Full-Duplex Transceiver Self-Interference Cancellation via Adaptive Filtering
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Solution Overview
Problem
Full Duplex transceivers face significant challenges in effectively canceling self-interference, which arises when high-power transmit signals leak into the receiver path, degrading signal quality and accuracy.
Innovation Solution
The method involves using an adaptive filter and a self-interference estimator to generate a filtered signal from an initial transmit signal, and then subtracting a cancellation signal derived from the filtered signal to remove self-interference from the received signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive isolation (separating transmit and receive antennas) is used to cancel self-interference, then self-interference cancellation is improved, but device complexity increases
Solution Approach 1:
The self-interference cancellation is divided into three separate stages: passive isolation (physical separation of antennas), RF cancellation (analog signal processing), and digital compensation (digital signal processing). Each stage addresses a specific portion of the self-interference problem, allowing the system to manage complexity by breaking down the overall cancellation task into manageable segments with different isolation requirements at each stage.
2Reliability
If digital compensation is used to cancel self-interference, then self-interference cancellation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The system performs preliminary RF cancellation in the analog domain before the signal is digitized. This preliminary action removes the bulk of the self-interference signal at a stage where it is still analog and can be handled by simpler circuitry, reducing the burden on the subsequent digital compensation stage and lowering the precision requirements for digital signal processing components.
3Reliability
If RF cancellation is used to cancel self-interference, then self-interference cancellation is improved, but device complexity increases
Solution Approach 1:
The RF cancellation stage acts as an intermediary between the passive isolation and digital compensation stages. It uses analog signal processing to create a cancellation signal that is subtracted from the received signal before digitization, serving as a bridge that reduces the strength of self-interference to a level that can be effectively handled by subsequent digital processing without overwhelming the system.
4Productivity
If high power transmit signals are used in Full Duplex, then productivity is improved, but self-interference increases
Solution Approach 1:
The system uses the leaked transmit signal itself to create the cancellation signal. By capturing a portion of the high-power transmit signal and processing it through the adaptive filter, the system converts the harmful self-interference into a useful cancellation signal that can be subtracted from the received signal, allowing high-power operation without proportional increase in net self-interference.
Data Source
AI summary
Methods and systems for cancelling self-interference in a full-duplex radio transceiver. The methods include transmitting a transmit signal from a transmit path of the transceiver and receiving a receive signal at a receive path of the transceiver. The receive signal has a self-interference signal component caused by self-interference between the transmit and receive paths. The methods further include generating a filtered signal by filtering an initial signal using an adaptive filter configured based on a target signal derived from the receive signal, wherein the initial signal is derived from the transmit signal; and subtracting a cancellation signal derived from the filtered signal from the receive signal. The target signal is derived from the receive signal by estimating the self-interference signal component in the receive signal, or the cancellation signal is derived from the filtered signal by estimating a part of the filtered signal equal to the self-interference signal component.