Broadband beam dispersion suppression method and system based on movable intelligent metasurface

Abstract

The invention provides a broadband beam dispersion suppression method and system based on a movable intelligent metasurface. The system comprises a base station and an intelligent reflecting surface, the base station is provided with a movable antenna array, and the intelligent reflecting surface is divided into a plurality of movable sub-arrays; jointly optimizing the position of each antenna in the movable antenna array and the position of each sub-array in the movable sub-array; wherein the joint optimization aims to maximize the minimum user received signal power on the whole frequency band, and meets the movement constraint of the movable antenna and the movable sub-array. The broadband THz communication system assisted by the intelligent reflecting surface is enabled by using the movable device, and the receiving power of each subcarrier at a user is remarkably improved and the dual-beam dispersion effect is almost completely eliminated by jointly optimizing the positions of the movable antenna and the intelligent reflecting surface subarray.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless communication, and in particular, to a wideband beam dispersion suppression method and system based on a movable intelligent metasurface. BACKGROUND

[0002] For the next generation of wireless communication systems, THz communication is considered a very promising technology. Due to the unique characteristics of large bandwidth, THz communication can play a key role in enhancing mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and Internet of Things (IoT) scenarios, etc. However, THz signals face serious path loss and atmospheric absorption problems, which significantly limit the practicalization process.

[0003] To solve this problem, the industry proposes to use the promising IRS technology to enhance the performance of the THz communication system. As a low-cost, low-power passive device, IRS can effectively improve the coverage and transmission rate of THz communication by adjusting the phase of the reflecting unit to reconfigure the wireless channel. Existing research shows that IRS can significantly improve the energy efficiency, anti-interference ability, and spectrum utilization rate of the THz communication system. Another technology that can improve THz communication is the movable antenna (MA). Unlike traditional fixed-position antennas, MA can dynamically adjust the antenna position to expand the signal coverage, enhance communication reliability, and improve communication rate, etc. Currently, MA has been verified to improve the beam gain of THz communication.

[0004] However, in a wideband THz system, due to the characteristics of large bandwidth, the subcarrier frequency difference is large, and the analog beamforming gain of the base station (BS) and the IRS will fluctuate dramatically with frequency, i.e. the so-called "beam dispersion" effect; Since the cascaded channel of BS-IRS-user is the product of BS-IRS channel and IRS-user channel, the analog beamforming gain seen at the user side is the product of the analog beamforming gain of BS and IRS, and this product characteristic will cause the analog beamforming gain seen at the user side to decay more severely with frequency, which is called the "double beam dispersion" effect. This effect will significantly reduce the array gain on different subcarriers, and thus reduce the communication rate. Existing work has shown that deploying a MA array on the BS can significantly suppress the beam dispersion effect of the millimeter wave wideband system, but existing work has not studied how to use the movable nature to suppress the double beam dispersion effect of IRS-assisted wideband THz communication.

[0005] Patent application document CN116781123A discloses a joint beam design method for overcoming beam dispersion in terahertz IRS communication, which comprises the following steps: first, an IRS-assisted terahertz multi-user communication system is built, a time delay alignment modulation is applied to the IRS, an additional delay is introduced, and the signal received by the user on the subcarrier is calculated; second, the signal-to-interference ratio of the user on the subcarrier is calculated according to the signal received by the user on the subcarrier, and the achievable sum rate of the user is calculated according to the signal-to-interference ratio; finally, the maximization of the achievable sum rate of the user is taken as the objective function; the objective function is decomposed into multiple sub-optimization objectives by using an alternating optimization algorithm, and the SDR and MM algorithms are used to solve the multiple sub-optimization objectives to obtain the maximum of the achievable sum rate of the user. However, the patent cannot completely solve the existing technical problems and cannot meet the needs of the present application. SUMMARY

[0006] In view of the defects in the prior art, the purpose of the present application is to provide a wideband beam dispersion suppression method and system based on a movable intelligent metasurface.

[0007] The wideband beam dispersion suppression system based on a movable intelligent metasurface provided by the present application comprises a base station and an intelligent reflecting surface.

[0008] The base station is equipped with a movable antenna array, and the intelligent reflecting surface is divided into multiple movable sub-arrays.

[0009] The position of each antenna in the movable antenna array and the position of each sub-array in the movable sub-array are jointly optimized.

[0010] The joint optimization aims to maximize the minimum user received signal power over the entire frequency band and satisfies the movement constraints of the movable antenna and the movable sub-array.

[0011] Preferably, the size of the movable antenna array of the base station is A BS,1 ×A BS,2 , and contains M movable antennas.

[0012] The size of the intelligent reflecting surface is A IRS,1 ×A IRS,2 .

[0013] The position of the mth movable antenna satisfies:

[0014]

[0015] wherein m∈M, C BS is the feasible movement area of the movable antenna, and (x, y) is the position of the movable antenna in a two-dimensional plane. ​

[0016] Preferably, the smart reflecting surface is divided into K sub-arrays, each containing J = J1J2 reflecting elements, where J1and J2are the number of reflecting elements in the horizontal and vertical directions, respectively;

[0017] The center position of the kth sub-array is The relative position of the jth reflecting element with respect to the center of the kth sub-array is

[0018] The position of each reflecting element satisfies:

[0019]

[0020] where C IRS represents the feasible movement region of the reflecting element, and (x', y') is the position of the reflecting element on a two-dimensional plane.

[0021] Preferably, the channel between the base station and the smart reflecting surface at the lth sub-carrier is represented as:

[0022]

[0023] where, and are the position vectors of the movable antenna and the sub-array of the smart reflecting surface, respectively; τ G is the path delay of the channel between the base station and the smart reflecting surface, f l is the frequency of the lth sub-carrier, are the azimuth and elevation angles of the angle of arrival at the smart reflecting surface, respectively, and θ B , are the azimuth and elevation angles of the angle of departure at the base station, respectively; represents the steering vector at the smart reflecting surface side, represents the steering vector at the base station; H is the conjugate transpose symbol; α G,l represents the path loss of the channel between the base station and the smart reflecting surface at the lth sub-carrier, and is represented as:

[0024]

[0025] where c, d G and κ abs (f l ) are the speed of light, the distance between the base station and the smart reflecting surface, and the molecular absorption factor, respectively.

[0026] Preferably, the signal received by the user from the lth sub-carrier is:

[0027]

[0028] where sl and n l are the transmit signal of the base station and the thermal noise at the user, respectively; f and Θ are the BS beamforming vector and the IRS phase shift matrix, respectively;

[0029]

[0030] where, is the channel between the IRS and the user at the l-th subcarrier, τ h is the path delay; and are the azimuth and elevation of the departure angle at the IRS, respectively; a h,l is the path loss of the channel between the IRS and the user at the l-th subcarrier; d h is the distance between the IRS and the user.

[0031] Preferably, the joint optimization problem is formulated as:

[0032]

[0033] where L is the total number of subcarriers, is the position of the s-th movable antenna, D BS is the spacing between the base stations, D IRS is the spacing between the IRSs, is the center position of the i-th subarray.

[0034] Preferably, a slack variable κ is introduced to convert the problem to:

[0035]

[0036] Preferably, the problem is solved by block coordinate descent algorithm, which alternately optimizes the position of a single movable antenna or a single subarray by fixing other variables each time.

[0037] According to the antenna position of each movable antenna of the base station, the optimization problem with respect to the position of the m-th MA is expressed as:

[0038]

[0039] Preferably, the position of each IRS subarray is optimized, and the subproblem with respect to the position of the k-th subarray is expressed as:

[0040]

[0041] The wideband beam dispersion suppression method based on the movable intelligent metasurface provided by the application comprises the following steps:

[0042] Step 1: Obtain the position information of each antenna in the base station side movable antenna array;

[0043] Step 2: Obtain the position information of each subarray in the intelligent reflector side multiple movable subarrays;

[0044] Step 3: Jointly optimize the position of each antenna in the movable antenna array and the position of each subarray in the movable subarray;

[0045] Wherein, the joint optimization aims to maximize the minimum user received signal power over the entire frequency band, and satisfies the movement constraints of the movable antenna and the movable subarray.

[0046] Compared with the prior art, the application has the following beneficial effects:

[0047] (1) The application optimizes the positions of the BS side MA and the IRS side movable subarray by deploying MA at the BS and deploying movable subarrays at the IRS, and designing an MM-based algorithm, so that the double beam dispersion effect of IRS-assisted wideband THz communication is significantly suppressed;

[0048] (2) The joint optimization algorithm can effectively configure the positions of the BS side MA and the IRS side movable subarray, and improve the performance and efficiency of the IRS-assisted wideband THz communication system; through the MM-based algorithm, the complex multi-dimensional optimization problem can quickly converge to find the optimal solution;

[0049] (3) The architecture of the application is simple and easy to deploy, and has significant advantages in hardware cost and power consumption. Compared with traditional antenna arrays and other signal enhancement technologies, the hardware cost of IRS is lower, and the signal enhancement effect is excellent, which is suitable for the next generation of efficient wireless communication system. In addition, the movable subarray deployed at the IRS in the application significantly reduces the hardware cost and power consumption under the premise of ensuring system performance compared with the scheme of deploying movable reflecting units;

[0050] (4) The IRS device used in the application has the characteristics of low power consumption, and is a new type of green auxiliary communication device. Through reasonable configuration and optimization, the system energy consumption can be significantly reduced while maintaining high performance, which meets the development needs of modern communication systems. BRIEF DESCRIPTION OF DRAWINGS

[0051] Other features, objects and advantages of the application will become more apparent through reading the following detailed description of the non-limiting embodiments with reference to the accompanying drawings:

[0052] Figure 1 For IRS assisted broadband THz communication system;

[0053] Figure 2 For the change of user received signal amplitude with subcarrier frequency under THz frequency band;

[0054] Figure 3 For the change of normalized array gain with subcarrier frequency under THz frequency band. DETAILED DESCRIPTION

[0055] The present application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that for those skilled in the art, without departing from the concept of the present application, a number of changes and improvements can be made. These are within the scope of the present application.

[0056] Embodiments

[0057] The present application provides a dual beam dispersion effect suppression system for intelligent reflecting surface (IRS) assisted broadband terahertz (THz) communication, as shown in Figure 1 The system includes a base station (BS) equipped with a movable antenna (MA) array, an IRS equipped with a movable subarray, and an optimization algorithm, etc. In addition, it also includes the position optimization of the BS side MA and the IRS side movable subarray, aiming to maximize the minimum user received signal power over the entire frequency band.

[0058] In the IRS assisted broadband THz communication system, the BS needs to adjust the MA position on the BS side according to the channel information of BS-IRS, and complete the transmit beamforming. The IRS needs to adjust the position of the movable subarray on the IRS side according to the channel information of BS-IRS and IRS-user, and complete the reflection phase configuration of each reflecting element. In the IRS assisted broadband THz communication system, the joint optimization design of the MA position on the BS side and the movable subarray position on the IRS side is considered together. The BS adjusts its MA position, and the IRS adjusts its movable subarray position.

[0059] The BS optimizes its MA position: after adjusting the MA position on the BS side, the beam dispersion effect at the BS can be suppressed, thereby further suppressing the dual beam dispersion effect.

[0060] The IRS optimizes its movable subarray: after adjusting the position of the movable subarray on the IRS side, the beam dispersion effect at the IRS can be suppressed, thereby further suppressing the dual beam dispersion effect.

[0061] The optimization scheme of the IRS-assisted wideband THz communication system: taking maximizing the minimum user received signal power in the whole frequency band as the performance target, and ensuring the constraints of the BS side MA and the IRS side movable sub-array when moving.

[0062] The scheme design of the IRS-assisted wideband THz communication system: the IRS device introduced in the scheme is passive, and does not need an additional radio frequency chain to process signals, so as to realize the reflection of signals in a passive manner. Compared with the traditional fixed position antenna, the introduction of MA also does not need to introduce an additional radio frequency chain. This enables the system to achieve better performance at a lower cost.

[0063] The optimization algorithm design of the IRS-assisted wideband THz communication system: the constructed optimization problem of maximizing the minimum user received signal power in the whole frequency band is a non-convex optimization problem, and the global optimal solution cannot be directly obtained. In the following, based on the MM algorithm, all optimization variables are optimized to obtain a local optimal solution with higher quality.

[0064] In view of the requirements of the next generation of wireless communication for THz system performance and system complexity, the application provides a new type of double beam dispersion effect suppression method and system design of IRS-assisted wideband THz communication.

[0065] According to the IRS-assisted wideband THz communication system provided by the application, the BS side MA position and the IRS side movable sub-array position are jointly optimized to significantly suppress the double beam dispersion effect.

[0066] The BS needs to adjust the position of its MA to suppress the beam dispersion effect at the BS, thereby further suppressing the double beam dispersion effect, while completing the transmit beamforming. The IRS needs to adjust the position of its movable sub-array to suppress the beam dispersion effect at the IRS, thereby further suppressing the double beam dispersion effect, while configuring the reflection phase of each reflection element to enhance the performance of the reflected signal.

[0067] The BS is equipped with a two-dimensional planar array of M MAs with a size of A BS,1 × A BS,2 . The IRS is a two-dimensional plane with a size of A IRS,1 × A IRS,2 . Define as the set of MAs, is the relative position of the m-th MA with respect to the center of the BS. Since all MAs can only move within the region of the BS array, each MA should satisfy: where C BS represents the feasible moving region of the MA.

[0068] The reflecting elements of the IRS are divided into K sub-arrays, each of which can move flexibly on the IRS surface. Each sub-array is a uniform planar array (UPA) consisting of J = J1J2 reflecting elements, where J1and J2are the number of reflecting elements in its horizontal and vertical directions, respectively. Thus, the IRS has N = KJ reflecting elements in total. Define and are the set of IRS sub-arrays and reflecting elements within a single sub-array, respectively. In addition, define as the relative position of the k-th sub-array center with respect to the center of the IRS surface, is the relative position of the j-th reflecting element with respect to the k-th sub-array center. Since all reflecting elements should remain within the IRS surface, each reflecting element needs to satisfy the constraint: where C IRS represents the feasible moving region of the reflecting element.

[0069] Without loss of generality, assume that the direct link between the BS and the user is heavily obstructed. Define as the frequency of the l-th sub-carrier, and f0<…< f L , then the channel between the BS and the IRS at the l-th sub-carrier can be expressed as:

[0070]

[0071] where and are the position vectors of the MA and IRS sub-arrays, respectively; τ G is the path delay of the BS-IRS channel; α G,l represents the path loss of the BS-IRS channel at the l-th sub-carrier, which can be expressed as:

[0072]

[0073] where c, d G and κ abs (f l ) are the speed of light, the distance between the BS and the IRS, and the molecular absorption factor, respectively; represents the steering vector at the IRS side, which is given by:

[0074]

[0075] where The steering vector of the k-th IRS subarray can be represented as:

[0076]

[0077] in and These are the azimuth and elevation angles at the IRS (angle of arrival, AoA), respectively. The steering vector at BS can be represented as:

[0078]

[0079] in θ B and Here, θ and θ are the azimuth and elevation angles of the departure angle (AoD) at BS, respectively. Similarly, the channel between the IRS and the user on the l-th subcarrier can be represented as:

[0080]

[0081] Where τ h For the path delay of the IRS-user channel; and These are the azimuth and elevation angles of AoD at IRS, respectively; α h,l The path loss of the IRS-user channel under the l-th subcarrier can be expressed as:

[0082]

[0083] Where d h Let be the distance between the IRS and the user. The signal received by the user from the l-th subcarrier is:

[0084]

[0085] Where s l and n l These are the transmitted signal from the BS and the thermal noise at the user, respectively, satisfying... and

[0086] f and Θ are the BS beamforming vector and IRS phase shift matrix, respectively. To simplify the calculation, assume s l and n l For all This is statistically irrelevant. Note that, in the following text, the amplitude and power of the received signal do not include thermal noise.

[0087] According to the above formula, the amplitude of the signal received by the user under the l-th subcarrier is:

[0088]

[0089] According to the above formula, to study the influence of wide spectrum on the amplitude of user received signal, the BS and IRS beamforming based on the center frequency f c are respectively:

[0090]

[0091] In addition, based on the formula of the amplitude of user received signal, it can be further expressed as:

[0092]

[0093] where and are the array gains of IRS and BS respectively. According to the above formula, it can be observed that the amplitude of user received signal is related to the subcarrier frequency f l . For narrowband systems, since the difference between f l corresponding to all l and f c is small enough the BS array gain and the IRS array gain produce a loss between all subcarriers, which is negligible. However, for wideband systems, f l corresponding to many l deviates significantly from f c , resulting in the array gains of BS and IRS producing dramatic fluctuations between different subcarriers, which is the beam dispersion effect at BS and IRS. In addition, according to the above formula, and have the product property, and the array gain suffers further more severe attenuation between different subcarriers, which is the so-called double beam dispersion effect.

[0094] To alleviate the above double beam dispersion effect and balance the communication rate of data streams on different subcarriers, an optimization problem is proposed by jointly optimizing the MA positions on the BS side and the movable subarray positions on the IRS side, so as to maximize the minimum user received signal power over the entire frequency band. The problem can be expressed as:

[0095]

[0096] where The first and third constraints respectively describe that each MA of BS and each subarray of IRS should be in the feasible region and The internal movement refers to the movement of the BS antenna array and the IRS surface; the second and fourth constraints describe that each MA of the BS and each subarray of the IRS should maintain a distance of at least D from other MAs / subarrays during movement. BS and D IRS The distance is needed to avoid antenna coupling and subarray collisions. (Problem) Because its objective function, second constraint, and fourth constraint are non-convex, it is difficult to solve.

[0097] This invention provides a configuration design for the BS-side MA position and the IRS-side movable subarray position in an IRS-assisted broadband THz communication system. Using an MM-based algorithm, the positions of the BS-side MA and the IRS-side movable subarray are designed to maximize the minimum user received signal power across the entire frequency band.

[0098] In order to get the question To obtain a high-quality solution, firstly, by introducing slack variables, the problem... This can be equivalently transformed into the following problem, which is easier to solve:

[0099]

[0100] Next, the block coordinate descent (BCD) algorithm will be used to address the problem. By keeping other variables constant each time, the position of a single MA or a single subarray is optimized alternately. Specifically, the antenna position of each MA of the BS is considered first, with regard to the position of the m-th MA... The optimization problem can be expressed as:

[0101]

[0102] The problem remains difficult to solve because the first and third constraints are non-convex. To address this, we use the MM method to make these two constraints convex. First, consider the first constraint... about Neither convex nor concave, we examine its position at a point. The second-order Taylor expansion formula at the given location is obtained by replacing the Hessian matrix with its lower bound. Construct a globally tightly lower bounded substitution function. about The second-order Taylor expansion formula is:

[0103]

[0104] in and They are respectively about The gradient and Hessian matrix. Note the gradient and Hessian matrix. It can be rewritten as:

[0105]

[0106] in So, gradient Hessian matrix They can be represented as follows:

[0107]

[0108] in

[0109]

[0110] Furthermore, it can be observed from the expression of the Hessian matrix that the function The curvature is bounded, which means that there must exist a semi-negative definite matrix. Make Next, we derive... Specifically, define but It can be rewritten as:

[0111]

[0112] Therefore, construct The task is simplified to constructing separately and The lower bound. First consider... Its lower bound can be calculated separately. and The lower bound is obtained. Since cos(·)∈[-1,1], according to the expression of the Hessian matrix, we have:

[0113]

[0114] The right sides of the two inequalities and Irrelevant. Therefore, substituting the right sides of the two inequalities above into... Can obtain The global lower bound is then derived. The following derivation... The lower bound of . Note the following inequality:

[0115]

[0116] This holds true naturally, where I² is a 2-order identity matrix. This indicates that... The lower bound can be calculated The upper bound is obtained. Since cos(·)∈[-1,1], The upper bound can be represented as:

[0117]

[0118] Since the right side of the above inequality is irrelevant to , by replacing in with the right side of the above inequality, a global lower bound of can be obtained, thus completing the derivation of . Finally, substituting into the second-order Taylor expansion formula of , a global concave lower bound of , denoted as , can be obtained, whose expression is:

[0119]

[0120] Next, the non-convexity of the third constraint in problem is solved, which is easier to handle since the left side of this constraint is convex. By utilizing the following first-order Taylor expansion formula:

[0121]

[0122] the convexification of this constraint can be achieved. Based on the two constructed concave lower bounds above, a convex optimization problem can be obtained, as follows:

[0123]

[0124] This problem can be solved by existing standard numerical solvers (such as CVX).

[0125] Next, fix the other variables and optimize the position of each IRS subarray. The subproblem regarding the position of the kth subarray can be expressed as:

[0126]

[0127] Since the first and third constraints of this problem are non-convex, it is difficult to solve. First, consider the first constraint, which is similar to the process of convexifying the first constraint in problem . By adopting the second-order Taylor expansion formula of and replacing its Hessian matrix with a smaller semi-negative definite matrix, the first constraint of this problem is handled. The second-order Taylor expansion formula of the function about at the point is:

[0128]

[0129] where and They are respectively about The gradient and Hessian matrix. With similar, It can be rewritten as:

[0130]

[0131] in

[0132] So, gradient Hessian matrix They can be represented as follows:

[0133]

[0134] in

[0135]

[0136]

[0137] According to the expression of the Hessian matrix, it can be observed that Since the curvature is bounded, we can construct a semi-negative definite matrix. Make To avoid repetition, follow the construction We will directly provide similar steps. The expression:

[0138]

[0139] Will The second-order Taylor expansion formula After replacing it with the above formula, we can get Global concave lower bound:

[0140]

[0141] Next, the convexity problem. The third constraint can be achieved using the following first-order Taylor expansion:

[0142]

[0143] Substitute the two concave lower bounds constructed into the problem. From the left side of the first and third constraints, we can obtain the following convex optimization problem:

[0144]

[0145] This problem can be solved by numerical toolkits such as CVX.

[0146] The present application particularly provides a dual-beam dispersion effect suppression system for IRS-assisted broadband THz communication, including system scheme design using MA and movable sub-array and maximum minimization of user received signal power over the entire frequency band. Figure 1 The basic structural components of the application are described, Figure 2 and Figure 3 Reasonable configuration of BS-side MA and IRS-side movable sub-array positions is given to suppress the dual-beam dispersion effect, wherein "BS MA+IRS movable sub-array" is the scheme proposed in the present application.

[0147] THz communication is considered as a promising technology for the next generation of wireless communication. Thanks to its unique characteristics of large bandwidth, THz communication is suitable for high-speed data transmission, imaging and security scanning and other applications. However, due to the severe path loss and atmospheric absorption of signals in the THz frequency band, the practical application potential of THz communication is limited. IRS has recently received extensive attention as it can effectively and adaptively reconstruct the propagation environment, becoming a promising technology for the next generation of wireless communication. For MIMO systems, IRS can reconstruct the wireless channel environment to provide sufficient multipath components, thereby improving the spatial multiplexing capability of the system. In addition, IRS can also solve the coverage problem caused by the blocking of line-of-sight links in communication. Existing work shows that IRS also has considerable potential in THz communication systems. However, due to the characteristics of large bandwidth, IRS-assisted THz communication systems suffer from severe dual-beam dispersion effects, which significantly reduce the performance of some subcarriers and thus affect the performance of the communication system.

[0148] The present application provides a new type of dual-beam dispersion effect suppression system for IRS-assisted broadband THz communication, and a joint optimization method under the system, which includes a BS equipped with an MA array, an IRS equipped with a movable sub-array, and an optimization algorithm. The core of the optimization algorithm is the MM algorithm.

[0149] In the IRS-assisted broadband THz communication system, the BS and the IRS jointly optimize the design of the BS-side MA position and the IRS-side movable sub-array position, and send the BS-side MA position and the IRS-side movable sub-array position to the MA array deployed at the BS and the IRS, respectively, to maximize the minimum user received signal power over the entire frequency band, thereby significantly suppressing the dual-beam dispersion effect.

[0150] Considering that the double-beam dispersion effect suppression effect under the system is greatly affected by the MA position of the BS side and the movable subarray position of the IRS side, the present application maximizes the minimum user received signal power on the entire frequency band as a performance index, and guarantees the constraints followed by the MA and the movable subarray when moving, and jointly optimizes and designs the new type of IRS assisted wideband THz communication system.

[0151] The IRS assisted wideband THz communication system provided by the present application does not additionally increase a large number of radio frequency links and complex signal processing units compared with the traditional THz system, and is a design with lower cost, lower power consumption and better performance. Through the joint design of the MA position of the BS side and the movable subarray position of the IRS side, the double-beam dispersion effect suppression effect given by the present application is significantly improved.

[0152] The present application also discloses a method for maximizing the minimum user received signal power on the entire frequency band in an IRS assisted wideband THz communication system, which applies the IRS assisted wideband THz communication system, jointly optimizes and designs the MA position of the BS side and the movable subarray position of the IRS side based on the MM algorithm, maximizes the minimum user received signal power on the entire frequency band, and obtains the optimal MA and movable subarray position configuration scheme.

[0153] Those skilled in the art know that, in addition to implementing the system, device and each module thereof provided by the present application in the form of pure computer readable program code, the same program can also be realized by logically programming the method steps to make the system, device and each module thereof provided by the present application in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers and embedded microcontrollers. Therefore, the system, device and each module thereof provided by the present application can be considered as a hardware component, and the modules included therein for realizing various programs can also be considered as structures in the hardware component; the modules for realizing various functions can also be considered as both software programs for realizing methods and structures in the hardware component.

[0154] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined with each other without conflict.

Claims

1. A wideband beam dispersion suppression system based on a movable smart metasurface, characterized in that, Comprise: a base station and a smart reflector; the base station is equipped with a movable antenna array, and the smart reflector is divided into multiple movable sub-arrays; jointly optimize the position of each antenna in the movable antenna array and the position of each sub-array in the movable sub-array; wherein the joint optimization aims to maximize the minimum user received signal power over the entire frequency band, and satisfies the movement constraints of the movable antenna and movable sub-array.

2. The movable smart metasurface-based broadband beam dispersion suppression system of claim 1, wherein, The size of the array of moveable antennas of the base station is A BS,1 × A BS,2 , comprising M moveable antennas; The size of the smart reflective surface is A IRS,1 x A IRS,2 ; Position of the mth moveable antenna satisfies: where m e M, C BS is the feasible movement region of the movable antenna, and (x, y) is the position of the movable antenna in a two-dimensional plane.

3. The movable smart metasurface-based broadband beam dispersion suppression system of claim 2, wherein, The smart reflector is divided into K sub-arrays, each containing J=J1J2 reflecting elements, where J1 and J2 are the number of reflecting elements in the horizontal and vertical directions, respectively; The center position of the kth subarray is k e K, the relative position of the jth reflecting unit relative to the center of the kth subarray is j e J; The position of each reflecting element satisfies: where C IRS represents the feasible movement region of the reflecting unit, and (x', y') is the position of the reflecting unit on a two-dimensional plane.

4. The movable smart metasurface-based broadband beam dispersion suppression system of claim 3, wherein, The channel between the base station and the smart reflector at the l-th subcarrier is represented as: wherein, and denote the position vectors of the movable antenna and the smart reflecting surface subarray, respectively; τ G is the path delay of the channel between the base station and the smart reflecting surface, f l is the frequency of the l-th subcarrier, are the azimuth and elevation angles of the angle of arrival at the smart reflecting surface, respectively, θ B , are the azimuth and elevation angles of the angle of departure at the base station, respectively; denotes the steering vector at the smart reflecting surface side, denotes the steering vector at the base station; H is the conjugate transpose symbol; α G,l denotes the path loss of the channel between the base station and the smart reflecting surface at the l-th subcarrier, and is given by: Among them, c and d G and κ abs (f l These represent the speed of light, the distance between the base station and the smart reflective surface, and the molecular absorption factor, respectively.

5. The movable smart metasurface-based broadband beam dispersion suppression system of claim 4, wherein, The signal received by the user from the l-th subcarrier is: where s l and n l are the transmitted signal of the base station and the thermal noise at the user, respectively; f and Θ are the BS beamforming vector and the smart reflector phase shift matrix, respectively; wherein, is the channel between the IRS and the user at the lth subcarrier, τ h is the path delay; and are the azimuth and elevation angles of the departure angle at the IRS, respectively; a h,l is the path loss of the channel between the IRS and the user at the lth subcarrier; d h is the distance between the IRS and the user.

6. The movable smart metasurface-based broadband beam dispersion suppression system of claim 5, wherein, The joint optimization problem is expressed as: wherein L is the total number of subcarriers, is the position of the s-th movable antenna, D BS is the spacing between base stations, D IRS is the spacing between intelligent reflecting surfaces, is the center position of the i-th subarray.

7. The movable smart metasurface-based broadband beam dispersion suppression system of claim 6, wherein, Introducing the slack variable k, the problem is converted to:

8. The movable smart metasurface-based broadband beam dispersion suppression system of claim 7, wherein, Utilizing block coordinate descent algorithm to handle the problem By fixing other variables each time, the position of a single movable antenna or a single subarray is alternately optimized; Based on the antenna position of each movable antenna of the base station, regarding the position of the m-th MA... The optimization problem is expressed as:

9. The movable smart metasurface-based broadband beam dispersion suppression system of claim 8, wherein, Optimizing the position of each smart reflector subarray, with respect to the position of the kthsubarray is expressed as the subproblem:

10. A suppression method based on the movable smart metasurface-based broadband beam dispersion suppression system of any one of claims 1 to 9, characterized in that, Comprise the following steps: Step 1: Obtain the position information of each antenna in the movable antenna array on the base station side; Step 2: Obtain the position information of each sub-array in the multiple movable sub-arrays on the smart reflector side; Step 3: Jointly optimize the position of each antenna in the movable antenna array and the position of each sub-array in the movable sub-array; wherein the joint optimization aims to maximize the minimum user received signal power over the entire frequency band, and satisfies the movement constraints of the movable antenna and movable sub-array.

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