A kind of joint inhibited based on polar code coding encrypting and ofdm system peak-to-average force ratioMethodTechnical field
The invention belongs to wirelessly communicate encryption technology field, and in particular to one kind is based on polar code coding encrypting and OFDMIntegrated processes of the system peak-to-average than inhibition.
Background technique
Development of Wireless Communications is rapid, and compared to wired communication system, wireless communication system has broadcast, mobility and opensThe features such as putting property.A possibility that these features make wireless communication be intercepted and captured and be eavesdropped increase, secure wireless communication problem dayBenefit is prominent.For secure wireless communication problem, traditional safety communication technology assumes that the transmission of physical layer is zero defect, andHigher on physical layer uses computation complexity height, is difficult to the Encryption Algorithm cracked in finite time, not according to physicsThe channel characteristics of layer design privacy mechanism.Radio physical layer makes full use of safely the feature of channel in radio physical layer, legalCommunicating pair can recover raw information, while listener-in can not obtain secret information.Generally, safety of physical layer is mainly wrappedInclude the technologies such as safe coding, cooperation interference and cipher key-extraction.Therefore, safety of physical layer coding take into account information transmission reliability andSafety.
Compared with single-carrier system, since the output of multicarrier modulation system is the superposition of multiple signals, so if moreWhen the phase of a signal is consistent, the instantaneous power of acquired superposed signal can be far longer than average power signal, result in largerPeak-to-average power ratio.Therefore radio-frequency power amplifier should work within very big dynamic linear response range, otherwise, work as signal peakWhen value enters the nonlinear area of power amplifier, distorted signals can be caused, this distortion can cause the intermodulation between subcarrierAnd out-of-band radiation, so that the orthogonality between each sub-channel signal be made to be destroyed, generation is interfered with each other.Solve the problems, such as thisOne of method is exactly to require power amplifier that should have very big linear working range, however, this will will lead to amplifier effectThe reduction of rate and the increase of transmitter apparatus complexity.
Arikan is taught was put forward for the first time the concept of Polar code in 2008, and Strict Proof nothing discrete for binary systemMemory channel (B.DMCs), Polar code can achieve shannon capacity[1].Polar code is a kind of theoretical based on channel-polarizationThe linear channel coding method of proposition, theoretical basis are channel-polarizations.As shown in figure 4, channel-polarization include channel combination andDecompose two processes.When aggregate channel number tends to infinity, polarization phenomena occur: the channel capacity of a part of channel tends to1 (noiseless channel), the channel capacity of another part tend to 0 (channel of making an uproar entirely).Using channel-polarization characteristic, Polar code coding becomesMust be very intuitive, useful information is transmitted on noiseless channel, in channel fixed bit of making an uproar entirely.It can as first theoretical proofUp to the code of shannon limit, Polar code will play huge potentiality in wireless communication and storage system.
OFDM (Orthogonal Frequency Division Multiplexing, OFDM) is that a kind of complexity is low,The multi-carrier transmission scheme of modulation /demodulation need to only be can be achieved with using IFFT and FFT, application is extremely wide.But OFDM was being usedThere are problems in journey, wherein peak-to-average force ratio PAPR (peak-to-average power ratio) is exactly one and significantly asksTopic.Due to the arbitrariness of coding, different sub-carrier is possible to generate peak value in the time domain just in synchronization, and to high powerLinear amplifier proposes very big requirement.Once peak value is more than the range of Linear Amplifer, the inelastic region amplification of these componentsNon-linear distortion can be generated, interfering with each other between subchannel is caused, to influence the performance of ofdm system.Reduce PAPR in OFDMMethod there are many kinds of, such as clipping[2], coding[3], interweave[4], selected mapping method[5], partial sequence transmission[6], non-linear compandingTransformation[7], constellation extension[8]Deng.But each existing method be all reduce system one party and performance cost under subtractSmall PAPR's, such as increase implementation complexity, reduce the availability of frequency spectrum, reduce transmission rate, increase transmission power[9][10].?The basic principle of coding class method is to generate the lesser OFDM symbol of peak-to-average power ratio using different coding, but availableCoding pattern it is considerably less, especially when number of subcarriers is larger, code efficiency can be very low, and the complexity of calculating is also veryGreatly.Furthermore SLM (Selected Mapping)[11][12]Method is by traversing some alternative libraries, then from these offersScheme base inside selection the smallest data group of peak-to-average force ratio transmitted.Particular reference is as follows:
[1]Arikan E.Channel polarization:a method for constructing capacity-achieving codes for symmetric binary-input memoryless channels[J].InformationTheory,IEEE Transactions on,2009 55(7):3051-3073.
[2]Lin Y,Song K,Yun M S.Iterative Clipping Noise Recovery of OFDMSignals Based on Compressed Sensing[J].IEEE Transactions on Broadcasting,2017,63(4):706-713.
[3]Liu Y C,Chang C F,Lee S K,et al.Deliberate Bit Flipping WithError-Correction for PAPR Reduction[J].IEEE Transactions on Broadcasting,2017,63(1):123-133.
[4]Gamage H,Rajatheva N,Latva-Aho M.High PAPR Sequence Scrambling forReducing OFDM Peak-to-Average Power Ratio[C]//European Wireless；EuropeanWireless Conference.2016.
[5]Xiao Y,Wang Z,Cao J,et al.Time-frequency domain encryption withSLM scheme for physical-layer security in an OFDM-PON system[J].IEEE/OSAJournal of Optical Communications&Networking,2018,10(1):46-51.
[6]Yoshida M,Nashimoto H,Miyajima T.PTS-Based PAPR Reduction byIterative p-Norm Minimization without Side Information in OFDM Systems[J].Ieice Transactions on Communications,2018,101(3).
[7]Anoh K,Adebisi B,Rabie K M,et al.Root-Based Nonlinear CompandingTechnique for Reducing PAPR of Precoded OFDM Signals[J].IEEE Access,2018,6(99).
[8]Paredes M C P,Escudero-Garzás J J.PAPR Reduction via ConstellationExtension in OFDM Systems Using Generalized Benders Decomposition and Branch-and-Bound Techniques[J].IEEE Transactions on Vehicular Technology,2016,65(7):5133-5145.
[9]Joo H S,Kim K H,No J S,et al.New PTS Schemes for PAPR Reduction ofOFDM Signals Without Side Information[J].IEEE Transactions on Broadcasting,2017,PP(99):1-9.
[10]Zhao H,Deng X,Tao J,et al.Null subcarrier assisted selectivemapping for PAPR reduction in OFDM systems without side information[C]//International Conference on Communications&Networking in China.2016.
[11]Hu W W.SLM-based ACO-OFDM VLC system with low-complexity minimumamplitude difference decoder[J].Electronics Letters,2018,54(3):144-146.
[12]Yan C,Wang J,Lu H,et al.Selective mapping and restorable clippingjoint scheme for light-emitting diode nonlinearity alleviation in visiblelight communication system[J].Optical Engineering,2016,55(5):056106.
Summary of the invention
In order to solve the above technical problems, the present invention provides it is a kind of effectively improve system stability and safety based onThe encryption in physical layer method that the ofdm system peak-to-average force ratio of polar code and chaos sequence inhibits.Specific technical solution is as follows:
A kind of integrated processes inhibited based on polar code coding encrypting and ofdm system peak-to-average force ratio, this method are specifically included:
Sender extracts key by main channel, and generates chaos for key as initial value input chaos sequence generatorChaos sequence is segmented by sequence, and assigns serial number index information to every section of chaos sequence, by serial number index information and to be passedDefeated signal value is placed as information source information in the information bit of polar code；
Chaos sequence corresponding to serial number index information and signal value to be transmitted are subjected to chaos encryption respectively, obtained eachThe corresponding encrypted message sequence of serial number index information；
Polar code coding is carried out to the corresponding encrypted message sequence of each serial number index information respectively, by the letter after codingNumber it is sent into ofdm system, chosen so that the corresponding Polar code of the smallest that section of chaos sequence of PAPR value encodes and believes in ofdm systemBreath is modulated transmission；
Recipient demodulates the signal received, is decoded using Polar code decoder, and using used in encryptionThe corresponding chaos sequence of serial number index information is decrypted, and recovers original transmission signal.
It is further, described that chaos sequence is subjected to fragmentation procedure are as follows:
It is segmented according to chaos sequence of the code length to generation, if code length is N-bit, the digit of serial number index information accounts for MBit, then every section of chaos sequence length is N-M bit.
Further, the chaos encryption is that chaos sequence and bit information to be transmitted carry out XOR operation.
Further, the Polar code coding is completed under binary system finite field gf (2).
Compared with prior art, usefulness of the present invention is: 1, the present invention extracts binary keys using channel characteristic,And it generates chaos sequence information is encrypted and encode again, so that scrambled combines together, so that the letter after codingBreath has safety.2, using SLM method, it is additionally contemplates that the peak-to-average force ratio for reducing ofdm system in an encoding process.Therefore, the calculationMethod both realizes safe coding, is minimized the peak-to-average force ratio of system, solvesThe high problem of peak-to-average power ratio in DFDM system avoids the problem that step-down amplifier efficiency and increase transmitter apparatus complexity,Reduce equipment manufacturing costs.3, since polar code coding/decoding complexity is lower, especially encode it is relatively easy, using SLM algorithmSystem complexity and calculation amount will not be affected, and relative to SLM algorithm, because key is extracted from channel,It does not need to store additional random sequence, further reduced system complexity.4, due to the unique property of polar code, i.e., willIt reduces serial number corresponding to the chaos sequence of PAPR in ofdm system to be stored in the best information bit of polar code, in informationMost reliable transmission key decryption information bit is found out during the selection of position, encodes same method relative to other,The stability of system, the high reliablity of information transmission can be increased.
Detailed description of the invention
The following further describes the present invention with reference to the drawings:
Fig. 1 is total system encrypted transmission of the invention and received process schematic；
Fig. 2 is sender's coding encrypting modulated process schematic diagram of the invention；
Fig. 3 is that recipient of the invention encodes decryption demodulating process schematic diagram；
Fig. 4 is polar code channel-polarization figure；
Fig. 5 is the method for the present invention and comparative result figure of the tradition SLM method under different code length.
Fig. 6 is influence diagram of the length of serial number index information to peak-to-average force ratio in the present invention in embodiment；
Fig. 7 is influence comparison diagram of the different modulating mode to this method and traditional OFDM peak-to-average ratio in embodiment；
Fig. 8 is influence of the selection of polar code information bit to error rate of system under different code length in embodiment；
Fig. 9 is influence of the selection of polar code information bit to error rate of system under different code rates in embodiment.
Specific embodiment
The technical scheme in the embodiments of the invention will be clearly and completely described below, it is clear that described implementationExample is only a part of the embodiments of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, this field is commonTechnical staff's all other embodiment obtained without making creative work belongs to the model that the present invention protectsIt encloses:
A kind of integrated processes inhibited based on polar code coding encrypting and ofdm system peak-to-average force ratio as shown in Figure 1, from objectReason layer encryption is set out, and extracts cipher controlled cataloged procedure by channel, and then obtain the joint that encryption is combined with channel codingThe theory and method of coding encrypting realizes the further protection to Radio Link, using the lower polar code of encoding and decoding complexityIt is encoded, by unique code construction method, most reliable transmission is found out during the selection of information bit and is closedKey decrypts information bit.The present invention is additionally contemplates that the peak for reducing ofdm system is equal using the method for tradition SLM in an encoding processThan.Therefore, which both realizes safe coding, drops the peak-to-average force ratio of systemIt is low, following steps are specifically included,
Step 1, sender extract key from main channel according to channel characteristic, input chaos sequence for key as initial valueColumn generator generates chaos sequence, is segmented according to chaos sequence of the code length to generation, and is indexed respectively with different serial numbersInformation indicates its corresponding several sections of chaos sequence, and the serial number index information and signal value to be transmitted are believed together as information sourceBreath is placed in the information bit of polar code, in practical application, it is assumed that chaos sequence is divided into four sections, i.e., with 00,01,10,11 etc.Serial number index information indicates its corresponding four sections of chaos sequence, by the serial number index information and signal value to be transmitted together asInformation source information is placed in the information bit of polar code, it is preferable that the serial number index information is placed on the last bit of polar codeOn position.
Chaos sequence corresponding to serial number index information in information bit and signal to be transmitted are carried out chaos and added by step 2Close, according to the digit of serial number index information, if the digit of serial number index information is M-bit, code length is N-bit, by M in code lengthStore chaos sequence serial number index information, then chaos sequence carries out exclusive or encryption with N-M bit informations, and M, N are positive integer,N is greater than M, as described in step 1, it is assumed that indicate its corresponding four sections of chaos sequence with 00,01,10,11 serial number index informationColumn, then need two in code length being used to store chaos sequence number, and chaos sequence is carried out exclusive or with N-2 bit informations and is addedClose, then the corresponding chaos sequence value of the serial number index information is also N-2.
Step 3 carries out Polar code coding to the corresponding encrypted message sequence of each serial number index information respectively；
If some information sequence obtained after chaos encryption is U, U is subjected to Polar code coding, encodes formula are as follows:
Wherein, N is coding code length, and N=2n, GNFor generator matrix, A is the random subset for gathering { 1,2,3 ..., N }；GNIt (A) is GNSubmatrix, GN(A) matrix is made of the corresponding row vector of element in set A；GN(Ac) it is GNRemove GN(A)Matrix,It is to freeze position, further, the Polar code coding is completed under binary system finite field gf (2).
Step 4 transmits into the signal after coding to ofdm system, the peak-to-average force ratio after obtaining different encrypted chaotic arrays,In the present embodiment, the signal after coding is transmitted into ofdm system, in an ofdm system, to bit stream carry out QAM orQPSK modulation, and converted by IFFT, the peak-to-average force ratio after finally obtaining different encrypted chaotic arrays, using SLM method, selection makesThe chaos sequence that peak-to-average ratio is minimum in ofdm system is obtained, chaos is carried out to signal to be transmitted with the chaos sequence, is then carried outPolar code coding, carries out transmission after modulation.If Fig. 2 is sender's coding encrypting modulation step flow diagram, SI in figureIndicate serial number index information.
Step 5, recipient demodulate by FFT transform and QAM or QPSK to the signal received, use Polar codeDecoder for decoding, and be decrypted using the corresponding chaos sequence of used serial number index information is encrypted, recover original biographyDefeated signal.Fig. 3 is that recipient encodes decryption demodulating process schematic diagram.
In embodiment, using the decoding of Polar code decoder (with specific reference to Hussami N, Korada S B, UrbankeR.Performance of polar codes for channel and source coding[C]//IEEEInternational Symposium on Information Theory.2009), decoding judgement expression formula is as follows:
WhereinTo decode bit, AcFor fixed bit set, value is 0 (polar code freezes place value and is set as 0) herein, and A isInformation bit set.Are as follows:
WhereinFor log-likelihood ratio (Likelihood-Ratio, LR).In the present embodiment, it is translated using SCCode calculates the transition probability of each bit channelAnd then likelihood ratio (LR) information by iterating to calculate bit channel,And then hard decision, likelihood ratio information therein are made to each transmission information is defined as:
Sequence after being decoded solves chaos sequence corresponding to sequence in best information bit to coding sequenceClose, after can must decrypting information sequence.In embodiment, recipient is also to extract key by the channel characteristic that two sides are transmitted,Therefore this key can not be stolen (channel is different) known to hearer, this key can be used as the initial value of chaos generator, fromAnd the initial value of receiving-transmitting sides is the same so chaos sequence value is also the same.
Specifically, by taking the detailed process of information transmission as an example, as shown in Figure 1, sender (Alice) sends message U to conjunctionThe recipient (Bob) of method, while listener-in (Eve) intentionally gets the message of transmission.In the process, Alice and Bob pass through masterChannel extracts key, due to wireless channel sky when uniqueness, eavesdropping side Eve do not know any information about key.WhenWhen Alice transmits message to Bob, the corresponding chaos sequence value of key and signal value to be transmitted are passed through into coding encrypting moduleIt is encrypted and is encoded, obtain ciphertext X, then be modulated device and obtain output waveform Y, and the legal Bob that receives receives Y, Y warpIt crosses after main channel and obtains Y ' and first carry out demodulation module obtaining X ', then by decoding deciphering module, obtain message U '.Due to that will encryptMove on to physical layer, coding while is encrypted, and that listener-in Eve is intercepted is encrypted out-of-order ciphertext Z, increases EveDecoding difficulty, increase the safety of system.
As shown in figure 5, the method for the present invention and comparative result figure of the tradition SLM method under different code length, the present invention is realizedThe effect of traditional drop peak-to-average force ratio.In specific embodiment, there is peak-to-average force ratio in length, the modulation system of serial number index informationIt influences, shown in Fig. 6, serial number index information bit length is longer, better, the length of V expression serial number index information of peak-to-average force ratio drop；FigureShown in 7, this method, that is, SLM-Polar performance substantially improves OFDM peak-to-average ratio, and under BPSK modulation, peak-to-average force ratio drops moreIt is good, P (PAPR > PAPR in figure0) indicate the CCDF of PAPR, that is, assess the parameter CCDF of peak-to-average force ratio.Fig. 8 gives differenceInfluence of the selection of polar code information bit to error rate of system under code length, emulation code length position is 128 and 64 in figure, is selectedFor polar code different location as serial number index information to the influence diagram of system error performance, Best-channel indicates this implementationBest polar code information bit is selected to carry out the transmission of ordinal index value in the process, and common-channel indicates to select itHis general information bit transmits (represent general encoding efficiency), it is seen that the selection of polar code information bit has performance certainIt influences.Fig. 9 gives influence of the selection of polar code information bit under different code rates to error rate of system, it is seen that the volume of polar codeCode code rate is very big to systematic influence, can be worse after especially selecting along with serial number index information.
One good secure encryption scheme requires very strong key sensibility, that is, is to say, when listener-in obtainsKey and correct key even there are when very small difference, it is also not possible to decryption restoration goes out source data.In this experiment,The bit key length of extraction is 128 bits, and being converted to precision is l0-39Decimal fraction as the initial close of chaos systemKey.By repeatedly testing, discovery is when two key initial values are in xnIt is randomly selected between (0, l), and differs l0-39When, generationChaos sequence variance rate is 50%, i.e., has half bit information difference by the chaos sequence that the two seed keys generate, such asTable 1 show the key sensitivity Detection of chaos sequence.Eve can not decode the cipher-text information received, i.e. this algorithmKey precision is high, there is very strong key sensibility.
The key sensitivity Detection of 1 chaos sequence of table
Encryption method of the present invention belongs to the encryption algorithm of safety of physical layer, is that safety, coding and drop peak-to-average force ratio three is sameWhen the algorithm held a concurrent post, wherein Polar code has lower encoder complexity and delay as a kind of efficient coding mode, andPolar code during transmission, is set as freezing position in the small error prone channels of channel capacity, passes in the big position of channel capacityDefeated Reliability Channel is as information bit.
It is emphasized that: the above is only presently preferred embodiments of the present invention, not make in any form to the present inventionLimitation, any simple modification, equivalent change and modification to the above embodiments according to the technical essence of the invention,All of which are still within the scope of the technical scheme of the invention.