Satellite broadcasting of UHDTV in Japan has used the 12-GHz band (11.7 to 12.75GHz) since 2018. The 21-GHz band (21.4 to 22.0GHz) has also been allocated to satellite broadcasting in Europe, Africa, and Asia Pacific. The BSAT-4a satellite not only has 12-GHz-band transponders for UHDTV services, but also 21-GHz-band experimental transponders for future broadcasting services. To receive services using these two frequency bands with a single antenna, we designed a 12- and 21-GHz dual-band horn antenna with a choke horn as the feed of a parabolic reflector antenna. Simulation results showed that an aperture efficiency of more than 70% was obtained in both bands.

In this paper, we examine a signal separation method that restores the desired signal by multiplying the power component and phase component of the reference signal, which is an unmodulated signal with the same frequency as the center frequency of the desired signal. Gaussian-filtered minimum shift keying (GMSK) that has not been evaluated in previous studies for synchronous detection method and feature demodulation method. The signal separation performance of GMSK modulation was quantitatively evaluated by computer simulation. We also investigated how changes in the window function and desired to undesired signal ratio (D/U) affect signal separation and demodulation. As a result, it was found that these effects can be reduced by using Hamming.

In this paper, we propose a multi-dimensional opinion formation model for online social networks. Previous studies have not taken into account the “curse of dimensionality” that comes from the higher-dimensional state space used in multi-dimensional opinion formation; the dimensionality is high as opinions with various types of preferences must be handled simultaneously. Conventionally, the interactions between users are limited to static models in which the topics that users discuss are predetermined and do not change. Our proposed method can avoid the above problems with previous studies by introducing low-dimensional subspaces for interacting user pairs by using word distributed representation. We propose a dynamic model that allows users to discuss various topics at each interaction. Simulations of the proposed model show that discussion focused on a particular topic encourages opinion formation.

As IoT devices spread, real-time data analysis and notification are increasingly important. To achieve low latency notifications in edge environments, we have proposed a distributed publish-process-subscribe system that allows multiple edge servers to handle a single topic. In our system, topic allocation to edge servers is formalized as a notification delay optimization problem. In this article, we introduce new metrics that consider the geographic distance of respective pub/sub pairs, or the permissible delay defined by each topic. Using these metrics succeeded in reducing the notification delay to neighboring subscribers and prioritizing topic allocation to meet the delay limit in simulation.

Various applications have been realized by wireless communications. However, evaluation metrics of wireless communications have not aligned with the requirements for individual applications. This causes a problem that increasing the capacity of wireless communication systems does not directly bring to the realization of applications. To solve the problem, this paper proposes Application Proportional Fairness (APF), which is a radio resource allocation technique using requirements for video transmission. APF improves video throughput that considers the requirements for video transmission. Computer simulation shows APF improves the video throughput compared with Proportional Fairness, which is a conventional resource allocation technique.

Achieving high-resolution 2-dimentional (2D) or 3-dimentional (3D) imaging with millimeter-wave radar requires a large number of antenna elements. Synthetic aperture radar (SAR) is commonly used to achieve high-resolution imaging. However, SAR usually requires long observation time due to mechanical scanning. In this study, we have developed a prototype high-resolution millimeter-wave MIMO (Multiple-Input Multiple-Output) radar with non-uniform planar arrays for both transmitter and receiver. We achieved high-resolution 3D imaging by applying virtual array processing to the received data. In this report, we provide the spatial resolution evaluation of the prototype millimeter-wave non-uniform 2D-MIMO radar by experiments.

Towards the Beyond 5G ultra-high-speed wireless system, the “virtualized terminal” system is studied. By connecting a user terminal to multiple peripheral devices over terahertz radio wave (300GHz) which are utilized as virtual antennae communicating with access points using millimeter radio wave, the spatial multiplexing capability is enhanced. In this system, the waveform is required to be robust against both phase noise from a terahertz-wave oscillator and multipath fading over the millimeter-wave since the baseband waveform is common to those frequencies. This work evaluates the effect of those factors and reveals that the effect of phase noise and multipath fading is dominant for OFDM and DFT-s-OFDM, respectively.

In this letter, we propose the variable low-PIM termination composed of a voltage-controlled IM-source, a fixed attenuator, and a linear attenuator. The design method for evaluating PIM-level of the fixed attenuator is presented in order not to limit the variable range of entire termination. It is possible to maintain low-PIM performance in spite of using active voltage-controlled IM-source, whose IM level is extremely high. This termination is used for a dynamic residual noise identification for PIM measurement systems by observing the saturation value for voltage sweep. The validity is confirmed by experiments in 2GHz band.

As various Internet of Things (IoT) devices have been developed, “smart remote control” products are attracting attention. A smart remote control enables controlling multiple conventional household appliances, i.e., controllable by an infrared remote control but incapable of WiFi/Bluetooth connectivity, from mobile devices like smartphones. One of the drawbacks is the difficulty of covering a whole indoor space with one smart remote control since infrared signals could be sheltered by physical obstacles such as walls, pillars, and furniture. Consequently, users are forced to control manually or install multiple smart remote controls. To solve this issue, we propose a drone-based movable smart remote control. The proposed system enables covering a broader space with a single smart remote control and makes it easy to adapt to the change in the position of household appliances. As a proof of concept, we conducted an experiment with actual devices and confirmed that the drone-based smart remote control makes infrared signals reach a wider area than placing a smart remote control on the wall.

In this report, we employ the iterative shrinkage-thresholding algorithm (ISTA), which is one of the sparse reconstruction methods, to solve multidimensional circular convolution problems. The novelties of this work are as follows: the derivation of the subgradient and the Lipschitz constant of a multidimensional deconvolution problem;the construction of a sparse reconstruction algorithm to solve the problem;the evaluation of the qualitative ability of the algorithm, especially computational complexities. The proposed method can not only solve the convolution problems but also achieve low computational complexity.

HAPS (High-Altitude Platform Station) is expected to extend the communication coverage in the beyond 5G era. This paper treats a HAPS backhaul system using 38GHz band. HAPS moves around at stratosphere of about 20km altitude and tries to make beams toward fixed locations on the earth by beamforming. An antenna system on ground stations needs to capture and track HAPS direction with aperture antenna, feeder part and capturing/tracking part. We adopt a method to combine lens antenna and array feeder with mechanically driven gimbal that controls the whole system. Array feeder executes precise tracking within +/-10 degrees of HAPS moving from the antenna radiated direction while mechanically driven gimbal executes tracking over +/-10 degrees. To enhance aperture efficiency and suppress radiation to outside of the lens, this paper proposes wavefront shaping by phased array feeder. Computer simulation shows that our proposed wavefront shaping can enhance antenna gain through aperture efficiency enhancement. Thanks to high and flat gain within the lens radius, it can suppress unnecessary radiation to outside of the lens, and it can widen beam control region with small array feeder.

HAPS (High-Altitude Platform Station) is expected to extend the communication coverage in the era of beyond 5G. This paper treats a HAPS backhaul system using 38GHz band with base station on-board. In this target system, huge number of antenna array elements for beamforming is needed to compensate free space loss in 38GHz band, and full digital beamforming is desired to connect multiple ground stations for feeder and service links at the same time. Real-time phase coherency calibration to directly measure in-band characteristics in 38GHz band is desired for every array antenna element in very low temperature and very low atmospheric pressure at stratosphere to achieve good beamforming performance. It is technically challenging because of huge number of array antenna element. In our previous work, we proposed real-time phase coherency calibration to directly measure in-band characteristics in 38GHz band without interrupting to transmit main signal by superimposing known spread spectrum signal with low power level. However, in addition, delay differences within one sample among antenna elements cause in-band phase slope within wide bandwidth and lead to bad beamforming performance. This paper proposes delay calibration utilizing many common parts of real-time phase coherency calibration in our previous work. Computer simulation shows that “early - late” correlation, whose sample timings are +/-1.0 sample from the center respectively, has precise linearity for calibration signal plus 5G NR signal. Based on the linearity, the amount of delay estimation within one sample is possible by using a look up table.

Inspections of infrastructure facilities using unmanned aerial vehicles (UAVs) are expected to improve operational efficiency. However, the costs of pilot training and travel to infrastructures are the problem. This letter proposes a Migratory UAV system (MiUAV) with multiple ports for automated infrastructure inspection. Multiple ports capable of accommodating and recharging UAVs are placed, and the UAVs can travel autonomously to distant destinations by using these ports. A routing algorithm not using edges to ports with high utilization ratio is also proposed. Computer simulations evaluate that the arrival time can be reduced while maintaining the same average number of hops.

In this paper, we propose a lens that enables array antennas to expand their scanning range and achieve high gain. Millimeter-wave band requires beam scanning with high gain. In addition, the demand for wide-angle scanning is increasing. Therefore, we propose the lens that enables these demands. The scanning angle of the array antenna, which consists of eight patch antennas, is 0° to 41° at 28GHz. The scanning angle is increased by about 1.5 times from 0° to 62° by the proposed lens. The realized gain has also been significantly improved, achieving more than 21dBi at all scan angles.

1-bit analog-to-digital converters (ADCs) have low power consumption and can easily speed up the analog-to-digital conversion and sampling. However, due to their resolution of only 1bit, the nonlinearity between the input with multiple amplitude levels and output is large. With the method of utilizing noise proposed in previous studies, 1-bit ADCs can be linearized to demodulate signals with multi-level amplitude modulation like pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM). In this letter, we construct a receiver circuit using a 1-bit ADC, evaluate its performance, and show its availability through demodulation experiments on 4-PAM signals.

With the accelerating increase in mobile traffic, high energy efficient utilization of millimeter-wave bands is required by further advancement in 5G networks, but low energy efficiency is an issue. The authors have proposed a millimeter-wave network system that combines a 60GHz-WLAN with a mobile network and communication timing control technology, including a wireless communication quality prediction technology. In this paper, we evaluated the dependency of the energy efficiency of communication timing control technology on downloading data.

Through the progress of Digital Twin technology and subsequent realization of Cyber-Physical Systems (CPS), the threat of cyber attacks to those systems is rising. Due to differing requirements in Operational Technology (OT) systems, existing IT security is insufficient to secure CPS. To overcome these challenges, we are developing a highly modular Security Digital Twin (SDT), targeting a wide variety of OT/IoT use-cases and scenarios. Due to its modular design, a naïve implementation of required data collection is highly cost-inefficient; to address this, a data collection abstraction layer for the SDT is proposed, utilizing upper layer data requirements through a unified interface. In a qualitative evaluation, the proposed solution is shown to be cost-effective.

This paper presents a far field estimation method using a phase-less spherical near field data, which overcomes OTA test problems such as measurement cost and time. The method is based on matrix equation of radiation from wire grid model by introducing three techniques such as a wire grid source model, an adjustment of matrix equation, and the optimal sampling method. We confirm that far field estimation is conducted with high accuracy by introducing three new techniques in simulation.

Network functions virtualization (NFV) enables the provisioning of a variety of network services by flexibly deploying virtualized network functions (VNFs) in the network. NFV is closely related to Software Defined Networking (SDN). Routing can be flexibly and dynamically controlled by using network virtualization by SDN. To reduce the effort required to conduct the route optimization task in such virtualized network, we developed a general-purpose and easily executable calculation module in Python, which can automate the generation of the linear programming problem formulation and its implementation as much as possible. We illustrate how we use the module to obtain the optimal routes for individual source-destination node pairs through VNFs and evaluate the effectiveness of the module.

The deployment of Internet of Things (IoT) services in a variety of fields has recently resulted in a rapid rise in the number of connected devices and the traffic volume generated by those devices across networks. In these cases, the problems of the Internet become remarkable. To address these issues, Pub/Sub type communication appears to be a viable option. This communication provides simplified communication sequences and is independent of IP flows. However, it may allow a DDoS attack because the Domain Name System (DNS) is not required and incoming traffic can be admitted without protection. This study proposes the traffic limitation function by Token Bucket Filter on Pub/Sub type communication. This study intends to utilize MQ Telemetry Transport (MQTT) as one of the most popular Pub/Sub type communication. It also reports the development of the prototype system, including the proposal and evaluation using this prototype system.

In this study, we propose a bandwidth assignment scheme designed to measure traffic from 5G systems at optical network units of optical access systems and reflect it in dynamic bandwidth allocation (DBA) at optical line terminals. The proposed algorithm applies a linear regression analysis and an extrapolation approximation to enable a simple implementation. Although DBA is conventionally performed independently in optical access networks, the proposed method links it with the amount of traffic from 5G systems to achieve seamless bandwidth allocation.

Small element spacing is typically employed in phased array antennas to avoid grating lobes. However, the small element spacing limits the element gain. We have proposed a grating lobe reduction technique for a sparse array antenna with radiation pattern reconfigurable elements. It can reduce the grating lobe and improve the gain of the scanning angle. In this paper, we propose an additional grating lobe reduction technique that utilizes reconfigurable radiation patterns and time-domain synthesis. Two radiation patterns are generated in the time-domain; the element pattern is changed whereas the phase of each element remains unchanged. An equivalent low grating lobe pattern can be obtained by synthesizing two patterns based on a simple equation. We apply this method to the measured result of our radiation pattern reconfigurable antenna and its simulation; this results in significant GL reduction.

In this study, digital communication based on antipodal signal transmission is analyzed under skewed alpha-stable noise whose parameters are assumed to be unknown. The receiver is modelled by suboptimal detectors such as soft limiter and sign correlator which determine the transmitted binary information directly from received noisy signals. Degradation effect of the skewness of the impulsive noise on bit error rate is indicated together with the proposed transceiver structure to compensate the effect of skewness by converting the channel noise to exhibit symmetrical behaviour. This operation can be called as noise symmetrization. The proposed approach can be used to overcome the effect of asymmetry in non-Gaussian noise when the probability density function of the channel noise is not known in advance.

High-performance optical communications require a very low bit error rate (BER) down to 10^-15 with soft-decision (SD) forward error correction (FEC). There are several performance metrics based on soft information for systems with SD-FEC, but system budgets are usually described with conventional Q-factor converted from pre-FEC BER, based on hard decision for its convenience and history. In this work, for enhancing the feasibility of the soft information, we propose an approximation method for deriving the Q-factor based on soft information. The proposed method improves the approximation accuracy by more than 20 times compared with the conventional scheme.

Our previous study quantitatively evaluated that digital twin computing was effective for remote control of a small vehicle by a cloud server through simulations. To confirm the effectiveness, we realized an experimental remote control system with digital twin model (DTM) of a small vehicle. Then, we evaluated the vehicle control accuracy on remote path tracking control. This letter shows the results. We confirmed that the DTM improved the control accuracy when there existed one-way transmission delay of 500ms. In addition, we evaluated reduction of the control accuracy due to modeling error between the DTM and the real vehicle.