Underwateracoustic Communication System Design Based Onadaptive Frequency-Hopping

In the past few years, China has paid much attention on the exploration of the ocean. Itresulted in an increasing demand for underwater communication and thus research inunderwater communication area has been more than before. Excellent propagationcharacteristics of sound in water makes underwater acoustic communication the only way toachieve reliable underwater information transmission.However, the development of underwater acoustic communication system has beengreatly limited by the characteritic of underwater acoustic channel. Underwater acousticchannel shows extremely complex random characteristic, severe multipath interference, delayspread, Doppler spread, a strong background noise, and many other features, all of whichimpact on underwater acoustic communication. Frequency-hopping(FH) technology has agreat potential against interference, especially against narrow-band interference, noise andmultipath. Moreover, adaptive frequency hopping is an optimization of frequency-hoppingtechnology for overcoming a weakness of ‘blind hopping’ in an normal FH communicationsystem. A new method based on this technology above is added to underwater acoustic FHsystem, in order to enhance the transmission capacity and reliability of the communicationsystem.After a lot of underwater acoustic communication related literature data has been studied,a underwater acoustic channel model basing on ray theory is built and simulated via theMatlab software, showing the impact of multi-path effects in underwater acousticcommunication channel. At the same time, the paper describes the characteristics of the FHand adaptive FH technology, as well as the advantage of implementation of FH technology inunderwater acoustic communication channel. Akind of new signal is set for the measurementof the transmission distance in the underwater acoustic FH system. When the result is got, thesystem selects the optimal default frequently points set as the carriers in the transmission.The shift of the frequency point-set is controlled by information in the chirp signal which isalso used for synchronization. The result of the simulation on the designed system is given toprove the feasibility of the design.