KR20230149277A - Superposition transmission method and apparatus for communication system - Google Patents

Abstract

A method and apparatus for overlapping transmission in a communication system are disclosed. The operation method of the first terminal includes receiving DCI from the base station, sending an overlapping signal including a first data signal of the first terminal and a second data signal of the second terminal at a time indicated by resource allocation information - Receiving through frequency resources, receiving a first message requesting transmission of a HARQ response for the second data signal, allocation of the MCS and the transmission power for the second terminal indicated by the MCS information Based on the transmission power for the second terminal indicated by information, decoding the second data signal included in the overlap signal and the result of decoding the second data signal in response to the first message. It may include transmitting the HARQ response to the base station. Therefore, the performance of the communication system can be improved.

Description

Method and apparatus for superposition transmission in a communication system {SUPERPOSITION TRANSMISSION METHOD AND APPARATUS FOR COMMUNICATION SYSTEM}

The present invention relates to overlapping transmission technology in a communication system, and more specifically, to a method of transmitting and receiving channel state information and HARQ (hybrid automatic repeat request) responses in an overlapping transmission procedure.

In the orthogonal frequency division multiplexing (OFDM)-based downlink of the ^3rd generation partnership project (3GPP) long term evolution-advanced (LTE-A) system, downlink superposition transmission can be used to further improve data rate. Downlink overlapping transmission may be a technique for transmitting by adding signals from a terminal close to the base station and a terminal far away. Downlink overlapping transmission may be a non-orthogonal transmission technique that non-uniformly allocates transmission power to two terminals in the same time and frequency resources.

To maximize the downlink data transmission rate, MU-MIMO (multi-user multiple-input multiple-output) transmission technique and overlapping transmission technique can be used together. In the MU-MIMO transmission technique, the base station can form multiple beams using different precoding. The base station can transmit data to multiple terminals at the same time and frequency resources using multiple beams formed. Therefore, the base station can apply overlapping transmission to each beam formed using MU-MIMO. However, if the orthogonality of the precoded channels of each terminal is small, there is significant mutual interference and the data transmission rate may be seriously reduced.

The purpose of the present invention to solve the above problems is to provide a method for transmitting and receiving channel state information and HARQ (hybrid automatic repeat request) responses in an overlapping transmission procedure.

A method of operating a first terminal according to an embodiment of the present invention to achieve the above object includes downlink control information (DCI) including resource allocation information, modulation and coding scheme (MCS) information, and transmission power allocation information. Receiving from the base station, receiving an overlapping signal including a first data signal of the first terminal and a second data signal of the second terminal from the base station through time-frequency resources indicated by the resource allocation information. receiving a first message requesting transmission of a hybrid automatic repeat request (HARQ) response to the second data signal from the base station, an MCS for the second terminal indicated by the MCS information, and the Decoding the second data signal included in the overlap signal based on transmission power for the second terminal indicated by allocation information of transmission power, and decoding the second data signal in response to the first message It may include transmitting the HARQ response, which is a decoding result of , to the base station.

According to the present invention, in a multi-antenna wireless communication system consisting of a base station and multiple terminals, when superposition transmission is applied to each beam formed using MU-MIMO (multi-user multiple-input multiple-output), mutual The problem of lower data transmission rate due to interference can be improved.

If the base station applies overlapping transmission to each beam, data can be transmitted to more terminals at the same time and frequency resources. However, if the orthogonality of the channels precoded in each terminal is small, there is significant mutual interference, which may reduce the data transmission rate.

According to the present invention, the base station can select an appropriate precoding method for each terminal and obtain additional channel state information to select an appropriate terminal pair. Additionally, during overlapping transmission, a terminal may transmit ACK/NACK (acknowledgment/negative ACK) information about another terminal's data to the base station. Therefore, interference between beams can be reduced and reliability of data transmission can be increased. Therefore, the performance of the communication system can be improved.

1 is a conceptual diagram showing a first embodiment of a communication system.
Figure 2 is a block diagram showing a first embodiment of a communication node constituting a communication system.
Figure 3 is a conceptual diagram showing a second embodiment of a communication system.
Figure 4 is a flowchart showing a first embodiment of a PMI transmission and reception method between a base station and terminals.
Figure 5 is a flowchart showing a second embodiment of a PMI transmission and reception method between a base station and terminals.
Figure 6 is a flowchart showing a first embodiment of a method for transmitting and receiving ACK/NACK information between a base station and terminals.
Figure 7 is a flowchart showing a second embodiment of a method for transmitting and receiving ACK/NACK information between a base station and terminals.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, the second component may also be named a first component without departing from the scope of the present invention. The term and/or includes any of a plurality of related stated items or a combination of a plurality of related stated items.

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

The terms used in this application are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an idealized or excessively formal sense. No.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In order to facilitate overall understanding when describing the present invention, the same reference numerals are used for the same components in the drawings, and duplicate descriptions for the same components are omitted.

A communication system to which embodiments according to the present invention are applied will be described. Communication systems to which embodiments of the present invention are applied are not limited to those described below, and embodiments of the present invention can be applied to various communication systems. Here, communication system may be used in the same sense as communication network.

1 is a conceptual diagram showing a first embodiment of a communication system.

Referring to FIG. 1, the communication system 100 includes a plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). In addition, the communication system 100 includes a core network (e.g., serving-gateway (S-GW), packet data network (PDN)-gateway (P-GW), mobility management entity (MME)). More may be included.

A plurality of communication nodes may support 4G communication (e.g., long term evolution (LTE), advanced (LTE-A)), 5G communication, etc. specified in the 3rd generation partnership project (3GPP) standard. 4G communications can be performed in frequency bands below 6GHz, and 5G communications can be performed in frequency bands above 6GHz as well as frequency bands below 6GHz. For example, for 4G communication and 5G communication, a plurality of communication nodes may use a communication protocol based on code division multiple access (CDMA), a communication protocol based on wideband CDMA (WCDMA), a communication protocol based on time division multiple access (TDMA), Communication protocol based on FDMA (frequency division multiple access), communication protocol based on OFDM (orthogonal frequency division multiplexing), communication protocol based on Filtered OFDM, communication protocol based on CP (cyclic prefix)-OFDM, DFT-s-OFDM (discrete Fourier transform-spread-OFDM)-based communication protocol, OFDMA (orthogonal frequency division multiple access)-based communication protocol, SC (single carrier)-FDMA-based communication protocol, NOMA (non-orthogonal multiple access), GFDM (generalized frequency) Division multiplexing)-based communication protocols, FBMC (filter bank multi-carrier)-based communication protocols, UFMC (universal filtered multi-carrier)-based communication protocols, and SDMA (space division multiple access)-based communication protocols can be supported. . Each of the plurality of communication nodes may have the following structure.

Figure 2 is a block diagram showing a first embodiment of a communication node constituting a communication system.

Referring to FIG. 2, the communication node 200 may include at least one processor 210, a memory 220, and a transmitting and receiving device 230 that is connected to a network and performs communication. Additionally, the communication node 200 may further include an input interface device 240, an output interface device 250, a storage device 260, etc. Each component included in the communication node 200 is connected by a bus 270 and can communicate with each other.

However, each component included in the communication node 200 may be connected through an individual interface or individual bus centered on the processor 210, rather than the common bus 270. For example, the processor 210 may be connected to at least one of the memory 220, the transmission/reception device 230, the input interface device 240, the output interface device 250, and the storage device 260 through a dedicated interface. .

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 220 and the storage device 260 may be comprised of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be comprised of at least one of read only memory (ROM) and random access memory (RAM).

Referring again to FIG. 1, the communication system 100 includes a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) and a plurality of terminals (130- 1, 130-2, 130-3, 130-4, 130-5, 130-6). Base stations (110-1, 110-2, 110-3, 120-1, 120-2) and terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) The communication system 100 that includes may be referred to as an “access network.” Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell. Each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may belong to the cell coverage of the first base station 110-1. The second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may belong to the cell coverage of the second base station 110-2. The fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 may belong to the cell coverage of the third base station 110-3. there is. The first terminal 130-1 may belong to the cell coverage of the fourth base station 120-1. The sixth terminal 130-6 may belong to the cell coverage of the fifth base station 120-2.

Here, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 is NodeB, evolved NodeB, gNB, ng-eNB, and BTS. (base transceiver station), radio base station, radio transceiver, access point, access node, RSU (road side unit), RRH (radio remote head), TP ( It may be referred to as transmission point), TRP (transmission and reception point), f (flexible)-TRP, etc. A plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, and 130-6) each include a user equipment (UE), a terminal, an access terminal, and a mobile device. Terminal, station, subscriber station, mobile station, portable subscriber station, node, device, IoT (internet of things) It may be referred to as a device supporting a function, a mounted module/device/terminal, an on board unit (OBU), etc.

Meanwhile, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may operate in different frequency bands or may operate in the same frequency band. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to each other through an ideal backhaul link or a non-ideal backhaul link. , information can be exchanged with each other through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 may be connected to the core network through an ideal backhaul link or a non-ideal backhaul link. Each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) transmits the signal received from the core network to the corresponding terminal (130-1, 130-2, 130-3, 130). -4, 130-5, 130-6), and the signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) is sent to the core network. can be transmitted to.

In addition, each of the plurality of base stations 110-1, 110-2, 110-3, 120-1, and 120-2 performs MIMO transmission (e.g., single user (SU)-MIMO, multi user (MU)- MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in an unlicensed band, direct device to device communication (D2D) (or ProSe ( proximity services)), etc. can be supported. Here, each of the plurality of terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 is connected to a base station 110-1, 110-2, 110-3, and 120-1. , 120-2) and operations corresponding to those supported by the base stations 110-1, 110-2, 110-3, 120-1, and 120-2. For example, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method, and the fourth terminal 130-4 may transmit a signal to the fourth terminal 130-4 based on the SU-MIMO method. A signal can be received from the second base station 110-2. Alternatively, the second base station 110-2 may transmit a signal to the fourth terminal 130-4 and the fifth terminal 130-5 based on the MU-MIMO method, and the fourth terminal 130-4 and the fifth terminal 130-5 can each receive a signal from the second base station 110-2 by the MU-MIMO method.

Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may transmit a signal to the fourth terminal 130-4 based on the CoMP method, and the fourth terminal 130-4 may transmit a signal to the fourth terminal 130-4. The terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 using the CoMP method. Each of a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) has a terminal (130-1, 130-2, 130-3, 130-4) within its cell coverage. , 130-5, 130-6), and signals can be transmitted and received based on the CA method. The first base station 110-1, the second base station 110-2, and the third base station 110-3 each control D2D between the fourth terminal 130-4 and the fifth terminal 130-5. and each of the fourth terminal 130-4 and the fifth terminal 130-5 can perform D2D under the control of each of the second base station 110-2 and the third base station 110-3. .

Next, a method for solving problems that arise when combining superposition transmission with MU-MIMO (multi-user multiple-input multiple-output) transmission is explained.

Figure 3 is a conceptual diagram showing a second embodiment of a communication system.

Referring to FIG. 3, the communication system may include a base station 300, terminal-1 (310), terminal-2 (320), terminal-3 (330), and terminal-4 (340). The base station 300 may provide a communication service to the terminals 310, 320, 330, and 340 based on a communication protocol (eg, 4G communication protocol, 5G communication protocol).

In a communication system using multiple antennas, a closed-loop precoding transmission method or an adaptive modulation and coding (AMC) method may be used to improve the data transmission rate. The closed-loop precoding transmission method can adjust the size and phase of multiple antenna channels. By adjusting the size and phase of multiple antenna channels, the terminal's received signal gain can be improved. The AMC method can adjust the MCS (modulation and coding scheme) level of transmitted data according to channel quality. By adjusting the MCS level of data, the data reception error rate can be kept low and the data transmission rate can be maximized.

Each terminal 310, 320, 330, and 340 can feed back downlink channel state information to the base station 300 through an uplink control channel. The base station 300 can receive feedback about channel state information from each terminal 310, 320, 330, and 340. The base station 300 can determine the closed-loop precoding transmission method and the AMC method through the channel state information received.

The single carrier-frequency division multiple access (SC-FDMA)-based uplink of the ^3rd generation partnership project (3GPP) LTE system defines a subframe as the basic transmission unit. A subframe may consist of 14 SC-FDMA symbols and multiple resource blocks (RBs). One RB may consist of 12 subcarriers. RB may be the basic unit of scheduling.

The uplink control channel includes ACK/NACK (acknowledgment/negative ACK) for HARQ (hybrid automatic repeat request) operation, RI (rank indicator), which is channel state information for downlink precoding and AMC, PMI (precoding matrix indicator), It may include CQI (channel quality indication) information, etc. For example, an LTE system using four transmit antennas can use a codebook as shown in Table 1 for feedback of PMI information.

The terminals 310, 320, 330, and 340 may transmit channel state information to the base station 300 through the uplink control channel at certain predetermined periods. Alternatively, the terminals 310, 320, 330, and 340 may aperiodically transmit channel state information to the base station 300 using the allocated uplink data channel at the request of the base station.

In the downlink based on orthogonal frequency division multiplexing (OFDM) of the 3GPP LTE system, downlink overlapping transmission can be used to further improve data rate. The downlink overlapping transmission technique uses a terminal close to the base station 300 (e.g., terminal-1 (310) or terminal-3 (330)) and a distant terminal (e.g., terminal-2 (320) or terminal-4 (340)) signals can be added and transmitted. Downlink overlapping transmission may be a non-orthogonal transmission technique that non-uniformly allocates transmission power to two terminals (e.g., terminal-1 (310) and terminal-2 (320)) in the same time and frequency resources. If the signal to be transmitted to a nearby terminal (e.g., terminal-1 (310)) is s1, and the signal to be transmitted to a distant terminal (e.g., terminal-2 (320)) is s2, overlapping coding for the two terminals The signal may be as shown in Equation 1.

In Equation 1, x may be an overlapping coding signal, and a1 and a2 may be transmission power allocation coefficients for the s1 signal and s2 signal. The overlapping coding signals received from Terminal-1 (310) and Terminal-2 (320) may be equivalent to Equation 2 and Equation 3, respectively.

In Equation 2, y1 may be a received signal of UE-1 (310), and h1 may indicate the channel state between the base station 300 and UE-1 (310). n1 may be a noise signal of terminal-1 (310). In Equation 3, y2 may be the received signal of UE-2 (320), and h2 may indicate the channel state between the base station 300 and UE-2 (320). n2 may be a noise signal of terminal-2 (320).

The channel quality of UE-1 (310), which is close to the base station 300, may be better than the channel quality of UE-2 (320), which is far from the base station 300. Therefore, each terminal can decode overlapping data assuming that the channel condition of a terminal (eg, terminal-1 (310)) close to the base station 300 is excellent.

If |h1|>|h2| (i.e., if the channel state between the base station 300 and UE-1 (310) is better than the channel state between the base station 300 and UE-2 (320)), the transmission power allocation coefficient may be a1<a2. That is, the base station 300 may allocate relatively large power to a terminal (eg, terminal-2 320) with relatively poor channel conditions in order to maintain reliability of the transmission signal.

When the received signal y1 is received from the base station 300, UE-1 (310) can obtain the s2 signal by decoding the received signal y1 using the information of h1 and a2. After acquiring the s2 signal from y1, UE-1 (310) uses the SIC (successive interference cancellation) technique to cancel the signal included in the received signal y1. can be removed. After this, terminal-1 (310) can decode s1. On the other hand, Terminal-2 (320) can directly decode signal s2 without removing signal s1. Here, the data signal component of terminal-1 (310) is can be treated as noise.

To improve the downlink data rate, MU-MIMO transmission technique and overlapping transmission technique can be used together. The base station 300 can form multiple beams to multiple terminals 310, 320, 330, and 340 through the MU-MIMO transmission technique. Multiple beams can be formed by using different precoding for multiple terminals. The base station 300 can transmit data to multiple terminals 310, 320, 330, and 340 at the same time and frequency resources using multiple beams.

The base station 300 can apply overlapping transmission to each beam formed using MU-MIMO. For example, the base station 300 can simultaneously transmit data to terminal-1 (310) and terminal-2 (320) by applying overlapping transmission to the first beam, and to terminal-3 by applying overlapping transmission to the second beam. Data can be transmitted simultaneously to (330) and terminal-4 (340). The base station 300 can transmit data to more terminals at the same time and frequency resources by applying overlapping transmission to each of the multiple beams.

However, if the orthogonality between the precoded channels of each terminal is small, mutual interference between beams may increase, resulting in a decrease in data transmission rate. Therefore, selection of an appropriate precoding method for each terminal and selection of an appropriate terminal pair may be important. The base station 300 may need additional channel state information to select a precoding method and UE pair.

In addition, during overlapping transmission, a terminal close to the base station 300 (e.g., terminal-1 (310)) receives the data signal (i.e., s2) of a terminal (e.g., terminal-2 (320)) far from the base station 300. ) is performed first, and then the decoding of its own data signal (i.e., s1) is performed sequentially, so whether the decoding of the data signal (i.e., s2) for terminal-2 (320) is successful or not is determined by the terminal- It may have a major impact on whether or not the data signal for 1 (310) (i.e., s1) is successfully decoded. Therefore, if UE-1 (310), which is close to the base station (300), transmits only ACK/NACK for its own data (i.e., s1) transmission, data transmission may be performed inefficiently. That is, terminal-1 (310) does not successfully receive the data signal (i.e., s2) for terminal-2 (320), so reception of the data signal (i.e., s1) for terminal-1 (310) is not successful. If this is not done successfully, terminal-1 (310) transmits only a NACK for s1 to base station 300, so base station 300 fails to receive signal s2 from terminal-1 (310) and receives signal s1. The fact that reception failed is unknown. Therefore, it may be difficult to provide desirable feedback. Therefore, the base station 300 may need ACK/NACK information regarding the reception of a data signal (i.e., s2) from terminal-1 (310) to terminal-2 (320).

Next, a method by which the base station 300 transmits and receives additional PMI information for the terminals 310, 320, 330, and 340 to resolve inter-beam interference is described.

In a communication system using multiple antennas, a closed-loop precoding technique can be used to support downlink MU-MIMO. Closed-loop precoding may be performed at the base station 300 based on control information (RI, PMI, CQI) transmitted from the terminals 310, 320, 330, and 340. Each terminal (310, 320, 330, 340) can select the RI and PMI to be transmitted within a predefined codebook as shown in Table 1. Each terminal (310, 320, 330, 340) can select RI and PMI that maximize beamforming gain. The base station 300 generates a precoding vector (or matrix) for each terminal for MU-MIMO transmission based on control information (i.e., RI, PMI, CQI) received from multiple terminals 310, 320, 330, and 340. ) can be determined. The base station 300 can obtain the total data rate (sum rate) for each UE pair based on the precoding vector (or matrix) of each UE. The base station 300 may select a pair of terminals that maximize the total data rate.

The transmission signal when overlapping transmission is applied to MU-MIMO transmission is as shown in Equation 4.

It is assumed that the number of transmission antennas of the base station 300 is N and the number of layers for each terminal is 1. In Equation 4, X may be an N-by-1 MU-MIMO and overlap coding signal matrix. a1, a2, a3, and a4 are the transmission power for data signals s1, s2, s3, and s4 of terminal-1 (310), terminal-2 (320), terminal-3 (330), and terminal-4 (340), respectively. It may be an allocation coefficient. class may mean an N-by-1 precoding vector for the first beam and the second beam formed in MU-MIMO, respectively. That is, the transmission signal It may be a signal transmitting data to Terminal-3 (330) and Terminal-4 (340).

When using a combination of MU-MIMO transmission and overlapping transmission, the data transmission rate can be increased. However, MU-MIMO transmission and overlapping transmission can be performed when inter-beam interference is small. When transmitting overlapping signals of two terminals having different channels in one beam (for example, when transmitting overlapping signals of terminal-1 (310) and terminal-2 (320) through the first beam), each The terminal may experience more severe inter-beam interference than normal MU-MIMO transmission.

The base station 300 can select RI and PMI one by one for each terminal. Since the PMI that the base station 300 can select is limited, interference in the terminals 310, 320, 330, and 340 may become more severe. Therefore, in order to reduce inter-beam interference, the base station 300 may require additional PMI feedback from each terminal.

In this embodiment, each terminal (310, 320, 330, and 340) does not provide only one PMI that provides the maximum beamforming gain, but may provide additional PMI feedback. Each terminal 310, 320, 330, and 340 may provide a PMI that provides the maximum beamforming gain as well as a PMI that provides the second or third largest beamforming gain. Through multiple PMI feedback, the base station 300 can increase its degree of freedom when selecting a precoding vector for each terminal. Therefore, the base station 300 can select a precoding vector that can reduce inter-beam interference between terminals. In addition, since the candidate group of terminal pairs that receive overlapping signals in each beam can be expanded, the number of cases in which the base station 300 selects terminal pairs that can increase the data transmission rate can increase.

There may be two methods for transmitting and receiving additional PMI information between the base station 300 and each terminal (310, 320, 330, and 340). There may be a method in which each terminal (310, 320, 330, and 340) feeds back PMI information to the base station 300 aperiodically and a method in which it feeds back PMI information periodically. Next, a method for transmitting and receiving PMI through the terminal's aperiodic feedback method is explained.

Figure 4 is a flowchart showing a first embodiment of a PMI transmission and reception method between a base station and terminals.

Referring to FIG. 4, the communication system may include a base station 300, terminal-1 (310), terminal-2 (not shown), terminal-3 (not shown), and terminal-4 (not shown). The base station 300 connects terminals (terminal-1 (310), terminal-2 (not shown), terminal-3 (not shown), terminal based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol). Communication services can be provided at -4 (not shown). The base station 300 in FIG. 4 may be the base station 300 in FIG. 3, and the terminal-1 (310) in FIG. 4 may be the terminal-1 (310) in FIG. 3.

The base station 300 may request that UE-1 (310) feed back one or more PMI information through a downlink control channel (S400). That is, the base station 300 may transmit a PMI feedback request message to UE-1 (310). The PMI feedback request message transmitted from the base station 300 to UE-1 (310) through the downlink control channel may include information on the number of additional PMIs requested. For example, the PMI feedback request message may include a field indicating the number of PMIs requested, and if the number of additional PMIs requested is 2, the field may indicate 2. The method of including additional PMI number information in the PMI feedback request message is not limited to the above embodiment and may be performed through other methods.

Terminal-1 (310) may receive a PMI feedback request message from the base station (300). Terminal-1 (310) can check information on the number of additional PMIs requested by base station 300 included in the received PMI feedback request message. Terminal-1 (310) can select PMIs corresponding to the number of additional PMIs requested by the base station 300 in order of increasing beamforming gain (S401). For example, when the number of additional PMIs requested by the base station 300 is 2, UE-1 (310) not only has the first priority PMI that provides the maximum beamforming gain, but also the second priority PMI with the second largest beamforming gain. All information about PMI and the 3rd priority PMI with the third largest beamforming gain can be selected.

Terminal-1 (310) may transmit a PMI feedback message including the selected PMI information to the base station (300) (S402). The base station 300 can receive the PMI feedback message from UE-1 (310) and check the PMI information included in the PMI feedback message.

The base station 300 can request a desired number of PMI information at a desired time and receive a desired number of PMI information. That is, in this embodiment, PMI transmission and reception can be performed aperiodically. Since the base station 300 can receive feedback from multiple PMIs, it can be advantageous when selecting a precoding vector for each terminal. Additionally, since the candidate group of terminal pairs receiving overlapping signals is expanded, it may be advantageous when selecting a terminal pair.

Although only the PMI transmission and reception method between the base station 300 and UE-1 (310) has been described, PMI transmission and reception is performed between the base station 300 and other terminals (i.e., UE-2 (not shown), UE-3 (not shown) ) and terminal-4 (not shown)) can be equally performed. Next, a method for transmitting and receiving PMI through the terminal's periodic feedback method is described.

Figure 5 is a flowchart showing a second embodiment of a PMI transmission and reception method between a base station and terminals.

Referring to FIG. 5, the communication system may include a base station 300, terminal-1 (310), terminal-2 (not shown), terminal-3 (not shown), and terminal-4 (not shown). The base station 300 connects terminals (terminal-1 (310), terminal-2 (not shown), terminal-3 (not shown), terminal based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol). Communication services can be provided at -4 (not shown). The base station 300 in FIG. 5 may be the base station 300 in FIG. 3, and UE-1 (310) in FIG. 5 may be UE-1 (310) in FIG. 3. The communication system of FIG. 5 may be the same or similar to the communication system of FIG. 4.

Terminal-1 (310) can periodically transmit one piece of PMI information to the base station (300) through the uplink control channel even without a request from the base station (S500). At this time, the base station 300 can determine the period at which UE-1 (310) transmits PMI information to the base station (300). The base station 300 may request a PMI of a specific desired rank from UE-1 310 through a downlink control channel or higher-order signaling. The ranking of PMIs can be determined based on how much beamforming gain a specific PMI provides. If the base station 300 does not request a PMI of a specific priority, UE-1 (310) may transmit PMI information providing the largest beamforming gain to the base station 300. That is, in step S500, UE-1 (310) may transmit the first priority PMI that provides the largest beamforming gain to the base station (300). The base station 300 may receive first priority PMI information from UE-1 (310).

If the base station 300 desires second-priority PMI information, the base station 300 may transmit a message requesting second-priority PMI to terminal-1 (310) (S501). Terminal-1 (310) may receive a message requesting a second-priority PMI. Terminal-1 (310) may periodically transmit a PMI message including one PMI information to the base station (300). If UE-1 (310) receives a message requesting a second-priority PMI from the base station 300 before one cycle (i.e., 1 cycle) has elapsed after transmitting the previous PMI message, UE-1 (310) The second-priority PMI may be transmitted to the base station 300 in the next transmission cycle (S502). The base station 300 may receive second-priority PMI information from UE-1 (310).

If the base station 300 desires 3rd priority PMI information, the base station 300 may transmit a message requesting 3rd priority PMI to UE-1 (310) (S503). Terminal-1 (310) may receive a message requesting a 3rd priority PMI. If UE-1 (310) receives a message requesting a 3rd priority PMI from the base station 300 before one cycle (i.e., 2 cycles) has elapsed after transmitting the previous PMI message, UE-1 (310) The 3rd priority PMI may be transmitted to the base station 300 in the next transmission cycle (S504). The base station 300 may receive 3rd priority PMI information from UE-1 (310).

Because the channel state continues to change, the base station 300 may need first-priority PMI information again. If the base station 300 desires first-priority PMI information, the base station 300 may transmit a message requesting first-priority PMI to terminal-1 (310) (S505). Terminal-1 (310) may receive a message requesting first priority PMI. If UE-1 (310) receives a message requesting a 1st priority PMI from the base station 300 before one cycle (i.e., 3 cycles) has elapsed after transmitting the previous PMI message, UE-1 (310) The first priority PMI may be transmitted to the base station 300 in the next transmission cycle (S506). The base station 300 may receive first priority PMI information from UE-1 (310).

Since the base station 300 can receive feedback on multiple PMIs by receiving multiple PMI messages, it can be advantageous when selecting a precoding vector for each terminal. Additionally, since the candidate group of terminal pairs receiving overlapping signals is expanded, it may be advantageous when selecting a terminal pair.

Although only the PMI transmission and reception method between the base station 300 and UE-1 (310) has been described, PMI transmission and reception is performed between the base station 300 and other terminals (i.e., UE-2 (not shown), UE-3 (not shown) ) and terminal-4 (not shown)) can be equally performed. Next, a method for a terminal to transmit ACK/NACK information for data of another terminal to a base station in overlapping transmission is described.

Figure 6 is a flowchart showing a first embodiment of a method for transmitting and receiving ACK/NACK information between a base station and terminals.

Referring to FIG. 6, the communication system may include a base station 300, terminal-1 (310), terminal-2 (320), terminal-3 (not shown), and terminal-4 (not shown). The base station 300 connects terminals (terminal-1 (310), terminal-2 (320), terminal-3 (not shown), and terminal-3) based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol). 4 (not shown)) can provide a communication service. The base station 300 in FIG. 6 may be the base station 300 in FIG. 3, the terminal-1 (310) in FIG. 6 may be the terminal-1 (310) in FIG. 3, and the terminal-2 (320) in FIG. ) may be terminal-2 (320) of FIG. 3.

In a communication system, when terminal-1 (310) and terminal-2 (320) are connected to the base station 300, the base station 300 provides channel state information-RS (CSI-RS) through a downlink subframe according to a preset period. reference signal) can be transmitted. UE-1 (310) and UE-2 (320) can each receive a CSI-RS from the base station 300 and perform a channel measurement operation based on the received CSI-RS. Here, the channel between the base station 300 and UE-1 (310) may be referred to as a “first channel”, and the channel between the base station 300 and UE-2 (320) may be referred to as a “second channel”. there is. Terminal-1 (310) may transmit measurement information (e.g., CSI) of the first channel to the base station 300, and Terminal-2 (320) may transmit measurement information (e.g., CSI) of the second channel. Can be transmitted to the base station 300.

The base station 300 may receive measurement information of the first channel from UE-1 (310) and may receive measurement information of the second channel from UE-2 (320). Alternatively, the base station 300 may obtain measurement information of the first channel by performing a channel measurement operation based on the sounding reference signal (SRS) received from terminal-1 (310) and from terminal-2 (320). Measurement information for the second channel can be obtained by performing a channel measurement operation based on the received SRS.

AMC technology, scheduling technology, etc. can be used to improve the transmission rate of data units in communication systems. When AMC technology is used, the base station 300 can adjust the MCS level according to the channel status between the base station 300 and the terminals 310 and 320 to maintain the target reception error rate. For example, when the channel condition is bad, the base station 300 may lower the MCS level so that the actual reception error rate in the terminals 310 and 320 is reduced to the target reception error rate. If the channel condition is good, the base station 300 can increase the MCS level so that the actual reception error rate in the terminals 310 and 320 increases to the target reception error rate. Therefore, when AMC technology is used, the actual reception error rate in the terminal can be maintained at the target reception error rate by adjusting the MCS level, and the maximum transmission rate of the data signal can be provided while the actual reception error rate is maintained at the target reception error rate. .

When scheduling technology is used, the base station 300 can selectively allocate resources (eg, time and frequency resources) to the terminals 310 and 320 by considering the channel status and quality of service of the terminals 310 and 320. Here, the scheduling technology may be a scheduling technology based on a greedy algorithm, a proportional fairness (PF) scheduling technology, etc.

When AMC technology, scheduling technology, etc. are used in the communication system, the base station 300 provides AMC information of the terminals 310 and 320 (e.g., MCS information for terminal-1 (310) and terminal-2 (320) ) and scheduling information (for example, time and frequency resource information allocated to the terminal) can be transmitted to the terminal through the control channel of the downlink subframe. AMC information, scheduling information, etc. may be transmitted through downlink control information (DCI), and the DCI format may include information elements listed in Table 2 below.

The base station 300 may set DCI including parameters necessary for overlapping transmission (S600). The overlapping transmission parameters may include at least one of resource allocation information, MCS information for UE-1 (310), MCS information for UE-2 (320), and information indicating a transmission power allocation coefficient.

DCI may include information indicating transmission power allocation coefficients (a1, a2). a1 and a2 Since the relationship between them may be "a1+a2=1", DCI may include information indicating either a1 or a2. In this case, a separate DCI containing information indicating the transmission power allocation coefficients (a1, a2) is not created, and the transmission power allocation coefficients (a1, a2) are added to the existing DCI (for example, the DCI listed in Table 2). ) may additionally include information indicating. Alternatively, the DCI size may vary depending on the number of bits of information indicating the transmission power allocation coefficient.

The base station 300 may transmit control information (e.g., DCI) including overlapping transmission parameters to terminal-1 (310) and terminal-2 (320) (S601). Terminal-1 (310) and Terminal-2 (320) can receive control information (e.g., DCI) from the base station 300, and from the received signal, resource allocation information, MCS information, MCS information for UE-2 (320), and transmission power allocation coefficients (a1, a2) can be obtained. a1 and a2 may be transmission power allocation coefficients for the s1 signal and s2 signal, respectively. If the channel state between the base station 300 and UE-1 (310) is different from the channel state between the base station 300 and UE-2 (320), the transmission power allocation coefficients (a1, a2) included in DCI may be different. there is.

When the data signal s1 to be transmitted to terminal-1 (310) and the data signal s2 to be transmitted to terminal-2 (320) are present in the base station 300, the base station 300 uses the same resources (e.g., time and frequency Resources) can be used to transmit the data signal s1 and data signal s2 (S602).

Terminal-1 (310) and Terminal-2 (320) can each obtain the data signal s1 and data signal s2 from the base station 300 based on parameters necessary for overlapping transmission. The overlapping coding signals received from Terminal-1 (310) and Terminal-2 (320) may be equivalent to Equation 2 and Equation 3, respectively. In Equation 2, y1 may be a received signal of UE-1 (310), and h1 may indicate the channel state between the base station 300 and UE-1 (310). n1 may be a noise signal of terminal-1 (310). In Equation 3, y2 may be the received signal of UE-2 (320), and h2 may indicate the channel state between the base station 300 and UE-2 (320). n2 may be a noise signal of terminal-2 (320).

The channel quality of UE-1 (310), which is close to the base station 300, may be better than the channel quality of UE-2 (320), which is far from the base station 300. If |h1|>|h2| (i.e., if the channel state between the base station 300 and UE-1 (310) is better than the channel state between the base station 300 and UE-2 (320)), the transmission power allocation coefficient may be a1<a2. That is, the base station 300 may allocate relatively large power to a terminal (eg, terminal-2 320) with relatively poor channel conditions in order to maintain reliability of the transmission signal.

When the received signal y1 is received from the base station 300, terminal-1 (310) obtains the s2 signal by decoding the received signal y1 using the information of h1 and a2 and the MCS information for terminal-2 (320). You can. After acquiring the s2 signal from y1, UE-1 (310) uses the SIC (successive interference cancellation) technique to cancel the signal included in the received signal y1. can be removed.

The base station 300 may request transmission of a HARQ response whether UE-1 (310) has received the overlapping coding signal and successfully decoded the data signal s2 included in the overlapping coding signal (S603). That is, the base station 300 may transmit a request message to terminal-1 (310) to feed back ACK/NACK information about the data signal (i.e., s2) for terminal-2 (320). The HARQ response request message for the data signal of another terminal (i.e., terminal-2 (320)) may include a HARQ response request indicator (e.g., 1 bit) for the data signal of the other terminal. Terminal-1 (310) may receive a HARQ response request message for another terminal data signal (i.e., s2). When there is an ACK/NACK information feedback request (i.e., HARQ response request) for another terminal's data signal, terminal-1 (310) receives ACK/NACK information for its own data signal s1 and the other terminal (i.e., terminal-2). ACK/NACK information for the data signal s2 (320)) can be transmitted to the base station 300 through an uplink data channel allocated by the base station 300 (S604). Alternatively, if there is a HARQ response request for another terminal's data signal, terminal-1 (310) may separately transmit ACK/NACK information for s1 and ACK/NACK information for s2 to the base station (300). If terminal-1 (310) does not receive a HARQ response request message for another terminal's data signal from the base station (300), it may transmit only ACK/NACK information for its own data signal (i.e., s1) to the base station (300). You can.

The base station 300 can request and receive a HARQ response for the data signal of another terminal (i.e., terminal-2 320) from terminal-1 (310) at any time. That is, in this disclosure, ACK/NACK transmission and reception of data signals from other terminals may be performed aperiodically.

Although only the ACK/NACK transmission and reception method performed between the base station 300 and the first terminal pair (i.e., terminal-1 (310) and terminal-2 (320)) has been described, the ACK/NACK transmission and reception is different from that of the base station (300). The same can be performed between terminal pairs (i.e., terminal-3 (330) and terminal-4 (340)). Next, a method of periodically transmitting and receiving ACK/NACK information about another terminal's data signal between the base station and the terminal is described.

Figure 7 is a flowchart showing a second embodiment of a method for transmitting and receiving ACK/NACK information between a base station and terminals.

Referring to FIG. 7, the communication system may include a base station 300, terminal-1 (310), terminal-2 (320), terminal-3 (not shown), and terminal-4 (not shown). The base station 300 connects terminals (terminal-1 (310), terminal-2 (320), terminal-3 (not shown), and terminal-3) based on a communication protocol (e.g., 4G communication protocol, 5G communication protocol). 4 (not shown)) can provide a communication service. The base station 300 in FIG. 7 may be the base station 300 in FIG. 3, the terminal-1 (310) in FIG. 7 may be the terminal-1 (310) in FIG. 3, and the terminal-2 (320) in FIG. ) may be terminal-2 (320) of FIG. 3. The communication system in FIG. 7 may be the same or similar to the communication system in FIG. 6.

In a communication system, when terminal-1 (310) and terminal-2 (320) are connected to the base station 300, the base station 300 may transmit CSI-RS through a downlink subframe according to a preset period. UE-1 (310) and UE-2 (320) can each receive a CSI-RS from the base station 300 and perform a channel measurement operation based on the received CSI-RS. Here, the channel between the base station 300 and UE-1 (310) may be referred to as a “first channel”, and the channel between the base station 300 and UE-2 (320) may be referred to as a “second channel”. there is. Terminal-1 (310) may transmit measurement information (e.g., CSI) of the first channel to the base station 300, and Terminal-2 (320) may transmit measurement information (e.g., CSI) of the second channel. Can be transmitted to the base station 300.

The base station 300 may receive measurement information of the first channel from UE-1 (310) and may receive measurement information of the second channel from UE-2 (320). Alternatively, the base station 300 may obtain measurement information of the first channel by performing a channel measurement operation based on the sounding reference signal (SRS) received from terminal-1 (310) and from terminal-2 (320). Measurement information for the second channel can be obtained by performing a channel measurement operation based on the received SRS.

The base station 300 may set DCI including parameters necessary for overlapping transmission (S700). The overlapping transmission parameters may include at least one of resource allocation information, MCS information for UE-1 (310), MCS information for UE-2 (320), and information indicating a transmission power allocation coefficient.

DCI may include information indicating transmission power allocation coefficients (a1, a2). a1 and a2 Since the relationship between them may be "a1+a2=1", DCI may include information indicating either a1 or a2. In this case, a separate DCI containing information indicating the transmission power allocation coefficients (a1, a2) is not created, and the transmission power allocation coefficients (a1, a2) are added to the existing DCI (for example, the DCI listed in Table 2). ) may additionally include information indicating. Alternatively, the DCI size may vary depending on the number of bits of information indicating the transmission power allocation coefficient.

The base station 300 may transmit control information (e.g., DCI) including overlapping transmission parameters to terminal-1 (310) and terminal-2 (320) (S701). Terminal-1 (310) and Terminal-2 (320) can receive control information (e.g., DCI) from the base station 300, and from the received signal, resource allocation information, MCS information, MCS information for UE-2 (320), and transmission power allocation coefficients (a1, a2) can be obtained. a1 and a2 may be transmission power allocation coefficients for the s1 signal and s2 signal, respectively. If the channel state between the base station 300 and UE-1 (310) is different from the channel state between the base station 300 and UE-2 (320), the transmission power allocation coefficients (a1, a2) included in DCI may be different. there is.

When the data signal s1 to be transmitted to terminal-1 (310) and the data signal s2 to be transmitted to terminal-2 (320) are present in the base station 300, the base station 300 uses the same resources (e.g., time and frequency Resources) can be used to transmit the data signal s1 and the data signal s2 (S702).

Terminal-1 (310) and Terminal-2 (320) can each obtain the data signal s1 and data signal s2 from the base station 300 based on parameters necessary for overlapping transmission. The overlapping coding signals received from Terminal-1 (310) and Terminal-2 (320) may be equivalent to Equation 2 and Equation 3, respectively. In Equation 2, y1 may be a received signal of UE-1 (310), and h1 may indicate the channel state between the base station 300 and UE-1 (310). n1 may be a noise signal of terminal-1 (310). In Equation 3, y2 may be the received signal of UE-2 (320), and h2 may indicate the channel state between the base station 300 and UE-2 (320). n2 may be a noise signal of terminal-2 (320).

The channel quality of UE-1 (310), which is close to the base station 300, may be better than the channel quality of UE-2 (320), which is far from the base station 300. If |h1|>|h2| (i.e., if the channel state between the base station 300 and UE-1 (310) is better than the channel state between the base station 300 and UE-2 (320)), the transmission power allocation coefficient may be a1<a2. That is, the base station 300 may allocate relatively large power to a terminal (eg, terminal-2 320) with relatively poor channel conditions in order to maintain reliability of the transmission signal.

When the received signal y1 is received from the base station 300, terminal-1 (310) obtains the s2 signal by decoding the received signal y1 using the information of h1 and a2 and the MCS information for terminal-2 (320). You can. After acquiring the s2 signal from y1, UE-1 (310) uses the SIC (successive interference cancellation) technique to cancel the signal included in the received signal y1. can be removed.

Terminal-1 (310) may transmit ACK/NACK information for its data signal (i.e., s1) to the base station 300 through the uplink control channel (S703). Terminal-1 (310) may periodically transmit ACK/NACK information to the base station (300), and the transmission period may be determined by the base station (300).

The base station 300 may receive ACK/NACK information about the data signal (i.e., s1) of terminal-1 (310) from terminal-1 (310). The base station 300 may request transmission of a HARQ response to determine if UE-1 (310) has received the overlapping coding signal and successfully decoded the data signal s2 included in the overlapping coding signal (S704). That is, the base station 300 may transmit a message to terminal-1 (310) requesting ACK/NACK information for the data signal (i.e., s2) of another terminal (i.e., terminal-2 (320)). A message requesting a HARQ response to a data signal of another terminal may include an indicator requesting a HARQ response to a data signal of another terminal (eg, 1 bit). Terminal-1 (310) can receive a HARQ response request message for the data signal of another terminal.

When Terminal-1 (310) receives a message requesting a HARQ response for data from another terminal from the base station 300 before one cycle (i.e., 1 cycle) has elapsed after transmitting the previous ACK/NACK feedback message, In the next transmission cycle, Terminal-1 (310) sends ACK/NACK information for its own data signal s1 and ACK/NACK information for the data signal s2 for another terminal (i.e., Terminal-2 (320)) to the base station ( It can be transmitted to the base station 300 through the uplink data channel allocated by 300 (S705). The base station 300 may receive ACK/NACK information for s1 and ACK/NACK information for s2 from UE-1 (310).

Terminal-1 (310) does not receive a message requesting ACK/NACK information for data of another terminal from the base station 300 before one cycle (i.e., 2 cycles) elapses after transmitting the previous ACK/NACK feedback message. If not, only ACK/NACK information for its own data signal s1 can be transmitted to the base station 300 (S706).

Methods according to the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. Computer-readable media may include program instructions, data files, data structures, etc., singly or in combination. Program instructions recorded on a computer-readable medium may be specially designed and constructed for the present invention or may be known and usable by those skilled in the computer software art.

Examples of computer-readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine language code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The above-described hardware device may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although the description has been made with reference to the above examples, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will be able to.

Claims (12)

As a method of the first terminal,
Receiving setting information of a precoding matrix indicator (PMI) transmission period from a base station;
Selecting a first PMI with the largest beamforming gain among PMIs based on a predefined codebook;
Transmitting the first PMI to the base station based on the PMI transmission period;
Receiving a PMI request requesting a second PMI corresponding to a specific rank of the beamforming gain from the base station;
selecting the second PMI of the specific rank among the PMIs based on the predefined codebook; and
Transmitting the second PMI to the base station based on the PMI transmission period; including,
Method of the first terminal. In claim 1,
Resource allocation information for an overlapping signal including first data of the first terminal and second data of the second terminal from the base station, a first transmission power allocation coefficient of the first data, and a second transmission of the second data Receiving control information including a power allocation coefficient;
Receiving the overlapping signal based on the resource allocation information; and
Further comprising decoding the first data signal from the overlapping signal based on the first transmission power allocation coefficient and the second transmission power allocation coefficient,
Method of the first terminal. In claim 1,
The PMI request requesting the second PMI is received through one of a downlink control channel or upper signaling,
Method of the first terminal. In claim 1,
After transmitting the first PMI to the base station, if the PMI request requesting the second PMI is not received from the base station until the PMI transmission time based on the PMI transmission period arrives, based on the PMI transmission period Further comprising: retransmitting the first PMI to the base station,
Method of the first terminal. In claim 1,
Receiving a request for the first PMI from the base station after transmitting the second PMI to the base station; and
Transmitting the first PMI to the base station based on the PMI transmission period; further comprising,
Method of the first terminal. As a method of a base station,
Determining a precoding matrix indicator (PMI) transmission period;
Transmitting setting information of the PMI transmission cycle to a first terminal and a second terminal;
Receiving a first PMI with the largest beamforming gain from each of the first terminal and the second terminal based on the PMI transmission period;
Transmitting a PMI request requesting a second PMI corresponding to a specific rank of beamforming gain to at least one of the first terminal and the second terminal;
Receiving the second PMI from the at least one terminal; and
Including, determining a precoding vector for each terminal based on the first PMI and the second PMI.
Base station method. In claim 6,
Resource allocation information for an overlapping signal including first data of the first terminal and second data of the second terminal, a transmission power allocation coefficient of the first data, and a second transmission power allocation coefficient of the second data. Transmitting control information including the control information to the first terminal and the second terminal, respectively; and
Further comprising transmitting the overlapping signal to the first terminal and the second terminal based on the control information,
Base station method. In claim 6,
The PMI request requesting the second PMI is transmitted through one of a downlink control channel or upper signaling,
Base station method. In claim 6,
After receiving the second PMI from at least one of the first terminal and the second terminal, checking whether a third PMI of the at least one terminal is needed;
transmitting a third PMI request to the at least one terminal when the third PMI of the at least one terminal is needed;
Further comprising receiving the third PMI from the at least one terminal based on the PMI transmission period,
Base station method. In claim 6,
If the third PMI of at least one of the first terminal or the second terminal is not needed, receiving the first PMI from each of the first terminal and the second terminal based on the PMI transmission period. Including more,
Base station method. As a method of the first terminal,
Receiving a PMI feedback request including additional precoding matrix indicator (PMI) number information from a base station;
Selecting additional PMI(s) corresponding to the number of additional PMIs in order of increasing beamforming gain based on information on the number of additional PMIs included in the PMI feedback request; and
Comprising transmitting a PMI feedback message including the first PMI with the largest beamforming gain and the additional PMI(s) to the base station,
Method of the first terminal. In claim 11,
Resource allocation information for an overlapping signal including first data of the first terminal and second data of the second terminal from the base station, a first transmission power allocation coefficient of the first data, and a second data of the second data. Receiving control information including a transmission power allocation coefficient;
Receiving the overlapping signal based on the resource allocation information; and
Further comprising decoding the first data from the overlapping signal based on the first transmission power allocation coefficient and the second transmission power allocation coefficient,
Method of the first terminal.