十字形QAM信号的盲均衡技术研究

Research on Blind Equalization of Cross-QAM Signals

提出两种适用于十字形正交幅度调制QAM(Quadrature amplitude modulation)信号的盲均衡算法:改进的常十字模算法(MCXA)和基于判决引导的改进的常十字模算法(DD-MCXA)。MCXA在CXA基础上重构了代价函数,在其代价函数中增加了星座图匹配误差(CME)函数,CXA部分提供了全局收敛,CME部分用来减少剩余误差和加快收敛速度。DD-MCXA在保持CXA部分提供良好的最初收敛的优点的同时,自动削弱了CXA部分在局部收敛区域的误差影响,从而进一步提高了均衡性能。通过对户外无线微波信道模型的仿真实验,验证了这两种算法良好的均衡性能。

Two new blind equalization algorithms suitable for cross-QAM signals are proposed, modified CXA （MCXA） and decision.directed MCXA （DD-MCXA）. By adding a constellation-matched error （CME） term to the cost function of the CXA, the MCXA is obtained. In the MCXA, the CXA term provides global convergence and the CME term helps to decrease the residual error and accelerate convergence. The DD-MCXA improves performance of the MCXA because it retains the good initial convergence charac- teristics of the CXA at the same time, and automatically decreases the effect of the CXA errors when the equalizer is near convergence. Two outdoor wireless microwave channel models are adopted in the simulation, and the simulation results demonstrate the good performance of the proposed algorithms.