L-band digital aeronautical communication system

Helping stakeholders define the future of aeronautical communications.

LDACS is a wideband terrestrial system with line-of-sight coverage intended to work along VDL2 for new and more demanding services. It operates in the L-band (around 1 GHz), which has excellent propagation characteristics. The operational compatibility (spectrum interference) with existing L-band systems (Navigation DME, GNSS, Military JTIDS/LINK16, mobile telephony) remains an important subject, and desirable technology features were identified that could make LDACS spectrally compatible.

LDACS illustration 1

LDACS is a modern communication system with scalability for future data link applications. A strong advantage is that it also features additional capabilities that might be considered in the framework of future “integrated CNS and Spectrum” developments. Studies and flight trials performed by SESAR and DLR have already demonstrated that LDACS is able to support Alternative Positioning Navigation and Timing (APNT), i.e. a navigation backup to GNSS. Furthermore, current studies are looking at how LDACS could support surveillance and RPAS Command and Control C2 link technologies and applications.

Technically, LDACS is a modern “4G-like” technology, with a frequency division duplex (FDD) configuration using orthogonal frequency division multiplexing (OFDM) modulation techniques, reservation-based access control and advanced network protocols.

Our role

At EUROCONTROL, we have been actively supporting European industry activities to define LDACS. We have contributed to the initial LDACS specifications in 2009 including recommendations for interference scenarios, compatibility criteria and test plans for various systems in the L-band.

We continue to support LDACS activities by working in close cooperation with industry partners in the context of several Single European Sky ATM Research (SESAR) projects. In SESAR, we coordinate the LDACS standardisation activities and oversee international harmonisation, civil-military coordination and dissemination efforts. A case in point is our participation in the ICAO Project Team on LDACS, which released the first LDACS ICAO SARPS in December 2018.

We are also actively involved in the spectral compatibility measurements with L-band systems.