Aerospace and Electronic Systems Magazine November 2017 - 24

Datalink Security in LDACS for Air Traffic Management

Figure 1.

LDACS subnetwork within the IP-based aeronautical telecommunications network called the FCI. The
LDACS subnetwork will be one of several wireless access networks connecting aircraft with the air traffic management networks on the ground. The other datalinks proposed for the aeronautical telecommunications network are the Iris satellite system and the AeroMACS datalink for airport operations.

Figure 2.

LDACS protocol stack and functional entities. The interface of LDACS to the IP-based aeronautical
telecommunications network called the FCI is the SNDCP. The functional entities within the LDACS datalink are the LME, DLS, voice interface (VI), medium access (MAC) entity, and physical (PHY) layer.
The LDACS protocol stack is identical for aircraft and ground station, although the ground station LME
and DLS have to be more sophisticated to serve multiple aircraft.

IEEE A&E SYSTEMS MAGAZINE

initiatives for the development of an
LDACS were started at the end of action plan 17.
One outcome of these initiatives
was the technology proposal for a
broadband LDACS system [15]. LDACS has been developed by merging aspects of the technologies investigated
in action plan 17: broadband aeronautical multicarrier communications [28],
wideband data standards P34 (Telecommunications Industry Association standard family TIA-902), and WiMAX
IEEE 802.16e technologies [29]. The
LDACS datalink is a long-range multiapplication cellular broadband system
capable of simultaneously providing
various kinds of air traffic services and
aeronautical operational control communication services via a network of
ground stations.
LDACS will be one of several
wireless access networks connecting
aircraft to the IP-based FCI displayed
in Figure 1 [2]. The LDACS subnetwork contains several ground stations,
each of them providing one LDACS
radio cell. Each ground station is the
central entity controlling all air-ground
communications within its radio cell
[7]. The deployment of the LDACS
communication infrastructure is independent of the airspace organization,
because LDACS supports transparent
handovers between cells.
The LDACS protocol stack defines
three layers, the physical layer, the datalink layer, and the subnetwork layer, as
illustrated in Figure 2 [30]. The physical layer (PHY in Figure 2) provides
the means to transfer data over the radio
channel. The datalink layer is organized
in two sublayers: the medium access
control sublayer and the logical link
control sublayer. The logical link control sublayer manages the radio link and
offers a bearer service, with different
classes of service to the higher layers. It
comprises the datalink services (DLSs)
and the voice interface. The medium access control sublayer contains only the
medium access (MAC in Figure 2) entity. Cross-layer management is provided
by the link management entity (LME).
The LDACS system interfaces with the
IP-based aeronautical telecommunicaNOVEMBER 2017

Table of Contents for the Digital Edition of Aerospace and Electronic Systems Magazine November 2017