Most of the previous research on the acquisition of the LED Array transmitter assumes that the onboard receiver approaches the LED transmitter from the car’s front. In this study, we considered a case where the vehicle’s receiver crosses the LED transmitter. This letter modifies the algorithm using spatial-temporal gradient values to detect LED arrays. As a result, we achieved error-free acquisition and successfully communicated up to 9728 [bits] at a vehicle speed of 25 [km/h].

The study presents a “virtual grid system” currently being developed by the authors. The system consists of a power supply, load, and virtual grid hub (VG-Hub) network connecting them. The VG-Hub network must have a large power distribution capability. Therefore, the challenge is to obtain a graph to evaluate the maximum feasible flow when multiple VG-Hubs are connected to a power source or load. In this paper, we propose a method for generating a graph to derive the maximum feasible flow. A quantitative evaluation of the proposed method is presented.

Unmanned aerial vehicles (UAVs) have garnered attention for disaster response because of their flexibility and mobility. In particular, a UAV-aided disaster communication network allows rescue teams to tackle various missions efficiently and flexibly. In this study, we investigate a UAV-aided information collection system in a disaster-affected area. Then, we propose a bandwidth allocation algorithm that improves the fairness among the ground user equipments (UEs) by utilizing their communication histories and location information. Finally, the simulation results demonstrate the considerable validity of the proposed method compared with the straightforward scheme in terms of fairness.

Spectrogram art communications exchange visual messages drawn on sound signals. This study attempts to reduce the crest factor of spectrogram art signals to improve their visibility. This paper describes some experimental results examining our proposed technique that employs clipping and filtering processes.

Recently, multi-point synchronous sensing, which is used for structural health monitoring, is desirable to allocate channels to many sensor tags in a short time. In this study, we have proposed an approach for accelerating channel allocation in the synchronous streaming protocol. A sensor tag uses subcarrier frequency for backscatter communication. The sensor tag requires recursive calibration of the subcarrier frequency due to the instability of the subcarrier frequency oscillator inside the tag’s circuit. We have demonstrated that recursive calibration of subcarrier frequency is a dominant factor in channel allocation time. Furthermore, we found that by combining the reduction of initial calibrations and threshold’s relaxation for terminal judgment. as well as its quantitative evaluation, Experimental evaluation shows that the proposed approach can accelerate channel allocation by up to 43% compared with existing approach.

Unmanned Aerial Vehicles (UAV) are used for many services in various fields. We propose a video transmission relay system in which a fixed-wing UAV is used as a relay station. In order to establish the video transmission link, it is necessary to accurately point the antenna onboard a fixed-wing UAV to both the target ground station and the UAV for photography while making the UAV turn over the designated area. In this study, we propose a new antenna pointing control system, which uses a 2-axis gimbal to greatly reduce the attitude motion of the UAV, and describe evaluation results of the performance of the antenna pointing control system.

Uplink non-orthogonal multiple access (NOMA) has attracted considerable attention as a key technology for beyond 5G/6G telecommunication. However, when adopting the uplink NOMA in multi-cell networks where an uplink signal may reach multiple base stations (BSs), the successive interference cancellation (SIC) process must be completed at every BS, resulting in smaller throughput owing to bottlenecks. To cope with this issue, we propose a novel approach called cooperative-SIC (C-SIC), where SIC processes at different BSs are mutually combined by exploiting signal transfer through backhaul links, which can prevent some signals from experiencing bottlenecks. Through performance comparison with the conventional NOMA, we reveal the significant potential of C-SIC for the uplink NOMA in a multi-cell network.

The key to realizing a smart city is the introduction of flexible services using a large number of IoT devices. Still, most research has focused on services using dedicated devices with limited applications. This research proposes an edge framework and cloud services using general-purpose devices. Specifically, we suggest implementing a new service deployment environment to support independent service installation for the edge processing system. As a prototype, we have implemented a surveillance camera service and measured the execution performance required to provide the service.

We have proposed Information-Centric Networking (ICN) based wireless Sensor Networks (ICSN). ICSN Platform (ICSNP) is an environment to provide multiple Internet of Things (IoT) services using a single sensor network. Excessive requests will cause load congestion at the sink node as the number of concurrently running services increases. To avoid sink node congestion, we propose a cloud-based load distribution model in this paper. As a result, the experimental results show that the load is distributed at the sink node with a reduction of about 45% compared to ICSNP.

On path tracking control of vehicles via the Internet, transmission delay and jitter prevent them from tracking a target path accurately. To improve the control accuracy, it is effective to apply digital twin computing and jitter buffer to the control system. The control system with jitter buffer has an issue of optimizing buffering time. Through simulations by using some realistic transmission delay models, we quantitatively evaluated the control accuracy depending on the buffering time. As a result, we showed that buffered packet rate (BPR) can be a key index to optimize the buffering time according to transmission delay.

The content-centric network (CCN) is a reasonable solution for the application of the Internet-of-Things (IoT) as it enables the efficient transfer of data in IoT services through simplified sequences and reduced traffic via a networked cache. Generally, low latency IoT services are provided by cyclic communication. In this case, however, the latency of the data stored in the cache may result in serious situations. To solve this problem, this study proposes a new cache control mechanism with timed control. This paper also describes the utility of the proposed mechanism on high-reliability services with hot standby redundant systems in addition to low latency services.

Unmanned Aerial Vehicles (UAV) are currently used to provide many kinds of services. A video transmission relay station system using fixed-wing UAV that can fly for a long time are now investigated. In the system, the fixed-wing UAV needs to keep turning in the area accurately as a relay station. To realize that we propose a new turning path control system by both switching the roll angle commands to satisfy the balance of both forces and azimuth control to correct the turning radius deviation. The effectiveness was confirmed by computer simulations assuming an actual flight aircraft.

Today, we can know our outdoor location through global positioning system (GPS). However, it is not easy to estimate our indoor location because satellite signals are difficult to reach. Therefore, we study indoor localization using wireless local area network (LAN). In this work, we attempted to rectify our position estimated using a convolutional neural network (CNN). CNN of indoor localization is based on fingerprinting, and it can only estimate pre-measured coordinates. Simultaneously, CNN is not considered relation by time series. Thus, we suggest using filters like the Kalman filter or particle filter. We can estimate the pre-measured coordinates and inter-coordinates among them using filters. Additionally, we can improve the position estimation accuracy based on the temporal dependency of the user assuming a pedestrian. Our experimental validation shows that the proposed method improves the accuracy. We evaluated and enhanced the position estimation accuracy using CNN with the particle filter. Consequently, we obtained that the mean, median, and max errors decreased 0.27, 0.24, and 4.72 m, respectively, compared with only CNN.

Free-space optics (FSO) is key technology for next-generation communication systems and is used for communications with mobile nodes. In an FSO system, both a client signal and a network operation and management (OAM) channel are required to maintain the system. Acquisition of a new radio wave does not occur during transference over an optical signal; however, misalignment tolerances for the laser beam and receiver aperture decrease and the loss of the OAM signal leads to the network control is lost for a while. Although a photodetector with a larger aperture than that of the client signal improves the tolerance, more devices are required. Therefore, we propose receiving the OAM signal with the quadrant photodiode (QPD), which is generally mounted onto FSO equipment for position detection of laser beams. We determined that the allowable displacement expanded to about three times the usual amount without requiring more optical components.

Amazon EC2 offers surplus instances, called Spot Instances, to consumers at a discounted price. Due to the nature of surplus resources, Spot prices change dynamically according to long-term demand trends. Consumers bid for Spot Instances and are allocated an instance if their bid exceeds the Spot price. On the other hand, if the bidding price falls below the Spot price, the instance is deallocated. Therefore, the setting of the bidding price significantly affects the availability of Spot Instances. In this study, by employing 10 types of bidding prices for Spot Instances and evaluating the usage time, we demonstrate that the availability of Spot Instances depends on the bidding price.

Semiconductor Optical Amplifier (SOA) has attracted attention as a key component in supporting large capacity transmission systems. However, SOAs cause waveform distortion depending on the carrier lifetime, which ranges from picoseconds to nanoseconds, and this distortion degrades the signal quality. Thus, we are investigating suppressing the distortion by controlling gain characters and the carrier time by changing the temperature of SOAs on in-line optical amplifier systems. This paper reports that the distortion is suppressed by setting the temperature of the amplifier lower within the settable range, as a result of evaluating the temperature dependence of the distortion in optical amplification with SOAs theoretically.