Performance of punctured trellis coded modulation over fading channels

Punctured convolutional codes allow an easy implementation of variable-rate encoders/decoders and compared to conventional codes of the same rate, the decoding complexity is significantly reduced. The puncturing technique has been applied to trellis-coded modulation, yielding PSK and QAM codes. Most of these codes have a free squared-Euclidean distance which is almost as large as that of the best known Ungerboeck codes. Hence, the advantages provided by the puncturing technique with binary convolutional codes are essentially maintained with trellis-coded modulation over additive white Gaussian noise channels. In this paper, the performance of punctured QAM trellis codes over Rayleigh fading channels is presented. It is shown that compared to Ungerboeck codes, a significant coding gain of several dB can be achieved. We also show that our codes are nearly as good as Du and Vucetic (1991) 16-QAM codes which have been specifically designed for fading channels. Furthermore, they offer more flexibility and are simpler to decode than Du and Vucetic codes