WO2011065763A2 - Method for transmitting precoding matrix information and user device, and method for transmitting data to plurality of user devices and base station - Google Patents

Abstract

The present invention relates to a precoding matrix information transmission method and a user device, and provides a method for transmitting precoding matrix information by a particular user device among a plurality of user devices that receive a signal transmitted from one base station. The method comprises the steps of: determining, from a predetermined codebook, a first precoding matrix which is a precoding matrix for the particular user device during signal reception, and determining one or more second precoding matrices for the other user devices which are to be multiplexed in a predetermined resource region with the particular user device, wherein the one or more second precoding matrices are determined within a codebook subset of the predetermined codebook linked with the first precoding matrix; and a precoding matrix information transmission step of transmitting, to the base station, first precoding matrix information that indicates the first precoding matrix and second precoding matrix information that indicates the one or more second precoding matrices.

Description

A method and base station for transmitting precoding matrix information and a method and base station for transmitting data to a plurality of user devices

The present invention relates to a wireless communication system. Specifically, the present invention relates to a method and apparatus for reducing channel interference between multiple user devices when simultaneously transmitting signals to multiple users.

Recently, multiple input multiple output (MIMO) systems have been in the spotlight as broadband wireless mobile communication technology. MIMO system refers to a system that increases the communication efficiency of data using a plurality of antennas.

The MIMO system can be divided into a spatial multiplexing technique and a spatial diversity technique according to whether the same data is transmitted. Spatial multiplexing refers to a method in which data can be transmitted at high speed without increasing bandwidth of a system by simultaneously transmitting different data through a plurality of transmit antennas. The spatial diversity scheme refers to a method in which transmit diversity can be obtained by transmitting the same data from a plurality of transmit antennas. One example of such a space diversity technique is space time channel coding.

In addition, the MIMO system is divided into a single user MIMO (SU-MIMO) and a multi-user MIMO (MU-MIMO) according to how many users are allocated in the same time / frequency domain. A section having a time / frequency domain may also be referred to as a resource region. In SU-MIMO, one user may be allocated to one resource region, and in MU-MIMO, multiple users may be allocated to one resource region. In general, when the number of users is small, the performance of SU-MIMO is good, and when the number of users is large, the performance of MU-MIMO is good.

On the other hand, SU-MIMO and MU-MIMO may be classified into an open loop method and a closed loop method according to whether feedback of channel information from a receiving side to a transmitting side is performed. In the open loop method, the transmitting end transmits the information in parallel, and the receiving end repeatedly detects signals using ZF (Zero Forcing) and MMSE (Minimum Mean Square Error) methods and increases the amount of information by the number of transmitting antennas. There is a Space-Time Trellis Code (STTC) scheme that can obtain transmission diversity and coding gain by using the space domain. In the closed loop scheme, the receiver estimates a state of a wireless channel, and then transmits the estimated channel state to the transmitter in the form of appropriate feedback information. The transmitter controls channel quality in consideration of the channel state obtained from the feedback information. That's the way. Closed loop schemes include TxAA (Transmit Antenna Array) schemes.

User equipments performing MU-MIMO in the same resource region operate in a group with each other, and channel performance is degraded due to channel interference between the user equipments. Therefore, a method for reducing channel interference between user equipments performing MIMO in the same resource region is required.

The present invention provides a method and apparatus for reducing channel interference between user equipments.

In addition, the present invention provides a method and apparatus that can reduce the feedback overhead by reducing the amount of feedback information that the user equipment transmits to the base station.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are apparent to those skilled in the art from the following detailed description. Can be understood.

In one aspect of the present invention, in a wireless communication system in which a plurality of user equipment simultaneously receives a signal transmitted from one base station, a method of transmitting a precoding matrix information by a specific user equipment of the plurality of user equipment, the signal In reception, a first precoding matrix, which is a precoding matrix for the specific user equipment, is determined from a predetermined codebook, and at least one second precoding matrix for another user equipment to be multiplexed in a predetermined resource region together with the specific user equipment. Determining the at least one second precoding matrix within a codebook subset of the predetermined codebook associated with the first precoding matrix; And transmitting precoding matrix information for transmitting the first precoding matrix information indicating the first precoding matrix and the second precoding matrix information indicating the at least one second precoding matrix to the base station. A method of transmitting precoding matrix information is provided.

In another aspect of the present invention, a base station in any one of the plurality of user equipment for transmitting the precoding matrix information in a wireless communication system in which a plurality of user equipment simultaneously receives a signal transmitted from one base station, A transmitter for transmitting a signal to the transmitter; And a first precoding matrix, which is a precoding matrix for the specific user equipment, is determined from a predetermined codebook in receiving the signal, and at least one second preamble for another user equipment to be multiplexed in a predetermined resource region together with the specific user equipment. Determine a coding matrix, wherein the at least one second precoding matrix is determined within a codebook subset of the predetermined codebook associated with the first precoding matrix; And a processor for controlling the transmitter to transmit first precoding matrix information indicating the first precoding matrix and second precoding matrix information indicating the second precoding matrix to the base station. Is provided.

According to another aspect of the present invention, in a wireless communication system in which one base station simultaneously transmits signals to a plurality of user equipments, the base station transmits data, wherein the corresponding user is determined in a predetermined codebook from the plurality of user equipments. The first precoding matrix as first precoding matrix information indicating a first precoding matrix, which is a precoding matrix for a user equipment, and a precoding matrix for another user equipment to be multiplexed in a predetermined resource region together with the corresponding user equipment. Receiving second precoding matrix information indicating at least one second precoding matrix determined within a codebook subset of a given codebook associated with the matrix; Selecting a precoding matrix for transmission data of each user equipment to be transmitted on the predetermined resource region based on the first precoding matrix information and the second precoding matrix information; And precoding the transmission data of the respective user equipment into the selected corresponding precoding matrix, and transmitting the transmitted data to the respective user equipment in the predetermined resource region.

In another aspect of the present invention, in a wireless communication system in which one base station simultaneously transmits signals to a plurality of user equipments, the base station is a precoding matrix for the corresponding user equipment determined in a predetermined codebook from the plurality of user equipments. Information in a codebook subset of a predetermined codebook associated with the first precoding matrix as first precoding matrix information indicating one precoding matrix and a precoding matrix for another user equipment to be multiplexed in a predetermined resource region together with the corresponding user equipment. An antenna configured to receive second precoding matrix information indicating the one or more second precoding matrices determined in U; And a precoder configured to precode the transmission data; Select a precoding matrix for transmission data of each user equipment to be transmitted on the predetermined resource region based on the first precoding matrix information and the second precoding matrix information, and transmit the corresponding transmission data to the selected precoding matrix. And a processor for controlling the precoder to precode and controlling the antenna to transmit the precoded transmission data to the respective user equipment in the predetermined resource region.

In each aspect of the invention, the second precoding matrix information may comprise an index of the second precoding matrix defined within the codebook subset.

Further, in each aspect of the present invention, the first precoding matrix information includes an index of the first precoding matrix defined within the predetermined codebook, or the codebook in codebook subsets belonging to the predetermined codebook. Information specifying a subset and an index of the first precoding matrix defined within the codebook subset.

In addition, in each aspect of the present invention, the second precoding matrix information may include information designating one of patterns that prioritize the precoding matrices in the codebook subset.

Further, in each aspect of the present invention, information specifying one of the codebook subsets belonging to the predetermined codebook and one of the patterns defining the priority of precoding matrices in the codebook subset may include: It may be sent to the base station as first and second precoding matrix information.

In addition, in each aspect of the present invention, the codebook subset may be configured with the first precoding matrix and a precoding matrix having a value below a predetermined correlation with the first precoding matrix.

According to a wireless communication system according to embodiments of the present invention, there is an advantage in that channel interference can be reduced through feedback information transmitted between a user equipment and a base station.

In addition, there is an advantage that the feedback overhead can be reduced by reducing the amount of feedback information transmitted between the user equipment and the base station.

The effects according to the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the detailed description of the present invention. There will be.

1 is a conceptual diagram illustrating a wireless communication system to which the present invention can be applied.

2 is a block diagram illustrating components of a user equipment and a base station for carrying out the present invention.

3 illustrates a signal processing procedure using an orthogonal frequency division multiple access (OFDMA) scheme.

4 is a diagram illustrating an outline of a MIMO operation.

5 is a diagram illustrating an example of a single user MIMO.

6 is a diagram illustrating an example of a multi-user MIMO.

7 is a conceptual diagram illustrating scheduling data for a plurality of users together for downlink transmission.

8 is a table illustrating an example of a 4-bit codebook.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates 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 system, but is applicable to any other mobile communication system except for the specific matter of 3GPP LTE.

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.

1 is a conceptual diagram illustrating a wireless communication system to which the present invention can be applied. The wireless communication system includes at least one base station (BS) 11. Each base station (110, 120, 130) provides a communication service for the user equipment (User Equipment, UE) located in a particular geographic area (commonly called a cell) (Cell A, Cell B, ..., Cell F) do. The user device may be fixed or mobile, and various devices that communicate with the base station to transmit and receive user data and / or various control information belong to the same. The user equipment may be a terminal equipment, a mobile station (MS), a mobile terminal (MT), a user terminal (UT), a subscriber station (SS), a wireless device, a personal digital assistant (PDA), a wireless modem ( It may be called a wireless modem, a handheld device, or the like. A base station generally refers to a fixed station that communicates with a user equipment and / or another base station, and communicates with the user equipment and other base stations to exchange various data and control information. The base station may be called in other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point.

In a multi-cell environment, there are intra base stations 110 and 120 and inter base stations 130. An intra base station consists of several cells (or sectors). Cells sharing a base station such as a cell to which a specific user equipment belongs are cells corresponding to intra base stations 110 and 120 with respect to a cell to which the specific user equipment belongs, and cells belonging to other base stations are cells to which the specific user equipment belongs. With respect to the cells corresponding to the inter base station 130. Meanwhile, an intra base station may be referred to as a serving base station and an inter base station may be referred to as a neighbor base station for a specific cell. As such, cells based on the same base station as a specific user equipment exchange information (for example, data and channel quality control information) through an x2 interface, but are based on another base station. They may exchange information between cells through a backhaul 140 or the like. As shown in FIG. 1, a single cell MIMO user 160 communicates with one base station in one cell (sector), and a multi-cell MIMO user 150 located at a cell boundary has multiple base stations in multiple cells (sectors). Communicate with For example, a single cell MIMO user 160 UE0 may communicate with eNB A in Cell A, UE2 in Cell B, UE4 in Cell E, and UE5 in Cell D with eNB B. The multi-cell MIMO user 150 can communicate with eNB A in Cell A and Cell C and UE3 communicates with eNB B in Cell B and Cell C while UE1 communicates with eNB A in Cell B and Cell C.

2 is a block diagram illustrating components of a user equipment and a base station for carrying out the present invention.

The user device 12 operates as a transmitter in uplink and as a receiver in downlink. On the contrary, the base station 11 may operate as a receiver in uplink and as a transmitter in downlink.

The user equipment 12 and the base station 11 are antennas 500a and 500b capable of receiving information and / or data, signals, messages and the like, and transmitters 100a and 100b which control the antennas and transmit messages. And a receiver (300a, 300b) for receiving a message by controlling the antenna, and memory (200a, 200b) for storing a variety of information related to communication in the wireless communication system. In addition, the user equipment 12 and the base station 11 control the components of the user equipment 12 or the base station 11, such as a transmitter, a receiver, a memory, etc., the processor 400a, 400b configured to perform the present invention. Each includes. The transmitter 100a, the receiver 300a, the memory 200a, and the processor 400a in the user device 12 may be embodied as independent components by separate chips, and two or more of them may be one. It may be implemented by a chip. Similarly, the transmitter 100b, the receiver 300b, the memory 200b, and the processor 400b in the base station 11 may each be implemented as separate components by separate chips, and two or more are one. It may be implemented by a chip of.

The antennas 500a and 500b transmit a signal generated by the transmitters 100a and 100b to the outside, or receive a radio signal from the outside and transmit the signal to the receivers 300a and 300b. A transmission / reception module supporting a multi-input multi-output (MIMO) function for transmitting and receiving data using a plurality of antennas may be connected to two or more antennas.

Processors 400a and 400b typically control the overall operation of various modules within user equipment 12 or base station 11. In particular, the processor 400a or 400b includes various control functions for performing the present invention, a medium access control (MAC) frame variable control function according to service characteristics and a propagation environment, a power saving mode function for controlling idle mode operation, and a hand. Handover, authentication and encryption functions can be performed. The processors 400a and 400b may also be referred to as controllers, microcontrollers, microprocessors, microcomputers, or the like. Meanwhile, the processors 400a and 400b may be implemented by hardware or firmware, software, or a combination thereof. When implementing the present invention using hardware, application specific integrated circuits (ASICs) or digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays) may be provided in the processors 400a and 400b. Meanwhile, when implementing the present invention using firmware or software, the firmware or software may be configured to include a module, a procedure, or a function for performing the functions or operations of the present invention, and configured to perform the present invention. The firmware or software may be provided in the processors 400a and 400b or may be stored in the memory 200a and 200b to be driven by the processors 400a and 400b.

Transmitters 100a and 100b perform predetermined coding and modulation on signals and / or data scheduled from the processors 400a and 400b and then transmitted to the antennas 500a and 500b. do. For example, the transmitters 100a and 100b convert the data sequence to be transmitted into K signal sequences through demultiplexing, channel encoding, and modulation. The K signal strings are transmitted through the transmit antennas 500a and 500b through a transmitter in the transmitter. The transmitters 100a and 100b and the receivers 300a and 300b of the user device 12 and the base station 11 may be configured differently according to a process of processing a transmission signal and a reception signal.

3 illustrates a signal processing procedure using an orthogonal frequency division multiple access (OFDMA) scheme.

The transmitter in the user equipment or the base station may transmit one or more code words. Each of the one or more codewords may be scrambled by the scrambling module 301 and modulated into a complex symbol by the modulation mapper 302. The layer mapper 303 maps the complex symbols to one or more transmission layers, and the precoder 304 multiplies the complex symbols of the transmission layers by a predetermined precoding matrix W selected according to channel conditions and outputs the complex symbols for each antenna. The precoder 304 may use both a codebook method and a non-codebook method. The complex symbols for each antenna are mapped to time-frequency resource elements to be used for transmission by the resource element mapper 305, and the complex symbols for each antenna mapped to the time-frequency resource elements are OFDM signal generators. 306 is converted into an OFDM signal for each antenna port and transmitted to each antenna port.

For reference, the OFDMA scheme is widely used for downlink transmission because frequency efficiency and cell capacity can be increased. However, the OFDMA scheme may be used for uplink transmission.

4 is a diagram illustrating an outline of a MIMO operation.

The base station has a precoding matrix W, and there is a channel matrix H between the base station and the user equipment (UE). The user equipment estimates such a channel matrix H through a reference signal (RS) from the base station, and generates and feeds back precoding matrix information that helps the base station set the precoding matrix W well. Estimating the channel quality and the number of transmittable signal streams from the reference signal, and transmitting a CQI (Channel Quality Indicator) indicating the channel quality and a RI (Rank Indicator) indicating how many signal streams can be transmitted simultaneously to the base station. It is also possible to transmit.

For reference, in setting the precoding matrix W, both a codebook method and a non-codebook method may be used. Hereinafter, the codebook method will be described as an example for convenience of description. In the codebook method, the precoding matrix is selected based on the codebook, but the user equipment actually reduces the amount of feedback information because the user equipment designates the precoding matrix by feeding back only the index of the codebook. Referring to FIG. 4, the user equipment selects a precoding matrix estimated to minimize channel interference with respect to the user equipment among codebooks that designate 'L' precoding matrices, and indicates a precoding matrix indicator. (Precoding Matrix Indicator, PMI) can be transmitted to the base station. The base station selects a precoding matrix based on the PMI, multiplies the data to be transmitted to the user equipment, and transmits the precoding matrix to the user equipment.

Table 1 shows an example of a codebook for 2-port antenna transmission, and Table 2 shows an example of a codebook for 4-port antenna transmission.

Table 1 is called a 2-bit codebook because it can specify a codebook index as 2 bits, and Table 2 is called a 4-bit codebook because it can specify a codebook index as 4 bits. Although only 2-bit and 4-bit codebooks are taken as examples, 8-bit, 16-bit, and 64-bit codebooks may be further defined as the number of antenna ports increases. In addition, the codebooks of Tables 1 and 2 designate a precoding matrix according to the LTE standard, and a different form of precoding matrix may be designated according to the wireless communication system standard. Hereinafter, embodiments of the present invention will be described using a 4-bit codebook as an example for convenience of explanation, but it is obvious that the present invention can be similarly applied to codebooks of other bits.

Table 1

TABLE 2

The base station selects a precoding matrix W in a codebook defined between the base station and the user equipment based on the PMI fed back from the user equipment, and performs precoding by multiplying the selected precoding matrix W by the complex symbols of the transmission layer. .

5 is a diagram illustrating an example of a single user MIMO, and FIG. 6 is a diagram illustrating an example of a multiuser-MIMO.

As shown in FIG. 5, single-user MIMO is a structure in which a plurality of different transport streams transmitted by a base station are all transmitted to one user. In the case of single-user MIMO, one transmitter and one receiver constitute a MIMO channel. In the case of single-user MIMO, one user can receive all signals. That is, only data for one user is scheduled in the same time / frequency domain.

As shown in FIG. 6, multi-user MIMO transmits a plurality of different transport streams transmitted by a base station to a plurality of users. In the case of multi-user MIMO, one transmitter and several receivers combine to form a MIMO channel. That is, data may be scheduled together for multiple users in the same time / frequency domain.

7 is a conceptual diagram illustrating scheduling data for a plurality of users together for downlink transmission.

The scheduler may schedule data of specific users to be transmitted together based on precoding matrix information from the user equipment or feedback information such as CQI and RI. Referring to FIG. 7, the scheduler may schedule transmission data for user equipment 0 (UE ₀ ) to user equipment K (UE _K ) in the same time / frequency domain.

For reference, the processor 400b in the base station may be configured to perform a function of a scheduler. It is also possible that the control station connected to the base station has a scheduler and transmits schedule information to the base station. The scheduler may be configured as an independent module and provided in the base station or the control station.

When various data allocated to a frequency band of a specific section is scheduled to be transmitted in a specific time section, it is referred to as being scheduled in the same time / frequency region (or the same resource region). For example, when data for multiple users are scheduled in the same frame or in the same slot, in the same resource grid, or in the same resource block, the multiple users are in the same time / frequency domain. (Or the same resource zone).

When there are a plurality of user equipments in a cell served by the base station, each of the plurality of user equipments has a CQI indicating the quality of a channel formed between itself and the base station, and a PMI for minimizing channel interference affecting itself. The RI is fed back to the base station indicating how many signal streams can be transmitted on the channel at the same time. The CQI, PMI, RI, etc. fed back from the user equipment to the base station indicate the state of the channel formed between the user equipment and the base station, and is called channel state information. The base station selects a transmission channel or improves the quality of the transmission channel. It is also used to control channel quality control information (channel quality control information).

The base station selects user equipments to be scheduled together based on PMIs, CQIs, RIs, etc. sent by the plurality of user equipments, and sets a precoding matrix W based on PMIs sent by the user equipments to be scheduled together. In this case, the precoding matrix indicated by the PMI for minimizing the channel interference affecting the specific user equipment may not be selected as the final precoding matrix by the PMI transmitted by other user equipment scheduled together. . For example, even if user equipment 0 (UE ₀ ) transmits a PMI indicating '0' of an N-bit codebook index, the best precoding matrix W ₀ is applied to user equipment 0 by PMIs transmitted by other user equipments. It may not be selected. That is, when a base station receives several PMIs from a plurality of user equipments, the base station arbitrarily selects a matrix for precoding data of user equipments to be scheduled together based on these PMIs. User device 0 may include something that is not the best precoding matrix. In this case, the interference by the channel of the other user equipments scheduled together may not be sufficiently reduced, resulting in degradation of downlink signal transmission performance to the user equipment 0. In addition, as transmission data of a plurality of user equipments are simultaneously transmitted in a predetermined resource region, channel interference occurs between transmission data of different user equipments transmitted together in the predetermined resource region, thereby degrading performance of a wireless communication system. Will result.

Therefore, one embodiment of the present invention is considered in the case that the data for a plurality of user equipment is scheduled together in the same time / frequency domain, only the information specifying the best precoding matrix for the transmission data for the user equipment Rather, information is transmitted to the base station together with information specifying a precoding matrix to be applied to transmission data of another user equipment scheduled together with the corresponding user equipment. In other words, when a specific user equipment transmits feedback information to a base station, a PMI indicating a precoding matrix to be used by another user equipment to be scheduled in a predetermined resource region together with the specific user equipment, in addition to the best PMI suitable for the specific user equipment. Select one or more to transmit to the base station together. For reference, hereinafter, a precoding matrix to be applied to transmission data of a specific user equipment will be referred to as a best precoding matrix, and the precoding matrix to be used by the other user equipment will be described as a best companion. On the other hand, when the user equipment feeds back information indicating the best companion to the base station, as the size of the codebook increases, the number of precoding matrices to be evaluated by the processor increases, and thus the processor and processing having higher processing performance. Higher memory capacity is required of the user equipment to temporarily store data.

Selected as best companion for MU-MIMO

Hereinafter, embodiments of the present invention for selecting a best companion without a sharp increase in processing performance and memory capacity will be described. 8 is a table illustrating an example of a 4-bit codebook to describe embodiments of the present invention. For convenience of explanation, a 4-bit codebook is described as an example, but it is obvious that embodiments of the present invention can be equally applied to codebooks of other bits.

According to an embodiment of the present invention, a base station of a serving cell to which a specific user equipment currently belongs is specified in addition to information specifying a precoding matrix that the base station wants to apply to transmission data of the specific user equipment. Transmitting information specifying a precoding matrix for transmission data of another user equipment to be transmitted, that is, information specifying a best companion, to the base station, and selecting the best companion from all precoding matrices in a base codebook. Instead, the best companion is obtained from a codebook subset consisting of matrixes having a constant relationship with a precoding matrix (hereinafter, best precoding matrix) to be applied to transmission data of the specific user equipment among precoding matrices of a basic codebook. It selects and transmits information about the PMI designating this to the base station.

When selecting the best companion from a codebook subset, preference is only given to precoding matrices belonging to the codebook subset, which reduces processing time and more than evaluating all the precoding matrices of the basic codebook to determine preference. The advantage is that you can choose the best companion with less processing capacity. In addition, since the codebook subset is composed of matrices having a constant relation with the best precoding matrix, when a base station cannot select the best precoding matrix designated by a specific user equipment, the codebook subset is arbitrarily selected from the entire precoding matrix of the basic codebook. There is an advantage that the precoding matrix selected in the codebook subset reduces the risk of worsening channel interference between user equipments rather than the precoding matrix.

Various criteria or algorithms for defining the codebook subset may be stored in the user equipment and the base station, respectively. For example, the user equipment and the base station may consist of precoding matrices indicated by codebook indices within a range from the best PMI specifying the best precoding matrix, or may be composed of precoding matrices orthogonal to the best PMI. An algorithm may be configured of precoding matrices having a value less than or equal to a predetermined correlation, or a codebook subset is determined from precoding matrices that are advantageous for reducing channel interference for each transmission mode determined according to a predetermined criterion.

Referring to FIG. 8, the base station and the user equipment select precoding matrices designated by n codebook indexes, m lines, or l codebook indexes indicated by the PMI transmitted by the user equipment as the codebook subset. You can decide in advance. 2 and 4, when a processor 400a in a specific user equipment selects a best precoding matrix for the specific user equipment, the codebook subset may store precoding matrices in a range from the best precoding matrix. And select the best companion in the codebook subset. The processor 400a generates precoding matrix information for designating the best precoding matrix and the best companion, and controls the transmitter 100a and the antenna 500a in the user equipment to transmit the precoding matrix information to the base station. Can be sent to. Based on the precoding matrix information from the specific user equipment, the processor 400b of the base station selects the best precoding matrix for the specific user equipment and the user equipment (s) multiplexed in a predetermined resource region together with the specific user equipment. We can check the precoding matrix (s) for. For example, assuming that the precoding matrix W ₃ corresponding to the codebook index 3 is the best precoding matrix for a specific user equipment, the user equipment and the base station are each n lines after the matrix designated by the codebook index 3, for example. And a set {W ₁ , W ₂ , W ₃ , W ₄ , W ₅ } including _two precoding matrices as a codebook subset corresponding to the best precoding matrix. Alternatively, in the case of configuring a set including m predecessors starting with the precoding matrix W _3, for example, four precoding matrices, as a codebook subset, the codebook subset {W ₃ , W ₄ , W _5, W ₆ } It may be determined as a codebook subset for the specific user equipment.

As another example, referring to FIG. 8, assuming that codebook indices 0 to 3, 4 to 7, 8 to 11, and 12 to 15 are orthogonal precoding matrices, a set of orthogonal precoding matrices is formed. It may be set as a codebook subset. For reference, a precoding matrix for minimizing channel interference between a channel of a specific user equipment and a channel of another user equipment is likely to have an orthogonal relationship with the precoding matrix that provides the best signal to the specific user equipment. That is, the smaller the best precoding matrix and correlation with respect to the specific user equipment, the more the channel interference of the other user equipment with respect to the channel of the specific user equipment may be minimized. 2 and 4, the processor 400a of the user equipment determines which of the precoding matrices in the basic codebook is the best precoding matrix for the user, and the best companion is the best precoding matrix. It can be configured to determine among the matrices that are orthogonal. The user equipment processor 400a may control the transmitter 100a and the antenna 500a of the user equipment to transmit the precoding matrix information specifying the best precoding matrix and the best companion to the user equipment.

As another example, if W _x , W _y , and W _z defined in the basic codebook in a particular transmission mode are predetermined to minimize channel interference, the set {W _x , W _y , W _z } consisting of them is codebook subset. It is also possible to specify. 2 and 4, a codebook subset according to a specific transmission mode may be predefined between a user equipment and a base station, and the processor 400a of the user equipment may use a codebook subset for itself from a codebook subset corresponding to the specific transmission mode. The best precoding matrix and the best companion for another user equipment may be determined, and the transmitter 100a and the antenna 500a may be controlled to transmit the information indicating the best precoding matrix and the best companion to the base station.

In the following description, for the convenience of description, the codebook subsets are defined by precoding matrices in orthogonal relations. However, it is apparent that the following embodiments can be applied in a similar manner to codebook subsets defined by other criteria as well as codebook subsets of orthogonal precoding matrices.

Referring to FIG. 8, the precoding matrices designated by codebook indices 0 to 3 are orthogonal to each other, the precoding matrices designated by codebook indices 4 to 7 are orthogonal to each other, and codebook indices 8 to 11 The precoding matrices specified by orthogonal to each other may be orthogonal to each other, and the precoding matrices designated by the codebook indexes 12 to 15 may be orthogonal to each other.

Assuming that the best precoding matrix of user equipment 0 corresponds to codebook index '1', the user equipment selects the best companion from the precoding matrices of codebook indexes 0, 2, and 3 that are orthogonal to each other, and selects the best The best companion PMI specifying the companion can be transmitted to the base station along with the best PMI specifying the best precoding matrix. The base station selects the best PMI that specifies the best precoding matrix sent by the user equipment 0 and the best companion PMI that specifies the best companion, and the best PMI and the best companion PMI sent by other user equipments to be scheduled together in a predetermined resource region. As a reference, each precoding matrix for data to be transmitted to these user equipments can be selected.

The number of best companions selected by the user equipment may depend on the number of user equipments that can be scheduled together or the number of signal streams that can be scheduled together. The number of selectable best companions depends on the number of user equipments that can be scheduled together or the number of signal streams, for example, when user 0 can receive three signal streams at the same time. ) it is '3', the user equipment 0 to of the best precoding matrix W _0, W _2, which is orthogonal to W ₁ W ₃ determines two, best Compassion, the best precoding matrix W ₁ and best Information specifying two companions may be fed back to the base station. For example, the best precoding matrix W orthogonal to W _{1 0} and W _2, W ₃ of the selection of the two best Compassion years for the user devices 0 to W ₃ and W ₀ in order, and W ₁ and W _3, W Information specifying ₀ respectively can be fed back to the base station. 2 and 4, the processor 400a of the user equipment is the best precoding matrix W for itself among the precoding matrices in the codebook stored in the user equipment processor 400a itself or the memory 200a of the user equipment. determining a _first and a transmitter (100a) of said W ₁ and orthogonal codebook subset comprised of the precoding matrix {W _0, W _1, W _2, W _3} selecting a W ₃ and W _0, respectively, and from the user equipment By controlling, the precoding matrix information for sequentially specifying W ₁ , W ₃ , and W ₀ may be transmitted to the base station.

 For reference, when the best companions are linked to the rank, the number of best companions indicates the number of signal streams that can be simultaneously transmitted by the user equipment. Thus, the same effect as that of transmitting RIs with PMI can be obtained. There are advantages to it. Therefore, when the number of precoding matrices selected by the user equipment depends on the rank, the processor 400a of the user equipment may not generate the RI, and the user may not transmit the RI to reduce the feedback overhead even if the user equipment generates the RI. It is also possible to control the device transmitter 100a. The base station processor 400b may check the number of precoding matrices designated by the user equipment, which precoding matrices are designated, and the number of streams each user equipment can receive from the feedback precoding matrix information.

On the other hand, regardless of the rank, it is also possible to select a certain number of best companions and feed back the information indicating these to the base station. For example, if the number of precoding matrices that a user equipment can specify is three, even if the rank of the user equipment is '2', the best precoding matrices and the two best companions are determined in order of preference. It is also possible to feed back information indicating the precoding matrix to the base station.

Feedback of best precoding matrix and best companion information

Hereinafter, embodiments of feeding back information to designate a best precoding matrix and a best companion to a base station will be described. For convenience of explanation, the user device 0 selected from the 4-bit codebook 0 is selected from the best precoding matrix W ₁ , the best companion W ₃ selected from the subset of codebooks constant with W ₁ , and the next preferred best year W. _{An example} of selecting ₀ and feeding back information indicating these to the base station will be described as an example. That is, the user device 0 selects a precoding matrix W ₁ that the base station wants to apply to the transmission data when transmitting data to the user device 0, and there are other user devices to be multiplexed in a predetermined resource region together with the user device 0. In consideration of the case, a case in which a best coding year for minimizing interference on the user device 0 is selected in order of W _{3 and} W ₀ is used as a precoding matrix that is desired to be applied to transmission data of another user device. Hereinafter, the PMI specifying the precoding matrix W _K will be described as PMI _K. In addition, below, the information which designates the best and best companion year is collectively demonstrated as precoding matrix information.

Feedback Example 1:

According to an embodiment of the present invention, the user equipment may transmit, as the precoding matrix information, the PMI for each of the best companions selected from the best precoding matrix and a codebook subset having a constant relation with the best precoding matrix.

For example, the user equipment 0 may transmit to the base station in the order of PMI ₁ for the precoding matrix W ₁ , PMI ₃ for the precoding matrix W ₃ , and PMI ₀ for the precoding matrix W ₀ .

2 and 4, the processor 400a of the user equipment determines PMI ₁ for the best precoding matrix W ₁ , PMI ₃ for the first best companion W ₃ , and PMI ₀ for the second best companion W ₀ . It can control the base station transmitter (100a) to transmit.

In the case of a 4-bit codebook, since each PMI is represented by 4 bits, a total of 12 bits are required for feedback of precoding matrix information according to the present embodiment. When the number of best companions to designate increases, the amount of feedback to be transmitted to the base station also increases proportionally as the number of best companions increases. In addition, even when the MIMO order increases and the codebook index increases, the amount of feedback information increases. For example, in the case of an 8-bit codebook, 3x8 bits, or 24 bits, are required to feed back three PMIs. As a result, there is a risk that an increase in the number of best companions or an increase in MIMO orders may lead to feedback overhead.

Feedback Examples 2 to 7 to be described below have an advantage in that feedback overhead can be reduced compared to the effects of Embodiment 1.

Feedback Example 2:

The user equipment and the base station may predetermine a pattern according to the priority of the matrixes of the codebook subset, and transmit the information specifying the user equipment preferred pattern as the precoding matrix information to the base station together with the information specifying the best precoding matrix. have.

For example, three precoding matrices are selected in order from the codebook subset {W ₀ , W ₂ , W ₃ } consistent with the best precoding matrix W ₁ , for a total of six for each particular best precoding matrix and codebook subset. It is also possible to predetermine two patterns ( ₃ P ₃ = 6). An example can be shown below. For reference, the codebook subset _{{W O, W 2, W} 3} can be obtained a pattern of the same number in the pick as the three precoding matrix sequence ₍₃ P ₂ = 6).

TABLE 3

Pattern Index	2nd best Matrix	3rd best Matrix	4th best Matrix
000	W 0	W 2	W 3
001	W 0	W 3	W 2
010	W 2	W 0	W 3
011	W 2	W 3	W 0
100	W 3	W 0	W 2
101	W 3	W 2	W 0

The best precoding matrix for user equipment 0 is W ₁ and the order of the preferred best companion, that is, the order of the precoding matrix that minimizes interference to the user equipment by other user equipment is W ₂ , W _O , W If the order is ₃ , the user equipment 0 can feed back the base station with 4 bits of PMI designating the best precoding matrix W ₁ and 3 bits of pattern index designating the best companions W ₂ , W _O , and W _{3 in} that order. For reference, if the best precoding matrix of user equipment 1 is W ₂ , the best companion pattern for user equipment 1 will be determined by combining W ₀ , W ₁ , and W ₃ , and the best precoding of user equipment 3 If the matrix belongs to a codebook subset different from W ₁ , the pattern of the precoding matrix for user equipment 3 will be determined by the combination of the precoding matrices of the other codebook subset.

2, 3, 8 and Table 3, the processor of the user equipment 0 configures the precoding matrix information using a total of 7 bits of the PMI bit string '0001' and the pattern index bit string '010'. The transmitter and the antenna of the user equipment 0 may be controlled to feed back the precoding matrix information to the base station. The antenna of the base station receives the precoding matrix information, and the processor of the base station can know the best precoding matrix W ₁ for user equipment 0 and the precoding matrix pattern group associated with the W ₁ by the first 4 bits. Then, it can be seen that the rank of the best companion for the user equipment 0 among the precoding matrix patterns associated with the W ₁ is in the order of W ₂ , W _O , and W ₃ by 3 bits.

The processor of the base station selects precoding matrices to be applied to user equipments to be scheduled together in a predetermined resource region based on 7 bits of precoding matrix information transmitted from user equipment 0 and precoding matrix information transmitted from other user equipments. can do. In addition, the base station processor 400b may control the transmitter 100b of the base station to precode data for the corresponding user equipment by applying the selected precoding matrices. In addition, the base station processor 400b may control the base station transmitter 100b to transmit data of the precoded user equipments in the predetermined resource region.

Feedback Example 3:

The user equipment and the base station predetermine patterns according to the priorities of the matrixes of the codebook subset, and the base station uses the information indicating the codebook subset including the preferred pattern of the user equipment and the information indicating the preferred pattern as the precoding matrix information. Can also be sent to.

For example, it is possible to divide a 4-bit basic codebook into four 2-bit codebook subsets, and to set a pattern of a precoding matrix of each codebook subset. If the codebook subset to which the best precoding matrix W ₁ of user equipment 0 belongs is {W _O , W ₁ , W ₂ , W ₃ }, four precoding matrices are sequentially selected from the codebook subset, and a total of 24 codebook subsets are selected. The pattern may be predetermined ( ₄ P ₄ = 24). For reference, the codebook subset _{{W O, W 1, W} 2, W 3} , can have from three precoding matrix to choose a pattern of the same number in the order information ₍₄ P ₃ = 24). An example of a pattern in which four matrices constituting the codebook subset {W _O , W ₁ , W ₂ , W ₃ } are arranged in order may be shown as follows.

Table 4

Pattern Index	Best matrix	2nd best Matrix	3rd best Matrix	4th best Matrix
00000	W 0	W 1	W 2	W 3
00001	W 0	W 1	W 3	W 2
00010	W 0	W 2	W 1	W 3
00011	W 0	W 2	W 3	W 1
00100	W 0	W 3	W 1	W 2
00101	W 0	W 3	W 2	W 1
00110	W 1	W 0	W 2	W 3
00111	W 1	W 0	W 2	W 3
01000	W 1	W 2	W 0	W 3
01001	W 1	W 2	W 3	W 0
01010	W 1	W 3	W 0	W 2
01011	W 1	W 3	W 2	W 0
01100	W 2	W 0	W 1	W 3
01101	W 2	W 0	W 3	W 1
01110	W 2	W 1	W 0	W 3
01111	W 2	W 1	W 3	W 0
10000	W 2	W 3	W 0	W 1
10001	W 2	W 3	W 1	W 0
10010	W 3	W 0	W 1	W 2
10011	W 3	W 0	W 2	W 1
10100	W 3	W 1	W 0	W 2
10101	W 3	W 1	W 2	W 0
10110	W 3	W 2	W 0	W 1
10111	W 3	W 2	W 1	W 0

A total of 2 bits are required to indicate the codebook subset {W _O , W ₁ , W ₂ , W ₃ } among the total of 4 codebook subsets, and a total of 5 bits to indicate the preferred pattern of the user equipment among the total 24 patterns. Is needed. The codebook subset {W _O , W ₁ , W ₂ , W ₃ } is the first codebook subset, user equipment 0's preferred best precoding matrix is W _1, and the best companions are W ₂ , W _O , and W ₃ . 2 and 8 and Table 4, the processor of the user equipment 0 has a bit string '00' 2 bits and the precoding matrix W ₁ , W ₂ , W _O , W ₃ that designate the codebook subset. The precoding matrix information may be configured using 5 bits of the pattern index bit string '01000', which specifies the order, and the precoding matrix information may be fed back to the base station by controlling the transmitter and the antenna of the user device _0. The base station antenna and the receiver receive the 7-bit precoding matrix information transmitted from the user equipment 0, and the processor of the base station is a precoding matrix preferred by the user equipment 0 by the preceding two bits of the precoding matrix information. The codebook subsets {W _O , W ₁ , W ₂ , W ₃ } belong to each other, and the next 5 bits indicate the best precoding matrix for user equipment 0 is W ₁ , and the preferred best companion is W in order. It can be seen that ₂ , W _O , W ₃ . The processor of the base station may be scheduled together in a predetermined resource region based on 7 bits of precoding matrix information transmitted from user equipment 0 and precoding matrix information transmitted from other user equipments, that is, multiplexed together in the predetermined resource region. A precoding matrix to be applied to each user device can be selected. For example, the base station processor selects a precoding matrix to be applied to the transmission data of the user equipment 0 based on the best precoding matrix W ₁ feedbacked by the user equipment 0 and the best companion transmitted by the other user equipment. Precodings to be applied to the transmission data of each of the other user devices may be selected based on the best companion designated by the user device 0 and the corresponding best precoding matrix fed back by the other user devices. The base station processor may control the transmitter 100b of the base station to precode transmission data of the corresponding user equipment multiplexed in the predetermined resource region by applying the selected precoding matrix. The base station processor may control the base station transmitter 100b to simultaneously transmit transmission data of user equipments scheduled together in the predetermined resource region to the user equipments through the predetermined resource region.

Feedback Example 4:

It is also possible to transmit the information specifying the predetermined codebook subset and the information specifying the precoding matrix in the codebook subset between the user equipment and the base station as the precoding matrix information to the base station.

For example, assuming that four user equipment and a base station have four codebook subsets of four precoding matrices defined, two bits are required to specify a codebook subset, and one precoding matrix is generated from the codebook subset. Each bit requires 2 bits. For example, the best precoding matrix of user equipment 0 is included in the first codebook subset {W ₁ , W ₂ , W _O , W ₃ }, and the best precoding matrix of user equipment 0 is W ₁ and the preferred best comp If the order of years is W ₁ , W ₂ , W _O , and W ₃ , the processor of user equipment 0 has the best precoding matrix W of 2 bits that designate the first codebook subset and the four precoding matrices of the first codebook subset. Preferred precoding matrix in the first codebook subset using a total of 8 bits, including 2 bits specifying ₁ , 2 bits specifying the best best companion W ₂ , and ₂ bits specifying the next best best year W _O. Can be specified in order. That is, the processor of the user equipment 0 configures 8-bit precoding matrix information, and transmits the precoding matrix information to the base station by controlling the transmitter and the antenna of the user equipment 0. A base station receives the 8-bit precoding matrix information transmitted from the user equipment 0 through an antenna and a receiver, and the processor of the base station selects the best value for the user equipment 0 by the first two bits of the precoding matrix information. The codebook subset {W _O , W ₁ , W ₂ , W ₃ } to which the precoding matrix and the Best Companion belong, can be seen, and the next 2 bits indicate that the best precoding matrix is W ₁ , and the next 2 bits It can be seen that the first best companion W ₂ , and then the second best companion is W _O by the next 2 bits. The processor of the base station selects precoding matrices to be applied to user equipments to be scheduled together in a predetermined resource region based on the 8 bits of the precoding matrix information transmitted from user equipment 0 and the precoding matrix information transmitted from other user equipments. Each can be selected. In addition, the base station processor may control the transmitter 100b of the base station to precode the transmission data of the user equipments scheduled together using the selected corresponding precoding matrix. The base station transmitter 100b may transmit the precoded transmission data to the predetermined user equipments through the predetermined resource region under the control of the base station processor 400b.

Feedback Example 5:

Information for specifying a predetermined codebook subset and information specifying a precoding matrix in the codebook subset between the user equipment and the base station is transmitted to the base station, but the best companions are the remaining matrices except the precoding matrix that has already been prioritized in the codebook subset. It is also possible to transmit the precoding matrix information to the base station in the form of choosing.

For example, assuming that four codebook subsets of four precoding matrices are defined in the user equipment and the base station, two bits are required to specify the codebook subset, and the user among the four matrices of the codebook subset. Two bits are needed to specify the best precoding matrix for the instrument, two bits are needed to specify the first best companion of the remaining three matrices, and one bit is needed to specify one of the other two matrices. need. That is, the user equipment can feed back to the base station by using a total of 7 bits in order to designate its preferred precoding matrix and the best companions to be applied to other user equipments in order.

For example, the best precoding matrix W ₁ of user equipment 0 is included in the first codebook subset {W _O , W ₁ , W ₂ , W ₃ }, and the best companion wants to apply it to the transmission data of other user equipments. Assuming that W ₂ , W _O , and W ₃ are preferred, the processor of user equipment 0 has the best precoding of the two bits that designate the first codebook subset of the four codebook subsets and the four precoding matrices of the first codebook subset. 2 bits specifying the matrix W ₁ , 2 bits specifying the first best companion W ₂ of the remaining three precoding matrices, and 7 bits total, 1 bit specifying the next best companion W _O of the other two precoding matrices. Precoding matrix information for sequentially designating a preferred precoding matrix and a best companion in the first codebook subset may be configured using. The processor of the user device 0 may control the transmitter and the antenna to feed back the precoding matrix information to the base station. A base station receives the 7-bit precoding matrix information transmitted from the user equipment 0 through an antenna and a receiver, and transmits the received 7-bit precoding matrix information to the processor of the base station. The codebook subset {W _O , W ₁ , W ₂ , W ₃ } to which device 0 prefers the precoding matrix and the best companion (s) belongs, and the next 2 bits are the best precoding of the user device 0. The matrix W ₁ can be known, and the next two bits show that the first best companion is W ₂ , and the next best bit is W ₀ . The processor of the base station selects precoding matrices to be applied to user equipments to be scheduled together in a predetermined resource region based on the 7 bits of the precoding matrix information transmitted from user equipment 0 and the precoding matrix information transmitted from other user equipments. Each can be selected. In addition, the base station processor may control the transmitter 100b of the base station to precode data about the user equipments scheduled together by applying the selected corresponding precoding matrices, respectively. The base station transmitter 100b may transmit the precoded transmission data to the predetermined user equipments through the predetermined resource region under the control of the base station processor 400b.

Feedback Example 5:

It is also possible for the user equipment to transmit the PMI specifying the best precoding matrix and the information specifying the best companion in the codebook subset to which the PMI belongs to the base station as the precoding matrix information.

For example, the best precoding matrix of user equipment 0 is W ₁ , the codebook subset containing W ₁ is {W _O , W ₁ , W ₂ , W ₃ } and user 0 is the preferred best companion. Assuming that the order is W ₂ , W _O , and W ₃ , the processor on the user equipment 0 is the codebook subset that belongs to 4 bits and W ₁ that specifies W ₁ in the 4-bit codebook {W _O , W ₁ , W ₂ , W _{In 3} }, a total of 8 bits of 2 bits designating W ₂ and 2 bits designating W _O are configured as precoding matrix information, and the transmitter and antenna of the user equipment 0 are controlled to transmit the precoding matrix information to the base station. Can transmit The base station receives the 8-bit precoding matrix information through the antenna and the receiver, and it can be seen that the best precoding matrix W ₁ for user equipment 0 from the previous 4 bits, whereby W ₁ is determined by W ₁ . It can be seen that the codebook subset {W _O , W ₁ , W ₂ , W ₃ } belonging to. In addition, it can be seen that the next best bit is W ₂ by the next two bits, and the next best year is W ₀ by the next two bits. The processor of the base station may select precoding matrices to be applied to user equipments to be scheduled together based on the 8 bits of the precoding matrix information transmitted from user equipment 0 and the precoding matrix information transmitted from other user equipments. have. In addition, the base station processor may control the transmitter 100b of the base station to precode data about the user equipments scheduled together by applying the selected corresponding precoding matrices, respectively. The base station transmitter 100b may transmit the precoded transmission data to the predetermined user equipments through the predetermined resource region under the control of the base station processor 400b.

Feedback Example 6:

The user equipment transmits the PMI designating the best precoding matrix and the information specifying the best companion in the codebook subset to which the PMI belongs to the base station as the precoding matrix information, but the best comparables already have priority in the codebook subset. It is also possible to transmit the precoding matrix information to the base station in a form of selecting from the rest of the matrix except the predetermined precoding matrix.

For example, the best precoding matrix of user equipment 0 is W ₁ , the codebook subset containing W ₁ is {W _O , W ₁ , W ₂ , W ₃ } and user 0 is the preferred best companion. Assuming that the order is W ₂ , W _O , and W ₃ , the processor on the user equipment 0 is the codebook subset that belongs to 4 bits and W ₁ that specifies W ₁ in the 4-bit codebook {W _O , W ₁ , W ₂ , W _{Of the three} precoding matrices except W ₁ , 2 bits designating W ₂ , and one bit designating W _O among two precoding matrices except W ₁ and W ₂ . It can transmit to the base station as. The base station receives the 7-bit precoding matrix information through a receiver and an antenna, so that the best precoding matrix W ₁ for the user equipment 0 from the previous 4 bits and the codebook subset {W _O , W ₁ to which W ₁ belongs. , W ₂ , W ₃ }. Further, that a {W _O, W _2, W _3} Best Compassion years W ₂ of by the next two bits, {W _0, W _3} yi W ₀ in the following Best Compassion of by the next one bit of the It can be seen that. The processor of the base station may select precoding matrices to be applied to user equipments to be scheduled together based on the 7 bits of the precoding matrix information transmitted from user equipment 0 and the precoding matrix information transmitted from other user equipments. have. In addition, the base station processor may control the transmitter 100b of the base station to precode data about the user equipments scheduled together by applying the selected corresponding precoding matrices, respectively. The base station transmitter 100b may transmit the precoded transmission data to the predetermined user equipments through the predetermined resource region under the control of the base station processor 400b.

For reference, in the embodiments of the feedback 4 to 5, it is described that the information specifying the lowest priority of the lowest codebook subset among the corresponding codebook subsets is not transmitted separately, but the information specifying the lowest ranking best companion W ₃ is described. It is also possible to include in the precoding matrix information and transmit it. However, even if the lowest ranking best companion is not specified, by specifying the remaining three precoding matrices, the base station knows that W ₃ of the four precoding matrices is the best companion having the lowest preference for user equipment 0. Can be.

Feedback Example 7:

When transmitting the information specifying the best companion, it is also possible to transmit only the variation amount based on the previously selected best companion.

For example, by sending a '1' to the next bit that specifies the W _1, it is possible to indicate that the best Compassion years W ₁ directly behind the matrix W _2.

Meanwhile, the base station may receive precoding matrix information from user equipments in the area served by the base station, and select user equipments that may be scheduled together based on the precoding matrix information of the user equipments. For example, user equipment 0 feeds back to the base station precoding matrix information specifying the best precoding matrix and the best companion in the order of W ₀ , W ₃ , and W ₁ , and user equipment ₁ sends W ₃ , W ₁ , Feedback to the base station the precoding matrix information specifying the best precoding matrix and the best companion in order of W ₂ , and user equipment 2 designates the best precoding matrix and the best companion in order of W ₅ , W ₇ , and W ₄ . Suppose that precoding matrix information is fed back to the base station, and user equipment 3 feeds back the precoding matrix information specifying the best precoding matrix and the best companion in order of W ₃ , W ₁ , and W ₀ to the base station. lets do it. The processor 400b of the base station selects to schedule user devices 0 and 3 together to which a common precoding matrix is applied, and transmits data of user device ₀ by using W ₀ and transmits the user device 3. Data may be controlled by the precoder of the base station to precode using W ₃ . The base station processor may control the resource element mapper to allocate transmission data of the precoded user equipment 0 and the user equipment 3 to a predetermined resource region. The base station transmitter, under the control of the base station processor, transmits the transmission data to the user equipment 0 and the user equipment 3 in the predetermined resource region, that is, the frequency and time region of the predetermined resource region.

As mentioned above, the above embodiments have been described using the 4-bit basic codebook as an example, but it is obvious that the basic codebooks of other bits can be extended in the same manner.

In this regard, embodiments of the present invention are equally applicable to single user MIMO as well as multi-user MIMO. Applying the embodiments of the present invention regardless of whether a multi-user MIMO or a single user, the user equipment can send some form of precoding matrix information to the base station without considering which user equipments are scheduled together and how many users are scheduled together. Send it.

In addition, embodiments of the present invention are the same when a single or a plurality of user equipments in one cell served by one base station feed back precoding matrix information to the base station, as well as when applying MIMO transmission in a multi-cell environment. Can be applied. That is, embodiments of the present invention can be equally applied to multi-cell MIMO as well as single-cell MIMO. Hereinafter, a case in which embodiments of the present invention are applied to a multi-cell MIMO will be described with reference to FIG. 1.

Referring to FIG. 1, a single cell MIMO user 160 within a single cell communicates with one serving base station in one cell (sector), and a multi cell MIMO user 150 located at a cell boundary is located in a multiple cell (sector). Communication with multiple serving base stations can improve inter-cell interference and throughput of users at cell boundaries, which is referred to as a Coordinated Multi-Point (CoMP) system (hereinafter referred to as CoMP system). CoMP systems are also referred to as multi-base station MIMO systems, network MIMO systems, and collaborative MIMO systems.

In single cell MIMO, each base station (cell) forms a MIMO with single or multiple user equipments in its own coverage area and transmits a signal. In this case, signals transmitted from base stations adjacent to each other are signals to be transmitted only within a radius of their own cells, and when the signals are transmitted to adjacent cells, interference between cells occurs. On the other hand, in the multi-cell MIMO, different symbols of the MIMO transmitted to one user equipment are transmitted from adjacent base stations, and each symbol is transmitted from different base stations far apart from each other. This results in an excellent channel matrix. In other words, applying the CoMP system can reduce inter-cell interference in a multi-cell environment. Using this CoMP system, the user equipment can be jointly supported with data from a multi-cell base station. In addition, each base station can improve the performance of the system by simultaneously supporting communication with one or more user equipments (UE ₀ , UE ₁ , ..., UE _K ) using the same radio frequency resource. . In addition, the base station may perform a space division multiple access (SDMA) method based on channel state information between the base station and the user equipment.

Such a CoMP scheme may be divided into cooperative MIMO-type joint processing through a data sharing and a coordinated scheduling scheme / beamforming scheme. CoMP systems also include inter-cell cooperative processing and cooperative scheduling / beamforming techniques, as well as geographically separated transmission processes (eg, multiple antennas).

In a CoMP system, a serving base station and one or more cooperative base stations are connected to a scheduler through a backhaul 140. Since each base station may include a scheduler for scheduling signals to be transmitted to user equipments in its own coverage area, a scheduler for scheduling signals of one or more base stations may be referred to as a master scheduler by distinguishing the scheduler from each base station. do. The master scheduler is a channel between each user equipment (UE ₀ , UE ₁ , ..., UE _K ) measured by each base station (BS ₀ , BS ₁ , ..., BS _M ) through the backhaul 140 and the cooperative base station. It can operate by receiving channel information about the status. For example, the master scheduler schedules information for collaborative MIMO operations for the serving base station and one or more cooperating base stations. That is, the scheduler may directly indicate the cooperative MIMO operation to each base station.

Embodiments of the present invention are equally applicable to this CoMP system. The user equipments receiving different symbols from the plurality of base stations may feed back information indicating the best precoding matrix and the best companion of the corresponding user equipment to each of the plurality of base stations according to an embodiment of the present invention. The master scheduler receives the precoding matrix information of each user equipment received by each base station through the backhaul 140, selects user equipments to be scheduled together among several user equipments in the region of the plurality of base stations, and selects the selected user equipment. Can be assigned to the same time / frequency domain. Each base station may allocate the user equipments selected in the self coverage area to the same time / frequency domain according to the control of the master scheduler.

For example, the user equipment 0 (UE ₀ ) feeds back the precoding matrix information specifying the best precoding matrix and the best companion in the order of W ₀ , W ₃ , and W ₁ to eNB A, and the user equipment 1 (UE _1). ) Feeds back the precoding matrix information specifying the best precoding matrix and the best companion in order of W ₂ , W ₁ , and W ₃ to eNB A, and UE2 (UE ₂ ) receives W ₅ , W ₇ , and W _{4 in} order. Feedback to eNB A, which specifies the best precoding matrix and the best companion, to UE A, and UE ₃ (UE ₃ ) specifies the best precoding matrix and the best companion in order of W ₃ , W ₁ , and W ₀ . The precoding matrix information is fed back to the eNB A and the eNB B, and the user equipment 4 (UE ₄ ) sends the precoding matrix information to the eNB B, which specifies the best precoding matrix and the best companion in the order of W ₈ , W ₁₁ , and W ₁₂ . feedback, the user equipment ₅ (UE 5) is W _1, W _2, W ₀ in order of best precoding matrix and in best Compassion Suppose a case where the feedback precoding matrix information given to the eNB B. The master scheduler receives precoding matrix information of user devices 0 and 1, 2, 3, 4, and 5 from eNB A and eNB B, and based on the received precoding matrix information, the best scheduler and best companion are preferred. The overlapping user equipment 0 and the user equipment 3 can be scheduled together and delivered to eNB A, and the preferred best precoding matrix and the best companion can be scheduled together and delivered to eNB B. In addition, the master scheduler may select a precoding matrix for user equipments scheduled together based on the precoding matrix information received from each base station and inform the base station of the precoding matrix. The best pre-coding matrix W ₀ is the best Compassion in your device's 0 W _3, and W _1, so the best pre-coding of the user equipment 3 matrix W ₃ is the best-Compassion-year W _1, W _0, the master scheduler user devices 0 The precoding matrix for may be W ₀ and the precoding matrix for user equipment 3 may be designated as W ₃ and transmitted to eNB A. In addition, since the best precoding matrix W ₂ of user equipment 1 and the best companions are W ₁ , W ₃ , the best precoding matrix W ₁ of user equipment 5 and the best companion years are W ₂ , W ₀ , the master scheduler is user. The precoding matrix for device 1 may be designated as W ₂ and the precoding matrix for user equipment 5 may be designated as W ₁ and transmitted to eNB B. Accordingly, the processor of the eNB A by precoding the data to be transmitted the data to be transmitted to the user device 0 to the user equipment 3 as W ₀ to W ₃ control the transmitter of the eNB A to send to the user's device 0 and 3, and the eNB B the processor may be pre-coded data to transmit the data to be transmitted to the user device 1 to user device 5 to W ₂ to W ₁ to control the transmitter of the B eNB to transmit the user equipment 1 and 5.

Meanwhile, the master scheduler selects user equipments to be scheduled together by each base station based on the precoding matrix information transmitted from each base station, schedules the selected user equipments, and transmits the selected user equipments to the corresponding base station, and the base station selects a precoding matrix. It is also possible. For example, when the master scheduler schedules user equipments 0 and 3 together and transmits them to eNB A, and schedules user equipments 1 and 5 together and sends them to eNB B, the eNB A processor may schedule the user equipments 0 and 3 together. Based on the precoding matrix information from the device 3, the precoding matrix to be applied to the transmission data of the user device 0 and the transmission data of the user device 3 can be selected. Similarly, the processor of eNB B may select a precoding matrix to be applied to transmission data of user equipment 1 and transmission data of user equipment 5 based on precoding matrix information from user equipment 1 and user equipment 5 scheduled together. It may be. The transmitter of the eNB A, according to the control of the processor, precodes the transmission data of the user equipment 0 and the user equipment 3 into the selected corresponding precoding matrix, and transmits the precoded transmission data in the predetermined resource region. Send to Device 0 and User 3 together. In the same manner, the transmitter of the eNB B precodes the transmission data of the user equipment 1 and the user equipment 5 to the selected corresponding precoding matrix and controls the precoded transmission data according to the control of the processor. It transmits to the user device 1 and the user device 5 together in the resource area.

In addition, the master scheduler designates only the user equipments that can be scheduled together and transmits the data to each base station, and the base station allocates data for the designated user equipments to the same time / frequency domain and to the data for the designated user equipments. It is also possible to select a precoding matrix to apply. For example, if the master scheduler sends information to eNB A that user equipments 0 and 3 can be scheduled together and informs eNB B that user equipment 1 and 5 can be scheduled together, the processor of eNB A Allocating data for user equipments 0 and 3 in the same time / frequency domain and based on precoding matrix information of user equipments 0 and 3, precoding matrix W ₀ for user equipment ₀ and precoding matrix W for user equipment 3 ₃ is selected, the processor of eNB B allocates data for user equipments 1 and 5 to the same time / frequency domain, and based on the precoding matrix information of user equipments 1 and 5, precoding matrix W ₂ and The precoding matrix W ₁ for the user device 3 may be selected. The transmitter of the eNB A precodes data to be transmitted to user device 0 with W ₀ and precodes data to be transmitted to user device 3 with W ₃ under the control of the corresponding processor. May transmit to the user devices 0 and 3, respectively. In addition, the transmitter of the eNB B, under the control of the processor, precodes data to be transmitted to the user equipment 1 to W ₂ and precodes the data to be transmitted to the user equipment 5 to W _{1 so} as to transmit a time of a predetermined resource region through an antenna. And the user equipments 1 and 5, respectively, at a frequency.

In addition, for each base station other than the master scheduler, it is also possible to receive feedback information received by another base station through the backhaul 140 and select a user equipment and a precoding matrix to be scheduled together. For example, the processor of the eNB A may schedule the user devices 0 and 3 together based on the precoding matrix information transmitted from the user devices 0 and 1, 2, 3, and W ₀ to transmit data to the user devices 0 and 3. And control the precoder of eNB A to precode each to W ₃ , and control the transmitter and antenna of eNB A to transmit the precoded data to user devices 0 and 3 through a predetermined resource region.

Application of the embodiments of the present invention to a CoMP system can reduce not only inter-cell interference occurring in an interview area between different cells, but also channel interference by a plurality of users scheduled together. There is this.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable those skilled in the art to implement and practice the invention. Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can. Thus, 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 may be used in a base station or terminal, or other equipment in a wireless communication system.

Claims (14)

1. In a wireless communication system in which a plurality of user equipment simultaneously receives a signal transmitted from one base station, a method of transmitting a precoding matrix information by a specific user equipment of the plurality of user equipment,

   In receiving the signal, a first precoding matrix, which is a precoding matrix for the specific user equipment, is determined from a predetermined codebook, and at least one second precoding for another user equipment to be multiplexed in a predetermined resource region together with the specific user equipment. Determining a matrix, wherein determining the at least one second precoding matrix within a codebook subset of the predetermined codebook associated with the first precoding matrix; And

   Transmitting precoding matrix information for transmitting the first precoding matrix information indicating the first precoding matrix and the second precoding matrix information indicating the at least one second precoding matrix to the base station.

   Method of transmitting precoding matrix information.
2. The method of claim 1,

   The second precoding matrix information includes an index of the second precoding matrix defined within the codebook subset,

   Method of transmitting precoding matrix information.
3. The method of claim 2,

   The first precoding matrix information includes an index of the first precoding matrix defined in the predetermined codebook, or specifies information in the codebook subset among the codebook subsets belonging to the predetermined codebook and the codebook subset. Comprising an index of the first precoding matrix,

   Method of transmitting precoding matrix information.
4. The method of claim 1,

   Wherein the second precoding matrix information includes information designating one of the prioritized patterns of precoding matrices in the codebook subset,

   Method of transmitting precoding matrix information.
5. The method of claim 2,

   The transmitting of the precoding matrix information may include: specifying the codebook subset from among codebook subsets belonging to the predetermined codebook and information specifying one of patterns defining priorities of precoding matrices in the codebook subset; And transmit to the base station as second precoding matrix information.

   Method of transmitting precoding matrix information.
6. The method according to any one of claims 1 to 5,

   Wherein the codebook subset consists of the first precoding matrix and a precoding matrix having a value less than or equal to a predetermined correlation with the first precoding matrix;

   Method of transmitting precoding matrix information.
7. In the specific user equipment of any one of the plurality of user equipment for transmitting the precoding matrix information in a wireless communication system in which a plurality of user equipment simultaneously receives a signal transmitted from one base station,

   A transmitter for transmitting a signal to a base station; And

   In receiving the signal, a first precoding matrix, which is a precoding matrix for the specific user equipment, is determined from a predetermined codebook, and at least one second precoding for another user equipment to be multiplexed in a predetermined resource region together with the specific user equipment. Determine a matrix, wherein the at least one second precoding matrix is determined within a codebook subset of the predetermined codebook associated with the first precoding matrix; And a processor controlling the transmitter to transmit first precoding matrix information indicating the first precoding matrix and second precoding matrix information indicating the second precoding matrix to the base station.

   User device.
8. The method of claim 7, wherein

   The second precoding matrix information includes an index of the second precoding matrix defined within the codebook subset,

   User device.
9. The method of claim 8,

   The first precoding matrix information includes an index of the second precoding matrix defined in the predetermined codebook, or specifies information in the codebook subset among the codebook subsets belonging to the predetermined codebook and the codebook subset. Comprising an index of the first precoding matrix,

   User device.
10. The method of claim 9,

    Wherein the second precoding matrix information includes information designating one of the prioritized patterns of precoding matrices in the codebook subset,

    User device.
11. The method of claim 8,

    The processor may be configured to control the transmitter to provide information for designating the codebook subset from among codebook subsets belonging to the predetermined codebook and information for designating one of patterns for prioritizing precoding matrices in the codebook subset. Configured to transmit to the base station as first and second precoding matrix information,

    User device.
12. The method according to any one of claims 7 to 11,

    Wherein the codebook subset consists of the first precoding matrix and a precoding matrix having a value below a predetermined correlation with the first precoding matrix,

    User device.
13. The method of claim 9,

    The processor may control the transmitter to transmit data to a base station in a wireless communication system in which one base station of the codebook among the codebook subsets belonging to the predetermined codebook simultaneously transmits signals to a plurality of user equipments. ,

    First precoding matrix information indicating a first precoding matrix, which is a precoding matrix for the corresponding user equipment determined in a predetermined codebook, from the plurality of user equipments, and another to be multiplexed in a predetermined resource region with the corresponding user equipment Receiving second precoding matrix information indicating one or more second precoding matrices determined within a codebook subset of a predetermined codebook associated with the first precoding matrix as a precoding matrix for a user equipment; And

    Selecting a precoding matrix for transmission data of each user equipment to be transmitted on the predetermined resource region based on the first precoding matrix information and the second precoding matrix information;

    And precoding the transmission data of each user equipment into the selected corresponding precoding matrix, and transmitting the data to each user equipment in the predetermined resource region.

    Data transfer method.
14. In a wireless communication system in which one base station simultaneously transmits signals to a plurality of user equipments,

    First precoding matrix information indicating a first precoding matrix, which is a precoding matrix for the corresponding user equipment determined in a predetermined codebook, from the plurality of user equipments, and another to be multiplexed in a predetermined resource region with the corresponding user equipment An antenna configured to receive second precoding matrix information indicating at least one second precoding matrix determined within a codebook subset of a predetermined codebook associated with the first precoding matrix as a precoding matrix for a user equipment; And

    A precoder configured to precode transmission data;

    Select a precoding matrix for transmission data of each user equipment to be transmitted on the predetermined resource region based on the first precoding matrix information and the second precoding matrix information, and transmit the corresponding transmission data to the selected precoding matrix. A processor for controlling the precoder to precode and controlling the antenna to transmit the precoded transmission data to the user equipment in the predetermined resource region;

    Base station.

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