Method and system for corrupt symbol handling for providing high reliability sequences
For corrupt symbol handling for providing high reliability sequences, an inter-symbol correlated (ISC) signal is received. During sequence estimation when demodulating the received ISC signal, partial response samples in the ISC may be processed utilizing an erasure mechanism. The partial response samples are spread (e.g. interleaved) over time during modulation by a modulator. A determination is made as to whether to utilize self erasure or external erasure to process the spread partial response samples. The determination may be based on whether or not events of low SNR for corresponding ones of the partial response samples are identified. The external erasure may be utilized for processing the corresponding ones of the partial response samples when the events of low SNR are identified and the self erasure is utilized when the events of low SNR are not identifiable. Erasure results maybe fed back to the modulator.
1. A method, comprising:
in a receiver:
receiving a sample of a signal;
determining, prior to calculating any branch metric values for said sample, whether low-signal-to-noise ratio events for said sample of said signal are detectable for said sample;
in instances that low-signal-to-noise ratio events for said signal are detectable prior to calculating any branch metric values for said sample, configuring said receiver to use external erasure for demodulating said sample;
in instances that low-signal-to-noise ratio events for said signal are not detectable for said sample prior to calculating any branch metric values for said sample, configuring said receiver to use self erasure for demodulating said sample; and
demodulating said sample.
2. The method of claim 1 , wherein, when said receiver is configured to use external erasure, said demodulating said sample comprises:
determining, prior to calculating any branch metric values for said sample, a signal-to-noise ratio of said sample;
in instances that said signal-to-noise ratio of said sample is above a threshold, calculating a branch metric value for said sample based on said sample;
in instances that said signal-to-noise ratio of said sample is below said threshold, setting said branch metric value for said sample to a predetermined value.
3. The method of claim 2 , wherein said predetermined value is zero.
4. The method of claim 2 , wherein, in said instances that said signal-to-noise ratio of said sample is below said threshold, said demodulating comprises determining whether to generate an indication of an error event based on signal-to-noise ratio of each of one or more other samples of said signal.
5. The method of claim 2 , wherein, in said instances that said signal-to-noise ratio of said sample is below said threshold, said demodulating comprises determining whether to generate an indication of an error event based on signal-to-noise ratio of each of one or more other samples of said signal.
6. A system comprising:
a receiver comprising an erasure circuit, wherein said receiver is operable to:
receive a plurality of samples of a signal;
demodulate a first one or more of said samples using said erasure circuit configured for external erasure; and
demodulate a second one or more of said samples using said erasure circuit configured for self erasure, wherein, when said erasure circuit is configured for external erasure, demodulation of said first one or more of said samples by said receiver comprises:
determination of a signal-to-noise ratio of said first one or more of said samples prior to calculating any branch metric values for said first one or more of said samples;
in instances that said signal-to-noise ratio of said first one or more of said samples is above a threshold, calculation of a branch metric value for said first one or more of said samples based on said first one or more of said samples;
in instances that said signal-to-noise ratio of said first one or more of said samples is below said threshold, setting of said branch metric value for said first one or more of said samples to a predetermined value.
7. The system of claim 6 , wherein, in said instances that said signal-to-noise ratio of said first one or more of said samples is below said threshold, said demodulation of said first one or more of said samples comprises a determination of whether to generate an indication of an error event based on a signal-to-noise ratio of each of one or more other samples of said signal.
8. A system comprising:
a receiver comprising an erasure circuit, wherein said receiver is operable to:
receive a plurality of samples of a signal;
demodulate a first one or more of said samples using said erasure circuit configured for external erasure; and
demodulate a second one or more of said samples using said erasure circuit configured for self erasure, wherein, when said erasure circuit is configured for self erasure, demodulation of a second one or more of said samples by said receiver comprises:
calculation of a branch metric value for said second one or more of said samples based on said second one or more of said samples;
determination of a signal-to-noise ratio for said second one or more of said samples based on said calculated branch metric value for said second one or more of said samples;
in instances that said signal-to-noise ratio is above a threshold, use of said calculated branch metric value for survivor selection; and
in instances that said signal-to-noise ratio is below said threshold, discarding of said branch metric value.
9. The system of claim 8 , wherein, in said instances that said signal-to-noise ratio is below said threshold, said demodulation of said second one or more of said samples comprises a determination of whether to generate an indication of an error event based on signal-to-noise ratio of each of one or more other samples of said signal.
10. A system, comprising:
a receiver comprising erasure circuitry and sequence estimation circuitry,
wherein said receiver is operable to:
receive a sample of a signal;
determine, prior to any calculation of branch metric values for said sample by said sequence estimation circuitry, whether low-signal-to-noise ratio events for said sample of said signal are detectable for said sample;
in instances that low-signal-to-noise ratio events for said signal are detectable prior to calculation of any branch metric values for said sample, configure said erasure circuitry to use external erasure for demodulation of said sample;
in instances that low-signal-to-noise ratio events for said signal are not detectable for said sample prior to any calculation of branch metric values for said sample, configure said erasure circuitry to use self erasure for demodulation of said sample; and
demodulate said sample.
11. The system of claim 10 , wherein, when said erasure circuitry is configured to use external erasure:
said receiver is operable to determine, prior to any calculation of branch metric values for said sample by said sequence estimation circuitry, a signal-to-noise ratio of said sample; and
said sequence estimation circuitry is operable to:
in instances that said signal-to-noise ratio of said sample is above a threshold, calculate a branch metric value for said sample based on said sample; and
in instances that said signal-to-noise ratio of said sample is below said threshold, set said branch metric value for said sample to a predetermined value.
12. The system of claim 11 , wherein said predetermined value is zero.
13. The system of claim 11 , wherein, in said instances that said signal-to-noise ratio of said sample is below said threshold, said receiver is operable to determine whether to generate an indication of an error event based on a signal-to-noise ratio of each of one or more other samples of said signal.
14. The system of claim 10 , wherein said receiver comprises an equalization circuit and said determination of whether low-signal-to-noise ratio events for said sample of said signal are detectable for said sample is based on whether said equalizer can detect said low-signal-to-noise ratio events for said sample.