Even with the predominance of the GSM technology, there are instances when the only coverage for a GSM outbound subscriber is from a CDMA (IS-41) network (that includes many fixed networks in the USA and the CDMA based Globalstar satphone services). Symmetrically a CDMA subscriber roaming in a GSM network after changing for a GSM handset, will need the number continuity service to receive his calls and SMS. Roaming Hubs able to convert the two signalling systems are required. We explain the differences into the mobility protocols (MAP GSM and MAP IS-41), the TCAP protocol (ANSI and ITU) and the network layers (14 bits ITU and 24 bits ANSI Point Codes). The eight possible combinations are handled by a multi-standard Roaming Hub architecture. Detailed protocol traces are included.

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The Number Continuity Service: Part II – GSM CDMA Seamless Technology Change

Mobile Number Portability is now a widely used service allowing users to keep their number if they change their subscribed operator. It was first deployed in Hong-Kong (1999). « Number Continuity » corresponds to the same service but with the switch to another technology, because the subscribed main terminal does not have coverage. The new terminal may be a PC, a smartphone / WiFi, a “satphone”, a GSM phone if the main one is CDMA, with (almost) the same service transparently. Making calls or SMS with its normal CLI shown, receiving calls, SMS, MMS to his normal GSM number (unlike « Skype »). This article explains the GSM satphone number continuity implementation. The Geostationnary and Low Earth Orbit characteristics are presented as well the consequences of orbit drifts for which the exact computation is given based on the formal integration of Kepler's area law. The handover implementation and cases for the satellite service are explained. The constellation and services of the main satellite operators are compared. The telecom core network implementation of the service is detailed in the cases of a GSM type core network and an IS-41 (CDMA) core network.

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Arnaud Henry Labordére

Papers

The Number continuity service, Part I GSM Satellite phone

The Number Continuity Service: Part II – GSM CDMA Seamless Technology Change