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Field of the Invention

The present invention relates to a method wherein roaming costs are reduced for international GSM (Global System for Mobile Communications) operators.

Background of the Invention

International GSM operators enable subscribers to talk with low-costs abroad by means of applications that they install to the SIM (Subscriber Identification Module) card. In methods wherein the said applications are used, when the subscriber is abroad s/he needs to enter the menu of the country where s/he is in and start the application by selecting the necessary application from the SIM card menu. The subscriber needs to have a specific training in order to use these applications.

Leaving the selection of international roaming to subscribers, who are unaware of the said service in the SIM card or do not know how to use it or forget to use this service, causes the subscribers to talk with high-costs by being charged over high tariff in countries where they go. In addition, it causes the subscribers not to be able to get GSM service in countries with which the GSM operator does not have international roaming agreement.

Various methods have been developed in order to enable the subscribers to talk over low-charge tariffs abroad.

One of the state of the art applications is the International patent document no. W09428683A1. In this application, there is a selection unit and a pricing unit which is in communication with this selection unit in the user equipment. In the International patent document no. W09912366A1, charging systems of all candidate operators are compared and the user is steered to the cheapest operator upon a request is received from the mobile terminal before the user starts to get service from an operator.

In the Great Britain patent document no. GB235562 A, the user is steered to the cheapest operator by the application recorded in the mobile terminal. Solutions in the state of the art cause operators to make change in communication networks. This leads to high costs.

Summary of the Invention The objective of the present invention is to realize a method wherein the subscriber avails of the best GSM tariff, by enabling the SIM card to automatically detect the country where the subscriber is in.

Another objective of the present invention is to realize a method wherein the subscriber is steered to the GSM operator having the cheapest cost of international roaming, by comparing the GSM operators in the country where the subscriber is in.

In the present invention; it is aimed to realize a method which reduces international roaming costs by enabling the operator of the subscriber's SIM card to be selected automatically, if any, in the country where the subscribers of operators, that are providing service as GSM operator in more than one country, are in. Yet another objective of the present invention is to realize a method which enables subscribers to take advantage of cheap costs for their in-operator calls or calls with other operators that they get service from in foreign countries where they are in.

A further objective of the present invention is to realize a method wherein the IMSI value in the SIM card is changed by taking a value from the IMSI range of an operator in the country where the roaming occurs and thus the SIM card gets service from the network in the foreign country directly over the said operator in the country where the roaming occurs. A yet further objective of the present invention is to realize a method which enhances quality of service.

Detailed Description of the Invention The method realized to fulfill the objective of the present invention is illustrated in the accompanying figure, in which:

Figure 1 is the flow diagram of the inventive method. The IMSI file in the SIM card memory is personalized with the IMSI code, which will be used by the subscribers at their home country, by the SIM card producer. Whereas the IMSI codes which will be used by the subscribers abroad are kept in a separate file in the SIM card memory. Country codes and which IMSI value will be used in response to each country code are defined in the SIM card memory.

In the inventive method, a STK (SIM Toolkit) application is installed into the SIM card which will be used by the subscriber. The SIM card is inserted into the device to be used. The said device is a mobile phone in a preferred embodiment of the invention.

The inventive method comprises the steps of: operating the device by inserting the SIM card into the device

(101) ;

the SIM card enabling information of countries with which the GSM operator has an international roaming agreement or not to be sent to the device by the GSM network, by interrogating the GSM network at time intervals which are predetermined by the producer

(102) ;

the SIM card interrogating from the GSM network whether the GSM operator has an international roaming agreement with the country where the subscriber is in at that point (103); if the operator does not has an international roaming agreement with the country where the subscriber is in at that point, sending a response to the SIM card by the GSM network regarding to the fact that the service is not supported (104);

sending the country code belonging to the GSM world of the country where the subscriber is in at that point by the GSM network to the SIM card (105);

finding out the IMSI code corresponding to the code of country where the subscriber is in from the IMSI codes file in the SIM card memory (106);

updating the IMSI code which is used in the SIM card at that point by the newly found IMSI code (107);

restarting the subscriber's device (108);

the SIM card getting service from the network directly if the GSM operator has an international roaming agreement with the country where the subscriber is in at that point (109).

In the present invention, the subscriber inserts his/her SIM card into his/her device and operates the device. The SIM card enables information of countries with which the GSM operator has an international roaming agreement or not to be sent to the device by the GSM network, by interrogating the GSM network at time intervals which are predetermined by the producer. The SIM card carries out the said interrogation operation by running "PROVIDE LOCAL INFO" proactive command in the device at certain intervals. Upon the proactive command is run in the device, the GSM network sends "SERVICE NOT GRANTED" response and the country code belonging to the GSM world of the country where the subscriber is in to the device in countries with which the GSM operator has not got an international roaming agreement.

If the GSM operator, from which subscriber gets service, has no international roaming agreement with the country where the subscriber is in then the STK application finds out the IMSI code corresponding to the code of country where the subscriber is in from the IMSI codes file in the SIM card memory. The IMSI code in the SIM card is updated with this newly found IMSI code. Thus, the IMSI code which will be used by the subscriber abroad is defined in the mobile phone. Then, the subscriber's device is enabled to be restarted. The said process occurs depending on the terminal profile of the device. Namely, if the subscriber's mobile device supports the "REFRESH" proactive command this command is run and the device is restarted. If the subscriber's mobile device does not support the "REFRESH" proactive command, the subscriber is notified to restart the mobile device by means of the "DISPLAY TEXT" proactive command.

After the SIM card runs the "PROVIDE LOCAL INFO" proactive command in the device, the SIM card is enabled to get service from the network directly if an international roaming agreement belonging to the GSM operator of the SIM card is found in the country where the subscriber is in.

With this invention, subscribers are steered automatically to the GSM operator having the cheapest cost of international roaming in the country where they are in. Thus, subscribers can talk with cheap costs without experiencing loss of service and number of subscribers who prefer the operator using the inventive method will increase. In addition, operators do not need to make change in communication networks and thus no additional cost occurs.

It is possible to develop a wide variety of embodiments of the inventive method (1). The invention cannot be limited to the examples described herein and it is essentially according to the claims.