CAPTIVE PORTAL AND LDAP

I have a BALANCE 210 (firmware 8.1.3) with some AP ONE AX lite and the need to create two captive portal (one for Students and the second for Teachers) that are linked to two user groups on windows server AD.
User Manual, at page 190, show image of captive portal settings with possibility to choise beetwen Radius and LDAP in the access mode.
In my Balance 210 there is only RADIUS.
is it a feature not avaible on 210?
Other solution without LDAP?