Selective Proxy for Full Duplex Cable ACI Mitigation
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Solution Overview
Problem
Full duplex cable networks experience significant adjacent channel interference (ACI) due to the simultaneous use of the same frequency spectrum for downstream and upstream traffic, which affects packet error rates and throughput, especially in legacy cable modems coexisting with FDX-enabled modems, and existing mitigation techniques like tap replacement are costly and reactive.
Innovation Solution
A selective proxy system intercepts and retransmits packets for cable modems experiencing ACI, dynamically calculating packet error rates and adjusting thresholds based on service level agreements, quality of service, and historical data to minimize interference and maintain throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If full duplex system is implemented to double throughput, then bandwidth capacity is improved, but adjacent channel interference increases
Solution Approach 1:
A selective proxy is introduced as an intermediary component between the CMTS and cable modems. The proxy intercepts downstream packets, monitors for ACI-induced errors, and selectively retransmits affected packets to cable modems, thereby mediating the harmful interference effect while preserving full duplex operation
Solution Approach 2:
The system implements feedback mechanisms where the selective proxy continuously monitors packet error rates and ACI conditions at cable modems, adjusting its retransmission behavior based on real-time network conditions and interference levels to optimize throughput while mitigating interference effects
2Object-affected harmful factors
If tap replacement is performed to mitigate ACI, then interference is reduced, but capital expenditure increases
Solution Approach 1:
Instead of physically replacing taps with higher isolation models, the system creates a virtual copy/backup of downstream packets at the selective proxy. This backup copy is used for retransmission when ACI causes packet loss, achieving interference mitigation without physical hardware changes
Solution Approach 2:
The patent replaces the mechanical/physical solution of tap replacement with a software-based packet interception and retransmission system. The selective proxy uses protocol-level interventions rather than physical RF isolation improvements, substituting mechanical hardware changes with software-based error correction
3Reliability
If selective proxy retransmits packets, then packet error rate is improved, but network complexity increases
Solution Approach 1:
The selective proxy functionality is segmented into distinct modular components: packet interception module, error detection module, backup packet storage module, and selective retransmission module. This segmentation allows for targeted implementation and easier management of complexity
Solution Approach 2:
The selective proxy does not retransmit all packets unconditionally, but only selectively retransmits packets that are determined to be affected by ACI based on error rate thresholds and packet monitoring. This partial action approach reduces unnecessary retransmissions and simplifies the overall system behavior
Data Source
AI summary
A method in an embodiment includes calculating a first packet error rate (PER) of a flow sent from a source to a cable modem over a first period of time in a full duplex cable network, tagging the flow based on determining the first PER satisfies a tag threshold associated with the flow, and intercepting, at a selective proxy, a packet of the tagged flow. The method further includes storing a backup of the packet, transmitting the packet to the cable modem, determining the cable modem did not receive the packet, and retransmitting the backup of the packet to the cable modem. Further embodiments include dynamically calculating a second PER of the tagged flow based on a second period of time, determining the second PER satisfies a de-tag threshold, and revoking the tagging of the flow based, at least in part, on determining the second PER satisfies the de-tag threshold.