CN112636782A - Cognitive anti-interference quick frame synchronization method with low overhead in frequency hopping communication - Google Patents

Cognitive anti-interference quick frame synchronization method with low overhead in frequency hopping communication Download PDF

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CN112636782A
CN112636782A CN202011512941.5A CN202011512941A CN112636782A CN 112636782 A CN112636782 A CN 112636782A CN 202011512941 A CN202011512941 A CN 202011512941A CN 112636782 A CN112636782 A CN 112636782A
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noise power
frequency point
network access
frequency
frame synchronization
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CN112636782B (en
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万佳君
张立冬
刘飞
段鹏
石伟明
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CETC 20 Research Institute
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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
    • 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
    • H04B1/715—Interference-related aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/382—Monitoring; Testing of propagation channels for resource allocation, admission control or handover
    • 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
    • H04B2001/71563—Acquisition
    • 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
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Abstract

The invention provides a low-overhead cognitive anti-interference rapid frame synchronization method in frequency hopping communication, which comprises the steps of carrying out frequency spectrum sensing and noise power updating before network access after starting up initialization, selecting an optimal synchronization frequency point before network access, then carrying out network access signal frame synchronization and noise power updating and on-network frequency spectrum sensing and noise power updating, selecting an optimal synchronization frequency when network is accessed, and carrying out signal frame synchronization and noise power updating when network is accessed. The invention dynamically avoids the frequency point with serious interference, reduces the influence of the interference on frame synchronization, improves the anti-interference capability of frequency hopping communication frame synchronization, automatically adapts to the change of a channel environment, has simple processing mechanism and does not increase network overhead.

Description

Cognitive anti-interference quick frame synchronization method with low overhead in frequency hopping communication
Technical Field
The invention relates to the technical field of frequency hopping communication, provides a method for carrying out low-overhead, anti-interference and rapid frame capture and synchronization by comprehensively utilizing redundant synchronization pulses and frequency point cognitive information, and is suitable for anti-interference rapid frame synchronization of a single-channel frequency hopping receiving terminal.
Background
The complexity of the electromagnetic environment and the existence of interference generally cause the deterioration of partial frequency point channels used for frequency hopping communication, which affects the communication performance, and especially after the frame synchronization signal is affected, the signal capture failure is easily caused, which causes the communication packet loss. For example, in a common non-anti-interference frequency hopping communication system, a transceiver and a receiver agree to a certain frequency point to transmit a synchronization pulse according to a time interval, a receiver holds on the frequency point to scan and detect to complete frame capture and synchronization, and if the agreed frequency point is subjected to strong interference, the system interrupts communication in the time interval. Frame capture synchronization is an important link influencing the anti-interference performance of a frequency hopping communication system, and the anti-interference performance of the frame capture synchronization is one of the key problems in a robust frequency hopping communication system (especially a military frequency hopping communication system).
At present, the anti-interference capturing and synchronizing methods of frequency hopping communication are mainly divided into two methods: the method for synchronizing the slow frequency hopping serial search and the method for synchronizing the multi-frequency point parallel receiving joint detection.
The slow frequency hopping serial search synchronization method is shown in fig. 1, a synchronization head is divided into a plurality of hopping pulses and continuously transmits for a plurality of times according to a non-repetitive pattern, a receiving end uses the same frequency point set to perform frequency point-by-frequency point slow scanning, and synchronous capture can be completed when the pulses are detected. The method is suitable for a single-channel receiving terminal (only can receive signals on one frequency point in real time, and cannot simultaneously receive multiple frequency points), has anti-interference capability, and can finish frame capture and synchronization when a receiving end scans the undisturbed frequency points alternately when some frequency points are subjected to strong interference; however, the method has large overhead of a synchronization head and long acquisition and synchronization time.
As shown in fig. 2, a synchronization head includes a plurality of pulses, a synchronization code sequence is dispersed in each synchronization pulse, a receiving end scans a plurality of frequency points simultaneously to perform correlation detection on the synchronization code sequence, and accumulates correlation values to obtain a joint detection result, and performs frame synchronization decision on the joint detection result according to a synchronization threshold. The method has the advantages that the overhead of the synchronization head is low, the synchronization speed is high, the anti-interference capability is realized, if partial frequency point interference occurs, the correlation value of the interfered frequency point is reduced at the synchronization alignment moment, but the correlation detection value of the non-interfered frequency point is unchanged, and the joint detection result can still exceed the judgment threshold, so that the partial frequency point interference can be resisted. However, this method is only suitable for a frequency hopping communication system employing a multi-channel receiving terminal. The multi-channel receiving terminal can simultaneously receive and cache signals of multiple frequency points so as to support multi-hop synchronous pulse joint detection, but the terminals need to design independent hardware circuits for different channels, and the complexity, the volume, the weight, the power consumption and the cost of the equipment are increased along with the increase of the number of the channels. Therefore, some small terminals, such as small unmanned aerial vehicle terminals and handheld terminals, often have only one receiving channel. In a small terminal application scene, the condition of using the multi-frequency point parallel receiving joint detection method is not provided.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a cognitive anti-interference quick frame synchronization method with low overhead in frequency hopping communication. Aiming at the defects of the anti-interference frame synchronization method in the existing frequency hopping communication and surrounding the anti-interference frame synchronization requirement of a single-channel small terminal, the invention provides a low-overhead cognitive anti-interference rapid frame synchronization method comprehensively utilizing redundant synchronization pulses and frequency point cognition, which is suitable for a single-channel terminal and can enable the frequency hopping communication to have anti-interference rapid frame capture and synchronization capability under low overhead.
The technical scheme adopted by the invention for solving the technical problem comprises the following steps:
(1) starting up and initializing: the terminal is provided with a cache of noise power of each frequency point in the frequency hopping frequency point set, and the cache is initialized after a receiving end is started, wherein the initialization value is 0;
(2) spectrum sensing and noise power updating before network access: the receiving end carries out periodic sensing on the frequency spectrum environment before network access, carries out network access signal detection after sensing, and carries out sensing and signal detection again if the detection fails, so that periodic circulation is formed until the detection is successful; sensing period T before network accesssens_outnetIncluding a sensing time tsensThe same as the network access signalStep detection time tdetect，tsensDetermined by a perception algorithm, in milliseconds, tdetectGreater than Tmsg_netThe method comprises the steps of obtaining the current noise power of each frequency point in a frequency hopping frequency point set by ensuring that a network access message is inevitably sent in a detection time, and updating the noise power cache of each frequency point by combining the noise power information of each frequency point forming the cache through perception;
(3) selecting the optimal synchronous frequency point before network access: after the receiving end finishes frequency spectrum sensing, according to the network access frequency hopping pattern and noise power information of each frequency point in the cache, selecting a frequency point with the minimum noise power as an optimal synchronization frequency point from frequency points used by a frame synchronization head pattern (frequency hopping patterns used by K synchronization pulses before a signal frame), and switching to the optimal synchronization frequency point for standing;
(4) network access signal frame synchronization and noise power updating: performing frame synchronization detection at the optimal synchronization frequency point, if detecting the network access signal, receiving the network access signal and completing network access, and if detecting the time tdetectWhen the network access signal is not detected, the step (2) is carried out, and then the detection is carried out again until the network access is carried out;
(5) spectrum sensing and noise power updating in the network: when the receiving end is on the network, carrying out spectrum sensing in a periodically appearing spectrum sensing time window, and updating the noise power cache of each frequency point, wherein the updating method is the same as the step (2);
(6) selecting the optimal synchronous frequency point during network: if the current time is in the network access time window, switching the current frequency hopping pattern into a network access pattern; if the current frequency hopping pattern is in the service time window, the current frequency hopping pattern is switched to a service pattern, the service pattern is obtained by pattern algorithm according to the current time and frequency hopping frequency point set calculation, then the best synchronous frequency point with the minimum noise power is selected from the frequency points used by the frame synchronization head in the current frequency hopping pattern, and the best synchronous frequency point is switched to the best synchronous frequency point for holding;
(7) signal frame synchronization and noise power update at network time: the received message is network access message or service message, no matter the signal of network access message or service message, the frame capture synchronous detection method and step (4)The detection methods of the correlation values of the medium network access signals are the same, when signal receiving processing is carried out after successful detection, the noise power estimation updating method which is the same as the noise power estimation updating method in the step (4) is adopted to estimate the noise power of the frequency point used by the data pulse, and the noise power cache is updated; but in the frame acquisition synchronization detection process of the service message, if the service pattern switching time (current T) is reachedfh_taskEnd time), then go to step (6); otherwise, continuing to detect until the sending time window of the network access message or the service message is finished.
When the noise power is updated, a weighted average algorithm is adopted, the noise power of a certain frequency point in the previous cache is P, the weighting coefficient is alpha, the noise power of the frequency point obtained by the current spectrum sensing is P ', the weighting coefficient is alpha', and then the updated noise power is: p ═ α P + α 'P', and updating the buffer, where α + α 'is 1 and α' is greater than or equal to α, so as to obtain a faster spectrum environment reaction speed; and if the first sensing is carried out, the updated noise power of each frequency point is taken as the current sensed noise power, namely P ═ P'.
The frame synchronization detection adopts a frame synchronization signal and local signal cross-correlation algorithm, if the detected signal correlation value is greater than a frame synchronization judgment threshold, the frame synchronization capture is marked to be successful, and the data segment follow-jump receiving is carried out by taking the maximum correlation value time as the frame synchronization time; after receiving the data segment signal, demodulating and decoding the data segment signal to obtain network access information, completing network access and entering a network-in state; and (3) carrying out channel estimation of data pulses while receiving and processing the data segment signals, obtaining the noise power of the used frequency points, and updating the noise power cache of each frequency point by adopting the noise power updating method in the step (2).
The signal correlation value is calculated as follows:
Figure BDA0002846977120000031
wherein the receiving signal is S (N), the local signal is L (N), the signal length is N, N is the signal sampling time, L (N)*Is the conjugate of L (n), r is the mean square of S (n)Root, the calculation formula is as follows:
Figure BDA0002846977120000032
wherein, S (n)*Is the conjugate of S (n).
The invention has the advantages that the frame synchronization head comprises a plurality of frequency hopping pulses with different frequency points, any one of the pulses can be used for completing frame capture and synchronization, and the receiving end uses the optimal synchronization frequency point with the minimum noise power for synchronous camping, so that the frequency point with serious interference is dynamically avoided, the influence of the interference on frame synchronization is reduced, and the anti-interference capability of the frequency hopping communication frame synchronization is improved; the receiving end can update the noise power condition of each frequency point in real time and can automatically adapt to the change of the channel environment; the invention does not need to transmit and receive the synchronous frequency points appointed to be used in advance at the two ends, has simple processing mechanism and does not increase network overhead; compared with the slow frequency hopping serial search method, the method has the advantages of less required synchronous pulse number, low synchronous overhead and high synchronous speed; the invention is suitable for a single-channel small receiving terminal.
Drawings
Fig. 1 is a schematic diagram of frequency sweeping of frame synchronization frequency points in a slow frequency hopping serial search method.
Fig. 2 is a schematic diagram of frame synchronization frequency point camping in a multi-frequency point parallel reception joint detection synchronization method.
Fig. 3 is a schematic diagram of synchronous frequency point camping according to the present invention.
Fig. 4 is a design example of network time allocation with spectrum sensing function.
FIG. 5 is a flow chart of frame synchronization detection according to the present invention.
Fig. 6 is a diagram illustrating a frame format and a frame synchronization timing.
Fig. 7 is a diagram of the frame synchronization anti-interference performance of a frequency hopping communication system using the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and examples.
In the invention, the frame synchronization head comprises a plurality of frequency hopping pulses (the number of the synchronization pulses is assumed to be K), different frequency points are used, and each pulse comprises a complete frame synchronization code sequence, so that when a receiving end independently performs synchronous detection on any one pulse, the frame capture and synchronization can be completed.
In the invention, when a sending end sends messages (including network access messages and service messages) in a frequency hopping manner, a frame synchronization head mode of redundant pulses is adopted, namely, a message frame synchronization head comprises a plurality of frequency hopping pulses (the number of the synchronization pulses is recorded as K) using different frequency points, and each synchronization frequency hopping pulse comprises a complete frame synchronization code, so that when a receiving end independently carries out synchronization detection on any one pulse, frame capture and synchronization can be completed. The receiving end selects the frequency point with the minimum noise power as the optimal synchronization frequency point among the multiple frequency points used by the frame synchronization head for performing the camping detection, thereby effectively avoiding interference, quickly completing the frame capture synchronization, and performing the hop following reception in the message data segment to obtain the message sent by the opposite end, as shown in fig. 3.
In practical applications, frame capture synchronization includes two cases: the messages before network entry (containing only network entry messages) are synchronized, and the messages on network (including service messages and network entry messages) are synchronized. The network access information is transmitted periodically by the central node, the used network access frequency hopping pattern is not changed generally, and the transmission period T ismsg_netThe network layer design determines that the network layer is generally second level or ten second level, and other nodes complete network access and system synchronization after receiving the network access message; the service message is sent by the participatory node (including the central node), the service frequency hopping pattern used is changed periodically, and the change period Tfh_taskIt is also determined by the network design, and is typically in the order of milliseconds or tens of millimeters, which is much larger than the system synchronization error. The service frequency hopping pattern is calculated by a pattern algorithm according to the frequency point set and the time information, and each node can obtain the same frequency hopping pattern by using the same frequency point set and the same time information. Before the nodes to be accessed are accessed to the network, the local time is not uniform with the network time, and the nodes to be accessed to the network use the network access frequency hopping pattern to carry out frame capture synchronous detection and receiving on the network access signals so as to complete system synchronization; after network entry, the nodes have completed system synchronization, based on network timeAnd calculating a service frequency hopping pattern, and detecting the capture synchronization of the service message frame by using the service frequency hopping pattern. The invention provides a better network time allocation design example with a spectrum sensing function, as shown in fig. 4, the time window is divided into time windows of spectrum sensing, network access message sending, service message sending and the like, and the window widths are respectively recorded as: wsens、Wnet、WtaskWherein W issensGreater than the time length t of spectrum sensingsensGenerally, the frequency spectrum sensing operation is carried out on all network access nodes in the window, and because no node sends the frequency spectrum sensing operation, the intra-network interference is effectively avoided; in the time window of sending the service message, access modes such as TDMA, CSMA and the like can be used; the time between two adjacent frequency spectrum sensing windows is a sensing period Tsens_innetDetermined by the network design, Tsens_innetThe larger the network overhead, Tsens_innetThe smaller the response to changes in the spectral environment.
In the invention, spectrum sensing can not be carried out during networking, namely, a spectrum sensing time window is not distributed, so that the network overhead is further saved, and the spectrum environment cognition and the real-time interference avoidance can still be carried out only by replacing the spectrum sensing result with the data pulse frequency point noise power estimation result during message receiving. Under the condition, if the data segment does not use all the frequency point sets, the noise power condition of part of the unused frequency points cannot be updated in time, and certain influence is exerted on the subsequent selection of the optimal synchronous frequency points.
In addition, when frame capture synchronous detection is carried out on the network access signal before network access, spectrum sensing is not needed, and a spectrum sensing window is not distributed, so that a spectrum sensing module is not added in the system, and the processing complexity of a receiving end is reduced. In this case, before accessing the network, one frequency point can be randomly selected as an "optimal synchronization frequency point" to perform frame capture synchronization detection on the access signal, and if the access signal is not detected in the detection period, the "optimal synchronization frequency point" is randomly replaced until the detection is successful. In this case, because the randomly selected "optimal synchronization frequency point" may be an interfered frequency point, it is difficult to detect successfully in a few detection periods, which causes a decrease in network access speed, but after network access, the frequency spectrum environment can still be recognized based on the data pulse frequency point noise power estimation information during message reception, so that the optimal synchronization frequency point is selected, and the synchronization overhead can still be reduced and the anti-interference capability of the system can still be improved.
As shown in fig. 5, the specific implementation method is as follows:
[ step 1]
And after the receiving end is started, initializing the noise power caches of all frequency points. Assuming that the frequency hopping frequency point set is F, the total frequency comprises Q frequency points, which are denoted as { F1,f2,f3,…,fq,,fQAnd recording the noise power of each frequency point in the cache as { P }1,P2,P3,…,Pq,,PQIt is initialized to 0 as follows:
Pq＝0,q＝1,2,3,…Q.
[ step 2]
And the receiving end senses the frequency spectrum environment and updates the noise power cache of each frequency point according to the sensing result. The specific substeps are as follows:
[ step 2.1]
Carrying out frequency spectrum sensing on the surrounding electromagnetic environment to obtain the noise power of each frequency point in the frequency hopping frequency point set, and recording as { P1',P2',P3',…,Pq',,PQ'}。
[ step 2.2]
And updating the cache by adopting a weighted average algorithm according to the noise power of each frequency point perceived by the current frequency spectrum and the noise power of each frequency point cached. The weighting coefficient of the noise power in the cache is alpha, the weighting coefficient of the noise power obtained by spectrum sensing is alpha', and the updated noise power { P1”,P2”,P3”,…,Pq”,…,PQ"}, the calculation is as follows:
Figure BDA0002846977120000061
where α + α' ═ 1, for example: α ═ 0.5, α' ═ 0.5. Then, let:
{P1,P2,P3,…,Pq,…,PQ}＝{P1”,P2”,…P3”,…,Pq”,…,PQ”}
and use it to buffer { P1,P2,P3,…,Pq,…,PQAnd (6) updating. In addition, alpha' is more than or equal to alpha, so that a faster spectrum environment reaction speed is obtained.
[ step 3]
And the receiving end selects the optimal synchronous frequency according to the noise power condition in the cache and the network access frequency hopping pattern. Suppose the network-entry hopping code sequence is { h }1,h2,h3,…,hm,…,hMIn which h ismM is the length of the network access message frequency hopping code sequence, and M is an integer ranging from 1 to M. Selecting frequency point sequences from the frequency point set F according to the frequency hopping code sequence to form a network access message frequency hopping pattern, wherein the first K frequency point sequences are frame synchronization head patterns and are recorded as
Figure BDA0002846977120000071
According to the noise power buffer, selecting the frequency point with the minimum noise power from the frequency points of the frame synchronization head pattern as the optimal synchronization frequency point foptThe following are:
Figure BDA0002846977120000072
then switch to foptAnd (5) performing parking.
[ step 4]
Receiving end at optimal synchronous frequency point foptAnd carrying out frame capture synchronous detection on the network access signal. The specific substeps are as follows:
[ step 4.1]
At the optimum synchronous frequency foptAnd performing frame capture synchronous detection on the network access signal by adopting a signal correlation algorithm. Assuming that the received signal is S (N), the local signal is L (N), and the signal length is N, the phases are equalThe way of calculating the closing value is as follows:
Figure BDA0002846977120000073
wherein n is the signal sampling time, L (n)*Is the conjugate of L (n), r is the root mean square of S (n), as follows:
Figure BDA0002846977120000074
[ step 4.2]
Judging according to frame synchronization judgment threshold B, if the correlation value is greater than the threshold, namely R is greater than B, marking that the frame synchronization detection is successful, namely capturing the network access signal, and taking the time of the maximum correlation value as the frame synchronization time tsThen, the data segment of the network access information is processed with the jump receiving, demodulation and decoding to obtain the network access information and complete the network access, and then the procedure goes to step 4.4](ii) a Otherwise, if the correlation value is not greater than the threshold, judging whether the current time reaches the detection time tdetectThe end time of (c). The following jump algorithm is shown in fig. 6, and it is assumed that the frame synchronization header time length is TsThe total length of the synchronous pulse and the pulse switching time is TpIf the synchronous camping frequency point is the frequency point used by the kth pulse in the synchronous head, the starting time of the data segment is calculated in the following way:
td＝ts+Ts-(k-1)Tp
[ step 4.3]
If the current time reaches tdetectGo to step 2.1](ii) a Otherwise, go to [ step 4.1]]And continuing to perform frame capture synchronous detection of the network access signal.
[ step 4.4]
When the data segment is subjected to the following hop and the signal is processed, channel estimation is carried out to obtain the noise power of the frequency point used by each data pulse
Figure BDA0002846977120000081
By usingAnd [ step 2.2]And updating the noise power cache of each frequency point by using the same weighted average algorithm.
[ step 5]
And after the receiving end enters the on-line state, judging whether the current moment is in a frequency spectrum sensing time window, and if not, turning to step 7.
[ step 6]
And the receiving end senses the frequency spectrum environment. The specific substeps are as follows:
[ step 6.1]
And the receiving end carries out frequency spectrum sensing on the electromagnetic environment, which is the same as the step 2.1.
[ step 6.2]
And updating the noise power buffer according to the spectrum sensing result, which is the same as step 2.2, and then turning to step 5.
[ step 7]
If the current time is in the network access message time window, the receiving end selects the frequency hopping pattern as the network access pattern; if the current time is in the service message time window, the receiving end calculates the current frequency hopping code sequence H (T, F) { H ] according to the current time information T and the size of the frequency point set F1,h2,h3,…,hi,…,hIIn which h isiAnd selecting a frequency point sequence from the frequency point set F according to the frequency hopping code sequence to form a service pattern as a current pattern, wherein the first K frequency point sequences are the frequency hopping patterns of the frame synchronization head. When the service pattern is calculated, the pattern algorithms at the transmitting end and the receiving end are the same, and the same frequency point set and the same time information are used, so that the same frequency hopping pattern is obtained.
[ step 8]
The receiving end selects the best synchronous frequency according to the noise power condition in the buffer and the current frequency hopping pattern (the network access frequency hopping pattern or the service frequency hopping pattern selected in the step 7), which is the same as the selection method in the step 3.
[ step 9.1]
And the receiving end carries out frame capture synchronous detection at the optimal synchronous frequency point, and the detection method is the same as the step 4.1.
[ step 9.2]
The receiving end carries out synchronous judgment according to the frame synchronous judgment threshold, the judgment method is the same as the step 4.2, if the frame capturing synchronization is successful, the step 10.1 is carried out.
[ step 9.3]
Judging whether the current time reaches the switching period T of the frequency hopping patternfhIf the end time of (2) has reached the end time, go to step 5](ii) a Otherwise, go to [ step 9.1]]. Wherein, TfhIs related to the time window in which it is located, as follows:
Figure BDA0002846977120000091
[ step 10.1]
And after the frame capturing synchronization is successful, the receiving end receives, demodulates and decodes the data segment of the message according to the current frequency hopping pattern, and the hop following algorithm is the same as the step 4.2.
[ step 10.2]
And (5) as in the step 4.4, updating the noise power of each frequency point in the cache according to the channel estimation result. And then go to step 9.3.
The anti-interference capability of the frame synchronization head can be measured by the successful probability of frame synchronization under different interference conditions, the size of the frequency point set is assumed to be Q, the number of frequency points used by the synchronization head is K (wherein K is less than Q), and the total length of the synchronization pulse and the pulse switching time is TpAnd the frequency point quantity proportion subjected to suppressing interference in the frequency hopping frequency point set is beta, the theoretical probability of successful frame synchronization of the invention is as follows:
Figure BDA0002846977120000092
the overall performance of the invention is compared to other methods and is detailed in the table below. The comprehensive performance of the invention is equivalent to the multi-frequency point parallel receiving joint detection synchronization method suitable for the multi-channel terminal.
Figure BDA0002846977120000093
In the invention, the frequency point set size is taken as Q being 50, and the specific theoretical probability of successful frame synchronization under the typical synchronization pulse number and interference ratio is shown in the following table:
Figure BDA0002846977120000101
in the frequency hopping communication system using the present invention, the size of the frequency point set is Q50, and the frame synchronization anti-interference theoretical curve and the simulation result are shown in fig. 7 under different numbers of synchronization pulses. The invention is degenerated to a common frame synchronization method of a single-channel terminal without anti-interference capability when K is 1, but the success probability of frame synchronization can be obviously improved under the condition of using a plurality of synchronization pulses, and the interference can be effectively resisted. For example, when 5 synchronization pulses are used, under the condition that a 50% proportion of frequency points are interfered, the frame synchronization success probability is over 95%, while the frame synchronization success probability of the common frame synchronization method of a single-channel terminal is only 50%.

Claims (5)

1. A cognitive anti-interference quick frame synchronization method with low overhead in frequency hopping communication is characterized by comprising the following steps:
(1) starting up and initializing: the terminal is provided with a cache of noise power of each frequency point in the frequency hopping frequency point set, and the cache is initialized after a receiving end is started, wherein the initialization value is 0;
(2) spectrum sensing and noise power updating before network access: the receiving end carries out periodic sensing on the frequency spectrum environment before network access, carries out network access signal detection after sensing, and carries out sensing and signal detection again if the detection fails, so that periodic circulation is formed until the detection is successful; sensing period T before network accesssens_outnetIncluding a sensing time tsensSynchronous detection time t with network access signaldetectTo ensure that there is a necessary entry in the detection timeThe network message is sent, the current noise power of each frequency point in the frequency hopping frequency point set is obtained, and the noise power cache of each frequency point is updated by combining the noise power information of each frequency point forming cache through perception;
(3) selecting the optimal synchronous frequency point before network access: after the receiving end finishes frequency spectrum sensing, according to the network access frequency hopping pattern and noise power information of each frequency point in the cache, selecting the frequency point with the minimum noise power as the optimal synchronous frequency point from the frequency points used by the frame synchronization head pattern, and then switching to the optimal synchronous frequency point for standing;
(4) network access signal frame synchronization and noise power updating: performing frame synchronization detection at the optimal synchronization frequency point, if detecting the network access signal, receiving the network access signal and completing network access, and if detecting the time tdetectWhen the network access signal is not detected, the step (2) is carried out, and then the detection is carried out again until the network access is carried out;
(5) spectrum sensing and noise power updating in the network: when the receiving end is on the network, carrying out spectrum sensing in a periodically appearing spectrum sensing time window, and updating the noise power cache of each frequency point, wherein the updating method is the same as the step (2);
(6) selecting the optimal synchronous frequency point during network: if the current time is in the network access time window, switching the current frequency hopping pattern into a network access pattern; if the current frequency hopping pattern is in the service time window, the current frequency hopping pattern is switched to a service pattern, the service pattern is obtained by pattern algorithm according to the current time and frequency hopping frequency point set calculation, then the best synchronous frequency point with the minimum noise power is selected from the frequency points used by the frame synchronization head in the current frequency hopping pattern, and the best synchronous frequency point is switched to the best synchronous frequency point for holding;
(7) signal frame synchronization and noise power update at network time: the received information is network access information or service information when in network, no matter the signal of the network access information or the service information, the frame capture synchronous detection method is the same as the correlation value detection method of the network access signal in the step (4), when the signal is received and processed after the detection is successful, the noise power estimation updating method which is the same as the noise power estimation updating method in the step (4) is adopted to estimate the noise power of the frequency point used by the data pulse, and the noise power cache is updated; but instead of the other end of the tubeIn the frame capture synchronous detection process of the service message, if the switching time (current T) of the service pattern is reachedfh_taskEnd time), then go to step (6); otherwise, continuing to detect until the sending time window of the network access message or the service message is finished.
2. The method according to claim 1, wherein the method for cognitive interference-free fast frame synchronization with low overhead in frequency hopping communication comprises:
when the noise power is updated, a weighted average algorithm is adopted, the noise power of a certain frequency point in the previous cache is P, the weighting coefficient is alpha, the noise power of the frequency point obtained by the current spectrum sensing is P ', the weighting coefficient is alpha', and then the updated noise power is: p ═ α P + α 'P', and updating the buffer, where α + α 'is 1 and α' is greater than or equal to α, so as to obtain a faster spectrum environment reaction speed; and if the first sensing is carried out, the updated noise power of each frequency point is taken as the current sensed noise power, namely P ═ P'.
3. The method according to claim 1, wherein the method for cognitive interference-free fast frame synchronization with low overhead in frequency hopping communication comprises:
the frame synchronization detection adopts a frame synchronization signal and local signal cross-correlation algorithm, if the detected signal correlation value is greater than a frame synchronization judgment threshold, the frame synchronization capture is marked to be successful, and the data segment follow-jump receiving is carried out by taking the maximum correlation value time as the frame synchronization time; after receiving the data segment signal, demodulating and decoding the data segment signal to obtain network access information, completing network access and entering a network-in state; and (3) carrying out channel estimation of data pulses while receiving and processing the data segment signals, obtaining the noise power of the used frequency points, and updating the noise power cache of each frequency point by adopting the noise power updating method in the step (2).
4. The method according to claim 1, wherein the method for cognitive interference-free fast frame synchronization with low overhead in frequency hopping communication comprises:
the signal correlation value is calculated as follows:
Figure FDA0002846977110000021
wherein the receiving signal is S (N), the local signal is L (N), the signal length is N, N is the signal sampling time, L (N)*Is the conjugate of L (n), r is the root mean square of S (n), and the calculation formula is as follows:
Figure FDA0002846977110000022
wherein, S (n)*Is the conjugate of S (n).
5. The method according to claim 1, wherein the method for cognitive interference-free fast frame synchronization with low overhead in frequency hopping communication comprises:
tsensdetermined by a perception algorithm, in milliseconds, tdetectGreater than Tmsg_net。
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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113595567A (en) * 2021-07-23 2021-11-02 华中科技大学 Anti-interference communication method and system
CN114696942A (en) * 2022-03-25 2022-07-01 电子科技大学 Interference method suitable for unmanned aerial vehicle communication link
CN115412126A (en) * 2022-08-29 2022-11-29 四川九洲电器集团有限责任公司 Anti-interference method and device suitable for TDMA communication system
CN116131880A (en) * 2023-04-19 2023-05-16 中国电子科技集团公司第五十四研究所 Anti-interference method for single-channel high-speed frequency hopping data chain

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070064770A1 (en) * 2005-09-22 2007-03-22 Kabushiki Kaisha Toshiba Wireless communication apparatus and wireless communication method
CN103441779A (en) * 2013-09-22 2013-12-11 郭建新 Frequency hopping communication anti-interference method based on cognitive radio
CN106849995A (en) * 2017-01-17 2017-06-13 北京泛讯信息技术有限公司 Self adaptive frequency-hopping system and method
CN110611915A (en) * 2019-11-16 2019-12-24 西南电子技术研究所（中国电子科技集团公司第十研究所） Method for self-adaptive control of self-organizing frequency hopping network frequency
CN111342921A (en) * 2020-03-06 2020-06-26 西京学院 Cognitive radio-based frequency spectrum sharing method, system and application in frequency hopping communication

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20070064770A1 (en) * 2005-09-22 2007-03-22 Kabushiki Kaisha Toshiba Wireless communication apparatus and wireless communication method
CN103441779A (en) * 2013-09-22 2013-12-11 郭建新 Frequency hopping communication anti-interference method based on cognitive radio
CN106849995A (en) * 2017-01-17 2017-06-13 北京泛讯信息技术有限公司 Self adaptive frequency-hopping system and method
CN110611915A (en) * 2019-11-16 2019-12-24 西南电子技术研究所（中国电子科技集团公司第十研究所） Method for self-adaptive control of self-organizing frequency hopping network frequency
CN111342921A (en) * 2020-03-06 2020-06-26 西京学院 Cognitive radio-based frequency spectrum sharing method, system and application in frequency hopping communication

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN113595567A (en) * 2021-07-23 2021-11-02 华中科技大学 Anti-interference communication method and system
CN114696942A (en) * 2022-03-25 2022-07-01 电子科技大学 Interference method suitable for unmanned aerial vehicle communication link
CN114696942B (en) * 2022-03-25 2023-10-10 电子科技大学 Interference method suitable for unmanned aerial vehicle communication link
CN115412126A (en) * 2022-08-29 2022-11-29 四川九洲电器集团有限责任公司 Anti-interference method and device suitable for TDMA communication system
CN115412126B (en) * 2022-08-29 2023-09-22 四川九洲电器集团有限责任公司 Anti-interference method and device suitable for TDMA communication system
CN116131880A (en) * 2023-04-19 2023-05-16 中国电子科技集团公司第五十四研究所 Anti-interference method for single-channel high-speed frequency hopping data chain

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