User manual

WideFly Ltd. WF28 User Manual
http://www.widefly.com rev 1.1
P.19
Wi-Fi Roaming
Wi-Fi reliability lies in the ability and performance of unattended Wi-Fi roaming. Enhanced at driver / firmware
level, WF28 typically roams across access points (with same SSID) less than one second. WF28 provides
genuine roaming, which online application should be unaware of roaming process while network session
(TCP/IP) could be maintained. This ensures no interruption on real-time application due to roaming issue.
To configure Wi-Fi roaming, tap Start > Settings > Control Panel > WLAN > Advance (Tab page).
Multiple Access Points (AP) Environment
For multiple AP site, it is important to perform wireless site survey to
figure out the best placement of APs, which provides best coverage
of wireless signal with least signal interference.
It should be optimal to configure Roaming Trigger Level around
-66dBm to -72dBm level. For example in the left screen, it means
when PDA detects signal strength weaker than -68dBm, Wi-Fi
module would start searching for nearby APs while obeying single
SSID rule. Once identified an AP with stronger signal, Wi-Fi would
roam to that AP transparent to application & user.
Note:
 For v1.0f or before, the default trigger level -72dBm may not be
optimal as it may be marginal for some online application and
thus -68dBm is recommended.
 Wi-Fi module always searches for an AP with 7dBm better, i.e.
if trigger level is -68dBm, it would search for an AP with -61dBm
or better. Defining a trigger level like -60dBm may not achieve
a good result because it needs to find a stronger AP with
-53dBm. (-53dBm is where AP is very close to the PDA in few
meters)
Single Access Point Environment
For single AP site, since there is no more AP with stronger signal
that would be roamed, defining -90dBm is optimal. This effectively
disables system from searching for nearby APs and thus save
power.
TIPS:
In other words, if roaming trigger level is -68dBm, it is equivalent to saying that the operating area of a site
(excluding kitchen / restroom for example) has been completely covered by good signal, in the sense that
the PDA should find at least one AP, in every single location, with -61dBm (search for one with 7dBm better)
or better signal strength. Otherwise, application delay and interruption would be anticipated. This
reveals the importance of wireless site survey to a successful wireless solution implementation.