Lo Presti, Ing. Magli and Ing. In fact, whereas the research is very active as for the aeronautical aspects of HALEs, up to now the telecommunication and signal processing methods to be applied for such platforms have been derived employing terrestrial or satellite models. No specific research has been devoted to a detailed study of the aerial radio channel, or to the analysis of specific features of a cellular telephony or a land surveillance application from a 15-30 km height station. The proposed system, with a moving platform which communicates with a mobile user, presents intrinsic features between terrestrial and satellite systems in terms of required power levels, propagation delays, channel Doppler spectrum, whose study has not been faced yet. For example, co-decoding methods which cannot be applied to satellite systems due to the excessive propagation delays, or to terrestrial systems due to the lack of a direct path between the transmitter and the receiver, may be suitable for a HALE system.
Similar considerations hold as for the signal processing aspects.
The lack of international literature on this subject depends on the fact that HALE platforms for telecommunications and surveillance have been very recently proposed, and the aeronautical problems themselves have not been completely solved yet, although the feasibility has been thoroughly demonstrated. Therefore, the time has come to analyze in detail the mentioned telecommunication features of the possible HALE platform payloads. In conclusion, the lack of literature on the subject witnesses the potential interest and impact of the proposed study, which could fill a gap in the international research. XXI, n.2., pp. 45, No. 12, pag.