Physical layer security communication method of unmanned aerial vehicle relay NOMA network

Abstract

The invention discloses a physical layer security communication method for an unmanned aerial vehicle relay NOMA network, and the method comprises the steps: selecting one antenna to transmit an NOMA signal by a multi-antenna ground base station at a first time slot, and selecting one antenna to transmit an artificial noise signal while receiving the signal by an unmanned aerial vehicle relay node; the near user also sends another artificial noise signal to interfere with the untrusted user and the external eavesdropping user; in the second time slot, the unmanned aerial vehicle adds the artificial noise signal in the first time slot and the decoded near user signal by exclusive OR to generate an NOMA signal, an antenna is reselected to send the NOMA signal, and the near user sends the artificial noise signal again to interfere with the eavesdropping user; each node calculates a signal-to-interference-noise ratio or a signal-to-noise ratio of each node, and calculates a corresponding interruption probability and a corresponding eavesdropping probability; according to the method, fair and safe communication between the near user and the untrusted remote user can be realized, and the problem of potential safety hazards in an unmanned aerial vehicle cooperative NOMA network communication scene actually suffered from mixed eavesdropping attacks can be solved.

Description

Technical Field

[0001] The present invention relates to a secure communication method, in particular to a physical layer secure communication method for wireless communication. Background Art

[0002] The development and progress of wireless communication technology have enabled more and more devices and terminals to connect to the communication network. The rapid increase in network users has led to a rapid growth in data transmission volume, making the already precious spectrum resources even more scarce. NOMA (Non-orthogonal multiple access) technology is another emerging spectrum sharing technology after spectrum sensing technology, which can effectively alleviate the current situation of scarce spectrum resources in wireless communication.

[0003] Drones can also be used for wireless communication. Moreover, drones can improve the flexibility of wireless communication network networking and expand the coverage of radio signals, and can be widely applied to scenarios such as emergency communication, line inspection and monitoring in various situations, and high-speed data transmission. Therefore, the combination of NOMA technology and drone communication applied to a wireless communication network can further enhance the performance of the wireless communication network.

[0004] Although the drone-assisted NOMA communication system has many advantages, the broadcast characteristic of wireless signals and the expansion of the radio signal coverage caused by drone communication make drone communication more vulnerable to eavesdropping attacks. Traditional cryptography technologies consume a large amount of network resources in aspects such as encryption, decryption, and key management.

[0005] Physical layer security technology is different from traditional cryptography technologies. It can achieve secure communication in the sense of information theory only by utilizing the physical characteristics of wireless channels or wireless signals. Artificial noise technology is a typical physical layer security technology, which can effectively weaken eavesdropping attacks in a wireless communication network. However, for a drone-assisted NOMA network with untrusted users and external eavesdropping users, if the artificial noise technology that is friendly to untrusted users is used, the security of trusted users deteriorates sharply, and if the artificial noise technology that is not friendly to untrusted users is used, the secure communication performance of untrusted users is severely damaged. Summary of the Invention

[0006] Object of the Invention: In the case of a drone-assisted NOMA network suffering from a mixed eavesdropping attack by external eavesdropping users and untrusted users, a physical layer secure communication method for a mixed eavesdropping drone relay NOMA network is proposed to fairly achieve secure communication between trusted near users and untrusted far users.

[0007] Technical solution: A physical layer secure communication method for an unmanned aerial vehicle (UAV) relay non-orthogonal multiple access (NOMA) network, which is applied to a communication scenario where a cooperative non-orthogonal multiple access (NOMA) network with a UAV as a relay node is attacked by untrusted users and external eavesdropping users. The network includes a multi-antenna ground base station, a UAV relay node equipped with multiple antennas, a trusted near user equipped with two antennas, an untrusted far user, and multiple external eavesdropping users. The external eavesdropping users and the untrusted far user adopt independent eavesdropping methods to eavesdrop on the confidential information of the trusted users.

[0008] The specific implementation steps of this secure communication method are as follows:

[0009] In the first time slot, the ground base station equipped with M antennas and the UAV relay node equipped with N antennas respectively use antenna selection technology to select one antenna each to transmit their respective signals. Specifically, the ground base station adopts NOMA technology and uses the selected antenna to transmit NOMA signals Among them, signal x1 is sent to the trusted near user, signal x2 is sent to the untrusted far user, and the coefficients α1 and α2 respectively represent the power allocation coefficients of signals x1 and x2, and α2 > α1 > 0, α1 + α2 = 1. At the same time, the UAV relay node uses the selected antenna to transmit artificial noise signal x J , and the remaining antennas receive the NOMA signal x; the trusted near user also transmits artificial noise signal x J1 to interfere with the untrusted far user and external eavesdropping users e1,..., e Q . Then, the UAV relay node, the trusted near user, the untrusted far user, and the external eavesdropping users calculate the signal-to-interference-plus-noise ratio (SINR) and signal-to-noise ratio (SNR) of the corresponding signals according to their respective received signals.

[0010] In the second time slot, the UAV relay node decodes signals x1 and x2, and XORs x1 and x J as bit strings to obtain signal Then, NOMA technology is used to obtain NOMA signal Based on the condition that the instantaneous channel state information in different time slots is independent of each other, the UAV relay node uses antenna selection technology to reselect one antenna to transmit signal x r ; the trusted user, as a friendly interference node for the untrusted user, simultaneously transmits artificial noise signal x J2 to interfere with the external eavesdropping users. Then, the trusted near user, the untrusted far user, and the external eavesdropping users calculate the signal-to-interference-plus-noise ratio (SINR) and signal-to-noise ratio (SNR) of the corresponding signals according to their respective received signals.

[0011] To make this method more practical, the untrusted far user and the external eavesdropping users have strong eavesdropping capabilities, that is, the untrusted far user and the external eavesdropping users can ignore the successive interference of the NOMA signal and directly decode r based on x Similarly, an external eavesdropping user can directly decode x2.

[0012] Finally, the legitimate near user, the untrusted far user, and the external eavesdropping user calculate the corresponding outage probability and eavesdropping probability according to the obtained signal-to-interference-plus-noise ratio (SINR) and signal-to-noise ratio (SNR).

[0013] Furthermore, in the first time slot, the UAV relay node selects an antenna k with the best channel quality from the set of N antennas Ψ to the legitimate near user to transmit the artificial noise signal x J , and the ground base station selects an antenna i from the set of M antennas Θ such that the SINR of the UAV relay node decoding signals x2 and x1 and reaches the maximum. The specific functional expression of the antenna selection rule is:

[0014]

[0015] where represents the instantaneous channel state information from the j-th antenna of the UAV relay node to the legitimate near user, and h jr represents the vector composed of the instantaneous channel state information from the j-th antenna of the ground base station to the remaining (N - 1) receiving antennas of the UAV relay node, is the precoding vector based on the null space technique from the j-th antenna of the ground base station to the (N - 1) unselected receiving antennas of the UAV relay node.

[0016] Furthermore, in the first time slot, the UAV relay node calculates the SINRs of decoding signals x2 and x1 from the received signal x as follows:

[0017]

[0018] where is the precoding vector based on the null space technique from the selected antenna i of the ground base station to the (N - 1) unselected receiving antennas of the UAV relay node, is the vector transpose symbol, and h ir represents the vector composed of the instantaneous channel state information from the selected antenna i of the ground base station to the (N - 1) unselected receiving antennas of the UAV relay node, and the length of this vector is (N - 1). P S is the transmission power of the source signal, is the noise power at any receiving antenna of the UAV relay node, and Γ rr is the residual self-interference of the UAV relay node.

[0019] The two NOMA users and the external eavesdropping user need to decode the artificial noise signal x J to obtain the source message x1. The legitimate user, the untrusted user, and the q-th external eavesdropping user e qDecoded signal x J The signal-to-interference-plus-noise ratios are respectively:

[0020]

[0021]

[0022] Wherein, and respectively represent the instantaneous channel state information from the antenna k selected by the UAV relay node to the trusted near user, the untrusted far user, and the external eavesdropping user e q ; and are the instantaneous channel state information from the trusted near user to the untrusted far user and the external eavesdropping user e q ; is the residual self-interference signal of the trusted near user in the first time slot, P r1 represents the power of the artificial noise signal transmitted by the UAV relay node in the first time slot, and are respectively the noise powers of the trusted near user and the untrusted far user, P1 is the transmission power of the trusted near user, is the noise power at the eavesdropping user e q .

[0023] Furthermore, in the first time slot, since the trusted near user simultaneously transmits the artificial noise signal x J1 , the signal received by the UAV relay node is:

[0024]

[0025] Wherein, is the vector composed of the channel state information from the trusted near user to the receiving antenna of the UAV relay node, h rr is the self-interference channel at the UAV relay node, n r represents the column vector composed of the additive white Gaussian noise of each signal receiving antenna at the UAV relay node. Wherein is used to eliminate the influence of the artificial noise signal x J1 on the UAV relay node, and satisfies and Then the signal-to-interference-plus-noise ratio and maximization is equivalent to maximizing and under the constraint conditions , and the following optimization problem is obtained:

[0026]

[0027] Solving the said optimization problem to obtain the precoding vector

[0028] In the first time slot, the received signals of the trusted near user, the untrusted far user, and the external eavesdropping user e q are respectively expressed as:

[0029]

[0030]

[0031] Among them, and respectively represent the additive white Gaussian noise at the near user, the untrusted far user, and the eavesdropping user e. According to the signals received by the NOMA users and the eavesdropping users, the signal-to-interference-plus-noise ratio for decoding x q is J and and

[0032] Furthermore, in the second time slot, one antenna is selected to transmit the signal The antenna selection rule is:

[0033]

[0034] Among them, is the instantaneous channel state information from the antenna j of the UAV relay node in the second time slot to the trusted near user.

[0035] Furthermore, in the second time slot, the trusted near user decodes the signal x2 and the corresponding signal-to-interference-plus-noise ratio and signal-to-noise ratio are respectively:

[0036]

[0037] Among them, is the instantaneous channel state information from the transmitting antenna of the UAV relay node in the second time slot to the trusted near user, and P r2 represents the signal transmission power of the UAV relay node in the second time slot, is the residual self-interference signal of the trusted near user in the second time slot.

[0038] The signal-to-interference-plus-noise ratio for the untrusted far user to decode the signal x2 is:

[0039]

[0040] According to the condition that the untrusted far user has strong eavesdropping ability, the signal-to-interference-plus-noise ratio for the untrusted far user to decode the signal is:

[0041]

[0042] Among them, is the instantaneous channel state information from the transmitting antenna of the UAV relay node in the second time slot to the untrusted far user.

[0043] External eavesdropping user e q Decode x2 and The signal-to-interference-plus-noise ratio of is:

[0044]

[0045] Where, is the channel state information from the transmitting antenna of the UAV relay node in the second time slot to the eavesdropping user e q of, is the channel state information from the near user to the eavesdropping user e q of.

[0046] In the second time slot, the received signals of the near user, far user, and eavesdropping user e q are respectively:

[0047]

[0048] Combined with the NOMA transmission mechanism, the signal-to-interference-plus-noise ratio and signal-to-noise ratio of the near user decoding the signals x2 and are and The signal-to-interference-plus-noise ratio of the far user decoding x2 is The far user with strong eavesdropping needs to decode the signal Combined with x obtained in the first time slot J to successfully eavesdrop x1. The signal-to-noise ratio of the far user decoding is External eavesdropping user E q is also a strong eavesdropper. The signal-to-interference-plus-noise ratios of its decoding x2 and are respectively and

[0049] Furthermore, the outage probability calculation process of the two NOMA users is as follows: According to the NOMA transmission mechanism and relay cooperation strategy, at the end of the data transmission in the first time slot, the conditions for the UAV relay node to successfully decode the signals x2 and x1 are and The condition for the trusted near user to successfully decode x J is In the second time slot, according to the NOMA mechanism and the properties of exclusive-or operation, the conditions for the trusted near user to successfully decode x2 and are and Based on this analysis, the outage probability of the trusted near user decoding the signal x1 is:

[0050]

[0051] Among them, γ1 is the threshold of the decoded signal x1, and γ2 is the threshold of the decoded signal x2.

[0052] The condition for the untrusted far user to successfully decode x2 is that the UAV relay node successfully decodes x2 and x1 in the first time slot and satisfies the condition Then the outage probability for the untrusted far user to decode x2 is:

[0053]

[0054] The calculation process of the probability that the source message is eavesdropped is as follows: The condition for the untrusted far user or the external eavesdropping user to successfully eavesdrop on the signal x1 is that the UAV relay node successfully decodes the source message, and at the same time the untrusted far user or the eavesdropping user obtains the signal x J and That is or Thus, the probability that the signal x1 is eavesdropped is:

[0055]

[0056] The probability that the signal x2 is eavesdropped is:

[0057]

[0058] Among them, γ e is the threshold for the confidential signal to be eavesdropped, and Ω = {e1,..., e Q} represents the set composed of all external eavesdropping users.

[0059] Beneficial effects: 1. Combining the cooperative NOMA technology with UAV communication can improve the networking flexibility, effectively increase the spectrum resource utilization rate, expand the coverage range of wireless communication signals, and provide services for more users.

[0060] 2. Combining the exclusive-or operation and the artificial noise technology, a secure communication scheme in the UAV NOMA network is constructed. While realizing the secure communication between the ground base station and the trusted near user, it can also ensure the physical layer security of the communication from the base station to the untrusted far user, that is, fairly realizing the secure communication of the trusted near user and the untrusted far user. Brief description of the drawings

[0061] Figure 1 It is the system model diagram of the method of the present invention;

[0062] Figure 2 It is the flow chart of the method of the present invention;

[0063] Figure 3This is a comparison chart of the interruption probability and eavesdropping probability of trusted near users and far users between the present invention and the comparative scheme;

[0064] Figure 4 This is a comparison chart of the security-reliability balance performance of trusted near users and untrusted far users between the present invention and the comparative scheme. Detailed implementation manners

[0065] The following further explains the present invention with reference to the accompanying drawings.

[0066] As Figure 1 In this embodiment, the UAV cooperative NOMA communication system model includes 1 ground base station equipped with 3 antennas, 1 UAV relay node equipped with 3 antennas, 1 trusted near user D1 equipped with 2 antennas, 1 single-antenna untrusted far user D2, and 3 single-antenna eavesdropping users E1, E2, and E3.

[0067] Figure 2 As shown, the specific implementation steps of the method of the present invention are as follows:

[0068] Step 1: The base station serving as the information source adopts the NOMA mechanism to generate from the signals x1 and x2, and then selects one antenna to transmit the signal x to the UAV relay node. While the UAV relay node receives the signal, it uses the selected antenna to transmit the artificial noise signal x in full-duplex mode J , and the near user also transmits another artificial noise signal x J1 to interfere with the untrusted far user and external eavesdropping users.

[0069] Step 2: The signal received by the UAV relay node is From this, the signal-to-interference-plus-noise ratio can be calculated as and The received signals of the trusted near user, untrusted far user, and external eavesdropping user e q are respectively: and From this, the signal-to-interference-plus-noise ratios of the trusted near user, untrusted far user, and eavesdropping user e q with respect to the signal x J are and

[0070] Step 3: If the UAV relay node correctly decodes the information source signals x1 and x2, it takes x1 and x J as the bit sequences, performs exclusive OR addition to obtain Then, it adopts the NOMA mechanism to generate the signal from Finally, it reselects one antenna to transmit x rSent to NOMA users; if the UAV relay node cannot correctly decode the source signals x1 and x2, go to step 5.

[0071] Step 4: The near user receives the signal Calculate the signal-to-interference-plus-noise ratio And the signal-to-noise ratio The untrusted far user receives the signal Calculate the signal-to-noise ratio If the untrusted far user wants to eavesdrop on x1, it needs to calculate the signal-to-noise ratio And combine it with the signal-to-interference-plus-noise ratio Decode x1, and the eavesdropping user E q The received signal is The signal-to-interference-plus-noise ratio can be calculated And

[0072] Step 5: The trusted near user and the untrusted far user calculate their respective outage probabilities based on the obtained signal-to-interference-plus-noise ratio and signal-to-noise ratio as follows: And The probability that the near user is eavesdropped is: The probability that the far user is eavesdropped is:

[0073]

[0074] The following gives the implementation of the outage probabilities of the trusted near user and the untrusted far user, as well as their eavesdropping probabilities, using Matlab simulation on a computer. In the simulation experiment, after normalization, the base station location is (0, -1, 0), the UAV relay node location is (0, 0, 1), the trusted near user location is (0, 2, 0), the untrusted far user location is (0, 3, 0), the external eavesdropping user E1 location is (1, 1, 0), the external eavesdropping user E2 location is (-1, 3, 0), and the external eavesdropping user E3 location is (0, 4, 0). The channel gains all follow the Nakagami distribution, the shape parameter is 2 for all, and the channel fading coefficient is 3. The signal transmission powers of each node are equal, all being P, and the noise powers of each node are equal, that is The transmission signal-to-noise ratio is The power allocation coefficients of the NOMA users are α1 = 0.1 and α2 = 0.9, and the residual self-interference λ rr = 0.02λ sr , λ 11 = 0.02λ r1 , γ I = 1. The threshold values are γ1 = 7 and γ2 = 3. For the external eavesdropping users and the untrusted far user with eavesdropping ability, the threshold value for stealing information is γ e=2, and the number of external eavesdroppers is 3. The security of NOMA users is characterized by the security-reliability tradeoff (SRT).

[0075] Figure 3 The figure is a comparison of the interruption probability and eavesdropping probability curves of the traditional artificial noise scheme based on friendly jamming (Traditional artificial noise-aided friendly jammer, TAN-FJ) and the non-traditional artificial noise scheme based on non-friendly jamming (Traditional artificial noise aided-non-friendly jammer, TAN-NFJ) applied to the drone cooperative NOMA network subjected to hybrid eavesdropping attacks. Figure 3 It can be seen that the interruption probability of the near user of the present invention is basically the same as that of the TAN-FJ scheme and the TAN-NFJ scheme, and the interruption probability of the far user of the present invention is basically the same as that of the TAN-FJ scheme, but the interruption performance is much better than that of the TAN-NFJ scheme. Figure 3 It can also be seen that the eavesdropping probability of the near user of the present invention is significantly smaller than that of the TAN-FJ scheme, and is much smaller than that of the TAN-NFJ scheme. The eavesdropping probability of the far user of the present invention is significantly smaller than that of the TAN-FJ and TAN-NFJ schemes at a low transmission signal-to-noise ratio. At a high signal-to-noise ratio, the eavesdropping probability of the present invention is slightly smaller than that of the TAN-FJ and TAN-NFJ schemes.

[0076] Figure 4 This is a comparison chart of the SRT performance curves of the present invention, the TAN-FJ solution and the TAN-NFJ solution. Figure 4 It can be seen that the SRT performance of the near user of the present invention is obviously better than that of the TAN-NFJ scheme, and is much better than that of the TAN-FJ scheme; the SRT performance of the far user of the present invention is slightly better than that of the TAN-FJ scheme, and is much better than that of the TAN-NFJ scheme. In summary, the TAN-FJ and TAN-NFJ schemes can only ensure that the SRT performance of one of the near user and the far user is better, while the SRT of the other user deteriorates sharply, but the present invention can simultaneously achieve the simultaneous improvement of the SRT performance of the near user and the untrusted far user, and the SRT performance of any user of the present invention is better than the SRT performance of the corresponding user of the TAN-FJ scheme and the TAN-NFJ scheme.

[0077] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A physical layer secure communication method for drone relay NOMA network, characterized in that: The invention comprises a ground base station with multiple antennas, a drone relay node with multiple antennas, a trusted near user with two antennas, an untrusted far user and multiple external eavesdropping users, and the method comprises: In the first time slot, the ground base station equipped with M antennas and the drone relay node equipped with N antennas use antenna selection technology to select one antenna to send their respective signals. Specifically, the ground base station uses NOMA technology to send NOMA signals with the selected antenna. The signal x1 is sent to the trusted near user, and the signal x2 is sent to the untrusted far user. The coefficients α1 and α2 represent the power allocation coefficients of the signals x1 and x2 respectively. At the same time, the drone relay node sends the artificial noise signal x1 using the selected antenna. J , the remaining antennas receive the NOMA signal x; the credible nearby user also sends an artificial noise signal x J1 Interfere with untrusted remote users and external eavesdropping users e1,...,e Q ; Then, the drone relay node, the trusted near user, the untrusted far user and the external eavesdropping user calculate the signal-to-interference-noise ratio and signal-to-noise ratio of the corresponding signal based on their respective received signals; In the second time slot, the drone relay node decodes the signals x1 and x2 and converts x1 and x2 into J As a bit string XOR addition, and then use NOMA technology to obtain NOMA signal The drone relay node uses antenna selection technology to reselect an antenna to send the signal x r , the trusted user simultaneously transmits an artificial noise signal x J2 Interfere with external eavesdropping users; then, the trusted near user, the untrusted far user and the external eavesdropping user calculate the signal-to-interference-noise ratio and signal-to-noise ratio of the corresponding signal based on their respective received signals; Finally, the trusted near user, untrusted far user and external eavesdropping user calculate the corresponding interruption probability and eavesdropping probability according to the obtained signal-to-interference-noise ratio and signal-to-noise ratio.

2. The physical layer secure communication method of the drone relay NOMA network according to claim 1 is characterized in that: In the first time slot, the drone relay node selects one antenna from the N antenna set Ψ to send an artificial noise signal x to the antenna k with the best channel quality for the trusted near user. J , the ground base station selects an antenna i from the M antenna set Θ so that the signal to noise ratio of the decoded signals x2 and x1 of the drone relay node is and To achieve the maximum, the specific function expression of the antenna selection rule is: in, represents the instantaneous channel state information from the antenna j of the drone relay node to the trusted nearby user, h jr represents the vector of instantaneous channel state information from antenna j of the ground base station to the remaining (N-1) receiving antennas of the drone relay node, It is the precoding vector based on null space technology from the antenna j of the ground base station to the unselected (N-1) receiving antennas of the UAV relay node.

3. The physical layer secure communication method of the drone relay NOMA network according to claim 1 is characterized in that: In the first time slot, the drone relay node obtains the signal-to-interference-noise ratios of the decoded signals x2 and x1 based on the received signal x: in, is the precoding vector based on the null space technology from the antenna i selected by the ground base station to the (N-1) unselected receiving antennas of the UAV relay node, is the vector transpose symbol, h ir represents the vector of instantaneous channel state information from the antenna i selected by the ground base station to the (N-1) unselected receiving antennas of the UAV relay node, P S is the source signal transmission power, is the noise power at any receiving antenna of the drone relay node, Γ rr is the residual self-interference of the drone relay node; Trusted users, untrusted users, and the qth external eavesdropping user e q Decoded signal x J The signal-to-interference-noise ratios are: in, and They represent the transmission from the drone relay node selected antenna k to the trusted near user, untrusted far user, and external eavesdropping user e. q The instantaneous channel state information, and From trusted near users to untrusted far users and external eavesdropping users q The instantaneous channel state information, is the residual self-interference signal of the credible user in the first time slot, P r1 represents the power of the artificial noise signal sent by the drone relay node in the first time slot, and are the noise power of the credible near user and the untrusted far user respectively, P1 is the transmit power of the credible near user, For eavesdropping user e q The noise power at .

4. The physical layer secure communication method of the drone relay NOMA network according to claim 3 is characterized in that: In the first time slot, since the reliable nearby users simultaneously send artificial noise signals x J1 , then the signal received by the drone relay node is: in, is the vector of channel state information from the trusted near user to the receiving antenna of the drone relay node, h rr is the self-interference channel at the UAV relay node, n r represents the column vector composed of additive Gaussian white noise of each signal receiving antenna at the drone relay node; Used to eliminate artificial noise signal x J1 Impact on drone relay nodes, and meet as well as Signal to Interference and Noise Ratio and The maximization of is equivalent to the constraint and Next pair The maximization of , we get the following optimization problem: Solve the optimization problem to obtain the precoding vector 5. The physical layer secure communication method of the drone relay NOMA network according to any one of claims 1 to 4, characterized in that: In the second time slot, an antenna is selected to send a signal The antenna selection rules are: Among them, g jd1 It is the instantaneous channel state information from the antenna j of the drone relay node to the trusted nearby user in the second time slot.

6. The physical layer secure communication method of the drone relay NOMA network according to claim 4 is characterized in that: In the second time slot, the credible user decoded signal x2 and The corresponding signal-to-interference-noise ratio and signal-to-noise ratio are: in, is the instantaneous channel state information from the transmitting antenna of the drone relay node to the trusted nearby user in the second time slot, P r2 Indicates the signal transmission power of the second time slot of the drone relay node, is the residual self-interference signal of the second time slot of the reliable user; Untrusted remote user decoded signal x2 and The signal-to-interference-noise ratios are: in, The instantaneous channel state information from the transmitting antenna of the drone relay node to the untrusted remote user in the second time slot; External eavesdropping user q Decoding x2 and The signal-to-interference-noise ratio is: in, The transmitting antenna of the drone relay node in the second time slot is transmitted to the eavesdropping user e q The channel state information, From the nearest user to the eavesdropping user q channel state information.

7. The physical layer secure communication method of the drone relay NOMA network according to claim 6 is characterized in that: The interruption probability calculation process of two NOMA users is as follows: In the first time slot, the condition for the drone relay node to successfully decode signals x2 and x1 is as well as Trusted user successfully decodes x J The condition is In the second time slot, the reliable user successfully decodes x2 and The condition is and Then the probability of interruption of the credible user decoding signal x1 is: Among them, γ1 is the threshold of the decoded signal x1, and γ2 is the threshold of the decoded signal x2; The condition for the untrusted remote user to successfully decode x2 is that the drone relay node successfully decodes x2 and x1 in the first time slot and satisfies the condition Then the probability of interruption of decoding x2 by the untrusted remote user is: The probability calculation process of the source message being eavesdropped is as follows: The condition for an untrusted remote user or an external eavesdropping user to successfully eavesdrop on the signal x1 is: the drone relay node successfully decodes the source message, and the untrusted remote user or the eavesdropping user obtains the signal x J and Right now or Therefore, the probability that signal x1 is eavesdropped is: The probability that signal x2 is eavesdropped is: Among them, γ e is the threshold of the confidential signal being eavesdropped, Ω={e1,...,e Q } represents the set of all external eavesdropping users.

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