ANALYSIS OF PROPAGATION FOR WIRELESS SENSOR NETWORKS IN OUTDOORS

A revision of main propagation mechanisms of radio waves for wireless sensor networks is presented in this paper. In order to address this topic, the free space model is firstly taken as a reference. Classical concepts like ground reflection, diffraction, and surface waves are included from a theoretical point of view, and some aspects related to wireless sensor networks are analyzed for each subject. A key parameter is the height of antennas which plays an important role on distinct formulations like reflection coefficient of the ground surface. From there, when antennas are very close to ground surface, the far field conditions could be different from that typical expression. Hence, some of propagation models involve a characterization of far field conditions, and practical settings of antennas for wireless sensor networks are analyzed by electromagnetic simulation. Attenuation due to vegetation is also reviewed, and models suitable for these networks are exposed.