On Construction of Bit-Interleaved Coded Modulation Systems with Iterative Decoding

A new construction of Bit-Interleaved Coded Modulation systems with Iterative Decoding (BICM-ID) is proposed to achieve the best performance over white additive Gaussian noise (AWGN) channels, assuming that the ideal feedback (IF) holds for iterative decoding. For a class of so-called regular IF mappings, new upper bounds for error probabilities are presented for both cases of BICM-ID systems using overall and in-line interleaving. Search results for component Recursive Systematic Convolutional (RSC) codes with and without puncturing are reported for 4-PSK and 8-PSK signal sets

Replacing the Soft FEC Limit Paradigm in the Design of Optical Communication Systems

The FEC limit paradigm is the prevalent practice for designing optical communication systems to attain a certain bit-error rate (BER) without forward error correction (FEC). This practice assumes that there is an FEC code that will reduce the BER after decoding to the desired level. In this paper, we challenge this practice and show that the concept of a channel-independent FEC limit is invalid for soft-decision bit-wise decoding. It is shown that for low code rates and high order modulation formats, the use of the soft FEC limit paradigm can underestimate the spectral efficiencies by up to 20%. A better predictor for the BER after decoding is the generalized mutual information, which is shown to give consistent post-FEC BER predictions across different channel conditions and modulation formats. Extensive optical full-field simulations and experiments are carried out in both the linear and nonlinear transmission regimes to confirm the theoretical analysis

Space-time coding techniques with bit-interleaved coded modulations for MIMO block-fading channels

The space-time bit-interleaved coded modulation (ST-BICM) is an efficient technique to obtain high diversity and coding gain on a block-fading MIMO channel. Its maximum-likelihood (ML) performance is computed under ideal interleaving conditions, which enables a global optimization taking into account channel coding. Thanks to a diversity upperbound derived from the Singleton bound, an appropriate choice of the time dimension of the space-time coding is possible, which maximizes diversity while minimizing complexity. Based on the analysis, an optimized interleaver and a set of linear precoders, called dispersive nucleo algebraic (DNA) precoders are proposed. The proposed precoders have good performance with respect to the state of the art and exist for any number of transmit antennas and any time dimension. With turbo codes, they exhibit a frame error rate which does not increase with frame length.Comment: Submitted to IEEE Trans. on Information Theory, Submission: January 2006 - First review: June 200

Turbo codes: convergence phenomena & non-binary constructions

The introduction of turbo codes in 1993 provided a code structure that could approach Shannon limit performance whilst remaining practically decodeable. Much subsequent work has focused on this remarkable structure, attempting to explain its performance and to extend or modify it. This thesis builds on this research providing insights into the convergence behaviour of the iterative decoder for turbo codes and examining the potential of turbo codes constructed from non-binary component codes. The first chapter of this thesis gives a brief history of coding theory, providing context for the work. Chapter two explains in detail both the turbo encoding and decoding structures considered. Chapter three presents new work on convergence phenomena observed in the iterative decoding process. These results emphasise the dynamic nature of the decoder and allow for both a stopping criteria and ARQ scheme to be proposed. Chapters four and five present the work on non-binary turbo codes. First the problem of choosing good component codes is discussed and an achievability bound on the dominant parameter affecting their performance is derived. Searches for good component codes over a number of small rings are then conducted, and simulation results presented. The new results, and suggestions for further work are summarised in the conclusion of Chapter six

Labelings and encoders with the uniform bit error property withapplications to serially concatenated trellis codes

The well-known uniform error property for signal constellations and codes is extended to encompass information bits. We introduce a class of binary labelings for signal constellations, called bit geometrically uniform (BGU) labelings, for which the uniform bit error property holds, i.e., the bit error probability does not depend on the transmitted signal. Strong connections between the symmetries of constellations and binary Hamming spaces are involved. For block-coded modulation (BCM) and trellis-coded modulation (TCM) Euclidean-space codes, BGU encoders are introduced and studied. The properties of BGU encoders prove quite useful for the analysis and design of codes aimed at minimizing the bit, rather than symbol, error probability. Applications to the analysis and the design of serially concatenated trellis codes are presented, together with a case study which realizes a spectral efficiency of 2 b/s/Hz