The Research Of Underwater Image Compression And Transmission Of AUV

Autonomous underwater vehicles (AUV) have gained considerable attention over the years for exploration of the ocean environment. The advantage of underwater acoustic communication makes it possible to transmit underwater image by wireless means. In fact, Video applications process large volumes of data and in order for an underwater channel to accommodate the transmission of this data, extremely high compression is required.The characteristic of underwater acoustic channel is analyzed in this thesis, with emphasis on the multipath propagation characteristic and the limited bandwidth. The thesis proposes that it is necessary to choose an algorithm that performs well both in low bit rate coding and error resistant to transmit image through underwater acoustic channel. Also the characteristic of the underwater image and wavelet transform are discussed in this thesis. In addition, past research has shown that the low contrast and low-detailed nature of underwater imagery allows for low bit rate coding of the data by wavelet-based image-coding algorithms.SPIHT algorithm is studied in this thesis. SPIHT is a progressive wavelet-based image compression coder. Our research has showed that SPIHT performs better than JPEG while the underwater images are coded in low bit rate. SPIHT also has a good progressive transmission characteristic. Based on the former study, the thesis employs SPIHT to compress underwater image during the image transmission of the AUV.In this thesis we have studied the implementation of wavelet transformation in hardware and present an implementation in FPGA. Also the simulation result based on VHDL of some functional modules of the wavelet transformation is given. We have also studied the implementation of the SPIHT. Both memory storage considerations and scan of the sets optimizations to the original SPIHT algorithm for use in hardware are discussed. Some modification of it is also proposed.