PRACH Beam Reporting for MPE-Compliant Uplink Switching

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Solution Overview

Problem

Existing wireless communication systems face challenges in managing maximum permissible exposure (MPE) conditions, leading to unreliable beam reselection methods that negatively impact downlink performance and latency.

Innovation Solution

A two-step or three-step physical random access channel (PRACH) transmission mechanism is employed by user equipment (UE) to indicate satisfaction of MPE conditions, allowing for the selection and communication of an updated uplink beam that does not exceed MPE limits, while maintaining an active downlink beam to reduce latency and improve throughput.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If beam reselection methods are used to manage MPE conditions, then MPE compliance is improved, but downlink performance and latency deteriorate

Engineering Contradiction:
ImproveMPE complianceVSAvoiddownlink performance
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent segments the beam management process by maintaining separate uplink beam selection (independent of downlink beam) and downlink beam continuity. The UE can indicate MPE satisfaction for a downlink beam while using a different uplink beam, allowing downlink performance to be optimized independently from uplink MPE constraints.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent introduces an intermediary indication mechanism where the UE signals MPE condition satisfaction to the network. This intermediary signal allows the network to make informed decisions about beam pairing without directly changing the downlink beam, thus maintaining downlink performance while ensuring MPE compliance.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If beam reselection methods are used to manage MPE conditions, then MPE compliance is improved, but latency increases

Engineering Contradiction:
ImproveMPE complianceVSAvoidlatency
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent enables preliminary action by allowing the UE to indicate MPE condition satisfaction in advance. The network can prepare appropriate uplink beam configurations before actual transmission, avoiding last-minute beam changes that would increase latency.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The patent maintains continuity of useful action by keeping the downlink beam active and unchanged while only adjusting the uplink beam indication. This continuous downlink operation prevents interruptions and reduces latency compared to full beam reselection procedures.

Inventive Principle:
Principle #20Continuity of useful action

3Object-affected harmful factors

If different UL/DL beam paths are used, then interference avoidance is improved, but system complexity increases

Engineering Contradiction:
Improveinterference avoidanceVSAvoidsystem complexity
Core Design Contradiction:
Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent segments beam management into independent uplink and downlink components. The UE independently selects uplink beams for MPE compliance while the network maintains downlink beams for performance optimization, reducing the complexity of coordinated beam management while still avoiding interference.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP4104539B1Reporting for maximum permissible exposure
Publication Date: 2025.11.05 QUALCOMM INC
  • EP4104539B1 patent drawingFigure 1
  • EP4104539B1 patent drawingFigure 2
  • EP4104539B1 patent drawingFigure 3

AI summary

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may determine that a maximum permissible exposure (MPE) condition is satisfied for the UE; transmit, to a base station, a message based at least in part on determining that the MPE condition is satisfied; and transmit, to the base station based at least in part on the MPE condition being satisfied, beam information indicating an updated transmit beam for the UE. Numerous other aspects are provided.