1. A first node provided in a communication system that provides mobility of packet data using tunneling, the first node comprising: 5 a tunnel control unit that releases a tunnel and deletes tunnel information; and a management unit that associates and manages an IP address allocated to a terminal to which the tunnel is established and subscriber identification infoiTnation of the terminal when the tunnel is released and the tunnel information is deleted. 10 2. A communication system comprising the first node according to claim 1.

3. The communication system according to claim 2, comprising a second node to which the tunnel is established with the first node, wherein the second node releases information about the tunnel and information about the terminal connected to the tunnel 15 when the tunnel is released.

4. The communication system according to claim 3, wherein the second node is selected again every time a recovery process of the tunnel is performed. 20 5. The communication system according to any one of claims 2 to 4, wherein the first node is a node serving as an anchor point that provides mobility of the terminal for a predetermined packet data network.

6. The communication system according to any one of claims 2 to 5, comprising a 25 third node that accommodates the terminal, wherein the third node performs a recovery OPdGrn^^ i 4 # \ 4 t x^^t% process of the tunnel using the IP address allocated to the terminal before the tunnel is released and information designating the first node when the released tunnel is recovered with transmission from the terminal as a trigger. 5 7. The communication system according to claim 6, wherein the first node issues the IP address to the terminal using the IP address again that has been notified from the third node and allocated to the terminal before the tunnel is released.

8. The communication system according to claim 6 or 7, comprising a fourth node 10 that identifies the third node in which the terminal is accommodated, wherein the first node performs a recovery process of the tunnel by inquiring the fourth node about the third node that accommodates the terminal when there is reception for the terminal after the tunnel established for the terminal is released. 15 9. A communication method for providing mobility of packet data using tunneling, the method comprising: releasing, by a first node, a tunnel and deleting tunnel information; and associating and managing, by the first node, an IP address allocated to a terminal to which the tunnel is established and subscriber identification information of the 20 terminal when the tunnel is released and the tunnel information is deleted.

10. A communication program that provides mobility of packet data using tunneling, the communication program causing a computer of a first node to execute: a step of releasing a tunnel and deleting tunnel information; and 25 a step of associating and managing an IP address allocated to a terminal to which IH^^" 26 ( \ ^ 4\^ 1,3 ft» the tunnel is established and subscriber identification information of the terminal when the tunnel is released and the tunnel information is deleted.

2
DESCRIPTION
TITLE OF INVENTION: COMMUNICATION SYSTEM, COMMUNICATION
METHOD, AND COMMUNICATION PROGRAM
5
TECHNICAL FIELD
[0001]
The present invention relates to a communication system, a communication
method, and a communication program.
10
BACKGROUND ART
[0002]
In an EPC disclosed in, for example, Non-Patent Document 1, which is a
standard related to an E-UTRAN (this term will be described later; the same applies to
15 other terms throughout this paragraph), Always-On in which each GW maintains a tunnel
is assumed. Thus, resources of a core network are necessary for the number of bearers
to be established by a UE, which is a mobile terminal or the like. For this reason, the
establishment of a tunnel and the assignment of an IP address are performed every time
transmission from the UE is performed when the tunnel of the core network is released,
20 and thus there is a possibility that the IP address issued to the UE is changed every time.
In addition, it is impossible to notify the UE of reception when the tunnel of the core
network is released.
[0003]
In the above paragraph, E-UTRAN is an abbreviation for an evolved universal
25 mobile telecommunications system (UMTS) terrestrial radio access network and
3
represents one scheme of a radio access network. EPC is an abbreviation for an evolved
packet core and is one scheme of a core network in which various radio access systems
or the like are accommodated. GW is an abbreviation for a gateway and is a node
which connects different types of networks. Here, a node is a logical representation of
5 an apparatus on a network. UE is an abbreviation for user equipment, and represents a
mobile terminal, a radio terminal, or the like. In addition, a tunnel refers to a virtual
communication line implemented using encapsulation or the like. Always-On refers to
a continuous Internet protocol (IP) connection. A core network refers to a portion
which does not depend upon radio access in an overall network system. A bearer refers
10 to a logical packet transfer path established between nodes.
[0004]
On the other hand, in a UMTS terrestrial radio access network (UTRAN), which
is another scheme of a radio access network described in, for example, Non-Patent
Literature 2, a gateway general packet radio service (GPRS) support node (GGSN)
15 manages UEs and IP addresses in a fixed manner, thereby making it possible to provide
means for establishing a tunnel triggered by reception of a packet addressed to the IP
address of a UE. However, there is a problem in that the UEs and the IP addresses are
managed in a fixed manner, and thus the GGSN available to the UE is limited and it is
necessary to set association information of the target UE and the IP address in the GGSN
20 in advance.
Prior Art Documents
Non-Patent Documents
[0005]
25 Non-Patent Document 1: 3gpp Technical Specification TS 23.401 V10.4.0
4
(2011-06), "3rd Generation Partnership Project; Technical Specification Group Services
and System Aspects; General Packet Radio Service (GPRS) enhancements for Evolved
Universal Terrestrial Radio Access Network (E-UTRAN) access (Release 10)"
Non-Patent Document 2: 3gpp Technical Specification TS 25.401 VI 0.2.0
5 (2011-06), "3rd Generation Partnership Project; Technical Specification Group Radio
Access Network; UTRAN overall description (Release 10)"
SUMMARY OF INVENTION
Problems to be solved by the Invention
10 [0006]
In a network system using the above-described E-UTRAN or UTRAN, it is
necessary to set a tunnel for providing mobility for each UE and maintain the tunnel for
reception. For this reason, it is necessary to install many network facilities. In
addition, because a state in which resources of a serving gateway (SGW) are secured is
15 assumed even when an S1 bearer in which communication is not in progress is released,
there is a problem in that it is impossible to recover the bearer at the time of SGW
failure. Here, SGW is a GW which accommodates various radio access networks such
as the E-UTRAN and performs data transfer with the core network. In addition, the S1
bearer refers to, for example, a bearer between the E-UTRAN and the SGW.
20 [0007]
An exemplary object of the present invention is to provide a communication
system, a communication method, and a communication program capable of solving the
above-described problems.
25 Means for Solving the Problems
5
[0008]
In order to solve the above problems, a first node of the present invention is
provided in a communication system that provides mobility of packet data using
turmeling, and includes: a tunnel control unit that releases a tunnel and deletes tunnel
5 information; and a management unit that associates and manages an IP address allocated
to a terminal to which the tunnel is established and subscriber identification information
of the terminal when the tunnel is released and the turmel information is deleted.
[0009]
Moreover, a communication method of the present invention is a communication
10 method for providing mobility of packet data using tunneling, and the communication
method includes: releasing, by a first node, a turmel and deleting tunnel information; and
associating and managing, by the first node, an IP address allocated to a terminal to
which the tunnel is established and subscriber identification information of the terminal
when the tunnel is released and the tunnel information is deleted.
15 [0010]
Furthermore, a communication program of the present invention is a
communication program that provides mobility of packet data using tunneling and causes
a computer of a first node to execute: a step of releasing a tunnel and deleting tunnel
information; and a step of associating and managing an IP address allocated to a terminal
20 to which the tunnel is established and subscriber identification information of the
terminal when the tunnel is released and the turmel information is deleted.
Exemplary Advantages of the Invention
[0011]
25 The present invention can release a tunnel while securing mobility without
6
securing resources in, for example, an SGW.
BRIEF DESCRIPTION OF DRAWINGS
[0012]
5 FIG. 1 is a network configuration diagram describing a communication system
as an exemplary embodiment of the present invention.
FIG. 2 is a sequence diagram describing an operation when radio resources are
released after a bearer has been established in the communication system of FIG. 1.
FIG. 3 is a sequence diagram describing an operation of a bearer recovery
10 process initiated by a UE in the communication system of FIG. 1.
FIG. 4 is a sequence diagram describing a tunnel recovery process triggered by
reception of an IP packet addressed to a UE in the communication system of FIG. 1.
FIG. 5 is a sequence diagram describing another example of the tunnel recovery
process triggered by the reception of the IP packet addressed to the UE in the
15 communication system of FIG. 1.
FIG. 6 is a diagram collectively illustrating features of the communication
system of FIG. 1.
MODES FOR CARRYING OUT THE INVENTION
20 [0013]
Hereinafter, an exemplary embodiment of a communication system in
accordance with the present invention will be described with reference to drawings.
FIG. 1 illustrates a network configuration diagram representing a communication system
10 serving as the exemplary embodiment of the present invention. The communication
25 system 10 illustrated in FIG. 1 is a communication system which provides mobility of
packet data using tunneling, and is configured to include a UE 1, an E-UTRAN Node B
(eNodeB) (also referred to as an eNB) 2, a mobility management entity (MME) 3, a
home subscriber server (HSS) 4, an SGW 5, a packet data network (PDN) gateway
(PGW) 6, and a PDN 7.
5 [0014]
It is to be noted that the communication system 10 normally includes a plurality
of structural elements (i.e., nodes). In addition, the communication system 10 also
includes, for example, a domain name system (DNS) (not illustrated) to be used when,
for example, the PGW 6 or the like inquires about, for example, an IP address of the
10 MME 3, and a node of a policy and charging rules function (PCRF) which performs
quality of service (QoS) control, charging control, and the like. In addition, an EUTRAN
8 is configured by including the eNodeB 2 illustrated in FIG. 1 and a plurality
of eNodeBs (not illustrated). Furthermore, a reference point SI-MME between the EUTRAN
8 and the MME 3 is defined, and a reference point Sl-U between the E-UTRAN
15 8 and the SGW 5 is defined. In addition, a link passing through the reference point S1 -
MME is used as a control signal interface, and a link passing through the reference point
Sl-U is used as a data transfer interface and a control signal interface. In addition, in
the communication system 10, a core network which does not depend upon radio access
is configured using the SGW 5, the PGW 6, and the like.
20 [0015]
In FIG. 1, the UE 1 is a mobile terminal which supports the E-UTRAN 8.
[0016]
The eNodeB 2 is a node such as a radio base station which manages a radio
connection, and establishes a tunnel of each bearer with the SGW 5 every time the
25 establishment of the radio connection with the UE 1 is performed. In addition, the
8
eNodeB 2 releases the tunnel with the SGW 5 with the release of the radio connection as
a trigger.
[0017]
The MME 3 is a node which performs authentication and mobility management
5 of the UE 1. The MME 3 registers the location of the UE 1 with the HSS 4 when newly
accommodating the UE 1. As a result, the HSS 4 can identify the MME 3 which
accommodates the UE 1. That is, in the present exemplary embodiment, the MME 3
holds attach information (i.e., registration information) of the UE 1, and manages the UE
1 in accordance with 3'^'' Generation Partnership Project (3gpp) standard rules (see, for
10 example, Non-Patent Document 1). In addition, the MME 3 also holds the IP address of
the UE 1 and information (hereinafter referred to as PGW information) about a selected
PGW 6, for example, predetermined for each UE 1, in accordance with the 3gpp standard
rules.
[0018]
15 The HSS 4 is a node which provides a database for managing subscriber data
and holds information of each MME 3 which manages and accommodates each UE 1 and
manages agreement information of each UE 1 or the like in accordance with the 3gpp
standard rules.
[0019]
20 The SGW 5 is a node which ensures the arrival of an IP packet for the UE 1 by
holding the tunnel between the SGW 5 and the PGW 6 and with a radio apparatus such
as the UE 1 in units of bearers.
[0020]
The PGW 6 is a node serving as an anchor point which provides mobility of the
25 UE 1 for the PDN 7, issues an IP address for the UE 1, and forwards an IP packet
9
addressed to the UE 1 to the tunnel established with the SGW 5. In addition, the PGW
6 has a storage apparatus storing information (i.e., a correspondence table of the IP
address of the UE 1 and subscriber identification information) in which the IP address is
associated with the subscriber identification information such as an international mobile
5 subscriber identity (IMSI) (unique identification information allocated to a
communication terminal such as a portable phone or an integrated circuit (IC) card for
the communication terminal) or a mobile station international subscriber directory
number (MSISDN) of the UE 1 to which the IP address is allocated. In addition, the
PGW 6 of the present exemplary embodiment dynamically selects and issues the IP
10 address for the UE 1 at the time of initial attach/bearer establishment of the UE 1 and
holds the association between the UE 1 and the IP address as the above-described
association information. Therefore, it is unnecessary to register the IP address of the
UE 1 in advance.
[0021]
15 The PDN 7 is an IP-based packet network such as an IP multimedia subsystem
(IMS).
[0022]
Because the tunnel between the SGW 5 and the PGW 6 is continuously
maintained in the 3gpp standard rules, the PGW 6 holds the IP address issued to the UE
20 1, the subscriber identification informafion such as the IMSI or the MSISDN of the UE 1,
and tunnel information (i.e., data and resources to be used for establishing and
maintaining the tunnel) between the PGW 6 and the SGW 5. However, in the present
exemplary embodiment, the PGW 6 holds the information in which the IP address is
associated with the subscriber identification information such as the IMSI or the
25 MSISDN of the UE 1 and thus can release the tunnel between the PGW 6 and the SGW
10
5. That is, in the present exemplary embodiment, when the tunnel is released, the PGW
6 holds only the information in which the IP address is associated with the subscriber
identification information such as the IMSI or the MSISDN of the UE 1 without holding
the tunnel information between the PGW 6 and the SGW 5.
5 [0023]
In addition, because the PGW 6 holds the association information (i.e., the
correspondence table) of the IP address and the subscriber identification information
such as the IMSI or the MSISDN of the UE 1, the SGW 5 can release not only the tunnel
related to the UE 1 but also all information including the IP address, the subscriber
10 identification information, and the like related to the UE 1.
[0024]
In the present exemplary embodiment, as described above, when the tunnel
between the PGW 6 and the SGW 5 is released, the PGW 6 holds the association
information of the IP address and the subscriber identification information such as the
15 IMSI or the MSISDN of the UE 1. In addition, the MME 3 holds the IP address of the
accommodated UE 1 and the PGW information in accordance with the 3gpp standard
rules. Therefore, for example, when the MME 3 receives the transmission from the UE
1, that is, a Service Request for an SI recovery via the eNodeB 2, it is possible to recover
the tunnel between the SGW 5 and the PGW 6 using the association information of the IP
20 address and the subscriber identification information of the UE 1 held by the PGW 6
represented by the PGW information by performing a bearer establishment process using
the IP address of each UE 1 and the PGW information held by the MME 3. It is to be
noted that although only one SGW 5 is illustrated in FIG. 1, the SGW 5 to be used during
the tunnel recovery may not necessarily be the same as the SGW 5 used before the tunnel
25 release.
11
[0025]
In addition, when the tunnel between the PGW 6 and the SGW 5 has already
been released and when a reception packet addressed to the UE 1 reaches the PGW 6
from the PDN 7, the PGW 6 can provide a reception notification to the MME 3 by
5 deriving subscriber identification information such as the IMSI from the IP address to
which the reception packet is addressed based on association information between the IP
address and the subscriber identification information such as the IMSI or the MSISDN of
the UE 1, which is held by the PGW 6 itself, and inquiring the HSS 4 about the MME 3
accommodating the UE 1 using the derived subscriber identification information. At
10 this time, it is possible to perform a bearer establishment process using the IP address of
each UE 1 and the PGW information held by the MME 3. That is, at this time, the
tunnel recovery triggered by the SI recovery is possible as in the transmission from the
UEl.
[0026]
15 In this manner, in the communication system 10 of the present exemplary
embodiment, only the association information of the IP address dynamically issued by
the PGW 6 and the subscriber identification information such as the IMSI or the
MSISDN of the UE 1 is stored, and the transmission from the UE 1 and the reception for
the UE 1 are possible when the tunnel between the SGW 5 and the PGW 6 and the
20 association information are released or deleted. Consequently, it is possible to
minimize necessary resources of a core network including the PGW 6, the SGW 5, and
the like and effectively utilize the resources.
[0027]
Next, an example of an operation of the communication system 10 described
25 with reference to FIG. 1 will be described with reference to FIGS. 2 to 5. It is to be
12
noted that because attach (a registration process for a network) and bearer establishment
operations of the UE 1 follow the 3gpp standard rules, a description thereof is omitted.
The attach process follows Item 5.3.2 "Attach procedure" of 3gpp TS 23.401 (Non-
Patent Document 1).
5 [0028]
First, an operation when the radio resource is released after bearer establishment
under the assumption that the bearer establishment operation in accordance with the 3gpp
standard rules has already been performed for a certain UE 1 will be described using
FIG. 2. Here, the operation when the radio resource is released is based on an operation
10 of Item 5.3.5 "SI release procedure" of 3gpp TS 23.401.
[0029]
For example, with initiation of a radio resource release process with the UE 1
triggered by any of various reasons provided as examples in the 3gpp standard rules,
such as that the UE 1 is not used for a predetermined time or more, the eNodeB 2
15 transmits an S1 UE Context Release Request message (hereinafter, the word "message"
will be omitted) to the MME 3 (S101). It is to be noted that the context refers to
information used in a communication path and communication control. In an operation
in accordance with the 3gpp standard rules, the MME 3 receiving the SI UE Context
Release Request performs only tunnel release between the SGW 5 and the eNodeB 2 by
20 transmitting a Release Access Bearers Request to the SGW 5. In the present exemplary
embodiment, imlike the 3gpp standard rules, a Delete Bearer Request is transmitted from
the MME 3 to the SGW 5 (S102). At this time, in order to notify the SGW 5 and the
PGW 6 of the tunnel release process triggered by the radio resource release, the MME 3
sets a "Hold flag" which is a flag newly adopted in the present exemplary embodiment in
25 the Delete Bearer Request.
13
[0030]
The SGW 5 receiving the Delete Bearer Request to which the Hold flag is
attached transmits the Delete Bearer Request to which the Hold flag is attached to the
PGW 6 (SI03), and then performs the turmel release process and the resource release
5 process related to the UE 1 (S104).
[0031]
The PGW 6 receiving the Delete Bearer Request to which the Hold flag is
attached holds only association information of the IP address of the UE 1 and the
subscriber identification information (hereinafter referred to as an IMSI) such as the
10 IMSI, and executes the turmel release with the SGW 5 and other resource release (S105).
[0032]
As a result of the above-described process, the SGW 5 and the PGW 6 release
all the tunnels with the UE 1, the SGW 5 releases all the resources related to the UE 1,
and the PGW 6 holds only the correspondence between the IP address of the UE 1 and
15 the IMSI. It is to be noted that when the PCRF is used, the resources of the PCRF are
also released along with the release processes of the SGW 5 and the PGW 6. In
addition, as described above, the MME 3 holds the IP address of the accommodated UE
1 and the PGW information in accordance with the 3gpp standard rules even after the
tunnel release.
20 [0033]
Thereafter, in accordance with the 3gpp standard rules, a Delete Bearer
Response is transmitted from the PGW 6 to the SGW 5 (S106). Then, the Delete Bearer
Response is transmitted from the SGW 5 to the MME 3 (S107). Next, an S1 UE
context release command is transmitted from the MME 3 to the eNodeB 2 (SI08).
25 Here, when a radio resource control (RRC) connection is not released, the eNodeB 2
14
transmits an RRC Connection Release to the UE 1 (SI09). Upon receiving an
acknowledgement (ACK) from the UE 1, the eNodeB 2 deletes the context of the UE 1
and transmits an SI UE Context Release Complete to the MME 3 (SI 10).
[0034]
5 Next, the operation in the bearer recovery process initiated by the UE 1 will be
described using FIG. 3. This operation is based on an operation of Item 5.3.4.1 "UE
triggered Service Request" of 3gpp TS 23.401.
[0035]
When the MME 3 receives a Service Request from the UE 1 via the eNodeB 2
10 (S201 and S202), a process of authenticating the UE 1 is executed among the UE 1, the
MME 3, and the HSS 4 (S203). Here, in the bearer recovery operation of the 3gpp
standard rules, related tunnel resources remain in the SOW 5 and the PGW 6 after the
authentication process in S203, and thus S204 to S208 of FIG. 3 are skipped, and an
Initial Context Setup Request (S209) is issued. Then, after Radio Bearer Establishment
15 (S210) and initial context setup completion (S211), a Modify Bearer Request is
transmitted from the MME 3 to the SGW 5 (S212). With these processes, it is possible
to perform the bearer recovery process initiated by the UE 1 by only handing over tunnel
information of the eNodeB 2 to the SGW 5.
[0036]
20 In contrast, in the present exemplary embodiment, because the SGW 5 and the
PGW 6 have already released the resources, a Create Session Request is transmitted from
the MME 3 to the SGW 5 and a tunnel establishment process is newly performed (S204).
At this time, in order to issue the same IP address as that of the tunnel deleted in the radio
resource release process described with reference to FIG. 2 to the UE 1, the MME 3 sets
25 the IP address issued to the UE 1 during first (or previous) bearer establishment as
15
designated IP address information in the Create Session Request. It is to be noted that
as in the process of the 3gpp standard rules when the Create Session Request is
transmitted, the IMSI is set as UE information in the Create Session Request to be
transmitted by the MME 3 in S204 (and by the SGW 5 in the next S205).
5 [0037]
The SGW 5 receiving the Create Session Request from the MME 3 performs the
tunnel establishment process and transmits the Create Session Request to which the IP
address is attached to the PGW 6 (S205). The PGW 6 checks whether the designated IP
address and the IMSI set in the received signal are the same as the IP address and the
10 IMSI in the correspondence table, which is held by the PGW 6 itself, and if both are the
same, determines the tunnel recovery process and performs the tunnel establishment
process using the IP address designated in the signal again (S206). Thereafter, the
PGW 6 transmits a Create Session Response for the Create Session Request of S205
(S207).
15 [0038]
The SGW 5 receiving the Create Session Response from the PGW 6 transmits
the Create Session Response to the MME 3 (S208). The MME 3 receiving the Create
Session Response from the SGW 5 in S208 transmits an Initial Context Setup Request to
the eNodeB 2 in accordance with the 3gpp standard rules (S209). Thereafter, in
20 accordance with the 3gpp standard rules, first, the eNodeB 2 performs a radio bearer
establishment process with the UE 1 (S210). Next, the eNodeB 2 transmits an Initial
Context Setup Complete to the MME 3 (S211). Next, the MME 3 transmits a Modify
Bearer Request to the SGW 5 (S212), and the SGW 5 transmits a Modify Bearer
Response to the MME 3 (S2I3).
25 [0039]
16
It is to be noted that when the PCRF is used, resources of the PCRF are also
recovered along with the tunnel recovery process of the SGW 5 and the PGW 6.
[0040]
Next, the tunnel recovery process triggered by the reception of an IP packet
5 addressed to the UE 1 will be described using FIG. 4. This operation is based on Item
5.3.4.3 "Network Triggered Service Request" of 3gpp TS 23.401. It is to be noted that
because the tunnel between the PGW 6 and the SGW 5 is still maintained in accordance
with the operation of the 3gpp standard rules, the IP packet addressed to the UE 1
reaches the SGW 5 by using the maintained tunnel and the SGW 5 transmits an IP packet
10 reception notification to the MME 3. In contrast, in the present exemplary embodiment,
because the SGW 5 and the PGW 6 have already released the resources, the PGW 6
receiving the IP packet (downlink data) addressed to the UE 1 from the PDN 7 (S301)
extracts the destination IMSI of the IP packet by referring to the correspondence table of
the IP address and the IMSI (S302). Thereafter, the PGW 6 inquires the HSS 4 about
15 the MME 3 which accommodates the UE 1 using the IMSI as a key (S303) and receives
a fully qualified domain name (FQDN) of the MME 3 from the HSS 4 (S304).
Thereafter, the PGW 6 inquires a predetermined DNS 20 about an IP address of the SGW
5 using the FQDN of the MME 3 (S305). After the PGW 6 has obtained the IP address
of the SGW 5 from the DNS 20 (S306), the PGW 6 additionally sets, in a Downlink Data
20 Notification, the IMSI, an access point name (APN), and a PGW address (i.e., an IP
address of the PGW 6) so as to specify a target bearer as well as the IP address defined in
the current 3gpp standard rules and performs transmission (S307). The SGW 5
receiving the Dovralink Data Notification from the PGW 6 transmits to the MME 3 the
Downlink Data Notification which includes additional setting of the IMSI, the APN, and
25 the PGW address to the 3gpp standard rules (S308).
17
[0041]
The MME 3 receiving the Dovmlink Data Notification from the SOW 5 selects
the SOW 5 to be connected based on the APN, the PGW address, and the like (S309).
The SOW 5 at this time may not be the SOW 5 used during initial (or previous) bearer
5 establishment. Next, as in the process of S204 of the bearer recovery process initiated
by the UE 1 described with reference to FIG. 3, the MME 3 transmits a Create Session
Request in which the IP address initially (or previously) issued to the UE 1 is set as
designated IP address information (S310). Thereafter, as in S205 to S208 of FIG. 3, the
SGW 5 receiving the Create Session Request from the MME 3 performs the tunnel
10 establishment process and transmits the Create Session Request to which the IP address
is attached to the PGW 6 (S311). The PGW 6 checks whether the designated IP address
and the IMSI set in the received signal are the same as the IP address and the IMSI in the
correspondence table, which is held by the PGW 6 itself, if both are the same, determines
the tunnel recovery process and performs the turmel establishment pro.cess using the IP
15 address designated in the signal again (S312). Thereafter, the PGW 6 transmits a Create
Session Response for the Create Session Request of S311 (S313). The SGW 5
receiving the Create Session Response from the PGW 6 transmits the Create Session
Response to the MME 3 (S314).
[0042]
20 Next, the MME 3 receiving the Create Session Response from the SGW 5
transmits Paging (i.e., a signal which pages the UE 1 of a standby state) toward the
registered UE 1 via the eNodeB 2 after the tunnel recovery (S315 and S316). The
paging here follows the 3gpp standard rules.
[0043]
25 As described above, in the present exemplary embodiment, with a state in which
18
the attached and bearer established UE 1 has released SI as a trigger, that is, with a state
in which the UE 1 has released connections passing through the reference points S1 -U
and Sl-MME as a trigger, the tunnel between the SGW 5 and the PGW 6 is released and
related resources are released and deleted. As a result, it is possible to save resources of
5 a core network compared to the number of accommodated UEs 1.
[0044]
That is, in the present exemplary embodiment, when the tunnel is released and
the tunnel information is deleted in the network which provides mobility of packet data
using tunneling, it is possible to effectively utilize resources of the core network by
10 dynamically associating and managing an IP address and a subscriber ID (subscriber
identification information).
[0045]
In addition, in order to enable Always-On, that is, transmission/reception, the
MME 3 performs the timnel establishment designating the IP address and the PGW
15 before the tunnel release during S1 recovery from the UE 1. Upon receiving a packet
addressed to the UE 1, the PGW 6 holds only association information of the IP address
and the UE 1 and cooperates with the HSS 4, and thus it is possible to transmit a
reception notification to the MME 3 which accommodates the UE 1 and perform the
turmel establishment triggered by packet reception. As a result, even in a state in which
20 the tunnel release is performed, it is possible to realize Always-On as in the 3gpp
standard rules.
[0046]
In addition, the PGW 6 is dynamically selected during the initial attach/bearer
establishment, the PGW 6 dynamically issues an IP address, and the association of the
25 UE 1 and the IP address is held. Accordingly, it is possible to make a fixed IP address
19
unnecessary, the UE 1 can select an optimum PGW 6 every time a bearer is newly
established, and a procedure of setting association information of the UE 1 and the IP
address in advance is also unnecessary.
[0047]
5 As described above, the present exemplary embodiment provides exemplary
advantages as described below.
As a first exemplary advantage, it is possible to improve the efficiency of
resources of the SGW 5 and the PGW 6 because the SGW 5 and the PGW 6 can release
the tunnel without affecting transmission to and reception from the UE 1.
10 As a second exemplary advantage, there is no influence due to a failure of the
SGW 5 during SI release because the SGW 5 is selected again and the tunnel is
recovered every time SI is recovered.
[0048]
Next, another exemplary embodiment of the present invention will be described
15 with reference to FIG. 5. Although the basic configuration of the present exemplary
embodiment is as illustrated in FIG. 1 as in the above-described exemplary embodiment,
an operation in the tunnel recovery process triggered by reception of an IP packet
addressed to the UE 1 is different. Another technique of the tunnel recovery process
triggered by the reception of the IP packet addressed to the UE 1 in the present
20 exemplary embodiment will be described using FIG. 5. The exemplary advantages
obtained fi"om the present exemplary embodiment are the same as those of the abovedescribed
exemplary embodiment.
[0049]
The PGW 6 receiving downlink data addressed to the UE 1 from the PDN 7
25 (S401) extracts a destination IMSI of the downlink data from the correspondence table of
20
the IP address and the IMSI, which is held by the PGW 6 itself (S402). Thereafter, the
PGW 6 inquires the HSS 4 about the attached MME 3 (S403).
[0050]
The HSS 4 receiving the inquiry about the attached MME 3 transmits a
5 Reception Notification to the MME 3 accommodating the UE 1 (S404). At this time, in
order for the MME 3 to determine the bearer, the HSS 4 attaches information about an
IMSI, an APN, an IP address, and a PGW address to the Reception Notification. The
MME 3 receiving the Reception Notification transmits a Reception Notification
Response to the HSS 4 (S405). Thereafter, as in S310 to S316 of FIG. 4, the MME 3
10 transmits a Create Session Request in which the IP address initially (or previously)
issued to the UE 1 is set as designated IP address information to the SGW 5 (S406).
Next, the SGW 5 receiving the Create Session Request from the MME 3 performs a
tunnel establishment process and transmits the Create Session Request to which the IP
address is attached to the PGW 6 (S408). The PGW 6 checks whether the designated IP
15 address and the IMSI set in the received signal are the same as the IP address and the
IMSI in the correspondence table, which is held by the PGW 6 itself, if both are the
same, determines the tunnel recovery process and performs the tunnel establishment
process using the IP address designated in the signal again (S408). Thereafter, the
PGW 6 transmits a Create Session Response for the Create Session Request of S407
20 (S409). The SGW 5 receiving the Create Session Response from the PGW 6 transmits
the Create Session Response to the MME 3 (S410).
[0051]
Next, the MME 3 receiving the Create Session Response from the SGW 5
transmits Paging (i.e., a signal which pages the UE 1 in a standby state) toward the
25 registered UE 1 via the eNodeB 2 after the tunnel recovery (S411 and S412). The
21
paging here follows the 3gpp standard rules.
[0052]
When the UE 1 receives the Paging (S412), thereafter a Service Request
Procedure initiated by the UE 1 is performed (S413).
5 [0053]
It is to be noted that features of the above-described exemplary embodiments are
collectively illustrated in FIG. 6. That is, a communication system 100 serving as an
exemplary embodiment of the present invention (corresponding to the communication
system 10 of FIG. 1) is a communication system which provides mobility of packet data
10 using tunneling. In addition, the communication system 100 includes a first node
(corresponding to the PGW 6 of FIG. 1)101 having the following functions. That is,
the first node 101 has a function 102 (tunnel control unit) of releasing a tunnel and
deleting tunnel information and a function 103 (management unit) of associating and
managing an IP address allocated to a terminial (corresponding to the UE 1 of FIG. 1) to
15 which the tunnel is established and subscriber identification information of the terminal
when the tunnel is released and the tunnel information is deleted.
[0054]
It is to be noted that although the case in which each exemplary embodiment
described above is applied to the E-UTRAN 8 has been described, each exemplary
20 embodiment described above is also applicable to other mobile networks such as
UTRAN and worldwide interoperability for microwave access (WiMAX).
[0055]
It is to be noted that the exemplary embodiments of the present invention are not
limited to the above; for example, the configuration illustrated in FIG. 1 is an example,
25 and a change can be appropriately made to integrate two or more structural elements
22
illustrated in FIG. 1 or to divide one structural element into a plurality of pieces. In
addition, a table storing the association information of the UE 1 and the subscriber
identification information provided in the PGW 6 can be embedded in a computer
apparatus constituting the PGW 6 or the like or can be provided outside the PGW 6 in an
5 integrated manner or in a distributed manner via a communication line or a
predetermined interface. In addition, the communication system of the present
invention has one or more computers and one or more programs to be executed by the
computers as structural elements, and the programs can be distributed via a computerreadable
recording medium or the communication line.
10 [0056]
In addition, the correspondence between the recitation of the claims and the
configurations of the above-described exemplary embodiments is as follows. A
"terminal" corresponds to the UE 1. A "first node" corresponds to the PGW 6. A
"second node" corresponds to the SGW 5. A "third node" corresponds to the MME 3.
15 A "fourth node" corresponds to the HSS 4.
[0057]
While the present invention has been described using the exemplary
embodiments, the technical scope of the present invention is not limited to the scope
disclosed in the above-described exemplary embodiments. It is apparent to one having
20 ordinary skill in the art that various modifications and improvements can be made to the
above exemplary embodiments. It is apparent from the recitation of the claims that
modes obtained by making the modifications and the improvements can be included in
the technical scope of the present invention.
[0058]
25 The present application is based upon and claims the benefit of priority from
23
Japanese patent application No. 2011-216103, filed on September 30, 2011, the
disclosure of which is incorporated herein in its entirety by reference.
INDUSTRIAL APPLICABILITY
5 [0059]
The present invention is applicable to, for example, communication in which
mobility of packet data is provided using tunneling. The present invention can release a
tunnel while securing mobility without securing resources in an SGW or the like.
10 Description of Reference Signs
[0060]
1 UE
2 eNodeB
3MME
15 4HSS
5 SGW
6PGW
7PDN
8 E-UTRAN
20

24 ^ A \ VJ (S\»«'^ WE CLAIM: V\ '^ r C^ l5^^^
1^
1. A first node provided in a communication system that provides mobility of
packet data using tunneling, the first node comprising:
5 a tunnel control unit that releases a tunnel and deletes tunnel information; and
a management unit that associates and manages an IP address allocated to a
terminal to which the tunnel is established and subscriber identification infoiTnation of
the terminal when the tunnel is released and the tunnel information is deleted.
10 2. A communication system comprising the first node according to claim 1.
3. The communication system according to claim 2, comprising a second node to
which the tunnel is established with the first node, wherein the second node releases
information about the tunnel and information about the terminal connected to the tunnel
15 when the tunnel is released.
4. The communication system according to claim 3, wherein the second node is
selected again every time a recovery process of the tunnel is performed.
20 5. The communication system according to any one of claims 2 to 4, wherein the
first node is a node serving as an anchor point that provides mobility of the terminal for a
predetermined packet data network.
6. The communication system according to any one of claims 2 to 5, comprising a
25 third node that accommodates the terminal, wherein the third node performs a recovery
OPdGrn^^ i 4 # \ 4 t
x^^t%
process of the tunnel using the IP address allocated to the terminal before the tunnel is
released and information designating the first node when the released tunnel is recovered
with transmission from the terminal as a trigger.
5 7. The communication system according to claim 6, wherein the first node issues
the IP address to the terminal using the IP address again that has been notified from the
third node and allocated to the terminal before the tunnel is released.
8. The communication system according to claim 6 or 7, comprising a fourth node
10 that identifies the third node in which the terminal is accommodated,
wherein the first node performs a recovery process of the tunnel by inquiring the
fourth node about the third node that accommodates the terminal when there is reception
for the terminal after the tunnel established for the terminal is released.
15 9. A communication method for providing mobility of packet data using tunneling,
the method comprising:
releasing, by a first node, a tunnel and deleting tunnel information; and
associating and managing, by the first node, an IP address allocated to a terminal
to which the tunnel is established and subscriber identification information of the
20 terminal when the tunnel is released and the tunnel information is deleted.
10. A communication program that provides mobility of packet data using
tunneling, the communication program causing a computer of a first node to execute:
a step of releasing a tunnel and deleting tunnel information; and
25 a step of associating and managing an IP address allocated to a terminal to which
IH^^"
26 ( \ ^ 4\^
1,3 ft»
the tunnel is established and subscriber identification information of the terminal when
the tunnel is released and the tunnel information is deleted.