Wireless local area networks. (WLANs) constitute ... Wireless LAN Standards and Applica- tions looks through ... characteristics, advantages, and prob- lems are ...
BOOK REVIEWS (Continued from page 30) in Chapter 6. The Chapter discusses both accessibility applying to intermittently used services (e.g., dialup telephone services) and continuously used services (e.g., email and data transfer services). Chapter 7 focuses on routing speed. Effects of this user concern distinctly differ from each other depending on whether the service employs circuit o r packet switching. The book gives a
solid base for the evaluation of both effects, although the study will not satisfy the more demanding reader interested in packet switching. Chapters 8 and 9 are devoted to connection reliability. Chapter 8 focuses on the reliability evaluated when the connection has been established. The other important aspect of reliability, the possibility of misroutes, is discussed in Chapter 9. The next two chapters deal with connection quality. In the 10th
chapter, theoretical aspects of the quality of voice signals are explained and accompanied by some real-life examples and scenarios from the author’s experience. Chapter 11 focuses on the connection quality for the exchange of data. Chapter 12 is devoted to the problem of spontaneous disconnections when quality of the connection is unacceptable, while Chapter 13 analyzes the disconnection reliability. Various QoS aspects such as service level agreements (SLAs) and economy aspects of QoS are covered in Chapter 14. The text of the book is accompanied by three appendices, a list of abbreviations, and an index. In my opinion, this book provides a straightforward and very accessible approach to measurement and evaluation of QoS in telecommunication networks. The book can be strongly recommended for all people, either experienced professionals o r graduates, involved in the area of networking, who want to go deeper in the subject of understanding telecommunications QoS. LAN STANDARDS AND APPLICATIONS
WIRELESS
ASUNCION SANTAMARI, FRANCISCO 1.
LOPEZ-HERNANDEZ, EDITORS, ARTECH HOUSE PUBLISHERS, BOSTON, LONDON, 2001, ISBN 0-89006-943-3, 234 PAGES REVIEWER:MAREK NATKANIEC
Wireless local a r e a networks (WLANs) constitute one of the most dynamically developing fields of telecommunications. They play a very important role in the network architecture as a provider of easy and unconstrained access to the wired infrastructure. They can be installed in places that are very difficult t o wire such as, for example, trading floors, manufacturing facilities, warehouses, or historical buildings. The new possibilities of WLANs allow provisioning some new services. Lastly, WLANs may be temporary or operational for a short period of time, where installation of wired networks is impractical. Wireless LAN Standards and Applications looks through the existing wireless systems standards. It contains Web addresses of main regulations and standardization organizations as well as a listing of the Web sites of the technological alliances that contribute to the development of wireless technology. The book presents application areas in which WLANs can be used, and also specifies new environments where wireless systems play a special role. It speci(Continued on page 34)
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IEEE Communications Magazine February 2002
BOOK REVIEWS (Continued from page 32) fies in detail manufacturers that offer mobile computing products. The book consists of six chapters, and begins with a short introduction to wireless local area networks. It discusses the need for standardization. Chapter 2 describes in detail the IrDA standard. This chapter starts from the evolution of IrDA, it also presents the protocol stack and typical applications. Physical layer, serial infrared link access, link management, and transport protocols are discussed. This chapter contains the description of IrLAN that uses fast IR link to support a LAN interface. Chapter 3 is devoted to the IEEE 802.11 standard. The expected features of a “good” WLAN MAC protocol are presented first. Then the standard medium access control sublayer is considered. Both standardized access methods are presented: the distributed coordination function (DCF) with optional handshaking, and the point coordination function (PCF). At the end of this section a comparison between IEEE 802.11 MAC and HIPERLAN MAC is given. Physical layer of the I E E E 802.11 standard is considered next. Both spread spectrum radio systems, frequency hopping (FH) and direct sequence (DS), and their characteristics, advantages, and problems are reviewed. Finally, the infrared system as physical layer for IEEE 802.11 standard is presented. The standard developed by ETSI, known as HIPERLAN, is described in Chapter 4. The authors consider three sections: physical layer, channel access control (CAC) and medium access control (MAC) sublayers. The three possible channel conditions controlled by the CAC are described in detail. T h e HIPERLAN MAC functions: differentiation and addressing, data encryption, power-saving, priorities and traffic lifetime, routing and information maintenance are also discussed. Three new BRAN standards, known as HIPERLAN 2-4, are introduced at the end of the chapter. Chapter 5 classifies number of wireless applications into four categories: public building, business environment, domestic building, and industrial sector WLANs. A short description of user and system needs given for each category is presented. The chapter details the commercial WLAN products. The last section discusses organizations that are involved in the research, development, and commercialization of wireless systems and products (WLANA, WECA, Bluetooth SIG, WLIF, Home RF, BWIF, IrDA, etc.).
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In the last chapter (Chapter 6) forthcoming standards and future trends are presented. The evolution of WLAN standards introduced in previous chapters is discussed. Some new wireless technologies (e.g., DECT, Bluetooth, WATM, H o m e RF) are briefly described at thc end of the chapter. Summarizing, the book provides a review of the existing WLAN standards and their implementation. It simply explains the three main standards, IrDA, IEEE 802.11, and HIPERLAN. The book describes the future of wireless technologies. Each chapter contains selected bibliography for further reading. Lots of illustrations help the reader to understand essential topics. It is a good textbook for undergraduate and graduate students. HIGHAVAILABILITY NETWORK FUNDAMENTALS: A PRACTICAL GUIDETO PREDICTING
NETWORK AVAILABILITY CHRISOGGERINO, CISCO PRESS,2001, ISBN 1-58713-01 7-3, HARDCOVER, 237 18 PAGES, CD-ROM INCLUDED
+
REVIEWER: PIOTRCHOLDA
The problems of reliability have been investigated for a long time. The reliability has played a very important role, espccially for telecommunications networks, because such networks have to assure an appropriate level of availability in order not to deprive the subscriber of critical services. Now, in time of convergence of the networks, the issue of the availability of data transmission networks has become more interesting not only for a small group of engineers. Cisco edited a book written by its serviceability expert. The goal of the book is to outline basic causes of unavailability and methods to estimate it. The book is divided into three parts, the first of which (Chapters 1-3) is a general introduction to availability, the second (Chapters 4 and 5 ) shows how to predict the availability, and the last (Chapters 6-9) gives very instructive examples of estimating the availability in some selected networks. In Chaptcr 1 there are definitions of basic concepts used in the book: availability as the percentage of time the network works without failure, mean time between failures (MTBF), mean time to restore (MTTR), M m F (Mean Time To Failure), parallel redundancy and serial redundancy. The equations used in estimating of the availability of both single and complex (serial, parallel or mixed serialiparallel configuration) components are described in Chapter 2. The effect of a network topology on the method of calculation of the availability is overviewcd in Chapter 3.
Chapter 4 discusses main factors which influence the availability of networks. The routines for estimating these factors are given as well. This chapter seems to be the most important in the whole book. The author considers five aspects which affect the availability: hardware, software, envir on men t a1 (which means power delivery), network operator staff (human error), and network design. This chapter also gives some remarks and assumptions, which may be helpful when trying to avoid downtimes caused by these factors. The end of the chapter contains a bibliography, which could be useful for engineers who would like to learn more about the availability theory. The SQcalled divide-and-conquer method is described in the next chapter. Such a procedure makes it possible to compute the availability of a network in case of different scenarios that occur when the network is used. There are a lot of examples in every chapter, but the last four chapters focus on thoroughly described cases of calculating availability in real situations. Obviously, all these examples include Cisco products. Chapter 6 shows how to calculate the availabilit of single devices. The next chapter concentrates on an example of a small Internet service provider network. Chapter 8 describes the case.of an enterprise network. The last, relatively long, chapter gives an example of a large data transmission network that offers voice over IP service. This chapter is v e q detailed, because it accumulates all the knowledge from the book. The included CD-ROM (less than 8 Mbytes capacity) contains only the most important information extracted from the book: main equations and some examples. The most useful is the System Hardware Availability and Reliability Calculator (SHARC) spreadsheet, which helps to compute availability. It is necessary to pay attention to the fact that the book places special emphasis on practical (although very rough) computation of availability. The author tried to avoid complex mathematics. This is the main reason, for example, an equation for estimating the availability of more complex parallel configurations with backups is not given. However, an introduction to the formal theory of availability is not the goal of this book. It gives lots of information to people starting to learn availability engineering. Because of this Chris Ogerrino’s book might be recommended to laymen or novices in these problems; it could also be good as supplementary reading for students and practicing engineers.
IEEE CommunicationsMagazine
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February 2002
