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Building Technologies
2015-11-06
4.3 Transmission field
In the open, the field strength falls with a factor of 1/r², i.e. a doubling of distance in
the open equates to a 6 dB increase in damping. In buildings, the factor in a first
approximation is 1/r
5
, i.e. a doubling of distance means that damping increases by
around 6 to 17 dB.
The table below illustrates the relationship between distance and damping for the
line of sight in the building:
Distance [m] 40 30 25 20 15 10 5
Damping [dB] 90 83 79 74 67 57 40
Maximum values: Distance 40 m / damping 90 dB
Table for converting to linear values
Damping factor 1 4 10 50 100 1000
Damping [dB] 0 6 10 17 20 30
The transmission field in the building is affected by walls and obstacles. These
constructions (walls, ceilings etc.) must be analyzed in detail to obtain a
statement on damping.
Radio damping when passing through obstacles
The approximate values listed in the table should be added together for
constructions encountered along the radio link in order to determine the actual
damping at the receiver location.
Construction Additional damping
Room divider <1 dB
Dry bricks around 6 dB
Dry concrete around 6 dB
Lime sand brick around 8 dB
Planar lime sand brick elements around 8 dB
Timber frame wall around 8 dB
Timber panel wall around 8 dB
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