Cerio OW-200N2, User Manual

Page: 121 / 290

User’s Manual
500mW eXtreme Power 11Na Outdoor Bridge
121
4.4.1.2 DTIM Interval : The DTIM interval is in the range of 1~255. The default is 1.
DTIM is defined as Delivery Traffic Indication Message. It is used to notify the
wireless stations, which support power saving mode, when to wake up to
receive multicast frame. DTIM is necessary and critical in wireless environment
as a mechanism to fulfill power-saving synchronization.
A DTIM interval is a count of the number of beacon frames that must occur
before the access point sends the buffered multicast frames. For instance, if
DTIM Interval is set to 3, then the Wi-Fi clients will expect to receive a multicast
frame after receiving three Beacon frame. The higher DTIM interval will help
power saving and possibly decrease wireless throughput in multicast
applications.
4.4.1.3 Fragment Threshold : The Fragment Threshold is in the range of
256~2346 byte. The default is 2346 byte.
Each Wi-Fi packet can be divided into smaller packets, marked with a
sequential fragment number and re-assemble in the receiving ends. The
purpose is to make a short frame, instead of long frame, transmitting by radio
in a heavy noisy environment. Because of sending smaller frames, corruptions
are much less likely to occur. The pros is obvious, the cons is the overhead for
transmission. So, in a clean environment, higher fragment threshold can be an
option to increase throughput.
Fragmentation will be triggered by setting the Fragment Threshold, usually in
Byte-length. Only when the frame size is over the Threshold, fragmentation will
take place automatically.
4.4.1.4 RTS Threshold : TRTS Threshold is in the range of 1~2347 byte. The
default is 2347 byte.
The main purpose of enabling RTS by changing RTS threshold is to reduce
possible collisions due to hidden wireless clients. RTS in AP will be enabled
automatically if the packet size is larger than the Threshold value. By default,
RTS is disabled in a normal environment supports non-jumbo frames.
4.4.1.5 Short Preamble : By default, it’s “Enable”. To Disable is to use Long
128-bit Preamble Synchronization field.
The preamble is used to signal "here is a train of data coming" to the receiver.
The short preamble provides 72-bit Synchronization field to improve WLAN
transmission efficiency with less overhead.