Pilot frequency sending method and device and storage medium

Abstract

The embodiment of the invention provides a pilot frequency sending method and device and a storage medium, relates to the technical field of communication, and is used for improving the security of a key. The method comprises the following steps: acquiring an estimated value of a first channel and an estimated value of a second channel; the first channel is a channel between the sending end and a first receiving end, and the second channel comprises a channel between the sending end and the intelligent metasurface and a channel between the intelligent metasurface and the first receiving end; a first pilot signal is obtained based on the estimated value of the first channel and the estimated value of the second channel, the first pilot signal is used for inhibiting reception of a second pilot signal by a second receiving end, and the second pilot signal is used for the first receiving end to determine a key shared with the sending end; and transmitting the first pilot signal and the second pilot signal.

Description

Technical Field

[0001] The present disclosure relates to the field of communication technologies, and in particular, to a pilot sending method, apparatus, and storage medium. Background Art

[0002] Physical layer secret key generation (SKG) technology extracts keys from the wireless channel characteristics of legitimate communication parties, has a relatively low implementation complexity, is suitable for resource-constrained electronic devices, and is an important part of the endogenous security technology. SKG technology relies on the reciprocity, time-variance, and spatio-temporal uniqueness of the wireless channel, and has relatively high requirements for the quality of the wireless channel. However, the locations of many small and medium-sized electronic devices are relatively fixed, and the surrounding environment changes relatively little. In a quasi-static scenario, the wireless channel remains nearly constant over time, and can only provide limited randomness, which cannot meet the high-quality requirements of SKG for the wireless channel, resulting in a relatively low secret key rate (SKR) and poor randomness. A reconfigurable intelligent surface (RIS) consists of a passive array structure and a controller, and can adjust the reflection coefficient or amplitude of the reflected signal within the fastest 1 us, thereby realizing intelligent configuration of the wireless channel. For a quasi-static scenario, RIS can regulate the reflected signal at a high frequency, which is one of the effective measures to synthesize a dynamic wireless channel with high entropy. Therefore, RIS can be applied to the key generation process in a quasi-static scenario.

[0003] However, in the key generation method assisted by RIS, the channel information obtained by the eavesdropper includes two parts: exactly the same sub-reflection channels and spatially correlated composite channels. Compared with the classical point-to-point key generation, the eavesdropper has a greater negative impact on the secret key rate (SKR), resulting in relatively low security of the key. Summary of the Invention

[0004] Embodiments of the present disclosure provide a pilot sending method, apparatus, and storage medium for improving the security of keys.

[0005] To achieve the above object, the present disclosure adopts the following technical solutions.

[0006] In a first aspect, a pilot sending method is provided, which is applied to a sending end. The method includes:

[0007] Obtain an estimated value of a first channel and an estimated value of a second channel; the first channel is the channel between the sending end and a first receiving end, and the second channel includes the channel between the sending end and the reconfigurable intelligent surface and the channel between the reconfigurable intelligent surface and the first receiving end;

[0008] Based on the estimated value of the first channel and the estimated value of the second channel, a first pilot signal is obtained. The first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end, and the second pilot signal is used by the first receiving end to determine the shared key with the sending end.

[0009] Transmit the first pilot signal and the second pilot signal.

[0010] In a second aspect, a pilot signal transmitting device is provided, which is applied to a sending end. The device includes:

[0011] An obtaining unit, configured to obtain the estimated value of the first channel and the estimated value of the second channel; the first channel is the channel between the sending end and the first receiving end, and the second channel includes the channel between the sending end and the intelligent metasurface and the channel between the intelligent metasurface and the first receiving end;

[0012] A processing unit, configured to obtain a first pilot signal based on the estimated value of the first channel and the estimated value of the second channel. The first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end, and the second pilot signal is used by the first receiving end to determine the shared key with the sending end;

[0013] A transmitting unit, configured to transmit the first pilot signal and the second pilot signal.

[0014] In a third aspect, a communication device is provided, including: a processor and a memory; the memory stores instructions executable by the processor; when the processor is configured to execute the instructions, the communication device implements the method provided in the first aspect as described above.

[0015] In a fourth aspect, a computer-readable storage medium is provided. The computer-readable storage medium stores computer instructions, and when the computer instructions run on a computer, the computer executes the method provided in the first aspect as described above.

[0016] In a fifth aspect, a computer program product including computer instructions is provided. When the computer instructions run on a computer, the computer executes the method provided in the first aspect as described above.

[0017] In the embodiments of the present disclosure, the first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end. The first pilot signal is obtained based on the estimated values of the first channel and the second channel, and both the estimated value of the first channel and the estimated value of the second channel are related to the first receiving end. Therefore, while the first pilot signal can interfere with the reception of the second pilot signal by the second receiving end, it will not affect the reception of the second pilot signal by the first receiving end. Thus, when the first pilot signal and the second pilot signal are transmitted, it can ensure that the first receiving end can normally receive the second pilot signal to determine the shared key with the transmitting end, while suppressing the reception of the second pilot signal by the second receiving end, preventing information leakage, enhancing the security of the key, and thus enhancing the SKR. Description of the Drawings

[0018] The drawings are used to provide a further understanding of the technical solutions of the present invention, and constitute a part of the specification. Together with the embodiments of the present disclosure, they are used to explain the technical solutions of the present invention, and do not constitute a limitation to the technical solutions of the present invention.

[0019] Figure 1 Schematic structural diagram of a communication system provided by an embodiment of the present disclosure;

[0020] Figure 2 Schematic flow diagram of a pilot transmission method provided by an embodiment of the present disclosure;

[0021] Figure 3 Schematic flow diagram of another pilot transmission method provided by an embodiment of the present disclosure; [[ID=??]]

[0022] Figure 4 Schematic diagram of time slot allocation within one coherence time provided by an embodiment of the present disclosure;

[0023] Figure 5 Schematic diagram of steps executed within one coherence time provided by an embodiment of the present disclosure;

[0024] Figure 6 Schematic diagram of a curve of SKR varying with the channel correlation coefficient provided by an embodiment of the present disclosure;

[0025] Figure 7 Schematic diagram of a curve of SKR varying with the pilot power ratio provided by an embodiment of the present disclosure;

[0026] Figure 8 Schematic diagram of a curve of SKR varying with the number of RIS reflection elements provided by an embodiment of the present disclosure;

[0027] Figure 9 Schematic diagram of a curve of SKR varying with the pilot length provided by an embodiment of the present disclosure;

[0028] Figure 10 Note: There seems to be a missing ID in the original text where it says " ", which is marked as "??" in the translation for now.Schematic diagram of the composition of a pilot transmission device provided by an embodiment of the present disclosure;

[0029] Figure 11 Schematic diagram of the structure of an electronic device provided by an embodiment of the present disclosure. Detailed implementation manners

[0030] Next, the technical solutions in the embodiments of the present disclosure will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present disclosure.

[0031] Unless otherwise required by the context, throughout the specification and claims, the term "comprise" and its other forms, such as the third-person singular form "comprises" and the present participle form "comprising", are interpreted as open and inclusive meanings, that is, "including, but not limited to". In the description of the specification, the terms "one embodiment", "some embodiments", "exemplary embodiments", "example", "specific example" or "some examples", etc. are intended to indicate that the specific features, structures, materials or characteristics related to the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0032] The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0033] In the description of the present disclosure, unless otherwise specified, the meaning of "a plurality" is two or more.

[0034] In the embodiments of the present disclosure, words such as "exemplary" or "for example" are used to represent examples, illustrations, or explanations. Any embodiment or design solution described as "exemplary" or "for example" in the embodiments of the present disclosure should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the use of words such as "exemplary" or "for example" is intended to present relevant concepts in a specific manner.

[0035] In addition, the use of "based on" implies openness and inclusiveness, because a process, step, calculation, or other action "based on" one or more of the stated conditions or values can, in practice, be based on additional conditions or values beyond those stated.

[0036] Currently, there are mainly two types of RIS-assisted key generation methods: beam optimization and constructing a fast-varying channel. Among them, beam optimization designs the optimal RIS reflection coefficient according to the characteristics within the channel coherence time, intelligently regulates the reflection channel, and optimizes the physical layer key generation system from the perspective of improving the channel signal-to-noise ratio. Constructing a fast-varying channel uses the high-frequency regulation of the RIS random reflection coefficient to reduce the coherence time, introduce artificial randomness, meet the high requirements of key generation for the time-varying nature of the channel environment, and thus improve the SKR. The essence of the constructing a fast-varying channel scheme is to utilize the agility of the RIS to regulate the signal at a high frequency and synthesize a dynamic channel with high entropy. The constructing a fast-varying channel scheme is applicable to quasi-static scenarios. By rapidly changing the RIS reflection coefficient, it fundamentally changes the problem of slow channel variation and effectively increases the SKR. Let the RIS act as a passive reflecting surface during the key generation process, and introduce artificial randomness through randomly switched reflection coefficients, providing a solution for SKG to overcome quasi-static scenarios.

[0037] However, beam optimization designs the optimal RIS reflection coefficient according to the characteristics within the channel coherence time, making the beams constructively add up, thereby improving the SKR and reducing information leakage. However, it also relatively fixes the RIS reflection coefficient within the same coherence time, that is, it improves the channel signal-to-noise ratio but does not increase the time-variation of the channel, and is not suitable for key generation in quasi-static scenarios. While the constructing a fast-varying channel can overcome quasi-static scenarios through high-frequency regulation, it lacks protection against eavesdroppers. During the RIS-assisted key generation process, due to the reflection effect of the RIS, an eavesdropper can no longer consider the channels to be independent just because it is more than half a wavelength away from the legitimate party. The eavesdropper can obtain channel information not only from the spatially correlated channels but also from the sub-reflection channels reflected by the RIS. The obtained channel information includes two parts: the sub-reflection channels that are exactly the same and the composite channels that are spatially correlated. Compared with the classical point-to-point key generation method, the eavesdropper has a greater negative impact on the SKR, resulting in lower key security.

[0038] Therefore, how to improve the security of keys in a quasi-static scenario is an urgent problem to be solved.

[0039] Based on this, embodiments of the present disclosure provide a pilot signal sending method, apparatus, and storage medium. A first pilot signal is obtained based on the estimated value of the first channel and the estimated value of the second channel. The first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end. Since the estimated values of both the first channel and the second channel are related to the first receiving end, the first pilot signal can interfere with the reception of the second pilot signal by the second receiving end without affecting the reception of the second pilot signal by the first receiving end. Therefore, when the first pilot signal and the second pilot signal are sent, it can ensure that the first receiving end can normally receive the second pilot signal to determine the key shared with the sending end, while suppressing the reception of the second pilot signal by the second receiving end, preventing information leakage, improving the security of keys in a quasi-static scenario, and thus improving the SKR.

[0040] The technical solutions of the present disclosure will be described below with reference to the accompanying drawings of the specification.

[0041] The technical solutions provided by the embodiments of the present disclosure can be applied to various mobile communication networks. For example, a new radio (NR) mobile communication network using the fifth generation mobile networks (5G), a future mobile communication network, or a multi-communication fusion system, etc. The embodiments of the present disclosure do not limit this.

[0042] Figure 1 It is a schematic diagram of the composition of a communication system provided by an embodiment of the present disclosure. Refer to Figure 1 , this communication system includes a sending end 11, an intelligent metasurface 21, and at least one receiving end (such as receiving end 31 and receiving end 32).

[0043] Among them, the sending end 11, the intelligent metasurface 21, and at least one receiving end can be connected to each other. The connection can be through a wired network or a wireless network. The embodiments of the present disclosure do not limit this.

[0044] In some embodiments, the receiving ends among at least one receiving end can also be connected through a wired network or a wireless network.

[0045] In some embodiments, the transmitting end 11 may be a base station. Among them, the base station may be any one of an evolved Node B (eNB), a next-generation Node B (gNB), a transmission receive point (TRP), a transmission point (TP), and some other access nodes. According to the size of the service coverage area provided, the base station can be further divided into a macro base station for providing a macro cell, a pico base station for providing a pico cell, and a femto base station for providing a femto cell. With the continuous evolution of wireless communication technology, future base stations may also adopt other names.

[0046] In some embodiments, the intelligent metasurface 21 may also be referred to as a "reconfigurable intelligent surface" or an "intelligent reflecting surface", which is an artificial electromagnetic surface structure with programmable electromagnetic characteristics. Through intelligent metasurface technology, numerous reflecting units can be intelligently controlled to effectively concentrate the diffused electromagnetic waves in space to areas with weak signals, achieving more efficient and uniform signal coverage. When moving, the reflected electromagnetic waves can also be tracked in real time to maintain good signal reception quality. In addition, the intelligent metasurface also has the characteristics of low energy consumption and high efficiency, which can increase the signal propagation efficiency while reducing power consumption.

[0047] In some embodiments, the intelligent metasurface 21 consists of a passive array structure and a controller. Exemplarily, the intelligent metasurface 2 is composed of a large number of passive elements, which are usually made of metamaterials and have adjustable electromagnetic characteristics. The passive elements can independently adjust their operating states and regulate wireless signals by changing their electromagnetic response characteristics. These elements are usually arranged in an array form to form a two-dimensional surface structure. The controller of the intelligent metasurface 21 is the key part responsible for controlling and adjusting the passive array elements. By sending control signals to each passive element, the controller can dynamically regulate the electromagnetic response characteristics of these elements. The controller can be programmed as needed to achieve the reconstruction of different wireless signal propagation characteristics. By controlling the operating states of the passive array elements, the intelligent metasurface can achieve the directional reflection, refraction, scattering, and absorption of wireless signals, thereby realizing the dynamic regulation of the wireless channel.

[0048] In some embodiments, the transmitting end 11 can control the turning on and off of each passive element of the intelligent metasurface 21 through the controller of the intelligent metasurface 21.

[0049] In some embodiments, for each of at least one receiving end (such as receiving end 31), the receiving end may be a terminal, where the terminal may be a device with wireless transceiver functions, such as a mobile phone, a tablet computer, a wearable device, a vehicle-mounted device, an augmented reality (AR) / virtual reality (VR) device, a laptop computer, an ultra-mobile personal computer (UMPC), a netbook, a personal digital assistant (PDA), etc. The specific types of terminals are not limited in the embodiments of the present disclosure.

[0050] In some embodiments, considering the channel characteristics of a quasi-static scenario, Figure 1 the shown communication system may be modeled as a quasi-static Rayleigh block fading model, that is, within the coherence time, the channel state information remains unchanged, and it is a fading channel between coherence times, the CSI changes, and each coherence time is further divided into L = T c / T s time slots, where T c represents the length of the coherence time, T s represents the time for performing a channel estimation, and the size of L is positively correlated with the size of the coherence time. The transmitting end 11 may adjust the intelligent metasurface 21 according to time slots t = 1, 2......, L.

[0051] It should be understood that Figure 1 is an exemplary structural diagram, Figure 1 the number of devices included in the shown communication system is not limited, for example, the number of transmitting ends and receiving ends is not limited. And, in addition to Figure 1 the shown devices, Figure 1 the shown communication system may further include other devices, which are not limited herein.

[0052] Next, as Figure 2 shown, the embodiments of the present disclosure provide a pilot sending method, which is applied to a transmitting end. The transmitting end may be the above-mentioned Figure 1 transmitting end 11, and the method includes the following steps:

[0053] S101. Obtain the estimated value of the first channel and the estimated value of the second channel.

[0054] In some embodiments, when the transmitting end needs to determine the shared key with the first receiving end, the transmitting end obtains the estimated value of the first channel and the estimated value of the second channel. Wherein, the first receiving end may be the above-mentioned Figure 1One of the at least one receiving end shown, for example, can be receiving end 31. The sending end can also have other names, for example, the transmitting end. The embodiments of the present disclosure do not limit this.

[0055] In some embodiments, the first channel is the channel between the sending end and the first receiving end, and the second channel includes the channel between the sending end and the intelligent metasurface and the channel between the intelligent metasurface and the first receiving end. Among them, the intelligent metasurface can be the intelligent metasurface 21 shown above Figure 1 The first channel and the second channel can also have other names. For example, the first channel can be called the direct channel, and the second channel can be called the cascaded channel. The embodiments of the present disclosure do not limit this.

[0056] In some embodiments, a pilot signal sending method provided by the embodiments of the present disclosure can be applied to a quasi-static scenario. Among them, the quasi-static scenario generally refers to an approximate static scenario, that is, the things in the scenario change slowly or are relatively stationary, or the dynamic process can be regarded as static in an approximate way. For example, in the field of communication, the quasi-static scenario generally refers to the slow change of the channel, and it can be considered that the channel is constant or changes very slowly within a certain time range.

[0057] For the description of how the sending end obtains the estimated value of the first channel and the estimated value of the second channel, reference can be made to the description of steps S1011 to S1014 below, which will not be elaborated here.

[0058] S102. Based on the estimated value of the first channel and the estimated value of the second channel, obtain the first pilot signal.

[0059] Among them, the first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end, and the second pilot signal is used for the first receiving end to determine the shared key with the sending end. The second receiving end can be one of the at least one receiving end shown above Figure 1 except the first receiving end. Taking the first receiving end as receiving end 31 as an example, the second receiving end can be receiving end 32. The first receiving end can be understood as a legitimate party, and the second receiving end can be understood as an eavesdropper. In the field of keys, the sending end can be called Alice, the first receiving end can be called Bob, and the second receiving end can be called Eve. The first pilot signal and the second pilot signal can also have other names. For example, the first pilot signal can be called the artificial noise pilot, and the second pilot signal can be called the normal pilot.

[0060] In some embodiments, the intelligent metasurface includes M reflection elements (i.e., the above-mentioned passive elements), where M is a positive integer. Each reflection element corresponds to a preset reflection coefficient. The reflection coefficients corresponding to the M reflection elements may be the same or different, and the embodiments of the present disclosure do not limit this. Based on this, the first pilot signal can be obtained based on the estimated value of the first channel and the estimated value of the second channel, and may be obtained based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix. Among them, the reflection coefficient matrix is determined based on the reflection coefficients corresponding to the M reflection elements included in the intelligent metasurface.

[0061] In some embodiments, the reflection coefficient matrix may also have other names. For example, it may be called a random phase shift matrix.

[0062] As an example, obtaining the first pilot signal based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix may include the following steps:

[0063] A1. Based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix, obtain the composite channel at the sending end.

[0064] As a possible example, obtaining the composite channel at the sending end based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix may be to determine the product of the estimated value of the first channel and the reflection coefficient matrix, and then use the sum of the product and the estimated value of the second channel as the composite channel at the sending end.

[0065] Exemplarily, obtaining the composite channel at the sending end based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix may be as follows ～ the formula ～ shown:

[0066]

[0067] where, h A (t,k) represents the composite channel at the sending end, represents the estimated value of the second channel, represents the estimated value of the first channel, represents the reflection coefficient matrix, t represents the t-th time slot, k represents the k-th correlation time, and both t and k are positive integers.

[0068] A2. Perform singular value decomposition on the composite channel to obtain the right singular vector matrix.

[0069] It should be understood that all vectors orthogonal to the composite channel are included in the right singular vector matrix of the composite channel. To obtain the first pilot signal, after obtaining the composite channel at the transmitting end, the transmitting end can perform singular value decomposition (SVD) on the composite channel to obtain the right singular vector matrix. Among them, SVD is a matrix decomposition method in linear algebra. For any m×n matrix A, it can be expressed as the product of three matrices: UΣV*, where U is an m-order orthogonal matrix, Σ is an m×n-order diagonal matrix, and V* is an n-order orthogonal matrix. Singular value decomposition can be regarded as the generalization of the diagonalization of symmetric matrices or Hermite matrices based on eigenvectors to arbitrary matrices. At the same time, singular value decomposition is also a method of matrix data compression, which can compress the original matrix into a smaller singular value matrix while retaining its main features. In addition, the compact singular value decomposition and the truncated singular value decomposition are two forms of singular value decomposition, where the compact singular value decomposition is a singular value decomposition with the same rank as the original matrix, and the truncated singular value decomposition is a singular value decomposition with a lower rank than the original matrix.

[0070] Exemplarily, the composite channel at the transmitting end can also be as shown in the following formula:

[0071] h A (t,k)=ΣUV H ;

[0072] where V H represents the right singular vector matrix.

[0073] A3. Determine the target vector in the right singular vector matrix as the first pilot signal.

[0074] Among them, the target vector is the vector orthogonal to the composite channel in the right singular vector matrix. That is, any vector in the vectors orthogonal to the composite channel in the right singular vector matrix is used as the first pilot signal.

[0075] It should be noted that the above step 102 is an exemplary description of the generation process of the first pilot signal, that is, the noise pilot signal. For the generation process of the second pilot signal, that is, the normal pilot signal, reference can be made to the description in the related art and will not be elaborated here.

[0076] S103. Transmit the first pilot signal and the second pilot signal.

[0077] As an example, transmitting the first pilot signal and the second pilot signal can be to transmit a third pilot signal, and the third pilot signal includes the first pilot signal and the second pilot signal. That is to say, the first pilot signal and the second pilot signal are transmitted through the same pilot signal.

[0078] Based onFigure 2 In the illustrated embodiment, a first pilot signal is obtained based on the estimated value of the first channel and the estimated value of the second channel. The first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end. Since both the estimated value of the first channel and the estimated value of the second channel are related to the first receiving end, the first pilot signal can interfere with the reception of the second pilot signal by the second receiving end without affecting the reception of the second pilot signal by the first receiving end. Therefore, when the first pilot signal and the second pilot signal are transmitted, it can be ensured that the first receiving end can normally receive the second pilot signal to determine the key shared with the transmitting end, while suppressing the reception of the second pilot signal by the second receiving end, preventing information leakage, improving the security of the key in the quasi-static scenario, and thus improving the SKR.

[0079] In some embodiments, in order to further improve the SKR, transmitting the first pilot signal and the second pilot signal, that is, the above step S103, may include the following steps:

[0080] B1. Determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal.

[0081] In some embodiments, in order to further improve the SKR, power allocation may be performed on the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal. Exemplarily, assuming that the preset transmission power for transmitting the second pilot signal is P, then P can be divided into the transmission power P z corresponding to the first pilot signal and the transmission power P X corresponding to the second pilot signal, and P X +P z =P. Since the preset transmission power is divided into P z and P X in two parts, the allocation of the transmission power of the two parts will affect the performance of the final SKG. The increase of P X can make the channel estimation more accurate, and make the key information obtained from the channel estimation between the transmitting end and the first receiving end have stronger reciprocity. The increase of P z is beneficial to enhancing the interference to the second receiving end (i.e., the eavesdropper Eve), reducing information leakage, and improving the security of the key. Therefore, it is necessary to balance P z and P X to achieve the optimal allocation of the transmission power. In order to perform the optimal allocation of the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal, the pilot method provided by the embodiments of the present disclosure proposes to perform the optimal allocation of the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the key capacity of the key.

[0082] Based on this, determining the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal may be to determine the key capacity of the key based on the conditional mutual information among the transmitter, the first receiver, and the second receiver, and then determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the key capacity.

[0083] Among them, the key capacity of the key refers to the length or size of the key used to encrypt information. The larger the key length, the higher the encryption strength that can be provided theoretically, and the stronger the ability to resist cryptographic analysis attacks. Conditional mutual information is a way to measure the degree of mutual dependence between two random variables. Conditional mutual information is based on conditional probability and represents the mutual information between two random variables given a third random variable. The mathematical expression of conditional mutual information is I(X;Y|Z), where X and Y are two random variables and Z is a random variable related to X and Y. Conditional mutual information can be used to evaluate the correlation between X and Y given additional information Z. Conditional mutual information can also be regarded as a measure of conditional independence, that is, if X and Y are independent given Z, then the conditional mutual information between X and Y is 0.

[0084] Exemplarily, taking the lower bound of the key capacity as the key capacity measurement criterion, the key capacity can be shown as the following formula:

[0085]

[0086] Among them, C represents the key capacity, represents the conditional mutual information between the transmitter and the first receiver, represents the conditional mutual information between the transmitter and the first receiver and the conditional mutual information between the transmitter and the second receiver, represents the composite channel information used by the transmitter to generate the key, represents the composite channel information used by the first receiver to generate the key, represents the composite channel information stolen by the second receiver. Since the solution of the present disclosure takes into account the existence of the second receiver (i.e., the eavesdropper), the lower bound of the key capacity is represented by in the embodiments of the present disclosure. Assuming the channel noise λ = P X / P, the key capacity can also be shown as the following formula:

[0087]

[0088] Among them, R() represents taking the content in () as a matrix, and det() represents the determinant of the content in (). ρ is the spatial correlation coefficient between the channels from the transmitter to the first receiver and from the transmitter to the second receiver. E{·} represents expectation, satisfying 0 ≤ |ρ| ≤ 1. l represents the pilot. σ12 refers to the noise variance of the channel between the transmitter and the first receiver. σ22 refers to the noise variance of the channel between the first receiver and the transmitter. σ32 refers to the noise variance of the channel between the transmitter and the second receiver.

[0089] In some embodiments, based on the key capacity, determining the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal may be based on the key capacity to determine the power ratio between the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal; and then based on the power ratio and the preset transmit power, determining the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal.

[0090] As a possible example, based on the key capacity, determining the power ratio between the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal may be to perform a one-dimensional search on the key capacity to obtain the power ratio.

[0091] It should be understood that when parameters such as channel variance, noise variance, pilot length, and preset transmit power are given, the key capacity can be regarded as a convex optimization problem with respect to λ:

[0092]

[0093] Performing a one-dimensional search on the key capacity can obtain the optimal power ratio between the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal to maximize C. That is, take P X when the key capacity reaches the peak as the transmit power of the first pilot signal, and take P z when the key capacity reaches the peak as the transmit power of the second pilot signal to obtain a higher SKR.

[0094] It should be noted that since λ = P X / P, that is, λ is the power ratio between the transmit power of the first pilot signal and the preset transmit power. After determining λ through a one-dimensional search on the key capacity, the power ratio between the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal can be determined based on λ and the preset transmit power, and then based on this power ratio and the preset transmit power, the transmit power corresponding to the first pilot signal and the transmit power corresponding to the second pilot signal can be determined. It can also be to determine the transmit power of the first pilot signal based on λ and the preset transmit power, and then determine the transmit power of the second pilot signal based on the transmit power of the first pilot signal and the preset transmit power.

[0095] B2. Transmit the first pilot signal based on the transmission power corresponding to the first pilot signal, and transmit the second pilot signal based on the transmission power corresponding to the second pilot signal.

[0096] In some embodiments, after determining the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal, the first pilot signal may be transmitted based on the transmission power corresponding to the first pilot signal, and the second pilot signal may be transmitted based on the transmission power corresponding to the second pilot signal.

[0097] In the embodiments of the present disclosure, the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal are determined based on the key capacity of the key, and then the first pilot signal is transmitted based on the transmission power corresponding to the first pilot signal, and the second pilot signal is transmitted based on the transmission power corresponding to the second pilot signal, so as to reduce the eavesdropping key capacity, increase the secure key capacity, enhance the security of the communication system, and further improve the SKR.

[0098] In some embodiments, as Figure 3 shown, the above step S101 may include the following steps:

[0099] S1011. Receive the common pilot transmitted by the first receiving end at the first moment.

[0100] Wherein, at the first moment, all M reflection elements of the intelligent metasurface are in the off state.

[0101] In some embodiments, in order to obtain the first pilot signal, the transmitter may control all M reflection elements of the intelligent metasurface to be in the off state through the controller of the intelligent metasurface, and then the transmitter receives the common pilot transmitted by the first receiving end at the first moment.

[0102] S1012. Perform channel estimation on the first channel based on the common pilot to obtain an estimated value of the first channel.

[0103] As can be seen from the above description of the first channel, the first channel can be referred to as the direct channel, that is, channel estimation is performed on the direct channel based on the common pilot to obtain an estimated value of the direct channel, that is, to obtain the CSI of the direct channel.

[0104] S1013. Receive the reflection signal from the i-th reflection element among the M reflection elements at the (i + 1)-th moment.

[0105] Among them, the (i + 1)-th moment is a moment after the first moment, where i is a positive integer less than or equal to M. At the (i + 1)-th moment, the i-th reflection element is in the on state, and the reflection elements among the M reflection elements other than the i-th reflection element are all in the off state. That is to say, after the transmitter obtains the estimated value of the first channel, the transmitter can control each of the M reflection elements on the intelligent metasurface to turn on in sequence through the controller of the intelligent metasurface, so as to obtain M reflected signals corresponding to the M reflection elements.

[0106] For example, the transmitter can control the i-th reflection element among the M reflection elements to turn on through the controller of the intelligent metasurface at the (i + 1)-th moment, and then receive the reflected signal of the i-th reflection element at the (i + 1)-th moment. Then at the (i + 2)-th moment, control the (i + 1)-th reflection element among the M reflection elements to turn on through the controller of the intelligent metasurface, and then receive the reflected signal of the (i + 1)-th reflection element at the (i + 2)-th moment, and control the i-th reflection element among the M reflection elements to turn off at the (i + 2)-th moment. And so on, until receiving M reflected signals corresponding to the M reflection elements.

[0107] It should be noted that it should be understood that after a reflection element is turned on, it can reflect the common pilot sent by the first receiving end. Based on this, a reflected signal can be understood as the signal after the common pilot sent by the first receiving end is reflected by the turned-on reflection element on the intelligent metasurface.

[0108] S1014. Obtain an estimated value of the second channel based on the reflected signals corresponding to the M reflection elements and the estimated value of the first channel.

[0109] As an example, obtaining an estimated value of the second channel based on the reflected signals corresponding to the M reflection elements and the estimated value of the first channel can be to perform channel estimation on each of the M reflected signals respectively to obtain M estimated values; then stack the M estimated values to obtain the stacked estimated value; and then eliminate the estimated value of the first channel from the stacked estimated value to obtain the estimated value of the second channel.

[0110] As another example, obtaining an estimated value of the second channel based on the reflected signals corresponding to the M reflection elements and the estimated value of the first channel can also be to stack the M reflected signals to obtain the stacked M reflected signals, then perform channel estimation on the stacked M reflected signals to obtain a target estimated value, and then eliminate the estimated value of the first channel from the target estimated value to obtain the estimated value of the second channel.

[0111] In some embodiments, after the transmitter sends the first pilot signal and the second pilot signal, the transmitter may generate a key based on the second pilot signal. The first receiver may generate a key based on the second pilot signal after receiving the first pilot signal and the second pilot signal. In this way, the transmitter and the first receiver generate a consistent key.

[0112] The following is an example of a pilot signal sending method provided by the embodiments of the present disclosure in combination with the complete process.

[0113] The present disclosure conducts research based on the quasi-static Rayleigh block fading model. By introducing RIS-assisted key generation, while constructing a fast-varying channel by high-frequency regulating the RIS reflection coefficient matrix, artificial noise (i.e., the first pilot signal) is designed to interfere with the eavesdropper (i.e., the second receiver), so as to reduce the eavesdropping key capacity, enhance the system security, and improve the SKR. The scheme includes the following three stages: (1) reference channel estimation; (2) artificial noise interference; (3) one-way key generation. Exemplarily, as Figure 4 shown, it is a schematic diagram of time slot allocation within a coherence time provided by the embodiments of the present disclosure. Refer to Figure 4 , assuming that there are L time slots in the coherence time, the transmitter (Alice) and the first receiver (Bob) extract symmetric keys from the channel, and the RIS has M reflection elements. In order to be able to interfere with the eavesdropper's ability to steal information while constructing a fast-varying channel through the RIS, the scheme of the present disclosure proposes to divide a coherence time into three stages: reference channel estimation, artificial noise interference, and one-way key generation. The reference channel estimation requires a total of (M + 1) time slots, and then L - (M + 1) rounds of artificial noise interference and one-way key generation can be performed.

[0114] Exemplarily, as Figure 5 shown, it is a schematic diagram of the steps executed within a coherence time provided by the embodiments of the present disclosure. Refer to Figure 5 , in the reference channel estimation stage, direct channel estimation and cascaded channel estimation need to be performed respectively to estimate the estimated value of the direct channel (i.e., the estimated value of the first channel) and the estimated value of the cascaded channel (i.e., the estimated value of the second channel) for subsequent steps. The artificial noise interference and one-way key generation need to use the information obtained in the reference channel estimation stage to interfere with the eavesdropper while enabling the legitimate receiving parties to obtain consistent symmetric keys to ensure the security of information transmission.

[0115] Combined with Figure 1Taking the communication system shown as an example where the solution of the present disclosure is applied to the key generation process assisted by RIS in a multiple-input single-output (MISO) system, the transmitter and the first receiver aim to generate keys from the wireless channel with the help of RIS adopting time division duplexing (TDD). Meanwhile, the eavesdropper Eve (i.e., the second receiver) is as close as possible to the first receiver, and the second receiver is ready to obtain key information from the signals received at the second receiver. It is assumed that the transmitter is equipped with N antennas, both the legitimate user the first receiver and the eavesdropper the second receiver are single-antenna, and RIS, as a trusted third party, consists of M passive reflection elements. The transmitter controls the reflection coefficient matrix of RIS through high-frequency regulation to control RIS to construct a fast-varying channel and simulate the fast fading caused by movement for key generation. It is assumed that the antenna element spacing of all device nodes is greater than half of the wavelength of the carrier signal, so the channels between different transceiver antennas can be approximated as independent of each other.

[0116] Considering the channel characteristics of the quasi-static scenario, the channel is modeled as a quasi-static Rayleigh block fading model, that is, the CSI remains unchanged within the coherence time, and it is a fading channel between the coherence times, and the CSI changes. Each coherence time is further divided into L = T c / T s time slots. The transmitter regulates RIS according to the time slots t = 1, 2......, L. It is assumed that the transmitter is Alice, the first receiver is Bob, and the second receiver is Eve. In the case where a pilot sending method provided by the embodiment of the present disclosure is not executed, in the t-th time slot of the k-th time block, the received signals received by the first receiver and the second receiver can be shown as follows:

[0117] Y i (t,k) = (h ai (k) + H ar (k)Φ(t,k)h ri (k))X + n Ai (t,k);

[0118] where, i ∈ {Bob, Eve}, Y i (t,k) represents the received signal, h ai (k) ∈ C N×1 represents the channel between Alice and Bob or Eve, H ar (k) ∈ C N×M represents the channel between Alice and RIS, h ri (k) ∈ C M×1 represents the channel between RIS and Bob or Eve. It is assumed that the composite channel follows a normal distribution with a mean of 0 and a variance of σ 2Gaussian distribution, n Ai (t, k) is the Gaussian white noise received at the receiver, X ∈ C l×1 is the transmitted pilot, where l is the pilot length. The reflection coefficient matrix of the RIS is shown in the following formula:

[0119]

[0120] where α ∈ (0, 1] represents the amplitude reflection coefficient, θ m,t,k ∈ [0, 2π) represents the reflection coefficient of the m-th reflection element of the RIS in the t-th time slot of the k-th time block, which follows a uniform distribution. The time block can be understood as the coherence time. Define the cascaded channel of two sub-reflection channels as:

[0121]

[0122] where, , then in the t-th time slot of the k-th time block, the received signal can be further expressed as:

[0123]

[0124] where, G ai (k) ∈ C N×M ,

[0125] The overall process of the solution of the present disclosure is introduced below.

[0126] Step 1, Reference channel estimation.

[0127] The reference channel estimation obtains the estimated values of the direct channel and the cascaded channel by consuming part of the coherence time, providing support for the artificial noise interference and one-way key generation phases. In the reference channel estimation phase, since the RIS usually consists of a large number of reflection elements, performing a reference channel estimation with the assistance of the RIS will require the pilot length to increase as the number of reflection elements increases, resulting in an increase in the delay of data transmission, making it unsuitable for delay-sensitive or short-packet transmissions. In addition, performing a reference channel estimation with the assistance of the RIS may be incompatible with the existing communication block structure, which only allocates a small number of pilot symbols in each time block. Therefore, the reference channel estimation needs to first perform a direct channel estimation (i.e., obtain the estimated value of the first channel), then configure the reflection coefficients of the RIS, perform M channel estimations to obtain M estimated values, then stack the M estimated values together to obtain the superimposed value of the direct channel and the cascaded channel, and then obtain the estimated value of the cascaded channel by eliminating the estimated value of the direct channel. The entire reference channel estimation phase requires a total of (M + 1) time slots, and the specific steps are as follows:

[0128] C1, Direct channel estimation.

[0129] First, Alice sets each reflecting element of the RIS to the OFF state. Bob transmits a common pilot, and Alice performs a channel estimation on the direct channel based on the common pilot to obtain the direct channel CSI (i.e., obtain the estimated value of the first channel).

[0130] The reflection coefficient of the RIS in the first time slot is defined as follows:

[0131]

[0132] φ 1,i = 0 - ε0, (i ≠ t), 1 ≤ i ≤ M;

[0133] where the non - negative constant ε0 represents the actual error existing in the reflecting element of the RIS in the OFF mode. The direct channel signal received by Alice in the first time slot is as follows:

[0134]

[0135] where, (h ba (k) represents the direct channel, G ba (k) represents the cascaded channel, represents the reflection coefficient matrix, n BA (1,k) represents the channel noise.

[0136] Then, Alice performs channel estimation on the received direct channel signal to obtain the direct channel and its estimated value, which can be specifically as follows:

[0137]

[0138] where, represents the estimated value of the direct channel, represents the estimated value of the channel, (·) H represents the conjugate transpose of the matrix. Then the noise variance can be as follows:

[0139]

[0140] where P is the preset transmission power of Alice, and σ 2 = ασ h 2 +(1 - α)σ G 2 , and α is the power ratio of the sub - reflection channel of the RIS.

[0141] C2. Cascaded channel estimation.

[0142] After Alice estimates the direct channel, she needs to estimate the M reflected signals corresponding to the M reflection elements of the RIS. At the t-th time slot, the t-th reflection element of the RIS is controlled to be in the ON state, and the remaining reflection elements are in the OFF state. Then, channel estimation is performed on the M reflected signals respectively to obtain M estimated values. Then, the M estimated values are stacked together, and the estimated value of the direct channel is eliminated from the stacked estimated values, so as to recover the cascaded channel and obtain the estimated value of the cascaded channel.

[0143] In the t time slots of the RIS, the reflection coefficient of the i-th reflection element is defined as follows:

[0144]

[0145]

[0146] Then Alice stacks the cascaded channel signals (i.e., the reflected signals) of each RIS element received from the 2nd to the M+1st time, to form a stacked signal, and the stacked signal is as follows:

[0147]

[0148] where N BA (k)=[n BA (2,k),n BA (3,k),......,n BA (M+1,k)], Θ represents the stack of the reflection coefficients of M groups of RIS. Then Alice performs channel estimation on the stacked signal to obtain the estimated value of the cascaded channel, which can be specifically shown as the following formula:

[0149]

[0150] where, in the case of, it can be as follows

[0151]

[0152] Step 2, artificial noise interference.

[0153] In the artificial noise interference stage, Alice first configures a random phase shift matrix (i.e., the reflection coefficient matrix) for the RIS for key generation in the next time slot, thus causing rapid fading changes in the time block. Then, Alice designs artificial noise pilots (i.e., the first pilot signal) based on the configured random phase shift matrix, the estimated value of the direct channel, and the estimated value of the cascaded channel. The essence of the artificial noise pilot is to perform noise design through the pre-acquired legitimate channel CSI. Since the artificial noise pilot is designed according to the direct channel CSI, the noise is mapped to the null space of the direct channel, which enables the artificial noise pilot to interfere with the eavesdropper's channel but does not affect the channel of the intended receiver (i.e., the first receiving end), thereby achieving more secure communication. The sender sends the artificial noise pilot and the normal pilot (i.e., the second pilot signal) to Bob together. The sent artificial noise pilot can effectively interfere with Eve's eavesdropping. The specific steps are as follows:

[0154] D1. Configure the random phase shift matrix.

[0155] Alice configures the random phase shift matrix Inject artificial randomness into the next time slot channel to overcome the problem of slow channel change in the quasi-static scenario.

[0156] When configuring the random phase shift matrix After that, based on the random phase shift matrix, the estimated value of the direct channel, and the estimated value of the cascaded channel, the composite channel of Alice can be obtained. The composite channel can be shown as follows:

[0157]

[0158] where h A (t,k) represents the composite channel.

[0159] D2. Artificial noise pilot design.

[0160] Alice performs SVD decomposition on the composite channel h A (t,k) of Alice, h A (t,k) = ΣUV H . It should be understood that all vectors orthogonal to the composite channel h A (t,k) are included in the right singular vector matrix. A vector orthogonal to the load channel is randomly selected from the right singular vector matrix as the artificial noise pilot for transmission. The power P z is used to transmit the artificial noise pilot, and the remaining power P z is used to transmit the normal pilot signal to the first receiving end. Since the transmit power P is divided into the transmit power of the normal pilot and the transmit power of the artificial noise pilot, the power allocation of the two parts will affect the performance of the final SKG. P XThe increase can make the channel estimation more accurate, giving the key information obtained from the channel estimations of Alice and Bob stronger reciprocity. And the increase of P z is beneficial to enhancing the interference to the eavesdropper Eve, reducing information leakage, and improving the security of the key.

[0161] D3. Optimal transmission power allocation.

[0162] For the description of how to achieve optimal transmission power allocation, reference can be made to the above description of step B2, which will not be elaborated here.

[0163] Step 3. One-way key generation.

[0164] The classical physical-layer key generation mechanism (PLKG) requires both Alice and Bob to estimate the uplink and downlink channels respectively. One round of key generation needs to perform two channel estimations to obtain a symmetric key with reciprocity. In the embodiments of the present disclosure, since the reference channel estimation is performed in advance in the previous stage, in the one-way key generation stage, only Bob needs to perform channel estimation to generate the key in the embodiments of the present disclosure, while Alice constructs the CSI based on the estimated values of the direct channel, the cascaded channel, and the RIS reflection coefficient matrix it has mastered to generate a key highly consistent with Bob's.

[0165] In some embodiments, after Alice sends the first pilot signal and the second pilot signal, when t ∈ [M + 2, L], one-way key generation is performed between Alice and Bob. Since in a quasi-static scenario, a Rayleigh fading block maintains a relatively long coherence time, resulting in limited randomness of the key source and a low SKR. To simulate the fast fading of the channel, Alice controls the RIS to construct a fast-varying channel in the remaining L - (M + 1) time slots through a random reflection coefficient matrix for one-way key generation. Specifically, it may include the following steps:

[0166] E1. Downlink channel estimation.

[0167] Bob performs channel estimation on the pilot signal sent by Alice, which includes the first pilot signal and the second pilot signal, to obtain an estimated value, and then generates a key based on the estimated value.

[0168] Exemplarily, after Alice sends the first pilot signal and the second pilot signal, the pilot signals received by Bob and Eve can be shown as the following formula:

[0169]

[0170] where Z = [z1, z1,......, z n, Z is a matrix jointly composed of different vectors Z during the pilot signal transmission of Alice's N transmitting antennas, and z n is the artificial noise matrix selected when the nth transmitting antenna transmits the pilot signal. Then, Bob and Eve perform channel estimation based on the above pilot signals respectively and obtain the following:

[0171]

[0172]

[0173] Among them, is the estimated value obtained by Bob, is the estimated value obtained by Eve, and n AE (t, k) is Gaussian white noise.

[0174] In the case of , it can be as shown in the following formula:

[0175]

[0176]

[0177] Among them, the noise variance It can be seen from the above formula that since the artificial noise pilot (i.e., the first pilot signal) is mapped to the null space of the legitimate receiver Bob, it will not affect the channel estimation at the Bob side.

[0178] E2. Uplink channel reconstruction.

[0179] Alice reconstructs a key consistent with the Bob side based on the estimated value of the direct channel, the estimated value of the cascaded channel, and the reflection coefficient matrix.

[0180] Exemplarily, Alice can perform uplink channel reconstruction as shown in the following formula:

[0181]

[0182] It should be understood that after the one-way key generation stage, the Bob side obtains the channel estimation value Alice obtains the channel estimation value h A (t, k) through the estimated value of the direct channel, the estimated value of the cascaded channel, and the reflection coefficient matrix. and h A (t, k) are highly consistent and have reciprocity. Alice uses h A (t, k) as the key source, and Bob uses As the key source, both parties generate random keys. The channel information obtained by Eve will be interfered by artificial noise pilots, reducing the useful information in the channel information and enhancing the security of the keys in the quasi-static scenario, thereby further increasing the key rate.

[0183] It should be noted that, in order to verify the feasibility and effectiveness of the solution of this embodiment of the present disclosure, a series of simulation experiments of the solution of this embodiment of the present disclosure are carried out in the MATLAB environment. Among them, the mutual information in SKR is calculated using the ITE toolbox (information theoretical estimator toolbox). It is assumed that both the transmitter and receiver perform digital signal processing and 8-bit quantization is adopted.

[0184] The solution of this embodiment of the present disclosure uses the Monte Carlo method to conduct multiple experiments. Each experiment randomly generates channel and noise data, ensuring the accuracy of the experiment. The solution of this embodiment of the present disclosure models the channel variance as where β0 = -30dB is the path loss when d0 = 1, d uv is the distance between Alice and Bob, ζ is the path loss exponent set to 4 in the indoor environment, the power ratio of the RIS sub-reflection channel is α = 0.8, and the eavesdropping channel is modeled as Let β = 1, w ∼ CN(0,σ 2 ), and in addition, T = 200 is set.

[0185] Figure 6 Shows the relationship between SKR and the correlation coefficient ρ of the Alice-Bob and Alice-Eve channels when SNR = 30dB. Figure 6 The dotted line and the solid line in [] represent the simulation values respectively, and the markers represent the theoretical values. It can be seen from Figure 6 that the simulation values and the theoretical approximate values are in good agreement, fully verifying the correctness of the theoretical analysis. In addition, after using the solution of this embodiment of the present disclosure, since a part of the preset transmission power of the transmitter is used to send noise pilots, the uplink and downlink mutual information after using the solution of this embodiment of the present disclosure is slightly decreased compared with the uplink and downlink mutual information without using the solution of this embodiment of the present disclosure. However, the key capacity should fully consider the eavesdropping key capacity obtained by the eavesdropper. It can be seen from Figure 6 that after using the solution of this embodiment of the present disclosure, the decreasing trend of the upper and lower bounds of SKR compared with not using the solution of this embodiment of the present disclosure as the correlation coefficient increases is weakened. In addition, after using the solution of this embodiment of the present disclosure, even when ρ = 0.9 and the legitimate channel and the eavesdropping channel are highly correlated, the solution of this embodiment of the present disclosure can effectively weaken the ability of the eavesdropper, fully proving the effectiveness of the solution of this embodiment of the present disclosure for improving SKR in RIS-assisted key generation. Among them, Figure 6 and the following Figures 7 to 9The AN in it all refers to a pilot transmission method provided by the embodiments of the present disclosure, which will not be elaborated below.

[0186] Figure 7 It shows the influence of the pilot power ratio on the SKR mentioned in the embodiments of the present disclosure when SNR = 30dB. Among them, Figure 7 the dotted line and the solid line in it respectively represent the simulation values, and the markers represent the theoretical values. Figure 7 The relative straight line in it is the SKR without using the solution of the embodiments of the present disclosure. From Figure 7 it can be seen that as the pilot power ratio increases, the uplink and downlink mutual information I(h A ,h B ) gradually coincides with the relative straight line part. And when the pilot power ratio starts from λ = 0.33, the upper and lower bounds of the SKR after using the solution of the embodiments of the present disclosure are better than those of the SKR without using the solution of the embodiments of the present disclosure. In addition, it can be seen from the upper and lower bound curves of the SKR that the SKR is a convex function of the pilot power λ. When 0.75 ≤ λ ≤ 0.8, the upper and lower bounds of the SKR reach the peak value, and the optimal pilot power ratio can be obtained through one-dimensional search to maximize the SKR of the solution of the embodiments of the present disclosure.

[0187] Figure 8 It shows a schematic diagram of the curve of the SKR varying with the number of RIS reflection elements. Figure 9 It shows a schematic diagram of the curve of the SKR varying with the pilot length. Among them, Figure 8 and Figure 9 the dotted line and the solid line in it respectively represent the simulation values, and the markers represent the theoretical values. Since the increase in the number of RIS elements will increase the time slots consumed for the reference channel estimation mentioned in the embodiments of the present disclosure, but at the same time will increase the information entropy of the uplink and downlink and reduce the information leakage to a certain extent, the SKR first increases and then decreases as the number of RIS reflection elements increases. And the increase in the pilot length is beneficial to improving the signal-to-noise ratio, thereby increasing the SKR.

[0188] The above mainly introduces the solution provided by the present disclosure from the perspective of the interaction between each node. It can be understood that each node, for example, the sending end, in order to implement the above functions, includes the corresponding hardware structure and / or software module for executing each function. Those skilled in the art should easily realize that, combined with the algorithm steps of each example described in the embodiments disclosed herein, the present disclosure can be implemented in the form of hardware or a combination of hardware and computer software. Whether a certain function is executed in the way of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present disclosure.

[0189] Embodiments of the present disclosure can divide the functional modules of the sending end according to the above method embodiments. For example, each functional module can be divided corresponding to each function, or two or more functions can be integrated into one functional module. The above integrated module can be implemented in the form of hardware or software. It should be noted that the division of modules in the embodiments of the present disclosure is illustrative, only a logical function division, and there may be other division methods in actual implementation. The following takes the example of dividing each functional module corresponding to each function for illustration.

[0190] Figure 10 The following shows a schematic composition diagram of a pilot sending device provided by an embodiment of the present disclosure. As Figure 10 shown, the pilot sending device 20 may include an acquisition unit 201, a processing unit 202, and a sending unit 203.

[0191] The pilot sending device 20 may be the above-mentioned sending end or a chip in the sending end. When the sending end is used to implement the functions of the sending end in the above embodiments, each unit is specifically used to implement the following functions.

[0192] The acquisition unit 201 is used to acquire the estimated value of the first channel and the estimated value of the second channel; the first channel is the channel between the sending end and the first receiving end, and the second channel includes the channel between the sending end and the intelligent metasurface and the channel between the intelligent metasurface and the first receiving end;

[0193] The processing unit 202 is used to obtain a first pilot signal based on the estimated value of the first channel and the estimated value of the second channel, and the first pilot signal is used to suppress the reception of the second pilot signal by the second receiving end, and the second pilot signal is used for the first receiving end to determine the key shared with the sending end;

[0194] The sending unit 203 is used to send the first pilot signal and the second pilot signal.

[0195] In some embodiments, the processing unit 202 is specifically used to obtain the first pilot signal based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix; the reflection coefficient matrix is determined based on the reflection coefficients corresponding to the M reflection elements included in the intelligent metasurface, and M is a positive integer.

[0196] In some embodiments, the processing unit 202 is specifically used to: obtain the composite channel of the sending end based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix; perform singular value decomposition on the composite channel to obtain a right singular vector matrix; determine the target vector in the right singular vector matrix as the first pilot signal, and the target vector is the vector orthogonal to the composite channel in the right singular vector matrix.

[0197] In some embodiments, the processing unit 202 is specifically configured to: determine the product of the estimated value of the first channel and the reflection coefficient matrix; and use the sum of the product and the estimated value of the second channel as the composite channel at the transmitter.

[0198] In some embodiments, the transmitting unit 203 is specifically configured to: determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal; and transmit the first pilot signal based on the transmission power corresponding to the first pilot signal, and transmit the second pilot signal based on the transmission power corresponding to the second pilot signal.

[0199] In some embodiments, the transmitting unit 203 is specifically configured to: determine the key capacity of the key based on the conditional mutual information among the transmitter, the first receiver, and the second receiver; and determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the key capacity.

[0200] In some embodiments, the transmitting unit 203 is specifically configured to: determine the power ratio between the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the key capacity; and determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the power ratio and the preset transmission power.

[0201] In some embodiments, the transmitting unit 203 is specifically configured to perform a one-dimensional search on the key capacity to obtain the power ratio.

[0202] In some embodiments, the obtaining unit 201 is specifically configured to: receive the common pilot signal sent by the first receiver at the first moment; where, at the first moment, the M reflection elements of the intelligent metasurface are all in the off state; perform channel estimation on the first channel based on the common pilot signal to obtain the estimated value of the first channel; receive the reflection signal from the i-th reflection element among the M reflection elements at the (i + 1)-th moment; where the (i + 1)-th moment is a moment after the first moment, i is a positive integer less than or equal to M, at the (i + 1)-th moment, the i-th reflection element is in the on state, and the reflection elements other than the i-th reflection element among the M reflection elements are all in the off state; and obtain the estimated value of the second channel based on the M reflection signals corresponding to the M reflection elements and the estimated value of the first channel.

[0203] In some embodiments, the obtaining unit 201 is specifically configured to: perform channel estimation on each of the M reflection signals respectively to obtain M estimated values; stack the M estimated values to obtain the stacked estimated value; and eliminate the estimated value of the first channel from the stacked estimated value to obtain the estimated value of the second channel.

[0204] It should be noted that Figure 10The units in [the above] can also be referred to as modules. For example, the sending unit can be referred to as the sending module. Additionally, in Figure 10 the embodiments shown, the names of the respective units may also not be Figure 10 the names shown in [the above]. For example, the obtaining unit can also be referred to as the communication unit, and the sending unit can also be referred to as the communication unit.

[0205] Figure 10 If the respective units in [the above] are implemented in the form of software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the embodiments of the present disclosure, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to enable a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to execute all or part of the steps of the methods of the various embodiments of the present disclosure. The storage media storing the computer software product include: various media such as USB flash drives, mobile hard disks, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical discs that can store program codes.

[0206] In the case where the above pilot sending device 20 implements the functions of the above integrated modules in the form of hardware, the embodiments of the present disclosure provide a structural schematic diagram of an electronic device. As Figure 11 shown, the electronic device 30 includes: a processor 302, a communication interface 303, and a bus 304. Optionally, the electronic device 30 may further include a memory 301.

[0207] The processor 302 can be used to implement or execute various exemplary logic blocks, modules, and circuits described in connection with the disclosure of the present disclosure. The processor 302 can be a central processing unit, a general-purpose processor, a digital signal processor, an application-specific integrated circuit, a field-programmable gate array, or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute various exemplary logic blocks, modules, and circuits described in connection with the disclosure of the present disclosure. The processor 302 can also be a combination that implements computing functions, such as a combination including one or more microprocessors, a combination of a DSP and a microprocessor, etc.

[0208] The communication interface 303 is used to connect to other devices through a communication network. The communication network can be an Ethernet, a wireless access network, a wireless local area network (WLAN), etc.

[0209] The memory 301 can be a read-only memory (ROM) or other types of static storage devices that can store static information and instructions, a random access memory (RAM) or other types of dynamic storage devices that can store information and instructions, or can also be an electrically erasable programmable read-only memory (EEPROM), a magnetic disk storage medium, or other magnetic storage devices, or any other medium that can be used to carry or store the desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto.

[0210] As a possible implementation, the memory 301 can exist independently of the processor 302. The memory 301 can be connected to the processor 302 through the bus 304 for storing instructions or program code. When the processor 302 calls and executes the instructions or program code stored in the memory 301, the pilot sending method provided by the embodiments of the present disclosure can be implemented.

[0211] In another possible implementation, the memory 301 can also be integrated with the processor 302.

[0212] The bus 304 can be an extended industry standard architecture (EISA) bus, etc. The bus 304 can be divided into an address bus, a data bus, a control bus, etc. For the sake of convenience of representation, Figure 11 only a thick line is used to represent it in the figure, but it does not mean that there is only one bus or one type of bus.

[0213] Through the description of the above embodiments, those skilled in the art can clearly understand that for the convenience and simplicity of description, only the above division of each functional module is used for illustration. In actual applications, the above functions can be allocated to different functional modules according to needs, that is, the internal structure of the sending end is divided into different functional modules to complete all or part of the functions described above.

[0214] Embodiments of the present disclosure also provide a computer-readable storage medium. All or part of the processes in the above method embodiments may be completed by computer instructions instructing relevant hardware. The program may be stored in the above computer-readable storage medium. When the program is executed, it may include the processes of the above method embodiments. The computer-readable storage medium may be the memory of any of the foregoing embodiments. The above computer-readable storage medium may also be an external storage device of the above sending end, such as a plug-in hard disk equipped on the above sending end, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. Further, the above computer-readable storage medium may also include both the internal storage unit of the above sending end and the external storage device. The above computer-readable storage medium is used to store the above computer program and other programs and data required by the above sending end. The above computer-readable storage medium may also be used to temporarily store data that has been output or will be output.

[0215] Embodiments of the present disclosure also provide a computer program product. The computer product includes a computer program. When the computer program product runs on a computer, the computer is caused to execute any one of the pilot sending methods provided in the above embodiments.

[0216] Although the present disclosure has been described in conjunction with various embodiments, however, in the process of implementing the claimed present disclosure, those skilled in the art can understand and implement other changes of the embodiments of the disclosure by viewing the drawings, the disclosure content, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps.

[0217] The word "a" or "an" does not exclude a plurality. A single processor or other unit may implement several functions recited in the claims. Certain measures are recited in mutually different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0218] Although the present disclosure has been described in conjunction with specific features and their embodiments, it is obvious that various modifications and combinations can be made without departing from the spirit and scope of the present disclosure. Accordingly, the present specification and the drawings are merely exemplary descriptions of the present disclosure defined by the appended claims, and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the present disclosure. Obviously, those skilled in the art can make various changes and modifications to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, if these modifications and variations of the present disclosure fall within the scope of the claims of the present disclosure and their equivalent technologies, the present disclosure is also intended to include these changes and modifications.

[0219] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present disclosure should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A pilot signal transmitting method, characterized in that Applied to the transmitter side, the method includes: Obtain the estimated value of the first channel and the estimated value of the second channel; the first channel is the channel between the transmitter side and the first receiver side, and the second channel includes the channel between the transmitter side and the intelligent metasurface and the channel between the intelligent metasurface and the first receiver side; Based on the estimated value of the first channel and the estimated value of the second channel, obtain a first pilot signal, where the first pilot signal is used to suppress the reception of the second pilot signal by the second receiver, and the second pilot signal is used by the first receiver to determine the key shared with the transmitter side; Transmit the first pilot signal and the second pilot signal.

2. The method according to claim 1, characterized in that, The obtaining of the first pilot signal based on the estimated value of the first channel and the estimated value of the second channel includes: Based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix, obtain the first pilot signal; the reflection coefficient matrix is determined based on the reflection coefficients corresponding to the M reflection elements included in the intelligent metasurface, and M is a positive integer.

3. The method according to claim 2, wherein The obtaining of the first pilot signal based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix includes: Based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix, obtain the composite channel of the transmitter side; Perform singular value decomposition on the composite channel to obtain a right singular vector matrix; Determine the target vector in the right singular vector matrix as the first pilot signal, where the target vector is the vector orthogonal to the composite channel in the right singular vector matrix.

4. The method according to claim 3, wherein The obtaining of the composite channel of the transmitter side based on the estimated value of the first channel, the estimated value of the second channel, and the reflection coefficient matrix includes: Determine the product of the estimated value of the first channel and the reflection coefficient matrix; Use the sum of the product and the estimated value of the second channel as the composite channel of the transmitter side.

5. The method according to claim 1, wherein The transmitting of the first pilot signal and the second pilot signal includes: Determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal; Transmit the first pilot signal based on the transmission power corresponding to the first pilot signal, and transmit the second pilot signal based on the transmission power corresponding to the second pilot signal.

6. The method according to claim 5, characterized in that The determining of the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal includes: Based on the conditional mutual information among the transmitter side, the first receiver side, and the second receiver side, determine the key capacity of the key; Based on the key capacity, determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal.

7. The method according to claim 6, wherein The determining of the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the key capacity includes: Based on the key capacity, determine the power ratio between the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal; Determine the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the power ratio and the preset transmission power.

8. The method according to claim 7, wherein The determining the power ratio between the transmission power corresponding to the first pilot signal and the transmission power corresponding to the second pilot signal based on the key capacity includes: Performing a one-dimensional search on the key capacity to obtain the power ratio.

9. The method according to claim 1, characterized in that, The intelligent metasurface includes M reflection elements, where M is a positive integer; the obtaining the estimated value of the first channel and the estimated value of the second channel includes: Receiving the common pilot signal transmitted by the first receiving end at the first moment; wherein, at the first moment, the M reflection elements of the intelligent metasurface are all in the off state; Performing channel estimation on the first channel based on the common pilot signal to obtain the estimated value of the first channel; Receiving the reflection signal from the i-th reflection element among the M reflection elements at the (i + 1)-th moment; wherein, the (i + 1)-th moment is a moment after the first moment, i is a positive integer less than or equal to M, at the (i + 1)-th moment, the i-th reflection element is in the on state, and the reflection elements other than the i-th reflection element among the M reflection elements are all in the off state; Obtaining the estimated value of the second channel based on the M reflection signals corresponding to the M reflection elements and the estimated value of the first channel.

10. The method according to claim 9, wherein The obtaining the estimated value of the second channel based on the M reflection signals corresponding to the M reflection elements and the estimated value of the first channel includes: Performing channel estimation on each of the M reflection signals respectively to obtain M estimated values; Stacking the M estimated values to obtain the stacked estimated values; Eliminating the estimated value of the first channel from the stacked estimated values to obtain the estimated value of the second channel.

11. A communication device, characterized in that, Comprising a memory, a processor, and computer program instructions stored on the memory and executable on the processor, wherein when the processor executes the computer program instructions, the method according to any one of claims 1 to 10 is implemented.

12. A computer-readable storage medium, characterized in that, The computer-readable storage medium includes computer program instructions; wherein, when the computer program instructions run on a computer, the computer is caused to execute the method according to any one of claims 1 to 10.

Images