Smart Phone and Next Generation Mobile Computing

Supporting Wireless Technologies 159

to an access point by reading beacon frames from it. Some vendors

have an option to disable SSID in beacon frames to enhance security.

The supported rates field in a beacon frame tells stations which data

rates are supported by the access point. The wireless capability field

indicates the requirements of stations that wish to participate in the

wireless LAN.

3.10.4 Roaming in a Wireless LAN

Roaming in wireless LANs is conduced in a nomadic way: Connection

to the current access point will be lost before a new one is discovered

and associated with it. If a mobile station is moving within a set

of access points sharing the same ESSID, what is needed is a layer-2

roaming procedure that does not involve IP change. The procedure ...