KR20100062862A - Method of reselecting cell and handover based on self-organazing operation in wireless communication system - Google Patents

Abstract

PURPOSE: A cell reselection method based on a self-organizing operation and a handover method in a wireless communication system are provided to use a load balancing parameter received from a serving base station in a cell reselection and a handover. CONSTITUTION: A first base station is connected to a serving base station(S400). A load balancing parameter is received from the serving base station(S410). A synchronization of the serving base station is cut(S420). A load balancing timer is opened(S430). The first base station is preferentially searched using the load balancing parameter after the synchronization is cut(S440). A terminal implements the first base station and a resynchronization(S450).

Description

Cell reselection method and handover method based on self-organization operation in wireless communication system {METHOD OF RESELECTING CELL AND HANDOVER BASED ON SELF-ORGANAZING OPERATION IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to wireless communication, and more particularly, to a cell reselection method and a handover method based on self-organization operation in a wireless communication system.

The Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard provides technologies and protocols to support broadband wireless access. Standardization has been in progress since 1999, and IEEE 802.16-2001 was approved in 2001. This is based on a single carrier physical layer called 'WirelessMAN-SC'. Later, in the IEEE 802.16a standard approved in 2003, 'WirelessMAN-OFDM' and 'WirelessMAN-OFDMA' were added to the physical layer in addition to 'WirelessMAN-SC'. After the completion of the IEEE 802.16a standard, the revised IEEE 802.16-2004 standard was approved in 2004. In order to correct bugs and errors in the IEEE 802.16-2004 standard, IEEE 802.16-2004 / Cor1 was completed in 2005 in the form of 'corrigendum'.

Currently, standardization of IEEE 802.16m, a new technical standard, based on IEEE 802.16e is in progress. IEEE 802.16m, a newly developed technical standard specification, should be designed to support IEEE 802.16e designed earlier. That is, the technology of the newly designed system (IEEE 802.16m) should be configured to efficiently cover the existing technology (IEEE 802.16e).

1 illustrates a wireless communication system combining a macro-cell and a femto-cell. In the 802.16m system, femtocell technology can be applied. Recently, active research is in progress. Femtocell refers to a very small mobile communication base station used indoors, such as home or office. A femtocell is connected to an IP network, which is widely used in homes and offices, and provides a mobile communication service by accessing a core network of a mobile communication system through an IP network. The user of the mobile communication system may be provided with a service through an existing macrocell outdoors, and may be provided with a femtocell indoors. Reducing the size of the cell can increase the efficiency of next-generation cellular systems that use high frequency bands, and it can be advantageous in terms of increasing the frequency reuse frequency by using multiple small cells. 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.

In order to apply the femtocell technology to the 802.16m standard, various technical elements must be achieved, one of which is a self-organizing network (SON). Self-organizing network refers to a network constructed by using the concept of self-organazation. Self-organization refers to the process of increasing the complexity of the entire system by interacting with the organizations inside the system without external influences, and can achieve the purpose of the whole system by the simple operation of each element of the whole. Nodes such as femtocells are not installed at the optimal location specified by the service provider, but are installed by the user. Since they cannot perform cell planning in advance, the nodes themselves can detect the environment and collect information to perform optimization. There is a need. In order to configure a self-organizing network in 802.16m, self-configuration, self-optimization, etc. should be performed, and even if the terminal is disconnected from the base station or the handover occurs, the terminal directly A procedure such as finding a cell should be performed.

The cell section process is a process in which the UE selects a cell for receiving a service. In general, the terminal selects a cell having the strongest signal characteristic value through a signal measurement process with a base station in all searchable frequency bands. The terminal reselects a suitable cell capable of receiving a better signal if it is far from the serving base station providing the service. This is called a cell reselection process. The terminal waits in the idle state to request a service from the network or to receive a service from the network. The idle terminal repeats the process of reselecting a cell having better signal characteristics through signal measurement of the serving base station and the neighbor base station.

In addition, handover may occur as the terminal moves. Handover refers to a process of moving from a radio interface provided by one station to a radio interface provided by another base station, also called a handoff. The handover starts when the terminal determines handover from the serving base station to the target base station. The handover decision may originate from the terminal, serving base station or network. The serving base station may send a BS handover request message when it wishes to initiate a handover. When the terminal wants to initiate a handover, the terminal may transmit an MS handover request message. The serving base station may transmit a base station handover response message in response to the terminal handover request message. When the terminal handover request message is sent by the terminal, the terminal may indicate one or more possible target base stations. Likewise, when a base station handover request message is sent by a serving base station, the serving base station may point to one or more possible target base stations.

In an 802.16m system, the mobility of a terminal increases due to femtocell support. Therefore, synchronization between the terminal and the base station may be frequently disconnected, and handover of the terminal from one cell to another may occur relatively frequently. Therefore, when synchronization between the terminal and the base station is lost, if the terminal reselects a cell using the existing method, unnecessary signal exchange may occur, and inequality of load of various base stations may occur during handover.

There is a need for a method and a handover method for efficiently reselecting cells based on self-organizing operations.

An object of the present invention is to provide a cell reselection method and a handover method based on self-organization operation in a wireless communication system.

In one aspect of the present invention, a method of cell reselection based on self-organizing operation in a wireless communication system is provided. The method comprises the steps of connecting the first base station to a serving base station in synchronization with a first base station, receiving a load balancing parameter from the serving base station, and synchronizing with the serving base station Disconnecting, and first searching for the first base station using the load equalization parameter after the synchronization is lost.

The load balancing parameter may include information regarding a load balancing timer. Starting the load equalization timer when the synchronization is lost, the first base station may be searched first while the load equalization timer is in operation. If the load equalization timer expires, the method may further include searching for another base station. The method may further include connecting the first base station to a serving base station after the synchronization is terminated. In addition, a type of base station includes a macro base station (macro BS) and a femto base station (femto BS), and the load equalization parameter depends on the type of the base station, and preferentially searches for a base station of the same type as the first base station. Can be.

In another aspect of the present invention, there is provided a handover method based on self-organizing operation in a wireless communication system. The method includes receiving a load equalization parameter from a serving base station and a neighbor base station, and determining whether handover to a target base station is possible using the load equalization parameter, wherein the serving base station And one of the neighbor base stations is a femto base station.

The method may further include transmitting a handover request message including information of a target base station to be handed over to the serving base station, and receiving a handover confirmation message from the serving base station. In addition, handover to a target base station may be enabled when the load equalization parameter is greater than or equal to a certain threshold.

When a load balancing parameter of each base station is set, the terminal may find another base station instead of the currently found base station. Unnecessary signal exchange can be prevented by performing cell reselection based on self-organization operation using the load balancing parameter. In addition, by performing a handover based on the self-organization operation using the load equalization parameter it is possible to solve the load imbalance between the base stations.

2 is a block diagram illustrating a wireless communication system using a femtocell. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 2, a wireless communication system includes a user equipment (UE) and a base station (BS). The terminal may be fixed or mobile, and may be called by other terms such as mobile station (MS), user terminal (UT), subscriber station (SS), and wireless device (wireless device). A base station generally refers to a fixed station communicating with a terminal, and may be referred to in other terms such as a NodeB, a base transceiver system (BTS), and an access point. One or more cells may exist in one base station.

 The base station may be divided into a femto base station 20 and a macro base station 50 according to a cell coverage or deployment scheme. The cell of the femto base station has a smaller size than the cell of the macro base station. All or some of the cells of the femto base station may overlap with the cells of the macro base station. The femto base station may be called in other terms such as a femto-cell, a home node-B, and a closed subscriber group (CSG). The macro base station may be referred to as a macro-cell, distinct from a femtocell.

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

A terminal accessing a femto base station is called a femto UE 10 and a terminal accessing a macro base station is called a macro UE 40. The femto terminal may be a macro terminal through a handover (HO) to the macro base station, and the macro terminal may be a femto terminal through a handover to the femto base station.

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

There is no limitation on the multiple access scheme applied to the wireless communication system. Various multiple access techniques such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Single-Carrier FDMA (SC-FDMA), and Orthogonal Frequency Division Multiple Access (OFDMA) are available. Can be.

3 illustrates a signaling operation for implementing a self-organazing network in an 802.16m system.

The base station 85 of each cell interoperates with each other to measure and exchange a system environment, and performs optimization of its own cell by requesting and receiving information about a neighboring environment such as a neighboring cell from the terminal 80. . In addition, a separate operation and maintenance server (Operation and Maintenance Center) 90 supports the optimization of the entire system, such as assigning an optimization strategy to the base station and reporting the state of the cell from the base station.

4 shows an example of a frame structure. A frame is a sequence of data for a fixed time used by physical specifications. This may be referred to section 8.4.4.2 of the IEEE standard 802.16-2004 "Part 16: Air Interface for Fixed Broadband Wireless Access Systems" (hereafter reference 1).

Referring to FIG. 4, the frame includes a downlink subframe and an uplink subframe. Time Division Duplex (TDD) is a method in which uplink and downlink transmissions share the same frequency but occur at different times. The downlink subframe is temporally ahead of the uplink subframe. The downlink subframe starts with a preamble, a frame control header (FCH), a downlink (DL) -MAP, an uplink (MAP) -MAP, and a burst region. The preamble is a signal used for acquiring synchronization in a cell search process, and is also called a midamble, a synchronization signal, or a synchronization channel according to a system. A guard time for distinguishing the downlink subframe and the uplink subframe is inserted in the middle part (between the downlink subframe and the uplink subframe) and the last part (after the uplink subframe) of the frame. Transmit / receive transition gap (TGT) is the gap between a downlink burst and a subsequent uplink burst. Receive / transmit transition gap (RTG) is the gap between an uplink burst and a subsequent downlink burst. Slots are the smallest possible data allocation units, defined by time and subchannels. The number of subchannels depends on the FFT size and the time-frequency mapping. The subchannel includes a plurality of subcarriers, and the number of subcarriers per subchannel depends on a permutation scheme. Permutation means mapping logical subchannels to physical subcarriers. In FUSC (Full Usage of Subchannels), a subchannel includes 48 subcarriers, and in Partial Usage of Subchannels (PUSC), a subchannel includes 24 or 16 subcarriers. A segment refers to at least one subchannel set. The bin includes 9 contiguous subcarriers on the OFDM symbol. A band refers to a group of four rows of bins, and an Adaptive Modulation and Coding (AMC) subchannel consists of six adjacent bins in the same band.

5 is a flowchart illustrating a network initialization process. The network initialization refers to a process in which a terminal initially enters a network, and initial ranging is a process of obtaining an accurate timing offset between the terminal and a base station and initially adjusting transmission power.

Referring to FIG. 5, in step S100, the terminal receives a preamble transmitted from a base station.

In step S110, the terminal reads the DL-MAP message transmitted from the base station. After initialization or loss of signal, the terminal should obtain the downlink channel. The terminal scans a radio channel, receives a frame structure, and synchronizes with the base station. When the terminal receives at least one DL-MAP message, it can obtain MAC (Medium Access Control) synchronization. Upon obtaining MAC synchronization, the terminal can continue to receive DL-MAP message, DCD message and UCD message. After synchronization, the terminal waits for a UCD message from the base station and obtains transmission parameters for possible uplink channels. The UCD message includes the time and frequency to send the ranging request. The UCD message may specify one or more groups of 6 (or 8) contiguous subchannels where contention based ranging is performed. The contention-based means that at least one terminal may transmit on the same subchannel at the same time.

In step S120, the UE reads a UL-MAP message to find an initial ranging interval. The base station allocates an initial ranging interval consisting of at least one transmission opportunity. The transmission opportunity refers to an allocation provided by UL-MAP so that a certain group of authorized terminals can transmit an initial ranging request.

In step S130, the terminal and the base station exchanges a series of ranging request (RNG-REQ) messages and ranging response (RNG-REP) messages. The ranging request message is sent from the terminal at initialization to determine the network delay and to request a power and / or downlink burst profile change. The ranging response message is a broadcast message. Through ranging, the base station determines symbol timing offset due to transmission delay, frequency offset due to Doppler shift or oscillator inaccuracy, and reception power. Using this information, the base station sends a calibration to the terminal. The terminal continues ranging until the power, timing and frequency are aligned.

In step S140, the base station and the terminal negotiate basic capabilities. Immediately after the ranging is completed, the terminal transmits a Basic Capability Request (SBC-REQ) message including its basic capability. The basic capability of the provided terminal is whether to support ARQ (Automatic Repeat Request) or MAC level CRC (Cyclic Redundancy Check). In response to the basic capability request message, the base station sends a Basic Capability Response (SBC-RSP) message.

In step S150, the terminal and the base station authenticate each other and exchange an authorization key.

In step S160, the UE sends a Registration Request (REG-REQ) message. The registration request message includes the primary management CID.

In step S170, the base station sends a registration response (REG-RSP) message in response to the registration request message. The registration response message includes a secondary management CID. The secondary management CID is the CID for the connection established during terminal registration and used to send standards-based messages such as Simple Network Management Protocol (SNMP) or Dynamic Host Configuration Protocol (DHCP).

After registration is made, IP connectivity is established, a time of day is established, and other operating parameters are transmitted. This sets up the connection.

Hereinafter, a cell reselection method based on self-organization operation according to an embodiment of the present invention will be described.

According to the cell reselection method based on the self-organizing operation proposed by the present invention, the terminal receives a load balancing parameter from a first base station connected to a serving base station, and the load is received when the connection between the terminal and the base station is lost. Reselect the cells using the equality parameters. The serving base station refers to a base station on which a terminal has recently completed registration. In this case, the terminal may search for the first base station preferentially, and if it is resynchronized with the first base station, it may prevent the unnecessary exchange of signals. When the load equalization parameter of each base station is set, the terminal may find another base station instead of the currently found base station.

6 is a block diagram illustrating a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

Referring to FIG. 6, in step S200, a first base station is connected to a terminal as a serving base station.

In step S210, the terminal receives a load equalization parameter from the serving base station. The load equalization parameter is a parameter or information used for balancing the number or traffic of terminals connected to each base station when there are a plurality of base stations. The load equalization parameter may include various information depending on the situation and is generally received from the serving base station. In addition, the load equalization parameter may be transmitted in various forms. It may be transmitted in the form of a value such as a processing speed, an amount such as a buffer size, a class, or a relative value with respect to a cell to which a terminal is connected. In addition, in the case of a base station supporting multiple carriers, a load equalization parameter may be transmitted for each base station.

In step S220, synchronization between the terminal and the serving base station is cut off.

In step S230, the terminal searches for a cell to connect to using the load equalization parameter. In this case, the first base station may be searched first.

In step S240, it is checked whether the cell search is successful.

In step S250, the terminal synchronizes with the discovered base station. If the found base station is the first base station, the terminal may immediately resume communication with the first base station without an initial access or the like. The terminal may additionally transmit location information when synchronization is lost to the first base station.

As the load balancing parameter, one including information on a load balancing timer may be used. That is, the terminal may receive the information on the load on the base station, and accordingly adjust the time for searching for the cell at the time of cell search and reselection, thereby achieving load balancing among a plurality of base stations.

FIG. 7 illustrates a case where a load equalization timer is used as a load equalization parameter in a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

Referring to FIG. 7A, a case in which the load equalization timer is resynchronized with the first base station before expiration is shown.

In step S300, the terminal and the first base station are in a synchronized state.

In step S310, the synchronization between the terminal and the first base station is cut off. The load equalization timer is started when synchronization is lost.

In step S320, the terminal searches for the first base station while the load equalization timer is operating.

In step S330, the terminal succeeds in the discovery of the first base station, and the load equalization timer is stopped. The terminal may resynchronize with the first base station and immediately resume communication with the first base station without an operation such as initial access. The terminal may additionally transmit location information when synchronization is lost to the first base station.

Referring to FIG. 7B, the load equalization timer has expired.

In step S350, the terminal and the first base station are in a synchronized state.

In step S360, the synchronization between the terminal and the first base station is cut off. The load equalization timer is started when synchronization is lost.

In step S370, the terminal searches for the first base station while the load equalization timer is operating. The terminal does not discover the first base station and the load equalization timer expires.

In step S380, the UE searches for a cell regardless of the first base station.

In step S390, the terminal performs synchronization with the discovered base station. The discovered base station may be the first base station or a new base station. If the found base station is the first base station, the terminal may immediately resume communication with the first base station without an operation such as initial access. The terminal may additionally transmit location information when synchronization is lost to the first base station.

8 illustrates an embodiment in which a load equalization timer is used as a load equalization parameter in a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

In step S400, the first base station is connected to the terminal as a serving base station.

In step S410, the terminal receives information about the load equalization timer as the load equalization parameter from the serving base station.

In step S420, it is checked whether synchronization has been lost. If the synchronization is not broken, the terminal and the serving base station continue to communicate, and periodically or aperiodically check the synchronization between the terminal and the serving base station.

In step S430, if the synchronization between the terminal and the serving base station is broken, the load equalization timer is started.

In step S440, the UE first searches for the first base station while the load equalization timer is operating.

When the discovery of the first base station is successful in step S450, the terminal resynchronizes with the first base station. The terminal may immediately resume communication with the first base station without an initial access or the like, and may additionally transmit location information when synchronization is lost to the first base station.

When the first base station is not found in step S460, the terminal searches for the base station irrespective of the first base station.

In step S470, the terminal performs synchronization with the discovered base station. The terminal may perform a procedure such as initial access with the discovered base station and may transmit identification information of the serving base station and / or location information when synchronization is lost to the searched base station.

9 illustrates another embodiment in which a load equalization timer is used as a load equalization parameter in a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

In step S500, the first base station is connected to the terminal as a serving base station.

In step S510, the terminal receives information on the load equalization timer as the load equalization parameter from the serving base station.

In step S520, it is checked whether synchronization is lost. If the synchronization is not broken, the terminal and the serving base station continue to communicate, and periodically or aperiodically check the synchronization between the terminal and the serving base station.

In step S530, if the synchronization between the terminal and the serving base station is broken, the load equalization timer is started.

In step S540, the UE first searches for the first base station while the load equalization timer is operating.

When the discovery of the first base station is successful in step S550, the terminal resynchronizes with the first base station. The terminal may immediately resume communication with the first base station without an initial access or the like, and may additionally transmit location information when synchronization is lost to the first base station.

When the terminal fails to discover the first base station in step S560, a new second timer is started.

In step S570, the terminal searches for the base station irrespective of the first base station while the second timer is operating.

In step S580, it is checked whether the base station found in step S570 is the first base station, and if the found base station is the first base station, step S550 is reached. If the found base station is a new base station, the process proceeds to step S595 which will be described later.

In step S590, when the base station is not found in step S570, the terminal searches for the base station irrespective of the first base station.

In step S595, the terminal performs synchronization with the base station found in step S590. The terminal may perform a procedure such as initial access with the discovered base station and may transmit identification information of the serving base station and / or location information when synchronization is lost to the searched base station.

One embodiment of the present invention described above may be applied differently depending on whether the downlink connection is disconnected or the uplink connection is disconnected. In general, when the downlink connection is lost, the operation of the embodiment of FIG. 8 or 9 may be used. When uplink synchronization is broken, the operation of the embodiment of FIG. 9 is used, and recovery may be used through the operation of the embodiment of FIG. 8.

Meanwhile, according to the cell reselection method based on another self-organization operation proposed by the present invention, the UE may perform different procedures according to the type of the base station connected before the synchronization is terminated. Specifically, the type of base station is divided into a macro base station (macro BS) and a femto base station (femto BS), and the base station of the same type as the base station connected before the synchronization is first searched. In this case, the operation of the embodiment of FIG. 8 and FIG. 9 may be applied. When the load equalization parameter of each base station is set, the terminal may find another base station instead of the currently found base station.

For example, when synchronization is lost in the macro base station, the cell may be reselected by selecting one of the following options.

First, the terminal may find the macro base station in the same carrier / the same frequency band (frequency) → other carrier / other frequency band in order. In this case, a threshold may be set for the number of times the macro base station is searched for, and when the number is exceeded, the femto base station may be found. Therefore, the femto base station can be found before both cases occur.

Secondly, the UE may select the carrier and the frequency of the base station in other combinations than the first case. In this case, an upper limit may be set for the number of times the macro base station is searched, and when the number is exceeded, the femto base station may be found.

Third, it is possible to find a base station having the strongest signal regardless of the macro base station and the femto base station.

If synchronization is lost at the femto base station, the cell may be reselected by selecting one of the following options.

First, the UE may find a femto base station in the order of the same carrier / same frequency band → other carrier / different frequency band.

Secondly, the UE may find the macro base station in the same carrier / same frequency band → other carrier / other frequency band. In this case, after accessing the macro base station, the femto base station may be transferred, and when the femto base station is passed, the handover may be carried out or another signaling process may be performed.

Third, it is possible to find a base station having the strongest signal regardless of the macro base station and the femto base station.

Meanwhile, in the 802.16m system, regardless of the target base station provided by the base station through a handover (HO) request or response message, the terminal selects a third base station as a target base station on its own based on conditions such as signal strength. Can be. The terminal is connected to the target base station in a state in which load information of the target base station is unknown, and handover may occur in a state in which load equalization is not performed between base stations. This handover is referred to as a UE-based handover (MS initiated HO).

Hereinafter, the serving base station refers to a base station to which the terminal has most recently registered, a target base station refers to a base station to which the terminal is registered as a result of handover, and a neighbor base station refers to a base station that is not a serving base station.

According to the handover method based on the self-organizing operation proposed by the present invention, the terminal may receive a load equalization parameter transmitted by the base station through the system information in preparation for the MS initiated HO, and use it for handover. The system information may be BCH or extended system information.

10 illustrates a handover method based on self-organization operation according to an embodiment of the present invention.

In step S600, the terminal is synchronized with the serving base station.

In step S610, the terminal receives the load equalization parameter from the serving base station and the adjacent base station. The neighbor base station may be one or more.

In step S620, the terminal determines the handover by using the load equalization parameter. The terminal searches for a target base station for handover and determines whether handover is possible to the target base station. In this case, the load equalization parameter may indicate whether the terminal can handover to the target base station absolutely or probabilistically. For example, handover to the target base station may be enabled only when the load equalization parameter is greater than or equal to a certain threshold. Alternatively, the probability of handover to the target base station may be determined according to the load equalization parameter.

In step S630, the terminal sends a handover request message (HO request message) for requesting a handover to the target base station. The handover request message may include information of the target base station, and in particular, may include an ID of a base station used in a higher layer.

In step S640, the terminal receives a handover confirm message (HO confirm message) from the serving base station.

In step S650, the UE hands over to the target base station.

The invention can be implemented in hardware, software or a combination thereof. (DSP), a programmable logic device (PLD), a field programmable gate array (FPGA), a processor, a controller, a microprocessor, and the like, which are designed to perform the above- , Other electronic units, or a combination thereof. In the software implementation, the module may be implemented as a module that performs the above-described function. The software may be stored in a memory unit and executed by a processor. The memory unit or processor may employ various means well known to those skilled in the art.

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

1 illustrates a wireless communication system combining a macro-cell and a femto-cell.

2 is a block diagram illustrating a wireless communication system using a femtocell.

3 illustrates a signaling operation for implementing a self-organazing network in an 802.16m system.

4 shows an example of a frame structure.

5 is a flowchart illustrating a network initialization process.

6 is a block diagram illustrating a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

FIG. 7 illustrates a case where a load equalization timer is used as a load equalization parameter in a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

8 illustrates an embodiment in which a load equalization timer is used as a load equalization parameter in a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

9 illustrates another embodiment in which a load equalization timer is used as a load equalization parameter in a cell reselection method based on a self-organizing operation according to an embodiment of the present invention.

10 illustrates a handover method based on self-organization operation according to an embodiment of the present invention.

Claims (9)

In a cell reselection method based on a self-organizing operation in a wireless communication system, Synchronizing with a first base station, connecting the first base station to a serving base station; And Receiving a load balancing parameter from the serving base station; And Breaking synchronization with the serving base station; And And first searching for the first base station by using the load equalization parameter after the synchronization is lost. The method of claim 1, The load balancing parameter includes a cell balancing information, characterized in that the information on the load balancing timer (load balancing timer). The method of claim 2, Starting the load equalization timer when the synchronization is lost; And first searching for the first base station while the load equalization timer is in operation. The method of claim 3, wherein And searching for another base station when the load equalization timer expires. The method of claim 4, wherein Preferentially synchronizing with the first base station when the first base station is re-discovered; And And after the synchronization is terminated, connecting the first base station to a serving base station. The method of claim 1, The base station includes a macro base station (macro BS) and a femto base station (femto BS), the load equalization parameter depends on the type of the base station, characterized in that the first base station of the same type as the first base station to search first A cell reselection method based on self-organization behavior. A handover method based on self-organization operation in a wireless communication system, Receiving a load equalization parameter from a serving base station and a neighbor base station; And Determining whether handover to a target base station is possible using the load equality parameter; And one of the serving base station and the neighbor base station is a femto base station. The method of claim 7, wherein Transmitting a handover request message including information of a target base station to be handed over to the serving base station; And And receiving a handover decision message from the serving base station. The method of claim 7, wherein A self-organizing operation based on the self-organizing operation that enables handover to a target base station when the load equalization parameter is above a certain threshold.

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