Iterative interference suppression using mixed feedback weights and stabilizing step sizes

Abstract

A receiver is configured for canceling intra-cell and inter-cell interference in coded, multiple-access, spread-spectrum transmissions that propagate through frequency-selective communication channels. The receiver employs iterative symbol-estimate weighting, subtractive cancellation with a stabilizing step-size, and mixed-decision symbol estimate. Receiver embodiments may be implemented explicitly in software of programmed hardware, or implicitly in standard Rake-based hardware either within the Rake (i.e., at the finger level) or outside the Rake (i.e., at the user of subchannel symbol level).

We claim: 
     
       1. An interference suppression method, comprising:
 receiving a plurality of constituent signals; 
 combining the plurality of constituent signals to produce a synthesized received signal; 
 subtracting the synthesized received signal from a received signal to produce a residual signal; and 
 scaling the residual signal by a stabilizing step size to produce a scaled residual signal. 
 
     
     
       2. The method of  claim 1 , further comprising combining the scaled residual signal with the plurality of constituent signals to form a plurality of interference-suppressed constituent signals. 
     
     
       3. The method of  claim 1 , further comprising combining the scaled residual signal with a subset of the plurality of constituent signals to form at least one interference-suppressed constituent signal. 
     
     
       4. The method of  claim 2 , further comprising:
 time-advancing at least one of the plurality of interference-suppressed constituent signals to produce at least one time-advanced signal; 
 weighting the at least one time-advanced signal; and 
 combining the time-advanced signals corresponding to a first user to produce a first combined user signal. 
 
     
     
       5. The method of  claim 1 , further comprising generating, by a Rake receiver, the plurality of constituent signals from the received signal. 
     
     
       6. The method of  claim 1 , further comprising advancing the received signal by a plurality of multipath-delay quantities to produce the plurality of constituent signals. 
     
     
       7. The method of  claim 6 , further comprising scaling the plurality of advanced signals by corresponding path gains prior to said combining. 
     
     
       8. The method of  claim 1 , further comprising multiplying the synthesized received signal by complex conjugates of a plurality of users' coded waveforms and integrating the resultant products to despread the synthesized received signal. 
     
     
       9. A non-transitory computer-readable storage medium, comprising a plurality of instructions, that in response to being executed, cause a receiver to:
 combine a plurality of constituent signals for a received multiple-access communications signal to produce a synthesized received signal; 
 subtract the synthesized received signal from the received multiple-access communications signal to produce a residual signal; and 
 scale the residual signal by a stabilizing step size to produce a scaled residual signal. 
 
     
     
       10. The non-transitory computer-readable storage medium of  claim 9 , wherein the plurality of instructions in response to being executed, further cause the receiver to combine the scaled residual signal with the plurality of constituent signals to form a plurality of interference-suppressed constituent signals. 
     
     
       11. The non-transitory computer-readable storage medium of  claim 9 , wherein the plurality of instructions in response to being executed, further cause the receiver to combine the scaled residual signal with a subset of the plurality of constituent signals to form at least one interference-suppressed constituent signal. 
     
     
       12. The non-transitory computer-readable storage medium of  claim 9 , wherein the plurality of instructions in response to being executed, further cause the receiver to:
 time-advance at least one of the plurality of interference-suppressed constituent signals to produce at least one time-advanced signal; 
 weight the at least one time-advanced signal; and 
 combine the time-advanced signals corresponding to a first user to produce a first combined user signal. 
 
     
     
       13. The non-transitory computer-readable storage medium of  claim 9 , wherein the plurality of instructions in response to being executed, further cause the receiver to advance the received multiple-access communications signal by a plurality of multipath-delay quantities to produce the plurality of constituent signals. 
     
     
       14. The non-transitory computer-readable storage medium of  claim 13 , wherein the plurality of instructions in response to being executed, further cause the receiver to scale the plurality of advanced signals by corresponding path gains prior to combining the plurality of constituent signals. 
     
     
       15. The non-transitory computer-readable storage medium of  claim 9 , wherein the plurality of instructions in response to being executed, further cause the receiver to multiply the synthesized received signal by complex conjugates of a plurality of users' coded waveforms and integrating the resultant products to despread the synthesized received signal. 
     
     
       16. A receiver, comprising:
 a front-end configured to receive a signal and generate a plurality of constituent signals for the received signal; and 
 an interference suppressor configured to:
 receive the plurality of constituent signals; 
 combine the plurality of constituent signals to produce a synthesized received signal; 
 subtract the synthesized received signal from the received signal to produce a residual signal; and 
 scale the residual signal by a stabilizing step size to produce a scaled residual signal. 
 
 
     
     
       17. The receiver of  claim 16 , wherein the interface suppressor is further configured to combine the scaled residual signal with the plurality of constituent signals to form a plurality of interference-suppressed constituent signals. 
     
     
       18. The receiver of  claim 17 , wherein the interface suppressor is further configured to:
 time-advance at least one of the plurality of interference-suppressed constituent signals to produce at least one time-advanced signal; 
 weight the at least one time-advanced signal; and 
 combine the time-advanced signals corresponding to a first user to produce a first combined user signal. 
 
     
     
       19. The receiver of  claim 16 , wherein the front end comprises a Rake receiver configured to generate the plurality of constituent signals. 
     
     
       20. The receiver of  claim 19 , wherein the Rake receiver is further configured to produce the plurality of constituent signals by:
 advancing the received signal by a plurality of multipath-delay quantities to obtain a plurality of advance signals; and 
 scaling the plurality of advanced signals by corresponding path gains to obtain the plurality of constituent signals.