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Siemens Desigo Desigo Room automation - Engineering, mounting and installation CM111043en_13
Smart Infrastrructure EnOcean RF networks 2020-04-30
15.5 Planning RF networks
Since RF signals are electromagnetic waves, the field strength at the receiver
decreases as the distance to the transmitter increases, in other words, the RF
range is limited. Any materials in the transmission field reduces the range
accordingly. RF waves do penetrate walls, but dampen the strength versus pure
line of sight.
Reduction in range from walls versus a free field of view:
Material Reduction in range versus a
free field of view
Wood, gypsum, uncoated glass, without metal
Brick, pressboards
Reinforced cement
Metal, aluminum lamination
0...10%
5...35%
10...90%
see Section 15.4
The geometric shape of the room
determines the RF range, since
transmission is not in the form of rays,
but rather requires a certain room
volume (ellipsoid with sender Tx and
receiver Rx in both focal points).
At 30 meter in range, the ellipsoid
center diameter is theoretically
around 10 m / 33 ft (868 MHz).
Narrow hallways with large walls are
unfavorable.
Fig: Narrow hallways with large walls.
The antenna setup and the distance from ceilings, floors and walls plays an
important role. Internal antennas typically have better RF properties versus flush-
mount receivers. People and objects in the room also reduce range. The generally
standard range of "30 m / 100 ft in buildings" should be viewed in a differential
manner dues to the numerous influences. Planning for reserves in the range is
necessary to achieve a reliable function of the RF system, even under unfavorable
conditions.
Robust and reliable installation in buildings is achieved by ensuring
sufficient range reserves.
· > 30 meter for very good conditions: Large free space, optimum antenna
installation and placement.
· Planning security with furniture and people in the room, through up to 5
gypsum drywall or 2 brick/aerated concrete:
– > 20 m / 66 ft for transmitters and receivers with solid antenna execution and
positioning.
– > 10 m / 33 ft for received installed in the room wall or corner. Or small
receives with internal antennas. Also together with switches on or wire
antenna near metal. Or narrow hallway.
· Vertical through 1-2 room corners depending on fixtures and antenna execution.
· Learning by EnOcean devices can greatly increase availability. A receiver can
work with multiple, received signals.
RF signal range
Practical hints