Weidmuller Wireless Ethernet Modem & Device Server WI-MOD-E-G/A User Manual
Rev.
2.16
www.weidmuller.com
50
When Fast Roaming is enabled the Client goes
off-channel
and periodically performs a background scan to identify
available AP’s. When AP’s are identified the RSSI is recorded as a potential connection. It takes 50msec to scan each
channel, with a 1 second delay between each scanned channel. So scanning 10 channels will take 10 second, during
which time latency of up to 50msec will occur and any throughput traffic is essentially paused and buffered for
retransmission when complete. It is therefore recommended the scan list is used to limit the number of channels the client
needs to scan thus reducing the overall scan time.
During the background scan a client will scan all of the channels in the Scan List to identify better AP's. If no channels are
configured it will scan all channels.
Figure 39 - Scan List
The above configuration shows that the Client will start scanning when the RSSI of its current connection to the Access
Point falls below -90dBm. When this happens it will scan the list of Access Points configured in the Roaming Scan List (in
this case channels 1, 4 & 6, as shown below) and if any of the RSSI levels are greater than -84dBm it will change to this
Access Point.
