Ultra-directional antenna array multi-user precoding method, device and medium

Abstract

This invention discloses a multi-user precoding method, device, and medium for a hyperdirectional antenna array, belonging to the field of wireless communication. The method includes: for user u, constructing a unitary matrix U, where the last N (N≤K-1) columns of the unitary matrix U are respectively the channel space of interfering users. i Let U be an orthonormal basis for the network device, i = 1, ..., K, i ≠ u, where N is the dimension of the interfering user channel space, represents the channel state information of the i-th terminal user, M is the total number of antennas on the network device side, and K is the total number of terminal users communicating, satisfying M ≥ K; and truncate matrix U. H h u The first M-N rows yield matrix η u , where h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose; the truncated matrix U is used. H The first M-N rows and first M-N columns of ZU are used to obtain matrix Ξ, where the elements in matrix Z represent the coupling coefficients of any two antennas; the precoding matrix of the u-th terminal user is calculated, which can significantly improve the spectral efficiency and capacity of the system to meet the growing communication demands.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication, and more specifically, relates to a multi-user precoding method, device and medium for a hyperdirectional antenna array. Background Technology

[0002] In early research on Massive MIMO, in-depth analyses were conducted on channel characteristics when the number of base station antennas approached infinity. However, in practical applications, due to the immaturity of technology and theory, the distance between antennas remained limited by half a wavelength. Therefore, deploying a large number of antennas on a fixed-size antenna panel to approach the theoretical channel capacity remained a challenge. In recent years, with the further maturation of Massive MIMO technology and the increasing demands for spectral efficiency in communication systems, solving the problem of improving system throughput through the deployment of ultra-dense antenna arrays has become a difficult issue in the field of wireless communication.

[0003] In the context of 5G, facing the drawbacks of large signal attenuation and the inability to deploy ultra-large-scale antenna arrays, hyperdirectional antenna arrays, as a type of narrow-beam hyperdirectional array, have the potential to become a key technology for next-generation wireless communication systems. In traditional antenna arrays, to reduce mutual coupling between antennas, a spacing of about half a wavelength is typically used. However, this means that the array gain is only proportional to the number of antennas, M. In hyperdirectional antenna arrays, by reducing the antenna spacing and fully utilizing the strong mutual coupling between antennas, the antenna array gain can be proportional to M. 2 A proportional performance improvement.

[0004] However, research on the application of hyperdirectional antenna arrays in wireless communication systems has not yet been extensive. Traditional MIMO arrays can achieve spatial multiplexing through beamforming, thereby significantly improving system throughput. However, considering coupling effects, there is currently no solution for how to utilize hyperdirectional antenna arrays to achieve multi-user wireless communication scenarios. Summary of the Invention

[0005] To address the above-mentioned deficiencies or improvement needs, this invention provides a multi-user precoding method, device, and medium for hyperdirectional antenna arrays. It aims to solve the technical problem that existing traditional multi-user beamforming schemes cannot achieve hyperdirectionality of the array due to neglecting the coupling effect between antennas, thus failing to improve the system spectral efficiency when the base station is a compact array.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a multi-user precoding method for a hyperdirectional antenna array, comprising:

[0007] Construct a unitary matrix for end user u. The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0008] Extracting matrix U H h u The first MN rows yield matrix η u ,in h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose.

[0009] Extracting matrix U H The first MN rows and first MN columns of ZU yield matrix Ξ, where... matrix The elements in Z represent the coupling coefficients of any two antennas;

[0010] The precoding matrix of the u-th terminal user is calculated. in superscript * Indicates conjugate.

[0011] Furthermore, in extracting matrix U H Before obtaining matrix Ξ by taking the first MN rows and first MN columns of ZU, the method further includes updating matrix Z to Z+Λ, where... Let be the regularization matrix of matrix Z.

[0012] Furthermore, the regularization matrix Λ is:

[0013]

[0014]

[0015] R rad ≈24.7 (kL / 2) 2.5

[0016] Where, r loss and R rad These represent the antenna loss and radiation impedance, respectively, I. M Let L be an M×M identity matrix, where L, a, f, μ, σ, and k are the antenna length, radius, operating frequency, permeability, conductivity, and wave number, respectively.

[0017] Furthermore, the regularization matrix Λ is:

[0018]

[0019] Where, ∈ 2 Let I be the Gaussian noise power, k(θ, φ) be the antenna pattern function, and θ and φ be the far-field coordinate components in spherical coordinates, respectively. M It is an M×M identity matrix.

[0020] Furthermore, the regularization matrix Λ is:

[0021]

[0022]

[0023] R rad ≈24.7 (kL / 2) 2.5

[0024] Where, r loss and R rad These represent the antenna loss and radiation impedance, respectively, I. M Let L be an M×M identity matrix, and let L, a, f, μ, σ, and k be the antenna length, radius, operating frequency, permeability, conductivity, and wavenumber, respectively. 2 Let θ be the Gaussian noise power, k(θ, φ) be the antenna pattern function, and θ and φ be the far-field coordinate components in spherical coordinates.

[0025] Furthermore, the construction of the unitary matrix Specifically:

[0026] Construct the total disturbance covariance matrix:

[0027]

[0028] For R int SVD decomposition yields:

[0029] R int =W H ΛW

[0030] The unitary matrix U is:

[0031] U = [W followed by MN columns, W followed by N columns].

[0032] Furthermore, matrix

[0033] Among them, z mn Let represent the coupling coefficient between the m-th and n-th antennas, k(θ, φ) be the antenna pattern function, θ and φ be the far-field coordinate components in spherical coordinates, and k be the wavenumber of the antenna. r is a unit vector in spherical coordinates. m and rn Let m and n be the coordinates of the m-th and n-th antennas, respectively, where m = 1, ..., M, and n = 1, ..., M.

[0034] Furthermore, the last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for the group i = 1, ..., K, i ≠ u, includes:

[0035] make For the matrix composed of interfering user channel vectors, if N = K-1, the last K-1 columns of the unitary matrix U are respectively in:

[0036]

[0037] If N < K-1, calculate Then, N non-zero vectors will be obtained, and the N non-zero vectors will be selected as the last N columns of U.

[0038] Secondly, the present invention provides a multi-user precoding method for a hyperdirectional antenna array, comprising:

[0039] Construct a unitary matrix for end user u. The first N (N≤K-1) columns of the unitary matrix W represent the interfering user channel space. i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0040] Extracting the last MN columns of the unitary matrix W yields matrix R, where...

[0041] The precoding matrix of the u-th terminal user is calculated. in superscript * Indicates conjugation, h u The matrix represents the channel state information of the u-th terminal user. The elements in Z represent the coupling coefficients of any two antennas, and the superscript H indicates the conjugate transpose.

[0042] Thirdly, the present invention provides a network device, comprising:

[0043] Construction unit, used to construct unitary matrix for end user u. The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h iAn orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0044] The first intercepting unit is used to intercept matrix U. H h u The first MN rows yield matrix η u ,in h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose.

[0045] The second interception unit is used to intercept matrix U. H The first MN rows and first MN columns of ZU yield matrix Ξ, where... matrix The elements in Z represent the coupling coefficients of any two antennas;

[0046] The computation unit is used to calculate the precoding matrix of the u-th terminal user. in superscript * Indicates conjugate.

[0047] Fourthly, the present invention provides a network device, comprising:

[0048] Construction unit, used to construct unitary matrix for end user u. The first N (N≤K-1) columns of the unitary matrix W represent the interfering user channel space. i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0049] The truncation unit is used to extract the last MN columns of the unitary matrix W to obtain matrix R, where

[0050] The computation unit is used to calculate the precoding matrix of the u-th terminal user. That superscript * Indicates conjugation, h u The matrix represents the channel state information of the u-th terminal user. The elements in Z represent the coupling coefficients of any two antennas, and the superscript H indicates the conjugate transpose.

[0051] Fifthly, the present invention provides an electronic device, comprising:

[0052] Processor; and

[0053] Memory for storing the executable instructions of the processor;

[0054] The processor is configured to execute the multi-user precoding method for a hyperdirectional antenna array as described in the first or second aspect by executing the executable instructions.

[0055] In a sixth aspect, the present invention provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the multi-user precoding method for a hyperdirectional antenna array as described in the first or second aspect.

[0056] In summary, compared with the prior art, the above technical solutions proposed by this invention can achieve the following beneficial effects:

[0057] (1) This invention utilizes the asymptotic orthogonality of different user channels to propose a low-complexity solution to the convex optimization problem. By constructing a unitary matrix and performing corresponding mathematical transformations, the precoding matrix of each terminal user is obtained. This scheme fully considers the coupling between antennas and can better distinguish and process communication signals between different terminal users, thereby significantly improving the spectral efficiency and capacity of the system to meet the ever-increasing communication demands.

[0058] (2) This invention introduces a regularization matrix to overcome the problem of reduced system capacity in actual hyperdirectional multi-user communication systems due to ohmic loss and inaccurate channel estimation.

[0059] (3) The present invention proposes a simplified scheme to solve convex optimization problems, specifically: first find the optimal solution of the objective function, and then project this optimal solution onto the null space of the interfering user; thereby avoiding multiple matrix operations. Attached Figure Description

[0060] Figure 1 The radiation pattern is obtained by performing super-directional zero-forcing beamforming on the target user using simulation provided by this invention;

[0061] Figure 2 This is a comparison chart of the spectral efficiency (SE-SNR) of Scheme 1 and Scheme 2 of the present invention under simulated multi-user conditions, as well as the traditional maximum ratio transmission and zero-forcing transmission schemes.

[0062] Figure 3This is a comparison chart of the spectral efficiency (SE-SNR) of Scheme 1 and Scheme 3 of the invention, as well as the traditional maximum ratio transmission and zero-forcing transmission schemes, under simulated multi-user conditions provided by the present invention. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0064] This invention can be applied to wireless communication systems. It should be noted that the wireless communication systems mentioned in the embodiments of this application include, but are not limited to: Narrow Band-Internet of Things (NB-IoT), Global System for Mobile Communications (GSM), Enhanced Data Rate for GSM Evolution (EDGE), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access 2000 (CDMA2000), Time Division-Synchronization Code Division Multiple Access (TD-SCDMA), Long Term Evolution (LTE), and the three major application scenarios of 5G mobile communication systems: Enhanced Mobile Broadband (eMBB), Ultra-reliable and Low Latency Communications (URLLC), and Massive Machine-Type Communications (mMTC).

[0065] The communication apparatus involved in this invention mainly includes network-side equipment or terminal equipment. In this invention, the transmitting end is a network-side device, and the receiving end is a terminal device; or, in this invention, the transmitting end is a terminal device, and the receiving end is a network-side device.

[0066] The terminal device of this invention can be a wireless terminal, which can be a device that provides voice and / or other service data connectivity to a user, a handheld device with wireless connectivity, or other processing devices connected to a wireless modem. The wireless terminal can communicate with one or more core networks via a radio access network (RAN). The wireless terminal can be a mobile terminal, such as a mobile phone (or "cellular" phone) and a computer with a mobile terminal, for example, a portable, pocket-sized, handheld, computer-embedded, or vehicle-mounted mobile device that exchanges voice and / or data with the radio access network. Examples include personal communication service (PCS) phones, cordless phones, session initiation protocol (SIP) phones, wireless local loop (WLL) stations, personal digital assistants (PDAs), and other devices. Wireless terminals can also be referred to as systems, subscriber units, subscriber stations, mobile stations, mobile stations, remote stations, remote terminals, access terminals, user terminals, user agents, user devices, or user equipment, without any specific definition here.

[0067] The network-side equipment of the present invention can be a device for communicating with terminal devices. For example, it can be a base station (BTS) in a GSM or CDMA system, a base station (nodeB, NB) in a WCDMA system, an evolved base station (eNB or eNodeB) in an LTE system, or a next-generation base station (ngeNB) in an LTE system. Alternatively, the network-side equipment can be a relay station, an access point (AP), a vehicle-mounted device, a wearable device, or a network-side device in a 5G network or a network-side device in a future evolved public land mobile network (PLMN), such as a generation base station (gNB or gNodeB).

[0068] The following section first describes the current state of technology for multi-user precoding methods for hyperdirectional antenna arrays.

[0069] 1.1 System Model

[0070] The channel between the s-th antenna of the base station and the u-th terminal user can be represented as:

[0071]

[0072] Where β p and τ p Let be the complex amplitude and time delay of the p-th path, respectively; λ0 is the wavelength of the center frequency; and let θ be the wavelength of the path. p，ZOD φ p，AOD θ p，ZOA φ p，AOA This represents the pitch departure angle, horizontal departure angle, pitch arrival angle, and horizontal arrival angle of the p-th path.

[0073] It has a horizontal arrival angle φ p，AOA and pitch angle θ p，ZOA spherical unit vector:

[0074]

[0075] It has a pitch start angle θ p，ZOD and horizontal starting angle φ p，AOD spherical unit vector:

[0076]

[0077] in, It is the position vector of the i-th terminal user in a 3D Cartesian coordinate system; similarly, It is the position vector of the s-th antenna of the base station; exponent term It is the Doppler of the p-th path, where t represents time; ω P for in Represents the velocity vector of the end user (UE):

[0078]

[0079] Where u and φ v θ v These are the UE's moving speed, horizontal angle of travel, and pitch angle of travel.

[0080] The base station contains N v Line N h The number of base station antennas is represented by N. t It means that N t =N v N h The number of UE antennas is represented by N. r This means that the total bandwidth includes N. f There are 1 subcarrier, with an interval of Δf between adjacent subcarriers.

[0081] use This represents the channels from all antennas of the base station to the u-th terminal user UE at time t and frequency f; it represents all N... f The channels on each subcarrier can be written in matrix form:

[0082]

[0083] Among them, f i Let be the frequency of the i-th subcarrier, and satisfy 1 ≤ i ≤ N. f .

[0084] The uth terminal user UE is at time t, subcarrier f i The signal received above is

[0085]

[0086] in Let n be the beamforming precoding vector of the u-th terminal user (UE) from the base station, where n is a vector with zero mean and variance σ. 2 Gaussian white noise. Consider a certain time t and frequency f. i , Simply put

[0087] 1.2. Traditional Multi-User Beamforming Scheme 1: Maximum Ratio Transmission

[0088] Maximum Ratio Transmission (MRT) is a multi-antenna technology that uses channel state information from the receiver to optimize the antenna weights at the transmitter, thereby maximizing the signal-to-noise ratio of the received signal.

[0089] The mathematical expression for the maximum ratio transmission beamforming vector can be expressed as:

[0090] w MRT =βh * (7)

[0091] Where β is the power constraint coefficient of the beamforming vector by the base station, and h is the channel state information (CSI) of the target user measured by the base station. * It is its conjugate. By assigning different beamforming vectors to different users based on their channel state information, the goal of multi-user communication is achieved. In traditional MIMO systems, the MRT scheme focuses on maximizing the signal gain of users. However, in multi-user system scenarios, as the correlation of the transmission channel increases, this scheme will lead to a rapid decline in the performance of the entire system because it does not consider how to handle interference between users.

[0092] 1.3 Traditional Multi-User Beamforming Scheme Two: Zero-Forcing Transmission

[0093] Maximum Ratio Transmission (MRT) focuses solely on the useful signal from the target user, ignoring interference from other users. Conversely, Zero Forcing (ZF) transmission aims to eliminate interference between different users, but disregards the effects of noise. Specifically, the precoding matrix of the MRT scheme can be represented as the product of the normalized channel vector of the target user and the transmitted signal, while the precoding matrix of the ZF scheme can be represented as the pseudo-inverse of the channel transmission matrix and the received signal vector, thereby eliminating interference between different users and obtaining the desired signal.

[0094]

[0095] Where H = [h1, h2, ..., h K W is a matrix composed of channel state information of K terminal users. ZF The k-th column in the diagram represents the precoding vector of the k-th terminal user. The ZF scheme achieves good system and speed performance in regions with high signal-to-noise ratios; however, in regions with low signal-to-noise ratios, due to its neglect of noise effects, the overall system speed is not as high as that of the MRT scheme.

[0096] 1.4 Superdirectional Beamforming

[0097] For ease of analysis, assume an antenna array consisting of M antennas spaced d apart, where the radiation pattern function of each antenna is k(θ, φ), and θ and φ are the far-field coordinate components in spherical coordinates. The far-field radiation pattern function f(θ, φ) of this array is:

[0098]

[0099] Where a m Let be the excitation coefficient of the m-th antenna, and k be the wave number. r is a unit vector in spherical coordinates. m Let be the coordinates of the m-th antenna, where m = 1, ..., M.

[0100] The directionality coefficient D(θ0, φ0) in the direction (θ0, φ0) is defined as follows:

[0101]

[0102] Simplify the denominator in the above formula:

[0103]

[0104] For the integral term in the above equation, let:

[0105]

[0106] Therefore, equation (11) can be rewritten as:

[0107]

[0108] For ease of representation, equation (10) can be simplified to

[0109]

[0110] in,

[0111] a = [a1, a2, ..., a M ] T (15)

[0112] and

[0113]

[0114] Z is the normalized real impedance matrix:

[0115]

[0116] The beamforming vector a that maximizes equation (14) can be solved as follows:

[0117] a = Z -1 e * (18)

[0118] The maximized directionality coefficient is:

[0119] D max =e H Z -1 e. (19)

[0120] Based on the above description, it can be seen that current research on hyperdirectional arrays only explores how to maximize directional gain from the perspective of antenna arrays, and has not yet been combined with actual communication systems. How to utilize them to improve the spectral efficiency of the entire system remains a challenge. Traditional multi-user beamforming schemes, by ignoring the coupling effect between antennas, cannot achieve hyperdirectionality of the array, and therefore cannot achieve the goal of improving the spectral efficiency of the system when the base station is a compact array.

[0121] To address this issue, a hyperdirectional beamforming algorithm suitable for multiple users needs to be developed. This algorithm should consider the coupling between antennas and be able to better distinguish and process communication signals between different users. By using this algorithm, the spectral efficiency and capacity of the system can be significantly improved to meet the ever-increasing communication demands.

[0122] In response, this invention incorporates the coupling between antennas into the analysis model in a compact antenna array, providing a multi-user beamforming precoding algorithm to improve spectral efficiency.

[0123] Example 1

[0124] 2.1 Scheme 1 of the Invention: Superdirectional Zero-Forcing Multi-User Transmission

[0125] Consider a base station with M antennas communicating simultaneously with K terminal users, each with channel state information [h1, h2, ..., h...]. K The directionality coefficient D of the u-th terminal user satisfies M≥K. According to equation (14), the directionality coefficient D of the u-th terminal user is... u for:

[0126]

[0127] Where a u Beamforming vectors are assigned to u terminal users. To suppress interference from other users and maximize the directional gain of the target user, this invention proposes the following optimization problem:

[0128]

[0129] This problem is a linearly constrained convex optimization problem, which can be solved using optimization toolkits such as CVX and Gurobi, but requires multiple iterative optimizations, resulting in high complexity and failing to meet the real-time communication requirements of base stations. This invention proposes an optimal, low-complexity solution by utilizing the asymptotic orthogonality of different user channels.

[0130] First, orthogonalize the interfering user channel, let... If the matrix is ​​composed of the channel vectors of the interfering users, then the orthogonalized orthogonal basis of the interfering users is: in:

[0131]

[0132] Consider constructing a unitary matrix Satisfy U H U = I M The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} Where N is the dimension of the interfering user channel space. If N < K-1, then the orthonormal basis consists of N non-zero column vectors, and these N non-zero column vectors are selected as the last N columns of U. It should be noted that in the last N columns of the unitary matrix U, the first column does not need to be zero. Column 2 is The order can be shuffled, as long as any two columns are different.

[0133] make

[0134]

[0135] in To satisfy the linear constraints in the optimization problem, let

[0136]

[0137] in

[0138] make

[0139]

[0140] in Ψ and γ are also block matrices.

[0141] but

[0142]

[0143] Therefore, the optimization problem (21) can be transformed into

[0144]

[0145] Analogous to equation (18), the closed-form solution to this problem is:

[0146]

[0147] According to equation (23), we can obtain

[0148]

[0149] For the construction of the unitary matrix U, it is only necessary that the last N (N≤K-1) columns of U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} is defined. This embodiment employs the following scheme; however, other schemes are also acceptable as long as the condition for U is met, such as Schmidt orthogonalization.

[0150] First, construct the total disturbance covariance matrix:

[0151]

[0152] For R int SVD decomposition

[0153] R int =W H ΛW (31)

[0154] The first N columns of W represent the unit orthogonal channel for interfering users, i.e. Since W itself is a unitary matrix, U can be constructed as follows:

[0155] U = [columns after W, columns N before W] (32)

[0156] The steps to obtain the hyperdirectional zero-forcing precoding matrix for each end user are as follows:

[0157] S1, Cycle 1: u = 1, ..., K;

[0158] S2. Calculate the interference covariance matrix according to formula (30);

[0159] S3. Calculate the SVD decomposition of the interference covariance matrix, as shown in formula (31);

[0160] S4. Construct the unitary matrix U according to formula (32);

[0161] S5. Refer to formula (24) to obtain η u ;

[0162] S6. Obtain matrix Ξ by referring to formula (25);

[0163] S7. Refer to formula (28) to obtain αu ;

[0164] S8. Refer to formula (29) to obtain the precoding matrix a of the u-th terminal user. u ;

[0165] End loop 1.

[0166] Therefore, this invention proposes a multi-user precoding method for hyperdirectional antenna arrays, comprising:

[0167] Construct a unitary matrix for end user u. The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0168] Extracting matrix U H h u The first MN rows yield matrix η u ,in h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose.

[0169] Extracting matrix U H The first MN rows and first MN columns of ZU yield matrix Ξ, where... matrix The elements in Z represent the coupling coefficients of any two antennas;

[0170] The precoding matrix of the u-th terminal user is calculated. in superscript * Indicates conjugate.

[0171] 2.2 Scheme Two of the Invention: Superdirectional Interference Null Space Projection Method

[0172] Considering that Scheme 1 requires multiple matrix operations, this invention proposes a simplified version of Scheme 1: the superdirectional interference null space projection method.

[0173] Reconsider the optimization problem

[0174]

[0175] The proposed solution to this optimization problem is to first find the optimal solution of the objective function, and then project this optimal solution onto the null space of the interfering users.

[0176] According to equation (18), the optimal solution of the objective function is:

[0177]

[0178] The null space of the interfering user can be obtained using equation (32), defined as follows:

[0179] R = W followed by column MN (35)

[0180] The projection of the optimal solution onto the null space of the interfering user is then...

[0181]

[0182] Therefore, this invention proposes another multi-user precoding method for hyperdirectional antenna arrays, including:

[0183] Construct a unitary matrix for end user u. The first N (N≤K-1) columns of the unitary matrix W represent the interfering user channel space. i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0184] Extracting the last MN columns of the unitary matrix W yields matrix R, where...

[0185] The precoding matrix of the u-th terminal user is calculated. in h u The matrix represents the channel state information of the u-th terminal user. The elements in Z represent the coupling coefficients of any two antennas, and the superscript H indicates the conjugate transpose. * Indicates conjugate.

[0186] 2.3 Scheme 3 of the Invention: Regularized Hyperdirectional Zero-Forcing Multi-User Transmission

[0187] In practical hyperdirectional multi-user communication systems, system capacity degradation can occur due to ohmic loss and inaccurate channel estimation. This invention proposes a third solution: regularized hyperdirectional zero-forcing multi-user transmission. Specifically, it addresses the following optimization problem:

[0188]

[0189] in

[0190] z R =Z+Λ (38)

[0191] Λ is the regularization matrix. Note that the solutions to optimization problems (37) and (21) are the same. Three methods for determining Λ are introduced below.

[0192] In the first method, Λ is determined by the material and structure of the antenna elements. Consider the antenna's radiation resistance as R. rad In the array, the radiation resistance of the entire antenna array is affected by coupling and becomes: R rad =R rad Z. Therefore, the antenna's radiation efficiency is:

[0193]

[0194] The antenna gain is the product of its radiation efficiency and its directivity coefficient.

[0195]

[0196] Substituting into formula (39), G can be expressed as

[0197]

[0198] achievable

[0199] For a dipole antenna, the antenna loss r loss for

[0200]

[0201] Where a is the radius of the dipole antenna, L is the length, f is the operating frequency, μ is the magnetic permeability of the material, and σ is the electrical conductivity of the material.

[0202] Radiation impedance R rad Then it is:

[0203] R rad ≈24.7 (kL / 2) 2.5 (43)

[0204] In the second method, Λ is determined by the inaccuracy of the channel estimation. Consider the scenario where the channel estimation for each user has zero mean and a variance of σ. 2 Gaussian white noise, i.e., the channel estimation for the u-th terminal user. for:

[0205]

[0206] Where n u To estimate Gaussian noise, satisfying η u ~C(0,∈ 2 ), that is, n uIt follows the law of zero mean and variance ∈ 2 The complex Gaussian distribution, ||h u ||=1. According to the calculation method of Z in equation (12), we can obtain Z R The calculation method for elements in the middle is as follows

[0207]

[0208] in Let be the expectation operator. Then...

[0209]

[0210] Where I M It is an M×M matrix.

[0211] The third method considers both ohmic loss and channel estimation error simultaneously.

[0212]

[0213] 3.1 Specific application steps

[0214] The precoding matrix a of the u-th terminal user can be calculated using Schemes 1 to 3 proposed in this invention. u .

[0215] Furthermore, let P tot The base station transmit power is allocated equally to each user, and the Gaussian white noise power is σ. 2 The transmit signal-to-noise ratio is then:

[0216]

[0217] Let K be the total number of terminal users communicating, and let a be the precoding matrix of the u-th terminal user. u The channel state information is h u Then the total system throughput SE is

[0218]

[0219] Each beamforming vector is subject to a power constraint, such that the transmit power of each user is [value missing]. (Considering ohmic loss or channel estimation error) ).

[0220] 3.2 Simulation Results

[0221] First, the signal enhancement effect of the proposed scheme on the target user and the signal suppression effect on other users are simulated. Without loss of generality, the number of antennas is set to 20, the spacing is 0.25 wavelengths, and the number of users is 4. The target user is located at 76°, and the other users are located at 51°, 9°, and 39° respectively. The radiation pattern obtained by performing super-directional zero-forcing beamforming on the target user is shown in the simulation. Figure 1 As shown.

[0222] from Figure 1 It can be seen that the signal strength is strongest at the target user's angle, while the signal strength at the other users' angles is close to 0, indicating that the first solution of the present invention can effectively enhance the signal of the target user while reducing interference to other users.

[0223] Next, we simulate the spectral efficiency-SNR comparison of Scheme 1 and Scheme 2 of this invention, as well as the traditional maximum ratio transmission and zero-forcing transmission schemes under a multi-user scenario. In this simulation, the number of antennas was set to 20, the spacing was 0.25 times the wavelength, and the number of users was 8. The simulation results are as follows: Figure 2 As shown.

[0224] from Figure 2 As can be seen, this invention, by considering the coupling in a compact array and utilizing its superdirectivity, achieves a significant improvement in spectral efficiency compared to traditional maximum specific transmission (MST) and zero-forcing transmission schemes. Across the entire SNR range, Scheme 1 of this invention performs best because it utilizes both the enhancement of user signals by superdirectivity and the influence of interference from other users. Scheme 2 of this invention, because it simply projects the optimal solution of superdirectivity shaping onto the null space of interfering users, does not perform as well as Scheme 1, but is still better than traditional MST and zero-forcing schemes. MST and zero-forcing transmission, because they ignore the coupling of the antenna array and do not utilize its superdirectivity, perform worse than the scheme proposed in this invention at all SNR levels.

[0225] The simulation next considers the system spectral efficiency under ohmic loss and includes a comparison with Scheme 3 of this invention. Each antenna operates in the 1.6 GHz band, is made of copper, has a radius of 0.75 mm, a length of 85 mm, and a permeability of 4π × 10⁻⁶. -7 The conductivity is 5.8 × 10⁻⁶. 7 With 20 antennas, a spacing of 0.25 wavelengths, and 8 users, the simulation results are as follows: Figure 3 As shown.

[0226] from Figure 3 As can be seen, Scheme 1 of the present invention performs poorly because ohmic loss is not taken into account, while Scheme 3 of the present invention achieves improved spectral efficiency by introducing a regularization matrix, and performs the best among all schemes.

[0227] Example 2

[0228] A network device, comprising:

[0229] Construction unit, used to construct unitary matrix for end user u. The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0230] The first intercepting unit is used to intercept matrix U. H h u The first MN rows yield matrix η u ,in h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose.

[0231] The second interception unit is used to intercept matrix U. H The first MN rows and first MN columns of ZU yield matrix Ξ, where... matrix The elements in Z represent the coupling coefficients of any two antennas;

[0232] The computation unit is used to calculate the precoding matrix of the u-th terminal user. in superscript * Indicates conjugate.

[0233] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0234] Another type of network device includes:

[0235] Construction unit, used to construct unitary matrix for end user u. The first N (N≤K-1) columns of the unitary matrix W represent the interfering user channel space. i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K;

[0236] The truncation unit is used to extract the last MN columns of the unitary matrix W to obtain matrix R, where

[0237] The computation unit is used to calculate the precoding matrix of the u-th terminal user. in superscript * Indicates conjugation, h u The matrix represents the channel state information of the u-th terminal user. The elements in Z represent the coupling coefficients of any two antennas, and the superscript H indicates the conjugate transpose.

[0238] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0239] Example 3

[0240] An electronic device, comprising:

[0241] Processor; and

[0242] Memory for storing the executable instructions of the processor;

[0243] The processor is configured to execute the multi-user precoding method for a hyperdirectional antenna array as described in Embodiment 1 by executing the executable instructions.

[0244] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0245] Example 4

[0246] A computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the multi-user precoding method for a hyperdirectional antenna array as described in Embodiment 1.

[0247] The relevant technical solutions are the same as in Embodiment 1, and will not be repeated here.

[0248] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A multi-user precoding method for a hyperdirectional antenna array, characterized in that, include: Construct a unitary matrix for end user u. The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K; Extracting matrix U H h u The first MN rows yield matrix η u ,in h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose. Extracting matrix U H The first MN rows and first MN columns of ZU yield matrix Ξ, where... matrix The elements in Z represent the coupling coefficients of any two antennas; The precoding matrix of the u-th terminal user is calculated. in The superscript * indicates conjugate.

2. The multi-user precoding method for hyperdirectional antenna arrays according to claim 1, characterized in that, In extracting matrix U H Before obtaining matrix Ξ by taking the first MN rows and first MN columns of ZU, the method further includes updating matrix Z to Z+Λ, where... Let be the regularization matrix of matrix Z.

3. The multi-user precoding method for hyperdirectional antenna arrays according to claim 2, characterized in that, The regularization matrix Λ is: R rad ≈24.7(kL / 2) 2.5 Where, r loss and R rad These represent the antenna loss and radiation impedance, respectively, I. M Let L be an M×M identity matrix, where L, a, f, μ, σ, and k are the antenna length, radius, operating frequency, permeability, conductivity, and wave number, respectively.

4. The multi-user precoding method for a hyperdirectional antenna array according to claim 2, characterized in that, The regularization matrix Λ is: Where, ∈ 2 Let I be the Gaussian noise power, k(θ, φ) be the antenna pattern function, and θ and φ be the far-field coordinate components in spherical coordinates, respectively. M It is an M×M identity matrix.

5. The multi-user precoding method for a hyperdirectional antenna array according to claim 2, characterized in that, The regularization matrix Λ is: R rad ≈24.7(kL / 2) 2.5 Where, r loss and R rad These represent the antenna loss and radiation impedance, I, respectively. M Let L be an M×M identity matrix, and let L, a, f, μ, σ, and k be the antenna length, radius, operating frequency, permeability, conductivity, and wavenumber, respectively. 2 Let θ be the Gaussian noise power, k(θ, φ) be the antenna pattern function, and θ and φ be the far-field coordinate components in spherical coordinates.

6. The multi-user precoding method for a hyperdirectional antenna array according to any one of claims 1 to 5, characterized in that, The construction of unitary matrix Specifically: Construct the total disturbance covariance matrix: For R int SVD decomposition yields: R int =In H ΛW The unitary matrix U is: U = [W followed by MN columns, W followed by N columns].

7. The multi-user precoding method for a hyperdirectional antenna array according to claim 1, characterized in that, matrix Among them, z mn Let represent the coupling coefficient between the m-th and n-th antennas, k(θ, φ) be the antenna pattern function, θ and φ be the far-field coordinate components in spherical coordinates, and k be the wavenumber of the antenna. r is a unit vector in spherical coordinates. m and r n Let m and n be the coordinates of the m-th and n-th antennas, respectively, where m = 1, ..., M, and n = 1, ..., M.

8. The multi-user precoding method for a hyperdirectional antenna array according to claim 1, characterized in that, The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for the group i = 1, ..., K, i ≠ u, includes: make For the matrix composed of interfering user channel vectors, if N = K-1, the last K-1 columns of the unitary matrix U are respectively in: If N < K-1, calculate Then, N non-zero vectors will be obtained, and the N non-zero vectors will be selected as the last N columns of U.

9. A multi-user precoding method for a hyperdirectional antenna array, characterized in that, include: Construct a unitary matrix for end user u. The first N (N≤K-1) columns of the unitary matrix W represent the interfering user channel space. i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K; Extracting the last MN columns of the unitary matrix W yields matrix R, where... The precoding matrix of the u-th terminal user is calculated. in h u The matrix represents the channel state information of the u-th terminal user. The elements in Z represent the coupling coefficients of any two antennas. The superscript H indicates the conjugate transpose, and the superscript * indicates the conjugate.

10. A network device, characterized in that, include: Construction unit, used to construct unitary matrix for end user u. The last N (N≤K-1) columns of the unitary matrix U are respectively the interference user channel space span{h i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K; The first intercepting unit is used to intercept matrix U. H h u The first MN rows yield matrix η u ,in h u This represents the channel state information of the u-th terminal user, with the superscript H indicating the conjugate transpose. The second interception unit is used to intercept matrix U. H The first MN rows and first MN columns of ZU yield matrix Ξ, where... matrix The elements in Z represent the coupling coefficients of any two antennas; The computation unit is used to calculate the precoding matrix of the u-th terminal user. in The superscript * indicates conjugate.

11. A network device, characterized in that, include: Construction unit, used to construct unitary matrix for end user u. The first N (N≤K-1) columns of the unitary matrix W represent the interfering user channel space. i An orthonormal basis for {i = 1, ..., K, i ≠ u} is given, where N is the dimension of the interfering user channel space. Let M represent the channel state information of the i-th terminal user, M be the total number of antennas on the network device side, and K be the total number of terminal users communicating, and satisfy M≥K; The truncation unit is used to extract the last MN columns of the unitary matrix W to obtain matrix R, where The computation unit is used to calculate the precoding matrix of the u-th terminal user. in The superscript * indicates conjugate, h u The matrix represents the channel state information of the u-th terminal user. The elements in Z represent the coupling coefficients of any two antennas, and the superscript H indicates the conjugate transpose.

12. An electronic device, characterized in that, include: processor; as well as Memory for storing the executable instructions of the processor; The processor is configured to execute the multi-user precoding method for a hyperdirectional antenna array according to any one of claims 1-9 by executing the executable instructions.

13. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer-executable instructions, which, when executed by the processor, implement the multi-user precoding method for a hyperdirectional antenna array as described in any one of claims 1-9.

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