Wired LANs require users to stay in one location. WLANs are an extension to
the wired LAN network. WLANs can also be a complete substitute for traditional
wired LAN networks. With Cisco WLANs, mobile users can do the following:
- Move freely around a facility
- Enjoy real-time access to the wired LAN, at wired Ethernet speeds
- Access all resources of the wired LANs
The basic service set (BSS) is the area of RF coverage provided by one
access point. It is also referred to as a microcell. As shown in Figure
, a BSS can be
extended by adding another AP. When more than one BSS is connected to a wired
LAN, it is referred to as an extended service set (ESS). Adding an AP is also a
way to add wireless devices and extend the range of an existing wired system.
The AP attaches to the Ethernet backbone and also communicates with all
the wireless devices in the cell area. The AP is the master for the cell. It
controls traffic flow to and from the network. The remote devices do not
communicate directly with each other. Rather, the devices communicate through
the AP.
If a single cell does not provide enough coverage, any number of
cells can be added to extend the range. It is recommended that adjacent BSS
cells have a 10 to 15 percent overlap, as shown in Figure
. This
allows remote users to roam without losing RF connectivity. Bordering cells
should be set to different non-overlapping channels, or frequencies, for best
performance.