Detection and mitigation of temporary impairments in a communications channel
View Patent ↗Systems and methods are disclosed for detecting temporary high level impairments, such as noise or interference, for example, in a communications channel, and subsequently, mitigating the deleterious effects of the dynamic impairments. In one embodiment, the method not only performs dynamic characterization of channel fidelity against impairments, but also uses this dynamic characterization of the channel fidelity to adapt the receiver processing and to affect an improvement in the performance of the receiver. For example, in this embodiment, the method increases the accuracy of the estimation of the transmitted information, or similarly, increases the probability of making the correct estimates of the transmitted information, even in the presence of temporary severe levels of impairment. The channel fidelity history may also be stored and catalogued for use in, for example, future optimization of the transmit waveform.
1. A method of impairment mitigation in a communication system comprising:
generating at least one error estimate of a signal;
determining a channel fidelity metric using the at least one error estimate;
generating a branch metric for a decoder;
modifying the branch metric based on the channel fidelity metric; and
decoding the signal using the modified branch metric.
2. The method of claim 1 wherein the decoder is a Viterbi decoder.
3. The method of claim 1 wherein modifying the branch metric comprises setting the branch metric to a low probability if the fidelity metric indicates a degraded channel.
4. The method of claim 1 wherein the decoder is a Reed-Solomon decoder.
5. The method of claim 1 wherein the decoder is a Turbo decoder.
6. The method of claim 1 wherein the decoder is a Forward Error Correction (FEC) decoder.
7. The method of claim 1 wherein the signal comprises one of at least one digital sample and at least one symbol, further comprising:
storing the channel fidelity metric; and
determining a transmit waveform using the stored fidelity metric.
8. The method of claim 1 wherein the signal comprises one of at least one digital sample and at least one symbol, further comprising:
storing the channel fidelity metric; and
selecting a receiver algorithm using the stored fidelity metric.
9. The method of claim, 1 wherein the signal comprises at least one symbol, and wherein generating at least one error estimate comprises:
determining at least one constellation point closest to the at least one symbol;
determining a distance between the at least one symbol and the at least one constellation point; and
squaring the distance.
10. The method of claim 1 , wherein the signal comprises at least one symbol, and wherein determining a channel fidelity metric comprises:
comparing the at least one error estimate to at least one predetermined threshold.
11. The method of claim 10 further comprising generating a first indication if the at least one error estimate is above the at least one predetermined threshold and a second indication if the at least one error estimate is not above the at least one predetermined threshold.
12. The method of claim 10 comprising keeping a select symbol if the at least one error estimate is below the at least one predetermined threshold, and erasing the select symbol if the at least one error estimate is above the at least one threshold.
13. A method of impairment mitigation in a communications system comprising:
generating at least one error estimate of a signal, wherein the signal comprises a sequence of symbols, and wherein a first portion of the sequence comprises at least one select symbol;
determining a channel fidelity metric using the at least one error estimate;
decoding the signal using the channel fidelity metric;
determining a first error estimate from the sequence of symbols;
determining a second error estimate from a second portion of the sequence of symbols including the at least one select symbol;
determining a third error estimate from a third portion of the sequence of symbols including the at least one select symbol;
comparing the first error estimate to a first predetermined threshold, and the second and third error estimates to a second predetermined threshold; and
erasing at least a portion of the at least one select symbol if the first is above the first predetermined threshold and if the second and third error estimate are above the second predetermined threshold.
14. The method of claim 13 wherein the decoder is a Reed-Solomon decoder.
15. The method of claim 13 wherein the decoder is a Turbo decoder.
16. The method of claim 13 wherein the decoder is a Forward Error Correction (FEC) decoder.
17. A method of impairment mitigation in a communications system comprising:
generating at least one error estimate of a signal received from a channel, wherein the signal comprises a sequence of symbols, and wherein a first portion of the sequence comprises at least one select symbol;
determining if the channel is degraded based on the at least one error estimate;
erasing a select symbol of the signal if the channel is degraded;
decoding the signal;
determining a first error estimate from the sequence of symbols;
determining a second error estimate from a second portion of the sequence of symbols including the at least one select symbol;
determining a third error estimate from a third portion of the sequence of symbols including the at least one select symbol;
comparing the first error estimate to a first predetermined threshold, and the second and third error estimates to a second predetermined threshold;
generating an indication that the channel is degraded if the first error e above the first predetermined threshold and if the second and third error estimates are above the second predetermined threshold.
18. The method of claim 17 wherein the decoder is a Reed-Solomon decoder.
19. The method of claim 17 wherein the decoder is a Turbo decoder.
20. The method of claim 17 wherein the decoder is a Forward Error Correction (FEC) decoder.
21. A method of impairment mitigation in a communications system comprising:
generating at least one error estimate of a signal;
determining a channel fidelity metric using the at least one error estimate;
decoding the signal using the channel fidelity metric;
storing the channel fidelity metric;
determining a transmit waveform using the stored fidelity metric; and
wherein the signal comprises one of at least one digital sample or at least one symbol.
22. The method of claim 21 wherein the decoder is a Reed-Solomon decoder.
23. The method of claim 21 wherein the decoder is a Turbo decoder.
24. The method of claim 21 wherein the decoder is a Forward Error Correction (FEC) decoder.
25. A method of impairment mitigation in a communications system comprising:
generating at least one error estimate of a signal;
determining a channel fidelity metric using the at least one error estimate;
decoding the signal using the channel fidelity metric;
storing the channel fidelity metric;
selecting a receiver algorithm using the stored fidelity metric; and
wherein the signal comprises one of at least one digital sample or at least one symbol.
26. The method of claim 25 wherein the decoder is a Reed-Solomon decoder.
27. The method of claim 25 wherein the decoder is a Turbo decoder.
28. The method of claim 25 wherein the decoder is a Forward Error Correction (FEC) decoder.