Planning
43
Planning Aastra 400 DECT systems as of R1.0
syd-0457/1.0 – R1.0 – 10.2012
If extensive interference occurs in a hotspot or if more than 30 simultaneous con-
nections are required, check the following measures:
• Distribute the radio units that cover the hotspot spaciously around the hotspot.
In doing so, especially walls can help attenuate the strong signals which the ra-
dio units mutually disturb each other. Also check the possibility of a spherical ar-
rangement of the radio units that cover the hotspot through floors and ceilings.
With this solution approach, ensure that cordless phones do not suddenly seize
the call channels of the hotspot radio units that were previously supplied by
other radio units (when setting up a connection, cordless phones always seize
channels of the radio unit that deliver the strongest signal). It may therefore oc-
cur that moving the hotspot radio units triggers a chain reaction and that other
radio units have to be re-positioned.
• If it is not possible to spatially move radio units, check the use of external anten-
nas that are connected to type SB-8ANT radio units by means of an attenuator.
Under certain circumstances the quality can be noticeably improved. The aim is
to reduce the transmitting power (and thereby the reception sensitivity) by 10 to
20 dB. In determining the attenuator the antenna gain is to be taken into ac-
count. Most antennas have a gain of 3 to 10 dB. A 20 dB attenuation is usually
right. The antenna diversity must not be discontinued, i.e. 2 antennas or a dual
antenna per SB-8ANT radio unit must always by connected. To ensure that all
calls are evenly distributed to all radio units, it is mandatory that all hotspot ra-
dio units are equipped with attenuators. Additionally, no non-attenuated radio
units not belonging to the hotspot are permitted in the vicinity. The hotspot
cordless phones otherwise seize, above all, the channels of the non-attenuated
radio units, which would then have fewer or no remaining channels at all for
their own coverage range.
For manufacturer recommendations and information about antennas and atten-
uations, please contact Support.
Note:
It is advisable to use not more than 6 SB-8 or SB-8ANT radio units in
one hotspot. Full capacity would then mean max. 48 simultaneous
connections. Although this is not an absolute system limit, the risk of
at least occasional disturbances increases with each additional call
channel.
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