本文選題：Massive + MIMO系統(tǒng)��； 參考：《北京交通大學(xué)》2017年碩士論文

【摘要】：Massive MIMO(multiple-input multiple output)技術(shù)在基站側(cè)部署大量天線,可以在同一時(shí)頻資源上同時(shí)服務(wù)大量用戶,不僅可以提高系統(tǒng)速率和可靠性,還可以降低基站發(fā)射功率,成為5G候選技術(shù)之一。Massive MIMO優(yōu)勢的實(shí)現(xiàn)依賴于準(zhǔn)確的信道狀態(tài)信息(channel statement information,CSI)。FDD(Frequency division duplex)模式下,CSI的獲得依賴用戶反饋,參考信號(hào)和用戶反饋的開銷隨著天線數(shù)目增加而不可接受。因而通常將Massive MIMO技術(shù)用于TDD(time-division duplex)模式,利用信道的互易性,根據(jù)用戶發(fā)送的上行導(dǎo)頻來做信道估計(jì),獲得CSI。真實(shí)系統(tǒng)中,導(dǎo)頻長度有限,小區(qū)間共用一套導(dǎo)頻,不同小區(qū)用戶發(fā)來的非正交導(dǎo)頻造成導(dǎo)頻污染。導(dǎo)頻污染嚴(yán)重制約了 Massive MIMO系統(tǒng)的性能。如何抑制導(dǎo)頻污染成為Massive MIMO系統(tǒng)亟待解決的問題。本文首先研究了線狀蜂窩網(wǎng)絡(luò)中的導(dǎo)頻污染,分析了系統(tǒng)的信道估計(jì)誤差和頻譜效率以及影響導(dǎo)頻污染的多種因素,包括天線數(shù)量、小區(qū)數(shù)量、導(dǎo)頻長度、交叉增益等。在研究面狀蜂窩網(wǎng)絡(luò)時(shí),充分借鑒了線狀蜂窩網(wǎng)絡(luò)的結(jié)論。面狀蜂窩網(wǎng)絡(luò)中,小區(qū)數(shù)目較多,小區(qū)間共用同一套正交導(dǎo)頻時(shí),導(dǎo)頻污染嚴(yán)重。針對這一現(xiàn)狀,本文從降低干擾和增強(qiáng)有用信號(hào)兩個(gè)方面尋找解決Massive MIMO系統(tǒng)中的導(dǎo)頻污染問題的方法。在降低干擾方面,對比了兩種常用導(dǎo)頻污染抑制算法:時(shí)隙偏移法和導(dǎo)頻功率控制法。研究表明這兩種方法都可以將交叉增益較大、干擾較強(qiáng)的小區(qū)用戶發(fā)送導(dǎo)頻的時(shí)隙與目標(biāo)小區(qū)用戶發(fā)送導(dǎo)頻時(shí)隙錯(cuò)開,在時(shí)域提供導(dǎo)頻正交性,抑制導(dǎo)頻污染。但在時(shí)隙偏移法中,消除導(dǎo)頻污染的同時(shí)引入了相鄰小區(qū)的數(shù)據(jù)干擾。而且需要頻繁修改幀結(jié)構(gòu),不靈活,實(shí)用性低。相比而言,導(dǎo)頻功率控制算法不會(huì)引入其他干擾,而且只需要縮短導(dǎo)頻長度就可以實(shí)現(xiàn),簡單實(shí)用。在增強(qiáng)有用信號(hào)方面,各小區(qū)基站采用低復(fù)雜度的混合模擬/數(shù)字波束賦形結(jié)構(gòu)。在模擬域,基站產(chǎn)生一系列不同方向的模擬波束,用戶通過測量選擇最佳模擬波束接入。顯然,模擬波束的設(shè)計(jì)和選擇關(guān)系到信道估計(jì)的準(zhǔn)確性和導(dǎo)頻接收質(zhì)量。本文詳細(xì)設(shè)計(jì)了模擬域波束的分布模型、波束集合、最佳波束的搜索等。并提出了基于角度和幅度的插值優(yōu)化算法。插值算法基于模擬波束之間的空間相關(guān)性,在插值算法中,基站可以動(dòng)態(tài)調(diào)整模擬波束,令波束更好地對準(zhǔn)用戶,增強(qiáng)目標(biāo)導(dǎo)頻的接收質(zhì)量,進(jìn)一步降低導(dǎo)頻污染,提升系統(tǒng)性能。對解決Massive MIMO系統(tǒng)中導(dǎo)頻污染問題有一定的理論價(jià)值和實(shí)踐意義。
[Abstract]:Massive MIMO(multiple-input multiple output (Massive MIMO(multiple-input multiple output) technology deploys a large number of antennas on the base station side, which can simultaneously serve a large number of users on the same time-frequency resource. It can not only improve the system speed and reliability, but also reduce the base station transmission power.As one of the 5G candidate technologies, the realization of passive MIMO advantage depends on the accurate channel statement information channel statement information CSI, FDD frequency division duplexe mode. The cost of reference signal and user feedback is unacceptable with the increase of the number of antennas.Therefore, the Massive MIMO technology is usually used in the TDD(time-division duplex mode. The channel estimation is based on the uplink pilot sent by the user and the CSI is obtained by using the reciprocity of the channel.In the real system, the pilot length is limited, and a set of pilots is shared in each cell, and the non-orthogonal pilots sent by different cell users cause pilot pollution.Pilot pollution seriously restricts the performance of Massive MIMO system.How to suppress pilot pollution has become an urgent problem in Massive MIMO system.In this paper, pilot pollution in linear cellular networks is studied firstly. The channel estimation error and spectral efficiency of the system are analyzed, as well as various factors affecting pilot pollution, including the number of antennas, the number of cells, pilot length, cross-gain and so on.In the study of planar cellular networks, the conclusion of linear cellular networks is fully used for reference.In planar cellular networks, the number of cells is large, and the pilot pollution is serious when the cells share the same set of orthogonal pilots.In view of this situation, this paper looks for ways to solve the pilot pollution problem in Massive MIMO system from the aspects of reducing interference and enhancing useful signals.In the aspect of reducing interference, two common pilot pollution suppression algorithms are compared: slot offset method and pilot power control method.The results show that both of the two methods can stagger the pilot time slots of the cell users with large cross-gain and strong interference with the target cell users to provide pilot orthogonality in time domain and suppress pilot pollution.However, in the time slot migration method, the data interference of adjacent cells is introduced while the pilot pollution is eliminated.Moreover, the frame structure needs to be modified frequently, which is inflexible and low practicability.In contrast, the pilot power control algorithm does not introduce other interference, and only need to shorten the pilot length can be achieved, simple and practical.In the aspect of enhancing useful signals, each cell base station adopts a low complexity hybrid analog / digital beamforming structure.In analog domain, the base station generates a series of analog beams in different directions, and users choose the best analog beam access through measurement.It is obvious that the design and selection of analog beam is related to the accuracy of channel estimation and the quality of pilot reception.In this paper, the beam distribution model, beam set and optimal beam search are designed in detail.An interpolation optimization algorithm based on angle and amplitude is proposed.The interpolation algorithm is based on the spatial correlation between the analog beams. In the interpolation algorithm, the base station can dynamically adjust the analog beam, make the beam better aimed at the user, enhance the receiving quality of the target pilot, and further reduce the pilot pollution.Improve system performance.It has certain theoretical value and practical significance to solve pilot pollution problem in Massive MIMO system.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TN919.3

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本文編號(hào)：1768959