Communications

BULATSA has and maintains one of the most developed communication infrastructures in Europe in the area of air navigation telecommunications. The offered services are numerous and have various areas of application.

The Aeronautical Telecommunication Network (ATN) has the purpose of providing continuous transfer of aeronautical information between the infrastructure units and the Air Traffic Services (ATS) Centers in the country. It’s comprised of two interconnected subnetworks, based respectively on ATM (Asynchronous Transfer Mode) and TDM (Time Devision Multiplexing) technologies. A third layer based on IP (Internet Protocol) is currently in process of realization, which will assure the VoIP (Voice over IP) communications between BULATSA centers and with remote VHF sites. The migration to VoIP technology is planned to be completed in 2019. The network nodes are linked to communication channels with different capacities hired from telecom operators, as well as by BULATSA’s own microwave network.

The international connectivity for conducting data and voice communications is provided through hired digital and analogous communication lines with different capacity. The built network is based on IP routers for more effective use of capacity of the hired lines and for automatic redirecting the traffic in the case of failure. The network encompasses the air traffic management centres at Sofia, Varna, Bucharest, Constanta, Skopje, Athens, Simferopol, Belgrade, Istanbul and Ankara.

In BULATSA are used three systems for operational voice communication – VCS (Voice Communication Systems), which maintain the standardized interfaces MFC-R2, CB and ISDN. The systems are installed at the ATS Centres at Sofia, Varna and Burgas and allow the VoIP communications between BULATSA centers and with remote VHF sites . They provide the necessary for the Air Traffic Controllers (ATCOs) functionalities regarding the voice connectivity with the aircraft crews, as well as with the ATCOs from the neighboring countries. The “air-ground” communication is realized through 16 VHF receiver-transmitter centres, where are stationed over 300 radio stations, servicing over 30 radio channels.

In BULATSA is operating an Air Traffic Services Message Handling System (AMHS) in relation with the ICAO requirements, according to which in Europe must be performed a migration from AFTN/CIDIN (Aeronautical Fixed Telecommunication Network / Common ICAO Data Interchange Network) to AMHS. The system provides exchange of aeronautical messages and is directly linked to the safety of aviation and the provision of air navigation services.

Since 2015 BULATSA provides A/G Data Link Services from/to the aircraft. Data communication infrastructure, managed and maintained by the communications provider SITA, was build, which will deliver to BULATSA the respective ATN/CPDLC messages (messages, part of the communication system, through which ATCOs can communicate with the pilots).

All BULATSA’s communication facilities and networks are encompassed with real time surveillance and management systems – a mandatory element, necessary for the timely diagnostics and fixing equipment failures.