Sensor device with synchronous measurement capability

Abstract

A sensor device, such as a consumption meter, has an LTE modem, a processor system connected with the LTE modem, and a sensor system including at least one sensor configured to sense a physical parameter and generate an output to the processor system accordingly. The sensor device is configured to receive an activation time via the LTE network, where the activation time includes an absolute time and / or an indication of a particular LTE frame number. The processor system is configured to cooperate with the LTE modem to time synchronize to a current LTE frame number. This can be particularly accomplished by the processor system sending a signal on the electrical pin to the LTE modem, in response, the LTE modem outputs the current LTE frame number, and the processor system starts a timer while sending the signal on the electrical pin. Accordingly, by starting a timer at a known LTE frame number, the sensor device can accurately calculate to initiate a predetermined action in synchronization with the absolute time indicated in the received activation time and the specific LTE frame number time. The action may involve performing a measurement using a sensor in the sensor device in time synchronization with the received activation time. This provides high precision time synchronization for a set of sensor devices, allowing the set of sensor devices to perform measurements simultaneously. This enables group measurements that cannot be achieved by the time accuracy of the internal clocks of a group of sensor devices, and this time synchronization may be very important for certain applications, such as acoustic leak detection in a utility network.

Description

Technical Field

[0001] The present invention relates to sensor devices, such as consumption meters, having the capability to perform time synchronization actions activated via a wireless communication network. More particularly, the present invention relates to synchronizing sensor devices via an LTE network. Background Art

[0002] Across utility networks, whether for water, gas, heating, cooling, or electricity, multiple consumption meters are distributed to measure utility consumption at each consumer site. Typically, these consumption meters are battery-powered and configured to enter a sleep mode of operation to conserve battery power. In addition to specialized sensors for utility meter functionality, these consumption meters may also have sensor capabilities for sensing one or more physical characteristics.

[0003] In some applications, such as leak detection in a utility network, collecting measurement data from sensors in a group of consumption meters distributed throughout the utility network can be crucial. For certain types of such measurement data, precise time synchronization of the measurements from a group of consumption meters is crucial. However, while consumption meters typically have built-in clocks that provide absolute time, these clocks are often imprecise, with deviations of more than one minute. Therefore, these clocks cannot be used for precise time synchronization across a group of consumption meters.

[0004] Purpose of the Invention

[0005] The object of the present invention is to wholly or partly overcome the drawbacks and disadvantages of the prior art. More specifically, the object is to provide a sensor device, such as a consumption meter, which is suitable for performing synchronized (eg simultaneous) measurements in a group of distributed devices. Summary of the Invention

[0006] In a first aspect, the present invention provides a sensor device comprising:

[0007] - an LTE modem configured to receive and transmit wireless signals on an LTE network,

[0008] - a processor system connected to an interface of the LTE modem, wherein the processor system includes a clock configured to provide an absolute time output, and wherein the processor system further includes a timer, and

[0009] - a sensor system comprising at least one sensor configured to sense a physical parameter and to generate an output accordingly to the processor system,

[0010] The sensor device is configured to:

[0011] - receiving a wireless signal on the LTE network, the signal comprising data indicating an activation time, the activation time comprising at least data indicating an absolute time or a relative time,

[0012] - cooperate with the LTE modem to time synchronize to the current LTE frame number, and

[0013] - Initiating a predetermined action involving the sensor system, such as initiating a measurement or reading an output from the sensor system, synchronously with the absolute time or relative time and with a specific LTE frame number, wherein the specific LTE frame number is received in the data indicating the activation time or is stored in the sensor device.

[0014] Such sensor devices (e.g., consumption meters) are advantageous because LTE networks provide a well-defined frame structure with consecutively numbered frames (superframes, frames, and subframes) that are precisely synchronized and continue in a repeating cycle. The inventors have recognized that exploiting the fact that an LTE modem has information about the current LTE frame number and possibly also the elapsed time of the current LTE subframe allows the sensor devices to achieve extremely high-precision time synchronization internally, thereby allowing time accuracy of less than one second, for example, down to 1-10 ms, or even better than 1 ms, or even better than 10 μs. Thus, a group of sensor devices can perform activities in a time-synchronized manner with a time accuracy far exceeding that provided by their internal clocks.

[0015] This allows for synchronized measurements using sensor systems across a group of meters, enabling new applications that require synchronized measurements, such as simultaneous measurement of electrical phases at various locations in the power grid. However, this high-precision time synchronization enables a variety of measurements, such as locating specific time events within or independent of the utility network.

[0016] High-precision time synchronization can provide meaningful sensing or measurement of various physical properties that are not possible with the time accuracy provided by a single unsynchronized clock.

[0017] The sensor device may be a consumption meter having one or more sensors dedicated to measurements not directly related to utility metering. Some consumption meters have an LTE modem and can therefore be modified to operate according to the present invention. However, the sensor device may be a dedicated sensor device, for example for acoustic leak detection in fluid networks such as water networks. Other examples of sensors may be temperature sensors, pressure sensors, sensors for measuring water or air pollution, turbidity sensors. All of the above sensors may be integrated into a sensor device in the form of a consumption meter or into other sensor devices. The sensor device may be a stand-alone sensor device or a sensor device integrated into any other suitable device.

[0018] The high time synchronization accuracy achievable by the present invention allows for simultaneous measurement of electrical parameters, which can be implemented, for example, in electricity meters. Other applications of simultaneous measurement can be acoustic leak detection (ALD) in flow meters or pressure transient detection in flow meters. Synchronizing the measurement times is advantageous, however, it should be noted that the time of sending the measurement data or results is preferably not synchronized, as this may cause congestion in the cellular network. The flow meter can be part of a water meter or a heat meter. The processor system of the sensor device can optionally be further arranged to store the output generated by the sensor system and to transmit the output to a backend system at a time point different from the activation time.

[0019] The sensor devices can be controlled from a backend system to perform synchronization, e.g., simultaneous measurements. A user (e.g., a utility provider) can decide to perform a measurement using one or more sensors from a group of sensor devices by sending a message to the group of sensor devices over the LTE network before a certain time at which the measurement is expected to be activated. In particular, if the sensor devices can enter a sleep mode of operation, it may be preferable to send the expected activation time to the sensor devices immediately after they wake up, e.g., after they send measurement data (e.g., consumption data) via the LTE network, which may be sent once or several times a day. In this way, the sensor devices can be kept in sleep mode until a few minutes or even just a few seconds before the expected synchronized measurement is to be performed.

[0020] "LTE network" refers to a cellular communication-compatible network, such as a 3GPP (3rd Generation Partnership Project) Long Term Evolution wireless network. Such LTE networks are based on a frame structure with numbered LTE frames that are synchronized in time. LTE frame numbers repeat over several hours. Examples of LTE frame numbers include a System Frame Number (SFN), which repeats / wraps around after 10.24 seconds, or a Super System Frame Number (H-SFN), which repeats / wraps around after approximately 2 hours and 55 minutes.

[0021] Hereinafter, preferred features and embodiments will be described.

[0022] In some embodiments, the processor system can be configured to initiate the predetermined action in synchronization with a specific LTE frame number. In particular, the processor system can be configured to initiate the predetermined action in synchronization with a specific LTE frame number received in data indicating an activation time or a specific LTE frame number stored in the sensor device. In some embodiments, the action can be pre-programmed in the sensor device, or the action can be defined in a wireless signal received over the LTE network.

[0023] Preferably, the processor system is configured to receive from the LTE modem a current LTE frame number and a value indicating the elapsed time (in μs) of the current LTE subframe in response to a signal on an electrical pin on the LTE modem. Since the LTE subframe has a time extension of 1 ms, this enables time synchronization with an accuracy better than 1 ms.

[0024] In a preferred embodiment, the processor system is configured to issue a signal on an electrical pin of the LTE modem and, in response, receive data indicating the current LTE frame number. This utilizes the LTE modem's ability to always know the LTE frame number. In versions of the LTE modem with an interface that supports this functionality, the processor system can receive the current LTE frame number from the LTE modem upon request via its interface with the modem. This enables time synchronization with the precise LTE frame number. Specifically, the processor system can pull up or down an electrical pin of the LTE modem. Specifically, the electrical pin can be a GPIO pin of the LTE modem.

[0025] In particular, the processor system can be configured to start a timer in synchronization with issuing a signal on an electrical pin of the LTE modem. Given the current LTE frame number, the timer can be used to time when to initiate a predetermined action because the time from the current LTE frame number to a specific LTE frame number can be determined.

[0026] In particular, the processor system can be configured to calculate in which timer state to initiate the predetermined action based on a specific LTE frame number and data indicating the current LTE frame number received from the LTE modem. In this way, although the timer may not provide ultra-high accuracy, a high degree of accuracy can still be achieved because the timer is only used to determine the activation time within a limited time period (such as from a few minutes to a few hours).

[0027] Wireless signals received over the LTE network can include data indicating both a specific LTE frame number and a specific absolute or relative time. In this way, wireless signals can be sent even days before the expected activation time. Specifically, the wireless signal can include data indicating a specific absolute future time, such as a specific absolute future time including data indicating a future date and the time of that future date. Thus, the sensor device can use its clock to remain in a sleep operating mode until minutes or even seconds before activation. Alternatively, the sensor device can be configured to initiate a predetermined action involving the sensor system in synchronization with the first occurrence of a specific LTE frame number after, or alternatively before, the absolute or relative time included in the received wireless signal. This is particularly advantageous because sensor devices may only access the LTE network infrequently, such as once or a few times per day, to reduce device energy consumption or network load. Sensor devices typically remain in sleep mode between each access to the LTE network and can only access the LTE network for a short period after each access. Therefore, to synchronize measurements across multiple sensor devices, wireless signals over the LTE network, including data indicating the activation time, must be sent hours or days in advance. Therefore, during the period from receiving the wireless signal to the activation time, the time drift of the internal timer or clock (such as the real-time clock) is very large. Therefore, the advantage of using absolute time in combination with the LTE frame number is that the accuracy of synchronization is significantly improved because the influence of drift or error of the internal timer or real-time clock is eliminated.

[0028] The processor system may be configured to utilize the clock to determine a date and an approximate time of day on which the predetermined action is to be initiated.

[0029] The sensor device can be configured to enter a sleep operating mode and, in response to an absolute time output from the clock reaching a predetermined time, enter a normal operating mode, wherein the processor system is configured to determine the time to enter the normal operating mode before the time defined by the activation time. In this manner, the sensor device is awakened using a less accurate clock in the sensor device, thereby preparing the sensor device for the activation action. For example, the sensor device can be programmed to wake up within 1-10 minutes before a time defined by a specific absolute time and a specific LTE frame number, such as within 1-60 seconds before a time defined by a specific absolute time and a specific LTE frame number. Nevertheless, if battery-powered, the sensor device can conserve battery by remaining in the sleep operating mode until the expected activation. In particular, it can be ensured that the LTE modem is in sleep mode most of the time, thereby conserving battery power.

[0030] The processor system may be configured to read the current LTE frame number from the LTE modem by issuing a signal on an electrical pin (e.g., a GPIO pin) of the LTE modem, and wherein the processor system is further configured to calculate a time and wait until the current LTE frame number equals a predetermined LTE frame number. To this end, a timer of the processor device may be used and synchronization may still be achieved.

[0031] In a particular embodiment, the processor system can be configured to program the LTE modem to indicate on an electrical pin (e.g., a GPIO pin) when a current LTE frame number is equal to a predetermined LTE frame number, wherein the predetermined LTE frame number is determined in response to an activation time received including data indicating a particular LTE frame number.

[0032] The predetermined action may involve initiating at least one measurement of a physical parameter using at least one sensor of the sensor system, and wherein the sensor device is configured to transmit data indicative of the at least one measurement in a wireless signal over the LTE network. In particular, the at least one sensor may be arranged to measure at least one of: fluid flow, temperature, fluid pressure, magnetic field strength, electrical impedance, voltage or current, turbidity measurement, and acoustic signal.

[0033] The processor system can be configured to receive data in a wireless signal on the LTE network indicating which type of action to initiate. This can be achieved by sending a code, wherein the processor system is configured to read the code and convert the code into a specific action.

[0034] The sensor device may be, in particular, a consumption meter, such as a water meter, a gas meter, a heat meter, a cooling meter, or an electricity meter, configured to measure the consumption of a utility and, in response, transmit a wireless signal including data indicative of the measured consumption over an LTE network. Specifically, the sensor device is a consumption meter selected from the group consisting of a water meter, a gas meter, a heat meter, and a cooling meter, wherein the consumption meter includes at least one ultrasonic transducer for measuring fluid flow. More specifically, the sensor device may include: a flow tube having a flow path for a fluid between an inlet and an outlet; a flow meter housing associated with the flow tube; and a meter system including a meter circuit connected to the transducer and configured to measure the consumption of the utility.

[0035] In some embodiments, a sensor device may be configured to transmit a first wireless signal over an LTE network, the first wireless signal including data indicating both: 1) a current LTE frame number determined by an LTE modem, and 2) an associated absolute time output from a clock. A backend receiver may utilize this to transmit a return signal to the sensor device to allow the sensor device to adjust its clock. Specifically, the sensor device may be configured to receive a second wireless signal over the LTE network in response to the first wireless signal, wherein the second wireless signal includes clock adjustment data, and wherein the sensor device is configured to adjust the clock accordingly.

[0036] The sensor device may in particular be powered by a battery, such as an internal battery. The proposed time synchronization approach may be implemented such that the LTE modem is only required to be in normal operating mode for a very limited period of time. This helps to conserve battery power.

[0037] The LTE modem may be configured to operate in at least one carrier frequency band selected from the group consisting of 450 MHz, 700 MHz, 800 MHz, 1700 MHz, 1800 MHz, 1900 MHz, 2100 MHz, and 2600 MHz. If desired, the LTE modem may be configured to operate at carrier frequencies within other frequency ranges.

[0038] In a variation of the first aspect of the invention, there is provided a sensor device comprising:

[0039] - an LTE modem configured to receive and transmit wireless signals on an LTE network,

[0040] - a processor system connected to an interface of the LTE modem, wherein the processor system comprises a clock configured to provide a time output or optionally an absolute time output, and wherein the processor system optionally further comprises a timer, and

[0041] - a sensor system comprising at least one sensor configured to sense a physical parameter and to generate an output accordingly to the processor system,

[0042] The sensor device is configured to:

[0043] - receiving a wireless signal on the LTE network, the signal comprising data indicating an activation time, the activation time comprising at least data indicating an absolute time or a relative time,

[0044] - cooperate with the LTE modem to time synchronize to the current LTE frame number, and

[0045] - Initiating a predetermined action involving the sensor system, such as initiating a measurement or reading an output from the sensor system, synchronously with the absolute time or relative time and with a specific LTE frame number, wherein the specific LTE frame number is received in the data indicating the activation time or is stored in the sensor device.

[0046] The sensor device according to the variant of the first aspect of the invention may be combined with all optional features of the first aspect of the invention.

[0047] In a second aspect, the present invention provides a system comprising:

[0048] - a plurality of sensor devices according to the first aspect, and

[0049] - A transmitter system configured to transmit a wireless signal including data indicating an activation time to a plurality of sensor devices over an LTE network.

[0050] In particular, the data indicative of the activation time may comprise data indicative of a specific LTE frame number and an absolute time, such as all of the following: a specific LTE frame number and an absolute time including an indication of at least the date and time.

[0051] The transmitter system may be implemented as a backend system of a utility meter reading system, and wherein the sensor device is a consumption meter.In addition to the sensor(s) operating to provide a metering function, the consumption meter may also include one or more sensors dedicated to additional functions.

[0052] The transmitter system may, among other things, allow the user to select an activation time, which is then sent to the sensor device.

[0053] The transmitter system may further include a receiver system configured to receive data from each of the plurality of sensor devices via the LTE network. In particular, the data may include data indicating at least one measurement performed by the respective sensor device at a time defined by the activation.

[0054] In a third aspect, the present invention provides a method for time synchronization of a plurality of sensor devices such as consumption meters, the method comprising:

[0055] - sending a wireless signal including data indicating an activation time over the LTE network,

[0056] - receiving wireless signals on the LTE network by a plurality of sensor devices,

[0057] - Each sensor device cooperates with the LTE modem in the sensor device to time synchronize to the current LTE frame number, and

[0058] - Initiation by each sensor device of a predetermined action, such as performing a measurement involving reading the sensor system output, synchronously with the activation time.

[0059] In particular, the activation time may include data indicating a specific LTE frame number and an absolute time.

[0060] The step of coordinating time synchronization with the LTE modem in the sensor device to the current LTE frame number can include a processor system in the sensor device signaling the LTE modem in the sensor device on an electrical pin. In response, the LTE modem transmits the current LTE frame number. Specifically, the processor system can start a timer simultaneously with signaling the LTE modem on the electrical pin, thereby allowing the sensor device to synchronize time with an accuracy of at least the length of the LTE frame number. In another embodiment, the timer is a running timer, and thus, simultaneously with signaling the electrical pin, a timer register is read and a timer state is calculated based on the read register time. In particular, if the received activation time includes a specific LTE frame number for initiating a synchronization action, the predetermined action can be initiated with LTE frame number accuracy.

[0061] The method may include receiving data indicating an LTE frame number from at least one sensor device, preferably receiving data indicating both: 1) an LTE frame number and 2) an absolute time associated with the LTE frame number. This preferably allows a backend system to estimate the timing between the LTE frame number and the absolute time in the sensor device. Further, this is preferably used to generate data indicating an activation time based on the received data. Thereby, a specific future LTE frame number can be unambiguously selected at which all sensor devices can perform synchronization actions. Thus, depending on the accuracy of the internal clock of the sensor device, it is possible to avoid selecting a future LTE frame number that overlaps with the specified activation time. In addition, if a specific LTE frame number is used as the activation time and this LTE frame number has already passed at the sensor device, this means that the internal timer in the sensor device needs to wait until the specific LTE frame number appears again, that is, wait for one LTE superframe sequence, which takes nearly 3 hours.

[0062] Based on the absolute time and LTE frame number received from at least one sensor device, an activation time can be calculated, such as an activation time at least 24 hours in the future. The activation time includes the absolute time and a specific LTE frame number, and the specific LTE frame number is determined to occur within a short period of the absolute time, such as within 60 seconds, 120 seconds, or 300 seconds of the absolute time. The advantage of this is that the sensor device only needs to power up the modem once every 24 hours (from sleep mode to normal operation), and the absolute time and specific LTE frame will be sent to all sensor devices for the next 24 hours, thereby achieving synchronization.

[0063] Furthermore, the method may include sending time adjustment data to one or more individual sensor devices in response to the received LTE frame number and associated absolute time. This may be used to adjust an internal clock in the sensor device.

[0064] The predetermined action may include performing, by each sensor device, a measurement synchronized with an activation time (e.g., a specific LTE frame number). The method may further include transmitting, by each sensor device, a wireless signal, wherein the wireless signal includes data indicating at least one measurement performed by the respective sensor device at a time defined by a specific absolute time and a specific LTE frame number.

[0065] The features and embodiments described above in the context of the aspects mentioned may each be combined with any other features and embodiments of the other features and embodiments of the aspects mentioned. These and other embodiments will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] The compact ultrasonic flow meter according to the present invention will now be described in more detail with reference to the accompanying drawings. These drawings illustrate one way of implementing the invention and should not be construed as limiting other possible embodiments that fall within the scope of the appended claims.

[0067] Figure 1 shows a block diagram of a system embodiment,

[0068] Figure 2 a block diagram showing selected portions of an embodiment of a sensor device, and

[0069] Figure 3 The steps of a method embodiment are shown. DETAILED DESCRIPTION

[0070] Figure 1 A block diagram of an embodiment of a system with a plurality of sensor devices in the form of consumption meters M_A, M_B, M_N is shown, each sensor device having a processor system P with an internal clock, a wireless LTE modem connected to the processor system P, and a sensor system S with one or more sensors configured to measure a physical parameter related to a predetermined function F.

[0071] A backend system with a control system CS can send wireless signals to each consumption meter M_A, M_B, and M_N via the LTE network. A user can select a future time T, i.e., an activation time. Preferably, the consumption meters M_A, M_B, and M_N perform time-synchronized measurements at that time. In response, the control system CS sends a wireless signal to each consumption meter M_A, M_B, and M_N via the LTE network. The wireless signal includes data indicating the activation time in the form of an absolute time A_T and a specific LTE frame number FN. Alternatively, the activation time may include only the absolute time A_T or only the specific LTE frame number FN.

[0072] Optionally, the wireless signal sent to the consumption meter M_A, M_B, M_N may include data indicating an action to be performed, for example a measurement to be performed or a type of measurement.

[0073] In response to the received activation times A_T and FN, the consumption meters M_A, M_B, and M_N perform synchronization actions, including reading the current frame number from the LTE modem MD. This allows the consumption meters M_A, M_B, and M_N to synchronize with the LTE network timing and, in conjunction with their internal clocks C, prepare to perform the intended actions precisely at the activation times A_T and FN.

[0074] If the activation time A_T, FN is sent to the consumption meters M_A, M_B, M_N one or more days in advance, the consumption meters M_A, M_B, M_N have time to remain in sleep mode until a few minutes, or even seconds, before the activation time, thereby saving power. In particular, it may be preferable to perform time synchronization involving reading the current LTE frame number shortly before the specified activation time, for example, when an internal timer is involved, in order to reduce the effects of timer inaccuracies and save battery power.

[0075] Time synchronization in the individual consumption meters M_A, M_B, M_N can be performed in various ways, all involving a time-synchronized LTE frame number that can be read by the LTE modem MD. In particular, the processor system P can start a timer at the time the current LTE frame number is read from the LTE modem MD.

[0076] By using LTE frame numbers for time synchronization, the activation time of measurements in consumption meters M_A, M_B, and M_N can be precisely determined. This may be important for metering purposes, but it is even more significant for measurements other than metering. For example, if consumption meters M_A, M_B, and M_N distributed across a certain area of ​​a power distribution network can be operated to perform measurements simultaneously, various events in the distribution network can be detected. This can be used, for example, for acoustic leak detection in fluid distribution networks (such as water distribution networks), locating leaks in pipelines by simultaneously measuring noise and knowing the location of the consumption meters.

[0077] A specific embodiment of a sensor device may be a dedicated acoustic leak detector having one or more sensors dedicated solely to measuring acoustic signals for leak detection purposes (i.e., detecting noise or vibration in the frequency range of 100-2,000 Hz). Such dedicated acoustic leak detection devices can be distributed at strategic locations in a fluid distribution network to facilitate rapid leak location.

[0078] Time synchronization achieved using LTE frame numbers can allow a group of consumption meters M_A, M_B, M_N to perform various measurement applications that are not possible without the insufficient time accuracy provided by a typical internal clock C. For example, the electrical phase in an electricity meter can be measured.

[0079] It should be understood that time-synchronized (e.g., simultaneous) actions to be performed by the consumption meters M_A, M_B, M_N can be achieved by various means of sending activation times to the meters. For example, this can include sending a relative time, such as a date and time, and wherein the consumption meters M_A, M_B, M_N are programmed to perform the action at a specific time relative to the received relative time.

[0080] Furthermore, the consumption meters M_A, M_B, M_N may receive an activation time in the form of an absolute time, and then the consumption meters M_A, M_B, M_N are programmed to initiate an action at a specific LTE frame number.

[0081] In summary, there are various ways to implement time-synchronized (eg simultaneous) actions based on the time synchronization of each individual consumption meter M_A, M_B, M_N with the current LTE frame number via its own LTE modem MD.

[0082] Figure 2 A block diagram of selected parts of an embodiment of a sensor device is shown. In this embodiment, a processor system shown in a dashed box comprises a processor P, at least one sensor SN, an internal clock CLK and an internal timer TM.

[0083] Processor P is connected to LTE modem MD via an interface. One way to implement LTE frame number synchronization is to program processor P to issue a signal on an electrical pin GPIO of LTE modem MD and, in response, receive data indicating the current LTE frame number CFN. This may require the interface of LTE modem MD to be prepared for this purpose. Simultaneously with issuing the signal on electrical pin GPIO, processor P starts timer TM. Using the state of timer TM and the current LTE frame number CFN at the time timer TM is started, processor P can provide precise timing synchronized with the LTE frame number, affected only by the inaccuracy of timer TM. For short time periods, this effect is negligible. Therefore, this type of time synchronization can achieve high-precision timing down to the length of one LTE frame or LTE subframe, if desired. Consequently, time synchronization of individual sensor devices within 1-10 ms, or even better than 1 ms, or even better than 10 μs, can be achieved.

[0084] In particular, the processor P may be configured to calculate, based on the received activation time and based on the current LTE frame number CFN, in which state of the timer TM a predetermined action is to be initiated, such as performing a measurement with the sensor SN.

[0085] For example, if the sensor device receives an activation time in the form of an absolute time in the future and a specific LTE frame number, the processor P can use its internal clock CLK to calculate the time to switch from the sleep operating mode to the normal operating mode, that is, the time to "wake up" well before the activation time, taking into account the possible inaccuracy of the clock CLK. When in the normal operating mode, the timer TM can be used for the above-mentioned time synchronization, and based on the state of the timer TM calculated for the execution of an action, the action can be initiated.

[0086] A message including the following data may also be preferably sent via the LTE network: the current LTE frame number CFN read from the LTE modem MD and the absolute time simultaneously read from the clock CLK. In response, the sensor device may receive an adjustment time to adjust the clock CLK to a more accurate absolute time.

[0087] Figure 3 Steps of an embodiment of a method are shown, namely, a method for time synchronization of multiple sensor devices (such as consumption meters). The method includes transmitting a T_AT wireless signal over an LTE network. The wireless signal includes data indicating an activation time, the activation time including data indicating an absolute time and, preferably, a specific LTE frame number. Furthermore, the wireless signal R_AT over the LTE network is received by multiple sensor devices (e.g., consumption meters distributed at various customer locations in a utility network).

[0088] Furthermore, the plurality of sensor devices cooperate with the LTE modems in the respective sensor devices to synchronize time to the current LTE frame number. This is preferably accomplished by issuing a signal SG_EP_MD to an electrical pin on the LTE modem, simultaneously starting a timer ST_TM, and reading the current LTE frame number R_A_FN corresponding to the current LTE frame number from the LTE modem. Preferably, the elapsed time (in μs) indicating the current LTE subframe is also read from the LTE modem.

[0089] Finally, each sensor device initiates an I_A predetermined action, such as performing a measurement involving reading the sensor system output, synchronously with the activation time. In particular, this may involve the aforementioned step of calculating the state of the timer C_T_AT corresponding to the activation time based on the received current LTE frame number, so as to accurately synchronize with the activation time with LTE frame timing accuracy, thereby simultaneously initiating the execution of the predetermined action by multiple sensor devices.

[0090] Further, the method may involve each sensor device transmitting data indicative of one or more measurement values ​​via the LTE network or by other means.

[0091] Furthermore, the method may include transmitting, by at least one sensor device, a wireless signal over the LTE network, the wireless signal including data indicating a current LTE frame number read from an LTE modem in the at least one sensor device and a corresponding absolute time read from a clock in the at least one sensor device. Thus, the backend system may determine a relationship between the absolute time in the sensor device and the LTE frame number. This may be used to generate an activation time comprising the absolute time and a specific LTE frame number, and transmit the activation time to the plurality of sensor devices via the wireless signal over the LTE network.

[0092] In summary, the present invention provides a sensor device, such as a consumption meter, having an LTE modem, a processor system connected to the LTE modem, and a sensor system comprising at least one sensor configured to sense a physical parameter and generate an output to the processor system accordingly. The sensor device is configured to receive an activation time via an LTE network, wherein the activation time includes an absolute time and / or an indication of a specific LTE frame number. The processor system is configured to cooperate with the LTE modem to synchronize time to the current LTE frame number. This can be achieved, in particular, by the processor system signaling the LTE modem on an electrical pin, in response to which the LTE modem outputs the current LTE frame number, and simultaneously with the signaling on the electrical pin, the processor system starts a timer. Thus, by starting the timer at a known LTE frame number, the sensor device can accurately calculate the time to initiate a predetermined action in time synchronization with the absolute time indicated in the received activation time and the specific LTE frame number. The action can involve performing a measurement using sensors in the sensor device in time synchronization with the received activation time. This provides highly accurate time synchronization for a group of sensor devices, allowing the group of sensor devices to perform measurements simultaneously. This enables group measurements that are not possible with the time precision of the internal clocks of a group of sensor devices, and such time synchronization can be very important for certain applications, such as acoustic leak detection in utility networks.

[0093] Although the present invention has been described in conjunction with specified embodiments, it should not be interpreted as being limited in any way to the examples given. The scope of the invention is set out by the appended claims. In the context of the claims, the term "comprises or comprises" does not exclude other possible elements or steps. Furthermore, references such as "one" or "an" should not be interpreted as excluding a plurality. The reference numerals used in the claims with respect to the elements indicated in the figures should also not be interpreted as limiting the scope of the invention. Furthermore, the individual features mentioned in different claims may be advantageously combined, and the mention of these features in different claims does not exclude that a combination of features is possible and advantageous.

Claims

1. A sensor device (M_A, M_B, M_N), comprising: an LTE modem (MD), the LTE modem being configured to receive and transmit wireless signals on an LTE network, a processor system (P, CLK, TM) connected to an interface of the LTE modem (MD), wherein the processor system (P, CLK, TM) comprises a clock (C, CLK) configured to provide an absolute time output, and wherein the processor system (P, CLK, TM) further comprises a timer (TM), and a sensor system (S, SN) comprising at least one sensor (SN) configured to sense a physical parameter and to generate an output accordingly to the processor system (P, CLK, TM), It is characterized in that the sensor device (M_A, M_B, M_N) is configured as follows: - receiving a wireless signal on the LTE network, the wireless signal comprising data indicating an activation time (A_T, FN), the activation time comprising at least data indicating an absolute (A_T) time or a relative time, - cooperate with the LTE modem (MD) to time synchronize to the Current LTE Frame Number (CFN), and - Initiating a predetermined action involving the sensor system (S, SN), such as initiating a measurement or reading an output from the sensor system (S, SN), synchronously with the absolute time (A_T) or the relative time and synchronously with a specific LTE frame number (FN), wherein the specific LTE frame number (FN) is received in the data indicating the activation time (A_T, FN) or is stored in the sensor device.

2. The sensor device according to claim 1, wherein The data indicating the activation time (A_T, FN) includes data indicating both: 1) an absolute time (A_T) and 2) a specific LTE frame number (FN).

3. The sensor device according to claim 1 or 2, wherein: The processor system (P, CLK, TM) is configured to issue a signal on an electrical pin (GPIO) of the LTE modem (MD) and in response receive data indicative of a current LTE frame number (CFN).

4. The sensor device according to claim 3, wherein The processor system (P, CLK, TM) is configured to start the timer (TM) in synchronization with issuing a signal on the electrical pin (GPIO) of the LTE modem (MD), such as simultaneously.

5. The sensor device according to claim 3 or 4, wherein: The processor system is configured to calculate in which timer state to initiate the predetermined action based on the specific LTE frame number and data received from the LTE modem indicating the current LTE frame number.

6. Sensor device according to any one of the preceding claims, wherein The wireless signal received over the LTE network includes data indicative of both the particular LTE frame number and a particular absolute time, such as a particular absolute future time, such as a particular absolute future time including data indicative of a future date and a time of the future date.

7. Sensor device according to any one of the preceding claims, wherein The processor system is configured to utilize the clock to determine a date and an approximate time of day on which the predetermined action is to be initiated.

8. Sensor device according to any one of the preceding claims, wherein The sensor device is configured to enter a sleep operating mode and enter a normal operating mode in response to an absolute time output from the clock reaching a predetermined time, and wherein the processor system is configured to determine the time to enter the normal operating mode before a time defined by the activation time.

9. The sensor device according to any one of the preceding claims, wherein The processor system is configured to read a current LTE frame number from the LTE modem by issuing a signal on an electrical pin (GPIO) of the LTE modem, and wherein the processor system is further configured to calculate time and wait until the current LTE frame number equals a predetermined LTE frame number.

10. The sensor device according to any one of the preceding claims, wherein The predetermined action involves initiating at least one measurement of a physical parameter using at least one sensor of the sensor system, and wherein the sensor device is configured to transmit data indicative of at least one measurement value in a wireless signal over the LTE network.

11. The sensor device according to claim 10, wherein The at least one sensor is arranged to measure at least one of: fluid flow, temperature, fluid pressure, magnetic field strength, electrical impedance, voltage or current, turbidity measurement, and an acoustic signal.

12. The sensor device according to any one of the preceding claims, wherein The processor system is configured to receive data in a wireless signal on the LTE network indicating which type of action to initiate.

13. The sensor device according to any one of the preceding claims, wherein The sensor device is a consumption meter, such as a water meter, a gas meter, a heat meter, a cooling meter, and an electricity meter, configured to measure consumption of a utility and in response transmit a wireless signal including data indicative of the measured consumption over the LTE network.

14. A system comprising: - a plurality of sensor devices (M_A, M_B, M_N) according to any one of claims 1 to 13, and a backend system (CS) configured to transmit a wireless signal to a plurality of sensor devices (M_A, M_B, M_N) over an LTE network, the wireless signal comprising data indicating an activation time (A_T, FN), such as an activation time comprising data indicating an absolute time (A_T) and a specific LTE frame number (FN).

15. A method for time synchronization of a plurality of sensor devices such as consumption meters, the method comprising: - sending a (T_AT) wireless signal over the LTE network, the wireless signal comprising data indicating an activation time, the activation time comprising data indicating at least an absolute time or a relative time, such as comprising data indicating a specific LTE frame number and an absolute time, - receiving (R_AT) wireless signals on the LTE network by a plurality of sensor devices, - Each sensor device cooperates with the LTE modem to time synchronize to the current LTE frame number (SG_EP_MD, ST_TM, R_A_FN), and - initiating (I_A) a predetermined action by each of the sensor devices, such as performing a measurement involving reading the output of the sensor system, in synchronization with the absolute time or relative time and with a specific LTE frame number, wherein the specific LTE frame number is received in the data indicating the activation time or is stored in the sensor device.

16. The method of claim 15 , comprising receiving data indicative of: 1) a current LTE frame number and 2) an absolute time associated with the current LTE frame number from at least one sensor device, so as to allow estimation of timing between the LTE frame number and the absolute time in the sensor device, and generating data indicative of the activation time based on the received data.

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