DMT analysis and optimization for cooperative multiuser OFDMA systems

In this paper, we adopt the DMT framework to study a cooperative downlink OFDMA system with multiple relays. We derive the closed-form expression of the DMT curve for the cooperative OFDMA system employing linear constellation precoding at the base station, and linear detection at the mobile users, and develop the optimal symbol loading, relay selection and subcarrier allocation strategy. Simulation results are presented to verify the theoretical analysis and show that our proposed resource allocation strategy can improve the system performance significantly.