Research On The Key Techniques Of MIMO Two-way Relaying Systems

With the rapid development of data services,future wireless communication systems should have better communication quality,higher data rates,broader coverage and better bandwidth efficiency.Relay technology which can significantly improve the system throughput and coverage is an indispensable technology for the next generation wireless communication systems.Moreover,it has been adopted in several wireless communication standards,such as LTE-A and IEEE 802.16 j.Two-way relay transmission(TWRT)using network coding requires less time slots than one-way relay transmission(OWRT),which can greatly improve the spectral efficiency.The combination of two-way relay transmission and multiple input multiple output(MIMO)technology can further enhance the system performance,which has attracted great attention.This thesis mainly studies the key technologies of MIMO two-way relaying systems,such as Alamouti coding,relay selection,antenna selection and power allocation.The performance of several transmission schemes under different scenarios are analyzed.Furthermore,the effects of imperfect channel state information(CSI)and time selective fading caused by node mobility on the system performance are analyzed,which can provide a theoretical guidance for the implementation of MIMO two-way relay system.The main contributions of this thesis are as follows:1)Considering time selective fading channel caused by node mobility,the decoding algorithm of the Alamouti-based two-way amplify-and-forward(AF)multi-relay systems is studied.By calculating the decision statistics,it is pointed out that the conventional maximum likelihood detection algorithm(MLDA)has an error floor problem in time selective fading channel.To solve this problem,a zero-forcing detection based decoding algorithm(ZFDA)and a low complexity decoding algorithm(LCDA)are proposed.The simulation results show that the proposed decoding algorithm has better symbol error rate performance,and they provide a guidance for the design of two-way communication system in high-speed mobile environment,which has a crucial realistic significance.2)For the MIMO two-way AF multi-relay system,considering the imperfect CSI and the time selective fading due to the node mobility in the actual scenario,the effect on the average outage performance of the joint relay and antenna selection transmission strategy is studied.Based on the method of adjusting integral region,the upper and lower bound expressions for the average outage probability are derived.In order to improve the performance of the MIMO system,based on minimizing the system outage probability which is subject to the sum-power constraint,a power allocation scheme combining the relay and antenna selection is proposed.The results indicate that the proposed power allocation scheme can achieve significant performance gain when compared with the equal power allocation scheme.