近年來多重使用者多輸入多輸出(MU-MIMO)這一項技術讓傳送端和接收端可以利用彼此的多根天線使得無線裝置的傳輸速度有機會呈現倍數成長，那這項技術的關鍵就在於選擇天線的機制好壞，如何挑選出彼此干擾最小的一群天線做同時傳輸變得很重要也不容易，所以在這篇論文當中我們提供了在干擾消除(Interference cancellation)這樣的訊號處理方式下的一個高傳輸速度導向的天線選擇機制。
我們的選擇天線條件是希望天線的訊號除了彼此互相盡可能地正交而且訊號強度要高，要滿足以上這兩個條件直觀地做法會是一個非多項式(NP)時間內可以解決的難題，因為每根檯面上的天線都要計算彼此的角度，更麻煩的是選擇順序的可能性達到階層等級般的多樣。所以我們用矩陣的表示方式，把這樣的難題對應到一個經典的數學分析上，叫做非等方性正交普洛克路斯忒斯分析(Anisotropic Orthogonal Procrustes Analysis)，再搭配虛擬天線數量的設計作配合，這樣一來可以達到近乎最佳的解決方法。
由於我們提出的是一個純粹的天線選擇機制，基本上不僅限於任何一種特定的協定(Protocol)，所以在應用的接軌上是可以非常廣泛的。

The aim of this thesis is to choose a group of transmit antennas which can transmit concurrently and produce higher system throughput. We know that the advent of multi-user multiple input multiple output (MU-MIMO) technology enables an access point (AP) to simultaneously communicate with multiple stations. In order to achieve this, we have proposed a transmit antenna selection strategy which adopts the virtual antennas and the help of block relaxation (BR) algorithm in anisotropic orthogonal Procrustes analysis. About the applicable protocol, we incorporate with the IEEE 802.11 family and add to a contention-based period that takes the transmission rate and the fairness into consideration. The performance evaluation indicates that our proposed antenna selection strategy improves the system throughput; and the modified protocol is still having the fairness to some extent.

[1] Sheng Zhou and Zhisheng Niu, "An Uplink Medium Access Protocol with SDMA Support for Multiple-Antenna WLANs," Wireless Communications and Networking Conference (WCNC), Apr 2008
[2] Tomoya Tandai, Hiroki Kiyoshi Toshimitsu, and Takahiro Kobayashi, "An efficient uplink multiuser MIMO protocol in IEEE 802.11 WLANs," IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, Sept 2009
[3] S. Sanayei and A.Nosratinia, "Antenna Selection in MIMO Systems," IEEE Communications Magazine, pp.68-73, Oct. 2004.
[4] Wei Zhong and Youyun Xu, "Joint user and transmit antenna selection for uplink multi-user MIMO systems," IEEE 20th International Symposium on Personal, Indoor and Mobile Radio Communications, Sept 2009
[5] K. Tan, H. Liu, J. Fang, W. Wang, J. Zhang, M. Chen, and G. M. Voelker, "SAM: Enabling Practical Spatial Multiple Access in Wireless LAN," In ACM MobiCom, 2009
[6] E. Aryafar, N. Anand, T. Salonidis, and E. W. Knightly, "Design and Experimental Evaluation of Multi-User Beamforming in Wireless LANs," In ACM MobiCom, 2010
[7] Wei-Liang Shen, Yu-Chih Tung, Kuang-Che Lee, Kate Ching-Ju Lin, Shyamnath Gollakota, Dina Katabi, and Ming-Syan Chen, "Rate adaptation for 802.11 Multiuser MIMO Networks," in Proc. of ACM Mobicom, pp. 29-40, Aug 2012
[8] Lara Deek, Eduard Garcia-Villegas, Elizabeth Belding, Sung-Ju Lee, and Kevin Almeroth, "Joint rate and channel width adaptation for 802.11 MIMO wireless networks," 10th Annual IEEE Communications Society Conference on Sensor, Mesh and Ad Hoc Communications and Networks (SECON), June 2013
[9] A. T. Alastalo, M. Kahola, "Smart-antenna operation for indoor wireless local-area networks using OFDM," IEEE Trans.Wireless Commun., vol.2, No. 2, pp. 392-399, Mar. 2003
[10] IEEE standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications, ISO/IEC 8802-11: 1999(E), Aug. 1999
[11] D. Tse and P. Vishwanath, "Fundamentals of Wireless Communications," Cambridge University Press, 2005.
[12] GOWER, J.C.,and DIJKSTERHUIS,G.B., "Procrustes Problems," Oxford University Press, 2004.
[13] Tzu-Shiang Hsu, "An Uplink Multi-User MIMO Protocol with Transmit Antenna Selection in 802.11 WLANs," Tsing Hua University Press, 2013.