Research On Power Allocation And Relay Selection In Cooperative Communication System

The high-speed railway communication system is continuously updated and it is now mainly the Long Term Evolution for Railway(LTE-R).The system has a better network architecture and a higher data transmission rate.The relay technology in cooperative communication is one of the key technologies in LTE-R.The communication network based on relay technology is a better choice for high-speed railway public network communication system.The principle of cooperative communication is that users use the antenna mutually in the wireless communication environment to help each other to send and receive signals so as to form a virtual MIMO system.Cooperative communication can improve the performance and capacity of the communication system.The power allocation of each node in cooperative communication system and relay selection are the two core issues studied in cooperative communication.The reasonable power allocation and excellent relay selection scheme can greatly improve the performance of the system and ensure the quality of communication.This thesis studies these two issues,the details are as follows:This paper first summarizes the cooperative communication,including the basic system model of cooperative communication,common diversity technology,merge technology,relay protocol and channel fading model.Secondly,the power allocation problem under multi-relay cooperative system is studied.The system has multiple antennas at the destination end and transcoding and forwarding protocol at the relay station.From the aspect of system performance,the disruption probability of the system is analyzed.In order to minimize the system outage probability,an adaptive power allocation method based on hybrid genetic particle swarm optimization algorithm is proposed.The influence of the proposed algorithm,the genetic algorithm and the equal power allocation method on the system outage probability is compared by simulation analysis.The impact of the number of relays and the number of antennas on the system outage probability is also analyzed.In addition,this paper also studies the cooperative communication system of multi-user multi-destination nodes using transcoding protocol at the relay.The energy efficiency of the system is analyzed,and the maximization of system energy efficiency is taken as the optimization goal.A scheme of relay selection based on Q learning is proposed.The proposed scheme is compared with other relay schemes through simulation,and the influence of different circuit power,number of relays and relay position on system energy efficiency is also analyzed.