Upstream Power Back-Off Method for DSL Crosstalk Control
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Solution Overview
Problem
Existing Upstream Power Back-Off (UPBO) methods in DSL systems either fail to effectively reduce crosstalk between short and long lines, leading to performance degradation of short lines, or overly reduce power spectral density, harming upstream rates, especially with increasing demands for high-speed services like VoIP, IPTV, and HDTV.
Innovation Solution
A method that collects subscriber line information to determine a reference line length and calculates UPBO parameters, including an original point parameter, back-off slope parameter, and maximal close frequency point, to generate a template for Customer Premise Equipment (CPE) to perform UPBO only on bands where crosstalk affects long lines, thereby minimizing bandwidth loss on short lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If existing UPBO methods reduce upstream power spectral density to reduce crosstalk from short lines to long lines, then crosstalk is reduced and long line stability is improved, but upstream rate of short lines decreases sharply
Solution Approach 1:
The patent segments the frequency spectrum into different bands and applies selective power back-off only to specific frequency ranges where crosstalk occurs, rather than uniformly reducing power across all frequencies. This allows short lines to maintain higher rates in bands where they don't interfere with long lines.
Solution Approach 2:
The patent introduces local quality by applying different power spectral density characteristics to different frequency bands. Specifically, it modifies the PSD mask to have less aggressive back-off in high-frequency bands for short lines, allowing them to transmit at higher rates while still controlling crosstalk in the bands that affect long lines.
2Ease of manufacture
If a reference line length is selected for UPBO calculation, then UPBO parameters can be determined systematically, but short lines suffer excessive power reduction on high bands not used by long lines
Solution Approach 1:
The patent applies partial action by selectively applying power back-off only where necessary (in frequency bands where long lines are active) rather than excessively reducing power across all bands. This prevents unnecessary energy loss on high-frequency bands that short lines use but long lines don't utilize.
3Ease of operation
If uniform power back-off is applied across all bands, then implementation is simple, but bandwidth of short lines is overly reduced
Solution Approach 1:
The patent changes the PSD mask parameters selectively for different frequency bands and line types. It introduces band-specific back-off parameters that allow short lines to operate at higher power levels in high-frequency bands, thereby preserving more bandwidth while still controlling crosstalk in the bands that matter.
Data Source
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AI summary
A method, a device and a system for Upstream Power Back-Off (UPBO) in a Digital Subscriber Line (DSL) are provided. The method includes: collecting subscriber line information (S50); determining a reference line length according to the subscriber line information (S52); obtaining UPBO parameters of each upstream band of each subscriber line according to the determined reference line length (S54), where the UPBO parameters include an original point parameter, a back-off slope parameter, and a maximal close frequency point (UPBOFMAX) corresponding to the band; and executing an UPBO process on the band of the corresponding subscriber line below the UPBOFMAX according to the UPBO parameters (S58). Thus, the stability of longer lines can be ensured, an upstream rate of short lines is maximally increased, and the existing UPBO mode is fully compatible.