Increasing the capacity of existing terrestrial outdoor radio mobile systems by means of UAV-HALE platforms

In this paper the use of a stratospheric platform as a novel technology for the development of telecommunication applications has been investigated, showing that it can be successfully used as a valid alternative to satellites. More in detail, we employ an unmanned aeronautical vehicle high altitude long endurance (UAV-HALE) platform as a base station for mobile communication systems and we focus the study on the topic of the adaptive antenna array required to provide a higher quality of service all over the cell and to increase the capacity of the system, while keeping at the same time the computational complexity as low as possible, because this is a basic requirement for systems placed on a UAV-HALE platform. In the first part of the paper we show the coverage achievable by the platform, considering constraints related to the geometry of the problem, the propagation environment and the communication system. Then, the architecture of the smart antenna system is considered, by analyzing the direction of arrival (DOA) estimator and the dynamic adaptive beamformer (DAB). The final part of the paper shows experimental results based upon computer simulations. The average error in both azimuth and the elevation angles estimation has been evaluated and the analysis of the results yield to the conclusion that a frequency reuse factor of 3 can be achieved by employing the proposed smart antenna based system as fundamental component of the base station mounted on the stratospheric platform.