Search Results (45)

IEEE 802.11ax (Wi-Fi 6) technologies provide high capacity, low latency, and increased security. While many network researchers have examined Wi-Fi security issues, the security implications of 802.11ax have not been fully explored yet. Therefore, in this paper, we investigate how security protocols (WPA2, WPA3) affect TCP/UDP throughput in IEEE 802.11ax client–server networks using a testbed approach. Through an extensive performance study, we analyze the effect of security on transport layer protocol (TCP/UDP), internet protocol layer (IPV4/IPV6), and operating systems (MS Windows and Linux) on system performance. The impact of packet length on system performance is also investigated. The obtained results show that WPA3 offers greater security, and its impact on TCP/UDP throughput is insignificant, highlighting the robustness of WPA3 encryption in maintaining throughput even in secure environments. With WPA3, UDP offers higher throughput than TCP and IPv6 consistently outperforms IPv4 in terms of both TCP and UDP throughput. Linux outperforms Windows in all scenarios, especially with larger packet sizes and IPv6 traffic. These results suggest that WPA3 provides optimized throughput performance in both Linux and MS Windows in 802.11ax client–server environments. Our research provides some insights into the security issues in Gigabit Wi-Fi that can help network researchers and engineers to contribute further towards developing greater security for next-generation wireless networks. Full article

In modern laptops, antenna design for Wi-Fi 7 is constrained by limited space and reduced ground plane size, conditions under which many compact designs exhibit degraded bandwidth or efficiency or require large device grounds. This paper presents a miniaturized tri-band inverted-F antenna (IFA) that supports the 2.4, 5, and 6 GHz Wi-Fi 7 bands within a radiator area of 20 × 5 × 0.8 mm³ and a ground plane of 60 × 40 mm². The proposed design achieves wideband impedance matching and stable radiation efficiency under intentionally reduced grounding conditions, addressing a scenario rarely considered in prior studies where both radiator and ground plane miniaturization must be satisfied. Measurements confirm efficiencies of 74–81% at 2.4 GHz and 64–90% across 5–7 GHz, with performance in the lower band exceeding that of many compact designs and upper-band coverage comparable to structures requiring larger footprints. By demonstrating tri-band operation under simultaneous radiator and ground reduction, this work provides a practical antenna solution for next-generation Wi-Fi 7 laptop integration. Full article

The advent of Industry 4.0 brought about digitalisation and the integration of advanced technologies into industrial processes, with wireless networks emerging as a key enabler in the interconnection of smart devices, cyber–physical systems, and data analytics platforms. With the development of Industry 5.0 and its emphasis on human–machine collaboration, Wi-Fi has positioned itself as a viable alternative for industrial wireless connectivity, supporting seamless communication between robots, automation systems, and human operators. However, its adoption in critical applications remains limited due to persistent concerns over latency, reliability, and interference in shared-spectrum environments. This study evaluates the practical performance of Wi-Fi standards from 802.11n (Wi-Fi 4) to 802.11be (Wi-Fi 7) across three representative environments: residential, laboratory, and industrial. Six configurations were tested under consistent conditions, covering various frequency bands, channel widths, and traffic types. Results prove that Wi-Fi 6/6E delivers the best overall performance, particularly in low-interference 6 GHz scenarios. Wi-Fi 5 performs well in medium-range settings but is more sensitive to congestion, while Wi-Fi 4 consistently underperforms. Early Wi-Fi 7 hardware does not yet surpass Wi-Fi 6/6E consistently, reflecting its ongoing development. Despite these variations, the progression observed across generations clearly demonstrates incremental gains in throughput stability and latency control. While these improvements already provide tangible benefits for many industrial communication scenarios, the most significant leap in industrial applicability is expected to come from the effective implementation of high-efficiency mechanisms. These include OFDMA, TWT, scheduled uplink access, and enhanced QoS features. These capabilities, already embedded in the Wi-Fi 6 and 7 standards, represent the necessary foundation to move beyond conventional best-effort connectivity and toward supporting critical, latency-sensitive industrial applications. Full article

With the rapid development of Wi-Fi 6/6E and dual-band wireless systems, there is an increasing demand for compact antennas with balanced high-gain performance across both 2.4 GHz and 5 GHz bands. However, most existing dual-band metasurface antennas face challenges in uneven gain distribution between lower/higher-frequency bands and structural miniaturization. This paper proposes a high-gain dual-band metasurface antenna based on an artificial magnetic conductor (AMC) array, which has a significant advantage in miniaturization and improving antenna performance. Two types of dual-band AMC structures are applied to design the metasurface antenna. The optimal antenna with dual-slot AMC array operates in the 2.42–2.48 GHz and 5.16–5.53 GHz frequency bands, with a 25% size reduction compared to the reference dual-band U-slot antenna. Meanwhile, high gains of 7.65 dBi and 8 dBi are achieved at 2.4 GHz and 5 GHz frequency bands, respectively. Experimental results verify stable radiation gains across the operation bands, where the total efficiency remains above 90%, agreeing well with the simulation results. This research provides an effective strategy for high-gain and dual-band metasurface antennas, offering a promising solution for integrated modern wireless systems such as Wi-Fi 6, Bluetooth, and MIMO technology. Full article

This paper presents a differential phase coupler design methodology in the IPD process. The coupler consists of a balun and two phase-shifter circuits. The compact balun was designed with lumped components and a common inductor. Each output of the balun circuit was connected to a phase shifter with an opposite phase to make a desired output phase. In the design example, a three-port 90-degree hybrid coupler was implemented on the IPD process to operate at the 6 GHz WIFI frequency. The post-simulation showed that all reflection coefficients were below −19 dB, with an insertion loss of 1.76 dB and isolation of 20 dB. The core chip size was only 0.02λ₀ × 0.018λ₀. Full article

Because of the involvement of π-electron cyclic constituents in their side chains, the so-called aromatic residues give rise to a number of strong, narrow, and well-resolved lines spread over the middle wavenumber (1800–600 cm⁻¹) region of the Raman spectra of peptides and proteins. The number of characteristic aromatic markers increases with the structural complexity (Phe → Tyr → Trp), herein referred to as (F_i = 1, …, 6) in Phe, (Y_i = 1, …, 7) in Tyr, and (W_i = 1, …, 8) in Trp. Herein, we undertake an overview of these markers through the analysis of a representative data base gathered from the most structurally simple tripeptides, Gly-Xxx-Gly (where Xxx = Phe, Tyr, Trp). In this framework, off-resonance Raman spectra obtained from the aqueous samples of these tripeptides were jointly used with the structural and vibrational data collected from the density functional theory (DFT) calculations using the M062X hybrid functional and 6-311++G(d,p) atomic basis set. The conformation dependence of aromatic Raman markers was explored upon a representative set of 75 conformers, having five different backbone secondary structures (i.e., β-strand, polyproline-II, helix, classic, and inverse γ-turn), and plausible side chain rotamers. The hydration effects were considered upon using both implicit (polarizable solvent continuum) and explicit (minimal number of 5–7 water molecules) models. Raman spectra were calculated through a multiconformational approach based on the thermal (Boltzmann) average of the spectra arising from all calculated conformers. A subsequent discussion highlights the conformational landscape of conformers and the wavenumber dispersion of aromatic Raman markers. In particular, a new interpretation was proposed for the characteristic Raman doublets arising from Tyr (~850–830 cm⁻¹) and Trp (~1360–1340 cm⁻¹), definitely excluding the previously suggested Fermi-resonance-based assignment of these markers through the consideration of the interactions between the aromatic side chain and its adjacent peptide bonds. Full article

The increasing deployment of IEEE 802.11ax (Wi-Fi 6) networks necessitates an accurate assessment of radiofrequency electromagnetic field (RF-EMF) exposure under realistic usage scenarios. This study investigates the duty cycle (DC) and corresponding exposure levels of Wi-Fi 6 in controlled laboratory conditions, focusing on bandwidth variations, multi-user scenarios, and application types. DC measurements reveal significant variability across internet services, with FTP upload exhibiting the highest mean DC (94.3%) under 20 MHz bandwidth, while YouTube 4K video streaming showed bursts with a maximum DC of 89.2%. Under poor radio conditions, DC increased by up to 5× for certain applications, emphasizing the influence of degraded signal-to-noise ratio (SNR) on retransmissions and modulation. Weighted exposure results indicate a reduction in average electric-field strength by up to 10× when incorporating DC, with maximum weighted exposure at 4.2 V/m (6.9% of ICNIRP limits) during multi-user scenarios. These findings highlight the critical role of realistic DC assessments in refining exposure evaluations, ensuring regulatory compliance, and advancing the understanding of Wi-Fi 6’s EMF exposure implications. Full article

Background: Patients with no-option chronic limb-threatening ischemia (NoCLTI), lacking suitable distal arteries for conventional revascularization, face major limb amputation. The 1-year mortality rate after major amputation is 48.3%, increasing to 70.9% in 3 years. Open deep venous arterialization (DVA) offers a promising alternative for limb salvage, achievable through open, endovascular, or hybrid approaches. We aim to provide a comprehensive, step-by-step guide to performing open DVA in NoCLTI patients, addressing preoperative and postoperative considerations as well as the technical details of the procedure. Methods: Patient selection for open DVA focuses on individuals with NoCLTI at high risk for amputation. Preoperative assessments include evaluating risk factors, determining limb threat severity using the Wound, Ischemia, and foot Infection (WIfI) score, and mapping anatomical patterns via the Global Limb Anatomic Staging System (GLASS). The procedure involves identifying the target artery using Doppler ultrasound, performing microdissection to expose the artery and vein, ligating proximal vein branches, and creating a side-to-side anastomosis. Venous valves are disrupted with a valvulotome to allow antegrade flow. A proximal bypass graft may be applied if necessary. Results: Postoperatively, patients are monitored for 2–4 days with frequent Doppler assessments. Anticoagulation therapy begins with a heparin drip, transitioning to oral agents and/or dual antiplatelet therapy. Wound care includes deferred debridement for 2–4 weeks and may involve negative-pressure therapy. Follow-up involves weekly visits for the first month, and then at 3 months, and every 6 months thereafter, with surveillance using transcutaneous oxygen measurement, the toe–brachial index, and arterial duplex ultrasound. Conclusions: Open DVA represents a viable limb salvage option for patients with NoCLTI, potentially avoiding major amputations and improving quality of life. Success depends on careful patient selection, a meticulous surgical technique, and comprehensive postoperative care. Full article

Background and Objectives: The primary objective of this study was to determine the predictive factors of limb salvage and wound healing in patients presenting with diabetic foot ulcers (DFUs) following successful below-the-knee endovascular angioplasty. Materials and Methods: Between January 2014 and January 2019, we retrospectively analyzed the wound healing and limb salvage rates of 85 patients (88 limbs) who underwent infra-popliteal endovascular treatment (EVT) for DFUs. Numerous variables were explored, including age, sex, comorbidities, and the scores from three DFU grading systems (Wagner grade, University of Texas (UT) grade and stage, and Wound, Ischemia, and foot Infection (WIfI) stage). Univariate and multivariate Cox proportional hazards analyses were conducted to determine the associations between adverse events and these variables. Results: During follow-up, 44 wounds healed completely, 47 limb amputations (major, 25; minor, 22) were required, and 17 limbs needed reintervention for wound healing. Nine patients who received treatment died of cardiovascular and cerebrovascular diseases, pneumonia, and other causes. At 1, 3, 6, 9, and 12 months, total wound healing rates were 4.6%, 16.9%, 27.5%, 34.5%, and 64.5%, respectively. At 6 months, 1 year, 2 years, and 5 years, amputation-free survival rates were 77.6%, 72.4%, 63.3%, and 63.3%, respectively. In multivariate Cox analyses, the UT grade and stage were associated with increased wound non-healing, while the UT grade and Wagner grade were associated with increased major lower-extremity amputation rates. Importantly, the UT grade was the only simultaneous risk factor predicting both wound healing and limb salvage. Conclusions: Despite successful below-the-knee angioplasty, a significant proportion of patients experienced wound non-healing and major amputation. The UT grade may serve as a predictor for both wound healing and limb salvage outcomes. Full article

Diabetic foot syndrome is often associated with inflammation. The aim of this study was to evaluate the impact of improved blood supply on the change in the clinical status and culturable bacteriota of chronic wounds. Patients with diabetic foot and peripheral arterial disease with a Rutherford score of 5 or 6 were included (n = 23). The blood supply to the limb was assessed with laboratory tests and two time-point qualitative cultures using a wound biopsy. The baseline parameters of the blood supply to the limb were Transcutaneous Oxygen Perfusion (TCPO2) of 15.0 mmHg, an Ankle Brachial Index (ABI) of 0.7, and a Toe Brachial Index (TBI) of 0.1, with an average Wound, Infection, Inflammation (WIfI) score of 5.7 (high). The most frequently isolated pathogens were Staphylococcus aureus (26.1%), followed by the Enterobacteriaceae family and Pseudomonas spp. (13.0%, each). Negative cultures were present in 47.8% (n = 11). The control parameters of blood supply improved; TCPO2 was 38.5 mmHg, the ABI was 0.9, and the TBI was 0.3, with a reduction in the average WIfI score to 3.7 (mild), while total colony-forming units (CFUs) increased by 13.5%. No cases of reocclusion or restenosis were observed during the study; however, small amputations were performed in two patients (8.7%). Five (21.7%) ulcers were significantly reduced and two (8.7%) progressed, while a negative culture at follow-up was obtained in five fewer patients than at baseline and nine patients presented growth despite having an initial negative result. Quantitative reduction was obtained in four (17.4%) cases. Pathogen distribution at follow-up resembled baseline findings. Optimizing clinical environments (enhancing blood flow and controlling inflammation) in general over focusing singularly on microbiota composition or revascularization seems to be crucial and arguably outweighed the impact of microbial change alone; in particular, reperfusion may increase the conditions to bacterial growth at the first stage. Full article

This article introduces a broadband sub-6 GHz 8 × 8 MIMO (multi-input multi-output) antenna array for 5G (fifth-generation) metal-frame mobile phone applications. The unique advantage of this compact antenna design is its placement in the corners of the mobile phone, allowing for significant PCB board space reduction. The proposed antenna’s 6 dB impedance bandwidth ranged from 3.3 to 6 GHz, covering the n77/78/79 and WiFi-5GHz bands. The main radiating element was an open-slot antenna coupled by a T-shaped structure connected to a 50-Ω transmission line. The size of the single-antenna element was 12.25 mm × 2.5 mm × 7 mm, and these antennas were symmetrical at four corners of the smartphone. A wide slot and neutral line were incorporated to reduce mutual coupling between adjacent antennas. The MIMO antenna array achieved isolation above 12 dB. The peak realized gain ranged from 2 to 5.28 dBi, and the total efficiency spanned 37% to 71%. The ECC (envelope correlation coefficient) was less than 0.34, and the CC (channel capacity) ranged from 33 and 41 bps/Hz. Full article

In the fast-changing technological landscape, novel applications are emerging with the potential to reshape the world. These applications, while promising, impose stringent requirements in terms of quality of service (QoS). The advent of wireless networks like 5G, 6G and Wi-Fi 6 brings about resource management solutions to ensure these requirements while meeting the user expectations within the interconnected environment. Nevertheless, user behaviors are also evolving, highlighting the importance of satisfaction and quality of experience (QoE). Furthermore, changes in user behavior trigger shifts in business models, where the quality of business (QoBiz) takes on a pivotal role. This evolving ecosystem, encompassing QoS, QoE, and QoBiz, demands a comprehensive and adaptable approach that conventional QoS management frameworks fail to perform. This paper introduces an implementation methodology for a global QoS management model named QoXphere. The implementation methodology is grounded in machine learning techniques and addresses the multifaceted aspects of quality of service (QoX) and their interconnections within wireless networks. The objective is to facilitate dynamic resource management that not only elevates user satisfaction but also optimizes provider benefits. Real-world examples illustrate the methodology’s applicability in widely deployed networks, complemented by simulated scenarios of modern network environments that further validate the approach. Full article

The recognition of human activity is crucial as the Internet of Things (IoT) progresses toward future smart homes. Wi-Fi-based motion-recognition stands out due to its non-contact nature and widespread applicability. However, the channel state information (CSI) related to human movement in indoor environments changes with the direction of movement, which poses challenges for existing Wi-Fi movement-recognition methods. These challenges include limited directions of movement that can be detected, short detection distances, and inaccurate feature extraction, all of which significantly constrain the wide-scale application of Wi-Fi action-recognition. To address this issue, we propose a direction-independent CSI fusion and sharing model named CSI-F, one which combines Convolutional Neural Networks (CNN) and Gated Recurrent Units (GRU). Specifically, we have introduced a series of signal-processing techniques that utilize antenna diversity to eliminate random phase shifts, thereby removing noise influences unrelated to motion information. Later, by amplifying the Doppler frequency shift effect through cyclic actions and generating a spectrogram, we further enhance the impact of actions on CSI. To demonstrate the effectiveness of this method, we conducted experiments on datasets collected in natural environments. We confirmed that the superposition of periodic actions on CSI can improve the accuracy of the process. CSI-F can achieve higher recognition accuracy compared with other methods and a monitoring coverage of up to 6 m. Full article

This study introduces innovative designs for frequency-reconfigurable antennas that utilize ring resonators combined with either PIN diodes or RF switches. These designs enhance the versatility, adaptability, and overall performance of the antennas in wireless communication systems. By controlling the switches and ring resonator, the antenna’s resonant frequencies and bandwidths can be adjusted, allowing for compatibility with various communication standards and frequency ranges. The proposed antenna exhibits four distinct operational states, each characterized by different resonance frequencies and operating frequency bands. Return loss, radiation pattern, radiation efficiency, and surface current distribution are analyzed for each state. State-1 (ON-ON) and State-2 (OFF-ON), which are characterized by resonance frequencies of 2.4 GHz and 3.33 GHz respectively, offer ranges suitable for Wi-Fi, Bluetooth, ISM, and IoT applications. State-3 (ON-OFF), with a resonance frequency of 3.0 GHz and bandwidth spanning from 2.59 GHz to 3.643 GHz, complies with Wi-Fi, Wi-Fi 6, and IoT requirements. State-4 (OFF-OFF) covers the band centered around 3.45 GHz. It is compatible with many applications such as 5G mid-band, Wi-Fi 6E, IoT, and cellular systems. The proposed antenna designs are versatile and compact since the overall antenna dimensions are 25 × 18 × 1.6 mm³. The radiation efficiency of the antenna configuration varies depending on operational states. By utilizing the advantages of both ring resonators and RF switches, the proposed antenna configurations offer new solutions that enhance their performance in wireless communication systems. This study compares the effects of using PIN diodes and SPDT switches on the performance of antennas and also examines the DC biasing effect on antenna characteristics. The simulation results are validated by the experimental analysis. The proposed antenna designs offer a new approach for wireless communication systems by using both ring resonators and RF switches. Full article

In this paper, a dual-band WiFi antenna and its Multiple Input Multiple Output (MIMO) system application is designed, fabricated, and measured based on the Chinese characters “Men” and “Wei”. The antenna uses a 40 × 40 × 1.6 mm³ FR4 substrate to analyze the combinatorial structure of Chinese characters using the theory of characteristic modes, to optimize the antenna dimensions by analyzing the mode current distribution, and to broaden the antenna bandwidth by etching rectangular slots on the ground. The measured and simulated results show that the four-element MIMO antenna covers 5.68–8.01 GHz, the isolation between the antennas is higher than 20 dB in the working band, the envelope correlation coefficient and the channel capacity losses of the simulation are lower than 0.001 and 0.18 bits/s/HZ, respectively. The efficiency of the antenna is higher than 90%, and it can be used for WiFi communication bands (5.8 GHz and 6 GHz). Full article