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3.5 Configure Wireless Advanced Setup
The administrator can change the
Slot Time, ACK Timeout, RTS threshold and
fragmentation threshold settings
for the system. Please click on
Wireless -> Advanced
Setup and follow the below setting.
Slot Time :
Slot time is in the range of 9~1489 and set in unit of microsecond. The default
value is 9 microsecond.
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.
ACK Timeout :
ACK timeout is in the range of 1~372 and set in unit of microsecond. The
default value is 64 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 will start to “Resend” packet
before ACK is received, and throughput become low due to excessively high
re-transmission.
