Covering the full range of channel codes from the most conventional through to the most advanced, the second edition of Turbo Coding, Turbo Equalisation and Space-Time Coding is a self-contained reference on channel coding for wireless channels. The book commences with a historical perspective on the topic, which leads to two basic component codes, convolutional and block codes. It then moves on to turbo codes which exploit iterative decoding by using algorithms, such as the Maximum-A-Posteriori (MAP), Log-MAP and Soft Output Viterbi Algorithm (SOVA), comparing their performance. It also compares Trellis Coded Modulation (TCM), Turbo Trellis Coded Modulation (TTCM), Bit-Interleaved Coded Modulation (BICM) and Iterative BICM (BICM-ID) under various channel conditions.The horizon of the content is then extended to incorporate topics which have found their way into diverse standard systems. These include space-time block and trellis codes, as well as other Multiple-Input Multiple-Output (MIMO) schemes and near-instantaneously Adaptive Quadrature Amplitude Modulation (AQAM). The book also elaborates on turbo equalisation by providing a detailed portrayal of recent advances in partial response modulation schemes using diverse channel codes.A radically new aspect for this second edition is the discussion of multi-level coding and sphere-packing schemes, Extrinsic Information Transfer (EXIT) charts, as well as an introduction to the family of Generalized Low Density Parity Check codes.This new edition includes recent advances in near-capacity turbo-transceivers as well as new sections on multi-level coding schemes and of Generalized Low Density Parity Check codesComparatively studies diverse channel coded and turbo detected systems to give all-inclusive information for researchers, engineers and students Details EXIT-chart based irregular transceiver designs Uses rich performance comparisons as well as diverse near-capacity design examples

Turbo Coding, Turbo Equalisation and Space-Time Coding: EXIT-Chart-Aided Near-Capacity Designs for Wireless Channels

Near-capacity performance may be achieved with the aid of iterative decoding, where extrinsic soft information is exchanged between the constituent decoders in order to improve the attainable system performance. Extrinsic Information Transfer (EXIT) charts constitute a powerful semi-analytical tool used for analysing and designing iteratively decoded systems. In this tutorial, we commence by providing a rudimentary overview of the iterative decoding principle and the concept of soft information exchange. We then elaborate on the concept of EXIT charts using three iteratively decoded prototype systems as design examples. We conclude by illustrating further applications of EXIT charts, including near-capacity designs, the concept of irregular codes and the design of modulation schemes.

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EXIT Charts for System Design and Analysis

This paper introduces new mappings of QPSK symbols, viewed as a multi-dimensional hypercube, to improve the performance of bit-interleaved coded modulation with iterative decoding (BICM-ID). By evaluating the upper bound of the bit error rate performance of BICM-ID, a condition to find the best mapping of a hypercube constellation in terms of the asymptotic performance under different channel models is established. A general and simple algorithm to construct the best mapping of a hypercube is then proposed. Analytical and simulation results show that the use of the proposed mappings together with very simple convolutional codes can offer significant coding gains over the conventional BICM-ID systems for all the channel models considered. Such coding gains are achieved without bandwidth or power expansion and with a very small increase in the system complexity.

Design and performance of BICM-ID systems with hypercube constellations

We present an overview of embedded network applications and discuss requirements arising from this analysis. Furthermore, we discuss selected in-network processing techniques and point out the analogy between neural and sensor networks. In the following neural networks are introduced in the sensor network context. We describe the motivation and the practical case for neural networks in the sensor networks context, and evaluate early results achieved with our test implementation. We argue that there is a high potential with these paradigms which promise a strong impact on the future research, especially if applied as a hybrid technology.

Neural Wireless Sensor Networks

Low-density parity-check (LDPC) codes are playing more and more important role in digital broadcasting standards due to their excellent error correction performance. In this paper, we study the combination of LDPC codes over GF(q) with q-ary modulations for bandwidth efficient transmission over AWGN channel and consider the design of the codes. Specifically, we develop the concept of quasi-regular codes, and propose an improved Monte Carlo method to optimize the quasi-regular codes. To justify the performance of our proposed scheme, simulation results are presented and analysed.

Combine LDPC Codes Over GF(q) With q-ary Modulations for Bandwidth Efficient Transmission

A method for the prediction of bit-error rates (BER) of bit-interleaved coded modulation systems with iterative decoding (BICM-ID) is presented, which is based solely upon the extrinsic information transfer (EXIT) chart and avoids extensive BER simulations. Comparisons show an accurate prediction, even for low BERs down to 10/sup -6/. Furthermore, an easy procedure to obtain the optimum rotation angle for a signal constellation set in conjunction with IQ Interleaving is described. Both methods can be applied to all types of channels.

BER prediction using EXIT charts for BICM with iterative decoding

Bit-interleaved coded modulation with iterative decoding (BICM-ID) is a transmission scheme with excellent performance on fading channels. The mapping of the bit patterns to the elements of the signal constellation set (SCS) is the key design element of BICM-ID, especially regarding the asymptotic performance of the BER. We demonstrate that SCSes of PSK (phase shift keying) with optimum bit pattern assignment are significantly superior in the asymptotic error-floor region to the respective square QAM (quadrature amplitude modulation) SCSes. When modifying the PSK SCSes to non-regular SCSes, performance gains of more than 1 dB are realizable in the case of 4 bits-per-channel symbols. The achievable gains are theoretically determined and analyzed, and verified by simulations.

PSK versus QAM for iterative decoding of bit-interleaved coded modulation

We propose the application of iterative demodulation at a DVB-S2 receiver. The demodulation is improved by feedback of extrinsic information from the decoder of the LDPC channel code. The presented simulation results show an enhancement of about 0.3 dB, which is notable taking the gap to the Shannon limit into account. The additionally required computational demand is negligible and the receiver only needs to be slightly modified. With the unmodified transmitter the proposed scheme is completely standard compliant

Iterative demodulation for DVB-S2

A cost function for the optimization of mappings for bit-interleaved coded modulation systems with iterative decoding (BICM-ID) for a Rayleigh channel with applied IQ interleaving is derived. For this channel model the optimum mapping depends on the channel quality and on the rotation of the signal constellation set. Simulation results reveal that mappings optimized with the new cost function yield a better performance than previously known mappings. Furthermore, a second, easy procedure to obtain the optimum rotation angle for a signal constellation set in conjunction with IQ Interleaving is described.

S. Godtmann

Papers

BER prediction using EXIT charts for BICM with iterative decoding

PSK versus QAM for iterative decoding of bit-interleaved coded modulation

Iterative demodulation for DVB-S2

Optimized Mappings for Iteratively Decoded BICM on Rayleigh Channels with Interleaving