A modified design of trellis-coded MPSK for the fading channel

Abstruct-Multiple trellis-coded modulation (MTCM) of MPSK employs separate designs, which are optimum at high SNR, for the Rayleigh fading channel and the AWGN channel, in order to meet the different design criteria for the two channels. The separate designs are no longer optimum if the channel conditions are interchanged, if the channel is Rician, or if the SNR’s are moderate. In this paper, a modified design MTCM (MD) is considered, wherein it is shown that the classical AWGN channel design can be retained for the Rician fading channel (which is Rayleigh and AWGN at the extremes) with any degree of fading, by choosing an appropriate signal set of size Mmin. The signal set size Mmin depends on the throughput rate and the number of parallel transitions between a given pair of states. For a given throughput rate and signal diversity, the proposed MTCM (MD) schemes achieve a higher value of &(free) and the same or higher value of branch distance product when compared to existing MTCM schemes designed for the Rayleigh fading channel. The improved performance ensuing on the Rician fading channel is demonstrated by asymptotic coding gains with respect to existing MTCM schemes and simulation results for some of the codes. The effect of phase errors due to fading on the MTCM (MD) schemes which have increased signal set size in some cases is also studied by simulation.