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23
Interleaver design for turbo codes
- IEEE J. Select. Areas Commun
, 2001
"... The performance of a Turbo code with short block length depends critically on the interleaver design. There are two major criteria in the design of an interleaver: the distance spectrum of the code and the correlation between the information input data and the soft output of each decoder correspondi ..."
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The performance of a Turbo code with short block length depends critically on the interleaver design. There are two major criteria in the design of an interleaver: the distance spectrum of the code and the correlation between the information input data and the soft output of each decoder corresponding to its parity bits. This paper describes a new interleaver design for Turbo codes with short block length based on these two criteria. A deterministic interleaver suitable for Turbo codes is also described. Simulation results compare the new interleaver design to different existing interleavers. 1
Upper Bound on the Minimum Distance of Turbo Codes Using a Combinatorial Approach
- IEEE Transactions on Communications
, 2000
"... By using combinatorial considerations, we derive new upper bounds on the minimum Hamming distance, which Turbo codes can maximally attain with arbitrary -- including the best -- interleavers. The new bounds prove that by contrast to general linear binary channel codes, the minimum Hamming distance o ..."
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Cited by 27 (1 self)
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By using combinatorial considerations, we derive new upper bounds on the minimum Hamming distance, which Turbo codes can maximally attain with arbitrary -- including the best -- interleavers. The new bounds prove that by contrast to general linear binary channel codes, the minimum Hamming distance of Turbo codes cannot asymptotically grow stronger than the third root of the codeword length.
A code-matched interleaver design for turbo codes
- IEEE Trans. on Communications
, 2002
"... Abstract—A code-matched interleaver design for turbo codes in which a particular interleaver is constructed to match the code weight distribution is proposed. The design method is based on the code distance spectrum. The low weight paths in the code trellis which give large contributions to the erro ..."
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Cited by 13 (0 self)
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Abstract—A code-matched interleaver design for turbo codes in which a particular interleaver is constructed to match the code weight distribution is proposed. The design method is based on the code distance spectrum. The low weight paths in the code trellis which give large contributions to the error probability in the signal-to-noise ratio region of interest for practical communication systems are eliminated so that they do not appear in the overall code trellis after interleaving. The proposed interleaver improves the code error performance at moderate to high signal-to-noise ratio and considerably increases the asymptotic slope of the error probability curves. Index Terms—Distance spectrum, interleaver design, relative contribution integral, turbo codes. I.
Maximum A Posteriori Decoding Algorithms For Turbo Codes
"... The symbol-by-symbol maximum a posteriori (MAP) known also as BCJR algorithm is described. The logarithmic versions of the MAP algorithm, namely, Log-MAP and Max-Log-MAP decoding algorithms along with a new Simplified-Log-MAP algorithm, are presented here. Their bit error rate (BER) performance and ..."
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The symbol-by-symbol maximum a posteriori (MAP) known also as BCJR algorithm is described. The logarithmic versions of the MAP algorithm, namely, Log-MAP and Max-Log-MAP decoding algorithms along with a new Simplified-Log-MAP algorithm, are presented here. Their bit error rate (BER) performance and computational cornplexity of these algorithms are compared. A new hardware architecture for implementing the MAP-based decoding algorithms suitable for chip design is also presented here.
Near-capacity turbo trellis coded modulation design
- in Vehicular Technology Conference, 2007. VTC-2007 Fall. 2007 IEEE 66th
, 2007
"... Abstract — Bandwidth efficient parallel-concatenated Turbo Trellis Coded Modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of In-phase (I) and ..."
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Abstract — Bandwidth efficient parallel-concatenated Turbo Trellis Coded Modulation (TTCM) schemes were designed for communicating over uncorrelated Rayleigh fading channels. A symbol-based union bound was derived for analysing the error floor of the proposed TTCM schemes. A pair of In-phase (I) and Quadrature-phase (Q) interleavers were employed for interleaving the I and Q components of the TTCM coded symbols, in order to attain an increased diversity gain. The decoding convergence of the IQ-TTCM schemes was analysed using symbol-based EXtrinsic Information Transfer (EXIT) charts. The best TTCM component codes were selected with the aid of both the symbol-based union bound and non-binary EXIT charts for the sake of designing capacity-approaching IQ-TTCM schemes in the context of 8PSK, 16QAM and 32QAM signal sets. It will be shown that our TTCM design is capable of approaching the channel capacity within 0.5 dB at a throughput of 4 bit/s/Hz, when communicating over uncorrelated Rayleigh fading channels using 32QAM. I.
Interleaving and termination in unpunctured symmetric turbo codes
- IEE Proceedings on Communications
, 2002
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Asymptotic Effect of Interleaver Structure on the Performance of Turbo-codes
, 2002
"... This work studies the effect of the interleaver optimization on the performance of Turbocodes for large block lengths, N # #. ..."
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This work studies the effect of the interleaver optimization on the performance of Turbocodes for large block lengths, N # #.
Optimised Turbo Codes for Wireless Channels This thesis is submitted in partial
, 2001
"... Error control codes have become a vital part of modern digital wireless systems, enabling reliable transmission to be achieved over noisy and fading channels. Over the past decade, turbo codes have been widely considered to be the most powerful error control code of practical importance. In the same ..."
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Error control codes have become a vital part of modern digital wireless systems, enabling reliable transmission to be achieved over noisy and fading channels. Over the past decade, turbo codes have been widely considered to be the most powerful error control code of practical importance. In the same time-scale, mixed voice/data networks have advanced further and the concept of global wireless networks, integrating satellite and terrestrial links, has emerged. Such networks present the challenge of optimising error control codes for different channel types, and for the different qualities of service demanded by voice and data. This thesis begins with an investigation of the optimisation of binary turbo codes through good interleaver design. An analysis is made of what makes a good interleaver, and a novel interleaver design is proposed. The design is a hybrid between random and deterministic designs and will be shown to exhibit a very low error floor; comparable with the best interleavers investigated here. The design, however, has simpler implementation than the other interleavers. A search is then made for bandwidth-efficient code schemes which produce good performance over both AWGN and Rayleigh channels. The search focusses on a technique called Multi-level Coded
Iterative Decoding and Channel Estimation over Hidden Markov Fading Channels
, 2000
"... Since the 1950s, hidden Markov models (HMMS) have seen widespread use in electrical en-gineering. Foremost has been their use in speech processing, pattern recognition, artificial intelligence, queuing theory, and communications theory. However, recent years have wit-nessed a renaissance in the appl ..."
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Since the 1950s, hidden Markov models (HMMS) have seen widespread use in electrical en-gineering. Foremost has been their use in speech processing, pattern recognition, artificial intelligence, queuing theory, and communications theory. However, recent years have wit-nessed a renaissance in the application of HMMs to the analysis and simulation of digital communication systems. Typical applications have included signal estimation, frequency tracking, equalization, burst error characterization, and transmit power control. Of special significance to this thesis, however, has been the use of HMMs to model fading channels typical of wireless communications. This variegated use of HMMs is fueled by their ability to model time-varying systems with memory, their ability to yield closed form solutions to otherwise intractable analytic problems, and their ability to help facilitate simple hardware and/or software based implementations of simulation test-beds. The aim of this thesis is to employ and exploit hidden Markov fading models within an iterative (turbo) decoding framework. Of particular importance is the problem of channel estimation, which is vital for realizing the large coding gains inherent in turbo coded schemes. This thesis shows that a Markov fading channel (MFC) can be conceptualized as a trellis, and that the transmission of a sequence over a MFC can be viewed as a trellis encoding process much like convolutional encoding. The thesis demonstrates that either maximum likelihood sequence estimation (MLSE) algorithms or maximum a posteriori (MAP) algo-rithms operating over the trellis defined by the MFC can be used for channel estimation. Furthermore, the thesis illustrates sequential and decision-directed techniques for using the aforementioned trellis based channel estimators en masse with an iterative decoder.
