On a Class of Constant Envelope Continuous Phase Modulation Schemes, Obtained by Imposing Continuous Phase Transitions on Trellis Coded Asymetric Psk

The problem of how to construct information carrying continuous phase functions, which yield power and bandwidth efficient schemes, is addressed. The additive white Gaussian noise channel and coherent maximum likelihood sequence detection are assumed. Our approach is to use trellis coded asymmetric PSK schemes of low complexity and with good distance properties. Consecutive phase values of the phase sequences generated by these schemes are interconnected by a continuous function. Thus, a continuous phase function is obtained. In conventional full response CPM, the Euclidean distance is bounded by an error event two symbols long. The continuous phase schemes obtained here, have a shift-register state trellis structure. This guarantees long error events, thus the schemes have a potential for large Euclidean distances related to the number of states in the trellis. There are schemes within the class with power and bandwidth efficiencies (d/sup 2/sub min/ versus 99% bandwidth) which are very good, considering the low complexity of the schemes. They are, in fact, competitive with and sometimes better than, some of the best coded continuous phase modulated schemes, of comparable complexity, previously published.