Users Guide

545| Access Points Dell Networking W-Series ArubaOS 6.5.x| User Guide
Adaptive Radio Management (ARM) profile. If you would like the ARM feature to dynamically select the best
channel and transmission power for the radio, verify that the RF management profile references an active and
enabled ARM profile. It can be useful to set the Max Tx EIRP parameter in the ARM profile to 127 (the
maximum power level permissible) until it determines the signal-to-noise radio on the links. If ARM is active, the
Max Tx EIRP can also be set to 127 to allow maximum power levels.
If you want to manually select a channel for each AP group, create separate 802.11a and 802.11g profiles for
each AP group and assign a different transmission channel for each profile. For example, one AP group could
have an 802.11a profile that uses channel 36 and an 802.11g profile that uses channel 11, and another AP
group could have an 802.11a profile that uses channel 40 and an 802.11g profile that uses channel 9.
With the implementation of the high-throughput 802.11n standard, 40 MHz channels were added in addition
to the existing 20 MHz channel options. Available 20 MHz and 40 MHz channels are dependent on the country
code entered in the regulatory domain profile. The newer very high-throughput (VHT) 802.11ac standard
introduces 80 Mhz channel options.
Changing the country code causes the valid channel lists to be reset to the defaults for the country.
The following channel configurations are available in ArubaOS:
l A 20 MHz channel assignment consists of a single 20 MHz channel. This channel assignment is valid for
802.11a/b/g and for 802.11n 20 MHz mode of operation.
l A 40 MHz channel assignment consists of two 20 MHz channels bonded together (a bonded pair). This
channel assignment is valid for 802.11n 40 MHz mode of operation and is most often utilized on the 5 GHz
frequency band.
l A 80 Mhz channel group for 5GHz radios. Only APs that support 802.11ac can be configured with 80 MHz
channels.
If high-throughput is disabled, a 40 MHz channel assignment can be configured, but only the primary
channel assignment is used. The 20 MHz clients can also associate using this configuration, but only the
primary channel is used.
APs initially start up with default ack-timeout, cts-timeout and slot-time values. When you modify the
maximum-distance parameter in an rf dot11a radio profile or rf dot11g radio profile, new ack-timeout, cts-
timeout and slot-time values may be derived, but those values are never less then the default values for an
indoor AP.
Mesh radios on outdoor APs have additional constraints, as mesh links may need to span long distances. For
mesh radios on outdoor APs, the effect of the default maximum-distance parameter on the ack-timeout,
cts-timeout and slot-time values depends on whether the APs are configured as mesh portals or mesh
points. This is because mesh portals use a default maximum-distance value of 16,050 meters, and mesh
points use, by default, the maximum possible maximum-distance value.
The maximum-distance value should be set correctly to span the largest link distance in the mesh network so
that when a mesh point gets the configuration from the network it will apply the correct ack-timeout, cts-
timeout and slot-time values. The values derived from the maximum-distance setting depend on the band
and whether 20Mhz/40MHz mode of operation is in use.
The following table indicates values for a range of distances:
Timeouts[usec] --- 5GHz radio --- --- 2.4GHz radio ---
Distance[m] Ack CTS Slot Ack CTS Slot
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0 (outdoor:16050m) 128 128 63 128 128 63
0 (indoor:600a,6450g) 25 25 9 64 48 9
200 (==default) 25 25 9 64 48 9
500 25 25 9 64 48 9