Method and System for Estimating Time of Arrival of Signals Using Multiple Different Time Scales

Abstract

A method and system ( 500 ) estimates a time of arrival of a signal received via a wireless communications channel. The energy in the received signal is conditioned at multiple different time scales to produce a conditioned signal ( 700 ). Then, a leading edge is detected in the conditioned signal ( 550 ). The leading edge corresponds to the time of arrival of the received signal ( 551 ).

1 . A method for estimating a time of arrival of a radio signal, comprising:
 conditioning, at multiple different time scales, an energy of a received signal to produce a conditioned signal; and   detecting a leading edge of the conditioned signal, the leading edge corresponding to a time of arrival of the received signal.   
   
   
       2 . The method of  claim 1 , further comprising:
 estimating a distance between two transceivers based on the time of arrival.   
   
   
       3 . The method of  claim 1 , in which the received signal is an ultra wideband radio signal. 
   
   
       4 . The method of  claim 1 , in which the received signal is a time-hopped, impulse-radio signal. 
   
   
       5 . The method of  claim 1 , in which the signal is received via a wireless channel, and further comprising:
 conditioning the received signal based on characteristics of the wireless channel.   
   
   
       6 . The method of  claim 1 , further comprising:
 conditioning the received signal based on parameters of the signal.   
   
   
       7 . The method of  claim 1 , in which the signal is received via a wireless channel, and further comprising:
 conditioning the received signal based on characteristics of the wireless channel and parameters of the signal.   
   
   
       8 . The method of  claim 1 , further comprising:
 applying multi-scale wavelet coefficients to the energy of the signal during the conditioning.   
   
   
       9 . The method of  claim 1 , further comprising:
 applying multi-scale filters to the energy of the signal during the conditioning.   
   
   
       10 . The method of  claim 1 , further comprising:
 receiving the signal; and   collecting the energy of the received signal.   
   
   
       11 . The method of  claim 5 , in which the characteristics of the channel include a signal to noise ratio. 
   
   
       12 . The method of  claim 6 , in which the parameters of the received signal include a bandwidth, a frame length, a symbol length, a chip length, and a block length of the received signal. 
   
   
       13 . The method of  claim 6 , further comprising:
 selecting wavelet scaling filters and coefficients of the multiple different time scales according to the parameters of the received signal.   
   
   
       14 . The method of  claim 1 , further comprising:
 excluding fine time scales during the conditioning at low signal to noise ratios.   
   
   
       15 . The method of  claim 1 , in which the conditioning enhances peaks relatively near the leading edge. 
   
   
       16 . The method of  claim 4 , in which multiple pulses are transmitted for each symbol in the received signal. 
   
   
       17 . The method of  claim 16 , in which the multiple pulses include delayed versions of a first one of the multiple pulses. 
   
   
       18 . The method of  claim 1 , in which the time of arrival is less than a length of a symbol represented by the received signal. 
   
   
       19 . The method of  claim 10 , in which collecting uses a square-law device. 
   
   
       20 . The method of  claim 10 , in which collecting uses a stored reference signal. 
   
   
       21 . The method of  claim 10 , in which collecting uses a transmitted reference signal. 
   
   
       22 . A system for estimating a time of arrival of a radio signal, comprising:
 means for conditioning, at multiple different time scales, an energy of a received signal to produce a conditioned signal; and   means for detecting a leading edge of the conditioned signal, the leading edge corresponding to a time of arrival of the received signal.