USING OPNET MODELER TO ANALYSE GALILEO COMMUNICATION NETWORKS.

Galileo is a European initiative to develop and deploy an independent global satellite-based navigation system. It consists of a Medium Earth Orbit sat ellite constellation transmitting navigation signals, a ground segment for monitoring and control of the constellation and for determining and disseminating the navigation messages and integrity warnings through the navigation signals to the user receivers. The Galileo Ground Segment is a worldwide-distributed system consisting of Control Centers, Sensor Stations and Up-Link Stations, interconnected with global communications networks, which need to fulfill strict quality of service (QoS) requirements in terms of availability and latency. This paper will present the results of simulations using a commercial simulation tool called "OPNet Modeler", in order to determine the factors impacting the QoS requirements and capacity of these global communications networks. Under the work presented, a Frame Relay Only network and a mixture of Frame Relay and Very Small Aperture Terminal (VSAT) satellite network have been simulated. Further, performance analyses have been carried out in order to determine whether the best option is to use a Permanent Virtual Circuit with or without prioritized data. [ABSTRACT FROM AUTHOR]