Adaptive OFDM Non-Uniform Modulation for Underwater Acoustic Communication

Underwater communication is one of the paramount parts of communication. It avails us in scientific research, studies and is used by the coast guard and the navy for our country's protection. We know that the underwater communication is difficult due to water currents, Doppler effect, ISI (Inter Symbol Interference), ICI (Inter Carrier Interference), surface noise, thrust noise, multiple path delay and it is also affected by any movement between the transmitter and receiver. OFDM (Orthogonal Frequency Division Multiplexing) is the most desirable mode of modulation underwater. It is spectrally efficient and immune to selective fading. We have implemented this OFDM to submarines with MIMO (Multiple Input Multiple Output), technology modelled using the equalizers ZF-MMFE for better Bit Error Rate (BER) Performance. This will overcome the present performance degradation in the single carrier domain equalization due to noise reconstruction in OFDM and the spectral scarcity due to the single user communication.