【摘要】：大規(guī)模MIMO是5G中的關鍵技術,其陣列天線增益,能在同一時頻資源下支持大量的數(shù)據(jù)流,成倍的提高系統(tǒng)容量和傳輸速率,已經成為了當今通信領域研究的熱點。在TDD系統(tǒng)的大規(guī)模MIMO中因為上下行鏈路具有互易性,基站端只要獲得上行預編碼矩陣,下行就可以利用轉置后的預編碼矩陣進行傳輸。基站處理方便,并且能充分利用大規(guī)模MIMO的天線增益,提高系統(tǒng)頻譜效率和能效。但是,因為導頻序列有限,基站對目標用戶進行導頻估計的時候,就會受到相鄰小區(qū)用戶的干擾,出現(xiàn)導頻污染問題,并且導頻污染并不會隨著基站天線的增加而降低,這嚴重限制了大規(guī)模MIMO多天線的性能。因此,本文從大規(guī)模MIMO TDD系統(tǒng)的概念和傳輸模式,分析多小區(qū)導頻污染的原因,然后通過多小區(qū)復用不同的導頻,來研究導頻污染問題,最后提出改進的方案和調度流程,對導頻污染進行分析驗證。主要工作如下:首先,介紹課題的研究背景,對大規(guī)模MIMO系統(tǒng)中導頻污染問題的研究現(xiàn)狀進行歸類總結,給出本文的研究意義和研究內容;從MIMO信道模型、信道容量和天線間的相關性進行分析,介紹大規(guī)模MIMO的基本模型和傳輸原理。分析討論常用的用于信道檢測的線性預編碼,并對檢測性能進行仿真分析。然后,論文對TDD系統(tǒng)的傳輸模式和導頻幀結構進行了介紹,引出了大規(guī)模MIMO TDD系統(tǒng)中的導頻污染問題。詳細分析了導頻污染的原因、導頻污染對大規(guī)模MIMO系統(tǒng)性能的影響,并進行仿真驗證。結果表明,存在導頻污染的多小區(qū)系統(tǒng),系統(tǒng)的可達和速率并不會隨著天線數(shù)的增加而提高,僅取決于小區(qū)間的交叉增益值,交叉增益值越大,導頻污染越嚴重�；趯ьl污染的分析,提出了多小區(qū)的導頻復用方案,通過多小區(qū)復用不同的導頻,對系統(tǒng)的能量效率進行分析。仿真表明高的導頻復用因子可以提高系統(tǒng)的能量效率,進而提高系統(tǒng)的和速率,減輕了導頻污染,但前提條件是犧牲多的導頻資源。最后,論文基于導頻的功率控制提出了改進的系統(tǒng)模型和導頻調度方案。通過對小區(qū)用戶的界定,將容易受到導頻干擾的邊緣用戶進行導頻的調度,從而避開了同時使用相同導頻的用戶。最后通過多小區(qū)線性預編碼對改進方案下系統(tǒng)的能量效率、頻譜效率和系統(tǒng)可達和速率進行仿真分析。仿真結果表明,相比于導頻污染系統(tǒng),改進方案能達到減輕小區(qū)導頻污染的效果。
[Abstract]:Large-scale MIMO is a key technology in 5G. Its antenna array gain, which can support a large number of data streams under the same time-frequency resource, has become a hot topic in the field of communication. In large scale MIMO of TDD system, because of the reciprocity between uplink and downlink, the base station can transmit by transposed precoding matrix as long as the uplink precoding matrix is obtained. The base station is convenient to process and can make full use of the antenna gain of large scale MIMO to improve the spectral efficiency and energy efficiency of the system. However, because of the limited pilot sequence, when the base station carries out pilot estimation of the target user, it will be interfered by the adjacent cell users, and the pilot pollution will not be reduced with the increase of the base station antenna. This severely limits the performance of large-scale MIMO multi-antennas. Therefore, from the concept and transmission mode of large-scale MIMO TDD system, this paper analyzes the causes of multi-cell pilot pollution, then studies the pilot pollution problem through multi-cell multiplexing different pilot frequencies, and finally puts forward an improved scheme and scheduling flow. The pilot pollution is analyzed and verified. The main work is as follows: firstly, the research background of the subject is introduced, and the research status of pilot pollution in large-scale MIMO system is classified and summarized. The research significance and content of this paper are given. The correlation between channel capacity and antenna is analyzed, and the basic model and transmission principle of large scale MIMO are introduced. The linear precoding used in channel detection is discussed, and the detection performance is simulated. Then, the transmission mode and pilot frame structure of TDD system are introduced in this paper, and the pilot pollution problem in large scale MIMO TDD system is introduced. The causes of pilot pollution and the influence of pilot pollution on the performance of large scale MIMO system are analyzed in detail and verified by simulation. The results show that in the multi-cell system with pilot pollution, the reachability rate of the system does not increase with the increase of the number of antennas, but only depends on the cross-gain value of the interval. The greater the cross-gain value, the more serious the pilot pollution. Based on the analysis of pilot frequency pollution, a multi-cell pilot multiplexing scheme is proposed. The energy efficiency of the system is analyzed by multi-cell multiplexing different pilots. The simulation results show that the high pilot multiplexing factor can improve the energy efficiency of the system, thus improve the sum rate of the system and reduce the pilot pollution, but the precondition is to sacrifice more pilot resources. Finally, the paper presents an improved system model and pilot scheduling scheme based on pilot power control. By defining the cell users, the edge users who are susceptible to pilot interference are scheduled for pilot frequency, thus avoiding the users who use the same pilot frequency at the same time. Finally, the energy efficiency, spectrum efficiency and reachability rate of the system under the improved scheme are simulated and analyzed by multi-cell linear precoding. The simulation results show that compared with pilot pollution system, the improved scheme can reduce pilot pollution.
【學位授予單位】：蘭州交通大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TN919.3;TN929.5

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本文編號：2234676