Fronthaul Delay Measurement for CU-DU Transmission Timing

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Solution Overview

Problem

The existing Common Public Radio Interface (CPRI) interface between Baseband Unit (BBU) and Remote Radio Unit (RRU) in 5G New Radio (NR) communication systems faces challenges with high transmission rates and bandwidth demands, leading to increased deployment costs and transmission delays, especially with the separation of control and user planes and delay-sensitive/insensitive functions.

Innovation Solution

A fronthaul network interface is designed to measure and optimize transmission delays between Centralized Units (CUs) and Distributed Units (DUs) by gathering and computing delay information using timestamps and average values, with separate control and user planes, enabling self-optimization and improved network performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the CPRI interface is used to connect BBU and RRU in 5G NR systems, then high transmission rates and bandwidth capacity are achieved, but transmission delay increases and deployment cost increases

Engineering Contradiction:
Improvetransmission rateVSAvoidtransmission delay
Core Design Contradiction:
SpeedVSLoss of time

Solution Approach 1:

The patent segments the base station into Centralized Unit (CU) and Distributed Unit (DU) with separate control plane and user plane interfaces. The fronthaul interface connects CU and DU specifically for user plane data, while control plane communications use a separate interface. This segmentation allows optimization of each interface for its specific function, reducing overall transmission delay while maintaining high transmission rates for user data.

Inventive Principle:
Principle #1Segmentation

2Speed

If the CPRI interface is used to connect BBU and RRU in 5G NR systems, then high transmission rates and bandwidth capacity are achieved, but deployment cost increases

Engineering Contradiction:
Improvetransmission rateVSAvoiddeployment cost
Core Design Contradiction:
SpeedVSEase of manufacture

Solution Approach 1:

The patent divides the base station functionality into CU and DU that can be deployed independently. The CU can be located in a centralized data center while DUs are deployed at remote locations, reducing the need for expensive high-capacity CPRI interfaces at every site. This segmentation enables flexible deployment architectures that reduce overall deployment costs while maintaining high transmission rates where needed.

Inventive Principle:
Principle #1Segmentation

3Adaptability or versatility

If control and user planes are separated in 5G NR systems, then network flexibility and service quality are improved, but system complexity increases

Engineering Contradiction:
Improvenetwork flexibilityVSAvoidsystem complexity
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent implements control plane and user plane separation by creating distinct interfaces: F1-C for control plane communications and F1-U for user plane data. This segmentation allows independent optimization and management of control and data traffic, improving network flexibility and service quality. The modular architecture enables flexible deployment while managing complexity through standardized interface definitions and protocols.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP3777365B1Measuring transmission delay
Publication Date: 2025.11.26 ZTE CORP
  • EP3777365B1 patent drawingFigure 1A~1B
  • EP3777365B1 patent drawingFigure 2A
  • EP3777365B1 patent drawingFigure 2B

AI summary

An example technique for communicating transmission delay includes receiving, at a first communication node, delay information from a second communication node for data packets transmitted from the second communication node to the first communication node, determining, by the first communication node, a transmission delay of the data packets based on the delay information, receiving, at the first communication node, a first message from a third communication node requesting the transmission delay of the data packets; and transmitting, from the first communication node in response to the first message, a second message to the third communication node, the second message including the transmission delay for the data packets.