Reseach On Key Technologies Of Terminal Cooperative D2D MU-MIMO

MIMO(Multi-Input-Multi-Output)technology can provide more freedom of space.It is a necessary method to increase the system capacity by using multiple antennas in the same time and frequency resources.MU-MIMO technology is a multi-user extension of traditional SU-MIMO Technology,which serve multiple users in the same time frequency resources.In downlink data transmission,if the base station is known to downlink channel state information,the signal can be pre processed by pre coding technology.The interference between multiple users can be eliminated or suppressed at the transmitter,so as to achieve multi-user communication and improve the performance of the downlink MU-MIMO system.The core precondition of precoding technology is that the transmitter knows the current channel state information.And the accuracy of the channel state information has an important influence on the performance of the cellular system.In the FDD system,because of the different frequency bands used in the uplink and downlink channels,there is no channel reciprocity.The transmitter can not directly obtain the downlink channel state information,and can only rely on the uplink channel feedback information from the receiver.D2 D communication technology has the characteristics of short distance communication and direct communication,so that the users can share the local information in short distance.It provides a new idea for the further improvement of MU-MIMO communication system.This paper mainly studies the MU-MIMO technology based on terminal cooperation.This paper will introduce the existing cellular systems D2 D communication technology.Optimization of the problem caused by no interaction between multiple users,the limited uplink feedback ability and the incomplete orthogonality of downlink precoding vectors.This paper hope to use the D2 D link between UE assisted MU-MIMO system to solve the above problems.It is hoped that the MU-MIMO and D2 D can be combined into a competitive scheme to improve the capacity of existing cellular systems,and to promote the standardization and commercialization of MU-MIMO+D2D.Specifically include the following aspects:Firstly,we analyze the potential performance of the new MU-MIMO system based on the codebook and the non codebook based precoding scheme.Secondly,analyzed the existing problems in MU-MIMO system.For example,MU-MIMO pairing probability is low,CQI mismatch,multi-user interference,uplink feedback information is too large and so on.Third,proposed a new scheme of terminal cooperation from the perspective of joint channel estimation.Based on the Rank-2 codebook,this paper proposes a cooperative MU-MIMO enhancement scheme based on broadcast mode.Based on Rank-1 codebook,This paper proposes a MU-MIMO enhancement scheme for CQI mismatch problem.Fourth,proposed a new scheme of terminal cooperation from the perspective of joint reception.Based on the detection data and the column norm interaction,the scheme of interference cancellation with terminal cooperation is proposed.Fifth,studied the user pairing based on terminal cooperation.Analyzed the theory limit of terminal cooperation user pairing.Based on the sharing of local CSI information,the maximum SU capacity pairing,the maximum singular value pairing and the codebook Based Orthogonal pairing are proposed.At the same time,the performance of these new schemes are simulated and compared.