SCADA Communications Over Low Speed, High Latency Links

Abstract

Controlling and monitoring a compressor station with more than 3,000 tags remotely can be a heavy burden for a low speed (9,600 bps) double-hop satellite link, over which an ICMP packet takes more than 2 seconds to traverse all the way across the spatial segments, forth and back. This paper presents an application named Datasync, specially developed to take full advantage of the scarce resources provided by the VSAT link. One of its main features is to enable the setting up of communication deadbands and the “hot” changing of these deadbands. Therefore, the operator is able to increase the deadband of a tag immediately after detecting that too many exceptions are reported on that tag, which would cause an undesirable increase on the traffic, ultimately resulting in unacceptable response times.