大規模多輸入多輸出系統於尺寸限制下之上行通道容量分析

Abstract

大規模多輸入多輸出系統已成為次世代蜂巢通訊系統中深具潛力的候選技術，在此之下許多容量分析、通道估計與偵測技巧等相應而生。然考量到現實的基站佈署，基站陣列的尺寸大小是一項重要的經濟考量因素。同時天線陣列在尺寸限制下接收功率的有效面積亦有上限，其提供通道效能也會受到配置型式與天線間距所影響。 綜合以上因素，我們使用適當的通道模型來探討所描述通道隨天線數目提昇時逼近之容量行為。在尺寸與接受功率之限制下，我們的數值結果顯示通道容量逼近收斂，而非大規模多輸入多輸出系統之初推論中隨著天線數目的對數成長。除此之外我們提出一項配置矩形天線陣列的啟發式方法，據以此配置達到更高的通道自由度。

Massive MIMO has become a promising candidate of technology for the next generation wireless cellular system, and many works have been devoted to capacity analysis, estimation schemes and detection techniques. In consideration of realistic cell deployment, dimension of the base station array is an important economic issue. Given constrained dimension the total received power is limited as well, and also the performance varies with the arrangements and spacing of antenna array. Combining the above factors, we consider these effects with a proper channel model and investigate the asymptotic capacity and behavior of the underlying channel. Under constrained dimension and power, we show that the rate would saturate rather than increase in terms of the logarithmic of antenna-number as the original work of massive MIMO. Also we suggest a heuristic approach to arrange the antennas of a uniform rectangular array in each dimension for maximizing channel degrees of freedom.