SSB QCL Determination in Unlicensed 5G NR Using PBCH Bit Fields

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Solution Overview

Problem

In 5G NR systems operating on unlicensed spectra, determining the Quasi-co-located (QCL) relationship between Synchronization Signal Blocks (SSBs) is challenging due to unpredictable channel availability, affecting system performance.

Innovation Solution

A method for determining the QCL relationship of SSBs by using bit fields and parameters in the Physical Broadcast Channel (PBCH) of the SSB, including an extended SSB index and a parameter N, to identify the QCL relationship between SSBs, even in unlicensed spectra.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LBT is performed on unlicensed spectrum channels, then channel access is achieved, but SSB transmission position becomes uncertain

Engineering Contradiction:

Improvechannel access reliabilityVSAvoidSSB transmission position uncertainty

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The network device pre-configures multiple candidate SSB transmission positions and informs the terminal device of these candidates before actual transmission. The terminal device can then identify the QCL relationship based on received SSBs from these pre-defined positions, resolving the timing uncertainty caused by LBT without sacrificing channel access reliability.

Inventive Principle:

Principle #10Preliminary action

2Area of stationary object

If multiple SSBs are transmitted in unlicensed spectrum, then coverage is improved, but QCL relationship determination becomes difficult

Engineering Contradiction:

Improvecoverage areaVSAvoidQCL relationship information

Core Design Contradiction:

Area of stationary objectVSLoss of information

Solution Approach 1:

The terminal device uses the identified QCL relationship as feedback to perform combining and filtering operations on multiple SSBs. By determining which SSBs share a QCL relationship through the extended SSB index and parameter N, the terminal can effectively combine signals from multiple transmissions to improve coverage while maintaining accurate channel estimation.

Inventive Principle:

Principle #23Feedback

3Productivity

If SSB combining and filtering is performed, then system performance is improved, but incorrect QCL determination degrades performance

Engineering Contradiction:

Improvesystem performanceVSAvoidQCL relationship accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent replaces the traditional mechanical approach of fixed SSB positioning with an information-based system using extended SSB indices and parameter N conveyed through bit fields. This substitution allows flexible QCL relationship determination that adapts to unlicensed spectrum conditions, ensuring both high system performance through combining and high reliability through accurate QCL identification.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS12520255B2Wireless communication method, terminal device and network device

Publication Date: 2026.01.06 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD

AI summary

A wireless communication method, a terminal device and a network device are disclosed. The method includes: a terminal device receives a first SSB on an unlicensed spectrum; according to a first bit field and/or a second bit field in PBCH of the first SSB, determines an extended SSB index of the first SSB and/or a first parameter N for determining the QCL relationship, N is a positive integer, the bit position of the first bit field in PBCH is the same as that of a subcarrier interval bit field in PBCH on a licensed spectrum, and the bit position of the second bit field in PBCH is partially or completely the same as that of a subcarrier offset bit field in PBCH on the licensed spectrum; and determines the QCL relationship of the first SSB and other SSBs according to the extended SSB index of the first SSB and N.