使用可適性天線陣列對於無線通訊系統性能之影響

Abstract

在行動通訊系統中,多重路徑傳遞會造成信號強度的衰減。為了減低這些通道所造成的損傷,天線陣列常被用來改善信號品質。由於天線陣列的性能會受到多重路徑通道的空間特性的影響,因此我們在第四、五、六章推導均勻分布線性陣列、均勻分布圓形陣列、同心圓陣列這三種天線陣列架構,個別在角度擴散為均勻分布和截高斯分布下的空間相關性函數,並且經由實驗模擬討論空間相關性對位元錯誤率的影響,以及比較天線陣列間在位元錯誤率的差異。 最小位元錯誤率準則的設計是為了直接最小化位元錯誤率,和其他藉由最佳化其他變數(如輸出信號對干擾加雜訊之功率比或均方誤差),間接地降低位元錯誤率的準則有所不同。最小位元錯誤率準則已被證實能比傳統的最小均方誤差準則達到較佳的位元錯誤率表現,在本論文中對最小位元錯誤率準則及其可適性演算法做一番討論,並且經由實驗模擬比較與最小均方誤差準值位元錯誤率上的差異。

In mobile radio communications, multipath propagation causes signal strength fluctuation. To mitigate these channel impairments, antenna arrays are usually used to improve signal quality. Since the functionality of the antenna array is based on spatial properties of the mulitipath channel , we derive spatial correlation equations of the uniform linear array (ULA), the uniform circular array(UCA), and the concentric ring array (CRA) for two types of angle spread distributions(uniform distribution and truncated Gaussian distribution) in chapters 4, 5, and 6. We discuss the effect of the spatial correlation on the bit error rate and also compare the difference of the bit error rate between these antenna arrays by simulation results. Unlike other algorithms that indirectly minimize the bit error rate by optimizing other variables (e.g. Signal to Interference plus Noise Ratio or Mean Square Error), the design of the minimum bit error rate (MBER) algorithm is used to directly minimize the bit error rate. It is demonstrated that the MBER algorithm can achieve better BER performance than the MMSE algorithm. We conduct researches on the MBER algorithm and the adaptive MBER algorithm. We compare the MEBR algorithm and the MMSE algorithm by BER simulation results.