Roaming - Phoenix Contact FL WLAN 24 AP 802-11 User Manual

Factory Line - Wireless LAN
1-12
PHOENIX CONTACT
Infrastructure mode and especially the use of ESS enables the operation of large networks
according to IEEE 802.11 and is also known as Wireless Ethernet.
PWR POE HOST
PWR HOST
LNK MODE LNK MODE LNK MODE LNK MODE
ACT 100 FD 1 1 1 1
2 2 2 2
MODE X1 X2 X3 X4
FL SWITCH MM HS
Ord. No. 28 32 32 6
Reset
US1
MAC 00A0451BDD
Address US2
Fail
US1 GND US2 GND R1 R2 V.24
PWR POE HOST
PWR HOST
Figure 1-8 Extended Service Set – Wireless Ethernet
Please note that in applications such as that shown in Figure 1-8 all access points must
have the same SSID.
1.3.3

Roaming

Roaming was defined in IEEE 802.11r to enable the transfer of a communication connection
from one access point to another. The following sequence was specified for roaming:
– If a device determines that the signal from an access point is too weak, it searches for
an access point with a stronger signal (scanning). A distinction is made between active
scanning and passive scanning:
Passive scanning: Tapping the medium to determine whether another access point is
available.
Active scanning: Transmitting a request to all channels. If a response is transmitted
from an access point, it contains all the information required to transfer the
communication.
– The device uses the signal strength to select the most suitable access point and sends
it an association request, which requests that it takes over the communication.
– If the response to the association request is positive, roaming was successful. If not, the
sequence starts again.
1 2 3 4
1 2 3 4
1 2 3 4
1 2 3 4
PWR POE HOST 1 2 3 4
PWR HOST 1 2 3 4
PWR POE HOST 1 2 3 4
PWR HOST 1 2 3 4
719000014
7190_en_02