Inter-Cell Mobility PRACH Configuration for Faster Cell Switching

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Solution Overview

Problem

Current inter-cell mobility designs in new radio (NR) systems suffer from undesirable latency and signaling overhead due to the inability of user equipment (UE) to transmit a PRACH preamble to a non-serving cell, necessitating a random access procedure and enlarging cell switching latency.

Innovation Solution

A wireless communication method and apparatus that enables UE to receive a configuration of candidate cells and RACH settings from a base station, allowing PRACH preamble transmissions to non-serving cells, with power ramping adjustments for reduced latency and signaling overhead.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the current PDCCH-order PRACH mechanism is used for inter-cell mobility, then the UE can transmit PRACH to the serving cell, but the UE cannot transmit PRACH to non-serving cells, resulting in enlarged cell switching latency

Engineering Contradiction:

Improvecell switching latencyVSAvoidPRACH transmission capability to non-serving cells

Core Design Contradiction:

Loss of timeVSAdaptability or versatility

Solution Approach 1:

The base station configures the UE with a list of candidate cells and their RACH parameters in advance before mobility switching is needed. This preliminary configuration enables the UE to immediately transmit PRACH to non-serving cells when mobility is triggered, eliminating the need for random access procedure setup during switching and thereby reducing cell switching latency

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The RACH configuration is segmented and specifically tailored for non-serving cells in the candidate cell list. By providing separate RACH parameters for non-serving cells rather than using serving cell parameters, the system enables targeted PRACH transmission to specific non-serving cells, improving both the adaptability and efficiency of inter-cell mobility

Inventive Principle:

Principle #1Segmentation

2Reliability

If random access procedure is performed to non-serving cell during cell switching, then the UE can establish connection, but the signaling overhead and latency are increased

Engineering Contradiction:

Improveconnection establishmentVSAvoidcell switching latency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

RACH parameters including preamble formats, time resources, and frequency resources are pre-configured for non-serving cells before mobility switching. When the UE needs to switch cells, it can directly use these pre-configured parameters to transmit PRACH, bypassing the need to perform a complete random access procedure setup and thereby reducing latency while maintaining connection reliability

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention allows the UE to skip the initial random access procedure setup steps by directly transmitting PRACH to non-serving cells using pre-configured parameters. This skipping of unnecessary procedural steps reduces signaling overhead and accelerates the cell switching process while still ensuring reliable connection establishment

Inventive Principle:

Principle #21Skipping (Rushing through)

Data Source

PatentUS20260020077A1Wireless communication method of inter-cell mobility and user equipment

Publication Date: 2026.01.15 GUANGDONG OPPO MOBILE TELECOMMUNICATIONS CORP LTD

AI summary

A wireless communication method of inter-cell mobility, by a user equipment (UE) includes receiving, from a base station, a configuration of a list of candidate cells for inter-cell mobility, receiving, from the base station, a random access channel (RACH) configuration of each candidate cell in the list of candidate cells, and receiving, from the base station, a signaling used to indicate the UE to perform a physical random access channel (PRACH) preamble transmission to a candidate cell in the list of candidate cells.