DE102012016087B4 - Method for synchronizing a message receiver with a message sender and synchronization device - Google Patents

Abstract

Method for synchronizing a message receiver with a message sender, with an input signal (3) with a sequence of symbols (5, 6, 11) being received in the message receiver for a message sent by the message sender, with a message beginning in the sequence being searched for for synchronization, characterized in that a recurring amount difference (13) of the input signal (3) is formed with an input signal (8) offset by a period of time, and that the beginning of the message is detected when the difference (13) formed has a detection threshold value (27 ) reached or falls below.

Description

The invention relates to a method for synchronizing a message receiver with a message sender and a synchronization device.

It is known to recognize the beginning of a sent message by sending a synchronization signal at the beginning of the message. This synchronization signal is often composed of at least two consecutive, identical symbols. To recognize the beginning of the message, the synchronization signal is searched for in the received signal by comparing the input signal with a duplicate that has been time-shifted by a previously known value. Such a method is, for example, from US 2004/0005018 A1 known, wherein a correlation of the two signals is determined and compared with a threshold value dependent on the signal strength.

The synchronization signal can also be recognized by monitoring the square of the difference between the received signal or input signal and the time-shifted signal. The identity results when this square is equal to zero.

From the US 2008/0165909 A1 describes a method for synchronizing devices in a wireless network, in which a sum or difference is formed over several symbols and compared with a threshold value.

From the US 2011/0051855 A1 is a method for determining synchronicity, in which a moving average is determined over a certain symbol period.

The invention is based on the object of reducing the computational effort required to recognize the start of a message.

To achieve this object, the features of claim 1 or 4 are provided in a method for synchronizing a message receiver with a message transmitter, and the features of claim 10 are provided in the invention of a synchronization device.

Important features of the invention of a method for synchronizing a message receiver with a message sender, with an input signal with a sequence of symbols being received in the message receiver for a message sent by the message sender, with a message beginning being sought in the sequence for synchronization, are that recurring one The difference in magnitude of the input signal is formed with an input signal that is time-shifted by a period of time and that the beginning of the message is detected when the difference in magnitude that is formed reaches or falls below a detection threshold value, preferably from above. The advantage here is that no multiplications are required for the evaluation. This considerably reduces the computational effort. The invention thus makes use of the knowledge that a sequence of identical symbols can be recognized by recurring, ie successive, subtraction of the current input signal with a time-shifted copy of the input signal. This is because the difference formed is small, for example, if the duration of the time offset is selected to be equal to the distance between the identical symbols.

The recurring execution of the difference formation can be set up and carried out, for example, by a program loop and / or an abort condition.

In an advantageous embodiment, it can be provided that the sent message has at least two identical symbols at the beginning of the message in a synchronization section, which are arranged offset in time with respect to one another by the time period. The message in the synchronization section preferably has two identical symbols which immediately follow one another in a sequence. The advantage here is that a match between the input signal and a time-shifted input signal can be easily identified.

In an advantageous embodiment of the invention, it can be provided that, for the detection of the message start, a recurring amount sum of the input signal and an input signal delayed by the or a further period of time is formed, the message start being detected only if previously or at the same time the amount formed, preferably in terms of amount Sum preferably reaches or exceeds a release threshold value from below. The advantage here is that incorrect detections, which can be triggered, for example, by an identically disappearing message signal, can be avoided. The release threshold value is preferably selected such that it reliably indicates the presence of any input signal.

The difference and the sum are preferably formed from the input signal in parallel or at the same time. The advantage here is that the detection threshold value and the release threshold value can be monitored simultaneously.

In general, a difference in amount is understood to mean a difference to which then the absolute value is calculated in order to eliminate the sign. Likewise, a sum in terms of amount is understood to mean a sum which is freed from the sign by forming the absolute value.

The described use of the absolute sum thus forms a release signal for the detection of the start of the message. If this detection is not released because the sum in terms of amount has not yet met the stated condition, it can be provided that reaching or falling below the detection threshold value due to the difference does not trigger detection of the start of the message.

In an advantageous embodiment of the invention, it can be provided that the detection threshold value is established as a fraction of the currently formed sum. The advantage here is that an adaptive condition is defined, which can be based on the transmission properties between the message sender and message recipient.

In an advantageous embodiment, it can be provided that the difference and / or the sum is / are formed with a sampling rate which resolves time intervals shorter than a length of the symbols. The advantage here is that a quasi-continuous or continuous calculation of the difference and / or the sum is made possible, so that the beginning of a message can be detected without a complete symbol having to be received.

As an alternative, important features of the invention of a method for synchronizing a message receiver with a message sender are that an input signal with a sequence of symbols is received in the message receiver for a message sent by the message sender Message at the beginning of the message has a synchronization section with three symbols, with two consecutive symbols of the three symbols of the synchronization section being identical to one another and two consecutive symbols of the three symbols being inverted to one another, and that the beginning of the message is detected if the input signal in a section with a coincides with an input signal that is time-shifted by a period of time. The advantage here is that the described configuration of the synchronization section defines a sequence of symbols which, on the one hand, enables simple detection of the beginning of the message by searching for matching symbols and, on the other hand, reduces false detections due to interference. It has been found that such interferences often occur at higher frequencies, so that such interferences generally do not form a synchronization section which would then be incorrectly recognized. The section and the synchronization section are preferably selected to be of equal length.

In the alternative embodiment according to the invention it is provided that in a first step of the detection of the beginning of the message it is repeatedly checked for the input signal whether the preferably absolute sum of the input signal and an input signal offset by a period of time from the input signal is the or a release threshold value, preferably from below reached or exceeded. The advantage here is that, in the method according to the invention, a condition can be defined with which the actual detection of the beginning of the message can be started or triggered.

In an advantageous embodiment of the invention it can be provided that in a second step of the detection of the beginning of the message it is repeatedly checked whether the or a preferably absolute difference between the input signal and an input signal offset by a period of time is the or a detection threshold value, preferably of reached above or below. The advantage here is that the already described recognition of the beginning of the message can be implemented in a computationally simple manner. The start of a message, which is characterized by a number of symbols that are identical to one another, can thus be detected in a simple manner by monitoring the difference in the signal with its time-shifted copy.

In an advantageous embodiment it can be provided that in a third step of the detection of the beginning of the message it is checked whether the preferably absolute sum of the input signal and one of the input signal reaches or exceeds one or the confirmation threshold value, preferably from below. The advantage here is that incorrect detections can be reduced by defining and verifying a confirmation condition.

In an advantageous embodiment of the invention, it can be provided that the detection threshold value is defined by a fraction of the preferably absolute sum of the input signal and an input signal that is offset in time with respect to the input signal by a period of time. The advantage here is that an adaptive operation is defined, which automatically adapts to the signal strength.

In an advantageous embodiment of the invention, it can be provided that the first step is carried out if the result is obtained in the third step the test is negative. The advantage here is that the detection of the message detection is aborted if the confirmation in the third step is missing and therefore no complete detection has been carried out.

In an advantageous embodiment of the invention, it can be provided that the detected beginning of the message is confirmed if the test in the third step is positive. The advantage here is that additional security is created to avoid false detections, for example due to external interference signals.

In an advantageous embodiment of the invention, it can be provided that the confirmation threshold value is defined by a fraction of the difference in absolute value between the input signal and an input signal that is offset in time with respect to the input signal by a period of time. The advantage here is that an adaptive condition is formulated for the third step, which can automatically adapt to the signal strength of the input signal and thus to the transmission properties between the message sender and message receiver.

In an advantageous embodiment of the invention, it can be provided that the duration is at least equal to a length of a symbol. It is particularly favorable if the time period for the offset between the input signal and a copy of the input signal is equal to the length of the symbol. The advantage here is that a sequence of identical symbols can be identified in a simple manner, since the time-shifted input signal assumes a value at any point in time which belongs to an adjacent symbol with respect to the current symbol of the unmoved input signal.

In an advantageous embodiment of the invention, it can be provided that the difference and / or the sum are formed as sliding mean values, preferably over the period of time. The advantage here is that the influence of interference is reduced.

In an advantageous embodiment of the invention, it can be provided that the input signal is an FDM or OFDM signal. The advantage here is that sinusoidal symbols can be used, which can be transmitted inductively better than square-wave pulses.

Important features of the invention in a synchronization device for synchronizing a message receiver with a message sender, with a signal input for an input signal with a message composed of a sequence of symbols, and a comparison unit for signaling the beginning of a message, are that a differential element for forming and providing an absolute value Difference of the input signal with an input signal offset by a period of time is set up as an output signal of the difference element and that the comparison unit is set up to signal the start of the message when the output signal of the difference element reaches or falls below a detection threshold value, preferably from above. The advantage here is that a synchronization device that can be implemented with comparatively little circuitry complexity and with which the beginning of a message can be recognized in an input signal is created.

In an advantageous embodiment of the invention, it can be provided that the summation element comprises an absolute value diagram which is set up to form an absolute value. The advantage here is that it can be easily achieved that symbols and inverted symbols are treated equally.

In an advantageous embodiment of the invention, it can be provided that the difference element comprises a difference former, which is set up to form a difference between the input signal and the time-shifted input signal. For example, the difference generator can be implemented by an adder or sum generator, at one input of which an inverter is connected upstream. The advantage here is that the difference in amount can be formed continuously or at least at a sampling rate with which time intervals can be resolved that are less than a symbol duration, in particular less than half a symbol duration or less than a quarter of the symbol duration or less than a tenth of the symbol duration or less than a hundredth of the symbol duration. A synchronization device is thus created with which the method according to the invention can be carried out without having to read in complete symbols in the form of blocks.

In an advantageous embodiment of the invention, it can be provided that the signal input is routed to two branches, a time delay element being arranged in one branch of the two branches. The advantage here is that a time shift of the input signal with respect to a copy of the input signal for carrying out the method according to the invention can be implemented in a simple manner. For this purpose, the synchronization device advantageously has a branch in order to route the signal input to the two branches.

In an advantageous embodiment of the invention, it can be provided that a summation element for forming and providing a Sum of the input signal in terms of amount is set up with the input signal or an input signal offset in time by the or a period of time as the output signal of the summing element. The advantage here is that the synchronization device can be set up to check whether the absolute sum of the input signal and the time-shifted input signal reaches or exceeds a release threshold value, preferably from below. It is thus possible to release the test as to whether the difference in amount preferably reaches or falls below the detection threshold value from above.

In general, it can be said that it is beneficial if the release threshold value is greater than the detection threshold value.

In an advantageous embodiment of the invention, it can be provided that the summing element comprises an amount generator which is set up to form and provide an absolute value as the output signal of the summing element. The advantage here is that the input signal and its inversion can be treated in the same way.

In an advantageous embodiment, it can be provided that the two branches are routed to the difference element and / or to the sum element. The advantage here is that the input signal or time-shifted input signal generated or transmitted in the branches can be made available for further processing.

In an advantageous embodiment of the invention, it can be provided that the or a further comparison unit is set up to check the or an output signal of the summing element for reaching or exceeding a release threshold value. The advantage here is that a release of the checking of the difference in order to detect the beginning of a message can be triggered if the second threshold value is preferably reached or exceeded from below.

In an advantageous embodiment of the invention, provision can be made for a release device to be set up to release the signaling when the output signal of the summing element reaches or exceeds a release threshold value, preferably from below. The advantage here is that an automated release can be implemented.

In an advantageous embodiment of the invention, it can be provided that mean value images are set up to form a sliding mean value of the output signal of the difference element and / or the output signal of the summation element. The advantage here is that the signals to be processed can be smoothed in order to reduce interference.

Further advantages result from the subclaims. For the person skilled in the art, there are further sensible possible combinations of claims and / or individual claim features and / or features of the description and / or the figures, in particular from the task and / or the task posed by comparison with the prior art.

The invention will now be described in more detail using an exemplary embodiment, but is not limited to this exemplary embodiment. Further exemplary embodiments result from the combination of the features of individual or several protection claims with one another and / or with individual or several features of the exemplary embodiment.

• 1: ein Datenflussdiagramm eines Verfahrens nach dem Stand der Technik,
• 2: eine Prinzipskizze zur Erläuterung des Datenflusses gemäß 1,
• 3: eine stark vereinfachte Prinzipskizze einer erfindungsgemäßen Synchronisationseinrichtung und
• 4: eine schematische Darstellung zur Erläuterung der Funktionsweise der Synchronisationseinrichtung gemäß 3 und des erfindungsgemäßen Verfahrens.

It shows:

• 1 : a data flow diagram of a method according to the prior art,
• 2 : a schematic diagram to explain the data flow according to 1 ,
• 3 : a greatly simplified schematic diagram of a synchronization device according to the invention and
• 4th : a schematic representation to explain the functioning of the synchronization device according to FIG 3 and the method according to the invention.

1 shows the data flow diagram of a synchronization device known from the prior art 1 .

At the synchronization device 1 is connected to a signal input 2 an input signal 3 received or provided, which in 2 is shown in more detail.

The input signal 3 points according to 2 in a synchronization section 4th a sequence of two identical symbols 5 , 6th on.

In the known synchronization device 1 according to 1 becomes from the input signal 3 (A) with a time delay element 7th a time-delayed input signal 8th (B) generated which is opposite to the input signal 3 about the length 9 of a symbol 5 , 6th is delayed.

From the input signal 3 and the time-delayed input signal 8th are in the in 1 shown way on the one hand the sum of the squares of the signals A and B and on the other hand the product AB of the input signal 3 with the delayed input signal 8th calculated, whereby the calculated quantities are treated as complex quantities.

The beginning of the message is according to the known method 1 and 2 detected when on the one hand the sum of the squares, A ² + B ² , exceeds a threshold value and, on the other hand, the difference between the sum of the squares and twice the product of the input signal with the time-delayed input signal, 2AB *, falls below a threshold value.

In this case the beginning of the message is indicated by two identical symbols 5 , 6th is marked one on the other in chronological order, detected.

The required data flow plan in 1 shows that complex arithmetic operations are required to carry out the method. In particular, two signals are to be multiplied with one another.

The invention drastically reduces the computational effort.

3 shows a synchronization device according to the invention in a greatly simplified, schematic representation 1 . In order to simplify the representation, individual components of the synchronization device were used 1 summarized or omitted entirely.

The synchronization device according to the invention 1 receives via a signal input 2 an input signal 3 (A), which is in 4th is shown by way of example.

In 4th can be seen that the input signal 3 from a sequence of symbols 5 , 6th , 7th and further symbols not shown further.

The input signal 3 can here in an analog-to-digital converter 9 from one at the signal input 2 applied signal must be generated.

The input signal 3 points in a synchronization section 4th two identical symbols 5 , 6th on that to each other by a length 9 of a symbol are offset in time and thus arranged one after the other.

The synchronization section 4th also has two symbols 6th , 11th which also follow one another and which are inverted to one another.

In the synchronization device 1 according to 3 becomes in a time delay element 7th from the input signal 3 a time-delayed input signal 8th (B) generated.

The delayed input signal 8th is thus a copy of the input signal 3 and differs from this only in that the symbols 5 , 6th , 11th in the delayed input signal 8th about the length 9 of a symbol are time shifted. The duration of this time shift can be determined by the exponent n in the time delay element 7th can be set as required.

The input signal 3 and time-shifted input signal 8th become, as in 3 shown, a differential term 12th supplied, in which an amount difference 13th , | AB |, from the input signal 3 (in 3 and 4th symbolically "A") and the time-delayed input signal 8th (in 3 and 4th symbolically represented by "B").

To this end, the differential element 12th an amount image 14th with which an absolute value can be formed.

To this end, the differential element 12th further a difference image 15th with which the described difference can be formed. The difference images 15th is the amount images 14th upstream in the data flow.

The difference images 15th is in 3 realized by an inverter at one input and a summation or adder. In further exemplary embodiments, the difference image can be implemented in a different way and / or with the amount image 14th in an integrated differential element 12th be implemented.

In 3 it can be seen that to calculate this difference, the input signal 3 on two branches 16 , 17th is split, being in the branch 17th the time delay element 7th arranged while in the branch 16 the input signal 3 is continued without delay. Both branches 16 , 17th become the differential term 12th supplied on the input side.

The synchronization device 1 according to 3 additionally has a summation term 18th on, which for the formation and provision of a sum in terms of amount 19th , | A + B |, from the input signal 3 and the time-delayed input signal 8th is set up.

The summation term 18th points to a sum image 20th and an amount image 21 on. The sum pictures 20th is the amount images 21 upstream in the data flow.

The amount images 21 is analogous to the amount images 14th set up during the summing images 20th - with the exception of the inversion described - analogous to the difference image 15th is set up.

The branches already mentioned 16 , 17th are also the sum term 18th supplied on the input side. In further exemplary embodiments, for the differential element 12th and the summation term 18th separate time delay elements 7th be trained.

In 3 it can be seen that the difference in amount 13th as an output signal 22nd at the exit 23 of the differential term 12th is provided.

The sum in terms of amount 19th is as an output signal 24 at an exit 25th of the summation term 18th provided.

A comparison unit (not shown) can be used to check whether the output signal 22nd a detection threshold 27 reaches or falls below the output signal 24 a release threshold 26th or exceeds and / or whether the output signal 22nd a confirmation threshold 28 reached or exceeded.

• Die Ausgangssignale 22, 24 werden in der Synchronisationseinrichtung 1 kontinuierlich oder nahezu kontinuierlich, jedenfalls mit einer Abtastrate, die eine Auflösung von Zeitabständen erlaubt, die deutlich kürzer als die Länge 9 der Symbole ist, aus dem Eingangssignal 3 gebildet.

In the synchronization device, the method according to the invention runs as follows:

• The output signals 22nd , 24 are in the synchronization facility 1 continuously or almost continuously, at least with a sampling rate that allows a resolution of time intervals that are significantly shorter than the length 9 of symbols is from the input signal 3 educated.

In a first step, it is repeatedly checked, that is, sequentially in time, for example in a loop, whether the output signal 24 , that is, the sum in terms of amount 19th , a release threshold 26th reached from below.

This is in 4th , in which the signal strengths of the output signals 22nd , 24 are marked in three stages in increasing signal strength with "0", "+" and "++" at the time I. the case.

The synchronization device recognizes this at this point in time 1 hence the fact that a message was sent at all that initially had a non-zero symbol 5 contains, as the time-delayed input signal 8th does not have a symbol at this point in time.

Until then I. has the synchronization device 1 the test for the release threshold value 26th already carried out several times.

After reaching the release threshold 26th by the amount 19th gives a release device, not shown, the signaling, which indicates whether the output signal 22nd a detection threshold 27 falls below, free.

After the release is in the synchronization device 1 in a second step of the detection of the beginning of the message, it is repeatedly checked whether the output signal 22nd , i.e. the difference in amount 13th , a detection threshold 27 reached or fallen below from above.

In the representation according to 4th is this at the time II the case.

At this point in time the output signal is received 22nd the difference in amount of the identical symbols 5 and 6th and is therefore equal to zero.

In general, it can be said that the detection threshold 27 less than the release threshold 26th is.

For example, the detection threshold 27 by a quarter of the output signal 24 , | A + B |, while the release threshold is defined by a fixed numerical value. The by the detection threshold 27 The defined condition is then for example | AB | <c ₁ * | A + B |, c ₁ = 1/4 or another numerical value, while the condition defined by the release threshold is for example | A + B |> C ₂ with a suitable value for C2.

As soon as the detection threshold 27 by the output signal 22nd is reached from above, the synchronization device 1 the identical symbols 5 , 6th at the synchronization section 4th recognized which is the beginning of the message in the input signal 3 Show.

In a third step, the output signal is now again 24 evaluated, and it is checked whether the output signal 24 below a confirmation threshold 28 falls.

This confirmation threshold 28 is again lower than the release threshold 26th chosen. For example, the confirmation threshold 28 equal to a quarter of the current output signal 22nd be chosen. The through the confirmation threshold 28 The defined condition is then, for example, | A + B | <c ₃ * | AB |, with c ₃ = 1/4 or another numerical value.

Becomes the confirmation threshold 28 reached from above, this is a sign that on the symbol 6th an inverted symbol 11th followed, so that incorrect signaling, which would be triggered by identical symbols occurring at random, can be avoided.

The signaling of the beginning of the message is therefore only confirmed when the output signal 24 the confirmation threshold 28 has achieved what in 4th at the time III the case is.

With the symbols 5 , 6th , 11th it can be voltage levels such as those used in the CAN protocol, for example. With the symbols 5 , 6th , 11th it can also be sinusoidal signals, such as those used, for example, in multi-frequency methods such as OFDM (Orthogonal Frequency-Division Multiplexing). Here, the inverted symbol can be formed by a phase shift by 180 ° or by inverting the signal level with respect to a zero value or in some other way.

the end 4th it can also be seen that for evaluating the output signals 22nd , 24 Moving averages (solid lines) are formed, each of which covers a period of time that is at least equal to the length 9 of a symbol. The moving averages, in the example from | AB | and from | A + B |, can be passed on as smoothed output signals to the mentioned comparison unit for threshold value monitoring.

At the synchronization device 1 To synchronize a message receiver with a message sender, it is proposed to use an input signal received from the message sender 3 and an input signal that is delayed at this point 8th an output signal 22nd provide and monitor which is a difference in amount 13th of the input signal 3 to the time-delayed input signal 8th describes, with a message beginning with at least two identical symbols 5 , 6th containing synchronization section 4th is detected when the output signal 22nd a detection threshold 27 reaches or falls below.

List of reference symbols

1

Synchronization device

2

Signal input

3

Input signal

4th

Synchronization section

5, 6

symbol

7th

Time delay element

8th

time-shifted input signal

9

Length of a symbol

10

Analog-to-digital converter

11th

symbol

12th

Differential term

13th

difference in amount

14th

Amount images

15th

Difference images

16, 17

branch

18th

Sum term

19th

amount in terms of amount

20th

Sum images

21

Amount images

22nd

Output signal

23

exit

24

Output signal

25th

exit

26th

Release threshold

27

Detection threshold

28

Confirmation threshold

I, II, III

Points in time

Claims (15)

Method for synchronizing a message receiver with a message sender, whereby an input signal (3) with a sequence of symbols (5, 6, 11) is received in the message receiver for a message sent by the message sender, with a message beginning in the sequence being searched for for synchronization, characterized in that a recurring amount difference (13) of the input signal (3) is formed with an input signal (8) offset by a period of time, and that the beginning of the message is detected when the difference (13) formed has a detection threshold value (27 ) reached or falls below. Procedure according to Claim 1 , characterized in that the sent message at the beginning of the message in a synchronization section (4) has at least two identical symbols (5, 6) which are arranged offset from one another by the time period, preferably two identical symbols (5, 6) immediately following one another in the sequence , and / or that for the detection of the beginning of the message a recurring sum (19) of the input signal (3) and an input signal (8) delayed by the or a further time period is formed, the beginning of the message being detected only if previously or at the same time, the total amount (19) formed reaches or exceeds a release threshold value (26). Method according to one of the preceding claims, characterized in that the detection threshold value (27) is set as a fraction of the currently formed sum (19) and / or that the difference (13) and / or sum (19) is formed with a sampling rate will / become, which resolves shorter time intervals than a length (9) of the symbols. Method for synchronizing a message receiver with a message sender, with an input signal (3) with a sequence of symbols (5, 6, 7) being received in the message receiver for a message sent by the message sender, with a message beginning being searched for for synchronization purposes, characterized in that the message sent has a synchronization section (4) with three symbols (5, 6, 7) at the beginning of the message, two consecutive symbols (5, 6) of the three symbols (5, 6, 11) of the synchronization section (4 ) are identical to one another and two consecutive symbols (6, 11) of the three symbols (5, 6, 11) are inverted to one another, so that a recurring difference (13) of the input signal (3) with an input signal ( 8) is formed and that the beginning of the message is detected when the input signal (3) with a by a time da coincides with the time-shifted input signal (8). Method according to one of the preceding claims, characterized in that in a first step of the detection of the beginning of the message, it is repeatedly checked whether the sum (19) of the input signal (3) and an input signal that is offset in time with respect to the input signal (3) by or by a period of time (8) reaches or exceeds a release threshold value, and / or that in a second step of the detection of the beginning of the message it is repeatedly checked whether the or an absolute difference (13) between the input signal (3) and the input signal (3) is around a time-delayed input signal (8) reaches or falls below a detection threshold value (27). Method according to one of the preceding claims, characterized in that, in a third step of the detection of the beginning of the message, it is checked whether the sum (19) of the input signal (3) and an input signal (8) that is offset by a period of time with respect to the input signal (3) reaches or exceeds a confirmation threshold value (28) and / or that the detection threshold value (27) is represented by a fraction of the sum (19) of the input signal (3) and an input signal (8 ) is defined. Method according to one of the preceding claims, characterized in that the first step is carried out if the result of the test is negative in the third step and / or that the detected message beginning is confirmed if the test in the third step is positive. Method according to one of the preceding claims, characterized in that the confirmation threshold value (28) is defined by a fraction of the absolute difference (13) between the input signal (3) and an input signal (8) offset by a period of time from the input signal (3) and / or that the duration is at least equal to a length (9) of a symbol (5, 6, 11), in particular is equal to the length (9) of the symbol (5, 6, 11). Method according to one of the preceding claims, characterized in that the difference (13) and / or the sum (19) are formed as sliding mean values, preferably over the period, and / or that the input signal is an OFDM signal. Synchronization device (1) for synchronizing a message receiver with a message sender, with a signal input (2) for an input signal (3) with a message composed of a sequence of symbols (5, 6, 11), and a comparison unit for signaling the start of a message, thereby characterized in that a difference element (12) is set up to form and provide an absolute difference (13) of the input signal (3) with an input signal (8) offset by a period of time as an output signal (22) of the difference element (12) and that the comparison unit is set up to signal the beginning of the message when the output signal (22) of the differential element (12) reaches or falls below a detection threshold value (27). Synchronization device (1) according to Claim 10 , characterized in that the difference element (12) comprises an amount generator (14) which is set up to form an absolute value, and / or that the difference element (12) comprises a difference element (15) which is used to form a difference in the input signal (8 ) is set up for the time-shifted input signal (8). Synchronization device (1) according to Claim 10 or 11th , characterized in that the signal input (2) is routed to two branches (16, 17), a time delay element (7) being arranged in one branch (17) of the two branches (16, 17). Synchronization device (1) according to one of the Claims 10 until 12th , characterized in that a summing element (18) is set up to form and provide an absolute sum (19) of the input signal (3) with the or an input signal (8) delayed by the or a period of time as the output signal (24) of the summing element (18) and / or that the summation element (18) comprises an amount generator (21) which is set up to generate and provide an absolute value as an output signal (24) of the summation element (18). Synchronization device (1) according to one of the Claims 10 until 13th , characterized in that the two branches (16, 17) are led to the differential element (1) and / or to the summing element (18) and / or that the or a further comparison unit for checking the or an output signal (24) of the summing element (18) is set up to reach or exceed a release threshold value (26). Synchronization device (1) according to one of the Claims 10 until 15th , characterized in that a release device is set up to release the signaling when the output signal (24) of the summing element (18) reaches or exceeds the release threshold value (26) and / or that mean value images for forming a moving mean value of the output signal (22) of the differential element (12) and / or the output signal (24) of the summing element (18) are set up.

Images