Research On MIMO And Multi-user Relay Selection With Energy Constraints

The high capacity and high spectral efficiency of wireless communication system can be realized by using the technique of multiple-Input-Multiple-Output(MIMO)without increasing power and bandwidth.Meanwhile,the relay cooperation technology can improve the reliability of link and system coverage.Therefore,wireless MIMO cooperative communication system has received extensive attention.As to cooperative system,the performance of the system is directly affected by the results of the relay selection.The existing MIMO relay selection methods usually choose relay based on the maximization of channel capacity,ignoring the fairness of energy utilization for relay nodes with energy bottleneck,which will lead to the reduction of network life time,the reduction of system energy efficiency and the coverage performance of the system.This paper studies this problem in wireless MIMO cooperative communication system,the specific contents are as follows:(1)The antenna and relay selection under the condition that the relay node is powered by battery is studied.Since the battery-powered relay nodes with good channel conditions will be frequently selected under the action of the existing relay selection methods,resulting in rapid energy consumption,once the energy is exhausted,the system capacity will be reduced.Contrary to the influence of existing relay selection methods on the capacity enhancement of the power supply relay nodes,the residual energy of the relay nodes is considered in this paper based on the fairness of energy utilization.In this paper,the antenna selection of wireless MIMO cooperative communication system is controlled by setting the life time threshold and the method of relay selection based on the antenna selection results is proposed,and compared with the antenna selection method based on traversal combination calculation.The computational complexity is greatly reduced.On this basis,the average channel capacity and network lifetime of the proposed method are simulated.he simulation results show that the proposed relay selection method can approach the optimal channel capacity and improve the network lifetime effectively,which is of positive scientific significance.(2)The multi-user relay selection is studied under the condition that the relay node is powered by energy harvesting.A multi-user wireless cooperative communication system model consisting of a source node,multiple EH relay nodes and multiple destination nodes is established.In the case of multi-user equal power transmission,the fairness of energy utilization is considered.A multi-user relay selection method based on energy constraints is proposed and analyzed theoretically.The mathematical expressions of average channel capacity and outage probability are derived.On this basis,the average channel capacity,outage probability and system energy efficiency of the proposed method are theoretically and numerically verified.The numerical results show that the proposed method can effectively improve the channel capacity and energy efficiency of the system and reduce the interruption probability of the system,which is of positive scientific significance.