PIM-Aware Link Adaptation for Wireless Interference
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Solution Overview
Problem
Current wireless communication systems are not effectively addressed in managing passive intermodulation (PIM) interference, which occurs in linear components like cables and antennas under high RF power, leading to unwanted spurious signals that interfere with desired receive signals, and existing link adaptation techniques are not PIM-aware.
Innovation Solution
Implementing PIM-aware link adaptation methods that determine the PIM power spectral density (PSD) at network nodes to adjust transmission parameters, such as SINR backoff factors, based on pre-calculated PIM levels and historical interference data, to mitigate PIM effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high RF power is transmitted in cellular systems, then transmission power and coverage are improved, but passive intermodulation distortion increases causing spurious signals
Solution Approach 1:
The system performs frequency planning and PIM analysis before transmission to identify and avoid problematic frequency combinations that would generate intermodulation products. By pre-calculating potential PIM frequencies using the formulas nF1−mF2 and nF2−mF1, the system can select transmit frequencies that minimize PIM generation while maintaining high power transmission capability.
Solution Approach 2:
The system dynamically adjusts transmission parameters including frequency selection, power allocation, and modulation schemes based on calculated PIM levels. When PIM is detected or predicted to be significant, the system changes operating parameters to avoid the harmful frequency combinations, thereby maintaining high power transmission where safe while avoiding PIM generation.
2Object-affected harmful factors
If frequency planning is performed to separate uplink and downlink frequencies, then self-interference is reduced, but network complexity and frequency coordination requirements increase
Solution Approach 1:
The frequency planning system performs multiple functions simultaneously: it separates uplink and downlink frequencies to prevent self-interference, calculates potential PIM products, identifies safe frequency combinations, and coordinates with other network nodes. This multi-functional approach consolidates what would otherwise be separate complex processes into a unified frequency planning procedure.
Solution Approach 2:
The system performs comprehensive frequency planning and PIM analysis in advance before actual transmission operations begin. By pre-identifying safe frequency combinations and storing this information for future use, the system avoids the need for complex real-time calculations and coordination during active transmission, thereby reducing operational complexity.
3Productivity
If link adaptation is used to maximize data throughput, then productivity is improved, but PIM-induced interference is not addressed leading to degraded performance
Solution Approach 1:
The system incorporates PIM level feedback into the link adaptation process. By continuously monitoring or calculating PIM levels and using this information to adjust modulation and coding schemes, the system adapts transmission parameters to maintain optimal throughput despite the presence of PIM interference. The feedback loop ensures that link adaptation decisions account for both channel conditions and PIM conditions.
Solution Approach 2:
The system dynamically changes transmission parameters including modulation order, coding rate, and power allocation based on real-time PIM level assessments. When PIM is detected to be significant, the system adjusts these parameters to maintain reliable communication and maximize throughput under the degraded conditions, rather than using fixed or conventional link adaptation schemes.
Data Source
AI summary
Methods and devices for PIM-aware link adaptation are disclosed. According to some aspects, a network node and a method for link adaptation that accounts for passive intermodulation (PIM) at the network node of a wireless communication system are disclosed. A PIM power spectral density (PSD) versus the set of receive frequencies is determined based on at least one transmission frequency of a set of transmission frequencies at at least one antenna. Link adaptation is performed based on the PIM PSD versus a set of receive frequencies. Performing the link adaptation includes choosing at least one transmission parameter of a transmitter scheduled to transmit on a frequency among the set of receive frequencies.