KR101498065B1 - METHOD OF ESTIMATING THE NUMBER OF ANTENA USED IN NEIGHBOR CELL PERFORMING CoMP OPERATION - Google Patents

Abstract

A method for estimating the number of antennas of a neighboring cell performing Coordinated Multi-Point (CoMP) operation is disclosed. In the first reference signal reception power measurement step, the UE receives the reference signal of the first antenna for each neighboring cell performing the CoMP operation and measures the first reference signal received power (RSRP). In the reference signal reception power comparison step, the UE compares at least one additional reference signal reception power of the reference signal of one or more additional antennas with the first reference signal reception power for each neighbor cell performing CoMP operation. In the step of estimating whether a signal of each neighboring cell is transmitted through the additional antenna, the comparison result indicates that the difference between the first reference signal and the first reference signal is smaller than a predetermined threshold, It is assumed that the signal of each neighboring cell is transmitted.

Handover, LTE, Antenna count

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of estimating the number of antennas used by a neighboring cell that performs a CoMP operation,

The present invention relates to a method for estimating the number of antennas, and more particularly, to a method for estimating the number of antennas of a neighboring cell performing a CoMP operation.

Recently, a standardization work for the development of 3GPP LTE-A (3rd Generation Partnership Project Long Term Evolution-Advanced: LTE-A) system is actively underway, and a 3GPP LTE (Third Generation Partnership Project Long Term Evolution (Hereinafter referred to as " LTE "), the initial LTE terminal and the base station have already been developed.

Mobility is one of the most important characteristics in all wireless communication systems currently under development as well as LTE systems. That is, as the terminal moves, the channel characteristics change, which may cause communication problems. In order to solve this problem, the UE continuously monitors the cell neighboring the current cell and measures the channel quality characteristics between the UE and the cell, and can change a cell that is effectively served according to the measurement result.

1 is a diagram illustrating a case where a mobile station moves to a coverage of a neighboring cell.

Referring to FIG. 1, if the UE is communicating with the cell A at time T1 but moves to the coverage of the cell B after the cell A is covered due to movement of the UE at time T2, It becomes difficult to communicate. At this time, if the terminal disconnects the communication channel with the existing cell A and the communication channel with the cell B is connected, reliable communication will be possible. This process is called cell reselection if the UE is in the RRC_Idle (Radio Resource Control_Idle) state to check system information and paging information while performing a low power consumption operation , Or otherwise handover if the UE is in a call or in a radio resource control-connected (RRC_connected: Radio Resource Control_connected) state in which data communication is in progress.

In order to perform the cell reselection or the handover, the UE continuously measures and monitors the channel quality status of a cell to which the UE itself belongs and a neighbor cell located around the cell with a specific period according to the current state desirable.

In a wideband code division multiple access (W-CDMA) system, a UE knows neighboring cell information such as the number of antennas for neighboring cells. However, in the LTE system, information on neighboring cells is not an essential matter but is an optional matter. Accordingly, in the system overhead, many systems do not separately signal information on the number of antennas of neighboring cells In the LTE system, the UE knows the structure of the downlink pilot according to the number of transmit antennas of the cell. However, in the LTE system, the UE knows the structure of the downlink pilot according to the number of transmit antennas of the cell. However, May not know the information.

Also, since all the cells in the LTE system have at least one antenna, conventionally, the channel quality is measured using only the pilot signal power value for the first antenna. However, when only the pilot signal power value for the first antenna is used, there is a problem that the channel quality measurement in the cells having two or four transmission antennas is inaccurate.

In addition, the LTE system specifies the parameter "sameRefSignalsInNeighbor". This parameter is a parameter that informs the UE whether or not neighboring cells have the same pilot signal structure as the current cell. For example, '0' indicates that the number of antennas of neighboring cells is equal to the number of antennas of the current cell. If the number of antennas of neighboring cells is' 1 ', the number of antennas of neighboring cells is' Which is different from the number of antennas of the cell to which it belongs. However, there is a problem that the " sameRefSignalsInNeighbor " parameter can only tell whether a plurality of neighboring cells all have the same antenna structure. In addition, under the environment where the channel quality status is continuously monitored up to thirty-two cells from the terminal's point of view, expanding the bits of the " sameRefSignalsInNeighbor " parameter has a limitation in accurately grasping the number of transmit antennas. As described above, in the LTE system, a method for measuring the channel quality by accurately grasping the number of transmission antennas and the like of neighboring cells by the UE has not been defined so far.

Coordinated Multi-Point (CoMP) system is a system for improving the throughput and communication performance of users at the cell edge by applying cooperative MIMO transmission in a multi-cell environment. When the CoMP system is used, the UE has an advantage of being able to receive data jointly from a multi-cell base station. However, a method for measuring the channel state by measuring the number of transmission antennas of neighboring cells performing CoMP operation has not been proposed so far.

SUMMARY OF THE INVENTION The present invention provides a method of estimating an antenna structure of a neighboring cell that performs a CoMP operation in a wireless communication system.

According to another aspect of the present invention, there is provided a method of estimating the number of antennas used by neighboring cells for CoMP operation, the method including receiving a reference signal of a first antenna for each neighboring cell, Measuring a first reference signal received power (RSRP); Comparing at least one additional reference signal received power for a reference signal of one or more additional antennas for each neighbor cell performing CoMP operation with the first reference signal received power; And estimating that the signal of each neighboring cell is transmitted through the antenna corresponding to the power of the additional reference signal, the difference between the first reference signal power and the first reference signal reception power being smaller than the predetermined threshold value.

Preferably, the method further includes the step of measuring the number of antennas of each neighboring cell through which the signal is transmitted via the antenna corresponding to the additional reference signal receiving power.

Preferably, the UE further includes a step of acquiring sequence information that each cell uses to transmit a reference signal through a synchronization channel of each cell that performs a CoMP operation.

Preferably, the step of measuring the channel quality of the cell based on the channel quality of each antenna corresponding to the estimated number of antennas of the neighboring cell in which the terminal performs the CoMP operation; And comparing the channel quality of the cell to which the terminal belongs with the channel quality of the measured neighboring cell to reselect the cell or transmit a message to the base station that the handover is required.

At this time, the channel quality state of each neighboring cell performing the CoMP operation is preferably measured by averaging or weighted average of channel quality values of each antenna.

Also, it is preferable that the UE measures the reference signal reception power using the reference signal reception power accumulated for a predetermined time for each antenna of the neighboring cell performing the CoMP operation.

According to the method of estimating the number of antennas according to the present invention, each terminal can effectively estimate the number of antennas of each cell.

Also, according to the present invention, the channel quality of each cell can be accurately measured according to the estimated number of antennas, and the mobile terminal can effectively perform cell reselection or handover.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. The detailed description set forth below in conjunction with the appended 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 incorporates specific details to facilitate a complete 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, in the following description, certain terms are mainly described, but they need not be limited to these terms, and they may have the same meaning when they are referred to as arbitrary terms. Further, the same or similar elements throughout the present specification will be described using the same reference numerals.

The techniques described below may be used in various communication systems, which may provide various communication services such as voice, packet data, and so on. The technology of the communication system can be used for a downlink or an uplink. A base station may be replaced with terms such as a fixed station, a Node B, an eNode B (eNB), an access point, and the like. Also, a mobile station (MS) can be replaced with terms such as a user equipment (UE), a subscriber station (SS), a mobile subscriber station (MSS), or a mobile terminal.

Also, the transmitting end refers to a node that transmits data or voice service, and the receiving end refers to a node that receives data or voice service. Therefore, in the uplink, the terminal may be the transmitting end and the base station may be the receiving end. Similarly, in the downlink, the terminal may be the receiving end and the base station may be the transmitting end.

The terminal of the present invention may be a PDA (Personal Digital Assistant), a cellular phone, a PCS (Personal Communication Service) phone, a GSM (Global System for Mobile) phone, a WCDMA (Wideband CDMA) Can be used.

Hereinafter, a method for effectively estimating the number of antennas of each neighboring cell in which the UE performs CoMP will be described.

The Coordinated Multi-Point (CoMP) system is a system for improving the throughput of a user at a cell boundary by applying improved MIMO transmission in a multi-cell environment. The CoMP system can reduce inter-cell interference in a multi-cell environment. Also, with the CoMP system, the UE can receive data jointly from a multi-cell base station. In addition, each base station can simultaneously support one or more MSs MS1, MS2,... MSK using the same radio frequency resource, thereby improving the performance of the system.

Under such CoMP environment, as the UE moves, the channel quality between the UE and the cell may be changed. That is, at a specific point in time, a cell having a channel quality better than the channel quality with the cell to which the terminal is currently belonging to the terminal may appear. If a cell having a channel quality that is better than the channel quality with the cell to which the terminal belongs for a certain period of time appears, the terminal will communicate with a cell having an excellent channel quality. In order to perform cell reselection or handover, the UE can continuously measure and monitor the channel quality state of a neighboring cell located near the current cell and the current cell.

In the LTE system, the UE can measure the channel quality state between the UE itself and the cell using a reference signal received power (RSRP) corresponding to the power of the pilot signal. Here, the reference signal reception power refers to a linear average of the power allocated to the resource element to which the cell-specific reference signal is allocated within the considered measurement frequency bandwidth. The power of each resource element on the resource block may be determined from the energy received from the effective interval of the symbol except for the cyclic prefix (CP). The reference signal reception power can be applied to the UE in both the RRC_idle state and the RRC_connected state. Also, when receiver diversity is used by the terminal, the reported value will be equal to the linear average of the power values of all diversity branches.

The terminal can measure the reference signal reception power of the cell by accumulating the pilot signal transmitted by each cell for a predetermined time and a corresponding bandwidth. In an environment where a cell to which the UE belongs and a neighbor cell exist, the UE can measure the RSRP for each neighboring cell according to the information provided by the BS.

A procedure for cell reselection in an RRC_idle situation in a terminal in an LTE system. When a terminal receives a list of neighbor cells to be monitored from a base station, the terminal measures and reports the channel quality of all cells included in the list in a predetermined period . If there is no list of neighboring cells to be monitored from the base station, the terminal may transmit an intra base station neighbor cell (intra frequency neighbor cell), an inter base station neighbor cell (E.g., an inter frequency neighbor cell), an inter RAT neighbor cell using another system, and can only measure the channel quality of a cell, and only when an event related to cell reselection occurs, . If the list does not come down from the base station, the cell to which the terminal belongs can transmit information on the carrier frequency and system to the neighboring cell to the terminal.

In the above-mentioned cell reselection or handover situation, the UE can observe the neighboring cell when the quality of the channel is greater than or equal to the specific threshold value, and observe the neighboring cell when the channel quality deteriorates and is equal to or less than the threshold.

The UE can perform a handover operation similar to the cell reselection process in the RRC_connected state. Similar to cell reselection, the channel quality of a neighboring cell can be observed above a threshold value. The UE can report the fact to the network if the channel quality of the cell to which the UE belongs and the neighboring cell are measured and the event for the handover is satisfied when they are compared with each other. If it is determined that handover is required, the network transmits a radio link setup message to the UE, which is an acknowledgment message for receiving a service from the neighboring cell. The UE replaces the cell that receives the current service with a neighbor cell according to the message, (E.g., a base station) by transmitting a radio link establishment completion message to the base station (e. G., A base station). The Evolved-Unversal Terrestrial Radio Access Network (E-UTRAN) provides measurement configuration information applicable to the UE in the RRC_Connected state through a dedicated channel using a message such as " RRCConnectionReconfiguration ". The terminal may report information consistent with the measurement configuration information provided by the E-UTRAN.

Hereinafter, a process of acquiring sequence information used for pilot signal transmission from a neighboring cell in which a mobile station performs a CoMP operation will be described.

2 is a diagram illustrating an example of a downlink frame structure of a Frequency Division Duplex (FDD) type in an LTE system.

Referring to FIG. 2, one downlink radio frame may be composed of 10 subframes. That is, 10 subframes may be used for downlink transmission. One subframe may be composed of two slots. One slot may include six or seven Orthogonal Frequency Division Multiplexing (OFDM) symbols. Specifically, in the case of a structure using a normal cyclic prefix (Normal CP), one slot may include 7 OFDM symbols, and in the case of an extended cyclic prefix (Extended CP) structure, OFDM symbols.

A Primary-Synchronization CHannel (P-SCH) and a Second-Synchronization CHannel (S-SCH) are respectively allocated to the first slot of the first subframe and the first slot of the fifth subframe Lt; / RTI > slots. The main synchronization signal may be mapped to the last OFDM symbol of the first slot and the tenth slot. The sub-sync signal may be mapped to a symbol immediately before the symbol to which the main synchronization signal is mapped in the first slot and the tenth slot.

In the LTE system, the UE may not know the information of the neighboring cell performing the CoMP operation. However, the terminal can receive cell ID set information including neighbor cell ID information from the base station. A UE can identify which cell is a neighbor cell through a cell ID set and a synchronization channel of cells.

There are 504 Physical Cell Identity (PCI) in the LTE system. This physical cell ID is divided into 168 cell ID groups, and each cell ID group has three cell IDs. This can be expressed by the following equation (1).

는 물리 셀 ID 개수를 나타내고,

은 물리 셀 ID 그룹의 개수를 나타내고,

는 물리 셀 그룹 ID 내의 셀 ID의 개수를 나타낸다.here,

Represents the number of physical cell IDs,

Represents the number of physical cell ID groups,

Represents the number of cell IDs in the physical cell group ID.

The UE can obtain three cell ID information in the cell ID group through the main synchronization channel of the cells and obtain 168 cell ID group information through the sub synchronization channel. Based on the cell ID information on the synchronization channel of the cell, the UE can determine whether each cell is a neighbor cell. Also, the UE can receive a reference signal for each neighbor cell through the cell group ID. That is, the UE can acquire the sequence information used by the neighboring cells for the pilot signal transmission from the synchronization channel of each neighboring cell. If the UE determines that it is a neighbor cell, it can continuously monitor the channel quality status.

은 다음 수학식 2에 따라 주파수 영역에서 자도프-츄(Zadoff-Chu) 시퀀스로부터 생성될 수 있다.At this time, a sequence used as a main synchronization channel signal of each neighboring cell

Can be generated from the Zadoff-Chu sequence in the frequency domain according to the following equation (2).

Here, the Zadoff-Chu root sequence index u can be given as shown in Table 1 below.

Root Index u 0 25 One 29 2 34

Table 1 shows root indexes for a primary synchronization signal (PSS), and a sequence for a main synchronization signal may be generated according to the root index of Table 1. [

는 2개의 31 길이 바이너리 시퀀스(two length-31 binary sequences)의 인터리빙된 연관(interleaved concatenation)이다. 연관 시퀀스는 주 동기 신호에 의해 소정의 스크램블링 시퀀스(scrambling sequence)와 스크램블링된다.In addition, a sequence for use as a secondary synchronization signal (SSS)

Is an interleaved concatenation of two length-31 binary sequences. The association sequence is scrambled with a predetermined scrambling sequence by the main synchronization signal.

The combination of the two 31 length sequences may define another sub-sync signal between subframe 0 and subframe 5 according to the following equation (3).

이고, 인덱스

및

은 다음 수학식 4에 따른 물리-계층 셀 ID 그룹

로부터 산출될 수 있다.here,

And the index

And

Is a physical-layer cell ID group < RTI ID = 0.0 >

Lt; / RTI >

FIG. 3 is a diagram schematically illustrating cells having multiple transmission antennas in an LTE system.

Under a Coordinated Multi-Point (CoMP) environment where multiple cells with multiple antennas are present, each cell may have a different antenna configuration. Referring to FIG. 3, in the LTE system, each cell 210, 220, 230, and 240 may have different antenna configurations. 3, the neighboring cell A 210 has one transmission antenna, the neighboring cell B 220 has two transmission antennas, the neighboring cell C 230 has four transmission antennas, The serving serving cell 240 may have two antennas.

4 to 6 are diagrams showing the structure of a downlink pilot signal in an LTE system, respectively.

Referring to FIG. 4 to FIG. 6, a structure is shown in which reference signals are allocated when the number of transmission antennas is 1, 2, and 4, respectively. That is, the LTE system has a different pilot signal (or reference signal) structure according to the number of antennas. In the LTE system, the total transmission power of the base station is generally fixed. For example, assuming that the total transmission power is 1, the power of all signals can be allocated to one antenna when there is one transmission antenna. However, when the number of transmission antennas is two or four, since the total transmission power is fixed, the power of signals transmitted from each antenna can be distributed to 0.5 and 0.25, respectively.

Likewise, the pilot signal can be distributed with power allocated to each antenna according to the number of transmission antennas. Therefore, it is most effective to estimate the channel quality estimated for each antenna considering the pilot signal for all the antennas for reliable channel quality measurement. To do so, the UE must know the antenna structure of all cells for channel quality measurement.

As shown in FIGS. 4 to 6, in the LTE system, since the pilot signal transmission frequency, time, and pilot signal position are fixed between transmitting and receiving ends for each antenna of a cell, the terminal can transmit a downlink pilot signal Structure can be known. However, the UE does not know the transmission antenna structure (for example, the number of transmission antennas of neighboring cells) of the neighboring cell excluding the cell to which the UE belongs. Accordingly, a process of estimating the number of transmit antennas of neighboring cells is required.

Hereinafter, a method for estimating the number of antennas of neighboring cells that effectively perform a CoMP operation will be described.

Fading occurs when electromagnetic waves fly through a space, which means that the receiving power of a signal varies with time as the medium changes in time. The fading channel changes phase and magnitude depending on time and frequency. Therefore, different distortions may occur depending on the time when the transmission signal passes through the channel, so that the accuracy of the channel quality may deteriorate. However, if the instantaneous measured channel values are constantly accumulated and averaged, they can converge to a certain value on average. For example, two terminals at the same distance from a cell will have statistically similar values if they compare their average values by accumulating the channel sizes although the instantaneous channel states with the cells are different.

7 is a flowchart illustrating a method for estimating the number of antennas of a neighboring cell in which a mobile station performs CoMP operation.

Referring to FIG. 7, the UE can acquire sequence information that each cell uses to transmit a pilot signal through a synchronization channel of each cell (S710). That is, the UE can determine which cell is neighboring to the cell to which it belongs through the cell ID set information including the neighbor cell ID information received from the base station, the primary synchronization channel and the secondary synchronization channel of each cell (S710 ).

Then, the terminal can acquire the sequence information that each cell uses to transmit the pilot signal through the synchronization channel of each cell (S720).

The UE can measure the reference signal received power (RSRP) of the pilot signal of the first antenna, which is common to each neighboring cell performing the CoMP operation (S730)

Each cell has at least one transmit antenna in an LTE system. The terminal can output a correlation value by correlating the pilot signal received from each antenna and the known pilot signal of each cell. That is, based on the fact that the average channel size value between terminals and cells at the same distance is similar, it is assumed that there are two or more antennas for all cells, and at the same time, A correlation value can be output by performing a correlation operation with a known pilot signal. For example, since there may be eight antennas in the LTE-A system, the reference signal received power for eight antennas can be measured.

As a process for measuring a reference signal reception power, a pilot signal is subjected to a correlation operation. For example, assume that there are two specific signals X and Y, and that each signal is of length N. Then, the signal X of length N may be composed of X0, X1, ..., XN-1, and the signal Y of length N may be composed of Y0, Y1, ... YN-1. At this time, the correlation value of the two signals can be expressed by Equation (2).

X,Y 신호의 상관 값 =

Correlation value of X and Y signals =

If X and Y are the same signal, the correlation value is a sum of positive values and therefore will have a relatively large value. If the values are different from each other, the sum of values having a random code (positive or negative sign) It will have a small value.

It is possible to perform a correlation operation with a received signal Y, assuming that a specific antenna is present, a pilot signal X corresponding to the antenna (the receiver knows already because it is a promised signal at the transmitting and receiving end), and the received signal Y. At this time, since the pilot signal X is a promised signal between the transmitting end and the receiving end, it corresponds to a signal already known by the receiving end. If two or more antennas are actually present in a particular cell, the X and Y signals for additional antennas other than the first antenna correspond to the same signal and the correlation value has a relatively large value. If there is no more antenna, a relatively small value will be obtained since the pilot signal X for the additional antenna other than the first antenna and the pilot signal data signal Y will be correlated.

The UE measures the reference signal reception power by performing a correlation operation on the pilot signal of the first antenna of the neighboring cell that performs the CoMP operation and then calculates a pilot signal for each antenna and an already known pilot signal for each remaining antenna The reference signal reception power can be measured by performing a correlation operation. Here, the reference signal reception power measured from the pilot signal of the first antenna is referred to as the first reference signal reception power, and the reference signal reception power measured from the remaining pilot signals of the respective antennas is referred to as the second reference signal reception power, power, … , And the Nth reference signal reception power. At this time, the reference signal reception power can be expressed in dBm units.

In step S740, the UE may compare one or more additional reference signal reception power for the reference signal of one or more additional antennas for each neighbor cell performing the CoMP operation with the first reference signal reception power. At this time, the UE receives the reference signal of the first antenna for each neighboring cell performing the CoMP operation and measures the first reference signal reception power first, then receives the reference signal for the additional antenna, And can be compared with the reference signal received power of the first antenna. Alternatively, after the terminal receives the reference signals of one or more additional antennas for each antenna, it can compare the first reference signal reception power by measuring the reference signal reception power of each antenna.

In step S750, the UE estimates that the signal of each neighboring cell is transmitted through the antenna corresponding to the power of the additional reference signal in which the difference from the first reference signal reception power is smaller than the predetermined threshold value.

In the case where the pilot signal of each neighboring cell is estimated to be transmitted through the antenna corresponding to the additional reference signal power, the terminal calculates the difference between the first reference signal reception power value and the reference signal reception power value of the additional antenna, (S760).

That is, the second reference signal reception power, the third reference signal reception power, , And the difference between the power of the Nth reference signal and the power of the first reference signal, respectively. It can be determined whether the difference value is larger or smaller than a specific threshold value. In the LTE system, since all cells have at least one transmission antenna, the presence or absence of another antenna can be determined based on the first reference signal reception power.

If there are two or more antennas in the neighboring cell performing the CoMP operation, the reference signal reception power value for the additional antenna other than the first antenna will be similar to the reference signal power of the first antenna depending on the number of used antennas . On the other hand, when there is only one antenna in the neighboring cell, the second reference signal reception power, the third reference signal reception power value, and the like will have different values from the first reference signal reception power value.

That is, when there is a second or more antennas, if a pilot signal transmitted through each antenna is correlated with a pilot signal known to the terminal and a cumulative average is taken, a value similar to the correlation value for the first antenna . In the case where there is no antenna, correlation operation with a pilot signal known to the UE will be greatly different from the correlation calculation result with respect to the first antenna since a correlation operation is performed with a general data signal.

The UE can measure the reference signal reception power of the corresponding antenna by averaging or weighted averaging the reference signal reception power values accumulated for a predetermined time for each antenna. In this way, the terminal can estimate the number of antennas of each cell by comparing the received power of the other reference signals based on the first reference signal reception power.

Then, the terminal can measure the channel quality of the cell based on the channel quality of each antenna corresponding to the estimated number of antennas (S770). That is, the terminal can measure the channel quality of each antenna by not only evaluating the channel quality of each antenna with only the reference signal reception power measured immediately, but also accumulating and averaging the reference signal reception power for a predetermined period . The UE can determine the channel quality state of the cell by simply averaging the reference signal reception power value or calculating a weighted average for each antenna based on the estimated number of antennas. As described above, if the UE can recognize the number of transmit antennas of neighboring cells, more reliable and accurate channel quality can be measured.

Then, the MS compares the channel quality of the neighbor cell with the channel quality of the neighbor cell and reselects the cell or transmits a message indicating that it is necessary to perform handover to the BS (S780). The UE must continuously monitor the channel status of its own cell and neighbor cells for cell reselection or handover. When the UE receives a cell reselection message or a message for a cell to be handed over from the base station, the UE replaces the cell receiving the current service with a neighbor cell according to the message, and transmits a radio link setup completion message, , The base station), thereby completing the handover procedure.

As described above, the UE can accurately measure the channel quality of each neighboring cell and the cell to which the UE belongs by determining the number of antennas of the neighboring cell performing the CoMP operation.

The embodiments described above are those in which the elements and features of the present invention are combined in a predetermined form. Each component or feature shall be considered optional unless otherwise expressly stated. Each component or feature may be implemented in a form that is not combined with other components or features. It is also possible to construct embodiments of the present invention by combining some of the elements and / or features. The order of the operations described in the embodiments of the present invention may be changed. Some configurations or features of certain embodiments may be included in other embodiments, or may be replaced with corresponding configurations or features of other embodiments. It is clear that the claims that are not expressly cited in the claims may be combined to form an embodiment or be included in a new claim by an amendment after the application.

Embodiments in accordance with the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs) Field Programmable Gate Arrays), a processor, a controller, a microcontroller, a microprocessor, or the like.

In the case of an implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, a procedure, a function, or the like which performs the functions or operations described above. The software code can be stored in a memory unit and driven by the processor. The memory unit may be located inside or outside the processor, and may exchange data with the processor by various well-known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Accordingly, the above description should not be construed in a limiting sense in all respects and should be considered illustrative. The scope of the present invention should be determined by rational interpretation of the appended claims, and all changes within the scope of equivalents of the present invention are included in the scope of the present invention.

1 is a diagram illustrating a case where a mobile station moves to a coverage of a neighboring cell,

2 is a diagram illustrating an example of a downlink frame structure in a Frequency Division Duplex (FDD) type in an LTE system,

3 schematically illustrates cells with multiple transmit antennas in an LTE system,

4 to 6 are diagrams illustrating a downlink pilot signal structure in an LTE system,

7 is a flowchart illustrating a preferred procedure of a method for a UE to estimate the number of antennas of neighboring cells.

Claims (8)

A method for estimating the number of antennas used by a neighboring cell performing a Coordinate Multi-Point (CoMP) operation for signal transmission, Measuring a first reference signal received power (RSRP) by receiving a reference signal of a first antenna for each neighbor cell in which the UE performs the CoMP operation; Comparing at least one additional reference signal received power for a reference signal of one or more additional antennas for each neighbor cell performing the CoMP operation with the first reference signal received power; And Estimating that a signal of each neighboring cell is transmitted through an antenna corresponding to an additional reference signal reception power at which a difference between the first reference signal reception power and the first reference signal reception power is smaller than a predetermined threshold value, Way. The method according to claim 1, Further comprising the step of measuring the number of antennas of each neighboring cell to which a signal is transmitted via an antenna corresponding to the additional reference signal reception power of the terminal. The method according to claim 1, Wherein the UE further acquires sequence information used by each cell for transmission of a reference signal through a synchronization channel of each cell performing a CoMP operation. The method according to claim 1, Measuring a channel quality of a cell based on a channel quality of each antenna corresponding to an estimated number of antennas of a neighboring cell in which the UE performs the CoMP operation; And Comparing the channel quality of the cell to which the terminal belongs with the measured channel quality of the neighboring cell, and transmitting the message to the base station that the cell needs to be reselected or handed over to the base station. 5. The method of claim 4, Wherein the channel quality state of each neighboring cell performing the CoMP operation is measured by averaging or weighted average of channel quality values of each antenna. The method according to claim 1, The UE measures the reference signal reception power by using the reference signal reception power accumulated for a predetermined time for each antenna of the neighboring cell performing the CoMP operation, The method according to claim 6, Wherein the terminal measures a value obtained by averaging or weighted average of the accumulated reference signal reception power as reference signal reception power. The method according to claim 1, Wherein the reference signal reception power is measured by performing a correlation operation between a pilot signal of each antenna previously known by the user equipment and a pilot signal received from each antenna of the neighboring cell.

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