62
Appendix
WAGO-I/O-SYSTEM 758
758-915
Bluetooth
®
ETHERNET Gateway
Manual
Version 1.1.0, applicable from FW/HW Version 01/01
8.4.2
Space-Division Multiplex (Adaptation of Transmitting
Power)
Bluetooth
®
technology implements automatic adaptation of transmitting power
based on the signal quality. When the devices receive a very strong signal they
reduce the transmitting power automatically; similarly, they also increase
transmitting power when weak signals are received. This can be a problem to the
extent that this mechanism does not recognize the cause for the poor signal. For
example, when two devices equipped with different technologies are installed
directly next to one another, this may degrade the reception quality on account of
transmission by the other device. Now, when the transmitting power is increased
due to poor reception, this may degrade reception even further. In cases like this
and other similar scenarios, space-division multiplex should be provided as a
better solution, based on proper installation and configuration.
It can usually be assumed that over a distance at which two devices with the same
technology can no longer receive signals the devices also will not cause any
interference.
By reducing the “Maximum transmit power” using the AT command
AT*AMMP=<v>
to the extent that reception is just possible at the planned
installation location you can limit the radius covered by transmission to a
minimum
The figure below illustrates the behavior for the maximum radius covered,
depending on the optional device settings, (assuming unobstructed propagation of
radio waves). A range difference of a factor of 10 exists between the highest and
lowest limit that can be selected.
Figure 26: Range and limiting of transmitting power
20 dBm
10 dBm
4 dBm
0 dBm
