KR101566212B1 - The method of transmitting feedback information - Google Patents

Abstract

A method for efficiently transmitting feedback information in order to reduce inter-cell interference in a terminal performing CoMP operation in a wireless communication system is disclosed. The UE can request to limit the use of a specific beam pattern group in the direction of the serving cell to adjacent cells that are subject to interference among the cells performing the CoMP operation. At this time, whether or not to make the restriction request can be determined based on the channel state value of the UE. When it is determined to make the restriction request, the serving base station can transmit a message requesting to restrict the use of the specific beam pattern group. At this time, the UE may request scheduling to limit the use of a specific beam pattern group in a specific resource region for a specific neighbor cell.

CoMP, beam pattern

Description

The method of transmitting the CoMP feedback information (CoMP feedback information)

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a wireless communication system, and more particularly, to a method for transmitting feedback information by a terminal performing CoMP operation.

Recently, a multiple input multiple output (MIMO) system has attracted attention as a broadband wireless mobile communication technology. A MIMO system refers to a system that increases data communication efficiency by using a plurality of antennas. The MIMO system can be divided into a spatial multiplexing scheme and a spatial diversity scheme depending on whether the same data is transmitted or not.

Spatial multiplexing refers to a method of transmitting data at high speed without increasing the bandwidth of the system by simultaneously transmitting different data through a plurality of transmission antennas. The spatial diversity scheme refers to a scheme in which transmission diversity can be achieved by transmitting the same data in a plurality of transmission antennas. One example of such a space diversity technique is space time channel coding.

In addition, the MIMO technique can be divided into an open loop method and a closed loop method depending on whether feedback of channel information from a receiving side to a transmitting side is performed. In the open-loop method, information is transmitted in parallel at the transmitting end. In the receiving end, a blast (BLAST) capable of detecting signals by repeatedly using ZF (Zero Forcing) and MMSE (Minimum Mean Square Error) And a space-time trellis code (STTC) scheme that can obtain transmission diversity and coding gain using a space region. And a closed antenna scheme is a TxAA (Transmit Antenna Array) scheme.

A Coordinated Multi-Point (CoMP) system (hereinafter referred to as a CoMP system) is a system that applies improved multiple-input multiple-output (MIMO) transmission in a multi-cell environment to improve user throughput System. The CoMP system can reduce inter-cell interference in a multi-cell environment. With the CoMP system, a UE can receive data jointly from a multi-cell base station.

Also, each base station can simultaneously support one or more UEs (UE 1, UE 2, ..., UE K) using the same radio frequency resource (Same Radio Frequency Resource) to improve the performance of the system. In addition, the BS may perform a Space Division Multiple Access (SDMA) method based on channel state information (CSI) between the BS and the MS.

The CoMP scheme can be divided into cooperative MIMO (Co-MIMO) joint processing (Joint Processing) and cooperative scheduling scheme / beamforming scheme (CS / CB) through data sharing .

1 is a diagram conceptually showing CoMP of an existing intra base station (intra eNB) and inter base station (inter eNB).

Referring to FIG. 1, intra-base stations 110 and 120 and inter-base stations 130 exist in a multi-cell environment. In LTE (Long Term Evolution), an intra base station consists of several cells (or sectors). The cells belonging to the base station to which the specific terminal belongs are related to the specific terminal and the intra base stations 110 and 120. That is, the cells sharing the same cell as the cell to which the UE belongs are the cells corresponding to the intra base stations 110 and 120, and the cells belonging to the other base stations are the cells corresponding to the inter base station 130. In this way, cells based on the same base station as a specific terminal receive and transmit information (e.g., data and channel state information (CSI)) through an x2 interface, And information can be exchanged between the cells through the backhaul 140 and the like.

1, a single-cell MIMO user 150 in a single cell communicates with one serving base station in one cell (sector), and a multi-cell MIMO user 160 located at a cell boundary communicates with multiple cells May communicate with multiple serving base stations.

In order to smoothly perform the CoMP operation described above, the mobile station must transmit a large amount of feedback information to the base station. This conventional feedback transmission method has a problem in that overhead of uplink resources due to feedback transmission increases. In addition, the overhead and delay of the backhaul due to excessive feedback information exchange can cause considerable problems in the system.

SUMMARY OF THE INVENTION The present invention provides a CoMP feedback information transmission method.

The technical problems to be solved by the present invention are not limited to the technical problems and other technical problems which are not mentioned can be understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a method for transmitting a CoMP feedback information of a base station, the method including transmitting a CoMP feedback information to a neighboring cell, Determining a beam pattern group in the specific direction to be limited for each adjacent cell based on the received message, and transmitting a message requesting to limit use of the determined beam pattern group in the specific direction To the neighboring cells performing the CoMP operation.

According to another aspect of the present invention, there is provided a method for transmitting CoMP feedback information of a base station, the method including receiving information on a channel state from a terminal, comparing the received information with a predetermined threshold, And transmitting a message to the neighboring cells requesting to restrict use of a specific beam pattern group for neighboring cells performing the neighboring cells.

According to another aspect of the present invention, there is provided a method for transmitting CoMP feedback information of a UE, the method comprising the steps of: determining a channel state value with the serving cell or an interference level measured from neighboring cells performing a CoMP operation; Comparing a channel state value of the neighbor cell with the interference level of the adjacent cell, and comparing the interference level of the adjacent cell with a threshold value, .

According to the present invention, inter-cell interference can be effectively reduced by using the cell-specific beam pattern limiting scheme in a multi-cell environment.

The effects obtained by the present invention are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood by those skilled in the art from the following description will be.

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 assumes that the mobile communication system is a 3GPP LTE system, but it is applicable to any other mobile communication system except for the specific aspects of 3GPP LTE.

In some instances, well-known structures and devices may be omitted or may be shown in block diagram form, centering on the core functionality of each structure and device, to avoid obscuring the concepts of the present invention. In the following description, the same components are denoted by the same reference numerals throughout the specification.

In the following description, it is assumed that the UE collectively refers to a mobile stationary or stationary user equipment such as a UE (User Equipment) and an MS (Mobile Station). It is also assumed that the base station collectively refers to any node of a network end that communicates with a terminal such as a Node B, an eNode B, and a base station.

In a mobile communication system, a user equipment can receive information through a downlink from a base station, and the terminal can also transmit information through an uplink. The information transmitted or received by the terminal includes data and various control information, and various physical channels exist depending on the type of information transmitted or received by the terminal.

2 is a view for explaining physical channels used in a 3rd Generation Partnership Project (3GPP) LTE (Long Term Evolution) system, which is an example of a mobile communication system, and a general signal transmission method using the same.

The terminal which is turned on again when power is turned off or the terminal which has entered a new cell performs an initial cell search operation such as synchronizing with the base station in step S201. To this end, the UE receives a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S-SCH) from a base station and synchronizes with the base station and acquires information such as a cell ID can do. Then, the terminal can receive the physical broadcast channel from the base station and acquire the in-cell broadcast information. Meanwhile, the UE can receive the downlink reference signal (DL RS) in the initial cell search step to check the downlink channel state.

Upon completion of the initial cell search, the UE receives a physical downlink control channel (PDCCH) and a physical downlink control channel (PDSCH) according to the physical downlink control channel information in step S202, Specific system information can be obtained.

On the other hand, if the base station is initially connected or there is no radio resource for signal transmission, the mobile station can perform a random access procedure such as steps S203 to S206. To this end, the UE transmits a specific sequence as a preamble through a physical random access channel (PRACH) (S203), and receives a response message for the random access on the PDCCH and the corresponding PDSCH (S204). In case of a contention-based random access except for handover, a contention resolution procedure such as transmission of additional PRACH (S205) and reception of PDCCH / PDSCH (S206) may be performed thereafter.

The UE having performed the procedure described above transmits PDCCH / PDSCH reception (S207) and Physical Uplink Shared Channel (PUSCH) / Physical Uplink Control Channel (PUCCH) as a general uplink / downlink signal transmission procedure : Physical Uplink Control Channel) transmission (S208). At this time, the control information transmitted by the UE to the BS through the uplink or received from the BS by the UE includes a downlink / uplink ACK / NACK signal, channel quality information (CQI) A coding matrix index (PMI), a rank indicator (RI), and the like. In the 3GPP LTE system, the UE can transmit control information such as CQI, PMI, and RI through a PUSCH and / or a PUCCH.

The term base station used in the present invention may be referred to as a cell or a sector when used in a regional concept. The serving base station (or cell) can be viewed as a base station (or cell) that provides a primary service to the terminal and can perform transmission and reception of control information on a coordinated multiple transmission point. In this sense, the serving base station (or cell) may be referred to as an anchor base station (or anchor cell). The serving base station can transmit various information received from the mobile station to a neighboring base station (cell). Likewise, an adjacent base station can be referred to as a neighboring cell when used as a local concept.

When the CoMP method is used in a multi-cell environment, the communication performance of the cell boundary terminal can be improved. This CoMP scheme includes collaborative MIMO joint processing (JP) through data sharing, collaborative scheduling / beamforming (CS / MIMO) to reduce inter-cell interference such as worst companion and best companion, CB: Coordinated Scheduling / Beamforming, and a geographically separated transmission process (e.g., multi-antenna).

In particular, the cooperative scheduling / beamforming (CS / CB) scheme is a method for reducing inter-cell interference, and can reduce interference from neighboring cells by transmitting limited and / or recommended PMI to a serving base station. Here, the worst companion scheme reports a PMI having the greatest interference to cells performing CoMP to the serving BS, so that neighboring cells can remove inter-cell interference using PMIs other than the corresponding PMIs Method. The best companion method is a method of reducing inter-cell interference by using the PMI corresponding to the neighboring cells by reporting the PMI having the least interference to the cells performing CoMP.

With this CoMP system, the UE can receive data jointly from a multi-cell base station. That is, the communication performance of the cell edge terminal can be improved by using the CoMP operation in a multi-cell environment.

In order to efficiently perform a multi-cell-based CoMP operation scheme such as joint processing (JP) scheme and cooperative scheduling / beamforming (CS / CB) scheme, a UE transmits channel information (for example, channel state information A CSI (Channel State Information), a CQI, a PMI, a RI, a noise and interference variance, a Carrier to Interference plus Noise Ratio (CINR) (or SINR value) measured when a neighboring cell uses a good PMI or a bad PMI (bad PMI), and a previously measured CINR value (or a SINR value) (Or SINR value) for a serving cell that indicates how the channel state of the serving cell is improved by comparing the difference between the serving cell and the neighboring base station. The cell receiving the channel information shares the channel information with the neighboring cell performing the CoMP operation, and can perform the CoMP operation efficiently based on the channel information.

As described above, efficient CoMP operation can be performed based on the feedback information of the UE, but the use of uplink resources due to the feedback increases and the backhaul overhead may increase when sharing information between cells. This may cause backhaul delays and other problems.

The UE performing the CoMP operation is highly likely to be located at a cell boundary that is subject to severe interference from neighboring cells or from a serving cell in which sufficient channel conditions may not be guaranteed. These cell edge terminals move at low speed and receive data mainly in rank 1 (rank 1). In addition to the method based on the feedback information of the UE that increases the uplink and the backhaul overhead in consideration of the cell boundary terminal performing CoMP operation, a predefined beam pattern (for example, PMI) at the time of cell deployment You can consider how to use it.

At the initial cell placement, the beam pattern of each cell can be preformed in a specific directionality. In particular, the beam pattern of rank 1 generally has a clearer directionality than a beam of higher rank. Each cell can share information about specific directional beam patterns that affect each other between adjacent cells. Therefore, when a beam pattern restriction request is received from a specific cell, the group of beams having a directivity toward the specific cell is restricted, thereby reducing interference to the cell.

In addition to UE-specific beam limiting schemes for limiting inter-cell interference by limiting and / or recommending specific PMIs that affect neighboring cells, Specific beam pattern limiting scheme (hereinafter, the cell-specific beam pattern limiting scheme may be abbreviated as a 'beam pattern limiting scheme') for limiting a beam pattern group of the beam pattern. At the time of cell placement, beam pattern groups having mutual directionality between cells may be formed in a uniform number or may be non-uniform according to a specific purpose.

3 is a diagram illustrating a concept of a cell-specific beam pattern limiting scheme according to the present invention.

Referring to FIG. 3, it is assumed that there are three cells (cells A, B, and C) that perform a CoMP operation. Here, UE 1 is a UE belonging to cell A (i.e., cell A is a serving cell and cells B and C are neighbor cells). Cell B has a beam pattern group W1, W2, W3 having directionality directed to cell A among the beam patterns of rank 1, and cell C has cells W6, W7, W8. This is a preset value at the time of cell placement. When the cell boundary terminal 1 belonging to the cell A receives a severe interference signal from the cells B and C, the terminal 1 or the serving cell (cell A) Restrictions may be requested. Cells B and C receiving such a request may limit the use of beam pattern groups W1, W2, W3 and W6, W7, W8, respectively. This beam pattern group (e.g., PMI) restriction can ensure the flexibility and efficiency of resource usage by limiting only to the specific resource (e.g., subframe or subband) requested by the serving cell or determined by the neighboring cell.

In order to operate in this cell-specific beam limiting (or avoiding) scheme, the terminal may transmit feedback information to the serving base station. For the cell-specific beam limiting scheme, the UE can send simple feedback information such as a message of a predetermined bit size (for example, 1 bit) requesting interference restriction to the neighboring cell to the serving base station. At this time, the uplink message bit-width may be different depending on how many beam pattern groups actually affect the interference to the UE. This feedback information may vary depending on whether the cell-specific beam limiting scheme is triggered on the UE side or triggered on the serving BS side.

First, the case of triggering the cell-specific beam limiting scheme at the terminal side will be described.

The terminal may request cell-specific beam limiting (or avoidance) to the serving base station. The UE compares the channel state value with a predetermined threshold, and if the channel state of the UE does not satisfy the threshold, the UE can request cell-specific beam limiting. The channel state of the UE may vary depending on whether the neighbor cell of the UE is measured or not.

When performing a single cell-based communication in a state where the UE does not measure the neighboring cell, the UE calculates the noise and interference level from the remaining cells excluding the channel state and the serving cell, such as CQI May determine whether to request a cell-specific beam limitation through comparison with a threshold value as a criterion. In this case, the UE can transmit a message of a predetermined bit size requesting the cell-specific beam limitation to the serving BS through a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), or an RRC message. And the serving base station can request the beam pattern group restriction to the neighboring cell that is capable of CoMP.

Alternatively, when the UE performs measurement on a neighboring cell, the UE compares the channel state of the serving cell with a threshold using an interference level of neighboring cells performing CoMP, and if the UE does not satisfy the threshold, You can decide whether to request a specific beam limit. In this case, it is possible to divide the measurement information into the case of transmitting the measurement information to the serving base station and the case of not transmitting the measurement information after performing the measurement again.

Consider a case where a UE performs measurements on neighbor cells and then transmits measurement information to a serving BS. The UE can transmit measurement information of a neighbor cell such as a reference signal received power (RSRP) and a reference signal reception quality (RSRQ) to the serving BS together with the cell ID of the neighbor cell. Then, the serving base station can know the neighboring cell ID information and the interference level of the corresponding terminal that transmitted the measurement information of the neighboring cell. Accordingly, the UE can determine whether to request limiting the cell-specific beam through comparison with the threshold using the interference level of each neighboring cell or the like.

If the terminal has determined to request cell-specific beam limiting, the terminal may make a beam pattern limit request for one or more neighboring cells that are most likely to interfere with itself. When a request is made for one or more neighboring cells, a restriction request may be made for a predetermined number of neighboring cells or a restriction request may be made for an entire neighboring cell exceeding a threshold value. The UE can transmit a cell-specific beam restriction request for a neighbor cell to a serving BS through a PUCCH, PUSCH, or RRC message with a predetermined bit size. Such a cell-specific beam limitation request may be transmitted in the order of the neighboring cells having a high interference level without a cell ID or a cell ID index. Alternatively, only the cell ID index or the cell ID index of the neighbor cell to be restricted may be transmitted. Using the measurement information received from the UE, the serving BS can classify the measurement information of the neighboring cells in the order of the interference level, and the classified information can be shared without any signaling between the UE and the BS. Based on this classification information, a restriction request for an adjacent cell can be transmitted without a cell ID index. In this way, the serving BS can request a restriction on a specific beam pattern group to the adjacent cell.

Consider a case where the UE does not transmit measurement information to the serving BS after performing the measurement. In this case, the UE may transmit the cell ID and the cell-specific beam limitation request message for the adjacent cell to be restricted together, or may transmit only the cell ID to the serving BS. In addition, it is possible to further transmit the interference level for the neighboring cell. The request for cell-specific beam limiting for a neighboring cell of the terminal may be determined through comparison of a threshold value and a measured value. As before, the terminal may make cell-specific beam pattern restriction requests to one or more neighbor cells. The serving base station can transmit a signal or a message requesting to limit the use of the specific beam pattern group to the neighboring cell.

When the UE transmits a request message to the serving BS after determining to request the cell-specific beam restriction, the serving BS does not limit the beam pattern limitation for unspecified neighbor cells, . ≪ / RTI > In this case, the UE transmits one restriction request message to the serving cell irrespective of the cell ID, and the serving cell is limited to one or more beam pattern groups having the direction to the serving cell for the neighboring cell located close to the serving cell .

And may arbitrarily trigger the cell-specific beam limitation at the serving base station side. The serving base station may periodically or aperidively receive the single cell based channel information from the terminal. The serving BS may compare the threshold value with the threshold value based on the channel information received from the UE, and may request a restriction on the beam pattern group arbitrarily to the adjacent cell if the threshold value is not satisfied. When the UE performs measurement and transmits the measurement information to the base station, the BS determines whether the neighboring cell having the strongest interference or a predetermined number of adjacent cells having the strong interference or the neighboring cell having the interference exceeding the specific threshold value For each of the cells, beam pattern group limitation with directionality to its own cell.

Hereinafter, the information exchanged between base stations (or cells) will be described.

4 is a diagram illustrating an example for cell-specific beam limiting in a CoMP operation according to the present invention.

Referring to FIG. 4, when a specific terminal transmits a message requesting cell-specific beam limiting to a serving base station (eNB_A) for the specific terminal, the serving base station eNB_A transmits it to the neighboring cell eNB_B, eNB_C. Or the serving base station eNB_A arbitrarily requests the cell-specific beam limiting for the neighboring cells eNB_B and eNB_C, the serving base station eNB_A may be referred to as a CoMP neighbor cell (ENB_B, eNB_C), beam pattern group restriction, and interference level. This allows efficient cell-specific beam limiting between cells.

In this manner, when the serving base station eNB_A for the specific terminal receives the influence of the interference from the neighboring cells eNB_B and eNB_C, the neighboring cells eNB_B and eNB_C use the directional beam pattern group toward the cell to which the neighboring cell eNB_B belongs (ENB_B, eNB_C) to the neighboring cell (eNB_B, eNB_C). At this time, the restriction request message can be transmitted to the adjacent cell with a predetermined bit size (for example, 1 bit or more). For example, the specific neighboring cell eNB_B receives the cell-specific beam limiting request message from a plurality of base stations (or cells) (eNB_A, eNB_C), and limits the beam pattern based on the received cell-specific beam limiting request message. However, when a specific neighboring cell eNB_B receives a restriction request from a plurality of base stations eNB_A and eNB_C, it is necessary to determine which beam pattern is most efficient to limit. This can be called a ranking problem.

In order to solve this ranking problem, the serving base station eNB_A adds the cell-specific beam limitation request message and the information on the interference levels generated by the neighboring cells eNB_B and eNB_C together with the neighboring cells eNB_B, eNB_C. The neighboring cell that receives the interference level information can use the interference level information to determine which beam pattern is most effective to limit. After determining the cell-specific beam pattern to be limited in this way, a response can be given to each serving base station (e.g., eNB_A) as to whether to restrict the specific beam pattern requested.

As described above, not only the beam pattern group restriction request message and the interference level information (or measurement information) are exchanged between the base stations, but also the scheduling information can be exchanged. When the beam pattern group restriction is applied to a neighboring cell due to a beam pattern group restriction request between the base stations, application of the beam pattern restriction in the entire band or entire radio frame may result in a large loss in the performance of the UE in its own cell . Therefore, efficient allocation of time / frequency resources among base stations and scheduling of transmission information can be efficiently used for transmission resources. That is, by sharing the scheduling information for applying a restriction on a specific cell to a specific resource (one subframe, one slot, two or more subframes, and two or more slots) among the base stations, the use of the beam pattern causing mutual interference Can be efficiently performed in a specific resource unit (for example, a specific subframe or a subband unit). At this time, the scheduling information may be shared through the X2 interface as L1 / L2 control information, or may be shared with L3 RRC connection control information.

5 is a diagram illustrating an example for cell-specific beam limiting in CoMP operation according to the present invention.

Referring to FIG. 5, each serving base station (eNB_A) receiving a beam pattern restriction request message from a specific terminal may request a beam pattern restriction to the neighboring cells eNB_B and eNB_C. The neighboring cells eNB_B and eNB_C collect the beam pattern limitation request information received from a plurality of cells and then perform scheduling to limit the use of a specific beam pattern having a direction for the specific cell to any resource . The particular resource for which the use is to be restricted may be a particular subframe or subband.

As shown in FIG. 5, for example, a specific neighboring cell eNB_B may perform scheduling and transmit the scheduled information to each of the serving base stations eNB_A and eNB_C that have transmitted the restriction request. That is, the specific neighboring cell eNB_B transmits to the serving base station eNB_A a message indicating that it is not used in the Jth subframe or subband for the beam pattern group requested to be restricted from the serving base station eNB_A Lt; / RTI > For example, the specific neighboring cell eNB_B may perform scheduling and transmit the scheduled information to each of the serving eNB_A and eNB_C that has sent the restriction request. That is, the specific neighboring cell eNB_B transmits a message indicating that the specific neighboring cell eNB_B does not use the specific resource (for example, the Kth sub-frame or the sub-band) for the beam pattern group requested to be restricted from the serving base station eNB_C To the serving base station eNB_C.

The serving base station receiving the scheduling information can perform scheduling for the terminals in its own cell based on the scheduling information. The cell-specific beam pattern limiting scheme described above with reference to FIG. 5 is for the case where neighboring cells perform scheduling.

6 is a diagram illustrating an example for cell-specific beam limiting in a CoMP operation according to the present invention.

Referring to FIG. 6, the UE may transmit a message requesting restriction of a specific beam pattern group to the serving base stations eNB 1 and eNB 3. The serving base stations eNB 1 and eNB 3 receiving the specific beam pattern group restriction request can transmit the scheduling information together with the received specific beam pattern group restriction request to the neighbor cell eNB 2. That is, each of the serving base stations eNB 1 and eNB 3 performs scheduling to request a neighboring cell (eNB 2) to restrict a beam pattern having a direction directed toward its cell toward a specific subframe or subband. In addition, the serving base stations eNB 1 and eNB 3 can additionally transmit information (related information) such as the interference level to the neighbor cell (eNB 2) to the corresponding neighbor cell (eNB 2). At this time, information (related information) such as the interference level may be measured by the UE and transmitted to the serving base stations eNB 1 and eNB 3.

The neighboring cell (eNB2) receiving the restriction request and the scheduling information from the plurality of cells performs scheduling for a plurality of neighboring cells based on the received scheduling information, and transmits the result to the cells (eNB 1 , eNB 3). This response includes the acceptance or rejection of a particular beam pattern group restriction request. In addition, when the neighbor cell eNB 2 rejects a specific beam pattern group restriction request, the neighbor cell eNB 2 may be transmitted to the serving base station (eNB 3, for example) with a proposal for the next best method. That is, information about sub-frames or sub-bands of a lane can be transmitted, rather than a specific resource (e.g., a specific sub-frame or sub-band) that made a specific beam pattern limitation request.

The UE can transmit the scheduling information on the neighbor cell to the serving BS. It is possible to consider a case in which the UE directly transmits the scheduling information on the neighboring cell to the serving BS, in addition to the scheduling information arbitrarily determined by the serving BS, which has received the specific beam pattern group restriction request from the MS, to the neighboring cell. When the UE directly transmits the scheduling information to the serving BS, it can be divided into two types.

7 is a diagram illustrating an example for cell-specific beam limiting in a CoMP operation according to the present invention.

Referring to FIG. 7, the UE can perform scheduling to limit a beam pattern group in a certain subframe or subband with respect to a neighbor cell. Then, the UE can transmit scheduling information to the serving base stations (eNB 1, eNB 3) together with a restriction request for a specific beam pattern group for a specific subframe or subband. The serving base stations eNB 1 and eNB 3 aggregate scheduling information transmitted from a plurality of terminals in its own cell, and then not only the scheduling information but also information (related information) such as an interference level for a neighbor cell, , The serving base stations eNB 1 and eNB 3 can perform scheduling for beam pattern group restriction requests themselves. That is, it is possible to perform scheduling for the terminal most affected by the interference, the neighboring cell having the greatest influence of the interference, and the like.

Thus, the serving base stations eNB 1 and eNB 3 can transmit the determined scheduling information to the neighboring cell eNB 2, and the neighboring cell eNB 2 can efficiently perform scheduling based on the received information. The neighboring cell eNB 2 may perform scheduling and report the result to the serving base stations eNB 1 and eNB 3. That is, the neighboring cell eNB 2 informs the serving base station eNB 1 of the restriction of the specific beam pattern group in a particular subframe or subband that is requested to restrict a specific beam pattern group from the serving base station eNB 1, . In addition, the neighboring cell eNB 2 transmits a message indicating that a specific beam pattern group in a specific subframe or subblock received from the serving base station eNB 3 should satisfy the restriction request possible for restriction, The eNB 3 may transmit a message to the serving base station eNB 3 indicating that the pattern group is not used in a specific subframe or subframe other than the requested subframe or subbands.

8 is a diagram illustrating an example for cell-specific beam limiting in a CoMP operation according to the present invention.

As a second case in which the UE directly performs scheduling, the UE can perform scheduling to limit beam pattern groups in a subframe or a subband with respect to a neighbor cell (eNB B). Then, the terminal transmits scheduling information together with a restriction request to a specific beam pattern group for a specific sub-frame or sub-

The serving base stations (eNB A and eNB C) can transmit the scheduling information transmitted from the UE to the neighboring cell without any special processing. That is, the UE can transmit scheduling information requesting the UE to limit a beam pattern group that interferes with the UE to a specific subframe or subband, to the serving base station (eNB A, eNB C), and the serving base station (eNB A, eNB C) Can send it to the neighboring cell (eNB B). The serving base stations eNB A and eNB C may further transmit information (related information) such as the interference level to the neighboring cell to the neighboring cell eNB B. At this time, information (related information) such as the interference level may be measured by the UE and transmitted to the serving base stations eNB 1 and eNB 3.

The neighboring cell (eNB B) receiving this information from the plurality of cells can efficiently perform scheduling based on the received information. The neighboring cell eNB B may perform scheduling and report the result to the serving base stations eNB A and eNB C. That is, the neighboring cell eNB B informs the serving base station eNB A of limiting the specific beam pattern group in a particular subframe or subbands received from the serving base station eNB A to restrict the specific beam pattern group, . In addition, the neighboring cell (eNB B) transmits a message indicating that the specific beam pattern group in a specific subframe or subband requested by the serving base station (eNB C) A message indicating that the pattern group is not to be used in a specific subframe or subframe other than the requested subframe or subband may be transmitted to the serving base station eNB C.

A method of limiting (or avoiding) beam limiting a specific beam pattern group of a neighboring cell having directionality toward the serving cell has been described above. The case where the beam pattern limiting method is applied to the cooperative scheduling / beamforming (CS / CB) scheme among the CoMP schemes has been mainly described. However, the cell-specific beam pattern limiting method according to the present invention is also applicable to the joint processing (JP) method between multiple cells in CoMP. In the case of independently transmitting data without sharing data among multiple cells, a specific beam pattern group having a directivity toward a serving cell may act as an interference to a serving cell.

However, in the case of a joint processing (JP) scheme that enhances the signal through sharing of data between multiple cells, a beam pattern group with directionality toward the serving cell may be the best beam pattern (e.g., PMI) group. Therefore, the technique of limiting the beam pattern group of the adjacent cell can be effectively applied to a joint processing method of enhancing the signal of the cell boundary terminal by sharing data among multiple cells.

In addition, when a joint processing method and a beam pattern limiting method are simultaneously applicable in an arbitrary system, various methods proposed in the present invention as a method for beam pattern limitation or beam pattern limitation and joint processing are simultaneously applied Can be applied.

For example, when a joint processing scheme is applied between cells in an intra base station and a beam pattern limiting scheme is applied between inter-base stations, it can be applied as a scheme for limiting a beam pattern group among inter-base stations.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The foregoing description of the preferred embodiments of the invention disclosed herein has been presented to enable any person skilled in the art to make and use the present invention. While the present invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. For example, those skilled in the art can utilize each of the configurations described in the above-described embodiments in a manner of mutually combining them.

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.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

FIG. 1 conceptually shows CoMP between an intra-base station (intra eNB) and an inter-base station (inter eNB)

FIG. 2 is a diagram for explaining physical channels used in a 3GPP LTE (Third Generation Partnership Project Long Term Evolution) system, which is an example of a mobile communication system, and a general signal transmission method using them;

3 is a diagram illustrating a concept of a cell-specific beam pattern limiting scheme according to the present invention,

FIG. 4 illustrates an example for cell-specific beam limiting in CoMP operation in accordance with the present invention; FIG.

Figure 5 illustrates an example for cell-specific beam limiting in CoMP operation in accordance with the present invention;

Figure 6 illustrates an example for cell-specific beam limiting in CoMP operation in accordance with the present invention;

FIG. 7 illustrates an example for cell-specific beam limiting in a CoMP operation according to the present invention,

FIG. 8 is a diagram illustrating an example for cell-specific beam limiting in a CoMP operation according to the present invention.

Claims (11)

A method for transmitting Coordinated Multi-Point (CoMP) feedback information in a serving cell in a wireless communication system, Receiving information on a channel state from a terminal; And compares the information on the channel state with a threshold value to limit the use of a beam pattern group directed to the serving cell in the first sub-frame or the first sub-band to one or more neighboring cells performing the CoMP operation Sending a request message requesting the request; And Receiving a response message indicating that the neighboring cells will limit use of a particular beam pattern group in a second sub-frame or a second sub-band that is different from the first sub-frame or the first sub-band, Wherein the request message includes information on the channel status, Wherein the second sub-frame or the second sub-band is determined by the neighboring cells based on information about the channel state. The method of claim 1, wherein the channel status of the UE is determined using CSI (Channel Status Information) of the UE or information on an interference level by the neighboring cells. 3. The method of claim 2, Wherein the information on the interference level is arranged in order of increasing interference. 3. The method of claim 2, And transmitting information on interference levels by the neighboring cells to the neighboring cells. delete delete delete delete delete delete delete

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