A Method and System for Optimizing RIS Phase Shifts and Deployment Locations in a Communication System

Abstract

The present invention discloses a method and system for optimizing the phase shift and deployment position of RIS in a communication system, which relates to the field of communication technologies. The method includes: based on the reference three-dimensional coordinates of the aerial RIS elements in a preset coordinate system, the reference three-dimensional coordinates of the base station in the preset coordinate system, the three-dimensional coordinates of multiple users in the preset coordinate system, the original array data corresponding to the aerial RIS elements, and the antenna array data corresponding to the base station, successively calculating the base station-RIS-user cascaded channel, the base station-user channel, the beam transmitted from the base station to any user, the first effective channel parameter, the second effective channel parameter, and the aerial RIS phase shift matrix; finally, jointly determining the RIS deployment position optimization model based on the beam data, the effective channel parameters, and the original array data corresponding to the aerial RIS elements; and performing convex optimization on the RIS deployment position optimization model to obtain the optimized deployment position of RIS. The present invention can maximize the weighted sum rate of all users in the communication system.

Description

Technical Field

[0001] The present invention relates to the field of communication technologies, and in particular, to a method and system for optimizing the RIS phase shift and deployment location in a communication system based on an aerial RIS element-assisted multi-input multi-user communication system. Background Art

[0002] To overcome the limitations of the coverage range of fixed reconfigurable intelligent surfaces (RISs) (such as RISs deployed on building surfaces or indoor walls / ceilings) and non-line-of-sight channels, and to improve the flexibility and availability of RISs, researchers have proposed the concept of aerial reconfigurable intelligent surfaces (ARISs) for three-dimensional (3D) wireless networks, installing RISs on aerial platforms such as balloons and drones to assist ground communication.

[0003] Regarding the application of ARISs, there have been records in the prior art: 1) ARISs are used to assist in the information exchange between two ground nodes; 2) ARISs are used to improve the freshness of collected data, but this solution is limited to the scenario where the transmitter has a single antenna; 3) For an RIS-assisted single-user communication system, flight effects and weather factors are considered when designing the ARIS phase shift, but this solution is not applicable to the scenario where ARIS serves multiple users simultaneously. Summary of the Invention

[0004] The purpose of the present invention is to provide a method and system for optimizing the RIS phase shift and deployment location in a communication system. By jointly optimizing the beamforming transmitted by the base station, the phase shift matrix of the aerial RIS element, and the deployment location, the weighted sum rate of all users is maximized.

[0005] To achieve the above purpose, the present invention provides the following solution:

[0006] A method for optimizing the RIS phase shift and deployment location in a communication system includes:

[0007] Obtain a first position, a second position, and a third position set in the communication system; the communication system includes an aerial RIS element, a base station, and multiple users; the first position is the reference three-dimensional coordinate of the aerial RIS element in a preset coordinate system; the second position is the reference three-dimensional coordinate of the base station in the preset coordinate system; the third position set includes the three-dimensional coordinates of multiple users in the preset coordinate system;

[0008] Calculate the cascaded channel of the base station RIS user according to the first position, the second position, the third position set, the original array data corresponding to the aerial RIS element, and the antenna array data corresponding to the base station; calculate the channel of the base station user according to the second position, the third position set, and the antenna array data corresponding to the base station; the cascaded channel of the base station RIS user is the cascaded channel from the base station, through the aerial RIS element, to any user; the channel of the base station user is the channel from the base station to any user;

[0009] Calculate the beam transmitted by the base station to any user according to the cascaded channel of the base station RIS user and the third position set;

[0010] Calculate the first effective channel parameter based on the cascaded channel of the base station RIS user and the first marked user beam; calculate the second effective channel parameter based on the channel of the base station user and the first marked user beam; the first effective channel parameter is the parameter of the channel from the first marked user, through the aerial RIS element, to the second marked user; the second effective channel parameter is the parameter of the channel from the first marked user to the second marked user; the first marked user and the second marked user are any two users; the first marked user beam is the beam transmitted by the base station to the first marked user;

[0011] Calculate the aerial RIS phase shift matrix according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix;

[0012] Determine the RIS deployment location optimization model according to the channel of the base station user, the cascaded channel of the base station RIS user, the aerial RIS phase shift matrix, the second marked user beam, the first effective channel parameter, the second effective channel parameter, the first position, the second position, the third position set, and the original array data corresponding to the aerial RIS element; the RIS deployment location optimization model includes a cascaded link distance constraint function and an objective function for optimizing the RIS deployment location; the second marked user beam is the beam transmitted by the base station to the second marked user;

[0013] Perform convex optimization on the RIS deployment location optimization model to obtain the optimized deployment location of the RIS.

[0014] Optionally, calculating the cascaded channel of the base station RIS user according to the first position, the second position, the third position set, the original array data corresponding to the aerial RIS element, and the antenna array data corresponding to the base station specifically includes:

[0015] Calculate the three-dimensional coordinates of each element in the airborne RIS element according to the original element array data corresponding to the airborne RIS element and the first position;

[0016] Calculate the three-dimensional coordinates of each antenna in the base station according to the antenna array data corresponding to the base station and the second position;

[0017] Calculate the base station RIS channel according to the first position, the second position, the three-dimensional coordinates of each element in the airborne RIS element, and the three-dimensional coordinates of each antenna in the base station; the base station RIS channel is the channel from the base station to the airborne RIS element;

[0018] Calculate the RIS user channel according to the first position, the third position set, and the three-dimensional coordinates of each element in the airborne RIS element; the RIS user channel is the channel from the airborne RIS element to any user;

[0019] Calculate the base station RIS user cascaded channel according to the base station RIS channel and the RIS user channel.

[0020] Optionally, calculating the base station RIS channel according to the first position, the second position, the three-dimensional coordinates of each element in the airborne RIS element, and the three-dimensional coordinates of each antenna in the base station specifically includes:

[0021] Calculate the base station RIS distance according to the first position and the second position; the base station RIS distance is the distance between the airborne RIS element and the base station;

[0022] Calculate the base station RIS path loss based on the base station RIS distance; the base station RIS path loss is the signal path loss from the base station to the airborne RIS element;

[0023] Calculate the received array response vector of the airborne RIS element according to the three-dimensional coordinates of each element in the airborne RIS element and the base station RIS distance;

[0024] Calculate the transmit array response vector from the base station to the airborne RIS element according to the three-dimensional coordinates of each antenna in the base station, the three-dimensional coordinates of each element in the airborne RIS element, and the base station RIS distance;

[0025] Calculate the base station RIS channel according to the base station RIS distance, the base station RIS path loss, the received array response vector of the airborne RIS element, and the transmit array response vector from the base station to the airborne RIS element.

[0026] Optionally, according to the first position, the third position set, and the three-dimensional coordinates of each element in the airborne RIS element, calculate the RIS user channel, specifically including:

[0027] According to the first position and the third position set, calculate the RIS user distance set; each RIS user distance in the RIS user distance set is the distance from the airborne RIS element to any user;

[0028] According to the RIS user distance set, calculate the RIS user path loss set; each RIS user path loss in the RIS user path loss set is the channel path loss from the airborne RIS element to any user;

[0029] According to the three-dimensional coordinates of each element in the airborne RIS element, the third position set, and the RIS user distance set, calculate the transmit array response vector from the airborne RIS element to any user;

[0030] According to the RIS user distance set, the RIS user path loss set, and the transmit array response vector from the airborne RIS element to any user, calculate the RIS user channel.

[0031] Optionally, according to the base station user channel, the base station RIS user cascaded channel, the airborne RIS phase shift matrix, the second marked user beam, the first effective channel parameter, the second effective channel parameter, the first position, the second position, the third position set, and the original element array data corresponding to the airborne RIS element, determine the RIS deployment location optimization model, specifically including:

[0032] According to the base station user channel, the base station RIS user cascaded channel, the airborne RIS phase shift matrix, and the second marked user beam, calculate the first auxiliary variable;

[0033] According to the first effective channel parameter, the second effective channel parameter, the first auxiliary variable, and the airborne RIS phase shift matrix, calculate the second auxiliary variable;

[0034] According to the first position, the second position, and the third position set, determine the cascaded link distance constraint function;

[0035] According to the original element array data corresponding to the airborne RIS element and the first position, calculate the three-dimensional coordinates of each element in the airborne RIS element;

[0036] According to the three-dimensional coordinates of each element in the airborne RIS element and the third position set, calculate the signal phase shift reflected from the airborne RIS element to any user;

[0037] Determine the objective function for optimizing the RIS deployment location based on the signal phase shift reflected by the airborne RIS element to any user, the first marked user beam, the second marked user beam, the first auxiliary variable, the second auxiliary variable, and the second effective channel parameter.

[0038] To achieve the above object, the present invention also provides the following technical solutions:

[0039] An RIS phase shift and deployment location optimization system in a communication system, comprising:

[0040] A location acquisition module, configured to acquire a first location, a second location, and a third location set in the communication system; the communication system includes an airborne RIS element, a base station, and multiple users; the first location is the reference three-dimensional coordinate of the airborne RIS element in a preset coordinate system; the second location is the reference three-dimensional coordinate of the base station in the preset coordinate system; the third location set includes the three-dimensional coordinates of multiple users in the preset coordinate system;

[0041] A channel calculation module, configured to calculate the base station RIS user cascaded channel according to the first location, the second location, the third location set, the original array data corresponding to the airborne RIS element, and the antenna array data corresponding to the base station; calculate the base station user channel according to the second location, the third location set, and the antenna array data corresponding to the base station; the base station RIS user cascaded channel is the cascaded channel from the base station, through the airborne RIS element, to any user; the base station user channel is the channel from the base station to any user;

[0042] A beam calculation module, configured to calculate the beam transmitted by the base station to any user according to the base station RIS user cascaded channel and the third location set;

[0043] A channel parameter calculation module, configured to calculate a first effective channel parameter based on the base station RIS user cascaded channel and the first marked user beam; calculate a second effective channel parameter based on the base station user channel and the first marked user beam; the first effective channel parameter is the parameter of the channel from the first marked user, through the airborne RIS element, to the second marked user; the second effective channel parameter is the parameter of the channel from the first marked user to the second marked user; the first marked user and the second marked user are any two users; the first marked user beam is the beam transmitted by the base station to the first marked user;

[0044] A phase shift matrix calculation module, configured to calculate the airborne RIS phase shift matrix according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix;

[0045] A deployment location model determination module, configured to determine an RIS deployment location optimization model according to the base station user channel, the base station RIS user cascaded channel, the air RIS phase shift matrix, the second tagged user beam, the first effective channel parameter, the second effective channel parameter, the first location, the second location, the third location set, and the original array data corresponding to the air RIS element; the RIS deployment location optimization model includes a cascaded link distance constraint function and an objective function for optimizing the RIS deployment location; the second tagged user beam is the beam transmitted from the base station to the second tagged user.

[0046] An optimized deployment location determination module, configured to perform convex optimization on the RIS deployment location optimization model to obtain the optimized deployment location of the RIS.

[0047] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0048] The present invention discloses a method and system for optimizing the phase shift and deployment location of an RIS in a communication system. According to the reference three-dimensional coordinates of the air RIS element in a preset coordinate system, the reference three-dimensional coordinates of the base station in the preset coordinate system, the three-dimensional coordinates of multiple users in the preset coordinate system, the original array data corresponding to the air RIS element, and the antenna array data corresponding to the base station, the cascaded channel from the base station through the air RIS element to any user is calculated, i.e., the base station RIS user cascaded channel; according to the reference three-dimensional coordinates of the base station in the preset coordinate system, the three-dimensional coordinates of multiple users in the preset coordinate system, and the antenna array data corresponding to the base station, the channel from the base station to any user is calculated; according to the base station RIS user cascaded channel and the three-dimensional coordinates of multiple users in the preset coordinate system, the beam transmitted from the base station to any user is calculated, and then, by combining the beams transmitted from the base station to the first tagged user and the second tagged user respectively, the parameters of the channel from the first tagged user through the air RIS element to the second tagged user and the parameters of the channel from the first tagged user to the second tagged user are calculated; the air RIS phase shift matrix is calculated according to the two channel parameters obtained above. Finally, according to the base station user channel, the base station RIS user cascaded channel, the air RIS phase shift matrix, the second tagged user beam, the first effective channel parameter, the second effective channel parameter, the first location, the second location, the third location set, and the original array data corresponding to the air RIS element, the RIS deployment location optimization model is determined, that is, the beam transmitted from the base station, the phase shift matrix of the air RIS element, and the deployment location of the air RIS element are associated, and through model optimization, the optimal deployment location of the air RIS element and the corresponding phase shift matrix are calculated quickly and accurately, so as to maximize the weighted sum rate of all users. Description of the Drawings

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0050] Figure 1 It is a schematic flowchart of the method for optimizing the RIS phase shift and deployment location in the communication system of the present invention;

[0051] Figure 2 It is a schematic diagram of the model of the communication system of the present invention;

[0052] Figure 3 It is a comparison diagram of the relationship between the user weighted sum rate and the transmit power in the example of the present invention;

[0053] Figure 4 It is a schematic diagram of the relationship between the user weighted sum rate and the number of RIS elements in the air in the present invention;

[0054] Figure 5 It is a schematic diagram of the structure of the system for optimizing the RIS phase shift and deployment location in the communication system of the present invention. Specific embodiments

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0056] The purpose of the present invention is to provide a method and system for optimizing the RIS phase shift and deployment location in a communication system, designing the phase shift matrix and deployment location method of the RIS elements in the air to maximize the weighted sum rate of all users.

[0057] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0058] Embodiment 1

[0059] As Figure 1 shown, this embodiment provides a method for optimizing the RIS phase shift and deployment location in a communication system, including:

[0060] Step 100, obtain the first position, the second position, and the third position set in the communication system; the communication system includes an aerial RIS element, a base station, and multiple users; the first position is the reference three-dimensional coordinate of the aerial RIS element in a preset coordinate system; the second position is the reference three-dimensional coordinate of the base station in the preset coordinate system; the third position set includes the three-dimensional coordinates of multiple users in the preset coordinate system.

[0061] Specifically, consider a wireless relay system supported by an aerial RIS element (ARIS), where the RIS element is installed on an aerial platform (such as a balloon or UAV) to assist a ground source node (such as a base station (BS) or an access point (AP)) in communicating with a group of ground users. The BS antenna array is denoted as M = M y M z The element array in ARIS is denoted as N = N x N y .

[0062] As Figure 2 shown, the BS is located at the origin of the 3D coordinate system, the height of the BS antenna is h BS , the BS antenna array is placed on the y - z plane, and the distance between adjacent antennas is l y = l z = λ / 2, the second position is c = [0, 0, h BS T . The ARIS reflecting element array is distributed on the x - y plane, the height of ARIS is h RIS , taking the position of the element in the first row and first column of ARIS as the reference point, then the first position is q = [q x , q y , h RIS T . The position of user k in the third position set is denoted as w k = [w x,k , w y,k T ,

[0063] where λ is the wavelength of the transmitted signal; η R and φ R respectively represent the azimuth angle and elevation angle of the RIS receiving channel, and η T and φ T respectively represent the azimuth angle and elevation angle of the RIS reflection channel, which can be calculated based on the positions of the BS and the RIS elements.

[0064] ​​​Step 200: Calculate the base station RIS-user cascaded channel according to the first position, the second position, the third position set, the original element array data corresponding to the airborne RIS element, and the antenna array data corresponding to the base station; calculate the base station-user channel according to the second position, the third position set, and the antenna array data corresponding to the base station.

[0065] Among them, the base station RIS-user cascaded channel is the cascaded channel from the base station, through the airborne RIS element to any user; the base station-user channel is the channel from the base station to any user.

[0066] In step 200, calculating the base station RIS-user cascaded channel according to the first position, the second position, the third position set, the original element array data corresponding to the airborne RIS element, and the antenna array data corresponding to the base station specifically includes:

[0067] (1) Calculate the three-dimensional coordinates of each element in the airborne RIS element according to the original element array data corresponding to the airborne RIS element and the first position.

[0068] Specifically, the original element coordinates of the element located in the n x -th column and the n y -th row of the airborne RIS element are expressed as:

[0069]

[0070] where the distance between adjacent elements is expressed as d x < λ / 2 and d y < λ / 2.

[0071] (2) Calculate the three-dimensional coordinates of each antenna in the base station according to the antenna array data corresponding to the base station and the second position.

[0072] Specifically, the coordinates of the antenna located in the m y -th column and the m z -th row of the base station are expressed as:

[0073]

[0074] (3) Calculate the base station RIS channel according to the first position, the second position, the three-dimensional coordinates of each element in the airborne RIS element, and the three-dimensional coordinates of each antenna in the base station; the base station RIS channel is the channel from the base station to the airborne RIS element.

[0075] Specifically, the calculation process of the base station RIS channel in step (3) is as follows:

[0076] A1) Calculate the base station RIS distance d based on the first position q and the second position c G ; The base station RIS distance is the distance between the airborne RIS element and the base station BS. The calculation process of the base station RIS distance is as follows:

[0077] d G = |c - q|.

[0078] B1) Calculate the base station RIS path loss β based on the base station RIS distance G ; The base station RIS path loss is the path loss of the signal from the base station to the airborne RIS element, that is, the path loss from the BS antenna array to the ARIS reflection element array. The calculation process of the base station RIS path loss is as follows:

[0079]

[0080] where β0 is the line-of-sight (LoS) path loss at the reference distance d0 = 1m.

[0081] C1) Calculate the received array response vector a of the airborne RIS element according to the three-dimensional coordinates of each element in the airborne RIS element and the base station RIS distance d G , calculate the received array response vector a of the airborne RIS element R , and the calculation process is as follows:

[0082]

[0083] D1) According to the three-dimensional coordinates of each antenna in the base station the three-dimensional coordinates of each element in the airborne RIS element and the base station RIS distance d G , calculate the transmitted array response vector a from the base station to the airborne RIS element T1 , and the calculation process is as follows:

[0084]

[0085] E1) Calculate the base station RIS channel G according to the base station RIS distance d G , the base station RIS path loss β G , the received array response vector a of the airborne RIS element R and the transmitted array response vector a from the base station to the airborne RIS element T1 , and the calculation process is as follows:

[0086]

[0087] (4) Calculate the RIS-user channel based on the first position, the third position set, and the three-dimensional coordinates of each element in the airborne RIS element; the RIS-user channel is the channel from the airborne RIS element to any user.

[0088] Specifically, the calculation process of the RIS-user channel in step (4) is as follows:

[0089] A2) Calculate the RIS-user distance set based on the first position and the third position set; each RIS-user distance in the RIS-user distance set is the distance from the airborne RIS element to any user; the position w of user k in the RIS-user distance set k The distance from the first position q The calculation process is as follows:

[0090]

[0091] B2) Calculate the RIS-user path loss set based on the RIS-user distance set; each RIS-user path loss in the RIS-user path loss set is the path loss of the channel from the airborne RIS element to any user, that is, the path loss from the ARIS reflection element array to user k. Any RIS-user path loss in the RIS-user path loss set The calculation process is as follows:

[0092]

[0093] C2) Calculate the transmit array response vector a from the airborne RIS element to any user based on the three-dimensional coordinates of each element in the airborne RIS element, the third position set, and the RIS-user distance set T2 , taking user k as an example, the calculation process of the RIS-user distance is as follows:

[0094]

[0095] D2) Calculate the RIS-user channel based on the RIS-user distance set, the RIS-user path loss set, and the transmit array response vector from the airborne RIS element to any user; the channel h from ARIS to user k r,k The specific calculation process is as follows:

[0096]

[0097] (5) Calculate the base station RIS-user cascaded channel based on the base station RIS channel and the RIS-user channel. Among them, the calculation process of the cascaded channel of BS-ARIS-user k is as follows:

[0098]

[0099] Among them, () H represents the conjugate transpose.

[0100] In step 200, according to the second position, the third position set, and the antenna array data corresponding to the base station, calculating the base station user channel specifically includes:

[0101] (1) Calculating a base station user distance set according to the second position and the third position set; each base station user distance in the base station user distance set is the distance from the base station to any user; the position w of user k in the base station user distance set k The distance from The calculation process is as follows:

[0102]

[0103] (2) Calculating a base station user path loss set according to the base station user distance set; each base station user path loss in the base station user path loss set is the signal path loss from the base station to any user, that is, the path loss from the BS antenna array to user k. Any base station user path loss in the base station user path loss set The calculation process is as follows:

[0104]

[0105] Among them, β1 is the non-line-of-sight (Non-LoS, NLoS) path loss when the reference distance d0 = 1m.

[0106] (3) Calculating the three-dimensional coordinates of each antenna in the base station according to the antenna array data corresponding to the base station and the second position.

[0107] (4) Calculating the transmit array response vector from the base station to any user according to the three-dimensional coordinates of each antenna in the base station, the third position set, and the base station user distance set; the transmit array response vector a from the base station BS to user k T3 The calculation process is as follows:

[0108]

[0109] (5) Calculating the base station user channel according to the base station user distance set, the base station user path loss set, and the transmit array response vector from the base station to any user; the channel h from BS to user k d,k The calculation process is as follows:

[0110]

[0111] Step 300: Calculate the beam transmitted from the base station to any user according to the base station RIS user cascaded channel and the third position set; specifically, the beam transmitted from the base station BS to user k is as follows:

[0112]

[0113] where χ k and κ k are both intermediate variables, I M represents the M - order identity matrix, represents the previous iteration value of v k , and the initial value of v k is randomly given, as long as it satisfies P T represents the transmission power of BS.

[0114] Step 400: Calculate the first effective channel parameter based on the base station RIS user cascaded channel and the first marked user beam; calculate the second effective channel parameter based on the base station - user channel and the first marked user beam; the first effective channel parameter is the parameter of the channel from the first marked user, through the RIS elements in the air, to the second marked user; the second effective channel parameter is the parameter of the channel from the first marked user to the second marked user; the first marked user and the second marked user are any two users; the first marked user beam is the beam v i .

[0115] Specifically, determine the first marked user as any user i and the second marked user as any user k. Then, the calculation process of the effective channel parameter of user i - ARIS - user k, that is, the first effective channel parameter, is as follows:

[0116] a i，k = H r，k v i .

[0117] The calculation process of the effective channel parameter of user i - user k, that is, the second effective channel parameter, is as follows:

[0118]

[0119] Step 500: Calculate the RIS phase - shift matrix in the air according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase - shift matrix.

[0120] Step 500 specifically includes:

[0121] (1) Calculate the Euclidean gradient based on the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix as follows:

[0122]

[0123] where, represents the previous iteration value, () * represents the conjugate, represents the noise power; w k represents the user location; θ = [θ1,... θ n ,..., θ N , θ k represents the phase shift of the nth RIS element, and the initial value of θ is randomly given as long as |θ n | = 1.

[0124] (2) Calculate the Riemannian gradient based on the Euclidean gradient as follows:

[0125]

[0126] where, Re() represents taking the real part of the complex number.

[0127] (3) Calculate the projection direction based on the Riemannian gradient as follows:

[0128]

[0129] where, τ represents the adjustment parameter, represents the previous iteration value of d, and the initial value of d is taken as the negative gradient direction, calculated by -grad θ η, represents the Polak - Ribière conjugate gradient direction.

[0130] (4) Calculate the aerial RIS phase shift matrix based on the projection direction as follows:

[0131]

[0132] where, ν represents the Armijo step size.

[0133] Step 600: Determine the RIS deployment location optimization model according to the base station-user channel, the base station-RIS-user cascaded channel, the aerial RIS phase shift matrix, the second tagged user beam, the first effective channel parameter, the second effective channel parameter, the first location, the second location, the third location set, and the original array data corresponding to the aerial RIS element; the RIS deployment location optimization model includes a cascaded link distance constraint function and an objective function for optimizing the RIS deployment location; the second tagged user beam is the beam transmitted from the base station to the second tagged user.

[0134] Step 600 specifically includes:

[0135] (1) Calculate the first auxiliary variable according to the base station-user channel, the base station-RIS-user cascaded channel, the aerial RIS phase shift matrix, and the second tagged user beam. Specifically, for user k, based on the channel h from the BS to user k d,k , the cascaded channel H of BS-ARIS-user k r,k , the phase shift matrix θ of the ARIS, and the beam v transmitted from the BS to user k k , use the following formula to calculate the first auxiliary variable

[0136]

[0137] where represents the weight factor of user k.

[0138] (2) Calculate the second auxiliary variable according to the first effective channel parameter, the second effective channel parameter, the first auxiliary variable, and the aerial RIS phase shift matrix, as follows:

[0139]

[0140] (3) Determine the cascaded link distance constraint function according to the first location, the second location, and the third location set.

[0141] Specifically, according to the formula

[0142]

[0143] Calculate the upper bound constraint function of the cascaded link distance product.

[0144] According to the formula

[0145]

[0146] Calculate the lower bound constraint function of the cascaded link distance product.

[0147] where Represents the previous iteration value of q, Represents the distance function from the BS to The distance function, Represents The distance function to user k, d G d(q) = |c - q|,

[0148] (4) Calculate the three-dimensional coordinates of each element in the aerial RIS element according to the original element array data corresponding to the aerial RIS element and the first position.

[0149] (5) Calculate the signal phase shift reflected by the aerial RIS element to any user according to the three-dimensional coordinates of each element in the aerial RIS element and the third position set.

[0150] (6) Determine the objective function for optimizing the RIS deployment position according to the signal phase shift reflected by the aerial RIS element to any user, the first marked user beam, the second marked user beam, the first auxiliary variable, the second auxiliary variable, and the second effective channel parameter.

[0151] The objective function for optimizing the RIS deployment position is:

[0152]

[0153]

[0154] where q * Represents the optimized deployment position of the RIS, ∈ k Represents the second auxiliary variable, β0 represents the LOS path loss when the reference distance d0 = 1m, Ξ i Represents the signal phase shift reflected by the aerial RIS element to the first marked user, Ξ k Represents the signal phase shift reflected by the aerial RIS element to the second marked user, v i Represents the first marked user beam, v k Represents the second marked user beam, b i,k Represents the second effective channel parameter, Re{} represents taking the real part of the negative number, Represents the first auxiliary variable, μ i and ξ k Both represent preset auxiliary variables, that is, the introduced auxiliary variables; q represents the current deployment position of the RIS, Represents the previous iteration value of q, Ω() represents the upper bound constraint function of the cascaded link distance product, and Λ() represents the lower bound constraint function of the cascaded link distance product.

[0155] In addition, for the phase shift of the signal reflected by the RIS element in the air to the second tagged user, it is calculated according to the following formula:

[0156]

[0157] where θ n represents the phase shift of the nth reflecting element in the RIS element in the air.

[0158] Step 700, perform convex optimization on the RIS deployment location optimization model to obtain the optimized deployment location of the RIS. Specifically, both the cascaded link distance constraint function and the RIS deployment location optimization model are convex functions with respect to q, so the above problem is a convex optimization problem and can be solved by the CVX tool to obtain the optimal result.

[0159] In a specific practical application, the noise power is set to σ 2 = -170 dBm, the operating frequency is set to f = 30 GHz, and the wavelength λ = 1 cm. The height of the BS is h BS = 5 m, the number of transmitting antennas of the BS is M = 2×2, and the distance between the transmitting antennas of the BS is l y = l z = λ / 2. The height of the ARIS is set to h RIS = 100 m, and the distance between adjacent elements on the ARIS is d y = d y = λ / 10. The number of ground users is K = 4, and the ground users are uniformly and randomly distributed in a horizontal circle with the center at (300 m, 200 m) and a radius of 30 m.

[0160] Based on the above settings, according to the BS transmission beam and RIS phase shift matrix obtained by alternative optimization (AO), the deployment location of the ARIS is obtained through an exhaustive search: the ARIS is fixed at q = [0, 0, 100] T m and q = [300, 200, 100] T m.

[0161] At the same time, a random phase shift scheme is set: the phase shift matrix θ of the ARIS takes random values in [0, 2π).

[0162] When N = 100, the comparison diagram of the relationship between the user weighted sum rate and the transmission power is as shown in Figure 3 The figure shows that the weighted sum rate obtained by the proposed scheme is close to the weighted sum rate obtained by the exhaustive search scheme, verifying that the proposed scheme is close to the optimal solution. By comparing the curves in the figure, it can be found that the weighted sum rate obtained by the proposed scheme is higher than that when the ARIS is fixed at q = [0, 0, 100] T m and q = [300, 200, 100]T The weighted sum rate obtained at \(m\) is because the proposed scheme designs the optimal deployment position of the ARIS based on the transmission beam of the BS and the phase shift matrix of the ARIS. In addition, the weighted sum rate obtained by the proposed scheme is higher than that obtained by the random phase shift scheme because the proposed scheme designs the phase shift matrix of the ARIS based on the transmission beam of the BS and the deployment position of the ARIS.

[0163] Transmission power \(P\) T When \(= 10\ dBm\), the schematic diagram of the relationship between the user weighted sum rate and the number of elements in the RIS elements in the air is as Figure 4 shown. It can be seen from the figure that as the number of elements increases, the advantage of the proposed scheme becomes more and more obvious. This is because the proposed scheme jointly optimizes the transmission beam of the BS, the deployment position of the ARIS, and the phase shift matrix of the ARIS according to the BS transmission antenna array, the ARIS reflection element array, and the distribution positions of the users, maximizing the utilization value of the ARIS.

[0164] Embodiment 2

[0165] As Figure 5 shown, in order to implement the technical solution in Embodiment 1, this embodiment provides an RIS phase shift and deployment position optimization system in a communication system, including:

[0166] A position acquisition module 101, configured to acquire a first position, a second position, and a third position set in the communication system; the communication system includes RIS elements in the air, a base station, and multiple users; the first position is the reference three-dimensional coordinate of the RIS elements in the air in a preset coordinate system; the second position is the reference three-dimensional coordinate of the base station in a preset coordinate system; the third position set includes the three-dimensional coordinates of multiple users in a preset coordinate system.

[0167] A channel calculation module 201, configured to calculate the base station RIS user cascaded channel according to the first position, the second position, the third position set, the original array data corresponding to the RIS elements in the air, and the antenna array data corresponding to the base station; calculate the base station user channel according to the second position, the third position set, and the antenna array data corresponding to the base station; the base station RIS user cascaded channel is the cascaded channel from the base station, through the RIS elements in the air to any user; the base station user channel is the channel from the base station to any user.

[0168] A beam calculation module 301, configured to calculate the beam transmitted from the base station to any user according to the base station RIS user cascaded channel and the third position set.

[0169] A channel parameter calculation module 401 is configured to calculate a first effective channel parameter based on the base station RIS user cascaded channel and the first marked user beam; calculate a second effective channel parameter based on the base station user channel and the first marked user beam; the first effective channel parameter is the parameter of the channel from the first marked user to the second marked user passing through the RIS elements in the air; the second effective channel parameter is the parameter of the channel from the first marked user to the second marked user; the first marked user and the second marked user are any two users; the first marked user beam is the beam transmitted from the base station to the first marked user.

[0170] A phase shift matrix calculation module 501 is configured to calculate an air RIS phase shift matrix according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix.

[0171] A deployment location model determination module 601 is configured to determine an RIS deployment location optimization model according to the base station user channel, the base station RIS user cascaded channel, the air RIS phase shift matrix, the second marked user beam, the first effective channel parameter, the second effective channel parameter, the first location, the second location, the third location set, and the original array data corresponding to the air RIS elements; the RIS deployment location optimization model includes a cascaded link distance constraint function and an objective function for optimizing the RIS deployment location; the second marked user beam is the beam transmitted from the base station to the second marked user.

[0172] An optimized deployment location determination module 701 is configured to perform convex optimization on the RIS deployment location optimization model to obtain the optimized deployment location of the RIS.

[0173] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the various embodiments can be referred to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description in the method part.

[0174] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for optimizing the RIS phase shift and deployment location in a communication system, characterized in that, Including: Obtaining a first position, a second position, and a third set of positions in a communication system; the communication system includes an aerial RIS element, a base station, and multiple users; The first position is the reference three-dimensional coordinate of the aerial RIS element in a preset coordinate system; The second position is the reference three-dimensional coordinate of the base station in a preset coordinate system; the third set of positions includes the three-dimensional coordinates of multiple users in a preset coordinate system; Calculating the base station RIS user cascaded channel according to the first position, the second position, the third set of positions, the original array data corresponding to the aerial RIS element, and the antenna array data corresponding to the base station; Calculating the base station user channel according to the second position, the third set of positions, and the antenna array data corresponding to the base station; The base station RIS user cascaded channel is the cascaded channel from the base station through the aerial RIS element to any user; The base station user channel is the channel from the base station to any user; Calculating the beam transmitted from the base station to any user according to the base station RIS user cascaded channel and the third set of positions; Calculating a first effective channel parameter based on the base station RIS user cascaded channel and the first marked user beam; Calculating a second effective channel parameter based on the base station user channel and the first marked user beam; the first effective channel parameter is the parameter of the channel from the first marked user, through the aerial RIS element, to the second marked user; the second effective channel parameter is the parameter of the channel from the first marked user to the second marked user; The first marked user and the second marked user are any two users; the first marked user beam is the beam transmitted from the base station to the first marked user; Calculating the aerial RIS phase shift matrix according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix; Determining a RIS deployment location optimization model according to the base station user channel, the base station RIS user cascaded channel, the aerial RIS phase shift matrix, the second marked user beam, the first effective channel parameter, the second effective channel parameter, the first position, the second position, the third set of positions, and the original array data corresponding to the aerial RIS element; the RIS deployment location optimization model includes a cascaded link distance constraint function and an objective function for optimizing the RIS deployment location; the second marked user beam is the beam transmitted from the base station to the second marked user; Performing convex optimization on the RIS deployment location optimization model to obtain the optimized deployment location of the RIS.

2. The method for optimizing the RIS phase shift and deployment location in the communication system according to claim 1, wherein, Calculating the base station RIS user cascaded channel according to the first position, the second position, the third set of positions, the original array data corresponding to the aerial RIS element, and the antenna array data corresponding to the base station, specifically including: Calculating the three-dimensional coordinates of each element in the aerial RIS element according to the original array data corresponding to the aerial RIS element and the first position; Calculating the three-dimensional coordinates of each antenna in the base station according to the antenna array data corresponding to the base station and the second position; Calculate the base station RIS channel according to the first position, the second position, the three-dimensional coordinates of each element in the airborne RIS element, and the three-dimensional coordinates of each antenna in the base station; the base station RIS channel is the channel from the base station to the airborne RIS element; Calculate the RIS user channel according to the first position, the third position set, and the three-dimensional coordinates of each element in the airborne RIS element; the RIS user channel is the channel from the airborne RIS element to any user; Calculate the base station RIS user cascaded channel according to the base station RIS channel and the RIS user channel.

3. The method for optimizing the RIS phase shift and deployment location in the communication system according to claim 2, characterized in that, Calculating the base station RIS channel according to the first position, the second position, the three-dimensional coordinates of each element in the airborne RIS element, and the three-dimensional coordinates of each antenna in the base station specifically includes: Calculate the base station RIS distance according to the first position and the second position; the base station RIS distance is the distance between the airborne RIS element and the base station; Calculate the base station RIS path loss based on the base station RIS distance; the base station RIS path loss is the signal path loss from the base station to the airborne RIS element; Calculate the receiving array response vector of the airborne RIS element according to the three-dimensional coordinates of each element in the airborne RIS element and the base station RIS distance; Calculate the transmitting array response vector from the base station to the airborne RIS element according to the three-dimensional coordinates of each antenna in the base station, the three-dimensional coordinates of each element in the airborne RIS element, and the base station RIS distance; Calculate the base station RIS channel according to the base station RIS distance, the base station RIS path loss, the receiving array response vector of the airborne RIS element, and the transmitting array response vector from the base station to the airborne RIS element.

4. The method for optimizing the RIS phase shift and deployment location in the communication system according to claim 2, wherein, Calculating the RIS user channel according to the first position, the third position set, and the three-dimensional coordinates of each element in the airborne RIS element specifically includes: Calculate the RIS user distance set according to the first position and the third position set; each RIS user distance in the RIS user distance set is the distance from the airborne RIS element to any user; Calculate the RIS user path loss set according to the RIS user distance set; each RIS user path loss in the RIS user path loss set is the signal path loss from the airborne RIS element to any user; Calculate the transmitting array response vector from the airborne RIS element to any user according to the three-dimensional coordinates of each element in the airborne RIS element, the third position set, and the RIS user distance set; Calculate the RIS user channel according to the RIS user distance set, the RIS user path loss set, and the transmitting array response vector from the airborne RIS element to any user.

5. The method for optimizing RIS phase shift and deployment location in the communication system according to claim 1, characterized in that, Calculate the base station user channel according to the second position, the third position set, and the antenna array data corresponding to the base station, specifically including: Calculate a base station-user distance set according to the second position and the third position set; each base station-user distance in the base station-user distance set is the distance from the base station to any user; Calculate a base station-user path loss set according to the base station-user distance set; each base station-user path loss in the base station-user path loss set is the channel path loss from the base station to any user; Calculate the three-dimensional coordinates of each antenna in the base station according to the antenna array data corresponding to the base station and the second position; Calculate the transmit array response vector from the base station to any user according to the three-dimensional coordinates of each antenna in the base station, the third position set, and the base station-user distance set; Calculate the base station-user channel according to the base station-user distance set, the base station-user path loss set, and the transmit array response vector from the base station to any user.

6. The method for optimizing the RIS phase shift and deployment location in the communication system according to claim 1, wherein Calculate the airborne RIS phase shift matrix according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix, specifically including: Calculate the Euclidean gradient based on the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix; Calculate the Riemannian gradient based on the Euclidean gradient; Calculate the projection direction based on the Riemannian gradient; Calculate the airborne RIS phase shift matrix based on the projection direction.

7. The method for optimizing the RIS phase shift and deployment location in the communication system according to claim 1, characterized in that Determine an RIS deployment location optimization model according to the base station-user channel, the base station-RIS user cascaded channel, the airborne RIS phase shift matrix, the second tagged user beam, the first effective channel parameter, the second effective channel parameter, the first position, the second position, the third position set, and the original array data corresponding to the airborne RIS element, specifically including: Calculate a first auxiliary variable according to the base station-user channel, the base station-RIS user cascaded channel, the airborne RIS phase shift matrix, and the second tagged user beam; Calculate a second auxiliary variable according to the first effective channel parameter, the second effective channel parameter, the first auxiliary variable, and the airborne RIS phase shift matrix; Determine a cascaded link distance constraint function according to the first position, the second position, and the third position set; Calculate the three-dimensional coordinates of each element in the airborne RIS element according to the original array data corresponding to the airborne RIS element and the first position; Calculate the signal phase shift reflected from the airborne RIS element to any user according to the three-dimensional coordinates of each element in the airborne RIS element and the third position set; Determine an objective function for optimizing the RIS deployment location according to the signal phase shift reflected from the airborne RIS element to any user, the first tagged user beam, the second tagged user beam, the first auxiliary variable, the second auxiliary variable, and the second effective channel parameter.

8. The method for optimizing the RIS phase shift and deployment location in the communication system according to claim 7, characterized in that, The cascaded link distance constraint function includes a cascaded link distance product upper bound constraint function and a cascaded link distance product lower bound constraint function; The objective function for optimizing the RIS deployment location is: where, q * represents the deployment location optimized by RIS, ∈ k represents the second auxiliary variable, β0 represents the LOS path loss at the reference distance d0 = 1m, Ξ i represents the signal phase shift of the airborne RIS element reflected to the first tagged user, Ξ k represents the signal phase shift of the airborne RIS element reflected to the second tagged user, v i represents the first tagged user beam, v k represents the second tagged user beam, b i,k represents the second effective channel parameter, Re{} represents taking the real part of a complex number, represents the first auxiliary variable, μ i and ξ k both represent preset auxiliary variables, q represents the current deployment location of RIS, represents the previous iteration value of q, Ω() represents the upper bound constraint function of the cascaded link distance product, Λ() represents the lower bound constraint function of the cascaded link distance product.

9. A RIS phase shift and deployment location optimization system in a communication system, characterized in that, Including: A location acquisition module, configured to acquire a first location, a second location, and a third set of locations in a communication system; the communication system includes an airborne RIS element, a base station, and multiple users; The first location is the reference three-dimensional coordinate of the airborne RIS element in a preset coordinate system; The second location is the reference three-dimensional coordinate of the base station in a preset coordinate system; the third set of locations includes the three-dimensional coordinates of multiple users in a preset coordinate system; A channel calculation module, configured to calculate the base station - RIS - user cascaded channel according to the first location, the second location, the third set of locations, the original element array data corresponding to the airborne RIS element, and the antenna array data corresponding to the base station; Calculate the base station - user channel according to the second location, the third set of locations, and the antenna array data corresponding to the base station; The base station - RIS - user cascaded channel is the cascaded channel from the base station, through the airborne RIS element, to any user; The base station - user channel is the channel from the base station to any user; A beam calculation module, configured to calculate the beam transmitted from the base station to any user according to the base station - RIS - user cascaded channel and the third set of locations; A channel parameter calculation module, configured to calculate a first effective channel parameter based on the base station - RIS - user cascaded channel and the first - marked user beam; Calculate a second effective channel parameter based on the base station - user channel and the first - marked user beam; the first effective channel parameter is the parameter of the channel from the first - marked user, through the airborne RIS element, to the second - marked user; the second effective channel parameter is the parameter of the channel from the first - marked user to the second - marked user; The first - marked user and the second - marked user are any two users; The first - marked user beam is the beam transmitted from the base station to the first - marked user; A phase shift matrix calculation module, configured to calculate the airborne RIS phase shift matrix according to the first effective channel parameter, the second effective channel parameter, and the initial random RIS phase shift matrix; A deployment location model determination module, configured to determine an RIS deployment location optimization model according to the base station - user channel, the base station - RIS - user cascaded channel, the airborne RIS phase shift matrix, the second - marked user beam, the first effective channel parameter, the second effective channel parameter, the first location, the second location, the third set of locations, and the original element array data corresponding to the airborne RIS element; the RIS deployment location optimization model includes a cascaded link distance constraint function and an objective function for optimizing the RIS deployment location; the second - marked user beam is the beam transmitted from the base station to the second - marked user; An optimized deployment location determination module, configured to perform convex optimization on the RIS deployment location optimization model to obtain the optimized deployment location of the RIS.

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