Virtual Clock One-Way Latency Measurement Network
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Solution Overview
Problem
Existing methods for measuring one-way latency in data networks, such as GPS and NTP synchronization, are either expensive or lack precision, and traditional round-trip delay measurements are not accurate for asymmetric latency.
Innovation Solution
A method for continuous clock synchronization between nodes using repetitive synchronization messages to calculate round-trip time, update synchronization points, and generate a virtual clock, allowing for precise one-way latency measurement through interpolation of multiple measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS synchronization is used, then clock synchronization accuracy is improved, but cost increases
Solution Approach 1:
The patent creates a virtual copy of the GPS reference clock by receiving GPS timing signals at a reference node and distributing this virtual reference clock to multiple client nodes via the network. This allows nodes to achieve GPS-level synchronization accuracy without each node requiring its own expensive GPS receiver, effectively copying the reference timing signal across the network.
Solution Approach 2:
The patent introduces a reference node as an intermediary that receives GPS signals and acts as a local timing authority for the network. This intermediary converts the GPS reference into network-distributable timing signals, eliminating the need for direct GPS receivers at each node while maintaining synchronization accuracy.
2Measurement precision
If GPS receivers are installed at each node, then clock synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
Instead of installing physical GPS receivers at each node, the patent copies the GPS reference timing signal to a central reference node and then distributes it network-wide. This eliminates the need for multiple complex GPS hardware installations while achieving the same synchronization accuracy.
Solution Approach 2:
The reference node performs multiple functions: receiving GPS signals, calculating timing parameters (offset and skew), and distributing synchronized timing to multiple client nodes. This multi-functional approach consolidates what would otherwise require separate GPS receivers at each node into a single universal timing source.
3Ease of manufacture
If NTP servers are used, then cost is reduced, but clock synchronization accuracy deteriorates
Solution Approach 1:
The patent changes the fundamental timing parameter reference from network-based NTP servers to GPS-based absolute time reference. By anchoring the synchronization system to GPS satellite timing (which provides microsecond or better accuracy) rather than relying on network path characteristics, the system achieves superior accuracy while remaining cost-effective through virtual clock distribution.
4Ease of operation
If round-trip delay measurements are used, then measurement capability is provided, but one-way latency accuracy deteriorates due to asymmetric latency
Solution Approach 1:
The patent copies the absolute reference time from GPS to create a virtual reference clock that both reference and client nodes can access. By having both nodes reference the same absolute time source, the system can calculate true one-way latency as the difference between absolute timestamps, eliminating the need for round-trip measurements and avoiding asymmetry errors.
Solution Approach 2:
Instead of measuring latency by sending test packets back and forth (round-trip approach), the patent inverts the approach by having both nodes independently timestamp events using the shared virtual reference clock and then calculating latency from these absolute timestamps. This reverses the traditional measurement paradigm and directly provides accurate one-way latency.
Data Source
AI summary
A method for indicating one-way latency in a data network, with continuous clock synchronization, between first and second node having clocks that are not synchronized with each other includes a continuous synchronization session and a measurement session. The method repetitively sends predetermined synchronization messages from the first node to the second node and from the second node to the first node, calculates a round trip time for each message at the first node, updates a synchronization point if the calculated round trip time is smaller than a previously calculated round trip time, stores the updated synchronization points of a synchronization window, and calculates a virtual clock from the updated synchronization points of the synchronization window. The measurement session collects multiple measurements of one-way latency between the first and second nodes using the virtual clock, and generates a latency profile by interpolating the multiple measurements.