WO2013048301A1

WO2013048301A1 - Methods and apparatuses for enabling access control in a network

Info

Publication number: WO2013048301A1
Application number: PCT/SE2012/050421
Authority: WO
Inventors: Gino Masini; Gunnar Mildh; Martin Israelsson
Original assignee: Telefonaktiebolaget L M Ericsson (Publ)
Priority date: 2011-09-26
Filing date: 2012-04-20
Publication date: 2013-04-04

Abstract

The exemplary embodiments described herein relate to apparatus and methods therein for enabling access control of a UE (1001) performing a handover from a source (1002) to a target base station (1003), The target base station (1003) is configured to provisionally accept the UE (1001) and is also configured to send a request message to a CN node (1004), the message including an identiiy which is used by the CN node to check if the UE is allowed or not to access the network. The CN node (1004) informs the target base station of the results of the access control.

Description

METHODS AND APPARATUSES FOR ENABLING ACCESS CONTROL IN

A NETWORK

TECHNICAL FIELD

Ι^'ΘΟΜ] The technology described herein relate to methods and apparatuses for radio communications; and in particular, radio communications that involve home base stations for enabling access of a user equipment performing handover from a source to a target base station,

BACKGOU D

[Θ0Θ2] The use of mobile broadband services using cellular networks has significantly increased during the latest years. In parallel to this, third generation (3G) and fourt generation (4G) cellular networks like high speed packet access (H SPA), long te m evolution (LTE) and W^'i aX continue to evolve in order to support ever increasing performance with regards to capacity, peak bit rates, and coverage. Operators deploying these networks are faced with a number of challenges, e.g., related to site and transport costs and availability, lack of wireless spectrum, etc. Indeed, emerging mobile networks trends call for denser deployments in urban areas, due to increasing traffic and user density. The question is how best to meet these challenges and provide cost-efficient mobile broadband. fO§iB] -Operators may deplo smaller cells (e.g., pico, femio, home cells) in the same areas as macro cells, with varying degrees of "cooperation^'' and integration between them according to the desired level of network performance;.- the so-called heterogeneou network "HetNet" deployments. Home or other small base stations such HeNBs in LTE. HNBs in-^'HSPA-, femto base station which is a name used by femtoforum.org,. complement traditional macro base stations. Advantages of these small base stations include lower site costs due to smaller physical, size and lower ouipui power as well as increased capacity and coverage due to the closer deployment to the end user. An important issue in such HetNet deployments is how to provide optimum mobile radio terminal e.g. user equipments (UEs)) mobility i.e., handover and/or roaming between small and large base stations with a low level of core network involvement in order to reduce signaling traffic. 10004] UE mobility is complicated by the fact that different ceils may have different UE access levels. An operator may configure a coverage cell as: Open, Hybrid, or Closed. Open cells are open for use by all UE subscribers with no preference to perform cell re-selection to specific individual cells. Closed cells broadcast a closed subscriber group (CSG) cell type; called a CSG Indication that may either indicate values "true" or "false", and identity (e.g., a CSG-ID). A closed ceil is only available to UEs that belong to the CSG associated with that closed cell. When a ceil is closed, a CSG Indication value of "true" is broadcasted b that cell's base station. Hybrid cells broadcast a CSG identity with a value "false," As result, hybrid cell are available for all UEs. .In addition. UEs belonging to the CSG have a preference for selecting CSG cells with the same CSG identity.

[0005] The third generation partnershi project radio access network 3 (3GPP AN3) has started work on an LTE Release-! 1 study item on enhanced mobility between evolved node Bs (e B^'s) and HeNBs aimed among other things to enable handover between .different size base stations in a .HetNet in cases where access control is required. Enhanced mobility scenarios between macro and hybrid/open HeNBs are of particular interest. A technical specification (TS) describing mobility enhancements for H(e)NB (Release 1 1) can be found in 3 GPP TS 37.803 the contents of which are incorporated herein by reference.

10006] 3GPP Release- 10 is described in E-U RA and E-UTRAN Overall Description; Stage 2 (Release 10) in the following technical specification 3 GPP TS 36,300 Rei-10, the contents of which are incorporated herein by reference. As explained in the X2 Application Protocol (X2AP) (Release 10), 3GPP TS 3 .423 VI 0.2.0 (201 1-06), the contents of which are incorporated herein by reference, X2 (X2 is the standardized LTE interface between eNBs and HeNBs) mobility between LTE HeNBs is allowed whenever access control at the core network is not needed, i.e., when a source base station and a target handover base station belong to the same CSG or when the target base station is an open-access HeNB as described in section 4.6.1 of 3GPP TS 36,300 Rel-10. If these conditions are true, both source and target base stations belong to the same security domain i.e. are connected through the same security gateway node (SeGW in LIE)), and are therefore both 'trusted" nodes. In this ease, there is no reason for an additional access control step involving the core network, e.g., the mobility management entity (MME) in LTE. |0β07| However for a UE handover from a macro base station to a hybrid access home base station or if more than one CSG ideniitler is involved, the core network must be invoived in orchestrating the handover with additional signaling load to the core network and potentially more delay, In LTE, this is referred to as an Si handover, and in. this case there is also signaling involved in preliminary access control by the MME.

[0008] Hence, it is would be desirable to have X2-type handovers from a (source) macro base station to a (target) home base station associated with a CSG with a minimum of core network involvement, while maintaining the security characteristics of CSG access. The technology described below provides such a solution.

[01509] An object according to embodiments described herein is to alleviate at least the problems mentioned above so that a minimum of core network involvement is achieved, while maintaining the security characteristics of CSG access,

(ββ1 | Thus, according to an aspect of exemplary embodiments, at least some of the above stated problems are solved by means of a method in a target base station for enabling access control of a UE, performing a handover from a source base station to the target base station, the method comprising: receiving a handover request message, from the source base station: the reques message comprising a CSG membership status of the UE; provisionally accepting the UE; sending a path switch request message, to a core network node (e.g. MME), the path switch request message comprising a CSG ID of the UE, for enabling the core network node to perform access controi based on the CSG ID. In the event the access control fails, the method further comprising receiving, by the target base station, a message from the core network node, the message including information that the access control failed.

[Ό011] According t a further aspect of exemplary embodiments, at least some of the above stated problems are solved by means, of method, in a core network node for enabling access control of a U performing a handover from a source base station to a target base station, the method comprising: receiving a path switch request message, from the target base station, the message comprising a CSG ID of the UE; performing access control based on the received CSG ID; and in the event the access control fails, sending a message to the target base station, the message including information that the access control failed.

[0012j According to a further aspect of exemplary embodiments, at least some of the above stated problems are solved by means of a base station acting as a target base station, for enabling access controi of a UE performing a handover from a source base station to the target base station; the target base station comprising: radio circuitr configured to receive a handover request message, from the source base station, the handover request message comprising a CSG membership status of the UE; a controller configured to provisionally accept the LIE; the radio circuitry is further configured to send a path switch request message, to a core network node, the path switch, request message comprising a CSG ID of the UE for enabling the core network node to perform access control based on the CSG ID; and in the event the access control fails, the radio circuitry is further configured to receive a message from the core network node, the message including information, that the access control failed,

10013] According to a further aspect of exemplary embodiments, at least some of the above stated problems are solved by means of a core network node, for enabling access control of a UE performing a handover from a source base station to a target base station; the core network node comprising: a network interface configured to receive a path switch request message, from the target base station, the path switch request message comprising a CSG ID, of the UE - a controller configured to perform access control based on the received CSG ID; and in the event the access control tails, the network interface is configured to send a message to the target base station, the message including information that the access control failed.

|0OI4| According to yet another aspec of exemplary embodiments, at least some of the above stated problems are solved by mean of a network for access control of a UE performing a handover from a source base station to a target base station of the network, the network comprising: the source base station configured to receive UE measurement reports and further configured to decide to handover the .UE to the target base station; the source base station is further configured to generate a handover request message and to send it to the target base station; the request message comprising a CSG membership status of the UE. The target base station is configured to receive the handover request message; arid is further configured to provisionally accept the UE and to send to a core network node a path switch request message including a CSG ID of the UE, for enabling the core network node to perform access control based on the CSG ID: and in the event the access control fails, the core network node is configured to send a message to the target base station, the message including information that the access control failed, f 0015] An advantage of embodiments of the technology described herein is to allow handovers from a macro or home base station to a home base station associated with a particular CSG with reduced core network involvement, while maintaining the security characteristics of CSG access. [0016J This is achieved by expediting access control by initially presumptively accepting the CSG UE into cell of the target base station, but at the same time, access control still resides in the core network and therefore, UE subscription information is not propagated into radio access network so therefore security is not compromised.

[0017| Still other objects and features of the exemplary embodiments will be described from the following detailed description in conjunction with the accompanying drawings, attention to he called to the fact, however, that the following drawings are illustrati ve only, and that various modifications and changes may be made in the specific embodiments illustrated. It should further be understood that, the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIE DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a diagram illustrating a simplified network scenario wherein various exemplary HetNet handovers- are shown.

[0019] Figure 2 is function block diagram shoxving a handover situation in according with an exemplary embodiment.

[0020] Figure 3 is function block diagram showing a handover situation in according with an exemplary embodiment.

[0021] Figure 4 is a diagram illustrating a flowchart of a method performed, in a target base station, according to the present exemplary embodiments.

[0022] Figure 5 is a diagram illustrating a flowchart of a method performed according to the present exemplary embodiments.

[0023] Fi gure 6 is a diagram illustrating a flowchart of a method performed , in a core network node, according to the present exemplary embodiments.-

[0024] Figure 7 is a block diagram of an exemplary base station according to the present embodiments.

[0025] Figure 8 is a block diagram of an exemplary core network node according to the present embodiments.

[8026] Figure 9 shows a simplified HetNet architecture in LTE in which the present embodiments may be applied.

[0027] ^"Figure- 16 illustrates a signalling diagram according to the present exemplary embodiments.

DETAILED DESCR!PT

[0028] in the following description, for purposes of explanation and not limitation,, specific details are set forth suc as particular architectures, scenarios, techniques, etc. in order to provide thorough understanding of the present embodiments. However, the difference exemplary embodiments may be practiced in other embodiments that depart from these specific details. In particular, the solution according to is described in a non-limiting general context in relation to establishing a relation between radio base stations and core network nodes in a LTE based system wherein a handover of a UE is performed. It should be noted that the present embodiments are not restricted to LTE but can be applicable in other wireless systems wherein setup procedures in connectio with enabling access control of a UE performing a handover from a source base station to a target base station.

[0029] Referring to Figure 1 , there is illustrated a block diagram of an exemplary wireless telecommunications network scenario 100 in which the different exemplary embodiment may be applied. The scenario of Figure 1 shows various exemplary HeiNet handovers. A representative macro base (radio) station e.g. an eNodeB 101 has one or more corresponding coverage cell i.e. macrocells and two representative smaller (relatively low power) home base stations are shown e.g. HeNB 105 and HeNB 106. The enibodimenis herein are not restricted to any particular number of macro base station s and smaller base stations. The same applies for tire number of mobile terminals or user equipments (UEs). The HeNBs 105. 106 are also shown connected- to a core network (CN) 107 via a backhaul connection, Note that the term home base station is used to refer to an type of relatively low power base station like pico, femto etc. Such a home base, station has a smaller coverage areas shown with the circled -HeNB 105,

[0030| A plurality of UEs 102, 104 and 105 are also depicted, A closed subscriber group (CSG) is associated with the circled HeNB. As an example, UE 102 are shown as being CSG members whereas UE 103 and 104 are non-CSG member UEs. A handover may occur between HeNBs, out from the HeNB to the macro eNodeB (or eNB), or in from the macro eNB. This i indicated in Figure 1 ; inter HeNB-HO; hand-oui hand-in; HO stands for handover. A base station: HeNB or macro eNodeB from which a HE is handed over is known as a source base station, and a base station to which a UE is handed over is know as a target base station. Hence in the context of the exemplary embodiments herein, a macro H eNB and/or can ac as a target base station or as source base station depending on the HO scenario.

[0031] In a handover, it is generally the source base station that decides whether a UE is to be handed over to a target bases station or not. For example, a source base station; either a macro base station or eNodeB or eNB or a home base station e.g. HeNB with different closed subscriber group (CSG) than a target home base station; is responsible in deciding whether HO of the U E connection is necessary to the target home base station.

[0032] Figure 2 illustrates a handover situation in according with an exemplary embodiment. The macro base station (source) 201 is serving UE 202 and received measurement reports from the UE 202. Based on such measurement reports or other information, the source base station 201 determines and decides that the UE connection should be handover over to a target base station 206, being in this example a Home base station e.g. HeNB 206. HeNB 206 is associated with a CSG identity denoted here CSG ID "A". If the decision is "YES", the source base station 201 generates a handover request message and includes in the request message the CSG membership information for/of the UE, and sends that message to the target base station 206, The CSG membership information ot for the UE 202 is e.g. an information indicating the CSG status e.g. member or not a member of the CSG.

10033] Accordin to embodiments herein, the target base station 206 processes that request and provisionally; without performing a core network CSG access check for the UE; continues with normal handover request processing i.e. the target base station provisionally accepts the UE 202. An advantage with this provisional acceptance is that the handover is not slowed down with CN signaling. As shown and in according with embodiments herein, the target base station 206 sends, towards the end of the handover process (not shown), a message to a CN node (not shown) which performs UE access control. This message is referred to herein as a path switch request message. That message includes the CSG information for/of the UE i.e. a CGS ID of the UE 22_» and in exemplary embodiment, it may also include access mode information for the target home base station 206. [Q034J When the CN node e.g. a MME, receives the path switch request message from the target base station 206, The CN node performs, according to an embodiment, access control based on the information provided i.e. based on the CSG ID received from the target base station 206, A decision is further made by the CN node whether the access control is successful, if so, the UE connection handover is completed. In that case, the target base station 206 receives a path switch request acknowledge message from the C node and then sends a UE context release request message to source base station 201 for enabling the source to delete or release the context of UE 202.

[0035J in the event the access control fails and according to embodiments herein, the CN node informs the target home base station 206, and the target home base station 206 either provides some service for the non- SG member UE connection, e.g., lower priority or privilege than for CSG members, or it drops the UE. In any case th CN node sends a message to the target base station and includes the information that the access control failed.

[0036] According to an embodiment, such a message, from the CN node to the target base station 206, is a path switch request acknowledge message and the information on the failure is an information element (IE) included in the acknowledge, message.

[0037] According to another embodiment, such a message, from the CN node to the target base station, is a path switch request failure message including a cause value informing the target base station that the access control failed.

10038] According to anothe embodiment, in the event the access control fails, the message from the C node to the target base station Is a UE context release.

| 039) According to another embodiment, in the event the access control fails, the target base station received from the CN node a UE context release command message including a. cause value that the access control failed,

[0040} According t an embodiment, if the target base station is a hybrid home eNB, it includes a cell access mode IE in the path switch request message prior to sending the path switch request message to the CN node,

[0041] The advantage of the above described embodiments is to reduce core network involvement, while maintaining the security characteristics of CSG access. This is thanks to the initial acceptance of the CSG UE into the cell of the target base station and that the access control -stii ] reskies in the CN node and as a consequence UE subscription infonnation is not propagates into the radio access network to not compromise security.

[0042] Further exemplary embodiments will further be described and illustrated below.

(00 3| Figure 3 is a function block diagram showing a handover situation in which the technology described herein may be applied. Here both the source base station 305 and the target base station 306 are considered home base stations. However, the source base station 305 belongs to a different CSG ID B than thai of the target base station. CSG ID B is of the source and CSG ID A is of the target.

[0044] As a result a UE 304 who is a member of CSG ID B being served by source base station 305 may not be a member of CSG A and therefore, the UE 304 does not have privileged access to service from home base station 306 with CSG ID A, As a result, similar signalling and embodiments as described in conjunction with Figure 2 above are also applicable.

10045] Referring to Figure 4 there is illustrated a flowchart of a method performed in a target base station according to previously described embodiments, for enabling access control of a UE performing a .handover (HQ.) from a source base station to the target base station As shown, the main steps comprise:

[0046] (401): receiving a HO request message from the source base station, the message comprising a CSG membership status of the UE;

|0047] (402): provisionally accepting the UE;

[0048] (403) sending a path switch request message to a CN node, the message comprising a CSG ID of the UE for enabling the CN node to perform access control based on the CSG ID; and

[0049] (404) in the event the access control fails, receiving a message from the CN node, message including infonnation that the access control failed.

j^'0050] The different detailed embodiments have already been described and Figure 5 illustrates non* limiting steps example states performed by the source base station; target base station and CN node. As previously explained the source base station (macro or home with different CSG) receives UE measurement reports and decides a HO of the UE connection is necessary to the target home base station. This is illustrated in. step 501. -The source base station generates a HO request message, includes CSG membership information for the UE, and sends that message to the target home base station (step 502). The target home base station processes (step 503) that request and provisionall (without performing a core network CSG access cheek for the UE) continues with normal handover request processing. Again, this provisional acceptance means the handover is not slowed down with CN signaling.

10051) Toward the end of the handover process, the target home base station sends a message to the CN node which performs access control (step 504). That message includes the CSG information for the UE, and in one example embodiment, it may also include access mode information for the target home base station. The core network node then performs access control based on the information provided (step 505), A decision is made by the CN node whether the access control is successful (step 506). If so, the UE connection HO is completed (step 507). If not, the CN node informs the target home base station (step 508), and the target home base station either provides some service, for the non~CSG member UE connection, e.g., lower priority or privilege than for CSG members, or it drops the UE (step S5Q9). The different types of messages and contents in them have already been described and are not unnecessarily repeated.

|O052| Note that here are multiple situations where the access control may be unsuccessful. For example, the. UE may have been configured with incorrect CSG information, and therefore cannot be recognized as a member by the target HeNB, or the CSG information associated with the UE may have expired due to a change in subscription, and the corresponding privileges have therefore been revoked. There also may be attack scenarios by a "rogue UE", deliberately configured with forged CSG information in order to gain access with higher privileges into the target e.g. HeNB. In all these cases, the C (node) needs to .be involved to- enforce access control and report the situation to the operator through the management systems.

[00S3] Referrin to Figure 6 there is illustrated a flowchart of a method performed in a CN node according to previously described embodiments, for enabling access control of a UE performing a HO from a source base station to a target base station As shown, the main steps comprise:

fO054| (601): receiving a path switch request message from the target base station; including/comprising a CSG ID of the UE; [0055] (602) performing access control based on the received CSG ID; and

[0056} (603) in the event the access control fails, sending a message to the target base station, the message including information thai the access control failed.

[flOSTJ This message may be a path switch request failure message including a cause value information thai the access control failed, or the message may be a UE context release command message including the cause value. Any other appropriate message may also be used,

[0058 A described, the technology allows HOs from a macro or home base station to a home base station associated with a particular CSG with reduced core network involvement, while maintaining the security characteristics of CSG access, Again, the introduction of a CSG ID check through path switch enables such handovers also fo the cases where access control is required. This improves integration of the small base station "layer" with the macro base station layer in high mobility arid, dense traffic scenarios which means the technology is an important complement for HetNet, deployments. Using LTE terminology, fast X2 handovers can be performed fo CSG UEs from any macro base station (o home base station with different CSG) to any of its home base station neighbors. -Successful access control is, as described, expedited by initially presumptively accepting the CSG UE into the target (H)e B. But at the same time, access control .still resides in the core network, e.g., the MME in LTE, and- UE subscription information is not propagated into the radio access network so that security is not compromised.

^'[0.059] It will be appreciated that other embodiments may be employed apart from these specific details. In some instances, detailed descriptions of well known methods, nodes, interfaces, circuits, and devices are omitted so as not obscure -the description with unnecessary detail. Furthermore, it will be appreciated that the functions described may be implemented in one or more nodes using hardware circuitry (e.g., analog and/or discrete logic gates interconnected to perform a specialized function, ASICs, PL As, etc.) and/or using software programs and data in conjunction with one or more digital microprocessors or general purpose computers. Nodes that communicate using the air interface also have suitable radio communications circuitry. Moreover, the technology can additionally be considered to be embodied entirely within any form of computer-readable memory, such as solid-state memory. magnetic disk, or opti cal disk containing an appropriate set of computer instructions that would cause a processor to cany out the techniques .described herein.

Ι0Θ60] Hardware implementation may include or encompass, without limitation, digital signal processor (DSP) hardware, a reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC) and/or field programmable gate artay(s) (FPGA(s)), and (where appropriate) state, machines capable of performing such functions.

[0061 | in terras of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer, processor, and controller may be employed interchangeably. When provided by a computer, processor, or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computet or processor or controller,, or by a plurality of individual computers or processors o controllers, some of ^'which may be shared or distributed. Moreover, the term "processor' or "controller" also refers to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

Figure 7 is a function block- diagram of an example base station 700 acting as a target base station for enabling access control of a UE performing a HO from a sourc base station to the target base station in accordance with the previously described embodiments. As shown, base station 700 comprises radio circuitry 701 configured to receive and transmit signals over the radio interface under the control, of a controller 702. The controller 702 is configured to send messages to other base stations and to one or more core network nodes via a network interface 704. ^'The controller 20 is also shown coupled to a memory 703. that includes data like CSG status/IDs for IJBs, the base station's access mode, etc, as well as program instructions executed by the controller 702. The program instructions, cause the controller to analyze received messages and formulate base station messages to be sent as described in this application. See the flow chart in Figure 5 previously. In general, the radio circuitry 701 is configured to recei e a HO request message, from the source base station, the HO request message comprising a closed subscriber group, CSG, membership status of the UE. The controller 702 is further configured to provisionall accept the UE; and the radio circuitr 702 is configured to send a path switch request message, to a CN node, the path switch request message comprising a CSG ID of the UE for enabling the CN node to perform access control based on the CSG ID; and in the event the access control fails, the radio circuitry 701 is further configured to receive a message from the CN node, the message including information that the access control failed. f0062] The radio circuitry 701 may be configured io receive, from the CN node, a. ath switch request acknowledge message comprising an information element, IE, informing that the access control failed. The radio circuitry 701 may also be configured to receive, from the CN node, a path switch request failure message including a cause value informing that the access control tailed. The radio circuitry 701 .ay also be configured to receive, from the CN node, a UE context release command message including a cause value informing that the access control tailed,

[8063] The controller 702 is configured, in the event the access control fails, to drop the UE or to treat the UH as a non-member.

10064] If the base station 70Q is a hybrid home eNB, the controller 702 is configured to include a cell access mode information element, IE, in the. path switch request message prior to radio circuitry sending the path switch request message to the CN node.

(0065) In the event the access control is successful, the radio circuitry 703 is configured to receive a path switch request acknowledge message from the CN node and the radio circuitry 701 is further configured to send a UE context release request message to the source base station,

(0066] Figure 8 is a function block diagram of an example CN node 800 for access control of UE performing_. -a handover from a source base station to a base station acting as a target base station, the CN node may be a ^'mobility management entity (M^'ME) or any other suitable CN node suitable for performing the embodiments herein. As an example, the CN node maybe a gatewa e.g. a serving gateway S-GW or it may be a combination of a MME and a S-GW.

[0067] As shown in Figure 8, the CN node comprises a network interface 801 configured to receive a path switch request message, from the target base station, the path switch request message comprising a CSGID, of the UE. A controller 802 of the CN node 800 is configured to perfonn access control based on the received CSG ID; and in the event the access control falls, the network interface 801 is configured to send a message to the target base station, the message including information that the access control failed.

|0Θ68| In the event the access control tails, the network interface 801 is configured to send, to the target base station, a path switch request acknowledge message comprising an IE, informing the target base station that the access control failed.

|0069] According to another embodiment, in the event the access control fails, said network interface is configured to send, to the target base station, a path switch request failure- message- including a cause value informing the target base station that the access control failed.

|007θ^'| According to another embodiment, in the event the access control fails, said network interface is configured to send, to the -target base station, a UE context release command message including a cause value informing the target base station that the access control failed.

|007i .Referring to Figure 9, there is illustrated a HetNet architecture in LTE i.e. an enhanced Universal telecommunications radio access network (E-UTRAN) with HeNBs 903cormeeted to ME/S-GWs 901 via HeNB gateways 902. The system of Figure 7 is also known as a L^'TE/SAE based system. The exemplary embodiments described herein are applicable is- such a system. As shown different- interfaces are^' used, e.g. X2 interface between HeNBs andSl interface connecting HeNBs to MME/S-OW and to HeNB GW,

(0072J An ^'HeNB GW "hides" the HeNB from the rest of the network. In such a system, a HeNB GW is optional, and therefore, the HeNB. GW communicates with other nodes using the SI -interface. For the rest of the network, the HeNB G W just looks like a large eNB with many cell^'s.. From the HeNB point of view, the HeNB GW looks like a CN node (e.g., an LTE MME node . 2 mobility is possible between peer HeNBs without an mobility signaling passing through the_. HeNB GW. A detailed, overview of this system is described in 3G.PP TS36.300 incorporated herei by reference.

[0073^'f As clear from previously described embodiments, signalling messages are involved in a handover of a UE from a source to a target base station. Figure 10 illustrates the rather detailed signalling diagram of a handover scenario in accordance with the present exemplary embodiments.

f 007 1 As shown, a UE 1001 , a source eNB 1002 e.g. a macro eNB or a HeNB, a target base station 1003 e.g. a hybrid HeNB or HeNB, a MME 1004 and a serving gateway 1005 are provided. As described above, the technology may be used when the source and target HeNBs have different CSG IDs, i.e., belong to different CSGs. or simplicity, the target HeNB 1003 is assumed not connected to a HeNB-GW. As an example, a HeNB-G W maybe present between the target HeNB and the MME as described above in conjunction with Figure 9. A HeNB-GW simply routes an. S I application protocol message SIAP PATH SWITCH REQUEST message to the MME according to its so-called globally unique mobilit management entity identifier (GUMMEI), as provided for in standard technical specification document 3GPP TS 36,300, and therefore, the HeNB-GW will not influence the signaling flow described here.

(0β75| The source and target eNBs follow signalling steps 0-3. The source eNB includes the CSG membership status of the UE set to "member" in an CSG Membershi Status information element (IE) included with the X2AP HANDOVER REQUEST message (step 4), as allowed by current X2AP. See sections 8.2.1 and 9.1.1.1 of X2 Application Protocol (X2AP) (Release 10), 30 PP TS 36,423 incorporated herein by reference. The target eNB 1003 carries on with step 5 implicitly but provisionally accepting the CSG UE according to previously described embodiments.. The source and target eNB follow steps 6-1 1, and then the target eNB sends a PATH S WITCH REQUEST message to the MME as per ste 12, including a CSG ID IE and in an LTE embodiment a Cell Access Mode IE set to "hybrid", as allowed by current SI AP in sections 8,4.4 and 9.1.5.8, of St. Application Protocol (SIAP) (Release 10); 3 GPP TS 36,413 incorporated herein by reference.

(0076] The MME 1004 now performs access control based on the information provided, if access control is successful, then the X2 handover procedure continues with steps 13-18 and completes, if access control is not successful, then the X2 handover procedure continues with steps 13- 1 8, but the MME 1004 informs the eNB that the access control failed. This may be performed using for example a new IE in the PATH SWITCH REQUEST ACKNOWLEDGE message (in a modified step 16) or with the UE CONTEXT RELEASE COMMAND message. The target eNB 1 03 now knows that the UE is not authorized,- and it may choose whether to treat it as a non- member, i.e.. with a lower priority, QoS, etc.. or to drop it altogether.

|0077| In another LIE example embodiment, the source eNB 1002 is a macro eNB or a HeNB, and the target is a closed-access HeNB. Again, this embodiment may also be applied to the case of two HeNBs having different CSG IDs. The signaling flow is the same as for the previous embodiment and as shown in Figure 10 except tha the target HeNB sends a PATH SWITCH REQUEST message to the MME 1004 as per step 12, including the CSG ID IE but not the Ceil Access Mode IE, as allowed by current SIAP sections 8.4.4 and 9.1.5.8 of (S I AP) (Release 10); 3GPP TS 36.413), The other exception is if access control is not successful, then the MME 1004 does not perform step 13, hut informs the target HeNB 1003 that the access control failed. This may be achieved for example using a new failure message, th existing PATH SWITCH REQUEST FAILURE message, or the exiting UE CONTEXT RELEASE COMMAND message to the target HeNB 1003 with an appropriate cause value (e.g.. invalid CSG ID), The target HeNB 1003 then knows that the UE is not authorized, and it drops the UE.

[0078] In any of the example embodiments above, the target HeNB may choose not to provide any data service to the UE in the target cell until the core network node (e.g., MME) indicates that the access control was successful.

[0079] Although the description above contains many specifics, they should not be construed as limiting but as merely providing illustrations of some presently preferred embodiments. For example, non-limiting, example embodiments of the technology were described in an LTE context. But the principles of the technology described ma also be applied to other radio access technologies. Indeed, the technology fully encompasses other embodiments. Reference, to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more." All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinar skill in the art are expressly incorporated herein by reference and are intended to be encompassed hereby. Moreover, it is not necessary for a device or method to address each and ev r problem sought to be solved by the described technology for it to be encompassed hereby.

Claims

1. A method in a target base station (1003) for enabling access control of a user equipment, UE, (1001 ) performing a handover from a source base station (1002) to the iarget base station (1003), the method comprising:

- receiving (401 ) a handover request message, from the source base station (1002), comprising a closed subscriber group, CSG, membership status of the UE ( 1001 );

- provisionally accepting (402) the UE (1001);

- sending (403) a. path switch request message to a core network node (1004), comprising a CSG identity, ID, of the UE for enabling the core network node (1004) to perform access control based on the CSG ID; and

- in the event the access control talis, receiving. (404) a message from the core network node ( 1004), the message including information thai the control failed.

2. The method according to claim 1 wherein, in the event the access control fails, said receiving (404) the message from the core network node (1004) comprising, receiving a path switch request acknowledge message comprising an information element, IE, informing that the access control failed,

3. The method according to ciaim 1 wherein, in the event the access control fails, said receiving (404) the message from the core network node (1004) comprising, receiving a path switch request failure message including a cause value informin that the access control failed.

4. The method according to claim 1 wherein, in the event the access control fails, said receiving (404) the message from the core network node ( 1004) comprising, receiving a UE context release command message including a cause value informing that d e access control failed,

5. The method according to anyone of claims 1-4 wherein in the event the access control fails, dropping the UE(I OOl ) or treating the UE (1001) as a non-member.

6. The method according to anyone of claims 1-5 further comprises, if the target base station (1003) is a hybrid home eNB, including a cell aecess mode infomiation element, IE, in the path switch request message prior to sending the path switch request message to the core network node (1004),

?. The method according to claim 1 further comprises, in the event the access control is successful receiving a path switch request acknowledge message from the core network node (1004) and sending a UE context release request message to the source base station

(1002) .

8. A method in a core network nod ( 1004) for access control of a user equipment HE (1001) performing a handover trom a source base station. (1002) to a target base station

( 1 03) , the method comprising:

- receiving (601) a path switch request message, from the target base station (1003), comprising a closed subscriber group, CSQ, identity. ID, of the UE (1001) ,

- performing (602) aecess control based on the received CSG ID; and

- in the event the access control fails, sending (603) a- message to the target base station (1003), the message including information that the -access control failed,

9. The method according to claim 8 wherein, in the event the access control fails, said sending (603) the message to the target base station (1003) comprising sending a path switch request acknowledge message comprising an information element, IE, informing th target base station (1003) that the access control failed.

10. The method according to claim 8 wherein, in the event the access control fails, said sending (603) the message to the target base station (1003) comprising sending a path switch request failure message including a cause value informing that the access control failed,

11 . The method according to claim 8 wherein, in the event the access control fails, said sending (603) the message to the target base station (1003) comprising sending a UE context release command message including a cause value informing that the access control failed.

12. A base station (700) acting as a target base station for enabling access control of a user equipment, UE, performing a handover from a source base station to the target base station, comprising:

- radio circuitry (701) configured to receive a handover request message, from the source base station, the handover request message comprising a closed subscriber group, CSG, membership status of the UE;

- a controller (702) configured to provisionally accept the UE;

- the radio circuitry (701 ) configured to -send a path switch request message, to a core network node, the path switch request message comprising a CSG identity, ID, of the UE for enabling the core network node to perform access control based on the CSG ID; and

- in the. event the access- control tails, the radio circui try (701) is further configured to receive a message from the core network node, the message including information that the access control failed.

13. The base station (700) according to claim 12 wherein in the event the access control fails, said radio circuitry (701) is configured to receive, from the core network node, a path switch request acknowledge message comprising an information element, IE, informing that the access control failed.

14. The base station (700) according to claim 12 wherein in the event the access control fails, radio circuitry (7.01 ) is configured to receive, from the core network node, a path switch request failure, message including a cause value informing that the access control failed.

15. The base station (700) according to claim! 2 wherein in the event the access control fails, radio circuitry (701 ) is configured to receive, from the core network node, a UE context release command message including a cause value informing that the access control failed.

16. The base station (700) according to anyone of claims 12-15 wherein the controller (702) is configured, in the event the access control fails, to drop the UE or to treat the UE as a non-member.

17. The base station (700) according to anyone of claims 12-16 wherein, if the base station is a hybrid home e^'NB, the controller (702) is configured to include a cell access mode information element, IE, in the path switch reques message prior to radio circuitry sending the path switch request message to the core network node.

18. The base station (700) according to claim 12 wherein, in the event the access control is successful, the radio circuitry (701 ) is configured to receive a path switch request acknowledge message from the core network node and the radio circuitry is further configured to send a UE context release request message to the.. source base station.

1 . A core network node (800) tor access control of a user equipment. UE, performing a handover from a source base station to base station acting as a target base station, the core network node comprising:

- a network interface (801) configured to receive a path switch request message (12), from the target base station, the path switch request message comprising a closed ■subscriber group , CSG, identity. ID, of the UE .

- a controller (802) configured to perform access control based on the received CSG ID;- and

- in the event the access control .falls, the network interface (801 ) is configured to. send a message (16) to the target base station, the message including information thai the access control failed.

20. The core network node (800) according to claim 19 wherein, in the event the access control falls, said network interface (801 ) is configured to send, to the target base station, a path switch request acknowledge message comprising an information element, IE. informing the target base station that the access control failed.

21. The core network node (800) according to claim 19 wherein, in the event the access control fails, said network interface (801 ) is configured to send, to the target base station, a path switch request failure message including a cause value informing the target base station that the access control failed.

22. The core network node (800) according to claim 1 wherein, in the event the access control fails, said network interface (801) is configured to send, to the target base station, a UE context release command, message including_, a cause value informing the target base station thai the access control failed.

23. The core network node (800) according to anyone of claims 18-22 is a mobility management entity, MME.

24. A network for access control of a user equipment, UE, (1001) performing a handover from a source base station (1002) to a. target base station (1003) of the network, the network comprising;

- the source base station (1002) configured to receive UE measurement reports and further configured to decide to handover the UE (1001 ) to the target base station (1003);

> the source base station (1 02) is further configured to generate a handover request message and to send it to the target base station (1003), the request message comprising a closed subscriber group, CSG, membership status of the UE (1001);

- the target base station (1003) is configured to receive the handover request message; and further configured to provisionally accept the UE and to send to a core network node (1004) a path switch request message including a CSG identity, ID, of the UE, for enabling the core network node (1004) to perform access control based on the CSG ID: and

- in the event the access control fai ls, the core network node (1004) is configured to send message to the target base station (1003), the message including information that the access control failed.