Low-delay synchronization clock transmission method and low-delay data transmission method

Abstract

Disclosed are a low-delay synchronization clock transmission method and a low-delay data transmission method, used for transmitting a synchronization clock and data at low delay by a transmission terminal. The transmission terminal receives an incoming synchronization header; the incoming synchronization header comprises a preamble A and a preamble B; the transmission terminal starts to send an outgoing synchronization header after detecting the preamble A; the transmission terminal continues to detect the preamble B after detecting the preamble A; if the transmission terminal detects the preamble A and detects the preamble B, the outgoing synchronization header sent by the transmission terminal is a first-type outgoing synchronization header; if the transmission terminal detects the preamble A but does not detect the preamble B, the outgoing synchronization header sent by the transmission terminal is a second-type outgoing synchronization header; the first-type outgoing synchronization header is different from the second-type outgoing synchronization header.

Description

Low-latency synchronous clock and data transmission method Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a low-latency synchronous clock and data transmission method. Background Art

[0002] In common in-vehicle audio transmission systems, audio data is often transmitted using a time-sharing method. Each time slot transmits one or more audio samples, and the system does not transmit data between time slots. This means that clock recovery circuits cannot rely on continuous data transmission. To perform clock recovery, the transmitter can add a special character to the beginning of the data in a time slot as a synchronization header. After receiving the synchronization header, the receiver uses the synchronization header position to perform clock recovery and generate a local clock. The synchronization header position is the time when the receiver receives and recognizes the synchronization header. After receiving and recognizing the synchronization header, the synchronization header position information is generated and fed into the phase-locked loop circuit to recover and generate the local clock.

[0003] In vehicle audio transmission systems, a multi-level topology is often used to connect nodes to save wires. When the node cascade depth is large, in order to ensure that the delay in the last-level node receiving the synchronization header is not too large relative to the delay in the first-level node sending the synchronization header, each level of node should maintain a low delay from the time it starts receiving the synchronization header from the previous level node to the time it starts sending the synchronization header to the next level node.

[0004] In order to keep the delay low from the time when each level node starts receiving the synchronization header from the upper level node to the time when it starts sending the synchronization header to the next level node, the method of reducing the length of the synchronization header bit sequence can usually be adopted. However, this method is prone to false detection of the synchronization header when no data is transmitted between time slices due to noise interference on the channel, or incorrect judgment of the synchronization header position, thereby increasing the false detection rate of the synchronization header.

[0005] Currently, there is a lack of a method that can recover the clock through the received synchronization header position, and has a small delay from starting to receive the synchronization header from the upper-level node to starting to send the synchronization header to the next-level node, while maintaining a low synchronization header false detection rate.

[0006] Summary of the Invention

[0007] The technical problem to be solved by the present invention is how to recover the clock through the received synchronization header position, and to reduce the delay from the start of receiving the synchronization header from the upper-level node to the start of sending the synchronization header to the next-level node, while maintaining a low synchronization header false detection rate.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] As a low-latency synchronous clock transmission method of the present invention, it is used for a transmission terminal to transmit a synchronous clock with low latency, the transmission terminal receives an input synchronization header, the input synchronization header includes a preamble code A and a preamble code B, the transmission terminal starts to send an output synchronization header after detecting the preamble code A, and continues to detect the preamble code B after detecting the preamble code A. If the transmission terminal detects the preamble code A and the preamble code B, the output synchronization header it sends is a first type of output synchronization header. If the transmission terminal detects the preamble code A but does not detect the preamble code B, the output synchronization header it sends is a second type of output synchronization header, and the first type of output synchronization header is different from the second type of output synchronization header.

[0010] Preferably, if the transmission terminal detects the preamble A and the preamble B, the transmission terminal uses the input synchronization header position to perform clock recovery to generate a local clock.

[0011] Preferably, if the transmission terminal fails to detect the preamble B after detecting the preamble A, the transmission terminal discards the input synchronization header.

[0012] Preferably, if the terminal receiving the outgoing synchronization header receives a first type of outgoing synchronization header, the terminal uses the outgoing synchronization header position to perform clock recovery to generate a local clock.

[0013] Preferably, if the terminal receiving the outgoing synchronization header receives a second type of outgoing synchronization header, the terminal discards the outgoing synchronization header.

[0014] Preferably, the time interval of the input synchronization header is a preset value T1, and the time interval of the output synchronization header is a preset value T2, and T1 is equal to T2.

[0015] Furthermore, the transmission terminal uses the generated local clock to send an outgoing synchronization header.

[0016] Preferably, the method for determining whether the transmission terminal detects the preamble A is that if there is a continuous N0-bit subsequence SA in the preamble A and the Hamming distance between the N0-bit preset codeword PA is less than a preset value N1, then the transmission terminal detects the preamble A.

[0017] Preferably, the method for determining whether the transmission terminal has detected the preamble B is that if the Hamming distance between the preamble B and the preset codeword PB is less than a preset value N2, the transmission terminal has detected the preamble B.

[0018] Preferably, the transmission terminal is implemented as an integrated circuit chip.

[0019] As a low-latency data transmission method of the present invention, it is used for a transmission terminal to transmit data with low latency, the transmission terminal receives an input synchronization header and a data field after the input synchronization header, the transmission terminal uses the input synchronization header to determine the position of the data field, the data field is used to transmit data, the input synchronization header includes a preamble C and a preamble D, the transmission terminal starts to send an output synchronization header after detecting the preamble C, the transmission terminal continues to detect the preamble D after detecting the preamble C, if the transmission terminal detects the preamble C and the preamble D, the output synchronization header it sends is a third-type output synchronization header, the transmission terminal sends the data field after sending the third-type output synchronization header, if the transmission terminal detects the preamble C but does not detect the preamble D, the output synchronization header it sends is a fourth-type output synchronization header, and the third-type output synchronization header is different from the fourth-type output synchronization header.

[0020] Preferably, if the transmission terminal fails to detect the preamble code D after detecting the preamble code C, the transmission terminal discards the input synchronization header and the data field after the input synchronization header.

[0021] Preferably, if the terminal receiving the outgoing synchronization header receives the fourth type of outgoing synchronization header, the terminal discards the outgoing synchronization header.

[0022] Preferably, the method for determining whether the transmission terminal has detected the preamble C is that if there is a continuous N3-bit subsequence SC in the preamble C and the Hamming distance between the N3-bit preset codeword PC is less than a preset value N4, then the transmission terminal has detected the preamble C.

[0023] Preferably, the method for determining whether the transmission terminal has detected the preamble D is that if the Hamming distance between the preamble D and the preset codeword PD is less than a preset value N5, the transmission terminal has detected the preamble D.

[0024] Preferably, the transmission terminal is implemented as an integrated circuit chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a block diagram of a transmission system of a low-latency synchronous clock transmission method of the present invention;

[0026] FIG2 is a structural diagram of an input synchronization header and an output synchronization header in a low-latency synchronous clock transmission method of the present invention;

[0027] 3 is a schematic diagram of a transmission terminal receiving a complete input synchronization header and sending a first type of output synchronization header in a low-latency synchronous clock transmission method of the present invention;

[0028] 4 is a schematic diagram of a low-latency synchronous clock transmission method according to the present invention, in which a transmission terminal does not receive a complete input synchronization header and sends a second type of output synchronization header;

[0029] FIG5 is a schematic diagram showing that, in a low-latency synchronous clock transmission method according to the present invention, after a transmission terminal receives an input synchronization header, the first several bits of a preamble A′ and a preamble A″ are identical when the transmission terminal sends a first type of output synchronization header and a second type of output synchronization header respectively;

[0030] 6 is a schematic diagram of an upstream transmission terminal sending an input synchronization header and a transmission terminal sending an output synchronization header in a low-latency synchronous clock transmission method of the present invention;

[0031] 7 is a schematic diagram of the position of the input synchronization header in a low-latency synchronous clock transmission method of the present invention;

[0032] 8 is a schematic diagram of the position of the first type of output synchronization head in a low-latency synchronous clock transmission method of the present invention;

[0033] FIG9 is an example of a preamble A and its subsequence in a low-latency synchronous clock transmission method of the present invention;

[0034] FIG10 is an example of a preamble A and its subsequence containing 2 bit errors in a low-latency synchronous clock transmission method of the present invention;

[0035] 11 is a structural diagram of an input synchronization header and data field, an output synchronization header and data field in a low-latency data transmission method of the present invention;

[0036] 12 is a schematic diagram of a low-latency data transmission method of the present invention, in which a transmission terminal receives a complete input synchronization header and data field, and sends a third type of output synchronization header and data field;

[0037] 13 is a schematic diagram of a low-latency data transmission method according to the present invention, in which a transmission terminal does not receive a complete input synchronization header and sends a fourth type of output synchronization header;

[0038] FIG14 is a schematic diagram showing that, in a low-latency data transmission method according to the present invention, after a transmission terminal receives an input synchronization header, the first several bits of a preamble C′ and a preamble C″ are identical when the transmission terminal sends a third type of output synchronization header and data field and a fourth type of output synchronization header, respectively;

[0039] 15 is a diagram showing two other structural diagrams of the second type of output synchronization header in a low-latency synchronous clock transmission method of the present invention;

[0040] 16 is a schematic diagram of a low-latency synchronous clock transmission method according to the present invention, in which the transmission terminal does not receive a complete input synchronization header and sends another second type of output synchronization header;

[0041] 17 is a schematic diagram of a low-latency synchronous clock transmission method of the present invention, in which the transmission terminal does not receive a complete input synchronization header and sends another second type of output synchronization header;

[0042] FIG18 is a diagram showing two other structural diagrams of the fourth type of output synchronization header in a low-latency data transmission method of the present invention;

[0043] FIG19 is a schematic diagram of a low-latency data transmission method according to the present invention, in which a transmission terminal does not receive a complete input synchronization header and sends another fourth type of output synchronization header;

[0044] FIG20 is a schematic diagram of a low-latency data transmission method according to the present invention, in which the transmission terminal does not receive a complete input synchronization header and sends another fourth type of output synchronization header.

[0045] Where: 1 Transmission terminal 2 Upstream transmission terminal 3 Downstream transmission terminal 4 Input synchronization header 5 Output synchronization header DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings. It should be understood that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative efforts shall fall within the scope of protection of the present invention.

[0047] As shown in Figure 1, in an application embodiment of the present invention, as a low-latency synchronous clock transmission method of the present invention, a transmission terminal in a transmission system transmits a synchronous clock with low latency. The transmission system includes a transmission terminal 1, an upstream transmission terminal 2, and a downstream transmission terminal 3. The upstream transmission terminal 2 is connected to the transmission terminal 1 and sends an input synchronization header 4 to the transmission terminal 1. The transmission terminal 1 receives the input synchronization header 4. The transmission terminal 1 is connected to the downstream transmission terminal 3 and sends an output synchronization header 5 to the downstream transmission terminal 3. The downstream transmission terminal 3 receives the output synchronization header 5.

[0048] The outgoing synchronization header 5 is divided into two categories, namely, a first-category outgoing synchronization header and a second-category outgoing synchronization header. The first-category outgoing synchronization header is an outgoing synchronization header sent after the transmission terminal 1 detects a complete incoming synchronization header, and the second-category outgoing synchronization header is an outgoing synchronization header sent after the transmission terminal 1 fails to detect a complete incoming synchronization header. The first-category outgoing synchronization header is different from the second-category outgoing synchronization header.

[0049] That the transmission terminal 1 detects a complete input synchronization header means that the transmission terminal 1 detects the preamble A and the preamble B.

[0050] As shown in Figure 2, in this embodiment, the input synchronization header 4 includes a preamble code A and a preamble code B; the first type of output synchronization header includes a preamble code A' and a preamble code B', the preamble code A and the preamble code A' can be the same or different, and the preamble code B and the preamble code B' can be the same or different; the second type of output synchronization header includes a preamble code A" and a preamble code B", the preamble code A' is different from the preamble code A", or the preamble code B' is different from the preamble code B", or the preamble code A' is different from the preamble code A", and the preamble code B' is different from the preamble code B".

[0051] As shown in Figure 3, in this embodiment, after the transmission terminal 1 detects the preamble code A of the input synchronization header 4, it starts to send the preamble code A' of the output synchronization header 5. After detecting the preamble code A, the transmission terminal 1 continues to detect the preamble code B. If the transmission terminal 1 detects the preamble code B, the transmission terminal 1 continues to send the preamble code B' after sending the preamble code A'. At this time, the output synchronization header 5 sent by the transmission terminal 1 is a first-type output synchronization header.

[0052] As shown in Figure 4, in this embodiment, after the transmission terminal 1 detects the preamble code A of the input synchronization header 4, it starts to send the preamble code A' of the output synchronization header 5 (the preamble code A' in this embodiment is the same as the preamble code A", and is shown as the preamble code A" in Figure 4). After detecting the preamble code A, the transmission terminal 1 continues to detect the preamble code B. If the transmission terminal 1 does not detect the preamble code B, the transmission terminal 1 continues to send the preamble code B" after sending the preamble code A' (preamble code A") (the preamble code B' in this embodiment is different from the preamble code B", and at this time, the output synchronization header 5 sent by the transmission terminal 1 is the second type of output synchronization header.

[0053] Taking a specific synchronization header sequence as an example, in this embodiment, preamble A, preamble A′, and preamble A″ are all binary sequences 0110101100, preamble B and preamble B′ are binary sequences 10001110, and preamble B″ is a binary sequence 01110001. When transmission terminal 1 detects that preamble A of input synchronization header 4 is 0110101100, it starts sending the binary sequence 10001100 of preamble A′ of output synchronization header 5. After detecting preamble A, transmission terminal 1 continues to detect preamble B. If transmission terminal 1 detects that the binary sequence of preamble B is 10001110, transmission terminal 1 sends the binary sequence 0110101100 of preamble A′ and then sends the binary sequence 10001110 of preamble B′. At this time, the output synchronization header sent by transmission terminal 1 is a first-type output synchronization header. If transmission terminal 1 detects preamble A but does not detect preamble B, the output synchronization header sent by transmission terminal 1 is a second-type output synchronization header. After sending the binary sequence 0110101100 (this sequence is preamble A″ in the second-type output synchronization header), transmission terminal 1 continues to send the binary sequence 01110001 of preamble B″.

[0054] In the embodiment shown in FIG4 , the preamble A′ is the same as the preamble A″. In other embodiments, the preamble A′ and the preamble A″ may also be different. However, the transmission terminal 1 cannot determine whether the first type of outgoing synchronization header or the second type of outgoing synchronization header should be sent before completing the detection of the preamble B. Therefore, the first several bits of the preamble A′ and the preamble A″ should be the same. As shown in FIG5 , the bit sequences of the shaded parts of the preamble A′ and the preamble A″ in the figure are the same.

[0055] As shown in Figure 6, in this embodiment, the upstream transmission terminal 2 sends an input synchronization header 4 to the transmission terminal 1 at a preset time interval T1. After receiving the input synchronization header 4, the transmission terminal 1 uses the input synchronization header position to perform clock recovery and generate a local clock. The transmission terminal 1 can use the generated local clock to send an output synchronization header 5 to the downstream transmission terminal 3 at a preset time interval T2. In order to enable the downstream transmission terminal 3 to correctly perform clock recovery and generate a local clock, the output synchronization header 5 is synchronized with the input synchronization header 4, that is, the time interval T1 between the upstream transmission terminal 2 sending the input synchronization header 4 is the same as the time interval T2 between the transmission terminal 1 sending the output synchronization header 5, T1=T2.

[0056] If transmission terminal 1 detects a complete incoming synchronization header 4 (transmission terminal 1 detects both preamble A and preamble B), transmission terminal 1 uses the incoming synchronization header position for clock recovery and generates a local clock. If transmission terminal 1 does not detect a complete incoming synchronization header 4 (transmission terminal 1 detects preamble A but fails to detect preamble B, or does not detect preamble A), transmission terminal 1 discards the incoming synchronization header 4. As shown in Figure 7, the incoming synchronization header position is the time when transmission terminal 1 receives and identifies the incoming synchronization header 4. After receiving and identifying the incoming synchronization header 4, the incoming synchronization header position information is generated and sent to the phase-locked loop circuit to recover and generate the local clock signal.

[0057] The present invention does not limit the implementation method of the synchronization header receiving circuit, nor does it limit how the input synchronization header position information is used to recover the clock. Various methods can be used to receive the input synchronization header 4. For example, an oversampling receiving circuit can be used. The oversampling rate is much higher than the transmission rate (generally 3 times or more). After identifying the input synchronization header 4, the input synchronization header position information is generated. This information is then sent to the phase-locked loop circuit to recover and generate the local clock signal.

[0058] Similar to the method used by transmission terminal 1 to process the detection results of the input synchronization header 4, if the downstream transmission terminal 3 detects a complete first-type output synchronization header (downstream transmission terminal 3 detects both preamble A' and preamble B'), downstream transmission terminal 3 uses the position of the first-type output synchronization header for clock recovery and generates a local clock. If the downstream transmission terminal 3 does not detect a complete first-type output synchronization header (downstream transmission terminal 3 detects preamble A' but fails to detect preamble B', or does not detect preamble A'), or detects a second-type output synchronization header, downstream transmission terminal 3 discards the output synchronization header 5. As shown in Figure 8, the first-type output synchronization header position is the time when the downstream transmission terminal 3 receives and identifies the first-type output synchronization header. After receiving and identifying the first-type output synchronization header, synchronization header position information is generated, which is sent to the phase-locked loop circuit to recover and generate the local clock signal.

[0059] Transmission terminal 1 begins transmitting the outbound synchronization header 5 upon detecting a portion of the inbound synchronization header 4 (preamble A) rather than the entire inbound synchronization header 4. This effectively reduces the delay between transmission terminal 1 receiving the inbound synchronization header 4 from upstream transmission terminal 2 and beginning to transmit the outbound synchronization header 5 to downstream transmission terminal 3. This ensures that the time it takes for the last-stage node in the transmission system to receive the synchronization header is not significantly longer than the delay required for the first-stage node to transmit the synchronization header. Although transmission terminal 1 begins transmitting the outbound synchronization header 5 immediately after detecting preamble A, this reduces the synchronization header transmission delay. However, due to the short bit sequence of preamble A, channel noise interference can easily lead to erroneous detection of the synchronization header during time slots when no data is transmitted, or misjudgment of the synchronization header position, thereby increasing the synchronization header misdetection rate. Transmission terminal 1 continues detecting preamble B after detecting preamble A to prevent this from occurring, maintaining a low synchronization header misdetection rate.

[0060] The embodiment shown in FIG1 is applied to an in-vehicle audio transmission system. In this transmission system, audio data is transmitted using a time-sharing method. Each time slot transmits one or more audio samples. The system does not transmit data between time slots. No data is transmitted before the preamble A in the input synchronization header 4. When the transmission terminal 1 detects the preamble A, it first generates a detection signal. The timing for generating the detection signal is not fixed. For example, at a 100 Mbps data transmission rate, it generally takes 1 to 4 bits to generate the detection signal. After the detection signal is generated, the binary sequence of the preamble A can be detected. The method for determining whether the transmission terminal 1 has detected the preamble A is as follows: if there is a continuous N0-bit subsequence SA in the preamble A that is identical to the N0-bit preset codeword PA, then the transmission terminal 1 is said to have detected the preamble A. The end of the subsequence SA is the end of the preamble A. Preamble A is followed by preamble B. The starting position of preamble B can be determined based on the ending position of preamble A. The method for determining whether transmission terminal 1 has detected preamble B is as follows: if preamble B is the same as the preset codeword PB, then transmission terminal 1 is said to have detected preamble B. The ending position of preamble B is the position of the input end synchronization header.

[0061] As shown in Figure 9, in this embodiment, preamble A is the binary sequence 0110101100, N0 is 6, the 6-bit preset codeword PA is the binary sequence 101100, and the 8-bit preset codeword PB is the binary sequence 10001110. A continuous 6-bit subsequence is extracted from preamble A, resulting in five subsequences: 011010, 110101, 101011, 010110, and 101100. Of these five subsequences, the fifth subsequence, 101100, is identical to the preset codeword PA. When transmitting terminal 1 detects preamble A, the end position of subsequence 101100 is the end position of preamble A. After detecting preamble A, transmitting terminal 1 continues to detect preamble B. If transmitting terminal 1 detects the binary sequence 10001110, which is identical to the preset codeword PB, transmitting terminal 1 detects preamble B, and the end position of binary sequence 10001110 is the input synchronization header position.

[0062] In the in-vehicle audio transmission system, since there may be noise interference in the in-vehicle environment, the synchronization header may have errors. In order to make the transmission system have a certain fault tolerance performance, in another embodiment, the judgment method for the above-mentioned transmission terminal 1 to detect the preamble code A and the preamble code B can be adjusted. In this embodiment, the judgment method for the transmission terminal 1 to detect the preamble code A is that if there is a continuous N0-bit subsequence SA in the preamble code A and the Hamming distance between the N0-bit preset code word PA is less than the preset value N1, then the transmission terminal detects the preamble code A; if the Hamming distance between the preamble code B and the preset code word PB is less than the preset value N2, then the transmission terminal detects the preamble code B.

[0063] As shown in Figure 10, in this embodiment, preamble A should be the binary sequence 0110101100. However, due to noise interference, the preamble A actually received by transmission terminal 1 contains two bit errors and is the binary sequence 0110101111. Assuming N0 = 6, N1 = 3, and N2 = 3, the 6-bit preset codeword PA is the binary sequence 101100, and the 8-bit preset codeword PB is the binary sequence 10001110. Consecutive 6-bit subsequences are extracted from the received preamble A, resulting in five subsequences: 011010, 110101, 101011, 010111, and 101111. Of these five subsequences, only the fifth subsequence, 101111, has a Hamming distance of less than 3 with the preset codeword PA (the Hamming distance is 2). Transmission terminal 1 detects preamble A, and the end point of subsequence 101111 is the end point of preamble A. After detecting preamble A, transmission terminal 1 continues to detect preamble B. If transmission terminal 1 detects the binary sequence 10010110, and the Hamming distance between it and the preset codeword PB is less than 3 (the Hamming distance is 2), transmission terminal 1 has detected preamble B. The position where the binary sequence 10010110 ends is the input synchronization header position.

[0064] In another application embodiment of the present invention, as a low-latency data transmission method of the present invention, a transmission terminal in a transmission system transmits data with low latency. The transmission system also adopts the structure shown in Figure 1, including a transmission terminal 1, an upstream transmission terminal 2, and a downstream transmission terminal 3. The upstream transmission terminal 2 is connected to the transmission terminal 1 and sends an input synchronization header 4 and a data field after the input synchronization header 4 to the transmission terminal 1. The data field is used to transmit data. The transmission terminal 1 receives the input synchronization header 4 and the data field after the input synchronization header 4. The transmission terminal 1 puts the data received from the data field after the input synchronization header 4 into the data field after the output synchronization header 5. The transmission terminal 1 is connected to the downstream transmission terminal 3 and sends the output synchronization header 5 and the data field after the output synchronization header 5 to the downstream transmission terminal 3. The downstream transmission terminal 3 receives the output synchronization header 5 and the data field after the output synchronization header 5.

[0065] The outgoing synchronization header 5 is divided into two categories, namely the third type of outgoing synchronization header and the fourth type of outgoing synchronization header. The third type of outgoing synchronization header is sent by the transmission terminal 1 after detecting a complete incoming synchronization header. The transmission terminal sends the data field after sending the third type of outgoing synchronization header. The fourth type of outgoing synchronization header is sent by the transmission terminal 1 after failing to detect a complete incoming synchronization header. The transmission terminal can choose to send the data field or not after sending the fourth type of outgoing synchronization header. The third type of outgoing synchronization header is different from the fourth type of outgoing synchronization header.

[0066] That the transmission terminal 1 detects the complete input synchronization header means that the transmission terminal 1 detects the preamble C and the preamble D.

[0067] As shown in Figure 11, in this embodiment, the transmission terminal 1 receives an input synchronization header 4 and a data field, and the input synchronization header 4 includes a preamble code C and a preamble code D; the transmission terminal 1 sends a third type of output synchronization header and a data field, and the third type of output synchronization header includes a preamble code C′ and a preamble code D′, and the preamble code C and the preamble code C′ can be the same or different, and the preamble code D and the preamble code D′ can be the same or different; the transmission terminal 1 can also send a fourth type of output synchronization header, and after sending the fourth type of output synchronization header, it can choose to send the data field or not send the data field, and the fourth type of output synchronization header includes a preamble code C″ and a preamble code D″, and the preamble code C′ is different from the preamble code C″, or the preamble code D′ is different from the preamble code D″, or the preamble code C′ is different from the preamble code C″ and the preamble code D′ is different from the preamble code D″.

[0068] As shown in Figure 12, in this embodiment, after detecting preamble C of the input synchronization header 4, transmission terminal 1 begins to transmit preamble C' of the output synchronization header 5. After detecting preamble C, transmission terminal 1 continues to detect preamble D. If transmission terminal 1 detects preamble D, it transmits preamble C' and then preamble D'. In this case, the output synchronization header 5 transmitted by transmission terminal 1 is a third-type output synchronization header. After detecting preamble D, transmission terminal 1 continues to receive the data field following preamble D and places the data in the data field following preamble D into the data field following preamble D'. After transmitting preamble D', transmission terminal 1 continues to transmit the data field following preamble D'.

[0069] As shown in FIG13 , in this embodiment, after the transmission terminal 1 detects the preamble C of the input synchronization header 4, it starts to send the preamble C′ of the output synchronization header 5 (the preamble C′ is the same as the preamble C″ in this embodiment, and is shown as the preamble C″ in FIG13 ). After detecting the preamble C, the transmission terminal 1 continues to detect the preamble D. If the transmission terminal 1 does not detect the preamble D, the transmission terminal 1 continues to send the preamble D″ after sending the preamble C′ (preamble C″) (the preamble D′ is different from the preamble D″ in this embodiment). At this time, the output synchronization header 5 sent by the transmission terminal 1 is the fourth type of output synchronization header. After sending the preamble D″, the transmission terminal 1 can choose to send the data field or not.

[0070] Taking a specific synchronization header sequence as an example, in this embodiment, preamble C, preamble C′, and preamble C″ are all binary sequences 0110101100, preamble D and preamble D′ are binary sequences 10001110, and preamble D″ is a binary sequence 01110001. Transmission terminal 1 detects that the preamble C of the input synchronization header 4 is 0110101100, and then starts to send the binary sequence 10001100 of the preamble C′ of the output synchronization header 5. After detecting the preamble C, transmission terminal 1 continues to detect the preamble D. If the transmission terminal 1 detects that the binary sequence of the preamble D is 10001110, then after sending the binary sequence 011010110 of the preamble C′, transmission terminal 1 continues to send the binary sequence 10001110 of the preamble D′. At this time, the output synchronization header sent by transmission terminal 1 is the third type output synchronization header. After detecting the binary sequence 10001110 of the preamble D, transmission terminal 1 continues to receive the data field after the preamble D. , and put the data in the data field after the preamble code D into the data field after the preamble code D′. After sending the binary sequence 10001110 of the preamble code D′, the transmission terminal 1 continues to send the data field after the preamble code D′; if the transmission terminal 1 detects the preamble code C but does not detect the preamble code D, the outgoing synchronization header sent by the transmission terminal 1 is the fourth type of outgoing synchronization header. After sending the binary sequence 0110101100 (this sequence is the preamble code C″ in the fourth type of outgoing synchronization header), the transmission terminal 1 continues to send the binary sequence 01110001 of the preamble code D″. After sending the binary sequence 01110001 of the preamble code D″, the transmission terminal 1 can choose to send the data field or not.

[0071] In the embodiment shown in FIG13 , the preamble C′ is the same as the preamble C″. In other embodiments, the preamble C′ and the preamble C″ may also be different. However, the transmission terminal 1 cannot determine whether the third type of outgoing synchronization header or the fourth type of outgoing synchronization header should be sent before completing the detection of the preamble D. Therefore, the first several bits of the preamble C′ and the preamble C″ should be the same, as shown in FIG14 . The bit sequences of the shaded parts of the preamble C′ and the preamble C″ in the figure are the same.

[0072] Transmission terminal 1 begins transmitting the outbound synchronization header 5 upon detecting a portion of the inbound synchronization header 4 (preamble C) rather than the entire inbound synchronization header 4. This effectively reduces the delay between when transmission terminal 1 begins receiving the inbound synchronization header 4 from upstream transmission terminal 2 and when it begins transmitting the outbound synchronization header 5 to downstream transmission terminal 3. It also reduces the delay between when transmission terminal 1 begins receiving the data field following the inbound synchronization header 4 and when it begins transmitting the data field following the outbound synchronization header 5. This ensures that the time it takes for the last-level node in the transmission system to receive data is not significantly longer than the delay required for the first-level node to send data. Although transmission terminal 1 begins transmitting the outbound synchronization header 5 immediately after detecting preamble C, this reduces the synchronization header transmission delay. However, due to the short bit sequence of preamble C, channel noise interference can easily lead to erroneous detection of the synchronization header during time slots when no data is transmitted, thereby increasing the synchronization header false detection rate. Transmission terminal 1 continues detecting preamble D after detecting preamble C to prevent this from occurring, maintaining a low synchronization header false detection rate.

[0073] This embodiment is applied to an in-vehicle audio transmission system. In this transmission system, audio data is transmitted using a time-sharing method. Each time slot transmits one or more audio samples. The system does not transmit data between time slots. No data is transmitted before the preamble C in the input synchronization header 4. When the transmission terminal 1 detects the preamble C, it first generates a detection signal. The timing for generating the detection signal is not fixed. For example, at a 100 Mbps data transmission rate, a transmission time of 1 to 4 bits is generally required to generate the detection signal. After the detection signal is generated, the binary sequence of the preamble C can be detected. The method for determining whether the transmission terminal 1 has detected the preamble C is as follows: if a continuous N3-bit subsequence SC in the preamble C is identical to the N3-bit preset codeword PC, then the transmission terminal 1 is said to have detected the preamble C. The end of the subsequence SC is the end of the preamble C. Preamble C is followed by preamble D. The starting position of preamble D can be determined based on the ending position of preamble C. Transmission terminal 1 detects preamble D if preamble D is identical to the preset codeword PD. Preamble D is followed by the data field, and the starting position of the data field can be determined based on the ending position of preamble D.

[0074] As shown in Figure 9, in this embodiment, preamble C is the binary sequence 0110101100, N3 is set to 6, the 6-bit preset codeword PC is the binary sequence 101100, and the 8-bit preset codeword PD is the binary sequence 10001110. Consecutive 6-bit subsequences are extracted from preamble C, resulting in five subsequences: 011010, 110101, 101011, 010110, and 101100. Of these five subsequences, the fifth subsequence, 101100, is identical to the preset codeword PC. When transmitting terminal 1 detects preamble C, the end point of subsequence 101100 is the same as the end point of preamble C. After detecting preamble C, transmitting terminal 1 continues to detect preamble D. If transmitting terminal 1 detects the binary sequence 10001110, which is identical to the preset codeword PD, the end point of binary sequence 10001110 is the beginning of the data field.

[0075] In an in-vehicle audio transmission system, since there may be noise interference in the in-vehicle environment, errors may occur in the synchronization header. In order to make the transmission system have a certain fault tolerance performance, in another embodiment, the judgment method for the above-mentioned transmission terminal 1 to detect the preamble code C and the preamble code D can be adjusted. In this embodiment, the judgment method for the transmission terminal 1 to detect the preamble code C is that if there is a continuous N3-bit subsequence SC in the preamble code C and the Hamming distance between the N3-bit preset codeword PC is less than the preset value N4, then the transmission terminal detects the preamble code C; if the Hamming distance between the preamble code D and the preset codeword PD is less than the preset value N5, then the transmission terminal detects the preamble code D.

[0076] As shown in Figure 10, in this embodiment, preamble C should be the binary sequence 0110101100. However, due to noise interference, the preamble C actually received by transmission terminal 1 contains two bit errors and is the binary sequence 0110101111. Assuming N3=6, N4=3, and N5=3, the 6-bit preset codeword PC is the binary sequence 101100, and the 8-bit preset codeword PD is the binary sequence 10001110. Consecutive 6-bit subsequences are extracted from the received preamble C, resulting in five subsequences: 011010, 110101, 101011, 010111, and 101111. Of these five subsequences, only the fifth subsequence, 101111, has a Hamming distance of less than 3 with the preset codeword PC (the Hamming distance is 2). Transmission terminal 1 detects preamble C, and the end position of subsequence 101111 is the end position of preamble C. After detecting preamble C, transmission terminal 1 continues to detect preamble D. If transmission terminal 1 detects the binary sequence 10010110, and the Hamming distance with the preset codeword PD is less than 3 (the Hamming distance is 2), transmission terminal 1 detects preamble D, and the position where the binary sequence 10010110 ends is the position where the data field begins.

[0077] In the present invention, the first type of output synchronization header is different from the second type of output synchronization header. In the embodiment shown in FIG2 , the second type of output synchronization header includes a preamble A″ and a preamble B″. In other application embodiments, the second type of output synchronization header may also include a preamble A″ and a portion of a preamble B″ (not shown in FIG2 ). In other application embodiments, the second type of output synchronization header may also include only a preamble A″ and not a preamble B″ (or the length of the preamble B″ is 0 bits), as shown in FIG15( a ), or the second type of output synchronization header may include only a portion of the preamble A″, as shown in FIG15( b ). The difference between the first type of output synchronization header and the second type of output synchronization header may be that the two have different lengths, or the two have equal lengths but different contents.

[0078] In the embodiment shown in Figure 16, after the transmission terminal 1 detects the preamble code A of the input synchronization header 4, it starts to send the preamble code A″ of the output synchronization header 5 (the preamble code A′ is the same as the preamble code A″ in this embodiment). After the transmission terminal 1 detects the preamble code A, it continues to detect the preamble code B. If the transmission terminal 1 does not detect the preamble code B, the transmission terminal 1 stops sending after sending the preamble code A″. At this time, the output synchronization header 5 sent by the transmission terminal 1 is the second type of output synchronization header Figure 15(a). Because the downstream transmission terminal 3 does not detect the complete first type of output synchronization header or detects the second type of output synchronization header Figure 15(a), the downstream transmission terminal 3 discards the output synchronization header 5.

[0079] In the embodiment shown in Figure 17, after the transmission terminal 1 detects the preamble A of the input synchronization header 4, it starts to send the preamble A″ of the output synchronization header 5 (the preamble A′ in this embodiment is the same as the first several bits of the preamble A″). After detecting the preamble A, the transmission terminal 1 continues to detect the preamble B. If the transmission terminal 1 does not detect the preamble B, the transmission terminal 1 stops sending after sending the first several bits of the preamble A″ (the shaded part of the preamble A″ in Figure 17). At this time, the output synchronization header 5 sent by the transmission terminal 1 is the second type of output synchronization header Figure 15(b). Because the downstream transmission terminal 3 does not detect the complete first type of output synchronization header or detects the second type of output synchronization header Figure 15(b), the downstream transmission terminal 3 discards the output synchronization header 5.

[0080] In the present invention, the third type of output synchronization header is different from the fourth type of output synchronization header. In the embodiment shown in FIG11 , the fourth type of output synchronization header includes a preamble C″ and a preamble D″. In other application embodiments, the fourth type of output synchronization header may also include a preamble C″ and a portion of the preamble D″ (not shown in FIG11 ). In other application embodiments, the fourth type of output synchronization header may also include only the preamble C″ and not the preamble D″ (or the length of the preamble D″ is 0 bits), as shown in FIG18 (a), or the fourth type of output synchronization header may include only a portion of the preamble C″, as shown in FIG18 (b). The difference between the third type of output synchronization header and the fourth type of output synchronization header may be that the two have different lengths, or the two have equal lengths but different contents.

[0081] In the embodiment shown in Figure 19, after the transmission terminal 1 detects the preamble code C of the input synchronization header 4, it starts to send the preamble code C″ of the output synchronization header 5 (the preamble code C′ is the same as the preamble code C″ in this embodiment). After the transmission terminal 1 detects the preamble code C, it continues to detect the preamble code D. If the transmission terminal 1 does not detect the preamble code D, the transmission terminal 1 stops sending after sending the preamble code C″. At this time, the output synchronization header 5 sent by the transmission terminal 1 is the fourth type of output synchronization header Figure 18 (a). Because the downstream transmission terminal 3 does not detect the complete third type of output synchronization header or detects the fourth type of output synchronization header Figure 18 (a), the downstream transmission terminal 3 discards the output synchronization header 5.

[0082] In the embodiment shown in Figure 20, after the transmission terminal 1 detects the preamble C of the input synchronization header 4, it starts to send the preamble C″ of the output synchronization header 5 (the preamble C′ in this embodiment is the same as the first several bits of the preamble C″). After detecting the preamble C, the transmission terminal 1 continues to detect the preamble D. If the transmission terminal 1 does not detect the preamble D, the transmission terminal 1 stops sending after sending the first several bits of the preamble C″ (the shaded part of the preamble C″ in Figure 20). At this time, the output synchronization header 5 sent by the transmission terminal 1 is the fourth type of output synchronization header Figure 18 (b). Because the downstream transmission terminal 3 does not detect the complete third type of output synchronization header or detects the fourth type of output synchronization header Figure 18 (b), the downstream transmission terminal 3 discards the output synchronization header 5.

[0083] In the application embodiment shown in FIG1 , the transmission system includes a transmission terminal 1 , an upstream transmission terminal 2 , and a downstream transmission terminal 3 . In other application embodiments, the transmission system may not include the upstream transmission terminal 2 or the downstream transmission terminal 3 .

[0084] In this embodiment, the transmission terminal 1 can be implemented in the form of an integrated circuit chip.

[0085] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A low-latency synchronous clock transmission method, used for transmitting a synchronous clock with low latency by a transmission terminal, characterized in that: The transmission terminal receives an input synchronization header, The input synchronization header includes a preamble A and a preamble B. The transmission terminal starts to send an outgoing synchronization header after detecting the preamble A. After the transmission terminal detects the preamble code A, it continues to detect the preamble code B. If the transmission terminal detects the preamble A and the preamble B, the outgoing synchronization header sent by the transmission terminal is a first type outgoing synchronization header, If the transmission terminal detects the preamble A but does not detect the preamble B, the outgoing synchronization header it sends is a second type of outgoing synchronization header. The first type of output synchronization header is different from the second type of output synchronization header.

2. A low-latency synchronous clock transmission method according to claim 1, characterized in that: If the transmission terminal detects the preamble code A and the preamble code B, the transmission terminal uses the input end synchronization header position to perform clock recovery to generate a local clock.

3. A low-latency synchronous clock transmission method according to claim 1, characterized in that: If the transmission terminal fails to detect the preamble B after detecting the preamble A, the transmission terminal discards the input synchronization header.

4. A low-latency synchronous clock transmission method according to claim 1, characterized in that: If the terminal receiving the outgoing synchronization header receives a first type of outgoing synchronization header, the terminal uses the outgoing synchronization header position to perform clock recovery and generate a local clock.

5. A low-latency synchronous clock transmission method according to claim 1, characterized in that: If the terminal receiving the outgoing synchronization header receives a second type of outgoing synchronization header, the terminal discards the outgoing synchronization header.

6. A low-latency synchronous clock transmission method according to claim 1, characterized in that: The time interval of the input synchronization header is a preset value T1, The time interval of the output synchronization header is a preset value T2. T1 is equal to T2.

7. A low-latency synchronous clock transmission method according to claim 2, characterized in that: The transmission terminal sends an outgoing synchronization header using the generated local clock.

8. A low-latency synchronous clock transmission method according to claim 1, characterized in that: The method for determining whether the transmission terminal has detected the preamble A is that if there are continuous N0-bit subsequences SA in the preamble A and the Hamming distance between the N0-bit preset codewords PA is less than a preset value N1, then the transmission terminal has detected the preamble A.

9. A low-latency synchronous clock transmission method according to claim 1, characterized in that: The method for determining whether the transmission terminal has detected the preamble B is that if the Hamming distance between the preamble B and the preset codeword PB is less than a preset value N2, the transmission terminal has detected the preamble B.

10. A low-latency synchronous clock transmission method according to claim 1, characterized in that: The transmission terminal is implemented as an integrated circuit chip.

11. A low-latency data transmission method, used for a transmission terminal to transmit data with low latency, characterized in that: The transmission terminal receives the input synchronization header and the data field after the input synchronization header, The transmission terminal uses the input synchronization header to determine the location of the data field, and the data field is used to transmit data. The input synchronization header includes a preamble C and a preamble D. After the transmission terminal detects the preamble C, it starts to send the outgoing synchronization header. After the transmission terminal detects the preamble code C, it continues to detect the preamble code D. If the transmission terminal detects the preamble C and the preamble D, the outgoing synchronization header sent by the transmission terminal is a third-type outgoing synchronization header, and the transmission terminal sends a data field after sending the third-type outgoing synchronization header. If the transmission terminal detects the preamble C but does not detect the preamble D, the outgoing synchronization header it sends is the fourth type of outgoing synchronization header. The third type of output synchronization header is different from the fourth type of output synchronization header.

12. A low-latency data transmission method according to claim 11, characterized in that: If the transmission terminal fails to detect the preamble D after detecting the preamble C, the transmission terminal discards the inbound synchronization header and the data field after the inbound synchronization header.

13. A low-latency data transmission method according to claim 11, characterized in that: If the terminal receiving the outgoing synchronization header receives the fourth type of outgoing synchronization header, the terminal discards the outgoing synchronization header.

14. A low-latency data transmission method according to claim 11, characterized in that: The method for determining whether the transmission terminal has detected the preamble C is that if there is a continuous N3-bit subsequence SC in the preamble C and the Hamming distance between the N3-bit preset codeword PC is less than a preset value N4, then the transmission terminal has detected the preamble C.

15. A low-latency data transmission method according to claim 11, characterized in that: The method for determining whether the transmission terminal has detected the preamble D is that if the Hamming distance between the preamble D and the preset codeword PD is less than a preset value N5, the transmission terminal has detected the preamble D.

16. A low-latency data transmission method according to claim 11, characterized in that: The transmission terminal is implemented as an integrated circuit chip.

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