X-Micro Tech. XWL-11GRTX Manual Do Utilizador

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.

4.11 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 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.

4.12 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