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TRENDnet User's Guide
Short Slot: By default, it's "Enable" for reducing the slot time from the standard 20
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microseconds to the 9 microsecond short slot time. Slot time is the amount of time a
device waits after a collision before retransmitting a packet. Reducing the slot time
decreases the overall back-off, which increases throughput. Back-off, which is a
multiple of the slot time, is the random length of time a station waits before
sending a packet on the LAN. For a sender and receiver own right of the channel the
shorter slot time help manage shorter wait time to re-transmit from collision
because of hidden wireless clients or other causes. When collision sources can be
removed sooner and other senders attempting to send are listening the channel
(CSMA/CA) the owner of the channel should continue ownership and finish their
transmission and release the channel. Then, following ownership of the channel will
be sooner for the new pair due to shorter slot time. However, when long duration of
existing collision sources and shorter slot time exist the owners might experience
subsequent collisions. When adjustment to longer slot time can't improve
performance then RTS/CTS could supplement and help improve performance.
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ACK Timeout: ACK timeout is in the range of 1~255 and set in unit of microsecond.
The default value is 32 microsecond. All data transmission in 802.11b/g request an
"Acknowledgement" (ACK) send by receiving radio. The transmitter will resend the
original packet if correspondent ACK failed to arrive within specific time interval,
also refer to as "ACK Timeout".
ACK Timeout is adjustable due to the fact that distance between two radio links
may vary in different deployment. ACK Timeout makes significant influence in
performance of long distance radio link. If ACK Timeout is set too short, transmitter
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will start to "Resend" packet before ACK is received, and throughputs become low
due to excessively high re-transmission. ACK Timeout is best determined by
distance between the radios, data rate of average environment. The Timeout value
is calculated based on round-trip time of packet with a little tolerance, So, if
experiencing re-transmissions or poor performance the ACK Timeout could be
made longer to accommodate.
Beacon Interval: Beacon Interval is in the range of 20~1024 and set in unit of
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millisecond. The default value is 100 msec.
Access Point (AP) in IEEE 802.11 will send out a special approximated 50-byte
frame, called "Beacon". Beacon is broadcast to all the stations, provides the basic
information of AP such as SSID, channel, encryption keys, signal strength, time
stamp, support data rate.
All the radio stations received beacon recognizes the existence of such AP, and may
proceed next actions if the information from AP matches the requirement. Beacon
is sent on a periodic basis, the time interval can be adjusted.
By increasing the beacon interval, you can reduce the number of beacons and
associated overhead, but that will likely delay the association and roaming process
because stations scanning for available access points may miss the beacons. You
can decrease the beacon interval, which increases the rate of beacons. This will
make the association and roaming process very responsive; however, the network
will incur additional overhead and throughput will go down.
DTIM Interval: The DTIM interval is in the range of 1~255. The default is 1.
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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.
RTS Threshold: TRTS Threshold is in the range of 1~2347 byte. The default is 2347
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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.
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Short Preamble: By default, it's "Enable". To Disable is to use Long 128-bit Preamble
TEW-738APBO
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