802.11n performance analysis for a real multimedia industrial application

In spite of their limitations, wireless networks are being increasingly used in industrial environments. The electromagnetic phenomena that can occur, along with the interference that may occur due to it being an open medium, mean that fluctuations in latencies are often produced. These drawbacks limit the use of wireless networks for distributed factory applications where timeliness is essential. Recent standards, such as 802.11n, offer some interesting characteristics applicable to factory automation. In particular, QoS support and a very high data rate aids their operation under non-saturation conditions, allowing their satisfactory use as an industrial network. In this paper, the potential of these networks is analyzed in a real world scenario and their performance is compared with an idealized scenario. In both cases the priorities behave as expected, however, the algorithms for an auto-rate functioning perform badly in real world situations, especially in industrial scenarios such as those analyzed here, where the mobility of sources and the interference produced by other sources produce frequent rate changes, leading to a reduction in network performance. (C) 2014 Elsevier B.V. All rights reserved.This work is supported by the MCYT of Spain under the project TIN2013-47272-C2-1-R.Silvestre Blanes, JL.; Berenguer Sebastiá, JR.; Sempere Paya, VM.; Todoli Ferrandis, D. (2015). 802.11n performance analysis for a real multimedia industrial application. Computers in Industry. 66:31-40. https://doi.org/10.1016/j.compind.2014.08.00331406

Average-Value Analysis of 802.11 WLANs with Persistent TCP flows

The widespread use of the IEEE 802.11 MAC as a layer-2 protocol for wireless local area networks has generated an extensive literature on its performance modeling. However, most of the available studies evaluate the capacity of WLANs in saturated conditions, while very little has been done on investigating the interactions between the 802.11 MAC protocol and the various transport protocols that are used to deliver users\u27 traffic. Recently there have been renewed efforts to understand and model the TCP dynamics in 802.11 WLANs. In general, these models employ multi-dimensional discrete-time Markov chains to analyze the distributions of the number of TCP packets enqueued in the stations\u27 buffers. Then, they exploit those distributions to derive both the average number of active TCP stations and the aggregate TCP throughput. However, this approach may rapidly lead to the explosion of the model state-space when the number of TCP flows is large. In this technical report we propose a novel modeling approach by developing an average-value analysis of TCP performance in 802.11 WLANs. Our model intuitively characterizes the equilibrium conditions for the network, and this method yields a precise estimate of the throughput of persistent TCP flows. Extensive simulations validate the accuracy of our analysis

High Performance WLAN Using Smart Antenna

The need for higher data rates in WLANs boosts drastically because tremendous consumer interest in emerging multimedia applications, such as HDTV, has been increased. Currently, the IEEE 802.11a/b/g WLANs provide a limited data rate for the current user application requirements. In order to overcome substantial limitations of the existing WLANs, the next generation of WLANs, IEEE 802.11n, is in the course of development and expected to support higher throughput, larger coverage area and better QoS. The high performance IEEE 802.11n WLAN can improve data rate significantly by using smart antenna systems in the physical layer to take advantage of multi-path fading of wireless channels. In this thesis, an analytical model is developed to study the MAC performance and the underlying smart antenna technologies used in multi-path fading channels. Multiple antennas employed in the AP arise two popular approaches to provide a significant performance improvement, diversity and multiplexing. Considering the diversity gain of multiple antennas at the AP in which the AP with multiple antennas serves one user at a time, the capacity and throughput can be obtained. In addition, the AP is possible to serve multiple users in the downlink, by exploiting the multiplexing gain of the wireless channel. We investigate the maximum network throughput when the traffic intensity of the AP approaches to one. Unlike most of previous research which focus on either the physical or the MAC layer performance, our analytical model jointly considers the MAC protocol and the smart antenna technology

Design, Development, and Implementation of a Wireless Local Area Network (WLAN): The Hartford Job Corps Academy Case Study

Wireless Local Area Networks (WLANs) offer flexibility, mobility, and scalability to educational institutions. Students are increasingly expecting anywhere, anytime access to online resources. Secondary school administrators, who serve a similar population as the National Job Corps Program (NJCP), realize that student success in the 21st century workplace depends upon the student\u27s ability to use new and emerging technologies, including wireless technology. Computer access anytime and anywhere is crucial to the success of students today. Wireless technology has been broadly deployed at educational institutions, such as the Hartford Job Corps Academy (HJCA), but little is known about how these networks are deployed and used, specifically at a Job Corps center. HJCA deployed a WLAN in 2005. Information about the core aspects of the design and implementation of anytime, anywhere initiatives, such as wireless solutions in education, is needed to complement the current research. The NJCP does not have a model for standardizing, organizing, and maintaining wireless networks. The goal of this investigation was to develop a model for planning, designing, and implementing a wireless solution for the Job Corps system. The case study findings from the investigation and the systems development life cycle (SDLC) provided the framework for structuring WLANs at other Job Corps centers. This framework also facilitated the investigation and a determination of the significance of the case study findings, and the analysis and development of the WLAN implementation model for the NJCP. The findings of the HJCA investigation from multiple sources are presented. Using the SDLC framework and the findings from the case study, the NJCP WLAN implementation model is presented. The NJCP WLAN implementation model may be used to facilitate the deployment of WLANs at government-operated, education and training facilities, such as the NJCP

Distributed algorithms for extending the functional lifetime of wireless sensor networks

The functional lifetime of a wireless sensor network (WSN) is among its most important features and serves as an essential metric in the evaluation of its energy-conserving policies. Approaches for extending the lifetime of a wireless sensor node include using an on/off strategy on the sensor nodes and using a topology control algorithm on each node to regulate its transmission power. However, the need to keep the network functional imposes certain additional constraints on strategies for energy conservation. A sensing constraint imposes that the sensing tasks essential to the functionality of the WSN are not compromised. A communication constraint similarly imposes that communications essential to an application on the network remain possible even as battery resources deplete on the nodes. This dissertation presents new distributed algorithms for energy conservation under these two classes of constraints: sensing constraints and communication constraints. One sensing constraint, called the representation constraint in this dissertation, is the requirement that active (on) sensor nodes are evenly distributed in the region of interest covered by the sensor network. This dissertation develops two essential metrics which together allow a rigorous quantitative assessment of the quality of representation achieved by a WSN and presents analytical results which bound these metrics in the common scenario of a planar region of arbitrary shape covered by a sensor network deployment. The dissertation further proposes a new distributed algorithm for energy conservation under the representation constraint. Simulation results show that the proposed algorithm is able to significantly improve the quality of representation compared to other related distributed algorithms. It also shows that improved spatial uniformity has the welcome side-effect of a significant increase in the functional lifetime of a WSN. One communication constraint, called the connectivity constraint, imposes that the network remains connected during its functional life. The connectivity required may be weak (allowing unidirectional communication between nodes) or strong (requiring bidirectional link layer communication between each pair of communicating nodes). This dissertation develops new distributed topology control algorithms for energy conservation under both the strong and the weak connectivity constraint. The proposed algorithm for the more ideal scenario of the weak connectivity constraint uses a game-theoretic approach. The dissertation proves the existence of a Nash equilibrium for the game and computes the associated price of anarchy. Simulation results show that the algorithms extend the network lifetime beyond those achieved by previously known algorithms.Ph.D., Computer engineering -- Drexel University, 201