I have multiple Access Points on the same network with a Radius server for authentication. When I switch from one AP to another, do I have to go through the complete re-authentication processes each time?
If your access points are independent, then yes, each time you connect to an access point, you need to authenticate. This happens automatically in the background but incurs some delay and the communication will be briefly cut.
This is one of the major issues with stand-alone APs.
To solve this, you can use access points managed centrally by a controller. In this case, you authenticate once and the controller manages the handover from an AP to another one with (almost) no delay.
It depends on how your access points are set up. If your access points are centrally managed by a wireless controller, then the wireless controller will synchronize authentication traffic from radius servers. The access points can reach the wireless controller for authentication every time it is required. The user won't experience an interruption when they are moving around in that wireless network.
In the case where access points are not integrated with a wireless controller then the access points have to authenticate the user every time the user switches access points