Dual Self-Interference Cancellation for Full Duplex Antennas
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Solution Overview
Problem
Full duplex radio communication systems face significant challenges in effectively canceling self-interference signals between transmission and reception antennas, which hinders efficient two-way communication due to high power interference and limited attenuation between these antennas.
Innovation Solution
The implementation of a dual self-interference signal cancellation system, comprising a first unit for linear channel cancellation and a second unit for nonlinear channel characteristics, utilizing coefficients to optimize cancellation performance, with a controller to compare transmitted and received signals and apply appropriate coefficients for linear and nonlinear element cancellations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full duplex radio communication is implemented to support simultaneous transmission and reception, then communication efficiency is improved, but self-interference between transmission and reception antennas deteriorates performance
Solution Approach 1:
The self-interference cancellation process is segmented into multiple stages: analog cancellation before ADC, digital cancellation after ADC, and iterative refinement. Each stage handles different aspects of interference cancellation, dividing the complex problem into manageable segments that can be processed separately and combined for overall cancellation.
Solution Approach 2:
An intermediary cancellation signal is generated by combining scaled and phase-adjusted versions of the transmitted signal. This intermediary signal acts as a proxy for the actual self-interference, allowing the system to cancel interference without directly measuring the contaminated received signal.
2Power
If transmission power is increased to improve signal strength, then communication range is improved, but self-interference power increases causing greater interference
Solution Approach 1:
The system converts the harmful high-power transmitted signal into a beneficial cancellation reference. The same strong transmitted signal that causes self-interference is captured, processed, and subtracted from the received signal, transforming the interference source into the solution for cancellation.
Solution Approach 2:
The system dynamically adjusts parameters of the cancellation signal including scaling factors, phase shifts, and time delays to match the actual self-interference characteristics. By changing these parameters adaptively, the system optimizes cancellation effectiveness across varying transmission power levels.
3Volume of moving object
If distance between transmission and reception antennas is reduced to improve device compactness, then device size is improved, but self-interference attenuation decreases worsening interference
Solution Approach 1:
The system moves the cancellation problem from the spatial domain to the signal processing domain. Instead of relying on spatial separation (physical distance) to attenuate interference, the system uses signal processing operations in the electrical domain to cancel interference, effectively solving the problem in a different dimension.
Solution Approach 2:
The system replaces the mechanical approach of physical antenna separation with an electronic signal processing approach. Rather than using physical distance for attenuation, the system uses digital and analog processing to generate and subtract cancellation signals, substituting mechanical separation with electronic intervention.
4Device complexity
If only linear channel characteristics are considered for cancellation, then cancellation complexity is reduced, but cancellation accuracy deteriorates due to nonlinear effects
Solution Approach 1:
The cancellation system is segmented into linear and nonlinear components. The linear cancellation unit handles the dominant linear interference using simple scaling and phase adjustment, while the nonlinear cancellation unit handles residual nonlinear effects. This segmentation allows the system to address different orders of interference separately.
Solution Approach 2:
The cancellation system dynamically adapts its complexity based on conditions. The linear cancellation provides a strong first-order cancellation, and the nonlinear cancellation dynamically adjusts to handle remaining interference. The system can activate or deactivate different cancellation levels based on performance requirements and computational resources.
Data Source
AI summary
An apparatus for cancelling a self-interference signal between a transmission antenna and a reception antenna is disclosed. The apparatus includes a first self-interference signal cancellation unit for cancelling a self-interference signal in consideration of a linear channel between the transmission antenna and the reception antenna, a second self-interference signal cancellation unit for cancelling a self-interference signal in consideration of nonlinear channel characteristic between the transmission antenna and the reception antenna or linear characteristic of a radio channel, and a controller for comparing a transmitted signal output from the transmission antenna and a received signal received by the reception antenna to provide a first coefficient to be applied to self-interference signal cancellation of a linear device in the first self-interference signal cancellation unit and a second coefficient to be applied to self-interference signal cancellation of a nonlinear device in the second self-interference signal cancellation unit.