Channel-Hole Based Cooperative Scheduling in Multiple Relay Systems

The relay-assisted Orthogonal Frequency-Division Multiple Access (OFDMA) cellular system is one of the most promising technology thanks to the enhancements of the system capacity and coverage it provides. However, some special features may lower its positive aspects. In multiple relay case, the asymmetric link problem in the two stages forming the relaying process may result in important resource wastage. Such resource wastage can even be more serious than in the case where only a single relay is used in the system. Only few works consider this resource wastage problem. In this paper, we first define a new term, channel holes, to denote the potential resource wastage in single and multiple relay systems. Then based on this new concept, we propose a novel resource management scheme for multiple relay systems, i.e. channel-hole based cooperative scheduling in multiple relay systems. In order to evaluate the performances of such resource management schemes, we build a system model and propose the corresponding analytical derivation, which helps analyzing the average queue length and the average packet delay. Simulations are used to validate and reinforce our theoretical analysis. Then using simulations, we compare our proposed scheduling algorithm to other algorithms from the literature. Hence, we show that our proposed algorithm performs better than others. In addition we also observe that our proposed scheduling algorithm performs a resource-aware relay selection that is more efficient than the one obtained using the ideal relay selection scheme.