使用天線陣列對於無線通訊系統通道容量影響之研究

Abstract

在無線通訊系統中，多路徑問題造成了通道衰落進而影響通訊品質及可靠度，而多輸入多輸出(MIMO)系統能利用衰落通道間獨立的特性，以及空間多工技術來提高傳輸品質與速率，多輸入多輸出系統利用多天線陣列作為其傳送端以及接收端，本研究著重在多天線陣列對於通訊系統的影響。本論文研究之多天線陣列造成的影響有兩種，其一，天線陣列幾何結構影響空間相關性，空間相關性進而影響通訊系統的通道容量；第二個影響為天線間相互耦合(Mutual coupling)效應。本論文將考慮以上兩個效應，並採用通道容量作為通訊系統效能的指標，利用群粒子最佳化演算法在一定搜尋範圍內找到擁有最大通道容量的天線陣列，並且模擬常見之均勻分布線性陣列、均勻分布圓形陣列及同心圓陣列，討論空間相關性及天線耦合效應對於通道容量的影響，並且比較相同大小且入射環境相同的天線陣列效能差異，以及與其相同情況下之最佳化天線陣列之差異。

In wireless communication systems, channel fading caused by multipath propagation influences the reliability of information transmission and transmission quality. To provide higher transmission quality and spectral efficiency, MIMO uses the characteristic of independence between fading channels and the spatial multiplexing. As MIMO systems uses the multi-antenna array as its receiver and transmitter, our research focuses on the effects produced by multi-antenna array on communication systems. In our research, we consider two effects of multi-antenna array. The first effect is spatial correlation. Spatial correlation caused by array geometries, reduces the channel capacity. The second effect is the mutual coupling between the antennas. Our research considers these two effects, and discusses communication system performance using channel capacity. In our research simulation, we search the optimal array geometry in order to maximize channel capacity using particle swarm optimization. Moreover, we analyze the performance of channel capacity using uniform linear array (ULA), uniform circular array (UCA) and concentric ring array (CRA). Finally, we compare the channel capacity between these different array geometries, considering spatial correlation and mutual coupling.