Transmitter Pair Research Articles

Reliable and secure memristor-based chaotic communication against eavesdroppers and untrusted foundries

Chaos is a deterministic phenomenon that occurs in a non-linear dynamic system under specific condition when the trajectories of the state vector become periodic and extremely sensitive to the initial conditions. While traditional resistor-based chaotic communications are primarily concerned with the safe transfer of information across networks, the transceivers themselves can be compromised due to outsource manufacturing. With the growth of wireless sensors in resource-constrained implantable and wearable devices, chaotic communication may be a good fit if the information transmitted is reliable and the transmitter devices are secure. We believe that memristor, as the fourth fundamental two-terminal circuit element, can close the gap between reliable communication and secure manufacturing since its resistance can be programmed and saved by the designer and not the foundry. Thus, in this paper, we propose a memristor-based Chua’s chaotic transceiver that is both reliable in the presence of eavesdroppers and secure against untrusted foundries. Specifically, we consider the pair of transmitter and receiver under the same memristor value to show the possibility of uninterrupted communication as well as cases where different values of memristors are used to find out the possible range in which the message can still be meaningfully decoded. Experimental results confirm that both reliable communication and secure design can be achieved via our proposed memristor-based chaos transceivers.

Physical Layer Security for RIS-Aided Wireless Communications With Uncertain Eavesdropper Distributions

In this article, the physical layer security (PLS) is investigated for reconfigurable intelligent surface (RIS)-aided wireless communication systems, where one RIS is deployed to assist the communications between a pair of transmitter (Alice) and receiver (Bob), under a passive eavesdropper (Eve) attack. For the Eve, different from the bounded channel state information uncertainty model, the distribution of the Eve’s location is introduced into the wiretap link. In the proposed system, considering that the Eve can overhear signals transmitted from Alice or reflected by the RIS, two scenarios are studied for RIS-aided secure communication systems: one is that the Eve distributes close to Alice without the RIS orientation, and the other is that the Eve locates close to Bob and in the presence of the RIS. After investigating the probability distribution functions of the Eve’s location and the wiretap link, the novel cumulative density functions (CDFs) of the received signal-to-noise ratios (SNRs) at the Eves are, respectively, derived for the two considered scenarios, taking into account the effects of RIS reflection coefficients, pathloss, and Eve’s location distribution. The closed-form expressions for the probability of the nonzero secrecy capacity and the ergodic secrecy capacity are obtained, providing insights into the impact of the Eve’s location uncertainty and the RIS design on the secrecy performance. Moreover, based on the derived CDFs for received SNRs at Eves, the secrecy outage probabilities are, respectively, analyzed. Specifically, under the constraint of the secrecy outage probability, the closed forms of the minimum required SNRs at Bob and the number of RIS elements are also obtained. Simulation and analytical results corroborate the derived expressions and reveal the tradeoff between the system’s energy efficiency and the number of RIS elements.

In situ elastic constant determination of unidirectional CFRP composites via backwall reflected multi-mode ultrasonic bulk waves using a linear array probe

The determination of elastic constants of a transversely isotropic carbon fiber reinforced plastic (CFRP) composite is the prerequisite of mechanical strength calculation, material degradation evaluation, ultrasonic non-destructive testing for main load-bearing CFRP structures both after manufacturing and in service. Conventional ultrasonic methods request extra sample preparation, water immersion condition or special designed goniometric devices to rotate the test structures, making the elastic constants measurement expensive, inconvenient and not in situ. In this paper, a novel ultrasonic method that enables in situ determination of elastic constants via backwall reflection method (BRM) using a linear array probe is proposed. The BRM can achieve single sided measurement of ultrasonic travel times in various directions including the fiber direction using different pairs of transmitter and receiver array elements. Both quasi longitudinal and quasi shear waves are captured via the mode conversions from the multiple surface reflections. All elastic constants are determined through the particle swarm optimization by minimizing the sum of the squared deviations between the BRM measured and theoretically calculated multi-mode bulk wave travel times in the fiber orthogonal and parallel planes. This method is experimentally verified on a 4.45 mm thick unidirectional T700 carbon fiber/epoxy CFRP composite. The BRM measured Young's modulus in the fiber direction agrees well with that measured by tensile test, with a small deviation of −4.58%. This work proves that the proposed method is single sided, easy to operate, without the necessity of sample preparation, water immersion and extra rotation device, and can determine all elastic constants with high precision, which is therefore promising for in situ applications.

Pre-Heart Attack Alarm System

Heart beat is a unit of computing or counting extremity of heart function, whose unit is beat per minute (bpm). Heart has pacemaker cells that creates electrical waves, these cells cause heart rhythm for right atrium with its spread throughout the heart, blood pumping occurs. The human heart naturally break about 60 to 100 bpm, which can vary from condition to condition. Any disorder in heartbeat will lead to heart attack. Which can be detect by human beings by measuring beats. I present a heart rate measuring system which will be first microcontroller system that continuously tracking the beats and wide awake human few months before heart attack. Infrared sensor (RX sensor) will send infrared lights to the body. This sensor has a pair of transmitter and receiver. Using Photodiode (RX sensor) we will detect reflective lights from the body and this signal is sent to the microcontroller which is embedded in the casual wearable (i.e. ring or bracelet etc.) to detect hearth beat. Using this device will generate an alert to the person having increasing cholesterol after before reaching threshold specified for heart attack.

On CSI and Passive Wi-Fi Radar for Opportunistic Physical Activity Recognition

The use of Wi-Fi signals for human sensing has gained significant interest over the past decade. Such techniques provide affordable and reliable solutions for healthcare-focused events such as vital sign detection, prevention of falls and long-term monitoring of chronic diseases, among others. Currently, there are two major approaches for Wi-Fi sensing: (1) passive Wi-Fi radar (PWR) which uses well established techniques from bistatic radar, and channel state information (CSI) based wireless sensing (SENS) which exploits human-induced variations in the communication channel between a pair of transmitter and receiver. However, there has not been a comprehensive study to understand and compare the differences in terms of effectiveness and limitations in real-world deployment. In this paper, we present the fundamentals of the two systems with associated methodologies and signal processing. A thorough measurement campaign was carried out to evaluate the human activity detection performance of both systems. Experimental results show that SENS system provides better detection performance in a line-of-sight (LoS) condition, whereas PWR system performs better in a non-LoS (NLoS) setting. Furthermore, based on our findings, we recommend that future Wi-Fi sensing applications should leverage the advantages from both PWR and SENS systems.

Intelligent Reflecting Surface assisted millimeter wave communication for achievable rate and coverage enhancement

In a wireless terrain, the presence of various obstacles leads to compliance of non-Line-of-sight (NLOS) norms between transmitter and receiver, which renders severe degradation in the service quality of the communication link and thereby limits the anticipated performance. The expected achievable rate is primarily affected by the location of the mobile receiver as well as the characteristics of the obstacles surrounding it for any wireless terrain. The achievable rate can be improved by deploying Intelligent Reflecting Surface (IRS) panels at properly identified locations. The presence of IRS panels stimulates a supplementary wireless channel that enhances reliable end-to-end connectivity between transmitter and receiver, especially when the direct path (Line-of-sight, LOS) is either experiences severe signal degradation or completely missing in shorter epochs. Using IRS, the performance of the wireless network can be improved by smartly re-configuring the passive reflecting elements which are embedded on a planar surface. In this paper, due to inherent geographical terrain specific attributes and the mobility aspects of a receiver, the end-to-end characterization of the wireless channel between a pair of transmitter and receiver is modeled using cascade arrangements of Time-Invariant (TI) and Time-Variant (TV) channel's impulse response. Further, the overall performance of wireless links is evaluated in terms of the key performance measures, namely, achievable rate and the span of network coverage. Obtained simulation results for two distinct geographical terrains validate the enhanced status of performance measures in IRS-assisted wireless terrains while regulating the system parameters, namely, IRS panel specifications, transmit power, and the velocity of the mobile receiver.

Adaptability of Ultrasonic Lamb Wave Touchscreen to the Variations in Touch Force and Touch Area.

Previous studies on Lamb wave touchscreen (LWT) were carried out based on the assumption that the unknown touch had the consistent parameters with acoustic fingerprints in the reference database. The adaptability of LWT to the variations in touch force and touch area was investigated in this study for the first time. The automatic collection of the databases of acoustic fingerprints was realized with an experimental prototype of LWT employing three pairs of transmitter–receivers. The self-adaptive updated weight coefficient of the used transmitter–receiver pairs was employed to successfully improve the accuracy of the localization model established based on a learning method. The performance of the improved method in locating single- and two-touch actions with the reference database of different parameters was carefully evaluated. The robustness of the LWT to the variation of the touch force varied with the touch area. Moreover, it was feasible to locate touch actions of large area with reference databases of small touch areas as long as the unknown touch and the reference databases met the condition of equivalent averaged stress.

Learning end-to-end codes for the BPSK-constrained Gaussian wiretap channel

Finite-length codes are learned for the Gaussian wiretap channel in an end-to-end manner assuming that the communication parties are equipped with deep neural networks (DNNs), and communicate through binary phase-shift keying (BPSK) modulation scheme. The goal is to find codes via DNNs which allow a pair of transmitter and receiver to communicate reliably and securely in the presence of an adversary aiming at decoding the secret messages. Following the information-theoretic secrecy principles, the security is evaluated in terms of mutual information utilizing a deep learning tool called MINE (mutual information neural estimation). System performance is evaluated for different DNN architectures, designed based on the existing secure coding schemes, at the transmitter. Numerical results demonstrate that the legitimate parties can indeed establish a secure transmission in this setting as the learned codes achieve points on almost the boundary of the equivocation region.

Design and implementation of reinforcement learning‐based intelligent jamming system

Here the intelligent jammer issue is studied. With the rapid development of cognitive radio technology, current cognitive terminals can adaptively or intelligently switch channel by spectrum sensing and decision-making. Most of the traditional jamming methods, such as swept jamming and comb jamming, generally work in a relatively fixed pattern, which are not able to effectively jam the terminals empowered with cognition and spectrum decision-making capability. In view of this problem, the authors propose an intelligent jamming decision-making system based on reinforcement learning. First, in order to jam a pair of transmitter and receiver with adaptive frequency hopping capability, a jammer with spectrum sensing, offline training and learning scheme is proposed. Second, a reinforcement learning-based algorithm for jamming decision-making is proposed and simulated. A special feature of the proposed scheme is that considering the reward is difficult to obtain in the actual communication system, a virtual jamming decision-making method is used to enable the jammer to learn and jam efficiently without the user's prior information. Finally, the proposed jamming model and algorithm are implemented and verified on Universal software radio peripheral testbed.

Reciprocity Calibration of TDD MIMO Channel for Interference Alignment

Interference alignment (IA) is a promising technique to boost the Multiple-input Multiple-output (MIMO) network throughput. Concurrent data transmission links between multiple pairs of transmitters (TX) and receivers (RX) can be established in the same spectrum via cooperation. To make the channel state information (CSI) available on the transmitter side, channel reciprocity in time division duplex (TDD) networks is assumed by a large number of distributed IA algorithms. The physical channel is reciprocal, but nevertheless the channel considered by IA is not, because it also involves the radio frequency (RF) front ends of the transceiver, which are different circuits for transmit and receive modes individually. The difference between the two circuits yields mismatch between the forward and backward channels. Given the mutual coupling effect of the antenna array, the channel's non-symmetry is further complicated. In this paper, we provide the modeling of the non-reciprocity for the TDD MIMO channels and propose a corresponding calibration method to minimize the mismatch. Experimental validation has been conducted with classic distributed IA algorithms. The results highlight the indispensability of the reciprocity calibration for approaching the network capacity gain promised by IA.

Terahertz-Wave Generation Based on Optical Frequency Comb and Single Mach-Zehnder Modulator

A novel Terahertz-wave (THz-wave) generation on the strength of optical frequency comb and single push-pull Mach-Zehnder modulator (MZM) with a pair of transmitter and receiver in 0.4-THz band is proposed. The advantages of the optical frequency comb based on phase modulator (PM) 1 and PM2 in series includes the uncomplicated operation and good stability to produce numerous subcarriers at 25-GHz intervals. THz-wave is generated based on two comb lines derived from the same optical frequency comb. One comb line is used as an optical local oscillator (LO) and the other is served as signal carrier for data modulation for heterodyne mixing. We investigate the generation and transmission of a 0.4 THz THz-wave signal carrying 4 Gbaud quadrature-phase-shift-keying (QPSK) or 1 Gbaud 16 quadrature amplitude modulation (16-QAM) data over back-to-back (BTB) transmission or 10 km standard single-mode fiber (SSMF) transmission, with the bit-error-rate (BER) performance below the hard decision forward error correction (HD-FEC) threshold of 3.8e-3.

Efficient physical layer key generation technique in wireless communications

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

An Efficient RSS Localization for Underwater Wireless Sensor Networks.

Localization is a key-enabling technology for many applications in underwater wireless sensor networks. Traditional approaches for received signal strength (RSS)-based localization often require uniform distribution for anchor nodes and suffer from poor estimates according to unpredictable and uncontrollable noise conditions. In this paper, we establish an RSS-based localization scheme to determine the location of an unknown normal sensor from a certain measurement set of potential anchor nodes. First, we present a practical path loss model for wireless communication in underwater acoustic environments, where anchor nodes are deployed in a random circumstance. For a given area of interest, the RSS data collection is performed dynamically, where the measurement noises and the correlation among them are taken into account. For a pair of transmitter and receiver, we approximate the geometry distance between them according to a linear regression model. Thus, we can obtain a quick access for the range information, while keeping the error, the communication head and the response time low. We also present a method to correct noises in the distance estimate. Simulation results demonstrate that our localization scheme achieves a better performance for certain scenario settings. The successful localization probability can be up to 90%, where the anchor rate is fixed at 10%.

Interference Avoidance Position Planning in Dual-Hop and Multi-Hop UAV Relay Networks

We consider unmanned aerial vehicle (UAV)-assisted wireless communication employing UAVs as relay nodes to increase the throughput between a pair of transmitter and receiver. We focus on developing effective methods to position the UAV(s) in the sky in the presence of interference in the environment, the existence of which makes the problem non-trivial and our methodology different from the current art. We study the optimal position planning, which aims to maximize the (average) signal-to-interference-ratio (SIR) of the system, in the presence of: i) one major source of interference, ii) stochastic interference. For each scenario, we first consider utilizing a single UAV in the dual-hop relay mode and determine its optimal position. Afterward, multiple UAVs in the multi-hop relay mode are considered, for which we investigate two novel problems concerned with determining the optimal number of required UAVs and developing an optimal fully distributed position alignment method. Subsequently, we propose a cost-effective method that simultaneously minimizes the number of UAVs and determines their optimal positions to guarantee a certain (average) SIR of the system. Alternatively, for a given number of UAVs, we develop a fully distributed placement algorithm along with its performance guarantee. Numerical simulations are provided to evaluate the performance of our proposed methods.

Concurrent Transmission Scheduling for Perceptual Data Sharing in mmWave Vehicular Networks

Sharing perceptual data with other vehicles enhances the traffic safety of autonomous vehicles because it helps vehicles locate other vehicles and pedestrians in their blind spots. Such safety applications require high throughput and short delay, which cannot be achieved by conventional microwave vehicular communication systems. Therefore, millimeter-wave (mmWave) communications are considered to be a key technology for sharing perceptual data because of their wide bandwidth. One of the challenges of data sharing in mmWave communications is broadcasting because narrow-beam directional antennas are used to obtain high gain. Because many vehicles should share their perceptual data to others within a short time frame in order to enlarge the areas that can be perceived based on shared perceptual data, an efficient scheduling for concurrent transmission that improves spatial reuse is required for perceptual data sharing. This paper proposes a data sharing algorithm that employs a graph-based concurrent transmission scheduling. The proposed algorithm realizes concurrent transmission to improve spatial reuse by designing a rule that is utilized to determine if the two pairs of transmitters and receivers interfere with each other by considering the radio propagation characteristics of narrow-beam antennas. A prioritization method that considers the geographical information in perceptual data is also designed to enlarge perceivable areas in situations where data sharing time is limited and not all data can be shared. Simulation results demonstrate that the proposed algorithm doubles the area of the cooperatively perceivable region compared with a conventional algorithm that does not consider mmWave communications because the proposed algorithm achieves high-throughput transmission by improving spatial reuse. The prioritization also enlarges the perceivable region by a maximum of 20%.

Simple laser transmitter pair as polarization-independent coherent homodyne detector.

Coherent optical reception promises performance gains for a wide range of telecom applications and photonic sensing. However, the practical implementation and the particular realization of homodyne detection is by no means straight-forward. Local oscillator requirements and polarization management need to be cost-effectively supported for accurate signal detection at high sensitivity, preferably without relying on digital processing resources. Towards this direction we propose a conceptually simple, laser-based homodyne receiver. We exploit the injection locking of a pair of externally modulated lasers that simultaneously serve as optically synchronized local oscillators and photodetectors in a polarization-diversity analogue coherent receiver arrangement. We demonstrate signal detection at 2.5 Gb/s over an optical budget of 35 dB and a dynamic range of >20 dB. Long-term measurements over field-installed fiber confirm the correct operation independent of the polarization state of light. Stability considerations for the injection locking process are drawn in view of even higher loss budgets.

Reflection probability in wireless networks with metasurface-coated environmental objects: an approach based on random spatial processes

An emerging and promising vision of wireless networks consists of coating the environmental objects with reconfigurable metasurfaces that are capable of modifying the radio waves impinging upon them according to the generalized law of reflection. By relying on tools from point processes, stochastic geometry, and random spatial processes, we model the environmental objects with a modified random line process of fixed length and with random orientations and locations. Based on the proposed modeling approach, we develop the first analytical framework that provides one with the probability that a randomly distributed object that is coated with a reconfigurable metasurface acts as a reflector for a given pair of transmitter and receiver. In contrast to the conventional network setup where the environmental objects are not coated with reconfigurable metasurfaces, we prove that the probability that the typical random object acts as a reflector is independent of the length of the object itself. The proposed analytical approach is validated against Monte Carlo simulations, and numerical illustrations are given and discussed.

3-D Energy Optimal Receiver Placement With Constraints on the LOS Delay and Angle

This paper investigates the receiver positioning problem in a communication network, where the transmitters are distributed arbitrarily on the XY-plane with known positions. The purpose is to find the optimal solution for the position of the receiver such that the maximum distance between the receiver and the transmitters is minimized, while two constraints are fulfilled as follows: for any pair of transmitters, the delay caused by the difference in the distances between the transmitters and the receiver is less than a certain value, and the angle between the line-of-sight paths from each transmitter toward the receiver is within a tolerable range. The optimization problem is studied in its general form and the characteristics of the constraints and the objective function are analytically analyzed. According to the conducted analyses, an appropriate sub-optimal solution is proposed and an extensively reduced feasible set to find the optimum solution is presented. Although this optimum positioning approach might act merely as a performance enhancer—such as an energy optimizer or a delay minimizer—in conventional system designs, it is a crucial component for signal processing and constellation design in many multiplexing transmission schemes, as well as in the fast detection scenarios.

Energy transfer provision based on RF-Radio Frequency as an established solution of learning process using laptops and wireless projector

Electrical energy is very crucial in whole aspects of our life. No exception with education. Closely related to education, this paper reports the research result concerning with mean, how to overcome power outage in a classroom. Research idea comes up from a situation in which electrical disruption occurs and its purpose is to propose the appropriate solution, namely by creating an apparatus consist of a pair of transmitter and receiver working on the base of radio frequency. There are former articles discussed how to transfer electrical energy by magnetic coupling, but have no invent in radio frequency transmission. It's different to them, the constructed apparatus will transmit the electrical energy through atmosphere media. The concept of radio frequency transmission and electrical generation are background of the creation of the prototype. In order to properly work, the prototype was composed from some modules. The purpose is to make it easier in case of replacement if there are malfunctions. The module consists of transmitter, receiver, multiplier, inverter and converter respectively. Simulation was carried out to optimize performance of the device before real construction. As a conclusion that the device can work well based on the observed output voltage.

Ultrasonic based determination of apple quality as a nondestructive technology

This research, aimed to apply ultrasonic based technology and develop a portable system for determination of the apple (Golden Delicious) mechanical properties as the quality factor. The main components of the designed portable system are a pair of transmitter and receiver transducers with 40 kHz center frequency, a signal generation unit, a measuring unit of the gain ratio (dB) and phase difference of two signals (input and transmitted), a microcontroller (Atmega 32) and a 16 × 2 LCD display. Mechanical properties of the specimens were distractively measured by an Instron universal testing machine based on the Magness−Taylor method. By combination the physical and ultrasonic attributes and developing the multiple linear regressions, for firmness the model with a good ability of prediction was developed with R and RMSE values of 0.73 and 2.35 N, respectively. For the elastic modulus, the best model had R and RMSE values of 0.64 and 0.18 MPa, respectively. Also for the rupture energy, the model with a high ability of prediction was developed with R and RMSE values of 0.73 and 5.18 mJ, respectively. It was concluded that by using the nondestructive ultrasonic based system to measure the ultrasonic velocity and attenuation of apple, it might be possible to nondestructively assess its mechanical properties.