Product manual

Configuration directions, Base station planning - additional information
Technical Product Manual - DCT1800-GAP
TD 92093 (1/LZBNB 103 108 R4D) / 2006-03-09/ Ver.C
© 2006
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4.2.7 Metal halls
General
When providing coverage in a metal hall (for example, a production hall or storage building), there are
a number of issues which call for additional attention. The dimensions of the hall and the material
used (metal, concrete, brick etc.) are very 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 what is in the hall is stationary or constantly moving.
In order to avoid a lot of subsequent problems, it is very sensible to involve the client in the whole
process (during a site survey both in an office complex and here). Let the client hear the speech quality
in the area with the worst radio reception and find out what his reaction is. Ensure that he is aware of
the situation so that you are not faced subsequently with tricky questions about certain areas where
it is almost impossible to improve the situation.
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. Both are explained in greater detail below.
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 reflections. These possibilities are illustrated in the figure below.
Fig. 9 Time delay spread
The base station at corner A reaches the cordless phone at corner B by means of a direct signal
(signal 1) and by means of a reflected indirect signal (signal 2). Generally there are many reflected
signals reaching the cordless phone. In general the paths travelled by these signals are not equal
which means in turn that they will arrive at the cordless phone at different times.
AB
1
2
2
025
Reflecting wall