Smart antenna system design for airborne GSM base-stations

A great interest has arisen in the international community for the employ of Unmanned Aeronautical Vehicles High-Altitude Very-Long-Endurance (UAV-HAVE) platforms as a new technology for the development of telecommunication services and remote sensing applications. We consider the use of a stratospheric, solar powered, UAV-HAVE platform, named HELIPLAT, that is currently being designed at the Politecnico di Torino, as a base station for the GSM mobile communication system. We present a study on the on-board smart antenna system, considering the constraints imposed to the payload by the GSM standard, and by the platform technology. The smart antenna system is realized by a direction of arrival (DOA) estimator, based on the PRIME algorithm, whose output is used by an optimum combiner to shape a suitable radiation pattern of the equivalent antenna; so that the interference due to co-channel users and background noise can be reduced and the transmitted power can be directed just towards the users´ location. Computer simulations have been performed in order to evaluate the average error in both azimuth and elevation angles estimation. The analysis of the results yield to the conclusion that a frequency reuse factor of 3 can be achieved