Soft-decision receiver and decoder for digital communication
AssigneeMitsubishi Denki Kabushiki Kaisha
InventorTakayuki Nagayasu
Life of this patent
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Abstract
A receiver for soft decision and decoding for deriving an appropriate soft-decision value so as to reduce the error rate at the output of a decoder such as a Viterbi decoder. A length V of transmission sequences that can be generated is set greater than a memory length L of a channel (V>L). By providing as many as 2N (N=2.sup.V) branch metric producing circuits and as many as N add/compare/select apparatus (ACS apparatus) for respective states corresponding to combinations of transmission sequence data of V, the accuracy of a soft-decision value is enhanced. Further, a soft-decision value producing circuit performs a process not based on path metrics but based on survivor metrics. This allows a digital signal processor to easily perform the process.
Claims20
A receiver for receiving encoded data signals via a channel causing intersymbol interference, wherein transmission conditions of the received signals correspond to different states;
- transitions from certain states to next states correspond to branch metrics as indices of said transitions;
- path metrics based on said branch metrics are derived as indices of paths through adjacent states, said paths representing transitions of a received encoded data sequence;
- a soft decision is performed on said received signals by selecting portions of said paths as current survivor states based on said path metrics;
- and decoding is performed using a result of said soft decision, said receiver comprising:
- a soft-decision device for deriving from said branch metrics survivor metrics corresponding to said current survivor states, said soft-decision device classifying said survivor metrics according to the values of prior survivor states corresponding to prior states leading to said current survivor states so as to derive a soft-decision value based on all of said classified survivor metrics;
- and
- a decoding circuit for performing decoding based on said soft-decision value.
A receiver for receiving encoded data signals via a channel causing intersymbol interference, wherein transmission conditions of the received signals correspond to different states;
- transitions from certain states to next states correspond to branch metrics as indices of said transitions;
- path metrics based on said branch metrics are derived as indices of paths through adjacent states, said paths representing transitions of a received encoded data sequence;
- a soft decision is performed on said received signals by selecting portions of said paths as current survivor states based on said path metrics;
- and decoding is performed using a result of said soft decision, said receiver comprising:
- a soft-decision device which increases the number of said states by setting a data sequence length of the received signals corresponding to said states to be greater than a memory length of the channel, said soft decision device deriving said path metrics per state, determining for each state a current survivor path metric, corresponding to a current survivor path, based on said path metrics per state, classifying said current survivor path metrics according to the values of prior survivor states forming part of said current survivor paths so as to derive a soft-decision value based on all of said classified current survivor path metrics;
- and
- a decoding circuit for performing decoding based on said soft-decision value.
Dependencies are inferred from the claim text.