DSL Modem PSD Calibration via Impedance Normalization
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Solution Overview
Problem
Existing DSL systems face inaccuracies in reporting noise and loss conditions due to varying input impedance of customer premises equipment (CPE) modems, leading to inconsistent subcarrier modulation and data assignment, as the ASICs calculating power spectral density (PSD) estimates are unaware of the actual input impedance.
Innovation Solution
Measuring received signal levels for each subcarrier, converting them into power levels, estimating terminal-to-terminal impedance, and calculating corrected power levels using a known reference input impedance, thereby normalizing PSD measurements to account for varying impedances and improve reporting accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If voltage measurements are performed by ASIC without knowledge of actual input impedance, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies preliminary action by measuring the actual input impedance of the analog front-end circuitry before performing PSD measurements. The ASIC is programmed with the measured impedance value in advance, allowing it to accurately convert voltage measurements to power levels without needing to know the impedance beforehand. This resolves the contradiction by preparing the necessary calibration data beforehand, maintaining simple ASIC operation while achieving accurate measurements.
2Ease of manufacture
If different vendors use different fixed division factors for voltage-to-power conversion, then ease of manufacture is improved, but reliability deteriorates
Solution Approach 1:
The patent applies parameter changes by replacing fixed vendor-specific division factors with dynamically determined conversion factors based on actual measured input impedance. Each modem measures its own impedance and uses that specific value for accurate power calculation. This allows different vendors to manufacture modems with different analog front-ends while maintaining reliable and consistent reporting, as each device uses its own measured parameters rather than generic fixed factors.
3Device complexity
If voltage measurements are used without impedance correction, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent applies self-service by having the measurement system automatically measure its own input impedance and use that information to correct its voltage measurements. The analog front-end circuitry's impedance is measured and stored, then the ASIC uses this self-measured value to accurately convert voltage to power. This eliminates the need for external impedance data or complex calibration procedures, maintaining system simplicity while achieving accurate measurements through self-calibration.
Data Source
AI summary
Received signal measurements are calibrated in a communication device by measuring a received signal level for each of one or more subcarriers of a transmitted signal received from another communication device, converting the measured received signal level for each of the one or more subcarriers into a corresponding measured power level, estimating a terminal-to-terminal impedance between the communication devices and calculating a corrected power level for each of the one or more subcarriers as a function of the measured power level for the subcarrier, a known reference input impedance for the communication device and the estimated terminal-to-terminal impedance.