基于改进梯度投影法的MIMO-NOMA系统迭代信号检测算法

针对多输入多输出-非正交多址(multiple-input multiple-output non-orthogonal multiple access，MIMO-NOMA)系统信号检测问题，基于改进梯度投影(improved gradient projection，IGP)方法，提出一种适用于多用户MIMO-NOMA系统的上行链路的迭代信号检测算法。在该算法中，利用MIMO-NOMA系统中活跃用户的稀疏特性，基于IGP方法实现对发送信号的迭代恢复；在每次迭代后，先对所得估计解向量进行预处理，以得到更为接近真实值的估计值，接着再对活跃用户支撑集进行更新，以便于下次迭代操作。仿真结果表明，与经典的基于压缩感知的信号检测算法相比，基于IGP的迭代算法具有更低的误比特率(bit error rate，BER)，在计算复杂度基本相同的条件下，可取得更佳的BER性能。

Iterative signal detection algorithm for MIMO-NOMA system based on improved gradient projection method

For the issue of the difficulty of signal detection in multiple-input multiple-output non-orthogonal multiple access (MIMO-NOMA)systems, based on the improved gradient projection (IGP) method, an iterative signal detection algorithm is proposed for the uplink of multi-user MIMO-NOMA systems. In the algorithm, according to the sparse characteristics of active users in the MIMO-NOMA system, the signal is recovered based on IGP method. Meanwhile, the pre-processing is performed on the current estimated solution vector after each iteration in order to make the estimate closer to the true value.Subsequently,the set of active users is updated for next iteration.The simulation results show that the IGP-based iterative algorithm has lower bit error rate (BER) compared with the classical compression-based signal detection algorithm, and the better BER performance achieves with almost the same complexity as the traditional gradient projection method.