SISNeT PLATFORM OVERVIEW

Architecture of the SISNeT platform

The four main components of the SISNeT platform are:

• Base Station (BS)
  A PC computer connected to an EGNOS receiver through a serial port. Several software components are installed on the computer, so that EGNOS messages can be obtained and sent to a remote computer (called Data Server) in real-time.
• Data Server (DS)
  A high-performance computer, optimised for running server applications with many users connected at the same time. The DS functionality is implemented through a software application called SISNeT Data Server (SDS). This software receives the EGNOS messages from the BS and transfers them to the remote SISNeT users in real time. In addition, the SDS implements all the extra services (present and future) provided by the SISNeT system to the users.
• User Application Software (UAS)
  A software application, which design complies with the SISNeT User Interface Document specifications. The UAS obtains EGNOS messages in real time (1 message/s or 250 bit/s) from the DS. The UAS can also access and apply the present and future additional SISNeT services. Each concrete SISNeT-based application is characterised by specific processing and output interface stages, which provide the desired functionality and user interface to the UAS. The software can be embedded in different kinds of computers and electronic devices (e.g. Personal Data Assistants).
• Web server
  The DS can store the received messages in a remote Web server via the FTP protocol, enabling future development of Web / WAP applications (accessible to the users through a Web browser or mobile device).
  

Presently, the BS and the DS are installed on the ESA Radionavigation Laboratory in the ESTEC centre (Noordwijk, The Netherlands). The ESA implementation of the UAS is run in the EGNOS Project Office (Toulouse, France) where the whole system is frequently updated. These enhancements are reported in the SISNeT User Interface Document.