The wireless signal propagation characteristics from a satellite-based transmitter to an airborne receiver are of special interest for supplying the aircraft itself or the passengers with communication abilities. Applications can be accessing the internet and multimedia content while on flight but also safety-of-life features like air traffic management. Especially applications incorporating safety-of-life features require not only an average reliability of the transmission link but rather a high availability and have stringent requirements on the continuity-of-service.
The main objectives of this project are to validate and extend existing satellite-to-aircraft channel propagation models and to investigate the characteristics of the satellite-to-helicopter channel. Several effects are considered such as ground reflections from various environmental patterns, multipath contributions originated by the aircraft itself, spatial and polarization diversity an the impact of aircraft structure and antenna location on the antenna pattern.
This project aims to elaborate a software tool modeling the satellite-to-aircraft propagation channel in order to understand and improve the satellite radio reception by the aircraft. The software development process is supported by experimental measurements focused on different antenna, satellite and flight configurations. The experimental plan comprises five different aircraft types and diverse ground-based as well as airborne scenarios.
The project also provides a first characterization of interference in the bands reserved for aeronautical satellite communications at L- and Ka-bands.
The key challenge of the project is to plan, set-up and conduct complex experimental campaigns involving several aircrafts on ground and in flight. This is key to the provision of accurate experimental data to feed the channel model.
This project does not only characterise the propagation channel but it also takes into account the full scenario determining the satellite-to-aircraft radio link (aircraft dynamics and manoeuvring). This includes impairing effects but also alternative system configurations like antenna/polarisation diversity.
The new channel model software simulator also characterises the satellite-to-helicopter channel, which differs from the satellite-aircraft-channel due to its rotating rotor-blades. The difference in both propagation links is analysed and modelled accurately.
The activity improves on the state-of-the-art channel model simulators that rely on a two-tap model with a Line Of Sight path and a ground-reflection path and imply several limitations. For example, they do not consider banking scenarios or satellites with changing positions despite the fact that such scenarios may have significant impact on the channel behaviour.
Therefore, an improved channel model simulator is implemented to allow propagation simulation for signals transmitted by a satellite and received by an aircraft for L- and Ka-band transmissions. The channel model is substantially allowing more scenarios to be simulated. This includes not only aircrafts but also helicopters and banking scenarios. The surface reflection is modelled considering different surface types such as water (representative of lakes and sea), grass or vegetated areas. As a basis for the channel model various measurements are performed and evaluated.
The project is divided in two phases.
During the first phase, the main tasks are:
1 Review of existing channel models and careful identification of gaps in the existing knowledge and experimental data and derivation of experimental,
2 Planning and design of the experiments with particular respect to the channel model’s demands,
3 Selection/Design of measurement equipment,.
4 Demonstration of the experimental data analysis concept.
During Phase 2 the main tasks are:
1 Integration of measurement equipment,
2 Execution of experiments,
3 Data evaluation,
4 Model development and testing,
5 Development of simulation software tool,
6 Additional measurements to countermeasure and verify the channel model and software tool.
The experimental design was approved at the Critical Design Review. The experimental campaign was divided into a summer and a winter campaign and comprised airborne as well as ground-based measurements.
The division of the experiments based on the season used for execution made it necessary to duplicate the EDR (Experimental Design Review) likewise. The first part covered data from the experimental winter campaign and was successfully approved. The second part covered the data from the spring campaign. The splitting allowed to already start the analysis of the winter data which is still on-going. After finally passing the EDR milestone, the project moved inot to the next stage (work package) where the channel model is validated in preparation of the subsequent development of the channel model simulator.