Within the current EUMETCast configuration, the multicast system for file distribution is based on the client/server software package TelliCast. The server is implemented at the EUMETSAT HQ in Darmstadt, and the clients installed on the individual EUMETCast Reception Stations.
On EUMETCast Satellite the multicast is transferred via a dedicated communications line from EUMETSAT to the uplink facility. There the multicast is encoded into a DVB signal and transmitted to a geostationary communications satellite for broadcast to user receiving stations. Each receiving station decodes the signal and recreates the original multicast stream.
On EUMETCast Terrestrial the multicast is transferred via a multicast-enabled dedicated network, currently using research networks, to the user. Users must be eligible to connect to the national research networks and the research network must be included in the EUMETCast Terrestrial network.
The EUMETCast Client stations decode the multicast back into files according to the subscription of the user.
The diagram on the right shows the architecture of the EUMETCast System, comprising the EUMETCast Satellite and EUMETCast Terrestrial Services.
EUMETCast Terrestrial is currently a demonstration service and is being evaluated for its potential to work as a back-up to the EUMETCast Satellite service.
Figure 1: EUMETCast system model, highlighting the satellite and terrestrial delivery mechanisms.
The key features of EUMETCast are:
Secure delivery of data, allowing multicasts to be targeted to a specific user or group of users, thus supporting any required distribution/access data policy;
Handling of any file format, allowing the dissemination of a broad range of products;
No limitations to file sizes;
Use of DVB turnarounds allowing the easy extension of geographical coverage
One-stop-shop delivery mechanism allowing users to receive many data streams via one Reception Station
An installed user-base of over 4000 Reception Stations
Use of off-the-shelf, commercially-available DVB reception equipment
Use of high-bandwidth managed global terrestrial networks
Highly scalable system architecture
System components and synergy
The dissemination of multicast data through terrestrial networks – instead of uplinking to satellites, is an end-to-end terrestrial dissemination. The emphasis is on achieving a best possible synergy between the two components and, in particular, as regards providing a harmonised interface to the end-user – irrespectively if the data was disseminated via satellite or terrestrial networks.
For both EUMETCast components the client software subscribes to the multicast channels that contain their desired data & products. Once subscribed, the files are in the case of EUMETCast terrestrial routed through terrestrial networks in a single transmission. For use cases in which the same data has to be sent to multiple users simultaneously, multicast allows to set up a highly- scalable dissemination system without the burden of duplicating the data volume for each new user as it would be the case in traditional one-to-one concepts.
A single reception station can receive any combination of the provided services. Data whose access is controlled will be encrypted using a combination of EUMETCast Key Unit and the EUMETCast Client Software. The decryption at the user station will be carried out by using an USB eToken decryption scheme.