多使用者中之大規模多輸入多輸出毫米波系統下混合式波束成型之設計

大規模多輸入多輸出(Massive-MIMO)目前被認為是實現毫米波蜂巢式通訊系統(mmWave cellular communication)的重要技術。其中大規模多輸入多輸出的主要應用是能同時在同頻段下服務多個使用者。然而使用傳統全數位波束成型(Fully-digital Beamforming)去實現大規模多輸入多輸出會造成硬體成本過大的問題。因此文獻提出了結合低維度之數位波束成型與低複雜度之類比波束成型的混合式波束成型來降低所需的硬體成本。本篇論文針對多使用者中之大規模多輸入多輸出系統去探討混合式波束成型之設計。為了在最大化訊號能量且不放大干擾的目標下，我們採用了群體最大訊號干擾雜訊比濾波器作為類比波束成型之設計。此外，我們將所提出的方法延伸到更通用的混合式波束成型之架構，讓基地台可以使用多出的射頻鏈(RF Chain)去提升系統效能或是能操作在射頻鏈數目少於使用者的狀況下。最後我們考慮當類比部分有硬體失真所造成的影響並提出在數位部分的補償方法減少效能損失。從模擬結果可以發現:比起其他現有的方法，所提出的混合式波束成型之架構可以在不同的狀況下，在複雜度和效能間取得較好的平衡。

關鍵字

大規模多用戶多輸入多輸出；多使用者傳輸；毫米波；混合式波束成形技術

並列摘要

Massive multiple-input multiple-output (MIMO) will be an important ingredient in millimeter-wave (mmWave) cellular communication systems. A natural application of massive MIMO is simultaneous transmission to multiple users. Unfortunately, the hardware constraints in massive MIMO make it difficult to apply conventional fully digital beamforming techniques, especially in mmWave. Thus hybrid beamforming (HB) in which the overall beamformer consists of a low-dimensional digital beamformer followed by an analog beamformer has been proposed for reducing the number of costly radio frequency (RF) chains in massive MIMO systems. This thesis considers HB design for the multiuser massive MIMO system. We adopt the group maximum signal-to-interference-plus-noise-ratio (SINR) filter bank (GMSINR-FB) as our analog beamformer which can maximum the signal power while considering the effect of interference. Furthermore, the proposed method is extended for generalized HB scheme which can use extra RF chains to increase the system performance and still can work when number of RF chains less than number of users. Finally, we consider the hardware impairment in analog part and proposed compensate method in digital part. The simulation results demonstrate that the proposed HB scheme can balance complexity and performance compare with other methods in various scenarios.