User manual

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Cooper Bussmann 245U-E Wireless Ethernet Modem & Device Server User Manual
Rev Version 2.19
Fast roaming will significantly reduce the time taken for a client to roam from access point to access point.
In addition, the discovery of access points is completed before the existing radio link deteriorates, therefore
eliminating the periods of poor performance during transition to the next access point.
Figure 49 Roaming
The following settings/thresholds can be configured to fine tune the fast roaming process.
Fast Roaming Fast roaming allows a client (station) to roam to an access point with a stronger
signal strength without disrupting communications, or roam seamlessly between
multiple access points based on configuration parameters, such as RSSI threshold.
Passive Scanning
(STA only)
Selecting this checkbox stops a client device from sending probe request messages
when it is searching for an access point to connect to. Instead, the client waits for
a beacon transmission from the access point. Passive scanning should be disabled
when fast roaming is enabled.
Roam Scan
Threshold
Background scan will be initiated when the RSSI to the currently connected access
point drops below this threshold and fast roaming (above) is enabled. Default is
-90dBm.
Roam Changeover
Threshold
This is the RSSI value above the foam scan threshold that is required for the client
to change to the new access point. In the example shown above, the access point
RSSI would need to be above -84 dB before it would change over. In general, the
roam changeover threshold should be at least 6 dB, otherwise changeovers could
occur too frequently.
Roam Check Interval If a better access point is not found, the background scan is repeated every roam
check interval while the signal strength to the currently connected access point is
below the roam scan threshold. Default is 30 seconds.
Channel Width Selects channel width bands for background scan. If 5 MHz is selected, only 5-MHz
channels will be scanned during the background scan. Default is Auto, which means
all channels will be scanned.
Save Changes Saves changes to non-volatile memory. Changes will not take effect until module is
reset.
Save Changes and
Reset
Saves changes to non-volatile memory and reset module
When fast roaming is enabled, the client goes off-channel and periodically performs a background scan to identify
available access points. When access points are identified, the RSSI is recorded as a potential connection. It takes
50-msec to scan each channel, with a 1-second delay between each scanned channel. Scanning 10 channels will
take 10seconds, during which time latency of up to 50 msec will occur and any throughput traffic is essentially
paused and buffered for retransmission when complete. It is therefore recommended that the scan list be used to
limit the number of channels the client needs to scan, thus reducing the overall scan time.