Signal propagation in aquaculture environment for wireless sensor network applications

This paper presents results of signal propagation studies for wireless sensor network planning in aquaculture environment for water quality and changes in water characteristics monitoring. Some water pollutants can cause widespread damage to marine life within a very short time period and thus wireless sensor network reliability is more critical than in crop farming. This paper shows that network coverage models and assumptions over land do not readily apply in tropical aquaculture environment where high temperatures are experienced during the day. More specifically, due to high humidity caused by evaporation, network coverage at 15 cm antenna height is better than at 5 m antenna heights due to the presence of a super-refraction (ducting) layer. For a 69 m link, the difference between the signal strength measured over several days is more than 7 dBm except under anomaly conditions. In this environment, the two-ray model has been found to provide high accuracy for signal propagation over water where there are no objects in close proximity to the propagation path. However, with vegetation in close proximity, accurate signal variation predication must consider contributions from scattered and diffused components, taking into account frequency selective fading characteristics to represent the temporal and spatial signal variations.