Receiving Filter Design for AP Self-Interference Mitigation
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Solution Overview
Problem
Access points (APs) with radios operating in the 5 GHz frequency band experience significant out-of-channel interference when one radio is transmitting signals, which can negatively affect the performance of the receiving radio, especially due to the limited number of non-overlapping channels and proximity of antennas.
Innovation Solution
An AP is designed with a controller that determines and applies a receiving filter to mitigate interference between the transmitting and receiving radios by using training signals and cost functions to optimize filter coefficients, reducing interference during simultaneous transmission and reception in the same frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a first radio transmits signals while a second radio receives signals in the same frequency band, then the AP can utilize the same frequency band for both transmission and reception, but the transmitted signals cause interference at the receiving radio which negatively affects its performance
Solution Approach 1:
The patent uses the transmitted signals themselves (the harmful interference source) as training data to create a filter that eliminates interference. The controller captures the transmitted signal characteristics and uses them to train a filter that selectively removes these interference components from received signals, converting the harmful self-interference into a useful training opportunity for interference cancellation
Solution Approach 2:
The patent introduces a receiving filter as an intermediary component between the receiving radio and the interference. This filter acts as a mediator that processes the received signals by removing interference components while preserving the desired signal content, enabling simultaneous transmission and reception in the same frequency band
2Reliability
If a receiving filter is applied to mitigate interference, then the receiving performance is improved, but the MIMO receiving capacity may be compromised
Solution Approach 1:
The patent applies different processing to different signal components. The filter is designed to selectively remove interference components while preserving the desired signal components. By training the filter using transmitted signal characteristics, it learns to distinguish between harmful interference and useful signals, applying local quality enhancement to specific portions of the received signal
3Productivity
If the AP uses two radios in the same frequency band, then channel utilization is improved, but out-of-channel interference occurs due to the proximity of antennas and limited non-overlapping channels
Solution Approach 1:
The patent implements a feedback mechanism where the transmitted signals are captured and fed back to the controller for filter training. The controller continuously monitors the transmitted signal characteristics and updates the filter coefficients based on this feedback, enabling adaptive interference cancellation that responds to changing transmission conditions
Solution Approach 2:
The patent dynamically adjusts filter parameters (coefficients) based on the transmitted signal characteristics. By changing the filter parameters in response to the specific transmission conditions, the system adapts to different scenarios and maintains effective interference cancellation while preserving MIMO receiving capacity
Data Source
AI summary
Receiving filter design that reduces out-of-channel interference for APs is disclosed. An AP includes a first radio and a second radio disposed in a body of the AP. The first radio transmits first signals in a frequency band while the second radio receives second signals in the same frequency band. The AP includes an interference mitigation controller that determines a receiving filter for the second radio to mitigate interference between the first radio and the second radio based on the second signals received by the second radio when the first radio transmits the first signals in the frequency band. The interference mitigation controller applies the receiving filter to signals received by the second radio during a time period that the first radio is transmitting signals in the frequency band while the second radio is receiving signals in the frequency band.