(CPS)^2: integration of center pivot systems with wireless underground sensor networks for autonomous precision agriculture

Precision agriculture (PA) refers to a series of practices and tools necessary to correctly evaluate farming needs and a high density of soil sensors is an essential part of this effort. The accuracy and effectiveness of PA solutions are highly dependent on accurate and timely analysis of the soil conditions. Traditional soil measurements techniques, however, do not provide real-time data and hence, cannot fully satisfy these requirements. Moreover, the use of wired sensors, which usually must be installed and removed frequently, impacts the deployment of a high density of sensor nodes for a certain area. In this paper, a novel cyber-physical system (CPS) is developed through the integration of center pivot systems with wireless underground sensor networks, i.e., (CPS)2 for precision agriculture (PA). The Wireless Underground Sensor Networks (WUSNs) consist of wirelessly connected underground sensor nodes that communicate untethered through soil. A CP provides one of the highest efficient irrigation solutions for agriculture and the integration of WUSNs with the CP structure can provide autonomous irrigation capabilities that are driven by the physical world, i.e., conditions of the soil. However, the wireless communication channel for the soil-air path is significantly affected by many spatio-temporal aspects, such as the location and burial depth of the sensors, the soil texture and moisture, the vegetation canopy, and also the speed of the center pivot engine. Due to the high number of real-time parameters to be considered, a cyber-physical system (CPS) must be developed. In this paper, as a proof-of-concept, the results of empirical experiments with these components are provided. The main characteristics of a precision agriculture CPS are highlighted as a result of the experiments realized with a WUSN built on top of a real-life center pivot system. The experiment results show that the concept of (CPS)2 is feasible and can be made highly reliable using commodity wireless sensor motes. Moreover, it is shown that the realization of (CPS)2 requires non-trivial management due to stochastic real-time communication constraints. Accordingly, guidelines for the development of an efficient (CPS)2 solution are provided. To the best of our knowledge, this is the first work that considers a CPS solution based on WUSNs for precision agriculture.