Modulation Level Determination via Logical Channel Ping Testing
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Solution Overview
Problem
Traditional return-path spectrum management techniques in cable networks are inadequate as they often require channel deactivation for noise power measurements, are biased by random data transmission, and may not accurately predict modulation changes, especially under transient conditions, leading to potential service disruptions and inefficient modulation level adjustments.
Innovation Solution
A method and apparatus that allow for remote testing of network elements by configuring a logical communication channel with a matching modulation profile, sending test signals, and measuring characteristics like signal-to-noise ratio and modulation error ratio to determine acceptable modulation profiles without impacting existing data services, thereby identifying the maximum supported modulation level without disrupting active communications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional noise power measurements are performed, then channel characteristics can be measured, but the channel must be deactivated causing service disruption
Solution Approach 1:
The system performs preliminary measurements of upstream noise power and distortion characteristics before making modulation changes. By measuring channel characteristics while the channel is active and before deactivation, the system obtains accurate baseline data without causing service disruption, then uses this preliminary information to guide subsequent modulation adjustments.
2Loss of time
If composite MER measurements are used to evaluate channels, then measurement time is reduced, but the measurements are biased by random data transmission and network element activity
Solution Approach 1:
The system extracts specific distortion characteristics from the composite MER measurement by analyzing individual upstream frequency bins. Instead of relying on the overall composite MER which is biased by random network element activity, the system extracts and measures specific distortion components (such as second-order distortion products) from the frequency domain representation, providing more accurate and consistent channel quality assessment.
3Productivity
If modulation levels are increased to improve data rates, then communication efficiency improves, but service disruptions occur when network elements cannot support the higher modulation
Solution Approach 1:
The system performs preliminary measurements of upstream noise power and distortion characteristics before making modulation changes. By measuring channel characteristics while the channel is active and before deactivation, the system obtains accurate baseline data without causing service disruption, then uses this preliminary information to guide subsequent modulation adjustments.
Solution Approach 2:
The system uses return-path spectrum management to continuously monitor upstream noise power and distortion characteristics, providing feedback on channel quality. This feedback mechanism allows the system to adjust modulation levels dynamically based on actual channel conditions, ensuring that modulation changes are made only when channel quality supports the higher order modulation, thereby preventing service disruptions.
Data Source
AI summary
A logical channel is configured to match a modulation profile of an active channel. A network element is assigned to the logical channel and a ping request is sent to the network element. A response from the network element is measured, such as measuring the MER. The modulation profile is increased in the logical channel and another ping request is sent to the network element. The response is measured again, and the process is repeated until a non-linearity is detected in the response. The acceptable modulation profiles are indicated before the non-linearity is detected in the response.