Comparison of Schemes for Joint Subcarrier Matching and Power Allocation in OFDM Decode-and-Forward Relay System

The combination of relay system and orthogonal frequency division multiplexing (OFDM) modulation is a promising way to increase capacity and coverage area. We consider several joint subcarrier matching and power allocation schemes to maximize channel capacity, where the relay strategy is decode-and-forward. We formulate the optimally joint subcarrier matching and power allocation problem as an optimization problem, which is prohibitive in terms of complexity. By separating the subcarrier matching and power allocation, the schemes with low complexity are proposed. The capacity of the proposed scheme 1 is close to the upper bound of the channel capacity with very low complexity. The complexity of the proposed scheme 2 is higher than that of the proposed scheme 1. However, the capacity of the proposed scheme 2 is almost equal to the upper bound, which proves that one-to-one subcarrier matching is approximately optimal.