KR20100130482A - Femto base station and method for expanding/shirking coverage thereof - Google Patents

Abstract

PURPOSE: A femto base station and a method for expanding/reducing a cell area are provided to minimize the interference with neighboring femto base station or other base station. CONSTITUTION: A controller(220) detects a terminal, which did not received a service in a cell external area. The controller determines whether the detected terminal is a permitted terminal or not. If the detected terminal a permitted terminal, the controller transmits an hand-over command to a femto base station which does not services. If a consent response about the handover command from a terminal is not received, the controller reduces the cell area.

Description

FEMTO BASE STATION AND METHOD FOR EXPANDING / SHIRKING COVERAGE THEREOF}

The present invention relates to a mobile communication system, and more particularly, to a femto base station in a mobile communication system.

Second generation mobile communication refers to digital transmission and reception of voice, such as CDMA and GSM. In addition to the GSM, GPRS has been proposed. The GPRS is a technology for providing a packet switched data service based on the GSM system.

Third generation mobile communication refers to the ability to transmit and receive images and data as well as voice, and the Third Generation Partnership Project (3GPP) developed the mobile communication system (IMT-2000) technology, and radio access technology (Radio Access). Technology, referred to as RAT). In this way, both IMT-2000 technology and radio access technology (RAT), for example, WCDMA, are collectively called UMTS (Universal Mobile Telecommunication System) in Europe. UTRAN stands for UMTS Terrestrial Radio Access Network.

Meanwhile, the third generation mobile communication is evolving to the fourth generation mobile communication.

The 4G mobile communication technology has been proposed as a Long-Term Evolution Network (LTE) technology under standardization in 3GPP and an IEEE 802.16 technology under standardization in IEEE. In the LTE, the term E-UTRAN (Evolved-UTRAN) is used.

In the fourth generation mobile communication technology, orthogonal frequency division multiplexing (OFDM) / orthogonal frequency division multiple access (OFDMA) is introduced. OFDM uses multiple orthogonal subcarriers. OFDM uses orthogonality between inverse fast Fourier Transform (IFFT) and fast Fourier Transform (FFT). The transmitter performs IFFT on the data and transmits it. The receiver recovers original data by performing FFT on the received signal. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

Meanwhile, attempts have been made to increase cell capacity in order to support high capacity services and interactive services such as multimedia contents and streaming in the 3rd or 4th generation mobile communication systems.

Approaches have been made to use higher frequency bands and reduce cell radius to increase cell capacity. Application of a small cell radius, such as a pico cell, enables the use of a higher band than the frequency used in existing cellular systems, which has the advantage of delivering more information. However, there is a disadvantage in that it is expensive because more base stations must be installed in the same area.

Recently, femtocells have been proposed in the approach of increasing cell capacity using such small cells.

Femtocell means that a small, low power base station is installed indoors for home / office to provide a small wireless environment. The femtocell is expected to improve the quality of the service by improving the indoor serviceable area and capacity, and is expected to completely settle the next generation mobile communication system by providing data service.

Such femtocells are being standardized under the name Home eNodeB in 3GPP WCDMA and LTE groups, and femtocells are actively being researched in 3GPP2.

Various schemes have been proposed for implementing such a femtocell in an existing mobile communication network as illustrated in FIGS. 1 and 2.

First, Figure 1 is an exemplary view showing a femtocell-based network structure according to the prior art.

As shown in FIG. 1, a macro base station (M-BS) serving a large area and a plurality of femto base stations (femto-BS: hereinafter referred to as 'f-BS') installed based on a user are shown. have.

The femto base station (f-BS) is connected to a femtocell network controller (FNC) via the Internet to be controlled or connected to the MME of the core network through the Internet to receive control and provide services to the user.

The terminal measures the signal of the cells of the surrounding cell and transmits it to its femto base station, through which the femto base station recognizes and manages the presence of neighboring cells in the vicinity. In addition, the femto base stations exchange information via a direct link or an indirect link through the FNC. The femto base station and the macro base station exchange information via an FNC and a Radio Network Controller (RNC) or a Mobility Management Entity (MME) that controls the femto base station in a mobile communication network.

2 is another exemplary diagram illustrating a femtocell-based network structure according to the prior art.

As shown in FIG. 2, the femto base stations (f-BSs) transmit and receive information through a direct link or an MME, unlike FIG. 1. In addition, the macro base station (M-BS) and the femto base station (f-BS) exchanges information through the MME.

3 shows an example of a frame structure used in a femtocell and a macro cell according to the prior art.

Referring to FIG. 3, each superframe is divided into four radio frames having the same size. The superframe may include a superframe header. The super frame header includes essential control information that a terminal must acquire at initial network entry or handover, and plays a role similar to that of a broadcast channel (BCH) in LTE technology. The superframe header may be allocated to the first radio frame among a plurality of radio frames constituting the superframe. The number of subframes constituting one frame may vary from 5, 6, 7, or 8 depending on the bandwidth or CP length of the system, and the number of symbols of OFDMA constituting one subframe is 5, 6 , 7, or 9. 3 illustrates an example in which the length of CP is 1 / 8Tb (Tb: Useful OFDMA symbol time) when the dual bandwidth is 5, 10, or 20 MHz.

The frame structure illustrated in FIG. 3 may be applied to a time division duplexing (TDD) scheme or a frequency division duplexing (FDD) scheme. TDD uses the entire frequency band as uplink or downlink, and distinguishes uplink transmission and downlink transmission in the time domain. In the FDD method, uplink transmission and downlink transmission occupy different frequency bands. Say what happens.

Each subframe is divided into at least one frequency partition. Each frequency partition is composed of at least one Physical Resource Unit (PRU). Each frequency partition comprises a Localized PRU and / or a Distributed PRU. Each frequency segment may be used for purposes such as fractional frequency reuse (FFR).

The physical resource unit (PRU) is a basic physical unit for resource allocation including N consecutive OFDM symbols and P consecutive subcarriers. Localized Resource Units (LRUs) are basic logical units for distributed resource allocation and local resource allocation. The LRU includes a P * N subcarrier. The LRU includes pilots used in the PRU. Thus, the appropriate number of subcarriers in one LRU depends on the number of pilots assigned.

4 is a structure of a synchronization channel (hereinafter, Advanced-Preamble, A-Preamble) of one IEEE 802.16m (or Advanced Air Interface) in the fourth generation mobile communication system technology. Four primary or secondary preambles, which extend one OFDMA symbol, are located in a 20ms superframe, and SFH to which essential control information is transmitted is transmitted after the secondary preamble symbol. In case of PA-Preamble, it is transmitted with frequency reuse 1, and in case of SA-Preamble, it is transmitted with frequency reuse 3. Accordingly, in the case of SA-Preamble, segments are allocated with three 1-to-1 mappings according to three sector indices.

In the above-described prior art, the femto base station (Femto-BS) is selected by the user installation location, has a small coverage compared to the macro base station and provides a service to a small number of fixed users.

Therefore, the location distribution of the user has a great influence on the interference relationship between the femto base station or between the femto base station and the macro base station. It may cause unnecessary redundant installation and overcrowded installation, and in the case of dense residential / office areas, there is a problem of narrowing the interval between installed femto base stations.

In addition, in the case of the macro base station installed outdoors, the distance between the existing macro base stations can be calculated from the upper RNC stage using GPS information, that is, latitude and longitude, and the newly installed base station is transmitted using the preset transmission power. You can set the value of the resource.

However, since the neighbor relationship of the femto base station becomes irregular according to the type of obstacle in the room, there is a problem that it is difficult to grasp only the GPS location information. In addition, the femto base station is mainly installed indoors (offices, homes, etc.), so it may be difficult to accurately determine the absolute position because the GPS signal is difficult to receive.

In addition, the environment in which the femto base station is installed has many obstacles such as walls, and the femto base station has an irregular cell structure due to a different path loss exponent depending on the type of obstacle. Can be.

In addition, when the femto base stations are distributed in buildings, apartments, and the like, vertical vertical relationships may occur instead of horizontal cell structures.

For these reasons, it is very difficult to avoid possible interference between base stations. In addition, since it is difficult to pinpoint the location where the femto base station is installed, it is more difficult to avoid interference.

Accordingly, an object of the present invention is to solve the above problems. That is, an object of the present invention is to minimize interference with a neighboring femto base station or another base station.

In order to achieve the above object, the present invention provides a cell area reduction method of a femto base station. The reduction method includes detecting a terminal that is not served by the femto base station; Transmitting a handover command to the femto base station to the non-service terminal; And when the accept response for the handover command is not received from the terminal, reducing the cell area.

The method may further include checking whether an identifier of the terminal is in an access allow list. The transmitting of the handover command may be performed when the identifier of the terminal is in the access permission list.

When the femto base station is operated based on a closed subscriber group, the step of checking the access allowance list may be to check whether the terminal belongs to the closed subscriber group.

The method may include determining whether a service provider of the terminal is the same as a service provider of the femto base station when the identifier of the terminal is not in the access allow list; If the service providers are the same, the method may further include determining whether interference occurs due to the terminal. In this case, the reducing of the cell area may be additionally performed even when it is determined that the interference occurs.

The method may further comprise applying a preset policy if the service providers are not identical.

The handover command may be a Femto_HO_Command message.

In this case, the Femto_HO_Command message may be transmitted directly from the femtocell to the user terminal or through a base station to which terminals are connected via a core network or an FNC.

When the handover command is transmitted to a plurality of terminals in the handover command transmission step, failing to receive the accept response may include a case where an accept from all of the plurality of terminals is not received.

If the handover command is transmitted to a plurality of terminals in the handover command transmission step, an acknowledgment response is received from some terminals, and an acknowledgment response is not received from another terminal, the method differs from the accepted terminal. Forcibly handing over to the base station, or the femto base station may include the step of canceling the handover of the terminal the terminal accepts the handover. In this case, the reducing step may be performed after the forced handover or handover cancellation.

On the other hand, in order to achieve the above object, the present disclosure provides a cell area expansion method of the femto base station. The extension method includes detecting a terminal located in an outer region of a cell area of the femto base station and which the femto base station does not serve; Checking whether the detected terminal is in an allow list; Transmitting a handover command to the femto base station if the terminal is in the allow list; When receiving the accept response for the handover command from the terminal, it may include expanding the cell area of the femto base station.

When the femto base station is operated on the basis of a closed subscriber group (Closed Subscriber Group), the step of checking the allow list may be to determine whether the terminal belongs to the closed subscriber group.

The method may further include maintaining a cell area of the femto base station when the identifier of the terminal is not in the allow list.

The method may further include maintaining a cell area when the acceptance response for the handover command is not received from the terminal.

On the other hand, in order to achieve the above object, the present specification provides a femto base station. The femto base station includes a transceiver; When controlling the transceiver unit to detect a terminal that is not provided with a service in a cell outer region, it is determined whether the detected terminal is an allowed terminal, and if it is allowed, hand the terminal to the non-service terminal to the femto base station. The processor may include a processor configured to transmit an over command and reduce the cell area when the terminal does not receive an acceptance response for the handover command from the terminal.

After the processor reduces the cell area and detects a terminal that is not provided with a service in the cell outer region, the processor determines whether the detected terminal is an allowed terminal, and if the terminal is allowed, the terminal not serving the service. When the handover command is transmitted to the femto base station and the acceptance response for the handover command is received from the terminal, the reduced cell area may be extended.

If the identifier of the terminal is not in the allow list, the processor determines whether the service provider of the terminal is the same as the service provider of the femto base station, and if the service providers are the same, whether the interference occurs due to the terminal. If the interference occurs, the cell area may be reduced.

The present invention considers not only cell expansion and contraction through power control based on traffic, but also characteristics of terminals searched outside the cell (CSG terminal, whether belonging to the same service provider), and channel condition (interference presence). Perform cell expansion and cell reduction. This allows the femto base station to minimize interference with neighboring femto base station and macro base station, and efficiently controls the power consumption of the femto base station. In addition, the femto base station may provide high quality services to the terminals.

The present invention applies to femtocells. However, the present invention is not limited thereto and may be applied to all communication systems and methods to which the technical spirit of the present invention may be applied.

It is to be noted that the technical terms used herein are merely used to describe particular embodiments, and are not intended to limit the present invention. It is also to be understood that the technical terms used herein are to be interpreted in a sense generally understood by a person skilled in the art to which the present invention belongs, Should not be construed to mean, or be interpreted in an excessively reduced sense. In addition, when the technical terms used herein are incorrect technical terms that do not accurately express the spirit of the present invention, they should be replaced with technical terms that can be understood correctly by those skilled in the art. In addition, the general terms used in the present invention should be interpreted as defined in the dictionary or according to the context before and after, and should not be interpreted in an excessively reduced sense.

Also, the singular forms "as used herein include plural referents unless the context clearly dictates otherwise. In the present application, terms such as “consisting of” or “comprising” should not be construed as necessarily including all of the various components, or various steps described in the specification, wherein some of the components or some of the steps It should be construed that it may not be included or may further include additional components or steps.

In addition, terms including ordinal numbers, such as first and second, as used herein may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component.

When an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may be present in between. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and the same or similar components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted. In addition, in describing the present invention, when it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted. In addition, it is to be noted that the accompanying drawings are only for easily understanding the spirit of the present invention and are not to be construed as limiting the spirit of the present invention by the accompanying drawings. The spirit of the present invention should be construed to extend to all changes, equivalents, and substitutes in addition to the accompanying drawings.

Hereinafter, the term terminal is used, but the terminal may be referred to as a user equipment (UE), a mobile equipment (ME), or a mobile station (MS). In addition, the UE may be a portable device having a communication function such as a mobile phone, a PDA, a smart phone, a laptop, or the like, or may be a non-portable device such as a PC or a vehicle-mounted device.

Hereinafter, described in detail with reference to the drawings.

5 is an exemplary view showing a cell expansion and contraction method according to a first embodiment of the present invention.

Referring to FIG. 5, at least one terminal 100, a femto base station 200, a macro base station 300, and another type of base station 400 are shown.

The femto base station 200 expands or contracts the cell range. This expansion and contraction is called cell breathing technique. The cell breathing technique means that the area covered by the base station is constantly changed according to traffic capacity. To this end, the femto base station 200 performs power control to appropriately adjust the transmission power (Tx Power).

When excessive traffic is imposed on the cell, the femto base station 200 reduces the size of the cell by reducing the transmission power. The traffic of the terminal located outside the cell of the femto base station 200 is moved to a serviceable neighbor cell.

Since all services provided by the femto base station 200 to the terminal 100 require a certain level of quality (QoS), the power level received by the femto base station 200 is theoretically determined for all terminals regardless of distance. Should be the same. Therefore, a terminal far away from the femto base station 200 should transmit a transmission power of a larger signal than a terminal located in a near position, and even when transmitting a signal having a high data rate, it should be transmitted at a larger transmission power. If the interference increases, the transmit power will have to be large. However, since the maximum size at which the transmission power can be increased is determined, the area covered by the cell of the femto base station 200 is reduced.

The cell expansion and contraction method according to the first embodiment described so far has several advantages, but the weight of one terminal of the total service traffic is high, and the neighboring base stations and the cell area overlap with the terminals receiving services from the neighboring base stations. There may be drawbacks that cannot adequately respond to situations where this can occur.

That is, when one to five terminals are allowed to access, one terminal occupies a large portion of the total traffic of the femtocell. Since the amount of traffic required by the cell of the femto base station 200 changes greatly according to the movement of the terminal, it is necessary to perform cell bridging through power control in consideration of the movement of the terminal entering and leaving the cell area of the femto base station 200. There is. Since a cell of the femto base station 200 may frequently interfere with a cell of an adjacent femto base station 200 or a terminal served by another base station, the terminal 100 to serve no longer is located outside the cell of the femto base station 200. When not present, the transmission power of the femto base station 200 should be lowered to reduce the service area of the cell. In addition, by reducing the cell area, unnecessary power consumption of the femto cell can be prevented.

Meanwhile, a cell of the femto base station 200 may be classified into a closed subscriber group (CSG) and an open access group (Open Access) according to an access permission policy. In the case of the closed subscriber group (CSG), only the user terminal allowed to the femto base station 200 cell is allowed to access the femto base station 200 cell. In the case of the open access group, the femto base station 200 provides a service without limitation to terminals that can be serviced.

In the current 3GPP, the femto base station 200 periodically transmits a closed subscriber group (CSG) ID in order to check whether the terminal can use the closed subscriber group, the terminal is the femto base station of the accessible It has been proposed to store a closed subscriber group (CSG) ID list for cells, that is, a Femto-cell White List in a universal subscriber identity module (USIM).

Therefore, it is necessary to consider the access permission policy in the expansion and contraction of the cell.

To this end, in the second embodiment to be described later, power control is not simply performed according to the traffic amount of the corresponding femto base station 200, but when the terminal is searched outside the cell, the cell is expanded or reduced according to the allowed access policy. To help. Specifically, in the second embodiment, when the terminal is searched outside the cell, the terminal selects a cell according to whether the terminal belongs to the CSG of the cell of the femto base station 200 or whether the terminal belongs to the same service provider (SP). Allows expansion and contraction.

In this case, the femto base station 200 determines whether the terminal detected in the cell foreign country is within the allowed access policy and whether the detected terminal belongs to the same operator. ), For example, by contacting the FNC or MME shown in FIGS. 1 and 2.

6 is a flowchart of a cell reduction method according to a second embodiment of the present invention.

The cell reduction method according to the second embodiment is not only when the amount of traffic acceptable to the cell, which is a reduction condition, but also when interference occurs with a terminal served by another base station outside the cell, and the current femto base station even if there is no actual interference. If there is no terminal serviced from the cell of 200, it may be performed to prevent a situation in which interference may occur and for power saving.

In this case, in the case of a terminal receiving a service located outside the cell of the femto base station 200, as the cell area of the femto base station 200 is reduced, the terminal is prevented from receiving a service. Can be handed over to a macro cell or a neighbor femtocell.

Specifically, it is as follows.

The terminal 100 or the femto base station 200 periodically performs channel searching of the femto cell (S111). In this case, the channel search may be a search of a super frame or an advanced-preamble shown in FIGS. 3 and 4. Or, it may be a search for a channel including system information.

The femto base station 200 determines whether the terminal 100 which does not serve by the channel search is detected (S112).

If the femto base station 200 is a terminal that does not serve, the terminal is identified. Identification of the terminal may be achieved by checking the ID of the terminal. Identification of the terminal may be achieved by the femto base station 200 receives information on the terminals currently serving in the macro cell to which the femto base station 200 belongs through a core network. Alternatively, the femto base station 200 may identify the terminal through a terminal in service or directly after receiving uplink control information (CQI, SRS) of the terminal and comparing the information received through the core network. have.

The femto base station 200 checks whether the terminal is an allowed terminal (S114). That is, it is checked whether the terminal belongs to the closed subscriber group (CSG). To this end, the femto base station 200 compares the information about the terminal with an allowed terminal list (Allowed List). The allowed terminal list is list information of a terminal accessible to the femto base station 200.

When the terminal is an allowed terminal, that is, when information on the terminal is written in the allowed terminal list (that is, the terminal is a closed subscriber group terminal), the terminal is sent to the femto base station 200. A handover command, for example, a Femto_HO_Command message is transmitted (S115).

The femto base station 200 confirms whether to receive a consent message for the handover command from the terminal (S116).

When the femto base station 200 receives the consent message for the handover command, the femto base station 200 maintains a cell range (S117).

When the femto base station 200 receives a disagreement message for the handover command, the femto base station 200 reduces the cell range (S121). In this case, the terminal may receive a service with a quality of service (QoS) that is satisfactorily satisfied at a serving BS, or may be rejected for the handover command when moving at a predetermined speed or more.

On the other hand, when the terminal is not allowed, that is, when the information about the terminal is not written in the allowed terminal list (that is, the terminal does not belong to the closed subscriber group), the femto base station 200 The terminal determines whether the terminal belongs to the same service provider (S118).

If the service provider of the terminal is not the same as the service provider of the femto base station, the femto base station 200 processes according to a preset policy. The policy may be set by an operator of the femto base station 200 or may be set by the service provider. In addition, the policy may be variously set.

On the other hand, if the service provider of the terminal is the same as the service provider of the femto base station 200, it is determined whether the interference exists (S120). In this case, since terminals generally transmit signal-to-intection ratio (SINR) information, which is a channel quality value periodically, the femto base station 200 determines whether the interference occurs through a change in the received SINR information. You can check it. In this case, since a terminal receiving a service indoors may assume low mobility, a sudden change in SINR reflects the influence of interference by an adjacent terminal.

If there is no interference, the femto base station 200 maintains the cell range (S117).

However, if there is interference, the femto base station 200 reduces the cell range (S121). That is, if the femto base station 200 dl maintains the current cell area, the neighboring terminal may be interfered with, thus reducing cell area.

Meanwhile, in the terminal identification process (S113), when the terminal cannot be identified and when the terminal is a terminal receiving a service from a base station of another service provider, the femto base station 200 performs a cell according to a service policy. You can reduce or keep the range.

On the other hand, when the femto base station 200 transmits a handover command to a plurality of terminals in the consent confirmation process (S116), some terminals do not accept but other terminals accept, the cell range for the other terminals You can keep it without shrinking. Alternatively, when the femto base station 200 transmits a handover command to a plurality of terminals, but some terminals do not accept and other terminals accept, the femto base station 200 replaces the accepted terminal with the macro base station instead of maintaining the cell range. You can force the handover and reduce the cell. Alternatively, if the terminal is to perform the handover, the handover cancellation request message may be transmitted to the terminal. In this case, in order to forcibly handover the terminal that has accepted the handover command to the macro base station, the accepted word should be located outside the cell of the femto base station 200 and handover to the macro cell or the neighbor femto base station. Should be possible. At this time, the femto base station 200 determines whether the forced handover in consideration of QoS, various information, policies, and the like. In this case, if there is a terminal accessing the femto base station in the cell outlying region, the corresponding terminal also makes a handover to the macro base station for cell reduction.

7 is a flowchart of a cell expansion method according to a second embodiment of the present invention.

As can be seen with reference to FIG. 7, the cell expansion is performed in a region outside the reduced cell where the femto base station 200 has reduced the cell area in order to reduce interference with neighboring base stations or to prevent power consumption. The femtocell may be performed when a serviceable terminal enters. Whether the terminal exists in the cell outer region may be achieved by receiving CQI (Channel Quality Information) or SLS from the terminal.

The cell area extension may be performed when the femto base station 200 finds a terminal that does not receive a service from itself, and the service provider of the terminal and the service provider of the femto base station 200 are the same. In this case, the cell area expansion may be performed after checking whether the terminal is an allowed terminal, that is, whether the terminal belongs to a closed subscriber group.

That is, when the service provider of the found terminal and the service provider of the femto base station 200 are the same, and the found terminal belongs to a closed subscriber group, the femto base station 200 increases transmission power to increase cell area. The service may be provided to the corresponding terminal. At this time, when the found terminal is receiving a service from the macro base station 300, the femto base station 200 may transmit a handover command, for example, an HNB_HO_Command message to the terminal. In this case, the cell determination may be performed only when the terminal accepts the handover command.

Specifically, it is as follows.

The terminal 100 or the femto base station 200 periodically performs channel searching of the femto cell (S211). In this case, the channel search may be a search of a super frame or an advanced-preamble shown in FIGS. 3 and 4. Or, it may be a search for a channel including system information.

The femto base station 200 checks whether the terminal 100 which is not served by the channel search is detected outside the cell (S212).

If the femto base station 200 is a terminal that does not serve, the terminal is identified (S213). Identification of the terminal may be achieved by checking the ID of the terminal. Identification of the terminal may be achieved by the femto base station 200 receives information on the terminals currently serving in the macro cell to which the femto base station 200 belongs through a core network. Alternatively, the femto base station 200 may identify the terminal through a terminal in service or directly after receiving uplink control information (CQI, SRS) of the terminal and comparing the information received through the core network. have.

The femto base station 200 checks whether the terminal is an allowed terminal (S214). That is, it is checked whether the terminal belongs to the closed subscriber group (CSG). To this end, the femto base station 200 compares the information about the terminal with an allowed terminal list (Allowed List). The allowed terminal list is list information of a terminal accessible to the femto base station 200.

When the terminal is an allowed terminal, that is, when information on the terminal is written in the allowed terminal list (that is, the terminal is a closed subscriber group terminal), the terminal is sent to the femto base station 200. A handover command, for example, a Femto_HO_Command message is transmitted (S215). However, at this time, the femto base station 200 may not transmit the handover command when the state of the terminal 100 is an idle mode (Idle mode) that is not being provided with the service. This is because the femto base station 200 does not need to service the terminal 100 because the terminal 100 is in the idle mode. Whether the femto base station 200 receives the location update information periodically from the terminal 100 in the idle mode whether the terminal 100 is in the idle mode.

The femto base station 200 confirms whether to receive a consent message for the handover command from the terminal 100 (S116). In this case, when the terminal 100 accepts the handover command, the terminal 100 has a higher QoS and higher bandwidth than the QoS (Quality of Service) of the serving base station (Serving BS). When a service can be provided from the femto base station 200.

When the femto base station 200 receives the consent message for the handover command, the femto base station 200 expands the cell range (S217).

On the other hand, when the femto base station 200 receives a disagreement message for the handover command, the femto base station 200 maintains a cell range (S218).

In this case, when the terminal 100 rejects the handover command, it is when the terminal 100 is satisfactorily satisfying the QoS of the serving BS (Serving BS) or is moving at a predetermined speed or more.

In addition, when the terminal 100 rejects the handover command, the terminal 100 is in an idle mode (Idle mode) where no service is provided.

The method according to the invention described thus far can be implemented in software, hardware, or a combination thereof. For example, the method according to the present invention may be stored in a storage medium (eg, internal memory, flash memory, hard disk, etc.) and may be executed by a processor (eg a microprocessor). It can be implemented as codes or instructions within a program. This will be described with reference to FIG. 9.

8 is a block diagram illustrating a configuration of a terminal 100 and a femto base station 200 according to the present invention.

As shown in FIG. 8, the terminal 100 includes a storage unit 110, a controller 120, and a transceiver 130. The femto base station 200 includes a storage means 210, a controller 220, and a transceiver 230.

The storage means 110, 220 store a method according to the first to second embodiments shown in FIGS. 5 to 7.

The controllers 120 and 220 control the storage means 110 and 210 and the transceivers 130 and 230. Specifically, the controllers 120 and 220 execute the methods stored in the storage terminals 110 and 210, respectively. The controllers 120 and 220 transmit the above-mentioned signals through the transceivers 130 and 230.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, May be modified, modified, or improved.

1 is an exemplary diagram showing a femtocell-based network structure according to the prior art.

2 is another exemplary diagram illustrating a femtocell-based network structure according to the prior art.

3 shows an example of a frame structure used in a femtocell and a macro cell according to the prior art.

4 shows a superframe structure according to the prior art.

5 is an exemplary view showing a cell expansion and contraction method according to a first embodiment of the present invention.

6 is a flowchart of a cell reduction method according to a second embodiment of the present invention.

7 is a flowchart of a cell expansion method according to a second embodiment of the present invention.

8 is a block diagram illustrating a configuration of a terminal 100 and a femto base station 200 according to the present invention.

Claims (16)

As a cell area reduction method of a femto base station Detecting a terminal that is not served by the femto base station; Transmitting a handover command to the femto base station to the non-service terminal; And reducing the cell area when receiving the acceptance response for the handover command from the terminal. The method of claim 1, Checking whether an identifier of the terminal is in an allow list; The transmitting of the handover command is performed when the identifier of the terminal is in the allow list. The method of claim 2, wherein when the femto base station is operated based on a closed subscriber group (Closed Subscriber Group), The acknowledgment list is a cell area reduction method of a femto base station, characterized in that whether the terminal belongs to the closed subscriber group. The method of claim 2, wherein if the identifier of the terminal is not in the allow list, Determining whether a service provider of the terminal is the same as a service provider of the femto base station; If the service providers are the same, determining whether the interference occurs due to the terminal, further comprising: Reducing the cell area is further performed even if it is determined that the interference occurs. The method of claim 4, wherein if the service providers are not the same, The method for reducing a cell area of a femto base station, further comprising applying a preset policy. The method of claim 1, wherein the handover command is Method for reducing the cell area of a femto base station, characterized in that the Femto_HO_Command message. The method of claim 1, When the handover command is transmitted to a plurality of terminals, The failure to receive the accept response may include a case in which the accept may not be received from all of the plurality of terminals. The method of claim 1, When the handover command is transmitted to a plurality of terminals, an acceptance response is received from some terminals, and an acceptance response is not received from other terminals, Forcibly handing over the accepted terminal to another base station, And the shrinking step is performed after the forced handover. As a cell area extension method of a femto base station Detecting a terminal located in an outer region of a cell area of the femto base station and which the femto base station does not serve; Checking whether the detected terminal is in an allow list; Transmitting a handover command to the femto base station if the terminal is in the allow list; And expanding the cell area of the femto base station when receiving the acceptance response for the handover command from the terminal. 10. The method of claim 9, wherein when the femto base station is operated based on a closed subscriber group (Closed Subscriber Group), The checking of the allow list may include checking whether the terminal belongs to the closed subscriber group or not. 10. The method of claim 9, further comprising maintaining a cell area of the femto base station if the identifier of the terminal is not in the allow list. 10. The method of claim 9, And if the terminal does not receive an acknowledgment of the handover command from the terminal, maintaining the cell area. As a femto base station, A transceiver; When controlling the transceiver unit to detect a terminal that is not provided with a service in a cell outer region, it is determined whether the detected terminal is an allowed terminal, and if it is allowed, hand the terminal to the non-service terminal to the femto base station. And a processor which transmits an over command and reduces the cell area when the terminal does not receive an acknowledgment of the handover command from the terminal. The method of claim 13, wherein after the processor reduces the cell area, When detecting a terminal that is not provided with a service in a cell outer region, it is determined whether the detected terminal is an allowed terminal, and if allowed, transmits a handover command to the non-service terminal to the femto base station, The femto base station, characterized in that for expanding the reduced cell area when receiving the acceptance response for the handover command from the terminal. The method of claim 13, wherein the processor determines whether the service provider of the terminal is the same as the service provider of the femto base station if the identifier of the terminal is not within the allow list, and if the service providers are the same, It is determined whether or not interference occurs, and if the interference occurs, the femto base station characterized in that the cell area is reduced. The method of claim 13, wherein the handover command is transmitted to a plurality of terminals. The failure to receive the acknowledgment includes the case where the acknowledgment is not received from all of the plurality of terminals.

Images