Method for mobile communication system, mobile communication system, mobile terminal, network node, and PGW

A communication system according to an exemplary embodiment of the invention includes an MME (25) that, by movement of a UE (45), performs Tracking Area Update processing that changes a location registration area of the UE (45) and manages the location registration area of the UE (45) before change, and a PGW (75) that sends, to the MME (25), a control signal required to be notified to the UE (45) during execution of the Tracking Area Update processing. When the MME (25) receives the control signal, it sends a response signal indicating that the Tracking Area Update processing is being executed to the PGW (75), and, after completion of the Tracking Area Update processing, the PGW (75) sends the control signal to an MME (35) that manages the location registration area of the UE (45) after change.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage application of International Application No. PCT/JP2015/002328 entitled “METHOD FOR MOBILE COMMUNICATION SYSTEM, MOBILE COMMUNICATION SYSTEM, MOBILE TERMINAL, NETWORK NODE, AND PGW,” filed on May 7, 2015, which claims the benefit of priority from Japanese Patent Application No. JP2014-098247, filed on May 12, 2014, the disclosures of which are incorporated herein in their entirety by reference thereto.

TECHNICAL FIELD

The present invention relates to a communication system, an MME and a communication method and, for example, relates to a communication system, an MME and a communication method that perform call control for an UE.

BACKGROUND ART

In the 3GPP (Third Generation Partnership Project) that defines a standard for mobile network systems, an EPC (Evolved Packet Core) is specified as the next generation mobile network system. The EPC is a network system that accommodates an LTE (Long Term Evolution) access network in addition to wireless access networks called the second generation and the third generation.

Incoming packet call processing in the EPC is described hereinafter. In Non-Patent Literature 1, incoming packet call processing in the case where a UE (User Equipment) representing a user terminal is in the idle mode is disclosed. The state where the UE is in the idle mode is the state where the UE is not connected with the EPC. In other words, a radio bearer between the UE and the EPC is disconnected in this state. In such a case, when an incoming packet call is made to the UE, an SGW (Serving Gateway), which is a bearer management device, sends an incoming call notification message to an MME (Mobility Management Entity) or an SGSN (Serving GPRS Support Node) that manages the UE. Receiving the incoming call notification message, the MME or SGSN sends a Paging message to an eNB (evolved Node B) or a NodeB, which is a base station, in order to call the UE. Receiving the Paging message, the eNB or NodeB performs Page processing on a plurality of UEs located in the area managed by itself. The UE to be called sends a response message to the eNB or NodeB and connects to the EPC.

In this manner, even when an incoming packet call is made to the UE in the idle mode which is not connected with the EPC, it is possible to perform data communication with the UE by calling the UE from the network side.

CITATION LIST

Non Patent Literature

[NPL1] 3rd Generation Partnership Project; Technical Specification Group Services and System Aspects; General Packet Radio Service (GPRS) enhancements for Evolved Universal Terrestrial Radio Access Network (E-UTRAN) access (Release 12), 3GPP TS 23.401 V12.0.0 (2013-03), clauses 5.3.4.3, 5.3.3.2

SUMMARY OF INVENTION

Technical Problem

However, in the incoming packet call processing disclosed in Non Patent Literature 1, the following problem occurs. Normally, when the UE moves out of a location registration area managed by the MME, the UE sends a location registration request (Tracking Area Update Request) message to a new MME that manages a location registration area to which the UE is to move. Receiving the location registration request message, the new MME performs location registration of the UE. After the location registration in the new MME is done, the UE becomes the state where it is registered in the new MME that manages the location registration area to which it is to move.

When an incoming packet call arrives to the UE after the UE sends the location registration request message and before processing for movement is done in the new MME, the problem that it is not possible to normally call the UE to be called occurs.

For example, when an incoming packet call arrives to the UE after the UE sends the location registration request message and before processing for movement is done in the new MME, the SGW sends the incoming call notification message to the MME that has managed the location of the UE before movement. Receiving the incoming call notification message, the MME sends a Paging message to a base station under its control; however, because the UE to be called has moved out to the area managed by the new MME, it is not possible to call the UE. In other words, when an incoming packet call is made while the UE is during its movement which involves a change in the MME, the problem that the UE cannot receive the incoming packet occurs.

Alternatively, when, after the UE sends the location registration request message, the SGW recognizes a new MME to manage the location of the UE after movement, the SGW sends the incoming call notification message to the new MME. In this case also, when the UE has not received a response message to the Tracking Area Update Request message, and Tracking Area Update processing is not done, the problem that the UE cannot normally receive the incoming packet occurs.

An exemplary object of the present invention is to provide a communication system, an MME and a communication method that perform control so as to reliably receive an incoming packet call that is made during movement of a UE.

Solution to Problem

A communication system according to a first exemplary aspect of the invention includes an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE before change, and a PGW that sends, to the MME, a control signal required to be notified to the UE during execution of the Tracking Area Update processing, wherein the MME receives the control signal, and sends a response signal indicating that the Tracking Area Update processing is being executed to the PGW, and, after completion of the Tracking Area Update processing, the PGW sends the control signal to an MME that manages the location registration area of the UE after change.

An MME according to a second exemplary aspect of the invention is an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE before change, wherein the MME receives a control signal sent from a PGW and required to be notified to the UE during execution of the Tracking Area Update processing, and in response to receiving the control signal, sends a response signal indicating that the Tracking Area Update processing is being executed to the PGW, and, after completion of the Tracking Area Update processing, causes the PGW to send the control signal to an MME that manages the location registration area of the UE after change.

A communication method according to a third exemplary aspect of the invention is a communication method in an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE before change, the method including receiving a control signal sent from a PGW and required to be notified to the UE during execution of the Tracking Area Update processing, in response to receiving the control signal, sending a response signal indicating that the Tracking Area Update processing is being executed to the PGW, and after completion of the Tracking Area Update processing, causing the PGW to send the control signal to an MME that manages the location registration area of the UE after change.

Advantageous Effects of Invention

According to an exemplary embodiment of the invention, it is possible to provide a communication system, an MME and a communication method that perform control so as to reliably receive an incoming packet call that is made during movement of a UE.

DESCRIPTION OF EMBODIMENTS

First Exemplary Embodiment

Exemplary embodiments of the present invention are described hereinafter with reference to the drawings. A configuration example of a communication system according to a first exemplary embodiment of the present invention is described hereinafter with reference toFIG. 1. In this figure, a mobile communication system that is defined in the 3GPP is described. The communication system inFIG. 1includes a PGW (Packet Data Network GateWay)75, an old SGW (Serving GateWay)15, a new SGW85, an old MME25, a new MME35, a UE45, an eNB55and an eNB65.

The UE45is a communication device that is specified as a mobile terminal device in the 3GPP. The UE45may be a cellular phone, a smartphone, a tablet terminal, a personal computer with a communication function or the like, for example. Further, the UE45may be an M2M (Machine To Machine) device that performs communications in an autonomous manner. The M2M device may be a device that does not often move such as an automatic vending machine or an electrical appliance having a communication function, or a watch worn by a user and the like, for example.

The eNB55and eNB65are node devices specified as base stations in the 3GPP. Each of the eNB55and eNB65forms a wireless communication area and communicates with the UE that is located in the wireless communication area managed by itself.

The PGW75is a node device that is located at the boundary between the mobile communication system and the external network. The PGW75sends a PGW75activation control signal to the old MME25or the new MME35. The PGW75activation control signal is a control signal that is generated in the PGW75and that needs to be notified to the UE45.

Each of the old MME25and the new MME35defines a location registration area that manages the location of the UE. In the location registration area managed by each of the old MME25and the new MME35, a plurality of eNB may be located. In other words, the location registration area may include a plurality of wireless communication areas formed by the eNB.

When the UE45moves from the location registration area defined by the old MME25to the location registration area defined by the new MME35, the UE45sends a location registration request message to the new MME35. Receiving the location registration request message sent from the UE45, the new MME35performs processing for movement of the UE45. The processing for movement of the UE45is processing that the new MME35registers the UE45as a device to be managed, for example. Further, when the new MME35receives the location registration request message sent from the UE45, it sends a message to the old MME25. The old MME25is an MME that manages the location registration area from which the UE45moves. The message that is notified from the new MME35to the old MME25is a message indicating that the UE45has moved to the location registration area defined by the new MME35. The UE45may add an identifier of the old MME25that manages the location registration area before movement to the location registration request message for the new MME35. The new MME35can thereby detect the old MME25that manages the location registration area from which the UE45moves. The old MME25receives the message from the new MME35and can thereby detect that the UE45has moved to the location registration area defined by the new MME35.

Although the case where the MME that manages the location registration area of the UE45is changed is described in this figure, there is also case where the UE45moves from an LTE communication to a 2G or 3G communication area. In this case, the node device that manages the location registration area of the UE45is changed from the MME to the SGSN. When the UE45moves to a 2G or 3G communication area, the UE45connects to a NodeB and an RNC (Radio Network Controller). Further, there is a case where the UE45moves from a 2G or 3G communication area to a 2G or 3G communication area. In this case, the SGSN that manages the location registration area of the UE45is changed in some cases.

Hereinafter, a flow of processing to connect the UE to the mobile communication system according to the first exemplary embodiment of the invention is described with reference toFIG. 2. First, when a power switch is pressed by a user and a power is turned on, the UE45sends an Attach Request message as the location registration request message to the eNB55(S11). Next, the eNB55sends the Attach Request message sent from the UE45to the old MME25(S12). Receiving the Attach Request message, the old MME25generates location registration information of the UE45. The location registration information contains information indicating that the UE45is located within the location registration area managed by its own device or subscriber information of the UE45, for example. The subscriber information of the UE45may be acquired from a subscriber information management device (not shown) that is placed in the mobile communication system. The subscriber information management device is specified as an HSS (Home Subscriber Server) in the 3GPP, for example. Then, the old MME25notifies the subscriber information of the UE45to the old SGW15using a Create Session Request message (S13). Then, the old SGW15sends a Create Session Response message to the old MME25as a response message to the Create Session Request message (S14). By receiving the Create Session Request message, the old SGW15can identify the MME that manages the location of the UE45. Further, by the sending of the Create Session Response message, a session for the UE45is established between the old MME25and the old SGW15.

Receiving the Create Session Response message, the old MME25sends an Attach Accept message to the eNB55(S15). The Attach Accept message corresponds to a response signal to the Attach Request message. By sending the Attach Accept message, the old MME25completes registration processing of the UE45. The completion of registration processing of the UE45means the completion of movement processing of the UE45. After that, the eNB55sends an Attach Accept message to the UE45(S16).

By receiving the Attach Accept message, the UE45becomes connected to the mobile communication system. The state where the UE45is connected to the mobile communication system may be referred to as the state where the UE45is attached to the mobile communication system.

Although the flow of processing when the power of the UE45is turned on is described above, the same processing is executed also when the location registration area where the UE45is located changes in order to generate location registration information in a new MME. When the location registration area where the UE45is located changes, the UE45sends a Tracking Area Update Request message instead of the Attach Request message. Further, the old MME25and the SGW15send and receive Modify Bearer Request/Modify Bearer Response messages instead of the Create Session Request/Create Session Response messages.

Hereinafter, a flow or processing performed when the PGW75according to the first exemplary embodiment of the present invention notifies a PGW75activation control signal to the UE45is described with reference toFIG. 3. In this example, it is assumed that the processing ofFIG. 2is completed, and the UE45is located in the location registration area managed by the old MME25.

First, when the UE45detects that it has moved from the location registration area managed by the old MME25to another location registration area, the UE45sends a Tracking Area Update Request message to the eNB65(S21). The eNB65manages the location registration area to which the UE45has moved. The UE45may detect that the location registration area has changed by receiving annunciation information delivered from the eNB65. Specifically, the UE45may detect that the location registration area has changed when the location registration area delivered from the eNB55before movement and the location registration area delivered from the eNB65after movement are different from each other.

Next, the eNB65transfers a Tracking Area Update Request message to the new MME35that manages the location registration area including the communication area of its own device (S22). At the same time, S1 Connection (S1 bearer) is established between the eNB65and the new MME35for communication of a control message between the UE45and the new MME35. The Tracking Area Update Request message may contain the identifier of the old MME25that used to manage the location registration area from which the UE45has moved, or GUTI (Globally Unique Temporary Identifier) that is temporarily assigned to the UE45by the old MME25.

Then, the new MME35sends a Context Request message to the old MME25in order to retrieve the user information of the UE45from the old MME25(S23). The user information may be the location registration information of the UE45, bearer context and the like, for example. Further, when the Tracking Area Update Request message contains GUTI, the new MME35may specify the address information of the old MME25by using the GUTI.

The old MME25receives, from the new MME35, a Context Request message requesting the transfer of the user information of the UE45. By receiving the Context Request message sent from the new MME35, the old MME25can detect that the UE45has moved out of the location registration area managed by itself. Further, by receiving the Context Request message sent from the new MME35, the old MME25can detect that the UE45has moved to the location registration area managed by the new MME35.

The old MME25sends a Context Response message to the new MME35as a response message to the Context Request message in Step S23(S24). Using the Context Response message, the old MME25notifies the user information of the UE45to the new MME35.

It is assumed that, after the Context Response message is sent from the old MME25to the new MME35in Step S24, a control signal notification message is sent from the PGW75to the old MME25via the old SGW15(S25). The control signal notification message is used to notify the PGW75activation control signal to the MME.

The old MME25has detected that the UE45is during its movement by receiving the Context Request message in Step S23. Therefore, the old MME25sends, to the PGW75, a response signal notification message to which Cause indicating that the UE45is moving and a call attempt to the UE45is temporarily unavailable is set. The old MME25sends the response signal notification message to the PGW75via the old SGW15as a response to the control signal notification message (S26). To the response signal notification message, “Cause=Temporarily Rejected due to mobility procedure in Progress” is set as Cause setting. “Cause=Temporarily Rejected due to mobility procedure in Progress” indicates that information indicating that the UE is moving and a call attempt is temporarily rejected is set to Cause.

Receiving response signal notification message to which “Cause=Temporarily Rejected due to mobility procedure in Progress” is set, the PGW75starts a locally configured guard timer for resending the control signal notification message.

Then, the new MME35sends a Context Acknowledge message to the old MME25as a response message to the Context Response message (S27). SGW change indication is set to the Context Acknowledge message. SGW change indication is information indicating that the new MME35has changed the SGW for sending data to the UE45from the to old MME25to the new MME35.

Then, the new MME35sends a Create Session Request message to the new SGW85in order to establish a session with the new SGW85or to activate a bearer. The new SGW85then sends a Modify Bearer Request message to the PGW75in order to establish or update a session or a bearer with the PGW75(S29). By receiving the Modify Bearer Request message, the PGW75can recognize that mobility procedure for the UE45has completed in the new MME35. The PGW75updates the bearer context between the new SGW85and the PGW75. Further, the PGW75sends a Modify Bearer Response message to the new SGW85as a response message to the Modify Bearer Request message (S30). At this time, the PGW75may stop the locally configured guard timer started when receiving the response signal notification message in Step S26.

Then, the new SGW85updates the bearer context between the new MME35and the new SGW85. Further, the new SGW85sends a Create Session Response message to the new MME35as a response message to the Create Session Request message (S31).

The old MME25and the new MME35perform location information change processing A for the movement of the UE45. The details of the location information change processing A are described later.

When the location information update processing A ends, the new MME35sends a Tracking Area Update Accept message to the eNB65as a response message in Step S22. Further, the eNB65sends the sent Tracking Area Update Accept message to the UE45(S32).

The Tracking Area Update Accept message contains GUTI assigned to the UE45by the new MME35. The GUTI is an identifier that is temporarily assigned to the UE by the new MME35in order to uniquely identify the UE.

When the Tracking Area Update Accept message contains GUTI, the UE45sends a Tracking Area Update Complete message to the new MME35(S33).

After that, the new MME35releases the S1 Connection that has been established between the eNB65and the MME35(S34).

Then, the PGW75sends a control signal notification message to the new MME35that manages the location registration area to which the UE45moves in order to notify a control signal to the UE45(S35). Thus, in Step S35, the processing of sending the control signal notification message to the old MME25in Step S25is performed for the new MME35that manages the location registration area to which the UE45moves. Then, the new MME35sends a Paging message to the eNB65in order to perform a call attempt to the UE45(S36). Further, the eNB65sends a Paging message to the UE located in the communication area under its control (S37). When sending the Paging message, the new MME35sets GUTI assigned to the UE45. In this manner, after moving to a new location registration area, the UE45can receive the control signal notification message that has been made during the movement of the UE45.

In the case where the locally configured guard timer that is started when the response signal notification message is received in Step S26expires before receiving the Modify Bearer Request message, the PGW75may end the control message notification processing to the UE45. Alternatively, the PGW75may send the control signal notification message to the old MME25again to continue the control signal notification processing.

The location information update processing A is described hereinafter in detail with reference toFIG. 4. When the new MME35receives the Create Session Response message in Step S31ofFIG. 3, it sends an Update Location message to the HSS (S201). The HSS is a node device that manages subscriber information of the UE45. To the Create Session Response, information indicating that the new MME35manages the location information about the UE45is set.

Then, the HSS sends a Cancel Location message to the old MME25so as to delete the location information about the UE45(S202). As a response message to the Cancel Location message, the old MME25sends a Cancel Location ACK message to the HSS (S203). The HSS then sends an Update Location ACK message to the new MME35as a response to the Update Location message in Step S201(S204).

Further, after sending the Cancel Location ACK message, the old MME25sends a Delete Session Request message to the old SGW15(S205). By sending the Delete Session Request message, the old MME25releases the communication resource (e.g. EPS bearer resource etc.) with the old SGW15. As a response message to the Delete Session Request message, the old SGW15sends a Delete Session Response message to the old SGW15(S206).

As described above, with use of the communication system according to the first exemplary embodiment of the present invention, the following effects can be obtained. Even when the PGW75activation control signal is made to the UE45while the UE45is during its movement which involves a change in the MME and the processing for movement of the UE45is not completed in a new MME, the UE45can normally receive the control signal.

Further, in the case where the old MME25and the new MME35are replaced by the SGSN and the eNB55and the eNB65are replaced by the RNC, the Tracking Area Update Request message in Steps S21and S22is replaced by a Routing Area Update Request message. Further, the Tracking Area Update Accept message in Steps S32and S2is replaced by a Routing Area Update Accept message.

Although the flow of processing when the control signal notification message is sent to the old MME25after Step S24is shown in the figure, the same processing as in this figure is performed also when the control signal notification message is sent to the old MME25during a period after Step S23and before Step S29.

Second Exemplary Embodiment

A processing sequence in a communication system according to a second exemplary embodiment of the present invention is described hereinafter with reference toFIG. 5. Processing when an incoming packet call is made to the new MME35that manages the location information of the UE45after movement is shown in this figure. It is assumed that the MME change processing for the movement of the UE45is not completed when the new MME35receives a message related to an incoming packet call or a PGW75activation control signal. To be specific, it is assumed that the UE45does not receive a response message to the Tracking Update Request message when the new MME35receives a message related to an incoming packet call or a PGW75activation control signal.

Steps S41to S49are the same as Steps S21to S24and Steps S27to S31inFIG. 3, and therefore detailed explanation thereof is omitted. Further, location information update processing A that is performed after Step S49is the same as the location information update processing A inFIG. 3, and therefore detailed explanation thereof is omitted.

In Step S46, the new SGW85receives a Create Session Request message, and it recognizes that the new MME35is managing the user information about the UE45. Further, in Step S47, the PGW75receives a Modify Bearer Request message and recognizes that the new SGW85is managing the session or the bearer context about the UE45. Therefore, in Step S50, when an incoming packet call or a PGW75activation control signal for the UE45is made, the PGW75sends the incoming packet call or a message about the PGW75activation control signal to the new SGW85.

Then, the new SGW85sends a Downlink Data Notification message indicating that an incoming packet call is made to the UE45or the PGW75activation control signal to the new MME35(S51).

Then, when the new MME35receives the Update Location ACK message in Step S204of the location information update processing A shown inFIG. 4, it sends a Tracking Area Update Accept message to the UE45via the eNB65(S52). Note that, after sending a Create Session Request message to the new SGW85in Step S46, the new MME35receives a Downlink Data Notification message that requires paging processing for the UE45. In this case, a user plane setup procedure is activated in conjunction with a Tracking Area Update Accept message. When, in Steps S41and S42, an active flag is set, and even when an active flag is not set, the user plane setup procedure is activated.

The user plane setup procedure in conjunction with a Tracking Area Update Accept message is described hereinafter. The new MME35sends an S1-AP Initial Context Setup Request message together with the Tracking Area Update Accept message in Step S52to the eNB65. In other words, the new MME35sends the Tracking Area Update Accept message and the S1-AP Initial Context Setup Request message at the same timing to the eNB65. Triggered by the S1-AP Initial Context Setup Request message, Radio Bearer Establishment (S54) takes place between the eNB65and the UE45. To notify the newly established bearer information, the eNB65sends an S1 AP Initial Context Setup Response message to the new MME35(S56). The new MME35sends a Modify Bearer request message to the new SGW85(S57). The new SGW85sends a Modify Bearer response message to the new MME35(S58). The user plane setup procedure is to set the communication resource for transferring data to be sent and received by the UE45in the eNB65, the new SGW85and the PGW75, for example.

Further, the Tracking Area Update Accept contains GUTI that is assigned to the UE45by the new MME35. The GUTI is an identifier that is temporarily assigned to the UE by the new MME35in order to uniquely identify the UE. When the UE45receives the Tracking Area Update Accept message that contains the GUTI, it sends a Tracking Area Update Complete message to the new MME35(S55).

Steps S53to S58indicate that, during execution of the Tracking Area Update processing, incoming packet call processing or control signal reception processing continues using an RRC connection that is already established between the UE45and the new MME35.

Further, a flow of the processing in the case where the Downlink Data Notification message is sent to the new MME35during execution of the Tracking Area Update processing is described in this figure. On the other hand, when the control signal notification message is sent to the new MME35, which is described inFIG. 3, the same processing as in the case where the Downlink Data Notification message is sent to the new MME35is performed.

Further, a flow of the processing when an incoming packet call in Step S50is made after Step S49and the location information update processing A is described in this figure. Note that, however, an incoming packet call in Step S50can be made at anytime between Step S47to Step S52. In this case also, the same processing as described in this figure is performed.

Further, although an example of using the new MME35is described in this figure, an SGSN may be used instead of the new MME35. In the figures described hereinafter also, an SGSN may be used instead of the new MME35.

As described above, the new MME35adds GUTI that is temporarily assigned to the UE45to the Tracking Area Update Accept message and thereby notifies the GUTI to the UE45. Therefore, the new MME35can perform Paging processing to the UE45and call the UE45immediately after completion of the Tracking Area Update processing.

Further, when the new MME35receives the Downlink Data Notification message, it activates the user plane setup procedure in conjunction with the Tracking Area Update Accept message. It is thereby possible to send Downlink Data to the UE45. In other words, by sending the S1-AP Initial Context Setup Request message in conjunction with the Tracking Area Update Accept message to the eNB65, it is possible to establish Radio Bearer between the UE45and the eNB65during execution of the Tracking Area Update processing. Therefore, the new MME35can identify the UE45and send data to the UE45without performing Page processing.

Modified Examples

Modified examples of the processing sequence ofFIG. 5are described hereinbelow. First, a processing sequence in a modified example of the processing according to the second exemplary embodiment of the invention is described with reference toFIG. 6. In this figure, a flow of the processing in the case where, when the UE45moves, the MME that manages the UE45is changed from the old MME25to the new MME35but the SGW is not changed from the old SGW15is described.

Steps S61to S65are the same as Steps S41to S45inFIG. 5, and therefore detailed explanation thereof is omitted. By the movement of the UE45, the MME that manages the UE45has changed from the old MME25to the new MME35. Therefore, the new MME35uses the bearer context received from the old MME25as the EPS (Evolved Packet System) bearer context of the UE45. The EPS is a communication system that is specified in the 3GPP. Note that the old SGW15is not changed for the UE45. Thus, to change the information about the UE45that is held by the old SGW15, the new MME35sends a Modify Bearer Request message to the old SGW15in Step S66.

Steps S67and S68are different from Steps S47and S48inFIG. 5in that the PGW75communicates with the old SGW15instead of the new SGW85; however, messages to be sent and received are the same as those in Steps S47and S48, and therefore detailed explanation thereof is omitted.

The old SGW15receives a Modify Bearer Response message in Step S68, and then updates the bearer context with the new MME35and sends a Modify Bearer Response to the new MME35(S69).

Processing after the location information update processing A is the same as processing after the location information update processing A inFIG. 5, and detailed explanation thereof is omitted. Further, Step S70is different from Step S50inFIG. 5in that the PGW75communicates with the old SGW15instead of the new SGW85. Further, Step S71is different from Step S51inFIG. 5in that the new MME35communicates with the old SGW15instead of the new SGW85. Further, Steps S77and S78are different from Steps S57and S58inFIG. 5in that the Modify Bearer Request/Response message is sent and received between the new MME35and the old SGW15. Steps S70to S78are the same as Steps S50to S58inFIG. 5in the other points, and detailed explanation thereof is omitted.

A flow of processing in the case where the SGSN is used instead of the new MME35and the RNC is used instead of the eNB65inFIG. 5is described hereinafter with reference toFIG. 7. Differences fromFIG. 5are mainly described below.

In Step S81, the UE45sends a Routing Area Update Request message, instead of the Tracking Area Update Request message in Step S41ofFIG. 5, to the RNC. Further, in Step S82, the RNC transfers the Routing Area Update Request message to the SGSN. Steps S83to S91are the same as Steps S43to S51ofFIG. 5, and detailed explanation thereof is omitted.

In Step S92, the SGSN sends a Routing Area Update Accept message instead of the Tracking Area Update Accept message in Step S51ofFIG. 5. When the SGSN receives, in Step S91, a Downlink Data Notification message or a PGW75activation control signal that requires Paging processing to the UE45, it sends a Routing Area Update Accept message to which a value “follow-on proceed” is set to an Update result parameter. The UE45receives the Routing Area Update Accept message and reuses the RRC connection that is established between the SGSN and the UE45without releasing it. The SGSN sets the value “follow-on proceed” to the Routing Area Update Accept message and thereby prompts the UE45to send a Service Request message. The UE45thereby sends the Service Request message to the SGSN by reusing the RRC connection that is held for the SGSN as a response to Page.

The Routing Area Update Accept message contains P-TMSI (Packet-Temporary Mobile Subscriber Identity). The P-TMSI is an identifier that is temporarily assigned to the UE45by the SGSN. The P-TMSI corresponds to the GUTI, which is an identifier that is temporarily assigned to the UE by the MME.

Then, the UE45sends a Routing Area Update Complete message to the SGSN (S93). The UE45then sends, to the SGSN, a Service Request message to which the P-TMSI is set (S94).

When the SGSN receives the Service Request message sent from the UE45, it sends an RAB Assignment Request message to the RNC to request the establishment of a radio access bearer (S95). The RNC establishes the radio access bearer and sends an RAB Assignment Response message to the SGSN (S96).

A flow of processing in the case where the SGW is not changed when the UE45moves is described with reference toFIG. 8. Differences fromFIG. 7are mainly described.

Steps S101to S105are the same as Steps S81to S85inFIG. 7, and detailed explanation thereof is omitted. In Step S106, the SGSN sends a Modify Bearer Request message to the old SGW15(S106). Steps S107and S108are the same as Steps S87and S88inFIG. 7. As a response to the Modify Bearer Request message, the old SGW15sends a Modify Bearer Response message to the SGSN. Processing after the location information update processing A is the same as processing after the location information update processing A inFIG. 7, and detailed explanation thereof is omitted.

InFIGS. 5 and 6described above, a processing flow in the case where, when the MME that manages the UE45is changed with the movement of the UE45from an LTE communication area to an LTE communication area, a Downlink Notification message or a PGW75activation control signal is sent to the new MME35, which is the MME after change, is described. Further, inFIGS. 7 and 8, a processing flow in the case where, when the node device that manages the UE45is changed from the MME to the SGSN with the movement of the UE45from an LTE communication area to a 3G communication area, a Downlink Notification message or a PGW75activation control signal is sent to the SGSN is described.

In addition to the examples of movement described inFIGS. 5 to 8, there is also a case where the UE45moves from a 3G communication area to a 3G communication area. In this case, the node device that manages the UE45is changed from an old SGSN to a new SGSN in some cases. When the node device that manages the UE45is changed from an old SGSN to a new SGSN, an SGSN Context Request message, an SGSN Context Response message and an SGSN Context Acknowledge message are used between the old SGSN and the new SGSN, instead of the Context Request message, the Context Response message and the Context Acknowledge message in Steps S103to S105inFIG. 8.

Further, when the node device that manages the UE45is changed from an old SGSN to a new SGSN, an Update PDP Context Request message is used instead of the Modify Bearer Request message in Steps S106and S107inFIG. 8, and an Update PDP Context Response message is used instead of the Modify Bearer Response in Steps S108and S109inFIG. 8, respectively between the new SGSN and a GGSN.

Further, in the case where the UE45moves between a 3G communication area and a 2G communication area also, the same processing as in the case where the node device that manages the UE45is changed from an old SGSN to a new SGSN is performed.

By performing the processing sequences described inFIGS. 5 to 8, it is possible to send data to the UE45even when an incoming packet call is made or a PGW75activation control signal is received during the Tracking Area Update processing or the Routing Area Update processing just like inFIGS. 3 and 4.

Third Exemplary Embodiment

Paging processing to the UE45in a communication system according to a third exemplary embodiment of the present invention is described hereinafter. In the third exemplary embodiment, when the Tracking Area Update processing or the Routing Area Update processing is done, the new MME35or the SGSN performs Paging processing to the UE45

To be specific, in the processing sequences ofFIGS. 5 and 6, the new MME35holds the Downlink Data Notification message received in Step S51or Step S71in a memory or the like of the device. After that, when the new MME35receives the Tracking Area Update Complete message in Step S53or S73, it performs Paging processing to the UE45in accordance with the held Downlink Data Notification message.

Further, in the processing sequences ofFIGS. 7 and 8, the SGSN holds the Downlink Data Notification message received in Step S91or Step S111in a memory or the like of the device. After that, when the SGSN receives the RAB Assignment Response message in Step S96or S116, it performs Paging processing to the UE45in accordance with the held Downlink Data Notification message.

As described above, by performing Paging processing according to the third exemplary embodiment of the invention, it is possible to perform Paging processing to the UE45in accordance with the held Downlink Data Notification message without waiting for the Downlink Data Notification to be sent again. It is thereby possible to reduce the number of signals between the SGW and the MME and advance the timing to perform Paging processing to the UE45.

Although the present invention is described as a hardware configuration in the above exemplary embodiments, the present invention is not limited thereto. The present invention may be implemented by causing a CPU (Central Processing Unit) to execute a computer program to perform the processing in each node device.

In the above example, the program can be stored and provided to the computer using any type of non-transitory computer readable medium. The non-transitory computer readable medium includes any type of tangible storage medium. Examples of the non-transitory computer readable medium include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (e.g. magneto-optical disks), CD-ROM (Read Only Memory), CD-R, CD-R/W, and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory), etc.). The program may be provided to a computer using any type of transitory computer readable medium. Examples of the transitory computer readable medium include electric signals, optical signals, and electromagnetic waves. The transitory computer readable medium can provide the program to a computer via a wired communication line such as an electric wire or optical fiber or a wireless communication line.

It should be noted that the present invention is not limited to the above-described exemplary embodiment and may be varied in many ways within the scope of the present invention.

This application is based upon and claims the benefit of priority from Japanese patent application No. 2014-098247 filed on May 12, 2014, the disclosure of which is incorporated herein in its entirety by reference.

A communication system including an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE before change, and a PGW that sends, to the MME, a control signal required to be notified to the UE during execution of the Tracking Area Update processing, wherein the MME receives the control signal, and sends a response signal indicating that the Tracking Area Update processing is being executed to the PGW, and after completion of the Tracking Area Update processing, the PGW sends the control signal to an MME that manages the location registration area of the UE after change.

A communication system including an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE after change, and an SGW that notifies a Downlink Data Notification message to the MME during execution of the Tracking Area Update processing, wherein the MME receives the Downlink Data Notification message, and activates a user plane setup procedure in conjunction with a Tracking Area Update Accept message to be sent to the UE.

A communication system including an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE after change, and an SGW that notifies a Downlink Data Notification message to the MME during execution of the Tracking Area Update processing, wherein the MME sends a Tracking Area Update Accept message to the UE after holding the Downlink Data Notification message, receives a Tracking Area Update Complete message from the UE, and then performs paging processing to the UE in accordance with the Downlink Data Notification message.

An MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE before change, wherein the MME receives a control signal sent from a PGW and required to be notified to the UE during execution of the Tracking Area Update processing, and in response to receiving the control signal, sends a response signal indicating that the Tracking Area Update processing is being executed to the PGW, and, after completion of the Tracking Area Update processing, causes the PGW to send the control signal to an MME that manages the location registration area of the UE after change.

An MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE after change, wherein the MME receives a Downlink Data Notification message sent from an SGW during execution of the Tracking Area Update processing, and in response to receiving the Downlink Data Notification, activates a user plane setup procedure in conjunction with a Tracking Area Update Accept message to be sent to the UE.

An MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE after change, wherein the MME receives a Downlink Data Notification message sent from an SGW during execution of the Tracking Area Update processing, and after holding the Downlink Data Notification message, sends a Tracking Area Update Accept message to the UE, receives a Tracking Area Update Complete message from the UE, and then performs paging processing to the UE in accordance with the Downlink Data Notification message.

A communication method in an MME that, by movement of a UE, performs Tracking Area Update processing that changes a location registration area of the UE and manages the location registration area of the UE before change, the method including receiving a control signal sent from a PGW and required to be notified to the UE during execution of the Tracking Area Update processing, in response to receiving the control signal, sending a response signal indicating that the Tracking Area Update processing is being executed to the PGW, and after completion of the Tracking Area Update processing, causing the PGW to send the control signal to an MME that manages the location registration area of the UE after change.

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