EP1554829A1 - Procede pour synchroniser des dispositifs utilisateurs d'un reseau - Google Patents

Procede pour synchroniser des dispositifs utilisateurs d'un reseau

Info

Publication number
EP1554829A1
EP1554829A1 EP03773521A EP03773521A EP1554829A1 EP 1554829 A1 EP1554829 A1 EP 1554829A1 EP 03773521 A EP03773521 A EP 03773521A EP 03773521 A EP03773521 A EP 03773521A EP 1554829 A1 EP1554829 A1 EP 1554829A1
Authority
EP
European Patent Office
Prior art keywords
time
subscriber
server
local
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03773521A
Other languages
German (de)
English (en)
Inventor
Andreas Heid
Andreas Kraut
Steffen Schwips
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jetter AG
Original Assignee
Jetter AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jetter AG filed Critical Jetter AG
Publication of EP1554829A1 publication Critical patent/EP1554829A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
    • H04J3/0658—Clock or time synchronisation among packet nodes
    • H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
    • H04J3/0664—Clock or time synchronisation among packet nodes using timestamps unidirectional timestamps
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J3/00—Time-division multiplex systems
    • H04J3/02—Details
    • H04J3/06—Synchronising arrangements
    • H04J3/0635—Clock or time synchronisation in a network
    • H04J3/0638—Clock or time synchronisation among nodes; Internode synchronisation
    • H04J3/0658—Clock or time synchronisation among packet nodes
    • H04J3/0661—Clock or time synchronisation among packet nodes using timestamps
    • H04J3/0667—Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays

Definitions

  • the invention relates to a method for synchronizing local timers of subscribers and / or processors of a network, in particular a segmented network and / or process control network, with a timer of a subscriber or server specified or predeterminable in the network as a reference, which is regular and / or stochastic Sends reference time signals or data packets comprising such signals, whereby unpredictably variable data transmission times can occur in the network, caused inter alia by changing loading and / or changed structure of the network and its subscribers, in particular at network nodes, and / or changing signal paths.
  • the basic difficulty of synchronizing a network is that there are regularly no network levels reserved exclusively for specific information between the participants. Rather, the signal paths between the participants are basically used for data packets with any information content. The consequence of this is that data packets sent by a subscriber are more or less strongly delayed on the way to the addressed subscriber, ie the data transmission times between two subscribers cannot be predicted reproducibly. This can, for example, the fact that based 'data packets must be stored at network nodes, to ensure a collision-free data transmission is connected to this network node conduction paths. If a collision-free data transmission is not guaranteed in the respective network or subnetwork, delays can also occur due to the fact that data packets that collide with each other cannot be regularly evaluated correctly by the addressed subscribers and must therefore be retransmitted by the sender subscriber.
  • a subscriber requests a reference time from the reference subscriber or server at a time Ti determined by the local timer of the aforementioned subscriber.
  • the data packet sent by the subscriber for this purpose which contains information at time Ti, is received by the reference subscriber or server at a time T 2 determined by its timer.
  • the reference subscriber or server then sends a data packet to the aforementioned subscriber with the information that the data packet sent at time Ti was received at time T 2 .
  • This data packet also contains the sending time T 3 .
  • the aforementioned subscriber may now receive this data packet at a time T 4 determined by his timer. The subscriber can thus estimate the transit time d for the data transmission from the subscriber to the reference subscriber or server and from the reference subscriber or server to the subscriber as follows.
  • time shift t between the participant's timer and the reference participant's or server's timer can be estimated as follows:
  • the time of the subscriber's timer can be compared to the time of the reference subscriber's or server's timer.
  • a certain degree of inaccuracy remains in terms of probability because it cannot be ensured that the signal propagation times on the way from the subscriber to the reference subscriber or server on the one hand and the way from the reference subscriber or server to the subscriber on the other hand are the same.
  • the object of the invention is now to create a new synchronization method which is distinguished by very high accuracy which can be increased in virtually any manner and is suitable for virtually any network, in particular also Ethernet systems.
  • a subscriber only approximates or adjusts his local time measurement to the time measurement of the reference subscriber or server if the difference between the reference time and local time at the time the reference time is received is smaller in amount as a predetermined small threshold value and / or a signal path between the subscriber and the reference unit or server or the network is kept free for delay-free signal transmission.
  • the invention makes use of the fact that it is used regularly, e.g. with known synchronization methods, it is possible to achieve a standard synchronization which has only a small remaining synchronization error.
  • the invention is based on the knowledge that such residual errors can only be corrected if time signals (GONGSCHLAG signals) from the reference subscriber or server arrive without delay or at least without any significant delay to the subscriber to be synchronized.
  • time signals GONGSCHLAG signals
  • a threshold value for the amount of the deviation at which the local time of a subscriber may be changed a sufficient condition can be specified that the GONGSCHLAG signal has reached the respective subscriber without delay and that the subscriber has reached the respective subscriber without delay can correctly compensate for the remaining synchronization errors.
  • the invention also makes use of the fact that data packets can be exchanged between the participants without delay even in heavily loaded networks. Even with a threshold value which is low in view of an extreme synchronization quality, there is a high probability that each participant can frequently receive GONGSCHLAG signals at which the reference time is close to the local time, so that these signals in accordance with the invention for synchronizing the local time Timer can be used. Additionally or alternatively, provision can be made to keep a signal path between a subscriber to be synchronized and the reference subscriber or server for delay-free signal transmission in order to be able to correct larger synchronization errors or to accelerate the aforementioned synchronization measures. In this context, it can be provided in particular that signal paths or preferably the entire network are kept free in a predetermined or predefinable time cycle for delay-free signal transmission.
  • the threshold value specified above can be comparatively large, so that when a subscriber is synchronized, it is also possible to take into account those GONGSCHLAG signals that have suffered a "moderate" delay on the way from the reference subscriber or server to the subscriber to be synchronized Since such delays occur only with a limited frequency and, as a result, only a fraction of them are included in the respective correction of the local timer, probability is that a rapid approximation of the local time to the reference time is guaranteed.
  • the subscriber to be synchronized in each case reports back to the reference subscriber or server that the GONGSCHLAG signal has been received.
  • the time between transmission and feedback (“echo" signal) of the GONGSCHLAG signal can thus be determined, and the subscriber may only adjust or approximate the local time to the reference time if the aforementioned time period falls below a predetermined or predeterminable maximum value.
  • This maximum value can be so narrow, taking into account the response time of the participant for the implementation of the aforementioned feedback that, when the maximum value is undershot, both the transmission of the GONGSCHLAG signal from the reference participant or server to the participant and its transmission of the echo signal to the participant Reference participants or servers must have occurred without delay. This means that falling below or maintaining the aforementioned maximum value is a sufficient condition for the subscriber to be synchronized to actually improve his degree of synchronization if he approaches the local time to the transmitted reference time.
  • FIG. 1 schematically shows the frequency density (D) for the occurrence of a delay as a function of the delay time (t) that a data packet suffers on the way between two users of a network
  • FIG. 4 shows a variant of the method of FIG. 3.
  • a data packet may be transmitted from one participant to another participant.
  • the signal speed corresponds to the speed of light, ie in the case of a spatially limited network, for example a process control network, the length is one Signal path extremely small compared to the signal speed, so that the signal speed can subsequently be assumed to be approximately "infinite".
  • the aforementioned data packet will probably not pass through the route from one subscriber to the other subscriber without delay. Rather, a delay time t will occur, which depends, among other things, on the load on the network and the number of network nodes traversed by the data packet.
  • the invention makes use of this in the synchronization of the local timer (not shown) of a subscriber with the reference timer of a reference subscriber or server.
  • FIG. 2 schematically shows a reference server 1, which among other things has the task of synchronizing a subscriber 2, likewise only shown schematically, or his local timer (not shown) with the (not shown) reference timer of server 1. It is now assumed that a relatively good synchronization has already been achieved. Accordingly, the local time TL of the subscriber 2 corresponds to the reference time TR of the reference server 1 except for a maximum deviation ⁇ , i.e.
  • the server 1 now issues a GONGSCHLAG- at regular intervals or at a reference time TRi for the purpose of synchronizing participants, here the participant 2.
  • a GONGSCHLAG- at regular intervals or at a reference time TRi for the purpose of synchronizing participants, here the participant 2.
  • the GONGSCHLAG signal hits subscriber 2 at time TL- . a, which is determined by the local timer of subscriber 2. From the following data packet with the time TRi, the subscriber 2 "recognizes" the time of sending the GONGSCHLAG signal.
  • the speed of the local timer of subscriber 2 is corrected by a measure dependent on the difference between TRi and TLi. If the above condition is not met, the local timer is not corrected.
  • the subscriber 2 can correspondingly frequently match his local timer to the reference timer. Since timers are usually quartz-controlled and have a high degree of accuracy anyway, the local time of subscriber 2 can only undergo a very slight shift compared to the reference time until the next synchronization correction. As a result, an extremely high degree of synchronization can be set.
  • the server 1 checks whether a GONGSCHLAG signal transmitted to a subscriber 2 at a time TRi for the purpose of synchronization was transmitted without delay, ie the server 1 checks whether the signal path between Server 1 and subscriber 2 was kept free for delay-free signal or data transmission.
  • the server 1 sends TR- at a time determined by its timer .
  • the GONGSCHLAG signal and subsequently a data packet with the reference time TRi.
  • the participant 2 receives the GONGSCHLAG signal at the local time TLi and stores the reference time TR- on receipt of the corresponding data packet .
  • it sends an "echo" of the GONGSCHLAG signal and a data packet with the times TLi and TL 2 to the server 1 at a time TL 2 recorded by the local timer.
  • Server 1 can thus determine the total runtime S of the aforementioned data packets between server 1 and subscriber 2 and between subscriber 2 and server 1 as follows:
  • the server 1 compares the value S with a predetermined threshold value ⁇ , which is dimensioned so small that both the GONGSCHLAG signal and the echo must have been transmitted without delay if ⁇ ⁇ S ⁇ + ⁇ .
  • the server 1 sends the subscriber 2 the command to adapt the local timer to the reference timer, ie to correct the speed of the local timer according to the difference TRi-TL X. If the aforementioned condition is not met, subscriber 2 receives the command to leave the local timer unchanged.
  • the aforementioned synchronization can be carried out sufficiently frequently to keep the local time TL in close agreement with the reference time TR.
  • the command sent by server 1 to adapt the local timer to the reference timer may also be transmitted with a greater delay without causing inaccuracies in the synchronization.
  • this synchronization method is also very accurate if the local time TL deviates relatively strongly from the reference time TR. Because this deviation has practically no influence on the determination of S, because only the difference between TL- . and TL 2 is needed.
  • server-side estimates and operations can also be carried out for subscriber 2.
  • the speed of the local timer can be changed on the one hand by changing the frequency of the clock.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
  • Data Exchanges In Wide-Area Networks (AREA)
  • Computer And Data Communications (AREA)

Abstract

Selon l'invention, une horloge d'un dispositif utilisateur (1) faisant office de référence dans un réseau envoie régulièrement et/ou de manière stochastique des signaux de temps de référence (TR1). Un dispositif utilisateur (2) rapproche sa mesure de temps local de la mesure de temps du dispositif utilisateur de référence (1) ou l'aligne sur cette dernière, uniquement lorsque la différence entre le temps de référence (TR) et le temps local (TL) est inférieure à une valeur seuil (ε) préallouée ou préallouable, au moment de la réception du signal de temps de référence, et/ou un trajet de signal est libéré entre le dispositif utilisateur (2) et le dispositif utilisateur de référence (1) ou le réseau pour la transmission de données sans retard.
EP03773521A 2002-10-22 2003-10-14 Procede pour synchroniser des dispositifs utilisateurs d'un reseau Withdrawn EP1554829A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10249296A DE10249296A1 (de) 2002-10-22 2002-10-22 Verfahren zur Synchronisation von Teilnehmern eines Netzwerkes
DE10249296 2002-10-22
PCT/DE2003/003406 WO2004038970A1 (fr) 2002-10-22 2003-10-14 Procede pour synchroniser des dispositifs utilisateurs d'un reseau

Publications (1)

Publication Number Publication Date
EP1554829A1 true EP1554829A1 (fr) 2005-07-20

Family

ID=32087110

Family Applications (1)

Application Number Title Priority Date Filing Date
EP03773521A Withdrawn EP1554829A1 (fr) 2002-10-22 2003-10-14 Procede pour synchroniser des dispositifs utilisateurs d'un reseau

Country Status (4)

Country Link
US (1) US20050232384A1 (fr)
EP (1) EP1554829A1 (fr)
DE (2) DE10249296A1 (fr)
WO (1) WO2004038970A1 (fr)

Families Citing this family (7)

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Publication number Priority date Publication date Assignee Title
DE102004032222B4 (de) * 2004-07-02 2011-02-10 Infineon Technologies Ag Empfänger eines Positionsbestimmungssystems mit verbesserter Sensitivität und Verfahren zur Positionsbestimmung
WO2009056638A1 (fr) * 2007-11-02 2009-05-07 Nortel Networks Limited Synchronisation de nœuds de réseau
JP5102383B2 (ja) * 2010-07-26 2012-12-19 エルジー エレクトロニクス インコーポレイティド デュアルモード端末におけるｓｍｓ受信方法及びそのためのデュアルモード端末
BR112013009402B1 (pt) * 2012-02-21 2022-04-26 Huawei Technologies Co., Ltd Método e dispositivo para compensação para um percurso de tempo
US9160473B2 (en) * 2013-03-13 2015-10-13 Microsemi Frequency And Time Corporation Asymmetry correction for precise clock synchronization over optical fiber
DE102016219663B4 (de) 2016-10-11 2018-08-02 Conti Temic Microelectronic Gmbh Verfahren zur Überwachung eines Netzwerks auf Anomalien
DE102018006867A1 (de) * 2018-08-30 2020-03-05 Diehl Metering Systems Gmbh Verfahren zur Ermittlung einer Zeitinformation

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US4538259A (en) * 1983-07-05 1985-08-27 International Business Machines Corporation System for digitized voice and data with means to compensate for variable path delays
US4831343A (en) * 1988-03-24 1989-05-16 Motorola, Inc. Crystal clock generator having fifty percent duty cycle
DE4313780C1 (de) * 1993-04-27 1994-07-28 Daimler Benz Ag Verfahren und Vorrichtung für die Zählung von Zeittaktimpulsen zur Periodendauermessung
US6389547B1 (en) * 1999-03-19 2002-05-14 Sony Corporation Method and apparatus to synchronize a bus bridge to a master clock
NO20002884L (no) * 2000-06-06 2001-12-07 Ontime Networks As Fremgangsmåte og apparat for å distribuere tidsinformasjon i et datamaskinnettverk
NO313778B1 (no) * 2000-06-06 2002-11-25 Ontime Networks As Fremgangsmåte for å sikre aksess til et transmisjonsmedium ved et forhåndsbestemt tidspunkt og en tidsserver som benytterfremgangsmåten
US7023816B2 (en) * 2000-12-13 2006-04-04 Safenet, Inc. Method and system for time synchronization
US7035246B2 (en) * 2001-03-13 2006-04-25 Pulse-Link, Inc. Maintaining a global time reference among a group of networked devices
US7185111B2 (en) * 2002-04-19 2007-02-27 Hewlett-Packard Development Company, L.P. Available server determination

Non-Patent Citations (2)

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See also references of WO2004038970A1 *

Also Published As

Publication number Publication date
DE10249296A1 (de) 2004-05-06
DE10393539D2 (de) 2005-06-30
US20050232384A1 (en) 2005-10-20
WO2004038970A1 (fr) 2004-05-06

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