Network Card User Manual

WLAN-IEEE802.11 Tutorial (Maximilian Riegel), 021018-wlan-tutorial.ppt Page 45 © Siemens, 2002
Scanning
n Scanning required for many functions.
– finding and joining a network
– finding a new AP while roaming
– initializing an Independent BSS (ad hoc) network
n 802.11 MAC uses a common mechanism for all PHY.
– single or multi channel
– passive or active scanning
n Passive Scanning
– Find networks simply by listening for Beacons
n Active Scanning
– On each channel
• Send a Probe, Wait for a Probe Response
n Beacon or Probe Response contains information
necessary to join new network.