Handling Communication Transferring Mobile Relay Nodes and Their Dependent Devices in 5G Networks

This patent addresses a fundamental challenge in 5G wireless backhaul: how to hand over a mobile relay node — and all the devices it is simultaneously serving — from one network node to another without dropping connections.

The Problem

Modern 5G networks are being designed to use wireless relay nodes, known in 3GPP standards as IAB nodes (Integrated Access and Backhaul nodes), to extend coverage without running fibre to every base station. An IAB node acts simultaneously as a base station for user devices and as a wireless relay hop that backhaults their traffic to the core network. This architecture works well for fixed relay nodes, but becomes complex when the relay node itself is mobile — mounted, for example, on a train, bus, or drone. When a mobile IAB node moves from one cell to another, it does not just need to hand over its own connection to a new parent network node (as a regular mobile device would). It also carries with it every device and every downstream relay node it is serving. Those downstream devices and nodes have their own active connections, routing paths, and quality-of-service parameters. Conventional handover procedures are designed for a single endpoint moving between cells, not a subtree of connected devices migrating together. Without a mechanism to transfer the complete picture of the relay node’s downstream connections, any handover causes all those dependent connections to fail simultaneously.

What This Invention Does

Ericsson’s invention defines a handover and cell reselection procedure in which the first radio network node (the current parent, or IAB-donor) sends a message to the second radio network node (the target parent) that contains not only data about the migrating IAB node itself, but also data about every node directly and indirectly served by the migrating node. This single message conveys the full downstream tree of connections in one transfer, so the target network node has all the context it needs to accept the migrating relay node and reconstitute the routing and service for every dependent device and intermediate relay hop. The patent covers the method performed by the first network node (transmitting the compound handover message), the corresponding method performed by the second network node (receiving and processing it), the network nodes themselves as apparatus, and computer program products implementing the methods.

Key Features

• Compound handover message. The key innovation is extending the handover signalling to carry data about the entire downstream tree, not just the migrating node’s own context. Both directly served nodes (one hop downstream) and indirectly served nodes (multiple hops downstream, via intermediate IAB relays) are included.
• Compatibility with 3GPP IAB architecture. The invention builds on the CU/DU split architecture standardised in 3GPP NR Release 16, reusing existing F1, NG, and X2 interfaces and the Backhaul Adaptation Protocol (BAP) routing layer, reducing the integration burden on network equipment vendors.
• Applicability to handover and cell reselection. The mechanism applies to both handover (network-controlled mobility) and cell reselection (device-initiated mobility) scenarios, covering the range of 5G mobility management procedures.
• Network node and computer program claims. Coverage extends to both the hardware apparatus (radio network nodes) and software implementations, important for licensing across both equipment manufacturers and network operators.

Who Is Behind It?

The applicant is Telefonaktiebolaget LM Ericsson (publ), the Swedish telecommunications giant and one of the world’s leading 5G infrastructure providers and standards contributors. The named inventors are Filip Barac, Oumer Teyeb, Gunnar Mildh, Paul Schliwa-Bertling, and Ajmal Muhammad, all researchers with expertise in wireless network architecture and 5G standardisation. This application is a divisional of AU 2024204005, which traces back through PCT/SE2021/050590 (published as WO2021/256982), placing the original invention in 2021. The Australian patent attorney is AJ Park in Wellington.

Why It Matters

Mobile relay technology is central to the economics of 5G deployment. Running optical fibre to every cell site in dense urban areas, rural zones, and on transport infrastructure is prohibitively expensive; wireless backhaul via IAB nodes is the alternative. But mobile IAB — relays that move with trains, buses, or maritime vessels — requires exactly the kind of compound handover this patent addresses. Australia, with vast distances, an extensive rail network, and a growing demand for connectivity on regional transport, has a direct stake in mobile relay technology. Ericsson’s position as a primary 5G equipment supplier and its active role in 3GPP standardisation means patents in this family are potentially essential to IAB implementations worldwide, with licensing implications for every network operator deploying 5G relay nodes.

Related Concepts

This application sits within the broader field of 5G New Radio network architecture, where relay-based coverage extension reduces the need to run fibre to every base station. The concept of mobile relay nodes – mounted on trains, buses, or vessels – is one of the more demanding use cases defined within 3GPP Release 16 and later, because the relay itself moves through cells while simultaneously serving downstream devices.

Managing the full tree of dependent connections during a handover is a problem that grows directly from the Integrated Access and Backhaul architecture. Patents covering the signalling protocols that orchestrate these compound handovers have direct relevance to essential patent declarations and licensing across all 5G network equipment vendors deploying IAB infrastructure.

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AU 2026201829 was published in the Australian Official Journal of Patents on 2 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.