ZyXEL Communications P-660HW-T - V2, User Manual

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P-660HW-T v2 User’s Guide
Appendix K Wireless LANs 325
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 several intermediate rate steps
between the maximum and minimum data rates. The IEEE 802.11g data rate and modulation
are as follows:
Table 146 IEEE 802.11g
DATA RATE (MBPS) MODULATION
1 DBPSK (Differential Binary Phase Shift Keyed)
2 DQPSK (Differential Quadrature Phase Shift Keying)
5.5 / 11 CCK (Complementary Code Keying)
6/9/12/18/24/36/48/54 OFDM (Orthogonal Frequency Division Multiplexing)