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多电平正交幅度调制(M-QAM)应用于平衰落信道时,解调器需要对信道状态信息(CSI)进行估计,而CSI的估计值不可能是完全准确的。针对此问题修改了传统的M-QAM软解调方案,同时在发送端可以得到CSI不准确程度的反馈的前提下,提出了一种方形M-QAM星座图的优化方法。仿真结果表明:在Rayleigh衰落信道下,CSI不理想时,文中提出的M-QAM调制解调优化方法应用于编码调制系统时,系统性能可以获得较大改善。对于64-QAM调制和1/2的编码效率,当CSI上归一化噪声功率为0.04时,系统性能改善可达7dB。
When multi-level quadrature amplitude modulation (M-QAM) is applied to a flat fading channel, the demodulator needs to estimate the channel state information (CSI), and the estimation of the CSI can not be completely accurate. In order to solve this problem, the traditional M-QAM soft demodulation scheme is modified. At the same time, a CSI-based square M-QAM constellation optimization method is proposed on the premise that the CSI can not obtain the CSI inaccuracy. The simulation results show that when the CSI is not ideal under the Rayleigh fading channel, the system performance can be greatly improved when the M-QAM modulation and demodulation optimization method proposed in the paper is applied to the modulation and coding system. For 64-QAM modulation and 1/2 coding efficiency, when the normalized noise power at CSI is 0.04, system performance can be improved by up to 7dB.