Derivative-Based AAS Power Limiting for RF Exposure Compliance

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Solution Overview

Problem

Existing power control methodologies in wireless communication networks with advanced antenna systems (AAS) struggle to prevent overshoots in average power due to unpredictable traffic changes, leading to violations of RF exposure regulations.

Innovation Solution

Implementing a derivative-based power control mechanism that triggers a hard limit when the derivative of time-averaged transmit power exceeds a threshold, using a Proportional-Integral (PI) control function to adjust resource allocation and momentary power output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional hard limit control is used based on time-averaged power threshold, then RF exposure compliance is maintained, but overshoots occur during traffic changes causing regulation violations

Engineering Contradiction:

ImproveRF exposure complianceVSAvoidpower overshoot

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent applies preliminary action by monitoring the derivative of time-averaged power and triggering the hard limit before the power threshold is actually exceeded. The control mechanism detects the rate of change of power and anticipates potential overshoots, activating protection measures in advance to prevent RF exposure violations during traffic changes.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the hard limit is triggered earlier to prevent overshoots, then RF exposure compliance is improved, but computational complexity increases

Engineering Contradiction:

ImproveRF exposure complianceVSAvoidcontrol mechanism complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex continuous power monitoring and prediction mechanisms with a simplified derivative-based threshold comparison approach. Instead of implementing complex predictive models or continuous optimization algorithms, the system uses a straightforward calculation of the derivative of time-averaged power and compares it against predefined thresholds, significantly reducing computational burden while maintaining effectiveness.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If advanced antenna systems are deployed to increase capacity and coverage, then network performance is improved, but RF exposure compliance distances increase

Engineering Contradiction:

Improvenetwork capacityVSAvoidexclusion zone distance

Core Design Contradiction:

ProductivityVSLength of stationary object

Solution Approach 1:

The patent applies dynamics by transitioning from static exclusion zone calculations based on maximum EIRP to dynamic power control that adapts to actual transmit conditions. The system continuously monitors time-averaged power and its derivative, adjusting the hard limit trigger points dynamically based on real-time power characteristics, thereby enabling shorter effective exclusion zones while maintaining RF exposure compliance.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4088515B1Derivative based hard limit triggering for average power control in aas

Publication Date: 2026.03.04 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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AI summary

According to one or more embodiments, a network node (160) for controlling transmit power is provided. The network node (160) includes processing circuitry (170) configured to estimate a derivative of time-averaged transmit power of the network node (160), determine that the estimated derivative meets a first threshold, and trigger at least one action to limit the time-averaged transmit power of the network node (160) based on the determination that the estimated derivative meets the first threshold.