ATSC 3.0 : Candidate Standards

This document is a revision of A/324, “Scheduler / Studio to Transmitter Link.” A/324 specifies the protocol on the Studio-to-Transmitter Link (STL) from studio side infrastructure to a Single Frequency Network (SFN) of Transmitters. It defines delivery protocols for ALP Transport. The document also defines possible interfaces among the studio infrastructure, for example the interconnection of the ATSC 3.0 Link Layer Protocol (ALP) and a Broadcast Gateway. A/324 specifies certain constraints on the scheduling of content and signaling on the Physical Layer. The described scheduling process enables Preamble generation and emission time management. It specifies certain aspects of Transmitter behavior and certain parameters of Transmitter operation.

This document is a Candidate Standard and may be updated from time to time by the originating specialist group, TG3/S32. The Candidate Standard period extends to 31 December 2026. The CS period may be shortened or extended by TG3.

Download “ATSC Candidate Standard: Revision of A/324:2024-04, Scheduler / Studio to Transmitter Link”, approved 10 April 2024. Accompanying schema is also available.

A redline showing changes relative to the current published version can be downloaded from this link: A/324 CS redline.

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This document describes the interactive content environment provided by an ATSC 3.0 receiver. This environment is comprised of a standard W3C User Agent with known characteristics, a WebSocket interface for obtaining information from the receiver and controlling various receiver functionality, and an HTTP interface for accessing files delivered over broadcast. This document also specifies the life cycle of the interactive content when delivered over broadband or broadcast or both.

Download “Candidate Standard Revision of A/344:2026-04, ATSC 3.0 Interactive Content”, 12 May 2026. This redline shows changes relative to the current published version of A/344:2026-04. A clean version, with all changes accepted, is also available: “Candidate Standard Revision of A/344:2026-04, ATSC 3.0 Interactive Content”. The CS period extends to 31 December 2026.

This revision includes updates and clarifications identified since the current version of A/344 was published.

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Future broadcast networks are expected to support multiple wireless services in addition to television. Such services may be multiplexed in time and frequency using OFDMA within a single RF carrier or across multiple RF carriers of a B2X Radio Access Network (BRAN). To enable discovery and entry in the BRAN, a bootstrap signal provides a universal entry point into the waveform, allowing BXEs to identify the signal type and determine how to receive the services associated with it.

This document uses concepts from A/321, “System Discovery and Signaling,” and specifies the normative structure of the bootstrap that provides the entry point to a B2X Physical Layer waveform. The syntax and semantics defined therein apply to system discovery and signaling of B2X Virtual Frames. Other ATSC B2X Standards may further constrain or supplement this bootstrap specification. This document does not modify A/321 or any other ATSC 3.0 Standard. It is designed to support independent discovery and entry into a B2X Physical Layer waveform and is optimized for B2X services delivered to B2X Endpoints (BXE) in both broadcast and IMT (International Mobile Telecommunications) bands.

Download “ATSC Candidate Standard:B2X System Discovery and Signaling”, 9 July 2026. The CS period extends to 30 September 2026.

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