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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.
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.
Slot Time and ACK Timeout settings are for long distance links. It is important
to tweak settings to achieve the optimal result based on requirement.
Beacon Interval : Beacon Interval is in the range of 40~3500 and set in unit of
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.
CERIO software core : cen_v3.0
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