2-6 Wireless Networks
JAMES T. GEIER
Over the past decade, people have become reliant on computer networks to support the access and retrieval of information from data bases, send files electronically, and communicate with other people via electronic mail. In addition, refined packaging techniques have allowed computer manufacturers to reduce the size of computers to laptop and palmtop sizes. As a result, people on-the-go (e.g., salespeople, business executives, and healthcare professionals), have begun using wireless networks to stay in touch with their customers, business associates, and information resources.
This chapter poses wireless networking as a possible solution to requirements specifying needs for mobility or the installation of networking in difficult-to-wire areas. The chapter identifies the pitfalls of traditional wireline networks, explains the benefits of wireless networks, describes the architecture of wireless networks, explains the various wireless LAN and WAN technologies and standards, and covers potential issues of implementing a wireless network.
CHALLENGES OF WIRELINE NETWORKS
Traditional wireline networks, as shown in Exhibit 2-6-1, consist of solid cable comprised of twisted pair wire, coaxial cable, or optical fiber. This wiring structure may result in problems because it:
- Is not feasible to install in difficult-to-wire situations.
- Is expensive to change.
- Is susceptible to potential reliability problems.
- Does not support user mobility.
Exhibit 2-6-1. Traditional Wireline Network
Many older buildings in the US and abroad have asbestos that protects stairwells and other building structures from fire damage. Because inhaling asbestor particles is a health hazard, extreme care must be exercised when installing network cabling within areas containing asbestos. This makes network installations very expensive and, in some cases, impossible. Asbestos can be professionally removed, making it safe to install cabling. To properly protect the building inhabitants, however, the cost can be tens of thousands of dollars to remove asbestos from just three flights of stairs. It is also difficult to install cabling in certain other facilities. For example, historical buildings are difficult because drilling holes in the walls is not permitted. Jails and hospitals are seldom conducive to cable installations.
Companies may occasionally renovate their facilities, and often may reorganize the layout of their organization. As a result, office cubicles and walls are moved, as well as the people. This incurs labor and material costs associated with recabling the network. In some cases, network cable reconfigurations can be substantial, especially with large enterprise networks. Networks consisting of 5,000 interconnected devices with a reorganization rate of 15% per year can result in yearly reconfiguration expenses as high as $250,000.
Another problem inherent with wireline networks is the network downtime often attributed to cable faults. Cabling is the leading cause of reliability problems in wired networks. Moisture can erode metallic conductors, improper splices cause disturbing signal reflections, and accidental cable cuts can quickly bring a network down. For example, a telephone technician repairing phone wire in a building can easily snip network cables by mistake. In addition, a saboteur can purposely cut network cables to keep users from accessing critical resources. These problems can wreak havoc for network users and network managers.
The most significant problem with traditional wireline networks, however, is that they do not support mobile users. The dependence on a physical tether between the user and the computer systems and other users on the network eliminates the possibility of accessing these resources while roaming (e.g., in a police car or ambulance), and makes them nearly impossible to access while moving about on a factory room floor or within a hospital.
BENEFITS OF WIRELESS NETWORKS
If a user has mobility requirements, a wireless network is the only option. The use of traditional cabling for mobile applications simply does not work. When dealing with difficult-to-wire situations, high reorganization rates, or low reliability as a result of cable faults, the implementation of a wireless network may equate to tangible cost savings. Wireless networks are easy to install in difficult-to-wire locations because it is not necessary to install cabling between computers, servers, and peripherals. Therefore, organizations do not have to remove asbestos to facilitate a safe installation, nor do they have to live with unattractive installations when it is impossible to hide wires above ceilings and behind walls.
In addition, wireless computers can be installed within a facility much more quickly and less expensively than when purchasing and paying the labor costs to install wireline media. Wireless networks are much easier to reconfigure because it is not necessary to recable the network to provide connectivity at the new end-user locations. Also, wireless networks tend to be more reliable because there is much less cabling that can fail.
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