Description

The present invention relates to an apparatus and a method which generate or receive a synchronization header.

In most communication systems, bursty transmissions occur. This means, over time there are quiet gaps, where no data is sent, and then, data bursts occur, where payload is transported.

For a plurality of communication systems and communication applications, it is desirable that a receiver recovers timing at the beginning of a data burst.

The object of the present invention is to provide improved concepts for data communication. The object of the present invention is solved by an apparatus according to claim 1 , by an apparatus according to claim 48, by a system according to claim 91 , by a method according to claim 92, by a method according to claim 93, by a computer program according to claim 94 and by a data stream according to claim 95.

An apparatus for generating a data stream according to an embodiment is provided. The apparatus is configured to generate the data stream, such that the data stream comprises header data and payload data. The apparatus is configured to generate the header data such that the header data comprises a synchronization header. Moreover, the apparatus is configured to generate the synchronization header using binary coding. Furthermore, the apparatus is configured to generate the synchronization header such that the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits.

Moreover, an apparatus for receiving a data stream according to an embodiment is provided. The data stream comprises header data and payload data. The header data comprises a synchronization header. The synchronization header is binary encoded, wherein the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits. The apparatus is configured to obtain the payload data of the data stream using the synchronization sequence of the synchronization header of the data stream. Furthermore, a system is provided. The system comprises an apparatus according for generating a data stream and an apparatus for receiving the data stream. The apparatus for generating the data stream is configured to generate the data stream, such that the data stream comprises header data and payload data. Moreover, the apparatus for generating the data stream is configured to generate the header data such that the header data comprises a synchronization header. Furthermore, the apparatus for generating the data stream is configured to generate the synchronization header using binary coding, wherein the apparatus for generating a data stream is configured to generate the synchronization header such that the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits. The apparatus for receiving the data stream is configured to obtain the payload data of the data stream using the synchronization sequence of the synchronization header of the data stream.

Moreover, a method for generating a data stream according to an embodiment is provided. The method comprises generating the data stream, such that the data stream comprises header data and payload data. Generating the header data is conducted such that the header data comprises a synchronization header. Generating the synchronization header is conducted using binary coding. Generating the synchronization header is conducted such that the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits.

Furthermore, a method for receiving a data stream according to an embodiment is provided. The data stream comprises header data and payload data. The header data comprises a synchronization header. The synchronization header is binary encoded, wherein the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits. The method comprises obtaining the payload data of the data stream using the synchronization sequence of the synchronization header of the data stream.

Moreover, computer programs are provided, wherein each of the computer programs is configured to implement one of the above-described methods when being executed on a computer or signal processor.

Furthermore, a data stream comprising header data and payload data according to an embodiment is provided. The header data comprises a synchronization header. The synchronization header is binary encoded. Moreover, the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits.

In the following, embodiments of the present invention are described in more detail with reference to the figures, in which:

Fig. 1 illustrates an apparatus for generating a data stream according to an embodiment.

Fig. 2 illustrates an apparatus for receiving a data stream according to an embodiment.

Fig. 3 illustrates a system according to an embodiment.

Fig. 4 illustrates an example of a synchronization sequence in a PAM representation according to an embodiment.

Fig. 5 illustrates the synchronization sequence of the embodiment depicted by Fig.

4 in a 0/1 representation.

Fig. 6 illustrates a version of a sync header, with first insertion and PRBS around it with doubled bits according to an embodiment.

Fig. 7 illustrates a version of a sync header, with first insertion with doubled bits according to another embodiment.

Fig. 8 illustrates a version of a sync header, with all insertions with single bits only, but whole sequence repeated, according to a further embodiment.

Fig. 1 illustrates an apparatus 100 for generating a data stream according to an embodiment.

The apparatus 100 is configured to generate the data stream, such that the data stream comprises header data and payload data. The apparatus 100 is configured to generate the header data such that the header data comprises a synchronization header. Moreover, the apparatus 100 is configured to generate the synchronization header using binary coding.

Furthermore, the apparatus 100 is configured to generate the synchronization header such that the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization sequence which comprises a number of bits, such that a total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the synchronization sequence is greater than or equal to 35 % of the number of the bits of the synchronization sequence.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization sequence such that the total number of transitions within the synchronization sequence is greater than or equal to 50 % of the number of the bits of the synchronization sequence.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises a pseudo-random binary sequence.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization sequence, which comprises a first number of bits, such that a first ratio of a first total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the synchronization sequence to the first number of bits is greater than a second ratio of a second total number of transitions from the first bit value to the second bit value, and from the second bit value to the first bit value within the pseudorandom binary sequence, which comprises a second number of bits, to the second number of bits.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the pseudorandom binary sequence by employing a linear feedback shift register.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the pseudo-random binary sequence such that the pseudo-random binary sequence is different from the synchronization sequence.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the pseudo-random binary sequence (PRBS) only partially by starting with a defined seed value and running for a predefined number of shifts before resetting to the seed value. The seed value and the run length may, for example, be chosen in such a way, that the longest same symbol run lengths close to the PRBS order are not included in the used fragment of PRBS. This avoids longer dead times for the CDR while still providing high variability in the bit pattern.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the pseudorandom binary sequence which comprises a number of bits, such that a total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the pseudo-random binary sequence is greater than or equal to 15 % of the number of the bits of the pseudo-random binary sequence. For example, the sequence 0001110001 comprises 10 bits, two transitions from 0 to 1 and one transition from 1 to 0, i.e. , a total number of transitions of 3. In this example of the sequence 0001110001 , the total number of transitions is not greater than or equal to 30 % of the number of bits of the sequence (in fact, it is 30 % = 3 / 10).

In another example, the sequence 0101010101 comprises 10 bits, five transitions from 0 to 1 and four transitions from 1 to 0, , i.e., a total number of transitions of 9. In this example of the sequence 0101010101 is greater than or equal to 30 % of the number of bits of the sequence (in fact, it is 90 % = 9 / 10).

For example, the synchronization sequence illustrated by Fig. 4 or Fig. 5 has 40 bit values and a total number of 21 transitions (10 transitions from -1 to +1 / from 0 to 1, and 11 transitions from +1 to -1 / from 1 to 0). This results in a total number of transitions to number of bits value of 21 / 40 = 52,5 %.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the pseudo-random binary sequence such that the total number of transitions within the pseudo-random binary sequence is greater than or equal to 30 % of the number of the bits of the pseudo-random binary sequence.

To find a synchronization sequence by correlation efficiently, the portions near the synchronization sequence (here, e.g., the PRBS-base sequence) should have a different density of transitions compared to the synchronization sequence. A high density may, e.g., come together with short (sub)sequences of same symbols, and many repetitions may, e.g., occur, such that the portions of the base sequence resemble the synchronization sequence to a higher degree. Additionally, with high density of transitions, much energy is concentrated in a narrow frequency band what results in a higher energy emission.

In an embodiment, a 40 bits synchronization sequence, e.g., the 40 bits synchronization sequence of Fig. 4 and Fig. 5 may, e.g., be dithered, to avoid that too much energy is emitted.

According to an embodiment, for example, PRBS10 to PRBS30 may, e.g., be employed for the pseudo-random binary sequence. A PRBS10 generates a sequence of length 2 ¹⁰ -1 of pseudo random values. Afterwards, the sequence generates the same previous values again (repeats the previous values).

A PRBS30 generates a sequence of length 2 ³⁰ -1 of pseudo random values. Afterwards, the sequence generates the same previous values again (repeats the previous values).

In general, a PRBSx generates a sequence of length 2 ^X -1 of pseudo random values. Afterwards, the sequence generates the same previous values again (repeats the previous values).

In an embodiment, the pseudo-random binary sequence may, e.g., be a selected pseudorandom binary sequence, and the apparatus 100 may, e.g., be configured to generate an initial pseudo-random binary sequence and to select a portion of the initial pseudo-random binary sequence, being smaller than the initial pseudo-random binary sequence, as the selected pseudo-random binary sequence. This has the advantage that a PRBSx with a larger than necessary x may, e.g., be employed, such that more randomness is created in the final selected PRBS.

For example, in an embodiment, a portion of a PRBS19 sequence may, e.g., be used, wherein the PRBS 19 sequence may, e.g., be different from a sequence comprising 19 succeeding 1 values (and, e.g., different from a sequence comprising 19 succeeding 0 values). In general, enough transitions will result while, at the same time, in general, enough variability will be present in the sequence. Thus, a compromise between fast-locking CDR and low emission is achieved.

In an embodiment, the apparatus 100 may, e.g., be configured to assign a bit of the pseudorandom binary sequence to a bit position of the synchronization header where the apparatus 100 may, e.g., be configured to insert a bit of the synchronization sequence, but may, e.g., be configured to not insert said bit of the pseudo-random binary sequence into the synchronization header.

According to an embodiment, the apparatus 100 may, e.g., be configured to stop using bits of the pseudo-random binary sequence when the apparatus 100 inserts bits of the synchronization sequence into the synchronization header. The apparatus 100 may, e.g., be configured to continue to insert a next bit of the pseudo-random binary sequence into the synchronization header, after the apparatus 100 has inserted the bits of the synchronization sequence into the synchronization header.

In an embodiment, the apparatus 100 may, e.g., be configured to insert a doubling or tripling of each of two or more bits of the pseudo-random binary sequence into the synchronization header.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises the synchronization sequence at least twice, e.g., such that the synchronization header comprises the synchronization sequence at least twice.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises the synchronization sequence more than twice.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header may, e.g., comprise the synchronization sequence at a beginning of the synchronization header, and such that the synchronization header may, e.g., comprise the synchronization sequence at an end of the synchronization header.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises the synchronization sequence two times, concatenated, at the beginning of the synchronization header, and two times, concatenated, at the end of the synchronization header. In other words, at the beginning of the synchronization header, the synchronization header comprises a concatenation of two synchronization sequences, and at the end of the synchronization header, the synchronization header comprises also a concatenation of two synchronization sequences.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that a second appearance of the synchronization sequence occurs immediately after a first appearance of the synchronization sequence within the synchronization header. In an embodiment, the synchronization sequence may, e.g., be a first synchronization sequence. The apparatus 100 may, e.g., be configured to generate the header data such that the header data comprises the first synchronization sequence and a second synchronisation sequence, the second synchronization sequence being different from the first synchronization sequence.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises the first synchronization sequence and the second synchronization sequence.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header which comprises a number of bits, such that a total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the synchronization header is greater than or equal to 15 % of the number of the bits of the synchronization header.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the total number of transitions within the synchronization header is greater than or equal to 30 % of the number of the bits of the synchronization header.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises a predefined short code.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the predefined short code is 8B10B and 4B5B.

In an embodiment, the apparatus 100 may, e.g., be configured to generate a first version of the synchronization sequence by doubling or tripling each bit of an initial sequence, and wherein the apparatus 100 may, e.g., be configured to generate the header data such that the synchronization header comprises the first version of the synchronization sequence.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the header data such that the synchronization header furthermore comprises a second version of the synchronization sequence, wherein the second version of the synchronization sequence is equal to the initial sequence.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the header data such that the first version of the synchronization sequence precedes the second version of the synchronization sequence within the header data.

According to an embodiment, the apparatus 100 may, e.g., be configured to obtain the synchronization sequence from the initial sequence by changing positions of bits of the initial sequence.

In an embodiment, the apparatus 100 may, e.g., be configured to change the positions of the bits of the initial sequence depending on a defined waveform.

According to an embodiment, the defined waveform may, e.g., have a triangle shape or may, e.g., be a sine wave or may, e.g., have a rectangular shape or may, e.g., have a sawtooth shape.

In an embodiment, the apparatus 100 may, e.g., be configured to employ a clocked digital waveform for changing the positions of the bits of the initial sequence.

According to an embodiment, the apparatus 100 may, e.g., be configured to change the positions of the bits of the initial sequence depending on a pseudo-random signal.

In an embodiment, the apparatus 100 may, e.g., be configured to change the positions of the bits of the initial sequence depending on a multiplication factor wherein the multiplication factor depends on how many times the synchronization sequence has already been inserted by the apparatus 100 into the header data.

According to an embodiment, for a second insertion of the synchronization sequence into the synchronization header, a second value of the multiplication factor may, e.g., be half of a first value of the multiplication factor used for a first insertion of the synchronization sequence into the header data.

In an embodiment, the first value of the multiplication factor may, e.g., be 2, and wherein the second value of the multiplication factor may, e.g., be 1. According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises a predefined field into the synchronization header to indicate that the synchronization header has a predefined length.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises an information field having a predefined length, wherein the information field comprises additional information.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the data stream such that the synchronization header of the data stream precedes the payload data of the data stream within the data stream.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the data stream such that the payload data is binary encoded.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the data stream such that the payload data is multi-level encoded.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header has a predefined length.

According to an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises two or more predefined header fields.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the data stream using pulse amplitude modulation.

According to an embodiment, the apparatus 100 may, e.g., be configured to transmit the data stream to a receiver.

In an embodiment, the apparatus 100 may, e.g., be configured to transmit the data stream via a shared medium. According to an embodiment, the apparatus 100 may, e.g., be suitable for being employed in an automotive environment or in an aerospace environment.

Fig. 2 illustrates an apparatus 200 for receiving a data stream according to an embodiment.

The data stream comprises header data and payload data. The header data comprises a synchronization header. The synchronization header is binary encoded, wherein the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits.

According to an embodiment, the synchronization sequence may, e.g., comprise a number of bits. A total number of transitions a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the synchronization sequence may, e.g., be greater than or equal to 35 % of the number of the bits of the synchronization sequence.

In an embodiment, the total number of transitions within the synchronization sequence may, e.g., be greater than or equal to 50 % of the number of the bits of the synchronization sequence.

According to an embodiment, the synchronization header may, e.g., comprise a pseudorandom binary sequence.

In an embodiment, the synchronization sequence may, e.g., comprise a first number of bits.

A first ratio of a first total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the synchronization sequence to the first number of bits, may, e.g., be greater than a second ratio of a second total number of transitions from the first bit value to the second bit value, and from the second bit value to the first bit value within the pseudorandom binary sequence, which comprises a second number of bits, to the second number of bits.

According to an embodiment, the apparatus 200 may, e.g., be configured to synchronize a clock timing using the synchronization sequence of the synchronization header of the data stream. The apparatus 200 may, e.g., be configured to obtain the payload data of the data stream using the using the clock timing.

In an embodiment, the apparatus 200 may, e.g., be configured to synchronize a phase of a sampling clock (a sampling phase) using the synchronization sequence of the synchronization header of the data stream to synchronize the clock timing.

According to an embodiment, the synchronization header comprises a pseudo-random binary sequence.

In an embodiment, the pseudo-random binary sequence may, e.g., be different from the synchronization sequence.

According to an embodiment, the pseudo-random binary sequence may, e.g., comprise a number of bits, wherein a total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the pseudo-random binary sequence is greater than or equal to 15 % of the number of the bits of the pseudo-random binary sequence.

In an embodiment, the total number of transitions within the pseudo-random binary sequence may, e.g., be greater than or equal to 30 % of the number of the bits of the pseudo-random binary sequence. According to an embodiment, the synchronization header may, e.g., comprise a doubling or tripling of each of two or more bits of the pseudo-random binary sequence.

In an embodiment, the synchronization header may, e.g., comprise the synchronization sequence at least twice, e.g., the synchronization header may, e.g., comprise the synchronization sequence at teas! twice.

According to an embodiment, the synchronization header may, e.g., comprise the synchronization sequence more than twice.

In an embodiment, the synchronization header may, e.g., comprise the synchronization sequence at a beginning of the synchronization header, and the synchronization header may, e.g., comprise the synchronization sequence at an end of the synchronization header.

According to an embodiment, the synchronization header may, e.g., comprise the synchronization sequence two times, concatenated, at the beginning of the synchronization header, and two times, concatenated, at the end of the synchronization header.

In an embodiment, a second appearance of the synchronization sequence may, e.g., occur immediately after a first appearance of the synchronization sequence within the synchronization header.

According to an embodiment, the synchronization sequence may, e.g., be a first synchronization sequence. The apparatus 100 may, e.g., be configured to generate the header data such that the header data comprises the first synchronization sequence and a second synchronisation sequence, the second synchronization sequence being different from the first synchronization sequence.

In an embodiment, the apparatus 100 may, e.g., be configured to generate the synchronization header such that the synchronization header comprises the first synchronization sequence and the second synchronization sequence.

According to an embodiment, the synchronization header may, e.g., comprise a number of bits, such that a total number of transitions from a first bit value to a second bit value, being different from the first bit value, and from the second bit value to the first bit value within the synchronization header may, e.g., be greater than or equal to 15 % of the number of the bits of the synchronization header.

In an embodiment, the total number of transitions within the synchronization header may, e.g., be greater than or equal to 30 % of the number of the bits of the synchronization header.

According to an embodiment, the synchronization header may, e.g., comprise a predefined short code.

In an embodiment, the predefined short code may, e.g., be 8B10B and 4B5B

According to an embodiment, the synchronization header may, e.g., comprise a first version of the synchronization sequence, the first version comprising a doubling or tripling each bit of an initial sequence.

In an embodiment, the synchronization header may, e.g., furthermore comprise a second version of the synchronization sequence, wherein the second version of the synchronization sequence may, e.g., be equal to the initial sequence.

According to an embodiment, the first version of the synchronization sequence may, e.g., precede the second version of the synchronization sequence within the header data.

In an embodiment, the synchronization header may, e.g., comprise a predefined field into the synchronization header to indicate that the synchronization header has a predefined length.

According to an embodiment, the synchronization header may, e.g., comprise an information field having a predefined length, wherein the information field comprises additional information.

In an embodiment, the synchronization header of the data stream may, e.g., precede the payload data of the data stream within the data stream.

According to an embodiment, the payload data may, e.g., be binary encoded. In an embodiment, the payload data may, e.g., be multi-level encoded

According to an embodiment, the synchronization header may, e.g., have a predefined length.

In an embodiment, the synchronization header may, e.g., comprise two or more predefined header fields.

According to an embodiment, the data stream may, e.g., be pulse amplitude modulation encoded.

In an embodiment, the apparatus 200 may, e.g., be configured to receive the data stream from a transmitter.

According to an embodiment, the apparatus 200 may, e.g., be configured to receive the data stream via a shared medium.

In an embodiment, the apparatus 200 may, e.g., be suitable for being employed in an automotive environment or in an aerospace environment.

According to an embodiment, the apparatus 200 may, e.g., be configured to recover the clock timing using the synchronization header when the apparatus 200 starts to receive the data stream.

In an embodiment, the apparatus 200 may, e.g., be configured to recover the dock timing using the synchronization header.

According to an embodiment, the apparatus 200 may, e.g., be configured to track a frequency of the clock timing during a reception of the data stream.

In an embodiment, the apparatus 200 may, e.g., be configured to detect a beginning of the payload data of the data stream using the synchronization sequence.

According to an embodiment, the apparatus 200 may, e.g., be configured to center the sampling clock in a symbol period using the synchronization header. In an embodiment, the apparatus 200 may, e.g., be configured to recover the clock timing using the pseudo-random binary sequence.

According to an embodiment, the apparatus 200 may, e.g., be configured to identify the synchronization sequence within the data stream by employing correlation.

Fig. 3 illustrates a system according to an embodiment.

The system comprises an apparatus 100 according for generating a data stream and an apparatus 200 for receiving the data stream.

The apparatus 100 for generating the data stream is configured to generate the data stream, such that the data stream comprises header data and payload data. Moreover, the apparatus 100 for generating the data stream is configured to generate the header data such that the header data comprises a synchronization header. Furthermore, the apparatus 100 for generating the data stream is configured to generate the synchronization header using binary coding, wherein the apparatus 100 for generating a data stream is configured to generate the synchronization header such that the synchronization header comprises a synchronization sequence being a predefined bit sequence comprising a plurality of bits.

The apparatus 200 for receiving the data stream is configured to synchronize a clock timing using the synchronization sequence of the synchronization header of the data stream. Moreover, the apparatus 200 for receiving the data stream is configured to obtain the payload data of the data stream using the clock timing.

In the following, further embodiments of the present invention are provided.

Some of the embodiments relate to data communication systems with bursty transmissions. As already outlined, this means, over time there are quiet gaps, where no data is sent, and then, data bursts occur, where payload is transported.

In this mode, the receiver is to recover timing at the beginning of a data burst. This is mostly the phase of the sampling clock as frequency will tracked/recovered during the entire data burst. For this purpose, the data burst is preceded by a synchronization header (in short, also referred to as sync header). In an embodiment, the quiet gap is for the purpose of a power saving a state of the data communication link and/or for a shared medium, for example, half-duplex data communication (on a cable, directional RF link, optical fiber or similar).

According to an embodiment, the transition from the quiet gap to payload inside the data burst is to happen fast for bandwidth efficiency and power efficiency as this transition phase neither carries payload data nor is saving power.

In an embodiment, each data burst is preceded by a synchronization or resynchronization header (sync header). This sync header is used for robust detection of the symbol position, so that the beginning of payload is known and data can be decoded correctly. When in the following, reference is made to a synchronization header, it is understood that in a particular, a synchronization header may, for example, be a resynchronization header.

The sync header may, e.g., also be used by the receiver for clock (phase) recovery to center the sampling clock to achieve the target signal-to-noise-ratio, when the payload starts.

At the same time, the sync header may, e.g., have properties to limit/avoid emissions because of a recurring identical sequence. This is especially important for a cycle of data burst and quiet gap with fixed periodic timing.

While the payload may, e.g., be implemented by any sort of coding (binary or multi-level), the sync header may, e.g., be implemented using binary coding for more robustness in detection and clear symbol transitions for a fast-locking CDR (clock and data recovery).

In an embodiment, the sync header may, e.g., in principle be of fixed length. One optional exception is mentioned below. The sync header may, e.g., be constructed from several fields, at least 5 or 6.

In an alternative embodiment, an alternate description would be that there is a base pattern, into which at least two distinct patterns (called a synchronization sequence, in short: a sync sequence) are inserted (replacing parts of the base pattern). The sync sequence may, e.g., be inserted more than twice, which effectively creates a sync header with more than 5 or 6 fields. According to an embodiment, the base pattern may, e.g., be used for phase recovery. It should therefore have a high enough transition density to allow the CDR to correct larger offsets fast. Patterns like a simple one-zero alternating or code words from short codes like 8B10B and 4B5B provide this property. However, the regular nature of these patterns also leads to peak/tones in the spectrum.

A class of patterns with statistically distributed edge density (same symbol running length) between 1 and some maximum value are PRBS (pseudo-random binary sequence), which can be generated by a linear feedback shift register (LFSR).

The order of the PRBS is preferably one with many symbol transitions (short same symbol run lengths) to enable faster CDR locking. At the same time, the PRBS has to be distinct enough from the sync sequence, so that the correlation of the sync sequence versus the sync header (distorted by the channel) does not yield false positives. Such a PRBS order would be, for example, in the range from 10 to 19.

In an embodiment, the sync sequence may, e.g., be a defined bit sequence, which can be found well by correlation.

Fig. 4 illustrates an example of a synchronization sequence being represented by -1 and +1 values according to an embodiment (PAM representation).

Fig. 5 illustrates the synchronization sequence of Fig. 4, wherein the synchronization sequence is represented by 0 and 1 values (0/1 representation).

In an embodiment, a value may, e.g., be mapped already to PAM2 signal levels (PAM2: pulse amplitude modulation 2). The 0/1 sequence may, e.g., be obtained by setting all -T values to O’. Any circular permutations and any inversion of circular permutations may, e.g., yield a sequence of comparable properties. Reversing the bit order of any of those permutations/inversions also keeps comparable properties.

The exact length of the sequence is secondary. However, this sequence has the important property of being robust in detection mixed in with a base PRBS of orders 10 and above. In a concatenation of those sequences, an inversion of the sync sequence (receiver input inverted) can also be easily found and hence corrected. To detect the inversion of a PRBS, close to the full PRBS sequence is searched for by correlation. According to an embodiment, the sync sequence may, e.g., be inserted in the sync header at the beginning and at the end. This may, for example, be done each time with a single instance of the sync sequence or two or more concatenated sync sequences.

In an embodiment, the sync sequence may, e.g., be inserted multiple times with a defined distance (in time). This can help detection robustness, because the distance of correlation peaks can be evaluated.

Alternatively, in another embodiment, a longer sync sequence may, e.g., be used. This has a disadvantage of increased hardware effort in the correlator in the receiver.

When the sync sequence is inserted, the base pattern PRBS may, e.g., be stopped and started again, or it may, e.g., just be kept running for the whole sync header and may, e.g., be masked out while the sync sequence is inserted.

According to an embodiment, the first insertion of the sync sequence may, for example, be done with each bit/symbol doubled or tripled (or repeated more often). Repeating symbols improves robustness in detection and can additionally be used for coarse phase corrections, because the receiver will automatically obtain two or more samples from the same repeated symbol. This allows additional filtering and data processing to suppress noise and disturbances from the channel.

In an embodiment, the PRBS around the first insertion may, e.g., be kept without symbol repetition or it can be inserted with repeated symbols as well. The repetition of symbols in the sync sequence can only exceed the repetition of symbols in the PRBS by a small amount, because a significantly stretched sync sequence would yield false positives of the correlation with the PRBS.

In an embodiment, the second (or last) insertion of the sync sequence may, e.g., be without repetition of symbols, so that a correlation can give the exact bit position and allow aligned decoding of the payload data.

According to an embodiment, the position of the sync sequences inside the header may, e.g., be dithered to reduce/avoid peaks in the transmitter spectrum (power spectral density)* which is important for electromagnetic sensitive applications such as Automotive and Aerospace. Dithering means shifting the position of the sync sequence by an integer number of symbols, e.g., inserting it into the sync header earlier or later with respect to a non-dithered “zero position” relative to the start of the payload data after the sync header.

In an embodiment, the dithering source may, for example, be a defined waveform (triangle, sine wave, rectangular, sawtooth, ...), or may, for example, be a pseudo-random signal like a PRBS. According to an embodiment, a clocked digital waveform for repeatable results may, e.g., be employed.

According to an embodiment, with each sync header, the dithering source may, e.g., be evaluated for a new position; which may, e.g., then be used for inserting the sync sequence(s) relative to their “zero position”. in an embodiment, there may, e.g., be a multiplication factor for the position obtained by the dithering source. This factor may, for example, be different for the first insertion of the sync sequence and the second (or last) insertion of the sync sequence.

For example, in an embodiment, the first insertion of the sync sequence with doubled bits/symbols may, for example, be shifted with a factor 2 while the second (or last) insertion may, for example, be shifted with a factor 1 (or more generally, with an integer ratio factor, that may, e.g., be half the value of the first sync sequence factor). This means, that the distance of correlator peaks of the first to second/last sync sequence is different from one data burst to the next data burst (and unique with each different position value obtained from the dithering source). This property can help to identify, which sync header (or data burst) within the period of the dithering source is currently evaluated.

For the first insertion of the sync sequence, it is not important, that the sync sequence is preceded by a field of PRBS. In an embodiment, this snippet of PRBS may, e.g., not be transmitted. This would lead to a sync header, which varies in length with each evaluation of the dithering source. If the first field is transmitted, the length of the sync header may, e.g., be always the same regardless of dithering state. This can be advantageous for CDR locking.

According to an embodiment, the sync header may, e.g., be appended by a fixed length info field, which may, for example, be used for transporting other data than the data burst payload. Fig. 6 illustrates a version of a sync header, with first insertion and PRBS around it with doubled bits according to an embodiment.

Fig. 7 illustrates a version of a sync header, with first insertion with doubled bits according to another embodiment.

Fig. 8 illustrates a version of a sync header, with all insertions with single bits only, but whole sequence repeated, according to a further embodiment.

Although some aspects have been described in the context of an apparatus, it is clear that these aspects also represent a description of the corresponding method, where a block or device corresponds to a method step or a feature of a method step. Analogously, aspects described in the context of a method step also represent a description of a corresponding block or item or feature of a corresponding apparatus. Some or all of the method steps may be executed by (or using) a hardware apparatus, like for example, a microprocessor, a programmable computer or an electronic circuit. In some embodiments, one or more of the most important method steps may be executed by such an apparatus.

Depending on certain implementation requirements, embodiments of the invention can be implemented in hardware or in software or at least partially in hardware or at least partially in software. The implementation can be performed using a digital storage medium, for example a floppy disk, a DVD, a Blu-Ray, a CD, a ROM, a PROM, an EPROM, an EEPROM or a FLASH memory, having electronically readable control signals stored thereon, which cooperate (or are capable of cooperating) with a programmable computer system such that the respective method is performed. Therefore, the digital storage medium may be computer readable.

Some embodiments according to the invention comprise a data carrier having electronically readable control signals, which are capable of cooperating with a programmable computer system, such that one of the methods described herein is performed.

Generally, embodiments of the present invention can be implemented as a computer program product with a program code, the program code being operative for performing one of the methods when the computer program product runs on a computer. The program code may for example be stored on a machine readable carrier. Other embodiments comprise the computer program for performing one of the methods described herein, stored on a machine readable carrier.

In other words, an embodiment of the inventive method is, therefore, a computer program having a program code for performing one of the methods described herein, when the computer program runs on a computer.

A further embodiment of the inventive methods is, therefore, a data carrier (or a digital storage medium, or a computer-readable medium) comprising, recorded thereon, the computer program for performing one of the methods described herein. The data carrier, the digital storage medium or the recorded medium are typically tangible and/or non- transitory.

A further embodiment of the inventive method is, therefore, a data stream or a sequence of signals representing the computer program for performing one of the methods described herein. The data stream or the sequence of signals may for example be configured to be transferred via a data communication connection, for example via the Internet.

A further embodiment comprises a processing means, for example a computer, or a programmable logic device, configured to or adapted to perform one of the methods described herein.

A further embodiment comprises a computer having installed thereon the computer program for performing one of the methods described herein.

A further embodiment according to the invention comprises an apparatus or a system configured to transfer (for example, electronically or optically) a computer program for performing one of the methods described herein to a receiver. The receiver may, for example, be a computer, a mobile device, a memory device or the like. The apparatus or system may, for example, comprise a file server for transferring the computer program to the receiver.

In some embodiments, a programmable logic device (for example a field programmable gate array) may be used to perform some or all of the functionalities of the methods described herein. In some embodiments, a field programmable gate array may cooperate with a microprocessor in order to perform one of the methods described herein. Generally, the methods are preferably performed by any hardware apparatus.

The apparatus described herein may be implemented using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer.

The methods described herein may be performed using a hardware apparatus, or using a computer, or using a combination of a hardware apparatus and a computer. The above described embodiments are merely illustrative for the principles of the present invention. It is understood that modifications and variations of the arrangements and the details described herein will be apparent to others skilled in the art. It is the intent, therefore, to be limited only by the scope of the impending patent claims and not by the specific details presented by way of description and explanation of the embodiments herein.