L1/L2 Triggered Mobility Handover Timing Advance

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Solution Overview

Problem

Current 5G mobile communication systems face delays during cell change procedures due to the need for uplink synchronization and random access, which can lead to increased latency and inefficiencies in handover processes.

Innovation Solution

The proposed method involves performing uplink synchronization on target cells in advance, using an L1/L2 triggered mobility (LTM) medium access control control element (MAC CE) that includes a timing advance (TA) value or a random access channel (RACH)-less handover indicator, thereby reducing the delay time during handovers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If uplink synchronization and random access are performed during handover, then reliable uplink connection is established, but handover delay time increases

Engineering Contradiction:

Improveuplink connection reliabilityVSAvoidhandover delay time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by performing uplink synchronization before handover using L1/L2 triggered mobility MAC CE with TA values. The UE receives and applies the TA value in advance, establishing uplink synchronization with the target cell before actual handover occurs, thereby eliminating the need for post-handover random access and reducing handover delay.

Inventive Principle:

Principle #10Preliminary action

2Speed

If RACH-less handover is performed, then handover speed increases, but uplink synchronization reliability may be compromised

Engineering Contradiction:

Improvehandover speedVSAvoiduplink synchronization reliability

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The patent performs uplink synchronization in advance through L1/L2 triggered mobility MAC CE reception, which includes TA values that enable the UE to synchronize with the target cell before handover. This preliminary synchronization ensures reliability while enabling RACH-less handover for speed.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent incorporates feedback mechanisms where the gNB provides TA values and handover indicators through MAC CE, and the UE applies these parameters to maintain accurate uplink timing. The feedback loop ensures that uplink synchronization reliability is maintained even when using RACH-less handover for faster switching.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS20250031109A1Method and device for operating uplink time adjustment timer during l1/l2-based handover in mobile communication system

Publication Date: 2025.01.23 SAMSUNG ELECTRONICS CO LTD

AI summary

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. According to one embodiment, a method for operating a user equipment (UE) in a wireless communication system may comprise receiving an L1/L2 triggered mobility (LTM) medium access control control element (MAC CE) from a base station, determining whether the LTM MAC CE includes a timing advance (TA) value or a random access channel (RACH)-less handover indicator, and when the LTM MAC CE includes the TA value or the RACH-less handover indicator, performing a handover procedure to a target cell based on the TA value or the RACH-less handover indicator.