Trellis-coded phase/frequency modulation with equal usage of signal dimensions

A trellis-coded modulation scheme, using a coded 2-FSK (frequency shift keyed)/2^m-PSK (phase shift keyed) modulation format instead of a conventional coded 2^m+1-PSK format for m-b/symbol data transmission, is considered. Previous work on coded 2-FSK/2^m-PSK modulation techniques featured two transmission frequencies equally often. In contrast, the method presented here selects the signal points in such a manner that each of the signal dimensions is used equally. The asymptotic coding gains of the proposed method are compared to those of the previous schemes, and an upper bound to the bit-error probability is calculated. The spectral characteristics of the proposed coded modulation scheme are also studied in relation to those of the coded 2^m+1 PSK format and to other coded 2-FSK/2^m-PSK formats. It is shown that the new scheme obtains higher coding gains, sometimes (but not always) at the expense of an increased bandwidth