CN117040995A - Distributed time-frequency synchronization method based on wireless microwave link - Google Patents
Distributed time-frequency synchronization method based on wireless microwave link Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2647—Arrangements specific to the receiver only
- H04L27/2655—Synchronisation arrangements
- H04L27/2657—Carrier synchronisation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
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Abstract
The invention discloses a distributed time-frequency synchronization method based on a wireless microwave link, and belongs to the technical field of time-frequency synchronization. The invention comprises the following steps: establishing a distributed time-frequency synchronous system based on a wireless microwave link, wherein the wireless microwave communication link adopts an FDD frequency division duplex communication mode; the slave nodes adopt a frequency division multiplexing mode, use different frequency points to perform time-frequency synchronization with the master node respectively, and each time of synchronization, the master node encodes clock frequency and time stamp signals in a communication physical layer bit stream, and realizes the frequency synchronization and phase synchronization of the master node and the slave node through clock recovery and time stamp measurement calculation; finally, the time-frequency synchronization of all the slave nodes and the master node is realized. The invention designs the time-frequency synchronization scheme from the physical layer, reduces the uncertainty of delay to the minimum, and can ensure the high-precision time-frequency synchronization performance.
Description
Technical Field
The invention belongs to the technical field of time-frequency synchronization, and particularly relates to a method for realizing high-precision distributed time-frequency synchronization in a wireless microwave mode.
Background
The time-frequency synchronization is used as a common technology and is widely applied to the fields of radio astronomy, navigation positioning, automatic driving and the like. Time-frequency synchronization media are classified into wired and wireless. Because the optical fiber medium has the advantages of low loss, electromagnetic interference resistance and high stability, high-precision wired time-frequency synchronization is often realized based on an optical fiber link. However, optical fiber time-frequency synchronization requires the laying of fixed optical fiber links, the node layout is costly, and flexibility is lacking. The wireless time-frequency synchronization nodes are simple and convenient to arrange, and the network is easy to expand. Therefore, the invention is directed to wireless time-frequency synchronization techniques.
Existing high-precision wireless time-frequency synchronization is usually realized based on GNSS. However, GNSS signals are susceptible to interference spoofing. Existing GNSS-independent typical wireless time-frequency synchronization techniques include UWB-based and wireless local area network-based techniques. However, UWB has a limited synchronization distance due to the special signal system. The time-frequency synchronization technology based on the wireless local area network has the advantage of strong expansibility of network nodes, but has low time-frequency synchronization performance. Currently, not completely relying on GNSS to realize high-precision distributed wireless time-frequency synchronization has become a problem to be solved in the industry.
Disclosure of Invention
In view of this, the present invention proposes a distributed time-frequency synchronization method based on wireless microwave links, so as to achieve the unification of time and frequency of all nodes in the regional network. The method designs a time-frequency synchronization scheme from a physical layer, reduces the uncertainty of delay to the minimum and ensures the high-precision time-frequency synchronization performance.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a distributed time-frequency synchronization method based on a wireless microwave link comprises the following steps:
(1) Establishing a distributed time-frequency synchronization system based on a wireless microwave link, wherein the distributed time-frequency synchronization system comprises 1 master node and a plurality of slave nodes, and the wireless microwave link adopts an FDD frequency division duplex communication mode;
(2) The slave nodes adopt a frequency division multiplexing mode, use different frequency points and respectively perform time-frequency synchronization with the master node; in the synchronization process, firstly, frequency synchronization is carried out, and then phase synchronization is carried out;
finally, the time-frequency synchronization of all the slave nodes is realized.
Further, in the step (2), the specific process of performing time-frequency synchronization between each slave node and the master node is as follows:
(201) Generating a synchronous frame by a master node signal, and recording the generation time as t 1 Combining bit information of the synchronous frame and bit information of the communication data to generate a bit stream; then, the main node embeds an internal 10MHz clock in the bit stream by using an Ethernet synchronization mode, and then carries out waveform mapping, DA conversion and wireless carrier modulation on the bit stream and transmits the bit stream through an antenna;
(202) After receiving signals transmitted by the main node through an antenna, the slave node restores bit streams transmitted by the main node through signal demodulation, AD conversion and waveform demapping; then, the slave node extracts 10MHz clock signal from the bit stream by using a clock recovery method to realize the frequency synchronization of the master node and the slave node, and the clock record of the slave node internal clock records that the detected synchronization frame bit time is t 2 ，t 2 The time stamp resolution is ns level; then, the time stamp t is carried out by utilizing a digital double mixing mode 2 Performing precise measurement to obtain a time stamp t' 2 The time stamp measurement accuracy is improved to ps level;
(203) Generating a response frame from the node, and recording the generation time as t 3 Combining bit information of the response frame and bit information of the communication data into a bit stream; next, using the ethernet synchronization mode, the slave node embeds the 10MHz clock signal in the bit stream; then, waveform mapping, digital-to-analog conversion and wireless carrier modulation are carried out on the bit stream, and the bit stream is transmitted through an antenna;
(204) After receiving the signal transmitted by the slave node through the antenna, the master node demodulates the analog baseband signal from the radio frequency signal by using a demodulator; subsequently, the master node recovers the 10MHz clock from the bit stream by AD conversion, waveform demapping and clock recovery,the internal clock record of the master node detects that the bit time of the response frame is the time stamp t 4 ，t 4 Resolution is ns level; then, the time stamp t is carried out by utilizing a digital double mixing mode 4 Performing precise measurement to obtain a time stamp t' 4 The time stamp measurement accuracy is improved to ps level;
(205) The master node stamps t1 and t' 4 The codes are sent to the corresponding slave nodes through wireless links;
(206) Using time stamp t from node 1 ，t′ 2 ，t 3 ，t′ 4 And calculating the phase deviation of the master node clock and the slave node clock, and realizing the phase synchronization of the master node and the slave node by using a phase-locked loop mode.
Further, the phase deviation in step (206) is calculated by:
compared with the prior art, the invention has the following beneficial effects:
1. the distributed time-frequency synchronization is based on a wireless microwave communication link, the communication data rate is adjustable, and the frequency spectrum width occupied by the time-frequency synchronization signal can be flexibly adjusted.
2. The invention embeds clock synchronization signals in the bit stream of the signal physical layer, and has high time-frequency synchronization performance.
3. The distributed time-frequency synchronization is realized based on a wireless mode, and compared with wired time-frequency synchronization, the distributed time-frequency synchronization method has the advantages that nodes are flexibly distributed, are used immediately after being put, and the distribution cost is reduced.
4. The invention can realize the simultaneous transmission of time, frequency and communication data of the master node and the slave node, realize the integration of communication and time-frequency synchronization technology, and has high wireless spectrum utilization rate.
Drawings
Fig. 1 is a schematic diagram of a distributed time-frequency synchronization system according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of time-frequency synchronization in an embodiment of the present invention.
Detailed Description
For better illustrating the objects and advantages of the present invention, the following description of the technical solution of the present invention refers to the accompanying drawings.
A distributed time-frequency synchronization method based on a wireless microwave link comprises the following steps:
(1) And establishing a distributed time-frequency synchronous system based on the wireless microwave link. Fig. 1 shows a time-frequency synchronization system comprising a master node and a plurality of slave nodes, wherein the distributed time-frequency synchronization technology is based on a wireless microwave communication link, the communication link adopts an FDD frequency division duplex communication mode, and the communication rate is adjustable.
(2) The slave nodes use frequency division multiplexing mode, and use different frequency points to perform time-frequency synchronization with the master node.
Fig. 2 is a schematic diagram of a principle of time-frequency synchronization of master-slave nodes, in which frequency synchronization is first performed, and then phase synchronization is performed. The specific process is as follows:
(201) The master node signal firstly generates a synchronous frame and records the generation time as t 1 . The sync frame bit information and the communication data information bits are combined to generate a bit stream, where the bit stream rate is adjustable. With synchronous ethernet technology, the master node embeds an internal 10MHz clock in the bit stream. The bit stream is then waveform mapped and digital to analog converted to an analog baseband signal, which modulates a wireless carrier and is transmitted via an antenna.
(202) The slave node receives the signal transmitted by the master node through the antenna, demodulates the analog baseband signal from the radio frequency signal by using the demodulator, and then restores the bit stream transmitted by the master node through AD conversion and waveform demapping. Then, the slave node extracts the 10MHz clock signal from the bit stream by using the clock recovery technology, thereby realizing the frequency synchronization of the master node and the slave node. Next, the slave node separates the sync frame bit from the data information frame bit, and the time t is the time t when the sync frame bit is detected from the internal clock record of the node 2 ，t 2 The timestamp resolution is 100ns. Time stamp t using digital double mixing technique 2 Performing precise measurement to obtain a time stamp t' 2 Time stamp measurement accuracy enhancementTo the ps stage.
(203) Generating a response frame from the node signal, and recording the generation time as t 3 . The acknowledgement frame bit information and the communication data information bits are combined to generate a bit stream. The slave node embeds the 10MHz clock signal in the bit stream using synchronous ethernet technology. Waveform mapping, digital-to-analog conversion and wireless carrier modulation are then performed and transmitted through the antenna.
(204) The master node receives the signals transmitted from the slave nodes through the antenna and demodulates the analog baseband signals from the radio frequency signals by using the demodulator. Subsequently, the master node recovers the 10MHz clock from the bit stream through AD conversion, waveform demapping and clock recovery. The internal clock record of the master node detects that the bit time of the response frame is the time stamp t 4 ，t 4 The resolution is 100ns. Time stamp t using digital double mixing technique 4 Performing precise measurement to obtain a time stamp t' 4 The time stamp measurement accuracy is ps-level.
(205) The master node stamps t1 and t' 4 The codes are sent to the corresponding slave nodes through wireless links;
(206) Using time stamp t from node 1 ，t′ 2 ，t 3 ，t′ 4 Calculating clock phase deviation of master-slave nodes as follows:
according to the phase deviation, the phase of the slave node clock is adjusted by using a phase-locked loop technology, so that the phase synchronization of the master node and the slave node is realized.
And a plurality of slave nodes of the distributed time-frequency synchronization system perform master-slave time-frequency synchronization, and finally time-frequency synchronization of all nodes of the system is realized.
Claims (3)
1. The distributed time-frequency synchronization method based on the wireless microwave link is characterized by comprising the following steps:
(1) Establishing a distributed time-frequency synchronization system based on a wireless microwave link, wherein the distributed time-frequency synchronization system comprises 1 master node and a plurality of slave nodes, and the wireless microwave link adopts an FDD frequency division duplex communication mode;
(2) The slave nodes adopt a frequency division multiplexing mode, use different frequency points and respectively perform time-frequency synchronization with the master node; in the synchronization process, firstly, frequency synchronization is carried out, and then phase synchronization is carried out;
finally, the time-frequency synchronization of all the slave nodes is realized.
2. The distributed time-frequency synchronization method based on a wireless microwave link according to claim 1, wherein in step (2), the specific process of performing time-frequency synchronization between each slave node and the master node is as follows:
(201) Generating a synchronous frame by a master node signal, and recording the generation time as t 1 Combining bit information of the synchronous frame and bit information of the communication data to generate a bit stream; then, the main node embeds an internal 10MHz clock in the bit stream by using an Ethernet synchronization mode, and then carries out waveform mapping, DA conversion and wireless carrier modulation on the bit stream and transmits the bit stream through an antenna;
(202) After receiving signals transmitted by the main node through an antenna, the slave node restores bit streams transmitted by the main node through signal demodulation, AD conversion and waveform demapping; then, the slave node extracts 10MHz clock signal from the bit stream by using a clock recovery method to realize the frequency synchronization of the master node and the slave node, and the clock record of the slave node internal clock records that the detected synchronization frame bit time is t 2 ，t 2 The time stamp resolution is ns level; then, the time stamp t is carried out by utilizing a digital double mixing mode 2 Performing precise measurement to obtain a time stamp t' 2 The time stamp measurement accuracy is improved to ps level;
(203) Generating a response frame from the node, and recording the generation time as t 3 Combining bit information of the response frame and bit information of the communication data into a bit stream; next, using the ethernet synchronization mode, the slave node embeds the 10MHz clock signal in the bit stream; then, waveform mapping, digital-to-analog conversion and wireless carrier modulation are carried out on the bit stream, and the bit stream is transmitted through an antenna;
(204) The master node passes through the skyAfter the line receives the signal transmitted from the node, the demodulator demodulates the analog baseband signal from the radio frequency signal; subsequently, the master node recovers the 10MHz clock from the bit stream by AD conversion, waveform demapping and clock recovery, and the master node internal clock records that the bit time of the response frame is detected as the time stamp t 4 ，t 4 Resolution is ns level; then, the time stamp t is carried out by utilizing a digital double mixing mode 4 Performing precise measurement to obtain a time stamp t' 4 The time stamp measurement accuracy is improved to ps level;
(205) The master node stamps t1 and t' 4 The codes are sent to the corresponding slave nodes through wireless links;
(206) Using time stamp t from node 1 ，t′ 2 ，t 3 ，t′ 4 And calculating the phase deviation of the master node clock and the slave node clock, and realizing the phase synchronization of the master node and the slave node by using a phase-locked loop mode.
3. The method for distributed time-frequency synchronization based on wireless microwave link according to claim 2, wherein the phase deviation in step (206) is calculated by:
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