KR20120072313A - Method for re-establishing rrc connection and mobile telecommunication system for the same - Google Patents

Abstract

PURPOSE: An RRC(Radio Resource Control) connection reestablishment method is provided to improve RRE(Radio resource control connection REestablishement) success rates by receiving terminal information from a target base station. CONSTITUTION: A serving base station apparatus transmits a handover request message to a first target base station(302). The serving base station notifies terminal information one or more handover candidate base stations(303). When an RRC connection reestablishment of a terminal which is not able to access the target base station apparatus is requested, one of the one or more handover candidate base station apparatuses selected as a second target base station apparatus execute an RRE procedure based on the terminal information(304~309).

Description

RRC connection resetting method and mobile communication system therefor {METHOD FOR RE-ESTABLISHING RRC CONNECTION AND MOBILE TELECOMMUNICATION SYSTEM FOR THE SAME}

The present invention relates to a mobile communication system, and more particularly, to increase the success rate of RRE (RRC Connection Re-establishment) performed when handover failure and radio quality deteriorate in a mobile communication system such as LTE and LTE-A. .

Recently, due to the rapid development of communication, computer network, and semiconductor technology, various services using wireless communication networks are being provided, and demands of consumers are increasing day by day, and the global market for wireless internet services is exploding. It is a trend. Accordingly, a service provided by a mobile communication system using a wireless communication network is developing not only a voice service but also a multimedia communication service for transmitting various data.

Currently, wireless data services such as Code Division Multiple Access (CDMA) 2000, Evolution Data Only (EV-DO), Wideband CDMA (WCDMA), and Wireless Local Area Network (WLAN) are commercially available. Demand is constantly increasing, and according to this trend, a method of providing a mobile communication service by installing a micro base station indoors to access a mobile communication core network through an indoor broadband network has been proposed. In particular, in the next generation network system, in order to satisfy the demand for high data rate and to provide various services stably, a method of arranging multiple small multi-cells (femtocells) has been proposed as an alternative. The micro base station that manages such a femtocell is called an indoor base station or a femto base station. By reducing the size of the cell, the efficiency of the next-generation network system using a high frequency band can be improved, and the use of multiple small cells can be advantageous in terms of increasing the frequency reuse frequency. In addition, the present invention can improve the channel deterioration problem due to the attenuation of radio waves, which is caused when a single base station covers the entire cell area, and the inability to service shadow users. Has this advantage. Based on these advantages, a combination of the existing macro cell (cell area managed by an outdoor base station) (femto-cell) and femtocell (cell area managed by an ultra-small base station such as an indoor base station or a femto base station) This is emerging.

Long Term Evolution (LTE) is a network for realizing the requirements of high data rate, low-latency, and packet optimized radio access for access networks. It is designed to accommodate high-speed rich media while guaranteeing backward compatibility with existing 3GPP / non-3GPP access networks. LTE is an All-IP-based network that excludes existing circuit-switched based communications.It has enhanced the quality of service (OoS) management function to provide real-time services (eg, voice communications, video communications) and non- By providing differentiated QoS for real-time services (eg web browsing, store and forward data transmission), the efficiency of network resources is improved. In addition, the introduction of smart antenna technology (ie MIMO) has expanded the bandwidth for wireless communication.

The general LTE network structure includes a macro base station (eNB: enhanced Node B), a small base station (home-eNB), a mobility management entity (MME), and a self organizing & optimizing network (SON) server. Since the micro base station and the macro base station each have their own connectivity to the core network, the user equipment (UE) may communicate through either the micro base station or the macro base station for communication. The MME is an entity used to perform handover management and call processing of the terminal. The SON server is any server that functions to perform macro / miniature base station installation and optimization and to provide the basic parameters or data required for each base station. The functions of the MME and SON server can all be performed from one network management device.

The UE can interwork with other networks such as E-UTRAN (Evolved UTRAN), which is a wireless access network of LTE, as well as other networks such as UMTS Terrestrial Radio Access Network (UTRAN) / GSM / EDGE Radio Access Network (GERAN).

A base station (eNB) of a UE and an E-UTRAN communicate through a radio resource control (RRC) protocol, and a broadcasting message from the base station eNB to a cell area controlled by the base station is defined as an RRC message. The RRC message may include control messages coming down from the Non-Access Stratum (NAS) protocol, which are not transparently read within the E-UTRAN and are transparently delivered to the UE or the core network. A channel frequency unit assigned to one base station is represented by a frequency assignment (FA) (for example, 4FA for WCDMA), and an identifier for identifying a cell in a physical layer in one FA, for example, a PCI (Physical Cell) in an LTE network. Identity), PSC (Primary Scrambling Code) is used in WCDMA, and PN (Pseudo Noise) offset is used in CDMA. For example, 504 physical layer cell identifiers exist in 1FA in LTE network, and 512 physical layer cell identifiers exist in 1FA in WCDMA network.

RRE (RRC Connection Re-establishment) is not able to transmit or receive data due to incomplete handover due to handover failure or transliteration area. Function.

In order to successfully perform this RRE procedure, the base station apparatus (eNB, Home-eNB), which is requested to reconnect from the terminal, must know the terminal information in advance. If the terminal attempts to RRE to the base station apparatus (eNB, Home-eNB) without the terminal information, the RRE procedure fails. For example, if the UE fails to handover to the target eNB1 (TeNB1) and moves to the target eNB2 (TeNB2) and attempts the RRE again, since the UE information is not included in the TeNB2, the corresponding RRE procedure can be successfully performed. There is no problem.

 TS 36.331. "The connection re-establishment succeeds only if the concerned cell is prepared i.e. has a valid UE context"

An object of the present invention is to provide a method and a mobile communication system for increasing the success rate of the RRE performed when handover failure and radio quality deterioration.

According to an aspect of the present invention, a method and a mobile communication system for increasing the success rate of the RRE performed in case of handover failure and radio quality deterioration are disclosed. According to an embodiment, upon receiving the measurement report message of the terminal for handover, the serving base station apparatus transmits a handover request message to the first target base station apparatus and informs the terminal information of at least one handover candidate base station apparatus. . Then, upon requesting an RRC connection reset (RRE) of a UE that fails to access the target base station apparatus, one of the at least one handover candidate base station apparatus selected as the second target base station apparatus successfully performs the RRE procedure based on the terminal information. do. According to another embodiment, upon receiving the measurement report message of the terminal for handover, the serving base station transmits a handover request message to the first target base station. In response to the RRC connection reestablishment request of the terminal not connected to the first target base station apparatus, the second target base station apparatus requests and receives the terminal information from the first target base station apparatus and successfully performs the RRE procedure based on the terminal information. do.

According to the present invention, the RRE success rate can be increased when communication is disconnected due to handover failure and shadow area.

1 illustrates a configuration of an exemplary mobile communication network in which the present invention may be practiced.
2 is a diagram illustrating a general handover triggering event occurrence condition.
3 illustrates an RRC connection reset (RRE) procedure according to a first embodiment of the present invention.
4 is a diagram illustrating an RRC connection reset (RRE) procedure according to a second embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, well-known functions or constructions will not be described in detail if they obscure the subject matter of the present invention.

1 is a diagram illustrating a configuration of an exemplary mobile communication network in which the present invention can be implemented.

In one embodiment, the mobile communication network includes, for example, Global System for Mobile communication (GSM), 2G wireless communication network such as CDMA, LTE network, wireless Internet such as WiFi, Wireless Broadband Internet (WiBro) and World Interoperability for Microwave Access. Mobile communication networks (e.g., 3G mobile networks such as WCDMA or CDMA2000, 3.5G mobile networks such as High Speed Downlink Packet Access (HSDPA) or High Speed Uplink Packet Access (HSUPA)) 4G mobile communication network currently in service, etc.) and macro base station (macro-eNB), micro base station (Home-eNB), and any other mobile communication network including UEs as components, but are not limited thereto. no. Hereinafter, an evolved universal terrestrial radio access network (e-UTRAN), which is a wireless access network of LTE, will be described.

As shown in FIG. 1, a mobile communication network may be composed of one or more network cells, and different types of network cells may be mixed in the mobile communication network. The mobile communication network is a small base station (11-15, 21-23, 31-33) that manages a small network cell (hereinafter referred to as 'femtocell'), such as indoors, and a wide range of cells (hereinafter referred to as 'macrocell'). Macro base station (macro-eNB or eNB) (10, 20, 30), terminal (UE) 40, Self Organizing & Optimizing Networks (SON) server 50, MME (60), S-GW (Serving Gateway) 80 and P-GW (PDN Gateway) (90). The number of components shown in FIG. 1 is exemplary, and the number of components of the wireless communication network to which the present invention can be implemented is not limited to the number shown in the drawings.

The macro base stations 10, 20, and 30 may be used in, for example, LTE, WiFi, WiBro, WiMax, WCDMA, CDMA, UMTS, GSM networks, for example, cells having a radius of about 1 km. It may include a feature of the macro cell base station for managing, but is not limited thereto.

The small base stations 11-15, 21-23, 31-33 can be used, for example, in LTE networks, WiFi networks, WiBro networks, WiMax networks, WCDMA networks, CDMA networks, UMTS networks, GSM networks, and the like. It may include features of an indoor base station or a femto base station for managing a cell having a radius of about m to several tens of meters, but is not limited thereto.

The micro base stations 11 to 15, 21 to 23, 31 to 33 and the macro base stations 10, 20 and 30 may each independently have connectivity of the core network.

The UE 40 is used in 2G wireless communication networks such as GSM networks, CDMA networks, wireless Internet networks such as LTE networks, WiFi networks, mobile Internet networks such as WiBro networks and WiMax networks, or mobile communication networks supporting packet transmission. It may include features of the mobile terminal, but is not limited thereto.

The micro base station management server (network management apparatus) 70 is responsible for the configuration information and management of the micro base stations 11 to 15, 21 to 23, 31 to 33 and the macro base stations 10, 20 and 30. The management server 70 may perform both functions of the SON server 50 and the MME 60. The SON server 50 may include any server that functions to perform macro / miniature base station installation and optimization and to provide basic parameters or data required for each base station. The MME 60 may include any entity used to manage mobility of the terminal 40 and the like. In addition, each MME (61, 62) performs a function of a base station controller (BSC), and performs resource allocation, call control, handover control, voice and packet processing for the base station (Home-eNB, eNB) connected to it can do.

In one embodiment, one network management device 70 may perform both the functions of the SON server 50 and the MME 60, and the SON server 50 and the MME 60 may include one or more macro base stations ( 10, 20, 30 and one or more micro base stations 11 to 15, 21 to 23, 31 to 33 may be managed.

In the mobile communication network, a macro cell and a femto cell are assumed to be mixed, but the network cell may be configured only by the macro cell or the femto cell.

In operation, access to the macro base stations 10, 20, and 30 is normally allowed to all terminals, but access to the micro base stations 11 to 15, 21 to 23, 31 to 33 is restricted to specific terminals (subscribers). There is an operation function that can be done. This is called a connection mode or an operation mode, and the connection modes of the small base stations 11 to 15, 21 to 23, 31 to 33 are classified according to which terminal provides a service. That is, it is divided into a closed connection mode, an open connection mode, and a hybrid connection mode. Closed access mode (closed access mode or CSG closed mode) allows access only to specific subscribers, and open access mode (open access mode or CSG open mode) allows any subscriber to access without access conditions. It can be seen as a compromise.

Specifically, the micro base stations 11 to 15, 21 to 23, 31 to 33 may broadcast system information block type 1 (SIB 1), which is system information, in a femtocell area managed by the base station (11 to 15, 21 to 23, 31 to 33). A Closed Subscriber Group indicator is included to indicate whether access to the femtocell is restricted. SIB 1 is a message in which a base station (Home-eNB, eNB) broadcasts information about its own cell to all terminals 40, and is a cell global identity (CGI) (the only cell delimiter in the network) and a CSG indication (miniature). A factor indicating that it is a base station), a CSG ID (an ID for a CSG), and the like.

When the small base station (11 ~ 15, 21 ~ 23, 31 ~ 33) is operated in a closed access mode (closed access mode or CSG closed mode) so that only a specific subscriber can access the service to the femtocell The base stations 11-15, 21-23, 31-33 set the CSG indicator in the SIB to a value of 'true', and then broadcast it to the terminal in the cell to manage. When operating in the open access mode (Open Access mode or CSG Open mode), broadcast after setting the CSG indicator to the value of 'false (false).

When the terminal 40 moves into the femtocell managed by the small base stations 11 to 15, 21 to 23, 31 to 33, after receiving the SIB 1 message from the small base station, the CSG indicator in the message has a value of 'true'. After confirming that, the terminal 40 can access the micro base station only when it is confirmed that the micro base station is included in the white list which is a list of the micro base stations accessible by the terminal 40. The white list is stored in the USIM of the terminal 40 or transmitted to the terminal 60 by the MME 60 in the Attatch / TAU Update procedure.

For the micro base station operating in the closed access mode, only the user (home user) defined in the home user table managed by the micro base station can be connected to and provided with the micro base station.

In addition, for the micro base station operating in the open access mode, not only the user defined in the home user table but also the non-home user can access and provide the service to the micro base station. You can get services that are more preferential than -home user. Specifically, the micro base stations 11 to 15, 21 to 23, 31 to 33 operated in the closed access mode are connected only to the terminal 40, for example, a terminal of a user registered as a micro base station service subscriber. Allow. The terminal 40 has a list of the smallest base stations called the white list, and can access only the smallest base stations belonging to the white list, and access to the smallest base stations is not allowed.

The terminal 40 may know whether access to the corresponding base station is restricted based on the CSG indicator of the SIB 1 broadcasted by the small base stations 11 to 15, 21 to 23, 31 to 33. In addition, as the identifier for identifying the small base station cell by the terminal 40, a physical layer cell identifier (PCI), which is a cell classification factor in the physical layer, and a global cell identifier, which is a unique cell discrimination factor in a wireless communication network, are identified. (GCI: Global Cell Identity).

If the mobile communication network is assumed to be an LTE network, the LTE network is interworked with an inter-RAT network (WiFi network, WiBro network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc.). If one of the inter-RAT networks (for example, WiBro network) is the mobile communication network, it is also linked to other networks (LTE network, WiFI network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc.). In the drawing, one network (for example, LTE network) and another network (WiFi network, WiBro network, WiMax network, WCDMA network, CDMA network, UMTS network, GSM network, etc.) are shown spaced apart from each other, but one network and the other network overlap. It is assumed that it is (Overlay).

Hereinafter, the micro base stations 11 to 15, 21 to 23, 31 to 33 and / or macro base stations 10, 20 and 30 will be collectively referred to as 'base station apparatuses'.

The E-UTRAN, which is composed of a base station apparatus of LTE, has a flat structure based on IP and processes data traffic between the terminal 40 and the core network. The MME 60 is responsible for controlling the signals between them. The MME 60 is responsible for signal control between the base station apparatus and the S-GW (Serving Gateway) 80, and determines where to route the incoming data from the terminal 40. S-GW (80) is responsible for the anchor (anchoring) function for the movement of the terminal between the base station and the base station, the 3GPP network and the E-UTRAN, P-GW (PDN (Packet Data Network) Gateway (90) Connect to IP network through

The MME 60 / S-GW 80, which is the core network equipment, manages a plurality of base station apparatuses, and each base station apparatus includes a plurality of cells. The C-plane / U-plane is controlled between the base station apparatus and the MME 60 / S-GW 80 through the S1 interface, and uses the X2 interface for the handover and the SON function between the base station apparatuses.

The handover is performed based on the UE measurement value, and the measurement report message of the terminal 40 is controlled by a parameter determined by the base station apparatus. The base station apparatus receiving the measurement report message determines which cell to hand over to. Specifically, the UE measurement value is based on a received power (RSRP / Reference Symbol Received Power) or a reception state (RSRQ / Reference Symbol Received Quality). As shown in FIG. 2, when a handover condition is satisfied within a time of {Hysteresis, timeToTrigger} set by the base station apparatus, a handover triggering event (HO triggering event) is generated. The measurement report message of the terminal 40 may be generated at the event triggering or periodically according to the setting of the base station apparatus. When the handover triggering event occurs, the terminal 40 sends a measurement report message to the base station apparatus and the base station apparatus performs handover.

As described above, the handover is triggered based on the reception power and the reception state. Especially, in the network where the macro cell and the femtocell are mixed, the terminal 40 serviced by the current base station apparatus (serving base station apparatus) is connected to the neighbor cell (macro cell or femtocell). A neighbor cell list (NCL) indicating how neighbor cells are configured when handing over to a base station device (target base station device) may include cells of different sizes (eg, macro cells, femto cells, etc.). . The neighbor cell list includes FA information of the base station apparatus and a physical layer cell identifier (eg, PCI) of each FA.

The RRE call processing procedure according to handover failure in LTE network is as follows. When using three sector cells, the α, β, and γ sector cells of the serving base station use PCI 0,1,2 and the first target base station use PCI 3,4,5 and the second It is assumed that the target base station apparatus uses PCI 6, 7, and 8.

When the terminal 40 moves from the cell of the serving base station apparatus S-eNB (cell PCI 0) to the cell of the target base station apparatus T-eNB during a call, the terminal 40 transmits to neighboring cells for handover. The PCI strength is transmitted in a measurement report message to the serving base station. At this time, it is assumed that the size of the PCI strength measurement value of neighboring base station devices is "PCI 3> PCI 6> PCI 4 ...". Then, the serving base station apparatus receiving the measurement report message finds a cell having PCI (PCI 3) having the highest PCI strength and transmits a handover request message to the base station apparatus (first target base station apparatus) of the corresponding cell. . At this time, the handover request message includes target cell information and terminal information.

Thereafter, the first target base station apparatus allocates a resource for handover and transmits the corresponding information in a handover request Ack message to the serving base station apparatus. Then, the serving base station apparatus transparently transmits the information received from the first target base station apparatus through an RRC connection reconfiguration message.

If the terminal 40 fails to perform a handover to the target cell (cell PCI 3) for a T304 time, it is regarded as a failure and searches for another communicationable cell (reconfiguration fail or T304 expired). That is, the terminal 40 does not handover to the cell of the first target base station apparatus (cell 3) during T304 time (fails) or detects a new cell when communication is lost due to the shadow area. In this case, assume a cell (eg, a cell of PCI 5) of the first target base station apparatus as the newly discovered cell.

Thereafter, the terminal 40 attempts an RRE procedure by transmitting an RRC connection re-establishment request message to a first target base station apparatus of a PCI 5 cell, and the first target base station apparatus previously received a handover. Since the information of the terminal is known in advance through the request message, the RRE procedure is successfully performed.

However, if one of the cells of the first target base station apparatus (cells of PCI 3, 4 and 5) fails to handover (fails) or the communication is disconnected due to the shadow area, the terminal 40 may change to a new cell (target to be handed over). Cell). As a result, when searching for a cell of PCI 8 of the second target base station apparatus, the terminal 40 attempts an RRE procedure to the second target base station apparatus of the newly discovered cell (cell of PCI 8). However, since the second target base station apparatus has not previously received the handover request message, it cannot know the information of the terminal and cannot successfully perform the RRE (RRC connection reconfiguration) procedure.

In order to solve this problem, according to the first embodiment, when the serving base station apparatus transmits a handover request message to the first target base station apparatus, handover candidate base station apparatuses (neighbor base station apparatuses not selected as target base station apparatuses). ) Is sent to the RRE preparation request message (RRE preparation request message). Like the handover request message, this message includes UE context information. Therefore, since the second target base station apparatus, which is one of the handover candidate base station apparatuses, knows the information of the terminal when the terminal 40 attempts the RRE procedure, the second target base station apparatus can successfully perform the RRE procedure. If the handover candidate base station apparatuses do not receive an RRC connection re-establishment request message from the terminal 40 during T_rre (the RRE preparation waiting time for the corresponding terminal), the terminal information (UE context information) Delete it. A detailed description will be given below with reference to FIG. 3.

In addition, according to the second embodiment, in the present invention, if the terminal 40 fails to handover to the cell of the first target base station apparatus or attempts an RRE procedure to the cell of the second target base station apparatus, the terminal does not have information of the terminal. 2 The target base station apparatus may request and receive the terminal information from the serving base station apparatus that knows the terminal information through a previous handover request message, and may successfully perform the RRE procedure based on the received terminal information. A detailed description will be given below with reference to FIG. 4.

3 is a diagram illustrating an RRC connection reset (RRE) procedure according to a first embodiment of the present invention. In one embodiment, the base station apparatus uses three sector cells, and the α, β, and γ sector cells of the serving base station apparatus use PCI 0, 1, 2, and the α, β, It is assumed that the gamma sector cells use PCI 3, 4, 5 and the alpha, beta, gamma sector cells of the second target base station apparatus use PCI 6, 7, and 8.

When the terminal 40 moves to a cell of the target base station apparatus T-eNB in a state in which the terminal 40 is connected to a cell of the serving base station apparatus S-eNB (a cell of PCI 0), the terminal 40 performs a PCI connection to the neighboring cells. The strength is included in a measurement report message and transmitted to the serving base station apparatus (301). At this time, it is assumed that the size of the PCI strength measurement value of the adjacent base station devices is "PCI 3> PCI 8> PCI 4 ...". Then, the serving base station apparatus receiving the measurement report message selects the base station apparatus for handover and RRE using PCI strength. In one embodiment, the RRE target base station apparatus may include all of the neighbor base station apparatuses in the handover candidate list.

Thereafter, the serving base station apparatus finds a cell having PCI (PCI 3) having the highest PCI strength and transmits a handover request message to the base station apparatus (first target base station apparatus) of the cell (302). At this time, the handover request message includes target cell information and terminal information. In particular, the serving base station transmits a handover request message to the first target base station apparatus (302), and a message for requesting preparation of an RRE to the RRE target base station apparatus (neighbor base station apparatuses not selected as the target base station apparatus). (RRE preparation request message) is transmitted (303). The RRE preparation request message includes information of the terminal. Optionally, the RRE target base station apparatus may transmit an RRE preparation request Ack message to the serving base station apparatus in response to the RRE preparation request message (307). This does not necessarily have to be done for simple checking.

The first target base station apparatus (T-eNB1) allocates resources for handover and transmits the corresponding information to the serving base station apparatus in a handover request Ack message (304). When the serving base station receives the handover request response message from the first target base station, the serving base station transparently transmits the information included in the message through an RRC connection reconfiguration message (305).

If the terminal 40 fails to perform a handover to the target cell (cell PCI 3) for a T304 time, it is regarded as a failure and searches for another communicationable cell (reconfiguration fail or T304 expired) 306.

If the handover to the cell of the first target base station apparatus (cells of PCI 3, 4, 5) fails (or fails) or the communication is disconnected due to the shadow area, the terminal 40 searches for a new cell and newly discovers it. The RRC connection re-establishment request message is transmitted to the second target base station apparatus T-eNB2 of the cell (eg, a cell that is PCI 8) (308), and the second target base station apparatus receives the previously received RRE. Since the information of the UE is known in advance through the preparation request message, the RRE procedure is successfully performed (309).

The RRE preparation request message and the RRE preparation request response message are transmitted through the X2 interface when the serving base station apparatus and the RRE target base station apparatus belong to the same MME, and transmitted through the S1 interface when belonging to a different MME. In addition, the RRE preparation request message and the RRE preparation request response message may be provided by adding or changing IE to an existing message.

4 is a diagram illustrating an RRC connection reset (RRE) procedure according to a second embodiment of the present invention. Assume the same environment as in FIG.

When the terminal 40 moves to a cell of the target base station apparatus T-eNB in a state in which the terminal 40 is connected to a cell of the serving base station apparatus S-eNB (a cell of PCI 0), the terminal 40 performs a PCI connection to the neighboring cells. The strength is included in the measurement report message and transmitted to the serving base station apparatus (401). Then, the serving base station apparatus receiving the measurement report message selects the base station apparatus for handover and RRE using PCI strength. In this case, the RRE target base station apparatus may include all of the neighbor base station apparatuses in the handover candidate list.

Thereafter, the serving base station apparatus finds a cell having PCI (PCI 3) having the highest PCI strength and transmits a handover request message to the first target base station apparatus of the corresponding cell (402). In this case, the handover request message includes information of the terminal in addition to the target cell information.

The first target base station apparatus (T-eNB1) allocates resources for handover and transmits the corresponding information to the serving base station apparatus in a handover request Ack message (403). When the serving base station receives the handover request response message from the first target base station, the serving base station transparently transmits the information included in the message through an RRC connection reconfiguration message (404). Thereafter, if the UE 40 fails to perform the handover to the target cell (cell PCI 3) for a T304 time, it is regarded as a failure and discovers another cell that can communicate (reconfiguration fail or T304 expired).

If the handover to the cell of the first target base station apparatus (cells of PCI 3, 4, 5) fails (or fails) or the communication is disconnected due to the shadow area, the terminal 40 searches for a new cell and newly discovers it. The RRC connection re-establishment request message is transmitted to the second target base station apparatus T-eNB2 of the cell (eg, a cell that is PCI 8) (405). In response, the second target base station apparatus that does not know the terminal information transmits a UE context request message (terminal information request message for RRE) to the serving base station apparatus that knows the terminal information through the handover request message (406). In response, the serving base station apparatus transmits a UE context response message (terminal information transfer message for RRE) to the second target base station apparatus (407) and informs the terminal information.

As a result, the second target base station apparatus may know the information of the terminal and perform the RRE procedure successfully (408).

Although the method has been described through specific embodiments, the method may also be embodied as computer readable code on a computer readable recording medium. Computer-readable recording media include all kinds of recording devices that store data that can be read by a computer system. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission over the Internet) . The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. In addition, functional programs, codes, and code segments for implementing the above embodiments can be easily deduced by programmers of the present invention.

Although the present invention has been described in connection with some embodiments thereof, it should be understood that various changes and modifications may be made therein without departing from the spirit and scope of the invention as understood by those skilled in the art. something to do. It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

10,20,30: Macro base station 11-15, 21-23, 31-33: Micro base station
40: terminal (UE) 50: SON server
60: MME 70: management server
80: Serving Gateway (S-GW) 90: PDN Gateway (P-GW)

Claims (9)

RRC (Radio Resource Control) connection reset (RRE) method,
Upon receiving the measurement report message of the terminal for handover, the serving base station apparatus transmits a handover request message to the first target base station apparatus and informs the terminal information of the at least one handover candidate base station apparatus; And
Performing an RRE procedure on the basis of the terminal information by one of the at least one handover candidate base station apparatus selected as a second target base station apparatus when an RRC connection reset request of the terminal not connected to the target base station apparatus is performed; RRC connection reset method comprising a. The method of claim 1,
The at least one handover candidate base station apparatus deletes the terminal information if the RRC connection resetting request message is not received from the terminal within a predetermined time. The method of claim 1,
The at least one handover candidate base station apparatus further comprises the step of reporting the reception of the terminal information to the serving base station apparatus RRC connection resetting method. RRC (Radio Resource Control) connection reset (RRE) method,
Transmitting, by the serving base station apparatus, a handover request message to the first target base station apparatus when the measurement report message of the terminal for handover is received;
Receiving, by the second target base station apparatus, requesting terminal information from the first target base station apparatus when the RRC connection reestablishment request of the terminal not connected to the first target base station apparatus is requested; And
And performing, by the second target base station apparatus, an RRE procedure based on the terminal information. 5. The method according to any one of claims 1 to 4,
The handover request message, RRC connection reconfiguration method comprising the target cell information and the terminal information. As a mobile communication system,
A serving base station apparatus for transmitting a handover request message to a first target base station apparatus and informing terminal information to at least one handover candidate base station apparatus when a measurement report message of a terminal for handover is received; And
The at least one handover candidate base station including a second target base station apparatus for performing an RRE procedure based on the terminal information when an RRC connection reconfiguration (RRE) request of the terminal not connected to the first target base station apparatus is performed; A mobile communication system comprising a device. The method of claim 6,
The at least one handover candidate base station apparatus deletes the terminal information if the RRC connection reset request message is not received from the terminal within a predetermined time, and reports the reception of the terminal information to the serving base station apparatus. . As a mobile communication system,
A serving base station apparatus, wherein the serving base station apparatus transmits a handover request message to the first target base station apparatus when the measurement report message of the terminal for handover is received; And
Upon requesting an RRC connection reset (RRE) of the terminal not connected to the first target base station apparatus, the second target base station apparatus requests and receives terminal information from the first target base station apparatus, and receives the second target base station apparatus. Mobile communication system comprising at least two target base station apparatus for performing the RRE procedure based on the terminal information. 9. The method according to any one of claims 6 to 8,
The handover request message includes a target cell information and the terminal information.

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