The support for 1121AP's was added in the WLC release 18.104.22.168. We were converting to LWAPP this past summer and thought that we were going to have to replace all of our 1121's. With this release we were able to convert them all from Autonomous to LWAPP successfully.
Connecting 1100 Series Access Points
LWAPP for Cisco Aironet 1100 Series Access Points (802.11g radio only) Allows the Cisco Aironet 1100 Series Access Point to be upgraded from autonomous access point mode to lightweight mode using the autonomous to lightweight mode upgrade tool.