近年來，干擾對齊技術在無線通訊系統中逐漸被重視，其原因為此技術可以有效消除使用者之間的干擾，並達到最大的訊號空間自由度。然而，標準的干擾對齊技術對通道估測誤差相當敏感，在非完美通道資訊的情況下，其效能表現會明顯下降。在本論文中，我們針對多輸入多輸出干擾通道發展一個具有強健特性的干擾對齊技術；根據通道估測誤差的統計平均特性，提出一個迭代式干擾對齊演算法以設計最佳的預編碼器與解碼器。在每一次迭代的過程中，我們使用傳統干擾對齊方法來更新預編碼器，並依據最大訊號干擾比(signal-to-interference ratio；SIR)準則來設計解碼器，其中SIR定義為：接收端所欲接收的訊號(投影於無干擾訊號子空間)與「洩漏」的干擾訊號(來自干擾訊號子空間)之間的比值。與現有相關干擾對齊技術比較，我們所提出之迭代式干擾對齊技術具有較大的通道容量與較少的運算複雜度。

Interference alignment (IA) has received great attention recently because it can exploit all available degrees of freedom in a multiuser interference channel to eliminate interference among users effectively. However, the standard IA approach is sensitive to channel estimation errors, and the performance would be degraded significantly when perfect channel state information (CSI) is not available. In this thesis, we consider how to design a robust IA scheme for multiuser multiple-input multiple-output interference channels under imperfect channel estimation. We propose an iterative IA scheme with the corresponding precoder and decoder optimally designed in an alternate way based on an independent and identically Gaussian distributed error model with bounded expected norm. At each iteration, the precoder design is updated using the conventional IA approach and the decoder design is updated according to the maximum signal-to-interference ratio (SIR) criterion, where the SIR is defined as the ratio of the desired signal projected onto the interference-free subspace and the “interference leakage” spilling out from the interference subspace. As compared to previous related works under a similar channel error model, the proposed iterative IA approach achieves better sum-capacity performance with less computational complexity.

Abstract..................i
Content..................ii
List of Figures..................iii
Chapter 1 Introduction..................1
Chapter 2 Background..................4
A. System Model..................4
B. The Conventional IA Scheme..................5
C. The Effect of Imperfect CSI on IA..................7
Chapter 3 A Robust Iterative IA Scheme..................8
A. An Initial Precoder Design..................8
B. A Decoder Design Based on SIR Maximization..................9
C. An Iterative Design of the Precoder and the Decoder..................12
D. Complexity Analysis..................13
Chapter 4 Simulation Results..................15
Chapter 5 Conclusion..................20
References..................21

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