Airport non-orthogonal multiple access method based on active omnidirectional smart metasurface

Abstract

The application relates to an airport non-orthogonal multiple access method based on an active omnidirectional intelligent super surface and belongs to the technical field of wireless communication, and solves the technical problem that it is difficult to meet the high-quality communication needs of large-scale airport communication terminals when facing complex airport environments in the prior art. The airport non-orthogonal multiple access method has the following specific steps: step one: constructing an airport non-orthogonal multiple access system model based on an active omnidirectional intelligent super surface; obtaining the total communication rate of all airport communication terminals in the system model; step two: taking the total communication rate of all airport communication terminals in the system model as an optimization target, establishing an optimization problem model, and setting a constraint condition; step three: dividing the optimization problem model after the constraint condition is set into a beamforming optimization sub-problem and a power distribution sub-problem, solving the two sub-problems, and finally obtaining an optimized airport non-orthogonal multiple access scheme with the maximum total system communication rate.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to an airport non-orthogonal multiple access method based on an active omnidirectional intelligent metasurface. Background Technology

[0002] In recent years, active omnidirectional intelligent metasurfaces have attracted widespread attention. As an emerging auxiliary communication technology, active omnidirectional intelligent metasurfaces employ numerous adjustable reflective elements and amplifiers to flexibly control the phase and amplitude of incident electromagnetic waves, thereby achieving intelligent signal reflection and retransmission. They are increasingly being applied to airport surface communication systems to address signal obstruction and transmission blind spots in existing communication systems. Traditional airport communication systems rely on fixed base stations and antennas, which often present challenges during aircraft takeoff and landing. Especially in the presence of large-scale obstructions such as jet bridges and terminal buildings, signal transmission is hindered, leading to a decrease in communication quality and coverage. Faced with these complex environmental conditions, fixed facilities often lack sufficient flexibility and struggle to effectively cope with dynamically changing obstructions and interference, resulting in unstable communication quality. Summary of the Invention

[0003] In view of the above problems, this invention provides an airport non-orthogonal multiple access method based on an active omnidirectional intelligent metasurface. This method solves the technical problems in the prior art, such as communication blind spots and dead zones caused by signal blockage and multipath effects in complex airport environments, which limit communication coverage and affect ground services and flight safety; fixed base stations and antennas are difficult to dynamically adjust and cannot adapt to rapidly changing environments, resulting in communication quality fluctuations and connection instability; and in high-density airport communication terminal scenarios, limited spectrum resources make it difficult to meet the high-quality communication needs of large-scale airport communication terminals.

[0004] This invention provides a non-orthogonal multiple access method for airports based on an active omnidirectional smart metasurface, the specific steps of which are as follows: Step 1: Construct a system model for airport non-orthogonal multiple access based on an active omnidirectional intelligent metasurface; obtain the sum of communication rates of all airport communication terminals in the system model; The system model includes a base station, an active omnidirectional smart metasurface, and K One airport communication terminal; An active omnidirectional intelligent metasurface is installed on the aircraft, located between the non-communication blind zone and the communication blind zone; K Among the airport communication terminals R Each airport communication terminal is located in the reflection zone of an active omnidirectional intelligent metasurface. T Each airport communication terminal is located in the transmission area of ​​an active omnidirectional intelligent metasurface and meets the following requirements: R +T = K ; Step 2: Establish an optimization problem model with the goal of maximizing the total communication rate of all airport communication terminals in the system model; set constraints; the constraints include base station power constraints, phase shift constraints of the active omnidirectional intelligent metasurface, power consumption constraints, and energy distribution constraints; Step 3: Divide the optimization problem model with constraints into a beamforming optimization subproblem and a power allocation subproblem, and solve the two subproblems iteratively. The beamforming optimization subproblem maximizes the total system communication rate by jointly optimizing reflected beamforming and transmitted beamforming. The power allocation subproblem optimizes the transmission power allocation of the base station to each airport communication terminal based on the optimization results of the beamforming optimization subproblem. Finally, the airport non-orthogonal multiple access scheme that maximizes the total system communication rate is obtained.

[0005] Optionally, the specific steps of step one are as follows: Using an active omnidirectional smart metasurface as a relay, the channel from the base station to the active omnidirectional smart metasurface and the channel from the active omnidirectional smart metasurface to the first... k Channels of airport communication terminals; Based on the channel from the base station to the active omnidirectional smart metasurface and from the active omnidirectional smart metasurface to the first... k The channel of the airport communication terminal is obtained. The signal received at the airport communication terminal; Based on the The signal received at the airport communication terminal was used to obtain the first... Communication rate at each airport communication terminal; According to the The communication rate at each airport communication terminal is the sum of the communication rates of all airport communication terminals in the system model.

[0006] Optionally, the constraints in step two may also include power consumption constraints for each component of the active omnidirectional smart metasurface, amplification gain constraints for the active omnidirectional smart metasurface, non-orthogonal multiple access decoding order constraints, and minimum communication rate constraints for the airport communication terminal.

[0007] Optionally, solving the beamforming optimization subproblem includes: Initialize beamforming variables and penalty factors; Under the current penalty factor, the non-convex rank-one constraint is relaxed into a convex constraint by successive convex approximation, and the objective function is approximated by convex approximation to solve the convex semidefinite programming problem and obtain the optimized beamforming matrix. Determine whether the penalty term used to relax the rank-one constraint is less than the set threshold, or whether the number of iterations has reached the maximum value; if yes, output the optimized active omnidirectional intelligent metasurface beamforming matrix; if no, adjust the penalty factor and continue iterating.

[0008] Optionally, in the beamforming optimization subproblem, the communication rate of the airport communication terminal is substituted by introducing the reciprocal variable of the useful signal power and the variable of the interference signal power, and the lower bound of the communication rate is obtained by using a first-order Taylor expansion, thereby transforming the non-convex objective function into a convex function.

[0009] Optionally, solving the power allocation subproblem includes: Based on the optimized active omnidirectional intelligent metasurface beamforming matrix obtained from the beamforming optimization subproblem, with the goal of maximizing the total system communication rate, the non-convex communication rate function is transformed into a lower bound of a convex function using a first-order Taylor expansion, and a convex optimization problem is established. The optimal transmission power allocation of the base station to each airport communication terminal is obtained by solving the problem.

[0010] Optionally, the optimized airport non-orthogonal multiple access scheme that maximizes the total system communication rate involves the base station sending signals to each airport communication terminal according to the optimized transmission power allocation, thereby achieving non-orthogonal multiple access.

[0011] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The airport non-orthogonal multiple access method based on active omnidirectional intelligent metasurface of the present invention can allocate and transmit input and output signals by intelligently controlling the phase, reflection characteristics and amplification amplitude of active omnidirectional intelligent metasurface, so as to ensure that the signal omnidirectional coverage and the system communication rate are maximized under the premise of meeting the minimum rate requirements of all airport communication terminals, thereby improving the continuity and stability of communication.

[0012] (2) The airport non-orthogonal multiple access method based on active omnidirectional intelligent metasurface of the present invention takes into account the complex and ever-changing environment of airports. The active omnidirectional intelligent metasurface can dynamically adapt to environmental changes, overcome the multiplicative fading effect through intelligent reflection and transmission of signals, enhance the robustness of the system, and ensure that high-quality communication services can still be provided under various uncertain conditions.

[0013] (3) The airport non-orthogonal multiple access method based on active omnidirectional intelligent metasurface of the present invention takes into account high-density environmental conditions. Active omnidirectional intelligent metasurface can effectively reduce interference and attenuation in signal transmission, significantly improve the quality of communication signals and the stability of the system, and ensure reliable communication in complex dynamic environments while maximizing the total communication rate of the system. Attached Figure Description

[0014] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0015] Figure 1 This is a schematic diagram of the communication system model of the airport non-orthogonal multiple access method based on an active omnidirectional intelligent metasurface according to the present invention.

[0016] Figure 2 This is a flowchart of the airport non-orthogonal multiple access method based on an active omnidirectional intelligent metasurface according to the present invention. Detailed Implementation

[0017] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0018] A specific embodiment of the present invention, such as Figure 2 As shown, a non-orthogonal multiple access method for airports based on an active omnidirectional smart metasurface is disclosed. The specific steps are as follows: Step 1: Construct a system model for airport non-orthogonal multiple access based on an active omnidirectional intelligent metasurface, such as... Figure 1 As shown; obtain the sum of communication rates of all airport communication terminals in the system model.

[0019] Furthermore, the system model includes a base station, an active omnidirectional smart metasurface, and K Airport communication terminals.

[0020] Furthermore, K Among the airport communication terminals R Each airport communication terminal is located in the reflection zone of an active omnidirectional intelligent metasurface. T Each airport communication terminal is located in the transmission area of ​​an active omnidirectional intelligent metasurface and meets the following requirements: R + T = K .

[0021] Furthermore, an antenna is installed between the base station and each airport communication terminal.

[0022] Furthermore, the active omnidirectional smart metasurface is deployed on the aircraft window, located between the non-communication blind zone and the communication blind zone. The deployed active omnidirectional smart metasurface has M components.

[0023] As we can understand, a communication dead zone is a place where a signal cannot directly reach. It can also be understood as a situation where the base station is not directly visible from the airport's communication terminal, and there is no direct line of sight between the terminal and the base station.

[0024] Furthermore, the direct communication link between the base station and the airport communication terminal is sometimes blocked by obstacles. This invention uses an active omnidirectional smart metasurface as a relay to obtain the channel from the base station to the active omnidirectional smart metasurface and the channel from the active omnidirectional smart metasurface to the first... k The channel for each airport communication terminal is expressed as follows: (1) (2) in, Indicates the first n A time slot for the channel from the base station to the active omnidirectional smart metasurface; Indicates the first n The time slots range from active omnidirectional intelligent metasurfaces to the first... k Channels of airport communication terminals; This represents the path loss parameter; and They represent the first n The distance between the base station and the active omnidirectional smart metasurface in each time slot, and the distance from the active omnidirectional smart metasurface to the first... The distance between airport communication terminals ; and Both represent path loss exponents; and These represent the Rice coefficients between the base station and the active omnidirectional smart metasurface, and between the active omnidirectional smart metasurface and the airport communication terminal, respectively. and They represent the first n The direct path from the base station to the active omnidirectional smart metasurface in each time slot, and the path from the active omnidirectional smart metasurface to the first... k The direct radius of each airport communication terminal; and Indicates the first n The non-direct path from the base station to the active omnidirectional smart metasurface in each time slot, and the path from the active omnidirectional smart metasurface to the first... k The non-direct path of the airport communication terminal; Indicates the matrix dimension; M This indicates the number of active omnidirectional smart metasurface elements.

[0025] Understandable, Indicates the reflective area or transmission area , . , They represent the first n The time slots range from active omnidirectional intelligent metasurfaces to the first... k A channel for reflecting airport communication terminals or a channel for transmitting airport communication terminals.

[0026] Furthermore, based on the channel from the base station to the active omnidirectional smart metasurface and from the active omnidirectional smart metasurface to the first... k The channel of the airport communication terminal is obtained. The signal received at each airport communication terminal is expressed as follows:

[0027] (3) in, Indicates the first n The base station transmits signals in each time slot, and ; Indicates the first n The beam phase shift matrix (including reflection beam matrix and transmission beam matrix) of the signal (including reflected signal and transmitted signal) of the active omnidirectional smart metasurface in a time slot. The beam energy distribution matrix (including the reflected beam energy distribution matrix and the transmitted beam energy distribution matrix) represents the signal (including reflected signal and transmitted signal) of the active omnidirectional smart metasurface. Indicates the first n Amplification gain matrix of active omnidirectional smart metasurface in one time slot; For the first n The thermal noise generated by the active omnidirectional smart metasurface in each time slot has a mean of 0 and a variance of . ; For the first n The first time slot The additive white Gaussian noise of the airport communication terminals has a mean of 0 and a variance of . .

[0028] Furthermore, the first The signal received at the airport communication terminal was used to obtain the first... n The first time slot Communication rate at each airport communication terminal The expression is: (4) (5) in, Indicates the first n The first time slot Signal-to-noise ratio at each airport communication terminal; Indicates the firstn The first time slot Useful signal power at each airport communication terminal; Indicates the first n The first time slot Decoding sequence of airport communication terminals Indicates the first n The first time slot k Decoding sequence of airport communication terminals Indicates the first n Airport communication terminal in time slot Decoding takes precedence over the first One airport communication terminal; Indicates the first n The time slot base station transmits to the first Signal power of the airport communication terminal; Indicates the first n The time slot base station transmits to the first Signal power of the airport communication terminal; Indicates the first n The variance of thermal noise generated by an active omnidirectional smart metasurface in a time slot; Indicates the first n The first time slot The variance of additive white Gaussian noise for each airport communication terminal.

[0029] Furthermore, the decoding order of the airport communication terminal is determined based on the distance between the airport communication terminal and the base station.

[0030] Furthermore, ; ,in, It is the first n The active omnidirectional intelligent metasurface in the first time slot m The power amplification factor of each component, .

[0031] It is understandable that wireless signals incident on the components of an active omnidirectional smart metasurface are divided into reflected signals and transmitted signals. n Reflection energy allocation matrix for each time slot , No. n Transmission energy allocation matrix for each time slot ,in, Indicates the first n The active omnidirectional intelligent metasurface in the first time slot m Energy distribution parameters for each component. n The reflection phase shift matrix of each time slot ,in, Indicates the first m The reflection phase shift of each element.n Each time-slot transmission beamforming matrix ,in, Indicates the first m The transmission phase offset of each component; This represents the phase parameter.

[0032] Furthermore, according to the first n The first time slot The communication rate at each airport communication terminal is the sum of the communication rates of all airport communication terminals in the system model.

[0033] Step 2: With the goal of maximizing the total communication rate of all airport communication terminals in the system model constructed in Step 1, establish an optimization problem model and set constraints.

[0034] This invention aims to maximize the total communication rate of communication terminals by jointly optimizing base station power allocation and active transmission and reflection beamforming of an active omnidirectional smart metasurface, while simultaneously satisfying base station power constraints, phase shift constraints, power consumption constraints, and energy allocation constraints of the active omnidirectional smart metasurface. Specifically, it is described as follows: (6a) (6b) (6c) (6d) (6e) (6f) (6g) (6h) (6i) (6g) in, Indicates the total number of time slots; This represents the transmission power vector allocated by the base station to the airport communication terminal within the nth time slot; This indicates the maximum transmission power of the base station; Indicates the first n The first active omnidirectional intelligent metasurface in the time slot m The power amplification factor of each component; The first part represents the distance from the base station to the active omnidirectional smart metasurface. m Channel vectors of each element; This indicates the first active omnidirectional intelligent metasurface. m The maximum power of each component; Denotes the F-norm of a matrix; This represents the total power of the active omnidirectional smart metasurface; Indicates the first n The first time slot contains the active omnidirectional intelligent metasurface reflection beam phase shift matrix. m One diagonal element; Indicates the first n The first time slot contains the active omnidirectional intelligent metasurface transmission beam phase shift matrix. m One diagonal element; Indicates the first n The active omnidirectional intelligent metasurface in the first time slot m Energy distribution parameters for each component; Indicates the first n An active omnidirectional intelligent metasurface power allocation vector is present in each time slot; Indicates the first n The first time slot Useful signal power at each airport communication terminal; Indicates the first n The first time slot Useful signal power at each airport communication terminal; This represents the minimum communication rate of the airport communication terminal. It can be understood that equation (6b) represents the first... m The power consumption constraints of each component; Equation (6c) represents the power consumption constraint of the active omnidirectional intelligent metasurface; Equation (6d) represents the phase shift constraint of the active omnidirectional intelligent metasurface; Equation (6e) represents the energy distribution constraint of the active omnidirectional intelligent metasurface; Equation (6f) represents the amplification gain constraint of the active omnidirectional intelligent metasurface; Equations (6g) and (6h) represent the non-orthogonal multiple access decoding constraint; Equation (6i) represents the base station transmit power constraint; and Equation (6g) represents the communication service quality constraint of the airport communication terminal.

[0035] Step 3: Divide the optimization problem model with constraints into two sub-problems, solve the two sub-problems, and finally obtain the optimized airport non-orthogonal multiple access scheme that maximizes the total system communication rate.

[0036] Specifically, sub-problem one: Shaping and optimizing active omnidirectional intelligent metasurface wave beams, the specific steps are as follows: First, the reflection coefficient vector and the transmission coefficient vector are defined as follows:

[0037]

[0038] in, Indicates the first n Reflection beamforming vector of a time-slotted active omnidirectional smart metasurface; Indicates the firstn Transmission beamforming vector of a time-slot active omnidirectional smart metasurface; Indicates angle.

[0039] Furthermore, , ,in, This represents the communication terminal from the base station to the airport communication terminal in the area (including the reflection area and the transmission area) in the nth time slot. k Inter-channel; Indicates the first n Beamforming vectors (including reflected beamforming vectors) of active omnidirectional smart metasurfaces in each time slot and transmission beamforming vector Hermitian matrix of ) Then, the optimization problem of subproblem one is rewritten as an objective function, expressed as: (7a) (7b) , (7c) (7d) (7e) (7f) (6g), (7g) in, Indicates the first n The Hermitian matrix of the beamforming vectors (including reflected beamforming vectors and transmitted beamforming vectors) of the active omnidirectional smart metasurface in each time slot; Indicates the first n The Hermitian matrix of the reflection beamforming vector of the active omnidirectional smart metasurface in each time slot. m One diagonal element; Indicates the first n The Hermitian matrix of the transmission beamforming vector of the active omnidirectional smart metasurface in each time slot. m One diagonal element; The vector consisting of the diagonal elements of the Hermitian matrix representing the beamforming vector (including the reflected beamforming vector and the transmitted beamforming vector) of the nth time slot; This represents the nth time slot from the base station to the region (including the reflection region and the transmission region). Hermitian matrix of the channels between airport communication terminals; This represents the communication terminal from the base station to the airport communication terminal in the area (including the reflection area and the transmission area) in the nth time slot.l The Hermitian matrix of the channel between them; This indicates taking the rank of the matrix; This represents the rank of the matrix.

[0040] Furthermore, .

[0041] Furthermore, .

[0042] Furthermore, The following conditions must be met:

[0043] in, The vector consisting of the diagonal elements of the Hermitian matrix representing the beamforming vector (including the reflection beamforming vector and the transmission beamforming vector) of the k-th airport communication terminal in the n-th time slot. This represents the parameter corresponding to the beamforming matrix of the m-th element in the n-th time slot.

[0044] Furthermore, the objective function (7a) is non-convex, and the present invention defines the inverse vector of the useful signal power. Interference signal power vector The expression is: (8) (9) in, Indicates the first n In the first time slot The reciprocal of the useful signal power of an airport communication terminal; Indicates the first n In the first time slot Interference signal power of airport communication terminals; Indicates the first n The time slot base station transmits to the first Signal power of the airport communication terminal; Indicates the first n There are active omnidirectional intelligent metasurfaces in each time slot and the first The Hermitian matrix of channel vectors between airport communication terminals.

[0045] Furthermore, .

[0046] Furthermore, in the subproblem below, based on the inverse vector of the useful signal power and the interference signal power vector, the first... Airport communication terminals The communication rate is substituted as a variable, and the expression is: (10).

[0047] Then, using a first-order Taylor expansion, we find the lower bound of equation (10), which is expressed as: (11) in, and Indicates after the first The result after the optimization is the first n In the first time slot The result of the reciprocal of the useful signal power and the interference signal power of the airport communication terminal; Indicates the first The lower bound of the communication rate at each airport communication terminal based on the first-order Taylor expansion of beamforming variables.

[0048] Furthermore, the optimization problem of subproblem one can be restated as follows: (12a) (12b) (12c) (12d) ,(7b)~(7f),(12e) Next, using a penalty method, the non-convex rank-one constraint (7c) is processed, and the rank-one constraint (7c) is equivalent to: (13) in, Representing the n The kernel norm of the Hermitian matrix of the beamforming vector of an active omnidirectional smart metasurface in a time slot; Representing the n The spectral norm of the Hermitian matrix of the beamforming vector of an active omnidirectional smart metasurface in a time slot.

[0049] It is worth noting that, for the first n Hermitian matrix of beamforming vectors of active omnidirectional smart metasurfaces in each time slot They all , where, if and only if The equality holds when the matrix is ​​rank-one. Therefore, equation (10) only applies to matrices. Only when the rank is established will it be satisfied; It represents the first largest singular value of the matrix.

[0050] Furthermore, , Represents the matrix of the first i A large singular value.

[0051] Furthermore, utilizing penalty factors Relaxing the rank-one constraint (7c) into a penalty term added to the objective function, the expression is: (14a) ,(7c)~(7f),(12b)~(12d)(14b) Furthermore, to avoid due to penalty factors An excessively large value causes the objective function to be affected by a penalty factor. Primarily, this invention first selects to initialize the penalty factor with a smaller initial value. Then, during the iteration process, the penalty factor is gradually increased. By reaching a sufficiently large value, a feasible rank-one matrix can eventually be obtained. Since the objective function is still non-convex, the optimization problem (14) is still non-convex.

[0052] Furthermore, using a successive convex approximation method, the convex upper bound of the penalty term is obtained, expressed as: (15) in, Indicates the first In the nth iteration n The Hermitian matrix of the beamforming vectors (including reflected beamforming vectors and transmitted beamforming vectors) of the active omnidirectional smart metasurface in each time slot; Indicates the first In the nth iteration n The spectral norm of the Hermitian matrix of the beamforming vector of an active omnidirectional smart metasurface in each time slot .

[0053] Furthermore,

[0054] in, Indicates the first In the nth iteration n Beamforming vectors of active omnidirectional smart metasurfaces in each time slot The eigenvector corresponding to the largest eigenvalue of the Hermitian matrix.

[0055] Furthermore, the optimization problem of subproblem one can be restated as follows: (16a) (7c)~(7f),(12b)~(12d),(16b) in, This is a penalty item.

[0056] Furthermore, optimization problems (16a) and (16b) are convex semidefinite programming problems, which are solved using the convex optimization solver CVX.

[0057] Step 1. Initialize variables and punishment factors Set the number of optimizations ,in, Indicates the first n The initial values ​​of the reflection beamforming matrix of the active omnidirectional smart metasurface in each time slot; Indicates the first n The initial values ​​of the transmission beamforming matrix of the active omnidirectional smart metasurface in each time slot; The initial value represents the reciprocal vector of the useful signal power; This represents the initial value of the interference signal power vector.

[0058] Step 2. Use the current variables and punishment factors Calculate optimization problems (16a) and (16b) to obtain updated values. ,renew ,in, Indicates the first n The reflection beamforming matrix of the active omnidirectional smart metasurface in the time slot is the first... The optimized value obtained in the next iteration; Indicates the first n The transmission beamforming matrix of the active omnidirectional smart metasurface in the time slot is the first... The optimized value obtained in the next iteration; The first vector representing the reciprocal of the useful signal power The optimized value obtained in the next iteration; The first element representing the power vector of the interference signal The optimized value obtained in the next iteration; Indicates the first n The reflection beamforming matrix of the active omnidirectional smart metasurface in the time slot is the first... The optimized value obtained in the next iteration; Indicates the first n The transmission beamforming matrix of the active omnidirectional smart metasurface in the time slot is the first... The optimized value obtained in the next iteration; The first vector representing the reciprocal of the useful signal power The optimized value obtained in the next iteration; The first element representing the power vector of the interference signal The optimized value obtained in the next iteration.

[0059] Step 3. Determine the penalty item. Is the amplitude lower than the set threshold? Or optimize the number of times Has the maximum value been reached? If the penalty amount is lower than the set threshold Or optimize the number of times Reaching the maximum value yields the optimized active omnidirectional intelligent metasurface beamforming matrix. Otherwise, update the penalty factor, making Return to step 2.

[0060] in, Indicates the maximum constraint accuracy.

[0061] Furthermore, The maximum constraint accuracy is a predefined violation of equation (15).

[0062] Furthermore, update the penalty factor. ,in, This represents the reduction factor of the penalty factor. .

[0063] The algorithm terminates when the growth rate of the objective function (16a) is less than the growth threshold. Therefore, with the penalty factor... As the value increases, equation (13) will eventually satisfy the maximum constraint accuracy. Also output the final variable. The objective function (16a) is non-increasing in each iteration of the inner loop, and the optimal objective function has a lower bound. Therefore, as η approaches infinity, the iterative algorithm converges to a stable point, i.e., the variable... .

[0064] The active omnidirectional intelligent metasurface beamforming optimization subproblem of this invention first undergoes stepwise optimization in an inner loop to ensure a local optimum is found under the current penalty factor conditions. Then, an outer loop is entered, parameters are adjusted, and the inner loop steps are repeated until global convergence is achieved. This combination of inner and outer loops progressively improves the optimization results, enabling the system to achieve more precise control and optimization effects.

[0065] Specifically, sub-problem two: power allocation, the specific steps are as follows: The optimized active omnidirectional intelligent metasurface beamforming matrix obtained in subproblem one The optimization problem for subproblem two is as follows: (18a) (6h),(6i),(6g),(18b) Furthermore, under subproblem two, regarding the first... Airport communication terminals The communication rate is substituted as a variable, and the expression is: (19) in, Indicates the first n The variance of thermal noise generated by an active omnidirectional smart metasurface in a time slot; Indicates from airport communication terminal k to airport communication terminal K The sum of the base station transmission power; Indicates from the first The airport communication terminal to the first The total base station transmission power of the airport communication terminals; Indicates the first n The first time slot The variance of additive white Gaussian noise for each airport communication terminal.

[0066] Furthermore, .

[0067] Since equation (19) is still a non-convex function at this point, and its form is a convex function minus another convex function, we can use the first-order Taylor expansion to transform equation (19) into a lower bound, which is expressed as: (20) in, Indicates after the first After the optimization, we get the result from the first... The airport communication terminal to the first The result of the sum of the base station transmission power of each airport communication terminal; Indicates the first The lower bound of the communication rate at each airport communication terminal based on the first-order Taylor expansion of the base station power allocation variable.

[0068] Furthermore, by replacing the objective function (18a) with the lower bound (20), the expression for the optimization problem of subproblem two is: (21a) (21b) (21c) (21d).

[0069] The optimization problem of subproblem 2 (21) is a convex optimization. The convex optimization solution tool CVX is used to solve this subproblem to obtain the allocated power of the base station.

[0070] This invention iteratively solves two sub-problems. First, given an initial point for all variables, it optimizes sub-problem one. Then, based on the optimized solution to sub-problem one, it optimizes sub-problem two. This process is repeated until the communication rate converges to a stable point, ultimately obtaining the allocated power (access) for each base station (multi-address). In the case of non-orthogonality, by allocating power to different base stations, it enables differentiated communication even between non-orthogonal base stations, ensuring communication quality for each user while facilitating multi-address access.

[0071] This invention proposes an airport non-orthogonal multiple access method based on an active omnidirectional intelligent metasurface. This method fully leverages the high flexibility and controllability of the metasurface, achieving omnidirectional coverage through intelligent reflection and signal transmission technologies. Specifically, the intelligent metasurface divides the incident signal into a transmission signal and a reflected signal, transmitting them to two regions surrounding the surface respectively. By adjusting the phase of the reflection unit and the amplitude of the amplifier, the signal transmission path is optimized. This not only reduces the overall system power consumption while meeting the minimum data rate requirements of airport communication terminals but also effectively improves communication continuity and stability. Furthermore, due to the advantages of flexible deployment and low cost of the active omnidirectional intelligent metasurface, it can rapidly improve communication coverage and signal quality at airports without significantly altering existing infrastructure. The introduction of the active omnidirectional intelligent metasurface allows the airport communication system to flexibly adapt to environmental changes, and the intelligent signal reflection mechanism effectively overcomes the negative impact of obstruction, thereby ensuring communication stability and continuity. By establishing a maximum system communication rate optimization model and employing advanced optimization algorithms (such as successive convex approximation and penalty methods), it is possible to effectively solve the problem under complex constraints, ensuring the feasibility and effectiveness of the optimization scheme, thereby achieving the goal of green communication.

[0072] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A non-orthogonal multiple access method for airports based on an active omnidirectional intelligent metasurface, characterized in that, The specific steps are as follows: Step 1: Construct a system model for airport non-orthogonal multiple access based on an active omnidirectional intelligent metasurface; obtain the sum of communication rates of all airport communication terminals in the system model; The system model includes a base station, an active omnidirectional smart metasurface, and K One airport communication terminal; An active omnidirectional intelligent metasurface is installed on the aircraft, located between the non-communication blind zone and the communication blind zone; K Among the airport communication terminals R Each airport communication terminal is located in the reflection zone of an active omnidirectional intelligent metasurface. T Each airport communication terminal is located in the transmission area of ​​an active omnidirectional intelligent metasurface and meets the following requirements: R + T = K ; Step 2: Establish an optimization problem model with the goal of maximizing the total communication rate of all airport communication terminals in the system model; set constraints; the constraints include base station power constraints, phase shift constraints of the active omnidirectional intelligent metasurface, power consumption constraints, and energy distribution constraints; Step 3: Divide the optimization problem model with constraints into a beamforming optimization subproblem and a power allocation subproblem, and solve the two subproblems iteratively. The beamforming optimization subproblem maximizes the total system communication rate by jointly optimizing reflected beamforming and transmitted beamforming. The power allocation subproblem optimizes the transmission power allocation of the base station to each airport communication terminal based on the optimization results of the beamforming optimization subproblem. Finally, the airport non-orthogonal multiple access scheme that maximizes the total system communication rate is obtained.

2. The airport non-orthogonal multiple access method according to claim 1, characterized in that, The specific steps for step one are as follows: Using an active omnidirectional smart metasurface as a relay, the channel from the base station to the active omnidirectional smart metasurface and the channel from the active omnidirectional smart metasurface to the first... k Channels of airport communication terminals; Based on the channel from the base station to the active omnidirectional smart metasurface and from the active omnidirectional smart metasurface to the first... k The channel of the airport communication terminal is obtained. The signal received at the airport communication terminal; Based on the The signal received at the airport communication terminal was used to obtain the first... Communication rate at each airport communication terminal; According to the The communication rate at each airport communication terminal is the sum of the communication rates of all airport communication terminals in the system model.

3. The airport non-orthogonal multiple access method according to claim 1, characterized in that, The constraints in step two also include power consumption constraints for each component of the active omnidirectional smart metasurface, amplification gain constraints for the active omnidirectional smart metasurface, non-orthogonal multiple access decoding order constraints, and minimum communication rate constraints for the airport communication terminal.

4. The airport non-orthogonal multiple access method according to claim 1, characterized in that, The solution to the beamforming optimization subproblem includes: Initialize beamforming variables and penalty factors; Under the current penalty factor, the non-convex rank-one constraint is relaxed into a convex constraint by successive convex approximation, and the objective function is approximated by convex approximation to solve the convex semidefinite programming problem and obtain the optimized beamforming matrix. Determine whether the penalty term used to relax the rank-one constraint is less than the set threshold, or whether the number of iterations has reached the maximum value; if yes, output the optimized active omnidirectional intelligent metasurface beamforming matrix; if no, adjust the penalty factor and continue iterating.

5. The airport non-orthogonal multiple access method according to claim 4, characterized in that, In the beamforming optimization subproblem, the communication rate of the airport communication terminal is substituted by introducing the reciprocal variable of the useful signal power and the variable of the interference signal power, and the lower bound of the communication rate is obtained by using a first-order Taylor expansion, thus transforming the non-convex objective function into a convex function.

6. The airport non-orthogonal multiple access method according to claim 1, characterized in that, The solution to the power allocation subproblem includes: Based on the optimized active omnidirectional intelligent metasurface beamforming matrix obtained from the beamforming optimization subproblem, with the goal of maximizing the total system communication rate, the non-convex communication rate function is transformed into a lower bound of a convex function using a first-order Taylor expansion, and a convex optimization problem is established. The optimal transmission power allocation of the base station to each airport communication terminal is obtained by solving the problem.

7. The airport non-orthogonal multiple access method according to claim 1, characterized in that, The optimized airport non-orthogonal multiple access scheme, which maximizes the total system communication rate, sends signals to each airport communication terminal according to the optimized transmission power allocation of the base station, thereby realizing non-orthogonal multiple access.

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