data and the position of the receiver device relative to the transmitter.   
     
     
         6 . The method of  claim 1 , wherein generating the virtual transmitted signal waveform comprises:
 applying a fast-fourier-transform algorithm to the received signal waveform to yield data output; and   transmitting the data output to an orthogonal frequency-division multiplexing demodulator to generate a virtual transmitted data stream.   
     
     
         7 . The method of  claim 6 , wherein generating the virtual transmitted signal waveform further comprises:
 transmitting the virtual transmitted data stream to an orthogonal frequency-division multiplexing modulator to generate a modulated data stream; and   applying an inverse fast-fourier-transform algorithm to the modulated data stream to generate the virtual transmitted signal waveform.   
     
     
         8 . The method of  claim 1 , wherein:
 receiving the radio signal from the transmitter comprises receiving, from a first transmitter, a first radio signal, from a second transmitter, a second radio signal, and from a third transmitter, a third radio signal;   the capturing and the generating are performed with respect to each of the first radio signal, the second radio signal, and the third radio signal; and   determining the position of the receiver device relative to the transmitter comprises determining the position of the receiver device relative to the first transmitter, the second transmitter, and the third transmitter.   
     
     
         9 . A system, comprising:
 a processor; and   a computer-readable medium comprising computer-executable instructions that, when executed by the processor, cause the processor to perform operations comprising:
 receiving, from a transmitter, a radio signal; 
 capturing the radio signal to yield a received signal waveform; 
 generating, based on the received signal waveform, a virtual transmitted signal waveform; and 
 determining, based upon the received signal waveform and the virtual transmitted signal waveform, a position of the receiver device relative to the transmitter. 
   
     
     
         10 . The system of  claim 9 , wherein the operation of determining the position of the receiver device relative to the transmitter is based also on transmission timing information relating to the transmitter. 
     
     
         11 . The system of  claim 9 , wherein the operation of generating the virtual transmitted signal waveform includes:
 generating a data stream being substantially identical to a transmitted data stream relating to the radio signal received from the transmitter; and   transmitting virtually the data stream to obtain the virtual transmitted signal waveform.   
     
     
         12 . The system of  claim 9 , wherein:
 the operations further comprise determining a time difference with respect to the signal;   the operation of determining the time difference comprises:
 comparing, by a time shift determiner associated with the receiver device, the virtual transmitted signal waveform and the received signal waveform; and 
 determining, by the time shift determiner, based on the comparing, the time difference being a time shift required to align the virtual transmitted signal waveform to the received signal waveform; and 
   the operation of determining the position of the receiver device relative to the transmitter is based also upon the time difference.   
     
     
         13 . The system of  claim 9 , wherein the operation of generating the virtual transmitted signal waveform comprises:
 applying a fast-fourier-transform algorithm to the received signal waveform to create a data output;   transmitting the data output to an orthogonal frequency-division multiplexing demodulator to generate a virtual transmitted data stream;   transmitting the virtual transmitted data stream to an orthogonal frequency-division multiplexing modulator to generate a modulated data stream; and   applying an inverse fast-fourier-transform algorithm to the modulated data stream to generate the virtual transmitted signal waveform.   
     
     
         14 . The system of  claim 9 , wherein:
 the operation of receiving the radio signal from the transmitter comprises receiving, from a first transmitter, a first radio signal, from a second transmitter, a second radio signal, and from a third transmitter, a third radio signal;   the operations of capturing and generating are performed with respect to each of the first radio signal, the second radio signal, and the third radio signal; and   the operation of determining the position of the receiver device relative to the transmitter comprises determining the position of the receiver device relative to the first transmitter, the second transmitter, and the third transmitter.   
     
     
         15 . A tangible computer-readable storage device comprising computer-executable instructions that, when executed by a processor, cause the processor to perform operations comprising:
 receiving, from a transmitter, a radio signal;   capturing the radio signal to yield a received signal waveform;   generating, based on the received signal waveform, a virtual transmitted signal waveform; and   determining, based upon the received signal waveform and the virtual transmitted signal waveform, a position of the receiver device relative to the transmitter.   
     
     
         16 . The tangible computer-readable storage device of  claim 15 , wherein the operation of determining the position of the receiver device relative to the transmitter is based also on transmission timing information related to the transmitter. 
     
     
         17 . The tangible computer-readable storage device of  claim 15 , wherein the operation of generating the virtual transmitted signal waveform includes:
 generating a data stream being substantially identical to a transmitted data stream relating to the radio signal received from the transmitter; and   transmitting virtually the data stream to obtain the virtual transmitted signal waveform.   
     
     
         18 . The tangible computer-readable storage device of  claim 15 , wherein:
 the operations further comprise determining a time difference with respect to the signal;   the operation of determining the time difference comprises:
 comparing, by a time shift determiner associated with the receiver device, the virtual transmitted signal waveform and the received signal waveform; and 
 determining, by the time shift determiner, based on the comparing, the time difference being a time shift required to align the virtual transmitted signal waveform to the received signal waveform; and 
   the operation of determining the position of the receiver device relative to the transmitter is based upon the received signal waveform, the virtual transmitted signal waveform, and the time difference determined.   
     
     
         19 . The tangible computer-readable storage device of  claim 15 , wherein the operation of generating the virtual transmitted signal waveform comprises:
 applying a fast-fourier-transform algorithm to the received signal waveform to create a data output;   transmitting the data output to an orthogonal frequency-division multiplexing demodulator to generate a virtual transmitted data stream;   transmitting the virtual transmitted data stream to an orthogonal frequency-division multiplexing modulator to generate a modulated data stream; and   applying an inverse fast-fourier-transform algorithm to the modulated data stream to generate the virtual transmitted signal waveform.   
     
     
         20 . The tangible computer-readable storage device of  claim 15 , wherein:
 the operation of receiving the radio signal from the transmitter comprises receiving, from a first transmitter, a first radio signal, from a second transmitter, a second radio signal, and from a third transmitter, a third radio signal;   the operations of capturing and generating are performed with respect to each of the first radio signal, the second radio signal, and the third radio signal; and   the operation of determining the position of the receiver device relative to the transmitter comprises determining the position of the receiver device relative to the first transmitter, the second transmitter, and the third transmitter.