Wireless Local Area Network Access Research Articles

VoWiFi Cell Capacity Evaluation using WiFi 7 considering VBR Traffic

The need for Wireless Local Area Network (WLAN) technology is experiencing substantial growth. The transmission of Voice over WiFi (VoWiFi) is half-duplex due to its single-talk nature. In order to mitigate the inefficient utilization of available bandwidth, the technique of silent suppression is employed. This feature decreases the level of ambient noise and provides Variable Bit Rate (VBR) communication. To enhance the VoWiFi cell capacity, we utilized VBR traffic instead of Constant Bit Rate (CBR) traffic. In this study, we developed a mathematical model to find the number of VoWiFi users possible within a WLAN Access Point (AP) considering G.729 vocoder. Arbitration inter-frame space (AIFS) has been utilized in our study to evaluate the channel state prior to transmitting real-time data between user equipment (UE) devices. Additionally, short inter-frame spacing (SIFS) has been employed to transmit Request To Send (RTS)/Clear To Send (CTS) and Acknowledgement (ACK) frames, enabling an examination of the VoWiFi cell capacity. Again, to increase the VoWiFi cell capacity, we incorporated the compressed RTP (cRTP) protocol. Further, we conducted an analysis on the impact of retransmission on VoWiFi cell capacity. This analysis involved a comparison of the results using VBR traffic with the previous WLAN standards, namely IEEE 802.11b/g/n/ac/ax. We observed that the improvement in VoWiFi cell capacity in VBR traffic is approximately 2.6 times more than the CBR traffic. Further, our research revealed that the enhancement in VoWiFi cell capacity is approximately 1.5% higher when utilizing AIFS compared to Distributed Coordination Function (DCF) inter-frame spacing (DIFS).

The impact of IMS mobility management with google mobile phone on quality of experience

The widespread of a Wireless Local Area Network (WLAN) access network in residential areas provides low-cost and high-speed access to the Third-Generation Partnership Project (3GPP) services for end users. This has virtually made WLAN to be a complementary access network to Universal Mobile Telecommunications System (UMTS). The interoperability of WLAN and UMTS is made possible with the use of a mobility management mechanism in IP Multimedia Subsystems (IMS) architecture. Current problems in mobility management mechanisms are found in device mobility such as mobile phones. Such problems affect several layers and disrupt services. In this paper, IMS mobility management mechanisms with G1 mobile phone as an IMS client testbed is implemented, and its impact on the Quality of Experience (QoE) during end-to-end VoIP call session and its conformity to the 3GPP requirements of seamless service continuity is evaluated. The QoE driven mobility management mechanism is then proposed and evaluated to improve the QoE and to meet the 3GPP requirements of seamless service continuity during the handover between UMTS and WLAN access networks. Preliminary results show that there is an improvement in QoE and the requirements of 3GPP service continuity were met. The proposed Quality of Service (QoS) driven mobility management mechanism will help in the development of dual-mode mobile handsets with QoE adaptability.

EMPIRICAL OBSERVATION OF WIRELESS NETWORK PERFORMANCE FOR TRANSMISSION CONTROL PROTOCOL (TCP) UPSTREAM AND DOWNSTREAM FOR DIFFERENT USERS SCENARIOS

The increase in demand for proper and fast access to network infrastructure around the University environment by staff, students, and visitors in the quest to carry out daily tasks or keeping up with trends/innovations around the globe is a daily experience resulting in some challenges. But these challenges are not unexpected. The access to network infrastructure around the environment encourages proper development. This paper presents an empirical observation of transmission control protocol upstream throughput (TCPupT) and downstream throughput (TCPdownT) performance for an IEEE 802.11g wireless local area network (WLAN) installed at a corridor space of University of Nigeria, Nsukka campus. This work measured the TCP upstream and downstream throughput values for single, double, and multiple users (several Users) accessing an installed WLAN access point. The paper adopted basic WLAN system setup approach while observing the TCP performance in relation to SNR. Data collected for each environment were statistically analyzed, equations and results were also presented. The observed TCP throughput values vary as users increase thereby affecting the observed round-trip time (RTT). The generated equations were also used to predict TCP throughput which would aid network engineers in the deployment of IEEE 802.11g WLAN systems especially around the university environment. It is now clear that the generated model equations can be used for predicting the expected performance of IEEE 802.11g WLAN systems during deployment. This work gives WLAN engineers, researchers and users an apparatus to rapidly estimate the TCP upstream and downstream throughput, by monitoring the received SNR for IEEE 802.11g systems.

An Improved Hybrid Indoor Positioning Algorithm via QPSO and MLP Signal Weighting

Accurate location or positioning of people and self-driven devices in large indoor environments has become an important necessity The application of increasingly automated self-operating moving transportation units, in large indoor spaces demands a precise knowledge of their positions. Technologies like WiFi and Bluetooth, despite their low-cost and availability, are sensitive to signal noise and fading effects. For these reasons, a hybrid approach, which uses two different signal sources, has proven to be more resilient and accurate for the positioning determination in indoor environments. Hence, this paper proposes an improved hybrid technique to implement a fingerprinting based indoor positioning, using Received Signal Strength information from available Wireless Local Area Network access points, together with the Wireless Sensor Networks technology. Six signals were recorded on a regular grid of anchor points, covering the research space. An optimization was performed by relative signal weighting, to minimize the average positioning error over the research space. The optimization process was conducted using a standard Quantum Particle Swarm Optimization, while the position error estimate for all given sets of weighted signals was performed using a Multilayer Perceptron (MLP) neural network. Compared to our previous research works, the MLP architecture was improved to three hidden layers and its learning parameters were finely tuned. These experimental results led to the 20% reduction of the positioning error when a suitable set of signal weights was calculated in the optimization process. Our final achieved value of 0.725 m of the location incertitude shows a sensible improvement compared to our previous results.

A Compact-Size and High-Efficiency Cage Antenna for 2.4-GHz WLAN Access Points

In this communication, a compact-size and high-efficiency air cavity antenna with a cage-like structure is proposed for 2.4 GHz wireless local area networks (WLAN). The air cavity antenna is constructed with four sides of hybrid metallized vias, including sparsely arranged blind vias and tightly arranged shorting vias. First, the antenna size is significantly reduced by utilizing the shorting vias, which makes the antenna operate at the high-order TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathrm {1/2,1/2}}$ </tex-math></inline-formula> mode. Then, by loading the capacitive blind vias at the radiating apertures, the antenna size is further miniaturized. Notably, high radiation efficiency is obtained attributed to the lower dielectric loss of the air-medium structure. Finally, a prototype of the proposed cage antenna has been fabricated and tested with good agreement between simulated and measured results. In such a compact size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.128\lambda _{0} \times 0.128 \lambda _{0} \times 0.10 \lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is the free-space wavelength at the center frequency), the measured total efficiency over 90% is achieved in the WLAN band by the cage structure. Compared with the existing 2.4 GHz antennas, the proposed one is with the ascendency of compact size and high radiating efficiency for WLAN applications.

WLAN Access Points Channel Assignment Strategy for Indoor Localization Systems in Smart Sustainable Cities

The idea of smart and sustainable cities is incomplete without using information and communication technologies. Wireless Local Area Network (WLAN) plays a vital role in connecting different services, transferring data and providing indoor localization. WLAN fingerprinting technique has become the most common approach for indoor localization in smart cities. This technique utilizes received signal strength (RSS) and channel status from the installed WLAN Access Points (AP). Currently, WLAN planning relies on the site survey, which is laborious and uneconomical for large areas. The WLAN has a limited number of channels assigned in the frequency reuse strategy. An inefficient channel assignment strategy will lead towards increased interference, thus degrading the overall service. This paper proposes a WLAN channel assignment strategy for large and crowded indoor areas. The proposed scheme assigns the channels to installed APs for indoor localization in fingerprinting framework. The proposed technique ensures that the proposed AP channel assignment algorithm in our network-planning scheme mitigates interference.

Compact Pattern Diversity Antenna with 3-D Printed All-dielectric Superstrate for WLAN Access Points

ABSTRACT This paper presents a four-port pattern diversity antenna with a 3-D printed all-dielectric superstrate for 5.2 GHz Wireless Local Area Network (WLAN) access points. The topology of four-port coaxial-fed circular patch antennas provides a beam tilt of ±45° and ±15° with an angular coverage of ±60°. The beam tilt is obtained through this unique topology, without the need for any additional phase shifting circuits. Then, a low-cost 3-D printed dielectric superstrate is designed to enhance and equalize the gain without compromising on the beam tilt and polarization purity of the antennas. The antenna module has an impedance bandwidth of 80 MHz (5.16 GHz–5.24 GHz), covering the IEEE 802.11ac band, for a gain of 9 dBi throughout the band and across the ports. The dielectric superstrate provides a gain enhancement of 3.8 dB for antennas 1 and 4, and 5.4 dB gain enhancement for antennas 2 and 3, respectively.

Security level evaluation system for wireless local area network access devices

Security level evaluation system for wireless local area network access devices

A Reconfigurable Antenna With Sum and Difference Patterns for WLAN Access Points

This letter presents a reconfigurable antenna with sum and difference patterns for the applications of wireless local area network (WLAN) access points. The proposed antenna consists of a 2 × 2 circularly polarized (CP) stacked-patch antenna array and a switchable monopulse comparator network. Utilizing this comparator network to excite the CP antenna array, sum, azimuth difference, elevation difference, and bidifference beams are produced and can be switched by controlling the dc voltages on the p-i-n diodes. Measurement reveals that the antenna's return loss is better than 10 dB in the frequency ranges of 2.26–2.58 GHz, 2.24–2.62 GHz, 2.25–2.61 GHz, and 2–3 GHz at the sum, azimuth difference, elevation difference, and bidifference modes, respectively. The measured axial ratios, gains, and radiation patterns also show that this antenna can be applied to enhance the communication-area coverage capability for WLAN access points.

SDN-assisted efficient LTE-WiFi aggregation in next generation IoT networks

Currently, the increasing demands of user terminals have surged drastically and pulled up the global data traffic along. According to 3rd Generation Partnership Project (3GPP), offloading is one of the most beneficial and advantageous options to handle this critical traffic bottleneck, however, both Long Term Evolution (LTE) and Wireless Local Area Network (WLAN) are loosely coupled. To mitigate the User Equipment (UE) from latency issues during offloading and for tighter integration of LTE and WLAN radio networks, LTE–WLAN Aggregation (LWA) was introduced by 3GPP that is apparently suitable for the Internet of Things (IoT) devices. However, LWA is not suitable for high mobility scenarios as UEs’ information need to be updated for every new environment because of the frequent aggregation triggers which are mostly non-optimal and demands for a high-level controller. To resolve the disadvantage of non-optimal aggregation triggers, in this paper, we proposed Software Defined Networking (SDN) based approach for LWA, named as LWA under SDN Assistance (LWA-SA). In this approach, SDN initiates aggregation appropriately between LTE and an optimal WLAN Access Point (AP) which avoids frequent reconnections and deprived services. As multiple parameters are required for selection of an optimal WLAN AP, so we use Genetic Algorithm (GA) that considers each parameter as fitness value for the selection of optimal WLAN AP. This maximizes the throughput of UE and reduces the traffic pressure over licensed spectrum. Further, a mathematical model is formulated that uses Karush–Kuhn–Tucker (KKT) to find the maximum attainable throughput of a UE. Using NS-3, we compared our approach with offloading scenarios and LWA. The simulation results clearly depict that LWA-SA outperforms existing schemes and achieves higher throughput.

Cluster-Based RF Fingerprint Positioning Using LTE and WLAN Signal Strengths

Wireless Local Area Network (WLAN) positioning has become a popular localization system due to its low-cost installation and widespread availability of WLAN access points. Traditional grid-based radio frequency (RF) fingerprinting (GRFF) suffers from two drawbacks. First it requires costly and non-efficient data collection and updating procedure; secondly the method goes through time-consuming data pre-processing before it outputs user position. This paper proposes Cluster-based RF Fingerprinting (CRFF) to overcome these limitations by using modified Minimization of Drive Tests data which can be autonomously collected by cellular operators from their subscribers. The effect of environmental changes and device variation on positioning accuracy has been carried out. Experimental results show that even under these variations CRFF can improve positioning accuracy by 15.46 and 22.30% in 95 percentile of positioning error as compared to that of GRFF and K-nearest neighbour methods respectively.

MIMO-configured WLAN access point antenna with high port isolation

A four-element MIMO (multiple-input multiple-output) antenna system utilizing planar inverted-F antenna for 5 GHz WLAN (wireless local area network, band 1: 5.15–5.35 GHz, band 2: 5.725–5.825 GHz) access point applications is presented in this paper. The detrimental effects of practical device environment on the antenna isolation performance are compensated using an array of metasurface-based isolator between the antenna elements. The proposed isolator partially absorbs the fields responsible for coupling and rotates the polarization of rest of the coupled fields. The working mechanism of the proposed isolator is explained with the surface current distribution. The proposed antenna also exhibits spatial/pattern diversity and thus, the lower values of envelope correlation coefficient make it suitable for the MIMO application.

Geometrical Characterization of Offloading through Wireless LANs

The offloading of cellular traffic through WLAN APs (wireless local area network access points) distributed in a homogeneous Poisson process (HPP) is theoretically evaluated. The probability $P_w$ that a user can use WLAN and the expected number of vertical handovers $N_h$ are evaluated as the basic performance metrics of WLAN AP coverage. Explicit formulas are derived for the metrics, and the fundamental relationships between the metrics and many parameters such as the shape of each WLAN coverage region $D_1,D_2,\ldots$ are described. These metrics depend on the size and perimeter length of $D_i$ but do not depend on their other shape parameters for a convex $D_i$ . In addition, it is proven that a disk-shaped $D_i$ minimizes $N_h$ for a fixed WLAN coverage size and that $P_w$ is often insensitive to the perimeter length of $D_i$ . It is also proven that the $P_w$ of a user at a random location is equal to that moving along a random straight line or a random bounded curve. One hundred empirical location data sets of WLAN APs in Japan, Korea, and the US were used to confirm the theoretical results. Although these locations do not follow an HPP, many theoretical results are shown to be valid. For example, $N_h$ is minimized by a disk-shaped $D_i$ . Simultaneously, we find that $P_w$ slightly increases when a slender $D_i$ is used for highly clustered AP locations.

ANDSF-Assisted vertical handover decisions in the IEEE 802.11/LTE-Advanced network

To address the challenging issues of energy-efficiency and seamless connectivity in heterogeneous networks, 3GPP and IEEE have recently incorporated several architectural and functional enhancements to the baseline operation of their standards for cellular and wireless local area network access, respectively. Based on the 3GPP Access Network Discovery and Selection Function (ANDSF) as well as the advanced measurement capabilities provided by the IEEE 802.11-2012 and the 3GPP Long Term Evolution–Advanced (LTE-A) Standards, we propose an ANDSF-assisted energy-efficient vertical handover decision algorithm for the heterogeneous IEEE 802.11-2012 / LTE-A network. The proposed algorithm enables multi-mode mobile terminals to select and associate with the network point of attachment that minimizes the average overall power consumption at the mobile terminal and guarantees a minimum supported quality of service for its ongoing connections. System-level simulations demonstrate the performance of the proposed algorithm and compare it against that of other competing solutions.

Distributed channel selection scheme based on the number of interfering stations in WLAN

In contention-based wireless local area networks (WLAN), adjacent WLAN access points (APs) and stations (STAs) using the same channel may degrade their performance due to contention. To solve this problem, researchers have studied various distributed channel selection schemes, where APs select the least congested channel among all available channels. However, the existing distributed channel selection schemes rarely consider contention from upstream transmission of STAs. Therefore, it is difficult to find the least congested channel in a WLAN environment where both upstream and downstream transmissions exist. In this paper, we propose a novel distributed channel selection scheme which decides a channel with minimum number of interfering STAs as the least congested channel. Unlike the existing schemes, the proposed scheme considers the contention from both downstream and upstream transmissions. In the proposed scheme, an AP can perceive the number of interfering STAs by receiving the beacon frames from its neighboring APs. For practical implementation of our proposed scheme, we also define the additional information elements of the beacon frame according to the IEEE 802.11 standard. By performing a system level simulation and experiment using a test bed, we evaluate and analyze the performance of the proposed scheme by comparing it with that of the least congested channel selection (LCCS) and the client-assisted channel assignment optimization (CACAO) schemes. The simulation result shows that the proposed scheme increases the network throughput by 11% and 20% compared to the LCCS and CACAO schemes, respectively. Under test environment, we confirm that the proposed scheme can enhance the data rate of AP up to three times comparing to that of the LCCS scheme.

COMPACT DUAL-BAND DIELECTRIC RESONATOR ANTENNA FOR 2.4/5.8 GHZ WLAN APPLICATIONS

Design of a Dual-Band Dielectric Resonator Antenna (DRA) for the radio-frequency identification (RFID) and wireless local area network (WLAN) is presented. The necessity of a compact sized dual-band antenna is to allow the manufacturers to produce small size high-performance WLAN access points. The proposed antenna consists of printed T-Shaped monopole antenna and rectangular dielectric resonator to operate simultaneously at 2.4 and 5.8 GHz. The monopole antenna was printed on a standard 1.6 mm FR4 substrate material. Impedance bandwidth for -10 dB return loss in the 2.35 GHz and 5.86 GHz center frequency reaches 0.25 GHz (2.22 GHz to 2.47 GHz) and 0.28 GHz (5.72 GHz to 6 GHz), respectively. A good agreement is achieved between measured and simulated results. This compact antenna fed by a 50 Ω microstrip line is a low-profile and easy to manufacture antenna.

A Low Complexity System Based on Multiple Weighted Decision Trees for Indoor Localization

Indoor position estimation has become an attractive research topic due to growing interest in location-aware services. Nevertheless, satisfying solutions have not been found with the considerations of both accuracy and system complexity. From the perspective of lightweight mobile devices, they are extremely important characteristics, because both the processor power and energy availability are limited. Hence, an indoor localization system with high computational complexity can cause complete battery drain within a few hours. In our research, we use a data mining technique named boosting to develop a localization system based on multiple weighted decision trees to predict the device location, since it has high accuracy and low computational complexity. The localization system is built using a dataset from sensor fusion, which combines the strength of radio signals from different wireless local area network access points and device orientation information from a digital compass built-in mobile device, so that extra sensors are unnecessary. Experimental results indicate that the proposed system leads to substantial improvements on computational complexity over the widely-used traditional fingerprinting methods, and it has a better accuracy than they have.

Faulty measurements impact on wireless local area network positioning performance

Indoor positioning methods based on wireless local area network (WLAN) signal measurements have gained popularity because of high localisation accuracy. These methods use radio-maps obtained from wireless signal measurement surveys on location grids. Measurement sets from various WLAN access points are called fingerprints and they can be used to identify locations where the measurements are collected. WLAN positioning methods face unexpected changes in signal patterns because of attenuation changes or transient faults in WLAN cards or access points that often make signal strength readings unavailable. This study studies the effect of faulty measurements on the performance of popular state-of-the-art WLAN indoor positioning methods. Additionally, an integrity monitoring preprocessing algorithm is provided that demonstrates a possibility of faulty measurements mitigation for conventional methods such as K-nearest-neighbour. This is achieved by detecting and excluding faulty measurements prior to classification. Performance figures are provided for both simulated and empirical environments.

Ensuring Predictable Contact Opportunity for Scalable Vehicular Internet Access on the Go

With increasing popularity of media-enabled handhelds and their integration with the in-vehicle entertainment systems, the need for high-data-rate services for mobile users on the go is evident. This ever-increasing demand of data is constantly surpassing what cellular networks can economically support. Large-scale wireless local area networks (WLANs) can provide such a service, but they are expensive to deploy and maintain. Open WLAN access points, on the other hand, need no new deployments, but can offer only opportunistic services, lacking any performance guarantees. In contrast, a carefully planned sparse deployment of roadside WiFi provides an economically scalable infrastructure with quality-of-service assurance to mobile users. In this paper, we present a new metric, called Contact Opportunity, to closely model the quality of data service that a mobile user might experience when driving through the system. We then present efficient deployment algorithms for minimizing the cost for ensuring a required level of contact opportunity. We further extend this concept and the deployment techniques to a more intuitive metric-the average throughput-by taking various dynamic elements into account. Simulations over a real road network and experimental results show that our approach achieves significantly better cost versus throughput tradeoff in both the worst case and average case compared to some commonly used deployment algorithms.

Performance Analysis of Grey-World-based Feature Detection and Matching for Mobile Positioning Systems

This paper introduces a new grey-world-based feature detection and matching algorithm, intended for use with mobile positioning systems. This approach uses a combination of a wireless local area network (WLAN) and a mobile phone camera to determine positioning in an illumination environment using a practical and pervasive approach. The signal combination is based on retrieved signal strength from the WLAN access point and the image processing information from the building hallways. The results show our method can handle information better than Harlan Hile’s method relative to the illumination environment, producing lower illumination error in five (5) different environments.