MIMO通信系统中QAM信号的快速半盲均衡算法研究

Study of Fast Semi-blind Equalization Algorithm for MIMO Systems with QAM Signal

该文针对传输正交幅度调制(QAM)信号的多输入多输出(MIMO)系统的均衡问题,结合方环算法(SCA)的简单性和软决策(SDD)算法的精确性,提出了一种既比较精确又简单的算法(SCA+SDD)。在优化该算法的代价函数过程中,首先用很少的训练序列(等于接收天线数)得到均衡器权向量的一个粗略估计,然后提出利用共轭梯度法进行迭代优化该代价函数的方法,该算法具有近似的二次收敛性,与传统梯度类算法相比较,该方法有非常快的收敛速度和较少的计算量。最后通过误码率(BER)和收敛速度分析该算法的可靠性和有效性,并且通过计算机仿真证明了该算法的良好性能。

This paper focuses on the semi-blind equalization for Multiple-Input Multiple-Output （MIMO） systems with Quadrature Amplitude Modulation （QAM） signal. Combining the advantages of simplicity of Square Contour Algorithm （SCA） and accuracy of Soft Decision-Directed （SDD） scheme together, the SCA added SDD （SCA＋ SDD） method is proposed, which has the good performances of both simplicity and accuracy. In the optimization procedure, a minimum number （equal to the number of receiving antennas） of training symbols are firstly utilized to derive the rough estimate of the spatial equalizers＇ weight vectors, and then the conjugate gradient algorithm is proposed to optimize the cost function, The new scheme possesses the performance of approximate quadratic convergent. Compared with traditional gradient-type algorithms, conjugate gradient algorithm has a faster convergent speed and less computational quantity complexity. Finally, the method＇s reliability and validity are evaluated by Bite Error Rate （BER） and convergent speed respectively. Computer simulation confirms the good performances of the algorithm.