Wireless Local Area Network Access Points 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).

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.

Aggregation-Based Dynamic Channel Bonding to Maximise the Performance of Wireless Local Area Networks (WLAN)

Channel bonding is considered by the IEEE 802.11ac amendment to improve wireless local area network (WLAN) performance. In this article, the channel bonding and aggregation method were proposed to increase wireless local area network performance (WLANs). It combines many channels (or lanes) to boost the capacity of modem traffic. Channel bonding is the combination of two neighbouring channels within a certain frequency band to increase wireless device throughput. Wi-Fi employs channel bonding, also known as Ethernet bonding. Channel bandwidth is equal to the uplink/downlink ratio multiplied by the operational capacity. A single 20 MHz channel is divided into two, four, or eight power channels. At 80 MHz, there are more main and smaller channels. Performance of short-range WLANs is determined through graph-based approach. The two-channel access techniques including channel bonding proposed for the IEEE 802.11ac amendment are analysed and contrasted. The novel channel sizing algorithm based on starvation threshold is proposed to expand the channel size to improve WLAN performance. Second-cycle throughput is estimated at 20 Mbps, much beyond the starvation threshold. Our test reveals access points (AP) 1, 2, and 4 have enough throughput. A four-AP WLAN with a 5-Mbps starvation threshold is presented. C160 = 1 since there is only one 160 MHz channel. MIR (3, 160 (a, a, a)) =0, indicating that AP 3’s predicted throughput is 0. The algorithm rejects the 160 MHz channel width since ST is larger than 0. The channel width in MHz is given by B =0,1 MIR. The MIR was intended to maximise simultaneous broadcasts in WLANs. The authors claim that aggregation with channel bonding outperforms so all WLAN APs should have a single-channel width. It usually outperforms fairness-based measures by 15% to 20%. Wi-Fi standards advise “channel bonding,” or using higher frequency channels. Later standards allow channel bonding by increasing bands and channel lengths. Wider channels enhance average WLAN AP throughput, but narrower channels reduce appetite. Finally, it is concluded that APs are more useful than STAs.

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.

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.

Opportunistic Transmission Scheme with Raptor Code in IEEE 802.11 Multirate WLANs

In IEEE 802.11 wireless local area networks (WLANs), a fixed low transmission rate is used for multicast transmissions regardless of the channel conditions of the receivers. This may lead to inefficient use of the wireless channel, especially when the access point (AP) has both unicast and multicast data frames in the transmission queue. In this paper, we propose an opportunistic transmission scheme with Raptor code for efficient use of the wireless channel. In contrast to the legacy WLAN AP that has a single first-in-first-out (FIFO) queue, the AP in the proposed scheme maintains two separate queues at the AP: one for unicast data and another for multicast data. When the AP accesses a wireless channel, it decides on the type of data (unicast or multicast) and the transmission rate according to the channel condition and the delay boundary of the multicast data. In addition, Raptor code is applied for reliable multicast data transmission. Our simulation results show that the proposed scheme increases the average data rate and energy consumption saving when compared to the auto rate fallback (ARF), receiver-based auto rate (RBAR), and IEEE 802.11aa, schemes, which determine the transmission data rate only by considering the channel condition.

Joint User Association and Data-Rate Allocation in Heterogeneous Wireless Networks

In this paper, the problem of joint data-rate allocation and mobile terminal (MT) assignment is investigated in a heterogeneous wireless network (HetNet) environment that consists of wireless local area network (WLAN) access points (APs) and cellular base stations (BSs) for a best-effort service. MTs are equipped with multiple radio interfaces and have multihoming capabilities. As a result, MTs can connect simultaneously to more than one wireless network (e.g., cellular network BS and WLAN AP) and aggregate the offered bandwidths from these networks to support applications with high required data rates. Unlike the existing research, to account for the MT's limited number of radio interfaces and the abundant wireless network options, the joint MT assignment and data-rate allocation problem is formulated to select the optimal subset of networks for each MT and allocate the optimal data rate share from this subset to maximize the HetNet total utility. The problem is formulated as a mixed-integer nonlinear program (MINLP), and due to its intractability and computational complexity, we transform the problem into a convex optimization problem via a binary variable relaxation approach. Based on the mathematical analysis of the problem, we present a heuristic algorithm for joint MT assignment and data-rate allocation. Numerical results demonstrate that the proposed solution achieves a near-optimal MT assignment and data-rate allocation at reduced computational complexity.

Mitigating anomalous measurements for indoor wireless local area network positioning

Indoor positioning methods using location-sensitive features of available wireless signals can achieve high accuracy. In particular, many state-of-the-art methods exploit quite unique sets of location-dependent received signal strength (RSS) measurements from multiple wireless local area network (WLAN) access points (APs), also called as wireless fingerprints. However, reception of signals from WLAN APs is not often stable, and RSS measurements tend to be unavailable due to WLAN card or AP transient effects, limited sensitivity of WLAN cards, and fluctuating attenuation and reflection of signals due to a multipath environment, structural changes and moving objects. In certain hostile scenarios, bogus APs may be installed to disorient WLAN localisation algorithms. In this study, two approaches are proposed to mitigate the impact of faulty signal strength measurements. Performance figures are provided for both simulated and empirical environments in order to support conclusions.

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.

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.

Particle-Filter-Based Radio Localization for Mobile Robots in the Environments With Low-Density WLAN APs

This paper proposes a new localization method for mobile robots based on received signal strength (RSS) in indoor wireless local area networks (WLANs). In indoor wireless networks, propagation conditions are very difficult to predict due to interference, reflection, and fading effects. As a result, an explicit measurement equation is not available. In this paper, an observation likelihood model is accomplished using kernel density estimation to characterize the dependence of location and RSS. Based on the measured RSS, the robot's location is dynamically estimated using the proposed adaptive local search particle filter (ALSPF), which adopts the covariance adaptation for correcting the system states and updating the motion uncertainty. To deal with low sensor density in large-space environments, we present a strategy based on the strongest signal with minimum variance to choose a subset of detectable access points (APs) for enhancing robot localization and reducing the computational burden. The proposed approaches are verified by realistic low-density WLAN APs to demonstrate the feasibility and suitability. Experimental results indicate that the proposed ALSPF provides approximately 1-m error and significant improvements over particle filtering.

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.

Dual‐band slot‐coupled patch antenna with broad bandwidth and high directivity for WLAN access point

A dual-band slot-coupled patch antenna for the external access point of the wireless local area network (WLAN) band is implemented. The antennas consist of two radiators on three layers. The first radiator is a slotted bow-tie antenna operating at the 2.4–2.483 GHz band. The second radiator is a patch antenna with parasitic elements operating at 4.095–5.845 GHz. To enhance the bandwidth, a coupled feeding was used in the first radiator and a parasitic patch was used in the second radiator. To improve the directivity and isolation in both the radiators a parasitic patch and chock were used. The peak gain was more than 6 dBi in the first antenna and more than 8 dBi in the second antenna.

A Novel 3D Indoor Localization Scheme Using Virtual Access Point

The global positioning system (GPS) is a popular choice for accurate location sensing and is often used in navigation systems. However, GPS fails to operate inside buildings because satellite signals are blocked. Thus, GPS cannot be used for localization indoors. Moreover, it is difficult to distinguish between the different floors. Research to overcome this problem using the ultrawideband (UWB), radio frequency identification (RFID), and infrared ray (IR) has been conducted. These methods, however, have drawbacks, such as the need for an additional communication module and database. Wireless local area network (WLAN) access point (AP) is widely installed at various locations, and using these WLAN APs can be a viable alternative. The proposed system in this paper indicates the location information in the service set identifier (SSID) of virtual AP. Therefore, merely by scanning the WLAN signals, mobile users can detect their location indoors.

Dynamic Online-Calibrated Radio Maps for Indoor Positioning in Wireless Local Area Networks

Context-awareness and Location-Based-Services are of great importance in mobile computing environments. Although fingerprinting provides accurate indoor positioning in Wireless Local Area Networks (WLAN), difficulty of offline site surveys and the dynamic environment changes prevent it from being practically implemented and commercially adopted. This paper introduces a novel client/server-based system that dynamically estimates and continuously calibrates a fine radio map for indoor positioning without extra network hardware or prior knowledge about the area and without time-consuming offline surveys. A modified Bayesian regression algorithm is introduced to estimate a posterior signal strength probability distribution over all locations based on online observations from WLAN access points (AP) assuming Gaussian prior centered over a logarithmic pass loss mean. To continuously adapt to dynamic changes, Bayesian kernels parameters are continuously updated and optimized genetically based on recent APs observations. The radio map is further optimized by a fast features reduction algorithm to select the most informative APs. Additionally, the system provides reliable integrity monitor (accuracy measure). Two different experiments on IEEE 802.11 networks show that the dynamic radio map provides 2-3m accuracy, which is comparable to results of an up-to-date offline radio map. Also results show the consistency of estimated accuracy measure with actual positioning accuracy.