輸入多輸出無線通訊中基於QR分解逐級偵測之最小錯誤率功率分配法

Abstract

新一代無線通訊中，空間多工（Spatial Multiplexing）和傳送多樣（Transmit Diversity）為廣受矚目的技術。在本論文中，吾人考慮空間多工系統搭配基於QR分解逐級偵測技術，提出一種最小錯誤率之功率分配法。吾人設計的方法是利用空間多工下QR分解的機率分布，針對降低整體通道的平均錯誤率做功率分配，可在中高訊號雜訊比的情況下改善系統的效能表現。此外透過雙重空時傳送多樣（Double Space-Time Transmit Diversity）下QR分解的機率分布，吾人提出的功率分配法亦可適用於雙重空間傳送多樣系統。儘管雙重空間傳送多樣系統中部份機率分布為估計得來，其平均錯誤率之公式仍相當準確。模擬結果顯示，吾人提出的方法應用在雙重空間傳送多樣系統時，亦可在中高訊號與雜訊比的環境中改善無線通訊系統效能。此外，電腦模擬顯示，吾人設計的功率分配法可延伸用在多重空間傳送多樣系統中。

It is well known that spatial multiplexing and transmit diversity are popular techniques in modern wireless communications. In this thesis, we first propose a BER-minimized power allocation strategy for spatial multiplexing systems over i.i.d. Rayleigh fading channels based on the QR-based successive detection scheme. With the knowledge of distribution of QR decomposition in spatial multiplexing, the design criterion for power loading is the overall BER averaged with respect to the channel distribution. Based on the closed-form solution, the optimal power allocation scheme is proposed, which aims to minimize the overall average BER performance of spatial multiplexing systems at medium-to-high SNR. Afterwards, with the distribution of the R matrix of QR decomposition for DSTTD systems, the design procedure of the power allocation scheme proposed for spatial multiplexing systems can be applied to DSTTD systems. Although parts of the distribution of the R matrix in DSTTD are merely approximations, the estimated average BERs are quite accurate. The power allocation scheme adapted for DSTTD systems are shown to be also effective at the high SNR regime by numerical simulations. Moreover, the proposed scheme can be further extended to multiple STTD systems