2.4 GHz RF Propagation Measurements and Modeling in A Paddy Field for A Wireless Sensor Network

This paper describes 2.4 GHz RF peer-to-peer propagation measurements and modeling in a Japonica paddy field during 5 stages of the growth season: transplantation, panicle initiation, booting, flowering, and grain filling. From the perspective of practicality for the various setting conditions of a sensor unit, the antenna heights were placed 55,105 and 155 cm from the ground in order to evaluate signal propagation through vegetation. Detailed measurement curves of RSSI (received signal strength indication) against distance indicate the presence of various vegetation types based on the moisture conditions of plant growth. The SRET (simplified radiative energy transfer)-based model fits well depending on leaf density for NLOS (non-line-of-sight) conditions. In the case of LOS (line-of-sight) conditions, a novel model named the “TRPF (two-ray paddy field) model” is proposed in order to express the influence of vegetation for a reflection wave.