Spectrum sensing for cognitive maritime VHF networks

The Automatic Identification System (AIS) is used worldwide as a maritime system for identifying and locating vessels by exchanging data in Very High Frequency (VHF) band with other nearby ships, AIS base stations and satellites. It is an important system for safety of navigation to assist collision avoidance and enables marine traffic supervision and management. However, the expanding use of AIS band by other emerging applications and services has caused significant increase on the maritime VHF Data Link (VDL) load, hampering smooth exchange of critical AIS information. Instead of assigning new frequency resources for new marine VDL services, in this paper we present a solution to overcome this spectrum scarcity issue by utilizing Cognitive Radio (CR) technology in maritime AIS VHF network. A preliminary analysis of the performance of such an approach is carried out taking into account the different properties and challenges of marine communication channels due to sea surface movement. The outcome of our study shows how the application of CR techniques to maritime VDL indeed represents an appealing alternative to static spectrum allocation schemes to deal with overloading issues in AIS networks.