Research On Multiple-Antenna Two-Way Cooperative Relay Transmission Scheme Based On Cyclic Delay Diversity

MIMO (Multiple Input Multiple Output) System transmits and receives signals by configuring multiple antennas at the terminals to get spatial diversity gain and increase system capacity drastically. However, MIMO system is restricted in terminal practical application, then this thesis introduces cooperative relaying. Research suggests that cooperative relaying can improve the rate and reliability of transmission system effectively. Two-way cooperative communication can break through the constraints of half-duplex work mode so as to improve spectral efficiency greatly. Based on the advantages of MIMO and cooperative relaying, multiple-antenna two-way collaboration communication can improve spatial diversity and increase the distributed wireless communications network coverage and it is very meaningful for studying. But some studies found that with the number increasement of relay nodes, the detection complexity and encoding complexity of the system are increased accordingly. For this purpose, this thesis proposes a multiple-antenna two-way cooperative relay differential transmission scheme based on CDD (Cyclic Delay Diversity). The main research work are as follows:(1) Researched the two-way collaboration communication model in the distributed network. Analyzed several classic transmission methods and the reason why detection complexity is increased. In addition, in order to reduce inter-symbol interference when transmitting signals, to improve the reliability of communication transmission and increase system diversity gain, this thesis researched the linear precoding.(2) Researched the realization way of CDD and principle of low detection complexity. This thesis used this technology in above-mentioned multiple-antenna two-way collaboration model and proposed a two-way cooperative relay transmission scheme based on CDD. The whole transmission process has three stages.The first stage, the first source node sends information which was linear precoded to the relay nodes and the second node. The second stage, the second source node sends information which was linear precoded to the relay nodes and the first source node. The third stage, the relay nodes use cyclic delay, amplify and forward signals which received from the previous two stages and forward it to two source nodes. This scheme can improve BER (Bit Error Rate) performance of the system.(3) Under the fast fading channel condition, the receiver can not guarantee the estimation problem of the CSI (Channel State Information) perfectly. In order to enhance the feasibility of the above scheme, differential coding was applied to the above scheme. This thesis proposed a multiple-antenna two-way cooperative relay differential transmission scheme based on CDD. Information which will be transmitted need to be differential coded after linear precoding, thus CSI does not need to be estimated effectively when transferring, and it can avoid transmission mistakes.The author’s scheme can be apply to the scene that has two source nodes and relay nodes configure multiple-antennas and CSI is unknown when transmitting. This scheme can reduce detection complexity, improve bit error performance of system significantly and enhance system’s communication reliability. It also has theoretical significance and some practical value.