Method and apparatus for performing membership verification or access control in wireless communication system

A method and apparatus for performing a membership verification or an access control in a wireless communication system is provided. A mobility management entity (MME) performs the membership verification or the access control of a user equipment (UE), and transmits verified UE membership information to a target HeNB.

TECHNICAL FIELD

The present invention relates to wireless communication, and more particularly, to a method and apparatus for performing a membership verification or an access control in a wireless communication system.

BACKGROUND ART

FIG. 1shows network structure of an evolved universal mobile telecommunication system (E-UMTS). The E-UMTS may be also referred to as an LTE system. The communication network is widely deployed to provide a variety of communication services such as voice over internet protocol (VoIP) through IMS and packet data.

As illustrated inFIG. 1, the E-UMTS network includes an evolved UMTS terrestrial radio access network (E-UTRAN), an evolved packet core (EPC) and one or more user equipment. The E-UTRAN may include one or more evolved NodeB (eNB)20, and a plurality of user equipment (UE)10. One or more E-UTRAN mobility management entity (MME)/system architecture evolution (SAE) gateways (S-GW)30may be positioned at the end of the network and connected to an external network.

As used herein, “downlink” refers to communication from eNB20to UE10, and “uplink” refers to communication from the UE to an eNB. UE10refers to communication equipment carried by a user and may be also referred to as a mobile station (MS), a user terminal (UT), a subscriber station (SS) or a wireless device.

An eNB20provides end points of a user plane and a control plane to the UE10. MME/S-GW30provides an end point of a session and mobility management function for UE10. The eNB and MME/S-GW may be connected via an S1 interface.

The eNB20is generally a fixed station that communicates with a UE10, and may also be referred to as a base station (BS) or an access point. One eNB20may be deployed per cell. An interface for transmitting user traffic or control traffic may be used between eNBs20.

The MME provides various functions including non-access stratum (NAS) signaling to eNBs20, NAS signaling security, access stratum (AS) security control, Inter core network (CN) node signaling for mobility between 3GPP access networks, Idle mode UE reachability (including control and execution of paging retransmission), tracking area list management (for UE in idle and active mode), packet data network (PDN) GW and serving GW selection, MME selection for handovers with MME change, serving GPRS support node (SGSN) selection for handovers to 2G or 3G 3GPP access networks, roaming, authentication, bearer management functions including dedicated bearer establishment, support for public warning system (PWS) (which includes earthquake and tsunami warning system (ETWS) and commercial mobile alert system (CMAS)) message transmission. The S-GW host provides assorted functions including per-user based packet filtering (by e.g. deep packet inspection), lawful interception, UE internet protocol (IP) address allocation, transport level packet marking in the downlink, UL and DL service level charging, gating and rate enforcement, DL rate enforcement based on APN-AMBR. For clarity MME/S-GW30will be referred to herein simply as a “gateway,” but it is understood that this entity includes both an MME and an SAE gateway.

A plurality of nodes may be connected between eNB20and gateway30via the S1 interface. The eNBs20may be connected to each other via an X2 interface and neighboring eNBs may have a meshed network structure that has the X2 interface.

FIG. 3shows a user-plane protocol and a control-plane protocol stack for the E-UMTS.

FIG. 3(a) is block diagram depicting the user-plane protocol, andFIG. 3(b) is block diagram depicting the control-plane protocol. As illustrated, the protocol layers may be divided into a first layer (L1), a second layer (L2) and a third layer (L3) based upon the three lower layers of an open system interconnection (OSI) standard model that is well known in the art of communication systems.

The physical layer, the L1, provides an information transmission service to an upper layer by using a physical channel. The physical layer is connected with a medium access control (MAC) layer located at a higher level through a transport channel, and data between the MAC layer and the physical layer is transferred via the transport channel. Between different physical layers, namely, between physical layers of a transmission side and a reception side, data is transferred via the physical channel.

The MAC layer of the L2 provides services to a radio link control (RLC) layer (which is a higher layer) via a logical channel. The RLC layer of the L2 supports the transmission of data with reliability. It should be noted that the RLC layer illustrated inFIGS. 3(a) and3(b) is depicted because if the RLC functions are implemented in and performed by the MAC layer, the RLC layer itself is not required. A packet data convergence protocol (PDCP) layer of the L2 performs a header compression function that reduces unnecessary control information such that data being transmitted by employing IP packets, such as IPv4 or IPv6, can be efficiently sent over a radio (wireless) interface that has a relatively small bandwidth.

A radio resource control (RRC) layer located at the lowest portion of the L3 is only defined in the control plane and controls logical channels, transport channels and the physical channels in relation to the configuration, reconfiguration, and release of the radio bearers (RBs). Here, the RB signifies a service provided by the L2 for data transmission between the terminal and the UTRAN.

As illustrated inFIG. 3(a), the RLC and MAC layers (terminated in an eNB20on the network side) may perform functions such as scheduling, automatic repeat request (ARQ), and hybrid automatic repeat request (HARQ). The PDCP layer (terminated in eNB20on the network side) may perform the user plane functions such as header compression, integrity protection, and ciphering.

As illustrated inFIG. 3(b), the RLC and MAC layers (terminated in an eNodeB20on the network side) perform the same functions for the control plane. As illustrated, the RRC layer (terminated in an eNB20on the network side) may perform functions such as broadcasting, paging, RRC connection management, RB control, mobility functions, and UE measurement reporting and controlling. The NAS control protocol (terminated in the MME of gateway30on the network side) may perform functions such as a SAE bearer management, authentication, LTE_IDLE mobility handling, paging origination in LTE_IDLE, and security control for the signaling between the gateway and UE10.

The RRC state may be divided into two different states such as a RRC_IDLE and a RRC_CONNECTED. In RRC_IDLE state, the UE10may receive broadcasts of system information and paging information while the UE specifies a discontinuous reception (DRX) configured by NAS, and the UE has been allocated an identification (ID) which uniquely identifies the UE in a tracking area and may perform PLMN selection and cell re-selection. Also, in RRC_IDLE state, no RRC context is stored in the eNB.

In RRC_CONNECTED state, the UE10has an E-UTRAN RRC connection and a context in the E-UTRAN, such that transmitting and/or receiving data to/from the network (eNB) becomes possible. Also, the UE10can report channel quality information and feedback information to the eNB.

In RRC_CONNECTED state, the E-UTRAN knows the cell to which the UE10belongs. Therefore, the network can transmit and/or receive data to/from UE10, the network can control mobility (handover and inter-radio access technologies (RAT) cell change order to GSM EDGE radio access network (GERAN) with network assisted cell change (NACC)) of the UE, and the network can perform cell measurements for a neighboring cell.

In RRC_IDLE state, the UE10specifies the paging DRX cycle. Specifically, the UE10monitors a paging signal at a specific paging occasion of every UE specific paging DRX cycle.

The paging occasion is a time interval during which a paging signal is transmitted. The UE10has its own paging occasion.

A paging message is transmitted over all cells belonging to the same tracking area. If the UE10moves from one tracking area to another tracking area, the UE will send a tracking area update message to the network to update its location.

FIG. 4shows an example of structure of a physical channel.

The physical channel transfers signaling and data between layer L1 of a UE and eNB. As illustrated inFIG. 4, the physical channel transfers the signaling and data with a radio resource, which consists of one or more sub-carriers in frequency and one more symbols in time.

One sub-frame, which is 1 ms in length, consists of several symbols. The particular symbol(s) of the sub-frame, such as the first symbol of the sub-frame, can be used for downlink control channel (PDCCH). PDCCHs carry dyn amic allocated resources, such as PRBs and modulation and coding scheme (MCS).

A transport channel transfers signaling and data between the L1 and MAC layers. A physical channel is mapped to a transport channel.

Downlink transport channel types include a broadcast channel (BCH), a downlink shared channel (DL-SCH), a paging channel (PCH) and a multicast channel (MCH). The BCH is used for transmitting system information. The DL-SCH supports HARQ, dynamic link adaptation by varying the modulation, coding and transmit power, and both dynamic and semi-static resource allocation. The DL-SCH also may enable broadcast in the entire cell and the use of beamforming. The PCH is used for paging a UE. The MCH is used for multicast or broadcast service transmission.

Uplink transport channel types include an uplink shared channel (UL-SCH) and random access channel(s) (RACH). The UL-SCH supports HARQ and dynamic link adaptation by varying the transmit power and potentially modulation and coding. The UL-SCH also may enable the use of beamforming. The RACH is normally used for initial access to a cell.

The MAC sublayer provides data transfer services on logical channels. A set of logical channel types is defined for different data transfer services offered by MAC. Each logical channel type is defined according to the type of information transferred.

Logical channels are generally classified into two groups. The two groups are control channels for the transfer of control plane information and traffic channels for the transfer of user plane information.

Traffic channels are used for the transfer of user plane information only. The traffic channels provided by MAC include a dedicated traffic channel (DTCH) and a multicast traffic channel (MTCH). The DTCH is a point-to-point channel, dedicated to one UE for the transfer of user information and can exist in both uplink and downlink. The MTCH is a point-to-multipoint downlink channel for transmitting traffic data from the network to the UE.

Uplink connections between logical channels and transport channels include a DCCH that can be mapped to UL-SCH, a DTCH that can be mapped to UL-SCH and a CCCH that can be mapped to UL-SCH. Downlink connections between logical channels and transport channels include a BCCH that can be mapped to BCH or DL-SCH, a PCCH that can be mapped to PCH, a DCCH that can be mapped to DL-SCH, and a DTCH that can be mapped to DL-SCH, a MCCH that can be mapped to MCH, and a MTCH that can be mapped to MCH.

The specification of a home eNB (HeNB) is currently ongoing in 3GPP LTE. It may be referred to Paragraph 4.6.1 of 3GPP (3rd generation partnership project) TS 36.300 V10.2.0 (2010-12). The HeNB is a small base station designed for use in residential or small business environment. The HeNB may be a femto cell or a pico cell. The HeNB is short range about tens of meter, installed by the consumer for better indoor voice and data reception.

Referring toFIG. 5, a HeNB50may be connected with an EPC60through an S1 interface. A HeNB gateway (55, HeNB GW) may be deployed between the HeNB50and the EPC60to allow the S1 interface and to scale to support a large number of HeNBs. The HeNB GW55serves as a concentrator for the C(control)-Plane, specifically the S1-MME interface. The S1-U interface from the HeNB50may be terminated at the HeNB GW55, or a direct logical U(user)-Plane connection between HeNB50and S-GW56may be used. The S1 interface may be defined as the interface between the HeNB GW55and the core network, between the HeNB50and the HeNB GW55, between the HeNB50and the core network, and between the eNB and the core network. Also, the HeNB GW55appears to the MME as an eNB. The HeNB GW55appears to the HeNB as an MME. The S1 interface between the HeNB50and the EPC60is the same whether the HeNB50is connected to the EPC60via a HeNB GW55or not.

A closed subscriber group (CSG) identifies subscribers of an operator who are permitted to access one or more cells but which have restricted access (CSG cells). A CSG cell broadcasts a CSG indicator set to true and a specific CSG identity. A HeNB may be a CSG cell. The CSG cell operates with an open mode or a closed mode. When the CSG cell operates with an open mode, the HeNB operates as a normal eNB. When the CSG cell operates with a closed mode, the HeNB provides services only to its associated CSG members. That is, the HeNB may perform access control which is a process that checks whether a UE is allowed to access and to be granted services in a CSG cell. A CSG whitelist is a list stored in a UE containing the CSG identities of the CSG cells to which the subscriber belongs.

A hybrid cell is a cell broadcasting a CSG indicator set to false and a specific CSG identity. This cell is accessible as a CSG cell by UEs which are members of the CSG cell and as a normal cell by all other UEs. The hybrid cell may check whether a UE is a member or non-member of the hybrid cell. This process may be referred as a membership verification. The UEs which are members of the CSG cell may have a higher priority than other UEs to access to the hybrid cell. The hybrid cell may be referred as a CSG cell which operates with a hybrid mode.

It may be referred to Paragraph 4.6.1 of 3GPP (3rd generation partnership project) TS 36.300 V9.3.0 (2010-03). Referring toFIG. 6, an E-UTRAN may include one or more eNB60, one or more HeNB70and a HeNB GW79. One or more E-UTRAN MME/S-GW69may be positioned at the end of the network and connected to an external network. The one or more eNB60may be connected to each other through the X2 interface. The one or more eNB60may be connected to the MME/S-GW69through the S1 interface. The HeNB GW79may be connected to the MME/S-GW69through the S1 interface. The one or more HeNB70may be connected to the HeNB GW79through the S1 interface or may be connected to the MME/S-GW69through the S1 interface. The one or more HeNB70may not be connected to each other.

Based on the structure inFIG. 6, if a user equipment (UE) served currently by an HeNB or an eNB requests handover to another HeNB, the path will go through the core network. That is, the handover should be performed through the S1 interface. This handover procedure can be big signaling impact on the core network, which has to deal with a lot of processing. In addition, a handover delay can occur as the handover is performed through the core network, which may be sensitive to UE in a certain situation.

It may be referred to Paragraph 4.6.1 of 3GPP (3rd generation partnership project) TS 36.300 V10.2.0 (2010-12). Referring toFIG. 7, the HeNBs90may be connected to each other through the X2 interface. The HeNBs90connected to each other through the X2 interface should have same CSG identifiers (IDs) or the target HeNB should operate with the open mode.

Referring toFIG. 8, the one or more HeNB90may be connected to the MME/S-GW89through the S1 interface. The HeNBs90may be connected to each other through the X2 interface directly. The HeNBs90connected to each other through the X2 interface should have same CSG identifiers (IDs) or the target HeNB should operate with the open mode.

That is, only the HeNBs with the same CSG IDs or the target HeNB which operate with the open mode can have the direct X2 interface even if some HeNB may support the hybrid mode, which can be accessed by any UEs. If the conditions are satisfied, a handover may be performed through the direct X2 interface between HeNBs.

However, the signaling impact problem on the core network and the handover delay problem may still exist due to the implementation limitations. If the CSG IDs are different for the source HeNB and the target HeNB or in case of a handover from the macro eNB to the HeNB, a handover through the S1 interface has to be used. The handover through the S1 interface also has to be used when the target HeNB operates with the hybrid mode even though a UE is not a member of the target HeNB.

In order to solve the problem described above, existing X2 handover procedure can be a solution. However, it is required that how to perform a membership verification of a UE for efficient X2 handover procedure when the target HeNB is a hybrid cell. In addition, it is required that how to perform an access control when the target HeNB operates with the closes mode.

SUMMARY OF INVENTION

Technical Problem

The present invention provides a method and apparatus for performing a membership verification or an access control in a wireless communication system. The present invention provides a method of performing a membership verification or an access control for HeNB mobility enhancement when the target HeNB is a hybrid cell or the target HeNB operates with a closed mode.

Technical Solution

In an aspect, a method for performing, by a mobility management entity (MME), a membership verification in a wireless communication system is provided. The method includes receiving a path switch request message including a closed group subscription (CSG) identifier (ID) of a target home eNodeB (HeNB) and an access mode of the target HeNB from the target HeNB, the target HeNB operating with a hybrid mode, performing the membership verification of a user equipment (UE) according to the CSG ID of the target HeNB, the access mode of the target HeNB and stored UE subscription information, and transmitting verified UE membership information to the target HeNB.

The verified UE membership information may indicate that the UE is a member of the target HeNB.

The verified UE membership information may indicate that the UE is not a member of the target HeNB.

The UE may be regarded as a member of the target HeNB before the membership verification is performed.

The UE may be not regarded as a member of the target HeNB before the membership verification is performed.

The verified UE membership information may be included in a path switch response message which is a response of the path switch request message.

The verified UE membership information may be included in the existing message or a new message.

In another aspect, a method for performing, by a target home eNodeB (HeNB) which operates with a hybrid mode, a handover procedure in a wireless communication system is provided. The method includes receiving a handover request message from a source eNB, deciding whether the handover procedure is acknowledge or not, if the handover procedure is acknowledged, transmitting a path switch request message including a closed group subscription (CSG) identifier (ID) of the target HeNB and an access mode of the target HeNB to a mobility management entity (MME), and receiving verified user equipment (UE) membership information from the MME.

The source eNB may be a macro eNB or a HeNB.

The handover request message may be received through a direct X2 interface or an indirect X2 interface.

If the handover procedure is acknowledged, the method may further include pre-deciding a UE as a member of the target HeNB before transmitting the path switch request message to the MME.

If the verified UE membership information indicates that the UE is not a member of the target HeNB, the method may further include down-prioritizing the UE as a non-member of the target HeNB or excluding the UE from the target HeNB.

If the handover procedure is acknowledged, the method further include pre-deciding a UE as a non-member of the target HeNB before transmitting the path switch request message to the MME.

If the verified UE membership information indicates that the UE is a member of the target HeNB, the method may further include adjusting the priority of the UE and preparing resources for the UE.

The verified UE membership information may be included in a path switch response message which is a response of the path switch request message.

The verified UE membership information may be included in the existing message or a new message.

In another aspect, a method for performing, by a mobility management entity (MME), an access control in a wireless communication system is provided. The method includes receiving a path switch request message including a closed group subscription (CSG) identifier (ID) of a target home eNodeB (HeNB) from the target HeNB, the target HeNB operating with a closed mode, performing the access control of a user equipment (UE) according to the CSG ID of the target HeNB and stored UE subscription information, and transmitting verified UE membership information to the target HeNB.

The verified UE membership information may indicate that the UE is a member of the target HeNB.

The verified UE membership information may indicate that the UE is not a member of the target HeNB.

Advantageous Effects

The membership verification or the access control can be performed efficiently.

MODE FOR INVENTION

For clarity, the following description will focus on the LTE-A. However, technical features of the present invention are not limited thereto.

In 3GPP LTE-A re11-11 or beyond, the following architectures may be considered to be deployed.

Referring toFIG. 9, the one or more HeNB100may be connected to the MME/S-GW109through the S1 interface. The HeNBs100may be connected to each other through the X2 interface directly. UnlikeFIG. 8, The HeNBs100connected to each other through the X2 interface need not to have same CSG identifiers (IDs) or the target HeNB need not to operate with the open mode.

Referring toFIG. 10, an E-UTRAN may include one or more eNB110, one or more HeNB120and a HeNB GW129. One or more E-UTRAN MME/S-GW119may be positioned at the end of the network and connected to an external network. The one or more eNB110may be connected to each other through the X2 interface. The one or more eNB110may be connected to the MME/S-GW119through the S1 interface. The HeNB GW129may be connected to the MME/S-GW119through the S1 interface. The one or more HeNB120may be connected to the HeNB GW129through the S1 interface or may be connected to the MME/S-GW119through the S1 interface. The HeNBs120may be connected to each other through the direct X2 interface. The HeNBs120may have same CSG IDs. Or, the HeNBs120may have different CSG IDs.

The overall architecture with deployed HeNB GW/X2-proxy ofFIG. 11is the same as that ofFIG. 10. But, inFIG. 11, the HeNBs140may be connected to each other through the indirect X2 interface. The HeNBs140may have same CSG IDs. Or, the HeNBs140may have different CSG IDs. The indirect X2 interface between the HeNBs140goes through the HeNB GW/X2-proxy149. The HeNB GW/X2-proxy149may be a HeNB GW having an X2-proxy functionality for supporting the X2 interface. Hereinafter, if the indirect X2 interface goes through the HeNB GW, the HeNB GW may be referred as the HeNB GW/X2-proxy.

FIG. 12shows another direct connection between a macro eNB and a HeNB without deployed HeNB GW.

Referring toFIG. 12, the macro eNB150and the HeNB151may be connected to the MME/S-GW159through the S1 interface. The macro eNB150and the HeNB151may be connected to each other through the X2 interface directly.

Referring toFIG. 13, an E-UTRAN may include one or more eNB160, macro eNB1161, HeNB1171, HeNB2172, HeNB3173and a HeNB GW/X2-proxy179. One or more E-UTRAN MME/S-GW169may be positioned at the end of the network and connected to an external network. The eNBs160may be connected to each other through the X2 interface. The eNBs160may be connected to the MME/S-GW169through the S1 interface. The HeNB GW/X2-proxy179may be connected to the MME/S-GW169through the S1 interface. The HeNB1171and the HeNB3173may be connected to the HeNB GW/X2-proxy179through the S1 interface. The HeNB2172may be connected to the MME/S-GW169through the S1 interface. The HeNBs171,172,173may be connected to each other through the direct X2 interface. The HeNBs171,172,173may have same CSG IDs. Or, the HeNBs171,172,173may have different CSG IDs. The macro eNB1161may be connected to the MME/S-GW169through the S1 interface. The macro eNB1161may be connected to the HeNBs171,173through the indirect X2 interface. The indirect X2 interface between the macro eNB1161and the HeNBs171,173goes through the HeNB GW/X2-proxy179.

Referring toFIG. 14, an E-UTRAN may include one or more eNB180, macro eNB1181, macro eNB2182, HeNB1191, HeNB2192, HeNB3193and a HeNB GW/X2-proxy199. One or more E-UTRAN MME/S-GW189may be positioned at the end of the network and connected to an external network. The eNBs180may be connected to each other through the X2 interface. The eNBs180may be connected to the MME/S-GW189through the S1 interface. The HeNB GW/X2-proxy199may be connected to the MME/S-GW189through the S1 interface. The HeNB1191and the HeNB3193may be connected to the HeNB GW/X2-proxy199through the S1 interface. The HeNB2192may be connected to the MME/S-GW189through the S1 interface. The HeNBs191,192,193may be connected to each other through the direct X2 interface. The HeNBs191,192,193may have same CSG IDs. Or, the HeNBs191,192,193may have different CSG IDs. The macro eNB1181may be connected to the MME/S-GW189through the S1 interface. The macro eNB1181may be connected to the HeNB3193through the direct X2 interface. There is no connection between the macro eNB1181and the HeNB GW/X2-proxy199. The macro eNB2182may be connected to the HeNB GW/X2-proxy199through the X2 interface.

FIG. 15shows an example of an intra-MME/S-GW handover procedure.

In E-UTRAN, network-controlled UE-assisted handovers may be performed in RRC_CONNECTED state. Part of the handover command comes from the target eNB and is transparently forwarded to the UE by the source eNB. To prepare the handover procedure, the source eNB passes all necessary information to the target eNB (e.g. E-RAB attributes and RRC context). When a carrier aggregation (CA) is configured and to enable secondary cell (SCell) selection in the target eNB, the source eNB can provide in decreasing order of radio quality a list of the best cells. Both the source eNB and the UE keep some context (e.g. C-RNTI) to enable the return of the UE in case of handover procedure failure. The UE accesses the target cell via a random access channel (RACH) following a contention-free procedure using a dedicated RACH preamble or following a contention-based procedure if dedicated RACH preambles are not available. If the RACH procedure towards the target cell is not successful within a certain time, the UE initiates radio link failure recovery using the best cell.

The preparation and execution phase of the handover procedure is performed without evolved packet core (EPC) involvement. It means that preparation messages are directly exchanged between the eNBs. The release of the resources at the source side during the handover completion phase is triggered by the eNB.

First, the handover preparation procedure is described.

0. Area restriction information is provided. The UE context within the source eNB contains information regarding roaming restrictions which where provided either at connection establishment or at the last timing advance (TA) update.

1. The source eNB configures the UE measurement procedures according to the area restriction information, and transmits a measurement control message to the UE through L3 signaling. Measurements provided by the source eNB may assist the function controlling the UE's connection mobility. Meanwhile, the packet data is exchanged between the UE and the source eNB, or between the source eNB and the serving gateway.

2. The UE transmits measurement reports by the rules set by i.e. system information, specification etc to the source eNB through L3 signaling.

3. The source eNB makes handover decision based on the measurement reports and radio resource management (RRM) information.

4. The source eNB transmits a handover request message through L3 signaling to the target eNB passing necessary information to prepare the handover procedure at the target side. UE X2/UE S1 signaling references enable the target eNB to address the source eNB and the EPC. The evolved radio access bearer (E-RAB) context includes necessary radio network layer (RNL) and transport network layer (TNL) addressing information, and quality of service (QoS) profiles of the E-RABs.

In the case of a UE under an RN performing handover procedure, the handover request message is received by the DeNB, which reads the target cell ID from the message, finds the target eNB corresponding to the target cell ID, and forwards the X2 message toward the target eNB.

In the case of a UE performing handover procedure toward an RN, the handover request is received by the DeNB, which reads the target cell ID from the message, finds the target RN corresponding to the target cell ID, and forwards the X2 message toward the target RN.

5. The target eNB performs admission control. The admission control may be performed dependent on the received E-RAB QoS information to increase the likelihood of a successful handover, if the resources can be granted by target eNB. The target eNB configures the required resources according to the received E-RAB QoS information and reserves a C-RNTI and optionally a RACH preamble. The AS-configuration to be used in the target cell can either be specified independently (i.e. an “establishment”) or as a delta compared to the AS-configuration used in the source cell (i.e. a “reconfiguration”).

6. The target eNB transmits a handover request acknowledge message to the source eNB through L3 signaling, and prepares the handover. The handover request acknowledge message may include a transparent container to be sent to the UE as an RRC message to perform the handover. The transparent container may include a new C-RNTI, target eNB security algorithm identifiers for the selected security algorithms, a dedicated RACH preamble, and possibly some other parameters i.e. access parameters, SIBs, etc. The handover request acknowledge message may also include RNL/TNL information for the forwarding tunnels, if necessary. Meanwhile, as soon as the source eNB receives the handover request acknowledge message, or as soon as the transmission of the handover command is initiated in the downlink, data forwarding may be initiated.

7. The target eNB transmits an RRC connection reconfiguration message including mobility control information to perform the handover, to be sent by the source eNB to the UE. The source eNB performs the necessary integrity protection and ciphering of the message. The UE receives the RRC connection reconfiguration message with necessary parameters. The UE is commanded by the source eNB to perform the handover procedure. The UE does not need to delay the handover execution for delivering the hybrid automatic repeat request (HARQ)/automatic repeat request (ARQ) responses to the source eNB.

Hereafter, the handover execution procedure will be described.

The UE detaches from old cell and synchronizes to new cell. In addition, the source eNB delivers buffered and in-transit packets to the target eNB.

8. The source eNB transmits a serial number (SN) status transfer message to the target eNB to convey the uplink packet data convergence protocol (PDCP) SN receiver status and the downlink PDCP SN transmitter status of E-RABs for which PDCP status preservation applies. The uplink PDCP SN receiver status may include at least the PDCP SN of the first missing UL SDU and a bit map of the receive status of the out of sequence UL SDUs that the UE needs to retransmit in the target cell, if there are any such SDUs. The downlink PDCP SN transmitter status indicates the next PDCP SN that the target eNB shall assign to new SDUs, not having a PDCP SN yet. The source eNB may omit sending this message if none of the E-RABs of the UE shall be treated with PDCP status preservation.

9. After receiving the RRC connection reconfiguration message including the mobility control information, the UE performs synchronization to the target eNB and access the target cell via RACH. The access to the target cell via the RACH may be a contention-free procedure if a dedicated RACH preamble was indicated in the mobility control information. Or, the access to the target cell via RACH may be a contention-based procedure if no dedicated preamble was indicated. The UE derives target eNB specific keys and configures the selected security algorithms to be used in the target cell.

10. The target eNB responds to the synchronization of the UE with UL allocation and timing advance.

11. When the UE has successfully accessed the target cell, the UE transmits an RRC connection reconfiguration complete message (C-RNTI) to confirm the handover procedure, along with an uplink buffer status report, whenever possible, to the target eNB to indicate that the handover procedure is completed for the UE. The target eNB verifies the C-RNTI sent in the RRC connection reconfiguration complete message. The target eNB can now begin transmitting data to the UE. The packet data is exchanged between the UE and the target eNB.

Hereafter, the handover completion procedure will be described.

12. The target eNB transmits a path switch request message to MME to inform that the UE has changed cell.

13. The MME transmits a user plane update request message to a serving gateway (S-GW).

14. The S-GW switches the downlink data path to the target side. The S-GW transmits one or more end marker packets on the old path to the source eNB and then can release any U-plane/TNL resources towards the source eNB.

15. The S-GW transmits a user plane update response message to MME.

16. The MME transmits a path switch acknowledge message to the target eNB to confirm the path switch request message.

17. The target eNB transmits a UE context release message to the source eNB to inform success of the handover procedure and trigger the release of resources by the source eNB.

18. When the UE context release message is received, the source eNB can release radio and C-plane related resources associated to the UE context. Any ongoing data forwarding may continue.

In the legacy S1 handover procedure, an access control or a membership verification may be performed by a MME. By the access control or the membership verification, prioritization of allocated resources may be performed based on the UE's membership status.

The access control may be performed when the target (H)eNB operates with the closed mode. The membership verification may be performed when the target cell is a hybrid cell. The access control or the membership verification is done by a two step process, where first the UE reports the membership status based on the CSG ID received from the target cell and the UE's CSG whitelist, and then the MME verifies the reported status.

However, in the case of X2 handover procedure, if the access control or the membership verification is still performed by the MME before the X2 handover procedure is acknowledged, some problems may be occurred. Firstly the original objective of reducing the signaling overhead of network and reducing the handover delay cannot be realized since the access control or the membership verification is performed by the MME. Secondly, the access control or the membership verification cannot be realized by the X2 interface technically since there is not any message transmitted to the MME before the handover procedure is acknowledged.

Accordingly, to solve the problem described above, a method of performing a membership verification or an access control according to the present invention can be proposed. At first, the case that the target cell is a hybrid cell is described.

FIG. 16shows an example of the proposed method of performing a membership verification according to an embodiment of the present invention.

In step S200, the UE transmits a membership status of the UE to the source (H)eNB. The membership status of the UE may be based on the CSG ID of received from the target HeNB and the UE's CSG whitelist. On receiving the membership status from the UE, the source (H)eNB may just trust the membership status received from the UE.

In step S210, the source (H)eNB transmits a handover request message to the target HeNB. The handover request message may be transmitted to the target HeNB directly when the direct X2 interface is established between the source (H)eNB and the target HeNB. The handover request message may go through the HeNB GW/X2-proxy when the indirect X2 interface is established between the source (H)eNB and the target HeNB)

In step S220, the target HeNB decides whether the handover is acknowledged or not. If it is acknowledged, the target HeNB also pre-decides whether the target HeNB treats the UE as a member of the target HeNB or not based on its rules. That is, the target HeNB may treat the UE as a member of the target HeNB. In this case, the UE may get a priority to use resources. Or, the target HeNB may treat the UE as a non-member of the target HeNB. In this case, the UE may have limitation compared with other CSG members in the case that resources are rare.

In step S230, if the target HeNB accepts the handover, the target HeNB transmits a path switch request message to the MME. The path switch request message may include the CSG ID of the target HeNB and an access mode in order to let the MME perform the membership verification.

In step S240, the MME performs the membership verification based on the CSG ID, the access mode included in the path switch request message and the stored CSG subscription data for the UE. In step S250, the MME transmits verified UE membership information to the target HeNB. The verified UE membership information may be included in a path switch response message which is a response of the path switch request message. Or, the verified UE membership information may be transmitted included in the existing message or a new message.

There are several cases depending on whether the UE is regarded as the member of the target HeNB and the result of the membership verification and.

1) If the target HeNB has already treated the UE as the member and has given the priority to the UE to prepare resources, and the UE is verified as a real member of the target HeNB by the MME, the MME transmits the verified UE membership information that the UE is a real member of the target HeNB. The target HeNB may not change anything.

2) The target HeNB has already treated UE as a non-member and has not given the priority to the UE to prepare resources, and the UE is verified as a real member of the target HeNB by the MME, the MME transmits the verified UE membership information that the UE is a real member of the target HeNB. The verified membership information is opposite to which the target HeNB acknowledges. Accordingly, the target HeNB may treat UE as a real member of the target HeNB and give some priority to UE.

3) If the target HeNB has already treated the UE as a member and has given the priority to UE to prepare resources, and the UE is verified as a faked member of the target HeNB by the MME, the MME transmits the verified UE membership information that the UE is a non-member of the target HeNB. The verified membership information is opposite to which the target HeNB acknowledges. Accordingly, the target HeNB may modify the membership status of the UE and treat the UE as a non-member. Or the target HeNB may just kick out the UE since the UE is a cheater.

4) If the target HeNB has already treated UE as a non-member and has not given the priority to UE to prepare resources, and the UE is verified as a faked member of the target HeNB by the MME, the MME transmits the verified UE membership information that the UE is a non-member of the target HeNB. The target HeNB may not change anything.

5) If the UE has reported that the UE is not a member of target HeNB and the target HeNB has already treated the UE as a non-member and has not given the priority to UE to prepare resources, the target HeNB may not change anything.

FIG. 16can be applied to an example of the proposed method of performing an access control according to an embodiment of the present invention. Here, the case that the target HeNB operates with the closed mode is described.

In step S200, the UE transmits a membership status of the UE to the source (H)eNB. The membership status of the UE may be based on the CSG ID of received from the target HeNB and the UE's CSG whitelist. On receiving the membership status from the UE, the source (H)eNB may just trust the membership status received from the UE. That is, the UE is regarded as a member of the target HeNB.

In step S210, the source (H)eNB transmits a handover request message to the target HeNB. The handover request message may be transmitted to the target HeNB directly when the direct X2 interface is established between the source (H)eNB and the target HeNB. The handover request message may go through the HeNB GW/X2-proxy when the indirect X2 interface is established between the source (H)eNB and the target HeNB)

In step S220, the target HeNB decides whether the handover is acknowledged or not. If it is acknowledged, the target HeNB pre-decides whether the target HeNB treats the UE as a member of the target HeNB or not as described in step S200. That is, the UE is regarded as a member of the target HeNB by the target HeNB. The target HeNB may prepare resources for the UE.

In step S230, if the target HeNB accepts the handover, the target HeNB transmits a path switch request message to the MME. The path switch request message may include the CSG ID of the target HeNB in order to let the MME perform the access control.

In step S240, the MME performs the access control based on the CSG ID included in the path switch request message and the stored CSG subscription data for the UE. In step S250, the MME transmits verified UE membership information to the target HeNB by a specific indication. The verified UE membership information may be included in a path switch response message which is a response of the path switch request message. Or, the verified UE membership information may be transmitted included in the existing message or a new message.

There are several cases depending on the result of the access control and.

1) If the UE is verified as a real member of the target HeNB, the MME transmits the verified UE membership information that the UE is allowed by the MME to the target HeNB by the specific indication. The verified UE membership information may be included in a path switch acknowledgement message. Or, the verified UE membership information may be included in the existing message or a new message. There will be no change for the UE's resources. The target HeNB may not change anything.

2) If the access control procedure fails, which means the UE is a fake member of the target HeNB, the MME transmits the verified UE membership information that the UE is not allowed by the MME to the target HeNB. The verified UE membership information may be included in a path switch acknowledgement (ACK) message. Or, the verified UE membership information may be included in a path switch non-acknowledgement (NACK) message. Or, the MME ends the handover procedure by replying with a handover rejection message to the target HeNB. Or, the verified UE membership information may be included in the existing message or a new message. The target HeNB may just kick out the UE since it is a cheater.

FIG. 17shows an example of an intra-MME/S-GW handover procedure according to an embodiment of the present invention.FIG. 17is a figure that proposed method of performing the membership verification or the access control according to the present invention is applied to an example of an intra-MME/S-GW handover procedure inFIG. 15. Hereinafter, a part which is different from the corresponding part ofFIG. 15is only described.

5. The target HeNB performs admission control. Also, the target HeNB pre-decides the UE membership of the target HeNB. This step may be explained by step S220inFIG. 16.

12. The target HeNB transmits a path switch request message to the MME to inform that the UE has changed cell. The path switch request message may include the CSG ID of the target HeNB. The path switch request message may also include the access mode of the target HeNB if the target HeNB is a hybrid cell.

13. The MME performs the membership verification or the access control. This step may be explained by step S240inFIG. 16.

17. The MME transmits a path switch request ACK/NACK message to the target HeNB. The path switch request ACK/NACK message may include the verified UE membership information. The present invention is not limited to only use this message. The other existing message may be utilized. This step may be explained by step S250inFIG. 16.

FIG. 18is a block diagram showing wireless communication system to implement an embodiment of the present invention.

A target HeNB800includes a processor810, a memory820, and an RF (radio frequency) unit830. The processor810may be configured to implement proposed functions, procedures, and/or methods in this description. Layers of the radio interface protocol may be implemented in the processor810. The memory820is operatively coupled with the processor810and stores a variety of information to operate the processor810. The RF unit830is operatively coupled with the processor810, and transmits and/or receives a radio signal.

A MME900may include a processor910, a memory920and a RF unit930. The processor910may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of the radio interface protocol may be implemented in the processor910. The memory920is operatively coupled with the processor910and stores a variety of information to operate the processor910. The RF unit930is operatively coupled with the processor910, and transmits and/or receives a radio signal.