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A decoder of digital data signals for a message sequence of N symbols from a data source, encoded with a tail-biting convolutional code, and for correcting all combinations of up to a preselected number e of bit errors, operates upon the sequentially-received collection of consecutive-encoded tail-b

A decoder of digital data signals for a message sequence of N symbols from a data source, encoded with a tail-biting convolutional code, and for correcting all combinations of up to a preselected number e of bit errors, operates upon the sequentially-received collection of consecutive-encoded tail-biting data symbols and selects an unmerged decision depth LU(e), a forward decision depth LF(e) and then a decoder decision depth L, before executing in a processor of the Viterbi type, which has a decision depth of L trellis levels, a decoding algorithm for a total of (N+LF(e)+LU(e)) trellis stages to produce a decoded data bit output sequence representative of the N transmitted source digital symbols.

대표청구항 ▼

[ What is claimed is:] [1.] A decoder for recovering data from a digital data signal comprising a plurality of N data symbols, each data symbol comprising A encoder output bits generated by a tail-biting trellis encoder in response to an input of B data bits, the decoder comprising:means for receivi

[ What is claimed is:] [1.] A decoder for recovering data from a digital data signal comprising a plurality of N data symbols, each data symbol comprising A encoder output bits generated by a tail-biting trellis encoder in response to an input of B data bits, the decoder comprising:means for receiving a sequence of the N encoded data symbols from a beginning symbol to a final symbol;means for selecting a forward decision depth LF(e) of trellis stages for correcting up to the preselected number e of errors in the bits of the received symbols corresponding to any LF(e) consecutive trellis stages;means for selecting an unmerged decision depth LU(e) of trellis stages for correcting up to the preselected number e of errors in the bits of the received symbols corresponding to any LU(e) consecutive trellis stages;means for selecting a backward decision depth LB(e) of trellis stages for correcting up to the preselected number e of errors in the bits of the received symbols corresponding to any LB(e) consecutive trellis stages;means for selecting a decoder initial processing width W.sub.I (e) responsive to the selected depths LU(e) and LB(e);means for executing a processing algorithm of the Viterbi algorithm type, having a decision depth of L trellis stages, where L is chosen responsive to LF(e), on the received symbols for producing a trellis having a stage corresponding to each processed received symbol, each stage comprising a plurality of possible and permissible state transitions representing, when connected, possible paths through the trellis, the stages being established responsive both to consecutive time periods and to the symbols received during the time periods, the means for executing including means for generating a path metric for the extension of each surviving path in the trellis, the path metric representing a distance measure between the extended path and the received sequence of symbols, the executing means also including means for selecting, at each trellis stage beginning at stage (L+1) and tracing back L levels to reach a node P, a most likely path which is a set of connected state transitions most closely corresponding to symbols received during the interval, the executing means further including means to output the B data bits that label the transition from node P to the node at the following stage on the most likely path as the decoded data bits corresponding to the symbol received from the channel during that period;means for forming an extended sequence of (N+W.sub.I (e)+L) received symbols obtained via a circular indexing of the N received data symbols such that the last (W.sub.I (e)+L) received symbols of the extended sequence are the same as the first (W.sub.I (e)+L) received symbols;means for causing the executing means to sequentially process the (N+W.sub.I (e)+L) received symbols in the extended sequence;means for recording the B decoded data bits outputted by the executing means for each trellis stage, beginning with stage (W.sub.I (e)+L+1), as a result of processing a received symbol; andmeans causing the recording means to operate a total of N times to produce an output sequence of (N*B) decoded data bits.