Rate-Adaptive Bit and Power Loading for OFDM Based DF Relaying

In this paper, we investigate the adaptive bit and power loading approach for the OFDM-based relaying communications. The relaying protocol is half-duplex outage symbol-level-selection detection-and-forward. The source and the relay has the separate power constraint. The maximum-ratio combining is employed at the destination to achieve the maximum distributed spatial diversity-gain. Assuming the perfect channel knowledge available at all nodes, we propose a sub-optimum rate-adaptive bit and power loading approach to maximize the number of bits/symbol for the target link performance. The proposed approach offers lower complexity for implementation as well as the integer number of bits/symbol. Computer simulations are used to examine the proposed approach for various scenarios with respect to the relay location and the distributed power allocation.