We investigate the joint admission control and discrete-phase multicast beamforming design for integrated sensing and commmunications (ISAC) systems, where sensing and communications functionalities have different hie...
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We investigate the joint admission control and discrete-phase multicast beamforming design for integrated sensing and commmunications (ISAC) systems, where sensing and communications functionalities have different hierarchies. Specifically, the ISAC system first allocates resources to the higher-hierarchy functionality and opportunistically uses the remaining resources to support the lower-hierarchy one. This resource allocation problem is a nonconvex mixed-integer nonlinear program (MINLP). We propose an exact mixed-integer linear program (MILP) reformulation, leading to a globally optimal solution. In addition, we implemented three baselines for comparison, which our proposed method outperforms by more than 39%.
Numerical optimization techniques are widely used in microwave circuits but are limited to fixed topologies, constraining their achievable performance and suffering from suboptimal designs. This letter presents a nove...
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Numerical optimization techniques are widely used in microwave circuits but are limited to fixed topologies, constraining their achievable performance and suffering from suboptimal designs. This letter presents a novel topological algorithm that can automatically synthesize practical circuit layouts that can satisfy prescribed specifications without preselecting the topology. To achieve this goal, the proposed method integrates a pixelated circuit generation strategy with the differential evolution algorithm (DEA). A new objective function is also developed to match the fundamental impedances while controlling harmonic responses. Good agreement between simulation and measurements for a wideband high-efficiency power amplifier (PA) validates the proposed algorithm.
The Iterative Closest Point (ICP) method, primarily used for transformation estimation, is a crucial technique in 3D signal processing, especially for point cloud fine registration. However, traditional ICP is prone t...
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The Iterative Closest Point (ICP) method, primarily used for transformation estimation, is a crucial technique in 3D signal processing, especially for point cloud fine registration. However, traditional ICP is prone to local optima and sensitive to noise, especially when there is no good initialization. Based on the observation that registration errors typically exhibit a multimodal distribution under large rotational offsets and noisy environments, the MultiKernel Correntropy (MKC), which can estimate the registration error distribution, is introduced to provide global information for ICP. Moreover, since MKC consists of multiple Gaussian kernels, it can effectively resist most of the noise. A MultiKernel Correntropy based Iterative Closest Point (MKCICP) is proposed. Extensive experiments on both simulated and real-world datasets show that MKCICP achieves better performance compared to other related methods in challenging scenarios involving large rotational angles, low partial overlap, and high noise levels.
In this paper, we propose a majorization-minimization (MM) based refinement strategy tailored for two-dimensional (2-D) unconditional maximum likelihood (UML) direction-of-arrival (DOA) estimation of a single source. ...
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In this paper, we propose a majorization-minimization (MM) based refinement strategy tailored for two-dimensional (2-D) unconditional maximum likelihood (UML) direction-of-arrival (DOA) estimation of a single source. We introduce two surrogate functions (linear and quadratic) for 2-D UML DOA estimation with the aim of successively reducing the objective function's value. The proposed MM method guarantees convergence to the objective function's stationary point. Furthermore, we employ the backtracking squared iterative method (SQUAREM) to accelerate the convergence speed of the proposed MM method. Numerical experiments further validate the efficiency of our proposed MM method.
With the advancement of monopulse radar technology, synthesis of the sum-and-difference patterns (SDPs) for the radome-enclosed arrays has emerged as a pressing area of research. Due to the influence of asymmetric rad...
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With the advancement of monopulse radar technology, synthesis of the sum-and-difference patterns (SDPs) for the radome-enclosed arrays has emerged as a pressing area of research. Due to the influence of asymmetric radome, active element patterns of the radome-enclosed linear array (RELA) are completely different. To accurately consider the array-element mutual couplings and array-and-radome interactions, a novel simultaneous synthesis technique for low-sidelobe-level (SLL) SDPs of the RELA with common weights is proposed. First, a nonconvex SDP synthesis problem with the nonconvex constraint and the nonconvex objective function is established. Then, by fixing the reference phases for the sum pattern (SP) radiation far-field and the difference pattern (DP) slope at the target direction, the original nonconvex synthesis problem is transformed into a convex minimum problem, which can be efficiently solved by the convex optimization methods. Finally, a 40-element RELA is implemented, demonstrating that the proposed synthesis technique can be used to simultaneously synthesize SDPs of the RELA with asymmetric active element patterns. The SPs with -25 dB SLL and the DPs with -20 dB SLL are simultaneously synthesized, and the obtained results verify effectiveness of the proposed synthesis technique.
This letter introduces weighted sum power (WSP), a new performance metric for wireless resource allocation during cooperative spectrum sharing in cognitive radio networks, where the primary and secondary nodes have di...
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This letter introduces weighted sum power (WSP), a new performance metric for wireless resource allocation during cooperative spectrum sharing in cognitive radio networks, where the primary and secondary nodes have different priorities and quality of service (QoS) requirements. Compared to using energy efficiency (EE) and weighted sum energy efficiency (WSEE) as performance metrics and optimization objectives of wireless resource allocation towards green communication, the linear character of WSP can reduce the complexity of optimization problems. Meanwhile, the weights assigned to different nodes are beneficial for managing their power budget. Using WSP as the optimization objective, a suboptimal resource allocation scheme is proposed, leveraging linear programming and Newton's method. Simulations verify that the proposed scheme provides near-optimal performance with low computation time. Furthermore, the initial approximate value selection in Newton's method is also optimized to accelerate the proposed scheme.
Intelligent reflecting surface (IRS)-assisted terahertz (THz) communication is becoming a key technology for next-generation wireless networks. Although IRS has great promise, it is severely hindered by the beam squin...
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Intelligent reflecting surface (IRS)-assisted terahertz (THz) communication is becoming a key technology for next-generation wireless networks. Although IRS has great promise, it is severely hindered by the beam squint problem resulting from the frequency-independent nature of the passive reflecting elements, especially in ultra-wide THz bands. To address this problem, we introduce time delay modules to the IRS and focus on the weighted sum rate maximization problem through the joint optimization of transmit beamforming, IRS phase shifts, and time delays. To solve the formulated optimization problem, an alternating optimization algorithm that decomposes the original problem into three subproblems is proposed. Specifically, we apply semidefinite relaxation and successive convex approximation techniques to solve each subproblem. Simulation results demonstrate the superiority of the proposed scheme over recent literature works. Particularly, it achieves near-optimal performance with slightly increased hardware cost.
To enhance straggler resilience in federated learning (FL) systems, a semi-decentralized approach has been recently proposed, enabling collaboration between clients. Unlike the existing semi-decentralized schemes, whi...
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To enhance straggler resilience in federated learning (FL) systems, a semi-decentralized approach has been recently proposed, enabling collaboration between clients. Unlike the existing semi-decentralized schemes, which adaptively adjust the collaboration weight according to the network topology, this letter proposes a deterministic coded network that leverages wireless diversity for semi-decentralized FL without requiring prior information about the entire network. Furthermore, the theoretical analyses of the outage and the convergence rate of the proposed scheme are provided. Finally, the superiority of our proposed method over benchmark methods is demonstrated through comprehensive simulations.
In this letter, we consider a new type of flexible-antenna system, termed pinching-antenna, where multiple low-cost pinching antennas, realized by activating small dielectric particles on a dielectric waveguide, are j...
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In this letter, we consider a new type of flexible-antenna system, termed pinching-antenna, where multiple low-cost pinching antennas, realized by activating small dielectric particles on a dielectric waveguide, are jointly used to serve a single-antenna user. Our goal is to maximize the downlink transmission rate by optimizing the locations of the pinching antennas. However, these locations affect both the path losses and the phase shifts of the user's effective channel gain, making the problem challenging to solve. To address this challenge and solve the problem in a low complexity manner, a relaxed optimization problem is developed that minimizes the impact of path loss while ensuring that the received signals at the user are constructive. This approach leads to a two-stage algorithm: in the first stage, the locations of the pinching antennas are optimized to minimize the large-scale path loss;in the second stage, the antenna locations are refined to maximize the received signal strength. Simulation results show that pinching-antenna systems significantly outperform conventional fixed-location antenna systems, and the proposed algorithm achieves nearly the same performance as the highly complex exhaustive search-based benchmark.
Due to the increasing demand for remote sensing imaging products, the agile Earth observation satellite scheduling problem (AEOSSP) has garnered significant attention. In response, this letter proposes a reinforcement...
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Due to the increasing demand for remote sensing imaging products, the agile Earth observation satellite scheduling problem (AEOSSP) has garnered significant attention. In response, this letter proposes a reinforcement learning-based dung beetle optimization (RLDBO) algorithm to address the AEOSSP. The proposed method dynamically adjusts the proportions of four types of dung beetles (ball-rolling beetle, brood ball beetle, small dung beetle, and thief beetle), enabling adaptive optimization of the scheduling scheme to better handle the complexities and uncertainties of the search space. The Q-learning mechanism guides the adjustment of these proportions, effectively balancing global exploration and local exploitation at different stages of the search process. Experimental results demonstrate that the RLDBO algorithm effectively solves the AEOSSP across multiple instances, and it outperforms other algorithms in various aspects, including optimization performance, convergence speed, and scheduling effectiveness. The experimental validation confirms that RLDBO significantly enhances the efficiency and effectiveness of agile Earth observation satellite (AEOS) scheduling.
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