Multicast Transmissions

Multicast transmission is a stream of packets that is transmitted at a specific data rate, to a group of hosts on a network.

Low data rates consume significantly more airtime than higher data rates. Hence, Vocera recommends that you enable higher 802.11 mandatory data rates (11 Mbps optimal) and remove support for lower rates (1, 2, 5.5 Mbps). This prevents choppy audio on badge broadcasts and push-to-talk conferences.

The Vocera B3000 badge can process frames sent at 11 Mbps. The lower data rates (9, 6, 5.5, 2 and 1 Mbps) can be disabled. Data rates higher than 24 Mbps can be left enabled or disabled. Disabling these higher data rates provides an advantage of avoiding issues when the phone rate-shifts between data rates, delaying frame transmission, compromising the performance of the transmission.

Ideally, you should set only one mandatory rate to be the lowest data rate that a Vocera badge might use in a unicast call. By using a wireless packet capture program, also known as a wireless sniffer, you can obtain a sniffer trace of a Vocera broadcast from a badge to determine the lowest data rate it shifts down to while roaming.

For more information on data rates, refer to: Data Rates.