Communication optimization method and related equipment based on millimeter wave PD-NOMA

Abstract

This invention relates to the field of wireless communication security, specifically to a communication optimization method and related equipment based on millimeter-wave PD-NOMA (Peripheral Detection and Detection of Multiple Access Points) (RIS) and an active RIS-assisted millimeter-wave PD-NOMA system model. The system comprises a base station, an active RIS, and three types of users: untrusted users (internal eavesdroppers), secure users, and external eavesdroppers. The system establishes a direct channel from the base station to the user and an indirect channel reflected by the RIS. The user signal transmission rate is obtained by decoding the transmitted signal, and the internal and external eavesdropping rates are calculated. To maximize the secure user confidentiality rate, the active RIS reflection coefficient matrix and PD-NOMA power allocation are jointly optimized to construct an objective function and solve for optimal parameters. These parameters are applied to the system model, and by dynamically adjusting the RIS beamforming and power allocation strategies, a secure transmission mechanism is established to effectively suppress internal and external eavesdropping, thereby improving communication security and spectral efficiency in the millimeter-wave band.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication security technology, and in particular to a communication optimization method and related equipment based on millimeter wave PD-NOMA. Background Art

[0002] NOMA (Non-Orthogonal Multiple Access), a key 5G technology, overcomes orthogonal resource constraints, allowing multiple terminals to transmit simultaneously. Multi-user signals are composited and transmitted at the transmitter through non-orthogonal superposition coding in the power or code domain. At the receiver, continuous interference cancellation (CIC) eliminates inter-user interference through an iterative decoding mechanism, creating a new multiple access system that supports large-scale connectivity, ultra-low latency, and high spectral efficiency. However, PD-NOMA (Power Domain Non-Orthogonal Multiple Access) has garnered greater attention than NOMA. Because PD-NOMA's power reuse characteristics are deeply coupled with the sparsity of millimeter-wave channels, power allocation significantly impacts system performance in millimeter-wave (mmWave) massive MIMO (Multiple-Input Multiple-Output) systems. This is especially true in scenarios with a large number of users, where the complexity of the dynamic power allocation algorithm directly impacts the feasibility of serial interference cancellation decoding. Furthermore, millimeter-wave channels have poor anti-interference capabilities, and numerous interfering signals pose a significant threat to the system's anti-interference performance. Therefore, it is necessary to rely on reasonable power allocation to enhance the coverage, user fairness, and system anti-interference capabilities of millimeter-wave PD-NOMA systems. Although PD-NOMA can more efficiently utilize limited bandwidth, it poses significant challenges to secure transmission.

[0003] Specifically, superposition coding at the transmitter increases the risk of eavesdropping between users, and the open nature of wireless channels makes legitimate signals susceptible to interception. Therefore, physical layer security has attracted significant attention as a potential method for preventing eavesdropping. Physical layer security is a key research area in information security. Fundamentally improving the security of communication systems and providing lightweight solutions for low-power, resource-constrained devices are potential future challenges for traditional encryption. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies in the above-mentioned existing technologies and provide a communication optimization method and related equipment based on millimeter wave PD-NOMA, so as to solve the technical problem of relatively low communication security performance of the current millimeter wave PD-NOMA system.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a communication optimization method based on millimeter wave PD-NOMA, comprising:

[0007] An active RIS-assisted millimeter-wave PD-NOMA system model is constructed, and base station transmission parameters, active RIS parameters, and receiving user parameters are obtained according to the millimeter-wave PD-NOMA system model; the millimeter-wave PD-NOMA system model includes a base station, an active RIS, and a receiving user, and the receiving user includes an untrusted user, a secure user, and an external eavesdropper; the untrusted user acts as an internal eavesdropper;

[0008] Establishing a first millimeter wave channel between the base station and an untrusted user or a secure user, and establishing a second millimeter wave channel between the base station and an external eavesdropper; both the first millimeter wave channel and the second millimeter wave channel include direct channels and indirect channels; a direct channel indicates direct communication between the base station and the receiving user, and an indirect channel indicates communication between the base station and the receiving user via an active RIS;

[0009] When the base station sends signals through the first millimeter wave channel and the second millimeter wave channel respectively, an optimization objective function is constructed according to the base station transmission parameters, active RIS parameters, and receiving user parameters. The optimal variable solution is calculated according to the optimization objective function, and the millimeter wave PD-NOMA system model is updated according to the optimal variable solution.

[0010] As a further improvement of the present invention, the active RIS includes M reflective elements, which are used to adjust the phase and amplitude of the signal according to the active RIS parameters, amplify the signal power and transmit it to the receiving user, where M is the total number of reflective elements.

[0011] As a further improvement of the present invention, the active RIS parameter is a reflection coefficient matrix, and the reflection coefficient matrix is:

[0012]

[0013] in,

[0014]

[0015] Where, is the reflection coefficient matrix of active RIS, is the reflection coefficient of the first reflective element, is the reflection coefficient of the mth reflective element, is the reflection coefficient of the Mth reflective element, is the amplitude of the signal corresponding to the mth reflection element, is the phase corresponding to the signal in the mth reflection element, is a diagonal matrix, For the dimension, is a complex exponential function, and j is the imaginary unit.

[0016] As a further improvement of the present invention, the first millimeter wave channel is expressed as:

[0017]

[0018] The second millimeter wave channel is expressed as:

[0019]

[0020] Where, is the first millisecond wave channel; It is a direct channel from the base station to untrusted users and secure users; It is the channel from active RIS to untrusted users and secure user equipment; is the reflection coefficient matrix of active RIS; It is the channel from the base station to the active RIS; is the second millimeter wave channel; It is a direct channel from the base station to the external eavesdropper; is the channel from active RIS to external eavesdroppers, Untrusted user or secure user, i=1, 2; when i is 1, it is an untrusted user, and when i is 2, it is a secure user; For the base station, For active RIS, For external eavesdroppers, H is the conjugate transpose operation, It is an indirect channel from the base station to untrusted users and secure users; It is an indirect channel from the base station to the external eavesdropper.

[0021] As a further improvement of the present invention, when the base station transmits signals through the first millimeter wave channel and the second millimeter wave channel respectively, the present invention further includes determining the eavesdropping rate and the confidentiality rate of the corresponding receiving user according to the transmitted signal, and using the eavesdropping rate and the confidentiality rate as constraints of the optimization objective function;

[0022] The step of determining the eavesdropping rate and confidentiality rate of the receiving user comprises:

[0023] Decoding the signal of the untrusted user to obtain a signal-to-interference-and-noise ratio (SINR) of the signal of the untrusted user, and obtaining a signal transmission rate of the untrusted user based on the SINR of the signal of the untrusted user;

[0024] After the signal of the untrusted user is successfully decoded, the secure user is decoded to obtain the signal-to-interference-and-noise ratio of the secure user signal. Based on the signal-to-interference-and-noise ratio of the secure user signal, the signal transmission rate of the secure user is obtained.

[0025] The internal eavesdropping rate is calculated based on the signal transmission rates of untrusted users and secure users;

[0026] Determine the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper; calculate the external eavesdropping rate based on the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper;

[0027] The confidentiality rate of the secure user is calculated based on the internal eavesdropping rate and the external eavesdropping rate.

[0028] As a further improvement of the present invention, the signal transmission rate of the untrusted user is:

[0029]

[0030] The signal transmission rate of the secure user is:

[0031]

[0032] The internal eavesdropping rate is:

[0033]

[0034] The external eavesdropping rate is:

[0035]

[0036] Where, Signal transmission rate for untrusted users; To decode confidential signals from untrusted users Signal-to-interference-and-noise ratio of untrusted users; To decode confidential signals from untrusted users Time, signal to interference and noise ratio of secure users; Confidential signals for untrusted users; is an untrusted user; Signal transmission rate for security users; To decode the confidential signal of the security user Time, signal to interference and noise ratio of security users; To decode the confidential signal of the security user Signal-to-interference-and-noise ratio of untrusted users; A confidential signal for secure users; For security users; is the internal eavesdropping rate; is the external eavesdropping rate; is the signal-to-interference-and-noise ratio of the legitimate signal corresponding to the external eavesdropper; For external eavesdroppers; is the logarithmic function with base 2.

[0037] As a further improvement of the present invention, the confidentiality rate of the secure user is expressed as:

[0038]

[0039] in, Confidentiality rate for secure users; , used to represent rate scaling, Signal transmission rate for security users; is the internal eavesdropping rate; is the external eavesdropping rate.

[0040] As a further improvement of the present invention, the optimization objective function is:

[0041]

[0042] Where, Confidentiality rate for secure users; To maximize the confidentiality rate; Data transmission rate for untrusted users; User service quality requirements for non-trusted users; The power allocated to the base station by the non-trusted user; Power allocated to safety users by the base station; is the precoding vector of the base station for untrusted users; Precoding vector for the base station for security users; is the transmission power of the base station; is the reflection coefficient of the mth reflective element; is the maximum amplitude corresponding to the signal in the reflective element; Transmission channel for untrusted users; Transmission channel for secure users; is the noise power at the active RIS; is the maximum reflected power; is the identity matrix; The transmission power allocated to untrusted users by the base station; Data transmission rate for untrusted users; The transmission power allocated to the secure user by the base station; is the reflected power of the downlink after reflection via the active RIS; is the reflection coefficient matrix of active RIS; The power consumed by the noise of the active RIS; is the 2-norm square of the vector, It is the channel from the base station to the active RIS.

[0043] As a further improvement of the present invention, the optimization objective function is decomposed into three optimization sub-problems when solving, and the three optimization sub-problems are solved respectively using a convex optimization algorithm to obtain the optimal variable solution;

[0044] The first optimization sub-problem is to optimize the precoding vector of the base station; the second optimization sub-problem is to optimize the reflection coefficient matrix of the active RIS; and the third optimization sub-problem is to optimize the power allocation of the receiving user.

[0045] In a second aspect, the present invention provides a communication optimization system based on millimeter wave PD-NOMA, which is used to implement the above-mentioned communication optimization method based on millimeter wave PD-NOMA, including:

[0046] A wireless communication model construction module is used to construct an active RIS-assisted millimeter wave PD-NOMA system model. The millimeter wave PD-NOMA system model includes a base station, an active RIS, and receiving users. The receiving users include untrusted users, secure users, and external eavesdroppers. The untrusted users serve as internal eavesdroppers.

[0047] A wireless communication transmission construction module establishes a first millimeter wave channel between the base station and an untrusted user or a secure user, and establishes a second millimeter wave channel between the base station and an external eavesdropper; the first millimeter wave channel and the second millimeter wave channel both include direct channels and indirect channels; a direct channel indicates direct communication between the base station and the receiving user, and an indirect channel indicates communication between the base station and the receiving user via an active RIS;

[0048] The data acquisition module is used to obtain base station transmission parameters, active RIS parameters, and receiving user parameters according to the millimeter wave PD-NOMA system model;

[0049] The communication optimization module constructs an optimization objective function based on the base station transmission parameters, active RIS parameters, and receiving user parameters, calculates the optimal variable solution based on the optimization objective function, and updates the millimeter wave PD-NOMA system model based on the optimal variable solution.

[0050] The beneficial effects of the present invention are as follows: the present invention provides a millimeter-wave PD-NOMA communication optimization method, which is mainly targeted at millimeter-wave communication wireless networks, specifically millimeter-wave PD-NOMA networks. The present invention constructs a millimeter-wave PD-NOMA network assisted by active RIS, which enhances the signal strength of the desired channel through active RIS, compensates for the high millimeter-wave path loss, and improves the signal-to-interference-and-noise ratio at the receiving end. Active RIS can amplify reflected signals, compensate for path loss, and reduce base station transmit power, improving energy efficiency. At the same time, the active RIS beam can replace part of the base station array, reducing the number of base station antennas.

[0051] Furthermore, the present invention establishes a first millimeter wave channel (i.e., base station to untrusted users or secure users) and a second millimeter wave channel (i.e., base station to external eavesdroppers), each channel including direct and indirect communication paths in a millimeter wave PD-NOMA network, and utilizes the alternating direction method of multipliers (ADMM) to iteratively solve the optimal phase matrix to maximize the legitimate channel gain and suppress the eavesdropping channel.

[0052] For new interference sources introduced by active RIS signals, the present invention can suppress both the new interference sources and the original interference by establishing an optimization objective function. Furthermore, the active RIS of the present invention can compensate for path loss by actively amplifying the signal, thereby increasing gain during millimeter-wave communications.

[0053] Furthermore, the base station's beamforming and RIS reflection coefficients were jointly optimized to enhance the signal in the direction of legitimate users and inject artificial noise in the direction of eavesdroppers. Numerical results show that the secure rate remains positive even when the eavesdropper is closer to the RIS. By dynamically adjusting the amplitude and phase, the system demonstrates significant advantages in signal quality, coverage flexibility, anti-interference capability, and energy efficiency, providing theoretical support and engineering practice for the integration of non-orthogonal multiple access and intelligent metamaterials.

[0054] Furthermore, by using the eavesdropping rate and confidentiality rate as constraints for the optimization objective function, the active RIS-assisted millimeter-wave PD-NOMA system achieves comprehensive improvements in security, spectrum efficiency, and dynamic adaptability. By fine-tuning the reflection coefficient matrix and base station beamforming, the system maintains stable communication and security performance in complex electromagnetic environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0056] Figure 1 Schematic diagram of the active RIS-assisted mmWave-PD-NOMA secure communication system model in the present invention;

[0057] Figure 2 It is a flow chart for realizing the method of the present invention;

[0058] Figure 3 1 is a graph showing the convergence performance simulation results of the alternating optimization algorithm of the present invention;

[0059] Figure 4 This is a simulation result diagram of the maximum transmission power of the base station according to the present invention and the confidentiality rate of the secure user;

[0060] Figure 5 1 is a simulation result diagram of the number of RIS reflection units according to the present invention and the confidentiality rate of the secure user;

[0061] Figure 6 This is a simulation result diagram of the number of external eavesdroppers versus the confidentiality rate of secure users in the present invention;

[0062] Figure 7 This is a simulation result diagram of the user service quality of internal eavesdropping according to the confidentiality rate of the secure user in the present invention. DETAILED DESCRIPTION

[0063] In order to make the purpose and technical solution of the present invention clearer and easier to understand, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0064] Explanation of terms:

[0065] Active RIS (reconfigurable intelligent surface): A reconfigurable intelligent surface composed of multiple passive reflective elements. By adjusting the phase shift of the incident signal, RIS can enhance the reception of the desired signal and suppress interference from unintended users, thereby artificially creating favorable propagation conditions and enhancing existing wireless communications.

[0066] BS (Base Station): Base station is a key infrastructure in mobile communication networks, used to achieve wireless communication between mobile terminals and the core network.

[0067] PD-NOMA (Power Domain Non-Orthogonal Multiple Access): Power domain non-orthogonal multiple access.

[0068] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings and specific embodiments. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0069] Example 1

[0070] like Figures 1 to 7 As shown, this embodiment provides a method for optimizing millimeter-wave PD-NOMA communication. By using active RIS to assist millimeter-wave PD-NOMA communication, security information can be protected, further improving system security performance. The following is a specific implementation method.

[0071] A millimeter-wave PD-NOMA system model assisted by active RIS is constructed. The millimeter-wave PD-NOMA system model includes a base station, an active RIS, and receiving users, including untrusted users, secure users, and external eavesdroppers.

[0072] The frequency range of the millimeter wave in this embodiment is 30-300 GHz, and the wavelength range is 1-10 mm.

[0073] The base station includes A transmitting antenna, an untrusted user and a secure user Among them, security users Set up remotely, it has higher security permissions. Not a trusted user Set to near end, after successfully decoding its own information, try to use serial interference elimination to intercept the security user confidential information, so the near-end user Also considered an internal eavesdropper. In addition, there are An external eavesdropper surrounds the secure user Around attempts to eavesdrop on secure users Unlike external eavesdroppers, internal eavesdroppers Not only trying to steal The confidential information must also meet the requirements of internal eavesdroppers in power domain non-orthogonal multiple access networks. user service quality.

[0074] An active RIS, on the other hand, consists of M reflective elements, which adjust the signal's phase and amplitude based on the active RIS parameters, amplifying the signal power before transmitting it to the receiving user. Each reflective element in the active RIS is equipped with a power amplifier, allowing for simultaneous adjustment of the signal's phase and amplification, but this requires an additional power supply.

[0075] Furthermore, the active RIS parameter is the reflection coefficient matrix. The reflection coefficient matrix is:

[0076]

[0077] in,

[0078]

[0079] Where, is the reflection coefficient matrix of active RIS, is the reflection coefficient of the first reflective element, is the reflection coefficient of the mth reflective element, is the reflection coefficient of the Mth reflective element, is the amplitude of the signal corresponding to the mth reflection element, is the phase corresponding to the signal in the mth reflection element, is a diagonal matrix, For the dimension, is a complex exponential function, and j is the imaginary unit.

[0080] A first millimeter wave channel is established between the base station and an untrusted or secure user, and a second millimeter wave channel is established between the base station and an external eavesdropper. Both the first and second millimeter wave channels include direct and indirect channels. A direct channel indicates direct communication between the base station and the receiving user, while an indirect channel indicates communication between the base station and the receiving user via an active RIS.

[0081] In this embodiment, the direct channel from the base station to the untrusted user (or secure user) is expressed as ; (i=1, 2) is an untrusted user or a secure user; when i is 1, it is an untrusted user, and when i is 2, it is a secure user; the channel from the base station to the active RIS is The channel from active RIS to untrusted user (or secure user) is expressed as ; The direct channel from the base station to the external eavesdropper is expressed as ; The channel from active RIS to the jth external eavesdropper is expressed as .

[0082] Then, the first millimeter wave channel is expressed as:

[0083]

[0084] The second millimeter wave channel is expressed as:

[0085]

[0086] Where, It is the first millimeter wave channel; It is a direct channel from the base station to untrusted users and secure users; It is the channel from active RIS to untrusted users and secure user equipment; is the reflection coefficient matrix of active RIS; It is the channel from the base station to the active RIS; is the second millimeter wave channel; It is a direct channel from the base station to the external eavesdropper; is the channel from active RIS to external eavesdroppers, Untrusted user or secure user, i=1, 2; when i is 1, it is an untrusted user, and when i is 2, it is a secure user; For the base station, For active RIS, For external eavesdroppers, H is the conjugate transpose operation, It is an indirect channel from the base station to untrusted users and secure users; It is an indirect channel from the base station to the external eavesdropper.

[0087] When the base station sends signals to the receiving user through the first millimeter wave channel and the second millimeter wave channel respectively, an optimization objective function is constructed according to the base station transmission parameters, active RIS parameters, and receiving user parameters. The optimal variable solution is calculated according to the optimization objective function. The optimal variable solution is used to update the millimeter wave PD-NOMA system model to achieve communication optimization.

[0088] In this embodiment, the base station sends signals to the receiving user through the first millimeter wave channel and the second millimeter wave channel respectively. Then the signals received by the receiving user are respectively expressed as:

[0089]

[0090]

[0091] in, Signals received by untrusted users (or secure users); The signal received by an external eavesdropper; The power allocated to the base station by the non-trusted user; Power allocated to safety users by the base station; is the precoding vector of the base station for untrusted users; Precoding vector for the base station for security users; and represents the RIS and the noise at the receiving user; Represents confidential information for untrusted users; Indicates a secure user confidential information.

[0092] In addition, when the base station transmits signals to untrusted users (or secure users) through the first millimeter wave channel and sends signals to external eavesdroppers through the second millimeter wave channel, it also includes determining the eavesdropping rate and confidentiality rate of the receiving user, and using the eavesdropping rate and confidentiality rate as constraints of the optimization objective function.

[0093] The steps for determining the eavesdropping rate and confidentiality rate of the receiving user include:

[0094] Decoding the confidential signal of the untrusted user to obtain the signal-to-interference-and-noise ratio of the untrusted user signal, and obtaining the signal transmission rate of the untrusted user based on the signal-to-interference-and-noise ratio of the untrusted user signal;

[0095] After the signal of the untrusted user is successfully decoded, the confidential signal of the secure user is decoded to obtain the signal-to-interference-and-noise ratio of the secure user signal. Based on the signal-to-interference-and-noise ratio of the secure user signal, the signal transmission rate of the secure user is obtained.

[0096] The internal eavesdropping rate is calculated based on the signal transmission rates of untrusted users and secure users;

[0097] Determine the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper; calculate the external eavesdropping rate based on the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper;

[0098] The confidentiality rate of the secure user is calculated based on the internal eavesdropping rate and the external eavesdropping rate.

[0099] Specifically, the order in which serial interference is eliminated between receiving users is primarily determined by channel quality. Stronger users must decode and remove the weaker user's information to obtain their own information. However, to preserve the confidentiality of the secure user, the untrusted user's information must be decoded first. Specifically, this is expressed as:

[0100]

[0101] Therefore, when decoding the confidential signal of an untrusted user When , the SINR (Signal-to-Interference-plus-Noise Ratio) corresponding to the untrusted user and the secure user are expressed as:

[0102]

[0103]

[0104] Where, To decode confidential signals from untrusted users Signal-to-interference-and-noise ratio of untrusted users; To decode confidential signals from untrusted users Time, signal to interference and noise ratio of secure users. is the noise power at the active RIS, is the thermal noise or additive white Gaussian noise of the untrusted user (or secure user).

[0105] Then, the signal transmission rate of the untrusted user is:

[0106]

[0107] Where, is the signal transmission rate of untrusted users.

[0108] When the confidential signal of an untrusted user After successful decoding, the secure user uses SIC (Successive Interference Cancellation) to eliminate the confidential signal of the untrusted user. , and then decode its own confidential signal , and the untrusted user decodes the confidential signal Finally, try to use SIC to decode the confidential signal of the secure user information.

[0109] Therefore, decoding the confidential signal of the secure user When , the SINRs corresponding to untrusted users and secure users are expressed as:

[0110]

[0111]

[0112] Where, To decode the confidential signal of the security user Signal-to-interference-and-noise ratio of untrusted users; To decode the confidential signal of the security user Time, signal to interference and noise ratio of secure users.

[0113] Then, the signal transmission rate of the secure user is:

[0114]

[0115] Where, Signaling rate for security users.

[0116] Therefore, the eavesdropping rate of an untrusted user on a secure user (i.e., the internal eavesdropping rate) is:

[0117]

[0118] in, is the internal tapping rate.

[0119] The SINR of the external eavesdropper's corresponding legitimate signal is expressed as:

[0120]

[0121] Where, is the signal-to-interference-and-noise ratio of the legitimate signal corresponding to the external eavesdropper.

[0122] Correspondingly, the eavesdropping rate of the external eavesdropper (i.e., the external eavesdropping rate) is:

[0123]

[0124] Therefore, the confidentiality rate of a secure user is expressed as:

[0125]

[0126] in, , used to represent rate scaling, Confidential rate for secure users.

[0127] When solving the problems of millimeter wave PD-NOMA communication security and anti-interference, it is necessary to consider the parameters corresponding to the base station, active RIS and receiving user. Therefore, this embodiment optimizes the communication by designing an optimization problem, that is, constructing an optimization objective function, and solving the optimal solution of the objective function. Specifically, by jointly optimizing the precoding vector at the base station and , active RIS reflection coefficient matrix Power allocation with base station power and , to maximize user safety Therefore, the final optimization objective function is:

[0128]

[0129] Where, Confidentiality rate for secure users; To maximize the confidentiality rate; Data transmission rate for untrusted users; User service quality requirements for non-trusted users; The power allocated to the base station by the non-trusted user; Power allocated to safety users by the base station; is the precoding vector of the base station for untrusted users; Precoding vector for the base station for security users; is the transmission power of the base station; is the reflection coefficient of the mth reflective element; is the maximum amplitude corresponding to the signal in the reflective element; Transmission channel for untrusted users; Transmission channel for secure users; is the noise power at the active RIS; is the maximum reflected power; is the identity matrix; The transmission power allocated to untrusted users by the base station; Data transmission rate for untrusted users; The transmission power allocated to the secure user by the base station; is the reflected power of the downlink after reflection via the active RIS; is the reflection coefficient matrix of active RIS; The power consumed by the noise of the active RIS; is the square of the 2-norm of the vector.

[0130] The optimization objective function in this embodiment constrains the following variables respectively, specifically:

[0131] constraint Ensure users Data transmission requirements, including for User service quality requirements;

[0132] constraint Indicates the transmit power limit of the base station;

[0133] constraint represents the reflection coefficient limit of active RIS;

[0134] constraint Ensures the decoding order of serial interference cancellation;

[0135] constraint Indicates the reflected power limit of the active RIS;

[0136] constraint Ensure power distribution for both users.

[0137] When solving the optimization objective function, the optimization objective function is first decomposed into three optimization sub-problems. The convex optimization algorithm is used to solve the three optimization sub-problems respectively to obtain the optimal variable solution. Among them, the first optimization sub-problem is to optimize the precoding vector of the base station; the second optimization sub-problem is to optimize the reflection coefficient matrix of the active RIS; and the third optimization sub-problem is to optimize the power allocation of the receiving user. The optimal variable solution is the optimal base station precoding vector 、 , the reflection coefficient matrix of active RIS , receiving the power allocated by the user and .

[0138] In order to verify the communication optimization quality of the method of the present invention, this embodiment also establishes active RIS assisted, passive RIS assisted and RIS-free millimeter wave PD-NOMA system models. And when the optimization problem converges, the maximum number of iterations is set to 30 times. The base station, active RIS, and untrusted user and security users The coordinates are set to , , and In addition, the transmitting antenna is set , base station power , active RIS =-75 =-95 = 2 / bit / s / Hz .

[0139] like Figure 3 As shown, the algorithm converges fastest when active RIS is used in this embodiment. Two baseline schemes are also considered for comparison. In the "passive RIS" scheme, RIS optimizes only the phase shift and does not consider the reflection amplitude. The "no RIS" scheme only considers the case where a direct link exists between the base station and the user. Comparing the confidentiality rate of this scheme with the baseline scheme shows that the introduction of RIS can improve system performance, with active RIS having a more significant impact.

[0140] In order to further determine the performance of the method of this embodiment, refer to Figure 4 , gives a comparison of the base station transmission power and the confidentiality rate in the present invention. By comparing various schemes, it can be seen that the active RIS auxiliary scheme proposed in this embodiment has superior performance.

[0141] Reference Figure 5 , the changes in the number of reflective elements and the confidentiality rate under various schemes are compared. Due to the increase in degrees of freedom, the confidentiality rate of both active and passive RIS cases increases with the increase of M. The algorithm with active RIS design proposed in this embodiment has significantly better confidentiality performance than the existing solution with passive RIS. In addition, due to the "double fading" effect, when M changes from 10 to 60, the confidentiality rate of passive RIS only increases by about 22%, which is less than when =20dB These results strongly suggest that using active RIS can save more reflection units, leading to better performance gains and significantly reducing the complexity of RIS.

[0142] Reference Figure 6 The present invention also compares the impact of the number of external eavesdroppers on the confidentiality rate. It can be seen that as the number of external eavesdroppers increases, the confidentiality rate gradually decreases, but the decreasing trend slows down significantly. This is because the external eavesdroppers are around the security users. The surrounding random generated, with the increase of the number of external eavesdroppers, the impact on the confidentiality rate gradually decreases without considering the conspiracy eavesdropping. At the same time, this embodiment also compares the untrusted user The relationship between user service quality and confidentiality rate, such as Figure 7As shown in the figure, as the user service quality of untrusted users increases, the confidentiality rate decreases significantly and the trend becomes more and more obvious. This is because as the user service quality of untrusted users increases, more power is required, which is correspondingly allocated to secure users. The power will be reduced, resulting in a decrease in the confidentiality rate.

[0143] Example 2

[0144] This embodiment provides a millimeter wave PD-NOMA-based communication optimization system for implementing the millimeter wave PD-NOMA-based communication optimization method in Example 1. The system specifically includes:

[0145] The wireless communication model construction module constructs an active RIS-assisted millimeter-wave PD-NOMA system model. The millimeter-wave PD-NOMA system model includes a base station, an active RIS, and receiving users. The receiving users include untrusted users, secure users, and external eavesdroppers; the untrusted users act as internal eavesdroppers.

[0146] The frequency range of the millimeter wave in this embodiment is 30-300 GHz, and the wavelength range is 1-10 mm.

[0147] The base station includes A transmitting antenna, an untrusted user and a secure user Among them, security users Set up remotely, it has higher security permissions. Not a trusted user Set to near end, after successfully decoding its own information, try to use serial interference elimination to intercept the security user confidential information, so the near-end user Also considered an internal eavesdropper. In addition, there are An external eavesdropper surrounds the secure user Around attempts to eavesdrop on secure users Unlike external eavesdroppers, internal eavesdroppers Not only trying to steal The confidential information must also meet the requirements of internal eavesdroppers in power domain non-orthogonal multiple access networks. user service quality.

[0148] An active RIS, on the other hand, consists of M reflective elements, which adjust the signal's phase and amplitude based on the active RIS parameters, amplifying the signal power before transmitting it to the receiving user. Each reflective element in the active RIS is equipped with a power amplifier, allowing for simultaneous adjustment of the signal's phase and amplification, but this requires an additional power supply.

[0149] Furthermore, the active RIS parameter is the reflection coefficient matrix. The reflection coefficient matrix is:

[0150]

[0151] in,

[0152]

[0153] Where, is the reflection coefficient matrix of active RIS, is the reflection coefficient of the first reflective element, is the reflection coefficient of the mth reflective element, is the reflection coefficient of the Mth reflective element, is the amplitude of the signal corresponding to the mth reflection element, is the phase corresponding to the signal in the mth reflection element, is a diagonal matrix, For the dimension, is a complex exponential function.

[0154] The wireless communication transmission construction module establishes a first millimeter wave channel between the base station and an untrusted user or a secure user, and establishes a second millimeter wave channel between the base station and an external eavesdropper; the first millimeter wave channel and the second millimeter wave channel both include direct channels and indirect channels; a direct channel indicates direct communication between the base station and the receiving user, and an indirect channel indicates communication between the base station and the receiving user through an active RIS.

[0155] Specifically, in this embodiment, the direct channel from the base station to the untrusted user (or secure user) is expressed as ; (i=1, 2) is an untrusted user or a secure user; when i is 1, it is an untrusted user, and when i is 2, it is a secure user; the channel from the base station to the active RIS is The channel from active RIS to untrusted user (or secure user) is expressed as ; The direct channel from the base station to the external eavesdropper is expressed as ; The channel from active RIS to the jth external eavesdropper is expressed as .

[0156] Therefore, the first mmWave channel is expressed as:

[0157]

[0158] The second millimeter wave channel is expressed as:

[0159]

[0160] Where, It is the first millimeter wave channel; It is a direct channel from the base station to untrusted users and secure users; It is the channel from active RIS to untrusted users and secure user equipment; is the reflection coefficient matrix of active RIS; It is the channel from the base station to the active RIS; is the second millimeter wave channel; It is a direct channel from the base station to the external eavesdropper; is the channel from active RIS to external eavesdroppers, Untrusted user or secure user, i=1, 2; when i is 1, it is an untrusted user, and when i is 2, it is a secure user; For the base station, For active RIS, For external eavesdroppers, H is the conjugate transpose operation, It is an indirect channel from the base station to untrusted users and secure users; Indirect channel from the base station to the external eavesdropper

[0161] When the base station sends signals to the receiving user through the first millimeter wave channel and the second millimeter wave channel respectively, an optimization objective function is constructed according to the base station transmission parameters, active RIS parameters, and receiving user parameters. The optimal variable solution is calculated according to the optimization objective function. The optimal variable solution is used to update the millimeter wave PD-NOMA system model to achieve communication optimization.

[0162] In this embodiment, the base station sends signals to the receiving user through the first millimeter wave channel and the second millimeter wave channel respectively. Then the signals received by the receiving user are respectively expressed as:

[0163]

[0164]

[0165] in, Signals received by untrusted users (or secure users); The signal received by an external eavesdropper; The power allocated to the base station by the non-trusted user; Power allocated to safety users by the base station; is the precoding vector of the base station for untrusted users; Precoding vector for the base station for security users; and represents the noise at the active RIS and receiving user; Represents confidential information for untrusted users; Indicates a secure user confidential information.

[0166] In addition, when the base station transmits signals to untrusted users (or secure users) through the first millimeter wave channel and sends signals to external eavesdroppers through the second millimeter wave channel, it also includes determining the eavesdropping rate and confidentiality rate of the receiving user, and using the eavesdropping rate and confidentiality rate as constraints of the optimization objective function.

[0167] The steps for determining the eavesdropping rate and confidentiality rate of the receiving user include:

[0168] Decoding the confidential signal of the untrusted user to obtain the signal-to-interference-and-noise ratio of the untrusted user signal, and obtaining the signal transmission rate of the untrusted user based on the signal-to-interference-and-noise ratio of the untrusted user signal;

[0169] After the signal of the untrusted user is successfully decoded, the confidential signal of the secure user is decoded to obtain the signal-to-interference-and-noise ratio of the secure user signal. Based on the signal-to-interference-and-noise ratio of the secure user signal, the signal transmission rate of the secure user is obtained.

[0170] The internal eavesdropping rate is calculated based on the signal transmission rates of untrusted users and secure users;

[0171] Determine the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper; calculate the external eavesdropping rate based on the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper;

[0172] The confidentiality rate of the secure user is calculated based on the internal eavesdropping rate and the external eavesdropping rate.

[0173] Specifically, the order in which serial interference is eliminated between receiving users is primarily determined by channel quality. Stronger users must decode and remove the weaker user's information to obtain their own information. However, to preserve the confidentiality of the secure user, the untrusted user's information must be decoded first. Specifically, this is expressed as:

[0174]

[0175] Therefore, when decoding the confidential signal of an untrusted user When , the SINR (Signal-to-Interference-plus-Noise Ratio) corresponding to the untrusted user and the secure user are expressed as:

[0176]

[0177]

[0178] Where, To decode confidential signals from untrusted users Signal-to-interference-and-noise ratio of untrusted users; To decode confidential signals from untrusted users Time, signal to interference and noise ratio of secure users.

[0179] Then, the signal transmission rate of the untrusted user is:

[0180]

[0181] Where, is the signal transmission rate of untrusted users.

[0182] When the confidential signal of an untrusted user After successful decoding, the secure user uses SIC (Successive Interference Cancellation) to eliminate the confidential signal of the untrusted user. , and then decode its own confidential signal , and the untrusted user decodes the confidential signal Finally, try to use SIC to decode the confidential signal of the secure user information.

[0183] Therefore, decoding the confidential signal of the secure user When , the SINRs corresponding to untrusted users and secure users are expressed as:

[0184]

[0185]

[0186] Where, To decode the confidential signal of the security user Signal-to-interference-and-noise ratio of untrusted users; To decode the confidential signal of the security user Time, signal to interference and noise ratio of secure users.

[0187] Then, the signal transmission rate of the secure user is:

[0188]

[0189] Where, Signaling rate for security users.

[0190] Therefore, the eavesdropping rate of an untrusted user on a secure user (i.e., the internal eavesdropping rate) is:

[0191]

[0192] in, is the internal tapping rate.

[0193] The SINR of the external eavesdropper's corresponding legitimate signal is expressed as:

[0194]

[0195] Where, is the signal-to-interference-and-noise ratio of the legitimate signal corresponding to the external eavesdropper.

[0196] Correspondingly, the eavesdropping rate of the external eavesdropper (i.e., the external eavesdropping rate) is:

[0197]

[0198] Therefore, the confidentiality rate of a secure user is expressed as:

[0199]

[0200] in, , used to represent rate scaling, Confidential rate for secure users.

[0201] The data acquisition module is used to obtain base station transmission parameters, active RIS parameters, and receiving user parameters based on the millimeter wave PD-NOMA system model.

[0202] The communication optimization module constructs an optimization objective function based on the base station transmission parameters, active RIS parameters, and receiving user parameters, and calculates the optimal variable solution based on the optimization objective function. The optimal variable solution is used to update the millimeter wave PD-NOMA system model to achieve communication optimization.

[0203] When solving the problems of millimeter wave PD-NOMA communication security and anti-interference, it is necessary to consider the parameters corresponding to the base station, active RIS and receiving user. Therefore, this embodiment optimizes the communication by designing an optimization problem, that is, constructing an optimization objective function, and solving the optimal solution of the objective function. Specifically, by jointly optimizing the precoding vector at the base station and , active RIS reflection coefficient matrix Power allocation with base station power and , to maximize user safety Therefore, the final optimization objective function is:

[0204]

[0205] Where, Confidentiality rate for secure users; To maximize the confidentiality rate; Data transmission rate for untrusted users; User service quality requirements for non-trusted users; The power allocated to the base station by the non-trusted user; Power allocated to safety users by the base station; is the precoding vector of the base station for untrusted users; Precoding vector for the base station for security users; is the transmission power of the base station; is the reflection coefficient of the mth reflective element; is the maximum amplitude corresponding to the signal in the reflective element; Transmission channel for untrusted users; Transmission channel for secure users; is the noise power at the active RIS; is the maximum reflected power; is the identity matrix; The transmission power allocated to untrusted users by the base station; Data transmission rate for untrusted users; The transmission power allocated to the secure user by the base station; is the reflected power of the downlink after reflection via the active RIS; is the reflection coefficient matrix of active RIS; The power consumed by the noise of the active RIS; is the square of the 2-norm of the vector.

[0206] The optimization objective function in this embodiment constrains the following variables respectively, specifically:

[0207] constraint Ensure users Data transmission requirements, including for User service quality requirements;

[0208] constraint Indicates the transmit power limit of the base station;

[0209] constraint represents the reflection coefficient limit of active RIS;

[0210] constraint Ensures the decoding order of serial interference cancellation;

[0211] constraint Indicates the reflected power limit of the active RIS;

[0212] constraint Ensure power distribution for both users.

[0213] When solving the optimization objective function, the optimization objective function is first decomposed into three optimization sub-problems. The convex optimization algorithm is used to solve the three optimization sub-problems respectively to obtain the optimal variable solution. Among them, the first optimization sub-problem is to optimize the precoding vector of the base station; the second optimization sub-problem is to optimize the reflection coefficient matrix of the active RIS; and the third optimization sub-problem is to optimize the power allocation of the receiving user. The optimal variable solution is the optimal base station precoding vector 、 , the reflection coefficient matrix of active RIS , receiving the power allocated by the user and .

Claims

1. A communication optimization method based on millimeter wave PD-NOMA, characterized in that: include: An active RIS-assisted millimeter-wave PD-NOMA system model is constructed, and base station transmission parameters, active RIS parameters, and receiving user parameters are obtained according to the millimeter-wave PD-NOMA system model; the millimeter-wave PD-NOMA system model includes a base station, an active RIS, and a receiving user, and the receiving user includes an untrusted user, a secure user, and an external eavesdropper; the untrusted user acts as an internal eavesdropper; Establishing a first millimeter wave channel between the base station and an untrusted user or a secure user, and establishing a second millimeter wave channel between the base station and an external eavesdropper; both the first millimeter wave channel and the second millimeter wave channel include direct channels and indirect channels; a direct channel indicates direct communication between the base station and the receiving user, and an indirect channel indicates communication between the base station and the receiving user via an active RIS; When the base station sends signals through the first millimeter wave channel and the second millimeter wave channel respectively, an optimization objective function is constructed according to the base station transmission parameters, active RIS parameters, and receiving user parameters. The optimal variable solution is calculated based on the optimization objective function, and the millimeter wave PD-NOMA system model is updated according to the optimal variable solution. The optimization objective function is: Where, Confidentiality rate for secure users; To maximize the confidentiality rate; Data transmission rate for untrusted users; User service quality requirements for non-trusted users; The power allocated to the base station by the non-trusted user; Power allocated to safety users by the base station; is the precoding vector of the base station for untrusted users; Precoding vector for the base station for security users; is the transmission power of the base station; is the reflection coefficient of the mth reflective element; is the maximum amplitude corresponding to the signal in the reflective element; Transmission channel for untrusted users; Transmission channel for secure users; is the noise power at the active RIS; is the maximum reflected power; is the identity matrix; The transmission power allocated to untrusted users by the base station; Data transmission rate for untrusted users; The transmission power allocated to the secure user by the base station; is the reflected power of the downlink after reflection via the active RIS; is the reflection coefficient matrix of active RIS; The power consumed by the noise of the active RIS; is the 2-norm square of the vector, It is the channel from the base station to the active RIS; The said m The reflection coefficient of a reflective element is: Where, For the m The amplitude corresponding to the signal in each reflective element, is the phase corresponding to the signal in the mth reflection element, is a complex exponential function, j is the imaginary unit.

2. The communication optimization method based on millimeter wave PD-NOMA according to claim 1, characterized in that The active RIS includes M A reflective element is used to adjust the phase and amplitude of the signal according to the active RIS parameters, amplify the signal power and transmit it to the receiving user. M is the total number of reflective elements.

3. The communication optimization method based on millimeter wave PD-NOMA according to claim 2, characterized in that The active RIS parameter is a reflection coefficient matrix, which is: Where, is the reflection coefficient matrix of active RIS, is the reflection coefficient of the first reflective element, For the m The reflection coefficient of each reflective element, For the M The reflection coefficient of each reflective element, is a diagonal matrix, For dimension.

4. The communication optimization method based on millimeter wave PD-NOMA according to claim 1, characterized in that The first millimeter wave channel is represented by: The second millimeter wave channel is expressed as: Where, is the first millisecond wave channel; It is a direct channel from the base station to untrusted users and secure users; It is the channel from active RIS to untrusted users and secure user equipment; is the reflection coefficient matrix of active RIS; It is the channel from the base station to the active RIS; is the second millimeter wave channel; It is a direct channel from the base station to the external eavesdropper; is the channel from active RIS to external eavesdroppers, For untrusted users or secure users, i =1,2; i When it is 1, it is a non-trusted user. i When it is 2, it is a safe user; For the base station, For active RIS, For external eavesdroppers, H is the conjugate transpose operation, It is an indirect channel from the base station to untrusted users and secure users; It is an indirect channel from the base station to the external eavesdropper.

5. The communication optimization method based on millimeter wave PD-NOMA according to claim 1, characterized in that When the base station transmits signals through the first millimeter wave channel and the second millimeter wave channel respectively, the method further includes determining the eavesdropping rate and the confidentiality rate of the corresponding receiving user according to the transmitted signals, and using the eavesdropping rate and the confidentiality rate as constraints of the optimization objective function; The step of determining the eavesdropping rate and confidentiality rate of the receiving user comprises: Decoding the signal of the untrusted user to obtain a signal-to-interference-and-noise ratio (SINR) of the signal of the untrusted user, and obtaining a signal transmission rate of the untrusted user based on the SINR of the signal of the untrusted user; After the signal of the untrusted user is successfully decoded, the secure user is decoded to obtain the signal-to-interference-and-noise ratio of the secure user signal. Based on the signal-to-interference-and-noise ratio of the secure user signal, the signal transmission rate of the secure user is obtained. The internal eavesdropping rate is calculated based on the signal transmission rates of untrusted users and secure users; Determine the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper; calculate the external eavesdropping rate based on the signal-to-interference-and-noise ratio of the legitimate signal of the external eavesdropper; The confidentiality rate of the secure user is calculated based on the internal eavesdropping rate and the external eavesdropping rate.

6. The communication optimization method based on millimeter wave PD-NOMA according to claim 5, characterized in that The signal transmission rate of the untrusted user is: The signal transmission rate of the secure user is: The internal eavesdropping rate is: The external eavesdropping rate is: Where, Signal transmission rate for untrusted users; To decode confidential signals from untrusted users Signal-to-interference-and-noise ratio of untrusted users; To decode confidential signals from untrusted users Time, signal to interference and noise ratio of security users; Confidential signals for untrusted users; is an untrusted user; Signal transmission rate for security users; To decode the confidential signal of the security user Time, signal to interference and noise ratio of security users; To decode the confidential signal of the security user Signal-to-interference-and-noise ratio of untrusted users; A confidential signal for secure users; For security users; is the internal eavesdropping rate; is the external eavesdropping rate; is the signal-to-interference-and-noise ratio of the legitimate signal corresponding to the external eavesdropper; For external eavesdroppers; is the logarithmic function with base 2.

7. The communication optimization method based on millimeter wave PD-NOMA according to claim 6, characterized in that The confidentiality rate of a secure user is expressed as: in, Confidentiality rate for secure users; Used to indicate rate scaling, Signal transmission rate for security users; is the internal eavesdropping rate; is the external eavesdropping rate.

8. The communication optimization method based on millimeter wave PD-NOMA according to claim 1, characterized in that The optimization objective function is decomposed into three optimization sub-problems when solving, and the three optimization sub-problems are solved respectively using a convex optimization algorithm to obtain the optimal variable solution; The first optimization sub-problem is to optimize the precoding vector of the base station; the second optimization sub-problem is to optimize the reflection coefficient matrix of the active RIS; and the third optimization sub-problem is to optimize the power allocation of the receiving user.

9. A millimeter wave PD-NOMA-based communication optimization system, used to implement the millimeter wave PD-NOMA-based communication optimization method according to any one of claims 1 to 8, characterized in that: include: A wireless communication model construction module is used to construct an active RIS-assisted millimeter wave PD-NOMA system model. The millimeter wave PD-NOMA system model includes a base station, an active RIS, and receiving users. The receiving users include untrusted users, secure users, and external eavesdroppers. The untrusted users serve as internal eavesdroppers. A wireless communication transmission construction module establishes a first millimeter wave channel between the base station and an untrusted user or a secure user, and establishes a second millimeter wave channel between the base station and an external eavesdropper; the first millimeter wave channel and the second millimeter wave channel both include direct channels and indirect channels; a direct channel indicates direct communication between the base station and the receiving user, and an indirect channel indicates communication between the base station and the receiving user via an active RIS; The data acquisition module is used to obtain base station transmission parameters, active RIS parameters, and receiving user parameters according to the millimeter wave PD-NOMA system model; The communication optimization module constructs an optimization objective function based on the base station transmission parameters, active RIS parameters, and receiving user parameters, calculates the optimal variable solution based on the optimization objective function, and updates the millimeter wave PD-NOMA system model based on the optimal variable solution.

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