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    Please use this identifier to cite or link to this item: http://ccur.lib.ccu.edu.tw/handle/A095B0000Q/803


    Title: 波束分群5G下鏈系統之多用戶傳輸技術設計;On the Design of Downlink Multi-user Transmission for Beam-group Division 5G System
    Authors: 郭庭翔;KUO, TING-HSIANG
    Contributors: 通訊工程研究所
    Keywords: 第五代移動通信系統;分波束群多重進接;使用者分群;波束掃描;5G;BgDMA;User grouping;Beam sweeping
    Date: 2017
    Issue Date: 2019-07-17 10:47:55 (UTC+8)
    Publisher: 通訊工程研究所
    Abstract: 4G無線通信系統在各個國家已經發展成熟,但在高科技數位媒體時代,無線網路需求爆炸式的增長,在有限的頻率資源下,如何得到更高、更穩定的系統資料傳輸量,是未來5G發展的關鍵。本論文所研究的波束分群多重進接(Beam-group Division Multiple Access, BgDMA)系統即是針對5G需求而設計。在此系統中有三個關鍵特性,第一,基地台和使用者皆形成多個波束,並且在波束域處理訊號。第二,利用波束處理技術消除通道的頻率選擇性。第三,將使用者進行分群,並且針對使用者分群設計多用戶傳收技術來降低系統複雜度。第四,利用通道稀疏性(channel sparsity),更進一步降低系統的複雜度。本研究專注在BgDMA下鏈系統,利用通道稀疏性設計低複雜度的多用戶預編碼器,還有基地台端使用分時波束掃描技術服務使用者的研究,總共包含四個重要的技術議題。第一,有無使用者分群對系統的影響。第二,不同使用者分群方法對系統的影響。第三,利用通道稀疏性,來降低系統複雜度。第四,分時波束掃描技術對系統的影響。依據系統模擬的結果,針對上述的議題得到以下這四點重要結論。第一,在進行使用者分群的時候,必須對使用者進行正交性的檢查,剔除使用者之間因為正交性低,而造成干擾太大的使用者,否則系統複雜度會很高,而且系統效能差。第二,將使用者分成多個群組,來設計預編碼的話,可以在預編碼的運算複雜度方面,比起沒有進行使用者分群可以改善98.9%的預編碼運算複雜度,讓系統在實際上更好實現,但是會因此降低9.9%的基地台吞吐量,這是系統效能跟複雜度的取捨。第三,利用通道稀疏性設計的預編碼器,減少使用者估測波束的數量,可以更進一步降低系統的複雜度,在基地台吞吐量損失1.2%效能中,預編碼器運算複雜度可以降低35.5%,通道估算的複雜度可以降低45.8%,這是系統性能與系統運算複雜度之間的取捨。第四,基地台使用不同掃描間格次數,在基地台吞吐量方面,當基地台使用兩次掃描時間來服務使用者,基地台的吞吐量會降低31.2%,當基地台使用四次掃描時間,基地台的吞吐量會降低55.6%,基地台使用越多次波束掃描間隔來服務使用者,基地台的吞吐量就會越低。
    4G (4th generation) wireless communication systems have been well-deployed around the world. On the other hand, wireless network demand is growing fast in the era of high-tech digital media. Therefore, with the very limited frequency resources, how to achieve higher and more stable data transmission is the key to the future development of 5G systems.BgDMA (Beam-group Division Multiple Access) system studied in this paper is designed to meet 5G requirements. There are three key features in this system. Firstly, the eNB side and the UE side form multiple beams and process the signal in the beam domain. Secondly, BgDMA resolves channel frequency selectivity in beam-domain.Thirdly, the UEs with severe interference to each other are put into the same group by user grouping, and a group-based multi-user processing can be designed to lower the complexity. Lastly, the channel sparsity can be exploited to further reduce the complexity of the system.This thesis focuses on the design of BgDMA downlink system, including the use of channel sparsity to design low-complexity multi-user precoder and the application of time-division beam sweeping at eNB side to serve the UEs. The key issues investigated including user grouping and its effects on system performance, the use of channel sparsity to reduce complexity and, the use of time-division beam sweeping and its impact on system capacity. According to simulation results, we have the following four important conclusions. Firstly, in terms of user grouping, one must check the UE's orthogonality and remove the UEs with severe interference to each other. If not, the system complexity will be high and the system performance will be significantly degraded. Secondly, dividing the UEs into multiple groups is possible to reduce the precoding complexity by 98.9%, as compared to the system without user grouping. In practice, it is much easier to implement, but the cell throughput will be reduced by 9.9%. Thirdly, the proposed group-based precoder utilizing channel sparsity can reduce system complexity; with a 1.2% loss in cell throughput, the precoding complexity can be reduced by 35.5%, and the channel estimation complexity can be reduced by 45.8%. Fourthly, cell throughput is reduced by 31.2% and 55.6% with two and four beam-sweeping at eNB, respectively. The more umbers of beam-sweeping, the lower the eNB complexity.
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