PLANET WNL-U554A - Manual (Page 59)

150Mbps 802.11n Wireless USB Adapte r
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21. Wi‐Fi Protected Access (WPA)
The Wi‐Fi Alliance put together WPA as a data encryption method for 802.11 wireless LANs.
WPA is an industry‐supported, pre‐standard version of 802.11i utilizing the Temporal Key
Integrity Protocol (TKIP), which fixes the problems of WEP, including using dynamic keys.
22. Wide Area Network (WAN)
A WAN consists of multiple LANs that are tied together via telephone services and / or fiber
optic cabling. WANs may span a city, a state, a country, or even the world
23. Wired Equivalent Privacy (WEP)
Now widely recognized as flawed, WEP was a data encryption method used to protect the
transmission between 802.11 wireless clients and APs. However, it used the same key among
all communicating devices. WEP’s problems are well‐known, including an insufficient key
length and no automated method for distributing the keys. WEP can be easily cracked in a
couple of hours with off‐the‐shelf tools.
24. Wireless LAN (WLAN)
A wireless LAN does not use cable to transmit signals, but rather uses radio or infrared to
transmit packets through the air. Radio Frequency (RF) and infrared are the commonly used
types of wireless transmission. Most wireless LANs use spread spectrum technology. It offers
limited bandwidth, usually under 11Mbps, and users share the bandwidth with other devices
in the spectrum; however, users can operate a spread spectrum device without licensing from
the Federal Communications Commission (FCC).
25. Fragment Threshold
The proposed protocol uses the frame fragmentation mechanism defined in IEEE 802.11 to
achieve parallel transmissions. A large data frame is fragmented into several 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.
26. RTS(Request To Send) Threshold
The RTS threshold is the packet size at which packet transmission is governed by the RTS/CTS
transaction. The IEEE802.11‐1997 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