User guide

Canopy System User Guide Selecting Sites for Network Elements
pmp-0229 (Mar 2013)
147
Non-Line of Sight (NLOS) Link
The 900-MHz and OFDM modules have a greater non-line of sight (NLOS) range than modules of
other frequency bands. NLOS range depends on RF considerations such as foliage, topography,
obstructions. A depiction of an NLOS link is shown in Figure 41.
Figure 41: Fresnel zone in non-line of sight link
Clearing the Radio Horizon
Because the surface of the earth is curved, higher module elevations are required for greater link
distances. This effect can be critical to link connectivity in link spans that are greater than 8 miles
(12 km).
To use metric units to find the minimum height required to reach the radio horizon use the
following equation:
Radio horizon distance (km) = 4.12 (SQRT(h1) + SQRT(h2))
Where: Is:
h1 height of the AP
h2 height of the SM
To use English standard units to find the angle of elevation, use the following formula:
Radio horizon distance (km) = 1.42 (SQRT(h1) + SQRT(h2))
Where: Is:
h1 height of the AP
h2 height of the SM