Users Guide

450| Adaptive Radio Management Dell Networking W-Series ArubaOS 6.5.x| User Guide
power settings if adjacent APs are added, removed, or moved to a new location within the network, minimizing
interference with other WLAN networks. ARM adjusts only the affected APs, so the entire network does not
require systemic changes.
ARM Support for 802.11n
ArubaOS version 3.3.x or later supports APs with the 802.11n standard, ensuring seamless integration of
802.11n devices into your RF domain. The Dell AP’s 5 Ghz band capacity simplifies the integration of new APs
into your legacy network. You can also replace older APs with newer 802.11n-compliant APs while reusing your
existing cabling and PoE infrastructure.
A high-throughput (802.11n) AP can use a 40 MHz channel pair comprised of two adjacent 20 MHz channels
available in the regulatory domain profile for your country. When ARM is configured for a dual-band AP, it will
dynamically select the primary and secondary channels for these devices. It can, however, continue to scan all
changes in the a+b/g bands to calculate interference and detect rogue APs.
Monitoring Your Network with ARM
When ARM is enabled, the Dell AP dynamically scans all 802.11 channels in its regulatory domain at regular
intervals and will report everything it sees to the controller on each channel it scans. (By default,
802.11n-capable APs scan channels in all regulatory domains.) This includes, but is not limited to, data
regarding WLAN coverage, interference, and intrusion detection. You can retrieve this information from the
controller to get a quick health check of your WLAN deployment without having to walk around every part of a
building with a network analyzer. (For additional information on the individual matrix gathered on the AP’s
current assigned RF channel, see
ARM Coverage and Interference Metrics on page 453.)
Maintaining Channel Quality
Hybrid APs and Spectrum Monitors determine channel quality by measuring channel noise, non-Wi-Fi
(interferer) utilization and duty-cycles, and certain types of retries. Regular APs using the ARM feature derive
channel quality values by measuring the noise floor for both 802.11 and non-802.11 noise on that channel.
The ARM algorithm is based on what the individual AP hears, so each AP on your WLAN can effectively “self
heal” by compensating for changing scenarios like a broken antenna or blocked signals from neighboring APs.
Additionally, ARM periodically collects information about neighboring APs to help each AP better adapt to its
own changing environment.
Configuring ARM Scanning
The default ARM scanning interval is determined by the scan-interval parameter in the ARM profile. If the AP
does not have any associated clients (or if most of its clients are inactive), the ARM feature will dynamically
readjust this default scan interval, allowing the AP obtain better information about its RF neighborhood by
scanning non-home channels more frequently. Starting with ArubaOS 6.2, if an AP attempts to scan a non-
home channel but is unsuccessful, the AP will make additional attempts to rescan that channel before skipping
it and continuing on to other channels.
The Over the Air Updates feature allows an AP to get information about its RFenvironment from its
neighbors, even the AP cannot scan. If you enable this feature, when an AP on the network scans a foreign
(non-home) channel, it sends an Over-the-Air (OTA) update in an 802.11 management frame that contains
information about that AP's home channel, the current transmission EIRP value of the home channel, and one-
hop neighbors seen by that AP.
Starting with ArubaOS 6.3.1, if ARM reports a high noise floor on a channel within a 40 MHz channel pair or 80
MHz channel set, ARM performs an additional 20 MHz scan on each channel within that channel pair or set, to
determine the actual noise floor of each affected channel. This allows ARM to avoid assigning the overused
channel, while still allowing channel assignments to the other unaffected channels in that channel pair or set.