Design of Rate-compatible Structured Low-density Parity-check Codes - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Design of Rate-compatible Structured Low-density Parity-check Codes write by Jaehong Kim. This book was released on 2006. Design of Rate-compatible Structured Low-density Parity-check Codes available in PDF, EPUB and Kindle. The main objective of our research is to design practical low-density parity-check (LDPC) codes which provide a wide range of code rates in a rate-compatible fashion. To this end, we first propose a rate-compatible puncturing algorithm for LDPC codes at short block lengths (up to several thousand symbols). The proposed algorithm is based on the claim that a punctured LDPC code with a smaller level of recoverability has better performance. The proposed algorithm is verified by comparing performance of intentionally punctured LDPC codes (using the proposed algorithm) with randomly punctured LDPC codes. The intentionally punctured LDPC codes show better bit error rate (BER) performances at practically short block lengths. Even though the proposed puncturing algorithm shows excellent performance, several problems are still remained for our research objective. First, how to design an LDPC code of which structure is well suited for the puncturing algorithm. Second, how to provide a wide range of rates since there is a puncturing limitation with the proposed puncturing algorithm. To attack these problems, we propose a new class of LDPC codes, called efficiently-encodable rate-compatible (E2RC) codes, in which the proposed puncturing algorithm concept is imbedded. The E2RC codes have several strong points. First, the codes can be efficiently encoded. We present low-complexity encoder implementation with shift-register circuits. In addition, we show that a simple erasure decoder can also be used for the linear-time encoding of these codes. Thus, we can share a message-passing decoder for both encoding and decoding in transceiver systems that require an encoder/decoder pair. Second, we show that the non-systematic parts of the parity-check matrix are cycle-free, which ensures good code characteristics. Finally, the E2RC codes having a systematic rate-compatible puncturing structure show better puncturing performance than any other LDPC codes in all ranges of code rates.
Design of Capacity-approaching Protograph-based LDPC Coding Systems
Design of Capacity-approaching Protograph-based LDPC Coding Systems - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Design of Capacity-approaching Protograph-based LDPC Coding Systems write by Thuy Van Nguyen. This book was released on 2012. Design of Capacity-approaching Protograph-based LDPC Coding Systems available in PDF, EPUB and Kindle. In this dissertation, a systematic framework is proposed to design practical protograph-based low-density parity check (LDPC) coding schemes that address simultaneously several important issues: structured coding that permits easy design, low encoding complexity, embedded structure for convenient adaptation to various channel conditions, and performance close to capacity with a reasonable block length. This dissertation consists of four closely inter-related parts. In the first part, the design of rate-compatible protograph codes for the hybrid automatic repeat request protocol is presented. A high-performance family of protograph codes that has the iterative decoding threshold within a gap of a fraction of dB to capacity in the AWGN channel over a wide range of rates is reported. In the second part, protograph-based LDPC coding schemes are designed for half-duplex relay channels. A simple new methodology for evaluating the end-to-end error performance of relay coding systems is then developed and used to highlight the performance of the proposed codes. In the third part, a general mapping method is devised for using protograph-based LDPC codes in bit-interleaved coded modulation. The reported coding scheme operates close to the coded modulation capacity. In the fourth part, the design of rate-compatible protograph codes in inter-symbol interference channels is proposed. The design problem is non-trivial due to the joint design of structured LDPC codes and the state structure of ISI channels using the BCJR equalizer. High-performance protograph-based LDPC codes that have iterative thresholds close to i.u.d capacity of ISI channels are reported.
Efficient Low-density Parity-check Codes for Cooperative Communication
Efficient Low-density Parity-check Codes for Cooperative Communication - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Efficient Low-density Parity-check Codes for Cooperative Communication write by Osso Vahabzadeh. This book was released on 2014. Efficient Low-density Parity-check Codes for Cooperative Communication available in PDF, EPUB and Kindle. 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.
Efficient Design and Decoding of the Rate-compatible Low-density Parity-check Codes
Efficient Design and Decoding of the Rate-compatible Low-density Parity-check Codes - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Efficient Design and Decoding of the Rate-compatible Low-density Parity-check Codes write by . This book was released on . Efficient Design and Decoding of the Rate-compatible Low-density Parity-check Codes available in PDF, EPUB and Kindle. HKUST Call Number: Thesis ECED 2009 WuXX.
Low-density Parity-check Codes with Erasures and Puncturing
Low-density Parity-check Codes with Erasures and Puncturing - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Low-density Parity-check Codes with Erasures and Puncturing write by Jeongseok Ha Ha. This book was released on 2003. Low-density Parity-check Codes with Erasures and Puncturing available in PDF, EPUB and Kindle. In this thesis, we extend applications of Low-Density Parity-Check (LDPC) codes to a combination of constituent sub-channels, which is a mixture of Gaussian channels with erasures. This model, for example, represents a common channel in magnetic recordings where thermal asperities in the system are detected and represented at the decoder as erasures. Although this channel is practically useful, we cannot find any previous work that evaluates performance of LDPC codes over this channel. We are also interested in practical issues such as designing robust LDPC codes for the mixture channel and predicting performance variations due to erasure patterns (random and burst), and finite block lengths. On time varying channels, a common error control strategy is to adapt the coding rate according to available channel state information (CSI). An effective way to realize this coding strategy is to use a single code and puncture it in a rate-compatible fashion, a so-called rate-compatible punctured code (RCPC). We are interested in the existence of good puncturing patterns for rate-changes that minimize performance loss. We show the existence of good puncturing patterns with analysis and verify the results with simulations. Universality of a channel code across a broad range of coding rates is a theoretically interesting topic. We are interested in the possibility of using the puncturing technique proposed in this thesis for designing universal LDPC codes. We also consider how to design high rate LDPC codes by puncturing low rate LDPC codes. The new design method can take advantage of longer effect block lengths, sparser parity-check matrices, and larger minimum distances of low rate LDPC codes.
