Concurrent RACH Procedures for Layer 1/2 Mobility

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Solution Overview

Problem

In wireless communication systems, particularly during Layer 1 or Layer 2 triggered mobility, the concurrent performance of random access channel (RACH) procedures between a serving cell and a candidate cell can lead to collisions, reducing effectiveness and interfering with operation, as existing technologies often require termination of one RACH procedure to initiate another.

Innovation Solution

The method involves initiating a second RACH procedure with a candidate cell either after the first RACH procedure has terminated or before it completes, while differentiating the random access response (RAR) to avoid ambiguity and reduce complexity, allowing concurrent performance of multiple RACH procedures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a first RACH procedure is initiated with a serving cell, then timing advance acquisition is performed, but if a trigger for a second RACH procedure with a candidate cell is received prior to terminating the first procedure, collision occurs reducing effectiveness

Engineering Contradiction:

ImproveRACH procedure effectivenessVSAvoidmobility execution speed

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent implements dynamic state tracking for RACH procedures, where the system transitions between different operational states (ongoing, terminated, colliding) based on real-time conditions. The UE dynamically adjusts its behavior by detecting whether a first RACH procedure is ongoing before initiating a second procedure, and by identifying colliding RARs through state-aware differentiation logic.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system employs feedback mechanisms where the UE monitors the status of ongoing RACH procedures and uses this information to make informed decisions about initiating new procedures. The network node provides feedback through triggered indications that help the UE distinguish between RARs from different RACH procedures, enabling reliable concurrent operation through adaptive response to system state.

Inventive Principle:

Principle #23Feedback

2Loss of time

If concurrent RACH procedures are performed with serving cell and candidate cell, then timing advance acquisition is timely, but collision occurs interfering with operation

Engineering Contradiction:

Improvetiming advance acquisition timeVSAvoidRACH procedure reliability

Core Design Contradiction:

Loss of timeVSReliability

Solution Approach 1:

The patent applies preliminary action by having the UE check whether a first RACH procedure is ongoing before initiating a second RACH procedure. This preventive check avoids unnecessary collisions by establishing a clear operational sequence. Additionally, the system preliminarily establishes differentiation rules for identifying RARs from different procedures, ensuring reliable timing advance acquisition without operational interference.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If one RACH procedure is terminated to initiate another, then collision is avoided, but delays occur in acquiring timing adjustments

Engineering Contradiction:

ImproveRACH procedure reliabilityVSAvoidtiming adjustment acquisition delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent enables continuous useful action by allowing multiple RACH procedures to overlap in time rather than requiring sequential execution. The UE maintains continuity of mobility-related operations by initiating second RACH procedures without waiting for first procedures to complete, while using state-aware RAR differentiation to ensure reliable timing advance acquisition from both procedures simultaneously.

Inventive Principle:

Principle #20Continuity of useful action

Data Source

PatentUS20240340961A1Random access channel collision during timing adjustment acquisition for layer 1 or layer 2 triggered mobility

Publication Date: 2024.10.10 QUALCOMM INC

AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may initiate a first random access channel (RACH) procedure with a serving cell of the UE. The UE may receive, prior to terminating the first RACH procedure, a trigger for a second RACH procedure with a candidate cell of the UE. The UE may initiate the second RACH procedure with the candidate cell. Numerous other aspects are described.