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One of the motivations towards the 5G cellular networks and beyond is the large increase in the supported data rate in both uplink and downlink. Deployment of small size cells, massive MIMO, wherein a large number of antennas are deployed at transmitters and receiver, are effective tools in these networks. Users under cell massive MIMO networks "mMIMO" can provide high data rate. However, the cell-edge user and users, under shadowing, can have a poor performance. Cell-Free networks can provide a satisfied data rate even for shadowed and cell-edge users. In this paper, cell-Free mMIMO networks are mathematically analyzed applying different cooperation mechanisms among the access points APs. Moreover, a new mathematical formula for the throughput, based on BER, is derived. Furthermore, closed formulas for the throughput-BER as well as energy efficiency (EE) performance are derived. Finally, the cognitive radio concept is proposed in order to limit the interference among users accessing the same resources in uplink. Simulation results show that the fully centralized cell-Free mMIMO network has a higher spectral efficiency and energy efficiency than the cellular mMIMO networks at different BER values especially when MMSE is applied. Furthermore, the cognitive radio theory can increase the SE and EE performance of the cell-Free networks when all cooperation mechanisms are applied. [ABSTRACT FROM AUTHOR]

In this paper, we systematize architectural and circuit design solutions applicable in the design of digital parts of multispeed transceivers of serial channels. Such variants of solutions, which allow using most of the possibilities of available technology for expanding this range, especially in its high-frequency part, are substantiated. The SpaceFibre multi-speed serial channel transceiver was designed by CMOS technology using the proposed solutions. The manufactured transceiver operates in the range of bit rates from 5 Mbps to 3.125 Gbps and, in terms of the set of measured parameters, is not inferior to the closest foreign analogs. [ABSTRACT FROM AUTHOR]

Singular value decomposition (SVD) beamforming is an attractive tool for reducing the energy consumption of data transmissions in wireless sensor networks whose nodes are equipped with multiple antennas. However, this method is often not practical due to two important shortcomings: it requires channel state information at the transmitter and the computation of the SVD of the channel matrix is generally too complex. To deal with these issues, we propose a method for establishing an SVD beamforming link without requiring feedback of actual channel or SVD coefficients to the transmitter. Concretely, our method takes advantage of channel reciprocity and a power iteration algorithm (PIA) for determining the precoding and decoding singular vectors from received preamble sequences. A low-complexity version that performs no iterations is proposed and shown to have a signal-to-noise-ratio (SNR) loss within 1 dB of the bit error rate of SVD beamforming with least squares channel estimates. The low-complexity method significantly outperforms maximum ratio combining diversity and Alamouti coding. We also show that the computational cost of the proposed PIA-based method is less than the one of using the Golub–Reinsch algorithm for obtaining the SVD. The number of computations of the low-complexity version is an order of magnitude smaller than with Golub–Reinsch. This difference grows further with antenna array size. [ABSTRACT FROM AUTHOR]

Data rates in optical fiber networks have increased exponentially over the past decades and core-networks are expected to operate in the peta-bit-per-second regime by 2030. As current single-mode fiber-based transmission systems are reaching their capacity limits, space-division multiplexing has been investigated as a means to increase the per-fiber capacity. Of all space-division multiplexing fibers proposed to date, multi-mode fibers have the highest spatial channel density, as signals traveling in orthogonal fiber modes share the same fiber-core. By combining a high mode-count multi-mode fiber with wideband wavelength-division multiplexing, we report a peta-bit-per-second class transmission demonstration in multi-mode fibers. This was enabled by combining three key technologies: a wideband optical comb-based transmitter to generate highly spectral efficient 64-quadrature-amplitude modulated signals between 1528 nm and 1610 nm wavelength, a broadband mode-multiplexer, based on multi-plane light conversion, and a 15-mode multi-mode fiber with optimized transmission characteristics for wideband operation. Space division multiplexing solutions are one way to increase future fiber information capacity. Here, the authors show peta-bit/s transmission in a standard-diameter, multimode fiber enabled by combining several practical multiplexing technologies. [ABSTRACT FROM AUTHOR]

In this paper, we devise a resource allocation scheme for secure communications in a device to device (D2D) communication scenario underlaying an existing orthogonal frequency division multiple access cellular network in which there are some eavesdroppers overhearing the information transmission of cellular network, i.e., from base station (BS) to cellular users. Given the uncertainty of perfect values of channel state information and channel distribution information (CDIs) for the transmitters such as BS and transmitters of D2Ds, the required knowledge about these parameters is feedbacked via some channels of limited capacity. The devised resource management scheme is written in an optimization problem whose solution is subcarrier allocations, transmit power allocations, and determination of the fading space boundaries and CDIs' boundaries, and are obtained using the particle swarm optimization method. We aim at maximizing the weighted sum of average rate of D2D pairs and average energy efficiency of them while the average secrecy rate of cellular network should be maintained above a predefined threshold. We consider the case where D2D pairs use only their batteries and the case where in addition to the battery, D2D pairs can harvest the energy and use it for the transmission purpose. Using simulations, we evaluate the proposed framework in different situations. [ABSTRACT FROM AUTHOR]

Authors propose a hardware based approach for reliable encryption in wireless network using Cellular Automata (CA). Distinct layers of encryption have been utilized in proposed model for enhancing data security. Transmitter and receiver modules are designed for performing state transition based encrypted activities. Transmitter module is required for capturing environmental turbulences (noise) from a specific geographical location and send encrypted signal to receiver module through wireless network. Receiver module analyses received signal after decryption for desired activities based on real time situations. Different hardware components are selected and compared based on market study targeting efficient construction of proposed modules. Time complexity and code break complexity are measured using different key lengths, keysets, and data sizes for proposed CA based encryption scheme achieving unique results in hardware based cryptography system. Encryption key length, index, and keyset are required for computing code break complexity in design model. Large data size is effectively managed to calculate protection ratio and reliability factor for realizing efficient protectiveness and accuracy. Comparative study between existing encryption technique and proposed CA based encryption technique is established based on time complexity and code break complexity. [ABSTRACT FROM AUTHOR]

Light-in-flight sensing has emerged as a promising technique in image reconstruction applications at various wavelengths. We report a microwave imaging system that uses an array of transmitters and a single receiver operating in continuous transmit-receive mode. Captures take a few microseconds and the corresponding images cover a spatial range of tens of square meters with spatial resolution of 0.1 meter. The images are the result of a dot product between a reconstruction matrix and the captured signal with no prior knowledge of the scene. The reconstruction matrix uses an engineered electromagnetic field mask to create unique random time patterns at every point in the scene and correlates it with the captured signal to determine the corresponding voxel value. We report the operation of the system through simulations and experiment in a laboratory scene. We demonstrate through-wall real-time imaging, tracking, and observe second-order images from specular reflections. The authors present a microwave imaging system that can operate in continuous transmit-receive mode. Using an array of transmitters, a single receiver and a reconstruction matrix that correlate random time patterns with the captured signal, they demonstrate real-time imaging and tracking through a wall. [ABSTRACT FROM AUTHOR]

We present a miniaturized quantum key distribution system, designed to augment the more mature quantum key distribution systems currently commercially available. Our device is designed for the consumer market, and so size, weight and power are more important than raw performance. To achieve our form factor, the transmitter is handheld and the receiver is a larger fixed terminal. We envisage users would bring their transmitters to centrally located receivers and exchange keys which they could use at a later point. Transmitting qubits at 80 MHz, the peak key rate is in excess of 20 kbps. The transmitter device fits within an envelope of <150 ml, weighs 65 g and consumes 3.15 W of power. [ABSTRACT FROM AUTHOR]

In this paper, a three-dimensional target localization problem in widely separated multiple-input multiple-output radars is solved using two specific techniques based on time difference of arrival measurements. These techniques are provided in terms of transmitter and receiver antennas, which are named as technique_t and technique_r, respectively. The localization problem is rewritten as a non-convex optimization problem which is based on a least-squares method without any initial estimation. Therefore, a convex semidefinite programming problem is obtained by utilizing the semidefinite relaxation method for the problem which can be performed via the CVX toolbox. Several simulations are provided to evaluate the positioning accuracy in terms of bi-static range error for 3 and 4 transmitter/receiver antennas, different antenna arrangements, and near/far target. In other simulations, the localization accuracy is evaluated in terms of the empirical cumulative density function of positioning error. The results show that the proposed techniques have better accuracy and performance in different scenarios in comparison with other compared methods. The last simulation also demonstrates that the computational time of the mentioned techniques is 0.69 s which is suitable for real-time processing. [ABSTRACT FROM AUTHOR]

Underwater acoustic channel, characterized by long propagation delay and low data rate, suffers from space time uncertainty which causes spatial unfairness in underwater sensor network. In this paper, we propose a spatially fair MAC protocol which divides all neighbor nodes of a receiving node into two groups based on their average propagation delay. The receiver then permits two different transmitters from each group by taking consideration of their earliest transmission time such that data packets sent from the two transmitters will never collide at the receiver end. A simulation model is developed to evaluate the performance of our proposed scheme. Simulation results show that the proposed scheme achieves better performance in terms of average RTS collision, network throughput and CTS success rate compared to the contemporary MAC protocols. [ABSTRACT FROM AUTHOR]

The rapid increase in internet services demands high capacity and brings high energy dissipation. For broadband access networks, energy efficient passive optical networks (PONs) are ubiquitously demonstrated to conserve energy. However, high cost components for monitoring, complexity, delays and synchronization issues in active/passive optical network unit (ONU) status are the utmost issues to be addressed. Energy efficient symmetrical Wavelength division multiplexed (WDM) and Time division multiplexed (TDM) hybrid passive optical network using Access-Load Difference between ONUs (ALD) approaches with dynamic wavelength switches has been proposed. Dual capacity providing system is presented where 2 Gbps and 12 Gbps sources are operated according to traffic at ONUs. Total capacity of individual low data rate transmitter are 8 Gbps (2 Gbps × 4) and 48 Gbps (12 Gbps × 4) for each ODN serving 64 ONU. Proposed approach is competent to only use specific transmitter module based on load at ONU and keep rest of the transmitters inactive. Design of ALD DWS is such that there is no service interruption even when any transmitter stops working. Moreover, nonlinear carrier generation eliminate the requirements of lasers for upstream transmission which saves cost as well as energy. It is observed that proposed system save 400% energy below 10 Gbps, 300% between 10–20 Gbps, 200% between 20–30 Gbps, 100% between 30–40 Gbps and 0% for beyond 50 Gbps. Therefore variable transmitters (Bandwidth) are operational in this architecture and provide economical in initial operational expenditure (OPEX). [ABSTRACT FROM AUTHOR]

This paper presents a high-efficiency Class FF - 1 DPA using the quad-mode coupled technique for new configurable front-end 5G transmitters. The proposed DPA consists of carrier PA, main PA, input–output matching network and hybrid power network (HPN). The HPN includes a quad-mode coupled technique which is four-section U-shaped transmission line. The HPN is used for even–odd mode impedance analysis to ensures the high-selectivity of output power and achieve a wideband response in the presence of harmonic control conditions. The optimum harmonic impedance is analyzed for the desired band to achieve high output power and efficiency. The DPA circuit is fabricated by using 0.25 µm GaN HEMT on silicon nitride monolithic microwave integrated circuit die process. At maximum output power level of 44.3 dBm, the delivered power-added efficiency (PAE) of 64.3–67.3% and drain efficiency (DE) of 71.7–73.7% at even–odd mode operation are achieved with a gain of 13.0–14.3 dB. For the output power level of 39.045 dBm corresponding to 9 dB output back-off (OBO), the drain efficiency lies between 55–62% with 73% fractional bandwidth. All the demonstrated transmission parameters are working in the band of 8–12 GHz. The size of the chip is 2.8 × 1.9 mm2 and it occupies less die area as compared to the existing DPAs. [ABSTRACT FROM AUTHOR]

In this paper we consider opportunistic routing in multiple-input–multiple-output (MIMO) random wireless ad-hoc networks (WANETs). Our analysis uses a proper model of the physical layer together with an abstraction of the higher communication layers. We assume that the nodes are distributed according to a Poisson point process and consider a routing scheme that opportunistically selects the next relay and the number of spatially multiplexed data streams. The routing decisions are based on geographic locations, the channel gains of the neighbor nodes, and the statistical characterization of all other nodes. Unlike the single antenna case, the optimal routing scheme cannot be explicitly expressed. Hence, we propose a smart-routing scheme for MIMO that adapts the number of data streams per user to the channel conditions. The numerical results demonstrate that this scheme outperforms all previously published schemes for this scenario. The findings highlight the importance of channel state information for efficient routing, and the need for an adaptive selection of the number of data streams at each transmitter. [ABSTRACT FROM AUTHOR]

In this paper, a reversible data hiding algorithm for audio files based on code division multiplexing (CDM) is proposed. In the scheme, the orthogonal spreading sequences are employed to carry the embedding data, and the host audio file can also be recovered completely after the secret message has been extracted accurately. At the same time, according the orthogonal character of the spreading sequences, the secret message can be embedded into the audio files repeatedly, and most elements of the spreading sequences are mutually canceled in the process of multi-level data embedding, which maintains the audio file in good auditory even at high data embedding capacity. Moreover, only the receiver who holds the same spreading sequences, as the sender can restore the embedded data, which enhance the security of the proposed scheme. As shown in the experimental results, the CDM based reversible data hiding (RDH) algorithm for audio files can achieve higher data embedding capacity at the same audio distortion compared with those state-of-the-art audio RDH algorithms. [ABSTRACT FROM AUTHOR]

This paper summarizes the ongoing research initiatives based on the advanced multiple access techniques towards the fifth generation (5G) wireless communication and beyond. Prior cellular network generations have embraced various multiple access techniques with a common feature that is to have orthogonal signals at the side of the receiver for different users. The diverse requirements of huge number of connections about latency and throughput is the need of the hour. Therefore, 5G wireless systems and beyond, are preferring the design method to shift towards non-orthogonal from orthogonal in multiple access techniques. The paper will mainly focus on the non-orthogonal multiple access techniques considering the types of its candidates in multiple domains which can help us in identifying the impacts on the designs of multiple access for 5G network and beyond. This survey aims to discover the obstacles and possibilities of utmost importance for multiple access designs for 5G networks. [ABSTRACT FROM AUTHOR]

Laser Communication is the most evolving arenas in the field of wireless communication. Presently, laser commutation is espoused in the satellite communication for the purpose of space research related activities because of its benefits such as less power consumption, low cost, flexibility and resistance to the radio interferences. This work is an application of laser communication for transmitting data between two ends. Laser Communication needs the transmitter and receiver to be aligned in line-of-sight. The carrier which transmits the signal is produced by a laser diode. The main objective of this work is to transmit audio signal from transmitter to receiver by using the laser beam as a medium. The complete system for this work consists of a transmitter and a reciever capable of transmititng and recieving the analog signal respectively. The results shows that input signal frequencies are preserved at the output with less distortion. However there is decrease in the amplitude of the received signal which can be increased at the output end and the original signal can be recovered. Signal to Noise Ratio is used as a performance metric and it is derived from experimentation that, for higher frequencies Signal to Noise Ratio is more, and for lower frequencies Signal to Noise Ratio is less. [ABSTRACT FROM AUTHOR]

We consider the Simultaneous Wireless Information and Power Transfer strategy optimization in the two-way transmission relay system under Power Splitting (PS) receiver. In such case, we propose two operational strategies for two-way transmission under PS receiver structure, (1) Delay-Limited-Relay strategy (PS-LDR) and (2) Delay-Tolerated-Relay strategy (PS-TDR). PS-LDR strategy is that both sending node and receiving node need synchronization of information transmission, so communication systems have higher Signal Noise Ratio (SNR) threshold for channels, or communication may break down. In order to explore the performance of PS-LDR strategy, we use outage probability to calculate the analytical expression of the actual maximum throughput (AMT). PS-TDR strategy allows that the information received by the receiving node delays with the information sent by the sending node. Communication system in PS-TDR strategy has lower SNR threshold than that in PS-LDR strategy. The analytical expression of the AMT is calculated by the ergodic capacity in PS-TDR strategy. The influences of system parameters on the optimal throughput in two strategies are discussed. [ABSTRACT FROM AUTHOR]

With the growth of mobile devices, consumer networks make the life more convenient and faster. Consumer networks consider mobile video as an important communication mode. Mobile video transmission faces complex environments, and the quality of service (QoS) of mobile video networks is very important for mobile entertainment applications. To evaluate the QoS of mobile video networks, outage probability (OP) is an important criterion. However, the mobile video networks gradually become complex, dynamic, and variable, which make it increasingly more difficult to predict the OP performance. In this paper, we investigate the OP performance analysis and prediction. The OP expressions are derived in exact closed-form. Then, based on the characteristics of mobile data, we have established a prediction model based on generalized regression (GR) neural network. A GR-based OP performance intelligent prediction algorithm is proposed. Compared with other methods, our proposed approach can obtain a better prediction effect. The prediction accuracy of the proposed approach can be increased by 64% and 58%, respectively. The running time is also the shortest. [ABSTRACT FROM AUTHOR]

Recurring insulin-induced hypoglycemia (RIIH) in males correlates with maladaptive glucose counter-regulatory collapse and acclimated expression of ventromedial hypothalamic nucleus (VMN) nitric oxide (NO) and γ-aminobutyric acid (GABA) metabolic transmitter biomarkers, e.g., neuronal nitric oxide synthase (nNOS) and glutamate decarboxylase65/67 (GAD). Hindbrain noradrenergic neurons innervate the VMN, where norepinephrine regulates nNOS and GAD expression. Current research investigated the hypothesis that antecedent hypoglycemia (AH) exposure causes sex-dimorphic habituation of VMN glucoregulatory biomarker proteins between and/or during serial hypoglycemic bouts, and that hindbrain catecholaminergic (CA) signaling may control sex-specific adaptation of one or more of these proteins. Data show that upon recovery from AH, females exhibit CA-mediated reductions in baseline VMN nNOS, GAD, steroidogenic factor-1 (SF-1), and brain-derived neurotrophic factor (BNDF) expression compared to euglycemic profiles. In males, however, AH caused 6-OHDA-insensitive suppression of only basal SF-1 levels in the VMN. VMN transmitter protein acclimation to RIIH was sex-contingent, as differential nNOS, GAD, SF-1, and BDNF responses to a single vs final bout of hypoglycemia occur in males, whereas females show acclimated reactivity of GAD and SF-1 only to renewed hypoglycemia. CA-mediated and -independent habituation of distinctive VMN protein profiles occurred in each sex. Further research is necessary to evaluate, in each sex, effects of altered baseline VMN metabolic neurotransmitter signals on glucose homeostasis as well as non-metabolic functions under the control of those neurochemicals. It would also be insightful to learn if and how sex-contingent habituation of VMN transmitter responses to hypoglycemia contribute to sex-dimorphic patterns of glucose counter-regulation during RIIH. [ABSTRACT FROM AUTHOR]

A scheme for transportation of information with minimum Rayleigh backscattering (RB) noise to the multi-users by employing Qdash laser diode as a source is designed and evaluated. In this paper, employing digital phase shift keying, millimeter wave, 16-quadrature amplitude modulation orthogonal frequency division multiplexing (16-QAM OFDM), and 32-QAM OFDM techniques, the data rates of 4 × 10 Gbps are transmitted simultaneously over 50 km single mode fiber, plus 15 m wireless link, 50 m free space optical (FSO) link, 10 m wireless respectively. Four selective self-injection locked modes of Qdash laser are utilized as optical carriers for downstream and upstream transmission. To ensure the matter of mitigation of RB noise, which mainly arises due to the transmission of light-wave of same wavelengths in bidirectional transportation, the carrier signals of different wavelength are used for modulation and remodulation in optical line terminal and optical network unit. Besides being a strong support to increase the tolerance level against RB noise, this architecture is capable to transmit less noisy information wirelessly in radio frequency sensitive areas too. The constancy of the proposed architecture is evaluated by very low power penalty (~ 1.5–1.7 dB, ~ 2.4–2.6 dB, ~ 1.4–1.6 dB, ~ 1.7–1.8 dB for four channels respectively), clear constellation, prominent eye opening, low bit-error-rate (< 10–9 for pseudo random bit sequence data stream and < 3.8 × 10–3 for OFDM signal) and low error vector magnitude (< 12.4% for 16 QAM, < 10% for 32 QAM). Therefore, the proposed architecture could be promising alternative not only due to the scheme for mitigation of RB noise but also be a potent in the field of applications of the communication world to provide less noisy information to the multi-users (wired/wireless/FSO). [ABSTRACT FROM AUTHOR]

The satellite laser ranging method is based on measuring the transit time of a laser pulse from the transmitter to the satellite and back to the receiver. A special feature of the TPL telescope is that the laser signal is transmitted and received by the same telescope. This requires auxiliary equipment to separate these signals. In addition, this telescope is also used for visual tracking of the object, which adds complexity to the optical design. In most cases, the signals are separated mechanically using rotating mirrors. In one position, the mirrors transmit the signal to a specific channel, and they reflect the optical signal into another channel in the other position. The rotational speed of the mirrors corresponds to the frequency of the laser transmitter. Both mirrors rotate at the same frequency but with a different phase. A logic circuit built on two D-triggers and one 2-input NAND element is used as a phase detector. The paper discusses the scheme and principle of operation of the device for mirror synchronization by signals of the control computer and mirror position sensors. This device has been successfully used at the Riga-1884 laser location station of the University of Latvia. [ABSTRACT FROM AUTHOR]

Varying a supply voltage using a DC-to-DC converter can significantly improve the efficiency of RF power amplifiers (PAs) for low-power RF transceivers. However, intrinsic switching noise from a conventional DC-to-DC converter operating in fixed Pulse-Width Modulation (PWM) can affect the system performance since the spectral components in the switching noise are confined in the fundamental switching frequency and its harmonics. This harmonic noise will have detrimental effects on the performance of the microwatt's transmitter due to its low output power. Especially for microwatts systems, the minimized size of the inductor will increase the spurious noise due to increased peak-to-peak inductor current. By relocating the spurious noise and reducing peak noise from a switching converter, this paper proposes the technique to prevent high noise spurs in a microwatt transmitter, combining both pseudo-random frequency stepping and monotonic frequency stepping. Both modulation circuits are implemented in CMOS 0.18 µm process and incorporated to achieve the proposed DC-to-DC converter system. The measurement results indicate that the proposed PWM ramp signal modulator with random frequency modulation in a DC-to-DC converter can reduce the peak of the spurious noise-power by 22 dB. Monotonic frequency modulation with various frequency steps reduces the peak of the spurious noise-power by 18 dB. [ABSTRACT FROM AUTHOR]

Media-based modulation (MBM) is a novel modulation technique that can improve the spectral efficiency of the existing wireless systems. In MBM, multiple radio frequency (RF) mirrors are placed near the transmit antenna(s) and are switched ON/OFF to create different channel fade realizations. In such systems, additional information is conveyed through the ON/OFF status of RF mirrors along with conventional modulation symbols. A challenging task at the receiver is to detect the transmitted information symbols and extract the additional information from the channel fade realization used for transmission. In this paper, we consider a massive MIMO (mMIMO) system where each user relies on MBM for transmitting information to the base station, and investigate the problem of symbol detection at the base station. First, we propose a mirror activation pattern (MAP) selection based modified iterative sequential detection algorithm. With the proposed algorithm, the most favorable MAP is selected, followed by the detection of symbol corresponding to the selected MAP. Each solution is subjected to the reliability check before getting the update. Next, we introduce a K favorable MAP search based iterative interference cancellation (KMAP-IIC) algorithm. In particular, a selection rule is introduced in KMAP-IIC for deciding the set of favorable MAPs over which iterative interference cancellation is performed, followed by a greedy update scheme for detecting the MBM symbols corresponding to each user. Simulation results show that the proposed detection algorithms exhibit superior performance-complexity trade-off over the existing detection techniques in MBM-mMIMO systems. [ABSTRACT FROM AUTHOR]

This paper studies the communication problem between UAVs and cellular base stations in a 5G IoT scenario where multiple UAVs work together. We are dedicated to the uplink channel modeling and the performance analysis of the uplink transmission. In the channel model, we consider the impact of 3D distance and multi-UAVs reflection on wireless signal propagation. The 3D distance is used to calculate the path loss, which can better reflect the actual path loss. The power control factor is used to adjust the UAV's uplink transmit power to compensate for different propagation path losses, so as to achieve precise power control. This paper proposes a binary exponential power control algorithm suitable for 5G networked UAV transmitters and presents the entire power control process including the open-loop phase and the closed-loop phase. The effects of power control factors on coverage probability, spectrum efficiency and energy efficiency under different 3D distances are simulated and analyzed. The results show that the optimal power control factor can be found from the point of view of energy efficiency. [ABSTRACT FROM AUTHOR]

In this paper, the speech signal is encrypted using multiple chaotic maps and cryptographic protocols. The input signal is fragmented and scrambled into four segments using cubic map. In order to make the signal invulnerable against attacks, scrambled signal is processed through various one-dimensional chaotic maps like cubic, logistic, skew-tent, and quadratic map. All chaotic maps are employed to provide an encryption at transmitter side; however, reversal of the same is carried out at other end. To protect the various parameters of all chaotic techniques, blowfish algorithm is employed with the private key. On top of that, additional layer of security is provided through hashing algorithm for authentication of shared data and the blowfish key of system between two ends. The computed message digest of secure hash algorithm should be same for successful communication, which authenticates and verify the parameters of chaotic maps. Furthermore, several tests have been performed on 8 KHz secured speech signal such as signal-to-noise ratio, power-spectral density, peak signal-to-noise ratio, and correlation test in order to check the efficiency of proposed system. The various statistical tests and analysis of adversary model validates the encryption model and embraces stronger security, thus making it as invulnerable to the attacks of intruder. The result promises that presented technique is extremely secure, provides end-to-end encryption and can be utilized in a real time speech communication. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the impact of small receiver displacement on a signal propagation in a typical conference room environment at a millimeter wave frequency of 60 GHz. While channel measurements provide insights on the propagation phenomena, their use for the wireless system performance evaluation is challenging. Whereas, carefully executed three-dimensional ray tracing (RT) simulations represent a more flexible option. Nevertheless, a careful validation of simulation methodology is needed. The first target of this article is to highlight the benefits of an in-house built three-dimensional RT tool at 60 GHz and shows the effectiveness of simulations in predicting different characteristics of the channel. To validate the simulation results against the measurements, two different transmitter (Tx) positions and antenna types along with ten receiver (Rx) positions are considered in a typical conference room. In first system configuration, an omnidirectional antenna is placed in the middle of the table, while in the second system configuration a directed horn antenna is located in the corner of the meeting room. After validating the simulation results with the measurement data, in the second part of this work, the impact of a small change, i.e., 20 cm in the receiver position, is studied. To characterize the impact, we apply as performance indicators the received power level, root mean square delay spread (RMS-DS) and RMS angular spread (RMS-AS) in azimuth plane. The channel characteristics are considered with respect to the direct orientation (DO), i.e., the Rx antenna is directed toward the strongest incoming path. Different antenna configurations at the Tx and Rx side are applied to highlight the role of antenna properties on the considered channel characteristics. Especially, in the second system configuration the impact of different antenna half power beamwidth on different considered channel characteristics is highlighted through acquired simulation results. The validation of results shows the RMS error of only 2–3 dB between the measured and simulated received power levels for different Tx configurations in the direction of DO. Results indicate that only a small change of the Rx position may result a large difference in the received power level even in the presence of line-of-sight between the Tx and Rx. It is found that the STD of received power level across the room increases with the decrease in HPBW of the antenna. As can be expected, directed antennas offer lower value of RMS-DS and RMS-AS compared with isotropic antenna. [ABSTRACT FROM AUTHOR]

In this paper, the main research object is evolution algorithm applied for an ultra-wideband three-dimensional (3D) circular antenna array and the significance of elevation angles and their influence on the system performance are highlighted. The 3D channel is calculated by means of 3D shooting and bouncing ray/image techniques which specify multipath elevation angles and azimuth for horizontal plane angles. The capacities of the two-dimensional (2D) and three-dimensional transmitting antenna arrays have been presented. Beam-synthesizing techniques are applied at the transmitter to focus the transmitter energy for the sake of mitigating the multi-path effect and improving channel capacity. A combination of asynchronous particle swarm optimization (APSO) and dynamic differential evolution (DDE) methods are introduced to make adjustment to the length of the feed line on each array element for the maximum capacity. In comparison with 2D azimuth-only antenna arrays, a higher directive gain can be achieved from the 3D antenna arrays results in high channel capacity. Besides, it is discovered that the capacity for the 3D array improves by as much as over 10% when compared to that for the 2D array. As revealed by numerical results, APSO is capable of obtaining better beam-forming pattern to improve the channel capacity than DDE by about 9%. Not only does our research provide qualitative outcomes, it also presents quantitative results. [ABSTRACT FROM AUTHOR]

Multiple-input multiple-output (MIMO) communications are believed as one of the key enabling technologies to fulfill the increasing requirements of future wireless networks. However, the asymptotic performance limits of MIMO vehicular ad hoc network (VANET) systems are not thoroughly investigated. All the related works on MIMO VANETs mainly focused on measurement and geometry based channel analyzing and modeling. In this paper, we present a framework for ergodic capacity analysis on MIMO communications among multi-antenna mounted vehicles. We model a Rayleigh fading channel with standard path-loss and lognormal shadowing, then adopt the tools of stochastic geometry to characterize the MIMO geocast channels. After analyzing the co-channel interference among MIMO geocast sessions, the upper and lower bounds on ergodic capacity of single link MIMO and MIMO geocast channels are derived with careful consideration of the important issues like antenna number, shadow fading, and transmission radius. Results reveal that ergodic capacity of MIMO VANETs can be significantly improved by appropriately mounting multiple transmit and receive antennas on vehicles. As the space for antenna mounting in a vehicle is rather limited, we further give a method to calculate the minimum number of antennas for each vehicle to guarantee the quality of service (QoS) requirements in safety oriented applications of IoV. [ABSTRACT FROM AUTHOR]

In this paper, we investigate a low-altitude unmanned aerial vehicle (UAV)-assisted wireless power- ed device-to-device (D2D) network with the "harvest-transmit-store" model, where a UAV broadcasts energy to all D2D transmitters and the transmitters then store or use the energy for transmission information. In the proposed model, the UAV does not transmit energy in the transmission information time, resulting in a limited charging time. In addition, the interference may be caused by communicating information of an arbitrary number of D2D pairs simultaneously. In this paper, we propose a hybrid time division duplex/frequency division duplex communication scheme, which performs the power transfer and information transmission simultaneously in the transmission information time. The scheme cancels the cochannel interference by using the time division duplex scheme and guarantees the charging time by using the frequency division duplex. We consider optimizing the throughput based on the scheme via joint power control, spectrum allocation, and scheduling time. We propose a two-step algorithm to solve the formulated nonconvex problem. The simulation results show that the proposed algorithm improves the average throughput compared to the other schemes. [ABSTRACT FROM AUTHOR]

Millimeter-wave (mmWave) and massive multi-input–multi-output (mMIMO) communications are the most key enabling technologies for next generation wireless networks to have large available spectrum and throughput. mMIMO is a promising technique for increasing the spectral efficiency of wireless networks, by deploying large antenna arrays at the base station (BS) and perform coherent transceiver processing. Implementation of mMIMO systems at mmWave frequencies resolve the issue of high path-loss by providing higher antenna gains. The motivation for this research work is that mmWave and mMIMO operations will be much more popular in 5G NR, considering the wide deployment of mMIMO in major frequency bands as per 3rd generation partnership project. In this paper, a downlink multi-user mMIMO (MU-mMIMO) hybrid beamforming communication system is designed with multiple independent data streams per user and accurate channel state information. It emphasizes the hybrid precoding at transmitter and combining at receiver of a mmWave MU-mMIMO hybrid beamforming system. Results of this research work give the tradeoff between multiple data streams per user and required number of BS antennas. It strongly recommends for higher number of parallel data streams per user in a mmWave MU-mMIMO systems to achieve higher order throughputs. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the problem of transceiver beamforming and power allocation in the downlink of a multiple input multiple output Cognitive radio system. In this system, a base station (BS) services multiple primary users (PU) and multiple secondary users (SU). In order to perform transceiver beamforming and power allocation, three new algorithms are proposed. The first one is an iterative single-objective constrained algorithm, in which the signal to interference plus noise (SINR) of SUs are improved at each iteration subject to constraints on quality of services of PUs (PUs SINR should be above a predefined threshold) and total transmit power of BS. The second and third algorithms, are based on a multi-objective constraint optimization problem, in which the goal is to improve both PUs and SUs SINR at each iteration subject to previous constraints of the first algorithm. The difference between the second and third algorithms is that in the joint maximization of the second algorithm, the cross-influence of each user on the others is ignored, but in the third algorithm, the cross effect of each users SINR on the others is considered. The novelty of these algorithms is the independency of the transmit precoding vectors from the receive beamforming vectors. Therefore, the feedback of receive beamforming to the BS is not needed. The performances of three proposed algorithms are evaluated in simulations vis bit error rate of PUs and SUs, SINR of PUs and SUs and the percent of BS power allocation to SUs. [ABSTRACT FROM AUTHOR]

This paper considers a passive target localization problem based on the noisy time of arrival measurements obtained from multiple receivers and a single transmitter. The maximum likelihood (ML) estimator for this localization problem is formulated as a highly nonlinear and non-convex optimization problem, where conventional optimization methods are not suitable for solving such a problem. Consequently, this paper proposes an improved adaptive hybrid firefly differential evolution (AHFADE) algorithm, based on hybridization of firefly algorithm (FA) and differential evolution (DE) algorithm to estimate the unknown position of the target. The proposed AHFADE algorithm dynamically adjusts the control parameters, thus maintaining high population diversity during the evolution process. This paper aims to improve the accuracy of the global optimal solution by incorporating evolutionary operators of the DE in different searching stages of the FA. In this regard, an adaptive parameter is employed to select an appropriate mutation operator for achieving a proper balance between global exploration and local exploitation. In order to efficiently solve the ML estimation problem, this paper proposes the well-known semidefinite programming (SDP) method to convert the non-convex problem into a convex one. The simulation results obtained from the proposed AHFADE algorithm and well-known algorithms, such as SDP, DE and FA, are compared against Cramér–Rao lower bound (CRLB). The statistical analysis has been performed to compare the performance of the proposed AHFADE algorithm with several well-known algorithms on CEC2014 benchmark problems. The obtained simulation results show that the proposed AHFADE algorithm is more robust in high-noise environments compared to existing algorithms. [ABSTRACT FROM AUTHOR]

In this paper, a Sparse Bayesian Learning (SBL) based channel estimation technique for frequency selective millimeter wave (mmWave) channel in the time domain approach is developed. Further, SBL based Kalman filter (SBL-KF) for time and frequency selective mmWave multiple-input multiple-output (MIMO) hybrid architecture is presented. Hybrid precoders and combiners are designed to estimate the channel of mmWave MIMO systems. The hybrid precoding technique provides low power consumption and high achievable rate performance at mmWave frequencies. mmWave channels are sparse in nature, and the sparse recovery problem is estimated using the channel estimation technique. A simulation result of SBL-KF is improved by 4 dB and 10 dB of SNR compared to the conventional SBL and Orthogonal Matching Pursuit based scheme, respectively. The proposed SBL-KF scheme provides low estimation error at smaller training overheads M = 50 compared to the other existing work. [ABSTRACT FROM AUTHOR]

In order to guarantee a robust transmission of JPWL (JPEG Wireless: Joint Photographic Experts Group Wireless) images through time and frequency selective wireless channels, an efficient adaptive communication strategy is proposed. It is based on an optimization of a closed-loop adaptive multiple-input multiple-output, orthogonal frequency division multiplexing (MIMO-OFDM) scheme associated with a shaping BICM (bit-interleaved coded modulation) technique composed of a duo binary turbo code (DBTC), high-order modulations such as 64–256 QAM (Quadrature Amplitude Modulation) and a shaping code. According to the CSI (channel state information) knowledge at the transmitter side, an algorithm based on unequal error protection (UEP) and unequal power allocation (UPA) is used to select the transmitter key parameters (source/channel encoder rate, modulation order, power, number of quality layers and number of iterations of the Turbo decoder) to achieve the target Quality of Service (QoS). The proposed DBTC-shaping BICM scheme reaches a shaping gain of 1.2 dB for a 256 QAM modulation over a SISO Gaussian channel, whereas only 0.7 dB of shaping gain can be achieved in a scheme that uses the LDPC shaping BICM scheme for the same modulation order. Based on a DBTC shaping BICM scheme and an adaptive algorithm, the proposed MIMO-OFDM strategy achieves better performance compared to a strategy using an iterative process between an RS (Reed-Solomon) and arithmetic decoders. As a result, and on the one hand, a gain of 5.38 dB can be achieved in terms of PSNR (peak signal-to-noise ratio). On the other hand, a gain of 78% in terms of power consumption is obtained for the same QoS level. Moreover, the adaptive number of iterations in the proposed strategy can minimize the computational complexity of the turbo decoding compared to a scheme using four iterations whatever the channel conditions. [ABSTRACT FROM AUTHOR]

In this paper, a reconfigurable multi-mode Class-AB/F power amplifier (PA) is proposed for 0.1–4.2 GHz multistandard applications. The PA operates in linear mode (class-AB) for variable-envelope modulated signals and switching mode (class-F) for constant-envelope modulated signals. The proposed linear mode PA design is suitable for multi-band LTE, IOT, WSN and multi-standard RF transmitter, while switching mode PA design can be used in multi-band IOT-LPWA and BLE (Bluetooth Low Energy) RF transmitter. The proposed PA has a reconfigurable off-chip inter-stage and output matching networks over the specified frequency band, while the input stage is Complementary Current-Reuse common-gate with active shunt feedback configuration to achieve Ultra-Wideband (UWB) input matching. The proposed multi-mode PA is designed using a 130 nm CMOS process. Class-AB PA has a saturated output power of 23.5 dBm ± 1 dB over 0.1–4.2 GHz, a power-added efficiency (PAE) of 41%, a third-order intercept point (OIP3) of 17 dBm, and adjacent channel power ratio (ACPR) of − 29.3 dBc for LTE 15 MHz channel bandwidth. The maximum PAE of 62.1% under the class-F operation is achieved at output power of 24.5 dBm. The PA occupies 0.64 mm2 of chip area, while the estimated off-chip area is 13.3 mm2. The proposed PA consumes 164 mW, and 16 mW in class-AB and class-F, respectively. [ABSTRACT FROM AUTHOR]

Quantum teleportation is the protocol of transmitting quantum states without physically moving them. After the proposal for the first scheme of quantum teleportation in 1993, different schemes have been proposed, according to the application required. In this paper, a new quantum teleportation protocol is proposed for an arbitrary number of users. First, an initial entangled stated made of n + 1 qubits is distributed between the sender and n users. In each run, the sender decides which user is the receiver of the transmitted state. The receiver can retrieve the sent state with the collaboration of the other users. The applications of this protocol are in quantum networks, cloud computing and also quantum cryptography. [ABSTRACT FROM AUTHOR]

Speech signals recorded in far-field or with a far receiver typically comprise additive noise and reverberation, which cause degradation and distortion in the reliability and intelligibility of speech signal, and the recognition performance of speaker recognition systems, with severe consequences in a wide range of real applications. Channel equalization, i.e. the removal or reduction or other cleaning methods of the channel effects, to some extent, mitigates the mismatching problem at the cost of added distortions to the vulnerable speech signal themselves, and therefore, its effectiveness is limited. Recent research indicates that a new speaker feature, gammatone frequency cepstral coefficients (GFCC), exhibits superior noise and reverberation robustness than other features. This paper proposed two methods to combat the effect of reverberation on speaker verification performance. The first method is using GFCC features as a robust feature to alleviate the effect of reverberation on system performance. While the second method is using multi training to combat the reverberation effect. Speaker verification experiments in the artificial and real reverberant conditions show the efficiency of the proposed methods in terms of decreased equal error rate EER and detection error trade-off DET. [ABSTRACT FROM AUTHOR]

Radiative communication using electromagnetic fields is the backbone of today's wirelessly connected world, which implies that the physical signals are available for malicious interceptors to snoop within a 5–10 m distance, also increasing interference and reducing channel capacity. Recently, Electro-quasistatic Human Body Communication (EQS-HBC) was demonstrated which utilizes the human body's conductive properties to communicate without radiating the signals outside the body. Previous experiments showed that an attack with an antenna was unsuccessful at a distance more than 1 cm from the body surface and 15 cm from an EQS-HBC device. However, since this is a new communication modality, it calls for an investigation of new attack modalities—that can potentially exploit the physics utilized in EQS-HBC to break the system. In this study, we present a novel attack method for EQS-HBC devices, using the body of the attacker itself as a coupling surface and capacitive inter-body coupling between the user and the attacker. We develop theoretical understanding backed by experimental results for inter-body coupling, as a function of distance between the subjects. We utilize this newly developed understanding to design EQS-HBC transmitters that minimizes the attack distance through inter-body coupling, as well as the interference among multiple EQS-HBC users due to inter-body coupling. This understanding will allow us to develop more secure and robust EQS-HBC based body area networks in the future. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the secrecy performance of short-packet transmissions in ultra-reliable and low-latency communications (URLLC). We consider the scenario where a multi-antenna source communicates with a single-antenna legitimate receiver requiring ultra-high reliability and low latency, in the presence of a single-antenna eavesdropper. In order to safeguard URLLC, the source transmits the artificial noise (AN) signal together with the confidential signal to confuse the eavesdropper. We adopt a lower bound on the maximal secrecy rate as the secrecy performance metric for short-packet transmissions in URLLC, which takes the target decoding error probabilities at the legitimate receiver and the eavesdropper into account. Using this metric, we first derive a compact expression of the generalized secrecy outage probability (SOP). Then, we formally prove that the generalized SOP is a convex function with respect to the power allocation factor between the confidential signal and the AN signal. We further determine the optimal power allocation factor that minimizes the generalized SOP. The results presented in this work can be useful for designing new secure transmission schemes for URLLC. [ABSTRACT FROM AUTHOR]

In this paper, we analyze the performance of Non Orthogonal Multiple Access (NOMA) Energy harvesting relaying system in presence of hardware impairments at both the transmitter and receiver over a Nakagami-m fading channel. The proposed system with destinations are allocated different power levels in which the source node communicates with the destinations via an energy harvesting (EH) relay employing a power-splitting relaying architecture and a direct link to the near destination. Moreover, the amplify-and-forward protocol at the EH relay is investigated to evaluate the performance of system. Additionally, the expressions for outage probability are derived, and these analyses are verified by a Monte Carlo simulation. Furthermore, these results are also compared to an orthogonal multiple access (OMA) system. Finally, the effects of various parameters, such as power allocation levels, position of EH relay node, channel coefficients, and hardware impairment levels on the outage performance and throughput of proposed NOMA-EH system and OMA system are investigated. These results demonstrate the advantage of NOMA-EH system as user fairness since multiple destinations compared to the OMA-EH system. [ABSTRACT FROM AUTHOR]

The integration of optical satellite links in the next-generation networks and in the fifth generation cellular systems has been proposed in order to guarantee the handling of the extreme data traffic growth and the high-pitched demand for networks' resources. The optical satellite communication downlink is studied and more specifically, a geostationary satellite with multiple transmitters and an optical ground station with multiple receiving terminals are considered. In this contribution a novel power allocation methodology is proposed for the downlink. The allocation methodology takes into account the scintillation effects due to atmospheric turbulence and maximizes the ergodic network capacity under total expected power and peak power constraints. The analytical optimizing schemes are based on convex optimization methods and have been inspired by waterfilling algorithm. We present emulated power allocation results using real experimental downlink data from ARTEMIS optical satellite campaign and then we investigate the performance of the proposed algorithm with extended numerical results and comparison with other allocation policies. In particular, the new power allocation strategy achieves the highest spectral efficiency, according to the power constraints, for various channel conditions and attenuation profiles and also surpasses two simple baseband allocation methods by intelligently taking advantage of the number of channels and the total expected power. [ABSTRACT FROM AUTHOR]

This study has investigated the mitigations necessary for successful compatibility between International Mobile Telecommunications (IMT) services and Fixed Satellite Service (FSS) Earth Stations operating in adjacent frequency bands. We consider a problem where IMT services operate in the 3.4–3.6 GHz frequency band and FSS Earth Stations operate in the adjacent 3.6–3.8 GHz band (both bands are within the frequency range designated C-band). The results presented in this paper are applicable to other boundaries between IMT and FSS operating in C-band. This is an adjacent band compatibility problem, hence the mitigation considered is based on frequency separation. We firstly perform a co-frequency interference analysis and then determine the Net Filter Discrimination available for a range of possible frequency separations including Guard Bands. These calculations rest on some assumptions regarding the IMT transmitter and FSS receiver spectrum masks. We present some results which show that an 18 MHz Guard Band is sufficient to mitigate interference. This analysis is based on the median aggregate interference-to-noise ratio Σ I / N delivered by our co-frequency analysis, using a − 10 dB threshold and covering all of the spectrum mask combinations considered in the study. [ABSTRACT FROM AUTHOR]

This paper presents the design, construction, and testing of a 183-GHz FMCW transceiver module for wireless fuse applications. The transmitter consists of a square-triangle wave converter, a Ku-band VCO, a 91.5-GHz × 2 × 3 multiplying and amplifying chain, a 10-dB multi-hole directional coupler, and a 183-GHz frequency doubler. For the multiplying chain, the generated 91.5-GHz signal power is partly coupled out by the 10-dB coupler. The coupled output power is used as local oscillator (LO) signal to pump the 183-GHz subharmonic mixer (SHM). The receiver is cascaded by a 183-GHz SHM and a low-noise immediate frequency (IF) amplifier. The measured typical output power of the 183-GHz transceiver is 48 mW and the minimum noise temperature of the receiver is 620 K at 181 GHz. At 5-mm and 10-mm detection distance, the measured signal noise ratio (SNR) of transceiver IF signal is higher than 30 dB and 17 dB at 10 KHz bandwidth, respectively. The SNR is high enough for the following signal processing. [ABSTRACT FROM AUTHOR]

Interest in wideband and medium distance underwater acoustic communication systems is increasing due to the practical application of underwater Internet of Things (IoT) networks. In this paper, we propose a simplified empirical channel model for the medium distance underwater acoustic channels based on real measurement results. The simple and tractable channel model is critical for the development of advanced underwater communications technology. The underwater channel measurements were performed at 20 m sea water depth, the transmitters (TXs) were located at 5 m and 15 m from the bottom, the receivers (RXs) were located at 4 m, 8 m, 12 m, and 16 m from the bottom, and the TX–RX distances were 21 m, 71 m, 127 m, and 273 m. We derived the path loss from the measured dataset, and modified the log-distance model to create a model suitable for an underwater IoT channel. Numerical results show that the proposed model is accurate and reliable enough to use in the development of advanced underwater communication technologies. [ABSTRACT FROM AUTHOR]

In this paper, we propose an architecture to implement IEEE 802.16e transmitter and receiver physical (PHY) layer on field programmable gate arrays. Several approaches are being proposed based on theoretical and simulation analyses for IEEE 802.16-e PHY layer, but there is a lack of processing each frame on the fly and low latency implementation, that allow for performance assessment under real channel conditions and front-end impairments on cloud radio access networks. In this paper, we explore the flexibility of the Xilinx ZC706 board with Zynq-7000 SoC (xc7z045ffg900), allowing for an easy integration between high-level synthesis and VHSIC Hardware Description Language (VHDL). The IEEE 802.16e Base station hardware has used 65.48 % of LUT resources, 66.79 % of BRAM blocks and 35 % of DSP cores. The practical time-synchronized transmit and receive pairs communication with real modems indicate the effective and real-time implementation of the proposed prototype in this paper. [ABSTRACT FROM AUTHOR]

This paper presents a resilient localization scheme for wireless sensor networks (WSNs). It suits well in estimation of node position under a corrupted radio environment. Position computation is based on information of angle-of-arrivals (AoA) and references obtained from a few mobile anchors. In the network, anchors are equipped with smart antennas and global positioning system receivers. They broadcast signals in a synchronous and periodic fashion. The neighboring nodes having the signals with received signal strength values above a prescribed threshold level, respond with their respective IDs. Anchors evaluate AoA information from these signals using estimation of signal parameters via rotational invariance technique (ESPRIT) algorithm. Next, they forward beacon messages, containing their references and estimated angles, to the corresponding nodes and move along random trajectories. After receiving three sets of such data, at least, nodes can initiate selective segregation of the inconsistent position estimations. Simulation results attaining higher degree of localization accuracy validate its competency over the existing schemes. [ABSTRACT FROM AUTHOR]

The aim of this work is the detection of surface defects by the refracted longitudinal wave and the study of the parameters that influence the use of this wave in transmission and reflection modes in order to optimize the non-destructive testing (NDT) conditions with the LCR waves. For this, two types of defects are considered, cylindrical defects of different lengths 5 and 8 mm with depth of 10 mm and a rectangular groove of length 8 mm, width 2 mm and depth of 10 mm. The LCR wave was generated by transducers of center frequencies fc = 1 MHz and fc = 3.5 MHz with an inclination at a fixed-angle equal to 27° in aluminum. This study is divided into two parts. The first explains the changes in the signals caused by this interaction from a temporal point of view. The second part analyzes the energy losses induced on the spectrum. The reference signal is acquired in a defect-free sample. By comparison between the time signals and the respective reference signals, it has been found experimentally a decrease in the amplitude and a time shift of the LCR wave due to the presence of the defect. The sample spectra with a defect are modified relative to the spectrum obtained for the sample without defect, these are narrowed particularly for high frequencies. A shift of the centre frequency to lower values can also be noticed. The influences of the sensor frequency and the transmitter/receiver distance have been studied. When the frequency-sensor increases, the effects on the LCR wave by the defect increase. The study showed, that the increase in frequency allows the detection of smaller defects. Also, because of the inclination of the LCR beam, the choice of the distance between the transmitter and the receiver affects the defect detection. The reducing of the distance between the transmitter and the receiver improves the defects detection. The natures of the defects influence also the defects detection. In reflection mode, it is also possible to detected defect and the results found are satisfactory. Therefore this method is very effective because it identifies the defect and its location. [ABSTRACT FROM AUTHOR]

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]

The 5G and beyond wireless networks will be more dynamic and heterogeneous, which needs to work on multistrand waveforms. One of the most significant challenges in such a dynamic network, especially non cooperated cases, is the identification of particular modulation type, which the transmitter uses at the given time to decode the data successfully. This research proposes a modulation classification algorithm using the combination architectures of modified convolutional neural network. The proposed deep learning architecture is developed by combining the convolutional neural network, dense network, and long short-term memory network (LSTM), which is named as convolutional LSTM dense neural network (CLDNN). Moreover, the mean cumulative sum metric (MCS) is introduced in the pooling layer for improved classification accuracy. Dimensionality reduction through Principal Component Analysis is also applied to minimize the training time, so that the proposed architecture can be adopted for its practical usage. The simulation results prove that the presented CLDNN outperforms an ordinary CNN, while taking less training time. [ABSTRACT FROM AUTHOR]

The current state of the telecommunications market exhibits a high potential to absorb efficient innovations in wireless connectivity, especially those that can be applied to the Internet of Things and similar domains. Contributing in that direction, this paper describes the design and implementation of a fully differential impulse-radio ultra-wideband (IR-UWB) transmitter using pulse-amplitude modulation, with an adaptive power spectrum density (PSD). The architecture can produce up to eight differential monocycles per clock pulse at its output. The number of monocycles controls the bandwidth (thus the PSD) in the mask of IR-UWB technologies, allowing adaptation to multiple standards. The complete transmitter has four main blocks: (a) a pulse generator, comprising two pulse generating circuit groups, to modulate and create a rectangular waveform; (b) an active balun with two amplifiers, to generate differential signals; (c) a digital demultiplexer, to alternate data to the pulse generating circuit groups; (d) a binary-to-thermometer decoder, to control the amount of generated monocycles per pulse. Simulations demonstrate an output pulse amplitude of 120 mV for the high logic level and of 70 mV for the low logic level, both at a 100 MHz Pulse Repetition Frequency. This produces a mean pulse duration of 277 ps, a mean central frequency of 3.8 GHz, and a mean power consumption 6.7 mW. The transmitter takes the form of an intellectual property core in a 130 nm CMOS technology. The complete transmitter area is 0.067 mm 2 , without I/O pads. The outcomes suggest that the proposed circuit can narrow or widen the output signal bandwidth, providing adaptability to different emission requirements. [ABSTRACT FROM AUTHOR]