Introducing Bluetooth LE Audio

Part 2—Learning the Intricacies of these New Specifications

- Nick Hunn

Bluetooth Low Energy (LE) Audio introduces a revolutionary set of specifications, following the Bluetooth Core 5.2 release, that redefine audio applications through isochronous channels and a new audio middleware. In this two-part series, Nick provides an overview of the new specifications and discusses new ways to experience and share sound.

This comprehensive framework supports bidirectional audio, broadcast capabilities for shared listening experiences, and utilizes the high-efficiency LC3 codec to enhance audio quality for various applications, including personal and public broadcasting. Here, we continue our overview of the new Bluetooth LE Audio specifications, including Broadcast Isochronous Streams (BISes).

BROADCAST ISOCHRONOUS STREAMS

BISes look much like Connected Isochronous Streams (CISes), but with one exception—there are no acknowledgments. Broadcast audio is a one-way process, where a Broadcast Transmitter (also defined as an Initiator) transmits with no knowledge of whether anything is present to receive its transmissions. It may be received by one device, or by a hundred. In a recent demonstration in the Alice Tully concert hall in New York's Lincoln Center, a single transmitter covered an auditorium of more than 1,000 people.

Although the basic structure of a BIS is similar to a CIS, there are a few subtle differences. Each Broadcast Transmitter is configured for a set number of retransmissions, which are unconditionally sent, as there are no acknowledgments to indicate that they have been received. Accepters can stop listening for them as soon as they have received a valid packet, putting their radio to sleep until the next Isochronous Interval.