摘要
详细论述了多电平PAM(脉冲幅度调制)系统的最佳均衡理论。首先建立了多电平PAM系统的一种二进制码间干扰等效模型,将之视为二进制多路系统,从而说明其均衡可以用多个独立的二进制均衡器联合完成。在将均衡问题视为分类判决问题的基础上,根据贝叶斯准则导出了多电平PAM系统的最佳均衡解表达式和所能取得的最小符号概率的计算公式和近似估算公式。从最佳均衡解可以看到,无论是二进制通信系统还是多电平PAM系统,其最佳均衡问题是一个固有的非线性问题。因此要实现最佳均衡必须采用非线性结构的均衡器。神经网络是一种非线性动力学系统,在二进制系统信道均衡实现方面得到非常成功的应用。显然,本文的研究成果也为神经网络应用于多电平PAM系统实现最佳信道均衡提供了一条有效的途径。
The optimum equalization theory for overcoming the intersymbol interferences (ISI) in multi-level pulse amplitude modulation (PAM) systems is establishead. A kind of equivalent binary ISI model of PAM systems is put forward. By viewing the PAM system as binary multiplexed systems, it is shown that its equalization may be implemented jointly by serval independent binary equalizers, based on the viewpoint that equalizations belong to classfication decision problems, the optimum equalization solutions are obtained according to the bayes decision rule. Both the exact and approximate formula to compute theminimum error-symbol -probability, which the PAM system can reach by usingthe ideal optimum equalizer, are also obtained. According to the optimum equalization solution expressions, it is explained that, the optimum equalization solutions are highly nonlinear; and the trditional linear structur equalizers are incapable of implemnting such optimum equalization, therefore the equalizers must be incorporeted into nonlinearity to do so. The neural network,which is a nonlinear dynamic system, has been successfully applied in the channel equalization of binary digital communication systems. Obviously, the results obtained in this paper also suggest an effective way, to apply neural network inmulti-level PAM systems to implement optimum channel equalizations.
出处
《通信技术》
1995年第1期1-13,共13页
Communications Technology
关键词
脉冲幅度调制
信道均衡
最佳均衡
数字通信
multi-level PAM, ISI, equivalent-model, optimal equalization, neural networks.
