Near-ground channel measurements over line-of-sight and forested paths

Near-ground radio-wave propagation is of interest for emerging military applications such as battlefield sensor networks and for wireless communication between dismounted soldiers. Narrowband and wideband channel measurement results at 300 and 1900 MHz are presented for near-ground propagation, characterising the effect of antenna heights, radiation patterns and foliage environments. An additional set of channel measurements was performed to study the effect of rain on near-ground propagation at 1900 MHz in a forest environment. Measured power-delay profiles indicate significant multipath propagation with the multipath components becoming stronger relative to the direct path for decreasing antenna heights. In the LOS measurements, the RMS delay spread decreased with the use of directional antennas and increasing antenna heights, and increased with distance. This effect was not evident in the forest measurements, suggesting a larger angle spread of the multipaths. Measurement results indicate that leaves and wet foliage do not contribute significantly to the scattering of radio waves. Foliage effects are more significant at 1900 MHz than 300 MHz. Results from near-ground sensor measurements demonstrate that path-loss varies inversely with the square of the receiving antenna height, as in the plane-Earth and Egli models.