CN117202171A

CN117202171A - Minimum safe rate resource allocation method for RIS (radio resource allocation system) auxiliary RSMA (RSMA) system

Info

Publication number: CN117202171A
Application number: CN202311122963.4A
Authority: CN
Inventors: 邓炳光; 伍志攀
Original assignee: Chongqing University of Post and Telecommunications
Current assignee: Chongqing University of Post and Telecommunications
Priority date: 2023-09-01
Filing date: 2023-09-01
Publication date: 2023-12-08

Abstract

The invention relates to a minimum safe rate resource allocation method for a RIS auxiliary RSMA system, belonging to the field of network security. Transceiver hardware impairments and eavesdroppers present in real-world communication systems are highly likely to significantly reduce the security performance of the communication system. Aiming at the problem, aiming at improving the utilization efficiency of system resources, taking the fairness of user rates into consideration, a minimum safe rate maximization scheme of the RIS auxiliary RSMA system under HIs is provided. After the original problem is simplified through variable substitution, the convex optimization methods such as alternating optimization, continuous convex approximation, penalty function and the like are used, the transmission precoding vector, public information security rate distribution and RIS phase shift are jointly optimized, and the minimum security rate of a user is maximized, so that the fairness of the user rate is effectively ensured, and the HIs resistance and confidentiality of the system are improved.

Description

Minimum safe rate resource allocation method for RIS (radio resource allocation system) auxiliary RSMA (RSMA) system

Technical Field

The invention belongs to the field of network security, and relates to a minimum security rate resource allocation method of a RIS (radio resource allocation system) auxiliary RSMA (reactive power management) system.

Background

With the landing of 5G businesses, people increasingly rely on wireless networks to transmit important information or private information, however, information leakage events occur frequently, and wireless secure communication has become an important problem for current and future wireless networks. Physical layer security (Physical Layer Security, PLS) is becoming a research hotspot in the industry as an effective solution for wireless secure communications. The PLS technology uses randomness and diversity of channels to weaken the signal reception intensity of AN Eavesdropper (Eve) by introducing Artificial Noise (AN) or a co-jammer, etc., thereby realizing information security transmission. However, these methods require complex processing of the signal by the transceiver to adapt the transmitted signal to the wireless environment changes, which can limit the safe transmission performance of the system.

Therefore, in order to cope with future flexible and complex communication scenarios and maintain communication security, the next-generation communication technology must find a new breakthrough, and recently, rate-splitting multiple access (Rate Splitting Multiple Access, RSMA) is widely focused by academia as a powerful wireless network transmission policy. RSMA handles by partially decoding the interference, partially treating it as noise, soft bridging spatial division multiple access (Space Division Multiple Access, SDMA) where the interference is totally noise, and Non-orthogonal multiple access (Non-Orthogonal Multiple Access, NOMA) where the interference is totally decoded. In AN RSMA wireless secure communication system, public information is not only useful information of users, but also can be used as AN AN interference eavesdropper, thereby improving system security and reducing hardware cost. Existing studies indicate that RSMA can significantly improve the security performance of a wireless communication system by jointly designing rate splitting and beamforming, and the achievable security and rate are higher compared with SDMA schemes and collaborative NOMA schemes.

At present, the research on the RIS auxiliary RSMA system is less, the aspects of the reachable speed and the energy efficiency are concentrated, and the existing research does not relate to the optimization problem of the speed fairness and the safety of the RIS auxiliary RSMA system user under HIs after searching. Patent application number CN202210798645.9, application date is 2022, 7 months and 7 days, discloses a RIS auxiliary safety communication method of a wireless energy-carrying RSMA network, but the influence of hardware damage on the safety performance of a system in an actual communication system is not considered, and the situation that the safety performance of the system is low due to the hardware damage of a transceiver can not be dealt with; patent application number CN202011211297.8, application date is 2020, 11 months and 3 days, discloses a power distribution method for maximizing and rate of a collaborative NOMA network under hardware damage, which does not consider fair distribution of resources among users and cannot meet the service quality requirements of all users. In summary, a method for maximizing resource allocation for minimum security rate of RIS assisted RSMA system user under hardware damage is provided.

The invention considers the influence of the transceiver HIs in the actual communication system, in order to further ensure the user rate fairness in the system, improve the HIs resistance capability and the physical layer security of the system, design a reasonable resource allocation strategy to maximize the performance of the system, and obtain the system through analysis and arrangement of related research at home and abroad, the research on the RIS auxiliary RSMA system is concentrated on the aspects of the reachable rate and the energy efficiency, and the existing research does not relate to the optimization problem of the user rate fairness and the security of the RIS auxiliary RSMA system under HIs, and the transceiver HIs and the link eavesdropping in the actual wireless communication system can greatly reduce the security performance of the system. In addition, the fairness of the user rate is used as an important performance index of the system, so that the fair allocation of resources among users of the wireless communication system can be ensured, and the transmission safety of the system can be improved. Therefore, the present invention designs a RIS-assisted RSMA transmission optimization scheme, establishes a Multi-Input Single-Output (MISO) Single-tap wireless communication system model of the RIS-assisted RSMA, aims at maximizing the minimum safe rate, considers the transceiver HIs, and models it as gaussian distortion noise. Meanwhile, considering the influence of AN eavesdropper on system safety, weakening the signal receiving intensity of the eavesdropper by taking public streams as AN, and constructing joint optimization problems about the transmission precoding vector, public information safety rate distribution and RIS phase shift under the constraints of maximum transmission power of a base station, minimum safety rate of a user and RIS phase shift. Finally, the influence of hardware damage on the system safety performance and the influence of changing the number of RIS reflecting units on the minimum safety rate are simulated.

Disclosure of Invention

In view of the above, the present invention aims to provide a minimum safe rate resource allocation method for an RIS-assisted RSMA system.

In order to achieve the above purpose, the present invention provides the following technical solutions:

a method for minimum safe rate resource allocation for a RIS-assisted RSMA system, the method comprising the steps of:

the system model consists of a base station, an RIS and K single-antenna legal users, and meanwhile, a single-antenna eavesdropper tries to eavesdrop on the information transmitted to the legal users, and the influence of the hardware damage of a receiving and transmitting end on the safety performance of the system is considered. The method comprises the following steps:

101. considering a minimum safe rate maximization resource allocation model of the RIS auxiliary RSMA system under a hardware damage condition, constructing an optimization problem, and judging whether the constructed problem has a feasible solution or not;

102. after simplifying the original problem by variable replacement (namely, introducing auxiliary variables to simplify and replace the original objective function), decomposing the problem into two sub-problems based on an alternative optimization algorithm to optimize the problem, and simultaneously increasing constraint containing the introduced variables; specifically, a transmission precoding vector and a public information safety rate allocation optimization sub-problem are solved through continuous convex approximation, and a RIS phase shift optimization sub-problem is solved through continuous convex approximation and a penalty function method;

103. then solving the convex optimization problem after the equivalent transformation in step 102, and solving the transmission precoding vector w and the public information security rateAnd RIS phase shift vector e, resulting in a maximum and minimum safe rate based on all constraints.

For the downlink of the RSMA communication system, the transmitting end transmits the message W of the user k _k Split into public parts W _c,k And private part W _p,k And share all users in common part W _c,1 ,…,W _c,k Packaged as public message W _c . Subsequently, W _c Encoded as a public data stream s _c Private message W of user k _p,k Encoded as a private data stream s _k Wherein user k divides decoding s _k In addition, all that is needed is to decode s _c . For ease of computation, these data streams are combined into s, s=s _c ,s ₁ ,s ₂ ,…,s _K ^T And satisfy E { ss ^H }＝I _K+1 . Considering the influence of HIs on the base station, transmitting signalsRepresented as

Wherein w=w _c ；w ₁ ；…；w _K Is an integrated pre-coding vector that is used to generate the data,respectively public data stream s _c User k private data stream s _k W should satisfy the power constraint w ^H w≤P ^max ，P ^max Is the maximum transmit power of the base station. Let->Is Gaussian distortion noise caused by the base station HIs, which can be further expressed as +.>Wherein mu _t And the value of not less than 0 is HIs factor of the transmitting end, and the ratio of the transmitting distortion noise power to the transmitting signal power is represented.

Considering the RIS auxiliary transmission scheme and the influence of the receiving end HIs, the received signal y of user k _k Can be expressed as

Wherein,phase matrix representing RIS reflection model, e _m Reflection coefficient for the mst element of RIS; n is n _k Is additive Gaussian white noise at user k, satisfying +.>δ _k Is Gaussian distortion noise caused by receiving end HIs, which is distributed as +>μ _r And the equal to or greater than 0 is the HIs factor of the receiving end, namely the ratio of the received distorted noise power to the undistorted received signal power.

Equivalent reflection coefficient vector of cascade channel and direct channelAnd equivalent user k channel gain matrix->Substituting formula (5), received signal y _k Re-expressed as

The consideration herein assumes that the system cannot obtain the entire state information of the eavesdropper, and considers the worst case that the eavesdropper uses a high quality eavesdropping device, is not affected by the receiving end HIs, and the eavesdropper receives the signal y _e Represented as

y _e ＝e ^H Y _e f+n _e (4)

Wherein,is an equivalent eavesdropper channel gain matrix, and the eavesdropper AWGN satisfies the following conditions

At the receiving end, the steps of restoring the original information of the user k are as follows: first, all private data streams are treated as noise decoded public data stream s _c Obtaining public informationFrom->Extracting part of exclusive oneself->Then use the serial interference cancellation technique to remove->Eliminating; subsequently, the other user private data stream s _j J+.k is considered as noise decoded private data stream s _k Obtain private information->Finally, will->And->Is combined into->Thus, the signal-to-interference-and-noise ratio of user k decoding the public data stream is expressed as

Wherein phi is _c,k (w, e) is the total interference signal of user k decoding the common data stream, expressed as

The first term of the formula is the interference of private data streams of all users, the second term is the noise interference at the base station HIs, the third, fourth and fifth terms are the received signal, the noise at the base station HIs, the noise interference at the receiving end HIs generated by the AWGN at the user due to the receiving end HIs, and the sixth term is the AWGN.

User k successfully decodes the public data stream s _c Rear slave y _k Subtracting the reconstruction term e from ^H Y _k w _c s _c . User k then decodes the private data stream s _k Signal-to-interference-and-noise ratio representation of (c)Is that

Wherein phi is _p,k (w, e) decoding the total interference signal of the private data stream for user k, expressed as

Thus, at a unit bandwidth, the achievable rates for decoding the public and private data streams by user k are respectively

To ensure that the public data stream is successfully decoded by each user, the public information actually reaches a rate R _c Satisfy the following requirementsEach user k will be assigned R _c Part r of (2) _c,k As its public information reachable rate, r _c,k Satisfy the following requirementsThrough the signal processing steps, the reachable rate of the k public information of the user is r _c,k The reachable rate of the private information is R _p,k 。

To prevent eavesdroppers from successfully decoding the public data stream, the decoding public data stream rate of each user cannot be lower than that of the eavesdropper, so that R _c,e Indicating the rate at which eavesdroppers have access to public information, R _c ≥R _c,e This is true. The public data stream may act as AN, to reduce the achievable rate at which AN eavesdropper decodes the legitimate user private data stream,and the signal-to-interference-and-noise ratios of the eavesdropper decoding the public data stream and the user k private data stream are respectively expressed as

Wherein phi is _c,e (w,e)、Φ _e,k (w, e) decoding the total interference signal of the public data stream and the private data stream of user k, respectively, for an eavesdropper, expressed as

Thus, the achievable rate of an eavesdropper decoding the public data stream and the achievable rate of the user k private data stream are respectively

R _c,e ＝log ₂ (1+γ _c,e ) (15)

Ultimately, the achievable safe rate for user k is

Wherein x is ⁺ ＝max{x,0}，Indicating the security rate of public information assigned to user k, < >>Not negative, so R _c,e ≤R _c Still, it is true.

Optimizing a transmit precoding vector, a public information security rate allocation, and a RIS phase shift under the constraints of a base station maximum transmit power, a user minimum security rate, and the RIS phase shift to maximize a user minimum reachable security rate in consideration of user rate fairness, the optimization problem being expressed as

C3:w ^H w≤P ^max ,

C5:e∈S,

Wherein,the public information security rate allocation vector is used for determining the public information security rate allocated to each user; constraint C1 ensures that public data streams can be successfully decoded by all legitimate users and cannot be decoded by eavesdroppers; constraint C2 ensures that the private information rate of each user is greater than the private information rate of an eavesdropper; c3 is the maximum transmit power constraint of the base station; constraint C4 ensures that the security rate of public information assigned to each user is not negative; c5 is RIS phase shift constraint, wherein the first M elements in e are reflection coefficients of each reflection unit of RIS, satisfy the mode 1 constraint, and the last element e _M+1 Representing the direct link reflection coefficient, fixed at 1, and therefore,/>

because the optimization variables w and e in the P1 are coupled, and the objective function, the constraint C1 and the constraint C2 are not convex, the problem is difficult to directly solve, and therefore, the AO method is adopted in the text to decouple the optimization variables w and e in the P1, and the sub-problem of dividing the P1 into 2 convex is solved. First, a relaxation variable is introducedAnd->Relaxing constraints (5), (7), (9), (10), (11), (12), (15), (16)

Then, an auxiliary variable t and a private information security rate vector are introducedConverting the original optimization problem P1 into P2, i.e

s.t.C3,C5,(18)-(21)

P2 is still not convex, and the AO method is used to turn P2 into two sub-problems. First, e is fixed, a transmission precoding vector w and a public information security rate allocation vector are optimizedPrivate information security rate vector->P2 is restated as P3, i.e

s.t.C3,C6,C7,C8,C9,(18)-(21)

At this point, the non-convex constraints (18), (20), (21) render P3 still non-convex, which may be approximated using a first order Taylor expansion linearity using an SCA-based iterative optimization algorithm to render P3 solvable. To facilitate the first-order Taylor expansion at the variable w of equations (18), (21), a simple transformation is performed using equation (22), letting Substitution is further transformed, and first-order Taylor expansion is performed at the variable. Equations (23), (24), (25) are obtained.

Thus, the solution obtained using the n-1 th iterationSolving P4:

s.t.C3,C6,C7,C8,C9,(19),(23)-(25)

to this end, the convex problem P4 may be solved using a CVX toolbox.

Given w,Residual variable +.>So as to obtain a convergence solution of the phase shift optimization sub-problem and improve the convergence performance of the optimization algorithm. Phase shift optimization sub-problem P5 is expressed as

s.t.C5,(19)-(21)

Likewise, P5 is not convex. Order theW _T ＝W _c +W _S Substituting (18) and (21), and performing first-order Taylor expansion to obtain formulas (26) and (27). Meanwhile, the first-order taylor expansion is performed on (21) to obtain a formula (28):

for the modulo-1 constraint C5, a penalty function is employed herein: (1) Rewriting C5 toC14; (2) Introducing penalty termsTo P5 objective function. Thus, P5 converts to P6:

s.t.(19),(26)-(28),C10,C11,C12,C13

wherein Q > 1 is a penalty factor, but the convex term |e is present in the P6 objective function _m | ² The P6 objective function is required to be set atWhere a first order taylor expansion is performed, P6 is restated as P7:

s.t.(19),(26)-(28),C10,C11,C12,C13,C14

p7 is a convex problem that can be solved using the CVX toolbox.

Outputting the optimal transmission precoding vector w of each round according to the two sub-problems ^opt Optimal RIS phase shift vector e ^opt Optimal public information security rate allocationSubstituting P2 to obtain minimum safe rate t ^opt Until convergence yields a solution to the problem.

The invention has the beneficial effects that:

the invention considers the situation that the hardware damage and the eavesdropper of the transceiver exist in the real communication system, and researches the minimum safety rate maximization problem of the RIS auxiliary RSMA system under the condition of hardware damage. Since the original problem is a non-convex one, how to give the optimal solution is a problem.

The invention considers the influence of transceiver hardware damage and eavesdroppers on the security performance of an actual communication system, and aims at maximizing the minimum security rate by using RSMA as a transmission strategy, and considers the transceiver HIs and models the transceiver as Gaussian distortion noise. Meanwhile, considering the influence of AN eavesdropper on system safety, weakening the signal receiving intensity of the eavesdropper by taking public streams as AN AN, constructing a joint optimization problem about transmitting precoding vectors, public information safety rate distribution and RIS phase shift under the constraint of maximum transmitting power of a base station, minimum safety rate of a user and RIS phase shift, converting AN original non-convex problem into two convex sub-problems through auxiliary variable replacement and AO alternating optimization methods, solving the two convex sub-problems, optimizing the transmitting precoding vectors, the public information safety rate distribution vectors and the RIS phase shift, and obtaining the minimum safety rate of the system under all constraint conditions.

Compared with other traditional RIS-based auxiliary RSMA systems, the method has the advantages of simplicity in solution and low complexity. From the physical layer perspective, the user rate fairness is guaranteed, and the hardware damage resistance and confidentiality of the system are improved. The method and the device for controlling the wireless communication system simultaneously consider the influence of the hardware damage of the transceiver and the eavesdropper in the actual communication system on the system safety performance innovatively, so that the method and the device are more in line with the actual situation, and have good feasibility.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.

Drawings

For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:

FIG. 1 is a RIS assisted RSMA communication system model under hardware impairment conditions provided by the present invention;

FIG. 2 shows the minimum safe rate of the system at different base station transmit powers according to the present invention and the comparison scheme;

FIG. 3 is a graph showing the minimum safe rate of the system for different RIS reflection unit numbers for the present invention and the comparative scheme;

FIG. 4 is a flowchart of a method for maximizing minimum safe rate of a RIS assisted RSMA system under hardware impairment according to one embodiment of the present invention.

Detailed Description

Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.

Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.

The technical scheme for solving the technical problems is as follows:

a minimum safe rate maximization resource allocation method based on an RIS auxiliary RSMA system under the condition of hardware damage. Which comprises the following steps:

the first step: calculating the feasibility of the problem, and ensuring that the problem has a feasible solution under the constraint of the problem;

and a second step of: the channel is subject to Rician fading, and assuming that the channel state information is known, the transmitting end and the receiving end of the legitimate user are affected by hardware impairments, and the worst case is considered, i.e. the eavesdropper is not affected by the hardware impairments of the receiving end.

And a third step of: the minimum safe rate maximization problem of the RIS auxiliary RSMA system under the condition of hardware damage is expressed as follows:

C3:w ^H w≤P ^max ,

wherein,the public information security rate allocation vector is used for determining the public information security rate allocated to each user; constraint C1 ensures that public data streams can be successfully decoded by all legitimate users and cannot be decoded by eavesdroppers; constraint C2 ensures that the private information rate of each user is greater than the private information rate of an eavesdropper; c3 is the maximum transmit power constraint of the base station; constraint C4 ensures that the security rate of public information assigned to each user is not negative; c5 is RIS phase shift constraint, wherein the first M elements in e are reflection coefficients of each reflection unit of RIS, satisfy the mode 1 constraint, and the last element e _M+1 Indicating the direct link reflection coefficient, fixed to 1, therefore,/->

Fourth step: introducing an auxiliary variable t and a private information security rate vectorConverting the original optimization problem P1 into P2, i.e

s.t.C3,C5,(18)-(21)

Fifth step: for transmitting pre-coding vector w and public information safety rate allocation vectorPrivate information security rate vector->Optimizing, fixing e, P2 is re-expressed as P3, i.e

s.t.C3,C6,C7,C8,C9,(18)-(21)

After converting the non-convex constraint to convex, the problem P3 is converted to a convex optimization problem P4:

s.t.C3,C6,C7,C8,C9,(19),(23)-(25)

sixth step: optimizing RIS phase shift e, fixing transmitting precoding vector w and public information safety rate distribution vectorPrivate information security rate vector->Problem P3 turns to P5:

s.t.C5,(19)-(21)

for the constraint C5 of the model 1, a penalty function method is adopted, and penalty items are introduced after the C5 is rewritten into C14To P5 objective function. Thus, P5 converts to P6:

s.t.(19),(26)-(28),C10,C11,C12,C13

p6 objective function atWhere a first order taylor expansion is performed, P6 is restated as P7:

s.t.(19),(26)-(28),C10,C11,C12,C13,C14

seventh step: updating the minimum safety rate t, wherein the method comprises the following specific steps of: transmitting precoding vector w and public information safety rate allocation vector obtained according to optimization of the first two sub-problemsPrivate information security rate vector->The RIS phase shift vector e is alternately iterated to obtain the minimum safe rate t of the system ^opt 。/>

In this embodiment, fig. 1 is a schematic diagram of a preferred embodiment of the present invention based on an RIS-assisted RSMA system model, in which a base station transmits signals directly to a legitimate user through wireless transmission, or may reflect signals to a legitimate user through an RIS. While a single antenna eavesdropper present in the system would eavesdrop on legitimate user information. Fig. 2 shows the relationship between the minimum safe rate and the maximum transmit power of each scheme under different HIs, where the parameters n=2, m=20, k=2, and user 1 and user 2 are located at (0, 20), (50, 0). Simulation results show that the minimum safety rate of each scheme increases with the increase of the transmission power, because the base station can provide more power for information transmission due to the increase of the transmission power, so that the minimum safety rate is improved. Conversely, the minimum safe rate for each scheme decreases as the HIs factor increases, because HIs causes distortion noise power to be proportional to the transceiver signal power, and the higher the base station transmit power, the faster the transceiver HIs distortion noise power increases resulting in increased decoding interference and reduced user received SINR. As can be seen from fig. 2, the minimum safe rate for SDMA schemes tends to be the upper limit in the-5 dBm to 20dBm power range first, while none of the remaining three schemes tends to be the upper limit due to the RSMA flexible interference management strategy and the RIS reconfiguration wireless environment characteristics. In addition, when the transmission power is sufficiently large (P ^max > 20 dBm), the HIs effect on the received SINR for the legitimate user is much higher than for an eavesdropper, and the minimum safe rate for the system will also approach the upper limit, since it is assumed here that the eavesdropper is not affected by the receiving end HIs. As expected, the protocol herein was clearly superior to the other protocols at the same HIs. In particular, the achievable minimum safe rate of the RSMA transmission scheme is higher than the achievable minimum safe rate of the SDMA transmission scheme, the achievable minimum safe rate of the RIS assistance scheme is higher than the achievable minimum safe rate of the no RIS assistance scheme, because the design optimization of the transmit precoding based on RSMA can achieve flexible and efficient interference management, i.e.The user public information can reduce the SINR of an eavesdropper and improve the signal receiving quality of legal users, thereby improving the PLS of the system. Furthermore, the quality of the wireless channel can be effectively improved by adjusting the phase shift of the RIS reflection unit, the receiving power of legal user signals is enhanced, and the signal strength of an eavesdropper is weakened. Numerical results show that the proposed scheme has obvious advantages in improving the HIs resistance and confidentiality of the system compared with the RSMA scheme and the SDMA-RIS scheme under the condition of the same HIs. FIG. 3 is a graph showing minimum safe rate versus number of RIS reflecting units for each scenario at different HIs, where P ^max =20 dBm. As can be seen from fig. 3, as the number of RIS reflection units increases, so does the minimum safety rate of the RIS auxiliary system. This is because increasing the number of RIS reflecting units provides more transmission paths for the signal, and by adjusting the phase shift of the RIS reflecting units, the directivity of the beam is stronger, reducing the information revealed to an eavesdropper, further improving the minimum security rate of the system. Although the transceiver HIs distortion noise reduces the reflection beamforming gain from the RIS, the achievable minimum safe rate for the RSMA-RIS scheme is better than the SDMA-RIS scheme, regardless of HIs. FIG. 4 is a flowchart of a method for maximizing minimum safe rate of a RIS assisted RSMA system under hardware impairment according to one embodiment of the present invention.

Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.

Claims

1. A minimum safe rate resource allocation method of an RIS auxiliary RSMA system comprises a base station, an RIS and a plurality of single-antenna legal users, wherein the base station transmits information to the single-antenna legal users through a direct link and a cascade link, and a single-antenna eavesdropper tries to eavesdrop the information transmitted to the legal users; wherein, the RIS reflection unit set M= {1, …, M }, M is not less than 1, the user set kappa= {1, …, K }, K is not less than 2, characterized in that the method comprises the following steps:

101. initializing the maximum transmitting power of a base station, the minimum safe rate of users, HIs coefficients of a transmitting end and a receiving end and the number of users, and establishing a mathematical model for the original safe rate optimization problem to obtain that the original optimization problem is a non-convex problem;

102. after simplifying the original problem through variable replacement, decomposing the problem into two sub-problems based on an alternative optimization algorithm to optimize, wherein the variable replacement is to introduce auxiliary variables to simplify and replace the original objective function, and meanwhile, the constraint containing introduced variables is increased; specifically, a transmission precoding vector and a public information safety rate allocation optimization sub-problem are solved through continuous convex approximation, and a RIS phase shift optimization sub-problem is solved through continuous convex approximation and a penalty function method;

103. then, solving the convex optimization problem after the equivalent transformation in step 102 by using an interior point method, and solving the transmission precoding vector w and the public information security rateAnd the RIS phase shift vector e, obtaining the maximum safety rate based on all constraint conditions, and carrying out resource allocation.

2. The method for minimum safe rate resource allocation for RIS-assisted RSMA system as set forth in claim 1, wherein channel state information of said system is known, and channel gains of BS-RIS, BS-user k, BS-eavesdropper, RIS-user k, RIS-eavesdropper are expressed as

For the downlink of the RSMA communication system, the transmitting end transmits the message W of the user k _k Split into public parts W _c,k And private part W _p,k And share all users in common part W _c,1 ,…,W _c,k Packaged as public message W _c The method comprises the steps of carrying out a first treatment on the surface of the Subsequently, W _c Encoded as a public data stream s _c Private message W of user k _p,k Is knitted and wovenThe code is a private data stream s _k Wherein user k divides decoding s _k In addition, all that is needed is to decode s _c The method comprises the steps of carrying out a first treatment on the surface of the For ease of computation, these data streams are combined into s, s=s _c ,s ₁ ,s ₂ ,…,s _K ^T And satisfy E { ss ^H }＝I _K+1 The method comprises the steps of carrying out a first treatment on the surface of the Considering the influence of HIs on the base station, transmitting signalsDenoted as->Wherein w=w _c ；w ₁ ；…；w _K Is an integrated precoding vector, ">Respectively public data stream s _c User k private data stream s _k W should satisfy the power constraint w ^H w≤P ^max ，P ^max Maximum transmit power for the base station; let->Is Gaussian distortion noise caused by a base station HIs, and the power of each antenna distortion noise is proportional to the power of a transmitted signal and is expressed asWherein mu _t And the value of not less than 0 is HIs factor of the transmitting end, and the ratio of the transmitting distortion noise power to the transmitting signal power is represented.

3. The method for allocating minimum safe rate resources of a RIS-assisted RSMA system according to claim 2, wherein a mathematical model of a maximization problem is established for the minimum safe rate of the user, and the maximization objective function is:

P1:

s.t.C1:

C2:

C3:w ^H w≤P ^max ,

C4:

C5:

wherein,r is the safe rate of the user _c R is the minimum security rate for decoding public information between users _c,e Secure rate of decoding public information for eavesdroppers, R _p,k Secure rate of decoding private information for user k, R _k,e Decoding the security rate of the private information of the user k for the eavesdropper; />The public information security rate allocation vector is used for determining the public information security rate allocated to each user; constraint C1 ensures that public data streams can be successfully decoded by all legitimate users and cannot be decoded by eavesdroppers; constraint C2 ensures that the private information rate of each user is greater than the private information rate of an eavesdropper; c3 is the maximum transmit power constraint of the base station; constraint C4 ensures that the security rate of public information assigned to each user is not negative; c5 is RIS phase shift constraint, wherein the first M elements in e are reflection coefficients of each reflection unit of RIS, satisfy the mode 1 constraint, and the last element e _M+1 Representing the direct link reflection coefficient, fixed at 1, < >>

4. A method for allocating minimum safe rate resources of a RIS-assisted RSMA system according to claim 3, wherein the variable substitution, i.e. the introduction of an auxiliary variable, simplifies the substitution of the original objective function by: introducing relaxation variablesAnd->Relaxation problem constraints:

wherein, gamma _c,k 、γ _p,k 、γ _c,e 、γ _k,e Decoding public information of the user k, decoding private information of the user k and decoding public information of an eavesdropper respectively, and decoding the signal-to-interference-and-noise ratio of the private information of the user k by the eavesdropper; then, an auxiliary variable t and a private information security rate vector are introducedThe original optimization problem is converted into the following optimization problems:

P2:

s.t.C3,C5,(1)-(4)

C6:

C7:

C8:

C9:

p2 is still not convex, and the method adopts the AO method to solve P2, and the solving steps are as follows: fixed e, optimizing the transmitted precoding vector w and the public information security rate allocation vectorPrivate information security rate vector->Fix w, & gt>Optimizing the phase shift vector e; alternating until t converges and a solution to the problem is obtained.

5. The method for minimum safe rate resource allocation for RIS-assisted RSMA system as set forth in claim 4, wherein said optimizing said transmit precoding vector w, said common information safe rate allocation vectorPrivate information security rate vectorThe method comprises the following steps:

the fixed phase shift vector e, P2 is restated to be P3, i.e

P3:

s.t.C3,C6,C7,C8,C9,(1)-(4)

The non-convex constraints (1), (3), (4) render P3 non-convex, which is linearly approximated using a first-order Taylor expansion with an SCA-based iterative optimization algorithm, to facilitate the first-order Taylor expansion at the constraints (1), (3), transformed with the following equation

Then, the non-convex problem P3 turns into a convex problem P4:

P4:

s.t.C3,C6,C7,C8,C9,(2),(5)-(10)

given e, P4 is a convex problem solved by the convex optimization tool box CVX.

6. The method for allocating minimum safe rate resources of a RIS-assisted RSMA system according to claim 5, wherein the optimized phase shift vector e is specifically:

given w,In the case of (2) introducing the residual variable +.>So as to obtain a convergence solution of the phase shift optimization sub-problem and improve the convergence performance of an optimization algorithm; phase shift optimization sub-problem P5 is expressed as

P5:

s.t.C5,(1)-(4)

C10:

C11:

C12:

C13:

Likewise, P5 is not convex; order the W _T ＝W _c +W _S Substituting and then performing first-order Taylor expansion on the constraints (1), (3) and (4):

for constraint C5 of the model 1, a penalty function method is adopted, and a penalty term is introduced after C5 is rewritten into C14The objective function to P5 converts P5 to P6:

P6:

000000000000-(16),C10,C11,C12,C10

C14:

wherein Q > 1 is a penalty factor, and the P6 objective function has a convex term |e _m | ² P6 objective function is set inPerforming first-order Taylor expansion, and converting P6 into P7:

P7:

s.t.(2),(11)-(16),C10,C11,C12,C13,C14

solving a convex problem P7 by using a CVX toolbox;

outputting an optimal transmission precoding vector w according to the P4 and the P5 ^opt Optimal RIS phase shift vector e ^opt Optimal public information security rate allocationUpdating the minimum safe rate until convergence to solve the problem t ^opt 。