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Wireless Telecommunication Facilities Master Plan - Town of Morrisville, NC – Adopted July 23, 2013
B-6
Topographic variable on theoretical coverage
As previously described in flat terrain and sparsely populated areas, base station prediction is an
easier art. The impact terrain has on a service area can be the most dramatic. Radio frequency
propagation is line-of-sight technology. Line of sight works best with an unobstructed path
between the base station and the handset. There are some variations of this principle. The
analogy of a light bulb works well to explain how a wireless signal gets from point A to point B.
In this manner communication signals perform very similar to light. The areas closest to the light
are illuminated the brightest. Adding a lampshade over the light bulb dims the light. Walls,
closed doors, and other opaque object obscure the light. Similarly for best results in wireless
communications there should be nothing in the transmission line of sight path between antenna
point A and antenna point B, but that is usually impossible. Reflected or refracted signal will fill
in some geographic areas but at a reduced power level.
Therefore, on flat terrain service areas with minimal vegetation, the coverage network from each
antenna propagates in an even circular pattern. In areas with varying terrain conditions, the line
of-sight coverage will be altered by higher and lower ground elevations. The Town has
topographical variations so terrain does alter the theoretical maps.
Using the same random grid antenna locations identified in Figure 1 (RMS 800 MHz Handoff
and Search Areas at 199’ Antenna Elevations) and Figure 2 (RMS 1900 MHz Handoff and
Search Areas at 199’ Antenna Elevations); Figures 3 and 4 illustrate how wireless service
coverage is affected when the topographic variables are added to the propagation formulas.
Geographic areas in gray indicate no coverage due to the change in terrain.