contrast, with a large fragment threshold, the overlap is small and the spatial reuse ratio is low.
However high fragment threshold leads to low fragment overhead. Hence there is a trade-off
between spatial re-use and fragment overhead.
Fragment threshold is the maximum packet size used for fragmentation. Packets larger than the
size programmed in this field will be fragmented.
If you find that your corrupted packets or asymmetric packet reception (all send packets, for
example). You may want to try lowering your fragmentation threshold. This will cause packets to
be broken into smaller fragments. These small fragments, if corrupted, can be resent faster than a
larger fragment. Fragmentation increases overhead, so you'll want to keep this value as close to
the maximum value as possible.
What is RTS (Request To Send) Threshold?
The RTS threshold is the packet size at which packet transmission is governed by the RTS/CTS
transaction. The IEEE 802.11-1997 standard allows for short packets to be transmitted without
RTS/CTS transactions. Each station can have a different RTS threshold. RTS/CTS is used when
the data packet size exceeds the defined RTS threshold. With the CSMA/CA transmission
mechanism, the transmitting station sends out an RTS packet to the receiving station, and waits
for the receiving station to send back a CTS (Clear to Send) packet before sending the actual
packet data.
This setting is useful for networks with many clients. With many clients, and a high network load,
there will be many more collisions. By lowering the RTS threshold, there may be fewer collisions,
and performance should improve. Basically, with a faster RTS threshold, the system can recover
from problems faster. RTS packets consume valuable bandwidth, however, so setting this value
too low will limit performance.
What is Beacon Interval?
In addition to data frames that carry information from higher layers, 802.11 includes management
and control frames that support data transfer. The beacon frame, which is a type of management
frame, provides the "heartbeat" of a wireless LAN, enabling stations to establish and maintain
communications in an orderly fashion.
Beacon Interval represents the amount of time between beacon transmissions. Before a station
enters power save mode, the station needs the beacon interval to know when to wake up to
receive the beacon (and learn whether there are buffered frames at the access point).
What is Preamble Type?
There are two preamble types defined in IEEE 802.11 specification. A long preamble basically
gives the decoder more time to process the preamble. All 802.11 devices support a long preamble.
The short preamble is designed to improve efficiency (for example, for VoIP systems). The
difference between the two is in the Synchronization field. The long preamble is 128 bits, and the
short is 56 bits.
What is SSID Broadcast?
Broadcast of SSID is done in access points by the beacon. This announces your access point
(including various bits of information about it) to the wireless world around it. By disabling that
feature, the SSID configured in the client must match the SSID of the access point.
