System and method for iterative compensation for linear and nonlinear interference in system employing FTN symbol transmission rates

1. An apparatus comprising:

a receiver configured to process a signal received over a non-linear wireless channel, wherein the received signal reflects a source signal comprising a plurality of source symbols, and includes linear and non-linear interference effects induced based on a faster-than-Nyquist (FTN) signaling rate applied to the source signal and high-power amplification and filtering for transmission over the non-linear wireless channel;

wherein the receiver is configured to estimate the plurality of source symbols of the received signal based on a plurality of outer-loop decoding iterations, wherein a current outer-loop decoding iteration is employed to at least determine an improved estimate of one or more of the plurality of source symbols based on a set of soft information of the current outer-loop decoding iteration, and the improved estimate of the one or more of the plurality of source symbols is fed to a next outer-loop decoding iteration to further improve the estimate of the one or more of the plurality of source symbols, and wherein the receiver comprises:

a likelihood metric processor configured to generate the set of soft information of the current outer-loop decoding iteration based on a current estimate of one or more of the source symbols and a final set of soft information from a previous outer-loop decoding iteration;

wherein the current estimate of the one or more source symbols is based on a previous estimate of the linear and non-linear interference effects exhibited by the received signal, which is based on the final set of soft information from the previous outer-loop decoding iteration.

2. The apparatus of claim 1 , wherein the likelihood metric processor comprises a log-likelihood ratio (LLR) processor, and the set of soft information of the current outer-loop decoding iteration comprises a set of extrinsic log-likelihood ratios (LLRs), generated by the LLR processor based on the current estimate of the one or more source symbols, and a set of extrinsic LLRs from the previous outer-loop decoding iteration.

3. The apparatus of claim 1 , wherein the receiver further comprises:

a mapping processor configured to bit-to-symbol map the final set of soft information from the previous outer-loop decoding iteration;

a filter configured to process the bit-to-symbol mapped information generated by the mapper module to generate the previous estimate of the linear and non-linear interference effects; and

an arithmetic processor configured to generate the current estimate of the one or more source symbols by subtracting the previous estimate of the linear and non-linear interference effects generated by the filter module from the received signal.

4. The apparatus of claim 3 , wherein the filter comprises a Volterra filter configured to generate the estimate of the linear and non-linear interference effects, wherein the Volterra filter comprises:

a first order component configured to generate an estimate of the first order interference, which reflects the linear interference effects; and

a third order component configured to generate an estimate of the third order interference, which reflects the non-linear interference effects.

5. The apparatus of claim 1 , wherein the final set of soft information from the previous outer-loop decoding iteration is generated based on a plurality of inner-loop likelihood metric computation iterations, wherein:

for each inner-loop likelihood metric computation iteration (except for a first iteration), the likelihood metric computing processor is configured to generate an updated set of soft information based on a set of soft information of a previous inner-loop likelihood metric computation iteration; and

the final set of soft information is based on the updated set of soft information generated by the likelihood metric computing processor as a result of a final inner-loop likelihood metric computation iteration.

6. The apparatus of claim 5 , wherein the receiver further comprises:

a decoder configured to decode, for each inner-loop likelihood metric computation iteration, the updated set of soft information generated by the likelihood metric computing processor;

wherein the final set of soft information is based on the decoded information generated by the decoder as a result of the final inner-loop likelihood metric computation iteration.

7. The apparatus of claim 6 , wherein the receiver further comprises:

a deinterleaver configured to deinterleave, for each inner-loop likelihood metric computation iteration, the updated set of soft information generated by the likelihood metric computing processor prior to being decoded by the decoder; and

an interleaver configured to interleave, for each inner-loop likelihood metric computation iteration, the decoded information generated by the decoder to generate the set of soft information of the previous inner-loop likelihood metric computation iteration;

wherein the final set of soft information is comprised of the interleaved information generated by the interleaver as a result of the final inner-loop likelihood metric computation iteration.

8. The apparatus of claim 7 , wherein the receiver further comprises:

a mapping processor configured to bit-to-symbol map the final set of soft information;

a filter configured to process the bit-to-symbol mapped information generated by the mapping processor to generate the previous estimate of the linear and non-linear interference effects; and

an arithmetic processor configured to generate the current estimate of the one or more source symbols by subtracting the previous estimate of the linear and non-linear interference effects generated by the filter from the received signal.

9. The apparatus of claim 8 , wherein the filter comprises a Volterra filter configured to generate the estimate of the linear and non-linear interference effects, wherein the Volterra filter comprises:

a first order component configured to generate an estimate of the first order interference, which reflects the linear interference effects; and

a third order component configured to generate an estimate of the third order interference, which reflects the non-linear interference effects.

10. The apparatus of claim 9 , wherein the likelihood metric computing processor comprises a log-likelihood ratio (LLR) processor, and the set of soft information of the current outer-loop decoding iteration comprises a set of extrinsic log-likelihood ratios (LLRs), generated by the LLR computation module based on the current estimate of the one or more source symbols, and a set of extrinsic LLRs from the previous outer-loop decoding iteration.

11. A method comprising:

processing a signal received over a non-linear wireless channel, wherein the received signal reflects a source signal comprising a plurality of source symbols, and includes linear and non-linear interference effects induced based on a faster-than-Nyquist (FTN) signaling rate applied to the source signal and high-power amplification and filtering of a transponder for transmission over the non-linear wireless channel;

wherein the processing of the received signal comprises estimating the plurality of source symbols of the received signal based on a plurality of outer-loop decoding iterations, wherein a current outer-loop decoding iteration is employed to at least determine an improved estimate of one or more of the plurality of source symbols based on a set of soft information of the current outer-loop decoding iteration, and the improved estimate of the one or more of the plurality of source symbols is fed to a next outer-loop decoding iteration to further improve the estimate of the one or more of the plurality of source symbols, and

wherein the estimation of the plurality of source symbols of the received signal comprises generating the set of soft information of the current outer-loop decoding iteration based on a current estimate of one or more of the source symbols and a final set of soft information from a previous outer-loop decoding iteration; and

wherein the current estimate of the one or more source symbols is based on a previous estimate of the linear and non-linear interference effects exhibited by the received signal, which is based on the final set of soft information from the previous outer-loop decoding iteration.

12. The method of claim 11 , wherein the set of soft information of the current outer-loop decoding iteration comprises a set of extrinsic log-likelihood ratios (LLRs), generated based on the current estimate of the one or more source symbols, and a set of extrinsic LLRs from the previous outer-loop decoding iteration.

13. The method of claim 11 , wherein the processing of the received signal further comprises:

bit-to-symbol mapping the final set of soft information from the previous outer-loop decoding iteration;

filtering the bit-to-symbol mapped information to generate the previous estimate of the linear and non-linear interference effects; and

generating the current estimate of the one or more source symbols by subtracting the previous estimate of the linear and non-linear interference effects from the received signal.

14. The method of claim 13 , wherein the filtering of the bit-to-symbol mapped information is based on a Volterra filter model configured to generate the estimate of the linear and non-linear interference effects, wherein the Volterra filter model comprises:

a first order component configured to generate an estimate of the first order interference, which reflects the linear interference effects; and

a third order component configured to generate an estimate of the third order interference, which reflects the non-linear interference effects.

15. The method of claim 11 , wherein the final set of soft information from the previous outer-loop decoding iteration is generated based on a plurality of inner-loop likelihood metric computation iterations, wherein:

for each inner-loop likelihood metric computation iteration (except for a first iteration), an updated set of soft information is generated based on a set of soft information of a previous inner-loop likelihood metric computation iteration; and

the final set of soft information is based on the updated set of soft information generated as a result of a final inner-loop likelihood metric computation iteration.

16. The method of claim 15 , wherein the processing of the received signal further comprises:

decoding, for each inner-loop likelihood metric computation iteration, the updated set of soft information;

wherein the final set of soft information is based on the decoded information generated as a result of the final inner-loop likelihood metric computation iteration.

17. The method of claim 16 , wherein the processing of the received signal further comprises:

deinterleaving, for each inner-loop likelihood metric computation iteration, the updated set of soft information prior to the decoding; and

interleaving, for each inner-loop likelihood metric computation iteration, the decoded information to generate the set of soft information of the previous inner-loop likelihood metric computation iteration; and

wherein the final set of soft information is comprised of the interleaved information generated as a result of the final inner-loop likelihood metric computation iteration.

18. The method of claim 17 , wherein the processing of the received signal further comprises:

bit-to-symbol mapping the final set of soft information;

filtering the bit-to-symbol mapped information to generate the previous estimate of the linear and non-linear interference effects; and

generating the current estimate of the one or more source symbols by subtracting the previous estimate of the linear and non-linear interference effects from the received signal.

19. The method of claim 18 , wherein the filtering of the bit-to-symbol mapped information is based on a Volterra filter model configured to generate the estimate of the linear and non-linear interference effects, wherein the Volterra filter model comprises:

a first order component configured to generate an estimate of the first order interference, which reflects the linear interference effects; and

a third order component configured to generate an estimate of the third order interference, which reflects the non-linear interference effects.

20. The method of claim 19 , wherein the set of soft information of the current outer-loop decoding iteration comprises a set of extrinsic log-likelihood ratios (LLRs), generated based on the current estimate of the one or more source symbols, and a set of extrinsic LLRs from the previous outer-loop decoding iteration.