Security power allocation and relay selection method in unknown eavesdropping cognitive internet of things

Abstract

This invention proposes a secure power allocation and relay selection method for a cognitive Internet of Things (IoT) with the possibility of unknown eavesdropping. The method includes establishing an IoT-based cognitive relay network comprising an IoT secondary transmitter (IoT-ST), an IoT secondary receiver (IoT-SD), a primary user (PU), an eavesdropper (Eve), and N+1 alternative relays (IoT-R). The transmission process is divided into two phases: In the first phase, the IoT-ST transmits confidential signals to all alternative relays via a local connection; in the second phase, power allocation and optimal relay selection are performed. The selected relay forwards confidential information to the IoT secondary receiver (IoT-SD), while the other N alternative relays act as friendly jammers, emitting artificial noise to deliberately confuse Eve. This invention can minimize the probability of security breaches even without prior information about Eve.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a secure power allocation and relay selection method in a cognitive Internet of Things (IoT) where there is unknown eavesdropping. Background Technology

[0002] The Internet of Things (IoT) integrates billions of smart devices into networks to provide enhanced wireless communication and smart applications such as smart transportation, smart industry, e-commerce, and smart cities. Future IoT networks will need to support massive connectivity and carry enormous amounts of wireless traffic. It is predicted that by 2030, the number of IoT devices in 6G-enabled IoT networks will reach 80 billion.

[0003] The rapid proliferation of IoT devices and the growing demand for broadband communication services have led to severe spectrum congestion. To alleviate this problem, cognitive radio (CR) technology is considered a potential solution for IoT networks because it enables dynamic spectrum sharing between the primary and CR networks. In a CR network, secondary users (SUs) can access carrier frequencies allocated to primary users (PUs), provided that interference caused by the secondary transmitters (STs) does not exceed a given threshold.

[0004] Due to the openness and broadcast nature of wireless signal propagation, passive eavesdropping can pose serious security risks to CR networks. To mitigate these risks, encryption techniques embedded in the protocol stack are typically used, assuming the eavesdropper has limited computational resources. However, with the rapid increase in the computational power of potential attackers, these encryption techniques can be decrypted by malicious attackers. Therefore, Physical Layer Security (PLS) is a promising solution that enhances communication security from within by exploring the inherent physical characteristics of the channel, without relying on eliminating the risk of attacker cryptanalysis. In the field of PLS, Wyner's pioneering work defined the fundamental concept of confidentiality as the difference between the master channel and the eavesdropping channel, and proved that perfect confidentiality can be ensured even when the conditions of the eavesdropping channel are worse than those of the master channel. In cases where the channel quality of the eavesdropping link is superior to that of the legitimate link, Goel et al. proposed using artificial noise (AN) at both the intended receiver and the eavesdropper under different channel conditions to achieve a guaranteed non-zero confidentiality rate. Inspired by this work, a series of serious studies have been conducted on AN-assisted PLS schemes, for example, in wirelessly powered IoT systems, intelligently connected vehicle networks, and multi-antenna CR systems.

[0005] Cooperative relaying has become an effective solution for mitigating the effects of shadowing and rapid fading in wireless channels. It can also enhance security by amplifying the desired signal at the intended receiver. Therefore, relay selection in cognitive networks has been extensively studied in the PLS (Proximity, Security, and Retention) framework for cognitive relay networks to enhance security. Summary of the Invention

[0006] To address the shortcomings of the aforementioned background technologies, this invention proposes a secure power allocation and relay selection method for cognitive IoT with unknown eavesdropping, which minimizes the probability of security interruption (SOP) in the absence of Eve's prior information.

[0007] The technical solution of this invention is implemented as follows:

[0008] A secure power allocation and relay selection method for cognitive IoT with unknown eavesdropping capabilities is proposed. This method establishes an IoT-based cognitive relay network, which includes one IoT secondary transmitter (IoT-ST), one IoT secondary receiver (IoT-SD), one primary user (PU), one eavesdropper (Eve), and N+1 backup relays (IoT-R). The transmission process consists of two phases: In the first phase, the IoT-ST transmits confidential signals to all backup relays via local connections; in the second phase, power allocation and optimal relay selection are performed, with the selected relay (IoT-R) being selected. kF Confidential information is forwarded to the IoT secondary receiver IoT-SD, and the other N backup relays IoT-R... kJ Acting as a friendly jammer, it emits artificial noise to deliberately confuse Eve.

[0009] The power allocation specifically includes:

[0010] Let P be the total transmit power of N+1 candidate relays, allocated to the optimal relay IoT-R. kF The power allocation factor is φ, and φ∈(0,1); therefore, IoT-R kF The transmission power is In the formula I th For the preset threshold, h kP The channel coefficients for relaying data to the primary user;

[0011] IoT-R kJ Emit AN vector Define a matrix g = [g kD g kP ], g kD Indicates from IoT-R kJ Channel gain to IoT-SD, g kP Indicates from IoT-R kJ The channel gain to PU; the precoding matrix of the AN vector is form An orthogonal basis; therefore, IoT-R kJ The transmission power is:

[0012] The optimal relay selection refers to establishing reliable transmission through a forwarding relay. The specific steps for establishing reliable transmission are as follows:

[0013] Step 1: Obtain the instantaneous confidentiality capability in the cognitive relay network, represented as: C S =[C D -C E ] + C D =log2(1+γ) d C is the channel capacity of the main link. E =log2(1+γ) e ) is the channel capacity of the eavesdropping link. For the instantaneous signal-to-noise ratio of IoT SD, Let this be Eve's instantaneous signal-to-noise ratio. h kD Indicates from IoT-R kF Channel gain to IoT-SD, h kE Indicates from IoT-R kF Channel gain to Eve This refers to the noise variance under IoT-SD;

[0014] When the following constraints are met: C D =log2(1+γ) d )≥R S R S Indicates the target secrecy rate, i.e. In the formula Then, proceed to step two;

[0015] Step 2: Determine the forwarding relay IoT-R kF X kd Is it below the preset threshold μ? If yes, proceed to step three; otherwise, proceed to step four.

[0016] Step 3: In the second phase, forwarding relay IoT-R kF During the cooperative transmission phase, power P r Broadcast message x;

[0017] Step 4: In the second phase, forwarding relay IoT-R kF Remain silent during the collaborative transmission phase.

[0018] The forwarding relay IoT-R kF The method for forwarding confidential information to the IoT secondary receiver IoT-SD is as follows:

[0019] The first step is to select the optimal power allocation factor.

[0020] Given μ and R SBelow, instantaneous security capacity C S Less than the target confidentiality rate R S The probability SOP is defined as: P out =Pr(C S <R S |X kd ≥μ);

[0021] Construct an optimization function with the goal of minimizing the SOP:

[0022] Given μ and R S The security breach event is defined as:

[0023] Arrange the CSIs, including the main channel and the Eve channel, on both sides of the inequality, that is:

[0024] In the formula,

[0025] Therefore, the confidentiality breach event is redefined as: P r Simplified to P r =φP, and Then P r Substituting φP into ω(φ), we get

[0026] Therefore, the optimal power allocation factor for the kth alternative relay. for: Right now, in,

[0027] The second step is power distribution among the backup relays.

[0028] For each candidate relay k = 1, 2, ..., N+1, we obtain

[0029] Without Eve's prior information, the optimal relay selection method is the forwarding relay IoT-R. kF The selection criteria are:

[0030] Therefore, the standard operating procedure (SOP) for the optimal relay selection method is:

[0031] The exact expression for the Standard Operating Procedure (SOP) of the optimal relay selection method is derived as follows: In the formula, M represents the number of Eve antennas, Φ, L, Ω, and Q are all parameters representing the trade-off between accuracy and complexity, and λ p λ represents the channel parameters at PU. d Let A = ε(N-2) and B = ε-1 represent the channel parameters at IoT-SD.

[0032] For the random relay selection method, forwarding relay IoT-R kF Select from all relays that have established secure transmissions that satisfy X. kd IoT-R with a resolution of ≥μ kF Through derivation, the Standard Operating Procedure (SOP) for the random relay selection method is:

[0033] The exact expression for the Standard Operating Procedure (SOP) of the random relay selection method is derived as follows: In the formula

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1) First, optimize the power allocation to obtain a closed-form solution of the optimal power allocation factor, and then use the channel state information of the legitimate link to perform the relay selection process.

[0036] 2) By employing a two-layer Gauss-Chebyshev quadrature, a new approximate closed-form expression for SOP is derived. As a benchmark, the confidentiality interruption performance of random and conventional relay selection under the proposed scheme is also obtained. Numerical results demonstrate the effectiveness of the analytical results of this invention and the superiority of the proposed scheme over the benchmark. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a flowchart of the present invention.

[0039] Figure 2 This is a structural diagram of the model of the present invention.

[0040] Figure 3 This is a graph showing the change in system outage probability as a function of total transmit power (P).

[0041] Figure 4 A preset threshold (I) is set for the system interruption probability based on the interference power at the PU. th The curve of change.

[0042] Figure 5 The graph shows the change in system outage probability as a function of the number of friendly jammers (N).

[0043] Figure 6 The system interruption probability varies with λ p The change curve.

[0044] Figure 7 The graph shows the system interruption probability as a function of the number of Eve antennas (M). Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] like Figure 1 As shown, this embodiment of the invention provides a method for secure power allocation and relay selection in a cognitive Internet of Things (IoT) with unknown eavesdropping capabilities, establishing a cognitive relay network based on the IoT, such as... Figure 2 As shown, this cognitive relay network includes one IoT secondary transmitter (IoT-ST), one IoT secondary receiver (IoT-SD), one primary user (PU), one eavesdropper (Eve), and N+1 alternative relays (IoT-R). The transmission process is divided into two phases: In the first phase, the IoT-ST transmits confidential signals to all alternative relays through local connections; in the second phase, power allocation and optimal relay selection are performed, and the selected relay, the IoT-R, is selected for forwarding. kF Confidential information is forwarded to the IoT secondary receiver IoT-SD, and the other N backup relays IoT-R... kJ Acting as a friendly jammer, it emits artificial noise to deliberately confuse Eve.

[0047] Power allocation specifically includes:

[0048] Let P be the total transmit power of N+1 candidate relays, allocated to the optimal relay IoT-R. kF The power allocation factor is φ, and φ∈(0,1). To ensure the Quality of Service (QoS) of the PU, the interference power at the PU should not exceed a preset threshold. Therefore, IoT-RkF The transmission power is In the formula I th For the preset threshold, h kP The channel coefficients for relaying data to the primary user.

[0049] IoT-R kJ Emit AN vector Each item in v has a P. n The variance. Here, we define a matrix g = [g kD g kP ], g kD Indicates from IoT-R kJ Channel gain to IoT-SD, g kP Indicates from IoT-R kJ The channel gain to PU; due to the low computational load, the precoding matrix of the AN vector is... Designed to be located in g H In the null space. Therefore, we have form An orthogonal basis. Due to IoT-R kF I don't know G k Therefore, the transmit power allocated to AN is evenly distributed to each term of v. Thus, IoT-R kJ The transmission power is:

[0050] Since the noise level at Eve is typically unknown, a worst-case scenario is considered to ensure safe secondary transmission, where the noise power at Eve is assumed to be zero. The instantaneous signal-to-noise ratio (SNR) of IoT SD and Eve can be written as follows: in h kD Indicates from IoT-R kF Channel gain to IoT-SD, h kE Indicates from IoT-R kF Channel gain to Eve It is the noise variance under IoT-SD.

[0051] Therefore, the instantaneous confidentiality capability in the cognitive relay system under consideration is expressed as: C S =[C D -C E ] + , where C D =log2(1+γ) d ) and C E =log2(1+γ) e These are the channel capacities of the main link and the eavesdropping link, respectively.

[0052] Forwarding relay IoT-R kF Transmission is only performed under conditions that guarantee reliable transmission to avoid unwanted security interruptions; otherwise, silence is maintained. The specific process of the method is as follows:

[0053] Step 1: To establish reliable transmission, the following constraints must be met: C D =log2(1+γ) d )≥R S R S Indicates the target secrecy rate, i.e. In the formula Proceed to step two.

[0054] Step 2: Determine the forwarding relay IoT-R kF X kd If the value is below the preset threshold μ, proceed to step three; otherwise, proceed to step four.

[0055] Step 3: In the second phase, forwarding relay IoT-R kF During the cooperative transmission phase, power P r Broadcast message x.

[0056] Step 4: In the second phase, forwarding relay IoT-R kF Remain silent during the collaborative transmission phase.

[0057] Forwarding relay IoT-R kF The method for forwarding confidential information to the IoT secondary receiver IoT-SD is as follows:

[0058] The first step is to select the optimal power allocation factor.

[0059] Given μ and R S Below, instantaneous security capacity C S Less than the target confidentiality rate R S The probability SOP is defined as: P out =Pr(C S <R S |X kd ≥μ); The goal of this embodiment is to optimize R S The SOP is minimized by setting the power allocation factor (PAF) for each relay. Therefore, the optimization function for minimizing the SOP is:

[0060] However, P out The analytical expressions are often cumbersome, and the closed-form solution of the optimal PAF can be tricky. Worse still, P... out The closed-form expression contains information prior to Eve. Based on the above analysis, P can be solved directly. outAchieving the optimal PAF is not feasible. To solve this tricky problem, the goal is to minimize the probability of each security breach, rather than using a Standard Operating Procedure (SOP). Mathematically, given μ and R... S The security breach event is defined as:

[0061] Observing the above formula, we can see that in order to minimize the risk of security breaches... Instantaneous security capacity C can be maximized by optimizing PAF. S However, C S This still involves Eve's prior information, which is considered unavailable. To counteract this, an attempt is made to arrange the CSI of both the main channel and Eve's channel on both sides of the inequality to offset the influence of Eve's prior information, i.e.: In the formula,

[0062] Therefore, the confidentiality breach event is redefined as: P r Simplified to P r =φP, and Then P r Substituting φP into ω(φ), we get

[0063] Therefore, the optimal power allocation factor for the kth alternative relay. for: Right now, in,

[0064] It is worth noting that when X kd When <μ, the optimal PAF is This means that message transmission is paused to avoid unwanted capacity disruptions.

[0065] The second step is power distribution among the backup relays.

[0066] To achieve the optimal PAF (Power Availability), the best forwarding relay is selected from those that successfully maintain reliable communication, minimizing the system's SOP (State of Operation). For each candidate relay k = 1, 2, ..., N+1, the following is obtained:

[0067] Without Eve's prior information, for the Best Relay Selection (BRS) method, the forwarding relay IoT-R... kF The selection criteria are:

[0068] Therefore, the standard operating procedure (SOP) for the optimal relay selection method is:

[0069] The exact expression for the Standard Operating Procedure (SOP) of the optimal relay selection method is derived as follows: In the formula, M represents the number of Eve antennas, Φ, L, Ω, and Q represent the trade-off parameters between accuracy and complexity, and λ p λ represents the channel parameters at PU. d Let A = ε(N-2) and B = ε-1 represent the channel parameters at IoT-SD.

[0070] For the Random Relay Selection (RRS) method, the forwarding relay IoT-R kF Select from all relays that have established secure transmissions that satisfy X. kd IoT-R with a resolution of ≥μ kF Through derivation, the Standard Operating Procedure (SOP) for the random relay selection method is:

[0071] The exact expression for the Standard Operating Procedure (SOP) of the random relay selection method is derived as follows: In the formula

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078] This invention proposes a novel joint optimal adaptive power allocation (OAPA) and optimal relay selection (BRS) scheme in the absence of prior information about Eve, aiming to minimize the probability of security interruption (SOP). A specific example is used to verify the method of this invention: assuming λ D =λ E =λ p =1, the average received noise power of IoT-SD is set to σ 2 =0dBm, threshold confidentiality rate set to R S = 1 bit / s / Hz. Gauss-Chebyshev parameters are L = 50, and the cutoff point is Φ = 50. This serves as the benchmark for the OAPA scheme. Figure 3-7The performance of exhaustive search and equal power allocation (EPA) schemes using BRS and CRS was also evaluated. Notably, for the EPA scheme, the PAF of the k-th relay is... In addition, some relevant parameters will be illustrated in the figure. (Through 10...) 6 Monte Carlo simulations were performed on different channel implementations to obtain the simulated performance. As can be seen from all these figures, the analysis results match the simulation results very well, verifying the accuracy of the derivation in this invention.

[0079] Figure 3 The standard operating procedures (SOPs) of the proposed system with P using three different relay selection schemes are described. Results show that the SOP of the OAPA scheme is actually slightly lower than that of the exhaustive search scheme across the entire transmit power range. This confirms that the OAPA scheme guarantees its worst-case optimality, even though it does not require Eve's prior information. It is observed that the proposed BRS scheme outperforms the CRS scheme in terms of security across the entire transmit power range, and both BRS and CRS schemes outperform the RRS scheme. This is because all three schemes utilize CSI available at different levels. Specifically, the BRS scheme fully utilizes CSI h... kD and h kP To implement the selection process, the CRS scheme only uses CSI h. kD Therefore, it is easy to know This results in a lower probability of a security breach in the BRS case. The RRS scheme performs the worst because it does not use prior information. It can also be seen that the SOP of all these schemes decreases with increasing P. A specific observation is that for larger P values, the performance gap increases because higher transmit power causes more interference to the PU, and using h... kP This will benefit the relay selection process. Another interesting observation is that the performance gap between the EPA and OAPA schemes decreases as P increases. This is because when P is large enough, the PAF of both the OAPA and EPA schemes should be [value missing]. To satisfy the maximum disturbance constraint at PU.

[0080] Figure 4 This explains the use of three different relay selection schemes and I th The proposed system's Standard Operating Procedure (SOP). It has been observed that the SOPs of the BRS and CRS schemes change with I... th The performance decreases as I increases, eventually converging to a certain value. This is because the transmit power is finite, and the security interruption performance cannot be improved indefinitely. The performance gap between the two schemes narrows because as I... th The increase, The conditions are more likely to be met, and in this case, the BRS scheme is equivalent to the CRS scheme. Interestingly, for the RRS scheme, the security interrupt performance decreases slightly. The reason is that with I... th With the increase in I, more power is allocated to the information signal, thus allowing more repeaters with poor channel conditions to communicate reliably with IoT-SD, resulting in worse security interruption performance. Another observation is that when I... th When the value is greater than 10 dB, the SOP of the EPA program first decreases and then increases, while when I th At P = 20 dBm, the ceiling effect begins to appear. This is because when P = 20 dBm, more power should be allocated to AN to minimize SOP; that is, the optimal PAF should be below 0.5. For the EPA scheme, when I... th When it is very small, PAF is mainly affected by I th The limitation is that it may be less than 0.5. However, when I th When the value is greater than 10 dB, the PAF becomes 0.5 in more trials, and when I th When large enough, the PAFs of all experiments eventually become 0.5.

[0081] Figure 5 SOPs for the proposed system using three different relay selection schemes with N are plotted. Clearly, for a larger N, the security performance is significantly improved. This is because more relays lead to a greater probability of selecting better forwarding relays to reduce information leakage. On the other hand, more degrees of freedom are provided to reduce Eve's received SNR. It was also observed that the performance gap can widen significantly with increasing N, especially when P = 20 dB. This is because when the total transmit power P is large, the information transmit power P... r Mainly affected by interference channels (i.e., X) kP The constraints of X, and more relays can enhance X. kP The impact on SOP. However, when P = 15 dBm, the performance improvement is small because, in this case, P... r Primarily constrained by P, therefore, X kP The impact on SOPs has been greatly reduced.

[0082] Figure 6 The standard operating procedure (SOP) and corresponding parameters for different relay selection schemes of the proposed system are plotted. s λ below p The relationship between λ and CRS is observed. It can be seen that the security breach performance of the BRS and CRS schemes increases with λ. p It increases with the increase of λ. This is because a larger λ... p This means the channel conditions of the interfering link are worse, and then PAFφ kThe range of λ is broadened, making it more likely to achieve its global optimum. It can also be seen that the performance gap increases with λ. p The increase leads to a decrease. This is because, for the BRS scheme, by using X... kD and X kP To select the best relay IoT-R kF However, for larger λ... p X kP The effect weakens, in this case, X kP Mainly composed of X kD Decision. Furthermore, for larger R... s Security interruption performance will be reduced.

[0083] Figure 7 SOPs for the proposed system using three different relay selection schemes and M are drawn. Clearly, as M increases, security interruption performance decreases. This is because, for larger M values, Eve is better able to eliminate IoT-R... kJ Interference. It was also observed that the performance gap narrowed as M increased.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for secure power allocation and relay selection in the presence of unknown eavesdropping cognitive IoT, characterized in that, A cognitive relay network based on the Internet of Things (IoT) is established, comprising one IoT secondary transmitter (IoT-ST), one IoT secondary receiver (IoT-SD), one primary user (PU), one eavesdropper (Eve), and N+1 backup relays (IoT-R). The transmission process consists of two phases: In the first phase, the IoT-ST transmits confidential signals to all backup relays via local connections; in the second phase, power allocation and optimal relay selection are performed, and the selected relay is forwarded. Confidential information is forwarded to the IoT secondary receiver IoT-SD, with N other backup relays. Acting as a friendly jammer, it emits artificial noise to deliberately confuse Eve; The power allocation specifically includes: Let P be the total transmit power of N+1 candidate relays, allocated to the best relay. The power allocation factor is ,and ;therefore The transmission power is In the formula For the preset threshold, , The channel coefficients for relaying data to the primary user; Emit AN vector Define a matrix , Indicates from Channel gain to IoT-SD Indicates from The channel gain to PU; the precoding matrix of the AN vector is , form An orthogonal basis; therefore, The transmission power is: .

2. The method for secure power allocation and relay selection in a cognitive Internet of Things with unknown eavesdropping capabilities as described in claim 1, characterized in that, The optimal relay selection refers to establishing reliable transmission through a forwarding relay. The specific steps for establishing reliable transmission are as follows: Step 1: Obtain the instantaneous confidentiality capability in the cognitive relay network, represented as: ,in It is the channel capacity of the main link. It is the channel capacity of the eavesdropping link. For the instantaneous signal-to-noise ratio of IoT SD, Let this be Eve's instantaneous signal-to-noise ratio. , Indicates from Channel gain to IoT-SD Indicates from Channel gain to Eve This refers to the noise variance under IoT-SD; When the following constraints are met: , Indicates the target secrecy rate, i.e. In the formula Then, proceed to step two; Step 2: Identify the forwarding relay of Is it below the preset threshold? If so, proceed to step three; Otherwise, proceed to step four; Step 3: In the second stage, forwarding relay During the cooperative transmission phase, power Broadcast message x; Step 4: In the second stage, forwarding relay Remain silent during the collaborative transmission phase.

3. The method for secure power allocation and relay selection in presence of unknown eavesdropper cognitive IoT networks as claimed in claim 2 wherein, The forwarding relay The method for forwarding confidential information to the IoT secondary receiver IoT-SD is as follows: The first step is to select the optimal power allocation factor. In a given and Below, instantaneous security capacity Less than the target confidentiality rate The probability SOP is defined as follows: ; An optimization function is constructed with the goal of minimizing the SOP: ; Given and The security breach event is defined as: ; Arrange the CSIs, including the main channel and the Eve channel, on both sides of the inequality, that is: In the formula, ; Therefore, the confidentiality breach event is redefined as: ,Will Simplified to ,and , Then Substitution ,get ; Therefore, the optimal power allocation factor for the kth alternative relay. for: ;Right now, ;in, ; The second step is power distribution among the backup relays. For each candidate relay k = 1, 2, ..., N+1, we obtain : , , ; In the absence of Eve's prior information, for the best relay selection method, the selection criteria of the forwarding relay are: ; Thus, the SOP of the optimal relay selection method is: ; The exact expression for the Standard Operating Procedure (SOP) of the optimal relay selection method is derived as follows: In the formula, , , , ; Indicates the number of Eve antennas. , , and Both represent parameters that represent the trade-off between accuracy and complexity. Indicates the channel parameters at PU. Indicates the channel parameters at IoT-SD. , , , , , , , , ; For the random relay selection method, forwarding relay Select from all relays that establish secure transmissions that meet the requirements. of Through derivation, the Standard Operating Procedure (SOP) for the random relay selection method is: ; The exact expression for the Standard Operating Procedure (SOP) of the random relay selection method is derived as follows: In the formula , , ; , , , , .

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