Unlicensed NR Small Data Transmission with TA Validation and LBT

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Solution Overview

Problem

Communicating small amounts of data in 5G NR networks while in a radio resource control (RRC) connected state is inefficient due to signaling overhead, and unlicensed radio frequency bands are prone to interference from other wireless devices, disrupting timing synchronization and uplink data transmission.

Innovation Solution

A wireless device manages small data transmission (SDT) in an RRC inactive state using an unlicensed RF band by performing timing advance validation, listen before talk (LBT) procedures, and managing interference through delayed or discarded data transmission based on successful synchronization and channel availability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a wireless device transmits small amounts of data while in RRC connected state, then data transmission can occur, but signaling overhead increases reducing efficiency

Engineering Contradiction:

Improvedata transmission efficiencyVSAvoidsignaling overhead

Core Design Contradiction:

ProductivityVSLoss of information

Solution Approach 1:

The patent extracts the data transmission function from the RRC connected state and enables it to operate independently in the RRC inactive state through configured grant resources. This separation allows small data transmission without requiring full RRC connection establishment, thereby reducing signaling overhead while maintaining data transmission capability.

Inventive Principle:

Principle #2Taking out (Extraction)

2Adaptability or versatility

If a wireless device uses an unlicensed RF band for SDT, then spectrum utilization improves, but interference from other wireless devices disrupts timing synchronization and uplink transmission

Engineering Contradiction:

Improvespectrum utilizationVSAvoidtiming synchronization reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements preliminary actions by performing LBT procedures before downlink synchronization signal transmission and before uplink data transmission. These advance channel assessments ensure that transmissions only occur when the channel is clear, preventing interference-induced synchronization failures and maintaining reliability in unlicensed bands.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent employs feedback mechanisms where the wireless device monitors downlink synchronization signals to detect timing synchronization status and adjusts uplink transmission timing accordingly. This closed-loop feedback ensures that timing synchronization is maintained despite potential interference in unlicensed RF bands.

Inventive Principle:

Principle #23Feedback

3Measurement precision

If a wireless device performs timing synchronization acquisition before CG-SDT occasion, then uplink transmission timing accuracy improves, but interference from other devices prevents successful synchronization

Engineering Contradiction:

Improvetiming synchronization accuracyVSAvoidinterference from other wireless devices

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent applies preliminary anti-action by implementing LBT procedures that detect and prevent interference before downlink synchronization signal transmission. By assessing channel availability in advance and canceling or delaying transmissions when interference is detected, the system protects timing synchronization acquisition from harmful interference effects.

Inventive Principle:

Principle #9Preliminary anti-action

4Reliability

If a wireless device performs LBT procedure before UL CG-SDT transmission, then channel availability is confirmed, but transmission delay increases if channel is occupied

Engineering Contradiction:

Improvechannel availability assuranceVSAvoidtransmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent implements dynamic adaptation by allowing the wireless device to flexibly adjust transmission timing based on LBT outcomes. If the channel is immediately available, transmission proceeds without delay. If the channel is occupied, the device dynamically waits for channel clearance or postpones transmission to the next available opportunity, optimizing the balance between reliability and timing.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS20260019971A1Managing small data transmission in unlicensed radio frequency band by wireless device

Publication Date: 2026.01.15 APPLE INC

AI summary

This application regards managing small data transmission (SDT) in an unlicensed radio frequency band by a wireless device while in a radio resource control (RRC) inactive state. The wireless device performs a timing advance (TA) validation procedure using measured reference signal received power (RSRP) values. The wireless device transmits uplink (UL) data during a configured grant SDT (CG-SDT) occasion after DL timing synchronization is successfully acquired and after confirming a portion of the unlicensed RF band is unoccupied. The wireless device can discard or delay transmission of the UL data to a subsequent CG-SDT occasion when DL timing synchronization is not successfully acquired before the CG-SDT occasion or when encountering a listen before talk (LBT) failure indicating the CG-SDT occasion cannot be used. The wireless device can re-measure RSRP values and re-validate a TA value when a time elapsed from the previous TA validation exceeds a TA time threshold.