VHF Data Exchange System On-air Trials: The Journey so far

The need to communicate from ship to ship, and from ship to shore, has been growing since the first time man went to sea. Today, the amount of information conveyed to and from a vessel during its passage is driven by automated reporting, weather information, safety updates, as well as crew requirements for entertainment, social interaction and so on. The introduction of the automatic identification system (AIS) in 2002 provided a novel means to convey safety related information between vessels and shore authorities. AIS has to some extent become a victim of its own success as it was soon used for other communication needs than safety information. Over the past 9 years, the General Lighthouse Authorities of the UK and Ireland’s research and development team, GRAD, has been supporting international efforts to develop the VHF Data Exchange System, commonly known as VDES. VDES includes the two existing AIS channels, but expands the available bandwidth to provide an enhanced throughput, supporting future e-Navigation services, such as authenticated Aids to Navigation (AtoN). This paper will report on the latest work of GRAD in the development of VDES, briefly recounting the driving need, frequency allocations and technical characteristics, but focusing on the latest developments of the UK’s first on-air VDES transmissions. Trials were conducted in early January 2021 off the east coast of the UK, with signals transmitted (under licence) from the GRAD radio lab in Harwich and received and responded to from equipment fitted to a GLA vessel at sea. The paper outlines the trial, test methodology, equipment used, approach to calibration, expected results from modelling and then concludes with the results of the trial including the signal strength, noise levels and packet error rates. All of this information is then used to refine and support GRAD VDES Coverage models which are also presented.