Trellis coded modulation applied to noncoherent detection or orthogonal signals

A method for the design of trellis codes for noncoherent detection of orthogonal signals on additive white Gaussian noise (AWGN) channels is presented. After examining the channel capacity, the authors show that a coding method requiring doubling the dimension of the orthogonal signal space and soft-maximum-likelihood (ML) decoding using the Viterbi algorithm can achieve large coding gains. An example of the coding technique using rate 2/3 binary convolutional codes of increasing constraint length is presented. Also included is a comparison with a nonbinary block code to indicate that trellis coding is superior to conventional algebraic block coding. Simulation results indicate that coding gains of approximately 3.5 dB are possible at 10-dB signal-to-noise ratio with a minimally complex (16-state) Viterbi decoder