| 摘要 |
A trellis coded modulation system comprises a source of successive 2-bit data symbols X1, X2 arranged in a frame format wherein each frame comprises a plurality of data segments each including a plurality of groups of interleaved data symbols. Each group of interleaved data symbols is separately coded by a precoder and convolution encoder to derive coded output symbols Z0, Z1, Z2, which are mapped to respective 8-level symbols for transmission together with periodically generated frame and segment sync symbols. The received signal may be filtered by a linear filter, e.g. a comb filter, to reduce co-channel interference and each group of filtered symbols is applied to a respective first Viterbi decoder for estimating data bits X1 X2. Each first decoder preferably comprises a reduced complexity Viterbi decoder responsive to a partial representation of the state of the linear filter. Each group of received symbols may also be directly applied to a respective second Viterbi decoder for estimating data bits X1 X2. Estimated data bits X1 X2 from the first or second decoders are selected for further processing. |
