Intermodulation Interference Detection in Wireless Network Nodes
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Solution Overview
Problem
In wireless communication systems, passive intermodulation (PIM) products caused by non-linear effects in radio frequency (RF) transmitters can lead to increased noise levels and reduced signal-to-noise ratios (SNR), particularly in full duplex systems, where interference from multiple transmitted signals falls into the receive band, affecting the coverage and reliability of wireless communication networks.
Innovation Solution
A method for detecting interference caused by inter-modulation in network nodes, which involves correlating statistics of received input signal interference levels and transmitted signal levels to determine if significant interference is present, allowing for the selection of communication resources and transmit power levels to mitigate this interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple downlink bands are transmitted simultaneously in an FDD RBS, then the network capacity and coverage are improved, but passive intermodulation products fall into the receive band causing increased noise and reduced SNR
Solution Approach 1:
The system performs preliminary detection of PIM interference by correlating statistics between received interference levels and transmitted signal levels before service degradation occurs. This early detection enables proactive identification of problematic frequency combinations, allowing the network to prevent or mitigate interference issues before they impact service quality.
Solution Approach 2:
The system establishes a feedback mechanism that continuously monitors the relationship between transmitted downlink signal levels and received uplink interference levels. By correlating these statistics in real-time, the system can identify PIM products and adjust transmission parameters to minimize interference while maintaining network capacity.
2Manufacturing precision
If external cavity filters are used to filter out unwanted components, then the 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 system introduces an intermediary detection and analysis mechanism that correlates transmitted signal statistics with received interference statistics. This intermediary approach identifies the specific frequency combinations generating PIM products, enabling targeted mitigation strategies that go beyond traditional filtering methods.
3Measurement precision
If service technicians are sent to the RBS site to find and replace causing elements, then the root cause of interference can be identified, but the RBS remains non-functional for a longer or shorter time
Solution Approach 1:
The system implements self-service capability by automatically detecting and identifying PIM interference sources through statistical correlation analysis of transmitted and received signals. This eliminates the need for manual site visits and technical investigations, allowing the network to autonomously diagnose and address interference issues while maintaining continuous operation.
4Reliability
If the receiver handles PIM products by improving receiver linearity, then the receiver SNR can be maintained, but the complexity and cost of the receiver increases
Solution Approach 1:
Instead of relying on improved receiver linearity to handle PIM products, the system performs preliminary detection and identification of PIM interference sources. This enables proactive mitigation at the transmitter or network level, avoiding the need for complex receiver modifications while maintaining SNR performance.
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 enables the detection and mitigation of intermodulation interference, improving the SNR and coverage of wireless communication networks by identifying and addressing interference issues before they lead to service disruptions or reduced coverage.
Implementation Method 1
distortion products caused by nonlinearities in the transmitter
Implementation Method 2
passive intermodulation (PIM) products caused by non-linear effects in radio frequency (RF) transmitters
Data Source
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Figure 3
Figure 4~5
AI summary
A method of detecting 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 determining a received input signal interference level on at least a part of communication resources for uplink communication, determining a transmitted signal level on at least a part of communication resources for downlink communication, wherein the at least part of communication resources for downlink communication corresponds in time with the at least part of communication for uplink communication, correlating statistics from the determined received input signal interference level and the determined transmitted signal level, and determining whether significant interference caused by inter-modulation is present based on the correlation. A computer program, a controller and a network node are also disclosed.