ADAPTIVE TRELLIS-CODED MULTIPLE-PHASE-SHIFT KEYING FOR RAYLEIGH FADING CHANNELS

An adaptive scheme for trellis-coded modulation of MPSK signals, calle d adaptive trellis-coded multiple-phase-shift keying (ATCMPSK), is pro posed for slowly Rayleigh fading channels. The adaptive scheme employs a slightly modified rate 1/2 convolutional encoder and the correspond ing Viterbi decoder to realize a family of codes of different rates wh ich are employed according to channel conditions. During poor channel conditions, trellis-coded QPSK (TCQPSK) together with repetition schem es are employed. As channel conditions improve, higher rate schemes su ch as trellis-coded 16 PSK are used. An interleaving/deinterleaving me thod suitable for the adaptive scheme is proposed. Theoretical bounds for the error performance and an exact expression for the throughput o f the proposed adaptive scheme are derived, and are compared against s imulation results. Simulations have been performed to measure the perf ormance of the scheme for different parameters and some nonideal condi tions. It is shown that ATCMPSK results in considerable improvement in bit-error-rate (BER) performance of MPSK signals. Under ideal conditi ons, gains in the range of 3-20 dB are achieved over conventional fixe d rate pragmatic trellis-coded schemes.