Non-linear Digital Self-interference Cancellation in Full-duplex Radios
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Solution Overview
Problem
Full-duplex wireless communication systems face challenges with self-interference due to non-linearities during signal conversion, limiting their power range and spectral efficiency, as existing solutions fail to effectively address non-linear digital self-interference.
Innovation Solution
A system and method for non-linear digital self-interference cancellation, comprising a pre-processor, non-linear transformer, transform adaptor, and post-processor, which samples digital transmit signals, generates non-linear cancellation signals, and combines them with received signals to reduce self-interference, using mathematical models like generalized memory polynomial models to account for non-linear effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full-duplex wireless communication systems are implemented to transmit and receive signals simultaneously, then spectral efficiency is improved, but self-interference from non-linear signal conversion limits the power range and system performance
Solution Approach 1:
The system applies preliminary anti-action by generating a cancellation signal that is the inverse of the expected self-interference signal before it corrupts the received signal. The non-linear transformer processes the transmit signal to predict the non-linear distortion, and this predicted interference is subtracted from the received signal in advance, preventing the harmful effect from degrading system performance
Solution Approach 2:
The patent introduces an intermediary cancellation signal path that mediates between the transmit and receive paths. The non-linear transformer and cancellation signal generator act as intermediaries that process the transmit signal to create a compensating signal, which is then combined with the received signal to eliminate self-interference without requiring changes to the fundamental full-duplex operation
2Reliability
If existing self-interference cancellation solutions are used, then some interference reduction is achieved, but non-linearities from baseband to RF conversion and back are not effectively addressed
Solution Approach 1:
The system applies parameter changes by using a non-linear transformer that models the specific non-linear characteristics of the RF power amplifier and converter. The transformer adapts its parameters to match the actual non-linear behavior of the hardware, allowing effective cancellation across different power levels and operating conditions rather than relying on fixed linear cancellation parameters
Solution Approach 2:
The patent implements dynamics by making the cancellation signal generation adaptive to changing transmit power levels and signal conditions. The non-linear transformer dynamically adjusts its processing based on the input signal characteristics, allowing the system to maintain effective interference cancellation across varying operating modes and power ranges
3Reliability
If transmission power is increased to improve signal quality, then communication reliability is improved, but non-linear distortion increases and limits the usable power range
Solution Approach 1:
The system converts the harmful non-linear distortion into a beneficial effect by using the distorted transmit signal to generate the cancellation signal. The non-linear transformer intentionally reproduces the same non-linear distortion that occurs in the RF path, and this reproduced distortion is then subtracted from the received signal, turning the previously harmful non-linearity into the key to solving the self-interference problem
Data Source
AI summary
A system and method for non-linear digital self-interference cancellation including a pre-processor that generates a first pre-processed digital transmit signal from a digital transmit signal of a full-duplex radio, a non-linear transformer that transforms the first pre-processed digital transmit signal into a non-linear self-interference signal according to a transform configuration, a transform adaptor that sets the transform configuration of the non-linear transformer, and a post-processor that combines the non-linear self-interference signal with a digital receive signal of the full-duplex radio.