ADSL Modem Bit Rate Adaptation for Repetitive Noise
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Solution Overview
Problem
Current ADSL modems are vulnerable to time-varying impairments such as non-stationary noise, leading to instability and poor synchronization, especially when faced with repetitive electrical impulse noise, as they rely on a scalar measure of operating margin that is not suitable for changing noise conditions, resulting in inconsistent bit rate calculations and poor customer experience.
Innovation Solution
The implementation of a method that classifies symbols as normal or abnormal based on error measurements, maintaining separate average margins for each condition, and dynamically adjusting bit rates and error-correcting code settings to adapt to changing noise environments, using a symbol-by-symbol error metric and state machine to differentiate between normal and abnormal signal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a scalar measure of operating margin is used, then the system is simple to implement, but it cannot handle time-varying noise impairments effectively
Solution Approach 1:
The patent segments the operating margin measurement into multiple components: a scalar measure for simple conditions and a vector measure that captures time-varying characteristics. The system divides the margin assessment into normal operation margins and abnormal condition margins, allowing differentiated handling of different noise scenarios without overwhelming complexity.
Solution Approach 2:
The system dynamically adapts the margin measurement approach based on detected noise conditions. When normal conditions are detected, the scalar measure is used; when abnormal time-varying noise is detected, the system switches to vector-based measures and adjusts bit rates accordingly. This dynamic adaptation resolves the contradiction by using simple measures when possible and complex measures only when needed.
2Stability of the object's composition
If modems use fixed bit rate calculations, then the system is stable under constant conditions, but it cannot adapt to changing noise environments
Solution Approach 1:
The bit rate calculation system dynamically adjusts based on detected abnormal conditions. The patent implements a mechanism that monitors operating margins in real-time and modifies bit rate allocations when time-varying noise is detected. The system maintains stability during normal operation while enabling adaptation when conditions change, resolving the contradiction between fixed stability and dynamic adaptability.
Solution Approach 2:
The system incorporates feedback loops that continuously monitor operating margins and adjust bit rate calculations accordingly. When abnormal conditions are detected through the feedback mechanism, the system modifies transmission parameters to maintain synchronization. This feedback-driven adaptation allows the system to combine stability during normal operation with responsiveness to changing conditions.
3Ease of operation
If modems do not account for abnormal noise conditions, then the transmission system is simple to operate, but synchronization is lost and customer experience deteriorates
Solution Approach 1:
The modem system performs self-diagnosis and self-adjustment by automatically detecting abnormal noise conditions and modifying its own operation. The patent implements mechanisms where the modem monitors its own operating margins, identifies when abnormal conditions occur, and autonomously adjusts bit rates and transmission parameters without external intervention. This self-service capability maintains synchronization while requiring minimal operational complexity from the user.
Data Source
AI summary
Following a transmission comprising a plurality of symbols, an error measurement is generated for each symbol, so that one may distinguish between symbols having a relatively low error and symbols having a relatively high error. A bit rate to be used for subsequent transmission is determined as a function of error measurements of those symbols that have relatively low error and as a function also of the proportion of symbols having a relatively high error, such that the bit rate reduces as the proportion increases. Measurement of the error rate and/or the durations of high and low error conditions may also be used to set other transmission parameters such as error-correcting code and interleaver settings.