Near-Field Self-Interference Cancellation in Full Duplex Systems
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Solution Overview
Problem
Wireless full duplex systems face challenges in reducing near-field reflected self-interference signals, which hinder spectral efficiency due to the difficulty in recognizing and canceling these signals with conventional methods, especially in environments where propagation distances and multi-path delays are short, making effective interference cancellation impractical.
Innovation Solution
A method and apparatus that utilize a sounding signal with a large time-bandwidth product, sent in a different timeslot than the communication signal, to separate and reconstruct near-field reflection signals, allowing for the determination of near-field reflection channel parameters and subsequent subtraction of the reconstructed self-interference from the received signal, employing techniques like matched filtering and super-resolution delay algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wireless full duplex technology is used to perform transmission and reception simultaneously on the same frequency band, then spectral efficiency is improved (doubled compared to FDD/TDD), but self-interference from transmitted signals to received signals occurs, preventing correct reception
Solution Approach 1:
The patent segments the self-interference cancellation process into multiple stages: analog domain cancellation using resistive networks and capacitors, digital domain cancellation using signal processing algorithms, and iterative refinement. This multi-stage segmentation allows progressive reduction of self-interference while maintaining full duplex operation
Solution Approach 2:
The patent introduces intermediary components including resistive networks, capacitors, and digital signal processors that act as mediators between the transmitted and received signals. These intermediaries enable the system to cancel self-interference by processing the transmitted signal and subtracting it from the received signal
2Measurement precision
If conventional interference cancellation methods are used with normal bandwidth communication signals (10-40 MHz), then far-field reflected self-interference can be recognized and canceled, but near-field reflected self-interference cannot be effectively recognized or reconstructed due to very small propagation delay differences
Solution Approach 1:
The patent changes the parameter of signal bandwidth by introducing wideband sounding signals (e.g., 200 MHz or 1 GHz bandwidth) that are much larger than normal communication signals. This parameter change enables the system to resolve the small delay differences characteristic of near-field reflections, allowing accurate channel estimation and interference cancellation
Solution Approach 2:
The patent performs preliminary channel sounding using wideband signals before actual communication takes place. This preliminary action allows the system to pre-characterize the near-field reflection channels and store the channel impulse responses, which are then used during communication to cancel the self-interference
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AI summary
Embodiments of the present invention provide a method for reducing a self-interference signal in a communications system, and an apparatus. The method includes: sending a sounding signal and a first communication signal; receiving an input signal; separating a near-field reflection signal corresponding to the sounding signal from an echo signal of the input signal; determining, based on the near-field reflection signal, a near-field reflection channel parameter; determining, based on the near-field reflection channel parameter, a reconstructed near-field reflected self-interference signal; and subtracting the reconstructed near-field reflected self-interference signal from a received second communication signal. The present invention can effectively recognize and reconstruct a near-field reflection signal, thereby reducing a near-field reflected self-interference signal in self-interference.