CN101667987A - Synchronization acquisition method based on PN sequence signal to noise ratio in FFH system - Google Patents
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Abstract
The invention discloses a synchronization acquisition method based on PN sequence signal to noise ratio in an FFH system, belonging to the technical field of communication interference resistance, relating to a fast frequency hopping (FFH) communication system, in particular to a synchronization method of the FFH communication system. In the invention, the synchronization acquisition head design with double patterns is adopted, and hop frequency and synchronization PN sequence information are fully utilized; an early and later gate signal is adopted to demodulate, so that the demodulation reliability can be improved when full synchronization is not completed on the basis that the realization complexity of the system is not added; and the signal to noise ratio based on frequency and PN sequence patterns is adopted as soft decision amount acquired synchronously, thus the loss of synchronization information is reduced. The synchronization acquisition method of the invention ensures that the FFH system has stronger robustness in interference channels and fading channels, and improves synchronization acquisition performance of the FFH system.
Description
Technical field
The invention belongs to communication Anti-Jamming Technique field, relate to fast frequency-hopped (Fast Frequency Hopping, the method for synchronous in FFH) communication system, especially the FFH communication system.
Background technology
Frequency-hopping communication system (Frequency Hopping Communication System) is the stronger radio communications system of a kind of anti-interference, anti-fading ability, is widely used in wireless communication field.In order to realize the proper communication between the frequency-hopping communication system, receiving-transmitting sides must be realized synchronously, promptly synchronously jump to same frequency hopping frequency (perhaps the two frequency hopping frequencies of sending out of transmitting-receiving differ a fixed intermediate frequency at one time) at one time, the carrier frequency pseudorandom of frequency-hopping communication system is changing, because there is Doppler frequency shift in transmission channel, there are factors such as relative error in timer clock, there is the uncertainty of frequency and time simultaneously in system, the uncertainty of time can use same frequency hopping pattern to solve by receiving-transmitting sides, and the uncertainty of time then will be eliminated by Frequency Hopping Synchronization Techniques (comprising synchronization acquistion and tracking synchronously).
The coincident indicator of general frequency hopping radio set and synchronizing signal require as follows: the settling time of (1) initial synchronisation is short, is no more than 0.3 second; (2) time that networks that lags is no more than 6 seconds; (3) synchro system is 0.1 o'clock at channel bit error rate, and the synchronization acquistion probability needs greater than 90%; (4) time of synchronizing signal existence will lack, and makes the side of intercepting be difficult to find in a short period of time synchronizing signal.
In the FFH system, frequency hopping speed is more than or equal to the character rate of information modulator output, and every jumping signal at most only carries a synchronous chip, and contained synchronizing information amount is few, need utilize the multi-hop signal could realize synchronization acquistion, thereby the difficulty more that realizes becoming synchronously.At present less about the synchronization acquiring method of FFH system, mainly be based on the catching method that the serial search matched filter combines with the diversity folding and proposes, this method has following limitation: (1) amalgamation result is also unreliable, in acquisition procedure, the also misalignment of transmitting-receiving window, the base band frequency energy (or signal to noise ratio) of every jumping not only is subjected to the influence of previous dive and back one jumping signal, and this moment, the baseband modulation frequency was also non-orthogonal in current jumper connection closes up; (2) choosing of thresholding is subjected to the channel influence on signal-to-noise ratio (SNR) bigger, accurately chooses the comparison difficulty.
Summary of the invention
The invention provides in a kind of FFH system synchronization acquiring method based on PN sequence signal to noise ratio, with realize the FFH communication system transmit-receive two send out synchronously.
Before setting forth the inventive method, at first introduce term used among the present invention:
(1) frequency hopping frequency-synchronic PN sequence digraph case
The synchronic PN sequence that transmit leg is N with M synchronising frequency hopping frequency modulation(FM) length (M≤N, K=N/M, K are positive integer), synchronous PN-chip of each frequency hopping frequency modulation(FM), M frequency hopping synchronizing frequency constituted a frequency hopping frequency patterns F={f
0, f
1, f
i..., f
M-1(f
iBe designated as the i synchronizing frequency, 0≤i≤M-1), N synchronous PN-chip constitutes a PN sequence pattern S={PN
0, PN
1, PN
i..., PN
N-1, frequency hopping frequency patterns and synchronic PN sequence pattern have constituted frequency hopping frequency-PN sequence digraph case jointly, and be shown in Figure 1 as Figure of description.
(2) synchronous PN-chip signal to noise ratio
The Frequency Hopping Signal that utilizes local Frequency Hopping Signal that current jumper connection is received carries out mixing and separates jumping, and generating solution is jumped postamble, this signal is carried out the A/D conversion, process | FFT|
2(FFT:Fast Fourier Transform, fast Fourier transformation algorithm; | x|
2: plural x mould square) and the noise normalized after, according to the signal to noise ratio that local PN sequential value takes out 2FSK baseband signal corresponding modulating frequency, this signal to noise ratio becomes to be called when the synchronous PN-chip signal to noise ratio of skip before.
(3) synchronous PN signal to noise ratio sequence
N continuous is jumped according to after above-mentioned (2) processing, and it is the synchronous PN signal to noise ratio sequence of N that each synchronous PN-chip signal to noise ratio forms length.
(4) synchronizing signal signal to noise ratio detection value
To carry out the algebraically summation when preamble PN signal to noise ratio sequence, the algebraical sum value that obtains is a synchronizing signal signal to noise ratio detection value.
(5) early slow gate signal,
To separating jumping when the skip before synchronizing signal, generating solution is jumped postamble, in time this is separated the synchronous letter in jumping back and is divided into two jumpings, and the preceding signal of partly jumping is called gate signal early, and accordingly, later half jumping signal is called slow gate signal.
Whole synchronization acquistion system link of the present invention as shown in Figure 2, comprising: 1, Frequency Hopping Signal is separated jumping, 2, intermediate frequency filtering, 3, A/D, 4, door early | FFT|
2, 5, door noise normalization module early, 6, the local PN sequence of door early, 7, door PN signal to noise ratio sequence synchronously early, 8, door late | FFT|
2, 9, slow door noise normalization module, 10, the local PN sequence of door late, 11, door PN signal to noise ratio sequence synchronously late, 12, the synchronous threshold judgement in K road, 13, synchronous control unit, 14, Frequency Hopping Synthesizer.
Detailed technology scheme of the present invention is as follows:
Based on the synchronization acquiring method of PN sequence signal to noise ratio, as shown in Figure 3, may further comprise the steps in a kind of FFH system:
Set FFH system transmit leg and adopt M synchronic PN sequence (M≤N that synchronising frequency hopping frequency modulation(FM) length is N, K=N/M, K is a positive integer), synchronous PN-chip of each frequency hopping frequency modulation(FM), M frequency hopping synchronizing frequency constituted a frequency hopping synchronizing frequency pattern F={f
0, f
1, f
i..., f
M-1(f
iBe designated as i synchronizing frequency, 0≤i≤M-1), N synchronous PN-chip constitutes a synchronic PN sequence pattern S={PN
0, PN
1, PN
i..., PN
N-1, frequency hopping synchronizing frequency pattern and synchronic PN sequence pattern constitute frequency hopping frequency-PN sequence digraph case jointly.
Step 1: when Synchronous Processing begins, the recipient adopts the frequency hopping synchronizing frequency pattern identical with transmit leg, separate jumping with any one frequency in this frequency hopping synchronizing frequency pattern as initial frequency and handle, the count value C of hop counter counts since 1 synchronously simultaneously.
Step 2: separate when jumping, respectively to C jump early door and late gate signal carry out the A/D conversion, pass through again fast Fourier transform and delivery square (promptly | FFT|
2Handle) handle and the noise normalized; Owing to there be K=N/M phase place to differ the morning into M, the local synchronic PN sequence value of slow door successively, so obtain C jump n (n=1,2 ..., K) individual local synchronic PN sequence value correspondence morning the door baseband signal the signal to noise ratio of 2FSK modulation frequency, i.e. door PN-chip signal to noise ratio X synchronously early
z NCObtain simultaneously C jump n (n=1,2 ..., the K) signal to noise ratio of the 2FSK modulation frequency of the slow door baseband signal of individual local synchronic PN sequence value correspondence, promptly slow door is PN-chip signal to noise ratio X synchronously
c NC
Step 3: the continuous C of step 2 gained is jumped the synchronous PN-chip signal to noise ratio X of door early
z NCWith the synchronous PN-chip signal to noise ratio X of slow door
c NCBy the sequencing of jumping figure form respectively n (n=1,2 ..., K) individual morning door signal to noise ratio sequence { X
z NCAnd slow door signal to noise ratio sequence { X
c NC.
Step 4: when C 〉=N, cast out door signal to noise ratio sequence { X early respectively
z NCAnd slow door signal to noise ratio sequence { X
c NCIn before C-N jump signal to noise ratio X
z NC(1≤C＜N) and X
c NC(1≤C＜N), obtaining length is the synchronous PN signal to noise ratio sequence of the slow door of synchronous PN signal to noise ratio sequence of K road door morning and K road of N, respectively to the K road early door synchronously PN signal to noise ratio sequence and late door synchronously a PN signal to noise ratio sequence ask algebraical sum, obtain a K door synchronizing signal signal to noise ratio detection value and K synchronizing signal signal to noise ratio detection value late early.
Step 5: early, late door carries out K road signal to noise ratio detection value threshold judgement respectively, judges in 2K the synchronizing signal signal to noise ratio detection value by step 4 gained whether exist more than or equal to synchronization acquistion thresholding ζ
Syn-thSituation; If exist, then change step 6 over to; If do not exist and C＜mN (m is a positive integer), then jump and return step 2 when synchronous hop counter C increases by 1 at next; If do not exist and C 〉=mN (m is a positive integer), then after next jumps synchronous hop counter C zero clearing, restart, and change local original frequency from 1 counting, return step 2.
Step 6: carry out the synchronic PN sequence location.
According to the frequency number i of the initial frequency that adopts in the step 1 (0≤i≤M-1), and according to occurring more than or equal to synchronization acquistion thresholding ζ
Syn-thThe synchronous PN likelihood ratio sequence at synchronizing signal likelihood ratio detection value place in the n value (n=1,2 ... K) and synchronously the count value C of hop count device, calculate the jumping figure W that the recipient need wait for, after the wait jumping figure is finished, can make next jump receiving-transmitting sides frequency No. 0 frequency f
0Last aligning, and the skew of PN sequence phase is 0 position; Wherein, wait for that the computing formula of jumping figure W is: W=(%N of m * N-i-C-n * M), (wherein symbol % represents to ask modular arithmetic).
Step 7: catch checking.
If V synchronous PN signal to noise ratio sequence all detects more than or equal to synchronization acquistion thresholding ζ continuously
Syn-thSynchronizing signal signal to noise ratio detection value, then synchronization acquistion success, system changes synchronous tracking mode over to; If any one fails to detect more than or equal to synchronization acquistion thresholding ζ in the individual PN signal to noise ratio sequence synchronously of V continuously
Syn-thSynchronizing signal signal to noise ratio detection value, then next jump to change local original frequency, changes step 2 over to and carries out synchronization acquistion again.
The invention provides the method for a kind of synchronization acquistion of FFH system, adopt the synchronization acquistion head design of digraph case, make full use of frequency hopping frequency and synchronic PN sequence information; Adopt the noise method for normalizing, make the selection of synchronization acquistion thresholding simple and reliable; Adopt morning, slow gate signal to carry out demodulation simultaneously, can on the basis that does not increase system's implementation complexity, improve demodulation reliability when being with fully synchronously; Employing has reduced the loss of synchronizing information based on the soft amount of declaring of frequency-PN sequence pattern signal to noise ratio as synchronization acquistion.Comprehensive above-mentioned each advantage makes the FFH system have stronger robustness under interference channel and fading channel, has improved the synchronization acquistion performance of system.
Description of drawings
Fig. 1 is frequency hopping frequency-PN sequence digraph case.
Wherein: M is a synchronising frequency hopping frequency number; N is a synchronic PN sequence length.
Fig. 2 is the whole chain graph of FFH system synchronization capture systems.
Wherein: 1 separates jumping for Frequency Hopping Signal, and 2 is intermediate frequency filtering, and 3 is A/D, and 4 is door early | FFT|
2, 5 is noise normalization module morning, and 6 is the local PN sequence of door morning, and 7 is synchronous PN signal to noise ratio sequence morning, and 8 is slow door | FFT|
2, 9 is slow door noise normalization module, and 10 is the local PN sequence of slow door, and 11 is slow PN signal to noise ratio sequence synchronously, and 12 is the synchronous threshold judgement in K road, and 13 is synchronous control unit, and 14 is Frequency Hopping Synthesizer.
Fig. 3 is based on the flow chart of the synchronization acquiring method of PN sequence signal to noise ratio in a kind of FFH provided by the invention system.
Embodiment
A kind of synchronization acquiring method based on frequency-PN sequence pattern signal to noise ratio of FFH of the present invention system, its main innovation are to adopt based on frequency-PN sequence pattern signal to noise ratio as synchronization acquistion soft-decision amount, have reduced the loss of synchronizing information; Adopt early slow door demodulation method to weaken the unreliability of the demodulation that does not bring fully synchronously, on the basis that does not increase system's implementation complexity, improve the synchronization acquistion performance of FFH system; Made full use of the digraph case information of frequency hopping frequency patterns and synchronic PN sequence pattern in addition.Various advantages make synchro system have stronger robustness under interference channel and fading channel.
Computer Simulation shows, get M=21 frequency hopping frequency, length is the PN sequence (specifically can adopt the good m sequence of autocorrelation) of N=63, synchronization acquistion head length degree is 9072 jumpings, after if 2N jumps, do not detect the then counter O reset of sync correlation peak yet, and force the local initial frequency of change, catching the checking number of times is V=3 time, frequency hopping rate was 100000 jumping/seconds, and every jumping sends the 1bit synchrodata, during every jumping signal sampling 256 each sampling point, under awgn channel, signal to noise ratio is 2dB, channel bit error rate is 0.2264 o'clock, and when choosing suitable synchronization acquistion thresholding and making PN sequence false alarm probability be 1E-5, the synchronization acquistion probability of whole system is 98%, satisfying FFH system requirements channel bit error rate fully is 0.1 o'clock, and the synchronization acquistion probability needs the net synchronization capability regulation greater than 90%.
Claims (4)
1, in a kind of FFH system based on the synchronization acquiring method of PN sequence signal to noise ratio, may further comprise the steps:
Setting FFH system M synchronising frequency hopping frequency modulation(FM) length of transmit leg employing is the synchronic PN sequence of N, M≤N, K=N/M, K are positive integer, synchronous PN-chip of each frequency hopping frequency modulation(FM), M frequency hopping synchronizing frequency constituted a frequency hopping synchronizing frequency pattern F={f
0, f
1, f
i..., f
M-1, f
iBe designated as i synchronizing frequency, 0≤i≤M-1, N synchronous PN-chip constitutes a synchronic PN sequence pattern S={PN
0, PN
1, PN
i..., PN
N-1, frequency hopping synchronizing frequency pattern and synchronic PN sequence pattern constitute frequency hopping frequency-PN sequence digraph case jointly;
Step 1: when Synchronous Processing begins, the recipient adopts the frequency hopping synchronizing frequency pattern identical with transmit leg, separate jumping with any one frequency in this frequency hopping synchronizing frequency pattern as initial frequency and handle, the count value C of hop counter counts since 1 synchronously simultaneously;
Step 2: when separating jumping, respectively C jumping door morning is carried out A/D with slow gate signal and change, pass through square processing of fast Fourier transform and delivery again, promptly | FFT|
2Handle, and carry out the noise normalized; Owing to there be K=N/M phase place to differ the morning into M, the local synchronic PN sequence value of slow door successively, jump n so obtain C, n=1,2 ..., K, individual local synchronic PN sequence value correspondence morning the door baseband signal the signal to noise ratio X of 2FSK modulation frequency
z NC, i.e. door PN-chip signal to noise ratio X synchronously early
z NCObtain C simultaneously and jump n, n=1,2 ..., K, the signal to noise ratio of the 2FSK modulation frequency of the slow door baseband signal of individual local synchronic PN sequence value correspondence, promptly slow door is PN-chip signal to noise ratio X synchronously
c NC
Step 3: the continuous C of step 2 gained is jumped the synchronous PN-chip signal to noise ratio X of door early
z NCWith the synchronous PN-chip signal to noise ratio X of slow door
c NCBy the sequencing of jumping figure form respectively n (n=1,2 ..., K) individual morning door signal to noise ratio sequence { X
z NCAnd slow door signal to noise ratio sequence { X
c NC;
Step 4: when C 〉=N, cast out door signal to noise ratio sequence { X early respectively
z NCAnd slow door signal to noise ratio sequence { X
c NCIn before C-N jump signal to noise ratio X
z NC, 1≤C＜N, and X
c NC1≤C＜N, obtaining length is the synchronous PN signal to noise ratio sequence of the slow door of synchronous PN signal to noise ratio sequence of K road door morning and K road of N, respectively to the K road early door synchronously PN signal to noise ratio sequence and late door synchronously a PN signal to noise ratio sequence ask algebraical sum, obtain a K door synchronizing signal signal to noise ratio detection value and K synchronizing signal signal to noise ratio detection value late early;
Step 5: early, late door carries out K road signal to noise ratio detection value threshold judgement respectively, judges in 2K the synchronizing signal signal to noise ratio detection value by step 4 gained whether exist more than or equal to synchronization acquistion thresholding ζ
Syn-thSituation; If exist, then change step 6 over to; If do not exist and C＜mN, m is a positive integer, then jumps at next and returns step 2 when synchronous hop counter C increases by 1; If do not exist and C 〉=mN, then after next jumps synchronous hop counter C zero clearing, restart, and change local original frequency from 1 counting, return step 2;
Step 6: carry out the synchronic PN sequence location;
According to the frequency number i of the initial frequency that adopts in the step 1,0≤i≤M-1, and according to occurring more than or equal to synchronization acquistion thresholding ζ
Syn-thThe synchronous PN likelihood ratio sequence at synchronizing signal signal to noise ratio detection value place in the n value and the count value C of hop count device synchronously, calculate the jumping figure W that the recipient need wait for, wait for that jumping figure is finished after, can make next jump receiving-transmitting sides frequency No. 0 frequency f
0Last aligning, and the skew of PN sequence phase is 0 position; Wherein, wait for that the computing formula of jumping figure W is: W=(%N of m * N-i-C-n * M), wherein symbol % represents to ask modular arithmetic;
Step 7: catch checking;
If V synchronous PN signal to noise ratio sequence all detects more than or equal to synchronization acquistion thresholding ζ continuously
Syn-thSynchronizing signal signal to noise ratio detection value, then synchronization acquistion success, system changes synchronous tracking mode over to; If any one fails to detect more than or equal to synchronization acquistion thresholding ζ in the individual PN signal to noise ratio sequence synchronously of V continuously
Syn-thSynchronizing signal signal to noise ratio detection value, then next jump to change local original frequency, changes step 2 over to and carries out synchronization acquistion again.
2, in the FFH according to claim 1 system based on the synchronization acquiring method of PN sequence signal to noise ratio, it is characterized in that it is characterized in that, described M gets positive integer 21, described N gets positive integer 63; Described PN sequence adopts the good m sequence of autocorrelation.
3, in the FFH according to claim 1 system based on the synchronization acquiring method of PN sequence signal to noise ratio, it is characterized in that m described in the step 5 gets positive integer 2.
4, in the FFH according to claim 1 system based on the synchronization acquiring method of PN sequence signal to noise ratio, it is characterized in that V described in the step 7 gets positive integer 3.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101964668A (en) * | 2010-09-21 | 2011-02-02 | 电子科技大学 | Difference frequency hopping communication method based on correlation capture of m sequence |
| CN102497240A (en) * | 2011-12-20 | 2012-06-13 | 北京泰美世纪科技有限公司 | Sampling synchronous device and sampling synchronous method of digital broadcasting system |
| CN106998586A (en) * | 2017-06-01 | 2017-08-01 | 电子科技大学 | The synchronization acquiring method of wireless communication system in a kind of high dynamic environment |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1172547C (en) * | 2001-01-22 | 2004-10-20 | 华为技术有限公司 | Wideband base station capable of implementing radio-frequency frequency hopping and baseband frequency hopping and its method |
| CN101262467B (en) * | 2008-03-03 | 2010-09-08 | 清华大学 | Realization method and realization device for digital baseband frequency spreading modulation system |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101964668A (en) * | 2010-09-21 | 2011-02-02 | 电子科技大学 | Difference frequency hopping communication method based on correlation capture of m sequence |
| CN101964668B (en) * | 2010-09-21 | 2013-06-12 | 电子科技大学 | Difference frequency hopping communication method based on correlation capture of m sequence |
| CN102497240A (en) * | 2011-12-20 | 2012-06-13 | 北京泰美世纪科技有限公司 | Sampling synchronous device and sampling synchronous method of digital broadcasting system |
| CN102497240B (en) * | 2011-12-20 | 2014-03-26 | 北京泰美世纪科技有限公司 | Sampling synchronous device and sampling synchronous method of digital broadcasting system |
| CN106998586A (en) * | 2017-06-01 | 2017-08-01 | 电子科技大学 | The synchronization acquiring method of wireless communication system in a kind of high dynamic environment |
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