PIM Removal in Antenna Systems via Codebook Beamforming
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Solution Overview
Problem
Current methods for passive intermodulation (PIM) mitigation in active antenna systems (AASs) are computationally costly and inefficient, particularly due to high complexity in modeling and tracking PIM, which compromises network performance and capacity.
Innovation Solution
A method using codebook-based beamforming to identify and correct PIM-impacted transmission radio chains by determining a correction signal based on the used codeword, which is then subtracted from receiver radio chains to remove PIM, reducing computational complexity and improving convergence of the PIM model.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing PIM cancellation functions designed for traditional approaches are implemented in AAS, then PIM mitigation is achieved, but computational cost becomes impractical
Solution Approach 1:
The patent segments the PIM cancellation process by identifying and isolating only the transmission radio chains that cause PIM impacts, rather than processing all radio chains. This selective approach reduces computational complexity while maintaining effective PIM mitigation for the affected chains.
Solution Approach 2:
The patent applies partial action by using a reduced set of transmission radio chains (only those identified as causing PIM) instead of processing all transmission radio chains. This partial approach achieves sufficient PIM cancellation without the excessive computational cost of full-system processing.
2Reliability
If PIM eigen components are used in uplink to steer nulls in downlink, then PIM sources are avoided, but capacity is reduced due to reduced power and spatial steering
Solution Approach 1:
The patent extracts and removes only the harmful PIM components from the received signal using correction signals generated from identified transmission radio chains. This selective removal approach avoids the need to steer nulls in the downlink, thereby preserving capacity while eliminating PIM impacts.
Solution Approach 2:
The patent converts the harmful PIM effects into beneficial correction signals by modeling the PIM impacts and generating corresponding correction signals. These correction signals are then subtracted from the received signal, transforming the harmful PIM into a manageable and correctable component without sacrificing capacity.
3Reliability
If polynomial modeling of PIM is used, then PIM cancellation is achieved, but complexity of third order non-linear modeling increases as O(N³)
Solution Approach 1:
The patent segments the PIM modeling process by focusing only on the identified transmission radio chains that cause PIM impacts, rather than modeling all possible interactions. This segmentation reduces the modeling complexity from O(N³) to a lower complexity level while maintaining effective PIM cancellation.
Solution Approach 2:
The patent applies local quality by modeling PIM effects locally at the identified transmission radio chains rather than globally across all radio chains. This localized modeling approach reduces computational complexity while achieving accurate PIM cancellation for the affected chains.
Data Source
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AI summary
There is provided mechanisms for PIM removal in an antenna system. A method is performed by a controller of the antenna system. The method comprises identifying, during transmission using codebook based beamforming, which transmission radio chains of the antenna system that cause a signal received by receiver radio chains of the antenna system to be impacted by PIM. These transmission radio chains are identified based on which codeword in the codebook is used for the beamforming. The method comprises determining a correction signal by subjecting the signals only as transmitted by the identified transmission radio chains to a model of the PIM. The method comprises removing PIM from the signal received by the receiver radio chains by subtracting the correction signal from the signal received by the receiver radio chains.