(19)
(11)EP 3 503 629 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
10.06.2020 Bulletin 2020/24

(21)Application number: 17209427.8

(22)Date of filing:  21.12.2017
(51)International Patent Classification (IPC): 
H04W 52/02(2009.01)
H04W 56/00(2009.01)

(54)

TRANSCEIVER DEVICE WITH REAL TIME CLOCK

SENDER-EMPFÄNGERVORRICHTUNG MIT ECHTZEITTAKT

DISPOSITIF ÉMETTEUR-RÉCEPTEUR COMPORTANT UNE HORLOGE EN TEMPS RÉEL


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(43)Date of publication of application:
26.06.2019 Bulletin 2019/26

(73)Proprietor: Stichting IMEC Nederland
5656 AE Eindhoven (NL)

(72)Inventor:
  • LIU, Yao-Hong
    3001 Leuven (BE)

(74)Representative: Patent Department IMEC 
IMEC vzw Patent Department Kapeldreef 75
3001 Leuven
3001 Leuven (BE)


(56)References cited: : 
US-A1- 2014 112 229
US-A1- 2016 150 474
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    Field of the invention



    [0001] The present invention is generally related to the field of sensor networks.

    Background of the invention



    [0002] Most data collected by sensor nodes which for example form a wireless sensor network, changes very slowly. Consequently, in many applications most data needs to be transmitted only once every few minutes or even every few hours.

    [0003] Sensor nodes typically comprise a transmitter/receiver structure (i.e. a transceiver), a sensor, a sensor interface, an energy source like e.g. a battery and a controller. The sensor and the energy source may be integrated in the sensor node or be external to it.

    [0004] There is a clear tendency towards the use of batteries with an ever increasing lifetime. To meet the tough goal of a 10-year battery life time with a one-time installation or energy harvest operation, an RF transceiver (which is by far the most power-hungry block in a sensor network) should have an extremely low duty cycle (i.e., the ratio of on-time to sleep time), to minimize the average power consumption. For example, the average power consumption of the RF transceiver should be lower than 1µW in order to sustain for 10 years with a 100mAh small battery.

    [0005] There are two key limiting factors for reaching a minimum average power consumption and duty cycle: leakage current and the accuracy of the real-time counter. To address the leakage issue, a sophisticated power management and non-volatile memory have been widely explored. However, the real-time-counter accuracy has so far received little attention. If the real-time-counter has a frequency error of 1%, the lowest duty cycle is also limited to approximately 1%, because the transceiver needs to be enabled longer in order not to lose synchronization. For a transceiver with 10mW peak power, the duty cycle need to be reduced to 10-5 to achieve an average power below 1µW, this requires the real-time-counter accuracy to be approximately 10ppm, i.e., an accuracy similar to that of a crystal oscillator (XO). Note the low-power RC-based real-time-counter typically has an accuracy in the order of 10000 ppm.

    [0006] Further reducing the duty cycle does not lead to a reduction of the average power either when the settling time of the main crystal oscillator or the system processing overhead becomes a dominant factor.

    [0007] In the art the use of a high precision external temperature compensated crystal oscillator has been proposed. Such a temperature-compensated XO may consume as much as 10 µA, i.e. 100 times more than an on-chip relaxation oscillator. An important drawback is that this is a very expensive solution.

    [0008] If a crystal oscillator is used to calibrate the real-time-counter, only the frequency offset is calibrated, but not the noise, temperature or supply voltage induced variation.

    [0009] Also in case the frequency is synchronized in the network level, only frequency drift is calibrated, but not the noise induced variation.

    [0010] Hence, there is a need for a synchronization method which is ultra-low power in order to enable a long operation life time or energy harvesting based operation.

    [0011] US patent application (US20140112229 A1) discloses methods and stations for wireless communication. In some aspects, the station may include a processing circuit configured to process a first signal transmitted to the station, the first signal indicating a target wake up time when an activation signal is expected to be received. The station may further include a wake-up circuit configured to transition a first receiver to an awake state based on the indicated target wake up time. The first receiver is configured to receive the activation signal at the indicated target wake up time. The station may further include a second receiver configured to transition to an awake state based on the first receiver receiving the activation signal and receive a second signal while in the awake state.

    Summary of the invention



    [0012] It is an object of embodiments of the present invention to provide for a transceiver device comprising a mechanism for accurate wake-up timing. Having such a transceiver device available is an important step towards establishing ultra-low power synchronization in a sensor network. It is also an object of the invention to provide for a method for calibrating such a transceiver device.

    [0013] The above objective is accomplished by the solution according to the attached claims.

    [0014] The proposed solution indeed allows for receiving in the wake-up receiver a calibration signal on a regular basis, so that network synchronization becomes possible with reduced power consumption and cost.

    [0015] In preferred embodiments the wake-up receiver is arranged for receiving a wake-up signal and for waking up the main receiver upon reception of the wake-up signal.

    [0016] In other preferred embodiments the real time clock is arranged for waking up said main receiver.

    [0017] In other preferred embodiments the wake-up receiver is arranged for being enabled periodically via the clock signal from the real-time clock.

    [0018] The receiving section preferably comprises a real time clock controller arranged to receive the clock timing information from a transceiver device acting as a master and to compare the received clock timing information with timing information of the real time clock to obtain a timing error for adjusting the real time clock of the transceiver device. The real time clock controller advantageously comprises a counter to extract the timing information of the real time clock.

    [0019] The transceiver device comprises in certain embodiments comparing means to perform the comparing of the received clock timing information and the timing information of the real time clock.

    [0020] In one embodiment the real time clock controller further comprises a digital loop filter to filter the timing error.

    [0021] Advantageously, the transceiver device further comprises a sensor device.

    [0022] In another aspect the invention relates to a device for use as a sensor node in a sensor network comprising a transceiver device as previously described.

    [0023] In one aspect the invention relates to a communication system comprising one or more transceivers as previously described.

    [0024] In a preferred embodiment the communication system comprises a further transceiver arranged to act as a master device.

    [0025] In another aspect the invention relates to a method for calibrating a real time clock of a first transceiver device operative as a slave in a network, the method comprising :
    • enabling a wake-up receiver forming part of a receiving section of said first transceiver device,
    • receiving in the wake-up receiver a calibration signal comprising clock timing information containing a time stamp and adjusting the real time clock based on the clock timing information.


    [0026] In embodiments of the method a main receiver forming part of said receiving section of said first transceiver device is woken up with said wake up receiver, once said calibration signal has been received.

    [0027] In certain embodiments the wake-up receiver is periodically enabled via a clock signal from the real-time clock.

    [0028] For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

    [0029] The above and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

    Brief description of the drawings



    [0030] The invention will now be described further, by way of example, with reference to the accompanying drawings, wherein like reference numerals refer to like elements in the various figures.

    Fig.1 illustrates a network structure with a master transceiver and slave transceivers.

    Fig.2 illustrates a block scheme of a transceiver according to an embodiment of the invention, showing the main blocks of the receiving section.

    Fig.3 illustrates a communication scheme that can be used with the network structure of Fig.1.

    Fig.4 illustrates another communication scheme, wherein the wake-up receiver is continuously enabled.

    Fig.5 illustrates a clock duty cycle reduction that can be achieved with the transceiver device of the invention.

    Fig.6 illustrates a block scheme illustrating the calibration and clock correction.


    Detailed description of illustrative embodiments



    [0031] The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims.

    [0032] Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

    [0033] It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

    [0034] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

    [0035] Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

    [0036] Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

    [0037] It should be noted that the use of particular terminology when describing certain features or aspects of the invention should not be taken to imply that the terminology is being redefined herein to be restricted to include any specific characteristics of the features or aspects of the invention with which that terminology is associated.

    [0038] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.

    [0039] In order to allow for low power synchronization the present invention discloses a transceiver device with a novel structure as well as a method for calibrating such a transceiver device when it is part of a network.

    [0040] To explain the invention an exemplary network structure as illustrated in Fig.1 is considered. A network of wireless nodes is shown. One wireless transceiver is used as a master node. Two more transceiver devices are shown that act as a slave node. Apart from the transmitter section and the receiver section each of the slave devices is provided with a real-time clock 20.

    [0041] According to the invention the transceiver devices acting as slave have a receiving section not only comprising a main receiver 40 that can receive communication signals, but also a wake-up receiver 10. The invention also unveils a calibration method wherein this wake-up receiver performs a crucial role.

    [0042] A more detailed view of the high level architecture of the transceiver of this invention is provided in Fig.2. In preferred embodiments of the invention the wake-up receiver (WuRX) 10 is periodically enabled by the clock signal of the real-time counter (RTC) 20. Note that in this description the terms 'real-time counter' and real-time clock' refer to the same and are used interchangeably. Once enabled the wake-up receiver is ready to receive from the master node a calibration signal containing clock timing information and/or wake-up signal. As illustrated in Fig.2, the receiving section also comprises a real time clock controller 30, which receives the clock timing information received from the master device.
    Based on the received clock timing information the slave device can then correct the clock signal of the real-time counter, as will be detailed below. The transmitter in the master node employs a precise crystal oscillator to generate a correct timing reference. It periodically transmits the calibration signal with the timing information, including a time stamp, to the slave devices. The precise crystal oscillator in the master node is further also used to generate a stable signal centre frequency.

    [0043] Alternatively, the wake-up receiver is continuously enabled. In this way the wake-up is at any time ready to listen to an incoming calibration signal.

    [0044] However, the invention will be described below with reference to the periodically enabled wake-up receiver.

    [0045] In one embodiment the wake-up receiver wakes up the main receiver in the receiving section of the slave transceiver device once the wake-up signal is received. This reduces the on time of the main receiver. The wake-up signal is sent just before the master node transmits a communication signal to the slave node.

    [0046] In other embodiments the main receiver is woken up directly via a clock signal from the real-time counter (RTC) 20. This is illustrated with a dashed line in Fig.2.

    [0047] Fig.3 illustrates a typical communication scheme. At regular times the wake-up receiver in the slave device is enabled. It can then receive the calibration signal that contains the clock timing information. Fig.3 also illustrates a second calibration signal transmission and a third signal - a wake-up signal - transmission. The wake-up signal transmission occurs just before transmitting the main burst signal.

    [0048] Fig.4 provides a similar scheme as Fig.3, but now for the case the wake-up receiver is continuously enabled. The wake-up receiver is then all the time ready for receiving a calibration signal containing clock timing information.

    [0049] The proposed approach regulates the real-time clock accuracy to a similar level as a crystal oscillator, i.e., from 10,000ppm to 10ppm, without increasing the power consumption of the slave node as in the case a crystal oscillator is used instead. The wake-up receiver itself consumes very low power and is only enabled for a short period of time. Fig.5 illustrates the calculated average power consumption (in µW) versus duty cycle. The upper curve is calculated based on a typical real time clock with calibration, whereas the lower curve is calculated based on a real time clock calibrated as proposed in this invention. As illustrated in Fig.5, the average power consumption with a real time clock without calibration is limited to around 10 µW, even the duty cycle is reduced to below 10-5. On the other hand, when the real time clock is being calibrated to an accuracy of 10ppm, it brings down the average power consumption of the slave node to 0.9µW when the clock duty cycle is reduced to 10-5.

    [0050] Details on the calibration and the real-time clock correction are now provided with reference to the block scheme of Fig.6. The wake-up receiver receives via its antenna the calibration signal comprising a time stamp. Fig.6 provides a more detailed view on the real time clock controller that receives the clock timing information from the master device. The real-time controller is further arranged for comparing this information with timing information derived from the real-time clock comprised in the slave transceiver. As also shown in Fig.6, the controller advantageously comprises a counter to extract real-time information from the real-time clock output of the slave device. The controller then can determine a timing error by comparing the received clock timing information, i.e. the time stamp contained therein, with timing information of the real time clock.

    [0051] In preferred embodiments a digital loop filter is provided to filter the timing error.

    [0052] It is to be noted that the above presented approach can be applied in a similar fashion to offer a solution for the problem how to provide a stable signal centre frequency without requiring a crystal oscillator at the slave node.

    [0053] Many wireless sensor networks use a "synchronous" network structure. In this kind of synchronous network there is a master node as the control centre that organizes the communication with one or more slave devices. These slave devices, which typically include sensors, collect the environmental information to send it to the master node. In such a network structure the master node periodically sends control information (or a beacon signal) and the slave nodes need to wake up periodically to receive this control information and possibly send back the sensor data to the master node if that is needed. To make sure these slave nodes do not miss the signal containing control information from the master, they need to wake up at the right time. Otherwise, they need to turn on much earlier in order not to miss the control signal, which causes unnecessary energy waste. With the presented invention, the slave nodes can wake up at the correct time because the real-time clock precision is being calibrated.

    [0054] Similarly to the abovementioned wireless sensor network, many wireless communication networks also use a similar master-slave network structure. For example, the base-station of a cellular system is equivalent to a master and the cell phones are the slave devices. The receivers of the cell phones need to periodically turn on to receive the control information from the base station. To extend the battery life time of the cell phones, a similar approach can be adopted to ensure the wake-up timing of the cell phones are precisely calibrated.

    [0055] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The foregoing description details certain embodiments of the invention. It will be appreciated, however, that no matter how detailed the foregoing appears in text, the invention may be practiced in many ways. The invention is not limited to the disclosed embodiments.

    [0056] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.


    Claims

    1. Transceiver device comprising a real time clock (20) arranged for providing a clock signal and a receiving section comprising

    - a main receiver (40) arranged for receiving communication signals,

    - a wake-up receiver (10) arranged for receiving a calibration signal comprising clock timing information containing a time stamp and for adjusting said real time clock (20) based on said clock timing information, characterised in that:
    the transceiver device additionally comprises a real time clock controller (30) arranged to receive said clock timing information and to compare said received clock timing information with timing information of said real time clock (20) to obtain a timing error for adjusting said real time clock (20) of the transceiver device.


     
    2. Transceiver device as in claim 1, wherein said wake-up receiver (10) is arranged for receiving a wake-up signal and for waking up said main receiver (40) upon reception of said wake-up signal.
     
    3. Transceiver device as in claim 1, wherein said real time clock (20) is arranged for waking up said main receiver (40).
     
    4. Transceiver device as in any of claim 1 to 3, wherein said wake-up receiver (10) is arranged for being enabled periodically via said clock signal from said real-time clock (20).
     
    5. Transceiver device according to any of the previous claims, wherein said real time clock controller (30) comprises a counter (32) to extract said timing information of said real time clock (20).
     
    6. Transceiver device as in any of the previous claims, comprising comparing means to perform said comparing of said received clock timing information and said timing information of said real timeclock (20).
     
    7. Transceiver device as in any of the previous claims, wherein said real time clock controller (30) further comprises a digital loop filter (33) to filter the timing error.
     
    8. Transceiver device as in any preceding claim, further comprising a sensor device.
     
    9. Device for use as a sensor node in a sensor network comprising a transceiver device as in any of the previous claims.
     
    10. Communication system comprising one or more transceivers as in any of claims 1 to 8.
     
    11. Communication system as in claim 10, comprising a further transceiver arranged to act as a master device.
     
    12. Method for calibrating a real time clock (20) of a first transceiver device operative as a slave in a network, the method comprising :

    - enabling a wake-up receiver (10) forming part of a receiving section of said first transceiver device,

    - receiving in said wake-up receiver (10) a calibration signal comprising clock timing information containing a time stamp and adjusting said real time clock (20) based on said clock timing information,
    characterised in that:
    the received clock timing information containing a time stamp is compared with timing information of the real time clock (20) to determine a timing error and thereby adjust the real time clock (20).


     
    13. Method for calibrating as in claim 12, wherein, once said calibration signal has been received, a main receiver forming part of said receiving section of said first transceiver device is woken up with said wake up receiver (10).
     
    14. Method for calibrating as in claim 12 or 13, wherein said wake-up receiver (10) is periodically enabled via a clock signal from said real-time clock (20).
     


    Ansprüche

    1. Sendeempfängervorrichtung, einen Echtzeittaktgeber (20), der zum Bereitstellen eines Taktsignals angeordnet ist, und eines Empfangsabschnitts umfassend, wobei der Empfangsabschnitt umfasst

    - einen Hauptempfänger (40), der für Empfangen von Kommunikationssignalen angeordnet ist,

    - einen Weckempfänger (10), der zum Empfangen eines Kalibrierungssignals angeordnet ist, das Taktzeitinformation umfasst, die einen Zeitstempel enthält, und zum Einstellen des Echtzeittaktgebers (20) basierend auf der Taktzeitinformation, dadurch gekennzeichnet, dass:
    die Sendeempfängervorrichtung zusätzlich eine Echtzeittaktgebersteuerung (30) umfasst, die angeordnet ist, die Taktzeitinformation zu empfangen und die empfangene Taktzeitinformation mit Taktzeitinformation des Echtzeittaktgebers (20) zu vergleichen, um einen Taktfehler zum Einstellen des Echtzeittaktgebers (20) der Sendeempfängervorrichtung zu erzielen.


     
    2. Sendeempfängervorrichtung nach Anspruch 1, wobei der Weckempfänger (10) zum Empfangen eines Wecksignals und zum Aufwecken des Hauptempfängers (40) bei Empfang des Wecksignals angeordnet ist.
     
    3. Sendeempfängervorrichtung nach Anspruch 1, wobei der Echtzeittaktgeber (20) zum Aufwecken des Hauptempfängers (40) angeordnet ist.
     
    4. Sendeempfängervorrichtung nach einem der Ansprüche 1 bis 3, wobei der Weckempfänger (10) angeordnet ist, periodisch über das Taktsignal von dem Echtzeittaktgeber (20) aktiviert zu werden.
     
    5. Sendeempfängervorrichtung nach einem der vorstehenden Ansprüche, wobei die Echtzeittaktgebersteuerung (30) einen Zähler (32) zum Extrahieren der Taktzeitinformation des Echtzeittaktgebers (20) umfasst.
     
    6. Sendeempfängervorrichtung nach einem der vorstehenden Ansprüche, Vergleichsmittel zum Durchführen des Vergleichs der empfangenen Taktzeitinformation und der Taktzeitinformation des Echtzeittaktgebers (20) umfassend.
     
    7. Sendeempfängervorrichtung nach einem der vorstehenden Ansprüche, wobei die Echtzeittaktgebersteuerung (30) weiter einen digitalen Schleifenfilter (33) zum Filtern des Taktfehlers umfasst.
     
    8. Sendeempfängervorrichtung nach einem der vorstehenden Ansprüche, weiter eine Sensorvorrichtung umfassend.
     
    9. Vorrichtung zur Verwendung als ein Sensorknoten in einem Sensornetzwerk, eine Sendeempfängervorrichtung nach einem der vorstehenden Ansprüche umfassend.
     
    10. Kommunikationssystem, einen oder mehrere Sendeempfänger nach einem der Ansprüche 1 bis 8 umfassend.
     
    11. Kommunikationssystem nach Anspruch 10, einen weiteren Sendeempfänger umfassend, der angeordnet ist, als eine Master-Vorrichtung zu agieren.
     
    12. Verfahren zum Kalibrieren eines Echtzeittaktgebers (20) einer ersten Sendeempfängervorrichtung, die als ein Slave in einem Netzwerk betriebsfähig ist, wobei das Verfahren umfasst:

    - Aktivieren eines Weckempfängers (10), der Teil eines Empfangsabschnitts der ersten Sendeempfängervorrichtung bildet,

    - Empfangen eines Kalibrierungssignals in dem Weckempfänger (10), das Taktzeitinformation umfasst, die einen Zeitstempel enthält, und zum Einstellen des Echtzeittaktgebers (20) basierend auf der Taktzeitinformation,
    dadurch gekennzeichnet, dass:
    die empfangene Taktzeitinformation, die einen Zeitstempel enthält, mit Taktzeitinformation des Echtzeittaktgebers (20) verglichen wird, um einen Taktfehler zu bestimmen und dadurch den Echtzeittaktgeber (20) einzustellen.


     
    13. Verfahren zum Kalibrieren nach Anspruch 12, wobei, nachdem das Kalibrierungssignal empfangen wurde, ein Hauptempfänger, der Teil des Empfangsabschnitts der ersten Sendeempfängervorrichtung bildet, mit dem Weckempfänger (10) aufgeweckt wird.
     
    14. Verfahren zum Kalibrieren nach Anspruch 12 oder 13, wobei der Weckempfänger (10) periodisch über ein Taktsignal von dem Echtzeittaktgeber (20) aktiviert wird.
     


    Revendications

    1. Dispositif émetteur-récepteur comprenant une horloge temps réel (20) agencée pour fournir un signal d'horloge et une section réceptrice comprenant

    - un récepteur principal (40) agencé pour recevoir des signaux de communication,

    - un récepteur de réveil (10) agencé pour recevoir un signal d'étalonnage comprenant des informations de synchronisation d'horloge contenant un horodatage et pour ajuster ladite horloge temps réel (20) sur la base desdites informations de synchronisation d'horloge, caractérisé en ce que :
    le dispositif émetteur-récepteur comprend en outre un organe de commande d'horloge temps réel (30) agencé pour recevoir lesdites informations de synchronisation d'horloge et pour comparer lesdites informations de synchronisation d'horloge reçues à des informations de synchronisation de ladite horloge temps réel (20) afin d'obtenir une erreur de synchronisation pour ajuster ladite horloge temps réel (20) du dispositif émetteur-récepteur.


     
    2. Dispositif émetteur-récepteur selon la revendication 1, dans lequel ledit récepteur de réveil (10) est agencé pour recevoir un signal de réveil et pour réveiller ledit récepteur principal (40) à la réception dudit signal de réveil.
     
    3. Dispositif émetteur-récepteur selon la revendication 1, dans lequel ladite horloge temps réel (20) est agencée pour réveiller ledit récepteur principal (40).
     
    4. Dispositif émetteur-récepteur selon l'une quelconque des revendications 1 à 3, dans lequel ledit récepteur de réveil (10) est agencé pour être activé périodiquement par l'intermédiaire dudit signal d'horloge provenant de ladite horloge temps réel (20).
     
    5. Dispositif émetteur-récepteur selon l'une quelconque des revendications précédentes, dans lequel ledit organe de commande d'horloge temps réel (30) comprend un compteur (32) pour extraire lesdites informations de synchronisation de ladite horloge temps réel (20).
     
    6. Dispositif émetteur-récepteur selon l'une quelconque des revendications précédentes, comprenant des moyens de comparaison pour effectuer ladite comparaison desdites informations de synchronisation d'horloge reçues et desdites informations de synchronisation de ladite horloge temps réel (20).
     
    7. Dispositif émetteur-récepteur selon l'une quelconque des revendications précédentes, dans lequel ledit organe de commande d'horloge temps réel (30) comprend en outre un filtre de boucle numérique (33) pour filtrer l'erreur de synchronisation.
     
    8. Dispositif émetteur-récepteur selon l'une quelconque des revendications précédentes, comprenant en outre un dispositif capteur.
     
    9. Dispositif destiné à être utilisé en tant que nœud de capteur dans un réseau de capteur comprenant un dispositif émetteur-récepteur selon l'une quelconque des revendications précédentes.
     
    10. Système de communication comprenant un ou plusieurs émetteurs-récepteurs selon l'une quelconque des revendications 1 à 8.
     
    11. Système de communication selon la revendication 10, comprenant un autre émetteur-récepteur agencé pour servir de dispositif maître.
     
    12. Procédé d'étalonnage d'une horloge temps réel (20) d'un premier dispositif émetteur-récepteur opérationnel en tant qu'esclave dans un réseau, le procédé comprenant :

    - l'activation d'un récepteur de réveil (10) faisant partie d'une section réceptrice dudit dispositif émetteur-récepteur,

    - la réception, dans ledit récepteur de réveil (10), d'un signal d'étalonnage comprenant des informations de synchronisation d'horloge contenant un horodatage et l'ajustement de ladite horloge temps réel (20) sur la base desdites informations de synchronisation d'horloge,
    caractérisé en ce que :
    les informations de synchronisation d'horloge reçues contenant un horodatage sont comparées à des informations de synchronisation de l'horloge temps réel (20) pour déterminer une erreur de synchronisation et ajuster de ce fait l'horloge temps réel (20).


     
    13. Procédé d'étalonnage selon la revendication 12, dans lequel, une fois que ledit signal d'étalonnage a été reçu, un récepteur principal faisant partie de ladite section réceptrice dudit premier dispositif émetteur-récepteur est réveillé avec ledit récepteur de réveil (10).
     
    14. Procédé d'étalonnage selon la revendication 12 ou 13, dans lequel ledit récepteur de réveil (10) est activé périodiquement par l'intermédiaire d'un signal d'horloge provenant de ladite horloge temps réel (20).
     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description