• Wireless Sensor Networks (WSN)
• Internet of Things (IoT)
• Energy consumption
• LoRa
• LoRaWAN
• Environment monitoring.

This work focuses on the development of a long-range, low-power, wireless sensor network (WSN) platform for the environmental monitoring and management of vineyards, aiming to provide methods to evaluate and improve the energy consumption of the sensor nodes. The goal of the monitoring system is to provide an efficient and reliable way to promptly detect conditions adverse to the plants by measuring local temperature and humidity levels around the crops. The platform comprises a set of data acquisition devices, scattered over large open-field areas, a gateway node, and a remote server to process and store the acquired data.

The sensor node prototypes are based on the STM32WL55JC wireless micro-controller unit from STMicroelectronics, which is composed of low-power ARM Cortex-M4 and M0+ cores and a sub-GHz radio transceiver module developed by Semtech, the latter supporting the long-range LoRa communication protocol, suitable for long range and low-power and lossy networks (LLNs) applications. The monitoring platform proposed is based on the LoRaWAN specification, which provides a reliable link layer protocol for the deployed End Nodes (sensor nodes) to access and transmit data to a central gateway, forming a star network topology. The gateway node then provides IP connectivity and will forward the frames from the WSN to a remote cloud-based server system. The telemetry data at the server is gathered and stored using open-source database management systems, providing flexibility in the use and access of the measured environmental conditions by third parties.

As the field usage of the system requires the sensor units to operate unattended for extended periods of time, lessening the power consumption of End Node devices and ensuring operational robustness are the main goals of this study. To evaluate and improve such metrics in the WSN a comprehensive analysis of the specific characteristics of the network architecture, devices, and the LoRawAN protocol is shown in this work. Also, an assessment of the wireless communication channel will be performed, considering that the sensor devices operate in an open-field environment with adverse conditions, such as the existence of terrain obstacles preventing a line of sight between participants in the radio link.

Finally, to complement the performance evaluation of the system and the channel characterization, a model for estimating the energy cost for an End Node to transmit frames over a certain distance in the open fields will be presented. The method developed then provides valuable information on the platform's maximum coverage area, radio link reliability, and autonomy of sensor devices. The model will also contribute to the development and validation of a proposed extension to the LoRaWAN MAC layer specification, as a way to overcome the protocol limitations in terms of network organization and packet routing mechanisms when transmitting information over long distances.