LDS多用户检测和LDPC码译码的联合迭代算法

为了提高低密度扩展(LDS)系统性能对LDS多用户检测算法进行研究,提出了一种LDS非正交多址系统中多用户检测和信道编码译码联合迭代的方案.将各用户低密度奇偶校验码(LDPC)译码后的软信息回传给多用户检测器,提高了多用户符号检测的可靠性,而多用户检测性能的提高又进一步提高了LDPC码译码的性能.在相同条件下与多用户检测和LDPC码译码单独进行的方案进行了仿真对比,结果表明,联合迭代算法明显改善了误比特率,系统负载越大,联合迭代带来的性能改善也越大.同时,联合迭代还缩小了不同用户误码性能的差异且即使在系统负载达到200％时,误码性能也与单用户的性能相差不大.联合迭代算法在不增加接收机计算复杂度的情况下,显著提升了LDS系统的性能.

A Joint Iterative Algorithm for LDS Mmultiuser Detecting and LDPC Code Decoding

The LDS multiuser detection algorithm was researched to improve the performance of LDS system.A joint scheme of multiuser detection and channel decoding in LDS non-orthogonal multiple access systems was introduced.The reliability of multiuser detection was improved by transmitting users' soft information after LDPC decoder back to multiuser detector.The performance of channel decoding was further improved by the enhancement of multiuser detection.Simulations,comparing with multiuser detecting and LDPC code decoding separately under the same conditions,indicate that the joint iterative algorithm can significantly improve the performance of BER.It is shown that the larger the system load is,the greater the performance improvements.At the same time,the difference in error performance between different users also reduces by the joint scheme.With the joint iterative algorithm,the performance of BER is almost same as that of single user even when the system load reaches 200％.The performance of the LDS system is significantly improved without increasing computational complexity of receiver by the joint scheme.