GDK-20W DIGITAL WIRELESS KEY TELEPHONE SYSTEM
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8. In multi-story environments, it is the best to plan coverage for each floor separately. However, because
RF signals can travel between floors, a single base station could support multiple floors as long as
base station broadcast area, traffic requirements, and other general guidelines are kept in mind.
Usually, DECT wave is attenuated by reflection indoors. In order to minimize attenuation, when you
install a base station on the wall, give at least three-wave-length intervals. The intervals should be at
least 45 centimeters because the wavelength is 15 centimeters at DECT frequency.
The best communication environment is when a base station and a user are in the same height. In
office environment, however, it is desirable to consider office furniture to minimize reflection, diffraction
and scattering of DECT wave when you set the position of a base station.
The appropriate position for a base station is where 1.8meter above from the floor and 0.5 meter below
from the ceiling. The top of iron office furniture such as a cabinet or a desk is not a good position. Keep
away from electronic equipment such as a copy machine, a printer or a computer. And the lower wall of
a corridor where many people pass by, corner of a wall, and narrow indoors also should be avoided.
Attenuation
When determining the location of base station, you should consider the effects of attenuation. Attenuation is
the loss of strength of a RF signal due to distance, antenna positioning, and obstructions. The guidelines
provided in Location of Base Station on sub-clause C take attenuation into account, but this section provides
additional important concepts.
The magnitude of change in signal strength is measured in decibel(dB). Increasing or reducing of 3dB
results in doubling or halving signal power strength.
[Table 3.6.1] shows the signal attenuation caused by distance in direct line of sight condition.
Distance Attenuation (dB)
1 meter 0
10 meters 20
100 meters 40
1000 meters 60
[Table 3.6.1] Signal Attenuation in Direct Line of Sight Condition
Obstructions
RF signals are also attenuated by obstructions in their paths. [Table 3.6.2] shows the attenuation caused by common
materials in a building. You should try to limit the loss to 60dB.
Object Approximate Loss in dB
Concrete
with metal siding
with window
15
30
8 to 9
Venetian blinds
Open
Closed
10
20
Soft partitioning 3 to 4
[Table 3.6.2] Signal Attenuation Caused by Building Materials
Although signals can travel through obstacles, you should place base stations so that signals begin their travel with a
clear line of sight and travel through obstacles afterwards. In the example shown in Figure 3.6.12, the base station is
placed to maximize line of sight in both corridors.