Power allocation schemes for multichannel two-hop relaying systems

The usage of relays and OFDM can improve the performance of wireless systems in terms of data rates, coverage and reliability. In this paper we study joint subcarrier matching and power allocation for two-hop relay systems with the purpose of maximizing the total spectral efficiency. The problem is formulated as a mixed integer (binary) problem, but due to its complexity, the problem is separated into subcarrier matching and power allocation subproblems. Methods to solve both problems have been presented in previous works, but the solution to the power allocation problem still presented a high complexity. In this paper we demonstrate that the power allocation problem can be reformulated into a more tractable form, allowing us to develop suboptimal solutions based on water-filling with low computational cost. Numerical results show that the proposed suboptimal solutions are near-optimal and offer a good trade-off between performance and complexity.