CN115102819B - Orthogonal time-frequency space safety transmission method, device and equipment based on unitary matrix transformation - Google Patents
Orthogonal time-frequency space safety transmission method, device and equipment based on unitary matrix transformation 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
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
- H04L27/34—Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
- H04L27/345—Modifications of the signal space to allow the transmission of additional information
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2614—Peak power aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/26—Systems using multi-frequency codes
- H04L27/2601—Multicarrier modulation systems
- H04L27/2626—Arrangements specific to the transmitter only
- H04L27/2627—Modulators
- H04L27/2634—Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L27/00—Modulated-carrier systems
- H04L27/32—Carrier systems characterised by combinations of two or more of the types covered by groups H04L27/02, H04L27/10, H04L27/18 or H04L27/26
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/001—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols using chaotic signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/0861—Generation of secret information including derivation or calculation of cryptographic keys or passwords
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L9/00—Cryptographic mechanisms or cryptographic arrangements for secret or secure communications; Network security protocols
- H04L9/08—Key distribution or management, e.g. generation, sharing or updating, of cryptographic keys or passwords
- H04L9/088—Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W12/00—Security arrangements; Authentication; Protecting privacy or anonymity
- H04W12/03—Protecting confidentiality, e.g. by encryption
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The application relates to an orthogonal time-frequency space safety transmission method, device and equipment based on unitary matrix transformation. The method comprises the following steps: the legal transmitting end carries out constellation mapping on the transmitting signal to obtain a signal to be transmitted; encrypting a signal to be transmitted according to the unitary matrix to obtain a delay-Doppler domain signal; performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal; performing Haisenberg transformation on the time-frequency domain signal to obtain a time domain signal; setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to perform linear amplification through a power amplifier to obtain an encrypted signal; and sending the encrypted signal to a wireless channel so that a legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain a sending signal. The method can effectively inhibit the peak-to-average ratio of the system on the premise of ensuring the reliability of the orthogonal time-frequency space system, and the decryption difficulty of an eavesdropper is increased by adopting unitary matrix transformation encryption, so that the safety of the system is ensured.
Description
Technical Field
The present application relates to the field of wireless communication encryption technologies, and in particular, to a method, an apparatus, and a device for orthogonal time-frequency space safe transmission based on unitary matrix transformation.
Background
With the continuous maturity of wireless communication systems and the appearance of various new technologies, future communication application scenes are more diversified, and performance indexes are more diversified, so that the method also brings new challenges to the performance requirements and security architecture of future wireless communication.
The physical layer security (PLS, physical layer security) technology provides a novel security mechanism different from the traditional computational complexity, and has the advantages of underlying maneuvering control, multi-scene adaptation, wireless communication symbiosis and the like. The physical layer security transmission technology is to perform security design on the existing communication transmission technology such as coding, modulation and spread spectrum, so that the security of the transmission layer can be further improved while the reliability of the system can be ensured. The physical layer encryption (PLE, physical layer encryption) technique is a PLS method, and mainly the security of the physical layer is achieved by implementing an encryption scheme in the physical layer, i.e. by means of wireless keys.
In a high mobility scenario, the wireless channel has dual selectivity, i.e., frequency selectivity and time selectivity, which can lead to multipath effects and doppler shift, and the waveforms currently used perform poorly in a high mobility scenario where the doppler shift is very high. Thus, for high mobility scenarios, an orthogonal time-frequency space (OTFS, orthogonal time and frequency space) technique is proposed that can efficiently accomplish highly reliable and high rate data transmission in time-frequency bi-selected channels, and can perform data modulation in the delay-Doppler (DD) domain and spread over the whole time-frequency domain, thus obtaining channel diversity in the whole time and frequency domains.
However, due to the limitation of the amplifying range of the power amplifier at the signal transmitting end, the signal with peak-to-average ratio (PAPR-to-average power ratio) in the OTFS system easily enters the nonlinear region of the power amplifier, so that serious nonlinear distortion is generated on the signal, and obvious spectrum interference and signal distortion are further caused, so that the problem of serious degradation of the transmission stability of the whole system is generated.
Disclosure of Invention
Based on the foregoing, it is necessary to provide a method, an apparatus and a device for orthogonal time-frequency space-based safe transmission based on unitary matrix transformation, which can ensure safe and stable transmission of signals in an orthogonal time-frequency system.
An orthogonal time-frequency space safety transmission method based on unitary matrix transformation, the method comprising:
the legal transmitting end carries out constellation mapping on the transmitting signal to obtain a signal to be transmitted;
encrypting a signal to be transmitted according to the unitary matrix to obtain a delay-Doppler domain signal;
performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal;
performing Haisenberg transformation on the time-frequency domain signal to obtain a time domain signal;
setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to perform linear amplification through a power amplifier to obtain an encrypted signal;
and sending the encrypted signal to a wireless channel so that a legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain a sending signal.
In one embodiment, encrypting a signal to be transmitted according to a unitary matrix to obtain a delay-doppler domain signal includes:
extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix;
and carrying out equidistant transformation on the signal to be transmitted according to the unitary matrix to obtain a delay Doppler domain signal.
In one embodiment, extracting the initial key from the delay-doppler domain of the wireless channel comprises:
detecting the delay-Doppler domain of the wireless channel to obtain a channel detection signal, and carrying out equivalent channel estimation on the channel detection signal to obtain a channel characteristic observation value;
carrying out characteristic quantization on the channel characteristic observation value to obtain inconsistent initial key bits;
carrying out information negotiation on inconsistent initial key bits to obtain consistent initial key bits;
and carrying out security enhancement on the consistent initial key bits to obtain the initial key.
In one embodiment, the chaotic sequence generator is a chaotic system;
inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, wherein the method comprises the following steps:
and inputting the initial key into a chaotic system to carry out quantization processing to obtain a chaotic sequence.
In one embodiment, performing unitary matrix transformation on a chaotic sequence to obtain a unitary matrix includes:
mapping the chaotic sequence according to the hash function to obtain a rotation direction vector;
and constructing and generating a rotation direction vector matrix according to the rotation direction vector, and orthogonalizing the rotation direction vector matrix to obtain a unitary matrix.
In one embodiment, sending the encrypted signal to the wireless channel, so that the legal receiving end receives and parses the encrypted signal in the wireless channel to obtain the sending signal, includes:
mapping the unitary matrix according to the index value information to obtain an index value corresponding to the encrypted unitary matrix of the encrypted signal;
and transmitting the encrypted signal and the index value to a wireless channel, so that a legal receiving end receives and analyzes the encrypted signal and the index value in the wireless channel to obtain a transmission signal.
In one embodiment, a legal receiving end receives and analyzes an encrypted signal in a wireless channel and an index value corresponding to an encryption unitary matrix to obtain a transmission signal, which includes:
the legal receiving end receives the encrypted signal and the index value in the wireless channel, and performs Wigner transformation on the encrypted signal to obtain a time-frequency domain encrypted signal;
performing the Fourier transform on the time-frequency domain encrypted signal to obtain a delay Doppler domain encrypted signal;
determining a corresponding decryption unitary matrix according to the index value, and decrypting the delay-Doppler domain encrypted signal according to the decryption unitary matrix to obtain a signal to be transmitted;
and constellation demapping is carried out on the signal to be transmitted to obtain a transmitting signal.
In one embodiment, determining a corresponding decrypted unitary matrix based on the index value comprises:
extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix;
mapping the unitary matrix according to the index value, and determining the corresponding decrypted unitary matrix from the unitary matrix.
An orthogonal time-frequency space-time safety transmission device based on unitary matrix transformation, the device comprising:
the mapping module is used for constellation mapping the transmission signal by the legal transmitting end to obtain a signal to be transmitted;
the unitary matrix encryption module is used for encrypting the signal to be transmitted according to the unitary matrix to obtain a delay Doppler domain signal;
the inverse octyl Fourier transform module is used for performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal;
the Hessenberg transformation module is used for performing Hessenberg transformation on the time-frequency domain signals to obtain time domain signals;
the peak-to-average ratio suppression module is used for setting a peak-to-average ratio threshold value of the time domain signal, selecting the time domain signal with the minimum peak-to-average ratio, and performing linear amplification through the power amplifier to obtain an encrypted signal;
and the signal transmission module is used for transmitting the encrypted signal to the wireless channel so that the legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain a transmitted signal.
A computer device comprising a memory storing a computer program and a processor which when executing the computer program performs the steps of:
the legal transmitting end carries out constellation mapping on the transmitting signal to obtain a signal to be transmitted;
encrypting a signal to be transmitted according to the unitary matrix to obtain a delay-Doppler domain signal;
performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal;
performing Haisenberg transformation on the time-frequency domain signal to obtain a time domain signal;
setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to perform linear amplification through a power amplifier to obtain an encrypted signal;
and sending the encrypted signal to a wireless channel so that a legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain a sending signal.
According to the orthogonal time-frequency space safe transmission method, the device and the equipment based on unitary matrix transformation, constellation mapping is carried out on the transmitted signals, and encryption design is carried out on the signals according to the unitary matrix, so that the Euclidean distance between the signals is unchanged, the legal receiving end can be guaranteed to correctly recover the transmitted signals, the signals encrypted by the unitary matrix have noise-like random characteristics, the modulation mode and the information are hidden, decryption difficulty of eavesdroppers is increased, and safety of signal transmission is guaranteed; the signal is converted into the time domain signal, and the time domain signal with the lowest peak-to-average ratio is transmitted, so that the peak-to-average ratio of an orthogonal time-frequency-space system can be effectively restrained, and the stability of signal transmission is ensured. The orthogonal time-frequency space safe transmission method based on unitary matrix transformation effectively reduces the PAPR of the OTFS system on the premise of ensuring the reliability of the system, and adopts the unitary matrix to encrypt signals, so that the signal modulation mode and information are concealed, the decryption difficulty of an eavesdropper is increased, and the safety of the system is ensured.
Drawings
Fig. 1 is a flow diagram of an orthogonal time-frequency space-time safety transmission method based on unitary matrix transformation in one embodiment;
FIG. 2 is a flow diagram of an orthogonal time-frequency space-time safe transmission model based on unitary matrix transformation in one embodiment;
fig. 3 is a schematic flow chart of inhibiting PAPR in an OTFS system by a legal transmitting end in one embodiment;
FIG. 4 is a schematic diagram of time-frequency domain characteristics of an OTFS system wireless channel in one embodiment;
FIG. 5 is a schematic diagram of delay-Doppler domain characteristics of an OTFS system wireless channel in one embodiment;
fig. 6 is a flow diagram of extracting an initial key from a delay-doppler domain of a wireless channel in one embodiment;
fig. 7 is a schematic diagram of a chaotic space formed by inputting an initial key into a chaotic system according to an embodiment: (a) an x-y-z space schematic of the chaotic space; (b) a chaotic space x-y plane schematic; (c) a chaotic space x-z plane schematic; (d) a chaotic space y-z plane schematic;
FIG. 8 is a diagram illustrating mapping of unitary matrices according to index value information in one embodiment;
fig. 9 shows CCDF for one embodiment with different Q values for n=16 and m=16;
fig. 10 shows CCDF for one embodiment with n=32 and m=32 for different Q values;
fig. 11 shows CCDF for one embodiment with different Q values for n=64 and m=64;
fig. 12 shows CCDF for one embodiment with different Q values for n=128 and m=128;
fig. 13 is a constellation diagram illustrating the constellation diagram before and after unitary matrix encryption in one embodiment: (a) a QPSK constellation before unitary matrix encryption; (b) a constellation diagram after unitary matrix encryption when nxm=8×8; (c) a constellation diagram after unitary matrix encryption when nxm=16×16; (d) a constellation diagram after unitary matrix encryption when nxm=32×32; (e) a constellation diagram after unitary matrix encryption when nxm=64×64; (f) a constellation diagram after unitary matrix encryption when nxm=128×128;
fig. 14 is a schematic diagram showing comparison of entropy of constellation information before and after unitary matrix encryption in one embodiment;
fig. 15 is a schematic diagram showing bit error rate comparison between legal receiving ends and eavesdropping ends before and after unitary matrix encryption in an embodiment;
fig. 16 is an internal structural view of a computer device in one embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In one embodiment, as shown in fig. 1, there is provided an orthogonal time-frequency space safety transmission method based on unitary matrix transformation, comprising the steps of:
step 102, the legal transmitting end performs constellation mapping on the transmitting signal to obtain a signal to be transmitted.
It can be understood that the legal transmitting end modulates the binary transmitting signal into complex signal through quadrature phase shift keying (Quadrature Phase Shift Keying, QPSK) constellation mapping, thereby improving the signal transmission rate; and the legal receiving end judges the point with the minimum distance as the transmitted signal by comparing the distance between the received signal and the point of the constellation diagram, thereby correctly demodulating the signal.
Step 104, encrypting the signal to be transmitted according to the unitary matrix to obtain the delay-doppler domain signal.
Specifically, equidistant transformation encryption is performed by adopting unitary matrix, and for European spaces X and Y with the same dimension, the corresponding measurement standard is d X And d Y Equidistant transformation means that for any a, b e X, there is a mapping f: X-Y, so that d Y (f(a),f(b))＝d X (a, b) assuming the dimensions of X and Y are W, the equidistant transformation is further used for the design of a mapping function of the complex vector space, i.e
X＝{X 1 X 2 ...X W }→Y＝{Y 1 Y 2 …Y W }
The correspondence is denoted as e x→y, i.e. y=e (X). By designing some sub-transformations e 1 ,e 2 ,e 3 .. and combining the sub-transforms to form a final cryptographic transform, denoted as
e(X)＝e 1 (e 2 (...(e W (X))))
All equidistant transforms between X and Y can be mapped by multiplying X by a unitary matrix U, i.e
Y＝e i (X)＝UX
And for the unitary matrix U,
UU H ＝U H U＝I W
in the ( H Is conjugate transpose, I W Representing a W-dimensional identity matrixThe columns and rows of the unitary matrix U are made up of a set of orthonormal bases.
The transmission end Alice modulates the signal to be transmitted encrypted by the unitary matrix U on the delay-doppler domain to obtain a symbol of the delay-doppler domain as x [ k, l ], wherein k=0, 1, & gt, N-1, l=0, 1, & gt, M-1, k and l respectively represent a column index and a row index of the whole delay-doppler domain grid, m×n transmission symbols are total, and N and M respectively represent the number of OTFS symbols and the number of subcarriers.
It can be understood that the application carries out equidistant transformation on the signal to be transmitted according to the unitary matrix, modulates the model to be transmitted on the delay-doppler domain to obtain the signal of the delay-doppler domain, ensures that the space of the constellation after the constellation diagram of the signal to be transmitted is unchanged after transformation, and the channel noise superimposed by the unitary matrix cannot be amplified after decryption and recovery, thereby ensuring that the legal receiving end correctly recovers the transmitted signal as much as possible.
And 106, performing inverse octyl Fourier transform on the delay-Doppler domain signal to obtain a time-frequency domain signal.
Specifically, as shown in fig. 2, the delay-doppler domain signal is subjected to inverse-octave fourier transform (ISFFT), so as to obtain a time-frequency domain signal, which is expressed as:
in the formula, X [ n, m ] represents a time-frequency domain signal, and n and m represent a column index and a row index of a time-frequency domain grid, respectively.
It will be appreciated that the time-frequency domain signal is obtained by transforming the delay-doppler domain signal from the delay-doppler domain to the time-frequency domain by an inverse-octave fourier transform.
Step 108, performing Haisenberg transformation on the time-frequency domain signal to obtain a time domain signal.
Specifically, the time-frequency domain signal X [ n, m ] is subjected to hessianberg transformation (Heisenberg), and a time domain signal is obtained, expressed as:
wherein s (t) represents a time domain signal, g t (T) represents a pulse shaping function transmitted by the transmitting end, T represents the current time, T d Is the time interval, Δf d Is the subcarrier frequency spacing.
It will be appreciated that the time-frequency domain signal is further transformed from the time-frequency domain to the time domain by the hessian transformation, resulting in a time domain signal.
Step 110, setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to perform linear amplification through a power amplifier to obtain an encrypted signal.
Specifically, the PAPR of the time domain signal s (t) obtained by Haisenberg transformation is
Wherein, the parameter db is decibel, max { |s (t) | 2 -maximum value of signal power; e { |s (t) | 2 -average value of signal power;
setting the peak-to-average ratio threshold value of the time domain signal as the PAPR 0 And represents that the peak-to-average ratio of the time domain signal exceeds the threshold value PAPR according to the complementary cumulative distribution function (CCDF, complementary cumulative distribution function) 0 Is expressed as the probability of
In the method, in the process of the application,
setting the peak-to-average ratio threshold value of the time domain signal as PAPR 0 On the premise that when carrier combinations of a plurality of time domain signals exist, the combination with the smallest PAPR is selected for transmission, and the method can be shownThe phenomenon of high peak power signal existing in the OTFS system is reduced, as shown in fig. 3, the transmitting end generates Q U matrices u= [ U ] at the same time 1 ,U 2 ,...U Q ]After the modulating signal is encrypted and transformed by the U matrix, the ISFFT and the Haisenberg transformation are carried out to obtain Q time domain signals with different PAPR values. The PAPR threshold value is the PAPR 0 On the premise of selecting the signal with the minimum PAPR in the Q time domain signals, carrying out linear amplification through a power amplifier to obtain an encrypted signal r (t), and effectively reducing the PAPR in the OTFS system.
It can be appreciated that since the power amplifier has a linear amplification range, it is necessary to suppress the peak-to-average ratio of the OTFS system, so that the signal is prevented from easily entering the nonlinear region of the power amplifier, which would cause serious nonlinear distortion of the signal.
It can be understood that by setting the peak-to-average ratio threshold value of the time domain signals, the time domain signals are ordered, and the time domain signal with the smallest peak-to-average ratio is selected to be amplified linearly by the power amplifier to obtain the final encrypted signal, so that the legal receiver can receive the clear signal.
Step 120, the encrypted signal is sent to the wireless channel, so that the legal receiving end receives and parses the encrypted signal in the wireless channel to obtain a sending signal.
It can be understood that the legal receiving end performs the inverse process of the transmitting end, receives the encrypted signal through the receiving antenna, and sequentially performs wigner transformation, symplectic fourier transformation, unitary matrix decryption and constellation demapping, thereby accurately acquiring the transmitted signal.
In the orthogonal time-frequency space safe transmission method based on unitary matrix transformation, constellation mapping is carried out on the transmitted signals, and the signals are encrypted according to the unitary matrix, so that the Euclidean distance between the signals is unchanged, the legal receiving end can be ensured to correctly recover the transmitted signals, the signals encrypted by the unitary matrix have noise-like random characteristics, the modulation mode and the information are hidden, the decryption difficulty of an eavesdropper is increased, and the safety of signal transmission is ensured; the signal is converted into the time domain signal, and the time domain signal with the lowest peak-to-average ratio is transmitted, so that the peak-to-average ratio of an orthogonal time-frequency-space system can be effectively restrained, and the stability of signal transmission is ensured. The orthogonal time-frequency space safe transmission method based on unitary matrix transformation effectively reduces the PAPR of the OTFS system on the premise of ensuring the reliability of the system, and adopts the unitary matrix to encrypt signals, so that the signal modulation mode and information are concealed, the decryption difficulty of an eavesdropper is increased, and the safety of the system is ensured.
In one embodiment, encrypting a signal to be transmitted according to a unitary matrix to obtain a delay-doppler domain signal includes: extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix; and carrying out equidistant transformation on the signal to be transmitted according to the unitary matrix to obtain a delay Doppler domain signal.
Specifically, as shown in fig. 4, the time-frequency domain characteristics of a wireless channel of an OTFS system change along with time and space changes, and the difficulty of key extraction is increased, the fast time-varying channel on the time-frequency domain is converted into a time-invariant channel on a delay-doppler domain through two-dimensional fourier transform, the channel response characteristics of the delay-doppler domain are shown in fig. 5, an initial key is extracted on the delay-doppler domain of the wireless channel, the initial key is input into a chaotic sequence generator to obtain a chaotic sequence, and the chaotic sequence is subjected to unitary matrix transformation to obtain a unitary matrix; equidistant transformation is carried out on the signals to be transmitted according to the unitary matrix, and delay-Doppler domain signals are obtained
It will be appreciated that in the delay-doppler domain, the channel has only a few distinct peaks, the impulse response can be used to equivalently represent the channel, and the channel in this domain exhibits sparse characteristics, which greatly reduces the frame structure overhead of the channel estimation. Also, extracting the initial key over the delay-doppler domain of the wireless channel is relatively easy and less prone to error.
In one embodiment, as shown in fig. 6, extracting the initial key from the delay-doppler domain of the wireless channel comprises:
both the legal sending end Alice and the legal receiving end Bob detect the delay Doppler domain of the wireless channel to obtain a channel detection signal, and perform equivalent channel estimation on the channel detection signal to obtain a channel characteristic observation value;
after obtaining the channel characteristic observed value, the two communication parties need to adopt a consistent quantization method to carry out characteristic quantization on the channel characteristic observed value to obtain inconsistent initial key bits;
due to the influence of noise, interference, estimation errors of the receiving and transmitting sides and other factors existing in the wireless channel, a small amount of inconsistent sequences possibly exist in initial key bits obtained by the communication sides, and correction and verification of the inconsistent key sequences are completed through certain information interaction at the moment, so that consistent initial key bits are obtained;
in the steps of channel detection and information negotiation, in order to prevent an eavesdropper Eve from stealing information about a key, a certain security enhancement means is also required to eliminate key related information obtained by Eve, and an extractor method and a hash function method are adopted to carry out security enhancement on consistent initial key bits to obtain an initial key.
It can be understood that the two communication parties use the delay-doppler domain of the wireless channel as a public random source to extract an initial key, so that one-time-pad is effectively ensured, and the initial key extracted by the two communication parties is a safe shared key through channel detection, feature quantization, information negotiation and confidentiality enhancement in sequence.
In one embodiment, the chaotic sequence generator is a chaotic system, expressed as:
wherein a, b, c are Lv system parameters, parametersTo bring the current value of x, y, z into the calculated value.
Specifically, the application takes the initial key as the initial seed of x, y and z, and sets the system parametersAt the moment, a=30, b=8/3 and c=28, the chaotic space diagram of Lv Jitong is shown in fig. 7, and the initial key is input into the chaotic system to be quantized to obtain a chaotic sequence S 0 。
It can be appreciated that by using the initial key as the input to the chaotic transmitter, more chaotic encryption keys can be generated by using a chaotic system.
In one embodiment, for a chaotic sequence S 0 Performing unitary matrix transformation to obtain a unitary matrix, comprising:
will chaos sequence S 0 Divided into W block sequences S 1 ,S 2 ,…,S i ，…，S W ；
Using a third generation secure hash algorithm (Secure Hash Algorithm, SHA-3) as a hash function, S is i Mapping to S i 'is denoted as S' i ＝hash(S i )；
According to S i ' generating a rotational direction vector θ, expressed asWherein θ is i Represented as
θ i ＝2π(S′ i modλ)/λ
Wherein S' i The value range [0,2 ] L -1]Wherein L is S i ' bit width, lambda is the phase accuracy, generally taking positive integer parameters;
performing the above steps circularly from i=1 to W2 until the cycle is ended;
and constructing a W multiplied by W rotation direction vector matrix U 'by using the rotation direction vector theta, and performing Gram orthogonalization on the rotation direction vector matrix U' to obtain a unitary matrix U.
Specifically, the rotational direction vector matrix U' is represented as
In the formula, v 1 ,v 2 ,…,v W Column vectors representing U';
the Gram orthogonalization of the rotation direction vector matrix U' is expressed as
u 1 ＝v 1
In the method, in the process of the application,representing orthogonal projection of a column vector v onto a linear extension of vector u; further unitary matrix U, column vector, denoted as
Obtaining a unitary matrix U according to the column vector of the unitary matrix U, wherein the unitary matrix U is expressed as U= [ e ] 1 ,e 2 ,e 3 ,…,e W ]。
It will be appreciated that the purpose of using a hash function is to re-shuffle the signal data so that the distribution of rotation angles is more uniform and random.
In one embodiment, as shown in fig. 8, the generated unitary matrix U needs to be mapped by indexes, and it is assumed that 4U matrices are generated, that is, q=4, and the index values of 00, 01, 10, and 11 can be used for mapping, and the index values of the encrypted unitary matrix corresponding to the encrypted signal are used as sideband information and the encrypted signal together as signal input (may not participate in the encryption transformation process), and are sent to the wireless channel, so that the legal receiving end receives and analyzes the encrypted signal and the index value in the wireless channel, and obtains the sending signal.
It can be understood that, by transmitting the encryption unitary matrix corresponding to the encrypted signal through the index value, the legal receiving end can correctly decrypt and demodulate after obtaining the index value, even if the eavesdropper Eve knows the index value, the eavesdropper cannot obtain the corresponding encryption U matrix because of no corresponding initial key.
In one embodiment, a legal receiving end receives and analyzes an encrypted signal in a wireless channel and an index value corresponding to an encryption unitary matrix to obtain a transmission signal, which includes:
the legal receiving end Bob receives the encrypted signal r (t) and the index value from the wireless channel through the receiving antenna, firstly performs Wigner transformation (namely inverse transformation of Haisenberg transformation) on the encrypted signal r (t) to obtain a time-frequency domain encrypted signal, which is expressed as
In the method, in the process of the application,representing a matched pulse filter function at the receiving end, which is matched with the transmission g t (t) satisfying the biorthogonal property, and then obtaining a delay-Doppler domain encrypted signal by the Fourier transform, which is expressed as
And determining a corresponding decryption unitary matrix by the legal receiving end according to the index value, decrypting the delay Doppler domain encrypted signals y [ k, l ] according to the decryption unitary matrix to obtain signals to be transmitted, and finally performing constellation demapping on the signals to be transmitted to restore correct transmitting signals.
In one embodiment, the determining, by the legal receiving end, the corresponding decrypting unitary matrix according to the index value includes: extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix; mapping the unitary matrix according to the index value, and determining the corresponding decrypted unitary matrix from the unitary matrix.
It can be understood that by controlling the selection of unitary matrix by index value, legal receiver can decrypt and demodulate correctly after obtaining index value, and even if eavesdropper obtains index value information, it can not decrypt because it has no corresponding unitary matrix, which ensures the security of system.
It should be understood that, although the steps in the flowcharts of fig. 1-3 are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in fig. 1-3 may include multiple sub-steps or phases that are not necessarily performed at the same time, but may be performed at different times, nor does the order in which the sub-steps or phases are performed necessarily occur sequentially, but may be performed alternately or alternately with at least a portion of the sub-steps or phases of other steps or other steps.
The technical scheme provided by the application is different from the prior art in generating beneficial effects, and simulation verification is also carried out.
Specifically, in the orthogonal time-frequency space safe transmission method based on unitary matrix transformation, the constellation mapping mode of OTFS adopts QPSK modulation, OTFS adopts n×m=16×16, n×m=32×32, n×m=64×64 and n×m=128×128 transmission formats, and the unitary matrix number Q respectively takes 1,2,4,8 and 16, as shown in fig. 9-12, it can be known that as n×m increases, the peak-to-average ratio of the system obviously increases, because the increase of the number of time-domain carriers increases the maximum power peak of the system. In addition, as the peak-to-average ratio of the Q value increases, the system is reduced, and the signal selectivity of the encryption transmission is higher due to the increase of the Q value, so that the time domain encryption signal with smaller peak-to-average ratio can be obtained more effectively. Finally, compared with the OTFS without the encryption algorithm, Q=1, the technical scheme provided by the application can obviously inhibit the PAPR of the OTFS system, and lower PAPR can be obtained by adjusting the Q value.
In order to further verify the safety performance of the orthogonal time-frequency space safety transmission method based on unitary matrix transformation, the constellation quantization information entropy is used for measuring the constellation confusion degree, which is defined as
In the method, in the process of the application,p (a, b) is the joint probability density of a, b, delta is the minimum scale of quantization of analog signals into digital signals, i and j are all points used for traversal, a and b are representations of constellation points, and as shown in fig. 13, it can be known that as n×m increases, the greater the entropy of constellation information, the higher the degree of confusion of constellation points, the more noise-like, and the more difficult the signals are intercepted and deciphered.
As shown in fig. 14, by comparing the information entropy of the constellation before and after the QPSK is subjected to the U-matrix encryption transformation, it can be seen that the information entropy of the constellation after the U-matrix encryption transformation is significantly improved compared with that of the constellation without encryption, and in addition, as N and M increase, the value of the constellation entropy after encryption is continuously increased while the system constellation entropy without encryption is unchanged, because the number of scrambled constellation points after the U-matrix encryption is increased, and the uncertainty thereof is increased. Therefore, the algorithm can obviously improve the entropy of constellation information, the scheme can lead the constellation to be highly chaotic, the leakage of the constellation information is less, and the safety can be ensured.
As shown in fig. 15, by comparing the bit error rates of the legal receiving end and the eavesdropping end before and after encryption, at this time, the OTFS modulation formats are set to nxm=32×32 and nxm=64×64 respectively, and since the eavesdropper does not have the same wireless channel key as the sender, the transformation unitary matrix mapped by the index value cannot be obtained, and therefore, the index mapping and constellation demapping cannot correctly recover the index bit information and the symbol bit information, so the bit error rate is always 0.5, which indicates that the technical scheme provided by the application can improve the security performance of the system. In addition, compared with the traditional OTFS system, the OTFS transmission scheme provided by the application has no obvious difference in bit error rate, because the unitary matrix encryption method provided by the application is equidistant transformation, does not change the Euclidean distance of signals, and is equivalent to the traditional OTFS modulation method in signal form after normal decryption. Therefore, the OTFS safe transmission method based on unitary matrix transformation can improve the safety performance of the traditional OTFS system while not affecting the reliability of the system.
In one embodiment, an orthogonal time-frequency space safety transmission device based on unitary matrix transformation is provided, and the device comprises:
and the mapping module is used for constellation mapping the transmission signal by the legal transmitting end to obtain a signal to be transmitted.
It can be understood that the legal transmitting end modulates the binary transmitting signal into complex signal through quadrature phase shift keying (Quadrature Phase Shift Keying, QPSK) constellation mapping, thereby improving the signal transmission rate; and the legal receiving end judges the point with the minimum distance as the transmitted signal by comparing the distance between the received signal and the point of the constellation diagram, thereby correctly demodulating the signal.
And the unitary matrix encryption module is used for encrypting the signal to be transmitted according to the unitary matrix to obtain the delay Doppler domain signal.
It can be understood that the application carries out equidistant transformation on the signal to be transmitted according to the unitary matrix, modulates the model to be transmitted on the delay-doppler domain to obtain the signal of the delay-doppler domain, ensures that the space of the constellation after the constellation diagram of the signal to be transmitted is unchanged after transformation, and the channel noise superimposed by the unitary matrix cannot be amplified after decryption and recovery, thereby ensuring that the legal receiving end correctly recovers the transmitted signal as much as possible.
And the inverse octyl Fourier transform module is used for performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal.
It will be appreciated that the time-frequency domain signal is obtained by transforming the delay-doppler domain signal from the delay-doppler domain to the time-frequency domain by an inverse-octave fourier transform.
The Hessenberg transformation module is used for performing Hessenberg transformation on the time-frequency domain signals to obtain time domain signals.
It will be appreciated that the time-frequency domain signal is further transformed from the time-frequency domain to the time domain by the hessian transformation, resulting in a time domain signal.
And the peak-to-average ratio suppression module is used for setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to be linearly amplified by the power amplifier to obtain an encrypted signal.
It can be appreciated that since the power amplifier has a linear amplification range, it is necessary to suppress the peak-to-average ratio of the OTFS system, so that the signal is prevented from easily entering the nonlinear region of the power amplifier, which would cause serious nonlinear distortion of the signal.
It can be understood that by setting the peak-to-average ratio threshold value of the time domain signals, the time domain signals are ordered, and the time domain signal with the smallest peak-to-average ratio is selected to be amplified linearly by the power amplifier to obtain the final encrypted signal, so that the legal receiver can receive the clear signal.
And the signal transmission module is used for transmitting the encrypted signal to the wireless channel so that the legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain a transmitted signal.
It can be understood that the legal receiving end performs the inverse process of the transmitting end, receives the encrypted signal through the receiving antenna, and sequentially performs wigner transformation, symplectic fourier transformation, unitary matrix decryption and constellation demapping, thereby accurately acquiring the transmitted signal.
For specific limitation of the orthogonal time-frequency space safety transmission device based on the unitary matrix transformation, reference may be made to the limitation of the orthogonal time-frequency space safety transmission method based on the unitary matrix transformation hereinabove, and the description thereof will not be repeated here. The above-mentioned all modules in the orthogonal time-frequency space safety transmission device based on unitary matrix transformation can be implemented completely or partially by software, hardware and their combination. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.
In one embodiment, a computer device is provided, comprising a memory storing a computer program and a processor that when executing the computer program performs the steps of: the legal transmitting end carries out constellation mapping on the transmitting signal to obtain a signal to be transmitted; encrypting a signal to be transmitted according to the unitary matrix to obtain a delay-Doppler domain signal; performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal; performing Haisenberg transformation on the time-frequency domain signal to obtain a time domain signal; setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to perform linear amplification through a power amplifier to obtain an encrypted signal; and sending the encrypted signal to a wireless channel so that a legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain a sending signal.
In one embodiment, a computer device is provided, which may be a terminal, and an internal structure diagram thereof may be as shown in fig. 15. The computer device includes a processor, a memory, a network interface, a display screen, and an input device connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage media. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program, when executed by a processor, implements an orthogonal time-frequency space-time secure transmission method based on unitary matrix transformation. The display screen of the computer equipment can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer equipment can be a touch layer covered on the display screen, can also be keys, a track ball or a touch pad arranged on the shell of the computer equipment, and can also be an external keyboard, a touch pad or a mouse and the like.
It will be appreciated by those skilled in the art that the structure shown in fig. 15 is merely a block diagram of a portion of the structure associated with the present inventive arrangements and is not limiting of the computer device to which the present inventive arrangements are applied, and that a particular computer device may include more or fewer components than shown, or may combine certain components, or have a different arrangement of components.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (8)
1. An orthogonal time-frequency space safety transmission method based on unitary matrix transformation, which is characterized by comprising the following steps:
the legal transmitting end carries out constellation mapping on the transmitting signal to obtain a signal to be transmitted;
encrypting the signal to be transmitted according to a unitary matrix to obtain a delay-Doppler domain signal;
performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal;
performing Haisenberg transformation on the time-frequency domain signal to obtain a time domain signal;
setting a peak-to-average ratio threshold value of the time domain signal, and selecting the time domain signal with the minimum peak-to-average ratio to perform linear amplification through a power amplifier to obtain an encrypted signal;
transmitting the encrypted signal to a wireless channel, so that a legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain the transmitted signal;
encrypting the signal to be transmitted according to the unitary matrix to obtain a delay-doppler domain signal, including:
extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix;
equidistant transformation is carried out on the signals to be transmitted according to the unitary matrix, and the delay-Doppler domain signals are obtained;
extracting an initial key from a delay-doppler domain of a wireless channel, comprising:
detecting the delay-Doppler domain of the wireless channel to obtain a channel detection signal, and carrying out equivalent channel estimation on the channel detection signal to obtain a channel characteristic observation value;
carrying out feature quantization on the channel feature observation value to obtain inconsistent initial key bits;
carrying out information negotiation on the inconsistent initial key bits to obtain consistent initial key bits;
and carrying out security enhancement on the consistent initial key bits to obtain the initial key.
2. The method of claim 1, wherein the chaotic sequence generator is a chaotic system;
inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, wherein the method comprises the following steps:
and inputting the initial key into the chaotic system to carry out quantization processing to obtain the chaotic sequence.
3. The method of claim 1, wherein performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix comprises:
mapping the chaotic sequence according to a hash function to obtain a rotation direction vector;
and constructing and generating a rotation direction vector matrix according to the rotation direction vector, and orthogonalizing the rotation direction vector matrix to obtain the unitary matrix.
4. The method of claim 1, wherein transmitting the encrypted signal to the wireless channel to enable a legitimate receiver to receive and parse the encrypted signal in the wireless channel to obtain the transmitted signal, comprises:
mapping the unitary matrix according to index value information to obtain an index value corresponding to the encrypted unitary matrix of the encrypted signal;
and sending the encrypted signal and the index value to the wireless channel so that a legal receiving end receives and analyzes the encrypted signal and the index value in the wireless channel to obtain the sending signal.
5. The method of claim 4, wherein the legal receiving end receives and parses the encrypted signal in the wireless channel and the index value corresponding to the unitary encryption matrix to obtain the transmission signal, and the method comprises:
the legal receiving end receives the encrypted signal and the index value in the wireless channel, and performs Wigner transformation on the encrypted signal to obtain a time-frequency domain encrypted signal;
performing the Fourier transform on the time-frequency domain encrypted signal to obtain the delay-Doppler domain encrypted signal;
determining a corresponding decryption unitary matrix according to the index value, and decrypting the delay-Doppler domain encrypted signal according to the decryption unitary matrix to obtain the signal to be transmitted;
and constellation demapping is carried out on the signal to be transmitted to obtain the sending signal.
6. The method of claim 5, wherein determining a corresponding decrypted unitary matrix from the index values comprises:
extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix;
and mapping the unitary matrix according to the index value, and determining a corresponding decrypted unitary matrix from the unitary matrix.
7. An orthogonal time-frequency space-time safety transmission device based on unitary matrix transformation, comprising:
the mapping module is used for constellation mapping the transmission signal by the legal transmitting end to obtain a signal to be transmitted;
the unitary matrix encryption module is used for encrypting the signal to be transmitted according to the unitary matrix to obtain a delay Doppler domain signal;
the inverse octyl Fourier transform module is used for performing inverse octyl Fourier transform on the delay Doppler domain signal to obtain a time-frequency domain signal;
the Hessenberg transformation module is used for performing Hessenberg transformation on the time-frequency domain signals to obtain time domain signals;
the peak-to-average ratio suppression module is used for setting a peak-to-average ratio threshold value of the time domain signal, selecting the time domain signal with the minimum peak-to-average ratio, and performing linear amplification through a power amplifier to obtain an encrypted signal;
the signal transmission module is used for transmitting the encrypted signal to a wireless channel so that a legal receiving end receives and analyzes the encrypted signal in the wireless channel to obtain the transmitted signal;
encrypting the signal to be transmitted according to the unitary matrix to obtain a delay-doppler domain signal, including:
extracting an initial key from a delay-doppler domain of a wireless channel, inputting the initial key into a chaotic sequence generator to obtain a chaotic sequence, and performing unitary matrix transformation on the chaotic sequence to obtain a unitary matrix;
equidistant transformation is carried out on the signals to be transmitted according to the unitary matrix, and the delay-Doppler domain signals are obtained;
extracting an initial key from a delay-doppler domain of a wireless channel, comprising:
detecting the delay-Doppler domain of the wireless channel to obtain a channel detection signal, and carrying out equivalent channel estimation on the channel detection signal to obtain a channel characteristic observation value;
carrying out feature quantization on the channel feature observation value to obtain inconsistent initial key bits;
carrying out information negotiation on the inconsistent initial key bits to obtain consistent initial key bits;
and carrying out security enhancement on the consistent initial key bits to obtain the initial key.
8. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor implements the steps of the method of any of claims 1 to 6 when the computer program is executed.
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