Advanced Signal Processors for Interference Cancellation in Baseband Receivers

• US 20100329402A1
• Filed: 08/30/2010
• Published: 12/30/2010
• Est. Priority Date: 09/20/2002
• Status: Active Grant

• Current Assignee: III Holdings 1, LLC (Intellectual Ventures LLC)
• Original Assignee: Rambus Inc.
• Inventors: Scharf, Louis L., Thomas, John K., Nagarajan, Vijay
• Granted Patent: US 9,647,708 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/1081 Reduction of multipath noise by equalising H04B7/005
• CPC Class Codes: H04B 1/126 having multiple inputs, e.g. auxiliary antenna for receiving interfering signal aerials in general H01Q
• CPC Class Codes: H04B 1/7105 Joint detection techniques, e.g. linear detectors
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 1/7117 Selection, re-selection, allocation or re-allocation of paths to fingers, e.g. timing offset control of allocated fingers
• 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 2001/1045 Adjacent-channel interference
• CPC Class Codes: H04B 2201/70719 CDMA2000
• CPC Class Codes: H04B 2201/70979 Fat finger issues in RAKE receivers
• CPC Class Codes: H04B 7/0678 using different spreading codes between antennas code allocation H04J13/16
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/20 having an orthogonal variable spreading factor [OVSF]

Abstract

A multi-mode receiver includes a channel decomposition module (e.g., a Rake receiver) for separating a received signal into multipath components, an interference selector for selecting interfering paths and subchannels, a synthesizer for synthesizing interference signals from selected sub channel symbol estimates, and an interference canceller for cancelling selected interference in the received signal. At least one of the channel decomposition module, the synthesizer, and the interference canceller are configurable for processing multi-mode signals.

Claims

1. A cancellation method comprising:

providing a received signal that is decomposable into one or more multiple-access interference (“

MAI”

)-channel signals;

applying a weight to each of the one or more MAI-channel signals to produce one or more weighted MAI channel signals; and

subtracting one or more of the weighted MAI channel signals from the received signal to create an interference canceled signal.

2. The method of claim 1, wherein a first weighted MAI-channel signal is coupled into a first stage of a first Rake finger.

3. The method of claim 1, wherein applying a weight comprises combining the one or more weighted MAI channel signals to produce at least one of an interference matrix and an interference vector.

4. The method of claim 1, wherein applying a weight comprises at least one of determining complex weights of each of the one or more MAI channel signals and determining estimation errors for each of the complex weights.

5. The method of claim 1, wherein providing a received signal comprises a multi-antenna operation comprising diversity combining and beam forming.

6. The method of claim 1, wherein applying a weight comprises producing a linear combination of the one or more weighted MAI channel signals.

7. A system for interference cancellation comprising:

a receiver configured to decompose a received signal into a plurality of signal paths, including one or more multiple-access interference (“

MAI”

)-channel paths;

a weighted decision combiner configured to apply a weight to each of the one or more MAI-channel paths to produce one or more weighted MAI-channel signals; and

a cancellation operator for subtracting one or more of the weighted MAI channel signals from the received signal to create an interference canceled signal.

8. The system of claim 7, further comprising a gain correction module configured for compensating for gain applied to one or more of the plurality of signal paths by one or more transmitters.

9. The system of claim 7, wherein the receiver is configured for receiving signals from a transmit diversity system.

10. The system of claim 9, wherein the receiver is configured for receiving signals from at least one of a space-time transmit diversity (STTD) system and a closed loop transmit diversity system.

11. The system of claim 7, wherein the receiver comprises a Rake receiver.

12. The system of claim 11, wherein the Rake receiver includes at least one multi-antenna receiver configured to provide at least one of diversity combining and beam forming.

13. The system of claim 11, further comprising a delay element coupled between the Rake receiver and the cancellation operator and configured to impart a delay to at least one of the plurality of signal paths.

14. The system of claim 11, wherein the Rake receiver includes at least one of a pulse-shaping filter, a combiner, and a searcher/tracker module.

15. The system of claim 11, wherein the Rake receiver and the cancellation operator are configured with an iterative feedback loop.

16. The system of claim 7, wherein the weighted decision combiner and the cancellation operator are coupled between at least one of a pair of system components, including a sampler and a descrambler, a channel compensator and a descrambler, a descrambler and a demultiplexer, and a demultiplexer and a gain correction module.

17. The system of claim 7, further comprising a gain correction module configured for compensating for gain applied to one or more of the plurality of signal paths by one or more transmitters.

18. A system for interference cancellation comprising:

a receiver configured to decompose a received baseband signal into a plurality of channels;

one or more interference selectors configured to select one or more of the plurality of channels that are likely to contribute MAI to at least one signal of interest;

one or more channel emulators configured to apply one or more complex gains to the selected one or more channels to produce one or more scaled MAI channel signals;

one or more cancellation operators configured to subtract one or more of the scaled MAI channel signals from the received signal to produce an interference canceled signal.

19. The system of claim 18, further comprising one or more baseband signal reconstruction modules configured for processing the selected one or more of the plurality of channels to produce one or more processed signals that are substantially in the same form as the received baseband signal.

20. The system of claim 18, further comprising a gain correction module configured for compensating for gain applied to one or more of the plurality of channels by one or more transmitters.

21. The system of claim 18, wherein the receiver comprises a Rake receiver.

22. The system of claim 18, wherein the one or more channel emulators and the one or more cancellation operators are coupled between at least one of a pair of system components, including a sampler and a descrambler, a channel compensator and a descrambler, a descrambler and a demultiplexer, and a demultiplexer and a gain correction module.

23. A system for interference cancellation comprising:

a receiver configured to decompose a received signal into a plurality of channels;

a sampler configured for sampling the received signal;

a channel estimator coupled to the sampler and configured for producing one or more complex channel estimates; and

a cancellation operator for subtracting one or more of the complex channel estimates from the received signal to create an interference canceled signal.

24. The system of claim 23, further comprising a matched baseband filter coupled to the sampler and configured for filtering the one or more of the plurality of channels.

25. The system of claim 23, further comprising a channel compensator configured for producing one or more channel-compensated signals.

26. The system of claim 25, wherein the channel compensator is configured to produce one or more channel-compensated signals that compensates for transmit antenna weights in addition to channel effects.

27. The system of claim 23, wherein the channel estimator is configured to receive primary common pilot channel (P-CPICH) data bits, the P-CPICH OVSF code, and the sampled signal from the sampler.

28. The system of claim 23, wherein the channel estimator is configured to receive secondary common pilot channel (S-CPICH) data bits, the S-CPICH OVSF code, and the sampled signal from the sampler.

29. The system of claim 23, further comprising a gain correction module configured for compensating for gain applied to one or more of the plurality of channels by one or more transmitters.