Uplink Synchronization Maintenance for Deactivated Secondary Cell Group

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Solution Overview

Problem

In wireless communications, maintaining uplink synchronization with a secondary cell group (SCG) while it is deactivated or dormant is challenging, as existing methods require frequent random access procedures for reactivation, leading to latency and power consumption issues.

Innovation Solution

A wireless transmit/receive unit (WTRU) is configured to receive UL configuration information for maintaining synchronization, including SRS and RACH preambles, and can keep a time alignment timer running during SCG deactivation, allowing for efficient UL signal transmission and synchronization status indication, enabling faster SCG reactivation without the need for continuous monitoring or frequent random access procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If frequent random access procedures are used for SCG reactivation, then UL synchronization can be maintained, but latency and power consumption increase

Engineering Contradiction:

ImproveUL synchronization maintenanceVSAvoidlatency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by keeping the time alignment timer running during SCG deactivation and pre-configuring UL signals (SRS and RACH preambles) that can be transmitted immediately when needed. This allows the WTRU to maintain UL synchronization without requiring frequent random access procedures, thereby reducing latency while ensuring reliability

Inventive Principle:

Principle #10Preliminary action

2Reliability

If frequent random access procedures are used for SCG reactivation, then UL synchronization can be maintained, but power consumption increases

Engineering Contradiction:

ImproveUL synchronization maintenanceVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent applies preliminary action by maintaining the time alignment timer and pre-configuring UL signals during the deactivated state. This preparation eliminates the need for power-intensive random access procedures during reactivation, significantly reducing power consumption while maintaining synchronization reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements periodic action through the time alignment timer that continues to run during SCG deactivation. This periodic mechanism ensures synchronization is maintained without requiring continuous monitoring or frequent random access, thereby reducing power consumption while maintaining reliability

Inventive Principle:

Principle #19Periodic action

3Use of energy by moving object

If SCG is deactivated, then power consumption is reduced, but UL synchronization cannot be maintained

Engineering Contradiction:

Improvepower consumptionVSAvoidUL synchronization

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies preliminary action by keeping the time alignment timer running and pre-configuring UL signals before SCG deactivation. This allows the system to enter low-power state while maintaining synchronization capability, resolving the contradiction between power savings and synchronization reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements continuity of useful action by maintaining the time alignment timer operation during SCG deactivation. This continuous timer ensures UL synchronization is preserved even when the SCG is deactivated and power consumption is reduced, allowing rapid reactivation when needed

Inventive Principle:

Principle #20Continuity of useful action

4Reliability

If continuous monitoring of SCG is performed, then UL synchronization can be maintained, but power consumption increases

Engineering Contradiction:

ImproveUL synchronizationVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent extracts the essential synchronization maintenance function from continuous monitoring. By keeping only the time alignment timer running and pre-configuring UL signals, the system removes the power-intensive continuous monitoring requirement while preserving synchronization reliability, thereby reducing power consumption

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS20240323873A1Methods and systems for efficient uplink (UL) synchronozation maintenance with a deactivated secondary cell group (SCG)

Publication Date: 2024.09.26 INTERDIGITAL PATENT HOLDINGS INC

AI summary

A wireless transmit/receive unit (WTRU) may receive indication information indicating an uplink (UL) configuration and one or more triggering conditions for transmission of UL signals. Based on reception of a deactivation command or fulfillment of a condition for WTRU-triggered deactivation of a secondary cell group (SCG), the WTRU may deactivate the SCG. Based on the UL configuration and the fulfillment of the one or more triggering conditions, the WTRU may transmit the UL signals via the SCG. The WTRU may receive, via a master cell group (MCG), an in-synch or out-of-synch indication for the SCG. Based on the reception of the out-of-synch indication including a timing advance (TA) delta value, the WTRU may update a UL TA towards the SCG based on the TA delta value. Using the updated UL TA towards the SCG, the WTRU may transmit one or more subsequent UL signals via the SCG.