7 Routeing of a call from a subscriber in a different country from the HPLMN

03.043GPPSignalling Requirements Relating to Routing of Calls to Mobile SubscribersTS

This clause considers three configurations: where the HLR is interrogated by a gateway exchange which is part of the HPLMN (the preferred configuration), where the HLR is interrogated by the incoming ISC in the country of the HPLMN, and where the HLR is interrogated by the outgoing ISC in the country of the calling subscriber.

7.1 Interrogation by a Gateway MSC

If the HLR is interrogated by a gateway exchange which is part of the HPLMN, the configuration is as shown in figureĀ 7. The call is handled as described in clause 4. If the called MS has roamed outside its HPLMN country the GMSC routes the call to the visited PLMN (VPLMN) via a second international route, as shown in figure 8.

Figure 7: Call from a subscriber in a different country from the called MS; interrogation by GMSC in the HPLMN

Figure 8: Call from a subscriber in a different country from the called MS; interrogation by GMSC in the HPLMN; called MS roamed to another PLMN

7.2 Interrogation by the Incoming ISC in the Destination Country

If the HLR is interrogated by the incoming ISC in the HPLMN country, the configuration is as shown in figure 9. After the HLR has returned the MSRN to the incoming ISC, the incoming ISC routes the call to the VMSC. If the called MS has roamed to another country the incoming ISC routes the call to the visited PLMN (VPLMN) as shown in figure 10. In this case, the routeing for the call does not pass through the HPLMN.

Figure 9: Call from a subscriber in a different country from the called MS; interrogation by incoming ISC

Figure 10: Call from a subscriber in a different country from the called MS; interrogation by incoming ISC; called MS roamed to another PLMN

7.3 Interrogation by the Outgoing ISC in the Originating Country

If the HLR is interrogated by the outgoing ISC in the originating subscriber’s country, the configuration is as shown in figure 11. After the HLR has returned the MSRN to the outgoing ISC, the outgoing ISC routes the call to the VMSC via an incoming ISC in the HPLMN country. If the called MS has roamed to another country the outgoing ISC routes the call to the visited PLMN (VPLMN) as shown in figure 12. In this case, the routeing for the call does not pass through the HPLMN country.

Figure 11: Call from a subscriber in a different country from the called MS; interrogation by outgoing ISC

Figure 12: Call from a subscriber in a different country from the called MS; interrogation by outgoing ISC; called MS roamed to another PLMN