Transmit data rates

Broadcast multicast traffic destined to wireless stations is forwarded differently than unicast data frames. When no optimization is performed, all broadcast and multicast frames are forwarded out each BSSID at the transmitting radios lowest configured transmit data rate consuming valuable airtime. The following default minimum transmit data rates are configured for each radio:

• 2.4 GHz – 1 Mbps

• 5 GHz – 6 Mbps

• 6 GHz – 6 Mbps

The data rate used to transmit broadcast multicast frames will impact channel utilization. When lower transmit rates are used, more time is required to transmit each broadcast multicast frame reducing the opportunity for the AP radio or stations to transmit data frames. The more broadcast multicast frames that are transmitted results in higher channel utilization and less time for data transmission at higher rates. An example of the impact to channel utilization on a 5 GHz radio for broadcast multicast frames transmitted at different frequencies and transmit rates is depicted below:

Recommendation

For modern Wi-Fi networks, HPE Aruba Networking recommends configuring the minimum transmit data rates of each radio to 12 Mbps or 24 Mbps depending on the AP density and RF environment. Higher transmit data rates are also achievable if the environment and stations allow. The minimum transmit data rate you select for each radio will need to be configured to suit your specific environment and lower rates may be required to accommodate your specific environment or client device needs.

Configuration

The minimum transmit data rates for 2.4 GHz and 5 GHz radios are configured within each WLAN profile. In classic Central,the transmit data rates are configured for each WLAN profile by following the the steps in the Advanced Settings section.

New Central includes intelligent defaults for each WLAN profile based on the Network Configuration selection. The selected Network Configuration option determines the minimum transmit data rates that are applied to 2.4 GHz and 5 GHz radios servicing the WLAN profile:

• Most Compatible – 1 Mbps for 2.4 GHz and 6 Mbps for 5 GHz
• Balanced – 12 Mbps for 2.4 GHz and 5 GHz
• High Density – 24 Mbps for 2.4 GHz and 5 GHz
• Custom – User defined Custom transmit data rates for 2.4 GHz and 5 GHz radios are configured under Data Rates

The minimum transmit data rates for 6 GHz radios are configured within the radio profile in classic Central and the RF profile in New Central. The configuration is separated from the WLAN profile to accommodate the multiple BSSID (MBSSID) implementation for Wi-Fi 6E and Wi-Fi 7 standards. In classic Central, the transmit data rates for 6 GHz radios are configured under Radio Profile for 6 GHz radios in the default or custom radio profile:

In New Central, the transmit data rates for 6 GHz radios are configured under the default or custom RF Profile.

Before and after

The following packet capture depicts broadcast multicast frames being forwarded out a 5 GHz radio at the default 6 Mbps data transmit rate:

The following packet capture depicts broadcast multicast frames being forwarded out a 5 GHz radio at the recommended 24 Mbps data transmit rate: