Wireless Links Research Articles

Electromagnetic Accessibility of Starlink User Terminals

The results of assessing the electromagnetic accessibility of radio emission sources of the Starlink satellite communication system are presented. The features of the organizational and technical structure of the system are considered. Its main technical capabilities for organizing the provision of telecommunications services to users of subscriber terminals are analyzed. The technical features of the infrastructure of the Starlink satellite communication system, which are essential for the electromagnetic accessibility of its sources, have been studied. The possibility of radio links for transmitting information content in the upstream and downstream channels of the Starlink satellite communication system was assessed. The main stages of the developed methodology for assessing the electromagnetic accessibility of sources are presented. Analytical expressions are given for calculating the probability of detection and attenuation of signals. The requirements for the sensitivity of the receiving equipment of monitoring equipment are substantiated. Dependences of the level of signal attenuation on the distance of control equipment were obtained.

Fuzzified swarm intelligence framework using FPSOR algorithm for high-speed MANET- Internet of Things (IoT)

Internet of things (IoT) is an inventive technology which permit the association of physical things by means of the digital world throughout the use of heterogeneous networks and communication technologies. Ad-hoc routing protocols may be dispersed and involve every node in route discovery process by making routing data more reliable. Mobile-Adhoc-Networks (MANETs) consist of many portable nodes that can commune directly with each other or through intermediate nodes. Repeatedly, nodes in a MANETs operate with batteries and can roam freely, and thus, a node may exhaust its energy or move away without providing any notice to its cooperative nodes. IoT system using a combination of MANET, a route consists of numerous links in sequence, and so, its lifetime is based on the lifetime of every node and also the wireless links among adjacent nodes. In this research work Fuzzified Particle Swarm Optimization oriented Routing (FPSOR) algorithm is planned to minimize data loss and computational overhead, which in turn maximizes the lifetime of MANETs. Particle Swarm Optimization oriented Routing protocol (PSOR) have taken energy competence as significant criterion for processing routing and driving optimized path for the data accelerating and processing to the source node. The PSOR produces a fresh route for routing by considering fitness value of energy to evaluate diverse path and to choose best-optimized path whose energy consumption is less as compared to ant colony optimization routing paths. This algorithm utilizes a good approach focusing energy levels/status of the nodes through fuzzification and the lengths of the routed ways. NS2 simulator is casted for performance evaluation.

Designing high-speed GEO-to-Moon optical wireless communication links

Moon exploration and colonization will strongly rely upon high-speed optical wireless communications over a huge distance (around 400,000 km). Here, we introduce a holistic model, including the propagation issues as well as the realistic communication limitations and the expected practical limitations. We focus on the communication issues in a link connecting a GEO satellite to a fixed Moon optical station: here, we consider the challenging 10 Gbit/s transmission rate, and we assume an optical pre-amplified receiver, which is today the only option for high speed; we then select three different modulation formats, with corresponding implementations and increasing complexity and performance. Under these assumptions, we estimate the common operating conditions at the forward error correction threshold and point out the role of the transmitter and receiver telescopes: for practical size (e.g., 1 m), relevant limitations arise, which we combine with the typical photons-per-bit sensitivity values in an optical link. We find that all considered modulation formats can be used at 10 Gbit/s, although with different margins and hardware requirements, particularly considering the size of the optical antennas. We then extend the analysis to higher rates, up to 40 Gbit/s. This work can open the way to the realization of optical wireless communication systems to/from the future Moon Village.

Rain Attenuations Based on Drop Size Distribution (DSD) Model and Empirical Model at Low THz Frequencies

Rain attenuation based on the drop size distribution (DSD) with different rainfall rates (R) at low THz frequencies is investigated in this paper. The rain attenuation is calculated using the DSD measured for one year and the extinction cross-section (ECS) by the Mie scattering theory. Moreover, the obtained specific rain attenuation is verified by the empirical model using the measurement system consisting of a transmitter, a receiver, and weather measurement units. We measured the received power against the uniform transmitted power at 240, 270, and 300 GHz on the rooftop of the National Radio Research Agency (RRA) in Korea during the same period as the DSD measurement period. After curve fitting by regression analysis, we compared both rain attenuations obtained in two methods with the recommendation International Telecommunication Union Radiocommunication Sector (ITU-R) P.838-3. The root mean square errors (RMSEs) of the DSD model are 2.8977, 2.8646, and 2.8331 at 240, 270, and 300 GHz, respectively. The calculated result using the Mie scattering and the measured DSD methods shows the best fit to the data of the ITU-R recommendation for a rainfall rate of up to 5 mm/h. On the other hand, the empirical results using the T/Rx antenna system are slightly higher compared to the data of the ITU-R recommendation. As the rainfall rate increases, the difference between our results and ITU-R recommendation increases. This study will be useful for predicting rain attenuation for terrestrial wireless links operating at low THz frequencies.

Obstacle-tolerant terahertz wireless link using self-healing Bessel beams

Wireless communications using highly directive terahertz (THz) waves exhibit lower immunity to obstructions than microwaves, limiting their applications. This study demonstrates an obstacle-tolerant THz wireless link established by a self-healing Bessel beam at 300 GHz. The Bessel beam is generated by sending a Gaussian beam through a dielectric axicon lens. Furthermore, experiments were conducted to investigate the short-range transmission (98 mm) reception characteristics with and without the dielectric cubic obstacle (7.5 λ in size) and the metallic obstacle (22 λ in length and 8 λ in width) in the Gaussian beam and self-healing Bessel beam cross sections. The maximum attenuation of the received power due to obstruction was 8.8 and 2.2 dB for the Gaussian and Bessel beams, respectively, when the dielectric obstacle is placed in the middle of the transmission path (49 mm from a transmission lens). This study further investigated the bit error rate (BER) characteristics (1 Gbps, on–off keying) with the dielectric obstacle crossing the beam cross section. When the obstacle crosses the Gaussian beam, the BER degrades as the obstacle approaches the optical axis, breaking the wireless link. In contrast, when the obstacle crosses the Bessel beam cross section, the BER is maintained at <3.8 × 10−3 (the forward error correction limit), and the wireless link is maintained. A self-healing beam, such as the Bessel beam, makes the THz wireless link more tolerant than the Gaussian beam to obstacle and expand applications for THz wireless communications.

Adaptive feedback-driven probabilistic shaping for high-order modulation formats in a fiber–THz seamless integration system at 320 GHz

In this Letter, we propose a novel, to the best of our knowledge, adaptive feedback-driven probabilistic constellation-shaping (FBD-PCS) method based on the robustness evaluation criteria and employ variational autoencoder (VAE)-based equalizers to implement polarization demultiplexing and nonlinear equalization for the recovery of high-order PCS-QAM signals. We experimentally demonstrate the fiber–THz 2 times 2 MIMO system with a net rate of 366.4 Gbit/s using dual-polarization 40 Gbaud PCS-64QAM signal over a 20 km SSMF and 6 m wireless link. Specifically, the feedback mechanism drives the fiber–THz system to solve optimization problems, adaptively matching the optimized distribution of transmitted symbols that maximizes normalized generalized mutual information (NGMI). We also examine six scenarios to explore nonlinear resistances of FBD-PCS symbols and the robustness of VAE-based equalizers. The results demonstrate the superiority of FBD-PCS over the Maxwell–Boltzmann (M–B) distributions in practical nonlinear-dominant systems. Additionally, the FBD-PCS signals can break limitations for ultrahigh rate transmission with the help of advanced equalizers.

Mobile Ad-Hoc network, Mobile application, aircraft performance, software development

In the past decade, a steady increase has been noticed in the number of mobile users and the use of mobile communication. In wireless communication links are stable. Duration of the link is the most important design by which the performance of the mobile Ad Hoc network (MANET) can be determined. In this research article, a derivative metric of graph theory attained from mobility model technique in Ad Hoc network of casually moving object, link duration of probability density function (PDF)been examined by using three mobility models namely random waypoint, random direction, and freeway model. The performance is based on the node speed, transmission range, the density of node, area of simulation, and computational complexity with time. By using Monte Carlo simulations, the reliability and robustness of models have been analyzed. The main advantage of the proposed scheme is implemented is an easy hardware platform because of the concept in mobility models and the easiness of code.

Improvising QoS through Cross-Layer Optimization in MANETs

In Mobile Adhoc Networks (MANETs), nodes are mobile and interact through wireless links. Mobility is a significant advantage of MANETs. However, due to the unpredictable nature of mobility, the link may fail frequently, degrading the Quality of Service (QoS) of MANETs applications. This paper outlines a novel Ad hoc On-Demand Distance Vector with Proactive Alternate Route Discovery (AODV-PARD) routing protocol that uses signal strength-based link failure time estimation. The node predicts the link failure time and warns the upstream node through a warning message about the failure. On the basis of this information, a mechanism for identifying alternate routes is started in order to reroute traffic to the alternate route prior to the link failure. It significantly reduces packet loss and improves all the QoS parameters. The suggested protocol is compared to the traditional Ad hoc On-Demand Distance Vector (AODV) routing protocol and shows that the outlined protocol results in an improvement in QoS.

Device-Free Localization Techniques: A Review

Device-free localization (DFL) has emerged as a transformative technology for tracking objects and individuals without requiring them to carry electronic devices. This paper reviews two pivotal techniques of DFL: Link Quality Measurement and Link Scattering techniques. Link Quality Measurement focuses on evaluating the quality of wireless links through metrics like Received-Signal-Strength and Channel-State-Information, offering simplicity and reliability. Meanwhile, Link Scattering harnesses signal reflections and diffractions caused by environmental obstacles to estimate device-free target positions. This review provides insights of Link Quality Measurement, Link Scattering methods and highlighting DFL metrics. By shedding light on these critical aspects, it offers valuable insights into the current state of DFL technology and its potential in diverse domains, ranging from smart environments to security systems.

Effect of water-waves on recognition of speech signals transmitted over a wireless optical communication channel

In many sea-exploration scenarios, a wireless optical communication link between an onshore station and a floating marine structure or between a floating buoy and an underwater vehicle is required. In order to establish high-quality wireless optical communication, the effect of sea-waves must be taken into consideration. In this work, we investigate the influence of surface water waves having various amplitudes, frequencies and waveforms on the quality of an analog speech signal transmitted over a wireless optical communication link. Such investigation is also carried out on an encrypted speech signal. The quality of the speech signals is determined by utilizing a deep learning neural network that is trained to recognize ten speech commands and produces classification probabilities. In our experiments, either the detector or the light source is non-stationary as a result of the water-waves, thus distorting the received analog signal. We also show a method of deriving the frequency of the water waves by using a remote tracking unit based on micro-electro-mechanical systems (MEMS) mirrors.

A method for maintaining a stable ISM band point-to-point wireless communication link in the presence of interference

This paper presents a new method that enables automatic channel change in case of intense interference on the active channel of a wireless communication point-to-point link. Channel change algorithms on the master and slave side of the communication link are presented, which enable the automatic selection of a new communication channel from a predefined set of available communication channels. By applying this method, it is possible to maintain a stable communication link in case of intense unpredictable interference on the transmitter or receiver side. The method applies to two-way master-slave communication links, regardless of the frequency spectrum and the number of used communication channels.

Analytical Techniques for Performance Evaluation of Fountain-Coded File Distribution in Packet Radio Networks

Convenient analytical techniques are developed for use in preliminary design of systems and protocols for the delivery of fountain-coded files from a source node to a destination node with the assistance of a relay node. Each node has a half-duplex packet radio, and the time-varying disturbance on each link is represented by a lumpable finite-state Markov chain. The analytical techniques include the use of first passage times and recurrence times in the derivation of an exact expression for the completion time of file transfer over a radio link and the application of results on Markov-correlated Bernoulli trials to obtain exact expressions for completion times of relay-aided file transfer in wireless networks. In the development of analytical techniques, we employ capacity-achieving channel codes and ideal fountain codes; however, we present simulation results for packet radios that employ practical channel codes and for which the fountain code is a standard systematic raptor code.

Communication and Energy Efficient Decentralized Learning Over D2D Networks

Device-to-device (D2D)-assisted decentralized learning has been proposed for mobile devices to collaboratively train artificial intelligence networks without the centralized parameter server. However, a densely connected network will cause large learning latency and energy consumption due to the limited computation and communication resources. In addition, link selection and aggregation weight have a significant impact on the learning performance. To cope with these challenges, we propose a joint computing power adjustment, wireless resource allocation, link selection, and aggregation weight adaptation mechanism to improve both communication and energy efficiencies. Specifically, the learning performances including the convergence rate, per-iteration learning latency, and per-iteration energy consumption are first analyzed. Then, an optimization problem is formulated to minimize the total learning cost, which is defined as the weighted sum of total learning latency and energy consumption. Given a network topology, the computing power and wireless resource allocation are optimized by the alternating optimization algorithm. Moreover, the optimal aggregation weight is obtained by semidefinite programming. With respect to link selection, we propose a tabu search based meta-heuristic algorithm to approximately achieve feasible solutions with a low computational complexity. Finally, extensive experiments demonstrate that the proposed link selection algorithm can significantly reduce the learning cost under the given learning accuracy requirement.

300 GHz Wireless Link Based on Whole Comb Modulation of Integrated Kerr Soliton Combs

300 GHz Wireless Link Based on Whole Comb Modulation of Integrated Kerr Soliton Combs

A Millimeter-Wave Wideband Antenna Module With Switchable Fan-Beam Radiation for Wide Coverage of 5G IoT Applications

Millimeter wave (mm-wave) antenna modules with switchable beam radiation provide a potential solution for enabling flexible wireless links and high data rate in Internet of Things (IoT) networks. Aiming to simultaneously fulfill a wide coverage and follow the cost-effective principle of IoT devices, a novel mm-wave wideband antenna module with switchable fanbeam radiation is proposed based on an air-filled planar Cassegrain beam-former. A comprehensive design procedure combing the theoretical calculation and differential evolution (DE) algorithm is first introduced to construct the beam-former with wide-angle scanning capability. The desirable apertureshared switchable fan-beam radiation with high crossover is then obtained with the aid of a proposed two-feed-per-beam (2FPB) scheme based on a low-loss integrated switch network. A prototype of the antenna in the Ka-band is fabricated by simultaneously adopting the metallic three-dimensional (3D) printing and printed circuit board (PCB) technology. Excellent operating characteristics, including a wide bandwidth of more than 32%, twenty stable fan-shaped radiation beams scanning over a wide angular range of ±45∘ in the H-plane, a high beam crossover of about -3 dB, a gain of up to 19.6 dBi, and a radiation efficiency of greater than 80% are demonstrated experimentally. With the ability to fulfill the radio coverage within a wide conical area, the presented antenna module would be an attractive candidate for the fifth generation (5G) IoT applications.

The Trends, Challenges, and Key Technologies of Beam-Space Multiplexing in the Integrated Terristrial-Satellite Communication for B5G and 6G

Along with the development of beam-space multiplexing theory, multi-layer beamforming has been applied successfully in 4G and 5G terrestrial wireless communication systems to increase the system capacity. For the future Integrated Terrestrial-Satellite Communication (ITSC), beam-space multiplexing is also expected to improve beamforming gain, wireless link quality and data transmission rate. This paper explores beam-space multiplexing in the ITSC towards B5G and 6G, including its application scenarios, evolution trends, technical challenges and key technologies. Based on the analysis of system capacity, performance evaluation is obtained by the simulation of several scenarios, and exposed the promising gain of beam-space multiplexing of the ITSC.

Compact OWC Receiver: Micro-Lens and PD Array on Glass Interposer

In this paper, we propose a compact optical wireless receiver based on micro-lens and photodiode array flip-chipped on a glass interposer. With simulation models and experiments, we verify the performance of two optical wireless communication receivers assembled based on this structure with gigabit and high-speed photodiodes. First, co-integrated gigabit photodiodes and micro-lenses indicate that micro-lenses can deliver a 3.5 dB gain of light collection efficiency to the gigabit photodiode array while keeping the field of view larger than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm$</tex-math></inline-formula> 18 degrees. Besides, a 5.5 Gbps maximum throughput has been verified by this optical wireless communication receiver with discrete multitone modulation. Moreover, co-integrated high-speed photodiodes and micro-lenses prove that micro-lenses realize a 26.6 dB improvement in light collection efficiency, enabling a 10 Gbps error-free connection using as little as -0.5 dBm transmission power. Those results conclude that the co-integration of micro-lenses on the photodiode array can enhance the light collection efficiency of the photodiode array while keeping a larger field of view, providing a high-performance, low-cost solution for the receiver of optical wireless links.

Validating Ionospheric Models Against Technologically Relevant Metrics

AbstractNew, open access tools have been developed to validate ionospheric models in terms of technologically relevant metrics. These are ionospheric errors on GPS 3D position, HF ham radio communications, and peak F‐region density. To demonstrate these tools, we have used output from Sami is Another Model of the Ionosphere (SAMI3) driven by high‐latitude electric potentials derived from Active Magnetosphere and Planetary Electrodynamics Response Experiment, covering the first available month of operation using Iridium‐NEXT data (March 2019). Output of this model is now available for visualization and download via https://sami3.jhuapl.edu. The GPS test indicates SAMI3 reduces ionospheric errors on 3D position solutions from 1.9 m with no model to 1.6 m on average (maximum error: 14.2 m without correction, 13.9 m with correction). SAMI3 predicts 55.5% of reported amateur radio links between 2–30 MHz and 500–2,000 km. Autoscaled and then machine learning “cleaned” Digisonde NmF2 data indicate a 1.0 × 1011 el. m3 median positive bias in SAMI3 (equivalent to a 27% overestimation). The positive NmF2 bias is largest during the daytime, which may explain the relatively good performance in predicting HF links then. The underlying data sources and software used here are publicly available, so that interested groups may apply these tests to other models and time intervals.

Optical Wireless Fronthaul-Enhanced High-Throughput FC-AE-1553 Space Networks

Existing space application networks in space stations are mainly fiber-optic cable-based networks due to their low size, weight, and power (SWaP) values. While fiber networks in space stations offer data transmission at high speeds with minimal signal loss, their major disadvantage is the lack of flexibility and mobility when new and unplanned space scientific equipment is added to the network. To enhance the flexibility of space networks while increasing their throughput, this paper introduces the hybrid space network (HSN), a new space network architecture that incorporates an optical wireless link, to meet the ever-increasing demands for larger bandwidth and higher mobile access capabilities in space scientific experiments. To best utilize the HSN’s system performance, we propose a multi-priority-based network scheduling scheme, which can dynamically adapt to the requirements of mass tasks and select the best transmission procedure. Through simulations, we find that by adding optical wireless communication (OWC) links to the state-of-the-art deterministic FC-AE-1553 space network, the HSN’s bandwidth can be increased by 20 times with an average latency reduction of 87.3%. We believe that the proposed HSN’s architecture may ultimately shape the future of space stations’ wireless connectivity, and in the meantime, innovate many advanced space applications with larger data rates and mobility requirements.

Internet in the Middle of Nowhere: Performance of Geoportals in Rural Areas According to Core Web Vitals

The spatial planning system in Poland is undergoing a fundamental reform. It emphasises the digital representation of spatial data. Low performance of geoportals, no Internet access, or poor connectivity can contribute to the exclusion from the spatial planning process, and consequently to the exclusion from a specific part of public life. Considering these developments, the present study seems relevant by pointing out the issue with geoportal performance and availability of quality Internet in rural areas. The primary contribution of the article is (1) results of performance measurements for selected geoportals; (2) presentation of measuring tools and performance indices combined with methods for ad-hoc performance measuring; and (3) presentation of potential actions to improve geoportal performance on the device with which it is used. The article offers case studies where the performance of selected geoportals was tested in rural mountainous areas with limited Internet access. Five geoportals were tested with PageSpeed Insights (PSI), WebPageTest, GTmetrix, Pingdom, and GiftOfSpeed. Core Web Vitals indices were analysed: Largest Contentful Paint (LCP), First Input Delay (FID), Cumulative Layout Shift (CLS), and First Contentful Paint (FCP). The author verified values of the Speed Index and Fully Loaded Time along with other performance indices, like GTmetrix Structure. The study failed to provide unambiguous evidence that radio link users in rural areas could experience problems with geoportal performance, although the results seem to suggest it indirectly. PSI Lab Data and Field Data tests revealed a relatively low performance of the geoportals. The Performance index remained below 50 in most cases, which is ‘Poor’ according to the PSI scale. The fully loaded time exceeded 10 s for all the geoportals and 20 s in some cases (Lab Data). It means that the perceived performance of the tested geoportals on a radio link in rural areas is most probably even lower. The case studies demonstrated further that the user has limited possibilities to speed up map applications. It is possible to slightly improve the geoportal experience through the optimisation of the device locally, but the responsibility to ensure geoportal performance is mainly the publisher’s.