Hotspots; Measuring Procedure - Mitel SIP-DECT Site Survey Kit User Manual

SIP-DECT Site Survey Kit User Guide
For each area you must determine the number of base stations currently being used to supply
them.
It may be necessary to boost the coverage with additional base stations for under-served areas
(in accordance with the customer's requirements). To do so, refer back to the base station
locations that were determined for the area coverage. For instance, it is a good idea to place
additional base stations at the center of an area with higher traffic volume, even if those units
end up between two installed base stations.
To determine the traffic volume, we assume three typical ranges: "low", "medium", "high".
"High" means that approx. 50% of all DECT phones make calls simultaneously. It is also important
to note that the volume of traffic can vary considerably throughout the day. The question is always
whether or not to cover a traffic volume that may be higher only briefly in a particular area.

HOTSPOTS

A hotspot is an area with an above-average number of DECT phones. Such an area can be
covered with several base stations as the resources in the coverage range of neighbouring base
stations are cumulated. It is recommended to cover hotspots with several base stations as they
operate in "Zero-Blind-Slot mode" and the calls can be spread out across 120 radio channels.
In practice, the interference from neighbouring channels in a hotspot without special measures
means that only approximately one quarter of the radio channels can be used simultaneously.
This means that approximately 30 simultaneous connections are possible, which require, for
example, four base stations. Thus, approximately 60 DECT phones can be used in a hotspot
with high traffic volume (simultaneous call connections of approximately 50% of the DECT
phone). It is essential to observe the minimum distances when installing the base stations.
If extensive interference occurs in a hotspot, or if more than 30 simultaneous connections are
required, check the following:
• Distribute the base stations that cover the hotspot spaciously around the hotspot. In doing
so, walls in particular can help attenuate the strong signals that the base stations mutually
interfere with each other.
• Check the possibility of a spherical arrangement of the base stations that cover the hotspot
through floors and ceilings.
• Ensure that DECT phones do not suddenly seize the call channels of the hotspot base stations
that were previously provided by other base stations (when setting up a connection, DECT
phones always seize channels of the base station that delivers the strongest signal). It may
therefore occur that moving the hotspot base stations triggers a chain reaction and that other
base stations have to be repositioned.

MEASURING PROCEDURE

Specifying limit values in different coverage areas
There are different requirements for the areas to be covered (e.g. office, basement) based on
the quality or use of the areas. Accordingly different limit values can be used for the
measurements. Even within a partial system different quality requirements can be specified for
the various base stations.
Generally speaking, it can be said that systems which measure out up to –60dBm provide good
quality. For measurements up to –70dBm it is necessary to verify and evaluate the measurement
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