Toward a battery-free wearable system, we have investigated a semi-passive human body communication wherein power and information are transmitted via the human body. In particular, we evaluated the effect of the position of the wearable device, the contact between the body and electrodes, and the contribution of the floor ground (GND) on the transmission between the HBC transceivers, using both subject experiment and numerical simulation. The results confirmed that, depending on the usage conditions, the floor GND deteriorates the transmission characteristics by increasing the electrical field that does not contribute to communication.
This paper discusses a visible light communication (VLC) system using a digital signage and an image sensor. We propose a modulation scheme that data information signals are superimposed on a chroma component of the displayed image of the digital signage by taking advantage of the fact that human eyes are difficult to perceive chroma difference than brightness difference. Especially, the proposed scheme utilizes uniform color space to realize hardly perceivable data signal modulation. We show that the proposed scheme has better performance than the conventional scheme with the non-uniform color space.
Dispersion compensation performance of a waveband-shift-free optical phase conjugator (WBSF-OPC) on multi-span transmission of 20-Gbit/s quadrature phase-shift keying × 3-ch. WDM signals is numerically investigated. Provided that linear distortion owing to chromatic dispersion is considered, the middle channel of the WDM signals is perfectly compensated by WBSF-OPCs. Further, it is shown that the 3-channel WDM signals with a 2.2-THz optical frequency interval can be transmitted via a 640-km transmission fiber owing to the WBSF-OPCs, although their signal qualities degrade owing to residual dispersion.
The deep-learning aided parameter optimization method for the average consensus problem with a complex network has been proposed by Kishida et al., which can significantly accelerate its convergence performance. However, the optimized parameters cannot be applied to the different network topology from the one used in the training. This work proposes a new optimization method constrained by the restriction caused by the network centrality, in which the optimized weighting factors can apply to the different network topology used in the training. Specifically, this work considers five types of network centralities and discusses which centrality is most suitable for the constraint of the proposed method.
This paper proposes a simple method of proportional fairness-based user pairing and power allocation for power-domain NOMA. Compared with the conventional method, the proposed method simplifies the fairness calculation and comparison algorithm, by which the computational complexity reduces significantly. Using computer simulations, we show that its characteristics are identical to those of the conventional method.
Telephone scams called "special scams" have become a major problem, with people being defrauded of nearly 30 billion yen every year in Japan. In this study, we used emotion analysis techniques based on speech analysis to detect whether victims were being deceived by analyzing multiple emotional parameters of victims in a special scam. In the verification, we first clarified the characteristics of the emotions generated in victims by two scam methods. Next, we improved the accuracy of detecting the risk of a victim being deceived by limiting the analysis section.
This paper considers the scenario where the base station and legitimate user are blocked by obstacles and uses an intelligent reflecting surface (IRS) to assist communication. To improve physical layer security, we model the eavesdropper channel as the Rican channel and establish a mathematical model with the goal of minimizing eavesdropper’s rate subject to eavesdropper’s outage probability constraint and legitimate user’s secrecy rate constraint. The resulting problem is very challenging due to the continuous angle range of the eavesdropper’s outage probability constraint and the coupling constraints imposed by the IRS. We first use a Bernstein-Type inequality to transform the continuous constraints into discrete constraints and then propose an alternating algorithm to obtain a sub-optimal solution. Numerical results show that the proposed algorithm can reduce the eavesdropper's communication rate in different cases, which verifies the effectiveness of the proposed algorithm.
When disasters such as earthquakes occur, telephone traffic to the disaster area increases rapidly, to confirm the safety of residents, leading to telephone network congestion. The existing congestion control for telephone networks consists of call regulation control, through which call demands at the subscriber network switches or cellular phones are suppressed. This results in a drastic decrease in the call completion rate. Disaster emergency message dial services do not meet users’ needs either to confirm the safety of people at the disaster area or to speak with them directly. In this paper, we propose a priority control scheme based on call reservations and evaluate its transient characteristics. We also propose an improved scheme to shorten the desired holding time by a fixed rate, when the number of waiting reservation calls exceeds a threshold, which can suppress the divergence of the number of reservations. We evaluated the average waiting time and threshold excess rate characteristics, and confirmed that the proposed scheme can provide stabilization.
With the proliferation of automotive electronic devices, electronic control units are increasingly used to share information within in-vehicle networks. This induces a range of security risks, such as information disclosure, spoofing, and tampering. In this paper, we propose a symmetric-key cipher. The method generates pseudo-random numbers using a chaotic and random neural network, and encrypts and decrypts frame messages of in-vehicle networks based on the symmetric key. We also propose a lightweight ID-based key sharing protocol. We evaluated the key sharing, encryption, and decryption in Controller Area Network.
We propose a new model that can accurately estimate the maximum output electrical power of an optical power supply system with low optical input power. The model includes dependence of open-end voltage on optical input power. The proposed model is compared with a conventional model that ignores the dependency. Our model shows that the maximum output power of an optical power supply significantly decreases as optical input power becomes weak.
We propose a simple channel-allocation method based on tug-of-war (TOW) dynamics, combined with the time scheduling based on nonlinear oscillator synchronization to efficiently use of the space (channel) and time resources in wireless communications. This study demonstrates that synchronization groups, where each node selects a different channel, are non-uniformly distributed in phase space such that every distance between groups is larger than the area of influence. New type of self-organized spatiotemporal patterns can be formed for resource allocation according to channel rewards.
Radio over fiber (RoF) technology, especially intermediate frequency over fiber (IFoF), is attracting much attention as one way to realize high frequency band systems. Such systems require beamforming to attain the desired link budget. Furthermore, highly accurate beamforming permits the adoption of space division multiplexing (SDM), with its greater system capacity. Since beamforming should be controlled by the central station to achieve simple base stations, we proposed a novel remote beamforming scheme with fixed wavelength allocation. This paper introduces experiments conducted on modulated signals to evaluate the characteristics of the scheme’s beamforming gain and signal to interference ratio (SIR).
We have been considering applying discrete wavelet transform (DWT) to heart-rate estimation using 77 GHz band FMCW radar. The detection accuracy and SNR were improved by using an elliptic High-pass filter (HPF) and a High-pass Chebyshev type Ⅱ filter. The High-pass Chebyshev Type Ⅱ filter has less ripple in the passband area, on the other the elliptic HPF has a steeper frequency response compared to the Chebyshev filter. Those filters were used in a pre-processing of DWT for the data acquired from the front and back to reduce respiratory signals and harmonics for comparison. In this letter, the detection accuracy and SNR estimated from the front and back were improved by using two types of filters in DWT pre-processing to decrease respiratory signals.
In recent years, with the widespread use of the Internet, the number of malicious denial-of-service (DoS) attacks on network servers has increased. Malicious traffic reaches the server through multiple routers, which results in heavy load on many links; thus, load suppression of malicious traffic is important. Therefore, we propose a throughput suppression control scheme using multiple communication routes obtained by ant colony optimization (ACO). The ACO algorithm is used to distribute the routing path. The effectiveness of this proposed scheme is confirmed through computer simulations, which shows that the throughput can be adjusted by the selection probability of the longest route and the number of available routes.
Blood pressure (BP) is one of the four main vital signs providing valuable medical information about the cardiovascular activity. In this paper, a new method for estimating systolic and diastolic BP in contact-free for comfort is proposed using a millimeter-wave (MMW) sensor. The MMW sensor is sensitive to small cardiac motion of 1mm or less included in chest surface motion because of the higher frequency and wider bandwidth available, thereby continuous systolic and diastolic BP per heartbeat would be able to be estimated from the time-domain features of unique cardiac motion waveform. Measurement was conducted with the MMW sensor system and the estimated systolic and diastolic BP are also compared with an intermittent BP monitor. As a result, the sensor system is found to estimate systolic and diastolic BP continuously.
The quality of experience (QoE) is an index that evaluates the application-level quality of network services. In adaptive video streaming, stabilization of playback buffer level improves the QoE by avoiding video freezing. Although control-theoretic approaches for stabilizing the buffer level are effective to improve the QoE for a single user, they have not considered user preferences of the QoE or bandwidth allocation for multiple users. This study proposes a dynamic bandwidth allocation method that satisfies the QoE requirements of multiple users with different preferences. Simulation results show that the proposed method increases the number of satisfied users and QoE fairness for prioritized users at the expense of the average QoE for all users.
In order to transmit BS/CS left-handed IF signals used in 8K4K broadcasting, it is necessary to expand the maximum transmission frequency of the FM conversion system from 2.1GHz to 3.2GHz. Our solution is a new FM conversion optical transmitter using a wideband phase modulator and narrow linewidth LD without frequency divider. In addition, we conduct transmission experiments on a prototype transmitter, and clarify that this transmitter offers long-distance transmission over a relay section of 250 km and access section of 10 km, with some bands excluded.
Amazon EC2 provides Spot Instances that may change prices with time. To use them more efficiently, it is necessary to understand the Spot price fluctuations. This study evaluates the Spot price fluctuations with normalized values by On-Demand prices and Historical Volatilities (HVs). Then, using evaluation results, we classify the Instances into five groups. Each group has features of the Spot price fluctuations. We conclude that the groups that have a small fluctuation range are able to bid easily. Therefore, for the groups that have a large fluctuation range, we need more detailed evaluation standards.
We have fabricated a transverse electromagnetic (TEM) horn for radiated immunity tests in close proximity as specified in standard IEC 61000-4-39 and compared its near-field characteristics with those of other typical test antennas such as broadband dipole and double-ridged guide (DRG) horn antennas. Experimental results show that the TEM horn generates a homogeneous field and maintains the field strength without a rapid change near the antenna.
Dedicated hardware and cluster configuration tend to be applied to legacy servers built for infrastructure systems (ex. call control server) to reduce the failure rate. The transition of legacy servers to a virtual environment with common hardware like general information services is being considered, due to the advancement of virtualization and improved performance of common hardware. In conjunction with this, a suitable method is needed for updating applications of servers. This letter suggests methods for updating applications of legacy servers built in a virtual environment.
We evaluate accuracy and reliability in a spatial location identification task (SpLIT) when workers know that their reward scheme is a majority vote (MV) reward scheme before processing SpLIT and when workers do not know that their reward scheme is MV before processing SpLIT. This evaluation was made to clarify how MV affects accuracy and reliability in SpLIT. When MV motivates workers, accuracy and reliability will be different in each condition. The answers of workers who knew that their reward scheme was MV before processing SpLIT had lower accuracy but higher reliability than the answers of workers who did not know this. We concluded that MV influences SpLIT by motivating workers.
In this study, we propose a three-dimensional (3D) imaging method for near-field scatterers that are mutually coupled with an antenna array, such as the support structure or fixtures of the antenna, based on bistatic microwave synthetic aperture imaging. This method can be used to evaluate the effectiveness of the antenna design with irremovable near-field scatterers. Numerical simulation and measurement results show the validity of the proposed imaging scheme.
In this paper, we investigate the path loss characteristics near metal ceiling in 920 MHz band for secure wireless communication of indoor-use equipment such as lighting systems. In order to clarify the propagation mechanism, experiment and electromagnetic simulation are conducted using two models as use cases: a simple model with only a metal ceiling and an office with a metal ceiling.
The results show that the path loss characteristics for vertical polarization near the metal ceiling has a smaller than the free space loss. The path loss characteristic for horizontal polarization, however, changes significantly depending on the floor condition.
The authors proposed Coherently Combining Sparse-Multiband Processing (CCSMP) , which coherently combines signals of the separated multi-band obtained by the stepped multiple frequency method . CCSMP implements the Recursive Signal Subtraction Frequency Estimation Method , which iteratively estimates the range of each target while separating the signals one by one from the observed signals from multiple targets obtained in each band. Hence, CCSMP can improve the range estimation performance in multiple-target situations where the main lobes of the targets overlap and interfere with each other. In this letter, we derive the Cramér-Rao Lower Bound (CRB) for the target range estimation by combining the separated multi-band signals, and the performance of CCSMP is discussed by comparing the derived CRB values with statistical evaluations by simulation.
This letter proposes a signal-to-Noise Ratio (SNR) based spreading factor adaptation for orthogonal frequency division multiple interleave division multiple access (OFDM-IDMA) incorporated with parallel interference cancellation (PIC) on visible light communication (VLC) systems. Orthogonal variable spread factor (OVSF) code is an effective solution to eliminate multiple access interference (MAI) in exchange for spectral resource consumption. Channel ranking based spreading factor optimization can maximize the system throughput performance. The major contribution of this letter is to achieve its adaptive allocation according to the estimated value of SNR. The computer simulation results clarify its effectiveness.
Zero Trust (ZT) Model  is a security approach to prevent malicious activities assuming the presence of an attacker in the environment. The fine-grained access control should be executed on ZT in accordance with various information, which requires a large complexity of access control policy due to the large patterns of attributes . Our focus is the low-complexity of policy management. We propose a method to reduce and evaluate the complexity of policies for network access control. This letter discloses the optimal grouping algorithm to reduce the complexity, and shows the higher performance in comparison with the existing methods.
In the hitless redundancy switching system, the selector of the redundancy switching device is controlled on the basis of the control information such as the connection status of the path to transmit frames, end-to-end delay of the path, and jitter. However, the control signal transmitted superimposed on the main signal channel in the hitless redundancy switching system is not highly confidential because all the information is transmitted superimposed on the two paths. In our previous study, we modulated the transmission timing of frames in the main signal channel by assigning “0” and “1” codes to the two paths in the hitless redundancy switching system. In this paper, we propose a method to efficiently modulate sub-signal channels in a hitless redundancy switching system to improve the communication bandwidth, and evaluate its effectiveness in a numerical simulation.
This paper presents a tool for the visual inspection of the small interacting objects (IOs) for the microwave propagation in urban environment, by utilizing 3D point cloud data of townscape and double directional channel sounding results. It is demonstrated that the tool can effectively visualize the location of the IOs.
To increase symbol rate and security at the physical layer for uplink optical camera communication from a smartphone screen to indoor camera at a distance of 3.5 m, space division multiplexing by adaptive thresholding is proposed and experimentally verified. The adaptive thresholding sets the optimal threshold for a center cell with each outer 8-cell pattern in 3x3 cells. Although the outer 8-cell pattern is estimated from conventional fixed threshold, the pattern helps to determine the threshold adaptively. The adaptive thresholding achieved 216.75 and 168.75 kilo symbol per second using 85x85 and 75x75 cells at luminance of 255 and 95, respectively.
HAPS (High-Altitude Platform Station) is expected to extend the communication coverage in the era of beyond 5G. HAPS moves around a circle at 20 km altitude and tries to make beams fixed on the earth by beamforming. However, if HAPS uses polarization like satellite communication, there is a possibility that received SNR (Signal to Noise power Ratio) degrades because the fluctuation of HAPS aircraft could generate polarization mismatch between HAPS and earth stations. This paper reports experimental results using on-air polarization signal from a satellite with artificial polarization offset to evaluate feasibility of polarization utilization in HAPS. The results show SNR loss due to the polarization offset can be confined within 0.5dB and good tracking performance thanks to the polarization diversity by MMSE (Minimum Mean Square Error) receiver.
In this letter, we have developed a novel and simple feature extraction that exploits the characteristics of I/Q signals received from ZigBee devices to represent RF circuit impairments such as the frequency offset and I/Q imbalance. Experiments have been carried out to evaluate the identification performance in several scenarios: line-of-sight (LOS) and non line-of-sight (NLOS) environments, varying distance between the transmitter and receiver. The results show that our method can identify twelve ZigBee devices with high accuracy. In addition, it is revealed that some features are sensitive to environmental change during the training and test phases.
Elastic optical networks (EONs) have attracted attention as a means of accommodating the rapidly increasing traffic in core networks. In EONs, the RMSA algorithm is implemented to flexibly allocate resources to optical paths. However, the application of EONs is limited because of the fragmentation of spectrum resources, which hinders further allocation of resources to new optical paths. Subsequently, the Min-RDDR method has been proposed to allocate resources for advance reservation requests. It defined an evaluation formula for calculating a metric to suppress fragmentation. Herein, we modified the Min-RDDR method and proposed a spectrum allocation method to further suppress fragmentation, wherein resources were considered not only within links but also between adjacent links. The simulation results confirmed that the proposed method causes a 47% reduction of request blocking probability, verifying its effectiveness toward fragmentation suppression.
When divers are doing rescue operations in the sea, they are in a hazardous environment. If it becomes possible to know their positions accurately, rescue operations can be carried out more safely and reliably. We propose a subsea position estimation system using received signal strength (RSS) of electromagnetic waves to assist rescue operations by locating divers in the sea. In this report, as a basic study for introducing machine learning into the subsea position estimation system, four supervised machine learning models were used for undersea position estimation and each model is compared. The best model is Multi-Layer Perceptron (MLP), and it is confirmed that there is no problem in real-time computation time for all models.
This letter proposes a defective judgment method for an automotive wire harness by a deep learning technique based on a convolutional neural network (CNN). In the proposed method, the CNN is used to find the relationship between the cross-sectional shape of the wire harness and a common mode current. We consider several patterns of the inputs and outputs of the CNN and discuss which input-output pattern is adequate for the judgment.
In this letter, we propose clipping and clip-noise compensation techniques that improve the self-interference (SI) cancellation and bit error rate (BER) performance of an in-band full-duplex transceiver under power amplifier (PA) nonlinearities. These techniques can be used to improve performance without increasing the order of the parallel Hammerstein canceller. We introduce a clipping at the transmitter that suppresses nonlinear amplification of a PA to improve the SI cancellation performance. Furthermore, clip-noise compensation is presented at the receiver that prevents degradation of the BER performance caused by clipping.
In this paper, we discuss a visible light communication (VLC) system using a digital signage and an image sensor. We focus on the demodulation part and propose a method that demodulates transmitted data signals from received images of the image sensor using machine learning. The performance of the proposed machine learning-based demodulation method is evaluated for various datasets that simulate noise, blurring, and misalignment that may occur in received images.
A base station scanner that can evaluate MIMO antennas for LTE downlink signaling has been proposed. In this system, all signal processing is done offline, so analysis is significantly delayed. Further, only FDD-LTE is supported. This report details a coherent base station scanner that offers real-time demodulation of not only FDD but also TDD. Experiments on LTE signals using both duplex modes confirm that the developed scanner offers excellent performance and reduced post analysis times.
In CP(Cyclic Prefix)-Free OFDM systems, an occurrence of IBI(Inter-Block-Interference) is inevitable due to the loss of CP. Since it deteriorates the system performance, a GSC(Generalized Sidelobe Canceller)-based equalizer for SIMO(MIMO)-OFDM systems have been proposed. In the equalizer, a set of basis of null space of channel matrix has to be found. In this letter, we propose a GSC equalizer using QR decomposition for CP-Free MIMO-OFDM systems, where the reduced complexity maximum likelihood detection by QR M-algorithm(QRM-MLD) can be applied after the equalization. By computer simulations, we show the BER performance can be improved as compared to the conventional GSC equalizer with the V-BLAST detection.
This paper evaluates QoS of the next-generation in-vehicle Ethernet-based networks in combination with the following three controls defined in IEEE 802.1TSN by simulation. The authors target Strict Priority Queueing (SPQ), Frame Replication and Elimination for Reliability (FRER) and Frame Preemption (FP). The experimental results indicate the followings. First, traffic of the highest priority should be applied SPQ to guarantee its QoS. Second, it is necessary to adopt an appropriate combination of QoS control for traffics of other priority in order to prevent them from deteriorating too much.
This paper reports a method for interconnecting local 5G networks and existing networks. Since the two networks are often separated, there is a demand to interconnect the two networks. However, operation gaps such as addressing policy and security policy between the two networks will not allow one to interconnect. To fill the gaps, an interconnection method consists of inter-layer address translation and tunneling in existing networks is proposed and implemented. The evaluation result using an actual local 5G network and an actual corporate intranet revealed that the proposed method works properly.