Carrier Current Signal Bit Allocation for VDSL Interference
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Solution Overview
Problem
Interference between carrier current signals transmitted over electrical lines and VDSL signals over telephone lines occurs due to shared frequency bands and multicarrier modulation, leading to signal contamination and rate losses, especially when the lines are close to each other.
Innovation Solution
A method that identifies carrier frequencies with high spectral power density levels in the VDSL signal and reduces the number of bits attributed to corresponding frequencies in the carrier current signal, while also redistributing these bits to non-interfering frequencies to maintain a constant transmission rate, thereby reducing interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the same frequency band is used for both VDSL and carrier current signals, then spectrum utilization is improved, but interference between the two signal types increases
Solution Approach 1:
The patent applies local quality by differentiating the treatment of different frequency components within the shared spectrum. Specifically, it identifies carrier frequencies that cause high interference to VDSL signals and selectively reduces the number of bits allocated to those specific frequencies in the carrier current signal, while maintaining normal operation at other frequencies. This localized adjustment resolves the contradiction by preserving overall spectrum utilization while eliminating harmful interference at critical frequencies.
Solution Approach 2:
The patent changes the parameter of bit allocation per carrier frequency based on the measured interference level. By dynamically adjusting the number of bits allocated to each carrier frequency according to its interference impact on VDSL signals, the system optimizes the trade-off between spectrum efficiency and interference reduction. This parameter change allows the system to maintain high spectrum utilization while minimizing harmful effects.
2Object-affected harmful factors
If the number of bits is reduced at interfering frequencies, then interference is reduced, but transmission rate decreases
Solution Approach 1:
The patent applies local quality by making selective bit allocation adjustments only at specific carrier frequencies that cause high interference, while maintaining full bit allocation at frequencies that do not interfere with VDSL signals. This localized approach ensures that the transmission rate is preserved as much as possible while still reducing interference at problematic frequencies.
Solution Approach 2:
The patent converts the harmful interference effect into a useful signal for optimization. By measuring the interference level at each carrier frequency and using this information to adjust bit allocation, the system turns the interference measurement into a beneficial control mechanism. The interference itself becomes the guide for optimizing the transmission rate, ensuring that bits are allocated efficiently across all frequencies.
3Object-affected harmful factors
If bit allocation is adjusted dynamically, then interference is reduced, but system complexity increases
Solution Approach 1:
The patent implements feedback by continuously measuring the interference level between carrier current and VDSL signals at each carrier frequency, and using this measurement to adjust the bit allocation. This closed-loop feedback mechanism automatically adapts the system parameters based on actual interference conditions, reducing the need for complex manual configuration while achieving effective interference reduction.
Solution Approach 2:
The system performs self-service by automatically measuring interference levels and adjusting its own bit allocation without external intervention. The carrier current modem monitors the interference caused by its transmission and autonomously optimizes its operation by adjusting bit allocation, thereby reducing interference while maintaining transmission rate. This self-service capability simplifies system operation compared to manual control mechanisms.
Data Source
AI summary
The present invention concerns a method of reducing interference between a carrier current signal (SCPL) transmitted over an electrical line (Le) and a signal of the VDSL type (SVDSL) transmitted over a telephone line (Lpots) that is situated close to the electrical line (Le). Said signals (SCPL, SVDSL) routing data in the form of bits that are attributed to carrier frequencies (Fk) distributed in the same frequency band on different frequency planes, characterized in that it comprises.a step (1) for determining at least one carrier frequency (FVDSL), referred to as the VDSL frequency, of a frequency plane used for transmitting the VDSL-type signal the spectral power density level of which is higher than a predetermined threshold (Th),a step (2) for determining at least one carrier frequency (FCPL), referred to as the CPL frequency, of another frequency plane used for transmitting the carrier current signal and which is common with at least one VDSL frequency thus determined (FVDSL), anda step (3) for reducing the number of bits (NCPL) attributed up until then to each so-called CPL frequency (FCPL) thus determined.