History of Related Art In order to make use of prepaid telecommunications services, several elements are needed: a telecommunications device (e. g. a mobile telephone), subscriber authorization (normally supplied by the service provider), a prepaid subscriber card purchased to establish credit, and some number of telephone calls made to deplete the credit available on the card until no more credit is available.

The difficulty encountered by many prepaid service users is that of verifying the monetary (or currency) remaining credit on a particular card. That is, the user typically must pay to make a telephone call to verify the amount of credit remaining. The user faces the dilemma of holding a credit balance which may be insufficient to make a desired call, and further depleting the balance in order to determine the amount remaining. Further, the user typically has no idea how much a short telephone call (e. g. one minute) will cost until the call is made, and the credit balance is depleted by the required amount. In such cases, a prepaid credit subscriber often does not understand why there is an insufficient credit balance to make a particular desired telephone call connection.

Thus, it would be useful to provide a"no-cost"method and apparatus for communicating a prepaid currency credit balance to a

telecommunications device. The method and apparatus would be most useful if the balance could thus be displayed or announced to the user at different times, according to user preference. For example, the credit balance (even if it is negative) might be displayed each time a mobile station is tuned on; on a periodic basis during the time a subscriber is party to an active call connection; or at the completion of each telephone call.

SUMMARY OF THE INVENTION The invention includes a method of communicating a prepaid currency credit balance to a telecommunications device which includes the steps of registering the device with a Mobile Service Center (MSC), detennining the existing prepaid currency credit balance, and sending the balance to the device from the MSC. The determination of the remaining balance can be accomplished by using the MSC to query a PrePaid Complex (PPC), and receiving a response from the PPC to the MSC with the remaining balance. Typically, the remaining balance is displayed and/or announced at the device.

The device registration may be confirmed by the MSC prior to sending the balance to the device. Registration may occur by receiving an indication at the MSC that the device is within the MSC service area, sending a message from the MSC to another node requesting the device subscriber profile, and receiving a response authorizing registration of the device. The message to request a subscriber profile is typically in the form of a RegistrationNotification message.

The method of the present invention may also comprise the steps of detecting that a call connection between the device and another party is to be terminated, querying the PrePaid Complex by the MSC to determine the remaining currency credit balance, responding to the query with the remaining balance information, and sending the remaining balance information to the device from the MSC. An indication that the call connection is to be terminated may include the step of detecting a disconnection trigger, such as an O Disconnect trigger caused by the device terminating (e. g. hanging up) the call connection. The trigger may also be

caused by the other party terminating the on-going call connection. The method may include sending an ODISCONNECT message from the MSC to the PrePaid Complex and playing an announcement message at the device which indicates the remaining balance. Alternatively, or in addition to the announcement, the remaining credit balance can be displayed at the device.

In addition, the method of the present invention may include the steps of making a call connection between the device and another party, querying the PrePaid Complex by the MSC during the call to determine the remaining currency credit balance, responding to the query with the balance information, and sending the information to the device according to a preselected time interval during the call. The information is typically displayed at the device, and maybe accompanied (or replaced) by an announcement message.

Finally, the invention includes a node enabling communication of a prepaid currency credit balance to a telecommunications device, wherein the node comprises a program module adapted to query the PrePaid Complex to determine the remaining currency credit balance, receive a response from the PrePaid Complex including the balance information, and sending the remaining balance information to the device. The program module may also be adapted to send the information to the device according to a preselected time interval.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the structure and operation of the present invention may be had by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein: FIG. 1 is a network operational diagram illustrating an embodiment of the method of the present invention as applied to the registration process; FIG. 2 is a network operational diagram illustrating an alternative embodiment of the method of the present invention as applied to a call termination process; FIG. 3 is a network operational diagram illustrating an alternative

embodiment of the method of the present invention as applied to periodic updates during an on-going call connection; and FIG. 4 is a block diagram of a node which embodies the present invention.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS Turning now to Fig. 1, a network operation diagram illustrating the method of the present invention as applied to registration operations for a mobile telephone can be seen. In this case, an interface 60 is established between a Mobile Station (MS) 10 and aMobile Switching Center (MSC) 20. The interface 60 is usually effected using an air interface between the MSC 20 and a base station (not shown), an electronic link between the base station and a base station controller (not shown), and another electronic link between the base station controller and the MSC 20.

After the MS 10 is turned on, the MSC 20 typically receives an indication that the MS 10 is within its service area. This occurs most often using paging location updates for mobile stations within the service area and receiving a response from the MS 10 at the MSC 20. A registration notification message (REGNOT) 70 is then sent from the MSC 20 to a Visitor Location Register (VLR) 30 to request a subscriber profile for the MS 10. If the VLR 30 determines that the MS 10 is not known to the VLR 30, then the REGNOT message 70 is forwarded to the home location register (HLR) 40 using a REGNOT message 80. A registration-notification response 90 is returned from the HLR 40 to the VLR 30 after a determination is made that the MS 10 is authorized to communicate. Authorization is granted after the registration notification response (regnot) messages 90 and 100 are received by the VLR 30 and MSC 20, respectively.

At this point, the MSC 20 sends a Balance Query message 110 to the PrePaid Complex (PPC) 50 to determine the actual remaining prepaid currency credit balance (even if it is negative) in monetary units, such as dollars, pesos, etc. This balance information is in sharp contrast to the information previously available to the

MSC 20, which indicates only the"minutes remaining"time supervision value returned to the MSC 20 by the PPC 50. In the instant case, the actual monetary balance, given in user-specified currency units (e. g. dollars) or currency units appropriate to the current location of the MS 10 (e. g. pesos if the service area includes Mexico) is returned in the balance response 120 from the PPC 50 to the MSC 20. Of course, the balance response 120 may also contain the number of"minutes remaining" for a standard call based on the monetary balance. The number of minutes remaining can be calculated by the PPC 50, or the MSC 20.

The MSC 20 may then confirm registration of the MS 10 using a confirmation message (confirm message) 130 which includes the prepaid currency credit balance in monetary units. The currency credit balance may be sent as a component of the confirm-message 130, or the MSC 20 may merely confirm registration of the MS 10 in the confinn message 130, with the actual credit balance information sent as a specific balance message 140. Thus, the specific balance message 140 is an optional feature of the present invention.

Turning now to Fig. 2, the method of the present invention as applied to a call termination scenario can be seen. In this case, there is an on-going call connection 150 between the MS 10 and another party 55. At some point during the connection time period, an indication that the call connection 150 between the MS 10 and the party 55 is to be terminated arises. This indication may be obtained by detecting a disconnection trigger, such as an O Disconnect trigger 160, which is a query from the MS 10 to the MSC 20 to disconnect the call. The 0Disconnect trigger 170 can also be provided from the party 55 to the MSC 20. In either case, the 0Disconnect triggers 160,170 may be initiated by the MS 10 or party 55 hanging up on the ongoing call connection 150, at which time the MSC 20 will detect the trigger in step 180. This initiates sending an ODISCONNECT query message 190 from the MSC 20 to the PPC 50. In return, a balance response 200 message is sent from the PPC 50 to the MSC 20 as a response to the ODISCONNECT query 190, containing the prepaid currency credit balance for the MS 10. The balance response message 200 may be accompanied by an announcement message 210 from the PPC 50 to the MSC

20 so that the balance message 220 can be displayed at the MS 10, and played at the MS 10 simultaneously. The announcement message 210 is optional, and can be used in conjunction with the display of the remaining credit balance at the MS 10, or by itself (i. e., without any specific display of the remaining prepaid currency credit balance at the MS 10.

The method of the present invention includes the possibility of supervising a call connection by an MSC for updating the prepaid currency credit balance by announcement message and/or display at the corresponding MS. Turning now to Fig. 3, the method of the present invention as applied during an ongoing call with periodic updates of the prepaid currency credit balance can be seen. In this case, the interface 60 between the MS 10 and MSC 20 is established as described above, and registration of the MS 10 with the MSC 20 occurs at step 230 so that an ongoing call connection 150 can be established. If selected by the service provider, or the subscriber, a periodic Balance Query message 110 can be sent from the MSC 20 to the PPC 50. In return, a balance response 120 can be provided by the PPC 50 to the MSC 20 in currency units, as described above. Then, a balance message 140 can be presented to the MS 10 by the MSC 20. This balance message 140 may include display information and be accompanied by an announcement, or may consist solely of an announcement and not include display information.

Balance messages 140, shown in Fig. 3, can be sent at periodic intervals from the MSC 20 to the MS 10 according to a preselected time interval. The interval may be selected by the service provider or the subscriber. In each case, the MSC 20 is responsible for supervising the on-going call connection 150 and proffering a periodic Balance Query message 110 to the PPC 50, receiving the prepaid currency credit balance information as the component is the balance response 120, and forwarding an updated balance message 140 to the MS 10. In this way, the MS 10 user is constantly apprised of the prepaid currency credit balance as the ongoing call connection 150 continues.

Turning now to Fig. 4, a node 250 (e. g. an MSC) which enables communicating the prepaid currency credit balance to a telecommunications device,

such as the MS 10 operating within the node 250 service area 300, can be seen. The node 250 typically comprises a program module 260 which is adapted to query a PPC 50 using one or more query-response interchanges 270 to determine a prepaid currency credit balance for the MS 10. Once the result of a query response interchange 270 is received from the PPC 50 at the program module 260, the prepaid currency credit balance for the MS 10 can be sent to the base station 240 as information 280, over the air interface 290 to the MS 10. The remaining balance information 280 can be passed along the MS 10 during registration of the MS 10, at the termination of a call, or on a periodic basis according to a preselected time interval, as described above.

Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limited sense. The various modifications of the disclosed embodiments, as well as alternative embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is, therefore, contemplated that the appended claims will cover such modifications that fall within the scope of the invention, or their equivalents.