Design Of Wireless Local Area Networks Research Articles

Investigation and Evaluation of IEEE 802.11n WLANs Link Features Performance Under Single Host and Concurrent Communication

For an efficient design of wireless local-area networks (WLANs), the simulation tools are important to accurately estimate the IEEE 802.11n/ac link features for WLANs. However, this true simulation of network behavior is critical in designing high-performance WLANs. Through testing, analysis, and modeling of the proposed scheme repetitively, the design of the WLAN can be enhanced with a small budget before making its practical implementation. Many network simulation tools have been established to give solutions for this request and ns-3 is the most widely used tools among them by the research industry as an open-source network simulator. In this paper, we examine the various link features of the 802.11n WLANs under several conditions. We investigate the effects of 802.11n WLAN modulation and coding schemes (MCSs), 20MHz single channel or 40 MHz bonded channel, guard intervals (GI), frame aggregation, data encoding, number of antennas and their data rate, and link distance features of 802.11n WLAN in ns-3 when only a unique host connects with the access point (AP) and generates data traffic. Besides, the performance for an enterprise scenario proposed by the IEEE 802.11ax study group is evaluated when several hosts are simultaneously creating traffic with their associated APs. The results demonstrate that ns-3 support most of the link features of the 802.11n protocol with significant accuracy.

A Review on Design and Implementation of Software-Defined WLANs

Wireless local area networks (WLANs) being the most common access technology, the use of software-defined networks (SDN) in WLANs is inevitable as SDN paradigm has been widely accepted and implemented in the networking industry. Currently, the main focus of SDN is on wired networks. OpenFlow, the most widely accepted protocol for SDN, does not fully support wireless medium, and thus, software-defined WLANs (SDWLANs) have not gained enough attention from the research community. We believe that SDN cannot only solve the long-existing issues for WLANs, but also enable researchers to bring more advanced techniques for higher data rates, better security, and quality of experience. In this article, we have emphasized the importance of integrating SDN into WLANs, and the benefits WLANs can gain by adopting SDN. More specifically, we have explained the advantages as well as the implementation details of SDN for WLANs along with the most prominent recent research efforts and contributions.

A Feasibility Study of IEEE 802.11 HCCA for Low-Latency Applications

Existing optical and wireless networks designed to support today’s services may not be suitable for the emerging services, such as machine-to-machine applications of the Internet-of-Things paradigm and tactile-haptic applications of the Tactile Internet paradigm. Some of these applications must adhere to stringent quality of service requirements, especially an ultra-low end-to-end latency constraint of approximately 1 ms. In this paper, we investigate the feasibility of the wireless local area network (WLAN) infrastructure, specifically the IEEE 802.11 HCF Controlled Channel Access (HCCA) media access control (MAC) protocol, in supporting low-latency applications. The scenario considered is tactile-haptic data transmission between body-worn data collection devices and a wireless access point. In particular, we focus on uplink direction rather than downlink direction, because uplink data transmission forms a latency bottleneck of this particular network. In this paper, we first formulate an analytical model of the HCCA using a queuing theory to evaluate the average uplink latency. We then carry out global sensitivity analyses to understand the implications of various timing and network parameters on the uplink latency. Using these insights, we propose a novel strategic parameter selection (SPS) algorithm that effectively reduces uplink latency of the IEEE 802.11 WLAN. This paper provides insights into WLAN design such that latency-sensitive applications can be supported in the near future.

Sum Rate Optimization of Multi-Standard IEEE 802.11 WLANs

Aimed at providing high data rate in wireless local area networks (WLANs), the IEEE 802.11ac standard has been developed with key enhancements, including increasing the transmission rate and enlarging the packet payload length. The improvement in the sum rate performance, nevertheless, could become marginal or even disappear when nodes of legacy 802.11a/n standards coexist. It is, therefore, of paramount importance to study how to optimize the network sum rate of a multi-standard WLAN. In this paper, a multi-group model is proposed to analyze the data rate performance of a multi-standard WLAN where nodes with different standards have distinct transmission rates and packet payload lengths. It is shown that the packet payload length is a key system parameter that has a crucial impact on both the network sum rate and the ratio of node data rates. The enhancement proposed in the latest 802.11ac standard on enlarging the packet payload length can improve the data rate performance of its own nodes, but it may lead to the starvation of the legacy 802.11a/n nodes, and even impair the sum rate performance. To maximize the network sum rate with given target ratios of node data rates, the optimal packet payload lengths with or without joint tuning of the initial backoff window sizes are further obtained, which shed important light on the optimal network design of WLANs.

Model for Optimizing the Location of the Access Point in 802.11ac Networks Supported in the Model Log-Normal Shadowing

Background/Objectives: Designing a Wireless Local Area Network (WLAN) assumes great importance in determining the optimal placement of Access Points (APs) and assigning channels in order to achieve maximum levels of coverage and performance. The aim of this paper is to develop an optimization model for the location of the AP in indoor environments, the 2.4GHz and 5GHz, supported on the propagation model Log-Normal Shadowing. Methods/Statistical Analysis: To estimate the optimal location of the AP model, nonlinear optimization was proposed based on the probability cutting frequency bands, the dimensions of the environment, the transmission power, sensitivity receptor and the coverage radius, which two routines in Matlab for systematization model, supported in the propagation model Log-Normal Shadowing path loss, which allows developed decompose the received power at an average power and attenuation term shadow. Topic Relevance: Although there have been several related resource optimization work WLANs are very few studies have considered engaging in their research strategies for optimizing the geographic location of the AP. Aspect by which developed in Matlab routines may be used in future research related to the design of WLANs. Results: Based on the results it was evident that it is possible to predict the optimum location of the AP for the 2.4GHz and 5GHz, depending on the transmission power, the detection threshold of the receiver, the probability estimated cut and characterization of the environment between the AP, either free space or obstacles, supported the use of a shadow attenuation model. In addition, routines allowed establishing the Cartesian coordinates in which the location of the AP function of the radius of coverage, frequency band and environmental conditions, with 95% confidence is suggested. Application/Improvements: The developed routines can be used as support tools in future research work, related to the design and analysis of wireless networks that use the 2.4GHz and 5GHz bands, in order to evaluate aspects of interference, coverage, performance, efficiency and QoS. Keywords: Coverage Area, Interference, Location, Optimization, Outage Probability, WLAN Networks

Design and Implementation of WLAN Based ZigBee for Personal Identification

In this research, a novel Wireless Local Area Network (WLAN) that can be used for personal identification has been proposed in order to control the entering of any building or facility for safety applications. The network consists of three parts; node carrying by authorized persons, Base Station (BS) to control the entering and gate controller. A Personal Computer (PC), which represented the BS, will display automatically some information like picture and state about the person that entered when he/she becomes in BS coverage area. The gate controller of protected building is received a command of PC after matching the data onto entire person and open by a period to allow only one person to pass the gate after being sensed by Human sensor of controller. While preventing any other body by maintaining the gate in case of closure and show alarm. For the experimental purpose, the control of the gate is virtually assumed as Light-Emitting Diode (LED) to represent the opening and closing by lighting and closing the LED respectively. An Arduino Uno is used as microcontroller and ZigBee S2 is used for communication link, because of their simplicity, small size and low cost. Results of running the proposed model confirmed that it could effectively and accurately control the entry and exit of people authorized to enter the important formation and recording the date and time of entry and exit form the need for intervention by people. On the other hand, it can easily review any person files and show his/her daily attendance.

The study of access point outdoor coverage deployment for wireless digital campus network

Wireless local area network design needs more development to obtain appropriate and effective results. Site surveys in the design process give realistic results, but require time and effort. Developing ways of predicting signal strength using empirical models can give appropriate results in access point placement to get good signal coverage. Geospatial analysis, such as inverse distance weighting, Kriging and global polynomial interpolation, has been compared. This study showed that Kriging analysis is an appropriate method to predict value the coverage area. Furthermore, predictive signal strength models such as classical, empirical and COST 231 Hatta models have been studied. The empirical model was shown to do the best predictive calculations. The empirical model used to predict signal strength combined with Kriging geographical statistical analysis gave usable signal coverage prediction for access point placement. This model will support GIS spatial analysis tools to perform effective planning in access point placement.

Design of Indoor WLANs: Combination of a ray-tracing tool with the BPSO method

This article presents an approach that combines a ray-tracing tool with the binary version of the particle swarm optimization (BPSO) method to the design of infrastructure-mode indoor wireless local area networks (WLANs). This approach uses the power levels of a set of candidate access point (AP) locations obtained with the ray-tracing tool at a mesh of potential receiver locations or test points to allow the BPSO optimizer to carry out the design of the WLAN. For this purpose, several restrictions are imposed through a fitness function that drives the search toward the selection of a reduced number of AP locations and their channel assignments while keeping low transmission power levels. During the design, different coverage priority areas can be defined, and the signal-to-interference ratio (SIR) levels are kept as high as possible to comply with the quality-of-service (QoS) requirements imposed. The performance of this approach in a real scenario at the authors' premises is reported, showing its usefulness.

Testing and Design of Indoor WLAN Using Artificial Intelligence Techniques

In this study, the performance of an indoor Wireless Local Area Network (WLAN) which is installed by using traditional methods and cellular design of a WLAN that is to be installed are tested. To implement the test and design, artificial intelligence methods are used. For the WLAN test, Artificial Neural Network (ANN) is used. Access Points (APs) and receiver coordinates are determined as ANN input parameters and optimum Receive Signal Strength (RSS) have been sought. For WLAN design, the Genetic Algorithm (GA) method is used. Wall structures and AP properties are taken into account to obtain optimum Receive Signal Strengths (RSSs). For the analytic solution of the optimum RSS, the indoor setting is divided into cellular areas. Thus, the most suitable locations for APs and the number of APs are determined. As a result, we have tested the performance of a WLAN, which is installed by means of traditional methods. According the experimental results, the indoor WLAN designed with the GA method has provided better performance. DOI: http://dx.doi.org/10.5755/j01.eee.20.6.7290

Infrastructure of a Wireless Local Area Network: T.Ü. Mehmet Akif Ersoy Lecture Center

Abstract Wireless Local Area Networks (WLAN), is a network structure which is used primarily for establishing connections between servers, printers and other endpoint devices found within smaller scale areas, such as a building or a group of buildings. These structures offer the superior advantages of shared access for applications and devices, means of file-transfer and electronic mail communication to users found within areas which include cafeterias, dormitories or miscellaneous intra-campus applications. The use of WLAN applications has become increasingly common with the integration of these structures into wired networks -especially with intra-campus wired infrastructures- and of new wireless devices that support high-speed communication, thanks to the introduction of the Institute of Electrical and Electronics Engineers (IEEE) 802.11n standard. In this paper the network infrastructure of T.Ü. Mehmet Akif Ersoy Lecture Center -and the established WLAN structure therein- shall be discussed. Experiences and examples obtained from this application will be given along with samples from wireless security policies employed. Keywords: 802.11n, WLAN, Wireless Security, Repeater, Metro Ethernet, WLAN Design.

Design and Evaluation of a Web-Based Tool for Teaching Computer Network Design to Undergraduates

Previous studies have shown that motivating students to learn about local area network (LAN) design can be difficult when presented in the traditional lecture format. To overcome this problem, a Web-based tool (“WebLan-Designer”) was developed as an aid in teaching and learning of LAN design at the introductory level. A WebLan-Designer provides a set of learning resources (tutorials, quizzes, network modeling, network design scenarios, key terms and definitions, and review questions and answers) and assists undergraduate students in learning the basics of both wired and wireless LAN design. The tool is Internet-based and can be accessed at any time so that students can study LAN design at their own pace and convenience. This flexible learning approach contributes positively to distance education and e-learning. The effectiveness of WebLan-Designer is evaluated both formally and informally; positive student and peer feedback indicates that the design and implementation of the tool has been successful and that using WebLan-Designer may have a positive impact on student learning and comprehension.

Agent-Based Optimization for Large Scale WLAN Design

The complex nature of wireless local area networks (WLAN) design has led many of the deployments being done in an ad-hoc fashion without efficient design methodologies. Although this approach may work for a small environment with a small number of access points, it is infeasible to use such a process when designing a larger wireless infrastructure. Due to the low cost that is indicative of WLAN deployments, many practitioners view formal optimization techniques as being too complex and costly to implement. There have been a number of research works that investigate the use of formal optimization techniques for the accurate design of a WLAN. Unfortunately, the approaches taken do not address one major issue when designing a complex and demanding wireless network infrastructure, namely scalability. An optimization algorithm must consider a multitude of design criteria and therefore needs to be scalable to be successfully applied to large scenarios. The main contribution of the work presented in this paper is the development of a scalable optimization algorithm based on the tools of distributed artificial intelligence, which overcomes the failings of current approaches and can be utilized for WLAN design regardless of size or complexity of site specific requirements.

Solving Nonlinear Covering Problems Arising in WLAN Design

Wireless local area networks (WLANs) are widely used for cable replacement and wireless Internet access. Because the medium access control (MAC) scheme of WLANs has a strong influence on network performance, it should be accounted for in WLAN design. This paper presents AP location models that optimize a network performance measure specifically for the MAC scheme of WLANs that represents the efficiency in sharing the wireless medium. For these models, we propose a solution framework based on an effective integer-linear programming Dantzig–Wolfe reformulation. This framework is applicable to any nonlinear covering problem where the objective function is a sum of contributions over the groundset elements (users in WLANs). Extensive computational results show that our solution strategy quickly yields optimal or near-optimal solutions for WLAN design instances of realistic size.

Cross-Layer Design of MIMO-Enabled WLANs With Network Utility Maximization

Wireless local area networks (WLANs) have become a ubiquitous high-speed data-access technology. The recent IEEE 802.11e standard provides quality-of-service (QoS) support, and the pending 802.11n standard further increases the transmission rate by using the multiple-input-multiple-output (MIMO) technique. Multiple antennas can be used to improve the performance gain by either increasing the transmission reliability through spatial diversity or increasing the transmission rate through spatial multiplexing. This new characteristic at the wireless physical (PHY) layer requires the corresponding adaptation at the medium access control (MAC) layer to reach the best performance gain. In this paper, we propose cross-layer design schemes for WLANs under two different MAC protocols: the carrier sense multiple access with collision avoidance (CSMA/CA)-based 802.11e MAC and the slotted Aloha MAC. For the 802.11e MAC, two different contention window (CW) size adaptation schemes, namely, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U-MAC</i> and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D-MAC</i> , are proposed, which facilitate the MAC protocol to jointly adapt its CW size with the PHY layer's MIMO operating parameters. For the slotted Aloha MAC, a cross-layer optimization framework <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NUM-O</i> is proposed to jointly optimize the MIMO configuration at the PHY layer and the persistent probabilities for different classes of multimedia traffic at the MAC layer. A distributed algorithm <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NUM-D</i> based on dual decomposition and a simplified version <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">NUM-S</i> are also proposed. Simulation results are presented to show the effectiveness of the proposed methods.

Using Large-Scale FDTD Method to Obtain Precise Numerical Estimation of Indoor Wireless Local Area Network Office Environment

The Finite-Difference Time-Domain (FDTD) technique is presented in this paper as an estimation method for radio propagation prediction in large and complex wireless local area network (WLAN) environments. Its validity is shown by comparing measurements and Ray-trace method with FDTD data. The 2GHz (802.11b/g) and 5GHz (802.11a) frequency bands are used in both the calculations and experiments. The electric field (E-field) strength distribution has been illustrated in the form of histograms and cumulative ratio graphs. By using the FDTD method to vary the number of human bodies in the environment, the effects on E-field distribution due to human body absorption are also observed for 5GHz WLAN design.

On a new class of nonlinear set covering problems arising in wireless network design

This is a summary of the author’s PhD thesis, supervised by Edoardo Amaldi and defended on 28 April 2006 at Politecnico di Milano, Dipartimento di Matematica. The thesis is written in English and is available from the author upon request. The thesis investigates a class of nonlinear set covering variants arising from the problem of designing single-frequency Wireless Local Area Networks (WLANs) with maximum efficiency. In the first part of the thesis a basic hyperbolic formulation of the problem is considered. After a complexity and approximability study, the problem is tackled by linearization techniques, and by Lagrangean and Dantzig–Wolfe decompositions. The second part of the thesis focuses on variants accounting for various relevant features of the WLAN application. A Branch-and-Price algorithm is presented, and extensions to the multiple-frequency WLAN design problem are considered.

On the wireless local area network design problem with performance guarantees

In this paper, we propose a model for the wireless local area network (WLAN) design problem with performance guarantees. This problem consists of selecting the location of the access points (APs) as well as the power and the channel of each AP. The performance guarantees we refer to are coverage and minimum bandwidth guarantees. Since this problem is NP -hard, we propose a tabu search algorithm to find solutions for real-size instances of the problem. Finally, numerical results are presented. The results show that good solutions can be found with the proposed algorithm in a reasonable amount of time.

Design considerations for minimal-power wireless spread spectrum circuits and systems

Wireless local area networks (WLANs) provide untethered access to digital data in both home and office environments. To preserve mobility for extended periods of time, low power design is a critical enabler. Low-power WLAN design requires consideration at every level from the system topology, protocol, and radio architecture to the detailed circuit design. Every level is required to work together in harmony to gain the maximum in power reduction. This paper discusses the performance requirements and design tradeoffs encountered in the design of minimal-power WLAN systems.