极化码的参数捷变技术及性能仿真

极化码是首个能够从理论上证明接近信道容量的纠错码,于2016年11月和低密度奇偶校验码一并作为第5代移动通信的标准。针对极化码特有的蝶形结构采用Trellis对其进行了重新描述,详细分析了串行抵消列表译码算法。同时,基于密度进化理论给出了极化码的码参数捷变技术,能够在不改变编译码器硬件结构与程序的情况下实时、快速地改变编译码参数。仿真结果表明,在编码参数近似相同的情况下极化码的性能要优于低密度奇偶校验码。     

Bilayer expurgated LDPC codes with uncoded relaying

Bilayer low-density parity-check (LDPC) codes are an effective coding technique for decode-and-forward relaying, where the relay forwards extra parity bits to help the destination to decode the source bits correctly. In the existing bilayer coding scheme, these parity bits are protected by an error correcting code and assumed reliably available at the receiver. We propose an uncoded relaying scheme, where the extra parity bits are forwarded to the destination without any protection. Through density evolution analysis and simulation results, we show that our proposed scheme achieves better performance in terms of bit erasure probability than the existing relaying scheme. In addition, our proposed scheme results in lower complexity at the relay.     

A high‐performance belief propagation decoding algorithm for codes with short cycles

The simplicity of decoding is one of the most important characteristics of the low density parity check (LDPC) codes. Belief propagation (BP) decoding algorithm is a well‐known decoding algorithm for LDPC codes. Most LDPC codes with long lengths have short cycles in their Tanner graphs, which reduce the performance of the BP algorithm. In this paper, we present 2 methods to improve the BP decoding algorithm for LDPC codes. In these methods, the calculation of the variable nodes is controlled by using “multiplicative correction factor” and “additive correction factor.” These factors are obtained for 2 separate channels, namely additive white Gaussian noise (AWGN) and binary symmetric channel (BSC), as 2 functions of code and channel parameters. Moreover, we use the BP‐based method in the calculation of the check nodes, which reduces the required resources. Simulation results show the proposed algorithm has better performance and lower decoding error as compared to BP and similar methods like normalized‐BP and offset‐BP algorithms.     

An explicit method for construction of CTBC codes with girth 6

A cylinder-type block-circulant (CTBC) code with circulant permutation matrix (CPM) size p is presented by a binary base matrix with a cylindrical structure and a slope-vector on ${\mathbb{Z}}_p$. The slope-vector is called proper if the corresponding CTBC code is 4-cycle free. In this paper, an algorithm is presented that for a given base matrix with a cylindrical structure, explicitly generates a proper slope-vector. This proper slope-vector provides a lower-bound on the CPM-sizes of the corresponding CTBC codes required to achieve girth at least 6. Interestingly, the lower bound, minimum distance and 6-cycle multiplicity of the constructed CTBC codes are better than some masked and unmasked known explicitly constructed 4-cycle free QC LDPC codes with the same regularity. Simulation results show that the constructed CTBC codes outperform some 4-cycle free QC LDPC codes in binary and nonbinary cases.     

DOCSIS3.1物理层新功能分析与应用研究

DOCSIS3.1标准逐步从标准制定走向规模化部署阶段,而网络性能的优化和网络的主动维护功能还有很大的提升空间,本文重点介绍了可变bit-loading的Profile管理功能,并针对Profile管理出现的一些问题,提出了一种新的单播Profile管理方法;同时介绍了DOCSIS3.1PNM运维功能,并分析了新功能面临的挑战以及走向智能运维的转型方向。     

低差错平底特性的非规则LDPC码的设计

介绍了非规则LDPC码的发展并给出了其优势及缺点，重点论述用ACE算法来构造非规则LDPC码从而降低其差错平底特性。对降低非规则LDPC码的差错平底特性的其它方法提出了展望。     

Belief-Propagation-Approximated Decoding of Low-Density Parity-Check Codes

In this paper, we propose a new reduced-complexity decoding algorithm of Low-Density Parity-Check (LDPC) codes, called Belief-Propagation-Approximated (BPA) algorithm, which utilizes the idea of normalization and translates approximately the intricate nonlinear operation in the check nodes of the original BP algorithm to only one operation of looking up the table. The normalization factors can be obtained by simulation, or theoretically. Simulation results demonstrate that BPA algorithm exhibits fairly satisfactory bit error performance on the Additive White Gaussian Noise (AWGN) channel.     

Performance Bound for LDPC Coded Unitary Space–Time Modulation

This paper is concerned with the bit error probability (BEP) of coded unitary space–time modulation systems based on finite-length low density parity check (LDPC) codes. The union bound on the BEP of the maximum likelihood (ML) decoding is derived for any code rate, unitary space–time constellation and mapping. The tightness of the bound is checked with simulation results of the ordered statistic decoding (OSD). Numerical and simulation results show that the union bound is also close to the error performance of the sum–product (SP) decoding at low BEP levels when Gray mapping is employed. The derived bound is useful to benchmark the error performance of finite-length coded unitary space–time modulation systems, especially for those that employ short-to-medium length LDPC codes.

Shannon限、时频不确定性和LDPC码

从信号分析和信息处理的观点论述了Shannon限所包含的实际物理意义,指出了时频不确定性对信号在信道传输中的限制,将信源和信宿、收端和发端、编码与解码接合起来,分析了LDPC码的主要性能。     

LDPC码译码算法的性能分析

LDPC码是一种优良的差错控制编码.鉴于其译码算法的复杂度直接影响到编码的应用前途,阐述了LDPC码的几种译码算法.重点介绍了基于Tanner图结构的BP算法,然后分析和比较了由FOSSORIER提出的BP-based算法和CHEN J提出的两种改进算法-Normalized BP-based、offset BP-based算法以及最优译码算法在AWGN信道下的性能特性.