A Wireless Sensor Network for Smart Irrigation and Environmental Monitoring: A Position Article

Traditional instrumentation based on discrete and wired solutions, presents many difficulties to measure or to compute plant physiological responses due to the large geographical areas that may be involved. This paper describes an implementation of a wireless sensor network for agriculture low data-rate applications. This network includes several solar powered wireless acquisition stations used on soil moisture measurements in greenhouses and open field crops in order to improve irrigation efficiency. Soil moisture is sensed by using the dual-probe heat-pulse method. Climate parameters such as air and soil temperature, solar radiation and relative humidity are also measured. After acquisition, data is routed to a base station where it is stored, analyzed and used to perform local control tasks. The network protocol uses a combination of TDMA (Time Division Multiple Access) and CSMA (Carrier Sense Multiple Access) techniques to allow easy deployment and to provide plug-in capabilities to the in-range acquisition stations. The out-range units employ a zone routing protocol where data flow converges to the in-range units, which are also responsible for data aggregation. It is also discussed actual trends in miniaturization, and how each acquisition node is being replaced by a CMOS single-chip, with a built-in soil moisture micro-sensor with wireless capabilities. Following the plant instrumentation approach, specific solar powered microsystems provide a convenient way to acquire several important parameters from the plant themselves. However, as their size and cost decreases, effective power supplies become a larger problem.