Remote PHY Self-Interference Cancellation for Upstream Band Extension
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Solution Overview
Problem
Cable broadcasting networks face an asymmetry in upstream and downstream frequency bands, leading to insufficient upstream transmission capacity, which hinders the provision of high-speed Internet and high-quality broadcasting services due to the limited upstream frequency band.
Innovation Solution
A method that determines signal interference among cable modems, categorizes them into groups to minimize interference, and uses a remote PHY device to cancel self-interference signals, allowing the upstream and downstream bands to share the same frequency band, thereby extending the upstream band without reducing the downstream band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Frequency-Division Duplexing (FDD) is used to allocate separate frequency bands for upstream and downstream transmission, then simultaneous bidirectional communication is enabled, but the upstream frequency band becomes insufficient compared to the downstream band
Solution Approach 1:
The system segments cable modems into multiple groups (e.g., Group 1 and Group 2) based on their upstream signal characteristics. Each group is assigned different frequency bands for upstream transmission, allowing the system to utilize the entire frequency spectrum more efficiently. This segmentation enables upstream bands to be extended into the high-split band while maintaining downstream band integrity.
Solution Approach 2:
The patent introduces a new dimension of frequency band allocation by allowing upstream and downstream bands to overlap in the same frequency range through group-based segmentation. Instead of strict frequency separation, the system uses group identification to manage interference, effectively transforming the problem from a one-dimensional frequency allocation to a multi-dimensional solution involving group, frequency, and time slots.
2Productivity
If the upstream band is extended to the high-split band to increase upstream capacity, then upstream transmission capability improves, but the downstream band size is reduced
Solution Approach 1:
The frequency band is segmented into different allocation schemes based on cable modem groups. In the first allocation scheme, upstream bands for different groups are arranged in ascending frequency order. In the second allocation scheme, upstream bands are arranged in descending frequency order. This flexible segmentation allows the upstream band to extend to the high-split band without encroaching on downstream band resources.
Solution Approach 2:
The system dynamically selects between different frequency band allocation schemes based on channel conditions and service requirements. The network can switch between the first allocation scheme (ascending frequency arrangement) and the second allocation scheme (descending frequency arrangement) to optimize performance under different conditions, allowing adaptive upstream band extension without fixed downstream band reduction.
3Productivity
If upstream and downstream signals share the same frequency band to double frequency usage efficiency, then frequency utilization improves, but self-interference signals occur
Solution Approach 1:
The patent converts the harmful self-interference effect into a useful signal characteristic for identification. By analyzing the self-interference signal properties, the system identifies cable modems that are experiencing interference and assigns them to appropriate groups. This group information is then used to allocate frequency bands in a way that eliminates interference while maintaining high frequency utilization through band sharing.
Solution Approach 2:
The system implements a feedback mechanism where cable modems report their received signal quality and interference conditions to the network. Based on this feedback, the network dynamically adjusts frequency band allocation and group assignments to minimize self-interference. This closed-loop control enables the system to maintain high frequency usage efficiency while actively managing and reducing harmful interference effects.
Data Source
AI summary
Disclosed herein are a method for simultaneously transmitting/receiving upstream and downstream signals using a remote PHY architecture and an apparatus for the same. The method determines whether to divide frequencies depending on whether signal interference occurs among multiple cable modems connected to a cable network, if it is determined to divide the frequencies, categorize the multiple cable modems into multiple groups so that signal interference occurs in each group, but signal interference does not occur between groups, set transmission bands for the multiple groups so that an upstream band and a downstream band of one group alternate with upstream bands and downstream bands of remaining groups by dividing the frequencies in accordance with a number of groups, and cancels, by a remote physical layer (PHY) device located at an optical network terminal of the cable network, self-interference signals for respective groups based on the transmission bands.