Sequence detection device using maximum likelihood sequence detection with programmable branch metric computation reduction and associated sequence detection method
A sequence detection device includes a feed-forward filter, a feedback filter, a combining circuit, a decision circuit, and a sequence detection circuit. The feed-forward filter processes a received signal to generate a first equalized signal. The feedback filter processes a symbol decision signal to generate a second equalized signal. The combining circuit combines the first and second equalized signals to generate a sample signal. The decision circuit performs hard decision upon the sample signal to generate the symbol decision signal. The sequence detection circuit performs sequence detection upon the first equalized signal, and includes a region estimation circuit and a trellis selection circuit. The region estimation circuit is independent of the decision circuit, and categorizes each sample of the sample signal into one region. The trellis selection circuit selects one trellis scheme for branch metric calculation according to region estimation results output from the region estimation circuit.
1 . A sequence detection device comprising:
a feed-forward filter, configured to process a received signal to generate a first equalized signal;
a feedback filter, configured to process a symbol decision signal to generate a second equalized signal;
a combining circuit, configured to combine the first equalized signal and the second equalized signal to generate a sample signal;
a decision circuit, configured to perform hard decision upon the sample signal to generate the symbol decision signal; and
a sequence detection circuit, configured to perform sequence detection upon the first equalized signal to generate and output a symbol sequence, wherein the sequence detection circuit comprises:
a region estimation circuit, independent of the decision circuit and configured to categorize each of a plurality of samples included in the sample signal into one of a plurality of regions; and
a trellis selection circuit, configured to select one of a plurality of trellis schemes for branch metric calculation according to region estimation results of two of the plurality of samples output from the region estimation circuit.
2 . The sequence detection device of claim 1 , wherein the plurality of samples comprise consecutive samples, the consecutive samples comprise a first sample and a second sample following the first sample, the region estimation circuit generates a first region estimation result for the first sample and a second region estimation result for the second sample, and the trellis selection circuit selects a trellis scheme, indexed by the first region estimation result and the second region estimation result, from the plurality of trellis schemes.
3 . The sequence detection device of claim 1 , wherein the sequence detection circuit further comprises:
a control circuit, configured to adjust the plurality of regions adaptively.
4 . The sequence detection device of claim 3 , wherein the plurality of trellis schemes are fixed.
5 . The sequence detection device of claim 3 , wherein the control circuit is further configured to obtain a signal quality indicator, and adaptively adjust a plurality of threshold values according to the signal quality indicator, where the plurality of regions are defined by the plurality of threshold values.
6 . The sequence detection device of claim 1 , wherein the sequence detection circuit further comprises:
a control circuit, configured to adjust the plurality of trellis schemes adaptively.
7 . The sequence detection device of claim 6 , wherein the plurality of regions are fixed.
8 . The sequence detection device of claim 6 , wherein the control circuit is further configured to obtain a signal quality indicator, and adaptively adjust the plurality of trellis schemes according to the signal quality indicator.
9 . The sequence detection device of claim 1 , wherein the received signal is derived from a pulse amplitude modulation (PAM) signal.
10 . The sequence detection device of claim 1 , wherein the received signal is derived from a quadrature amplitude modulation (QAM) signal.
11 . A sequence detection method comprising:
performing a feed-forward filtering operation upon a received signal to generate a first equalized signal;
performing a feedback filtering operation upon a symbol decision signal to generate a second equalized signal;
combining the first equalized signal and the second equalized signal to generate a sample signal;
performing a hard decision operation upon the sample signal to generate the symbol decision signal; and
performing a sequence detection operation upon the first equalized signal to generate and output a symbol sequence, wherein the sequence detection operation comprises:
performing a region estimation operation to categorize each of a plurality of samples included in the sample signal into one of a plurality of regions, wherein the region estimation operation is independent of the hard decision operation; and
performing a trellis selection operation to select one of a plurality of trellis schemes for branch metric calculation according to region estimation results of two of the plurality of samples output from the region estimation operation.
12 . The sequence detection method of claim 11 , wherein the plurality of samples comprise consecutive samples, the consecutive samples comprise a first sample and a second sample following the first sample, the region estimation operation generates a first region estimation result for the first sample and a second region estimation result for the second sample, and the trellis selection operation selects a trellis scheme, indexed by the first region estimation result and the second region estimation result, from the plurality of trellis schemes.
13 . The sequence detection method of claim 11 , wherein the sequence detection operation further comprises:
adjusting the plurality of regions adaptively.
14 . The sequence detection method of claim 13 , wherein the plurality of trellis schemes are fixed.
15 . The sequence detection method of claim 13 , wherein adjusting the plurality of regions adaptively comprises:
obtaining a signal quality indicator; and
adaptively adjusting a plurality of threshold values according to the signal quality indicator, where the plurality of regions are defined by the plurality of threshold values.
16 . The sequence detection method of claim 11 , wherein the sequence detection operation further comprises:
adjusting the plurality of trellis schemes adaptively.
17 . The sequence detection method of claim 16 , wherein the plurality of regions are fixed.
18 . The sequence detection method of claim 16 , wherein adjusting the plurality of trellis schemes adaptively comprises:
obtaining a signal quality indicator; and
adaptively adjusting the plurality of trellis schemes according to the signal quality indicator.
19 . The sequence detection method of claim 11 , wherein the received signal is derived from a pulse amplitude modulation (PAM) signal.
20 . The sequence detection method of claim 11 , wherein the received signal is derived from a quadrature amplitude modulation (QAM) signal.