Research On Energy Efficiency Optimization Key Technologies For Massive MIMO Systems

With the development of wireless mobile communication,the wireless network needs to provide higher data transmission rate to meet the requirements of mobile users.By deploying the large-scale antenna arrays at the base station,Massive MIMO systems can significantly improve the rate of the system without adding extra system bandwidth.Therefore it becomes the key technology of the next generation mobile communications.However,the cost and energy loss of the system are greatly increased with the increasing number of base station antennas.In order to meet people's demand for green communication,the energy efficiency optimization technology is of more practical significance which consider the transmission rate and power consumption.Antenna selection and power allocation technology are two important technologies to improve energy efficiency of Massive MIMO systems.However,in previous studies,antenna selection technology was used to find the optimal subset of transmitting antennas,ignoring the influence of transmitting antennas number and transmitting power on energy efficiency.In the sense of power allocation,it is common to assume that the base station allocates power equally for each user,but the energy efficiency was not analyzed when the transmitting power are allocated unequally among users.To solve these issues,this paper has done a deeper study,the main contents of this paper are as follows:1.We research the influence of transmitting antenna number and transmitting power on energy efficiency of Massive MIMO downlink systems.It is proved that there exists the optimal transmitting power and transmitting antennas number to maximize energy efficiency,and then a joint antenna selection and power allocation algorithm is proposed to find the optimial values.Firstly,a new power consumption model is established,which considers the transmitting power as well as the circuit power consumption,the influence of transmitting antennas number and the users' number on the total power consumption are analyzed.Then the energy efficiency optimization model is found,and energy efficiency is proved to be the convex function of transmitting antennas number and the transmitting power.Based on convex optimization theory,a joint optimization algorithm is proposed to obtain theoptimal transmitting power and the optimal number of transmitting antennas.Simulation results show the existence of the optimal values and the effectiveness of the joint optimization algorithm in improving the energy efficiency of Massive MIMO systems.2.We study the problem of energy efficency optimization when the base station allocate transmitting power unequally for each user,and a new power allocation strategy is proposed in Massive MIMO downlink systems.Firstly,an energy efficiency optimization model aim to maximize energy efficiency is established,and we demonstrate that energy efficiency is a convex function of the user' power.Then energy efficiency optimization algorithm in two different scenarios are analyzed.In the absence of power constraint scenario,an power iterative allocation algorithm is proposed to get the optimal value of users' power.Under the constraint of users' power and transmitting power,the Lagrangian optimization is used to obtain the approximate expression of each user's power optimal value.Finally,the simulation results show that,compared with the equal power allocation algorithm,the proposed algorithm can significantly improve energy efficiency of Massive MIMO systems.