Three-Dimensional EXIT Chart Analysis of Iterative Detection Aided Coded Modulation Schemes

The iterative convergence of iteratively detected coded modulation schemes having different block lengths, decoding complexity and an unequal error protection capability is studied, when communicating over AWGNchannels using 8PSK modulation. More specifically, the coded modulation schemes investigated include Multilevel Coding (MLC), Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) as well as Bit-Interleaved Coded Modulation employing Iterative Decoding (BICM-ID). A novel three dimensional EXIT chart was introduced for studying the iterative convergence behaviour of the Multistage Decoding (MSD) scheme used in MLC

Bit-interleaved coded modulation

The principle of coding in the signal space follows directly from Shannon’s analysis of waveform Gaussian channels subject to an input constraint. The early design of communication systems focused separately on modulation, and error correcting codes. Bit-interleaved coded modulation (BICM) is a pragmatic approach combining the best out of both worlds: it takes advantage of the signal-space coding perspective, whilst allowing for the use of powerful families of binary codes with virtually any modulation format. As matter of fact, has established itself as a quasi-standard (de-facto) for bandwidth - and power - efficient communication, like DSL, wireless LANs, WiMax. The aim of this thesis is to describe the main aspects of the system, focusing the attention on model characteristics and on the error analysis (based on bit-error rate approximations). Finally I also consider the BICM with iterative decoding and I conclude with an overview of some applications of BIC

Bit-interleaved coded modulation in the wideband regime

The wideband regime of bit-interleaved coded modulation (BICM) in Gaussian channels is studied. The Taylor expansion of the coded modulation capacity for generic signal constellations at low signal-to-noise ratio (SNR) is derived and used to determine the corresponding expansion for the BICM capacity. Simple formulas for the minimum energy per bit and the wideband slope are given. BICM is found to be suboptimal in the sense that its minimum energy per bit can be larger than the corresponding value for coded modulation schemes. The minimum energy per bit using standard Gray mapping on M-PAM or M^2-QAM is given by a simple formula and shown to approach -0.34 dB as M increases. Using the low SNR expansion, a general trade-off between power and bandwidth in the wideband regime is used to show how a power loss can be traded off against a bandwidth gain.Comment: Submitted to IEEE Transactions on Information Theor

On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation

Two decoder structures for coded modulation over the Gaussian and flat fading channels are studied: the maximum likelihood symbol-wise decoder, and the (suboptimal) bit-wise decoder based on the bit-interleaved coded modulation paradigm. We consider a 16-ary quadrature amplitude constellation labeled by a Gray labeling. It is shown that the asymptotic loss in terms of pairwise error probability, for any two codewords caused by the bit-wise decoder, is bounded by 1.25 dB. The analysis also shows that for the Gaussian channel the asymptotic loss is zero for a wide range of linear codes, including all rate-1/2 convolutional codes

TCM, TTCM, BICM and Iterative BICM Assisted OFDM-based Digital Video Broadcasting to Mobile Receivers

In this contribution, the performance of trellis coded modulation (TCM), bit-interleaved coded modulation (BICM), BICM with iterative decoding (BICM-ID) and turbo trellis coded modulation (TTCM) is studied in comparison to the pan-European terrestrial Digital Video Broadcasting (DVB) system. The decoding complexity and bandwidth efficiency trade-offs of the various systems under study are quantified