Research On Relay Technology For Wireless Communication System

Relay technology can enlarge the coverage of wireless communication system with low construction cost. Especial when the direct link between the source and destination exists, the reliability of wireless communication link can be significantly improved by using relay cooperative transmission, obtaining the so-called cooperative diversity. Recently, relay protocols with high spectral efficient and relay selection algorithms with low complexity are the most attractive research fields.However, there exists spectral efficient loss due to the half-duplex property of the relay node. Two-way relay is a relaying protocol which is proposed to recover the spectral efficient loss. This paper studies power control of two-way relay protocol and proposes two effective power control algorithm to improve the power efficiency. But two-way relay protocol can only be used in bilateral wireless system. With this consideration, a spectral efficient relaying protocol which can be used in unilateral wireless system is proposed, and power control of this new protocol is researched.The selection of relay partners is a key element for the success of the overall relay technology. In a wireless system with multiple sources and multiple relays, due to the inherent competitive nature among the sources, centralized relay selection algorithm which have high complexity often be adopted. In this paper, a semi-distributed relay selection algorithm is proposed for the relaying systems which have multiple sources and multiple relays. The proposed algorithm can significantly reduce the computational complexity and have outstanding performance. Especially when the transmitted SNR is low, the performance of the proposed relay selection algorithm is near to the optimal one (using centralized algorithm).