CDMA receiver with parallel interference suppression and optimized synchronization

Abstract

A receiver for transmission and parallel interference has multiple access interference suppression stages having K channels, each comprising a correlation device corresponding to a particular pseudorandom sequence and interference generation and suppression device. Each stage delivers to the following stage signals at least partly freed from multiple access interferences. A decision stage receives the signals from the channels of the preceding suppression stage. Each decision stage has a correlation device corresponding to one of the pseudorandom sequences and decision device to deliver data. Devices for producing synchronization signals can control the interference suppression and the decision device. The devices producing the synchronization signals have components placed in the channels of the final stage. Further, the synchronization signals produced by these devices control the decision device of the channels of the final stage and the interference estimation device of the at least one interference suppression stages following appropriate time shifts.

1. A receiver for code distribution multiple access transmission and parallel multiple access interference suppression, the receiver comprising:
 at least one multiple access interference suppression stage ESI i  constituted by K channels, each comprising a correlation means corresponding to a particular pseudorandom sequence, an interference estimation means and an interference suppression means, each stage delivering to a following stage K signals at least partly freed from multiple access interferences,  
 a final, decision stage (ED) constituted by K channels receiving the K signals from the K channels of a preceding suppression stage and each comprising a correlation means corresponding to one of the pseudorandom sequences and decision means delivering a data item,  
 means for producing synchronization signals able to control the at least one multiple access interference suppression stage and  
 control the decision means of the final stage (ED), said receiver being characterized in that the means for producing the synchronization signals are constituted by K means solely placed in the K channels of the final stage (ED), the K synchronization signals produced by said K means controlling the K decision means of the K channels of the final stage (ED) and the interference estimation means of the K channels of the at least one interference suppression stages ESI i  following appropriate time shifts.  
 
     
     
       2. Receiver according to  claim 1 , wherein the K synchronization signals also control the K correlation means of the K channels of the at least one multiple access interference suppression stage. 
     
     
       3. Receiver according to  claim 1 , wherein the K correlation means of the K channels of the final stage (ED) are constituted by K matched filters with K pseudorandom sequences and the K correlation means of the K channels of each interference suppression stage ESI i  are constituted by K sliding correlators. 
     
     
       4. A spread spectrum receiver, comprising:
   an interference suppression stage comprising three or more correlator circuits on three or more signal paths, the correlator circuits capable of providing an estimated signal based at least in part on a signal received at an input of said interference suppression stage; and        a decision stage capable of providing three or more data items contained in the received signal based at least in part on the estimated signal provided by the correlator circuits;        said decision stage comprising three or more decision circuits and three or more synchronization circuits having outputs coupled to the three or more correlator circuits of said interference suppression stage and being further coupled to the three or more decision circuits of said decision stage.     
     
     
       5. A spread spectrum receiver as claimed in  claim 4 , further comprising three or more time shift circuits coupled between the outputs of the three or more synchronization circuits and the three or more correlator circuits of said interference suppression stage. 
     
     
       6. A spread spectrum receiver as claimed in  claim 4 , further comprising three or more time shift circuits coupled between the outputs of the three or more synchronization circuits and the three or more correlator circuits of said interference suppression stage, the time shift of the time shift circuits comprising a symbol period or approximately the symbol period. 
     
     
       7. A spread spectrum receiver as claimed in  claim 4 , further comprising three or more time shifts circuits coupled between the outputs of the three or more synchronization circuits and the three or more correlator circuits of said interference suppression stage, the time shift of the time shift circuits comprising a processing time or approximately the processing time. 
     
     
       8. A spread spectrum receiver as claimed in  claim 4 , further comprising a second interference suppression stage coupled between said first interference suppression stage and said decision stage, said second interference suppression stage comprising three or more subtractor circuits capable of subtracting an interference estimation from the received signal prior to processing by said decision stage. 
     
     
       9. A spread spectrum receiver as claimed in  claim 4 , wherein the correlator circuits of said interference suppression stage comprise sliding correlators. 
     
     
       10. A spread spectrum receiver as claimed in  claim 4 , further comprising three or more correlator circuits in said decision stage coupled to inputs of the three or more decision circuits of said decision stage. 
     
     
       11. A spread spectrum receiver as claimed in  claim 4 , further comprising three or more correlator circuits in said decision stage coupled to inputs of the three or more decision circuits of said decision stage, the three or more correlator circuits of the decision stage comprising matched filters. 
     
     
       12. A spread spectrum receiver as claimed in  claim 4 , wherein the correlator circuits of said interference suppression stage comprise sliding correlators, and further comprising three or more correlator circuits in said decision stage coupled to inputs of the three or more decision circuits of said decision stage. 
     
     
       13. A spread spectrum receiver as claimed in  claim 4 , wherein the correlator circuits of said interference suppression stage comprise sliding correlators, and further comprising three or more correlator circuits in said decision stage coupled to inputs of the three or more decision circuits of said decision stage, the three or more correlator circuits of said decision stage comprising matched filters. 
     
     
       14. A spread spectrum receiver, comprising:
   means for suppressing interference in a received signal, said interference suppressing means comprising three or more correlation means on three or more signal paths, the correlation means being capable of providing an estimated signal based at least in part on the received signal; and        means for providing three or more data items contained in the received signal based at least in part on the estimated signals provided by the correlation means;        said data item providing means comprising three or more decision means and three or more synchronization means having outputs coupled to the three or more correlation means of said interference suppression means and being further coupled to the three or more decision means of said data item providing means.     
     
     
       15. A spread spectrum receiver as claimed in  claim 14 , further comprising three or more time shifting means coupled between the outputs of the three or more synchronization means and the three or more correlation means of said interference suppression means. 
     
     
       16. A spread spectrum receiver as claimed in  claim 14 , further comprising three or more time shifting means coupled between the outputs of the three or more synchronization means and the three or more correlation means of said interference suppression means, a time shift of the time shifting means comprising a symbol period or approximately the symbol period. 
     
     
       17. A spread spectrum receiver as claimed in  claim 14 , further comprising three or more time shifting coupled between the outputs of the three or more synchronization means and the three or more correlation means of said interference suppression stage, a time shift of the time shifting means comprising a processing time or approximately the processing time. 
     
     
       18. A spread spectrum receiver as claimed in  claim 14 , further comprising means for further suppressing interference in the received signal, said further interference suppressing means being coupled between said first interference suppression means and said data item proving means, said further interference suppression means comprising three or more subtracting means capable of subtracting an interference estimation from the received signal prior to processing by said data item providing means. 
     
     
       19. A spread spectrum receiver as claimed in  claim 14 , wherein the correlation means of said interference suppression stage comprise sliding type correlating means. 
     
     
       20. A spread spectrum receiver as claimed in  claim 14 , further comprising three or more correlating means in said decision stage coupled to inputs of the three or more decision means of said data item providing means. 
     
     
       21. A spread spectrum receiver as claimed in  claim 14 , further comprising three or more correlating means in said data item providing means coupled to inputs of the three or more decision means of said data item providing means, the three or more correlating means of the data item providing means comprising matched filtering means. 
     
     
       22. A spread spectrum receiver as claimed in  claim 14 , wherein the correlating means of said interference suppression stage comprise sliding type correlation means, and further comprising three or more correlating means in said data item providing means coupled to inputs of the three or more decision means of said data item providing means. 
     
     
       23. A spread spectrum receiver as claimed in  claim 14 , wherein the correlating means of said interference suppression means comprise sliding type correlating means, and further comprising three or more correlation means in said data item providing means coupled to inputs of the three or more decision means of said data item providing means, the three or more correlating means of said data item providing means comprising matched type filtering means. 
     
     
       24. A method, comprising:
   estimating a signal based at least in part on a received signal by correlating the received signal with a pseudorandom sequence on three or more signal paths to provide three or more estimated signals; and        deciding three or more data items contained in the received signal based at least in part on the estimated signals;        said deciding comprising synchronizing said deciding with said estimating or said correlating, or combinations thereof.     
     
     
       25. A method as claimed in  claim 24 , further comprising time shifting said synchronizing with respect to said correlating. 
     
     
       26. A method as claimed in  claim 24 , further comprising time shifting said synchronizing with respect to said correlating, a time shift of said time shifting comprising a symbol period or approximately the symbol period. 
     
     
       27. A method as claimed in  claim 24 , further comprising time shifting said synchronizing with respect to said correlating, a time shift of said time shifting comprising a processing time or approximately the processing time. 
     
     
       28. A method as claimed in  claim 24 , further subtracting an interference estimation from the received signal prior to said deciding. 
     
     
       29. A method as claimed in  claim 24 , wherein said correlating of said estimating comprising a sliding type correlating. 
     
     
       30. A method as claimed in  claim 24 , said deciding further comprising correlating the estimated signals prior to said deciding. 
     
     
       31. A method as claimed in  claim 24 , said deciding further comprising correlating the estimated signals prior to said deciding, said correlating the estimated signals comprising matched filter type correlating. 
     
     
       32. A method as claimed in  claim 24 , wherein said correlating of said estimating comprising a sliding type correlating, and said deciding further comprising correlating the estimated signals prior to said deciding. 
     
     
       33. A method as claimed in  claim 24 , wherein said correlating of said estimating comprising a sliding type correlating, and said deciding further comprising correlating the estimated signals prior to said deciding, said correlating the estimated signals comprising matched filter type correlating.