A hierarchical multiuser diversity (HMD) transmission scheme

Deep shadowing and "hot-spots" are two challenging issues in wireless networks. Aiming to resolve these issues, we take a cross-layer design approach and devise a hierarchical multiuser diversity (HMD) transmission scheme, in which a user can choose to communicate with the base station either directly or using multiple hops via relay stations. Using a throughput-based criterion, we develop a direct/relay link construction algorithm. We then explore opportunistic scheduling under performance-based fairness constraints, for both direct links and relay links; a key goal is to achieve multiuser diversity in both tiers. Our results show that the HMD scheme can combat shadowing and "hot-spots" effectively in the sense that the total system throughput is increased significantly while the throughput requirements of the users are met.