GMSK信號在同頻干擾下的性能分析

Abstract

在行動無線通訊中，為了提高單位區域使用者的密度，頻率重覆使用（frequency reuse）是主要的概念。如此一來，通訊品質不免受到同頻干擾的影響。行動通訊品質可用通訊鏈路中斷率（outage probability）來衡量，而在數位通訊系統中，通話鏈路中斷率則由位元錯誤率（bit error rate）高低做為判斷標準。 此外，在行動無線通訊中，通道的特性對一個無線通訊系統的性能表現（performance）是個重要的影響。本篇論文是考慮當系統處於頻率選擇性的衰褪通道（frequency - selective fading channel）的性能表現。在空曠的郊區或微細胞式系統中，信號和同頻干擾信號很可能都會通過萊斯衰褪通道（Rician fading channel）。我們首先分析三種非同調檢測器（noncoherent detector）：一位元相位差檢測器（one - bit differential phase detector），一位元相位差回授檢測器（one - bit differential phase with decision feedback detector）和二位元相位差檢測器（two - bit differential phase detector），在此情況下的性能表現。 接下來，我們則討論利用羅倫氏分解（Laurent Decompostition）與腓特比演算法（Viterbi Algorithm）所建構的一種同調檢測器的性能。 這些結果可供細胞的覆蓋區域預測及基地臺位置、分佈規劃的參考。

The service quality of a mobile communication system is often measured by the outage probability, i.e., the probability that a receiver's BER (or carrier - to - noise ratio, CIR) performance is below a pre - specified threshold. Based on the outage probability, a system's capacity is defined as the number of active users it can support without incurring outage. Although frequency reuse enhances the capacity of a cellular mobile communication system, the co - channel interference (CCI) it induces also put a limit on the system capacity. The purpose of this thesis is to investigate the performance of several GMSK receivers in the presence of CCI and frequency - selective fading.We consider the case when both the desired signal and co - channel interference suffer from Rician fading. The group of noncoherent receivers we study include i) one - bit differential detection, ii) one - bit differential detection with decision feedback and iii) two - bit differential detection. We also examine a coherent receiver based on Laurent decomposition and Viterbi - type detection.