Investigating signal propagation and strength distribution characteristics of wireless sensor networks in date palm orchards

To efficiently plan and deploy wireless sensor networks in palm orchards, it is crucial to obtain preliminary knowledge of radio signal propagation and strength distribution characteristics. Various received signal strength indicator (RSSI) measurements were taken with antennas, operating with a 2.4-GHz band and located 0.05 m away from trunks. The RSSI measurements, at seven different antenna heights along one certain horizontal line, revealed that there were three distinct signal propagation characteristics resulting from the morphological features of the date palm trees. Compared with other heights, the attenuation rate was lower when the antennas were placed below the crown base due to the relative lack of obstacles in the propagation paths, which also provided good options for installing the antennas. In addition, off-shoots had a slightly negative impact on signal propagation. Comparison analyses showed that the logarithm model was the most accurate and convenient of all the empirical signal attenuation models for predicting low power wireless signal propagation characteristics in date palm orchards. Further measurements were conducted to investigate the received signal strength distribution around individual trunks and between the orchards of different ages. Results indicated that the reliable communication range showed an increasing trend with increasing orchard age. Moreover, the trunks negatively impacted the signal propagation, and the interference strength depended on the position relationship among the trunks, the Tx and Rx antennas. Finally, the specific and detailed references were provided for the planning and deployment of wireless sensor networks in date palm orchards. Concluding remarks address potential future research. 2016 Elsevier B.V. All rights reserved.