WO2012134181A2

WO2012134181A2 - Apparatus and method for transmitting interference control information between heterogeneous cells

Info

Publication number: WO2012134181A2
Application number: PCT/KR2012/002296
Authority: WO
Inventors: 권기범
Original assignee: 주식회사 팬택
Priority date: 2011-03-30
Filing date: 2012-03-29
Publication date: 2012-10-04
Also published as: KR20120110841A; WO2012134181A3

Abstract

The present invention relates to an apparatus and a method for transmitting interference control information between heterogeneous cells. The present invention discloses a base station comprising: a signal reception unit for receiving wireless network information including an additional ABS pattern, which indicates whether a subframe, in which a synchronization signal transmission from a base station is scheduled, based on time division multiplexing, is a subframe (ABS) in which the transmission power of the synchronization signal is reduced so as not to cause interference with a heterogeneous base station; a measurement unit for measuring the signal which is received by the heterogeneous base station; and a power adjustment unit for adjusting the transmission power of the synchronization signal based on the measured signal and the additional ABS pattern. According to the present invention, interference between synchronization cells, which is generated between the heterogeneous cells, is reduced, and error in searching and selecting a cell, which is accessible by a user equipment in a resting state not having a femtocell membership, can also be reduced.

Description

Apparatus and method for transmitting interference coordination information between different cells

The present invention relates to wireless communication, and more particularly, to an apparatus and method for transmitting inter-cell interference coordination information.

The 3rd Generation Partnership Project (3GPP) long term evolution (LTE), an improvement of the Universal Mobile Telecommunications System (UMTS), is introduced as a 3GPP release 8. 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) in uplink. A multiple input multiple output (MIMO) with up to four antennas is employed. Recently, a discussion on 3GPP LTE-Advanced (LTE-A), an evolution of 3GPP LTE, is underway.

As wireless communication technology develops, a heterogeneous network (hereinafter referred to as a heterogeneous network) environment is emerging.

The heterogeneous network environment includes a macro cell, a femto cell, a pico cell, and the like. The femto cell and pico cell are systems that cover an area smaller than the radius of the existing mobile communication service as compared to the macro cell.

In such a communication system, a user terminal present in any one of a macrocell, a femtocell, and a picocell may cause inter-cell interference in which signal interference is caused by a signal generated from another cell. In particular, when a terminal communicating with a macrocell enters an interference region of a femtocell, there is a problem in that a synchronization signal cannot be properly obtained from the macrocell.

The present invention provides an apparatus and method for transmitting interference coordination information between heterogeneous cells.

Another object of the present invention is to provide an apparatus and a method for adjusting power of interference between synchronization signals between different cells.

Another technical problem of the present invention is to provide an apparatus and method for adjusting interference of a synchronization signal between heterogeneous cells using a TDM-based intercell interference coordination scheme.

Another technical problem of the present invention is to provide an apparatus and method for providing an ABS pattern for adjusting interference of a synchronization signal.

According to an aspect of the present invention, there is provided a base station for coordinating intercell interference in a heterogeneous network system. The base station is a subframe in which the transmission power of the synchronization signal is reduced so that the subframe scheduled for transmission of the synchronization signal of the base station does not cause interference to a heterogeneous base station based on time division multiplexing (Almost Blank Subframe: ABS). A signal receiving unit for receiving wireless network information including an additional ABS pattern indicating whether or not, a measuring unit measuring a signal received from the heterogeneous base station, and the measured signal and the additional ABS pattern. And a power adjusting unit for adjusting the transmission power of the synchronization signal.

According to another aspect of the present invention, there is provided a method for coordinating intercell interference by a base station in a heterogeneous network system. The method further includes an additional ABS pattern indicating whether or not a subframe in which transmission of a synchronization signal of a base station is scheduled based on time division multiplexing is a subframe in which transmission power of the synchronization signal is reduced so as not to interfere with a heterogeneous base station. Receiving wireless network information comprising a; measuring a signal received from the heterogeneous base station; and based on the measured signal and the additional ABS pattern, adjusting the transmission power of the synchronization signal; .

According to another aspect of the present invention, there is provided an Operation and Management (OAM) for coordinating intercell interference in a heterogeneous network system. The maintenance apparatus configures a basic ABS pattern of the femto base station based on synchronization with the ABS pattern of the macro base station including the coverage of the femto base station or the macro base station and the neighboring femto base station, the synchronization signal of the femto base station The pattern configuration unit constituting the additional ABS pattern for the sub-frame is mapped, and a transmission unit for transmitting the cell interference adjustment information including the basic ABS pattern and the additional ABS pattern to the femto base station.

According to another aspect of the present invention, there is provided a method for coordinating interference between maintenance cells in a heterogeneous network system. The method may include configuring a basic ABS pattern of the femto base station based on synchronization with an ABS pattern of a macro base station including coverage of a femto base station or a macro base station neighboring to the femto base station, wherein the synchronization signal of the femto base station is Constructing additional ABS patterns for the mapped subframes, and transmitting cell interference coordination information including the basic ABS pattern and the additional ABS pattern to the femto base station.

Interference between synchronization signals occurring between heterogeneous cells can be reduced, and errors in cell search and cell selection accessible to a terminal in idle state without membership of a femto cell can be reduced.

1 shows a wireless communication system to which the present invention is applied.

2 is an exemplary diagram illustrating a cell selection process of a UE in an RRC idle state according to the present invention.

3 is a diagram schematically illustrating a concept of a heterogeneous network including a macro base station, a femto base station, and a pico base station according to the present invention.

4 is a diagram schematically illustrating that a terminal is affected by interference between a macro cell, a femto cell and a pico cell in downlink.

5 is a diagram illustrating a frame pattern for inter-cell interference coordination in a heterogeneous network system according to an embodiment of the present invention.

6 is a TDD radio frame structure according to the present invention.

7 is a flowchart illustrating a method of transmitting inter-cell interference coordination information according to the present invention.

8 is an explanatory diagram illustrating a method of constructing an ABS pattern according to an embodiment of the present invention.

9 is a flowchart illustrating a method for receiving inter-cell interference coordination information by a femto base station according to an embodiment of the present invention.

10 is a flowchart illustrating a method for transmitting, by a maintenance apparatus, inter-cell interference coordination information according to an embodiment of the present invention.

11 is a block diagram illustrating a femto base station and a maintenance apparatus according to an embodiment of the present invention.

Hereinafter, the present disclosure will be described in detail with reference to the accompanying drawings and examples, together with the contents of the present disclosure. In adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even though they are shown in different drawings. In addition, in describing the embodiments of the present specification, when it is determined that the detailed description of the related well-known configuration or function may obscure the subject matter of the present specification, the detailed description thereof will be omitted.

In addition, the present specification describes a wireless communication network, the operation performed in the wireless communication network is performed in the process of controlling the network and transmitting data in the system (for example, the base station) that is in charge of the wireless communication network, or the corresponding wireless Work may be done at the terminal coupled to the network.

1 shows a wireless communication system to which the present invention is applied. This may also be called an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN), or Long Term Evolution (LTE) / LTE-A system.

Referring to FIG. 1, the E-UTRAN includes a base station (BS) 20 that provides a control plane and a user plane to a user equipment (UE). The terminal 10 may be fixed or mobile and may be called by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device (Wireless Device), and the like. . The base station 20 refers to a station that communicates with the terminal 10, and includes an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, an access point, a home eNB, and a relay. ), Or a remote radio head (RRH).

The base stations 20 may be connected to each other through an X2 interface. The base station 20 is connected to the Serving Gateway (S-GW) through the Mobility Management Entity (MME) and the S1-U through the Evolved Packet Core (EPC) 30, more specifically, through the S1 interface. The S1 interface exchanges OAM (Operation and Management) information for supporting the movement of the terminal 10 by exchanging signals with the MME.

EPC 30 is composed of MME, S-GW and P-GW (Packet Data Network-Gateway). The MME has access information of the terminal 10 or information on the capability of the terminal 10, and this information is mainly used for mobility management of the terminal 10. S-GW is a gateway having an E-UTRAN as an endpoint, and P-GW is a gateway having a PDN as an endpoint.

Layers of the Radio Interface Protocol between the terminal 10 and the network are based on the lower three layers of the Open System Interconnection (OSI) reference model, which is widely known in communication systems. Layer), L2 (second layer), and L3 (third layer), among which the physical layer belonging to the first layer provides an information transfer service using a physical channel. The RRC (Radio Resource Control) layer located in the third layer plays a role of controlling radio resources between the terminal 10 and the network. To this end, the RRC layer exchanges an RRC message between the terminal 10 and the base station.

A physical layer (PHY) layer provides an information transfer service to a higher layer by using a physical channel. The physical layer is connected to a medium access control (MAC) layer belonging to a second layer through a transport channel. Data is moved between the MAC layer and the physical layer through the transport channel. Transport channels are classified according to how and with what characteristics data is transmitted over the air interface.

Data moves between physical layers between physical layers, that is, between physical layers of a transmitter and a receiver. The physical channel is modulated by an orthogonal frequency division multiplexing (OFDM) scheme and utilizes time and frequency as radio resources.

The functions of the MAC layer include mapping between logical channels and transport channels and multiplexing / demultiplexing into transport blocks provided as physical channels on transport channels of MAC service data units (SDUs) belonging to the logical channels. The MAC layer provides a service to a Radio Link Control (RLC) layer through a logical channel.

Functions of the RLC layer belonging to the second layer include concatenation, segmentation, and reassembly of the RLC SDUs. In order to guarantee the various Quality of Service (QoS) required by the radio bearer (RB), the RLC layer has a transparent mode (TM), an unacknowledged mode (UM), and an acknowledged mode (Acknowledged Mode). Three modes of operation (AM). AM RLC provides error correction through an automatic repeat request (ARQ).

Functions of the Packet Data Convergence Protocol (PDCP) layer in the user plane include delivery of user data, header compression, and ciphering. The functionality of the Packet Data Convergence Protocol (PDCP) layer in the user plane includes the transfer of control plane data and encryption / integrity protection.

A Radio Resource Control (RRC) layer belonging to the third layer is defined only in the control plane. The RRC layer is responsible for the control of logical channels, transport channels, and physical channels in connection with configuration, re-configuration, and release of radio bearers. RB means a logical path provided by the first layer (PHY layer) and the second layer (MAC layer, RLC layer, PDCP layer) for data transmission between the terminal 10 and the network. The establishment of the RB means a process of defining characteristics of a radio protocol layer and a channel to provide a specific service, and setting each specific parameter and operation method. RB can be further divided into SRB (Signaling RB) and DRB (Data RB). The SRB is used as a path for transmitting RRC messages in the control plane, and the DRB is used as a path for transmitting user data in the user plane.

If there is an RRC connection between the RRC layer of the terminal 10 and the RRC layer of the E-UTRAN, the terminal 10 is in an RRC CONNECTED state, otherwise the RRC idle (RRC IDLE) ) State.

The downlink transport channel for transmitting data from the network to the terminal 10 includes a BCH (Broadcast Channel) for transmitting system information and a downlink shared channel (SCH) for transmitting user traffic or control messages. Traffic or control messages of a downlink multicast or broadcast service may be transmitted through a downlink SCH or may be transmitted through a separate downlink multicast channel (MCH). Meanwhile, the uplink transport channel for transmitting data from the terminal 10 to the network includes a random access channel (RACH) for transmitting an initial control message and an uplink shared channel (SCH) for transmitting user traffic or control messages. have.

It is located above the transport channel, and the logical channel mapped to the transport channel is a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic (MTCH). Channel).

The physical channel is composed of several symbols in the time domain and several sub-carriers in the frequency domain. One sub-frame consists of a plurality of symbols in the time domain. One subframe consists of a plurality of resource blocks, and one resource block consists of a plurality of symbols and a plurality of subcarriers. In addition, each subframe may use specific subcarriers of specific symbols (eg, the first symbol) of the corresponding subframe for a physical control channel called a physical downlink control channel (PDCCH). The transmission time interval (TTI), which is a unit time for transmitting data, is 1 ms corresponding to one subframe.

Hereinafter, the RRC state and the RRC connection method of the UE will be described in detail.

The RRC state refers to whether or not the RRC layer of the UE is in a logical connection with the RRC layer of the E-UTRAN. If connected, the RRC connected state is connected. Idle state. Since the UE in the RRC connected state has an RRC connection, the E-UTRAN can grasp the existence of the corresponding UE in a cell unit, and thus can effectively control the UE. On the other hand, the terminal of the RRC idle state is not identified by the E-UTRAN and managed by the core network in units of a tracking area, which is a larger area unit than the cell. That is, the presence of the terminal in the RRC idle state is identified only in a large area unit, and must move to the RRC connected state in order to receive a normal mobile communication service such as voice or data.

When the user first turns on the terminal, the terminal attempts to make a connection with the Public Land Mobile Network (PLMN). The specific PLMN connected can be selected automatically or manually. Here, PLMN refers to a wireless communication system for use by a user in a vehicle or on the ground while walking. Alternatively, the PLMN may indicate all mobile wireless networks using land-based base stations other than satellites. Home PLMNs are Mobile Country Codes (MCCs) and MNCs (IMCs) contained within the International Mobile Subscriber Identity (IMSI), a unique 15-digit code used to identify individual users in a Global System for Mobile Communication (GSM) network. Mobile Network Code) is the same PLMN. An equivalent HPLMN list (EHPLMN) refers to a PLMN code list that replaces the HPLMN code extracted from IMSI to allow the provision of multiple HPLMN codes. The EHPLMN list is stored in a universal subscriber identity module (USIM). The EHPLMN list may include HPLMN codes extracted from IMSI. If the HPLMN code extracted from IMSI is not included in the EHPLMN list, the HPLMN should be treated as Visited PLMN when selecting a PLMN. Visited PLMNs are PLMNs different from HPLMNs and EHPLMNs, if any. A Registered PLMN (RPLMN) is a PLMN from which certain LR results occur. In general, in a shared network, an RPLMN is a PLMN defined by the PLMN identification of a core network operator that allows LR.

The UE searches for the appropriate cell of the selected PLMN and stays in the RRC idle state in the cell. The UE in the RRC idle state selects a cell capable of providing possible services and adjusts to the control channel of the selected cell. This process is called "camp on a cell." When camping is completed, the terminal may register its presence in the registration area of the selected cell. This is called location registration (LR). The terminal regularly registers its presence in the registration area or when entering a new tracking area (TA). The registration area refers to any area where the terminal may roam without a location registration procedure.

If the UE leaves the service area of the cell or finds a more suitable cell, the UE reselects the most suitable cell in the PLMN and camps on. If a new cell is included in another registration area, a location registration request is performed. If the terminal leaves the service area of the PLMN, a new PLMN may be automatically selected or a new PLMN may be manually selected by the user.

The purpose of proceeding camp on the terminal of the RRC idle state is as follows.

1) UE receives system information from PLMN

2) The terminal initially accesses the network through the control channel of the camped cell after initiating a call.

3) Receiving a paging message: When the PLMN receives a call for the terminal, the PLMN knows the registration area of the cell where the terminal is camped on. Therefore, the PLMN may send a paging message for the terminal through the control channel of all cells in the registration area. The terminal may receive a paging message since it is already adjusted for the control channel of the camped cell.

4) receive the cell's broadcasting message

If the terminal cannot find a suitable cell to camp on, or if a subscriber identity module (SIM) card is not inserted or if a specific response to a location registration request is received (for example, an "illegal terminal"), the terminal is connected to the PLMN. Regardless, try to camp on and enter the "limited service" state. The limited service state is an emergency call only state.

When the UE in the RRC idle state needs to establish an RRC connection, it establishes an RRC connection with the E-UTRAN through an RRC connection procedure and transitions to the RRC connected state. There are several cases in which the UE in RRC idle state needs to establish an RRC connection. For example, an upstream data transmission is necessary due to a user's call attempt, or a paging message is sent from E-UTRAN. If received, a response message may be sent.

Referring to FIG. 2, the terminal selects a PLMN and a radio access technology (RAT) to be serviced (S210). The user of the terminal may select the PLMN and the RAT, or may use the one stored in the USIM.

The terminal selects a cell having the largest value among the measured base station and a cell whose signal strength or quality is greater than a specific value (S220). The terminal receives system information periodically transmitted by the base station. A specific value is a value defined in the system to ensure the quality of a physical signal in data transmission / reception. Therefore, the value may vary depending on the RAT applied.

The terminal determines whether network registration is necessary (S230), and if necessary, registers its information (eg, IMSI) in order to receive a service (eg, paging) from the network (S240). The terminal does not register with the network to which it connects every time the cell is selected. For example, if the system information of the network to be registered (for example, Tracking Area Identity (TAI)) is different from the information of the network known to the user, the network is registered in the network.

If the value of the strength or quality of the signal measured from the base station being served is lower than the value measured from the base station of the adjacent cell, the terminal selects another cell that provides better signal characteristics than the cell of the base station to which the terminal is connected ( S250). This process is referred to as cell reselection, distinguished from initial cell selection in step S220. In this case, a time constraint may be set in order to prevent the cell from being frequently reselected according to the change of the signal characteristic.

Next, a procedure of selecting a cell by the terminal will be described in detail.

When the power is turned on or staying in the cell, the terminal selects / reselects a cell of appropriate quality and performs procedures for receiving service.

The UE in the RRC dormant state should always select a cell of appropriate quality and prepare to receive service through this cell. For example, a terminal that has just been powered on must select a cell of appropriate quality to register with the network. When the UE in the RRC connected state enters the RRC idle state, the terminal should select a cell to stay in the RRC idle state. As such, the process of selecting a cell satisfying a certain condition in order for the terminal to stay in a service standby state such as an RRC idle state is called cell selection. Importantly, since cell selection is performed in a state in which the UE does not currently determine a cell to stay in the RRC idle state, it is most important to select the cell as soon as possible. Therefore, if the cell provides a radio signal quality of a predetermined criterion or more, even if this cell is not the cell providing the best radio signal quality to the terminal, it may be selected during the cell selection process of the terminal.

There are two main cell selection processes.

First, as an initial cell selection process, the terminal does not have any prior information on the radio channel. Therefore, the terminal searches all radio channels to find an appropriate cell. In each channel, the terminal finds the strongest cell. Thereafter, the terminal selects a corresponding cell if it finds a suitable cell that satisfies the cell selection criteria.

The other is a cell selection process using stored information. In this process, cell selection is performed by using information stored in a terminal for a wireless channel or by using information broadcast in a cell. Therefore, the cell selection may be faster than the initial cell selection process. The UE selects a corresponding cell if it finds a cell that satisfies a cell selection criterion. If a suitable cell that satisfies the cell selection criteria is not found through this process, the UE performs an initial cell selection process.

The cell selection criterion used by the terminal in the cell selection process is shown in Equation 1 below.

Equation 1

Here, Srxlev = Q _rxlevmeas- (Q _rxlevmin + Q _{rxlevminoffset} ) + Pcompensation. Q _rxlevmeas is the reception level of the measured cell (RSRP), Q _rxlevmin is the minimum required reception level (dBm) in the cell, Q _{rxlevminoffset} is the offset for Q _rxlevmin , Pcompensation = max (P _EMAX -P _UMAX , 0 (dB), P _EMAX is the maximum transmit power (dBm) that the terminal can transmit in the cell, P _UMAX is the maximum transmit power (dBm) of the terminal radio transmitter (RF) according to the performance of the terminal.

In Equation 1, the UE can know that the cell selected to the strength and quality of the measured signal is greater than a specific value. The specific value is defined in the cell providing the service. In addition, parameters used in Equation 1 are broadcast through system information, and the terminal receives these parameter values and uses them in cell selection criteria.

When the terminal selects a cell that satisfies the cell selection criteria, the terminal receives information necessary for the RRC idle state operation of the terminal in the cell from the system information of the cell. After the UE receives all the information necessary for the RRC idle state operation, the UE waits in the idle mode to request a service (eg, an originating call) or to receive a service (eg, a terminating call) from the network.

After the terminal selects a cell through a cell selection process, the strength or quality of a signal between the terminal and the base station may change due to a change in mobility or a wireless environment of the terminal. Therefore, if the quality of the selected cell is degraded, the terminal may select another cell that provides better quality. When reselecting a cell in this way, a cell that generally provides better signal quality than the currently selected cell is selected. This process is called cell reselection. The cell reselection process is aimed at selecting a cell that provides the best quality to a terminal in view of the quality of a radio signal.

In addition to the quality of the wireless signal, the network may determine the priority for each frequency and notify the terminal. Upon receiving this priority, the UE considers this priority prior to the radio signal quality criteria in the cell reselection process.

Hereinafter, a heterogeneous network will be described.

Simple cell division of macro and micro cells is difficult to meet the growing demand for data services. Therefore, data services for indoor and outdoor small areas can be operated using pico cells, femto cells, and wireless relays. Although the use of small cells is not particularly limited, pico cells can generally be used in communication shadow areas that are not covered by macro cells alone, or in areas with high data service requirements, so-called hot zones. A femto eNB is generally used in an indoor office or home. In addition, the wireless relay can supplement the coverage of the macro cell. By configuring a heterogeneous network, not only the shadow area of the data service can be eliminated, but also the data transmission speed can be increased.

3 is a diagram schematically illustrating a concept of a heterogeneous network including a macro base station, a femto base station, and a pico base station according to the present invention. Although FIG. 3 illustrates a heterogeneous network composed of a macro base station, a femto base station, and a pico base station for convenience of description, the heterogeneous network may include a relay or another type of base station.

Referring to FIG. 3, a macro base station 310, a femto base station 320, and a pico base station 330 are operated together in a heterogeneous network. The macro base station 310, the femto base station 320, and the pico base station 330 provide the cell coverage of the macro cell, the femto cell, and the pico cell, respectively, to the terminal.

The femto base station 320 is a low power wireless access point, for example, a micro mobile base station used indoors, such as at home or office. The femto base station 320 may access a mobile communication core network using a DSL or cable broadband of a home or office. The femto base station 320 may support a self-organization function. Self-organization functions are classified into a self-configuration function, a self-optimization function, and a self-monitoring function.

Self-configuration is a feature that allows a wireless base station to be installed on its own based on an initial installation profile without going through a cell planning step. Self-configuration functions shall satisfy the following requirements. First, the femto base station 320 must be able to establish a secure link (Mobile Operation and Management Network (MON)) according to the network operator's security policy. Second, the femto base station 320 management system (HMS) and the femto base station 320 should be able to initiate the software download and activation of the femto base station 320. Third, the femto base station 320 management system should be able to initiate the provision of transport resources to the femto base station 320 in order to establish a signaling link with the PLMN. Fourth, the femto base station 320 management system should provide the femto base station 320 with wireless network specific information that allows the femto base station 320 is automatically set to an operational state.

Self-Optimization is a function that identifies neighboring base stations, obtains information, optimizes the neighboring base station list, and optimizes coverage and communication capacity according to subscriber and traffic changes. Self-Monitoring is a function to control service performance not to be degraded through collected information.

The femtocell may distinguish registered users from unregistered users and allow access only to registered users. Cells that allow access only to registered users are called Closed Subscriber Groups (hereinafter referred to as "CSGs"), and those that allow access to general users are also called Open Subscriber Groups ("OSGs"). It is called. It is also possible to mix these two methods.

The femto base station 320 is called a Home NodeB (HNB) or Home eNodeB (HeNB) in 3GPP. The femto base station 320 aims to provide specialized services only to members belonging to the CSG. In terms of providing a service, when the femto base station 320 provides a service only to the CSG group, the cell provided by the femto base station 320 is referred to as a CSG cell.

Each CSG has its own unique identifier, which is called a CSG identity (CSG identity). The UE may have a list of CSGs belonging to its members, which is also called a white list. You can check which CSG your CSG cell supports by reading the CSG ID included in the system information. The terminal reading the CSG ID is regarded as a cell that can access the cell only when the UE is a member of the CSG cell, that is, when the CSG corresponding to the CSG ID is included in its CSG whitelist.

The femto base station 320 does not always need to allow access to the CSG terminal. In addition, depending on the configuration setting of the femto base station 320, it is possible to allow the connection of the terminal other than the CSG member. Which terminal is allowed to access is changed according to the configuration setting of the femto base station 320, where the configuration setting means the setting of the operation mode of the femto base station 320. The operation mode of the femto base station 320 is divided into three types according to which UE provides a service.

1) Closed access mode: A mode in which a service is provided only to a specific CSG member. The femto base station 320 provides a CSG cell.

2) Open access mode: A mode in which a service is provided without restriction of a specific CSG member like a general BS. The femto base station 320 provides a general cell that is not a CSG cell.

3) Hybrid access mode: A mode in which a CSG service can be provided to a specific CSG member and a service is provided to a non-CSG member like a normal cell. CSG member UEs are recognized as CSG cells, and non-CSG member UEs are recognized as normal cells. Such a cell is called a hybrid cell.

When the femto cell is in an open access mode in a heterogeneous network in which the femto cell is operated together with the macro cell, the user can access a desired cell among the macro cell and the femto cell to use the data service.

If the femto cell is in, for example, a closed mode, the end user using the macro cell will not be able to use the femto cell even if the macro cell is interfering with the femto cell transmitting a strong signal.

Macro base stations are connected to each other via an X2 interface. The X2 interface maintains the operation of seamless and lossless handover between base stations and supports management of radio resources. Therefore, the X2 interface plays a large role in inter-cell interference coordination (ICIC) between macro base stations.

In contrast, there is no interface such as X2 between the macro base station and the femto base station 320. Therefore, dynamic signaling is not performed between the macro base station 310 and the femto base station 320.

Referring to FIG. 4, the terminal 450 may access a femto base station 430 and use a femto cell. However, if the femto base station 430 is in the CSG mode, and the terminal 460 near the femto base station 430 is not a registered user terminal of the CSG, the terminal 460 cannot access the femto cell with strong signal strength. There is no choice but to access the macro base station 410 which has a relatively weak signal strength compared to the signal strength of the femto cell. Therefore, in this case, the terminal 460 may receive the interference signal from the femto cell.

In addition, the terminal 440 may access the pico base station 420 and use the pico cell. However, at this time, the terminal 440 may receive interference by the signal of the macro base station 410.

As such, inter-cell interference is a macro cell or a pico cell that is more affected by the interference or has to be protected from the interference. On the other hand, an aggressor cell that affects or is less affected by the Victim cell by the interference is a femto cell.

Inter-Cell Interfernce Coordination (ICIC) is a method of reducing inter-cell interference. In general, inter-cell interference coordination is a method for supporting reliable communication to a user when a user belonging to a big team cell is near an aggregator cell. In order to coordinate inter-cell interference, for example, a scheduler may be imposed on the use of certain time and / or frequency resources. It may also impose a constraint on the scheduler how much power to use for a particular time and / or frequency resource.

5 is a diagram illustrating a frame pattern for inter-cell interference coordination in a heterogeneous network system according to an embodiment of the present invention. In FIG. 5, for convenience of description, a frame pattern for inter-cell interference coordination between a macrocell of a macro base station and a femtocell of a femto base station is illustrated, but this is only an example, and the frame pattern of FIG. The same may be applied to the pico base station, the macro base station and the micro base station, the femto base station and the pico base station.

Referring to FIG. 5, a frame pattern is configured such that interference does not occur between different types of cells (macro cell and femto cell). For example, in the third subframe of the macro cell, the macro cell hardly transmits a signal, so the transmission power is very low. Therefore, in this case, since there is almost no signal transmitted in the subframe, such a subframe is called ABS (almost blank subframe: ABS). ABS is used by the femto cell and used to rule out interference with the macro cell. Here, ABS is defined as a subframe that reduces or does not transmit power such as control information, data information, and signaling (signals transmitted for channel measurement and synchronization) transmitted through the subframe. Of course, it is necessary to transmit control information, data information, signaling, and system information necessary for the terminal for backwards compatibility. In addition, a pattern to which ABS is applied is called an ABS pattern, and the ABS pattern may be configured, for example, in units of 40 ms. Alternatively, ABS is formed in a specific pattern in a radio frame for coordination of interference, which is also called a frame pattern. Using the frame pattern, the interference is adjusted by variably configuring the ABS in any periodic section composed of a plurality of subframes.

ABS is a time division multiplexing (TDM) based inter-cell interference coordination scheme in which heterogeneous cells share time resources such as subframes. The interference can be adjusted by variably configuring the frame pattern structure itself within any periodic interval composed of multiple subframes.

The synchronization signal will be described below. A primary synchronization signal (hereinafter referred to as PSS) and a secondary synchronization signal (hereinafter referred to as SSS) are used for the UE to perform a cell search. The synchronization signal is generated based on a physical cell ID (PCI) for identifying a base station or a cell. When the terminal checks the PCI from the PSS and the SSS, it can distinguish from which cell the signal is received.

The synchronization signal may be transmitted every subframe (for example, five subframes) of a certain period in each frame, or may be transmitted in a variable period. The synchronization signal is physically mapped to at least one multiplexing symbol, for example an OFDM symbol. However, the synchronization signal may be mapped not only to initial synchronization and cell information but also to additional OFDM symbols for synchronization and cell information during handover. The synchronization signal may be called a preamble. The PSS may be used for the terminal to obtain synchronization of an OFDM symbol or slot. The SSS may be used by the UE to acquire synchronization of a subframe or a frame.

The above-described interference between the heterogeneous cells is equally applied to the synchronization signal. For example, suppose that a UE that does not belong to the CSG belongs to the femto cell coverage. If the UE is camped on the macro cell, the UE does not receive the PSS and SSS of the macro cell due to interference from the PSS or SSS of the femto cell. As a result, the cell search of the terminal cannot be performed smoothly. Hereinafter, interference between heterogeneous cells generated by the synchronization signal is referred to as interference between synchronization signals. In the case of a frequency division duplex (FDD) system, each base station may operate in an asynchronous manner to adjust interference between synchronization signals. For example, by setting different subframe offsets for each base station, interference between synchronization signals can be avoided.

On the other hand, in a time division duplex (TDD) system, subframe synchronization is performed between all base stations in order to avoid interference between downlink and uplink, and thus, each base station cannot operate in an asynchronous manner to adjust interference between synchronization signals.

6 is a TDD radio frame structure according to the present invention.

Referring to FIG. 6, a radio frame includes two half-frames. Each half frame has the same structure. The half frame includes five subframes and three fields Downlink Pilot Time Slot (DwPTS), Guard Period, and Uplink Pilot Time Slot (UpPTS). DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. The guard period is a period for removing interference generated in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

Table 1 shows an example of configuration information of a radio frame. The configuration information of a radio frame is information indicating which rule is allocated (or reserved) for uplink and downlink to all subframes in one radio frame.

Table 1

Configuration

Switch-point periodicity

Subframe number

0

One

2

3

4

5

6

7

8

9

0

5 ms

D

S

U

D

S

U

One

5 ms

D

S

U

D

S

U

D

2

5 ms

D

S

U

D

S

U

D

3

10 ms

D

S

U

D

4

10 ms

D

S

U

D

5

10 ms

D

S

U

D

6

5 ms

D

S

U

D

S

U

D

Referring to Table 1, 'D' indicates that the subframe is used for downlink transmission, and 'U' indicates that the subframe is used for uplink transmission. 'S' indicates that the subframe is used for a special purpose, and is used for frame synchronization or downlink transmission. Hereinafter, a subframe used for downlink transmission is simply called a downlink subframe, and a subframe used for uplink transmission is simply called an uplink subframe. Each configuration has a different position and number of downlink subframes and uplink subframes in one radio frame.

The point of time from the downlink to the uplink or the time from the uplink to the downlink is called a switching point. The switch-point periodicity means a period in which an uplink subframe and a downlink subframe are repeatedly switched in the same manner, and are 5 ms or 10 ms. For example, in setting 0, D-> S-> U-> U-> U is switched from 0th to 4th subframe, and D-> S is the same as before from 5th to 9th subframe. Switch to-> U-> U-> U. Since one subframe is 1ms, the periodicity at the switching time is 5ms. That is, the periodicity of the switching time is less than one radio frame length (10ms), and the switching mode in the radio frame is repeated once.

In all configurations, the 0th, 5th subframe, and DwPTS are used for downlink transmission. The first subframe of all settings and the sixth subframe of

settings

0, 1, 2, and 6 consist of DwPTS, guard period, and UpPTS. The length of time for each field depends on the setting. The remaining eight subframes, except for the first and sixth subframes, consist of two slots.

If the period of switching time is every 5ms, UpPTS and the 2nd and 7th subframes are reserved for uplink transmission. On the other hand, when the switching period is every 10 ms, UpPTS and the second subframe are reserved for uplink transmission, and DwPTS, the seventh and ninth subframe are reserved for downlink transmission.

The SSS may be mapped to the last OFDM symbol of the first slot belonging to the 0th subframe or the last OFDM symbol of the 11th slot belonging to the fifth subframe. The SSS is mapped to an antenna port such as PSS. On the other hand, the PSS is transmitted in the first and sixth subframe, it may be mapped to the third OFDM symbol of the OFDM symbols constituting each subframe. In particular, the PSS transmitted in the 'S' subframe is mapped to the DwPTS.

In order to adjust the interference between synchronization signals in the TDD system, it is necessary to limit the ABS pattern. In other words, heterogeneous cells such as a macro cell, a micro cell, a pico cell, a femto cell, etc. based on a TDD system coexist, and in a wireless communication system using a TDM scheme for coordination of inter-cell interference, a transmission power of a synchronization signal of a femto cell is adjusted. Method is required. For example, the method may configure a subframe carrying a synchronization signal of the femto cell with ABS, change an ABS pattern, or apply a restriction. The configuration of the ABS pattern may be performed by an operation and management (OAM) device that is responsible for the maintenance, maintenance, management of femto cells.

7 is a flowchart illustrating a method of transmitting inter-cell interference coordination information according to the present invention. In FIG. 7, it is assumed that a subject for coordinating inter-cell interference is a femto base station and a maintenance apparatus. However, in the technical concept of FIG. Of course, the same applies to the management device.

Referring to FIG. 7, a UE is camped on a macro cell provided by a macro eNB. The macro cell transmits a synchronization signal to the terminal so that the camped-on terminal acquires synchronization (S700). The UE camped on the macro cell receives a general cell signal and a synchronization signal from the macro cell. The UE, the macro base station, and the femto eNB may all operate based on a TDD-based frame structure, for example, the frame structure of FIG. 6. The terminal may be in an RRC idle state. When the femto base station is powered on (S702), the femto base station transmits the security link setting information for establishing a secure link with the OAM (S705). The security link is set up based on the information stored in the memory when the product of the femto base station is shipped. In addition, the femto base station transmits a synchronization signal to the terminal in a subframe of a predetermined position (S707). At this time, the synchronization signal of the femto base station may interfere with the synchronization signal of the macro base station. As a result, the terminal receives the synchronization signal of the macro base station interfered with the synchronization signal of the femto base station.

The maintenance apparatus configures an elementary ABS pattern of the femto base station based on whether the femto base station is synchronized with the ABS pattern of the macro base station including the coverage of the femto base station or the macro base station neighboring to the femto base station, An additional ABS pattern, which is an ABS pattern for subframes to which a sync signal is mapped, is configured (S710).

The additional ABS pattern indicates whether or not the subframe in which the transmission of the synchronization signal of the base station is scheduled based on time division multiplexing is an ABS in which the transmission power of the synchronization signal is reduced so as not to interfere with the heterogeneous eNB. For example, if the subframe transmitting the PSS and SSS of the femto cell is the same as the subframe transmitting the PSS and SSS of the macro cell, since the interference between synchronization signals occurs in the PSS and SSS of the macro cell, the maintenance apparatus is added. ABS pattern can be configured. The maintenance unit may optionally configure additional ABS patterns, such as setting additional ABS patterns only when necessary. The additional ABS pattern may be configured periodically or randomly. This may be determined according to the correlation between the cell search period of the terminal in the wireless communication system and the additional ABS pattern.

The maintenance apparatus may configure one integrated ABS pattern considering interference between synchronization signals without distinguishing the basic ABS pattern from the additional ABS pattern.

The basic ABS pattern and the additional ABS pattern may be referred to as a first pattern and a second pattern, respectively. In this case, the first pattern is configured to have a controlled transmit power in a subframe determined in consideration of the femto base station and a macro base station, and the second pattern is configured to have a controlled transmit power in a subframe determined in consideration of the femto base station. Further, the first pattern may be an ABS pattern configured to include controlled coverage of the femto base station or to have a controlled transmission power in consideration of the macro base station neighboring the femto base station. In addition, the second pattern may be an ABS pattern configured to have a controlled transmission power in a subframe in which a synchronization signal of the femto base station is to be transmitted.

Referring to FIG. 8, the basic ABS pattern and the additional ABS pattern are combined to form one combined ABS pattern. The basic ABS pattern is repeated in units of 40 ms, and indicates whether the ABS for the entire subframe of the femto cell as a bitmap. For example, if the bit is 0, the corresponding subframe is non-ABS. If the bit is 1, the corresponding subframe is ABS. The default ABS pattern is 011001... 01, so that the subframes to which each bit is mapped are sequentially non-ABS, ABS, ABS, non-ABS, non-ABS, ABS. non-ABS, ABS.

Meanwhile, the additional ABS pattern collects only subframes scheduled to transmit a synchronization signal of the femto base station among all subframes of the femto cell and indicates whether the ABS or non-ABS is a continuous bitmap. The nth (n≥0) bits from the left significant bit (LSB) correspond to the subframe in which the nth sync signal is transmitted. For example, the subframe in which the 0th synchronization signal is transmitted is actually the 0th subframe, and the subframe in which the 1st synchronization signal is transmitted is actually the 5th subframe.

The additional ABS pattern is 1100111100... As shown in FIG. 8. If configured as 111, the bits corresponding to the subframes through which the 0th and 1st sync signals are transmitted are all represented by 1, so the corresponding subframes are ABS. Subframes in which the second and third synchronization signals are transmitted are non-ABS. The additional ABS pattern may be repeated in 1280 ms units, for example.

The additional ABS pattern takes precedence over the basic ABS pattern. That is, even if a specific subframe is set to ABS in the basic ABS pattern, if the specific subframe is non-ABS in the additional ABS pattern, the specific subframe is set to non-ABS in the integrated ABS pattern. On the contrary, even if a specific subframe is set to non-ABS in the basic ABS pattern, if the specific subframe is ABS in the additional ABS pattern, the specific subframe is set to ABS in the integrated ABS pattern. This is called a priority rule.

8, the basic ABS pattern 011001... 01 is repeated, in addition to the repeated basic ABS pattern ABS pattern 1100111100... If 111 is combined, then 1xx--1... --00 --- 1... An integrated ABS pattern of 3200 ms length, such as -11 --- is formed. Here, 'x' is a subframe set to ABS in the basic ABS pattern and is a subframe irrelevant to the additional ABS pattern. Here, the subframe irrelevant to the additional ABS pattern means a subframe in which the synchronization signal is not transmitted. '-' Is a subframe set to non-ABS in the basic ABS pattern and is a subframe independent of the additional ABS pattern. '1' is a subframe set to ABS by the additional ABS pattern. '0' is a subframe set to non-ABS by the additional ABS pattern.

Referring back to FIG. 7, the maintenance apparatus transmits wireless network information necessary for the femto base station to the femto base station (S715). The radio network information includes at least one of inter-cell interference coordination information and radio configuration information. Inter-cell interference coordination information (ICIC information) includes a basic ABS pattern and an additional ABS pattern of the femto cell, or includes an integrated ABS pattern. If the inter-cell interference coordination information includes a basic ABS pattern and an additional ABS pattern, the femto base station may configure an integrated ABS pattern as shown in FIG. 8 based on the basic ABS pattern and the additional ABS pattern.

The radio configuration information includes radio parameters of an existing radio environment for a macro base station including coverage of a femto base station, or a macro base station neighboring to a femto base station.

The macro base station transmits the macro cell signal to the terminal (S720). The macro cell signal is transmitted to the terminal, but the femto base station may also receive the macro cell signal.

Therefore, the femto base station measures the macro cell signal received from the macro base station (S725). The macro cell signal may be a synchronization signal of the macro base station. The femto base station measures the strength of the synchronization signal transmitted from the macro base station, that is, the PSS and the SSS based on the radio configuration information. The measure of the strength of the synchronization signal may be a reference signal received power (RSRP) and a reference signal received quality (RSSRQ). The definitions of RSRP and RSRQ are as follows. RSRP is obtained as a linear average of the power contribution of the resource elements. Here, the resource elements carry cell specific reference signals within the considered measurement frequency bandwidth. The reference point of the RSRP is an antenna connector of the terminal. Meanwhile, RSRQ is defined as a ratio between RSRP and Received Signal Strength Indicator (RSSI) as shown in Equation (2).

Equation 2

Here, N is the number of resource elements of the carrier RSSI measurement bandwidth of the radio access network. In Equation 2, the measurements of the numerator and the denominator are performed on the same set of resource blocks. RSSI includes a linear average of the total received power. The total received power is observed only within an OFDM symbol containing reference symbols within the measurement bandwidth and is a value obtained over N resource blocks. The reference symbols may be OFDM symbols in which a cell-specific reference signal (CRS) exists. Alternatively, the reference symbols may be all OFDM symbols in a subframe.

The femto base station adjusts the transmission power of the synchronization signal based on the measured strength of the synchronization signal and the additional ABS pattern (S730). For example, the femto base station reduces the transmission power size of the synchronization signal to be transmitted in the subframe set to ABS by an additional ABS pattern to a certain size, or changes the transmission power size of the synchronization signal to be transmitted in the subframe set to non-ABS. Operation may be performed.

Here, the femto base station can determine whether to adjust the transmission power of the PSS or SSS based on the subframe information of neighboring macro base stations. For example, when it is not necessary to set synchronization in subframe units of neighboring macro base stations, the femto base station does not adjust the transmission power of the PSS or SSS signal.

The femto base station maps the femtocell synchronization signal of which the transmission power is adjusted to a predetermined subframe (that is, additional ABS) and transmits the same to the terminal. At this time, the synchronization signal of the femto base station whose transmission power is adjusted may be transmitted to the terminal without causing interference to the synchronization signal of the macro cell (S735). On the other hand, the terminal receives the synchronization signal of the macro cell transmitted by the macro base station, which is not disturbed by the femtocell synchronization signal through the ABS defined by the additional ABS pattern (S737).

In other words, the terminal may receive the synchronization signal transmitted from the femto base station and the synchronization signal transmitted from the macro base station in any particular subframe. In this case, the synchronization signal transmitted from the femto base station is a synchronization signal to which the basic ABS pattern, which is the first pattern of the present invention, and the additional ABS pattern, which is the second pattern, are applied. It is a signal. Here, the transmission power is set so that the power of the synchronization signal is close to zero according to the ABS technique. In addition, it is actually set to 0, that is, may not receive a synchronization signal from the femto base station (S735).

Therefore, the terminal can properly receive the synchronization signal of the macro base station as the interference coordination receives the synchronization signal from the actual femto base station. That is, the synchronization signal of the femto base station whose transmission power is adjusted does not interfere with the synchronization signal of the macro cell. Accordingly, the terminal can properly receive the synchronization signal transmitted from the macro base station (S737).

Here, although the femto base station is shown to transmit a synchronization signal of the transmission power is adjusted to the terminal, this is only an example, it may be transmitted to other terminals belonging to the CSG of the femto base station.

The terminal receives the synchronization signal of the macro cell in the intact state without interference, and acquires synchronization with the macro base station (S740).

As such, when heterogeneous cells of various types such as macro cells, micro cells, pico cells, femto cells, etc. coexist and use a TDM scheme such as an ABS pattern to control interference between heterogeneous cells, a femto based on the TDM scheme By controlling the transmission power of the PSS and the SSS of the cell, errors in cell search and cell selection accessible to idle mode terminals, especially terminals without membership of the femto cell, can be reduced.

Although FIG. 7 has been described as an inter-cell interference coordination method in a TDD frame structure, this is only an example, and the inter-cell interference coordination method in FIG. 7 may be equally applied to the FDD frame structure.

Referring to FIG. 9, the femto base station transmits security link configuration information for establishing a security link with the maintenance apparatus OAM to the maintenance apparatus OAM (S900). The security link is set up based on the information stored in the memory when the product of the femto base station is shipped. The femto base station receives wireless network information from the maintenance apparatus (S905). The radio network information includes at least one of inter-cell interference coordination information and radio configuration information. Inter-cell interference coordination information includes the basic ABS pattern and the additional ABS pattern of the femto cell, or includes an integrated ABS pattern. If the inter-cell interference coordination information includes a basic ABS pattern and an additional ABS pattern, the femto base station may configure an integrated ABS pattern as shown in FIG. 8 based on the basic ABS pattern and the additional ABS pattern. The radio configuration information includes radio parameters of an existing radio environment for a macro base station including coverage of a femto base station, or a macro base station neighboring to a femto base station.

The femto base station measures the macro cell signal received from the macro base station (S910). The macro cell signal may be a synchronization signal of the macro base station. The femto base station measures the strength of the synchronization signal transmitted from the macro base station, that is, the PSS and the SSS based on the radio configuration information. The measure of the strength of the synchronization signal may be RSRP or RSRQ.

The femto base station adjusts the magnitude of the transmission power of the synchronization signal based on the measured strength of the synchronization signal and the additional ABS pattern (S915). For example, the femto base station reduces the transmission power size of the synchronization signal to be transmitted in the subframe set to ABS by an additional ABS pattern to a certain size, or changes the transmission power size of the synchronization signal to be transmitted in the subframe set to non-ABS. Operation may be performed. Here, the femto base station can determine whether to adjust the transmission power of the PSS or SSS based on the subframe information of neighboring macro base stations. For example, when it is not necessary to set synchronization in subframe units of neighboring macro base stations, the femto base station does not adjust the transmission power of the PSS or SSS signal.

The femto base station maps and transmits the synchronization signal whose transmission power is adjusted to a predetermined subframe (S920). Here, although the femto base station is shown to transmit a synchronization signal of the transmission power is adjusted to the terminal, this is only an example, it may be transmitted to other terminals belonging to the CSG of the femto base station.

Referring to FIG. 10, the maintenance apparatus receives security link configuration information from the femto base station requesting the establishment of a secure link (S1000). The maintenance apparatus configures the basic ABS pattern of the femto base station based on whether the femto base station is synchronized with the ABS pattern of the macro base station including the coverage of the femto base station or the macro base station neighboring the femto base station, and the synchronization signal of the femto cell is An additional ABS pattern that is an ABS pattern for subframes to be mapped is configured (S1005). For example, if the subframe transmitting the PSS and SSS of the femto cell is the same as the subframe transmitting the PSS and SSS of the macro cell, since the interference between synchronization signals occurs in the PSS and SSS of the macro cell, the maintenance apparatus is added. ABS pattern can be configured. The maintenance unit may optionally configure additional ABS patterns, such as setting additional ABS patterns only when necessary.

The maintenance apparatus may construct additional ABS patterns periodically or randomly. This may be determined according to the correlation between the cell search period of the terminal in the wireless communication system and the additional ABS pattern. The maintenance apparatus may configure one integrated ABS pattern considering interference between synchronization signals without distinguishing the basic ABS pattern from the additional ABS pattern.

The maintenance apparatus transmits wireless network information required for the femto base station to the femto base station (S1010). The radio network information includes at least one of inter-cell interference coordination information and radio configuration information. Inter-cell interference coordination information includes the basic ABS pattern and the additional ABS pattern of the femto cell, or includes an integrated ABS pattern. If the inter-cell interference coordination information includes a basic ABS pattern and an additional ABS pattern, the femto base station may configure an integrated ABS pattern as shown in FIG. 8 based on the basic ABS pattern and the additional ABS pattern. The radio configuration information includes radio parameters of an existing radio environment for a macro base station including coverage of a femto base station, or a macro base station neighboring to a femto base station.

Referring to FIG. 11, the femto base station 1100 includes a security link setting unit 1105, a signal receiving unit 1110, a measuring unit 1115, a power adjusting unit 1120, and a signal transmitting unit 1125.

The security link setting unit 1105 generates security link setting information for the femto base station 1100 to establish a security link with the maintenance apparatus 1150, and transmits it to the signal transmission unit 1125. The security link is set up based on the information stored in the memory when the product of the femto base station is shipped.

The signal receiver 1110 receives wireless network information from the maintenance apparatus 1150 and sends the wireless network information to the power adjuster 1120, and receives the macro cell signal from the macro base station 1170 and sends it to the measurement unit 1115.

The radio network information includes at least one of inter-cell interference coordination information and radio configuration information. Inter-cell interference coordination information includes the basic ABS pattern and the additional ABS pattern of the femto cell, or includes an integrated ABS pattern. The radio configuration information includes radio parameters of an existing radio environment for a macro base station including coverage of a femto base station, or a macro base station neighboring to a femto base station. The basic ABS pattern and the additional ABS pattern may be referred to as a first pattern and a second pattern, respectively. At this time, the first pattern is configured to have a controlled transmission power in a subframe determined in consideration of the femto base station 1100 and the macro base station 1170, and the second pattern is controlled in a subframe determined in consideration of the femto base station 1100. It is configured to have a transmitted power. In addition, the first pattern may include an coverage of the femto base station 1100 or an ABS pattern configured to have a controlled transmission power in consideration of the macro base station 1170 neighboring the femto base station 1100. In addition, the second pattern may be an ABS pattern configured to have a controlled transmission power in a subframe in which a synchronization signal of the femto base station 1100 is to be transmitted.

The measuring unit 1115 measures the strength of the macro cell signal. The measure of the macro cell signal measured by the measurer 1115 may be RSRP or RSRQ. The macro cell signal may be a synchronization signal of the macro base station.

The power adjuster 1120 configures the ABS pattern of the femto base station 1100. As an example, the power adjusting unit 1120 includes the coverage of the femto base station 1100 or in consideration of the macro base station 1170 adjacent to the femto base station 1100, the ABS is configured so that the first pattern has a controlled transmission power (almost blank subframe) pattern is confirmed, and the second pattern is the ABS pattern configured to have a controlled transmission power in the subframe to which the synchronization signal of the femto base station 1100 is transmitted.

As another example, when the inter-cell interference coordination information includes a basic ABS pattern and an additional ABS pattern, the power adjusting unit 1120 configures an integrated ABS pattern as shown in FIG. 8 based on the basic ABS pattern and the additional ABS pattern, and is measured. The transmission power of the synchronization signal is adjusted based on the strength of the synchronization signal and the configured integrated ABS pattern or the additional ABS pattern.

As another example, the power adjusting unit 1120 is configured with at least one subframe in which the second pattern is scheduled to transmit a synchronization signal of the femto base station 1100, and successively whether each subframe is ABS or non-ABS. Check that the instruction is in bitmap form.

If the inter-cell interference coordination information includes the integrated ABS pattern, the power adjusting unit 1120 adjusts the transmission power of the synchronization signal based on the measured strength of the synchronization signal and the received integrated ABS pattern or the additional ABS pattern.

For example, the power adjusting unit 1120 reduces the transmission power of the synchronization signal to be transmitted in the subframe set to ABS by a further ABS pattern to a certain size, or transmit power of the synchronization signal to be transmitted in the subframe set to non-ABS. Actions such as not changing the size can be taken. Here, the power adjuster 1120 may determine whether to adjust the transmission power of the PSS or the SSS based on the subframe information of neighboring macro base stations. For example, when it is not necessary to set synchronization in units of subframes of neighboring macro base stations, the power adjuster 1120 does not adjust the transmission power of the PSS or SSS signal.

The signal transmitter 1125 transmits the security link setting information to the maintenance apparatus 1150, and transmits a synchronization signal whose transmission power is adjusted to a terminal (not shown) in a subframe set to ABS.

The maintenance apparatus 1150 may include a security information receiver 1155, a pattern constructer 1160, and a transmitter 1165.

The security information receiver 1155 receives the security link configuration information from the femto base station 1100.

The pattern configuring unit 1160 is based on whether the macro base station 1170 including coverage of the femto base station 1100 or the femto base station 1100 is synchronized with the ABS pattern of the macro base station neighboring to the femto base station 1100. An ABS pattern is configured, and an additional ABS pattern which is an ABS pattern for subframes to which a synchronization signal of a femtocell is mapped is configured.

More specifically, the pattern configuring unit 1160 has a controlled transmission power in consideration of the macro base station 1170 including the coverage of the femto base station 1100 or the first pattern includes the femto base station 1100. Configure ABS pattern. In addition, the pattern configuring unit 1160 configures the ABS pattern so that the second pattern has a controlled transmission power in a subframe in which the synchronization signal of the femto base station 1100 is to be transmitted. The pattern configuration unit 1100 may be configured such that the second pattern has priority over the first pattern.

On the other hand, the pattern configuration unit 1160 consists of at least one subframe in which the second pattern is scheduled to transmit the synchronization signal of the femto base station 1100, a continuous bitmap whether each subframe is ABS or non-ABS It can be configured to indicate in the form.

For example, when the subframe transmitting the PSS and SSS of the femto cell is the same as the subframe transmitting the PSS and SSS of the macro cell, interference between synchronization signals occurs in the PSS and SSS of the macro cell. ) May constitute an additional ABS pattern. The pattern configuration unit 1160 may selectively configure additional ABS patterns, such as setting additional ABS patterns only when necessary. The pattern configuring unit 1160 may periodically configure the additional ABS pattern or randomly. The pattern configuring unit 1160 may configure one integrated ABS pattern considering interference between synchronization signals without distinguishing the basic ABS pattern from the additional ABS pattern.

The transmitter 1165 transmits wireless network information including intercell interference coordination information including a basic ABS pattern, an additional ABS pattern, or an integrated ABS pattern to the femto base station 1100.

The terminal 1180 includes a receiver 1185, a transmitter 1190, and a synchronization performer 1119.

The receiver 1185 receives a cell signal and a synchronization signal from various base stations of the heterogeneous network system. In particular, the receiver 1185 may receive the synchronization signal of the macro base station 1170 by giving priority to the second pattern over the first pattern. In addition, the receiver 1185 controls the first pattern configured to have a controlled transmission power in a predetermined subframe in consideration of the femto base station 1100 and the macro base station 1170, and controls in a predetermined subframe in consideration of the femto base station 1100. The synchronization signal of the macro base station 1170 may be received based on the second pattern configured to have a predetermined transmission power.

The terminal 1180 may be located in the cell coverage of the femto base station 1100 in a state of camping on a macro cell of the macro base station 1170 and may be in a state of receiving an interference signal from the femto base station 1100. In particular, when the femto base station 1100 transmits the synchronization signal to the CSG terminal, the receiver 1185 receives both the synchronization signal of the macro cell and the synchronization signal of the femto cell.

The synchronization performing unit 1119 performs a synchronization acquisition procedure using a synchronization signal transmitted from a cell camped on by the terminal 1180, and acquires synchronization. If the receiving unit 1185 receives the synchronization signal of the macro cell interfered by the synchronization signal of the femto cell, the synchronization performing unit 1119 cannot successfully acquire synchronization for the macro cell.

On the other hand, if the femto base station 1100 lowers the transmission power of the synchronization signal to a certain size in a subframe defined by the additional ABS pattern, the receiver 1185 is an intact macro not interfered by the synchronization signal of the femtocell in the corresponding subframe. Receive the synchronization signal of the cell. In this case, the synchronization performing unit 1119 may successfully acquire synchronization for the macro cell using the synchronization signal of the macro cell in which interference is removed or reduced, at least in the ABS defined by the additional ABS pattern.

The transmitter 1190 transmits an uplink signal to the macro base station 1170 based on the synchronization obtained using the synchronization signal of the macro cell in which the interference is eliminated or reduced.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

The above-described embodiments include examples of various aspects. While not all possible combinations may be described to represent the various aspects, one of ordinary skill in the art will recognize that other combinations are possible. Accordingly, the invention is intended to embrace all other replacements, modifications and variations that fall within the scope of the following claims.

Claims

In a femto base station for coordinating inter-cell interference in a heterogeneous network system,

Receiving a first pattern configured to have a controlled transmission power in a subframe determined in consideration of the femto base station and a macro base station, and a second pattern configured to have a controlled transmission power in a subframe determined in consideration of the femto base station, Receiving unit;

A measuring unit measuring the strength of a synchronization signal transmitted from the macro base station; And

It includes a power adjustment unit for adjusting the transmission power of the synchronization signal of the femto base station by applying the first pattern and the second pattern based on the measured strength of the synchronization signal,

Each of the first pattern and the second pattern has a controlled transmission power for at least one or more subframes among a plurality of subframes periodically.

And at least one subframe is configured to be variably configured.
The method of claim 1, wherein the power adjustment unit

The first pattern is an ABS (almost blank subframe) pattern configured to have a controlled transmission power in consideration of the macro base station adjacent to the femto base station or the coverage of the femto base station,

Confirming that the second pattern is an ABS pattern configured to have a controlled transmission power in a subframe in which the synchronization signal of the femto base station is to be transmitted,

Here, the femto base station, characterized in that the second pattern has a priority over the first pattern.
The method of claim 1, wherein the power adjustment unit

Confirming that the second pattern includes at least one subframe in which transmission of a synchronization signal of the femto base station is scheduled, and indicates whether each subframe is ABS or non-ABS in a continuous bitmap form. Said, femto base station.
The method of claim 1,

And the power adjusting unit configures an integrated ABS pattern reflecting ABS of each of the first pattern and the second pattern, and adjusts transmission power of a synchronization signal of the femto base station by applying the configured integrated ABS pattern. A femto base station.
The method of claim 1,

The receiving unit further comprises receiving an integrated ABS pattern reflecting the ABS of each of the first pattern and the second pattern from the maintenance device, femto base station.
In a method for coordinating intercell interference in a heterogeneous network system,

A first pattern configured to have a controlled transmit power in a subframe determined in consideration of the femto base station and a macro base station by the femto base station, and a first transmit pattern configured to have a controlled transmit power in a subframe determined in consideration of the femto base station Receiving two patterns from the maintenance apparatus;

Receiving, by the femto base station, a synchronization signal from the macro base station;

Measuring the strength of the received synchronization signal; And

Adjusting, by the femto base station, the transmission power of the synchronization signal of the femto base station by applying the first pattern and the second pattern based on the measured strength of the synchronization signal;

Here, each of the first pattern and the second pattern, periodically, has a controlled transmit power for at least one subframe selected from among a plurality of subframes,

And the at least one subframe is variably configured.
The method of claim 6,

The first pattern is an ABS (almost blank subframe) pattern configured to have a controlled transmission power in consideration of the macro base station neighboring to the femto base station or the coverage of the femto base station,

The second pattern is characterized in that the ABS pattern configured to have a controlled transmission power in a subframe in which the synchronization signal of the femto base station is to be transmitted,

Wherein the second pattern has a higher priority than the first pattern.
The method of claim 6,

The second pattern is composed of at least one or more subframes scheduled to transmit the synchronization signal of the femto base station, characterized in that each subframe indicates whether the ABS or non-ABS in the form of a continuous bitmap, inter-cell How to adjust for interference.
The method of claim 6,

Configuring, by the femto base station, an integrated ABS pattern reflecting the ABS of each of the first pattern and the second pattern;

And adjusting the transmission power of the synchronization signal of the femto base station by applying the configured integrated ABS pattern.
The method of claim 6,

Receiving, by the femto base station, an integrated ABS pattern reflecting the ABS of each of the first pattern and the second pattern from the maintenance apparatus; Further comprising, inter-cell interference adjustment method.
In an operation and management (OAM) for coordinating inter-cell interference in a heterogeneous network system,

A pattern constituting a first pattern configured to have controlled transmission power in a subframe determined in consideration of the femto base station and a macro base station, and a pattern constituting a second pattern configured to have controlled transmission power in a subframe determined in consideration of the femto base station Component; And

Including a transmitter for transmitting the information about the first pattern and the information about the second pattern to the femto base station,

Each of the first pattern and the second pattern has a controlled transmission power for at least one or more subframes among a plurality of subframes periodically.

And the at least one subframe is variably configured.
The method of claim 11, wherein the pattern configuration portion

The first pattern includes an coverage of the femto base station or in consideration of the macro base station adjacent to the femto base station, configures an ABS (almost blank subframe) pattern to have a controlled transmission power,

The second pattern is characterized by configuring an ABS pattern to have a controlled transmission power in a subframe in which the synchronization signal of the femto base station is to be transmitted,

Here, the maintenance apparatus, characterized in that configured to have a priority over the first pattern.
The method of claim 11, wherein the pattern configuration portion

The second pattern is composed of at least one or more subframes scheduled to transmit the synchronization signal of the femto base station, and configured to indicate whether each subframe is ABS or non-ABS in a continuous bitmap form. , Maintenance device.
The method of claim 11,

The pattern configuration unit constitutes an integrated ABS pattern reflecting the ABS of each of the first pattern and the second pattern,

The transmitter is characterized in that for transmitting the information on the integrated ABS pattern to the femto base station, maintenance apparatus.
In a method for coordinating intercell interference by a maintenance apparatus in a heterogeneous network system,

Configuring a first pattern configured to have controlled transmission power in a predetermined subframe in consideration of a femto base station and a macro base station, and a second pattern configured to have controlled transmission power in a predetermined subframe in consideration of the femto base station ; And

And transmitting information about the first pattern and information about the second pattern to the femto base station,

Each of the first pattern and the second pattern has a controlled transmission power for at least one or more subframes among a plurality of subframes periodically.

And wherein said at least one subframe is variably configured.
The method of claim 15,

The first pattern is an ABS (almost blank subframe) pattern configured to have a controlled transmission power in consideration of the macro base station neighboring to the femto base station or the coverage of the femto base station,

The second pattern is characterized in that the ABS pattern configured to have a controlled transmission power in a subframe in which the synchronization signal of the femto base station is to be transmitted,

Wherein the second pattern has a higher priority than the first pattern.
The method of claim 15,

The second pattern is composed of at least one or more subframes scheduled to transmit the synchronization signal of the femto base station, characterized in that each subframe indicates whether the ABS or non-ABS in the form of a continuous bitmap, inter-cell How to adjust for interference.
The method of claim 15,

Constructing an integrated ABS pattern reflecting ABS of each of the first pattern and the second pattern; And

And transmitting the information about the integrated ABS pattern to the femto base station.
A terminal for receiving a synchronization signal in a heterogeneous network system,

A first pattern configured to receive a synchronization signal transmitted from a femto base station or a signal transmitted from a macro base station, the first pattern configured to have a controlled transmission power in a predetermined subframe in consideration of the femto base station and the macro base station, and the femto base station A receiver for receiving a synchronization signal of the macro base station based on a second pattern configured to have a controlled transmission power in a predetermined subframe;

A synchronization acquisition unit for obtaining synchronization of the macro base station based on the received synchronization signal; And

Including a transmitter for transmitting an uplink signal to the macro base station based on the obtained synchronization,

Each of the first pattern and the second pattern has a controlled transmit power for at least one or more subframes among a plurality of subframes periodically.

The predetermined at least one subframe is characterized in that it is configured variably.
According to claim 19, The receiving unit;

The synchronization signal of the macro base station is received by giving priority to the second pattern to the first pattern.

The first pattern is an ABS (almost blank subframe) pattern configured to have a controlled transmission power in consideration of the macro base station neighboring to the femto base station or the coverage of the femto base station,

The second pattern is characterized in that the ABS pattern configured to have a controlled transmit power in a subframe in which the synchronization signal of the femto base station is to be transmitted.
20. The apparatus of claim 19, wherein the receiver;

Synchronization of the macro base station on the basis of the second pattern indicated in the form of a continuous bitmap whether at least one subframe scheduled transmission of the synchronization signal of the femto base station, each subframe is ABS or non-ABS Receiving a signal, characterized in that the terminal.
A method for receiving a synchronization signal by a terminal in a heterogeneous network system,

Receiving a signal transmitted by the femto base station or a signal transmitted by the macro base station, in consideration of the femto base station and the macro base station, the first pattern configured to have a controlled transmission power in a predetermined subframe, and in consideration of the femto base station Receiving a synchronization signal of the macro base station based on a second pattern configured to have a controlled transmission power in a predetermined subframe;

Acquiring synchronization of the macro base station based on the received synchronization signal; And

Transmitting an uplink signal to the macro base station based on the obtained synchronization;

Each of the first pattern and the second pattern periodically has a controlled transmit power for at least one subframe selected from among a plurality of subframes.

And at least one subframe is variably configured.
The method of claim 22, wherein the receiving of the synchronization signal comprises:

Receiving a synchronization signal of the macro base station by giving priority to the second pattern over the first pattern,

The first pattern is an ABS (almost blank subframe) pattern configured to have a controlled transmission power in consideration of the macro base station neighboring to the femto base station or the coverage of the femto base station,

The second pattern is a method of receiving a synchronization signal, characterized in that the ABS pattern configured to have a controlled transmission power in a subframe in which the synchronization signal of the femto base station is to be transmitted.
The method of claim 22, wherein the receiving of the synchronization signal comprises:

Comprising at least one or more subframes scheduled to transmit the synchronization signal of the femto base station, in consideration of the second pattern indicated in the form of a continuous bitmap whether each subframe is ABS or non-ABS, And receiving a synchronization signal.