2-12
DOC00101-01
CTPhone 1900 System Planning
wave and may cause fading (See Fading on page 2-14) of the intended
signal (Figure 2-9).
Figure 2-9. Reflection of Radio Frequency
Multipath is the condition when two or more signals from the same origin
arrive at a receiving antenna out of phase with one another. Radio wave
reflections off of metallic surfaces and users’ mobility create conditions for
multipath propagation.
To avoid multipath interference...
Attenuation
When determining base station placement, you must consider the effects
of attenuation. Attenuation is the loss of strength of an RF signal due to
distance, antenna positioning, and obstructions. The guidelines provided
in Determining Base Station Placement on page 2-9 take attenuation into
account, but this section provides additional important concepts.
The magnitude of change in signal strength is measured in decibels (dB).
Increases or reductions of 3 dB result in doubling or halving signal power
strength.
You should try to limit total loss (accumulated by range and obstructions)
to 100 dB.
Distance
Figure 2-10 illustrates the signal attenuation caused by distance in direct
line of sight conditions.
Arriving Angle
Arriving Wave
Metal
Sur
face
Reflected Wave
Reflected Angle
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