Image transmission over underwater acoustic environment using OFDM technique with HQAM mapper

Performance of underwater acoustic communication system is influenced on channel characteristic. Especially, an important feature of the underwater acoustic communication is multipath propagation and Doppler spread cause by the surface and bottom reflections. In this paper, we study the application of high speed image transmission using multi-carrier modulation, where this capability can enable the next generation of undersea expeditions. We use Hierarchical Quadrature Amplitude Modulation (HQAM) as Zero-padded (ZP) orthogonal frequency division multiplexing (OFDM) mapper to be unequal error protection for the transmitted bit stream. We proved capability of ZP-OFDM multi-carrier modulation based on HQAM mapper with Reed Solomon channel coder in sensitive bit error reduction without receiver equalizer. Proposed scheme evaluated using different types of images for different values of the modulation parameter and underwater channel physical parameters.