IS-54無線通信標準之數位接收器模擬

Abstract

在本篇論文中，我們探討在設計IS-54 北美數位蜂巢式行動通訊系統之接 收器時很重要的兩個項目：一是中頻 (IF) 訊號的解調，另一個則是衰變 訊號的等化 (Equalization) 。關於中頻的解調，我們研究採用一種硬體 架構十分簡單的數位複取樣技術 (Digital Complex Sampling) ；而在訊 號的等化方面，我們探討兩種在數位通訊上最常用的方法：分量間寬之決 策回授等化 (Fractionally-spaced Decision Feedback Equaliza- tion) 以及最大相似之序列估算 (Maximum-Likelihood Sequence Esti- mation) 。在以上兩種等化方法中，我們採用一種雙向等化的技術，它可 以增加系統的性能。在等化器內部的適應性處理上，則採用一種多重訓練 的最小均方演算法 (Multiple Training LMS Algorithm)，它可以解決初 始收歛不足的問題。最後，我們利用電腦模擬得出這兩種等化器在不同狀 況下的效能。 In this thesis, two important issues in the design of the digital mobile receiver for the IS-54 specifications of the North American Digital Cellular (NADC) system are investigated. One is the IF demodulation and the other is the equalization. A digital complex sampling technique is studied for the IF demodulation for its hardware simplicity. On the equalization, two most popular equalization methods, Fractionally-spaced Decision Feedback Equalization (FSDFE) and Maximum-Likelihood Sequence Estimation (MLSE), are investigated. A bi-directional equalization technique is incorporated with both equalization methods and a "Multiple Training" LMS algorithm (MT-LMS) is used as the adaptive algorithm for filter coefficients update. The performances of both equalization methods are given by computer simulations.