RIS and artificial noise assisted SWIPT system physical layer security communication method

Abstract

The invention discloses an RIS and artificial noise assisted SWIPT system physical layer secure communication method. The secure communication method comprises the steps that a base station sends training signals to all receiving ends; the receiving end estimates legal channel state information of the SWIPT system according to the training signal; calculating channel state information of an illegal channel by using a quasi-static stationary characteristic; the system obtains an information security transmission scheme; the base station performs beam forming on the information signal and the energy signal; and the base station sends the information to the legal user. According to the method, on the premise of meeting the requirements of maximum transmitting power limitation and minimum energy collection, eavesdroppers in the SWIPT system are effectively inhibited, and the secure communication rate of the SWIPT system is maximized.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a physical layer security communication method suitable for a Simultaneous Wireless Information and Power Transfer (SWIPT) system. Background Art

[0002] Physical layer security communication uses the randomness of wireless channels to achieve confidential communication. Compared with traditional encryption methods, it has higher security. Reconfigurable Intelligent Surface (RIS) is a passive reflective surface array composed of a large number of passive components. It can adjust the phase, amplitude and frequency of radio waves to optimize the performance of the network. Applying RIS to physical layer security is expected to further improve the security of wireless networks.

[0003] At present, some scholars have conducted some research on artificial noise-assisted RIS communication systems. The patent "Anti-eavesdropping secure communication method and device based on reconfigurable intelligent reflective surface" applied by Li Qiang et al. proposed an anti-eavesdropping secure communication method, but it did not consider the operation of the receiving end under energy-constrained conditions. In the paper "Secrecy Wireless Information and Power Transfer With MISO Beamforming" published in "IEEE TRANSACTIONS ON SIGNAL PROCESSING", Liang Liu et al. proposed adding multiple artificial noises to perform confidential and secure communication of the SWIPT system in the presence of multiple eavesdropping ends. The disadvantage is that when there is a lack of reflection link between the transmitter and the receiver, and when there are obstacles in the line-of-sight link, the communication effect is not ideal and the security rate is low. Summary of the invention

[0004] The purpose of the present invention is to solve the above-mentioned defects in the prior art and provide a physical layer secure communication method for a SWIPT system assisted by RIS and artificial noise. Considering the scenario where the receiving end has limited energy, the base station's legal signal precoding matrix, the artificial noise covariance matrix, and the passive beamforming matrix of the reconfigurable intelligent reflector are jointly optimized with the goal of maximizing the secure transmission of the system. In this way, while providing wireless charging function for terminal nodes, the information transmission rate of legal terminals is improved and the eavesdropping capability of eavesdropping terminals is reduced, thereby achieving the purpose of secure communication.

[0005] The purpose of the present invention can be achieved by adopting the following technical solutions: The purpose of the present invention can be achieved by adopting the following technical solutions: A physical layer secure communication method for a SWIPT system assisted by RIS and artificial noise. The SWIPT system includes a base station equipped with M transmitting antennas, an intelligent reflecting surface with N reflecting units, a legal user equipped with a single antenna, and K eavesdropping terminals equipped with single antennas, wherein the base station is composed of M transmitting antennas arranged in a uniform linear array, the intelligent reflecting surface is hereinafter represented by RIS, the RIS is composed of N reflecting units arranged in a uniform rectangular array, and the legal user is hereinafter represented by IR. The implementation steps of the physical layer secure communication method are as follows: S1. Before transmission starts, the base station sends a training signal to all receiving ends including IR and RIS; S2. The receiving end estimates the legal downlink channel of the SWIPT system based on the received training symbols and obtains the channel information between the base station and the RIS. , base station and IR channel information , channel information between RIS and IR ,in represents the channel information between the i-th antenna of the base station and the RIS, i = 1, 2, …, M, represents the channel information between the i-th antenna of the base station and the IR, represents the channel information between the jth reflection unit of RIS and IR, j = 1, 2, ..., N, represents a complex domain; S3, using the quasi-static steady fading characteristics of the channel between the base station and the eavesdropping end, calculate the distance between the base station and the first eavesdropping end according to the statistical information of the channel. The channel state information between the eavesdropping terminals , among which, The following eavesdropping terminals are used express, Indicates the base station Antenna with The channel information between Channel state information with RIS ,in Indicates the first Reflection unit and Channel information between them; S4. Define base station information beamforming vector , Base station No. The information weight coefficient of the root antenna; defines the base station energy beamforming vector ,in Indicates that the base station has allocated energy beamforming vectors, Indicates the base station energy beamforming vectors, Indicates the base station The energy beamforming vector is Energy weight coefficient of the root antenna; defines the reflection coefficient vector of RIS ,in Indicates the first The reflection coefficient of each unit, It is The phase shift coefficient of each unit; S5, SWIPT system obtains the optimal base station information beamforming vector , the optimal RIS reflection vector , the optimal base station energy beamforming vector ; S6. Base station generates signal and , represents the information signal of the base station, which obeys a Gaussian distribution with a mean of 0 and a variance of 1; Indicates the base station The energy signal can be any independent random signal with unit average power. Since the information is secretly transmitted to IR in this method, the energy signal also plays the role of artificial noise. It also obeys a Gaussian distribution with a mean of 0 and a variance of 1; using Adjust the RIS array elements to the optimal phase angle when transmitting energy and information; use the information beamforming vector ,right Perform beamforming using energy beamforming vector ,right Perform beamforming; the base station and Generate send signal And send it out.

[0006] Furthermore, we first define the optimization problem of maximizing the system’s secure transmission rate, and use the AO,SDR method to decompose the non-convex optimization problem into several sub-problems; Furthermore, the convex optimization toolkit CVX is used to iteratively solve the defined optimization problem; Finally, the optimal base station information beamforming vector is obtained , the optimal RIS reflection vector , the optimal base station energy beamforming vector ; The process of step S5 is as follows: S5.1. Define the optimization problem of maximizing the system security transmission rate as follows: The secure transmission rate of the SWIPT system is expressed as ,symbol express ; represents the information receiving rate of IR, where represents the received signal-to-noise ratio at IR, represents the noise power at IR, , , , It represents the total channel gain of the downlink base station sending the signal to the IR; represents the information rate at the eavesdropping end with the best channel status, where express The signal-to-noise ratio, , Indicates base station and The total channel gain between express The noise power; Indicates the maximum transmit power of the base station; Indicates the maximum eavesdropping rate of the eavesdropping end within the tolerance limit; express Energy conversion efficiency coefficient at ; express Minimum energy harvesting requirements; constraints The information beamforming vector and energy beamforming vector of the base station are subject to the maximum transmit power of the base station. The constraint condition is express Energy harvesting requirements, constraints Represents each reflection factor The phase shift is continuous and the modulus is always 1. The constraint condition express Information rate constraints; S5.2, using convex optimization to solve the above optimization problem of maximizing the system security transmission rate, we get The optimal solution of the iteration ; S5.3. According to , calculate the SWIPT system in Second and The safety capacity of the iterations is , ; S5.4. Judgment Is it established? If If the condition holds, the iteration stops and the optimal solution to the optimization problem of maximizing the system's secure transmission rate is output. Otherwise, , , , , return to step S5.2.

[0007] Furthermore, the alternating optimization method is used to fix the irrelevant variables of each round of optimization problem. After the optimization is completed, the optimization variables are updated and the next round of alternating optimization is entered until the conditions for stopping the optimization iteration are met, thereby solving the optimization problem and obtaining the optimal base station information beamforming vector. , the optimal RIS reflection vector , the optimal base station energy beamforming vector , the process of step S5.2 is as follows: S5.2.1. Initialization number of iterations , Convergence Tolerance , information beamforming vector , energy beamforming vector , RIS reflection coefficient vector ;get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective element Iteration value; get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; set iteration variable ; S5.2.2. Utilize feasible points , and , using the convex optimization toolkit CVX to solve the optimization problem of maximizing the system's secure transmission rate, we obtain The optimal solution of the iteration ; S5.2.3. Utilization , and , using the convex optimization toolkit CVX to solve the optimization problem of maximizing the system's secure transmission rate, we obtain The optimal solution of the iteration; S5.2.4. Utilization , and , using the convex optimization toolkit CVX to solve the optimization problem of maximizing the system's secure transmission rate, we obtain The optimal solution of the iteration .

[0008] Further, the conditions for stopping the alternating optimization iteration are determined. If the iteration converges, the loop is stopped. If the iteration does not converge, a new round of alternating optimization is entered. Not established, order , , , , return to step S5.2.2.

[0009] Compared with the prior art, the present invention has the following advantages and effects: 1. The present invention uses RIS technology to improve the security of the communication network at the physical layer security level, and on this basis constructs a non-convex optimization problem; the mutually coupled non-convex multivariable optimization problem is split into multiple convex sub-problems containing a single optimization variable through an alternating optimization method, which has low complexity and can quickly and accurately obtain the optimal base station information beamforming vector , the optimal RIS reflection vector , the optimal base station energy beamforming vector , to achieve anti-eavesdropping communication.

[0010] 2. The method proposed in the present invention introduces artificial noise, which can greatly improve the system's secure communication rate under the same transmission power. It can reduce the eavesdropping interference of the wireless communication system while meeting the user's received signal quality without increasing additional energy.

[0011] 3. The present invention proposes a RIS-assisted SWIPT physical layer secure communication method under the condition of considering the energy harvesting model, so as to ensure that the SWIPT system can achieve high-speed secure communication when the energy node is operating. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of the RIS-assisted SWIPT communication system model in the present invention; Figure 2 It is a flow chart for implementing the RIS-assisted SWIPT system physical layer secure communication method disclosed in the present invention; Figure 3 It is a flowchart of the implementation of obtaining the system security transmission rate of the present invention; Figure 4 It is a system model comparison diagram of the RIS-assisted SWIPT fixed base station disclosed in the present invention when the transmission power is 15dBm, with and without artificial noise, and with and without RIS; Figure 5 It is a comparison diagram of the change of the system security transmission rate with the transmission power of the RIS-assisted SWIPT disclosed in the present invention when artificial noise is added and when no artificial noise is added, and when RIS is equipped and when RIS is not equipped; Figure 6 It is a comparison chart of system security transmission rate with and without artificial noise, and with and without RIS when the fixed base station transmission power of the present invention is 15 dBm, as the minimum energy collection requirement changes. DETAILED DESCRIPTION

[0013] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0014] Example 1 This embodiment discloses a physical layer secure communication method of a SWIPT system assisted by a RIS. The SWIPT system includes a base station equipped with four transmitting antennas, a RIS with 64 reflecting units, an IR and three eavesdropping terminals, wherein the four transmitting antennas of the base station are arranged in a uniform linear array, and the 64 reflecting units of the RIS are arranged in a uniform rectangular array.

[0015] In this embodiment, the specific parameters are set as follows The SWIPT system is set up in a two-dimensional coordinate system, with the base station located at (0m, 0m), the RIS at (5m, 5m), the IR at (30m, 0m), and the three eavesdropping terminals at (30m, -5m), (35m, 0m), and (35m, -5m) respectively; the base station is equipped with The maximum transmission power of the base station is set to ; The energy harvesting requirement is set to RIS equipment Reflectors, convergence tolerance , Noise Power In this embodiment, all channels are Rice channels, and the channel model is ,in represents the Rice factor, ; Indicates the line-of-sight wireless transmission part, Indicates the non-line-of-sight wireless transmission part; is the path loss function, and its calculation formula is ,in is the path loss function parameter, is the Euclidean distance of the link, and the path loss function parameters related to RIS 2.2, base station to IR and base station to energy harvesting node The path loss parameter is 3.

[0016] The steps for implementing the physical layer secure communication method are as follows: S1. Before transmission starts, the base station sends a training signal to all receiving ends including IR and RIS; S2. The receiving end estimates the legal downlink channel of the SWIPT system based on the received training symbols and obtains the channel information between the base station and the RIS. , base station and IR channel information , channel information between RIS and IR ,in Indicates the base station Channel information between the root antenna and RIS, Indicates the base station Channel information between the root antenna and IR, Indicates the first Channel information between the reflection unit and IR, represents a complex domain; S3, using the quasi-static steady fading characteristics of the channel between the base station and the eavesdropping end, the base station and the eavesdropping end are calculated based on the statistical information of the channel. Channel state information between ,in Indicates the base station Antenna with The channel information between Channel state information with RIS ,in Indicates the first Reflection unit and Channel information between them; S4. Define base station information beamforming vector , Base station No. The information weight coefficient of the root antenna; defines the base station energy beamforming vector ,in Indicates that the base station has allocated energy beamforming vectors, Indicates the base station energy beamforming vectors, Indicates the base station The energy beamforming vector is Energy weight coefficient of the root antenna; defines the reflection coefficient vector of RIS ,in Indicates the first The reflection coefficient of each unit, It is The phase shift coefficient of each unit; S5. The system obtains the optimal base station information beamforming vector , the optimal RIS reflection vector , the optimal base station energy beamforming vector , step S5 comprises: S5.1. Define the problem of maximizing the system's secure transmission rate as follows: The secure transmission rate of the SWIPT system is expressed as ,symbol express ; represents the information receiving rate of IR, where represents the received signal-to-noise ratio at IR, represents the noise power at IR, , , , It represents the total channel gain of the downlink base station sending the signal to the IR; represents the information rate at the eavesdropping end with the best channel status, where express The signal-to-noise ratio at , Indicates base station and The total channel gain between express The noise power; Indicates the maximum transmit power of the base station; Indicates the maximum eavesdropping rate of the eavesdropping end within the tolerance limit; express Energy conversion efficiency coefficient at ; express Minimum energy harvesting requirements; constraints The information beamforming vector and energy beamforming vector of the base station are subject to the maximum transmit power of the base station. The constraint condition is express Energy harvesting requirements, constraints Represents each reflection factor The phase shift is continuous and the modulus is always 1. The constraint condition express Information rate constraints; S5.2, using convex optimization to solve the above optimization problem of maximizing the system security transmission rate, we get The optimal solution of the iteration , the process is as follows: S5.2.1. Initialization number of iterations , Convergence Tolerance , information beamforming vector , energy beamforming vector , RIS reflection coefficient vector ;get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; set iteration variable ; S5.2.2. Utilize the feasible points , and , using the convex optimization toolkit CVX to solve the problem of maximizing the system's secure transmission rate, we get The optimal solution of the iteration ; S5.2.3. Utilization , and , using the convex optimization toolkit CVX to solve the problem of maximizing the system's secure transmission rate, we get The optimal solution of the iteration ; S5.2.4. Utilization , and , using the convex optimization toolkit CVX to solve the problem of maximizing the system's secure transmission rate, we get The optimal solution of the iteration ; S5.3. According to the objective function described in S5.1, the computing system is Second and The safety capacity of the iterations is , ; S5.4. Judgment Is it established? If If the condition holds, the iteration is stopped and the optimal solution of the optimization problem is output. Otherwise, , , , , return to S5.2.2; S6. Base station generates signal and , represents the information signal of the base station, which obeys a Gaussian distribution with a mean of 0 and a variance of 1; Indicates the base station The energy signal can be any independent random signal with unit average power. Since the information is secretly transmitted to IR in this method, the energy signal also plays the role of artificial noise. It also obeys a Gaussian distribution with a mean of 0 and a variance of 1; using Adjust the RIS array elements to the optimal phase angle when transmitting energy and information; use the information beamforming vector ,right Perform beamforming using energy beamforming vector ,right Perform beamforming; the base station and Generate send signal And send it out.

[0017] Figure 4 This is a comparison diagram of the system model when artificial noise is added and not added, and when RIS is equipped and not equipped when the RIS-assisted SWIPT fixed base station disclosed in the present invention has a transmission power of 15dBm. It can be seen from the figure that with the increase in the number of iterations, the system security transmission rate gradually converges. Under the same transmission power, adding RIS and artificial noise has a significant effect on improving the system security transmission rate.

[0018] Figure 5 The figure is a comparison diagram of the system model of the present invention under different base station transmission powers, with and without artificial noise, equipped with RIS and without RIS. It can be seen from the figure that as the transmission power gradually increases, the safe transmission rate of the method proposed by the present invention steadily increases, while the safe transmission rate in other cases tends to be flat in advance, which shows that when the maximum transmission power of the base station is greater than When the transmission power is increased, this method will be more conducive to improving the communication quality.

[0019] Example 2 This embodiment discloses a physical layer secure communication method of a SWIPT system assisted by a RIS. The SWIPT system includes a base station equipped with four transmitting antennas, a RIS with 64 reflecting units, an IR and three eavesdropping terminals, wherein the four transmitting antennas of the base station are arranged in a uniform linear array, and the 64 reflecting units of the RIS are arranged in a uniform rectangular array.

[0020] In this embodiment, the specific parameters are set as follows The SWIPT system is set up in a two-dimensional coordinate system, with the base station located at (0m, 0m), the RIS at (5m, 5m), the IR at (30m, 0m), and the three eavesdropping terminals at (30m, -5m), (35m, 0m), and (35m, -5m) respectively; the base station is equipped with Antenna, maximum transmit power of base station ; The energy harvesting requirements are set to RIS is equipped with Reflectors, convergence tolerance , Noise Power In this embodiment, all channels are Rice channels, and the channel model is ,in represents the Rice factor, ; Indicates the line-of-sight wireless transmission part, Indicates the non-line-of-sight wireless transmission part; is the path loss function, and its calculation formula is ,in is the path loss function parameter, is the Euclidean distance of the link, and the path loss function parameters related to RIS is 2.2, base station to IR and base station to The path loss parameter is 3.

[0021] The steps for implementing the physical layer secure communication method are as follows: S1. Before transmission starts, the base station sends a training signal to all receiving ends including IR and RIS; S2. The receiving end estimates the legal downlink channel of the SWIPT system based on the received training symbols and obtains the channel information between the base station and the RIS. , base station and IR channel information , channel information between RIS and IR ,in Indicates the base station Channel information between the root antenna and RIS, Indicates the base station Channel information between the root antenna and IR, Indicates the first Channel information between the reflection unit and IR, represents a complex domain; S3, using the quasi-static steady fading characteristics of the channel between the base station and the eavesdropping end, the base station and the eavesdropping end are calculated based on the statistical information of the channel. Channel state information between ,in Indicates the base station Antenna with The channel information between Channel state information with RIS ,in Indicates the first Reflection unit and Channel information between them; S4. Define base station information beamforming vector , Base station No. The information weight coefficient of the root antenna; defines the base station energy beamforming vector ,in Indicates that the base station has allocated energy beamforming vectors, Indicates the base station energy beamforming vectors, Indicates the base station The energy beamforming vector is Energy weight coefficient of the root antenna; defines the reflection coefficient vector of RIS ,in Indicates the first The reflection coefficient of each unit, It is The phase shift coefficient of each unit; S5. The system obtains the optimal base station information beamforming vector , the optimal RIS reflection vector , the optimal base station energy beamforming vector , step S5 comprises: S5.1. Define the problem of maximizing the system's secure transmission rate as follows: The secure transmission rate of the SWIPT system is expressed as ,symbol express ; represents the information receiving rate of IR, where represents the received signal-to-noise ratio at IR, represents the noise power at IR, , , , It represents the total channel gain of the downlink base station sending the signal to the IR; represents the information rate at the eavesdropping end with the best channel state, where express The signal-to-noise ratio at , Indicates base station and The total channel gain between express The noise power; Indicates the maximum transmit power of the base station; Indicates the maximum eavesdropping rate of the eavesdropping end within the tolerance limit; express Energy conversion efficiency coefficient at ; express Minimum energy harvesting requirements; constraints The information beamforming vector and energy beamforming vector of the base station are subject to the maximum transmit power of the base station. The constraint condition is express Energy harvesting requirements, constraints Represents each reflection factor The phase shift is continuous and the modulus is always 1. The constraint condition express Information rate constraints; S5.2, using convex optimization to solve the above optimization problem of maximizing the system security transmission rate, we get The optimal solution of the iteration , the process is as follows: S5.2.1. Initialization number of iterations , Convergence Tolerance , information beamforming vector , energy beamforming vector , RIS reflection coefficient vector ;get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; set iteration variable ; S5.2.2. Utilize the feasible points , and , using the convex optimization toolkit CVX to solve the problem of maximizing the system's secure transmission rate, we get The optimal solution of the iteration ; S5.2.3. Utilization , and , using the convex optimization toolkit CVX to solve the problem of maximizing the system's secure transmission rate, we get The optimal solution of the iteration ; S5.2.4. Utilization , and , using the convex optimization toolkit CVX to solve the problem of maximizing the system's secure transmission rate, we get The optimal solution of the iteration ; S5.3. According to the objective function described in S5.1, the computing system is Second and The safety capacity of the iterations is , ; S5.4. Judgment Is it established? If If the condition holds, the iteration is stopped and the optimal solution of the optimization problem is output. Otherwise, , , , , return to S5.2.2; S6. Base station generates signal and , represents the information signal of the base station, which obeys a Gaussian distribution with a mean of 0 and a variance of 1; Indicates the base station The energy signal can be any independent random signal with unit average power. Since the information is secretly transmitted to IR in this method, the energy signal also plays the role of artificial noise. It also obeys a Gaussian distribution with a mean of 0 and a variance of 1; using Adjust the RIS array elements to the optimal phase angle when transmitting energy and information; use the information beamforming vector ,right Perform beamforming using energy beamforming vector ,right Perform beamforming; the base station and Generate send signal And send it out.

[0022] Figure 6 The fixed base station transmission rate of the present invention is The figure shows a comparison of the system security transmission rate under different energy collection requirements when the maximum transmission power of the base station is fixed. As the energy collection requirements increase, the system security transmission rate decreases in each case. However, when artificial noise is added and RIS is equipped, the system security transmission rate is much less affected by the energy collection requirements than in other cases. This shows that this method is more suitable for applications where energy collection is more stringent and high-quality secure communication is required.

[0023] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A physical layer secure communication method for a SWIPT system assisted by RIS and artificial noise, characterized in that: The SWIPT system includes a base station equipped with M transmitting antennas, an intelligent reflecting surface with N reflecting units, a legal user equipped with a single antenna, and K eavesdropping terminals equipped with single antennas, wherein the base station is composed of M transmitting antennas arranged in a uniform linear array, the intelligent reflecting surface is hereinafter represented by RIS, the RIS is composed of N reflecting units arranged in a uniform rectangular array, and the legal user is hereinafter represented by IR. The implementation steps of the physical layer secure communication method are as follows: S1. Before transmission starts, the base station sends a training signal to all receiving ends including IR and RIS; S2. The receiving end estimates the legal downlink channel of the SWIPT system based on the received training symbols and obtains the channel information between the base station and the RIS. , base station and IR channel information , channel information between RIS and IR ,in represents the channel information between the i-th antenna of the base station and the RIS, i = 1, 2, …, M, represents the channel information between the i-th antenna of the base station and the IR, represents the channel information between the jth reflection unit of RIS and IR, j = 1, 2, ..., N, represents a complex domain; S3, using the quasi-static steady fading characteristics of the channel between the base station and the eavesdropping end, calculate the distance between the base station and the first eavesdropping end according to the statistical information of the channel. The channel state information between the eavesdropping terminals , among which, The following eavesdropping terminals are used express, Indicates the base station Antenna with The channel information between Channel state information with RIS ,in Indicates the first Reflection unit and Channel information between them; S4. Define base station information beamforming vector , Base station No. The information weight coefficient of the root antenna; defines the base station energy beamforming vector ,in Indicates that the base station has allocated energy beamforming vectors, Indicates the base station energy beamforming vectors, Indicates the base station The energy beamforming vector is Energy weight coefficient of the root antenna; defines the reflection coefficient vector of RIS ,in Indicates the first The reflection coefficient of each unit, It is The phase shift coefficient of each unit; S5, SWIPT system obtains the optimal base station information beamforming vector , the optimal RIS reflection vector , the optimal base station energy beamforming vector ; S6. Base station generates signal and , represents the information signal of the base station, which obeys a Gaussian distribution with a mean of 0 and a variance of 1; Indicates the base station The energy signal can be any independent random signal with unit average power. Since the information is secretly transmitted to IR in this method, the energy signal also plays the role of artificial noise. It also obeys a Gaussian distribution with a mean of 0 and a variance of 1; using Adjust the RIS array elements to the optimal phase angle when transmitting energy and information; use the information beamforming vector ,right Perform beamforming using energy beamforming vector ,right Perform beamforming; the base station and Generate send signal And send it out.

2. According to claim 1, a RIS and artificial noise assisted SWIPT system physical layer secure communication method is characterized in that: The process of step S5 is as follows: S5.

1. Define the optimization problem of maximizing the system security transmission rate as follows: The secure transmission rate of the SWIPT system is expressed as ,symbol express ; represents the information receiving rate of IR, where represents the received signal-to-noise ratio at IR, represents the noise power at IR, , , , It represents the total channel gain of the downlink base station sending the signal to the IR; represents the information rate at the eavesdropping end with the best channel status, where express The signal-to-noise ratio, , Indicates base station and The total channel gain between express The noise power; Indicates the maximum transmit power of the base station; Indicates the maximum eavesdropping rate of the eavesdropping end within the tolerance limit; express Energy conversion efficiency coefficient at ; express Minimum energy harvesting requirements; Constraints The information beamforming vector and energy beamforming vector of the base station are subject to the maximum transmit power of the base station. The constraint condition is express Energy harvesting requirements, constraints Represents each reflection factor The phase shift is continuous and the modulus is always 1. The constraint condition express Information rate constraints; S5.2, using convex optimization to solve the above optimization problem of maximizing the system security transmission rate, we get The optimal solution of the iteration ; S5.

3. According to , calculate the SWIPT system in Second and The safety capacity of the iterations is , ； S5.

4. Judgment Is it established? If If the condition holds, the iteration stops and the optimal solution to the optimization problem of maximizing the system's secure transmission rate is output. ; Otherwise, , , , , return to step S5.

2.

3. The physical layer secure communication method of a SWIPT system assisted by RIS and artificial noise according to claim 2, characterized in that: The process of step S5.2 is as follows: S5.2.

1. Initialization number of iterations , Convergence Tolerance , information beamforming vector , energy beamforming vector , RIS reflection coefficient vector ;get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; get Initial value at ,in Indicates the base station Information beam of the root antenna Iteration value, ,in Indicates the base station Energy beam Iteration value, ,in Indicates RIS Reflective elements Iteration value; Setting the iteration variable ; S5.2.

2. Utilize feasible points , and , using the convex optimization toolkit CVX to solve the optimization problem of maximizing the system's secure transmission rate, we obtain The optimal solution of the iteration ; S5.2.

3. Utilization , and , using the convex optimization toolkit CVX to solve the optimization problem of maximizing the system's secure transmission rate, we obtain The optimal solution of the iteration ; S5.2.

4. Utilization , and , using the convex optimization toolkit CVX to solve the optimization problem of maximizing the system's secure transmission rate, we obtain The optimal solution of the iteration .

4. The physical layer secure communication method of a SWIPT system assisted by RIS and artificial noise according to claim 3, characterized in that: In step S5.4, if Not established, order , , , , return to step S5.2.2.

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