LDAP and CUA are two different subjects. They can work together but do not require each other.
To set up LDAP for user data synchronization I think this is a good starting point: http://help.sap.com/saphelp_nw73/helpdata/en/48/74337175bb501ae10000000a42189b/content.htm?frameset=/en/48/7412dc75bb501ae10000000a42189b/frameset.htm
(SAP Help -> Identity Management -> Directory Services)