Differential Frequency Hopping (DFH) Modulation For Mobile Underwater Sensor Networks

摘要

The long-term goal of this research effort is to develop underwater acoustic communications algorithms based on differential frequency hopping (DFH) modulation that enable networked operations (i.e. multiple simultaneous users), as well as providing low probability of detection and intercept (LPD/LPI) and anti-jamming (AJ) capabilities. The specific objective of this effort is to adapt existing DFH algorithms developed for terrestrial communications for use in the doubly spread underwater acoustic channel. Key research goals are: (a) development of synchronization and demodulation schemes that are robust to various aspects of the environment using the DFH signal itself, and (b) development of equalization algorithms that exploit available spatial diversity for improving the bit error rate (BER). Variations in water depth, bottom type, sound speed profile, and source/receiver location can provide for wide ranges of multipath interference (resulting in time spread). Different wind and surface wave conditions in combination with platform motion can result in varying degrees of Doppler shift and spreading. The developed algorithms must work well across the range of conditions that might be encountered in real-life scenarios.