Research On Cross-Layer Power Allocation And Relay Selection Scheme For Wireless Relay Networks

In recent years,the relay cooperative communication technology is developing at a rapid speed.It can effectively reduce the impact of wireless channel fading on the signal,and it has been widely concerned.In wireless relay networks,the reasonable power allocation of source nodes and relay nodes is necessary.The traditional power allocation scheme is only studied on the physical layer,and can not provide users with quality of service(Quality of Service,QoS).In this thesis,we study the cross-layer power allocation scheme based on statistical delay QoS guarantee from the viewpoint of guaranteeing QoS requirements.In addition;the joint optimization scheme of cross-layer power allocation and relay selection is studied in the multi-relay cooperative system.The relay selection technology can avoid the waste of resources caused by the relay node forwarding information because of poor channelconditions,and using power allocation for relay selection to optimize can significantly improve the system performance.Firstly,the statistical delay QoS guarantee and the effective capacity are researched.Because the service process of wireless transmission is time-varying,the concept of effective capacity can be used to analyze the performance of statistical delay QoS,based on the concept of effective capacity,the mapping relationship between physical layer(power allocation)and link layer(delay QoS index)can be established,it is the theoretical basis for the research of cross-layer power allocation and relay selection scheme.Then,the cross-layer power allocation scheme for single relay cooperative diversity system is discussed.Considering that the relay nodes have two duplex.They are full duplex relay nodes(Full Duplex,FD)and half duplex(Half Duplex,HD)relay nodes.So the cross-layer power allocation of relay nodes in FD and HD mode are discussed in this thesis.We also made simulation analysis and comparison.On this basis,we add a relay node,when there are two relay nodes,we discuss power allocation scheme based on QoS delay guarantee,and compare with the power allocation based on network search(NSPA)scheme and the equal power allocation(EPA)scheme.The results show that the cross-layer power allocation scheme in this thesis is superior to the other two power allocation schemes.Finally,for the multi-relay cooperative system,in order to further improve the system effective capacity,power allocation and relay selection will be combined together.This thesis discusses joint optimization scheme of power allocation and relay selection,which can maximize the effective capacity and meet certain delay constraints.The simulation results show that the combination of the two techniques can improve the effective capacity performance of the system.