Wireless LANs

Wireless LANs

by Jim Geier, Jim Geier
     
 

This book provides the following benefits to readers:

  • Ability to select the most effective wireless LAN type from a wide assortment of recent and emerging standards.
  • Independent assessment of competing wireless LAN technologies.
  • More efficient design and operational support of wireless LANs because of an understanding of wireless LAN

Overview

This book provides the following benefits to readers:

  • Ability to select the most effective wireless LAN type from a wide assortment of recent and emerging standards.
  • Independent assessment of competing wireless LAN technologies.
  • More efficient design and operational support of wireless LANs because of an understanding of wireless LAN protocol operations and frame structures.
  • Definition of typical requirements and technology assessment parameters, providing a basis for evaluating wireless LANs.
  • Vision of the future of wireless LANs.
  • Real-world experiences through case studies and implementation tips located throughout the book.
  • Quick overview of the features, pros, and cons of each of the wireless LAN standards located at the beginning of each chapter.

Editorial Reviews

Overviews wireless network technologies with an emphasis on the IEEE 802.11 wireless LAN standard and implementation steps. The author examines frame structure and different types of physical layers, and walks through the planing and implementation of a case study project. The second edition adds sections on the high-rate direct sequence and orthogonal frequency-division multiplexing physical layers. Annotation c. Book News, Inc., Portland, OR (booknews.com)

Product Details

ISBN-13:
9780672320583
Publisher:
Sams
Publication date:
07/28/2001
Series:
Sams White Books Series
Pages:
345
Product dimensions:
7.20(w) x 9.00(h) x 0.80(d)

Read an Excerpt

Chapter 3: Overview of the IEEE 802.11 Standard

In this chapter:
  • The Importance of Standards 64
  • IEEE 802 LAN Standards Family 69
  • Introduction to the IEEE 802.11 Standard 77
  • IEEE 802.11 Topology 79
  • IEEE 802.11 Logical Architecture 82
  • IEEE 802.11 Services 83

The Importance of Standards

Vendors and some end users initially expected markets to dive head first into implementing wireless networks. Markets did not respond as predicted, and flat sales growth of wireless networking components prevailed through most of the 1990s. Relatively low data rates, high prices, and especially the lack of standards kept many end users from purchasing the wirefree forms of media.

For those having applications suitable for lower data rates and enough cost savings to warrant purchasing wireless connections, the only choice before 1998 was to install proprietary hardware to satisfy requirements. As a result, some organizations today still have proprietary wireless networks for which you have to replace both hardware and software to be compliant with the IEEE 802.11 standard. In response to lacking standards, the Institute for Electrical and Electronic Engineers (IEEE) developed the first internationally recognized wireless LAN standard: IEEE 802.11.

Types of Standards

There are two main types of standards: official and public. An official standard is published and known to the public, but it is controlled by an official standards organization, such as IEEE. Government or industry consortiums normally sponsor official standards groups. Official standards organizations generally ensure coordination at both the international and domestic level.

A public standard is similar to an official standard, except it is controlled by a private organization, such as the Wireless LAN Interoperability Forum. Public standards, often called de facto standards, are common practices that have not been produced or accepted by an official standards organization. These standards, such as TCP/IP, are the result of widespread proliferation. In some cases, public standards that proliferate, such as the original Ethernet, eventually pass through standards organizations and become official standards.

Companies should strive to adopt standards and recommended products within their organizations for all aspects of information systems. What type of standards should you use? For most cases, focus on the use of an official standard if one is available and proliferating. This will help ensure widespread acceptance and longevity of your wireless network implementation. If no official standard is suitable, a public standard would be a good choice. In fact, a public standard can often respond faster to changes in market needs because it usually has less organizational overhead for making changes. Be sure to avoid non-standard or proprietary system components, unless there are no suitable standards available.

Case Study 3.1:
802.11 Versus Proprietary Standards

A large retail chain based in Sacramento, California, had requirements to implement a wireless network to provide mobility within its 10 warehouses located all over the U.S. The application called for clerks within the warehouse to use new handheld wireless data collectors that perform inventory management functions.

The company, already having one vendor's data collection devices (we'll call these brand X), decided to use that vendor's brand Y proprietary wireless data collectors and its proprietary wireless network (the vendor didn't offer an 802.11-compliant solution). This decision eliminated the need to work with additional vendors for the new handheld devices and the wireless network.

A year passed after the installation, and enhancement requirements began to pour in for additional mobile appliances that were not available from the brand X vendor. This forced the company to consider the purchase of new brand Z appliances from a different vendor. The problem, though, was that the brand Z appliances, which were 802.11-compliant, didn't interoperate with the installed proprietary brand Y wireless network. Because of the cost associated with replacing its network with one that was 802.11-compliant (the brand Y wireless network had no upgrade path to 802.11), the company couldn't implement the new enhancement cost effectively.

The company could have eliminated the problem of not being able to implement the new enhancement if it would have implemented the initial system with 802.11- compliant network components because most vendors offer products that are compatible with 802.11, but not all the proprietary networks. The result would have been the ability to consider multiple vendors for a wider selection of appliances.

Institute for Electrical and Electronic Engineers (IEEE)

The IEEE is a non-profit professional organization founded by a handful of engineers in 1884 for the purpose of consolidating ideas dealing with electrotechnology. The IEEE plays a significant role in publishing technical works, sponsoring conferences and seminars, accreditation, and standards development. With regard to LANs, the IEEE has produced some very popular and widely used standards. For example, the majority of LANs in the world use network interface cards based on the IEEE 802.3 (ethernet) and IEEE 802.5 (token ring) standards.

Before someone can develop an IEEE standard, he must submit a Project Authorization Request (PAR) to the IEEE Standards Board. If the board approves the PAR, IEEE establishes a working group to develop the standard. Members of the working groups serve voluntarily and without compensation, and they are not necessarily members of the institute. The working group begins by writing a draft standard and then submits the draft to a balloting group of selected IEEE members for review and approval. The ballot group consists of the standard's developers, potential users, and other people having a general interest.

Before publication, the IEEE Standards Board performs a review of the Final Draft Standard and then considers approval of the standard. The resulting standard represents a consensus of broad expertise from within IEEE and other related organizations. All IEEE standards are reviewed at least once every five years for revision or reaffirmation.

Note

In May 1991, a group led by Victor Hayes submitted a Project Authorization Request (PAR) to IEEE to initiate the 802.11 working group. Hayes became chairman of the working group and led the standards effort to its completion in June 1997.

Benefits of the 802.11 Standard

The benefits of using standards such as those published by IEEE are great. The following sections explain the benefits of complying with standards, especially IEEE 802.11.

Appliance Interoperability

Compliance with the IEEE 802.11 standard makes possible interoperability between multiple-vendor appliances and the chosen wireless network type. This means you can purchase an 802.11-compliant scanner from Symbol and a Pathfinder Ultra handheld scanner/printer from Monarch Marking Systems and they will both interoperate within an equivalent 802.11 wireless network, assuming 802.11 configuration parameters are set equally in both devices. Standard compliance increases price competition and enables companies to develop wireless LAN components with lower research and development costs. This enables a greater number of smaller companies to develop wireless components.

As shown in Figure 3.1, appliance interoperability prevents dependence on a single vendor for appliances. Without a standard, for example, a company having a non-standard proprietary net-work would be dependent on purchasing only appliances that operate on that particular net-work. With an 802.11-compliant wireless network, you can use any equivalent 802.11-compliant appliance. Because most vendors have migrated their products to 802.11, you have a much greater selection of appliances for 802.11 standard networks.

Fast Product Development

The 802.11 standard is a well-tested blueprint that developers can use to implement wireless devices. The use of standards decreases the learning curve required to understand specific technologies because the standard-forming group has already invested the time to smooth out any wrinkles in the implementation of the applicable technology. This leads to the development of products in much less time....

Meet the Author

Jim Geier is an independent consultant, assisting companies with the development of wireless network products and integration of wireless networks into corporate information systems. He is the principal consultant of his consulting firm, Wireless-Nets, Ltd.

Jim's 20 years of experience deals with the analysis, design, software development, installation, and support of numerous client/server and wireless network-based systems for retail, manufacturing, warehousing, health-care, education, and airline industries throughout the world. Jim is the author of three other books: Wireless LANs (1999, MTP), Wireless Networking Handbook (1996, New Riders), and Network Reengineering (1996,McGraw-Hill), as well as numerous articles for publications such as Network World and Communications System Design. Jim also speaks regularly at seminars, conferences, and trade shows in the United States, Europe, and Asia.

Jim has served as chairman of the Institute of Electrical and Electronic Engineers (IEEE) Computer Society, Dayton Section, and as chairman of the IEEE International Conference on Wireless LAN Implementation. He also was an active member of the IEEE 802.11 Working Group, responsible for developing international standards for wireless LANs. His education includes a bachelor's and master's degree in electrical engineering (with emphasis in computer networking and software development), and a master's degree in business administration.

As part of his Web site (http://www.wireless-nets.com), Jim maintains the Online Guide to Wireless Networking, which includes many of his articles and links to other sites. He is the editor of the monthly Wireless-Nets Newsletter, which is available free on his Web site at http://www.wireless-nets.com/newsletter.htm

You can reach Jim via e-mail at jimgeier@wireless-nets.com

D. Ed Lamprecht is a manager of the Professional Services Group at Monarch Marking Systems which focuses on custom software and network solutions. He has more than 17 years of programming experience in applications, operating systems, and network programming. He received a bachelor's degree in 1983 from the University of Northern Iowa and started his career with NCR Corporation programming operating systems in assembly for retail computing systems. It was during this time that Ed also developed applications for other platforms, including UNIX and DOS.

In 1988, Ed joined Monarch Marking Systems, a company specializing in bar code printers and labels. Here he developed bar code applications for MS-DOS and Microsoft Windows as early as version 2.0, including PC drivers, TSRs, and connectivity software. Since 1996, Ed has been involved in data collection systems providing wireless network connectivity solutions of handheld printers and data collection terminals for retail, industrial, manufacturing, and health care markets.

At Monarch, Ed has developed client/server applications, visited customer sites for analysis and problem solving, and provided international training on products and wireless connectivity. Ed holds seven patents in bar code software and handheld printer/data collectors. He lives with his wife, Michelle, and his son, Colin, in Dayton, Ohio. When not tinkering with PCs and networks at home, he enjoys model railroading, railroad memorabilia collecting, golfing, traveling, and spending time with his family.

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