This letter addresses the resource allocation issue for hybrid free-space optics (FSO)/radio frequency (RF)-based satellite-assisted multiple users. Specifically, we present the rate adaptation-aided data frame allocation design for hybrid FSO/RF satellite-assisted multiple unmanned aerial vehicles (UAVs). The considered allocation scheme ensures latency fairness among UAVs serving as flying base stations (BSs). Numerical results confirm the effectiveness of the proposed solution over the state-of-the-art. Moreover, we investigate the feasibility of a case study over the Japan networks using practical SpaceX’s Starlink satellite constellation.

Herein, we present an effective analysis using the finite-difference time-domain (FDTD) method for vehicle-to-vehicle (V2V) radio propagation in the 700 MHz band at urban intersections. By combining the FDTD (2,4) method with multi-core processors, a high-precision computation and visualization analysis of the propagation phenomena is realized using practical computation resources for V2V communication systems in a large and complex propagation environment. We demonstrate that the causal relationship between the radio propagation process and reception characteristics can be analyzed both quantitatively and qualitatively.

Adopting polarization for orbital angular momentum (OAM) multiplexing can suppress beam divergence because of using the lower OAM modes, which leads to extending the link distance. In this study, we investigate the effectiveness of multiple-input multiple-output (MIMO) on the polarized OAM multiplexing under the restriction of the same total transmit power and total number of antenna elements. To evaluate the combined effects of polarization and MIMO on system capacity, we conducted computer simulations. Moreover, we investigate the system capacity when only lower OAM modes are available, and compare it with the case without mode limitations. The results of our study provide valuable insights into the potential benefits of using polarization and MIMO for OAM multiplexing.

In this letter, we propose a device identification method from observed Bluetooth Low Energy (BLE) advertising packets for tracking BLE devices even if their MAC addresses are changed periodically and randomly. In our proposed method, the combination of MAC addresses is formulated as a linear assignment problem. In addition, in a cost function of linear assignment, we combine two types of cost: time-based cost and received signal strength-based cost, which is calculated based on regression of received signal strength. Through experimental evaluations, we confirmed that the accuracy of our proposed method is the highest compared to traditional methods.

This paper studies non-integer power of two-ary quadrature amplitude modulation (QAM) for long-haul optical fiber transmission systems. Numerical simulations show that 12-QAM and 24-QAM provide intermediate solutions on reachable transmission distances among traditional M-QAM such as C8-QAM, 16-QAM, and 32-QAM. In addition, short block length probabilistic shaping of 24-QAM not only provides an intermediate solution with nonlinear tolerance, but also yields greater transmission distances than 16-QAM for the same information data rates.

This letter proposes a secure transmission method using spatially parallel channels formed in a multi-input multi-output (MIMO) communication scenario. In the proposed method, the transmitted information is divided into pieces using a secret-sharing method. These generated pieces are then transmitted separately to the destination through the parallel sub-channels of the MIMO communication link. The secret-sharing method ensures that the transmitted information remains unrevealed unless all the divided pieces are obtained, thus achieving secure communication by establishing an advantageous situation for the legitimate receiver to gather the divided pieces against wiretappers in the surrounding area. Computer simulations demonstrate that allocating transmission power inverse-proportionally to the channel gains among the MIMO sub-channels creates a secure link to the receiver from the channel capacity perspective. The secret capacity of the link increases with the number of antenna elements in the MIMO configuration at the expense of power gain.

This study aims to establish an adaptive video quality control method that satisfies object-detection accuracy and reduces bandwidth consumption simultaneously for remote real-time video analysis systems. Existing video quality control methods determine video quality by considering human perceptual characteristics; this reduces bandwidth consumption while providing a high quality of experience. However, it cannot reduce bandwidth consumption in systems that use object-detection engines to detect people and vehicles. Thus, this study proposes a video quality control method to reduce bandwidth consumption. To this end, the bandwidth consumption and ratio of the number of frames satisfying the mean average precision requirements to the total number of frames (herein referred to as the success rate) are evaluated. The results confirm that the proposed method can reduce bandwidth consumption to 49% of that of the existing video quality control method at the same success rate.

We propose a network management method using a novel adapter that translates OpenFlow-based commands and vendor-specific commands using a single-board computer to achieve a low-cost centralized management of heterogeneous network devices including various vendors. The adapter is implemented in wired and wireless network devices and its operation is verified. Moreover, we compare the cost in two scenarios, i.e., the management of a smart home network and a small- and medium-sized enterprise network. The results show that the proposed method works efficiently and is low-cost than the conventional method.

This letter investigates a novel 6G near-field simultaneous wireless information and power transfer (SWIPT) system, in which a single hybrid transmitter, equipped with an extremely large-scale antenna array, concurrently provides wireless data and energy access to mobile terminals. In this pioneering scenario, we delve into the optimal beam-focusing design with the goal of maximizing the weighted-sum energy harvested by all energy receivers while ensuring the achievable rate requirements of information receivers. Despite the inherent non-convexity of the associated optimization problem, we achieve a globally optimal solution by employing the technique of semi-definite relaxation. Our numerical results affirm the remarkable effectiveness of the proposed optimal beam-focusing design.

This letter proposes a new method for tuning compensation capacitances of wireless power transfer (WPT) systems using an artificial neural network (ANN). A field solver is used to analyze the compensation capacitances that maximize the output power at a set resonant frequency in a WPT system with ferrite shields. The compensation capacitances can be tuned using the ANN learned from the results acquired by the field solver. The electrical parameters for tuning the compensation capacitances acquired by the proposed method have maximum errors within 3.40% and mean absolute errors within 1.38%.

Unmanned aerial vehicle (UAV) base stations have a variety of applications due to their ability to be quickly and freely deployed. They provide a promising solution when existing terrestrial networks are damaged during a disaster and network connectivity is lost, helping to restore connectivity in disaster-affected areas. However, moving UAVs provide unfair network connectivity for ground-based user equipment. To solve this, we need to integrate speed control and bandwidth allocation. In this paper, we give an overview of the algorithms integrating them and demonstrate how they further improve fairness. Moreover, we provide an architecture based on the Open-RAN architecture for running integrated algorithms. Finally, we use computer simulations to demonstrate its effectiveness.