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3.9.4.4 Maintenance
shaft
In larger buildings there is usually the requirement that coverage also be
provided in maintenance rooms. The most common are the rooms for
the lift and ventilation system. The lift maintenance room is often on the
roof or in the basement. The ventilation maintenance room is usually on
the roof. Do not omit these rooms they should be discussed with the
client to avoid the client being faced with surprises. A well-positioned
base station on the top floor (20 to 30 metres at most from the room
where coverage is required) usually provides sufficient coverage for the
maintenance rooms on the roof.
3.9.4.5 Basement
and indoor car park
It can be difficult to provide sufficient coverage in basements and indoor
car parks due to the usually heavy constructions.
3.9.5 Reflective
Environment
When providing coverage in a metal hall (for example, a production hall
or storage building), there are a number of issues which call for addi-
tional attention. The dimensions of the hall and the material used (metal,
concrete, brick etc.) are important deciding factors in the hall’s radio
reception. Every hall is different, and it is very difficult to predict the radio
reception. Check carefully, therefore, whether the walls are made of
metal, what the hall’s dimensions are, whether the roof is reflective, what
is contained in the hall, and whether objects in the hall are stationary or
constantly moving.
In the case of poor speech quality in a metal hall, this can be attributed
to time delay spread and/or the actuation of the soft suppressor.
3.9.5.1
Time delay spread
Time delay spread can be compared with dispersion in cables and fibres.
This means that the radio signal can travel by various paths to reach the
user because the signal can reach the user directly but also via reflec-
tions. These possibilities are illustrated in the figure below.
