Users Guide

In an 802.11ac AP deployment, clients indicate VHT capabilities for probe requests and association requests,
including MU-MIMO support. The APs and controllers use this information to determine whether the client is
MU-MIMO-capable.
After the MU-MIMO-capable clients are located, they are steered to an appropriate MU-MIMO-capable radio.
MU-MIMO Steering ensures that steers are compatible with existing trigger thresholds, such as sticky clients
and load-balancing. The multi-user SNR threshold of the target radio must be greater than the sticky client SNR
threshold, and radios that exceed the client threshold are avoided to prevent the need for load-balancing.
Removing VBR Dependency on Probe Requests
Client Match has shifted its dependency on probe requests to the AM data feed for virtual beacon report (VBR)
data. Instead of relying solely on client background scans during probe requests, which can cause limitations
due to low scanning frequency, Client Match uses AM data feeds to gain more continuous, comprehensive
client RSSI feeds. Along with probe requests, AM data feeds collect client information during AP scanning using
the following frames:
l Block ACK
l Management frames
l NULL data frames
l Data frames with rates no higher than 36Mbps
l Control frames
ARM Coverage and Interference Metrics
ARM computes coverage and interference metrics for each valid channel, and chooses the best performing
channel and transmit power settings for each AP’s RF environment. Each AP gathers other metrics on their
ARM-assigned channel to provide a snapshot of the current RF health state.
The following two metrics help the AP decide which channel and transmit power setting is best.
l Coverage Index: The AP uses this metric to measure RF coverage. The coverage index is calculated as x/y,
where “x” is the AP’s weighted calculation of the Signal-to-Noise Ratio (SNR) on all valid APs on a specified
802.11 channel, and “y” is the weighted calculation of the Dell AP's SNR the neighboring APs see on that
channel.
To view these values for an AP in your current WLAN environment, issue the CLI command show ap arm
rf-summary ap-name <ap-name>, where <ap-name> is the name of an AP for which you want to view
information.
l Interference Index: The AP uses this metric to measure co-channel and adjacent channel interference. The
Interference Index is calculated as a/b//c/d, where:
l Metric value “a” is the channel interference the AP sees on its selected channel.
l Metric value “b” is the interference the AP sees on the adjacent channel.
l Metric value “c” is the channel interference the AP’s neighbors see on the selected channel.
l Metric value “d” is the interference the AP’s neighbors see on the adjacent channel.
To manually calculate the total Interference Index for a channel, issue the CLI command show ap arm rf-
summary ap-name <ap-name>, then add the values a+b+c+d.
Each AP also gathers the following additional metrics, which can provide a snapshot of the current RF health
state. View these values for each AP using the CLI command show ap arm rf-summary ip-addr <ap ip
address>.
l Amount of Retry frames (measured in %)
l Amount of Low-speed frames (measured in %)
Dell Networking W-Series ArubaOS 6.5.x | User Guide Adaptive Radio Management | 453