Communications make the key role in providing efficient and safe air traffic control. Air navigation service providers manage a wide range of analogue and digital radio and telecommunication systems for transmission of voice and data communications. The communication systems have to provide fast, safe and reliable flow of information between aircraft in the controlled airspace and ATC centres (A/G communications), as well as between local and foreign ATC centers (G/G communications). In the maintenance of these communications they rely on national providers of telecommunication services, as well as on their systems. Under this thesis parameters of digital radio microwave system like: frequency, transmission rate, modultion technique, modulation procedures and procedures for error correction are elaborated. Not only basic principle of spreding electomagnetic wave is descibed, but also atmospheric influence, noise and fading on transmission path between transmitter and receiver. Two commonly used modulation transmission techniques are described. In National Instruments Modulation Toolkit for LabVIEW two models of digital system are programmed. First model uses digital fase modulation and second one uses digital amplitude modulation for transmission method. Comparation between these two models is done where the same imput is used. Results of the simulationa are shown trough various diagrams and numerical values that valorise digital connection. At the end results of these simulations are compared to the real values provided by the domestic telecommunication provider.