The Study Of The Coding And Modulation Technologies And Applications For OFDM In High-Speed UWA Communication

Underwater acoustic (UWA) communications is a rapidly growing field of research, which once was exclusively military, is extending into commercial field, such as remote control in off-shore oil industry, pollution monitoring in environmental systems, speech transmission between divers etc. The needs for underwater wireless communications are increased.Since the underwater acoustic channel is temporal and spatial variability and multipath propagation, signal degradation is severe. In order to achieve high data rates on the severely band-limited UWA channels, Orthogonal Frequency Division Multiplexing(OFDM) technology with high spectrum efficiency should be employed, together with the band-width efficient modulation of subcarrier and channel coding, to improve the data rate and reliability for UWA communication.The main content in this paper is the research of key techniques of high-speed underwater communications based on OFDM. The main work is as follows:1. The characteristies of underwater acoustieehannel are introdueed, and the main obstacles in high data rate communication are studied.2. To attain reliable high data rate transmition over underwater acoustic channels,high band-width efficient modulation of subcarrier on OFDM are studied. Inorder to find a modulation technology with high spectrum efficiency,large capability, strong ability of overcoming multi-path and impulse noise and efficient utilization of power.3. The principle performance and arithmetic of coding and decoding of RS code,convolutional code, turbo code ,serial RS concatenated convolutional code and trellis coded modulation are studied. And the simulation results under the model of UWA channel are given.4. Experiment in pond is made to validate the performance of algorithms. Checking the performance of different channel coding and modulation technologies in UWA communications is main intension. The bit of error rates is commonly 10^-2 without channel coding and can be greatly reduced by using the channel coding proposed in this paper in the experiment.5. RS code and convolutional code are realized in real-time on DSP platform.