Trellis - Coded P hase / Frequency Modulation with Equal Usage of Signal ~ imensionst

A trellis-coded modulation scheme, using a coded 2-FSK/2"-PSK modulation format instead of a conventional coded 2"+'-PSK format for m-bitslsymbol data transmission, is considered. Previous work [I, 21 on coded 2FSK/2"-PSK modulation techniques choose two transmission frequencies equally often. In contrast, our method selects the signal points in such a manner that each of the signal dimensions is used equally. We compare the asymptotic coding gains of the proposed method to those of the previous schemes and calculate an upper bound to the bit-error probability. The spectral characteristics of the proposed coded modulation scheme are also studied vis-a-vis those of the coded 2"+' PSK format and of the other [I, 21 coded 2-FSK/2"-PSK formats. We show that the new scheme obtains higher coding gains, sometimes (but not always) a t the expense of an increased bandwidth.