A Satellite Communications Systems for Helicopters

Paper number

IAC-06-B3.6.08

Author

Prof. Otto Koudelka, Graz University of Technology, Austria

Year

2006

Abstract

Airborne platforms are indispensable for emergency relief and disaster management. They can be used for remote-sensing and emergency communications applications. Air-to-ground links have been traditionally used for this purpose. Satellite communications systems on the other hand have the advantage to provide high bandwidth and long-distance communications. Helicopters are suitable to operate in difficult terrain (e.g. mountains, flood or landslide areas). The problem with civil helicopters is the periodic interruption of the satellite link due to the rotor blades, because the antennas have to be attached to the fuselage below the main rotor. There are several possibilities to overcome this difficulty. Interleaving may be used to cope with the interruptions. Another option is burst transmission and reception synchronised with the rotor movement.
Joanneum Research and Graz University of Technology have developed an advanced satellite communications system under an ESA contract. This system is called L*IP. Emphasis has been put on efficient modulation and coding as well as a dynamic multi-frequency time division access scheme which is highly scalable and optimised for  IP traffic. The communications system utilises a software-radio platform which allows easy modification of transmission and networking parameters. 
In the framework of a national project studies and investigations have been made to adapt the L*IP system for aeronautical applications. In particular, the effects of the helicopter rotor on the reception of DVB and MF-TDMA receive signals have been measured using a civil rescue helicopter. Measurement antennas were installed underneath the rotor. The fade depth and duration were determined for different antenna positions. The access scheme has been modified to cope with this influence subsequently. Furthermore, investigations concerning mobility effects on the synchronisation scheme have been made.

The paper describes the design of the helicopter-based satellite transmission system as well as measurements during tests with a rescue helicopter. The adaptation of the transmission and access scheme, especially the synchronisation are described. Finally, applications in the field of emergency communications and disaster relief are presented.

Abstract document

IAC-06-B3.6.08.pdf

Manuscript document

IAC-06-B3.6.08.pdf (🔒 authorized access only).

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