Mitigating Passive Intermodulation in Wireless Networks
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Solution Overview
Problem
Existing wireless communication systems face interference challenges due to passive intermodulation (PIM) products generated from multiple sources, which are difficult to manage and can significantly reduce the carrier-to-interference ratio and coverage in cellular networks, especially when PIM sources have different round trip delays.
Innovation Solution
A method and apparatus that generate simulated PIM products with varying delays to create a replica of interference, which is then combined with the received waveform to reduce interference, by processing streams of time samples to reduce correlation and apply appropriate weighting factors based on correlation analysis with the received waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If simulated interference signals are generated to cancel PIM interference from a single source, then interference cancellation is effective, but the system cannot handle PIM from multiple sources with different round trip delays
Solution Approach 1:
The patent segments the interference cancellation process by creating separate simulated interference signal streams for each PIM source, with each stream processed independently to account for different round trip delays. This allows the system to handle multiple PIM sources while maintaining cancellation effectiveness for each individual source.
Solution Approach 2:
The patent adds the time delay dimension to the interference cancellation process by introducing different round trip delay values for each PIM source. This dimensional extension allows the system to distinguish between multiple PIM sources and process their interference signals appropriately, transforming a single-dimension cancellation approach into a multi-dimensional one.
2Reliability
If the system processes multiple PIM sources with different delays, then coverage and carrier-to-interference ratio improve, but processing complexity increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing round trip delay values for each PIM source before actual interference cancellation. This preparation step allows the system to efficiently process multiple PIM sources during real-time operation without excessive computational complexity, as the delay parameters are already determined and ready for use.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the delay parameter for each simulated interference signal to match the specific round trip delay of each PIM source. This parameter adaptation allows the system to handle multiple sources with different characteristics while maintaining a unified processing framework, balancing complexity and effectiveness.
3Productivity
If real-time processing is maintained for multiple PIM sources, then system responsiveness is preserved, but computational load increases
Solution Approach 1:
The patent reduces real-time computational load by performing preliminary calculations of round trip delays and storing them for later use. This pre-processing approach allows the system to maintain real-time processing capability for multiple PIM sources while minimizing energy consumption during actual interference cancellation operations.
Solution Approach 2:
The patent uses copying by creating simulated copies of the transmitted signal for each PIM source, applying the appropriate delay to each copy. This copying approach allows real-time processing of multiple sources without requiring complex simultaneous calculations, as each copied signal can be processed independently and efficiently.
Data Source
AI summary
Interference (I1, I2) is mitigated in a waveform received at the input of a receiver in a wireless network, the interference comprising passive intermodulation PIM products of at least a first signal (C1). A first stream of time samples (5) is generated of a simulated first PFM product of at least the first signal (C1), and a second stream of time samples (6) is generated of the simulated first PIM product. The second stream has a delay with respect to the first stream. A replica (8) is generated of the interference by processing (7) at least the first stream and the second stream, the processing comprising reducing a degree of correlation between the first stream and the second stream, and the replica of the interference is combined with a stream of time samples of the received waveform (40) to reduce the interference in the received waveform.