現代無線通訊系統中，多天線是一個用來提高傳輸速率的關鍵技術。在常發生散射的環境中，傳送端與接收端之間並不存在能視線所及的路徑，接收端收到的訊號在這些路徑中會受到反射、散射、繞射的影響，造成接收天線之間的干擾。為了要改善多天線干擾對系統效能的影響，疊代軟式干擾消除(Iterative soft-decision interference cancellation, ISIC)方法結合了連續干擾消除與渦輪解碼器的協同設計已吸引不少關注，如何克服因錯誤傳遞(Error propagation)而降低了疊代軟式干擾消除的效能，是一個重要的議題。
在本論文中，我們首先提出一個可在每次疊代中調整干擾消除順序的疊代軟式干擾消除法來降低錯誤傳遞發生的機率，其干擾消除的順序是由前一次疊代的變異數升序來決定；接著提出簡化的對數最大事後機率解(Log-MAP)演算法，可透過累積每一次疊代的軟式資訊(Soft information)來加速收斂速度；最後提出一個低複雜度的疊代QR分解來降低改變干擾消除順序的額外付出，在4×4系統下透過複雜度分析使用4次疊代運算時約可降低35%的執行時間，本論文所提出的方法使用4次疊代運算約能增加0.9dB的系統效能。

Multiple antenna technique is one of the key technologies in modern wireless communication systems to increase transmission rate. In rich scattering environment, there is no clear line-of-sight (LOS) path between transmitter and receiver. The signals in these environments are reflected, scattered or diffracted among multiple paths before being received at the receiver, which may interfere other receiving antennas and causing multiple antenna interference. In order to limit the impact of multiple antenna interference on system performance, an iterative soft-decision interference cancellation (ISIC) method was presented to mitigate interference by using a combination of a successive interference cancellation and a turbo decoder. However, error propagation is a source of performance degradation in the ISIC scheme.
In this thesis, a modified ISIC scheme is proposed to reduce the probability of error propagation with an adjustable cancellation order in each iteration. The cancellation order is decided by ascending variance values from the previous iteration. To increase system convergence speed, an accumulated max-log-MAP algorithm is presented to accumulate soft information over iterations. Furthermore, a low-complexity iterative QR decomposition method is proposed to reduce the effort of changing the cancellation order. In the complexity analysis, the overall execution time is reduced by about 35% in a 4×4 system using 4 iterations. Compared to the ISIC scheme, the modified scheme can obtain 0.9dB performance gain in a 4×4 system with 4 iterations.

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