STMicroelectronics 2024 13
STM32WBA5
Multiprotocol
Wireless Radio
MCU
Learn More
STM32WBA55G-DK1
Discovery Kit
Learn More
BIS can be used to broadcast gate announcements at an
airport terminal, or music to attendees at a concert, among
many other use cases. BIS is the mode underlying the audio
broadcasting capabilities that the Bluetooth organization
has branded as Auracast™ (Figure 2).
Inherent with BIS/CIS is the ability of both sources and sinks
to handle multiple channels simultaneously. This ensures
that an earbud user could be listening to music from their
smartphone and monitoring public-address announcements
at the same time.
Now, let's take a closer look at broadcast mode. Under
Bluetooth Classic, connections are 1:1—one source
connected to one sink. Bluetooth LE Audio allows a source
to simply broadcast streams of packets to whoever might
be listening. This ability of a source to simply broadcast
content, allowing users to subscribe if they wish, opens new
categories of use cases, from individuals sharing content
Broadcast
Sink
Broadcast
Sink
Broadcast
Sink
Broadcast
Source
Train Station
Announcements
Audio
Streams
Broadcast Use Case
Figure 2: Example of a broadcast use case. (Source: Mouser Electronics)
with each other to delivering messages or music in crowded
public spaces. Bluetooth SIG has branded a collection of
these capabilities as Auracast.
But broadcast raises an issue with the way to handle data
integrity. Bluetooth Classic assumes every data transaction
must be lossless. If a packet is dropped or corrupted, the
source device will repeat the transmission until it receives
a positive acknowledgment. Broadcast is inherently
unidirectional, so acknowledgments are not possible. Rather
than waiting for an acknowledgment, broadcast mode will
continue on, depending on LC3's packet loss concealment
(PLC) algorithm in the receiving device to reconstruct the
missing data so that the loss is inaudible. It is also possible
for broadcast mode to do multiple retransmissions to ensure
that a wide variety of receiving devices in different reception
environments get a usable copy of the data.
