Tone Reordering for Multitone Transmission
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Solution Overview
Problem
The existing methods for tone reordering in multi-tone digital communication systems, such as ADSL and VDSL, require substantial memory resources and are computationally intensive, especially when dealing with a large number of subcarriers, as they need to group one-bit tones together and reorder tables frequently due to changes in line conditions.
Innovation Solution
The proposed solution involves reordering the tone-order table by pairing one-bit tones and encoding them as constellation points, minimizing position shifts and computational burden, allowing for on-the-fly computation or storage of the reordered table, reducing memory requirements and computational load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the receiver determines tone order arbitrarily and passes it to the transmitter, then forward error correction capability is improved, but memory resource consumption increases
Solution Approach 1:
The patent segments the tone-order table into multiple blocks, where each block contains a subset of tone indices. Instead of storing the complete tone-order table in memory, the system processes and transmits tone assignment information in smaller, manageable blocks. This segmentation reduces the memory footprint while maintaining the ability to implement arbitrary tone ordering for error correction.
2Adaptability or versatility
If the transmitter reorders tone tables to group one-bit tones together, then encoding compatibility is improved, but computational complexity increases
Solution Approach 1:
The patent performs preliminary reordering of the tone-order table during the training phase, before actual data transmission begins. The receiver determines the optimal tone order and pre-calculates the reordered table, which is then stored for use during data transmission. This preliminary action eliminates the need for complex real-time reordering operations during active communication, reducing computational complexity while maintaining encoding compatibility.
Solution Approach 2:
Instead of dynamically reordering tone tables during operation, the system creates a copied and pre-processed version of the tone-order table that is already in the required format. This copied table is prepared in advance with one-bit tones grouped together, allowing the transmitter to use it directly without performing complex reordering operations during data transmission.
3Adaptability or versatility
If tone reordering is performed frequently due to line condition changes, then adaptation to channel conditions is improved, but processing time increases
Solution Approach 1:
The patent implements a dynamic tone reordering strategy where the tone-order table is reordered during the training phase based on initial line condition measurements. When line conditions change during operation, the system can trigger a reordering operation, but the block-based structure allows this to be done efficiently. The dynamic adaptation is achieved without requiring complete reprocessing of all tones, as the block structure enables selective updates.
4Productivity
If VDSL systems use up to 4096 tones instead of ADSL's 256 tones, then transmission capacity is improved, but memory and computational burden increase proportionally
Solution Approach 1:
The patent divides the large tone-order table for VDSL (with up to 4096 tones) into multiple smaller blocks. Each block contains a subset of tone indices that can be processed and stored separately. This segmentation reduces the memory burden from storing a single large 4096-element table to storing multiple smaller blocks, making the system scalable to high-capacity VDSL implementations.
Solution Approach 2:
The patent transforms the problem from a one-dimensional array storage issue to a two-dimensional block structure. Instead of storing tones as a single long sequence, the system organizes them into a matrix-like structure with multiple blocks, where each block is a smaller sequence. This dimensional change allows for more efficient memory management and reduces the computational burden of operations on the complete tone set.
Data Source
AI summary
A method for data communication includes providing an order for assigning bits of an input data stream to tones in a multi-tone modulation scheme, and allocating respective bit-loading values to the tones, such that some of the tones are allocated a first bit-loading value and other tones are allocated at least one second bit-loading value. The order is modified so as to form pairs of the tones that are allocated the first bit-loading value, with one or more of the other tones intervening between at least some of the pairs. The input data stream is modulated by assigning the bits to the tones in accordance with the modified order and the respective bit-loading values, and encoding the bits that are assigned to each of the pairs of the tones as a constellation point.