DECODING A CONCATENATED CONVOLUTIONAL-ENCODED AND BLOCK ENCODED SIGNAL

摘要

Encoded symbols of a concatenated convolutional-encoded and block encoded signal (21) are presented to a conventional first stage (20) of a concatenated decoder (300), comprising in sequence a soft metric generator (22), a Viterbi decoder (23), a first de-interleaver (25) and a first block decoder such as a Reed-Solomon decoder (26). The encoded symbols (21) are also presented to a delay chain to produce progressively delayed encoded symbols. Where an output block of the conventional decoder (20) is indicated as being a valid codeword by the first block decoder (26), the bytes in this block are marked as being correct. These bytes that are known to be correct are then used after interleaving and serialisation as known bits input to a second stage (30') of the decoder process operating on the delayed encoded symbols (21') and incorporating a modified soft metric generator constrained by the known bits. This process can be extended to further iterations as required. A modified Viterbi decoder, which is also constrained by the known bits, may also be used in the second and subsequent iterative stages.