Specifications
28 AP Configuration
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.
Beacon Period
A beacon is a periodic broadcast transmission from the AP to all STAs in the BSS. The beacon
has multiple purposes:
• To synchronize all clients within a BSS
• Beacon contains a traffic indication to notify STAs in power-save mode that the AP has buffered
packets waiting for delivery
• To advertise capabilities or changes in capabilities
The most important issue for configuration of the beacon period is the traffic indication for power-
saving STAs. STAs in power-save mode wake up at every beacon transmission and check the traf
-
fic indication message for any frames being buffered in the AP (i.e. delivery of frames to a STA in
power-save mode is only done after a beacon transmission).
This means that a long beacon period will increase the battery life, but also increase the response
time to power-save clients.
A short beacon period will decrease battery life and response time. See also Section , “DTIM In-
terval”, on page -28.
The beacon period is specified in number of 802.11 TUs (Time Units). One TU is 1.024 ms, how-
ever to make it easier most APs asks for the value in number of ms. The recommended default
value is 100 ms.
DTIM Interval
DTIM (Delivery Traffic Indication Message) interval is the periodic interval when broadcasts and
multicasts are delivered in a BSS.
The handset in idle mode utilizes power-save mode and wakes up only at every DTIM interval to
receive broadcasts/multicasts and to check the traffic indication message for any buffered frames
in the AP. (See section about beacon period).
This means that the DTIM interval in conjunction with the beacon period affects the battery life and
the data response time. For good battery conservation and reasonable response times we recom
-
mend a DTIM interval of 5 if a beacon period of 100ms is used.
113
219.5
326
439
552
658.5
765
MCS Index Data Rates Mbps 20 MHz Channel