基于高阶累计量的大气光通信自适应信号处理

Adaptive Signal Reception Based on HOS Cumulants in Optical Wireless Communication System over Strong Turbulence

针对强湍流信道下信号衰落的特点,分析了对数正态分布模型与K分布模型的适用范围.基于K分布模型建立大气光通信接收信号模型,并给出了自适应最优门限检测方法.采用四阶和六阶累计量对强湍流信道参量进行估计,采用二阶累计量对其它高斯噪音进行估计,得到K分布参量及高斯噪音统计量的预测值,实现自适应门限更新.基于MonteCalro算法进行仿真,给出了门限更新算法对通信系统误码率的影响,同时分析了信号采样率对估计参量偏差的影响.计算表明,在强湍流情况下,大气光通信系统的误码率性能得到极大的改善。

Applied fields of log-normal distributed model and K-distributed model were analyzed for the signal fading over strong turbulence. The received signal model of the Free-space optical （FSO） communication was presented based on K-distributed model. According to the optimal maximum a posteriori （MAP） criterion,the optimum decision strategy was proposed. An adaptive algorithm based on second-and higher order cumulants was proposed to estimate the parameter of correlated K-distributed channel and other Gaussian-distributed noise. The performance of the adaptive threshold updating algorithm has been evaluated by means of Monte Cairo simulations. The bit-error rate （BER） performance and the effect of the signal sapmling rate were evaluted simultaneously. It was shown that in the FSO system over strong turbulence with adaptive processing scheme based on K-distributed model surpass the MLSD system based on log-normal distributed model. The adaptive signal receiver based on HOS cumulants was effectively and practical to predict the parameter of the channel.