Self-Interference Cancellation in Full-Duplex DOCSIS 3.1 Systems
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Solution Overview
Problem
In full-duplex communication systems like DOCSIS 3.1, self-interference signals generated by downstream and upstream traffic using the same frequency band interfere with upstream signal demodulation, requiring effective methods to remove these signals for accurate data transmission.
Innovation Solution
An apparatus and method utilizing processors to generate downstream signals with autocorrelation characteristics, replicate self-interference signals in both time and frequency domains, and remove them from upstream signals using channel impulse responses estimated through convolution and Fourier transforms, improving channel estimation and interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If downstream and upstream traffic simultaneously use the same frequency band in full-duplex mode, then traffic capacity and spectral efficiency are improved, but self-interference signal power increases causing upstream signal demodulation failure
Solution Approach 1:
The patent segments the self-interference cancellation process into two distinct domains: analog domain cancellation using a circulator to reduce self-interference signal power before amplification, and digital domain cancellation using signal processing to remove remaining interference. This segmentation allows each domain to address specific aspects of the interference problem effectively
Solution Approach 2:
The patent introduces a circulator as an intermediary device in the analog domain to isolate and redirect the self-interference signal path. The circulator acts as a mediator that separates the transmitted downstream signal from the received upstream signal, reducing the harmful interference before it reaches the amplifier and receiver
2Reliability
If self-interference signal power is reduced using a circulator in the analog domain, then upstream signal reception is improved, but self-interference signal is not completely blocked requiring additional digital processing
Solution Approach 1:
The patent merges analog domain cancellation (using circulator) with digital domain cancellation (using signal processing algorithms) into a unified self-interference cancellation system. The analog processing handles the bulk of interference reduction, while digital processing eliminates residual interference, achieving complete cancellation through the combination of both domains
Solution Approach 2:
The patent performs preliminary self-interference cancellation in the analog domain using a circulator before the signal enters the amplifier and receiver chain. This preliminary action reduces the self-interference signal power significantly before digital processing is applied, making the subsequent digital cancellation more effective and efficient
3Measurement precision
If self-interference signal is replicated and removed in both time and frequency domains, then interference cancellation accuracy is improved, but computational complexity and processing requirements increase
Solution Approach 1:
The patent performs channel estimation and self-interference signal replication in advance before the actual upstream signal reception and cancellation. By preparing the cancellation signal beforehand based on channel characteristics, the system reduces the computational burden during real-time processing while maintaining high cancellation accuracy
Solution Approach 2:
The patent applies self-interference cancellation in both time and frequency domains, which is more processing than strictly necessary. However, this excessive action in certain aspects (dual-domain processing) provides superior cancellation accuracy by addressing interference from multiple perspectives, with the benefit outweighing the additional computational complexity
Data Source
AI summary
Disclosed herein are an apparatus and method for removing a self-interference signal. The apparatus includes one or more processors and executable memory for storing at least one program executed by the one or more processors. The at least one program receives an upstream signal for removing self-interference, generates a downstream signal for channel estimation, replicates a self-interference signal in a time domain and a self-interference signal in a frequency domain using the upstream signal and the downstream signal, and removes the self-interference signal from the upstream signal using the replicated self-interference signal in the time domain and the replicated self-interference signal in the frequency domain.