T. H. Liew

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

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

Space-time codes and concatenated channel codes for wireless communications

Following a brief historical perspective on channel coding, an introduction to space-time block codes is given. The various space-time codes considered are then concatenated with a range of channel codecs, such as convolutional and block-based turbo codes as well as conventional and turbo trellis codes. The associated estimated complexity issues and memory requirements are also considered. These discussions are followed by a performance study of various space-time and channel-coded transceivers. Our aim is first to identify a space-time code/channel code combination constituting a good engineering tradeoff in terms of its effective throughput, bit-error-rate performance, and estimated complexity. Specifically, the issue of bit-to-symbol mapping is addressed in the context of convolutional codes (CCs) and convolutional coding as well as Bose-Chaudhuri-Hocquenghem coding-based turbo codes in conjunction with an attractive unity-rate space-time code and multilevel modulation is detailed. It is concluded that over the nondispersive or narrow-band fading channels, the best performance versus complexity tradeoff is constituted by Alamoutis twin-antenna block space-time code concatenated with turbo convolutional codes. Further comparisons with space-time trellis codes result in similar conclusions.

Adaptive redundant residue number system coded multicarrier modulation

The novel class of nonbinary maximum minimum distance redundant residue number system (RRNS) codes is invoked in the context of adaptively RRNS coded, symbol-by-symbol adaptive multicarrier modulation, in order to combat the effects of frequency-selective fading inflicted by dispersive wide-band channels. The systems performance can be adjusted in order to maintain a given target bit error rate (BER) and bit per symbol (BPS) performance. The proposed adaptive RRNS scheme outperforms the convolutional constituent code based turbo coded benchmarker system for channel signal-to-noise ratios (SNR) in excess of about 15 dB at a target BER of 10/sup -4/.

Space-time block coded adaptive modulation aided OFDM

Space-time block codes provide substantial diversity advantages for multiple transmit antenna systems at a low decoding complexity. We investigate the achievable diversity advantages in the context of adaptive modulation aided turbo coded OFDM. The two-transmitter, one-receiver G/sub 2/ block space-time coded scheme using no channel coding or gradually increasing rate turbo coding strikes the best trade-off in terms of its overall performance and complexity. Adaptive OFDM performs impressively, when the extra complexity of space-time coding is not affordable, but no adaptive modulation is necessary in conjunction with the more complex multiple transmit and receive antenna associated scenario.

Comparative study of space time block codes and various concatenated turbo coding schemes

Space-time block codes provide substantial diversity advantages in multiple transmit antenna assisted systems at a low decoding complexity. In this contribution, we concatenate space-time codes with three turbo coding schemes, namely turbo BCH (TBCH) codes, turbo convolutional (TC) codes and turbo trellis coded modulation (TTCM) schemes for the sake of achieving significant coding gain. The issues of mapping coded bits of the TBCH and TC schemes to different protection classes of various multilevel modulation schemes is also addressed. Finally, the performance and associated complexity of the three turbo schemes is compared.

Space-time trellis and space-time block coding versus adaptive Modulation and coding aided OFDM for wideband channels

The achievable performance of channel coded space-time trellis (STT) codes and space-time block (STB) codes transmitted over wideband channels is studied in the context of schemes having an effective throughput of 2 bits/symbol (BPS) and 3 BPS. At high implementational complexities, the best performance was typically provided by Alamoutis unity-rate G/sub 2/ code in both the 2-BPS and 3-BPS scenarios. However, if a low complexity implementation is sought, the 3-BPS 8PSK space-time trellis code outperforms the G/sub 2/ code. The G/sub 2/ space-time block code is also combined with symbol-by-symbol adaptive orthogonal frequency division multiplex (AOFDM) modems and turbo convolutional channel codecs for enhancing the systems performance. It was concluded that upon exploiting the diversity effect of the G/sub 2/ space-time block code, the channel-induced fading effects are mitigated, and therefore, the benefits of adaptive modulation erode. In other words, once the time- and frequency-domain fades of the wideband channel have been counteracted by the diversity-aided G/sub 2/ code, the benefits of adaptive modulation erode, and hence, it is sufficient to employ fixed-mode modems. Therefore, the low-complexity approach of mitigating the effects of fading can be viewed as employing a single-transmitter, single-receiver-based AOFDM modem. By contrast, it is sufficient to employ fixed-mode OFDM modems when the added complexity of a two-transmitter G/sub 2/ scheme is affordable.

Comparative study of TCM, TTCM, BICM and BICM-ID schemes

Coded modulation is a bandwidth efficient scheme that combines the functions of coding and modulation. A comparative study of trellis coded modulation (TCM), turbo trellis coded modulation (TTCM), bit-interleaved coded modulation (BICM) and iterative decoding assisted BICM (BICM-ID) schemes over Gaussian and uncorrelated narrowband Rayleigh fading channels is presented in the context of 8-level phase shift keying (8PSK), 16-level quadrature amplitude modulation (16QAM) and 64QAM. We study comparatively the associated decoding complexity, block length and bandwidth efficiency. It is shown that TTCM constitutes the best compromise scheme, followed by BICM-ID.

Soft-decision redundant residue number system based error correction coding

Soft-decision-based redundant residue number system (RRNS)-assisted error control coding is proposed and its performance is evaluated. An RRNS(n,k) code is a maximum-minimum distance block code, exhibiting identical distance properties to Reed-Solomon (RS) codes. Hence their error correction capability is given by t=(n-k)/2. Different bit mapping methods are proposed, which result in systematic and non-systematic RRNS encoders. We show that the classic Chase algorithm can be invoked, in order to contrive soft-decision detection for RRNS codes and to exploit the soft channel outputs, which provide the relative reliability of each of the received binary digits. We found that soft decision-based RRNS decoding is at least 1.5 dB better compared to hard decision-assisted RRNS decoding.

Concatenated space-time block codes and TCM, turbo TCM, convolutional as well as turbo codes

Space-time block codes provide substantial diversity advantages for multiple transmit antenna systems at a low decoding complexity. We concatenate space-time codes with convolutional codes (CC), turbo convolutional codes (TC), turbo BCH codes (TBCH), trellis coded modulation (TCM) and turbo trellis coded modulation (TTCM) schemes for achieving a high coding gain. The associated performance and complexity of the the coding schemes is compared.

LDPC and turbo coding assisted space-time block coded OFDM

Space-time block coded OFDM is capable of achieving substantial diversity gains, while supporting high bit-rates in wireless communications. By concatenating a space-time block coded OFDM scheme with powerful channel codes, the performance of the system can be further enhanced. In this contribution both low-density parity-check (LDPC) coding and turbo coding assisted G/sub 2/ space-time block coded OFDM is investigated. The achievable performance is studied as a function of the number of iterations, coding delay, code rate and decoding complexity.