Wireless Communication Transmission Research Articles

OFDM Spectrum Sensing Analysis and Implementation Method

OFDM is a carrier modulation technology, which realizes the parallel transmission of high-speed serial data through frequency division multiplexing. OFDM has an excellent ability to resist multipath fading and is commonly used in wireless communication transmission technology. Spectrum sensing technology is a technology that allows cognitive users to accurately obtain the authorized spectrum usage in wireless networks through signal detection and other processing methods. It is the basis for effectively using different idle channels in different time domains. This paper mainly discusses the OFDM technology, deduces the algorithm of the implementation principle and mathematical characteristics of OFDM, analyses its spectrum characteristics and performance advantages, focuses on the principle and method of OFDM spectrum sensing based on spectrum sensing technology, combs the characteristics of several existing commonly used OFDM spectrum sensing methods, and analyses the implementation cost, hardware requirements, transmission performance The performances of interference factors and other aspects are sorted out, the advantages and disadvantages of several existing OFDM spectrum sensing methods are compared, their respective applicable environments are compared, and their possible problems in the future development prospect of OFDM technology and the direction that needs further research and improvement are put forward.

Covert Communication in Downlink NOMA Systems With Channel Uncertainty

With the gradual promotion of the fifth generation (5G) mobile communication and Internet of Things (IoT) applications, wireless communication transmission will be more vulnerable to illegal interceptions and/or attacks. To ensure communication security, we study covert communication of downlink nonorthogonal multiple access (NOMA) systems, where the channel knowledge of users is uncertain. A multiantenna transmitter tries to covertly transmit information to a covert user (strong user) through the shield of a public communication link (weak user), while the warden tries to detect the communication behavior between the transmitter and the covert user. To improve security and energy efficiency, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> th best antenna of the transmitter is selected, since the optimal antenna may be not available due to some schedule and/or other reasons. Aiming to evaluate the proposed framework performance, we start by deriving exact expressions for the minimum detection error probability and the optimal detection threshold of the warden, followed by a calculation analysis of the expected minimum detection error probability (EMDEP) and the outage probability of NOMA users. The asymptotic behavior for the outage probability is investigated at high signal-to-noise ratio (SNR) to acquire greater useful insights. With the goal of improving the system covertness performance, we propose that a scheme is optimized to enhance the covert throughput of the system to the maximum. Simulation results show that the following hold: 1) channel estimation errors have a significant effect on system performance; 2) reliability performance tends to build up, as the total number of antennas grows large; and 3) as the transmitting power and number of antennas increases, there is an upper bound for maximizing the covert throughput.

Performance Evaluation of Integrated Antennas on Photovoltaic Solar Cells

The performance of antennas is critical to ensuring reliable wireless communication and robust data transmission. Unfortunately, antennas’ performance gets degraded when loaded with lossy materials. This paper presents the numerical and experimental evaluation of low-profile antennas’ performance when integrated with photovoltaic (PV) solar cells for potential use in smart grid and green power networks. Such integrated antennas can serve as a communication unit and sensors to monitor PV solar cells. For convenience, a microstrip patch antenna was used in this assessment study, where the antenna was designed, numerically simulated, and experimentally tested. After which, it was installed on top of a PV solar cell at different orientations. The antenna is designed to operate within the 2.45 GHz ISM band. Based on the results, the antenna performed well when placed at the middle of the PV solar cell with a peak gain of 2.58 dBi compared to other placements within the PV solar cell. Moreover, creating a small air gap between the antenna and the PV solar cell results in better performance. Based on the findings of this study, the antenna has satisfactory performance when integrated with PV cells, which is promising to deploy in many applications, including smart grid networks.

Multitask learning-based secure transmission for reconfigurable intelligent surface-aided wireless communications

Reconfigurable intelligent surfaces (RISs) represent a highly promising technology that enhances the capacity and coverage of wireless networks by intelligently reconfiguring the wireless propagation environment in highly advanced wireless communications. The objective of this study is to solve the problem of secrecy rate maximization for multiple RIS-aided millimeter-wave communications by jointly optimizing the active RISs and the RIS phase shifts of the considered system. For this nonconvex problem, we propose multitask learning in a deep neural network to predict the RIS phase shift and active RISs. Numerical results based on realistic, three-dimensional, ray-tracing simulations show that the proposed solution can predict the RIS phase and active RIS with an accuracy rate > 96%. These results confirm the viability of RIS-aided secure wireless communications.

Mathematical Methods on Optimal Frequency Selection Model for Wireless Communication Transmission Signal under 5G Internet of Everything

Adaptive 5G communication has been accelerated thanks to the catalytic advances in the stable Internet of Things (IoT) which is a growing industry. This essay examines the impact of IoT, describes the evolution of the Internet under beneficial 5G communications, and explores 5G adaptive exchange and coordinating IoT advances. The reproduction evaluation was compatible with the evolution of telephone breathing, and developments in base station rigidity lowered base station energy consumption and club energy under the specification of ensuring communication quality, which means to further reassure compatibility. According to research, in a thick and uniform client course condition, power consumption has dwindled due to the extension of force use, but it has fundamentally improved and the correspondence quality has increased beyond what many would imagine achievable. It can ensure the client’s reasonableness and plan ability to execute, as well as fulfill the rate requirements of a variety of clients. The quick outcomes greatly test the speculative accuracy examination.

Research on Distributed Multisensor Spectrum Semantic Sensing and Recognition in Internet of Things Environment

The development of 5G technology has brought about a new era of Internet of Thing (IoT), and at the same time, electromagnetic spectrum monitoring and sensing have also ushered in huge challenges. Digital modulation recognition technology is an important content of electromagnetic spectrum sensing. In the increasingly complex wireless communication transmission environment, especially in noncooperative communication, it becomes more and more difficult to receive target signals and accurately extract effective semantic information from diverse modulation signals of the electromagnetic spectrum. At this stage, with the rapid development of network information and wireless communication technology, within a prescribed distance, the IoT built by many sensors has attracted wide attention from people in related fields. This paper proposes a distributed collaborative sensing spectrum semantic recognition architecture for communication signals based on feature fusion. Perform wireless communication and transmission between multiple sensors to form a self-organizing network to cooperatively sense signal semantic information, and extract the signal features of each sensor in the distributed network structure. Finally, the extracted sensor features are semantically analyzed and modeled, and the effective features are fused to complete the entire perception and recognition process. Even if the channel environment of a small number of receiving nodes deteriorates in a complex transmission environment, the signal quality features can still be accurately extracted, the classification and recognition effect like or higher than the best channel state performance can be achieved, and the fault tolerance of the system can be effectively improved. It can also enhance the performance of spectral semantic information sensing and recognition in the IoT environment.

A metasurface-based light-to-microwave transmitter for hybrid wireless communications.

Signal conversion plays an important role in many applications such as communication, sensing, and imaging. Realizing signal conversion between optical and microwave frequencies is a crucial step to construct hybrid communication systems that combine both optical and microwave wireless technologies to achieve better features, which are highly desirable in the future wireless communications. However, such a signal conversion process typically requires a complicated relay to perform multiple operations, which will consume additional hardware/time/energy resources. Here, we report a light-to-microwave transmitter based on the time-varying and programmable metasurface integrated with a high-speed photoelectric detection circuit into a hybrid. Such a transmitter can convert a light intensity signal to two microwave binary frequency shift keying signals by using the dispersion characteristics of the metasurface to implement the frequency division multiplexing. To illustrate the metasurface-based transmitter, a hybrid wireless communication system that allows dual-channel data transmissions in a light-to-microwave link is demonstrated, and the experimental results show that two different videos can be transmitted and received simultaneously and independently. Our metasurface-enabled signal conversion solution may enrich the functionalities of metasurfaces, and could also stimulate new information-oriented applications.

130-m Image sensor based Visible Light Communication (VLC) using under-sample modulation and spatial modulation

Visible light communication (VLC) allows low-cost, simple and flexible optical wireless communication (OWC) transmission. In this work, we put forward and demonstrate for the first time 100 m non-flickering image sensor based VLC using under-sampled phase shift on-off keying (UPSOOK) and 6-bit 4-light-emitting-diode (LED) spatial modulation. As each light emitting diode (LED) can provide three well distinguished intensity states, 6-bit data can be realized by using only 4 LEDs in the vehicle rear lamps. Bit-error-rate (BER) measurements at different camera ISO values are also studies. Experimental results show that 130 m long distance 120 bit/s image sensor based VLC system can be achieved using a single white-LED at ISO = 800. Results also show that 100 m long distance 720 bit/s image sensor based VLC system can be realized using 4 LEDs at ISO = 800. Both results satisfy the pre-forward error correction BER (pre-FEC, BER = 3.8 × 10−3).

Pulsewidth Modulated Three-Level Buck Converter Based on Stacking Switch-Cells for High Power Envelope Tracking Applications

Envelope tracking is a well-known RF technique that alleviates the efficiency problem of linear power amplifiers used in wireless communication transmitters. It consists in varying the supply voltage of the amplifier, which is commonly constant, according to the envelope of the communication signal. Therefore, a switching-mode power converter with a bandwidth of several megahertz is required to perform the fast voltage changes needed for tracking the envelope properly. Another important requirement is that the converter needs to be able to achieve high efficiency not only at peak output power, but also at low output power because it operates in that power range most of the time due to the characteristics of modern communication signals. Taking into account these requirements, the design of the converter is very challenging, especially in the case of base stations, where higher power levels are reached by means of higher voltage levels. As a result, transistors with low breakdown voltages (20&#x2013;30 V), which offer the highest speed, cannot be used in the converter. In this article, a novel multilevel converter able to use transistors with low breakdown voltages is proposed to alleviate that problem. Moreover, it shows a better switching behavior than the previously proposed multilevel converters, thus reducing the switching losses and, consequently, increasing the efficiency. In order to experimentally validate the proposed topology, a 73-W prototype with a switching frequency of 8 MHz was built. The efficiency is 94&#x0025; and 81.7&#x0025; at peak output power and at one-tenth of peak output power, respectively.

Reconfigurable Radio‐Frequency High‐Electron Mobility Transistors via Ferroelectric‐Based Gallium Nitride Heterostructure

AbstractThe wireless communication and power transmission environment varies widely depending on time and place, and thus reconfigurable devices and circuits are in high demand due to the significant increase in complexity of the power stage and chip size required for current non‐reconfigurable device‐based systems. Reconfigurable radio‐frequency (RF) devices, however, are difficult to demonstrate due to the lack of suitable materials with desirable material properties that can also be integrated with conventional high‐power materials. Here, reconfigurable gallium nitride (GaN) high‐electron mobility transistors (HEMTs) that are heterointegrated with 2D van der Waals‐interfaced α‐In2Se3 semiconductor are demonstrated. The switchable ferroelectric polarization of the 2D α‐In2Se3 layer is exploited to control the 2D electron gas charge density in the GaN channel. Further, a native interfacial indium oxide layer between the gate dielectric and α‐In2Se3 functions as a charge trapping layer, boosting the effect of the ferroelectric α‐In2Se3 layer. The fabricated HEMTs exhibit the sharpest subthreshold slope with tunable threshold voltage, transconductance, and maximum frequency in the range of several GHz under the application of a fast pulsed gate‐voltage signal without sacrificing the performance. The results clearly demonstrate the immense potential of ferroelectric‐based mixed‐dimensional heterostructures as a viable pathway toward simple and compact reconfigurable RF systems.

Node localization algorithm for detecting malicious nodes to prevent connection failures and improve end-to-end delay

In sensor network applications, the measured data makes sense only if the location is known. The location of the node is known, and the wireless communication line and transmission method between the two nodes can be an unknown collaboration process where a sensor with a known location is used to locate the node in an unknown location. Various localization algorithms are available that use linear and nonlinear methods to find nodes. Security is a major issue in localization. After the data is sent from the beacon node to the binding node, an error occurs because the virus-safe or unsafe mobile beacon acts like the original mobile beacon, sending the wrong message. One of the basic problems of wireless sensor networks is the localization and security of nodes. This article analyses the performance of optimization algorithms like Ant Colony Optimization algorithms, opportunity routing algorithms, and the proposed Buffalo optimization algorithm. The performance of the buffalo algorithm is compared with these optimization algorithms. Performance metrics such as throughput, residual energy, packet forwarding rate, packet loss rate, delay, and cost were measured. Then the algorithm is implemented as a hardware system for measuring system performance in real-time. Based on a detailed analysis of the performance of optimization algorithms in wireless sensor networks, the buffalo algorithm provides higher efficiency and performance in wireless sensor network applications.

Performance of Non-Line of Sight Underwater Optical Wireless Communication Links with Spatial Diversity

Line-of-sight (LOS) underwater optical wireless communication (UOWC) transmission may suffer blocking and are not always possible due to obstructions from sea creatures, bubbles, large suspended particles and features of the seabed, especially in coastal and turbid water environments. Thus, we present the performance of a spatially diverse non-line-of-sight (NLOS) UOWC system employing continuous phase modulation (CPM), which is shown to offer sensitivity benefits of several dBs over on–off keying (OOK) without coherent reception. We obtain the channel impulse response (CIR) by using Monte Carlo simulation, including absorption and multiple scattering. Turbulence is included by conditioning the CIR on log-normal statistics. To mitigate the resultant fading, we exploit spatial diversity with equal gain combining at the receiver side. Photon counting at the receiver is employed to accommodate shot noise. We compare the saddlepoint and Gaussian approximations for bit error rate (BER) calculations, using the latter for later calculations as it delivers excellent results and is simpler. Our results show that spatial diversity offers performance improvements, for example an 8 dB sensitivity gain at 10^-9 BER using 1 Gbps 3×1 multiple-input single-output (MISO) transmission over a 20 m link with 0.16 log-amplitude variance. We determine using an upper bound that Intersymbol Interference (ISI) has a significant impact at high bit rates, producing error floors for multiple-output arrangements.

Intelligent Reflecting Surface-Aided Wireless Energy and Information Transmission: An Overview

Intelligent reflecting surface (IRS) is a promising technology for achieving spectrum and energy-efficient wireless networks cost-effectively. Most existing works on IRS have focused on exploiting IRS to enhance the performance of wireless communication or wireless information transmission (WIT), while its potential for boosting the efficiency of radio frequency (RF) wireless energy transmission (WET) still remains largely open. Although IRS-aided WET shares similar characteristics with IRS-aided WIT, they differ fundamentally in terms of design objective, receiver architecture, practical constraints, and so on. In this article, we provide a tutorial overview on how to efficiently design IRS-aided WET systems as well as IRS-aided systems with both WIT and WET, namely, IRS-aided simultaneous wireless information and power transfer (SWIPT) and IRS-aided wireless powered communication network (WPCN), from a communication and signal processing perspective. In particular, we present state-of-the-art solutions to tackle the unique challenges in operating these systems, such as IRS passive reflection optimization, channel estimation, and deployment. In addition, we propose new solution approaches and point out important directions for future research and investigation.

Performances enhancement of underwater wireless optical communications (UWOC) using pulse position modulation

Abstract In this work, we study the performance analysis of underwater optical wireless communication (UOWC) transmission link by incorporating optical code division multiple access (OCDMA) using pulse position modulation (PPM) to enhance the channel range and cardinality. Bit error rate (BER) variations are examined versus the range, modulation type (on–off keying (OOK), quadrature amplitude modulation (QAM), etc.), number of users as well as the channel attenuation caused by different water types. The power and transmitter inclination angle limitation, of the enhanced system, are also presented in order to determine the threshold for which the minimum BER 10−9 is achievable.

Fabrication and Characterization of Dual Functional InGaN LED Arrays as the Optical Transmitter and Receiver for Optical Wireless Communications

The feasibility of using InGaN/GaN multiple-quantum-well light-emitting diode arrays (LED arrays) as photodiodes (PDs) is investigated experimentally in addition to their light emitting function. Two discrete LED arrays are produced from one 4 × 4 LED array with a parallel-connected pixel configuration. Such compact designs are useful for light emission or detection at the transmitting/receiving terminals of optical wireless communication systems. Despite 4 × 2 LED arrays achieving a light output power of 67.4 mW at 250 mA, they exhibit an optical responsivity (detectivity) of 0.183 A/W (1.61 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm Hz <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup> W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ) under ultraviolet light illumination (λ = 380 nm) at zero bias. For 4 × 2 LED arrays, the presence of an appreciable ultraviolet light response, together with a high 3-dB bandwidth (~8 MHz) for modulated light detection, allowed us to build a 15 Mbit/s directed optical link with these LEDs functioning as both the optical transmitter and the receiver. Finally, the unitary LED array-based optical link is capable of real-time transmission of digital audio signals (data rate = 6 Mbit/s) at a propagation distance of 100 cm in free space even though some of the constituent pixels are inactive for light detection.

Implementation of a fiber-based resonant beam system for multiuser optical wireless information and power transfer

A fiber-based resonant beam system is proposed for a simultaneous optical wireless information and power transfer (OWIPT) system. A fiber Bragg grating and an optical circulator are used to achieve simultaneous wireless optical communication and power transmission. In the receiver subsystem, a communication and energy harvesting circuit is employed to separate alternating current (AC) and direct current (DC) outputs. The AC output is used for information transmission, and the DC output is used for power transfer. We conducted experiments to test the built-in safety mechanism to verify whether the resonant beam stops immediately if any obstacle obstructs the line of sight of the system. The proposed architecture can be constructed for indoor and outdoor multiuser applications. The results demonstrated that the proposed fiber-based resonant beam system can be implemented successfully for simultaneous OWIPT.

An optimized deep neural network based DoS attack detection in wireless video sensor network

Due to the technological advancements in sensor and modern devices, the Wireless Multimedia Sensor Network (WNSMs) have gained attraction among various communities. It makes it firm and remarkable achievements in wireless communication, media transfer and digital transmission by adopting portable technologies. In recent decades, in applications such as agriculture and industry the sensor nodes are intended to measure the parameters such as temperature, moisture content and other environmental factors. WNSMs have also facilitates the applications by providing the devices with self-governing access for sending and processing the data associated with suitable audio and video information.Numerous video sensor network researches focus on reducing power consumption and optimizing transmission capacity, but data reliability is the real need. The hindrance involved in the sensor nodes result into various attacks on WMSN especially Denial of Service (DoS) attacks. The core of this attack is to incapacitate proper functioning of the network. Both Attacker and attackers, focus on attacking and preventing the legitimate network nodes from using the network resources. Distributed attack is defined as the network which is being attacked by multiple attackers. This type of attack causes significantly more issues in functionality of the network than attacks involved on a single node. Redemption of the network from the threats of DoS attacks, an enhanced machine learning algorithm has to be presented. For detecting DoS in WMSN an optimized Deep Neural Network algorithm is proposed. The parameters required are chosen from adaptive particle swarm optimization algorithm. The approach’s efficiency to be measured by the ratio of packet transmission, energy consumption, latency, network length, and throughput.

Adaptive Transmission for Reconfigurable Intelligent Surface-Assisted OFDM Wireless Communications

Reconfigurable intelligent surfaces (RISs) have recently emerged as an innovative technology for improving the coverage, throughput, and energy/spectrum efficiency of future wireless communications. In this paper, we propose a new transmission protocol for wideband RIS-assisted single-input multiple-output (SIMO) orthogonal frequency division multiplexing (OFDM) communication systems, where each transmission frame is divided into multiple sub-frames to execute channel estimation simultaneously with passive beamforming. As the training symbols are discretely distributed over multiple sub-frames, the channel state information (CSI) associated with RIS cannot be estimated at once. As such, we propose a new channel estimation method to progressively estimate the associated CSI over consecutive sub-frames, based on which the passive beamforming at the RIS is fine-tuned to improve the achievable rate for data transmission. In particular, during the channel training, the RIS plays two roles of embedding training reflection states for progressive channel estimation and performing passive beamforming for data transmission on the data tones. Based on the estimated CSI in each sub-frame, we formulate an optimization problem to maximize the average achievable rate by designing the passive beamforming at the RIS, which needs to balance the received signal power over different sub-carriers and different receive antennas. As the formulated problem is non-convex and thus difficult to solve optimally, we propose two efficient algorithms to find high-quality solutions. Simulation results validate the effectiveness of the proposed channel estimation and beamforming optimization methods. It is shown that the proposed joint channel estimation and passive beamforming scheme is able to drastically improve the average achievable rate and reduce the delay for data transmission as compared to existing schemes.

Compressive sensing based PAPR reduction in OFDM systems: Modified orthogonal matching pursuit approach

Abstract Orthogonal frequency division multiplexing (OFDM) has been proposed to achieve high data rate transmission in wireless communications. The OFDM system usually suffers from the high envelope fluctuations called peak-to-average power ratio (PAPR). The high PAPR causes a signal clipping distortion, and consequently, the performance is degraded. To mitigate the PAPR, we introduce a new PAPR reduction approach using a compressive sensing approach at the transmitter side and an orthogonal matching pursuit (OMP) reconstruction algorithm at the receiver end. Numerical results show the significant reduction of the PAPR compared with the traditional OFDM system without degrading the bit error rate performance.

Detecting active eavesdropper in large-scale antenna systems over Rician fading channels

Physical layer security is efficient in improving the security of transmission in wireless communications. It is effective in relaxing the complexity of the required cryptographic technologies. In this paper, we propose two detection schemes of an active eavesdropper in the physical layer of wireless communications. The system consists of a multi-antenna base station, a single-antenna legitimate user, and a single-antenna active eavesdropper. The large number of antennas at the base station is arranged as a planar array. It is assumed that the system is time division duplex (TDD) and the channels are of Rician distribution. The proposed two detection schemes are used to detect the eavesdropper by the base station and legitimate user, respectively. In both methods, the statistical characteristics of the received signals are analyzed and two test-statistics are constructed to detect the eavesdropper. The performances of the two methods are also analyzed. Simulation results show that both approaches are effective in detecting the active eavesdropper.