Adaptive Modulation for Underwater Acoustic OFDM Communication

Rapidly varying multipath propagation and limitation of bandwidth are major constraints of underwater acoustic (UA) communication systems. In order to improve the spectral efficiency, adaptive modulation schemes are considered in the context of UA orthogonal frequency division multiplexing (OFDM) systems. The objective of this paper is developing self-adapting modulation algorithms by analyzing the characteristics of the UA channel and varying transmission parameters according to the channel condition. The signal-to-noise ratio (SNR) is estimated at the receiver and used as a performance metric to switch the modulation mode and fed back to the transmitter for data transmission. Simulation results show that the system performance is better than fixed modulation schemes.