Phoenix Contact FL WLAN 24 AP 802-11 User Manual page 84

Factory Line - Wireless LAN
Fast roaming
3-50
PHOENIX CONTACT
SNR roaming threshold
The threshold specifies the signal/noise ratio (SNR), which is used to trigger a roaming
operation. The specified number of successive packets must be less than the set SNR
threshold.
Number of packets below threshold
Specifies the number of packets. Roaming is triggered when the number of successive data
packets without interruption is below the specified threshold.
SNR neighbor roaming trigger value
The client also handles packets from other access points on the same or neighboring
channels. Roaming to this type of access point is triggered as soon as packets are received
with an SNR that is better by the set value than the signal from the AP with which the client
is currently connected.
3.5.4.8 Fast roaming overview
The "Fast roaming" function enables specific dial-in to available access points without
starting a scan operation.
For tabular roaming, the individual WLAN clients have a list of MAC addresses for the
access points. A receive strength is also assigned to each MAC address, and if this strength
is not reached the client changes (roams) to the next access point in the list.
Modbus/TCP control is available for controlling client roaming, which provides the following
functions:
– Read current number of dialed-in stations
– Current receive level, transmit level, and MAC address of all dialed-in stations
– Read current AP number
– Control of 24-hour scan operation for the list of valid channels
– Write current access point number (roaming)
– This control can be used to control roaming triggers externally, and the table is similar
to an AP MAC whitelist
Modbus/TCP control
To simplify control, a list of all available access points via web interface is stored on the
WLAN devices. The list contains the MAC address of the AP and an assigned number. The
assignment of the MAC address and channel is compared automatically by the devices
using the IAPP protocol.
The Modbus/TCP client can be used to request the following status data of an AP or a client:
– Current receive level
– Current channel and AP in the form of the AP number
The following function can be used actively for the APs:
– Control of 24-hour scan operation for the list of valid channels
The following function can be used actively for the clients:
7190_en_02