Installation guide

TD 92408EN
9 December 2011 / Ver. G
System Planning
Ascom VoWiFi System
29
10 AP Configuration
10.1 Regulatory Domains - 802.11d
IEEE 802.11d was developed to support the use of equipment across regulatory domains
around the world without violation of local frequency rules.The 802.11d regulatory domain
information is broadcasted in beacons and contains information on which channels and
power levels that are allowed. Since this capability is broadcasted, no regulatory domain
configuration is needed at the client side.
To ensure that there is no viol
atio
n of local frequency rules, the recommendation is to
enable the use of 802.11d. At start-up, the VoWiFi Handset is listening passively for
information about which regulatory domain is present before making any transmissions.
This ensures that there is no violation of local frequency rules.
In the WLAN infrastructure, the AP must have t
he ability to include the country cod
e
information element in its beacons and probe r
esponses (Support of IEEE 802.11d). If the
WLAN infrastructure does not support the 802.11d information, the VoWiFi Handset must
be configured manually with regulatory domain information.
10.2 Transmission Data Rates
For 2.4 GHz, the option to enable/disable some data rates should not be left to much
consideration. As a rule of thumb, all data rates may be enabled. If a transmission fails, the
STA will use the next suitable data rate for the re-transmission. In many cases, the STAs rate
fallback algorithms is based and optimized for the use of all rates.
If 802.11b only clients should not be allowed to associate to the network and the AP does
not have a specific
“802.11g clients only” option, this can be accommodated by setting at
least one of the 802.11g data rates to “required”.
n-radio
MCS Index Data Rates Mbps 20 MHz Channel
800ns Standard Guard Interval
0 6.5
1 13
2 19.5
3 26
4 39
5 52
6 58.5
7 65
10.3 Short/Long Radio Preamble
This only affects the transmissions at 802.11b speeds. The use of short preamble reduces
the time spent on the preamble considerably. Only old 802.11b equipment uses long
preamble and should not be present on a high performing VoWiFi system.
The 5 GHz band uses a preamble but there is no option to use short or long.