CN111555773B - Frequency hopping synchronization method - Google Patents
Frequency hopping synchronization method Download PDFInfo
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- CN111555773B CN111555773B CN202010457431.6A CN202010457431A CN111555773B CN 111555773 B CN111555773 B CN 111555773B CN 202010457431 A CN202010457431 A CN 202010457431A CN 111555773 B CN111555773 B CN 111555773B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
- H04B1/7156—Arrangements for sequence synchronisation
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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
Abstract
The invention discloses a frequency hopping synchronization method.A synchronization head of a broadcast time slot of a frequency hopping transmitter is captured by each frequency hopping receiver through a duty frequency slow scanning method, so as to obtain the initial TOD time of a network system and realize the TOD time coarse synchronization of each frequency hopping receiver; the frequency hopping receiver and the frequency hopping transmitter transmit RTT round trip timing messages in pre-allocated time slots, so that time correction is calculated to adjust initial TOD time, and precise synchronization of the TOD time of each frequency hopping receiver is realized; and each frequency hopping transmitter and each frequency hopping receiver generate a service time slot frequency hopping pattern according to the precise synchronization TOD time, so that the frequency hopping synchronization of each frequency hopping receiver and each frequency hopping transmitter is realized. The invention does not need special equipment to maintain the initial time of each frequency hopping receiver, has strong universality of a hardware platform, does not need a special time service module, reduces the complexity of the system and reduces the cost of products.
Description
Technical Field
The invention relates to a frequency hopping synchronization method in a frequency hopping network, in particular to a frequency hopping synchronization method suitable for a multi-user frequency hopping network.
Background
Frequency hopping synchronization means that the frequency hopping receiver and the frequency hopping transmitter use the same frequency at the same time. The content of the frequency hopping synchronization comprises: the frequency hopping frequency tables are the same, the frequency hopping sequences are the same, and the jumping starting and stopping moments are the same. In the frequency hopping network, even though each node in the network has the same frequency hopping sequence, the time difference still exists between each node and each node before synchronization is realized, and in order to realize synchronous frequency hopping, the real-Time (TOD) (time of day) is introduced. In a multi-node centerless ad hoc network system, the anti-interference capability of the system can be enhanced by adopting a carrier high-speed frequency hopping technology, but the network access time of a plurality of network nodes is random, a uniform time reference is not provided before network access, and under the condition that the application of a time service subsystem is limited, the frequency hopping synchronization cannot be realized by adopting a traditional frequency hopping synchronization method.
Patent 1 (a method for implementing frequency hopping synchronization based on time information, CN108521287A, 2018) sends TOD time information through a sending end, and a receiving end receives the TOD information of the sending end and corrects the local TOD information to implement frequency hopping synchronization of sending and receiving. The frequency hopping synchronization algorithm requires that the initial error of TOD values of the transmitting end and the receiving end is smaller than an allowable deviation value, which cannot be realized by a multi-node ad hoc network system with completely uncertain network access time, such as random network access, interception network access and the like.
Patent 2 (based on the synchronous realization method of frequency hopping of big dipper time service chip, CN102983881B, 2015) is through big dipper time service system to frequency hopping transmitter and frequency hopping receiver timing, also be exactly in order to maintain that a plurality of frequency hopping transmitters of receiving and dispatching frequency hopping synchronization and receiver all need be equipped with big dipper time service subsystem in addition, has increased system complexity like this, has increased the cost simultaneously.
Disclosure of Invention
The invention provides a frequency hopping synchronization method suitable for a multi-user frequency hopping network, which is based on a time division multiple access networking protocol and realizes the synchronization of network access and on-network frequency hopping of nodes.
In order to achieve the above object, the present invention provides a frequency hopping synchronization method, which includes the following steps:
s1, each frequency hopping receiver captures a synchronization head of a broadcast message sent by a frequency hopping transmitter, and obtains the initial TOD time of the network system to realize the TOD time coarse synchronization of each frequency hopping receiver;
s2, each frequency hopping receiver generates an initial frequency hopping pattern of the RTT time slot according to the initial TOD time, and adjusts the initial TOD time of the network according to the RTT response message obtained by the initial frequency hopping pattern, so as to realize the precise synchronization of the TOD time of each frequency hopping receiver;
and S3, each frequency hopping transmitter and each frequency hopping receiver generate service time slot frequency hopping patterns according to the current fine synchronization TOD time, and the frequency hopping synchronization of each frequency hopping receiver and each frequency hopping transmitter is realized.
Preferably, the S1 includes the following steps:
s1.1, the main node of each frequency hopping transmitter transmits a broadcast message according to a time slot format of a synchronous head plus a data part;
s1.2, each frequency hopping receiver monitors the broadcast sent by the frequency hopping transmitter and generates a synchronization head of a broadcast time slot sent by a service frequency capture main node, so that the initial frequency hopping synchronization of the frequency hopping receivers is realized;
s1.3, the frequency hopping receiver demodulates and decodes the sensed broadcast message according to the synchronous head of the broadcast time slot, and obtains the initial TOD time of the network system, so that the TOD time coarse synchronization of the frequency hopping receiver and the frequency hopping transmitter is realized.
Preferably, the S2 includes the following steps:
s2.1, the slave nodes of all frequency hopping receivers use the initial TOD time of the network system obtained in the coarse synchronization as the local time to generate an initial frequency hopping pattern of an RTT time slot, then send RTT inquiry messages in the pre-allocated RTT time slot according to the generated initial frequency hopping pattern of the RTT time slot and receive RTT response messages replied by the master node in the same time slot;
and S2.2, the slave nodes of all the frequency hopping receivers calculate a time correction value according to the time information and the time slot length in the RTT response message, and adjust the local time to obtain the precisely synchronized TOD time.
Preferably, the service frequency is generated by a predetermined time factor and a frequency hopping key.
Preferably, each frequency hopping receiver adopts a service frequency slow scanning mode to capture a synchronization head of a broadcast time slot transmitted by the main node
The invention has the following advantages:
the invention realizes the frequency hopping synchronization of the multi-user frequency hopping network through two steps of coarse synchronization and fine synchronization. The rough synchronization is realized by capturing a broadcast time slot synchronization head on the service frequency, the error deviation of the initial time of each frequency hopping receiver is not limited, special equipment is not needed for maintaining the initial time of each frequency hopping receiver, and the hardware platform has strong universality; the precision synchronization is realized by transmitting RTT round trip timing messages in the preassigned time slots through the master node and the slave node, calculating a time correction value and correcting the time, and the method has the advantages of reducing the complexity of a system and reducing the cost of products at the cost of small time overhead and without a special time service module.
Drawings
Fig. 1 is a flowchart of a frequency hopping synchronization method according to an embodiment of the present invention;
FIG. 2 is a diagram of a network data frame format according to an embodiment of the present invention;
fig. 3 is a slow scanning search method for the service frequency of the sync head according to an embodiment of the present invention.
Detailed Description
The following describes a frequency hopping synchronization method according to the present invention in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are all used in a non-precise ratio for the purpose of facilitating and distinctly aiding in the description of the embodiments of the invention.
The invention realizes the difference of multi-node frequency hopping in the network based on the time division multiple access networking protocol. As shown in fig. 1, the present invention provides a frequency hopping synchronization method, which includes the following steps:
s1, each frequency hopping receiver captures a synchronization head of a broadcast message sent by a frequency hopping transmitter, and obtains the initial TOD time of the network system to realize the TOD time coarse synchronization of each frequency hopping receiver;
the main node of the frequency hopping transmitter sends the broadcast message according to the time slot format of the synchronous head plus the data part, the node sending the broadcast message is selected as the main node, and other nodes are slave nodes. As shown in fig. 2, each slot time is 10ms, where RTT (round trip timing) slots are divided into two 5ms and minislots of slave-to-master and master-to-slave. The service frequency of the broadcast slot is generated by a pre-agreed time factor TODH _ RADIO (which may be a finite set) and a frequency hopping key.
Each frequency hopping receiver monitors the broadcast sent by the frequency hopping transmitter, and initiates a network access application after successfully receiving the broadcast in a monitoring period. The network access node of each frequency hopping receiver captures the synchronous head of the broadcast time slot, and the frequency hopping receiver and the frequency hopping transmitter can achieve initial frequency hopping synchronization. The broadcast message contains TOD information of the broadcast node, each frequency hopping receiver can know the network system time by detecting the broadcast node, and the error is the propagation path delay between the node and the broadcast node.
Specifically, the S1 includes the following steps:
s1.1, the main node of each frequency hopping transmitter transmits broadcast according to a time slot format of a synchronous head plus a data part;
assuming that the time factor TODH _ RADIO of the broadcast slot is a finite set of [ TODH _ RADIO1TODH _ RADIO2], [ TODH _ RADIO1TODH _ RADIO1+1TODH _ RADIO1+2], [ TODH _ RADIO2 TODH _ RADIO2+1TODH _ RADIO2+2], the hopping frequencies generated with the hopping keys are [ f00, f01, f02] and [ f10, f11, f12], respectively. As shown in fig. 3, the synchronization header of the broadcast transmitted by the master node of the frequency hopping transmitter adopts a spread spectrum sequence to perform cyclic transmission, and 2 groups of frequencies are adopted, and each group of 3 frequency points performs cyclic transmission for 4 times.
S1.2, each frequency hopping receiver monitors the broadcast sent by the frequency hopping transmitter and generates a synchronization head of a broadcast time slot sent by a service frequency capture main node, so that the initial frequency hopping synchronization of the frequency hopping receivers is realized;
the service frequency of the slave node of each frequency hopping receiver consists of a time factor and a frequency hopping key, the time factor of the slave node randomly selects one from a finite set [ TODH _ RADIO1TODH _ RADIO2] as TODH _ RADIO, and the service frequency [ f00 ', f01 ', f02 ' ]isgenerated. The slave node of the frequency hopping receiver searches for a sequence of sync heads in a slow scan fashion at the duty cycle frequency of the frequency hopping transmitter 1/4. When the local synchronization head sequence of the frequency hopping receiver and the relevant peak of matched filtering of the frequency hopping transmitter exceed the threshold, the frequency hopping frequency point of the broadcast time slot is considered to be successfully captured, and the initial frequency hopping synchronization of the frequency hopping receiver can be realized.
S1.3, the frequency hopping receiver demodulates and decodes the sensed broadcast message according to the synchronous head of the broadcast time slot, and obtains the initial TOD time of the network system, so that the TOD time coarse synchronization of the frequency hopping receiver and the frequency hopping transmitter is realized.
After the frequency hopping initial synchronization is realized, the frequency hopping receiver knows the frequency of the message sent by the frequency hopping transmitter, and each frequency hopping receiver can demodulate and decode the sensed broadcast message. The broadcast message contains TOD information of broadcast broadcasting nodes, and each frequency hopping receiver demodulates and decodes the sensed broadcast message, so that the initial TOD time of the network system can be obtained, and the time coarse synchronization of the frequency hopping receiver and the frequency hopping transmitter is realized.
S2, each frequency hopping receiver generates an initial frequency hopping pattern of the RTT time slot according to the initial TOD time, and adjusts the initial TOD time of the network according to the RTT response message obtained by the initial frequency hopping pattern, so as to realize the precise synchronization of the TOD time of each frequency hopping receiver;
after the initial frequency hopping synchronization is completed, the starting and stopping time of the frequency hopping receiver and the frequency hopping transmitter reaches coarse synchronization, but due to clock drift, relative motion and the like of the transmitter or the receiver, each node also needs to continuously adjust the clock of the local frequency hopping sequence generator to maintain the consistency of the frequency hopping time and the frequency hopping pattern among the nodes. The invention realizes time calibration by adopting a Round Trip Timing (RTT) algorithm. The slave node sends RTT inquiry information in an RTT time slot, receives RTT response information replied by the master node in the same time slot, and calculates the correction quantity of the slave node system clock according to the arrival time of the response information. And the plurality of slave nodes adopt the same method to respectively carry out time correction through the master node at the RTT time slots pre-allocated by the slave nodes, and the TOD time of each node in the network realizes fine synchronization.
Specifically, the S2 includes the following steps:
s2.1, the slave nodes of all frequency hopping receivers use the initial TOD time of the network system obtained in the coarse synchronization as the local time to generate an initial frequency hopping pattern of an RTT time slot, then send RTT inquiry messages in the pre-allocated RTT time slot according to the generated initial frequency hopping pattern of the RTT time slot and receive RTT response messages replied by the master node in the same time slot;
in the invention, RTT time slots of all 12 nodes are distributed in continuous 3 frames, and idle service time slots can be randomly selected as RTT time slots by monitoring a time slot occupation identifier in a broadcast message.
And S2.2, the slave nodes of all the frequency hopping receivers calculate a time correction value according to the time information and the time slot length in the RTT response message, and adjust the local time to obtain the precisely synchronized TOD time.
Specifically, the slave node of each frequency hopping receiver calculates a time correction value according to the RTT message arrival time and the time slot length in the RTT response message, and adjusts the local time, thereby obtaining the TOD time that is precisely synchronized with the frequency hopping transmitter. After each frequency hopping receiver in the network realizes time fine synchronization, each frequency hopping receiver in the network has uniform TOD time, the frequency hopping edges of each frequency hopping receiver and each frequency hopping transmitter are ensured to be consistent, and the frequency hopping patterns are also ensured to be consistent.
And S3, each frequency hopping transmitter and each frequency hopping receiver generate service time slot frequency hopping patterns according to the current fine synchronization TOD time, and the frequency hopping synchronization of each frequency hopping receiver and each frequency hopping transmitter is realized.
In each service time slot, the master node of each frequency hopping transmitter transmits service data according to the service time slot frequency hopping pattern, and the slave node of each frequency hopping receiver receives the service data according to the service time slot frequency hopping pattern. During service communication, the master node of each frequency hopping transmitter periodically corrects the slave node of each frequency hopping receiver through the RTT time slot, and the frequency hopping transceiver is in the TOD time fine synchronization and frequency hopping synchronization state with the frequency hopping transmitter. In addition, the frequency hopping transmitter in the network is judged to send the message according to the ID received in the service data message.
The invention realizes the frequency hopping synchronization of the multi-user frequency hopping network through two steps of coarse synchronization and fine synchronization. The rough synchronization is realized by capturing a broadcast time slot synchronization head on the service frequency, the error deviation of the initial time of each frequency hopping receiver is not limited, special equipment is not needed for maintaining the initial time of each frequency hopping receiver, and the hardware platform has strong universality; the precision synchronization is realized by transmitting RTT round trip timing messages in the preassigned time slots through the master node and the slave node, calculating a time correction value and correcting the time, and the method has the advantages of reducing the complexity of a system and reducing the cost of products at the cost of small time overhead and without a special time service module.
While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims.
Claims (2)
1. A frequency hopping synchronization method, comprising the steps of:
s1, each frequency hopping receiver captures a synchronization head of a broadcast message sent by a frequency hopping transmitter, and obtains the initial TOD time of the network system to realize the TOD time coarse synchronization of each frequency hopping receiver;
s2, each frequency hopping receiver generates an initial frequency hopping pattern of the RTT time slot according to the initial TOD time, and adjusts the initial TOD time of the network according to the RTT response message obtained by the initial frequency hopping pattern, so as to realize the precise synchronization of the TOD time of each frequency hopping receiver;
s3, each frequency hopping transmitter and each frequency hopping receiver generate service time slot frequency hopping patterns according to the current fine synchronization TOD time, and frequency hopping synchronization of each frequency hopping receiver and each frequency hopping transmitter is realized;
the S1 includes the following steps:
s1.1, the main node of each frequency hopping transmitter transmits a broadcast message according to a time slot format of a synchronous head plus a data part;
s1.2, each frequency hopping receiver monitors the broadcast sent by the frequency hopping transmitter and generates a synchronization head of a broadcast time slot sent by a service frequency capture main node, so that the initial frequency hopping synchronization of the frequency hopping receivers is realized;
s1.3, demodulating and decoding the sensed broadcast message by the frequency hopping receiver according to a synchronous head of the broadcast time slot, and acquiring the initial TOD time of the network system, so as to realize the TOD time coarse synchronization of the frequency hopping receiver and the frequency hopping transmitter;
the S2 includes the following steps:
s2.1, the slave nodes of all frequency hopping receivers use the initial TOD time of the network system obtained in the coarse synchronization as the local time to generate an initial frequency hopping pattern of an RTT time slot, then send RTT inquiry messages in the pre-allocated RTT time slot according to the generated initial frequency hopping pattern of the RTT time slot and receive RTT response messages replied by the master node in the same time slot;
and S2.2, the slave nodes of all the frequency hopping receivers calculate a time correction value according to the time information and the time slot length in the RTT response message, and adjust the local time to obtain the precisely synchronized TOD time.
2. A frequency hopping synchronisation method as claimed in claim 1, in which each frequency hopping receiver uses a duty frequency slow scan to capture the synchronisation header of the broadcast slot transmitted by the master node.
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| CN114124154B (en) * | 2020-08-31 | 2023-02-10 | 如般量子科技有限公司 | Frequency hopping synchronization method and system based on TOD |
| CN114726399B (en) * | 2022-03-14 | 2023-05-23 | 中国电子科技集团公司第十研究所 | Space-frequency two-dimensional frequency hopping transmission system and transmission method of non-ground network |
| CN114978236A (en) * | 2022-05-20 | 2022-08-30 | 湖南国科锐承电子科技有限公司 | Frequency hopping synchronization method based on TOD |
| CN115102577B (en) * | 2022-07-01 | 2023-06-16 | 西安宇飞电子技术有限公司 | Single carrier time-frequency domain anti-interference method, system and storage medium |
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| CN110839269B (en) * | 2019-11-26 | 2021-04-02 | 中国电子科技集团公司第五十四研究所 | Broadband frequency hopping clustering multilevel self-organizing network waveform design method |
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| CN102710286A (en) * | 2012-06-19 | 2012-10-03 | 电子科技大学 | Fast frequency hopping synchronization method based on time of day (TOD) information |
| CN103391114A (en) * | 2013-07-29 | 2013-11-13 | 大连大学 | Fast capture method of frequency hopping communication during satellite communication |
| CN104468013A (en) * | 2014-11-21 | 2015-03-25 | 中国运载火箭技术研究院 | Time slot structure determination method for wireless networking communication |
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