Research And Simulation Implementation Of Highly Energy-efficient Multi-relay Selection Algorithm For Heterogeneous Wireless Networks

Wireless communication has been continuously developed under people's pursue of convenient communication.As a result,MIMO(Multiple Input Multiple Output)technology was proposed to solve the problems like limited bandwidth,complicated channel environment,low transmitted rate.However,MIMO cannot be carried out for wireless terminals which are limited of power.At the same time,with the development of ICT(Information Communication Technology),the continuous increase of energy consumption of communication devices,and the improvement of energy demands and carbon emissions make the problem of energy crisis and global warming become worse and worse.VMIMO(Virtual Multiple Input Multiple Output),the cooperative network among multi-nodes,was proposed to solve the two problems mentioned in the above paragraph.The cooperative communication uses diversity reception method to reduce the transmission rate of each link efficiently in order to reduce the energy consumption and enhance energy efficiency.The problem of relay selection has become the key issue that should be solved urgently for the mobility of nodes in wireless network which leads to the changes of network topology.Meanwhile,we notice that the wireless network's trend would be the heterogeneous network,which are a series of networks having different characteristics.Accessing to different networks according to different businesses will make the users have better services and improve the energy efficiency of network.In this thesis,we will introduce the selection algorithm of heterogeneous network into the cooperative communication network and study the multi-relay selection facing highly energy-efficiency in heterogeneous network.Firstly,the multi-relay selection problem facing energy efficiency in single cell of heterogeneous network was studied in this thesis.This algorithm was considered as the condition of down-link of multicast with only one kind of business.Different from the traditional method of multi-relay selection,this algorithm was divided by three time slots.In the first slot,the destination nodes were selected for relay retransmission.In the second slot,the selected algorithm of heterogeneous network was introduced into the multi-relay selection algorithm.Firstly,the candidate relay nodes were chosen for the destination nodes that were waiting for treatment.Secondly,the optimal access network was selected for each candidate relay node in order to make sure the energy consumption of each candidate relay node.Thirdly,the optimal relay nodes were found for each destination node with the goal of maximum energy efficiency and the constraints of network's quality of service.In the third slot,the information from the source node was retransmitted for the destination nodes that found no proper relay nodes in the second slot.The simulation results showed that this algorithm could obtain better relay nodes' energy efficiency under the condition of guaranteeing the business' requests of service and the fairness of relay selection.Secondly,the condition of cooperative communication crossing cells was considered further in this thesis,which was the problem of multi-relay selection facing energy efficiency among multi-cells in heterogeneous network.In this algorithm,we considered the problem of down-link unicast with multi-businesses crossing cells.When the source node needed to transmit information to the destination node staying in the edge of the other cell,three networks as follows could be chosen.In the first network,the information was transmitted through the relay nodes that were lieing in the same cell with the source node.In second network,the information was transmitted through the extend cell in the edge of the cell the source lieing.In the third network,the information was transmitted to the base station that lied in the same cell with the destination node,and then we used the method mentioned above to carry out the relay transmission.In this algorithm,firstly,the source node computed the energy efficiency of each access network and obtained the optimal relay nodes of them.Secondly,the energy efficiency was compared and the network that had the maximum energy efficiency was selected.The simulation results showed that this algorithm could improve the energy efficiency of network under the condition of satisfying the requests of business.