DSL Signal Transmission via Frequency Domain Equalization
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Solution Overview
Problem
Existing DSL technologies face challenges in effectively transmitting high-frequency signals over twisted metallic pairs due to crosstalk interference, especially when indirect coupling approaches the strength of direct coupling, leading to reduced data rates and increased noise.
Innovation Solution
A method and system that utilize discrete multi-tone protocols to transmit related signals over both pairs of wires, employing frequency domain equalization coefficients based on both direct and crosstalk channel transfer functions, and switching between vectoring and Combined Multi-path Related Signal DSL Reception (CMRSDR) modes to optimize signal-to-noise ratio, with a Vectoring/CMRSDR switch mechanism to adapt to changing noise environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high frequency signals are transmitted over twisted metallic pairs, then bandwidth potential and data rates are improved, but crosstalk interference increases significantly
Solution Approach 1:
The patent applies vectoring technology to convert the harmful crosstalk effect into a beneficial signal. By pre-distorting the transmitted signal based on known crosstalk characteristics, the crosstalk that would normally degrade the signal actually helps to cancel itself out at the receiver, improving signal quality and enabling higher data rates over the metallic pairs
Solution Approach 2:
The patent changes the frequency parameters and signal characteristics dynamically. It uses discrete multi-tone modulation where different frequency tones are activated based on channel conditions, and adjusts transmission parameters adaptively to optimize the balance between achieving high data rates and managing crosstalk interference levels
2Reliability
If indirect coupling approaches the strength of direct coupling, then signal transmission becomes more complex, but conventional vectoring techniques become ineffective
Solution Approach 1:
The patent introduces an intermediary processing stage that explicitly models and compensates for both direct and indirect coupling paths. Rather than relying on conventional vectoring assumptions, the system uses frequency domain equalization with coefficients that account for the actual measured channel characteristics including indirect coupling, effectively mediating between the complex physical reality and the signal processing requirements
Solution Approach 2:
The patent performs preliminary channel characterization and equalization coefficient calculation before actual data transmission. By pre-computing the frequency domain equalization coefficients based on training sequences and channel estimates, the system prepares for the complex indirect coupling scenario in advance, reducing the processing burden during active data transmission and improving overall reliability
3Productivity
If redundant wire pairs are utilized for data transmission, then bandwidth utilization is improved, but crosstalk management becomes more difficult
Solution Approach 1:
The patent merges the transmission channels by bonding multiple wire pairs together to create a single logical high-bandwidth connection. It combines the signals from multiple pairs using vectoring and frequency domain equalization, treating the crosstalk between pairs as a manageable characteristic rather than a prohibitive factor, thereby achieving effective bandwidth aggregation while controlling interference
Solution Approach 2:
The patent moves the problem from the time domain to the frequency domain by using discrete multi-tone modulation and frequency domain equalization. This dimensional change allows independent management of different frequency components, enabling the system to exploit bandwidth across multiple wire pairs while managing crosstalk selectively in the frequency domain rather than being constrained by time-domain interference
Data Source
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AI summary
A system (100), (200), (310), (320) for transmitting data between an upstream transceiver (100) and a downstream transceiver (200) via two pairs of wires (310), (320) extending between the transceivers. The system comprises: the upstream transceiver (100) which includes first (110) and second (120) transmitter portions; the downstream transceiver (200) which includes first (210) and second (220) receiver portions for receiving signals transmitted by the upstream transceiver in a differential mode; and the two pairs of wires (310), (320) extending between the transceivers, the wires forming a composite channel through which signals transmitted by the upstream transceiver travel before being received by the downstream transceiver, the composite channel including direct differential mode channels h11 and h22 between the first and second transmitter portions on the one hand and the first and second receiver portions respectively on the other hand, and indirect channels h21 and h12 between the first and second transmitter portions on the one hand and the second and first receiver portions respectively on the other hand. The upstream transceiver is operable to transmit, to the downstream transceiver, using a discrete multi-tone protocol capable of using up to a number of different tones, a data signal in which related signals are transmitted onto both pairs of wires in a differential mode, such that, in use, each of the first and second receiver portions receives a respective one of the transmitted signals after modification by the composite channel together with some portion of the other related signal. Each receiver portion includes a fast Fourier Transform module for converting the received signal into the frequency domain and a related-signals processing frequency domain equaliser for further processing the resulting signal using frequency domain equalisation coefficients calculated in dependence upon estimated channel transfer functions associated with the direct differential mode channel terminating at the respective receiver portion and additionally in dependence upon estimated channel transfer functions associated with the indirect channel terminating at the respective receiver portion.