Signalling interoperability as a key enabler to GSM/PCS roaming with North America

The world-wide success of GSM is commonly acknowledged to its most innovative feature: roaming, that allowed one to extend GSM services from the original target (Europe) to four continents. America could not passively assist to this popularity growth and, in spite of the unavailability of the 900 MHz frequencies, adopted the GSM platform in the 1900 MHz band, opening the door to plastic roaming, based on the use of a GSM SIM card in another mobile terminal possibly working at a different frequency. Hence, the evolutionary path of GSM roaming with North America is a necessary introduction to the paper. It makes a historical survey over all the available roaming alternatives, starting from the rough mechanisms of call forwarding to a North American mobile, passing through the intermediate solution offered by GlobalRoam/sup TM/ now commercially available through an intelligent network platform. The potentialities of SIM card roaming, in relation to dual/triple band terminals, are eventually covered in the perspective of an evolutionary path to a personal communication system. For each roaming alternative, pros and cons (e.g. maintenance of the same number, fraud implications, friendly procedures) are finally compared.