DELIVERY OF MOBILE TERMINATED CALL DURING INTER-VLR

LOCATION UPDATE

CROSS-REFERENCE TO RELATED APPLICATIONS This U.S. Nonpro visional Application for Patent claims the benefit of the filing date of U.S. Provisional Patent Application entitled, 2 ^nd SRI Solutions (with/without OR) to the Mobile Termination Call During the Inter- VLR Location Update, Attorney Docket No. 800295, having Serial No. 60/825,291, filed on September 12, 2006, which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

Technical Field of the Invention

The present invention relates in general to wireless communication systems, and in particular, to handling of mobile terminated calls during location updates.

Description of Related Art

Today's wireless telecommunications networks provide telephone subscribers with the ability to access telecommunications services from almost anywhere in the world. The key to facilitating such world-wide access is mobility management. With mobility management, wireless networks are able to track the location of mobile subscribers so that mobile services can be delivered to them.

A wireless network is typically formed of a number of cells, each covering a small geographic area within which a mobile device, such as a mobile station, may receive mobile services. Each cell is equipped with a base station that provides radio

coverage to the cell, thereby enabling communication with mobile devices located within the cell. By integrating the coverage of multiple base stations, a wireless network is able to provide radio coverage to mobile subscribers over a large geographic area.

The coverage area of a collection of neighboring base stations is commonly referred to as a location area. Each location area is served by a mobile switching center/visitor location register (MSC/VLR), and each MSC/VLR may serve multiple location areas. The MSC/VLR is the network node that provides circuit-switched calling, mobility management and other telecommunications/mobile services to mobile subscribers. In particular, the MSC/VLR maintains subscriber data for all mobile subscribers that are currently located within one of the location areas served by the MSC/VLR. For example, the subscriber data for each mobile subscriber typically includes the location area and serving base station of the mobile subscriber, which allows the MSC/VLR to page, communicate with and connect incoming calls to that mobile subscriber. When a mobile subscriber moves or "roams" into a new location area, the mobile subscriber must inform the wireless network of the change in location area by performing what is commonly referred to as a location update procedure. Each mobile device is responsible for maintaining the location area code (LAC) of the current location area and comparing the stored LAC with subsequent LACs that are broadcast and received by the mobile device. If the mobile device finds that the received LAC is different from the stored LAC, the mobile device sends a location update request to the wireless network. If the new location area is served by a different MSC/VLR than the previous location area, an inter- VLR location update is performed.

During the inter- VLR location update, the new MSC/VLR that receives the location update request from the mobile subscriber transmits an update location message to the Home Location Register (HLR) of the mobile subscriber. The HLR is a database that maintains permanent subscriber records for mobile subscribers. Upon receiving the update location message, the HLR forwards the subscriber data associated with the mobile subscriber to the new MSC/VLR for temporary storage in the new MSC/VLR while the mobile subscriber is within the MSC/VLR coverage area and updates its records to indicate that the mobile subscriber is now present in a location area served by the new MSC/VLR. In addition, the HLR asks the old MSC/VLR to delete its subscriber record for this mobile subscriber since the mobile subscriber is no longer located in a location area served by the old MSC/VLR.

Once the location update procedure is complete, the mobile subscriber can continue to receive mobile services through the new MSC/VLR. For example, in a typical mobile terminated call scenario, an incoming call to the mobile subscriber is first routed to a gateway mobile switching center (GMSC) serving the wireless network of the mobile subscriber. Upon receiving the mobile terminated call, the GMSC queries the HLR to determine the current location of the mobile subscriber. For example, the HLR typically returns routing information to the GMSC that includes the identity of the MSC/VLR serving the mobile subscriber. The GMSC uses the routing information to route the mobile terminated call to the MSC/VLR. The MSC/VLR accesses its subscriber data for the mobile subscriber to determine the location area of the mobile subscriber, and pages the mobile device of the mobile subscriber within that location area to set-up a call connection to the mobile device for the mobile terminated call.

However, if the mobile terminated call is received during the time that the mobile subscriber is performing an inter-VLR location update, the mobile terminated call may not be completed to the mobile subscriber. For example, if the HLR has not yet been informed of the change in location when the GMSC queries the HLR for routing information, the HLR will return the routing information for the old MSC/VLR to the GMSC. Thus, the GMSC will route the call to the old MSC/VLR, and the old MSC/VLR will attempt to page the mobile station. However, since the mobile subscriber is no longer in the MSC/VLR area, the mobile device will not be able to answer the page. Currently, when a mobile device does not answer a page for a mobile terminated call, the call is rejected, and therefore is not delivered to the mobile subscriber. Instead, other call handling, such as voice mail, is applied to the mobile terminated call. This is dissatisfactory for many mobile subscribers and network providers.

Therefore, what is needed is mechanism for delivering mobile terminated calls to mobile subscribers during inter-VLR location updates.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide a method and apparatus for delivering a mobile terminated call to a mobile device communicating with a wireless communication network. The method includes receiving the mobile terminated, in which the mobile terminated call has old routing information associated therewith that identifies an old mobile switching center/visitor location register (MSC/VLR) previously serving the mobile device, determining that the mobile device is performing a location update to a new MSC/VLR prior to connection of the mobile terminated call and enabling the mobile terminated call to be routed to the new MSC/VLR for connection of the mobile terminated call to the mobile device.

In one embodiment, the old MSC/VLR determines that the mobile device is performing a location update to the new MSC/VLR by receiving a cancel location message from a Home Location Register (HLR) associated with the mobile device. In an exemplary embodiment, upon receiving the cancel location message, the old MSC/VLR determines new routing information for the mobile terminated call that identifies the new MSC/VLR and routes the mobile terminated call to the new MSC/VLR for connection of the mobile terminated call to the mobile device.

In another exemplary embodiment, upon receiving the cancel location message, the old MSC/VLR sends a resume call handling (RCH) message to a gateway mobile switching center (GMSC) that originally routed the mobile terminated call to the old MSC/VLR. The RCH message including a roaming retry indicator instructing the GMSC to re-route the mobile terminated call to the new MSC/VLR. In a further exemplary embodiment, the GMSC determines new routing information for the mobile terminated

call that identifies the new MSC/VLR and routes the mobile terminated call to the new MSC/VLR for connection of the mobile terminated call to the mobile device.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be obtained by reference to the following detailed description when taken in conjunction with the accompanying drawings wherein: FIGURE 1 is a block diagram illustrating an exemplary wireless network for delivering a mobile terminated call to a mobile station during an inter- VLR location update, in accordance with embodiments of the present invention;

FIGURE 2 is a flowchart illustrating an exemplary process for delivering a mobile terminated call to a mobile station during an inter-VLR location update, in accordance with embodiments of the present invention;

FIGURE 3 is a block diagram illustrating one embodiment for delivering a mobile terminated call to a mobile station during an inter-VLR location update;

FIGURE 4 is a flowchart illustrating an exemplary process for delivering a mobile terminated call to a mobile station during an inter-VLR location update according to the embodiment shown in FIGURE 3;

FIGURE 5 is a signaling diagram illustrating exemplary signaling for delivering a mobile terminated call to a mobile station according to the embodiment shown in FIGURE 3;

FIGURE 6 is a block diagram illustrating another embodiment for delivering a mobile terminated call to a mobile station during an inter-VLR location update;

FIGURE 7 is a flowchart illustrating an exemplary process for delivering a mobile terminated call to a mobile station during an inter-VLR location update according to the embodiment shown in FIGURE 6; and

FIGURES 8A and 8B are signaling diagrams illustrating exemplary signaling for delivering a mobile terminated call to a mobile station according to the embodiment shown in FIGURE 6.

DETAILED DESCRIPTION OF THE DRAWINGS

FIGURE 1 is a block diagram illustrating an exemplary wireless network 10 for delivering a mobile terminated call 20 to a mobile station 80 during an inter- VLR location update, in accordance with embodiments of the present invention. The wireless network 10 includes a Gateway Mobile Switching Center (GMSC) 30, Mobile Switching Center/Visitor Location Registers (MSC/VLR) 50 and 60, Base Station System (BSS) 70 and Home Location Register (HLR) 40. MSC/VLR 50 serves location area 55, while MSC/VLR 60 serves location area 65. It should be understood that each MSC/VLR 50 and 60 may serve multiple location areas. However, for simplicity, only one location area for each MSC/VLR is shown.

As illustrated in FIGURE 1, mobile station 80 has recently moved from location area 65 served by MSC/VLR 60 into location area 55 served by MSC/VLR 50. Thus, MSC/VLR 60 is labeled "old MSC/VLR", while MSC/VLR 50 is labeled "new MSC/VLR." Once the mobile station 80 realizes that it has roamed into the new location area 55 served by the new MSC/VLR 50 (i.e., by determining that the location area code (LAC) received from BSS 70 is new), the mobile station 80 sends a location update request to the new MSC/VLR 50 via BSS 70.

Upon receiving the location update request, the new MSC/VLR 50 transmits an update location message to the HLR 40 to retrieve the subscriber data associated with the mobile station 80 and to update the HLR 40 with the new location area 55 served by the new MSC/VLR 50. In addition, the HLR 40 transmits a cancel location message to the old MSC/VLR 60 instructing the old MSC/VLR 60 to delete the mobile station's 80

subscriber data from its records since the mobile station 80 is no longer located in the location area 65 served by the old MSC/VLR 60.

If an incoming mobile terminated call 20 for the mobile station 80 is received at the GMSC 30 during the location update process, as in conventional wireless networks, the GMSC 30 queries the HLR 40 for routing information to deliver the incoming call to the mobile station 80. If the HLR 40 has not yet received the update location message from the new MSC/VLR 50 when the GMSC query is received, the HLR 40 returns the routing information for the old MSC/VLR 60 to the GMSC 30. Thus, the GMSC routes the mobile terminated call 20 to the old MSC/VLR 60 for call handling. When the old MSC/VLR 60 receives the call 20, the old MSC/VLR 60 accesses its subscriber data for the mobile subscriber to determine the location area 65 of the mobile station 80, and pages the mobile station 80 within that location area 65 to attempt to set-up a call connection to the mobile station 80 for the mobile terminated call. However, since the mobile station 80 has moved out of location area 65 and into location area 55, and is currently performing a location update to the new MSC/VLR 50, the mobile station 80 will not be able to answer the page from the old MSC/VLR.

Therefore, in accordance with embodiments of the present invention, once the old MSC/VLR 60 receives the cancel location message from the HLR 40 that requests the old MSC/VLR 60 to delete the subscriber record for mobile station 80, the MSC/VLR 60 stops paging the mobile station 80 and redirects the call 20 to enable the call 20 to be routed to the new MSC/VLR 50 and ultimately delivered to the mobile station 80 upon completion of the location update. For example, in one embodiment, the old MSC/VLR 60 queries the HLR 40 for new routing information for the mobile station 80, and uses

the new routing information to forward the call to the new MSC/VLR 50. In another embodiment, the old MSC/VLR 60 releases the call back to the GMSC 30. The GMSC 30, in turn, re-queries the HLR 40 for new routing information for the mobile station 80 and uses the new routing information to re-route the call to the new MSC/VLR 50. Turning now to FIGURE 2, an exemplary process 200 for delivering a mobile terminated call to a mobile station during an inter- VLR location update is shown. Initially, at block 210, a mobile terminated call to a mobile station is received with routing information identifying the old MSC/VLR as the serving MSC/VLR. For example, in one embodiment, the mobile terminated call is received at the old MSC/VLR from the GMSC. In another embodiment, the mobile terminated call is received at the GMSC after being re-routed back to the GMSC from the old MSC/VLR. In addition, at block 220, a determination is made that the mobile station is currently performing a location update to a new MSC/VLR (e.g., by receiving a cancel location message at the old MSC/VLR or by releasing the call back to the GMSC). Thereafter, at block 230, the mobile terminated call is routed to the new MSC/VLR either directly from the old MSC/VLR or from the GMSC, as will be described in further detail below.

FIGURE 3 is a block diagram illustrating one embodiment for delivering a mobile terminated call to a mobile station during an inter- VLR location update. In FIGURE 3, the mobile terminated call is routed from the old MSC/VLR 60 to the new MSC/VLR 50 for delivery of the call to the mobile station. Initially, when the GMSC 30 first receives the incoming mobile terminated call from the network, the GMSC 30 sends a Send Routing Information (SRI) message 305 to the HLR 40. The HLR 40 accesses the subscriber record for the mobile station to determine the serving MSC/VLR, here the old

MSC/VLR 60, and transmits a Provide Roaming Number (PRN) message 310 to the old MSC/VLR 60. In response to the PRN message, the old MSC/VLR 60 sends a message 315 including a Mobile Station Roaming Number (MSRN) back to the HLR 40. The MSRN is an E.164 number that is temporarily assigned to the mobile station for the mobile terminated call and can be used to route the mobile terminated call to the old MSC/VLR 60. Upon receipt of the MSRN, the HLR 40 forwards the MSRN in another message 320 back to the GMSC 30. The GMSC 30 uses the MSRN to route an Initial Address Message (IAM) 325 for the mobile terminated call to the old MSC/VLR 60.

At the same time that the GMSC 30 is retrieving the MSRN from the HLR 40 and transmitting the IAM 325 to the old MSC/VLR 60, as shown in FIGURE 3, the new MSC/VLR 50 is transmitting an update location message 328 for the mobile station to the HLR 40. As a result, the HLR 40 transmits a cancel location message 330 to the old MSC/VLR 60. In accordance with embodiments of the present invention, upon receiving the cancel location message 330 from the HLR 40, the old MSC/VLR 60 transmits a second Send Routing Information (SRI) message 335 to the HLR 40 for the mobile terminated call. This time, since the mobile station has performed the location update to the new MSC/VLR 50, the HLR 40 sends a Provide Roaming Number (PRN) message 340 to the new MSC/VLR 50 to retrieve a new MSRN in message 345 for the mobile terminated call from the new MSC/VLR 50. The HLR 40 forwards the MSRN for the new MSC/VLR 50 in message 350 to the old MSC/VLR 60, and the old MSC/VLR 60 uses the received MSRN to route an IAM 355 for the mobile terminated call to the new MSC/VLR 50.

FIGURE 4 is a flowchart illustrating an exemplary process 400 for delivering a mobile terminated call to a mobile station during an inter- VLR location update according to the embodiment shown in FIGURE 3. When, at block 410, an IAM for a mobile terminated call to a mobile station is received at an old MSC/VLR, and at block 420, a cancel location message for the mobile station is also received at the old MSC/VLR, at block 430, the old MSC/VLR sends an SRI message to the HLR to retrieve the MSRN of the mobile station for the new MSC/VLR. Upon receiving the MSRN at block 440, at block 450, the old MSC/VLR uses the MSRN to forward the IAM for the mobile terminated call to the new MSC/VLR. FIGURE 5 is a signaling diagram illustrating exemplary signaling for delivering a mobile terminated call to a mobile station according to the embodiment shown in FIGURE 3. As described above in connection with FIGURE 3, when the GMSC 30 receives a mobile terminated call for a mobile station, at 500, the GMSC 30 transmits a Send Routing Information (SRI) message to the HLR 40 to retrieve routing information for routing of the call to the serving MSC/VLR. The HLR 40 accesses the subscriber record for the mobile station to identify the serving MSC/VLR (i.e., old MSC/VLR 60) and transmits a Provide Roaming Number (PRN) message at 502 to the old MSC/VLR 60.

In response, the old MSC/VLR 60 transmits a PRN acknowledgment message at 504 back to the HLR that includes a Mobile Station Roaming Number (MSRN) for the mobile terminated call. The HLR 40 forwards the MSRN to the GMSC 30 in an SRI acknowledgment message at 506. Using the received MSRN, the GMSC 30 generates and transmits an Initial Address Message (IAM) at 508 for the call to the old MSC/VLR

60. Upon receipt of the IAM, the old MSC/VLR accesses the temporary subscriber record for the mobile station to determine the location area within which the mobile station last reported it was located, and at 510, pages the mobile station within that location area. Prior to paging by the old MSC/VLR 60, the mobile station 80 transmits a location update request at 512 to the new MSC/VLR 50. After authentication of the mobile station 80 at 514, the new MSC/VLR 50 transmits an update location message at 516 to the HLR 40 to update the HLR 40 with the new location (i.e., new MSC/VLR identity and/or new location area) of the mobile station 80. Upon receiving the update location message, the HLR 40 transmits a cancel location message at 518 to the old MSC/VLR 60, requesting the old MSC/VLR to delete the temporary subscriber record for the mobile station. Once the old MSC/VLR deletes the subscriber record for the mobile station, the old MSC/VLR transmits a cancel location acknowledgement message at 520 back to the HLR 40. In addition, in accordance with embodiments of the present invention, at 522, the old MSC/VLR stops paging the mobile station (e.g., by stopping the paging timer for the mobile station) and initiates a second SRI message at 524 for the mobile terminated call to the HLR 40. In other embodiments, if the cancel location message is received during the pre-paging (i.e., before PRN ACK at 504), the old MSC/VLR 60 stops paging and returns the PRN acknowledgement message (at 504) to the HLR 40 with an indication that the mobile subscriber is absent (i.e., "Absent Subscriber"). In this case, the HLR 40 re-transmits the PRN message to the new MSC/VLR 50, and sends the MSRN associated with the new MSC/VLR 50 back to the GMSC 30. In yet another embodiment, if the

cancel location message is received before the IAM arrives but after the PRN ACK is sent, the old MSC/VLR 60 triggers the second SRI message to the HLR 40 at Send Info for Incoming Call. In still another embodiment, if the cancel location message is received before paging, but after the Send Info for Incoming Call message, the old MSC/VLR 60 triggers the second SRI message to the HLR 40 without paging.

When the HLR 40 receives the second SRI message for the mobile terminated call from the old MSC/VLR 60 at 524, if the HLR is still processing the location update for the mobile station, at 526, the HLR 40 delays sending out the Provide Roaming Number (PRN) message to the new MSC/VLR 50 until the location update is complete. For example, as shown at 528, multiple insert subscriber data messages are sent from the HLR 40 to the new MSC/VLR 50 during the location update process to provide the new MSC/VLR with the subscriber data associated with the mobile station 80. In addition, each time the new MSC/VLR 50 receives subscriber data for the mobile station from the HLR 40, the new MSC/VLR 50 provides an insert subscriber data acknowledgement message at 530 back to the HLR 40.

Once all of the subscriber data for the mobile station has been sent to the new MSC/VLR 50, and the location update is complete, the HLR 40 transmits an update location acknowledgement message at 532 to the new MSC/VLR 50. Afterwards, the HLR 40 is able to transmit a Provide Roaming Number (PRN) message at 534 to the new MSC/VLR 50. In response, the new MSC/VLR 50 transmits a PRN acknowledgment message at 536 back to the HLR 40 that includes a new Mobile Station Roaming Number (MSRN) for the mobile terminated call. The HLR 40 forwards the new MSRN to the old MSC/VLR 60 in a second SRI acknowledgment message at 538. Using the received new

MSRN, the old MSC/VLR 60 generates and transmits an Initial Address Message (IAM) at 540 for the call to the new MSC/VLR 50.

At 542, the new MSC/VLR 50 delays setup of the call to the mobile station until the location update procedure finishes. For example, the new MSC/VLR 50 may need to transmit a location update accept message at 544 that assigns a new Temporary Mobile Subscriber Identity (TMSI) to the mobile station for the new MSC/VLR 50. In addition, at 546, the mobile station 80 may need to reply back that the TMSI allocation has been completed. Thereafter, the new MSC/VLR can use the existing connection (used for location update) to the mobile station 80 or page the mobile station 80 and at 548 transmit a call setup message to the mobile station. At 550, a call confirmation message is transmitted back to the new MSC/VLR 50 from the mobile station 80. Normal mobile terminated call procedure follows at 552 to connect the mobile terminated call to the mobile station 80.

FIGURE 6 is a block diagram illustrating another embodiment for delivering a mobile terminated call to a mobile station during an inter- VLR location update. In FIGURE 6, the mobile terminated call is routed back to the GMSC 30 from the old MSC/VLR 60, and re-routed from the GMSC 30 to the new MSC/VLR 50 for delivery of the call to the mobile station. As in FIGURE 3, in FIGURE 6, when the GMSC 30 first receives the incoming mobile terminated call from the network, the GMSC 30 sends a Send Routing Information (SRI) message 605 to the HLR 40. The HLR 40 accesses the subscriber record for the mobile station to determine the serving MSC/VLR, here the old MSC/VLR 60, and transmits a Provide Roaming Number (PRN) message 610 to the old MSC/VLR 60. In response to the PRN message, the old MSC/VLR 60 sends a message

615 including a Mobile Station Roaming Number (MSRN) for the mobile terminated call to be used in routing to the old MSC/VLR 60 back to the HLR 40. Upon receipt of the MSRN, the HLR 40 forwards the MSRN in another message 620 back to the GMSC 30. The GMSC 30 uses the MSRN to route an Initial Address Message (IAM) 625 for the mobile terminated call to the old MSC/VLR 60.

At the same time that the GMSC 30 is retrieving the MSRN from the HLR 40 and transmitting the IAM 625 to the old MSC/VLR 60, as shown in FIGURE 6, the new MSC/VLR 50 is transmitting an update location message 628 for the mobile station to the HLR 40. As a result, the HLR 40 transmits a cancel location message 630 to the old MSC/VLR 60. In accordance with embodiments of the present invention, upon receiving the cancel location message 630 from the HLR 40, the old MSC/VLR 60 transmits a resume call handling (RCH) message 635 back to the HLR 40. The RCH message 635 includes a call reference number that identifies the mobile terminated call and a roaming retry indicator that instructs the GMSC 30 to obtain a new MSRN and re-route the mobile terminated call.

Therefore, the GMSC 30 sends a second Send Routing Information (SRI) message 640 to the HLR 40 for the mobile terminated call. This time, since the mobile station has performed the location update to the new MSC/VLR 50, the HLR 40 sends a Provide Roaming Number (PRN) message 645 to the new MSC/VLR 50 to retrieve a new MSRN in message 650 for the mobile terminated call from the new MSC/VLR 50. The HLR 40 forwards the MSRN for the new MSC/VLR 50 in message 655 to the GMSC 30, and the GMSC 30 uses the received MSRN to route an IAM 660 for the mobile terminated call to the new MSC/VLR 50.

FIGURE 7 is a flowchart illustrating an exemplary process 700 for delivering a mobile terminated call to a mobile station during an inter- VLR location update according to the embodiment shown in FIGURE 6. As shown in FIGURE 7, when, at block 710, an IAM for a mobile terminated call to a mobile station is received at an old MSC/VLR from the GMSC, and at block 720, a cancel location message for the mobile station is also received at the old MSC/VLR, at block 730, the old MSC/VLR sends an Resume Call Handling (RCH) message with the roaming retry indicator back to the GMSC, which instructs the GMSC to obtain a new MSRN associated with the new MSC/VLR and to reroute the mobile terminated call to the new MSC/VLR using the new MSRN. FIGURES 8A and 8B are signaling diagrams illustrating exemplary signaling for delivering a mobile terminated call to a mobile station according to the embodiment shown in FIGURE 6. As described above in connection with FIGURE 6, when the GMSC 30 receives a mobile terminated call for a mobile station, at 800, the GMSC 30 transmits a Send Routing Information (SRI) message with the address of the GMSC 30 and a call reference for the mobile terminated call to the HLR 40 to retrieve routing information for routing of the call to the serving MSC/VLR. The HLR 40 accesses the subscriber record for the mobile station to identify the serving MSC/VLR (i.e., old MSC/VLR 60) and transmits a Provide Roaming Number (PRN) message at 802 to the old MSC/VLR 60. In response, the old MSC/VLR 60 transmits a PRN acknowledgment message at

804 back to the HLR 40 that includes a Mobile Station Roaming Number (MSRN) for the mobile terminated call. The HLR 40 forwards the MSRN to the GMSC 30 in an SRI acknowledgment message at 806. Using the received MSRN, the GMSC 30 generates

and transmits an Initial Address Message (IAM) at 808 for the call to the old MSC/VLR 60. Upon receipt of the IAM, the old MSC/VLR 60 accesses the temporary subscriber record for the mobile station to determine the location area within which the mobile station last reported it was located, and at 810, pages the mobile station within that location area.

Prior to paging by the old MSC/VLR 60, the mobile station 80 transmits a location update request at 812 to the new MSC/VLR 50. After authentication of the mobile station 80 at 814, the new MSC/VLR 50 transmits an update location message at 816 to the HLR 40 to update the HLR 40 with the new location (i.e., new MSC/VLR identity and/or new location area) of the mobile station 80. Upon receiving the update location message, the HLR 40 transmits a cancel location message at 818 to the old MSC/VLR 60, requesting the old MSC/VLR to delete the temporary subscriber record for the mobile station. Once the old MSC/VLR 60 deletes the subscriber record for the mobile station, the old MSC/VLR 60 transmits a cancel location acknowledgement message at 820 back to the HLR 40.

In addition, in accordance with embodiments of the present invention, at 822, the old MSC/VLR stops paging the mobile station (e.g., by stopping the paging timer for the mobile station) and informs the GMSC 30 that the mobile station has roamed into a new location area served by a new MSC/VLR 50. In particular, the old MSC/VLR 60 transmits a resume call handling (RCH) message at 826 to the GMSC 30. The RCH message includes the call reference identifying the mobile terminated call and a roaming retry indicator that informs the GMSC 30 that a new MSRN is needed for the mobile

terminated call. An example of the parameters within the RCH message is shown below in Table 1.

Table 1 : MAP_RESUME_CALL_HANDLING parameters

Although in FIGURE 8A, the call redirection is handled by the old MSC/VLR after receipt of the IAM at 808, in other embodiments, if the cancel location message is received during the pre-paging (i.e., before PRN ACK at 804), the old MSC/VLR 60 stops paging and returns the PRN acknowledgement message (at 804) to the HLR 40 with an indication that the mobile subscriber is absent (i.e., "Absent Subscriber"). In this case, the HLR 40 re-transmits the PRN message to the new MSC/VLR 50, and sends the MSRN associated with the new MSC/VLR 50 back to the GMSC 30. In yet another embodiment, if the cancel location message is received before the IAM arrives but after the PRN ACK is sent, the old MSC/VLR 60 triggers the RCH with roaming retry to the GMSC during the Send Info for Incoming Call after the IAM is received. In still another

embodiment, if the cancel location message is received before paging, but after the Send Info for Incoming Call message, the old MSC/VLR 60 triggers the RCH instead of paging.

In any case, when the GMSC 30 receives the RCH message from the old MSC/VLR 60, the GMSC 30 transmits an RCH acknowledgement message at 828 back to the old MSC/VLR 60. In addition, at 830, the GMSC 30 instructs the old MSC/VLR 60 to release the call, and in response, the old MSC/VLR 60 releases the call and at 832 transmits a release complete message back to the GMSC. Thereafter, the GMSC 30 transmits a second SRI message for the mobile terminated call at 834 to the HLR 40. When the HLR 40 receives the second SRI message from the GMSC at 834, if as shown in FIGURE 8B, the HLR 40 is still processing the location update for the mobile station, at 836, the HLR 40 delays sending out the Provide Roaming Number (PRN) message to the new MSC/VLR 50 until the location update is complete. For example, as shown at 824 and 838, multiple insert subscriber data messages are sent from the HLR 40 to the new MSC/VLR 50 during the location update process to provide the new MSC/VLR with the subscriber data associated with the mobile station 80. In addition, each time the new MSC/VLR 50 receives subscriber data for the mobile station from the HLR 40, the new MSC/VLR 50 provides an insert subscriber data acknowledgement message back to the HLR 40. Once all of the subscriber data for the mobile station has been sent to the new

MSC/VLR 50, and the location update is complete, the HLR 40 transmits an update location acknowledgement message at 840 to the new MSC/VLR 50. Afterwards, the HLR 40 is able to transmit a Provide Roaming Number (PRN) message at 842 to the new

MSC/VLR 50. In response, the new MSC/VLR 50 transmits a PRN acknowledgment message at 844 back to the HLR 40 that includes a new Mobile Station Roaming Number (MSRN) for the mobile terminated call. The HLR 40 forwards the new MSRN to the GMSC 30 in a second SRI acknowledgment message at 846. Using the received new MSRN, the GMSC 30 generates and transmits an Initial Address Message (IAM) at 848 for the call to the new MSC/VLR 50.

At 850, the new MSC/VLR 50 delays setup of the call to the mobile station until the location update procedure finishes. For example, the new MSC/VLR 50 may need to transmit a location update accept message at 852 that assigns a new Temporary Mobile Subscriber Identity (TMSI) to the mobile station for the new MSC/VLR 50. In addition, at 854, the mobile station 80 may need to reply back that the TMSI allocation has been completed. Thereafter, the new MSC/VLR can use the existing connection (used for location update) to the mobile station 80 or page the mobile station 80 and at 856 transmit a call setup message to the mobile station. At 858, a call confirmation message is transmitted back to the new MSC/VLR 50 from the mobile station 80. Normal mobile terminated call procedure follows at 860 to connect the mobile terminated call to the mobile station 80.

As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a wide range of applications. Accordingly, the scope of patents subject matter should not be limited to any of the specific exemplary teachings discussed, but is instead defined by the following claims.