This letter proposes the symmetrical small trapezoid dipole antenna for lower distorted radiation patterns. For broadband communication, a non-uniform planar antenna has been proposed; however, the radiation pattern at the high-frequency band is distorted. When the cell area is designed, it becomes difficult to design the directivity due to distortion of the radiation pattern. To overcome this issue, this letter proposes the symmetrical small trapezoid dipole antenna, which has the same dimension conductors at the opposite angle. The electromagnetic field simulation results evaluate that the proposed antenna has a small deviation of the radiation patterns at the high-frequency band.

A radial line slot antenna (RLSA) was proposed as a candidate for short-range transmission. The introduction of the dog-bone cross-slot feed improves the field distribution of the rotating mode excited in the radial waveguide. The method of the dog-bone cross-slot based on eigenmode analysis is presented to radiate the rotating mode at the design frequency. The short-range transmission improvement between two antennas is demonstrated experimentally.

This paper presents the far field estimation using only the amplitude data on a single hemispherical surface of monopole antennas on finite sized ground plane. We propose to use the initial phase information in the Phase Retrieval (PR) method to reconstruct the phase information. The initial phase information is given by the information of measured amplitude and feeding position. By introducing this, the far field estimation can be achieved in high accuracy. This paper shows our proposed algorithm and verify it by the simulation and measurement.

This manuscript discusses special assignments of the phase differences between adjacent output ports per input ports providing interesting configurations of generalized one-dimensional parallel switching matrices out of all the permutations of the assignments possible. This includes in particular assignments leading to the configuration based on two N/2-beam Nolen matrices in parallel in a matrix with an even number N of beams and to the configurations using only four values of phase shift, 0, 0.5π, π and -0.5π, for all the phase shifters in a matrix with an odd number of beams.

Recently, signal source separation technique using independent component analysis (ICA) have been attracting attention in the field of wireless communications. Furthermore, TDL-ICA, which combined a tapped delay line with ICA to increase the number of separatable signals with fewer elements, has been proposed. However, the application to the digital modulation has not been considered enough. In this paper, it is shown that the TDL-ICA can separate the overlapped digital modulated signals in the frequency domain by setting the appropriate parameters of the TDL, and the relationship between the number of taps of the TDL and the separation performance is clarified.

Massive MIMO is a promising wireless communication technology that realizes large capacity. However, it has the problem that circuit mounting becomes difficult due to the narrow antenna spacing and increased loss and phase deviation of connectors and wiring, especially in the millimeter-wave band. To solve these problems, we propose a novel Massive MIMO device configuration using a stacked Butler matrix and a staircase array antenna. From the simulation results, the radiation patterns are the same between the proposed and conventional antenna at stairs up to about 0.1λ.

In this paper, a generalized equivalent circuit model that can accurately describe the reflection characteristic for normal and TE oblique incidence is proposed based on the normal incidence model proposed in [1]. This TE model simply consists of a transmission line and a resistor in addition to the model of normal incidence, where the transmission line corresponds to the phase delay between adjacent cells and the resistor corresponds to the power coupling to the grating lobes. Decent agreement was achieved between the simulated reflection responses and those from the proposed equivalent circuit model up to an incident angle of 50^° from 7 to 13GHz. Empirical formulae for the RLC values used in the proposed circuit model are also provided.

In this paper, a broadband tunable power divider (TPD), whose power division ratio (PDR) can be theoretically tuned from -∞ to +∞, is proposed. The new design is based on a Wilkinson power divider, a branch line coupler, and a new combination of phase reconfigurable synthesized transmission lines (PRSTLs) that comprises varactor diodes as the phase shifters (PSs). The operating principles and design equations will be provided with thorough discussion. For proof-of-concept demonstration, a prototype was designed at 2.4GHz. The performance in the measurement is summarized as follows: the operating bandwidth = 25% (2.1GHz-2.7GHz), very wide PDR tuning range of ±29dB, maximum insertion loss = 1.6dB, and switchable output phase of 0° or 180°.

This paper evaluates transmission performance depending on the installation method of LED lighting and photodetectors in LED visible light wireless communication with spatially parallel signal transmission by computer simulations. The evaluation results clarify that the optimal combination of the distance between LED lighting and the angle between photodetectors can maximize the number of parallel signal sequences.

The hidden terminal problem in wireless local area networks (WLANs) causes packet collisions and thus a significant drop in throughput. To overcome the quality deterioration, adaptive modulation and coding selects the low modulation and coding scheme (MCS), and its protocol is a data rate shift algorithm (DRSA) in WLAN. However, for quality deterioration caused by packet collisions, additional packet collisions occur because of an enlarging packet length composed of the low MCS. This study describes the performance degradation of WLANs due to the hidden terminal problem for the DRSA, and we show that the performance can be improved by designating a higher MCS using an access point. From the experimental evaluation of a WLAN, we confirm the improvement of the throughput due to the prevention of packet collision because the designated higher MCS shortens the packet length.

In MQTT for IoT communication, multiple brokers should be deployed to accommodate a number of end devices. However, routing mechanisms among these brokers have yet to be specified. In this paper, a new routing mechanism for this purpose is proposed. This mechanism is aimed at layer 2 base control. It provides co-operations with MQTT and the Spanning Tree Protocol and invokes a traffic reduction and simplified transfer by an independent IP flow. In this paper, the detailed communication sequences are proposed, and the reasonability of the proposed mechanism based on a performance evaluation using prototyping is highlighted.

This study proposes a noncontact, accurate sensing method for heartbeat R-R intervals and heart rate variability from the video of a target person’s face. The proposed method comprises three steps: (1) automatic face recognition and tracking, (2) the detection of skin-tone pixels in the face region, and (3) heart rate estimation using the topology algorithm. We applied the proposed method to facial video recordings of 55 participants and evaluated its accuracy. The results demonstrate that the root-mean-square error in estimating the heart rate variability was 2.7 ms using the proposed method, demonstrating the effectiveness of the proposed approach.

In this paper, in order to establish the storage batch signal processing technology on the network, we investigate the signal separation method using feature extraction by Short-time Fourier transform to separate the IoT / M2M terminal signal that collided or interfered which cannot be realized by the conventional receivers. We evaluated the signal separation performance when two signals of BPSK, QPSK, 8PSK, and 16QAM modulation signals interfere with each other, and clarified the effectiveness of our method. Furthermore, we quantitatively evaluated the separation performance for each combination of modulation systems and referred to the way of selecting the desired signal in the separation by this method.

Crowdsourcing is an effective way to generate subtitles for videos with multiple speakers. This study proposes and evaluates a word-by-word majority voting method as a new approach to creating high-accuracy subtitles from multiple types of subtitles created by multiple workers in crowdsourcing. In the word-by-word majority voting method, the accuracies of the subtitles themselves remarkably vary between high and low, since even a slight difference in word order, for example, can significantly reduce incorrect generation. This remarkable difference shows that the proposed method has potential to generate appropriate subtitles for videos having multiple speakers.

In recent years, due to the development of radar technology, the research of the remote heart rate measurement system has matured. However, most subjects in previous studies were at a stationary state during the experiment. In contrast to traditional radar-based heart rate measurement methods, this article proposed a novel trackable measurement method. We consider the FMCW radar module placed on a rotary stand with a stepping motor. The subject’s position is calculated by radar signal processing to drive the corresponding rotation of the stand. The results of the simulations prove the validity of the proposed solution.

Link addition is a promising approach for improving the robustness of networks against targeted attacks. Existing link addition methods do not assume any knowledge about an attacker’s strategy. This paper examines the benefits that knowledge about the attacker’s strategy has for link addition. We propose a link addition method that assumes the attacker’s strategy. We evaluate the effectiveness of the proposed method both when the assumed strategy and the actual attacker’s strategy are the same and when they are different. Our experimental results show that knowing an attacker’s strategy has benefits for improving the robustness of scale-free networks.

The impact of multiple antennas on a hybrid multiple access scheme was investigated considering the desired user traffic volume as well as channel conditions. In the proposed approach, by using both non-orthogonal multiple access (NOMA) and orthogonal multiple access (OMA) in the same bandwidth, a resource pattern combined with different user requirements is introduced to effectively meet the demands of diversified wireless services beyond 5G. In this study, maximum ratio transmission (MRT) is applied to NOMA and OMA, considering that recent base stations (BSs) are equipped with multiple antennas. Thus, the spatial diversity gain is considered when calculating the actual throughput used for choosing the best resource pattern. The effectiveness of the proposed scheme is demonstrated through computer simulations by considering the antenna configuration under diversified user traffic for enhanced mobile broadband (eMBB) and ultra-reliable and low-latency communications (URLLC).

Space Time Adaptive Processing (STAP) has been proposed to suppress the clutter in airborne radars. In real situation, the sample covariance matrix is used to estimate the optimum weight to suppress the clutter, resulting its improved Signal to Interference plus Noise Ratio (SINR). The weight is estimated by an eigenvector set of the covariance matrix of received signals. Conventionally, all of the eigenvectors are included in the weight, assuming all eigenvectors belong to the signal subspace, which means the eigenvectors derive from the clutter. However, when the weight includes some eigenvectors belonging to the noise subspace, the resultant SINR is degraded, because the components other than the clutter are subtracted from the received signals. Therefore, in order to avoid this degradation in STAP, we have proposed the new weight estimation method which selects eigenvectors included in the weight based on Akaike Information Criteria (AIC). The evaluation for our proposed method was carried out using the data measured at the Sea of Japan by an airborne side-looking radar, which include a ship as a target and sea clutters in real environment. The results show that the proposed method which limits eigenvectors included in the weight achieves better SINRs than the conventional method.

This study investigated the performance of radar-based detection methods for sleep apnea, by comparing a machine learning approach and a non-machine learning approach. We applied a 79-GHz millimeter-wave multiple-input and multiple-output array radar with 12 virtual array elements and performed radar and polysomnography measurements simultaneously to monitor a sleep apnea patient during overnight inspection in a hospital setting. Both radar-based methods successfully estimated the number of apnea events per hour of sleep, with root-mean-square error values of 4.1 and 4.0, indicating that the two methods had comparable accuracy in the radar-based noncontact monitoring of a sleep apnea patient.