Research On User-relay And Antenna Selection Scheme In Multi-user AF Cooperative Communication System

In wireless communication system,the development of Multiple-Input Multiple-output(MIMO)technology makes it possible to break through Shannon limit.Cooperative communication technology is based on MIMO technology,which can expand the coverage of communications and improve the communication reliability by the cooperative information transmission among the distributed nodes.Cooperative communication overcomes the disadvantages of MIMO technology which has strict demands for the distances among the antennas.The characteristics of cooperative technology makes its research and development become a hot topic and attract world-wide concern in the wireless communication field.Cooperative communication improves system performance by the spatial diversity gain,which provides a new idea for the development of wireless communication.However,there are still many problems to be solved,especially in multi-user concurrent communication system,how to choose the cooperative relays to improve system performance,how to guarantee user's quality of service(QoS)and user fairness,and how to decrease the transmission delay,and improve the transmission data rate,these are all difficult problems of multi-user cooperative strategy research.Most of the researches which focuses on performance analysis and cooperative strategy design have been carried out for single-user cooperative system.However,less research focus on relay selection,performance optimization and data transmission rate improvement of multi-user multi-relay system.This thesis mainly research the relay selection strategy and system transmission design in multi-user multi-relay cooperative communication system.We propose a low complexity suboptimal user-relay selection scheme and three antenna selection schemes for multi-user amplify-and-forward(AF)cooperative space shift keying(SSK)user-relay system.The proposed schemes can make further improvements of data transmission rate and communication reliability.The main contents are as follows.Firstly,a low complexity suboptimal user-relay selection scheme is proposed in multi-user multi-relay system.The existing user-relay selection algorithms are mainly proposed to optimize single performance,which can't give consideration to the optimization of both overall system performance and individual user performance,and the problem of algorithm complexity.The proposed suboptimal user-relay selection scheme can guarantee these aspects simultaneously.The algorithm performance and computational complexity of the proposed scheme and other existing algorithms are compared.Secondly,antenna selection schemes for multi-user AF user-relay cooperative system are proposed.Based on the proposed user-relay selection scheme,SSK modulation is applied in multi-user multi-relay cooperative system.According to the analysis of system average bit error rate(BER),we propose the maximum likelihood(ML)detection criterion and three improved antenna selection schemes for multi-user system.According to the actual transmission antenna,the proposed antenna selection schemes realize the transmission path selection between links of multi-antenna source node,multiple relay nodes and multiple user nodes,and the schemes further improve the system average BER and transmission data rate.Computer simulations verified that the proposed schemes can improve the system BER performance effectively.The influence of the simulation parameters on the system BER is also analyzed.Finally,the problems and further research points of relay selection technology and the optimization of antenna selection algorithm in multi-user cooperative system are summarized in the thesis,which can be further studied in the future.