5G Multicast Broadcast Handover for Seamless Session Continuity

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Solution Overview

Problem

Multicast/Broadcast services are not currently supported on 5G NR, and there is a need for improved systems and methods to ensure session continuity during handovers in 5G networks, particularly for Mission Critical Services and V2X applications.

Innovation Solution

The proposed solution involves enhancing the 5G Xn and N2 handover procedures to support multicast broadcast sessions by establishing resources in the target NG-RAN during the preparation phase, using new parameters in existing messages, and optimizing signaling to ensure seamless session continuity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If existing handover procedures in TS 23.502 are used, then handover between NG-RAN nodes can be performed, but Multicast Broadcast Session continuity is not supported

Engineering Contradiction:

ImproveMulticast Broadcast Session continuity supportVSAvoidhandover procedure complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by establishing MB Session resources in the target NG-RAN during the handover preparation phase, before the actual handover execution. This ensures that when the UE completes handover, the multicast broadcast resources are already available, preventing service interruption and maintaining session continuity without requiring complex post-handover setup procedures

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent segments the handover procedure into distinct phases (preparation and execution) with specific MB Session resource establishment actions in each phase. By dividing the complex handover process and assigning specific resource management tasks to each phase, the system can support MB Session continuity while maintaining manageable procedural complexity through clear phase-based resource establishment

Inventive Principle:

Principle #1Segmentation

2Reliability

If resources are established in Target NG-RAN during Xn Handover preparation phase, then service continuity is improved, but signaling overhead increases

Engineering Contradiction:

Improveservice continuityVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent merges the MB Session resource establishment procedure with the existing Xn Handover preparation phase procedures. By combining these operations and reusing existing signaling message structures (such as incorporating MB Session resource establishment information in Handover Request messages), the system achieves service continuity while minimizing additional signaling overhead through procedural integration rather than separate dedicated signaling exchanges

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent makes existing handover signaling messages multi-functional by enabling them to carry both traditional handover information and MB Session resource establishment information. This universal approach allows a single signaling exchange to accomplish multiple tasks (handover coordination and MB resource setup), reducing overall signaling overhead while ensuring service continuity through integrated resource preparation

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If resources are established in Target NG-RAN during N2 Handover preparation phase, then session continuity is maintained, but network complexity increases

Engineering Contradiction:

Improvesession continuityVSAvoidnetwork procedure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent applies preliminary action in the N2 Handover context by triggering AMF to start setup of MB Session resources in the target NG-RAN during the N2 Handover preparation phase. This advance resource establishment ensures that when the handover is executed, the multicast broadcast resources are already in place, maintaining session continuity without requiring complex real-time resource allocation during the actual handover execution

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces the AMF as an intermediary that coordinates the MB Session resource establishment between the source and target NG-RAN nodes during N2 Handover. The AMF receives handover information, triggers the target NG-RAN to establish MB resources, and manages the overall coordination, thereby simplifying the network procedure complexity by centralizing the coordination function in an existing network element rather than requiring direct complex interactions between RAN nodes

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12414015B25G multicast broadcast service handover

Publication Date: 2025.09.09 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Systems and methods for session continuity of Multicast Broadcast (MB) Sessions are provided. In some embodiments, a method performed by a base station for session continuity of MB Sessions includes at least one of: providing at least one MB Session to a wireless device connected in 5G; determining that the wireless device is handed over to a target Next Generation Radio Access Network (NG-RAN); and providing session continuity of the at least one MB Session to the wireless device. In some embodiments, being handed over to the target NG-RAN comprises an Xn handover. In some embodiments, being handed over to the target NG-RAN comprises a N2 handover. Some embodiments of the current disclosure provide support for Multicast Broadcast Session continuity (aka “Handover”) at Inter-gNB Xn Handover and Inter-gNB N2 Handover in the 5G NR radio access.