Studies On The Multi-Relay Selection And Cooperative Transmission With The Consideration Of Energy Utilization Optimization

In the wireless cooperative communication system,the relay nodes are often mobile,the power protection of mobile relay nodes is a difficult problem,the battery life of a battery-powered relay node is limited,when the power consumption of this kind of relay node is exhausted,the overall performance of the system will be affected.With the development of green communication technology,relay nodes adopting energy harvesting technology are expected to overcome this bottleneck and obtain sustained and stable power supply.Relay selection is one of the key technologies of wireless cooperative communication,the performance of relay selection is related to the merits of the system performance,relay selection includes single relay selection and multiple relay selection.Compared with single relay selection,multiple relay selection can provide diversity gain and improve the reliability and effectiveness of the system.In this paper,two types of relay nodes are considered for battery power supply and energy harvesting,from the angle of optimizing the energy utilization,the multiple relay selection and cooperative transmission of the wireless cooperative communication system are studied,the specific contents are as follows:(1)In the wireless cooperative communication system consisting of battery powered relay nodes,the transmitting power of relay nodes is obtained by using the water injection power algorithm,considering the residual capacity of the battery,a multiple relay selection method considering the channel state and battery power is proposed.This method can meet the different demands of users for data rate,and achieve a balance between transmission efficiency and system life time.On this basis,the battery powered relay node is changed to energy harvesting relay node,from the perspective of optimization energy utilization,the multiple relay selection problem under the energy harvesting technology is studied,on the basis of the above method,a multiple relay selection method based on energy efficiency is proposed.The simulation results show that the above two methods can improve the system lifetime and energy efficiency while ensuring the data rate of the system,and have good system performance.(2)In the wireless EH cooperative communication system containing energy harvesting relay nodes,the traditional fixed bandwidth allocation method will lead to the waste of resourcesand no longer apply because of the use of energy harvesting technology to supply the power to the system.In this paper,based on the fairness of bandwidth allocation and the rational utilization of collected energy,a cooperative transmission method of shared bandwidth in the wireless EH cooperative communication system is proposed,through the shared bandwidth of the source nodes and relay nodes,the relay nodes assist the source nodes to transmit data and ensure the data transmission of the self service.The simulation results show that the proposed method can achieve the dual goal of optimizing cooperative transmission and self data transmission,and improve the energy efficiency of the system.