“Connectivity for all” sometimes lies in the details.

In our region, forests pose the primary obstacle to radio communication. Currents flow over the Earth’s continuously curved surface. However, the geometry of treetops significantly differs.

Improving radio transmission in forests

While researchers have addressed radio wave diffraction over the Earth’s surface, forests remain underexplored. As a result, forests modeled as an “opaque Earth surface” do not yield satisfactory results.

The main objective in calculating a line-of-sight radio link is to determine optimal antenna heights. In practice, new antenna masts are expensive. Consequently, organizations install antennas on rooftops, existing high structures, or pre-existing towers.

Our research focuses on methodology to calculate radio wave attenuation in small forest areas, considering both direct and diffracted radio waves at treetop level.

ITU recommendations for calculations are based on the radio link’s frequency range, including ITU P.530-18, ITU P.2001-4, ITU P.452-17, and ITU P.1812-6.

These recommendations mostly do not account for buildings or vegetation, though some include nearby structures and vegetation that screen terminal antennas. Only ITU P.1812-6 suggests “raising” the terrain profile by a “typical” forest or building height. This “typical” height is always lower than the actual height, as it accounts for radio wave propagation over vertical and horizontal obstacles. Statistical data from practical measurements determines calibration coefficients for specific areas.

To solve this problem, direct radio wave losses are accounted for according to ITU P.833-10, which provides statistical data on wave attenuation through forests.

Testing wave losses over treetops

Three models are being tested to determine wave losses. Their applicability is being assessed by collecting statistical data that measures the receiver’s signal power and the number of outages exceeding 10 seconds. The models are: