ASTRID assesses impact of Brussels terror attacks on TETRA radio network

Belgium’s emergency services communications operator recommends increasing capacity in Brussels, faster deployment of mobile base stations and introducing communications priority over the 4G Blue Light Mobile data service

ASTRID assesses impact of Brussels terror attacks on TETRA radio network

The operator of Belgium’s ASTRID emergency services communications TETRA radio network has assessed the impact of the terrorist attacks in Brussels in March on its operational performance and made some recommendations for improvements, particularly around capacity.

On Tuesday 22 March 2016, the ASTRID network processed an unprecedented amount of radio communications from all of the emergency and security services that were mobilised in Brussels. ASTRID immediately convened a meeting with the ASTRID User Advisory Committee, which represents all emergency and security services, in order to make an initial analysis.

ASTRID has since conducted a thorough technical analysis of the communications on the day of the attacks, while the Committee conducted a study from an operational perspective and immediately made recommendations to the relevant users.

These unprecedented terror attacks have brought a new reality to our country. ASTRID wants to bring all stakeholders involved in security together to see how everyone can prepare even better for potential new emergency situations.

On the day of the attacks, some of the ASTRID base stations in Brussels became saturated due to:

• The exceptional nature of the emergency, which involved violent attacks that were carried out successively at different locations, within a few hours and within a limited radius.
• Emergency and security services from across the country were mobilised to provide assistance in Brussels, which required additional network capacity in Brussels.
• The saturation of the commercial mobile phone networks. This resulted in an increased number of individual calls on ASTRID that would normally take place over the mobile phone network.

Some facts about the 22 March 2016 attacks

• More than 4,300 active radio users in Brussels, instead of 2,500 as is the case on a typical day
• Up to 600 active talk groups (each group has an average of 34 radio users) instead of the 200 or so on a typical day.
• 26,000 successful group communications
• 8,400 unsuccessful (or interrupted) group communications
• 1,000 individual communications.

The ASTRID TETRA radio network is built around the concept of ‘talk groups’: The dynamic creation of groups of people who need to communicate with each other according to their duties. These groups are either predetermined or can be tailored by the emergency and security services in the event of an incident.

Despite an overall heavy load, not a single ASTRID system experienced a technical breakdown: the radio network and the paging system as well as the control rooms (emergency centres 100/112-101) never faltered.

Shortly after the attacks, seven ASTRID base stations (five in Brussels and two in Flemish Brabant), including the base station near the Maalbeek metro station, reached their maximum capacity (saturation), preventing a part of the communications from proceeding trouble-free at times, in particular between 10:00 and 12:00.

Following the attacks, ASTRID immediately convened its Crisis Management Team and took a number of measures. Consultations with the Federal Crisis Centre and the main users of the network, putting the main suppliers of its infrastructure on standby and deploying the mobile ASTRID base station to temporarily boost radio capacity. At the request of the user organisations, ASTRID also logged 210 additional radios onto the network on the day of the attacks.

Supplemental to the technical aspects, use is also an important factor. Therefore, on 25 March, ASTRID requested the User Advisory Committee to conduct an operational analysis as well. The use of the radios has an impact on network capacity. Especially in crisis situations, compliance with communication procedures and plans can prevent network saturation.

Technical action points and proposals for improvement

• A series of technical measures in the short term have been discussed with the users; in particular a faster deployment of the mobile base station (via satellite connection) and a clearer framework for communication with the Federal Crisis Centre.
• Increasing the capacity of the radio network in Brussels: The capacity of the base stations in Brussels (or big cities) can be increased by the end of 2016. To achieve this, ASTRID requires additional frequencies. This issue is currently being discussed with the BIPT (Belgian Institute for Postal services and Telecommunications) and Defence.
• Approval of the business plan and the management contract of ASTRID: This will enable the optimisation and technical renewal of all ASTRID systems. This is already included in the business plan of ASTRID which was approved by the Board of Directors of ASTRID pending the approval of the Belgian government. The inter-cabinet working group has started talks on this matter.
• New communications priority over data service broadband (Blue Light Mobile).

ASTRID already offers emergency services an opportunity for high speed data transmission through national roaming on the networks of the three mobile network operators (

ASTRID plans to expand this service in the future to allow the emergency services to carry priority voice communications not only via the existing ASTRID TETRA radio network, but also via Blue Light Mobile. Talks are being held with the Federal Public Service of Telecommunications, the BIPT and the three mobile network operators.

Operational action points and proposals for improvement

With regard to the operational aspects, the ASTRID User Advisory Committee, which represents all emergency and security services, has already launched several actions to avoid such disruptions to communications in the future.

The Committee has included all operational aspects in a report (dated 17/05/2016) which has also been presented to the Parliamentary Inquiry Committee.

The overall conclusion cites: "We can conclude from the information available that the capacity problems were caused by both technical and operational aspects."

For the operational aspects, the ASTRID User Advisory Committee cites "…that raising awareness and the training of staff still remains one of the key success factors for the optimal use of network and radio communication means”.

Within the context of future improvements, the Committee states that “…therefore, improvement concerns everybody":

• "The federal authorities for legal and budgetary aspects
• The provincial/municipal authorities to assess the emergency and intervention plans for the education and training of the user organisations (i.e. through the provincial steering committees of ASTRID), for the organisation of multidisciplinary exercises etc.
• The user organisations for the mono-disciplinary intervention plans, raising awareness and basic and in-service training of staff as well as the improvement of processes and procedures
• A.S.T.R.I.D. for the technical aspects, the support of the authorities and organisations and to sensitise and inform the users
• The ASTRID User Advisory Committee for sharing its expertise on an organisational and operational level in terms of the guidance of the authorities and organisations with informing and sensitising the users."

The ASTRID network technology
The 100% digital ASTRID radio network is based on TETRA (TErrestrial Trunked RAdio), a standard that was developed in Europe specifically for the digital radio communication of emergency and security services.

Almost all European countries opted for TETRA, while Germany and Luxembourg are currently putting the finishing touches on their networks. The ASTRID network meets the current technological requirements and also follows the latest developments closely.

Since its roll-out, the network has already been updated several times and new developments are planned in the near future, especially in the new management contract. There is currently no other technology that meets the specific criteria of the emergency services.


Leave a Comment