Network Node Site Passive Intermodulation Detection and Mitigation
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Solution Overview
Problem
In wireless communication systems, passive intermodulation (PIM) products caused by nonlinear effects in radio base stations can lead to reduced receiver signal-to-noise ratio (SNR) and decreased coverage, especially in multi-operator FDD sites and carrier aggregation setups, due to interference from multiple transmitted signals, which existing methods struggle to fully mitigate.
Innovation Solution
A method is developed to detect passive intermodulation issues by correlating statistics from received and transmitted signal levels, allowing for adaptive adjustments in communication resources to limit the impact of PIM, including assigning communication resources to reduce interference and protecting specific user equipment (UEs) from PIM effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple downlink transmissions are performed simultaneously in multi-operator FDD sites, then network capacity and service coverage are improved, but passive intermodulation products are generated that degrade receiver SNR and cause desensitization
Solution Approach 1:
The system performs preliminary detection of PIM conditions by monitoring the relationship between downlink transmit power and uplink received signal quality. When PIM is detected, the system proactively adjusts resource allocation and transmit power before severe SNR degradation occurs, preventing service deterioration rather than reacting after the fact.
Solution Approach 2:
The patent implements dynamic resource allocation where the network node continuously monitors PIM conditions and adapts the allocation of time-frequency resources and transmit power levels in real-time. This allows the system to optimize network capacity while dynamically avoiding PIM-affected resources, creating a flexible balance between productivity and signal quality.
2Manufacturing precision
If external cavity filters are used to filter unwanted transmission components, then transmit spectrum compliance is improved, but intermodulation products caused by multiple transmitted signals cannot be filtered and remain in the receive band
Solution Approach 1:
The patent introduces an intermediary detection and management layer that monitors the interaction between multiple downlink signals and identifies PIM product frequencies. This intermediary system then coordinates resource allocation to avoid scheduling uplink receptions on frequencies where PIM products are generated, effectively mediating between the need for multiple simultaneous transmissions and the avoidance of intermodulation interference.
3Reliability
If service technicians are sent to RBS sites to find and replace causing elements, then the root cause of PIM is eliminated, but service interruption time increases and network availability decreases
Solution Approach 1:
The system implements self-service PIM management through automated detection, identification, and mitigation. The network node autonomously monitors for PIM conditions, identifies affected resources, and adjusts resource allocation without human intervention. This eliminates the need for manual site visits and hardware replacement, resolving PIM issues while maintaining continuous service availability.
Solution Approach 2:
The patent establishes a feedback loop where the network node continuously monitors uplink received signal quality and correlates it with downlink transmit power levels. This feedback mechanism enables real-time detection of PIM conditions and automatic adjustment of resource allocation, creating a closed-loop system that resolves PIM issues dynamically without manual intervention.
4Use of energy by moving object
If downlink transmit power is increased to improve coverage, then signal strength is improved, but PIM product levels increase and cause greater desensitization in the receive band
Solution Approach 1:
The patent applies local quality optimization by adjusting transmit power and resource allocation on a per-resource-block basis rather than uniformly across the entire bandwidth. The system identifies specific frequency-time resources where PIM is generated and applies power reduction or resource avoidance only to those affected locations, while maintaining full power on unaffected resources. This localized approach preserves overall network capacity while mitigating PIM interference.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively identifies and mitigates PIM interference, enhancing the SNR and coverage of wireless communication systems by adapting transmission power and resource allocation, thereby reducing the likelihood of dropped connections and improving network performance.
Implementation Method 1
passive intermodulation (PIM) products caused by nonlinear effects in radio base stations
Implementation Method 2
nonlinear effects caused by for instance excitation of ferromagnetic materials or other physical properties
Data Source
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AI summary
There is provided a method of handling interference caused by inter- modulation in a network node site comprising a set of network nodes for wireless communication capable of communication with a set of stations for wireless communication. The stations are wireless transceiver devices and communication from the network node to any of the stations is considered to be downlink communication and communication from any of the stations is considered to be uplink communication. The method comprises detecting likely passive intermodulation, determining at least one station having an uplink resource being a likely to be affected by the detected likely passive intermodulation, and limiting downlink transmission, when the determined at least one station is scheduled or expected to transmit on the uplink resource, on a downlink resource likely to be affecting the uplink resource by the detected likely passive intermodulation. A computer program, a controller and a network node site are also disclosed.