9.1 Charging requirements for optimal routeing

23.0793GPPRelease 17Support of Optimal Routeing (SOR)Technical realizationTS

MoU have imposed two constraints for the charging of optimally routed calls:

– No subscriber shall pay more for a call which has been optimally routed than he would do under the present routeing scheme described in GSM 03.04 [1] in the clauses describing the call cases where the GMSC is in the same PLMN as the HLR.

– At least for the first phase of Support of Optimal Routeing, the charge for one leg of a call shall be paid for entirely by one subscriber.

These constraints mean that the direct route for a call cannot always be used. For example, if the calling mobile subscriber (the A subscriber) is in Germany, and the B subscriber’s HPLMN is in Switzerland but he has roamed to Finland, the charge payable by the A subscriber to route the call by the direct route to Finland would be greater than the charge payable to route the call to HPLMNB, so the HPLMN route must be used.

In the first phase of Support of Optimal Routeing, it cannot be assumed that a GMSC is able to calculate the charge payable for the direct route and the charge payable for the HPLMN leg. The MoU requirements can be met by applying more stringent (but simpler) criteria for deciding whether the direct route may be used:

– If the country code of the destination exchange and the country code of the GMSC are the same, then the direct route may be used.

– Otherwise, for a call leg which is chargeable to the A subscriber, if the country code of the destination exchange and the country code of HPLMNB are the same, then the direct route may be used.

– Otherwise, the HPLMN route shall be used.

In certain cases, the second criterion above (equality of country codes for the HPLMN and the destination exchange) may not be enough to determine equality of the charges payable for the direct route and the HPLMN route. In these cases, analysis of the national destination code as well as the country code is required; however the principle is still that if the two numbers are the same to the depth of analysis required then the direct route may be used.

For optimal routeing of late call forwarding, the constraints are satisfied if the following criteria are applied:

– if the country code of the forwarded-to exchange and the country code of the GMSC are the same, then the forwarded call may be routed directly from the GMSC to the forwarded-to exchange;

– otherwise, if the country code of the forwarded-to exchange and the country code of HPLMNB are the same, then the forwarded call may be routed directly from the GMSC to the forwarded-to exchange;

– otherwise, if the country code of the forwarded-to exchange and the country code of VPLMNB are the same, then the forwarded call may be routed directly from the GMSC to the forwarded-to exchange;

– otherwise the forwarded call shall be routed through VPLMNB.