Use of correlation combination to achieve channel detection

Abstract

Combinations of correlation results are used to achieve detection of multiple coded signals at a receiver in a wireless communications system. The code applied to signals includes a lower rate code and a higher rate code. The lower rate code is a nested or tiered code such that it comprises at least two code sequences of the higher rate code. The received coded signal is correlated with the higher rate code using a single higher rate correlator to provide a higher rate code correlation result. The higher rate code correlation results are fed to two or more lower rate code correlators that combine multiple higher rate code correlation results, each using a different lower rate code, to provide corresponding lower rate code correlation results. The presence of at least one coded signal or mutually exclusive coded signals can be determined from the lower rate code correlation results.

1 . A base station comprising:
 a receiver configured to receive and detect a coded signal wherein the code applied to the signal includes a lower rate code comprising at least two code sequences of a higher rate code;   a first correlator configured to correlate the received coded signal with the higher rate code to provide a higher rate code correlation result, and   a second correlator configured to correlate the higher rate code correlation results with a first lower rate code to provide a first lower rate code correlation result, and to correlate the higher rate code correlation results with a second lower rate code to provide a second lower rate code correlation result;   the first lower rate code correlation result compared to the second lower rate code correlation result to determine the presence of the received coded signal.   
     
     
         2 . The base station of  claim 1 , wherein the second correlator is configured to determine the presence of a first indication corresponding to the first lower rate code and the first lower rate code correlation result. 
     
     
         3 . The base station of  claim 1 , wherein the second correlator is configured to determine the presence of a second indication corresponding to the second lower rate code from the second lower rate code correlation result. 
     
     
         4 . The base station of  claim 1 , wherein the second correlator is configured to determine the presence of one or another of two mutually exclusive coded signals form the first and second lower rate code correlation results. 
     
     
         5 . The method of  claim 1  wherein the received coded signal is received periodically. 
     
     
         6 . The method of  claim 1  wherein the lower rate codes are orthogonal to each other. 
     
     
         7 . The method of  claim 1  wherein the lower rate codes are Walsh codes. 
     
     
         8 . The method of  claim 1  wherein the lower rate codes are Gutleber codes. 
     
     
         9 . The method of  claim 1  wherein the lower rate codes are M-sequences. 
     
     
         10 . The method of  claim 1  wherein the lower rate codes are PN-sequences. 
     
     
         11 . The method of  claim 1  wherein the higher rate code is 32 chips in length and the lower rate codes are 128 chips in length. 
     
     
         12 . The method of  claim 1  wherein the lower rate codes are used for timing signals.