A wireless LAN (WLAN) supports mobile clients connecting to the enterprise network. The mobile clients do not have a physical connection to the network because WLANs replace the Layer 1 traditional wired network (usually Category 5 cable) w transmissions through the air. WLANs are for local networks, either in-building, line-of-sight outdoor bridging applications, or a combination of both.

In a wireless network, many issues can arise to prevent the RF signal from reaching all parts of the facility, including multipath distortion, hidden node problems, interference from other wireless sources, and near/far issues. A site survey helps find the regions where these issues occur by defining the contours of RF coverage in a particular facility, discovering regions where multipath distortion can occur, areas where RF interference is high, and finding solutions to eliminate such issues.

Privacy and security issues must also be considered in a wireless network. Because WLANs are typically connected to the wired network, all the modules within the enterprise infrastructure must be considered to ensure the success of a wireless deployment.

Centralized WLAN Components

As illustrated in below Figure, the four main components in a centralized WLAN deployment are as follows:

■ End-user devices: A PC or other end-user device in the access layer uses a wireless NIC to connect to an access point (AP) using radio waves.

■ Wireless APs: APs, typically in the access layer, are shared devices that function similar to a hub. Cisco APs can be either lightweight or autonomous.

Lightweight APs are used in centralized WLAN deployments. A lightweight AP receives control and configuration from a WLAN controller (WLC) with which it is associated, providing a centralized point of management and reducing the security concern of a stolen AP. An autonomous AP has a local configuration and requires local management, which might make consistent configurations difficult and add to the cost of network management.

■ WLC: A WLC provides management and support for wireless services such as roaming. The WLC is typically in the core layer of an enterprise network.

■ Existing switched and routed wired network: The wireless APs connect to the wired enterprise network.ith radio frequency (RF)

Figure: Centralized WLAN Components