Method for synchronizing a clock signal, transceiver and transmitter

Abstract

The invention concerns a method for synchronizing a clock signal (CLK) to a reference clock (RCLK), wherein the clock signal is derived from a local master clock and an adjustable multiplication factor. The method uses the master clock signal to synchronize the multiplication factor to compensate of a frequency deviation. The respective signals are transmitted and received in the gaps between data packages of a communication standard like Bluetooth.

Description

[0001] METHOD FOR SYNCHRONIZING A CLOCK SIGNAL, TRANSCEIVER AND TRANSMITTER

[0002] The present application claims priority of Danish application PA 2023 70393 dated August 02 , 2023 , the disclosure of which is incorporated herein by reference in its entirety . The present invention concerns a method for synchronizing a clock signal with a reference clock . The present application also concerns a transceiver as well as a transmitter device .

[0003] BACKGROUND

[0004] In certain applications , particularly involving communication between a master and a slave device , time synchronization between a master clock and a clock within the slave device might be important to provide a smooth functionality and data communication in between . Usually, such synchronization may involve the exchange of special data packages referred to time synchronization packages between the master and the slave . Moreover, certain data communication protocols include functionality for compensating a delay between the communication signals to achieve an error-prone data communication .

[0005] In certain media applications , for instance , during sound recording or video recording, actual sound or video acquisition can be performed by a variety of different devices , each of those being independent of each other . For example , one may record signals by one or more sound sources using different devices that a spatially separated . Each device will then record the sound but with a certain delay depending on its distance to the one or more sound sources .

[0006] The recorded material can then be processed to obtain certain functionality, like for instance identifying the position of a certain sound source in order to generate a complete sound environment . When also using video material , the recorded video and sound components can be synchronized . Consequently, apart from synchronizing the data communication in such applications , the actual recording time , including an internal time stamp for recording sound or video data , is required . Such synchronization becomes even more important in cases , in which the distance between the various devices recording the sound or video components is substantial . For example , as sound travels only with a relatively small speed, various devices having different distance to the one or more sound sources will record sound at different times . To align the various recorded sound signals in time , one may use a cross-correlation functionality . Nevertheless , such crosscorrelation is still not error-prone . In addition, apart from the above-mentioned delay, an equal sampling rate in each of the devices is mandatory, particularly with longer recordings . Finally, the various devices should all rely on a common start and end time for the recordings , in order to enable the above-mentioned cross-correlation and alignment of the different recorded sound signals for processing .

[0007] While those aspects can be addressed with certain hardware , like OCXOs , those hardware solutions are expensive and do not guarantee to fully work over a longer lifetime . However, the issue remains in masterslave configurations .

[0008] It is therefore an obj ective of the present application to provide method for synchronizing a clock signal to a reference clock, which allows a compensation in the case of a time or frequency deviation even in environments , in which the communication between the devices is not continuous and can be interrupted .

[0009] SUMMARY OF THE INVENTION

[0010] This and other obj ects are addressed by the subj ect matter of the independent claims . Features and further aspects of the proposed principles are outlined in the dependent claims .

[0011] The inventors propose a new and improved method for synchronizing a clock signal of the device to a reference clock, wherein the reference clock is separated from the actual device using the clock signal . This configuration is similar to a master slave configuration, wherein the master comprises a reference clock that is used to synchronize the clock of the slave . The reference clock is usually provided as a global master clock used for synchronizing other clock signals in the respective system, and more particularly in the master-slave configuration . Usually, the other clock signals can be derived from a local master clock, said local master clock being part of a slave device .

[0012] However, instead of adj usting the local master clock of the slave device as in conventional systems , the inventors propose to perform the synchronization by adj usting a multiplication factor to derive an adj usted clock signal from the local master clock but leave the actual master clock unchanged and unadj usted .

[0013] Such approach provides the benefit of adj usting one or more clock signals independently of each other . For example , if a slave device comprises a master clock and several other clock signals derived therefrom (used to achieve different functionalities ) , the proposed method enables adj ustment of one or more of these clock signals without affecting any other . This might be beneficial , if there are other mechanism of synchronization available , i . e . time synchronization via a communication protocol and the like . The proposed method is therefore applicable without affecting other mechanism being available .

[0014] As a result , the proposed method allows compensating a frequency deviation between a clock signal and a global reference clock irrespectively of a deviation over time or change of the local master clock in the slave device .

[0015] Moreover , the proposed method can be used for a plurality of slave devices being in a communicative connection with a respective master device providing the reference clock .

[0016] In some aspects , the inventors propose a method, in which a first data package is received via a wireless communication interface , said first data package comprising a first value corresponding to a relative time value derived from a reference clock . The first data package comprising the first value corresponding to a relative time is usually provided by the master device . Upon receiving the first data package , the method comprises triggering a timer to start counting events derived from either the clock signal or the local master clock or a signal derived therefrom. Usually, those events are pulses from one of the mentioned clocks . In addition, the first data package may be recorded to obtain the first value and optionally temporarily store the first value .

[0017] After a certain period, a second data package is received via the wireless communication interface . The second data package comprises a second value which corresponds to a relative time derived from the reference clock provided by the master device . In accordance with the proposed principle , the second value as well as the first value should be different , and its difference substantially corresponds to the time passed since generating the first and second values or the first and second data packages , respectively . Upon receiving the second data package , the timer is again triggered to store the counted events since the previous triggering . In other words , upon receiving the second data package , the events counted so far are temporarily stored . Those events correspond to the time passed since the first triggering in the local clock domain . The second data package may also be decoded to obtain the second value .

[0018] To obtain a possible time or frequency deviation, the counted events between the reception of the first and second data packages are compared with the difference of the first and second values . The counted events correspond to the time passed in the local clock domain . The difference of the first and second values correspond to the time passed in the reference clock domain . Under ideal circumstances , both clock domains should run equal , that is , no time delay ( in positive or negative direction) should occur . Hence , the frequencies given by the counted events and time pass should be the same as well . Hence , no or no significant gap between the first and second value difference and the counted events indicates that no frequency deviation took place .

[0019] However, if a substantial gap between the difference of first and second values and the counted events occur, then one can assume frequency deviation between the reference clock signal and the clock signal . Consequently, the multiplication factor is adj usted in response to the obtained frequency deviation to accordingly align the clock signal and the reference clock signal .

[0020] In this regard, the frequency of the clock signal is adj usted to the reference clock signal such that both frequencies are now aligned .

[0021] For the purpose of this application, the term "reference clock signal" as well as "frequency of the reference clock signal" are taken synonymously . Likewise , the expressions "clock signal" and "frequency of clock signal" are used synonymously throughout the application .

[0022] The benefit of the proposed method lies in the fact that the method is independent of any data communication or network protocol and can be used for a variety of applications , including the synchronization between classical master-slave configurations . However , it is not limited to a single master slave communication but can be used to synchronize various different clock signals being generated in a slave device to a common global reference clock provided by a master device .

[0023] In some aspects , the starting as well as stopping point of the respective counted events is of importance to reduce possible inherent arrows in the adj usting process .

[0024] Consequently, one may consider to actually trigger the time of counting the respective events very early, even while the full reception of the data package is not finished . In other words , the timer is triggered while the data package is still received . This is possible if that data package contains some header or identifier, which starts , -when demodulated correctly- the trigger . Usually such approach is implemented on very basic hardware level , that is for example on levels 1 or 2 in the OSI model . This will prevent any potential delay, which can occur during processing the data package in accordance with the communications stack or any higher protocol level .

[0025] Consequently, the step of triggering the timer upon receiving the first or second data package may comprise triggering the timer during the reception of the first or second data package . More particularly, the timer may be triggered as soon as a sub portion or subset of the first and said second data package is received, demodulated and being identified as part of the first or second data package . This will allow triggering the respective timer for counting the events even prior to completely limit relating or receiving the respective data package . This aspect may be suitable , the data package being a received is rather long or the frequency of the event counter is rather high ( e . g . In the range or higher than the reception data rate ) . In some other aspects , the timer may be triggered after receiving the first or second data package .

[0026] Some aspects relate to an identification of the data package and its alignment with a respective slave device . This may be suitable if there are more slave devices to be synchronized . Consequently, a subset of the first and second data package may be demodulated, and the timer triggered in response to a comparison of the demodulated subset with a reference pattern . In other words , the timer will only be triggered, if the subset in the received data package indicates a correct identification . This will allow to individually trigger the event counter in different slave devices . Rather the subset may indicate either a slave device and / or specific clock in a slave device to be synchronized . Hence , the proposed solution enables to adj ust various different clock signals within the slave device , those clock signals being identified by the content of the first subset .

[0027] In a further aspect , the timer may be triggered after reception of the first or second data package and after those data packages have been fully received and evaluated in regard to possible transmission errors . Of course , the event counter can be reset , and counting events can be stopped if the first and second data packages have been not fully and correctly received .

[0028] In this regard, the events being counted may correspond to pulses of the clock signal or signal derived therefrom . Alternatively, the events may correspond to pulses provided by a local master clock located in the slave device . In a further aspect , the events may correspond to pulses from the local master clock or the clock signal with an adj ustable multiplication factor . Simply speaking, the number of events counted over time corresponds to the frequency of the respective clock signal . Hence , one could also say that counting the events corresponds to measuring the frequency of the respective clock signal , the local master clock signal or signal derived therefrom.

[0029] As indicated above , the proposed method is independent of any underlying data communication protocol . More particularly, the method can also be used in a certain data communication protocols without interfering with the data communication protocol or utilizing any of its functionality . Consequently, in some aspects , the method may further comprise transceiving one or more data packets in accordance with the wireless and packet-oriented communication standard . The wireless and packet-oriented communication standard is using a time division multiplexing, wherein the communication standard defines time slots for transmission or reception of the one or more data packets . These time slots may be continuous but can also be separated by a certain time period, in which no transmission or reception of data packets occur . Hence , during such time intervals , the transmission or reception of the data packages in accordance with the proposed principle can take place without interfering with the communication protocol or blocking the transceiver hardware .

[0030] In this regard, it is possible for example to receive the first and second data packages between the time slots indicated or scheduled for transceiving the one or more data packets . However, it is not necessary to receive such data packages in each of those time slots . Rather , several of those one or more data packets may be transmitted or received prior to receiving the first or second data package . In some aspects , the transmission and / or reception of the first and second data packages are schedule in certain time intervals , for example about every 500ms or every second . In such cases , one may schedule the transmission and reception within a time period, in which no transceiving according to the communication protocol takes place . Such scheduling is also beneficial , as it allows to power down hardware if not needed, thereby reducing the overall power consumption of the slave device . Wireless packet-oriented communication standards may include , for example , blue cruise , sickly as well as the 802 . 11 standard, although the proposed method is not limited thereto .

[0031] In a further aspect , the first and second data package may each comprise a first date subset having a first pattern or a bit length, as well as a second data subset with a second length . The first and second data subsets may each comprise a value corresponding to different timestamps . Consequently, in some aspects of the proposed principle , different timestamps may correspond to different time periods , like for instance , microseconds or milliseconds , but may alternatively also correspond and utilized to adj ust a different clock signals within the slave device , in which the proposed method is used . Furthermore , the first and second length may be different . However, in some aspects , at least one of the bit length may correspond to 10 bits , being able therefore to provide counted events between 1 and 1024 .

[0032] Some aspects relate to the evaluation step and obtaining the frequency deviation between the global reference clock and the clock signal to be adj usted .

[0033] For this purpose , the step of evaluating the first and second values may comprise forming a difference between the second value and the first value . The difference corresponds to a time interval and more particularly to a time interval , which has passed between the provision of the first data package and the second data package , respectively as seen from the reference clock . Said difference may then be compared with the stored counted events or value derived therefrom to obtain a possible time deviation and thus a possible frequency deviation between the global master clock and the reference clock signal .

[0034] Some aspects relate to the adj ustment in case of a possible frequency deviation . There might be occurrences , in which the frequency deviation is a rather small such that an adj ustment of the multiplication factor may either not be possible or not worth it for the time being . This is for example the case for small j itters , which are usually compensating themselves over time . However, drifts in the clock signal should be compensated, as they accumulate over time . Consequently, in some aspects , the frequency deviation can be compared with a threshold value to identify a possible drift . In response to that comparison, the multiplication factor can be maintained if the frequency deviation is smaller than the threshold value . If the frequency deviation is between the threshold value and a second threshold value , the multiplication factor is adj usted in a single step in order to minimize the frequency deviation between the master reference clock and the clock signal .

[0035] In some occurrences , the frequency deviation may be rather large and can exceed a value , which is significantly larger than the threshold value and may also be larger than a second threshold value . In such cases , a single adj ustment of the multiplication factor may not be overly beneficial and probably lead to interruptions or any other adverse effects in the slave device or in a circuitry using the clock signal during the adj ustment step . Consequently, if the frequency deviation is larger than the second threshold value , the multiplication factor may be adj usted in various smaller steps in order to reduce any adverse effect on the circuits while still minimizing the deviation . The adj ustment may also occur over a certain period of time to minimize possible adverse effect of the adj ustment .

[0036] In some further aspects , a flag may be set to indicate that a frequency deviation is present . This flag can be particularly set if the deviation is below the threshold value . The status of the flag can subsequently be used to expand the measurement time or use a longer counting and more data packages to evaluate the deviation over a longer period . In some aspects , the time of counting the respective events is expanded by for example storing of the first value and replacing a new first value with the stored first value and subsequently storing the counted events as an intermediate count . Alternatively, in such case , the event counter can simply be continued .

[0037] In a subsequent step , the replaced stored first value as well as the continued events are used to evaluate the frequency deviation between the master clock reference and the clock signal over a longer timeframe . Another aspect relates to a transceiver . The transceiver comprises a local master clock generator to generate a local master clock . The transceiver further comprises an adj ustable clock generator to generate a clock signal derived from the local master clock and an adj ustable multiplication factor . The clock signal is to be used to supply one or more modules , components and the like of the transceiver , for instance for recording certain data like sound or visual information .

[0038] The transceiver further comprises a communication interface , which is configured to transceive one or more data packets in accordance with a wireless packet-oriented communication standard . The standard may include but not limited to one of Bluetooth, ZigBee , and 802 . 11 and its derivatives . The communication interface is further configured to receive the first data package , said first data package comprising a first value corresponding to a relative time value derived from a reference clock . Upon receiving the first data package , a timer is triggered to count events derived from one of the clock signal or the local master clock .

[0039] The communication interface is further configured to receive a second data package sometime after receiving the first data package . The second data package comprises a second value corresponding to a relative time value derived from the reference clock . Upon receiving the second data package , the timer is again triggered to stop the event counting . The counted events may then be stored in a memory and correspond for example to a number of pulses of the clock signal or a signal derived from it . The counted events thus reference the time that has passed between the reception of the first data packet and the second data package , respectively . The respective first and second data packages may also be decoded and demodulated to obtain a respective first and second values . The first and second data packages are provided by a master device .

[0040] In accordance with the proposed principle , the transceiver also comprises a control unit , which is configured to detect a frequency deviation between the reference clock and the clock signal based on the first and second values and the stored counted events . The first and second value reference information from a reference clock . The difference between the first and second value correspond to time or frequency of the reference clock . As stated previously, the gap between the difference of the first and second value and the counted events correspond to a drift of the reference clock with respect to the master clock . The multiplication factor is adj usted by the control unit in response to detection of a frequency deviation between the reference clock signal and the clock signal . The adj ustment factor does not change the local master clock, but only the clock for which the deviation is minimized .

[0041] In this regard, it should be noted that the communication interface is configured to transceive data packets in accordance with the communication standard as well as a plurality of data packages , those data packages usually being different compared to data packets that may comply with any proprietary standard . In other words , the first and second data package do not correspond to the data packets according to the communication standard . This will offer a proprietary generation and reception of data packages independently from an underlying communication standard . More particularly, the data packages can trigger the timer without being fully demodulated and processed in accordance with the communication standard, thereby bypassing any possible glitch or a time delay caused by higher layers of the OSI model during processing of the data packets and packages . Even more , the processing of the data packages in accordance with the proposed principle is independent of the communication standard and can be implemented directly on a low hardware level .

[0042] The communication interface can be configured to trigger the timer during the reception of the first and second data package , and in particular prior to having those data packages completely received . In some aspects , the communication interface is triggered after having received a subset of the respective first and second data packages . This will bypass possible delay in error correction or any other processing , thereby offering a quick trigger of the timer substantially independent of further processing . In an alternative , a subset of the first and second data package may be demodulated to derive an identifier therefrom. The timer is then triggered to start the event counter in response to the identifier . This will allow adj usting the clock signals of a plurality of different receivers / slave devices or different clock signals in the same receiver / slave device .

[0043] In some aspects , the communication standard defines time slots for transmission or reception of one or more data packets . However, the first and second data package are usually not received during those time slots , but during those time slots and thus in between time slots dedicated or scheduled for transmission or reception . This will ensure that the reception of the first and second data packages are not interfering with the transmission or reception of data packets in accordance with the communication standard . The functionality of the transceiver / slave device is therefore not hampered, while at the same time enabling the adj ustment of the clock signal in the transceiver / slave device .

[0044] In some aspects , the control unit is configured to detect a frequency deviation by forming a difference between the second value and the first value . Said differences corresponds to the time interval between the generation or the reception of the respective values . If the number of values in itself is associated with or corresponds to the pulses or frequency of the reference clock, the difference corresponds directly to a time interval reference clock . Said difference can then be compared with the stored counted events or a value derived therefrom. If the difference between the stored counted events and the difference of the first and second value is very small , the frequency deviation is small as well . In response to that frequency deviation, the multiplication factor can then be maintained or adj usted only slightly . In some aspects , if the frequency deviation is large ( i . e . above a certain threshold) , the adj ustment can be one of several smaller steps to avoid glitches in any circuity making use of the clock signal .

[0045] Further aspects relate to a transmitter . Said transmitter comprises in some aspects the reference clock generator to generate a reference clock . A data package generators is coupled to the reference clock generator to provide a plurality of subsequent data packages , wherein each data package includes a value based on or derived from said reference clock . The value corresponds to a timestamp . Consequently, subsequent data packages thereby correspond to the time passed between the generation of each data package .

[0046] The transmitter also comprises a communication interface , that is configured to transmit or receive data packets in accordance with the packet-oriented communication standard . The packet-oriented communication standard may comprise one of Bluetooth, ZigBee , and 802 . 11 standards or derivatives therefrom . The communication interface of the transmitter in accordance with the proposed principle is also configured to receive the plurality of subsequent data packages provided by the package generator . In contrast to the data packets , the data packages may be proprietary packages and can differ in some aspects from data packages in accordance with the communication used to transmit or receive the data packets .

[0047] The communication interface is configured to transmit the data package of the plurality of data packages between receiving two or more subsequent data packets in accordance with the packet-oriented communication standard . Alternatively, the data package of the plurality of data packages can be transmitted between transmitting two or more subsequent data packets in accordance with the packet-oriented communication standard . Furthermore , the data package can be transmitted between receiving a data packet and transmitting another data packets in accordance with the packet-oriented communication standard or between transmitting and receiving data packets in accordance with the packet-oriented communication standard .

[0048] SHORT DESCRIPTION OF THE DRAWINGS

[0049] Further aspects and embodiments in accordance with the proposed principle will become apparent in relation to the various embodiments and examples described in detail in connection with the accompanying drawings in which Figure 1 shows an example of a transceiver arrangement in a master slave configuration to outline some aspects of the proposed principle ;

[0050] Figures 2 illustrates a flow chart of various data packages and data packets to outline some aspects of the proposed principle ;

[0051] Figure 3 shows a time diagram illustrating several data packets and data packages in accordance with some aspects of the proposed principle ;

[0052] Figure 4 illustrates the structure of an exemplary data package ;

[0053] Figure 5 shows some further aspects of the proposed principle ;

[0054] Figure 6 illustrates an example of a portion of a transceiver in accordance with some aspects of the proposed principle ;

[0055] Figure 7 illustrates an example of an exemplary method for synchronizing a clock signal to a reference clock in accordance with some aspects of the proposed principle ;

[0056] Figure 8 shows some aspects of an exemplary method for synchronizing a clock signal to a reference clock in accordance with the proposed principle ;

[0057] Figure 9 illustrates some further aspects of an exemplary method for synchronizing a clock signal to a reference clock;

[0058] Figure 10 illustrates some further aspects of an exemplary method for synchronizing a clock signal to a reference clock;

[0059] Figure 11 shows a time deviation diagram with adj ustment of the multiplication factor in accordance with some aspects ;

[0060] Figure 12 illustrates another time-deviation diagram for a clock signal including the correction signal ; Figure 13 is an illustration of an application, in which the proposed method and transceiver can be used .

[0061] DETAILED DESCRIPTION

[0062] The following embodiments and examples disclose various aspects and their combinations according to the proposed principle . The embodiments and examples are not always to scale . Likewise , different elements can be displayed enlarged or reduced in size to emphasize individual aspects . It goes without saying that the individual aspects of the embodiments and examples shown in the figures can be combined with each other without further ado , without this contradicting the principle according to the invention . Some aspects show a regular structure or form . It should be noted that in practice slight differences and deviations from the ideal form may occur without , however , contradicting the inventive idea .

[0063] In addition, the individual figures and aspects are not necessarily shown in the correct size , nor do the proportions between individual elements have to be essentially correct . Some aspects are highlighted by showing them enlarged . However , terms such as "above" , "over" , "below" , "under" "larger" , "smaller" and the like are correctly represented with regard to the elements in the figures . So it is possible to deduce such relations between the elements based on the figures .

[0064] Figure 13 illustrates a typical application, in which the method as well as the transceiver according to the proposed principle can be used . In this particular application, a sound recording device MD acting as a master device is placed in a defined space environment to record various sound signals coming from various sound sources SSI , SS2 .

[0065] Two or more sound sources SSI , SS2 are located distanced from the recording device MD, whereas the recording device also corresponds to a reference point in regard to the position and the environment . The two or more sound sources may include two or more persons talking to each other . Their speech, that shall be recorded, is referred to as use signals . Usually, other sound sources SS3 like background people and other sources are present that emit sound signals , too . However , in contrast to the use signals , these are undesired and usually referred to as noise . In this regard, the one or more sound sources may be stationary, although such is not required for the proposed application . The sound sources may walk or move around, noise sound sources may also move , resulting in a dynamic sound environment .

[0066] Each of the one or more sound sources ( or at least some of them) , for example a speaker , also contains a local microphone device acting as a slave device SD1 , SD2 . The local microphone devices SD1 , SD2 are arranged very close to the respective sound source SS , SS2 and assigned to the respective sound source .

[0067] Each of the local microphone devices ( slave devices ) as well as the recording device (master device ) will now record the speech or any other sound signal within the environment . However , due to the various distance from each other, the microphone devices and the recording device will record the respective sound signals coming from the sound sources at different times .

[0068] For example , local microphone device SD1 will record the sound signal from sound source SSI first . Due to the speed of sound, local microphone device SD2 and the recording device MD will record the respective sound signal a little later in time . The centrally arranged recording device MD will record the sound signals from both sources SSI , SS2 as well as nose . Likewise , the Local devices will record the sound signals from its sound source assigned to it , but also with some delay the speech of the other sound sources , or its own sound being reflective in the environment , referred to as crosstalk . The delay, which the respective sound signals are recorded corresponds to the distance of the sound sources towards a central reference point , for instance of the position of the recording device .

[0069] In a subsequent processing, the various sound signals recorded by the respective local microphone devices LD1 , LD2 and the recording device MD can be combined, for instance to remove noise or other artifacts . Furthermore , one can calculate the distance of the sound sources by evaluating the delay of the various sound signals being recorded . This will not only require a certain correlation as such ( e . g . the sound signals should not be skewed or lost during the distance ) , but also require a good knowledge of the timing events in the respective microphone devices LD1 , LD2 and the recording device MD . Furthermore , all the three signals need to be recorded with the same or at least a defined and known data rate to prevent artifacts and mismatches in the subsequent alignment and processing algorithms .

[0070] Usually, one can solve these issues by various means . For instance , the respective devices may include a very precise timer or local master clock generator, which is synchronized to a common reference clock . However, in cheaper devices such clock is not easily available due to costs . Apart from the costs , the clock generators nevertheless drift and misalign over time , thereby creating a delay or a gap in between different clock frequencies of the respective devices .

[0071] The current method now proposes using the clock frequency of the recording device as master device , and periodically synchronize the respective clock frequencies of the microphone devices and slave devices , respectively . It has been found to synchronize in particularly clock frequency in the slave devices used for certain function i . e . actual recording of the sound signals . While it is also possible to synchronize the local master clock signal , it can also be left unadj usted . This approach is beneficial , because it does not influence the master cock, that usually provides the clock signal for a variety of circuitry . Consequently, the other circuitry does not risk any glitches that can lead to disruptions of the application or require additional circuit for error correction or preventing such disruptions . Furthermore , while the local master clock in the microphone devices as well as the recording devices is usually clocked with a frequency of several megahertz , the clock rate for recording the sound signal ( or another application whose clock is to be synchronized ) is usually lower and for example within the range of several 100 kHz . It is sufficient for recording sounds to have a clock signal of a few 100 kHz to fulfil the Nyquist criteria with a high sampling rate . Consequently, a frequency deviation of the clock frequency of a few milliseconds may affect the recorded signal , resulting in the above- mentioned adverse effects . The time synchronization must therefore exceed this value in order to minimize and reduce the disadvantages thereof .

[0072] Figure 1 illustrates a master-slave configuration in accordance with the present invention, which is suited to transmit and receive data packages having time synchronization content , allowing a slave device to adj ust a clock frequency to a common time base .

[0073] The transmitter or master device 11 comprises one or more antennas 200 and 201 , which are suited to communicate with the slave device 10 in accordance with one or more wireless communication protocols . The wireless communication protocols are time-division multiplexed and packet-oriented protocols , meaning that the communication takes place in defined data packets being transmitted or received over the wireless communication interface using the antennas 200 , 201 . A time gap can occur between data packets being transmitted or received . Example for packet-oriented data packages with such time gap are Bluetooth, ZigBee , and 802 . 11 . The transmitter 11 further comprises a respective communication interface 101 that is coupled to the antennas 201 . The communication interface 101 is connected to a data packet generator 170 generating a plurality of one or more data packets in accordance with the communication protocol . This will allow the master device to communicate with the slave device in accordance with the communication protocol .

[0074] The communication interface 101 is further connected to a data package generator 160 for receiving the data packages in accordance with the proposed principles . These data packages are generated by the data package generator 160 using a global reference clock from a reference clock generator 150 . The reference clock generator 150 provides a signal with a reference clock frequency, to which the slave device and, more particularly, the clock frequency of the slave device in accordance with the proposed principle is to be synchronized .

[0075] The reference clock generator 150 also provides all necessary clock signals to the respective components of the transmitter . For this purpose , the reference clock generator 150 is connected with its output 151 to a clock input of the communication interface 101 for providing a clock signal to the communication interface . Reference clock generator is also connected to an input 162 of the data package generator 160 . The package generator 160 uses the reference clock to provide a first and date second data package in accordance with the proposed principle , by generating a value corresponding to the reference clock . The data packages are transmitted via the communication interface to the slave device .

[0076] The slave device 10 comprises two or more antennas 200 connected to a communication controller 502 . The communication controller 502 is connected to a control unit 430 . Control unit 430 , communication controller 502 and the antennas form the communication interface 100 of the transceiver 10 . The communication controller 502 is also connected to a control device 501 . The control device 501 is coupled to a recording device 500 , which in turn is connected to an input device 310 , for example , a microphone . In operation of the transceiver , the microphone 310 records a sound signal using the recording device 500 , which is forwarded to the control device 501 . The recorded sound signal is then transmitted via the communication controller 502 using a packet-oriented communication protocol to the transmitter 11 .

[0077] The recording device 500 is supplied by clock frequency provided by an adj ustable clock generator 410 . The adj ustable clock generator 410 utilizes a local clock signal provided by a local master clock generator 400 and in adj ustable multiplication factor . Consequently, the clock frequency provided to the recording device 500 is derived from the multiplication factor and the local master clock generator 400 by changing either the local master clock generator or the multiplication factor . The clock signal can therefore be adj usted . The transceiver 10 further comprises a timer or counter 420 , which is connected with its input either to the adj ustable clock generator 410 or the local master clock generator 400 . The timer or counter 420 is used to count pulses from one of the clock signals provided by generators 400 and 410 , thereby simply speaking measuring the respective frequency thereof . The timer or counter 420 is controlled by the control device 430 .

[0078] In accordance with the proposed principle , the transmitter 11 first and second data packages in accordance with the proposed principle , which are subsequently received by transceiver 10 and used to adj ust the multiplication factor of adj ustable clock generator 410 . This process is exemplary illustrated in Figure 2 .

[0079] In such configuration, the transceiver 11 acts as a master device communicating with transceiver 10 using usually a packet-oriented communication protocol . Such packet-oriented communication protocol may comprise for example Bluetooth, in which the transceiver 11 are Bluetooth packages to transceiver 10 . Likewise , transceiver 10 records sound signals and transmits the recorded sound signal via Bluetooth to transceiver 11 for further processing .

[0080] In accordance with the proposed principle , the transceiver 11 will , upon identification of transceiver 10 using the Bluetooth communication protocol , issue a clock sync signal Clk sync to provide a common time base , both for transceiver 11 and transceiver 10 if needed . In some aspects , the Clk sync signal is used to adj ust the local master clock generator within transceiver 10 . Further, Clk sync will allow a common starting point for both transceiver 11 and transceiver 10 for subsequent recordings of the sound signals .

[0081] In subsequent steps , one or more Bluetooth packets BP1 , BP2 to BPn are exchanged between the transceiver 11 and transceiver 10 . For example , transceiver 11 may transmit a plurality of Bluetooth packets including settings for the subsequent recording sessions to transceiver 10 . Likewise , transceiver 11 may transmit a start signal for starting the recording sessions via Bluetooth packets and the packet-oriented communication protocol . Likewise , transceiver 10 may transmit a plurality of Bluetooth packets including recorded sound to transceiver 11 .

[0082] At some point in time , between the various transmission of Bluetooth packets as indicated in Figure 2 , the transceiver 10 transmit a data package DPI to the transceiver 10 including first value corresponding to the value provided by the data packet generator and from the signal of the reference clock generator 150 in transceiver 11 . Upon reception of that particular data packet , which does not follow the Bluetooth standard, but is transmitted between the Bluetooth packets , the transceiver 10 triggers the timer and counter 420 to count events either from the adj ustable clock generator or from the local master generator . In other words , these counted events corresponds to the pulses ( and thus represent a frequency) of one of the clock signals in transceiver 10 . In a subsequent process step, the value included in the data package DPI is obtained and stored as a temporary value VAL1 .

[0083] The transceiver 10 as well as transceiver 11 may then continue to transmit and receive one or more packets BPx in accordance with the Bluetooth standard . The transceiver 11 will transmit a second data package DP2 after a certain period of time T in accordance with the proposed principle , including a second value derived from the reference clock generator and the reference clock thereof . This value corresponds to the time passed between the first value VAL1 and the second value the VAL2 , and substantially corresponds to the frequency of the reference clock .

[0084] Upon reception of the second data package DP2 , the transceiver 10 stops the timer and counter 410 or restart the timer and stores the counted events so far in a temporary memory . The counted events somewhat represent or corresponds to the frequency of the clock generator or the local clock generator in the transceiver 10 . Furthermore , the obtained second data packet is demodulated to obtain the value VAL2 . Subsequently, one or more data packets BPy may be transmitted or received between the master and slave devices 11 and 10 independently of the processing of the content within the data packages .

[0085] The difference between the two obtained values VAL1 , VAL2 is now calculated and subsequently compared with the counted events . This step somewhat corresponds to or at least is similar to obtaining the frequency of the signals provided by the adj ustable clock generator or the local master clock generator , respectively, and compare the obtained frequency with the frequency given by the difference of the two obtained values .

[0086] In an ideal case , both results will correspond to each other and substantially indicate that no deviation ( either in frequency, by a time gap ) between the clock frequency and the reference clock took place . However, in case of a deviation, the two results will differ from each other, wherein the sign of that difference indicates the direction of the shift of the clock signal in the slave device . Correspondingly, in a subsequent step, the transceiver 10 now adj usts the multiplication factor of the clock generator to minimize the deviation .

[0087] As stated before , the timer or counter is re-started upon reception of the second data package . After another defined time period T , yet another data package DP3 is received, triggering the timer to stop counting the events , store them and restart it again . The third value VAL3 included in the data package DP3 is obtained by demodulating the package . The transceiver 10 will then compare the third value VAL3 with the second value VAL2 to derive the difference , representing the reference clock frequency and compare those with the newly counted events representing the clock frequency of the local clock in the slave device . Consequently, another possible deviation can be adj usted . The process can be repeated after another dedicated time period to periodically adj ust the deviation of the clock frequency and minimize the frequency gap between the reference clock and the local clock . The proposed principle is not limited to adj ust a single clock but can be used in a plurality of different applications .

[0088] For example , Figure 5 illustrates a possible example , in which a master device is communicating with a plurality of slave devices 10A, 10B and IOC . The respective data packages can be distinguished using an identifier ID1 , ID2 and ID3 . Upon reception, the slave devices demodulate the identifier and trigger the respective timer accordingly . This will allow each slave device to adj ust the clock frequency individually and separately by using the identification header in the data package . The timer is triggered upon reception of the correct header to start event counting, while data packages having a different identifier are simply ignored .

[0089] This process in accordance with Figure 5 can also be implemented in a single slave device , in which a plurality of different clocks with their respective adj ustable modification factors shall be adj usted . For this purpose , the respective identifier does not identify a slave device , but dedicated clocks or adj ustment factors in a specific slave device . Upon reception of the respective identifier, the timer for the respective clock is triggered to count the events .

[0090] As indicated in Figure 2 , the data packets are transmitted in between the transceiving ( that is , between transmission or reception) of one or more Bluetooth packets or more general in accordance with a packet- oriented communication standard . Figure 3 illustrates a possible embodiment , in which one or more Bluetooth packets BPx are transmitted, each of those Bluetooth packets may comprise the same or different length as indicated . However, the Bluetooth packets are not transmitted continuously, but in certain intervals , in which no transmission or reception between the respective Bluetooth packets BPx takes place .

[0091] This is indicated in Figure 3 by certain time slots on the time axis . Bluetooth packets are transmitted at certain times T whereas the lengths of the respective packets may vary in accordance with the data content to be transmitted or received . However, data packages DPI and DB2 are transmitted between the time periods T , in particular approximately in the middle of the intermediate intervals , in which no transmission or reception take place . Furthermore , due to the limited content of the data packages DPI , DP2 , the packet length is limited and does correspond to the lengths of the Bluetooth packets . This is also due to the fact that no complicated error correction, either bit or block error correction, may take place . Rather , the content of the data packets DPI and DB2 being transmitted from the master device to the slave device can be demodulated in a simple way with no significant error correction necessary and subsequently processed on a low hardware level according to the OSI model . The layer on which the data packages DPI and DB2 are usually handled are layer 0 or layer 1 in the OSI model and normally do not extend to higher levels . This is beneficial , as this low-level processing can quickly trigger any hardware counter , thereby reducing overhead and a possible delay or glitches due to processing on higher OSI layers . More particularly, processing on these lower layers can be implemented in real time , or almost real-time , without any significant delay .

[0092] The data packages DPI , DB2 being transmitted may comprise a bit pattern as indicated in Figure 4 . Each data package contains a header or identifier ID of a certain bit length . The bit lengths are chosen such that on the one hand, the demodulator is able to detect a proper identifier of the data package compared to possibly demodulated noise . The identifier may identify a slave device among a plurality of slave devices , as indicated in Figure 5 . Alternatively, the identifier ID can be used to identify or select a specific clock frequency and multiplication factor , respectively, to be adj usted within a certain slave device . The identifier can also have no further meaning and j ust be used to trigger the counter and indicate the reception of the data package . The identifier is usually placed at the start of the respective data package but can also be arranged at the end or in the central portion thereof .

[0093] In the present example , the data package contains two further subsets referred to as Patternl and Pattern! , each of those having a certain bit length . As illustrated herein both subsets , comprise the same bit lengths . The subsets contain values corresponding to events or pulses or any other characteristics of the reference clock, to which the clock frequency is to be adj usted . For example , subset Patternl may comprise a first value indicating the time in milliseconds , which has passed since a certain start time . Subset Pattern2 may comprise a time value in microseconds . Consequently, each data package contains a value consisting of the milliseconds and microseconds which have passed as evaluated by the reference clock since a certain start time . The bit lengths of subset Pattern2 in this regard may be set to 10 bits , which corresponds to a maximum value of 1024 indicating that thousand microseconds correspond to 1 ms . The separation in two subsets within the data package can be beneficial in later processing . Furthermore , these two subsets can also be used to adj ust different clock signals within the same slave device identified by identifier ID in the data package .

[0094] Figure 6 illustrates a further embodiment of a transceiver in accordance with the proposed principle . The transceiver 10 comprises an antenna portion 200 , which is connected to a low noise amplifier 106 . The antenna 200 is configured to receive various signals over a wireless air interface . These signals may correspond to a packet- oriented communication protocol like Bluetooth, ZigBee , 802 . 11 and similar protocols . The antenna 200 is also configured to receive the data packages DPI and DB2 in accordance with the proposed principle . Those data packages do not correspond to the data packets as defined by the underlying communication protocol . The data packets are demodulated on a low hardware layer with its content processed thereon to avoid the processing on higher layers of the OSI model , thereby avoiding possible delays during the processing .

[0095] Antenna 200 of transceiver 10 is coupled to a low noise amplifier 106 , whose output is connected to an IQ demodulator 107 . Although the current example utilizes an IQ demodulator 170 , other demodulation units like an OFDM demodulator and others are also suitable . The IQ demodulator comprises a local oscillator signal input ( not shown herein) , which in turn is coupled to a local master clock oscillator 400 . The output of the demodulator is connected to a pre-processing device 108 , which in turn is connected to a memory 109 . The preprocessing device 108 receives several clock signals from the local master generator, not shown herein . Furthermore , the preprocessing device is coupled to timer circuit or counter 420 as well as to a comparator unit 601 , which also receives data from a local memory 600 . The output of the preprocessing device 108 is connected to a memory 109 to store the content of the data packages received in accordance with the proposed principle . The output of the memory 109 is coupled to a comparator 431 , which in turn is connected to an adj ustment circuit 433 to provide an adj ustment signal on output 433 . A possible deviation is adj usted by changing the multiplication factor of the clock signal ( not shown herein) that is also driven by the local master clock generator 400 .

[0096] In a possible exemplary operation of the transceiver, a data package is received via antenna 200 and amplified by the low noise amplifier 106 . The IQ demodulator 107 demodulates the received signal and provides a bit sequence to the preprocessing device 108 . The preprocessing device uses the first bit of the sequence corresponding to a possible header and forwards the bits to the comparator 601 . The comparator 601 compares the received bit sequence with a stored sequence provided by memory 600 , corresponding to an identification tag . If the bit sequences re not equal , the comparator transmits a signal indication to ignore the rest of the received message .

[0097] Upon a correct identification, the comparator 601 triggers the timer or counter 420 to start the event counter . The preprocessing device 108 is also provided with a corresponding feedback of a positive identification and continues to demodulate the rest of the received data package . The remaining bits are saved as a pattern in the temporary memory, wherein the pattern corresponds to a value .

[0098] After a certain period, a new data package is received via antenna 200 . The received signal is again amplified and demodulated via demodulator 17 . The preprocessing device 108 provides the first bits , corresponding to the header , to the comparator 601 , which compares it again with the stored sequence in memory 600 to evaluate the identification . Upon the correct identification, the content of the received data package is processed, and the second value obtained by preprocessing device 108 . The value is stored in the memory 109 .

[0099] Furthermore , upon correct identification, the timer and counter 420 is triggered by the comparator to stop the event counting . So far , the counter has counted the pulses of the local reference clock provided by the master clock generator 400 between the two triggering events , that is , between reception of the first and second data package . The counted pulses are forwarded to comparator 431 , which also receives the two values from the temporary memory 109 . These results are compared to estimate a possible time gap or frequency deviation between the values received in the data packages and the counted pulses in between the received data packages . Any possible gap or deviation is forwarded to the adj ustment circuit 433 , which adj ust the multiplication factor and provides an adj usted multiplication factor at the output 433 .

[0100] The process can then continue or be repeated with another data package , which is subsequently demodulated, pre-processed and stored in the memory area . Consequently, a possible deviation either in time or frequency ( given by the difference of the counted pulses and the value in the received packages ) is estimated at the reception of the subsequent data packages . This will result in a periodical update of the adj ustment factor .

[0101] Figure 7 illustrates a possible embodiment of a method for synchronizing a clock signal to a reference clock, wherein the clock signal is derived from a local master clock and an adj ustable modification factor . In step SI , a first data package is received via a wireless communication interface . The first data package comprises a first value corresponding to a relative time value derived from a reference clock, said reference clock provided by a master device . Furthermore , upon receiving the first data package , a timer or counter is triggered in step S2 to count events or pulses derived from either the clock signal to be adj usted or the local master clock signal from which the clock signal to be adj usted is derived from. The method continues with step S3 , in which the first data package is decoded completely to obtain a first value , which is subsequently temporarily stored . After a certain period of time , a second data package is received via the wireless communication interface . The second data package comprises a second value corresponding to a relative time value derived from the reference clock provided by the master device .

[0102] The reception via the wireless communication of the first and second data package may usually include the use of a proprietary protocol and not follow a dedicated communication protocol . Particularly it is independent of the data packet-oriented communication protocol like a ZigBee , Bluetooth or 802 . 11 to avoid processing, correction and error handling of such data packages in accordance with the protocol , thereby significantly increasing the speed to trigger the timer . More particularly, the avoidance of bit and block error correction according to a complex communication standard protocol usually has the benefit that an almost real-time processing on the low layer hardware structure can be performed without making use of higher layers in the OSI model . These higher layers may in some circumstances delay a complete decoding and reception, thereby inserting or adding an uncertainty in triggering the timer and counter .

[0103] The method then continues with step S5 , wherein upon receiving the second data package , the timer is triggered again to store the counted events and pulses since the previous triggering of the timer . In other words , the pulses of the clock signal or the local master clock signal are counted between the two triggering events corresponding to or associated with the frequency of the respective clock signal , or local master clock .

[0104] The second data package is also decoded completely to obtain a second number value in step S6 . The first and second obtained values are then evaluated and compared with stored counted events to obtain a deviation, gap or difference between those results in step S7 . Any possible difference can correspond particularly to a frequency deviation between the clock signal on the slave device and the reference clock on the master device . In response to such evaluated deviation between the clock signal and the reference clock, the process either stops and restarts with step SI or continues with step S8 . In step S8 , the multiplication factor is adj usted to minimize the deviation . This step may be performed optionally, i . e . only if the frequency deviation exceeds a certain threshold value .

[0105] Figure 9 in this regard illustrates a possible extension thereof . As illustrated in Figure 9 , step S7 contains the evaluation of the first and second values with the stored counted events to obtain the frequency deviation . For this purpose , a difference between the first and second values is first calculated in step S71 , corresponding to a count number of the reference clock between generation of the first data package and second data package . Then this difference is compared with the counted events in step S72 . The result in step S73 is either 0 or close to 0 or contains a sign indicating a shift forward or backwards between the reference clock and the local clock .

[0106] In an ideal world, and with no frequency deviation, the count number is a value that corresponds to the counted events from the clock signal or the local master clock with a certain correction factor . The correction factor in itself in this regard should be constant and basically reflect the difference in the hardware between the respective frequencies of the reference clock and the clock signal or the local master clock . Consequently, with no gap between the difference of the first and second value and the counted events , no frequency deviation is assumed in step S74 , and the method can continue with step SI .

[0107] However, in case of a possible frequency deviation, the process continues in Figure 9 with a certain evaluation to check whether the frequency deviation is above a second threshold value in step S75 . If this is not the case , meaning that the frequency deviation is smaller than the first threshold value , the multiplication factor may be maintained, and certain actions are conducted like setting a flag or storing the second value the first value and replacing the older second value with the new value , when new data package is received . Likewise , the counted events may be stored as an intermediate count and later added to it . Alternatively, the event counting may j ust continue . Some or all of these steps are conducted in step S10 also illustrated in Figure 10 .

[0108] This will allow utilizing the set flag or the replaced stored second value in a subsequent step when re-evaluating the first and second values .

[0109] However, if the frequency deviation is between the threshold value and a second threshold value ("Y" ) , the multiplication factor is adj usted in a single step to minimize the frequency deviation in step S8 . Finally, if the frequency deviation is larger than the second threshold value ("Y' " ) , the process continues with step S8 ' . In this step, the adj ustment factor is adj usted in several incremental steps to minimize the overall frequency deviation . These incremental steps are chosen to avoid and reduce possible glitches and errors in the circuitry making use of the clock signal . This will allow continuing for example a recording session uninterrupted, as no significant j umps in the sampling rate or the clock signal will occur .

[0110] Figure 10 illustrates step S10 , SI ' and S2 ' , in which further additional data packages are received, and correspondingly demodulated and decoded to store the second value as the first value and replacing the second value with a new value . Steps SI ' and S2 ' represent a possible implementation of a repetition of the method, which makes use of the previously received data packages . While it is possible to conduct the method such that subsequent packages are considered to follow be either the first package or the second package ( i . e . the third package contains a new first value , the fourth package contains a new second value and so forth) , it is also possible to provide a more continues adj ustment by simply restarting the counter after a second package is received ( i . e . this means that the third package contains a new second value , while the previous second value becomes the new first one and so forth) .

[0111] In the latter case , a possible frequency deviation is identified with each reception of a data package and subsequently corrected, while the former allows to correct a possible frequency deviation only every second data package . If the time between the data package in the range of 500ms is small compared to a possible shift , one can choose between the different options .

[0112] Figure 11 shows a time deviation diagram for the clock signal overtime . As shown, the frequency deviation on the x-axis given by curve Cl basically j itters around an average value . Curve C2 illustrates the adj ustment factor applied to the multiplication factor to compensate for possible frequency deviation overtime . As illustrated herein, the overall deviation ranges within a few tens of microseconds .

[0113] Figure 12 illustrates a similar diagram, in which the deviation of the local clock signal and the corresponding adj ustment factor are illustrated over a time period of approximately 3000s . Curve Cl shows the counter offset of the local clock over time . The straight curve C2 is the delay between the recorded signals from a local microphone ( slave device ) in regard to the reference microphone in the master device . As illustrated, due to the frequency drift in the clock signal , this delay increases overtime if not corrected by a corresponding adj ustment factor . Curve C2 ' given by the crosses represents the evaluated difference . Finally, curve C3 represents the calculated adj ustment factor to compensate for the drift in the local clock signal given by curve Cl .

[0114] LIST OF REFERENCES

[0115] 10 transceiver

[0116] 11 transmitter

[0117] 100 communication interface

[0118] 101 communication interface

[0119] 102 clock input

[0120] 106 amplifier

[0121] 107 demodulator

[0122] 108 pre-processing

[0123] 109 memory

[0124] 103 data package input

[0125] 150 reference clock generator

[0126] 151 output

[0127] 160 data package generator

[0128] 161 output

[0129] 162 reference clock input

[0130] 170 data packet generator

[0131] 200 , 201 antenna

[0132] 310 microphone , input device

[0133] 400 local master clock generator

[0134] 410 adj ustable clock generator

[0135] 420 timer

[0136] 430 control unit

[0137] 431 comparator

[0138] 432 adj ustment circuit

[0139] 433 adj ustment output

[0140] 500 recording device

[0141] 501 control device

[0142] 502 communication controller

[0143] 600 ID memory

[0144] 601 comparator

[0145] RCLK reference clock

[0146] CLK clock

[0147] LCLK local reference clock

[0148] DPI , DP2 data packages

[0149] VAL1 VAL2 values

Claims

CLAIMS1. Method for synchronizing a clock signal (CLK) to a reference clock (RCLK) , wherein the clock signal (CLK) is derived from a local master clock (LCLK) and an adjustable multiplication factor; the method comprising the steps : receiving, via a wireless communication interface (100) , a first data package (DPI) , said first data package comprising a first value corresponding to a relative time value derived from the reference clock (RCLK) ; upon receiving the first data package (DPI) , triggering a timer (420) to count events derived from one of the clock signal (CLK) or the local master clock (LCLK) ; decoding the first data package (DPI) to obtain the first value (VAL1) ; receiving via the wireless communication interface (100) , a second data package (DP2) , said second data package (DP2) comprising a second value (VAL2) corresponding to a relative time value derived from the reference clock; upon receiving the second data package triggering the timer (420) to store counted events since a previous triggering of the timer; decoding the second data package (DP2) to obtain the second value (VAL2 ) ; evaluating the first and second values with the stored counted events to obtain deviation in particular a frequency deviation between the reference clock and the clock signal (CLK) ; in response to frequency deviation between the reference clock and the clock signal (CLK) : o Adjusting the multiplication factor to minimize the deviation, if the frequency deviation exceeds a threshold value .

2. Method according to claim 1, wherein the step of triggering the timer upon receiving the first and / or second data package, comprises :triggering the timer during receiving the first and / or second data package and after receiving a first subset of the first and / or the second package ; and / or demodulating a subset of the first and second data package and triggering the timer in response to a comparison result of the subset with a refence pattern; or triggering the timer after the first and / or the second data package have been fully received .3 . Method according to any of the preceding claims , wherein the events correspond to pulses of the clock signal ; or a signal derived from pulses of the clock signals ; or the events correspond to pulses from the local master clock ( LCLK) and an adj ustable multiplication factor .4 . Method according to any of the preceding claims , further comprising : transceiving one or more data packets in accordance with a wireless , packet-oriented communication standard in particular one of Bluetooth, Zigbee and 802 . 11 , wherein the communication standard defines time-slots for transmission or reception of the one or more data packets ; wherein the steps of receiving the first and / or second data package are performed between time slots dedicated or scheduled for transceiving one or more data packets .5 . Method according to any of the preceding claims , wherein the first and second data package each comprise a first data subset having a first bit length and a second data subset having a second bit length, wherein the first and second data subset each comprise a value corresponding to different time stamps , in particularly one of ps and ms .6 . Method according to claim 5 , wherein the first and second bit length are different ; and / or wherein at least one of the bit length corresponds to at least 10 bits .7 . Method according to any of the preceding claims , wherein the step of evaluating the first and second number values comprises :Forming a difference between the second value and the first number value , said difference corresponding to a time interval ;Comparing the difference with the stored counted events , or a value derived therefrom .8 . Method according to any of the preceding claims , wherein in response to frequency deviation between the reference clock signal and the clock signal :Comparing the frequency deviation with a threshold value ;In response to comparing frequency deviation with a threshold value : o If the frequency deviation is smaller than the threshold value , maintaining the multiplication factor; or o If the frequency deviation is between the threshold value and a second threshold value , adj usting the multiplication factor in a single step to minimize the frequency deviation; o If the frequency deviation is larger than the second threshold value , adj usting the multiplication factor in a various steps to minimize the frequency deviation .9 . Method according to claim 8 , further comprising at least one of :Setting a flag indicating the deviation;Storing the second value as first value and replacing the second value with a new value ; and / or storing the counted events as an intermediate count and adding the intermediate count to newly stored counted events ; and utilizing the set flag or the replaced stored second value and the newly stored counted event in a subsequent step of evaluating the first and second values .10 . Transceiver comprising : a local master clock generator ( 400 ) to generate a local master clock ( LCLK) ;an adjustable clock generator (410) to generate a clock signal (CLK) derived from the local master clock (LCLK) and an adjustable multiplication factor (MF) ; a communication interface (100) configured to transceive data packets in accordance with a packet-oriented communication standard in particular one of Bluetooth, Zigbee and 802.11; the communication interface (100) further configured to : o receive a first data package, said first data package comprising a first value corresponding to a relative time value derived from a reference clock (RCLK) ; o upon receiving the first data package (DPI) , triggering a timer (420) to count events derived from one of the clock signal (CLK) or the local master clock (LCLK) ; o decode the first data package (DPI) to obtain the first value (VAL1) ; o receive a second data package (DP2) , said second data package (DP2) comprising a second value (VAL2) corresponding to a relative time value derived from the reference clock (RCLK) ; o upon receiving the second data package (DP2) triggering the timer (420) to store counted events since the previous timer trigger; o decode the second data package (DP") to obtain the second value (VAL2) ; and a control unit (430) configured to o detect a frequency deviation between the reference clock (RCLK) and the clock signal (CLK) based on the first and second number values (VAL1, VAL2 ) and the stored counted events ; o in response to detection of a frequency deviation between the reference clock signal and the clock signal (CLK) : o adjust the multiplication factor (MF) in order to minimize the deviation.

11. Transceiver according to claim 10, wherein the communication interface is configured to:trigger the timer during reception of the first and / or second data package and after receiving a first subset of the first and / or the second package ; and / or demodulate a subset of the first and second data package and trigger the timer in response to a comparison result of the subset with a refence pattern; or trigger the timer after the first and / or the second data package have been fully received .12 . Transceiver according to any of claims 9 to 11 , wherein packet- oriented communication standard defines time slots for transmission or reception of the one or more data packets ; wherein the communication interface is configured to : receive the first and / or second data package between time slots dedicated or scheduled for transmission or reception of the one or more data packets .13 . Transceiver according to any of claims 9 to 12 , wherein the events correspond to pulses of the clock signal ; or a signal derived from pulses of the clock signals ; or the events correspond to pulses from the local master clock and an adj ustable multiplication factor .14 . Transceiver according to any of claims 9 to 13 , wherein the first and second data package each comprise a first data subset having a first bit length and a second data subset having a second bit length, and wherein at least one of the bit length corresponds to at least 10 bits .15 . Transceiver according to any of claims 9 to 14 , wherein the control unit is configured to detect a frequency deviation by :Forming a difference between the second value and the first number value , said difference corresponding to a time interval ; andComparing the difference with the stored counted events , or a value derived therefrom .16 . Transceiver according to any of claims 9 to 15 , wherein in response to frequency deviation between the reference clock signal and the clock signal (CLK) the control unit is configured to :Compare the frequency deviation with a threshold value ;In response to comparing frequency deviation with a threshold value : o If the frequency deviation is smaller than the threshold value , maintain the multiplication factor ; or o If the frequency deviation is between the threshold value and a second threshold value , adj ust the multiplication factor in a single step to minimize the deviation; o If the frequency deviation is larger than the second threshold value , adj ust the multiplication factor in a various steps to minimize the deviation .17 . Transceiver according to any of claims 9 to 15 , wherein the control unit is further configured to at least one of :Set a flag indicating the deviation;Store the first value and replace a new first value with the stored first value and store the counted events as an intermediate count and add the intermediate count to newly stored counted events ; and utilize the set flag or the replaced stored first number and the newly stored counted event to detect a frequency deviation .18 . Transmitter comprising : a reference clock generator ( 150 ) to generate a refence clock ( RCLK) ; a data package generator ( 160 ) coupled to the reference clock generator ( 150 ) to provide a plurality of subsequent data packages ( CLKP ) , each data package including a value based on or derived from said refence clock and corresponding to a time stamp ; a communication interface ( 101 ) configured to transmit and / or receive data packets in accordance with a packet-orientedcommunication standard in particular one of Bluetooth, Zigbee and 802 . 11 ; wherein the communication interface ( 101 ) is configured : o receive the plurality of subsequent data packages provided by the package generator; and o transmit a data package of the plurality of data packages between one of :■ receiving two subsequent data packets in accordance with a packet-oriented communication standard; ■ transmitting two subsequent data packets in accordance with a packet-oriented communication standard; or■ receiving and transmitting data packets in accordance with a packet-oriented communication standard; and ■ transmitting and receiving data packets in accordance with a packet-oriented communication standard .

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