X-Micro WLAN 11b Access Point User Manual

 
 

fragments each of size equal to fragment threshold. By tuning the fragment threshold 

value, we can get varying fragment sizes. The determination of an efficient fragment 

threshold is an important issue in this scheme. If the fragment threshold is small, the 

overlap part of the master and parallel transmissions is large. This means the spatial 

reuse ratio of parallel transmissions is high. In 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. 

 

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 

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