| According to the development of mobile communication in recent years, mobile data services are increasingly localized, more and more applicat ions are related to proximity services among users. Under this background, D2D(Device-to-Device) as a kind of short-range wireless communication technique is widely studied and has already become a key technique in the 5t h communication system. And relevant technical standards are being drafted. In the future, existing MU-MIMO(Multi- user Multiple-Input Multiple-output) system will coexist with many D2 D communication systems. Traditional cellular users and D2 D communication users will have mutual interference under the new system, which will affect each other’s communication performance.Meanwhile, the existing MU-MIMO system itself also has many problems, such as large amount of feedback information and low matching probability etc. D2 D communication technique as a new technique has more potential application areas. Aiming to some problems in the existing MU-MIMO system, D2 D technique can be used as a means to help the MU-MIMO system to achieve more efficient and fast MU-MIMO communication mode without changing the existing system architecture. This thesis focuses on the interference management and user scheduling problems in the MU-MIMO and D2 D coexistence system, as well as the MU-MIMO system improving scheme design based on D2 D communication technique. The main works are as follows:First of all, this thesis studies the interference problem in the MU-MIMO and D2 D heterogeneous transmission. The expression of signal to interference plus noise ratio of received signals for different types of user are derived, and the source and interaction of each interference are analyzed. Respectively according to different types of users, this thesis design corresponding interference management scheme. Through the pre-coding mode selection and user scheduling strategy design, interferences are suppression; Specific to the user matching during scheduling procedure, this thesis gives the detailed user scheduling process. The final simulation results show that both the MU-MIMO transmission rate and the D2 D transmission rate have been improved, and the performance of the whole system is improved;Secondly, this thesis studies the scheme using the D2 D communication technique to improve the performance of existing MU-MIMO system. It is proposed that the users who have no data trans mission requirement act as assisted users, who transmit data through the communication link between the users with data transmission requirement. Based on the existing D2 D related protocols, combined with the application scenarios, this thesis proposed an assisted users’ discovery and communication scheme, as well as the impact of the proposed scheme on the existing MU-MIMO system. Specific to the user scheduling matching, this thesis gives a detailed user scheduling process. The simulation results show tha t the proposed scheme can significantly improve the average frequency efficiency of the system. When the base station transmits power to 40 d Bm, average spectral efficiency can be improved to 2bps/Hz.Again, this thesis uses the USRP(Universal Software Rad io Peripheral) to build a link simulation platform. 3 hardware devices are used to realize MU-MIMO communication, and the BER performance of the received signal is simulated. O n the basis of the MU-MIMO system, the D2 D direct communication is conducted, and the BER performance of receiver show that the result of D2 D forwarding is close to direct sending.Finally, the full text is summarized, and the future research directions of MU-MIMO technique and D2 D technique combination are discussed in this thesis. |
