Performance evaluation of SFBC-SOFDM for underwater acoustic channels

This paper investigates the performance of spread orthogonal frequency division multiplexing (SOFDM) with space frequency block coding (SFBC) technique for underwater acoustic communication through simulation and semi realistic experimentation. Performance of Walsh-Hadamard code spread OFDM (WHSOFDM) and carrier interferometry code spread (CISOFDM) has been evaluated for underwater acoustic communication along with transmit diversity technique. The spreading technique helps overcome frequency-selectivity and provides reduced peak-to-average power ratio (PAPR) whereas the transmit diversity technique improves the data rate and reliability. CISOFDM with SFBC offers a SNR gain of 2.4 dB for a bit-error-rate (BER) of 1×10^-6 over WHSOFDM with SFBC. The present work also demonstrates the design of a low cost experimental setup (testbed) to perform a large number of experiments related to underwater communication and prototype algorithm testing. A simple two-transmit-one receive SFBC-CISOFDM scheme is used to transmit images through the underwater channel to validate the simulation.