KR20120053943A - Method for mitigating interference by base station in downlink and base station and terminal for supporting that method - Google Patents

Abstract

PURPOSE: An interference mitigation method, base station, and terminal thereof are provided to enable a terminal to receive normal communication services from a macro base station by alleviating interference generated by a small base station in downlinks. CONSTITUTION: In case interference levels for a first terminal are over threshold values, a small base station allocates resources for the first terminal(S210,S220). The small base station transmits data to the first terminal through the allocated resources(S230). In case the interference levels for the first terminal are under the threshold values, the small base station does not allocate the resources for the first terminal(S240).

Description

Method for Mitigating Interference by Base Station in Downlink and Base Station and Terminal for Supporting That Method}

The present invention relates to a wireless communication system, and more particularly, to a method for mitigating interference by a small base station in downlink of a wireless communication system.

In a wireless communication system, due to geographical requirements within a cell, a distance between a terminal and a base station, or a movement of the terminal, a poor channel condition may cause communication between the terminal and the base station to be performed smoothly.

For example, even within a service area of a base station, a radio wave shading area may be formed by an enclosed building such as an office or a house. If the terminal is located in the radio shadow region, the channel state between the base station and the terminal is poor, so that the smooth communication cannot be performed between the base station and the terminal.

Accordingly, the use of small cells located within a macro cell in a Long Term Evolution (LTE) and LTE-Advanced system of the 3rd Generation Partnership Project (3GPP) or an IEEE 802.16 series communication system has been proposed. The capacity of the communication system can be increased.

Here, the small cell refers to a small cell area formed by a small base station connected to a mobile communication core network through a broadband network installed indoors such as an office or a house.

These small cells are closed subscriber groups (CSGs) that can be used only by specific users depending on access restrictions, open access that allows access to general users, and hybrids that use a combination of both methods. Access).

1 is a diagram illustrating a configuration of a general wireless communication system in which a macro cell and a small cell are mixed. As shown in FIG. 1, the wireless communication system 100 includes a macro base station 112 that manages the macro cell 110 and a first small base station 122 that manages the first small cell 120.

At this time, the macro base station 112 provides a communication service to the first terminal 114 located in the macro cell 110, the first small base station 122 that manages the first small cell 120 is a first The communication service is provided to the second terminal 124 located in the small cell 120.

In the downlink of the wireless communication system configured as described above, the first small base station 122 may act as a serious interference source to the first terminal 114 provided with the service by the macro base station 112.

As such, when the small base station 122 acts as an interference source to the first terminal 114 in downlink, the first terminal 114 cannot normally receive the control signal from the macro base station 112, The first terminal 112 has a problem in that it cannot receive a normal service from the macro base station 112.

The present invention has been made to solve the above-described problem, and a base station supporting a method and a method for mitigating interference by the small base station in the downlink that can mitigate the interference of the small base station to the terminal receiving the service from the macro base station in the downlink And providing a terminal is a technical problem.

In the downlink according to an aspect of the present invention for achieving the above object, an interference mitigation method by a small base station comprises: receiving an access request from a first terminal provided with a service from a first base station; Allocating resources for the first terminal when the access request is received; And transmitting data to the first terminal through the allocated resource, wherein the small base station is a small base station of a closed subscriber group (CSG) type, and the first terminal is connected to a CSG of the small base station. Characterized in that the terminal is not included.

The method may further include determining an interference level of the small base station with respect to the first terminal. When the resource allocation step determines that the interference degree with respect to the first terminal is greater than or equal to a threshold value, It is characterized by allocating resources for one terminal.

The present invention may further include determining a number of second terminals that are already connected to the small base station among the terminals provided with the service from the first base station, and in the step of allocating the resource, When the number of connected second terminals is less than or equal to a reference value, the resource for the first terminal may be allocated.

The method may further include determining a resource usage rate of the small base station, and in the step of allocating the resource, allocating a resource for the first terminal when the resource usage rate of the small base station is less than or equal to a predetermined value. It features.

In one embodiment, the small base station is a femto base station that manages a small cell included in the macro cell.

In addition, the first base station is characterized in that the macro base station for managing a macro cell including a small cell managed by the small base station.

According to another aspect of the present invention, there is provided a method for mitigating interference by a small base station in a downlink, the method comprising: determining whether the small base station interferes with a terminal in downlink; If it is determined that interference of the small base station occurs, transmitting a request for access to the small base station; And if a resource is allocated from the small base station in response to the access request, receiving data from the small base station through the allocated resource.

In the step of determining whether the interference occurs, when the downlink control signal is not received from the first base station providing a service to the terminal or the downlink control signal received from the first base station is interference by the small base station It is characterized by determining that this has occurred.

In one embodiment, the first base station is characterized in that the macro base station located in the macro cell including the small cell managed by the small base station.

In the determining of whether the interference occurs, when the strength of the signal transmitted from the small base station is greater than a threshold transmitted from the signal transmitted from the first base station providing the service to the terminal, the interference caused by the small base station is generated. It is characterized by judging.

In one embodiment, the small base station is a closed type small base station, the terminal is characterized in that the terminal is not included in the CSG of the small base station.

In the transmitting of the access request, when there are a plurality of small base stations causing interference, the access request is transmitted to the small base station causing the highest interference among the small base stations.

A base station according to another aspect of the present invention for achieving the above object, a processor for allocating resources for the terminal when a connection request from a terminal receiving a service from a macro base station; And an RF unit for transmitting a downlink control signal and downlink data to the terminal through resources allocated by the processor, wherein the terminal is a terminal not included in its closed subscriber group (CSG). It is characterized by.

In an embodiment, the processor may further determine the number of other terminals receiving services from the macro base station among the terminals connected to the base station, and the number of other terminals connected to the base station is smaller than a reference value. In this case, the resource is allocated to the terminal.

In another embodiment, the processor may determine the resource usage rate of the base station, and allocates a resource for the terminal when the resource usage rate is equal to or less than a predetermined value.

The processor may determine the degree of interference with respect to the terminal and allocate resources for the terminal when the degree of interference with respect to the terminal is greater than or equal to a threshold.

According to another aspect of the present invention for achieving the above object, the terminal determines whether interference by the femto base station of the closed type, and if it is determined that the interference by the femto base station is connected to the femto base station A processor generating a request; And an RF unit for transmitting a connection request generated by the processor to the femto base station and receiving a downlink control signal and downlink data from the femto base station through resources allocated by the femto base station in response to the access request. It is characterized by including.

In one embodiment, the terminal is characterized in that the terminal is not included in the CSG of the femto base station.

The processor may be configured to have a strength of a signal transmitted from the femto base station greater than or equal to a threshold of a signal transmitted from a serving base station of the terminal, or not to receive a downlink control signal from the serving base station within a predetermined time. If the downlink control signal is abnormal, characterized in that it is determined that the interference by the femto base station.

In addition, when it is determined that there are a plurality of femto base stations causing interference, the processor generates an access request for the femto base station having the largest interference among the interfering femto base stations.

According to the present invention, when it is determined that the small base station affects the terminal receiving the macro base station service as an interference source in the downlink, the terminal accesses the small base station, thereby mitigating interference caused by the small base station in the downlink. It can be effective.

In addition, the present invention has the effect that the terminal receiving the service from the macro base station can normally receive the communication service by mitigating the interference caused by the small base station in the downlink.

1 is a block diagram schematically illustrating a configuration of a general wireless communication system.
2 is a flowchart showing an interference mitigation method by a small base station in downlink according to the first embodiment of the present invention.
3 is a flowchart showing an interference mitigation method by a small base station in downlink according to a second embodiment of the present invention.
Figure 4 is a block diagram schematically showing the configuration of a base station and a terminal according to an embodiment of the present invention.

In the following description, for convenience of description, a user and a terminal are used in the same concept and a cell and a base station are used in the same concept.

The description set forth herein is intended to describe exemplary embodiments of the invention, not to describe the only embodiments in which the invention may be practiced. In addition, in the following description, descriptions of well-known structures or devices may be omitted in order to avoid obscuring the essential features of the present invention.

In the following embodiments, on the other hand, each component or feature is to be considered as optional unless otherwise stated. Accordingly, each component or feature may be embodied in a form that is not combined with other components or features, and it may be possible to combine some components and / or features to constitute an embodiment of the present invention. In addition, the order of the operations described in the embodiments of the present invention may be changed, and some components or features in a specific embodiment may be included in another embodiment or replaced with corresponding components or features in another embodiment. have.

Embodiments of the present invention have been described based on the data transmission and reception relationship between the base station and the terminal. Here, the base station has a meaning as a terminal node of the network that directly communicates with the terminal. Certain operations described as being performed by the base station herein may be performed by an Upper Node of the base station in some cases.

That is, various operations performed for communication with a terminal in a network including a plurality of network nodes including a base station may be performed by the base station or network nodes other than the base station. The base station may be replaced by terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like, and the terminal may be a user equipment (UE), a mobile station (MS), or a mobile MSS (mobile station). Subscriber Station).

In addition, the data transmission method and apparatus according to the present invention include Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), and SC-FDMA (Single). It can be applied to various radio access technologies such as Carrier Frequency Division Multiple Access.

Meanwhile, wireless access technologies may be implemented in various wireless communication standard systems. For example, WCDMA (Wideband CDMA) may be implemented with wireless techniques, such as UTRAN (Universal Terrestrial Radio Access Network) by a standardization organization ^{(3 rd Generation Partnership Project) 3GPP} . In addition, CDMA2000 is a wireless technology based on CDMA, and High Rate Packet Data (HRPD) by a 3rd Generation Partnership Project 2 (3GPP2) standardization organization is a wireless technology providing high packet data service in a CDMA2000-based system. evolved HRPD (eHRPD) is a wireless technology in which HRPD is evolved, and TDMA can be implemented in wireless technologies such as Global System for Mobile communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). have. OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved-UTRAN (EUTRAN), or the like. Long Term Evolution (LTE) is part of Evolved-UMTS (E-UMTS) using E-UTRAN, and employs OFDMA in downlink and Single Carrier Frequency Division Multiple Access (SC-FDMA) in uplink. LTE-A (Advanced) is a wireless technology in which LTE has evolved.

As will be described below, the present invention provides a service from a macro base station 112 that manages a macro cell 110 in a wireless communication system in which a small cell 122 is disposed in a macro cell 110. When the receiving first terminal 114 receives interference from the small base station 122 that manages the small cell, it is to mitigate the interference by the small base station 122.

In the case of the interference caused by the small base station 122 in the downlink of the wireless communication system of FIG. 1 described above, the first terminal 114 cannot receive the downlink control signal from the macro base station 112 and thus the first terminal. 114 cannot normally receive the communication service.

In this case, the first terminal 114 may receive the downlink control signal from the macro base station 112 by reducing the transmission power of the small base station 122, but in the case of the present invention the first terminal through a more aggressive method 114 allows a normal communication service to be provided from the macro base station 112.

Hereinafter, embodiments of the present invention will be described in more detail with reference to FIGS. 2 to 4.

First, an interference mitigation method by a small base station in downlink according to the present invention will be described in detail with reference to FIGS. 2 and 3.

2 is a flowchart showing an interference mitigation method by a small base station in downlink according to the first embodiment of the present invention. The interference mitigation method shown in FIG. 2 may be performed by a small base station.

First, as shown in FIG. 2, the small base station receives an access request from a first terminal provided with a service from the first base station (S200).

In one embodiment, the first base station may be a macro base station (serving base station) that provides a communication service to the first terminal is located in the macro cell as shown in FIG.

In addition, the small base station manages a small cell located in the macro cell as shown in FIG. 1, and is a femto base station of a closed subscriber group (CSG) type that only a predetermined specific terminal can access. Can be.

Thereafter, the small base station determines the degree of interference that the small base station has on the first terminal (S210).

In one embodiment, the small base station may determine the degree of interference on the first terminal through the information transmitted from the macro base station.

In another embodiment, the small base station may determine the degree of interference on the first terminal using the strength of the signal received from the first terminal.

Then, if it is determined that the degree of interference with respect to the first terminal is greater than or equal to a threshold, the small base station allocates resources for the first terminal (S220) and transmits data to the first terminal through the allocated resources. (S230). In this case, the transmitted data may include a downlink control signal and downlink data.

On the other hand, when the degree of interference is smaller than the threshold in S210, the small base station does not allocate resources for the first terminal, thereby disallowing access to the first terminal (S240).

In the above-described embodiment, when the degree of interference by the small base station is greater than or equal to the threshold, it has been described as allocating resources to the first terminal.

However, in the modified embodiment, even if the degree of interference by the small base station is greater than or equal to the threshold, the number of second terminals provided with the service by the first base station among the terminals already connected to the small base station is additionally added. In consideration of this, resources may be allocated to the first terminal.

Specifically, before the first terminal transmits a resource allocation request to the small base station, if the number of second terminals already connected to the small base station is greater than or equal to the reference value, the resource is not allocated to the first terminal. Instead, resources may be allocated to the first terminal only when the number of the second terminals is smaller than a reference value.

In a modified embodiment, even if the interference by the small base station is greater than or equal to a threshold, the resource usage rate of the small base station is further determined, and the resource allocation for the first terminal is allocated when the resource usage rate of the small base station is less than or equal to a predetermined value. You could do it.

This is because the small base station is a closed type (CSG) type of base station that can be accessed only by a predetermined specific terminal should be able to connect only a predetermined specific terminal, the present invention is an exception to the connection of the first terminal is not a predetermined terminal This is because it is necessary to limit the number of terminals that can access the small base station among the terminals provided with the communication service by the first base station.

As described above, when the closed type small base station interferes with the first terminal, under the normal communication environment, the first terminal that is not included in the CSG of the small base station and cannot access the small base station may access the small base station. By doing so, the first terminal can be provided with a normal communication service.

3 is a flowchart illustrating an interference mitigation method by a small base station in downlink according to a second embodiment of the present invention. The interference mitigation method illustrated in FIG. 3 may be performed by a first terminal provided with a service by a macro base station.

First, the first terminal determines whether interference by the small base station occurs in the downlink (S300).

In this case, the small base station may be a closed type femto base station. In this case, since the first terminal is not a terminal included in the CSG of the small base station, the first terminal cannot connect to the small base station under a normal communication environment.

In one embodiment, the first terminal may determine that the interference by the small base station occurs when the strength of the signal transmitted from the small base station is greater than the reference value.

In another embodiment, the first terminal may determine that interference by the small base station occurs if the downlink control signal transmitted from the macro base station is not received within a predetermined time, or even if the downlink control signal is not normally received. .

As a result of the determination in S300, when it is determined that interference by the small base station occurs, the first terminal transmits a connection request to the small base station to the small base station (S310).

Thereafter, when resources are allocated from the small base station in response to the access request (S320), data is received from the small base station through the allocated resources (S330).

In one embodiment, the data received from the small base station may include a downlink control signal and downlink data.

Meanwhile, when it is determined that there are a plurality of small base stations causing interference in S300, the access request may be transmitted to the small base station causing the highest interference among the small base stations causing interference in S310.

As described above, in the present invention, when the first terminal cannot be normally provided with the communication service due to the interference by the small base station of the closed type, the first terminal connects to the small base station of the closed type so that the first terminal is normally operated. Ensure that you receive communication services.

4 is a block diagram schematically showing the configuration of a small base station and a terminal according to an embodiment of the present invention.

The small base station 400 illustrated in FIG. 4 manages a small cell included in a macro cell managed by the macro base station, and may be a closed type femto base station. In addition, the terminal 500 is a terminal that receives a communication service from the macro base station, and may be a terminal that is not included in the CSG of the small base station 400.

As shown in FIG. 4, first, the small base station 400 includes a processor 410, a memory 420, and an RF unit 430.

First, the processor 410 implements the functions or features of the base station shown in FIG. 2 described above. That is, the processor 410 receives an access request from the terminal 500 that receives a communication service from the macro base station, and when the access request is received from the terminal 500, determines the degree of interference that the processor 410 has on the terminal 500.

In one embodiment, the small base station 400 may determine the degree of interference on the terminal 500 through the information transmitted from the macro base station, or may be determined using the strength of the signal received from the terminal 500.

In addition, if it is determined that the degree of interference with respect to the terminal 500 is greater than or equal to a threshold, the processor 410 allocates resources for the terminal 500 and transmits data to the terminal 500 through the allocated resources. In this case, the data transmitted to the terminal 500 may include a downlink control signal and downlink data.

On the other hand, when the degree of interference is less than the threshold, the processor 410 does not allocate resources for the terminal 500, thereby disallowing the connection of the terminal 500 to the small base station 400.

In addition, the processor 410 further considers the number of other terminals receiving communication service from the macro base station among the terminals already connected to the small base station 400 even if the degree of interference by the small base station 400 is greater than or equal to the threshold. The resource may be allocated to the terminal 500.

In detail, before the resource allocation request is received from the terminal 500, the processor 410 may determine that the number of other terminals provided with the communication service by the macro base station among the terminals already connected to the small base station 400 is increased. If the reference value is greater than or equal to, the resource may not be allocated to the terminal 500, and the resource may be allocated to the terminal 500 only when the number of other terminals is smaller than the reference value.

In a modified embodiment, the processor 410 further determines the resource usage rate of the small base station even if the interference by the small base station is greater than or equal to a threshold, and the terminal 410 when the resource usage rate of the small base station is less than or equal to a predetermined value. You might be able to allocate resources for them.

This is because the small base station 400 is a closed type (CSG) type of base station that can be accessed only by a predetermined specific terminal should be able to access only a predetermined specific terminal, the present invention is exceptionally interfered by the small base station This is because it is necessary to limit the number of terminals that can be connected to the small base station because the connection of the terminals is allowed.

In addition, the processor 410 performs general functions performed by the base station such as transmission mode determination or scheduling for the terminal.

The memory 420 is connected to the processor 410 and stores various information for driving the processor 410.

The RF unit 430 is connected to the processor 410, receives a connection request for the small base station 400 from the terminal 500, and transmits data to the terminal 500.

In addition, the RF unit 430 may receive an access request or channel state information from the terminal 500 and transmit the received connection request or channel state information to the processor 410.

Next, the terminal 500 includes a processor 510, a memory 520, and an RF unit 530.

First, the processor 510 determines whether interference by the small base station 400 occurs. In one embodiment, the processor 510 may determine that interference by the small base station 400 has occurred when the strength of the signal transmitted from the small base station 400 is greater than or equal to a reference value.

In another exemplary embodiment, the processor 510 may indicate that interference by the small base station 400 occurs when the downlink control signal transmitted from the macro base station is not received within the predetermined time, or even if the downlink control signal is not normally received. You can judge.

In addition, when it is determined that interference by the small base station 400 occurs, the processor 510 generates a connection request for the small base station and transmits the generated request to the RF unit 530.

In one embodiment, if it is determined that there are a plurality of small base stations causing interference, the processor 510 generates an access request for the small base station having the largest interference degree among the small base stations causing interference and the RF unit 530. Can be delivered to.

Subsequently, data received from the small base station 400 is received and processed through the RF unit 530 according to the access request.

In addition, layers of the air interface protocol may be implemented by the processor 510.

Next, the memory 520 is connected to the processor 510 and stores various information for driving the processor 510.

The RF 530 transmits an access request to the small base station 400 and, when resources are allocated from the small base station 400 in response to the access request, receives data from the small base station 400 through the allocated resources. do. In one embodiment, the data received from the small base station 400 may include a downlink control signal and downlink data.

Thereafter, the RF unit 530 transmits the received data to the processor 510.

In the above-described embodiment, the processors 410 and 510 may include an application-specific integrated circuit (ASIC), another chipset, a logic circuit, a data processing device and / or a converter for converting baseband signals and radio signals to and from each other. .

The memories 420 and 520 may include read-only memory (ROM), random access memory (RAM), flash memory, memory cards, storage media, and / or other storage devices. The RF unit 430 or 530 may include one or more antennas for transmitting and / or receiving a radio signal.

When the above-described embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in the memories 420 and 520 and executed by the processors 410 and 510. The memories 420 and 520 may be inside or outside the processors 410 and 510, and may be connected to the processors 410 and 510 through various well-known means.

In the above-described downlink, the interference mitigation method of the small base station may be implemented as a program that can be performed using various computer means. In this case, the program for performing the interference mitigation method of the small base station may be a hard disk or a CD-ROM. In a computer-readable recording medium such as DVD, ROM, ROM, or flash memory.

Those skilled in the art to which the present invention pertains will understand that the above-described present invention can be implemented in other specific forms without changing the technical spirit or essential features.

Therefore, it is to be understood that the embodiments described above are exemplary in all respects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

Claims (20)

An interference mitigation method by a small base station in downlink,
Receiving an access request from a first terminal receiving a service from a first base station;
Allocating resources for the first terminal when the access request is received;
Transmitting data to the first terminal through the allocated resource;
The small base station is a small base station of the Closed Subscriber Group (CSG) type, the first terminal is a terminal not included in the CSG of the small base station, interference mitigation method by the small base station in the downlink. The method of claim 1,
Determining the degree of interference of the small base station with respect to the first terminal;
In the step of allocating the resource, if it is determined that the degree of interference with respect to the first terminal is greater than or equal to the threshold, the interference mitigation method by the small base station in the downlink, characterized in that for allocating resources for the first terminal. The method of claim 1,
Determining the number of second terminals already connected to the small base station among the terminals provided with the service from the first base station,
In the step of allocating the resource, when the number of the second terminal connected to the small base station is less than the reference value, the interference mitigation method by the small base station in the downlink, characterized in that for allocating the resource for the first terminal. The method of claim 1,
Determining a resource usage rate of the small base station;
In the step of allocating the resources, when the resource usage rate of the small base station is less than a predetermined value, the interference mitigation method by the small base station in the downlink, characterized in that for allocating resources for the first terminal. The method of claim 1,
The small base station is an interference mitigation method by a small base station in the downlink, characterized in that the femto (Femto) base station that manages the small cell included in the macro cell. The method of claim 1,
And the first base station is a macro base station managing a macro cell including a small cell managed by the small base station. An interference mitigation method by a small base station in downlink,
Determining whether the small base station interferes with the terminal in downlink;
If it is determined that interference of the small base station occurs, transmitting a request for access to the small base station; And
And receiving data from the small base station through the allocated resource if the resource is allocated from the small base station in response to the access request. The method of claim 7, wherein
In the step of determining whether the interference occurs, when the downlink control signal is not received from the first base station providing a service to the terminal or the downlink control signal received from the first base station is interference by the small base station The interference mitigation method by the small base station in the downlink characterized in that it is determined that the generated. The method of claim 8,
And the first base station is a macro base station located in a macro cell including a small cell managed by the small base station. The method of claim 7, wherein
In the step of determining whether the interference occurs, if the strength of the signal transmitted from the small base station is greater than the threshold transmitted from the signal transmitted from the first base station providing a service to the terminal, it is determined that the interference by the small base station occurs An interference mitigation method by a small base station in downlink characterized in that the. The method of claim 7, wherein
The small base station is a closed type small base station, the terminal is a terminal that is not included in the CSG of the small base station interference mitigation method by the small base station in the downlink. The method of claim 7, wherein
In the transmitting of the access request, when there are a plurality of small base stations causing interference, the access request is transmitted from the downlink to the small base station, wherein the access request is transmitted to the small base station causing the highest interference among the small base stations. Interference mitigation method. A processor for allocating resources for the terminal when a connection request is received from a terminal receiving a service from a macro base station; And
And an RF unit for transmitting a downlink control signal and downlink data to the terminal through resources allocated by the processor.
The terminal is a base station, characterized in that the terminal is not included in its CSG (Closed Subscriber Group). The method of claim 13,
The processor may further determine the number of other terminals receiving services from the macro base station among the terminals connected to the base station, and the resource for the terminal when the number of other terminals connected to the base station is smaller than a reference value. The base station, characterized in that for assigning. The method of claim 13,
The processor determines a resource usage rate of the base station, and if the resource usage rate is less than a predetermined value, the base station, characterized in that for allocating resources for the terminal. The method of claim 13,
The processor, the base station, characterized in that for determining the degree of interference with respect to the terminal and allocates resources for the terminal when the degree of interference for the terminal is greater than the threshold. A processor configured to determine whether interference by a closed type femto base station occurs and generate a connection request to the femto base station when it is determined that interference by the femto base station occurs; And
An RF unit for transmitting a connection request generated by the processor to the femto base station and receiving a downlink control signal and downlink data from the femto base station through resources allocated by the femto base station in response to the access request. Terminal, characterized in that. The method of claim 17,
The terminal is a terminal which is not included in the CSG of the femto base station. The method of claim 17,
The processor may be configured to have a strength of a signal transmitted from the femto base station greater than or equal to a threshold of a signal transmitted from a serving base station of the terminal, or not to receive a downlink control signal from the serving base station within a predetermined time. If the downlink control signal is abnormal, characterized in that the terminal determines that the interference by the femto base station. The method of claim 17,
If it is determined that there are a plurality of femto base stations causing interference, the processor generates a connection request for the femto base station having the greatest interference among the causing femto base stations.

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