具回饋的多用戶多天線通道之天線選擇及傳輸方式的設計與分析

Abstract

為了加強在多天線輸入、多天線輸出的多重存取通道下分集與多工增益權衡的效能，我們提出兩種天線選擇的方法。這兩種方法都需要利用通道反饋讓傳送端獲得通道資訊，但僅以極低的通道回饋率。第一種方法是選擇單一用戶作為傳輸，第二種方法是利用[3]所提出的快速天線選擇演算法，同時選擇用戶與天線來作為傳輸。此外，第二種方法需要利用獲得的通道資訊來設計分配給不同被選擇用戶的傳輸速率來達到最佳的分集與多工增益權衡效能。結果證明我們所提出的兩種天線選擇方法在絕大部分的多工增益區域，它們的分集增益都會遠優於沒有使用反饋的多用戶多天線通道。模擬的結果更證實在某一特定情況下，第二種方法能在中斷機率為10的負六次方下，提供比沒有使用反饋的多用戶多天線通道還好15.4dB的訊雜比。

In order to improve the DMT performance in MIMO-MAC, we propose two antenna selection schemes. The schemes require a channel feedback, but the feedback rate is extremely low. The first scheme allows only one user for transmission, and the second scheme selects users and antennas at the same time by using a fast antenna selection algorithm proposed by Jiang and Varanasi [3]. Moreover, the second scheme requires an additional design of rate-assignment functions that maximizes the DMT performance. It is shown that the DMT performances achieved by these two schemes are significantly better than MIMO-MAC without channel feedback in most multiplexing gain regimes. The simulation result also confirms that in a certain case the second scheme can provide an astonishing SNR gain of 15.4 dB at outage probability 10^-6 compared to MIMO-MAC without channel feedback.