Coded differential modulations for orthogonal transmit diversity systems

As block based forms of space-time coding, Orthogonal Transmit Diversity (OTD) systems achieve full diversity advantage with simple decoding algorithms. Since OTD systems are block based and consequently have limited time spans, their performance can be further enhanced by combining with channel codes. This thesis considers coded differential modulations for OTD in point-to-point and multipoint-to-point scenarios. In point-to-point scenario, the problems around the single and multi-carrier transmission environments are addressed. In single carrier transmission, trellis coding is applied to the extended time domain of OTD systems. A set of practical decoders are proposed and code design criteria from the analysis of pair-wise error probability are derived both in static and selective channels. Also proposed is a Multiple Trellis Coded Modulation (MTCM) based signal design method that outperforms previously reported coded modulation systems.; In multi-carrier transmission, the trellis and block codings are applied to the frequency domain to collect the diversity from the multi-paths. Combined with OTD, the total diversity gain achieved is the product of spatial and multi-path diversities when the frequency code has the minimum code word Hamming distance greater than or equal to the number of multi-paths. Sub-channel grouping, corresponding to perfect interleaving in time selective channels is adopted to maximize the coding gain. It is shown the combination of time and frequency domain codings enjoys both the time and frequency selectivities in multi-carrier systems.; As a stepping stone for the application of the coded modulations to the multi-point to point scenario in Direct-Sequence Code Division Multiple Access (DS-CDMA) environment, a set of multiuser detection schemes are developed. Multiple Access Interference (MAI) is shown to be effectively suppressed while the spatial diversity is utilized.