the handbook of ad hoc wireless networks

THE HANDBOOK OF
AD HOC
WIRELESS
NETWORKS
CRC PRESS
Boca Raton London New York Washington, D.C.
Edited by
Mohammad Ilyas
Florida Atlantic University
Boca Raton, Florida
THE HANDBOOK OF
AD HOC
WIRELESS
NETWORKS
The Electrical Engineering Handbook Series
Series Editor
Richard C. Dorf
University of California, Davis
Titles Included in the Series
The Handbook of Ad Hoc Wireless Networks, Mohammad Ilyas
The Avionics Handbook, Cary R. Spitzer
The Biomedical Engineering Handbook, 2nd Edition, Joseph D. Bronzino
The Circuits and Filters Handbook, Second Edition, Wai-Kai Chen
The Communications Handbook, 2nd Edition, Jerry Gibson
The Computer Engineering Handbook, Vojin G. Oklobdzija
The Control Handbook, William S. Levine
The Digital Signal Processing Handbook, Vijay K. Madisetti & Douglas Williams
The Electrical Engineering Handbook, 2nd Edition, Richard C. Dorf
The Electric Power Engineering Handbook, Leo L. Grigsby
The Electronics Handbook, Jerry C. Whitaker

The Engineering Handbook, Richard C. Dorf
The Handbook of Formulas and Tables for Signal Processing, Alexander D. Poularikas
The Handbook of Nanoscience, Engineering, and Technology, William A. Goddard, III,
Donald W. Brenner, Sergey E. Lyshevski, and Gerald J. Iafrate
The Industrial Electronics Handbook, J. David Irwin
The Measurement, Instrumentation, and Sensors Handbook, John G. Webster
The Mechanical Systems Design Handbook, Osita D.I. Nwokah and Yidirim Hurmuzlu
The Mechatronics Handbook, Robert H. Bishop
The Mobile Communications Handbook, 2nd Edition, Jerry D. Gibson
The Ocean Engineering Handbook, Ferial El-Hawary
The RF and Microwave Handbook, Mike Golio
The Technology Management Handbook, Richard C. Dorf
The Transforms and Applications Handbook, 2nd Edition, Alexander D. Poularikas
The VLSI Handbook, Wai-Kai Chen
Forthcoming Titles
The CRC Handbook of Engineering Tables, Richard C. Dorf
The Engineering Handbook, Second Edition, Richard C. Dorf
The Handbook of Optical Communication Networks, Mohammad Ilyas and
Hussein T. Mouftah
© 2003 by CRC Press LLC

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Library of Congress Cataloging-in-Publication Data

The handbook of ad hoc wireless netw

orks / edited by Mohammad Ilyas.
p. cm. (The electrical engineering handbook series)
Includes bibliographical references and index.
ISBN 0-8493-1332-5 (alk. paper)
1. Wireless LANs. I. Ilyas, Mohammad, 1953- II. Series
TK5105.78 .H36 2002
621.382 dc21 2002031316
© 2003 by CRC Press LLC

Preface

T

o meet the need for fast and reliable information exchange, communication networks have become an
integral part of our society. The success of any corporation largely depends upon its ability to commu
-
nicate. Ad hoc wireless networks will enhance communication capability significantly by providing
connectivity from anywhere at any time. This handbook deals with wireless communication networks
that are mobile and do not need any infrastructure. Users can establish an ad hoc wireless network on
a temporary basis. When the need disappears, so will the network.
As the field of communications networks continues to evolve, a need for wireless connectivity and
mobile communication is rapidly emerging. In general, wireless communication networks provide wire
-
less (and hence) mobile access to an existing communication network with a well-defined infrastructure.
Ad hoc wireless networks provide mobile communication capability to satisfy a need of a temporary
nature and without the existence of any well-defined infrastructure. In ad hoc wireless networks, com
-

munication devices establish a network on demand for a specific duration of time. Such networks have
many potential applications including the following:
•Disaster recovery situations
•Defense applications (army, navy, air force)
•Healthcare
•Academic institutions
•Corporate conventions/meetings
This handbook has been prepared to fill the need for comprehensive reference material on ad hoc
wireless networks. The material presented in this handbook is intended for professionals who are design
-
ers and/or planners for emerging telecommunication networks, researchers (faculty members and grad-
uate students), and those who would like to learn about this field.
The handbook is expected to serve as a source of comprehensive reference material on ad hoc wireless
networks. It is organized in the following nine parts:
•Introduction
•Wireless transmission techniques
•Wireless communication systems and protocols
•Routing techniques in ad hoc wireless networks — part I
•Routing techniques in ad hoc wireless networks — part II
•Applications of ad hoc wireless networks
•Power management in ad hoc wireless networks
•Connection and traffic management in ad hoc wireless networks
•Security and privacy aspects of ad hoc wireless networks
© 2003 by CRC Press LLC

T

he handbook has the following specific salient features:
•It serves as a single comprehensive source of information and as reference material on ad hoc
wireless networks.

•It deals with an important and timely topic of emerging communication technology of tomorrow.
•It presents accurate, up-to-date information on a broad range of topics related to ad hoc wireless
networks.
•It presents material authored by experts in the field.
•It presents the information in an organized and well-structured manner.
Although the handbook is not precisely a textbook, it can certainly be used as a textbook for graduate
courses and research-oriented courses that deal with ad hoc wireless networks. Any comments from
readers will be highly appreciated.
Many people have contributed to this handbook in their unique ways. The first and foremost group
that deserves immense gratitude is the group of highly talented and skilled researchers who have con
-
tributed 32 chapters. All of them have been extremely cooperative and professional. It has also been a
pleasure to work with Nora Konopka, Helena Redshaw, and Susan Fox of CRC Press, and I am extremely
grateful for their support and professionalism. My wife Parveen and my four children Safia, Omar, Zakia,
and Maha have extended their unconditional love and strong support throughout this project, and they
all deserve very special thanks.

Mohammad Ilyas

B

oca Raton, Florida
© 2003 by CRC Press LLC

The Editor

M

ohammad Ilyas

is a professor of computer science and engineering at Florida Atlantic University, Boca
Raton, Florida. He received his B.Sc. degree in electrical engineering from the University of Engineering
and Technology, Lahore, Pakistan, in 1976. In 1978, he was awarded a scholarship for his graduate studies,
and he completed his M.S. degree in electrical and electronic engineering in June 1980 at Shiraz University,
Shiraz, Iran. In September 1980, he joined the doctoral program at Queen’s University in Kingston,
Ontario. He completed his Ph.D. degree in 1983. His doctoral research was about switching and flow
control techniques in computer communication networks. Since September 1983, he has been with the
College of Engineering at Florida Atlantic University. From 1994 to 2000, he was chair of the Department
of Computer Science and Engineering. During the 1993–94 academic year, he spent a sabbatical leave
with the Department of Computer Engineering, King Saud University, Riyadh, Saudi Arabia.
Dr. Ilyas has conducted successful research in various areas including traffic management and con-
gestion control in broadband/high-speed communication networks, traffic characterization, wireless
communication networks, performance modeling, and simulation. He has published one book and more
than 120 research articles. He has supervised several Ph.D. dissertations and M.S. theses to completion.
He has been a consultant to several national and international organizations. Dr. Ilyas is an active
participant in several IEEE technical committees and activities and is a senior member of IEEE.
© 2003 by CRC Press LLC

List of Contributors

Geor

ge N. Aggélou

I

nstitute of Technology
Athens, Greece

Rober

to Baldoni

U

niversita’ di Roma, “La Sapienza”
Roma, Italy

Rober

to Beraldi

U

niversita’ di Roma, “La Sapienza”
Roma, Italy

Ezio Biglieri

P

olitecnico di Torino
To r ino, Italy

Satyabrata Chakrabar

ti

S

ylvaine Algorithmics
Aurora, Illinois

Chaou-T

ang Chang

N

ational Chiao Tung University
Hsinchu, Taiwan

Chih Min Chao

N

ational Central University
Chung-Li, Taiwan

Xiao Chen

S

outhwest Texas State University
San Marcos, Texas

Chua Kee Chaing

N

ational University of Singapore
Singapore, Singapore

Marco Conti

C

onsiglio Nazionale delle Ricerche
Pisa, Italy

José Fer

reira de
Rezende

F

ederal University of Rio de Janeiro
Rio de Janeiro, Brazil

Nelson Fonseca

Stat

e University of Campinas
Campinas, Brazil

Holger Füßler

U

niversity of Mannheim
Mannheim, Germany

Silvia Giordano

L

CA-IC-EPFL
Lausanne, Switzerland

Zygmunt J. Haas

C

ornell University
Ithaca, New York

Hannes Har

tenstein

NEC E

urope Ltd.
Heidelberg, Germany

Xiao Hannan

N

ational University of Singapore
Singapore, Singapore

Hossam S. Hassanein

Que

en's University
Kingston, Ontario, Canada

Chih-Shun Hsu

N

ational Central University
Chung-Li, Taiwan

Cheng-T

a Hu

N

ational Central University
Chung-Li, Taiwan

Pei-Kai Hung

N

ational Central University
Chung-Li, Taiwan

Aditya Kar

nik

I

ndian Institute of Science
Bangalore, India

W

on-Ik Kim

ETRI

T

aejon, South Korea

Anurag Kumar

I

ndian Institute of Science
Bangalore, India

Dong-Hee Kwon

POSTECH

P

ohang, South Korea

Chiew-T

ong Lau

N

anyang Technological University
Singapore, Singapore

Ben Lee

Or

egon State University
Corvallis, Oregon

Bu-Sung Lee

N

anyang Technological University
Singapore, Singapore

Bo Li

H

ong Kong University of Science
and Technology
Kowloon, Hong Kong

Michele Lima

Stat

e University of Parana West
Cascavel, Brazil
© 2003 by CRC Press LLC

T

ing-Yu Lin

N

ational Chiao-Tung University
Hsinchu, Taiwan

Jiang Chuan Liu

H

ong Kong University of Science
and Technology
Kowloon, Hong Kong

Pascal Lorenz

U

niverstiy of Haute Alsace
Colmar, France

Mar

tin Mauve

U

niversity of Mannheim
Mannheim, Germany

Amitabh Mishra

V

irginia Polytechnic Institute and
State University
Blacksburg, Virginia

Sangman Moh

ETRI

T

aejon, South Korea

Hussein T

. Mouftah

Que

en's University
Kingston, Ontario, Canada

Ketan M. Nadkar

ni

V

irginia Polytechnic Institute and
State University
Blacksburg, Virginia

Panagiotis

Papadimitratos

C

ornell University
Ithaca, New York

Marc R. Pearlman

C

ornell University
Ithaca, New York

Matthew Sadiku

P

rairie View A&M University
Prairie View, Texas

Ahmed M. Safwat

Que

en's University
Kingston, Ontario, Canada

Prince Samar

C

ornell University

Ithaca, New York

Boon-Chong Seet

N

anyang Technological University
Singapore, Singapore

Jang-Ping Sheu

N

ational Central University
Chung-Li, Taiwan

Y

antai Shu

T

ianjin University
Tianjin, People’s Republic of China

Kazem Sohraby

Lucent Technologies
Lincroft, New Jersey
Ivan Stojmenovic

University of Ottawa
Ottawa, Ontario, Canada
Young-Joo Suh
POSTECH
Pohang, South Korea
Yu-Chee Tseng
National Chiao-Tung University
Hsinchu, Taiwan
Kuochen Wang
National Chiao Tung University
Hsinchu, Taiwan
Lei Wang
Tianjin University
Tianjin, People’s Republic of China
Jörg Widmer
University of Mannheim
Mannheim, Germany
Seah Khoon Guan
Winston
National University of Singapore
Singapore, Singapore
Jie Wu
Florida Atlantic University
Boca Raton, Florida
Oliver Yang
University of Ottawa
Ottawa, Ontario, Canada
Sal Yazbeck
Barry University
Palm Beach Gardens, Florida

Hee Yong Youn
Sungkyunkwan University
Jangangu Chunchundong, South
Korea
Chansu Yu
Cleveland State University
Cleveland, Ohio
Qian Zhang
Microsoft Research
Beijing, People’s Republic of China
Dan Zhou
Florida Atlantic University
Boca Raton, Florida
Wenwu Zhu
Microsoft Research
Beijing, People’s Republic of China
© 2003 by CRC Press LLC

T

able of Contents

1



B

ody, Personal, and Local Ad Hoc Wireless Networks

M

arco Conti

2

M

ulticasting Techniques in Mobile Ad Hoc Networks

X

iao Chen
and Jie Wu

3

Qualit

y of Service in Mobile Ad Hoc Networks

Sat

yabrata Chakrabarti and Amitabh Mishra

4

P

ower-Conservative Designs in Ad Hoc Wireless Networks

Y

u-Chee Tseng
and Ting-Yu Lin



5

P

erformance Analysis of Wireless Ad Hoc Networks

A

nurag Kumar
and Aditya Karnik

6



C

oding for the Wireless Channel

Ezio Big

lieri

7

U

nicast Routing Techniques for Mobile Ad Hoc Networks

R

oberto Beraldi
and Roberto Baldoni

8



S

atellite Communications



M

atthew N.O. Sadiku

9



W

ireless Communication Protocols



P

ascal Lorenz

10

A

n Integrated Platform for Ad Hoc GSM Cellular Communications


George N. Aggélou

11

IEEE 802.11 and B

luetooth: An Architectural Overview

Sal

Yazbeck



12

P

osition-Based Routing in Ad Hoc Wireless Networks

Jörg Widmer, Martin Mauve,
Hannes Hartenstein, and Holger Füßler

© 2003 by CRC Press LLC

13

St

ructured Proactive and Reactive Routing for Wireless Mobile Ad Hoc
Networks



A

hmed M. Safwat, Hossam S. Hassanein, and Hussein T. Mouftah

14

Hybrid Routing: The Pursuit of an Adaptable and Scalable Routing Framework
for Ad Hoc Networks



P

rince Samar, Marc R. Pearlman, and Zygmunt J. Haas

15

A

daptive Routing in Ad Hoc Networks



Y

antai Shu, Oliver Yang,
and Lei Wang

16

P

osition-Based Ad Hoc Routes in Ad Hoc Networks

S

ilvia Giordano
and Ivan Stojmenovic

1

7

R

oute Discovery Optimization Techniques in Ad Hoc Networks



B

oon-Chong Seet, Bu-Sung Lee, and Chiew-Tong Lau



18

L

ocation-Aware Routing and Applications of Mobile Ad Hoc Networks

Yu-Chee Tseng and Chih-Sun Hsu

19



Mobility over Transport Control Protocol/Internet Protocol (TCP/IP)

J

osé Ferreira de Rezende, Michele Mara de Araújo Espíndula Lima, and
Nelson Luis Saldanha da Fonseca



20

A

n Intelligent On-Demand Multicast Routing Protocol in Ad Hoc Networks




Kuochen Wang and Chaou-Tang Chang

21



GPS-Based Reliable Routing Algorithms for Ad Hoc Networks

Yo ung-Joo Suh, Won-Ik Kim, and Dong-Hee Kwon

22

P

ower-Aware Wireless Mobile Ad Hoc Networks



A

hmed Safwat, Hossam S. Hassanein,
and Hussein T. Mouftah

23

Ene

rgy Efficient Multicast in Ad Hoc Networks



H

ee Yong Youn, Chansu Yu, Ben Lee,
and Sangman Moh

24

Energy-Conserving Grid Routing Protocol in Mobile Ad Hoc Networks

J

ang-Ping Sheu, Cheng-Ta Hu, and Chih-Min Chao

25



Routing Algorithms for Balanced Energy Consumption in Ad Hoc Networks

H

ee Yong Youn, Chansu Yu, and Ben Lee

© 2003 by CRC Press LLC

26



Resource Discovery in Mobile Ad Hoc Networks



J

iangchuan Liu, Kazem Sohraby,
Qian Zhang, Bo Li, and Wenwu Zhu

27



An Integrated Platform for Quality-of-Service Support in Mobile Multimedia
Clustered Ad Hoc Networks

G

eorge N. Aggélou



28



Quality of Service Models for Ad Hoc Wireless Networks

X

iao Hannan, Chua
Kee Chaing, and Seah Khoon Guan Winston
29 Scheduling of Broadcasts in Multihop Wireless Networks Jang-Ping Sheu,
Pei-Kai Hung, and Chih-Shun Hsu
30 Security in Wireless Ad Hoc Networks — A Survey Amitabh Mishra
and Ketan M. Nadkarni

31 Securing Mobile Ad Hoc Networks Panagiotis Papadimitratos
and Zygmunt J. Haas
32 Security Issues in Ad Hoc Networks Dan Zhou
© 2003 by CRC Press LLC

© 2003 by CRC Press LLC

1

Body, Personal, and


Local Ad Hoc Wireless

Networks

A

bstract
1.1 Introduction
1.2 Mobile Ad Hoc Networks

B

ody Area Network • Personal Area Network • Wireless Local
Area Network

1.3

Technologies for Ad Hoc Networks

1.4 IEEE 802.11 Architecture and Protocols

EEE 802.11 D

CF • EEE 802.11 RTS/CTS

1.5

A Technology for WBAN and WPAN: Bluetooth

A B

luetooth Network • Bluetooth Data Transmission

A

cknowledgment
References

Abstract

A mo

bile ad hoc network (MANET) represents a system of wireless mobile nodes that can freely and
dynamically self-organize into arbitrary and temporary network topologies, allowing people and devices
to seamlessly internetwork in areas without any preexisting communication infrastructure. While many
challenges remain to be resolved before large scale MANETs can be widely deployed, small-scale mobile
ad hoc networks will soon appear. Network cards for single-hop ad hoc wireless networks are already on
the market, and these technologies constitute the building blocks to construct small-scale ad hoc networks
that extend the range of single-hop wireless technologies to few kilometers. It is therefore important to

understand the qualitative and quantitative behavior of single-hop ad hoc wireless networks. The first
part of this chapter presents the taxonomy of single-hop wireless technologies. Specifically, we introduce
the concept of Body, Personal, and Local wireless networks, and we discuss their applicative scenarios.
The second part of the chapter focuses on the emerging networking standards for constructing small-
scale ad hoc networks: IEEE 802.11 and Bluetooth. The IEEE 802.11 standard is a good platform to
implement a single-hop local ad hoc network because of its extreme simplicity. Furthermore, multi-hop
networks covering areas of several square kilometers could be built by exploiting the IEEE 802.11
technology. On smaller scales, the Bluetooth technologies can be exploited to build ad hoc wireless
Personal and Body Area Networks, i.e., networks that connect devices placed on a person’s body or inside
a small circle around it. The chapter presents the architectures and protocols of IEEE 802.11 and
Bluetooth. In addition, the performance of these two technologies is discussed.

Marco Conti

Consiglio Nazionale delle Ricerche

© 2003 by CRC Press LLC

1.1

Introduction

I

n recent years, the proliferation of mobile computing devices (e.g., laptops, handheld digital devices,
personal digital assistants [PDAs], and wearable computers) has driven a revolutionary change in the
computing world. As shown in Fig. 1.1, we are moving from the Personal Computer (PC) age (i.e., one
computing device per person) to the Ubiquitous Computing age in which individual users utilize, at the
same time, several electronic platforms through which they can access all the required information
whenever and wherever they may be [47]. The nature of ubiquitous devices makes wireless networks the

easiest solution for their interconnection. This has led to rapid growth in the use of wireless technologies
for the Local Area Network (LAN) environment. Beyond supporting wireless connectivity for fixed,
portable, and moving stations within a local area, wireless LAN (WLAN) technologies can provide a
mobile and ubiquitous connection to Internet information services [10]. It is foreseeable that in the not-
so-distant future, WLAN technologies will be utilized largely as means to access the Internet.
WLAN products consume too much power and have excessive range for many personal consumer
electronic and computer devices [40]. A new class of networks is therefore emerging:

Personal Area
Networks

. A Personal Area Network (PAN) allows the proximal devices to dynamically share information
with minimum power consumption [49].
LANs and PANs do not meet all the networking requirements of ubiquitous computing. Situations
exist where carrying and holding a computer are not practical (e.g., assembly line work). A wearable
computer solves these problems by distributing computer components (e.g., head-mounted displays,
microphones, earphones, processors, and mass storage) on the body [21,49]. Users can thus receive job-
critical information and maintain control of their devices while their hands remain free for other work.
A network with a transmission range of a human body, i.e., a

Body Area Network

(BAN), constitutes the
best solution for connecting wearable devices. Wireless connectivity is envisaged as a natural solution
for BANs.
One target of the ubiquitous computing revolution is the ability of the technology to adapt itself to the
user without requiring that users modify their behavior and knowledge. PCs provided to their users a
large set of new services that revolutionized their lives. However, to exploit the PC’s benefits, users have
had to adapt themselves to PC standards. The new trend is to help users in everyday life by exploiting
technology and infrastructures that are hidden in the environment and do not require any major change

in the users’ behavior. This new philosophy is the basis of the

ambient intelligence

concept [1]. The objective
of ambient intelligence is the integration of digital devices and networks into the everyday environment.
This will render accessible, through easy and “natural” interactions, a multitude of services and applica
-
tions. Ambient intelligence places the user at the center of the information society. This view heavily relies
on wireless and mobile communications [36,37]. Specifically, advances in
wireless communication will

F

IGURE 1.1

F

rom PC age (one-to-one) to ubiquitous computing (one-to-many).
Personal
Computing
Ubiquitous
Computing

© 2003 by CRC Press LLC

e

nable a radical new communication paradigm: self-organized information and communication systems
[17]. In this new networking paradigm, the users’ mobile devices are the network, and they must coop

-
eratively provide the functionality that is usually provided by the network infrastructure (e.g., routers,
switches, and servers). Such systems are sometimes referred to as mobile ad hoc networks (MANETs) [33]
or as infrastructure-less wireless networks.

1.2

Mobile Ad Hoc Networks

A

Mobile Ad hoc NETwork (MANET) is a system of wireless mobile nodes that dynamically self-organize
in arbitrary and temporary network topologies. People and vehicles can thus be internetworked in areas
without a preexisting communication infrastructure or when the use of such infrastructure requires
wireless extension [17].
As shown in Fig. 1.2, we can classify ad hoc networks, depending on their coverage area, into four
main classes: Body, Personal, Local, and Wide Area Networks.
Wide area ad hoc networks are mobile multi-hop wireless networks. They present many challenges
that are still to be solved (e.g., addressing, routing, location management, security, etc.), and they are
not likely to become available for some time. On smaller scales, mobile ad hoc networks will soon appear
[6]. Specifically, ad hoc, single-hop BAN, PAN, and LAN wireless networks are beginning to appear on
the market. These technologies constitute the building blocks to construct small multi-hop ad hoc
networks that extend the range of the ad hoc networks’ technologies over a few radio hops [16,17].

1.2.1

Body Area Network

A B

ody Area Network is strongly correlated with wearable computers. The components of a wearable
computer are distributed on the body (e.g., head-mounted displays, microphones, earphones, etc.), and
a BAN provides the connectivity among these devices. Therefore, the main requirements of a BAN are
[18,19]:
1. The ability to interconnect heterogeneous devices, ranging from complete devices (e.g., a mobile
phone) to parts of a device (microphone, display, etc.)
2. Autoconfiguration capability (Adding or removing a device from a BAN should be transparent to
the user.)
3. Services integration (Isochronous data transfer of audio and video must coexist with non–real
time data, e.g., Internet data traffic.)
4. The ability to interconnect with the other BANs (to exchange data with other people) or PANs
(e.g., to access the Internet)
The communicating range of a BAN corresponds to the human body range, i.e., 1–2 meters. As wiring
a body is generally cumbersome, wireless technologies constitute the best solution for interconnecting
wearable devices.

F

IGURE 1.2

A

d hoc networks taxonomy.
LAN WAN
~1m ~10m ~500m Range
BAN
PAN

© 2003 by CRC Press LLC

One o

f the first examples of BAN is the prototype developed by T.G. Zimmerman [48], which could
provide data communication (with rates up to 400,000 bits per second) by exploiting the body as the
channel. Specifically, Zimmerman showed that data can be transferred through the skin by exploiting a
very small current (one billionth of an amp). Data transfer between two persons (i.e., BAN interconnec
-
tion) could be achieved through a simple handshake.
A less visionary BAN prototype was developed in the framework of the MIThril



project where a wired
Ethernet network was adopted to interconnect wearable devices [35].
Marketable examples of BANs have just appeared (see [19], [32], and [38]). These examples consist
of a few electronic devices (phone, MP3 player, headset, microphone, and controller), which are directly
connected by wires integrated within a jacket. In the future, it might be expected that more devices (or
parts of devices) will be connected using a mixture of wireless and wired technologies.

1.2.2

Personal Area Network

P

ersonal area networks connect mobile devices carried by users to other mobile and stationary devices.
While a BAN is devoted to the interconnection of one-person wearable devices (see part a of Fig. 1.3),
a PAN is a network in the environment around the person. A PAN communicating range is typically up
to 10 meters, thus enabling (see part b of Fig. 1.3):
1. The interconnection of the BANs of people close to each other

2. The interconnection of a BAN with the environment around it
Wireless PAN (WPAN) technologies in the 2.4 GHz ISM



band ar

e the most promising technologies
for widespread PAN



d

eployment. Spread spectrum is typically employed to reduce interference and utilize
the bandwidth.
The technologies for WPANs offer a wide space for innovative solutions and applications that could
create radical changes in everyday life. We can foresee that a WPAN interface will be embedded not only
in such devices as cellular phones, mobile computers, PDAs, and so on, but in every digital device. Obvious
applications arise from the possibility of forming ad hoc networks with our workspace electronic devices,
e.g., a PDA that automatically synchronizes with the desktop computer to transfer e-mail, files, and
schedule information. Moreover, PANs make possible the design of innovative pervasive applications. For
example, let us imagine a PDA (with a PAN interface) that upon your arrival at a location (e.g., home,
office, airport, etc.) automatically synchronizes (via the PAN network interface) with all the electronic
devices within its 10-meter range. For example, when you arrive at home, your PDA can automatically
unlock the door, turn on the house lights while you are getting in, and adjust the heat or air conditioning
to your preset preferences. Similarly, when you arrive at the airport you can avoid the line at the check-
in desk by using your handheld device
to present an electronic ticket and automatically select your seat.

(a)

(b)

F

IGURE 1.3

R

elationship between a Body (part a) and a Personal Area Network (part b).

© 2003 by CRC Press LLC

1.2.3

Wireless Local Area Network

I

n the last few years, the use of wireless technologies in the LAN environment has become more and
more important, and it is easy to foresee that the wireless LANs (WLANs) — as they offer greater flexibility
than wired LANs — will be the solution for home and office automation.
Like wired LANs, a WLAN has a communication range typical of a single building or a cluster of
buildings, i.e., 100–500 meters.
A WLAN should satisfy the same requirements typical of any LAN, including high capacity, full
connectivity among attached stations, and broadcast capability. However, to meet these objectives,
WLANs should be designed to face some issues specific to the wireless environment, such as security on
the air, power consumption, mobility, and bandwidth limitation of the air interface [39].
Two different approaches can be followed in the implementation of a WLAN (see Fig. 1.4): an

infra-
structure-based

approach or an

ad hoc networking

approach [39]. An infrastructure-based architecture
imposes the existence of a centralized controller for each cell, often referred to as the

Access Point

(see
Fig. 1.4b). The Access Point is normally connected to the wired network, thus providing Internet access
to mobile devices. In contrast, an ad hoc network is a peer-to-peer network formed by a set of stations
within the range of each other that dynamically configure themselves to set up a temporary network (see
Fig. 1.4a). In the ad hoc configuration, no fixed controller is required, but a controller is dynamically
elected among all the stations participating in the communication.

1.3

Technologies for Ad Hoc Networks

T

he success of a network technology is connected to the development of networking products at a com-
petitive price. A major factor in achieving this goal is the availability of appropriate networking standards.
Currently, two main standards are emerging for ad hoc wireless networks: the IEEE 802.11 standard for
WLANs [25] and the Bluetooth specifications

1

f

or short-range wireless communications [3,4,34].
The IEEE 802.11 standard is a good platform for implementing a single-hop WLAN ad hoc network
because of its extreme simplicity. Multi-hop networks covering areas of several square kilometers could
also be built by exploiting the IEEE 802.11 technology. On smaller scales, technologies such as Bluetooth
can be used to build ad hoc wireless Body and Personal Area Networks, i.e., networks that connect devices
on the person, or placed around the person inside a circle with a radius of 10 meters.

(a)

(b)

F

IGURE 1.4

WL

AN configurations: (a) ad hoc networking; (b) infrastructure-based.

1



The Bluetooth specifications are released by the Bluetooth Special Interest Group [12].
Server

Legend:
access point
wired network

© 2003 by CRC Press LLC

H

ere we present the architecture and protocols of IEEE 802.11 and Bluetooth. In addition, the per-
formances of these technologies are analyzed. Two main performance indices will be considered: the
throughput and the delay.
As far as throughput is concerned, special attention will be paid to the Medium Access Control (MAC)
protocol capacity [15,30], defined as the maximum fraction of channel bandwidth used by successfully
transmitted messages. This performance index is important because the bandwidth delivered by wireless
networks is much lower than that of wired networks, e.g., 1–11 Mb/sec vs. 100–1000 Mb/sec [39]. Since
a WLAN relies on a common transmission medium, the transmissions of the network stations must be
coordinated by the MAC protocol. This coordination can be achieved by means of control information
that is carried explicitly by control messages traveling along the medium (e.g., ACK messages) or can be
provided implicitly by the medium itself using the carrier sensing to identify the channel as either active
or idle. Control messages or message retransmissions due to collision remove channel bandwidth from
that available for successful message transmission. Therefore, the capacity gives a good indication of the
overheads required by the MAC protocol to perform its coordination task among stations or, in other
words, of the effective bandwidth that can be used on a wireless link for data transmission.
The delay can be defined in several forms (access delay, queuing delay, propagation delay, etc.) depend-
ing on the time instants considered during its measurement (see [15]). In computer networks, the
response time (i.e., the time between the generation of a message at the sending station and its reception
at the destination station) is the best value to measure the Quality of Service (QoS) perceived by the
users. However, the response time depends on the amount of buffering inside the network, and it is not
always meaningful for the evaluation of a LAN technology. For example, during congested periods, the
buffers fill up, and thus the response time does not depend on the LAN technology but it is mainly a

function of the buffer length. For this reason, hereafter, the MAC delay index is used. The MAC delay
of a station in a LAN is defined as the time between the instant at which a packet comes to the head of
the station transmission queue and the end of the packet transmission [15].

1.4

IEEE 802.11 Architecture and Protocols

I

n 1997, the IEEE adopted the first wireless local area network standard, named IEEE 802.11, with data
rates up to 2 Mb/sec [27]. Since then, several task groups (designated by letters) have been created to
extend the IEEE 802.11 standard. Task groups 802.11b and 802.11a have completed their work by
providing two relevant extensions to the original standard [25]. The 802.11b task group produced a
standard for WLAN operations in the 2.4 GHz band, with data rates up to 11 Mb/sec. This standard,
published in 1999, has been very successful. Currently, there are several IEEE 802.11b products available
on the market. The 802.11a task group created a standard for WLAN operations in the 5 GHz band,
with data rates up to 54 Mb/sec. Among the other task groups, it is worth mentioning task group 802.11e
(which attempts to enhance the MAC with QoS features to support voice and video over 802.11 networks)
and task group 802.11g (which is working to develop a higher-speed extension to 802.11b).
The IEEE 802.11 standard specifies a MAC layer and a physical layer for WLANs (see Fig. 1.5). The
MAC layer provides to its users both contention-based and contention-free access control on a variety
of physical layers. Specifically, three different technologies can be used at the physical layer: infrared,
frequency hopping spread spectrum, and direct sequence spread spectrum [27].
The basic access method in the IEEE 802.11 MAC protocol is the

Distributed Coordination Function

(DCF), which is a

Carrier Sense Multiple Access with Collision Avoidance

(CSMA/CA) MAC protocol.
Besides the DCF, the IEEE 802.11 also incorporates an alternative access method known as the

Point
Coordination Function

(PCF). The PCF operates similarly to a polling system [15]; a point coordinator
provides (through a polling mechanism) the transmission rights at a single station at a time. As the PCF
access method cannot be adopted in ad hoc networks, in the following we will concentrate
on the DCF
access method only.

© 2003 by CRC Press LLC

1.4.1

IEEE 802.11 DCF

T

he DCF access method, hereafter referred to as

Basic Access

, is summarized in Fig. 1.6. When using the
DCF, before a station initiates a transmission, it senses the channel to determine whether another station
is transmitting. If the medium is found to be idle for an interval that exceeds the

Distributed InterFrame
Space

(DIFS), the station continues with its transmission.

2

T

he transmitted packet contains the projected
length of the transmission. Each active station stores this information in a local variable named

Network
Allocation Vector

(NAV). Therefore, the NAV contains the period of time the channel will remain busy
(see Fig. 1.6a).

3

T

he CSMA/CA protocol does not rely on the capability of the stations to detect a collision by hearing
their own transmissions. Hence, immediate positive acknowledgments are employed to ascertain the
successful reception of each packet transmission. Specifically, the receiver after the reception of the data
frame (1) waits for a time interval, called the

Short InterFrame Space

(SIFS), which is less than the DIFS,

and then (2) initiates the transmission of an acknowledgment (ACK) frame. The ACK is not transmitted
if the packet is corrupted or lost due to collisions. A Cyclic Redundancy Check (CRC) algorithm is
adopted to discover transmission errors. Collisions among stations occur when two or more stations
start transmitting at the same time (see Fig. 1.6b). If an acknowledgment is not received, the data frame
is presumed to have been lost, and a retransmission is scheduled.

F

IGURE 1.5

IEEE 802.11 ar

chitecture.

(a) (b)

F

IGURE 1.6

IEEE 802.11 D

CF: (a) a successful transmission; (b) a collision.

2

T

o guarantee fair access to the shared medium, a station that has just transmitted a packet and has another
packet ready for transmission must perform the backoff procedure before initiating the second transmission.

3

T

his prevents a station from listening to the channel during transmissions. This feature is useful to implement
(among others) power-saving policies.
Point Coordination
Function
Physical Layer
contention free
services
contention
services
Distributed Coordination
Function
DATA
ACK
NAV
CW
DIFS
DIFS
SIFS
Source
Destination
Other
Collision Length =L
A
DIFS
EIFS

A
CW
A
CW
B
CW
C
B
C
LA
LB
LC

© 2003 by CRC Press LLC

A

fter an erroneous frame is detected (due to collisions or transmission errors), the channel must
remain idle for at least an

Extended InterFrame Space

(EIFS) interval before the stations reactivate the
backoff algorithm to schedule their transmissions (see Fig. 1.6b).
To reduce the collision probability, the IEEE 802.11 uses a mechanism (

backoff mechanism

) that
guarantees a time spreading of the transmissions.

When a station

S

, with a packet ready for transmission, observes a busy channel, it defers the
transmission until the end of the ongoing transmission. At the end of the channel busy period, the
station

S

initializes a counter (called the

backoff timer

) by selecting a random interval (

backoff interval

)
for scheduling its transmission attempt.



The backoff timer is decreased for as long as the channel is
sensed as idle, stopped when a transmission is detected on the channel, and reactivated when the channel
is sensed as idle again for more than a DIFS. The station transmits when the backoff timer reaches zero.
Specifically, the DCF adopts a slotted binary exponential backoff technique. The time immediately
following an idle DIFS or EIFS is slotted, and a station is allowed to transmit only at the beginning of
each

Slot Time

.

4

T

he backoff time is uniformly chosen in the interval (0,

CW –

1), defined as the Backoff
Window, also referred to as the

Contention Window

. At the first transmission attempt

CW

=

CW

min

,

and

then

CW

is doubled at each retransmission up to

CW

max

.

The

CW

min

and

CW

max

v

alues depend on the
physical layer adopted. For example, for the frequency hopping, CW

min

and

CW

max

ar

e 16 and 1024,
respectively [27].
An IEEE 802.11 WLAN can be implemented with the access points (i.e., infrastructure based) or with
the ad hoc paradigm. In the IEEE 802.11 standard, an ad hoc network is called an

Independent Basic
Service Set

(IBSS). An IBSS enables two or more IEEE 802.11 stations to communicate directly without
requiring the intervention of a centralized access point or an infrastructure network. Due to the flexibility
of the CSMA/CA algorithm, synchronization (to a common clock) of the stations belonging to an IBSS
is sufficient for correct receipt or transmission of data. The IEEE 802.11 uses two main functions for the
synchronization of the stations in an IBSS: (1) synchronization acquisition and (2) synchronization
maintenance.
Synchronization Acquisition — This functionality is necessary for joining an existing IBSS. The
discovery of existing IBSSs is the result of a scanning procedure of the wireless medium. During the
scanning, the station receiver is tuned on different radio frequencies, searching for particular control
frames. Only if the scanning procedure does not result in finding any IBSS may the station initialize a
new IBSS.
Synchronization Maintenance — Because of the lack of a centralized station that provides its own
clock as common clock, the synchronization function is implemented via a distributed algorithm that

shall be performed by all of the members of the IBSS. This algorithm is based on the transmission of
beacon frames at a known nominal rate. The station that initialized the IBSS decides the beacon interval.
1.4.1.1 IEEE 802.11 DCF Performance
In this section we present a performance analysis of the IEEE 802.11 basic access method by analyzing
the two main performance indices: the capacity and the MAC delay. The physical layer technology
determines some network parameter values relevant for the performance study, e.g., SIFS, DIFS, backoff,
and slot time. Whenever necessary, we choose the values of these technology-dependent parameters by
referring to the frequency hopping spread spectrum technology at a transmission rate of 2 Mb/sec.
Specifically, Table 1.1 reports the configuration parameter values of the IEEE 802.11 WLAN analyzed in
this chapter
[27].
1.4.1.1.1 Protocol Capacity
The IEEE 802.11 protocol capacity was extensively investigated in [14]. The main results of that analysis
are summarized here. Specifically, in [14] the theoretical throughput limit for IEEE 802.11 networks was
4
A slot time is equal to the time needed at any station to detect the transmission of a packet from any other sta-
tion.
© 2003 by CRC Press LLC
analytically derived,
5
and this limit was compared with the simulated estimates of the real protocol
capacity. The results showed that, depending on the network configuration, the standard protocol can
operate very far from the theoretical throughput limit. These results, summarized in Fig. 1.7a, indicate
that the distance between the IEEE 802.11 and the analytical bound increases with the number of active
stations,
M. In the IEEE 802.11 protocol, due to its backoff algorithm, the average number of stations
that transmit in a slot increases with
M, and this causes an increase in the collision probability. A
significant improvement of the IEEE 802.11 performance can thus be obtained by controlling the number
of stations that transmit in the same slot.

Several works have shown that an appropriate tuning of the IEEE 802.11 backoff algorithm can
significantly increase the protocol capacity [2,13,46]. In particular, in [13], a distributed algorithm to
tune the size of the backoff window at run time, called
Dynamic IEEE 802.11 Protocol, was presented and
evaluated. Specifically, by observing the status of the channel, each station gets an estimate of both the
number of active stations and the characteristics of the network traffic. By exploiting these estimates,
each station then applies a distributed algorithm to tune its backoff window size in order to achieve the
theoretical throughput limit for the IEEE 802.11 network.
The Dynamic IEEE 802.11 Protocol is complex due to the interdependencies among the estimated
quantities [13]. To avoid this complexity, in [7] a
Simple Dynamic IEEE 802.11 Protocol is proposed and
evaluated
. It requires only simple load estimates for tuning the backoff algorithm. An alternative and
interesting approach for tuning the backoff algorithm, without requiring complex estimates of the
network status, has been proposed in [5]. In this work a distributed mechanism is defined, called
Asymptotically Optimal Backoff (AOB), which dynamically adapts the backoff window size to the current
load. AOB guarantees that an IEEE 802.11 WLAN asymptotically (i.e., for a large number of active
stations) achieves its optimal channel utilization. The AOB mechanism adapts the backoff window to
the network contention level by using two load estimates: the slot utilization and the average size of
transmitted frames. These estimates are simple and can be obtained with no additional costs or overheads.
It is worth noting that the above mechanisms that tune the IEEE 802.11 protocol to optimize the
protocol capacity also guarantee quasi-optimal behavior from the energy consumption standpoint (i.e.,
minimum energy consumption). Indeed, in [11] it is shown that the optimal capacity state and the
optimal energy consumption state almost coincide.
1.4.1.1.2 MAC Delay
The IEEE 802.11 capacity analysis presented in the previous section is performed by assuming that the
network operates in asymptotic conditions (i.e., each LAN station always has a packet ready for trans
-
mission). However, LANs normally operate in normal conditions, i.e., the network stations generate an
aggregate traffic that is lower (or slightly higher) than the maximum traffic the network can support. In

these load conditions, the most meaningful performance figure is the MAC delay (see Section 1.3 and
[15]). Two sets of MAC delay results are presented here, corresponding to traffic generated by 50 stations,
made up of short (two slots) and long (100 slots) messages, respectively. Stations alternate between idle
and busy periods. In the simulative experiments, the channel utilization level is controlled by varying
the idle periods’ lengths.
Figure 1.7b (which plots the average MAC delay vs. the channel utilization) highlights that, for light
load conditions, the IEEE 802.11 exhibits very low MAC delays.
However, as the offered load approaches
TABLE 1.1 IEEE 802.11 Parameter Values
Parameter t
slot
DIFS EIFS SIFS ACK CW
min
CW
max
Bit Rate
Va lue
50 µsec ≤1 µsec 2.56 t
slot
340 µsec 0.56 t
slot
240 bits 8 t
slot
256 t
slot
2 Mb/sec
5
That is, the maximum throughput that can be achieved by adopting the IEEE 802.11 MAC protocol and using
the optimal tuning of the backoff algorithm.
τ

© 2003 by CRC Press LLC
the capacity of the protocol (see Fig. 1.7a), the MAC delay sharply increases. This behavior is due to the
CSMA/CA protocol. Under light-load conditions, the protocol introduces almost no overhead (a station
can immediately transmit as soon as it has a packet ready for transmission). On the other hand, when
the load increases, the collision probability increases as well, and most of the time a transmission results
in a collision. Several transmission attempts are necessary before a station is able to transmit a packet,
and hence the MAC delay increases. It is worth noting that the algorithms discussed in the previous
section (i.e., SDP, AOB, etc.) for optimizing the protocol capacity also help prevent MAC delays from
becoming unbounded when the channel utilization approaches the protocol capacity (see [5] and [7]).
1.4.2 IEEE 802.11 RTS/CTS
The design of a WLAN that adopts a carrier-sensing random access protocol [24], such as the IEEE
802.11, is complicated by the presence of hidden terminals [42]. A pair of stations is referred to as being
hidden from each other if a station cannot hear the transmission from the other station. This event makes
the carrier sensing unreliable, as a station wrongly senses that the wireless medium has been idle while
the other station (which is hidden from its standpoint) is transmitting.
For example, as shown in Fig. 1.8,
let us assume that two stations, say
S
1
and S
2
, are hidden from each other, and both wish to transmit to
a third station, named
Receiver. When S
1

is transmitting to Receiver, the carrier sensing of S
2

does not

trigger any transmission, and thus
S
2
can immediately start a transmission to Receiver as well. Obviously,
this event causes a collision that never occurs if the carrier sensing works properly.
The hidden stations phenomenon may occur in both infrastructure-based and ad hoc networks.
However, it may be more relevant in ad hoc networks where almost no coordination exists among the
stations. In this case, all stations may be transmitting on a single frequency, as occurs in the WaveLAN
IEEE 802.11 technology [45].
To avoid the hidden terminal problem, the IEEE 802.11 basic access mechanism was extended with a
virtual carrier sensing mechanism, called
Request To Send (RTS)/Clear To Send (CTS).
In the RTS/CTS mechanism, after access to the medium is gained and before transmission of a data
packet begins, a short control packet, called RTS, is sent to the receiving station announcing the
upcoming
transmission. The receiver replies to this with a CTS packet to indicate readiness to receive the data. RTS
and CTS packets contain the projected length of the transmission. This information is stored by each
active station in its NAV, the value of which becomes equal to the end of the channel busy period.
Therefore, all stations within the range of at least one of the two stations (receiver and transmitter) know
how long the channel will be used for this data transmission (see Fig. 1.9).
The RTS/CTS mechanism solves the hidden station problem during the transmission of user data. In
addition, this mechanism can be used to capture the channel control before the transmission of long
packets, thus avoiding “long collisions.” Collisions may occur only during the transmissions of the small
RTS and CTS packets. Unfortunately, as shown in the next section, other phenomena occur at the physical
layer making the effectiveness of the RTS/CTS mechanism quite arguable.
FIGURE 1.7 IEEE 802.11 performance: (a) protocol capacity; (b) average MAC delay
0
0.2
0.4
0.6

0.8
1
7502550 100
Packet size (slots)
M=100
M=50
M=10
M=5
Theoretical bound
Capacity
(a)
0E+00
5E+03
1E+04
2E+04
2E+04
2E+04
Channel utilization
100 slots
2 slots
MAC delay (µsec)
0 0.1 0.2 0.3 0.4 0.5
(b)
© 2003 by CRC Press LLC
1.4.2.1 RTS/CTS Effectiveness in Ad Hoc Networks
The effectiveness of the RTS/CTS mechanism was studied in [44] in a real field trial. The main results
of that study are summarized here. The testbed analyzed the performance of the TCP protocol over an
IEEE 802.11 ad hoc network. To reduce the complexity of the study, static ad hoc networks were
considered, i.e., the network nodes did not change their positions during an experiment. Both indoor
and outdoor scenarios were investigated.

1.4.2.1.1 Indoor Experiments
In this case the experiments were performed in a scenario characterized by hidden stations. The scenario
is shown in Fig. 1.10. Nodes 1, 2, and 3 are transferring data, via ftp, toward node 4. As these data transfers
are supported by the TCP protocol, in the following the data flows will be denoted as TCP #
i, where i is
the index of the transmitting station.
In the analyzed scenario, a reinforced concrete wall (the black rectangle in the figure) is located between
node 1 and node 2 and between node 2 and node 3. As a consequence, the three transmitting
nodes are
hidden from each other, e.g., nodes 2 and 3 are outside the transmission range of node 1.
6 N
ode 4 is in
the transmission range of all the other nodes.
Two sets of experiments were performed using the DCF mechanism with or without the RTS/CTS
mechanism. In Table 1.2, the results of the experiments are summarized. Two main conclusions can be
reached from these experiments:
1. No significant performance differences exist between adopting the RTS/CTS mechanism vs. the
basic access mechanism only.
2. Due to the additional overheads of the RTS and CTS packets, the aggregate network throughput
with the RTS/CTS mechanism is a bit lower with respect to the basic access mechanism.
FIGURE 1.8 The hidden stations phenomenon.
FIGURE 1.9 The RTS/CTS mechanism.
6
Specifically, the ping application indicated no delivered packet.
Sender S1
Sender S2
Receiver
DIFS
SIFS
DATA

ACK
NAV RTS
BACKOFF
DIFS
SIFS
SIFS
NAV CTS
NAV DATA
RTS
CTS
Source
Destination
Other stations
access to the medium is deferred
Contention Window
© 2003 by CRC Press LLC
These results seem to indicate that the carrier sensing mechanism is still effective even if transmitting
stations are “apparently” hidden from each other. Indeed, a distinction must be made between transmis
-
sion range, interference range, and carrier sensing range, as follows:
•The Transmission Range (TX_Range) represents the range (with respect to the transmitting
station) within which a transmitted packet can be successfully received. The transmission range
is mainly determined by the transmission power and the radio propagation properties.
•The Physical Carrier Sensing Range (PCS_Range) is the range (with respect to the transmitting
station) within which the other stations detect a transmission.
•The Interference Range (IF_Range) is the range within which stations in receive mode will be
“interfered with” by a transmitter and thus suffer a loss. The interference range is usually larger
than the transmission range, and it is a function of the distance between the sender and receiver
and of the path loss model.
Normally, the following relationship exists between the transmission, carrier sensing, and interference

ranges: TX_Range
≤ IF_Range ≤ PCS_Range.
7 T
he relationship among TX_Range, IF_Range, and PCS_Range
helps in explaining the results obtained in the indoor experiments: even though transmitting nodes are
outside the transmission range of each other, they are inside the same carrier sensing range. Therefore, the
physical carrier sensing is effective, and hence adding a virtual carrier sensing (i.e., RTS/CTS) is useless.
1.4.2.1.2 Outdoor Experiments
The reference scenario for this case is shown in Fig. 1.11. The nodes represent four portable computers,
each with an IEEE 802.11 network interface. Two ftp sessions are contemporary active. The arrows
represent the direction of the ftp sessions.
Several experiments were performed by varying the transmission, the carrier sensing, and the inter-
ference ranges. This was achieved by modifying the distance, d, between nodes 2 and 3. In all the
experiments, the receiving node was always within the transmission
range of its transmitting node —
FIGURE 1.10 Indoor scenario.
TABLE 1.2 Indoor Results — Throughput (Kbytes/sec)
TCP #1 TCP #2 TCP #3 Aggregate
No RTS/CTS 42 29.5 57 128.5
RTS/CTS 34 27 48 109
7
For example, in NS2 the following values are used: TX_Range = 250 m, IF_Range = PCS_Range = 550 m.
12
3
4