Product and Software: This article applies to all Aruba controllers and ArubaOS 126.96.36.199 and later.
The single chain legacy parameter is applicable only with Aruba 802.11n APs and is configured in the RF HT radio profile. The ht-radio-profile configures high-throughput settings for networks using the IEEE 802.11n draft standard, which supports 40 MHZ channels and operates in the 2.4 GHZ and 5 GHZ frequency bands.
This feature was introduced in ArubaOS 188.8.131.52 to help interoperability with some voice over WLAN devices like Cisco 7921g VoIP phones. This feature is disabled by default, but when it is enabled, the AP transmits only on one chain to legacy devices (non-802.11n). As a best practice, Aruba recommends that you enable it only on the phy-type (802.11a or 802.11g) where a voice over WLAN device is being used and is experiencing problems that cannot be solved by basic troubleshooting of the controller configuration, RF, 802.11, 802.1x, and IP connectivity. The Aruba validated reference design guide titled "Optimizing Aruba WLANs for Roaming Devices" can also be referenced because it lists best practice configuration of several known voice devices.
To enable the single chain legacy feature, use the CLI or WebUI and follow these steps:
Using the CLI
rf ht-radio-profile 80211a_HT_radio
Using the WebUI
Navigate to Configuration > Wireless > AP Configuration > AP Group > Edit > RF Management > 802.11a Radio Profile > High-throughput Radio Profile and choose Legacy station workaround.