# UAV Path Optimization for Precision Agriculture Wireless Sensor Networks
###### Abstract  
The use of monitoring sensors is increasingly present in the context of precision agriculture. Usually, these sensor nodes (SNs) alternate their states between periods of activation and hibernation to reduce battery usage. When employing unmanned aerial vehicles (UAVs) to collect data from SNs distributed over a large agricultural area, we must synchronize the UAV route with the activation period of each SN. In this article, we address the problem of optimizing the UAV path through all the SNs to reduce its flight time, while also maximizing the SNs' lifetime. Using the concept of timeslots for time base management combined with the idea of flight prohibition list, we propose an efficient algorithm for discovering and reconfiguring the activation time of the SNs. Experimental results were obtained through the development of our own simulator--UAV Simulator. These results demonstrate a considerable reduction in the distance traveled by the UAV and also in its flight time. In addition, the model provides a reduction in transmission time by SNs after reconfiguration, thus ensuring a longer lifetime for the SNs in the monitoring environment, as well as improving the freshness and continuity of the gathered data, which support the decision-making process. a 20202019 October 202026 August 20202019 October 202026 August 20202019 October 202  
use of collaborative UAVs to create communication networks between users in disaster situations. [PERSON] et al. [4] formulated a new problem for the optimal placement of UAVs geared towards wireless coverage provision for voice over WiFi service to a set of ground users confined in an open area. [PERSON] et al. [5] use a collaborative network created by UAVs for search and rescue missions, achieving success rates 50% higher than those led by just a single UAV. [PERSON] et al. [6] created an optical system using a laser to guide UAVs in urban environments so that they can land safely in case of failures on GPS signal reception. [PERSON] et al. [7] studied the application of a radiation monitoring system through sensors in nuclear power plants, citing Fukushima in Japan as an example. They adopted the use of UAVs to collect this sensory data at monitoring points. [PERSON] et al. [8] created a route planning system for UAVs to patrol highways and urban environments, achieving up to 16% of path reduction when compared to conventional vehicles doing the same job. [PERSON] et al. [9] presented a scalable approach to model uncertainties within a UAV embedded mission manager; this proposal considers the context of the mission including external constraints, the health of the UAV, and the computing resource availability. [PERSON] et al. [10] used a collaborative network of UAVs to assist in the processing of IoT devices activities that are computationally limited. [PERSON] et al. [11] applied the use of UAVs to monitor livestock through aerial images, using machine learning techniques to distinguish between different breeds of cattle. Estimates made by the World Bank indicate that in 2050 there will be about 9.7 billion human beings living on our planet, demanding an increase of 70% in agricultural production [12]. There is no doubt that the use of technology will bring greater productivity to this sector. In [13], [PERSON] et al. address how technology can help in food production, protection, processing, packaging, transportation, and traceability. As an example, a producer carrying a backpack sprayer takes a whole day to spray one hectare of land, while a drone equipped with a spraying system can perform the same job in just one hour [14]. Furthermore, there are more than three million cases of pesticide poisoning and disease in farmers registered by the World Health Organization (WHO) in India alone [15], a situation that can be easily resolved with the use of UAVs. Drones have better precision during poison application, avoiding waste and direct handling of toxic substances by human beings.