KR101221532B1 - Method And Apparatus For Interference Adjustment of Femto BS - Google Patents

Abstract

The present invention relates to a method for performing an interference coordination by a femto base station and an apparatus therefor. To this end, the femto base station reports the identification information of the macro cell user equipment to the macro base station by detecting uplink signals of one or more macro cell user equipment, and the macro base station adds the femto base station to the measurement target of the macro cell user equipment. To obtain interference information of the femto base station. The femto base station receives from the macro base station an interference coordination signal determined by the macro base station based on the measurement result report received from the macro cell user device, and receives a downlink signal transmitted to one or more femtocell user devices according to the received interference coordination signal. I can adjust it.

Description

Method for interference coordination of femto base station and apparatus therefor {Method And Apparatus For Interference Adjustment of Femto BS}

The present invention relates to a mobile communication system, and more particularly, to a method and an apparatus therefor for a femto base station to perform interference coordination.

Advances in traditional cellular systems have been developed with two major pillars of the 3GPP family based on GSM, 3GPP2 based on CDMA, and the recent WiMAX camp. The most important factor in cellular wireless communication technology is to obtain high-speed yield. In recent years, the explosive increase in wireless communication yield is achieved through an increase in signal to noise ratio (SNR) due to the reduction in cell size.

One of the latest technologies that contributes to an increase in SNR due to a decrease in cell size in cellular wireless communication systems is femto cell technology. A femtocell is a general term for an ultra-small base station having a tens of meters of coverage that can be installed directly by a user in an office or a home, the resulting small cell, and its technology. Here, the micro base station for such a femtocell may be referred to as a femto base station, a femto AP, a femto ABS, and also femtocell itself in some cases. Hereinafter, such a micro base station will be referred to as a 'femto base station'. On the other hand, a general base station having a large coverage in contrast to this may be referred to as a 'macro base station'.

A femto base station is a type of base station that may be installed in a shaded area that the macro base station does not cover. The femto base station is a compact version of the macro base station that can perform most of the functions of the macro base station. The femto base station has a network configuration that operates independently and will be installed much more than a relay base station in the city or indoors. Therefore, the femto base station list is not included in the neighbor base station list transmitted by the base station to the terminal because the amount of information is too large.

1 is a configuration diagram of a wireless communication system to which a femto base station is added.

As shown in FIG. 1, a wireless communication system to which a femto base station is added includes a femto base station 110, a macro base station 120, a femto network gateway (FNG) 130, and an access service network. (access service network, hereinafter referred to as "ASN") 140 and connectivity service network (hereinafter referred to as "CSN") 150. The macro base station 120 refers to a general base station of a conventional wireless communication system.

The femto base station 110 operates directly as a macro base station 120 by directly connecting to a transmission control protocol / internet protocol (TCP / IP) network, and has a coverage of about 0.1 to 30 m, and one femto base station 110 The number of terminals that can accommodate is about 10-20. The femto base station 110 may use the same frequency as the macro base station 120 or may use another frequency.

The femto base station 110 may be connected to the macro base station 120 through an R1 interface to receive a downlink channel of the macro base station 120, and the femto base station 110 may control a control signal to the macro base station 120. signal) can be sent.

The femto base station 110 may cover an indoor or shadowed area that the macro base station 120 does not cover, and may support high data transmission. The femto base station 110 may be installed in an overlay form in the macro, or may be installed in a non-overlay form in an area not covered by the macro base station 120.

Femto base station 110 is classified into two types. The first type is a closed subscriber group (CSG) femto base station, and the second type is an open subscriber group (OSG) femto base station. The CSG femto base station groups the terminals accessible to it and grants a CSG ID (identification), and only the terminal to which the CSG ID is assigned can access the CSG femto base station. The OSG femto base station is a base station to which all terminals can access. In addition, mixed forms thereof are also possible.

The FNG 130 is a gateway for controlling the femto base station 110 and is connected to the ASN 140 and the CSN 150 through the Rx interface and the Ry interface. The femto base station 110 may receive a service from the CSN 150 through the FNG 130, and the terminal connected to the femto base station 110 may provide functions such as authentication and IMS to the FNG 130 or the CSN 150. You can get the service from. The CSN 150 provides a terminal with a connection of an application service such as the Internet, VoIP, and the like, and provides an authentication and charging function, and the ASN 140 controls the macro base station 120 and the macro base station 120 and the CSN 150. Manages connections.

In the femtocell environment, the interference problem is expected to be more severe than before. Firstly, interferences caused by femtocells in addition to the interference between macrocells have increased, and secondly, unlike the macrocell method in which a limited number of base stations are intentionally arranged by a telecommunications company, femto base stations have a large amount of user bases. Because it will be installed. Finally, the femto base station will be more difficult to control directly than the macro base station.

As described above, femto base stations can determine their own operating frequency and transmit power level for smooth operation, while self-configuring network operation due to femto base stations is not easy to optimize.

On the other hand, information on the interference of the uplink signal transmission of the femto base station to the macro base station is relatively easy to obtain, while various studies have been conducted, while the downlink signal transmission of the femto base station is subject to interference. Since there is no special method, it is not easy to obtain information on the interference of the femto base station.

Accordingly, the present invention to be described below proposes an operation mechanism of a femto base station, a macro base station, and a macro cell user equipment for efficiently coordinating interference caused by downlink signal transmission of a femto base station.

In an aspect of the present invention for solving the above problems, in the interference coordination method of the femto base station, by identifying the uplink signal of one or more macrocell user equipment, identification information for the one or more macrocell user equipment Reporting to the macro base station to which the at least one macro cell user device belongs; Receiving, from the macro base station, an interference coordination signal determined by the macro base station based on a measurement result report received from the one or more macro cell user equipments; And adjusting a downlink signal transmitted to one or more femtocell user equipments according to the received interference coordination signal.

In this case, the identification information of one or more macrocell user equipments reported to the macro base station may be used to include the femto base station in a measurement target of one or more macrocell user equipments identified by the identification information.

The reporting of the identification information may include detecting an uplink signal of the at least one macrocell user device; Receiving uplink resource allocation information for macrocell user equipments including the one or more macrocell user equipments from the macro base station; Identifying one or more user equipments from which the uplink signal is detected based on the received uplink resource allocation information; And reporting the identification information on the identified user equipment to the macro base station.

In addition, after the femto base station detects an uplink signal of the at least one macrocell user equipment, the femto base station stores information about the detected uplink signal until receiving uplink resource allocation information from the macro base station. .

The femto base station may transmit and receive a signal through the macro base station and the Internet network.

On the other hand, in another aspect of the present invention for solving the above problems, in the femto base station apparatus configured to perform the interference coordination function, detecting the uplink signal of one or more macrocell user equipment, one or more femtocell user equipment A wireless transceiver configured to transmit and receive an uplink signal and a downlink signal; Report identification information about the one or more macrocell user equipments to a macro base station to which the one or more macrocell user devices belong, and from the macro base station, to a measurement result report received by the macro base station from the one or more macrocell user equipments. An internet transmission / reception module configured to receive an interference coordination signal determined based on the; And a processor configured to adjust a downlink signal transmitted by the wireless transceiver to the one or more femtocell user equipments according to the interference coordination signal received by the macro base transceiver station from the macro base station.

In this case, the identification information of one or more macrocell user equipments reported to the macro base station may be used to include the femto base station in a measurement object of one or more macrocell user equipments identified by the identification information.

The Internet transceiving module may further receive uplink resource allocation information for macrocell user devices including the one or more macrocell user devices from the macro base station, and the processor detects the one detected by the wireless transceiver. The uplink signal of the macro cell user device may be compared with the uplink resource allocation information received by the Internet transmission / reception module to identify one or more user devices from which the uplink signal is detected.

The femto base station is configured to store information on the detected uplink signal until the uplink resource allocation information is received from the macro base station after detecting the uplink signal of the at least one macrocell user equipment. It may further include.

On the other hand, in another aspect of the present invention for solving the above problems, in a method for the macro base station to support the downlink interference coordination of the femto base station, at least one macrocell user belonging to the macro base station from the femto base station Receiving identification information about the device; Transmitting a command to the at least one macrocell user device to add the femto base station to a measurement object of the at least one macrocell user device; Receiving a measurement result report from the at least one macrocell user device; And transmitting, to the femto base station, an interference coordination signal determined based on the measurement result report received from the one or more macro cell user equipments.

In this case, the femto base station provides uplink resource allocation information for the macrocell user equipments including the one or more macrocell user equipments so that the femto base station identifies the one or more macrocell users whose uplink signal is detected by the femto base station. The method may further include transmitting to.

In addition, the interference coordination signal may be for downlink signal transmission transmitted by the femto base station to one or more femtocell user equipment.

On the other hand, in another aspect of the present invention for solving the above problems, in the macro base station supporting the downlink interference coordination of the femto base station, from the femto base station to one or more macro cell user equipment belonging to the macro base station A backhaul interface module configured to receive identification information for the device; A wireless transceiver configured to transmit a command to add the femto base station to a measurement object of the one or more macrocell user equipment, and to receive a measurement result report from the one or more macrocell user equipment; A macro base station including a processor configured to determine an interference coordination signal based on a measurement result report received from the at least one macrocell user device and to transmit the determined interference coordination signal to the femto base station through the backhaul interface module; Suggest.

In this case, the processor may provide uplink resource allocation information for macrocell user devices including the one or more macrocell user devices so that the femto base station identifies the one or more macrocell users for which an uplink signal is detected at the femto base station. The backhaul interface module may be controlled to transmit to the femto base station.

In addition, the interference coordination signal may be for downlink signal transmission transmitted by the femto base station to one or more femtocell user equipment.

On the other hand, in another embodiment of the present invention for solving the above problems, in the method for the user equipment to perform the measurement report for downlink interference coordination of the femto base station, it is specified from the macro base station to which the user equipment belongs; Receiving a command to add a specific femto base station to a measurement object according to a request to a femto base station; Detecting a preamble of the femto base station according to the received command, and performing measurement on a channel on which a downlink signal of the specific femto base station is transmitted; And reporting the performed measurement result to the macro base station.

Lastly, in another aspect of the present invention for solving the above problems, in a user equipment performing measurement report for downlink interference coordination of a femto base station, a specific femto base station from the macro base station to which the user equipment belongs; A transceiver configured to receive a command to add the specific femto base station to a measurement object upon request, and to report a measurement result to the macro base station; And detecting a preamble of the femto base station according to the received command, performing measurements on a channel on which a downlink signal of the specific femto base station is transmitted by using the transceiver, and performing the measured result on the transceiver. A user device including a processor for controlling reporting to the macro base station through the present invention is proposed.

According to the embodiments of the present invention as described above, by controlling the operation of the femto base station, the macro base station and the macro cell user equipment it is possible to efficiently adjust the interference due to the downlink signal transmission of the femto base station.

1 is a configuration diagram of a wireless communication system to which a femto base station is added.
2 illustrates a femtocell architecture proposed by the femto forum.
3 is a diagram for explaining a mechanism in which interference coordination of a femto base station is performed according to an embodiment of the present invention.
4 is a diagram for explaining a mechanism of transmitting a macro UE identifier to a macro base station by a femto base station according to an embodiment of the present invention.
FIG. 5 is a conceptual diagram illustrating a mechanism in which a UE receives channel quality measurement configuration information from a base station and reports a channel quality measurement result in a 3GPP LTE system.
6 shows an example of measurement settings set in a terminal.
FIG. 7 is a diagram illustrating a mechanism in which a macrocell UE reports a measurement result by performing a measurement on a femto base station according to an embodiment of the present invention.
8 is a diagram for explaining a mechanism for coordinating downlink signal transmission by receiving an interference coordination signal from a macro base station according to an embodiment of the present invention.
FIG. 9 is a diagram showing a simulation environment for explaining the effect of the embodiment of the present invention. FIG.
10 is a diagram showing simulation results for explaining the effects of the embodiment of the present invention.
FIG. 11 is a diagram for explaining a mechanism in which a macrocell UE performs a handover to a femtocell and directly delivers an interference control message to a femto base station according to an embodiment of the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description, together with the accompanying drawings, is intended to illustrate exemplary embodiments of the invention and is not intended to represent the only embodiments in which the invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, those skilled in the art will appreciate that the present invention may be practiced without these specific details. For example, the following detailed description will be described in detail on the assumption that the mobile communication system is a 3GPP LTE or IEEE 802.16 based system, but any other mobile communication system except for the unique features of the 3GPP LTE or IEEE 802.16 based system. Applicable to

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

In addition, in the following description, it is assumed that a user equipment (UE) includes a terminal, a mobile station (MS), a personal computer (PC), and the like.

For simplicity of description, a simplified architecture of the femtocell network described above with reference to FIG. 1 will be described.

2 illustrates a femtocell architecture proposed by the femto forum.

In the architecture shown in Figure 2, the femto base station is characterized in that the connection to the backbone network (backbone network) using a wired Internet network installed in the house, such as xDSL or cable modem. Therefore, the carrier that deployed the femtocell has the advantage of not having to pay for the backbone network. However, because of the private Internet network, it may be more exposed to the threat of data security and it may be difficult to guarantee QoS. In addition, femto base stations are more difficult to centrally manage than macro base stations that use traditional private networks.

In order to overcome such disadvantages of femtocells, it is assumed that a system operator has a femto gateway (FGW) and a femto management system (FMS). This FGW may be considered to perform all or part of the functionality of the ASN 140 and CSN 150 in the network shown in FIG. 1 and the FNG 130 in the network shown in FIG. That is, the FMS is responsible for managing control data sent between or between femto base stations, and the FGW considers using IPSec between the femto base station and the FGW for security. Such FGWs and FMSs may be installed in one device by functional separation. Since the communication with the femto base station through the FGW / FMS is through a commercial Internet network, it may be difficult to control a few msec units like the existing macro base station. However, even data communication using a commercial network is expected to be able to transmit control data in a few seconds.

In the femtocell network as described above, the interference problem is expected to be more severe than the existing environment. This is because the spacing between the base stations is narrowed due to the appearance of small cells, the position of the femto base stations to be installed based on the user base cannot be controlled, and there is no explicit communication line between the femto base stations.

In an embodiment of the present invention, the femto base station requests the macro base station to include itself in the channel measurement object of the macro cell UE through signal detection of the macro cell UE, whereby the macro base station is received from the macro cell UE. We propose a mechanism for coordination of femto base stations through measurement reports.

3 is a diagram for explaining a mechanism in which interference coordination of a femto base station is performed according to an embodiment of the present invention.

3 illustrates a femto base station 310, a femtocell UE 340 provided with a service from a femto base station, a macrocell UE 330 capable of receiving interference due to a downlink signal of the femto base station 310, and the macrocell UE ( A macro base station 320 that provides a service to 330 is shown. In FIG. 3, only one macrocell UE 330 and one femtocell UE 340 are illustrated for convenience of description, but a plurality of UEs may be included in the macro base station 320 and the femto base station 310.

The femto base station according to the present embodiment detects an uplink signal of at least one macrocell UE 330 which is located geographically close and may be interfered with by its downlink signal (S301), and at least one macro identified through Identification information regarding the cell UE 330 may be reported to the macro base station 320 to which the corresponding macro cell UE 330 belongs (S302). A detailed method of identifying the identification information of the macro UE 330 by the femto base station 310 will be described later in detail with reference to FIG. 4.

Meanwhile, the macro base station 320 that has received identification information about one or more macro cell UEs 330 belonging to the macro base station 320 from the femto base station 310, the corresponding UE (s) to the corresponding UE (s) 330. The command to add the femto base station 310 to the measurement target of the may be transmitted (S303). Accordingly, the macro UE 330 may perform the measurement on the channel through which the downlink signal of the femto base station 310 is transmitted (S304), and report the measurement result based on this to the macro base station 320 (S305). The measurement target addition command of the macro base station 320 and the measurement report of the macro UE 330 will be described later with reference to FIGS. 5 to 7.

The macro base station 320 receiving the measurement report including the measurement result for the channel through which the downlink signal of the femto base station 310 is transmitted from the macro UE 330 transmits the downlink signal of the femto base station 310 based on the measurement report. The interference coordination signal for may be transmitted to the femto base station 310 (S306). Upon receiving the interference coordination signal, the femto base station 310 coordinates downlink signal transmission to the femto UE 340 (S307).

Through the above-described mechanism, the femto base station 310 may include the measurement for itself in the measurement operation of the macro UE 330 to obtain interference information and perform interference coordination.

4 is a diagram for explaining a mechanism of transmitting a macro UE identifier to a macro base station by a femto base station according to an embodiment of the present invention.

The femto base station 310 may be disposed as an overlay in the macro base station 320 area, and when the femto base station 310 is installed, the femto base station 310 may undergo a process of exchanging basic configuration information with the macro base station 320 (S410).

According to an embodiment of the present invention as described above, in order for the femto base station 310 to obtain identification information of the macro cell UE, the femto base station 310 may first detect an uplink signal of the macro UE (S420). The macro cell UE in which the uplink signal is detected by the macro base station 310 may be viewed as a macro cell UE located in close proximity to the femto base station 310, and accordingly, the downlink signal transmission of the femto base station 310 is transmitted. This may mean a macro cell UE that may receive interference.

However, only the uplink signal detection of the macrocell UE makes it difficult for the femto base station 310 to obtain an identifier of the macrocell UE specifying the macrocell UE. Accordingly, the femto base station 310 according to the present embodiment may receive uplink scheduling information (or uplink resource map) transmitted by the macro base station 320 to obtain an identifier of the macro cell UE where the uplink signal is detected. It may be (S430). In general, the uplink scheduling information transmitted by the macro base station 320 includes resource allocation information for uplink signal transmission of the macro cell UE together with information for specifying the macro cell UE. Therefore, the femto base station 310 according to the present embodiment may identify the macro cell UE from which the uplink signal is detected (S420) through the uplink resource map information received from the macro base station 320 (S440).

In this case, since the uplink resource map transmitted from the macro base station 320 to the femto base station 310 is transmitted through the backhaul network, it can be seen that a relatively large transmission delay occurs. Accordingly, when the femto base station 310 according to the preferred embodiment of the present invention receives the uplink resource map from the macro base station 320 with uplink signal information detected for post detection of the macro cell UE, the femto base station 310 receives the uplink resource map. It is desirable to have a means (e.g. a memory) for storing until.

As described above, the femto base station 310 receiving the uplink resource map from the macro base station 320 and obtaining the identification information of the macro cell UE may report the identification information to the macro base station 320 (S450). That is, the femto base station 310 according to the present embodiment provides the macro base station 320 with identification information on the macro cell UE, which may interfere with its downlink signal transmission, so that the macro base station 320 can access the macro base station 320. It is proposed to be able to obtain the interference information due to the femto base station 310 from the cell UE.

Specifically, in the 3GPP LTE system or the IEEE 802 series system, the UE performs channel quality measurement periodically or according to a specific event for mobility support of the UE, and supports a mechanism for reporting the result to the (macro) base station. According to one embodiment of the present invention, as described above in the measurement mechanism, a method of securing interference information of a femto base station by using the macro UE identification information reported to the macro base station by the femto base station is proposed. To this end, a brief description of the measurement mechanism, for example in the 3GPP LTE system.

FIG. 5 is a conceptual diagram illustrating a mechanism in which a UE receives channel quality measurement configuration information from a base station and reports a channel quality measurement result in a 3GPP LTE system.

First, the terminal may receive measurement configuration information from the base station (S710). Hereinafter, a message including such measurement setting information is called a measurement setting message. The terminal may perform measurement based on the measurement setting information (S720). If the measurement result satisfies the reporting condition in the measurement configuration information, the terminal may report the measurement result to the base station (S730). Hereinafter, a message including a measurement result is called a measurement report message.

Meanwhile, the measurement configuration message received from the base station in the 3GPP LTE system may have a structure as follows.

The measurement setting information in the measurement setting message illustrated in Table 1 will be described below.

(1) Measurement object information: Information about an object to be measured by the terminal. The measurement target includes at least one of an intra-frequency measurement target for intra-cell measurement, an inter-frequency measurement target for inter-cell measurement, and an inter-RAT measurement target for inter-RAT measurement. For example, the intra-frequency measurement object indicates a neighboring cell having the same frequency band as the serving cell, the inter-frequency measurement object indicates a neighboring cell having a different frequency band from the serving cell, and the inter-RAT measurement object is The RAT of the serving cell may indicate a neighboring cell of another RAT.

(2) Reporting configuration information: Information on a reporting condition and a report type relating to when a terminal reports a measurement result. The reporting condition may include information about an event or a period at which the reporting of the measurement result is triggered. The report type is information on what type of measurement results are to be constructed.

(3) Measurement identity information: This is information about a measurement identifier that associates a measurement object with a report configuration, and allows the terminal to determine what type and when to report to which measurement object. The measurement identifier information may be included in the measurement report message to indicate which measurement object the measurement result is and in which reporting condition the measurement report occurs.

(4) Quantitative configuration information: information on a parameter for setting filtering of a measurement unit, a reporting unit, and / or a measurement result value.

(5) Measurement gap information: Information about a measurement gap, which is a section in which a UE can only use measurement without considering data transmission with a serving cell because downlink transmission or uplink transmission is not scheduled. .

The terminal may have a measurement target list, a measurement report configuration list, and a measurement identifier list to perform a measurement procedure.

In 3GPP LTE, the base station may set only one measurement target for one frequency band to the terminal. According to section 5.5.4 of 3GPP TS 36.331 V8.5.0 (2009-03) "Evolved Universal Terrestrial Radio Access (E-UTRA) Radio Resource Control (RRC); Protocol specification (Release 8)", The events that trigger the event are defined.

If the measurement result of the terminal satisfies the event (channel quality measurement report criteria) set as described above, the terminal transmits a measurement report message to the base station.

6 shows an example of measurement settings set in a terminal.

In the example of FIG. 6, first, measurement identifier 1 connects an intra-frequency measurement object and report configuration 1. In this case, the terminal performs intra frequency measurement, and report setting 1 is used to determine a criterion and report type of the measurement result report.

The measurement identifier 2 is connected to the intra-frequency measurement object like the measurement identifier 1, but is connected to the setting 2 by viewing the intra-frequency measurement object. The terminal performs intra-frequency measurement, and report configuration 2 is used to determine a criterion and report type of the measurement result report.

By the measurement identifier 1 and the measurement identifier 2, the terminal may transmit the measurement result to the network even if the measurement result for the intra-frequency measurement object satisfies any one of the report configuration 1 and the report configuration 2.

Measurement identifier 3 connects inter-frequency measurement object 1 and reporting configuration 3. The terminal may report the measurement result to the network when the measurement result for the inter-frequency measurement object 1 satisfies the reporting condition included in the report configuration 1.

Measurement identifier 4 connects inter-frequency measurement object 2 and reporting configuration 2. The terminal may report the measurement result to the network when the measurement result for the inter-frequency measurement object 2 satisfies the reporting condition included in the report configuration 2.

On the other hand, the measurement object, the report setting and / or the measurement identifier can be added, changed and / or deleted. This can be indicated by the base station sending a new measurement setup message to the terminal or by sending a measurement setup change message.

FIG. 7 is a diagram illustrating a mechanism in which a macrocell UE reports a measurement result by performing a measurement on a femto base station according to an embodiment of the present invention.

As described above with reference to FIG. 4, the macro base station 320 that has received the identification information of the macro cell UE from the femto base station 310 sends the femto to the corresponding macro cell UE 330 to the measurement target of the macro cell UE 330. A command for adding the base station 310 may be transmitted to the macrocell UE 330 (S710). In the present embodiment, the femto base station 310 which requests the macro base station 320 to be added as a measurement target of a specific macro cell UE 330 may be plural, which is the first femto base station 310-1 and the second femto base station. (310-2).

Specifically, referring to the example of the 3GPP LTE system, the macro base station 320 is a macro cell to the measurement setup message for adding femto base stations (310-1, 310-2) to the measurement target of the macro UE (330) The information may be transmitted to the UE 330, and this information may be included in a field shown in Table 3 below in the message structure of Table 1 and transmitted.

In Table 3, "measObjectToAddModList" may indicate a list of objects to be added as measurement objects, and "Optional" indicates that this field is not an essential field in the measurement configuration message. "ON" in "Need ON" is an abbreviation of "optionally No-action". If the corresponding field value is empty, it means that no action is required. That is, in the present embodiment, when the macro base station is requested to add itself to the measurement target of a specific macro cell UE from the femto base station, the macro base station may add the requested femto base station to this field and transmit it to the corresponding macro cell UE. This field value can be omitted and transmitted.

As such, the macro cell UE 330 to which the femto base stations 310-1 and 310-2 are added to the measurement target detects signals of the femto base stations 310-1 and 310-2 (S820 and S840). Through this, measurement may be performed on a channel through which downlink signals of the femto base stations 310-1 and 310-2 are transmitted (S830 and S850). The 3GPP LTE system may use the signature of the preamble of each of the femto base stations 310-1 and 310-2 to detect the signal of the femto base stations 310-1 and 310-2 by the macrocell UE 330. For example, although a cell identifier included in a reference signal of each of the femto base stations 310-1 and 310-2 may be used, a specific method may vary depending on a system to be implemented.

Meanwhile, as described above, the macro cell UE 330 having performed the channel measurement may report the measurement result to the macro base station 320 (S860). The measurement result report of the macrocell UE 330 may be periodically performed or may be performed according to a specific event. For example, in the 3GPP LTE system, measurement report events defined as shown in Table 2 above are mainly focused on the case in which the serving cell quality is degraded to support mobility of the UE. As in the present embodiment, the femto base station 310 is implemented. It may not be appropriate as an event for interference coordination of -1, 310-2. Therefore, in a preferred embodiment of the present invention, measurement report events as shown in Table 4 below may be further defined.

In Table 4, the event F1 stipulates performing a measurement report when the interference from a specific femto base station exceeds a predetermined threshold. Through this, if the interference caused by the femto base station is above a certain level, it can be reported to the macro base station so that the femto base station can perform interference coordination.

In Table 4, the event F2 defines that the measurement report is performed when the channel quality of the serving macro base station is worse than that of the femto base station. If the channel quality of the macro base station is worse than the femto base station, the macro cell UE may operate as a femtocell UE by performing a handover to the femto base station. This will be described later as another embodiment of the present invention.

8 is a diagram for explaining a mechanism for coordinating downlink signal transmission by receiving an interference coordination signal from a macro base station according to an embodiment of the present invention.

As described above with reference to FIG. 7, the macrocell base station that has received the measurement result report from the macrocell UE may transmit an interference coordination signal to the femto base station 310 in consideration of this (S910). If, for example, a network that prioritizes maximizing the sum of the throughputs, the interference information obtained as described above may be utilized using constraints of the following optimization formula (Equation 1).

Equation 1 represents an example in which all femto base stations are set to have an objective function to maximize the sum of Shannon capacities that can be achieved. Where i represents the index of the femtocell and U represents the set of all femtocells. The p and f vectors represent the transmission power and the operating frequency selected by all femto base stations, respectively, and the gamma function represents the Signal to Interference plus Noise Ratio (SINR) function that can be achieved by the femto base station i given p and f . Indicates.

The constraint means that the difference between the SINRs of all macrocell UEs, that is, the eta function does not exceed the eta threshold. Where j is the index of the macrocell UE and U _m represents the set of all macrocell UEs.

However, in the present invention, the interference coordination due to the transmission of the downlink signal of the femto base station may be utilized in various conventional techniques, and as long as it utilizes the interference information of the femto base station obtained through the above-described mechanism, the specific interference coordination criteria may be applied. There is no need to be limited.

As described above, the femto base station 310 receiving the interference coordination signal from the macro base station 320 follows the received interference coordination signal in transmitting the downlink signal to the femtocell UE 340 belonging thereto (S920).

9 is a diagram illustrating a simulation environment for explaining the effects of the embodiment of the present invention.

In this embodiment, consider an environment in which a 50 m × 50 m square three story building is located at the macrocell (0, 200 m) location. Four femto base stations, 5 m and 25 m away from the wall, were installed on each floor, and a 15 m distance around the building was considered for outage measurements. It is assumed that the macrocell is divided into three sectors, and each sector uses a different frequency channel. In this environment, the location of the simulation shows that the macrocell UEs communicate with the macrocell on two frequency channels. It is assumed that the macro base station uses a transmission power of up to 20 W, and the femtocell uses a transmission power of up to 100 mW.

10 is a diagram showing simulation results for explaining the effects of the embodiment of the present invention.

In FIG. 10, four CDFs of SINR values measured inside the building and (Indoor xxx) and four CDFs of SINR measured outside the building are plotted (outdoor xxx). First, when nothing is installed, the SINR inside and outside the building can be seen by looking at the lines "Indoor w / o femto BS" and "outdoor w / o femto BS", respectively. And the optimized result in this environment is "indoor opt." And "ourdoor opt". At this time, the SINR reduction of the macro users was proposed and experimented with 1 dB. As can be seen from the graph, it can be seen that the SINR reduction of all users is within 1 dB.

In comparison with this, the results of randomly setting the transmission power and frequency of the femto base stations without any constraints can be seen from "indoor random" and "outdoor random". It can be seen that SINRs of macrocell UEs have dropped by a large difference compared with when no femto base station is installed. On the other hand, when the algorithm is performed based on Equation 1 in consideration of the SINR reduction of the macro cell UEs, "indoor Tabu." As can be seen from the results of " outdoor Tabu. &Quot;, it can be seen that the SINR reduction constraint of the macrocell UEs is satisfied while showing a result close to the optimum value.

Meanwhile, in another embodiment of the present invention, the femto base station provides the macro base station with identification information on the macro cell UE that may be interfered by its downlink signal transmission, but performs measurement of the macro cell UE. As a result, we propose a mechanism for performing handover to a femto base station.

FIG. 11 is a diagram for explaining a mechanism in which a macrocell UE performs a handover to a femtocell and directly delivers an interference control message to a femto base station according to an embodiment of the present invention.

In the embodiment shown in FIG. 11, the processes from steps S1001 to S1003 are performed in the same manner as the processes from steps S301 to S303 in the embodiment described above with reference to FIG. 3. That is, the femto base station 310 transmits identification information of the macro cell UE 330 to the macro base station 320 through the uplink signal detection of the macro cell UE 330 (S1001) (S1002), and the macro base station 320 ) May transmit a message for adding the femto base station 310 to the measurement target of the macrocell UE 330 that has received the identification information (S1003).

However, in the present embodiment, when the macrocell UE 330 performs channel measurement on the femto base station 310, when the channel of the femto base station 310 is better than the channel state of the expected level, that is, interference is expected. If it is determined as above, it is proposed to directly transmit the interference restriction message by performing network entry into the femtocell (S1004). In order to support such a mechanism, the macrocell base station 320 may designate the event F2 described above with reference to Table 3 or an equivalent event thereof as a measurement result report event in the message (measurement setting message) transmitted in step S1003. If the measurement result reporting event is satisfied (not shown), the macrocell UE 330 may be instructed to move to the femtocell.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable any person skilled in the art to make and practice the invention. While the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will understand that various modifications and changes can be made without departing from the scope of the present invention. For example, those skilled in the art can use each configuration described in the above embodiments in a manner that combines with each other.

Accordingly, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Embodiments of the present invention as described above may be applied to various wireless communication systems using a femto base station. The above description focuses on an example of a 3GPP LTE series system, but may be equally applicable to other mobile communication systems using a femto base station such as an IEEE 802 series system.

Claims (17)

In the interference coordination method of a femto base station,
Reporting identification information of the one or more macrocell user equipments to a macro base station to which the one or more macrocell user equipments belong, by detecting uplink signals of one or more macrocell user equipments;
Receiving, from the macro base station, an interference coordination signal determined by the macro base station based on a measurement result report received from the one or more macro cell user equipments; And
Adjusting a downlink signal transmitted to at least one femtocell user equipment according to the received interference coordination signal. The method of claim 1,
Identification information for one or more macrocell user equipments reported to the macro base station is used to include the femto base station in a measurement object of one or more macrocell user equipments identified by the identification information. Way. 3. The method according to claim 1 or 2,
The identification information reporting step,
Detecting an uplink signal of the one or more macrocell user equipments;
Receiving uplink resource allocation information for macrocell user equipments including the one or more macrocell user equipments from the macro base station;
Identifying one or more user equipments from which the uplink signal is detected based on the received uplink resource allocation information; And
Reporting the identification information for the identified user equipment to the macro base station. The method of claim 3, wherein
The femto base station detects an uplink signal of the at least one macrocell user equipment, and then stores information on the detected uplink signal until receiving uplink resource allocation information from the macro base station. Adjustment method. The method of claim 4, wherein
The femto base station transmits and receives a signal to and from the macro base station via the Internet network, interference coordination method of the femto base station. A femto base station configured to perform an interference coordination function,
A wireless transceiver configured to detect an uplink signal of at least one macrocell user device and to transmit and receive an uplink signal and a downlink signal with at least one femtocell user device;
Report identification information about the one or more macrocell user equipments to a macro base station to which the one or more macrocell user devices belong, and from the macro base station, to a measurement result report received by the macro base station from the one or more macrocell user equipments. An internet transmission / reception module configured to receive an interference coordination signal determined based on the; And
And a processor configured to adjust a downlink signal transmitted by the wireless transceiver to the at least one femtocell user device in accordance with an interference coordination signal received by the Internet base transceiver module from the macro base station. The method according to claim 6,
Identification information for one or more macrocell user equipments reported to the macro base station is used to include the femto base station in a measurement object of one or more macrocell user equipments identified by the identification information. The method according to claim 6 or 7,
The Internet transceiving module further receives uplink resource allocation information for macrocell user devices including the one or more macrocell user devices from the macro base station.
The processor compares an uplink signal of the at least one macrocell user device detected by the wireless transceiver with the uplink resource allocation information received by the internet transceiver module, and determines at least one user device from which the uplink signal is detected. Configured to identify the femto base station. The method of claim 8,
After the femto base station detects an uplink signal of the at least one macro cell user equipment, the femto base station additionally includes a memory configured to store information on the detected uplink signal until receiving uplink resource allocation information from the macro base station. Including, femto base station. In the macro base station to support the downlink interference coordination of the femto base station,
Receiving identification information about one or more macrocell user equipments belonging to the macro base station from the femto base station;
Transmitting a command to the at least one macrocell user device to add the femto base station to a measurement object of the at least one macrocell user device;
Receiving a measurement result report from the at least one macrocell user device; And
And transmitting to the femto base station an interference coordination signal determined based on a measurement result report received from the one or more macro cell user equipments. 11. The method of claim 10,
Transmitting uplink resource allocation information for macrocell user devices including the one or more macrocell user devices to the femto base station so that the femto base station identifies the one or more macrocell users for which an uplink signal is detected at the femto base station. Further comprising the step of, interference coordination support method of the macro base station. 11. The method of claim 10,
And the interference coordination signal is for downlink signal transmission transmitted by the femto base station to one or more femtocell user equipments. A macro base station supporting downlink interference coordination of a femto base station,
A backhaul interface module configured to receive identification information about one or more macrocell user equipments belonging to the macro base station from the femto base station;
A wireless transceiver configured to transmit a command to add the femto base station to a measurement object of the one or more macrocell user equipment, and to receive a measurement result report from the one or more macrocell user equipment;
And a processor for determining an interference coordination signal based on a measurement result report received from the at least one macrocell user device, and controlling the interference coordination signal to be transmitted to the femto base station via the backhaul interface module. . The method of claim 13,
The processor is configured to backlink uplink resource allocation information for macrocell user devices including the one or more macrocell user devices so that the femto base station identifies the one or more macrocell users for which an uplink signal is detected at the femto base station. And transmit to the femto base station via an interface module. The method of claim 13,
Wherein the interference coordination signal is for downlink signal transmission transmitted by the femto base station to one or more femtocell user equipment. A method for performing measurement report by a user equipment for downlink interference coordination of a femto base station,
Receiving a command from a macro base station to which the user equipment belongs to add a specific femto base station to a measurement object according to a request from a specific femto base station;
Detecting a preamble of the femto base station according to the received command, and performing measurement on a channel on which a downlink signal of the specific femto base station is transmitted; And
Reporting the performed measurement result to the macro base station. A user equipment for performing measurement report for downlink interference coordination of a femto base station,
A transceiver configured to receive a command to add a specific femto base station to a measurement object from a macro base station to which the user equipment belongs to a specific femto base station, and to report a measurement result to the macro base station; And
The preamble of the femto base station is detected according to the received command, the transceiver performs the measurement on the channel through which the downlink signal of the specific femto base station is transmitted, and the measurement result is transmitted through the transceiver. And a processor for controlling reporting to the macro base station.

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