Well the MSE is also the db for history record keeping.
Q. Do I need an MSE and Adaptive wIPS software license if I just want to do rogue detection?
A. No. Rogue detection capabilities come with the WLAN controllers and WCS. MSE and Adaptive wIPS software licenses are required to detect over-the-air threats such as reconnaissance, encryption cracking, authentication cracking, denial-of-service (DoS) attacks, and potential threats indicated by anomalous traffic patterns. MSE and Adaptive wIPS also provide full-forensics traffic captures, long-term security event archiving, and reporting, wIPS default tuning profiles, and a threat knowledgebase with plain-English attack descriptions and response guidance for ease of operations.
Differences between Controller IDS and MSE-Based Adaptive wIPS