1. A core network system comprising: a plural i ty of core network nodes; and a server5 , wherein a UE (User Equipment ) sends a message to a fi rst core network node through a radio base stat ion, wherein the UE is redirected from the fi rst core network node to a second core network node based on subscript ion informat ion of the UE provided by the 10 server, wherein the fi rst core network node sends a f irst message including informat ion on the redirect ion t o the radio base stat ion, and wherein the radio base stat ion sends a second message including the informat ion to the second core network node. 15

2. The core network system according to Claim 1, wherein the fi rst core network node does not authent icate th e UE before the redirect ion and the second core network node authent icates the UE after the redi rect ion. 20

3. The core network system according to Claim 1, wherein the fi rst core network node sends the fi rst message wi thout authent icat ing the UE, and wherein the second core network node authent icates the UE upon 25 receiving the second message.

4. The core network system according to any one of Claims 1 to 3, wherein the fi rst and second core network nodes each comprise an MME (Mobi l i ty Management Ent i ty) . 30

5. The core network system according to any one of Claims 1 to 4, wherein the server comprises an HSS (Home Subscriber Server ).

6. The core network system according to any one of Claims 1 to 5, 27 wherein the fi rst core network node selects the second core network node that serves the UE by using the subscript ion informat ion.

7. The core network system according to any one of Claims 1 to 6, wherein the second core network node extracts informat ion fo5 r authent icat ing the UE f rom the second message.

8. A method for a core network system including a plural i ty of core network nodes and a server, the method comprising: 10 a step that a UE (User Equipment ) sends a message to a first core network node through a radio base stat ion; a step that the UE is redi rected f rom the f irst core network node to a second core network node based on subscr ipt ion informat ion of the UE provided by the server ; 15 a step that the fi rst core network node sends a fi rst message including informat ion on the redirect ion to the radio base stat ion; and a step that the radio base stat ion sends a second message including the informat ion to the second core network node. 20 9. The method according to Claim 8, wherein the fi rst core network node does not authent icate the UE before the redirect ion and the second core network node authent icates the UE after the redi rect ion. 25 10. The method according to Claim 8, wherein the fi rst core network node sends the fi rst message wi thout authent icat ing the UE, and wherein the second core network node authent icates the UE upon receiving the second message. 30

11. The method according to any one of Claims 8 to 10, wherein the fi rst and second core network nodes each comprise an MME (Mobi l i ty Management Ent i ty) . 28

12. The method according to any one of Claims 8 to 11, wherein the server comprises an HSS (Home Subscriber Server ).

13. The method according to any one of Claims 8 to 12, wherein the fi rst core network node selects the second core network nod5 e that serves the UE by using the subscript ion in format ion.

14. The method according to any one of Claims 8 to 13, wherein the second core network node extracts informat ion for 10 authent icat ing the UE f rom the second message.

15. A UE (User Equipment) comprising: means for sending a message to a fi rs t core network node through a radio base stat ion, 15 wherein the UE is redirected f rom the fi rst core network node received the message to a second core network node based on subscript ion informat ion of the UE provided by a server, and wherein in the redi rect ion, the fi rst core network node sends a first message including informat ion on the redi rect ion to the radio base stat ion, and 20 the radio base stat ion sends a second message including the informat ion to the second core network node.

16. The UE according to Claim 15, wherein the UE is not authent icated by the fi rst core network node before the redirect ion, and the UE is authent icated by 25 the second core network node after the redirect ion.

17. A method for a UE (User Equipment ) comprising: a step that the UE sends a message to a fi rst core network node through a radio base stat ion; and 30 a step that the UE is redi rected f rom the f irst core network node received the message to a second core network node based on subscript ion informat ion of the UE provided by a server, wherein in the redi rect ion, the fi rst core network node sends a first message including informat ion on the redi rect ion to the radio base stat ion, and 29 the radio base stat ion sends a second message including the informat ion to the second core network node.

18. The method according to Claim 17, wherein the UE is not authent icated by the first core network node before the redi rect ion, and the UE i5 s authent icated by the second core network node after the redirection.

Title of Invention
APPARATUS, SYSTEM AND METHOD FOR DEDICATED CORE
NETWORK
5
Technical Field
[0001]
The present invent ion relates to an apparatus, a system and a method for a
Dedicated Core Network, and part icularly to a technique to ensure that a UE
10 (User Equipment ) is served by the appropriate core network.
Background Art
[0002]
Recent l y, enhancement to support the Dedicated Core Network has been
15 studied by 3GPP (3rd Generat ion Partnership Project ).
[0003]
The Dedicated Core Network intends that for example, a speci fic type of
subscriber (i .e. , a specific type of UE) is redi rected to an MME (Mobi l i ty
Management Ent i ty) /SGSN (Serving GPRS (General Packet Radio Service)
20 Support Node) dedicated to serve that UE. The Dedicated Core Network is also
somet imes referred to as "Speci fic Cor e Network" or "Overlay Core Network".
[0004]
NPL 1 discloses the most prompt ing message flow to real ize the
Dedicated Core Network. In this message flow, when a UE sends an At tach
25 Request message to new MME through an eNB (evolved Node B) (i .e. , in a case
of IMSI ( Internat ional Mobi le Subscriber Ident i ty) at tach), the one MME obtains
informat ion to use another speci fic MME f rom an HSS (Home Subscriber
Server ). Then, the one MME inst ru cts the eNB to redi rect the At tach Request
message to the speci fic MME. Upon the redi rect ion, the eNB per forms the
30 At tach procedure again to the specific MME.
[0005]
NPL 2 also discloses a message flow simi lar to that disclosed in NPL 1.
Citat ion List
3
Non Patent Literature
[0006]
NPL 1: TSG SA WG2 #99 S2-133304, "Addi t ion of Subscr ipt ion
Informat ion for Select ing a Speci fic Network", 2013-09, pp. 4
NPL 2: SA WG2 #100 S2-133910, "23.401 CR2606R3: Addi t ion o5 f
Subscr ipt ion Informat ion for Select ing a Speci fic Network", 2013 -11, pp. 7 and 9
NPL 3: TSG SA WG2 #100 S2-133909, "Discussion on Core Network Type
Select ion based on the Subscript ion Informat ion", 2013 -11
10 Summary of Invention
Technical Problem
[0007]
However, the inventors of this appl icat ion have found that there is a
problem that the message f low disclosed in NPLs 1 and 2 decreases the efficiency
15 upon support ing the Dedicated Core Network.
[0008]
Speci fical ly, upon the re-per formance of At tach procedure, the speci fic
MME redundant ly performs AKA (Authent icat ion and Key Agreement ) procedure
and NAS (Non-Access St ratum) SMC (Securi ty Mode Command) procedure that
20 have been al ready performed by the di fferent MME to which the UE at tempted to
at tach. Therefore, there are caused signal ing overload to devices/nodes
involved in the redundant AKA/NAS SMC procedures and al l inter face
therebetween, as wel l as overload to the speci fic MME.
[0009]
25 Moreover, NPLs 2 and 3 each discloses another message flow for GUTI
(Global ly Unique Temporary Ident i ty) at tach, in which the speci fic MME
contacts an MME referenced by the GUTI to retr ieve securi ty context .
[0010]
However, even in this message flow, there are also caused the
30 above-ment ioned signal ing overload and overload to the speci fic MME. This is
because the GUTI merely indicates the old MME which may has removed the
securi ty context af ter the expi rat ion of t imer, after al l the speci fic MME
redundant ly performs the AKA/NAS SMC procedures.
[0011]
4
Note that detai ls of these problems wi l l be discussed more ful ly in the
fol lowing descript ion.
[0012]
Accordingl y, an exemplary object of the present invent ion is to provide a
solut ion for more effect ively support ing a Dedicated Core Network5 .
Solution to Problem
[0013]
In order to achieve the above -ment ioned object , a network sys tem
10 according to fi rst exemplary aspect of the present invent ion includes: a f irst node
that establ ishes secure connect ion wi th a UE (User Equipment ) ini t ial ly
at tempt ing to at tach to a network, through a radio base stat ion; and a second node
to which the UE is redirected f rom the fi rst node through the radio base stat ion.
Upon the redirect ion, the fi rst no de sends informat ion on the f irst node i tsel f to
15 the second node through the radio base stat ion. The second node uses the
informat ion to retr ieve securi ty context necessary for establ ishing the connect ion
wi th the UE f rom the fi rst node.
[0014]
Further, according to second exemplary aspect of the present invent ion,
20 there is provided a method of cont rol for a network system including a fi rst node
that establ ishes secure connect ion wi th a UE ini t ial ly at tempt ing to at tach to a
network, through a radio base stat ion, and a second node to which the UE is
redi rected f rom the f irst node through the radio base stat ion. This method
includes: sending, upon the redirect ion, informat ion on the fi r st node f rom the
25 first node to the second node through the radio base stat ion; and using, by the
second node, the informat ion to retr ieve securi ty context necessary for
establ ishing the connect ion wi th the UE f rom the fi rst node.
[0015]
Further, a network system according to third exemplary aspect of the
30 present invent ion includes: a f irst node that receives an at tach request f rom a UE
ini t ial ly at tempt ing to at tach to a network, through a radio base stat ion; and a
second node to which the at tach request is redirected f rom the fi rst node through
the radio base stat ion. Upon the recept ion of the at tach request , the fi rst node
skips establ ishment of secure connect ion wi th the UE through t he radio base
5
stat ion. Upon the redi rect ion, the f irst node sends, to the second node through
the radio base stat ion, subscript ion informat ion indicat ing that the UE is one to
be redi rected to the second node. In response to receiving the subscript ion
informat ion, the second node establ ishes the secure connect ion wi th the UE.
[5 0016]
Further, according to four th exemplary aspect of the present invent ion,
there is provided a method of cont rol for a network system including a fi rst node
that receives an at tach request f rom a UE ini t ial ly at tempt ing to at tach to a
network, through a radio base stat ion, and a second node to which the at tach
10 request is redi rected from the f irst node through the radio base stat ion. This
method includes: skipping, by the first node upon the recept ion of the at tach
request , establ ishment of secure connect ion wi th the UE through the radio base
stat ion; sending, upon the redi rect ion, from the fi rst node to the se cond node
through the radio base stat ion, subscript ion informat ion indicat ing that the UE is
15 one to be redi rected to the second node; and establ ishing, by the second node in
response to receiving the subscript ion informat ion, the secure connect ion wi th
the UE.
[0017]
Further, a network system according to f i fth exemplary aspect of the
20 present invent ion includes: a fi rst node that establ ished secure connect ion wi th a
UE through a radio base stat ion when the UE at tached to a network previousl y,
and that assigned a temporary ident i ty to the UE; a second node that receives an
at tach request including the temporary ident i ty f rom the UE through the radio
base stat ion; and a third node to which the at tach request is redirected f rom the
25 second node through the radio base stat ion. The second node ret rieves securi ty
context necessary for establ ishing the connect ion wi th the UE f rom the fi rst
node, and upon the redi rect ion, sends informat ion on the second node i tself to the
third node through the radio base stat ion. The thi rd node uses the informat ion
to ret rieve the securi ty context from the second node.
30 [0018]
Further, according to sixth exemplary aspect of the present invent ion,
there is provided a method of cont rol for a network system including a fi rst node
that establ ished secure connect ion wi th a UE through a radio base stat ion when
the UE at tached to a network previously and that assigned a temporary ident i ty to
6
the UE, a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion, and a thi rd node to which the
at tach request is redi rected f rom the second node th rough the radio base stat ion.
This method includes: ret rieving, by the second node, securi ty context necessary
for establ ishing the connect ion wi th the UE f rom the fi rst node; sending, upo5 n
the redi rect ion, informat ion on the second node from the second n ode to the thi rd
node through the radio base stat ion; and using, by the third node, the informat ion
to ret rieve the securi ty context from the second node.
[0019]
10 Further, a network sys tem according to seventh exemplary aspect of the
present invent ion includes: a fi rst node that establ ished secure connect ion wi th a
UE through a radio base stat ion when the UE at tached to a network previousl y,
and that assigned a temporary ident i ty to the UE; a second node that receives an
at tach request including the temporary ident i ty f rom the UE through the radio
15 base stat ion; and a third node to which the at tach request is redirected f rom the
second node through the radio base stat ion. The second node ret rieves securi ty
context necessary for establ ishing the connect ion wi th the UE f rom the fi rst
node, and upon the redi rect ion, sends the securi ty context to the thi rd node
through the radio base stat ion.
20 [0020]
Further, according to eighth exemplary aspect of the present invent ion,
there is provided a method of cont rol for a network system including a fi rst node
that establ ished secure connect ion wi th a UE through a radio base stat ion when
the UE at tached to a network previously and that assigned a temporary ident i ty to
25 the UE, a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion, and a thi rd node to which the
at tach request is redi rected f rom the second node through the radio base stat ion.
This method includes: ret rieving, by the second node, securi ty context necessary
for establ ishing the connect ion wi th the UE f rom the fi rst node; and sending,
30 upon the redi rect ion, the securi ty context from the second node to the thi rd node
through the radio base stat ion.
[0021]
Further, a network system according to ninth exemplary aspect of the
present invent ion includes: a fi rst node that establ ished secure connect ion wi th a
7
UE through a radio base stat ion when the UE at tached to a network previousl y,
and that assigned a temporary ident i ty to the UE; a second node that receives an
at tach request including the t emporary ident i ty f rom the UE through the radio
base stat ion; and a third node to which the at tach request is redirected f rom the
second node through the radio base stat ion. The fi rst node maintains securi 5 ty
context necessary for establ ishing the secure c onnect ion wi th the UE t i l l an
ident i ficat ion request is received f rom the thi rd node. Upon the redi rect ion, the
third node sends the ident i ficat ion request to the first node to retrieve the
securi ty context from the fi rst node.
10 [0022]
Further, according to tenth exemplary aspect of the present invent ion,
there is provided a method of cont rol for a network system including a fi rst node
that establ ished secure connect ion wi th a UE throug h a radio base stat ion when
the UE at tached to a network previously and that assigned a temporary ident i ty to
15 the UE, a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion, and a thi rd nod e to which the
at tach request is redi rected f rom the second node through the radio base stat ion.
This method includes: maintaining, by the fi rst node, securi ty context necessary
for establ ishing the secure connect ion wi th the UE t i l l an ident ificat ion req uest is
20 received f rom the thi rd node; and sending, by the third node upon the redirect ion,
the ident ificat ion request to the fi rst node to retr ieve the secur i ty context f rom
the fi rst node.
[0023]
Further, a core network system according to eleventh exemplary aspect of
25 the present invent ion includes: a plural i ty of core network nodes; and a server.
In this system, a UE sends a message to a first core network node through a radio
base stat ion. The UE is redirected f rom the fi rst core network node to a second
core network node based on subscript ion informat ion of the UE provided by the
server. The f irst core network node sends a fi rst message including informat ion
30 on the redirect ion to the radio base stat ion. The radio base stat ion sends a
second message including the informat ion to the second core network node.
[0024]
Further, according to twel fth exemplary aspect of the present invent ion,
there is provided a method for a core network system including a plural i ty of
8
core network nodes and a server. This method includes : a step that a UE (User
Equipment ) sends a message to a fi rst core network node through a radio base
stat ion; a step that the UE is redi rected from the fi rst core network node to a
second core network node based on subscr ipt ion informat ion of the UE provided
by the server; a step that the fi rst core network node sends a fi rst messag5 e
including informat ion on the redi rect ion to the radio base stat ion; and a step that
the radio base stat ion sends a second message including the informat ion to the
second core network node.
[0025]
10 Further, a UE according to thir teenth exemplary aspect of the present
invent ion includes : means for sending a message to a fi rst core network node
through a radio base stat ion. The UE is redi rected f rom the f irst core network
node received the message to a se cond core network node based on subscr ipt ion
informat ion of the UE provided by a server. In the redi rect ion, the f irst core
15 network node sends a fi rst message including informat ion on the redirect ion to
the radio base stat ion, and the radio base stat ion s ends a second message
including the informat ion to the second core network node.
[0026]
Furthermore, according to fourteenth exemplary aspect of the present
20 invent ion, there is provided a method for a UE. This method includes : a step
that the UE sends a message to a fi rst core network node through a radio base
stat ion; and a step that the UE is redi rected f rom the fi rst core network node
received the message to a second core network no de based on subscript ion
informat ion of the UE provided by a server. In the redi rect ion, the f irst core
25 network node sends a fi rst message including informat ion on the redirect ion to
the radio base stat ion, and the radio base stat ion sends a second messag e
including the informat ion to the second core network node.
Advantageous Ef fects of Invention
30 [0027]
According to the present invent ion, i t is possible to solve at least one of
the above-ment ioned problems, and thus to provide a solut ion for more
effect ively suppor t ing a Dedicated Core Network.
9
Brief Description of Drawings
[0028]
[Fig. 1]
Fig. 1 is a block diagr am showing a conf igurat ion example of a network
system according to a fi rst exemplary embodiment of the present invent ion5 .
[Fig. 2]
Fig. 2 is a sequence diagram showing a fi rst example of operat ions in the
network system according to the f irst exemplary embodiment .
[Fig. 3]
10 Fig. 3 is a sequence diagram showing a second example of operat ions in
the network system according to the fi rst exemplary embodiment .
[Fig. 4]
Fig. 4 is a sequence diagram showing a first example of operat ions in a
network system according to a second exemplary embodiment of the present
15 invent ion.
[Fig. 5]
Fig. 5 is a sequence diagram showing a second example of operat ions in
the network system according to the second exemplary embodiment .
[Fig. 6]
20 Fig. 6 is a sequence diagram showi ng a third example of operat ions in the
network system according to the second exemplary embodiment .
[Fig. 7]
Fig. 7 is a sequence diagram for explaining problems in typical IMSI
at tach procedure.
25 [Fig. 8]
Fig. 8 is a sequence diagram for explaining prob lems in typical GUTI
at tach procedure.
Description of Embodiments
30 [0029]
Hereinafter, several exemplary embodiments according to the present
invent ion wi l l be descr ibed wi th reference to the accompanying drawings.
[0030]

10
As shown in Fig. 1, a network system according to this exemplary
embodiment includes MMEs 30 and 40 by way of example only. Among them,
the MME 30 is the one to which a UE 10 ini t ial ly at taches through an eNB 20
serving as a radio base stat ion, and thus somet imes referred to as "New MME" in
the fol lowing descript ion. On the other hand, the MME 40 is the one dedicate5 d
to serve the UE 10 according to subscript ion and to which the UE 10 is redirected
from the MME 30, and thus referred to as "Dedicated MME" or "DMME". Note
that the MME 40 can also be refer red to as "Specif ic MME", in conformi ty wi th
the Dedicated Core Network being somet imes refer red to as "Speci fic Core
10 Network". If necessar y, each of the MMEs 30 and 40 can obtain, from an HSS
50, subscript ion informat ion on the UE 10, informat ion necessary for
authent icat ing the UE 10, and the l ike. The New MME 30 is al so connected to
an S-GW (Serving Gateway) and/or a P-GW (PDN (Publ ic Data Network)
Gateway) . Simi larly, the Dedicated MME 40 is also connected to a Dedicated
15 S-GW and/or a Dedicated P-GW.
[0031]
In general , this exemplary embodiment deals wi th IMSI at tach in
E-UTRAN (Evolved Universal Ter rest rial Radio Access Network), part icularly
wi th a case where the New MME 30 redirects an At tach Request message
20 received from the eNB 20 to the DMME 40, according to the subscr ipt ion
informat ion on the UE 10 obtained f rom the HSS 50.
[0032]
Next , prior to describing operat ion examples of this exemplary
embodiment , there are fi rst l y defined problems in typical IMSI at tach procedure
25 as disclosed by NPLs 1 and 2 wi th reference to Fig. 7. Then, there wi l l be
described solut ions for addressing these problems as the operat ion examples.
The solut ions include Opt ion 1 shown in Fig. 2 and Opt ion 2 shown in Fig. 3.
[0033]
Problem Defined:
30 As shown in Fig. 7, in the typical IMSI at tach procedure, a UE 110 sends
an At tach Request message including i ts IMSI to an eNB 120 (step S101) , and the
eNB 120 forwards the At tach Request message to an New MME 130 (step S102).
[0034]
Upon receiving the At tach Request message, the New MME 130 sends an
11
Authent icat ion data request message to an HSS 150, and as a response thereto,
receives an Authent icat ion data response message including AVs (Authent icat ion
Vectors) (step S103). Then, the New MME 130 corporates wi th the UE 110 to
perform AKA procedure and NAS SMC proc edure (step S104). As a resul t , The
UE 10 and the New MME 130 each can share Kasme (Key for access securi 5 ty
management ent i ty) and NAS keys, so that secure connect ion is establ ished
between them (step S105).
[0035]
After that , the New MME 130 sends an Update Locat ion Request message
10 to the HSS 150, and as a response thereto, receives an Update Locat ion Re sponse
message (step S106). The Update Locat ion Re sponse message includes the
IMSI and the subscript ion informat ion/data. Moreover, the subscr ipt ion
informat ion includes informat ion on a Dedicated MME 140 (hereinafter, such
informat ion wi l l be somet imes referred to as "DMME informat ion").
15 [0036]
Then, the New MME 130 selects the Dedicated MME 140 to which the UE
110 should be redirected based on the DMME informat ion (step S107) , and sends
a Redi rect message to the eNB 120 (step S108). Upon receiving the Redi rect
message, the eNB 120 forwards the At tach Request message to the Dedicated
20 MME 140 (step S109).
[0037]
However, at this t ime, the fol lowing problems arise:
(a) Since the At tach Request message is not protected, the Dedicated
MME 140 starts AKA procedure to the UE 10;
25 (b) due to (a) , the Dedicated MME 140 sends/ receives Authent icat ion data
request / response messages and Update Locat ion Request /Response messages
to/f rom the HSS 150, and al so corporates wi th the UE 110 to per form AKA
procedure and NAS SMC procedure; and
(c) due to (a) and (b) , there are caused signal ing overload to the HSS 150,
30 the Dedicated MME 140, the eNB 120, the UE 110 and al l interfaces
therebetween, as wel l as overload to the Dedicated MME 140 for key
computat ion.
[0038]
Solut ions:
12
(Opt ion 1)
Fig. 2 shows a sequence diagram for this opt ion. Processes at steps S1
to S7 are per formed in a simi lar manner to those at the above -ment ioned steps
S101 to S107 shown in Fig. 7.
[5 0039]
Meanwhi le, upon the redirect ion, the New MME 30 sends to the eNB 20 a
Redi rect message including informat ion on the New MME 30 i tsel f (herein after,
such informat ion wi l l be somet imes refer red to as "MME informat ion") (step S8).
For example, the MME informat ion includes an ID (ident if icat ion, ident i ty) , an
10 FQDN (Ful ly Qual i fied Domain Name) or an IP ( Internet Protocol) address
assigned to the New MME 30. Then, the eNB 20 forwards to the Dedicated
MME 40 the MME informat ion wi th being included in an At tach Request message
(step S9).
[0040]
15 The Dedicated MME 40 uses the received MME informat ion to ret rieve,
from the New MME 30, secur i ty context concerning secure connect ion which has
been establ ished between the UE 10 and the New MME 30. Speci fical ly, the
Dedicated MME 40 sends an Ident i f icat ion Request message to the New MME 30
(step S10), and as a response thereto, receives an Ident if icat ion Response
20 message including UE context (step S11). The UE context includes the AVs and
al l securi ty context . Then, the Dedicated MME 40 extracts th e Kasme and the
NAS keys f rom the ret rieved UE context (step S12).
[0041]
After that , a message 5b and the subsequent message sequences as
25 disclosed in 3GPP TS 23.401, sect ion 5.3.2.1 fol lows.
[0042]
According to this opt ion, the Dedicated MME 40 is indicated about the
MME informat ion such that the Dedicated MME 40 can retrieve necessary
securi ty context from the New MME 30. Therefore, unl ike the typical IMSI
30 at tach procedure, the Dedicated MME 40 needs not to perform AKA procedure
and NAS SMC procedure. Thus, compared wi th the typical IMSI at tach
procedure, i t is possible to drast ical ly reduce signal ing overload, as wel l as
overload to the Dedicated MME for key computat ion. Moreover, since the
exist ing message sequences can be reused (the Ident i ficat ion Request /Response
13
messages are also the exist ing ones as wi l l be described later ) , i t is possible to
minimize the impact on the mobi le communicat ion system.
[0043]
Further, at the above-ment ioned step S11, the New MME 30 may include,
in the Ident i ficat ion Response message, an Authent icat ion Indic at ion whic5 h
indicates that the UE 10 has been authent icated as the one to be redi rected to the
Dedicated MME 40. In this case, the Dedicated MME 40 needs not to contact
the HSS 50 for the purpose of authent icat ing the UE 10, so that i t is possible to
further reduce signal ing over load.
10 [0044]
(Opt ion 2)
Fig. 3 shows a sequence diagram for this opt ion. Processes at steps S21
and S22 are per formed in a simi lar manner to those at the abov e-ment ioned steps
S1 and S2 shown in Fig. 2.
15 [0045]
Meanwhi le, upon receiving the At tach Request message, the New MME 30
first ly ret rieves f rom the HSS 50 the subscr ipt ion informat ion including the
DMME informat ion (step S23a).
[0046]
20 As described above, the DMME informat ion indicates that the UE 10
should be redirected to the Dedicated MME 40. Therefore, the New MME 30
skips establ ishment of secure connect ion wi th the UE 10. Speci fical ly, the New
MME 30 does not perform the AKA procedure, the NAS SMC procedure, the
computat ion of NAS keys, and the l ike.
25 [0047]
Then, the New MME 30 selects the Dedicated MME 40 based on the
DMME informat ion (step S24) , and sends to the eNB 20 a Redi rect message
including the subscript ion informat ion (which also includes the DMME
informat ion) (step S25) . Then, the eNB 20 forwards to the Dedicated MME 40
30 the subscript ion informat ion wi th being included in an At tach Request message
(step S26).
[0048]
In response to receiving the subscript ion inf ormat ion (i .e. , DMME
informat ion), the Dedicated MME 40 establ ishes secure connect ion wi th the UE
14
10 through the eNB 20, as a subst i tute for the New MME 30. Speci fical l y,
Dedicated MME 40 sends an Authent icat ion data request message to the HSS 50,
and as a response thereto, receives an Authent icat ion data response message
including the AVs (step S27). Then, the Dedicated MME 40 corporates wi th the
UE 10 to per form AKA procedure and NAS SMC procedure (step S28) . As 5 a
resul t , The UE 10 and the Dedicated MME 40 each can share Kasme and NAS
keys, so that secure connect ion is establ ished therebetween through the eNB 20
(step S29).
[0049]
10 After that , a message 5b and the subsequent message sequences as
disclosed in 3GPP TS 23.401, sect ion 5.3.2.1 fol lows.
[0050]
According to this opt ion, as wi l l be understood by comparing the
sequence shown in Fig. 3 wi th that shown in Fig. 2, i t is possible to reduce the
15 amount of signal ing compared to the above -ment ioned Opt ion 1. Moreover,
since the New MME 30 skips the establ ishment of secure connect ion, i t is also
possible to reduce over load to the New MME 30.
[0051]
Further, as a subst i tute for the above -ment ioned step S23a, the DMME
20 informat ion may be preconfigured in the New MME 30 (step S23b). In this
case, the New MME 30 can also skip the retrieval of subsc ript ion informat ion
from the HSS 50 when i t receives the ini t ial At tach Request f rom the UE 10, so
that i t is possible to further reduce the amount of signal ing.
[0052]
25 Furthermore, at the above-ment ioned step S23a, the New MME 30 may
further retrieve the AVs f rom the HSS 50. The ret rieved AVs can be transfer red
to the Dedicated MME 40 through the eNB 20 wi th the Redi rect message shown
at the above-ment ioned step S25 and the At tach Req uest message shown at the
above-ment ioned step S26. In this case, the Dedicated MME 40 can skip the
30 acquisi t ion of AVs from the HSS 50 shown at the above -ment ioned step S27, so
that i t is possible to further reduce the amount of signal ing.
[0053]

As shown in Fig. 4, a network system according to this exemplary
15
embodiment further includes an MME 60 in addi t ion to the above -ment ioned
MMEs 30 and 40. The MME 60 is the one to which the UE 10 previously
at tached, and thus somet imes refer red to as "Ol d MME" in the fol lowing
descript ion. If necessar y, the Old MME 60 can also obtain, f rom the HSS 50,
the subscript ion informat ion, the DMME informat ion, the AVs and the l ike5 .
Note that there is a case where the UE 10 previously at tached to an SGSN (i .e. ,
"Old SGSN"). Even in this case, the fol lowing descript ion about the Old MME
can be simi larly appl ied to that about the Old SGSN.
[0054]
10 In general , this exemplary embodiment deals wi th GUTI at tach in
E-UTRAN, part icularly wi th a case where the New MME 30 redi rects an At tach
Request message received f rom the eNB 20 to the DMME 40, according to th e
DMME informat ion obtained f rom the Old MME 60.
[0055]
15 Next , prior to describing operat ion examples of this exemplary
embodiment , there are fi rst ly defined problems in typical GUTI at tach procedure
as disclosed by NPLs 2 and 3 wi th reference to Fig. 8. Then, there wi l l be
described solut ions for addressing these problems as the operat ion examples.
The solut ions include Opt ion 1 shown in Fig. 4, Opt ion 2 shown in Fig. 5, and
20 Opt ion 3 shown in Fig. 6.
[0056]
Problem Defined:
As shown by dot ted l ines in Fig. 8, assume that the UE 110 previously
at tached to an Old MME 160, and the Old MME 160 assigned a GUTI to the UE
25 110, so that the UE has got ten the GUTI.
[0057]
In the typical GUTI at tach procedure, the UE 110 sends an At tach Request
message including the GUTI to the eNB 120 (step S201) , and the eNB 120
forwards the At tach Request message to the New MME 130 (step S202) .
30 [0058]
Upon receiving the At tach Request message, the New MME 130 sends to
the Old MME 160 an Ident if icat ion Request message including the GUTI and the
complete At tach Request message (step S203), and as a response thereto,
receives an Ident ificat ion Response message including the IMSI of the UE 110
16
and MM (Mobi l i ty Management ) Context (step S204) .
[0059]
Then, the New MME 130 selects the Dedicated MME 140 (step S205), and
sends a Redirect message to the eNB 120 (step S206) . Upon receiving the
Redi rect message, the eNB 120 forwards the At tach Request message to th5 e
Dedicated MME 140 (step S207) .
[0060]
However, the Old MME 160 might remove UE context ( i .e. , securi ty
context ) after a predetermined t imer expi red. Moreov er, the GUTI merely
10 indicates the Old MME 160. Therefore, the Dedicated MME 140 fai ls in
retrieving the AVs and the securi ty context f rom the Old MME 160, and thus
starts AKA procedure.
[0061]
Accordingl y, as wi th the typical IMSI at tach procedure, the fol lowing
15 problems arise:
signal ing overload to the HSS 150, the Dedicated MME 140, the eNB 120,
the UE 110 and al l inter faces therebetween; and
overload to the Dedicated MME 140 for key computat ion.
[0062]
20 Solut ions:
(Opt ion 1)
Fig. 4 shows a sequence diagram for this opt ion. Processes at steps S31
to S35 are per formed in a simi lar manner to those at the above -ment ioned steps
S201 to S205 shown in Fig. 8.
25 [0063]
Meanwhi le, upon the redirect ion, the New MME 30 sends to the eNB 20 a
Redi rect message including informat ion on the New MME 30 i tsel f (i .e. , MME
informat ion) (step S36) . Then, the eNB 20 forwards to the Dedicated MME 40
the MME informat ion wi th being included in an At tach Request message (step
30 S37) .
[0064]
The Dedicated MME 40 uses the received MME informat ion to ret rieve,
from the New MME 30, the securi ty context which has been obtained at the
above-ment ioned step S34 by the New MME 30 from the Old MME 60.
17
Speci fical ly, the Dedicated MME 40 sends an Ident ificat ion Request message to
the New MME 30 (step S38), and as a response thereto, receives an Ident i ficat ion
Response message including UE context (step S39) . As descr ibed above, the
UE context includes the AVs and al l secur i ty context . Then, the Dedicated
MME 40 extracts the Kasme and the NAS keys f rom the retr ieved UE contex5 t
(step S40).
[0065]
After that , a message 5b and the subsequent message sequences as
disclosed in 3GPP TS 23.401, sect ion 5.3.2.1 fol lows.
10 [0066]
According to this opt ion, the Dedicated MME 40 is indicated about the
MME informat ion such that the Dedicated MME 40 can retrieve necessary
securi ty context from the New MME 30. Therefore, unl ike the typical GUTI
at tach procedure, the Dedicated MME 40 needs not to contact the Old MME 60
15 for the purpose of retrieving the AVs and the securi ty context f rom the Old MME
60, and thus needs not to start AKA procedu re i f i t fai ls in ret rieving the securi ty
context f rom the Old MME 60. Thus, compared wi th the typical GUTI at tach
procedure, i t is possible to drast ical ly reduce signal ing overload, as wel l as
overload to the Dedicated MME for key computat ion. Moreover, since the
20 exist ing message sequences can be reused, i t is possible to minimize the impact
on the mobi le communicat ion system.
[0067]
Further, at the above-ment ioned step S39, the New MME 30 may include,
in the Ident i ficat ion Response message, an Authent icat ion Indicat ion which
25 indicates that the UE 10 has been authent icated as the one to be redi rected to the
Dedicated MME 40. In this case, the Dedicated MME 40 needs not to contact
the HSS 50 for the purpose of authent icat ing the UE 10, so that i t is possible to
further reduce signal ing over load.
[0068]
30 (Opt ion 2)
Fig. 5 shows a sequence diagram for this opt ion. Pr ocesses at steps S41
to S45 are per formed in a simi lar manner to those at the above -ment ioned steps
S31 to S35 shown in Fig. 4.
[0069]
18
Meanwhi le, upon the redirect ion, the New MME 30 s ends to the eNB 20 a
Redi rect message including the UE context (step S46) . Then, the eNB 20
forwards to the Dedicated MME 40 the UE context wi th being included in an
At tach Request message (step S47). As described above, the UE context
includes the AVs and al l securi ty context 5 .
[0070]
Then, the Dedicated MME 40 extracts the Kasme and the NAS keys f rom
the received UE context (step S48).
[0071]
10 After that , a message 5b and the subsequent message sequences as
disclosed in 3GPP TS 23.401, sect ion 5.3.2.1 fol lows.
[0072]
According to this opt ion, the Dedicated MME 40 needs not to contact any
MME to retr ieve the UE context . Therefore, i t is possible to reduce the amount
15 of signal ing compared to the above -ment ioned Opt ion 1, and i t is also possible to
reduce to reduce overload to the Dedicated MME 40 .
[0073]
Further, this opt ion may be opt imized such that the Old MME 60
remembers that integri ty check for the At tach Request message is done at the
20 above-ment ioned step S43. In this case, the Dedicated MME 40 needs not to do
the integri ty check again at the above -ment ioned step S47, so that i t is possible
to further reduce the overload to the Dedicated MME 40.
[0074]
(Opt ion 3)
25 Fig. 6 shows a sequence diagram for this opt ion. Processes at steps S51
to S55 are per formed in a simi lar manner to those at the above -ment ioned steps
S31 to S35 shown in Fig. 4.
[0075]
Meanwhi le, in this opt ion, since the Old MME 60 served as the DMME for
30 subscriber, the Old MME 60 maintains the securi ty context for a whi le wi thout
removing i t just t i l l a second Ident if icat ion Request message is received f rom a
dedicated MME.
[0076]
Upon the redirect ion, the New MME 30 sends a Redirect message to the
19
eNB 20 (step S56). Then, the eNB 20 forwards the At tach Request message to
the Dedicated MME 40 (step S57).
[0077]
Upon receiving the At tach Request message, the Dedicated MME 40 sends
to the Old MME 60 an Ident i ficat ion Request message including the GUTI an5 d
the complete At tach Request message (step S58).
[0078]
Now, since the second Ident i ficat ion Request message is received, the Old
MME 60 sends back to the Dedicated MME 40 an Ident if icat ion Response
10 message including the maintained MM Context (securi ty context) (step S59) .
[0079]
Then, the Dedicated MME 40 extracts the Kasme and the NAS keys f rom
the received MM context (step S60).
[0080]
15 After that , a message 5b and the subsequent message sequences as
disclosed in 3GPP TS 23.401, sect ion 5.3.2.1 fol lows.
[0081]
According to this opt ion, l ike the typical GUTI at tach procedure, the
Dedicated MME 40 can ret rieve necessary securi ty context f rom the Old MME 60
20 by only using the GUTI, and thus needs not to start AKA procedure. Therefore,
i t is possible to drast ical ly reduce signal ing overload, as wel l as overload to the
Dedicated MME for key computat ion. Moreover, since the Dedicated MME
only has to contact the MME indicated by the GUTI, in other words, since the
Dedicated MME only per forms the exist ing message sequences, i t is possible to
25 minimize the impact on the Dedicated MME.
[0082]
Further, i t is preferable that the New MME 30 informs, through the
Redi rect message and the At tach Request message shown at the above -ment ioned
steps S56 and S57, the Dedicated MME 40 that no AV is consumed, and the Old
30 MME 60 informs only val id AVs to the Dedicated MME 40 in the second
Ident i ficat ion Response message shown at the above -ment ioned step S59. This
ensures that the Dedicated MME 40 can use the received AVs for conduct ing
communicat ion wi th the UE 10. Note that as a subst i tute for the val id AVs or in
addi t ion thereto, the Old MME 60 may inform other addi t ional informat ion to the
20
Dedicated MME 40.
[0083]
Furthermore, this opt ion may be opt imized such that the Old MME 60
remembers that integri ty check for the At tach Request message is done at the
above-ment ioned step S53. In this case, the Dedicated MME 40 needs not to d5 o
the integri ty check again at the above -ment ioned step S57, and the Old MME 60
also needs not do the integri ty check again at the above -ment ioned step S58, so
that i t is possible to reduce the overload to the Dedicated MME 40 and the Old
MME 60.
10 [0084]
Note that al though the exemplary embodiments have been descr ibed
hereinbefore by taking as an example E-UTRAN, the present invent ion can also
be appl ied to IMSI at tach and P-TMSI (Packet -TMSI (Temporary Mobi le
Subscr iber Ident i ty) ) at tach in UTRAN. The mechanism is basical ly the same as
15 for at tach in E-UTRAN, except that e.g. , the message is changed to car ry
Dedicated MME/SGSN informat ion.
[0085]
If the exemplary embodiments are refer red to the UTRAN and GERAN
(GSM (Global System for Mobi le communicat ions) EDGE (Enhanced Data GSM
20 Envi ronment ) RAN), then the fol lowing r eplacements need to be made:
replacing MME wi th SGSN;
replacing DMME wi th DSGSN;
replacing eNB wi th BTS (Base Transceiver Stat ion)/BSC (Base Stat ion
Cont rol ler);
25 replacing HSS wi th HLR (Home Locat ion Register )/HSS; and
replacing GUTI wi th P-TMSI.
[0086]
Further, al though the i l lustrat ion is omi t ted, the New MME 30, the
Dedicated MME 40 and the Old MME 60 each can be configured by, for example,
30 one or more transceivers which conduct communicat ion wi th the UE 10 through
the eNB 20, which conduct communicat ion between the MMEs 30, 40 and 60
through or not trough the eNB 20 and which conduct communicat ion wi th the
HSS 50, and a cont rol ler such as a CPU (Cent ral Processing Uni t) which cont rols
these transceivers to execute the processes shown in the accompany sequence
21
diagrams or processes equivalent thereto.
[0087]
Note that the present invent ion is not l imi ted to th e above-ment ioned
exemplary embodiments, and i t is obvious that various modi ficat ions can be
made by those of ordinary ski l l in the art based on the reci tat ion of the claims5 .
[0088]
The whole or part of the exemplary embodiment s disclosed above can be
described as, but not l imi ted to, the fol lowing supplementary notes.
[0089]
10 (Supplementary note 1)
A network system comprising:
a fi rst node that establ ishes secure connect ion wi th a UE (User
Equipment ) ini t ial ly at tempt ing to at tach to a network, through a radio base
stat ion; and
15 a second node to which the UE is redi rected f rom the fi rst node through
the radio base stat ion,
wherein upon the redirect ion, the fi rst node sends informat ion on the f irst
node i tself to the second node through the radio base stat ion, and
wherein the second node uses the informat ion to retr ieve secur i ty context
20 necessary for establ ishing the connect ion wi th the UE from the fi rst node.
[0090]
(Supplementary note 2)
A method of cont rol for a network system including a f irst node that
establ ishes secure connect ion wi th a UE ini t ial ly at tempt ing to at tach to a
25 network, through a radio base stat ion, and a second node to which the UE is
redi rected f rom the f irst node through the radio base stat ion, the method
comprising:
sending, upon the redirect ion, informat ion on the fi rst node from the fi rst
node to the second node through the radio base stat ion; and
30 using, by the second node, the informat ion to ret rieve securi ty context
necessary for establ ishing the connect ion wi th the UE from the fi rst node.
[0091]
(Supplementary note 3)
A network system comprising:
22
a fi rst node that receives an at tach request f rom a UE ini t ial ly at tempt ing
to at tach to a network, through a radio base stat ion; and
a second node to which the at tach request is redi rected f rom the f irst node
through the radio base stat ion,
wherein upon the recept ion of the at tach request , the first node skip5 s
establ ishment of secure connect ion wi th the UE through the radio base stat ion,
wherein upon the redirect ion, the fi rst node sends, to the second node
through the radio base stat ion, subscript ion informat ion indicat ing that the UE is
one to be redi rected to the second node, and
10 wherein in response to receiving the subscr ipt ion informat ion, the se cond
node establ ishes the secure connect ion wi th the UE.
[0092]
(Supplementary note 4)
A method of cont rol for a network system including a f irst node that
15 receives an at tach request f rom a UE ini t ial ly at tempt ing to at tach to a network,
through a radio base stat ion, and a second node to which the at tach request is
redi rected f rom the f irst node through the radio base stat ion, the method
comprising:
skipping, by the f irst node upon the recept ion of the at tach request ,
20 establ ishment of secure connect ion wi th the UE through the radio base stat ion;
sending, upon the redirect ion, f rom the fi rst node to the second node
through the radio base stat ion, subscript ion informat ion indicat ing that the UE is
one to be redi rected to the second node; and
establ ishing, by the second node in response to receiving the subscr ipt ion
25 informat ion, the secure connect ion wi th the UE.
[0093]
(Supplementary note 5)
A network system comprising:
a fi rst node that establ ished secure connect ion wi th a UE through a radio
30 base stat ion when the UE at tached to a network previousl y, and that assigned a
temporary ident i ty to the UE;
a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion; and
a third node to which the at tach request is redirected f rom the second
23
node through the radio base stat ion,
wherein the second node ret rieves s ecur i ty context necessary for
establ ishing the connect ion wi th the UE f rom the fi rst node, and upon the
redi rect ion, sends informat ion on the second node i tsel f to the third node through
the radio base stat ion, an5 d
wherein the thi rd node uses the informat ion to retrieve the securi ty
context f rom the second node.
[0094]
(Supplementary note 6)
10 A method of cont rol for a network system including a f irst node that
establ ished secure connect ion wi th a UE through a radio base stat ion when the
UE at tached to a network previously and that assigned a temporary ident i ty to the
UE, a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion, and a thi rd node to which the
15 at tach request is redi rected f rom the second node through the radio base stat ion,
the method compr ising:
retrieving, by the second node, securi ty context necessary for establ ishing
the connect ion wi th the UE from the fi r st node;
sending, upon the redirect ion, informat ion on the second node f rom the
20 second node to the third node through the radio base stat ion; and
using, by the third node, the informat ion to ret rieve the securi ty context
from the second node.
[0095]
(Supplementary note 7)
25 A network system comprising:
a fi rst node that establ ished secure connect ion wi th a UE through a radio
base stat ion when the UE at tached to a network previousl y, an d that assigned a
temporary ident i ty to the UE;
a second node that receives an at tach request including the temporary
30 ident i ty f rom the UE through the radio base stat ion; and
a third node to which the at tach request is redirected f rom the second
node through the radio base stat ion,
wherein the second node ret rieves secur i ty context necessary for
establ ishing the connect ion wi th the UE f rom the fi rst node, and upon the
24
redi rect ion, sends the securi ty context to the thi rd node through the radio base
stat ion.
[0096]
(Supplementary note 8)
A method of cont rol for a network system including a f irst node tha5 t
establ ished secure connect ion wi th a UE through a radio base stat ion when the
UE at tached to a network previously and that assigned a temporary ident i ty to the
UE, a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion, and a thi rd node to which the
10 at tach request is redi rected f rom the second node through the radio base stat ion,
the method compr ising:
retrieving, by the second node, securi ty context necessary for establ ishing
the connect ion wi th the UE from the fi rst node; and
sending, upon the redirect ion, the securi t y context from the second node
15 to the thi rd node through the radio base stat ion.
[0097]
(Supplementary note 9)
A network system comprising:
a fi rst node that establ ished secure connec t ion wi th a UE through a radio
20 base stat ion when the UE at tached to a network previousl y, and that assigned a
temporary ident i ty to the UE;
a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base s tat ion; and
a third node to which the at tach request is redirected f rom the second
25 node through the radio base stat ion,
wherein the fi rst node maintains securi ty context necessary for
establ ishing the secure connect ion wi th the UE t i l l an ident if icat ion request is
received from the thi rd node, and
wherein upon the redirect ion, the thi rd node sends the ident i ficat ion
30 request to the fi rst node to ret rieve the securi ty context from the fi rst node.
[0098]
(Supplementary note 10)
A method of cont rol for a network system including a f irst node that
establ ished secure connect ion wi th a UE through a radio base stat ion when the
25
UE at tached to a network previously and that assigned a temporary ident i ty to the
UE, a second node that receives an at tach request including the temporary
ident i ty f rom the UE through the radio base stat ion, and a thi rd node to which the
at tach request is redi rected f rom the second node through the radio base stat ion,
the method compr ising5 :
maintaining, by the f irst node, securi ty context necessary for establ ishing
the secure connect ion wi th the UE t i l l an ident i ficat ion request is received from
the thi rd node; and
sending, by the third node upon the redi rect ion, the i dent if icat ion request
10 to the fi rst node to ret rieve the securi ty context f rom the fi rst node.
[0099]
This appl icat ion is based upon and claims the benefi t of prior i ty from
Japanese patent appl icat ion No. 2014-112269 fi led on May 30, 2014, the
disclosure of which is incorporated herein in i ts ent irety by reference.
15
Reference Signs List
[0100]
10, 110 UE
20, 120 eNB
20 30, 40, 60, 130, 140, 160 MME
50, 150 HSS

WE CLAIM:
1. A core network system comprising:
a plural i ty of core network nodes; and
a server5 ,
wherein a UE (User Equipment ) sends a message to a fi rst core network
node through a radio base stat ion,
wherein the UE is redirected from the fi rst core network node to a second
core network node based on subscript ion informat ion of the UE provided by the
10 server,
wherein the fi rst core network node sends a f irst message including
informat ion on the redirect ion t o the radio base stat ion, and
wherein the radio base stat ion sends a second message including the
informat ion to the second core network node.
15
2. The core network system according to Claim 1,
wherein the fi rst core network node does not authent icate th e UE before
the redirect ion and the second core network node authent icates the UE after the
redi rect ion.
20
3. The core network system according to Claim 1,
wherein the fi rst core network node sends the fi rst message wi thout
authent icat ing the UE, and
wherein the second core network node authent icates the UE upon
25 receiving the second message.
4. The core network system according to any one of Claims 1 to 3,
wherein the fi rst and second core network nodes each comprise an MME
(Mobi l i ty Management Ent i ty) .
30
5. The core network system according to any one of Claims 1 to 4,
wherein the server comprises an HSS (Home Subscriber Server ).
6. The core network system according to any one of Claims 1 to 5,
27
wherein the fi rst core network node selects the second core network node
that serves the UE by using the subscript ion informat ion.
7. The core network system according to any one of Claims 1 to 6,
wherein the second core network node extracts informat ion fo5 r
authent icat ing the UE f rom the second message.
8. A method for a core network system including a plural i ty of core
network nodes and a server, the method comprising:
10 a step that a UE (User Equipment ) sends a message to a first core network
node through a radio base stat ion;
a step that the UE is redi rected f rom the f irst core network node to a
second core network node based on subscr ipt ion informat ion of the UE provided
by the server ;
15 a step that the fi rst core network node sends a fi rst message including
informat ion on the redirect ion to the radio base stat ion; and
a step that the radio base stat ion sends a second message including the
informat ion to the second core network node.
20 9. The method according to Claim 8,
wherein the fi rst core network node does not authent icate the UE before
the redirect ion and the second core network node authent icates the UE after the
redi rect ion.
25 10. The method according to Claim 8,
wherein the fi rst core network node sends the fi rst message wi thout
authent icat ing the UE, and
wherein the second core network node authent icates the UE upon
receiving the second message.
30
11. The method according to any one of Claims 8 to 10,
wherein the fi rst and second core network nodes each comprise an MME
(Mobi l i ty Management Ent i ty) .
28
12. The method according to any one of Claims 8 to 11,
wherein the server comprises an HSS (Home Subscriber Server ).
13. The method according to any one of Claims 8 to 12,
wherein the fi rst core network node selects the second core network nod5 e
that serves the UE by using the subscript ion in format ion.
14. The method according to any one of Claims 8 to 13,
wherein the second core network node extracts informat ion for
10 authent icat ing the UE f rom the second message.
15. A UE (User Equipment) comprising:
means for sending a message to a fi rs t core network node through a radio
base stat ion,
15 wherein the UE is redirected f rom the fi rst core network node received the
message to a second core network node based on subscript ion informat ion of the
UE provided by a server, and
wherein in the redi rect ion, the fi rst core network node sends a first
message including informat ion on the redi rect ion to the radio base stat ion, and
20 the radio base stat ion sends a second message including the informat ion to the
second core network node.
16. The UE according to Claim 15, wherein the UE is not authent icated by
the fi rst core network node before the redirect ion, and the UE is authent icated by
25 the second core network node after the redirect ion.
17. A method for a UE (User Equipment ) comprising:
a step that the UE sends a message to a fi rst core network node through a
radio base stat ion; and
30 a step that the UE is redi rected f rom the f irst core network node received
the message to a second core network node based on subscript ion informat ion of
the UE provided by a server,
wherein in the redi rect ion, the fi rst core network node sends a first
message including informat ion on the redi rect ion to the radio base stat ion, and
29
the radio base stat ion sends a second message including the informat ion to the
second core network node.
18. The method according to Claim 17, wherein the UE is not
authent icated by the first core network node before the redi rect ion, and the UE i5 s
authent icated by the second core network node after the redirection.