Network Planning and Diagnostics
Wireless Communication Stability Considerations
64
SKF Wireless Machine Condition Sensor
Service Manual
Figure 34
.
The Gateway’s
Details
Web Page With RSSI and Stability.
Coexistence with WLAN
The Wireless Local Area Network (WLAN) and WirelessHART networks both fully utilize
the 2.4 GHz band. WLAN divides the 2.4 GHz band into 11 overlapping channels (see
the figure below), whereas WirelessHART divides the 2.4 GHz band into 15 distinct
channels. To avoid interference between WLAN channels, it is typical to use only
channels 1, 6, and 11 within the same frequency space because they do not overlap.
This allows WirelessHART to use some channels between 1 and 6, and some between 6
and 11. However, efficiency will be adversely affected.
Also, WLAN does not utilize the channels on a continuous basis. This allows
WirelessHART to use the full bandwidth when there is no WLAN traffic. In this case, the
efficiency of WirelessHART will be severely affected in periods with a lot of WLAN
activity (as transmit power for WLAN is high compared with WirelessHART).
A much better solution is achieved, for example, if the frequency space between WLAN
channels 7 through 11 is reserved for WirelessHART only, which is equivalent to
WirelessHART channels 10 through 16. This allows for continuous activity with
reasonable efficiency for the WirelessHART network.
Figure 35
.
WLAN Channels in the 2.4 GHz Frequency Band.