Power allocation for non-regenerative OFDM relaying channels

Relayed transmission is an efficient way to combat wireless channel fading and to increase system throughput. By allocating the overall power to the transmitter and the relay optimally, the system performance can be further improved. This paper discusses the optimal power allocation in frequency-selective non-regenerative relaying channels, where OFDM is employed. Firstly, the optimal power allocation between a cooperative subcarrier pair is analyzed and an equivalent channel gain model for subcarrier pairs is developed. Based on this, a sub-optimal subcarrier pair selection method is given by applying the Hungarian algorithm. Finally, the optimal power allocation on the selected subcarrier pairs can be obtained by the water-filling approach. Simulation results show that the proposed power allocation algorithm not only outperforms the direct OFDM transmission with optimal power allocation, but also achieves a higher system capacity than uniform power allocation scheme between the transmitter and relay.