WO2017026863A1

WO2017026863A1 - Method and apparatus for transmitting and receiving reference signal in communication system

Info

Publication number: WO2017026863A1
Application number: PCT/KR2016/008940
Authority: WO
Inventors: 노지환; 김태영; 유현일
Original assignee: 삼성전자 주식회사
Priority date: 2015-08-13
Filing date: 2016-08-12
Publication date: 2017-02-16

Abstract

Disclosed is a 5G or pre-5G communication system for supporting a data transmission rate higher than that of a 4G communication system such as LTE. A method for receiving a reference signal, according to the present disclosure, comprises the steps of: receiving configuration information on a reference signal; determining whether the aperiodic transmission of the reference signal is instructed on the basis of the configuration information; receiving a signal for requesting a measurement of the reference signal; measuring the reference signal on the basis of the configuration information when the received reference signal measurement request is aperiodic; generating channel state information on the basis of the measured result of the reference signal; and transmitting the channel state information.

Description

Method and apparatus for transmitting and receiving a reference signal in a communication system

The present disclosure discloses an apparatus and method for transmitting or receiving a reference signal in a communication system.

Efforts are being made to develop improved 5G (5 ^th- Generation) or pre-5G communication systems to meet the increasing demand for wireless data traffic since the commercialization of 4G (4 ^th- Generation) communication systems. . For this reason, a 5G communication system or a pre-5G communication system is called a system of a Beyond 4G network or a Long Term Evolution (LTE) system.

In order to achieve high data rates, 5G communication systems are being considered for implementation in the ultra-high frequency (mmWave) band (e.g., 60 gigabyte (60 GHz) band). In 5G communication systems, beamforming, massive array multiple input and output (FD-MIMO), and full dimensional MIMO (FD-MIMO) are used in 5G communication systems to mitigate the path loss of radio waves and to increase the propagation distance of radio waves. Array antenna, analog beam-forming, and large scale antenna techniques are discussed.

In addition, in order to improve the network of the system, 5G communication systems have advanced small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network (ultra-dense network) Device to device communication (D2D), wireless backhaul, moving network, cooperative communication, coordinated multi-points, and interference cancellation The development of such technology is being done.

In addition, in 5G systems, advanced coding modulation (ACM), hybrid FSK and QAM modulation (SWM) and sliding window superposition coding (SWSC), and advanced access technology, FBMC (filter bank multi carrier) and NOMA Non-orthogonal multiple access (SAP), and sparse code multiple access (SCMA) are being developed.

In a communication system, a user equipment (UE) reports channel state information between the terminal and the base station to the base station in order to communicate with the base station (eNodeB or eNB). In order for the terminal to report channel state information, the base station transmits a channel state information-reference signal (CSI-RS, hereinafter referred to as 'CSI-RS') to the terminal. That is, the CSI-RS is a signal transmitted by the base station to the terminal for the purpose of causing the terminal to feed back CSI.

The present disclosure is to provide a BF-CSI-RS transmission scheme for the base station to support a plurality of terminals in the FD-MIMO system. Here, BF-CSI-RS (beamformed CSI-RS) means a CSI-RS transmitted to a specific terminal.

A method of receiving a reference signal according to the present disclosure may include receiving configuration information about a reference signal, determining whether aperiodic transmission of the reference signal is indicated based on the configuration information, and requesting measurement of the reference signal. Receiving a signal, if the request for measuring the received reference signal is aperiodic, measuring a reference signal based on the configuration information, and generating channel state information based on the measurement result of the reference signal And transmitting the channel state information.

A method of transmitting a reference signal according to the present disclosure may include transmitting configuration information about the reference signal to be aperiodically transmitted, transmitting a signal for requesting the reference signal measurement, and a channel state for the reference signal. Receiving information.

An apparatus for receiving a reference signal according to the present disclosure includes a transceiver for receiving configuration information about a reference signal, receiving a signal for requesting the reference signal measurement, and transmitting channel state information, based on the configuration information. It is determined whether aperiodic transmission of the reference signal is instructed, and if the received request for measuring the reference signal is aperiodic, the reference signal is measured based on the configuration information, and based on the measurement result of the reference signal. And a controller for generating channel state information.

An apparatus for transmitting a reference signal according to the present disclosure transmits configuration information about the reference signal to be transmitted aperiodically, transmits a signal for requesting measurement of the reference signal, and receives channel state information about the reference signal. And a control unit for controlling the transmission and reception unit.

1 is a diagram illustrating a resource pattern of CSI-RS according to the number of antenna ports;

FIG. 2 is a diagram illustrating a CSI reporting by a terminal using a plurality of CSI-RSs received from a base station; FIG.

3 illustrates an embodiment in which a base station allocates orthogonal CSI-RS resources to each terminal in a cell and transmits a BF-CSI-RS according to the present disclosure;

4 is a diagram illustrating an embodiment of transmitting a CSI-RS configuration additionally allocated by a base station for each terminal group in a cell according to the present disclosure;

FIG. 5 is a diagram illustrating a radio resource control (RRC) message for transmitting UE group CSI-RS subframe configuration information to an MS as an example; FIG.

6 illustrates a method of allocating CSI-RS resources based on a shared CSI-RS candidate pool according to the present disclosure;

7 is a flowchart illustrating a terminal according to an embodiment of the present disclosure;

8 is a flowchart illustrating a base station according to an embodiment of the present disclosure;

9 illustrates a configuration of a terminal according to an embodiment of the present disclosure;

10 is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure.

DETAILED DESCRIPTION Hereinafter, embodiments of the present disclosure will be described in detail with the accompanying drawings. In addition, in describing the present disclosure, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present disclosure, the detailed description thereof will be omitted. In addition, terms to be described below are terms defined in consideration of functions in the present disclosure, and may vary according to a user's or operator's intention or custom. Therefore, the definition should be made based on the contents throughout the specification.

Hereinafter, a base station is a subject for transmitting a reference signal to a terminal, and may be at least one of an eNode B, a Node B, a base station (BS), a wireless access unit, a base station controller, or a node on a network. The terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function.

Embodiments of the present disclosure will be described based on the CSI-RS, but this description can be applied to other reference signals. For example, it may be applied to channel state information-interference measurement (CSI-IM).

For example, the base station may transmit CSI-RS to the terminal using one, two, four, or eight antenna ports. At this time, the antenna port number p is mapped to p = 15, p = 15 ~ 16, p = 15 ~ 18, and p = 15 ~ 22, respectively.

1 is a diagram illustrating a pattern of a CSI-RS according to the number of antenna ports on a resource.

Referring to FIG. 1, a resource region corresponding to a CSI-RS port is mapped on a resource region including 14 orthogonal frequency division (OFDM) symbols on a horizontal axis and 12 subcarriers on a vertical axis.

When a CSI reference signal configuration (or CSI reference signal configuration) number of the CSI-RS configuration (or configuration) is transmitted to the terminal by a higher layer signal, the terminal identifies the resource location to which the CSI-RS is mapped through Table 1. The number of CSI-RS antenna ports can be determined. The resource location of the CSI-RS allocated to the UE by the CSI-RS configuration is the same for each resource block pair (RBP) and for each subframe.

<Table 1> CSI-RS mapping according to the number of antenna ports

Table 1

In Table 1, k 'and l' denote a subframe index and a subcarrier index, respectively, and n _s denotes a subframe.

Table 2 is a table used to define the position of a subframe in which the CSI-RS exists. Table 2 shows a period (T _CSI _- _RS ) and an offset (Δ _CSI-RS ) in which CSI-RS is repeatedly transmitted on a subframe. Similar to the CSI-RS configuration of Table 1, the UE may estimate a subframe in which the CSI-RS is located using CSI-RS subframe configuration information. For example, if the base station transmits I _CSI _- _RS = 7 as CSI-RS subframe configuration information to the UE, the UE repeatedly transmits the CSI-RS in 10 subframes and has an offset of 7-5 = 2. It can be estimated that it is 2 subframes. Referring to Table 2, it can be seen that the minimum period during which the CSI-RS is repeatedly transmitted is 5 subframes and the maximum period is 80 subframes.

<Table 2> CSI-RS Subframe Configuration

TABLE 2

According to the 3GPP LTE Rel-12 standard, terminals belonging to a cell use the same CSI-RS resources. That is, cell-specific CSI-RS is transmitted. The terminal measures the CSI-RS transmitted by the base station even without a specific indication. The terminal reports the channel state information (CSI) generated based on the measurement value of the CSI-RS to the base station. This is called CSI reporting, and the CSI reporting is divided into periodic reporting and aperiodic reporting. In addition, the CSI may include at least one of a channel quality indicator (CQI), a precoding matrix indicator (PMI), and a rank indicator (RI).

As a method for increasing the accuracy of the CSI report, the UE may configure the CSI using measurement values for several recently received CSI-RSs instead of one CSI-RS.

FIG. 2 is a diagram illustrating an operation of reporting CSI using a plurality of CSI-RSs received from a base station.

Referring to FIG. 2, for example, three CSI-RS measurement values used for one CSI 201 report are 211, 213, and 215, and a measurement window is used to measure CSI-RS measurement units for such CSI reporting. window) 221. The measurement window of the terminal may be set differently according to implementation characteristics of each terminal or according to the environment of each terminal.

In a full dimension multi-input multi-output (FD-MIMO) system, a base station (i.e., a transmitting device) transmits a UE-specific beamforming (UE) to transmit a CSI-RS to a specific terminal (i.e., a receiving device). -specific beamforming) can be applied. Such a CSI-RS transmission method is called a beamformed CSI-RS (hereinafter, referred to as a 'BF-CSI-RS') method, and a CSI-RS transmitted by a base station to a specific user equipment is called a BF-CSI-RS. The BF-CSI-RS has an advantage that the base station can improve the CSI-RS measurement performance by sending a beamforming (beamforming) suitable for a specific terminal. The subframe in which the BF-CSI-RS is to be transmitted should be pre-configured, and the BF-CSI-RS may be periodically transmitted in units of subframes. Since the BF-CSI-RS has a characteristic unique to the terminal, the base station should assign resources for different BF-CSI-RS to each of the terminals in the cell. However, if the number of UEs to transmit the BF-CSI-RS in the cell increases, the overhead for the resource may increase. Accordingly, there is a need for a method for transmitting BF-CSI-RS for supporting a plurality of terminals.

The present disclosure is to provide a BF-CSI-RS transmission scheme for the base station to support a plurality of terminals in the FD-MIMO system. Since the BF-CSI-RS is not at all different from the CSI-RS, the BF-CSI-RS and the CSI-RS may be used interchangeably below.

The base station allocates CSI-RS resources, i.e., resources for transmitting BF-CSI-RS, to each UE for UE-specific BF-CSI-RS transmission. The CSI-RS resource may include a CSI-RS configuration and a CSI-RS subframe configuration. When the BF-CSI-RS is transmitted to the terminal, the terminal measures the CSI-RS to configure the CSI. The terminal sets a measurement window to increase the accuracy of the CSI-RS measurement, and configures and reports the CSI using the CSI-RSs received within the set measurement window.

Hereinafter, a method for BF-CSI-RS transmission and CSI-RS measurement and CSI reporting operation in a terminal to support a plurality of terminals will be proposed.

According to an embodiment of the present disclosure, a base station allocates orthogonal CSI-RS resources to each user equipment for BF-CSI-RS transmission. The orthogonal CSI-RS resource means different CSI-RS configurations or different CSI-RS subframes allocated to respective terminals. Orthogonal CSI-RS resources may be used even if the base station sets one of the CSI-RS configuration and the CSI-RS subframe configuration differently to each terminal. Therefore, at least one of the CSI-RS configuration and the CSI-RS subframe configuration of each UE allocated to the orthogonal CSI-RS resource may be different from each other.

In the embodiment, the base station transmits information on the CSI-RS configuration and the CSI-RS subframe configuration allocated to each terminal through a higher layer signal. Each terminal estimates and measures the CSI-RS allocated to the terminal using the received signal. Each terminal configures and reports the CSI to the base station based on the measurement result of the CSI-RS. In this case, the base station can easily transmit UE-specific BF-CSI-RS by allocating orthogonal CSI-RS resources to each terminal.

FIG. 3 is a diagram illustrating an operation of a base station allocating orthogonal CSI-RS resources to each terminal in a cell and transmitting a BF-CSI-RS according to an embodiment of the present disclosure.

Referring to FIG. 3, the base station allocates a CSI-RS configuration or a CSI-RS subframe configuration to K terminals. For example, the CSI-RS subframe configuration indicating the CSI-

RS subframes

311, 313, 315, and 317 allocated to the first terminal 301 by the base station and the CSI allocated to the second terminal 303. The CSI-RS subframe configuration indicating the -

RS subframes

321, 323, 325, and 327 is the same. However, the CSI-RS configuration 341 allocated to the first terminal 301 by the base station is different from the CSI-RS configuration 343 assigned to the second terminal 303.

As another example, the CSI-RS configuration 343 allocated to the second terminal 303 by the base station and the CSI-RS configuration 345 allocated to the third terminal 305 are the same. However, the CSI-RS subframe configuration indicating the CSI-

RS subframes

321, 323, 325, and 327 allocated to the second terminal 303 by the base station and the third terminal 305 are allocated. The CSI-RS subframe configuration indicating the CSI-

RS subframes

331, 333, 335, and 337 is different. In other words, a period (hereinafter, referred to as a 'CSI-RS period') 353 for transmitting the CSI-RS indicated by the CSI-RS subframe configuration of the third terminal 305 is the second terminal 303. The offset 351 of the CSI-RS subframe configuration of the third terminal 305 is the CSI-RS subframe of the second terminal 303 even if the same as the CSI-RS period of the CSI-RS subframe configuration. If different from the offset of the configuration, the second terminal 303 and the third terminal 305 is considered to have different CSI-RS subframe configuration.

When orthogonal CSI-RS resources are allocated to UEs in a cell as shown in FIG. 3, as the number of UEs in a cell increases, overhead for CSI-RS resources increases. As a method for mitigating the overhead problem, a method of setting a long CSI-RS period of each UE may be considered. However, when the CSI-RS period of each terminal becomes longer, the frequency at which each terminal reports CSI to the base station decreases. If the frequency of reporting the CSI is reduced, a problem may arise in that the channel state at the time of data transmission and reception and the channel state at the time of channel measurement are mismatched. Although there may be a problem, it may be applicable when the number of terminals is small, and thus the embodiment is not excluded from the present invention.

In order to solve a problem caused by setting a long CSI-RS period of each terminal, another embodiment according to the present disclosure additionally or in parallel allocates CSI-RS resources for each group of terminals. It is assumed that terminals belonging to a specific terminal group use the same CSI-RS configuration. In addition, UEs belonging to the specific UE group share a CSI-RS subframe configuration, that is, a CSI-RS subframe configuration for each UE group. The base station may allocate CSI-RS subframes within the terminal group CSI-RS subframe configuration to each terminal.

4 is a diagram illustrating an embodiment of transmitting a CSI-RS configuration additionally allocated by a base station for each terminal group in a cell according to the present disclosure.

Referring to FIG. 4, the first terminal group in the cell includes the first terminal 401, the second terminal 403,. And a K-th terminal 405. The base station may allocate the CSI-RS configuration and the CSI-RS subframe configuration differently to each of the first terminal 401, the second terminal 403, and the K-th terminal 405. However, the CSI-RS period may be set long to solve the overhead problem. The base station may further allocate a CSI-RS configuration for the first terminal group. In FIG. 4, the CSI-RS configuration of the

terminals

401, 403, and 405 belonging to the first terminal group and the CSI-RS configuration of the first terminal group may be identical or different. In addition, in FIG. 4, the CSI-RS subframe configuration of all the UEs belonging to the first UE group is included in the CSI-RS subframe configuration of the first UE group, but is not necessarily included.

In the above embodiment, in order to solve a problem occurring in a long CSI-RS period, the base station transmits a CSI-RS to the terminal in which the problem occurs and receives a CSI report. Referring to FIG. 4, the CSI-RS transmitted by the base station when necessary is one of the CSI-RSs included in the CSI-RS subframe configuration of each UE group of the group to which the problem occurs. For example, the first terminal 401 periodically receives the CSI-RSs 411 and 413 according to the configured CSI-RS configuration and the CSI-RS subframe configuration. If the base station determines that the channel state according to the CSI reported by the first terminal 401 does not match the actual channel state, the base station determines that the CSI- is uniquely assigned to the first terminal 401 by the terminal. In addition to the RS, unscheduled CSI-

RSs

425 and 427 included in the CSI-RS subframe configuration of the first terminal group to which the first terminal 401 belongs may be additionally transmitted. At this time, the base station transmits a signal to transmit the CSI-RS to the first terminal 401 to receive the CSI from the first terminal 401. The signal may be an aperiodic CSI trigger (AP-CSI trigger) signal.

However, the first CSI-RS 425 additionally transmitted to the first terminal 401 together with the aperiodic CSI trigger signal is not transmitted to any of the terminals belonging to the first terminal group, The second CSI-RS 427 additionally transmitted to the first terminal 401 together with the aperiodic CSI trigger signal may be allocated to the K-th terminal 405 by the base station. In this case, a collision situation of the CSI-RS may occur. In other words, by receiving the aperiodic CSI trigger signal, the first terminal 401 recognizes that the CSI-RS 427 that is not intended for the user is newly allocated, and measures the newly allocated CSI-RS 427. can do. However, the K-th terminal 405 will recognize the CSI-RS 427 newly allocated to the first terminal 401 as the CSI-RS 429 allocated to the first terminal 401. In this situation, if there is no additional indication to the K-th terminal 405, the K-th terminal 405 determines that the CSI-RS 427 transmitted to the first terminal 401 is its own. This can cause problems to include in the measurement window. Although there may be a problem, the above embodiment is not excluded from the present invention.

In the above embodiment, the shorter the UE group CSI-RS period, the higher the degree of freedom for AP-CSI reporting of the base station. Since the CSI-RS is transmitted only when all CSI-RSs of the UE group CSI-RS subframe configuration are actually transmitted to the UEs belonging to the UE group, the UE group CSI-RS period is short. If you do, it will not actually increase the overhead. Therefore, the CSI-RS period of the CSI-RS subframe configuration for each UE group is preferably short. For example, referring to Table 2, the CSI-RS subframe configuration may be set to zero. In this case, the UE group CSI-RS subframe configuration may be set to transmit the CSI-RS in all subframes.

FIG. 5 illustrates an example of a radio resource control (RRC) message for transmitting UE group CSI-RS subframe configuration information to UE.

Referring to FIG. 5, the RRC message includes CSI-RS-ConfigNZP information including UE group CSI-RS subframe configuration information, and CSI-RS-ConfigNZP information includes a csi-RS-ConfigNZId indicating a CSI-RS configuration number. , An antennaPortsCount indicating the number of antenna ports, a resourceConfig indicating a CSI-RS resource configuration, a subframeConfig indicating a CSI-RS subframe configuration, and a scramblingIdentity indicating a scrambling identifier.

Hereinafter, embodiments according to the present disclosure will be described in detail.

According to an embodiment of the present disclosure, the base station operates one CSI process and two CSI-RS subframe configurations for each terminal. The CSI process refers to a series of processes from the base station transmitting the CSI-RS to the terminal to receive the CSI from the base station until the CSI is reported from the terminal. In general, the base station operates one CSI-RS subframe configuration per one CSI process for one UE.

A new CSI process may be defined such that the base station can configure two CSI-RS subframe configurations in order to operate two CSI-RS subframe configurations in one CSI process for one UE. Or, it may be changed to use two CSI-RS subframe configurations in an existing CSI process. One of the two CSI-RS subframe configurations may be used for UE group CSI-RS subframe configuration.

Specifically, it is assumed that the UE periodically reports the CSI for the UE-specific CSI-RS subframe configuration, and reports the CSI to the base station aperiodically for the CSI-RS subframe configuration for each UE group. The UE basically performs CSI-RS measurement according to the UE-specific CSI-RS subframe configuration, but if the AP-CSI trigger signal is transmitted from the base station, the AP-CSI interval (from the time the AP-CSI trigger signal is transmitted) CSI-RS according to the UE group CSI-RS subframe configuration existing between CRS reporting time) is added to the measurement window. That is, the measurement of the UE group CSI-RS subframe configuration is not basically performed. As described above, only when the AP-CSI trigger signal is transmitted, the CSI-RS according to the CSI-RS subframe configuration in the corresponding section is performed. Reflect RS in the measurement.

For example, when the base station attempts to transmit an aperiodic CSI-RS that is not scheduled to the UE, the base station performs AP-CSI triggering timing so that the corresponding CSI-RS subframe is included in the AP-CSI report. Should be set. Since the AP-CSI trigger signal also includes the meaning of the measurement indication for the UE group CSI-RS subframe, the AP-CSI triggering timing should be equal to or higher than the unscheduled CSI-RS subframe.

Hereinafter, some measurement limitation methods for CSI-RS measurement in each terminal will be described.

The first method is to limit the measurement window in the UE by one subframe. Even if a CSI-RS collision occurs, if the measurement window is 1, the base station does not have to give an additional instruction to a terminal (eg, K-th terminal in FIG. 4) to which a UE-specific CSI-RS is allocated. Limiting the measurement window to one subframe may reduce CSI-RS measurement accuracy, but is the simplest method to solve the measurement window related problem that may occur when transmitting BF-CSI-RS.

The second is a method of informing the UE of a measurement reset point using a DCI format. In the second method, in a situation where a CSI-RS collision occurs, the base station may instruct the terminal assigned the UE-specific CSI-RS to reset the measurement in the next CSI-RS subframe of the CSI-RS collision. That is, a new measurement is started in the next CSI-RS subframe of the CSI-RS collision. Since the second method does not impose a constraint on the measurement window to the terminal except for the measurement reset, the second method has a higher degree of freedom than the first method in terms of implementation of the terminal.

Third is a method of not specifying a measurement limit to the terminal. The third method is a method of giving the terminal the maximum degree of freedom for CSI-RS measurement. In the case of using the third method, if a CSI-RS collision occurs, the base station may ignore the CSI report of the UE for several subframes, that is, for a predetermined time, that is, do not reflect the scheduling.

According to another embodiment of the present disclosure, the base station may operate two CSI processes for each terminal. The first CSI process is a CSI process for UE specific CSI-RS configuration, and the second CSI process is a CSI process for UE group CSI-RS configuration. In this case, the first CSI process supports both periodic and aperiodic CSI reporting. As described above, the UE measures and reports the CSI-RS according to the UE-specific CSI-RS subframe configuration. However, since the second process only needs aperiodic CSI reporting for unscheduled CSI-RS, it is not necessary to perform periodic CSI reporting. Therefore, there is a need for a scheme for the second process, that is, a scheme for reporting CSI aperiodically.

Table 3 shows the CSI reporting period that the terminal periodically reports to the base station according to the higher layer signal.

In Table 3, I _CQI _/ _PMI is an index for a CSI reporting period, N _pd is a CSI reporting period, and N _{OFFSET, CQI} means an offset of a subframe in which CSI is reported. For example, if I _CQI _/ _PMI = 30 is transmitted as a higher layer signal, the UE sets CSI by setting 20 subframes and a offset of I _CQI _/ _PMI -17 = 30-17 = 13 subframes in a period of reporting CSI. report.

However, in the above Table 3 I _CQI _/ _PMI = 317 or 542≤I _CQI _/ _PMI ≤1023 the period is not defined the CSI reporting cycle (N _pd). By using a specific I _CQI _/ _PMI value or an I _CQI _/ _PMI interval of a section in which the CSI reporting period is not defined, a setting in which the period is infinite (meaning not reporting CSI) may be defined. Therefore, when the base station is configured to the terminal with I _CQI _/ _PMI including an infinite CSI reporting period, the terminal may not perform periodic CSI reporting for the terminal group CSI process.

TABLE 3

The second process assumes to perform CSI-RS measurement for AP-CSI reporting. Here, each UE may know the UE group CSI-RS subframe configuration using the UE group CSI process, but does not know whether a specific subframe included in the UE group CSI-RS subframe configuration is allocated to another UE. Thus, the measurement window in the second process is set in units of one subframe. When the base station tries to transmit the unscheduled CSI-RS to the terminal, it instructs the AP-CSI trigger signal to the second process. In addition, since the second process is measuring the CSI-RS, it is also possible to indicate the AP-CSI trigger signal after an unscheduled CSI-RS subframe. As described above, the unit of the second measurement window is one subframe. In addition, CSI-RS measurement restriction methods in each terminal described above may be applied.

Another embodiment of the present disclosure is a method of distinguishing periodic CSI-RS resources from aperiodic CSI-RS resources. The difference from the above-described embodiments is that UE-specific periodic CSI-RS resources and CSI-RS resources shared by a plurality of UEs use different CSI-RS configurations. The CSI-RS resources shared by the plurality of terminals are referred to as “shared CSI-RS candidate pools” and are used as aperiodic CSI-RS resources. CSI-RSs in the shared CSI-RS candidate pool may be regarded as aperiodic CSI-RSs because they are not periodically allocated to themselves from the viewpoint of a specific UE.

6 is a diagram illustrating a method of allocating CSI-RS resources based on a shared CSI-RS candidate pool according to the present disclosure.

Referring to FIG. 6, it is confirmed that the CSI-RS configuration 611 of the periodic CSI-RS resources of each UE and the CSI-RS configuration 613 of the shared CSI-RS candidate pool, that is, the aperiodic CSI-RS resources are different from each other. Can be. Each terminal receives periodic CSI-RS configuration information and CSI-RS configuration information for a shared CSI-RS candidate pool from an eNB through an RRC message. The base station may allocate a corresponding subframe in the shared CSI-RS candidate pool to the specific terminal by transmitting an AP-CSI trigger signal (or CSI request signal) to the specific terminal. In this embodiment, unlike in FIG. 4, since the CSI-RS configuration 621 of the UE and the CSI-RS configuration 623 in the shared CSI-RS candidate pool of another UE are different, the CSI-RS collision is allocated to the same subframe. This does not happen.

As an embodiment, the base station may utilize a CSI request field of downlink control information (DCI) to allocate an aperiodic CSI-RS. The CSI request signal is for triggering CSI reporting, but further includes a function of allocating aperiodic CSI-RS, so that the base station can perform aperiodic CSI-RS allocation and request for CSI reporting at once with one DCI indication. Make sure

To this end, the base station is aperiodic CSI-RS configuration CSI- RS of the RRC message - can be added to the ConfigNZP. Hereinafter, several methods for adding an aperiodic CSI-RS configuration are proposed.

The first approach is to set both the CSI-RS configuration (ie, CSI-RS location in the subframe) and the CSI-RS subframe configuration (subframe period and offset) for the aperiodic CSI-RS resource. Here, it is assumed that periodic CSI-RS resources may or may not exist. There are two options for the CSI-RS allocation method using DCI indication.

The first option is to allocate an aperiodic CSI-RS to a CSI-RS subframe candidate indicated by DCI or a first CSI-RS subframe candidate indicated by DCI among CSI-RS subframe candidates through the CSI-RS subframe configuration. will be.

The second option is to allocate the aperiodic CSI-RS to the CSI-RS subframe candidate closest to the subframe indicated by the DCI among the CSI-RS subframe candidates through the CSI-RS subframe configuration.

The aperiodic CSI-RS is allocated to the same subframe as the subframe indicated by the DCI or subsequent subframes according to the first option, and also to a subframe before the DCI indicated by the second option. Aperiodic CSI-RS may be allocated.

The second method is to set only CSI-RS configuration for aperiodic CSI-RS resources. Since the base station does not set up a CSI-RS subframe configuration, it is possible to assign an aperiodic CSI-RS to any subframe. An aperiodic CSI-RS is allocated to a subframe indicated by DCI.

The first scheme and the second scheme are methods for distinguishing periodic CSI-RS resources from aperiodic CSI-RS resources.

The third method is to configure one or more CSI-RS resources to the UE and to activate or deactivate each CSI-RS resource. Like the first scheme, both CSI-RS configuration (ie, CSI-RS location in a subframe) and CSI-RS subframe configuration (period and offset) are required for CSI-RS resource configuration. In addition, the CSI-RS resource is activated or deactivated using the indication of the DCI, and this is referred to as a CSI-RS activation field ('CSI-RS activation field') for convenience. There are two options for activating or deactivating CSI-RS resources using the CSI-RS activation field.

In the first option, the base station allocates the CSI-RS according to the CSI-RS resource configuration after the first DCI activation for the CSI-RS activation ('CSI-RS activation'). In addition, the base station does not allocate the CSI-RS after deactivation of the second indication of the DCI. The number of bits of the 'CSI-RS activation field' is determined according to the number of CSI-RS resources. For example, if the number of CSI-RS resources is N, the number of bits is

Becomes

In the second option, '1' or '0' is indicated through the CSI-RS activation field to indicate activation or deactivation of the CSI-RS resource. The UE determines that the CSI-RS resource is activated when the command is '1', and determines that the CSI-RS resource is inactivated when the command is '0'. The number of bits of the 'CSI-RS activation field' in the second option is determined according to the number of CSI-RS resources. If the number of CSI-RS resources is N, the number of bits becomes N.

The fourth method is to inform the base station by setting whether the corresponding CSI-RS resources are periodic or aperiodic when the base station transmits CSI-RS resource configuration through the RRC message. If the set CSI-RS resources are periodic, the terminal operates in the same manner as the conventional scheme, and if the CSI-RS resources are aperiodic, the terminal may operate in any of the above-described embodiments. In addition, the number of CSI-RS resources configured by the base station in one CSI process may be one or more.

Hereinafter, a method of setting parameters required for CSI-RS resource configuration will be described.

Parameters required for the CSI-RS resource configuration may be set semi-fixed. Such a method may be referred to as a semi-static parameter configuration method. This method sets the parameters via an RRC message. The base station may set parameters such as the number of CSI-RS ports, the CSI-RS configuration, the CSI-RS subframe configuration, etc. to the UE through the RRC message.

Another method is a method of dynamically setting one or more of parameters required for CSI-RS resource configuration through DCI. Parameters that can be set through the DCI may be the number of CSI-RS ports, the CSI-RS configuration, and the like. For example, the base station can change the number of CSI-RS ports using the DCI. If the base station supports 2, 4, 8, or 12 CSI-RS ports, the number of CSI-RS ports may be indicated using 2 bits of the DCI. In addition, the base station may change the CSI-RS configuration. That is, N CSI-RS configurations may be set per CSI-RS resource using the RRC message, and one CSI-RS configuration among the N may be selected through DCI.

Hereinafter, a method for solving the overhead and rate matching due to the introduction of aperiodic CSI-RS will be described. Since the aperiodic CSI-RS is not periodically allocated, a method for using a subframe to which the actual CSI-RS is not allocated as a physical downlink shared channel (PDSCH) is needed. In addition, when aperiodic CSI-RS is allocated to a specific UE, a method for preventing other UEs from interpreting the aperiodic CSI-RS resource as a PDSCH is needed.

According to an embodiment of the present disclosure, a terminal is a scheme for recognizing a set aperiodic CSI-RS resource as a PDSCH. When the first terminal is allocated an aperiodic CSI-RS in the kth subframe using the DCI, the first terminal assumes that the CSI-RS exists in the kth subframe. However, since other UEs do not know whether a CSI-RS exists in the kth subframe, the UE may recognize the CSI-RS transmitted in the kth subframe as a PDSCH signal. In order to prevent this, when aperiodic CSI-RS is allocated to a specific terminal, a new DCI field is required for informing the corresponding information to other terminals except the specific terminal. In the present disclosure, the DCI field will be referred to as 'Dynamic ZP CSI-RS'. When a specific UE is instructed to 'Dynamic ZP CSI-RS' through DCI, the specific UE may interpret that the aperiodic CSI-RS is assigned to another UE.

According to an embodiment of the present disclosure, a terminal is a scheme for recognizing a set aperiodic CSI-RS resource as a CSI-RS. If the aperiodic CSI-RS resource is not allocated to any one UE, the subframe reserved for the aperiodic CSI-RS resource may be allocated. In order to prevent this, when aperiodic CSI-RS is not allocated to any UE, a DCI field is required to allow UEs assigned a corresponding subframe to PDSCH to recognize aperiodic CSI-RS resources as data through DCI. . In the present disclosure, the DCI field will be referred to as 'data mapping'. When a specific UE is instructed to 'data mapping' through DCI, the UE may interpret the aperiodic CSI-RS resource as its own data.

7 is a flowchart illustrating a terminal according to an embodiment of the present disclosure.

Referring to FIG. 7, the terminal receives a CSI-RS resource configuration through an RRC message from the base station (701).

The terminal determines whether the received CSI-RS resource configuration indicates an aperiodic CSI-RS resource (703).

If the received CSI-RS resource configuration indicates an aperiodic CSI-RS resource, the terminal receives a DCI indication. The terminal may determine that an aperiodic CSI-RS is allocated to a specific subframe based on the DCI indication (705). In one embodiment, the DCI indication may be CSI request bits included in the DCI.

The terminal receives and measures the CSI-RS in a subframe corresponding to the DCI based on the aperiodic CSI-RS resource (707).

The terminal generates a CSI and reports it to the base station based on the measurement result of the CSI-RS (709).

If the received CSI-RS resource configuration indicates a periodic CSI resource in step 703, the UE receives a DCI indication (711). The DCI indication may be CSI request bits included in DCI.

The terminal measures the CSI-RS in a subframe corresponding to the DCI based on the periodic CSI-RS resources (713).

The terminal performs step 709 described above.

8 is a flowchart illustrating a base station according to an embodiment of the present disclosure.

Referring to FIG. 8, the base station transmits configuration information on a reference signal to be transmitted aperiodically to the terminal (801).

The base station transmits a signal for requesting the reference signal measurement (803).

The base station receives 805 channel state information for the reference signal.

9 illustrates a configuration of a terminal according to an embodiment of the present disclosure. For convenience of description, components that are not directly related to the present disclosure will not be shown and described.

Referring to FIG. 9, the terminal 900 may include a controller 901 and a transceiver 903. Herein, the control unit 901 and the transceiver unit 903 are described as being performed. However, if necessary, all operations may be performed in one configuration. It may also be divided into more components.

The transceiver 903 receives information related to CSI-RS from a base station, for example, CSI-RS configuration, CSI-RS subframe configuration, CSI-RS, etc., and reports CSI to the base station.

The controller 901 may perform not only the operation of the transceiver 903 but also all operations described in the present disclosure, such as generating a CSI.

10 is a diagram illustrating a configuration of a base station according to an embodiment of the present disclosure. For convenience of description, components that are not directly related to the present disclosure will not be shown and described.

Referring to FIG. 10, the base station 1000 may include a controller 1001 and a transceiver 1003. Herein, the controller 1001 and the transmitter / receiver 1003 are described as being performed separately. However, if necessary, all operations may be performed in one configuration. It may also be divided into more components.

The transceiver 1003 transmits CSI-RS related information, for example, CSI-RS configuration, CSI-RS subframe configuration, CSI-RS, etc., to the terminal and receives CSI report from the terminal.

The controller 1001 may not only control the operation of the transceiver 1003 but also perform all the operations described in the present disclosure.

On the other hand, the embodiments of the present invention disclosed in the specification and drawings are merely presented specific examples to easily explain the technical contents of the present invention and help the understanding of the present invention, and are not intended to limit the scope of the present invention. That is, it will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be implemented. In addition, each of the above embodiments can be combined with each other if necessary to operate.

Claims

In the method for receiving a reference signal,

Receiving configuration information on a reference signal,

Determining whether aperiodic transmission of the reference signal is indicated based on the configuration information;

Receiving a signal requesting the reference signal measurement;

Measuring a reference signal based on the configuration information if the received request for measuring the reference signal is aperiodic,

Generating channel state information based on the measurement result of the reference signal, and

Transmitting the channel state information.
The method of claim 1,

The configuration information about the reference signal includes at least one of the number of antenna ports, resource configuration information, and subframe configuration information.
The method of claim 1,

The configuration information on the reference signal indicated to the aperiodic transmission is characterized in that the information set in common to a plurality of terminals.
The method of claim 1,

The signal for requesting the reference signal measurement is characterized in that the DCI.
The method of claim 1,

The process of receiving the configuration information on the reference signal

Receiving a plurality of configuration information about the reference signal,

Receiving a signal for requesting the reference signal measurement,

And transmitting a signal for requesting the reference signal measurement together with one of the plurality of configuration information.
In the method for transmitting a reference signal,

Transmitting configuration information about the reference signal to be transmitted aperiodically,

Transmitting a signal requesting measurement of the reference signal; and

And receiving channel state information on the reference signal.
The method of claim 6,

The configuration information about the reference signal includes at least one of the number of antenna ports, resource configuration information, and subframe configuration information.
The method of claim 6,

The configuration information of the reference signal to be transmitted aperiodically is information set in common to a plurality of terminals.
The method of claim 6,

The signal for requesting the reference signal measurement is characterized in that the DCI.
The method of claim 6,

The process of transmitting the configuration information for the reference signal,

A process of transmitting a plurality of configuration information for the reference signal,

The process of transmitting a signal for requesting the reference signal measurement,

And transmitting a signal for requesting the reference signal measurement together with one of the plurality of configuration information.
An apparatus for receiving a reference signal,

A transceiver for receiving configuration information on a reference signal, receiving a signal for requesting measurement of the reference signal, and transmitting channel state information;

It is determined whether the aperiodic transmission of the reference signal is instructed based on the configuration information. If the request for measuring the received reference signal is aperiodic, the reference signal is measured based on the configuration information, and the reference signal is measured. And a controller for generating the channel state information based on a result.
The method of claim 11,

Apparatus characterized in that it operates according to any one of claims 2 to 5.
The apparatus for transmitting the reference signal,

A transceiver for transmitting configuration information about the reference signal to be aperiodically transmitted, transmitting a signal for requesting the reference signal measurement, and receiving channel state information for the reference signal;

Device including a control unit for controlling the transceiver.
The method of claim 13,

Apparatus characterized in that it operates according to any one of claims 7 to 10.