Artificial Noise Controller for DSL Line Stability
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Solution Overview
Problem
DSL systems face instability due to crosstalk interference and noise, which can lead to service interruptions and reduced data rates, as existing methods like bit swapping and virtual noise may not be effective in rapidly changing noise conditions.
Innovation Solution
An artificial noise (AN) controller is used to adjust the signal-to-noise ratio (SNR) by adding artificial noise to the downstream signal, allowing dynamic adjustment based on actual noise levels to maintain stability and data rate, compatible with bit swapping and seamless rate adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If virtual noise method is used to improve DSL stability by limiting maximum bit-loading, then line stability is improved, but it requires CPEs to support VN function which is not available in legacy systems
Solution Approach 1:
The patent introduces artificial noise as an intermediary element that mediates between the transmitter and legacy CPEs. This artificial noise mimics the effect of virtual noise by degrading the signal quality in a controlled manner, allowing the system to achieve stability improvements without requiring CPEs to understand or support VN functionality. The artificial noise acts as a bridge that translates the stability-control mechanism into a form compatible with legacy equipment.
Solution Approach 2:
The patent copies the effect of virtual noise through artificial noise generation. Instead of implementing the actual VN mechanism that requires CPE support, the system creates a copy of its effect by adding artificial noise to the transmitted signal. This copied effect achieves the same stability improvement goal while being compatible with legacy CPEs that cannot process VN information.
2Reliability
If extra noise margin is reserved during line initialization to reduce re-initialization, then line stability is improved, but achievable data rates are substantially reduced
Solution Approach 1:
The patent implements dynamic adjustment of artificial noise levels based on actual line conditions. Rather than reserving a fixed extra noise margin that permanently reduces data rates, the system dynamically adds artificial noise only when and where needed to maintain stability. The AN level is adjusted in real-time based on measured line conditions, allowing the system to achieve stability without permanently sacrificing data rate capacity.
Solution Approach 2:
The patent changes the noise parameter dynamically through artificial noise injection. Instead of permanently reducing the signal power or reserving a fixed noise margin that limits data rates, the system modifies the noise parameter by adding controlled artificial noise. This allows flexible adjustment of the effective SNR to maintain stability while preserving the potential for higher data rates when conditions permit.
3Reliability
If bit swapping and seamless rate adaption are used to stabilize the system by adjusting bit-loading, then system stability is improved, but they are not fast enough to adapt to rapidly changing noise conditions
Solution Approach 1:
The patent applies preliminary action by adding artificial noise to the transmitted signal before the receiver processes it. This preemptive noise injection proactively compensates for rapidly changing line conditions, preventing instability before it occurs. Unlike reactive methods like BS and SRA that adjust after conditions change, the artificial noise is added in advance based on predicted or measured conditions, enabling faster response to rapidly changing noise environments.
Solution Approach 2:
The patent skips the slow iterative process of bit-loading adjustments by directly injecting artificial noise. Instead of going through the multi-step BS/SRA process that adjusts bit-loading parameters, the system rushes through the adaptation need by immediately adding artificial noise to achieve the desired stability effect. This bypasses the slower adaptation mechanism and provides faster response to changing conditions.
Data Source
AI summary
An apparatus comprising an artificial noise (AN) controller coupled to a digital subscriber line (DSL) transmitter and configured to adjust an AN level for a signal transmitted by the DSL transmitter, wherein the AN level is adjusted based on an actual signal to noise ratio (SNR) of the signal from the receiver to achieve a desired SNR for the signal. Also disclosed is a method comprising maintaining a data rate in a line at about a desired level by adjusting an AN level in a transmitted signal based on a SNR of a received signal.