由於對室內無線通訊高傳輸速率需求的提高，在六十秭赫附近廣大的無須執照頻寬受到了很多的關注。IEEE 802.15.3c工作團隊制定了中心頻率於六十秭赫的無線個人區域網路的通道模型和實體層的標準。在IEEE 802.15.3c通道模型下，我們所使用的是多輸入多輸出正交分頻多工 (Multiple-Input-Multiple-Output Orthogonal Frequency Division Multiplexing, MIMO-OFDM) 系統。我們考慮同時有多組的傳送端接收端在進行通訊的情況，他們在通訊過程中會干擾到彼此而影響到通訊品質。干擾對齊技術 (Interference Alignment, IA) 是近期一種有效降低干擾影響的方法。
在本論文中，我們將不同干擾對齊方法應用於多用戶多輸入多輸出正交分頻多工六十秭赫室內通訊系統，包含閉合形式干擾對齊 (Closed-form Interference Alignment, CIA)、最小投影誤差 (Minimum Projection Error, MPE) 演算法、疊代干擾對齊 (Iterative Interference Alignment, IIA) 演算法和最大訊號干擾雜訊比 (Maximum Signal-to-Interference-Plus-Noise Ratio, MSINR) 演算法。我們比較了不同干擾對齊方法的效能，並討論在IEEE 802.15.3c通道模型中直視性 (Line-of-Sight, LOS) 和非直視性 (Non-Line-of-Sight, NLOS) 通道模型的效能差異。閉合形式干擾對齊、最小投影誤差演算法、疊代干擾對齊演算法有相似的效能，而最大訊號干擾雜訊比演算法則和其他三個方法有較不相同的效能。相對於其他三個干擾對齊方法，在最大訊號干擾雜訊比演算法中，多加考慮了雜訊 (Noise) 的影響。因此在雜訊影響較大的情況時，最大訊號干擾雜訊比演算法會比其他演算法有更好的效能增益。另外對於最小投影誤差演算法、疊代干擾對齊演算法和最大訊號干擾雜訊比演算法，演算法的初始值會影響效能。因此我們也進一步在直視性和非直視性通道模型中，討論初始值對於演算法效能影響的差異。

Due to the increasing demand for high data-rate indoor wireless communications, the large amount of unlicensed bandwidth around 60 GHz has attracted much attention. The IEEE 802.15.3c Task Group established a channel model and developed a physical layer framework to support the wireless personal area networks operating at the 60 GHz band. In this thesis, the multiple-input-multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) scheme is used over the IEEE 802.15.3c channel model. We consider the scenario in which multiple transmitter-receiver pairs communicate simultaneously such that the transmitter-receiver pairs interfere each other. Interference alignment (IA) is applied to mitigate the effects of the inter-user interference by aligning and suppressing the inter-user interference with the precoding matrices at the transmitters and the combining matrices at the receivers.
The performances of the closed-form IA (CIA), the minimum projection error (MPE) algorithm, the iterative interference alignment (IIA) algorithm, and the maximum signal-to-interference-plus-noise ratio (MSINR) algorithm are compared. The difference of the performance phenomena between IEEE 802.15.3c line-of-sight CM1.1 and non-line-of-sight CM2.1 channel models is investigated. In CM2.1, the MSINR algorithm has better performance than CIA, MPE, and IIA since the power of additive white Gaussian noise is considered in MSINR. In CM1.1, the MSINR algorithm outperforms other algorithms at low signal-to-noise ratios while the four IA algorithms have similar performance at medium to high signal-to-noise ratios. It is also found that different closed-form solutions may result in different performances. For iterative algorithms, initialization of the precoding matrices also affects the performance. Random initialization may result in the convergence to the local optimum, instead of the global optimum. In CM1.1, using the results of the iterative procedure in the previous channel realization as the initialization of the precoding matrices can improve the performance; yet, however, no improvement can be obtained by using this method in CM2.1.

1. Introduction
2. 60 GHz Indoor Channel and System Models
2.1 Overview of 60 GHz Indoor Channel Model
2.2 Multi-user MIMO-OFDM System Model
3. Interference Alignment Algorithm
3.1 Closed-form Interference Alignment
3.2 Minimum Projection Error Algorithm
3.3 Iterative Interference Alignment Algorithm
3.4 Maximum SINR algorithm
4. Simulation Results
4.1 Performance Comparison between the Interference Alignment Algorithms
4.2 Non-Uniqueness of Closed-Form Interference Alignment
4.3 Effect of Initialization on Interference Alignment Algorithms
5. Conclusions

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