2-Step RACH Timing Control Without Closed-Loop Alignment

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing wireless communication systems face interference issues in 2-step random access channels (RACH) due to the lack of closed loop timing alignment information, particularly in scenarios where 4-step RACH is not available, leading to degraded performance.

Innovation Solution

User equipment (UE) determines transmission gap adjustments (TGA) based on downlink timing estimation and reference signals, allowing it to transmit messages in a 2-step RACH procedure without relying on closed loop TA information, while base stations receive and respond with appropriate messages.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If 2-step RACH is used without closed loop TA information, then access speed is improved, but timing alignment accuracy deteriorates

Engineering Contradiction:

Improveaccess speedVSAvoidtiming alignment accuracy

Core Design Contradiction:

SpeedVSMeasurement precision

Solution Approach 1:

The system performs preliminary timing alignment by estimating downlink timing based on reference signals before the random access procedure. The UE determines a transmission gap adjustment based on this estimation and applies it to the msgA transmission, preparing the timing in advance without requiring closed loop feedback

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces transmission gap adjustment as an intermediary mechanism that bridges the gap between open loop timing estimation and actual uplink transmission. This intermediary parameter allows the UE to compensate for timing offsets without direct closed loop TA feedback from the base station

Inventive Principle:

Principle #24Intermediary (Mediator)

2Object-affected harmful factors

If transmission gap adjustment is applied to msgA, then interference is reduced, but device complexity increases

Engineering Contradiction:

ImproveinterferenceVSAvoiddevice complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The UE performs self-service timing adjustment by autonomously estimating downlink timing from reference signals and calculating the appropriate transmission gap adjustment. This self-service approach eliminates the need for complex closed loop feedback mechanisms while still achieving interference reduction through proper timing alignment

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS12477494B2Open loop timing control for 2-step RACH

Publication Date: 2025.11.18 QUALCOMM INC

AI summary

In some aspects, a user equipment (UE) determines a transmission gap adjustment (TGA) for a first message (msgA) of a 2 step random access channel (RACH) procedure based on measurement of a reference signal transmitted by a base station as well as the radio resource configuration (RRC) configurations for msgA. In other aspects, a base station transmits a system information block (SIB) or RRC signaling that indicates at least one possible configuration of the TGA, and UEs determine the TGA depending on RRC state. Connected mode UEs having a timing alignment (TA) timer running may determine the TGA based on a previous TA. UEs in other RRC modes determine the TGA based on the possible configuration transmitted in the SIB or RRC signaling. Advantageously, 2 step RACH UEs are able to communicate with the base station without the closed loop TA information provided by a 4 step RACH.