One of the crucial challenges of capacitive two-dimensional wireless power transfer (2-D WPT) is the variation in transfer efficiency depending on the RX position. In this paper, we suppress this variation using an inversion of the electric field distribution. First, we analyze the E-field distribution on a comb-like TX electrode for use in capacitive 2-D WPT. The null points are generated on the comb-like electrode, and their positions are identified by deriving the input admittance. Then, we confirm that they are inverted by open-/short-termination switching. Finally, the variation in the power transfer efficiency is suppressed by switching the termination condition.

In order to dramatically reduce the operation work needed for switch replacement, we propose a new operation method that allows connections among arbitrary port pairs. We build and test a system that implements our proposal. The system detects wiring mistakes, and supports replacement with different or same switch models. A wiring experiment shows our proposal can enhance wiring efficiency.

In this study, we propose a method for reducing angle error in position estimation of a moving target. The distance between the transmitting array and target is approximated by two receiving sensors close to the transmitting array. This enables more accurate distance measurement between the receiving sensor and the target.

We have been advancing research on P-VCASS (Pedestrian - Vehicle Collision Avoidance Support System) to avoid collision between pedestrians and vehicles using wireless communications. However, there are only two judgments as to give a warning or not in this system. To match the human senses, we propose a new risk calculation algorithm using fuzzy reasoning to decide the traffic state between vehicles and pedestrians is dangerous or safe, that is collision risk. Through several real experiments, we show that the proposed system can give warning at appropriate timing and properly.

In order for drivers to detect pedestrians at an early stage and prevent traffic accidents, we have been conducting research on P-VCASS (Pedestrian-Vehicle Collision Avoidance Support System). However, this system cannot adapt to cases where pedestrians suddenly run out to the road. In addition, since warnings are given only on the condition that the warning areas overlapped, there is a problem that warnings are given even when the risk of collision is low. To solve these problems, we propose a new method for determining the warning area based on pedestrian behavior. We show the effectiveness of the proposed method through experiments.

This paper presents a modified version of the method of direction estimation (MODE) that can estimate a greater number of sources than the original MODE. It is well-known that M-element arrays can basically estimate up to (M-1) direction of arrivals (DOAs), whereas MODE can only estimate up to M/2 DOAs because of its error-sensitive computation procedure. We propose a modified version of MODE that can estimate up to (M-1) DOAs. The performance of the proposed method was evaluated through computer simulation.

This letter considers optimal adaptive wireless streaming of a scalable coding-based multi-view video (MVV) to multiple users. To improve quality of service (QoS), we propose a transceiver design based on rate splitting and successive interference cancellation (SIC) and optimize the design parameters to maximize the sum encoding rate of the enhanced versions of the requested views. We obtain a KKT point of the non-convex problem using complementary geometric programming (CGP) and successive convex approximation (SCA).

For emergency situations, the network system based on wireless multihop networks such as a mobile ad hoc network (MANET) has been developing to exchange messages among users without the aid of the infrastructure networks. However, many MANET-based systems have been evaluated through the simulation experiments. In this paper, we propose an evaluation framework combining simulator and game engine to simulate MANET-based systems in more realistic environment and present the case study of the evaluation framework.

In Japan, the number of water accidents is approximately 1,300 per year, which is almost constant in recent years. Although divers rescue people in the case of water accidents, there are various obstacles in the sea. Then, divers are always surrounded by a lot of dangers in the rescue activities. Therefore, assuming that identifying the locations of divers supports their rescue operations, we investigate an undersea positioning system using radio waves in the VLF band (10-kHz). According to previous research, radio waves of 10-kHz are theoretically attenuated at 3.5 dB/m, and can be transmitted in the distance of 30 m and more. In addition, a numerical simulation of a three-dimensional undersea position-estimation system has already been reported. In this study, we measured received signals at the real sea and showed the position-estimation results employing the algorithm for an undersea position estimation.

In recent years, the number of people using the bicycle as a means of transportation has increased due to heightened health awareness and environmental protection and COVID-19 pandemic, instead of public such as train and bus. Further, bicycle-related traffic accidents have rapidly increased due to the rapid growth of the food-delivery business with bicycle use, and thus countermeasures are urgently needed. In this paper, we propose a method for a bicycle to detect pedestrian separating from road obstacles such as guard poles and guardrails installed in an urban-narrow bicycle-pedestrian road with the use of frequency modulated continuous wave multi-input multi-output (FMCW-MIMO) radar. In the proposed method, from the distribution of the relative velocity of the detected objects, the objects gathering around the mode of the relative-velocity distribution are judged as the road obstacles, and the objects far from the mode are judged as pedestrian. In an experiment, a bicycle equipped with 77 GHz-band FMCW-MIMO radar, ran at a speed of 2 m/s and a pedestrian walked ahead at a speed of 1 m/s in a narrow bicycle-pedestrian road (school zone) in central Tokyo. Experimental result shows that the pedestrian was detected with about 1m/s-higher relative velocity than around 1.5 m/s of mode relative velocity, where road obstacles group distributed in the range of ±0.5 m/s.