Physical-Layer Frequency Transfer for Unsynchronized Network Hops
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Solution Overview
Problem
Existing methods for clock synchronization in network devices, such as Synchronous Ethernet (SyncE) and Precision Time Protocol (PTP), fail to effectively propagate a master clock frequency across a network when intermediate devices lack synchronization capabilities, leading to inaccurate one-way latency measurements.
Innovation Solution
A device measures frequency differences between its local clock and the receive rate from a remote device, generating a message with this data to enable other devices to adjust their local clocks, allowing the master clock frequency to be propagated through intermediate devices without direct synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SyncE and PTP synchronization methods are used, then clock synchronization is achieved between directly connected devices, but master clock frequency cannot be propagated through intermediate devices lacking synchronization capabilities
Solution Approach 1:
The patent introduces an intermediary mechanism where non-synchronized intermediate devices can still forward frequency comparison information. The device measures frequency differences between its local clock and received signals, then transmits this comparison data to remote devices, enabling indirect frequency propagation through devices that do not perform direct synchronization.
Solution Approach 2:
Instead of directly synchronizing clocks, the system copies frequency comparison measurements through intermediate devices. Each device measures the frequency relationship between its local clock and the incoming signal, then transmits this copied frequency information onward, allowing the master clock frequency to be propagated indirectly through the network.
2Measurement precision
If direct clock synchronization is implemented, then accurate time alignment is achieved between synchronized devices, but one-way latency measurements become inaccurate due to synchronization assumptions
Solution Approach 1:
The patent replaces the mechanical/time-based synchronization approach with a frequency-based measurement approach. Instead of relying on time-stamped packets and complex two-way synchronization protocols, the system uses physical layer frequency measurements and counter values to determine frequency comparisons, simplifying the mechanism while improving latency measurement accuracy.
Solution Approach 2:
The patent extracts the frequency comparison measurement from the complex synchronization protocol stack and places it at the physical layer. By measuring frequency differences directly from the received signal and local clock without relying on higher-layer protocol timing, the system obtains accurate measurements that are independent of protocol complexity.
Data Source
AI summary
In one embodiment, a device includes a network interface to send first data at a transmission rate and receive second data at a receive rate, and processing circuitry to send a message to a remote device over a packet data network, the message including data indicative of a measurement of a local clock and a measurement of the receive rate.