KR20110007052A - Method of transmitting data for reducing interference in hierarchical cell structure - Google Patents

Abstract

PURPOSE: A data communications method for reducing the interference in a hierarchical cell structure of enhancing the transmission efficiency of data is provided to reduce the interference of the femto base station by changing the carrier wave of the terminal. CONSTITUTION: If there is interference from a femto base station, a macro MS(Mobile Station) performs a channel scan(S125). The terminal transmits the channel measurement report(S140). A macro BS varies a PC(Primary Carrier) of A terminal into mark into label(S150). The base station transfers the carrier wave change to label to label to the terminal(S155). The terminal alleviates the interference of the femto base station to label to the base station and label through the changed carrier wave(S160).

Description

Data transmission method to reduce interference in hierarchical cell structure {METHOD OF TRANSMITTING DATA FOR REDUCING INTERFERENCE IN HIERARCHICAL CELL STRUCTURE}

The present invention relates to wireless communication, and more particularly, to a data transmission method for reducing interference in a hierarchical cell structure.

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

The IEEE 802.16 Task Group, which defines the next generation of air interface standards, and the WiMAX Forum, a non-profit organization that provides services and network specifications for IEEE 802.16-based broadband wireless access systems, increases system efficiency and indoors. In order to improve the quality of service (QoS) in the environment, standards standardization for a wireless access system supporting femtocells is underway. The WiMAX Forum defines femto base stations as low-power, low-cost base stations that connect to IP networks through fixed wireless links or local broadband wired links. The femto base station is connected to an IP network spread in homes and offices, and provides a mobile communication service by accessing a core network of a mobile communication system through an IP network. That is, the femto base station may be connected to the core network of the mobile communication system through a digital subscriber line (DSL). The user of the mobile communication system may be provided with a service through an existing macro-cell outdoors, and may be provided with a femtocell indoors. Femtocell improves indoor coverage of mobile communication system by supplementing the deterioration of existing macrocell service in the building, and can provide service only to specific users. Can provide services. In addition, femtocells can provide new services that are not provided by macrocells, and the deployment of femtocells can accelerate fixed-mobile convergence (FMC) and reduce industrial infrastructure costs.

The femto base station may be installed by a home or a user of a small office home office (SOHO). The femto base station may be plug & play to provide a service such as a macro base station including an idle mode. Tens to hundreds of femto base stations can be installed in the cell area of the macro base station, and the femto base station can replace the existing repeater and improve the service of the shadow area and reduce the load of the macro base station. However, the femto base station may be installed so that the macro base station or another femto base station and the cell area overlap each other, thereby causing interference between femtocells or interference between femtocells and macrocells. In particular, when the femto base station and the macro base station use the same frequency or adjacent frequencies, not only the service user of the femto base station but also the service user of the macro base station around the femto base station may be severely interrupted. For femto base station interference mitigation, a femto base station transmission control and cell-level Fractional Frequency Reuse (FFR) method has been proposed, but an interference mitigation method for individual users at a cell boundary has not been proposed.

Therefore, there is a need for an interference mitigation method for an individual user at a cell boundary of a femto base station.

An object of the present invention is to provide an individual user-based interference mitigation method that can reduce interference to a cell boundary user of a femto base station.

According to an aspect of the present invention, a data transmission method for reducing interference in a hierarchical cell structure including a macro base station providing a multi-carrier and a femto base station providing a single carrier includes channel state information and Performing a channel scan in a carrier where interference occurs to obtain neighbor femto base station information, transmitting a channel measurement report including the channel state information and the neighbor femto base station information to the macro base station, and the macro Receiving carrier change information from a base station and transmitting data through the changed carrier;

According to another aspect of the present invention, a data transmission method for reducing interference in a hierarchical cell structure including a macro base station providing a multi-carrier and a femto base station providing a single carrier includes a channel state of a carrier where interference from the femto base station occurs. Receiving a channel measurement report including information and neighboring femto base station information from the terminal, and transmitting data through the changed carrier by changing a carrier of the terminal based on the channel measurement report.

In a hierarchical cell structure including a macro cell and a femtocell, interference from adjacent femtocells can be reduced and data transmission / reception efficiency can be improved.

1 is a block diagram illustrating a wireless communication system.
2 shows an example of a frame structure.
3 illustrates an example of movement of a macro terminal operating in a multi-carrier mode in a hierarchical cell structure including a macro base station providing a multicarrier and a femto base station providing a single carrier.
4 illustrates a data transmission and reception procedure for reducing interference in the scenario of FIG. 3.
5 illustrates an example of movement of a macro terminal operating in a single carrier mode in a hierarchical cell structure including a macro base station providing a multicarrier and a femto base station providing a single carrier.
6 illustrates a data transmission and reception procedure for reducing interference in the scenario of FIG. 5.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification. In addition, even if the detailed description is omitted, descriptions of parts easily understood by those skilled in the art are omitted.

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

1 shows an example of a WiMAX system structure supporting a femtocell.

Referring to FIG. 1, a general wireless communication system includes a user equipment (UE) and a base station (BS). Wireless communication systems are widely deployed to provide various communication services such as voice and packet data.

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

The base station may be divided into a femto base station (femto BS) and a macro base station (macro BS) according to the cell coverage (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. As such, a structure in which a small range of cells are overlapped and disposed in a wide range of cells is called a hierarchical cell structure. The femto base station may be referred to by other terms such as a femto-cell, a home node-B, a closed subscriber group (CSG), and a WiMAX Femto Access Point (WFAP). The macro base station may be referred to as a macro-cell differently from a femtocell.

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

The femto base station enables broadband connection through digital subscriber line (DSL), cable, optical fiber, wireless, etc. to the Internet provided by an internet service provider (ISP). Do. The femto base station may be connected to a femtocell management system and an access service network (ASN) of a mobile communication system through the Internet. The femtocell management system may perform the registration, authentication and security procedures of the femto base station so that the femto base station can access the CSN (Connectivity Service Network) of the mobile communication system.

A femto base station for an Open Subscriber Group (OSG) behaves like a macro base station when calling a terminal. A femto base station for a closed subscriber group (CSG) may broadcast a paging message only to a terminal belonging to the CSG. For the definition of OSG and CSG for the support of the femto base station can refer to the 'IED 802.16 Task Group m System Description Document (SDD)'.

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.

2 shows an example of a frame structure. The hierarchical cell structure may be a frame structure of at least one of a macrocell and a femtocell.

Referring to FIG. 2, a superframe includes a superframe header (SFH) and four frames (frames, F0, F1, F2, and F3). The size of each superframe is 20ms and the size of each frame is illustrated as 5ms, but is not limited thereto. The superframe header may be disposed at the earliest in the superframe, and a common control channel is assigned to the superframe header. The common control channel is a channel used for transmitting control information that can be commonly used by all terminals in a cell, such as information on frames or system information of a superframe. A synchronization channel for transmitting a synchronization signal may be arranged in the superframe header or adjacent to the superframe header. The synchronization signal may indicate cell information such as a cell ID.

One frame includes a plurality of subframes (Subframe, SF0, SF1, SF2, SF3, SF4, SF5, SF6, SF7). Each subframe may be used for uplink or downlink transmission. The subframe may consist of 6 or 7 OFDM symbols, but this is only an example. A time division duplexing (TDD) scheme or a frequency division duplexing (FDD) scheme may be applied to the frame. In the TDD scheme, each subframe is used for uplink transmission or downlink transmission at different times at the same frequency. That is, the subframes in the frame of the TDD scheme are classified into an uplink subframe and a downlink subframe in the time domain. In the FDD scheme, each subframe is used for uplink transmission or downlink transmission at different frequencies at the same time. That is, subframes in the frame of the FDD scheme are divided into an uplink subframe and a downlink subframe in the frequency domain. Uplink transmission and downlink transmission occupy different frequency bands and may be simultaneously performed. Each subframe may include a subframe header. The subframe header may include radio resource allocation information of the subframe.

The subframe includes at least one frequency partition. The frequency partition is composed of at least one Physical Resource Unit (PRU). The frequency partitions may include Localized PRUs and / or Distributed PRUs. Frequency partitioning may be used for other purposes such as Fractional Frequency Reuse (FFR) or Multicast and Broadcast Services (MBS).

A PRU is defined as a basic physical unit for resource allocation that includes a plurality of consecutive OFDM symbols and a plurality of consecutive subcarriers. The number of OFDM symbols included in the PRU may be equal to the number of OFDM symbols included in one subframe. For example, when one subframe consists of 6 OFDM symbols, the PRU may be defined with 18 subcarriers and 6 OFDM symbols. Logical Resource Units (LRUs) are basic logical units for distributed resource allocation and localized resource allocation. The LRU is defined by a plurality of OFDM symbols and a plurality of subcarriers and includes pilots used in a PRU. Thus, the appropriate number of subcarriers in one LRU depends on the number of pilots assigned.

Logical Distributed Resource Units (DRUs) may be used to obtain frequency diversity gain. The DRU includes subcarrier groups distributed in one frequency partition. The size of the DRU is equal to the size of the PRU. The smallest unit that forms a DRU is one subcarrier.

Logical Contiguous Resource Units (CRUs) may be used to obtain frequency selective scheduling gains. The CRU includes a local subcarrier group. The size of the CRU is equal to the size of the PRU.

Now, a carrier management method of a user for interference mitigation for a cell operation scenario according to an operation mode of a user of a macro base station providing a multi-carrier in a wireless communication system supporting a femto base station will be described. A method for mitigating interference in a first scenario for a macro terminal operating in a multi-carrier mode and a second scenario for a macro terminal operating in a single carrier mode for a macro base station providing a multi-carrier will be described.

<First scenario>

3 illustrates an example of movement of a macro terminal operating in a multi-carrier mode in a hierarchical cell structure including a macro base station providing a multicarrier and a femto base station providing a single carrier. 4 illustrates a data transmission and reception procedure for reducing interference in the scenario of FIG. 3.

3 and 4, it is assumed that the macro base station operates four carriers (RF1, RF2, RF3, RF4). The macro terminal transmits and receives data with the macro base station using RF1 as a primary carrier (PC) (S110), and transmits and receives data with the macro base station using RF3 as a second carrier (secondary carrier, SC) ( S115). That is, the macro terminal operates in a multi-carrier mode for transmitting and receiving data to and from a macro base station using a plurality of carriers. In this case, it is assumed that the femto base station located in the cell area of the macro base station provides a service using RF1. That is, some of the carriers of the plurality of carriers used by the macro base station are jointly used with the femto base station. Part of the frequency band used by the macro base station is jointly used with the femto base station may be referred to as a partial co-channel method. The macro terminal may transmit / receive data to / from the macro base station without interfering with the femto base station at the position 1 that is not adjacent to the cell area of the femto base station.

The macro terminal may move to position 2 adjacent to the cell area of the femto base station (S120). If the macro terminal does not enter within the range a to perform handover to the femto base station but enters the range b to receive interference from the femto base station, the macro terminal does not perform the handover to the femto base station without performing the handover to the femto base station. Serious interference may occur. In addition, when the femto base station is a CSG femto base station allowing access to only a specific specific terminal and the macro terminal does not belong to the CSG group, when the macro terminal enters the cell area of the femto base station, severe interference may be caused by the femto base station.

The macro terminal is interfered with data transmission and reception using the first carrier RF1 by the carrier RF1 used by the femto base station (S125). At this time, the femto base station may also be interfered by the first carrier RF1 used by the macro terminal.

When the interference from the femto base station occurs, the macro terminal performs a channel scan (S130). The macro terminal may perform a channel scan within the carrier RF1 where interference occurs. The channel scan refers to a process of measuring a channel state and acquiring system information by receiving a pilot, broadcast message, etc. transmitted through a corresponding channel. The macro terminal may measure the channel state of the carrier RF1 and obtain neighbor femto base station information.

The macro terminal transmits a channel measurement report including channel state information and neighbor femto base station information for the carrier RF1 (S140). The neighbor femto base station information may include an ID of the femto base station or a preamble index of the femto base station. The neighbor femto base station information may be referred to for selecting a carrier allocated to the macro terminal by the macro base station. The channel measurement report may be transmitted through the first carrier RF1 or the second carrier RF3. Since the channel measurement report is for the first carrier RF1, the channel measurement report may be transmitted using the first carrier RF1. Alternatively, since the first carrier RF1 is a channel which is interfered by the femto base station, a channel measurement report for the first carrier RF1 may be transmitted using the second carrier RF3.

The macro base station may change the first carrier of the macro terminal in which interference occurs based on the channel measurement report transmitted from the macro terminal (S150). If the femto base station is a base station for the CSG and the terminal does not belong to the CSG group, or if the terminal does not want to handover to the femto base station, the macro base station may change the first carrier to mitigate interference of the macro terminal. The macro base station may receive the femto base station information detected by the terminal to obtain femto base station information located near the macro terminal, and the macro terminal to be changed by referring to the frequency, resource allocation, power information, etc. of the carrier used by the neighbor femto base station. The frequency band of the first carrier can be determined. The macro base station may change the first carrier of the macro terminal to RF2 or RF4. Here, it is assumed that RF4, which is not an adjacent frequency of RF1, that is, less interference, is selected as the first carrier of the macro terminal.

The macro base station may notify the macro terminal of the change of the carrier (S155). The carrier change notification may include carrier change information indicating whether the carrier to be changed is a first carrier or a second carrier and indicating to which frequency the carrier is changed, and information on a carrier change time. The carrier change notification may be transmitted through the second carrier RF3 or through the first carrier RF1 before the change. The macro terminal may receive a carrier change notification and obtain information about a frequency and a change time of the changed first carrier.

The macro base station and the macro terminal may transmit and receive data by mitigating interference of the femto base station using the changed first carrier RF4 (S160). In addition, the macro base station and the macro terminal may transmit and receive data using the second carrier RF3 (S165).

In the above, the first carrier of the macro terminal is the same as the carrier of the femto base station to change the frequency of the first carrier as an example. If the second carrier of the macro terminal is the same as the carrier of the femto base station to change the frequency of the second carrier may be performed according to the same procedure as the change of the first carrier. In addition, when the first carrier and the second carrier of the macro terminal are interfered by the adjacent femto base station, both the first carrier and the second carrier may be changed according to the decision of the macro base station.

<Second scenario>

5 illustrates an example of movement of a macro terminal operating in a single carrier mode in a hierarchical cell structure including a macro base station providing a multicarrier and a femto base station providing a single carrier. 6 illustrates a data transmission and reception procedure for reducing interference in the scenario of FIG. 5.

Referring to FIGS. 5 and 6, assume that the macro base station operates four carriers RF1, RF2, RF3, and RF4, and the macro terminal transmits and receives data to and from the macro base station using the carrier RF1 (S210). That is, the macro terminal operates in a single carrier mode for transmitting and receiving data to and from the macro base station using one carrier. In this case, it is assumed that the femto base station located in the cell area of the macro base station provides a service using RF1. The macro terminal may transmit / receive data to / from the macro base station without interfering with the femto base station at the position 1 that is not adjacent to the cell area of the femto base station.

The macro terminal may move to position 2 adjacent to the cell area of the femto base station (S220). If the macro terminal does not enter within the range a to perform handover to the femto base station but enters the range b to receive interference from the femto base station, the macro terminal does not perform the handover to the femto base station without performing the handover to the femto base station. Serious interference may occur. In addition, when the femto base station is a CSG femto base station allowing access to only a specific specific terminal and the macro terminal does not belong to the CSG group, when the macro terminal enters the cell area of the femto base station, severe interference may be caused by the femto base station.

The macro terminal is interfered with data transmission and reception using the carrier RF1 by the carrier RF1 used by the femto base station (S225). At this time, the femto base station may also be interfered by the carrier RF1 used by the macro terminal.

The macro terminal performs a channel scan when interference from the femto base station occurs (S230). The macro terminal may perform a channel scan within the carrier RF1 where interference occurs. The macro terminal may measure the channel state of the carrier RF1 and obtain neighbor femto base station information. The macro terminal may scan different frequency bands for inter-frequency handover in the same cell. That is, the macro terminal may measure the channel state of the carriers RF1 to RF4 operated by the macro base station.

The macro terminal transmits a channel measurement report including channel state information and neighbor femto base station information (S240). The channel state information may include information about the channel state of the carriers RF1 to which interference occurs and the carriers RF2 to RF3 of other frequency bands operated by the macro base station. The neighbor femto base station information may include an ID of the femto base station or a preamble index of the femto base station. The channel measurement report message may be referred to as a scanning report message. The neighbor femto base station information may be referred to for selecting a carrier allocated to the macro terminal by the macro base station. The channel measurement report may be transmitted through the carrier RF1.

The macro base station performs an inter-frequency handover in the same cell based on the channel measurement report transmitted from the macro terminal (S250). That is, the macro base station may change the carrier of the macro terminal in which interference occurs. If the femto base station is a base station for the CSG and the terminal does not belong to the CSG group, or if the terminal does not want to handover to the femto base station, the macro base station may change the carrier of the macro terminal to mitigate interference of the macro terminal. The macro base station may receive the femto base station information detected by the terminal to obtain femto base station information located near the macro terminal, and the macro terminal to be changed by referring to the frequency, resource allocation, power information, etc. of the carrier used by the neighbor femto base station. The frequency band of the carrier can be determined.

Inter-frequency handover in the same cell may be performed according to an initial handover of the terminal or an initial handover procedure of the base station after scanning of another frequency band of the terminal. Handover messages for handover between frequencies within the same cell include a handover request message (HO-REQ), a handover command message (HO-CMD), a handover indication message (handover indication message, HO-IND) message is included.

Table 1 shows the handover messages.

Message Notes HO-REQ Indication of Intra-Cell inter-carrier handover
Recommended target carrier information of the current serving BS HO-CMD Indication of Intra-Cell inter-carrier handover
Recommended target carrier information of the current serving BS HO-IND Target carrier information of the current serving BS

In the case of initial handover of the base station, the macro base station transmits a handover request message to the macro terminal. The handover request message indicates handover between frequencies in the same cell and recommends a target carrier of the current serving base station. After receiving the handover request message from the macro base station, the macro terminal scans the recommended target carrier. The macro terminal transmits a handover information message including information on the scanned target carrier to the macro base station. The macro base station transmits a handover command message indicating a handover between frequencies in the same cell to the macro terminal. The handover command message may include target carrier information of the current serving base station.

In case of initial handover of the terminal, the macro terminal transmits a handover request message including scan information of another frequency band to the macro base station. The handover request message may indicate handover between frequencies within the same cell and may recommend a target carrier of the current serving base station. The macro base station determines a carrier to be allocated to the macro terminal and transmits a handover command message including target carrier information.

When the terminal receives multi-carrier configuration information, only the carrier index may be included in the target carrier information. If the terminal does not receive the multi-carrier configuration information, the target carrier information includes the center frequency (for example, band class index and channel index), channel bandwidth, and carrier type (for example, fully / partially) with respect to the target carrier. configured), a duplexing mode, a preamble index, transmission power, and the like.

 The macro base station may change the carrier of the macro terminal to any one of RF2, RF3, and RF4, and the macro terminal may obtain carrier change information through inter-frequency handover in the same cell. Herein, it is assumed that RF4 having less interference with RF1 is selected as a carrier of a macro terminal.

The macro base station and the macro terminal may transmit and receive data by mitigating interference of the femto base station by using the changed carrier RF4 (S260).

As such, when the macro terminal moves near the cell area of the femto base station and causes interference with the femto base station, the macro base station is informed of the information to the macro base station and the carrier used is changed to mitigate the interference by the femto base station and to the individual user. Data transmission efficiency can be improved.

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

Although the present invention has been described above with reference to the embodiments, it will be apparent to those skilled in the art that the present invention may be modified and changed in various ways without departing from the spirit and scope of the present invention. I can understand. Therefore, the present invention is not limited to the above-described embodiment, and the present invention will include all embodiments within the scope of the following claims.

Claims (15)

A data transmission method for reducing interference in a hierarchical cell structure including a macro base station providing a multicarrier and a femto base station providing a single carrier,
Performing channel scan in a carrier in which interference occurs to obtain channel state information and neighbor femto base station information when interference from the femto base station occurs;
Transmitting a channel measurement report including the channel state information and the neighbor femto base station information to the macro base station; And
And receiving carrier change information from the macro base station and transmitting data through the changed carrier, thereby reducing interference in the hierarchical cell structure.
The method of claim 1, wherein the neighbor femto base station information includes a femto base station identifier (ID) or a preamble index of the femto base station.
2. The method of claim 1, further comprising performing a channel scan of a frequency band other than a carrier on which the interference occurs for inter-frequency handover in the same cell. Transmission method.
4. The method of claim 3, wherein the inter-frequency handover in the same cell is performed according to an initial handover of a terminal or an initial handover procedure of a base station.
The method of claim 4, wherein the initial handover procedure of the terminal comprises transmitting a handover request message including an indication of inter-frequency handover in the same cell and a recommendation of a target carrier to the macro base station. A data transmission method for reducing interference in a hierarchical cell structure.
6. The layer of claim 5, wherein the initial handover process of the terminal further comprises receiving a handover command message including target carrier information from the macro base station in response to the handover request message. Data transmission method to reduce interference in red cell structure.
The method of claim 4, wherein the initial handover procedure of the base station comprises receiving a handover request message from the macro base station indicating an indication of inter-frequency handover in the same cell and recommending a target carrier of a current serving base station. A data transmission method for reducing interference in a hierarchical cell structure.
8. The layer of claim 7, wherein the initial handover process of the base station further comprises transmitting a handover information message including target carrier information to the macro base station in response to the handover request message. Data transmission method to reduce interference in red cell structure.
4. The method of claim 3, wherein target carrier information for changing a carrier is exchanged with the macro base station in the inter-frequency handover process in the same cell, and when the multi-carrier configuration information is received, the target carrier information includes only a carrier index. A data transmission method for reducing interference in a hierarchical cell structure, characterized in that.
The target carrier information of claim 3, wherein target carrier information for changing a carrier is exchanged with the macro base station in the inter-frequency handover process in the same cell, when the multi-carrier configuration information is not received. A method for reducing interference in a hierarchical cell structure, comprising information on frequency, channel bandwidth, carrier type, duplex mode, preamble index, transmit power, and the like.
A data transmission method for reducing interference in a hierarchical cell structure including a macro base station providing a multicarrier and a femto base station providing a single carrier,
Receiving a channel measurement report including channel state information and adjacent femto base station information of a carrier from which interference from the femto base station occurs; And
And changing the carrier of the terminal based on the channel measurement report and transmitting data through the changed carrier.
12. The method of claim 11, wherein the terminal operates in a multi-carrier mode for transmitting and receiving data using a plurality of carriers.
12. The method of claim 11, wherein the UE operates in a single carrier mode for transmitting and receiving data using one carrier.
The channel measurement report transmitted from a terminal operating in the single carrier mode further includes channel state information of a frequency band other than a carrier in which the interference is generated for inter-frequency handover in the same cell. A data transmission method for reducing interference in a hierarchical cell structure, characterized in that.
15. The method of claim 14, wherein the inter-frequency handover in the same cell is performed according to an initial handover procedure of a terminal or an initial handover procedure of a base station.

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