CNet WNOR5305 user manual download (Page 65 of 69)

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5.11 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 actu-
al 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.
5.12 What is Beacon Interval?
In addition to data frames that carry information from higher layers, 802.11 include 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).
5.13 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 bit
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