C-RAN Synchronization Using Radio Environment Monitoring

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Synchronizing a cloud radio access network (C-RAN) to a Network Time Protocol (NTP) grandmaster clock is challenging due to network delays and jitter, leading to prolonged convergence times and initialization periods.

Innovation Solution

The implementation of a radio environment monitoring (REM)-based procedure to estimate an initial phase error between the baseband controller and neighboring base stations, allowing quicker synchronization by using timing and frequency errors determined through IEEE 1588 synchronization and REM processes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If NTP synchronization is implemented in a C-RAN, then timing precision of 20-30 parts-per-billion is achieved, but convergence time is prolonged due to network delays and jitter

Engineering Contradiction:

Improvetiming precisionVSAvoidconvergence time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent performs REM-based frequency error estimation before NTP synchronization to obtain an initial phase error estimate. This preliminary action provides a head start for the NTP synchronization process, allowing the system to converge to the required 20-30 parts-per-billion timing precision within 1-2 minutes instead of taking much longer due to network delays and jitter.

Inventive Principle:

Principle #10Preliminary action

2Ease of operation

If traditional synchronization methods are used, then initialization is straightforward, but Plug and Play initialization period is prolonged

Engineering Contradiction:

Improveinitialization simplicityVSAvoidinitialization period

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The system performs radio environment monitoring and frequency error estimation during the initialization phase, before full synchronization is required. This preliminary action enables the baseband controller to start NTP synchronization with an accurate initial phase error estimate, significantly reducing the Plug and Play initialization period while maintaining ease of operation through automated procedures.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The C-RAN system performs self-synchronization by automatically conducting REM procedures and using the estimated frequency errors to initialize NTP synchronization without requiring manual configuration or intervention. This self-service approach accelerates Plug and Play initialization while keeping the system easy to deploy and operate.

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11134460B2Synchronizing a cloud radio access network to a network time protocol reference clock

Publication Date: 2021.09.28 OUTDOOR WIRELESS NETWORKS LLC

AI summary

A cloud radio access network (C-RAN) includes a baseband controller communicatively coupled to a plurality of radio points (RP) via a fronthaul network. Each of the plurality of RPs are configured to exchange radio frequency (RF) signals with at least one user equipment (UE). At least one of the RPs is configured to determine a timing difference while synchronizing to the baseband controller; and determine a frequency error, between the RP and a neighboring base station, based on a radio environment monitoring (REM) procedure. A phase error is determined, between the baseband controller and the neighboring base station, phase error is determined based on the timing difference for the RP and baseband controller, and the frequency error for the RP and the neighboring base station.