ezWAVE Cards Users’ Guide
Version 1.6
Copyright© Widelink 2000
DOC – 2001.02.01
Page 8 of 36
When an 802.11 client enters the range of one or more APs, it chooses an access point
to associate with (also called joining a Basic Service Set), based on signal strength and
observed packet error rates. Once accepted by the access point, the client tunes to the
radio channel to which the access point is set. Periodically it surveys all 802.11 channels
in order to assess whether a different access point would provide it with better
performance characteristics. If it determines that this is the case, it
reassociates
with the
new access point, tuning to the radio channel to which that access point is set.
Reassociation usually occurs because the wireless station has physically moved away
from the original access point, causing the signal to weaken. In other cases,
Reassociation occurs due to a change in radio characteristics in the building, or due
simply to high network traffic on the original access point. In the latter case this function
is known as “load balancing,” since its primary function is to distribute the total WLAN
load most efficiently across the available wireless infrastructure. This process of
dynamically associating and reassociating with APs allows network managers to set up
WLANs with very broad coverage by creating a series of overlapping 802.11b cells
throughout a building or across a campus. To be successful, the IT manager ideally will
employ “channel reuse,” taking care to set up each access point on an 802.11 DSSS
channel that does not overlap with a channel used by a neighboring access point.
Figure 3.
Roaming
Backbone Network
Access Point (AP)
Inter-Cell Roaming
