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Wireless Telecommunication Facilities Master Plan - Town of Morrisville, NC – Adopted July 23, 2013
B-2
COST 231 Coverage Predictions
Antenna mounting height
50’
80’
100’
115’
150’
Radius, miles
1.33
1.64
1.82
1.95
2.32
Allow for handoff
1.07
1.31
1.46
1.56
1.79
Search area, miles
0.27
0.33
0.36
0.39
0.45
Table 2: COST 231 Coverage Predictions for 1900 MHz
Wireless search areas are usually circles of approximately one-quarter the radius of the proposed
cell. In practice it is fairly simple to determine whether the search area radius is reasonable. The
distance from the closest existing site is determined, halved, and a handoff overlap of about
twenty percent is added. One fourth of this distance is the search area radius. CityScape
provides the Coverage Prediction tables for antenna mounting elevations between 50 and 150
feet to allow communities the opportunity to evaluate this variable. Generally in areas where
initial coverage is the objective taller towers allow the antenna to service a larger geographic
coverage area and additional collocations by other service providers. Shorter tower limit the
geographic coverage area and reduce the number of collocations resulting in a greater number of
towers within each search area.
Tower height and antenna mounting elevation considerations
Taller structures (towers, rooftops, and water tanks) may offer more opportunity for collocation,
which could theoretically decrease the number of additional towers and antennas required in an
area, but capacity issues could circumvent any advantage of taller towers. An RF engineering
review on a case-by-case basis must verify the extent to which height may increase collocation
opportunities. In geographic areas where there is a larger wireless phone subscriber base or
terrain concerns, build-out plans may require lowers antenna-mounting elevations, especially in
densely populated areas. Antennas located at higher elevations on the antenna support facility
are indicative of rural areas. In some cases, the wireless providers seek to limit the height in
more populous geographic areas because they may need differing heights on a single tower to
reduce the potential for interference between the same provider and/or a competing wireless
provider.
Master plan design process
This Appendix of the Master Plan evaluates wireless coverage for the most populated areas of
the Town of Morrisville (Town) and is accomplished by:
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Designing an engineered search radii template and applying it over the jurisdictional
boundary of the Town to evaluate theoretical build-out conditions.
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Researching the inventory of existing antenna locations on support structures and
buildings and evaluating the possible 800 MHz and 1900 MHz coverage from those sites.