Position location using phase-adjusted transmitters

Abstract

Systems and methods are provided for determining position location information in a wireless network. In one embodiment, timing offset information is communicated between multiple transmitters and one or more receivers. Such information enables accurate position or location determinations to be made that account for timing differences throughout the network. In another embodiment, transmitter phase adjustments are made that advance or delay transmissions from the transmitters to account for potential timing differences at receivers. In yet another embodiment, combinations of timing offset communications and/or transmitter phase adjustments can be employed in the wireless network to facilitate position location determinations.

1 . A system to adjust position information in a wireless network, comprising:
 means for determining timing differences between at least two transmitters and at least one receiver in the wireless network; and   means for adjusting transmission of the transmitters according to a signal phase to account for the timing differences by cyclically shifting and transmitting signals from each of the transmitters.   
     
     
         2 . The system of  claim 1 , further comprising:
 means for determining a position at the receiver in view of an adjusted signal phase from the adjusting transmission of the transmitters according to signal phase.   
     
     
         3 . The system of  claim 1 , further comprising:
 means for generating a signal from at least two transmitters that is advanced or delayed to account for timing differences in the wireless network.   
     
     
         4 . The system of  claim 3 , further comprising:
 means for computing a linear convolution of a channel estimate with a transmitted signal.   
     
     
         5 . The system of  claim 1 , further comprising:
 means for advancing or delaying transmission timing of the transmitters in a network to regulate an effective channel delay spread as perceived by the receiver.   
     
     
         6 . The system of  claim 5 , further comprising:
 means for performing a linear convolution of a channel with a transmitted signal that is processed as a cyclic convolution if the delay spread of the channel is less than a cyclic prefix employed by an Orthogonal Frequency Division Multiplexing (OFDM) signal.   
     
     
         7 . The system of  claim 1 , further comprising:
 means for generating at least two timing offsets denoted as d a  and d b .   
     
     
         8 . The system of  claim 7 , further comprising:
 means for determining a first parameter τ′ a  that is an actual delay perceived by a line of sight propagation component based on a distance between a first transmitter A and the receiver, and determining a second parameter τ′ b  that is an actual delay that is perceived by a line of sight component from a second transmitter B to the receiver.   
     
     
         9 . The system of  claim 8 , further comprising:
 means for processing additional delays d a  and d b  at the first and second transmitters when a delay spread τ′ b −τ′ a  exceeds a cyclic prefix.   
     
     
         10 . The system of  claim 9 , further comprising:
 means for processing the following equation:   y(n)=h a (n)*x a (n−d a )+h b (n)*x b (n−d b )+w(n), where y(n) represents a signal received at the receiver, h a (n) and x a (n) are a channel and a signal with respect to the first transmitter A, * represents a linear convolution operation, w(n) is noise added at the receiver.   
     
     
         11 . The system of  claim 10 , further comprising:
 means for processing the following equation:   y(n)=h a (n−d a )*x(n)+h b (n−d b )*x(n)+w(n), where a perceived channel delay spread is given by (τ′ b −d b )−(τ′ a −d a ) and controlled by introducing timing offsets at the transmitter.   
     
     
         12 . The system of  claim 10 , further comprising:
 means for determining a cyclic convolution when an effective delay spread is less than a cyclic prefix as in the following equations:
     y ( n )= h   a ( n ) {circle around (x)}x   a ( n−d   a )+ h   b ( n ) {circle around (x)}x   b ( n−d   b )+ w ( n ), 
   or 
     y ( n )=( n−d   a ) {circle around (x)}x   a ( n )+ h   b ( n−d   b ) {circle around (x)}x   b ( n )+ w ( n ) 
   
       where {circle around (x)} denotes circular convolution. 
     
     
         13 . The system of  claim 12 , further comprising:
 means for delaying transmissions from transmitters to meet length requirement of cyclic prefix.   
     
     
         14 . The system of  claim 12 , further comprising:
 means for employing a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away.   
     
     
         15 . The system of  claim 14 , further comprising:
 means for undoing an effect of physical delays by a cyclic shift of the positioning signal, where x a,p (n) is an intended positioning signal from the transmitter A with timing delay da, and a transmitter sends a cyclically shifted version given by x a,p (n+d a ).   
     
     
         16 . The system of  claim 15 , further comprising:
 means for processing the following equation
     y ( n )= h   a ( n ) {circle around (x)}x   a,p ( n )+ n   b ( n ) {circle around (x)}x   b,p ( n )+ w ( n ), 
   to mitigate sending transmitter delay information to a receiver.   
     
     
         17 . The system of  claim 1 , further comprising:
 means for determining transmitter timing adjustments from an offline network source.   
     
     
         18 . The system of  claim 17 , further comprising:
 means for measuring pseudo ranges for the transmitter timing.   
     
     
         19 . The system of  claim 18 , further comprising:
 means for relaying the pseudo ranges to a network almanac.   
     
     
         20 . The system of  claim 1 , wherein adjusting an amount of the cyclic shift comprises employing a cyclic shift of an Orthogonal Frequency Division Multiplexing (OFDM) symbol carrying a signal of the transmitted signals to form a shifted OFDM symbol. 
     
     
         21 . The system of  claim 20 , further comprising:
 means for forming a cyclic prefix of the OFDM symbol based on the shifted OFDM symbol.   
     
     
         22 . The system of  claim 20 , wherein the OFDM symbol comprises an OFDM symbol carrying pilot positioning signals. 
     
     
         23 . The system of  claim 1 , wherein the timing difference includes fixed timing offset information. 
     
     
         24 . The system of  claim 1 , further comprising:
 means for employing triangulation techniques to determine a position for the at least one receiver.   
     
     
         25 . The system of  claim 1 , further comprising:
 means for determining at least one parameter.   
     
     
         26 . The system of  claim 1 , further comprising:
 means for decoding a data stream.   
     
     
         27 . A wireless communications apparatus, comprising:
 a memory for storing instructions; and   a processor that reads the instructions from the memory, and determines an adjusted time base between a plurality of receivers and a plurality of transmitters over a wireless network and adjusts a signal phase by cyclically shifting and transmitting a signal transmitted from at least one of the transmitters in order to determine a location for at least one wireless apparatus based on the instructions.   
     
     
         28 . The apparatus of  claim 27 , further comprising:
 a component to determine a location for the wireless apparatus.   
     
     
         29 . The apparatus of  claim 27 , further comprising:
 one or more components to decode a data stream.   
     
     
         30 . The apparatus of  claim 27 , wherein the processor generates a signal from at least two transmitters that is advanced or delayed to account for timing differences of transmissions between the transmitters in the wireless network. 
     
     
         31 . The apparatus of  claim 30 , wherein the processor computes a linear convolution of a channel estimate with a transmitted signal. 
     
     
         32 . The apparatus of  claim 27 , wherein the processor advances or delays transmission timing of the at least one of the transmitters in the wireless network to regulate an effective channel delay spread as perceived by the at least one wireless apparatus. 
     
     
         33 . The apparatus of  claim 32 , wherein the processor performs a linear convolution of a channel with a transmitted signal that is processed as a cyclic convolution if a delay spread of the channel is less than a cyclic prefix employed by an Orthogonal Frequency Division Multiplexing (OFDM) signal. 
     
     
         34 . The apparatus of  claim 27 , wherein the processor generates at least two timing offsets denoted as d a  and d b . 
     
     
         35 . The apparatus of  claim 34 , wherein the processor determines a first parameter τ′ a  that is an actual delay perceived by a line of sight propagation component based on a distance between a first transmitter A and the at least one wireless apparatus, and determining a second parameter τ′ b  that is an actual delay that is perceived by a line of sight component from a second transmitter B to the at least one wireless apparatus. 
     
     
         36 . The apparatus of  claim 35 , wherein the processor processes additional delays d a  and d b  at the first and second transmitters when a delay spread τ′ b −τ′ a  exceeds a cyclic prefix. 
     
     
         37 . The apparatus of  claim 36 , wherein the processor processes the following equation:
 y(n)=h a (n)*x a (n−d a )+h b (n)*x b (n−d b )+w(n), where y(n) represents a signal received at the at least one wireless apparatus, h a (n) and X a (n) are a channel and a signal with respect to the first transmitter A, * represents a linear convolution operation, w(n) is noise added at the at least one wireless apparatus.   
     
     
         38 . The apparatus of  claim 37 , wherein the processor processes the following equation:
 y(n)=h a (n−d a )*x(n)+h b (n−d b )*x(n)+w(n), where a perceived channel delay spread is given by (τ′ b −d b )−(τ′ a −d a ) and controlled by introducing timing offsets at the transmitter.   
     
     
         39 . The apparatus of  claim 37 , wherein the processor determines a cyclic convolution when an effective delay spread is less than a cyclic prefix as in the following equations:
     y ( n )= h   a ( n ) {circle around (x)}x   a ( n−d   a )+ h   b ( n ) {circle around (x)}x   b ( n−d   b )+ w ( n ),     or       y ( n )= h   a ( n−d   a ) {circle around (x)}x   a ( n )+ h   b ( n−d   b ) {circle around (x)}x   b ( n )+ w ( n )   
       where {circle around (x)} denotes circular convolution. 
     
     
         40 . The apparatus of  claim 39 , wherein the processor delays transmissions from the transmitters to meet length requirements of cyclic prefix. 
     
     
         41 . The apparatus of  claim 39 , wherein the processor employs a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away. 
     
     
         42 . The apparatus of  claim 41 , wherein the processor undoes an effect of physical delays by a cyclic shift of a positioning signal, where x a,p (n) is an intended positioning signal from the transmitter A with timing delay d a , and a transmitter sends a cyclically shifted version given by x a,p (n+d a . 
     
     
         43 . The apparatus of  claim 42 , wherein the processor processes the following equation
 y(n)=h a (n){circle around (x)}x a,p (n)+h b (n){circle around (x)}x b,p (n)+w(n), to mitigate sending transmitter delay information to the at least one wireless apparatus.   
     
     
         44 . The apparatus of  claim 27 , wherein the processor determines transmitter timing adjustments from an offline network source. 
     
     
         45 . The apparatus of  claim 44 , wherein the processor measures pseudo ranges for transmitter timing. 
     
     
         46 . The apparatus of  claim 45 , wherein the processor relays the pseudo ranges to a network almanac. 
     
     
         47 . The apparatus of  claim 27 , wherein the processor cyclically shifts the signal by employing a cyclic shift of an Orthogonal Frequency Division Multiplexing (OFDM) symbol to form a shifted OFDM symbol. 
     
     
         48 . The apparatus of  claim 47 , wherein the processor forms a cyclic prefix of the OFDM symbol based on the shifted OFDM symbol. 
     
     
         49 . The apparatus of  claim 47 , wherein the OFDM symbol comprises an OFDM symbol carrying pilot positioning signals. 
     
     
         50 . The apparatus of  claim 27 , wherein the processor employs triangulation techniques with a subset of transmitter clocks to determine the location. 
     
     
         51 . The apparatus of  claim 27 , wherein the processor determines at least one parameter. 
     
     
         52 . The apparatus of  claim 27 , further comprising:
 a layer component having at least one of a physical layer, a stream layer, a medium access layer, and an upper layer.   
     
     
         53 . The apparatus of  claim 52 , the physical layer further comprising at least one of a frame field, a pilot field, an overhead information field, a wide area field, and a local area field. 
     
     
         54 . The apparatus of  claim 53 , the physical layer further comprising an error correction field. 
     
     
         55 . An apparatus for operating base station resources in a wireless network, comprising:
 means for determining timing differences for a subset of transmitters and at least one receiver;   means for adjusting the timing differences by cyclically shifting and transmitting signals from the subset of transmitters; and   means for determining a position for the receiver based on at least one of the transmitted signals that have been cyclically shifted.   
     
     
         56 . The apparatus of  claim 55 , further comprising:
 means generating a signal from at least two transmitters of the subset that are advanced or delayed to account for timing differences in the wireless network.   
     
     
         57 . The apparatus of  claim 56 , further comprising:
 means for computing a linear convolution of a channel estimate with a transmitted signal.   
     
     
         58 . The apparatus of  claim 55 , further comprising:
 means for advancing or delaying transmitter timing in the wireless network to regulate an effective channel delay spread as perceived by the receiver.   
     
     
         59 . The apparatus of  claim 58 , further comprising:
 means for performing a linear convolution of a channel with a transmitted signal that is processed as a cyclic convolution if the delay spread of the channel is less than a cyclic prefix employed by an Orthogonal Frequency Division Multiplexing (OFDM) signal.   
     
     
         60 . The apparatus of  claim 55 , further comprising:
 means for generating at least two timing offsets denoted as d a  and d b .   
     
     
         61 . The apparatus of  claim 60 , further comprising:
 means for determining a first parameter τ′ a  that is an actual delay perceived by a line of sight propagation component based on a distance between a first transmitter A and the receiver, and determining a second parameter τ′ b  that is an actual delay that is perceived by a line of sight component from a second transmitter B to the receiver.   
     
     
         62 . The apparatus of  claim 61 , further comprising:
 means for processing additional delays d a  and d b  at the first and second transmitters when a delay spread τ′ b −τ′ a  exceeds a cyclic prefix.   
     
     
         63 . The apparatus of  claim 62 , further comprising:
 means for processing the following equation:   y(n)=h a (n)*x a (n−d a )+h b (n)*x b (n−d b )+w(n), where y(n) represents a signal received at the receiver, h a (n) and x a (n) are a channel and a signal with respect to the first transmitter A, * represents a linear convolution operation, w(n) is noise added at the receiver.   
     
     
         64 . The apparatus of  claim 63 , further comprising:
 means for processing the following equation:   y(n)=h a (n−d a )*x(n)+h b (n−d b )*x(n)+w(n), where a perceived channel delay spread is given by (τ′ b −τ′ b )−(τ′ a −d a ) and controlled by introducing timing offsets at the transmitter.   
     
     
         65 . The apparatus of  claim 63 , further comprising:
 means for determining a cyclic convolution when an effective delay spread is less than a cyclic prefix as in the following equations:
     y ( n )= h   a ( n ) {circle around (x)}x   a ( n−d   a )+ h   b ( n ) {circle around (x)}x   b ( n−d   b )+ w ( n ) 
   or 
     y ( n )= h   a ( n−d   a ) {circle around (x)}x   a ( n )+ h   b ( n−d   b ) {circle around (x)}x   b ( n )+ w ( n ) 
   
       where {circle around (x)} denotes circular convolution. 
     
     
         66 . The apparatus of  claim 65 , further comprising:
 means for delaying transmissions from transmitters to cyclic prefix.   
     
     
         67 . The apparatus of  claim 65 , further comprising:
 means for employing a long cyclic prefix to enable an estimation of delay from weak transmitters that are far away.   
     
     
         68 . The apparatus of  claim 67 , further comprising:
 means for undoing an effect of physical delays by a cyclic shift of a positioning signal, where x a,p (n) is an intended positioning signal from the transmitter A with timing delay d a , and a transmitter sends a cyclically shifted version given by x a,p (n+d a ).   
     
     
         69 . The apparatus of  claim 68 , further comprising:
 means for processing the following equation   y(n)=h a (n){circle around (x)}x a,p (n)+h b (n){circle around (x)}x b,p (n)+w(n), to mitigate sending transmitter delay information to a receiver.   
     
     
         70 . The apparatus of  claim 55 , further comprising:
 means for determining transmitter timing adjustments from an offline network source.   
     
     
         71 . The apparatus of  claim 70 , further comprising:
 means for measuring pseudo ranges for the transmitter timing.   
     
     
         72 . The apparatus of  claim 71 , further comprising:
 means for relaying the pseudo ranges to a network almanac.   
     
     
         73 . The apparatus of  claim 55 , wherein the means for adjusting the timing differences by cyclically shifting and transmitting signals comprises means for employing a cyclic shift of an Orthogonal Frequency Division Multiplexing (OFDM) symbol carrying the signals to form a shifted OFDM symbol. 
     
     
         74 . The apparatus of  claim 73 , further comprising:
 means for forming a cyclic prefix of the OFDM symbol based on the shifted OFDM symbol.   
     
     
         75 . The apparatus of  claim 73 , wherein the OFDM symbol comprises an OFDM symbol carrying pilot positioning signals. 
     
     
         76 . The apparatus of  claim 55 , wherein the timing differences comprise fixed timing offset information. 
     
     
         77 . The apparatus of  claim 55 , further comprising:
 means for employing triangulation techniques with a subset of transmitter clocks to determine the position.   
     
     
         78 . The apparatus of  claim 55 , further comprising:
 means for determining at least one parameter.   
     
     
         79 . The apparatus of  claim 55 , further comprising:
 means for decoding a data stream.   
     
     
         80 . A method to adjust position information in a wireless network, comprising:
 determining timing differences between at least two transmitters and at least one receiver in the wireless network; and   adjusting transmission of the transmitters according to a signal phase to account for the timing differences by cyclically shifting and transmitting signals from each of the transmitters.   
     
     
         81 . The method of  claim 80 , further comprising:
 determining a position at the receiver in view of an adjusted signal phase from the adjusting transmission of the transmitters according to the signal phase.   
     
     
         82 . The method of  claim 80 , further comprising:
 generating a signal from at least two transmitters that is advanced or delayed to account for timing differences in the wireless network.   
     
     
         83 . The method of  claim 82 , further comprising:
 computing a linear convolution of a channel estimate with a transmitted signal.   
     
     
         84 . The method of  claim 80 , further comprising:
 advancing or delaying transmission timing of the transmitters in a network to regulate an effective channel delay spread as perceived by the receiver.   
     
     
         85 . The method of  claim 84 , further comprising:
 performing a linear convolution of a channel with a transmitted signal that is processed as a cyclic convolution if the delay spread of the channel is less than a cyclic prefix employed by an Orthogonal Frequency Division Multiplexing (OFDM) signal.   
     
     
         86 . The method of  claim 80 , further comprising:
 determining transmitter timing adjustments from an offline network source.   
     
     
         87 . The method of  claim 86 , further comprising:
 measuring pseudo ranges for the transmitter timing.   
     
     
         88 . The method of  claim 80 , wherein adjusting an amount of the cyclic shift comprises employing a cyclic shift of an Orthogonal Frequency Division Multiplexing (OFDM) symbol carrying a signal of the transmitted signals to form a shifted OFDM symbol. 
     
     
         89 . The method of  claim 88 , further comprising:
 forming a cyclic prefix of the OFDM symbol based on the shifted OFDM symbol.   
     
     
         90 . The method of  claim 88 , wherein the OFDM symbol comprises an OFDM symbol carrying pilot positioning signals.