Echo Cancellation Training for Full Duplex Amplifiers
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Solution Overview
Problem
In Hybrid Fiber-Coaxial (HFC) networks, there is a need for an effective echo cancellation process that can accurately observe and characterize upstream echoes at the downstream receiver without muting the continuous downstream signal, which is essential for proper operation of Full Duplex (FDX) amplifiers.
Innovation Solution
A staircase 2-dimensional Downstream (DS) echo cancellation training window is generated by subtracting DS scattered pilots from the DS signal, allowing for the observation and characterization of upstream echoes at specific locations, enabling accurate echo cancellation without interrupting the downstream signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the downstream signal is muted to observe upstream echoes, then measurement precision of echoes is improved, but loss of information and interruption of downstream service occur
Solution Approach 1:
The downstream signal is segmented by identifying and removing scattered pilot components from the continuous downstream signal, creating training windows that contain only the downstream pilots. This segmentation allows echo observation in specific time-frequency regions without muting the entire downstream signal, thus maintaining downstream service continuity while enabling precise echo measurement.
Solution Approach 2:
Downstream scattered pilots serve as an intermediary reference signal. By correlating the received downstream signal with the known scattered pilot sequence, the system can isolate and measure upstream echoes without directly muting the downstream signal. The scattered pilots act as a mediator that enables echo observation while preserving the continuous downstream transmission.
2Productivity
If the downstream signal is continuous for uninterrupted service, then productivity is improved, but difficulty of detecting and measuring upstream echoes increases
Solution Approach 1:
The continuous downstream signal is conceptually segmented into regions containing scattered pilots and regions containing other downstream data. By focusing echo measurement only on the scattered pilot regions, the system maintains continuous downstream service while creating observable windows for echo detection without requiring signal interruption.
Solution Approach 2:
The system uses the distinct spectral characteristics (frequency domain properties) of scattered pilots as a marker or 'color' that distinguishes echo-containing regions from other downstream signal regions. By identifying these frequency-specific markers, the system can detect and measure echoes embedded within the continuous downstream signal.
Data Source
AI summary
Echo Cancellation (EC) training for a Full Duplex (FDX) amplifier may be provided. First, a Downstream (DS) signal at a fixed location on a subcarrier frequency may be received. Next, an Upstream (US) echo may be determined from the received DS signal at the fixed location on the subcarrier frequency. Determining the upstream echo may comprise subtracting a known value from the received DS signal at the fixed location on the subcarrier frequency. An Echo Cancelation (EC) coefficient may then be determined. Determining the EC coefficient may comprise dividing the determined US echo by a reference signal comprising an US signal. Next, EC may be performed. Performing EC may comprise subtracting the echo from the DS signal.