The CISCO-DOT11-IF-MIB sometimes does not give the correct output. This is a known issue. You could try using the other MIBs that Aironet products support. Some of the MIBs are 
BRIDGE-MIB
CISCO-AAA-SERVER-MIB
CISCO-CDP-MIB
CISCO-CLASS-BASED-QOS-MIB
CISCO-CONFIG-COPY-MIB
CISCO-CONFIG-MAN-MIB
CISCO-DDP-IAPP-MIB
CISCO-DOT11-ASSOCIATION-MIB
CISCO-DOT11-CONTEXT-SERVICES-CLIENT-MIB
CISCO-DOT11-IF-MIB
CISCO-DOT11-RADIO-DIAGNOSTIC-MIB
CISCO-DOT11-RADIO-DIAGNOSTIC-CAPABILITY
CISCO-ENTITY-VENDORTYPE-OID-MIB
CISCO-FLASH-MIB