CN110166400B

CN110166400B - Synchronization method, device, network equipment and storage medium of high-speed industrial communication system

Info

Publication number: CN110166400B
Application number: CN201910606566.1A
Authority: CN
Inventors: 康良川; 邵枝晖; 史兢
Original assignee: Beijing Neuron Network Technology Co ltd
Current assignee: Beijing Neuron Network Technology Co ltd
Priority date: 2019-07-05
Filing date: 2019-07-05
Publication date: 2021-07-02
Anticipated expiration: 2039-07-05
Also published as: CN110166400A

Abstract

The embodiment of the application discloses a synchronization method, a synchronization device, network equipment and a storage medium for a high-speed industrial communication system. The control equipment broadcasts a frame head synchronization pilot signal, the frame head synchronization pilot signal comprises two continuous synchronization OFDM symbols, and frequency domain subcarriers of the two synchronization OFDM symbols load the same pilot sequence. The synchronization method comprises the following steps: extracting consecutive first and second target synchronization OFDM symbols according to a transmission mode; performing time domain autocorrelation operation on the first target synchronous OFDM symbol; and determining the initial moment of the signal according to the result of the time domain autocorrelation operation. According to the high-speed industrial communication system and the method, the problems that the traditional industrial field bus is low in bandwidth, cannot simultaneously bear real time and non-real time and is complex in network structure are solved, IPV6 address communication is supported, time-triggered industrial communication is supported, and security mechanisms such as TSN, white list, depth detection and data encryption are supported.

Description

Synchronization method, device, network equipment and storage medium of high-speed industrial communication system

Technical Field

The embodiment of the application relates to the field of industrial communication and control, in particular to a synchronization method, a synchronization device, network equipment and a storage medium for a high-speed industrial communication system.

Background

In the industrial field, a plurality of industrial devices (e.g., measurement instruments) are usually attached to a high-speed industrial control bus, and each industrial device can communicate via the high-speed industrial control bus, for example, transmit control signals for controlling the industrial devices to perform industrial production activities.

The high-speed industrial control bus has high requirements for real-time transmission of data, and industrial equipment needs to perform time synchronization (for example, time synchronization, clock synchronization, carrier frequency synchronization) to realize high-precision industrial production activities. At present, a Network Time Protocol (NPT) or IEEE1588 of the Institute of Electrical and Electronics Engineers (IEEE) is mostly adopted for a high-speed industrial control bus, and Network Time synchronization is realized by stamping a timestamp.

With the development of big data and the popularization of intelligent devices, more and more data need to be transmitted in high-speed industrial control, and the transmission rate requirement is higher. At the same time, the complexity of the data and the transmission difficulty also increase greatly. For the above problems, NPT is affected by queue delay, exchange delay, medium access delay, and other factors, and the error of time synchronization becomes large, which cannot meet the current requirement of data real-time transmission. Meanwhile, IEEE1588 is affected by frequency error of the oscillator, network symmetry, network delay, and the like, and the error of time synchronization becomes large, and the current requirement for real-time data transmission cannot be met.

Disclosure of Invention

The embodiment of the application provides a synchronization method, a synchronization device, network equipment and a storage medium for a high-speed industrial communication system, which can improve the synchronization precision of high-speed industrial control and meet the requirement of real-time data transmission.

According to a first aspect of the present application, a synchronization method for a terminal node device in a high-speed industrial communication system is provided, where the high-speed industrial communication system includes a control device and the terminal node device, the high-speed industrial communication system provides multiple transmission modes with different OFDM symbol time widths, a physical layer signal frame of the high-speed industrial communication system includes a frame header synchronization pilot signal broadcasted by the control device, the frame header synchronization pilot signal includes two consecutive synchronization OFDM symbols, frequency domain subcarriers of the two synchronization OFDM symbols are loaded with a same pilot sequence, and a frequency domain subcarrier at an even position or a frequency domain subcarrier at an odd position in a preceding synchronization OFDM symbol in a time domain position is set to zero, and the synchronization method includes:

extracting continuous first target synchronization OFDM symbols and second target synchronization OFDM symbols according to a transmitting mode, wherein the time domain position of the first target synchronization OFDM symbol is in front;

performing time domain autocorrelation operation on the first target synchronous OFDM symbol;

and determining the initial moment of the signal according to the result of the time domain autocorrelation operation.

According to a second aspect of the present application, there is provided a synchronization method for a high speed industrial communication system, the high speed industrial communication system comprising a control device and the terminal node device, the high speed industrial communication system providing a plurality of transmission modes differing in OFDM symbol time width, the synchronization method comprising: according to the transmitting mode, the control equipment broadcasts a frame header synchronization pilot signal, the frame header synchronization pilot signal comprises two continuous synchronization OFDM symbols, the frequency domain subcarriers of the two synchronization OFDM symbols are loaded with the same pilot sequence, and the frequency domain subcarriers at even positions or the frequency domain subcarriers at odd positions in the former synchronization OFDM symbols are set to zero.

According to a third aspect of the present application, there is provided a frame header structure for a physical layer signal frame in a communication process of a high-speed industrial communication system, including: two continuous synchronous OFDM symbol resources, wherein the synchronous OFDM symbol resources are used for carrying pilot signals; the pilot sequences to be loaded corresponding to the two synchronous OFDM symbol resources are the same, and the frequency domain subcarriers at even positions or the frequency domain subcarriers at odd positions in the former synchronous OFDM symbol resources are zeroed.

According to a fourth aspect of the present application, a synchronization apparatus for a terminal node device in a high-speed industrial communication system is provided, where the high-speed industrial communication system includes a control device and the terminal node device, the high-speed industrial communication system provides multiple transmission modes with different OFDM symbol time widths, a physical layer signal frame of the high-speed industrial communication system includes a frame header synchronization pilot signal broadcast by the control device, the frame header synchronization pilot signal includes two consecutive synchronization OFDM symbols, frequency domain subcarriers of the two synchronization OFDM symbols are loaded with a same pilot sequence, and a frequency domain subcarrier at an even position or a frequency domain subcarrier at an odd position in a preceding synchronization OFDM symbol in a time domain position is set to zero, the synchronization apparatus includes: the device comprises an extraction module, a transmission module and a control module, wherein the extraction module is used for extracting a first target synchronization OFDM symbol and a second target synchronization OFDM symbol which are continuous according to a transmission mode, and the time domain position of the first target synchronization OFDM symbol is in front; the correlation operation module is used for performing time domain self-correlation operation on the first target synchronous OFDM symbol; and the judging module is used for determining the initial moment of the signal according to the result of the time domain autocorrelation operation.

According to a fifth aspect of the present application, there is provided a network device comprising a memory, a processor and instructions stored on the memory and executable on the processor, wherein the processor executes the instructions to implement any of the synchronization methods described above.

According to a sixth aspect of the present application, there is provided a machine-readable storage medium having stored thereon computing instructions which, when executed by a processor, implement the synchronization method of any of the preceding claims.

According to the embodiment of the application, the synchronous OFDM pilot frequency symbols are utilized in the high-speed industrial communication system, time synchronization and clock synchronization are achieved, the time synchronization and clock synchronization precision of the high-speed industrial communication system can be improved, and therefore the requirement for real-time data transmission is met.

Therefore, the high-speed industrial communication system and the method can solve the problems that the traditional industrial field bus is low in bandwidth, cannot simultaneously bear real time and non-real time and is complex in network structure, support IPV6 address communication, support time-triggered industrial communication, and support security mechanisms such as TSN, white list, depth detection and data encryption.

Drawings

Fig. 1 shows a network topology diagram of a high-speed industrial communication system to which a synchronization method according to an embodiment of the present application can be applied;

FIG. 2 illustrates a communication protocol stack architecture used by embodiments of the present application;

fig. 3 shows a structure of a signal frame and OFDM symbols used in an embodiment of the present application;

FIG. 4 shows a block diagram of a communication signal frame used by an embodiment of the present application;

fig. 5 shows a physical layer process diagram of a signal transmission and reception system according to an example embodiment;

FIG. 6 shows a scrambling code sequence generation diagram in accordance with an example embodiment;

FIG. 7a shows a convolutional encoder with a code rate of 1/2, according to an example embodiment;

FIG. 7b shows an m-sequence generator according to an example embodiment;

fig. 8 illustrates a synchronization method that can be used for the terminal node device in the aforementioned high-speed industrial communication system according to an embodiment of the present application;

fig. 9 shows a schematic diagram of autocorrelation characteristics of an OFDM symbol according to an embodiment;

fig. 10 shows a synchronization apparatus for a terminal node device in a high-speed industrial communication system according to an example embodiment;

fig. 11 shows a schematic structural diagram of a network device according to an embodiment of the present application.

Detailed Description

The present application will now be described in further detail with reference to the accompanying drawings and examples. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the implementations set forth herein. These embodiments are provided so that this disclosure will be thorough and detailed, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar parts, and thus their repetitive description will sometimes be omitted.

In the following description, the terms "first" and "second" are used for descriptive purposes only and are not intended to indicate or imply relative importance. The following description provides embodiments of the present application, where different embodiments may be substituted or combined, and thus the present application is intended to include all possible combinations of the same and/or different embodiments described. Thus, if one embodiment includes feature A, B, C and another embodiment includes feature B, D, then this application should also be considered to include an embodiment that includes one or more of all other possible combinations of A, B, C, D, even though this embodiment may not be explicitly recited in text below.

The following description provides examples, and does not limit the scope, applicability, or examples set forth in the claims. Changes may be made in the function and arrangement of elements described without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For example, the described methods may be performed in an order different than the order described, and various steps may be added, omitted, or combined. Furthermore, features described with respect to some examples may be combined into other examples.

Fig. 1 shows a network topology diagram of a high-speed industrial communication system to which a synchronization method according to an embodiment of the present application can be applied.

As shown in fig. 1, the communication system is a two-wire non-bridging medium that supports 254 active nodes, one of which is a control node and the other of which is a termination node. The control node is responsible for managing, distributing and recovering system resources, pushing system configuration to all nodes in real time, distributing communication bandwidth and the like. The communication system can provide fixed bandwidth data service and variable bandwidth data service supporting burst data by using bus type networking through a system pre-configuration or dynamic application mode. The communication system provides reliable and deterministic bearers for periodically sampled data, bursty control, alarms, and IPv4/IPv6 data in the ISO/IEC/IEEE 8802-3 Ethernet format. The communication system has a high-precision clock synchronization function and provides deterministic data transmission service for time-sensitive and non-time-sensitive services based on time triggering.

The protocol stack architecture of the communication system is shown in fig. 2 and includes three parts, namely a physical layer, a data link layer and an application layer.

The physical layer may be based on OFDM technology, which realizes that a fieldbus based on a shared medium is created on two lines, and conversion of a physical signal is completed to ensure high-reliability transmission, but the application is not limited thereto. And carrying out division and management on physical resources on an OFDM time domain and a frequency domain so as to bear data of a data link layer. The physical layer provides three major interfaces of clock management service, data transmission service and physical layer management service to the data link layer. OFDM (Orthogonal Frequency Division Multiplexing) techniques divide a target channel into a plurality of subchannels that are Orthogonal in the Frequency domain. In addition, modulation may be performed in different manners for each subchannel, and in practice OFDM converts data signals into data streams and modulates the data streams onto each subchannel for transmission. A carrier is a periodic, oscillating signal transmitted over a channel and modulated to transmit a desired signal. The OFDM technique is generated to improve the spectrum utilization of carriers or to improve the modulation of multiple carriers, and because the subcarriers are orthogonal to each other, the spectrum after spread spectrum modulation can be overlapped with each other, thereby reducing the mutual interference between the carriers.

By applying OFDM, a high-speed industrial communication system with multiple nodes, high bandwidth and time sensitivity can be realized, the method is used for transmission and application of real-time data and non-real-time data of automation control industrial fields such as process control, discrete control and the like, and the method is compatible with applications such as ISO/IEC/IEEE 8802-3 Ethernet, IPv6 and the like. The communication system has the characteristics of high bandwidth, high real-time performance, long distance and high reliability in transmission, is simple in wiring and installation, provides convenient network maintenance, and supports utilization of existing cable assets.

The Data Link Layer (DLL) mainly includes two layers, an LLC sublayer and a MAC sublayer. The LLC sublayer comprises an LLC module, a time synchronization module and an ISO/IEC/IEEE 8802-3LLC module. The MAC sub-layer includes MAC and a MAC sub-layer supporting ISO/IEC/IEEE 8802-3 MAC. The data link layer provides three service interfaces of data link service, data link management service and clock synchronization service for the application layer.

The Application Layer (AL) comprises a data service module and a system management service module based on real-time application and non-real-time application, a time service module, and a TCP/UDP module based on IPv4/IPv 6. The data service module provides the user to complete the processing of real-time and non-real-time related services and distinguish real-time and non-real-time service data buffer areas. The system management service module realizes the management and maintenance of the system topology and state. The time service module provides services such as clock synchronization, clock query and the like.

The communication system adopts the physical layer design based on the OFDM technology and can simultaneously support the working modes of time division multiplexing and frequency division multiplexing. In the frequency domain, the communication system may provide, for example, four different transmission modes (0, 1, 2, 3). The user can select different transmission modes according to the signal-to-noise ratio condition under the actual application condition. The time width of one OFDM symbol may be, for example, 64us, 32us, 16us, and 8us, respectively, for different transmission modes.

In the communication system, for example, 64 OFDM symbols may be fixedly employed as one frame, but the present application is not limited thereto. The frame period of the communication system can be varied from 500us to 4.0ms according to the transmission mode selected by the user, and the parameter configuration can meet the requirements of different sampling periods under different application conditions. The corresponding parameters of each mode of the system can be shown in table 1.

TABLE 1

In the communication system, digital code streams sent by a data link layer are respectively corresponding to physical resources specified by OFDM symbols and subcarriers after RS coding, convolutional coding and QAM mapping of a physical layer, FFT modulation is carried out, and then physical layer signal frames are formed and transmitted to cables. The receiving end recovers the digital signal and the data stream through the reverse process.

The sampling interval of the communication system in the time domain is, for example:

i.e. the sampling intervals are all fixed values in different transmission modes, in which communication system T is a fixed value_SMay take a value of 10.17 ns.

The basic unit of the physical layer signal of the communication system is an OFDM symbol, for example, 64 OFDM symbols constitute one signal frame. Each OFDM symbol is in turn divided equally over the frequency domain subcarriers into two parts, an upper sideband and a lower sideband. The high frequency subcarrier portion (e.g., 16.896-32.256 MHz) is referred to as the upper sideband and the low frequency subcarrier portion (e.g., 1.536-16.896 MHz) is referred to as the lower sideband. The upper and lower sidebands may be allocated to different device nodes when the communication system allocates channel resources. The structure of the signal frame and the OFDM symbols may be as shown in fig. 3.

Fig. 4 shows a block diagram of a signal frame of the communication system.

As shown in fig. 4, the resolvable elements of the communication system signal frame include: frame pilot signals, downlink subframes, allocable resources, etc.

The frame pilot signal is used for identifying the start of a signal frame and has the functions of signal frame synchronization and frame head positioning. The frame pilot signal may be fixed, for example, in the lower sideband portion of the 1 st, 2 nd OFDM symbol of each frame (e.g., the frame pilot portion in fig. 4).

The downlink subframe may be used for data and information transmitted from the control node to each terminal node, and may include a plurality of contents such as a channel, a bandwidth allocation condition, system maintenance information, transmission data, and the like. The downlink subframe may contain the lower sideband portion of 2 OFDM symbols or more (e.g., the downlink portion in FIG. 4).

The minimum unit of allocable resources may be a half sideband of 1 OFDM symbol (when mode a is selected) or a half sideband of 2 OFDM symbols (when mode B is selected). In fig. 4, all blank portions are system allocable resources, and the control node and each terminal node can apply for corresponding resources according to requirements and transmit related data.

Mode a is to transmit both data and pilot signals in a single OFDM half sideband, where the ratio of the number of subcarriers occupied by the pilot signal to the data is, for example, 1: 8.

Mode B is to transmit pilot signals in the first OFDM half sideband of the applied allocable resource and data in the following 1 to n OFDM symbols.

Since the start of a resource needs to be distinguished and confirmed by pilot information in the communication system, in addition to sending a frame pilot signal at the start of each signal frame, after allocable resources are allocated to a control node or each terminal node, pilot information needs to be inserted in the resource according to a specific form, so that a receiving end can decode corresponding information quickly and accurately. Allocatable resources support two usage modes, e.g., mode a and mode B. The two modes of use differ in the way the pilot signal is inserted and the data carrying structure. The use mode A is generally used as an application for periodically cycling data transmission, and if the communication system adopts the operation mode of the use mode A, the use of the communication system can support 8 user intervals at most; meanwhile, the mode A also supports a mode of uniformly distributing multi-user cross-interval resources. The usage pattern B can be used for periodic cyclic fixed rate data transmission as well as for variable rate data transmission.

The physical layer of the communication system can configure a plurality of working modes when carrying data of a data link layer. Different operating modes are adapted to different channel environments and data transmission requirements. The transmission mode, frame format, modulation and coding strategy in each operating mode will affect the relationship between the physical resources and the amount of available data that can be carried.

The data link layer data is transmitted to the physical layer in the form of bit streams, which are divided into RS code blocks of different lengths according to the corresponding RS codes. The RS code block is a unit of physical layer data processing, and the effective byte number carried by one OFDM symbol is integral multiple of the effective byte number of the code block. The communication system supports 22 operation modes in total, wherein 10 operation modes are supported in the use mode A, and 12 operation modes are supported in the use mode B.

Fig. 5 shows a physical layer process diagram of the communication system transmitting and receiving system according to an example embodiment.

As shown in fig. 5, in the transmission process, data streams are respectively subjected to scrambling, RS coding, and convolutional coding, then interleaved, modulated by 16QAM, 64QAM, or 256QAM to form OFDM signals, and the data are combined into frames according to different transmission modes and then transmitted on a cable. The receiving system is the inverse process of the transmitting system and is used for accurately decoding and restoring the data stream from the line coding signal.

The transmission of the physical layer signal adopts OFDM modulation, the core process for generating the OFDM signal is IFFT (inverse fast Fourier transform), and the restoration OFDM signal processing corresponds to FFT (fast Fourier transform). Given the system bandwidth and sampling interval, different FFT/IFFT sample points result in different subcarrier spacing and OFDM symbol length. The system supports four different transmission modes of 0,1, 2 and 3, which respectively correspond to 4096, 2048, 1024 and 512 sampling points.

To avoid the occurrence of consecutive 0,1, the bit stream contained by the MAC layer transport block is scrambled prior to encoding. The scrambling sequence is an m-sequence of length 11 with a generator polynomial of x¹¹+x²+1, initialization phase is 11111111111. The sequence generator is reinitialized at the beginning of each code block. The scrambling sequence generation process is shown in fig. 6, where enable indicates the control switch, data is the input bit stream to be scrambled, and output is the output scrambled bit stream.

The physical layer coding may employ, for example, concatenated codes where the inner code is a convolutional code and the outer code is an RS code. The transmission block which is subjected to CRC firstly enters an outer code encoder for RS encoding, and then enters an inner code encoder for convolutional code encoding. And the coded bits enter a bit interleaver for interleaving.

The RS code adopts shortened codes of original RS (255,247), RS (255,239) and RS (255,223) systematic codes, the original RS code is 255 bytes in length, the check byte length is 8, 16 or 32 bytes, the RS code is a cyclic code based on a finite field GF (256), and the field generator polynomial is p (x) x⁸+x⁴+x³+x²+1. When the RS code generator polynomial is

L is the check bit length and the input information sequence polynomial is

K is the length of the information bit, the system code outputs the polynomial

Wherein

The RS-encoded transmission data is sent with high bit-first mapping each byte into an 8-bit stream, which is sent to the convolutional encoder with code rates of, for example, 1/2, 2/3, and 3/4, respectively. The convolutional encoder uses a convolutional encoder with constraint length of 7 and code rate of 1/2, and the generator polynomial is G₁＝171₈And G₀＝133₈As shown in fig. 7 a. The initial value of the shift register of the encoder may be set to a value corresponding to the last 6 information bits of the input stream such that the initial and final states of the shift register are the same. According to fig. 7a, the coded bit stream is output in A, B order. By deleting the coded bits, convolutional codes with code rates of 2/3 and 3/4 can be obtained.

The encoded bit stream needs to be interleaved. Converting the bit stream by N_CBIBFor the interleaving block grouping, all encoded data bit interleaving is performed on half subbands of one OFDM symbol in downlink. The interleaving is divided into two permutations, the first permutation ensuring that adjacent coded bits are mapped to non-adjacent subcarriers, the second permutation ensuring that adjacent coded bits are alternately mapped to more significant bits and less significant bits of the constellation. Specific interleaving rules are, for example:

first replacement:

i＝(N_CBIB/N_COL)(kmodN_COL)+floor(k/N_COL)k＝0,1,...N_CBIBwhere N is_CBIBFor the interleaving block length, k is the code bit number before the first permutation, and i is the code bit number after the first permutation.

And (3) second replacement:

j＝s*floor(i/s)+(i+N_CBIB-floor(i*N_COL/N_CBIB))mods i＝0,1,...N_CBIB s＝max(N_BPS/2,1), where j is the code bit number after the second permutation, N_BPSThe number of bits corresponding to one modulation symbol. The downlink interleaving configuration parameters are shown in table 6, where interleaving modes 3 and 4 are selectable using mode a and

interleaving modes

0,1 and 2 are selectable using mode B.

The modulation mapper takes the

binary digit

0,1 as input and produces a complex modulated output symbol x. The modulation mapping scheme is 16QAM, 64QAM and 256 QAM. The binary number obtains a constellation point Z according to a modulation mode, and then normalization is carried out to obtain a correct complex modulation symbol x.

The communication system supports various code modulation modes, and the main modulation and coding strategies in the use mode A and the use mode B are shown in tables 2 and 3.

Table 2: using modulation coding strategy in mode A

Table 3: using modulation coding strategy in mode B

The pilot sequence is formed, for example, by a generator polynomial of x¹¹+x⁸+x⁵+x²The m-sequence of +1 results, and the generation circuit can be as shown in fig. 7 b.

BPSK modulation may be performed on the m sequence obtained in fig. 7b to obtain a pilot sequence r (m).

For pilot symbols, the pilot sequence r (m) is mapped to resource elements (k, l) mainly according to:

a_k,l＝r(8*l+k) l＝0,1

i.e. pilots should be mapped to the 0,1 OFDM symbol of the frame, r (m) should be mapped to resource elements (k, l) in ascending order from k to 0, m to 8 l + k, for pilot symbol 0, even numbers are taken with only even subcarriers, i.e. k.

Fig. 8 shows a synchronization method that can be used for the terminal node device in the aforementioned high-speed industrial communication system according to an embodiment of the present application. As mentioned above, the high speed industrial communication system comprises a control device and the terminal node device, and provides a plurality of transmission modes with different OFDM symbol time widths. In addition, the physical layer signal frame of the high-speed industrial communication system includes a frame header synchronization pilot signal broadcasted by the control device, the frame header synchronization pilot signal includes two continuous synchronization OFDM symbols, frequency domain subcarriers of the two synchronization OFDM symbols load the same pilot sequence, and frequency domain subcarriers at even positions or frequency domain subcarriers at odd positions in the synchronization OFDM symbols before the time domain position is set to zero. The apparatus can be implemented in software and/or hardware, and can be generally integrated into an electronic device. The frame header synchronization pilot signal may be a pseudo-random sequence. The signal frame, the high-speed industrial communication system, the control device, the target OFDM symbol, the frame header resource allocation information, the synchronization time-frequency domain resource, the synchronization subcarrier, and the like of the present embodiment can all refer to the foregoing description.

Referring to fig. 8, at S810, according to a transmission mode, consecutive first and second target synchronization OFDM symbols are extracted, the first target synchronization OFDM symbol being located at a previous time domain position. As previously mentioned, in the frequency domain, the system may provide, for example, four different transmission modes (0, 1, 2, 3). The user can select different transmission modes according to the signal-to-noise ratio condition under the actual application condition. The time width of one OFDM symbol may be, for example, 64us, 32us, 16us, and 8us, respectively, for different transmission modes. The terminal node device may extract the target synchronization pilot signal according to the transmission mode. For example, the target synchronization pilot signal is extracted according to energy and a transmission pattern, but the present application is not limited thereto.

At S820, a time domain autocorrelation operation is performed on the first target synchronous OFDM symbol.

The first pilot frequency symbol frequency domain only has even or odd subcarrier data, and shows two sections of same time domain signals in the time domain. Therefore, the autocorrelation characteristic of the pilot symbols can be utilized to find the initial time of the signal through the time domain correlation detection, so as to perform time synchronization.

In S830, an initial time of the signal is determined according to the result of the time-domain autocorrelation operation. For example, the initial time of the signal is determined according to the correlation spike result of the correlation operation.

The correlation peak result of the correlation operation indicates that the autocorrelation of the target OFDM symbol is strongest, and the time position corresponding to the peak is the initial time of the signal, as shown in fig. 9.

In addition, the flexibility of time synchronization calculation can be increased by configuring various related calculations to determine the time synchronization estimation value.

According to an example embodiment, after determining the initial time of the signal according to the result of the time domain autocorrelation operation, the correlation between the first target synchronization OFDM symbol and the second target synchronization OFDM symbol may be further utilized to perform preliminary clock synchronization, so that the time synchronization estimation value may be obtained quickly for a scenario with poor time synchronization, but the accuracy is low.

According to an example embodiment, performing preliminary clock synchronization with the correlation of the first and second target synchronous OFDM symbols comprises performing a time domain correlation calculation or a frequency domain correlation operation on the first and second target synchronous OFDM symbols.

According to an example embodiment, after determining a signal initial time according to a result of the time domain autocorrelation operation, a next synchronization OFDM symbol may be acquired, and a clock synchronization finer than a preliminary clock synchronization may be performed using a correlation of the second target synchronization OFDM symbol and the next synchronization OFDM symbol.

According to an example embodiment, after determining an initial time of a signal according to a result of the time domain autocorrelation operation, two synchronous OFDM symbols spaced at least one frame apart may be acquired, and a clock synchronization finer than a preliminary clock synchronization is performed using a correlation of the two synchronous OFDM symbols.

The two methods for further synchronizing have poor ambiguity. Thus, two methods can be used in combination to achieve clock synchronization.

Optionally, after determining the initial time to complete the synchronization, the method may further include: determining data time-frequency domain resources allocated to the terminal node equipment in the signal frame according to frame body resource allocation information, wherein the data time-frequency domain resources are located in a frame body of the signal frame and are used for bearing data signals and/or pilot signals sent by the terminal node equipment; when detecting that a data transmission condition is met, generating a data OFDM symbol to be transmitted by using at least one data subcarrier matched with the data OFDM symbol resource; and transmitting the data OFDM symbol at a time domain position matched with the data time-frequency domain resource in the signal frame, wherein the data OFDM symbol is used for indicating a device hung on the communication system to transmit data.

The data time-frequency domain resources may be used to specify time-frequency domain resources for carrying valid data, and the data time-frequency domain is located in a frame body of the signal frame. The data time-frequency domain resources may include one, two, or more consecutive OFDM symbol resources. The data time-frequency domain resource can be used for designating a plurality of subcarriers which can be used by any device (control device or terminal node device) on the high-speed industrial communication system in one time slot, and the type of a signal transmitted by each subcarrier is a data signal or a pilot signal.

The data sending condition is used for judging whether to send valid data, and may include that a time slot specified by the data time-frequency domain resource is matched with the current system time. The data subcarriers are used to carry data signals or pilot signals. The data signal includes valid data; the pilot signal may be used for channel estimation.

And generating a data OFDM symbol to be transmitted by using the data subcarrier matched with the data time-frequency domain resource. The matched data subcarriers may be modulated with data signals or pilot signals, and the modulated data subcarriers may be superimposed to form a data OFDM symbol. Thus, after receiving the data OFDM symbol, other devices may demodulate a data signal or a pilot signal for subsequent processing.

By configuring the frame resource allocation information, any device on the high-speed industrial communication system is appointed to generate a data OFDM symbol and bear effective data, so that real-time data transmission of the high-speed industrial communication system is realized.

According to the embodiment of the application, the terminal node equipment receives the target OFDM symbol sent by the control equipment and is used for time synchronization, so that the time synchronization precision is improved, and real-time data transmission is realized.

According to another embodiment, there is provided a synchronization method for a high-speed industrial communication system including a control device and the terminal node device, the high-speed industrial communication system providing a plurality of transmission modes different in OFDM symbol time width, the synchronization method including: according to the transmitting mode, the control equipment broadcasts a frame header synchronization pilot signal, the frame header synchronization pilot signal comprises two continuous synchronization OFDM symbols, the frequency domain subcarriers of the two synchronization OFDM symbols are loaded with the same pilot sequence, and the frequency domain subcarriers at even positions or the frequency domain subcarriers at odd positions in the former synchronization OFDM symbols are set to zero.

Therefore, according to the embodiment, the present application further provides a frame header structure, which is applied to a physical layer signal frame in a communication process of a high-speed industrial communication system, and includes two consecutive synchronous OFDM symbol resources, where the synchronous OFDM symbol resources are used for carrying pilot signals; the pilot sequences to be loaded corresponding to the two synchronous OFDM symbol resources are the same, and the frequency domain subcarriers at even positions or the frequency domain subcarriers at odd positions in the former synchronous OFDM symbol resources are zeroed.

Fig. 10 illustrates a synchronization apparatus for a terminal node device in a high-speed industrial communication system according to an example embodiment. The high-speed industrial communication system comprises a control device and a terminal node device, the high-speed industrial communication system provides multiple emission modes with different OFDM symbol time widths, a physical layer signal frame of the high-speed industrial communication system comprises a frame header synchronization pilot signal broadcasted by the control device, the frame header synchronization pilot signal comprises two continuous synchronization OFDM symbols, frequency domain subcarriers of the two synchronization OFDM symbols load the same pilot sequence, and frequency domain subcarriers at even positions or frequency domain subcarriers at odd positions in the former synchronization OFDM symbols in time domain position are set to zero. The synchronization apparatus 1000 includes an extracting module 1010, configured to extract a first target synchronization OFDM symbol and a second target synchronization OFDM symbol that are consecutive, where a time domain position of the first target synchronization OFDM symbol is in front; a correlation operation module 1020, configured to perform time domain autocorrelation operation on the first target synchronization OFDM symbol; and a judging module 1030, configured to determine an initial time of the signal according to the result of the time domain autocorrelation operation. The device performs functions similar to those of the previously provided method and will not be described in detail here.

As shown in fig. 11, network device 12 is in the form of a general purpose computing device. The components of network device 12 may include, but are not limited to: one or more processors or processing units 16, a system memory 28, and a bus 18 that couples various system components including the system memory 28 and the processing unit 16. The network device 12 may be a device that is hooked up to a high-speed industrial communication system.

Bus 18 represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, such architectures include, but are not limited to, Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, enhanced ISA bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnect (PCI) bus.

Network device 12 typically includes a variety of machine system readable media. Such media may be any available media that is accessible by network device 12 and includes both volatile and nonvolatile media, removable and non-removable media.

The system memory 28 may include machine-system readable media in the form of volatile memory, such as Random Access Memory (RAM)30 and/or cache memory 32. Network device 12 may further include other removable/non-removable, volatile/nonvolatile machine system storage media.

An instruction/utility 40 having a set (at least one) of instruction modules 42 may be stored, for example, in system memory 28, such instruction modules 42 including, but not limited to, an operating system, one or more application instructions, other instruction modules, and instruction data, each or some combination of which may comprise an implementation of a network environment. The instruction module 42 generally performs the functions and/or methods of the embodiments described herein.

Network device 12 may also communicate with one or more external devices 14 (e.g., keyboard, pointing device, display 24, etc.), with one or more devices that enable a user to interact with the network device 12, and/or with any devices (e.g., network card, modem, etc.) that enable the network device 12 to communicate with one or more other computing devices. Such communication may be through an Input/Output (I/O) interface 22. Also, the Network device 12 may communicate with one or more networks (e.g., Local Area Network (LAN), Wide Area Network (WAN)) via the Network adapter 20. As shown, the Network adapter 20 communicates with other modules of the Network device 12 via the bus 18. it should be understood that although not shown in FIG. 11, other hardware and/or software modules may be used in conjunction with the Network device 12, including but not limited to microcode, device drivers, Redundant processing units, external disk drive Arrays, (Redundant Arrays of Inexpersive Disks, RAID) systems, tape drives, and data backup storage systems, among others.

The processing unit 16 executes various functional applications and data processing, such as implementing the synchronization methods provided in any of the embodiments of the present application, by executing instructions stored in the system memory 28.

The present application also provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the above-described method. The computer-readable storage medium may include, but is not limited to, any type of disk including floppy disks, optical disks, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs, EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or optical cards, nanosystems (including molecular memory ICs), or any type of media or device suitable for storing instructions and/or data.

Embodiments of the present application also provide a computer program product comprising a non-transitory computer-readable storage medium storing a computer program operable to cause a computer to perform some or all of the steps of any one of the methods for 3D distortion correction of a wide-angle lens as set forth in the above method embodiments.

It is clear to a person skilled in the art that the solution of the present application can be implemented by means of software and/or hardware. The "unit" and "module" in this specification refer to software and/or hardware that can perform a specific function independently or in cooperation with other components, where the hardware may be, for example, a Field-ProgrammaBLE Gate Array (FPGA), an Integrated Circuit (IC), or the like.

It should be noted that, for simplicity of description, the above-mentioned method embodiments are described as a series of acts or combination of acts, but those skilled in the art will recognize that the present application is not limited by the order of acts described, as some steps may occur in other orders or concurrently depending on the application. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required in this application.

In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.

In the embodiments provided in the present application, it should be understood that the disclosed apparatus may be implemented in other manners. For example, the above-described embodiments of the apparatus are merely illustrative, and for example, the division of the units is only one type of division of logical functions, and there may be other divisions when actually implementing, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not implemented. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of some interfaces, devices or units, and may be an electric or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.

The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable memory. Based on such understanding, the technical solution of the present application may be substantially implemented or a part of or all or part of the technical solution contributing to the prior art may be embodied in the form of a software product stored in a memory, and including several instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method described in the embodiments of the present application. And the aforementioned memory comprises: various media capable of storing program codes, such as a usb disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a removable hard disk, a magnetic disk, or an optical disk.

Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable memory, which may include: flash disks, Read-Only memories (ROMs), Random Access Memories (RAMs), magnetic or optical disks, and the like.

The above description is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure should not be limited thereby. That is, all equivalent changes and modifications made in accordance with the teachings of the present disclosure are intended to be included within the scope of the present disclosure. Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A synchronization method for a terminal node device in a high-speed industrial communication system, wherein the high-speed industrial communication system includes a control device and the terminal node device, the high-speed industrial communication system provides multiple transmission modes with different OFDM symbol time widths, a physical layer signal frame of the high-speed industrial communication system includes a frame header synchronization pilot signal broadcasted by the control device, the frame header synchronization pilot signal includes two continuous synchronous OFDM symbols, frequency domain subcarriers of the two synchronous OFDM symbols load a same pilot sequence, and frequency domain subcarriers with even-numbered positions or frequency domain subcarriers with odd-numbered positions in a preceding synchronous OFDM symbol are set to zero, the synchronization method includes:

2. The synchronization method according to claim 1, further comprising, after determining an initial time of the signal according to the result of the time-domain autocorrelation operation:

and performing preliminary clock synchronization by using the correlation of the first target synchronous OFDM symbol and the second target synchronous OFDM symbol.

3. The synchronization method according to claim 2, wherein the performing preliminary clock synchronization by using the correlation of the first and second target synchronization OFDM symbols comprises:

and performing time domain correlation calculation or frequency domain correlation operation on the first target synchronization OFDM symbol and the second target synchronization OFDM symbol.

4. The synchronization method according to claim 1, further comprising, after determining an initial time of the signal according to the result of the time-domain autocorrelation operation:

and acquiring a next synchronous OFDM symbol, and performing fine clock synchronization by using the correlation between the second target synchronous OFDM symbol and the next synchronous OFDM symbol.

5. The synchronization method according to claim 1, further comprising, after determining an initial time of the signal according to the result of the time-domain autocorrelation operation:

acquiring two synchronous OFDM symbols separated by at least one frame, and performing fine clock synchronization by using the correlation of the two synchronous OFDM symbols.

6. The synchronization method according to claim 1, wherein the determining an initial time of a signal according to the result of the time-domain autocorrelation operation comprises:

and determining the initial moment of the signal according to the correlation peak result of the time domain autocorrelation operation.

7. The synchronization method according to any of claims 1-6, wherein the frame header synchronization pilot signal is a pseudo-random sequence.

8. A synchronization method for a high speed industrial communication system, the high speed industrial communication system comprising a control device and the terminal node device, the high speed industrial communication system providing a plurality of transmission modes with different OFDM symbol time widths, the synchronization method comprising: according to the transmitting mode, the control equipment broadcasts a frame header synchronization pilot signal, the frame header synchronization pilot signal comprises two continuous synchronization OFDM symbols, the frequency domain subcarriers of the two synchronization OFDM symbols are loaded with the same pilot sequence, and the frequency domain subcarriers at even positions or the frequency domain subcarriers at odd positions in the former synchronization OFDM symbols are set to zero.

9. A synchronization apparatus for a terminal node device in a high-speed industrial communication system, wherein the high-speed industrial communication system includes a control device and the terminal node device, the high-speed industrial communication system provides multiple transmission modes with different OFDM symbol time widths, a physical layer signal frame of the high-speed industrial communication system includes a frame header synchronization pilot signal broadcasted by the control device, the frame header synchronization pilot signal includes two consecutive synchronization OFDM symbols, frequency domain subcarriers of the two synchronization OFDM symbols load a same pilot sequence, and a frequency domain subcarrier at an even position or a frequency domain subcarrier at an odd position in a preceding synchronization OFDM symbol in a time domain position is set to zero, the synchronization apparatus comprising:

the device comprises an extraction module, a transmission module and a control module, wherein the extraction module is used for extracting a first target synchronization OFDM symbol and a second target synchronization OFDM symbol which are continuous according to a transmission mode, and the time domain position of the first target synchronization OFDM symbol is in front;

the correlation operation module is used for performing time domain self-correlation operation on the first target synchronous OFDM symbol;

and the judging module is used for determining the initial moment of the signal according to the result of the time domain autocorrelation operation.

10. A network device comprising a memory, a processor, and instructions stored on the memory and executable on the processor, wherein the processor implements the synchronization method of any of claims 1-8 when executing the instructions.

11. A machine readable storage medium having stored thereon computing instructions, characterized in that the computing instructions, when executed by a processor, implement the synchronization method according to any one of claims 1-8.