Interference cancellation in variable codelength systems for multi-acess communication

• US 8,064,498 B2
• Filed: 03/19/2010
• Issued: 11/22/2011
• Est. Priority Date: 05/11/2006
• Status: Active Grant

• Current Assignee: III Holdings 1, LLC
• Original Assignee: Rambus Inc.
• Inventors: Nagarajan, Vijay, Scharf, Louis L., Narayan, Armand P.
• Primary Examiner(s): Tran, Khai
• Application Number:
  US12/727,880
• Publication Number:
  US 20100238981A1
• Time in Patent Office: 613 Days
• Field of Search: 375/148, 375/130, 375/147, 375/347, 375/342, 375/267, 375/152, 375/349, 370/337, 370/342, 455/132, 455/137, 455/138
• US Class Current: 375/148
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04B 2201/709727 GRAKE type RAKE receivers

Abstract

A receiver employs low-rate processing to synthesize the effect of high-rate interference in a received multi-rate signal. Each high-rate subchannel is analyzed on its low-rate descendents to produce symbol estimates for each low-rate symbol interval. The symbol estimates are applied to low-rate descendent subchannels, which are then combined to synthesize the effects of the high-rate interference. An interference canceller processes the synthesized interference with the received signal for producing an interference-cancelled signal. Alternatively, analogous steps may be applied at high-rate to analyze, synthesize, and cancel the effects of low-rate interference in a multi-rate signal.

Claims

1. A method for processing at least one of high-rate subchannels and low-rate subchannels, the method comprising:

configuring a processor to perform at least one of a high-rate analysis and a low-rate analysis for a plurality of coded subchannels in a received baseband signal;

configuring the processor to calculate a signal-to-interference-and-noise ratio (SINR) for each of the plurality of coded subchannels;

configuring the processor to employ a function of the SINR for processing high-rate and low-rate subchannels in the received baseband signal;

configuring the processor to calculate a plurality of low-rate SINRs for a plurality of low-rate subchannels and at least one high-rate SINR for at least one high-rate subchannel; and

configuring the processor to combine the plurality of low-rate SINRs to produce a summed SINR and to scale the at least one high-rate SINR by a ratio of the high rate and the low rate.

2. The method of claim 1, wherein configuring the processor to employ the function comprises configuring the processor to calculate a variance of the SINR and to determine whether the variance is substantially zero or substantially non-zero.

3. A method for processing at least one of high-rate subchannels and low-rate subchannels, the method comprising:

configuring a processor to perform at least one of a high-rate analysis and a low-rate analysis for a plurality of coded subchannels in a received baseband signal;

configuring the processor to calculate a signal-to-interference-and-noise ratio (SINR) for each of the plurality of coded subchannels;

configuring the processor to employ a function of the SINR for processing high-rate and low-rate subchannels in the received baseband signal;

configuring the processor to generate first-order statistics from symbol estimates of the plurality of subchannels; and

configuring the processor to process the first-order statistics to determine the presence of at least one of a high-rate subchannel and a low-rate subchannel.

4. A method for processing at least one of high-rate subchannels and low-rate subchannels, the method comprising:

configuring a processor to perform at least one of a high-rate analysis and a low-rate analysis for a plurality of coded subchannels in a received baseband signal;

configuring the processor to calculate a signal-to-interference-and-noise ratio (SINR) for each of the plurality of coded subchannels;

configuring the processor to employ a function of the SINR for processing high-rate and low-rate subchannels in the received baseband signal; and

configuring the processor to compare instantaneous symbol estimates to at least one predetermined value to determine the presence of the at least one of high-rate subchannels and low-rate subchannels.

5. A method for cancelling interference effects of at least one low-rate subchannel at a high rate in a multi-rate communication system, the method comprising:

configuring a processor to analyze the at least one low-rate subchannel on its high-rate ancestor subchannel for generating symbol estimates;

configuring the processor to apply weighted symbol estimates to at least one synthesized high-rate ancestor subchannel to generate a plurality of high-rate interference signals; and

configuring the processor to use a sequence of the plurality of high-rate interference signals to model the interference effects from a low-rate transmission;

wherein the at least one low-rate subchannel comprises a code-multiplexed subchannel having a high spreading factor, and the high-rate ancestor subchannel comprises a plurality of code-multiplexed subchannels, each having a low spreading factor.

6. A method for cancelling interference effects of at least one low-rate subchannel at a high rate in a multi-rate communication system, the method comprising:

configuring a processor to analyze the at least one low-rate subchannel on its high-rate ancestor subchannel for generating symbol estimates;

configuring the processor to apply weighted symbol estimates to at least one synthesized high-rate ancestor subchannel to generate a plurality of high-rate interference signals; and

configuring the processor to use a sequence of the plurality of high-rate interference signals to model the interference effects from a low-rate transmission;

wherein configuring the processor to apply weighted symbol estimates comprises configuring the processor to employ a function of merit of the symbol estimates for calculating weights used to produce the weighted symbol estimates.

7. The method recited in claim 6, wherein the function of merit is a function of SINR for the high-rate ancestor subchannel.

8. A chipset configured to perform the method recited in claim 6.

9. A digital computer system programmed to perform the method recited in claim 6.

10. A computer-readable medium storing a computer program implementing the method of claim 6.

11. A base station configured to perform the method of claim 6.

12. A handset configured to perform the method of claim 6.