Lower-Layer Split RAN Synchronization Without CSR Port Upgrades

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Solution Overview

Problem

Existing synchronization plane configurations in Lower-Layer Split (LLS) deployments face challenges in providing nanosecond-scale accuracy and scalability, particularly due to limited port availability on Cell Site Routers (CSRs), which can be costly and labor-intensive to upgrade.

Innovation Solution

Implementing a combination of synchronization configurations, including dual synchronization configurations supported by a containerized Cell Site Router (CSR) and Precision Time Protocol (PTP), to synchronize Radio Units (RUs) and Distributed Units (DUs) within a fronthaul network, allowing for efficient timing synchronization without the need for physical CSR upgrades.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If physical CSR upgrades are implemented to improve synchronization port availability, then synchronization capability is improved, but cost and labor intensity increase

Engineering Contradiction:

Improvesynchronization capabilityVSAvoidcost and labor intensity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent creates a virtual copy of the CSR functionality through a containerized virtual CSR that runs on existing physical infrastructure. This virtual CSR provides the necessary synchronization ports and PRTC functionality without requiring physical hardware upgrades, thereby resolving the contradiction between improving synchronization capability and avoiding increased cost and labor intensity.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The patent replaces the mechanical/physical CSR hardware system with a software-based virtual CSR implementation using containerization technology. This substitution allows the system to achieve enhanced synchronization capabilities through software rather than physical hardware modifications, eliminating the need for costly and labor-intensive physical upgrades.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Adaptability or versatility

If traditional synchronization configurations are used, then implementation simplicity is maintained, but scalability is limited

Engineering Contradiction:

ImprovescalabilityVSAvoidsynchronization configuration complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The containerized virtual CSR provides multiple synchronization configurations (dual synchronization modes, PRTC options, different fronthaul architectures) within a single universal platform. This allows the system to adapt to various deployment scenarios and scale flexibly without requiring separate hardware configurations for each scenario, thereby improving scalability while managing complexity through software abstraction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements dynamic synchronization configurations where the virtual CSR can adapt its behavior based on operational requirements. The system can dynamically switch between different synchronization modes (dual sync configurations), adjust PRTC settings, and reconfigure fronthaul connections without physical hardware changes, enabling scalable deployment while maintaining manageable complexity through software-based flexibility.

Inventive Principle:

Principle #15Dynamics

3Measurement precision

If dual synchronization configurations are implemented, then timing accuracy is improved, but configuration complexity increases

Engineering Contradiction:

Improvetiming accuracyVSAvoidconfiguration complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The containerized virtual CSR acts as an intermediary that manages dual synchronization configurations. It abstracts the complexity of implementing and coordinating multiple synchronization paths, PRTC instances, and timing sources behind a unified software interface. This allows the system to achieve nanosecond-scale timing accuracy through dual sync configurations while hiding the configuration complexity from operators and administrators.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20260040245A1Synchronization management in lower-layer split radio access networks

Publication Date: 2026.02.05 DISH WIRELESS LLC

AI summary

Techniques for synchronizing components of a Lower-Layer Split Radio Access Network (RAN) are provided. In one example, a RAN includes a Cell Site Router (CSR). A first Distributed Unit (DU) and a first Radio Unit (RU) managed by the first DU are both connected to the CSR and synchronized to a Primary Reference Time Clock (PRTC) via reference timing information received from the CSR. A second DU connected to the CSR, the first DU, or both, is synchronized to the PRTC via reference timing information received from the CSR or the first DU. A second RU connected to, and managed by, the second DU, is synchronized to the PRTC via reference timing information received from the second DU.