Upstream RF Input Level Scaling in HFC Networks
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Solution Overview
Problem
Hybrid Fiber Coaxial (HFC) cable networks face signal degradation and errors due to mismatched power levels between client devices and head-end devices, leading to thermal noise, quantization noise, clipping, and intermodulation distortion, especially with advanced services requiring higher bandwidth and modulation densities.
Innovation Solution
The head-end device determines the power level difference between received upstream signals and a target power level, using a level scaler to adjust the signal before analog-to-digital conversion, thereby ensuring the signal is within the optimal range to prevent degradation and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the received signal level is below the target level, then the signal may be lost in thermal noise and quantization noise, but increasing the client device transmit power may not be sufficient due to device limitations
Solution Approach 1:
The patent introduces an intermediary component (amplifier or variable gain amplifier) between the received RF signal and the A/D converter to boost weak signals before conversion. This mediator allows the system to overcome client device power limitations by providing additional gain in the head-end device, thereby improving signal reception reliability without requiring increased transmit power from the client device.
Solution Approach 2:
The patent dynamically changes the gain parameter of the amplifier or variable gain amplifier based on the detected signal level. When the received signal is below the target level, the system increases the amplifier gain to boost the signal to the appropriate level for A/D conversion, thereby compensating for insufficient client device transmit power and improving reception reliability.
2Reliability
If the received signal level is above the target level, then clipping and intermodulation distortion occur, but reducing client device transmit power may cause the signal to fall below the target level
Solution Approach 1:
The patent introduces an intermediary component (attenuator or variable gain amplifier operating in reduction mode) between the received RF signal and the A/D converter to reduce strong signals before conversion. This mediator prevents clipping and intermodulation distortion by ensuring that even strong client device signals are reduced to the appropriate level for the A/D converter, thereby eliminating harmful distortion effects.
Solution Approach 2:
The patent dynamically changes the gain parameter of the amplifier or variable gain amplifier to a reduction value when the received signal exceeds the target level. This parameter adjustment reduces the signal level to prevent clipping and intermodulation distortion while maintaining the ability to handle both weak and strong signals reliably.
3Adaptability or versatility
If a long loop Automatic Level Control system is used to adjust client device transmit power, then adaptation to location-specific network characteristics is achieved, but client devices may be unable to transmit at the desired power level due to device limitations
Solution Approach 1:
The patent introduces an intermediary component (amplifier) in the head-end device that compensates for client device power limitations. This mediator allows the system to maintain adaptability to location-specific characteristics through the long loop ALC while providing additional power amplification for weak signals, thereby overcoming the transmit power capability limits of client devices.
Solution Approach 2:
The patent inverts the traditional approach by moving the power adjustment function from the client device (transmit end) to the head-end device (receive end). Instead of requiring client devices to increase transmit power, the system uses an amplifier at the head-end to boost weak signals after reception, thereby achieving the desired power level adaptation without being constrained by client device power capabilities.
4Reliability
If signal power level mismatches are not corrected, then signal degradation and errors occur, but adding complex power adjustment mechanisms increases device complexity
Solution Approach 1:
The patent introduces a single intermediary component (amplifier or variable gain amplifier) that performs both functions of boosting weak signals and reducing strong signals through dynamic gain control. This unified mediator simplifies the overall system architecture compared to having separate mechanisms for power increase and power reduction, thereby improving signal reception reliability while minimizing the increase in device complexity.
Solution Approach 2:
The patent implements a universal power adjustment mechanism using an amplifier or variable gain amplifier that can operate in both gain-increasing and gain-reducing modes. This multi-functional component handles both weak signal amplification and strong signal attenuation, eliminating the need for separate mechanisms and thereby reducing overall device complexity while maintaining high signal reception reliability.
Data Source
AI summary
Embodiments include systems and methods for scaling power level of an upstream signal by a device processor of a head-end device in a communication network. In embodiments, the device processor may determine a power level of the signal received at the head-end device from a client device. The device processor may determine a difference between the power level of the received signal and a target power level of an analog-to-digital converter of the head-end device, and may adjust the power level of the received signal at the head-end device based on the determined difference. In embodiments, the device processor may determine a power level of an upstream signal to be received by the head-end device, may determine a difference between the power level of the received signal and the target power level, and may adjust the power level of a received signal at the head-end device based on the determined difference.