Performance Of Wireless Communication Research Articles

Terahertz mode switching of spin reflection and vortex beams based on graphene metasurfaces

Gradient metasurface provides a new way for controlling electromagnetic wave, and vortex beam can be widely used to improve the performance of wireless communication. Here, graphene-based metasurfaces are proposed for mode switching, which can dynamically adjust the wavefront of circularly polarized wave in terahertz band. The designed meta-atom is composed of quasi-I-shaped metal structure, graphene layer, spacer, and metal substrate. 360° phase cover is realized by rotating the top metal structure. Two examples are presented to demonstrate mode switching of metasurface, namely gradient metasurface and vortex beam generator. By setting Fermi energy level of graphene as 0.015 eV and 0.70 eV, the designed gradient metasurface realizes the switching between anomalous reflection and mirror reflection for left-handed/right-handed circular polarization based on Pancharatnam-Berry phase theory at 1.2 THz. Then, mode number of orbital angular momentum generated by vortex beam generator can be reconstructed by changing Fermi energy level. The proposed scheme could be applied in many fields, such as terahertz switch and wireless communication.

Cooperative SWIPT MIMO-NOMA for Reliable THz 6G Communications

In this paper, cooperative simultaneous wireless information and power transfer (SWIPT) terahertz (THz) multiple-input multiple-output (MIMO) nonorthogonal multiple access (NOMA) are considered. The aim is to improve wireless connectivity, resource management, scalability, and user fairness, as well as to enhance the overall performance of wireless communications and reliability. We optimized the current wireless communication systems by utilizing MIMO-NOMA technology and THz frequencies, exploring the performance and gains obtained. Hence, we developed a path-selection mechanism for the far user to enhance the system performance. The EH SWIPT approach used to improve THz communications performance was investigated. Moreover, we proposed a reliable transmission mechanism with a non-LoS (NLoS) line of THz communications for open areas or any location where the intelligent reflecting surface (IRS) cannot be deployed, in addition to using the cheap decode-forward (DF) relaying instead of IRS. The performance and scalability of the upgradeable system were examined, using adjustable parameters and the simplest modulation scheme. The system presents a noticeable improvement in energy efficiency (EE) and spectral efficiency (SE), in addition to reliability. Accordingly, the outcome showed an improvement in the overall reliability, SE, EE, and outage probability as compared to the conventional cooperative networks of the recent related work (e.g., cooperative MIMO-NOMA with THz) by multiple times with a simpler design, whereas it outperformed our previous work, i.e., cooperative SWIPT SISO-NOMA with THz, by more than 50%, with a doubled individual user gain. This system reduces the transceiver hardware and improves reliability with increasing transmission rates.

3D UAV Trajectory and Data Collection Optimisation Via Deep Reinforcement Learning

Unmanned aerial vehicles (UAVs) are now beginning to be deployed for enhancing the network performance and coverage in wireless communication. However, due to the limitation of their on- board power and flight time, it is challenging to obtain an optimal resource allocation scheme for the UAV-assisted Internet of Things (IoT). In this paper, we design a new UAV-assisted IoT system relying on the shortest flight path of the UAVs while maximising the amount of data collected from IoT devices. Then, a deep reinforcement learning-based technique is conceived for finding the optimal trajectory and throughput in a specific coverage area. After training, the UAV has the ability to autonomously collect all the data from user nodes at a significant total sum-rate improvement while minimising the associated resources used. Numerical results are provided to highlight how our techniques strike a balance between the throughput attained, trajectory, and the time spent. More explicitly, we characterise the attainable performance in terms of the UAV trajectory, the expected reward and the total sum-rate.

Medium access control protocol design for wireless communications and networks review

<p><span>Medium access control (MAC) protocol design plays a crucial role to increase the performance of wireless communications and networks. The channel access mechanism is provided by MAC layer to share the medium by multiple stations. Different types of wireless networks have different design requirements such as throughput, delay, power consumption, fairness, reliability, and network density, therefore, MAC protocol for these networks must satisfy their requirements. In this work, we proposed two multiplexing methods for modern wireless networks: Massive multiple-input-multiple-output (MIMO) and power domain non-orthogonal multiple access (PD-NOMA). The first research method namely Massive MIMO uses a massive number of antenna elements to improve both spectral efficiency and energy efficiency. On the other hand, the second research method (PD-NOMA) allows multiple non-orthogonal signals to share the same orthogonal resources by allocating different power level for each station. PD-NOMA has a better spectral efficiency over the orthogonal multiple access methods. A review of previous works regarding the MAC design for different wireless networks is classified based on different categories. The main contribution of this research work is to show the importance of the MAC design with added optimal functionalities to improve the spectral and energy efficiencies of the wireless networks.</span></p>

Comparative analysis of underwater wireless optical communication system

The performance of an underwater wireless optical communication (UWOC) system is affected by many factors, such as channel conditions, modulation and detection techniques, type of optical source, etc. The UWOC system performance was investigated in the presence of weak and strong turbulence. Pure sea was the water type used for the performance analysis. Binary phase shift keying, quadrature phase shift keying (QPSK), 16-quadrature amplitude modulation, and non-return to zero-on–off keying were used for comparison. Further, a continuous wave laser was used as the optical source, and photodetectors are at the receiver. The performance of the UWOC system was analyzed in terms of the bit error rate (BER). The BER performance was evaluated using the log-normal probability density function (PDF) in weak turbulence and the gamma-gamma PDF in strong turbulence. In all modulation techniques, QPSK had the best BER performance. The BER was reduced further using avalanche photodiode (APD) as the photodetector instead of positive-intrinsic-negative diode for the same transmitter power and channel conditions. In weak turbulence, a BER of 10 − 8 was achieved at a transmitter power of 12.5 dBm using the QPSK modulation technique and APD as the photodetector. For the same conditions, a BER of 9 × 10 − 7 was achieved in strong turbulence. The multiplication gain, dark current, and carrier ionisation ratio of the photodetector were optimized for better BER performance in the UWOC system.

Underwater optical wireless communication performance enhancement using 4D 8PAM trellis-coded modulation OFDM with DFT precoding.

A 4D 8-pulse amplitude modulation trellis-coded modulation-based orthogonal frequency division multiplexing (4D 8PAM TCM-OFDM) scheme combined with discrete Fourier transform (DFT) precoding is proposed and experimentally demonstrated in an underwater optical wireless communications system. It can resist power fading caused by the attenuation, scattering, and reflection in the water channel. The experimental results show that, after transmission over the water-air channel and at the bit error rate of 3.8×10-3, the improvement in the receiver sensitivity is 0.88 dB using the 4D 8PAM TCM-OFDM scheme, compared to the conventional 64QAM-OFDM scheme. In addition, the proposed 4D 8PAM TCM-OFDM scheme combined with DFT precoding can compensate for unbalanced impairments, and it can obtain 1.28 dB receiver sensitivity improvement, compared to the conventional 64QAM-OFDM scheme with DFT precoding.

Cooperative SWIPT THz-NOMA/6G Performance Analysis

In this paper, cooperative simultaneous wireless information and power transfer terahertz (THz)-nonorthogonal multiple access (NOMA) is considered to overcome the challenging shortages that THz communications have due to THz characteristics. The proposed system presents a noticeable improvement in energy efficiency (EE) and spectral efficiency (SE), in addition to other important metrics. By utilizing NOMA technology and THz frequencies, it aims to improve connectivity, resource management, SE, reliability, scalability, user fairness, and to enhance the overall performance of wireless communications. Accordingly, the outcome shows how the introduced energy harvesting technique manages to improve EE and SE compared with the conventional cooperative networks of the recent related work (e.g., cooperative MIMO-NOMA with THz) by 70%. The author also minimizes the transmission power and maximizes the EE by using a decode-and-forward relay rather than an intelligent reflecting surface, which aims to reduce the dissipation in the transceiver hardware, computational complexity, and improves reliability and transmission rate.

Stretchable 3D Wideband Dipole Antennas from Mechanical Assembly for On-Body Communication.

The development of wearable/stretchable electronics could largely benefit from advanced stretchable antennas with excellent on-body performance upon mechanical deformations. Despite recent developments of stretchable antennas based on intrinsically stretchable conductors, they are often affected by lossy human tissues and exhibit resonant frequency shifts upon stretching, preventing their applications in on-body wireless communication and powering. This work reports a three-dimensional (3D) stretchable wideband dipole antenna from mechanical assembly to simultaneously reduce the frequency detuning and enhance on-body performance. The large bandwidth is achieved by coupling two resonances from two pairs of radiation arms, which is well-maintained even when the antenna is directly placed on human bodies or stretched over 25%. Such an excellent on-body performance allows the antenna to robustly transmit the wireless data and energy. The design of the 3D stretchable wideband dipole antenna with significantly enhanced on-body wireless communication performance was validated by an experimental demonstration that features a small difference in the wirelessly received power between the on-body and off-body use. The combination of the mechanically assembled 3D geometries and the coupled mechanical-electromagnetic properties can open up new opportunities in deformable 3D antennas and other microwave devices with excellent on-body performance and tunable properties.

Guest Editorial Special Issue on Intelligent Reflecting Surface for Green Communication, Computing, and Sensing

Driven by the emergence of promising Internet-of-Everything (IoE) applications ranging from extended reality and automated systems to the tactile Internet, 6G is expected to provide diverse services including, e.g., communication, computing, and sensing, as well as achieve more ambitious network performance than 5G. To meet the future demands of 6G, an innovative concept referred to as the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">smart radio environment</i> has been recently proposed, which suggests that random and time-varying wireless channels can be dynamically controlled/reconfigured to enhance wireless communication performance, by leveraging digitally-controlled low-cost <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">intelligent reflecting surface</i> (IRS) or its various equivalents such as <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">reconfigurable intelligent surface</i> (RIS) and others. Besides communication, IRS can also be exploited to improve the computing and sensing performance of future 6G wireless networks. The aim of this special issue is to motivate innovative research on IRS for achieving green communication, computing, and sensing in future 6G wireless networks. The issue attracted 18 high-quality submissions from all over the world, among which 6 original contributions were eventually selected for publication. The special issue covers diverse applications of IRS and various design issues in IRS-aided wireless systems. The novelty and key contributions of these articles are summarized as follows.

Impact of orientation-based solar light noise on the performance of underwater optical wireless communication system and noise cancellation

Absorption, scattering, turbulence, and ambient light affect the performance of underwater optical wireless communication (UOWC) systems. Solar light is a form of undersea ambient light that causes interference to the UOWC system severely, and various optical components have been used to suppress solar noise. Therefore, the UOWC channel realization must ensure suitable system-based parameters to offer optimal performance. However, UOWC system performance lacks verification with the system receiver (Rx) facing multiple orientations in a high intense solar light at undersea depth. This work discusses the impact of solar light on the UOWC system with its Rx facing different orientations. It is found that the Rx orientation plays a significant role in determining the system performance. Furthermore, we numerically demonstrate the cancellation of solar noise interference using back-to-back Rx with differential amplifier mechanisms and better noise cancellation for Rx horizontal orientation.

Deep-Learning-Based Resource Allocation for Time-Sensitive Device-to-Device Networks.

Ultra-reliable and low-latency communication (URLLC) is considered as one of the major use cases in 5G networks to support the emerging mission-critical applications. One of the possible tools to achieve URLLC is the device-to-device (D2D) network. Due to the physical proximity of communicating devices, D2D networks can significantly improve the latency and reliability performance of wireless communication. However, the resource management of D2D networks is usually a non-convex combinatorial problem that is difficult to solve. Traditional methods usually optimize the resource allocation in an iterative way, which leads to high computational complexity. In this paper, we investigate the resource allocation problem in the time-sensitive D2D network where the latency and reliability performance is modeled by the achievable rate in the short blocklength regime. We first design a game theory-based algorithm as the baseline. Then, we propose a deep learning (DL)-based resource management framework using deep neural network (DNN). The simulation results show that the proposed DL-based method achieves almost the same performance as the baseline algorithm, while it is more time-efficient due to the end-to-end structure.

An energy efficient resource allocation and transmit antenna selection scheme in mm‐wave using massive multiple‐input multiple‐output technology

SummaryThe massive multiple‐input multiple‐output (MIMO) improves the reliability of transmission and capacity of the channel. Resource allocation (RA) and transmit antenna selection (TAS) can minimize the complexity in implementation and hardware costs. In this research, both the RA and the TAS of wireless communication in millimeter‐wave (mm‐wave) with massive MIMO technology are considered. Two different solutions are developed for this research such as the deep learning method for efficient resource allocation process and optimization algorithm for TAS process. Here, the RA process is done with the help of attention‐based capsule auto‐encoder (ACAE) architecture which allocates the radio resources like power, space, time and frequency to all the available users in the system. Further, battle royale optimization (BRO) algorithm is utilized to select an efficient antenna from multiple antennas at BS. This optimization algorithm optimally selects an efficient antenna so that, user equipment (UEs) can create high quality links and achieves a reduced power consumption rate of the whole architecture. The overall system performance depends on the selection of optimal antenna which in terms enhances spectral efficiency (SE), energy efficiency (EE), reliability, and diversity gain of MIMO technology. In this way, both RA and optimal antenna selection schemes are performed to maximize the overall performance of wireless communication with massive MIMO technology for 5G wireless communication applications. The implementation of the proposed methodology is evaluated on MATLAB. Finally, the efficiency of the developed method is improved with respect to the capacity, EE, and SE.

Second Order Statistics of -Fisher-Snedecor Distribution and Their Application to Burst Error Rate Analysis of Multi-Hop Communications

An advantage of using the composite fading models (CFMs) is their ability to concurrently address the impact of multi-path and shadowing phenomena on the system performance in wireless communications. A Fisher-Snedecor (FS) F CFM has been recently proposed as an experimentally verified and tractable fading model that can be efficiently applied for 5G and beyond 5G wireless communication systems. This paper provides second-order (s-order) performance analysis of the product of N independent but not identically distributed (i.n.i.d) FS F random variables (RVs). In particular, accurate and closed-form approximations for level crossing rate (LCR) and average fade duration (AFD) of the product of N i.n.i.d FS F ( N-FS F) RVs are successfully derived by exploiting a general property of a Laplace approximation method for evaluation of the N-folded integral-form LCR expression. Based on the obtained s-order statistical results, the burst error rate and maximum symbol rate of the N-FS F distribution are addressed and thoroughly examined. The numerical results of the considered performance measures are discussed in relation to the N-FS F multi-path and shadowing severity parameters. Moreover, the impact of the number of hops ( N) of the N-FS F CFM on the s-order metrics, the burst error rate and maximum symbol rate are numerically evaluated and investigated. The derived s-order statistical results can be used to address the cooperative relay-assisted (RA) communications for vehicular systems. Monte-Carlo (M-C) simulations for the addressed statistical measures are developed in order to confirm the provided theoretical results.

Influence of Low-Altitude Atmospheric Turbulence on Performance of Wireless Ultraviolet Communication

Influence of Low-Altitude Atmospheric Turbulence on Performance of Wireless Ultraviolet Communication

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.

Induced electron radiation effect on the performance of inter-satellite optical wireless communication.

This paper provides the details of a study on the effects of electron radiation on the Performance of Inters-satellite Optical Wireless Communication (IsOWC). Academia and industry focus on solutions that can improve performance and reduce the cost of IsWOC systems. Spacecraft, space stations, satellites, and astronauts are exposed to an increased level of radiation when in space, so it is essential to evaluate the risks and performance effects associated with extended radiation exposures in missions and space travel in general. This investigation focuses on LEO, especially in the near-equatorial radiation environment. Radiation experiments supported with simulations have made it possible to obtain and evaluate the electron radiation impact on optoelectronics at the device level and system level performances. The electron radiation has induced a system degradation of 70%. This result demonstrates the importance of such an investigation to predict and take necessary and suitable reliable quality service for future space missions.

An overview on integrated localization and communication towards 6G

while the fifth generation (5G) cellular system is being deployed worldwide, researchers have started the investigation of the sixth generation (6G) mobile communication networks. Although the essential requirements and key usage scenarios of 6G are yet to be defined, it is believed that 6G should be able to provide intelligent and ubiquitous wireless connectivity with Terabits per second (Tbps) data rate and sub-millisecond (sub-ms) latency over three-dimensional (3D) network coverage. To achieve such goals, acquiring accurate location information of the mobile terminals is becoming extremely useful, not only for location-based services but also for improving wireless communication performance in various ways such as channel estimation, beam alignment, medium access control, routing, and network optimization. On the other hand, the advancement of communication technologies also brings new opportunities to greatly improve the localization performance, as exemplified by the anticipated centimeter-level localization accuracy in 6G by extremely large-scale multiple-input multiple-output (MIMO) and millimeter wave (mmWave) technologies. In this regard, a unified study on integrated localization and communication (ILAC) is necessary to unlock the full potential of wireless networks for dual purposes. While there are extensive studies on wireless localization or communications separately, the research on ILAC is still in its infancy. Therefore, this article aims to give a tutorial overview on ILAC towards 6G wireless networks. After a holistic survey on wireless localization basics, we present the state-of-the-art results on how wireless localization and communication inter-play with each other in various network layers, together with the main architectures and techniques for localization and communication co-design in current two-dimensional (2D) and future 3D networks with aerial-ground integration. Finally, we outline some promising future research directions for ILAC.

Three-dimensional trajectory optimization for secure UAV-enabled cognitive communications

Unmanned aerial vehicles (UAVs) are envisioned as a promising means of providing wireless services for various complex terrains and emergency situations. In this paper, we consider a wireless UAV-enabled cognitive communication network, where a rotary-wing UAV transmits confidential information to a ground cognitive user over the spectrum assigned to primary users (PUs), while eavesdroppers attempt to wiretap the legitimate transmission. In order to enhance the secrecy performance of wireless communications, the secrecy rate (SR) of the UAV-enabled cognitive communication system is maximized through optimizing UAV three-dimensional (3D) flying trajectory while satisfying the requirements of UAV's initial and final locations and guaranteeing the constraint of maximum speed of UAV and the interference threshold of each PU. However, the formulated SR maximization (SRM) problem is non-convex. For the purpose of dealing with this intractable problem, we employ the difference of two-convex functions approximation approach to convert the non-convex optimization problem into a convex one, which is then solved through applying standard convex optimization techniques. Moreover, an iterative 3D trajectory optimization algorithm for SRM scheme is proposed to achieve the near-optimal 3D trajectory. Simulation results show that our proposed 3D trajectory optimization based SRM algorithm has good convergence, and the proposed SRM scheme outperforms the benchmark approach in terms of the SR performance.

Bit Error Performance of APD and SPAD Receivers in Optical Wireless Communication

This review concentrates on the state-of-the-art hardware-oriented receiver aspects for optical wireless communication (OWC), and points to the importance of BER performance analysis and modeling in presence of non-perpendicular light incidence. Receivers in OWC networks for 6G applications have to work for strongly different light incidence angles, to allow the formation of connections to locally separated transceivers without the need for rotation units and accurate adjustment. In turn, and in combination with fully integrated optical receivers, reduction of cost and increased comfort can be achieved. Fully integrated [bipolar] complementary metal-oxide-semiconductor ([Bi]CMOS) receivers with on-chip avalanche photodiodes (APDs) and single-photon avalanche diodes (SPADs) are presented and their performance in optical wireless communication is summarized. Impressive data rates up to 2 Gbit/s and free-space transmission distances up to 27 m at bit error ratios (BER) below 10−9 are reached with linear-mode APD receivers. The importance of optical interference in the isolation and passivation stack on top of the integrated photodiodes is illuminated. To be able to predict the dependence of the BER of single-photon avalanche diode (SPAD) receivers on the light incidence angle, a model, which includes a model for the photon detection probability and a standing-wave model for the isolation and passivation stack, is extended. The dependence of the BER on the light incidence angle onto the photodiodes is investigated by electromagnetic simulation for optical transmission of the layers on top of the photodiode, device simulation for the avalanche triggering probability and BER modeling with MATLAB. It is found that incidence angles up to 30° have moderate influence on the BER and that the BER degrades significantly for incidence angles larger than 50°.

Dual-UAV Enabled Secure Data Collection With Propulsion Limitation

Unmanned aerial vehicles (UAVs) have been widely utilized to improve the end-to-end performance of wireless communications. However, its line-of-sight makes UAV communication vulnerable to malicious eavesdroppers. In this paper, we propose two cooperative dual-UAV enabled secure data collection schemes to ensure security, with the practical propulsion energy consumption considered. We first maximize the worst-case average secrecy rate with the average propulsion power limitation, where the scheduling, the transmit power, the trajectory and the velocity of the two UAVs are jointly optimized. To solve the non-convex multivariable problem, we propose an iterative algorithm based on block coordinate descent and successive convex approximation. To further save the on-board energy and prolong the flight time, we then maximize the secrecy energy efficiency of UAV data collection, which is a fractional and mixed integer nonlinear programming problem. Based on the Dinkelbach method, we transform the objective function into an integral expression and propose an iterative algorithm to obtain a suboptimal solution to secrecy energy efficiency maximization. Numerical results show that the average secrecy rate is maximized in the first scheme with propulsion limitation, while in the second scheme, the secrecy energy efficiency is maximized with the optimal velocity to save propulsion power and improve secrecy rate simultaneously.