Optimal Bit and Power Loading for Amplify-and-Forward Cooperative OFDM Systems

In this paper, we investigate bit and power allocation strategies for an orthogonal frequency division multiplexing (OFDM) cooperative network over frequency-selective fading channels. We assume amplify-and-forward relaying and consider the bit error rate (BER) performance as our performance measure. Aiming to optimize the BER under total power constraint and for a given average data rate, we propose three adaptive algorithms; optimal power loading (OPL), optimal bit loading (OBL), and optimal joint bit and power loading (OBPL). Our Monte Carlo simulation results demonstrate performance gains through adaptive bit and power loading over conventional non-adaptive systems as well as currently available adaptive cooperative scheme in the literature. The impact of practical issues on the performance of proposed adaptive schemes such as imperfect channel estimation and limited feedback is further discussed.