36
Function Description
WAGO-I/O-SYSTEM 757
757-801 Bluetooth® Module RS-232
Manual
1.0.0
4.6
Special Coexistence Properties
Bluetooth
®
technology uses the unlicensed ISM frequency band for international
use from 2.4 GHz for data transfer. This frequency band is also used by devices
that use other technologies such as WLAN in accordance with IEEE 802.11 b/g.
To minimize interference,
Bluetooth
®
technology offers the following effective
coexistence mechanisms:
•
Frequency Hopping Spread Spectrum (FHSS)
When transmitting, the frequency is switched up to 1600 times per second.
The actual narrowband radiant power (1 MHz channel bandwidth) is
distributed time-averaged over a wide band (79 MHz).
•
Adaptive Frequency Hopping (AFH)
If interference occurs from other radio systems (see figure, violet),
Bluetooth
®
systems (blue/red) can avoid the affected channels in future
transmissions (red transparent). Radio systems that do not support the
automatic adjustment can continue to use these frequencies.
Figure 12: Adaptive Frequency Hopping (AFH)
•
Adaptive Transmit Power
If there is a connection between two
Bluetooth
®
devices with a high signal
strength, the devices automatically reduce their transmit power.
The specified mechanisms are used automatically by the WSA. Beyond the
mechanisms contained in the standard, the device provides other setting options to
further improve coexistence that can be configured via AT commands: