JP2015177385A - gateway and session control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable continuation of a voice phone when a PGW detects that a PCRF gets out of order.SOLUTION: Session management information storing information on each session controlled by a PGW is provided in the PGW of EPC of LTE. When a failure in a policy/accounting control device is detected, the session management information is referred to; the session during a call is maintained; a call state is monitored; and the session is released after the completion of the call.

Description

  The present invention relates to a communication session control technique, and more particularly to a session control technique when a failure occurs in a wireless communication system.

  LTE (LongTerm Evolution) is a standard that speeds up the data communication of the third generation (3G) mobile phone. Specifications were formulated in the month.

  The LTE network includes a policy / charging control device (PCRF), a packet data network gateway (PGW), a serving gateway (SGW), and a mobility management device (PGW). An EPC (Evolved Packet Core) that is a core network made up of MME (Mobility Management Equipment), an eNB (evolved Node B) that is a radio base station device, and an access network made up of the MME.

  The EPC provides functions such as mobility management and session management of a mobile terminal device (UE: User Equipment), routing and transfer of user packets, and plays a central role in LTE. In addition, the access network has radio resource management and UE mobility management functions, and has a role of transferring user packets by connecting to the EPC.

  A technology for providing a voice call service in LTE is called VoLTE (Voice Over LTE). As efforts to realize voice call service and short message service (SMS) in LTE, mobile phone operators and terminal / communication equipment manufacturers launched “One Voice Initiative”, and “One Voice; Voice over IMS” The “profile” specification has been created, and the industry group “GSM (Registered Trademark) Association” of the mobile communication operator is proceeding with the formulation of the VoLTE standard.

  In LTE, as described in Non-Patent Document 1, a control plane (Control Plane), which is an interface for connecting EPC devices and a protocol for control signals used for control in the network for each interface, is provided. And a function for performing user plane transfer, which is a protocol for transmitting and receiving user signals.

  In the EPC, when the UE is powered on, a connection request from the UE is transmitted to the MME, and a control plane or user plane session in each interface is generated between the above-described devices. The User Plane session created when the power is turned on is called a default bearer, and a dedicated bearer is generated for user plane transfer for each UE service request. The generic name of the Default bearer and the Dedicated bearer associated with the 1UE session is called a PDN (Packet Data Network) connection. For voice data in VoLTE, a user plane session (Dedicated bearer) for voice data is generated by Control Plane for each call, the voice data is transferred through the Dedicated bearer, and the voice bearer is transferred at the end of the call. To release.

  In addition, according to the standard, each device receives a message indicating resumption due to restart after a failure from a device that is opposed via an interface, or when a failure of the opposite device is detected, a session related to the opposite device There are provisions to release Session management in EPC is performed by UE, MME, SGW, and PGW. As described above, a session related to the opposite device is released due to a restart or a failure message from the opposite device. Patent Document 1 discloses a technology that enables recovery of a gateway control session or the like without affecting a bearer when a temporary service stop due to a PCRF failure occurs.

International Publication No. 2011/099523

3GPP TS 23.007 (Release 10)

  Patent Document 1 is an invention in the case of a temporary service stop of the PCRF, and the PCRF needs to always transmit and hold session information to the PCRF client node, and it is necessary to provide a special device and sequence. is there. In the case of a failure of a device that controls only the control plane that does not affect the voice call without providing a special device or a sequence not defined in the standard, the present invention relates to the failed device while continuing the voice call. The purpose is to be able to release unnecessary sessions.

  In order to solve the above problems, in the present invention, as an example, in a network composed of a plurality of devices, an interface for transmitting and receiving control signals and an interface for transmitting and receiving user signals are separately defined, and each device is both When a session is established between each device and a control signal or user signal is transmitted / received, a device having a session control function is connected to the opposite device via the interface. When a failure is detected, if the opposite device is a device having only an interface for transmitting and receiving a control signal, the session of the user signal during a call related to the opposite device is maintained until the end of the call.

  As another example, when a session management information storing information of each session controlled by the PGW is provided in the LTE EPC PGW and a failure of the policy / billing control device is detected, the session management information is referred to For the middle session, the call state is monitored, and the session is released after the call ends.

  According to the present invention, it is possible to release an unnecessary session related to a failed device while continuing the voice call when a device that controls only the control plane that does not affect the voice call fails.

It is a figure explaining the apparatus structure of the network communication system in one Example of this invention, and the interface structure of a user plane and a control plane. It is a figure explaining the sequence from the terminal power supply ON in one Example of this invention to registration to a SIP server. It is a figure explaining the sequence of the general call transmission in one Example of this invention, and an incoming call. It is a figure explaining the sequence of the general call transmission in one Example of this invention, and an incoming call. It is a figure explaining the sequence of the general call transmission in one Example of this invention, and an incoming call. It is a figure explaining the release sequence of the session at the time of the conventional failure and resumption detection. It is a figure explaining the release sequence of the session at the time of the failure and resumption detection in one Example of this invention. It is a flowchart explaining the processing content of the session at the time of the failure and resumption detection in one Example of this invention. It is a flowchart explaining the session release object confirmation and disconnection request process at the time of the end of a call in one Example of this invention. It is a figure explaining the functional structure of PGW in one Example of this invention. It is a figure explaining the session management information in one Example of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating an apparatus configuration of a network communication system and an interface configuration of a user plane and a control plane according to an embodiment of the present invention.
FIG. 1 shows the configuration of an access network and LTE-EPC.

  Table 1 shows an overview of the devices constituting the access network and LTE-EPC, Table 2 shows an overview of the interfaces between the devices, and Table 3 shows the operation when a failure is detected in each interface of Table 2. .

In FIG. 1, UE 101, UE 102, and eNB 103 used by a user are connected using LTE-Uu of a radio interface, and transmit / receive User Plane and Control Plane. The eNB has a function of informing control information to the UE, a function of informing emergency breaking information, and the like.
The MME 104 that performs UE mobility management, session management, and security management has a function of performing terminal authentication processing. The eNB and MME are connected by an S1-MME interface, and control plane is transmitted and received.
The SGW 105 is a device having a gateway function as a connection point between the access network on the wireless side and the EPC, and the MME-SGW is connected by the S11 interface, and transmits and receives the control plane. The eNB-SGW is connected by the S1-U interface, and transmits and receives User Plane.
The PGW 106 is a device having a gateway function as a connection point between the EPC and a packet data network (PDN) that is an external IP network. The SGW and the PGW are connected by an S5 / S8 interface, and the User Transfer Plane and Control Plane. The PGW transmits / receives the User Plane to / from the external IP network.
The PCRF 107 is a device that controls policies such as service and billing, and has a function of controlling a data band. The PGW and PCRF are connected by a Gx interface, and control plane is transmitted and received.
Thus, in the access network and LTE-EPC, the User Plane is transmitted and received between the UE and the PDN using the eNB 103, the SGW 105, and the PGW 106.

  In order to perform User Plane transfer between the UE and an external IP network (PDN) on LTE, it is necessary to establish a logical connection. This logical connection is called a PDN connection as standard. One or more PDN connections need to be established when performing data communication with one PDN. The PDN connection includes one Default bearer and zero or more Dedicated bearers.

Next, a method for establishing a PDN connection will be described.
FIG. 2 is a diagram for explaining a registration sequence from the terminal power ON to the SIP server in one embodiment of the present invention.
In VoLTE, SIP (Session Initiation Protocol) is used for voice calls, and a PDN connection is established with a P-CSCF (Proxy-Call Session Control Function) which is a SIP server. In FIG. 2, a sequence from when the UE 101 is turned on in the LTE-EPC network until the default bearer is established using the control plane will be described. Each sequence in FIG. 2 describes an interface name before the colon and a message name after the colon. The same applies to FIGS. 3 to 5 below.

  When the UE 101 is turned on, a connection between access networks (wireless section) is first established. In FIG. 2 and subsequent sequence diagrams, the sequence of the wireless section (between access and network) is omitted. The MME 104 transmits a Create Session Request message 201 from the MME 104 to the SGW 105 using the S11 interface. The SGW 105 receives a request from the MME 104 and transmits a Create Session Request message 202 to the PGW 106 using the S5 / S8 interface.

  The PGW 106 transmits a CCR (Credit-Control-Request) message 203 of a PGW-PCRF session establishment request to the PCRF 107 using the Gx interface according to the Create Session Request message 202 from the SGW 105. The PCRF 107 transmits a CCA (Credit-Control-Answer) message 204 in which a PCC rule for SIP signaling is set as a default bearer to the PGW 106. The PGW 106 transmits a Create Session Response message 205 in which the P-CSCF IPv6 Address is set to the SGW 105.

The SGW 105 transmits a Create Session Response message 206 including the IP address of the U-Plane of the SGW 105 to the MME 104. The MME 104 stores the S1-U transfer control information and sends a Modify Bearer Request message 207 to the SGW 105. The SGW 105 responds to the MME 104 with a Modify Bearer Response message 208.
With the above sequence, the PDN Connection is established, and User Plane can be transmitted and received between the UE 101 and the P-CSCF 108.

The UE transmits a Register message 209 to the P-CSCF 108 using the SIP interface as User Plane information. The P-CSCF 108 returns a 200 OK response message 210 to the UE 101. The default bearer is for uplink and downlink, but for the sake of easy understanding, only the uplink is shown in the figure and the downlink is omitted.
With the above sequence, it is possible to make and receive calls by SIP. Similarly, for the UE 102, the UE 102 is turned on, and then the connection in the wireless section (between access networks) is established. The PDN Connection is established by the same sequence as the UE 101, and the User Plane is connected between the UE 102 and the P-CSCF 108. Can be sent and received. The UE 102 sends a Register message 211 to the P-CSCF 108 as User Plane information using the SIP interface, and the P-CSCF 108 returns a 200 OK response message 212 to the UE 102.
Next, control from calling to calling will be described.
FIGS. 3A, 3B and 3C are diagrams for explaining a general call origination / incoming sequence in one embodiment of the present invention.

[Call]
In FIG. 3A, when the user of the UE 101 performs a call origination operation to the UE 102, the UE 101 transmits an INVITE request message 301 to the UE 102.
When receiving the INVITE request message 301, the P-CSCF 108 transmits a 100 Trying provisional response message 302 indicating that processing is in progress to the UE 101, and transfers the INVITE request message 303 to the UE 102. Upon receiving the INVITE request message 303, the UE 102 transmits a 100 Trying provisional response message 304 indicating that processing is being performed to the P-CSCF (108). Further, the UE 102 transmits a 180 Ringing provisional response message 305 to the UE 101. The P-CSCF 108 transfers the 180 Ringing provisional response message 306 from the UE 102 to the UE 101.

[response]
Subsequently, when the user of the UE 102 responds to the call, it transmits a 200 OK response message 307 to the UE 101 as a final response of the INVITE request message 303.
The P-CSCF 108 transmits an AAR (AA-Request) [Type RER] message 308 to the PCRF 107 in order to establish a voice bearer for the UE 101. The PCRF 107 transmits an AAA (AA-Answer) [Type AAA] message 309 to the P-CSCF 108 as an AAR confirmation response.

  The PCRF 107 transmits an RAR (Re-Auth-Request) [Type AR] message 310 to the PGW 106. The PGW 106 transmits an RAA (Re-Auth-Answer) [Type RAA] message 311 to the PCRF 107 as a confirmation response of the RAR 310. The PGW 106 transmits a Create Bearer Request message 312 to the SGW 105 in order to request generation of the Dedicated bearer. The SGW 105 transmits a Create Bearer Request message 313 to the MME 104 in order to request addition of a bearer.

FIG. 3B shows a sequence subsequent to FIG.
After the SGW 105 adds the Dedicated bearer, the MME 104 transmits a Create Bearer Response message 314 to the SGW 105 as an acknowledgment of the Create Bearer Request message 313. The SGW 105 transmits a Create Bearer Response message 315 as a confirmation response to the Create Bearer Request message 312 from the PGW 106.
The Dedicated bearer is generated by the above sequence.
Also, the UE 102 performs the sequence of 316 to 323 similarly to the UE 308 to 315 of the UE 101, and generates a Dedicated bearer.

FIG. 3C shows the sequence shown in FIG.
The P-CSCF 108 transfers 324 the 200 OK final response message of the message 307 received from the UE 102 to the UE 101. The UE 101 starts the media flow of the session, and transmits an ACK request message 325 addressed to the UE 102 to the P-CSCF 108 as a response to the 200 OK response message 324. The P-CSCF 108 forwards 326 the ACK request message 325 to the UE 102.
Through the above sequence, the user of UE 101 and the user of UE 102 are in a call state, and a voice call can be made through the Dedicated bearer. In SIP, RTP (Real-time Transport Protocol) protocol is used for voice packet transfer.

[Fault detection]
A process when the PGW detects a failure of the opposite device via the interface or receives a restart notification will be described.
First, a conventional sequence will be described.

FIG. 4 is a diagram for explaining a release sequence of sessions belonging to a device that detects a conventional failure and restart.
After the failure of the PCRF 107, when the failure is detected by the expiration of the alive monitoring timer or when the restart message transmitted after the PCRF 107 is restarted, the PGW 106 performs the failure and restart in order to release the junk session which is an unnecessary session. Release the session belonging to the detected device. The PGW 106 sends a Delete Bearer Request message 402) to the SGW 105 in order to release the default bearer assigned to the PDN address for releasing the PDN connection and related resources. The SGW 105 transmits a Delete Bearer Request message 404 to the MME 104.

  The MME 104 transmits a Delete Bearer Response message 405 to the SGW 105. The SGW 105 transmits a Delete Bearer Response message 406 to the PGW 106. The session is released by the above sequence. The PGW 106 performs release processing for all the sessions belonging to the apparatus that detected the failure in accordance with the session management information (described later with reference to FIG. 9) held by the PGW.

  In the conventional sequence, only the control plane, such as the PCRF 107, is controlled, and even if there is a failure in the device that does not affect the user plane transfer required for the call, the sessions belonging to the failed device are uniformly included, including the session during the call. In order to release, there is a problem that the call cannot be continued. If the failure of the PCRF is temporary, there is a method of providing a special device and a special sequence as in Patent Document 1 mentioned in the background art section to restore the PCC session while holding the bearer. A PCRF failure is not necessarily temporary.

  Therefore, in this embodiment, since the PCRF failure does not affect the user plane transfer, even if the PCRF fails, the PGW connection release process is suspended until the call ends for the session in which the PGW is talking. Continue the call.

A specific problem solving method will be described with reference to FIGS.
FIG. 5 is a diagram for explaining a session release sequence when failure and resumption are detected in an embodiment of the present invention.
FIG. 6 is a flowchart for explaining processing contents for a session when a failure and resumption are detected in an embodiment of the present invention.
FIG. 7 is a flowchart for explaining session release target confirmation and disconnection request processing at the end of a call in an embodiment of the present invention.
FIG. 8 is a diagram illustrating the functional configuration of the PGW according to an embodiment of the present invention.
FIG. 9 is a diagram for explaining session management information according to an embodiment of the present invention.

The session release sequence at the time of detecting the failure and restart of the present embodiment shown in FIG. 5 is that the call processing control unit 801 of the PGW 106 shown in FIG. 8 performs the processing of FIG. It is realized with.
In FIG. 5, when the PGW 106 detects the failure and restart of the opposing device (501), the PGW 106 performs a disconnection process according to the flow of FIG. 6. As shown in FIG. 6, the PGW 106 detects whether the failure and restart source device is a device on the voice call route and affects the user plane transfer, the message received from the opposite device, or the IP of the target device for alive monitoring. The target device is determined (S601) with reference to the information representing the origin. If it is determined that the target device of the failure or restart source is the SGW 105 that affects the User Plane transfer that is the voice call route, the PGW 106 belongs to the failure / restart source device as in the conventional process described in FIG. Perform release request setting processing for all sessions. When the detection source is the SGW 105, the release request setting process performed by the PGW 106 refers to the session management information of FIG. 9 for all sessions held by the PGW 106, and determines whether the connection destination SGW information 901 matches the failure and restart source SGW (S606) and a disconnection request is set for the matched session (S607).

  In the case of the PCRF 107 in which the failure and restart source device controls only the control plane and is not a voice call route device, the PGW 106 refers to the session management information in FIG. It is determined whether the information 902 matches the failure and the restart source PCRF (S602). If the connection destination PCRF information 902 of the session management information in FIG. 9 is a session to be disconnected that matches the failure and restart source PCRF, it is determined whether or not a call is in progress from the Dedicated bearer establishment state (904) of the session management information (S603). )I do. If the session to be disconnected is not in a call (no established bearer established), a disconnect request for the session is set (S604). When the session to be disconnected is in a call (Dedicated bearer is being established), the session management information session release information of the PGW 106 indicates that the session needs to be released after the call ends without disconnecting immediately. In the execution information 905, the release execution is recorded (S605).

  At this time, a call data monitoring function is created in the user packet control unit 802 of the PGW 106 in FIG. In the call data monitoring function unit of the user packet control unit, after the call is ended, it is determined from the session release execution information 905 set in step 605 that the session is released, and in the case of the target session, a disconnection request is issued after the call ends. Set (S604). For example, RTP, which is a voice packet transfer protocol of VoLTE, is defined as a method for transferring voice packets at a cycle of 10 to 100 ms, so that a call can be made in a non-communication state for a fixed time. There are a method for determining the end of the call, and a method for determining the end of the call by detecting a SIP end call packet in the Default bearer.

  After detecting the end of the call of the session where the call data was monitored by these methods, the PGW 106 determines whether the session is a target session for releasing session resources (S701), and sets a disconnect request in the case of the target session (S604). . The call processing control unit 801 of the PGW 106 performs PDN connection release processing by transmitting a Delete Bearer Request message (402 in FIG. 4) to the SGW (105) in accordance with the disconnection request (S604) as in the conventional processing. In the subsequent PDN connection release processing, the session is released by performing the conventional sequence of the messages 401 to 406 in the same manner.

According to the embodiment described above, when the device PCRF (107) that controls only the control plane becomes a failure, the PDN connection release processing is suspended until the call is terminated for the session in progress, and the call is continued. It becomes possible to do.
When a PCRF that controls only the Control Plane that does not affect the User Plane for voice calls and is not a voice call route device fails, when the PGW detects a message indicating PCRF failure detection or resumption, the PCRF The session during the voice call is not disconnected, and the voice call can be continued. In addition, it records that the session is released after the call ends and monitors the call data, so that the end of the call can be detected and the session can be reliably disconnected after the call ends, and an unnecessary junk session remains in the PGW. There is nothing.

101, 102 Mobile terminal device 103 Radio base station device 104 Mobility management device 105 Serving gateway 106 Packet data network gateway 107 Policy / billing control device 108 SIP server 801 Call processing control unit 802 User packet control unit 803 Maintenance management Function control unit 804 Device management function control unit

Claims (6)

A session control method in a network composed of a plurality of devices, wherein an interface for transmitting / receiving control signals and an interface for transmitting / receiving user signals are separately defined, and the plurality of devices are interfaces or control signals for transmitting / receiving control signals. Both the interface for transmitting and receiving and the interface for transmitting and receiving user signals, and establishes a session between the plurality of devices to transmit and receive control signals and / or user signals,
When a device having a function of controlling the session among the plurality of devices detects a failure of a device opposed to the device via the interface, an interface and a user signal that transmit / receive a control signal to / from the device opposed to the device In the case of a device having only an interface for transmitting and receiving a control signal, it is determined whether it has both an interface for transmitting and receiving a control signal or only an interface for transmitting and receiving a control signal. Is maintained until the end of the call. A session control method in PGW (Packet data network Gateway) of LTE (Long Term Evolution) EPC (Evolved Packet Core),
The PGW has session management information that stores information on each session controlled by the PGW. When a failure of the policy / billing control device is detected, the PGW refers to the session management information. A session control method characterized by monitoring a call state and releasing a session after the call ends.   The session management information includes, for each session, connection destination serving gateway information, connection destination policy / billing control device information, session establishment state information, and information indicating whether the session is to be released after the call ends. The session control method according to claim 2.   The PGW refers to the information on the state of establishment of the session, and for a session during a call, the information indicating whether the session is to be released after the call is ended is a target for releasing the session after the call is ended. The session control method according to claim 3, wherein:   3. The call state is monitored by determining whether or not the call is ended by monitoring whether or not no communication continues for a predetermined time or more, or monitoring a packet including a control signal indicating an end of call. Session control method described in 1. A packet data network gateway of LTE (Long Term Evolution) EPC (Evolved Packet Core),
It has session management information that stores information on each session controlled by the gateway, and when a failure of the policy / billing control device is detected, the session management information is referred to. A gateway characterized by monitoring and releasing a session after a call ends.

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