Adaptive transmission technique for short range mobile underwater acoustic OFDM communication

An underwater acoustic orthogonal frequency-division multiplexing (OFDM) system for short range application, which employs adaptive transmission technique to improve its performance is presented. Firstly, new channel parameters that can provide information on the instantaneous state of the channel with respect to the receiver´s movement are derived. Secondly, the new channel parameters are used to adapt the subcarrier spacing and guard interval to the instantaneous channel state. Finally, the performance of the proposed system in terms of bit error rate (BER) and data rate is presented using simulations. Results indicate that the proposed adaptive system outperforms the conventional non-adaptive system (in which system parameters are fixed and chosen based on the worst-case scenario) in terms of providing optimal performance between the BER and data rate.