Wireless Local Area Network Services Research Articles

Broadband Multiple Input Multiple Output antenna for sub‐6‐GHz 5G communications

SummaryThis paper presents the design of a miniaturized broadband monopole antenna for 5G and Wireless Local Area Network (WLAN) applications in mobile handsets. The proposed monopole evolved from a rectangular geometry of size 12 × 5 mm. The slot and stub loading techniques are used to improve the impedance matching offered by the antenna. Furthermore, bandwidth broadening is achieved using lumped elements loaded onto the aperture of the antenna. The proposed miniaturized antenna exhibits a measured impedance bandwidth of 63.6% (3.0–5.8 GHz) covering the 5G spectrum allocations under sub‐6 GHz and the WLAN services. The antenna elements are replicated along the sides of the mock mobile handset PCB to study the functionality of the eight‐element MIMO antenna. The prototype MIMO antenna fabricated and tested in the laboratory offers a peak gain of 3 dBi and total efficiency greater than 72%. Owing to miniaturization, the spatial distribution of the antenna element provides a low envelope correlation (ECC) of less than 0.2 and good diversity gain (DG) greater than 7.8 dB. In addition, the mean effective gain (MEG), channel capacity loss (CCL), multiplexing efficiency (ME), and total active reflection coefficient (TARC) are evaluated and presented. The estimated MIMO metrics are within the desired range of operation and hence make the antenna suitable for a complex propagation environment. The prototype antenna is developed on a thin microwave laminate with low‐loss characteristics and tested under laboratory conditions. The outcomes indicate that the proposed eight‐element antenna can be applied to 5G MIMO communications.

Flat Yarn Fabric Substrates for Screen‐Printed Conductive Textiles

Herein, flat yarn‐based polyethylene terephthalate (PET) fabrics as substrates for screen printing conductive inks are described. The effect of the screen‐printing parameters, such as the screen mesh size (70 or 120 pixels in.−1) and the number of printing cycles, is investigated. The uniformity of the screen‐printed layers and their electrical properties are directly related to the yarn shape, substrate roughness, and printing conditions. Minimum average sheet resistance of 16 ± 3 mΩ sq−1 is achieved on the flat yarn PET fabrics, and there is little change in the electrical performance after 1000 bending cycles. To demonstrate the impact of yarn shape on an E‐textile application, wearable antennas are fabricated using the screen‐printed PET fabrics. The antennas are designed to operate at 2.4 GHz, which is a widely used unlicensed frequency for public wireless local area network services, Bluetooth, and radio frequency identification (RFID) services. The effects of the uniformity and conductivity of the printed layers on the antenna performance are analyzed. In open‐area field tests, the textile antennas show better performance than commercial antennas. The results of this study will help improve the understanding of how the ink/substrate interface affects the screen‐printing process and to advance the manufacturing technology for conductive patterns.

A miniaturized electromagnetically coupled patch antenna design using eroded ground plane

AbstractA novel electromagnetically coupled circular patch antenna (CPA) with an eroded ground plane is proposed for the wireless local area network (WLAN) application. First, a simple CPA is designed for 2.4‐GHz WLAN band. At this frequency, the physical size of the CPA is large. Therefore, a CPA is designed at a higher frequency with much lesser dimensions, and some portion of the ground plane is eroded to observe the percentage of resonant frequency reduction. In order to avail the WLAN services at 2.4 GHz, a CPA is optimally designed at 5.76 GHz based on the same proportionality technique with an eroded ground plane. This miniaturized antenna resonates at 2.4 GHz frequency with excellent reflection and radiation characteristics. The simulation software ANSYS high‐frequency structure simulator is considered for the design of the proposed CPA. The CPA is physically fabricated and its characteristics are validated with the simulation result. It is also compared with some of the antennas available in the literature for the WLAN application. The comparative study shows that the proposed CPA is a miniaturized one with attractive performance parameters.

Spectrum sharing analysis for unlicensed use in 6 GHz using Risk-Informed Interference Assessment

In October of 2018, the FCC proposed new rules for opening 1.2 GHz of spectrum in the 6 GHz band, from 5925 to 7125 MHz, for unlicensed Wireless Local Area Networks (WLAN) devices. The objective is to allow WLAN in the 6 GHz band while sharing the spectrum with current incumbents. The traditional spectrum sharing approach relies on the worst-case scenario analysis of single events of severe consequences, regardless of their probability of occurrence, which leads to over-conservative use of the spectrum. Risk-Informed Interference Assessment (RIIA) is a quantitative approach that can be successfully applied for spectrum sharing analysis. Based on statistical analysis, RIIA estimates the probability and the consequence of interference. The objective is to allow flexible use of spectrum without being overprotective. It has been applied to a few coexistence studies in the last years and has shown great potential in providing informed insight to spectrum sharing analysis. To date, however, it has not been yet applied to coexistence studies in the 6 GHz band. In this work, we apply RIIA to analyze coexistence between WLAN and each type of incumbent service in this band and propose spectrum sharing mechanisms to reduce the probability of harmful interference. To facilitate sharing in the 6 GHz band, the FCC has divided it into four sub-bands, from U-NII-5 to U-NII-8, and proposed mitigation rules for each of them depending on the incumbents. This band is allocated to Broadcast Auxiliary Service (BAS) and Cable Television Relay Service (CARS) fixed and mobile links, Fixed Satellite Service (FSS) and fixed point-to-point links. These systems use narrow beamwidth antennas located at elevated heights, while WLANs employ low-power transmitters, mostly indoors, and, typically, omnidirectional antennas at few meters above the ground, which suggests the possibility that little energy from the incumbent links is perceptible on the ground and vice versa. To investigate this hypothesis, we apply RIIA to quantify the level of risk and its consequences to both, incumbent links and WLANs devices. Our analysis is based upon a four-step method. First, we make an inventory of all significant harmful interference hazards, in our case, 6 GHz Wi-Fi APs or incumbent links that could cause co-channel interference to the incumbents or Wi-Fi devices, respectively. Second, we define the interference protection criteria for each of them as consequence metrics to characterize the severity of hazards. Third, the likelihood and consequence of each hazard are analyzed. Using Monte Carlo simulations, we calculate the likelihood of downlink and aggregate interference from/to current incumbents to/from future WLANs and, using an interference protection criterion, determine if this interference can be tolerable. Finally, the likelihood-consequence results are aggregated and compared for different scenarios. This approach provides detailed coexistence analysis between WLAN and incumbent services in the 6 GHz band using the RIIA methodology. The results suggest that there is a low risk of harmful interference to terrestrial incumbent links in the U-NII-6 and U-NII-8 bands, which consider low-power indoor APs only. For the U-NII-5 and U-NII-7 bands, considering outdoor APs transmitting at full power, the probability of harmful interference ranges from low to high, depending on the scenario. To reduce this risk, it is suggested to implement a mitigation technique. In the case of a satellite incumbent, coexistence is possible without the need of mitigation techniques. Ultimately, this work will provide decision-makers with information regarding the risks associated with coexistence in the 6 GHz band.

Deploying WLAN service with OpenFlow technology

SummaryIn this paper, we proposed a feasible software‐defined networking (SDN) wireless local area network (WLAN) solution that leverages OpenFlow technique and provides affordable centralized WLAN service without the proprietary restrictions of centralized thin access point WLAN architecture. On the basis of an SDN‐enabled WLAN architecture with fat access points, we implement and deploy a wireless network test bed, where network administrators can exploit the extensibility and flexibility of OpenFlow‐based SDN switches and controller. Service providers can develop customized application modules and required features. We build our system with open sources and commercial off‐the‐shelf hardware and develop a mechanism to control wireless bandwidth. Field experimental results show that our SDN wireless bandwidth control application can effectively manage bandwidth in a dynamic and flexible way via the SDN WLAN.

Cloudlet- and NFV-based carrier Wi-Fi architecture for a wider range of services

Over the past few years, Wireless Local Area Networks (WLANs) have been extensively deployed and have significantly evolved. However, the deployment of large-scale WLAN still presents management issues. Moreover, while newer WLAN technologies and services have been emerging at a prolific rate, the architecture of WLAN networks has been quite static and has seen difficulties to evolve. In this paper, we present a novel architecture for carrier-managed WLAN networks which leverages Network Function Virtualization concepts and virtualization technology in general. It is based on a WLAN Cloudlet which offloads MAC layer processing from access points and consolidates network functions and value-added services. All these functions and services are based on software instances. This brings more flexibility and adaptability and allows operators to easily implement new services while reducing CAPEX/OPEX and network equipment costs (e.g., access points).

Compact dual‐band antenna for 2.4/5.2/5.8 GHz WLAN service for laptop computer applications

ABSTRACTIn this study, a compact dual‐band antenna for wireless universal serial bus dongle applications is proposed. The proposed structure consists of a conventional folded monopole antenna (driven element) and a strip pattern that extends from the ground (GND) plane (shorten parasitic element). The proposed antenna exhibits triple‐resonance (f1, f2, and f3). The first two resonance frequencies (f1 and f2) are generated by adding the shorted parasitic element. The third resonance frequency (f3) is generated by the folded monopole antenna. The first resonance frequency (f1) covers 2.4‐GHz wireless local area network (WLAN) service, whereas the second and third resonance frequencies (f2 and f3) cover 5.2/5.8‐GHz WLAN service. Thus, dual‐band operation for 2.4/5.2/5.8‐GHz WLAN service can be easily performed. The antenna occupies a small area of 7 × 20 mm2. It can be easily connected to the edge of the system GND plane or the supporting metal frame of a laptop computer. Details of the proposed antenna are presented and studied. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2207–2213, 2015

Wireless local area network service providers’ price competition in presence of heterogeneous user demand

Consider wireless local area network (WLAN) service providers (SPs) operating in an overlapping service area. The SPs compete with each other to attract users. The price charged is utilised by the SPs as a tool to maximise revenue, resulting in a price competition between the WLAN SPs. The users are assumed to be selfish, trying to maximise their individual utility. They have varied sensitivity towards quality of service experienced and the price charged. In such a scenario, the user demand distribution is the one that achieves Wardrop equilibrium. Approximate analytical expressions are obtained for the best response of SPs to each other's price. Existence of a Nash equilibrium (NE) between the competing SPs is proved and the price vector at which the NE occurs is obtained. It is found that, while in one extreme monopoly leads to very high revenue for WLAN SPs with minimal consumer surplus, in the other extreme unregulated duopoly/oligopoly leads to high consumer surplus at the cost of minimal revenue generation for the competing SPs. Thus, price regulation is proposed in the WLAN market for equitable distribution of the surplus among the SPs and the users.

WLAN Service Providers' Price Competition with Uncertainty in User Demand

In this letter, uncertainty in users' network selection is modeled by a Markov chain. In the presence of such uncertainty, the price competition game of wireless local area network (WLAN) service providers (SPs) is analyzed and the existence of Bayesian Nash equilibrium is proved. Using the price of anarchy as a metric of efficiency for social welfare maximization, it is shown that an increase in competition does not result in significant losses in efficiency. Compared to a monopoly, an unregulated duopoly of WLAN SPs is recommended as it results in a more equitable distribution of surplus amongst the SPs and the users.

Low-SAR, Miniaturized Printed Antenna for Mobile, ISM, and WLAN Services

Recently, the mobile handsets support both the mobile and wireless LAN services. Thus, our target is to introduce a new antenna that supports both services. The antenna operates for most of the mobile applications such as the GSM 850, GSM 900, DCS 1800, PCS 1900, UMTS 2100, and most of the LTE bands, especially the low-frequency LTE 700 band. The antenna also supports the WiMAX, wireless local area network (WLAN), and the Industrial, Scientific, and Medical (ISM) bands. The antenna not only has a compact size, but also it supports a low specific absorption rate (SAR) radiation at all the operating frequencies. It consists of a monopole, a meander line, and an electromagnetic band-gap (EBG) structure. In order to cover the low frequency bands, a meander line is utilized due to its compact size, but unfortunately it is a narrowband antenna that is difficult to cover both LTE700 and GSM 900 bands. The solution stems from the use of an EBG structure that widens the band to cover the two low frequency bands and to reduce the maximum SAR. The higher frequency bands are supported by both the monopole and the meander line since they acts as traveling-wave antennas at the high frequency bands. The antenna meets three challenging parameters: the compact size, the multiband operation including the low frequency bands, and the low SAR radiation. Good agreement is found between the experimental and the simulated results.

간섭을 고려한 무선 LAN 주파수 소요량 예측

최근 스마트폰의 등장에 따른 무선 트래픽 증가에 효율적으로 대처하기 위해서는 능동적인 주파수 정책이 필요하다. 이에 이동통신 주파수 소요량 예측과 함께 미래에 요구되는 무선 LAN 주파수 소요량을 예측할 필요가 있다. 미래에 요구되는 무선 LAN의 주파수 소요량은 미래의 무선 LAN 트래픽을 예측하고, 이를 무선 LAN의 시스템 효율로 나눔으로써 계산된다. 본 논문에서는 기존에 전통적인 무선 LAN 트래픽 예측법과 함께 이동통신으로부터 offloading하는 스마트폰 트래픽을 고려한 새로운 무선 LAN 트래픽 예측법을 제안하였다. 또한, AP의 증가에 따른 주파수 간섭 효과를 통계적으로 모델링하여 무선 LAN의 시스템 효율 계산 시 적용함으로써 실제 환경에 근접한 무선 LAN 주파수 소요량을 예측할 수 있도록 하였다. 예측된 주파수 소요량을 바탕으로 미래의 무선 LAN 활성화에 대비하여 AP간 간섭을 최소화할 수 있는 정책 방향을 제안하였다. Owing to the proliferation of smart phone users, a proactive spectrum policy is needed in order to deal with increasing data traffic. Therefore, the prediction of frequency requirements for future wireless local area network (WLAN) as well as a licensed cellular communication is necessary. In this paper, we proposed a new prediction method for WLAN spectrum requirements. This method includes both a traditional prediction method and an offloading percentage from cellular network, Also, it can consider a frequency interference between access points using a statistical approach. Based on these approaches, we can predict the spectrum requirements of future domestic WLAN services considering the frequency interference. Finally, we suggest the spectrum policy for WLAN which can prevent spectrum shortage of future WLAN services.

Demo

We present a demo of Odin, an SDN framework to program enterprise wireless local area networks (WLANs). Enterprise WLANs need to support a wide range of services and functionalities. This includes authentication, authorization and accounting, policy, mobility and interference management, and load balancing. WLANs also exhibit unique challenges. In particular, access point (AP) association decisions are not made by the infrastructure, but by clients. In addition, the association state machine combined with the broadcast nature of the wireless medium requires keeping track of a large amount of state changes. To this end, Odin builds on a light virtual AP abstraction that greatly simplifies client management. Odin does not require any client side modifications and its design supports WPA2 Enterprise. With Odin, a network operator can implement enterprise WLAN services as network applications.

Design of a compact multiband internal antenna for mobile application

AbstractA compact multiband internal antenna for global system for mobile communication, digital cellular system, and wireless local area network services is proposed. The proposed antenna is composed of a multiple input and multiple output (MIMO) antenna and a dual‐band printed inverted F antenna. In particular, projected ground structure is adopted to improve isolation characteristic between the two elements of the MIMO antenna. The experimental results show that sufficient bandwidths, reasonable radiation patterns, and antenna gains are achieved for each frequency band. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2865–2868, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26413

Analysis on the Interference Effect of WLAN on WiBro

This paper analyzes the interference effect of WLAN(Wireless Local Area Network) service on WiBro(Wireless Broadband) service in adjacent frequency band by using Monte Carlo method. For the analysis, we make scenario that WLAN service operates on frequency band of 2401 MHz ~ 2423 MHz and WiBro service operates on frequency band of 698 MHz ~ 704 MHz. In case of WiBro receiver is close to WLAN AP(Access Point), the interference will be increased. So, we calculate the protection distance between WiBro receiver and WLAN AP to meet interference probability of 5 % below and required interference power of WLAN AP to meet interference probability of 5 % below in the case of fixed protection distance. As a result, the protection distance of 60 m and -9.5 dBm of required interference power of WLAN AP at 10 m of the fixed protection distance are analyzed.

The capacity of VoIP over 802.11

As Voice over IP (VoIP) technology becomes a reality, service providers will be able to offer enhanced VoIP applications not presently possible with circuit-switched type networks. Combining new applications and services with the IP Multimedia Subsystem (IMS) network will increase revenue potential. The combination of wireless local area network (WLAN) technology with VoIP and IMS features could become an attractive solution for enterprise voice infrastructure. Service providers can quickly enable enterprise Voice over WLAN (VoWLAN) services, which does not require any investment in re-wiring the premise. In this paper, we introduce the VoIP architecture over WLAN, and study, through both queuing analysis and simulations, the limiting capacity of such systems when operating in the distributed coordination function (DCF) or enhanced distributed channel access function (EDCAF) mode as defined in the IEEE 802.11b/802.11e standards. Our major conclusions are that: 1) packet aggregation and using short preambles can significantly increase VoIP capacity; 2) request to send (RTS)/clear to send (CTS) message exchange does not benefit VoIP; 3) In order to support simultaneous data and voice traffic on the same carrier, it is necessary to employ EDCAF as defined in 802.11e. © 2007 Alcatel-Lucent.

On the Impact of Quality of Protection in Wireless Local Area Networks with IP Mobility

Wireless local area networks (LANs) are vulnerable to malicious attacks due to their shared medium in unlicensed frequency spectrum, thus requiring security features for a variety of applications even at the cost of quality of service (QoS). However, there is very little work on investigating to what extent system performance is affected by security configurations with respect to mobility scenarios, heterogeneous networks, and different applications. In order to exploit the full potential of existing security solutions, we present a detailed experimental study to demonstrate the impacts of security features on performance by integrating cross-layer security protocols in a wireless LAN testbed with IP mobility. We introduce a quality of protection (QoP) model to indicate the benefits of security protocols and then measure the performance cost of security protocols in terms of authentication time, cryptographic overhead and throughput. Our measurements demonstrate that the effects of security protocols on QoS parameters span a wide range; for example, authentication time is between 0.11 and 6.28 s, which can potentially affect packet loss dramatically. We also find that for the same security protocol throughput in nonroaming scenarios can be up to two times higher than that in roaming scenarios. However, some protocols are robust against mobility with little variation in system performance; thus, it is possible to provision steady service by choosing security protocols when users' mobility pattern is unknown. Furthermore, we provide observations on cross-layer security protocols and suggestions to the design of future security protocols for real-time services in wireless LANs.

Consumer preferences for wireless internet access networks and their affecting factors: a conjoint analysis

This paper compares service characteristics and analyses consumer preferences between the two current wireless internet access alternatives: 3G cellular networks and public wireless Local Area Network (LAN). A conjoint analysis was employed to find significant service attributes behind consumers' preferences. Major findings of this study are twofold. First, there was a significant difference in consumer preferences among four wireless internet service categories consisting of three wireless LAN services and one 3G service. Secondly, consumers considered price and network speed more important than service coverage, which implies wireless LAN has an advantage over 3G as far as wireless internet access is concerned. These results are expected to be of help to both government policy makers and telecommunications service providers in designing and implementing industrial promotion and competition policies in the wireless industry. Furthermore, they can also shed light on the decision-making regarding the commercial introduction of the mobile broadband wireless services in the near future.

Project-WLAN: a longitudinal study of WLAN experiments

With the improved cost and performance of Wireless Local Area Network (WLAN) systems and the growing availability of standards-based solutions, WLAN services and acceptance have mushroomed in both research and application domains. In the technological world as well as this paper, most concerns surround the security and quality of service of WLAN. The WLAN research paradigm used in this paper takes the form of empirical measurements of Radio Frequency site surveying modelling. This paper presents the design of Hong Kong's most comprehensive longitudinal WLAN experimental study, code-named Project-WLAN, and the various implications associated with the findings.

On the performance of telemedicine system using 17-GHz orthogonally polarized microwave links under the influence of heavy rainfall

This paper describes the design of a telemedicine system based on next-generation wireless local area networks (WLANs) operating at 17 GHz. Seventeen gigahertz is proposed for next-generation WLAN services offering numerous advantages over traditional IEEE 802.11 networks that operate in the range of 2.4-5 GHz. Orthogonal polarization is often used to increase spectrum efficiency by utilizing signal paths of horizontal and vertical polarization. Radio waves exceeding 10 GHz are particularly vulnerable to signal degradation under the influence of rain which causes an effective reduction in isolation between polarized signal paths. This paper investigates the influence of heavy rain in a tropical region on wide-band microwave signals at 17 GHz using two links provided by a fixed broad-band wireless access system for two-way data exchange between paramedics attending an accident scene and the hospital via microwave equipment installed in the ambulance. We also study the effects of cross polarization and phase rotation due to persistent heavy rainfall in tropical regions.