Mitigation of inadvertent roaming in the Macao SAR

This paper describes a system to mitigate the occurrence of 'inadvertent roaming' (also called 'false roaming') where a user's mobile terminal is in a roaming state (attached to a mainland Chinese network) even when geographically in Macao; such inadvertent roaming led to many complaints from local Macao users. It is clear from the tests that inadvertent roaming is an issue in Macao as modern mobile phones can roam onto all network modes of both mainland GSM networks and that users on some networks are more susceptible than on others. Inadvertent roaming can occur when a user returns from the mainland and the terminal does not switch back to its home network after crossing the border but there is also a probability of roaming to a Chinese network when a user is travelling in Macao. In some places, in-building coverage may be very poor for users at home and this is one cause of the large number of complaints and this can also cause inadvertent roaming. In this paper we discuss the problem and present a solution for mitigation using an Android APP. This will be demonstrated during the session.