Study on Opportunistic Beamforming with Multiple Receive Antennas

[[abstract]]機會波束形成(Opportunistic Beamforming)可以增加通道波動的幅度與速率，因此在多用戶排程(Scheduling)下可提升多用戶分集(Multiuser Diversity)增益與公平性。在本論文中，我們於接收端利用多根接收天線，提供空間分集(Spatial Diversity)增益，進一步地增加系統效能，使系統吞吐量、等待延遲時間與公平性上的表現皆有所提升，然而卻仍保有與傳統機會波束形成相同的迴授量。我們提出的方法也證實不管是在較少的使用者、較慢的波束形成權重變化或是較為平緩之通道波動中，依然能維持相近的系統吞吐量。這都有助於更有效益的獲得多用戶分集增益。另一方面，透過通道預測(Channel prediction)機制，在通道較能準確預測下，使用預編排(Pre-scheduling)將可使我們所提出的系統進一步地提升系統吞吐量，而等待延遲時間與公平性也能有所改善。[[abstract]]Opportunistic beamforming can increase the fluctuation of channel dynamic range and rate, and so enhance the multiuser diversity gain and fairness in the content of multiuser scheduling. In this thesis, we further improve the system performance by employing multiple antennas at the receivers. Additional spatial diversity gain can then be provided. System throughput, waiting time and fairness are all enhanced, and the amount of feedback information is kept the same as that of the conventional opportunistic beamforming. We show that even with smaller number of users, slower changing rate of the beamforming weights, or less fluctuated channels, the same system capacity can be kept by the proposed scheme. All these help to obtain the multiuser diversity gain more effectively. On the other hand, with the channel prediction mechanism, we demonstrate that pre-scheduling can be used to further improve the system capacity of the proposed scheme. The waiting time and fairness performance can be enhanced as well provided that accurate channel-prediction information is available.[[note]]碩