ZyXEL Communications 802.11a/g Wireless CardBus Card ZyXEL AG-120, User Manual

Page: 323 / 396

Appendix B Wireless LANs
NWA-3500/NWA-3550 User’s Guide
323
Fragmentation Threshold
A Fragmentation Threshold is the maximum data fragment size (between 256
and 2432 bytes) that can be sent in the wireless network before the AP will
fragment the packet into smaller data frames.
A large Fragmentation Threshold is recommended for networks not prone to
interference while you should set a smaller threshold for busy networks or
networks that are prone to interference.
If the Fragmentation Threshold value is smaller than the RTS/CTS value (see
previously) you set then the RTS (Request To Send)/CTS (Clear to Send)
handshake will never occur as data frames will be fragmented before they reach
RTS/CTS size.
Preamble Type
Preamble is used to signal that data is coming to the receiver. Short and Long
refer to the length of the synchronization field in a packet.
Short preamble increases performance as less time sending preamble means
more time for sending data. All IEEE 802.11b/g compliant wireless adapters
support long preamble, but not all support short preamble.
Select Long preamble if you are unsure what preamble mode the wireless
adapters support, and to provide more reliable communications in busy wireless
networks.
Select Short preamble if you are sure the wireless adapters support it, and to
provide more efficient communications.
Select Dynamic to have the AP automatically use short preamble when wireless
adapters support it, otherwise the AP uses long preamble.
Note: The AP and the wireless adapters MUST use the same preamble mode in order
to communicate.
IEEE 802.11g Wireless LAN
IEEE 802.11g is fully compatible with the IEEE 802.11b standard. This means an
IEEE 802.11b adapter can interface directly with an IEEE 802.11g access point
(and vice versa) at 11 Mbps or lower depending on range. IEEE 802.11g has