Fronthaul Layer Subgrouping for Lower C-Plane Messaging Overhead

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Solution Overview

Problem

The existing O-RAN WG4 open-fronthaul CUS specification's layer grouping method is inefficient for conveying WD-specific DMRS configuration parameters and measurement data, leading to increased signaling overhead and complexity in SU-MIMO and MU-MIMO scenarios, particularly with large eAxC ID groups.

Innovation Solution

Implement flexible layer grouping by defining subgroups within eAxC ID groups using M-plane configuration, allowing for subgroup specification through section extensions, which enable efficient scheduling and measurement reporting for both SU-MIMO and MU-MIMO, reducing the number of C-plane messages and overhead.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If control plane messages are sent over the fronthaul interface, then centralized control and management functions are enabled, but fronthaul interface bandwidth is consumed and message transmission delays occur

Engineering Contradiction:
Improvecentralized control capabilityVSAvoidfronthaul bandwidth consumption
Core Design Contradiction:
Adaptability or versatilityVSQuantity of substance

Solution Approach 1:

The patent segments control plane messages into different categories (e.g., critical vs. non-critical, frequent vs. infrequent) and routes them through different paths or mechanisms. Critical messages use the fronthaul interface with higher priority, while non-critical messages are handled through alternative routes or deferred, thereby reducing overall fronthaul bandwidth consumption while maintaining centralized control capability.

Inventive Principle:
Principle #1Segmentation

2Adaptability or versatility

If control plane messages are sent over the fronthaul interface, then centralized control and management functions are enabled, but message transmission delays increase

Engineering Contradiction:
Improvecentralized control capabilityVSAvoidmessage transmission delay
Core Design Contradiction:
Adaptability or versatilityVSLoss of time

Solution Approach 1:

The patent introduces intermediary elements such as buffer queues, priority schedulers, and message aggregation mechanisms between the control plane applications and the fronthaul interface. These intermediaries manage message flow, prioritize critical communications, and batch non-urgent messages, thereby reducing transmission delays while preserving centralized control functionality.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Adaptability or versatility

If multiple control plane applications communicate with multiple network elements, then comprehensive control is achieved, but message routing complexity increases

Engineering Contradiction:
Improvecontrol coverageVSAvoidmessage routing complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements a universal message routing framework that can handle multiple control plane applications and network elements through a single, standardized interface and routing logic. This multi-functional routing system uses common protocols, shared message formats, and centralized routing tables, thereby achieving comprehensive control coverage while reducing routing complexity compared to dedicated routing paths for each application-element pair.

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP4696099B1Flexible layer grouping for fronthaul control plane messaging
Publication Date: 2026.05.20 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
  • EP4696099B1 patent drawingFigure 1
  • EP4696099B1 patent drawingFigure 2
  • EP4696099B1 patent drawingFigure 3

AI summary

A method, system and apparatus are disclosed. A method in a network node is described. The network node includes a distributed unit (DU), where the DU is configured to communicate with a radio unit (RU) via a fronthaul interface (FI). The FI is in a signal path between the DU and the RU. The method includes selecting a plurality of identifiers to create one or more subgroups within an identifier group. The identifier group is represented by a group identifier, and each identifier represents a processing entity in the RU. The method also includes creating the one or more subgroups within the identifier group and determining one or more section extensions usable by one or more control plane (C-plane) messages sent with the group identifier to specify one subgroup of the one or more subgroups. The one subgroup is associated to a C-plane section.