Reference Clock Distribution in Packet Networks
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Solution Overview
Problem
Existing packet networks lack efficient methods to distribute synchronized clocks, particularly for services that require multiple reference clocks, leading to poor wander performance and incompatibility with legacy TDM network connections.
Innovation Solution
A method that uses a single basis clock per node, synchronized across slave nodes via time-stamped synchronization packets, numerically encoding multiple reference clocks relative to the master node's basis clock for accurate reconstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If adaptive clock recovery is used to distribute multiple reference clocks, then compatibility with legacy TDM network connections is improved, but wander performance deteriorates
Solution Approach 1:
The patent introduces a basis clock as an intermediary reference that mediates between the packet network and multiple TDM connections. Each slave node uses its local basis clock (synchronized to the master's basis clock) to recover multiple reference clocks, avoiding the need for adaptive averaging while maintaining compatibility with legacy TDM connections that require multiple reference clocks.
Solution Approach 2:
The patent segments the clock distribution function by separating the basis clock synchronization from the reference clock recovery. The basis clock provides a stable local reference at each slave node, while the reference clocks are derived from this segmented function, allowing independent optimization of wander performance for each reference clock without affecting others.
2Adaptability or versatility
If multiple reference clocks are distributed using traditional methods, then compatibility with TDM services is improved, but network complexity increases
Solution Approach 1:
The basis clock serves multiple functions: it provides a stable local reference for clock recovery, enables synchronization to the master node, and supports the distribution of multiple reference clocks. This multi-functional approach simplifies the network architecture compared to traditional methods that would require separate mechanisms for each function.
Solution Approach 2:
The patent changes the fundamental parameter of clock distribution from centralized adaptive recovery to distributed basis clock synchronization. Each slave node independently maintains its basis clock with controlled wander characteristics, and derives reference clocks from this local reference, fundamentally changing how multiple reference clocks are distributed across the network.
3Measurement precision
If time-stamped synchronization packets are used for basis clock synchronization, then synchronization accuracy is improved, but bandwidth consumption increases
Solution Approach 1:
The basis clock provides continuous local reference functionality at each slave node, eliminating the need for continuous adaptive clock recovery calculations. The time-stamped synchronization packets provide periodic corrections to the basis clock, maintaining continuous synchronization accuracy while using bandwidth only when corrections are needed, rather than continuously.
Solution Approach 2:
Instead of using full adaptive clock recovery that processes every packet to calculate bit clock, the patent uses partial action by only sending synchronization packets when basis clock corrections are needed. The basis clock runs independently most of the time, requiring only periodic adjustments, thus using less bandwidth than continuous adaptive recovery while maintaining synchronization accuracy.
Data Source
AI summary
Disclosed is a method of distributing a number of reference clocks across a packet network. The packet network has a master node and one or more slave nodes, the master node and each slave node having basis clocks. A sender sends time-stamped synchronization packets to said one or more slave nodes, and a receiver at the slave nodes receives the time-stamped synchronization packets and synchronizes the basis clocks in the slave nodes with the basis clock in the master node. Multiple reference clocks are encoded with respect to the basis clock in the master node to generate numerical information describing the reference clock(s) in relation to the basis clock in the master node. The basis clock in each of the slave node is synchronized to the basis clock in the master node using time-stamped synchronization packets. The one or more reference clocks are recovered at the slave nodes using said numerical information describing the reference clock(s) in relation to the basis clock in the master node.