UWB多径信道下RAKE接收和均衡的作用分析

在超宽带(UWB)通信系统中存在码间干扰(ISI)的多径信道下,RAKE接收机和均衡的作用关系还没有定论.有观点认为UWB中RAKE接收具备信道均衡的特性,因而RAKE接收时不需要均衡器,其出发点是将RAKE接收机中ISI视为与当前符号不相关的高斯噪声,或认为RAKE接收能缩短信道时延扩展.本文针对这两种观点及其依据进行了探讨,通过对存在ISI的RAKE接收机的性能进行分析,并利用IEEE 802.15标准中的多径信道模型进行了RAKE接收与均衡的仿真对比试验.结果表明:RAKE并不能起到抑制ISI的作用,故而对多径信道环境ISI仍然需要均衡器来消除.

Analysis on RAKE Receiver and Equalization under Ultra-wideband Multipath Channel

Does RAKE receiver need channel equalization under Ultra Wideband (UWB) multipath channel with inter-symbol interference (ISI)? The conclusion has not been explicitly drawn up so far. By considering the ISI as AWGN in RAKE receiver, or the channel delay spread being reduced by RAKE receiver, researchers hold the optimistic argument that RAKE receiver can play the role of equalization. This paper investigated these existing viewpoints. By analyzing the conditions and foundations from which the controversy originates, we also theoretically studied the performance of RAKE receiver under ISI. The RAKE receiver and equalization simulations, where the multipath channel models under IEEE 802.15 standard were adopted, were designed to validate the analysis. It comes to the opposite conclusion that RAKE receiver does not have the ability to suppress ISI. Therefore, it needs channel equalization to tackle ISI under UWB multipath channel environment.