Physical Layer Enhancements for High-Reliability Multicast and Broadcast Services in 5G Release-17.

The exponential growth of the demand for higher data rates has motivated the 5G ecosystem to continually evolve and add new features to the system. 3GPP enhanced Release-17 specifications in order to add new capabilities to 5G that will address new services and verticals. One of the key enhancements currently being done relates to the support for multicast/broadcast, or point-to-multipoint (PTM) transmissions, with a key focus on enhanced reliability. These new features are targeting a wide variety of use cases ranging from network-to-vehicle communication to immersive multimedia content delivery. In this work, we present some of the key physical layer procedures and enhancements that were standardized to support the group scheduling of users for multicast traffic with near-unicast level of reliability, as well as support for idle/inactive users to receive broadcast traffic. We also present some performance results, which validate the need to support NACK-only HARQ feedback for multicast which provides significantly improved radio resource efficiencies for uplink feedback, with comparable performance as currently defined ACK/NACK feedback.