Fair-Rate Allocation in Multiuser OFDM-SDMA Networks

We propose algorithms for rate allocation in a multiuser orthogonal-frequency-division multiple-access (OFDMA) system, which aim to maximize the system throughput and maintain fairness among users. The system comprises of variable-rate users (with specified minimum rates) as well as constant-rate users communicating with a base station. Rate allocation criteria based on the Nash bargaining solutions are formulated. Proportional fair-rate allocation as well as fair-rate allocation in classical OFDMA systems with orthogonality constraints, are subsumed as special cases of our formulations. The resulting optimization problems, which also accommodate practical per-user power constraints, are solved using the dual decomposition techniques. The efficiencies of our proposed methods are demonstrated through simulation results.