Image Transmission with Joint Time Reversal and OFDM in Underwater Acoustic Environment

The development of technology and applications in the underwater acoustic field are a challenge for researchers. The OFDM system is an interesting research topic to date because of its high-rate and high-quality wireless capabilities. In a multipath environment, OFDM can reduce the effect of multipath fading by converting frequency selective channel to a flat subchannels parallel collection of frequency. Time reversal with its spatial and temporal focal properties is a technique that can be relied upon in reducing channel fading and intersymbol interference which causes distortion in the received signal. In this paper, we present a study of transmitting images in underwater acoustic environments using a combined time reversal and OFDM (TR-OFDM) technique. The estimation technique based on the MMSE algorithm is used in the image restoration process. The simulation results show that transmitting image with the TR-OFDM system has superior performance compared to traditional OFDM system. With BPSK modulation and MMSE estimation technique, the BER obtained by TR-OFDM is 10^-3 at SNR 8.2 dB. Modulation schemes such as M-PSK and M-QAM are also presented in this paper. BPSK modulation is proven to have the best performance on SNR 20 dB with zero resulting error.