LDACS from a technical perspective

SESAR is holding a series of webinars on the topic of LDACS and how it might fit as a solution to support future air/ground communications. Following on the last webinar, part two of a four part series focused on the technical implications included speakers in addition to SESAR from ENAIRE, DLR, Frequentis and Leonardo.

Let’s start with a brief review of the definition of LDACS to ensure we’re all coming from the same  understanding. LDACS is an aeronautical air/ground communication system consisting of three areas: Airborne, Ground and A/G. It has been designed for the specific requirements of an aeronautical communication system in the L-band. It addresses key topics such as:

  • transport of safety-critical data (Latency, QoS, security, and robustness)
  • existing systems in the aeronautical L-band
  • efficient coverage of the airspace
  • support for very high user mobility
  • limitations of the existing systems.

We’ll touch on a few key points from the webinar but suggest watching the entire session. Starting with the ANSP point of view shared by ENAIRE, they took a closer look at how LDACS could solve the current communications priorities for ANSPs. Let’s consider what they are and how there could be a fit. The core of everything is safety, which is of no surprise to anyone reading this article. Surrounding safety are six key priorities – performance, capacity, cybersecurity, interoperability, scalability and cost efficiency. LDACS functionality can help to support these priorities with the following features:

  • increased quality of service, application-based prioritisation and digital voice to improve performance
  • increased bandwidth will translate to increased capacity
  • cybersecurity as a core attribute along with encryption and compression
  • integration to the multi-link concept to ensure interoperability
  • spectrum efficiency in support of cost containment.

In summary, more traffic can be supported with a higher level of performance.

Frequentis addressed the technical implementation of LDACS and how it relates to the topics raised with the ANSP. As security is paramount to safety critical communications, let’s consider how LDACS addresses security. All entities using the LDACS network are required to authenticate to ensure that only trusted entities are using the system. This happens during a mutual authentication at the time of login between the aircraft and the LDACS access network. Security is applied to all data that is sent over the network independent of other security functions the ANSP may already have in place and therefore provides an extra layer of security. LDACS protects authenticity and integrity of its control data, ensuring all messages in transit are real.

In summary, LDACS brings many attributes to the conversation for future evolution of A/G communications. Safety-critical communications require guaranteed data throughput and latency, efficient coverage of the airspace and spectrum-efficient use in the aeronautical L-band. As IP communications continue to evolve, this solution integrates with the Future IPv6 based communication infrastructure. It extends the current VDLM2 and can adjunct satellite links. This is a distributed system with no central single point of failure, which results in high resiliency and existing radio sites can be reused for LDACS, cutting the time and cost of deployment.  All in all, there are a lot of pros to this alternative for consideration.