# Unmanned Aerial System-Based Data Ferrying over a Sensor Node Station Network in Maize
###### Abstract  
Agriculture is considered a hotspot for wireless sensor network (WSN) facilities as they could potentially contribute towards improving on-farm management and food crop yields. This study proposes six designs of unmanned aerial system (UAS)-enabled data ferries with the intent of communicating with stationary sensor node stations in maize. Based on selection criteria and constraints, a proposed UAS data ferrying design was shortlisted from which a field experiment was conducted for two growing seasons to investigate the adoptability of the selected design along with an established WSN system. A data ferry platform comprised of a transceiver radio, a mini-laptop, and a battery was constructed and mounted on the UAS. Real-time monitoring of soil and temperature parameters was enabled through the node stations with data retrieved by the UAS data ferrying. The design was validated by establishing communication at different heights (31 m, 61 m, and 122 m) and lateral distances (0 m, 38 m, and 76 m) from the node stations. The communication success rate (CSR) was higher at a height of 31 m and within a lateral distance of 38 m from the node station. Lower communication was accredited to potential interference from the maize canopy and water losses from the maize canopy. unmanned aerial systems; wireless communication; crop canopy interference; long-range radios; multi-rotor unmanned aerial system; flight scheduling; data ferry; communication success rate 4.0.0.0000-0000-0000-0000-0000-00000-0000-00000-00000-00000-00000-00000-00000-00000-000000-000000-000000-000000-000000-000000-0000000-0000000-0000000-000000  
and disease control [7], controlled use of fertilizers [8], cattle movement monitoring [9], groundwater quality monitoring [10], greenhouse gases monitoring [11], asset tracking [12], and remote control and diagnosis [13; 14]. The most promising applications for WSN in precision agriculture are irrigation management, farming monitoring, disease control, and fertilizer accuracy [15]. However, some challenges in WSN applications have been identified such as low battery power, limited computation capability, and sensor node low memory storage [2; 16] as well as energy consumption, cost, communication range, optimum deployment schemes, measurement periods, routing protocols, scalability, and fault tolerance [17]. Thus, innovations and creativity in WSN design are needed to be effectively used in agricultural applications. Unmanned aerial systems (UASs) have been widely used in wireless communication applications because of their high maneuverability and low cost. For an existing WSN, the UAS can be an ideal carrier to form a UAS-based WSN (UWSN). A UAS-based WSN could provide a faster moving speed, longer deployment range, and a relatively longer operating time [18] than WSNs employing other traditional mobile sensor nodes. Recently, the potential scope of a UWSN was identified as a research topic to be investigated for various precision farming applications. [PERSON] et al. [11] presented the development of a solar-powered UWSN to monitor greenhouse gases (methane and carbon dioxide). [PERSON] and [PERSON] [19] developed analytical and simulation models of a flying ubiquitous sensor network and concluded that such a device is suitable for transferring a small amount of data (transmission rate of 240-280 bits/s) over long distances. [PERSON] et al. [20] investigated the dynamics of uplink and downlink communication using multiple UAS-mounted aerial base stations to serve a ground-based group of users. A rotary-wind UAS-based WSN system for wireless communication was proposed by [PERSON] et al. [21] and required minimum energy to operate. A remotely pil piloted unmanned lighter-than-air platform was recently proposed by [PERSON] et al. [22] for the purpose of land use monitoring. In this study, a UWSN system design is proposed which would comprise hybrid terrestrial surface and sub-surface sensor network stations that communicate with an airborne data ferry deployed on a UAS.