Synchronization method and arrangement
First Claim
1. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
- controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
, using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, wherein said transmission time is evaluated with necessary certainty by giving said time stamps the highest priority over all other information transmissions within said delimited network.
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Abstract
The present invention relates to a method and to an arrangement for synchronising at least one local oscillator (21) with a central time-generating unit (11). The local oscillator (21) serves a so-called element (2) included in a network (A), and the time-generating unit (11) is included in a so-called main unit (1) also included in the network (A). The frequency of the local oscillator (21) can be controlled by periodic and automatic calibration. The physical requirements within a part of the network (A) that includes the main unit (1) and all elements (2, 3, 4) concerned, said part being referred to here as a limited network (B), are so well defined that the transmission time of a time stamp from the main unit (1) to an element (2) will be known with a given degree of certainty. The inter-arrival time of the time stamps is used to calibrate the local oscillator (11) together with the known transmission time.
46 Citations
40 Claims
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1. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
,using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, wherein said transmission time is evaluated with necessary certainty by giving said time stamps the highest priority over all other information transmissions within said delimited network. - View Dependent Claims (2, 3, 4)
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5. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, wherein a mathematical method in which the arrival times of said time stamps are used to effect said calibration, wherein variations are described in a time error which constitutes the difference between said pre-defined and the actual time interval between received time stamps measured by said local oscillator, wherein said time error is divided into an oscillator-dependent component and a network-dependent component;
wherein said oscillator-dependent component is determined by the characteristic of said local oscillator;
wherein said network-dependent component is determined by the variations in transmission times from said time-generating unit to said elements for respective time stamps and any measurement error of the measuring method used;
wherein an evaluation period for calibration of a local oscillator is divided into a first phase and a second phase;
wherein said first phase is continued at least until said network-dependent component no longer has a deleterious effect on a calculation of the relative synchronizing frequency deviation of said local oscillator;
wherein said second phase is commenced immediately after said first phase;
wherein said second phase includes continuous evaluation of said time error; and
,wherein said second phase is terminated with calibration and adjustment of said local oscillator. - View Dependent Claims (6, 7)
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8. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time wherein a mathematical method in which the arrival times of said time stamps are used to effect said calibration, wherein variations are described in a time error which constitutes the difference between said pre-defined and the actual time interval between received time stamps measured by said local oscillator, wherein said mathematical method includes an evaluation of the relative frequency deviation of said local oscillator in accordance with the formula where Y is the relative frequency deviation, N is the number of time stamps received, τ
0 is the time interval between transmitted time stamps, TEi is the time error at respective received time stamps, and where Nτ
0 is thus the time duration of said phase.
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9. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, further comprising the step of;
evaluating the drift in frequency of said local oscillator; and
using said drift for correcting said local oscillator in the event of the time stamps from said central time-generating unit being lost.- View Dependent Claims (10)
where D is the drift of the local oscillator, M is the number of time stamps, τ
1 is the time interval between transmitted time stamps, and TEj is the time error pertaining to respective time stamps.
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11. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, further comprising the step of;
storing the results of the various calibrations so as to obtain a value characteristic of the drift of said local oscillator for use in adjusting said oscillator in the event of the time stamps from the central time-generating unit being lost.
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12. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, further comprising the step of;
using a time interval between transmitted time stamps that is much shorter than the time interval for transmitting time stamps in a calibration process, for initially evaluating an oscillator in the initiation of a new oscillator belonging to an element in said delimited network during an initiation interval for said new local oscillator.- View Dependent Claims (13, 14)
wherein said initiation interval is 30 minutes.
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14. A method according to claim 12, wherein said time stamps are ordered from the element that includes said new oscillator to said main unit, through the medium of a request stating the desired time interval, the desired initiation interval.
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15. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
,using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, wherein upon an initiation of a new oscillator, the main unit sends requisite parameters to the element that includes said new oscillator, the requisite parameters include at least anticipated time intervals between transmitted time stamps, time period for a first phase, and time period for a second phase.
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16. A method of synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator serves an element included in a network, and where said time-generating unit is included in a main unit which is also included in said network, comprising the steps of:
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controlling the frequency of said local oscillator by periodic and automatic calibration, wherein the time-generating unit sends a time stamp at pre-defined time intervals;
evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said elements, and wherein the network is a delimited network; and
using the inter-arrival time of the time stamps to calibrate the local oscillator together with a known transmission time, wherein said elements collect information required to effect a calibration during a second phase;
wherein said elements send this information to said main unit;
wherein said main unit performs the computations necessary to produce a value for calibration of said local oscillator;
wherein said main unit sends to said element a local oscillator adjustment value; and
wherein said element makes the necessary adjustment.
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17. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network; and
,a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time, wherein said nodes included in said delimited network are adapted to give said time stamps the highest priority over all other information transmissions, whereby said known transmission time is evaluated with certainty.
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18. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network;
a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time wherein said calibrating unit is adapted to use a mathematical oscillator calibration method which uses the arrival times of said time stamps in said calibration;
wherein said variations are time errors that constitutes the difference between pre-defined time intervals and the actual time interval between received time stamps; and
wherein said local oscillator is adapted to measure said actual time interval, wherein said calibrating unit is adapted to divide said time error into an oscillator-dependent component and a network-dependent component;
wherein said oscillator-dependent component can be determined on the basis of the local oscillator characteristic;
wherein said network-dependent component can be determined by the variations in transmission times from said transmitting unit to said receiving unit for respective time stamps and possible measuring errors of the measuring method used;
wherein said calibrating unit is adapted to divide an evaluating period for calibration of a local oscillator into a first phase and a second phase;
wherein said calibrating unit is adapted to allow said first phase to continue at least until said network-dependent component no longer has any deleterious affect on a calculation of the relative frequency deviation of said local oscillator;
wherein said calibrating unit is adapted to commence said second phase immediately after said first phase;
wherein said calibrating unit includes an evaluating unit which is adapted to evaluate said time error continuously during said second phase; and
,wherein said calibrating unit is adapted to terminate said second phase with calibration and adjustment of said local oscillator. - View Dependent Claims (19, 20)
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21. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network;
a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time wherein said calibrating unit is adapted to use a mathematical oscillator calibration method which uses the arrival times of said time stamps in said calibration;
wherein said variations are time errors that constitutes the difference between pre-defined time intervals and the actual time interval between received time stamps; and
,wherein said local oscillator is adapted to measure said actual time interval, wherein said calibrating unit is adapted to evaluate the relative frequency deviation of said local oscillator by means of a mathematical method according to the formula where Y is the relative frequency deviation, N is the number of time stamps received, τ
0 is the time interval between transmitted time stamps, TEi is the time error at which respective time stamps are received, and where Nτ
0 is thus the time duration of said second phase.
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22. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network;
a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time, wherein said evaluating unit is adapted to evaluate the drift in frequency of said local oscillator;
wherein the value of said drift can be stored in a storage space that is available to said calibrating unit; and
wherein said calibrating unit is adapted to use said stored value for correcting or adjusting the local oscillator when the time stamps from the central generating unit are lost. - View Dependent Claims (23)
where D is the drift of the local oscillator, M is the number of time stamps, τ
1 is the time interval between transmitted time stamps, and TEj is the time error relating to respective time stamps.
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24. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network;
a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time, wherein said calibrating unit is adapted to store the results of different calibrations in a storage space; and
wherein the calibrating unit is adapted to use the stored results for adjusting said oscillators in the event of the time stamps from said central time-generating unit being lost.
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25. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network; and
,a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time, wherein said time-generating unit is adapted to generate time stamps at a time interval between transmitted time stamps that is much shorter than the time interval for transmitted time stamps in a calibrating process, during an initial stage of a new oscillator belonging to an element included in said delimited work. - View Dependent Claims (26, 27)
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28. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network; and
,a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time, wherein upon an initiation of a new oscillator said main unit functions to send necessary parameters to the element that includes said new oscillator as anticipated time intervals between transmitted time stamps, first phase time periods and second phase time periods.
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29. An arrangement for synchronizing at least one local oscillator with a central time-generating unit, where said local oscillator is adapted to serve an element included in a network, where said time-generating unit is included in a main unit included in said network, and where the arrangement comprises:
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means for controlling the frequency of said local oscillator by periodic and automatic calibration;
a main unit that includes a transmitting unit and said transmitting unit is adapted to transmit a time stamp generated by said time-generating unit at a predefined time intervals;
means for evaluating the transmission time of said time stamp from said main unit to a respective element with a given degree of certainty by evaluating against well defined physical requirements of that part of said network including said main unit and said element and referred to as a delimited network;
a calibrating unit belonging to said element is adapted to calibrate said local oscillator with the aid of the inter-arrival time of the time stamps together with a known transmission time, wherein said element includes a collecting unit;
wherein said collecting unit is adapted to collect information required to effect calibration during a second phase and to send this information to said main unit;
wherein said main unit includes a computing unit which is adapted to perform computations necessary to obtain a local oscillator calibrating value and to send said value to said element; and
wherein said element is adapted to effect necessary adjustment in accordance with the value received.
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30. A method of synchronizing at least one local oscillator with a central time-generating unit, comprising the steps of:
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transmitting a time stamp at predefined time intervals, wherein said transmitting is performed by said time-generating unit;
evaluating the transmission of said time stamp, according to physical requirements of a communication network which comprises said at least one local oscillator and said central time-generating unit;
calibrating said at least one local oscillator according to said time stamp and a known transmission time wherein said step of transmitting comprises transmitting a group of time stamps within a short time period wherein said step of calibrating further comprises;
determining time error variations, which comprise the difference between a pre-defined time interval between each time stamp of said group of time stamps and actual time intervals between received time stamps of said group of time stamps as measured by said local oscillator, wherein said step of calibrating further comprises;
analyzing an oscillator-dependent component and a network-dependent component of said time error, wherein said network-dependent component is determined by variations in transmission times of said time stamps from said time generating unit to said oscillators and any measurement error of the measuring method used. - View Dependent Claims (31, 32, 33)
wherein said first phase is continued at least until said network-dependent component no longer has a negative effect on a calculation of a relative frequency deviation of said local oscillator; and
wherein said second phase is commenced immediately after said first phase, includes an evaluation of said time error, and is terminated with adjustment of said local oscillator.
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32. The method of claim 31, wherein said step of calibrating further comprises terminating said second phase of said evaluation period before the relative frequency deviation of said local oscillator reaches a maximum accepted relative frequency deviation.
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33. The method of claim 31, wherein said second phase of said evaluation period is terminated before said time error reaches a predetermined value equal to or less than a maximum accepted time error.
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34. A method of synchronizing at least one local oscillator with a central time-generating unit, comprising the steps of:
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transmitting a time stamp at predefined time intervals, wherein said transmitting is performed by said time-generating unit;
evaluating the transmission of said time stamp, according to physical requirements of a communication network which comprises said at least one local oscillator and said central time-generating unit; and
calibrating said at least one local oscillator according to said time stamp and a known transmission time wherein said step of transmitting comprises transmitting a group of time stamps within a short time period wherein said step of calibrating further comprises;
determining time error variations, which comprise the difference between a pre-defined time interval between each time stamp of said group of time stamps and actual time intervals between received time stamps of said group of time stamps as measured by said local oscillator, wherein said step of evaluating comprises evaluating a relative frequency deviation of said local oscillator using the following formula;
where Y represents the relative frequency deviation, n represents the number of time stamps received, τ
0 represents the time interval between transmitted time stamps, TEi represents the time error at various received time stamps, and where Nτ
0 represents the time duration of the second phase.
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35. A method of synchronizing at least one local oscillator with a central time-generating unit, comprising the steps of:
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transmitting a time stamp at predefined time intervals, wherein said transmitting is performed by said time-generating unit;
evaluating the transmission of said time stamp, according to physical requirements of a communication network which comprises said at least one local oscillator and said central time-generating unit; and
calibrating said at least one local oscillator according to said time stamp and a known transmission time, wherein said step of evaluating comprises evaluating a drift in frequency of said local oscillator, and said step of calibrating comprises utilizing said drift for correcting said local oscillator. - View Dependent Claims (36)
where D represents the drift in frequency of the local oscillator, M represents the number of time stamps, τ
l represents the time interval between transmitted time stamps, and TEj represents the time error of various time stamps.
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37. A method of synchronizing at least one local oscillator with a central time-generating unit, comprising the steps of:
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transmitting a time stamp at predefined time intervals, wherein said transmitting is performed by said time-generating unit;
evaluating the transmission of said time stamp, according to physical requirements of a communication network which comprises said at least one local oscillator and said central time-generating unit;
calibrating said at least one local oscillator according to said time stamp and a known transmission time; and
storing results of various calibrations performed according to said calibrating step in order to obtain a value characteristic of a drift in frequency of said local oscillator. - View Dependent Claims (38)
adjusting said local oscillator according to said results stored in said step of storing in the event that said time stamps transmitted in said transmitting step are temporarily not received.
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39. A method for evaluating a relative frequency deviation of a local oscillator utilizing time stamps received from time stamps transmitted by a time-generating unit at predefined time intervals, wherein said evaluation is defined by the following formula
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. 006 N τ 0 ∑ i = 1 N TE i ( 2 i N 2 - 1 - 1 N - 1 ) wherein Y represents a relative frequency deviation, N represents a number of time stamps received, τ
0 represents a time interval between transmitted time stamps, TEi represents a time error of received time stamps, and Nτ
0 represents a continuous evaluation period of the time error.
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40. A method for calculating drift in frequency of a local oscillator according to time stamps received from time stamps transmitted by a time-generating unit at predetermined time intervals, wherein the said drift in frequency is defined by the following formula:
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where D represents the drift in frequency of a local oscillator, M represents a number of time stamps, τ
l represents a time interval between transmitted time stamps, and TEj represents a time error of respective time stamps.
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Specification