Wireless Local Area Network Communication Research Articles

Multiusers parallel competitive channel protocol based on unsaturated service

In order to enhance the area throughput of next generation wireless local area network (WLAN) in high density scenarios, orthogonal frequency division multiple access (OFDMA) has been adopted as one of the key technologies in the next generation WLAN communication standards. However, the performance of the existing media access control (MAC) degrades significantly under unsaturated services. Therefore, this paper proposes a multi-user parallel contention channel MAC (MU-MAC) based on unsaturated services, which can effectively reduce the channel access conflict and improve the OFDMA access efficiency of cluster member nodes. On this basis, MU-MAC is enhanced for the spatial clustering group (SCG) formation protocol and support for the unsaturated service characteristics. Further, the optimal access radius when the service is in a non-saturated state is analyzed to make the relevant theoretical analysis more generally, and the expressions for the throughput and area throughput of the proposed protocol are modeled and derived. The simulation results verify the correctness of the theoretical analysis and the efficiency of the protocol performance. The results show that MU-MAC outperforms IEEE 802.11ax and OMAX protocol in area throughput by 40.72% and 104.15%, respectively.

Circularly Polarized L-Shaped Defected Ground Antenna for WLAN Communication Systems

With Industry 4.0, the evolution of technology has accelerated. As the information shared by people has increased, homes, cities and working environments have begun to be equipped with smart systems with the requirements of the age. IOT (internet of things) is spreading around the world. As a benefit of the advantages of wireless communication, technologies that provide information transmission using radio waves have gained importance. The increasing population in the world and its direct effect on demand require factories to keep production under control. This allows for renewal in manufacturing by triggering the contemporary transformation of the world. The transfer of this data has become an important issue as well as the increase in the amount of data generated. Wireless communication is provided by using radio frequency and studies are carried out on the 2.4 GHz ISM band frequency, which is the most frequently used. In this paper, circular polarized reader antenna with resonance frequency at 2.4 GHz and gain of 4.7 dBi is proposed. Resonance frequency covered by WLAN (wireless local area network) (2.4, 2.5 GHz). Impedance bandwidth -10 dB is between the frequencies 2.28 GHz and 2.53 GHz. The size of the designed antenna is 114mm x 65mm x 0.8mm.

Towards a Fair Allocation and Effective Utilization of Resource Units in Multi-User WLANs-based OFDMA technology

To promote the MU (Multi-User) communications in High-Efficiency WLANs (Wireless Local Area Networks), the new IEEE 802.11ax standard introduced the concept of RU (Resource Unit) by means of the OFDMA (Orthogonal Frequency Division Multiple Access) transmission technique. Although the OFDMA MU communications enable multiple users to be served at the same time in both DL (Down-Link) and UL (Up-Link) directions, several challenges remain to be met in order to design a MAC (Medium Access Control) protocol that fairly allocates and effectively utilizes the RUs. The challenges addressed are: (1) define when and how using 802.11ax control frames, (2) establish a fair sending policy of UL needs, (3) adopt a strategy to select a channel structure, and (4) avoid loss in spectral efficiency and timeout BA (Block Acknowledgment). In this paper, we proposed the FAEU-RUs protocol (Fair Allocation and Effective Utilization of RUs) by meeting each of the challenges of OFMDA MU communications. The performance evaluation demonstrates that the FAEU-RUs protocol significantly enhances the overall performance of the network but also the individual performance of each type of traffic (DL and UL) and each category of station.

A Coupled-Fed Broadband Dual-Polarized Magnetoelectric Dipole Antenna for WLAN and Sub-6 GHz 5G Communication Applications

This paper presents a novel coupled-fed broadband dual-polarized magnetoelectric dipole antenna for wireless local area network (WLAN) and 5G communication applications. The proposed magnetoelectric dipole antenna is composed of a planar electric dipole and shorting pins as a magnetic dipole to obtain a broad operation frequency band. Two coupled microstrip lines perpendicular to each other are coupled through a cross-shaped slot to excite the vertical and horizontal polarizations. The proposed antenna features a simple structure, high gain, and high polarization isolation. The measured impedance bandwidth of the proposed antenna is 1.8–4.2 GHz (fractional bandwidth of 80%). The measured realized antenna gain value is 3.7–8.5 dBi, and polarization isolation level is 25 dB at the operation frequency band.

Interventional Teleoperation Protocol that Considers Stair Climbing or Descending of Crawler Robots in Low Bit-rate Communication

In teleoperation of a crawler robot in a disaster-stricken enclosed space, distress of the crawler robot due to communication breakdown is a problem. We present a robot teleoperation system using LoRaWAN as a subcommunication infrastructure to solve this problem. In this system, the crawler robot is operated by teleoperation using a subcommunication infrastructure in a place where a wireless local area network (LAN) communication is possible. In this study, we assume an environment in which the crawler robot must ascend and descend stairs to evacuate to a place where wireless LAN communication is possible. In addition, the disaster-stricken environment is considered as an environment where obstacles are expected to suddenly occur, and the crawler robot has difficulty avoiding obstacles on the stairs. In this paper, we propose a teleoperation communication protocol that considers the risk of sudden appearance of obstacles and confirm its effectiveness using evaluation experiments in a real environment.

Performance Analysis of 1x4 RMPA Array using Step Cut and DGS Techniques with Different Feed Techniques for LTE, Wi-Fi, WLAN and Military Communications

This paper presents four different models of 1x4 antenna arrays excited by quarter wave transformer and mitered bend feeding techniques. These four antennae were designed and developed to examine the various radiation performance characteristics. The Ansys HFSS tool was used to simulate the four antenna models over the frequency range (1-5GHz). The simulation results were compared to identify the optimized design model. Both types of 1X4 arrays with mitered bend feed network showed better results than quarter wave transformer and were resonating at 2.4, 3.6, 4.5 and 4.7 GHz frequencies with a maximum gain of 13.118dB. The proposed antennae are suitable for Wi-Fi, Long Term Evolution (LTE), Wireless Local Area Network (WLAN) and military communication applications. The optimized four 1x4 array models were fabricated and tested using Vector Network Analyzer E507C. The measured results had good matching with the numerical values of the simulation results.

Textile Via-Loaded Bandwidth-Enhanced Half-Mode Substrate-Integrated Cavity Antenna for WLAN Communications

A textile via-loaded bandwidth-enhanced half-mode substrate-integrated cavity (HMSIC) antenna is presented in this article for wireless local area network (WLAN) communications. A strategy for adding shorting vias within the cavity is proposed based on the simulated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}$ </tex-math></inline-formula> -field distributions of different modes of the HMSIC antenna. More specifically, the number and positions of vias are studied for maximum shift of lower resonance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rm TM_{1,1,0}^{HM}$ </tex-math></inline-formula> mode) so that it merges with higher resonance (rotated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rm TM_{2,2,0}^{HM}$ </tex-math></inline-formula> mode) to achieve a wide 10 dB return loss impedance band. Two prototypes of the designed structure are realized using textile manufacture techniques. A first realization uses embroidered sidewalls to create the cavity and metallic rivets for the shorting vias, and a second prototype uses embroidered vias and a stripline feed. The proposed antenna can operate from 5.09 to 5.9 GHz with a fractional bandwidth of 14.7% according to measurements. The simulated radiation efficiency is above 95% in free space and 82% when worn on the human body in the 5 GHz WLAN band (5.15–5.825 GHz).

Compact Substrate Integrated Waveguide Filtering Antennas: A Review

In recent years, with the rapid development of integrated circuits, the filtering antenna (FA) circuit of the substrate integrated waveguide (SIW) has attracted widespread attention in wireless communications. Numerous structures have been proposed to improve the performance of SIW FA. Hence, this paper presents the development and miniaturization trend of the SIW FA, and briefly introduces the structure and historical development of the SIW FA. In terms of the mode, multi-mode cavities and incomplete mode cavities are constructed. Multi-layer structures, special structures and the slow-wave technology are constructed in physical structure. Several methods and design examples of the SIW FA miniaturization are introduced from these two aspects. Based on the combination of the filter and antenna, the FA remains the advantages of the SIW structure, mainly including small size, low insertion loss, high quality-factors, and easy integration in planar radio frequency components. Therefore, it can further reduce the circuit, allowing SIW FAs to be applied in many aspects such as the 5G (5th generation mobile communication technology) and wireless local area network communications.

Quintuple Band Antenna for Wireless Applications with Small Form Factor

A coplanar waveguide-fed quintuple band antenna with a slotted circular-shaped radiator for wireless applications with a high isolation between adjacent bands is presented in this paper. The proposed antenna resonates at multiple frequencies with corresponding center frequencies of 2.35, 4.92, 5.75, 6.52, and 8.46 GHz. The intended functionality is achieved by introducing a circular disc radiator with five slots and a U-shaped slot in the feed. The proposed antenna exhibits coverage of the maximum set of wireless applications, such as satellite communication, worldwide interoperability for microwave access, wireless local area network (WLAN), long-distance radio telecommunications, and X-band/Satcom wireless applications. The simulation and measurement results of the proposed fabricated antenna demonstrate the high isolation between adjacent bands. A stable realized gain with an advantageous radiation pattern is achieved at the operating frequency bands. The proposed simple design, compact structure, and simple feeding technique make this antenna suitable for integration in several wireless communication applications, where the portability of devices is a significant concern. The proposed antenna is anticipated to be an appropriate candidate for WLAN, long-term evolution, and fifth-generation mobile communication because of its multi-operational bands and compact size for handheld devices.

GreenMAC Protocol: A Q-Learning-Based Mechanism to Enhance Channel Reliability for WLAN Energy Savings

We have seen a promising acceptance of wireless local area networks (WLANs) in our day-to-day communication devices, such as handheld smartphones, tablets, and laptops. Energy preservation plays a vital role in WLAN communication networks. The efficient use of energy remains one of the most substantial challenges to WLAN devices. Several approaches have been proposed by the industrial and institutional researchers to save energy and reduce the overall power consumption of WLAN devices focusing on static/adaptive energy saving methods. However, most of the approaches save energy at the cost of throughput degradation due to either increased sleep-time or reduced number of transmissions. In this paper, we recognize the potentials of reinforcement learning (RL) techniques, such as the Q-learning (QL) model, to enhance the WLAN’s channel reliability for energy saving. QL is one of the RL techniques, which utilizes the accumulated reward of the actions performed in the state-action model. We propose a QL-based energy-saving MAC protocol, named greenMAC protocol. The proposed greenMAC protocol reduces the energy consumption by utilizing accumulated reward value to optimize the channel reliability, which results in reduced channel collision probability of the network. We assess the degrees of channel congestion in collision probability as a reward function for our QL-based greenMAC protocol. The comparative results show that greenMAC protocol achieves enhanced system throughput performance with additional energy savings compared to existing energy-saving mechanisms in WLANs.

Mobile Phone Signals Interference Cancellation With Improved WLAN Transmission and Thermal Insulation of Buildings Using FSS and RC Film

For macro-femto network, intratier and cross-tier interference (CI) must be canceled to achieve the quality of service, better indoor coverage, and higher data rates. Moreover, for better wireless local area network (WLAN) and mobile communication services while ensuring WLAN security, appropriate temperature in modern buildings with reduced energy cost is also required. To address these issues, RadioClear (RC) film can be pasted on an ordinary glass and installed in different sections to cancel the intratier interference between the femto network as well as CI between the femto and macro network. Moreover, this technique can also ensure enhanced WLAN security and thermal insulation in modern buildings. For WLAN transmission, a fractal dual bandpass frequency selective surface (FSS) designed in the RC sheet can be used to improve the WLAN communication in a situation where two or more than two rooms are served through a single WLAN router. Theoretical results are presented which are further verified through the experimental results.

A CSRR DGS Loaded Dual-Frequency Microstrip Antenna in Ground Plane for Application in PCS and WLAN Communication System

In this paper, a rectangular microstrip antenna which is inset-fed by the microstrip line with a complementary split ring resonator (CSRR) defected ground structure (DGS) cell in the ground plane just below the microstrip line (substrate present in between) for the dual frequency operation at 1.92 GHz and 5.22 GHz is presented, which are the operation bands of personal communication system (PCS) and wireless local area network (WLAN) respectively. The fundamental mode TM10 and one strongly activated higher order mode are excited which are responsible for the dual-band operation. Smaller broadside radiation and same polarization planes are the characteristics of these modes.

Omnidirectional WLAN Antenna With Common-Mode Current Suppression

An omnidirectional wireless local area network (WLAN) loop-slot antenna with common-mode current (CMC) suppression is proposed in this communication. First, based on the analysis of the equivalent model of odd-even mode, the feeding coaxial line is led out at the voltage-zero point of the loop-slot element, which suppresses the CMC over the full band. Second, through the theory of array, three loop-slot elements form an array to obtain omnidirectional radiation. Finally, the physical size is reduced by loading Stubs T in the slot. The roundness of the radiation pattern is modified by the Stubs T and the chamfering edge of the antenna. A prototype of the proposed antenna was fabricated and measured. The measured results show that the antenna achieves |S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> | <; -10 dB in bands of 2.15-2.65 and 4.85-5.92 GHz. In addition, the roundness is 0.95 dB at 2.4 GHz, 1.84 dB at 5.2 GHz, and 2.43 dB at 5.8 GHz. The antenna effectively suppresses the CMC to keep a favorable roundness over a wide band, showing its potential in WLAN communication systems.

Design of printed monopole antenna with band notch characteristics for ultra‐wideband applications

A novel design of printed monopole antenna for the ultra-wideband (UWB) applications with band notch characteristics at wireless local area network (WLAN) and X-band satellite communication system has been proposed in this manuscript. Two different types of feed lines, that is, simple and tapered are used to excite the proposed antenna. Initially, designed antenna is excited by using simple 50 Ω transmission line after that tapered transmission line is introduced to enhance the impedance matching throughout the UWB frequency range (3.1-10.6 GHz). A comparison of designed antenna with simple and tapered feed line on the basis of impedance matching has also been made in this article, and found that later case reports better impedance matching in terms of Voltage Standing Wave Ratio (VSWR) bandwidth (2.45-12.0 GHz). Further, the notch bands are embodied into the designed antenna by using two split ring slots and one horizontal slot. The antenna with outer ring slot rejects the WLAN frequency band and antenna with inner ring junks the X-band satellite communication signal. The notch frequency has been adjusted by optimizing the dimensions of split ring slots as well as horizontal slot, which are incised on the structure of proposed antenna. By adjusting all the parameters of the etched slots of proposed antenna, dual band notched characteristics centered at frequencies 5.4 and 7.4 GHz has been achieved. Designed antenna is also compact (30 × 30 mm2) and capable to suppress the interference of WLAN and X-band satellite communication signal from the entire range of UWB passband. The proposed antenna is designed on low cost FR4 glass epoxy substrate with 1.6 mm thickness and dielectric constant 4.4. Antenna is designed and simulated by using HFSS V13 simulator and further, it is fabricated and tested for the validation of results. Simulated and measured results are also juxtaposed and found in good agreement with each other.

A Novel Dual-Band Dipole Antenna for WLAN and LTE Applications

In this letter, a dual-band dipole antenna, both in the strip and the wired structures, for possible 4G long-term evolution (LTE) and wireless local area network (WLAN) applications is presented. The proposed antenna bandwidth covers the low and the high bands of WLAN (2.4 GHz, 5 GHz) and TD-LTE (1880–2655 MHz) in dual-band frequency, the impedance bandwidth in the low and the high bands are 63% (1.6–3.1 GHz) and 15% (4.75–5.55 GHz) respectively. The omnidirectional radiation patterns are desirable for WLAN and LTE communications. The maximum gains of 6.23 dBi and 5.13 dBi in both WLAN bands are adequate for stable gain applications. To avoiding the dissemination of the outer surface of the coaxial cable a copper cylinder is employed as a balun. Simple structure, use of printed circuit technology and FR4 material in the construction of the proposed antenna make it economical and easily-fabricated. The proposed antenna is also designed with the wired structure for similar purposes. Finally, the strip prototype of the antenna is implemented. Experimental results along with the simulation results have validated the merits of the proposed antenna involving simple and inexpensive structure, simultaneously covering WLAN and LTE frequency bands and almost high and stable gain in both bands.

Provisioning QoS in Wi-Fi Systems With Asymmetric Full-Duplex Communications

The traffic volume carried by wireless local area networks (WLANs) continues to increase at a rapid pace. Full-duplex communication is a key solution for satisfying the growing traffic demand, enhancing spectrum efficiency, and reducing latency for WLAN users. In this paper, we consider the application of asymmetric full-duplex (AFD) communications in WLANs, exemplified by a Wi-Fi system. Our system model relies on a full-duplex-enabled Wi-Fi access point to simultaneously transmit uplink and downlink to a pair of half-duplex Wi-Fi stations. Providing QoS guarantees in WLANs with AFD communication capabilities is challenging due to inter-node as well as residual self-interference. The heterogeneity of the QoS requirements between paired uplink and downlink stations further complicates the problem. To tackle these challenges, we introduce a framework called AFD-QoS, which incorporates AFD communications in WLANs and supports QoS. AFD-QoS consists of three components: 1) AFD-enabled uplink/downlink station-pair selection algorithm; 2) AFD-enabled block-acknowledgment session initiation/termination protocol; and 3) joint transmission rate/AFD communication mode adaptation scheme. Our adaptation scheme relies on intelligent and cognitive approaches to improve Wi-Fi networks awareness about channel dynamics as well as inter-node and self-interference. We introduce new intelligent MAC-layer procedures for supporting QoS services in AFD communications, and cast light on many challenges and their solutions. Our simulation results indicate that AFD-QoS outperforms classical half-duplex frameworks and achieves up to 90% of the optimal AFD performance.

Spatial Clustering Group Based OFDMA Access Protocol for the Next Generation WLAN

The next generation wireless local area network (WLAN) needs to significantly improve the area throughput in high dense scenario. Orthogonal Frequency Division Multiple Access (OFDMA), considered as the key technology of next generation WLAN, has been adopted by next generation WLAN communication standard. However, the existing studies on the OFDMA protocol have the interference extensions problem, i.e. multiple users are located in the dispersive area, and then the geographical interference area is enlarged. In this paper, a spatial clustering group based OFDMA multiple access protocol (SCG-OFDMA) is proposed. SCG-OFDMA enables the users in close area to form spatial clustering groups dynamically, then the users in the spatial clustering group access channel and transmit data by OFDMA. It reduces the geographical interference area, and enhances the area throughput. The theoretical analysis of SCG-OFDMA is also carried out. The simulation results of SCG-OFDMA are in agreement with the theoretical analysis. Simulation results show that the area throughput of SCG-OFDMA is higher than existing OFDMA protocol and distributing coordination function by 15.98% and 31.26% respectively. It provides a reference to design media access control protocol of the next generation WLAN.

A Low-Power WLAN Communication Scheme for IoT WLAN Devices Using Wake-Up Receivers

In this paper, we propose a delay- and power-efficient, multi-user, low-power wireless local area network (WLAN) communication scheme for Internet of Things (IoT) WLAN devices. Extremely low-power operation is one of the key requirements of emerging IoT devices. However, the current duty-cycle-based power saving approach may incur large access delay times owing to the trade-offs between the power consumption and the access delay. In order to reduce this delay and enhance the power-saving performance, wake-up receiver-based schemes have been proposed. However, because wake-up receiver-based schemes do not consider multiuser operation in dense communication environments, large delays are inevitable in the case of multiuser operation. In order to provide extremely low-power operation and under 1-mW standby power with reduced delay, we employed the optimized multiuser transmission scheduling of IEEE 802.11ax in the proposed scheme and proper enhanced distributed channel access (EDCA) parameter settings. This is with the aim to reduce the delay caused by long wake-up times, and to avoid collisions caused by simultaneous transmission in uplink multiuser scenario. By using the proposed scheme, simultaneous IoT communication with multiple mobile IoT devices is possible while providing low-power operation. Simulation results verified the outstanding delay performance of the proposed scheme.

A Virtual WLAN Device Model for High-Fidelity Wireless Network Emulation

The recent popularization of mobile devices has increased the amount of communication traffic. Hence, it is necessary both in academia and industry to research load distribution methods for mobile networks. An evaluation environment for large-scale networks that behaves like a practical system is necessary to evaluate these methods, and either a physical environment or simulation environment can be used. However, physical and simulation environments each have their advantages and disadvantages. A physical environment is suitable for practical operation because it is possible to obtain data from a real environment. In contrast, the cost for a large number of nodes and the difficulty of field preparation are its disadvantages. Reproducing radio propagation is also a challenge. Network simulators solve the disadvantages of the physical environment by modeling the entire evaluation environment. However, they do not exactly reproduce the physical environment because the nodes are abstracted. This article presents an evaluation environment that combines a network simulator and virtual machines with virtual wireless Local Area Network (LAN) devices. The virtual machines reproduce the physical environment with high fidelity by running the programs of the physical machines, and the virtual wireless LAN devices make it possible to emulate wireless LAN communication using default operating system drivers. A network simulator and virtual machines also reduce the cost for nodes, ease the burden of field preparation, and reproduce radio propagation by modeling the evaluation environment. In the evaluation, the proposed method decreased the difference from the physical environment to 5% in terms of transmission control protocol throughput. In the case of user datagram protocol, the proposed method decreased the difference from the physical environment down to 1.7%. The number of virtual machines available on a host machine and the practical use of the proposed method are also discussed.

Design of Miniaturized Dual-Band Microstrip Antenna for WLAN Application.

Wireless local area network (WLAN) is a technology that combines computer network with wireless communication technology. The 2.4 GHz and 5 GHz frequency bands in the Industrial Scientific Medical (ISM) band can be used in the WLAN environment. Because of the development of wireless communication technology and the use of the frequency bands without the need for authorization, the application of WLAN is becoming more and more extensive. As the key part of the WLAN system, the antenna must also be adapted to the development of WLAN communication technology. This paper designs two new dual-frequency microstrip antennas with the use of electromagnetic simulation software—High Frequency Structure Simulator (HFSS). The two antennas adopt ordinary FR4 material as a dielectric substrate, with the advantages of low cost and small size. The first antenna adopts microstrip line feeding, and the antenna radiation patch is composed of a folded T-shaped radiating dipole which reduces the antenna size, and two symmetrical rectangular patches located on both sides of the T-shaped radiating patch. The second antenna is a microstrip patch antenna fed by coaxial line, and the size of the antenna is diminished by opening a stepped groove on the two edges of the patch and a folded slot inside the patch. Simulation experiments prove that the two designed antennas have a higher gain and a favourable transmission characteristic in the working frequency range, which is in accordance with the requirements of WLAN communication.