Dynamic Frequency Selection (Dfs); Rts/Cts Medium Reservation - Proxim AP-4000 User Manual

Performing Advanced Configuration
Interfaces
• Frequency Channel: When Auto Channel Select is enabled, this field is read-only and displays the Access Point's current operating
Channel. When Auto Channel Select is disabled, you can specify the Access Point's operating channel. If you decide to manually set the
unit's Channel, ensure that nearby devices do not use the same frequency (unless you are setting up WDS links). Available Channels
vary based on regulatory domain. See
802.11a products operating in Europe's middle frequency band (see
• Transmit Rate: Use the drop-down menu to select a specific transmit rate for the AP. The values depend on the Operational mode. Auto
Fallback is the default setting; it allows the AP unit to select the best transmit rate based on the cell size.
– For 802.11b only -- Auto Fallback, 1, 2, 5.5, 11 Mbits/sec.
– For 802.11g only -- Auto Fallback, 6, 9, 12, 18, 24, 36, 48, 54 Mbits/sec
– For 802.11b/g -- Auto Fallback, 1, 2, 5.5, 6, 9, 11, 12, 18, 24, 36, 48, 54 Mbits/sec
– For 802.11a only -- Auto Fallback, 6, 9, 12, 18, 24, 36, 48, 54 Mbits/s.
NOTE
Turbo mode is supported in 802.11a and 802.11g mode. If turbo mode is enabled, then this is displayed in the web UI and the
transmit speeds and channels pull-down menus are updated with the valid values.
• DTIM Period: The Deferred Traffic Indicator Map (DTIM) is used with clients that have power management enabled. DTIM should be left
at 1, the default value, if any clients have power management enabled. This parameter supports a range between 1 and 255.
• RTS/CTS Medium Reservation: This parameter affects message flow control and should not be changed under normal circumstances.
Range is 0 to 2347. When set to a value between 0 and 2347, the Access Point uses the RTS/CTS mechanism for packets that are the
specified size or greater. When set to 2347 (the default setting), RTS/CTS is disabled. See
information.
• Enable Closed System: Check this box to allow only clients configured with the Access Point's specific Network Name to associate with
the Access Point. When enabled, a client configured with the Network Name "ANY" cannot connect to the AP. This option is disabled by
default.
• Wireless Service Status: Select shutdown to shutdown the wireless service on a wireless interface, or resume to resume wireless
service. See Wireless Service Status
• Load Balancing Max Clients: Load balancing distributes clients among available access points. Enter a number between 1 and 63 to
specify the maximum number of clients to allow.
• Wireless Distribution System: A Wireless Distribution system can be used to establish point-to-point (i.e. wireless backhaul)
connections with other access points. See

Dynamic Frequency Selection (DFS)

AP-4000s sold in Europe and operating the in middle freqency band (5.25-5.35 GHz) use a technique called Dynamic Frequency Selection
(DFS) to automatically select an operating channel. During boot-up, the AP scans the available frequency and selects a channel that is free of
interference. If the AP subsequently detects interference on its channel, it automatically reboots and selects another channel that is free of
interference.
DFS only applies to AP-4000s used in Europe that operate in the middle freqency band (i.e., units whose regulatory domain is set to ETSI and
who operate in the 5.25-5.35 GHz frequency range.). The European Telecommunications Standard Institute (ETSI) requires that these
802.11a Access Points use DFS to prevent interference with radar systems and other devices that already occupy the 5 GHz band.
If you are using an 802.11a AP in Europe's middle frequency band, keep in mind the following:
• DFS is not a configurable parameter. It is always enabled and cannot be disabled.
• You cannot configure the Auto Channel Select option. Within the HTTP or CLI interface, this option always appears enabled.
• You cannot manually select the device's operating channel; you must let DFS select the channel.
In 802.11a APs operating in Europe's lower frequency band, however:
• DFS is a configurable parameter.
• The Auto Channel Select option is configurable.
• The AP's operating channel is selectable. Channel options are limited to those in the lower band.

RTS/CTS Medium Reservation

The 802.11 standard supports optional RTS/CTS communication based on packet size. Without RTS/CTS, a sending radio listens to see if
another radio is already using the medium before transmitting a data packet. If the medium is free, the sending radio transmits its packet.
However, there is no guarantee that another radio is not transmitting a packet at the same time, causing a collision. This typically occurs when
there are hidden nodes (clients that can communicate with the Access Point but are out of range of each other) in very large cells.
When RTS/CTS occurs, the sending radio first transmits a Request to Send (RTS) packet to confirm that the medium is clear. When the
receiving radio successfully receives the RTS packet, it transmits back a Clear to Send (CTS) packet to the sending radio. When the sending
Radio Specifications for more information. Note that you cannot manually set the channel for
for more information.
Wireless Distribution System (WDS)
Dynamic Frequency Selection (DFS)
RTS/CTS Medium Reservation
for configuration information.
AP-4000 User Guide
for details).
for more
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