Channel Estimation using Pilot-Assisted OFDM for Underwater Acoustic Communication

Abstract

Underwater communications research is significant to researchers because of the challenges and difficulties in transmitting wireless signals within this environment. Underwater Acoustic Communications (UWA) are characterized by the fact that they can travel long distances compared to the radio signal, which makes it very effective compared to other types, in addition to the lack of costs in establishing these types of systems. OFDM technique has been used widely in 4G communication systems, and recently it was approved to be successfully implemented in 5G. One of the most important aims of developing communications systems is to reduce the bit error rate (BER), and since the underwater communication signal is subject to many influencing factors that reduce the accuracy of the signal when it reaches the receiver, such as absorption and multipathing, researchers must improve the performance of the OFDM system by removing this effect. The channel effect is reduced by selecting some subcarriers from the OFDM system and assigning them as pilots. These Pilots are given higher power to determine the channel effect and then use the appropriate equalizer to reduce the effect and improve signal accuracy. In this study we tested the appropriate number of pilots to estimate the channel response, with a linear equalizer to reduce the effect at the receiver, then compared the BER before and after adding the equalizer.