Performance Analysis And Optimization In Dense Hotspot Wireless Networks

The 5th-generation mobile communication technology(5G)will begin commercial application around 2020.Compared to the 4th-generation mobile communication tech-nology(4G),the capacity requirement of the 5G network will increase by 1,000 times.The ultra-dense networks(UDNS)improves the network performance by placing more base stations in the area.It is a very reliable technology that can provide huge capacity gains.However,the UDNs makes the distance between SBSs closer,and the interference between SBSs gets more obvious.In UDNs,since the distance between SBSs is rela-tively close,it is easier to get the channel state information(CSI)of the communication link formed by SBS and the user and submit to the controler.The controler instructs SBSs to send data,achieving the cooperation between SBSs.Since the distance between the antennas of the cooperative SBSs is much larger than the coherence distance of the anten-nas,the cooperative SBSs can form a distributed multiple-input multiple-output(MIMO)system.The users of the cooperative SBS can use the beamforming(BF)method to or-thogonalize the user's received signal vectors in the space domain,achieving the purpose of interference cancellation.Firstly,the grid-based base station deployment methods are introduced,including the ring-shaped base station deployment method and the grid point base station deployment method.The topology structure of the above two base station deployment methods is in-troduced and the performance is analyzed.For the ring-shaped base station deployment method,the effect of the ring radius R and the number of base stations N on the perfor-mance of the entire network is discussed.For the grid points base station deployment method,the influence of the horizontal spacing between SBSs l1 and the vertical spacing l2 on the performance of the network is discussed.Next,the performance of base station deployments based on the Poisson Point Pro-cess(PPP)is discussed.It is assumed that the user's distribution is a mixed two-dimensional Gaussian distribution to reflect the user's heterogeneity and aggregation in the network.A tractable method is proposed to calculate the coverage area rate and spectral efficiency under this scenario.And related parameters that affect network performance are discussed.Finally,the user's receive signal-to-interference ratio(SIR)performance in the net-work is optimizated.The optimization process is divided into two steps.At the first step,considering the requirements of synchronization and complexity of the network,cluster-ing based on th depth-first search and user-centric clustering algorithm are proposed.At the second step is the Zero-Forcing Beamforming(ZFBF)technique based on SBS co-operation are used to optimize the user's receive SIR in the network,besides,simulation analysis is used to discuss the performance of the optimized network.