Wireless
Definitions
Access point
A single wireless ethernet device serving a small area (hundreds of feet at most). This device connects to a wired network at either 10 or 100 Mbs. A number of vendors make access points, which can be equipped with different options and antennae. The campus is using the Cisco access point and an external ceiling-mount antenna sold at the Techstore. The range for an 11Mbs connection can vary from about 50 to 200 feet and is highly dependent on the obstacles between the access point and the client card.
Frequencies
The access point can operate on one of eleven possible frequencies, which overlap. When access points are used adjacent to each other, only three frequencies are available: channels 1, 6, and 11. To cover a large area with more than three access points, the channels must be selected so they do not interfere with each other. A simple example is below:
Channels 1 and 6 overlap, and channels 6 and 11 overlap. Then, channel 1 is used again without overlapping with the first channel 1. By building the network this way, you can cover larger areas than you could with only the three channels.
Roaming
Users may wander around, possibly switching access points without any interruption of service. Users can wander in an area serviced by multiple access points and not lose connectivity. In the example above, a user can freely move between the four access points on the three channels 1, 6, and 11 and not know they changed access points. The change is transparent to the user. This is a feature of the 802.11b wireless Ethernet standard. Currently, all access points must be from the same vendor for this function to work.VLAN
Virtual Local Area Network, a large logical network (using ATM and LANE) serving an extended area (in this case the campus). For wireless, a single VLAN connects all the access points in the WiscWorld wireless network.