Today it's possible to virtualize the controller. By running it in a distributed way, smart APs can manage themselves with coordinated intelligence.
WLAN controllers (a rack mounted appliance or server) works with thin APs that retrieve their firmware and configuration from the WLAN controller: a single point of management for the entire wireless network. It also acts as a switch and as a firewall for all the wireless traffic that is tunneled through the controller: a single point of control and termination for all wireless traffic.
Today it's possible to virtualize the controller and deploy it and run it in a distributed way in the APs themselves with coordinated intelligence. Smart and advanced APs are managed as a single system or cluster and handle the control and forwarding planes in a distributed and coordinated manner.
A Unified Management and Distributed Control solution eliminates the previously required controller from wireless deployment architectures, offering many potential benefits to organizations and their IT departments.