Patent US6327274B1 successfully refreshed from Google Patents.
US6327274B1
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Method for estimating relative skew between clocks in packet networks
Assignee: Nokia Oyj
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Filing: 1998-09-15
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Granted: 2001-12-04
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Expires: 2018-09-15
Abstract
Abstract A method, a system, and an article of manufacture for measuring a relative skew between clocks in a packet based communication network. The method utilizes the timestamps available in packets sent from a sender to a receiver, as well as the times at which the receiver receives such packets. Such timestamps can be incorporated in packets, or in a separate protocol.
Inventors
- 👤 Rayadurgam Ravikanth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-10 02:07
CPC Classifications
H; H04; H04J; H04J3/00; H04J3/02; H04J3/06; H04J3/0635; H04J3/0638; H04J3/0658; H04J3/0661; H04J3/0664
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
182 words
A method for determining a clock skew between at least a first and second clocks in a network, comprising: transmitting a plurality of packets from a first network node to a second network node, each of the packets having a timestamp which records time measured by the first clock at the first network node; receiving one of the packets at the second network node and recording time measured by the second clock at the second network node; obtaining the timestamp of the one packet; computing a time delay between a time of transmitting the one packet and a time of receiving the one packet; computing a jitter between the time delay for the one packet and the time delay for a next packet consecutively transmitted after the one packet; averaging jitters after transmitting the plurality of packets; averaging inter-packet times, each of the inter-packet times being a time interval between transmitting two consecutive of the plurality of packets at the first network node; and determining the clock skew by dividing an average of the jitters by an average of the inter-packet times.
Claim 2
Independent Claim
182 words
A method for determining a clock skew between at least a first and second clocks in a network, comprising: transmitting a plurality of packets from a first network node to a second network node, each of the packets having a timestamp which records time measured by the first clock at the first network node; receiving one of the packets at the second network node and recording time measured by the second clock at the second network node; obtaining the timestamp of the one packet; computing a time delay between a time of transmitting the one packet and a time of receiving the one packet; computing a jitter between the time delay for the one packet and the time delay for a next packet consecutively transmitted after the one packet; averaging jitters after transmitting the plurality of packets; averaging inter-packet times, each of the inter-packet times being a time interval between transmitting two consecutive of the plurality of packets at the first network node; and determining the clock skew by dividing an average of the jitters by an average of the inter-packet times.
Claim 3
Dependent Claim
15 words
The method of claim 1 , wherein the network is a packet based communication network.
Claim 4
Dependent Claim
21 words
The method of claim 1 , wherein time recordings by the first and second clocks are relative to a global clock.
Claim 5
Independent Claim
239 words
A system of determining a clock skew between at least a first and second clocks in a network, comprising: a transmitter for transmitting a plurality of packets from a first network node to a second network node, each of the packets having a timestamp which records time measured by the first clock at the first network node; a receiver for receiving one of the packets at the second network node and recording time measured by the second clock at the second network node; and means for determining a clock skew between the first and second clocks based on the timestamps and the time measured by the second clock, wherein the clock skew determining means includes: means for obtaining the timestamp of the one packet recorded at the first clock; means for computing a time delay between a time of transmitting the one packet and a time of receiving the one packet; means for computing a jitter between the time delay for the one packet and the time delay for a next packet consecutively transmitted after the one packet; a first averager averaging jitters after transmitting the plurality of packets; and a second averager averaging inter-packet times, each of the inter-packet times being a time interval between transmitting two consecutive of the plurality of packets at the first network node; wherein the clock skew is determined by dividing an average of the jitters by an average of the inter-packet times.
Claim 6
Independent Claim
239 words
A system of determining a clock skew between at least a first and second clocks in a network, comprising: a transmitter for transmitting a plurality of packets from a first network node to a second network node, each of the packets having a timestamp which records time measured by the first clock at the first network node; a receiver for receiving one of the packets at the second network node and recording time measured by the second clock at the second network node; and means for determining a clock skew between the first and second clocks based on the timestamps and the time measured by the second clock, wherein the clock skew determining means includes: means for obtaining the timestamp of the one packet recorded at the first clock; means for computing a time delay between a time of transmitting the one packet and a time of receiving the one packet; means for computing a jitter between the time delay for the one packet and the time delay for a next packet consecutively transmitted after the one packet; a first averager averaging jitters after transmitting the plurality of packets; and a second averager averaging inter-packet times, each of the inter-packet times being a time interval between transmitting two consecutive of the plurality of packets at the first network node; wherein the clock skew is determined by dividing an average of the jitters by an average of the inter-packet times.
Claim 7
Dependent Claim
15 words
The system of claim 4 , wherein the network is a packet based communication network.
Claim 8
Dependent Claim
22 words
The system of claim 4 , wherein the time recordings by the first and second clocks are relative to a global clock.
Claim 9
Dependent Claim
209 words
An article of manufacture for a computer-based data processing system, the article of manufacture comprising a computer readable medium having instructions for causing a computer to perform a method for determining a clock skew between at least a first and second clocks in a network, comprising: transmitting a plurality of packets from a first network node to a second network node, each of the packets having a timestamp which records time measured by the first clock at the first network node; receiving one of the packets at the second network node and recording time measured by the second clock at the second network node; obtaining the timestamp of the one packet; computing a time delay between a time of transmitting the one packet and a time of receiving the one packet; computing a jitter between the time delay for the one packet and the time delay for a next packet consecutively transmitted after the one packet; averaging jitters after transmitting the plurality of packets; averaging inter-packet times, each of the inter-packet times being a time interval between transmitting two consecutive of the plurality of packets at the first network node; and determining the clock skew by dividing an average of the jitters by an average of the inter-packet times.
Claim 10
Dependent Claim
209 words
An article of manufacture for a computer-based data processing system, the article of manufacture comprising a computer readable medium having instructions for causing a computer to perform a method for determining a clock skew between at least a first and second clocks in a network, comprising: transmitting a plurality of packets from a first network node to a second network node, each of the packets having a timestamp which records time measured by the first clock at the first network node; receiving one of the packets at the second network node and recording time measured by the second clock at the second network node; obtaining the timestamp of the one packet; computing a time delay between a time of transmitting the one packet and a time of receiving the one packet; computing a jitter between the time delay for the one packet and the time delay for a next packet consecutively transmitted after the one packet; averaging jitters after transmitting the plurality of packets; averaging inter-packet times, each of the inter-packet times being a time interval between transmitting two consecutive of the plurality of packets at the first network node; and determining the clock skew by dividing an average of the jitters by an average of the inter-packet times.
Claim 11
Dependent Claim
15 words
The article of claim 7 , wherein the network is a packet based communication network.
Claim 12
Dependent Claim
23 words
The article of manufacture of claim 7 , wherein time recordings by the first and second clocks are relative to a global clock.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-12-03 | 2005-06-04 | 2005-12-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-12-03 | 2009-06-04 | 2009-12-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-12-03 | 2013-06-04 | 2013-12-04 | $7700.00 | Window Closed / Lapsed |