Secure communication method based on intelligent reflective surface assistance of unmanned aerial vehicle

Abstract

A secure communication method assisted by an unmanned aerial vehicle (UAV) intelligent reflecting surface. The UAV intelligent reflecting surface-assisted wireless communication system consists of a base station, a UAV intelligent reflecting surface, K legitimate users, and an eavesdropper. The base station uses beamforming technology to simultaneously transmit the information data of all users in the same frequency band. The UAV intelligent reflecting surface reflects the received base station signal after a certain phase shift. The users and the eavesdropper respectively decode the received signals; calculate the information rate r of user k when receiving its data k and the eavesdropping rate r of the eavesdropper for the data of user k e,k , so as to obtain the secrecy rate R of each user in the system sec,k ; The users and the eavesdropper respectively decode the received signals. The present invention provides a secure communication method assisted by a UAV intelligent reflecting surface that can effectively resist the eavesdropping of the eavesdropper on the information sent by the base station to multiple users.

Description

Technical Field

[0001] The invention belongs to the field of physical layer security technology in the field of wireless communications, and in particular to an intelligent reflective surface relay physical layer security communication method. Background Art

[0002] With the development of science and technology, wireless communication networks are becoming more and more mature. However, due to the broadcast and open nature of wireless channels, the secure transmission of wireless communication signals has received more and more attention from the academic community. The intelligent reflective surface is composed of a large number of passive reflective units, which can intelligently configure the propagation environment of wireless signals. Each reflective unit can adjust the phase shift and amplitude of the received signal in a software-controlled manner. By jointly controlling the phase shift of all reflective elements, the transmission direction of the reflected signal is changed, thereby improving the safe transmission of the communication system. The intelligent reflective surface of drones can take advantage of the high flexibility and easy scheduling of drones, provide more degrees of freedom for the location deployment of intelligent reflective surfaces, and further improve the safe transmission performance of wireless communication systems.

[0003] The existing secure communication methods based on the assistance of UAV intelligent reflective surfaces do not consider the secure communication problems in the downlink multi-user situation. However, the information data of the downlink is usually large, and the loss caused by eavesdropping is greater. In addition, the research on system secure communication problems in the multi-user situation is more complicated. Summary of the invention

[0004] In order to overcome the shortcomings of the existing secure communication method based on the assistance of the intelligent reflective surface of the drone without considering the secure communication problem when there are multiple users in the downlink, the present invention provides a secure communication method based on the assistance of the intelligent reflective surface of the drone, which can effectively resist eavesdroppers from eavesdropping on the information sent by the base station to multiple users.

[0005] The technical solution adopted by the present invention to solve the technical problem is:

[0006] A secure communication method based on the assistance of an intelligent reflective surface of a drone. The wireless communication system assisted by the intelligent reflective surface of a drone consists of a base station, an intelligent reflective surface of a drone, K legitimate users and an eavesdropper. The secure communication method based on the assistance of an intelligent reflective surface of a drone includes the following steps:

[0007] 1) The base station uses beamforming technology to send the information data of all users at the same frequency band at the same time. The drone's intelligent reflective surface reflects the received base station signal after a certain phase shift. The user and the eavesdropper decode the received signal respectively;

[0008] 2) Calculate the information rate r of user k when receiving its data k and the eavesdropper’s eavesdropping rate r for user k’s data e,k , thereby obtaining the confidentiality rate R of each user in the systemsec，k ;

[0009] The location optimization and wireless resource allocation problem between the UAV intelligent reflective surface and K users is modeled as:

[0010]

[0011] Meet the following conditions

[0012] 0≤x u ≤X,0≤y u ≤Y (2)

[0013]

[0014] θ n ∈[0,2π],n=1,...,N (4)where w u =[x u ,y u ] T Indicates the horizontal position of the drone, x u and u Respectively represent the horizontal coordinate and vertical coordinate of the UAV’s horizontal position, W = [ω 1 ,...,ω K ] represents the set of beamforming vectors of the base station for all user data, ω k represents the beamforming vector of the base station for the kth user data, X and Y represent the maximum horizontal and vertical coordinates of the drone service area, and P represents the maximum transmission power of the base station. represents the phase shift matrix of the smart reflector, θ n represents the phase shift of the nth reflection unit in the smart reflection surface, and N represents the number of reflection units in the smart reflection surface;

[0015] Using the continuous convex optimization method and the idea of ​​alternating optimization, the above problem is transformed into two sub-problems. First, the position of the UAV's intelligent reflective surface is optimized, and then the phase shift of the intelligent reflective surface and the beamforming vector of the base station are optimized. The non-convex sub-problem is transformed into a convex optimization problem through the Taylor first-order expansion method, and then it is solved iteratively to obtain the optimal solution to the problem.

[0016] Furthermore, in step 2), the information rate r from the base station to user k is k and the eavesdropper’s eavesdropping rate r on user k’s data e,k Respectively expressed as

[0017] r k =log 2 (1+γ k ) (5)

[0018] r e,k =log2 (1+γ e,k ) (6)

[0019] where γ k and γ e，k They represent the signal-to-interference-noise ratio at user k and the eavesdropper, respectively, and are expressed as

[0020]

[0021]

[0022] in and are the noise power at user k and the eavesdropper respectively, and denote the transposition of the channel coefficients between the smart reflection surface and user k, the base station and the smart reflection surface, and the smart reflection surface and the eavesdropper respectively;

[0023] The confidentiality rate of each user k in the system is expressed as

[0024] R sec,k =max(r k -r e,k ,0) (9).

[0025] The technical concept of the present invention is: the existing secure communication method assisted by the intelligent reflective surface of unmanned aerial vehicles does not consider the secure communication problem when there are multiple users in the downlink. However, the information data of the downlink is usually large, and the loss caused by eavesdropping is greater, and the research on the secure communication problem of the system in the case of multiple users is more complicated. The patented method provides a secure communication method based on the assistance of the intelligent reflective surface of unmanned aerial vehicles that can resist eavesdroppers from eavesdropping on the information sent by the base station to multiple users. By optimizing the position and phase shift of the intelligent reflective surface of the unmanned aerial vehicle and the beamforming vector of the base station, the secure communication performance of the system can be effectively improved.

[0026] The beneficial effects of the present invention are mainly manifested in: solving the problem of secure communication when the existing secure communication method based on the assistance of the intelligent reflective surface of the drone does not consider the multi-user situation of the downlink, and improving the secure communication performance of the system by optimizing the position, phase shift and beamforming vector of the drone intelligent reflective surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of a system model of a safe communication method based on the assistance of an intelligent reflective surface of an unmanned aerial vehicle according to the present invention;

[0028] Figure 2 is a graph showing the change of the minimum confidentiality rate of the system with the number of reflective units of the intelligent reflective surface at different UAV altitudes of the present invention;

[0029] Figure 3 This is a graph showing how the minimum confidentiality rate of the system changes with the number of base station antennas under different numbers of intelligent reflective surface reflection units of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] Reference Figure 1 to Figure 3 A secure communication method based on the assistance of an intelligent reflective surface of a UAV is implemented based on an existing wireless communication system assisted by an intelligent reflective surface of a UAV. The wireless communication system assisted by an intelligent reflective surface of a UAV consists of a base station, an intelligent reflective surface of a UAV, an eavesdropper and K legitimate users.

[0032] In the method of this embodiment, the base station uses beamforming technology to send the information data of all users at the same frequency band at the same time. The intelligent reflective surface of the drone reflects the received base station signal after a certain phase shift. The user and the eavesdropper decode the received signals respectively; the information rate of each user for the corresponding user data and the eavesdropper's eavesdropping rate for different user data are calculated, so as to obtain the confidentiality rate of each user in the system.

[0033] In this embodiment, the information rate from the base station to user k is r k and the eavesdropper’s eavesdropping rate r for user k’s data e,k Respectively expressed as

[0034] r k =log 2 (1+γ k ) (5)

[0035] r e,k =log 2 (1+γ e,k ) (6)

[0036] where γ k and γ e,k They represent the signal-to-interference-noise ratio at user k and the eavesdropper, respectively, and are expressed as

[0037]

[0038]

[0039] in and are the noise power at user k and the eavesdropper respectively, and denote the transposition of the channel coefficients between the smart reflection surface and user k, the base station and the smart reflection surface, and the smart reflection surface and the eavesdropper, respectively. represents the phase shift matrix of the smart reflector, θn represents the phase shift of the nth reflection unit in the smart reflection surface;

[0040] The confidentiality rate of each user k in the system is expressed as

[0041] R sec,k =max(r k -r e,k ,0) (9)

[0042] In this embodiment, the method for optimizing the trajectory of the drone and allocating wireless resources is specifically as follows:

[0043] The location optimization and wireless resource allocation problem between the UAV and K users is modeled as:

[0044]

[0045] Meet the following conditions

[0046] 0≤x u ≤X,0≤y u ≤Y (2)

[0047]

[0048] θ n ∈[0,2π],n=1,...,N (4)

[0049] where w u =[x u ,y u ] T Indicates the horizontal position of the drone, x u and u Respectively represent the horizontal coordinate and vertical coordinate of the UAV’s horizontal position, W = [ω 1 , ...,ω K ] represents the set of beamforming vectors for the base station and all user data, ω k represents the beamforming vector of the base station for the kth user data, X and Y represent the maximum horizontal and vertical coordinates of the drone service area, P represents the maximum transmit power of the base station, and N represents the number of reflection units in the smart reflection surface;

[0050] Using the continuous convex optimization method and the idea of ​​alternating optimization, the above problem is transformed into two sub-problems. First, the position of the UAV's intelligent reflective surface is optimized, and then the phase shift of the intelligent reflective surface and the beamforming vector of the base station are optimized. The non-convex sub-problem is transformed into a convex optimization problem through the Taylor first-order expansion method, and then it is solved iteratively to obtain the optimal solution to the problem.

[0051] The secure communication method based on the assistance of the intelligent reflective surface of a drone in this embodiment solves the secure communication problem when the downlink multi-user situation is not considered in the existing secure communication method based on the assistance of the intelligent reflective surface of a drone, and improves the secure communication performance of the system by optimizing the position of the drone's intelligent reflective surface, the phase shift of the intelligent reflective surface and the beamforming vector of the base station.

[0052] In this embodiment, the transmission channels from the drone to the base station, from the drone to the user and the eavesdropper are all assumed to be line-of-sight transmission channels, and the horizontal position of the base station is [0,0] T , the height is 20m, and the horizontal position of user 1 is [10,100] T , user 2's horizontal position is [20,80] T , the eavesdropper's position is [80,0] T , both the user and the eavesdropper are located on the ground.

[0053] Figure 2 It shows that as the number of reflective units on the intelligent reflective surface increases, the minimum confidentiality rate of the system increases accordingly. At the same time, the increase in the altitude of the drone will reduce the minimum confidentiality rate of the system.

[0054] Figure 3 It shows that as the number of base station antennas increases, the system's minimum confidentiality rate increases accordingly.

[0055] The contents described in the embodiments of this specification are merely enumerations of implementation forms of the inventive concept and are for illustrative purposes only. The protection scope of the present invention should not be considered to be limited to the specific forms described in this embodiment, and the protection scope of the present invention also extends to equivalent technical means that can be thought of by ordinary technicians in this field based on the inventive concept.

Claims

1. A secure communication method based on the assistance of UAV intelligent reflective surface. The wireless communication system assisted by the UAV intelligent reflective surface consists of a base station, a UAV intelligent reflective surface, K legitimate users and an eavesdropper. It is characterized in that The secure communication method based on the assistance of the intelligent reflective surface of the unmanned aerial vehicle comprises the following steps: 1) The base station uses beamforming technology to send all user information data at the same time in the same frequency band. The drone's intelligent reflective surface reflects the received base station signal after a certain phase shift. The user and the eavesdropper decode the received signal respectively; 2) Calculate the information rate r of user k when receiving its data k and the eavesdropper’s eavesdropping rate r for user k’s data e,k , thereby obtaining the confidentiality rate R of each user in the system sec,k ; The location optimization and wireless resource allocation problem between the UAV intelligent reflective surface and K users is modeled as: Meet the following conditions 0≤x u ≤X,0≤y u ≤Y (2) i n ∈[0,2π],n=1,...,N (4) Among them, w u =[x u ,y u ] T Indicates the horizontal position of the drone, x u and u Respectively represent the horizontal coordinate and vertical coordinate of the UAV’s horizontal position, W = [ω 1 ,...,ω K ] represents the set of beamforming vectors of the base station for all user data, ω k represents the beamforming vector of the base station for the kth user data, X and Y represent the maximum horizontal and vertical coordinates of the drone service area, and P represents the maximum transmission power of the base station. represents the phase shift matrix of the smart reflector, θ n represents the phase shift of the nth reflection unit in the smart reflection surface, and N represents the number of reflection units in the smart reflection surface; Using the continuous convex optimization method and the idea of ​​alternating optimization, the above problem is transformed into two sub-problems. First, the position of the UAV's intelligent reflective surface is optimized, and then the phase shift of the intelligent reflective surface and the beamforming vector of the base station are optimized. The non-convex sub-problem is transformed into a convex optimization problem through the Taylor first-order expansion method, and then it is solved iteratively to obtain the optimal solution to the problem.

2. The secure communication method based on the assistance of the intelligent reflective surface of the unmanned aerial vehicle according to claim 1, Features: In step 2), the information rate from the base station to user k is r k and the eavesdropper’s eavesdropping rate r for user k’s data e,k Respectively expressed as r k =log 2 (1+c k ) (5) r e,k =log 2 (1+c e,k ) (6) where γ k and γ e,k They represent the signal-to-interference-noise ratio at user k and the eavesdropper respectively, and are expressed as in and are the noise power at user k and the eavesdropper respectively, and denote the transpose of the channel coefficients between the smart reflection surface and user k, and between the smart reflection surface and the eavesdropper, respectively; h b represents the channel coefficient between the base station and the smart reflective surface; The confidentiality rate of each user k in the system is expressed as R sec,k =max(r k -r e,k ,0) (9)。

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