Introduction to Wireless LANs
Why wireless?

Current wired Ethernet LANs operate at speeds around 100 Mbps at the access layer, 1 Gbps at the distribution layer, and up to 10 Gbps at the core layer. Most WLANs operate at 11 Mbps to 54 Mbps at the access layer and are not intended to operate at the distribution or core layers. The cost of implementing WLANs is competitive with wired LANs. So why install a system that is at the lower end of the current bandwidth capabilities? One reason is that in many small LAN environments, the slower speeds are adequate to support the application and user needs. With many offices now connected to the Internet by broadband services such as DSL or cable, WLANs can handle the bandwidth demands. Another reason is that WLANs allow users to roam a defined area with freedom and still remain connected. During office reconfigurations, WLANs do not require rewiring and its associated costs. Figure lists many of the benefits provided by WLANs.

WLANs have numerous benefits for home offices, small businesses, medium businesses, campus networks, and larger corporations. The environments that are likely to benefit from a WLAN have the following characteristics:

  • Require standard Ethernet LAN speeds
  • Benefit from roaming users
  • Reconfigure the physical layout of the office often
  • Expand rapidly
  • Utilize a broadband Internet connection
  • Face significant difficulties installing wired LANs
  • Need connections between two or more LANs in a metropolitan area
  • Require temporary offices and LANs

Figure provides additional examples of situations in which a WLAN would be beneficial.

WLANs do not eliminate the need for Internet Service Providers (ISPs). Internet connectivity will still require service agreements with local exchange carriers or ISPs for Internet access. There is a current trend for ISPs to provide wireless Internet service. These ISPs are referred to as Wireless Internet Service Providers (WISPs). Furthermore, WLANs do not replace the need for traditional wired routers, switches, and servers in a typical LAN.

Even though WLANs are primarily designed as LAN devices, they can be used to provide site-to-site connectivity at distances up to 40 km (25 miles). The use of WLAN devices is much more cost effective than using WAN bandwidth or either installing or leasing long fiber runs. For instance, the cost of installing a WLAN between two buildings will incur a one-time cost of several thousand U.S. dollars. A dedicated leased T1 link, which only provides a fraction of the bandwidth of a WLAN, will easily cost hundreds of U.S. dollars per month or more. Installing fiber across a distance of more than 1.6 km (1 mile) is difficult and would cost much more than a wireless solution.