Research On Two Users Multi-antenna Cooperative Communication Transmission Scheme

Multi-user Multiple Input Multiple Output (MIMO) wireless communication network allows multiple users working under the same time-frequency resources, which can increase the system capacity effectively, but the interference problems among users restricts it to achieve a better possible system performance. What’s more, collaboration communication technology can excavate inner space diversity gain of multi-user MIMO system better, extend the signal range, and improve the overall system performance. But the multi-user collaborative communication scheme which combines two kinds of technologies tends to have problems of complicated network structure and high complexity of coding and testing. In this thesis, the main research works are carried out as follows:(1) Researching the basic channel model of the multi-user MIMO system and interference processing method, this mainly researches two schemes of classic interference alignment. One is the interference alignment scheme based on Alamouti coding structure, in order to eliminate interference between users by using the orthogonality of the Alamouti structure. In given condition of channel state information is unknown to the transmitter, the other scheme can implement interference alignment under the MIMO interference channel through designing a reasonable space-time coding transmission mode.(2) Analyzing the basic model of collaborative communication and classic forwarding method of collaboration relay transmission, which deeply studies the inner mechanism of MIMO system using Cyclic Delay Diversity (CDD) technology to reduce the complexity of coding and testing. The research results show that by using the CDD technology can not only achieve potential diversity gain of distributed wireless communication network, but also simplify the implementation complexity of the whole communication system.(3) Based on the above research results, the thesis puts forward a kind of two users multi-antenna collaborative communication transmission scheme which has low detection complexity. In this transmission scheme, all nodes are equipped with multiple antennas, the whole transport process can be divided into two stages. In the first stage, the two communication users have to modulate transmission signal by the way of Orthogonal Frequency Division Multiplexing (OFDM), then to code each sub-carrier modulation signal by using space-time block codes based on the thinking of interference alignment design, in order to obtain system diversity gain and to realize interference dissociation, then the users send the encoded signal to all relay nodes. In the second stage, the thesis introduces CDD technology in the process of relay transmitting so as to reduce the detection complexity. At the meantime, in order to remove interference among users and to get the desired signal in the receiving nodes, the thesis designs the appropriate matrix forced zero to eliminate, which is based on the space-time coding principle of transmitters.Theoretical analysis and simulation results show that the author’s proposed transmission scheme can achieve coding and testing in two user multi-antenna collaborative communication system, access larger space diversity gain and better performance of bit error. The number increasement of relay nodes will not affect the detection complexity at the receiving end, and the scheme has a certain practicality.