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This paper presents a discussion on a low-profile, frequency-reconfigurable penta-band antenna. This antenna consists of two asymmetric L-shaped rectangular patches electrically connected by a single PIN diode. The proposed antenna operates at five frequency bands depending upon the switching states of the PIN diode. It operates at 2.4 GHz (WLAN) and 5.3 GHz (5G) during forward bias of the diode, 3.3 GHz (5G) and 5.9 GHz (WLAN) during reverse bias of the diode and 4 GHz during zero bias condition providing a wide bandwidth (3.6–4.8 GHz) at this state. The antenna has voltage standing wave ratio (VSWR) ranges from 1 to 2, gain value ranges from 2.6 to 5.0 dBi, and a maximum radiation efficiency of 85%. This antenna can be integrated with modern devices such as smart phones, laptops, and other handheld devices due to its simplistic geometry. A prototype of the model is fabricated, and the results are validated.

This paper proposes a dual-band Fabry-Perot Cavity Antenna (FPCA) operating at two important WLAN bands – the 2.4 GHz band and 5.8 GHz band. It exhibits Circular Polarization (CP) at 2.4 GHz and Linear Polarization (LP) at5.8 GHz. The proposed antenna uses only a single Partially Reflecting Surface (PRS) layer to achieve good 3dB gain bandwidths in both the bands. The cavity height of the antenna is also significantly reduced by using an Artificial Magnetic Conductor (AMC) ground plane. The antenna achieves a 3dB axial ratio bandwidth (AR-BW) of 7.9% at 2.4 GHz with peak measured gains of 14.3 dBi and 15.5 dBi at 2.4 GHz and 5.8 GHz respectively. The antenna also exhibits a 3dB gain BW of 7.8% in the first band and 5.5% in the second band.

In the last two decades, Wireless Local Area Networks (WLANs) based on 802.11 have become crucial in offering Internet services with high data transmission rates. Under crowded scenarios like airports, shopping centers, and stadiums, WLANs can be easily congested due to their random access nature and limited operational capability. This may result in a reduced user multimedia experience. With a proper Transmission Opportunity (TXOP) allocation and scheduling scheme, the user service quality could be improved under such scenarios. In this paper, a Congestion-Aware Transmission Opportunity (CA-TXOP) scheme is proposed, allocating transmission resources by considering network level congestion and information like buffer status, channel quality, and data rates. The CA-TXOP scheme prioritizes congested and noncongested user stations and improves the overall network performance. Simulation results show that the CA-TXOP scheme attained 45%, 35%, and 20% enhancement compared with Fixed, Bi-level, and FRA-TXOP scheduling schemes. Such scheme applies to future congested scenarios like smart buildings and organizations that require satisfying video quality to all the user stations.

Monitor mode packet capturing of WLAN is used to derive Access points and devices in the range for localization or occupancy purposes. The general modality of capturing and analysis in almost all available studies is to capture packets by being static (STT) at a location and indoors. In STT mode, the beacon and probe packets extract insights about the localization of devices and occupancy estimation. We propose scanning a predetermined path in an urban locality on the move (OTM) using monitor mode WLAN packet capturing. We also propose that in OTM, devices (STA) and Access Points (APs) can be traced from other packets like CTS, ATS, and ACKs apart from beacons and frames. We performed a case study of monitor mode packet capturing in an on-the-move and outdoor setup. The primary focus of the study was to validate the OTM modality and the methodology of detecting devices and APs. We studied all the packet types that were captured, including Beacons and Probes. The sensed devices and APs counts using probe and beacon packets were compared with the sensed devices, and APs counts using the new methodology. We found that considering other packets helps detect a more significant number of devices and APs. We also found that channel hoping strategy plays an essential role in maximizing the sensed items. The overall exercise revealed that the air is full of WLAN/Wi-Fi traffic, and using OTM can assimilate lots of valuable data and generate relevant information for various purposes. Essentially, on-the-move outdoor capture setups can be used to produce Wi-Fi access points and user devices related heat maps of the scanned locations. This can be useful in many governance and related matters. Briefly, we put forward an application architecture for the same.

Visible light communication (VLC) has emerged as a promising technology for wireless communication as it offers higher data rates and secure data transmission along with providing indoor illumination. However, VLC is restricted by the line of sight (LoS) nature of the optical channel that consequently results in light path blockages. Therefore, an effective solution would be to combine VLC with a radio frequency (RF) system to form a hybrid VLC/RF network that would take into account the preferences of an end-user with the practicality of implementation. In such networks, an efficient vertical handover (VHO) technique is the most critical element as it ensures a seamless transition between the two networks. In this work, we propose a vertical handover technique that utilizes the user's location information to make a handover decision. We found that the frequency of light path blockages increases with the increasing number of users in a confined space, resulting in significant performance deterioration. This additional information is then utilized so that the VHO algorithm effectively selects the most feasible network. The proposed algorithm has been tested against the immediate vertical handover algorithm (I-VHO) and the dwell vertical handover algorithm (D-VHO) with two different dwell times. The average number of handovers, quality of experience (QoE), and packet loss have been set as performance metrics. We show from several simulation scenarios that the proposed method results in a fewer number of handovers while maintaining higher QoE and lower packet loss. Türkiye Bilimsel ve Teknolojik Araştırma Kurumu (TÜBİTAK)

A variety of wireless communication technologies have been developed to provide services to a large number of users. The future integrated 5G-WLAN wireless networks will support seamless and secure roaming, and various types of real-time applications and services, which will be the trend of next-generation computing paradigm. In this paper, we discuss the privacy and security problems in 5G-WLAN heterogeneous networks and present a logical 5G-WLAN integrated architecture. We also propose a novel USIM and ECC based design of handover authentication for next-generation 5G-WLAN heterogeneous networks that can provide secure and seamless Internet connectivity. Our scheme accomplishes the features of strong security and has better performance in terms of computation cost, energy cost, and storage cost as compared with the state-of-the-art schemes.

A VLAN is a logical connection that allows hosts to be grouped together in the same broadcast domain, so that packets are delivered only to ports that are combined to the same VLAN. We can improve wireless network performance and save bandwidth through the characteristic VLAN network. In addition, the implementation of VLAN greatly improves wireless network security by reducing the number of hosts receiving copies of frames broadcast by switches, thus keeping hosts holding critical data on a separate VLAN. In this paper we compare wireless network with VLAN via wireless network. The proposed network is evaluated within terms of delay and average throughput using web browsing applications and file transfer in heavy traffic. The simulation was carried out using OPNET 14.5 modeler and the results show that the use of VLAN via wireless network improved performance by reducing traffic resulting in a minimized delay time. Furthermore, VLAN implementation reduces network throughput because the traffic received and transmitted has a positive relationship with throughput. Eventually, we investigated the use of adhoc routing protocols such as AODV, DSR, OLSR, TORA and GPR to improve the performance of wireless VLAN networks.

Location-based services (LBS) are a significant permissive technology. One of the main components in indoor LBS is the indoor positioning system (IPS). IPS utilizes many existing technologies such as radio frequency, images, acoustic signals, as well as magnetic sensors, thermal sensors, optical sensors, and other sensors that are usually installed in a mobile device. The radio frequency technologies used in IPS are WLAN, Bluetooth, Zig Bee, RFID, frequency modulation, and ultra-wideband. This paper explores studies that have combined WLAN fingerprinting and image processing to build an IPS. The studies on combined WLAN fingerprinting and image processing techniques are divided based on the methods used. The first part explains the studies that have used WLAN fingerprinting to support image positioning. The second part examines works that have used image processing to support WLAN fingerprinting positioning. Then, image processing and WLAN fingerprinting are used in combination to build IPS in the third part. A new concept is proposed at the end for the future development of indoor positioning models based on WLAN fingerprinting and supported by image processing to solve the effect of people presence around users and the user orientation problem.

A compact grounded asymmetric coplanar strip (GACS)-fed flexible multiband frequency reconfigurable antenna with two PIN diodes is proposed. The investigated antenna is backed by a flexible polyamide substrate with compact dimensions of 24 mm $\times19$ mm and a thickness of 1.53 mm. The investigated antenna structure contains a monopole patch that facilitates operation for wireless LAN applications, whereas inverted L-shaped and F-shaped monopoles facilitate operation for Bluetooth and 5G NR applications. The investigated antenna operates at 2.4, 3.8, and 5.6 GHz with measured impedance bandwidths of 5.8%, 6.3%, and 6.6%, respectively, over the three frequency bands, thus facilitating coverage for Bluetooth, 5G NR, and WLAN standards. The two PIN diodes are employed to tune the investigated antenna among four modes, including a single band mode (WLAN 5.5 GHz), two dual-band modes (5G NR 3.8/5.6 GHz, and Bluetooth 2.48/5.6 GHz), and one multiband mode with Bluetooth (2.4 GHz), 5G New Radio (NR) N77 band (3.8 GHz), and WLAN (5.6 GHz) modes. The investigated antenna radiates unidirectionally with a peak gain of 3.73 dBi at 5.6 GHz. Measurements are carried out on the human body to investigate the behaviour of the wearable antenna. The simulated SAR values are in a safe limit of 1.6 W/kg for 1 g of tissue, according to the FCC. Moreover, the investigated antenna shows extremely low vulnerability to degradation in performance as a result of bending effects concerning impedance matching with acceptable acquiescence between measurements and simulations.

Full-duplex (FD) communication is capable of simultaneously transmitting and receiving data on the same frequency band. To effectively utilize FD in a wireless local area network (WLAN), one must use medium access control (MAC) protocols that consider the characteristics of FD. Many researchers have proposed and analyzed FD MAC protocols for WLANs. Most of this work revealed that as the number of nodes increases, the overall throughput decreases due to collisions. We have found, however, that with a smart MAC protocol, the throughput actually improves as the number of nodes increases. In this paper, we propose an asymmetric FD MAC protocol and then design an FD WLAN analytical model to evaluate saturation throughput. In our analytical model, we consider FD pair probability-the probability that a node capable of FD communication exists. To validate our model, we calculate FD pair probability values based on the modulation and coding scheme (MCS) levels and self-interference cancellation (SIC). We then analyze the effect of the FD pair probability on throughput. Simulation results verify the accuracy of our analytical model. Moreover, we compare the fairness of the proposed and conventional FD MAC protocols. As demonstrated through extensive evaluations, the fairness of the proposed FD MAC protocol is improved.

Precise time synchronization becomes a vital constituent due to the rigorous needs of several time-sensitive applications. The clock synchronization protocol is one of the fundamental factors that can define the quality of communication. Our study starts with a brief discussion on the application domain of precise time synchronization and comes with an in-depth study of the synchronization with the main focus on the IEEE 1588 Precision Time Protocol (PTP). We have compared the well-known synchronization techniques and conclude that the PTP is the most appropriate answer to robust clock synchronization though challenges are there that requires thoughtful efforts and modification in the current version. The working mechanism and main components of the PTP network are discussed. We have established a testbench using commercially available devices and development boards to evaluate the PTP performance under different configurations. Major sources of synchronization error and other aspects contributing to precision are examined. This paper discussed numerous approaches that could enhance the performance of the PTP protocol. Structures for PTP based wireless clock synchronization required by advanced applications has also been discussed. In the end, paper focuses on the main industrial application areas in which PTP plays an important role, including WLAN, optical data centers, Smart grid, IEC 61850, etc. We conclude the paper by identifying the future trends and research directions for PTP based clock synchronization.

The location of radiation sources in wireless networks is a key factor to characterize their contribution to electromagnetic exposure levels in order to deploy future networks that account for minimizing electromagnetic field levels. In relation to wireless local area networks, considering that mobile communication devices comply with the SAR (Specific Absorption Rate) limits imposed by the international standardization organizations for preserving human health, the interest is nowadays focused on the signal levels coming from the WiFi access points. This paper presents a methodology to determine the threshold distance at which the field strength levels from the AP are negligible in comparison with the radiation generated by a user equipment. The theoretical concepts, which can be applied to other technologies, were implemented by means of simulations and experimental measurements. For the simulations, actual WiFi antennas were modelled. Experimental measurements completed the results obtained in simulations, resulting in a greater number of real situations. Results showed that the threshold distance depends on the WiFi standard employed by the devices connected to the network.

Due to the unreliability of wired communications and the risks of controlling the process of transmitting data besides the complications that affecting data protection and the high costs of systems infrastructure, led to use wireless communications instead of wires media, but these networks are vulnerable towards illegal attacks. The side effects of these attacks are modifying data or penetrate the security system and discover its weaknesses, which leads to great material losses. These risks and difficulties led to the reluctance of wires communications and propose intelligent techniques and robust encryption algorithms for preventing data transmitted over wireless networks to keep it safe from cyber security attacks. So, there is a persistent need for providing intelligent techniques and robust algorithms to preserve conveyed information using wireless network. This paper introduces scenario for proposing intelligent technique to increase data reliability and provides a new way to improve high level of protection besides reduces infrastructure cost. The proposed system relies on two models, where the first model based on producing a knowledge base of risk rules while the aim of the second module is a risk assessment outcomes and encryption process according to attacks type. In this system, reducing risks levels based on renewable rules whereas a novel security system established on non-periodic keys with unsystematic operations using fuzzy system. We concluded that the proposed system has the ability to protect the transmitted data, increases its reliability and reduce the potential risks. MATLAB Toolkit 2014 then Weka open source package was used in encryption and data mining for the proposed system.

Proceedings of: 2021 International Symposium on Antennas and Propagation (ISAP), 19-22 October, 2021, Taipei, Taiwan. Design and analysis of a wideband compact flexible antenna is presented in this paper. The bandwidth enhancement of conventional triangular quarter wave monopole antenna is achieved by utilizing the combination of a fractal structure along with open ended stub. Moreover, the flexibility analysis was studied to show the stability of presented work for conformal analysis. Furthermore, compact size, wideband, stable performance in flexibility condition makes the proposed work potential candidate for WLAN, Wi-Fi and C-band Applications. This project has received funding from Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant Agreement No 801538. Also, this work is partially supported by Antenna and Wireless Propagation Group (AWPG); https://sites.google.com/view/awpgrp.

Modern technology is essential for all healthy, economic, and educational sectors. Using modern technology involves high-performance networks in terms of quality of service (QoS) parameters such as delay, throughput, bandwidth, and security. A campus network involves wire and the wireless environment with and without virtual local area network (VLAN) technology has been simulated using optimized network engineering tools (OPNET). The simulation model includes four scenarios that involve heavy-loaded File transfer protocol (FTP) and web browsing applications with two logical groups of users. The simulation results show that the VLAN overcome LAN networks in terms of bandwidth and security. This has been done by reducing the throughput in both sending and receiving levels to the confidential servers. The VLAN has also reduced the broadcast domain which results in a high-power efficiency. Moreover, the VLAN network technology has been proved to have lower values of delay in transferring files and packets than LAN network technology. In addition, VLAN technology generally has been decreased values of throughput regardless of the way of connection between servers and workstations. This, in turn, allows taking advantage of wireless connection features in terms of flexibility of installation and speed of configuration.

IEEE 802.11ax uplink orthogonal frequency division multiple access (OFDMA)-based random access (UORA) is a new feature for random channel access in wireless local area networks (WLANs). Similar to the legacy random access scheme in WLANs, UORA performs the OFDMA backoff (OBO) procedure to access the channel and decides on a random OBO counter within the OFDMA contention window (OCW) value. An access point (AP) can determine the OCW range and inform each station (STA) of it. However, how to determine a reasonable OCW range is beyond the scope of the IEEE 802.11ax standard. The OCW range is crucial to the UORA performance, and it primarily depends on the number of contending STAs, but it is challenging for the AP to accurately and quickly estimate or keep track of the number of contending STAs without the aid of a specific signaling mechanism. In addition, the one for this purpose incurs an additional delay and overhead in the channel access procedure. Therefore, the performance of a UORA scheme can be degraded by an improper OCW range, especially when the number of contending STAs changes dynamically. We first observed the effect of OCW values on channel efficiency and derived its optimal value from an analytical model. Next, we proposed a simple yet effective OBO control scheme where each STA determines its own OBO counter in a distributed manner rather than adjusting the OCW value globally. In the proposed scheme, each STA determines an appropriate OBO counter depending on whether the previous transmission was successful or not so that collisions can be mitigated without leaving OFDMA resource units unnecessarily idle. The results of a simulation study confirm that the throughput of the proposed scheme is comparable to the optimal OCW-based scheme and is improved by up to 15 times compared to the standard UORA scheme.

In the steel mills, in order to improve the circulation efficiency of iron ladles and steel ladles, save energy and promote the development of industrial automation, an iron ladles and steel ladles tracking management system based on radio frequency identification (RFID) and wireless local area network (WLAN) is proposed in this study. Meanwhile, to obtain the optimal number of online iron ladles, the theory of queuing is proposed for optimising the logistics of iron ladles. The system uses RFID and readers to obtain relevant location information. WLAN is used to realise communication between the crane terminals and the main control. Two queuing models are analysed and compared, then the optimal solution of online iron ladles is quantitatively calculated. Moreover, in order to intuitively reflect the on-site scheduling situation, a visualised operation interface is designed accordingly. The system has been used in a steel mill in Northeast China and achieved good performance.

In this paper a new antenna design technique is introduced in order to achieve tri-band operation as well as antenna miniaturization. The technique consists of using two concentric first-iterative hexagonal rings connected to each other as a radiating patch fed with a Y-shaped microstrip line. The proposed antenna operates at three frequency bands to cover 2.4/5.8 GHz WLAN and 3.5GHz WiMAX bands. The numerical analysis and simulation are carried out with CST MWS. The measured return losses of the proposed antenna show good performance and good agreement with the simulated results. Consequently the proposed antenna with compact size of 9.77 mm x 17 mm x 1.63 mm is well suited for wireless applications.

A comprehensive study of approaches for the estimation of the local average of the received signal strength (RSS) for indoor multipath propagation is presented. The effects of the required number of the RSS data samples and the Euclidean distances between the neighboring samples are investigated over 1D, 2D, and 3D configurations. It was found that the effect of fast fading was reduced to an acceptable level using a 2D horizontal arrangement with a relatively large spacing configuration. Furthermore, averaging was enhanced with a larger spacing compared to smaller spacing when considering the same number of samples.

Probe-fed hexagonal patch antenna suffers from impedance mismatch especially when feed is located at one of the vertices of polygon. Hexagonal planar antennas also suffer from high cross polar levels. This paper proposes a method to overcome impedance mismatch and to increase co-polarization level by reducing ground plane. Vertex feeding is demonstrated in this paper to establish improvement in impedance values more clearly. The impedance at any vertex of a hexagonal patch is too high when compared to the characteristic impedance of the probe. Three vertex-fed hexagonal antennas are developed to demonstrate the effect of ground plane reduction within C-Band. The proposed technique can be optimized to match the impedance and achieve good return loss where monopole radiation characteristics are not an issue. A vertex-fed reduced ground hexagonal antenna is proposed here that operates around 5 GHz with a frequency span of 600 MHz. Thus, the proposed antenna is quite suitable for indoor wireless LAN (UNII-1) applications.

A compact wideband dual-polarized omnidirectional antenna with good isolation for the fifth generation/wireless local area networks communication is presented in this paper. The dual-polarized characteristic of the proposed antenna is achieved by combining a vertical polarization (VP) monopole antenna and horizontal polarization (HP) cross bow-tie antenna, which is excited by a 50 Ω Sub-Miniature-A (SMA) connector and a broadband feeding network, respectively. The size of the proposed antenna is only 0.38λ×0.38λ×0.27λ (with λ being the wavelength of the lowest frequency). The simulated isolation of the proposed dual-polarized omnidirectional antenna is below -38dB in the bandwidth from 2.3 GHz to 3.7 GHz (about 46.7%, |S11

A very compact and small sized 2-element planar Ultra Wide band (UWB) antenna having high isolation with band rejection characteristics designed on a FR4 substrate (23 × 26 × 0.8 mm3) is presented in this paper. Each antenna element have a rectangular stepped-slot and a z-shaped slot, both etched in ground plane. The rectangular slot, proximity fed by a 50 Ω micro-strip transmission line, acts as a main radiator while z-shaped slot acts as a filter for rejecting the full WLAN band (5.15-5.85 GHz). Use of an inverted T-shaped slot near top end of ground plane improves isolation more than 24.5 dB in lower UWB band i.e. 3-5 GHz, while the rectangular vertical slot etched at center of the ground plane near the bottom edge reduces the mutual coupling at lower as well as at higher UWB band i.e. 5 - 10.6 GHz. Both measured and simulated results are presented which are found generally in good agreement.

So far, the handoff management involved in the wireless local area network (WLAN) has mainly fallen into the handoff mechanism and the decision algorithm. The traditional handoff mechanism generates noticeable delays during the handoff process, resulting in discontinuity of service, which is more evident in dense WLANs. Inspired by software-defined networking (SDN), prior works put forward many seamless handoff mechanisms to ensure service continuity. With respect to the handoff decision algorithm, when to trigger handoff and which access point to reconnect to, however, are still tricky problems. In this paper, we first design a self-learning architecture applicable to the SDN-based WLAN frameworks. Along with it, we propose DCRQN, a novel handoff management scheme based on deep reinforcement learning, specifically deep $Q$ -network. The proposed scheme enables the network to learn from actual users’ behaviors and network status from scratch, adapting its learning in time-varying dense WLANs. Due to the temporal correlation property, the handoff decision is modeled as the Markov decision process (MDP). In the modeled MDP, the proposed scheme depends on the real-time network statistics at the time of decisions. Moreover, the convolutional neural network and the recurrent neural network are leveraged to extract fine-grained discriminative features. The numerical results through simulation demonstrate that DCRQN can effectively improve the data rate during the handoff process, outperforming the traditional handoff scheme.

Energy is a vital resource in wireless computing systems. Despite the increasing popularity of wireless local area networks (WLANs), one of the most important outstanding issues remains the power consumption caused by wireless network interface controller. To save this energy and reduce the overall power consumption of wireless devices, most approaches proposed to-date are focused on static and adaptive power saving modes. Existing literature has highlighted several issues and limitations in regards to their power consumption and performance degradation, warranting the need for further enhancements. In this paper, we propose a novel context-aware network traffic classification approach based on machine learning (ML) classifiers for optimizing WLAN power saving. The levels of traffic interaction in the background are contextually exploited for application of ML classifiers. Finally, the classified output traffic is used to optimize our proposed context-aware listen interval power saving modes. A real-world dataset is recorded, based on nine smartphone applications’ network traffic, reflecting different types of network behavior and interaction. This is used to evaluate the performance of eight ML classifiers in this initial study. The comparative results show that more than 99% of accuracy can be achieved. This paper indicates that ML classifiers are suited for classifying smartphone applications’ network traffic based on the levels of interaction in the background.

Recent years have seen an exponential rise in the demand for indoor wireless connections that have driven future generation networks to aim for higher data rates with extended coverage and affordable rates. The two most prominent technologies for providing indoor wireless connections, WLAN and LTE, have their limitations and they can not coexist in a single band to form heterogeneous networks (HetNets). Visible light communication (VLC) has seen rapid growth in recent years as it has the capability to seamlessly merge with the existing technologies and provide wireless connections with high data rates. VLC based hybrid indoor network effectively combines the preferences of an end-user with the practicality of implementation. In this work, we investigate specific VLC/WLAN and VLC/LTE hybrid scenarios to perform a detailed analysis on the effect of user mobility on the performance of the system and how the performance of the network (in terms of throughput) can be maximized. The study aims to show how different technologies complement each other in the best and even the worst-case scenarios. Publisher's Version WOS:000892556200021

Adopting OFDMA and MU-MIMO techniques for both downlink and uplink IEEE 802.11ax will help next-generation WLANs efficiently cope with large numbers of devices but will also raise some research challenges. One of these is how to optimize the channelization, resource allocation, beamforming design, and MCS selection jointly for IEEE 802.11ax-based WLANs. In this paper, this technical requirement is formulated as a mixed-integer non-linear programming problem maximizing the total system throughput for the WLANs consisting of unicast users with multicast groups. A novel two-stage solution approach is proposed to solve this challenging problem. The first stage aims to determine the precoding vectors under unit-power constraints. These temporary precoders help re-form the main problem into a joint power and radio resource allocation one. Then, two low-complexity algorithms are proposed to cope with the new problem in stage two. The first is developed based on the well-known compressed sensing method while the second seeks to optimize each of the optimizing variables alternatively until reaching converged outcomes. The outcomes corresponding to the two stages are then integrated to achieve the complete solution. Numerical results are provided to confirm the superior performance of the proposed algorithms over benchmarks.

A coplanar waveguidefed ultra-wideband antenna with extended transmission band to WLAN frequency is investigated. The proposed antenna consists of a modified semi-circular patch and staircase of ground plane. The prototype is fabricated on a low cost FR4 substrate with dielectric constant of 4.4 with thicknes of 0.8 mm. The overall dimensions of proposed UWB antenna are 34 mm x 40 mm. The simulation and experimental results have been shown that the proposed antenna archives low VSWR over transmission bandwidth from 2.10 - 12.7 GHz to cover both WLAN and UWB bands. The average gain is 3.87 dBi. It depicts nearly omni-directional radiation pattern like dipole antenna. Moreover, the fabricated prototype antenna shows a good agreement between the simulated and measured results

A new generation of Wireless Local Area Networks (WLANs) will make its appearance in the market in the forthcoming years based on the amendments to the IEEE 802.11 standards that have recently been approved or are under development. Examples of the most expected ones are IEEE 802.11aa (Robust Audio Video Transport Streaming), IEEE 802.11ac (Very-high throughput at < 6 GHz), IEEE 802.11af (TV White Spaces) and IEEE 802.11ah (Machine-to-Machine communications) specifications. The aim of this survey is to provide a comprehensive overview of these novel technical features and the related open technical challenges that will drive the future WLAN evolution. In contrast to other IEEE 802.11 surveys, this is a use case oriented study. Specifically, we first describe the three key scenarios in which next-generation WLANs will have to operate. We then review the most relevant amendments for each of these use cases focusing on the additional functionalities and the new technologies they include, such as multi-user MIMO techniques, groupcast communications, dynamic channel bonding, spectrum databases and channel sensing, enhanced power saving mechanisms and efficient small data transmissions. We also discuss the related work to highlight the key issues that must still be addressed. Finally, we review emerging trends that can influence the design of future WLANs, with special focus on software-defined MACs and the internet-working with cellular systems.

In this paper, we present an approach and an algorithm aimed at minimising the energy consumption of enterprise Wireless Local Area Networks (WLANs) during periods of low user activity. We act on two network management aspects: powering off some Access Points (APs), and choosing the level of transmission power of each AP. An efficient technique to allocate the user terminals to the various APs is the key to achieving this goal. The approach has been formulated as an integer programming problem with nonlinear constraints, which comes from a general but accurate characterisation of the WLAN. This general problem formulation has two implications: the formulation is widely applicable, but the nonlinearity makes it NP-hard. To solve this problem to optimality, we devised an exact algorithm based on a customised version of Benders’ decomposition method. The computational results proved the ability to obtain remarkable power savings. In addition, the good performance of our algorithm in terms of solving times paves the way for its future deployment in real WLANs.

With a target to maximize the throughput, a fast link rate adaptation algorithm for IEEE 802.11a/b/g/n/ac is proposed, which is basically preamble based and can adaptively compensate for the discrepancy between transmitter and receiver radio frequency performances by exploiting the acknowledgment signal. The target system is a 1 &times, 1 wireless local area network chip with no null data packet or sounding. The algorithm can be supplemented by automatic rate fallback at the initial phase to further expedite rate adaptation. The target system receives wireless channel coefficients and previous packet information, translates them to amended signal-to-noise ratios, and then, via the mean mutual information, selects the modulation and coding scheme with the maximum throughput. Extensive simulation and wireless tests are carried out to demonstrate the validity of the proposed adaptive preamble-based link adaptation in comparison with both the popular automatic rate fallback and ideal link adaptation. The throughput gain of the proposed link adaptation over automatic rate fallback is demonstrated over various packet transmission intervals and Doppler frequencies. The throughput gain of the proposed algorithm over ARF is 46% (15%) for a 1-tap (3-tap) channel over 10 m&ndash, 250 m (16 m&ndash, 160 m) normalized Doppler frequencies. Assuming a 3-tap channel and 30 m&ndash, 50 m normalized Doppler frequencies, the throughput of the proposed algorithm is about 31 Mbps, nearly the same as that of ideal link adaptation, whereas the throughput of ARF is about 24 Mbps, leading to a 30% throughput gain of the proposed algorithm over ARF. The firmware is implemented in C and on Xilinx Zynq 7020 (Xilinx, San Jose, CA, USA) for wireless tests.

Nowadays, several wireless communication solutions targeted at low-power devices (e.g. sensors, actuators) compete for market dominance. As a consequence, the deployment of the Internet of Things is slowed by fragmentation. However, Cross-Technology Communication (CTC) has appeared as a solution capable of bridging the compatibility gap between non-interoperable devices. In this way, we propose using Wake-up Radio (WuR) to achieve high rate bidirectional CTC, introducing WuR assisted CTC (WuR-CTC). Although WuR was originally proposed to reduce radio power consumption, it provides a secondary communications channel that can be used for high-speed and bidirectional CTC. With WuR-CTC, we demonstrate that WuR can lead to interoperability between non-compatible wireless devices, therefore, providing a compelling reason for the harmonization of the nascent WuR specifications. This article presents a WuR-CTC solution implemented on an heterogeneous testbed with IEEE 802.11 and IEEE 802.15.4 devices. The resulting testbed achieves reliable CTC with an effective throughput of 26.7 kbps. Moreover, the addition of WuR to the testbed devices provides energy savings, and, in a clear advantage over traditional duty-cycled solutions, allows devices to asynchronously maintain communications.

The demand for high-data-rate and time-sensitive applications, such as 4k/8k video streaming and real-time augmented reality (AR), virtual reality (VR), and gaming, has increased significantly. Addressing the inefficiency of distributed channel access and the fairness problem between uplink and downlink flows is crucial for the development of wireless local area network (WLAN) technologies. In this study, we propose a novel transmission scheme for IEEE 802.11be networks that addresses the fairness problem and improves the system throughput. Utilizing the concept of multi-AP coordinated OFDMA introduced in the 7th-generation WLAN IEEE 802.11be, the proposed transmission scheme allows an AP to share a granted transmission opportunity (TXOP) with nearby APs. A mathematically analysis of the throughput performance of the proposed schemes was performed using a Markov chain model. The simulation results verify that the scheme effectively improves the downlink fairness and the system throughput. Combined with the advanced multiuser (MU) features of IEEE 802.11ax, such as TUA, MU cascading sequence, and MU EDCA, the proposed scheme not only enhances downlink AP transmission, but also guarantees improved control over the medium. The scheme is carefully designed to be fully compatible with conventional IEEE 802.11 protocols, and is thus potentially universal.

One of significant change in learning process is exam implementation applying a computer-based test (e-exam) rather than paper-based test. Many institutions currently use wireless network with bring your own device (BYOD) policy for their e-exam implementation, due to limitation of space and user terminals. Moreover it is hard to maintain the availability of reliable signal quality in wireless network for all users during e-exam process. Therefore, this research proposes a development of time adaptive for mobile exam (TAMEx) framework to provide all users with good quality of service of e-exam in wireless network environment when dealing with signal quality variations. The received signal strength indication (RSSI) is the main indicator of the signal quality. The framework supports e-exam implementation in wireless local area network and the use of BYOD mechanism. The research shows that the framework successfully has provided time compensation for the users who experienced temporary connection loss due to bad signal quality. The result exhibits that tiny processing time has been needed for signal loss detection, user’s request of compensation time, and server’s execution. In conclusion, the TAMEx could guarantee good services for all users who doing e-exam in wireless network environment.

In this paper, a slotted conical patch connected to a small triangular patch multiband antenna for both microwave and millimeter-wave applications is presented. The designed antenna has three characteristics. The proposed antenna is a multiband, having a compact size of 0.35λ0 × 0.35λ0 × 0.004λ0 at its lowest operational frequency, i.e., 2.4 GHz, and more importantly, it can cover both the microwave and millimeter-wave bands with a single feeding. According to the −10 dB matching bandwidth, experimental results show that the antenna operates at (2.450–2.495) GHz, (5.0–6.3) GHz, and (23–28) GHz. The reduced size, simple design, and multiband large bandwidth are some of the advantages over the reported designs in the latest literature. Both simulated and experimental results show a good agreement, and the proposed antenna can be used for wireless local area network (WLAN) applications and fifth-generation (5G) wireless communication devices.

Reduced lightweight microstrip patch antennas have attracted considerable attention in ultra‐wideband (UWB) applications. In this article, a novel modified circular ultra‐wideband monopole antenna with dual‐band notch characteristics is proposed. A circular split‐ring slot and a mushroom‐electromagnetic bandgap‐type structure are employed to realize the dual‐band notch characteristics. The proposed antenna exhibits the bandwidth of 2.0‐12 GHz with a Voltage Standing Wave Ratio

The Wireless Local Area Network (WLAN) has become a dominant piece of technology to carry wireless traffic for Internet of Things (IoT). The next-generation high-density WLAN scenario is very suitable for the development trend of the industrial wireless sensor network. However, in the high-density deployed WLAN scenarios, the access efficiency is low due to severe collisions, and the interference is diffused due to the scattered locations of the parallel access stations (STAs), which results in low area throughput, i.e., low spatial reuse gain. A spatial group-based multi-user full-duplex orthogonal frequency division multiple access (OFDMA) (GFDO) multiple access control (MAC) protocol is proposed. Firstly, the STAs in the network are divided into several spatial groups according to the neighbor channel sensing ability. Secondly, a two-level buffer state report (BSR) information collection mechanism based on P-probability is designed. Initially, intra-group STAs report their BSR information to the group header using low transmission power. After that, group headers report both their BSR information collected from their members and inter-group interference information to the access point (AP). Finally, AP schedules two spatial groups without mutual interference to carry on multi-user full duplex transmission on the subchannels in cascading mode. The closed-form formulas are theoretically derived, including the number of uplink STAs successfully collected by AP, the network throughput and area throughput under saturated traffic. The simulation results show that the theoretical analysis coincide with the simulation results. The system throughput of the GFDO protocol is 16.8% higher than that of EnFD-OMAX protocol.

In order to meet the ever-increasing traffic demand of Wireless Local Area Networks (WLANs), channel bonding is introduced in IEEE 802.11 standards. Although channel bonding effectively increases the transmission rate, the wider channel reduces the number of non-overlapping channels and is more susceptible to interference. Meanwhile, the traffic load differs from one access point (AP) to another and changes significantly depending on the time of day. Therefore, the primary channel and channel bonding bandwidth should be carefully selected to meet traffic demand and guarantee the performance gain. In this paper, we proposed an On-Demand Channel Bonding (O-DCB) algorithm based on Deep Reinforcement Learning (DRL) for heterogeneous WLANs to reduce transmission delay, where the APs have different channel bonding capabilities. In this problem, the state space is continuous and the action space is discrete. However, the size of action space increases exponentially with the number of APs by using single-agent DRL, which severely affects the learning rate. To accelerate learning, Multi-Agent Deep Deterministic Policy Gradient (MADDPG) is used to train O-DCB. Real traffic traces collected from a campus WLAN are used to train and test O-DCB. Simulation results reveal that the proposed algorithm has good convergence and lower delay than other algorithms.

With the development of network technology, WLAN-based indoor localization plays an increasingly important role. Most current localization methods are based on the comparison between the received signal strength indication (RSSI) and the RSS in the database, whose nearest reference point is the location point. However, since a uniform standard for measuring components of smartphones has not yet been established, the Wi-Fi chipsets on different smartphones may have different sensitivity levels to different Wi-Fi access points (APs) and channels. Even for the same signal, RSSI values obtained by different terminals at the same time and the same location may be different. Therefore, the impact of terminal heterogeneity on localization accuracy can be overlooked. To address this issue, a fusion method based on received signal strength difference and compressive sensing (RSSD-CS) is proposed in this paper, which can reduce the influence caused by the terminal heterogeneity. Besides, a fingerprint database is reconstructed from the existing reference point data. Experiments show that the proposed RSSD-CS algorithm can achieve high localization accuracy in indoor localization, and the accuracy is enhanced by 20.5% and 15.6% compared to SSD and CS algorithm.

Recently, we often see the environment where many one-to-one Wireless Local Area Networks (WLANs) exist in a small area. In this environment, the network throughput of certain WLAN reduces significantly because of the interference from other networks (i.e., inter-network interference). The inter-network interference is the effect of carrier-sensing activities when there are ongoing transmissions in neighbor networks. This paper presents analytical expressions using airtime concept, which newly take into account the inter-network interference, for network throughputs of WLANs. There are existing works that similarly address the WLAN&rsquo, s carrier-sensing duration. However, they either consider a simple interference model or assume the simultaneous transmission time is negligible. Different from them, we consider the significant impact of simultaneous transmission. As a result, our analytical model can precisely express each network carrier-sensing duration by subtracting the simultaneous transmission time. More specifically, we have successfully obtained each network throughput by expressing frame-existence probabilities concerning each network&rsquo, s End Device (ED). We also confirm the validity of the analysis by comparison with simulation. The analytical results and the simulation results agree well.

This paper shows the inefficiency of TCP BBR in exploiting the Wi-Fi bandwidth. This limitation of BBR has been observed with both IEEE 802.1ln and IEEE 802.11ac, where the mechanism of frame aggregation is used to boost the throughput of data transmission. In the last years, many TCP variants have been introduced to limit the bufferbloat phenomena and bound the latency, through a reduction of the queue backlog injection rate. However, this mechanism impacts on the Wi-Fi frame aggregation logic, impeding TCP congestion controls to reach the full throughput potential of a Wi-Fi interface. While this problem can be solved with TCP CUBIC allowing the sender node to enqueue more packets, for TCP BBR the fix is not the same, as it has a customized pacing algorithm. With this contribution, we propose BBR+, a new BBR version that allows to fine tune the congestion control pace, achieving 6 times more throughput over IEEE 802.1ln channels and 16 times more throughout over IEEE 802.11ac channels, at the cost of an increased latency that is however always less than the latency obtainable with TCP CUBIC.

This paper proposes a design of two-ports circularly polarized stacked patch antenna with square ring slot feeding technique for multiple-input-multiple-output (MIMO) application. The antenna with a quarter-wavelength slot and chamfering patch., which radiates at 2.4 GHz., occupies an overall area of $\mathbf{96}\times\mathbf{96}\times\mathbf{42\ mm}^{\mathbf{3}}$ . The 7.6-dBic gain antenna prototype presents an axial ratio lower than 0.4 dB in the operating frequency band (2.4 to 2.485 GHz) as well as a port isolation higher than 27 dB. Therefore., this antenna demonstrates good port-to-port isolation., axial ratio (AR) as well as a compact dimension and is suitable to be used in systems that operate in a wireless local area network (WLAN) frequency band.

The IEEE 802.11ay wireless communication standard consents gadgets to link in the spectrum of millimeter wave (mm-Wave) 60 Giga Hertz band through 100 Gbps bandwidth. The development of promising high bandwidth in communication networks is a must as QoS, throughput and error rates of bandwidth-intensive applications like merged reality (MR), artificial intelligence (AI) related apps or wireless communication boggling exceed the extent of the chronic 802.11 standard established in 2012. Thus, the IEEE 802.11ay task group committee has newly amended recent physical (PHY) and medium access control (MAC) blueprints to guarantee a technical achievement especially in link delay on multipath fading channels (MPFC). However, due to the congestion of super bandwidth intensive apps such as IoT and big data, we propose to diversify a propagation delay to practical extension. This article then focuses on a real-world situation and how the IEEE 802.11ay design is affected by the performance of mm-Wave propagation. In specific, we randomize the unstable MPFC link capacity by taking the divergence of congested network parameters into account. The efficiency of congested MPFC-based wireless network is simulated and confirmed by advancements described in the standard.

This paper presents a regular hexagonal antenna for ultra wide bandwidth (UWB). Then this antenna is modified to obtain a dual band with single band notched.The Bluetooth band is integrated in ultrawideband (UWB) when the antenna is loaded by pair of inverted 𝛤-shaped strips.To avoid interference with the uwb systems , the wireless local area network of 5.72–5.825 GHz (IEEE 802.11a) is notched by incorporating a complementary split ring resonator (SRR) slot within the hexagonal shaped . The operating frequency ranges of the proposed antenna are 2.22 GHz - 2.52 GHz and 3.5 GHz - 10 GHz, which covers Bluetooth (2.4 GHz - 2.484 GHz) and UWB (3.1 GHz - 10.6 GHz) band, besides the range of Wlan (5.72 GHz - 5.825 GHz) with return loss more than 10 dB. The performance of the antenna is simulated and optimized by CST Microwave Studio and validated against using Ansoft HFSS . Surface current distributions is used to analyze the effects of the slot and strips. The antenna shows an acceptable gain over both Bluetooth and UWB bands. In the band notched regions, the gain reduces from its normal value to about 4 dBi at 5.75GHz.

The proposed planar antenna with different asymmetrically hanging type arms for WLAN /Bluetooth/ Zigbee/ WiMAX/ HYPERLAN and Military applications.The proposed antenna consists asymmetrically three arms and defected ground plane to resonates 2.44GHz, 3.4GHz 5.3GHz and 7.5GHz cover WLAN,Bluetooth, Zigbee, WiMAX , HYPERLAN and Military applications. The dimension of antenna is 32×12×1.6mm3 .The fabricated antenna shows good measured results for the multiband operation as per simulated.

Microstrip radiators with Circular Polarization (CP) are paid much attention in wireless and navigational applications. In this paper, four microstrip rectangular radiators with axially centered asymmetric Triangular-Semi Elliptic (TSE) slots along the square boundary of the patch is proposed. The probe feed is applied along the diagonal of the square patch and it is optimized for its position to get CP radiation. The first Asymmetric Slotted Patch (ASP#1) of 50 mm X 50 mm provides 10dB RL (Return Loss) bandwidth of 200 MHz (2320 to 2520 MHz) with CP and 3dB AR (Axial Ratio) bandwidth of 40 MHz with a gain of 3.3dBi. A 10dB RL bandwidth of 340MHz (2320 to 2660 MHz) with CP and 3dB AR bandwidth of 60MHz (2370 to 2430 MHz) with a gain of 3.8dBi is obtained for second Asymmetric Slotted Patch (ASP#2) of 50 mm X 50 mm. The scale down versions of ASP#2 presented are ASP#3 (40 mm X 40 mm) and ASP#4 (30 mm X 30 mm) suitable to operate in IEEE 802.11y (3.65-3.7 GHz) and 802.11a (5.2 GHz) Wi-Fi applications with CP radiation. The proposed ASP#3 offers 10dB RL bandwidth of 390 MHz, 3dB AR bandwidth of 100 MHz and a peak gain of 4.3dBi with CP. ASP# 4 offers 10dB RL bandwidth of 590 MHz, 3dB AR bandwidth of 160 MHz and a peak gain of 3.95dBi with CP. It is evident from the results the proposed ASP#1 and ASP#2 are suitable for WLAN (2.4 GHz) and ISM (2.4-2.483 GHz) band applications. All the proposed four antennas are fabricated, measured results are compared with the simulation results.

In this paper, an efficacious and impermeable undeviating MIMO consist of 70 x 50 x 0.4 mm3 is used for WLAN, defence system & radio astronomy and WiMAX applications. To keep in order abandoning the reactive connection between the antennas, a neutralizing line is connected between the two symmetrical radiating elements. Another technique to reducing isolation (mutual coupling) between the antennas, four small slits of small size are etched onto to the ground plane. This has resulted in the proposed antenna giving a good bandwidth at the three resonant frequencies of (3.2–3.7 GHz) for Wireless LAN, (5.1–5.6 GHz) WiMAX and (6.7–7.5 GHz) defence system & radio astronomy applications with |S11|< -10 dB and mutual coupling |S12|< -20 dB for the entire operating band. The simulation results and measured results demonstrate that tri-band MIMO antenna is more acceptable for the design in portable device applications.

This work presents a compact, quad-band planar antenna intended for assimilation into flexible and conformal devices. The CPW-fed semicircular shaped prototype with rake-shaped slots is designed, realized and characterized experimentally. The frequency bands covered by the proposed radiator are centered at 2.5, 3.7, 5.5 and 8 GHz with measured impedance bandwidths of 16%, 13.5%, 11.8% and 14.63% respectively. The proposed antenna is thus enabled to support WLAN, ISM, Bluetooth, WiMAX, LTE and X-band applications. The antenna exhibits a significant gain. The radiation characteristics of the proposed radiator are measured in concave and convex bent shapes at various radii to analyze its flexibility. Performance of the antenna remains almost unaffected in the bent situation. Measurements demonstrate good coherence with simulations. The compactness and good performance of the design both in bent and unbent conditions proves it to be the better contender for future multiband conformal wireless applications.

This paper examines a dual-band circularly polarized (CP) Rectangular Dielectric Resonator Antenna (RDRA). The RDRA is excited by using triangular ring-shaped aperture and an additional parasitic strip, which is connected to the one side of the RDRA. Three striking features of the proposed design are: (i) modified feeding structure (triangular ring-shaped aperture along with microstrip line) and parasitic strip create dual-radiating modes in the RDRA (i.e. ${\mathrm {TE}}_{1,\delta ,1}^{\mathrm {y}}$ and ${\mathrm {TE}}_{\mathrm {1,4,1}}^{\mathrm {y}}$ ); (ii) modified feeding structure with parasitic strip generates CP wave in both the frequency bands; and (iii) The left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) of proposed antenna can be controlled by taking the mirror image of triangular ring-shaped aperture and parasitic strip. Simulated outcomes have been practically confirmed with the help of developed prototype of the proposed antenna. Measured and simulated results show high harmony to each other. The experimental results confirm that the proposed RDRA is operated over two frequency bands, i.e., 3.4–3.58 GHz and 5.1–5.9 GHz. The 3-dB axial ratio bandwidth of the proposed antenna is about 3.46–3.54 GHz (LHCP) and 5.18–5.34 GHz (RHCP) in lower and upper frequency band, respectively. The proposed antenna is fairly applicable for worldwide interoperability for microwave access and wireless local area network applications.

A novel coplanar waveguide-fed rectenna with high efficiency is proposed and implemented in this paper for 2.45-GHz Bluetooth/ wireless local area network applications. The antenna has compact dimensions of 18 mm $\times \,\, 30$ mm, which is simulated and manufactured using a low-cost FR4 substrate with a thickness of 1.6 mm. A tuning stub technique with rectangular slots is used for better impedance matching and enhancing the impedance bandwidth of the antenna with a peak gain of 5.6 dB. The proposed novel antenna for RF energy harvesting applications exhibits dipolelike radiation pattern in $H$ -plane and omnidirectional pattern in $E$ -plane with improved radiation efficiency. Single-stage Cockcroft–Walton rectifier with L-shaped impedance-matching network is designed in advance design system and fabricated on FR4 substrate. The dc output of the rectenna is measured as 3.24 V with a load resistance of 5 $\text{k}\Omega $ . A simulated peak conversion efficiency of 75.5% is attained, whereas the measured one is observed to be 68% with an input signal power of 5 dBm at 2.45 GHz.

Traditionally employed human-to-human and human-to-machine communication has recently been replaced by a new trend known as the Internet of things (IoT). IoT enables device-to-device communication without any human intervention, hence, offers many challenges. In this paradigm, machine’s self-sustainability due to limited energy capabilities presents a great challenge. Therefore, this paper proposed a low-cost energy harvesting device using rectenna to mitigate the problem in the areas where battery constraint issues arise. So, an energy harvester is designed, optimized, fabricated, and characterized for energy harvesting and IoT applications which simply recycles radio-frequency (RF) energy at 2.4 GHz, from nearby Wi-Fi/WLAN devices and converts them to useful dc power. The physical model comprises of antenna, filters, rectifier, and so on. A rectangular patch antenna is designed and optimized to resonate at 2.4 GHz using the well-known transmission-line model while the band-pass and low-pass filters are designed using lumped components. Schottky diode (HSMS-2820) is used for rectification. The circuit is designed and fabricated using the low-cost FR4 substrate ( ${h}$ = 16 mm and $\varepsilon _{r} = 4.6$ ) having the fabricated dimensions of 285 mm $\times \,\,90$ mm. Universal software radio peripheral and GNU Radio are employed to measure the received RF power, while similar measurements are carried out using R&S spectrum analyzer for validation. The received measured power is −64.4 dBm at the output port of the rectenna circuit. Hence, our design enables a pervasive deployment of self-operable next-generation IoT devices.