What is known as a split-MAC architecture as regards the cisco unified wireless network?

http://www.cisco.com/c/en/us/td/docs/wireless/controller/4-0/configuration/guide/ccfig40/c40mint.htm

this is the division of labor between the LAP:light weight access point and the WLC;wireless lan controller where the normal mac operations are pulled apart into two distinct locations

while LAPS handles real-time processes including actual sending 802.11 frames, AP beacons and probe message

WLC handles management processes becoming the central hub:including RF management, associations/roaming, client authentication, qos