Research On The Relay Selection And Relay Matrix Optimization In The Cooperative Communication System

With the development of mobile communication technology, people enjoyed the convenient it offered, but at the same time people propose further requirements of the higher transmission rates and higher transmission quality. In order to achieve the high data rate, high spectral efficiency and high-coverage targets of the future wireless mobile communication systems, new technologies continue to emerge, which the multi-input multi-output (MIMO) technology and the cooperative communication technology are the typical representatives. MIMO technology make full use of the airspace resources so that it can enhance system capacity multiply in case that does not increase the spectrum resources and transmit power. Relay cooperative communication has many advantages such as expand signal coverage, eliminate the cover of'blind spots' and improve the transmission quality. However, MIMO relay communication network is composition of the two technologies, so it will further enhance system performance. The research in this paper is about one of the key problems relay selection in the relay cooperative communication system and the relay matrix optimization in MIMO relay network.In the paper, the main research content and innovations as follows:1. Study the basic knowledge of cooperative communication. Meanwhile the cooperative diversity technology, the combining technology and the cooperative forwarding mode are introduced in detail and have simulation researches on them. Describes pre-coding and detection technology which used commonly in MIMO system, and the reference is given for the relay matrix optimization through the comparison of simulation results.2. When the primary users (PU) and secondary users (SU) share the same spectrum, in order not to interfere the PU, the transmission power of SU is very small and the outage probability of SU network is very high in cognitive radio system. If SU can obtain cooperation from surrounding nodes and select the best relay set, outage probability of SU will reduce. Therefore, under the interference temperature constraints, a Best Selective Relays (BSR) algorithm is proposed in the cooperative relay network which based on beamforming, a threshold is determined which only allocates the transmission power to the efficient relay links. Simulation results demonstrate that BSR algorithm can decrease outage probability of the SU network and outperforms AAF and SAF algorithms.3. MIMO relay network usually divided the relay matrix into receiving part and sending part and design them respectively. In the traditional relay matrix, such as MFR-RZFT, the system's performance is not satisfactory because of the bad performance of MF receiving part. Firstly describes the relay matrix optimization principles based on the equivalent matrix triangulation and the equivalent matrix diagonalization. Then the new relay matrix design schemes MMSER-MFT and MMSER-RZFT are proposed based on the pre-coding and detection technology in MIMO system. Finally, comparing with two traditional relay matrix design schemes, the simulation results show the superior performance of the proposed schemes in this paper.