A method for distributed security transmission of information

Abstract

The application discloses a distributed secure transmission method of information, which comprises the following steps: dividing transmission symbols corresponding to secret information expected to be transmitted into two information-carrying symbols through serial-parallel conversion, and respectively sending each information-carrying symbol to different users for activation; all activated users cooperate with each other to recover the transmission symbols through parallel-serial conversion by receiving the information; and demodulating the transmission symbols to obtain the secret information. The application is applicable to the case that a eavesdropping user and an expected receiver are located in a similar direction under a line-of-sight channel, and can maximally inhibit the acquisition of secret information by the eavesdropping user while not affecting the decoding of expected symbols by the receiver. Therefore, the negative influence of a poor eavesdropping environment on the performance of a communication system is avoided, and the secure transmission performance of a signal is enhanced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of secure communication, and particularly relates to a method for distributing secure transmission of information. BACKGROUND

[0002] Wireless communication plays an increasingly important role in military and civilian fields, however, the broadcast nature of wireless communication brings unprecedented challenges to the security of wireless communication, and pure reliance on traditional encryption cannot meet the needs of physical layer security. Direction modulation technology for physical layer secure communication, as a supplement to traditional high layer encryption, effectively improves the information security of wireless communication, and has received extensive attention in recent years.

[0003] The traditional single base station direction modulation method is analyzed in the scenario of a single base station, and a large amount of confidential information will be leaked when the eavesdropping user is located in the vicinity of the legitimate receiver. SUMMARY

[0004] The present application aims to overcome the defects of the prior art, and provides a method for distributing secure transmission of information, which divides the expected symbol into two parts and sends them by two transmitters, and activates two different receivers by different transmitting base stations. Under the cooperation of the activated users, the receiving end can successfully demodulate the confidential information, avoids the eavesdropping of useful signals by the eavesdropping user without affecting the reception of confidential symbols, and solves the problem that single base station modulation is subject to the position information of the eavesdropper.

[0005] The present application is achieved by the following technical solutions:

[0006] A method for distributing secure transmission of information, the method comprising:

[0007] dividing the transmission symbol corresponding to the expected confidential information by serial-parallel conversion into two information-carrying symbols, and sending each information-carrying symbol to different users for activation;

[0008] all activated users cooperate with each other to recover the transmission symbol by parallel-serial conversion of the received information;

[0009] demodulating the transmission symbol to obtain the confidential information.

[0010] Further, the transmission symbol is divided into a quadrature component information-carrying symbol and an in-phase component information-carrying symbol, and is sent by two distributed transmitters.

[0011] Further, when sending the information-carrying symbol, the information-carrying symbol is expressed as

[0012]

[0013] wherein e i j are the i-th and j-th columns of N R ×N R identity matrix respectively; b m is the symbol transmitted by the transmitter, and satisfies b m ∈{b1,b2,…,b M}; represents taking the real part, represents taking the imaginary part.

[0014] Further, the transmitting each symbol carrying information to different users for activation specifically includes:

[0015] calculating the precoding matrix of the transmitter, and transmitting to the receiver after adding artificial noise to the null space of the channel matrix.

[0016] Further, the calculating the precoding matrix of the transmitter specifically includes:

[0017] expressing the elements in the received signal vector y I of different legitimate users as defining the matrix

[0018] the condition for activating the i-th receiver is At this time, only user i in the space can receive the symbol transmitted from the I-path transmitter, wherein β is a constant;

[0019] singular value decomposition of to obtain wherein matrix Σ i is a (N R -1) × (N R -1) diagonal matrix, and the diagonal elements are the N R -1 singular values of ; and represent left and right singular matrices respectively; is the null space of , and has the equation relationship ;

[0020] define a (N T -N R -1) order vector r i , which satisfies vector p i is expressed as so as to obtain the precoding matrix P I of the I-path transmitter.

[0021] ​Furthermore, the step of adding artificial noise to the null space of the channel matrix and then transmitting it to the receiving end specifically includes:

[0022] The transmit signal vector of transmitter I is in, For matrix H I null space; u I Represents an arbitrary column vector.

[0023] Furthermore, the cooperation among all activated users to recover the transmitted symbols from the received information through parallel-to-serial conversion specifically includes:

[0024] The receiving end uses bandpass filters for bandpass filtering, and the center frequency of the bandpass filters is the same as the carrier frequency of the transmitting end.

[0025] After filtering, the signal is down-converted to obtain the down-converted signal.

[0026] The transmission symbol is obtained by performing parallel-to-serial conversion on all down-converted signals.

[0027] Furthermore, the process of down-converting the filtered signal to obtain the down-converted signal specifically includes:

[0028] The down-converted signal at the receiving end is expressed as:

[0029]

[0030] In the formula, n k Describing channel noise, the probability distribution satisfies

[0031] The beneficial effects of this invention are as follows:

[0032] This invention employs a multi-user collaborative distributed modulation approach, which is applied to model poor eavesdropping scenarios, thereby reducing the probability of private information being intercepted in such scenarios. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the information distributed secure transmission method provided in an embodiment of the present invention;

[0034] Figure 2 This is a model diagram of a multi-user collaborative distributed directional modulation system according to an embodiment of the present invention;

[0035] Figure 3 This is a block diagram of a dual-array multi-user directional modulation transmitter according to an embodiment of the present invention;

[0036] Figure 4 This is a flowchart of the demodulation process of the confidential information receiving end in an embodiment of the present invention;

[0037] Figure 5 This is a constellation diagram of the eavesdropping user's received signal according to an embodiment of the present invention, wherein, Figure 5 (a) is a constellation diagram of the eavesdropping user's received signal under single-base station modulation. Figure 5 (b) is the constellation diagram of the eavesdropping user's received signal under dual-base station modulation;

[0038] Figure 6 This is a graph showing the change in symbol error rate of the receiver and the eavesdropping user as a function of the signal-to-noise ratio of the receiver in an embodiment of the present invention.

[0039] Figure 7 This is a graph showing the change of vector amplitude error of the receiver and the eavesdropping user as a function of the signal-to-noise ratio of the receiver in an embodiment of the present invention. Detailed Implementation

[0040] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0041] Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Currently, traditional single-base station directional modulation methods are all analyzed in the context of a single base station. If the eavesdropping user is located near a legitimate receiver, a large amount of confidential information will be leaked.

[0043] To address the aforementioned technical problems, the following embodiments of the information distributed secure transmission method of the present invention are proposed.

[0044] Example 1

[0045] Reference Figure 1 ,like Figure 1 The diagram shown is a schematic flowchart of the information distributed secure transmission method provided in this embodiment. The method uses QPSK modulation and specifically includes the following steps:

[0046] Step 1: Divide the transmission symbols corresponding to the confidential information to be sent into two information-carrying symbols through serial-to-parallel conversion, and send each information-carrying symbol to a different user for activation.

[0047] This embodiment designs a distributed base station multi-user directional modulation system. (Refer to...) Figure 2 ,likeFigure 2 The diagram illustrates a multi-user cooperative distributed directional modulation system model in this embodiment. The desired symbol is evenly distributed to two distributed transmitters for transmission via serial-to-parallel conversion, while each of the two base stations activates different users. Finally, the activated users cooperate to convert the received information from parallel to serial to recover the confidential symbol. In this scenario, even if an eavesdropping user is located in the same direction as one of the activated users, the confidential information will not be completely lost, thus significantly reducing the probability of the desired information being intercepted.

[0048] Among them, reference Figure 3 ,like Figure 3 The diagram shown is a block diagram of the dual-array multi-user directional modulation transmitter in this embodiment. The difference from the single-transmitter model is that different base stations transmit independent information streams, and their carrier frequencies are different. Furthermore, the carrier frequencies of the different transmit arrays are represented as f... c1 f c2 Therefore, when transmitting desired symbols using distributed base stations, the information-carrying symbols can be expressed as follows:

[0049]

[0050] Among them, e i e j N R ×N R The i-th and j-th columns of the unit matrix; b m Let b be the symbol transmitted by the transmitter, and satisfy b. m ∈{b1,b2,…,b M}; These represent operations that extract the real and imaginary parts, respectively.

[0051] Analysis focuses on the I-channel transmitter. The vector of the signal received by different receivers from the I-channel base station is...

[0052]

[0053] in, This is the precoding matrix for the I-channel base station; This represents the matrix formed by concatenating the channel vectors between transmitter 1 and different users.

[0054] In order for base station 1 to activate the i-th receiver, the following equation must be satisfied:

[0055]

[0056] At this point, only user i in the space can receive the symbols transmitted from transmitter I. Clearly, different legitimate users receive signal vectors y. I The elements in can be represented as

[0057]

[0058] Definition matrix Therefore, may be equivalent to

[0059]

[0060] where β is a constant. The above formula shows that the vector p i is in the null space of the matrix Therefore, N T ≥ N R , and in addition, the singular value decomposition is performed on , and

[0061]

[0062] where the matrix Σ i is an (N R -1) × (N R -1) diagonal matrix, and the diagonal elements are the N R -1 singular values of and represent the left and right singular matrices, respectively; is in the null space of , and the equality relationship holds.

[0063] According to the orthogonality of p i and in , p i can be expressed as a linear combination of the column vectors of the matrix . Define an (N T -N R -1) order vector r i , which satisfies , and the vector p i can be expressed as

[0064]

[0065] Based on this, the precoding matrix P I of the I-way transmitter at the transmitting end can be obtained, and further, the artificial noise is projected into the null space of the channel matrix H I to construct the artificial noise. Therefore, the transmitting signal vector of the I-way transmitter is

[0066]

[0067] where is the matrix H I ​null space; u I Represents an arbitrary column vector.

[0068] Similarly, this method can be used to activate user j at base station Q, and the precoding matrix P of Q-path can be obtained using the same method as before. Q And the artificial noise vector. The transmitted signal vector of transmitter 2 can be modeled as...

[0069]

[0070] in, For matrix H Q The zero space; This represents the matrix formed by concatenating the channel vectors between transmitter 2 and different users; u Q Represents an arbitrary column vector.

[0071] Reference Figure 4 ,like Figure 4 The diagram shown is a flowchart of the demodulation process for the confidential information receiving end in this embodiment. Figure 4 This illustrates the process of recovering the secret symbol at the receiving end. After passing through the line-of-sight channel, signals carried by two different carriers arrive simultaneously at users i and j. At this point, the activated users cooperate to recover the complete desired information. After receiving the information, users i and j respectively use a center frequency of f... c1 and f c2 Bandpass filtering is performed using a bandpass filter. Then, the mixture is multiplied by a carrier wave of the corresponding frequency f. c1 and f c2 Down-conversion is performed. Based on this, the down-converted signal at the receiving end can be expressed as:

[0072]

[0073] In the formula, n k Describing channel noise, the probability distribution satisfies

[0074] Step 2: All activated users cooperate to recover the transmission symbols from the received information through parallel-to-serial conversion.

[0075] Step 3: Demodulate the transmitted symbols to obtain the confidential information.

[0076] Example 2

[0077] Consider the following scenario. This embodiment assumes that both transmitters are equipped with uniform linear arrays and the number of array elements is N. T =18 and the location coordinates of the two base stations are set to (-50,0) and (50,0) respectively; the space contains K=3 receivers, and each receiver is equipped with a single antenna. It is also assumed that different users are located in... The azimuth angles of different users relative to the I-channel transmitter are θ. I,1 = -30°, θ I,2 =30°,θ I,3 =60°, the azimuth of each receiver relative to the Q-channel base station is θ Q,1 = -60°, θ Q,2 = -30°, θ Q,3 =30°. Furthermore, assume that the active coordinates of transmitter 1 are located at... The user at that location, transmitter 2 is activated at the following coordinates. The user at the location. In the eavesdropping environment considered in this embodiment, it is assumed that the azimuth angle of the eavesdropping user relative to transmitter 1 is consistent with the user activated by the I-channel base station, i.e., θ I,e =θ I,2 =30°. The modulation method is QPSK modulation, and the carrier frequency is set to f. c =3×10 9 Hz, signal wavelength is taken as λ = c / 2f c To make the experimental results more accurate, the transmitter sent 10 [units of data] to the legitimate user under each signal-to-noise ratio constraint and user azimuth estimation error. 6 A symbol.

[0078] After transmitting information using the information distributed secure transmission method provided in the aforementioned embodiments, the reception of transmitted symbols by eavesdropping users under poor eavesdropping conditions is analyzed.

[0079] Reference Figures 5-7 ,like Figure 5 The diagram shown is a constellation diagram of the signal received by the user in this embodiment of the eavesdropping. Figure 5 (a) is a constellation diagram of the eavesdropping user's received signal under single-base station modulation. Figure 5 (b) is the constellation diagram of the eavesdropping user's received signal under dual-base station modulation; such as Figure 6 The figure shown is a graph illustrating the variation of the symbol error rate of the receiver and the eavesdropping user with the signal-to-noise ratio of the receiver in this embodiment; as shown... Figure 7 The figure shown is a graph showing the change of vector amplitude error of the receiver and the eavesdropping user as a function of the receiver's signal-to-noise ratio in this embodiment.

[0080] When the position of the eavesdropper relative to transmitter 1 is approximately the same as the position of the i-th receiver relative to the I-channel transmitter, i.e., θ I,e =θ I,i The received signal of the eavesdropping user at this time can be represented as:

[0081]

[0082] Where, d I,i ,d I,e h(θ) represents the distance from user i and the eavesdropping user to base station I, respectively;I,e ), h(θ Q,e ) represent the channel vectors between the eavesdropper and the transmitter 1 and the transmitter 2 respectively; n e represents the channel noise, the probability distribution of which satisfies

[0083] It can be seen that even if the eavesdropper is located in the direction close to one of the activated users, the eavesdropper can only recover half of the information. At the same time, the eavesdropper is also interfered by the signal transmitted by the other base station and the artificial noise vector, so that the received signal of the eavesdropper is severely distorted. Based on this, the method proposed in the embodiment can overcome the influence of the aforementioned bad eavesdropping environment on the security of the communication system.

[0084] The embodiment adopts a multi-user cooperative distributed modulation mode, applies it to modeling in a bad eavesdropping scenario, and reduces the probability that the private information is intercepted in the scenario. The embodiment divides the expected symbol into in-phase components and quadrature components at the transmitting end and transmits them by two distributed transmitters, thereby disturbing the received signal of the eavesdropper and ensuring the security of the private information transmission.

[0085] The above merely describes the preferred embodiment of the present application and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for secure transmission of information in a distributed manner, characterized in that, The method comprises: The transmission symbol corresponding to the secret information to be sent is divided into two information-carrying symbols through serial-parallel conversion, and each information-carrying symbol is sent to different users for activation; All activated users cooperate with each other to recover the transmission symbol through parallel-serial conversion of the received information; The transmission symbol is demodulated to obtain the secret information; The transmission symbol is divided into a quadrature component information-carrying symbol and an in-phase component information-carrying symbol, and is sent by two distributed transmitters; different base stations transmit independent information streams, and the carrier frequencies are different from each other; two base stations activate different users respectively; When the information-carrying symbol is sent, the information-carrying symbol is expressed as ； wherein, are respectively the first i column and the first j column of the identity matrix of order is the symbol transmitted by the transmitting end, and satisfies ; denotes taking the real part, denotes taking the imaginary part; The step of sending each information-carrying symbol to different users for activation specifically comprises: A precoding matrix of the transmitter transmitting end is calculated, and artificial noise is added to the zero space of the channel matrix and then sent to the receiving end.

2. The information distributed security transmission method of claim 1, wherein, The step of calculating the precoding matrix of the transmitter transmitting end specifically comprises: Different legitimate user received signal vectors The elements in are represented as Define matrix ； The condition for activating the ith receiver is At this time, only the user i can receive the symbol transmitted from the ith transmitter, where is a constant; right Singular value decomposition yields , where the matrix for A diagonal matrix of order n, with diagonal elements of order n. of One singular value; and These represent the left and right singular matrices, respectively. for The null space has the following equation relationship. Established; Definition Rank vector , satisfying , vector is expressed as , so as to obtain the precoding matrix of the I-way transmitter transmitting end ; is the precoding matrix of the I-way base station.

3. The information distributed security transmission method according to claim 2, wherein, The step of adding artificial noise to the zero space of the channel matrix and then sending to the receiving end specifically comprises: The transmission signal vector of the Ith transmitter is wherein is the null space of the matrix ; and denotes an arbitrary column vector.

4. The information distributed security transmission method of claim 3, wherein, The step of all activated users cooperating with each other to recover the transmission symbol through parallel-serial conversion of the received information specifically comprises: The receiving end uses a band-pass filter for band-pass filtering, and the center frequency of the band-pass filter is the same as the carrier frequency of the transmitting end; After filtering, a down-conversion signal is obtained through down-conversion; All down-conversion signals are parallel-serial converted to obtain the transmission symbol.

5. The information distributed security transmission method of claim 4, wherein, The step of obtaining the down-conversion signal through down-conversion after filtering specifically comprises: The down-conversion signal of the receiving end is expressed as: ； wherein represents the channel noise, the probability distribution of which satisfies ; representative transmitter i a matrix of concatenated channel vectors between different users; representative transmitter Q a matrix of concatenated channel vectors between different users; For Q The precoding matrix of the road.

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