Channel Estimation for Ultrasonic Communication using OFDM on Steel Pipe Channel

Ultrasonic communication through solid channels suffers from wave dispersion, attenuation, and multipath effect. It can be observed that the channel is frequency selective, and some frequencies will severely be attenuated as the distance between transmitter and receiver increases. Besides, when the pipes are used as the communication channels, the limited bandwidth and the adversarial reverberations are even worse. Orthogonal frequency division multiplexing (OFDM) has been widely used in modern wireless communication systems due to its robustness against frequency selectivity. The method can separate narrowband channels at different frequencies, which can reduce interference and crosstalk. In this study, we investigate the feasibility of using OFDM to realize intersymbol interference (ISI) mitigation through the steel pipe channel by using a reconfigurable FPGA-based SoC platform. Quadrature Phase Shift Keying (QPSK) modulation scheme and varied bitrates are selected to determine the feasible and reliable transmission rate. The communication bitrate exceeded 716 kbps without any error despite dispersion, intersymbol interference, and the multipath effect within the steel pipe channel.