User's Manual

3 Detailed Description
APCD-LM043-4.0 35
The following key conclusions that can be drawn from the simple example and analysis shown
above:
• Coverage range and fade margins are maximum when paths are clear and
unobstructed.
• Coverage range and fade margins are reduced for specific EUMs
if there is
obstructing clutter and terrain in the vicinity of these specific EUMs.
• Coverage range and fade margins are reduced for all EUMs
if there is obstructing
clutter or terrain in the vicinity of the CCU. For this reason, it is critical that the CCU
location be chosen and the antenna height be sufficient to eliminate local obstructions
for all possible radio links from the CCU. By local, it is recommended that the radio
paths be obstruction-free between the CCU and halfway to the limit of the coverage
range.
Table 7 shows the typical radio coverage (distance from the CCU) that the LMS4000 900 MHz
Radio Networks can achieve. Table 7 should be used as a planning guideline only, due to the
difficulty of accurately predicting radio coverage.
Table 7 Typical Radio Coverage
The following assumptions have been made in calculating the above ranges:
• For practical purposes, assume that typically 80% of the subscribers in the predicted
coverage area will be able to receive service. Higher coverage is possible but often
requires more extensive RF engineering.
• LOS (line of sight) means optical view and radio Fresnel clearance between the EUM
premise and the CCU antenna.
• Typical CCU antenna height of 130 ft. (40 m), at least 10 ft. (3 m) above the trees.
• Typical EUM antenna height (for outdoor antennas) of at least 13 ft. (4 m).
• The CCU EIRP has been maximized to +36 dBm in all cases. Refer to Appendix D on
page 181 for further guidelines.
• The EUM outdoor antenna (Yagi antenna, for example) has a gain of 9 dBi, and the
indoor antenna (WaveRider switched-beam diversity antenna) has a gain of 6.6 dBi.
• Coverage with the WaveRider indoor switched-beam diversity antenna depends on
the composition of the exterior walls and structure of the end-user’s premises. For
best results, the EUM antenna should be installed behind a window.
Actual results vary significantly due to local conditions. Coverage-area prediction that takes
into account local terrain and clutter factors provides a better estimate of coverage.
EUM Installation Typical LOS Range Typical NLOS Range
Indoor Antenna
(path to CCU is through a
window)
3mi(5km) 1mi(1.6km)
Outdoor Antenna 5 mi (8 km) 2 mi (3.2 km)