A kind of frequency hopping communications anti-interference method based on cognitive radio
Technical field
The present invention cognitive radio is combined with frequency hopping communications field, be specifically related to a kind ofly in order to the anti-random disturbances, the bursty interference that improve frequency hopping radio set and mix the channel capacity under disturbed condition, reduces the method for the communication error rate of system under interference environment.
Background technology
Frequency hopping communications has good confidentiality, anti-near-far interference because of it and the performance such as anti-interference receives much concern, and is widely used in modern military shortwave, ultrashort wave and Data-Link signal equipment.Along with the complexity day by day of electromagnetic environment, existing frequency-hopping communication system is facing increasing problem and challenge, has influence on gradually the performance of frequency hopping jam-resistant communication system.
Validity (bandwidth, power system capacity) and reliability (error rate) are the main performance index of communication system.In actual application, there is following problem in the validity and reliability that runs into frequency hopping communications while disturbing:
In conventional frequency-hopping communication system, the frequency hopping pattern that receiving-transmitting sides carries out is to plan in advance, once communication link is set up, both sides will order travel through each frequency in frequency hopping pattern in communication process, seldom the frequency of frequency set carried out to quality analysis, we claim this frequency-hopping mode for " blindly jumping ".Under this pattern, even some frequency is subject to severe jamming, in order to guarantee the synchronous of receiving-transmitting sides frequency hopping pattern, system is still used these frequencies, and the interference on these frequencies mainly gains to suppress by system hops gain, frequency hopping rate and channel decoding.Day by day intensive along with the increasingly sophisticated and electromagnetic signal of electromagnetic environment, originally comparatively will be introduced into increasing unwanted signal and artificial disturbance in the frequency hopping communications frequency range of " totally ", the existence of these signals can destroy the frequency communication on more and more original frequency hopping frequency sets, cause a large amount of error codes, thereby reduce the antijamming capability of system.Frequency hopping point " collision " probability increases, and restriction frequency hopping communications networks capacity promotes.Along with Frequency Hopping Multiple Access FHMA, the extensive use of frequency hopping networking in radio communication, available frequency resources between between the interior different user of net, with the frequency range net being is also by growing tension, the orthogonality of frequency hopping pattern collection will more seldom arrive assurance, thereby cause the collision phenomenon of frequency hopping point day by day obvious, the capacity that directly restricts frequency hopping communications networks is promoted.
This method is dissolved into the relevant thought of cognitive radio among frequency hopping communications, by detecting periphery electromagnetic environment (disturbing intentionally, be not intended to interference, noise etc.), dynamically select the transmission band that " spectral window " that several interference temperatures are lower is used as Frequency Hopping Signal, can improve frequency hopping radio set to the adaptability of electromagnetic environment, increase the utilance of frequency spectrum resource, further suppress the network capacity of certainly disturbing, improve frequency hopping communications networks between enemy's malicious interference and radio station, reduce error rate of system.
Summary of the invention
Purpose of the present invention is exactly the advanced features in conjunction with cognitive radio thought, and a kind of reasonable in design, frequency hopping communications Anti-jamming of being easy to realize, do not change existing broadcasting station structure is provided, and significantly improves the capacity of system, reduces the error rate.
This technical scheme:
A kind of frequency hopping communications anti-interference method based on cognitive radio, it is characterized in that, described anti-interference method comprises three parts: the anti-interference spectral window detection method of frequency hopping communications, and reject to disturb frequency to obtain frequency hopping key under the method for spectral window and disturbed condition and share transmission method.
The anti-interference spectral window detection method of described frequency hopping communications is specially:
A, the whole frequency band used according to system hops and the bandwidth of each frequency, be divided into several relatively narrow sub-bands;
B, utilize the frequency spectrum sensing method of cognitive radio energy measuring, all frequency bands that system is supported carry out periodic perception detection, obtain the energy feature of each frequency band;
C, according to " interference temperature " situation in channel, detect whether there be " spectral window ", and provide the qualitative character of each " spectral window " according to corresponding criterion.
Described rejecting disturbs frequency to obtain the method for spectral window, is specially:
A, the signal detected in said method is carried out to windowing process and FFT conversion;
Statistic in B, calculation procedure A, determine and reject thresholding;
C, utilize the continuous average of FCME(to reject algorithm), reject to disturb and be not suitable for more greatly the frequency that frequency hopping is used, obtain not " spectral window " of disturbed applicable frequency hopping communications;
Spectral window and its management information that D, basis obtain, determine the usable frequency collection made new advances, and generates new frequency hopping pattern.
Under described disturbed condition, the frequency hopping key is shared transmission method, is specially:
1), newly-generated frequency hopping key information is divided into groups by the every jumping limit bandwidth of system;
2), the information after dividing into groups, in conjunction with the fountain codes coding rule, form and meet under disturbed condition the debit and easily receive and be difficult for the information frame that disturbed side intercepts and captures;
3), after the debit receives complete key information, send the ACK confirmation signal to originating party;
4), receiving-transmitting sides starts to carry out normal frequency hopping communications according to new frequency hopping pattern.
The invention has the beneficial effects as follows:
By periodic frequency spectrum detection, obtain the feature of system electromagnetic environment related communication frequency band, reject and disturb frequency to obtain being applicable to the spectral window of system hops communication and generating new frequency set, the new frequency hopping key of transmission under disturbed condition, realize the shared antijam communication of carrying out of receiving-transmitting sides, by increase corresponding detection, computing module to radio station, improve frequency hopping radio set antijam communication ability.The present invention is reasonable in design, be easy to realize, do not change the frequency hopping communications Anti-jamming of existing broadcasting station structure, can significantly improve the capacity of system, reduces the error rate.
the accompanying drawing explanation
Fig. 1 is principle framework schematic diagram of the present invention.
Fig. 2 is the frequency-hopping communication system schematic diagram that the inventive method forms.
Fig. 3 is the schematic diagram that system spectrum of the present invention detects and spectral window utilizes.
Fig. 4 is that the present invention disturbs frequency to reject the step schematic diagram.
Fig. 5 is frequency hopping pattern product process figure of the present invention.
Fig. 6 is receiving-transmitting sides of the present invention sharing and communication flow diagram information.
Embodiment
Below in conjunction with embodiment, the present invention is described further.
Embodiment:
As depicted in figs. 1 and 2, a kind of frequency hopping communications anti-interference method based on cognitive radio, described anti-interference method comprises three parts: the anti-interference spectral window detection method of frequency hopping communications, and reject to disturb frequency to obtain frequency hopping key under the method for spectral window and disturbed condition and share transmission method.
The anti-interference spectral window detection method of described frequency hopping communications is specially:
A, the whole frequency band used according to system hops and the bandwidth of each frequency, be divided into several relatively narrow sub-bands;
B, utilize the frequency spectrum sensing method of cognitive radio energy measuring, all frequency bands that system is supported carry out periodic perception detection, obtain the energy feature of each frequency band;
C, according to " interference temperature " situation in channel, detect whether there be " spectral window ", and provide the qualitative character of each " spectral window " according to corresponding criterion.
Described rejecting disturbs frequency to obtain the method for spectral window, is specially:
A, the signal detected in said method is carried out to windowing process and FFT conversion;
Statistic in B, calculation procedure A, determine and reject thresholding;
C, utilize the continuous average of FCME(to reject algorithm), reject to disturb and be not suitable for more greatly the frequency that frequency hopping is used, obtain not " spectral window " of disturbed applicable frequency hopping communications;
Spectral window and its management information that D, basis obtain, determine the usable frequency collection made new advances, and generates new frequency hopping pattern.
Under described disturbed condition, the frequency hopping key is shared transmission method, is specially:
1), newly-generated frequency hopping key information is divided into groups by the every jumping limit bandwidth of system;
2), the information after dividing into groups, in conjunction with the fountain codes coding rule, form and meet under disturbed condition the debit and easily receive and be difficult for the information frame that disturbed side intercepts and captures;
3), after the debit receives complete key information, send the ACK confirmation signal to originating party;
4), receiving-transmitting sides starts to carry out normal frequency hopping communications according to new frequency hopping pattern.
Specific implementation principle and method:
As shown in Figure 3 and Figure 4, at first system is detected the electromagnetic spectrum situation in the frequent section of particular hop, draws some " spectral windows " that meet certain requirements.Frequency spectrum perception theory according to cognitive radio, we can regard all irrelevant signals that enter in the frequency hopping working frequency range as " main signal ", frequency hopping user itself is exactly the perception user, it needs the spectrum utilization situation around perception before work, then could select suitable frequency hopping channel to communicate.Like this, frequency hopping user just need to do two work aspect frequency spectrum detection: the one, and whether all frequency hopping channels (frequency hopping point) in the testing frequency range exist " main signal " that power is larger, thereby determine that whether this channel is available; The 2nd, periodically detect the situation of change of these channels, once occur high-power " main signal " in some channel, the perception user will detect it and abandon this channel with the fastest speed in the very first time.In Fig. 3 a), b) and frequency hopping point and interference signal situation that c) the first half in three subgraphs is a certain moment, the latter half is the spectral window generated after frequency spectrum detection.The width of interference signal qualitative reflection disturbed occupied bandwidth, highly qualitative reaction the size of interference power; The width of spectral window has reflected the bandwidth of a certain tuftlet usable spectrum, has highly reflected the quality of this bunch of frequency spectrum.
A) hypothesis in
t 0constantly in whole frequency hopping working frequency range, there is no interference signal, the result of frequency spectrum detection should be that each frequency hopping channel (point) can just be commonly used to communicate;
B) hypothesis in
t 1in time, is engraved in the frequency hopping working frequency range and multiple interference occurred, and so according to concrete frequency spectrum detection algorithm, we can draw the b as figure) spectral window as shown in the latter half subgraph, then according to the characteristic of these spectral windows, plan frequency hopping pattern, reliable communication in real time; Equally,
C) hypothesis in
t 2variation has occurred in constantly multiple interference in the frequency hopping working frequency range, then the usable spectrum window also can dynamic change (as figure c) the latter half subgraph as shown in), corresponding frequency hopping pattern will the spectral window after these change in planning again.
In above-mentioned frequency hopping frequency range is carried out to the spectral window testing process, because all interference signals that we are concerned about can be regarded " main signal " on broader terms as, so can adopt primary user's transmitting terminal detection method to determine spectral window, its detection model is
Wherein, the signal received for native system perception unit, for primary user's signal, namely disturb, it is additive white Gaussian noise, for the channel complex gain, mean judgement amount when there be not (namely spectral window can produce) in main signal, be the judgement amount of main signal while having (not producing at this frequency corresponding to spectral window) equally.This model makes the spectral window test problems of frequency hopping frequency range become a typical Hypothesis Testing Problem.Utilize improved FCME algorithm, can judge whether the frequency detected is " spectral window " that system hops can be used.
Under described disturbed condition, the frequency hopping key is shared transmission method, concrete methods of realizing:
As shown in Figure 5, according to the spectral window detected and its management information, system will be determined the usable frequency collection made new advances to frequency hopping pattern generation method, generate new frequency hopping pattern.Set up Mathematical Modeling as follows: while supposing not disturb, all frequency hopping points of frequency hopping working frequency range are as channel space, the a certain moment is after spectral window detects, this contained frequency hopping point formation another one set of all spectral windows constantly,, obviously. and ensuing work determines that those Frequency points are for communication exactly from this subset.
Frequency hopping key sharing method under disturbed condition, as shown in Figure 6, at the connection setup initial stage, threaten maximum artificial hostile interference generally also not occur to system, even or occurred, interference effect is not necessarily best in a short time.Now, receiving-transmitting sides adopts conventional frequency-hopping mode, transmission spectral window perception information separately and the frequency hopping pattern of plan reception on each frequency hopping channel, after both sides shake hands and confirm, proceed to the cognitive frequency hopping stage of communication, all frequency spectrum perception information and the frequency hopping pattern according to the other side carries out the frequency hopping transmission, thereby guarantees that the recipient is in best communications reception state.For guarantee cognitive process continue carry out, receiving-transmitting sides includes the cognitive situation of spectral window of own current time and intends receiving frequency hopping pattern in the information data that sends the other side, for the information that provides is provided next communication constantly of the other side.
Front provides the description to preferred embodiment, so that any technical staff in this area can use or utilize the present invention.Various modifications to these embodiment are evident for personnel skilled in the art, and can total application of principle described here not used to creativeness to each other embodiment.Thereby, the present invention will be not limited to here shown in embodiment, and should be according to meeting the principle that disclosed and the wide region of new feature here.