Design and analysis of trellis codes for orthogonal signal sets

This paper studies trellis codes to be used with orthogonal signal constellations. The intended application is in direct-sequence code-division multiple-access communication systems. The problem of designing good codes is addressed showing how to construct trellis codes from block codes with good burst-error detecting capabilities. Several examples are given resulting in codes equivalent to those found previously by computer search (Ryan and Wilson, 1991). The procedure presented can be done by hand and is applicable for designing codes with long constraint lengths and large signal sets where a computer search becomes prohibitive. Performance of such coded systems can be determined through transfer functions of the specific codes used. A general transfer function is given which provides a reasonable approximation to the actual transfer function of good codes. Thus, a first-order approximation to the performance of a given system can be determined without actually going through the process of designing and analyzing a specific code.<>