KR20110023726A - Method of transmitting service state information of femto base station in wireless communication system - Google Patents

Abstract

PURPOSE: A service state information transmission method of a femto base station in a wireless communication system which transmits service state information of a femto base station to a neighboring base station is provided to efficiently update a neighboring base station list in a wireless communication system. CONSTITUTION: A femto base station(20) is scheduled to interrupt a service. The service interruption data includes prediction service interruption time according to the scheduling of the service interruption. The service interruption data includes a handover control flag of femto bases station execution in a hand-over process. The service interruption data are transmitted through a broadcast message or a paging message.

Description

Method of transmitting service state information of femto base station in wireless communication system

The present invention relates to wireless communication, and more particularly, to a method for transmitting service state information of a femto base station to an adjacent base station.

Along with the development of communication and the spread of multimedia technology, various high-capacity transmission technologies have been applied to wireless communication systems. There is a method for allocating more frequency resources as a method for increasing radio capacity, but there are limitations in allocating more frequency resources to a plurality of users with limited frequency resources. One way to make more efficient use of limited frequency resources is to make cells smaller. Making the size of the cell smaller reduces the number of users that one base station must serve, so that the base station can allocate more frequency resources to the user. By making the cell smaller, you can provide better capacity and larger capacity for many users.

Recently, research on femto base station technology installed in homes or offices has been actively conducted. The femto base station refers to a very small mobile communication base station used indoors, such as home or office. A femto base station is used in a similar sense to a pico-cell, and a femto base station is used to have a more advanced function than a pico cell. The femto base station is connected to an IP network spread in homes and offices, and provides a mobile communication service by accessing a core network of a mobile communication system through an IP network. That is, the femto base station is connected to the core network of the mobile communication system through a digital subscriber line (DSL). The user of the mobile communication system may be provided with a service through an existing macro base station outdoors, and may be provided with a femto base station indoors. The femto base station may allow access to a closed subscriber group (CSG) or allow access to all users. The femto base station must be able to support handover between the macro base station or another femto base station. A large number of femto base stations can be installed in a compact manner. In this case, the femto base station must be operated and the location information of the femto base station must also be grasped. The femto base station supports a low duty operation (LDO) mode to reduce interference with neighboring base stations. The femto base station in the LDO mode is capable of performing synchronization and signal transmission for paging or ranging and transmission of control information for data transmission of the terminal and any information over the air. It operates by repeating the UAI (Unavailability Interval) interval that is not transmitted. The UAI interval of femto base stations may be configured differently according to the situation of each base station. The femto base station may be connected over the air for fast control signal transmission with the macro base station where the cell regions overlap.

The femto base station improves indoor coverage of the mobile communication system by supplementing the deterioration of the existing macro base station service in a building, and provides a service to only a specific user. Provide data services. The femto base station can provide new services not provided by the macro base station, and the spread of the femto base station can accelerate the fixed-mobile convergence (FMC) and reduce the industrial base cost.

The service of the femto base station is affected by poor circuit conditions or software reboot of the IP network. For example, the power of the femto base station may be temporarily turned off or the connection with the core network of the mobile communication system may be interrupted, and thus the service of the femto base station may be interrupted (out of service). Terminals receiving services from the femto base station should receive a continuous service by performing a handover to the target base station according to the service interruption of the femto base station. At this time, the handover procedure may not be completed between the femto base station and the target base station due to the service interruption of the femto base station, and the target base station may not receive information on the terminal from the femto base station.

Accordingly, there is a need for a method in which handover according to service interruption of a femto base station can be performed more efficiently and a method for transmitting service state information of a femto base station to an adjacent base station.

An object of the present invention is to provide a method for delivering out-of-service state information of a previously femto base station to a target base station when a handover occurs due to a service interruption of the femto base station.

In a wireless communication system according to an aspect of the present invention, the method for transmitting out-of-service state information of a femto base station comprises the steps of: receiving, by the terminals, service interruption information including a service interruption reason of the femto base station; The terminal includes a ranging request message for handover to the recommended base station or neighboring base station of the recommended base station ID included, wherein the ranging request message includes an incapability indicator indicating a service interruption reason of the femto base station do.

In a wireless communication system according to another aspect of the present invention, the neighbor list update method may include an indicator indicating a reason for a service interruption of a power-off or backhaul linkdown of a femto base station from a terminal, and an ID of a neighbor base station or a terminal to be handed over by the terminal. Receiving a ranging request message for handover including information indicating a base station ID holding information, and updating a neighbor base station list including status information for the femto base station.

The handover of the terminal according to the service interruption of the femto base station can be performed more efficiently, and information about the service interruption and recovery of the femto base station can be transmitted to the neighbor base station so that the neighbor base station list update of the neighbor base station can be performed more effectively. .

1 is a block diagram illustrating a wireless communication system.
2 illustrates a handover process according to a scheduled service interruption of a femto base station according to an embodiment of the present invention.
3 illustrates a handover process according to a scheduled service interruption of a femto base station according to another embodiment of the present invention.
4 illustrates a handover process according to an unscheduled service interruption of a femto base station according to an embodiment of the present invention.
5 shows a handover process according to service recovery of a femto base station according to an embodiment of the present invention.
6 is a block diagram illustrating elements of a terminal.

The following techniques include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. It can be used in various wireless communication systems. CDMA may be implemented with a radio technology such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented by wireless technologies such as Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16e (WiMAX), IEEE 802-20, and Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of an Evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. IEEE 802.16m is an evolution of IEEE 802.16e.

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

Referring to FIG. 1, a general wireless communication system includes a user equipment (UE) and a base station (BS). The terminal may be fixed or mobile, and may be referred to in other terms, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a wireless device. A base station generally refers to a fixed station for communicating with a terminal, and may be referred to as other terms such as Node-B, Base Transceiver System, and Access Point. One or more cells may exist in one base station.

The base station may be divided into a femto base station 20 and a macro base station 60 according to a cell coverage or deployment scheme. The cell of the femto base station 20 has a smaller size than the cell of the macro base station 60. All or some of the cells of the femto base station 20 may overlap with the cells of the macro base station 60. As such, a structure in which a small range of cells are overlapped and disposed in a wide range of cells is called a hierarchical cell structure.

The femto base station 20 may be called by other terms such as a femto-cell, a home node-B, and a closed subscriber group (CSG). The macro base station 60 may be referred to as a macro-cell by distinguishing it from a femtocell.

The femto base station 20 is connected to a femto gateway 30 through an Iuh interface. Iuh interface means an interface between the femto base station 20 and the femto gateway 30 through the IP network. The femto gateway 30 is an entity managing at least one femto base station 20. The femto gateway 30 may perform registration, authentication, and security procedures of the femto base station 20 so that the femto base station 20 may access the core network 90 of the wireless communication system. The macro base station 60 is connected to a radio network control (RNC) 70 via an Iub interface. The RNC 70 is an entity managing at least one macro base station 60 and connects the macro base station 60 to the core network 90. The macro base station 60 is connected to the core network 90 by a dedicated line, while the femto base station 20 is connected to the core network 90 through an IP network.

A terminal connected to the femto base station 20 is called a femto UE 10, and a terminal connected to the macro base station 60 is called a macro UE 50. The femto terminal 10 may be a macro terminal 50 through a handover to a macro base station, and the macro terminal 50 may be a femto terminal 10 through a handover to a femto base station.

Hereinafter, downlink means transmission from the base station to the terminal, and uplink means communication from the terminal to the base station. In downlink, a transmitter may be part of a base station and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal and a receiver may be part of a base station.

Now, the service state information transmission method and the handover method of the femto base station according to the service interruption and recovery of the femto base station will be described. The service state of the femto base station includes an out of service and a service recovery state. The service outage of the femto base station may be divided into scheduled service outages and unscheduled service outages. For example, when it is necessary to reboot by downloading / installing software or the like, the femto base station may operate by scheduling its own service interruption. Unscheduled service outages may occur when a femto base station fails to schedule service outages, such as a sudden power outage or backhaul link of a femto base station.

FIG. 2 shows that when a handover occurs due to a scheduled service interruption of a femto base station according to an embodiment of the present invention, the handover process of each terminal is not performed by the femto base station before the service interruption, and the terminal is handed to the recommended base station of the femtocell. The case of over is shown.

2, the femto base station schedules an out of service (S110). The femto base station schedules service outages according to reboots for software download / installation and femtocell operating policies. The scheduled service interruption of the femto base station may be performed when all terminals provided with the service from the femto base station are in an idle mode or a sleep mode. Alternatively, the scheduled service interruption of the femto base station may be performed according to a reboot of the femto base station, an operation policy, or the like even when a terminal that performs data transmission and reception exists. On the other hand, when the femto base station can use the battery, if the main power of the femto base station is cut off, the scheduled service interruption process using the battery may be performed for a predetermined time.

The femto base station transmits service interruption information to the terminal (S120). The service interruption information may be transmitted through a broadcast message or a paging message. The service interruption information may include a service interruption reason, an expected service interruption time, an expected service recovery time, a recommended base station identifier, a handover coordination flag, and the like. The service interruption reason indicates a reason that a service such as a shutdown of a femto base station, a backhaul linkdown, or the like is interrupted. The estimated service downtime indicates the time when the service of the femto base station is stopped according to the scheduling of the service interruption, and the estimated service recovery time indicates the time when the service of the femto base station is restored and resumes service or after the service is stopped. It means the period until becoming. The service outage information may include only the estimated service down time and may not include the estimated service recovery time. The recommended base station ID indicates identifier information of the target base station to which the terminal can handover the identifier information of the base station that has delivered the information or the context of the terminal in service. The recommended base station ID includes an ID of at least one neighboring base station. The adjacent base station may be a macro base station or another femto base station where the femto base station and the cell region overlap each other. The handover coordination flag indicates whether the corresponding femto base station performs the handover process according to service termination of the femto base station with the target base station. When the handover coordination flag is set as the femto base station performs a handover process with the target base station, the terminal receives a handover command from the femto base station and performs a handover process to the target base station, while the handover coordination flag is performed. If the handover coordination flag is set to not be included in the service interruption information or the femto base station does not perform the handover process with the target base station in advance, the terminal receives the service interruption information from the femto base station or the adjacent base station immediately. Perform a handover with. The terminal may preferentially consider any one of the recommended base stations as a target base station for handover.

If the handover coordination flag is not set, the femto base station may transmit UE information in service to the recommended base station through a backbone network (S130). The recommended base station may be a macro base station or another femto base station. Considering that the handover of the terminal due to the service interruption of the femto base station is mainly performed to the macro base station, the macro base station may be selected as the recommended base station to which the terminal information is transmitted. The femto base station transmits terminal information to the recommended base station so that handover of the terminal is performed more quickly. The recommended base station may transmit an ACK / NACK signal in response to the transmission of the terminal information of the femto base station (S135).

The terminal transmits a ranging request message for handover to the recommended base station (S140). In this case, the ranging request message includes information on service interruption of the femto base station. Table 1 shows an example of a ranging request message including service interruption information of a femto base station.

The ranging request message includes a disability indication of the femto base station that provided the service. The disable indicator indicates the out of service reason of the femto base station. For example, if the outage indicator is 'Out-of-service reason = 00', it indicates shutdown of the femto base station, and if 'Out-of-service reason = 01', the backhaul link of the femto base station down). The reason for the service interruption other than the off and backhaul linkdown of the femto base station may be expressed as 'Out-of-service reason = 10 ~ 11'. Although the number of bits of the disable indicator is shown as 2 bits, this is only an example and the number of bits and the bit value of the disable indicator are not limited.

The ranging request message may include disability information. The disable information may be included in the ranging request message when the disable indicator indicates off or backhaul linkdown of the femto base station. The disable information may include a base station ID holding the terminal information. The target base station can know the base station holding the terminal information through the disable information received from the terminal. If the target base station is not the recommended base station of the previous service femto base station that has changed to the out of service state, the terminal information was not received, but the terminal information is obtained by making a request to the base station having the corresponding terminal information using the disability information included in the ranging request message. can do. Therefore, the target base station can efficiently support network re-entry of the terminal by using the obtained terminal information.

The target base station updates a neighbor list based on the disable indicator included in the ranging request message received from the terminal (S150). The neighbor base station list means information on neighbor base stations held by each base station for interference, handover, service efficiency, and the like. In this case, the ranging request message of the terminal includes the serving base station ID, that is, the femto base station ID and includes the inability indicator 'Out-of-service reason = 00', so that the target base station turns off the state of the femto base station based on this. Update to. That is, the femto base station may be excluded from the neighbor base station list of the target base station.

The target base station transmits the ranging response message in response to the ranging request message of the terminal (S160). In the case of FIG. 3, the target base station may know that the terminal information is transmitted to itself through the disable information included in the ranging request message, and may support network re-entry of the terminal using the terminal information held by the target base station.

As such, the terminal may inform the target base station of the service termination of the femto base station by using a ranging request message in the handover process according to the service termination of the femto base station, and the target base station efficiently supports handover using the terminal information. You can update the neighbor list quickly.

3 illustrates a handover process according to a scheduled service interruption of a femto base station according to another embodiment of the present invention.

Referring to FIG. 3, when the handover is not performed by the femto base station with the target base station before the service is stopped, the handover of the terminal is performed to a target base station other than the recommended base station having the terminal information. The description of FIG. 3 applies mutatis mutandis for the description that is mainly focused on differences from and.

The femto base station schedules service interruption (S210).

The femto base station transmits service interruption information to the terminal (S220). The service interruption information may be transmitted through a broadcast message or a paging message. The service interruption information may include a service interruption reason, an expected service interruption time, an expected service recovery time, a recommended base station ID, a handover coordination flag, and the like. The reason for the service interruption is assumed to be a shutdown of the femto base station.

The femto base station transmits the UE information (UE context) to the recommended base station (S230). The recommended base station may be a macro base station. The recommended base station may transmit an ACK / NACK signal in response to the terminal information to the femto base station (S235).

The terminal transmits a ranging request message for handover to the target base station (S240). Here, it is assumed that the terminal transmits the ranging request message to the target base station that does not have the terminal information. The target base station may be a femto base station or a macro base station. The disable indicator included in the ranging request message indicates the off of the femto base station with 'Out-of-service reason = 00', and the disable information includes the recommended base station ID holding the terminal information.

The target base station updates the neighbor list based on the ranging request message received from the terminal (S250). The target base station updates the service state of the femto base station to the off state. The target base station can know the recommended base station holding the terminal information through the disable information included in the ranging request message.

The target base station requests the terminal information to the recommended base station through the backbone network (S260).

The recommended base station transmits the terminal information to the target base station (S270). The target base station may obtain the terminal information from the recommended base station through the backbone network.

The target base station transmits the ranging response message in response to the ranging request message of the terminal (S280). The target base station may support network re-entry of the terminal by using the terminal information obtained from the recommended base station.

In this way, the target base station can obtain the terminal information from the recommended base station to efficiently support the handover while obtaining service interruption information of the femto base station from the terminal to quickly update the neighbor list.

4 illustrates a handover process according to an unscheduled service interruption of a femto base station according to an embodiment of the present invention.

Referring to FIG. 4, when a handover of a terminal is performed due to unscheduled service interruption due to a backhaul linkdown of a femto base station, a description of the difference from FIG. 3 will be given. do.

The backhaul linkdown of the femto base station may occur due to a poor circuit state of the IP network (S310). When the backhaul linkdown occurs, the femto base station transmits service interruption information to the terminal (S320). The service interruption information may be transmitted through a broadcast message or a paging message. The service interruption information may include a service interruption reason, an expected service interruption time, an expected service recovery time, a recommended base station ID, a handover coordination flag, and the like. The reason for the service interruption is indicated by the backhaul linkdown of the femto base station. In case of unscheduled backhaul linkdown, the recommended base station ID may not indicate a base station ID having terminal information, but may indicate a neighbor base station ID of a femto base station, or may not be included in service interruption information. Since the femto base station cannot perform the handover process with the target base station because the backhaul link is disconnected, the handover coordination flag may be set to not perform the handover process or may not be included in the service interruption information. Meanwhile, the femto base station may transmit the terminal information to the neighbor base station before the backhaul link down.

The terminal transmits a ranging request message for handover to the target base station (S330). The target base station may be a macro base station or another femto base station where the femto base station and the cell area overlap. Since the handover adjustment flag in the service interruption information is set as the femto base station does not perform the handover process, the terminal immediately sends the ranging request message for handover to the target base station after receiving the service interruption information. When the recommended base station ID is included in the service interruption information, the target base station may be selected based on this. When the recommended base station ID is not included in the service interruption information, the target base station may be selected according to the neighbor base station information of the terminal. The disable indicator included in the ranging request message may indicate the backhaul linkdown of the femto base station with 'Out-of-service reason = 01'. The disable information may not be included in the ranging request message. Alternatively, the disable information may indicate a recommended base station ID indicating a base station adjacent to the femto base station.

The target base station updates the neighbor list based on the ranging request message received from the terminal (S340). The target base station updates the service state of the femto base station with backhaul linkdown.

The target base station transmits the ranging response message in response to the ranging request message of the terminal (S350). When the target base station acquires the terminal information from the femto base station in advance, the target base station may support network re-entry of the terminal. When the target base station does not acquire the terminal information from the femto base station in advance, it may support network reentry of the terminal through the authentication process of the terminal.

As such, the target base station can obtain service interruption information of the femto base station from the terminal and quickly update the neighbor list.

5 illustrates a handover process according to service recovery of a femto base station according to an embodiment of the present invention.

Referring to FIG. 5, a handover of a terminal according to service recovery of a femto base station is performed after a service interruption due to an off or backhaul linkdown of the femto base station.

The femto base station transmits service interruption information to the terminal according to the service interruption (S410), and the terminal performs a handover process according to the service interruption of the femto base station (S420). The handover process according to the service interruption of the femto base station includes any one of the handover process of FIG. 3, 4, or 5.

When the power of the femto base station is normally turned on or the backhaul link is restored, the service of the femto base station is restored (S430). Notify the femto base station of its service recovery to an adjacent macro base station or another femto base station. The femto base station may notify service recovery to an adjacent macro base station or another femto base station through the backhaul network. Alternatively, when a radio link between a femto base station and an adjacent macro base station or another femto base station is established, the femto base station may notify service recovery through the wireless link. Here, it is assumed that the femto base station notifies the neighbor macro base station or another femto base station, that is, the target base station through the radio link to the service recovery. When a femto base station is connected to an adjacent macro or another femto base station through a radio link, the femto base station operates as one terminal in the macro base station or another femto base station and is given a terminal identifier distinguished from the base station.

The femto base station transmits the ranging request message including the service recovery information to the target base station (S440). In this case, it may be indicated as 'Power Down Indicator = 1' of the ranging request message. That is, the service recovery of the femto base station may be indicated by using an indicator indicating a location update according to power down. The 'Previous STID' of the ranging request message indicates the identifier information of the femto base station previously assigned from the corresponding target base station, and the femto base station includes its identifier information in the ranging request message and transmits it. The target base station can know the femto base station that has sent the ranging request message through the 'Previous STID' included in the ranging request message, and the 'femto base station is in the service recovery state from the service interruption state through' Power Down Indicator = 1 '. You can see that it has been converted.

The target base station updates the neighbor base station list based on the ranging request message received from the femto base station (S450). The target base station updates the service state of the femto base station to the serviceable state.

The target base station may maintain information on the terminal that performed the handover process according to the service interruption of the femto base station, and may transmit service recovery information of the femto base station to the corresponding terminal (S460). The service recovery information may be transmitted through a broadcast message or a paging message. The service recovery information may include a femto base station ID for which the service state is changed to the serviceable state.

When receiving the service recovery information, the terminal transmits a ranging request message for handover to the femto base station (S470). The ranging request message may include a target base station ID and a terminal ID.

The femto base station transmits the ranging response message in response to the ranging request message of the terminal (S480). The femto base station may maintain the terminal ID providing the service before the service stops, and may preferentially allow access to the ranging request message using the terminal ID. The femto base station may obtain terminal information from the target base station and support the network connection of the terminal.

As such, information on service recovery of the femto base station may be transmitted using a ranging request message, and the target base station may obtain service recovery information of the femto base station and quickly update the neighbor list. In addition, by allowing the terminal, which has performed the handover process to the target base station according to the service interruption of the femto base station, to perform the handover process again to the femto base station according to the service recovery of the femto base station, the large capacity service of the femto base station can be effectively performed. Can be.

6 is a block diagram illustrating elements of a terminal.

Referring to FIG. 6, the terminal 50 includes a processor 51, a memory 52, an RF unit 53, a display unit 54, and a user interface unit. , 55). The terminal 50 may be provided with a plurality of transmission antennas.

The processor 51 implements the layers of the air interface protocol to provide a control plane and a user plane. The functions of each layer may be implemented through the processor 51. The processor 51 may implement the service information transmission and the handover process of the proposed femto base station. The memory 52 is connected to the processor 51 to store a terminal driving system, an application, and a general file. The memory 52 may store a codebook defined to support codebook based precoding. The display unit 54 displays various information of the terminal, and may use well-known elements such as liquid crystal display (LCD) and organic light emitting diodes (OLED). The user interface unit 55 may be a combination of a well-known user interface such as a keypad or a touch screen. The RF unit 53 is connected to the processor 51 and transmits and / or receives a radio signal.

All of the above functions may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), or the like according to software or program code coded to perform the function. The design, development and implementation of the code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

Claims (15)

Receiving service interruption information including a reason for service termination of the femto base station from a femto base station; And
And transmitting a ranging request message for handover to a recommended base station or a neighboring base station according to the recommended base station ID included in the service interruption information for handover of the terminal, wherein the ranging request message is transmitted by the femto base station. A method of transmitting service unavailable state information of a femto base station in a wireless communication system including a disable indicator indicating a service interruption reason and disable information indicating a base station ID received from the terminal.
The femto base station of claim 1, wherein the service interruption of the femto base station is scheduled at the femto base station, and the service interruption information includes an estimated service interruption time according to the scheduling of the service interruption. How to send service status information.
The service of claim 1, wherein the service interruption information includes a handover coordination flag indicating whether the femto base station performs the handover procedure. How to send status information.
The method of claim 1, wherein the service interruption information is transmitted through a broadcast message or a paging message.
The method of claim 1, wherein the recommended base station is a base station through which terminal information is transmitted from the femto base station.
The method of claim 1, wherein the service interruption reason may include power-off or backhaul link down of the femto base station.
The wireless communication system of claim 1, wherein the ranging request message includes an ID of the femto base station and a base station ID having neighboring base station ID or terminal information for handover recommended by the femto base station. Method for transmitting service status information of a femto base station in the.
The method of claim 1, further comprising receiving service recovery information of the femto base station from the recommended base station or the adjacent base station.
10. The method of claim 8, wherein the handover is performed to the femto base station after receiving the service recovery information of the femto base station.
For handover including an indicator indicating the reason for the service interruption of the power-off or backhaul link down of the femto base station from the terminal and the information indicating the neighbor base station ID to be handed over by the terminal or the base station ID holding the information of the terminal Receiving a ranging request message; And
Updating neighbor list in a wireless communication system comprising the step of updating the neighbor list including the state information for the femto base station.
The method of claim 10, further comprising receiving information of the terminal from the femto base station.
The method of claim 11, further comprising transmitting an ACK / NACK signal to the femto base station in response to the terminal information.
The method of claim 10, further comprising: obtaining a terminal information by performing a terminal information request to a base station having the terminal information.
The method of claim 10, further comprising receiving service recovery information of the femto base station through a ranging request message from the femto base station.
The method of claim 14, further comprising transmitting service recovery information of the femto base station to the terminal.

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