適用於毫米波頻段之強韌性混合式波束成型技術應用於多使用者傳輸系統

在ㄧ般常見的混合式波束成型技術，都是假設已取得完全的通道資訊下去設計的，但在實際情況，通道資訊的取得會受通道估計的誤差或通道時變的特性以及回傳的延誤等而有所影響，如此之下，用ㄧ般的波束成型技術去設計會導致最後的效能不如預期。因此本篇論文針對，在通道資訊無法準確估計的情況下，去設計強韌性混合式波束成型演算法，比起ㄧ般不強韌性的波束成形技術更能維持住最後的效能。而採用的混合式波束成型設計方法是群體最大信號干擾訊雜比濾波器來作為類比波束成型之設計。在ㄧ般情況下，通道估計受到的誤差為高斯分布時，我們把波束成型的問題轉換成機率限制條件動態最佳化的問題去解決，然後在最佳化問題之限制條件存在機率的隨機變數時，沒有完整的解析解，因此我們針對機率限制條件去處理，並各別拆開去作推導與處理，最關鍵的點是最後把它們都轉換成凸函數限制條件，因此可以解出該情況下之最佳解。另外，我們善用毫米波通道稀疏的特性去效率地分配傳輸能量以及抑制干擾，甚至達到在大規模多輸入多數出的系統下，比起傳統強韌性方法，大幅度降低運算複雜度。從模擬結果可以發現，對比其他的強韌性方法有更好的效能以及更低的運算複雜度，而我們提出的設計演算法保障了系統的信號干擾雜訊比的最低要求。

關鍵字

混合式波束成型波束成型技術；群體最大信號干擾訊雜比濾波器；機率限制條件動態最佳化問題；毫米波通道；大規模多輸入多數出

並列摘要

Conventional algorithms of Hybrid Beamforming design are based on the assumption that the channel state information (CSI) is perfectly known at the transmitter. In fact, the perfect CSI may not be obtained easily in practice because of the channel estimation errors or time-varying of channels and feedback delay. And the performance of these algorithms may degrade severely when the CSI is imperfect. This thesis considers the problem of robustness of hybrid beamforming system against imperfect CSI. The traditional technique is to maximize the output signal-to-interference-plus-noise ratio (SINR) of each user to get the maximum sum rate. Provided that the CSI mismatch is Gaussian distribution, we formulate the design problem of hybrid as probabilistically constrained stochastic optimization problems. The probabilistic constraints, in general, have no closed-form expression and difficult to handle. Therefore, we separate the interference into three terms and restrict them respectively, the most important is to convert them into convex constraints. In addition, the sparsity of millimeter wave band channel will be used for allocating the transmit power more efficiently and suppressing the interference. Simulation results show that the proposed method has better performance and lower complexity, it guarantees the receiver's SINR requirement with lower outage probability.

並列關鍵字

Hybrid Beamforming ； Channel State Information Mismatch ； Probabilistically Constrained Stochastic optimization problems ； Sparsity of millimeter wave band channel

參考文獻

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適用於毫米波頻段之強韌性混合式波束成型技術應用於多使用者傳輸系統

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