Wireless LAN Research Articles

Low‐profile wideband four‐element MIMO array using Giuseppe Peano AMC surface with improved efficiency and isolation for WLAN systems

AbstractA low profile four‐element multiple‐input multiple‐output (MIMO) array of printed dipole antenna (PDA) backed by second iteration of Giuseppe Peano fractal artificial magnetic conductor (AMC) is introduced for broadband wireless communications. First, a suggested PDA with a pair of microstrip E‐shaped dipoles excited by an E‐shaped microstrip feedline is used to expand the bandwidth in the range of 5.47–6.92 GHz (S11 ≤ −10 dB). Then, the suggested 4 × 4 Giuseppe Peano fractal AMC reflector is loaded into the PDA to exhibit −10 dB measured impedance bandwidth from 4.21 to 7.06 GHz (50.61%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The proposed four‐element MIMO array loaded by 6 × 6 AMC reflector with diverse polarizations of elements introduces a low profile wideband structure. The measured results of four elements include the broad bandwidths from 4.3 to 7.05 GHz with enhanced gains (more than 8 dBi) and high efficiencies. The high isolations between the four elements with diverse polarizations are obtained larger than 26.5 dB and they reach 66 dB over the operating bandwidth for MIMO systems. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 51.33%, enhanced radiation efficiency up to 94%, and excellent impedance matching with uni‐directional radiation patterns.

Improving Isolation in MIMO Antenna for WLAN Applications

The system Wireless Local Area Network (WLAN) presents minimum bandwidths to provide required transmission data rates, isolation can also be improved using multiple input multiple output (MIMO) scheme increasing their capacity. In this paper, the Decoupling Networks technique is presented to reduce the coupling between the elements of the MIMO antenna and thus improve data rate with a 2x2 MIMO antenna system. The dielectric used was FR4 substrate with dielectric constant εr = 4.4 and thickness of substrate 1.544 mm. The S11 and S12 scattering parameters were obtained as well as ECC at the resonance frequency and bandwidth. The radiation pattern and the current density are simulated by HFSS. The antenna size is 80x65mm^2.

Two-level frame aggregation with enhanced A-MPDU for signal-to-noise ratio efficiency in IEEE 802.11n WLANs

<p>One of the most important frame aggregation features for enhancing the speed of IEEE 802.11n wireless local area networks (WLANs) through sharing headers and timing overheads is an aggregate MAC protocol data unit (A-MPDU). However, because aggregation overhead affects A-MPDU frame size, the A-MPDU performance falls short of user expectations. The variable signal-to-noise ratio (SNR) is significantly decreased as a result of the influence of lost sub-frame on the volume of sub-frames that may be aggregated (the level of aggregation). In order to solve this issue, this study suggests an improved A-MPDU with reduced header overheads as well as a efficient two-level aggregation technique based on enhanced A-MPDU. To test the suggested plan, a simulation experiment was run on NS-3. The results show that the suggested two-level aggregation approach works better than the existing methods by achieving higher throughput, SNR, and a efficient medium access control (MAC) layer.</p>

Characterizing User Association Patterns for Optimizing Small-Cell Edge System Performance

Edge computing is a promising paradigm to support multifarious time-sensitive applications. In this article, we shed light on data-driven approaches to optimize edge system performance via mining user association patterns in the wireless local area network (WLAN). Particularly, we first describe the association traces (containing more than 50,000 users) that are collected in one operational WLAN network. We then conduct the data analytics to mine user association patterns that have impacts on edge system performance. To leverage our findings, we propose three data-driven approaches to optimize the edge system performance, i.e., efficient edge resource deployment, mobility-aware user service migration, and distributed cooperative learning for edge intelligence. Finally, we cast a case study on distributed learning by devising a cooperation scheme, named CoLo (i.e., Co-Located learning), which can leverage the user association patterns to distribute learning tasks. Extensive data-driven experiments corroborate the efficacy of CoLo in comparison with state-of-the-art schemes.

When the Tertiary Care Hospital Becomes Technologically Austere: Communication Lessons Learned from an American Health System Cyberattack

Introduction:Cyberattacks continue to plague medical systems across the world with nearly 24% of all cyber breaches impacting health systems. In Fall 2021, a large, tertiary care county hospital in Indianapolis, Indiana, USA suffered a cyberattack, causing over four weeks of downtime, forcing the system to revert to paper charting and to operate without the electronic medical record (EMR) or internet. Communication in the Emergency Department is structured through the EMR system or wireless local area network (WLAN) phones, causing communication difficulties when online systems are disrupted.Method:In the twelve months following the breach, a series of communications-focused interviews with stakeholders including residents, faculty, nurses, and consultants were analyzed using a thematic analysis.Results:Through interviews, four key themes and recommendations were identified for every internet-dependent tertiary care system to establish and maintain communication links when the primary form of communication is compromised and access to internet is limited or nonexistent: Expect systems to fail–plan aheadDevelop multilayered communication tools that are stored and structured at different sitesNotify all affected teams immediately and initiate the downtime action planReassess and adapt the downtime action plan as information becomes availableConclusion:While every system is going to experience different struggles during cyberattacks and downtime, all hospitals can benefit from improving communication structures when the established communication pathways are no longer available. Consider cybersecurity threats in your emergency planning meetings and designate systems to protect your communication abilities during downtime.

Is proportional fair scheduling suitable for age-sensitive traffic?

Proportional Fair (PF) scheduling with successful deployments in various cellular wireless networks and wireless LANs, aims at maximizing the sum of the logarithms of user throughputs. PF scheduling is known to strike an appropriate balance between fairness and throughput, for conventional data traffic. On the other hand, there has recently been a surge of interest in status update networks carrying age-sensitive traffic for which information freshness is crucial and therefore network performance metrics driven by Age of Information (AoI) are instrumental, as opposed to conventional performance metrics such as delay, loss, or throughput, used for conventional data traffic. This paper studies the scheduling problem for the downlink of a cellular wireless network with a transmitter sending age-sensitive status update packets from multiple information sources to users with the goal of keeping the information as fresh as possible for the users. For this purpose, under the generate-at-will scenario, an age-agnostic model-free scheduler is proposed with the goal of minimizing the weighted sum peak AoI of the network, which is the performance metric used in this paper for quantifying information freshness. With numerical examples, the proposed scheduler is compared and contrasted with weighted PF scheduling in terms of implementation and performance, in both non-opportunistic and opportunistic scenarios.

A Retransmission Scheme in IEEE 802.11be Synchronized Multi-Link WLANs

A novel retransmission scheme, considering both transmission rate and frame error rate, is proposed to alleviate the inefficiencies caused by head-of-line blocking and null padding problems during retransmission in IEEE 802.11be synchronous multi-link wireless local area networks. Simulation results show that the proposed scheme improves throughput by up to 200% over the legacy scheme by reallocating lost subframes and adding effective duplicate subframes to multiple links.

A Methodology to Plan Wireless Network in Indonesian Rural Areas

Wireless telecommunication networks have been widely implemented in Indonesia. However, the planning methodology hasn’t been intensively studied. In this paper, we proposed a novel methodology for wireless local area network planning in Indonesian rural area. Our proposed method consists of eleven steps of work emphasizes the ease of implementation, market survey consideration, Indonesian Government standard application, and free tools usage optimization. At the end, an example of a network design created by following the proposed methodology for Sebira Island is presented.

A Novel Cloud Approach for Connected Vehicles

Cooperative intelligent transport systems (C-ITSs) are being deployed all around the world. Shortly, in addition to vehicles, bicycles, pedestrians, buses, and all moving equipment will be compatible with C-ITS. These systems are connected through wireless local area networks based on WIFI IEEE 802.11p. The large number of C-ITSs and services will lead to a glut in the bandwidth of wireless networks. To overcome this limitation, we propose in this paper a new approach using the information-centric networking (ICN) paradigm which allows vehicles to communicate with the cloud environment. This scheme is denoted by vehicular central data networking (GeoVCDN). Our approach aims to reduce bandwidth consumption and improve data freshness by taking benefit from the existing application beacons and the geographical routing used by C-ITS actors. We have compared the performances (in terms of the network overhead and data freshness) of our solution to two other well-known ICN-based solutions. Each of them represents one of ICN categories, in particular, rendez-vous network (RENE) and named data networking (NDN). To do so, we have proposed a probabilistic model that allows us to evaluate the freshness and the load of the network. Furthermore, we have implemented these methods in a simulator. Our proposal outperforms the other methods in terms of network overhead and data freshness.

MODEL OF A CHAOTIC ULTRA-WIDEBAND INFORMATION TRANSMISSION SYSTEM FOR WIRELESS SENSOR NETWORKS

Distributer measuring systems, consisting of interconnected wireless sensor nodes with autonomous supply, have plenty of applications in different areas of engineering end technology. Therefore, wireless sensor network design and optimization is a vital problem in informational technologies and computer engineering. Regardless of particular application and architecture, a wireless sensor network consists of several small sensor nodes somehow distributed in an area of inspection. Such a design ensures a distributed parameter measuring, according to which, each node performs preprocessing procedures for the data, which are to be aggregated by a so-called sink node and sent via other networks, e.g., wired or wireless local area network. For healthcare solutions, it is important to ensure a stable connection with the network and server back-end to provide a high-level analysis based on predicting methods of machine learning algorithms. This paper describes an application of an ultra-wideband communication model based on chaos synchronization as a low-power and efficient alternative solution for building wireless sensor networks. Thus, using chaotic signals as information carriers in wireless communication has several advantages, including a wide smooth spectrum, high information capability, cybersecurity, and low power consumption. The synchronization problem is one of the most vital tasks to be solved to design a chaos application for ultra-wide-band communication. Being well-studied for periodic signals, modern synchronization theory contains plenty of solutions for classical telecommunication and radio engineering systems, however, it is not developed enough for chaotic systems. Hence, a one-directional dissipative synchronization between two Chen systems is studied in the first section. The second section is devoted to the computer simulation of the model, described in the previous section. All the models built and the simulations performed have been done using MATLAB/Simulink software. The negative impact of channel noise and inequality of system parameters is considered. The possible way how to improve technical characteristics is also provided. Proposed models are to be used to design and develop low-cost wireless sensor networks for multi-channel healthcare solutions.

Activity‐related multifractal properties of Wi‐Fi signals

AbstractIn wireless local area networks (WLANs) compliant with the IEEE 802.11n standard, channel state information (CSI) is known to embed information about the surrounding environment, including the positions and movements of people. So far, this information has been inferred by exploiting certain temporal and spectral features of the related WLAN signals. In this letter, their multifractal, i.e. structural properties are examined by means of detrended fluctuation analysis. Preliminary results support the claims that (a) CSI traces exhibit multifractal properties and (b) these are influenced by human presence and activity/posture within the room.

Broadband Multiple Input Multiple Output antenna for sub‐6‐GHz 5G communications

SummaryThis paper presents the design of a miniaturized broadband monopole antenna for 5G and Wireless Local Area Network (WLAN) applications in mobile handsets. The proposed monopole evolved from a rectangular geometry of size 12 × 5 mm. The slot and stub loading techniques are used to improve the impedance matching offered by the antenna. Furthermore, bandwidth broadening is achieved using lumped elements loaded onto the aperture of the antenna. The proposed miniaturized antenna exhibits a measured impedance bandwidth of 63.6% (3.0–5.8 GHz) covering the 5G spectrum allocations under sub‐6 GHz and the WLAN services. The antenna elements are replicated along the sides of the mock mobile handset PCB to study the functionality of the eight‐element MIMO antenna. The prototype MIMO antenna fabricated and tested in the laboratory offers a peak gain of 3 dBi and total efficiency greater than 72%. Owing to miniaturization, the spatial distribution of the antenna element provides a low envelope correlation (ECC) of less than 0.2 and good diversity gain (DG) greater than 7.8 dB. In addition, the mean effective gain (MEG), channel capacity loss (CCL), multiplexing efficiency (ME), and total active reflection coefficient (TARC) are evaluated and presented. The estimated MIMO metrics are within the desired range of operation and hence make the antenna suitable for a complex propagation environment. The prototype antenna is developed on a thin microwave laminate with low‐loss characteristics and tested under laboratory conditions. The outcomes indicate that the proposed eight‐element antenna can be applied to 5G MIMO communications.

Six-port mid-bands Low-SAR MIMO antenna for WLAN, 5G mobile terminals, and C-band applications

This article investigates a six-port multiple-input multiple-output antenna which operates in mid-bands with a resonating frequency at 4.8 GHz. The overall dimensions of proposed antenna are 0.60 λ0×1.32λ0×0.024λ0, where λ0 is free space wavelength corresponding to resonating frequency of 4.8 GHz. The proposed geometry consists of six-port electromagnetic wave components along with a plane rectangular patch, slotted partial ring ground, circular cutting ground plane, and inset feeding. For enhancing isolation, I-shaped stubs and slotted ring ground are responsible. Inset feeding, circular cutting ground plane, and partial ground plane are used for enhancing reflection coefficient. The overall −10 dB impedance bandwidth of proposed antenna is ranging from 3.92 GHz to 5.2 GHz. The achieved isolation between all the ports of proposed work is ¿15 dB. The peak values of gain and radiation efficiency provided by this prototype are 6.45 dB & and 86% respectively. The achieved diversity parameters such as envelope correlation coefficients are ¡0.002, diversity gain is 9.98, channel capacity loss is ¡0.014 bits/sec/Hz, and branch power ratio is ¡−1 dB. The proposed antenna can be considered as a suitable candidate for wireless local area network, n77 bands, 5G wireless communications applications, and C-band operations.

RANCANG BANGUN ANTENA MONOPOLE MIKROSTRIP MENGGUNAKAN DEFECTED GROUND STRUCTURE BENTUK PERSEGI UNTUK OPTIMASI BANDWIDTH PADA APLIKASI KOMUNIKASI ULTRA-WIDEBAND

The development of UWB technology is very helpful in supporting high-speed data access. UWB offers a solution for large capacity for wide bandwidth. The frequency range for UWB systems between 3.1–10.6GHz will cause interference to wireless communication systems via wireless local area networks (WLANs) for IEEE 802.11a operating at 5.15–5.35GHz and 5.725–5.825GHz. This research aims to obtain a design of a rectangular printed monopole patch microstrip antenna and a slit using the Defected Ground Structure (DGS) technique to obtain bandwidth optimization on the UWB spectrum. For the implementation of the antenna design, the simulation method is used with the support of the RT/ Duroid substrate material. Realization of the design with the results of a manufactured antenna prototype with a minimalist size. The simulation and measurement results of the Absolute UWB bandwidth parameter at return loss < -10 dB (VSWR <2) the measurement value is 600MHz narrower than the simulation and for fractional bandwidth the measurement value is narrower by 0.21%. Resonance at the 5.2GHz frequency produces polarization with a gain value of 3.29dBi, omnidirectional and vertical polarization. As a prototype antenna to support the application of indoor wireless access communication devices that are low profile, compact with minimalist dimensions.

A Simulation Study of Triband Low SAR Wearable Antenna

The proposed paper presents a flexible antenna that is capable of operating in several frequency bands, namely 2.45 GHz, 5.8 GHz, and 8 GHz. The first two frequency bands are frequently utilized in industrial, scientific, and medical (ISM) as well as wireless local area network (WLAN) applications, whereas the third frequency band is associated with X-band applications. The antenna, with dimensions of 52 mm × 40 mm (0.79 λ × 0.61 λ), was designed using a 1.8 mm thick flexible kapton polyimide substrate with a permittivity of 3.5. Using CST Studio Suite, full-wave electromagnetic simulations were conducted, and the proposed design achieved a reflection coefficient below −10 dB for the intended frequency bands. Additionally, the proposed antenna achieves an efficiency value of up to 83% and appropriate values of gain in the desired frequency bands. In order to quantify the specific absorption rate (SAR), simulations were conducted by mounting the proposed antenna on a three-layered phantom. The SAR1g values recorded for the frequency bands of 2.45 GHz, 5.8 GHz, and 8 GHz were 0.34, 1.45, and 1.57 W/Kg respectively. These SAR values were observed to be significantly lower than the 1.6 W/Kg threshold set by the Federal Communication Commission (FCC). Moreover, the performance of the antenna was evaluated by simulating various deformation tests.

Research on Communication Stability of Inter-Cannonball Network Based on OPNET

In modern warfare, achieving strikes against military targets commonly involves utilizing methods such as fire coverage and missile precision guidance. While effective, fire coverage requires significant ammunition support, and missiles can be costly. Therefore, an intelligent strike solution can be an effective way to address these challenges. The inter-cannonball wireless communication network provides a solid foundation for inter-cannonball networking and joint strikes. The synergy improves the strike’s range and precision, ensuring own safety and destroying the enemy’s core with success. In this paper, the reliability of inter-cannonball group communication is studied. The vast array of activities and short striking distance of cannonballs make wireless networking between cannonballs a technological challenge. For this unique communication environment, the network of cannonballs is discussed, the self-organizing structure model of the network is proposed, the corresponding node topology is established, the protocol framework of inter-cannonball communication is presented, and the simulation parameters of the communication network are set. On this premise, discrete event simulation is performed by using the OPNET program to validate the impact of failure rate and node movement speed on the inter-cannonball network communication reliability. And the main performance indices of the inter-cannonball communication system are derived. The simulation results indicate that it can maintain basic communication stability, with wireless LAN delays of less than 100 ms, even when the node failure rate reaches 20%. The simulation verification method, on the other hand, overcomes the limitations of the real environment, optimizes the design phase, reduces research costs, and accelerates the development of intelligent cannonballs.

A Study of the Active Access-Point Configuration Algorithm under Channel Bonding to Dual IEEE 802.11n and 11ac Interfaces in an Elastic WLAN System for IoT Applications

Currently, Internet of Things (IoT) has become common in various applications, including smart factories, smart cities, and smart homes. In them, wireless local-area networks (WLANs) are widely used due to their high-speed data transfer, flexible coverage ranges, and low costs. To enhance the performance, the WLAN configuration should be optimized in dense WLAN environments where multiple access points (APs) and hosts exist. Previously, we have studied the active AP configuration algorithm for dual interfaces using IEEE802.11n and 11ac protocols at each AP under non-channel bonding (non-CB). In this paper, we study the algorithm considering the channel bonding (CB) to enhance its capacity by bonding two channels together. To improve the throughput estimation accuracy of the algorithm, the reduction factor is introduced at contending hosts for the same AP. For evaluations, we conducted extensive experiments using the WIMENT simulator and the testbed system using Raspberry Pi 4B APs. The results show that the estimated throughput is well matched with the measured one, and the proposal achieves the higher throughput with a smaller number of active APs than the previous configurations.

Microstrip patch antenna review on various parameters, methods and its applications

<p>The implementations of the microstrip patch antenna for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) are analysed in the literature in this research. Dual or multiband antenna has played a significant part in meeting the expectations of wireless service in this quickly developing world of wireless communication. Basically, a transitory guide, an antenna is a device that emits or absorbs radio waves. Numerous benefits exist for microstrip patch antennas, including affordability, portability, simplicity of construction, and compatibility with integrated circuits. This has several important uses in the military, radar, mobile communications, global positioning system (GPS), remote sensing, and more. In mobile devices like portable computers and smart phones, WLAN and WiMAX are often used.</p>

Polarization-Insensitive Triband FSS for RF Shielding at Normal and Higher Temperatures by Retrofitting on Ordinary Glass Windows

A comprehensive novel framework for retrofitting frequency-selective surface (FSS) shields to any glass surface using low-cost copper foils has been proposed in this work. The realization technique is demonstrated through a novel triband FSS shield. Global System for Mobile Communication (GSM)-1800, Wi-Fi 2.5 GHz, and wireless local area network (WLAN) 5.6 GHz spectrum, with–10 dB bandwidth of 680, 190, and 1300 MHz, respectively, are suppressed by the shield. The unit cell is made up of a combination of square and circular concentric loops with some alterations. The design is entirely polarization-insensitive and has a steady frequency response for oblique angles up to 60°. The unit element is highly miniaturized for triband operation measuring <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> /9 at 1.8 GHz frequency. An equivalent circuit model (ECM) is also derived to better elaborate the working mechanism of the shield. The pattern is chemically etched on low-cost copper adhesive foil and affixed to ordinary glass as a sticker. The design retains the visual transparency of 72% allowing enough light to enter through windows while rejecting the intended frequencies by at least 28 dB or more in all three bands. The design exhibits a very high shielding efficiency of above 98% for all three bands. Experimental demonstration for single-layer glass, sandwiched glass, as well as air-filled double-glazed glass is carried out. The thermal stability of the proposed design is measured and found intact up to the ambient temperature of 50 °C.

FCLoc: A Novel Indoor Wi-Fi Fingerprints Localization Approach to Enhance Robustness and Positioning Accuracy

For wireless local area network (WLAN) fingerprint-based indoor localization approach, wireless fidelity (Wi-Fi) received signal strength (RSS) is widely focused because it is easy to obtain and inexpensive. However, RSS measurements are vulnerable to environmental fluctuations and there is a lot of noise in the measured signal, which seriously affects the stability of RSS-based positioning systems. Meanwhile, the unreasonable value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> will also cause large positioning errors in the fingerprint-based <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -nearest neighbors (KNN) and weighted KNN algorithms. Therefore, a novel flexible reference points and confidence access points localization (FCLoc) method is proposed in this article, to enhance the robustness of the system while improving positioning accuracy. First, considering that there is outlier noise in the sampling data, this article proposes to filter out noise by the robust principal. Then, the more reliable access points (APs) are selected according to the stability of the online data, as a more stable AP should have more weight to reduce the impact of the weak APs. When at least three APs are available, the system can work normally. Finally, the Jenks natural breaks algorithm (JNBA) in statistics is introduced to realize a flexible reference point (RP) selection, that is, a more reasonable value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> is adaptively selected for position estimation to improve the positioning accuracy. The proposed method only applies to scenarios where at least three APs are available. Simulation and the real-world experimental results show that the proposed algorithm is superior to those existing algorithms in terms of robustness and positioning accuracy.