Full-Duplex Interference Cancellation via Pre-ADC Signal Feedback
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Solution Overview
Problem
Current digital cancellation techniques in wireless full-duplex communications face limitations in achieving sufficient self-interference cancellation due to the dynamic range and quantization resolution of analog-to-digital converters (ADCs), particularly in wideband and frequency-selective channels, making it difficult to isolate self-interference signals effectively.
Innovation Solution
The proposed solution involves enhancing the effective resolution and dynamic range of digital cancellation systems by feeding back the canceling signal prior to analog-to-digital conversion and employing the theory of sparse signal recovery to efficiently estimate and cancel self-interference in both wideband and narrowband channels, using algorithms like matching pursuit and orthogonal matching pursuit for channel estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If digital cancellation techniques are used in full-duplex communications, then self-interference cancellation is achieved, but the dynamic range and quantization resolution of ADCs limit the isolation levels that can be achieved
Solution Approach 1:
The patent segments the self-interference cancellation process into multiple stages: analog cancellation before ADC and digital cancellation after ADC. This segmentation allows each stage to handle different portions of the interference, with analog cancellation reducing the bulk of self-interference before it enters the limited-resolution ADC, thereby overcoming the ADC resolution limitation.
Solution Approach 2:
The patent introduces an analog cancellation stage as an intermediary between the self-interference signal and the ADC. This intermediary component pre-processes the signal by canceling a portion of self-interference in the analog domain, so that the remaining signal presented to the ADC has reduced dynamic range requirements and can be processed within the ADC's quantization resolution capabilities.
2Device complexity
If analog-to-digital converters with limited dynamic range are used, then system complexity is reduced, but the ability to process signals with large dynamic range is compromised
Solution Approach 1:
The patent applies preliminary action by performing analog cancellation of self-interference before the signal enters the ADC. This pre-processing reduces the dynamic range of the signal that the ADC must handle, allowing simpler ADCs with limited dynamic range to achieve the required signal isolation capability that would otherwise require complex high-resolution ADCs.
3Productivity
If digital cancellation is applied in wideband and frequency-selective channels, then communication bandwidth is increased, but the difficulty of detecting and measuring self-interference increases
Solution Approach 1:
The patent segments the wideband frequency-selective channel into multiple frequency sub-channels or paths, each with its own channel estimate. This segmentation allows the system to handle the complexity of wideband detection by processing narrower bandwidth segments individually, making self-interference detection and cancellation feasible in wideband scenarios.
Solution Approach 2:
The patent changes the parameter of channel representation by using channel impulse response estimates and channel frequency response models to characterize the frequency-selective channel. This parameter transformation enables the detection and measurement of self-interference in wideband channels by converting the complex wideband problem into manageable parameter estimation tasks.
Data Source
AI summary
A communications apparatus used in a wireless full duplex system is disclosed. The communications apparatus includes a receiver chain connected to an antenna and an interference cancelling chain. One or more cancellation signals generated by the interference cancelling chain are fed back to the receiver chain prior to the first baseband amplifier which uses the first automatic gain control and the second automatic gain controller. Other methods and systems also are disclosed.