Upstream Funneling Noise Suppression in HFC Networks
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Solution Overview
Problem
In Hybrid Fiber-Coaxial (HFC) networks, upstream noise funneling degrades the Signal-to-Noise Ratio (SNR) due to combined noise from multiple output ports, which is not acceptable for Full Duplex (FDX) operations, especially in N+2 FDX networks with 4 output ports, leading to significant SNR degradation.
Innovation Solution
Implementing a funneling noise suppression process that determines the power level of each mini-slot in a two-dimensional time-frequency space and mutes those with power levels below a predetermined threshold, thereby suppressing noise on unused channels at the input port of FDX amplifiers, preventing noise accumulation and improving SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If multiple output ports are used in FDX amplifiers to support more Cable Modems, then the network capacity and number of supported users increase, but upstream noise funneling degrades the SNR
Solution Approach 1:
The upstream frequency spectrum is segmented into multiple mini-slots in the time-frequency domain. The noise suppressor divides the spectrum into distinct segments and selectively mutes specific mini-slots that contain funneling noise, allowing other mini-slots to carry useful upstream signals. This segmentation enables simultaneous support for multiple Cable Modems while suppressing noise in specific frequency segments.
Solution Approach 2:
Instead of uniformly suppressing noise across the entire upstream spectrum, the invention applies local quality by selectively muting only those specific mini-slots where funneling noise is detected. The noise suppressor analyzes each mini-slot individually and applies muting only where necessary, preserving signal quality in mini-slots that do not contain noise while maintaining support for multiple users.
2Reliability
If noise suppression is applied to all mini-slots, then SNR is improved, but useful upstream signals from active Cable Modems may be suppressed
Solution Approach 1:
The noise suppressor employs feedback mechanisms by continuously monitoring the upstream signals from multiple Cable Modems and the downstream signals from the amplifier. Based on this feedback, the system identifies which mini-slots contain funneling noise versus useful upstream signals. The feedback loop enables intelligent decision-making about which mini-slots to mute, ensuring that useful signals are preserved while noise is suppressed.
Solution Approach 2:
Rather than applying noise suppression uniformly across all mini-slots (excessive action), the invention applies partial action by selectively muting only the specific mini-slots where funneling noise is detected. This partial suppression approach maintains the useful upstream signals from active Cable Modems in other mini-slots while still achieving SNR improvement in the affected frequency segments.
3Reliability
If mini-slots are muted to suppress noise, then SNR is maintained, but the available bandwidth for upstream transmission is reduced
Solution Approach 1:
The upstream bandwidth is segmented into multiple mini-slots in the time-frequency domain. By muting only specific noisy mini-slots rather than reducing the overall bandwidth, the system maintains most of the available upstream bandwidth for active Cable Modems. The segmentation allows selective noise suppression in minimal frequency segments while preserving the majority of the bandwidth for useful transmissions.
Solution Approach 2:
The system dynamically changes parameters by adjusting which mini-slots are muted based on real-time detection of funneling noise. The noise suppressor modifies the operational state of specific frequency segments without changing the overall upstream bandwidth allocation. This parameter change approach maintains effective SNR while minimizing the impact on available bandwidth for active users.
Data Source
AI summary
Upstream (US) funneling noise suppression may be provided. First, a signal comprising a plurality of mini-slots in a two dimensional time frequency space may be received by a funneling noise suppressor. Next, the power level in each of the plurality of mini-slots may be determined. The received signal may then be outputted. Outputting the received signal may comprises outputting the received signal with mini-slots muted in the received signal that have a power level less than a predetermined threshold.