ATSC (B2X) Multicast Broadcast Neutral-Host O-RAN System Architecture

Abstract

ATSC 3.0 is the most advanced digital broadcast standard. This paper introduces Broadcast-to-Everything (B2X), a new physical layer Radio Access Network (RAN) standard being developed by ATSC. B2X enables multiple users to share multiple radio frequency (RF) carriers in various IMT and broadcast bands (ranging from 5 MHz to 50 MHz). B2X is optimized for battery-powered devices.

B2X builds on ATSC 3.0's Layer 1 (L1) and Layer 2 (L2) protocols where applicable and includes new L1/L2 control signalling. It operates within a Neutral-Host shared Open RAN (O-RAN) system, supporting a variety of services such as wearables, IoT, and Smart City applications with flexible Fast Fourier Transform (FFT) sizes of 128, 256, 512, and 1024.

To ensure reliable and scalable performance, Orthogonal Frequency Division Multiple Access (OFDMA) is used, breaking the physical layer into Physical Resource Blocks (PRBs), each containing 24 subcarriers spaced 3 kHz apart. A scheduler allocates PRBs based on service needs, with Virtual Bandwidth Parts (VBP) assigned to each application.

B2X is designed for efficient multicast and broadcast with carrier aggregation to increase capacity. It enhances mobile performance using intelligent Single Frequency Network (SFN) topologies, allowing content delivery over a wide-area SFN or cloud-based edge networks.

For 5G/6G interworking and traffic offloading, B2X uses the O-RAN F1 interface to encapsulate the 5G/6G-PDCP (Packet Data Convergence Protocol) layer 2. The data is transmitted via B2X baseband over O-RAN fronthaul to SFN transmitter sites for emission. Dual-connected user equipment (UE/UBE (User Broadcast Equipment)) retrieves and passes the PDCP layer 2 to the 5G/6G UE PDCP buffer, completing the offload process.