Research Of Resource Allocation In Wireless Relay Communication Networks With Energy Harvesting

With the rapid development of wireless mobile communication and the glaring problem of energy consumption,Energy Harvesting(EH)and transmission of wireless communication have become hot research topics in recent years.The traditional communication networks with constrained energy are of limited operational life-time.Workers need to replace or charge the batteries frequently so as to maintain the continuity of the equipment like relays,which may bring about more complexity and unfeasibility in realizing the design of network.Therefore,the function of wireless communication network has been redefined and expanded by the international academia.The researchers began to consider the transmission of information and energy in parallel.The problem of limited operational life-time of traditional energy constrained communication networks can be completely solved if radio frequency signals could be harvested through communication network.Consequently,wireless communication technology based on energy harvesting develops rapidly in recent years.Although cellular network of wireless communication network has been widely used,it still has its own defects in the structure.For example,the quality of service can hardly be guaranteed due to serious path loss caused by the far distance of users at the edge of the cell.The base station must increase the power of transmission to improve the rate of the users,which will not only reduce the efficiency,but also produce more radiation.Relay can well solve this problem.The base station can not only cover the edge users with smaller power,but also achieve spatial diversity and increase capacity of the system.Besides,relay can also overcome deep fading.Therefore,power supply of the relay may determine the performance of the communication network.In the wireless relay communication network based on energy harvesting,we should consider not only the information transmission,the causality of harvest and use of energy and user fairness,but also the resource allocation of transmission power between nodes and time for transmission of energy and information in order to maximize the capacity of communication network,reduce the complexity,save energy and protect the environment,which will solve the problems of complexity,large energy consumption and small range of communication caused by the traditional wireless communication network.The thesis is therefore carried out based on this background.The main work and contributions of this thesis are described as follows:A resource allocation algorithm that maximizes the average throughput of the network is proposed and an optimal model is thus built to deal with the problems of joint resource allocation and optimization of relay power and user power presented in the DF cellular heterogeneous network.Both users and relays harvest RF energy from base station,then users use the harvested energy to transmit information to the receiver via the relay by way of TDMA.By utilizing the Lagrange multiplier method and the KKT optimal conditions through equivalent channel gains,the co-optimization of relay power and user power is simplified into optimization of user power,and the optimal power allocation through the sub-gradient algorithm is obtained.Simulation results show that,compared with the average power allocation algorithm subject to the causality of energy harvested by the relay and users,the algorithm stated in this thesis can effectively improve the average throughput and the performance of the network.A resource allocation algorithm that maximizes the throughput of the network is proposed and an optimal model is thus built to deal with time allocation and optimization of energy and information transmission in the circumstances that several relays need to do relay selection in the network of energy harvesting wireless communication.The throughput of the network is limited to the causality of energy and transmission power.Among them,several relays harvest RF energy sent from base station.Users transmit the information by way of TDMA,and the optimal relay is selected via protocol of maximum system capacity.Then the information is sent to the chosen relay,which makes use of the harvested energy and transmits the information to base station by AF.By utilizing the Lagrange multiplier method and the KKT optimal conditions to get the maximum throughput of the network,optimal time allocation is done to downlink energy transmission and uplink information transmission,and the optimal result is achieved through the sub-gradient algorithm.Simulation results show that,compared with the resource allocation algorithm without relay selection,the algorithm with relay selection can obviously improve the total throughput and the performance of the network.