Near-Field Reflected Self-Interference Cancellation in Full Duplex Systems
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Solution Overview
Problem
Conventional wireless full duplex systems face challenges in effectively canceling near-field reflected self-interference signals, which can cause saturation in receiver front-end modules, reducing spectral efficiency and impacting proper signal reception.
Innovation Solution
An interference cancellation apparatus and method that utilize a main receive antenna, a divider, a main-path self-interference canceller, and a near-field reflected self-interference canceller to estimate and reconstruct near-field reflected self-interference signals, allowing for their cancellation in the radio frequency receive signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wireless full duplex technology is implemented to achieve simultaneous transmission and reception on the same radio channel, then spectral efficiency is improved (theoretically twice that of FDD or TDD), but self-interference from transmit signal to receive signal occurs, causing adverse impact on proper reception of wanted signal
Solution Approach 1:
The patent segments the self-interference cancellation process into three distinct modules: spatial interference suppression unit (antenna isolation), radio frequency front-end analog interference cancellation module (analog domain cancellation before LNA), and digital interference cancellation module (digital domain cancellation after ADC). Each module addresses different components of self-interference at different stages of the signal chain, collectively achieving the goal of enabling full duplex operation with high spectral efficiency while managing self-interference.
2Object-generated harmful factors
If radio frequency front-end analog interference cancellation module is used to cancel self-interference before LNA, then analog domain cancellation is achieved, but near-field reflected self-interference signal components cause saturation in receiver front-end modules
Solution Approach 1:
The patent applies preliminary action by performing analog interference cancellation in the radio frequency front-end before the LNA using a reference signal from the power amplifier. This preliminary cancellation reduces the strength of main-path self-interference signals before they reach the LNA, preventing saturation. The system estimates channel parameters and adjusts the reference signal to match the self-interference signal characteristics, canceling it in advance before the sensitive LNA stage.
Solution Approach 2:
The patent uses a reference signal as an intermediary to cancel self-interference. The reference signal, derived from the transmit signal through the same path as the self-interference, serves as a mediator that can be adjusted (amplitude and phase) to match and cancel the self-interference component in the receive signal. This intermediary approach allows cancellation without directly modifying the transmit or receive paths.
3Object-generated harmful factors
If spatial interference suppression unit is used to suppress self-interference, then some interference reduction is achieved, but strength of self-interference signal in receive signal remains far higher than wanted signal, causing blocking of front-end modules
Solution Approach 1:
The patent segments the interference suppression function across multiple modules operating at different stages: spatial interference suppression unit (physical layer/antenna level), radio frequency front-end analog interference cancellation module (RF level before LNA), and digital interference cancellation module (baseband level after ADC). This segmentation allows each module to address specific interference components with appropriate techniques, achieving comprehensive suppression while distributing complexity across modular components.
Solution Approach 2:
The patent transitions from single-domain interference suppression to multi-domain cancellation: spatial dimension (antenna isolation and beamforming), analog domain (RF front-end cancellation before LNA), and digital domain (baseband cancellation after ADC). By operating in multiple dimensions/domains, the system achieves comprehensive self-interference suppression that cannot be accomplished in a single domain, while managing complexity through modular architecture.
Data Source
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AI summary
Embodiments of the present invention relate to the field of communications technologies, and provide an interference cancellation apparatus and method, which can cancel a near-field reflected self-interference component. The method includes: obtaining a radio frequency reference signal generated according to a transmit signal; obtaining a radio frequency receive signal by using a main receive antenna; performing interference cancellation processing on the radio frequency receive signal according to the radio frequency reference signal to generate a first processed signal; performing near-field reflected self-interference channel estimation according to a digital baseband reference signal corresponding to the radio frequency reference signal and according to a first digital signal obtained by sampling the first processed signal to obtain a near-field reflected self-interference component parameter; performing near-field reflected self-interference signal reconstruction according to the near-field reflected self-interference component parameter and the radio frequency reference signal to obtain a near-field reflected self-interference signal; and performing interference cancellation processing on the first processed signal according to the near-field reflected self-interference signal to obtain a second processed signal. The present invention is used for interference cancellation.