Two-Step RACH MsgA Beam Prediction via SSB Indices

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Solution Overview

Problem

Current wireless communication systems face challenges in efficiently managing beam prediction during the two-step random access channel procedure, leading to sub-optimal beam selection and potential communication interruptions, especially before RRC connection setup.

Innovation Solution

A method where user equipment (UE) transmits a message type-A identifying synchronization signal blocks (SSBs) and reference signal received powers (RSRPs) in a two-step random access channel procedure, allowing the base station to select and confirm a downlink beam, enabling dynamic beam indication and reducing the likelihood of communication interruptions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional beam selection methods are used in two-step RACH procedure, then beam selection can be performed, but sub-optimal beam selection occurs leading to communication interruptions

Engineering Contradiction:

Improvecommunication reliabilityVSAvoidbeam selection accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The UE performs beam measurement and reports SSB indices and RSRP values to the base station before the RRC connection setup is complete. This preliminary beam information exchange enables the base station to determine an appropriate downlink beam for communication before the connection is fully established, preventing communication interruptions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The UE provides feedback to the base station by reporting measured SSB indices and corresponding RSRP values in the msgA transmission. The base station uses this feedback to determine the optimal downlink beam and provides confirmation to the UE, creating a closed-loop feedback mechanism that ensures accurate beam selection.

Inventive Principle:

Principle #23Feedback

2Measurement precision

If detailed SSB information is transmitted in msgA, then beam prediction accuracy improves, but communication resource utilization increases

Engineering Contradiction:

Improvebeam prediction accuracyVSAvoidcommunication resource utilization

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent extracts only the essential beam identification information (SSB indices and RSRP values) from the complete beam measurement data and transmits only this extracted information to the base station in msgA. This selective extraction provides sufficient beam prediction accuracy while minimizing the amount of data transmitted and the associated resource consumption.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS20250008570A1Two-step random access channel procedure

Publication Date: 2025.01.02 QUALCOMM INC

AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit a message type-A (msgA), of a two-step random access channel (RACH) procedure, identifying information associated with a plurality of synchronization signal blocks (SSBs), wherein the information includes at least one of a plurality of SSB indices associated with the plurality of SSBs or a plurality of reference signal received powers (RSRPs) associated with the plurality of SSBs. The UE may receive a message type-B (msgB) in the two-step RACH procedure, identifying a downlink beam associated with an SSB based at least in part on transmitting the msgA. The UE may transmit a response message, based at least in part on receiving the msgB, indicating a confirmation of an SSB index identified in the msgB or indicating a reversion to a different SSB index. Numerous other aspects are described.