The amount of air traffic is rapidly recovering from the COVID-19 pandemic and beginning to rise above previous levels. As a result, the VHF band is expected to become saturated in the near future, harmfully affecting air traffic management. As one solution for the increased need for aeronautical connectivity, the terrestrial LDACS data link has been designed and is in the process of ICAO standardization. However, LDACS development has been primarily focused on data communication and digital voice protocols have not been fully defined yet. This paper presents the proposed LDACS digital voice architecture developed in the framework of the Single European Sky ATM Research (SESAR) program. The LDACS digital voice air-ground communication protocol is validated and evaluated in computer simulations. It is shown that the SESAR-specified functional and performance requirements are satisfied.