4.4 USSD interworking and Cross-phase compatibility

23.0943GPPFollow-Me (FM)Release 17Stage 2TS

All the messages between MS and the mobile network and internal to the mobile network, which are used for control of Follow Me, are USSD Phase 2 messages.

A Cross-phase compatibility mechanism specified in 3GPP TS 23.011 [6] for networks or MS not supporting USSD Phase 2 is not required.

Networks subject to the Interoperability Directive have to implement FM using USSD Phase 2.

NOTE: As an option, these networks may also implement FM using USSD Phase 1.