Method and associated equipment for synchronizing a wireless data transmission system

Abstract

The invention relates to an equipment (1) of a data remote transmission system in accordance with a wireless communication standard, comprising a processing unit (50) coupled to a radio front-end unit (20) which ensures two-way radio frequency communication with a remote equipment, the radio front-end unit comprising an analog block (30) and a digital block (40) which exchange digital samples of waveforms. The processing unit (50) comprises a synchronization module (52) configured to trigger the exchange with the remote equipment of synchronization pulses chosen from messages of the wireless communication standard. The digital block (40) comprises an identification module (43) configured to detect and date the synchronization pulses exchanged with the remote equipment. Figure for abstract: Figure 1

Description

Title of the invention: Method and associated equipment for synchronizing a wireless data transmission system Technical field

[0001] The field of the invention is that of the wireless remote transmission of data between slave equipment and a master equipment. The invention relates more particularly to the synchronization of the different slave equipment on a reference time base of the master equipment. The invention finds particular application with the instrumentation of industrial tests, for example in the field of transport, maritime or aerospace (flight tests). Prior art

[0002] Previously, industrial testing instrumentation was mainly carried out by connecting sensors to data conditioning and acquisition systems using conductive cables. Today, we are seeking to eliminate these cables, which are long and difficult to install, require structural modifications (drilling), and are intrusive, heavy, and ultimately expensive.

[0003] Instrumentation is therefore increasingly turning towards wireless instrumentation networks. To create small and inexpensive systems, it is possible to use wireless communication standards widely used by the general public, designed for local networks or loTs (Internet of Things), such as Wi-Fi™, Bluetooth™, ZigBee™ or Impulse Radio Ultra Wide Band (IR-UWB). These standards specify waveforms on the air interface (radiofrequency signal transmitted or received) and shaping protocols to transport useful data. It is also possible to use cellular telephone technology (3G, 4G or 5G) or a long-distance proprietary network (LoRaWan® or SigFox for example).

[0004] Operating such a wireless instrumentation network requires synchronizing all the different terminations (slave devices) that acquire data collected by sensors. Indeed, each acquisition must be dated ("time-stamped" in English) so as to be able to reconstruct a global history of the acquisitions and reveal the correlation links between the different physical phenomena observed by a plurality of sensors. Most of the standards mentioned above synchronize the terminations by broadcasting a message containing the date of a master device (base station or access point). The slave devices then set their clocks to the received date. Given the variation in the flight time (propagation time) of the message and uncertainties in processing time, this technique does not allow synchronization of slave endpoints with a precision better than several tens of microseconds, or even much more in the case of Wi-Fi™ for example.

[0005] This synchronization precision proves insufficient for certain instrumentation systems which may require synchronizations of less than 100 nanoseconds. This is the case, for example, of systems which carry out modal analysis of large-scale deformations of a ship or an aircraft, up to 20 or 30 kHz.

[0006] One of the aforementioned communication standards allows for finer synchronization. This is the Ultra Wide Band Radio Pulse (IR-UWB) which uses very short pulses and a wide frequency spectrum and is thus capable of very precise localization in enclosed spaces by precisely measuring the flight times of the communication with the endpoints. However, IR-UWB in its current commercial implementation suffers from a power restriction and is therefore not used for high-speed data transmission, its performance being typically much lower than 10 Mbps.

[0007] To overcome this restriction, a solution described in the article “Hybridization of wireless technologies for the aerospace instrumentation”, International Telemetering Conference Proceedings, Volume 55 (2019) consists of a hybridization of IR-UWB with another high-speed wireless communication standard, in particular Wi-Fi.

[0008] But this solution suffers from other constraints. First of all, it is very dependent on suppliers of components for general use which are different for the two technologies, which requires a new design almost every year whereas the life cycle of users in the particular application of industrial instrumentation is typically fifteen to twenty years. Then, hybridization requires coupling several signals and usage bands, which imposes constraints on the equipment (duplication of electronic chains, increased consumption) and the antennas (multiplexing of spectral bands). Finally, this solution does not allow to exploit all the interconnection topologies of equipment using heterogeneous bandwidths or which may require partitioning the system into several subnets, because it is also limited by the functions offered by Wi-Fi.

[0009] The heterogeneity of needs (number of nodes, flow rate, range, consumption, dissipation, topology, etc.) and associated regulatory constraints (in particular frequency bands and transmission powers) require the provision of a generic solution compatible with all wireless communication protocols. Statement of the invention

[0010] The invention aims to meet this need by proposing a generic solution which provides a fine synchronization capacity to any wireless communication protocol, even if it is not designed for this.

[0011] To this end, it proposes equipment for a data remote transmission system in accordance with a wireless communication standard, comprising a processing unit coupled to a radio front-end unit which provides two-way radio frequency communication with a remote device. The radio front-end unit comprises an analog block and a digital block which exchange digital samples of waveforms. The processing unit comprises a synchronization module configured to trigger the exchange with the remote device of synchronization pulses chosen from messages of the wireless communication standard. The digital block comprises an identification module configured to detect and date the synchronization pulses exchanged with the remote device.

[0012] The invention thus provides a solution which is independent of wireless communication protocols and which is capable of guaranteeing high-performance synchronization (typically with a sub-microsecond time difference, for example less than 100ns) at any remote point of a wireless network, for example instrumentation. In such a way, depending on the need, whether to obtain very high-speed transmissions, interconnect remote equipment with a minimum of topology constraints or be very resistant to interference or propagation environments with multi-paths, the selection of the protocol used can be made on this communication criterion alone without worrying about the synchronization performance.

[0013] Some preferred but non-limiting aspects of this equipment are as follows: - to detect synchronization ticks, the identification module is configured to perform a correlation of the messages exchanged with the remote equipment with a known profile of the messages of the wireless communication standard chosen for synchronization ticks; - the digital block includes a chronometer operating in a local time base and the identification module uses the chronometer in order to associate a chronological date with each of the detected synchronization ticks; - it comprises a clock signal generator and the timer is incremented by the clock signal, by a multiple or sub-multiple of the clock signal or by a signal synchronized to the clock signal; - the identification module is configured to make available to the synchronization module the chronological dates of the detected synchronization tops; - the synchronization module is configured to translate chronological dates into calendar dates; - it operates as a slave device of the remote device and the synchronization module is configured to determine a time resetting instruction; - the synchronization module is configured to determine the time resetting instruction by measuring the cumulative outward flight time and the return flight time of synchronization pulses exchanged with the remote equipment; - the synchronization module is further configured to estimate a drift of a calendar time base by deriving successive time recalibration instructions; - the synchronization module is further configured to determine a clock signal recalibration instruction; - the processing unit includes a module for acquiring and formatting data from a sensor; - it operates as master equipment of the remote equipment and the synchronization module is further configured to determine calendar dates from local chronological dates corresponding to the dates of transmission and reception of synchronization ticks detected and dated by the identification module and, on the other hand, to generate and transmit to the transceiver useful data comprising the values ​​of said calendar dates to be transmitted in signaling messages. Brief description of the drawings

[0014] Other aspects, aims, advantages and characteristics of the invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example, and made with reference to the appended drawings in which:

[0015] [Fig-1] is a diagram of equipment according to a possible embodiment of the invention;

[0016] [Fig.2] is a diagram illustrating an example of message exchange of synchronization between a master device (left dotted arrow) and a slave device (right dotted arrow).

[0017] DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

[0018] The invention relates to a data transmission system comprising a master device and a plurality of slave devices, each slave device being in bidirectional wireless communication with the master device. The bidirectional wireless communication takes place in accordance with a wireless communication standard, for example WiFi, LTE, Bluetooth or UWB.

[0019] All the devices (master and slaves) all have a local time base. These devices are functionally identical, the only difference being that the time base of the master device, which may or may not be synchronized on a universal time base (satellite positioning system, coordinated universal time, etc.) or an ultra-stable time base (atomic clock), constitutes by definition the reference time base of the teletransmission system on which the slave devices are synchronized.

[0020] With reference to [Fig.l], the invention thus proposes a piece of equipment 1 which can act as master or slave depending on whether its local time base is controlled in accordance with the mechanism presented below. This piece of equipment 1 is in bidirectional radiofrequency communication on the air interface with a remote piece of equipment, this remote piece of equipment being the master piece of equipment if the piece of equipment 1 is a slave piece of equipment or, on the contrary, a slave piece of equipment if the piece of equipment 1 is the master piece of equipment.

[0021] The equipment 1 comprises a local clock signal generator 10 which clocks the digital processing, a radio front-end unit 20 coupled, on the one hand, to an antenna 2 to ensure bidirectional radiofrequency communication on the air interface with the remote equipment and, on the other hand, to a processing unit 50 configured to process the digital samples of the waveforms exchanged according to the wireless communication standard implemented. At the other end, the teletransmitted useful data are exchanged by the processing unit 50 with one or more applications 3 which may be external to the equipment.

[0022] The local clock generator 10 contains an oscillator which provides a periodic signal of good stability alternating between the high and low logic levels, called the clock signal CLK. The clock signal CLK sets the clock for all the operations of the radio front-end unit 20 because it controls the conversions. The clock signal CLK or a derived synchronous clock signal CLK', a multiple or sub-multiple of CLK, also sets the clock for the calculations of the processing unit 50. The local clock generator 10 may have an adjustment control ("tune" in English) which makes it possible to tune its timing over a small relative frequency range, for example in voltage for a voltage-controlled quartz oscillator (VCXO for "Voltage Controlled Xtal Oscillator").

[0023] The radio front-end unit 20 has the function, in transmission, of transforming the samples representing the waveform to be transmitted into a radiofrequency signal transmitted by the antenna 2 and, in reception, of transforming the received radiofrequency signal into samples representing the waveform to be processed. It comprises an analog block 30 and a digital block 40 which exchange digital samples of waveforms. For the reception of a signal, the analog block 30 comprises an input radiofrequency circuit 33 conventionally responsible for filtering and amplifying the radiofrequency signal incident on the antenna 2 as well as transforming it into an intermediate frequency signal. The analog block 30 also comprises an analog-to-digital converter (ADC for "Analog to Digital Converter") 34 which samples the intermediate frequency signal to provide a digital signal to the digital block 40.Within the digital block 40, the digital signal then passes through a digital down converter 45 (DDC for “Digital Down Converter”) and through a decimation filter 46 which convert the signal either into baseband or onto a digital carrier.

[0024] This sampled signal is supplied to the processing unit 50 (i.e., a digital signal processor) which comprises a transceiver 51 (in English “transceiver” which is the contraction of “transmitter and receiver”) here responsible, among other things, for demodulating and decoding the signal supplied by the digital block 40.

[0025] The reception of a signal by the equipment 1 has been described above. The transmission of a signal by the equipment 1 is carried out according to an inverse process. The transceiver 51 in this case, among other things, codes and modulates the signal in baseband or on a digital carrier, a sampled signal which is then passed to the digital block 40. In the digital block, this signal passes through an interpolation filter 48 and through a digital up-converter 47 (DUC for "Digital Up Converter") which convert it into an intermediate frequency signal. The intermediate frequency signal is supplied to a digital-to-analog converter (DAC for "Digital to Analog Converter") 33 of the analog block 30 then to an output radiofrequency circuit 31 which transforms it into a radiofrequency signal transmitted by the antenna 2.

[0026] The analog block 30 uses the clock signal CLK to clock the conversion operations carried out by the analog-to-digital converter 34 and the digital-to-analog converter 33.

[0027] The digital block 40 is a unit which processes the sampled signal at the fast rate CLK of the samples of the converters 33 and 34. It can typically be implemented in a field programmable gate array (FPGA) or in an integrated circuit dedicated to the conversion functions. Its interface with the processing unit 50 exchanges samples at a lower rate, typically a submultiple of the CLK / n clock signal with n being an integer. Also, the decimation filter 46 has the role of filtering the bandwidth by avoiding spectrum aliasing and of providing only one sample out of n at the output. Conversely, the interpolation filter 48 has the role of increasing the rate of the samples by providing n samples per sample at the input while filtering the spectrum images created by this oversampling.

[0028] Some radio front-end units 20 do not contain all the elements listed above. So-called direct sampling units thus sample the radio frequency without passing through an intermediate frequency. There are then no longer converters 33 and 34. When the processing unit 50 manipulates the samples directly at the rate of CLK of the analog block 30 (n=1), the filters 46 and 48 become simple shaping filters of the finite impulse response (FIR) type which can possibly be incorporated into the processing unit 50.

[0029] The processing unit 50 can be implemented in a system on chip (SoC for "System On Chip"), in an application specific integrated circuit (ASIC for "Application Specific Integrated Circuit"), in a field programmable gate array (FPGA for "Field Programmable Gate Array") or on a processor unit such as a central processing unit (CPU for "Central Processing Unit") of a computer. Typically, the processing unit 50 has a calculation unit with a processor on which it is possible to execute the instructions of a code and to program algorithms. The processing unit 50 comprises at least the transceiver 51 and a synchronization module 52.

[0030] The receiving function of the transceiver 51 receives the samples of the received waveform from the radio front-end unit 20 and provides the received useful data. The transmitting function of the transceiver 51 receives the useful data to be transmitted and provides the samples of the waveform to be transmitted by the radio front-end unit. To do this, the transceiver 51 executes in particular algorithms for (de)coding and (de)modulation, as well as for synchronizing the symbol rate and the carrier frequency, making it possible firstly, in reception, to interpret the received waveform into a transmitted useful data message and then, in transmission, to transform a useful data message to be transmitted into a transmitted waveform, all this strictly according to the implemented wireless communication standard. The standard may not include any time base synchronization mechanism.This is particularly the case if it does not provide any signaling message allowing any date information to be sent to the counterpart. Advantageously, the transceiver 51 can be software operating on a fully programmable processing architecture on FPGA, CPU or SoC and is then referred to as “radio- . software". This can then be freeware and there is no need to develop it. In general, a "transceiver" supplied off the shelf, whether it is a pure software radio or incorporates hardware elements, does not integrate a mechanism for precise timestamping of the instants of transmission or reception of messages or frames from the standard on the air interface.

[0031] The processing unit 50 can also host other functions, such as an embedded application module processing the useful data transmitted or received 53. This architecture is preferable to that of an external application 3 because it is more economical and compact. It can be a module for acquiring and formatting data from a sensor, for example in an industrial test instrumentation application or the Internet of Things (IoT). The acquisition of this data can include an analog conversion clocked by the local clock signal CLK or a submultiple thereof. Several useful data processing applications can be hosted by the processing unit 50, others can be external to the processing unit 50.

[0032] According to the invention, the digital block 40 comprises a chronometer or “timer” 42 operating in a local time base which regulates the exchange of digital samples with the analog block 30.

[0033] The local time base may be derived from a local clock, for example the clock signal CLK timing the conversion of the converters 33, 34. In particular, the chronometer 42 may be a binary counter of a certain depth M which is incremented by the clock signal CLK at the rising or falling edge thereof, otherwise by a multiple or a sub-multiple of the clock signal CLK or by a signal synchronized thereto. This counter may have a depth M which is a power of two (M = 2P) or be reset to zero after a number M of clock periods designed so that its cycle has a duration congruent with the millisecond or the second.

[0034] In a preferred embodiment, the chronometer 42 operates at the rate of the digital samples exchanged between the digital block 40 and the analog block 30 of the radio front unit 20, namely CLK. In another embodiment, the chronometer operates at the rate of the signal which is a sub-multiple of the local clock CLK / n which sets the pace for the samples exchanged between the radio front unit 20 and the processing unit 50.

[0035] In the first case, dating consists of associating an order number with the samples exchanged between the analog block 30 and the digital block 40. In the second case, the dating then associates an order number with one sample out of n exchanged between the analog block 30 and the digital block 40. The dating therefore operates on the lowest layers of the communication system, thus guaranteeing a deterministic and fixed transit time to the radio medium and a dating free of variability effects due to higher-level protocol layers. The associated date is a sequence number at the rate of chronometer 42 with a cyclic sequence of depth 2P, this cyclic date will thus be called a chronological date.

[0036] The digital block 40 further comprises an identification module 43 for specific messages exchanged with the remote equipment, in particular messages defined by the wireless communication standard which, in the context of the invention, are used to constitute receiver synchronization pulses. By receiver synchronization pulse, we mean here a message transmitted recurrently by the communication standard for the purpose of recovery by the receiver of the symbol rhythm and the carrier frequency of the transmitter, in the master-slave direction or in the slave-master direction, this message containing a known profile which is easily identifiable.Thanks to its identification module 43, the digital block 40 can detect and date the synchronization pulses (on transmission and / or reception) and make available to a synchronization module 52 of the processing unit 50 information P bearing the detection of a synchronization pulse of the receiver and information D of chronological date corresponding here to the instant of reception and / or transmission of the detected synchronization pulse.

[0037] To detect the synchronization ticks, the identification module 43 can be configured to carry out a correlation of the messages exchanged with the remote equipment, on transmission and / or reception, with a known profile of the messages constituting the synchronization ticks.

[0038] The known profiles which are unique words, preambles, training sequences or dedicated frames, can be programmed residently in the identification module 43 or be loaded there upon initialization by the processing unit 50. For example, if the WiFi standard is used, then the identification module 43 can advantageously be configured to identify the PLCP preamble (“Physical Layer Convergence Procedure”) which is placed at the beginning of each frame transmitted on the air interface. In a preferred embodiment, the identification module 43 calculates the correlation of the known profile with the message transmitted or received at the rate of the CLK samples between the filters 46 and 48 and the converters 45 and 47. In another embodiment, the correlation is carried out on the samples exchanged with the processing unit 50 and in particular with the transceiver 51, therefore at the rate of CLK / n.The preferred implementation has n times finer time resolution but requires n times more operations. The identification module 43 selects the relevant correlation peaks according to an algorithm that can have many variations. In general, it searches for the highest peak over a certain sliding window in which there cannot be two known profiles and keeps only those above a predefined correlation ratio with the signal energy. For a selected peak, it provides . then to the processing unit 50 and in particular to the synchronization module 52 the chronological date on which the correlation ended. Some correlators are capable of interpolating the correlation curve between the samples and can therefore provide a slightly more precise fractional date of the peak.

[0039] The synchronization module 52 can be configured to translate the chronological dates into calendar dates defined in days, hours, minutes, seconds and fractions of a second. For this, the synchronization module 52 has a "reset" date, that is to say the calendar date which was effective at the instant of the last passage to 0 of the chronometer 42, noted T0, which takes place every M cycles of the clock CLK which it uses. In this case, the calendar date at the instant q of the chronometer 42 is equal to To+qT with T the period of the clock signal CLK. By taking q=M, the update of the next reset date can be determined in advance. There are several techniques for resetting the calendar date. In a preferred embodiment, the synchronization module is configured so that the reset date To can take any value with a resolution of T.In an alternative embodiment, the resolution of the reset date is only MT, the cycle of the chronometer, which can be congruent to the millisecond or to the second to simplify the calculation of calendar dates. In this case, the calendar reset date is accompanied by a chronological reset date which can be worth from 1 to M and sets the chronometer 42 to zero before it reaches M. Resetting the time here therefore involves a simultaneous reset of the calendar date and the chronometer.

[0040] When the equipment 1 operates as slave equipment, the reset date takes into account a CRT time resetting instruction of the calendar time base and / or the chronological time base with respect to the reference time base of the master equipment. This CRT time resetting instruction can be determined by the synchronization module 52 by means of the joint exploitation of local chronological dates and calendar dates extracted from the useful data of signaling messages received from the transceiver 51. The local chronological dates correspond to the correlation peaks of the remarkable profiles at the transmission or reception of the synchronization pulses and are provided by the identification module 43.

[0041] The determination of the CRT time resetting instruction can be carried out according to a mechanism, based on a bidirectional exchange and a time of flight measurement, which is similar to the PTP protocol (“Precision Time Protocol”, IEEE1588). The synchronization module 52 of the equipment, master or slave, regularly and repeatedly triggers the sending by the transceiver 51 of synchronization ticks and signaling messages by providing it with useful data to be transmitted. These messages are chosen from the range proposed by the protocol of the standard implemented by the transceiver 51 and may have been designed, among other things, to perform a face-to-face receiver synchronization function. There is therefore no need to adapt the transceiver algorithm incorporated in the processing unit 50 to implement the invention.

[0042] As shown in [Fig.2], the synchronization comprises the sending, by the master equipment, of a first synchronization pulse “Sync” containing a known profile of the communication standard used, such as a unique word, a preamble or a synchronization frame of the forward direction. On transmission, the identification module 43 of the master equipment determines the instant of the correlation peak which dates the end of the passage of the unique word or of the synchronization frame in the digital block of the radio front end. The synchronization module of the master equipment transforms this chronological date into a calendar date of transmission noted T1, which is by definition in the reference time base. On reception by the digital block of the slave equipment, the latter identifies the synchronization pulse “Sync” and dates the end of the passage of the unique word in the digital block of the radio front end by means of its identification module 43.Its chronological date of reception is transformed by the synchronization module of the slave equipment into a local calendar date of reception noted T2.

[0043] The master equipment then transmits a signaling message, in this case a “Follow-Up(Tl)” message containing the exact calendar date Tl of transmission of the first synchronization pulse. The transceiver 51 of the slave equipment extracts the useful data from the “Follow-Up” message and the value of Tl is recovered by the synchronization module of the slave equipment.

[0044] In the other direction, the slave equipment then transmits a second “Delay-Req” synchronization tick containing a profile known to the communication standard as a unique word, a preamble or a synchronization frame for the return direction. When this tick is transmitted, the identification module 43 of the slave equipment determines the instant of the correlation peak which dates the end of the passage of the unique word or the synchronization frame in the digital block of the radio front end. The synchronization module of the slave equipment transforms this chronological date into a local calendar date of transmission noted T3. When the master equipment receives the second “Delay-Req” synchronization tick, the latter identifies the correlation peak and dates the end of the passage of the unique word in the digital block of the radio front end of the master equipment, by means of its identification module 43.Its chronological date of receipt is transformed by the synchronization module into a calendar date of receipt noted T4 in the reference time base.

[0045] The master equipment then transmits a second signaling message, in this case a delay response message “Delay-Resp(T4)” containing the date exact calendar of reception T4 of the second synchronization top “Delay-Req”. The transceiver 51 of the slave equipment extracts the useful data from the delay response message “Delay-Resp” and the value of T4 is recovered by its synchronization module 52.

[0046] The synchronization module 52 of the slave equipment now has all the elements to carry out the recalibration of the local time base on the reference time base of the master equipment. As explained below, to determine the recalibration instruction of the calendar time base of the slave equipment, the synchronization module 52 measures the cumulative outward flight time with the return flight time (i.e. T4-T3+T2-T1) of the synchronization ticks exchanged with the remote equipment.

[0047] T1 and T4 are expressed in the reference calendar time base while T2 and T3 are expressed in the local calendar time base of the slave equipment. Therefore T4-T1 and T3-T2 define time intervals of value independent of the time base assumed to be very stable and precise. We see in [Fig.2] that the difference of these two intervals corresponds to the outward flight time of the “Sync” top and to the return flight time of the “Delay-Req” top. In practice, the flight time varies slowly with the propagation channel and is therefore identical in both directions. We then deduce that this is worth TV = (T4-T3 + T2-Tl) / 2 and that the recalibration instruction to be carried out on the local calendar time base of the slave equipment is worth CRT = T1-T2 + TV = T4-T3-TV = (T4-T3-T2 + Tl) / 2, that is to say that CRT must be added to the local calendar time base of the slave equipment to synchronize it with the time base of the master equipment.When the local time base of the slave equipment is synchronized, we observe that (Tl+T4) / 2 = (T2+T3) / 2 therefore CRT=0.

[0048] There are several ways to apply CRT recalibration. The simplest is simply to add the CRT setpoint to the reset date To when this has a resolution of T. When the resolution is only MT, the cycle of the chronometer 42, this must also be reset to 0 from the value of CRT, modulo MT. If the period of the local clock signal T is considered as a fixed nominal value, then the relative frequency deviation of the local clock will cause a drift of the local time base. This is not necessarily a problem when the recalibrations are carried out frequently enough to be significantly less than the period T. If this is not the case or if it is desired to improve the accuracy, then this drift must be taken into account.To do this, the synchronization module can also be configured to estimate a drift in the calendar time base by deriving successive instructions for recalibrating the calendar time base. In doing so, it is then possible to simultaneously correct To and the value of the period T with the estimate of the drift. The value of the CRT recalibration divided by the time interval. elapsed since the application of the previous CRT recalibration constitutes an estimator of this recalibration. In other words, if we denote by CRT(k) the kth recalibration applied to the date Tk, T must be corrected by T[l+CRT(k) / (Tk-Tk_i)]. It should be noted that a clock recalibration alone without date recalibration is also possible, T must then be corrected by T[l+(CRT(k)-CRT(kl)) / (Tk-Tkl)].

[0049] In a possible embodiment, the synchronization module is further configured to determine a setpoint Tu for resetting the clock signal CLK. Certain useful data applications 53 in fact require clock synchronization so that the date resetting must therefore be accompanied by the resetting of the local clock CLK to make it synchronous with the reference clock. In this case, T is left at its nominal value and the drift estimate is filtered to correct the clock generator by means of its “tune” command. The synchronization module 52 generates this command Tu to the local clock generator 10 by incrementing it by a value proportional to the estimator CRT(k) / (Tk-Tk4), or to [CRT(k)-CRT(kl)] / (Tk-Tk_i) when it is desired to recalibrate the clock alone without recalibrating the date, the whole constituting a phase-locked loop (PLL for “Phased Locked Loop”).

[0050] There are many variants to the implementation of the synchronization module algorithms. In particular, the sequence of synchronization ticks and signaling messages described above corresponds to the implementation of PTP on Ethernet. A reversed message order is possible starting with the slave as well as a grouping of the signaling sending of the values ​​of T1 and T4, or a sending of T2 and T3 by the slave followed by a recalibration calculation by the master which would return the CRT instruction to the slave. The two-step dating by the cyclic chronometer then the establishment of the calendar correspondence can also be modified. For example, it is possible for the chronometer to calculate the seconds (MT is an integer number of seconds), or even the minutes and hours.Since the exchange of synchronization ticks and signaling messages takes place in a very small fraction of a second, the signaling messages could carry chronological dates T1 and T4, without calendar translation. Fine synchronization would therefore be done modulo MT (a few seconds or minutes) and the updating of the slave time and date, in the usual sense, would be left to an existing network protocol such as NTP (Network Time Protocol, over IP). One can also imagine a digital block directly generating calendar dates, but the implementation of a fast binary counter in hardware and a calendar in software remains simpler. Algorithms for estimating clock frequency drift can also be more complex and . incorporate filter functions to determine the corrected value of the period T or the “tune” command.

[0051] It is understood from the above that when the equipment 1 operates as master equipment of the remote equipment, its synchronization module is configured, on the one hand, to determine calendar dates from local chronological dates corresponding to the transmission and reception dates T1, T4 of the synchronization ticks “Sync”, “Delay-Req” detected and dated by the identification module of the master equipment and, on the other hand, to generate and transmit to the transceiver useful data comprising the values ​​of the calendar dates T1 and T4 to be transmitted in signaling messages “Follow-Up(T1)”, “Delay-Resp(T4).

[0052] According to a second aspect, the invention relates to a data remote transmission system comprising a master device as previously described and a plurality of slave devices as previously described.

[0053] According to a third aspect, the invention relates to a method implemented within equipment such as previously described, comprising the steps of identification and dating in a local time base, by means of the identification module of the digital block, of the synchronization ticks exchanged with the remote equipment.

[0054] When the equipment operates as slave equipment, these steps can be supplemented by a step of determination by the synchronization module of the processing unit, of an instruction for resetting the local time base with respect to a reference time base of the master equipment by jointly exploiting the dating of the synchronization ticks, carried out by the identification module of the digital block, and the useful data extracted from signaling messages by the transceiver.

[0055] According to a fourth aspect, the invention relates to a computer program product comprising instructions which, when the program is executed by a digital block of equipment as previously described, lead the latter to implement the identification and dating steps of the method according to the third aspect of the invention.

[0056] According to a fifth aspect, the invention relates to a computer program product comprising instructions which, when the program is executed by a data processing unit of a piece of equipment as previously described, lead the latter to implement the step of the method according to the fourth aspect of the invention of determining the instruction for resetting the local time base with respect to the reference time base of the master equipment.

[0057] The invention offers ultra-high-performance synchronization by implementing a synchronization mechanism in parallel and independently of the processing of the protocol contained in the implemented wireless communication standard. This synchronization mechanism is therefore operational for any wireless communication protocol that would be selected, even if it is not designed for fine synchronization. Its performance depends only on the synchronization ticks chosen from the standard's message panoply, according to the characteristics of the unique words, preambles, training sequences or synchronization frames. It can be as fine as a few tens of nanoseconds depending on the recurrence of the synchronization tick communications and the specific drift of the local time bases. The invention therefore makes it possible to communicate data with any wireless communication protocol while simultaneously achieving efficient synchronization.

Claims

Claims

1. Equipment (1) of a data remote transmission system comprising a processing unit (50) coupled to a radio front unit (20) which ensures two-way radio frequency communication with a remote equipment in accordance with a wireless communication standard, the radio front unit comprising an analog block (30) and a digital block (40) which exchange digital samples of waveforms, the equipment being characterized in that the processing unit (50) comprises a synchronization module (52) configured to trigger the exchange with the remote equipment of synchronization tops chosen from messages of the wireless communication standard, and in that the digital block (40) comprises an identification module (43) configured to detect (P) and date (D) the synchronization tops exchanged with the remote equipment.

2. Equipment according to claim 1, in which, to detect the synchronization ticks, the identification module (43) is configured to carry out a correlation of the messages exchanged with the remote equipment with a known profile of the messages of the wireless communication standard chosen for synchronization ticks.

3. Equipment according to one of claims 1 and 2, in which the digital block (40) comprises a chronometer (42) operating in a local time base and in which the identification module (43) uses the chronometer in order to associate a chronological date with each of the synchronization ticks detected.

4. Equipment according to claim 3, comprising a clock signal generator (10) (CLK) and in which the stopwatch (42) is incremented by the clock signal, by a multiple or sub-multiple of the clock signal or by a signal synchronized to the clock signal.

5. Equipment according to one of claims 3 and 4, in which the identification module (43) is configured to make available to the synchronization module the chronological dates of the detected synchronization tops.

6. Equipment according to claim 5, in which the synchronization module is configured to translate the chronological dates into calendar dates.

7. Equipment according to one of claims 1 to 6 operating as slave equipment of the remote equipment, in which the synchronization module (52) is configured to determine a time resetting instruction.

8. Equipment according to claim 7, in which the synchronization module (52) is configured to determine the time resetting instruction by measuring the cumulative outward flight time and the return flight time of synchronization pulses exchanged with the remote equipment.

9. Equipment according to one of claims 7 and 8, in which the synchronization module (42) is further configured to estimate a drift of a calendar time base by deriving successive time resetting instructions.

10. Equipment according to one of claims 7 to 8 taken in combination with claim 4, in which the synchronization module (42) is further configured to determine a setpoint (Tu) for resetting the clock signal (CLK).

11. Equipment according to one of claims 7 to 10, in which the processing unit (50) comprises a module (53) for acquiring and formatting data from a sensor.

12. Equipment according to one of claims 1 to 6 operating as master equipment of the remote equipment, in which the synchronization module (52) is further configured to determine calendar dates from local chronological dates corresponding to the dates of transmission and reception (Tl, T4) of synchronization ticks detected and dated by the identification module (43) and, on the other hand, to generate and transmit to the transceiver (50) useful data comprising the values ​​of said calendar dates (Tl, T4) to be transmitted in signaling messages (Follow-Up(Tl), Delay-Resp(T4)).

13. Data remote transmission system comprising a master device according to claim 12 and a plurality of slave devices according to one of claims 7 to 11.

14. Method implemented in equipment according to one of claims 1 to 12, comprising the steps of identification and dating in a local time base, by means of the digital block identification module, of the synchronization tops exchanged with the remote equipment.

15. Method according to claim 14 implemented in equipment according to one of claims 7 to 11, further comprising a step of determination by the synchronization module of the processing unit of an instruction for resetting the local time base with respect to a reference time base of the master equipment by jointly exploiting the dating of the synchronization ticks, carried out by the identification module of the digital block, and useful data extracted from signaling messages by the transceiver.

16. Computer program product comprising instructions which, when the program is executed by a digital block of equipment according to one of claims 1 to 12, cause the latter to implement the identification and dating steps of the method according to claim 14.

17. Computer program product comprising instructions which, when the program is executed by a data processing unit of equipment according to one of claims 7 to 11, cause the latter to implement the step of determining the method according to claim 15.

Images