Distributed Boundary Clock Timing Transfer Over Dedicated Channel
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In packet-switched networks, particularly in wireless telephony backhaul applications using microwave radio links, there is a challenge in providing on-path timing support between book-end units when the communication link is not packet-based, leading to transit delay variation that affects timing synchronization between Grand Master and slave clocks.
Innovation Solution
A method is developed to synchronize clocks over a dedicated low-speed channel by using forward and reverse error estimates to adjust the slave clock, aligning it with the master clock through a Proportional-Integral phase-locked-loop arrangement, and estimating frequency errors to correct the numerically controlled oscillator, enabling the formation of a distributed boundary clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dedicated low-speed channel (not packet-based) is used for timing transfer between book-end units, then the channel provides stable transmission, but transit delay variation occurs that affects timing synchronization precision
Solution Approach 1:
The patent implements a feedback mechanism where the slave clock measures the transit delay of timing packets sent by the master clock, calculates the delay variation, and uses this information to compensate for timing errors. The slave clock sends delay measurements back to the master clock, which adjusts its timing packet transmission based on the feedback, thereby resolving the contradiction between stable transmission and timing precision.
Solution Approach 2:
The patent replaces the traditional packet-based timing transfer mechanism with a dedicated low-speed channel for timing information transfer. This substitution allows for more stable transmission characteristics while using computational methods (software-based delay measurement and compensation) to achieve the required timing precision, rather than relying solely on packet network properties.
2Adaptability or versatility
If packet-based timing methods are used over packet-switched networks, then timing information can be delivered to slave clocks, but transit delay variation acts like additive noise that degrades timing accuracy
Solution Approach 1:
The patent extracts the timing information transfer from the packet-based communication channel and moves it to a dedicated low-speed channel. This separation removes the timing transfer from the statistical variations of packet switching, eliminating the source of transit delay variation while maintaining the ability to deliver timing information to slave clocks.
Solution Approach 2:
The dedicated low-speed channel acts as an intermediary between the master and slave clocks for timing information transfer. This intermediary provides a stable transmission path that is independent of packet network variations, while still allowing the packet-based network to handle data traffic, thus resolving the contradiction between adaptability and precision.
3Adaptability or versatility
If boundary clocks are deployed in microwave radio backhaul applications, then on-path timing support is provided, but the book-end configuration with dedicated low-speed channel requires new synchronization methods
Solution Approach 1:
The patent creates a universal synchronization method that works across different backhaul configurations (packet-based and dedicated channel). The master-slave clock architecture and delay measurement techniques can be applied regardless of the underlying transmission medium, providing on-path timing support while maintaining relatively simple synchronization procedures through standardized delay measurement and compensation algorithms.
Data Source
AI summary
Implementing a distributed boundary clock in situations where book-end devices such as microwave TX/RX pairs must collaborate in achieving PTP on-path support is described. A dedicated channel, generally low-speed compared to the main channel is used to transfer timing from the master side to the slave side using framing and super-framing applied to the digital channel. Time-stamps of events such as super-frame boundaries are communicated between the two sides to enable timing transfer.