CN109150234A - A kind of direct sequence signal transmission method based on direct differential coherent accumulation - Google Patents
A kind of direct sequence signal transmission method based on direct differential coherent accumulation Download PDFInfo
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- CN109150234A CN109150234A CN201810888494.XA CN201810888494A CN109150234A CN 109150234 A CN109150234 A CN 109150234A CN 201810888494 A CN201810888494 A CN 201810888494A CN 109150234 A CN109150234 A CN 109150234A
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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
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J13/00—Code division multiplex systems
- H04J13/0007—Code type
- H04J13/0022—PN, e.g. Kronecker
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Abstract
The invention discloses a kind of direct sequence signal transmission methods based on direct differential coherent accumulation, belong to spread-spectrum signal and receive processing technology field.The direct sequence signal catching method that signal after descrambling is carried out to front and back conjugate multiplication and coherent integration, wherein front and back conjugate multiplication this operation is known as differential coherence；Wherein receiving after signal descrambles should be two sections of identical PN sequences, that is, the pseudo-random sequence sent should be two sections of identical PN sequences before scrambling.Core of the invention is to be specifically designed the thick synchronous head of signal, receiving end eliminates the influence of frequency deviation by carrying out front and back conjugate multiplication (differential coherence) to the thick synchronous head for receiving signal, so that being no longer influenced by the influence of Doppler shift bring data bit jump when coherent integration.Since the sequence length of needs is only related with signal-to-noise ratio, this algorithm can search for the direct sequence signal in very big frequency range under certain signal-to-noise ratio under certain sequence length.
Description
Technical field
The invention belongs to spread-spectrum signals to receive processing technology field, and being related to one kind can complete under large doppler frequency deviation
The synchronous thick catching method of Direct Sequence Spread Spectrum Signal.Specially a kind of direct expansion based on difference conjugate multiplication and coherent integration
Signal synchronizing method.
Background technique
Direct sequence spread spectrum skill (referred to as " direct expansion ") is one of core realm of digital communication, direct sequence spread spectrum skill
Apply to military communication network initially as resisting interference and intercepting and capturing the means threatened, but nowadays as 4G/5G is representative
The commercial signal communication systems and network such as mobile communication system, cognitive radio, Sensor Network and Internet of Things fast development, extensively
It is general to apply to commercial system, and have become several wireless, mobile communication standard a part.Direct Sequence Spread Spectrum Signal usually has
There is extremely strong concealment, and can be transmitted under Arctic ice area and realize that zero defect restores in receiving end.But direct sequence expands
Synchronizing for frequency signal is very sensitive to Doppler shift, and the pseudo-random sequence for spread spectrum is longer, easier after despreading because more
Data bit caused by general Le frequency deviation jumps and synchronization failure.That application No. is the patents of invention of CN201710307117.8 is " a kind of
In Rapid Acquisition for Direct Sequence Spread-Spectrum Signals method ", propose that a kind of there are the simultaneous techniques of direct sequence signal under frequency deviation.The technology
First to receive signal zero padding carry out FFT, secondly will receive the FFT sequence cyclic shift of signal and with local reference sequences
FFT carries out conjugate multiplication, and does IFFT and no-coherence cumulating to the FFT sequence of conjugate multiplication, is finally maximized as thick
The decision value of capture carries out FFT and finds frequency deviation frequency point after decision value is more than thresholding.This algorithm can be compared with low signal-to-noise ratio, one
Determine to capture direct sequence signal under frequency deviation.But its calculation amount is directly proportional to frequency search range, wants that obtaining bigger frequency searches
Rope range, it is necessary to increase the points and number of FFT.Therefore, direct sequence signal is searched under big frequency deviation need to pay biggish meter
Calculation amount.Therefore, when being directed to the wireless communication of high-speed mobile, with the increasing of relative moving speed, Doppler shift will be got over
Come bigger, the cost to realize that direct sequence signal is synchronous and pays will be increasing.
Summary of the invention
Aiming at the problem that present invention data bit jump occurs after direct sequence signal despreading under big frequency deviation, propose a kind of based on straight
The direct sequence signal transmission method for connecing differential coherence accumulation synchronizes thick capture to complete direct sequence signal under big frequency deviation.
Signal after descrambling is carried out the direct sequence signal catching method of front and back conjugate multiplication and coherent integration by the present invention,
It is middle that front and back conjugate multiplication this operation is known as differential coherence；Wherein receiving after signal descrambles should be two sections of identical PN sequences
Column, that is, the pseudo-random sequence sent should be two sections of identical PN sequences before scrambling.Core of the invention is to signal
Thick synchronous head is specifically designed, and receiving end is by carrying out front and back conjugate multiplication (differential coherence) to the thick synchronous head for receiving signal
The influence of frequency deviation is eliminated, so that being no longer influenced by the influence of Doppler shift bring data bit jump when coherent integration.
Since the sequence length of needs is only related with signal-to-noise ratio, this algorithm, can be long in certain sequence under certain signal-to-noise ratio
Direct sequence signal in the very big frequency range of the lower search of degree.
Technical solution of the present invention is a kind of direct sequence signal transmission method based on direct differential coherent accumulation, this method packet
It includes:
Step 1, setting originator sample rate, guarantee the sampling of at least one spread-spectrum code chip more than twice；Parameter is set, including is expanded
The length of frequency code, if the PN code PNCode that spread spectrum uses, the spread spectrum pseudo-random sequence s [n] of transmitting terminal is two sections of identical PN sequences
Column, if the last period is PN1, latter section is PN2, then s [n] should meet following format:
S [n]=[PN1PN2]=[PNCode PNCode]
Step 2 carries out scrambling code to s [n], and scrambling the pseudo-code that uses is ScrPNCode, ScrPNCode period and s [n's]
Equal length, so that despreading will not be played to directly related to latter section of pseudo-code progress to its last period pseudo-code after s [n] scrambling
Effect；
Step 3, receiving end are sampled according to fixed time interval to signal is received, and still guarantee at least one spreading code
Piece samples more than twice；By RAM in the data indentation storage queue of present sample；RAM meets:
RAM=[RAM1RAM2]
Step 4 descrambles the data in RAM using pseudo-code ScrPNCode；
Step 5, will descrambling after RAM1In sequence and RAM2In sequence conjugate be multiplied, obtain correlated series:
R [n]=RAM1[n]*RAM2[n]*；
Step 6 carries out coherent integration to R [n], and modulus value obtains final correlation COR=| ∑ R [n] |；
COR is compared by step 7 with the threshold T hreshold of setting, if COR > Threshold, illustrates
Signal has been captured, and has obtained the initial position for receiving signal, has completed the thick capture of signal；Carry out subsequent offset estimation mistake
Journey.
It can be seen that this method has three big features: the first, by being specifically designed to thick synchronous head, so that receiving end
The effect of despreading is played when carrying out step 5；The second, the front and back conjugate multiplication effect that plays demodulation, can remove
Frequency deviation, therefore when considering using sequence length, it is only necessary to carry out from antimierophonic angle with this method.Third, due to every
It is just repeated above operation every half of spread-spectrum code chip, so that the real-time of system is higher.From the angle analysis of algorithm complexity, step
5 conjugate multiplication operation needs more multiplier to complete, this is the main source of calculation amount needed for this method.
Detailed description of the invention
Fig. 1 is the flow chart that the present invention is initialized in the call parameter of originator；
Fig. 2 is process flow diagram of the present invention in receiving end.
Specific embodiment
With reference to the accompanying drawings and examples, technical solution of the present invention is described in detail.But it is above-mentioned that this should not be interpreted as to the present invention
The range of main body is only limitted to following embodiment, all to be all belonged to the scope of the present invention based on the technology that the content of present invention is realized.
It is the flow chart of the call parameter initialization of the transmitting terminal of a specific embodiment of the invention shown in Fig. 1.
The following steps are included:
Step 1 samples 2 points in one spread-spectrum code chip period of setting, i.e. sample rate is twice of data transfer rate, is exactly equal to
Nyquist rate.
Step 2, select length for 1024 m-sequence as PNCode.
PNCode is copied into two sections of identical thick synchronous head frequency expansion sequence s [n] of PN Sequence composition by step 3, at this time s [n]
Length should be 2048
Step 4 chooses the m-sequence that a segment length is 2048 as pseudo-code ScrPNCode, and enabling its first 1024 is Scr1,
1024 data are Sc afterwards2R, i.e. ScrPNCode=[Scr1Scr2].S [n] is scrambled, the transmission signal s after being scrambledScr
=s*ScrPNCode=[PNCode*Scr1PNCode*Scr2]
It is the receiving end processing system block diagram of the specific embodiment the present invention is based on Fig. 1 shown in Fig. 2.
The following steps are included:
Step 1 does not consider noise, is fully received if sending signal, therefore after sampling, signal r under the frequency deviation received
[n] are as follows:
1.
WhereinFor frequency deviation, after Δ θ expression between the frequency deviation of 1024 data bands and the frequency deviation of preceding 1024 data bands
The phase difference of corresponding position.R [n] is pressed into storage queue RAM, then
Step 2 descrambles the data in RAM, the information sequence m [n] after being descrambled:
2.
From the above operation it can be seen that scrambling this operation does not influence the quality of reception of signal.
Step 3, by two parts conjugate multiplication before and after RAM sequence m [n] after descrambling, obtain correlated series R [n]:
By operate above can one see front and back conjugation match after, frequency deviation be removed.
Step 4 sets N=1024；Coherent integration is carried out to R [n], obtains ∑ R [n]=Ne-jΔθ, therefore COR=| ∑ R [n]
|=N.After threshold judgement, as this captures situation.It is fully received due to sending signal, the result of threshold judgement must
So it is COR=N > Threshold, shows acquisition success.Therefore storing the m [n] being descrambled in the queue at this time can be utilized for
Offset estimation.It is numerous about frequency deviation estimating method, it no longer enumerates herein.
It is worth noting that, noise when front and back conjugate multiplication is understood is amplified because of being multiplied when considering the influence of noise.
Spreading gain equivalent at this time is actually:If expanded at this time using conventional Direct Sequence Spread Spectrum
Frequency gain are as follows:By comparison it can be found that this algorithm is more sensitive to noise, it is therefore desirable to more straight than routine
The longer sequence length of sequence spread spectrum is connect to resist the noise of equal-wattage.But since frequency deviation is removed, calculation amount will not
Increase with the expansion of frequency search range.
Claims (1)
1. a kind of direct sequence signal transmission method based on direct differential coherent accumulation, this method comprises:
Step 1, setting originator sample rate, guarantee the sampling of at least one spread-spectrum code chip more than twice；Parameter, including spreading code are set
Length, if the PN code PNCode that uses of spread spectrum, the spread spectrum pseudo-random sequence s [n] of transmitting terminal is two sections of identical PN sequences, if
The last period is PN1, latter section is PN2, then s [n] should meet following format:
S [n]=[PN1 PN2]=[PNCode PNCode]
Step 2 carries out scrambling code to s [n], and scrambling the pseudo-code used is ScrPNCode, the length in ScrPNCode period and s [n]
It is equal, so that directly to its last period pseudo-code effect that will not play despreading related to latter section of pseudo-code progress after being scrambled to s [n]
Fruit；
Step 3, receiving end are sampled according to fixed time interval to signal is received, and still guarantee that at least one spread-spectrum code chip is adopted
Sample is more than twice；By RAM in the data indentation storage queue of present sample；RAM meets:
RAM=[RAM1 RAM2]
Step 4 descrambles the data in RAM using pseudo-code ScrPNCode；
Step 5, will descrambling after RAM1In sequence and RAM2In sequence conjugate be multiplied, obtain correlated series:
R [n]=RAM1[n]*RAM2[n]*；
Step 6 carries out coherent integration to R [n], and modulus value obtains final correlation COR=| ∑ R [n] |；
COR is compared by step 7 with the threshold T hreshold of setting, if COR > Threshold, illustrates to capture
Signal has been arrived, and has obtained the initial position for receiving signal, has completed the thick capture of signal；Carry out subsequent frequency offset estimation procedure.
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Cited By (2)
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| CN111245473A (en) * | 2020-01-16 | 2020-06-05 | 电子科技大学 | Down-sampling-serial FFT-based high-dynamic low-signal-to-noise-ratio signal coarse capturing method |
| CN112666582A (en) * | 2020-12-11 | 2021-04-16 | 南京大鱼半导体有限公司 | Satellite signal processing method and device, storage medium and electronic equipment |
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| CN111245473A (en) * | 2020-01-16 | 2020-06-05 | 电子科技大学 | Down-sampling-serial FFT-based high-dynamic low-signal-to-noise-ratio signal coarse capturing method |
| CN111245473B (en) * | 2020-01-16 | 2021-04-30 | 电子科技大学 | Down-sampling-serial FFT-based high-dynamic low-signal-to-noise-ratio signal coarse capturing method |
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| CN112666582B (en) * | 2020-12-11 | 2022-07-05 | 南京大鱼半导体有限公司 | Satellite signal processing method and device, storage medium and electronic equipment |
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