combining bicm with trellis based constellation shaping
In a bandwidth limited channel the constellation shaping can easily provide 1 dB SNR improvement. The conventional view is to handle coding and shaping as two separate operations. Because of that, it is usually difficult to incorporate shaping into decoder structure. In this paper we propose to combine a trellis based constellation shaping and turbo code. We suggest to select the shaping code and the turbo code to have a same trellis structure. The resulting code can be turbo decoded by iterating between the shaping and the channel code. Because the trellises have the same structure we could tap into shaping gain without changing the conventional turbo decoder structure. Accordingly to the simulations the proposed structure provides 0.8 dB gain over the comparable bit interleaved coded modulation (BICM) system. This gain is achieved without the increase of turbo decoder complexity.
constellation shaping turbo decoding high data rate