CN104780133B - A kind of frequency hopping anti-intercepting and capturing method in ofdm system - Google Patents
A kind of frequency hopping anti-intercepting and capturing method in ofdm system Download PDFInfo
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- CN104780133B CN104780133B CN201410831990.3A CN201410831990A CN104780133B CN 104780133 B CN104780133 B CN 104780133B CN 201410831990 A CN201410831990 A CN 201410831990A CN 104780133 B CN104780133 B CN 104780133B
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Abstract
The method that the present invention proposes the frequency hopping anti-intercepting and capturing in a kind of ofdm system, Signal to Interference plus Noise Ratio is improved, reduce the influence that broadband interference is brought.Random frequency hopping method during small size frequency-hopping method and broadband interference when being disturbed including arrowband.Each frequency at intervals of a subcarrier bandwidth, and without using excessive frequency, choose several subcarriers transmission data, and shifted in each OFDM symbol interval sub-carrier using pseudo-random sequence.So signal bandwidth increase is seldom, but and can plays fast frequency-hopped and anti-intercepting and capturing effect simultaneously.And the scheme of random frequency hopping is taken under broadband interference, relatively small number of subcarrier transmission data are randomly selected at each OFDM symbol interval, so as to improve Signal to Interference plus Noise Ratio, reduce the influence that broadband interference is brought.
Description
Technical field
The present invention relates to a kind of method of the frequency hopping anti-intercepting and capturing in ofdm system, belong to the technical field of radio communication.
Background technology
Frequency hopping is a kind of spread spectrum mode commonly used in radio communication, and its operation principle is the carrier wave of receiving-transmitting sides transmission signal
Frequency carries out Discrete Change according to predetermined rule.For the implementation of the communication technology, frequency hopping is one kind code sequence
Carry out the frequency shift keyed communication mode of multifrequency.From the point of view of signal spectrum angle, Frequency Hopping Signal typically constitutes from using very wide frequency band.
Conventional frequency hopping code sequence is the pseudo-random sequence based on designs such as m-sequence, RS codes.These pseudo-random code sequences lead to
Cross shift register and add feedback arrangement to realize, simple in construction, stable performance, can comparatively fast realize synchronization, they can be realized
Longer cycle, Hamming correlation property are also relatively good.
The advantages of frequency hopping communications is anti-interference, and compared with frequency fixing communication, frequency hopping communications is more hidden to be also difficult to be trapped.It is fixed
Frequency interference meeting interference sections frequency, as long as other side does not know the rule of carrier frequency saltus step, is difficult to communication interception content.It is but conventional
The shortcomings that frequency hopping communications is：1) occupied bandwidth is big；2) frequency hopping limited speed；3) no rejection ability is disturbed to high-power broadband.
We are described in detail respectively to these shortcomings below.
1) conventional frequency hopping communications changes carrier frequency at random, completely not overlapping between the signal spectrum of different carrier frequency or only
Fraction is overlapping.If signal bandwidth is B, if signal spectrum is not overlapping between different carrier frequency, the frequency-hopping system of N number of frequency
The total bandwidth used is NB.Currently due to the transmission data rate demand more and more higher to communication system, the signal band of single frequency point
Width also becomes more and more wider, such as when being 20MHz only with 15 frequencies, single frequency point signal bandwidth, total signal bandwidth is just
It is up to 300MHz.So big bandwidth will all bring very big difficulty to radio frequency link design and AD/DA conversion etc..
2) output frequency of change oscillator is needed during conventional frequency-hopping system conversion work frequency, and needs phaselocked loop weight
Newly enter tenacious tracking state, this needs longer time, therefore at present most fast frequency hopping speed only have tens of thousands of times it is per second.
3) when being disturbed in face of high-power broadband, if whole frequencies of interference spectrum covering frequency-hopping system work, often
Rule frequency-hopping system loses antijamming capability, and communication performance drastically deteriorates.
The content of the invention
The purpose of the present invention is to propose to a kind of method of the frequency hopping anti-intercepting and capturing in ofdm system, so as to improve Signal to Interference plus Noise Ratio,
Reduce the influence that broadband interference is brought.
The present invention is achieved through the following technical solutions：
A kind of method of frequency hopping anti-intercepting and capturing in ofdm system, including arrowband disturb when small size frequency-hopping method and broadband do
Random frequency hopping method when disturbing, wherein small size frequency-hopping method comprises the following steps：
(1) the subcarrier number N of communication system is determined, wherein null subcarrier number is N0, data subcarrier number is N1,
Pilot sub-carrier number N2, data subcarrier is marked as k=0,1 ..., N1- 1, data inserted during non-frequency hopping after pilot tone carries
Ripple is marked as f (k)；
(2) the pseudo-random sequence a (n), wherein n=1 ..., T that the cycle is T are generated, then it is T to intercept a wherein segment length1
Sequence a1(n) M system sequence b (n), length T are converted into, and2, whereinFor integer, n=1,
2,...,T2,M≤N0；
(3) position of data subcarrier in each OFDM symbol is adjusted according to the value of pseudo-random sequence；
(4) subcarrier after insertion pilot tone is mapped to obtain final frequency domain sequence, then launched by IFFT；
(5) receiving terminal obtains receiving terminal frequency domain sequence, regeneration and transmitting terminal phase after FFT demappings, deletion pilot tone
Same M system sequences, corresponding data value on the original label of each data subcarrier is further solved, complete dehop；
Wherein broadband interference when random frequency hopping method comprise the following steps：
(1) the corresponding N under non-frequency hopping state0Individual null subcarrier and N1N is randomly selected in individual data subcarrier2Height carries
Ripple, then with this N2Subcarrier corresponding to individual label is used for transmitting data；
(2) subcarrier after insertion pilot tone is mapped to obtain final frequency domain sequence, then launched by IFFT；
(3) receiving terminal obtains receiving terminal frequency domain sequence after FFT demappings, deletion pilot tone, according to the random letter solved
Several seeds, that is, the N randomly selected2Individual subcarrier, further solve this N2Data value on individual subcarrier, complete solution
Frequency hopping.
The process that label is randomly selected in step (1) wherein in random frequency hopping method is mutual in different OFDM symbols
It is independent, and in N0+N1On individual subcarrier meet be uniformly distributed, and record used by random function seed, be attached in data.
Beneficial effects of the present invention：
The method of fast frequency hopping proposed by the present invention can effectively tackle various disturbed conditions, and implementation complexity is low, fit
Ying Xingguang.Under arrowband disturbed condition, using the method for the small size frequency hopping in the present invention, each frequency carries at intervals of a son
Wavestrip is wide, and does not almost increase without using excessive frequency, such signal bandwidth, but and can plays the work of anti-intercepting and capturing simultaneously
With using the characteristic of coded OFDM systems contrary frequency Selective intensity, this method can also be to arrowband fast frequency-hopped while
Interference is effectively suppressed；In the case of broadband interference, using the method for the random frequency hopping in the present invention, accorded with each OFDM
Number interval randomly selects relatively small number of subcarrier transmission data, can effectively improve receiving terminal Signal to Interference plus Noise Ratio, and can pass through
The co-design of sending and receiving end extracts data exactly.
Embodiment
The present invention proposes that a kind of fast frequency-hopped method for coping with various disturbed conditions in ofdm system, including arrowband are done
Random frequency hopping method during small size frequency-hopping method and broadband interference when disturbing.
This method includes small size frequency hopping and random frequency hopping two parts.In order to tackle the disturbed condition of various conditions, Wo Men
Small size hopping scheme is taken in arrowband when disturbing, each frequency at intervals of a subcarrier bandwidth, and without using excessive frequency
Point, several subcarriers transmission data are chosen, and moved using pseudo-random sequence in each OFDM symbol interval sub-carrier
Position.So signal bandwidth increase is seldom, but and can plays fast frequency-hopped and anti-intercepting and capturing effect simultaneously.And under broadband interference,
We take the scheme of random frequency hopping, and relatively small number of subcarrier transmission data are randomly selected at each OFDM symbol interval,
So as to improve Signal to Interference plus Noise Ratio, the influence that broadband interference is brought is reduced.Assuming that an ofdm communication system sub-carriers number is N,
Wherein null subcarrier number is N0, data subcarrier number is N1, pilot sub-carrier number N2, data subcarrier marked as k=0,
1,...,N1- 1, the data subcarrier inserted during non-frequency hopping after pilot tone is marked as f (k).
Under arrowband disturbed condition, using the method for small size frequency hopping, the generation cycle is T pseudo-random sequence a (n), wherein n
=1 ..., T, then it is T to intercept a wherein segment length1Sequence a1(n), and M system sequence b (n) are converted into, length is
T2, whereinFor integer, n=1,2 ..., T2,M≤N0.Each OFDM is adjusted further according to the value of pseudo-random sequence
The position of data subcarrier in symbol, i.e.,
Wherein f (k) represents the initial label of data subcarrier, and mod represents complementation computing, and s (n, k) represents nth symbol
When the original data subcarrier marked as k corresponding to position.Finally the subcarrier after insertion pilot tone is mapped to obtain most
Whole frequency domain sequence, then launch by IFFT.In receiving terminal, receiving terminal frequency is obtained after FFT demappings, deletion pilot tone
Domain sequence r (n), regeneration and transmitting terminal identical M system sequence b (n), then it is original can further to solve each data subcarrier
Corresponding data value on label, complete dehop.
In the case of broadband interference, using the method for random frequency hopping, the corresponding null subcarrier sum under non-frequency hopping state
According to randomly selecting N in subcarrier2Individual subcarrier, then with this N2Subcarrier corresponding to individual label is used for transmitting data.Wherein random choosing
Take the process of label separate in different OFDM symbols, and in N0+N1Meet to be uniformly distributed on individual point, and record and adopted
The seed of random function, is attached in data.Again the subcarrier after insertion pilot tone is mapped to obtain final frequency domain sequence
Row, then launch by IFFT.In receiving terminal, receiving terminal frequency domain sequence r is obtained after FFT demappings, deletion pilot tone
(n), according to the seed of the random function solved, you can the N randomly selected2Individual subcarrier, further solve this N2Height
Data value on carrier wave, complete dehop.
Consider an ofdm communication system using the inventive method.System sub-carriers number is 64, wherein data
Variable number is 48, and pilot sub-carrier number is 4, and null subcarrier number is 12, and data subcarrier is original marked as k=0,
1,...,47.Mapping mode of the data subcarrier when inserting pilot tone be
For arrowband disturbed condition, using the method for small size frequency hopping, the pseudo-random sequence a (n) that the cycle is 1024 is first generated,
Wherein n=1 ..., 1024, then 4 system sequence b (n), wherein n=1 are converted into, 2 ..., 512.Then according to pseudorandom
The value of sequence adjusts the position of data subcarrier in each OFDM symbol, i.e.,
S (n, k)=f (k)+b (nmod1024) -2
Wherein f (k) represents the initial label of data subcarrier, and mod represents complementation computing, and s (n, k) represents nth symbol
When the original data subcarrier marked as k corresponding to position.Connect in receiving terminal after FFT demappings, deletion pilot tone
Receiving end frequency domain sequence r (n), regeneration and the system sequence b (n) of transmitting terminal identical 4, then it is original can to solve each data subcarrier
Corresponding data value on label, complete dehop.Choose 10 OFDM symbols, using OFDM symbol as transverse axis, each OFDM symbol
In the frequency range of shared subcarrier be the longitudinal axis, data subcarrier therein is observed, identical face in different OFDM symbols
Same subcarrier under the corresponding non-frequency hopping state of the subcarrier of color.
For broadband interference situation, using the method for random frequency hopping, the corresponding null subcarrier sum under non-frequency hopping state
A total of 52 according to subcarrier, 8 labels are randomly selected in this 52 subcarriers correspond to label, then it is corresponding with this 8 labels
Subcarrier be used for transmit data.It is separate in different OFDM symbols wherein to randomly select the process of label, and 52
Meet to be uniformly distributed on individual point, and record used by random function seed, be attached in data.Again to the son after insertion pilot tone
Carrier wave is mapped to obtain final frequency domain sequence, then is launched by IFFT.In receiving terminal, by FFT demappings, delete
Receiving terminal frequency domain sequence r (n) is obtained after pilot tone, according to the seed of the random function solved, you can 8 sons randomly selected
Carrier wave, the data value on this 8 subcarriers is further solved, complete dehop.10 OFDM symbols are chosen, with OFDM symbol
For transverse axis, the frequency range of shared subcarrier is the longitudinal axis in each OFDM symbol, data subcarrier therein is observed, no
With the same subcarrier under the corresponding non-frequency hopping state of subcarrier of same color in OFDM symbol.
Claims (2)
1. a kind of method of the frequency hopping anti-intercepting and capturing in ofdm system, including small size frequency-hopping method and broadband interference during arrowband interference
When random frequency hopping method, it is characterised in that wherein small size frequency-hopping method comprises the following steps：
(1) the subcarrier number N of communication system is determined, wherein null subcarrier number is N0, data subcarrier number is N1, pilot tone
Subcarrier number N2, data subcarrier is marked as k=0,1 ..., N1- 1, the data subcarrier mark inserted after pilot tone during non-frequency hopping
Number it is f (k)；
(2) the pseudo-random sequence a (n), wherein n=1 ..., T that the cycle is T are generated, then it is T to intercept a wherein segment length1Sequence
a1(n) M system sequence b (n), length T are converted into, and2, whereinFor integer, n=1,2 ..., T2,M
≤N0；
(3) position of data subcarrier in each OFDM symbol is adjusted according to the value of pseudo-random sequence；
(4) subcarrier after insertion pilot tone is mapped to obtain final frequency domain sequence, then launched by IFFT；
(5) receiving terminal obtains receiving terminal frequency domain sequence, regeneration and transmitting terminal identical M after FFT demappings, deletion pilot tone
System sequence, corresponding data value on the original label of each data subcarrier is further solved, complete dehop；
Wherein broadband interference when random frequency hopping method comprise the following steps：
(1) the corresponding N under non-frequency hopping state0Individual null subcarrier and N1N is randomly selected in individual data subcarrier2Individual subcarrier, then
With this N2Subcarrier corresponding to individual label is used for transmitting data；
(2) subcarrier after insertion pilot tone is mapped to obtain final frequency domain sequence, then launched by IFFT；
(3) receiving terminal obtains receiving terminal frequency domain sequence after FFT demappings, deletion pilot tone, according to the random function solved
Seed, that is, the N randomly selected2Individual subcarrier, further solve this N2Data value on individual subcarrier, complete dehop.
2. the method for the frequency hopping anti-intercepting and capturing in a kind of ofdm system as claimed in claim 1, it is characterised in that wherein random to jump
It is separate in different OFDM symbols that the process of label is randomly selected in step (1) in frequency method, and in N0+N1Height
On carrier wave meet be uniformly distributed, and record used by random function seed, be attached in data.
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| CN105516031A (en) * | 2015-12-18 | 2016-04-20 | 北京航空航天大学 | Channel estimation and channel equalization method of fast frequency hopping system |
| CN109391389B (en) * | 2017-08-04 | 2021-08-24 | 维沃移动通信有限公司 | Transmission method of reference signal, base station and terminal |
| CN112152664B (en) * | 2020-09-25 | 2021-07-27 | 中国电子科技集团公司第五十四研究所 | Anti-multipath anti-interference signal sending method based on time division multiple access |
| CN112737997B (en) * | 2020-12-25 | 2022-09-13 | 上海微波技术研究所（中国电子科技集团公司第五十研究所） | Navigation communication integrated signal waveform construction method and system based on FH-OFDM |
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| US6549784B1 (en) * | 1998-12-28 | 2003-04-15 | At&T Corp. | Method and apparatus for implementing measurement based dynamic frequency hopping in wireless communication systems |
| CN1901529A (en) * | 2006-07-20 | 2007-01-24 | 清华大学 | Quick frequency hopping and expanding communication method based on orthogonal frequency division duplexing |
| JP2008278161A (en) * | 2007-04-27 | 2008-11-13 | Fuji Electric Device Technology Co Ltd | Ofdm signal receiver, reception method of ofdm signal, and demodulation method of ofdm signal |
| CN102208919A (en) * | 2003-05-12 | 2011-10-05 | 高通股份有限公司 | Fast frequency hopping with a code division multiplexed pilot in an OFDMA system |
| CN103609047A (en) * | 2011-04-11 | 2014-02-26 | 日本科技资源株式会社 | Transmission signal generating/detecting method by using code sequences, communication system using the same and measurement system using the same |
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Patent Citations (5)
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| US6549784B1 (en) * | 1998-12-28 | 2003-04-15 | At&T Corp. | Method and apparatus for implementing measurement based dynamic frequency hopping in wireless communication systems |
| CN102208919A (en) * | 2003-05-12 | 2011-10-05 | 高通股份有限公司 | Fast frequency hopping with a code division multiplexed pilot in an OFDMA system |
| CN1901529A (en) * | 2006-07-20 | 2007-01-24 | 清华大学 | Quick frequency hopping and expanding communication method based on orthogonal frequency division duplexing |
| JP2008278161A (en) * | 2007-04-27 | 2008-11-13 | Fuji Electric Device Technology Co Ltd | Ofdm signal receiver, reception method of ofdm signal, and demodulation method of ofdm signal |
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