Product and Software: This article applies to all Aruba controllers and ArubaOS 3.3.2.x or later and to all 11n APs, including APs 92, 93, 105, 120, 121, 124, and 125.
Most deployments of 802.11n APs support newer 802.11n clients and legacy clients that do not support 802.11n. Voice handsets are a good example, as well as older laptops that only support a/b/g.
So, 802.11n APs still need to work with legacy clients, because many older clients are still being used. While 802.11n benefits by sending more than one stream to 802.11n clients (Multiple In, Multiple Out = MIMO), the APs will also send more than one stream to legacy clients. Some legacy clients may work fine, but others work better if only a single stream is sent.
Aruba has a feature that sends only one stream to legacy clients when the feature is enabled in the configuration. This feature works particularly well for legacy voice handsets and can enhance voice call quality.
To configure this feature, issue the following commands:
rf ht-radio-profile <profile name>
single-chain-legacy
rf dot11a-radio-profile <profile name>
ht-radio-profile <profile name>
rf dot11g-radio-profile <profile name>
ht-radio-profile <profile name>
When this feature is enabled, single streams are sent to legacy clients (non-802.11n capable clients) when 802.11n APs are used.
So, is it necessary to enable single chain if high throughput capability is disabled on an 802.11n AP?
The answer is yes, it is still necessary to enable single chain for legacy clients even if high throughput is disabled for an 802.11n AP.
You can disable high throughput on Aruba 802.11n APs in one of two ways:
- Per SSID by using the WLAN ht-ssid-profile:
wlan ht-ssid-profile <profile name>
no high-throughput-enable
wlan ssid-profile <profile name>
ht-ssid-profile <profile name>
- Per radio using the RF dot11a or RF dot11g radio profiles:
rf dot11a-radio-profile <profile name>
no high-throughput-enable
rf dot11g-radio-profile <profile name>
no high-throughput-enable
When you disable high throughput in the WLAN HT SSID profile, high throughput is only disabled for that SSID. Other SSIDs can still have high throughput enabled.
When you disable high throughput in the radio profiles, high throughput is disabled for the entire radio. All configured SSIDs on that AP will have high throughput disabled.
Even if high throughput is disabled on an SSID or a radio using one of the two methods described here, the 802.11n AP will still try to use multiple streams for clients. This means that single chains MUST still be enabled in the RF HT radio profile so that only one stream is used for legacy clients.