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We present results of a statistical study of a possible influence of the seismic activity on the intensity of very low frequency (VLF) transmitter signals observed by a low-altitude satellite. Electric field measurements performed by the Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) satellite during its entire mission spanning almost 6.5 years were used. Among various VLF transmitter signals detected, we focused particularly on the NWC and JJI transmitters, because of their favorable locations close to seismically active areas. We evaluate the intensities of the detected transmitter signals at the times when they passed in the vicinity of an imminent earthquake during the propagation in the Earth-ionosphere waveguide, and we statistically compare them with the intensities measured at the times when there was no earthquake present. Only earthquakes with magnitudes larger than or equal to 5 and depths shallower than or equal to 40 km were considered in the analysis. Moreover, due to the low intensity of detected transmitter signals during the day, the analysis is limited exclusively to the nightside. Although the amount of relevant data is rather low, the obtained results show that there is a decrease of the detected intensity shortly (0–3 hours) after the times of the main shocks observed both for the NWC and JJI transmitter signals. The effect is spatially rather limited, observed when the signal passes within about 4 degrees from the earthquake epicenter. The intensity decrease appears to be consistent with acoustic-gravity waves propagating from the earthquake region and influencing the bottom of the ionosphere. [ABSTRACT FROM AUTHOR]

Body channel communications (BCCs) were investigated, to enhance requirements for low power and high-reconfiguration power within permitting technology of wireless measurement systems for wireless communication applications. Standard options for BCC are targeted totally toward channel modeling with a potency measuring technique, a transmission technique, and a wireless transceiver style. Wireless digital transmission designed as a personalized methodology meant for the body channel offers significantly the necessary pathway to implement versatile and low-power BCC systems. In addition to the developing level of wearable communication protocol and applications, there is also an increasing reliability on a flexible BCC transmitter which helps to reconfigure power and meet power reduction conditions. This paper proposes an ultra-low-power, Hamming encoding-based, and body channel communication receiver for wireless body area network applications. Proposed BCC transmitter uses a channel of 1–100 MHz frequency to enhance the transmitter frequency and time domain properties. Hamming-based BCC transmitter makes use of a two-stage low-power analog processing circuit and digital information restoration circuit. Analog processing circuit consists of a dual op-amp adjustable preamplifier. Proposed BCC transceiver has higher data reliability because of the orthogonal characteristic of the Hamming codes. Moreover, the proposed Hamming code concatenated method strengthens the jitter tolerance and improves the code rate. Proposed BCC transceiver was verified using a field-programmable gate array board. Proposed data transceiver achieves a data speed rate of 20 Mbps. Bit error reduction values achieved were < 10−6 and < 10−5 at 60 Mbps and 100 Mbps, respectively. It uses a primary space of 0.14 mm × 0.2 mm when it is functioning below a 15 Mb/s data rate (low-power) condition. BCC transmitter utilizes the power of only 1.0 mW. [ABSTRACT FROM AUTHOR]

A novel distributed power allocation scheme for analog network coding (ANC) in high signal-to-noise ratio (SNR) is proposed by using statistical channel knowledge at the transmitters only. The scheme considers nonorthogonal amplified-and- forward (NAF) protocol. In the derivation, a general Rayleigh fading multiple hop network is accurately approximated by a simpler two hop network, and the closed-formed expression for the outage probability of the simplified two hop network is obtained and optimized with respect to the power allocation. Numerical results show that the derived power allocation scheme has significant performance gain over the equal power scheme. In some cases, it approaches the optimal scheme. [ABSTRACT FROM AUTHOR]

The emergence of the semi-quantum concept makes it possible for people without quantum capabilities to communicate securely. An offline arbitrated semi-quantum signature scheme based on four-particle cluster states is put forward, in which two classical parties could complete the signature with the assistance of the quantum arbitrator. Different from the typical arbitrated quantum signature schemes, the arbitrator in our protocol acts as a relay station for delivering signature and no longer intervenes in the direct authentication of signature, leaving the signature receiver with full authentication rights. There is no additional direct communication between the signer and the receiver, which reduces the complexity of transmission. Besides, security analysis manifests that the proposed semi-quantum signature scheme is secure. [ABSTRACT FROM AUTHOR]

The paper presents the results of the reconstruction of the effective height h' and the slope of the profile β of the electron concentration in the D layer of the ionosphere during X-ray flares of M- and X-classes at the midlatitudes. The reconstruction was carried out with data from measurements at the observatory of the Institute of Geospheres Dynamics of the Russian Academy of Sciences at the Mikhnevo observatory of amplitudes and the phases of signals from VLF transmitters GQD (19.6 kHz) and GBZ (22.1 kHz) that propagate along one mid-latitude path. Based on the calculations, the empirical dependencies of the parameters h' and β on the flare energy according to the X-ray flux measurements on the GOES satellite are in the range 0.05–0.4 nm. Criteria are proposed for the selection of solar flares for the verification of theoretical computational models. [ABSTRACT FROM AUTHOR]

This paper presents a fixed point design and implementation of a low-complexity high-throughput digital predistorter (DPD) on FPGA. Based on the memory polynomial model, a parallel structure is proposed for the implementation of the DPD and the effects of the fixed-point implementation on the performance are analyzed employing fidelity metrics such as modulation error ratio and adjacent channel power ratio. According to this analysis, an optimized fixed-point hardware implementation of the proposed DPD with proper word lengths is presented. Besides some simplifications to the proposed structure, a number of effective modifications are proposed for clock enhancement. The improved clock frequency of the proposed implementation makes it a fit choice for application over communication signals with considerable bandwidth. The required hardware and the maximum clock rate corresponding to these modifications are evaluated and reported. The performance of the proposed DPD in linearization of an actual power amplifier (PA) is also experimentally evaluated, through application of an appropriate hardware setup. Experimental results show about 11 dB ACPR improvement in the PA output for a 128-QAM test signal. The moderate hardware resource requirement of the proposed high-throughput DPD is also verified through comparison with some remarkable works in the same area. [ABSTRACT FROM AUTHOR]

Using a change of basis in the algebra of symmetric functions, we compute the moments of the Hermitian Jacobi process. After a careful arrangement of terms and the evaluation of the determinant of an "almost upper-triangular" matrix, we end up with a moment formula which is considerably simpler than the one derived in [8]. As an application, we propose the Hermitian Jacobi process as a dynamical model for an optical fiber MIMO channel and compute its Shannon capacity in the case of a low-power transmitter. Moreover, when the size of the Hermitian Jacobi process is larger than the moment order, our moment formula can be written as a linear combination of balanced terminating -series evaluated at unit argument. [ABSTRACT FROM AUTHOR]

In this paper, we consider an energy harvesting device-to-device (D2D) communication system, where D2D transmitter can use mode A to directly communicate with D2D receiver or use mode B as a relay to assist cellular communication while communicating with D2D receiver by adopting non-orthogonal multiple access technology. Firstly, the outage probability expression in two modes is derived, and the communication mode is determined according to outage performance. Then, assuming that the full system information is available, the channel allocation and relay selection are completed by Kuhn–Munkres algorithm, and the offline power allocation of D2D users is realized by reinforcement learning. Next, the offline optimization results are taken as the training data set to train the neural network, and the optimal model of the transmission power is obtained. Considering the transmission power constraint, the online power allocation optimization algorithm is further proposed. Numerical results demonstrate the accuracy of derived outage probability, and the proposed resource allocation algorithm can improve the performance of hybrid system. [ABSTRACT FROM AUTHOR]

Applications of digital micromirror device for lidar are overviewed. A large Lagrange invariant value makes DMD as one of the attractive beam steering transmitter and receiver solutions for a time-of-flight lidar, especially with its an extended angular throw by synchronized pulsed laser illumination. [ABSTRACT FROM AUTHOR]

A communication scenario is described involving a series of events triggered by a transmitter and observed by a receiver experiencing relativistic time dilation. The message selected by the transmitter is assumed to be encoded in the events' timings and is required to be perfectly recovered by the receiver, regardless of the difference in clock rates in the two frames of reference. It is shown that the largest proportion of the space of all k-event signals that can be selected as a code ensuring error-free information transfer in this setting equals ζ(k)−1, where ζ is the Riemann zeta function. [ABSTRACT FROM AUTHOR]

The distribution of NO and H2S in the arterial vessels of the anterior abdominal wall after implantation of a polypropylene mesh was studied by immunohistochemical methods at different stages of healing of the surgical wound in mature male Wistar rats. The presence of enzymes of NO and H2S synthesis in the wall of arterial vessels of the soft tissues of the anterior abdominal wall has been established. It has been shown that endothelial NO synthase is localized exclusively in the endothelium of both large and small vessels. Cystathionine γ lyase in small vessels is located only in the endothelial lining, whereas in large arteries and vessels of medium caliber, it is located in the endothelium and in myocytes. Inducible NO synthase appears in the artery wall only in animals with implanted polypropylene mesh by day 5 of the postoperative period, reaching the maximum by day 10. The content and localization of cystathionine γ lyase in the vascular wall of sham-operated and experimental rats did not much differ from the control values. [ABSTRACT FROM AUTHOR]

In a cellular network (CN), cellular users (CUs) located nearby machine type communications (MTC) devices (MTC-Ds) may act as uplink gateways to relay data to the base station (BS). We consider non-orthogonal multiple access (NOMA) and successive interference cancellation (SIC) at the receiver to increase the number of connected devices and the spectrum efficiency. Both underlay and overlay spectrum access modes (SAMs) are considered. We introduce a dynamic user grouping (UG) concept as a practical constraint for SIC, in order to decrease the receiver complexity. Moreover, SIC constraints are introduced based on a minimum signal-to-noise-plus-interference ratio (SINR) at the receiver. We formulate a joint dynamic UG, power allocation, and resource block (RB) assignment problem, aiming at maximizing the total sum-rate of both CUs and MTC-Ds. We transform the obtained non-convex mixed-integer programming problem into a convex problem by using a quadratic fractional programming (FP). A heuristic method is also proposed to reduce complexity. Simulation results demonstrate that the proposed solution outperforms the conventional CN (C-CN) method and the results of the proposed optimization methods are close to optimal solution obtained by the exhaustive search (ES) algorithm in terms of total average sum-rate and network connectivity, while requiring less transmit power. The heuristic method decrease the computational complexity of the FP method at the expense of a small reduction in spectrum efficiency. [ABSTRACT FROM AUTHOR]

In 5G networks, a massive number of connections of high data rate services, e.g., video streaming services, certainly make the networks deteriorated because of extreme traffic congestion at the backhaul links of macro base stations (MBSs). Although ultra-dense networks (UDNs) have been considered as a promising architecture to stimulate the 5G networks, the congestion problem hampers the UDNs to provide mobile users (MUs), i.e., represented by device-to-device (D2D) pairs and shared downlink resource users (SUs), with high video delivery capacity. In this paper, we propose a social-aware caching and resource sharing (SCS) strategy for video streaming services in 5G UDNs. Particularly, we formulate the SCS problem by taking into account the social relationship of each D2D pair, the available storage of femtocell base stations (FBSs) and transmitters (TXs) of D2D pairs, the target signal to interference plus noise ratio (SINR) of SUs, and the popularity of videos. The SCS problem is then solved for 1) optimal number of caching copies of each video and optimal caching placements in the FBSs and 2) optimal resource sharing allocation between the SUs and the D2D pairs for D2D communications. This way, the workload at the backhaul links of the MBSs can be reduced. Simultaneously, an arbitrary MU can retrieve the videos alternately from the MBSs, FBSs, and TXs at high cache-hit ratio and maximum delivery capacity. Simulation results are analyzed to show the benefits of the proposed SCS strategy compared to other conventional schemes. [ABSTRACT FROM AUTHOR]

To balance the output stability and maximum efficiency of a system, an efficiency optimization method based on adaptive frequency control is proposed. In this paper, load transmission is carried out using a DC–DC converter at the receiving end. When the load changes, controlling the rectified output voltage is carried out to realize the maximum efficiency point tracking. Meanwhile, the duty cycle of the rear stage DC–DC converter is changed to keep the output voltage constant. The sampled rectified voltage is compared with the estimated value and the resulting error data are sent to the system transmitter through ASK modulation wireless communication. Then the transmitter demodulation communication information through PID algorithm control is used to achieve the frequency of the adaptive adjustment. The feasibility of the proposed method has been verified by the simulation and experimental results. When the output voltage is 5 V, the constant voltage accuracy is within ± 1%, the maximum efficiency is up to 79.2%, and the dynamic response time is only 160 ms. [ABSTRACT FROM AUTHOR]

This paper presents a new on–off keying modulation circuit for a Class-E power transmitter used in high-data-rate wireless links used for powering medical implants. A circuit technique is proposed to keep the current of the RF choke of the power transmitter constant, while the transmitter turns on and off. This allows the transmitter to quickly turn on and off. To prove the feasibility of the proposed circuit, a wireless power and data transfer link based on the proposed circuit was designed and implemented. At a carrier frequency of 2.5 MHz, the measured data rate was 625 kbps, which means that a data-rate-to-carrier-frequency ratio of 25% has been achieved. The power transfer efficiency and the power delivered to the load, with a 2.37-μH transmitter coil and a 1.4-μH receiver coil separated by a 1.0-cm air gap, were measured to be 21% and 80 mW, respectively. The measured bit error rate of the link was less than 10−5. [ABSTRACT FROM AUTHOR]

In this paper, we derive the optimal packet length for automatic repeat request (ARQ) protocols and hybrid ARQ I (HARQ I) protocols with chase combining. Chase combining consists of a maximum ratio combination of received packets. The average signal-to-noise ratio is measured at the receiver and sent back to the transmitter to adapt packet length. The study is valid for any M-QAM (quadrature amplitude modulation). HARQ I protocol uses a convolutional encoder. Simulation results have shown that the proposed adaptive link layer protocol using optimal packet length allows 0.7–4 dB gains with respect to fixed packet length. [ABSTRACT FROM AUTHOR]

Escherichia coli strains are part of the normal biota of humans and animals; however, several clinical reports have implicated E. coli as the etiological agent of diarrhea in humans and companion animals. Thus, the aim of the present study was to know if companion dogs in the city of San Luis Potosi are colonized with virulent potentially harmful E. coli strains. Rectal swabs from 30 dogs, 13 with and 17 without diarrhea were analyzed. Phylogenetic and virulence genes analysis was performed to the E. coli isolates. Additionally, the Kirby-Bauer test was used to analyze the sensitivity to 32 different antimicrobials from 14 families. Eighty-five isolates were identified as E. coli and detected in 97% of healthy and diarrheic dog samples. E. coli isolates from healthy dogs carried several virulence genes, in contrast with those from diarrheic animals that presented only eaeA. In healthy dogs, phylogenetic analysis showed that 57% and 43% of E. coli isolates belonged to commensal (A and B1) and virulent (B2 and D) groups respectively. Meanwhile, diarrheic dogs showed that 69% of the isolates were identified as virulent B2 and D phylogroups. Moreover, E. coli resistant to β-lactams, aminoglycosides, tetracycline, quinolones, and folate inhibitors were detected in both groups of dogs. The presence of E. coli with eaeA virulence gene in diarrheic dogs, suggest that these strains are associated with the animal´s condition. Finally, major attention must be drawn to the careful handling of dogs because of their capability to harbor and disseminate virulent E. coli strains. [ABSTRACT FROM AUTHOR]

Rendezvous control of multiple robots without losing network connectivity has important implications in multi-robot system including formation control, coordinated task assignments, and cooperative robotic missions. This paper introduces a new coordinate-free, bearing-based algorithm to enable rendezvous of distributed mobile robots at any designated leader robot node using hierarchical tracking of wireless network topology. An assumption is made that the robot can only sense and communicate with their neighbors (i.e., local sensing). The proposed approach preserves connectivity during the rendezvous task, adapts to dynamic changes in the network topology (e.g., losing or re-gaining a communication link), and is tolerant of mobility faults in the robots. We theoretically analyze the proposed algorithm and experimentally demonstrate the approach through simulations and extensive field experiments. The results indicate that the method is effective in a variety of realistic scenarios in which the robots are distributed in a cluttered environment. [ABSTRACT FROM AUTHOR]

Crowd counting is of great importance to many applications. Conventional vision-based approaches require line of sight and pose privacy concerns, while most radio-based approaches involve high deployment cost. In this paper, we propose to utilize WiFi channel state information (CSI) to infer crowd count in a device-free way, with only one pair of WiFi transmitter and receiver. The proposed method establishes the statistical relationship between the variation of CSI and the number of people with deep neural networks (DNN) and thereafter estimates the people count according to the real-time CSI through the trained DNN model. Evaluations demonstrate the effectiveness of the method. For the crowd size of 6, the counting error was within 1 person for 100% of the cases. For the crowd size of 34, the counting error was within 1 person for 97.7% of the cases and within 2 persons for 99.3% of the cases. [ABSTRACT FROM AUTHOR]

The present article proposes an approach to ensuring the stable position of an active satellite navigation antenna relative to the inertial measuring unit when installing an inertial navigation system on a vehicle. The task of determining the coordinates of the navigation antenna relative to the inertial unit is accomplished by integrating the two elements into a single structure – an integrated antenna. When manufacturing an integrated antenna, the described approach allows the required coordinates to be determined under factory conditions. As well as explaining the operating principles of individual integrated antenna units, the article considers practical aspects of the integrated antenna's use in inertial GNSS navigation systems. A specific consideration of the two-way digital information exchange between the antenna and computing device is presented. It is shown that the use of single-type cable modems provides the opportunity for a half-duplex exchange of information between the integrated antenna and the navigation receiver. Various uses of this information exchange to perform common navigation tasks are proposed. The independent measurement basis of the integrated antenna is noted. Approaches to acccounting for the orientation of this basis in the practical application of integrated antennas in single-antenna and multi-antenna inertial GNSS navigation systems are discussed. [ABSTRACT FROM AUTHOR]

Shape-shifting, a phenomenon wide-spread in folklore, refers to the ability to physically change from one identity to another, typically from an innocuous entity to a destructive one. The amino acid d-serine over the last 25 years has "shape-shifted" into several identities: a purported glial transmitter activating N-methyl-d-aspartate receptors (NMDARs), a co-transmitter concentrated in excitatory glutamatergic neurons, an autocrine that is released at dendritic spines to prime their post-synaptic NMDARs for an instantaneous response to glutamate and an excitotoxic moiety released from inflammatory (A1) astrocytes. This article will review evidence in support of these scenarios and the artifacts that misled investigators of the true identity of d-serine. [ABSTRACT FROM AUTHOR]

This paper presents a D-band (110–170 GHz) transmitter/receiver (Tx/Rx) chipset with end-fire on-chip antennas (OCAs) using 0.13-μm SiGe BiCMOS technology. The input LO signal frequency of the chipset is 31.25 GHz. A 62.5-GHz frequency doubler, a D-band 2nd-harmonic up-conversion mixer, a power amplifier (PA), and an end-fire antenna are integrated in the Tx. An end-fire antenna, a D-band low-noise amplifier (LNA), a 2nd-harmonic down-conversion mixer, and a 62.5-GHz frequency doubler are integrated in the Rx. The end-fire OCA has gain and efficiency of 4.1 dBi and 83%, respectively. Maximum measured effective isotropic radiation power (EIRP) of 9.2 dBm and conversion gain of 21 dB are achieved for the Tx and Rx, respectively. The Tx/Rx are packaged on PCBs through wire bonding and chip-to-chip wireless communication using 16QAM modulation with the data rate of 4 Gb/s is demonstrated. The DC power consumption of the whole chip is ~1150 mW, and the total chip size is 2 × 3.5 mm2. [ABSTRACT FROM AUTHOR]

Cognitive radio (CR) technology is designed to improve reliability in communication between users through efficient and dynamic spectrum exploitation. CRs address the problems in spectrum allocation and channel access and improve the rate of radio resource utilization. The flexibility of the CR networks (CRN) and communication medium exposes it to a variety of threats; primary user emulation attack (PUEA) is a malicious and denial-of-service kind of adversary that defaces CRN performance. This manuscript proposes an adaptive learning-based attack detection in CRN for detecting and mitigating PUEA by analyzing the received power of the transmitter. The learning process endorses some beneficial features by distinguishing low spectrum legitimate PU from an adversary. The learning process adopts cyclostationary feature analysis for distinguishing adversaries and low power PU in CR communications. The process of learning is further enhanced by estimating distance variance and communication time-based analysis for improving the rate of signal classification and SU communication rate. The experimental analysis proves the stability of the proposed detection method by improving the SU throughput, with lesser signal classification time and misdetection probability. [ABSTRACT FROM AUTHOR]

This paper studies the achievable total throughput of an energy harvesting cooperative cognitive radio (CR) network. A CR transmitter cooperates with a primary user (PU) transmission if PU is found to be present in the given channel while it transmits its own data in the absence of PU. The CR transmitter is an energy harvesting node which harvests simultaneously from non-RF signal as well as RF signal of PU. The CR transmitter uses the harvested energy on shared basis for cooperation and transmission. The same study is also extended for cooperation of multiple CRs in multiple PU band scenario. In cooperation in muti-band scenario, all CRs sense all PU channels and sensing informations are fused at fusion centre to know about the status of PU. Performance is investigated in terms of total network throughput for several parameters such as sensing time, energy splitting parameter, and energy allocation ratio etc. Novel analytical expressions for total useful throughput and optimal energy allocation ratio parameter under the considered network scenario are developed. Useful throughput and optimal energy allocation ratio parameter are also estimated for a target secondary network (CR network) throughput under a quality of service constraint of PU such as collision probability. It is observed that the value of optimal energy allocation parameter gets reduced if the number of CRs in cooperation increases or the number of PU channels increases. [ABSTRACT FROM AUTHOR]

Interference from primary transmitters in underlay cognitive networks is practically neither neglected nor integrated into noise terms although most literature inversely addressed. This paper firstly employs a helpful jammer to secure information transmission of a secondary transmitter. Then, its efficacy through secrecy outage probability under practical considerations consisting of exponentially distributed interference from primary transmitter, peak transmission power limitation, interference power limitation, and Rayleigh fading channels are analytically assessed. Finally, results are provided to illustrate significant security performance improvement thanks to exploiting the jammer while considerable security performance degradation due to interference from primary transmitter. [ABSTRACT FROM AUTHOR]

This paper is concerned with the identification of important edges in a network, in both their roles as transmitters and receivers of information. We propose a method based on computing the matrix exponential of a matrix associated with a line graph of the given network. Both undirected and directed networks are considered. Edges may be given positive weights. Computed examples illustrate the performance of the proposed method. [ABSTRACT FROM AUTHOR]

Wireless communications between two devices can be protected by secret keys. However, existing key generation schemes suffer from the high bit disagreement rate and low bit generation rate. In this paper, we propose an efficient physical layer key generation scheme by exploring the Received Signal Strength (RSS) of signals. In order to reduce the high mismatch rate of the measurements and to increase the key generation rate, a pair of transmitter and receiver separately apply adaptive quantization algorithm for quantifying the measurements. Then, we implement a randomness extractor to further increase key generation rate and ensure randomness of generated of keys. Several real-world experiments are implemented to verify the effectiveness of the proposed scheme. The results show that compared with the other related schemes, our scheme performs better in bit generation rate, bit disagreement rate, and randomness. [ABSTRACT FROM AUTHOR]

This paper presents a new type of a transmitter coil for wireless power transfer (WPT) to assist in the achievement of a constant output power and in the reduction of magnetic field leakage under misaligned electric vehicle (EV) wireless-charging conditions. The proposed DDP coil is an improvement upon the conventional DD coil and can be adaptively reconfigured depending on the misalignment of different sizes or types of receiver coils. The reconfigurable resonant circuit is designed to compensate various coil structures and to maintain a high-energy efficiency. The reconfiguration strategy is presented by studying the characteristics of the magnetic field and mutual inductance of the coils. A precise human anatomic model and a full-scale Tesla EV model are built to evaluate the magnetic field leakage and human exposure to the WPT system. Simulation results show that the power transfer efficiency (PTE) reaches 99.16% and that the maximum electric field induced in humans is − 1.11 dBV/m, while the transfer power is 6.6 kW with a 12 cm lateral offset on both the x-axis and y-axis. The effectiveness of the proposed type of transmitter coil is verified through simulation and experimental results. [ABSTRACT FROM AUTHOR]

An electromagnetic transmitter transmits electromagnetic waves with variable frequencies to the ground to obtain underground structure information and the distribution of mineral resources. In order to improve the power factor and reduce the volume and weight of the transmitter, a novel transmitter topology with pulse width modulation (PWM) rectifier is designed. Similar with the flux-oriented control in the motor speed regulation system, this paper provides flux-oriented control for a permanent magnet synchronous generator PWM rectifier. The mathematical model of the generator rectifier is established under the rotating coordinate system. Then, a novel decoupling control strategy without the exact value of the generator stator inductance is proposed to regulate the active current and the reactive current, and an outer voltage linear control strategy with the control amount of the square of the voltage is proposed to regulate the output voltage. Simulation and experimental results demonstrate the effectiveness of the system. [ABSTRACT FROM AUTHOR]

We studied the effects of melatonin on the oxygen transport in blood and prooxidant−antioxidant balance in males aged from 18 to 21 years in submaximal physical exercise. The subjects received 3 mg of melatonin once a day for two months. As a result of melatonin administration, we observed a shift of oxyhemoglobin dissociation to the right, which results in reduced manifestation of oxidative stress after physical exercise. We found that the increased level of gas transmitters (nitrogen monoxide and hydrogen sulfide) after melatonin administration can influence oxygen transport in blood and prooxidant–antioxidant balance in exercise. [ABSTRACT FROM AUTHOR]

An important challenge in the wireless power transfer is the sizing of the coils for transmission and energy reception. The output power in a wireless power transfer system can be determined by analytical formulation; however, the effects of using some geometry or material for the transmitter and receiver coil assembly are not easily quantifiable by the analytical method. This work quantifies by numerical simulation the impact on output power changing the separation between the transmitter coil and receiver, materials, geometries and number of turns. The quantities obtained allowed to determine a model for coupling coefficient to compute optimal frequency for the power transfer. The analysis and evaluation of these parameters were developed through an electromagnetic simulator with finite element; the work considers planar circular and square coils. Experimental results were obtained in order to validate the proposed model to compute the wireless power transferred. The document contributes to identify the important parameters to be controlled or modified in the coils with the purpose to optimize the power transmission for a wireless system. [ABSTRACT FROM AUTHOR]

Filter bank multi-carrier (FBMC) is very important to achieve high spectral efficiency in the wireless communication process. Previously, orthogonal frequency division multiplexing (OFDM) technique is used to obtain a high spectral efficiency. But area, power and delay is high than the FBMC transmitter technique. The main aim of this work is to design an optimized FBMC transmitter for high speed, low power and low area applications. There is a tradeoff between power and speed. To overcome this challenge, a new compact FBMC transmitter will be introduced in the paper. Generally, the FBMC transmitter consists of serial to parallel converter, QAM modulation, inverse FFT, parallel to serial converter and filter. The existing FBMC transmitter is designed by using inverse radix 2 FFT and poly phase filter. It requires more area, power and delay. To overcome this problem, a new radix2 multipath delay commutator (R2MDC) based inverse FFT and multiple constant multiplication (MCM) based FIR filter are used in the proposed FBMC transmitter. Because MCM based FIR filter doesn't needs multiplier structure. The multiplication process is done by shift, add and subtract operation. Hence area and power is low in MCM based FIR filters, when compared to poly base filter. Also R2MDC FFT is used for high speed application. Comparison between conventional FBMC transmitter and proposed FBMC transmitter is carried out to analyze the performance, area, complexity and power. Also the functionality of FBMC transmitter is verified by using Xilinx ISE Virtex5 device. From the comparison results, it shows that the proposed FBMC transmitter offers 17% average area, delay and power (ADP) product than the existing FBMC transmitter. [ABSTRACT FROM AUTHOR]

We study the dynamics of a particle moving in one-dimensional Lorentz lattice-gas where particle performs mainly three different kinds of motion viz ballistic motion, diffusion and confinement. There are two different types of scatterers, viz reflector and transmitters, randomly placed in the lattice. Reflectors are such that they reverse the particle's velocity direction and transmitters let it pass through. Scatterers also change their character with flipping probability 1 - α , once the particle interacts with a scatterer. Hence the system is defined by two sets of parameters, r, which is the initial density of reflector/transmitter and α . For α = 0 and α = 1 dynamics of the particle is purely deterministic else it is probabilistic. In the pure deterministic case dynamics of the particle is either propagation in one direction or confined between two near-by reflectors present. For the probabilistic case α ≠ 1 and ≠ 0 , although the dynamics of particle shows anomalous diffusion where dynamics is faster, slower and comparable to normal diffusion on the variation of system parameters (α , r) , but the asymptotic behaviour of the particle is normal diffusion. We plot the phase diagram for the asymptotic behaviour, in the plane of α and r. [ABSTRACT FROM AUTHOR]

In this paper, we propose a game theoretic framework to analyze a passive eavesdropping attack in millimeter-wave-based wireless personal area networks. As the interaction between defenders and attackers in network security issues can be considered as a game, devices can be considered as players. Usually a player has insufficient information of other players such as strategies and payoffs especially in static situation. We assume that each player selects its strategy based on its belief about the information on opponents and the belief is known as a prior probability. The Bayesian game model is a relevant framework for this situation. It is assumed that each device is equipped with a directional antenna and knows the channel state. In the analysis, the exposure region (ER) that is determined by the antennas directions of players is considered and the ratio of ER for the total area of a network is calculated by using the probability density function of distance between players. The optimal strategies of two players, a transmitter and an eavesdropper, are derived in terms of Bayesian Nash equilibriums and payoffs for the players are computed for pure and mixed strategies in static situation. The analysis shows how the effects of using a directional antenna and the prior probability of transmitters belief are involved in the Nash equilibriums. Numerical results show the equilibriums and two players payoffs. Those values depend on several parameters such as beamwidth and prior probability of belief as well as its opponents strategies. It also shows the effect of directional antennas in the eavesdropping attack; the use of directional antenna seems to increase the transmitters payoff, while it seems to decrease the eavesdroppers payoff. The obtained results will provide the criteria for selecting appropriate strategy to transmitters when an eavesdropper exists in the network. [ABSTRACT FROM AUTHOR]

Spatial modulation (SM) is a spectrum and energy-efficient simple digital modulation scheme, which uses the transmitter antenna indices to convey the additional bits. The conventional SM variants have high complex receivers and offer poor performance under spatially correlated and line-of-sight (LOS) channel conditions. In this work, a new variant, modified spatial modulation (MSM) for 8 × 8 multiple input multiple output (MIMO) configuration is proposed, which uses one or two transmitter antennas based on the incoming bit patterns. The adaptive mapping used at the transmitter side for antenna selection and modified maximum likelihood (ML) detection used at the receiver side reduces the computational complexity. Every possible bit per channel use (bpcu) is mapped to a unique transmit symbol vector, which minimizes the receiver complexity, while combating the effect of spatial correlation. Through simulation results, it is observed that the average bit error rate (ABER) performance of the MSM-ML scheme is much better than that of the conventional SM-ML, generalized spatial modulation (GSM)-ML and redesigned spatial modulation (ReSM)-ML schemes under spatially correlated and LOS channel conditions. The promising results prove that the proposed scheme can be a better alternative to spatial multiplexing (SMX) in battery-driven compact handheld devices, which can be used for international mobile telecommunication-2020 (IMT-2020). [ABSTRACT FROM AUTHOR]

This article presents the design of an antenna feeder system (AFS) for extremely-high-frequency radio interferometers equipped with a small transmitter, which is intended for diagnostics of fast gas-dynamic processes in closed volumes with a limited internal space. Numerical simulation and experimental studies proved the fundamental possibility of developing an AFS with an aperture size that does not exceed (3–5)λ. The designed AFS forms an axisymmetric radiation pattern of the probing field with a major lobe width of at most 30°–40° and a minimum level of lateral radiation. This research has shown that the required characteristics are achieved using transmitters with rod and conical dielectric inserts of a specific design. [ABSTRACT FROM AUTHOR]

We prove that every bipartite hypertournament without transmitters contains at least two 4-kings and present all their possible distributions. [ABSTRACT FROM AUTHOR]

In this paper, we propose two cooperative spectrum sharing protocols for cognitive radio networks which consist of an automatic repeat request based primary user with a primary transmitter (PT) and a primary receiver (PR), and a bidirectionally communicating secondary user (SU) with two nodes, S1 and S2. PT transmits a packet to PR by accessing the spectrum alone or by the cooperation of SU or under the interference of SU in the underlay transmission, according to the acknowledgement/negative acknowledgement feedback from PR. The two protocols differ by the application of decode-and-forward and amplify-and-forward strategies at SU during cooperation. Analytical expressions are derived for the throughputs of both users for both protocols and the results are compared with the corresponding reference protocols given in the literature. The theoretical results which are in perfect match with the simulation results show the advantages of the proposed protocols. [ABSTRACT FROM AUTHOR]

The possibility of using acousto-optic multiband filters for construction of code division multiple-access communication networks has been experimentally proved. Correlation interference has been studied for a set of bands with a spectrum close to sin(x)/x function which are used for encoding/decoding. For the case of several transmitters, a special technology was developed and realized that made it possible to perform studies on a transmission line based on two filters. The key component of this technology lies in emulating the sum signal from two to five transmitters on the first filter. The measured signal-to-interference ratio was more than 11 dB and decreased by less than 3 dB due to correlation interference from the network neighborhood and the emulation error of the sum signal. [ABSTRACT FROM AUTHOR]

A wireless link using quasi-optic transmitter and receiver modules is demonstrated, enabling carrier wave frequency selection within various millimeter-wave bands from E-band to D-band without changing the modules. The photonics-based transmitter driven by an optical heterodyne source uses an ultra-wideband PIN photodiode transmitter module. The receiver is composed of zero-bias Schottky barrier diode envelope detector, with a minimum of – 30 dBm measured sensitivity leading to a calculated link distance of 15 m. Error-free data transmission also enables real-time HDTV streaming. [ABSTRACT FROM AUTHOR]

Training sequence is used in multiple antenna systems to estimate channel state information and mitigate channel distortion between transmitter and receiver. However, the training sequence or pilot must be limited to a certain size in order to reduce the impact of overhead loss due to limited channel coherence length in mobile users. In this paper, we proposed to use training size optimization in cell-free massive MIMO system. In addition, we proposed and compared the performance of different training size optimization algorithms, namely exhaustive search optimization, bisection optimization and min–max optimization, with each method has different level of calculation complexities. The results showed that in general, all of the 3 training length optimization methods improved the downlink rate compared to the conventional pilot length method. We also showed that the training optimization methods are more effective when the coherence length is small or the number of users is very large. In the case of large number of users or small coherence length, the exhaustive search has the best median downlink rate, followed closely by min–max optimum and finally the bisection method. Even though the exhaustive search optimization has the best downlink rate, we showed that the proposed reduce optimization complexity methods has significantly less calculation complexity. In addition, the median downlink rate performance of min–max optimization method is only slightly less than that of the exhaustive search method for various number of users and coherence length. [ABSTRACT FROM AUTHOR]

In 2015–2016 regular observations within the SETI program were carried out at the RATAN-600 radio telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. The aim of observations was to search for artificial signals from about 30 Sun-like stars and two metal-rich globular clusters. The main underlying idea of these studies was to perform multiple repeated observations (monitoring) of the same objects. The data were analyzed using three methods: we (1) searched for a strong single signal, (2) estimated the flux averaged over the entire observing time, and (3) analyzed the correlations between signals at different frequencies. Collecting the data over two observing years made it possible to perform a search for weak signals at the detection level of several mJy at 2.7 and 6.3 cm wavelengths. The power limits on the signals of extraterrestrial civilizations averaged over the entire data set lie in the 1016–1020 Winterval practically for all objects, whereas the upper luminosity limits for single observations (the beam crossing time was 7–19 s) are 1017–1021 W and the effective isotropic emitted power of the hypothetical transmitters of the said civilizations do not exceed 2 × 109–2 × 1013 W, which is close to the corresponding parameter for the biggest planetary radars. The resulting luminosity limits are indicative of the absence of radio emission from the observed Sun-like stars, which is stationary on average and exhibits flare-like behavior during some observing sessions. [ABSTRACT FROM AUTHOR]

Summary: In order to test the potential influence of short wave radiation on the homing behaviour of pigeons we positioned two lofts with adult homing pigeons in the vicinity of a short wave transmitter. One loft was next to the transmitter and fully exposed to the radiation, the second protected against the radiation (a) by topographical features and (b) by its position in a sector that was not used for transmission during daytime. In both lofts young pigeons were raised and used for experimental flights at the age of three months. Adults accustomed to the new sites as well as young birds from the exposed and non-exposed lofts, respectively, were released some 11 km from the loft for homeward flights towards the transmitter, with and without transmission towards the relevant sector. Vanishing direction and vanishing time were not affected by the short wave radiation in any of the groups, thus corroborating earlier experiments with pigeons flying homewards from the transmitter towards distant lofts. However, all three groups raised in the absence of short wave radiation (A−, A+, J−) homed tendentially faster in situations where radiation was absent compared to situations with radiation. Pooled in one data set the three groups were significantly faster without radiation. On the other hand, the two juvenile groups raised under radiation (J1+ and J2+) homed at the same speed under both short wave situations. Furthermore, all five groups tended to choose lower flight altitudes when released under the influence of short wave radiation (significantly when groups were pooled). Besides the experiments, observations near the loft gave the impression that the pigeons kept in the exposed loft were reluctant to fly in the neighbourhood of the loft, particularly the adults. We conclude that short wave radiation can be felt by the pigeons, but does not interfere with their initial orientation. Reduced homing speeds of birds grown up without experiencing radiation, low flight levels in flights under radiation in all groups, and a general reluctance to fly of the pigeons next to the exposed loft, suggest that the radiation has an undefined negative effect on the birds. Unimpaired homing speeds in juveniles having grown up under varying field strengths suggest that homing pigeons can become accustomed to short wave radiation to a certain extent. [ABSTRACT FROM AUTHOR]

During the recent years studies of bat activity are predominantly based on ultrasound detection. However this method suffers from several biases such as different species call ranges, temporal and habitat-related variability. In order to test the bias linked to the detection of whispering gleaning bats in temperate lowland forests, we equipped several individuals of Myotis bechsteinii and Plecotus auritus with transmitters and followed them on their foraging grounds where we simultaneously recorded echolocation calls. Our results highlight the very low detectability of these species whose presence was ascertained at the recording station. On the other hand, we detected the presence of many other species. We suggest methodological recommendations for ultrasound detection whenever gleaning bat species are concerned. [ABSTRACT FROM AUTHOR]

This paper analyzes the performance of quadrature spatial modulation (QSM) multiple-input multiple-output (MIMO) system in cooperative decode and forward (DF) networks over correlated and imperfect η-μ fading channels. QSM is a recently proposed propitious MIMO technique that promises significant advantages over conventional MIMO schemes including high spectral efficiency with single RF-chain transmitter and very low receiver complexity. In this study, DF cooperative communication system adopting QSM technique is presented and throughly analyzed. Single or multiple DF relays are placed between the source and the destination to cooperate in the transmission process. Only the relays that decode the signal correctly will participate in the retransmission process. The end to end performance of the considered system is analyzed over correlated and imperfect η-μ fading channels. The η-μ channel is a general fading distribution that includes some other well-known channels, such as Rayleigh and Nakagami-m, as spacial cases. Monte Carlo simulation results are presented to corroborate the accuracy of the conducted analysis. The impact of spatial correlation, imperfect channel estimation and the fading parameters η and μ on the overall performance is investigated and exhaustively discussed. [ABSTRACT FROM AUTHOR]

This paper proposes a novel scheme for the slow block fading Gaussian multiple access relay channel inspired by the compute-and-forward (CoF) relaying strategy. The CoF relaying strategy exploits interference to obtain significantly higher rates between users in a network by decoding linear functions of the transmitted messages. Unlike other approaches in the literature, our approach is valid for any number of transmitters and, most importantly, it only requires channel state information at the receiver side, while it still attains similar or higher rates than the other approaches found in the literature. [ABSTRACT FROM AUTHOR]

To enhance the spectrum scarcity of cooperative heterogeneous networks (HetNets) with unreliable backhaul connections, we examine the impact of cognitive spectrum sharing over multiple small-cell transmitters in Nakagami-m fading channels. In this system, the secondary transmitters are connected to macro-cell via wireless backhaul links and communicate with the secondary receiver by sharing the same spectrum with the primary user. Integrating cognitive radio (CR) network into the system, we address the combined power constraints: 1) the peak interference power at the primary user and 2) the maximal transmit power at the secondary transmitters. In addition, to exclude the signaling overhead for exchanging channel-state-information (CSI) at the transmitters, the selection combining (SC) protocol is assumed to employ at the receivers. To evaluate the performance, we first derive the closed-form statistics of the end-to-end signal-to-noise (SNR) ratio, from which the exact outage probability, ergodic capacity and symbol error rate expressions are derived. To reveal further insights into the effective unreliable backhaul links and the diversity of fading parameters, the asymptotic expressions are also attained. The two interesting non-cooperative and Rayleigh fading scenarios are also investigated. Numerical results are conducted to verify the performance of the considered system via Monte-Carlo simulations. [ABSTRACT FROM AUTHOR]

Device-to-Device (D2D) communication and wireless small cell networks (SCNs) are two of the most promising paradigms in next generation cellular technologies. However, interference management is a major issue in regard to the use of either or both technologies. In this paper, we propose a D2D pair underlying SCNs using Wireless Power Transfer (WPT) technology. In particular, we have a D2D transmitter and D2D receiver underlying SCNs and operate in close proximity to a SCN primary user (PU). Two scenarios are proposed. The first scenario is when the best base station (BS) link is chosen to harvest energy from, and a second scenario where energy is harvested from all available SCN BSs. The transmission between the D2D pair is kept under a certain threshold so it could not have any harmful effects on the transmission link of PU. The results reveal that the number of interference users shows negative effect on the performance of the considered system. Besides, the primary network's peak interference constraint has significant influence on the optimal value of energy harvesting time at the D2D transmitter. [ABSTRACT FROM AUTHOR]

The concept of frequency interleaving (FI) for digital-to-analog converters (DACs) has recently experienced renewed interest, in order to overcome the DACs’ bandwidth limitations. In this concept, the output signals of multiple DACs are interleaved in the frequency domain in order to generate a combined output signal that exceeds both the sampling rate and the bandwidth of a single DAC. In this paper, a mathematical framework for FI-DACs with a large number of DACs is presented and the inherent interdependencies between sampling rate, the number of samples, LO frequencies, symbol rate and analog frequency responses are highlighted. A mathematical expression for the distribution of data samples among the DACs is presented, taking into account bandwidth limitations of the analog components as well as guard bands to mitigate cross talk. In order to balance the FI-DAC’s parameters a mathematical optimization approach is introduced and illustrated with examples. Both simulation and experimental results validate the FI-DAC concept, and an outlook on implementation issues completes this paper. [ABSTRACT FROM AUTHOR]

Recently, distributed transmit-antenna selection schemes have attracted great interest, since they capture the essential benefits of multi-antenna systems while reducing their cost, complexity, delay, and feedback overhead. In those distributed schemes, the antenna selection is based on local channel-state information, in contrast to their optimal centralized counterparts, which require knowing the channel state of all links. Herein, we design two such distributed schemes for a dual-hop variable-gain amplify-and-forward relaying system with one multi-antenna source, one single-antenna relay, and one single-antenna destination. The two schemes differ in the diversity method used at the destination, namely, selection combining or maximal-ratio combining, and in the selection rule accordingly. In addition to conceiving these new schemes, we analyze their outage performance. Since an exact analysis proves intractable, we tackle the outage probability in terms of lower-bound expressions and their asymptotes at high signal-to-noise ratio. Importantly, the derived bounds turn out to be almost indistinguishable from the true performance, assessed via simulation. Our results reveal that the proposed distributed schemes achieve the same diversity order of their optimal centralized counterparts and perform closely to these, specially when the relay is near the source or destination. [ABSTRACT FROM AUTHOR]