Achieving reliable underwater communication in shallow water acoustic channels is a difficult task because of the random time-varying nature of multipath propagation

severe amplitude fluctuation

and spatial variability of the channel conditions. This paper describes a new signal processing technique-frequency coding and decoding by means of real-time measurement of signal width

jamming and suppressing multipath interference and using redundant coder. The application of the technique to the model ZIY-1 status monitor for underwater system of scabed is introduced in this paper. The main principle

the technique specifications and the key techniques of the system are discussed here. Theoretical estimations and experimental results proved that the performance of the system is excellent. The method can be used for some other related low-data-rate data transmission detecting in shallow water acoustic channel.