Method and system for roaming of a mobile communications unit

摘要

A method when roaming by a mobile communication device including a SIM card identifying itself using an IMSI roams between a home network and one or several visited networks, which networks are interconnected by a PSTN. The method a) stores on the SIM card a first IMSI associated with a first collaborating network; b) initiates a location update procedure using the first IMSI; c) triggered by the location update procedure and based on the first IMSI, causes an STP (Signal Transfer Point) of the first collaborating network to send a location update message to an ITP (Internet Transfer Point); and d) causes the first ITP to forward the message to an STP of the home network via a wide area network and not using the PSTN.

主权项

1. A method for use when a mobile communication device roams between a mobile communication home network in a home country and one or several mobile communication networks in one or several visited countries, which home network and networks in said visited countries are interconnected by a PSTN (Public Switched Telephone Network) operated by one or several PSTN operators, via which PSTN telephone signaling can be performed during roaming using a telephony signaling protocol, which mobile communication device comprises a Subscriber Identity Module (SIM) card identifying itself to each network using an International Mobile Subscriber Identity (IMSI), wherein the method comprises the steps of:
a) storing on the SIM card a first visited country IMSI which is associated with a first collaborating mobile communication network in the first visited country, and using it for network identification of the SIM card; b) when the mobile device is located within the coverage area of the first collaborating network, causing the mobile device to initiate a location update procedure using the first visited country IMSI; wherein the method further comprises the subsequent steps of c) triggered by the said location update procedure and based on the first visited country IMSI used therein, causing the first collaborating network to investigate the contents of the said first IMSI, and, depending on the contents of said first IMSI, causing a first STP (Signal Transfer Point) of the first collaborating network to send a location update message to a first ITP (Internet Transfer Point) without using the PSTN; d) in case the location update message was sent to the first ITP, causing the first ITP to simply forward the location update message to a home ITP via the internet and not using the PSTN, and in turn causing the home ITP to forward the location update message to a home STP of the home network; and e) causing a subsequent signaling message addressed to the mobile device and using the first visited country IMSI to be sent by the home STP to the home ITP, which uses the first visited country IMSI to identify the first ITP and then forwards the subsequent message to the first ITP, over the internet and without using the PSTN, whereupon the first ITP forwards the subsequent message to the first STP for distribution to the mobile device.