| 摘要 |
An apparatus and method decode information signals which have been encoded using a tailbiting error-correction codeword. The method generally includes the steps of initializing a number of decoder states corresponding to all possible starting states of the encoder to have equal associated likelihood metrics. The metrics are updated to reflect a likelihood metric for each of the decoder states given the received information signals. Further information signals, representative of further coded symbols, are received and a decoder state having the highest associated likelihood metric is extended by updating the likelihood metric to produce new likelihood metrics for each possible hypothesized extended decoded information symbol, given the further received information signals. An assumed value for the extended decoder information symbol is appended to the symbol history for the extended decoder state. The method continues to receive further information signals and to extend the decoder state having the highest likelihood metric by hypothesizing additional information symbols to produce extended decoder states until a last information symbol coded in the tailbiting codeword has been hypothesized. Final metrics are computed for each of the corresponding extended decoder states and if one of the final metrics is indicative of the highest likelihood metric, then the symbol history of the associated decoder state is used as the decoded information.
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