Estimating time delays in a simulcast communication system

Abstract

A method for facilitating an equalization of a simulcast signal comprising: (a) receiving a simulcast signal comprising known data simulcast from at least two different sites; (b) generating a number of simulated simulcast signals, each simulated simulcast signal being based on at least two sites transmitting said known data with a presumed time delay, each simulated simulcast signal having a different presumed time delay; (c) determining which of said simulated simulcast signals is an optimum simulated simulcast signal that correlates most closely to said simulcast signal; and (d) providing time delay data of said optimum simulated simulcast signal for use in equalization of said simulcast signal.

1 . A method for equalizing a number of signals in a simulcast network, said method comprising: 
 (a) receiving a simulcast signal comprising known data simulcast from at least two different sites;    (b) generating a number of simulated simulcast signals, each simulated simulcast signal being based on at least two sites transmitting said known data with a presumed time delay, each simulated simulcast signal having a different presumed time delay;    (c) determining which of said simulated simulcast signals is an optimum simulated simulcast signal that correlates most closely to said simulcast signal; and    (d) providing time delay data of said optimum simulated simulcast signal for use in equalization of said simulcast signal.    
     
     
         2 . The method of  claim 1 , wherein at least a portion of said simulcast signal is a synchronization signal.  
     
     
         3 . The method of  claim 1 , wherein generating a number of simulated simulcast signals comprises at least: 
 i. calculating a vector of channel coefficients as a product of filters and said simulcast signal; and    ii. using said vector of channel coefficients to generate said simulated simulcast signals.    
     
     
         4 . The method of  claim 3 , wherein said filters are calculated prior to receiving said simulcast signal and are stored in memory.  
     
     
         5 . The method of  claim 4 , wherein said filters comprises two or more sets, a coarse set having coarsely-incremented time delays, and at least one fine set having finely-incremented time delays.  
     
     
         6 . The method of  claim 5 , wherein said filters are least square filters.  
     
     
         7 . The method of  claim 1 , wherein the number of simulated signals is two.  
     
     
         8 . The method of  claim 1 , wherein said simulcast signal has an expected range of time delay and wherein said simulated simulcast signals have time delays spanning essentially said expected range.  
     
     
         9 . The method of  claim 1 , wherein said range is about 50 to about 200 μsec.  
     
     
         10 . The method of  claim 1 , wherein said simulated simulcast signals are generated in increments of time delay.  
     
     
         11 . The method of  claim 1 , wherein, 
 step (b) generates initially a coarse set of simulated simulcast signals using coarsely-incremented time delays;    step (c) determines initially a coarse optimum simulated simulcast signal from said coarse set of simulated simulcast signals;    step (b) then generates a fine set of simulated simulcast signals based on said time delay of said coarse optimum simulated simulcast signal using finely-incremented time delays which are finer than those used initially; and    step (c) then determines said optimum simulated simulcast signal from said fine set of simulated simulcast signals.    
     
     
         12 . The method of  claim 13 , wherein a coarsely-incremented time delay is 5 to 20 times a finely-incremented time delays.  
     
     
         13 . The method of  claim 12 , wherein said coarsely-incremented time delay is about 10 times said finely-incremented time delay.  
     
     
         14 . The method of  claim 1 , wherein step (c) comprises calculating least square error between each simulated simulcast signal and said simulcast signal.  
     
     
         15 . The method of  claim 1 , further comprises: 
 (e) equalizing said data simulcast from said different sites.    
     
     
         16 . A mobile unit for use in a simulcast network comprising: 
 a receiver for receiving a simulcast signal;    a transmitter for transmitting a signal to a simulcast network;    a processor operatively connected to said receiver and said transmitter; and    memory operatively connector to said processor and being configured to instruct said process to perform the following steps: 
 (a) receiving a simulcast signal comprising known data simulcast from at least two different sites;  
 (b) generating a number of simulated simulcast signals, each simulated simulcast signal being based on at least two sites transmitting said known data with a presumed time delay, each simulated simulcast signal having a different presumed time delay;  
 (c) determining which of said simulated simulcast signals is an optimum simulated simulcast signal that correlates most closely to said simulcast signal; and  
 (d) providing time delay data of said optimum simulated simulcast signal for use in equalization of said simulcast signal.  
   
     
     
         17 . The mobile unit of  claim 16 , wherein generating a number of simulated simulcast signals comprises: 
 i. calculating a vector of channel coefficients as a product of filters and said received simulcast signal; and    ii. using said vector of channel coefficients to generate said simulated simulcast signals; and    wherein said filters are resident in said memory prior to receiving said signal.    
     
     
         18 . A simulcast network comprising: 
 at least two sites for simulcasting a signal having known data    a mobile unit positionable between said two sites such that a simulcast signal received from said two sites has a time delay, and comprising: 
 a receiver for receiving a simulcast signal;  
 a transmitter for transmitting a signal to a simulcast network;  
 a processor operatively connected to said receiver and said transmitter; and  
 memory operatively connector to said processor and being configured to instruct said process to perform the following steps: 
 (a) receiving a simulcast signal comprising known data simulcast from at least two different sites;  
 (b) generating a number of simulated simulcast signals, each simulated simulcast signal being based on at least two sites transmitting said known data with a presumed time delay, each simulated simulcast signal having a different presumed time delay;  
 (c) determining which of said simulated simulcast signals is an optimum simulated simulcast signal that correlates most closely to said simulcast signal; and  
 (d) providing time delay data of said optimum simulated simulcast signal for use an equalization of said simulcast signal.