Showing papers on "Communications system published in 2023"

Beyond Transmitting Bits: Context, Semantics, and Task-Oriented Communications

Abstract: Communication systems to date primarily aim at reliably communicating bit sequences. Such an approach provides efficient engineering designs that are agnostic to the meanings of the messages or to the goal that the message exchange aims to achieve. Next generation systems, however, can be potentially enriched by folding message semantics and goals of communication into their design. Further, these systems can be made cognizant of the context in which communication exchange takes place, thereby providing avenues for novel design insights. This tutorial summarizes the efforts to date, starting from its early adaptations, semantic-aware and task-oriented communications, covering the foundations, algorithms and potential implementations. The focus is on approaches that utilize information theory to provide the foundations, as well as the significant role of learning in semantics and task-aware communications.

Outage Probability and Average BER of UAV-assisted Dual-hop FSO Communication with Amplify-and-Forward Relaying

Abstract: Unmanned aerial vehicles (UAVs) can be harnessed as relay nodes in free-space optical (FSO) communication systems to realize a flexible and cost-effective approach for delivering on-demand communication in next-generation wireless communications. However, fading channels can adversely affect the performance of UAV-assisted dual-hop FSO systems owing to various factors. This paper presents a unified system performance analysis of UAV-assisted dual-hop FSO/FSO systems with the amplify-and-forward relaying protocol and intensity modulation/direct detection technique. For general applicability, the influence of the attenuation loss, atmospheric turbulence, pointing error impairments, and angle-of-arrival (AOA) fluctuations on the FSO link between the source and the UAV is considered. Meanwhile, the FSO link between the UAV and the destination is modeled using Málaga distribution channels, which are affected by atmospheric turbulence. The tight closed-form expressions for the outage probability and the average bit error rate of the dual-hop system are derived, followed with the diversity order of the system in the high signal-to-noise ratio range. Furthermore, the impact of various system parameters and channel parameters correlated with the attenuation loss, atmospheric turbulence, pointing error impairments, and AOA fluctuations on the system performance is studied, and a detailed comparative investigation of the various modulation schemes is conducted. Finally, simulation results are presented to validate the analytical results.

Intelligent-Reflecting-Surface-Aided Bidirectional Full-Duplex Communication System With Imperfect Self-Interference Cancellation and Hardware Impairments

Abstract: In this article, we combine two new technologies [full-duplex (FD) transmission and intelligent reflecting surface (IRS)] in a wireless communication system for investigation. Specifically, we evaluate the performance of an IRS-aided bidirectional FD communication system in a practical scenario where imperfect self-interference (SI) cancellation and hardware impairments (HIs) are taken into consideration. We successfully derive the closed-form expressions of ergodic capacity (EC) and symbol error rate (SER) of the IRS-aided FD-HI system over Rayleigh fading channels. We confirm the correctness of the derived expressions via Monte-Carlo simulations. To clarify the effects of residual SI and HIs, we compare the performance of the IRS-aided FD-HI system with that of the IRS-aided FD-ideal hardware (ID), half-duplex (HD)-HI, and HD-ID systems. Numerical results clarify a strong impact of residual SI and HIs on the EC and SER of the IRS-aided FD-HI system. Thus, the EC and SER of the IRS-aided FD-HI system go to the saturated values in a high signal-to-noise regime even with a large number of reflecting elements in the IRS. Therefore, depending on the residual SI and HI levels as well as the requirements about the EC and SER in practice, we can use appropriately the transmit power of terminals and number of reflecting elements in the IRS for enhancing the performance and saving the energy consumption of the IRS-aided FD-HI system.

Enhancing the security of free space optical communication system by employing chaos-based modulation scheme

Abstract: Abstract Security and privacy are two main dominant features of any communication system. In this paper, physical layer security of free space optical communication system using chaotic modulation scheme i.e., differential chaos shift keying (DCSK) is analyzed, where eavesdropper is actively present near the receiver and interfering between the transmission of secret messages from a transmitter to the receiver. In this manuscript, we have derived analytical expressions for the average secrecy capacity and secrecy outage probability which is used as a metric for secrecy performance analysis. The channel characterization is carried out using gamma–gamma model for weak-to-strong turbulence conditions. The effect of physical layer parameters like transmission link length, spreading length, etc. are considered for evaluating the security performance of the system. Numerical analysis is carried out and graphical results are presented. The results depicted that a very good average secrecy capacity can be achieved even in the presence of eavesdropper, however, it requires a tradeoff between high signal-to-noise ratio of main channel and large values of spreading factor. The proposed system is very promising for the future secured communication systems.

RIS-Aided Integrated Sensing and Communication: Joint Beamforming and Reflection Design

Abstract: Integrated sensing and communication (ISAC) has been envisioned as a promising technique to alleviate the spectrum congestion problem. Inspired by the applications of reconfigurable intelligent surface (RIS) in dynamically manipulating wireless propagation environment, in this paper, we investigate to deploy a RIS in an ISAC system to pursue performance improvement. Particularly, we consider a RIS-assisted ISAC system where a multi-antenna base station (BS) performs multi-target detection and multi-user communication with the assistance of a RIS. Our goal is maximizing the weighted summation of target detection signal-to-noise ratios (SNRs) by jointly optimizing the transmit beamforming and the RIS reflection coefficients, while satisfying the communication quality-of-service (QoS) requirement, the total transmit power budget, and the restriction of RIS phase-shift. An efficient alternating optimization algorithm combining the majorization-minimization (MM), penalty-based, and manifold optimization methods is developed to solve the resulting complicated non-convex optimization problem. Simulation results illustrate the advantages of deploying RIS in ISAC systems and the effectiveness of our proposed algorithm.

Hybrid Index Modulation for Dual-Functional Radar Communications Systems

Abstract: Dual-functional radar communications (DFRC) systems, which jointly design radar and communication functionalities on one common platform, have been recognized as an attractive approach for leveraging the scarce spectral efficiently in diverse applications, such as autonomous driving. Index modulation (IM), a promising communication technique with high energy utilization and spectral efficiency, has been successfully integrated into DFRC systems. Most existing IM-based DFRC schemes utilize the degrees of freedom (DoFs) from one or two domains for separate information embedding, without utilizing the full diversity of the integrated waveform. In this paper, we propose a novel DFRC scheme, referred to as hybrid index modulation (HIM), operating on frequency hopping multiple-input multiple-output (FH-MIMO) radar. The HIM embeds communication information into the index of the 3-tuples in the hybrid dictionary, which is the outer product of DoFs from the frequency, phase, and antenna index of the integrated waveform. Since the HIM entwines waveform diversities from different domains, it increases the communication rate by multiples. We also apply the HIM to the non-orthogonal FH-MIMO radar to improve spectral efficiency, in addition to the conventional orthogonal case. Furthermore, we propose a constrained HIM scheme to enhance the radar detection performance, where the FH pattern has been optimized in terms of ambiguity function. System performance is evaluated both theoretically and experimentally in metrics of communication rate, ambiguity function and symbol error rate.

Integrated Human Activity Sensing and Communications

Abstract: Advances in wireless communication and signal processing facilitate integrated sensing and communication (ISAC) – a compelling technology that intrinsically combines sensing and communication functionalities for the dual-purpose exploitation of wireless/hardware resources and pursues mutual benefits. Consequently, the next-generation communications network will be perceptive. In this article, we provide a review of human-related sensing in the context of ISAC. We first present a general ISAC receiver signal processing framework, with a focus on human activity recognition (HAR). Based on its specific spatial deployments, we then categorize ISAC HAR into monostatic, bi-static, and distributed deployments, and discuss their properties, critical research problems and solutions. To facilitate the system's realization and improve its recognition performance, we then explore the inherent connections between the physical-layer system parameters and HAR performance metrics. Experimental results are presented for characterizing the sensing potentials of different ISAC systems. Finally, we review the technical challenges and identify the open research problems.

Deep-Learning-Based Recovery of Frequency-Hopping Sequences for Anti-Jamming Applications

Abstract: The frequency-hopping communication system has been widely used in anti-jamming communication due to its anti-interception and anti-jamming performance. With the increasingly complex electromagnetic environment, the frequency-hopping communication system needs more flexible frequency-hopping patterns to deal with interferences, which brings great challenges to the communication receiver. In this paper, an intelligent receiving scheme of frequency-hopping sequences is proposed, which combines time–frequency analysis with deep learning to realize an intelligent estimation of frequency-hopping sequences. A hybrid network module is designed by combining a convolutional neural network (CNN) with a gated recurrent unit (GRU). In the proposed network module, the combination of a residual network (ResNet) and squeeze and extraction (SE) improves the feature extraction and expression capabilities of the CNN network. The GRU network is proposed to solve the problem of dealing with signals with variant input lengths. A transfer learning scheme is further proposed to deal with communications systems with different frequency-hopping sets. Simulation results show that the proposed method has strong generalization ability and robustness, and the bit error rate (BER) performance of intelligent receiving is close to the receiving performance under ideal conditions.

Deep-Learning Channel Estimation for IRS-Assisted Integrated Sensing and Communication System

Abstract: Integrated sensing and communication (ISAC), and intelligent reflecting surface (IRS) are envisioned as revolutionary technologies to enhance spectral and energy efficiencies for next wireless system generations. For the first time, this paper focuses on the channel estimation problem in an IRS-assisted ISAC system. This problem is challenging due to the lack of signal processing capacity in passive IRS, as well as the presence of mutual interference between sensing and communication (SAC) signals in ISAC systems. A three-stage approach is proposed to decouple the estimation problem into sub-ones, including the estimation of the direct SAC channels in the first stage, reflected communication channel in the second stage, and reflected sensing channel in the third stage. The proposed three-stage approach is based on a deep-learning framework, which involves two different convolutional neural network (CNN) architectures to estimate the channels at the full-duplex ISAC base station. Furthermore, two types of input-output pairs to train the CNNs are carefully designed, which affect the estimation performance under various signal-to-noise ratio conditions and system parameters. Simulation results validate the superiority of the proposed estimation approach compared to the least-squares baseline scheme, and its computational complexity is also analyzed.

An overview and multicriteria analysis of communication technologies for smart grid applications

Abstract: The inclusion of renewable energy in the conventional grid system and the digitalization of the various aspects of the power system have precipitated the transformation of the traditional grid system to a smart grid. Key to the implementation of the smart grid is various communication technologies. The emerging dominance of communication technologies in power systems applications is pivotal to modernizing the conventional grid system. This research presented an overview of the application of communication technologies in the digitalization of the power systems network. It reviews smart grid communication technologies, their features, relevance, and various roles being played toward delivering an effective electrical service to stakeholders. Hence, this study focused on wireless and wired communication technologies applicable to smart grid applications. Based on the review, each communication technology has its strengths and weaknesses; hence in selecting the most appropriate technology for application in a smart grid, a compromise must be made. Therefore, for choosing the most preferred communication technology in any smart grid application, it is important to deploy the efficacy of multi-criteria methods. To serve as a case study, a framework for selecting a communication technology for advanced metering infrastructure is proposed and applied. Based on the spectrum, data rate, and coverage range, the study revealed that WiMAX communication technology is the most preferred, followed by Zigbee; the least preferred communication technology for smart grid communication is Power Line Communication (PLC).

Joint Waveform and Beamforming Design for RIS-Aided ISAC Systems

Abstract: In this paper, we consider the problem of joint waveform and passive beamforming design for MIMO integrated sensing and communication (ISAC) systems, where a reconfigurable intelligent surface (RIS) is deployed to assist the downlink communication. The objective is to maximize the signal-to-interference-and-noise-ratio (SINR) for radar and meanwhile minimizing the multi-user interference for communication. To address this problem, a block coordinate descent (BCD) method is proposed. Specifically, given the fixed waveform, an Element-wise Closed-Form (ECF) technique is derived for the reflection coefficients optimization, where the high-dimensional problem is divided into multiple one-dimensional problems with closed-form solution. Then, given fixed reflection coefficients, a dinkelbatchs-ECF algorithm is developed to optimize the waveform. Simulation results show that the proposed method achieves joint sensing and communication improvement and presents a clear performance advantage over existing methods.

Performance Analysis of Vilnius Chaos Oscillator-Based Digital Data Transmission Systems for IoT

Abstract: The current work is devoted to chaos oscillator employment in digital communication systems for IoT applications. The paper presents a comparative performance analysis of two different chaos data transmission systems: frequency-modulated chaos shift keying (FM-CSK) and quadrature chaos phase-shift keying (QCPSK), and a comparison to their non-chaotic counterparts: frequency-shift keying (FSK) and quadrature amplitude modulation (QAM). For both chaotic communication systems, the Vilnius oscillator and substitution method of chaotic synchronization are chosen due to simple circuitry implementation and low power consumption properties. The performance of the systems in the fading channel with additive white Gaussian noise (AWGN) is evaluated. Also, the systems’ performance in the case phase noise is investigated, and the benefits of chaotic waveforms employment for data transmission are demonstrated.

THz Systems Exploiting Photonics and Communications Technologies

Abstract: Terahertz (THz) systems open up the possibility of new applications of electromagnetic waves. Enormous bandwidths up to several terahertz enable the development of powerful spectroscopy systems that can provide insights into the structure and material of objects with micrometer resolution. New high power and compact THz time-domain spectroscopy (TDS) systems will be presented. The wide bandwidth also enables high-resolution imaging under far-field conditions to analyze arbitrary objects from a distance. In addition, a near-field system-on-a-chip imaging system is presented that achieves a resolution of 10 μm. Additionally, the application of terahertz waves presents challenges due to the low transmit power of the sources, high attenuation in free space, and the high noise figures of the receivers. These challenges can be overcome by antennas with high gain. Since - depending on the application - spatial scanning or focusing in a time-varying direction is required, beam steering is an essential component of many THz systems. In terms of communications, terahertz carrier frequencies offer wide bandwidths, enabling correspondingly high data rates of 100 Gbit/s and more. As a result, the frequency bands between 250 GHz and 450 GHz have already been identified and/or allocated for communication services and are being discussed as a component of 6G mobile communications. Concepts and demonstrations for 6G terahertz mobile communications will be presented. The high bandwidth of terahertz waves can also be used for high-accuracy indoor localization.

A Cross-Domain Optimization Framework of PMU and Communication Placement for Multidomain Resiliency and Cost Reduction

Abstract: Phasor measurement units (PMUs) play a crucial role in real-time monitoring and control of power grids. They rely on a communication network to transfer measurement data to the phasor data concentrator (PDC) for further processing and analysis. In this paper, a resilient cross-domain PMU and communication link placement method for minimizing the overall installation cost of the wide-area measurement system (WAMS) is proposed. The main idea is to break down the barrier between the power grid domain and the communication domain, and consider the impact of one when design the other. The PMU placement in the power grid domain takes into account the cost of communication links by generating multiple solutions with equally minimum PMU costs for communication link placement evaluation. On the other hand, the communication link placement problem reduces the cost by customizing the routing policies based on the different roles of PMUs in grid observability. The proposed WAMS design is capable of withstanding any single component failure in the power domain (PMU failure or power branch failure) or in the communication domain (communication link failure or PDC failure). Numerical study on the IEEE 57-bus system reveals that the developed cross-domain optimization framework can significantly reduce the overall installation cost of WAMS while attaining multi-domain resiliency.

Performance Analysis of RIS-Assisted Communications With Element Grouping and Spatial Correlation

Abstract: We investigate the performance of a reconfigurable intelligent surface (RIS) assisted single-input single-output (SISO) communication system where RIS elements are narrowly spaced so that the channels between the RIS elements and receiver are spatially correlated. Adjacent RIS elements are grouped together to reduce the channel estimation overhead. The statistical properties of the optimal received SNR are analytically derived and these are used to characterize the coverage probability of the system. An analytical upper bound for the average achievable rate is also derived. This analysis provides insight into the impact of the grouping strategy and element spatial channel correlation level on the coverage probability and the achievable rate of the system. Numerical results validate the tightness of the closed-form expressions. Our results show that the average achievable rate for a given group size is higher for the spatially correlated RIS elements as compared to the uncorrelated configuration.

An aeronautical data communication demand model for the North Atlantic oceanic airspace

Abstract: Abstract Information exchange via aeronautical data communication is of increasing importance for the communication between pilots and air traffic control, providing the basis for surveillance of aircraft in oceanic or remote airspaces, as well as enabling the communication between an airlines’ fleet and its operational control. The aeronautical data communication that is being transmitted via data link encompasses, among others, surveillance-related aircraft position updates, clearances for flight path change requests, maintenance-related status reports, estimated arrival times and weather information in accordance with the required performance, that is set by technical standards. Aeronautical data communication events are driven by an aircraft’s flight phase, the current airspace or may occur in a randomized manner throughout the flight. As the usage of aeronautical data communication is expected to grow in future, ample data link technologies are being evaluated and developed. The usability and operational value of new data link technologies for aeronautical applications can be evaluated by applying suitable models of the respective data link communication pattern combined with operational simulations. Current models for aeronautical data communication demand support the design and evaluation of direct aircraft-to-ground communication networks. The geographical location of the data communication demand is secondary for these models, since coverage areas can be defined, where direct communication links are available. New data link technologies offer the opportunity of direct data transfer between aircraft and forwarding of messages from sending aircraft to a ground entity via ad-hoc communication networks between aircraft. This is of special interest for the North Atlantic oceanic airspace, an airspace with high traffic density and little ground infrastructure, where communication currently relies mostly on satellite-based systems. For these airborne ad-hoc networks the definition of coverage areas around ground or space-based entities is not possible. To assess the new data link technology a model for aeronautical data link communication demand is needed, that accounts for operationally derived communication events such as handover procedures at boundaries of oceanic control areas or status reports at route-specific waypoints, which cause an accumulation in certain geographical regions that pose a challenge to the dynamic connectivity coverage of aeronautical ad-hoc networks. Addressing this issue, we present a new modelling approach for air traffic service communication that considers the operational context of the simulated airspace and provides a geospatial data communication demand distribution, which is derived from air traffic management procedures, airspace geometries and events inherent to each flight path. The air traffic service communication is then validated based on 2019 air traffic and performance monitoring data provided by ICAO supplemented by an existing model for communication related to airline operational control. In a next step, the communication demand per area in the North Atlantic Oceanic airspace is being assessed. The aeronautical data traffic model shows deviations of less than one message per aircraft and airspace when compared to recorded data traffic from 2019 for two key services in the most frequented North Atlantic oceanic control areas. Therefore, it is assumed to be suitable for the evaluation of network-based data link technology and operational impact assessments.

Performance Analysis of Reconfigurable Intelligent Surface-Assisted Wireless Communication Systems Under Co-Channel Interference

Abstract: Reconfigurable Intelligent Surface (RIS) can intelligently control the wireless propagation environment by adjusting the signal phase and amplitude in real time, which is considered as one of the key technologies of 6G. Although RIS-assisted wireless communication systems greatly improve transmission efficiency under ideal conditions, there are various uncertainties in actual communication systems. In this paper, RIS-assisted communication system is investigated where the RIS cannot completely eliminate the phase error and the user location is randomly distributed with uncertainty. In addition, there are some interference sources around the user, which are simplified as co-channel interference (CCI). Then we study the performance of RIS-assisted communication system, and derive the closed-form expressions for the outage probability (OP) and channel capacity of the system. Furthermore, we analyze the effects of various parameters on the OP and channel capacity. Finally Monte Carlo simulation is carried out which verify the accuracy of the derivation.

Boost Distribution System Restoration With Emergency Communication Vehicles Considering Cyber-Physical Interdependence

Abstract: Enhancing restoration capabilities of distribution systems is one of the main strategies for resilient power systems to cope with extreme events. However, most of the existing studies assume the communication infrastructures are intact for distribution automation, which is unrealistic. Motivated by the applications of the emergency communication vehicles (ECVs) in quickly setting up wireless communication networks after disasters, in this paper, we propose an integrated distribution system restoration (DSR) framework and optimization models, which can coordinate the repair crews, the distribution system (physical sectors), and the emergency communication (cyber sectors) to pick up unserved power loads as quickly as possible. Case studies validated the effectiveness of the proposed models and proved the benefit of considering ECVs and cyber-physical interdependencies in DSR.

A Survey on Optimal Channel Estimation Methods for RIS-Aided Communication Systems

Abstract: Next-generation wireless communications aim to utilize mmWave/subTHz bands. In this regime, signal propagation is vulnerable to interferences and path losses. To overcome this issue, a novel technology has been introduced, which is called reconfigurable intelligent surface (RIS). RISs control digitally the reflecting signals using many passive reflector arrays and implement a smart and modifiable radio environment for wireless communications. Nonetheless, channel estimation is the main problem of RIS-assisted systems because of their direct dependence on the system architecture design, the transmission channel configuration and methods used to compute channel state information (CSI) on a base station (BS) and RIS. In this paper, a concise survey on the up-to-date RIS-assisted wireless communications is provided and includes the massive multiple input-multiple output (mMIMO), multiple input-single output (MISO) and cell-free systems with an emphasis on effective algorithms computing CSI. In addition, we will present the effectiveness of the algorithms computing CSI for different communication systems and their techniques, and we will represent the most important ones.

Semantic Communication System Based on Semantic Slice Models Propagation

Abstract: Traditional communication systems treat messages’ semantic aspects and meaning as irrelevant to communication, revealing its limitations in the era of artificial intelligence (AI), such as communication efficiency and intent-sharing among different entities. Through broadening the scope of the traditional communication system and the AI-based encoding techniques, in this manuscript, we present a novel semantic communication system, which involves the essential semantic information exploration, transmission and recovery for more efficient communications. Compared to other state-of-the-art semantic communication-related works, our proposed semantic communication system is characterized by the “flow of the intelligence” via the propagation of the model. Besides, the concept of semantic slice-models (SeSM) is proposed to enable flexible model-resembling under the different requirements of the model performance, channel situation and transmission goals. Specifically, a layer-based semantic communication system for images (LSCI) is built on the simulation platform to demonstrate the feasibility of the proposed system and a novel semantic metric called semantic service quality (SS) is proposed to evaluate the semantic communication systems. We evaluate the proposed system on Cityscapes and Open Images datasets, resulting in averaged 10% and 2% bit rate reduction over JPEG and JPEG2000, respectively. In comparison to LDPC, the proposed channel coding scheme can averagely save 2dB and 5dB in AWGN channel and Rayleigh fading channel, respectively.

Optical Communication Infrastructure in New Generation Mobile Networks

Abstract: ABSTRACT In this study, predictions by leading network technology companies and current literature on 5 G technologies have been investigated to shed a light on the foreseeable future of the developing communication systems infrastructure. Research has been carried out on the new-generation optical communication infrastructure, which is developing in parallel with the requirements of 5 G and beyond mobile communication systems, and optical-wireless communication (OWC), free-space optical communication (FSOC), visible-light communication (VLC), and optical-camera communication (OCC) is presented. Also, there is information about fiber-wireless (FiWi) and radio-over fiber (RoF) transmission systems and FSO system integration (RoFSO), which finds use as an infrastructure component in the next-generation high-frequency communication.

On the Feasibility of Remote Driving Applications Over mmWave 5G Vehicular Communications: Implementation and Demonstration

Abstract: This paper presents a study conducted for the feasibility validation of a remote driving application, which is one of the use cases of 5G Vehicle-to-everything (V2X), over millimeter-wave (mmWave) 5G New Radio (NR) vehicular communications. First, the overall network architecture of a typical mmWave 5G NR communication system and design details of essential system components for remote driving applications are provided. Then, we discuss key technologies, including beam switching, automatic gain control, uplink transmit power control, and hybrid automatic repeat request with soft combining, enabling the system to offer reliable communication links for remote driving support. Lastly, we describe the implementation and deployment of testbeds and provide the experimental results obtained from field trials. The field trial results reveal that leveraged by the key enabling technologies and mmWave providing a wider spectrum and shortened latency, the mmWave 5G NR vehicular communication system has the capability to provide broadband, reliable, and low-latency communication links for the realization of remote driving applications, which eventually paves the road towards expanding the applicability of mmWave communication systems.

Joint Design of Phase Shift and Transceiver Beamforming for Intelligent Reflecting Surface Assisted Millimeter-Wave High-Speed Railway Communications

Abstract: With the emerging demands of new communication services, the contradiction between capacity demand and spectrum shortage of railway communication systems becomes more severe. How to provide broadband communication services has become the key goal of future smart high-speed railway (HSR) systems. Millimeter wave (mm-wave) frequency band has abundant spectrum resources and can provide communication services with large bandwidth. However, due to the high-speed of the train as well as the complexity and dynamics of environments, the communication link may be blocked randomly for a short time and will also lead to frequent handovers. In this paper, we adopt the promising intelligent reflecting surface (IRS) technology for a mm-wave HSR communication system. In order to improve system capacity, IRS is deployed to improve reflection transmission links, and optimization algorithms are designed for transceiver beamforming and IRS phase shift. In addition, given the specificity of the HSR scenario, we also formulate the average system ergodic capacity maximization problem and obtain upper bound on the average system ergodic capacity with statistical channel state information (CSI). Through extensive simulations, we verify that the proposed scheme performs significantly better than the other two baseline schemes in terms of average system throughput and average system ergodic capacity.

Comparing of the effect of changing weather factors on FSO communication system performance using iterative improvement technique

Abstract: The issue of providing a communications system, with large frequencies within the range, is one of the main challenges that are required to be provided to users of the free-space optical communications service. In this work, the factors affecting the quality of performance of a free communication system (10 Gbps) were investigated and studied. The obtained results of this system are compared with two wavelengths 1550 nm and 850 nm in terms of farthest data transmission distance, BER, factor of quality and chart of eye in different weather situations using an iterative optimization.

Evaluation and Improvement of System-of-Systems Resilience in a Simulation of Wildfire Emergency Response

Abstract: Because of the increasing threat that wildfires pose, there is interest in leveraging new technologies to improve firefighting. Specifically, unmanned aerial systems (UAS) and UAS traffic management promise to improve firefighters’ situational awareness, coordination, communications, safety, and strategy. While these technologies could be beneficial, there has been little formal investigation into how much benefit would occur and whether these benefits would outweigh hazards introduced by these systems. To better understand the impacts of these technologies, this article presents a high-level dynamic simulation for evaluating wildfire response performance and resilience incorporating fire propagation, surveillance and communication, response planning, and the resulting mitigation actions. This simulation is then used to study the impact of communications and surveillance improvement, considering 1) the effect on fire containment and ground crew injuries and 2) the effect of introduced and existing disruptive fault scenarios. Simulating this model over a large number of scenarios finds that these changes can improve containment and reduce ground crew injuries. While these improvements generalize over both existing and introduced single-fault scenarios and, thus, result in a more resilient system, they could be negated if the introduced communications infrastructure is prone to full-scale outages.

Fiberless optical communication: issues and challenges

Abstract: Abstract To fulfill the requirement of high data rate with variable quality of service, optical wireless communication is a better option in comparison to existing RF system and is a favorable technological candidate for future optical communication. In wireless optical communication, information is transmitted by propagation of optical wave through the atmosphere. The detrimental effects of channel parameters can acutely limit the utility of an optical wireless communication system. The paper first reviews different channel models in the context to outdoor wireless communication. Different impairments that affect the performance of outdoor optical communication systems and different techniques to mitigate these impairments are then investigated. The upper layer protocols for free space optical communication are also discussed.

Broadband wireless communication with space-time-varying polarization-converting metasurface

Abstract: Abstract Reconfigurable metasurfaces have emerged as a promising alternative to the conventional transmitter of wireless communication systems, due to their abilities of encoding digital information onto electromagnetic properties without complex radio-frequency chains. However, most of them are still limited to narrow operation bandwidth. Here, we propose a broadband metasurface-based wireless communication system that can actively adapt to multiple users located at versatile directions through joint modulation of digital signals in the time domain and wave scatterings in the space domain. As exemplary demonstrations, highly directive beams are generated to enhance regional signals in real-time customized for users in desired directions and reduce the signal leakage in undesired directions. Experiments are carried out to verify that the system can provide stable wireless communication service in a broad band of 3.7–5.1 GHz, within which the transmitted color picture enabled by the time-varying spatial modulation of metasurface can be successfully recovered at the user terminals. The proposed system may offer untapped potentials for next-generation communications and radar systems where regional signal enhancement, active adaption to users, and large channel capacities are required.

Energy-Efficient Interference Cancellation in Integrated Sensing and Communication Scenarios

Abstract: Recently, integrated sensing and communication (ISAC) has been a hot topic to alleviate the issue of low spectrum efficiency, pursuit the hardware gain and integration gain as far as possible. However, the coexistence of sensing and communication functions triggers the mutual interference therein, seriously affecting their respective performance. To solve this problem, the communication model and sensing model are built respectively in this paper, considering the interference between communication signals and between sensing signals and communication signals. Then, the ratio of the total transmitting data rate and the total power consumption is regarded as the optimization objection of this paper for energy-efficient interference cancellation. After that, the approximate solution of the optimization objection is obtained by Dinkelbach based scheme and semi-definite relaxation (SDR). Finally, the numerical simulations are conducted and the simulation results state that the proposed scheme can obtain a higher energy efficiency and outperforms the classical scheme.