Design method of intelligent reconfigurable fading-enhanced secure wireless communication system

Abstract

The invention provides a method for designing an intelligent reconfigurable fading-enhanced secure wireless communication system, which comprises the following steps of: assuming that a multi-input single-output wireless communication system comprises a base station, a legal user and a passive eavesdropper positioned near the user, and assuming that the base station completely knows the channel state information of the eavesdropper; when the system is in a congestion environment, an obstacle exists between the base station and a legal user, and a direct link does not exist; an active reconfigurable intelligent surface is deployed to assist legal communication and construct reconfigurable intelligent fading to interfere with an eavesdropper so as to ensure transmission security; comprising the following steps: designing transmitting beam forming of confidential signals; transmitting beam forming is set to be w, so that the transmitting beam is aligned with a channel phase between the base station and the active reconfigurable intelligent surface, and energy of useful signals received by legal users is maximized; determining an expected signal-to-noise ratio of the legal user, and determining a channel keeping constant of the legal user according to the expected signal-to-noise ratio of the legal user; and designing a reflection coefficient of the active reconfigurable intelligent surface.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a design method for an intelligent reconfigurable fading-enhanced secure wireless communication system. Background Art

[0002] The openness of wireless networks makes wireless transmissions extremely vulnerable to eavesdropping and malicious attacks. How to ensure the security of wireless transmission has become an important issue. In existing literature, multi-antenna technology has become an effective way to improve system security because it can utilize spatial multiplexing gain. Most existing studies assume that the base station knows the channel state information (CSI) of the eavesdropper. However, the channel state information of the eavesdropper is not always available because they usually work in a passive state and their location or even their existence is unknown. In this case, artificial noise (AN) methods are usually used to interfere with the eavesdropper (see literature: Negi R, Goel S. Guaranteeing secrecy using artificial noise [J]. IEEE Transactions on Communications, 2008, 7 (6): 2180-2189). Specifically, a reference signal is sent together with the confidential information signal to interfere with the eavesdropper without affecting the legitimate receiver. However, the eavesdropper can obtain CSI by intercepting the training signal or using blind channel estimation technology, and then coherently detect the intercepted signal. When the eavesdropper has enough antennas, its equivalent channel will be better than that of the legitimate user. When the number of eavesdropper antennas is more than twice the number of transmitter antennas, the AN scheme will be completely ineffective (see reference: Khisti A, Wornell G W. Secure transmission with multiple antennas I: The MISOME wiretap channel [J]. IEEE Transactions on Information Theory, 2010, 56 (7): 3088-3104.). Therefore, we need to design a new method to prevent the eavesdropper from obtaining its own channel state information and can only use the statistical knowledge of the equivalent channel to detect information symbols in an incoherent way. In this way, the information leakage rate will be greatly reduced.

[0003] Active reconfigurable intelligent surfaces (RIS) is an emerging technology. It is a reflective planar array, each element of which is equipped with a reflective amplifier that can amplify the signal while adjusting the phase shift of the incident signal, thereby reconfiguring the wireless propagation environment. It has significant advantages in improving channel capacity and expanding communication coverage. Dong et al. also verified that deploying active reconfigurable intelligent surfaces in wireless systems can significantly improve security performance (see reference: Dong L, Wang HM, Bai J. Active reconfigurable intelligent surface aided secure transmission [J]. IEEE Transactions on Vehicular Technology, 2022, 71 (2): 2181-2186). In summary, active reconfigurable intelligent surfaces may be used to achieve reliable and secure transmission in scenarios where the eavesdropper's channel state information is unknown. Summary of the invention

[0004] According to the technical problems mentioned in the above background technology, a design method of an intelligent reconfigurable fading-enhanced secure wireless communication system is provided.

[0005] The technical means adopted by the present invention are as follows:

[0006] A design method for a secure wireless communication system with intelligent reconfigurable fading enhancement is proposed. Assume that a multiple-input single-output wireless communication system includes a base station, a legitimate user, and a passive eavesdropper located near the user. Assume that the base station is completely unaware of the channel state information of the eavesdropper.

[0007] The system is in a congested environment, there are obstacles between the base station and the legitimate users, and there is no direct link;

[0008] An active reconfigurable smart surface is deployed to assist legitimate communications while constructing a reconfigurable smart fading jammer to ensure transmission security;

[0009] The following steps are involved:

[0010] Step 1: Design the transmit beamforming of the confidential signal; set the transmit beamforming to w, aligning it with the channel phase between the base station and the active reconfigurable smart surface to maximize the energy of the useful signal received by the legitimate user;

[0011] Step 2: Determine the expected signal-to-noise ratio of the legitimate user, and determine the constant c of the legitimate user channel maintenance according to the expected signal-to-noise ratio of the legitimate user;

[0012] Step 3: Design the reflectance coefficient of the active reconfigurable smart surface.

[0013] Furthermore, the step 3 comprises the following steps:

[0014] Step 31: Design the reflection coefficients of M-1 elements except the i-th element;

[0015] Step 32: In order not to affect the communication quality of legitimate users, the reflection coefficient of the i-th element is determined by combining the reflection coefficients of the M-1 elements that have been determined, the constants maintained by the legitimate user channels, the transmit beamforming, the channel between the base station and the reconfigurable smart surface, and the channel between the reconfigurable smart surface and the user.

[0016] Furthermore, the selection principle of the i-th element is:

[0017]

[0018] Among them, g m represents the channel between the mth reflective element and the base station; the i-th element is selected to prevent the amplification factor of a certain reflective element from being too large and exceeding the amplification capacity of the active reconfigurable smart surface;

[0019] The signal received by the eavesdropper is expressed as:

[0020] in, represents the channel between the reconfigurable smart surface and the eavesdropper, n e represents additive white Gaussian noise.

[0021] Furthermore, in the wireless communication system, each channel is a flat fading channel, and the channel between the base station and the reconfigurable intelligent surface and the channel between the reconfigurable intelligent surface and the legitimate user are known.

[0022] Furthermore, the efficiency of the reconfigurable smart fading depends on the speed at which the reflective elements of the active reconfigurable smart surface change.

[0023] Furthermore, the reflection coefficient of the i-th element of the active reconfigurable smart surface is expressed as:

[0024]

[0025] Where c is the constant maintained by the legitimate user channel, w n represents the nth element of the transmit beamforming w, G jn represents the channel coefficient between the nth antenna of the base station and the jth element of the active reconfigurable smart surface, h r,j represents the channel between the jth element of the active reconfigurable smart surface and the legitimate user.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The present invention has strong robustness against the number of eavesdropper antennas in ensuring communication security. Although the increase in the number of eavesdropper antennas will slightly reduce the security of the system, even when the number of eavesdropper antennas increases to more than twice the number of base station antennas, the eavesdropper bit error rate still remains at a high level, and the system security can be guaranteed. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0029] Figure 1 It is a schematic diagram of the system architecture in the present invention;

[0030] Figure 2 Design a flow chart for the example of the present invention;

[0031] Figure 3 It is a schematic diagram of the positions of various components of the system in an example of the present invention;

[0032] Figure 4 is the received signal constellation diagram;

[0033] Figure 5 Simulation plot of eavesdropper bit error rate versus power budget of active reconfigurable smart surface;

[0034] Figure 6 Simulation diagram of the eavesdropper's bit error rate versus the horizontal distance between the base station and the reconfigurable smart surface;

[0035] Figure 7 Simulation diagram of the bit error rate of the eavesdropper versus the number of components of the active reconfigurable smart surface;

[0036] Figure 8 Simulation diagram of eavesdropper's bit error rate versus base station power budget;

[0037] Fig. 9 Simulation diagram of the eavesdropper's bit error rate versus the number of base station antennas. DETAILED DESCRIPTION

[0038] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0039] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0040] See also Figure 1 This embodiment provides a general reconfigurable intelligent fading enhanced secure wireless communication system applicable to the present invention. The base station is equipped with N t antennas arranged in a uniform linear array, serving a single-antenna legitimate user. There is a network with N e A passive eavesdropper with a single antenna tries to intercept confidential information sent by the base station to a legitimate user. Its location and channel state information are completely unknown to the base station. The system is in a congested environment. There are obstacles between the base station and the user, and there is no direct link. An active reconfigurable smart surface is deployed to establish a cascade link between the base station and the user. It is assumed that the channel state information between the base station and the reconfigurable smart surface and between the reconfigurable smart surface and the base station is known. It is assumed that the channels between the base station and the reconfigurable smart surface, between the reconfigurable smart surface and the user, and between the reconfigurable smart surface and the eavesdropper are all flat fading and block-invariant within a coherent fading block.

[0041] In order to ensure legal transmission, it is necessary to design an active reconfigurable smart surface reflection coefficient to enhance the cascade channel between the base station and the legal user. However, the eavesdropper is located near the user and the channel state information is highly correlated. The design that only enhances the quality of the legal channel will inevitably lead to an improvement in the quality of the eavesdropping channel. Therefore, the design principle of the active reconfigurable smart surface reflection coefficient should be to weaken the eavesdropper channel while ensuring the quality of legal transmission services. Based on the above considerations, an attempt is made to utilize the characteristics of the configurable propagation environment of the active reconfigurable smart surface to construct the link between the user and the eavesdropper as a fast fading channel, so that the eavesdropper will not be able to obtain the channel state information using blind channel estimation technology. When the eavesdropper only has the statistical information of the channel, it can only detect the information signal in an incoherent way, the decoding rate will be greatly reduced, and the system security will be guaranteed. In order to implement the above solution to enhance the transmission security of the communication system, please refer to the appendix. Figure 2 The specific secure communication implementation scheme flow chart, the specific steps are:

[0042] S1: First, design the signal transmission beamforming. The expression of the legitimate user receiving signal is:

[0043]

[0044] Among them, h r represents the channel between the reconfigurable smart surface and the legitimate user, represents additive white Gaussian noise. In order to maximize the energy of the useful signal received at the user, it is necessary to align the transmit beamforming w with the angle between the base station and the active reconfigurable smart surface. Assuming that the channel G between the base station and the active reconfigurable smart surface is a direct channel determined by their relative angle, the expression of the transmit beamforming w can be written as:

[0045] Where P b is the transmit power budget of the base station;

[0046] S2: Design legitimate user channels;

[0047] In order to ensure that the legitimate user channel is not affected by the fast fading and channel path loss caused by the active reconfigurable smart surface, so that it can decode the information from the base station even if the cascade channel state information cannot be obtained, the cascade channel between the base station and the user should be kept as a fixed constant c, that is, In this way, the signal received by the legitimate user is y=cs+n, and the user can directly decode it after receiving it;

[0048] The signal-to-noise ratio of a legitimate user is SNR = c 2 / σ 2 , so the value of the constant c is determined by the expected legitimate user SNR and user noise:

[0049] S3: Designing reflective elements for active reconfigurable smart surfaces The cascade channel of the eavesdropper is made to be in a fast fading state to prevent it from using blind channel estimation technology to obtain its own channel state information, and then perform coherent detection on the intercepted confidential information signal; at the same time, in order to ensure that the legitimate user channel is a fixed constant, a certain element of the active reconfigurable smart surface is designed to make its reflection coefficient change in a prescribed way to meet this requirement;

[0050] S3_01: The reflection coefficients of the M-1 elements of the active reconfigurable smart surface except the i-th element are randomly changed k times within a coherent fading block T:

[0051]

[0052] Among them, a m Indicated in Any real number in the range represents the amplification factor of the component. is the maximum amplitude that the predefined active reconfigurable smart surface can provide, θ m is any angle in the range [0,2π), Where t is the duration of a single information symbol;

[0053] In order to prevent the amplification factor of a certain component of the reconfigurable smart surface from being too large and exceeding the amplification capacity of the reconfigurable smart surface, the selection principle of i is the component subscript of the maximum signal incident on the reconfigurable smart surface:

[0054] S3_02: Design the amplification factor of the i-th element of the active reconfigurable smart surface;

[0055]

[0056] Where c is the constant of the legitimate user channel, w n represents the nth element of the transmit beamforming w, G jn represents the channel coefficient between the nth antenna of the base station and the jth element of the active reconfigurable smart surface, h r,j represents the channel between the jth element of the active reconfigurable smart surface and the legitimate user.

[0057] The amplification factor of the i-th element of the active reconfigurable smart surface depends on the constant c and the transmit beamforming w, the channel between the base station and the reconfigurable smart surface G, and the channel between the reconfigurable smart surface and the user h r , whose expression is:

[0058] The signal received by the eavesdropper can be expressed as:

[0059] in is the channel between the reconfigurable smart surface and the eavesdropper, n e represents additive white Gaussian noise, and the cascade channel between the base station and the user becomes an equivalent fast fading channel, which keeps changing within a coherent fading block. In this way, the eavesdropper will not be able to obtain channel state information through blind channel estimation technology, and can only detect the information signal incoherently through the statistical information of the channel, which greatly reduces the probability of successful decoding and ensures the transmission security of the system.

[0060] The above technical solution can effectively improve the transmission security of the wireless communication system. In order to prove the feasibility of the above technical solution, the following simulation results are given, in which the base station transmits a QPSK signal and the positions of the system components are as shown in the attached figure. Figure 3 shown.

[0061] Attached Figure 4 The constellation diagram of the received signal is displayed, from which it can be seen that the signals received by legitimate users can be easily distinguished, while the signals received by eavesdroppers are mixed together and difficult to distinguish, which greatly increases the security of the system.

[0062] Attached Figure 5 The curve of the bit error rate of the eavesdropper changing with the power budget of the active reconfigurable smart surface is given. Figure 5 It can be seen that the larger the power budget of the active reconfigurable smart surface, the greater the eavesdropper's bit error rate and the higher the system security.

[0063] Attached Figure 6 The curve of the eavesdropper’s bit error rate versus the horizontal distance between the base station and the reconfigurable smart surface is given. Figure 6 It can be seen that the closer the active reconfigurable smart surface is deployed to the base station, the stronger the interference to the eavesdropper will be. Therefore, in practical applications, the active reconfigurable smart surface should be deployed as close to the base station as possible.

[0064] Attached Figure 7 A curve of the bit error rate of the eavesdropper versus the number of elements on the reconfigurable smart surface is given. The more elements there are, the higher the bit error rate is, because more elements provide greater degrees of freedom, and it is more complicated for the eavesdropper to decode the information using beamforming.

[0065] Attached Figure 8 A curve of the eavesdropper's bit error rate versus the base station's power budget is given. It can be seen that the larger the base station's power budget, the stronger the interference to the eavesdropper and the greater the eavesdropper's bit error rate.

[0066] Attached Fig. 9 A curve of the eavesdropper's bit error rate versus the number of base station antennas is given. The more base station antennas there are, the greater the degree of freedom provided, which also increases the difficulty for the eavesdropper to decode the information.

[0067] By the attached Figure 5-9 It can be seen that the present invention has strong robustness against the number of eavesdropper antennas in ensuring communication security. Although the increase in the number of eavesdropper antennas will slightly reduce the security of the system, even if the number of eavesdropper antennas increases to more than twice the number of base station antennas, the eavesdropper bit error rate still remains at a high level, and the system security can be guaranteed.

[0068] The serial numbers of the above embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0069] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0070] In the several embodiments provided in this application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of the units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0071] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0072] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0073] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A design method for a secure wireless communication system with intelligent reconfigurable fading enhancement. Assume that a multiple-input single-output wireless communication system includes a base station, a legitimate user, and a passive eavesdropper located near the user. Assume that the base station is completely unaware of the channel state information of the eavesdropper. The system is in a congested environment, there are obstacles between the base station and the legitimate users, and there is no direct link; An active reconfigurable smart surface is deployed to assist legitimate communications while constructing a reconfigurable smart fading jammer to ensure transmission security; It is characterized by comprising the following steps: Step 1: Design the transmit beamforming of the confidential signal; set the transmit beamforming to w, aligning it with the channel phase between the base station and the active reconfigurable smart surface to maximize the energy of the useful signal received by the legitimate user; Step 2: Determine the expected signal-to-noise ratio of the legitimate user, and determine the constant c of the legitimate user channel maintenance according to the expected signal-to-noise ratio of the legitimate user; Step 3: Design the reflectance coefficient of the active reconfigurable smart surface.

2. The method for designing a secure wireless communication system with intelligent reconfigurable fading enhancement according to claim 1, characterized in that: The step 3 comprises the following steps: Step 31: Design the reflection coefficients of M-1 elements except the i-th element; Step 32: In order not to affect the communication quality of legitimate users, the reflection coefficient of the i-th element is determined by combining the reflection coefficients of the M-1 elements that have been determined, the constants maintained by the legitimate user channels, the transmit beamforming, the channel between the base station and the reconfigurable smart surface, and the channel between the reconfigurable smart surface and the user.

3. The method for designing a secure wireless communication system with intelligent reconfigurable fading enhancement according to claim 2, characterized in that: The selection principle of the i-th element is: Among them, g m represents the channel between the mth reflective element and the base station; the i-th element is selected to prevent the amplification factor of a certain reflective element from being too large and exceeding the amplification capacity of the active reconfigurable smart surface; The signal received by the eavesdropper is expressed as: in, represents the channel between the reconfigurable smart surface and the eavesdropper, n e represents additive white Gaussian noise.

4. The method for designing a secure wireless communication system with intelligent reconfigurable fading enhancement according to claim 1, characterized in that: In the wireless communication system, each channel is a flat fading channel, and the channel between the base station and the reconfigurable intelligent surface and the channel between the reconfigurable intelligent surface and the legal user are known.

5. The method for designing a secure wireless communication system with intelligent reconfigurable fading enhancement according to claim 1, characterized in that: The efficiency of the reconfigurable smart fading depends on the speed at which the reflective elements of the active reconfigurable smart surface change.

6. The method for designing a secure wireless communication system with intelligent reconfigurable fading enhancement according to claim 1, characterized in that: The reflection coefficient of the i-th element of the active reconfigurable smart surface is expressed as: Where c is the constant of the legitimate user channel, w n represents the nth element of the transmit beamforming w, G jn represents the channel coefficient between the nth antenna of the base station and the jth element of the active reconfigurable smart surface, h r,j represents the channel between the jth element of the active reconfigurable smart surface and the legitimate user.

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