LoRa signal propagation and path loss prediction in Tunisian date palm oases
Takoua Mahjoub, Adel Ben Mnaouer, Maymouna Ben Said, Hatem Boujemâa
Abstract
The development of smart agriculture solutions has recently become a popular trend in our lives with the wide expansion of Agriculture 4.0. Low Power Wide Area Networks (LPWANs) are an effective and useful communication tool that would help farmers monitor the status of their plantations on demand. Long Range (LoRa) is a popular LPWAN technology that features low cost, low power consumption and wide coverage. Implementing LoRa for smart agriculture applications in oases requires a prior understanding of the transmission characteristics of radio signals. This work covers an empirical study of LoRa signal propagation in date palms located in the governorate of Kebili, southern Tunisia. Measurements of the Received Signal Strength (RSS) and the Signal Noise Ratio (SNR), performed at different transmitter and receiver heights, were made using antennas operating over the 868 MHz frequency band with a bandwidth of 125 kHz. We first investigate the impact of environment, gateway height, and Spreading Factor (SF) on the distribution of the RSS. Next, we analyze the impact of SF on the Packet Delivery Ratio (PDR). Finally, we focus on the characterization of the signal path loss; we discuss the adequacy of the existing propagation models for the palm environment and propose an optimized signal attenuation model that depends on the palm tree characteristics (tree density and trunk diameter). The proposed model is then tested and validated in three different oasis sites. The results showed that the proposed model corresponds well to the measured path loss with a Root Mean Square Error (RMSE) of 4.