Ovislink Air Live WIAS-3200N v2 User Manual page 89

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.
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.
*Note: 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.
RSSI Threshold: RSSI (Received Signal Strength Indication) Threshold is in the
range of -127 ~ 128. The default value is 24. RSSI Threshold can be used to control
the level of noise received by the device.
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.
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.
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AirLive WIAS-3200N v2 User's Manual
5 Configure Wireless Connection