Radiobeacon DGNSS station selection strategies -can we do better?

David Last, Alan Grant and Nick Ward

Abstract:	Maritime radiobeacons are used by the marine community world-wide as an efficient means of broadcasting differential data to users at sea. In Europe and North America large numbers of these DGNSS beacons now serve not only coastal regions and waterways but also substantial inland areas. As a result, there is often overlapping coverage and a choice of stations. Choosing the best beacon ensures the highest quality of DGNSS service. With many receivers, the user must select the station manually, but there is little guidance as to how to make that choice. Other receivers perform the selection automatically, some choosing the nearest station, others the one that provides the strongest signal. In this paper we also investigate a third approach: the best station is the one with the best signal-to-noise ratio (SNR) and hence the highest quality of data link performance. We develop a computer model to compare the three strategies and implement this novel approach. The computation is based on well-established techniques for DGNSS radiobeacon coverage analysis and system design. At each geographical point we estimate the signal strength of each beacon, of the atmospheric noise, and of the interference from the other stations in the band, and thus compute each beacon's SNR. Using this model, the "best beacon" choices made by the three strategies are mapped across the area (the British Isles in this case). The paper identifies the regions in which receivers that employ the current nearest beacon or strongest beacon strategies fail to select the beacon with the highest SNR. It shows that these simplified methods choose non-optimal stations across a significant proportion of the region examined. As a result, users in those areas may not be receiving the beacon that provides the best service. The paper also shows how to identify the optimum choice of alternate beacon to be used should the preferred station fail.
Published in:	Proceedings of the 2001 National Technical Meeting of The Institute of Navigation January 22 - 24, 2001 Westin Long Beach Hotel Long Beach, CA
Pages:	657 - 664
Cite this article:	Last, David, Grant, Alan, Ward, Nick, "Radiobeacon DGNSS station selection strategies -can we do better?," Proceedings of the 2001 National Technical Meeting of The Institute of Navigation, Long Beach, CA, January 2001, pp. 657-664.
Full Paper:	ION Members/Non-Members: 1 Download Credit Sign In