Performance assessment of wireless sensor networks in agricultural settings

Wireless Sensor Network (WSN) utilizes radios operating primarily in the 900 MHz and 2.4 GHz frequency bands. In general, as frequency increases, bandwidth increases allowing for higher data rates but power requirements are also higher and transmission distance is considerably shorter. In general, depending on the operating environment, significant signal loss can occur at these frequencies particularly when the radios require line-of-sight for optimal performance, with 2.4 GHz more susceptible than 900 MHz. For agricultural applications, WSN must be able to operate in a range of environments, from bare fields to orchards, from flat to complex topography, and over a range of weather conditions, all of which affect radio performance. However, there are limited data on radio performance as affected by agricultural setting and no standard tests are available for quantifying WSN performance in agricultural applications. Using a low powered, 10 mW 900 MHz frequency hopping spread spectrum radio, we developed a range of tests intended to quantify the performance of agricultural WSN in fields, vineyards, and orchards over a range of crop and weather conditions. Performance data include different metrics of radio performance such as packet delivery and signal strength along with power consumption tests under different supply strategies. This paper evaluates the extent to which various tests can be used to quantify WSN performance and how WSN perform under various cropping systems. Extensive field tests are in progress at Washington State University, with the objective of generating a greater understanding of environmental variables affecting the performance of WSN in outdoor conditions. The field deployment uses a radio system of 900 MHz Spread Spectrum technology based on a low-power, radio transceiver (Chipcon-CC1100) and applied to a variety of spatial configurations. Performance evaluation tests include different metrics of radio performance such as packet delivery and signal strength. Moreover power consumption is tested under different supply strategies.