A model with leaf area index and apple size parameters for 2.4 GHz radio propagation in apple orchards

Wireless sensor networks (WSN) are a very promising technology in agriculture. Application of WSN in apple orchards could improve the data collection and precision farming level of the Chinese apple planting industry. WSN nodes communicate with each other via wireless signals. Prior knowledge of coverage range and attenuation speed is necessary for WSN deployment and application. Most of the existing empirical propagation models do not contain environmental parameters. However, leaf density and apple size change with time in apple orchards from spring to winter. An empirical model was created through a large number of measurements. Two parameters related to the environment were considered: the leaf area index and the apple size. Validation results showed that most of the determination coefficients (R-2) were larger than 0.9 and most RMSE values were smaller than 5. The new model was suitable for estimating the path loss in apple orchards. Simulation experiments were conducted to evaluate the performance of the new model on energy conservation in the WSN application. Simulation results indicated that energy consumption could be reduced by 82, 45, and 39 % when the antenna height was 1, 2 and 3 m respectively.