CN110324065A - A kind of multi-user's underwater acoustic communication method based on cyclic shift keying band spectrum modulation - Google Patents

A kind of multi-user's underwater acoustic communication method based on cyclic shift keying band spectrum modulation Download PDF

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CN110324065A
CN110324065A CN201910488731.8A CN201910488731A CN110324065A CN 110324065 A CN110324065 A CN 110324065A CN 201910488731 A CN201910488731 A CN 201910488731A CN 110324065 A CN110324065 A CN 110324065A
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csk
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underwater acoustic
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CN110324065B (en
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景连友
殷洪玺
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Dalian University of Technology
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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
    • H04B1/7097—Interference-related aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0056—Systems characterized by the type of code used
    • H04L1/0071—Use of interleaving

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  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Error Detection And Correction (AREA)
  • Detection And Prevention Of Errors In Transmission (AREA)

Abstract

The invention belongs to technical field of underwater acoustic communication, and in particular to a kind of multi-user's underwater acoustic communication method based on cyclic shift keying band spectrum modulation.Step 1: transmitting terminal, utilizes the bit interleaver π of m-th of usermTo cmIt is interleaved, it is rear to carry out CSK modulation to improve traffic rate, then be interleaved to distinguish user；Step 2: using underwater sound communication transmitter by data it is carrier-modulated after transmitting；Step 3: receiving end, inverse processing when carrying out passive to pretreated multipath reception signal to compression channel and improve signal interference ratio.Next the soft demodulation mode of CSK is used, by CSK modulation and tradition IDMA iterative demodulation system perfect combination, system detection performance can be effectively improved.Method of the invention can effectively improve the traffic rate of each user, while can improve number of users.

Description

A kind of multi-user's underwater acoustic communication method based on cyclic shift keying band spectrum modulation
Technical field
The invention belongs to technical field of underwater acoustic communication, and in particular to a kind of based on the more of cyclic shift keying band spectrum modulation User's underwater acoustic communication method.
Background technique
Demand with ocean development to subsurface communication network constantly expands, and underwater sound communication has become current ocean neck The research hotspot in domain.But the features such as the long delay spreads of underwater acoustic channel, Bandwidth-Constrained, quick time-varying and ambient noise height Limit the development of underwater sound communication.For multi-user's underwater sound communication system, influence of the channel characteristics to communication system performance is then more It is obvious.Frequency division multiple access (Frequency Division Multiple Access, FDMA), time division multiple acess (Time Division Multiple Access, TDMA), CDMA (Code Division Multiple Access, CDMA) It is three kinds of common multiple access technologies in wireless communication, but application all face of these three technologies in multi-user's underwater sound communication system Face respective problem.For FDMA, since the available bandwidth of underwater acoustic channel is limited, cause the supported number of users of system by Limit, using less in underwater sound communication.And TDMA system needs preferable time synchronization, while its channel utilization is lower, This also limits it and applies in underwater sound communication.CDMA distinguishes user using spreading code, and different users can share time and frequency Spectrum, while spreading gain can also improve performance of the system under high background noise underwater acoustic channel.Therefore, CDMA is in multi-user's water Using relatively wide in sound communication.But the long delay spreads by underwater acoustic channel multipath are influenced, existing CDMA multi-user's underwater sound The number of users that communication system is supported is relatively fewer, well below the number of users of land multi-user wireless communication.In addition, Traffic rate by spread spectrum communication characteristic, each user of cdma system is very low, is far from satisfying the communication of current rapid growth Demand.
In recent years, researcher proposes through interleaver the interlacing multi-address (Interleave for distinguishing user Division Multiple Access, IDMA) technology.IDMA system not only has the anti-multi-access inference of cdma system and anti-ageing Ability is fallen, multiple access users number can also be effectively improved, there are more wide Research Prospects in wireless communications, But at present IDMA technology in underwater sound communication using less.
Cyclic shift keying (CSK) spread-spectrum modulation technique indicates information using the shift size of spreading code, can be effective The traffic rate for improving spread spectrum communication, is widely used in underwater sound communication in recent years.
It mentions in patent " a kind of IDMA system communicating method (CN 107612861A) based on CCSK modulation " by CSK skill Art is applied to multi-user's IDMA system.It but is that a CSK tune is separately increased on the basis of IDMA system in the invention System, although increasing anti-interference ability in this way, further decreases communication system rate, therefore be not suitable in traffic rate Used in very low underwater sound communication system.In addition, the CSK demodulation in the invention belongs to hard decision, certain property is had lost Energy.
Summary of the invention
It is less and every the technical problem to be solved by the present invention is to can access user in current multi-user underwater sound communication system The low problem of a user's traffic rate.
Technical scheme is as follows:
A kind of multi-user's underwater acoustic communication method based on cyclic shift keying band spectrum modulation comprising the steps of:
Step 1: transmitting terminal
1.1 are equipped with M user, the primary data information (pdi) b of m-th of usermIt indicates, is compiled by the channel that rate is R Code, the signal after being encoded is cm；The M of m=1,2,3 ....
1.2 utilize the bit interleaver π of m-th of usermTo cmIt is interleaved, obtains data dm；The bit interleaver Effect is the burst error for breaing up concentration.
1.3 couples of data dmCSK modulation is carried out, sequence s is obtainedm；
1.4 utilize the code interleaver Π of m-th of usermTo smIt is interleaved, obtains data xm.The code interleaver Effect is for distinguishing user；
Step 2: using underwater sound communication transmitter by data xmTransmitting after carrier-modulated.
Step 3: receiving end
The signal that 3.1 pairs of each reception energy converters receive pre-processes, and pretreatment includes synchronous, down coversion and sampling Processing etc..
3.2 pairs carry out channel estimation by pretreated reception signal；
Inverse processing when 3.3 pairs of pretreated multipath reception signals carry out passive, it is dry to compression channel and raising letter Than；
Mean value, variance and the corresponding CSK symbol probability of the 3.4 each subscriber signals of initialization, i.e., default one will solve Adjust the initial value of signal；
3.5 calculate the mean value and variance of i-th of user signal after inverse processing when passive；
3.6 calculate the mean value and variance of the interference signal of i-th of user；
3.7 calculate the outer likelihood ratio that i-th of user sends signal, and utilize the code interleaver of i-th of userInto Row deinterleaves；
The outer likelihood ratio of signal after 3.8 pairs of deinterleavings carries out the soft demodulation of CSK, the Soft Inform ation after being demodulated；
The soft demodulation of the CSK are as follows: utilize the estimation for sending the outer likelihood ratio calculating of signal and sending signal after deinterleaving Value.Obtained signal estimated value and CSK modulation frequency expansion sequence used are subjected to relevant treatment, obtain correlated results θi。θi's Value is influenced by two factors: sending the secondary lobe of the evaluated error of signal and the autocorrelation result of frequency expansion sequence.Assuming that the two because Element all meets Gaussian Profile, and calculates respective variance, can derive θiPosterior probability density function.In conjunction with CSK symbol Prior probability, calculate demodulation after coded data outer likelihood ratio.So far, that is, the soft demodulating process of CSK is completed.
3.9 utilize the solution bit interleaver of i-th of userOuter likelihood ratio after the soft demodulation of CSK is deinterleaved, Channel decoding, the outer likelihood ratio of the coded data after the information bit estimated and decoding are carried out using decoder later；
3.10 utilize the bit interleaver π of i-th of useriInterweave to the outer likelihood ratio after the decoding of decoder output, and Re-start the soft mapping of CSK.Obtained CSK symbol probability is re-entered into the soft demodulator of CSK, for the soft solution of CSK next time It adjusts；
The soft mapping of the CSK are as follows: the outer likelihood ratio exported using decoder after interweaving calculates each coded-bit Probability.If each coded-bit is mutually indepedent, according to the mapping ruler that CSK is modulated, the CSK mapped by coded-bit is calculated Symbol probability.
Further, in the soft mapping process of CSK, removal cannot be mapped to the probability of CSK symbol, to improve systematicness Energy.
3.11 repeat (3.8)-(3.10) until reaching the soft demodulation the number of iterations upper limit of CSK；
3.12 utilize the code interleaver Π of i-th of useriInterweaved again to the result of the soft mapping of CSK, and again Calculate the mean value and variance of i-th of subscriber signal；
3.13 calculate next subscriber signal.It repeats (3.5)-(3.12), until all users have been calculated.
3.14 repeat (3.5)-(3.13), until reaching the IDMA iteration upper limit of setting.
Beneficial effects of the present invention:
Communication means of the invention improves traffic rate using CSK modulation on the basis of traditional IDMA.In receiving end, First using it is passive when anti-technology come compression channel, while the signal interference ratio of each user can be effectively improved.Next CSK is used CSK modulation and tradition IDMA iterative demodulation system perfect combination can be effectively improved system detection performance by soft demodulation mode.With Existing multi-user's underwater acoustic communication method is compared, and method of the invention can effectively improve the traffic rate of each user, while energy Improve number of users.
Detailed description of the invention
Fig. 1 is transmitting terminal structural schematic diagram of the invention.
Fig. 2 is receiving end structural schematic diagram of the invention.
Fig. 3 (a) is the equivalent channels of the user 1 after inverse processing when passive.
Fig. 3 (b) be by it is passive when inverse processing later from the interference channel of user 2.
Fig. 3 (c) be by it is passive when inverse processing later from the interference channel of user 3.
Fig. 3 (d) be by it is passive when inverse processing later from the interference channel of user 4.
Fig. 3 (e) be by it is passive when inverse processing later from the interference channel of user 5.
Fig. 3 (f) be by it is passive when inverse processing later from the interference channel of user 6.
Fig. 3 (g) be by it is passive when inverse processing later from the interference channel of user 7.
Fig. 3 (h) be by it is passive when inverse processing later from the interference channel of user 8.
Specific embodiment
A specific embodiment of the invention is described in detail below in conjunction with attached drawing.
Present invention relates solely to the baseband modulation stages in communication system, therefore tell about the Part Methods emphatically, for carrier wave Modulation and demodulation stage content is ignored.
It is as shown in Figure 1 to emit end structure.If user's number of system is M, for m (M of m=1,2,3 ...) a use Family, transmitting terminal are mainly made of 5 modules: channel encoder, bit interleaver πm(for breaing up the burst mistake of concentration Accidentally), CSK modulator, code interleaver Πm(for distinguishing user) and carrier modulator.Below with the transmitting of m-th of user Illustrate for the specific embodiment of end.
The specific embodiment of transmitting terminal include it is following step by step:
T1. the information data b of m-th of usermAfter channel coding, the signal after being encoded is cm.It utilizes m-th The bit interleaver π of usermTo cmIt is interleaved, obtains data dm；T2. α=[α is used1,α2,…,αG] indicate frequency expansion sequence, The length is G, then corresponding CSK order of modulation is Q=log2G.To data dmIt is grouped according to length Q.It, will if being divided into Z group Q bit binary data in every group is converted to decimal system Δz。
T3. cyclic shift Δ to the right is distinguished to Z frequency expansion sequence αzPosition, after parallel-serial conversion, obtains sequence sm, smI.e. For data dmBy the modulated signal of CSK.
T4. the code interleaver Π of m-th of user is utilizedmTo cmIt is interleaved, obtains data xm。
T5. to data xmCarrier modulation is carried out, and is sent in underwater acoustic channel.
It is as shown in Figure 2 to receive end structure.Receiving end include: preprocessing module, channel estimator, it is passive when inverse processing device, Baseband signal estimator, decoding piece interleaverThe soft demodulator of CSK, solution bit interleaverChannel decoder, bit Interleaver pim, the soft mapper of CSK and code interleaver Πm, wherein pretreatment template includes synchronous, down coversion and sampling etc. Reason, mainly becomes baseband signal for the passband signal received, is not described here.
The specific embodiment of receiving end base band signal process include it is following step by step:
R1. N number of receiving hydrophone, channel h of m-th of user to n-th of receiving hydrophone are equipped withn,m=[hn,m(0), hn,m(1),...,hn,m(L-1)]TIt indicates, wherein L indicates channel impulse response length, then n-th of receiving hydrophone receives To signal be
Wherein wnIt (j) is additive white Gaussian noise, variance isChannel estimation is carried out to signal is received, is obtained It arrivesConventional channel estimation method can be used in channel estimation methods.
R2. the mean value E (x of all subscriber signals is initializedi=0 and variance Var (x (j))i(j))=1, bit di(q) Prior probability P (di(q)=0)=P (di(q)=1)=1/2, i=1,2 ... M.
R3. system parameter is initialized.Setting IDMA the number of iterations is Nouter, iouter=1.I=1 is set.
R4. the number of iterations that the soft demodulator of CSK is arranged is Ninter, iinter=1.To reception signal rn(j) when carrying out passive Inverse processing.For i-th of user, obtain
WhereinIndicate convolution operation,
According to it is passive when reflexive matter, Qi,iIt (t) is an approximation Sinc function, and its gain is far longer than Qm,i(t)(m ≠i).Fig. 3 gives in certain 8 user's underwater sound communication experiments, for of equal value letter of the user 1 after inverse processing when passive Road can be seen from the chart that desired equivalent channels gain is significantly larger than the interference channel gain of other users, and it is expected Channel has already been through compression, and energy all concentrates on main path position.So using it is passive when anti-technology can effectively carry out channel Compression, and the signal interference ratio of each user is improved, and then improve detection performance.
R5. signal y is calculated(i)(t) mean value and variance:
WhereinIt is the equivalent channels Q after inverse processing when passivei,i(l) length.
R6. interference signal of i-th of user on l paths is calculatedMean value and variance, l=1,
E(ζi (l)(j))=E (y(i)(j+l))-Q(i,i)(l)E(xi(j))
Var(ζi (l)(j))=Var (y(i)(j+l))-||Q(i,i)(l)||2Var(xi(j))
R7. it calculates i-th of user and obtains external information after baseband signal estimator:
R8. the decoding piece interleaver of i-th of user is utilizedTo eESE(xi(j)) it is deinterleaved, obtains eESE(si (j))。
R9. to eESE(si(j)) it is grouped according to length G, and calculates signal si(g) mean value and variance
R10. it utilizesIt is related to local frequency expansion sequence α progress, the result after obtaining correlation
Wherein, indicate that the element in vector carries out dot product,*Indicate conjugation, F is Fourier transform matrix, F-1It is in Fu Leaf transformation inverse of a matrix matrix.
R11. the local autocorrelative variance of frequency expansion sequence α is calculated
R12. after calculation code data di(q) prior information:
R13. d is calculatedi(q) posterior information
Wherein P (di) it is according to bit di(q) prior information calculates,
Corresponding conversion is the binary sequence that value size is Δ -1 after the decimal system.
R14. d is calculatedi(q) outer likelihood ratio eCSK(di(q))=Lposter(di(q))-Lpriori(di(q)), eCSK(di) just It is the result of the soft demodulation of CSK.
R15. the solution bit interleaver of i-th of user is utilizedTo eCSK(di) be deinterleaved, and input channel decodes Device obtains the information bit estimation of i-th of userWith the outer likelihood information e of coded-bitDEC(ci)。
R16. the bit interleaver π of i-th of user is utilizediTo eDEC(ci) interweave, obtain eDEC(di)。
R17. according to eDEC(di) calculate P (di(q)=0), P (di(q)=1),
P(di(q)=0)=1-P (di(q)=1)
R18. if iinter< Ninter, iinter=iinter+ 1, return to step R12；
R19. the signal obtained after the soft mapping of CSK is calculatedProbability,
Wherein, It isThe sequence obtained after CSK is modulated.
R20. the code interleaver Π of i-th of user is utilizediIt is rightInterweave, obtainsCalculate corresponding mean value and side Difference.
R21. if i < M, next user is calculated, i=i+1 is enabled, return to step R4；
R22. if iouter< Nouter, enable iouter=iouter+ 1, i=1 return to step R4；
R23. terminate to demodulate.
From the foregoing, it will be seen that method of the invention and traditional multi-user's underwater acoustic communication method have it is huge It is different.In transmitting terminal, is modulated using CSK modulation instead of conventional Direct Sequence Spread Spectrum, can effectively improve each user's Traffic rate, while the chip interleaving technology in IDMA system is used, improve number of users；In receiving end, use first Anti-technology carries out channel shortening and improves the signal interference ratio of each user when passive, next using baseband signal estimator come Estimate symbol probability is carried out, is iterated the soft demodulation of CSK using the symbol probability of estimation later.Method of the invention can be very well In conjunction with the Iterative detection algorithm of traditional IDMA, can effectively improve existing underwater sound multi-user comm communication quality and User's number.

Claims (5)

1. a kind of multi-user's underwater acoustic communication method based on cyclic shift keying band spectrum modulation, which is characterized in that include following step It is rapid:
Step 1: transmitting terminal
1.1 are equipped with M user, the primary data information (pdi) b of m-th of usermIt indicates, the channel coding for being R by rate obtains Signal after coding is cm；The M of m=1,2,3 ...；
1.2 utilize the bit interleaver π of m-th of usermTo cmIt is interleaved, obtains data dm；
1.3 couples of data dmCSK modulation is carried out, sequence s is obtainedm；
1.4 utilize the code interleaver Π of m-th of usermTo smIt is interleaved, obtains data xm；
Step 2: using underwater sound communication transmitter by data xmTransmitting after carrier-modulated；
Step 3: receiving end
The signal that 3.1 pairs of each reception energy converters receive pre-processes；
3.2 pairs carry out channel estimation by pretreated reception signal；
Inverse processing when 3.3 pairs of pretreated multipath reception signals carry out passive to compression channel and improves signal interference ratio；
Mean value, variance and the corresponding CSK symbol probability of the 3.4 each subscriber signals of initialization, i.e., default one will demodulate letter Number initial value；
3.5 calculate the mean value and variance of i-th of user signal after inverse processing when passive；
3.6 calculate the mean value and variance of the interference signal of i-th of user；
3.7 calculate the outer likelihood ratio that i-th of user sends signal, and utilize the code interleaver of i-th of userIt is solved Interweave；
The outer likelihood ratio of signal after 3.8 pairs of deinterleavings carries out the soft demodulation of CSK, the Soft Inform ation after being demodulated；
The soft demodulation of the CSK are as follows: utilize the estimated value for sending the outer likelihood ratio calculating of signal and sending signal after deinterleaving；Will Signal estimated value and the CSK modulation arrived frequency expansion sequence used carry out relevant treatment, obtain correlated results θi, derive θiPosteriority Probability density function calculates the outer likelihood ratio of coded data after demodulation in conjunction with the prior probability of CSK symbol；
3.9 utilize the solution bit interleaver of i-th of userOuter likelihood ratio after the soft demodulation of CSK is deinterleaved, later Channel decoding, the outer likelihood ratio of the coded data after the information bit estimated and decoding are carried out using decoder；
3.10 utilize the bit interleaver π of i-th of useriInterweave to the outer likelihood ratio after the decoding of decoder output, and again Carry out the soft mapping of CSK；Obtained CSK symbol probability is re-entered into the soft demodulator of CSK, is used for the soft demodulation of CSK next time；
3.11 repeat (3.8)-(3.10) until reaching the soft demodulation the number of iterations upper limit of CSK；
3.12 utilize the code interleaver Π of i-th of useriInterweaved again to the result of the soft mapping of CSK, and is recalculated The mean value and variance of i-th of subscriber signal；
3.13 calculate next subscriber signal；(3.5)~(3.12) are repeated, until all users have been calculated；
3.14 repeat (3.5)~(3.13), until reaching the IDMA iteration upper limit of setting.
2. multi-user's underwater acoustic communication method as described in claim 1 based on cyclic shift keying band spectrum modulation, feature exist In, in step 3.10, the soft mapping of the CSK are as follows: the outer likelihood ratio exported using decoder after interweaving calculates each encoding ratio Special probability；If each coded-bit is mutually indepedent, according to the mapping ruler that CSK is modulated, calculate by coded-bit mapping CSK symbol probability.
3. multi-user's underwater acoustic communication method as claimed in claim 1 or 2 based on cyclic shift keying band spectrum modulation, feature It is, in the soft mapping process of CSK of step 3.10, removal cannot be mapped to the probability of CSK symbol, to improve system performance.
4. multi-user's underwater acoustic communication method as claimed in claim 1 or 2 based on cyclic shift keying band spectrum modulation, feature It is, in step 3.1, the pretreatment includes synchronous, down coversion and sample process.
5. multi-user's underwater acoustic communication method as claimed in claim 3 based on cyclic shift keying band spectrum modulation, feature exist In in step 3.1, the pretreatment includes synchronous, down coversion and sample process.
CN201910488731.8A 2019-06-06 2019-06-06 Multi-user underwater acoustic communication method based on cyclic shift keying spread spectrum modulation Active CN110324065B (en)

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