Efficient Algorithms for Leveraging Spatial Reuse in OFDMA Relay Networks

We consider the problem of scheduling users with backlogged and finite buffers on the multiple OFDM carriers (channels) over the two hops of the relay-enabled wireless network. Motivated by the recent 802.16j standard, we consider two sub-carrier grouping models (PUSC, AMC). While the extent of diversity gain varies depending on the model, spatial reuse is common to both the models and is crucial in delivering the promised throughput benefits of relays. Hence leveraging spatial reuse forms the prime focus of this work with diversity gains being leveraged when available. We establish the hardness of the problem under these two models and propose efficient approximation algorithms for the scheduling problem considered. Our solutions are simple to implement at the base station, while also providing worst case guarantees. The proposed solutions are evaluated to highlight their benefits in a variety of network conditions.