Vehicle relay-assisted covert communication position optimization method for Internet of Vehicles

Abstract

The invention discloses a vehicle relay-assisted covert communication position optimization method for the Internet of Vehicles, and the method comprises the following steps: (1) building a covert communication model in an urban environment, which comprises a sender Alice, a receiver Bob, a relay and a detector Eve; (2) modeling the channel gain in the urban environment; (3) determining an optimal detection threshold value and a minimum total error probability of a detection party Eve; (4) calculating the maximum transmission rate between the Relay and the Bob based on the concealed communication transmission outage probability constraint; (5) optimizing the position of the Relay through a geometric method by taking the maximum transmission rate as a target function; according to the method, the transmission rate of the covert communication can be remarkably improved on the premise of ensuring the reliability and the safety of the covert communication.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a vehicle relay-assisted covert communication position optimization method for vehicle networking. Background Art

[0002] The Internet of Vehicles (IOV) is a network system for wireless communication and information exchange between vehicles, roads, pedestrians, and the Internet. In order to increase the network rate of the IoV to support multimedia applications, existing methods propose a network path selection technology to meet the network throughput requirements. This method is based on an attractor selection model that enables vehicles to switch from a path directly connected to a cellular network to a relay-type path that accesses the Internet through neighboring vehicles; in order to improve the security of IoV communications, existing technologies use an improved multi-server-based IOV authentication and key protocol. This protocol uses passwords and smart cards to hide private keys and is suitable for vehicle environments that support privacy and security requirements in IOV systems, where vehicles and trusted authorities (TAs) do not need to store any certificates for verification and tracking. They also proved that the proposed CL-CPPA protocol is able to resist modification attacks, impersonation attacks, and other existing attacks.

[0003] Current covert communication methods in IoVs usually adopt schemes that do not use relay assistance or rely on fixed relay assistance. Analysis shows that applying relay selection leads to reduced PDE. Although there are many studies on IoV communications, most of them focus on rate optimization and latency reduction of communication methods, and only fixed detectors are considered in detection research, without considering the threat posed by the mobility of detectors to the transmission rate and security of covert communications. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a vehicle relay-assisted covert communication position optimization method for the Internet of Vehicles, which utilizes a mobile relay to cope with the challenges posed by a mobile detection party to the security of covert communications, optimizes the covert communication transmission rate while ensuring the security of covert communications, and obtains the optimal position of the relay based on the relative positions of the receiver and the detection party.

[0005] Technical solution: The vehicle relay-assisted covert communication location optimization method for vehicle networking described in the present invention includes the following steps: (1) Establish a covert communication model in an urban environment, including the sender Alice, the receiver Bob, the relay Relay, and the detector Eve; (2) Modeling channel gain in urban environments; (3) Determine the optimal detection threshold and minimum total error probability of the detector Eve; (4) Based on the probability constraint of covert communication transmission interruption, calculate the maximum transmission rate between Relay and Bob; (5) Taking maximizing the transmission rate as the objective function, the position of relays is optimized through geometric methods.

[0006] Furthermore, the modeling formula in step (2) is as follows: ; ; in, represents the channel gain from Relay to Bob, and represents the channel gain from Relay to Eve, A represents the antenna gain of the vehicle antenna, c represents the speed of light in vacuum, Indicates the carrier frequency; and They represent the distance between Relay and Bob and the distance between Relay and Eve respectively, and d is the path attenuation index of the channel; and is the Rayleigh fading factor, which obeys the Rayleigh distribution.

[0007] Furthermore, the formula in step (3) is as follows: ; ; in, is the optimal detection threshold, is the optimal total error rate; Indicates the transmission power of the relay. is the channel gain between Relay and Eve, is the variance of the additive white Gaussian noise AWGN at Eve, for The mean of represents Bob’s self-interference power.

[0008] Furthermore, the detection threshold in step (3) The specific method for determining is as follows: Calculate Eve's false alarm rate and false negative rate , the total error probability ; Through analysis The monotonicity of hour, Get the minimum value.

[0009] Furthermore, the maximum transmission rate formula of step (4) is as follows: ; in, is the channel transmission rate between Relay and Bob, B is the channel bandwidth, Indicates the transmission power of the relay. is the channel gain between Relay and Bob, for The mean of represents the artificial noise power transmitted from Eve to Bob, is a small positive number between 0 and 1. is the variance of the additive white Gaussian noise AWGN at Bob.

[0010] Furthermore, in step (4), the constraints are as follows: ; Among them, when Get the maximum value hour, will take the maximum value; is the transmission interruption probability between Relay and Bob, Indicates the transmission power of the relay. is the channel gain between Relay and Bob, for The mean of represents the artificial noise power transmitted from Eve to Bob, is the channel transmission rate between Relay and Bob, B is the channel bandwidth, is the variance of the additive white Gaussian noise AWGN at Bob.

[0011] Furthermore, in step (5), let Bob’s position be the origin, that is, ,set up for Then the objective function is: ; ; when , ;when : ; in, , and are the two-dimensional coordinates of Bob, Eve and Relay, c is the speed of light in vacuum, is the carrier frequency, A represents the antenna gain of the vehicle antenna, is the Rayleigh fading factor of the channel between Relay and Eve, Indicates the transmission power of the relay. for The mean of represents Bob’s self-interference power, A small positive number between 0 and 1.

[0012] Furthermore, the hidden constraint parameter The value range is 0< <0.2.

[0013] Furthermore, step (5) further includes: monitoring the position of Eve in real time; recalculating according to the updated position of Eve , and dynamically adjust the position of Relay to meet the constraints.

[0014] The vehicle relay-assisted concealed communication position optimization system for vehicle networking according to the present invention comprises: Covert module: used to establish a covert communication model in an urban environment, including the sender Alice, the receiver Bob, the relay Relay and the detector Eve; Gain module; used to model channel gain in urban environments; Error probability module: used to determine the optimal detection threshold and minimum total error probability of the detector Eve; Transmission module: used to derive the maximum transmission rate between Relay and Bob based on the probability constraint of covert communication transmission interruption; Geometry module: It is used to optimize the location of relays through geometric methods with the objective function of maximizing the transmission rate.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: the present invention analyzes the channel characteristics of the covert communication receiver, covert communication relay and covert communication detector, fully considers the mobility of the relay, receiver and detector, uses mobile relay to counter mobile detector, and optimizes the covert transmission rate by optimizing the position of the relay. Simulation results show that the proposed method improves the transmission rate and security of communication. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of the present invention; Figure 2 It is a relay vehicle assisted covert communication model of the present invention; Figure 3 It is a visual schematic diagram of the objective function P3 of the present invention; Figure 4 This is a practical operation flow chart of optimizing the relay vehicle Relay position of the present invention; Figure 5 is the different Eve artificial noise power of the present invention The effect of Eve's horizontal and vertical coordinates on the information transmission rate between Relay and Bob under the following conditions The impact of Figure 6 are different hidden constraint parameters of the present invention Eve artificial noise power under the condition The information transmission rate between Relay and Bob impact. DETAILED DESCRIPTION

[0017] The technical solution of the present invention is further described below in conjunction with the accompanying drawings.

[0018] like Figure 1 As shown, an embodiment of the present invention provides a vehicle relay-assisted covert communication position optimization for vehicle networking, including the following steps: S1. Establishing a communication model like Figure 2 As shown in Figure 1, a model of covert communication in the Internet of Vehicles in an urban environment is described. In this model, Alice is the sender, Bob is the receiver, and Eve is the listener. Bob and Eve will send artificial noise to each other to interfere with each other's signal reception and signal detection. At the same time, Bob and Eve will generate self-interference.

[0019] In an urban environment, assume that Bob, Eve, and the relay vehicle are on the same altitude plane, and their position coordinates are set as , and .

[0020] Considering the obstruction of buildings and trees in urban environments, Relay can only support non-line-of-sight (NLOS) connections. Based on the path loss model and Rayleigh fading model in wireless communication, the channel gain between Relay and Bob, and the channel gain between Relay and Eve can be expressed as: (1); (2); in, A represents the antenna gain of the vehicle antenna, Indicates the carrier frequency; and They represent the distance between Relay and Bob and the distance between Relay and Eve respectively, and d is the path attenuation index of the channel; and is the Rayleigh fading factor, which obeys the Rayleigh distribution; and represents the self-interference channel between Bob and Eve; represents the channel gain from Bob to Eve, and represents the channel gain from Eve to Bob. The distance is added by 5 in the formula to take into account that the communication participants are vehicles with a volume, which also avoids the situation where the channel gain is infinite in subsequent analysis and derivation. c represents the speed of light in a vacuum.

[0021] Because of the multipath effect, and Not the same. It follows an exponential distribution with mean , and It follows an exponential distribution with a mean of , When the relay forwards the signal from Alice, the signal received by Bob can be expressed as: (3); in Indicates the transmission power of the relay. represents Bob’s self-interference power, represents the artificial noise power transmitted from Eve to Bob. Represents the signal from Alice forwarded by Relay. . represents Bob’s self-interference signal, . represents the artificial noise signal transmitted by Eve to Bob, . Refers to a complex Gaussian distribution with mean 0 and variance 1. is Bob’s self-interference coefficient, where it is assumed that the self-interference is completely eliminated, that is, . represents the additive white Gaussian noise (AWGN) at Bob, .

[0022] S2. Detect Eve Depending on whether the relay forwards the signal, the signal detected by Eve can be divided into two cases: (4); in represents the null hypothesis that the relay does not forward the signal, Represents the null hypothesis that the relay forwards the signal. is the self-interference coefficient of Eve. Similarly, assuming that the self-interference is completely eliminated, that is, . is the additive white Gaussian noise (AWGN) at Eve, .

[0023] So we can get Eve's detection rules as follows: (5); here represents the average signal power received by Eve, is the detection threshold of Eve. represents the binary decision made by Eve on the relay forwarding signal, Represents the binary decision made by Eve on the signal not forwarded by the Relay.

[0024] then , can be rewritten as: (6); Then we can express Eve’s total error probability as: (7); in is the false alarm rate, is the false negative rate. According to equations (5) and (6), they can be specifically expressed as: (8); (9); Eve's goal is to minimize , which represents the best detection performance of Eve. The key to minimizing the detection threshold is to determine Instead, Relay aims to make Approaching 1 indicates optimal communication concealment. The optimal total error probability can be expressed as ,in is a small positive number.

[0025] According to formula (8), There is only one variable in the false alarm rate ,at the same time .set up for X . Therefore, its probability density function and probability distribution can be written as: (10); (11); Next, simplify the false alarm rate .because , formula (8) can be rewritten as: (12); According to the distribution function (11), formula (12) is further rewritten as: (13); Similarly, because , formula (9) can be rewritten as: (14); According to the distribution function, equation (14) can be rewritten as: (15); Therefore, according to equations (7), (13) and (15), Eve’s total error probability can be expressed as a piecewise function: (16); It can be found that hour, Always equal to 1. hour, In the segment Decreasing. season right The derivation is as follows: (17); because , so , so the numerator in the above formula is greater than zero, and the entire fraction is also greater than zero, so in this interval Inside With increasing.

[0026] In summary, through analysis The monotonicity of When The minimum value of , that is: (18); (19); S3. Optimize communication performance In order to obtain the maximum communication transmission rate, the following objective function is proposed: (20); (twenty one); (twenty two); in Indicates the covert transmission rate between Relay and Bob. Represents the probability of transmission interruption. and is a small positive number between 0 and 1.

[0027] Then, according to Shannon's formula, the channel capacity can be expressed as: (twenty three); Where B is the channel bandwidth. , the above formula can be simplified to: (twenty four); Due to the existence of self-interference and artificial noise, May be greater than , which will cause the transmission to be interrupted. According to this definition, can be written as: (25); because , continue to simplify: (26); According to formula (26), we can find Follow Incrementally, similarly, Also follow Therefore, when Get the maximum value hour, will reach the maximum value. ,Right now: (27); According to equations (1) and (27), we find Follow Increasing, and Follow Therefore Also follow Decreasing, in order to maximize , which needs to be minimized .

[0028] First, we derive the constraints on . According to equations (2), (19) and (20), we can obtain: (28); For simplicity, for Therefore, the objective function can be obtained as follows: (29); (30); Without affecting the correctness of the derivation, assume that Bob's position is the origin, that is, , so the objective function can be simplified to: (31); (32); To understand this objective function, a geometric method can be used. The objective function means that the point It is at the point is the center of the circle, The goal is to make the point Closest to the origin.

[0029] when When Figure 3 As shown on the left, the origin is at point is the center of the circle, On or outside a circle with a radius of The point closest to the origin can be located at the origin, that is: (33); when When Figure 3 As shown on the right, the origin is at point is the center of the circle, is the radius of the circle. The point closest to the origin should be on the circle and coincide with the point , the origin is collinear. Use equation (34) to solve the point Location: (34); This system of equations has two solutions. After discarding the solution far from the origin, we get the point Location: (35); (36); In summary, the optimal position of Relay is as follows: (37); Finally, all the parameters that need to be optimized and their optimal values ​​are obtained, as shown in Table 1.

[0031] Table 1 Optimization parameters .

[0032] At the same time, we also get the actual operation of executing the proposed optimization method when the vehicle moves, that is, the actual operation of optimizing the relay vehicle Relay position, the step flow is as follows: Figure 4 As shown, the specific operations are as follows: aCalculated based on actual channel parameters and target performance index parameters ( ); b takes Eve's position as the center of the circle, Make a circle with radius; c. If Bob is on or outside the circle, then in order to achieve the maximum covert communication rate, the relay can be at Bob's location, that is, the two cars should be as close as possible; dIf Bob is in this circle, in order to achieve the maximum covert communication rate, the Relay needs to be in the same line with Bob and Eve as much as possible, and the distance between Relay and Eve should be kept as close as possible. .

[0033] S4. Performance Analysis In order to verify the performance of the model, the parameters are assigned as shown in Table 2.

[0034] Table 2 Simulation parameters ; like Figure 5 As shown, is the information transmission rate between Relay and Bob, is the artificial noise power transmitted from Eve to Bob, and are Eve's plane horizontal and vertical coordinates respectively. According to formula (27), because , , and Inversely proportional. When reaching a stable maximum value, Increase, When When the values ​​of are 8, 10 and 12 (dbm), The maximum values ​​are 4.7, 4.3 and 3.8 (bps / Hz) respectively. Increase ( Increase at the same time), will decrease, so as and The increase of and will reach a constant value of 0 more quickly, It will also reach a stable maximum value more quickly. When the values ​​of are 8, 10 and 12 (dbm), When the stable maximum value is reached, the distances between Eve and the origin (Bob) are 5.7, 5.3, and 4.9 (m), respectively.

[0035] like Figure 6 As shown, is the information transmission rate between Relay and Bob, is the artificial noise power transmitted from Eve to Bob, is a small positive number, representing the hidden constraint parameter. When other parameters remain unchanged, The increase will cause For example, when When the values ​​of are 0.1, 0.15 and 0.2 respectively, The maximum values ​​of are approximately 1.7, 2.2, and 2.5 (bps / Hz) respectively; and when the distance between Eve and the origin (Bob) is the same, the larger will always produce greater This shows that the higher the tolerance to covert communication being detected, the higher the transmission rate, which is consistent with our theoretical deduction and actual observation.

[0036] also, About The reason for the unimodal function of Increase, However, with the Increase, also increases (because ), which will result in decrease, which then leads to and Increase. and is a negative number, so the distance between Relay and Bob ( ) will decrease, will increase, resulting in There is a trend of increasing. When is smaller, the latter trend dominates, while When is larger, the former trend is dominant. The increase of First increase and then decrease.

[0037] Through the above analysis and verification, the results show that the present invention can significantly improve the transmission rate of covert communication while ensuring the reliability and security of covert communication.

Claims

1. A vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: The following steps are involved: (1) Establish a covert communication model in an urban environment, including the sender Alice, the receiver Bob, the relay Relay, and the detector Eve; (2) Modeling channel gain in urban environments; (3) Determine the optimal detection threshold and minimum total error probability of the detector Eve; (4) Based on the probability constraint of covert communication transmission interruption, derive the maximum transmission rate between Relay and Bob; (5) Taking maximizing the transmission rate as the objective function, the position of relays is optimized through geometric methods.

2. According to claim 1, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: The modeling formula in step (2) is as follows: ； ； in, represents the channel gain from Relay to Bob, and represents the channel gain from Relay to Eve, A represents the antenna gain of the vehicle antenna, c represents the speed of light in vacuum, Indicates the carrier frequency; and They represent the distance between Relay and Bob and the distance between Relay and Eve respectively, and d is the path attenuation index of the channel; and is the Rayleigh fading factor, which obeys the Rayleigh distribution.

3. According to claim 1, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: The formula in step (3) is as follows: ； ； in, is the optimal detection threshold, is the optimal total error rate; Indicates the transmission power of the relay. is the channel gain between Relay and Eve, is the variance of the additive white Gaussian noise AWGN at Eve, for The mean of represents Bob’s self-interference power.

4. According to claim 3, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: Detection threshold in step (3) The specific method for determining is as follows: Calculate Eve's false alarm rate and false negative rate , the total error probability ; Through analysis The monotonicity of hour, Get the minimum value.

5. According to claim 1, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: Step (4) The maximum transmission rate formula is as follows: ； in, is the channel transmission rate between Relay and Bob, B is the channel bandwidth, Indicates the transmission power of the relay. is the channel gain between Relay and Bob, for The mean of represents the artificial noise power transmitted from Eve to Bob, is a small positive number between 0 and 1. is the variance of the additive white Gaussian noise AWGN at Bob.

6. According to claim 5, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: In step (4), the constraints are as follows: ； Among them, when Get the maximum value hour, will take the maximum value; is the transmission interruption probability between Relay and Bob, Indicates the transmission power of the relay. is the channel gain between Relay and Bob, for The mean of represents the artificial noise power transmitted from Eve to Bob, is the channel transmission rate between Relay and Bob, B is the channel bandwidth, is the variance of the additive white Gaussian noise AWGN at Bob.

7. According to claim 1, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: In step (5), let Bob’s position be the origin, that is, ,set up for Then the objective function is: ； ； when , ;when : ； in, , and are the two-dimensional coordinates of Bob, Eve and Relay; c is the speed of light in vacuum, is the carrier frequency, A represents the antenna gain of the vehicle antenna, is the Rayleigh fading factor of the channel between Relay and Eve, Indicates the transmission power of the relay. for The mean of represents Bob’s self-interference power, A small positive number between 0 and 1.

8. According to claim 7, a vehicle relay-assisted covert communication location optimization method for vehicle networking, characterized in that: Hidden Constraint Parameters The value range is 0< < 0.2.

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