功率多樣性分配於多輸入多輸出系統上之應用

Abstract

隨著無線通訊技術的應用增加，高傳輸率已經變成一個重要的研究課題。垂直分層空時碼(V-BLAST)是一種可支援高傳輸速率之多輸入多輸出技術。在本論文中，我們提出利用功率多樣性分配以最小化垂直分層空時碼之位元錯誤率。功率多樣性分配的要旨是利用在傳輸端非均等的分層功率分配，刻意的造成各分層在接收端之接收功率之差異性。經由優化過之傳輸功率分配，可顯著 提升接收端之連續干擾消除程序之效能，進而有效降低各分層之位元錯誤率。 本論文首先分析垂直分層空時碼於快速及慢速雷利衰減效應下之位元錯誤率，繼而以數值方式尋得兩種衰減效應下之最佳功率分配方式。此外，針對慢速雷利衰減效應下之垂直分層空時碼系統，本論文提出兩種最佳及次佳之功率控制方法。前者可達到最小化之位元錯誤率；而後者則是犧牲部分位元錯誤率以減少所需之計算複雜度。數值模擬實驗顯示本論文之位元錯誤率分析非常準確與模擬結果完全吻合。模擬結果並顯示本論文所提出之功率多樣性分配可顯著提升垂直分層空時碼效能。

As the multimedia applications become popular in our daily life, there is an increasing demand for wireless communication technology that supports high transmission rate. Vertical Bell Laboratories Layered Space-Time (V-BLAST) is one of the most popular Multiple Input Multiple Output (MIMO) architectures that achieve very high spectral efficiency and thus high transmission rate. In this thesis, we propose the use of power diversity scheme to minimize the bit error rate of V-BLAST systems. The essence of power diversity scheme is to intentionally cause different received power from each layer at the receiver. By judiciously allocating the transmitting power to the layers, the performance of the successive interference cancellation at the receiver can be significantly improved. The exact bit error rate (BER) of the V-BLAST systems with non-uniform power allocation under is analyzed for both fast and slow Rayleigh fading cases. The BER is optimized for each of the fading cases to find the optimal power allocation pattern for the V-BLAST systems. For slow fading cases, we propose the optimal and a suboptimal power control to achieve power diversity on the V-BLAST systems. While the optimal power control minimizes the BER, the suboptimal power control offers a good balance between the BER and the computation complexity required. Simulations show that our BER analysis is accurate and the proposed power diversity scheme significant improve the performance of the V-BLAST systems.