Full-Duplex Self-Interference Cancellation via Auxiliary Receiver Chain
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Solution Overview
Problem
Full-duplex wireless systems face challenges in managing self-interference signals, which degrade the Signal to Noise Ratio (SNR) and impact throughput due to hardware imperfections and limitations in existing self-interference cancellation techniques.
Innovation Solution
An all-digital self-interference cancellation technique using an auxiliary receiver chain that shares the same oscillator with the main receiver chain, down-converts and samples a copy of the transmitted RF signal, weights it by an estimate of the wireless channel, and subtracts it from the received signal, with additional cancellation steps to accommodate multi-path and time-varying channel effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-duplex mode is used to double spectral efficiency, then bidirectional communication throughput is improved, but self-interference signals degrade the Signal to Noise Ratio
Solution Approach 1:
The patent segments the self-interference cancellation process into three distinct stages: analog cancellation (using passive structures like diplexers and active cancellation using analog circuits), digital cancellation (using digital signal processing to subtract modeled self-interference from received signals), and post-processing cancellation (using adaptive filtering and interference suppression algorithms). This multi-stage segmentation allows progressive reduction of self-interference signals while maintaining full-duplex spectral efficiency.
Solution Approach 2:
The patent introduces an intermediary auxiliary receiver chain that mirrors the main receiver chain's oscillator and down-conversion process. This auxiliary chain receives a copy of the transmitted signal and processes it through the same path, creating an intermediary representation of self-interference that can be subtracted from the actual received signal. The intermediary processing chain acts as a mediator to generate accurate self-interference models for cancellation.
2Object-affected harmful factors
If self-interference cancellation techniques are implemented, then Signal to Noise Ratio is improved, but device complexity increases
Solution Approach 1:
The patent merges the auxiliary receiver chain with the main receiver chain by having them share common components such as oscillators, mixers, and local oscillators. The auxiliary chain is integrated into the existing receiver architecture rather than being a completely separate system, reducing overall device complexity. The cancellation processing is also merged with the normal signal processing pipeline, allowing self-interference suppression without adding entirely independent processing paths.
Solution Approach 2:
The system uses the transmitted signal itself to generate the cancellation signal through the auxiliary receiver chain. The same oscillator and down-conversion process that creates the transmitted signal also processes a copy to model the self-interference, making the system self-sufficient. The transmitted signal's own characteristics (phase, frequency, amplitude) are used to create the cancellation reference, eliminating the need for external calibration signals or additional reference sources.
3Ease of manufacture
If hardware imperfections are present in transmitter and receiver, then manufacturing is simplified, but self-interference cancellation precision deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where the system continuously monitors the residual self-interference after cancellation and adjusts the cancellation parameters accordingly. The adaptive filtering algorithms use feedback from the received signal to refine the self-interference model and improve cancellation precision. The system measures the actual self-interference characteristics and feeds this information back to adjust the cancellation process, compensating for hardware imperfections through closed-loop control.
Solution Approach 2:
The patent employs parameter changes in the digital domain to compensate for hardware imperfections. By adjusting digital gain, phase, and timing parameters in the signal processing chain, the system can correct for analog hardware variations. The adaptive algorithms dynamically change processing parameters based on measured channel conditions and interference characteristics, maintaining high cancellation precision despite manufacturing tolerances in physical components.
Data Source
AI summary
Embodiments of full-duplex self-interference cancellation systems are described. In one embodiment, a full-duplex transceiver includes a digital signal processor that processes digital signals, a transmit chain that receives a first digital baseband signal from the digital signal processor and converts it to a first RF signal, a receive chain that receives a second RF signal and converts the second RF signal to a second digital baseband signal, and an auxiliary receive chain that receives a portion of the first RF signal and converts it to an auxiliary digital baseband signal. The transceiver may further include a self-interference canceller that applies a channel transfer function to the auxiliary digital baseband signal to generate a cancellation signal and subtracts the cancellation signal from the second digital baseband signal to cancel self-interference at the transceiver. The suppression of self-interference in the transceiver assists the transceiver to achieve higher efficiency in full-duplex communications.