Heterogenous networks scenarios Current cellular networks use access dependant user identifiers Movement between two different access technologieswithin the same administrative domain implies re-authentication and authorisation Seamless mobility requires avoiding re-authentication/authorisation at the new AR. An access independent user identifier will allow the transfer of user credentials to the new AR regardless of the type of access technology used. The alternative to the above is to ‘mandate ’ one identifier to be used for all current and future L2 ’s. A possible but difficult target to achieve.