Frame Phase Control via Stuffing Symbol Injection
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Solution Overview
Problem
In plesiochronous communication methods, such as S(H)DSL, the injection or omission of stuffing data symbols to control frame length can lead to timing jitter in the recovered data clock on the receiving side, especially when the data source frequency is not exactly synchronous with the symbol frequency, causing phase deviations that are difficult to suppress.
Innovation Solution
A method and device that determine the phase difference between the frame transmission clock and data clock over multiple frames, averaging this difference to accurately adjust the frame phase and interrupting the alternating stuffing pattern to minimize jitter, using a control system with both proportional and integral sections and a phase measurement frequency to produce an adjusting signal that controls the injection or omission of stuffing data symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stuffing data symbols are injected or omitted to control frame length, then the average frame length becomes synchronous with the data source frequency, but timing jitter is introduced in the recovered data clock
Solution Approach 1:
The patent applies preliminary action by determining the phase difference over multiple frames before making adjustments. The phase detector measures the phase difference between the frame transmission clock and data clock over a period of multiple frames, and only then does the control system activate stuffing data symbol injection. This advance measurement and planning prevents reactive adjustments that would cause jitter, instead using a measured average phase difference to guide controlled frame length adjustments.
Solution Approach 2:
The patent implements feedback through a closed-loop control system where the phase detector continuously monitors the phase difference between the frame transmission clock and data clock, feeds this information back to the control system, which then adjusts the stuffing data symbol injection accordingly. This feedback mechanism ensures that frame length adjustments are made based on actual measured phase differences, preventing excessive jitter while maintaining synchronization.
2Measurement precision
If the phase difference is determined over multiple frames, then the phase adjustment accuracy is improved, but the response time is increased
Solution Approach 1:
The patent applies preliminary action by pre-determining the phase difference over multiple frames before implementing adjustments. The phase detector operates continuously in the background, measuring phase differences over multiple frames and maintaining an average value. This advance measurement allows the control system to respond more quickly once adjustment is needed, as the phase difference information is already prepared and averaged, reducing the effective response time while maintaining high accuracy.
3Ease of operation
If stuffing data symbols are injected alternately, then the frame length is controlled, but the alternating pattern creates difficulty in suppressing timing errors
Solution Approach 1:
The patent applies preliminary action by determining the phase difference over multiple frames before activating stuffing adjustments. This advance measurement allows the control system to identify the optimal timing for injecting stuffing symbols, avoiding reactive alternating patterns that create timing errors. By planning adjustments based on measured average phase differences, the system achieves frame length control while minimizing timing errors.
Solution Approach 2:
The patent implements feedback through continuous monitoring of phase difference and adaptive adjustment of stuffing symbol injection. The phase detector provides ongoing feedback on the actual phase relationship between frame transmission and data clock, allowing the control system to adjust stuffing injection dynamically rather than using fixed alternating patterns. This feedback-driven approach maintains frame length control while suppressing timing errors through adaptive response to actual phase conditions.
Data Source
AI summary
A method and device for controlling the phase of successively transmitted frames, in which data symbols are transmitted at a constant symbol frequency, in which a phase difference between the clock of the frame transmission and a data clock is determined and, dependent on the phase difference, an adjusting signal is produced for controlling the injection of stuffing data symbols into the frames for changing the frame length and the phase of the frame transmission, whereby the phase of the frame transmission is controlled so that the frames are transmitted on average synchronously with the data clock, wherein the adjusting signal is produced dependent on the phase difference determine from N frame in each successively transmitted, whereby N is at least 2.