CN108924073B - A kind of quick self-adapted Doppler estimation synchronous based on pseudo-random sequence - Google Patents
A kind of quick self-adapted Doppler estimation synchronous based on pseudo-random sequence Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
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- H04B13/00—Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
- H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/0014—Carrier regulation
- H04L2027/0024—Carrier regulation at the receiver end
- H04L2027/0026—Correction of carrier offset
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Abstract
The invention discloses a kind of quick self-adapted Doppler estimations synchronous based on pseudo-random sequence, which comprises receiver received signal sequence inputting bandpass filter is filtered out out-of-band noise by step 1)；Step 2) carries out copy correlation using matched filter to the signal sequence that bandpass filter exports, and realizes Doppler's rough estimate, obtains Doppler's rough estimate resultStep 3) i-th estimation in, be with Doppler by received signal sequenceWithLocal signal sequence carry out related, obtain i-th Doppler's estimated resultΔiFor i-th stepping, i is incremented to N since 1, and N is iteration maximum times；Step 4) is by n-th Doppler's estimated resultAs final Doppler's estimated result, Variable sampling is carried out to received signal sequence, realizes Doppler effect correction.Method of the invention highly shortened the estimation time, reduce computation complexity, have adaptive characteristic well.
Description
Technical field
The present invention relates to, and in particular to a kind of quick self-adapted Doppler estimation synchronous based on pseudo-random sequence.
Background technique
In recent years, each state was all in the construction for stepping up progress ocean development, detection and seabed information network.Wherein, underwater nothing
People's aircraft (Unmanned Underwater Vehicle, UUV) is due to having intelligence, concealment, mobility, portability
Etc. advantages, particularly important effect has been played in ocean engineering field.Therefore, design is applied in UUV high speed motions
Mobile underwater sound communication system is one of the new and high technology for covering the countries in the world urgent need of marine technology and information technology.
Wireless communication in air uses Electromagnetic Wave Propagation information, and electromagnetic wave propagation speed is approximately the light velocity, Neng Gouda
To 3 × 108M/s, therefore in wireless communications, influence of the Doppler effect due to caused by relative motion to actual transmissions system
It is not obvious.But under water, since using sound wave, as transmission medium, transmission speed is about 1520m/s, works as speed of related movement
When for 5m/s, Doppler factor can reach 10-3Magnitude, and this is enough sharply to decline with leading to communication performance.Therefore for
For the mobile underwater sound communication of High Data Rate again, it is necessary to first accurately be estimated Doppler, then be adopted to reception signal
Sample compensating for doppler eliminates signal broadening or compression, to realize the underwater wireless information transmission of low error rate.
In addition to this, underwater sound communication channel is also increasingly complex and changeable: sound ray is in the reflection of bottom and surface of sea and in difference
Refraction in density water layer causes serious multipath effect, and the multidiameter delay of shallow sea horizontal channel is up to a few tens of milliseconds, this makes
It must receive in signal that there are serious intersymbol interferences；Due to transmitting-receiving energy converter between relative motion and propagation medium exist with
Machine rises and falls, and underwater acoustic channel has the characteristic of random quickly time-varying.These all increase the tired of Doppler's estimation to a certain extent
It is difficult.
The Doppler estimation in underwater sound communication is mostly based on ambiguity function, the good sequence of selection correlation properties at present
As synchronizing sequence, by related realization, Doppler estimates.Concrete methods of realizing includes two classes: one kind is to utilize HFM, LFM etc.
Good and insensitive to the Doppler sequence of correlation properties, is respectively inserted into a Duan Xulie before and after sending data, and receiver is by front and back sequence
Column carry out correlation, according to correlation peak location bias estimation Compression and Expansion coefficient, that is, Doppler factor；Another kind of is to utilize puppet
The correlation properties such as random sequence are good and sequence to Doppler sensitivity, are only inserted into a Duan Xulie, receiver sending Data Frontend
It will receive that sequence is related with local sequence copy, and corresponding Doppler factor is as final estimation when selecting related coefficient maximum
As a result.
First kind method estimated accuracy is high, can meet high-speed underwater sound communication well and want to estimating carrier frequencies precision
It asks, but is had the disadvantage in that in practical application
1) head and the tail sequence is carried out the related acquisition time difference, it is therefore desirable to first save a complete frame signal, occupy
Memory is very big, does not utilize real-time implementation, reduces the validity of high-speed underwater sound communication；
2) this method is only applicable to Doppler's estimation when channel circumstance is stablized.When channel finds acute variation or UUV
When high-speed motion causes channel circumstance to change, the channel impulse response that head and the tail sequence is passed through is different, the time difference between relevant peaks
It is no longer only determined by Doppler, Doppler's estimated accuracy, which can be substantially reduced even, at this time estimation mistake occurs；
It 3) is more time-varying Doppler in practical underwater acoustic channel environment, and on-fixed Doppler, head and the tail sequence correlation are past
Average toward the approximation that can only obtain Doppler in this period, stability is poor.
Second class algorithm only estimates current time sequence, therefore has stability well, can expire well
Doppler's potential demand under sufficient time-variant channel environment, but some problems are equally existed in practical application:
1) resolution ratio of Doppler's estimation depends on the length of pseudo-random sequence, and pseudo-random sequence is longer, and resolution ratio is higher,
The estimated accuracy that can be realized is also higher.Therefore performance is preferably estimated in order to obtain, it is necessary to increase the length of pseudo-random sequence
Degree, but in practical application, this can not only occupy the actual data transfer time, reduction transmission rate also results in matched filtering
Device length increases, and calculation amount increases；
2) in the enough situations of resolution ratio, the final estimated accuracy of algorithm is determined by estimation stepping.When stepping is 1m/s,
Estimated accuracy only up to reach 1/1520=7 × 10-4Magnitude；When stepping is reduced into 0.2m/s, estimated accuracy can reach 1 ×
10-4Magnitude.Therefore consider from performance, should select stepping small as far as possible, but in practical application, with stepping diminution,
Number with filter group can obviously increase, and calculation amount and resource consumption can all significantly increase.
Using pseudo-random sequence copy related realization Doppler estimation method, have versatility it is good, can with absolutely mostly
The compatible advantage of number communication systems, at the same have well robustness, remain to preferably be applicable under time varying channel.In resolution ratio
It is designed in enough situations with estimation stepping, can satisfy the demand that most systems estimate Doppler.But the technology is deposited
In two very big problems, first is that the promotion of estimation performance must be using the sharp increase of calculation amount and resource as cost, this is in very big journey
The application of this method in systems in practice, system especially more demanding to Doppler's estimated accuracy are limited on degree；Two
It is that estimation performance is determined by the design of sequence length and matched filter, once design is completed, is difficult flexible according to actual scene
Adjustment estimation performance, adaptivity are poor.
Summary of the invention
It is an object of the invention to overcome the above problem existing for mesh Doppler estimation, propose it is a kind of based on it is pseudo- with
The quick self-adapted Doppler estimation of machine sequence synchronization, be divided into rough estimate and carefully two steps of estimation: rough estimate is used and is copied
Shellfish related realization, due to not needing very high resolution ratio and stepping, calculation amount also can be therewith to estimating that performance requirement is not high
It reduces；Binary chop is used in thin estimation procedure, it is only right to search every timeWithIt is general more than three
Le estimated, whereinFor a preceding estimated result, ΔiCurrently to estimate stepping.Stepping is constantly reduced simultaneously in estimation procedure
Resolution ratio is improved by integral multiple interpolation, finally approaches correct result.
To achieve the goals above, the invention proposes a kind of quick self-adapted Doppler synchronous based on pseudo-random sequence
Estimation method, which comprises receiver received signal sequence inputting bandpass filter is filtered out band and made an uproar outside by step 1)
Sound；Step 2) carries out copy correlation using matched filter to the signal sequence that bandpass filter exports, and realizes Doppler's rough estimate
Meter, obtains Doppler's rough estimate resultStep 3) i-th estimation in, be with Doppler by received signal sequenceWithLocal signal sequence carry out related, obtain i-th Doppler's estimated resultΔiFor
I-th stepping, i are incremented to N since 1, and N is iteration maximum times；Step 4) is by n-th Doppler's estimated resultAs
Final Doppler's estimated result carries out Variable sampling to received signal sequence, realizes Doppler effect correction.
As a kind of improvement of the above method, the step 2) is specifically included:
Step 2-1) according to Doppler's initial estimation range [- V1,V1] and initial stepping Δ0, obtain a1、a2…aL, whereinal=-V1+Δ0*l；V1For preset maximum relative shifting range；1≤l≤L, l are integer；
Step 2-2) Variable sampling is carried out to local signal sequence x (t), generate matched filter coefficient x ((1+a1)t)…x
((1+aL)t)；
Step 2-3) matched filtering processing is carried out to received signal sequence y (t), set detection threshold rT, when max | rMF
(·)|2It is more than detection threshold rT, it is t at the time of appearance that signal, which occurs,1；
rMF() is output and the related coefficient of matched filter, | rMF() | it is rMFThe modulus value of ():
Wherein, a a1、a2…aLIn one, max | rMF(·)|2Be modulus value maximum value；
Step 2-4) take t1Each Δ before and after momenttIn duration matched filter output max | rMF(·)|2Be compared,
Selection maximum output corresponds to moment t2For final synchronization point
Step 2-5) in synchronization pointOutput max | rMF(·)|2The corresponding initial factor a of Dopplerl, alIt is thick to strangle
Estimated result
As a kind of improvement of the above method, the step 3) is specifically included:
Step 3-1) enable estimation number i=1；Corresponding correlation isEstimation range is
Step 3-2) setting i-th stepping beVariable sampling is carried out to local signal sequence x (t), how general is obtained
Le isWithTwo sequence x1(t) and x2(t)；
Step 3-3) according to pseudo random sequence length calculating resolution, if resolution ratio is less than Δi, then to x1(t)、x2(t) and
Y (t) carries out integral multiple interpolation, generates new sequence x '1(t)、x′2(t) and y ' (t)；
Step 3-4) calculate separately y ' (t) and x '1(t), y ' (t) and x '2(t) correlation ri1、ri2, by ri1、ri2WithThree is compared；If ri1Maximum, thenIf ri2Maximum, then IfMaximum, then
Step 3-5) repeat step 3-2) to step 3-4), until Δi≤ΔN, ΔNFor the stepping of setting, at this time how general
Strangle estimated resultFor final Doppler's estimated result.
Present invention has an advantage that
Compared with traditional Doppler estimation synchronous based on pseudo-random sequence, method of the invention greatly shortens
The estimation time reduces computation complexity, and can quickly adjust estimation performance according to actual needs, has adaptive well
Characteristic solves the difficulty in practical applications based on the synchronous Doppler's algorithm for estimating of pseudo-random sequence, in high-speed mobile water
There is very strong application value in sound communication system.
Detailed description of the invention
Fig. 1 is the flow chart of the adaptive Doppler estimation method synchronous based on pseudo-random sequence of the invention；
Fig. 2 is the schematic diagram of matched filter of the invention；
Fig. 3 is the schematic diagram for Doppler's evaluated error that benefit is obtained by the present invention.
Specific embodiment
The present invention will be described in detail with reference to the accompanying drawing.
As shown in Figure 1, the invention proposes a kind of quick self-adapted Doppler estimation sides synchronous based on pseudo-random sequence
Method, including the following steps:
1) receiver reception signal enters bandpass filter, filters out out-of-band noise；
2) copy correlation is carried out using matched filter, realizes Doppler's rough estimate, estimation range is [- V1,V1], stepping
For Δ0, estimated result is
3) it carries out Doppler using binary chop thought carefully to estimate, will receive sequence with Doppler is
WithLocal sequence carry out related, obtain current estimated resultN times are repeated, stepping Δ is constantly reducediAnd it combines
Integral multiple interpolation improves resolution ratio；
4) willAs final Doppler's estimated result, Variable sampling is carried out to sequence is received, realizes Doppler effect correction.
It will estimate that two emphasis steps describe in detail to Doppler's rough estimate and carefully below.
1.1 Doppler's rough estimates
Doppler's rough estimate is exactly that will to receive corresponding local sequence progresss of sequence and different Doppler related, select and
The best corresponding Doppler of local sequence of serial correlation is received as Doppler's rough estimate as a result, formula is expressed are as follows:
As shown in Fig. 2, realizing above-mentioned algorithm using matched filter.
Specific processing step is as follows:
1) according to Doppler's estimation range [- V1,V1] and stepping Δ0, obtain a1、a2…aL, whereinal=-V1+
Δ0*l；
2) Variable sampling is carried out to local sequence x (t), generates matched filter coefficient x ((1+a1)t)…x((1+aL)t)；
3) to sequences y (t) progress matched filtering processing is received, detection threshold r is setT, when max | rMF(·)|2Be more than
Detection threshold, then it is assumed that signal occurs, and note is t at this time1Moment；
4) t is taken1Each Δ before and after momenttIn duration matched filter output max | rMF(·)|2Be compared, selection is most
It is big to export corresponding moment t2For final synchronization point, i.e.,
5) in synchronization point, export max | rMF(·)|2Corresponding Doppler factor alAs Doppler's rough estimate knot
Fruit.
So far, the synchronization and Doppler's rough estimate to signal is received are realized.It can be found that matching filter in step (1)
Wave device number L depend on estimation range and stepping, and as rough estimate, required precision is low, can choose biggish stepping,
To reduce calculation amount, mitigates and realize difficulty.
1.2 Doppler carefully estimate
In Doppler's rough estimate, estimation stepping is Δ0, Doppler's estimated result isCorresponding to correlation isIt connects down
To needMore accurate Doppler's estimation is realized in range.Doppler's evaluated error according to needed for system,
Determine final estimation stepping ΔN, using binary chop thought, realize that Doppler carefully estimates, in the case where estimated accuracy is constant,
Realize the effect that calculation amount is greatly reduced.
Specific processing step is as follows:
1) initiation parameter: i is estimation number, i=1；For the initial Doppler factor, corresponding correlation isEstimate
Counting range is
2) current stepping is arranged isVariable sampling is carried out to local sequence x (t), obtaining Doppler is WithTwo new sequence x1(t)、x2(t)；
3) according to pseudo random sequence length, calculating resolution, if resolution ratio is less than stepping Δi, then to two local sequences
Integral multiple interpolation is carried out with sequence is received, generates new sequence x '1(t)、x′2(t) and y ' (t), as stepping is constantly reduced, interpolation
Multiple steps up；
4) y ' (t) and x ' are calculated separately1(t)、x′2(t) correlation ri1、ri2, and by its withCompare.If ri1Most
Greatly, thenIf ri2Maximum, thenIfMaximum, then
5) repeat 2)~4), until Δi≤ΔNPosition records Doppler's estimated result at this timeEstimate for final Doppler
Count result.
In the present invention, using traditional copy related realization pseudo-random sequence Doppler estimation as Doppler's rough estimate
Biggish estimation stepping is arranged in method, to reduce matched filter group number.It uses for reference binary chop thought carefully to be estimated, spirit
Stepping is estimated in adjustment of living, and integral multiple interpolation is cooperated to promote resolution ratio, realizes quick, high-precision doppler estimation method.It should
Invention has the advantages that quick, adaptive, can greatly reduce calculation amount, meanwhile, using integral multiple interpolation raising pseudorandom sequence
Column split rate, can effectively shorten synchronizing sequence length in practical application.
It is illustrated by taking M sequence as an example, when evaluated error requires to be estimated using traditional algorithm less than 0.1m/s, be
Meet resolution requirement, synchronizing sequence length is at least 8192, and estimation stepping is at least 0.1m/s, when estimation range is [- 5,
5] when m/s, 10/0.1=100 group matched filter is needed, and matched filter length is 2048 × 4=8192.From calculation amount
Consider with resource consumption angle, is difficult to realize in practical applications.And use that introduces in the present invention quick self-adapted to estimate
Calculating method, synchronizing sequence are 2048 points, to reach same performance, and calculation amount is only original 1/10th or so.
Above situation is emulated with MATLAB, estimation performance is indicated with mean square error:
Fig. 3 is that simulation result is as follows:
Abscissa is signal-to-noise ratio in figure, and ordinate is the mean square error of Doppler's estimation.Black line is that tradition copy is related
Algorithm performance, sequence length is 8192 at this time, stepping 0.1m/s.Line 1 and No. 3 lines are quick self-adapted estimation of the invention
Method performance.Obtained estimated result when Line 1 is 4 times of final interpolation, stepping 0.1m/s, it can be seen that same stepping and interior
In the case of inserting multiple, there are 0.01m/s for adaptive approach, that is, about 1/10th performance loss.No. 3 lines are final interpolation
Obtained estimation performance when 8 times of multiple, stepping are 0.05m/s, compared with Line 1, it is only necessary to mostly progress an iteration, i.e. phase twice
It closes, performance but improves a quarter, it can be seen that, the present invention has well solved between performance boost and calculation amount sharp increase
Contradiction.Estimation performance promotes about 1/5th for conventional method at this time, but calculation amount is still far below conventional method.
It should be noted last that the above examples are only used to illustrate the technical scheme of the present invention and are not limiting.Although ginseng
It is described the invention in detail according to embodiment, those skilled in the art should understand that, to technical side of the invention
Case is modified or replaced equivalently, and without departure from the spirit and scope of technical solution of the present invention, should all be covered in the present invention
Scope of the claims in.
Claims (1)
1. a kind of quick self-adapted Doppler estimation synchronous based on pseudo-random sequence, which comprises
Receiver received signal sequence inputting bandpass filter is filtered out out-of-band noise by step 1)；
Step 2) carries out copy correlation using matched filter to the signal sequence that bandpass filter exports, and realizes Doppler's rough estimate
Meter, obtains Doppler's rough estimate result
Step 3) i-th estimation in, be with Doppler by received signal sequenceWith Sheet
Earth signal sequence carries out correlation, obtains i-th Doppler's estimated resultΔiFor i-th stepping, i is incremented to N, N since 1
For iteration maximum times；
Step 4) is by n-th Doppler's estimated resultAs final Doppler's estimated result, to received signal sequence into
Row Variable sampling realizes Doppler effect correction；
The step 2) specifically includes:
Step 2-1) according to Doppler's initial estimation range |-V1, V1| and initial stepping Δ0, obtain a1、a2…aL, whereinal=-V1+Δ0*l；V1For preset maximum relative shifting range；1≤l≤L, l are integer；
Step 2-2) Variable sampling is carried out to local signal sequence x (t), generate matched filter coefficient x ((1+a1)t)...x((1+
aL)t)；
Step 2-3) matched filtering processing is carried out to received signal sequence y (t), set detection threshold rT, when max | rMF(·)
|2It is more than detection threshold rT, it is t at the time of appearance that signal, which occurs,1；
rMF() is output and the related coefficient of matched filter, | rMF() | it is rMFThe modulus value of ():
Wherein, a a1、a2...aLIn one, max | rMF(·)|2Be modulus value maximum value；
Step 2-4) take t1Each Δ before and after momenttIn duration matched filter output max | rMF(·)|2Be compared, it selects
Maximum output corresponds to moment t2For final synchronization point
Step 2-5) in synchronization pointOutput max | rMF(·)|2The corresponding initial factor a of Dopplerl, alIt is thick for Doppler
Estimated result
The step 3) specifically includes:
Step 3-1) enable estimation number i=1；Corresponding correlation isEstimation range is
Step 3-2) setting i-th stepping beVariable sampling is carried out to local signal sequence x (t), obtaining Doppler isWithTwo sequence x1(t) and x2(t)；
Step 3-3) according to pseudo random sequence length calculating resolution, if resolution ratio is less than Δi, then to x1(t)、x2(t) and y (t)
Integral multiple interpolation is carried out, new sequence x ' is generated1(t)、x′2(t) and y ' (t)；
Step 3-4) calculate separately y ' (t) and x '1(t), y ' (t) and x '2(t) correlation ri1、ri2, by ri1、ri2WithThree
Person is compared；If ri1Maximum, thenIf ri2Maximum, then IfMaximum, then
Step 3-5) repeat step 3-2) to step 3-4), until Δi≤ΔN, ΔNFor the stepping of setting, Doppler at this time estimates
Count resultFor final Doppler's estimated result.
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| CN102868659B (en) * | 2012-08-31 | 2015-05-13 | 中国船舶重工集团公司第七一五研究所 | Symbol synchronization and Doppler compensation method for mobile orthogonal frequency division multiplexing (OFDM) underwater sound communication signal |
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| CN104253774B (en) * | 2014-09-16 | 2017-07-25 | 重庆邮电大学 | Doppler shift estimating system and method under a kind of high dynamic environment |
| CN104901718A (en) * | 2015-05-22 | 2015-09-09 | 哈尔滨工程大学 | Doppler estimation method based on measurement of carrier frequency of direct sequence spread spectrum signal |
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| CN106998237A (en) * | 2017-04-05 | 2017-08-01 | 大唐联诚信息***技术有限公司 | A kind of time-frequency synchronization method and device |
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Effective date of registration: 20201217 Address after: 311800 Room 101, 1st floor, 22 Zhongjie building, 78 Zhancheng Avenue, Taozhu street, Zhuji City, Shaoxing City, Zhejiang Province Patentee after: Zhejiang wanghaichao Technology Co.,Ltd. Address before: 100190, No. 21 West Fourth Ring Road, Beijing, Haidian District Patentee before: INSTITUTE OF ACOUSTICS, CHINESE ACADEMY OF SCIENCES |