Random Access Completion Rules for LTM Cell Switch Recovery

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Solution Overview

Problem

In scenarios where a random access triggered by the Physical Downlink Control Channel (PDCCH) order during L1L2 Triggered Mobility (LTM) cell switch results in the absence of a random access response (RAR), the terminal device and network device are unable to determine the completion of the random access process, hindering further processing such as re-initiation or service provision.

Innovation Solution

A method for the terminal device and network device to perform first preset processing after sending a random access preamble, determining completion based on a preset strategy, including starting or not starting response windows, and responding to message receipt or timeouts to confirm process completion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the terminal device sends a random access preamble during LTM cell switch without receiving a random access response, then the cell switch process can be initiated, but the terminal and network device cannot determine whether the random access is completed

Engineering Contradiction:
Improvecell switch speedVSAvoidrandom access completion status
Core Design Contradiction:
ProductivityVSLoss of information

Solution Approach 1:

The patent introduces a feedback mechanism where the terminal device monitors for a trigger message (such as a MAC CE or DCI) from the network device that indicates whether the random access process is considered completed. This feedback loop allows both the terminal and network device to synchronize their understanding of the random access status, resolving the information loss problem while maintaining fast cell switching capability

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent establishes predetermined strategies and preset processing rules that are configured in advance for handling random access completion determination. These pre-configured rules allow the terminal and network device to quickly determine random access status without requiring real-time negotiation, thus maintaining high cell switch speed while eliminating the completion status uncertainty

Inventive Principle:
Principle #10Preliminary action

2Reliability

If the terminal device cannot determine random access completion, then it cannot perform further processing such as re-initiating random access or obtaining network services

Engineering Contradiction:
Improverandom access process reliabilityVSAvoidprocessing logic complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The feedback mechanism provides explicit completion status information from the network device to the terminal device. This clear feedback signal simplifies the terminal's processing logic by providing a definitive indicator of random access completion, eliminating the need for complex uncertainty handling while improving process reliability

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The patent changes the parameter of random access completion determination from an implicit state (requiring complex inference) to an explicit state (indicated by trigger messages). This parameter change transforms the completion status from an uncertain condition that requires complex processing logic into a clear signal that simplifies device operation while enhancing reliability

Inventive Principle:
Principle #35Parameter changes

3Productivity

If the network device cannot complete random access with the terminal, then it cannot execute connection configuration or provide services

Engineering Contradiction:
Improveservice provision efficiencyVSAvoidrandom access status information
Core Design Contradiction:
ProductivityVSLoss of information

Solution Approach 1:

The feedback mechanism enables the network device to receive explicit completion status information from the terminal device. This information feedback allows the network device to reliably determine whether to proceed with connection configuration and service provision, improving service provision efficiency by eliminating delays caused by status uncertainty

Inventive Principle:
Principle #23Feedback

Solution Approach 2:

The pre-configured strategies and preset processing rules allow the network device to quickly assess random access completion status and immediately proceed with appropriate actions (connection configuration or service provision). This preliminary preparation of processing logic eliminates delays while maintaining accurate status information

Inventive Principle:
Principle #10Preliminary action

Data Source

PatentEP4648531A1Processing method, communication device, and storage medium
Publication Date: 2025.11.12 SHENZHEN TRANSSION HLDG CO LTD
  • EP4648531A1 patent drawingFigure 1
  • EP4648531A1 patent drawingFigure 2
  • EP4648531A1 patent drawingFigure 3~4

AI summary

The present application provides a processing method, a communication device and a storage medium. The processing method includes: performing, via a terminal device, a first preset processing in response to sending a random access preamble, and determining whether a preset process is completed according to a preset strategy. Through the technical solution of the present application, the terminal device and/or the network device can determine whether random access is completed in the target cell, so as to perform further processing, such as having a corresponding processing flow after determining that the random access is not completed.