MIMO OFDM系統之訊號偵測技術研究

Abstract

在本篇論文中，分別探討了數種MIMO OFDM系統於時變或非時變多重路徑衰減通道之訊號偵測技術。於非時變通道中，其訊號偵測技術著重在多天線之間的干擾。根據目前已被提出的方法，我們整合一些演算法使其能達到更低的複雜度。而於時變通道中，除了天線之間彼此的干擾，OFDM系統符元內的通道變化，將會破壞載波彼此間的正交性，其所造成的干擾會使系統效能下降。此效能誤差量將會隨著移動的速度、載波頻率或是符元的持續時間增加而變得嚴重。基於現有的訊號偵測技術，我們提出了一些改進的方式。相對於其他的方法，它的位元錯誤率有明顯的降低且複雜度也減少很多。

In this thesis, several signal detection methods for MIMO OFDM systems in time-varying and quasi-state multipath fading channels are investigated, respectively. In quasi-state multipath fading channels, signal detection schemes focuses on interantenna interference cancellation. The proposed methods effectively combine some algorithms to get better ones with lower complexity. Next, in time-varying multipath fading channels, except interantenna interference, channel variations over an OFDM symbol destroy the orthogonality between subcarriers. The corresponding intercarrier interference degrades the system performance. This error floor becomes more serious as mobile speed, carrier frequency, or symbol duration increases. Based on existing signal detection methods, several modifications to improve the system performances or to reduce the system computational complexity are proposed. Compared with other algorithms, the proposed ones have not only better performance but also lower complexity.