Automatic Identification System VHF Data Link Loading under Anomalous Tropospheric VHF Propagation

In paper the method for the VHF Data Link (VDL) loading estimation based on the processing of the “number of received stations” parameter of the “SOTDMA communication state” field of AIS messages No. 1, 2, 4 is proposed. Since the messages being processed contain the coordinates of the targets, it is also possible to build a map of the VDL loading. It is also shown that the VDL loading of Vessel Traffic Service (VTS) base stations for the Black Sea coast in conditions of anomalous propagation of radio waves can be 90% or more. The statistics of inconsistent AIS messages is considered.