On QoS-Guaranteed Downlink Cooperative OFDMA Systems with Amplify-and-Forward Relays: Optimal Schedule and Resource Allocation

This paper considers joint schedule and resource allocation in downlink cooperative OFDMA systems with multiple sources, multiple relays and a single destination. Each user has individual QoS requirements and the relays operate in amplify-and-forward and half-duplex mode. We try to find optimal power allocation, relay selection and subcarrier assignment to maximize overall system rates. The problem is formulated as a Mixed Binary Integer Programming (MBIP). Although the original problem is comprehensive in nature, a novel two-level dual-primal decomposition based algorithm is proposed to tackle the problem. Optimal solutions are given in closed-form and the algorithm has a polynomial complexity in general. The efficiency of the algorithm is finally illustrated by numerical results.