Weidmuller WI-I/O-9-U2: Wireless Mesh I/O & Gateway User Manual V1.2.2 - Manual (Page 98)

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“Get Graph”. After the units have been running for a few minutes, and passing radio
data, the graph will fill with RSSI readings across all of the radio channels in use.
If the graph is approximately flat, i.e. Figure 86 - Neighbour RSSI above then there is no
multipath fading between these units. If the graph shows large dips (typically one or
two) across several channels, there is multipath fading between units. E.g. Figure 87 -
Multipath Fading below
Figure 87 - Multipath Fading
RSSI is gathered from the normal radio communications from that site. If
communications is sparse the graph may take a while to fill all channels. If after some
time the graph is not filling then it may indicate a multipath a communications problem.
The multipath RSSI algorithm calculates a path RSSI that will be used when
establishing mesh links between neighbours. The calculated link RSSI is compared to
the configured RSSI threshold. If the calculated RSSI is stronger than the threshold,
then a link will be established.
Using this calculated path RSSI ensures that the radio data messages have the best
chance of reaching the neighbour once a link is established, taking into account the
multipath fading.
Once a link has been established between two units, the connectivity webpage also
shows the calculated RSSI value.