2024 AGENDA

Phase Shift Keying for ADS-B, also known as Phase Overlay, is a feature that was introduced in the EUROCAE ED-102B & ED-73F and RTCA DO-260C & DO-181F normative documents. This new phase modulation (based on 8-PSK), which overlays the original amplitude modulation (PPM) of the ADS-B, has its main improvement in the data capacity, as it enables to increase it from 112 to 448 raw bits, effectively from 56 to 260 bits. This new feature avoids the need to modify the structure of the current Extended Squitter message or its assigned spectrum (1090 MHz), maintaining the backwards compatibility of this surveillance system.
Indra has been part of the definition of Phase Shift Keying for ADS-B since its beginnings, participating in different working groups and R&D projects partially funded by the European Commission and with the collaborative work of ANSPs and industry stakeholders. In total, Indra participated in three different projects, each one increasing the complexity of the system and its validations.
In the last one, Phase Shift Keying technology was validated in a real environment, where several transmissions of ADS-B information were tested with a transmitter and receiver system prototype with this feature implemented. This exercise returned successful outcomes, as the information form the phase modulation message was retrieved as expected without modifying the message of the original amplitude modulation.
This R&D project allow to confirm the technological and technical feasibility of this new feature for ADS-B, demonstrating that this additional data can be used for several purposes, such as the provision of more detailed weather information, the reduction of the 1090MHz frequency spectrum congestion or the authentication of ADS-B transmissions in order to avoid threats like spoofing.
In this sense, Indra is participating in a new R&D project, also funded partially by the European Commission and with the participation of an ANSP, international organizations and industry stakeholders, to study the potential introduction of an authentication algorithm for ADS-B. The objective of this project is to study whether the implementation of this new feature in the data capacity provided by Phase Shift Keying is feasible, which would provide an additional security layer to the ADS-B surveillance system. In other words, this will help to know if an aircraft is real or not, as all ADS-B messages broadcasted by the aircraft will be signed and checked.