Frequency Domain Interference Suppression for Full Duplex Transceivers

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Solution Overview

Problem

Existing communication systems face performance degradation due to interfering signals from transmitters, which traditional echo cancellers struggle to fully suppress, especially in full duplex modes where interference is bidirectional and affects both time and frequency domains.

Innovation Solution

The system employs a transceiver with a transmission chain and a reception chain, utilizing an interference suppressor that generates suppression signals by filtering reference signals in both time and frequency domains to produce an interference-suppressed signal, synchronized with the transmitter and receiver to effectively cancel echoes and noise interference.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional echo cancellers are used to suppress interfering signals, then some echo suppression is achieved, but receiver performance is still degraded due to insufficient suppression capability in full duplex modes

Engineering Contradiction:

Improvereceiver performanceVSAvoidinterference signal

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent transitions from traditional time-domain echo cancellation to frequency-domain interference suppression. By transforming the interference suppression problem into the frequency domain using FFT, the system can more effectively handle the complex bidirectional interference characteristics in full duplex modes, achieving better receiver performance through dimensional transformation of the processing domain.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The system dynamically adjusts filtering parameters including frequency-selective filter coefficients, FFT size, and suppression signal generation parameters based on channel conditions and interference characteristics. This parameter optimization enables adaptive suppression that maintains high receiver performance across varying full duplex operating conditions.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If frequency-domain filtering is applied to suppress echo interference, then suppression effectiveness is improved, but computational complexity increases

Engineering Contradiction:

Improveinterference suppression effectivenessVSAvoidcomputational load

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The frequency-domain processing is segmented into discrete frequency bins through FFT, allowing independent filtering operations on each subcarrier. This segmentation enables efficient parallel processing and reduces the overall computational complexity compared to full time-domain convolution, while maintaining effective interference suppression across the entire bandwidth.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces complex time-domain adaptive filtering mechanics with frequency-domain filtering mechanics. By using FFT-based filtering and frequency-selective suppression, the system achieves equivalent or superior interference cancellation with reduced computational operations, substituting the mechanical complexity of time-domain adaptation with more efficient frequency-domain transformations.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If full duplex bidirectional transmission is implemented, then spectrum utilization is improved, but mutual interference between transmit and receive signals increases

Engineering Contradiction:

Improvespectrum utilizationVSAvoidbidirectional interference

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The system uses the transmitted signal itself as a reference to generate the suppression signal. By leveraging the known transmitted waveform and its frequency-domain characteristics, the system converts the harmful transmitted signal into a useful reference for creating the cancellation signal, effectively turning the interference source into a solution enabler.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system implements a feedback mechanism where the received signal is processed to estimate the interference component, which is then subtracted from the received signal. This feedback loop continuously adapts to the actual interference conditions in full duplex mode, maintaining effective suppression while enabling simultaneous bidirectional transmission and improving overall spectrum utilization.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS10581647B2Synchronized interference suppression in frequency domain

Publication Date: 2020.03.03 CAPACICOM LTD

AI summary

An apparatus for communication includes a transmission chain, an interference suppressor and a reception chain. The transmission chain is configured to transmit a transmitted signal. The interference suppressor is configured to produce suppression signals, by filtering reference signals drawn from the transmission chain. At least one of the reference signals is filtered in a frequency domain. The reception chain is configured to receive a signal distorted by at least an attenuated and delayed replica of the transmitted signal. The transmitted signal and the received signal are (i) synchronized in time and (ii) each includes one or more subcarriers selected from a common subcarrier-resource. The reception chain is further configured to process the received signal up to selected points, to subtract the suppression signals from the received signal at the selected points to produce an interference-suppressed signal, and to recover data carried in the received signal from the interference-suppressed signal.