A Semi-Distributed Resource Allocation Scheme for OFDMA Relay-Enhanced Downlink Systems

We propose a efficient semi-distributed resource allocation scheme for OFDMA relay-enhanced downlink systems. Firstly, an adaptive subframe partitioning (ASP) algorithm that considers user´s queue length and achievable data rate is used by base station to assign resources to relay stations. Regarding the slot allocation, we suggest two ways to extend conventional single-hop scheduling algorithms into multihop scenarios: link-based and end-to-end approaches. Simulation results indicate that the ASP algorithm reduces the amount of data buffered in relay stations, and hence increases system utilization and reduces the data loss caused by buffer overflow and handovers. Comparison of link-based and end-to-end approaches on max carrier-to-interference ratio (Max C/I) and proportional fairness (PF) scheduling algorithms shows that algorithms using the end-to-end approach can obtain higher throughput than those using the link-based approach, but at the expense of extra overhead for information exchange between the base station and relay stations. By using the ASP with the end-to-end PF scheduling, our frame-based resource allocation scheme achieves a tradeoff between system throughput maximization and fairness.