Chapter 10
Iteratively Decoded Variable-Length Space–Time Coded Modulation: Code Construction and Convergence Analysis1
10.1 Introduction
In this chapter an Iteratively Decoded Variable-Length Space–Time Coded Modulation (VL-STCM-ID) scheme capable of simultaneously providing both coding and iteration gain as well as multiplexing and diversity gain is investigated. Non-binary unity-rate precoders are employed in order to assist the iterative decoding of the VL-STCM-ID scheme. The discrete-valued source symbols are first encoded into variable-length codewords that are spread to both the spatial and the temporal domains. Then the variable-length codewords are interleaved and fed to the precoded modulator. More explicitly, the proposed VL-STCM-ID arrangement is a jointly designed iteratively decoded scheme combining source coding, channel coding and modulation as well as spatial diversity/multiplexing. We demonstrate that, as expected, the higher the source correlation, the higher the achievable performance gain of the scheme becomes. Furthermore, the performance of the VL-STCM-ID scheme is about 14 dB better than that of the Fixed-Length STCM (FL-STCM) benchmark at a source symbol error ratio of 10−4.
To elaborate a little further, recall from Chapter 1 that Shannon’s separation theorem stated that source coding and channel coding are best carried out in isolation ...
