A multi-user broadcast communication method based on reconfigurable pixel antenna array

Abstract

The application belongs to the technical field of wireless communication, and particularly relates to a multi-user broadcast communication method based on a reconfigurable pixel antenna array. The application deploys a reconfigurable pixel antenna array at a base station, utilizes the flexible switching characteristics of the radiation pattern, and realizes efficient transmission of public broadcast information to multiple users. Compared with a traditional fixed-position antenna, the method can significantly improve the reception performance of the worst user in the broadcast system. Compared with a mechanically movable antenna scheme, the application uses electronic switches to realize antenna radiation state reconstruction, and does not need to rely on mechanical motion structures, so it has the advantages of fast switching speed, low implementation complexity, and low cost. Through simulation verification, the proposed scheme can effectively improve the public information transmission rate of the multi-user broadcast system, and the partially connected architecture can improve the performance at a low hardware complexity, and the fully connected architecture can better approach the performance upper bound of the ideal movable antenna system.

Description

Technical Field

[0001] This invention belongs to the field of wireless communication technology, specifically relating to a multi-user broadcast communication method based on a reconfigurable pixel antenna array. Background Technology

[0002] Multi-antenna technology is one of the key supporting technologies in modern wireless communication systems. By configuring multiple antennas at the transmitting or receiving end, communication systems can fully utilize spatial resources, thereby significantly improving spectral efficiency, transmission reliability, and system capacity. Existing multi-antenna systems typically employ fixed-position antenna (FPA) structures. After deployment, the positions of each antenna element and the array geometry remain unchanged, making it difficult to flexibly adjust according to changes in instantaneous channel conditions, thus limiting performance gains. To overcome these shortcomings, the academic community has proposed fluid antenna systems (FAS) in recent years. These systems treat antenna radiation characteristics as a reconfigurable physical layer resource. By changing the antenna's position or shape, the wireless system can dynamically adjust its radiation state according to channel conditions, providing additional spatial degrees of freedom. Movable antennas (MA) are a typical implementation of fluid antennas. Their core principle is to optimize wireless channel conditions by dynamically moving the antenna position, thereby improving communication performance. However, these antennas typically rely on mechanical devices for position adjustment, and their movement speed is limited by the hardware itself, making it difficult to meet the real-time reconfiguration requirements under rapidly changing wireless channels. Meanwhile, mechanical mobility also suffers from problems such as complex structure, difficulty in integration, and high maintenance costs, which further limit its application in practical wireless communication systems.

[0003] In recent years, reconfigurable pixel antennas (RPA) have gradually attracted attention as an alternative implementation of fluid antenna systems. RPAs typically consist of a large number of closely packed metallic pixel units, with adjacent units connected via radio frequency switches. By changing the connection states between the pixel units, the current distribution on the antenna surface can be dynamically adjusted, thus creating different radiation states. Existing research shows that this switching process can be completed within microseconds. Therefore, reconfigurable pixel antennas hold promise for overcoming the drawbacks of slow mechanical movement and high implementation complexity while maintaining the spatial reconfiguration advantages of mechanically movable antennas. Summary of the Invention

[0004] The main content of this invention is to propose a multi-user broadcast communication method based on a reconfigurable pixel antenna array, involving system structure, multi-user broadcast communication process, and joint design method of candidate antenna activation state and transmit beamforming at the base station.

[0005] The technical solution of this invention is as follows:

[0006] The technical solution adopted in this invention is a multi-user downlink broadcast communication system based on a reconfigurable pixel antenna array, and the system structure is as follows: Figure 1 As shown, it consists of a base station (BS) with a reconfigurable pixel antenna array (RPAA) and K single-antenna users (users 1 to K). The reconfigurable pixel antenna array is composed of... It consists of several reconfigurable pixel antenna elements, each containing... For each candidate antenna, the entire array can adopt a fully connected (FC-RPAA) or partially connected (PC-RPAA) architecture. In the fully connected architecture, the base station-side RF link is connected to the entire pixel antenna array through a switching network, allowing for flexible activation of candidate antennas across the entire array. In the partially connected architecture, each RF link connects to only one pixel antenna element, activating at most one candidate antenna within that connected pixel antenna element.

[0007] The specific method of this invention is as follows:

[0008] The base station first sends a pilot signal, and each user performs downlink channel estimation based on the received pilot signal and feeds back the estimated channel state information to the base station.

[0009] The base station jointly designs the activation states of candidate antennas and the transmit beamforming scheme in the reconfigurable pixel antenna array based on the channel state information and array connection structure fed back by each user, thereby configuring a transmit antenna array suitable for the current channel conditions; specifically, the problem of establishing the joint configuration of candidate antenna activation states and transmit beamforming on the base station side is as follows:

[0010] ,

[0011] in, It is the rate of user k. It is the transmitted beamforming vector. It is the maximum transmission power of the base station. It is the antenna selection matrix of the candidate antenna activation states. It is the total number of activated candidate antennas. It represents the number of candidate antennas within the minimum spacing length range. It is the carrier wavelength, a constraint. This indicates the constraint that at most one candidate antenna can be activated within each additional reconfigurable pixel antenna element in a partially connected architecture; antenna activation and beamforming schemes are obtained by solving the joint configuration problem.

[0012] The base station sends public broadcast signals to users within the system, and each user demodulates the received broadcast signals to complete multi-user broadcast communication.

[0013] Specifically, the base station's transmitted signal is defined as follows: 's' represents the information symbol broadcast by the base station. This represents the transmitted beamforming vector. The broadcast signal received by user k from the base station is... ,in, Let K be the channel vector from the base station to user k. Antenna Selection Matrix The corresponding diagonal matrix, The noise at user k is additive white Gaussian noise and follows a distribution. The signal-to-noise ratio of the signal received by user k is obtained as follows: Thus, the rate of user k is obtained as .

[0014] Specifically, the solution to the joint configuration problem is an alternating optimization method. This involves transforming the subproblem into a semidefinite programming problem by combining a positive semidefinite relaxation method with the given candidate antenna activation states, and then using a binary search method to find the optimal beamforming vector under the current antenna activation state. Given the beamforming vector, the antenna activation matrix is ​​updated using continuous relaxation and successive convex approximation methods. Iterate until convergence to obtain the final antenna activation and beamforming scheme.

[0015] The beneficial effects of this invention are as follows: Compared with traditional fixed-position antennas, the method proposed in this invention can significantly improve the reception performance of the worst-performing user in a broadcast system, thereby enhancing system fairness; compared with mechanically movable antenna schemes, this invention uses electronic switches to reconstruct the antenna radiation state, eliminating the need for mechanical movement structures, thus offering advantages such as fast switching speed, low implementation complexity, and lower cost. Simulation verification shows that the proposed scheme can effectively improve the public information transmission rate of a multi-user broadcast system. Partial connection architectures achieve performance improvements with low hardware complexity, while the fully connected architecture can closely approach the performance upper bound of an ideal movable antenna system. Therefore, this invention has significant practical value and development potential. Attached Figure Description

[0016] Figure 1 : Schematic diagram of the system composition of this invention;

[0017] Figure 2 : A schematic diagram of the convergence performance curve of the alternative optimization algorithm submitted in this invention;

[0018] Figure 3 Schematic diagram of the relationship between the minimum achievable rate and signal-to-noise ratio of the system under different schemes;

[0019] Figure 4 : A schematic diagram showing the relationship between the minimum achievable rate of the system and the number of users under different schemes. Detailed Implementation

[0020] The present invention will now be described in detail with reference to the accompanying drawings and simulation examples.

[0021] This invention utilizes a reconfigurable pixel antenna array deployed at a base station, leveraging its flexible switching radiation pattern to achieve efficient transmission of public broadcast information to multiple users. Specifically, when a base station broadcasts the same information to multiple users, the received signal quality varies significantly due to differences in spatial location and path loss. Traditional fixed antenna arrays can only mitigate performance differences between users through beamforming or power allocation, failing to fully utilize spatial domain freedom. In the proposed solution, the base station is equipped with a reconfigurable pixel antenna array. By selecting and activating suitable candidate antennas, and combining this with transmit beamforming design, the transmitting antennas form a radiation state suitable for the current multi-user channel environment before broadcast transmission, thereby improving the communication performance of the broadcast system. Furthermore, to balance system performance and implementation complexity, this invention considers both fully connected and partially connected antenna array architectures. The fully connected architecture offers higher antenna selection freedom, while the partially connected architecture has limited antenna selection flexibility but lower hardware complexity. Since the number of candidate antenna states in a reconfigurable pixel antenna array is large, and the system is simultaneously constrained by transmit power, number of active antennas, minimum spacing, and array connection architecture, this invention further proposes a joint design method based on alternating optimization to achieve coordinated optimization of candidate antenna active states and transmit beamforming scheme on the base station side.

[0022] The system structure of this invention is as follows: Figure 1 As shown, it consists of a base station (BS) configured with a reconfigurable pixel antenna array (RPAA) and K single-antenna users (users 1 to K). The reconfigurable pixel antenna array consists of... It consists of several reconfigurable pixel antenna elements, each containing... For each candidate antenna, the entire array can adopt a fully connected (FC-RPAA) or partially connected (PC-RPAA) architecture. In the fully connected architecture, the base station-side RF link is connected to the entire pixel antenna array through a switching network, allowing for flexible activation of candidate antennas across the entire array. In the partially connected architecture, each RF link connects to only one pixel antenna element, activating at most one candidate antenna within that connected pixel antenna element.

[0023] The basic working principle of multi-user broadcast communication based on reconfigurable pixel antenna arrays is as follows: The base station first transmits a pilot signal. Each user performs downlink channel estimation based on the received pilot signal and feeds back the estimated channel state information to the base station. Subsequently, the base station jointly designs the activation states of candidate antennas in the reconfigurable pixel antenna array and the transmit beamforming scheme based on the channel state information fed back by each user and the array connection structure, thereby configuring a transmit antenna array suitable for the current channel conditions. Afterward, the base station transmits a public broadcast signal to users within the system. Each user demodulates the received broadcast signal, thus completing the multi-user broadcast communication. The transmitted signal at the base station can be represented as:

[0024] (1)

[0025] Where 's' represents the information symbol broadcast by the base station. This represents the transmitted beamforming vector. In this invention, the base station transmits broadcast signals to each user through a reconfigurable pixel antenna array, denoted as... This is the antenna selection matrix that characterizes the activation state of candidate antennas.

[0026] The broadcast signal received by user k from the base station can be represented as:

[0027] (2)

[0028] in, Let K be the channel vector from the base station to user k. Choose the diagonal matrix corresponding to the antenna selection matrix. The noise at user k is additive white Gaussian noise and follows a distribution. From equation (2), the signal-to-noise ratio of the signal received by user k can be expressed as:

[0029] (3)

[0030] The rate of user k can be expressed as:

[0031] (4)

[0032] Since the base station sends the same broadcast signal to all users, the achievable broadcast rate of this public information needs to ensure that all users can demodulate it. Therefore, the system's public broadcast rate can be expressed as:

[0033] (5)

[0034] As can be seen from the above signal model, before broadcasting, the base station needs to determine the activation state of candidate antennas and the transmit beamforming scheme, taking into account the limitations of antenna array structure and transmit power. and The following constraints need to be met:

[0035] (1) The power of the base station's transmitted signal is limited by the maximum transmit power P, which can be expressed as:

[0036] (6)

[0037] (2) The activation state of the candidate antenna is a binary variable, meaning that each candidate antenna can only be in an active or inactive state. This constraint can be expressed as:

[0038] (7)

[0039] (3) The total number of activated candidate antennas is fixed at 1. ,and The constraint, which is not greater than the number of available radio frequency links, can be expressed as:

[0040] (8)

[0041] (4) The distance between any two activated candidate antennas shall not be less than a preset minimum spacing to reduce the influence of electromagnetic coupling. In this invention, the minimum spacing is set to ,in Given the carrier wavelength, this constraint can be expressed as:

[0042] (9)

[0043] in, This indicates the number of candidate antennas within the minimum spacing length range.

[0044] (5) In particular, for a partially connected architecture, at most one candidate antenna is activated within each reconfigurable pixel antenna element, and this constraint can be expressed as:

[0045] (10)

[0046] Therefore, under the premise of satisfying the above constraints, the joint configuration problem of candidate antenna activation state and transmit beamforming on the base station side can be summarized as follows:

[0047] (11)

[0048] To solve the aforementioned mixed-integer nonconvex optimization problem, this invention proposes an alternating optimization method. The basic idea is as follows: given the candidate antenna activation states, the subproblem is transformed into a semidefinite programming problem by combining the semidefinite relaxation (SDR) method, and the optimal beamforming vector under the current antenna activation state is obtained using a binary search method. Given a beamforming vector, the antenna activation matrix is ​​updated using the Successive Convex Approximation (SCA) method with continuous relaxation. Iterate through the above steps until convergence to obtain the final antenna activation and beamforming scheme.

[0049] The entire system processing flow is as follows: (1) The base station sends pilot signals, and users estimate and feed back their respective downlink channel information; (2) The base station determines the initial activation state of the candidate antennas based on the array connection structure and channel state information; (3) The base station alternately updates the joint configuration of the candidate antenna activation state and beamforming scheme; (4) The pixel antenna array controls the connection of the RF switches according to the obtained candidate antenna activation state to form the target radiation state, and sends broadcast signals to users in combination with the beamforming scheme; (5) Each user demodulates the received broadcast signal; (6) In subsequent communication time slots, the base station can update the candidate antenna activation state and beamforming vector again according to the channel state changes.

[0050] The beneficial effects of this invention will be verified through simulation below. The simulation parameters are set as follows: the number of users is 4, and the antenna array contains a total of There are 1 reconfigurable pixel antenna element, each with a size of 1. Unless otherwise specified, each antenna element contains Root candidate antennas, number of active antennas The signal-to-noise ratio is 10dB, and the noise power is normalized.

[0051] like Figure 2 As shown, with the update of base station-side parameter configuration, the minimum reachable rate of the system rapidly increases and tends to stabilize after three iterations, indicating that the multi-user broadcast communication method can form a stable broadcast transmission scheme with fewer configuration iterations. Furthermore, with the increase of the number of active antennas, the minimum reachable rate obtained by the system further improves.

[0052] like Figure 3As shown, the reconfigurable pixel antenna-based scheme proposed in this invention is significantly superior to the fixed-position antenna scheme. In particular, as the candidate antenna density within each reconfigurable pixel antenna element increases, the system performance is further improved. When the number of candidate antennas within each reconfigurable pixel antenna element reaches 36, the fully connected reconfigurable pixel antenna array scheme can approximate the performance upper bound of the ideal movable antenna scheme quite well. These results demonstrate that this invention can achieve performance gains close to the ideal spatial reconfiguration scheme without requiring mechanical movement.

[0053] like Figure 4 As shown, with the increase in the number of users, the minimum achievable rate of the broadcast system in each scheme decreases. The scheme proposed in this invention consistently outperforms the fixed-position antenna scheme, and the fully connected reconfigurable pixel antenna array architecture consistently approaches the performance of the ideal movable antenna scheme. This demonstrates that this invention can effectively improve system fairness in multi-user broadcast scenarios.

[0054] Finally, the above embodiments are merely a simple implementation of the present invention, but the implementation of the present invention is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention should be considered equivalent substitutions and are included within the protection scope of the present invention.

Claims

1. A multi-user broadcast communication method based on a reconfigurable pixel antenna array, used in a multi-user downlink broadcast communication system, characterized in that, The communication system is defined as consisting of a base station configured with a reconfigurable pixel antenna array and K single-antenna users. The reconfigurable pixel antenna array is composed of... It consists of several reconfigurable pixel antenna elements, each containing... The candidate antennas and the antenna array adopt a fully connected architecture or a partially connected architecture. The communication method includes: The base station first sends a pilot signal, and each user performs downlink channel estimation based on the received pilot signal and feeds back the estimated channel state information to the base station. The base station jointly designs the activation states of candidate antennas and the transmit beamforming scheme in the reconfigurable pixel antenna array based on the channel state information and array connection structure fed back by each user, thereby configuring a transmit antenna array suitable for the current channel conditions; specifically, the problem of establishing the joint configuration of candidate antenna activation states and transmit beamforming on the base station side is as follows: ， in, It is the rate of user k. It is the transmitted beamforming vector. It is the maximum transmission power of the base station. It is the antenna selection matrix of the candidate antenna activation states. It is the total number of activated candidate antennas. It represents the number of candidate antennas within the minimum spacing length range. It is the carrier wavelength, a constraint. This indicates the constraint that at most one candidate antenna can be activated within each additional reconfigurable pixel antenna element in a partially connected architecture; antenna activation and beamforming schemes are obtained by solving the joint configuration problem. The base station sends public broadcast signals to users within the system, and each user demodulates the received broadcast signals to complete multi-user broadcast communication.

2. The multi-user broadcast communication method based on a reconfigurable pixel antenna array according to claim 1, characterized in that, Define the base station's transmitted signal as 's' represents the information symbol broadcast by the base station. This represents the transmitted beamforming vector. The broadcast signal received by user k from the base station is... ,in, Let K be the channel vector from the base station to user k. Antenna Selection Matrix The corresponding diagonal matrix, The noise at user k is additive white Gaussian noise and follows a distribution. The signal-to-noise ratio of the signal received by user k is obtained as follows: Thus, the rate of user k is obtained as .

3. The multi-user broadcast communication method based on a reconfigurable pixel antenna array according to claim 1, characterized in that, The specific solution method for the joint configuration problem is the alternating optimization method. Specifically, given the active states of candidate antennas, the subproblem is transformed into a semidefinite programming problem by combining a positive semidefinite relaxation method, and a binary search method is used to obtain the optimal beamforming vector under the current antenna active state. Given the beamforming vector, the antenna activation matrix is ​​updated using continuous relaxation and successive convex approximation methods. Iterate until convergence to obtain the final antenna activation and beamforming scheme.

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