Pilots based LSE Channel Estimation for Underwater Acoustic OFDM Communication

Underwater acoustic (UWA) communication techniques have gained popularity for wireless communication in shallow and deep seas. Orthogonal frequency division multiplexing (OFDM) has established to be a reliable multicarrier modulation method for a UWA communication for fending-off inter symbol interference (ISI). Since the UWA channel happens to be frequency selective in nature because of having multipath signals as a result of transmitted signals bouncing off the sea floor and/or the surface, equalization techniques must be utilized to counter the effect of fading. Therefore, we propose a least-squares error (LSE) based channel estimation technique using pilot subcarriers for UWA OFDM. Simulation results using a Rician fading based underwater channel model show that a reasonable number for the pilots is one-fourth of the number of sub-carriers. Any further increase in the number of pilots does not improve error performance. Moreover, error performance degrades as the energy of the pilots is increased.