WO2012147291A1

WO2012147291A1 - Communication node and network node

Info

Publication number: WO2012147291A1
Application number: PCT/JP2012/002509
Authority: WO
Inventors: 隆二杉崎; 啓吾阿相
Original assignee: パナソニック株式会社
Priority date: 2011-04-28
Filing date: 2012-04-11
Publication date: 2012-11-01

Abstract

Disclosed is a technology for restraining the occurrence of a processing load caused by a handover between different RATs (radio access technologies) in order to reduce the number of messages to be exchanged. According to this technology, if connection to a first network (MME 120 of E-UTRAN) is rejected, and a first back-off time is set for the transmission of the next connection request, a communication node (UE100) notifies a second network (SGSN 121 of UTRAN) of the first back-off time, for example, when transmitting a connection request (Step S6021). When the SGSN has subsequently made an attempt to hand over the connection of the applicable UE, but the handover is rejected by the MME, and a second back-off time is set for the transmission of the next handover request, if the expiration of the second back-off time is sooner than the expiration of the first back-off time, a message is transmitted to the UE so as to switch to the first network after the second back-off time is expired, for example (Step S608).

Description

Communication node and network node

The present invention provides a communication node for performing communication by switching connection to a network using different RATs (Radio Access Technology), and a handover for the communication node (Inter-RAT Handover (HO)). It relates to a network node capable of

Currently, standardization activities for technologies used in mobile phones (User Equipment: UE, also referred to as communication nodes) are being conducted by 3GPP (The Third Generation Partnership Project), and network connection procedures and handover procedures are defined. Yes. In recent years, data from MTC (Machine Type Communication) devices (for example, communication modules incorporated in machines and machines such as vending machines, street advertising displays, smoke sensors, security cameras, and human sensors, or generic names thereof). There are efforts to implement the exchange on the network for the UE. That is, there is an effort to enable the UE and the MTC device to communicate by sharing a network that has been used only by the UE. However, in 3GPP, since the number of MTC devices is estimated to be very large compared to the UE, a congestion avoiding method is provided so that the network is not congested and a loss (for example, system down) is not caused to an existing system. Is being formulated. An example of the configuration of a network (communication system) shared by the UE and the MTC device is shown in FIG.

FIG. 1 shows a UE 100, an MTC device 105, a base station wirelessly connected to the UE 100 and the MTC device 105 (eNB (eNode B) 110 in E-UTRAN 114, NB (Node B) 111 in UTRAN 115), E-UTRAN 114, An exchange in charge of communication line control and movement control of the UE 100 and the MTC device 105 on the UTRAN 115 (the exchange connected to the E-UTRAN 114 is MME (Mobility Management Entity) 120, and the exchange connected to the UTRAN 115 is SGSN (Service General packet). radio service support node) 121), the radio channel of UE 100 and MTC device 105 on UTRAN 115 SGW (Serving Gateway: Serving Gateway, MAG (Mobility Anchor Gateway: MG) that controls user data distribution to RNC (Radio Network Controller) 112 of UE and MTC device 105 UTRAN 115 and E-UTRAN 114. 130), PGW (Packet Data Network Gateway, HA (Home) that performs address control and user data transfer between PDN (Packet Data Network: packet data network) 155 and SGW 130, and path control. Agent: Home Agent Interface) with the server (MME 120) that manages and holds the subscription data (subscription data) of the UE 100 and the MTC device 105, the communication context, and the like, and the LMA (Local Mobility Anchor). (With the target of UE 100 and MTC device 105 using E-UTRAN 114) having an interface with HSS (Home Subscriber Server) 125 and SGSN 121 (targeting UE 100 and MTC device 105 using UTRAN 115) (Referred to as HLR (Home Location Register) 126) and MTC device 105 Network including MTC server 150 that is a server that provides communication control and status management, and application services, and MTC user 160 that performs application management and control and application data management for MTC device 105 and MTC server 150 An example configuration is shown. In the following, for ease of explanation, UE 100 and MTC device 105 are collectively referred to as UE 100.

In FIG. 1, when the UE 100 communicates with an external network (for example, the PDN 155 illustrated in FIG. 1) through the E-UTRAN 114, the UE 100 communicates with the PGW 140 through a PDN connection and an EPS bearer (EPS Bearer, bearer). Must be established). The UE 100 acquires an IP (Internet Protocol) address through the establishment of the PDN connection, and establishes an EPS bearer for communicating with the PDN 155 (see Non-Patent Document 1 below). When establishing a PDN connection, information such as the IP address assigned to the UE 100 and the address of the SGW 130 used by the UE 100 is treated as context information of the UE 100 and held in the entity of the core network 145. As a result, the entity of the core network 145 can transfer, for example, data transmitted from the PDN 155 to the UE 100. The UE 100 establishes a PDN connection with the PGW 140 by transmitting a request message such as “Attach request” or “PDN connectivity request” disclosed in Non-Patent Document 1 to the network.

However, when the PDN 155 is congested, the MME 120 or the PGW 140 discloses a request message (for example, Attach request, PDN connectivity request, etc.) for establishing a PDN connection transmitted from the UE 100 in Non-Patent Document 1. As described above, “APS (Access Point Name: access point name, usage will be described later) reaches the maximum number of active EPS bearers (has reached)”, “Activation of EPS bearers per APN” (E.g., establishment request) rate (e.g., transmission rate) reaches (reached) maximum rate "," no response from one or more PGWs 140 associated with APN (link is broken (broken)) Or, the MME 120 is notified of the congestion state of the APN (notified), “the ratio of the MM signaling requests by the UE 100 related to the specific subscribed APN reaches the maximum rate”, “network management setting May be rejected based on criteria such as

As shown in FIG. 1, there are a plurality of PDNs 155, and each PDN 155 is identified by an identifier called APN. The APN is used as information indicating a connection destination of a connection (PDN connection) in a request message exchanged between the UE 100 and the network. The MME 120 and the PGW 140 select the PGW 140 and the PDN 155 based on the APN and the operator policy of the connection destination information stored in the request message transmitted from the UE 100. When it is determined that the PDN 155 selected in this way is congested, the MME 120 and the PGW 140 reject the request message transmitted from the UE 100.

Also, as a congestion avoiding method based on the congestion state of the PDN 155, the priority (hereinafter also referred to as Priority) held by the UE 100 can be used. In this priority, a low priority (hereinafter, also referred to as “low priority”) and a standard priority (hereinafter, also referred to as “normal priority”) are defined. Currently, there are only two types defined: Low priority UE100 and non-low priority (normal priority) UE100, but in the future, for example, by introducing high priority (High priority), Low / There may be cases in which there are three types of Normal / High or more types.

In the congestion avoidance method based on priority, the priority is controlled in order from the UE 100 of the low priority. That is, when the PDN 155 is congested, as soon as it is detected by the MME 120 or the PGW 140, the congestion countermeasure is controlled from the UE 100 of the low priority based on the operator policy or the determination of the entity in the network. For example, when the APN of the connection destination information of the request message transmitted from the UE 100 indicates “PDN1” and it is detected that “PDN1” is congested, the MME 120 or the PGW 140 determines that the UE 100 has a low priority. The request message sent from is preferentially rejected. Furthermore, if there is a reason such as wanting to eliminate the congestion state in a short time, it is possible to expand the object of rejection in the order of Normal Priority, High Priority, followed by Low Priority. Currently, the network stores priority information stored in the request message transmitted from the UE 100 (based on LAPI (Low Access Priority Indicator) disclosed in Non-Patent Document 1 or whether LAPI is stored. It is defined to determine whether to reject the request message based on whether or not (see Non-Patent Document 1).

Further, in addition to being assigned to the UE 100, this priority is also considered when it is assigned to a connection (PDN connection) established by the UE 100. For example, if the UE 100 has already established two connections with the network, one connection may have a priority of Low priority and another connection may have a priority of Normal priority. When the priority is assigned to the connection (PDN connection), this priority information includes priority information related to the application held by the UE 100 (for example, “If the amount of data exchanged by the MTC application is small, the connection of the low priority ( Context information or setting file in which “Use (PDN connection)” is registered) or priority information notified from the network operator or the MTC server 150 / user 160 (for example, “sensing data required by the MTC application”) May be set on the basis of high priority (information instructing “use of connection (PDN connection))” etc. Also in a request message in which such priority information is stored The network is transmitted from the UE 100. Based on the priority information stored in the Est message, or based on whether LAPI is stored, it may reject the request message.

In this way, when the network rejects a request message transmitted from the Low priority UE 100 or a request message for establishing a Low priority connection, the network waits to avoid retransmission of the request message for a certain period of time. The UE 100 may be notified of the time (standby time, also called a back-off timer) stored in the rejection message. The UE 100 that has received the rejection message storing the waiting time sends a request message (for example, Attach Request or Bearer Resource Modification Request disclosed in Non-Patent Document 1) to the same APN until the waiting time expires. ) Is not sent. This waiting time does not affect request messages for other APNs.

In addition, in the waiting time disclosed in Non-Patent Document 1, a message for mobility management of the UE 100 (for example, Attach request, Tracking Area Update Request, Service Request, Extended Service Request, and Detach Management MM) ) Back-off timer (also called EMM back-off timer).

In addition to the case where the request message from the UE 100 is rejected due to the congestion of the PDN 155 as described above, the network device (core network 145 or RAN (Radio Area Network, E-UTRAN 114 and UTRAN 115 in FIG. 1) (Equivalent) entity) can reject the request message even when, for example, the number of request messages transmitted from the UE 100 is too large and is in a congested state (overload state) ( (Refer nonpatent literature 1).

For example, when the MME 120 of the core network 145 is overloaded, the eNB 110 requests the eNB 110 to restrict request messages addressed to the MME 120, and the eNB 110 requests messages from the UE 100 (messages exchanged between the UE 100 and the eNB 110). Includes a message called an RRC connection request message (see Non-Patent Document 2 below), thereby restricting request messages from the UE 100 to the MME 120 and means for distributing the load among the MMEs 120. (For example, by performing MME Load rebalancing procedure disclosed in Non-Patent Document 1), other MMEs 120 that are not overloaded By transferring the request message from the E100, it is possible to and control the request message to MME120 from UE100 overload. Further, the MME 120 itself may preferentially reject (reject) a request message transmitted from the low priority UE 100 because the network device is overloaded. The same applies to other core networks 145 and RAN entities.

In 3GPP, a message requesting the MME 120 to restrict the request message from the UE 100 to the eNB 110 is referred to as an OVERLOAD START message. When the MME 120 determines that the overload state of the MME 120 is eliminated and the eNB 110 does not need to further reject the request message from the UE 100, the MME 120 transmits an OVERLOAD STOP message to the eNB 110, and the request message from the UE 100. The state of the eNB 110 that rejects may be reset.

The MME 120 can control the UE 100 that is the transmission source of the request message rejected by the eNB 110 for each Subcategory (subcategory) by sending this OVERLOAD START message. This Subcategory may be classified based on the priority used in the congestion avoiding method based on the congestion state of the PDN 155 or the network device as described above, and whether the UE 100 is roaming (for example, It may be classified based on PLMN (Public Land Mobile Network) type (see Non-Patent Document 1).

Similarly, in a state where the network device is overloaded, the Back-off timer may be used in order to avoid retransmission of the request message from the UE 100 in a short time. Similarly to the case where the PDN 155 is congested, the MM back-off timer disclosed in Non-Patent Document 1 may be used for avoiding the congested state in the MME 120, the PGW 140, and the like.

Further, when different RATs such as E-UTRAN 114 and UTRAN 115 shown in FIG. 1 exist, a method of moving the connection of UE 100 between different RATs while maintaining communication between UE 100 and the network. For example, Non-Patent Document 1 discloses “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” and the like. “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” disclosed in Non-Patent Document 1 is a conventional technique used when a handover from UTRAN 115 to E-UTRAN 114 is performed. This “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” is divided into two phases, “Preparation phase” and “Execution phase”. By correctly completing these two phases, the UE 100 can be changed from the UTRAN 115 to the ETRAN. -Hand over to UTRAN 114. Hereinafter, “Preparation phase” and “Execution phase” will be described.

First, the detailed operation of “Preparation phase” of “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” will be described with reference to FIG. FIG. 2 is a sequence diagram for explaining the “Preparation phase” of the conventional technique “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure”. In addition, a device that is used in the network to which the UE 100 is currently connected, and that is changed by executing “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” (the UE 100 uses before handover) Device) is prefixed with the word “Source” (for example, the source SGSN 121), and the device that the UE 100 intends to use in the network after the handover is preceded by the device name. The word “Target” is used (for example, the target MME 120).

First, it is assumed that the UE 100 has established a PDN connection for communicating with the PDN 155 in the UTRAN 115 and has established a plurality of EPS bearers. Here, the source RNC 112 decides to hand over the UE 100 from the UTRAN 115 to the E-UTRAN 114 based on an operator policy such as a communication state of the UE 100 and a load state of the NB 110 supporting the UE 100 (step S201 in FIG. 2). ).

The source RNC 112 is a device used in the handover destination network of the UE 100 (for example, the target eNB 110, the target MME 120, and the target SGW 130). A message is transmitted (step S202 in FIG. 2).

The source SGSN 121 determines a handover from the parameter (for example, Target eNB Identifier) stored in the Relocation Required message received in step S202 to the E-UTRAN 114. Subsequently, the source SGSN 121 starts a Handover Required resource allocation procedure by transmitting a Forward Relocation Request message to the target MME 120 in order to secure resources for the EPS bearer established before the handover by the UE 100 (Step S203 in FIG. 2). .

The target MME 120 establishes the EPS bearer indicated by the parameter stored in the Forward Relocation Request message received in step S203. Also, the target MME 120 determines whether reassignment of the SGW 130 is necessary. If the SGW 130 is to be reassigned, the target MME 120 selects the target SGW 130 and transmits a Create Session Request message to the SGW 130 (step S204 in FIG. 2). In the configuration example illustrated in FIG. 1, the source SGW 130 and the target SGW 130 are the same.

The SGW 130 that has received the Create Session Request message allocates resources for the UE 100, and transmits a Create Session Response message to the target MME 120 (Step S205 in FIG. 2). Note that when the SGW 130 is not reassigned, the message exchange in steps S204 and S205 in FIG. 2 can be omitted.

Subsequently, the target MME 120 transmits a Handover Request message to the target eNB 110 in order to request radio resource allocation by the target eNB 110. (Step S206 in FIG. 2).

The target eNB 110 that has received the Handover Request message allocates radio resources for the UE 100, stores parameters applied for the radio resources of the UE 100 in the Handover Request Acknowledgment message, and transmits them to the target MME 120 (Step S207 in FIG. 2). . At this time, the target eNB 110 prepares to receive user data sent from the SGW 140.

When the reassignment of the SGW 130 is applied in “Indirect Forwarding”, or when the direct tunnel (Direct Tunnel) is not used in “Indirect Forwarding”, the messages shown in Step S208 and Step S209 in FIG. And SGW 130 are exchanged.

Subsequently, the target MME 120 sends a Forward Relocation Response message to the source SGSN 121 that stores a result of securing radio resources, a parameter indicating that a new SGW 130 has been selected, and the like, as a result of processing by the E-UTRAN 114 and the target MME 120 of the handover destination. Transmit (step S210 in FIG. 2).

Further, when “Indirect Forwarding” is applied, the messages shown in steps S211 and S212 in FIG. 2 are further exchanged between the source SGSN 121 and the SGW 130.

Next, the detailed operation of “Execution phase” of “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” will be described with reference to FIG. FIG. 3 is a sequence diagram for explaining “Extraction phase” of “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure”, which is a conventional technique.

At the beginning of “Execution phase”, the source SGSN 121 completes the “Preparation phase” by sending a Relocation Command message to the source RNC 112. Further, the source SGSN 121 stores, in the Relocation Command message, parameters necessary for the UE 100 generated by the “Preparation phase” to transfer data via the handover destination E-UTRAN 114 (step S301 in FIG. 3).

The source RNC 112 that has received the Relocation Command message transmits a HO from E-UTRAN Complete message to the UE 100 in order to hand over the UE 100 to the handover destination E-UTRAN 114 (step S302 in FIG. 3).

After this step, the UE 100 performs a general “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure”, and hands over from the UTRAN 115 to the E-UTRAN 114.

By correctly implementing “Preparation phase” and “Execution phase” divided into these two, the “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” is completed, and the UE 100 moves from the UTRAN 115 to the E-UTRAN 114. Handover is possible.

Here, the case where the UE 100 is handed over from the UTRAN 115 to the E-UTRAN 114 according to the contents disclosed in the Non-Patent Document 1 has been described. Handover can be performed according to the disclosure of Document 1.

After the UE sends a request message for establishing a PDN connection to the MME via E-UTRAN and the MME is overloaded and rejected with a waiting time (eg MM back-off timer), the UE In an environment where a PDN connection is established via UTRAN, an Inter-RAT handover procedure from UTRAN to E-UTRAN is implemented based on the network operator policy after establishing a PDN connection via UTRAN. Request message for Inter-RAT handover (“Forward Relocation Requests” shown in FIG. 2) ") Latency (e.g., back-off timer (hereinafter to a request message for handover, HO (Handover) is called a back-off timer) is considered to be rejected with a).

In such a case, after completion of the HO back-off timer, a request message for the Inter-RAT handover is transmitted again (“Forward Relocation Request” transmitted from the source SGSN 121 to the target MME 120 in step S203 in FIG. 2), Execution of Inter-RAT Handover is attempted. However, the execution of Inter-RAT Handover procedure has a problem that the processing load is high for the network device and the number of messages exchanged between the network devices is large.

In order to solve the above problem, the present invention attempts to perform a handover when a handover (Inter-RAT Handover) is rejected for a connection of a communication node (UE) and a waiting time (HO back-off timer) occurs. The purpose is to connect efficiently to the network. It is another object of the present invention to perform processing with a small processing load and a small number of exchanged messages.

In order to achieve the above object, the communication node of the present invention is configured by first and second networks using different radio access technologies, and the communication node is connected between the first network and the second network. A communication node connected to a communication system for handing over
A first connection request transmitter for transmitting a first connection request to the first network;
Connection until the first connection request can be retransmitted to the first network when the first connection request to the first network by the first connection request transmission unit is rejected. A waiting time acquisition unit for acquiring a request waiting time;
A second connection request transmitter for transmitting a second connection request to the second network when the first connection request to the first network by the first connection request transmitter is rejected;
A connection establishment unit for establishing a connection with the second network;
The second network sends a handover request for handing over the connection established with the communication node to the first network, and the first network rejects the handover request. And switching the connection to the first network transmitted from the second network when notifying the second network of a handover waiting time until a handover request can be retransmitted to the first network. A message receiver for receiving a trigger message including an instruction;
A determination unit that determines whether the first connection request transmission unit retransmits the first connection request to the first network based on the trigger message received by the message reception unit;
Have.
With this configuration, when a handover (Inter-RAT Handover) is rejected with respect to connection of a communication node (UE) and a waiting time (HO back-off timer) occurs, it is possible to efficiently connect to a network to be handed over. In this case, it is possible to perform processing with a small processing load and a small number of exchanged messages.

In order to achieve the above object, the network node of the present invention includes first and second networks using different radio access technologies, and a communication node between the first network and the second network. A network node located in the second network in a communication system for handing over the connection of:
A connection request receiving unit that receives a second connection request to the second network from the communication node in which the first connection request to the first network is rejected;
A connection response transmitting unit that transmits a connection response indicating acceptance of the second connection request to the second network by the communication node to the communication node;
A handover request transmitter for transmitting a handover request for handing over a connection established with the communication node to the first network, to the first network;
A handover standby time acquisition unit that acquires a handover standby time until the handover request can be retransmitted to the first network when the first network rejects the handover request;
A message transmitting unit that transmits a trigger message including a connection switching instruction to the first network to the communication node;
Have.
With this configuration, when a handover (Inter-RAT Handover) is rejected with respect to connection of a communication node (UE) and a waiting time (HO back-off timer) occurs, it is possible to efficiently connect to a network to be handed over. In this case, it is possible to perform processing with a small processing load and a small number of exchanged messages.

According to the present invention, when a handover (Inter-RAT Handover) is rejected with respect to connection of a communication node (UE) and a waiting time (HO back-off timer) occurs, it efficiently connects to the network to be handed over. It becomes possible. At this time, it is possible to perform processing with a small processing load and a small number of exchanged messages.

Further, according to the present invention, a connection request transmitted from a communication node (UE) to a certain network (first network) is rejected and a first waiting time (MM back-off timer) is set. Even in this case, the second standby time (HO back) set by the handover from the second network to the first network (Inter-RAT Handover) is established by establishing a connection with another network (second network). By using -off timer, it is possible to avoid the execution of a handover process (inter-RAT Handover procedure) between networks.

Further, according to the present invention, when the end time of the second standby time (HO back-off timer) is earlier than the end time of the first standby time (MM back-off timer), a communication node Can connect to the first network earlier, leading to improved service quality and improved user convenience. In addition, the communication node selects an optimal network by determining whether or not to switch the connection in consideration of the communication status of the communication node (for example, the remaining amount of data to be transmitted / received). Is possible.

The figure which shows an example of the system configuration common to 1st and 2nd embodiment of this invention, and the prior art Sequence diagram for explaining the “Preparation phase” of the conventional technology “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” Sequence diagram for explaining the “Extraction phase” of the conventional technology “UTRAN Iu mode to E-UTRAN Inter RAT handover procedure” FIG. 3 is a sequence diagram for explaining an example of a system operation according to the first and second embodiments of the present invention, which is an example of a system operation according to a conventional technique. Sequence diagram for explaining an example of the operation of the conventional technology “UTRAN to E-UTRAN lu mode Inter RAT handover” (handover case from UTRAN to E-UTRAN) The sequence diagram for demonstrating an example of operation | movement of the 1st Embodiment of this invention The figure which shows an example of a structure of UE in the 1st Embodiment of this invention The flowchart which shows an example of operation | movement of UE in the 1st Embodiment of this invention. The figure which shows an example of a structure of the source SGSN in the 1st Embodiment of this invention The flowchart which shows an example of operation | movement of SGSN in the 1st Embodiment of this invention. The figure which shows the example of a format of the request message (Trigger request) used in the 1st Embodiment of this invention. Sequence diagram for explaining an example of the operation of Attach procedure in the prior art The sequence diagram for demonstrating an example of the system operation | movement (handover case from UTRAN to E-UTRAN) in the 2nd Embodiment of this invention The figure which shows an example of a structure of UE in the 2nd Embodiment of this invention. The flowchart which shows an example of operation | movement of UE in the 2nd Embodiment of this invention. The figure which shows the example of a format of the request message (Trigger request) used in the 2nd Embodiment of this invention. The figure which shows the example of a format of the request message (Attach request) used in the 2nd Embodiment of this invention.

Hereinafter, first and second embodiments of the present invention will be described with reference to the drawings.

First, a system configuration common to the first and second embodiments of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing an example of a system configuration common to the first and second embodiments of the present invention and the conventional technology.

As described above, the network illustrated in FIG. 1 includes at least a base station (to E-UTRAN 114) that is wirelessly connected to UE 100 or MTC device 105 (UE 100 and MTC device 105 are collectively referred to as UE 100). ENB 110 that provides a connection to the UTRAN 115, or an NB 111 that provides a connection to the UTRAN 115), an RNC 112 that performs radio channel control and mobility control of the UE 100 connected to the UTRAN 115, and is responsible for mobility management of the UE 100 (MME 120 or SGSN 121). Server holding subscription information (HSS 125 or HLR 126), SGW 130 for performing user data distribution control, address assignment for UE 100, user data transfer and routing between PDN 155 and SGW 130 The performed PGW140, utilizing MTC service UE100 by the control and state management of the communication has a MTC server 150 provides a server for such application services. Note that the UE 100 and the MTC user 160 can communicate with this network. In FIG. 1, the MTC server 150 is located in the PDN 155, but may be located in the core network 145. For example, the PGW 140 may be responsible for the function of the MTC server 150.

Here, the UE 100 has at least one communication interface and can be connected to a network (for example, the E-UTRAN 114 or the UTRAN 115). Note that the UE 100 may be connected to the illustrated network (for example, the E-UTRAN 114 or the UTRAN 115) simultaneously or exclusively. Only. The UE 100 can communicate with the MTC server 150 through the connected communication system, and the MTC server 150 can communicate with the MTC user 160. Note that the MME 120 and the PGW 140 of the core network request messages transmitted from the UE 100 with a waiting time when the PDN 155 is congested or the entities (such as the MME 120 and the PGW 140) of the core network 145 are overloaded. Can be rejected.

Further, as described above, the UE 100 can perform handover between different RATs (for example, from the UTRAN 115 to the E-UTRAN 114) while maintaining communication by using the procedure established by 3GPP. In the following, a case where a handover is mainly performed from the UTRAN 115 to the E-UTRAN 114 will be described, but the present invention can also be applied when a handover is performed from the E-UTRAN 114 to the UTRAN 115. In this specification, E-UTRAN 114 and UTRAN 115 are illustrated as a plurality of RATs to which UE 100 can be connected. However, the present invention is also applicable.

Hereinafter, an example of a system operation assumed in the first and second embodiments of the present invention will be described with reference to FIG. FIG. 4 is a sequence diagram for explaining an example of a system operation according to the prior art, and an example of a system operation assumed in the first and second embodiments of the present invention. Here, as an illustrative example of the first and second embodiments of the present invention, the UE 100 establishes a connection via either the MME 120 (connected via the E-UTRAN 114) or the SGSN 121 (connected via the UTRAN 115). This will be described using a case where

UE 100 transmits a request message (for example, Attach request) to MME 120 in order to establish a PDN connection via E-UTRAN 114 (step S401 in FIG. 4). The MME 120 that has received the Attach request transmitted from the UE 100 is in an overload state, for example, due to processing of a request message from another UE 100 or a message transmitted from an entity of the core network 145, and is a rejection for rejecting the Attach request. A message (for example, Attach reject) is returned to the UE 100 (step S402 in FIG. 4). Note that the MME 120 wants to return from the overload state to a normal state (a state in which a request message from the UE 100 can be processed) as soon as possible, or a waiting time (MM back) to avoid a request message retransmitted from the UE 100 for a certain period of time. -Off timer) is stored in the rejection message. As described above, the processing in steps S401 and S402 represents processing in which the UE 100 to which the connection via the E-UTRAN 114 is rejected receives a waiting time (MM back-off timer).

The UE 100 that has received the rejection message including the MM back-off timer transmits a request message (for example, Attach request) for establishing a PDN connection via a different network (for example, UTRAN 115 which is a different RAT) (FIG. 4). Step S403). The SGSN 121 that has received the Attach request transmitted from the UE 100 performs processing in accordance with a general Attach procedure established by 3GPP in order to authorize the Attach request, and returns an authorization message (for example, Attach accept) to the UE 100. (Step S404 in FIG. 4). As a result, the UE 100 can establish a PDN connection with the PGW 140 via the UTRAN 115 and, for example, can transmit user data to the PDN 155. As described above, the processing in steps S403 and S404 represents processing in which the UE 100 to which connection via the E-UTRAN 114 is rejected establishes a PDN connection via the UTRAN 115. In the present invention, as described later, a flag indicating an instruction to use the MM back-off timer or the HO back-off timer is inserted into the Attach request transmitted from the UE 100 in step S403.

After the UE 100 establishes a PDN connection with the PGW 140 via the UTRAN 115, a handover process from the UTRAN 115 to the E-UTRAN 114 is triggered by the network operator policy, and a message (for example, Forward Relocation Request) from the SGSN 121 to the MME 120 (details) The sequence will be described later) (step S405 in FIG. 4). The MME 120 that has received the Forward Relocation Request transmitted from the SGSN 121 is in an overload state due to processing of a request message from another UE 100 or a message transmitted from an entity of the core network 145, and so on to reject the Forward Relocation Request. A rejection message (for example, Forward Relocation Response storing parameters indicating “No resource available” and “Relocation failure” disclosed in Non-Patent Document 5) is returned to the SGSN 121 (step S406 in FIG. 4). The MME 120 wants to return as soon as possible from an overload state to a normal state (a state in which a request message from the UE or a message from an entity of the core network (for example, a handover request) can be processed), or a request retransmitted from the SGSN 121 In order to avoid the message for a certain period of time, it is possible to store a waiting time (HO back-off timer) in the rejection message. When the MME 120 returns to the normal state and receives the Handover request in Step S405, the Inter-RAT handover procedure is executed.

As described above, the processing in steps S405 and S406 represents processing in which the Inter-RAT handover from the UTRAN 115 to the E-UTRAN 114 is rejected and a waiting time (HO back-off timer) is received. In the present invention, as shown in the above-described series of processing (processing from step S401 to step S406), for example, the MME 120 in the overload state receives an attach request including an MM back-off timer in response to an attach request from the UE 100. (Reject message) is returned, and Forward Relocation Response (reject message) including HO back-off timer is returned to Forward Relocation Request from SGSN 121.

In the conventional technique, the SGSN 121 that has received the Forward Relocation Response including the HO back-off timer transmits the Forward Relocation Request to the MME 120 again after the HO back-off timer has elapsed (step S407 in FIG. 4). The MME 120 that has received the Forward Relocation Request accepts the Forward Relocation Request when the overload state is resolved, and stores a handover permission message (for example, a parameter indicating “Request Accepted” disclosed in Non-Patent Document 5). Forward Relocation Response) is returned to the SGSN 121 (step S408 in FIG. 4). As described above, the SGSN 121 performs the handover process by retransmitting the Forward Relocation Request after the completion of the HO back-off timer, but this handover process (Inter-RAT handover procedure) has a high processing load on the network device. In addition, there is a problem that a large number of messages are exchanged.

Hereinafter, the Inter-RAT handover procedure in the prior art will be described in detail with reference to FIG. FIG. 5 is a sequence diagram for explaining an example of the operation of the conventional technique “UTRAN to E-UTRAN lu mode Inter RAT handover” (handover case from UTRAN 115 to E-UTRAN 114). Note that the device used by the UE 100 before the Inter-RAT handover procedure is prefixed with the word “Source” before the device name (for example, the source SGSN 121), and after the Inter-RAT handover procedure, the UE 100 A device scheduled to be used in the network is prefixed with the word “Target” (for example, target MME 120). In FIG. 5, the reassignment of the SGW 130 is not taken into consideration, and when the reassignment of the SGW 130 is performed, the messages indicated by the dotted lines in FIGS. 2 and 3 are exchanged.

First, it is assumed that the UE 100 has already established a PDN connection with the PGW 140 via the UTRAN 115 ((A) and (B) in FIG. 4 have been performed). Here, regarding the connection of the UE 100, execution of Inter-RAT handover from the UTRAN 115 to the E-UTRAN 114 is determined based on the network operator policy (step S501 in FIG. 5). Based on the network operator policy, when Inter-RAT handover is performed, the source RNC 112 is a device used in the handover destination network of the UE 100 (for example, the target eNB 110, the target MME 120, the target SGW 130), and the UE 100 is established before the handover. A relocation required message for securing resources for the EPS bearer is transmitted to the source SGSN 121 (step S502 in FIG. 5).

The source SGSN 121 that has received the Relocation required message from the source RNC 112 determines the handover from the parameters stored in the Relocation required message (for example, Target eNB Identifier) to the E-UTRAN 114 according to the general Inter-RAT handover procedure. A Forward Relocation Request message is transmitted to the target MME 120 (step S503 in FIG. 5).

If the target MME 120 that has received the Forward Relocation Request message is not in an overload state, a general Inter-RAT handover procedure process (for example, after executing Step S 506 to Step S 508 shown in FIG. Process). On the other hand, when the target MME 120 is in an overload state, a message that rejects the Forward Relocation Request message (for example, a parameter indicating “No resource available” or “Relocation failure” disclosed in Non-Patent Document 5) is stored. The Forward Relocation Response message) is returned to the source SGSN 121 (step S504 in FIG. 5). As described above, the target MME 120 wants to return as soon as possible from the overload state to a normal state (a state in which a request message from the UE 100 or a message from a core network entity (for example, a Handover request) can be processed). Alternatively, when a request message retransmitted from the source SGSN 121 or the like is to be avoided for a certain period of time, a waiting time (HO back-off timer) is stored in the Forward Relocation Response message transmitted in step S504. 4C corresponds to step S501 to step S504 in FIG.

After the completion of the HO back-off timer, the source SGSN 121 transmits a Forward Relocation Request message to the target MME 120 again (step S505 in FIG. 5). At this time, for example, when the overload state of the target MME 120 has been resolved (when the target MME 120 has returned to the normal state), in steps S506 to S508 in FIG. The request is accepted, and then the execution phase process shown in FIG. 5 is executed. 4D corresponds to steps S505 to S508 in FIG.

As can be seen from FIG. 5, in the Inter-RAT HO procedure, for example, when a message (Forward Relocation Response message) rejecting the Forward Relocation request from the target MME 120 to the source SGSN 121 is returned from the source SGSN 121 to the Target MME 120, the Forward Requeue Request It takes a minimum of 18 steps from the time when the message is sent again until Inter-RAT HO procedure is completed (the processing after step S505 in FIG. 5), and various message exchanges (for example, dotted lines in FIGS. 2 and 3). (For example, when the SGW 130 changes) A. In other words, Inter-RAT HO procedure has a problem that the processing load on the network device is high and the number of messages to be exchanged is large.

<First Embodiment>
Hereinafter, a first embodiment of the present invention will be described. FIG. 6 is a sequence diagram for explaining an example of the operation of the first exemplary embodiment of the present invention. 6 is created based on FIG. 5, step S601 in FIG. 6 is shown in FIG. 4A, step S602 in FIG. 6 is in FIG. 4B, and steps S603 to S606 in FIG. Corresponds to (C) in FIG. 4 and steps S501 to S504 in FIG.

In the first embodiment of the present invention, when the UE 100 transmits an Attach request to the SGSN (source SGSN) 121 via the UTRAN 115, the MM back- stored in the Attach reject message received via the E-UTRAN 114. A flag indicating an instruction to use the off timer or the HO back-off timer is stored in the Attach request (step S6021 in FIG. 6).

Subsequently, the Inter-RAT HO from the UTRAN 115 to the E-UTRAN 114 is triggered by the network operator policy, and Steps S603 to S606 are performed. Here, it is assumed that the Forward Relocation Request in Inter-RAT HO transmitted from the source SGSN 121 is rejected by the target MME 120, and Steps S603 to S606 in FIG. 6 are performed from Step S501 to Step S606 in FIG. Since it is the same as S504, the description is omitted.

Subsequently, after the source SGSN 121 receives the Forward Relocation Response message including the HO back-off timer transmitted from the target MME 120, the source SGSN 121 receives the MM back-off timer notified from the UE 100 in step S6021, and the target MME 120 in step S606. Each end time (elapsed state) of the notified HO back-off timer is compared (step S607 in FIG. 6).

If the source SGSN 121 determines that the end time of the HO back-off timer is earlier, after the HO back-off timer ends, the trigger request message for triggering the Attach procedure by the UE 100 (for example, NAS (Non Access Signal) ) To the UE 100 (step S608 in FIG. 6).

If the source SGSN 121 clearly uses the HO back-off timer without receiving the MM back-off timer from the UE 100 in step S6021, the source SGSN 121 indicates an instruction to use the HO back-off timer, for example. The UE 100 does not need to store the MM back-off timer in the Attach request in step S6021 if it is possible to determine whether to use the HO back-off timer according to the presence or absence of the flag. In this case, the process of comparing the end time between the MM Back-off timer and the HO Back-off timer by the source SGSN 121 in step S607 can also be omitted, and the source SGSN 121 performs step S608 after the completion of the HO Back-off timer. , A Trigger request message is transmitted to the UE 100. Further, even when the source SGSN 121 receives a normal Attach request in step S6021, a flag that explicitly indicates that the MM back-off timer and the HO back-off timer are used for the Attach request. Even when the HO back-off timer is terminated, a Trigger request may be transmitted to the UE 100.

Upon receiving the Trigger request message in step S608, the UE 100 transmits an Attach request to the target MME 120 via the E-UTRAN 114, and establishes a PDN connection with the PGW 140 via the E-UTRAN 114 (step S609 in FIG. 6). The process executed in step S609 is a normal Attach procedure, and specifically, a series of processes illustrated in FIG. 12 is executed (here, a detailed description of the normal Attach procedure in FIG. 12 is given). (Omitted).

In addition, when the UE 100 transmits an Attach request via the E-UTRAN 114 in step S609, the waiting time (MM back-off timer) notified from the MME 120 in step S601 in FIG. 6 has not yet ended. The UE 100 disables the MM back-off timer (stop / ignore / pause, etc.) so that the Attach request can be transmitted.

In addition, the target MME 120 generally notifies the UE SG 100 of the MM back-off timer (step S601) and the source SGSN 121 to determine the length of the back-off timer according to the overload state. The length of the waiting time is different from the HO back-off timer (step S606). For example, when the overload state when the HO back-off timer is notified to the source SGSN 121 is more relaxed than the overload state when the UE 100 notifies the MM back-off timer, The end time of the HO back-off timer may be earlier than the end time of the MM back-off timer. In such a case, the source SGSN 121 transmits a trigger request to the UE 100 in step S608, and the UE 100 After waiting for only the HO back-off timer notified from the target MME 120 to the source SGSN 121, the Attach request is transmitted via the E-UTRAN 114, and the E-UTRAN It is possible to establish a PDN connection via 14.

Next, the configuration of the UE in the first embodiment of the present invention will be described with reference to FIG. FIG. 7 is a diagram illustrating an example of a configuration of the UE in the first embodiment of the present invention. In FIG. 7, a UE 100 is connected to a network (for example, E-UTRAN 114 or UTRAN 115) to perform communication processing in a lower layer and packet communication processing such as IP in an upper layer, mobility management and communication path Communication control unit 702 that performs management (for example, PDN connection established with PGW 140, QoS control for EPS bearer, etc.) and RAT (for example, E-UTRAN 114 and UTRAN 115), wait time received from the network (for example, , MM back-off timer, etc.) and at least a timer control unit 703 for measuring time based on the waiting time. When the communication control unit 702 has the function of the timer control unit 703, the timer control unit 703 can be omitted. Further, when the timer control unit 703 exchanges information with only the communication control unit 702, only a direct link may be provided between the timer control unit 703 and the communication control unit 702.

Specifically, the communication control unit 702 illustrated in FIG. 7 creates and processes a message for connecting to the E-UTRAN 114 and the UTRAN 115 (for example, extracts information such as an MM back-off timer from the message). To establish a connection with the E-UTRAN 114 and the UTRAN 115. Furthermore, the communication control unit 702 extracts information included in, for example, the Trigger indication field illustrated in FIG. 11 and creates and processes a new message (for example, a connection switching process to another RAT). It is also possible to determine whether or not to perform.

Note that the UE 100 converts hardware (for example, a message or a packet) into an electrical signal or modulates and demodulates a signal that is physically connected to the network (for example, to communicate with the network). Interface), an integrated circuit for realizing the functions of the UE 100, or a processor capable of executing software (program). The functions for connecting to the network (transmission of connection requests and connection establishment) and the functions for determining whether or not to perform connection requests or connection establishment (functions included in the communication processing unit 701 or the communication control unit 702) are as described above. It may be realized by hardware, or may be realized by causing a processor to execute a program. Further, the UE 100 may have a memory for temporarily storing information, and information such as an MM back-off timer may be temporarily stored in the memory. Further, the timer control unit 703 may be realized by hardware as described above, or may be realized by causing a processor to execute a program.

Next, the UE 100 having the configuration shown in FIG. 7 will be described in detail with reference to FIG. 8, focusing on the characteristic processing in the present invention. FIG. 8 is a flowchart showing an example of the operation of the UE in the first embodiment of the present invention.

The UE 100 transmits an Attach request in order to establish a PDN connection via the E-UTRAN 114 (step S801 in FIG. 8). However, the UE 100 receives the Attach reject message for the Attach request because the MME 120 that has received the Attach request is in an overload state. At this time, the MME 120 stores the MM back-off timer in the Attach reject message in order to avoid the Attach request transmitted from the UE for a certain period of time (step S802 in FIG. 8).

Subsequently, the UE 100 confirms whether or not the Attach request can be transmitted via the UTRAN 115 (for example, the setting information of the UE 100 (for example, the RAN priority information (for example, the E-UTRAN 114 is the UTRAN 115 with the high priority)). For example, a medium priority, etc.) or a file showing accessible RAT Type), or whether it is located within the UTRAN 115 cover area). That is, the UE 100 confirms whether or not an Attach request message can be transmitted via the UTRAN 115 (step S803 in FIG. 8).

If the Attach request can be transmitted via the UTRAN 115, the UE 100 stores the MM back-off timer received via the E-UTRAN 114 in the Attach request that is transmitted via the UTRAN 115, and the Attach with the MM back-off timer inserted. Request is transmitted (step S804 in FIG. 8). And UE100 establishes a PDN connection between PGW140 by receiving an Attach accept message from SGSN121 via UTRAN115 (Step S805 of Drawing 8).

Here, in the state where the PDN connection is established via the UTRAN 115, the Inter-RAT HO is triggered on the network side based on the network operator policy. However, since the handover target MME 120 is overloaded, It is assumed that a request message (for example, Forward Relocation Request) from the SGSN 121 is rejected. At this time, the target MME 120 stores the reply time (HO back-off timer) in a rejection message (for example, Forward Relocation Response) and returns it to avoid retransmission of the request message from the source SGSN 121 for a certain period of time. . The source SGSN 121 compares the end times of the HO back-off timer received from the target MME 120 and the MM back-off timer received from the UE 100 in step S802. If the source SGSN 121 determines that the end time of the HO back-off timer is earlier, the UE 100 receives a trigger request message from the source SGSN 121 after the end of the HO back-off timer (step S806 in FIG. 8). .

The UE 100 that has received the Trigger request transmits the Attach request again via E-UTRAN (step S807 in FIG. 8). Since the UE 100 receives the Trigger request after transmitting the HO back-off timer and transmits the Attach request, the target MME 120 is likely to have an overloaded state (and further communicates with the UE 100). It ’s likely that you have resources.) When the target MME 120 accepts an Attach request from the UE 100, a PDN connection is established between the UE 100 and the PGW 140 via the E-UTRAN 114.

Note that if the Attach request cannot be transmitted via the UTRAN 115 in step S803, the UE 100 waits until the MM back-off timer ends (step S808 in FIG. 8), and ends the MM back-off timer. Thereafter, the Attach request is transmitted again via the E-UTRAN 114 (step S807 in FIG. 8).

Further, as described above, the UE 100 inserts a flag explicitly indicating that the HO back-off timer is used without inserting the MM back-off timer into the Attach request message transmitted in step S804. In addition, a normal Attach request message may be transmitted.

Next, the configuration of the source SGSN in the first embodiment of the present invention will be described with reference to FIG. FIG. 9 is a diagram illustrating an example of the configuration of the source SGSN according to the first embodiment of the present invention. In FIG. 9, the source SGSN 121 performs communication processing on the UTRAN 115, a communication processing unit 901 that performs packet communication processing such as IP, a HO back-off timer transmitted from the target MME 120, and an MM back− transmitted from the UE 100. The timer comparison unit 902 that compares the end time of the off timer, the NAS message generation unit 903 that generates the trigger request message to be transmitted to the UE 100 when it is determined that the HO back-off timer ends earlier, and the UE 100 has transmitted It has at least a communication control unit 904 that manages the mobility of the UE 100 such as Attach request. When the NAS message generation unit 903 retains the function of the timer comparison unit 902, the timer comparison unit 902 can be omitted. The reverse is also possible. Similarly, when the communication control unit 904 holds the functions of the NAS message generation unit 903 and the timer comparison unit 902, the NAS message generation unit 903 and the timer comparison unit 902 can be omitted.

Specifically, the communication control unit 904 illustrated in FIG. 9 creates and processes a message for enabling the UE 100 to connect to the network (for example, extracts information such as an MM back-off timer from the message). Etc.) to establish a connection with the UE 100. Further, the communication control unit 904 has a function of executing Inter-RAT Handover procedure.

Note that the source SGSN 121 converts hardware (for example, a message or a packet) to be electrically connected to the network (for example, to perform communication with the network), or performs signal modulation and demodulation. Interface), an integrated circuit for realizing the function of the source SGSN 121, or a processor capable of executing software (program). Function for managing connection to the network by UE 100 (establishing network connection by UE 100), function for executing Inter-RAT Handover procedure, function for determining whether or not to accept a connection request from UE 100, function for processing communication messages ( The functions included in the communication processing unit 901, the NAS message generation unit 903, and the communication control unit 904) may be realized by hardware as described above, or may be realized by causing a processor to execute a program. . The source SGSN 121 may have a memory for temporarily storing information, and may temporarily store information such as the MM back-off timer and the HO back-off timer in the memory. Further, the timer comparison unit 903 may be realized by hardware as described above, or may be realized by causing a processor to execute a program.

In the description of the first embodiment of the present invention, it is mainly assumed that Inter-RAT HO is performed from UTRAN 115 to E-UTRAN 114. However, when Inter-RAT HO is performed from E-UTRAN 114 to UTRAN 115, The configuration in FIG. 9 is applied to the MME 120.

Next, the SGSN 121 having the configuration shown in FIG. 9 will be described in detail with reference to FIG. 10, focusing on the characteristic processing in the present invention. FIG. 10 is a flowchart showing an example of the operation of the SGSN 121 according to the first embodiment of this invention.

The SGSN 121 receives the Attach request in which the MM back-off timer is stored from the UE 100 (step S1001 in FIG. 10). The SGSN 121 confirms the operator policy and the load state (confirms that it is not an overload state), and if it can accept the Attach request, it returns an Attach accept to the UE 100 (Step S1002 in FIG. 10). As a result, a PDN connection is established between the UE 100 and the PGW 140 via the UTRAN 115.

Here, it is assumed that the UTRAN 115 determines that the E-UTRAN 114 causes the Inter-RAT HO for the PDN connection of the UE 100 based on the policy of the operator of the UTRAN 115. In this case, the source SGSN 121 receives an Inter-RAT HO request message (for example, Relocation Required) from the source RNC 112 (step S1003 in FIG. 10).

The source SGSN 121 that has received the Inter-RAT HO request message transmits an Inter-RAT HO request message (for example, Forward Relocation Request) to the target MME 120 (step S1004 in FIG. 10).

Here, since the target MME 120 is overloaded, it is assumed that the Inter-RAT HO request message is rejected. At this time, in order to avoid retransmission of the request message from the source SGSN 121 for a certain time, the target MME 120 sets a waiting time (HO back-off timer) as a rejection message (for example, “No resource available” disclosed in Non-Patent Document 5). The SGSN 121 receives this refusal message (step S1005 in FIG. 10). The SGSN 121 stores the response in the Forward Relocation Response) in which a parameter indicating “or“ Relocation failure ”is stored.

The source SGSN 121 that has received the rejection message (for example, Forward Relocation Response) in which the HO back-off timer is stored compares the end times of the HO back-off timer and the MM back-off timer received from the UE 100 in step S1001. (Step S1006 in FIG. 10).

If it is determined that the end time of the HO back-off timer is earlier than the end time of the MM back-off timer, the source SGSN 121 performs an Attach procedure via the E-UTRAN 114 by the UE 100 after the HO back-off timer ends. A request message (for example, Trigger request) for triggering is transmitted (step S1007 in FIG. 10).

If it is determined in step S1006 that the end time of the HO back-off timer is later than the end time of the MM back-off timer, the source SGSN 121 ends the process. In this case, the UE 100 can transmit an Attach request via the UTRAN 115 after the MM back-off timer ends (that is, earlier than the end time of the HO back-off timer). In addition, as described above, when it is clear that the source SGSN 121 uses the HO back-off timer without receiving the MM back-off timer from the UE 100 in step S1001 (for example, the HO back-off timer is used). (It is possible to determine whether to use the HO back-off timer by the presence or absence of a flag indicating an instruction to use), and the processing of comparing the end time between the MM Back-off timer and the HO Back-off timer by the source SGSN 121 in step S1006 is omitted. The source SGSN 121 transmits a Trigger request message to the UE 100 in step S608 after the HO Back-off timer ends.

Further, as described above, the description of the first embodiment of the present invention mainly assumes Inter-RAT HO from UTRAN 115 to E-UTRAN 114, but Inter-RAT from E-UTRAN 114 to UTRAN 115. When HO is executed, the processing flow of FIG. 10 is applied to the MME 120.

Next, in step S1007 of FIG. 10, as an example of a request message (Trigger request) configuration transmitted from the source SGSN 121 to the UE 100 in order to trigger the Attach procedure performed via the E-UTRAN of the UE 100, FIG. An example of the format of the request message will be described.

FIG. 11 includes a “conventional NAS message field” in which information necessary for general NAS signaling is stored, and a “Trigger indicator field” for triggering the UE's Attach procedure. In the Trigger indicator field, information indicating that the UE 100 can transmit an Attach request via the E-UTRAN 114 (information for instructing connection switching) is stored.

Note that, for example, using the messages (Relocation Command and HO from UTRAN Command) transmitted from the source SGSN 121 to the UE 100 via the source RNC 112 in Step S301 and Step S302 of FIG. 3, the Attach request transmission of the UE 100 is triggered. May be. Further, NAS signaling disclosed in Non-Patent Document 3 (for example, Downlink NAS Transport, EMM INFORMATION message, EMM STATUS message, etc.) may be used to trigger the Attach request to the UE 100. Also, for example, as disclosed in

Non-Patent Documents

1, 2, and 4, a paging message is transmitted from the SGSN 121 via the UTRAN 115 to instruct the UE 100 to perform an Attach request transmission process. Also good. For example, the UE 100 may be instructed to read the information stored in the system information in the paging message, and an instruction to transmit the Attach request may be stored in the system information.

As described above, according to the first embodiment of the present invention, when the Inter-RAT HO procedure is rejected, the Inter-RAT HO procedure has a high processing load on the network device and a large number of messages to be exchanged. Instead, it is possible to realize switching of the RAT by the Attach procedure where the processing load of the network device is lower and the number of exchanged messages is smaller. Specifically, Inter-RAT HO procedure (see Fig. 5) requires a minimum of 18 steps (additional additional steps exist), whereas Attach procedure (see Fig. 12) requires a maximum of 17 steps. It is possible to realize connection to the RAT (RAT switching). Furthermore, according to the first embodiment of the present invention, when the end time of the HO back-off timer is earlier than the end time of the MM back-off timer, the RAT is switched according to the HO back-off timer. As a result, more rapid RAT switching can be realized.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. Hereinafter, an example of the system operation in the second exemplary embodiment of the present invention will be described in detail with reference to FIG. FIG. 13 is a sequence diagram for explaining an example of a system operation (handover case from UTRAN 115 to E-UTRAN 114) according to the second embodiment of the present invention. As in the first embodiment of the present invention, the device used by the UE 100 before the Inter-RAT handover procedure is prefixed with the word “Source” (for example, the device name). , The source SGSN 121), and the device that the UE 100 intends to use in the network after the Inter-RAT handover procedure, the word “Target” is attached before the device name (for example, the target MME 120). The second embodiment of the present invention is based on the first embodiment of the present invention and will be described focusing on differences.

Since steps S1301 to S1307 in FIG. 13 are the same as steps S601 to S607 in FIG. 6 in the first embodiment of the present invention, description thereof will be omitted.

When the source SGSN 121 determines that the end time of the HO back-off timer is earlier than the end time of the MM back-off timer, the source SGSN 121 inserts the HO back-off timer into the Trigger request message and transmits it to the UE 100 (FIG. 13). Step S1308). After receiving the Trigger request message, the UE 100 confirms information related to transmission / reception data (for example, the remaining amount of data transmitted or received by the UE 100 (for example, a state where data transmission is completed in the remaining few seconds)). The optimal RAN (E-UTRAN 114 or UTRAN 115) is selected (step S1309 in FIG. 13).

In the second embodiment of the present invention, the source SGSN 121 sends the Trigger request message with the HO back-off timer inserted to the UE 100 at an arbitrary timing (for example, immediately after acquiring the HO back-off timer). You may send it. Thereby, the UE 100 refers to the HO back-off timer stored in the Trigger request message, for example, the time until the Attach accept can be transmitted via the E-UTRAN 114 (the HO back-off timer End time). Further, it is predetermined that the source SGSN 121 transmits a Trigger request message after the HO back-off timer ends, or “Trigger indication” shown in FIG. 11 as in the first embodiment of the present invention is set. When stored, the Trigger back request message need not necessarily include the HO back-off timer. In this case, the UE 100 can recognize that the HO back-off timer has already ended by receiving the Trigger request message.

Since the UE 100 is currently communicating by establishing a PDN connection via the UTRAN 115, the UE 100 can transmit an Attach accept via the E-UTRAN 114 and / or information related to transmission / reception data ( In consideration of the remaining amount of data to be transmitted or received), it may be selected to send Attach accept to E-UTRAN 114 again to establish a connection via E-UTRAN 114, or to continue to connect to UTRAN 115 May be. For example, when the remaining amount of data transmitted by the UE 100 is very small (for example, the state in which data transmission is completed in the remaining few seconds), even if the Attach procedure is performed via the E-UTRAN 114, the load on the UE 100 and the network side as a result However, in such a case, it is possible to suppress an increase in load by selecting that the UE 100 continues to connect to the UTRAN 115.

In addition, as information used when the UE 100 selects an optimal RAN, the RAN priority information held by the UE 100 (for example, E-UTRAN 114 is a high priority and UTRAN 115 is a medium priority, etc.) Optimal RAN using available priority information, information statically held by the UE 100, information assigned by network operators (eg, GBR (Guaranteed Bit Rate) or QCI (QoS Class Identifier)), etc. (RAT) may be selected.

In addition, when the UE 100 selects to send an Attach request via the E-UTRAN 114, the UE 100 indicates that the UE 100 is rejected in the Inter-RAT HO procedure started between the source SGSN 121 and the target MME 120. Therefore, a UE identifier may be generated (step S1310 in FIG. 13). This UE identifier can be inserted into the Attach request transmitted in Step S1311 described later, and the target MME 120 that has received the Attach request refers to the UE identifier in the Attach request, and rejects the UE 100 with the Inter-RAT HO procedure. And the correlation (that is, the same) with the UE 100 that is the transmission source of the Attach request may be recognized. The MME 120 recognizes the correlation between the UE 100 rejected by the Inter-RAT HO procedure and the UE 100 that is the transmission source of the Attach request, so that the MME back-off timer is not terminated due to the reason that the MM back-off timer has not ended. Without rejection, it is possible to identify that the target of the communication resource secured after the end of the HO back-off timer is the UE 100 that is the transmission source of the Attach request, and accept the Attach request.

The UE 100 is also used in UE-specific information such as IMSI (International Mobile Subscriber Identity), IMEI (International Mobile Equipment Identity), IP address, etc. as Inter-RAT HO procedure, and MME 120 is Inter- If the information that can identify the UE 100 that rejected the RAT HO procedure is stored in the conventional Attach request by a general process, there is no need to store it, so step S1310 can be omitted.

Also, the UE 100 may generate a UE identifier using information stored in the Trigger request message (information notified from the source SGSN 121). For example, in the message exchange (Inter-RAT HO procedure processing) executed between the source SGSN 121 and the target MME 120, the source SGSN 121 shares some information (hereinafter referred to as token information) with the target MME 120, and By notifying the token information to the UE 100, the UE 100 may generate a UE identifier based on the token information. By inserting the UE identifier based on the token information into the Attach request transmitted in Step 1311 described later, the target MME 120 that confirms the Attach request, the UE 100 rejected by the Inter-RAT HO procedure, and the transmission source of the Attach request It is possible to recognize the correlation (that is, it is the same) with UE100 which is.

The UE 100 that has received the Trigger request message in step S1308 transmits the Attach request to the target MME 120 via the E-UTRAN 114 and establishes a PDN connection with the PGW 140 via the E-UTRAN 114 (step 13 in FIG. 13). Step S1311).

When the UE 100 transmits an Attach request via the E-UTRAN 114 in step S1311, the waiting time (MM back-off timer) notified from the MME 120 in step S1301 in FIG. The UE 100 disables the MM back-off timer (stop / ignore / pause, etc.) so that the Attach request can be transmitted.

Next, the configuration of the UE in the second embodiment of the present invention will be described with reference to FIG. FIG. 14 is a diagram illustrating an example of a configuration of the UE according to the second embodiment of the present invention. In FIG. 14, a UE 100 is connected to a network (for example, E-UTRAN 114 or UTRAN 115) to perform communication processing in a lower layer and packet communication processing such as IP in an upper layer, mobility management and communication path Communication control unit 1402 for performing management (for example, PDN connection established with PGW 140, QoS control for EPS bearer, etc.), RAT (for example, E-UTRAN 114 or UTRAN 115), waiting time received from network (for example, In addition to the timer control unit 1403 that manages the MM back-off timer, etc., the optimal RAT (E-UTRAN 114 or UTRAN 115) is selected by checking information related to transmission / reception data, for example. At least with UE identifier generating unit 1405 T selection processing section 1404, Inter-RAT HO procedure generates information indicating that the UE100 was rejected. The communication processing unit 1401, the communication control unit 1402, and the timer control unit 1403 illustrated in FIG. 14 are basically the same as the communication processing unit 701, the communication control unit 702, and the timer control unit 703 illustrated in FIG. These functions may be realized by hardware, or may be realized by causing a processor to execute a program. Similarly, the optimum RAT selection processing unit 1404 and the UE identifier generation processing unit 1405 may be realized by hardware, or may be realized by causing a processor to execute a program.

If the communication control unit 1402 has the function of the optimum RAT selection processing unit 1404, the optimum RAT selection processing unit 1404 can be omitted. The same applies to other processing units. For example, when the optimum RAT selection processing unit 1404 exchanges information with only the communication control unit 1402, only a direct link may be provided between the optimum RAT selection processing unit 1404 and the communication control unit 1402.

Specifically, the communication control unit 1402 illustrated in FIG. 14 creates and processes a message for connecting to the E-UTRAN 114 and the UTRAN 115 (for example, extracts information such as an MM back-off timer from the message). To establish a connection with the E-UTRAN 114 and the UTRAN 115. Further, the communication control unit 702 or the optimum RAT selection processing unit 1404 extracts information included in the Trigger indicator field shown in FIG. 16, for example, and creates and processes a new message (for example, another message). It is also possible to determine whether or not to perform a connection switching process to the RAT.

Next, the UE having the configuration shown in FIG. 14 will be described in detail with reference to FIG. 15, focusing on the characteristic processing in the present invention. Note that steps S1501 to S1505 (until Attach accept is received) in FIG. 15 are the same as steps S801 to S805 in FIG.

Subsequently, the UE 100 receives a trigger request including a HO back-off timer (step S1506 in FIG. 15). The UE 100 that has received the trigger request confirms, for example, the HO back-off timer and / or information related to transmission / reception data, and selects the optimum network (E-UTRAN 114 or UTRAN 115) (step in FIG. 15). S1507).

When the selected optimal RAN is a network to which the UE 100 is to be connected (in the second embodiment of the present invention, the E-UTRAN 114), the UE 100 is the UE 100 that is rejected in the Inter-RAT HO procedure. A UE identifier indicating that the UE 100 is rejected in step S1306 in FIG. 13 is generated (step S1508 in FIG. 15). Note that UE100 also uses UE-specific information such as IMSI (International Mobile Subscriber Identity), IMEI (International Mobile Equipment Identity), IP address, etc., as Inter-RAT HO Procedure. If the information that can identify the UE that rejected the RAT HO procedure is stored in the conventional Attach request by a general process, there is no need to store it, so step S1508 can be omitted.

And UE100 transmits Attach request which stored the information (UE identifier) which can identify UE100 via E-UTRAN114 (Step S1509 of Drawing 15). Note that the UE 100 needs to transmit the Attach request in step S1509 after waiting for at least the HO back-off timer to end. When the MME 120 accepts the Attach request, the general Attach procedure is continued, and the PDN connection is established between the UE 100 and the PGW 140 via the E-UTRAN 114.

Further, for example, regarding the UE 100 rejected in the Inter-RAT HO procedure, the MME 120 may reserve communication resources for the UE 100 after the HO back-off timer. When the UE identifier is stored in the Attach request, the MME 120 uses the UE identifier to make the UE 100 that rejects the Inter-RAT HO procedure (the UE 100 that has secured the communication resource after the HO back-off timer). It becomes possible to recognize that there is.

Next, in step S1308 of FIG. 13, a request message (Trigger request) storing a HO back-off timer transmitted from the source SGSN 121 to the UE 100 to trigger an Attach procedure performed via the E-UTRAN of the UE. ) As an example of the configuration, a request message format example will be described with reference to FIG.

FIG. 16 shows a target in addition to the “conventional NAS message field” in which information necessary for general NAS signaling shown in FIG. 11 is stored and the “Trigger indicator field” for triggering the Attach procedure of the UE. It is composed of a “HO back-off timer field” for storing a waiting time received from the MME 120 (for example, a HO back-off timer). If the UE 100 can recognize that the Attach procedure by the UE 100 is triggered only by the HO back-off timer field, the Trigger indication field can be omitted. Similarly, in the HO back-off timer field, when the source SGSN 121 transmits this Trigger request to the UE 100 after the HO back-off timer elapses, the HO back-off timer field can be omitted. Further, as described above, the source SGSN 121 may notify the UE 100 of token information that can be used to generate a UE identifier, and a field for storing this token information may be provided.

Further, as an example of an Attach request configuration that the UE 100 transmits via the E-UTRAN 114 in Step S1311 in FIG. 13, an example format of the Attach request will be described with reference to FIG.

FIG. 17 shows a “conventional Attach request message field” in which information necessary for a general Attach request is stored, and the target device (for example, the target MME 120) is the UE 100 that rejects the Inter-RAT HO procedure. It consists of a “UE identifier field” for storing a UE identifier for identifying the ID. In addition, when there is information that can identify the UE 100 in the conventional Attach request message field (for example, when the target MME 120 identifies the UE 100 that rejects the Inter-RAT HO procedure by the IMSI, and the IMSI is included in the Attach request. If stored), the UE identifier field can be omitted.

As described above, according to the second embodiment of the present invention, as in the first embodiment of the present invention, when Inter-RAT HO procedure is rejected, the processing load on the network device is high, and RAT switching can be realized not by Inter-RAT HO procedure with a large number of messages to be exchanged but by Attach procedure with a lower processing load on the network device and a smaller number of messages to be exchanged. Further, according to the second embodiment of the present invention, when the end time of the HO back-off timer is earlier than the end time of the MM back-off timer, as in the first embodiment of the present invention. By switching the RAT according to the HO back-off timer, the RAT can be switched more quickly. Furthermore, according to the second embodiment of the present invention, the UE 100 can perform RAT switching timing (for example, the HO back-off timer end time) and transmission / reception data related information (for example, the UE 100 can transmit or receive). By selecting the optimum RAT in consideration of a small amount of remaining data (for example, a state in which data transmission is completed in the remaining few seconds), there is no extra load on both the UE 100 and the network side. The RAT can be switched. Further, according to the second embodiment of the present invention, the network side (for example, the target MME 120) identifies the UE 100 rejected by the Inter-RAT HO procedure and the UE 100 that is the transmission source of the Attach request. Thus, it becomes possible to recognize the correlation (that is, the same) between the UE 100 rejected by the Inter-RAT HO procedure and the UE 100 that is the transmission source of the Attach request.

In the present specification, the present invention has been described by dividing it into the first embodiment and the second embodiment, but the technical features disclosed in each embodiment may be combined. . For example, the UE identifier may be used in the first embodiment of the present invention. Accordingly, in the first embodiment, the target MME 120 rejects the Inter-RAT HO procedure with the UE 100 and the Attach request. You may enable it to recognize the correlation (that is, it is the same) with UE100 which is a transmission source.

Also, the functional blocks used in the description of the above-described embodiment of the present invention are typically realized as an LSI (Large Scale Integration) that is an integrated circuit. These may be individually made into one chip, or may be made into one chip so as to include a part or all of them. Here, LSI is used, but depending on the degree of integration, it may be called IC (Integrated Circuit), system LSI, super LSI, or ultra LSI.

Also, the method of circuit integration is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array) that can be programmed after manufacturing the LSI or a reconfigurable processor that can reconfigure the connection and setting of circuit cells inside the LSI may be used.

Furthermore, if integrated circuit technology that replaces LSI emerges as a result of advances in semiconductor technology or other derived technology, it is naturally also possible to integrate functional blocks using this technology. For example, biotechnology can be applied.

The present invention has an effect of efficiently connecting to a network to be handed over when a handover (Inter-RAT Handover) is rejected and a waiting time (HO back-off timer) is generated with respect to connection of a communication node (UE). At that time, it has the effect of performing processing with a small processing load and a small number of messages to be exchanged, and connecting to a network using a different RAT (Radio Access Technology: radio access technology). It can be applied to a communication technology for performing communication by switching between.

Claims

A communication node configured by first and second networks using different radio access technologies, and connected to a communication system for handing over the connection of the communication node between the first network and the second network,
A first connection request transmitter for transmitting a first connection request to the first network;
Connection until the first connection request can be retransmitted to the first network when the first connection request to the first network by the first connection request transmission unit is rejected. A waiting time acquisition unit for acquiring a request waiting time;
A second connection request transmitter for transmitting a second connection request to the second network when the first connection request to the first network by the first connection request transmitter is rejected;
A connection establishment unit for establishing a connection with the second network;
The second network sends a handover request for handing over the connection established with the communication node to the first network, and the first network rejects the handover request. And switching the connection to the first network transmitted from the second network when notifying the second network of a handover waiting time until a handover request can be retransmitted to the first network. A message receiver for receiving a trigger message including an instruction;
A determination unit that determines whether the first connection request transmission unit retransmits the first connection request to the first network based on the trigger message received by the message reception unit;
Having communication nodes.
The communication node according to claim 1, wherein the second connection request transmission unit notifies the second network of the connection request waiting time together with the transmission of the second connection request.
The second connection request transmission unit includes information indicating that the handover waiting time is used when the handover request from the second network to the first is rejected together with the transmission of the second connection request. The communication node according to claim 1, which notifies the second network.
The communication node according to claim 1, wherein the trigger message is transmitted from the second network after expiration of the handover standby time.
The communication node according to claim 1, wherein the message receiving unit receives the trigger message further including the handover waiting time.
When the message reception unit receives the trigger message further including the handover waiting time, the determination unit compares the connection request waiting time with the handover waiting time, and re-establishes the first connection request. The communication node according to claim 5, which decides to transmit.
The determination unit determines whether to retransmit the first connection request based on a remaining amount of data transmitted or received using the connection established with the second network. The communication node according to claim 1.
The first connection request transmission unit notifies the identification information indicating the relevance with the handover request rejected by the first network together with the retransmission of the first connection request to the first network. The communication node according to claim 1.
Having a timing unit for timing the connection request waiting time acquired by the waiting time acquisition unit;
2. The communication node according to claim 1, wherein the first connection request transmission unit invalidates timing by the timing unit when the determination unit determines to retransmit the first connection request.
A network located in the second network in a communication system configured by first and second networks using different radio access technologies and handing over connection of a communication node between the first network and the second network A node,
A connection request receiving unit that receives a second connection request to the second network from the communication node in which the first connection request to the first network is rejected;
A connection response transmitting unit that transmits a connection response indicating acceptance of the second connection request to the second network by the communication node to the communication node;
A handover request transmitter for transmitting a handover request for handing over a connection established with the communication node to the first network, to the first network;
A handover standby time acquisition unit that acquires a handover standby time until the handover request can be retransmitted to the first network when the first network rejects the handover request;
A message transmitting unit that transmits a trigger message including a connection switching instruction to the first network to the communication node;
Have network nodes.
The connection request receiving unit receives, together with the second connection request, a connection request waiting time until the communication node can retransmit the first connection request to the first network. The network node according to 10.
The network node according to claim 10, wherein the message transmission unit transmits the trigger message after expiration of the handover standby time.
The network node according to claim 10, wherein the message transmission unit transmits the trigger message further including the handover waiting time.
A time comparison unit that compares the connection request standby time with the handover standby time, and instructs the message transmission unit to transmit the trigger message when the handover standby time ends earlier than the connection request standby time. The network node according to claim 11, comprising:
The connection request receiving unit receives, together with the second connection request, information indicating that the handover waiting time is used when the handover request from the second network to the first network is rejected. Item 11. The network node according to Item 10.