KR101737398B1 - Method and apparatus for handover control and handover blacklist management in a mobile communication system - Google Patents

Abstract

A handover control method and a handover black list management method performed by a base station apparatus of a mobile communication system are disclosed. The disclosed handover control method includes receiving a measurement report message for at least one neighbor base station device from a terminal in the serving area of the base station device and for receiving the measurement report message by referring to the handover blacklist, And designating one of the adjacent base station apparatuses as a target base station apparatus. The disclosed handover blacklist management method includes receiving at least one handover result information from at least one terminal for at least one neighbor base station apparatus and using the at least one handover result information, And determining whether to register the device in the handover blacklist.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a handover control method and apparatus for handover control and handover blacklist management in a mobile communication system,

The present invention relates to handover in a mobile communication system, and more particularly, to handover control and handover black list management in a base station of a mobile communication system.

As is well known, a mobile communication system includes mobile communication terminals used by subscribers to access a wireless network to receive services, and base stations that transmit / receive control signals and data signals to / from mobile communication terminals. A mobile communication terminal communicates with a base station to transmit or receive data including voice calls and messages over a wireless network. The mobile communication terminal and the wireless network perform various mobility management functions in order to ensure that the mobile communication terminal can continuously communicate with the optimal base station even in the case where the mobile communication terminal moves. For example, the mobile communication system may initiate a "handover " to connect the mobile communication terminal from the first base station to the second base station.

Long Term Evolution (LTE) is a wireless network standard designed for high-speed data transmission. LTE and LTE-Advanced (LTE-Advanced) are the latest wireless network technologies developed in cellular networks. LTE delivers data packets based on Internet Protocol (IP) to all data including voice data. The current LTE implements "hard handover" in which the mobile communication terminal disconnects from the first base station before establishing a normal connection with the second base station.

The LTE wireless network handles cell selection, cell reselection and handover based on the currently received signal strength. The received signal strength is a measure of the signal power received at the mobile communication terminal. The mobile communication terminal can predict the expected quality that can be served by the base station (the "target base station") to be handed over based on the signal intensities received from the plurality of base stations.

In recent years, as a demand for mobile phone use and mobile data in a building has been rapidly increasing, a method for providing a wireless communication service by installing an ultra-small base station in the indoor or the like to connect to a wireless communication core network through an indoor broadband network has been proposed In a next generation network system, a method of arranging a plurality of small cells (femtocells) is proposed in order to meet a demand for a high data rate and to stably provide various services. An ultra-small base station that manages such a small cell is called an indoor base station or a femto base station. In 3GPP, it is called Home-eNB or HeNB. Reducing the size of a cell to such a small area can increase the efficiency of a next generation network system using a high frequency band. Also, using a small number of cells increases the frequency reuse frequency It provides advantages in terms of being able to do.

Meanwhile, a small serving area of the micro-base station may allow the mobile communication terminals to frequently disconnect and re-establish the connection with the base station. In addition, the LTE network may be configured to maximize overall network performance, e.g., the base station may abruptly terminate service for any terminal to provide better services to other mobile terminals. Similarly, a handover in a wireless network may not always be serviced (e.g., if the target base station can not service a handover request due to network congestion, etc.). The LTE network can disconnect the connection to the mobile communication terminal even when the mobile communication terminal is in a good reception state (e.g., high received signal strength). As a result, in LTE networks, unlike previous cellular network technologies, the strength of the received signal may not accurately reflect the quality of service that the mobile communication terminal can expect from the target base station. Therefore, it is necessary to consider factors other than quality of received signal in handover in LTE network.

In addition, since cells of various sizes are installed at a high density for the purpose of accepting data traffic and resolving the translucency area in a wireless communication environment, overlapping of cells and border regions between cells are increased. In this boundary region, handover is frequently occurred as well as being greatly affected by interference from neighboring cells. Therefore, it is important to manage the user 's sensory performance in the boundary area between the cells.

An object of the present invention is to provide a handover control method and a handover control method of a handover method for managing a handover black list by analyzing a handover failure rate of a neighbor base station apparatus and analyzing the handover failure rate, And a list management method.

Another object of the present invention is to determine a target base station apparatus for handover by referring to a black list in which a neighbor base station apparatus with a high handover failure rate is registered, A handover control method is provided in which a terminal does not perform a handover to a neighboring base station apparatus having a high handover failure rate and consequently a handover failure rate can be reduced.

It is a further object of the present invention to provide a method of determining a target base station apparatus for handover by determining a neighbor base station apparatus having a high handover failure rate as a target base station apparatus by referring to a black list in which a neighbor base station apparatus with a high handover failure rate is registered The present invention provides a handover control method for preventing a terminal from performing a handover to a neighbor base station apparatus having a high handover failure rate, thereby improving the quality of a user's perceived communication and preventing waste of network resources.

According to one aspect of the present invention, a handover control method performed by a base station apparatus of a mobile communication system is provided. The handover control method includes receiving a measurement report message from at least one neighbor base station device in a serving area of the base station device and, in response to receiving the measurement report message, And transmitting the message to the terminal. Herein, the handover command message designates one of the at least one neighbor base station apparatus as a target base station apparatus, and the step of transmitting the handover command message to the terminal refers to a handover black list stored in the base station apparatus .

In one embodiment, the step of transmitting the handover command message to the terminal further comprises determining whether the at least one neighbor base station device is registered in the handover black list.

In one embodiment, the measurement report message comprises measurements for each of the at least one neighbor base station device. In one embodiment, the step of determining whether the at least one neighbor base station device is registered in the handover black list may include determining whether the at least one neighbor base station device is registered in the handover black list, And designating a large neighbor base station apparatus as the target base station apparatus.

In one embodiment, the present handover control method further comprises managing the handover blacklist. In one embodiment, managing the handover blacklist may include receiving at least one handover result information from the at least one terminal for at least one base station device, using the at least one handover result information Calculating a handover failure rate for the at least one base station apparatus based on the handover failure rate for the at least one base station apparatus and determining whether to register the at least one base station apparatus in the handover black list based on the handover failure rate for the at least one base station apparatus .

According to another aspect of the present invention, there is provided a handover black list management method performed by a base station apparatus of a mobile communication system. The handover black list management method includes receiving at least one handover result information from at least one terminal in a serving area of a base station apparatus to at least one neighbor base station apparatus and using the at least one handover result information And determining whether to register the at least one neighbor base station device in the handover black list.

In one embodiment, the step of determining whether to register the at least one neighbor base station device in the handover black list may include determining at least one handover result information to be used for handover to the at least one neighbor base station device Calculating a failure rate and determining whether to register the at least one neighbor base station device in the handover black list based on the calculated handover failure rate for the at least one neighbor base station device.

In one embodiment, the step of determining whether to register the at least one neighbor base station device in the handover blacklist based on the calculated handover failure rate for the at least one neighbor base station device comprises: And registering the at least one neighboring base station apparatus in the handover black list when the handover failure rate for the base station apparatus is equal to or greater than a predetermined threshold value.

In one embodiment, registering the at least one neighbor base station device in the handover blacklist includes including an ID of the at least one neighbor base station device in the handover blacklist.

According to another aspect of the present invention, there is provided an apparatus for handover control mounted in a serving base station. The apparatus for handover control includes a blacklist storage unit and a handover control unit storing IDs of at least one neighboring base station apparatus of the first group having a handover failure rate equal to or higher than a predetermined threshold value. Here, the handover control unit may be configured to transmit a measurement report message to at least one neighboring base station of the second group from a terminal in the serving area of the serving base station, 2 group of at least one neighboring base station device in response to receiving the at least one neighboring base station device's ID and searching for the blacklist store in response to receiving the at least one neighboring base station device's ID, It is determined whether there is an ID that matches the ID of the adjacent base station apparatus.

According to another aspect of the present invention, there is provided an apparatus for handover control mounted in a serving base station. The apparatus for handover control includes a blacklist storing unit and a handover control unit storing a black list including IDs of at least one neighboring base station apparatus of the first group. In response to the serving base station receiving a measurement report message from at least one neighboring base station of the second group from a terminal in the serving area of the serving base station, And designates one of the at least one neighboring base station apparatus of the second group as a target base station apparatus by referring to the black list stored in the list storage unit.

In one embodiment, the measurement report message includes an ID of at least one neighbor base station apparatus of the second group, and the handover controller transmits the measurement report message to the target base station apparatus to designate the one neighbor base station apparatus as the target base station apparatus. Is configured to compare an ID of the at least one neighbor base station apparatus of the first group and an ID of at least one neighbor base station apparatus of the second group.

According to another aspect of the present invention, there is provided an apparatus for handover control mounted in a serving base station. The apparatus for handover control includes a blacklist storage unit storing at least one ID of a first group and a handover control unit. Here, the handover controller may receive a measurement report message from the terminal in the serving area of the serving base station, the measurement report message including at least one ID of the second group And to determine whether there is an ID that matches at least one ID of the second group among at least one ID of the first group stored in the blacklist storage unit.

In one embodiment, the handover control unit selects one ID among at least one of the IDs of the second group excluding the matching ID, according to a predetermined criterion, and transmits a handover command message including the selected ID To the terminal.

According to various embodiments of the present invention, by reducing the handover failure rate, i.e., unnecessary handover, by reflecting the state of the neighbor base station apparatus, which is a new variable not considered in the existing handover scheme, to the determination of the target base station apparatus for handover It is possible to improve the perceived communication quality of the user and to prevent waste of network resources.

Also, according to various embodiments of the present invention, the status of each neighboring base station device, which is obtained through analysis of handover result information for each neighboring base station device provided from the terminal, is notified to HeMS and information necessary for network operation is provided to the manager .

1 is a block diagram of a mobile communication system according to an embodiment of the present invention.
2 is a block diagram of a terminal according to an embodiment of the present invention.
3 is a block diagram of a base station apparatus according to an embodiment of the present invention.
4 is a graph illustrating handover triggering event generation in a mobile communication system according to an embodiment of the present invention.
5 is a diagram for explaining a handover control method in a mobile communication system according to an embodiment of the present invention.
6 is a message flow diagram illustrating an exemplary handover control method in a mobile communication system according to an embodiment of the present invention.
7 is a flowchart of an embodiment of a handover black list management method executed in a base station apparatus.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of attaining them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. To fully disclose the scope of the invention to a person skilled in the art, and the invention is only defined by the scope of the claims.

In this specification, the terms first, second, etc. are used for describing various components and are used for the purpose of distinguishing one component from another component. However, the first component and the second component may be arbitrarily named according to the convenience of the person skilled in the art without departing from the technical idea of the present invention. Also, terms such as a first group, a second group, and the like should not be understood as meaning that objects belonging to the group have technological features or functions that are necessarily different from those belonging to other groups. The terms first group, second group, and the like are used for arbitrarily classifying objects for convenience of explanation, and do not preclude the possibility that such objects may have some or all of the technical features or functions in common.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. For example, an element expressed in singular < Desc / Clms Page number 5 > terms should be understood to include a plurality of elements unless the context clearly dictates a singular value. In addition, in the specification of the present invention, it is to be understood that terms such as "include" or "have" are intended to specify the presence of stated features, integers, steps, operations, components, The use of the term does not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, parts or combinations thereof.

As used herein, the term " module " or " module " means a functional part that performs at least one function or operation, and may be implemented in hardware or software or a combination of hardware and software. In addition, a plurality of 'modules' or a plurality of 'parts' may be integrated into at least one module except for 'module' or 'module' which needs to be implemented by specific hardware, and may be implemented by at least one processor.

In addition, all terms used herein, including technical or scientific terms, unless otherwise defined, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be construed as meaning consistent with meaning in the context of the related art and may be interpreted in an ideal or overly formal sense unless explicitly defined in the specification of the present invention It does not.

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 block diagram of a mobile communication system according to an embodiment of the present invention.

The mobile communication system 100 in which the present invention can be implemented is a wireless communication system such as a Global System for Mobile communication (GSM), a 2G wireless communication network such as CDMA, an LTE network, a wireless Internet such as WiFi, a Wireless Broadband Internet (WiBro) Such as 3G wireless communication network such as WCDMA or CDMA2000, HSDPA (High Speed Downlink Packet Access) or HSUPA (High Speed Uplink Packet Access) G wireless communication network or a 4G wireless communication network currently in service, and any other wireless communication network including a macro-base station (macro-eNB), a micro-base station (home-eNB) But is not limited thereto. Hereinafter, the configuration of the mobile communication system 100 will be described focusing on an Evolved Universal Terrestrial Radio Access Network (E-UTRAN), which is a radio access network of LTE.

As shown in FIG. 1, the mobile communication system 100 may be composed of one or more homogeneous or heterogeneous network cells.

The mobile communication system 100 includes miniature base stations 111-114, 121-123, and 131-133 for managing a small-sized network cell (hereinafter referred to as 'femtocell') such as indoors, (Macro-eNodeB or eNodeB) 110, 120, and 130 for managing a plurality of macro cells (hereinafter referred to as 'macro cells').

For example, the macro base stations 110, 120, and 130 may be used in an LTE network, a WiFi network, a WiBro network, a WiMax network, a WCDMA network, a CDMA network, a UMTS network, The functions of the macro base stations 110, 120, and 130 are not limited thereto. The micro base stations 111-114, 121-123 and 131-133 can be used for example in an LTE network, a WiFi network, a WiBro network, a WiMax network, a WCDMA network, a CDMA network, a UMTS network, the functionality of the indoor base station or the femto base station managing a cell having a radius of about m to several tens of meters may be included, but the function of the ultra-small base stations 111-114, 121-123, 131-133 may be limited to this It is not. As will be apparent to those skilled in the art, the micro base stations 111-114, 121-123, and 131-133 and the macro base stations 110, 120, and 130 may independently have connectivity to the core network.

The mobile communication system 100 may further include a UE 140 that is capable of moving within or between femtocells / macrocells. The UE 140 may be used in a portable Internet network such as a 2G wireless communication network such as a GSM network and a CDMA network, a wireless Internet network such as an LTE network and a WiFi network, a WiBro network and a WiMax network or a wireless communication network supporting packet transmission , But the functionality of terminal 140 is not limited thereto. The UE 140 can perform intra-EUTRA handover, which is a handover in the LTE network, and can perform an inter-RAT handover, which is a handover between the LTE network and the heterogeneous network.

The mobile communication system 100 may further include an ultra-small base station management server (network management device) 170. The management server 170 is responsible for the configuration and management of the micro base stations 111-114, 121-123 and 131-133 and the macro base stations 110, 120 and 130. As shown in the figure, the management server 170 may be configured to perform functions of both a HeMS (HeNB Management System) server 150 and an MME (Mobility Management Entity) 160. In one embodiment, the HeMS server 150 includes any server that performs outdoor / mini base station installation and optimization as a server for cell operation and management, and provides basic parameters or data required for each base station . In one embodiment, the MME 160 may include any entity used to manage the mobility of the terminal 140, and the like. In one embodiment, the HeMS server 150 may be configured to manage one or more micro-base stations 111-114, 121-123, 131-133.

Although a network cell in which a macro cell and a femtocell are mixed is assumed in the above-described configuration of the mobile communication system 100, the network cell may be composed of only a macro cell or a femtocell. Also, the number of each component shown in FIG. 1 is an example, and the number of each component of the mobile communication system 100 is not limited to the number shown in the drawings.

Hereinafter, the micro base stations 111-114, 121-123, and 131-133 and / or the macro base stations 110, 120, and 130 will collectively be referred to as a 'base station device'.

2 is a block diagram of a terminal according to an embodiment of the present invention. As shown, the terminal 140 may include a controller 220, a storage 240, and a communication unit 260. 1 does not reflect all the functions of the terminal 140 that is operable in the mobile communication system 100 and is not essential so that the terminal 140 includes more components than the illustrated components It should be appreciated that fewer components may be included.

The control unit 220 may be generally configured to control the overall operation of the terminal 140. [ The control unit 220 may be implemented to perform control and processing for handover, for example, related control for voice communication, data communication, video call, etc., but the function of the control unit 220 is limited thereto no. The storage unit 240 may store a program and / or data for operation of the controller 220, and may store input / output data, a permanent black list, and the like. The storage unit 240 may be a flash memory type, a hard disk type, a multimedia card micro type, a card type memory (for example, SD or XD memory) (Random Access Memory), SRAM (Static Random Access Memory), ROM (Read Only Memory), EEPROM (Electrically Erasable Programmable Read-Only Memory), PROM A disk, and / or an optical disk. In one embodiment, the terminal 140 may be configured to operate in association with a web storage that performs storage functions on the Internet, either separately from or in conjunction with the storage 240. [ have. The communication unit 260 may be implemented with hardware and / or firmware that enables the terminal 140 to perform wireless communication with a wireless communication system such as a base station device or with a network in which another terminal is located. In one embodiment, the communication unit 260 may be implemented to comply with a wireless communication interface standard such as LTE-Ue.

3 is a block diagram of a base station apparatus according to an embodiment of the present invention. 3, the base station apparatus 110 may include a handover control unit 320, a blacklist storage unit 340, and a communication unit 360. It should be noted that the components shown in Figure 3 do not necessarily reflect and are not necessarily all of the functionality of the base station device 110 so that the base station device 110 includes or includes fewer components than the components shown. It is possible to do so.

When the handover controller 320 receives a measurement report message for at least one neighbor base station from a terminal that is located in a service area of the base station and satisfies a handover condition, And to transmit a handover command message. Here, the measurement report message may include a UE measurement for each of the at least one neighbor BS. The handover controller 320 refers to the handover black list to select the most suitable neighbor base station apparatus (target base station apparatus) from among the at least one neighbor base station apparatuses and instructs the terminal through the handover command message . In one embodiment, the handover controller 320 checks whether the at least one neighbor base station apparatus is registered in a handover blacklist, and registers the at least one neighbor base station apparatus in the handover black list of the at least one neighbor base station apparatus And selects the adjacent base station apparatus having the largest measured value as the target base station apparatus.

The handover controller 320 may collect information on handover results from the UEs to the neighbor BSs and calculate the handover failure rate for each of the neighbor BSs using the collected information. Here, 'handover failure rate for each of the neighboring base station apparatuses' means a ratio of the number of handover failures to the total number of handover attempts to the neighboring base station apparatus. In one embodiment, the handover control unit 320 may be configured to collect information on the handover result from the UEs to the neighbor BSs for a predetermined period (e.g. Ts). In one embodiment, the handover controller 320 calculates a handover failure rate for each of the neighboring base station apparatuses from the handover result information about the neighboring base station apparatuses provided from the serving terminals, And determine the state of each neighbor base station apparatus using the handover failure rate for the base station apparatus. In one embodiment, the state of each neighbor base station device is a steady state, a state that can not be selected by the target base station by being stored in the handover black list, a state that is stored in the permanent handover black list, . ≪ / RTI >

The blacklist storage unit 340 may be configured to store a handover blacklist and a permanent handover blacklist. Based on the status determination result of each neighboring base station apparatus provided from the handover control unit 320 under the control of a controller (not shown), each neighboring base station apparatus selectively transmits a handover black list of the black list storage unit 340 And can be registered in a list form in the permanent handover black list. In this case, the registration of each neighbor base station apparatus in the handover black list or the permanent handover black list is performed by storing the IDs of the respective neighbor base station apparatuses, for example, PCI (Physical Cell Identity) thereof in the handover black list or permanent handover black list . ≪ / RTI > In one embodiment, it is also possible to store the cell global ID, TAC, and PLMN received from the UE through the measurement report message in addition to PCI in the handover black list. The blacklist storage unit 340 may be implemented as a memory device as described above in connection with the storage unit 240 of the terminal 140. [ The blacklist storage unit 340 may include various memory devices including, but not limited to, ROM, EPROM, or EEPROM, for example.

The communication unit 360 may be implemented as a hardware module and / or a software / firmware module between the corresponding base station device and the terminals for supporting wireless communication between the corresponding base station device and the adjacent base station device and / or between the corresponding base station device and the management server have. In one embodiment, the communication unit 360 may be implemented to comply with the X2 wireless communication interface standard for communication between the base transceiver station and the adjacent base transceiver station, that is, between the base transceiver stations, and communication between the base transceiver station and the management server Lt; RTI ID = 0.0 > S1 < / RTI >

The embodiments described above, and particularly the control units 220 and 320, may be implemented in hardware in terms of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) and may be implemented using at least one of field programmable gate arrays, processors, controllers, micro-controllers, and microprocessors. Embodiments that include procedures, steps, or functions The software code may be implemented by a software application written in a suitable programming language. In this case, the software code may be implemented as a software / And may be stored in the storage units 240 and 340 or may be stored in the storage units 240 and 340 and the control units 220 and 320, And can be executed by the control units 220 and 320. [

4 is a graph illustrating handover triggering event generation in a mobile communication system according to an embodiment of the present invention. 5 is a diagram for explaining a handover control method in a mobile communication system according to an embodiment of the present invention. 6 is a message flow diagram illustrating an exemplary handover control method in a mobile communication system according to an embodiment of the present invention. Hereinafter, referring to FIGS. 4 to 6, a handover process occurs when a UE 140 receives a service from the serving base station 510 and enters a service area of a plurality of neighbor BSs 520, 530, and 540 The handover in the same system will be specifically described as an example. It will be appreciated by those skilled in the art that the following description can be applied in the same or a similar manner or even through modifications that are clearly perceived as necessary in the case of an inter Radio Access Technology (RAT) handover. Prior to the following description, refer to the symbols in Table 1 below.

sign Explanation Ms, Mn RSRP or RSRQ of the serving base station apparatus and the neighbor base station apparatus Ofs, Ofn The frequency specific offset of the serving base station apparatus and the neighbor base station apparatus Ocs, Ocn The cell specific offset of the serving base station apparatus and the neighbor base station apparatus Hys Handover margin

The terminal 140 is in the service area of the neighboring base station apparatuses 520, 530 and 540 while receiving the service of the serving base station apparatus 510 and the serving base station apparatus 510 and the plurality of neighboring base station apparatuses 520, 530, (RSRP) or RSRQ (Reference Signal Received Quality) of the RSs 540 and 540 periodically. In an embodiment, the initiation of a handover may be initiated by the serving base station apparatus 510 to a reference signal received power (RSRP) or a reference signal received quality (RSRQ) measurement of neighboring base station apparatuses measured by the terminal 140 And a handover metric to which a handover related parameter is applied. The handover metrics Q _S and Q _N may be obtained by applying a handover offset received from the serving base transceiver station 510 to the measured value measured by the terminal 140. The handover metrics Q _S and Q _N may be defined as Equation 1 and Equation 2, respectively.

When the A3 event is defined as a handover triggering event, that is, when the offset of the neighbor base station apparatus is larger than the offset of the serving base station apparatus, the start and end conditions of the A3 event are as shown in the following equations (3) and (4), respectively.

4), the terminal 140 transmits a measurement report message to the serving base station apparatus 510 (601; see FIG. 6). When the A3 event start condition is satisfied during the time to trigger (TTT) . The measurement report message can be controlled by parameters set in the serving base station apparatus. The measurement report message may be generated at the time of A3 event triggering or periodically according to the setting of the serving base station apparatus. In one embodiment, the measurement report message includes the reason why the measurement report was triggered and the measurement result, and the measurement result may include the ID of the base station device and the UE measurement. In one embodiment, the UE measurement may include a received symbol power (RSRP) or a reference symbol received quality (RSRQ) of the neighbor base station apparatus. In one embodiment, the terminal 140 may transmit a plurality of measurement results when there are multiple base station apparatuses satisfying the handover triggering condition. In one embodiment, the maximum number of measurement results that may be included in the measurement report message may be determined by the serving base station device and reported to the terminal 140. [

In step 602, the serving base station 510 receives the measurement report message and determines the neighbor base station apparatus 520 to be handed over based on the status information of the neighbor base station 520-540. The serving base station apparatus 510 refers to the handover black list and selects the most appropriate one of the plurality of neighboring base station apparatuses 520, 530, 540 considering the states of the neighboring base station apparatuses 520, 530, (Assuming the base station device 520). In one embodiment, the serving base station apparatus 510 determines whether the IDs of measured base station apparatuses included in the measurement result of the measurement report message received from the terminal 140 are stored in the handover black list, The handover can be determined to the adjacent base station apparatus having the largest measured value among the neighboring base station apparatuses whose IDs are not stored in the handover black list. In one embodiment, the serving base station apparatus 510 may be configured to reference the blacklist stored in the blacklist storage unit 340 in determining the most appropriate base station apparatus.

When the serving base station apparatus 510 determines handover to the neighbor base station apparatus 520, for example, in case of the X2 handover, the serving base station apparatus 510 transmits a handover request message to the neighbor base station apparatus 520 (603). Upon receiving the handover request message, the neighbor BSC 520 may transmit a Handover Request Acknowledge message to the serving BS 510 in response to the handover request message (604). The serving base station 510 transmits a handover command message to the terminal 140 to instruct the terminal 140 to perform handover to the neighboring base station 520 in operation 605.

In response to receiving the handover command message, the terminal 140 performs handover to the base station apparatus 520 by connecting the physical layer and the data link layer with the neighbor base station apparatus 520 (606) 520 in step 607. In step 607, If the handover is normally performed, the neighbor base station 520 transmits a terminal context release message to the serving base station 510 to complete the handover (608). According to the handover control method described above, the handover failure rate and the radio link failure (RLF) can be greatly reduced.

7 is a flowchart of an embodiment of a handover blacklist management method executed in a serving base station apparatus. The handover black list management method described below with reference to FIG. 7 can be performed by the handover control unit 320 of the serving base station 510. The handover black list management method includes a handover result collection and analysis procedure, And may include a blacklist update procedure. Refer to the symbols in Table 2 in the following description.

sign Explanation

Number of handover failures to base station device with ID m

Number of handover attempts to base station device with ID m

In S1 handover, a timer indicating the time to wait for receiving a handset context release command from the MME after issuing a handover command to the terminal

Handover failure rate to base station device with ID m

A predetermined threshold value for the handover failure rate determining the registration to the handover black list,

The number of statistical cycles in which the base station device is registered in the handover blacklist

The criteria to be registered in the permanent handover blacklist (successive to the handover blacklist)

Th registered base station device is registered in the permanent handover black list)

Handover result information gathering and analysis

In the handover management method, the serving base station 510 collects handover result information from the terminals in the serving area for a predetermined period of time (T _S ), analyzes the handover result information, and transmits the handover result information to each of the neighboring base station apparatuses 520, 530 and 540 (S702). The serving base station apparatus 510 may determine the status of the neighboring base station apparatuses 520, 530, and 540. In this case, in case of a handover failure which should be included in the handover failure rate, the handover failure due to a problem in the target base station apparatus or the target system, which is not a handover failure due to a problem occurring in the serving base station apparatus 510, have.

과

을 다음과 같이 정의한다:

은 ID가 m인 타겟 기지국장치에 대해 핸드오버가 실패한 횟수를 의미하는 값이고,

은 ID가 m인 타겟 기지국장치로 시도한 전체 핸드오버 횟수를 의미한다.

과

은 서빙 영역 내의 단말들로부터 수집한 핸드오버 결과 정보로부터 산출 가능하다. 여기서, 기지국장치의 ID는 PCI(Physical Cell Identity), cell global ID(CGI 또는 ECGI), TAC(Tracking Area Code) 및 PLMN을 포함할 수 있으나 이에 한정되는 것은 아니다. 또한, 핸드오버가 실패한 경우는 다음의 경우를 포함할 수 있다:For convenience of explanation

and

Is defined as:

Is a value indicating the number of times the handover has failed for the target base station apparatus whose ID is m,

Denotes the total number of handover attempts made by the target base station apparatus with ID m.

and

Can be calculated from the handover result information collected from the terminals in the serving area. Here, the ID of the base station apparatus may include, but is not limited to, a PCI (Physical Cell Identity), a cell global ID (CGI or ECGI), a TAC (Tracking Area Code) and a PLMN. In addition, when the handover has failed, the following cases may be included:

1. In case of LTE X2-based handover, after the serving base station apparatus 510 issues a handover command to the terminal 140, in a state in which the terminal context release message is not received from the target base station apparatus, When receiving the RLF Indication message for the corresponding terminal,

타이머가 만료될 때까지 MME(160)로부터 단말 Context Release 명령 메시지를 받지 않은 경우, 및2. In case of handover based on the LTE S1, after the serving base station apparatus 510 issues a handover command to the terminal 140

If the terminal context release command message is not received from the MME 160 until the timer expires, and

3. If the cause of the handover Preparation Failure message is for a specific reason defined by the operator

Therefore, the handover failure rate for the target base station apparatus whose ID is m can be defined by the following equation (5).

을 수학식 5에 의해 계산한다(S402).In this manner, the serving base station apparatus 510 transmits a predetermined time period T _S , The handover result information for the neighbor base station apparatus is collected and the handover failure rate

(5) (S402).

In the above description, the handover result information for each neighbor base station apparatus is collected from the terminals and the handover failure rate for each neighbor base station apparatus is calculated from the handover result information. However, It is not. For example, after the serving base station apparatus 510 transmits a handover command message to the terminal 140 to perform handover to one of the neighboring base station apparatuses, in response to the handover command message from the MME 160 until the T _w timer expires, (Context Release) command message, and accumulates the number of handover attempts and the number of handover failures for the neighbor base station apparatus according to whether the message is received or not, Related data can be constructed. It is possible to calculate a handover failure rate for each adjacent base station apparatus using this data.

Handover Blacklist Update

)이 도과한 경우, 해당 인접 기지국장치의 ID를 핸드오버 블랙리스트에서 삭제한다(S703). 단계(S704)에서, 서빙 기지국장치(510)는 T_S 시간 주기 동안 수집한 핸드오버 결과 정보를 통해 인접 기지국장치별 핸드오버 실패율

이

미만인지 여부를 판단한다(S704). 만약 당해 인접 기지국장치에 대한 핸드오버 실패율

이 선정된 임계값(predetermined threshold)(

) 미만일 경우, 당해 인접 기지국장치에 대한 핸드오버 실패율이

를 초과한 횟수(

)를 0으로 초기화할 수 있다(S705). 한편, 당해 인접 기지국장치에 대한 핸드오버 실패율

이

이상인 경우, 당해 인접 기지국장치에 대한 핸드오버 실패율이

를 초과한 횟수(Nm)를 증가시킨다(S706). 단계(S707)에서는, 당해 인접 기지국장치에 대한 핸드오버 실패율이

를 초과한 횟수(Nm)가 영구 핸드오버 블랙리스트에 등록되는 기준을 충족하는지, 즉 그 횟수가 선정된 횟수(

) 이상인지를 판단한다(S707). 만약, 당해 인접 기지국장치에 대한 핸드오버 실패율이

를 초과한 횟수(Nm)가 영구 핸드오버 블랙리스트에 등록되는 기준을 충족하지 못하는 경우, 즉

미만인 경우, 당해 인접 기지국장치를 블랙리스트에 추가하여 등록할 수 있다(S708). 일 실시예에서, 당해 인접 기지국장치의 블랙리스트에의 등록은 당해 인접기지국장치의 ID, 예컨대 그 PCI를 블랙리스트에 포함시키는 것에 의해 이루어질 수 있다. 일 실시예에서, 블랙리스트에의 등록은 당해 기지국장치의 PCI 및/또는 단말로부터 측정 보고 메시지를 통해 전달받은, 당해 인접 기지국장치의 cell global ID, TAC 및 PLMN을 핸드오버 블랙리스트에 저장하는 것에 의해 이루어질 수 있다.In step S703, for each neighboring base station device listed in the black list, a handover black list holding period (

), The ID of the corresponding neighbor base station apparatus is deleted from the handover black list (S703). In step S704, the serving base station apparatus 510 determines a handover failure rate per neighbor base station apparatus through the handover result information collected during the T _S time period

this

(S704). If the handover failure rate for the neighbor base station apparatus

The predetermined threshold (

), The handover failure rate for the neighbor base station apparatus is

Times (

Can be initialized to 0 (S705). On the other hand, the handover failure rate

this

, The handover failure rate for the neighbor base station apparatus is

(Nm) (step S706). In step S707, the handover failure rate for the neighbor base station apparatus is

(Nm) exceeds the criterion registered in the permanent handover black list, that is, the number of times the number of times

) (Step S707). If the handover failure rate for the neighbor base station apparatus is

(Nm) exceeds the criterion registered in the permanent handover black list, that is,

, The neighbor base station apparatus can be added to the black list and registered (S708). In one embodiment, registration of the neighbor base station apparatus in the black list can be performed by including the ID of the neighbor base station apparatus, for example, its PCI in the black list. In one embodiment, the registration in the black list is performed by storing the cell global ID, TAC, and PLMN of the neighbor base station apparatus, which are received via the measurement report message from the PCI and / or the terminal of the base station apparatus, ≪ / RTI >

를 초과한 횟수(Nm)가 영구 핸드오버 블랙리스트에 등록되는 기준을 충족하는 경우, 즉 당해 인접 기지국장치에 대한 핸드오버 실패율이

번 연속으로

이상인 경우, 당해 인접 기지국장치는 잘못 등록된 인접 기지국장치로 판단되어 영구 핸드오버 블랙리스트에 추가될 수 있다(S709). 영구 핸드오버 블랙리스트에 추가된 기지국장치는 핸드오버 블랙리스트 갱신 절차에 의해서 삭제되지 않을 수 있다. 영구 핸드오버 블랙리스트에 추가의 인접 기지국장치가 등록된 경우 서빙 기지국장치(510)는 이를 HeMS로 알려 관리자가 확인할 수 있도록 한다(S711).On the other hand, if the handover failure rate for the neighbor base station apparatus is

(Nm) exceeds the criterion registered in the permanent handover black list, that is, when the handover failure rate for the neighbor base station apparatus satisfies the criterion

In succession

, The neighboring base station apparatus is determined to be a wrongly registered neighboring base station apparatus and added to the permanent handover black list (S709). The base station apparatus added to the permanent handover black list may not be deleted by the handover black list updating procedure. When an additional neighbor base station apparatus is registered in the permanent handover black list, the serving base station apparatus 510 informs it to the HeMS so that the manager can confirm it (S711).

In one embodiment, the serving base station 510 may send both the ID of the neighbor base station device additionally registered in the permanent handover black list or the IDs contained in the permanent handover black list to the HeMS. In one embodiment, the neighbor base station apparatus registered in the permanent handover black list can be manually deleted by the manager. The serving base station apparatus 510 informs the terminals in the serving area of the serving base station apparatus 510 of the ID (for example, its PCI) of the neighbor base station apparatus registered in the permanent handover black list through measConfig of the RRC Connection Reconfiguration message It is possible to prevent the UEs from performing measurement on the neighboring base station apparatus (S712).

In one embodiment, if the administrator determines that the base station included in the permanent handover black list has been recovered and issues a command to delete the base station from the permanent handover black list, a message indicating that the base station has been deleted from the permanent handover black list The UE may be notified so that the UE periodically measures RSRP (Reference Signal Received Power) or RSRQ (Reference Signal Received Quality) to the corresponding base station device. In one embodiment, a message that one base station has been deleted from the permanent handover black list may be communicated via an RRC Connection Reconfiguration message.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention, The technical scope of the present invention should be determined only by the appended claims.

110, 120, 130, 140: Base Station Device
111-114, 121-123, 131-133: Very Small Base Station
140: terminal
150: HeMS server
160: MME server
170: management server
220:
240:
260:
320: handover control unit
340: Blacklist storage unit
360: communication section
510-540: base station device

Claims (18)

delete delete delete delete delete delete delete delete delete delete An apparatus for handover control mounted in a serving base station,
A black list storage unit storing an ID of at least one neighboring base station apparatus of a first group having a handover failure rate equal to or higher than a predetermined threshold value,
And a handover control unit,
Wherein the handover control unit is operable to receive a measurement report message from the terminal in the serving area of the serving base station for at least one neighboring base station of the second group, Of the at least one neighboring base station device of the first group and the ID of at least one neighboring base station device of the second group, And to determine whether there is an ID that matches the ID of the device,
The handover control unit collects handover result information for at least one neighbor base station device or at least one neighboring base station device of the first group from an MME (Mobility Management Entity) of the first group, And to use the result information to calculate the handover failure rate for the at least one neighboring base station device of the first group. An apparatus for handover control mounted in a serving base station,
A black list storage unit storing a black list including IDs of at least one neighbor base station apparatus of the first group,
And a handover control unit,
Wherein the handover control unit is operable to store the blacklist information in response to receiving a measurement report message from the terminal in the serving area of the serving base station to the at least one neighboring base station apparatus of the second group, And designates one of the at least one neighboring base station apparatus of the second group as a target base station apparatus by referring to the ID of at least one neighboring base station apparatus of the first group included in the black list stored in the first group ,
Wherein the handover failure rate for at least one neighboring base station apparatus of the first group is greater than or equal to a predetermined threshold,
The handover control unit collects handover result information of at least one neighboring base station apparatus of the first group from at least one neighboring base station apparatus or MME of the first group and uses the collected handover result information And to calculate the handover failure rate for at least one neighbor base station device of the first group. 14. The target base station apparatus of claim 12, wherein the measurement report message includes at least one neighbor base station apparatus ID of the second group, And compare the ID of the at least one neighbor base station device of the first group included in the list with the ID of the at least one neighbor base station device of the second group. delete An apparatus for handover control mounted in a serving base station,
A blacklist storage unit storing at least one ID of the first group, and
And a handover control unit,
The handover controller may be configured to receive the measurement report message from the terminal in the serving area of the serving base station, the measurement report message including at least one ID of the second group In response to the at least one ID of the first group stored in the blacklist storage unit,
Wherein the at least one ID of the first group is associated with at least one specific neighbor base station device and the handover failure rate for the at least one particular neighbor base station device is greater than or equal to a predetermined threshold,
The handover control unit collects handover result information for the at least one specific neighbor base station device or the at least one specific neighbor base station device from the at least one specific neighbor base station device or the MME, And to calculate the handover failure rate for the base station device. The handover control method according to claim 15, wherein the handover control unit selects one ID among at least one ID of the second group excluding the matching ID, according to a predetermined criterion, And transmit the message to the terminal. delete delete

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