The Global Communications Infrastructure
With monitoring data and analysis reports at its core, the global alarm system designed by the Comprehensive Nuclear-Test-Ban Treaty (CTBT) depends on a well functioning communication system for the timely, reliable and accurate transmission of data and data bulletins. The Global Communications Infrastructure (GCI) was developed to meet this expectation.
The GCI is a communication system of truly global character. It connects places distributed all over the globe with the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) in Vienna and all CTBT States Signatories.
The Global Communication Infrastructure (GCI) was developed
to provide a functioning communication system for the timely,
reliable and accurate transmission of data and data bulletins.
The GCI was designed to ensure data transmission from the 337 facilities of the International Monitoring System (IMS) in near-real time to the International Data Centre (IDC) in Vienna where data are processed and analysed. The GCI is also used to distribute the raw data from IMS stations as well as IDC data bulletins to Member States. This very detailed information enables Member States to assume their rights and responsibilities under the CTBT.
The GCI is the first global satellite communications network
based on Very Small Aperture Terminal (VSAT) technology
comprising an earth stations, a dish antenna and a PC interface.
Satellite based technology
The GCI is the first global satellite communications network based on Very Small Aperture Terminal (VSAT) technology. A VSAT is a set-up on the ground called earth station that allows for communication via a satellite. It employs a dish antenna to send and receive signals, and an interface to a PC.
Satellite based technology cont.
More than 210 VSAT links have been established so far to ensure communication with IMS monitoring facilities and national data centres (NDCs). The number continues to increase with more IMS stations being built. Each station needs to be equipped with communication devices to enable the sending of data for analysis to the IDC in Vienna. When several IMS monitoring stations are co-located, they use one VSAT set-up for the communication needs of all stations.
VSATs connect to six communication satellites which are located at a height of 36,000 kilometres above the equator. The satellites are geostationary, i.e. they rotate along with the Earth. Three of the satellites cover the areas of the Atlantic, Pacific and Indian Oceans. The other three satellites are stationed above North America, Europe and the North Pacific Region to provide for a more efficient coverage of the Northern Hemisphere.
Over 200 VSATs connect to six communication satellites that
rotate along with the Earth at a height of 36,000 kilometres
above the equator.
Transmissions are routed from the satellites to three hubs on the ground which forward transmissions through terrestrial links to the CTBTO in Vienna. Two of the hubs are located in the United States of America and one in Norway.
The hub on the west coast of the USA transmits data coming from the satellites covering the Pacific Ocean, the American and the North Pacific region. The hub on the east coast of the USA transmits data via the satellite covering the Atlantic Ocean region, and the hub in Norway covers transmissions from satellites above the European and the Indian Ocean region.
From the satellites transmissions are routed to three hubs on
the ground and from there through terrestrial links to the
CTBTO in Vienna.
Non-satellite based data transmission
Although satellite based communication is used for the bulk of data transmission, there are several alternative means of communication. In 2003, the CTBTO first tested and then started utilizing the virtual private network (VPN) technology. VPN makes use of public telecommunication infrastructure, like the internet, to connect outside users to an organization’s network. Specially designed encrypting methods are applied to maintain the required level of security and protect against unauthorized access.
The CTBTO uses alternative means of communication such as
the virtual private network technology or VPN which relies on
public telecommunication infrastructure like the internet.
There are currently close to 30 connections to the GCI network through VPN. Tsunami warning centres in the Pacific and Indian Ocean regions use this set-up to receive data directly from IMS monitoring stations. A number of IMS monitoring stations also use VPN to communicate as the usual satellite based structure is not feasible in their locations.
Connecting remote monitoring stations
Some stations are so remote that none of the six satellites can be used for communication with these stations. This particularly applies to stations in the near-polar regions.
An auxiliary seismic station at the South Pole, AS114, is one of those few exceptions. The station’s extreme geographic location at exactly 90o south does not allow for a connection to any of the satellites above the equator as these satellites are not visible above the horizon.
Alternative communication set-ups have to be established for
extremely remote stations such as an auxiliary seismic station
at the South Pole.
Alternative satellites are used to connect this station to the GCI. Two satellites circle the globe in an inclined orbit above the equator and one moves round the Earth on a pole-to-pole orbit. These three satellites take turns to act as intermediaries between this remote monitoring station and the GCI network.
New service provider
To build, maintain and operate the entire GCI network, the CTBTO engages a contractor who specializes in the field of global communication. The first ten-year contract with a communication service provider expires in 2008 and a new service provider has already been contracted.
The organization is currently migrating the entire GCI network infrastructure to the network of the new service provider. This involves changing satellites, shifting VSAT antennas to the new satellites and installing new communications equipment at more than 210 VSAT locations all over the world. Communication set-ups for newly built monitoring stations are already being integrated into the new network.
Like the previous network, the new GCI network will use both terrestrial and satellite connections. In combination with independent subnetworks of various Member States, the new network will reach IMS stations and NDCs in approximately 100 countries.
The volume of data transmitted daily by the GCI from monitoring
stations to the IDC and from the IDC to Member States increases
constantly and is expected to reach 26 gigabytes per day.
Increasing data volume
As more monitoring stations and NDCs join the global alarm system, the volume of data transmitted daily by the GCI is constantly increasing. Currently, 16 gigabytes of data are being transmitted by the GCI every single day. Of this, nine gigabytes are incoming data from monitoring stations and the volume of outbound data traffic to Member States comprises seven gigabytes. The data volume transmitted through the GCI is soon expected to reach 26 gigabytes per day.
With worldwide connectivity being the daily business at the GCI, a key principle is being observed throughout – information security. Every element in the GCI network structure needs to meet high standards of data availability, confidentiality and reliability. The new GCI network incorporates a high level of network security to ensure required data integrity and data availability, and to provide for necessary data encryption and authentication.
Worldwide connectivity requires a high level of network security to
ensure data integrity and data availability.
The CTBTO Operations Centre is an important partner for the GCI in monitoring the status of its network links. A specially designed web portal depicting the so-called workflow can be accessed in the Operations Centre. This tool shows how the GCI communication network is actually working. Outages and failing connections can be identified and addressed quickly.