DMT Training Signals With Cyclic Extension
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Solution Overview
Problem
In DMT modulation systems like VDSL, altering the cyclic extension during training can cause loss of synchronization and tone orthogonality, making it difficult to apply time-domain equalization for efficient bandwidth use, especially on low-frequency tones.
Innovation Solution
Generating training signals with a variable phase rotation that is periodic in 1/Δf, maintaining orthogonality and allowing for channel response measurement without changing the cyclic extension, and applying TEQ only to specific tones for efficient equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the cyclic extension is altered during training to enable time-domain equalization, then channel response measurement is improved, but synchronization and tone orthogonality are lost
Solution Approach 1:
The patent applies parameter changes by introducing a variable phase rotation factor that changes with the training signal index. This allows the training signal to maintain periodicity with period 1/Δf while having a non-integer number of periods within each data block, enabling channel response measurement without altering the cyclic extension length that would破坏 synchronization
Solution Approach 2:
The training signal is designed to be periodic with period 1/Δf through the use of phase rotation that repeats every 2N samples. This periodic action allows the signal to maintain tone orthogonality while providing sufficient variation in the time domain for effective channel response measurement and time-domain equalization
2Productivity
If time-domain equalization is applied to all tones, then bandwidth efficiency is improved, but processing complexity increases
Solution Approach 1:
The patent applies local quality by selectively applying time-domain equalization only to specific tones (e.g., low-frequency tones) rather than all tones. This allows bandwidth efficiency to be improved for the most critical frequency range while reducing overall processing complexity by excluding tones that do not require equalization
Data Source
AI summary
A method for digital communication includes generating time-domain symbols having a predetermined symbol duration in accordance with a discrete multi-tone (DMT) modulation scheme. A cyclic extension is added to each of the time-domain symbols so as to form data blocks having a block length that is not an integer multiple of the symbol duration. A training pattern is generated on one or more tones of the DMT modulation scheme, wherein the training pattern is periodic over a sequence of the data blocks with a period equal to the symbol duration. The sequence of the data blocks is transmitted over a communication channel to a receiver, which processes the training pattern so as to determine a response of the channel to the one or more tones.