Mapper and Demapper for LDPC-Coded Systems

Low Density Parity Check (LDPC) codes are state-of-art error correcting codes, included in several standards for broadcast transmissions. Iterative softdecision decoding algorithms for LDPC codes reach excellent error correction capability; their performance, however, is strongly affected by finite-precision issues in the representation of inner variables. Great attention has been paid, in recent literature, to the topic of quantization for LDPC decoders, but mostly focusing on binary modulations and analyzing finite precision effects in a disaggregrated manner, i.e., considering separately each block of the receiver. Modern telecommunication standards, instead, often adopt high order modulation schemes, e.g. M-QAM, with the aim to achieve large spectral efficiency. This puts additional quantization problems, that have been poorly debated in previous literature. This paper discusses the choice of suitable quantization characteristics for both the decoder messages and the received samples in LDPC-coded systems using M-QAM schemes. The analysis involves also the demapper block, that provides initial likelihood values for the decoder, by relating its quantization strategy with that of the decoder. A signal label for a signal in a 2m-ary modulation scheme is simply the m-bit pattern assigned to the signal. A mapping strategy refers to the grouping of bits within a codeword, where each mbit group is used to select a 2m-ary signal in accordance with the signal labels. The most obvious mapping strategy is to use each group of m consecutive bits to select a signal. . We will call this the consecutive-bit (CB) mapping strategy. An alternative strategy is the bit-reliability (BR) mapping strategy which will be described below. A new demapper version, based on approximate expressions, is also presented, that introduces a slight deviation from the ideal case but yields a low complexity hardware implementation

Parallel concatenated convolutional codes from linear systems theory viewpoint

The aim of this work is to characterize two models of concatenated convolutional codes based on the theory of linear systems. The problem we consider can be viewed as the study of composite linear system from the classical control theory or as the interconnection from the behavioral system viewpoint. In this paper we provide an input–state–output representation of both models and introduce some conditions for such representations to be both controllable and observable. We also introduce a lower bound on their free distances and the column distances

Turbo codes and turbo algorithms

In the first part of this paper, several basic ideas that prompted the coming of turbo codes are commented on. We then present some personal points of view on the main advances obtained in past years on turbo coding and decoding such as the circular trellis termination of recursive systematic convolutional codes and double-binary turbo codes associated with Max-Log-MAP decoding. A novel evaluation method, called genieinitialised iterative processing (GIIP), is introduced to assess the error performance of iterative processing. We show that using GIIP produces a result that can be viewed as a lower bound of the maximum likelihood iterative decoding and detection performance. Finally, two wireless communication systems are presented to illustrate recent applications of the turbo principle, the first one being multiple-input/multiple-output channel iterative detection and the second one multi-carrier modulation with linear precoding

전송효율 향상을 위한 MIMO-FTN 전송기법 연구

차세대 무선통신에서는 높은 전송률을 가지는 통신 깁버을 요구한다. 하지만 대역폭이 제한적이기 때문에 전송률을 높이기 위한 많은 방안들이 연구되어지고 있지만 전송률과 성능은 trade-off 관계이기에 전송률을 향상시킴에 따라 성능은 저하시키기 때문에 성능을 최대한 유지하면서 높은 전송률을 갖는 전송기법들이 대두되고 있다. DVB-S2 기반 위성 통신에서는 전송률 향상을 위한 많은 방안들 중에 가장 대표적인 복호 속도를 개선시켜 전송률을 향상시키는 방안은 이미 연구가 포화상태에 있다. 이에 본 논문에서는 전송률을 향상시키는 여러 가지 방법 중 Nyquist 속도보다 빠르게 신호를 전송하여 전송률을 향상시키는 기법인 FTN 기법과 두 개 이상의 송수신 안테나를 사용하여 전송률을 높이는 MIMO 깁버을 사용하여 MIMO-FTN 송수신구조를 제안한다.제 1 장 : 서론 제 2 장 : 무선통신에서 전송률 향상을 위한 기법 2.1 FTN 기법 2.2 High-Order Modulation 기법 2.3 MIMO 기법 2.4 MIMO-FTN 연접 기법 제 3 장 : SISO채널에서의 FTN 적용 기법 3.1 채널 부호화 기법 3.1 터보 부호 기반의 FTN 복호기 구조 제 4 장 : MIMO-FTN의 최적 송수신기법 제안 4.1 FTN 기법을 적용한 계층적 시공간 복호 구조 제안 4.2 FTN 기법을 적용한 ZF 복호 구조 제안 제 5 장 : 시뮬레이션 및 성능분석 제 6 장 : 결론Maste

Turbo codes with rate-m/(M+1) constituent convolutional codes

International audienceThe original turbo codes (TCs), presented in 1993 by Berrou et al., consist of the parallel concatenation of two rate-1/2 binary recursive systematic convolutional (RSC) codes. This paper explains how replacing rate-1/2 binary component codes by rate-m/(m + 1) binary RSC codes can lead to better global performance. The encoding scheme can be designed so that decoding can be achieved closer to the theoretical limit, while showing better performance in the region of low error rates. These results are illustrated with some examples based on double-binary (m = 2) 8-state and 16-state TCs, easily adaptable to a large range of data block sizes and coding rates. The double-binary 8-state code has already been adopted in several telecommunication standards

Double binary turbo codes analysis and decoder implementation

Ankara : The Department of Electrical and Electronics Engineering and the Institute of Engineering and Sciences of Bilkent University, 2008.Thesis (Master's) -- Bilkent University, 2008.Includes bibliographical references leaves 60-61.Classical Turbo Code presented in 1993 by Berrau et al. received great attention due to its near Shannon Limit decoding performance. Double Binary Circular Turbo Code is an improvement on Classical Turbo Code and widely used in today’s communication standards, such as IEEE 802.16 (WIMAX) and DVBRSC. Compared to Classical Turbo Codes, DB-CTC has better error-correcting capability but more computational complexity for the decoder scheme. In this work, various methods, offered to decrease the computational complexity and memory requirements of DB-CTC decoder in the literature, are analyzed to find the optimum solution for the FPGA implementation of the decoder. IEEE 802.16 standard is taken into account for all simulations presented in this work and different simulations are performed according to the specifications given in the standard. An efficient DB-CTC decoder is implemented on an FPGA board and compared with other implementations in the literature.Yılmaz, ÖzlemM.S

An Iterative Coded Turbo Equalization Model in High Data Rate Wireless Application System

In next-generation wireless communication and 5G-based mobile communication, error-free communication with high transmission efficiency and reliability in a limited bandwidth is required along with diverse services. Highly reliable communication is difficult with wireless communication systems due to surrounding environment, movement of transmitters and receivers, and various noises. Channel coding technology should be applied to overcome these problems. In addition, an algorithm that can overcome the loss of transmission efficiency caused by the application of channel coding technology should be applied. However, since there is a trade-off relationship between improved transmission rates and performance, it is difficult to satisfy both. Thus, recently, methods to improve both transmission rates and performance simultaneously are being studied. Accordingly, this dissertation proposes a channel coded turbo equalization model that enables improved performance in a high transmission wireless communication system with improved transmission efficiency. The topic of this dissertation can be largely divided into two aspects: performance improvement and high transmission efficiency. First, a turbo equalization model combined with iterative codes for performance improvement in a wireless communication system was investigated, and a soft decision-based iterative coding schemes such as the convolutional code-based BCJR, turbo codes and LDPC codes were introduced. Subsequently, the performance of these coding schemes was comparatively analyzed. The BER performance analysis through the simulation showed that the LDPC code was approximately 1.2 [dB] at BER , which was the closest to the Shannon's channel capacity limit. In addition, the LDPC coding method was suggested as a channel coding scheme suitable for high-speed wireless communication by comparatively analyzing the characteristics of each coding scheme for complexity, decoding speed and performance. Second, the algorithm that achieved high transmission efficiency was investigated. Conventional high-transmission efficiency algorithms such as punctured, FTN and MIMO algorithms were introduced, and these three were comparatively analyzed from the perspective of the same transmission rate. In addition, MIMO-FTN and P-FTN algorithms, which combined each of the punctured and MIMO algorithms with the FTN algorithm to maximize the transmission efficiency, were proposed. The performances of the proposed algorithms were analyzed through the simulation from the perspective of the same transmission rate, and the W-ZF based MIMO-FTN algorithm was found to be the best. However, the performance degradation due to the application of FTN occurred, and subsequently, a turbo equalization model of FTN signals based UEP was proposed to overcome this problem. The UEP scheme was applied to the MIMO-FTN algorithm to maximize the improvement in transmission rates, and the UEP-FTN transmission scheme applying the OFDM scheme in multi-path channels was proposed. The performance of the proposed UEP-based FTN transmission scheme was analyzed through simulation, which showed that the application of the UEP scheme led to the improved performance. Based on this study, a turbo equalization model to achieve the performance improvement and high transmission efficiency was proposed. In addition, not limiting its usage only in the surface wireless communication but expanding its scope to underwater acoustic communication, the way to apply the model to underwater acoustic communication was investigated. Based on the decoded data and the turbo equalization-based UEP-FTN model that improved the transmission efficiency and performance in underwater acoustic communication, a method to calibrate the frequency and phase of the following packet was proposed. Its efficiency was verified through the actual underwater experiment at Gyeongcheon Lake in Mungyeong-si, Geyongsangbuk-do. The results of the experiment showed that the proposed method worked efficiently.제 1 장 서론 1 제 2 장 직렬 연접된 반복 부호화 결합 된 터보 등화 모델 5 2.1 터보 등화 모델 5 2.2 터보 등화 모델과 결합된 반복 부호화 기법 11 2.2.1 BCJR 13 2.2.2 터보 부호 16 2.2.3 LDPC 부호 22 2.2.3.1 DVB-S2 기반 LDPC 부호(Long size) 23 2.2.3.2 IEEE 802.11n 기반 LDPC 부호(Short size) 29 2.2.4 고속 무선 통신을 위한 최적 부호화 기법 34 제 3 장 고전송 효율 알고리즘 37 3.1 기존 고전송 효율 알고리즘 38 3.1.1 Punctured 알고리즘 38 3.1.2 FTN 알고리즘 41 3.1.3 MIMO 알고리즘 48 3.1.3.1 시공간 부호화 기반 MIMO 알고리즘 50 3.1.3.2 ZF 기반 MIMO 알고리즘 54 3.1.4 기존 고전송 효율 알고리즘 전송률 분석 56 3.2 FTN과 결합한 고전송 효율 알고리즘 및 터보 등화 모델 제안 58 3.2.1 FTN 신호에 대한 터보 등화 모델 58 3.2.2 P-FTN 터보 등화 모델 59 3.2.3 MIMO-FTN 터보 등화 모델 62 3.2.3.1 W-ZF를 이용한 채널 분리 알고리즘 63 3.3 FTN과 결합한 고전송 효율 알고리즘 성능 분석 66 제 4 장 비균일 오류 확률 기반 FTN 신호의 터보 등화 모델 제안 71 4.1 비균일 오류 확률 기반 FTN 신호의 터보 등화 모델 71 4.1.1 비균일 오류 확률 기반 우선 순위 설정 방법 74 4.1.2 우선 순위에 따른 부호어 배치 방법 77 4.2 UEP 기법이 적용된 MIMO-FTN 터보 등화 모델 79 4.3 OFDM 기법이 적용된 UEP-FTN 터보 등화 모델 80 4.4 비균일 오류 확률 기반 FTN 신호의 성능 분석 85 4.4.1 UEP-FTN 신호의 성능 분석 85 4.4.2 UEP 기법이 적용된 MIMO-FTN 신호의 성능 분석 90 4.4.3 OFDM 기법이 적용된 UEP-FTN 신호의 성능 분석 93 제 5 장 수중 무선 통신에서의 응용 96 5.1 UEP-FTN 방식의 수중 통신 적용 96 5.2 복호된 데이터를 이용한 연속적인 주파수 보정 방식 98 5.3 실험 환경 100 5.4 실험 결과 105 5.4.1 UEP-FTN 신호의 실험 결과 105 5.4.2 복호된 데이터를 이용한 주파수 보정 방식 실험 결과 107 제 6 장 결 론 110 참고문헌 113Docto