European Space Agency

Technical Assistance for Iris Communication Standards Evaluation - DLR


The main objective of the project was to provide technical support to ESA during the current Phase A of the Iris programme.


Aviation’s regulatory bodies place stringent requirements for safety critical communications to/from aircraft in terms of performance and existence of a protected spectrum (due to stringent availability and integrity requirements), which shall be met by any communication systems aiming at providing safety critical applications.


Forecasted air traffic growth is being seriously hampered by frequency channel congestion in current communications infrastructure using the VHF frequency bands. This underpins the need to alleviate saturation by additional capacity in congested regions on the one side, and the need for improved operational efficiency in oceanic and remote airspace on the other side.

Satellite communications is considered in this context as a potentially valuable resource and shall be hence regarded at as an integral part of the foreseen global long term solution.


The suitability of different radio access technologies for the provision of aeronautical safety critical communications services over satellite was investigated.

Pre-selected candidates were taken either from the most promising terrestrial systems for the provision of aeronautical safety critical communications services or from state-of-the-art satellite communications technologies.


The following tasks were part of the project plan:

  • Perform a first assessment if B-AMC is suitable for inclusion into Iris system and identify necessary adjustments,
  • Derive the overall Iris traffic volume generated to serve the entire coverage area,
  • Evaluation of candidate communication protocols defined during the Communication system studies.

Current status

The work in the technical assistance activity has been completed.

Simulations to assess the performance of B-AMC waveform over satellite, together with a first attempt to adapt the terrestrial B-AMC design to a satellite scenario have been carried out, showing that the peak to average ratio can cause performance degradations which make the application of countermeasures necessary. It was also shown that a moderate back-off (3-4 dB) would be a promising approach to operate the system. The study showed that the adaptation of B-AMC to the satellite allows a very high flexibility for resource assignment and that adaptive coding and modulation can be easily applied. Additionally, several items have been identified as issues for a design modification, especially with respect to Doppler compensation, net entry procedure and resource request and assignment mechanisms.

For the estimation of the protocol and management overhead and the total traffic volume analysis in a DVB-S2/RCS based system, simulative analyses have been carried out for the Iris system coverage area and for different time horizons. An estimation of the overall capacity requirements has been performed and the efficiency of different encapsulation schemes and the impact of signalling and different services have been assessed. The investigations have shown that DVB-S2/RCS offers in principle a suitable framework, providing all necessary mechanisms, but that several critical topics (contention based signalling access and transmission of transport layer acknowledgements) have implications on the practical suitability for deployment and need further investigations.

Status date

Thursday, March 5, 2009 - 11:34