MAKING A CALL BY A PREPAID SUBSCRIBER ROAMING IN A VISITED NON-CAMEL NETWORK

摘要

A SIM (201) within mobile device or terminal (202) is programmed with the list of Mobile Switching Centers (MSC) /Visitor Location Registers (VLRs) that cannot support CAMEL. The SIM (201) is programmed with a USSD (Unstructured Supplementary Service Data) Code (e.g. *BAL#) which is used for obtaining a balance inquiry from a prepaid system (205). When the subscriber is visiting in a non-CAMEL MSC (203), a SIM application (201A) loaded in the SIM (201) launches the USSD balance inquiry (e.g. *BAL#) while the call set up is on-going. The mobile device or terminal (202) communicates via the subscriber's HLR (204) to the prepaid system (203), then returns the balance. This is an existing feature in many prepaid systems. The SIM application (201A) authorizes the call if the balance is above a certain threshold. As an extension, the SIM application (201A) can launch the USSD balance inquiry during the call at a regular intervals and let the call continue if the balance is sufficient. If the balance goes below a threshold, the mobile device or terminal (202) through SIM application (201A) will tear down the call.