Adaptive Transmission And Interference Coordination For FD-MIMO Systems Exploiting Three Dimensional Statistical Channel State Information

In recent years,massive multiple-input multiple-output(MIMO)has been widely recognized as an effective means of improving capacity and reliability in wireless communication systems,and has attracted significant attention in both wireless industry and academia.Massive MIMO can provide high spectral and energy efficiency,exploit the space resources,enhance the transmit signal and suppress the interference.However,there remains several challenges to build massive MIMO in practice.One of the main challenges is to obtain the channel state information(CSI)at the base station(BS).The downlink training represents a significant bottleneck and the corresponding CSI feedback yields an unacceptably high overhead for the uplink in frequency division duplexing(FDD)system.Using statistical CSI is an effective way to reduce the frequency and amount of computation and data exchange.Another main challenge is that the number of antennas that can be equipped at the BS is limited.Placing the antennas in a two-dimensional(2D)grid is an effective way to reduce the antenna panel size,which is referred to as three-dimensional MIMO(3D-MIMO)or full-dimension MIMO(FD-MIMO).Therefore,in this thesis,the adaptive transmission and interference coordination exploiting statistical CSI are investigated for FD-MIMO systems with 2D unitary planar antenna array at BS.Firstly,the downlink adaptive transmission and user scheduling algorithm exploiting only statistical CSI is introduced for single cell FD-MIMO systems.Using Mullen's inequality,a closed-form lower bound of each user's average signal-to-leakage-and-noise ratio(SLNR)is derived.Based on the maximization of the derived lower bound,it is obtained that the BS should schedule the users which are orthogonal in strongest horizontal or vertical eigen-direction.Furthermore,a low complexity 3D beamforming space division multiple access(SDMA)transmission algorithm is derived.Simulation results show that the achievable sum rate performance of the 3D beamforming transmission algorithm with only statistical CSI at BS is comparable to or even better than the traditional zero-forcing(ZF)and matched filter(MF)algorithm when the instantaneous CSI obtained at BS is imperfect.Moreover,it requires much less feedback overhead for FDD systems and is of lowcomplexity.Next,the downlink adaptive transmission scheme and interference coordination strategy exploiting only statistical CSI are investigated for heterogeneous networks(HetNets)where 2D large-scale antenna array is deployed at macro BS,while conventional multiple antenna array is deployed at each small cell.First,a closed-form approximation of the signal-to-interference-plus-noise ratio(SINR)of macro users and a lower bound of the average SINR of small cell users are derived.Then,based on the maximum of macro users' SINR approximation,the 3D beamforming transmission algorithm for FD-MIMO homogeneous network is extended to the FD-MIMO HetNets we considered.Based on this transmission algorithm,and the derived SINR approximation and lower bound,a low-complexity interference coordination strategy using only statistical CSI is proposed,and closed-form approximated ergodic rate of macro users and small cell users are derived.Simulation results show that the proposed downlink transmission and interference coordination strategy can achieve good tradeoff between the throughput of macro and small cells.Finally,the downlink transmission and interference coordination for multi-cell FD-MIMO systems taking into account both fairness and throughput are investigated.First,the 3D beamforming transmission algorithm is extended to multi-cell FD-MIMO downlink systems,and a priority is introduced for each user.Then,a 3D beamforming transmission algorithm based on the priority is proposed to improve the fairness of users.Next,the users of each cell are divided into center users and edge users based on the statistical CSI of each users.In order to reduce the complexity and information exchange,we ignore the center users,and only consider the interference coordination for the edge users.Based on these results,using the closed-form lower-bound of the average signal-to-interference ratio,an interference coordination strategy using statistical CSI and priority is proposed.The proposed strategy has low complexity,and low feedback and information exchange overhead.Simulation results show that the proposed downlink transmission algorithm and interference coordination strategy effectively improve the cell-edge rate and average user rate,and can achieve good fairness between users.