Low Density Parity Check Code Designs For Distributed Joint Source-Channel Coding Over Multiple Access Channels PDF Download

Author: Iqbal Shahid
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Source Coding -- Joint Source and Channel Coding -- LDPC Code Design -- Multi-user Communication.

Author:
Publisher:
ISBN: 9780542720390
Category : Code generators
Languages : en
Pages :

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Random-like codes with iterative decoding, also referred to as turbo-like codes, have been shown to provide near optimal performance for error control over noisy channels. Low-density parity check (LDPC) codes and parallel concatenated convolutional (turbo) codes are by far the two most well-known turbo-like coding schemes. This dissertation is dedicated to a new code family, Low Density Generator Matrix codes (LDGM codes), investigating its applications in source, channel, and joint-source-channel coding of single and multiple users. The first problem that naturally arises is the use of LDGM codes for error control coding of single users. This dissertation shows that it is possible to design LDGM codes with performance comparable to that of state-of-the-art LDPC and turbo codes with lower computational complexity. A typical engineering approach is followed in this study: first a practical solution is proposed, and then it is analyzed and optimized. Specifically, the density evolution technique is adopted for the analysis and optimization of two types of designs in order to drive the performance. This work then focuses on the use of LDGM codes for distributed coding of multiple correlated users, considering the cases of source and joint source-channel coding. This problem is far from resolved, and plays a critical role in many important applications, such as sensor networks and emerging techniques in video compression. In the case of pure source coding (data compression), hidden Markov models (HMM's) are utilized to define the correlation between sources, which provides a good approximation for the real-world data. The HMM has to be exploited at the decoder site in order to optimize performance. When channel noise is present, two types of scenarios are considered: separated channels between each source and the common receiver and multi-access schemes. In the former case, where separation between source and channel coding is optimum, the resulting performance is close to that limit. For the case of multiple-access channels, separation between source and channel coding does not lead to the optimum performance, since the correlation between the users should not be destroyed in the coding procedure. However, no practical schemes have been able to outperform this bound until now; the proposed scheme is shown to provide reliable communications even with signal-to-noise-ratios below the separation limit. The use of LDGM in this context is critical, since thanks to them the codewords of the different users keep a high degree of correlation. (Abstract shortened by UMI.).

Author: Shuang Wang
Publisher: John Wiley & Sons
ISBN: 1118705971
Category : Science
Languages : en
Pages : 384

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Book Description
Distributed source coding is one of the key enablers for efficient cooperative communication. The potential applications range from wireless sensor networks, ad-hoc networks, and surveillance networks, to robust low-complexity video coding, stereo/Multiview video coding, HDTV, hyper-spectral and multispectral imaging, and biometrics. The book is divided into three sections: theory, algorithms, and applications. Part one covers the background of information theory with an emphasis on DSC; part two discusses designs of algorithmic solutions for DSC problems, covering the three most important DSC problems: Slepian-Wolf, Wyner-Ziv, and MT source coding; and part three is dedicated to a variety of potential DSC applications. Key features: Clear explanation of distributed source coding theory and algorithms including both lossless and lossy designs. Rich applications of distributed source coding, which covers multimedia communication and data security applications. Self-contained content for beginners from basic information theory to practical code implementation. The book provides fundamental knowledge for engineers and computer scientists to access the topic of distributed source coding. It is also suitable for senior undergraduate and first year graduate students in electrical engineering; computer engineering; signal processing; image/video processing; and information theory and communications.

Author: Souvik Dihidar
Publisher:
ISBN: 9781109870688
Category :
Languages : en
Pages : 98

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In Chapter 1, we give an introduction to some conventional Cryptographic protocols. Chapter 2 discusses the BB84 protocol in Quantum key Cryptography. The problem of constructing codes for wiretap channels is considered in Chapter 3. Chapter 4 deals with the problem of congestion localization in networks. Chapter 5 summarizes our work in the problem of localizing link failures in networks.

Author: Andrea Goldsmith
Publisher: Cambridge University Press
ISBN: 9780521837163
Category : Computers
Languages : en
Pages : 676

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Book Description
A comprehensive introduction to the basic principles, design techniques and analytical tools of wireless communications.

Author:
Publisher:
ISBN:
Category : Computers
Languages : en
Pages : 630

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Author: Debarnab Mitra
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Channel coding theory offers advanced mathematical techniques that have proven to be highly effective at improving the reliability of traditional communication systems such as wireless communication, storage in memories, and many more. However, modern data driven applications such as blockchains and quantum communications encounter a new set of challenges resulting in new metrics of concerns, e.g., storage requirements, communication costs, security, data rates, etc., compared to traditional systems. These new metrics necessitate new and specialized channel code designs to improve the performance of these systems. In this dissertation, we aim to mitigate the challenges encountered in certain widely used data-driven applications viz. blockchains and quantum communications by designing specialized channel codes that are tailor-made for each specific application. The first line of the dissertation is focused on specialized Low-Density Parity-Check (LDPC) code design to mitigate challenges present in blockchain systems. These systems are known to suffer from a security vulnerability known as Data Availability (DA) Attacks where system users accept an invalid block with unavailable portions. Existing work focused on utilizing random LDPC codes and 2D Reed-Solomon (2D-RS) codes to mitigate DA attacks. Although effective, these codes are not necessarily optimal for this application, especially for blockchains with small block sizes. For these types of blockchains, we propose a co-design of specialized LDPC codes and code word sampling strategies to result in good system performance in terms of DA detection probability and communication cost. We devise our co-design techniques to tackle adversaries of varying strengths and demonstrate that they result in a higher probability of detection of DA attacks and lower communication cost compared to approaches in earlier literature. The second line of the dissertation is focused on specialized polar code design to mitigate DA attacks in blockchains with large block sizes. Previously used 2D-RS codes and LDPC codes are difficult to apply to blockchains with large block sizes due to their large decoding complexity and coding fraud proof size (2D-RS codes), and intractable code guarantees for large code lengths (LDPC codes). To mitigate DA attacks in blockchains with large block sizes, we propose a novel data structure called Graph Coded Merkle Tree (GCMT): a Merkle tree encoded using the encoding graph of polar codes. Additionally, we propose a specialized polar code design algorithm for the GCMT. We demonstrate that the GCMTbuild using the above specialized polar codes simultaneously performs well in the various performance metrics relevant to DA attacks at large block sizes including DA detection probability, communication cost, tractable code guarantees, and decoding complexity. The third line of the dissertation is focused on an important application in quantum communication known as Quantum Key Distribution (QKD). QKD aims to provide private keys to multiple users at a large key generation rate. LDPC codes have been previously utilized to extract private keys in QKD. However, the existing LDPC codes do not fully utilize the properties of the QKD channel to optimize the key rates. In this dissertation, we propose novel and specialized channel coding techniques to result in high key generation rates in QKD systems. Firstly, we propose a joint code rate and LDPC code design algorithm that is tailored to use the properties of the QKD channel for high key rates. Secondly, we propose an interleaved decoding algorithm to extract the private key from raw quantum data. We demonstrate that the above techniques significantly improve the private key generation rate in QKD systems compared to approaches in earlier literature.

Author: Osso Vahabzadeh
Publisher:
ISBN:
Category : Coding theory
Languages : en
Pages : 110

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Book Description
In this dissertation, we address code design problem for cooperative communication over different channel models with emphasis on low complexity designs and structured codes that are attractive for practical implementation. We start with the problem of designing efficient codes for the relay node in Gaussian relay channels. For a class of capacity approaching codes for this channel model, called bilayer lengthened LDPC (BL-LDPC) codes, we calculate a measure of decoding complexity as a function of the number of decoding iterations and propose a technique to design complexity-optimized BL-LDPC codes by minimizing the complexity measure of these codes. This is made possible by generalizing the EXIT charts to the case of BL-LDPC codes. Motivated by the fact that there are usually stricter hardware restrictions at the relay node, our technique targets minimizing the decoding complexity of the relay code. Furthermore, excessive delay due to decoding high rate codes at the relay results in additional delay at the destination. Using our technique, we design bilayer codes with noticeable reduction in decoding complexity and delay compared to the rate-optimized codes reported in the literature. Next, we study the achievable rates for the decode-and-forward (DF) relaying strategy for the Rayleigh fading relay channel where the links have independent normalized Rayleigh fading coefficients and the channel side information is perfectly known at the corresponding receivers but not at the transmitters. We design BL-LDPC codes for this scenario for the case when the source-relay link is much stronger than the source-destination link as well as for the case when these two links have comparable SNRs. We also propose a novel two-user cooperation scheme for the block fading channel model that employs protograph-based LDPC codes. The proposed scenario is based on time division where each user transmits its message to the base station (BS) in two successive frames. Cooperation is performed by employing the Alamouti scheme Whenever it is possible. Additionally, the users encode their information over protograph-based LDPC codes that allow flexible selection of rates and code lengths. Finally, we introduce rate-compatible protograph-based root LDPC (RCPB-R-LDPC) codes for cooperative communication over block fading channels and propose two methods to construct these codes. The proposed techniques are based on the extension technique and offer broad design rates resulting in high flexibility. Furthermore, they are based on protograph constructions with minimum distance growing linearly with the block length, a property that improves the error floor performance of the designed codes. The outage probability limit under BPSK modulation is obtained for the cooperative scheme employed in this work and was used to evaluate the WER performance of the designed codes.

Author:
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ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 946

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Author: Chung-Li Wang
Publisher:
ISBN: 9781124223643
Category :
Languages : en
Pages :

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Book Description
Low-density parity-check (LDPC) codes are currently the most promising coding technique to achieve the Shannon capacities for a wide range of channels. These codes were first discovered by Gallager in 1962 and then rediscovered in late 1990's. Ever since their rediscovery, a great deal of research effort has been expended in design, construction, encoding, decoding, performance analysis, generalizations, and applications of LDPC codes. This research is set up to investigate two major aspects of LDPC codes: weight distributions and code constructions. The research focus of the first part is to analyze the asymptotic weight distributions of various ensembles. Analysis shows that for generalized LDPC (G-LDPC) and doubly generalized LDPC (DG-LDPC) code ensembles with some conditions, the average minimum distance grows linearly with the code length. This implies that both ensembles contain good codes. The effect of changing the component codes of the ensemble on the minimum distance is clarified. The computation of asymptotic weight and stopping set enumerators is improved. Furthermore, the average weight distribution of a multi-edge type code ensemble is investigated to obtain its upper and lower bounds. Based on them, the growth rate of the number of codewords is defined. For the growth rate of codewords with small linear, logarithmic, and constant weights, the approximations are given with two critical coefficients. It is shown that for infinite code length, the properties of the weight distribution are determined by its asymptotic growth rate. The second part of the research emphasizes specific designs and constructions of LDPC codes that not only perform well but can also be efficiently encoded. One such construction is the serial concatenation of an LDPC outer code and an accumulator with an interleaver. Such construction gives a code called an LDPCA code. The study shows that well designed LDPCA codes perform just as well as the regular LDPC codes. It also shows that the asymptotic minimum distance of regular LDPCA codes grows linearly with the code length.