EP1166570A1

EP1166570A1 - Inter-exchange carrier selection system and method

Info

Publication number: EP1166570A1
Application number: EP00921267A
Authority: EP
Inventors: Donald Joong; Nikos Katinakis; Akabar Rahman
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 1999-03-31
Filing date: 2000-03-28
Publication date: 2002-01-02
Also published as: WO2000059241A1; AU4160100A; AR023186A1

Abstract

In a radio telecommunications network (10), a system and method of allowing inter-exchange long-distance carrier selection to a caller is provided. The system includes a mobile terminal (22), a serving mobile switching center (S-MSC) (18) for serving the mobile terminal, and a gateway mobile switching center (G-MSC) (14) for receiving an incoming call from a caller for the mobile terminal. The system also includes at least one inter-exchange carrier (IXC) (35, 37) allowing communication between the S-MSC and the G-MSC, a roaming detector (24) for detecting a roaming condition of the mobile terminal, and a charging module (26) for informing the caller of the roaming condition of the mobile terminal. The method begins by receiving at the G-MSC an incoming call placed by a caller to a mobile terminal served by the S-MSC, determining the IXC associated with the caller, and detecting a roaming condition associated with the mobile terminal. The method continues by informing the caller about the roaming condition, determining whether the caller accepts roaming charges associated with the roaming condition and completing the call between the G-MSC and the S-MSC on the IXC if the caller accepted the roaming charges.

Description

INTER-EXCHANGE CARRIER SELECTION SYSTEM AND METHOD

BACKGROUND OF THE INVENTION

Technical Field of the Invention

The present invention relates to a cellular telecommunications system and, in particular, to the selection of inter-exchange long-distance carrier by a calling party in a mobile terminating call.

Description of Related Art

With the advent and development of mobile telecommunications systems, telecommunications users are no longer physically bound to wireline terminals or locations for telecommunications network communications. Using the added capabilities of roaming and interoffice handoffs, mobile subscribers may travel between multiple public land mobile networks (PLMN) utilizing the same telephone number and the same mobile terminals (MT) to originate outgoing calls and to receive incoming calls. Thus, a mobile subscriber may access telecommunications service from multiple locations utilizing multiple service providers with any incurred bills being charged to his own subscription.

Furthermore, calling parties do not necessarily have to know where the mobile subscriber is physically located in order to properly route the call and to establish a speech connection. Data signals between Visiting Location Registers (VLRs) and a Home Location Register (HLR) automatically update and store subscriber information enabling the network to reroute incoming calls to the appropriate

Mobile Switching Center (MSC) serving the mobile subscriber.

However, such added mobility is not always desirable for a subscriber who has a subscription obligation with a service provider. Unlike wireline communications, cellular subscribers are responsible for charges incurred for both incoming and outgoing calls. The charges incurred include: air-time charges, roaming charges and long-distance charges.

As an example, if the mobile subscriber is roaming outside of his home area, and receives an incoming long-distance call, the mobile subscriber is responsible for the roaming charges associated with his or her roaming condition, he or she is also responsible for the long-distance charges which are always inevitably associated with the roaming condition of the subscriber (unless he or she receives an incoming call to a roamer access port which would not be considered a long-distance call), and he or she is further responsible for air-time charges. The scenario could be further aggravated if the subscriber receives an unwanted call. In such a situation, the subscriber is not so willing to answer calls unless he or she knows that these are important enough to warrant the expense, e.g., an emergency call from a family member or an important business call. Radio telecommunications operators could thus be faced with decreased revenues in such instances.

N number of systems have been developed to block unwanted incoming calls within a telecommunications system. These systems are provided either by a module within the MT or servicing MSC where incoming calls are selectively barred. Typically, incoming calls from certain predefined telephone directory numbers are barred.

Furthermore, other systems have been developed to reverse the charging to the calling party. However, these systems normally charge the calling party an excessive lump sum for roaming charges, long-distance charges, and air-time charges. These systems do not offer the flexibility to charge the calling subscriber only for both the roaming and long-distance charges. Furthermore, these systems do not allow the calling party to select a preferred inter-exchange carrier, which would reduce the long-distance charges incurred for the call.

It would be a distinct advantage to have a method in a radio telecommunications system allowing a calling party to accept roaming and long-distance charges and to select a preferred inter-exchange carrier in the scenario where the charging is reversed.

SUMMARY OF THE INVENTION The present invention is a system and method of selecting of inter-exchange long-distance carrier by a calling party in a mobile terminating call.

In one aspect, the present invention is a method of operating a radio telecommunications network. The method begins by receiving at a gateway mobile switching center (G-MSC) an incoming call placed by a caller to a mobile terminal served by a serving mobile switching center (S-MSC), determining an inter-exchange carrier (IXC) associated with the caller, and detecting a roaming condition associated with the mobile terminal. The method continues by informing the caller about the roaming condition, determining whether the caller accepts roaming charges associated with the roaming condition and completing the call between the G-MSC and the

S-MSC on the inter-exchange carrier (LXC) if the caller accepted the roaming charges.

In another aspect, the method of the present invention begins by receiving at a gateway mobile switching center (G-MSC) an incoming call placed by a caller to a mobile terminal served by a serving mobile switching center (S-MSC), detecting a roaming condition associated with the mobile terminal, informing the caller about the roaming condition, and determining whether the caller accepts roaming charges associated with the roaming condition. The method continues by providing the caller with an inter-exchange carrier (IXC) selection, obtaining an inter-exchange carrier

(IXC) selection from the caller, and completing the call between the G-MSC and the

S-MSC on the inter-exchange carrier (IXC) selected if the caller accepted the roaming charge.

In yet another aspect, the present invention is a system for allowing inter-exchange carrier selection in a radio telecommunications network. The system includes a mobile terminal, a serving mobile switching center (S-MSC) for serving the mobile terminal, and a gateway mobile switching center (G-MSC) for receiving an incoming call from a caller to the mobile terminal. The system also includes at least one inter-exchange carrier (LXC) allowing communication between the S-MSC and the G-MSC, a roaming detector (RD) for detecting a roaming condition of the mobile terminal, and a charging module (CM) for informing the caller of the roaming condition of the mobile terminal. The charging module verifies whether the caller accepts roaming charges for the call, and if the caller accepts the charges, the charging module verifies which at least one inter-exchange carrier (LXC) the caller selects for completing the call between the G-MSC and the S-MSC. BRLEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and its numerous obj ects and advantages will become more apparent to those skilled in the art by reference to the following drawings, in conjunction with the accompanying specification, in which: FIGURE 1 is a block diagram of an inter-exchange carrier selection system of the present invention;

FIGURE 2 illustrates representative parameters of an Initial Address Message (IAM) of an Integrated Services Digital Network (ISDN) User Part (ISUP) signal;

FIGURE 3 illustrates representative parameters of a Toll Ticket Record; FIGURE 4A is a message flow diagram illustrating the flow of messages in the present invention for allowing completion of a call between a G-MSC and a S-MSC on an inter-exchange carrier associated with a caller;

FIGURE 4B is a message flow diagram similar to FIGURE 4A according to a first variant of the invention; FIGURE 4C is a message flow diagram similar to FIGURE 4A according to a second variant of the invention;

FIGURE 4D is a message flow diagram similar to FIGURE 4A according to a third variant of the invention;

FIGURE 5A is a message flow diagram illustrating the flow of messages according to a second embodiment of the present invention for allowing inter-exchange carrier selection and completion of a call between a G-MSC and a S-MSC;

FIGURE 5B is a message flow diagram similar to FIGURE 5 A according to a first variant of the second embodiment of the invention; FIGURE 5C is a message flow diagram similar to FIGURE 5 A according to a second variant of the second embodiment of the invention; and

FIGURE 5D is a message flow diagram similar to FIGURE 5 A according to a third variant of the second embodiment of the invention. DETALLED DESCRIPTION OF EMBODIMENTS

Reference is now made to FIGURE 1 wherein there is shown a block diagram of a radio telecommunications network 10 in which the inter-exchange carrier selection system of the present invention has been implemented, to FIGURE 2 wherein there is shown representative parameters of an Initial Address Message (LAM), and to

FIGURE 3 wherein there is shown representative parameters of a Toll Ticket Record. Networks 12 such as the Public Switched Telephone Network (PSTN) or the Public Land Mobile Network (PLMN) or the Integrated Services Digital Network (ISDN) are connected to the radio telecommunications network 10 through a gateway mobile switching center (G-MSC) 14. The PSTN/PLMN/ISDN 12 and the G-MSC 14 are interconnected with each other for communication via both signaling links 11 (illustrated with solid lines) and voice trunks 13 (illustrated with broken lines) providing a known ISDN User Part (ISUP) type connection. The signaling links 11 carry commands signals between the PSTN 12 and the G-MSC 14. The voice trunks 13 provide voice and data communications paths used to carry subscriber communications between the PSTN/PLMN/ISDN 12 and the G-MSC 14. Although direct communication links (signaling and or trunk) are illustrated in FIGURE 1 , it is understood by those skilled in the art that the links are not necessarily direct between the illustrated nodes, and may instead pass through many other communication nodes (not shown) of the radio telecommunications network, and perhaps even utilize other communications networks. Illustration of the links in the "virtual" manner shown in FIGURE 1 is therefore byway of simplification of the drawing. The G-MSC 14 may also be an originating MSC (O-MSC) if the incoming call is a mobile originated call rather than coming from a landline network such as the PSTN. Although only one G-MSC 14 is shown, it will be understood that the network 10 likely includes many more interconnected nodes.

The G-MSC 14 is connected to a home location register (HLR) 16 by means of signaling links (not shown) providing a known Mobile Application Part (MAP) or ANSI-41 type connection. The HLR 16 stores information concerning mobile terminals comprising location information and service information.

The HLR 16 is connected by means of MAP or ANSI-41 signaling links to a serving MSC (S-MSC) 18. The S-MSC 18 is connected to one or more base stations (BS) 20 which transmit and receive radio information with one or more mobile terminals (MT) 22. Normally, visitor location registers (VLRs) are used for communications between MSCs and HLRs, but these VLRs have been omitted from the figures in order to simplify the illustration. The exact network architecture may vary without affecting the scope of the present invention.

The radio telecommunications network 10 may comprise Global System for Mobile (GSM) communications, an Advanced Mobile Phone System (AMPS), a Digital Advanced Mobile Phone System (D- AMPS), a Code Division Multiple Access (CDMA) system or the like. Applicable standards, which are hereby incorporated by reference, include the GSM standard the IS-136 TDMA standard, the IS-95 CDMA standard, and the ANSI-41 standard.

Normally, when a call to a mobile terminal 22 comes in from the PSTN 12, it is trunked to the G-MSC 14. The G-MSC 14 interrogates the HLR 16 for the location of the called mobile terminal 22. The HLR 16 interrogates the S-MSC 18 for routing instructions. The S-MSC 18 returns a routing number through the HLR 16 to the G-MSC 14. The call is then trunked from the G-MSC 14 to the S-MSC 18 and connected to the called mobile terminal 22 through the serving base station 20.

In the situation where the called mobile terminal 22 is roaming outside of his home area, the call is usually trunked via an inter-exchange carrier that connects the

G-MSC 14 to S-MSC 18. The inter-exchange carrier is preset by a network operator in the Integrated Services Digital Network (ISDN) User Part (ISUP) signals that are sent from the G-MSC 14 to the inter-exchange carrier and to the S-MSC 18. These ISUP signals carry an Initial Address Message (LAM) which includes a parameter called Carrier Identification Code (CIC) or Preferred Inter-exchange Carrier (PIC).

The CIC parameter determines which inter-exchange carrier, out of a plurality of inter-exchange carriers, will trunk the call. In FIG. 1 , only two inter-exchange carriers LXC- A 35 and LXC-B 37 are shown in order to simplify the illustration.

In the above situation, all incoming calls to the mobile terminal's home number are charged as long-distance calls, which are in addition to roaming charges.

In such a situation, the call is completed between the G-MSC 14 and the S-MSC 18 on the preset inter-exchange carrier as explained above.

Furthermore, the caller may have his inter-exchange carrier (for e.g. LXC-A 35) overwrite the inter-exchange carrier preset by the network operator (for e.g. LXC-B 37). When the call is initially setup, an ISUP signal is sent from the PSTN 12 to the G-MSC- 14 to provide routing information. In the prior art, the CIC parameter was provided by the HLR in a locreq return result message. In this invention, the CIC parameter corresponding to the caller's network is provided by an ISUP signal that is sent from the PSTN 12 to the G-MSC 14. As discussed above, the ISUP signal includes the IAM, which in turn includes the CIC parameter. The CIC is associated with the caller and is received at the G-MSC 14 where it is used to overwrite the CIC in subsequent IAM messages that are sent to other nodes from the G-MSC 14.

In the present invention, the G-MSC 14 is connected to a roaming detector (RD) 24 which detects a roaming condition of the mobile terminal 22. The RD 24 determines that the mobile terminal 22 is roaming based on the Temporary Location Directory Number (TLDN) that is returned to the G-MSC 14 via the HLR 16. The locreq return result is used to send the TLDN from the S-MSC 18 through the HLR 16 back to the G-MSC 14.

The RD 24 is shown to be connected to the G-MSC 14, but may also conveniently reside in the G-MSC 14 or in the S-MSC 18, or in another node, as needed by a particular design architecture. The RD 24 normally being a software application, it allows for these changes to be easily implemented. Thus, these changes may be made without departing from the scope of the present invention.

The G-MSC 14 is further connected to a charging module (CM1) 26, which informs a caller of the roaming condition of the mobile terminal. The CM1 26 has been shown to be connected to the G-MSC 14, but may also conveniently reside in the G-MSC 14 or in the S-MSC 18, or in another node, as needed by a particular design architecture. The CM1 26 normally being a software application, it allows for these changes to be easily implemented. Thus, these changes may be made without departing from the scope of the present invention. In the present invention, once the RD 24 detects a roaming condition of the mobile terminal 22, the CM1 26 informs the caller thereof. The CM1 26 further verifies whether the caller accepts roaming charges for the call, which also include long-distance charges. It will be understood that the CMl 26 may also only verify whether the caller accepts long-distance charges for the call without including the roaming charges per se. The CMl 26 functions as an automated interactive system by prompting the caller to accept the roaming charges. The caller may accept the charges by dialling keys on his terminal and the information may be sent using DTMF coding. This information is returned to the G-MSC 14, which can then proceed with the call setup.

As explained above, when the call is initially setup, the G-MSC 14 receives an IAM message from the PSTN 12, including the CIC parameter identifying the inter-exchange carrier preferred by the caller. Thus, once the G-MSC 14 has the acknowledgement of the caller, the G-MSC 14 then sends a further IAM message, including the CIC, to the inter-exchange carrier identified by the CIC, which is IXC-A 35 in this example. The IAM message is sent over a signaling link 33 (illustrated in solid lines) to the IXC-A 35. The call is then completed between the G-MSC 14 and the S-MSC 18 on the IXC-A 35. This scenario will assure that the call is always trunked on the inter-exchange carrier preferred by the caller.

In the preferred embodiment of the invention, once the call is over, the CMl 26 produces a toll ticket record 100 which includes the following representative parameters: calling party number 102, called party number 104, charge number 106,

CIC 36, and the toll ticket billing identification 108.

In the prior art, the charge number 106 was the same as the called party number

104 and the CIC corresponded to the inter-exchange carrier preset by the network operator. In the present invention, this has been modified so that the charge number 106 corresponds to the calling number 102 and the CIC corresponds to the inter-exchange carrier associated with the caller.

Although the toll ticket record 100 has been shown to be produced by the CMl

26, it could be produced at the G-MSC 14 or at another node, as needed by a particular design architecture. For billing purposes, the nodes in the network usually produce toll ticket records. For instance in this example, the PSTN 12, the G-MSC 14, the LXC- A 35, and the S-MSC 18 produce toll ticket records. These toll ticket records are normally sent to a billing center (not shown). At the billing center, all toll ticket records received are consolidated periodically (e.g every month) and the charges are assessed according to the information included in the toll ticket records. In a second embodiment of the invention, and inihe situation where the called mobile terminal 22 is roaming outside of his home area, once the RD detects a roaming condition of the mobile terminal 22, the CMl 26 informs the caller thereof. The CMl 26 further verifies whether the caller accepts roaming charges for the call, which also include long-distance charges. It will be understood that the CMl 26 may also only verify whether the caller accepts long-distance charges for the call without including the roaming charges per se. The CMl functions as an automated interactive system by prompting the caller to accept the roaming charges. The caller may accept the charges by, for example, dialling keys on his terminal and the information may be sent using Dual Tone Multi Frequency (DTMF) coding. This information is returned to the G-MSC 14, which can then proceed with the call setup.

In the second embodiment of the invention, an announcement machine system

(AMS) 38 may be connected to the CMl 26. Once roaming charges are accepted by the caller, the AMS 38 prompts the caller for selecting an inter-exchange carrier through DTMF tones. For example, the AMS 38 may ask the caller to dial a three-digit code associated with an inter-exchange carrier of his choice. The caller would then dial, for example, "1-7-1", which would correspond to the selection of

LXC- A 35. Alternatively, the AMS 38 may give a menu selection of inter-exchange carriers to choose from. Accordingly, in this example, the AMS 38 may ask the caller to dial 1 for IXC-A 35 or dial 2 for IXC-B 37. Once the G-MSC 14 receives the inter-exchange carrier selection, the G-MSC

14 sends a IAM message, including a CIC corresponding to the inter-exchange carrier selection, to the inter-exchange identified by the CIC. The call is the completed between the G-MSC 14 and the S-MSC 18 on the inter-exchange carrier selected by the caller. Once the call is over, toll ticket records and billing charges are produced as explained above.

The present invention may also include a second charging module (CM2) 34 for verifying whether the caller accepts air-time charges for the call. Similarly as for the CMl 26, the CM2 34 functions as an automated interactive system by prompting the caller to accept the air-time charges. The caller may accept the charges by dialing keys on his terminal and the information may be sent using DTMF coding. This information is returned to the G-MSC 14, which can then proceed with the call setup if the caller accepts the air-time charges. The CM234 has been shown to be connected to the G-MSC 14, but may also be connected to the S-MSC 18, or in another node, as needed by a particular design architecture. Furthermore, it will be understood that CMl 26 and CM2 34 may in fact be a unique entity. In addition, the present invention may comprise some security features. These features can function either by themselves or in concurrence with each other. The security features may be activated on demand by the mobile terminal user, e.g. by dialing a code.

One such security feature is the use of a personal identification number (PIN). Such feature is useful when the mobile terminal user does not want to be disturbed but by people deemed important and willing to incur the roaming charges (e.g. family members). The present invention may also include a validating module (VM) 28, which requests and receives a PLN from a caller. When the call is initially setup, a called party number parameter 41 is included in the IAM message sent from the PSTN 12 to the G-MSC 14. This called number parameter is transmitted to the VM 28. The

VM includes a list of called telephone numbers each associated with one PIN. The VM validates the PIN entered by the caller by verifying that the PIN corresponds to the associated called number, and allows completion of the call between the G-MSC 14 and the S-MSC 18 if the PIN entered by the caller is valid. Another such security system is the use of a white list of calling subscribers.

The present invention may also include a database (DB) 30, which stores a list of approved calling telephone numbers and an approving module (AM) 32, connected to the DB 30, which determines whether a calling number is on the list of approved telephone numbers. When the call is initially setup, a calling party number parameter 39 is included in the IAM message sent from the PSTN 12 to the G-MSC 14. This calling number parameter is transmitted to the AM 32. The AM 32 allows the call upon determining that the caller telephone number (calling party number) is on the list of approved calling telephone numbers, and disables the call upon determining that the caller telephone number is not on the list of approved calling telephone numbers.

The DB 30 is shown to be connected to the AM 32 in a local database, but the DB 30 may preferably be in the HLR 16, and the AM 32^' may work to verify whether the caller telephone number is on the white list with the HLR 16.

Reference is now made to FIGURE 4A wherein there is shown a message flow diagram illustrating the flow of messages in the present invention for allowing completion of a call between the G-MSC 14 and the S-MSC 18 on the inter-exchange carrier of the caller. Referring to FIGS. 1, 2, 3 and 4A, an incoming call 44 is received at the G-MSC 14 from the PSTN 12, which could also be the ISDN or PLMN. At call setup, the PSTN 12 sends an inter-exchange carrier via ISUP signaling. The ISUP signals carry an Initial Address message (IAM) 42 associated with the incoming call 44. The IAM 42 includes a parameter corresponding to the inter-exchange carrier associated with the network of the caller. This parameter is called the Carrier

Identification Code (CIC) 36. The G-MSC 14 then sends a Location Request (LOCREQ) Invoke message 46 to the HLR 16 requesting location information for the called mobile terminal 22. Normally, visitor location registers (VLRs) are used for communications between MSCs and HLRs, but these VLRs have been omitted from the figures in order to simplify the illustration. The HLR 16 then sends a Routing

Request (ROUTREQ) Invoke message 48 to the S-MSC 18. The S-MSC 18 then pages 50 for the called mobile terminal 22. If a page return result 52 is received at that time, the S-MSC 18 sends a routreq return result 54 containing a routing number such as a Temporary Location Directory Number (TLDN) to the HLR 16. The HLR 16 then returns the location information (TLDN) to the G-MSC 14 in a locreq return result message 56. At 57, the RD 24 detects a roaming condition of the mobile terminal 22 by way of the TLDN returned in locreq return result message 56. A trunked connection 58 is established between the PSTN 12 and the G-MSC 14 wherein the calling party is informed about the roaming condition of the mobile terminal 22 and is asked if he or she is willing to incur the long-distance and roaming charges. If the calling party accepts the long-distance and roaming charges 60 the G-MSC 14 then sends an IAM message 43, including the CIC 36 associated with the caller, to the inter-exchange carrier identified by the CIC, in this example IXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22. Reference is now made to FIGURE 4B, which is a variant of FIGURE 4A.

The messages shown in FIGURE 4B are the same as in FIGURE 4A up to 60 wherein the calling party accepts the long-distance and roaming charges. Once the charges are accepted, a trunk connection 66 is maintained between the PSTN 12 and the G-MSC 14 wherein the calling party is asked if he or she is willing to incur the air-time charges. If the calling party accepts the air-time charges at 68, the G-MSC 14 then sends an IAM message 43, including the CIC 36 associated with the caller, to the inter-exchange carrier identified by the CIC, in this example IXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22. Reference is now made to FIGURE 4C, which is a variant of FIGURE 4A.

The messages shown in FIGURE 4C are the same as in FIGURE 4A up to 60 wherein the calling party accepts the long-distance and roaming charges. Once the charges are accepted, a trunk connection 70 is maintained between the PSTN 12 and the G-MSC 14 wherein the calling party is asked to enter a PLN. If the PIN is validated at 72 by the validating module 28, the G-MSC 14 then sends an IAM message 43, including the CIC 36 associated with the caller, to the inter-exchange carrier identified by the CIC, in this example LXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22. Reference is now made to FIGURE 4D, which is a variant of FIGURE 4A.

The messages shown in FIGURE 4D are similar to those shown in FIGURE 4A. At call setup, the PSTN 12 sends an inter-exchange carrier via ISUP signaling. The ISUP signals carry an IAM 42 message associated with the incoming call 44. The IAM 42 includes the CIC 36 parameter corresponding to the inter-exchange carrier associated with the network of the caller. The IAM further includes the calling party number parameter 39. Similarly as in FIGURE 4A, at 57 when the RD 24 detects a roaming condition of the mobile terminal 22, a further verification is made at 74 wherein the AM 32 determines whether the calling party number 39 is on a list of approved calling telephone numbers stored in the DB 30. If the calling party number 39 is on the list of approved calling telephone numbers, a trunked connection 58 is established between the PSTN 12 and the G-MSC 14 wherein the calling party is informed about the roaming condition of the mobile terminal 22 and is asked if he or she is willing to incur the long-distance and roaming charges. If the calling party accepts the long-distance and roaming charges at 60, the G-MSC 14 then sends an IAM message 43, including the CIC 36 associated with the caller, to the inter-exchange carrier identified by the CIC, in this example LXC- A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22.

FIGURE 5 A is a message flow diagram illustrating the flow of messages in a second embodiment of the present invention for allowing inter-exchange carrier selection and completion of a call between the G-MSC 14 and the S-MSC 18.

Referring to FIGURES 1, 2, and 3 and similarly as in FIG. 4A, an incoming call 44 is received at the G-MSC 14 from the PSTN 12, which could also be the ISDN or PLMN. The G-MSC 14 then sends a Location Request (LOCREQ) Invoke message 46 to the HLR 16 requesting location information for the called mobile terminal 22. Normally, visitor location registers (VLRs) are used for communications between

MSCs and HLRs, but these VLRs have been omitted from the figures in order to simplify the illustration. The HLR 16 then sends a Routing Request (ROUTREQ) Invoke message 48 to the S-MSC 18. The S-MSC 18 then pages 50 for the called mobile terminal 22. If a page return result 52 is received at that time, the S-MSC 18 sends a routreq return result message 54 containing a routing number such as a

Temporary Location Directory Number (TLDN) to the HLR 16. The HLR 16 then returns the location information (TLDN) to the G-MSC 14 in a locreq return result message 56. At 57, the RD 24 detects a roaming condition of the mobile terminal 22 by way of the TLDN returned in locreq return result message 56. A trunked connection 58 is established between the PSTN 12 and the G-MSC 14 wherein the calling party is informed about the roaming condition of the mobile terminal 22 and is asked if he or she is willing to incur the long-distance and roaming charges. If the calling party accepts the long-distance and roaming charges at 60, a trunk connection 76 is maintained between the PSTN 12 and the G-MSC 14 wherein the G-MSC 14 obtains an inter-exchange carrier (LXC) selection from the caller at 64. The G-MSC 14 may obtain the selected LXC after the caller is prompted via an announcement machine system 38 for selecting the LXC through DTMF tones (for example: LXC-A 35 or IXC-B 37). The G-MSC 14 then sends an IAM message 43, including a CIC 36 associated with the LXC selected by the caller, to the inter-exchange carrier identified by the CIC, in this example IXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22.

Reference is now made to FIGURE 5B, which is a variant of FIGURE 5A. The messages shown in FIGURE 5B are the same as in FIGURE 5 A up to 60 wherein the calling party accepts the long-distance and roaming charges. Once the charges are accepted, a trunk connection 66 is maintained between the PSTN 12 and the G-MSC

14 wherein the calling party is asked if he or she is willing to incur the air-time charges. If the calling party accepts the air-time charges at 68, a trunked connection 76 is maintained between the PSTN 12 and the G-MSC 14 wherein the G-MSC 14 obtains an inter-exchange carrier (LXC) selection from the caller at 64. The G-MSC 14 then sends an IAM message 43, including a CIC 36 associated with the LXC selected by the caller, to the inter-exchange carrier identified by the CIC, in this example IXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22. Reference is now made to FIGURE 5C, which is a variant of FIGURE 5 A.

The messages shown in FIGURE 5C are the same as in FIGURE 5A up to 60 wherein the calling party accepts the long-distance and roaming charges. Once the charges are accepted, a trunk connection 70 is maintained between the PSTN 12 and the G-MSC 14 wherein the calling party is asked to enter a PLN. If the PIN is validated at 72 by the validating module 28, a trunked connection 76 is maintained between the PSTN

12 and the G-MSC 14 wherein the G-MSC 14 obtains an inter-exchange carrier (LXC) selection from the caller at 64. The G-MSC 14 then sends an IAM message 43, including a CIC 36 associated with the LXC selected by the caller, to the inter-exchange carrier identified by the CIC, in this example IXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22.

Reference is now made to FIGURE 5D, which is a variant of FIGURE 5 A. The messages shown in FIGURE 5D are similar to those shown in FIGURE 5A. At call setup, the PSTN 12 sends an inter-exchange carrier via ISUP signaling. The ISUP signals carry an IAM 42 message associated with the incoming call 44. The IAM 42 includes the calling party number parameter 39. Similarly as in FIGURE 5 A, at 57 when the RD 24 detects a roaming condition of the mobile terminal 22, a further verification is made at 74 wherein the AM 32 determines whether the calling party number 39 is on a list of approved calling telephone numbers stored in the DB 30. If the calling party number 39 is on the list of approved calling telephone numbers, a trunked connection 58 is established between the PSTN 12 and the G-MSC 14 wherein the calling party is informed about the roaming condition of the mobile terminal 22 and is asked if he or she is willing to incur the long-distance and roaming charges. If the calling party accepts the long-distance and roaming charges at 60, a trunked connection 76 is maintained between the PSTN 12 and the G-MSC 14 wherein the G-MSC 14 obtains an inter-exchange carrier (LXC) selection from the caller at 64. The

G-MSC 14 then sends an IAM message 43, including a CIC 36 associated with the LXC selected by the caller, to the inter-exchange carrier identified by the CIC, in this example IXC-A 35. A connection is established between the G-MSC 14 and the S-MSC 18 via the IXC-A 35. Finally, the call is completed at 62 between the PSTN 12 and the mobile terminal 22.

It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. While the method and system shown and described has been characterized as being preferred, it will be readily apparent that various changes and modifications could be made therein without departing from the spirit and scope of the invention as defined in the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method of operating a radio telecommunications network, comprising the steps of: receiving at a gateway mobile switching center (G-MSC) an incoming call placed by a caller to a mobile terminal served by a serving mobile switching center (S-MSC) in the radio telecommunications network; determining an inter-exchange carrier (LXC) associated with the caller; detecting a roaming condition associated with the mobile terminal; informing the caller about the roaming condition; determining whether the caller accepts roaming charges associated with the roaming condition; and completing the call between the G-MSC and the S-MSC on the inter-exchange carrier (LXC) if the caller accepted the roaming charges.

2. The method of operating a radio telecommunications network of claim 1, wherein the step of determining an inter-exchange carrier (LXC) comprises the step of receiving Integrated Services Digital Network (ISDN) User Part (ISUP) signals used to route the call, said ISUP signals carrying an Initial Address message (IAM) associated with the call, and said IAM comprising a parameter including the inter-exchange carrier (LXC) associated which the caller.

3. The method of operating a radio telecommunications network of claim 1 , wherein the step of detecting a roaming condition associated with the mobile terminal, further includes the steps of: requesting a personal identification number (PIN) from the caller if the roaming condition is detected; validating the PIN entered by the caller; and completing the call between the caller and the mobile terminal if the caller entered a valid PIN.

4. The method of operating a radio telecommunications network of claim 1 , further including: a step of storing in a database a list of approved calling telephone numbers; wherein the step of receiving an incoming call further includes a step of receiving the caller telephone number; and wherein the step of detecting a roaming condition associated with the mobile terminal, further includes the steps of: determining whether the caller telephone number is on the list of approved calling telephone numbers; allowing the call upon determining that the caller telephone number is on the list of approved calling telephone numbers; and disabling the call upon determining that the caller telephone number is not on the list of approved calling telephone numbers.

5. The method of operating a radio telecommunications network of claim 1 , wherein the step of determining whether the caller accepts roaming charges further includes the steps of: determining whether the caller accepts air-time charges associated with the mobile terminal; and completing the call between the caller and the mobile terminal if the caller accepts the air-time charges.

6. A method of operating a radio telecommunications network, comprising the steps of: receiving at a gateway mobile switching center (G-MSC) an incoming call placed by a caller to a mobile terminal served by a serving mobile switching center (S-MSC) in the radio telecommunications network; detecting a roaming condition associated with the mobile terminal; informing the caller about the roaming condition; determining whether the caller accepts roaming charges associated with the roaming condition; providing the caller with an inter-exchange carrier (LXC) selection; obtaining an inter-exchange carrier (LXC) selection from the caller; and completing the call between the G-MSC and the S-MSC on the inter-exchange carrier (LXC) selected if the caller accepted the roaming charge.

7. The method of operating a radio telecommunications network of claim 6, further comprising a step of sending from the G-MSC Integrated Services Digital Network (ISDN) User Part (ISUP) signals used to route the call, said ISUP signals carrying an Initial Address message (IAM) associated with the call, said IAM comprising a parameter including the inter-exchange carrier (LXC) selection from the caller.

8. The method of operating a radio telecommunications network of claim 6, wherein the step of providing the caller with inter-exchange carrier (LXC) selection further comprises the step of prompting the caller via an announcement machine for selecting an inter-exchange carrier (LXC) through Dual Tone

Multi-Frequency (DTMF) tones.

9. The method of operating a radio telecommunications network of claim 6, wherein the step of providing the caller with inter-exchange carrier (LXC) selection, further comprises the step of prompting the caller via an announcement machine for selecting an inter-exchange carrier (LXC) through a menu selection.

10. The method of operating a radio telecommunications network of claim 6, wherein the step of detecting a roaming condition associated with the mobile terminal, further includes the steps of: requesting a personal identification number (PIN) from the caller if the roaming condition is detected; validating the PIN entered by the caller; and completing the call between the caller and the mobile terminal if the caller entered a valid PLN.

11. The method of operating a radio telecommunications network of claim 6, further including: a step of storing in a database a list of approved calling telephone numbers; wherein the step of receiving an incoming call further includes a step of receiving the caller telephone number; and wherein the step of detecting a roaming condition associated with the mobile terminal, further includes the steps of: determining whether the caller telephone number is on the list of approved calling telephone numbers; allowing the call upon determining that the caller telephone number is on the list of approved calling telephone numbers; and disabling the call upon determining that the caller telephone number is not on the list of approved calling telephone numbers.

12. The method of operating a radio telecommunications network of claim 6, wherein the step of determining whether the caller accepts roaming charges, further includes the steps of: determining whether the caller accepts air-time charges associated with the mobile terminal; and completing the call between the caller and the mobile terminal if the caller accepts the air- time charges.

13. A system for allowing inter-exchange carrier selection in a radio telecommunications network, the system comprising: a mobile terminal capable of communicating with the radio telecommunications network; a serving mobile switching center (S-MSC) for serving the mobile terminal when communicating with the radio telecommunications network; a gateway mobile switching center (G-MSC) for receiving an incoming call from a caller to the mobile terminal; at least one inter-exchange carrier (LXC) allowing communication between the S-MSC and the G-MSC; a roaming detector (RD) for detecting a roaming condition of the mobile terminal; and a charging module (CM 1 ) for informing the caller of the roaming condition of the mobile terminal, the charging module verifying whether the caller accepts roaming charges for the call, and if the caller accepts the charges, the charging module verifies which at least one inter-exchange carrier (IXC) is associated with the caller for completing the call between the G-MSC and the S-MSC.

14. The system of claim 13, wherein the inter-exchange carrier (LXC) associated with the caller is sent to the G-MSC via Integrated Services Digital Network (ISDN) User Part (ISUP) signals used to route the call, said ISUP signals carrying an Initial Address message (IAM) associated with the call, and said IAM comprising a parameter including the inter-exchange carrier (LXC) associated with the caller.

15. The system of claim 13 , further comprising: a validating module (VM) for requesting and receiving a personal identification number (PIN) from the caller if the roaming condition is detected, the validating module for validating the PIN entered by the caller, and allowing completion of the call between the G-MSC and the S-MSC if the PIN entered by the caller is valid.

16. The system of claim 13, further comprising: a database (DB) for storing a list of approved calling telephone numbers; and an approving module (AM) for determining whether a calling telephone number received in the incoming call is on the list of approved calling telephone numbers if the roaming condition is detected, the approving module allowing the call upon determining that the caller telephone number is on the list of approved calling telephone numbers, and for disabling the call upon determining that the caller telephone number is not on the list of approved calling telephone numbers.

17. The system of claim 13, further comprising: a second charging module (CM2) for verifying whether the caller accepts air-time charges for the call, and for allowing completion of the call between the G-MSC and the S-MSC if the caller accepts the air-time charges.

18. The system of claim 13, further comprising: an announcement machine system (AMS) connected to the charging module for prompting the caller for selecting an inter-exchange carrier (LXC) through Dual Tone Multi-Frequency (DTMF) tones.

19. The system of claim 13, further comprising: an announcement machine system (AMS) connected to the charging module for prompting the caller with a menu selection for selecting an inter-exchange carrier (LXC).