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Understand the technological issues associated with wireless local area networks (WLANs) as a means of providing cable-free data access, easy upgrading and flexible reconfiguration compared to the extensive multimedia and intensive application support provided by terrestrial and satellite asynchronous transfer mode (ATM) networks using this new resource. You see the benefits and the issues related to developing wireless ATM and get a comprehensive overview of both WLAN and WATM technologies, as well as their ...
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Understand the technological issues associated with wireless local area networks (WLANs) as a means of providing cable-free data access, easy upgrading and flexible reconfiguration compared to the extensive multimedia and intensive application support provided by terrestrial and satellite asynchronous transfer mode (ATM) networks using this new resource. You see the benefits and the issues related to developing wireless ATM and get a comprehensive overview of both WLAN and WATM technologies, as well as their global standards, performance evaluations of the two network options, and the pros and cons of each, written by an acknowledged expert in the fields of wireless communications and high-speed networking.
"...examines the technological pros & cons associated with wireless local area networks (WLANs) and asynchronous transfer mode (ATM) networks...explains global standards and offers performance evaluations for the two technologies.
The World Wide Web (WWW) is perhaps the largest source of distributed information. The network that drives the Web is the Internet. While the size of the Internet has been increasing at a rapid rate, the use of the Web has grown at an explosive pace. With the advent of dynamic content (e.g., HTML, CGI, XML) and executable content (e.g., Java), the Web is poised to play a central role in the process of making information ubiquitously accessible. The Internet runs on internetworking devices called routers that forward network layer Internet Protocol (IP) packets among networks with different link layers. Managing the network layer is much more flexible than the link layer since network administrators can assign structured IP addresses as opposed to unstructured MAC (link layer) addresses. However, mobile computing poses a problem if nodes with fixed IP addresses are moved from one location to another. Although a wireless LAN provides mobility support with roaming services, true mobility for large IP networks can only be realized if the IP addresses are assigned dynamically. This is because IP addresses are location dependent and therefore need to be changed to reflect the different locations of a mobile node. Hence, the problem of mobility in IP networks lies with the way IP addresses are structured, with or without wireless connectivity. Dynamic allocation of IP addresses is usually applied to mobile nodes and not to wireless access points since the access points occupy static (fixed) locations.
The dynamic host configuration protocol (DHCP) is one method of configuring IP addresses dynamically regardless of location. A dynamically assigned IPaddress is known as an active lease. The active lease usually has an expiration date, which allows automatic reallocation of IP addresses that are no longer in use. Thus, DHCP relieves the administrative burden of managing IP addresses in addition to providing mobile IP addresses. When DHCP is implemented on a wired IP network, a mobile client is able to connect to the network in different locations (e.g., in different subnets). This is achieved by physically disconnecting the network cable from a fixed outlet or socket and reconnecting at the new site. Hence, ongoing connections will have to be broken when a client on a wired network moves to a new location. However, when DHCP is applied to wireless LANs, IP connections can be maintained (and applications can continue to run) even as a mobile client changes location. This removes the need to log in and out of the network. Thus, wireless LANs with mobile IP addresses can provide continuous and location independent access to Internet services.
Load balancing allows wireless LANs to serve greater loads more efficiently. Each access point can monitor the traffic load within its coverage area and then try to balance the number of nodes serviced according to the traffic load in adjacent access points. To achieve this, access points must exchange traffic load information through the backbone network. Most load balancing methods do not depend on signal strength as this may complicate the roaming algorithm. Typically, roaming has priority over load balancing since a mobile node must first be able to connect to an access point with reasonable signal quality/ strength before load balancing can be performed.
3.5.9 Securing wireless access
The free-space wireless link is more susceptible to eavesdropping, fraud, and unauthorized transmission than its wired counterpart. Being an open medium with no precise bounds makes it impractical to apply physical security like in wired networks. Nevertheless, several alternative security mechanisms can be used to prevent unauthorized access of data transmitted over a wireless LAN. These are:
Portable wireless LAN devices rely on limited battery power to conduct communications over a wireless link that is prone to error bursts due to fading and other propagation impairments. As current battery research does not predict a substantial change in the available energy in a consumer battery, it is crucial that wireless mobile devices are designed to be efficient in energy usage. Minimizing energy usage is a significant constraint since it impacts design at all levels of network control. There has been substantial research in energy-efficient hardware (e.g., low power electronics, processor sleep-time, and powerefficient modulation) for mobile communications. However, due to fundamental physical limitations, progress towards further efficiency will become mostly a software-level issue. In wireless LANs, the software protocol can be designed to allow an idle network device to turn off its receiver most of the time, thereby saving considerable amounts...
Introduction to Wireless Local Area Networks. Wireless LAN Standards. Performance Evaluation of Wireless LANs. Introduction to Wireless ATM Networks. The Wireless Mobile Environment. Multimedia Communications Using Wireless ATM. Wireless ATM Prototypes. ATM Over Satellite. Wireless ATM Standardization Activities.
Posted February 16, 2000
This book has been highly commended by Vic Hayes, Chairman of the IEEE 802.11 Working Group on Wireless LANs. The book provides a concise discussion on current wireless LAN technology and offers a glimpse of where the field of broadband wireless ATM is heading. The approach taken in the book is to emphasize core concepts and underlying principles rather than factual descriptions. In addition, many carefully prepared illustrations are used throughout the book to enhance the textual explanations. By distilling details down to the basic issues needed for intuitive understanding, both serious and novice readers are able to gain valuable insights into the exciting field of high-speed wireless communications and mobile computing. However, the purpose of the book goes beyond making the reader merely proficient in these issues. The many problems discussed serve to stimulate reflection and further research. To encourage readers to fully explore the topics covered, useful Internet resources and references have been included. Most of the references are chosen because they are either informative or particularly well written. Hence, the book can serve as an ideal course reader on advanced wireless networks. The chapters of this book are organized as follows. Chapter 1 highlights the major technical problems associated with the indoor wireless environment and recommends some solutions to cope with these problems. Various types of wireless LANs are described in Chapter 2. Chapter 3 deals with issues related to wireless LAN implementation while in Chapter 4, the structure of the IEEE 802.11, HIPERLAN and other emerging industry-standards such as Bluetooth and HomeRF are explained. Chapter 5 focuses on the performance evaluation of several commercial wireless LANs, including those complying to the IEEE 802.11 standard. Chapter 6 surveys the technical and service issues related to the deployment of ATM in third-generation wireless networks. The requirements for multimedia communications using ATM are also examined. Several wireless ATM prototypes and products are then described. The chapter concludes with an interesting account of how ATM cells can be transported over satellite networks. Chapter 7 provides a brief overview on the current wireless ATM standardization activities in the US, Europe and Japan. Finally, a list of references is included in a bibliography. Updates and useful web resources are posted in the book's web site. Send an email to firstname.lastname@example.org to request for the URL.Was this review helpful? Yes NoThank you for your feedback. Report this reviewThank you, this review has been flagged.