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

It is shown that the classical additive white Gaussian noise (AWGN) channel design can be retained for the fading channel with any degree of fading, if carried out with the appropriate signal set size M=M_min. The size of the signal set M _min is shown to depend upon the number of parallel transitions between a given pair of states and the throughput rate. In the proposed multiple trellis-coded modulation (MTCM) scheme with a modified design (MTCM (MD)), the output bits from a rate m/m+1 trellis encoder are assigned multiple signals from an M_min-PSK signal set. Compared to the MTCM with set partitioning proposed for the fading channel (SPF) design, the MTCM (MD) scheme provides the same signal diversity and the same or increased values of the branch distance product, and always leads to increased value of d²(free). As a result, the performance is always improved on the Rician fading channel due to the increased d²(free), and is improved on any fading channel when an increase in branch distance produce P takes place. When compared to the MTCM with the set partitioning optimum for the AWGN channel (SPA) design, the MTCM (MD) scheme, under certain conditions, provides the same value of d²(free) as the MTCM (SPA) design, and is then asymptotically optimum for both the AWGN channel and the fading channels