複數展頻多重碼CDMA RAKE接收器之設計與性能分析

Abstract

在本篇論文中，我們以cdma2000上行鏈路系統 ( reverse link ) 為架構，討論複數展頻多重碼之同調RAKE接收器的一些重要設計問題。 RAKE接收器是一個最大比率結合 ( MRC ) 的多重路徑偵測器，在此我們使用簡單的低通濾波器取代理想的Wiener濾波器來做通道的估計，以分析通道估計錯誤 ( estimation error ) 對性能的影響。在RAKE接收器的位元錯誤率 ( BER ) 性能分析上，我們考慮了通道估計的錯誤和有限頻帶多重路徑的衰退通道 ( fading channel )，以及其他對系統性能有關的影響，包括 (1) 通道的延遲分佈 ( delay profile )、 (2) 展頻參數 ( spreading factor )、 (3) 杜普勒偏移 ( Doppler offset )、 (4) 系統中使用者數目，及 (5) 多重路徑的能量分布。經過繁複的數學推導，我們提供了一些可以在設計上達到理想性能的參數。

This thesis examines several critical design issues associated with a coherent RAKE receiver for the reverse link of the cdma 2000 system that employs complex spreading in conjunction with multiple Walsh code channels. The RAKE receiver is a maximum ratio combining (MRC) diversity detector in which we use a simple low-pass filter to replace the optimal Wiener filter for channel estimation. In analyzing the RAKE receiver's bit error rate (BER) performance, we take into account the effects of imperfect channel estimation and band-limited multipath Rayleigh fading channels. Other effects investigated include (1) channel delay profile, (2) spreading factor, (3) Doppler offset, (4) number of users, and (5) power distribution of multiple code channels on the system performance. Through extensive numerical evaluations, we are able to provide a set of design parameters that render an optimal performance.