Resource Allocation Optimization for OFDM-Based Amplify-And-Forward Multi-Relay System

A two-hop relaying system where a source communicates with its destination through multiple relay nodes is studied for capacity maximization. Amplify-and-forward (AF) relaying is adopted for its simplicity. Taking the independent channel transfer function of different subcarriers and links into consideration, we formulate a resource allocation optimization problem for joint subcarrier assignment, subcarrier matching and power allocation of the two-hop transmission. A heuristic suboptimal algorithm which decomposes the joint problem is proposed. First, equal power allocation is assumed in a partial-update manner to help assigning subcarriers to each relay for matching; then optimal power allocation is achieved by joint waterfilling of source and relays under separate power constraints to further increase system capacity. Numerical results show that the proposed algorithm has a near-optimal performance.