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Location Determination of Base Station and Precoding Matrix Selection of Hybrid Beamforming for 5G Wireless Communications
|Authors: ||Lin, Tsung-Ching|
|Contributors: ||NTOU:Department of Communications Navigation and Control Engineering|
Millimeter Wave;Hybrid Beamforming;Precoding;Green Communication
|Issue Date: ||2020-07-09T02:52:31Z
|Abstract: ||近年來為了因應第五代行動通訊技術需求，毫米波(Millimeter Wave)逐漸成為無線通訊領域中非常熱門的研究項目。然而利用毫米波進行無線通訊會受到嚴重的路徑衰減(path loss)問題，以及前端天線射頻設計上的困難。5G系統將可能大量布建小型基地站(small cell)來維持細胞邊緣(cell edge)的通道容量(channel capacity)及彌補訊號無法穿透牆壁或建築物的問題；另一方面，利用混合式波束成形架構(Hybrid Beamforming)可以有效克服巨量天線(Large Scale Antenna Arrays)場景下較高的硬體成本及功率耗損。因此本文致力於研究基地位站位置選擇方法，以及混合式波束成形中預編碼(Precoder)的決定。 本文根據使用者在不同分布的場景下，推導出一合理的基地站位置，最後將理論位置與模擬位置進行比較。根據模擬結果，本文提出之方法可以使基地站到使用者間距離平均最短，達成降低通道衰減之目的。在混合式預編碼方面，本文將射頻(RF)和基頻(BB)分開討論，在RF部分本文提出一方法，其將天線陣列指向空間中擁有最大增益之路徑角度，經過模擬可以證明，提出方法對訊號的增益比子陣列(subarray)方法要大；而在BB部分本文參考LTE系統預設之碼書，降低系統回傳的資料量。本文將提出方法與Beam Steering、Sparse Precoding及Precise SVD等方法進行電腦模擬與分析。在訊號增益的模擬比較中，本文提出方法在TDD系統中約比Sparse precoding高1.2 dB，比Beam steering高2.7 dB；而在FDD系統中，提出方法約比Precise SVD高出7.4 dB。|
Due to the various requirements of fifth generation (5G) cellular network technology, millimeter wave transmission has become an important issue in wireless communications in recent years. However, transmissions at millimeter wave bands suffer from significantly high path loss and heavy complexity of hardware design. The 5G system may use numerous small cells to maintain the capacity of cell edge users and avoid signals being blocked by walls and buildings. On the other hand, using hybrid beamforming architecture can effectively reduce the cost and power consumption when large scale antenna arrays are used. Therefore, this thesis dedicates to studying the location determination methods of base station and precoding matrix selection of hybrid beamforming. In this thesis, we derive a proper location of base station based on different user distributions, and compare the theoretical location with simulated one. According to the simulation results, the derived results can have the minimum average distance between base station and users, which leads to reducing the path loss to radio signals. For the hybrid precoding, we divide the issue into two parts, RF and baseband respectively. In respect of analog precoder, we propose the principle that steers whole antenna array to the main path of the channel. This thesis also proves that the proposed scheme has better received signal strength than the methods of dividing the antenna array into subarrays. In addition, we adopt codebook defined by LTE system as reference to determine the baseband precoder. Finally, we compare the proposed method with Beam Steering, Sparse Precoding and Precise SVD in terms of the performance of sum rate and signal gain. The simulation shows that our proposed method has good performance in both TDD and FDD systems, and has the advantage of reducing feedback overhead.
|Appears in Collections:||[通訊與導航工程學系] 博碩士論文|
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