DSL Line Initialization Crosstalk Cancellation via Precoding
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In digital subscriber line (DSL) systems, the initial stage of line initialization faces challenges with crosstalk cancellation, as nonlinear precoding requires known crosstalk channels, which are not available initially, and linear precoding leads to a significant increase in transmit power, potentially exceeding limits.
Innovation Solution
A method that involves sending data signals using only low-frequency subcarriers to acquire a first precoding matrix, establishing a feedback channel, and then using higher subcarriers to acquire a second precoding matrix, allowing for crosstalk cancellation without exceeding transmit power limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If linear precoding is used for crosstalk cancellation during line initialization, then crosstalk can be canceled, but transmit power increases dramatically and may exceed limits
Solution Approach 1:
The patent applies preliminary action by establishing a feedback channel first before performing full crosstalk cancellation. The system initially uses only a first part of subcarriers to set up the feedback mechanism, then gradually activates the second part of subcarriers. This staged approach allows the system to prepare necessary channel information and control structures in advance, preventing uncontrolled power increases during full crosstalk cancellation.
Solution Approach 2:
The patent segments the crosstalk cancellation process into distinct phases: first establishing a feedback channel using a first part of subcarriers, then using a second part of subcarriers for full crosstalk cancellation. This segmentation allows the system to break down the complex power management problem into manageable stages, where each phase prepares necessary conditions for the next phase, thereby controlling overall transmit power within limits.
2Power
If nonlinear precoding is used for crosstalk cancellation, then transmit power can be controlled within limits, but crosstalk channels must be known in advance which are not available during initial line initialization
Solution Approach 1:
The patent applies preliminary action by using the first part of subcarriers to establish the feedback channel and acquire necessary crosstalk channel information before activating the second part of subcarriers for full crosstalk cancellation. This preliminary phase prepares all necessary channel state information in advance, enabling the system to switch to nonlinear precoding without requiring crosstalk channels to be known beforehand during the entire initialization process.
3Productivity
If all subcarriers are used simultaneously for line initialization, then initialization speed is improved, but crosstalk cancellation becomes ineffective due to power constraints
Solution Approach 1:
The patent segments the subcarriers into a first part and a second part, using the first part to establish the feedback channel and then activating the second part for full crosstalk cancellation. This segmentation enables the system to progress through initialization stages systematically, maintaining crosstalk cancellation effectiveness while progressively utilizing more subcarriers to improve overall initialization speed.
Solution Approach 2:
The patent applies preliminary action by using the first part of subcarriers to establish the feedback channel and acquire necessary channel information before activating the second part of subcarriers. This preliminary preparation enables the system to subsequently use all subcarriers effectively for initialization while maintaining crosstalk cancellation performance, as the necessary control structures are already in place.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively cancels crosstalk during line initialization while maintaining transmit power within acceptable limits, improving the reliability and efficiency of DSL system performance.
Implementation Method 1
By using two DSL lines, that is, a first line 103 established between a central office end transceiver 1011 and a subscriber end 1021 and a second line 104 established between a central office end transceiver 1012 and a subscriber end 1022, as an example, according to an electromagnetic induction principle, crosstalk is generated between signals of the first line 103 and the second line 104 accessed to the DSLAM.
Data Source
Figure 1(a)~2
Figure 3~4
Figure 5~6
AI summary
The present invention provides a method and a device for line initialization. In the method, first, a first precoding matrix required by a first part of subcarriers is acquired in a downstream direction, and then multiple data signals of all data signals that need to be sent in an initialization process are sent by using only the first part of subcarriers; afterward, a second precoding matrix required by at least a second part of subcarriers of all available subcarriers is acquired, and remaining data signals of all the data signals exclusive of the multiple data signals are sent by using the at least second part of subcarriers to complete line initialization. By using the foregoing manner, the present invention can cancel crosstalk between lines while completing line initialization, and does not easily cause transmit power to exceed a limit.