Adaptive Cooperation Strategy for Multiple Relays in 4G Wireless Systems

In wireless systems, a relay station (RS) is introduced to overcome capacity degradation in a shadowing area or a cell edge. Various relay schemes have been proposed to improve capacity by increasing link quality and diversity gain. However, there is no study about relay scheme in multiple cooperative relay network environments which means that more than one RS are cooperatively operated in same domain : time, frequency and space. In conventional relay scheme, RSs operates individually and independently, so resources are allocated exclusively due to interference. It brings inefficient and nonflexible use of resources problem. Therefore, although it brings the increase of performance for specific RS coverage, total system performance is not improved. In this paper, we propose a novel relay system model and frame structure. Also, cooperation strategy of multiple relays for adaptive transmission modes which maximizes diversity gain is described. Simulation shows our proposed scheme has better performance compared with existing schemes.