WO2019127431A1

WO2019127431A1 - Locating serving msc for mt voice call service recovery

Info

Publication number: WO2019127431A1
Application number: PCT/CN2017/120010
Authority: WO
Inventors: Zhiwei Qu; Yixin Chen; Huiping DING; Xiaoming Li; Chuanxin LIU; Wei Song; Lu Wang; Lei Xia; Ping Zhou
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2017-12-29
Filing date: 2017-12-29
Publication date: 2019-07-04

Abstract

The embodiments herein relate to locating serving MSC for MT voice call service recovery. In one embodiment, there proposes a method in a first mobility management node, comprising: receiving a message indicating a Mobile Termination (MT) call for a wireless device; checking whether the wireless device is registered on the first mobility management node; if the wireless device is not registered on the first mobility management node, interrogating a subscriber server for a second mobility management node which is currently serving the wireless device or a Mobile Switching Center (MSC) associated with the second mobility management node; and transferring the MT call towards the second mobility management node. With embodiments herein, the MT call service can be recovered, and thus the user experience of both MO and MT user can be improved.

Description

LOCATING SERVING MSC FOR MT VOICE CALL SERVICE RECOVERY

Technical Field

The embodiments herein relate generally to wireless communication, and more particularly, the embodiments herein relate to locating serving MSC for MT voice call service recovery.

Background

In fourth generation (4G) of mobile communication, the operators need to access Circuit Switching (CS) services via evolved Packet System (EPS) network. The voice call support could be a typical use case of communication service for access CS domain.

Figure 1 is a schematic block diagram showing a typical 4G communication system 100 including a SGs interface, according to the prior art. As shown in Figure 1, the SGs interface connects the Mobile Switching Center (MSC) /Visitor Location Register (VLR) and the Serving GPRS support Node (SGSN) -Mobility Management Entity (MME) . The SGs interface can be used to register User Equipment (UE) in the MSC/VLR by performing combined registration procedures, to page the UE on behalf of the MSC/VLR, and to convey CS-related services. By using SGs interface, the CS call could fall back to for example Wideband Code Division Multiple Access (WCDMA) and Global System for Mobile Communication (GSM) to perform voice calls for a UE initially connected to EPS, which also can be referred as Circuit Switching Fall Back (CSFB) .

As shown in third Generation Partnership Project (3GPP) Technical Specification TS29.118 CR0213 (Release 11.2.0) : when a Cancel Location message is lost, and the UE returns to the previous VLR, such VLR when supporting MSC in pool cannot detect that a Cancel Location message was previously lost, WHEN the SGs interface is deployed. In case SGs interface is not deployed, the VLR detects that the Cancel Location message was lost by TMSI verification, but TMSI is not available in the current specification when the SGs interface is deployed. Hence, TS29.118 CR0213 proposes a solution in which the UE includes a ten bit subset of TMSI (when available) in combined registration procedures, and the MME forwards the ten bit subset of TMSI to the selected VLR in the subsequent Location Update Request.

Besides, as shown in TS29.118 CR0228 (Release 11.3.0) : dual VLR registration problem for MSC in Pool for combined procedures has previously been addressed in Release 11 by adding information in NAS messages. This CR addresses pre-Release 11 UEs and provides a partial solution to the dual VLR problems that covers many but not all network deployments. Hence, TS29.118 CR0213 further proposes a solution, in this solution, for pre Rel-11 UEs, the MME sets the old LAI to a non-broadcasted LAI (not associated with any VLR) in the SGsAP-LOCATION-UPDATE-REQUEST message if the MME determines that the serving VLR of the UE is being changed.

Summary

As shown in the above TS29.118 CR0213 and TS29.118 CR0228, for the prior art communication system 100 including the SGs interface, there may be dual VLR registration. In case Cancel Location was lost in the inter-MSC mobility, the previous MSC still holds the UE's information. When UE moves to LTE access and MME selects the previous MSC for SGs association, the previous MSC does not update Home Location Register (HLR) , which results in that the MT call always fail until manual intervention to correct it.

Besides, when a Mobile Termination (MT) call comes to CS domain and UE just left 2G/3G and moved to LTE, MME may select a new MSC for SGs association by using International Mobile Subscriber Identification (IMSI) hash mechanism.

There may have some alternative solution e.g. the configuration CS network architecture on the MME pool side with implementation TS29.118 CR0228, but this alternative solution has its own drawback:

1) this alternative solution can’t thoroughly solve the existing problems since the UE (old version) may not fully provide sufficient information to support this alternative solution. As shown by the statement in TS29.118 CR0228, the TS29.118 CR0228 just provides a partial solution to the dual VLR problems;

2) it’s complicated to configure the MSC network in MME side and this configuration should be exposed in the whole MME pool;

3) if there is some change in the MSC side, e.g. the MSC pool may have some scale in or scale out, such change may have flood to MME side. Otherwise this may cause some unexpected problem.

In view of above typical case, thus the network may have the mis-alignment for the status; there might be some problems in the network to fail to deliver some important message. In above case, the HLR still keeps the information of the old MSC therein and informs the Mobile Origination (MO) MSC to incorrectly connect the old MSC as MT MSC.

In several embodiments herein, this problem can be fixed by two steps: 1) to restore the serving MSC for next MT call, in which the UE side can be not impacted and the impact on the legacy CS domain can be minimized; 2) to restore the current MT call. Note that, the above two steps can be perform in any manner, for example, performed in any sequence, performed at the same time, or performed separately.

In the above step 1) , the HLR is updated with current serving MSC, then at least next MT call won’t be missed. So firstly, the old MME should find the serving MME. Then, the serving MME should indicate serving MSC to trigger an update location to HLR, and thus later in next MT call, the HLR should locate the correct MSC for that UE. This won’t impact the UE, neither impact the legacy CS domain.

In the above step 2) , the ongoing MT call can be recovered. For example, once the serving MME trigger the serving MSC to update the location to HLR, the HLR would inform the old MSC to cancel location and the old MSC might trigger the call forwarding to new MSC (serving MSC will trigger paging for that UE) . And meanwhile the serving MME should trigger the CS paging to the UE, then UE would trigger CS service request in the serving MSC when it fallback to CS domain, and thus CS call could recover.

In one embodiment, there proposes a method in a first mobility management node, comprising: receiving a message indicating a Mobile Termination (MT) call for a wireless device; checking whether the wireless device is registered on the first mobility management node; if the wireless device is not registered on the first mobility management node, interrogating a subscriber server for a second mobility management node which is currently serving the wireless device or a Mobile Switching Center (MSC) associated with the second mobility management node, and transferring the MT call to the second mobility management node. In particular, the above transferring step further comprising: indicating the MT call to the second mobility management node. For example, the above indicating step further comprising: sending a "CS Paging Indication" message, which includes an International Mobile Subscriber Identification (IMSI) number of the wireless device, to the second mobility management node.

In another embodiment, there proposes a method in a second mobility management node, comprising: receiving a message indicating a Mobile Termination (MT) call for a wireless device, wherein the MT call is transferred from a first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device; and handling the MT call. In particular, the step of handling the MT call further comprising: paging to the wireless device for the MT call; and receiving an "Extended Service Request" message from the wireless device.

In yet another embodiment, there proposes a method in a second mobility management node, comprising: receiving a message indicating a Mobile Termination (MT) call for a wireless device, wherein the MT call is transferred from a first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device; and updating the location information of the wireless device. In particular, the updating step further comprising: sending a location update request to a Mobile Switching Center (MSC) associated with the second mobility management node, to update a Home Location Register (HLR) by the MSC.

In yet another embodiment, there proposes a method in a first Mobile Switching Center (MSC) node, for facilitating to transfer a Mobile Termination (MT) call for a wireless device from a first mobility management node associated with the first MSC node to a second mobility management node, comprising: receiving a message, which includes information of a second MSC node associated with the second mobility management node, from the first mobility management node; and transferring the MT call to the second MSC node, wherein the MT call is transferred from the first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device.

In yet another embodiment, there proposes a method in a second Mobile Switching Center (MSC) node, for facilitating to transfer a Mobile Termination (MT) call for a wireless device from a first mobility management node to a second mobility management node associated with the second MSC node, comprising: transferring the MT call from a first MSC associated with the first mobility management node to the second MSC node; and sending a message indicating the MT call for the wireless device, to the second mobility management node, wherein the MT call is transferred from the first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device.

In yet another embodiment, there proposes a first mobility management node, comprising: at least one processor; and a non-transitory computer readable medium coupled to the at least one processor, the non-transitory computer readable medium containing instructions executable by the at least one processor, whereby the at least one processor is configured to: receive a message indicating a Mobile Termination (MT) call for a wireless device; check whether the wireless device is registered on the first mobility management node; if the wireless device is not registered on the first mobility management node, interrogate a subscriber server for a second mobility management node which is currently serving the wireless device or a Mobile Switching Center (MSC) associated with the second mobility management node; and transfer the MT call to the second mobility management node. In particular, when transferring, the at least one processor is further configured to: indicate the MT call to the second mobility management node. For example, when indicating, the at least one processor is further configured to: send a "CS Paging Indication" message, which includes an International Mobile Subscriber Identification (IMSI) number of the wireless device, to the second mobility management node.

In yet another embodiment, there proposes a second mobility management node, comprising: at least one processor; and a non-transitory computer readable medium coupled to the at least one processor, the non-transitory computer readable medium containing instructions executable by the at least one processor, whereby the at least one processor is configured to:receive a message indicating a Mobile Termination (MT) call for a wireless device, wherein the MT call is transferred from a first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device; and handle the MT call. In particular, when handling the MT call, the at least one processor is further configured to: page to the wireless device for the MT call; and receive an "Extended Service Request" message from the wireless device.

In yet another embodiment, there proposes a second mobility management node, comprising: at least one processor; and a non-transitory computer readable medium coupled to the at least one processor, the non-transitory computer readable medium containing instructions executable by the at least one processor, whereby the at least one processor is configured to:receive a message indicating a Mobile Termination (MT) call for a wireless device, wherein the MT call is transferred from a first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device; and update the location information of the wireless device. In particular, when updating, the at least one processor is further configured to: send a location update request to a Mobile Switching Center (MSC) associated with the second mobility management node, to update a Home Location Register (HLR) by the MSC.

In yet another embodiment, there proposes a first Mobile Switching Center (MSC) node, for facilitating to transfer a Mobile Termination (MT) call for a wireless device from a first mobility management node associated with the first MSC node to a second mobility management node, comprising: at least one processor; and a non-transitory computer readable medium coupled to the at least one processor, the non-transitory computer readable medium containing instructions executable by the at least one processor, whereby the at least one processor is configured to: receive a message, which includes information of a second MSC node associated with the second mobility management node, from the first mobility management node; and transfer the MT call to the second MSC node, wherein the MT call is transferred from the first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device.

In yet another embodiment, there proposes a second Mobile Switching Center (MSC) node, for facilitating to transfer a Mobile Termination (MT) call for a wireless device from a first mobility management node to a second mobility management node associated with the second MSC node, comprising: at least one processor; and a non-transitory computer readable medium coupled to the at least one processor, the non-transitory computer readable medium containing instructions executable by the at least one processor, whereby the at least one processor is configured to: transfer the MT call from a first MSC associated with the first mobility management node to the second MSC node; and send a message indicating the MT call for the wireless device, to the second mobility management node, wherein the MT call is transferred from the first mobility management node since the wireless device is not registered on the first mobility management node, and wherein the second mobility management node is currently serving the wireless device.

In yet another embodiment, there proposes a computer readable medium comprising computer readable code, which when run on an apparatus, causes the apparatus to perform any of the above method.

With embodiments herein, which provide an efficient way to locate the serving MSC to fully recover the MT voice call service, the MT call service can be recovered, and thus the user experience of both MO and MT user can be improved, without significantly impacting the signaling UE side and the legacy CS domain.

Brief Description of the Drawings

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments of the present disclosure and, together with the description, further serve to explain the principles of the disclosure and to enable a person skilled in the pertinent art to make and use the embodiments disclosed herein. In the drawings, like reference numbers indicate identical or functionally similar elements, and in which:

Figure 1 is a schematic block diagram showing a typical 4G communication system including a SGs interface, according to the prior art;

Figure 2 is a schematic block diagram showing an example wireless communication system, in which the embodiments herein can be implemented;

Figure 3 is a schematic signaling chart showing an example method for recovering the MT call, according to the embodiments herein;

Figure 4 is a schematic signaling chart showing another example method for recovering the MT call, according to the embodiments herein;

Figure 5 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein;

Figure 6 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein;

Figure 7 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein;

Figure 8 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein;

Figure 9 is a schematic flow chart showing an example method in the first MME, according to the embodiments herein;

Figure 10 is a schematic flow chart showing an example method in the second MME, according to the embodiments herein;

Figure 11 is a schematic flow chart showing another example method in the second MME, according to the embodiments herein;

Figure 12 is a schematic flow chart showing an example method in the first MSC, according to the embodiments herein;

Figure 13 is a schematic flow chart showing an example method in the second MSC, according to the embodiments herein;

Figure 14 is a schematic block diagram showing an example first MME, according to the embodiments herein;

Figure 15 is a schematic block diagram showing an example second MME, according to the embodiments herein;

Figure 16 is a schematic block diagram showing an example first MSC, according to the embodiments herein;

Figure 17 is a schematic block diagram showing an example second MSC, according to the embodiments herein; and

Figure 18 is a schematic block diagram showing an apparatus, according to the embodiments herein.

Detailed Description of Embodiments

Embodiments herein will be described in detail hereinafter with reference to the accompanying drawings, in which embodiments are shown. These embodiments herein may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. The elements of the drawings are not necessarily to scale relative to each other.

Reference to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase "in one embodiment" appearing in various places throughout the specification are not necessarily all referring to the same embodiment.

Figure 2 is a schematic block diagram showing an example wireless communication system 200, in which the embodiments herein can be implemented.

In one embodiment, the wireless communication system 200 may include several MSCs coupled with each other, for example, a MSC acting as MO MSC 208, a MSC acting as old MSC 207, and a MSC acting as serving MSC 206. The MSCs may be coupled to a HLS 210. Each MSC may be associated with one or more mobility management node via SGs interface. For example, the old MSC 207 may be associated with the old MME 205 via SGs interface, the MO MSC 208 may be associated with a respective MO MME (not shown) via SGs interface, and the serving MSC 206 may be associated with the serving MME 204 via SGs interface. In one embodiment, each mobility management node may connect to a subscriber server, for example, a Home Subscriber Server (HSS) 209. In one embodiment, the subscriber server and the mobility management node may be embodied differently according to a different mobile communication standard, for example, 5G or beyond.

In one embodiment, each MME may manage one or more base stations. For example, the old MME 207 may manage an old eNodeB 202, and the serving MME 204 may manage a serving eNodeB 203. The serving eNodeB 203 can serve one or more wireless device (such as UE) , for example, UE 201. The old eNodeB 202 can also serve one or more wireless device (such as UE, not shown) . In one embodiment, the old eNodeB 202 may be the serving base station for UE 201 before the UE moving to the eNodeB 203, which is shown by a dashed line for UE 201 in Figure 2. That is, the UE may move from one eNodeB to another eNodeB belonging to different MSC.

In one embodiment, the wireless device may be embodied differently according to a different mobile communication standard, for example, the wireless device may be embodied as UE, device to device (D2D) UE, proximity capable UE (i.e., ProSe UE) , machine type UE or UE capable of machine to machine (M2M) communication, Personal Digital Assistant (PDA) , PAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE) , laptop mounted equipment (LME) , USB dongles, etc.

In one embodiment, the base station may be embodied differently according to a different mobile communication standard, for example, the wireless device may be embodied as the base station may be embodied as for example eNodeB (eNB) , network controller, radio network controller (RNC) , base station controller (BSC) , relay, donor node controlling relay, base transceiver station (BTS) , access point (AP) , transmission points, transmission nodes, etc.

In one embodiment, when the UE 201 moves from the old eNodeB 202 belonging to the old MSC 207 to the serving eNodeB 203 belonging to the serving MSC 206, a Cancel Location message is used to indicate the above change. However, in case Cancel Location was lost in the above inter-MSC mobility, the old MSC 207 still holds the information of UE 201, thus there may be the above mentioned dual VLR registration problem. In this case, the HLR 210 still keeps the information of the old MSC 207 therein, and will inform the MO MSC 208 to incorrectly connect the old MSC 208, for any incoming MT call destined to the UE 201 (i.e., MT call for UE) . That is, for MT call for the UE 201, which is now served by eNodeB 203 belonging to the serving MSC 206, the HLR will incorrectly direct the MT call to the old MSC 208.

In view of the above situation, the embodiments herein, which will be described by referring to Figure 2, aim to avoid the failure of the MT call and solve dual VLR registration problem.

Figure 3 is a schematic signaling chart showing an example method for recovering the MT call, according to the embodiments herein. In one embodiment, the signaling chart in Figure 3 can be implemented in the wireless communication system 200.

The flow in the example signaling chart in Figure 3 may comprise the following steps:

1. The old MSC receives a MT call request (IAM) since the HLR side still keeps the info that this MSC as serving MSC. In one embodiment, this step can be implemented by the signaling "IAM" as shown in Figure 3.

As described above in connection to Figure 2, in case Cancel Location was lost in the inter-MSC mobility, the HLR 210 still keeps the information of the old MSC 207 therein, and will inform the MO MSC 208 to incorrectly connect the old MSC 208, for any incoming MT call destined to the UE 201 (i.e., MT call for UE) .

2. This old MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 3.

In one embodiment, the old MSC 207 may send a SGsAP-Paging-Request message to the old MME 205 to indicate an incoming MT call for UE 201.

3. But this MME can’t find this UE on this node. In one embodiment, this step can be shown by the block "UE NOT FOUND! " as shown in Figure 3.

In one embodiment, upon receiving, from the old MSC 207, the above SGsAP-Paging-Request message indicating the incoming MT call for UE 201, the old MME 205 may check whether the wireless device is registered thereon. For example, the old MME 205 may check its database to see whether the UE 201 is registered on this MME node, and if not found, this MME node is not serving the UE at this moment. In one embodiment, if the UE 201 is not found on the old MME 205, the old MME 205 will decide to transfer the MT call to a MME currently serving the UE 201.

4. This old MME then trigger the “Send Routing Info” to the HSS to interrogate which MME is now serving for this UE. In one embodiment, this step can be implemented by the signaling "Sending Routing Info (IMSI) " as shown in Figure 3.

In one embodiment, the old MME 205 may interrogate a subscriber server (for example the HSS 209) for the serving MME, by sending a "Send Routing Info" message, which includes the IMSI number of the wireless device.

In one embodiment, the "Send Routing Info" message may be adapted as: the following form:

5. HSS replies with the current serving MME in the “Send Routing Info ACK” . HSS should have the similar functionality to provide the serving MME like in S6c interface to the SMS-C about the serving MME info for the SM delivery purpose. And in HLR, there has the MAP message “Send Routing Info” procedure. In one embodiment, this step can be implemented by the signaling "Sending Routing Info Answer (serving MME Info) " as shown in Figure 3.

In one embodiment, the information of the MME currently serving the UE 201 (for example, information of the serving MME 204) can be sent in a "Send Routing Info Answer" message from the subscriber server (for example the HSS 209) to the old MME 205. Then, the old MME 205 know the serving MME 204 is currently serving the UE 201, and thus this MT call should be transferred to the serving MME 204.

In one embodiment, the "Send Routing Info Answer" message may be adapted to the following form:

6. This MME will trigger GTPv2 message “CS Paging Indication” with IMSI to the serving MME, the “CS Paging Indication” message is originally designed for the ISR (Idle Signaling Reduction) sent from MME to SGSN via S3 interface to transfer the CS paging request from SGs interface to Gs interface, here this message can be re-used to transfer the CS paging request from old MME to the new MME over S10 interface. In one embodiment, this step can be implemented by the signaling "CS Paging Indication (IMSI) " as shown in Figure 3.

In one embodiment, upon knowing the information of the serving MME 204, the old MME 205 will transfer the MT call to the serving MME 204. For example, in one embodiment, the old MME 205 may indicate the MT call to the serving MME 204. In particular, in one embodiment, the old MME 205 may send a "CS Paging Indication" message, which includes the IMSI number of the UE 201, to the serving MME 204. In another embodiment, the old MME 205 may use any other manner to transfer the MT call to the serving MME 204.

7. The serving MME will trigger a CS paging request to this UE. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 3.

In one embodiment, upon receiving the message indicating the MT call for the UE 201 (such as "CS Paging Indication" message, which includes the IMSI number of the UE 201) from the old MME 205, the serving MME 205 may page to the UE 201 for the MT call, in order to handle the MT call.

8. The UE will respond with Extended Service Request. In one embodiment, this step can be implemented by the signaling "Extended Service Request" as shown in Figure 3.

In one embodiment, after receiving the paging from the serving MME 205 via the serving eNodeB 203, the UE 201 may respond to the serving MME 205 by sending for example "Extended Service Request" message.

9. The serving MME sets the old LAI to a non-broadcasted LAI (not associated with any VLR) and triggers the SGsAP-Location-Update-Request to the serving MSC which could trigger MSC to update the HLR. In one embodiment, this step can be implemented by the signaling "SGsAP-Location-Update-Request Procedure" as shown in Figure 3.

Note that: when MME triggers SGsAP-Location-Update-Request procedure, the MSC might trigger the TMSI reallocation procedure after receiving SGsAP-Location-Update-Request. It is possible that the MSC legacy mechanism is used to remember the old TMSI or MME initiates IMSI detach the UE to trigger a combined procedure. For the former option, MME will ignore the new TMSI from MSC if MSC really allocate a new TMSI.

In one embodiment, upon receiving the message indicating the MT call for the UE 201 (such as "CS Paging Indication" message, which includes the IMSI number of the UE 201) from the old MME 205, the serving MME 205 may trigger the "SGsAP-Location-Update-Request" message, in order to update the location information of the UE 201. That is, this step may be performed before or after the transferring of the MT call, or they can be performed in parallel. Besides, it is also possible that only one of them is performed.

In one embodiment, the serving MME 204 may send a location update request (such as the "SGsAP-Location-Update-Request" message) to the serving MSC 206, which is associated with the serving MME 204. Then, the serving MSC 206 may update the location information of the UE 201, for example the information of the UE 201 in the HLR.

In one embodiment, the "Update Location Request" message may be adapted to the following form:

Note: MME could provide its info with FQDN format or IP address directly in the Update Location procedure to HSS, the IP address would be much direct and save the latency to interrogate the DNS.

The updating of the location information of UE can be done by the following step 10-16, which is shown in Figure 4 in more details. Figure 4 is a schematic signaling chart showing another example method for recovering the MT call, according to the embodiments herein.

10. The serving MSC/VLR supporting the MTRF feature includes the MTRF Supported flag in the MAP Update Location message sent to the HLR.

11. If MTRF is authorized, the HLR includes the MTRF Supported and Authorized flag and the new MSC/VLR numbers in the MAP Cancel Location message sent to the old VLR.

12. Upon receipt of a MAP Cancel Location message while on-going paging, the old MSC/VLR stops paging. And the old MSC/VLR reply with Cancel Location Ack.

13. The HLR reply with Update Location Ack to the serving MSC/VLR.

14. If the old MSC supports both the MT Roaming Retry and the MT Roaming Forwarding procedures, and if the conditions for using these procedures are met, the MSC can decide based on operator policy to send MAP Provide Roaming Number Request to the new MSC/VLR.

15. The new MSC/VLR sends MSRN to the old VLR within the MAP Provide Roaming Number response.

16. Receipt of the MSRN from the new MSC/VLR enables the old MSC to relay the call towards the new MSC.

Note: the above steps 10-16 are handled in the legacy CS domain. It is possible to refer to 3GPP TS23.018 for more details.

Returning to Figure 3, the signaling chart in Figure 3 further comprising:

17. The UE will trigger CS Service Request in CS domain. If the ongoing MT could be continued to handle, this MT call will be recovered. In one embodiment, this step can be implemented by the signaling "CS Service Request" as shown in Figure 3.

In one embodiment, the UE 201 may send for example "CS Service Request" message to the serving MSC 206 when it falls back to the CS domain. That is, the UE may trigger the procedure in 3GPP TS23.272 Chapter 7.5a) with the serving MSC. Then, upon receiving the "CS Service Request" message, the serving MSC 206 can connect the MO UE to the UE 201 (i.e., the MT UE) , and thus the MT call is done by the serving MSC 206. The connection of the MO UE and the MT UE can be done by any approach known, and thus the details are omitted herein.

Figure 5 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein. In one embodiment, the signaling chart in Figure 5 can be implemented in the wireless communication system 200.

The flow in the example signaling chart in Figure 5 may comprise the following steps:

1. The old MSC receives a MT call request (IAM) since the HLR side still keeps the info that this MSC as serving MSC. In one embodiment, this step can be implemented by the signaling "IAM" as shown in Figure 5. This step is similar to the step 1 of Figure 3, the details thereof is omitted here.

2. The old MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 5. This step is similar to the step 2 of Figure 3, the details thereof is omitted here.

3. This MME can’t find this UE on this node. In one embodiment, this step can be shown by the block "NO UE context is found! " as shown in Figure 5. This step is similar to the step 3 of Figure 3, the details thereof is omitted here.

4. This old MME then trigger the “Send Routing Info” to the HSS to interrogate which MME is now serving for this UE. In one embodiment, this step can be implemented by the signaling "Sending Routing Info (IMSI) " as shown in Figure 5. This step is similar to the step 4 of Figure 3, the details thereof is omitted here.

5. HSS replies with the current serving MME in the “Send Routing Info ACK” . In one embodiment, this step can be implemented by the signaling "Sending Routing Info Answer (serving MME Info) " as shown in Figure 5. This step is similar to the step 5 of Figure 3, the details thereof is omitted here.

6. This MME will trigger the message “Context Request” . In one embodiment, this step can be implemented by the signaling "Context Request (IMSI) " as shown in Figure 5.

In one embodiment, the old MME 205 may send a "Context Request" message, which includes the IMSI number of the wireless device, to the serving MME 204.

7. The serving MME may reply with "Context Response" . In one embodiment, this step can be implemented by the signaling "Context Response (new MSC number) " as shown in Figure 5.

In one embodiment, the serving MME 204 will send a "Context Response" message, which includes MSC number of the serving MSC 206, to the old MME 205.

8. This old MME will send "Context Ack" when receiving the reply from the serving MME. In one embodiment, this step can be implemented by the signaling "Context Ack (#XXX no relocation) " as shown in Figure 5, wherein XXX in a number.

In one embodiment, the old MME 205 may send a "Context Ack" message, to the serving MME 204.

9. The old MME may send "SGsAP-UE-ACTIVITY-INDICATION" to the old MSC. In one embodiment, this step can be implemented by the signaling "SGsAP-UE-ACTIVITY-INDICATION (new MSC number) " as shown in Figure 5.

In one embodiment, the old MME 205 may send the MSC number of the serving MSC 206 associated with the serving MME 204 to the old MSC 205 associated with the old MME 205, in order to tell the old MSC which MSC is currently serving the UE 201.

10. If the old MSC supports both the MT Roaming Retry and the MT Roaming Forwarding procedures, and if the conditions for using these procedures are met, the MSC can decide based on operator policy to send MAP Provide Roaming Number Request to the new MSC/VLR. In one embodiment, this step can be implemented by the signaling "PRN (MTRF indication, old MSC number) " as shown in Figure 5.

In one embodiment, the old MSC 207 send a message, which includes roaming forwarding indication and information of the old MSC 207, to the serving MSC 206.

11. The new MSC/VLR sends MSRN to the old VLR within the MAP Provide Roaming Number response. In one embodiment, this step can be implemented by the signaling "PRN ACK (MSRN) " as shown in Figure 5.

In one embodiment, the serving MSC 206 will send a message, which includes a roaming number of the UE 201, to the old MSC 207, wherein the roaming number is assigned by the serving MSC 206 for the UE 201. In one embodiment, the roaming number may be Mobile Station Roaming Number (MSRN) .

12. Receipt of the MSRN from the new MSC/VLR enables the old MSC to relay the call towards the new MSC. In one embodiment, this step can be implemented by the signaling "IAM (MSRN) " as shown in Figure 5.

In one embodiment, the old MSC 207 may send an IAM message, which includes the roaming number of the UE 201, to the serving MSC 206.

13. The new MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 5.

In one embodiment, the serving MSC 206 may send a SGsAP-Paging-Request message to the serving MME 204 to indicate the incoming MT call for UE 201.

14. The serving MME will trigger a CS paging request to this UE. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 5.

In one embodiment, upon receiving the message indicating the MT call for the UE 201 (such as "CS Paging Request" message) from the serving MSC 206, the serving MME 205 may page to the UE 201 for the MT call, in order to handle the MT call.

15. The UE will respond with Extended Service Request. In one embodiment, this step can be implemented by the signaling "Extended Service Request" as shown in Figure 5.

16. The UE will trigger CS Service Request in CS domain. If the ongoing MT could be continued to handle, this MT call will be recovered. In one embodiment, this step can be implemented by the signaling "CS Service Request" as shown in Figure 5. This step is similar to the step 17 of Figure 3, the details thereof is omitted here.

In addition to the above step 1-16, upon receiving the message indicating the MT call for the UE 201, the serving MME 205 may update the location information of the UE 201. In one embodiment, this step can be implemented by the signaling "MME will trigger new ULR to new MSC" as shown in Figure 5. That is, this step may be performed before or after the transferring of the MT call, or they can be performed in parallel. Besides, it is also possible that only one of them is performed.

Figure 6 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein. In one embodiment, the signaling chart in Figure 6 can be implemented in the wireless communication system 200.

1. The old MSC receives a MT call request (IAM) since the HLR side still keeps the info that this MSC as serving MSC. In one embodiment, this step can be implemented by the signaling "IAM" as shown in Figure 6. This step is similar to the step 1 of Figure 3, the details thereof is omitted here.

2. The old MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 6. This step is similar to the step 2 of Figure 3, the details thereof is omitted here.

3. This MME can’t find this UE on this node. In one embodiment, this step can be shown by the block "NO UE context is found! " as shown in Figure 6. This step is similar to the step 3 of Figure 3, the details thereof is omitted here.

4. This old MME then trigger the “Send Routing Info” to the HSS to interrogate which MME is now serving for this UE. In one embodiment, this step can be implemented by the signaling "Sending Routing Info (IMSI) " as shown in Figure 6. This step is similar to the step 4 of Figure 3, the details thereof is omitted here.

5. HSS replies with the current serving MME in the “Send Routing Info ACK” . In one embodiment, this step can be implemented by the signaling "Sending Routing Info Answer (serving MME Info) " as shown in Figure 6. This step is similar to the step 5 of Figure 3, the details thereof is omitted here.

6. This MME will trigger GTPv2 message “CS Paging Indication” with IMSI and old MSC number to the serving MME, the “CS Paging Indication” message is originally designed for the ISR (Idle Signaling Reduction) sent from MME to SGSN via S3 interface to transfer the CS paging request from SGs interface to Gs interface, here this message can be re-used to transfer the CS paging request from old MME to the new MME over S10 interface. In one embodiment, this step can be implemented by the signaling "CS Paging Indication (IMSI, old MSC number) " as shown in Figure 6.

In one embodiment, upon knowing the information of the serving MME 204, the old MME 205 will transfer the MT call to the serving MME 204. For example, in one embodiment, the old MME 205 may indicate the MT call to the serving MME 204. In particular, in one embodiment, the old MME 205 may send a "CS Paging Indication" message, which includes the IMSI number of the UE 201 and the number of the serving MSC 206, to the serving MME 204.

7. The new MME may send "SGsAP-UE-ACTIVITY-INDICATION" to the old MSC. In one embodiment, this step can be implemented by the signaling "SGsAP-UE-ACTIVITY-INDICATION (new MSC number) " as shown in Figure 6.

In one embodiment, the serving MME 204 may send the MSC number of the serving MSC 206 associated with the serving MME 204 to the old MSC 205 associated with the old MME 205, in order to tell the old MSC which MSC is currently serving the UE 201.

8. If the old MSC supports both the MT Roaming Retry and the MT Roaming Forwarding procedures, and if the conditions for using these procedures are met, the MSC can decide based on operator policy to send MAP Provide Roaming Number Request to the new MSC/VLR. In one embodiment, this step can be implemented by the signaling "PRN (MTRF indication, old MSC number) " as shown in Figure 6. This step is similar to the step 10 of Figure 5, the details thereof is omitted here.

9. The new MSC/VLR sends MSRN to the old VLR within the MAP Provide Roaming Number response. In one embodiment, this step can be implemented by the signaling "PRN ACK (MSRN) " as shown in Figure 6. This step is similar to the step 11 of Figure 5, the details thereof is omitted here.

10. Receipt of the MSRN from the new MSC/VLR enables the old MSC to relay the call towards the new MSC. In one embodiment, this step can be implemented by the signaling "IAM (MSRN) " as shown in Figure 6. This step is similar to the step 12 of Figure 5, the details thereof is omitted here.

11. The new MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 6. This step is similar to the step 13 of Figure 5, the details thereof is omitted here.

12. The serving MME will trigger a CS paging request to this UE. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 6. This step is similar to the step 14 of Figure 5, the details thereof is omitted here.

13. The UE will respond with Extended Service Request. In one embodiment, this step can be implemented by the signaling "Extended Service Request" as shown in Figure 6. This step is similar to the step 15 of Figure 5, the details thereof is omitted here.

14. The UE will trigger CS Service Request in CS domain. If the ongoing MT could be continued to handle, this MT call will be recovered. In one embodiment, this step can be implemented by the signaling "CS Service Request" as shown in Figure 6. This step is similar to the step 17 of Figure 3, the details thereof is omitted here.

In addition to the above step 1-14, upon receiving the message indicating the MT call for the UE 201, the serving MME 205 may update the location information of the UE 201. In one embodiment, this step can be implemented by the signaling "MME will trigger new ULR to new MSC" as shown in Figure 6. That is, this step may be performed before or after the transferring of the MT call, or they can be performed in parallel. Besides, it is also possible that only one of them is performed.

Figure 7 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein. In one embodiment, the signaling chart in Figure 7 can be implemented in the wireless communication system 200.

1. The old MSC receives a MT call request (IAM) since the HLR side still keeps the info that this MSC as serving MSC. In one embodiment, this step can be implemented by the signaling "IAM" as shown in Figure 7. This step is similar to the step 1 of Figure 3, the details thereof is omitted here.

2. The old MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 7. This step is similar to the step 2 of Figure 3, the details thereof is omitted here.

3. This MME can’t find this UE on this node. In one embodiment, this step can be shown by the block "NO UE context is found! " as shown in Figure 7. This step is similar to the step 3 of Figure 3, the details thereof is omitted here.

4. This old MME then trigger the “Send Routing Info” to the HSS to interrogate which MSC is now serving for this UE. In one embodiment, this step can be implemented by the signaling "Sending Routing Info (IMSI) " as shown in Figure 7.

In one embodiment, the old MME 205 may interrogate a subscriber server (for example the HSS 209) for the serving MSC, by sending a "Send Routing Info" message, which includes the IMSI number of the wireless device.

In one embodiment, the "Send Routing Info" message may be adapted as the similar form to step 4 of Figure 3.

5. After the HSS finding the information of the serving MME, it will query the serving MME for information of serving MSC. In one embodiment, this step can be implemented by the signaling "Insert Subscriber Data Request (Indication for Query Serving MSC Number) " as shown in Figure 7.

6. The serving MME will return the information of serving MSC. In one embodiment, this step can be implemented by the signaling "Insert Subscriber Data Answer (Serving MSC Number) " as shown in Figure 7.

7. HSS replies with the current serving MME in the “Send Routing Info ACK” . HSS should have the similar functionality to provide the serving MME like in S6c interface to the SMS-C about the serving MME info for the SM delivery purpose. And in HLR, there has the MAP message “Send Routing Info” procedure. In one embodiment, this step can be implemented by the signaling "Sending Routing Info Answer (new MSC number) " as shown in Figure 7.

In one embodiment, the information of the MSC currently serving the UE 201 (for example, information of the serving MSC 206) can be sent in a "Send Routing Info Answer" message from the subscriber server (for example the HSS 209) to the old MME 205. Then, the old MME 205 know the serving MSC 206 is currently serving the UE 201, and thus this MT call should be transferred to the serving MSC 206.

8. The old MME may send "SGsAP-UE-ACTIVITY-INDICATION" to the old MSC. In one embodiment, this step can be implemented by the signaling "SGsAP-UE-ACTIVITY-INDICATION (new MSC number) " as shown in Figure 7. This step is similar to the step 9 of Figure 5, the details thereof is omitted here.

9. If the old MSC supports both the MT Roaming Retry and the MT Roaming Forwarding procedures, and if the conditions for using these procedures are met, the MSC can decide based on operator policy to send MAP Provide Roaming Number Request to the new MSC/VLR. In one embodiment, this step can be implemented by the signaling "PRN (MTRF indication, old MSC number) " as shown in Figure 7. This step is similar to the step 10 of Figure 5, the details thereof is omitted here.

10. The new MSC/VLR sends MSRN to the old VLR within the MAP Provide Roaming Number response. In one embodiment, this step can be implemented by the signaling "PRN ACK (MSRN) " as shown in Figure 7. This step is similar to the step 11 of Figure 5, the details thereof is omitted here.

11. Receipt of the MSRN from the new MSC/VLR enables the old MSC to relay the call towards the new MSC. In one embodiment, this step can be implemented by the signaling "IAM (MSRN) " as shown in Figure 7. This step is similar to the step 12 of Figure 5, the details thereof is omitted here.

12. The new MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 7. This step is similar to the step 13 of Figure 5, the details thereof is omitted here.

13. The serving MME will trigger a CS paging request to this UE. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 7. This step is similar to the step 14 of Figure 5, the details thereof is omitted here.

14. The UE will respond with Extended Service Request. In one embodiment, this step can be implemented by the signaling "Extended Service Request" as shown in Figure 7. This step is similar to the step 15 of Figure 5, the details thereof is omitted here.

15. The UE will trigger CS Service Request in CS domain. If the ongoing MT could be continued to handle, this MT call will be recovered. In one embodiment, this step can be implemented by the signaling "CS Service Request" as shown in Figure 6. This step is similar to the step 17 of Figure 3, the details thereof is omitted here.

In addition to the above step 1-15, upon receiving the message indicating the MT call for the UE 201, the serving MME 205 may update the location information of the UE 201. In one embodiment, this step can be implemented by the signaling "MME will trigger new ULR to new MSC" as shown in Figure 7. That is, this step may be performed before or after the transferring of the MT call, or they can be performed in parallel. Besides, it is also possible that only one of them is performed.

Figure 8 is a schematic signaling chart showing yet another example method for recovering the MT call, according to the embodiments herein. In one embodiment, the signaling chart in Figure 8 can be implemented in the wireless communication system 200.

1. The old MSC receives a MT call request (IAM) since the HLR side still keeps the info that this MSC as serving MSC. In one embodiment, this step can be implemented by the signaling "IAM" as shown in Figure 8. This step is similar to the step 1 of Figure 3, the details thereof is omitted here.

2. The old MSC will trigger the SGsAP CS paging to the associated MME. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 8. This step is similar to the step 2 of Figure 3, the details thereof is omitted here.

3. This MME can’t find this UE on this node. In one embodiment, this step can be shown by the block "NO UE context is found! " as shown in Figure 8. This step is similar to the step 3 of Figure 3, the details thereof is omitted here.

4. This old MME then trigger the “Send Routing Info” to the HSS to interrogate which MME is now serving for this UE. In one embodiment, this step can be implemented by the signaling "Sending Routing Info (IMSI) " as shown in Figure 8. This step is similar to the step 4 of Figure 3, the details thereof is omitted here.

5. HSS replies with the current serving MME in the “Send Routing Info ACK” . In one embodiment, this step can be implemented by the signaling "Sending Routing Info Answer (serving MME Info) " as shown in Figure 8. This step is similar to the step 5 of Figure 3, the details thereof is omitted here.

6. This MME will trigger GTPv2 message “CS Paging Indication” with IMSI and old MSC number to the serving MME. In one embodiment, this step can be implemented by the signaling "CS Paging Indication (IMSI, old MSC number) " as shown in Figure 8. This step is similar to the step 6 of Figure 6, the details thereof is omitted here.

7. The serving MME will trigger a CS paging request to this UE. In one embodiment, this step can be implemented by the signaling "CS Paging Request" as shown in Figure 8. This step is similar to the step 7 of Figure 3, the details thereof is omitted here.

8. The UE will respond with Extended Service Request. In one embodiment, this step can be implemented by the signaling "Extended Service Request" as shown in Figure 8. This step is similar to the step 8 of Figure 3, the details thereof is omitted here.

9. The serving MME sets the old LAI to a non-broadcasted LAI (not associated with any VLR) and triggers the SGsAP-Location-Update-Request to the serving MSC which could trigger MSC to update the HLR. In one embodiment, this step can be implemented by the signaling "SGsAP-Location-Update-Request Procedure" as shown in Figure 8. This step is similar to the step 9 of Figure 3, the details hereof is omitted here.

10. The UE will trigger CS Service Request in CS domain. If the ongoing MT could be continued to handle, this MT call will be recovered. In one embodiment, this step can be implemented by the signaling "CS Service Request" as shown in Figure 8. That is, the UE may trigger the procedure in 3GPP TS23.272 Chapter 7.5a) with the serving MSC. This step is similar to the step 17 of Figure 3, the details hereof is omitted here.

Figure 9 is a schematic flow chart showing an example method 900 in the first MME, according to the embodiments herein. In one embodiment, the flow chart in Figure 9 can be implemented in the old MME 205 in Figure 3.

The method 900 may begin with step S901, in which the old MME 205 may receive a message indicating a MT call for a wireless device (for example the UE 201) . As shown in step 2 of Figure 3-8, in one embodiment, the old MSC 207 may send a SGsAP-Paging-Request message to the old MME 205 to indicate an incoming MT call for UE 201.

Then, the method 900 may proceed to step S902, in which the old MME 205 may check whether the wireless device is registered on thereon. As shown in step 3 of Figure 3-8, in one embodiment, the old MME 205 may check its database to see whether the UE 201 is registered on this MME node, and if not found, this MME node is not serving the UE at this moment.

Then, the method 900 may proceed to step S903, in which the old MME 205 may interrogate a subscriber server for a MME which is currently serving the wireless device or a MSC associated with the serving MME, in the case that the wireless device is not registered on the old MME 205.

As shown in step 4 of Figure 3-4, 5-6, 8, in one embodiment, the old MME 205 may interrogate the HSS 209 for the serving MME, by sending a "Send Routing Info" message, which includes the IMSI number of the UE 201. As a response, the HSS 209 may return the information of the serving MME 204 to the old MME 205.

Besides, as shown in step 4 of Figure 7, in another embodiment, the old MME 205 may interrogate the HSS 209 for the serving MSC, by sending a "Send Routing Info" message, which includes the IMSI number of the UE 201. As a response, the HSS 209 may return the information of the serving MSC 206 to the old MME 205.

Then, the method 900 may proceed to step S903, in which the old MME 205 will transfer the MT call towards the serving MME 204.

As shown in step 6 of Figure 3 and 4, the old MME 205 can directly indicate the MT call to the serving MME 204. For example, in one embodiment, the old MME 205 may send a "CS Paging Indication" message, which includes the IMSI number of the UE 201, to the serving MME 204. Then the serving MME 204 can handle the MT call by for example step 7, 8 of Figure 3-4, the details thereof is omitted here.

Besides, in another embodiment shown in step 6 of Figure 6, 8, the old MME 205 may send a "CS Paging Indication" message to the serving MME 204, wherein the "CS Paging Indication" message further includes MSC number of the old MSC 205, in addition to the IMSI number of the UE 201. Then, the serving MME 204 may locate the serving MSC 206 by step 7-10 of Figure 6 or the serving MME 204 handle the MT call by for example step 7, 8, and 10 of Figure 8, the details thereof is omitted here.

Besides, as shown in step 6-13 of Figure 5, the old MME 205 can transfer the MT call to the serving MME via the serving MSC. In order to locate the MSC for the MT call, the old MME 205 may send a "Context Request" message, which includes the IMSI number of the wireless device, to the serving MME 204; then the serving MME 204 may reply with a "Context Response" message, which includes a MSC number of the serving MSC 206. Upon knowing the MSC number of the serving MSC, the old MME 207 may send the MSC number of the serving MSC 206 to the old MSC 207. The old MSC 207 may transfer the MT call to the serving MSC by performing the step 10-12 of Figure 5; and then the serving MSC 206 may further transfer the MT call to the serving MME 204, as shown in the step 13 of Figure 5. The details are omitted for step 10-13.

Besides, as shown in step 8-11 of Figure 7, upon knowing the number of the serving MSC 206, the old MME 205 may locate the serving MSC 206 by sending the serving MSC number to the old MSC 207; thereby the old MSC 207 can locate the serving MSC 206 by step 9-11 of Figure 7.

The above steps are only examples, and the old MME 205 can perform any actions that are shown or not shown in Figures 3-8, to transfer the MT call to the serving MME or serving MSC.

Figure 10 is a schematic flow chart showing an example method 1000 in the second MME, according to the embodiments herein. In one embodiment, the flow chart in Figure 10 can be implemented in the new MME 204 in Figure 3.

The method 1000 may begin with step S1001, in which the new MME 204 may receiving a message indicating a MT call for a wireless device (for example the UE 201) . The MT call is transferred from the old MME 205, since the UE is not registered on the old MME 205, and the serving MME 204 is currently serving the UE 201.

As shown in in step 6 of Figure 3 and 4, the serving MME 204 may receive an indication of the MT call from the old MME 205. For example, in one embodiment, the serving MME 204 may receive a "CS Paging Indication" message, which includes the IMSI number of the UE 201, from the old MME 205.

Besides, in another embodiment shown in step 6 of Figure 6, 8, the serving MME 204 may receive a "CS Paging Indication" message from the old MME 205, wherein the "CS Paging Indication" message further includes MSC number of the old MSC 205, in addition to the IMSI number of the UE 201.

As shown in step 13 of Figure 5 and step 12 in Figure 7, the serving MME 204 may receive a CS paging request from the serving MSC 206.

Then, the method 1000 may proceed to step S1002, in which the serving MME 204 may handle the MT call, for example by step 7, 8 of Figure 3-4, or step 14-15 of Figure 5, or step 12-13 of Figure 6, or step 13-14 of Figure 7, or step 7, 8 of Figure 8. The handling of the MT call may further includes: the serving MME 204 page to the UE 201 for the MT call; and the UE 201 reply with an "Extended Service Request" message. The serving MME 204 may use any approach known to handle the MT call, and the details is omitted here. Later, the UE 201 may send for example "CS Service Request" message to the serving MSC 206 when it falls back to the CS domain.

The above steps are only examples, and the serving MME 205 can perform any actions that are shown or not shown in Figures 3-8, to accept the transferring of the MT call and handling the MT call.

Figure 11 is a schematic flow chart showing another example method 1100 in the second MME, according to the embodiments herein. In one embodiment, the flow chart in Figure 11 can be implemented in the new MME 204 in Figure 3.

The method 1100 may begin with step S1101, in which the new MME 204 may receiving a message indicating a MT call for a wireless device (for example the UE 201) . The MT call is transferred from the old MME 205, since the UE is not registered on the old MME 205, and the serving MME 204 is currently serving the UE 201.

Then, the method 1100 may proceed to step S1102, in which the serving MME 204 may update the location information of the wireless device. For example, the serving MME 204 may update the location information of the UE 201 at the HLR 210. In one embodiment, the serving MME 204 may update the location information of UE 201 by sending a location update request to the serving MSC 206, then the serving MSC 206 may update the HLR by using the step 10-16 shown in Figure 4. Besides, the serving MME 204 may update the location information of UE 201 by using the procedure "MME will trigger new ULR to new MSC" in Figure 5-7.

The above steps are only examples, and the serving MME 205 can perform any actions that are shown or not shown in Figures 3-8, to accept the transferring of the MT call and update the location information of the wireless device.

Figure 12 is a schematic flow chart showing an example method 1200 in the first MSC, according to the embodiments herein. In one embodiment, the flow chart in Figure 12 can be implemented in the old MSC 207 in Figure 3.

In one embodiment, the method 1200 is used for facilitating to transfer a MT call for the UE 201 from the old MME 205 to the serving MME 204. The MT call is transferred from the old MME 205 since the UE 201 is not registered on the old MME 205, and the serving MME 204 is currently serving the UE 201.

The method 1200 may begin with step S1201, in which the old MSC 207 may receive a message, which includes information of the serving MSC 206, from the old MME 205. For example, as shown in step 9 of Figure 5, step 7 of Figure 6, and step 8 of the Figure 7, the old MME 205 may send a "SGsAP-UE-ACTIVITY-INDICATION" message, which includes the MSC number of the serving MSC 206 associated with the serving MME 204 to the old MSC 205 associated with the old MME 205, in order to tell the old MSC which MSC is currently serving the UE 201.

Then, the method 1200 may proceed to step S1202, in which the old MSC 207 may transfer the MT call to the serving MSC 206. In one embodiment, as shown in step 10 of Figure 5, step 8 of Figure 6, and step 9 of Figure 7, the old MSC 207 may send a message, which includes roaming forwarding indication and information of the old MSC 207, to the serving MSC 206. Then, as shown in step 11 of Figure 5, step 9 of Figure 6, and step 10 of Figure 7, the old MSC 207 may receive a message, which includes a roaming number of the UE 201, from serving MSC 206, wherein the roaming number is assigned by the serving MSC 206 for the UE 201. In one embodiment, the roaming number may be Mobile Station Roaming Number (MSRN) . Then, as shown in step 12 of Figure 5, step 10 of Figure 6, and step 11 of Figure 7, the old MSC 207 may send an IAM message, which includes the roaming number of the UE 201, to the serving MSC 206.

The above steps are only examples, and the old MSC 207 can perform any actions that are shown or not shown in Figures 3-8, to accept the transferring of the MT call from the old MME 205 and transfer the MT call to the serving MSC 206.

Figure 13 is a schematic flow chart showing an example method 1300 in the second MSC, according to the embodiments herein. In one embodiment, the flow chart in Figure 13 can be implemented in the serving MSC 206 in Figure 3.

In one embodiment, the method 1300 is used for facilitating to transfer a MT call for the UE 201 from the old MME 205 to the serving MME 204. The MT call is transferred from the old MME 205 since the UE 201 is not registered on the old MME 205, and the serving MME 204 is currently serving the UE 201.

The method 1300 may begin with step S1301, in which the new MSC 206 may transfer the MT call from the old MSC 207. In one embodiment, as shown in step 10 of Figure 5, step 8 of Figure 6, and step 9 of Figure 7, the serving MSC 206 may receive a message, which includes roaming forwarding indication and information of the old MSC 207, from the old MSC 207. Then, as shown in step 11 of Figure 5, step 9 of Figure 6, and step 10 of Figure 7, the serving MSC 206 may send a message, which includes a roaming number of the UE 201, to the old MSC 207, wherein the roaming number is assigned by the serving MSC 206 for the UE 201. In one embodiment, the roaming number may be Mobile Station Roaming Number (MSRN) . Then, as shown in step 12 of Figure 5, step 10 of Figure 6, and step 11 of Figure 7, the serving MSC 206 may receive an IAM message, which includes the roaming number of the UE 201, from the old MSC 207.

Then, the method 1300 may proceed to step S1302, in which the serving MSC 206 may send a message indicating the MT call for the UE 201, to the serving MME 204. For example, as shown in step 13 of Figure 5, step 11 of Figure 6, and step 12 of the Figure 7, the serving MSC 206 may send a CS Paging Request message to the serving MME 204 to indicate the incoming MT call for UE 201.

The above steps are only examples, and the serving MSC 206 can perform any actions that are shown or not shown in Figures 3-8, to accept the transferring of the MT call from the old MSC 207 and transfer the MT call to the serving MME 204.

Figure 14 is a schematic block diagram showing an example first MME 1400, according to the embodiments herein. In one embodiment, the first MME 1400 can be implemented as the old MME 205 in Figure 3.

In one embodiment, the first MME 1400 may include at least one processor 1401; and a non-transitory computer readable medium 1402 coupled to the at least one processor 1401. The non-transitory computer readable medium 1402 containing instructions executable by the at least one processor 1401, whereby the at least one processor 1401 is configured to perform the steps in the example method 900 as shown in the schematic flow chart of Figure 9.

Note that, the first MME 1400 can be performed as hardware, software, firmware and any combination thereof. For example, the first MME 1400 may include a plurality of units, circuities, or modules, each of which can be used to perform a step of the example method 900 or any step shown in Figure 3-8 related to the old MME 205.

Figure 15 is a schematic block diagram showing an example second MME 1500, according to the embodiments herein. In one embodiment, the second MME 1500 can be implemented as the serving MME 204 in Figure 3.

In one embodiment, the second MME 1500 may include at least one processor 1501; and a non-transitory computer readable medium 1502 coupled to the at least one processor 1501.

In one embodiment, the non-transitory computer readable medium 1502 containing instructions executable by the at least one processor 1501, whereby the at least one processor 1501 is configured to perform the steps in the example method 1000 as shown in the schematic flow chart of Figure 10.

In another embodiment, the non-transitory computer readable medium 1502 containing instructions executable by the at least one processor 1501, whereby the at least one processor 1501 is configured to perform the steps in the example method 1100 as shown in the schematic flow chart of Figure 11.

Note that, the second MME 1500 can be performed as hardware, software, firmware and any combination thereof. For example, the second MME 1500 may include a plurality of units, circuities, or modules, each of which can be used to perform a step of the example method 1000 (or 1100) or any step shown in Figure 3-8 related to the old MME 205.

Figure 16 is a schematic block diagram showing an example first MSC 1600, according to the embodiments herein. In one embodiment, the first MSC 1600 can be implemented as the old MSC 207 in Figure 3.

In one embodiment, the first MSC 1600 may include at least one processor 1601; and a non-transitory computer readable medium 1602 coupled to the at least one processor 1601. The non-transitory computer readable medium 1602 containing instructions executable by the at least one processor 1601, whereby the at least one processor 1601 is configured to perform the steps in the example method 1200 as shown in the schematic flow chart of Figure 12.

Note that, the first MSC 1600 can be performed as hardware, software, firmware and any combination thereof. For example, the first MSC 1600 may include a plurality of units, circuities, or modules, each of which can be used to perform a step of the example method 1200 or any step shown in Figure 3-8 related to the old MSC 207.

Figure 17 is a schematic block diagram showing an example second MSC 1700, according to the embodiments herein. In one embodiment, the second MSC 1700 can be implemented as the serving MSC 206 in Figure 3.

In one embodiment, the first MSC 1700 may include at least one processor 1701; and a non-transitory computer readable medium 1702 coupled to the at least one processor 1701. The non-transitory computer readable medium 1702 containing instructions executable by the at least one processor 1701, whereby the at least one processor 1701 is configured to perform the steps in the example method 1300 as shown in the schematic flow chart of Figure 13.

Note that, the second MSC 1700 can be performed as hardware, software, firmware and any combination thereof. For example, the second MSC 1700 may include a plurality of units, circuities, or modules, each of which can be used to perform a step of the example method 1300 or any step shown in Figure 3-8 related to the serving MSC 206.

Figure 18 is a schematic block diagram showing an apparatus 1800, according to the embodiments herein. In one embodiment, the apparatus 1800 can be configured as the above mentioned apparatus, such as the old MME 205, the serving MME 204, the old MSC 207, or the serving MSC 206.

In one embodiment, the apparatus 1800 may include but not limited to at least one processor such as Central Processing Unit (CPU) 1801, a computer-readable medium 1802, and a memory 1803. The memory 1803 may comprise a volatile (e.g. Random Access Memory, RAM) and/or non-volatile memory (e.g. a hard disk or flash memory) . In one embodiment, the computer-readable medium 1802 may be configured to store a computer program and/or instructions, which, when executed by the processor 1801, causes the processor 1801 to carry out any of the above mentioned methods.

In one embodiment, the computer-readable medium 1802 (such as non-transitory computer readable medium) may be stored in the memory 1803. In another embodiment, the computer program can be stored in a remote location for example computer program product 1804, and accessible by the processor 1801 via for example carrier 1805.

The computer-readable medium 1802 and/or the computer program product 1804 can be distributed and/or stored on a removable computer-readable medium, e.g. diskette, CD (Compact Disk) , DVD (Digital Video Disk) , flash or similar removable memory media (e.g. compact flash, SD (secure digital) , memory stick, mini SD card, MMC multimedia card, smart media) , HD-DVD (High Definition DVD) , or Blu-ray DVD, USB (Universal Serial Bus) based removable memory media, magnetic tape media, optical storage media, magneto-optical media, bubble memory, or distributed as a propagated signal via a network (e.g. Ethernet, ATM, ISDN, PSTN, X. 25, Internet, Local Area Network (LAN) , or similar networks capable of transporting data packets to the infrastructure node) .

Example embodiments are described herein with reference to block diagrams and/or flowchart illustrations of computer-implemented methods, apparatus (systems and/or devices) and/or non-transitory computer program products. It is understood that a block of the block diagrams and/or flowchart illustrations, and combinations of blocks in the block diagrams and/or flowchart illustrations, can be implemented by computer program instructions that are performed by one or more computer circuits. These computer program instructions may be provided to a processor circuit of a general purpose computer circuit, special purpose computer circuit, and/or other programmable data processing circuit to produce a machine, such that the instructions, which execute via the processor of the computer and/or other programmable data processing apparatus, transform and control transistors, values stored in memory locations, and other hardware components within such circuitry to implement the functions/acts specified in the block diagrams and/or flowchart block or blocks, and thereby create means (functionality) and/or structure for implementing the functions/acts specified in the block diagrams and/or flowchart block (s) .

These computer program instructions may also be stored in a tangible computer-readable medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable medium produce an article of manufacture including instructions which implement the functions/acts specified in the block diagrams and/or flowchart block or blocks. Accordingly, embodiments of present inventive concepts may be embodied in hardware and/or in software (including firmware, resident software, micro-code, etc. ) that runs on a processor such as a digital signal processor, which may collectively be referred to as “circuitry, ” “amodule” or variants thereof.

It should also be noted that in some alternate implementations, the functions/acts noted in the blocks may occur out of the order noted in the flowcharts. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Moreover, the functionality of a given block of the flowcharts and/or block diagrams may be separated into multiple blocks and/or the functionality of two or more blocks of the flowcharts and/or block diagrams may be at least partially integrated. Finally, other blocks may be added/inserted between the blocks that are illustrated, and/or blocks/operations may be omitted without departing from the scope of inventive concepts. Moreover, although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

Many variations and modifications can be made to the embodiments without substantially departing from the principles of the present inventive concepts. All such variations and modifications are intended to be included herein within the scope of present inventive concepts. Accordingly, the above disclosed subject matter is to be considered illustrative, and not restrictive, and the appended examples of embodiments are intended to cover all such modifications, enhancements, and other embodiments, which fall within the spirit and scope of present inventive concepts. Thus, to the maximum extent allowed by law, the scope of present inventive concepts are to be determined by the broadest permissible interpretation of the present disclosure including the following examples of embodiments and their equivalents, and shall not be restricted or limited by the foregoing detailed description.

Abbreviations

4G fourth generation of mobile communication

5G fifth generation of mobile communication

CS Circuit Switching

CSFB Circuit Switching Fall Back

EPS evolved Packet System

GSM Global System for Mobile Communication

HLR Home Location Register

HSS Home Subscriber Server

IMSI International Mobile Subscriber Identification

MME Mobility Management Entity

MO Mobile Origination

MSC Mobile Switching Center

MT Mobile Termination

SGSN Serving GPRS support Node

UE User Equipment

VLR Visitor Location Register

WCDMA Wideband Code Division Multiple Access.

Claims

A method (900) in a first mobility management node (205) , comprising:

-receiving (S901) a message indicating a Mobile Termination (MT) call for a wireless device (201) ;

-checking (S902) whether the wireless device (201) is registered on the first mobility management node (205) ;

-if the wireless device (201) is not registered on the first mobility management node (205) , interrogating (S903) a subscriber server (209) for a second mobility management node (204) which is currently serving the wireless device (201) or a Mobile Switching Center (MSC) (206) associated with the second mobility management node (204) ; and

-transferring (S904) the MT call towards the second mobility management node (204) .
the method (900) according to claim 1, wherein the transferring (S904) step further comprising:

-indicating the MT call to the second mobility management node (204) .
the method (900) according to claim 2, wherein the indicating step further comprising:

-sending a "CS Paging Indication"message, which includes an International Mobile Subscriber Identification (IMSI) number of the wireless device (201) , to the second mobility management node (204) .
the method (900) according to claim 1, wherein the interrogating (S903) step further comprising:

-interrogating the subscriber server (209) by sending a "Send Routing Info"message, which includes an IMSI number of the wireless device (201) ; and

-receiving information of the second mobility management node (204) in a "Send Routing Info Answer"message from the subscriber server (209) .
the method (900) according to claim 1, wherein the transferring (S904) step further comprising:

-sending a "Context Request"message, which includes an IMSI number of the wireless device (201) , to the second mobility management node (204) ;

-receiving a "Context Response"message, which includes a MSC number of the MSC (206) associated with the second mobility management node (204) , from the second mobility management node (204) ; and

-sending the MSC number of the MSC (206) associated with the second mobility management node (204) to a MSC (207) associated with the first mobility management node (205) , thereby facilitating to transfer the MT call to the second mobility management node (204) .
the method (900) according to claim 3, wherein the "CS Paging Indication"message further includes a MSC number of a MSC (207) associated with the first mobility management node (205) .
the method (900) according to claim 1, wherein the interrogating (S903) step further comprising:

-interrogating the subscriber server (209) by sending a "Send Routing Info"message, which includes an IMSI number of the wireless device (201) ; and

-receiving information of the MSC (206) associated with the second mobility management node (204) in a "Send Routing Info Answer"message from the subscriber server (209) ;

and wherein the transferring step (S904) further comprising:

-sending information of the MSC (206) associated with the second mobility management node (204) to a MSC (207) associated with the first mobility management node (205) , thereby facilitating to transfer the MT call to the second mobility management node (204) .
A method (1000) in a second mobility management node (204) , comprising:

-receiving (S1001) a message indicating a Mobile Termination (MT) call for a wireless device (201) , wherein the MT call is transferred from a first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) ; and

-handling (S1002) the MT call.
the method (1000) according to claim 8, wherein the step of handling (S1002) the MT call further comprising:

-paging to the wireless device (201) for the MT call; and

-receiving an "Extended Service Request"message from the wireless device (201) .
the method (1000) according to claim 8, wherein the step of receiving (S1001) a message indicating the MT call further comprising:

-receiving an indication of the MT call from the first mobility management node (205) .
the method (1000) according to claim 10, wherein the step of receiving an indication of the MT call further comprising:

-receiving a "CS Paging Indication"message, which includes an International Mobile Subscriber Identification (IMSI) number of the wireless device (201) , from the first mobility management node (205) .
the method (1000) according to claim 8, wherein the step of receiving (S1001) a message indicating the MT call further comprising:

-receiving a CS paging request from a Mobile Switching Center (MSC) (206) associated with the second mobility management node (204) .
the method (1000) according to claim 11, wherein the "CS Paging Indication"message further includes a MSC number of a MSC (207) associated with the first mobility management node (205) .
A method (1100) in a second mobility management node (204) , comprising:

-receiving (S1101) a message indicating a Mobile Termination (MT) call for a wireless device (201) , wherein the MT call is transferred from a first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) ; and

-updating (S1102) the location information of the wireless device (201) .
the method (1100) according to claim 14, wherein the updating (S1102) step further comprising:

-sending a location update request to a Mobile Switching Center (MSC) (206) associated with the second mobility management node (204) , to update a Home Location Register (HLR) (210) by the MSC (206) .
A method (1200) in a first Mobile Switching Center (MSC) node (207) , for facilitating to transfer a Mobile Termination (MT) call for a wireless device (201) from a first mobility management node (205) associated with the first MSC node (207) to a second mobility management node (204) , comprising:

-receiving (S1201) a message, which includes information of a second MSC node (206) associated with the second mobility management node (204) , from the first mobility management node (205) ; and

-transferring (S1202) the MT call to the second MSC node (206) ,

wherein the MT call is transferred from the first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) .
the method (1200) according to claim 16, wherein the step of the transferring (S1202) the MT call further comprising:

-sending a message, which includes roaming forwarding indication and information of the first MSC node (207) , to the second MSC node (206) ;

-receiving a message, which includes a roaming number of the wireless device (201) , from the second MSC node (206) , wherein the roaming number is assigned by the second MSC node (206) for the wireless device (201) ; and

-sending a message, which includes the roaming number of the wireless device (201) , to the second MSC node (206) .
A method (1300) in a second Mobile Switching Center (MSC) node (206) , for facilitating to transfer a Mobile Termination (MT) call for a wireless device (201) from a first mobility management node (205) to a second mobility management node (204) associated with the second MSC node (206) , comprising:

-transferring (S1301) the MT call from a first MSC (207) associated with the first mobility management node (205) to the second MSC node (206) ; and

-sending (S1302) a message indicating the MT call for the wireless device (201) , to the second mobility management node (204) ,

wherein the MT call is transferred from the first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) .
the method (1300) according to claim 18, wherein the step of the transferring (S1301) the MT call further comprising:

-receiving a message, which includes roaming forwarding indication and information of the first MSC node (207) , from the first MSC node (207) ;

-sending a message, which includes a roaming number of a wireless device (201) , to the first MSC node (207) , wherein the roaming number is assigned by the second MSC node (206) for the wireless device (201) ; and

-receiving a message, which includes the roaming number of the wireless device (201) , from the first MSC node (207) .
A first mobility management node (1400, 205) , comprising:

at least one processor (1401) ; and

a non-transitory computer readable medium (1402) coupled to the at least one processor (1401) , the non-transitory computer readable medium (1402) containing instructions executable by the at least one processor (1401) , whereby the at least one processor (1401) is configured to:

-receive (S901) a message indicating a Mobile Termination (MT) call for a wireless device (201) ;

-check (S902) whether the wireless device (201) is registered on the first mobility management node (205) ;

-if the wireless device (201) is not registered on the first mobility management node (205) , interrogate (S903) a subscriber server (209) for a second mobility management node (204) which is currently serving the wireless device (201) or a Mobile Switching Center (MSC) (206) associated with the second mobility management node (204) ; and

-transfer (S904) the MT call towards the second mobility management node (204) .
the first mobility management node (1400, 205) according to claim 20, wherein when transferring (S904) , the at least one processor (1401) is further configured to:

-indicate the MT call to the second mobility management node (204) .
the first mobility management node (1400, 205) according to claim 21, wherein when indicating, the at least one processor (1401) is further configured to:

-send a "CS Paging Indication"message, which includes an International Mobile Subscriber Identification (IMSI) number of the wireless device (201) , to the second mobility management node (204) .
the first mobility management node (1400, 205) according to claim 20, wherein when interrogating (S903) , the at least one processor (1401) is further configured to:

-interrogate the subscriber server (209) by sending a "Send Routing Info"message, which includes an IMSI number of the wireless device (201) ; and

-receive information of the second mobility management node (204) in a "Send Routing Info Answer"message from the subscriber server (209) .
the first mobility management node (1400, 205) according to claim 20, wherein when transferring (S904) , the at least one processor (1401) is further configured to:

-send a "Context Request"message, which includes an IMSI number of the wireless device (201) , to the second mobility management node (204) ;

-receive a "Context Response"message, which includes a MSC number of the MSC (206) associated with the second mobility management node (204) , from the second mobility management node (204) ; and

-send the MSC number of the MSC (206) associated with the second mobility management node (204) to a MSC (207) associated with the first mobility management node (205) , thereby facilitating to transfer the MT call to the second mobility management node (204) .
the first mobility management node (1400, 205) according to claim 22, wherein the "CS Paging Indication"message further includes a MSC number of a MSC (207) associated with the first mobility management node (205) .
the first mobility management node (1400, 205) according to claim 20, wherein when interrogating (S903) , the at least one processor (1401) is further configured to:

-interrogate the subscriber server (209) by sending a "Send Routing Info"message, which includes an IMSI number of the wireless device (201) ; and

-receive information of the MSC (206) associated with the second mobility management node (204) in a "Send Routing Info Answer"message from the subscriber server (209) ;

and wherein when transferring (S904) , the at least one processor (1401) is further configured to:

-send information of the MSC (206) associated with the second mobility management node (204) to a MSC (207) associated with the first mobility management node (205) , thereby facilitating to transfer the MT call to the second mobility management node (204) .
A second mobility management node (1500, 204) , comprising:

at least one processor (1501) ; and

a non-transitory computer readable medium (1502) coupled to the at least one processor (1501) , the non-transitory computer readable medium (1502) containing instructions executable by the at least one processor (1501) , whereby the at least one processor (1501) is configured to:

-receive (S1001) a message indicating a Mobile Termination (MT) call for a wireless device (201) , wherein the MT call is transferred from a first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) ; and

-handle (S1002) the MT call.
the second mobility management node (1500, 204) according to claim 27, wherein when handling (S1002) the MT call, the at least one processor (1501) is further configured to:

-page to the wireless device (201) for the MT call; and

-receive an "Extended Service Request"message from the wireless device (201) .
the second mobility management node (1500, 204) according to claim 27, wherein when receiving a message indicating the MT call, the at least one processor (1501) is further configured to:

-receive an indication of the MT call from the first mobility management node (205) .
the second mobility management node (1500, 204) according to claim 29, wherein when receiving an indication of the MT call, the at least one processor (1501) is further configured to:

-receive a "CS Paging Indication"message, which includes an International Mobile Subscriber Identification (IMSI) number of the wireless device (201) , from the first mobility management node (205) .
the second mobility management node (1500, 204) according to claim 27, wherein when receiving (S1001) a message indicating the MT call, the at least one processor (1501) is further configured to:

-receive a CS paging request from a Mobile Switching Center (MSC) (206) associated with the second mobility management node (204) .
the second mobility management node (1500, 204) according to claim 30, wherein the "CS Paging Indication"message further includes a MSC number of a MSC (207) associated with the first mobility management node (205) .
A second mobility management node (1500, 204) , comprising:

at least one processor (1501) ; and

a non-transitory computer readable medium (1502) coupled to the at least one processor (1501) , the non-transitory computer readable medium (1502) containing instructions executable by the at least one processor (1501) , whereby the at least one processor (1501) is configured to:

-receive (S1101) a message indicating a Mobile Termination (MT) call for a wireless device (201) , wherein the MT call is transferred from a first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) ; and

-update (S1102) the location information of the wireless device (201) .
the second mobility management node (1500, 204) according to claim 33, wherein when updating (S1102) , the at least one processor (1501) is further configured to:

-send a location update request to a Mobile Switching Center (MSC) (206) associated with the second mobility management node (204) , to update a Home Location Register (HLR) (210) by the MSC (206) .
A first Mobile Switching Center (MSC) node (1600, 207) , for facilitating to transfer a Mobile Termination (MT) call for a wireless device (201) from a first mobility management node (205) associated with the first MSC node (207) to a second mobility management node (204) , comprising:

at least one processor (1601) ; and

a non-transitory computer readable medium (1602) coupled to the at least one processor (1601) , the non-transitory computer readable medium (1602) containing instructions executable by the at least one processor (1601) , whereby the at least one processor (1601) is configured to:

-receive (S1201) a message, which includes information of a second MSC node (206) associated with the second mobility management node (204) , from the first mobility management node (205) ; and

-transfer (S1202) the MT call to the second MSC node (206) ,

wherein the MT call is transferred from the first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) .
the first MSC (1600, 207) according to claim 35, wherein when transferring (S1202) the MT call, the at least one processor (1601) is further configured to:

-send a message, which includes roaming forwarding indication and information of the first MSC node (207) , to the second MSC node (206) ;

-receive a message, which includes a roaming number of the wireless device (201) , from the second MSC node (206) , wherein the roaming number is assigned by the second MSC node (206) for the wireless device (201) ; and

-send a message, which includes the roaming number of the wireless device (201) , to the second MSC node (206) .
A second Mobile Switching Center (MSC) node (1600, 206) , for facilitating to transfer a Mobile Termination (MT) call for a wireless device (201) from a first mobility management node (205) to a second mobility management node (204) associated with the second MSC node (206) , comprising:

at least one processor (1601) ; and

a non-transitory computer readable medium (1602) coupled to the at least one processor (1601) , the non-transitory computer readable medium (1602) containing instructions executable by the at least one processor (1601) , whereby the at least one processor (1601) is configured to:

-transfer (S1301) the MT call from a first MSC (207) associated with the first mobility management node (205) to the second MSC node (206) ; and

-send (S1302) a message indicating the MT call for the wireless device (201) , to the second mobility management node (204) ,

wherein the MT call is transferred from the first mobility management node (205) since the wireless device (201) is not registered on the first mobility management node (205) , and wherein the second mobility management node (204) is currently serving the wireless device (201) .
the second MSC (1600, 206) according to claim 37, wherein when transferring (S1301) the MT call, the at least one processor is further configured to:

-receive a message, which includes roaming forwarding indication and information of the first MSC node (207) , from the first MSC node (207) ;

-send a message, which includes a roaming number of a wireless device (201) , to the first MSC node (207) , wherein the roaming number is assigned by the second MSC node (206) for the wireless device (201) ; and

-receive a message, which includes the roaming number of the wireless device (201) , from the first MSC node (207) .
A computer readable medium (1402, 1502, 1602, 1702, 1802, 1804) comprising computer readable code, which when run on an apparatus (1800) , causes the apparatus (1800) to perform the method (900, 1000, 1100, 1200, 1300) according to any one of claims 1-19.