Noise recycling
Described are concepts, systems, devices and methods that enhance decoding performance of channels subject to correlated noise. The concepts, systems, devices and methods can be used with any combination of codes, code-rates and decoding techniques. In embodiments, a continuous realization of effective noise is estimated from a lead channel by subtracting its decoded output from its received signal. This estimate is then used to improve the accuracy of decoding of an otherwise orthogonal channel that is experiencing correlated effective noise. In this approach, channels aid each other through the post-decoding provision of estimates of effective noise. In some embodiments, the lead channel is not pre-determined, but is chosen dynamically based on which of a plurality of decoders completes first, or using soft information including an estimate of effective noise that is least energetic or most likely to have occurred.
1. A system for decoding signals, the system comprising:
one or more antennas for receiving a plurality of channels having correlated, effective noise;
a lead channel selector for determining a lead channel in the plurality of channels;
a first decoder for decoding signals in the lead channel to form a first decoded codeword;
a subtraction unit for determining an estimate of effective noise on the lead channel by subtracting the first decoded codeword from the signals received in the lead channel; and
a second decoder for decoding signals in another channel in the plurality of channels using the determined estimate of effective noise on the lead channel to form a second decoded codeword.
2. The system according to claim 1 , wherein the plurality of channels would be orthogonal or quasi-orthogonal but for the correlated, effective noise.
3. The system according to claim 1 , wherein the plurality of channels comprises a wireless, multiple access channel.
4. The system according to claim 1 , wherein the plurality of channels comprise: an orthogonal frequency-division multiplexing (OFDM) channel, or a frequency-division multiple access (FDMA) channel, or a time-division multiplexing (TDM) channel, or a time-division multiple access (TDMA) channel, or a channel that interleaves data over time or frequency, or a packetized access channel, or a code-division multiple access (CDMA) channel, or any combination thereof.
5. The system according to claim 1 , wherein the lead channel selector operates by selecting, prior to decoding, a given channel in the plurality of channels as the lead channel.
6. The system according to claim 5 , wherein the given channel has a lowest code rate among the plurality of channels.
7. The system according to claim 1 , wherein the lead channel selector operates by (a) receiving parallel decodings of the signals received by the one or more antennas, and (b) selecting a channel in the plurality of channels as the lead channel on the basis of the parallel decodings.
8. The system according to claim 7 , wherein the lead channel selector operates by selecting the channel whose decoding completed first.
9. The system according to claim 7 , wherein the lead channel selector operates using soft information.
10. The system according to claim 9 , wherein the soft information comprises a least energetic estimated effective noise sequence.
11. The system according to claim 9 , wherein the soft information comprises a most likely effective noise sequence.
12. The system according to claim 1 , further comprising:
a second subtraction unit for determining an estimate of effective noise on the other channel by subtracting the second decoded codeword from the signals in the other channel;
wherein the first decoder is configured for re-decoding the signals in the lead channel using the determined estimate of effective noise on the other channel to form a third decoded codeword that is different than the first decoded codeword.
13. The system according to claim 1 , wherein the plurality of channels comprise a plurality of time slots created by time division multiplexing, and the correlated, effective noise comprises burst noise.
14. The system according to claim 1 , comprising a multiple-input multiple-output (MIMO) system, wherein the correlated, effective noise comprises effective noise relating to signals received by each of the one or more antennas.
15. The system according to claim 14 , further comprising a plurality of nodes, each node having a plurality of antennas, wherein two or more of the nodes share with each other information regarding effective noise that they have received by their respective plurality of antennas.
16. The system according to claim 1 , further comprising a plurality of additional decoders for decoding signals in respective additional channels in the plurality of channels, each such additional decoder using a determined estimate of effective noise on another decoder.
17. The system according to claim 1 , wherein the first and second decoders perform successive interference cancellation (SIC) on the plurality of channels.
18. The system according to claim 1 , wherein the first and second decoder are configured for decoding signals according to an interleaving of the plurality of channels.
19. A method of decoding signals, the method comprising:
receiving a plurality of channels having correlated, effective noise;
determining a lead channel in the plurality of channels;
decoding signals in the lead channel to form a first decoded codeword;
determining an estimate of effective noise on the lead channel by subtracting the first decoded codeword from the signals received in the lead channel; and
decoding signals in another channel in the plurality of channels using the determined estimate of effective noise on the lead channel to form a second decoded codeword.
20. The method according to claim 19 , wherein the plurality of channels would be orthogonal or quasi-orthogonal but for the correlated, effective noise.
21. The method according to claim 19 , wherein the plurality of channels comprises a wireless, multiple access channel.
22. The method according to claim 19 , wherein the plurality of channels comprise: an orthogonal frequency-division multiplexing (OFDM) channel, or a frequency-division multiple access (FDMA) channel, or a time-division multiplexing (TDM) channel, or a time-division multiple access (TDMA) channel, or a channel that interleaves data over time or frequency, or a packetized access channel, or a code-division multiple access (CDMA) channel, or any combination thereof.
23. The method according to claim 19 , wherein determining the lead channel comprises selecting, prior to decoding, a given channel in the plurality of channels as the lead channel.
24. The method according to claim 23 , wherein the given channel has a lowest code rate among the plurality of channels.
25. The method according to claim 19 , wherein determining the lead channel comprises (a) receiving parallel decodings of the signals in the plurality of channels, and (b) selecting a channel in the plurality of channels as the lead channel on the basis of the parallel decodings.
26. The method according to claim 25 , wherein selecting the lead channel comprises selecting the channel whose decoding completed first.
27. The method according to claim 25 , wherein selecting the lead channel comprises using soft information.
28. The method according to claim 27 , wherein the soft information comprises a least energetic estimated effective noise sequence.
29. The method according to claim 27 , wherein the soft information comprises a most likely effective noise sequence.
30. The method according to claim 19 , further comprising:
determining an estimate of effective noise on the other channel by subtracting the second decoded codeword from the signals in the other channel; and
re-decoding the signals in the lead channel using the determined estimate of effective noise on the other channel to form a third decoded codeword that is different than the first decoded codeword.
31. The method according to claim 19 , wherein the plurality of channels comprise a plurality of time slots created by time division multiplexing, and the correlated, effective noise comprises burst noise.
32. The method according to claim 19 , wherein the plurality of channels comprise a multiple-input multiple-output (MIMO) system having one or more antennas, and the correlated, effective noise comprises effective noise relating to signals received by each of the one or more antennas.
33. The method according to claim 32 , wherein the MIMO system comprises a plurality of nodes, each node having a plurality of antennas, the method further comprising two or more nodes in the plurality of nodes sharing with each other information regarding effective noise they have respectively estimated.
34. The method according to claim 19 , further comprising decoding signals in additional channels in the plurality of channels, each such decoding using a determined estimate of effective noise from a prior decoding.
35. The method according to claim 19 , further comprising performing successive interference cancellation (SIC) on the plurality of channels.
36. The method according to claim 19 , further comprising decoding signals according to an interleaving of the plurality of channels.