Full Duplex Cable Modem Front End Interference Suppression
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Solution Overview
Problem
Full duplex communication in cable networks faces interference issues due to self-interference and adjacent channel interference, which limit bandwidth and throughput, especially in existing cable network architectures where upgrading components is costly and technologically constrained.
Innovation Solution
Implementing advanced filtering techniques, including switched filters and echo cancellation methods, both analog and digital, to suppress self-interference and adjacent channel interference, allowing for full band communication and spectrum sharing without impeding the data path, thereby enhancing the dynamic range of cable modems and improving interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full duplex communication is implemented in existing cable network architectures, then bandwidth and throughput are improved, but self-interference and adjacent channel interference worsen
Solution Approach 1:
The patent extracts and removes the harmful interference components from the received signal through filtering operations. Switched filters extract and remove adjacent channel interference, while echo cancellation circuits extract and remove self-interference components, allowing the desired signal to be recovered without contamination from these harmful factors.
Solution Approach 2:
The patent introduces intermediary filtering components between the received signal and the signal processing chain. Switched filters and echo cancellation circuits act as intermediaries that selectively remove interference components while preserving the desired signal, enabling full duplex operation without being overwhelmed by self-interference or adjacent channel interference.
2Reliability
If filtering techniques are applied to suppress interference, then interference cancellation is improved, but device complexity increases
Solution Approach 1:
The patent employs dynamically switchable filters that can be configured based on the operating mode and interference conditions. The switched filter architecture allows the system to dynamically select appropriate filter characteristics, providing adaptive interference suppression without requiring a permanently complex filtering structure for all possible scenarios.
Solution Approach 2:
The echo cancellation circuit uses the transmitted signal itself as a reference to generate and subtract the self-interference component from the received signal. This self-service approach allows the system to cancel its own interference without requiring external reference signals or additional complex calibration equipment.
3Measurement precision
If switched filters are used to suppress adjacent channel interference, then signal separation is improved, but manufacturing precision requirements increase
Solution Approach 1:
The switched filter implementation uses dynamic switching mechanisms that can be controlled through digital signal processing. The filter switching is synchronized with the modulation scheme and can be adjusted in real-time, reducing the need for extremely precise static manufacturing tolerances while maintaining effective signal separation through adaptive control.
Data Source
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AI summary
Designs for a front end for suppressing adjacent channel interference (ACI) and adjacent leakage interference (ALI) in a full duplex cable modem (CM) for a Data Over Cable Service interface Specification ("DOCSIS") network are described. The CM includes an upstream (US) signal path receiving a digital US input signal and transmitting an analog-converted US signal in a US frequency range to a cable modem termination system (CMTS); a downstream (DS) signal path receiving an analog DS signal in a DS frequency range and converting the analog DS signal into a digital DS signal; and an echo cancellation (EC) circuit configured to subtract, from at least one of the analog DS signal and the digital DS signal, a correction signal generated from the digital US input signal or a correction signal generated from the analog-converted US signal to generate an echo-cancelled digital DS input signal without ACI and ALI.