【作者】 李慧；

【导师】 韩昌彩；

【作者基本信息】 天津大学 ， 电路与系统， 2020， 硕士

【摘要】 针对高可靠高实时无线通信中传输短数据包的应用需求,高性能短码长信道编码的设计受到广泛关注。中短码长多进制低密度奇偶校验(LDPC)码具有卓越的纠错性能,而错误平层的存在限制了多进制LDPC码在极低错误率场景中应用。针对短码长多进制LDPC码的错误平层现象,本文提出了一种短码长多进制LDPC码构造方法。进一步,多进制LDPC码与高阶调制结合可获得高传输效率,但由于译码信息初始化复杂度高,导致了较高的译码复杂度和延迟。因此,本文提出了一种高阶调制下多进制LDPC码译码信息初始化的简化方法。首先,提出了一种基于渐进弦边增长的短码长多进制LDPC码构造方案。将连接哈密顿环上两个不相邻顶点的弦边依次添加到哈密顿环中,根据当前子图中与弦边相关的环的满秩条件(FRC),确定弦边对应的非零元素配置。基于提出的方法,构造了一种具有高效编码结构的多进制LDPC码。复杂度的分析证明了提出的构造方法具有比传统方法更低的复杂度,仿真结果表明所构造的短码长多进制LDPC码具有较低的错误平层,且无需很高的迭代次数,具有应用于高可靠高实时通信的潜力。进一步,将构造的短码长多进制LDPC码与高阶调制结合,提出了一种简化的高阶调制下译码信息初始化方案。由于与接收符号欧氏距离较大的星座点具有较小的符号概率度量值,采用仅计算距离接收符号较近的若干星座点对应的概率信息的截短方案。使用比较接收符号与星座点的坐标值的近似方案确定距离接收符号较近的若干星座点,从而避免了欧氏距离的计算。以256阶振幅移相键控(APSK)和256阶正交振幅调制(QAM)两种高阶调制为例,利用星座图的特点设计了低复杂度的译码信息初始化方案。结合所设计的短码长多进制LDPC码,分析了提出的简化方案的译码性能。结果表明,提出的方法可在保证性能的基础上有效降低译码信息初始化的复杂度,具有潜在的应用价值。更多还原

【Abstract】 For the application requirements of transmitting short data packets in high-reliability and low-latency wireless communication,the design of efficient short codes has attracted widespread interest.Non-binary low-density parity-check(LDPC)codes with short or moderate-length have the potential applications in low-latency and highreliability communication attributed to the strong error correction capability and parallel decoding.However,the existence of error floor limits the application of nonbinary LDPC codes in extremely low error rate scenarios.To low the error floor,a construction method of non-binary LDPC codes with short code-length is proposed.Furthermore,a simplified method for the initialization of decoding information of nonbinary LDPC codes under high-order modulation is proposed.Firstly,a low-complexity method is proposed to optimize the minimum distance of the non-binary LDPC codes in a progressive chord edge growth manner.Specifically,each chord edge connecting two non-adjacent vertices is added to the Hamiltonian cycle one by one.For each newly added chord edge,the configuration of non-zero entries corresponding to the chord edge is determined according to the so-called full rank condition(FRC)of all cycles related to the chord edge in the obtained subgraph.Based on the proposed method,the non-binary LDPC codes with an efficient encoding structure is constructed.The analysis results show that the method for designing nonbinary LDPC codes using progressive chord edge growth has lower complexity than traditional methods.The simulation results show that the proposed method can effectively improve the performance of the non-binary LDPC codes in the high signalto-noise ratio(SNR)region.Furthermore,combining the optimized short code-length non-binary LDPC code with high-order modulation,a simplified initialization scheme for decoding soft information under high-order modulation is proposed.Since the constellation points with a larger Euclidean distance from the received symbol have smaller symbol probability measurement values,the truncation scheme that only the probability information of the constellation points which are close to the received symbols is calculated is proposed.In order to determine the set of constellation points close to each received symbol,an approximate scheme of directly comparing the coordinate values of the received symbol and the constellation points is proposed,thereby avoiding many Euclidean distance calculations.Taking 256-order Amplitude Phase Shift Keying(APSK)and 256-order Quadrature Amplitude Modulation(QAM)as examples,the low-complexity schemes for the decoding information initialization of the two modulations are designed using the characteristics of the constellations.Combined with the designed short code-length non-binary LDPC codes,the decoding performance of the proposed simplified scheme is analyzed.The results show that the proposed method can effectively reduce the complexity of decoding information initialization on the basis of ensuring performance,and has potential application value.更多还原