Uplink Probing for Passive Intermodulation Avoidance

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Solution Overview

Problem

Current methods for mitigating passive intermodulation (PIM) interference suffer from high computational complexity, limited applicability to advanced antenna systems, and variations in signal-to-interference-plus-noise ratio (SINR) due to sporadic and non-continuous downlink muting.

Innovation Solution

A method involving a controller that performs uplink probing for a set of downlink PIM avoidance actions, measures the improvement in uplink PIM, selects the most effective action, and applies it to downlink transmission resources, thereby optimizing PIM avoidance without the limitations of existing techniques.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If PIM cancellation algorithms are used to estimate and subtract predicted PIM signals, then uplink PIM reduction is achieved, but computational complexity increases significantly

Engineering Contradiction:

Improveuplink PIM interferenceVSAvoidcomputational complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent applies preliminary action by performing uplink probing measurements before actual data transmission to identify PIM-affected resource blocks. The controller proactively detects PIM interference patterns in advance and configures avoidance actions for subsequent transmissions, rather than attempting complex real-time cancellation during data processing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent extracts and isolates the PIM measurement function into a separate uplink probing mechanism. By dedicating specific resource blocks solely for PIM detection and measurement, the system separates the interference detection task from regular data transmission, enabling simpler avoidance logic without requiring complex real-time signal processing

Inventive Principle:

Principle #2Taking out (Extraction)

2Object-affected harmful factors

If downlink transmission muting is applied to avoid PIM, then uplink PIM interference is reduced, but SINR varies due to sporadic and non-continuous transmission

Engineering Contradiction:

Improveuplink PIM interferenceVSAvoidSINR stability

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent applies dynamics by implementing adaptive resource block selection based on real-time PIM measurements. The system dynamically identifies which specific resource blocks are affected by PIM interference and selectively mutes only those blocks, while maintaining continuous transmission on unaffected blocks. This dynamic adaptation ensures stable SINR by keeping transmission ongoing wherever possible

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies local quality by treating different resource blocks differently based on their individual PIM susceptibility. Instead of uniformly muting all downlink transmissions, the system identifies and applies avoidance actions only to specific resource blocks where PIM interference is detected, maintaining high-quality transmission on clean channels while protecting vulnerable blocks

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If beamformed transmission is used to avoid PIM sources, then PIM interference is reduced, but the technique is limited to advanced antenna systems with large antenna arrays

Engineering Contradiction:

ImprovePIM interferenceVSAvoidapplicability to different antenna systems

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent achieves universality by implementing a PIM avoidance mechanism that works with any antenna configuration. The uplink probing and resource block-based avoidance approach is independent of antenna array size or beamforming capability, making it applicable to both advanced antenna systems with large arrays and conventional systems with simpler antenna configurations

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent replaces the mechanical/physical approach of beamforming (which requires specific antenna hardware) with a signal processing approach using uplink probing and resource block management. This substitution allows PIM avoidance to be achieved through software-controlled resource allocation rather than hardware-dependent beam steering, enhancing versatility across different system types

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS20250183938A1Techniques for passive intermodulation avoidance

Publication Date: 2025.06.05 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

Mechanisms for PIM avoidance. A method is performed by a controller. The method includes performing, for a set of downlink PIM avoidance actions, uplink probing of a radio channel over which uplink PIM is received. The uplink probing for each downlink PIM avoidance action in the set of downlink PIM avoidance actions comprises obtaining, in a probing instant, a measured improvement of the uplink PIM when having applied the downlink PIM avoidance action. The method includes selecting one of the downlink PIM avoidance actions based on the measured improvement for each of the downlink PIM avoidance actions as obtained during the uplink probing. The method includes applying the selected downlink PIM avoidance action to downlink transmission resources transmitted in a data transmission instant following the probing instant.