Research On Key Theory And Technoglogy Of Wireless Massive MIMO System

With the rapid popularity of smart-terminals, wireless data traffic and energy consumption are showing explosive growth. In view of above situation, spectral efficiency and energy consumption are become the most important metrics for the development of the future wireless communication networks. Recently, massive multiple-input multiple-output (MIMO) has drawn considerable attention from both the academia and industry, since it can improve spectral efficiency, decrease tramsmit power, induce intra/inter-cell interference without extra spectrum resource.This dissertation mainly focuses on key theories and technologies of massive MIMO system for the further wireless communication to improve spectral efficiency and reduce energy consumption. My research encompasses the moment matching method for massive distributed MIMO (D-MIMO) systems, the receive techniques and performance analyses for single cell three-dimensional (3D) massive MIMO systems, the precoding techniques and performance analyses for noncooperative 3D massive MIMO systems, and the receive techniques and performance analyses for cooperative 3D massive MIMO systems. The main works and contributions of my dissertation are shown as follows:1. For two-dimensional (2D) D-MIMO systems, we propose a moment-matching based method to approximate the composite fading channels and excute a large-antenna analysis. In D-MIMO systems, each radio link is effected by composite fading channels. However, the probability density functions (PDFs) of receive signal-to-noise ratio (SNR), cumulative distribution function (CDF), achievable sum rate, symbol error rate (SER), and outage probability involve special functions such as Bessel, Meijer-G, and Hypergeometric functions, which can not be further analysis. Thus, we propose an approximate analytic method by using moment-matching method, and performance analysis for approximate KG fading channels is also investigated. The main research as follows:Firstly, we use a PDF to approximate the PDF of the composite fading channels. Secondly, we derived the relationships between parameters of approximate PDF and the composite PDF by matching the mean and the variance of these two functions. Thirdly, we obtain the approximate PDF by the parameter relationships. Finally, the approximate analytical expressions for the achievable sum rate, SER, outage probability of the D-MIMO system with ZF receivers are deduced, and then the large-system analysis is excuted in this chapter. Our proposed method does not only involve simple functions, but also can be applied in massive MIMO technique.2. For single cell multiuser 3D massive MIMO systems, we propose a low bound of the achievable sum rate in closed-form expression for ZF receivers and pursue a large-antenna analysis.3D MIMO not only consider the effects of horizontal dimension of antenna as 2D MIMO, but also consider the effects of elevation in the vertical dimension. In this case,3D MIMO is a promising technology to improve the performance and enhance the cell-edge coverage. Therefore, we propose closed-form lower bound on the achiebable sum rate employing ZF receivers, account for both 3D MIMO technique and high-rise 120 propagation environments, as well as user 3D distributions. By flexibly adjusting the BS antenna tilt angle, we can derive the achievable sum rate for different user distributions and pursue large-antenna analysis.3. For noncooperative multi-cell 3D massive MIMO systems, we deduce novel, exact analytical expressions for downlink data rate, SER, and outage probability by using MRT precoding and pursue large-antenna analysis. In noncooperative multi-cell 3D massive MIMO systems, the performance is not only effected by small-scale fading and large-scale fading, but also effected by inter-cell interference (co-channel interference). Therefore, we propose novel closed-form expressions of the achievable data rate, SER, and outage probability by employing normalized MRT precoding. Then, we investigate the effects of BS antenna tilt angle on system performance and pursue the large-antenna and interference analyses.4. In order to cancel inter-cell interference and pilot contamination, we further investigate cooperative multi-cell 3D massive MMO system and propose a low bound on the achievable sum rate by using ZF receivers, accounting for spatial correlation at the transmit side. First, the multi-cell 3D MIMO model is introduced, accommodating 120 high rise propagation environments, Rayleigh/Log-Normal composite fading model, and antenna correlation at the transmit side. Second, a closed-form lower bound on the achievable sum rate of the 3D MIMO by employing ZF receivers is provided. This closed-form expression involves simple functions, which can be more efficiently evaluated compared to brute-force Monte-Carlo simulations. Third, with the help of the proposed lower bound, we analyze the asymptotic lower bound for 3D massive MIMO systems under the case that the average and total powers are fixed, respectively. Finally, we provide a closed-form approximated solution for the number of users, which maximizes the sum rate under a fixed receive antenna number.