In this paper, we present a flexible and efficient ternary parallelization approach for the multilevel fast multipole algorithm (MLFMA) for the solution of extremely large 3D scattering problems with over 10 billion unknowns. In the ternary parallelization approach, a binary clustering tree of all the message passing interface (MPI) processes is built firstly. Then, the MLFMA tree is categorized into plane wave partitioning, hierarchical-structure partitioning and box partitioning levels via a top-down approach to match the process clustering tree. Compared with the bottom-up approach, inter-process communications in the far interaction are reduced. An inner-group transition level is designed for switching partitions on the intermediate level between the hierarchical-structure partitioning and box partitioning levels. The ternary strategy can realize as high parallel efficiency as the hierarchical partitioning strategy while maintaining flexibility in selecting the total number of processes. An auxiliary-tree-based parallel mesh refinement technique and a hybrid octree storage strategy are designed to facilitate the realization of fast full-wave simulation on a scale of over 10 billion unknowns with the ternary MLFMA. The accuracy of the solutions is validated by comparing the radar cross-sections (RCSs) of a sphere of diameter 3042 wavelengths with 10,773,415,728 unknowns via MLFMA and the Mie series, which is the largest number of unknowns to be computed via full wave numerical methods to date. Furthermore, the solutions for complicated objects, namely, a ship and an aircraft model, both of which have maximum lengths that exceed 10 thousand wavelengths and over 10 billion unknowns, are presented.

The design challenge of new functional composite materials consisting of multiphase materials has attracted an increasing interest in recent years. In particular, understanding the role of distributions of ordered and disordered particles in a host media is scientifically and technologically important for designing novel materials and devices with superior spectral and angular properties. In this work, the effective medium property of disordered composite materials consisting of hyperuniformly distributed hard particles at different filling fractions is investigated. To accurately extract effective permittivity of a disordered composite material, a full-wave finite element method and the transmission line theory are used. Numerical results show that the theory of hyperuniformity can be conveniently used to design disordered composite materials with good accuracy compared with those materials with randomly dispersed particles. Furthermore, we demonstrate that a Luneburg lens based on the proposed hyperuniform media has superior radiation properties in comparison with previously reported metamaterial designs and it may open up a new avenue in electromagnetic materials-by-design.

ADS-B has been widely deployed on aircraft to facilitate aviation information exchange and improve air traffic safety. However, its broadcast nature and lack of security considerations like encryption and authentication have caused the counterfeit of automatic-dependent surveillance-broadcast (ADS-B) messages to be straightforward. Flooding forged messages to legitimate aircraft, Denial-of-Service (DoS) attacks threaten flight security severely. In this article, we propose a practical security solution against DoS attacks on ADS-B based on high-precision timestamp and position information. The solution achieves high feasibility and reliability by accommodating measurement errors of physical quantities. Besides, it preserves ADS-B frame size and ensures efficient computation in frame generation and verification. Comprehensive security analyses demonstrate robust filtrations of the proposed solution on malicious messages from DoS adversaries with different capabilities. Further simulations on real-world aviation data exhibit significant defensive performance realized by the DoS-immune ADS-B security solution. Whether adversaries can only intercept ciphertext, or they have opportunities to acquire decrypted messages, all DoS attacks on ADS-B are successfully thwarted by the solution. Even for adversaries with victim aircraft location estimation capacity, the solution resists all DoS attacks transmitting less than 50 forged messages per second.

To enhance the capability of the characteristic mode analysis (CMA) for electrically large problems, fast multipole algorithms (FMAs) are incorporated into this increasingly popular technique in antenna community. In this communication, an improvement formulation of CMA with FMAs is presented and studied. Numerical results show that the proposed formulation has a better convergence behavior than the previous formulation when it is used for electrically large antenna platforms.

Swarm targets consisting of multiple aircraft, such as unmanned aerial vehicles (UAVs), have become an emerging tool in modern applications due to their agility and vast coverage. Because of the complicated coupling and shading effects among different units, accurate, flexible, and computationally efficient scattering analysis for this novel target remains challenging. To overcome this difficulty, in this work, a so-called plane wave expansion (PWE) algorithm is proposed. Unlike the multilevel fast multipole algorithm (MLFMA), which treats swarm targets as a single entity, PWE deals with individual units separately, allowing for the reuse of data structures for identical targets. The low computational complexity and the effectiveness of the proposed method are achieved by combining three calculation strategies, a) evaluating the coupling effects between two close units using a rigorous fast plane wave expansion technique and ignoring those of well-separated units, b) determining the threshold defining "well-separated" through an adaptive procedure so that the overall accuracy is controllable, and c) quickly estimating the initial solution to accelerate convergence. Extensive numerical simulations, including one with up to 56 electrically large UAVs, are carried out to demonstrate the accuracy, effectiveness, and robustness of the proposed method.

Beamspace multiple-input multiple-output (B-MIMO) provides a promising solution for reducing the number of required expensive radio frequency (RF) chains without obvious performance loss. However, the high computational complexities of beam selection algorithms prohibits their practical applications in 5G millimeter wave (mmWave) massive MIMO communication systems. Reviewing existing beam selection procedures and using the matrix perturbation theory, the complexity reduction on beam selection for beamspace MIMO is considered in this letter. Two beam selection algorithms, one for B-MIMO systems with classic zero-forcing (ZF) precoder and the other for the systems with QR precoder are proposed. Theoretical analyses and numerical simulations all show that the proposed beam selection algorithms possess a much lower complexity than conventional ones.