Mobile, Wireless, and Sensor Networks: Technology, Applications, and Future Directions (IEEE Press) - Hardcover

Hardcover

ISBN 10: 0471718165 ISBN 13: 9780471718161

Verlag: Wiley-IEEE Press, 2006

Inhaltsangabe

This publication represents the best thinking and solutions to a myriad of contemporary issues in wireless networks. Coverage includes wireless LANs, multihop wireless networks, and sensor networks. Readers are provided with insightful guidance in tackling such issues as architecture, protocols, modeling, analysis, and solutions. The book also highlights economic issues, market trends, emerging, cutting-edge applications, and new paradigms, such as middleware for RFID, smart home design, and "on-demand business" in the context of pervasive computing.

Mobile, Wireless, and Sensor Networks is divided into three distinct parts:
* Recent Advances in Wireless LANs and Multihop Wireless Networks
* Recent Advances and Research in Sensor Networks
* Middleware, Applications, and New Paradigms

In developing this collected work, the editors have emphasized two objectives:
* Helping readers bridge the gap and understand the relationship between practice and theory
* Helping readers bridge the gap and understand the relationships and common links among different types of wireless networks

Chapters are written by an international team of researchers and practitioners who are experts and trendsetters in their fields. Contributions represent both industry and academia, including IBM, National University of Singapore, Panasonic, Intel, and Seoul National University.

Students, researchers, and practitioners who need to stay abreast of new research and take advantage of the latest techniques in wireless communications will find this publication indispensable. Mobile, Wireless, and Sensor Networks provides a clear sense of where the industry is now, what challenges it faces, and where it is heading.

Über diesen Titel

Über die Autorin bzw. den Autor

A. ANANDA, PhD, is Associate Professor, Department of Computer Science, National University of Singapore. He has published more than eighty technical papers and is cofounder of Innvo Systems Pte Ltd.

MUN CHOON CHAN, PhD, is Assistant Professor, Department of Computer Science, National University of Singapore. He has published more than twenty technical papers and holds four patents.

WEI TSANG OOI, PhD, is Assistant Professor, Department of Computer Science, National University of Singapore. His research interests focus on multimedia and distributed applications.

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This publication represents the best thinking and solutions to a myriad of contemporary issues in wireless networks. Coverage includes wireless LANs, multihop wireless networks, and sensor networks. Readers are provided with insightful guidance in tackling such issues as architecture, protocols, modeling, analysis, and solutions. The book also highlights economic issues, market trends, emerging, cutting-edge applications, and new paradigms, such as middleware for RFID, smart home design, and "on-demand business" in the context of pervasive computing.

Mobile, Wireless, and Sensor Networks is divided into three distinct parts:

• Recent Advances in Wireless LANs and Multihop Wireless Networks
• Recent Advances and Research in Sensor Networks
• Middleware, Applications, and New Paradigms

In developing this collected work, the editors have emphasized two objectives:

• Helping readers bridge the gap and understand the relationship between practice and theory
• Helping readers bridge the gap and understand the relationships and common links among different types of wireless networks

Chapters are written by an international team of researchers and practitioners who are experts and trendsetters in their fields. Contributions represent both industry and academia, including IBM, National University of Singapore, Panasonic, Intel, and Seoul National University.

Students, researchers, and practitioners who need to stay abreast of new research and take advantage of the latest techniques in wireless communications will find this publication indispensable. Mobile, Wireless, and Sensor Networks provides a clear sense of where the industry is now, what challenges it faces, and where it is heading.

Mobile, Wireless, and Sensor Networks is divided into three distinct parts:

• Recent Advances in Wireless LANs and Multihop Wireless Networks
• Recent Advances and Research in Sensor Networks
• Middleware, Applications, and New Paradigms

In developing this collected work, the editors have emphasized two objectives:

• Helping readers bridge the gap and understand the relationship between practice and theory
• Helping readers bridge the gap and understand the relationships and common links among different types of wireless networks

Chapters are written by an international team of researchers and practitioners who are experts and trendsetters in their fields. Contributions represent both industry and academia, including IBM, National University of Singapore, Panasonic, Intel, and Seoul National University.

Students, researchers, and practitioners who need to stay abreast of new research and take advantage of the latest techniques in wireless communications will find this publication indispensable. Mobile, Wireless, and Sensor Networks provides a clear sense of where the industry is now, what challenges it faces, and where it is heading.

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Mobile, Wireless, and Sensor Networks

Technology, Applications, and Future Directions

John Wiley & Sons

Copyright © 2006 John Wiley & Sons, Inc.
All right reserved.
ISBN: 978-0-471-71816-1

Chapter One

Measuring Wireless LANs

TRISTAN HENDERSON and DAVID KOTZ Department of Computer Science, Dartmouth College, Hanover, New Hampshire

1.1 INTRODUCTION

Wireless local area networks (WLANs) have appeared in many venues, including academic and corporate campuses, residences, and wireless "hotspots." It becomes increasingly important to understand how these networks are used, as they continue to appear in more numerous and varied environments. Measuring and collecting data from production WLANs in a usage study is one way of fulfilling this need for understanding.

Wireless usage studies and usage data are valuable for many aspects of wireless network research. Understanding how and where clients use the network, what applications clients are using, and how applications are using the network can help with network provisioning and deciding where to expand or augment coverage in an existing WLAN. Models of wireless application workloads can aid the design of future network protocols. Measurements of client mobility in a WLAN can help with the design of location-aware applications, or for developing and improving mobile handoff algorithms.

Collecting data on a WLAN can be difficult, however. There are many technical and nontechnical logistical hurdles involved in collecting high-quality wireless measurements. We have been continuously monitoring a campus WLAN for over 3 years in the course of conducting two of the largest wireless measurement studies to date, and we have encountered many of these hurdles. In this chapter we describe some of the tools that the research community has used for measuring WLANs, and provide hints for their effective use obtained from our real-world experiences. We also discuss some of the usage studies that have been conducted using these tools, both on our own campus and elsewhere. In particular we concentrate Mobile, Wireless, and Sensor Networks: Technology, Applications, and Future Directions on the most common type of wireless LAN, the IEEE 802.11 infrastructure network, as this has seen the highest number of deployments, and thus most usage studies have considered infrastructure networks.

This chapter is laid out as follows. In Section 1.2 we examine some of the tools that are available for measuring a WLAN. Section 1.3 surveys various wireless measurement studies, considering both the tools that were used and the insights that were learned. Section 1.4 concludes the chapter with a checklist of items that a potential wireless usage researcher should consider.

1.2 MEASUREMENT TOOLS

The purpose of a wireless usage study is to collect data about the operations of a WLAN. There are several tools available to the researcher for this purpose. The most commonly used tools include syslog, SNMP, network sniffing, authentication logs, and developing client-side applications. Figure 1.1 shows how some of these tools might be deployed in an example WLAN. In this section, we summarize the pros and cons of using each of these tools, and offer some advice from our own experiences.

1.2.1 Syslog

Syslog is a somewhat loosely specified standard for sending and receiving logging messages. Messages can be stored locally or transmitted across a network to another host.

Many 802.11 access points (APs) can be configured to send syslog messages. By choosing appropriate events to be logged, syslog messages can be used to understand the state of clients on the network. For instance, an AP can send a time-stamped syslog message whenever a client authenticates, deauthenticates, associates, disassociates, or roams to that AP. By collecting these syslog messages from all of the APs in a network, it is possible to determine the state of the clients on the network.

Once an AP has been configured to send syslog messages to a particular host, no further information is required from the receiving host. This makes syslog a simple tool to set up. The receiving host, however, must take care to ensure that messages are being received correctly, as network problems, firmware upgrades, or malfunctioning APs, may lead APs failing to send syslog messages.

There is no standard format for a syslog message, and there is also no standard format for an 802.11 syslog message. The messages that APs send can vary in format, and in the amount of information that is contained. Figures 1.2 and 1.3 show two sets of syslog messages. These messages are both taken from the same Cisco Aironet 350 802.11b AP. Figure 1.2 shows messages from the AP when it was running the VxWorks operating system, whereas Figure 1.3 is a set of messages from the AP after it had been upgraded to the Cisco Internetworking Operating System (IOS). Both sets of messages contain the same basic information: client 802.11 events. They differ, however, in the way that this information is presented; in Figure 1.3 there are multiple timestamps (from the syslog daemon and the AP itself), and the client MAC addresses are formatted differently. Parsing syslog messages can therefore be a tedious process, as the format can change between different AP firmware versions. A long-term measurement study should monitor syslog messages for format changes, and also monitor changes in firmware, either through close communication with network administrators, or by using SNMP (see Section 1.2.2).

A further consideration when parsing AP syslog messages is that not all messages may accurately correspond to 802.11 events. Figure 1.4 shows a set of syslog messages from a "wireless switch." This switch is representative of the newest type of 802.11 infrastructure network, where "dumb" APs are deployed across the area to be covered, and a centralized switch handles authentication, association, and access control. In this setup is the switch that sends syslog messages, not the APs. Rather than sending an individual message for each authenticate, associate, roam, disassociate, and deauthenticate event, the switch sends only two types of message: "station up" and "station down." The types of message available from the APs in the WLAN to be measured may impact the suitability of syslog as a measuring tool, depending on the type of data required for the study.

In a mixed AP environment such as ours, with multiple types of AP and thus multiple types of syslog messages, we have found it useful to translate syslog messages into an intermediate format prior to data analysis. Figure 1.5 shows this intermediate format. The time, client MAC address, event, and AP hostname are extracted from the syslog messages. The year is added to the time, as syslog messages do not contain a year, and the time is replaced with a Unix timestamp. Some syslog messages contain only the MAC address of an AP and not the hostname, as in Figure 1.4 (e.g., bssid 00:11:22:33:44:55). For these APs, we keep a separate mapping of AP names to AP MAC addresses, and refer to this when translating syslog messages.

Once the syslog messages have been collected and translated into a parsable format, it is possible to create a state machine that can calculate a session for each MAC address observed in the syslog trace. Figure 1.6 shows the session state machine that we have used in our campus wireless traces. A session consists of an association, followed by zero or more roam events, and ends with a disassociate or deauthenticate event.

This session structure assumes that a MAC...

Details zur Ausgabe

• Verlag: Wiley-IEEE Press
• Erscheinungsdatum: 2006
• Sprache: Englisch
• ISBN 10: 0471718165
• ISBN 13: 9780471718161
• Einband: Gebundene Ausgabe
• Auflage: 1
• Anzahl der Seiten: 456
• Herausgeber: Shorey Rajeev, Ananda A., Chan Mun Choon, Ooi Wei Tsang
• Kontakt zum Hersteller: Wiley-VCH GmbH; product_safety@wiley.com; ; Boschstrasse 12; Weinheim; 69469; Deutschland