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The rapid evolution of passive optical network (PON) technologies has been driven by the necessity to accommodate 5th-generation system requirements. This research introduces a PON wavelength division multiplexing-based optical transmitter that is improved in both fiber link and bit rate. The transmitter is designed to connect many clients to a single-mode optical fiber. The optical transmitter under consideration is designed to provide an optimum data rate up to 20 Gbps per user. The data is modulated using a 2-bit per symbol Quadrature Phase Shift Keying (QPSK), and an M-array pulse coder. The R.F. signal is optically modulated during the optical system stage using a Mach–Zehnder external modulator supplied with an optical carrier generated by a vertical cavity surface emitting laser (VCSEL). Two PON configurations are devised in this context: initially, 16 VCSELs spanning 193.1–194.6 THz with a 10 GHz separation are utilized to modulate 16 data sources with 16 MZM. In contrast, in the second configuration, to reduce input laser power and system complexity, 16 data consumers share a single 193.1 THz VCSEL. Simulations of the performance measurements were conducted by Optisystem 19 for both configurations. The initial system configuration permits 20 Gbps transmission to 120 km with a Q-factor of at least 6. The power penalty of this configuration was reduced from − 970 to − 930 dB. The second configuration guarantees the dependability of data transmission over a distance of 100 km. The maximal Q-factors for the first and second configurations are 12 and 10, respectively, at a distance of 20 km. It has been established that the ideal input bias current for a VCSEL is 2 mA. The effects of the quadrature phase shift keying modulation QPSK is clearly appeared, as the current results are surpassed the peer publications regarding the utmost achievable fiber link length, Q-factor and supported data rate. [ABSTRACT FROM AUTHOR]

Achieving three-dimensional (3D) omnidirectional wireless power transfer (OWPT) without any active control is challenging. This paper proposes a square polyhedron transmitter (SPTx) based on the reverse current of parallel coil, which can create a 3D omnidirectional magnetic field. To minimize the counteracting of the reverse magnetic field, each coil is equipped with magnetic shielding material. The coils of SPTx are connected in series and excited by a single power supply without any current amplitude or phase control circuits. The performance of SPTx system is validated with different receivers (Rx) by experiments. In the experiment with dual Rxs, the maximum transmission efficiency is 79.6% with an efficiency stability rate of 49%. In addition, the output power does not affect the efficiency, and more Rxs will increase transmission efficiency. [ABSTRACT FROM AUTHOR]

The electromagnetic detection method is the main method of marine oil and gas resource exploration, and the marine electromagnetic transmitter is the key equipment of marine electromagnetic detection systems. At present, the power factor of the controllable source circuit of the electromagnetic transmitter is low, energy cannot be fed back, and the capacitance of the filter capacitor is large, which results in a large volume of the electromagnetic transmitter and high maintenance costs. Thus, a cascaded H-bridge controllable source circuit combined with active power decoupling technology is introduced in this paper. First, the topological structure and working principle of the controllable source circuit of the electromagnetic transmitter are analyzed, and an improvement plan is proposed for the existing problems of the controllable source circuit. Second, the working principle of the improved controllable source circuit is analyzed, and the advantages of the improved scheme are expounded. Then a control strategy based on linear active disturbance rejection control (ADRC) is proposed, and a linear ADRC controller is designed. Simulation results show that the improved controllable source circuit reduces the capacitance value, improves the power factor, reduces the volume of the underwater towing body, and reduces the maintenance cost of the system. The proposed control strategy makes the DC voltage have better anti-disturbance performance, and improves the reliability of the electromagnetic transmitter in deep sea exploration. [ABSTRACT FROM AUTHOR]

Wireless Network-on-Chip (WNoC) incorporating on-chipantennas has emerged as a promising alternative to overcome the communication bottleneck due to high frequency operation, propagation delay, crosstalk delay, noise and need for repeaters inwired interconnects in chip-multiprocessors (CMPs). Recent advancements in nano materials, such as graphene have enabled the development of novel plasmonic graphene devices, which intrinsically operate in THz band. This ultra-low power andcompact graphene-based nano-antennas (GNA) establishes ultra-high bandwidth THz-on-chip wireless links for intra/inter-chip communication. In this article, we design and simulate a novel fork-shaped planarplasmonic nano-patch antenna using grapheneon SiO2/Si substrate that can be integrated into transceivers working at THz frequencies operating from 0.5 THz to 2.6 THz. By simulation at THz band, proposed antenna performance as a wireless inter/intra-chip link is investigated by numericallyobtaining itssignal transmission coefficient characteristics between the two on-chip antennas, acting as transmitter and receiver or vice-verse for short-range THz communication among wireless NoC based multi-core processors integrated on same substrate. Theresults are obtained by placing the antennas in broadside orientation, that can communicate with intra-chip transmission coefficients ranging from − 20 dB to − 60 dB while sustaining bandwidths upto 0.13–0.2 THz. Further, the effect of transmission and radiation performance of proposed antennas with increase in distance dlink is studied along with reconfigurable nature of graphene with varying chemical potentials from 0.1 eV − 0.5 eV. Proposed antenna has obtained maximum gain and radiation efficiency of 3.89 dB and 58% at 1.83 THz when chemical potential of 0.1 eV is applied. This concept can broadly be applied to future systems as it can be directly integrated into transceivers as graphene is compatible with CMOS processes.Fabrication process steps of proposed on-chip antenna and its feasibility as a real device in chip environment isalso discussed. [ABSTRACT FROM AUTHOR]

A scheme for the compensation of chromatic dispersion in Radio over Fiber systems with enhanced performance is proposed and demonstrated. The system implements a cascade of an Ideal Dispersion Compensation Filter and a tanh apodized, linearly chirped Fiber Bragg Grating for mitigating the degradation caused by chromatic dispersion. The analysis probes variations in transmission distance and channel spacing while investigating vital performance parameters like the Q factor and Bit Error Rate. Two-channel spacings of 100 GHz and 50 GHz, transmission distances ranging between 70 and 120 km and effective refractive index of the apodized and linearly chirped FBG extending between 1.3 and 1.5 are considered for the study. The analysis also covers the analysis of optical signal to noise ratio as the fiber length is varied. Additionally, the system performance is evaluated when the transmitted power of the continuous wave Laser in the transmitter segment is altered. The simulation results demonstrate that the system provides acceptable Q factor and BER values even at a transmission distance of 120 km. The comparative analysis with the formerly published results validates the performance enhancement achieved by the proposed system. [ABSTRACT FROM AUTHOR]

Empirical evidence suggests that marine animals perceive and orient to local distortions in the earth's natural magnetic field. Magnetic fields (MFs) generated by electrified underwater cables may produce similar local distortions in the earth's main field. Concern exists that these distortions may impact migration movements of MF-sensitive animals. The Trans Bay Cable (TBC) is a ± 200-kV, 400-megawatt, 85-km high-voltage direct current transmission line buried through San Francisco Bay (37° 56′ 8.81″ N, 122° 27′ 0.19″ W). Detections of adult green sturgeon implanted with acoustic transmitters were used from six cross-bay receiver arrays from 2006 to 2015 to investigate how inbound and outbound migration movements through lower portions of their route to/from upstream breeding grounds are related to the TBC's energization status (off/on) and other local environmental variables. Here, we assess how these variables impacted transit success, misdirection from the migration route, transit times, and migration path locations within stretches between the Bay's mouth and the start of the Sacramento River. Overall, there was varied evidence for any effect on migration behavior associated with cable status (off/on). A higher percentage of inbound fish successfully transited after the cable was energized, but this effect was nonsignificant in models including temperature. Outbound fish took longer to transit after cable energization. Inbound and outbound migration path locations were not significantly influenced by cable energization, but results suggest a potential subtle relationship between energization and both inbound and outbound paths. Overall, additional migration-based studies are needed to investigate the impact of anthropogenic cables on marine species. [ABSTRACT FROM AUTHOR]

To address the rising demand for high-speed wireless data links, communication systems operating at frequencies beyond 100 GHz are being targeted. A key enabling technology in the development of these wireless systems is the phased antenna array. Yet, the design and implementation of such steerable antenna arrays at frequencies over 100 GHz comes with a multitude of challenges. In particular, the cointegration of active electronics at each antenna element poses a major hurdle due to the inherent space constraints in the array. This article proposes a novel scalable concept for opto-electronic phased antenna arrays operating at 140 GHz. It details the system architecture of a transmitter that enables the implementation of large scale, wideband, 2D steerable phased antenna arrays and presents the design and measurement of a compact SiGe power amplifier (PA) chip to be used as one of its key building blocks. The amplifier achieves a gain of 20 dB at 135 GHz, features a P 1 d B of 14.6 dBm and can support data rates up to 45 Gbps in a limited footprint of only 540μm × 550μm. This makes it one of the fastest, most powerful D-band power amplifiers in literature with a footprint compatible with λ 2 -spaced phased array integration. [ABSTRACT FROM AUTHOR]

Equipping Galileo satellites with a VLBI transmitter (VT) will allow to observe satellites next to quasars with Very Long Baseline Interferometry (VLBI) radio telescopes. This concept will facilitate the direct estimation of the satellite orbits in the celestial reference frame. Moreover, these observations along with usual Galileo observations can be used to transfer the space tie between the VT and the antenna on the Galileo satellite to the Earth surface realizing the frame tie at the geodetic site with VLBI radio telescope and Galileo antenna. In this study, we assess the accuracy of that frame tie by simulating the estimation of station coordinates from VLBI observations to Galileo satellites next to quasars. We find that at least two or three satellites need to be equipped with a VT with the best results if all satellites with a VT are placed in the same plane. Concerning the ratio between satellite and quasar observations within a schedule, the results suggest that the optimal ratio is around 30% to 40% satellite observations out of the total number of observations in order to have enough observations for the estimation of the station coordinates but still enough quasar observations to ensure a sufficient sky-coverage for the estimation of troposphere parameters. The best scenario with two satellites yields repeatabilities for the east and north components between 7.5 and 10 mm, and for the up component between 9.5 and 12 mm. In case there is a third satellite with a VLBI transmitter in the same plane, the repeatabilities are reduced by up to 2 mm for the horizontal components and up to 3 to 4 mm for the up component. Rotating the schedules over the constellation repeat cycle of Galileo of 10 days reveals that there are differences between the individual days, but there are no days with a significantly worse precision of the estimated station coordinates. [ABSTRACT FROM AUTHOR]

This paper studies overlay-based cognitive radio networks (ObCRNs) where transmission from a licensed transmitter (LT) to a licensed receiver (LR) is supported by an unlicensed transmitter (UT) who has its own communication to an unlicensed receiver (UR). To improve power efficiency of UT and diversity gain at UR and LR, UT operates in direct transmission (DT) or amplify-and-forward (AF) mode or decode-and-forward (DF) mode, and UR and LR combine signals with selection combining (SC) and maximum ratio combining (MRC) from LT and UT. Explicit outage probability expressions for ObCRNs with MRC/SC and DT/AF/DF are proposed to promptly rate its performance. Numerous results reveal the efficacy of the proposed solution and its flexibly-controlled performance. [ABSTRACT FROM AUTHOR]

Home ranges of free-living mammals have typically been studied via radio-tracking to understand how individuals use their environment. Recently, GPS collars have become popular in large mammals. However, GPS collars are rarely used in small mammals, as they are too heavy, especially when needing coating to protect against gnawing. Here we test the efficiency of mini-GPS collars to measure range estimates compared to the use of radio-collars in a small rodent of 100 g body mass. We equipped 20 bush Karoo rats with mini-GPS loggers and thereafter with radio-transmitters to determine ranges. We validated the accuracy of the mini-GPS loggers by comparing them with the fixes from a handheld GPS and found both to be similar. We estimated range sizes using both traditional methods of Kernel and minimum convex polygon estimates as well as modern methods from movement ecology taking the location error of the mini-GPS into account. Using modern methods led to smaller range estimates, but results were in so far consistent that daily ranges for bush Karoo rats determined using mini-GPS were much larger than home range estimates from radio tracking. Using radio-tracking enabled us to establish the central shelter, while the mini-GPS revealed areas where rats had been observed foraging. We found a distinct location error and therefore suggest using modern approaches from movement ecology which can take this error into account. In sum, mini-GPS revealed more accurate estimates of the ranges than radio-tracking in a small rodent of 100 g body mass. [ABSTRACT FROM AUTHOR]

A new method for capacity and spectral efficiency increases is a full-duplex communication, where sending and receiving are done simultaneously. Hence, severe interference leaked from the transmitter to the receiver, which can disrupt the system's operation completely. For interference reduction, the transceiver tries to estimate the interfering symbols to remove their effects. A typical method is to use the Hammerstein model. In this method, nonlinear power amplifier (PA) and multipath channel are modeled with a successive nonlinear system and a finite impulse response filter. Then, the model parameters are adjusted, and interference symbols are estimated from the transmitted symbols. In the Hammerstein method, the interference symbols are estimated directly from the transmitted symbols. But practically, the transmitted symbols first pass through the pulse-shaping filter and become a signal. Then, this signal passes through the nonlinear PA and communication channel. Finally, the received signal is filtered by the matched filter (MF) at the receiver and converted to the symbols again. In this procedure, the amplifier and the communication channel affect the transmitted signal directly and distort transmitted symbols indirectly. Therefore, in the practical situation, when we consider the transmitter's pulse-shaping filter and the receiver's MF, the estimated symbols with the Hammerstein method are erroneous. To solve this problem, a new MF at the receiver is proposed and adjusted according to the interfering signal. We have shown that this method is far better than the Hammerstein method. [ABSTRACT FROM AUTHOR]

In this paper, an array multi-transmitter multi-mode wireless power transfer system is proposed. The system realizes the joint modulation of three transmitter coil working modes of single transmitter coil, dual transmittercoil and four transmitter coils in the wireless power transfer system through PI closed-loop control, which can realize the stable output of WPT system in three different transmitter coil work modes. It effectively compensates for the shortcomings of the single working mode of a single transmitter coil and the limited range of effective working areas, and improves the robustness of the wireless power transfer system. [ABSTRACT FROM AUTHOR]

Distributed wireless network devices are mostly battery-powered. Transmitting a message on distributed wireless networks uses more energy than receiving one, which in turn uses more energy than internal computations. Therefore, in this paper, we study the problem of randomized leader election in synchronous distributed single-hop networks with a special focus on the energy complexity. We provide algorithmic solutions to the implicit version of leader election problem where non-leader nodes need not be aware of the identity of the leader. Because the size of a message impacts the energy consumption, we highlight that the solutions we propose consume very little energy: each device is allowed to send a single one-bit message only once and listen to the network during two time slots at most. We first consider four well-studied variants of the radio network (RN) model depending on the transmission and reception abilities of the participating devices: RNstrongCD: both transmitters and listeners can detect collision, RNsenderCD: only transmitters can detect collision, RNCD: only listeners can detect collision, RNnoCD: no device can detect collision. Next, we study the beeping network model. The time and energy complexities of all our algorithms are deterministic and they succeed in electing a unique leader with high probability even under the restriction that each node can only send once a single one-bit signal. When the nodes are aware of the total number n of the participants, our algorithm elects a leader in O (log n) rounds. When n is not known beforehand but an upper bound u on n with log u = Θ (log n) is known by all participating nodes, we design a randomized algorithm with O (log 2 n) time complexity for the RN models. For beeping networks, our algorithm has O (n ε) time complexity ( 0 < ε < 1 ). The parameter ε can be tuned to increase the probability of success of the algorithms. [ABSTRACT FROM AUTHOR]

We present a 3-D ultrasound imaging system utilizing a light-based ultrasound transmitter. The system achieves high spatial resolution through a plain surface coated with a thin layer of carbon nanotubes (CNTs), which is optically scanned by a pulsed laser. The transmitter is fabricated by depositing a CNT-polydimethylsiloxane composite onto a glass substrate using techniques such as dip coating, dropping, and spin coating. The transmission characteristics are dependent on the laser beam width and CNT layer thickness, with the spin-coated layer demonstrating a center frequency of 9.08 MHz and bandwidth of 12.65 MHz. The imaging system boasts an axial resolution of 200 μm and lateral resolution of 190 μm. 3-D imaging was successfully performed on a chicken heart with a penetration depth up to 30 mm, providing a potential replacement for complex high voltage pulser circuits with a simple and manufacturable optical ultrasound transmitter. [ABSTRACT FROM AUTHOR]

Adaptive analog beamforming is a key technology to enable spatial control of millimeter-wave wireless signals radiated from phased array antennas (PAAs) which is essential to maximize the capacity of future mobile networks and to ensure efficient usage of scarce spectrum. Intermediate frequency-over-fiber (IFoF), on the other hand, is a promising technology for the millimeter-wave (mm-wave) mobile fronthaul due to its low complexity, high optical spectral efficiency, and low latency. The combination of IFoF and PAA is key to implement mm-wave mobile communications in a scalable, centralized, efficient, and reliable manner. This work presents, for the first time to the best of the authors' knowledge, an extensive outdoor measurement campaign where an experimental IFoF mm-wave wireless setup is evaluated by using PAAs with adaptive beamforming on the transmitter and receiver sides. The configuration of the experimental setup is according to 5G standards, transmitting signals wirelessly at 27 GHz central frequency in the n258 band. The employed PAAs are composed of 8-by-8 patch antenna arrays, allowing beam steering in the azimuth and elevation angles. Furthermore, different end-user locations, antenna configurations, and wireless scenarios are tested in the outdoor experiment, showing excellent EVM performance and achieving 64-QAM transmission over up to 165.5 m at up to 1.88 Gbit/s. The experimental results enable optimization of the experimental setup for different scenarios and prove the system's reliability in different wireless conditions. In addition, the results of this work prove the viability and potential of IFoF combined with PAA to be part of the future 5G/6G structure. [ABSTRACT FROM AUTHOR]

The purpose of this study is to evaluate the role of asprosin in the regulation and mechanisms of oxygen transport in the blood and the gas transmitter system in men with different body mass index. The indicators of lipid and carbohydrate metabolism, as well as the oxygen transport function of the blood and the concentration of gas transmitters, nitrogen monoxide and hydrogen sulfide in it, were determined. A higher concentration of asprosin was found in individuals with an increased body mass index and grade I obesity. With an increased content of asprosin, there is a decrease in the main indicators of blood oxygenation and an increase in the affinity of hemoglobin for oxygen. An increase in the concentration of nitrogen monoxide and a decrease in hydrogen sulfide were revealed at a high content of asprosin, which may be important for the formation of the mechanisms of oxygen transport in the blood. [ABSTRACT FROM AUTHOR]

Inductive power transfer (IPT) technology is a promising solution for charging the electric vehicles (EVs) by enabling an EV to charge its energy storage system (battery) without any connecting wires through magnetic coupling. This paper proposes a new receiver design named Hollow Solenoid receiver that is compatible with the standard double-D transmitter defined by the SAE J2954 standard. A deep design analysis for the proposed Hollow Solenoid receiver is presented to define the optimum design parameters for coil (inductances, number of turns, dimensions, wires, etc.) and ferrite core (dimensions, number, arrangement, etc.). Several WPT3 (11.1kVA) solenoid receiver (SR) designs were presented and analyzed based on efficiency, weight, size, volume, and cost. The performance of the proposed SR was compared with the global Double-D receiver (DDR) presented by the SAE J2954 standard under different lateral and rotational alignment and loading conditions considering coupling factor, transmission power and efficiency, and stray electromagnetic fields (EMFs). The entire IPT system including coils, compensation network, power converters, controls, and battery load was modeled and analyzed for both SR and DDR coils. The results reveal that the proposed SR is compatible with the global DD transmitter at different alignment and loading conditions and is able to transmit the desired power (11 kW) at an efficiency > 85%. Hollow SR design shows the highest efficiency and lowest size, weight, and cost compared to DDR and other designs. [ABSTRACT FROM AUTHOR]

In this paper, we study a cognitive radio wireless-powered communication network with an integrated intelligent reconfigurable surfaces system. Actually, massive connectivity and limited energy are the primary challenges to implementing ultra-reliable and low-latency services, as it is extremely difficult to maintain the quality of service and manage the connection of a huge number of users to small cells. So, this paper investigates the application of NOMA-based simultaneous wireless information and power transfer (SWIPT) for massive mobile systems in which the underlay spectrum sharing network is designed to mitigate the interlayer interference such that interference with the primary network is kept less than a predefined level. Problem modeling takes into account residual hardware impairments and channel estimation errors under practical conditions. The communications between the servers and users of NOMA-based small cells are accomplished via an interference-limited multihop connection through intermediate relays. Based on the partial relay selection (PRS) protocol, an optimal relay is selected from K relays to transmit the received signal to multiple user equipment, namely, the far users (FU) and the near users (NU). In addition, to maximize the system total throughput, we formulate the transmitter (Tx)-relay-receiver (Rx) matching problem, which is a mixed-integer nonlinear programming (MINLP) problem. To address this nondeterministic polynomial-time NP-hard problem, we applied a gradient algorithm to obtain a stable matching. The impact of the transmission power, the number of Tx/Rx pairs, and the number of intermediate relays on the sum rate are investigated. Based on the simulation results, the hardware failure parameter has a negative impact on system performance, whereas the channel estimation index is always advantageous to outage probability (OP). Also, the analysis of the energy efficiency and key performance indicators proves that the proposed approach outperforms other similar schemes from the power saving and QoS assurance perspectives. [ABSTRACT FROM AUTHOR]

It is extremely important to accurately measure the liquid level as a process variable of a storage tank used by any plant. The transmitted electrical signal from a liquid level transducer or any other transducer to a remote indicator or controller may sometimes suffer from the measurement error due to its contamination with noise signal. This may be easily avoided by using modern optical fiber communication technique wherein we see the production of optical signal from the transducer output and its noise free communication through fiber-optic cable. In thie present paper, an opto-electronic liquid level transmission technique has been proposed for liquid which is conducting in nature and generally, collected in a storage tank. The electronic part of the transmitter unit consists of a modified capacitive transducer with a signal conditioner unit which produces an electrical DC output voltage which is linearly related with the level of the conducting liquid in the storage tank. This DC voltage is transformed into an optical signal with the help of Mach–Zehnder Interferometer (MZI) based electro- optic converter. Generated Optical signal may be dispatched to any location which is remote in nature by using fiber optic cable. Thus, various types of measurement error observed in the conventional capacitive level transmitter are minimized by using the proposed system. In the preset paper, a prototype model of the proposed system has been designed and developed to test its functionality. A good linear characteristic of the normalized optical output in support of the derived equations is observed. [ABSTRACT FROM AUTHOR]

On-line performance monitoring of RF integrated circuits throughout their operating lifetime is a promising way to enhance their reliability. This paper explores the feasibility of adapting the indirect test strategy to implement on-line RF performance monitoring. After stating the principle of the proposed solution, we consider the fundamental requirements necessary to adapt the indirect test strategy. Finally, a proof of concept is established through a practical case of study by monitoring the power level delivered by the RF transmitter of a wireless microcontroller: hardware measurement results demonstrate the potential of this approach. [ABSTRACT FROM AUTHOR]

We consider the feasibility of detection of electromagnetic response in the upper ionosphere to ground-based large-scale extremely low-frequency (ELF) transmitters by low-orbiting satellites. As an example of such mega transmitters, we consider the ZEVS 82-Hz transmitter and the FENICS facility with decommissioned electric power lines driven by an 0.5–100 Hz oscillator. We numerically simulated the ELF wave energy leakage into the upper ionosphere, generated by an oscillating grounded linear current of finite length suspended above a high-resistance ground. An altitudinal profile of the plasma parameters has been reconstructed using the ionospheric IRI model. The main step in the analysis of the problem is the solution of Maxwell equations in the atmosphere–ionosphere system with the source in the form of a horizontal current dipole. The electromagnetic field is split into potential and vortex components using the potentials introduced. This problem is devoid of axial symmetry, but the potential and vortex components have this symmetry individually. This approach has enabled us to separate the variables and pass to a one-dimensional boundary-value problem using the Hankel transform. A perturbation excited by a horizontal current of finite length is calculated by summing the fields of horizontal current dipoles that are densely distributed along the current line. According to the model proposed, the horizontal ELF antennas with a length of 60 to 100 km driven by a 100–200 A current can provide electric response amplitudes of up to 60–70 μV/m in the upper nightside ionosphere. [ABSTRACT FROM AUTHOR]

The performance of free space optical (FSO) communication is primarily dependent on atmospheric turbulence and pointing errors, where pointing error compromises of boresight error and jitter. However, most of the existing work considered pointing error by counting zero-boresight error or jitter while evaluating the performance of FSO communications. In this paper, a generalized distribution, Nakagami-m fading, for the radial displacement of pointing error is considered by taking account of both boresight and jitter error for performance analysis of FSO communication. Two subsequent auto-tracking mechanisms are designed and developed at the transmitter to combat the issues of boresight error and jitter. First is a coarse tracking system to minimize the boresight error and second is fine tracking to remove leftover boresight error known as jitter. FSO received power is continuously monitored, and the link status is feedback to the transmitter via the RF link to initiate the corresponding tracking. The proposed auto-tracking mechanism has experimented with a wide range of non-zero boresight angles, which is from ± 10 ∘ to ± 180 ∘ with a fine-tuning of horizontal displacement up to ± 8 cm from the receiver center. A closed-form outage probability is derived over generalized phenomenon where the analytical results are compared with simulation, measurement, and with existing methods. [ABSTRACT FROM AUTHOR]

Mode division multiplexing (MDM) has emerged as a futuristic and potential technology for next-generation optical wireless networks. However, the inter-channel interference in multi-channel systems and the modes coupling in mode division multiplexed systems are the two predominant limitations and need to be addressed. Therefore, in this work, an inter-channel interference suppression technique based on the opting transmitter diversity (TD) technique is presented in 2λ × 2HG modes × 10 Gbps IsOWC system. For the realization of TD technique, two diverse arrangements such as Non return to zero (NRZ)-return to zero, and NRZ-alternate mark inversion (AMI) are proposed and also compared with non-TD arrangement such as NRZ–NRZ over 5000 km IsOWC distance. Hermite Gaussian (HG) modes like HG00 and HG01 are modulated with 850 nm and 850.8 nm each and provide 40 Gbps capacity. The proposed multichannel MDM-TD-IsOWC system is investigated for different IsOWC distances and pointing errors in terms of Log Bit error rate (BER) and compared with different reported studies. It is observed that IsOWC system provide improved performance by incorporating an N–A (NRZ-AMI) arrangement and offer maximum log BER for N–N (NRZ–NRZ) (non-TD) system. [ABSTRACT FROM AUTHOR]

The paper presents the concept of a low-power, low-area, near-lossless image compressor for resource-constrained devices such as wireless capsule endoscopy (WCE). The compressor directly processes the raw data from the Bayer Color Filter Array (CFA) imager to avoid the high cost of color interpolation. To improve the efficiency of the compressor in terms of energy consumption, silicon area and compression ratio, the main part of the compressor, i.e., the entropy encoder, uses the existing correlations between the color components of a captured CFA image. The proposed image compressor requires only 12.4% of the memory needed by other high-quality CFA compressors based on the JPEG-LS standard. Despite this significant reduction in memory size, the proposed image compressor outperforms other state-of-the-art coding schemes on capsule endoscopy images. At the same time, it offers only slightly lower performance on standard test images. The proposed image compressor has been implemented as an intellectual property (IP) core using two different low-cost CMOS processes. The design, implemented in UMC 180 nm CMOS process, requires a very low silicon area (534 × 426 μ m 2 ) and consumes very low energy (22 μ J per a single 512 × 512 image frame). Even higher energy efficiency (12 μ J per the same image frame) has the IP core implemented in the TSMC 130 nm CMOS process. Both of the selected technologies are low-cost and well-suited to implement a radio frequency transmitter and a low-power successive approximation register analog-to-digital converter in addition to the compressor to provide a cost-effective System on Chip for resource-constrained devices like WCE or wireless camera sensor network. [ABSTRACT FROM AUTHOR]

Flutter-detecting foragers require specific adaptations of the transmitter and the receiver of their echolocation systems to detect and evaluate flutter information in the echoes of potential prey. These adaptations include Doppler shift compensation (DSC), which keeps the echo frequency from targets ahead constant at a reference frequency (fref), and an auditory fovea in the cochlea, which results in foveal areas in the hearing system with many sharply tuned neurons with best frequencies near fref. So far, this functional match has been verified only for a very few key species, but is postulated for all flutter-detecting foragers. In this study we determined both, the transmitter and receiver properties within individuals of the Bourret's horseshoe bat (Rhinolophus paradoxolophus), an allometric outlier in the rhinolophid family. Here we show that the transmitter and receiver are functionally matched in a similar way as postulated for all flutter-detecting foragers. The performance of DSC, measured as the ability to keep the echo frequency constant at fref, had a precision similar to that found in other flutter-detecting foragers, and the audiogram showed the characteristic course with a minimum at fref. Furthermore, we show for a rhinolophid bat a variation over time of the coupled resting frequency and fref. Finally, we discuss the tight match between transmitter and receiver properties, which is guaranteed by the link between the foveal areas of the receiver and the audio–vocal control system for DSC. [ABSTRACT FROM AUTHOR]

This paper aims the development of a new reduced-cost algorithm for a multi-objective robust transmitter placement under uncertainty. Toward this end, we propose a new hybrid Kriging/Grey Wolf Optimizer (GWO) approach combined with robust design optimization to estimate the set of Pareto frontier by searching robustness as well as accuracy (lower objective function) in a design space. We consider minimization of the energy power consumption for transmitting as well as maximization of signal coverage in a multi-objective robust optimization model. The reliability of the model to control signal overlap for multiple transmitting antennas is also provided. To smooth computational cost, the proposed method instead of evaluating all receiver test points in each optimization iteration approximates signal coverages using Kriging interpolation to obtain optimal transmitter positions. The results demonstrate the utility and the efficiency of the proposed method in rendering the robust optimal design and analyzing the sensitivity of the transmitter placement problem under practically less-expensive computational efforts (350% and 320% less than computational time elapsed using standalone GWO and NSGAII respectively). [ABSTRACT FROM AUTHOR]

Research on quantum sensors for the detection of magnetic fields (quantum magnetometers) is one of the fast-moving areas of Quantum Technologies. Since there exist expectations about their use in geophysics, this work will provide a brief overview on the various developing quantum technologies and their individual state of the art for implementing quantum magnetometers. As one example, the developments on superconducting quantum interference devices, so-called SQUIDs as a specific implementation of a quantum magnetometer, are presented. In the course of this, SQUID instrument implementations and associated demonstrations and case studies will be presented. An airborne vector magnetometer with ultra-low noise ( < 10 fT / Hz ) and high dynamic range of > 32 bit will be introduced which has the prospect to be applied for the magnetic method in parallel with electromagnetic methods such as passive audio-frequency magnetics or semi-airborne methods using active transmitters such as elongated grounded dipole sources. The according signals are separated in the frequency domain. A second implementation is an airborne full tensor gradiometer instrument will be discussed which has shown already a number of successful case studies and which turned into commercial operation in the past years. Besides the airborne instrument, a very successful implementation of quantum magnetometers is the SQUID-based receiver for the ground-based transient electromagnetic method. Today it is a mature technology which has been in commercial use for more than a decade and has led to a number of discoveries of conductive ore bodies. One case study will be presented which demonstrates the performance of this instrument. Finally, future prospects of using quantum magnetometers, including SQUIDs and new optically pumped magnetometers, in geophysical exploration will be discussed. Particular applications for both sensor types will be introduced. [ABSTRACT FROM AUTHOR]

Four-Wave Mixing (FWM) is a performance constraint in WDM Radio over Fiber(RoF) systems. This article uses several equations to analyze & investigate the performance of FWM crosstalk power and Signal to Crosstalk Ratio (SXR) corresponding to channel spacing, transmission distance & input optical power for different kinds of fiber like Alcatel Teralight, Corning Leaf, Furukawa SM-332 and Lucent Truewave under the influence of higher-order dispersion terms up to 10th order. An improved optical network including a polarization rotator at the transmitter and modern state of art optical fibers is proposed to combat FWM-induced crosstalk. It is reported that the use of a polarization rotator reduces FWM crosstalk by 7.5 dBm with an input power of 20 dBm. Further, it is also revealed that Corning LEAF performs better compared to the rest of fibers while minimizing FWM-induced crosstalk. [ABSTRACT FROM AUTHOR]

Underwater visible light communication emerges as a promising technique to enhance the capacity of underwater wireless communication networks for upcoming generation. Major technical problem with underwater visible light communication systems in motion is the pointing, acquisition, and tracking. To ease pointing, acquisition, and tracking, hence it is important to navigate optical information beam over broad range and adjust the transmitter beam divergence angle according to the link condition, which is adjusted by the Optisystem software. In this paper, performance comparison among wide range of transmittance optical beams in underwater visible light communications system for high-speed communication is presented for PIN as well as for Avalanche photodiode. The effect of using variable transmittance beam-divergence angle on the bit-error rate, signal-to-noise ratio, communication link distance is also investigated. OptiSystem and MATLAB software is used to implement the underwater visible light communication transceiver system. Finally, it is shown in the paper that in the presence of pointing errors, adaptive beam control techniques improve the performance of high-speed Underwater visible light communication system. [ABSTRACT FROM AUTHOR]

For several years, the fields of new technologies have been experiencing a real boom. The use of the terahertz band is an appropriate solution to meet the requirements of these technology. However, this technology has special requirements among which its antennas must have high bandwidth of few THz and achieve high gain for high productivity. In this paper, we will focus on the design and analysis of an antenna for THz technology. The antenna structure proposed in this work has better performance in terms of bandwidth and gain. In fact, multiples slots were added to the antenna to enhance the antenna's bandwidth. In addition, to enhance the antenna performance in terms of gain and protect the antenna feed line against environmental jeopardies a thin layer as superstrate is used. The suggested antenna covers a wide −10 dB bandwidth from 0.9 to 17.3 THz with a peak gain of 12.8 dBi. Moreover, a VSWR less than 2 at the operating band is obtained. Furthermore, the suggested antenna has circular polarized radiations with an axial ration (AR) less than 3 dB over a wide band 13.6–17.3 THz which mean that the proposed antenna is well suited for application where the transmitter and receiver are moving which is the most case for wireless system. Thus, the suggested THz antenna could be a successful choice for terahertz application like future high-speed short-range indoor wireless communication, explosive detections, arms detection, medical imaging, pharmaceutical analysis, and material characterization in the THz regime industrial inspections. [ABSTRACT FROM AUTHOR]

Super-PON is a 16-wavelength passive optical network with 50 km reach and 64 ONUs per λ , providing up to 10 Gb/s to sparsely populated areas. To bridge its challenging loss-budget, Super-PON includes an EDFA located next to the OLT, thus compromising transceiver integration and future spectral expansion. An alternative for downstream transmission consists in using a powerful directly-modulated semiconductor optical amplifier (SOA) and an avalanche photodiode. Here, we numerically demonstrate the technical feasibility of this proposal. By combining a sensitivity of − 24.9 dBm and an optimized SOA transmitter output of +19.4 dBm, error-free (BER ≤ 3.8x10 - 3 ) transmission is demonstrated. This achievement relies on the use of PAM-4 modulation to combat the limited opto-electronic bandwidth of the SOA, and Tomlinson-Harashima precoding (THP) to mitigate fiber transmission and receiver impairments. It is also shown that THP enhances the direct modulation capability of SOAs, leveraging their use in integrated transceivers aimed for high-loss photonic systems. [ABSTRACT FROM AUTHOR]

The use of various technologies to increase efficiency and safety has been continuously increasing. Wireless power transfer (WPT) has emerged as a key technology to increase in this regard. WPT can simplify complex wiring and improve safety by eliminating the need for mechanical contact. Most electronic devices used in buildings are of medium power, and research is being conducted to increase the output power of WPT through the combination of different technologies. This study proposes a 4-Tx WPT system using four transmitters (Tx) to satisfy the power requirements of medium-power electronic devices used in buildings. The existing WPT methods, 1-Tx and 2-Tx, were compared with the proposed 4-Tx WPT. The characteristics of efficiency and output power were analyzed through each Tx phase control of the 4-Tx system. The mutual inductance based on the distance between Tx and Rx was measured, and the relationship between the efficiency and output power was analyzed. Experimental results show that the proposed 4-Tx system is more advantageous in terms of medium power than the existing WPT methods. The proposed WPT system has power control capability, high output power, and high efficiency by adapting the phase control of each Tx. Moreover, it is confirmed that the range of the distance between Tx and Rx that is satisfying the minimum output power of medimum-power electronic device based on the relationship between the efficiency and the output power with the separation distance of Tx and Rx. [ABSTRACT FROM AUTHOR]

In multi-input wireless power transfer (WPT) systems, it is plagued to create a destructive interference between the multiple transmitters to result in a relatively low voltage delivered to the receiving coil and load, due to the phase differences of the received voltages from different transmitters. In this regard, it is essential to synchronize the phases of the received voltages of the receiving coil from different transmitters. However, the existing offline synchronization methodologies rely heavily on an analytical form solution of the received voltage in a receiver. In most engineering application scenarios, such close-form solution is almost impossible. Moreover, the close form solution, even if possible, will vary with the operating conditions and environments. To eliminate these deficiencies of existing synchronization methodologies, an online synchronization methodology is proposed for a multi-input WPT system. In the proposed methodology, the received voltages from different transmitters are determined from a series of online voltage samplings under different offset phases, and a synchronization strategy is then proposed and implemented. A multi-input WPT prototype is developed to test the feasibility of the proposed synchronization methodology. The experimental results have demonstrated that the received voltage is significantly enhanced by applying the proposed online phase synchronization methodology. [ABSTRACT FROM AUTHOR]

Metasurfaces are artificial structures that can display uncommon and exotic electromagnetic properties like negative permittivity and permeability. Metamaterials along with metasurfaces have attracted a lot of attention because of their unusual properties which seem to be a prominent technology for escalating the performance of microwave components and overthrowing the constraints, especially of an antenna. The investigation and development of Multiple-Input Multiple-Output (MIMO) wireless access technology are inspired by the lack of bandwidth shortage globally. MIMO is a key enabler that integrates antennas not only at the transmitter and receiver end to achieve incredible data rates and energy efficiency while requiring minimal computation. The extensive study into fifth-generation (5G) systems points to a digital revolution to meet the increasing demands and desires for high-speed connectivity-based applications. The third generation partnership project (3GPP) releases timely upgrades in 5G technology standards, allowing researchers to modify their scientific objectives and contribute to advancement. Not even just smartphones will support 5G technology, but also various Internet of Things (IoT) devices will provide various kinds of services such as smart buildings, smart cities, and more, all of which will necessitate 5G antennas. Many antennas based on metamaterial or metasurface are suggested until now, but an extensive review is yet to be performed based on key enhancement techniques. As a result, we have intended to examine the various types of 5G metamaterial/metasurface-based MIMO antenna designs holistically in this work. [ABSTRACT FROM AUTHOR]

In this contribution, we generalize PPP–RTK theory by allowing the transmitters to transmit on different frequencies. The generalization is based on the integer-estimability theory of Teunissen (A new GLONASS FDMA model. GPS Solutions, 2019). As the theory and associated algorithms provided are generally applicable, they apply to satellite-based carrier-phase positioning as well as to terrestrial interferometric sensory networks. Based on an identification of the constraints imposed on the admissible ambiguity transformations by PPP–RTK, a fundamental network+user condition is found that determines whether PPP–RTK is possible or not. The discriminating contributions of both the network and user observation equations to this PPP–RTK condition are analysed, followed by a description of PPP–RTK enabling classes of measurement scenarios. [ABSTRACT FROM AUTHOR]

Energy efficiency and data gathering are the primary goals of wireless sensor networks (WSNs), challenging. Mobile sink and mobile chargers are two promising techniques for data collection by visiting (a set of) sensor nodes and energy replenishment, respectively. These two operations joined in a single mobile element for data gathering and energy replenishment simultaneously to prolong the energy efficiency in WSNs. However, it is challenging to identify the optimal set of anchor points and their visiting order. In this context, this paper proposed an efficient algorithm called Joint Mobile Wireless Energy Transmitter and Data Collector (J-METDC) to mitigate the above-discussed challenges. The J-METDC algorithm uses the Spectral clustering (SC) algorithm to partition the network where the centroid is in the communication range of the mobile element to recharge or data gathering purposes. Next, a cat swarm optimization (CSO) algorithm decides the order of visiting to recharge an SN by trade-offing the available number of packets and residual energy. The SC executes once, whereas the CSO is performed multiple times depending on the request received from any partition. The SC and CSO are lightweight algorithms over the traditional machine learning and swarm intelligence algorithms. So, these two algorithms address the challenge with quick decisions by providing the optimal solution. [ABSTRACT FROM AUTHOR]

We propose a single laser source-based free space optical link for transmission of bidirectional data of three different channels between modular data centers, where each channel has a data rate of 20 Gbps. The downlink channels are transmitted using a combination of differential quadrature phase shift keying (DQPSK) and pulse amplitude modulation (PAM). The uplink channels are transmitted using On-Off keying (OOK). The optical signals are transmitted over a 500-m free space optical (FSO) link based on Gamma–Gamma channel model. A regenerative wavelength converter is used to generate multiple optical pulsed carriers from the received downlink optical signals. The performance of the proposed architecture is evaluated under medium turbulence condition, which represents the FSO channel in a data center scenario. Our simulation results show that the proposed architecture gives acceptable bit-error-rate (BER) results. The architecture can be used as a potential substitute to fiber-based interconnects in a data center or a general point link in a passive optical network (PON), enabling high data-rate and cost-efficient transmission. [ABSTRACT FROM AUTHOR]

This paper aims the development of a new reduced-cost algorithm for a multi-objective robust transmitter placement under uncertainty. Toward this end, we propose a new hybrid Kriging/Grey Wolf Optimizer (GWO) approach combined with robust design optimization to estimate the set of Pareto frontier by searching robustness as well as accuracy (lower objective function) in a design space. We consider minimization of the energy power consumption for transmitting as well as maximization of signal coverage in a multi-objective robust optimization model. The reliability of the model to control signal overlap for multiple transmitting antennas is also provided. To smooth computational cost, the proposed method instead of evaluating all receiver test points in each optimization iteration approximates signal coverages using Kriging interpolation to obtain optimal transmitter positions. The results demonstrate the utility and the efficiency of the proposed method in rendering the robust optimal design and analyzing the sensitivity of the transmitter placement problem under practically less-expensive computational efforts (350% and 320% less than computational time elapsed using standalone GWO and NSGAII respectively). [ABSTRACT FROM AUTHOR]

In this paper, a novel chaos-based cryptosystem is proposed to ensure the communication security of video/audio streaming in the network environment. Firstly, by the proposed synchronization controller for the master and slave chaotic systems, respectively, embedded in the transmitter and receiver, the cryptosystem can generate the synchronized and dynamic chaotic random numbers at the transmitter and receiver simultaneously. Then integrating the chaotic random numbers with SHA3-256 (Secure hash algorithm 3), the design of synchronized dynamic key generators (SDKGs) is completed. Continuously, we can apply the SDKGs to encrypt/decrypt streaming audio/video data. In our design, we introduce the AES CFB (Advanced encryption standard cipher feedback) encryption algorithm with SDKGs to encrypt the video/audio streaming. Then the cipher-text is transmitted to the receiver via the network public channel and it can be fully decrypted with the dynamic random keys synchronously generated at the receiver. A duplex audio/video cryptosystem is realized to illustrate the performance and feasibility of this proposed research. Finally, many tests and comparisons are performed to stress the quality of random sequences generated by proposed SDKGs. [ABSTRACT FROM AUTHOR]

Dual polarization quadrature phase-shifting keying (DP-QPSK) wavelength division multiplexing (WDM) systems are currently acting as the backbone of long-haul optical networks. It has provided a cost-effective solution for network up-gradation due to its backward compatibility on legacy infrastructure of standard single-mode fiber. Encoding of two bits per symbol per polarization, low BER over long haul transmission reach, and simple digital equalization techniques are the main features of 100G DP-QPSK technology. A large amount of voice, video, and high-speed data services are being provided by DP-QPSK WDM-based optical networks. This paper reviews the progress happened in the DP-QPSK WDM system since its introduction. The work is focused on reviewing important incorporations researched and developed related to the transmitter and digital coherent receiver. [ABSTRACT FROM AUTHOR]

Reference-frame-independent quantum key distribution (RFI-QKD) can generate secret keys without the alignment of reference frames. However, in most RFI-QKD systems, the afterpulse inherent in single-photon avalanche detectors at the receiver's side is always ignored, which will lead to a large deviation from the data obtained by the existing analytical models. In this paper, we establish an afterpulse-compatible analytical model to fix this deviation. Simulation results show that the secret key rate is overestimated when the afterpulse is ignored. Furthermore, based on the afterpulse-compatible model, we investigate the effect of the intensity fluctuation of the source at the transmitter's side. Simulation results show that both the afterpulse and the intensity fluctuation affect the secret key rate, which should be carefully considered in practical RFI-QKD systems. [ABSTRACT FROM AUTHOR]

With exponential growth in the number of wireless devices and limited available spectrum, the problem of spectrum sharing remains in forefront of the research community. Due to the large number of wireless sensing devices, even a small percentage of savings can translate into significant spectrum efficiencies. One of the main hurdles in efficient spectrum sharing in wireless sensor networks (WSN) is the problem of power management at the node level to promote longevity without polluting the spectrum, while promoting collaboration. This problem is even more challenging in extreme (harsh) environments where access to power and battery replacement and charging is limited, if not impossible. Passive sensor technology can be used to eliminate the need for batteries, but it suffers from short communication range. Recently, wireless energy transfer (WET) for powering remote sensor nodes in a WSN has drawn considerable research attention, since it can charge sensing circuits remotely and relieve the need for battery replacement. Modeling the charging and power utilization processes can help with smart transmission decisions, which can eliminate unnecessary transmissions and not only save limited battery power at the node level, but also efficiently utilize the shared spectrum. In this paper, we consider a general relay energy assisted scenario, where a transmitter is powered by an energy source through both direct and relay links. We model data and energy channels separately, transmit energy to power the transmitter battery and schedule data transmission based on stochastic models for data. We also consider various static, mobile and highly scattered channel models. We will set a threshold on required transmission energy and channel quality to decide whether the transmission can be successful (efficient use of spectrum) or the packet may not reach the destination (polluting the spectrum unnecessarily). An energy efficient scheduling method is proposed for the system model to determine whether to transmit data or stay silent based on the stored energy level and channel state. An analytical expression has been derived to approximate outage probability of the system in terms of energy and data thresholds. All theoretical results are validated by numerical simulations and verify the effectiveness of energy relaying and proposed energy efficient scheduling method in reducing the outage probability of the system [ABSTRACT FROM AUTHOR]

In the unmanned ship networking scenario, the position of the unmanned ship changes continuously, leading to the result that the desired transmitters and the interference transmitters may exchange identities at any time. The traditional interference alignment technique cannot solve the interference. To solve this problem, this paper proposes an adaptive interference alignment scheme based on the dynamic selection of the desired transmitters for the unmanned ship network. Firstly, according to the characteristics of the unmanned ship networking scene, a new measurement value the non-directional user signal to interference ratio W is proposed, and the desired user set and connection mode are selected through the calculation of W. Secondly, the corresponding interference alignment scheme is designed. The iterative interference alignment algorithm is used for non-directional users, while partial interference alignment algorithm is used for directional users, and the proof of algorithm convergence is given. Lastly, the scheme can dynamically select and update the desired user set and connection mode when the position of the unmanned ship changes, and the corresponding interference alignment scheme will also perform adaptive updates. Experimental results indicate that the scheme can select the optimal connection mode according to the current position of the unmanned ship and eliminate the interference caused by the undesired transmitter. [ABSTRACT FROM AUTHOR]

We present a novel approach to coherent photonic THz systems supporting complex modulation. The proposed scheme uses a single optical path avoiding the problems of current implementations, which include: phase decorrelation, 3-dB power loss, and polarization and power matching circuits. More importantly, we show that our novel approach is compatible with direct modulation of the output of an optical frequency comb (i.e., not requiring the demultiplexing of two tones from the comb), further simplifying the system and enabling an increase in the transmitted RF power for a fixed average optical power injected into the photodiode. [ABSTRACT FROM AUTHOR]

By exploiting the carrier frequency offset (CFO) between a transmitter-receiver pair, this paper proposes a CFO-based physical layer authentication scheme for dynamic multiple-input-multiple-output (MIMO) systems. We first provide analytical modeling of dynamic CFO in such MIMO systems by jointly taking into account the intrinsic oscillator mismatch and Doppler frequency shift caused by node mobility, and employ the self-correlating and extended Kalman filtering techniques for the CFO estimation and prediction. By quantizing the difference between the estimated CFO and predicted one, we then apply the statistical signal processing techniques to develop a CFO-based physical layer authentication scheme for transmitter identity verification. With the help of tools from stochastic process and hypothesis testing theories, we further derive the analytical expressions for false alarm rate as well as detection rate to evaluate the performance of the proposed scheme. Finally, we provide extensive numerical results to demonstrate the efficiency of the proposed scheme. [ABSTRACT FROM AUTHOR]

We present a novel approach to coherent photonic THz systems supporting complex modulation. The proposed scheme uses a single optical path avoiding the problems of current implementations, which include: phase decorrelation, 3-dB power loss, and polarization and power matching circuits. More importantly, we show that our novel approach is compatible with direct modulation of the output of an optical frequency comb (i.e., not requiring the demultiplexing of two tones from the comb), further simplifying the system and enabling an increase in the transmitted RF power for a fixed average optical power injected into the photodiode. [ABSTRACT FROM AUTHOR]

The efficiency of Internet of Things (IoT) mobile networks is limited by the battery's capacity in IoT devices. In addition to their replacement/recharge problem, batteries delimit devices' processing and data forwarding capabilities, hence degrading the performance of IoT networks. Recent advances in Wireless Power Transmission (WPT) technology provide an attractive solution, namely Wireless Powered Communication (WPC), in which wireless devices are charged through wireless power transmitters. However, the design and prospect of WPC applications are challenged by the poor efficiency of long-distance WPT. On the other hand, solar energy harvesting is a conventional and natural method for conveying energy wirelessly to devices. This article reviews WPT technology as well as solar energy harvesting and investigates their challenges in IoT networks. It is shown that smart integration of these two energy supply methods to power IoT networks wirelessly leads to more efficient WPCs called green WPC. Three frameworks for green WPC have been investigated in this article. These methods are simulated and analyzed in a network and energy model in separate scenarios. Green WPC is a potential solution to create networks with a longer lifetime and higher reliability and flexibility than conventional battery-based methods. [ABSTRACT FROM AUTHOR]

In this simulation study, the dynamics of a twin vertical-cavity surface-emitting laser (VCSEL) subjected to optical injection are studied. A special novel configuration includes two laser devices, of which one is considered as the injector, while the other is considered as the transmitter. The signal for the first laser, LD1, is directed towards the second, LD2, which is responsible for chaotic transmission. During the signal trip from LD1 to LD2, the signal is separated into two parts by fibre Bragg grating (FBG). This is to change some signal properties. Results indicated that moderate bandwidth chaotic emission is available outside the laser device cavity. Contrary to conventional edge-emitting lasers, it is found that VCSELs operate with fewer modes and higher amplitudes. The selected properties for the simulated signal are: LD SEED, polarisation, FBG applied stress and temperature. The resulting lasing modes range from chaotic to enhanced modes. To ensure independent dynamics, cross-correlation (CC) between LD1 (which is responsible for perturbation) and LD2 antisynchronisation is approved. The CC for these two lasers ranged from - 0.0028 to - 6.5 E - 05 . [ABSTRACT FROM AUTHOR]

We present an emulation design method for converting asymmetrical transmitters to nonreciprocal isolators equipped with time-varying metasurfaces. To illustrate the model, we design a structure using a combination of the photonic crystal (PhC) and time-varying metasurface. Moreover, we propose a general approach for numerical analysis of the time-modulated proposed structure using the extension of the transfer matrix method (TMM) which consists of working through the device one layer at a time and calculating an overall transfer matrix including the time-variation of the permittivity and permeability in each layer. Also, we use an optimization algorithm that is less used in the field of electromagnetism but is suitable for fast and accurate parameter optimization. The results show that the proposed method, using pure time-varying metasurfaces which cannot prepare full nonreciprocity alone, is a promising procedure for breaking the Lorentz reciprocity in the general isolator system as well as maintaining the main core of previously asymmetric designed structure. [ABSTRACT FROM AUTHOR]

Digital Terrestrial Television (DTV) has been widely deployed globally for more than a decade. The transmitter identification (Tx-ID) technique specified in modern DTV standards becomes important today as the number of DTV transmitters grows with the expanded coverage area. In the ATSC standards, Kasami sequences, a crucial class of pseudo random sequences, are considered as feasible Tx-ID sequences because they possess several favorable properties leading to nearly Dirac-delta autocorrelation/cross-correlation functions and large sequence capacities. It is well known that the interference-pluse-noise level (INL) or signal-to-interferenec-plus-noise ratio (SINR) plays a very important role in the Tx-ID system performance. Nontheless, such a crucial factor has been evaluated only in the statistical average due to the difficulty of characterizing the exact pertinent probabilitistic analysis. In this work, we combat the aforementioned difficulty by applying a probability-density approximation method to statistically characterize random variables like INL and SINR. With the exact probability density functions of INL and SINR, we can analyze the detailed statistical characteristics of numerous Tx-ID related parameters, including Tx-ID capacity and reception quality in terms of SINR. Extensive numerical experiments are also undertaken to justify the effectiveness of our proposed new analysis and explore detailed quantitative insight for critical Tx-ID system parameters and performance metrics. [ABSTRACT FROM AUTHOR]