H3C Technologies H3C WX3000E Series Wireless Switches - Manual (Page 502)

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Item Description
Transmit Distance Maximum coverage of a radio.
Client Max Count Maximum number of clients that can be associated with one radio.
Fragment Threshold
Specify the maximum length of frames that can be transmitted without
fragmentation. When the length of a frame exceeds the specified fragment
threshold value, it is fragmented.
• In a wireless network where error rate is high, you can decrease the
fragment threshold by a rational value. In this way, when a fragment of
a frame is not received, only this fragment rather than the whole frame
needs to be retransmitted, and the throughput of the wireless network is
improved.
• In a wireless network where no collision occurs, you can increase the
fragment threshold by a rational value to decrease acknowledgement
packets, and increase network throughput.
Disable WMM before you configure the fragment threshold.
Beacon Interval
Interval for sending beacon frames. Beacon frames are transmitted at a
regular interval to allow mobile clients to join the network. Beacon frames
are used for a client to identify nearby APs or network control devices.
RTS (CTS)
There are two data collision avoidance mechanisms, RTS/CTS and
CTS-to-Self.
• RTS/CTS—In this mode, an AP sends an RTS packet before sending
data to a client. After receiving the RTS packet, all the devices within the
coverage of the AP will not send data within the specified time. Upon
receiving the RTS packet, the client sends a CTS packet, ensuring that all
the devices within the coverage of the client will not send data within
the specified time. The RTS/CTS mechanism requires two frames to
implement data collision avoidance, and has a higher cost.
• CTS-to-Self—In this mode, an AP uses its IP address to send a CTS
packet before sending data to a client, ensuring that all the devices
within the coverage of the AP will not send data within the specified
time. The CTS-to-Self mechanism uses only one frame to avoid data
collision. However, if another device is in the coverage of the client, but
not in the coverage of the AP, data collision still might occur.
Compared with RTS/CTS, CTS-to-Self reduces the number of control
frames. However, data collisions still occur when some clients are hidden
and cannot receive the CTS frames sent by the AP. Therefore, the RTS/CTS
mechanism can solve the data collision problem in a larger coverage than
RTS/CTS.
RTS (CTS) Threshold
If a frame is larger than the RTS (CTS) threshold, the data collision
avoidance mechanism is used.
A smaller RTS/CTS threshold causes RTS/CTS packets to be sent more
often, consuming more bandwidth. However, the more often RTS/CTS
packets are sent, the quicker the system can recover from collisions.
In a high-density WLAN, you can decrease the RTS threshold to reduce
collisions in the network.
IMPORTANT:
The data collision avoidance mechanism occupies bandwidth. Therefore,
this mechanism applies only to data frames larger than the RTS/CTS
threshold.