A RIS phase shift optimization method and system in a V2V communication system

Abstract

The present invention discloses a RIS phase shift optimization method and system in a V2V communication system, which relates to the field of communication technology. The method comprises: based on a first position, a second position and a third position, respectively determining an incident channel elevation angle, an incident channel azimuth angle, a reflected channel elevation angle and a reflected channel azimuth angle, as well as a vehicle-to-vehicle channel delay, a channel delay from a first vehicle to each component in a RIS element, and a channel delay from each component in a RIS element to a second vehicle, and then sequentially calculating the signal receiving power of the second vehicle and the maximum power RIS phase shift; further calculating the minimum Doppler spread RIS phase shift; and determining the optimal RIS phase shift in the V2V communication system based on the maximum power RIS phase shift and the minimum Doppler spread RIS phase shift. The present invention realizes the phase shift optimization of the RIS element in the V2V communication system, which helps to improve communication efficiency and stability.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a RIS phase shift optimization method and system in a V2V communication system. Background Art

[0002] RIS (Reconfigurable Intelligent Surface) has gained great attention in the field of wireless communications and signal processing due to its potential to control the wireless propagation environment. RIS brings significant performance improvements in a cost-effective manner, accompanied by challenges in communication, optimization, and probability theory, such as maximizing achievable rates and energy efficiency, physical layer security, and efficient channel estimation and channel modeling methods.

[0003] At present, researchers have studied the resource management of RIS-assisted vehicle network communication systems, aiming to maximize the received power on the RIS reflection path, but they ignore the Doppler effect caused by vehicle mobility and the multipath effect caused by multiple RIS reflection paths. Other researchers have designed communication protocols to alleviate the Doppler effect associated with high vehicle mobility, but the performance of their solutions depends on the accuracy of channel estimation. Considering the mobility of the signal receiving end, other researchers have designed various channel models for RIS-assisted mobile communications, but most of these models are based on far-field transmission formulas, making them unsuitable for urban vehicle networks or millimeter-wave vehicle communications. Summary of the invention

[0004] The object of the present invention is to provide a method and system for optimizing RIS phase shift in a V2V communication system, so as to optimize the phase shift of RIS elements in the V2V communication system and thereby improve the communication efficiency of the communication system.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] A RIS phase shift optimization method in a V2V communication system, comprising:

[0007] Acquire a first position, a second position and a third position in a V2V communication system at any time slot; the V2V communication system includes a first vehicle, a second vehicle and a RIS element; the first position is a three-dimensional coordinate of the first vehicle in a preset three-dimensional Cartesian coordinate system, the second position is a three-dimensional coordinate of the second vehicle in a preset three-dimensional Cartesian coordinate system; the third position is a three-dimensional coordinate of a reference position of the RIS element in a preset three-dimensional Cartesian coordinate system;

[0008] Determine an incident channel elevation angle and an incident channel azimuth angle according to the first position and the RIS element reference position; determine a reflection channel elevation angle and a reflection channel azimuth angle according to the second position and the RIS element reference position;

[0009] Based on the first position and the second position, calculating the channel delay between vehicles; based on the first position and the third position, calculating the channel delay from the first vehicle to each component in the RIS element; based on the second position and the third position, calculating the channel delay from each component in the RIS element to the second vehicle;

[0010] Calculate the signal receiving power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle;

[0011] calculating a power maximum RIS phase shift based on a signal received power of the second vehicle;

[0012] Calculate the Doppler spread minimum RIS phase shift based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element;

[0013] Based on the maximum power RIS phase shift and the minimum Doppler spread RIS phase shift, an optimal RIS phase shift in the V2V communication system is determined.

[0014] Optionally, calculating the signal reception power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle includes:

[0015] calculating an inter-vehicle channel gain based on the first position and the second position;

[0016] Calculate a receiving array response vector of each element in the RIS element based on the first position, the third position, the incident channel elevation angle, and the incident channel azimuth angle;

[0017] Calculate a channel gain from the first vehicle to each element in the RIS element according to a receiving array response vector of each element in the RIS element, the first position, and the third position;

[0018] Calculate a reflection array response vector of each element in the RIS element based on the second position, the third position, the reflection channel elevation angle, and the reflection channel azimuth angle;

[0019] Calculate the channel gain from each element in the RIS element to the second vehicle based on the reflection array response vector of each element in the RIS element, the second position and the third position;

[0020] Calculate the passband signal received by the second vehicle based on the inter-vehicle channel delay, the inter-vehicle channel gain, the channel delay and channel gain from the first vehicle to each component in the RIS element, the channel delay and channel gain from each component in the RIS element to the second vehicle, and the passband signal transmitted by the first vehicle;

[0021] calculating a complex baseband signal received by the second vehicle based on the passband signal received by the second vehicle;

[0022] Calculating a first channel angle according to a receiving array response vector of each element in the RIS element and a reflecting array response vector of each element in the RIS element; the first channel angle is a cascade channel angle of the first vehicle, the RIS element and the second vehicle;

[0023] The signal reception power of the second vehicle is calculated according to the first channel angle, the complex baseband signal received by the second vehicle, and the signal transmission power of the first vehicle.

[0024] Optionally, calculating the inter-vehicle channel gain based on the first position and the second position specifically includes:

[0025] Calculating the distance between vehicles based on the first position and the second position;

[0026] Calculating the channel path loss between vehicles according to the distance between vehicles;

[0027] The inter-vehicle channel gain is calculated according to the inter-vehicle channel path loss.

[0028] Optionally, calculating the receiving array response vector of each element in the RIS element based on the first position, the third position, the incident channel elevation angle, and the incident channel azimuth angle specifically includes:

[0029] Calculating a first RIS distance according to the first position and the third position; the first RIS distance being the distance between the first vehicle and the RIS element;

[0030] Based on the third position, determining the position coordinates of each original in the RIS element;

[0031] Calculate a receiving array response vector of each element in the RIS element according to the incident channel elevation angle, the incident channel azimuth angle, the position coordinates of each element in the RIS element, the first position and the first RIS distance;

[0032] Calculating a channel gain from the first vehicle to each component in the RIS element according to a receiving array response vector of each component in the RIS element, the first position, and the third position, specifically comprising:

[0033] Calculating the distance from the first vehicle to each component in the RIS component according to the first position and the position coordinates of each component in the RIS component;

[0034] Calculate a first RIS channel path loss based on the distance from the first vehicle to each component in the RIS element; the first RIS channel path loss is the channel path loss from the first vehicle to each component in the RIS element;

[0035] A channel gain from the first vehicle to each component in the RIS element is calculated according to a receiving array response vector of each component in the RIS element and the first RIS channel path loss.

[0036] Optionally, based on the first position and the third position, calculating the channel delay from the first vehicle to each component in the RIS element specifically includes:

[0037] Based on the third position, determining the position coordinates of each original in the RIS element;

[0038] Calculating the distance from the first vehicle to each component in the RIS component according to the first position and the position coordinates of each component in the RIS component;

[0039] Based on the distance from the first vehicle to each component in the RIS element, a channel delay from the first vehicle to each component in the RIS element is calculated.

[0040] Optionally, calculating the reflection array response vector of each element in the RIS element based on the second position, the third position, the reflection channel elevation angle, and the reflection channel azimuth angle specifically includes:

[0041] Calculating a second RIS distance according to the second position and the third position; the second RIS distance being the distance between the second vehicle and the RIS element;

[0042] Based on the third position, determining the position coordinates of each original in the RIS element;

[0043] Calculate a reflection array response vector of each element in the RIS element according to the reflection channel elevation angle, the reflection channel azimuth angle, the position coordinates of each element in the RIS element, the second position and the second RIS distance;

[0044] Calculating a channel gain from each element in the RIS element to the second vehicle according to the reflection array response vector of each element in the RIS element, the second position, and the third position, specifically comprising:

[0045] Calculating the distance from each component in the RIS component to the second vehicle according to the second position and the position coordinates of each component in the RIS component;

[0046] Calculate a second RIS channel path loss based on the distance from each component in the RIS element to the second vehicle; the second RIS channel path loss is the channel path loss from each component in the RIS element to the second vehicle;

[0047] The channel gain from each element in the RIS element to the second vehicle is calculated according to the reflection array response vector of each element in the RIS element and the second RIS channel path loss.

[0048] Optionally, calculating the Doppler spread minimum RIS phase shift based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element specifically includes:

[0049] Calculate the Doppler spread of a first communication path based on the channel delay between the vehicles, the channel delay from the first vehicle to each component in the RIS element, and the channel delay from each component in the RIS element to the second vehicle; the first communication path is a communication path that is sent from the first vehicle, passes through the RIS element, and reaches the second vehicle;

[0050] Calculating the Doppler spread of a second communication path based on the channel delay of each element in the RIS element in the reflection channel; the second communication path is a communication path from the RIS element to the second vehicle;

[0051] Calculating a Doppler spread of the V2V communication system according to a Doppler spread of the first communication path and a Doppler spread of the second communication path;

[0052] Based on the Doppler spread of the V2V communication system, a Doppler spread minimum RIS phase shift is determined.

[0053] To achieve the above object, the present invention also provides the following technical solutions:

[0054] A RIS phase shift optimization system in a V2V communication system, comprising:

[0055] A position determination module, configured to obtain a first position, a second position and a third position in a V2V communication system in any time slot; the V2V communication system comprises a first vehicle, a second vehicle and a RIS element; the first position is a three-dimensional coordinate of the first vehicle in a preset three-dimensional Cartesian coordinate system, the second position is a three-dimensional coordinate of the second vehicle in a preset three-dimensional Cartesian coordinate system; the third position is a three-dimensional coordinate of a reference position of the RIS element in a preset three-dimensional Cartesian coordinate system;

[0056] a channel angle determination module, configured to determine an incident channel elevation angle and an incident channel azimuth angle according to the first position and the RIS element reference position; and to determine a reflected channel elevation angle and a reflected channel azimuth angle according to the second position and the RIS element reference position;

[0057] a channel delay calculation module, configured to calculate the channel delay between vehicles based on the first position and the second position; calculate the channel delay from the first vehicle to each component in the RIS element based on the first position and the third position; and calculate the channel delay from each component in the RIS element to the second vehicle based on the second position and the third position;

[0058] a signal receiving power determination module, configured to calculate the signal receiving power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle;

[0059] a first phase shift determination module, configured to calculate a power maximum RIS phase shift based on a signal received power of the second vehicle;

[0060] A second phase shift determination module is used to calculate a Doppler spread minimum RIS phase shift based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element;

[0061] The optimal phase shift determination module is used to determine the RIS optimal phase shift in the V2V communication system based on the maximum power RIS phase shift and the Doppler spread minimum RIS phase shift.

[0062] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0063] The present invention discloses a RIS phase shift optimization method and system in a V2V communication system. First, the first position of the first vehicle, the second position of the second vehicle and the third position of the RIS element in the V2V communication system are determined, and the three positions are in the same coordinate system; the incident channel elevation angle and the incident channel azimuth angle are determined according to the first position and the reference position of the RIS element, and the reflected channel elevation angle and the reflected channel azimuth angle are determined according to the second position and the reference position of the RIS element; then, according to the first position, the second position and the third position, the channel delay between vehicles, the channel delay from the first vehicle to each element in the RIS element, and the channel delay from each element in the RIS element to the second vehicle are calculated accordingly. According to the above three positions, the different channel delays, channel elevation angles and azimuth angles calculated are combined with the bandpass signal transmitted by the first vehicle and the signal transmission power of the first vehicle to calculate the signal reception power of the second vehicle, and then the maximum power RIS phase shift is calculated. The minimum RIS phase shift for Doppler spread is calculated according to the obtained different channel delays; the optimal RIS phase shift in the V2V communication system is determined based on the maximum power RIS phase shift and the minimum Doppler spread RIS phase shift, thereby optimizing the phase shift of the RIS element, which is beneficial to the subsequent reduction of the Doppler spread caused by the high mobility of the vehicle and the multipath spread caused by the RIS reflection channel, while maximizing the signal reception power gain, thereby improving the communication efficiency and stability of the V2V communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0065] Figure 1 It is a flow chart of the RIS phase shift optimization method in the V2V communication system of the present invention;

[0066] Figure 2 Schematic diagram of a system model of a V2V communication system of the present invention;

[0067] Figure 3 is a comparison diagram of channel gains corresponding to different time slots in a specific example of the present invention;

[0068] Figure 4 It is a comparison diagram of delay spread corresponding to different time slots in a specific example of the present invention;

[0069] Figure 5 is a comparison diagram of channel gain and delay spread at different moving speeds in a specific example of the present invention;

[0070] Figure 6 It is a schematic diagram of the structure of the RIS phase shift optimization system in the V2V communication system of the present invention. DETAILED DESCRIPTION

[0071] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0072] The purpose of the present invention is to provide a RIS phase shift optimization method and system in a V2V communication system, which can reduce the Doppler expansion caused by the high mobility of the vehicle and the multipath expansion caused by the RIS reflection channel by optimizing the phase shift of the RIS element, and at the same time maximize the signal receiving power gain.

[0073] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0074] like Figure 1 As shown, the RIS phase shift optimization method in the V2V communication system of the present invention includes:

[0075] Step 100, obtaining a first position, a second position and a third position in a V2V communication system at any time slot; the V2V communication system includes a first vehicle, a second vehicle and a RIS element; the first position is a three-dimensional coordinate of the first vehicle in a preset three-dimensional Cartesian coordinate system, the second position is a three-dimensional coordinate of the second vehicle in a preset three-dimensional Cartesian coordinate system; the third position is a three-dimensional coordinate of a reference position of the RIS element in a preset three-dimensional Cartesian coordinate system.

[0076] Step 100 specifically includes:

[0077] 1) Determine a preset three-dimensional Cartesian coordinate system;

[0078] 2) Based on the preset three-dimensional Cartesian coordinate system, determine a first x-axis coordinate, a first z-axis coordinate, a second x-axis coordinate and a second z-axis coordinate; the first x-axis coordinate is the initial x-axis coordinate of the first vehicle in the preset three-dimensional Cartesian coordinate system; the second x-axis coordinate is the initial x-axis coordinate of the second vehicle in the preset three-dimensional Cartesian coordinate system; the first z-axis coordinate is the z-axis coordinate of the first vehicle in the preset three-dimensional Cartesian coordinate system; the second z-axis coordinate is the z-axis coordinate of the second vehicle in the preset three-dimensional Cartesian coordinate system.

[0079] 3) Determine a time block of a preset length and divide the time block into multiple time slots. Specifically, set a time block of a preset length T, divide the time block T into M time slots, and the length of each time slot is Δ=T / M. If the length of the time slot is within 100ms, the position of the vehicle will not change significantly during this period, so it can be assumed that the path loss of the V2V communication channel in any time slot is constant.

[0080] 4) For any of the time slots, the three-dimensional coordinates of the first vehicle are calculated according to the time slot, the first x-axis coordinate, the moving speed of the first vehicle and the first z-axis coordinate; the three-dimensional coordinates of the first vehicle are the first position.

[0081] Specifically, at the mth time slot, the x-axis position x of the first vehicle is S The calculation formula for [m] is:

[0082] x S [m] = mΔv S +x S0

[0083] Among them, x S0 Indicates the first x-axis coordinate, v S Indicates the moving speed of the first vehicle.

[0084] The three-dimensional coordinates c of the first vehicle s The calculation formula for [m] is:

[0085] c S [m]=(x S [m],0,z S ) T

[0086] Among them, z S Indicates the first z-axis coordinate.

[0087] 5) Calculating the three-dimensional coordinates of the second vehicle according to the time slot, the second x-axis coordinate, the moving speed of the second vehicle and the second z-axis coordinate; the three-dimensional coordinates of the second vehicle are the second position.

[0088] Specifically, at the mth time slot, the x-axis position x of the second vehicle is D The calculation formula for [m] is:

[0089] x D [m] = mΔv D +x D0

[0090] Among them, x D0 Indicates the second x-axis coordinate, v D Indicates the moving speed of the second vehicle.

[0091] The three-dimensional coordinates c of the second vehicle D The calculation formula for [m] is:

[0092] c D [m]=(x D [m],0,z D ) T

[0093] Among them, z D Indicates the second z-axis coordinate.

[0094] Step 200, determining the incident channel elevation angle and the incident channel azimuth angle according to the first position and the RIS element reference position; determining the reflection channel elevation angle and the reflection channel azimuth angle according to the second position and the RIS element reference position. Specifically, the positions of the incident channel elevation angle, the incident channel azimuth angle, the reflection channel elevation angle and the reflection channel azimuth angle are as follows: Figure 2 shown.

[0095] Step 300, based on the first position and the second position, calculate the channel delay between vehicles; based on the first position and the third position, calculate the channel delay from the first vehicle to each component in the RIS element; based on the second position and the third position, calculate the channel delay from each component in the RIS element to the second vehicle.

[0096] The step of calculating the inter-vehicle channel delay based on the first position and the second position specifically includes:

[0097] 1) At the mth time slot, based on the first position and the second position, calculate the distance between the first vehicle and the second vehicle The calculation formula is as follows:

[0098]

[0099] 2) Based on the distance between the first vehicle and the second vehicle Calculate the channel delay from the first vehicle to the second vehicle, that is, calculate the channel delay between vehicles The calculation formula is as follows:

[0100]

[0101] Here, c0 represents the speed of light.

[0102] Based on the first position and the third position, calculating the channel delay from the first vehicle to each component in the RIS element specifically includes:

[0103] 1) Based on the third position, determine the position coordinates of each original in the RIS element; specifically, assume that N=N x ×N y elements, where N x and N y They represent the number of elements of the RIS panel parallel to the x-axis and y-axis of the coordinate system respectively; the distances between adjacent elements along the x-axis and y-axis are d x <λ / 2 and d y <λ / 2, where λ is the signal wavelength. x Column y The elements in a row represent the nth instance of the RIS element.

[0104] According to the formula n=(n x -1)N x +n y , calculate the serial number n of the original.

[0105] According to the formula Calculate the position coordinates of each element in the RIS component; where, Indicates the coordinates of the reference position of the RIS element, i.e. the third position.

[0106] 2) According to the first position and the position coordinates of each component in the RIS component, the distance from the first vehicle to each component in the RIS component is calculated. The specific calculation formula is as follows:

[0107]

[0108] in, represents the distance from the first vehicle to the nth element in the RIS element at the mth time slot, q n represents the position coordinates of the nth original component in the RIS element, c S [m] represents the three-dimensional coordinates of the first vehicle at the mth time slot, that is, the first position.

[0109] 3) Based on the distance from the first vehicle to each component in the RIS component, the channel delay from the first vehicle to each component in the RIS component is calculated. The specific calculation formula is as follows:

[0110]

[0111] in, Represents the channel delay from the first vehicle to the nth component in the RIS element in the mth time slot.

[0112] Based on the second position and the third position, calculating the channel delay from each component in the RIS element to the second vehicle specifically includes:

[0113] 1) According to the second position and the position coordinates of each component in the RIS component, the distance from each component in the RIS component to the second vehicle is calculated. The specific calculation formula is as follows:

[0114]

[0115] in, represents the distance from the nth component to the second vehicle in the RIS element at the mth time slot, c D [m] represents the three-dimensional coordinates of the second vehicle at the mth time slot, that is, the second position.

[0116] 3) Based on the distance from each component in the RIS element to the second vehicle, the channel delay from each component in the RIS element to the second vehicle is calculated. The specific calculation formula is as follows:

[0117]

[0118] in, It represents the channel delay from the nth component to the second vehicle in the mth time slot within the RIS element.

[0119] Step 400, calculating the signal receiving power of the second vehicle based on the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle.

[0120] Step 400 includes:

[0121] 1) calculating a vehicle-to-vehicle channel gain based on the first position and the second position; specifically comprising:

[0122] 11) Calculate the distance between the vehicles based on the first position and the second position; that is, the distance between the first vehicle and the second vehicle

[0123] 12) Calculate the channel path loss between vehicles based on the distance between the vehicles The specific calculation formula is as follows:

[0124]

[0125] Where C0 represents the path loss at the reference distance D0 = 1m, β d is the path loss exponent.

[0126] 13) Calculate the inter-vehicle channel gain according to the inter-vehicle channel path loss; the specific calculation formula is as follows:

[0127]

[0128] in, Represents h d The Rayleigh fading component of

[0129] 2) calculating the receiving array response vector of each element in the RIS element based on the first position, the third position, the incident channel elevation angle and the incident channel azimuth angle; specifically comprising:

[0130] 21) Calculate a first RIS distance based on the first position and the third position The first RIS distance is the distance between the first vehicle and the RIS element, and is calculated as follows:

[0131]

[0132] 22) Based on the third position, determine the position coordinates of each original in the RIS element.

[0133] 23) According to the incident channel elevation angle The incident channel azimuth The position coordinates of each element in the RIS element, the first position and the first RIS distance, calculate the receiving array response vector of each element in the RIS element The specific calculation formula is as follows:

[0134]

[0135] in,

[0136]

[0137] 3) calculating the channel gain from the first vehicle to each component in the RIS element according to the receiving array response vector of each component in the RIS element, the first position and the third position; specifically comprising:

[0138] 31) Calculating the distance from the first vehicle to each component in the RIS component based on the first position and the position coordinates of each component in the RIS component.

[0139] 32) Calculate the first RIS channel path loss based on the distance from the first vehicle to each component in the RIS element The first RIS channel path loss is the channel path loss from the first vehicle to each component in the RIS element, and the specific calculation formula is as follows:

[0140]

[0141] 33) Calculate the channel gain G from the first vehicle to each component in the RIS element according to the receiving array response vector of each component in the RIS element and the first RIS channel path loss. n [m]; the specific calculation formula is as follows:

[0142]

[0143] Here, the constant K is the Rician factor.

[0144] 4) calculating the reflection array response vector of each element in the RIS element based on the second position, the third position, the reflection channel elevation angle and the reflection channel azimuth angle; specifically comprising:

[0145] 41) Calculate a second RIS distance based on the second position and the third position The second RIS distance is the distance between the second vehicle and the RIS element, and is calculated as follows:

[0146]

[0147] 42) Based on the third position, determine the position coordinates of each original in the RIS element.

[0148] 43) According to the elevation angle of the reflection channel The reflection channel azimuth The position coordinates of each element in the RIS element, the second position and the second RIS distance are used to calculate the reflection array response vector of each element in the RIS element; the specific calculation formula is as follows:

[0149]

[0150] in

[0151]

[0152] 5) calculating the channel gain from each component in the RIS element to the second vehicle according to the reflection array response vector of each component in the RIS element, the second position and the third position; specifically comprising:

[0153] 51) Calculating the distance from each component in the RIS component to the second vehicle based on the second position and the position coordinates of each component in the RIS component.

[0154] 52) Calculate the second RIS channel path loss based on the distance from each component in the RIS element to the second vehicle The second RIS channel path loss is the channel path loss from each component in the RIS element to the second vehicle; the specific calculation formula is as follows:

[0155]

[0156] 53) Calculate the channel gain from each component in the RIS element to the second vehicle according to the reflection array response vector of each component in the RIS element and the second RIS channel path loss The specific calculation formula is as follows:

[0157]

[0158] 6) Based on the inter-vehicle channel delay, the inter-vehicle channel gain, the channel delay and channel gain from the first vehicle to each component in the RIS element, the channel delay and channel gain from each component in the RIS element to the second vehicle, and the passband signal transmitted by the first vehicle, calculate the passband signal received by the second vehicle; the specific calculation formula is as follows:

[0159]

[0160]

[0161] Among them, y p [m] represents the passband signal received by the second vehicle in the mth time slot; f c represents the carrier frequency, x p (t) represents the bandpass signal emitted by the first vehicle, n p represents Gaussian white noise, θ n[m] represents the phase shift of the nth element in the RIS component in the mth time slot.

[0162] 7) Calculate the complex baseband signal y[m] received by the second vehicle according to the passband signal received by the second vehicle; the specific calculation formula is as follows:

[0163]

[0164] 8) Calculate the angle A from the first channel according to the receiving array response vector of each element in the RIS element and the reflection array response vector of each element in the RIS element. n [m]; the first channel angle is the cascade channel angle of the first vehicle, the RIS element and the second vehicle; the specific calculation formula is as follows:

[0165]

[0166] 9) According to the first channel angle, the complex baseband signal received by the second vehicle and the signal transmission power P of the first vehicle T , calculate the signal receiving power P of the second vehicle R [m]; the specific calculation formula is as follows:

[0167]

[0168] Step 500, based on the signal receiving power of the second vehicle, combined with the distance from the first vehicle to the nth component in the RIS element in the mth time slot At the mth time slot, the distance from the nth element in the RIS element to the second vehicle is Calculate the maximum power RIS phase shift y n [m]; the specific calculation formula is as follows:

[0169]

[0170] Among them, the integer k n [m] is a piecewise constant function, and λ represents the signal wavelength.

[0171] Step 600, calculating the Doppler spread minimum RIS phase shift based on the channel delay between the vehicles, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element.

[0172] Step 600 specifically includes:

[0173] 1) Calculate the Doppler spread D of the first communication path based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, and the channel delay from each component in the RIS element to the second vehicle. s,0 [m]; the first communication path is the communication path from the first vehicle VS, through the RIS element, to the second vehicle VD, that is, the VS-RIS-VD communication path; the specific calculation formula is as follows:

[0174]

[0175] in

[0176] 2) Based on the channel delay of each element in the RIS element in the reflection channel, calculate the Doppler spread D of the second communication path s,RIS [m]; the second communication path is the communication path from the RIS element to the second vehicle, that is, the RIS-VD communication path; the specific calculation formula is as follows:

[0177]

[0178] Among them, f c represents the carrier frequency, θ n It represents the phase shift of the nth RIS element, n' represents the serial number of the RIS element, n'≠n.

[0179] 3) Calculating the Doppler spread D of the V2V communication system according to the Doppler spread of the first communication path and the Doppler spread of the second communication path s [m]; the specific calculation formula is as follows:

[0180] D s [m] = max{D s,0 [m],D s,RIS [m]}.

[0181] 4) Based on the Doppler spread of the V2V communication system, determine the Doppler spread minimum RIS phase shift u n [m]; the minimum RIS phase shift for Doppler spread is the RIS phase shift that minimizes the Doppler spread; the specific calculation formula is as follows:

[0182]

[0183] Between step 600 and step 700, the delay spread T of the V2V communication system is calculated. d [m], the calculation process is as follows:

[0184] 1) Based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, and the channel delay from each component in the RIS element to the second vehicle, calculate the delay difference T between the third communication path and the first communication path d,0 [m]; the third communication path is the communication path from the first vehicle to the second vehicle, that is, the VS-VD communication path; the specific calculation formula is as follows:

[0185]

[0186] 2) Based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, and the channel delay from each component in the RIS element to the second vehicle, calculate the delay difference T of the fourth communication path d,RIS [m]; the fourth communication path is the communication path from the RIS element to the first vehicle, that is, the RIS-VS communication path; the specific calculation process is as follows:

[0187]

[0188] 3) Calculate the delay spread T of the V2V communication system according to the delay difference between the third communication path and the first communication path and the delay difference of the fourth communication path. d [m]; The specific calculation process is as follows:

[0189] T d [m] = max{T d,0 [m],T d,RIS [m]}.

[0190] 4) Based on the delay spread of the V2V communication system, determining the minimum RIS phase shift for delay spread; the minimum phase shift for delay spread is the RIS phase shift that minimizes the delay spread, at which time c n [m]=0.

[0191] Based on the RIS phase shift v that maximizes the power gain n [m] and the RIS phase shift c that minimizes the delay spread n [m], it can be found that it is impossible to maximize power gain and minimize delay spread at the same time by optimizing the RIS phase shift. Therefore, it is necessary to make a trade-off between maximizing power gain and minimizing Doppler spread and delay spread.

[0192] Based on this, step 700 is proposed to determine the optimal RIS phase shift in the V2V communication system based on the maximum power RIS phase shift and the minimum Doppler spread RIS phase shift. The specific calculation formula is as follows:

[0193]

[0194] Among them, mod means to find the remainder.

[0195] Preferably, the RIS phase shift optimization method further comprises:

[0196] According to the formula

[0197]

[0198] A maximum received power of the second vehicle is determined.

[0199] Among them, P R,max [m] represents the maximum received power of the second vehicle in the mth time slot, P T represents the signal transmission power of the first vehicle, represents the inter-vehicle channel path loss in the mth time slot, K represents a constant, is the Rician factor, represents the first RIS channel path loss in the mth time slot, represents the second RIS channel path loss in the mth time slot, θ n [m] represents the optimal phase shift of the RIS in the mth time slot of the V2V communication system.

[0200] This indicates that the maximum power gain at the vehicle receiving end (received by the second vehicle) depends on the distance from the first vehicle to the RIS element and the distance from the RIS element to the second vehicle.

[0201] Based on the maximum received power of the second vehicle, the maximum channel gain of the V2V communication system with RIS assistance is calculated; the specific calculation formula is as follows:

[0202]

[0203] Where N0 represents the noise power and B represents the bandwidth.

[0204] Shift the optimal phase of the RIS of the V2V communication system in the mth time slot Substitute the Doppler spread D of the V2V communication system into s The minimum Doppler spread of the V2V communication system is obtained from the expression of [m], which is as follows:

[0205] D s,min [m]=0.

[0206] Shift the optimal phase of the RIS of the V2V communication system in the mth time slot Substitute the delay spread T of the V2V communication system into d The minimum delay spread of the V2V communication system is obtained from the expression of [m], which is as follows:

[0207]

[0208] in, Indicates the upper limit of its argument.

[0209] In a specific practical application, a three-dimensional Cartesian coordinate system is first established, in which the coordinates of the reference position of the RIS element are z S =z D =50m, first x-axis coordinate x s0 =-100m, second x-axis coordinate x d0 = -70m. The vehicle moving speed is v = 60km / h, and the V2V communication duration, i.e., the time block is T = 10s, which is evenly divided into 100 time slots. Carrier frequency f c =3GHz, wavelength l = 0.1m, the number of RIS elements is N x =N y =128, the distance between adjacent elements is The Rician coefficient is K=10dB.

[0210] Based on the above data, the RIS phase shift optimization in the V2V communication system is performed, that is, the following steps are performed in sequence: Calculate the power gain P at the vehicle receiving end R [m]; Based on the power gain of the vehicle receiving end, calculate the RIS phase shift v that maximizes the power gain n [m]; Calculate the Doppler spread D of RIS-assisted V2V communication s [m]; Based on the Doppler spread of V2V communication, calculate the RIS phase shift u that minimizes the Doppler spread n [m]; Calculate the delay spread T of RIS-assisted V2V communication d [m]; Based on the delay spread of V2V communication, calculate the RIS phase shift c that minimizes the delay spread n [m]; Calculation of the optimal phase shift of RIS based on power gain, delay spread and Doppler spread of RIS-assisted V2V communication Optimal phase shift based on RIS Calculate the maximum power gain P at the vehicle receiving end R,max [m], minimum Doppler spread D s,min [m] and minimum delay spread T d,min [m], and then compared with other solutions, we finally get Figure 3 , Figure 4 and Figure 5 .

[0211] in, Figure 3 The figure shows the channel gain corresponding to the RIS phase shift optimization of the present invention, the channel gain obtained by the random phase shift scheme, and the channel gain of the scheme without RIS assistance. Figure 3 It can be seen that the present invention achieves significant performance improvement, especially in the 53rd time slot. However, for the random phase shift scheme, the performance gain brought by RIS is significantly weakened, and the channel gain of the direct link may be reduced.

[0212] Figure 4 The delay spread under different schemes is compared. Although the RIS element effectively eliminates the Doppler spread, it is difficult to eliminate the delay spread because the signal directly received by the second vehicle from the first vehicle is not within the control range of the RIS element. In this case, the RIS phase shift optimization scheme of the present invention keeps the delay spread at a low level.

[0213] Figure 5 The channel gain and delay spread obtained by the RIS phase shift optimization scheme of the present invention are shown at different vehicle moving speeds. Figure 5 It can be seen that for different vehicle moving speeds, When reaching the minimum value at different time slots, the channel gain and delay spread reach the maximum and minimum values ​​at different time slots respectively; the maximum channel gain and minimum delay spread corresponding to different vehicle moving speeds are the same. In addition, when the vehicle travels to a position far away from the RIS element, the channel gain of the cascaded VS-RIS-VD link can be ignored, while the delay spread increases sharply.

[0214] Embodiment 2

[0215] like Figure 6 As shown, in order to execute the method corresponding to the above-mentioned embodiment 1 to achieve corresponding functions and technical effects, this embodiment provides a RIS phase shift optimization system in a V2V communication system, including:

[0216] The position determination module 101 is used to obtain a first position, a second position and a third position in a V2V communication system in any time slot; the V2V communication system includes a first vehicle, a second vehicle and a RIS element; the first position is a three-dimensional coordinate of the first vehicle in a preset three-dimensional Cartesian coordinate system, the second position is a three-dimensional coordinate of the second vehicle in a preset three-dimensional Cartesian coordinate system; the third position is a three-dimensional coordinate of a reference position of the RIS element in a preset three-dimensional Cartesian coordinate system.

[0217] The channel angle determination module 201 is used to determine the incident channel elevation angle and the incident channel azimuth angle according to the first position and the RIS element reference position; and to determine the reflected channel elevation angle and the reflected channel azimuth angle according to the second position and the RIS element reference position.

[0218] The channel delay calculation module 301 is used to calculate the channel delay between vehicles based on the first position and the second position; calculate the channel delay from the first vehicle to each component in the RIS element based on the first position and the third position; calculate the channel delay from each component in the RIS element to the second vehicle based on the second position and the third position.

[0219] The signal receiving power determination module 401 is used to calculate the signal receiving power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle and the signal transmission power of the first vehicle.

[0220] The first phase shift determination module 501 is used to calculate the maximum power RIS phase shift based on the signal received power of the second vehicle.

[0221] The second phase shift determination module 601 is used to calculate the Doppler spread minimum RIS phase shift based on the channel delay between the vehicles, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element.

[0222] The optimal phase shift determination module 701 is used to determine the optimal RIS phase shift in the V2V communication system based on the maximum power RIS phase shift and the Doppler spread minimum RIS phase shift.

[0223] In this specification, each embodiment is described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the embodiments can be referred to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part.

[0224] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A RIS phase shift optimization method in a V2V communication system, characterized in that: The RIS phase shift optimization method comprises: Acquire a first position, a second position and a third position in a V2V communication system at any time slot; the V2V communication system includes a first vehicle, a second vehicle and a RIS element; the first position is a three-dimensional coordinate of the first vehicle in a preset three-dimensional Cartesian coordinate system, the second position is a three-dimensional coordinate of the second vehicle in a preset three-dimensional Cartesian coordinate system; the third position is a three-dimensional coordinate of a reference position of the RIS element in a preset three-dimensional Cartesian coordinate system; Determine an incident channel elevation angle and an incident channel azimuth angle according to the first position and the RIS element reference position; determine a reflection channel elevation angle and a reflection channel azimuth angle according to the second position and the RIS element reference position; Based on the first position and the second position, calculating the channel delay between vehicles; based on the first position and the third position, calculating the channel delay from the first vehicle to each component in the RIS element; based on the second position and the third position, calculating the channel delay from each component in the RIS element to the second vehicle; Calculate the signal receiving power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle; calculating a power maximum RIS phase shift based on a signal received power of the second vehicle; Calculate the Doppler spread minimum RIS phase shift based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element; Based on the maximum power RIS phase shift and the minimum Doppler spread RIS phase shift, an optimal RIS phase shift in the V2V communication system is determined.

2. The RIS phase shift optimization method in a V2V communication system according to claim 1, characterized in that: The method calculates the signal receiving power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle, including: calculating an inter-vehicle channel gain based on the first position and the second position; Calculate a receiving array response vector of each element in the RIS element based on the first position, the third position, the incident channel elevation angle, and the incident channel azimuth angle; Calculate a channel gain from the first vehicle to each element in the RIS element according to a receiving array response vector of each element in the RIS element, the first position, and the third position; Calculate a reflection array response vector of each element in the RIS element based on the second position, the third position, the reflection channel elevation angle, and the reflection channel azimuth angle; Calculate the channel gain from each element in the RIS element to the second vehicle based on the reflection array response vector of each element in the RIS element, the second position and the third position; Calculate the passband signal received by the second vehicle based on the inter-vehicle channel delay, the inter-vehicle channel gain, the channel delay and channel gain from the first vehicle to each component in the RIS element, the channel delay and channel gain from each component in the RIS element to the second vehicle, and the passband signal transmitted by the first vehicle; calculating a complex baseband signal received by the second vehicle based on the passband signal received by the second vehicle; Calculating a first channel angle according to a receiving array response vector of each element in the RIS element and a reflecting array response vector of each element in the RIS element; the first channel angle is a cascade channel angle of the first vehicle, the RIS element and the second vehicle; The signal reception power of the second vehicle is calculated according to the first channel angle, the complex baseband signal received by the second vehicle, and the signal transmission power of the first vehicle.

3. The RIS phase shift optimization method in a V2V communication system according to claim 2, characterized in that: Calculating a vehicle-to-vehicle channel gain based on the first position and the second position specifically includes: Calculating the distance between vehicles based on the first position and the second position; Calculating the channel path loss between vehicles according to the distance between vehicles; The inter-vehicle channel gain is calculated according to the inter-vehicle channel path loss.

4. The RIS phase shift optimization method in a V2V communication system according to claim 3, characterized in that: Calculating a receiving array response vector of each element in the RIS element based on the first position, the third position, the incident channel elevation angle, and the incident channel azimuth angle specifically includes: Calculating a first RIS distance according to the first position and the third position; the first RIS distance being the distance between the first vehicle and the RIS element; Based on the third position, determining the position coordinates of each original in the RIS element; Calculate a receiving array response vector of each element in the RIS element according to the incident channel elevation angle, the incident channel azimuth angle, the position coordinates of each element in the RIS element, the first position and the first RIS distance; Calculating a channel gain from the first vehicle to each component in the RIS element according to a receiving array response vector of each component in the RIS element, the first position, and the third position, specifically comprising: Calculating the distance from the first vehicle to each component in the RIS component according to the first position and the position coordinates of each component in the RIS component; Calculate a first RIS channel path loss based on the distance from the first vehicle to each component in the RIS element; the first RIS channel path loss is the channel path loss from the first vehicle to each component in the RIS element; A channel gain from the first vehicle to each component in the RIS element is calculated according to a receiving array response vector of each component in the RIS element and the first RIS channel path loss.

5. The RIS phase shift optimization method in a V2V communication system according to claim 1, characterized in that: Based on the first position and the third position, calculating the channel delay from the first vehicle to each component in the RIS element specifically includes: Based on the third position, determining the position coordinates of each original in the RIS element; Calculating the distance from the first vehicle to each component in the RIS component according to the first position and the position coordinates of each component in the RIS component; Based on the distance from the first vehicle to each component in the RIS element, a channel delay from the first vehicle to each component in the RIS element is calculated.

6. The RIS phase shift optimization method in a V2V communication system according to claim 4, characterized in that: Calculating the reflection array response vector of each element in the RIS element based on the second position, the third position, the reflection channel elevation angle, and the reflection channel azimuth angle specifically includes: Calculating a second RIS distance according to the second position and the third position; the second RIS distance being the distance between the second vehicle and the RIS element; Based on the third position, determining the position coordinates of each original in the RIS element; Calculate a reflection array response vector of each element in the RIS element according to the reflection channel elevation angle, the reflection channel azimuth angle, the position coordinates of each element in the RIS element, the second position and the second RIS distance; Calculating a channel gain from each element in the RIS element to the second vehicle according to the reflection array response vector of each element in the RIS element, the second position, and the third position, specifically comprising: Calculating the distance from each component in the RIS component to the second vehicle according to the second position and the position coordinates of each component in the RIS component; Calculate a second RIS channel path loss based on the distance from each component in the RIS element to the second vehicle; the second RIS channel path loss is the channel path loss from each component in the RIS element to the second vehicle; The channel gain from each element in the RIS element to the second vehicle is calculated according to the reflection array response vector of each element in the RIS element and the second RIS channel path loss.

7. The RIS phase shift optimization method in a V2V communication system according to claim 1, characterized in that: Calculating the Doppler spread minimum RIS phase shift based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element, specifically includes: Calculate the Doppler spread of a first communication path based on the channel delay between the vehicles, the channel delay from the first vehicle to each component in the RIS element, and the channel delay from each component in the RIS element to the second vehicle; the first communication path is a communication path that is sent from the first vehicle, passes through the RIS element, and reaches the second vehicle; Calculating the Doppler spread of a second communication path based on the channel delay of each element in the RIS element in the reflection channel; the second communication path is a communication path from the RIS element to the second vehicle; Calculating a Doppler spread of the V2V communication system according to a Doppler spread of the first communication path and a Doppler spread of the second communication path; Based on the Doppler spread of the V2V communication system, a Doppler spread minimum RIS phase shift is determined.

8. The RIS phase shift optimization method in a V2V communication system according to claim 6, characterized in that: The RIS phase shift optimization method further comprises: According to the formula determining a maximum received power of the second vehicle; Among them, P R,max [m] represents the maximum received power of the second vehicle in the mth time slot, P T represents the signal transmission power of the first vehicle, represents the inter-vehicle channel path loss in the mth time slot, K represents a constant, is the Rician factor, represents the first RIS channel path loss in the mth time slot, represents the second RIS channel path loss in the mth time slot, θ n [m] represents the optimal phase shift of the RIS in the mth time slot of the V2V communication system.

9. The RIS phase shift optimization method in a V2V communication system according to claim 1, characterized in that: The obtaining of the first position and the second position in the V2V communication system in any time slot specifically includes: Determine a preset three-dimensional Cartesian coordinate system; Based on the preset three-dimensional Cartesian coordinate system, a first x-axis coordinate, a first z-axis coordinate, a second x-axis coordinate and a second z-axis coordinate are determined; the first x-axis coordinate is an initial x-axis coordinate of the first vehicle in the preset three-dimensional Cartesian coordinate system; the second x-axis coordinate is an initial x-axis coordinate of the second vehicle in the preset three-dimensional Cartesian coordinate system; the first z-axis coordinate is a z-axis coordinate of the first vehicle in the preset three-dimensional Cartesian coordinate system; the second z-axis coordinate is a z-axis coordinate of the second vehicle in the preset three-dimensional Cartesian coordinate system; Determine a time block of a preset duration, and divide the time block into a plurality of time slots; For any of the time slots, calculating the three-dimensional coordinates of the first vehicle according to the time slot, the first x-axis coordinate, the moving speed of the first vehicle and the first z-axis coordinate; the three-dimensional coordinates of the first vehicle are the first position; The three-dimensional coordinates of the second vehicle are calculated according to the time slot, the second x-axis coordinate, the moving speed of the second vehicle and the second z-axis coordinate; the three-dimensional coordinates of the second vehicle are the second position.

10. A RIS phase shift optimization system in a V2V communication system, characterized in that: The RIS phase shift optimization system comprises: A position determination module, configured to obtain a first position, a second position and a third position in a V2V communication system in any time slot; the V2V communication system comprises a first vehicle, a second vehicle and a RIS element; the first position is a three-dimensional coordinate of the first vehicle in a preset three-dimensional Cartesian coordinate system, the second position is a three-dimensional coordinate of the second vehicle in a preset three-dimensional Cartesian coordinate system; the third position is a three-dimensional coordinate of a reference position of the RIS element in a preset three-dimensional Cartesian coordinate system; a channel angle determination module, configured to determine an incident channel elevation angle and an incident channel azimuth angle according to the first position and the RIS element reference position; and to determine a reflected channel elevation angle and a reflected channel azimuth angle according to the second position and the RIS element reference position; a channel delay calculation module, configured to calculate the channel delay between vehicles based on the first position and the second position; calculate the channel delay from the first vehicle to each component in the RIS element based on the first position and the third position; and calculate the channel delay from each component in the RIS element to the second vehicle based on the second position and the third position; a signal receiving power determination module, configured to calculate the signal receiving power of the second vehicle according to the first position, the second position, the third position, the incident channel elevation angle, the incident channel azimuth angle, the reflected channel elevation angle, the reflected channel azimuth angle, the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, the passband signal transmitted by the first vehicle, and the signal transmission power of the first vehicle; a first phase shift determination module, configured to calculate a power maximum RIS phase shift based on a signal received power of the second vehicle; A second phase shift determination module is used to calculate a Doppler spread minimum RIS phase shift based on the inter-vehicle channel delay, the channel delay from the first vehicle to each component in the RIS element, the channel delay from each component in the RIS element to the second vehicle, and the channel reflection delay of each component in the RIS element; The optimal phase shift determination module is used to determine the RIS optimal phase shift in the V2V communication system based on the maximum power RIS phase shift and the Doppler spread minimum RIS phase shift.

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