DESCRIPTION
Title of Invention
ACCESS CONTROL FAILURE HANDLING FOR HeNB INBOUND MOBILITY
Technical Field
[0001]
A method and system is provided for handling access control failure during User
Equipment (UE) handover to a Home evolved Node B (HeNB) in Long Term Evolution (LTE).
This will prevent handover to a target HeNB repeatedly to which UE is not allowed to access
anymore. It also provides solution to synchronize Closed Subscriber Group (CSG)
management between UE and network.
Background Art
[0002]
In System Architecture Evolution (SAE)/LTE, Mobility Management Entity (MME)
performs access control for the target CSG HeNB when there is a handover required from the
source eNB/HeNB which UE attached to. MME determines if UE can access the target CSG
HeNB based on the CSG ID received from Handover required message and stored CSG
subscription data for the UE. If the access control fails, MME sends Handover preparation
failure to source eNB/HeNB (see Non Patent Literature (NPL) 1). Source eNB/HeNB will then
not send Handover command to UE therefore handover procedure will not be carried on.
[0003]
However, the discarded handover is caused by access control failure, which can be
caused by out of date CSG subscription data in MME and/or UE. Firstly, MME should verify if
its CSG subscription data is still fresh, if not, it should retrieve a fresh one from Home
Subscriber Server (HSS), and according to which MME should perform access control. If
access control failed, source eNB/HeNB should indicate UE about the access control failure so
that UE can update its whitelist.
Citation List
Non Patent Literature
[0004]
NPL 1: 3GPP TS 36.300, "Evolved Universal Terrestrial Radio Access (E-UTRA) and
Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2
(Release 9)", V9.4.0, 2010-06, section 10.5, pp. 69-72
Summary of Invention
[0005]
This invention considers access control failure and CSG management in inbound
mobility procedure. When MME receives Handover required from source eNB/HeNB which
contains CSG ID, it will verify whether the CSG subscription data it stores is fresh or expired.
If it is expired, or if MME does not have any association data for this UE, it will retrieve the
latest CSG subscription data from HSS. MME will rewrite its stored CSG subscription data
with the one retrieved from HSS, if they are different.
[0006]
MME will perform access control for the UE according to the CSG ID received from
Handover required message and its CSG subscription data. When the access control is failed, a
new message List Update Indication is proposed to be sent from source eNB/HeNB to UE. In
order to indicate what caused the failure, an appropriate cause in the message is proposed.
Upon receiving the List Update Indication message, UE updates its stored whitelist, such that the
CSG subscription data in UE and MME are synchronized.
Advantageous Effects of Invention
[0007]
MME downloads the latest CSG subscription data from HSS if its own one is expired or
it does not have any, such that MME is able to keep it up-to-date. This will prevent a wrong
access control thus it improves efficiency.
[0008]
UE is informed about the access control failure, such that the handover procedure can be
completed and UE can update its whitelist and keep it fresh.
[0009]
To remove that CSG which could not pass access control prevents initializing handover
procedure repeatedly, so that the signaling can be reduced and a better service can be provided
by the operator.
[0010]
UE and MME both are able to update their data of allowed CSG IDs, which completes
the CSG management and synchronization of CSG whitelist.
J
Brief Description of Drawings
[0011]
[Fig. 1] Fig. 1 is a sequence diagram showing an example of Access Control and Verification
failure handling.
[Fig. 2] Fig. 2 is a block diagram showing a configuration example of a network system
according to an exemplary embodiment of the present invention.
[Fig. 3] Fig. 3 is a block diagram showing a configuration example of a node according to an
exemplary embodiment of the present invention.
[Fig. 4] Fig. 4 is a block diagram showing a configuration example of a base station according to
an exemplary embodiment of the present invention.
[Fig. 5] Fig. 5 is a block diagram showing a configuration example of a UE according to an
exemplary embodiment of the present invention.
Description of Embodiments
[0012]
Hereafter, an exemplary embodiment of a node, a base station and a UE according to the
present invention, and a network system to which these node, base station and UE are applied
will be described with reference to Figs. 1 to 5. Note that the same signs are assigned to the
same elements throughout the drawings, and their duplicated explanation is omitted as
appropriate for clarifying the description.
[0013]
The object of the invention is achieved by MME verifying its stored CSG subscription
data and indicating UE about access control failure by a new message with a new cause. The
message to inform updating list upon access control failure is named as List Update Indication.
Based on which, UE can update its CSG whitelist and to synchronize the data with MME.
[0014]
As shown in Fig. 2, the network system according to this exemplary embodiment
includes a UE 10, an eNB 20_1, a HeNB 20_2, an MME 30, a HeNB GW (Gateway) 40, a
HeNB 50, and a HSS 60. Note that the eNB 20 1 and the HeNB 20 2 are sometimes
collectively referred as to the sign 20. The UE 0 includes the ability of accessing a cell
formed by the eNB/HeNB 20 and a CSG cell formed by the HeNB 50. The MME 30 controls
at least access from the UE 10 to the CSG cell, and retrieves subscription data on the CSG cell
from the HSS 60 if necessary. The HeNB GW40 relays traffic between the MME 30 and each
ofthe HeNBs 20 2 and 50.
[0015]
Next, an operation example of this exemplary embodiment will be described in detail
with reference to Fig. 1. This operation example assumes the case of performing handover of
the UE 10 from the eNB/HeNB 20 to the HeNB 50. Note that configuration examples of the
UE 10, the eNB/HeNB 20 and the MME 30 will be described later with reference to Figs. 3 to 5.
[0016]
In handover to HeNB 50, source eNB/HeNB 20 will send Handover required message
to MME 30 with a CSG ID included (Step S101 shown in Fig. 1). MME 30 is responsible to
perform access control for the target HeNB 50 based on the received CSG ID and its stored CSG
subscription data.
[0017]
MME 30 verifies if its CSG subscription data is expired, e.g, by a timer set when last
time the CSG subscription data was updated (Step SI 02). If its CSG subscription data is
out-of-date, MME 30 send request to HSS 60 and download a latest one (Step S103). MME 30
will update its CSG subscription data if they are different (Step SI 04).
[0018]
MME 30 performs access control, and when it is failed (Step SI05), MME 30 will send
an Handover Preparation Failure message to source eNB/HeNB 20 (Step SI 06). After received
Handover Preparation Failure message, source eNB/HeNB 20 which UE 10 is attached to, sends
List Updating Indication message to UE 10 with a proper cause (Step SI07). UE 10 then
removes the target HeNB's CSG ID from its whitelist (Step S108).
[0019]
Change Request will be proposed for sub-clause 8.2 and clause 10 in 3GPP TS 33.320,
VI 0.0.0 as follows.
[0020]
8.2 Access Control Mechanisms for H(e)NB
8.2.1 Non-CSG Method
The ACL (Access Control List) based access control mechanism for a non CSG capable
UE accessing the HNB or a UE accessing a non CSG capable HNB is handled in [12, 28]. The
ACL shall be securely stored in and integrity protected in the HNB if the HNB performs access
control.
[0021]
8.2.2 CSG Method
The CSG based access control mechanism for a CSG capable UE accessing the CSG
capable H(e)NB is handled in [12].
[0022]
HSS shall be able to push the latest CSG Lists (Allowed CSG List and Operator CSG
List) to MME/SGSN/MSC. MME/SGSN/MSC shall update the CSG Lists on receiving
updated list from the HSS. MME/SGSN/MSC shall request HSS for the latest CSG List when
the CSG List expires or when the MME does not have a CSG List for the given UE.
[0023]
10 Security Aspects for Mobility
10.1 Inbound mobility
In mobility from macro NB or HNB towards HNB CSG/hybrid, access control or
membership verification for CSG capable UE and non CSG capable UE shall be performed as
described in [12].
[0024]
Key management is done in core network as described in [20].
[0025]
Access control or membership verification for UE in mobility from macro eNB or
HeNB towards HeNB CSG/hybrid is handled in mobility scenario in [27].
[0026]
Key handling shall follow that in [21].
[0027]
When the access control of a UE fails at handover to a CSG H(e)NB the MME/SGSN
shall indicate the cause of access control failure to the source (e)NB/H(e)NB and the source
(e)NB/H(e)NB shall inform the cause to UE. The UE shall remove the given cell ID from its
CSG List.
[0028]
10.2 Outbound mobility
For mobility from HNB, the normal procedure can be applied as stated in [28]. Key
handling shall follow the macro mobility procedure.
[0029]
For mobility from HeNB, the normal procedure can be applied as stated in [27]. Key
handling shall follow the macro mobility procedure.
[0030]
Further, Reason for change of the above-mentioned sub-clause 8.2 and clause 10,
Summary thereof, and Consequences if not approved are as follows.
[0031]
Reason for change of sub-clause 8.2:
Description of CSG list (operator and allowed CSG list) management is spread out in
different specifications that has left some holes. One such holes is the lack of synchronization
of CSG lists between the HSS and MME/SGSN when it is modified. This can either lead to a
UE being accepted in a CSG cell even though it should not be or vice versa. Therefore a
solution is needed to synchronize the CSG list at MME/SGSN when it is actualized in HSS or
when it expires in the MME/SGSN.
[0032]
Summary of change of sub-clause 8.2:
Added text regarding CSG list actualization in MME/SGSN.
[0033]
Consequences if not approved:
Incorrect access control can happen and that will lead to business impact to operators.
[0034]
Reason for change of clause 10:
Cause #25 (Not authorized for this CSG) is defined for NAS messages in TS 24.301 .
[0035]
On reception of cause #25 in NAS messages at the UE, the CSG ID of the given cell is
removed from the CSG Lists (Allowed CSG List or Operator CSG List) in the UE. However
there is no such mechanism defined for handover case i.e. AS. This can lead to a UE repeatedly
trying to access a given cell even though it is not allowed to. The scenario is further detailed
below:
[0036]
Say a CSG capable UE has CSG Lists where the CSG ID of a given cell exists while the
MME/SGSN do not have the given CSG ID in their CSG Lists. Now if the UE performs a
handover to a such cell then it will receive a failure message. Not knowing that the cause of
handover failure is access control failure, the UE will try to access the given cell again. Thus a
cause of access control failure should be indicated to the UE that will lead to the removal of the
CSG ID from the CSG Lists in the UE.
[0037]
Summary of change of clause 10:
UE is indicated about the access control failure during handover and it updates its CSG
List.
[0038]
Consequences if not approved:
UE could end up endlessly trying to access a given cell although it is not allowed to do
so.
[0039]
Next, configuration examples of the UE 10, the eNB/HeNB 20 and the MME 30 will be
described with reference to Figs. 3 to 5.
[0040]
As shown in Fig. 3, the MME 30 includes a verifying unit 31, a retrieving unit 32, a
performing unit 33, and a notifying unit 34. The verifying unit 31 verifies the freshness of the
subscription data on the CSG cell, upon receiving the Handover required message. When it is
verified that the subscription data is expired, the retrieving unit 32 retrieves the latest
subscription data from the HSS 60. The performing unit 33 performs access control for the
CSG cell, based on the retrieved subscription data. When the access control is failed, the
notifying unit 34 notifies the Handover Preparation Failure message to the eNB/HeNB 20.
[0041]
These units 3 to 34 can be configured by, for example, transceivers which respectively
conduct communication with the HSS 60 and the eNB/HeNB 20, and a controller which controls
their transceivers to execute the processes shown in Fig. 1 or processes equivalent thereto.
Note that although the illustration is omitted, the above-mentioned SGSN can be similarly
configured.
[0042]
As shown in Fig. 4, the eNB/HeNB 20 includes a transmitting unit 21, a receiving unit
22, and a notifying unit 23. The transmitting unit 2 1 transmits the Handover required message
to the MME 30. The receiving unit 22 receives the Handover Preparation Failure message from
the MME 30. The notifying unit 23 notifies the List Updating Indication message, thereby
making the UE 10 update subscription data stored in the UE 10.
[0043]
These units 2 1 to 23 can be configured by, for example, a transceiver which conducts
communication with the MME 30, a transceiver which conducts wireless communication with
the UE 10, and a controller which controls their transceivers to execute the processes shown in
Fig. 1 or processes equivalent thereto. Note that although the illustration is omitted, the
above-mentioned NB/HNB can be similarly configured.
[0044]
As shown in Fig. 5, the UE 10 includes a receiving unit 11 and an updating unit 12.
The receiving unit 11 receives the List Updating Indication message from the eNB/HeNB 20.
The updating unit 2 updates subscription data stored in the UE 10, upon reception of the List
Updating Indication message.
[0045]
These units 11 and 12 can be configured by, for example, a transceiver which conducts
wireless communication with the eNB/HeNB 20, and a controller which controls this transceiver
to execute the processes shown in Fig. 1 or processes equivalent thereto.
[0046]
Note that the present invention is not limited to the above-mentioned exemplary
embodiment, and it is obvious that various modifications can be made by those of ordinary skill
in the art based on the recitation of the claims.
[0047]
This application is based upon and claims the benefit of priority from Japanese patent
applications No. 2010-182383, filed on August 17, 2010, and No. 2010-207581, filed on
September 16, 2010, the disclosures of which are incorporated herein in their entirety by
reference.
[0048]
The whole or part of the exemplary embodiment disclosed above can be described as,
but not limited to, the following supplementary notes.
[0049]
(Supplementary note 1)
MME verifies its CSG subscription data in handover procedure:
MME storages a timer to show the freshness of CSG subscription data. It will verify
the freshness by checking this timer. If it shows that the CSG subscription data is expired,
MME will request to HSS to download a latest version. That also applies when MME does not
have any CSG subscription data.
This verification can be used in other NAS (Non-Access Stratum) procedures when
access control is required (e.g. ATTACH/DETACH REJECT, Combined ATTACHREJECT,
Tracking Area Updating Reject, Combined Tracking Area Updating Reject, SERVICE REJECT,
extended SERVICE REJECT and potentially any other NAS message that might be added in
future).
[0050]
(Supplementary note 2)
New message of List Update Indication:
This message is sent from source eNB/HeNB to inform UE that the CSG ID it sent in
measurement report can not pass access control in MME, i.e. UE has an out-of-date whitelist, or
any other unexpected reason. This message is sent with a proper cause to indicate the failure.
[0051]
(Supplementary note 3)
New causes due to access control failure:
Proper causes are proposed to be sent together with List Updating Indication message.
Moreover, in case of handover to CSG HeNB/hybrid cell, new causes are proposed so that
Handover failure message is reused with a proper cause due to verification by target CSG HeNB.
[0052]
(Supplementary note 4)
Synchronization CSG management in UE and MME
After received List Updating Indication message with a cause that access control is
failed, both UE and MME should update their data of CSG to keep it up-to-date and
synchronized.
Reference Signs List
[0053]
10 UE
11, 22 RECEIVING UNIT
12 UPDATING UNIT
20 eNB/HeNB
20_1 eNB
20_2, 50 HeNB
2 1 TRANSMITTING UNIT
23, 34 NOTIFYING UNIT
30 MME
3 1 VERIFYING UNIT
32 RETRIEVING UNIT
33 PEFORMING UNIT
40 HeNB GW
60 HSS
CLAIMS
[Claim 1]
A node that controls access from a UE (User Equipment) to a CSG (Closed Subscriber
Group) cell, the node comprising:
first means for verifying the freshness of subscription data on the CSG cell, upon a
request for the access;
second means for retrieving, when it is verified that the subscription data is expired, the
latest subscription data from a server; and
third means for performing access control for the CSG cell, based on the retrieved
subscription data.
[Claim 2]
The node according to Claim 1, further comprising,
fourth means for notifying, when the access control is failed, a cause for the failure to
the transmission source of the request.
[Claim 3]
The node according to Claim 2,
wherein the request is transmitted from a base station to which the UE attaches, the
request being for handover of the UE to the CSG cell,
wherein the fourth means includes the cause in a response to be notified to the base
station.
[Claim 4]
The node according to any one of Claims 1 to 3, wherein the first means verifies
whether or not the subscription data is expired, based on time elapsed from the previous updating
of the subscription data.
[Claim 5]
The node according to any one of Claims 1 to 4, wherein the second means retrieves the
latest subscription data from the server, when the node does not have any subscription data.
[Claim 6]
A base station that conducts wireless communication with a UE, the base station
comprising:
first means for transmitting a request for handover of the UE to a CSG cell to a node
that controls access from the UE to the CSG cell;
second means for receiving a response to the request from the node, the response
including a cause for the failure of access control performed by the node for the CSG cell; and
third means for notifying the cause to the UE to make the UE update subscription data
stored in the UE.
[Claim 7]
A UE being capable of accessing a CSG cell, the UE comprising:
first means for receiving, from a base station to which the UE attaches, a cause for the
failure of access control performed by a node for the CSG cell, the node controlling access from
the UE to the CSG cell; and
second means for updating subscription data stored in the UE, upon reception of the
cause.
[Claim 8]
A method of controlling a node that controls access from a UE to a CSG cell, the
method comprising:
verifying the freshness of subscription data on the CSG cell, upon a request for the
access;
retrieving, when it is verified that the subscription data is expired, the latest subscription
data from a server; and
performing access control for the CSG cell, based on the retrieved subscription data.
[Claim 9]
The method according to Claim 8, further comprising,
notifying, when the access control is failed, a cause for the failure to the transmission
source of the request.
[Claim 10]
The method according to Claim 9,
wherein the request is transmitted from a base station to which the UE attaches, the
request being for handover of the UE to the CSG cell,
wherein the cause is included in a response to be notified to the base station.
[Claim 11]
The method according to any one of Claims 8 to 10, wherein the verification is
performed based on time elapsed from the previous updating of the subscription data.
[Claim 12]
The method according to any one of Claims 8 to 11, further comprising,
retrieving the latest subscription data from the server, when the node does not have any
subscription data.
[Claim 13]
A method of controlling a base station that conducts wireless communication with a UE,
the method comprising:
transmitting a request for handover of the UE to a CSG cell to a node that controls
access from the UE to the CSG cell;
receiving a response to the request from the node, the response including a cause for the
failure of access control performed by the node for the CSG cell; and
notifying the cause to the UE to make the UE update subscription data stored in the UE.
[Claim 14]
A method of controlling a UE being capable of accessing a CSG cell, the method
comprising:
receiving, from a base station to which the UE attaches, a cause for the failure of access
control performed by a node for the CSG cell, the node controlling access from the UE to the
CSG cell; and
updating subscription data stored in the UE, upon reception of the cause.