scope:

The present document contains the technical realization of the Optimal Routing (OR) function within the GMR-1 Mobile Satellite System. The present document specifies:

• The operational requirements for the mobile satellite OR functionality
• The functional requirements on a network nodal basis
• The functional requirements for the MES

The purpose of mobile satellite OR is to reduce the number of PLMN and PSTN call legs required to complete a call using the mobile satellite system.

The OR function for mobile satellite systems consists of the following:

• Mobile Origination Gateway Selection. This gateway feature enables the selection of a gateway station and subsequent reregistration within that gateway station to minimize the PSTN/PLMN terrestrial network usage or facilitate MES-MES single-hop calls.
• Mobile Termination OR. This network feature enables calls to be routed directly to the mobile subscriber's actual location or to his/her forwarded-to destination while minimizing the use of network trunks.

The present document addresses the system approach for mobile-originated gateway selection. Mobile termination OR is addressed in detail in GSM 02.79 [7] and GSM 03.79 [8] (not addressed in the present document).