多用户大规模LDPC-SM-MIMO联合分层消息传递检测

Joint Layered Message Passing Detection for Multi-user Large-scale LDPC-SM-MIMO System

对于多用户大规模空间调制多输入多输出(Spatial Modulation Multiple Input Multiple Output,SM-MIMO)系统,消息传递检测(Message Passing Detection,MPD)是常用的检测算法,但其复杂度较高。针对该问题,引入基于分层消息传递机制的分层MPD(Layered MPD,LMPD)算法以加快算法收敛速度,降低算法复杂度。进一步,将低密度奇偶校验码(Low-density Parity-check,LDPC)与SM-MIMO系统相结合,提出联合LMPD-BP(Joint LMPD Belief Propagation,JLMPD-BP)算法,LMPD算法可利用BP算法反馈的概率信息,提升系统检测性能。理论分析与仿真结果表明:与传统MPD算法相比,LMPD算法在不损失误码率性能的前提下可加快算法收敛速度,当信噪比(Signal-to-Noise Ratio,SNR)为4 dB时,MPD算法需3次迭代才能达到收敛,而LMPD算法仅需2次迭代即可收敛;同时,通过与LDPC码结合,JLMPD-BP算法极大地降低了系统误码率,如在迭代次数为(2,2,2)、SNR=2 dB时,与迭代次数为(4,4,0)的LMPD-BP算法相比,JLMPD-BP算法的误码率由10-2降至5×10-3。

Message passing detection(MPD)is the most commonly used detection algorithm in multi-user large-scale spatial mo-dulation multi-input multi-output(SM-MIMO)systems,but the traditional MPD algorithm is still complex.To overcome this pro-blem,the layered MPD(LMPD)algorithm isused to accelerate the convergence speed of the algorithm.Then,low-density parity-check(LDPC)codes are combined with SM-MIMO systems,and a joint LMPD-belief propagation(JLMPD-BP)algorithm in which the LMPD can use the feedback information of BP decoding is proposed to further improve the system detection perfor-mance.Theoretical analysis and simulation results show that,compared with the traditional MPD algorithm,the LMPD algorithm accelerates the convergence speed of the algorithm without losing the bit error rate(BER)performance.For example,when the signal-to-noise ratio is 4 dB,LMPD algorithm need only 2 iterations,while MPD algorithm need 3 iterations.At the same time,thanks to the great advantages of LDPC codes,JLMPD-BP algorithm greatly reduces BER of the system.When the iteration number is(2,2,2)and SNR=2 dB,compared with LMPD-BP algorithm with iteration(4,4,0),the BER of JLMPD-BP algorithm deceases from 10-2 to 5×10-3.