US 11,502,765 B2Granted

Robust clock synchronization over computer network

AssigneeZoox, Inc.

InventorsMehran Ferdowsi, Turhan Karadeniz, Minh Nguyen, Subasingha Shaminda Subasingha, Harrison Thomas Waschura

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Abstract

Techniques for facilitating a robust clock synchronization across a computer network that presumes network jitter exists are discussed herein. A first device and a second device transceive a plurality of sets of time-synchronization messages to synchronize a synchronization clock of the second device to a first clock of the first device. The second device calculates a smoothing of time delay data of a plurality of sets. The time delay data is associated with a transmission duration of time-synchronization messages of the sets of the plurality. The second device sets a synchronization clock based on a time at the first device and the smoothed time delay data.

Claims19

Dependent claims

A system comprising:

a first device having a first clock;
a second device having a second clock;
one or more processors;
and
one or more non-transitory computer-readable media storing computer-executable instructions that, when executed, cause the system to perform operations comprising:
transceiving, via a communication network between the first device and second device, a plurality of sets of time-synchronization messages, a set of time-synchronization messages of the plurality including information about times at the first device according to the first clock that time-synchronization messages of a set were sent and received by the first device;
determining, for a set of the plurality and based, at least in part, on the information of the set, a message-transmission duration of the time-synchronization messages transceived;
determining, over the plurality, a moving average of message-transmission durations based on the sets of the plurality;
setting the second clock of the second device to a combination of a time at the first device and the moving average;
determining, using a sensor of the second device, a measurement of a condition observable by the sensor at a measurement time according to the second clock;
generating a timestamp based on the measurement time;
and
sending, to a computing system via the communication network, the measurement and the timestamp.

10 more elements

A method comprising:

receiving, by a second device and at a second-device receipt time according to a second clock, an initial time-synchronization message that was sent by a first device and comprising a first-device send time according to a first clock;
sending, by the second device an acknowledgment time-synchronization message to the first device comprising a second-device send time according to the second clock;
receiving, by the second device, a responsive time-synchronization message from the first device, the responsive time-synchronization message comprising second timing data including a first-device receipt time according to the first clock that the first device received the acknowledgment time-synchronization message from the second device;
and
determining a time delay data, wherein the time delay data is associated with a transmission duration of the initial time-synchronization message and the acknowledgment time-synchronization message.

2 more elements

One or more non-transitory computer-readable media storing instructions executable by one or more processors, wherein the instructions, when executed, cause the one or more processors to perform operations comprising:

receiving, by a second device and at a second-device receipt time according to a second clock, an initial time-synchronization message that was sent by a first device and comprising a first-device send time according to a first clock;
sending, by the second device an acknowledgment time-synchronization message to the first device comprising a second-device send time according to the second clock;
receiving, by the second device, a responsive time-synchronization message from the first device, the responsive time-synchronization message comprising second timing data including a first-device receipt time according to the first clock that the first device received the acknowledgment time-synchronization message from the second device;
and
determining a time delay data, wherein the time delay data is associated with a transmission duration of the initial time-synchronization message and the acknowledgment time-synchronization message.

2 more elements

Dependencies are inferred from the claim text.

Facts

Application: 17/248,755Filed 5 Feb 2021
Published: US 2022/0255653 A111 Aug 2022
Granted: 15 Nov 2022
Term ends: Not estimatedThe source records don’t support an estimate.

Classification8 codes

H04J 3/065
Synchronisation among TDM nodes: using timestamps
H04J 3/0667
Using timestamps: bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays
H04J 3/025
Details: filter arrangements
H04J 3/0697
Clock or time synchronisation in a node; Intranode synchronisation: synchronisation in a packet node