Some Selected Aspects of HAP Communications Channel Model for Wireless Sensor Networks

The coming of sensor networks technology is supporting the development of new data sensing and collection applications. One such application involves a Wireless Sensor Network (WSN) able to process the sensed environmental data and transmit them to a far gathering centre, like a High Altitude Platform (HAP). In this system the possibility of disconnection is one of the fundamental new networking problems presented by sensor networks. There are problems of both visibility and meteorological precipitation in the radio communications by HAP platforms. Model of signal channel must also contain these two parts, because their impact on the communications quality is high. Here the calculation of transmitter visibility is described for both stationary user and moving user either in the road or rail vehicle. At the same time there are some necessary geodetic terms and problems explained. The second part of the article is devoted to modeling precipitation attenuation of communications signal by use of ITU recommendations. Some simulated experiments with real map data in Matlab environment and their results are described for both problems.