CODED MODULATIONS FOR FADING CHANNELS - AN OVERVIEW

It is by now well known that combined channel coding and digital modul ation (in short coded modulation) yield power and bandwidth efficient digital transmission schemes for the Gaussian channel. These schemes p erform closer to channel capacity than those where coding and modulati on are treated separately. More recently, coded modulation methods hav e been investigated for transmission over Rayleigh fading channels. It has been discovered that systems optimized for the Gaussian channel a re not optimum for fading channels. This is primarily due to the impor tance of built-in time diversity of the coded modulation scheme for fa ding channels. In this paper we give a brief overview of recent develo pments in signal design for Rayleigh fading channels. Mainly schemes b ased on phase shift keying are presented. Theoretical guidance for des ign and identification ol the most important system parameters are giv en. A couple of detailed examples of code designs and their error prob ability performance are also given. Optimum and suboptimum receivers a re discussed. An overview of analytical performance analysis tools, as well as code designs for both trellis coded modulation and block code d modulation is included in the paper. Methods for unequal error prote ction are given. Potential application areas are identified. An extens ive reference list is supplied.