Non-Uniform Non-Orthogonal Multicarrier Underwater Communication for Compressed Sonar Image Data Transmission

Efficient and reliable underwater sonar image transmission is increasingly desired for underwater investigation by autonomous underwater vehicles (AUV). However, it is extremely challenging due to the severe interference nature of underwater acoustic channels and the large data size of sonar images. In this paper, we first combine multicarrier modulation techniques with characteristics of compressed sonar image data to improve the transmission performance, where in previous research, image compression and multicarrier modulation were investigated separately. The compressed bitstream of sonar images is regarded as a new type of image with unique frequency characteristic. A non-uniform non-orthogonal multicarrier modulation scheme based on frequency characteristics of compressed sonar image data (F-NNMC) is proposed to meet the requirements of efficient and reliable sonar image transmission. The non-orthogonality between subcarriers improves the spectrum efficiency, and the non-uniform subcarrier structure can carry more effective information of the transmitted compressed data to improve the reliability. The simulation and experiment show that the proposed F-NNMC needs less frequency resource and has better peak signal-to-noise ratio (PSNR), structural similarity (SSIM), as well as lower bit error rate (BER) compared to orthogonal and non-orthogonal modulations.