KR20230004395A - Method and apparatus for transmitting downlink reference signal - Google Patents

Abstract

Provided is a method for a base station to transmit a channel state information (CSI)-reference signal (RS). The base station sets a resource block (RB) bundle including a plurality of RB pairs having different frequencies, and then the base station maps a CSI-RS resource element (RE) group for the transmission of the CSI-RS to at least one RB of a plurality of RBs belonging to the RB bundle. Therefore, the present invention is capable of efficiently transmitting an RS for channel estimation in a full dimension-MIMO system.

Description

Method and apparatus for transmitting downlink reference signal {METHOD AND APPARATUS FOR TRANSMITTING DOWNLINK REFERENCE SIGNAL}

The present invention relates to a method and apparatus for transmitting a downlink reference signal.

A multiple-input multiple-output (MIMO) method is a method of transmitting and receiving data using a plurality of transmit antennas and a plurality of receive antennas. In the MIMO system, a plurality of radio channel paths are generated between transmit/receive antennas, and a transmit/receive end separates or merges them to increase data transmission capacity or improve transmission quality. MIMO techniques include a spatial multiplexing technique and a spatial diversity technique. Downlink MIMO techniques introduced in a long term evolution (LTE) system include transmit diversity, cyclic delay diversity (CDD), beamforming, and spatial multiplexing. In addition, a multi-user MIMO (MU-MIMO) technique for simultaneously transmitting data to a plurality of terminals in the same resource is supported.

In the LTE standard, an antenna port is a logical antenna unit implemented by a weighted sum of one or more physical antenna elements, and is mainly defined by a transmitter. An antenna port is also a basic unit through which a reference signal (RS) is transmitted, and therefore, a UE estimates a channel for each antenna port, not a physical antenna element, and measures and reports channel state information (CSI) based on this estimation. carry out Different antenna port numbers are assigned to LTE downlink reference signals, cell-specific RS (CRS), user equipment-specific RS (URS), and channel state information-RS (CSI-RS). Since the purpose of the URS is to decode a physical downlink shared channel (PDSCH) of a UE, in this specification, it will be referred to as a demodulation RS (DMRS) for convenience. CRSs can be configured from 0 to 3, URSs from 7 to 14, and CSI-RSs from 15 to 22. The mapping between antenna ports and physical antenna element(s) is called antenna virtualization. The UE cannot basically know which virtualization is applied to each antenna port.

CSI-RS is a downlink reference signal transmitted by a base station for the purpose of acquiring CSI by a terminal, and was introduced in LTE Release 10. In the existing Release 8/9 system, CRS was used for CSI acquisition of the UE, but in Release 10, simultaneous transmission of up to 8 downlink layers was introduced, and a new reference signal for channel estimation having a lower density than the existing CRS introduction was necessary. The CSI-RS may be configured to have an interval of 6 resource elements (REs) or 12 REs on the frequency axis and a period of 5, 10, 20, 40, or 80 ms on the time axis. CSI-RS configuration information is transmitted through user equipment-specific radio resource control (RRC) signaling. The number of CSI-RS antenna ports configurable for the UE is 1, 2, 4, 8, 12, and 16 up to Release 13, and for each CSI-RS antenna port number, per physical resource block (PRB) pair. The total number of REs occupied by CSI-RS transmission is 2, 2, 4, 8, 12, and 16.

Meanwhile, according to the current LTE standard, when a normal CP (cyclic prefix) is configured, a total of 40 REs that can be used for CSI-RS transmission within one PRB pair. Research on how to extend REs that can be set as such CSI-RS resources is being conducted.

A problem to be solved by the present invention relates to a method and apparatus for extending an RE that can be configured as a CSI-RS resource.

In addition, a problem to be solved by the present invention relates to a method and apparatus for transmitting CSI-RS using the extended RE.

According to an embodiment of the present invention, a method for transmitting a channel state information (CSI)-reference signal (RS) by a base station is provided. The CSI-RS transmission method of the base station may include setting an RB bundle including a plurality of resource block (RB) pairs having different frequencies; and mapping a CSI-RS resource element (RE) set for transmission of the CSI-RS to at least one RB among a plurality of RBs belonging to the RB bundle.

According to an embodiment of the present invention, a resource pool for channel estimation RSs can be expanded by setting RSs for channel estimation (eg, CSI-RSs) using a plurality of PRB pairs adjacent to each other in the frequency axis. Through this, an RS for channel estimation can be efficiently transmitted in a full dimension (FD)-MIMO system.

In addition, according to an embodiment of the present invention, in a MIMO antenna communication system, a base station can set a plurality of RS antenna ports for channel estimation to a terminal for channel estimation and transmit them to the terminal.

1 is a diagram illustrating mapping of a CSI-RS RE set when the number of CSI-RS antenna ports is 2.
2 is a diagram illustrating mapping of a CSI-RS RE set when the number of CSI-RS antenna ports is 4.
3 is a diagram illustrating mapping of a CSI-RS RE set when the number of CSI-RS antenna ports is 8.
4 is a diagram illustrating a method of configuring CSI-RS resources using method Mb100 according to an embodiment of the present invention.
5A and 5B are diagrams illustrating a method of configuring CSI-RS resources using method Mb100 according to another embodiment of the present invention.
6 is a diagram illustrating a method of configuring CSI-RS resources using method Mb100 according to another embodiment of the present invention.
7 is a diagram illustrating a method of configuring resources for 16 CSI-RS antenna ports using method Mb200 according to an embodiment of the present invention.
8A and 8B are diagrams illustrating a method of configuring resources for 12 CSI-RS antenna ports using method Mb200 according to an embodiment of the present invention.
9 is a diagram illustrating a method of configuring resources for 32 CSI-RS antenna ports using method Mb200 according to an embodiment of the present invention.
10 is a diagram illustrating a method of configuring CSI-RS resources using method Mb200 according to another embodiment of the present invention.
11A and 11B are diagrams illustrating a method of configuring resources for six CSI-RS antenna ports using method Mb201 according to an embodiment of the present invention.
12 is a diagram illustrating a method of aggregating component CSI-RS configurations using method Mb110 according to an embodiment of the present invention.
13 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations using method Mb110 according to another embodiment of the present invention.
14 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations using method Mb130 according to an embodiment of the present invention.
15 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations when PRB bundling of method Mb200 is used according to an embodiment of the present invention.
16 is a diagram illustrating a method of transmitting a CSI-RS by temporally crossing indices of bundled PRB pairs according to an embodiment of the present invention.
17 is a diagram illustrating a base station according to an embodiment of the present invention.
18 is a diagram illustrating a terminal according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, a terminal includes a mobile terminal, a mobile station, an advanced mobile station, a high reliability mobile station, a subscriber station, and a mobile station. It may also refer to a portable subscriber station, access terminal, user equipment, etc. It may include all or some functions of an access terminal, user equipment, and the like.

In addition, a base station (BS) includes an advanced base station, a high reliability base station, a node B, an evolved node B (eNodeB), an access point (access point), radio access station, base transceiver station, mobile multihop relay (MMR)-BS, relay station that serves as a base station, and high-reliability relay that serves as a base station (high reliability relay station), repeater, macro base station, small base station, etc., base station, advanced base station, HR-BS, NodeB, eNodeB, access point, wireless access station, transceiver base station, MMR-BS, It may include all or some functions of a repeater, a high reliability repeater, a repeater, a macro base station, and a small base station.

Meanwhile, in the present specification, 'A or B' may include 'A', 'B', or 'both A and B'.

1. CSI-RS resource configuration

Mapping of resource elements (REs) through which CSI-RSs are transmitted follows a predetermined pattern for each number of antenna ports, and may be configured within a predetermined CSI-RS resource pool. CSI-RS resource configuration (CSI-RS resource configuration, hereinafter 'CSI-RS configuration') is defined for each of a normal cyclic prefix (CP) and an extended CP. In this specification, CSI-RS configuration may mean CSI-RS resource configuration itself, and in some cases, CSI-RS resource configuration set by CSI-RS resource configuration Alternatively, it may mean a CSI-RS RE set. In addition, CSI-RS configuration is divided into one that can be set for both frequency division duplex (FDD) and time division duplex (TDD) and one that can be set only for TDD. For example, CSI-RS configuration for a normal CP follows Table 1 below.

CSI-RS configuration for normal CP CSI-RS
configuration Number of CSI reference signals configured 1 or 2 4 8 (k', l') n _s mod 2 (k', l') n _s mod 2 (k', l') n _s mod 2 Frame structure type 1 and 2 0 (9,5) 0 (9,5) 0 (9,5) 0 One (11,2) One (11,2) One (11,2) One 2 (9,2) One (9,2) One (9,2) One 3 (7,2) One (7,2) One (7,2) One 4 (9,5) One (9,5) One (9,5) One 5 (8,5) 0 (8,5) 0 6 (10,2) One (10,2) One 7 (8,2) One (8,2) One 8 (6,2) One (6,2) One 9 (8,5) One (8,5) One 10 (3,5) 0 11 (2,5) 0 12 (5,2) One 13 (4,2) One 14 (3,2) One 15 (2,2) One 16 (1,2) One 17 (0,2) One 18 (3,5) One 19 (2,5) One Frame structure type 2 only 20 (11,1) One (11,1) One (11,1) One 21 (9,1) One (9,1) One (9,1) One 22 (7,1) One (7,1) One (7,1) One 23 (10,1) One (10,1) One 24 (8,1) One (8,1) One 25 (6,1) One (6,1) One 26 (5,1) One 27 (4,1) One 28 (3,1) One 29 (2,1) One 30 (1,1) One 31 (0,1) One

In Table 1, CSI-RS configurations 0 to 19 can be commonly applied to FDD and TDD, and CSI-RS configurations 20 to 31 can be applied only to TDD. In the TDD system, there is a possibility that the DMRS of antenna port 5 may be transmitted for a terminal set to transmission mode (TM) 7, so to avoid resource overlap with the DMRS of antenna port 5, CSI-RS configurations 20 to 31 are further defined. In Table 1, an index pair (k', l') indicated by each CSI-RS configuration means an RE that is a reference point of a CSI-RS RE set. How the CSI-RS RE set is determined within one PRB pair based on (k', l') is predefined in the standard.

1 to 3 respectively show mapping of RE sets for CSI-RS configurations 0 to 19 when a normal CP is configured and the number of CSI-RS antenna ports is 2, 4, or 8. . CSI-RS set A indicated in the drawings of this specification means CSI-RS configuration No. A, and X and Y represent CSI-RS antenna port numbers. X _A , Y _A indicated in the drawings of this specification represent CSI-RS antenna ports X and Y in CSI-RS configuration A, or UE A (UE-A = UE-a, UE -b, UE-c, ...) may indicate CSI-RS antenna ports X and Y. In this specification, transmission of CSI-RS antenna port or CSI-RS antenna port X includes transmission of the CSI-RS of the CSI-RS antenna port or the CSI-RS of CSI-RS antenna port X.

1 is a diagram illustrating mapping of a CSI-RS RE set when the number of CSI-RS antenna ports is 2, and FIG. 2 is a diagram illustrating mapping of a CSI-RS RE set when the number of CSI-RS antenna ports is 4 3 is a diagram illustrating mapping of a CSI-RS RE set when the number of CSI-RS antenna ports is 8.

One downlink subframe illustrated in FIGS. 1 to 3 includes two time slots. Specifically, when a normal CP is set, one subframe includes even-numbered time slots (hereinafter referred to as 'slot 0') and odd-numbered time slots subsequent to slot 0 (hereinafter referred to as 'slot 1'). Each of slot 0 and slot 1 includes 7 orthogonal frequency division multiplexing (OFDM) symbols (0 to 6) on the time axis and 12 subcarriers (0 to 11) on the frequency axis. That is, 84 (= 7x12) REs exist in each of slot 0 and slot 1 in one PRB pair. Some of the REs in one PRB pair may be set as REs for CRS transmission, some may be set as REs for DMRS transmission, and some may be set as REs for CSI-RS transmission. For example, in FIG. 1, CSI-RS antenna ports 15 and 16 of CSI-RS configuration 0 are mapped to two REs corresponding to OFDM symbols 5 and 6 of slot 0 and corresponding to subcarrier 9 ( set). That is, two CSI-RS antenna ports (Nos. 15 and 16) for each of CSI-RS configurations 0 to 19 are mapped to two REs. Hereinafter, for convenience of explanation, an RE corresponding to OFDM symbol n in a slot and corresponding to subcarrier k in a PRB pair is referred to as RE(n, k).

For another example, in FIG. 2, CSI-RS antenna ports 15 and 16 of CSI-RS configuration 1 are mapped to REs (2, 11) and REs (3, 11) of slot 1, and REs of slot 1 ( 2, 5) and REs (3, 5), CSI-RS antenna ports 17 and 18 of CSI-RS configuration 1 are mapped. That is, four CSI-RS antenna ports (No. 15 to No. 18) for each of CSI-RS configurations No. 0 to No. 9 are mapped to four REs.

As another example, in FIG. 3, CSI-RS antenna ports 15 and 16 of CSI-RS configuration 0 are mapped to REs (5, 9) and REs (6, 9) of slot 0, and REs of slot 0 are mapped. (5, 3) and RE (6, 3) are mapped to CSI-RS antenna ports 17 and 18 of CSI-RS configuration 0, and to RE (5, 8) and RE (6, 8) of slot 0 CSI-RS antenna ports 19 and 20 for CSI-RS configuration 0 are mapped, and REs (5, 2) and REs (6, 2) of slot 0 are CSI-RS for CSI-RS configuration 0 Antenna ports 21 and 22 are mapped. That is, 8 CSI-RS antenna ports (15 to 22) for each of CSI-RS configurations 0 to 4 are mapped to 8 REs.

On the other hand, code division multiplexing (CDM) is applied as a multiplexing method between antenna ports between CSI-RS antenna ports (eg, CSI-RS antenna ports 15 and 16) transmitted through the same RE. For example, in FIG. 1, CSI-RS antenna ports 15 and 16 are transmitted through REs (5, 9) of slot 0, and CSI-RS antenna ports 15 are transmitted through REs (6, 9) of slot 0. and number 16 are transmitted. In this case, in order to distinguish CSI-RS antenna ports 15 and 16 transmitted through the same RE, CDM is applied between CSI-RS antenna ports 15 and 16.

On the other hand, frequency division multiplexing (FDM) is applied as a multiplexing method between antenna ports between CSI-RS antenna ports (eg, CSI-RS antenna ports 15 and 17) transmitted through different REs. For example, in FIG. 2, CSI-RS antenna port 15 is transmitted through REs (5, 9) and REs (6, 9) of slot 0, and REs (5, 3) and REs (6, 3) of slot 0 are transmitted. ) through CSI-RS antenna port 17 is transmitted. In this case, in order to distinguish CSI-RS antenna ports 15 and 17 transmitted through different REs, FDM is applied between CSI-RS antenna ports 15 and 17.

In this specification, the CSI-RS pattern means a CSI-RS resource configuration predefined in the standard within the CSI-RS resource pool for each CSI-RS antenna port number, and in some cases, the CSI-RS antenna port It may include up to frequency axis resource density. As shown in FIGS. 1 to 3, in the current standard, CSI-RS patterns are defined for 1, 2, 4, and 8 CSI-RS antenna ports.

Meanwhile, for the 12 and 16 CSI-RS antenna ports introduced in Release 13, one fixed CSI-RS pattern is not defined, but the CSI-RS of the existing 4 or 8 CSI-RS antenna ports. A plurality of configurations are aggregated to configure resources. Specifically, 12 CSI-RS antenna ports are configured by aggregating 3 CSI-RS configurations of the existing 4 antenna ports, and 16 CSI-RS antenna ports are composed of the CSI-RS configuration of the existing 8 antenna ports. It is composed of two aggregates. In this specification, a CSI-RS configuration used as an element of CSI-RS resource aggregation is referred to as a component CSI-RS configuration.

In addition, for 12 and 16 CSI-RS antenna ports, one of length-2 CDM (hereinafter referred to as 'CDM-2') and length-4 CDM (hereinafter referred to as 'CDM-4') may be selectively applied.

Meanwhile, the CSI reporting type of the UE introduced in Release 13 is divided into Class-A and Class-B. When the transmission mode is 10, the base station may configure Class-A or Class-B CSI reporting to the terminal using a parameter indicating the CSI reporting type in the CSI process. In the present specification, a set of CSI-RS configuration parameters set in the UE for Class-A CSI reporting without distinction of transmission mode is referred to as 'first CSI-RS configuration', and is assigned to the UE for Class-B CSI reporting. A set of configured CSI-RS configuration parameters is referred to as 'second CSI-RS configuration'. When the transmission mode is 10, the first CSI-RS configuration means a set of CSI-RS configuration parameters within the CSI process for Class-A CSI reporting, and the second CSI-RS configuration refers to Class-B CSI reporting. means a set of CSI-RS configuration parameters within the CSI process for

The first CSI-RS configuration may include resource configuration information of 12 or 16 CSI-RS antenna ports. That is, the first CSI-RS configuration includes a parameter indicating a plurality of component CSI-RS configurations for resource aggregation of 12 or 16 CSI-RS antenna ports and a CDM type (ie, CDM-2 or CDM-4). can do. The second CSI-RS configuration includes one or a plurality of CSI-RS configurations, and at this time, each CSI-RS configuration included in the second CSI-RS configuration includes 1, 2, 4, or 8 existing CSI-RS antennas. This is the CSI-RS configuration of the port. Within one second CSI-RS configuration, CSI-RS configurations may have different numbers of CSI-RS antenna ports, and when the transmission mode is 10, each may have a different unique NZP CSI-RS ID.

2. How to extend the first CSI-RS configuration

The first CSI-RS configuration may be extended to the number of CSI-RS antenna ports other than 8, 12, and 16. For example, the first CSI-RS configuration may be extended to the number of CSI-RS antenna ports that is a multiple of 8 over 16. Alternatively, the first CSI-RS configuration may be extended to the number of CSI-RS antenna ports that is a multiple of 4 over 16. Alternatively, the first CSI-RS configuration may be extended to an even number of CSI-RS antenna ports greater than 16. Alternatively, the first CSI-RS configuration may be extended to include the number of CSI-RS antenna ports that are an even number greater than or equal to 8. In this case, the number of configurable CSI-RS antenna ports may be limited not to exceed N. where N is any natural number greater than 16. For example, N can be 32 or 64.

Similarly to the current standard, a method of aggregating a plurality of component CSI-RS configurations may be applied to the new number of CSI-RS antenna ports. For example, 20 CSI-RS antenna ports can be configured by aggregating 5 CSI-RS configurations of 4 existing antenna ports, and 24 CSI-RS antenna ports are CSI-RS configurations of 4 existing antenna ports. It can be configured by aggregating 6 RS configurations or by aggregating 3 CSI-RS configurations of existing 8 antenna ports.

Alternatively, a method of having the number of independent CSI-RS antenna ports for each component CSI-RS configuration may be applied to some or all of the new CSI-RS antenna ports and/or the number of existing CSI-RS antenna ports. . For example, 20 CSI-RS antenna ports may be configured by aggregating two CSI-RS configurations of existing 8 antenna ports and one CSI-RS configuration of existing 4 antenna ports.

Alternatively, for some or all of the number of new CSI-RS antenna ports and/or the number of existing CSI-RS antenna ports, all component CSI-RS configurations have the same number of CSI-RS antenna ports, but one component among them For CSI-RS configuration, a method of assuming that a UE receives only some CSI-RS antenna ports and uses them for CSI measurement and reporting may be applied. For example, the terminal may assume only some CSI-RS antenna ports for the last component CSI-RS configuration among the component CSI-RS configuration(s) constituting the first CSI-RS configuration. For example, 20 CSI-RS antenna ports are configured by aggregating 3 CSI-RS configurations of the existing 8 antenna ports, but for the last component CSI-RS configuration, the terminal uses 4 out of 8 antenna ports (eg , it can be assumed that only CSI-RS antenna ports 15 to 18) are received. For component CSI-RS configuration in which the UE assumes only some CSI-RS antenna ports, the number of CSI-RS antenna ports assumed by the UE may be signaled to the UE by the base station.

In this specification, it is assumed that the methods that can be applied to the first CSI-RS configuration can be equally or similarly applied to the configuration of the number of new CSI-RS antenna ports by the extension.

3. How to extend CSI-RS resource configuration

As illustrated in FIGS. 1 to 3 , according to the current LTE standard, when a normal CP is configured, a total of 40 REs that can be used for CSI-RS transmission within one PRB pair. Hereinafter, a set of REs that can be configured as CSI-RS resources within a PRB pair (or within a plurality of PRB pairs when PRB bundling is used) is referred to as a CSI-RS resource pool. Extending the CSI-RS resource pool can help transmit multiple CSI-RS antenna ports in an FD-MIMO system. As a method for extending the CSI-RS resource pool within one subframe, two methods can be considered.

A first method is a method of increasing the number of REs included in a CSI-RS resource pool within one PRB pair. The second method is a method of extending the CSI-RS resource pool by bundling a plurality of PRB pairs adjacent to each other in the frequency axis while maintaining the number of REs included in the CSI-RS resource pool within one PRB pair at 40. According to the latter method, while the number of REs that can be used for CSI-RS resource configuration increases, the number of REs allocated to each CSI-RS antenna port within the entire system bandwidth decreases. For example, when a PRB pair bundle includes two adjacent PRB pairs, the CSI-RS resource pool within one PRB pair bundle includes a total of 80 REs, but constitutes a sequence of each CSI-RS antenna port. The number of symbols used is reduced by half. If the density of REs on the frequency axis for each CSI-RS antenna port decreases, the number of channel samples available for channel estimation of the UE decreases, which may affect channel estimation performance depending on channel characteristics and channel estimation algorithms. On the other hand, according to the current standard, CSI measurement and reporting by the UE is performed at least in subband units, and thus accuracy of actually reported CSI or deterioration of scheduler performance may be insignificant.

Hereinafter, a method of extending a CSI-RS pattern will be described, focusing on the latter method. That is, a method of extending an existing CSI-RS pattern to a plurality of antenna ports using a PRB pair bundle as a basic unit will be described.

In addition, a method of using PRB bundling for 1, 2, 4, or 8 CSI-RS antenna ports will be described so that the CSI-RS pattern has a lower frequency axis density than before. In addition, a method of configuring the terminal by combining the extended CSI-RS patterns will be described. Each of the methods described below will be sequentially described by dividing them into the following four cases. The first case will be mainly described, and the remaining cases will be briefly described.

- When a normal CP is configured, CSI-RS resource configuration that can be applied to both FDD and TDD

- When a normal CP is configured, CSI-RS resource configuration that can be applied only to TDD

- When an extended CP is configured, CSI-RS resource configuration that can be applied to both FDD and TDD

- When an extended CP is configured, CSI-RS resource configuration that can be applied only to TDD

Meanwhile, the effects of methods according to embodiments of the present invention may vary according to antenna virtualization schemes. In this specification, virtualization means mapping between antenna ports and physical antenna element(s), and antenna virtualization in a digital signal processing based communication system may include antenna port virtualization and TXRU (transceiver unit) virtualization. Here, TXRU means a unit of an RF device capable of independently controlling and outputting the phase and amplitude of an input signal, and is also commonly referred to as an RF chain. Antenna port virtualization means mapping between antenna ports and TXRU(s), and TXRU virtualization means mapping between TXRU and physical antenna element(s). The terminal cannot know the virtualization applied to each antenna port by default.

In this specification, it is assumed that CSI-RS means a non-zero-power (NZP) CSI-RS as generally used, and is distinguished from a zero-power (ZP) CSI-RS.

3.1. CSI-RS resource configuration method that can be applied to both FDD and TDD when a normal CP is configured

First, a CSI-RS resource configuration method commonly applied to FDD and TDD frame structures when a normal CP is configured will be described.

Before explaining the proposed method, a PRB pair bundle is first defined. In this specification, a PRB pair bundle (hereinafter, 'PRB bundle') is a basic unit in which a CSI-RS pattern is defined, and means a bundle (or set) of adjacent PRB pairs in the frequency axis. That is, a CSI-RS pattern is defined within one PRB bundle, and the CSI-RS pattern is repeatedly mapped to a plurality of PRB bundles over the entire band. At this time, the size of the PRB bundle, that is, the number of PRB pairs included in the PRB bundle, is defined as N^bundle_RB, and the number of PRB bundles with the total system bandwidth is defined as N^DL_bundle. If the number of PRBs in the entire band is N^DL_RB, then N^DL_bundle = ceil (N^DL_RB/N^bundle_RB). For example, in an LTE system, when the system bandwidth is 10 MHz, N^DL_RB is 50, and at this time, if the size of the PRB bundle is set to 3, the total number of PRB bundles is N^DL_bundle = ceil(50/3) = 17, and the size of the last PRB bundle is 2. The CSI-RS pattern defined in the existing LTE standard corresponds to the case where N^bundle_RB = 1.

Hereinafter, PRB bundling (where N^bundle_RB > 1) will be described. A CSI-RS pattern may be defined using a plurality of PRB pairs included in a PRB bundle. In this case, as a method of extending the CSI-RS pattern, method Mb100 and method Mb200 may be largely considered.

Method Mb100 is a method in which an RE set of CSI-RS antenna ports included in a CSI-RS pattern is mapped (configured) within only one PRB pair among a plurality of PRB pairs included in a PRB bundle.

Method Mb100 may recycle a CSI-RS pattern of an existing standard to which PRB bundling is not applied. That is, method Mb100 may reuse existing CSI-RS configuration signaling using Table 1 when 1, 2, 4, or 8 CSI-RS antenna ports are to be configured. In this case, the base station may need to additionally inform the terminal of the size of the PRB bundle (N^bundle_RB) and/or the index of the PRB pair to which the CSI-RS RE set within the PRB bundle is mapped. Here, among the PRB pairs included in the PRB bundle, the index of the PRB pair to which the CSI-RS RE set is mapped may be expressed as an integer greater than or equal to 0 and less than N^bundle_RB, which is referred to as PRB shift for convenience in this specification. N^bundle_RB and/or PRB shift may have a fixed value according to a predetermined rule or may be set for each terminal.

As an example of the former, N^bundle_RB may have a predetermined value for each CSI-RS antenna port number. For example, N^bundle_RB is 1 up to the number of X CSI-RS antenna ports, and may be set to a value greater than 1 for the number of CSI-RS antenna ports greater than X. Here, X may be expressed as an integer value greater than or equal to 1. Meanwhile, as an example of the latter, when the UE is set to transmission mode 10, N^bundle_RB may be configured for each CSI process in the UE.

4 is a diagram illustrating a method of configuring CSI-RS resources using method Mb100 according to an embodiment of the present invention.

Specifically, in FIG. 4, the base station applies bundling to two PRB pairs, and to each of the terminals (UE-a, UE-b, UE-c, UE-d) within the same subframe 8, 4, 2, Alternatively, a case of configuring one CSI-RS antenna port is exemplified.

At this time, in the case of all terminals, N^bundle_RB is 2 in common, the PRB shift for the terminal (UE-a) and the terminal (UE-d) is 1, and the terminal (UE-b) and the terminal (UE-c) ), the PRB shift is 0. Since the size of the PRB bundle is 2, the frequency axis density of all the antenna ports illustrated in the figure becomes half of the conventional one.

For example, RE(2, 11), RE(3, 11), RE(2, 5), RE(3, 5), RE(2, 10), RE(3) of slot 1 in PRB pair 1 , 10), REs (2, 4), and REs (3, 4) are set as CSI-RS REs (eg, CSI-RS antenna ports 15 to 22) for the UE (UE-a). REs (5, 3) and REs (6, 3) of slot 0 in PRB pair #1 are configured as CSI-RS REs (eg, CSI-RS antenna port #15) for the UE (UE-d). REs (2, 11), REs (3, 11), REs (2, 5), and REs (3, 5) of slot 1 in PRB pair 0 are CSI-RS REs for the terminal UE-b ( For example, it is set as CSI-RS antenna ports 15 to 18). REs (5, 9) and REs (6, 9) of slot 0 in PRB pair 0 are configured as CSI-RS REs (eg, CSI-RS antenna ports 15-16) for the UE (UE-c). do. In the drawings of this specification, a PRB pair having a lower frequency band is illustrated as having a lower PRB pair index, but it may be assumed that a PRB pair having a higher frequency band has a lower PRB pair index.

According to method Mb100, a plurality of terminals may alternately use some REs in one PRB pair by alternating the PRB pair on the frequency axis. In the embodiment illustrated in FIG. 4, UE-a and UE-b are RE(2,5), RE(3,5), RE(2,11), and RE( 3,11) is used.

In method Mb100, the size of a PRB bundle (N^bundle_RB) can be any natural number. However, if the base station bundles too many PRB pairs, CSI measurement accuracy decreases, so the maximum value of the PRB bundle size (N^bundle_RB) may be predefined as an appropriate value. For example, the size of a PRB bundle may be limited so that it does not exceed the size of a subband (ie, N^bundle_RB is less than or equal to the number of RBs in one subband). Alternatively, the size of the PRB bundle may be limited to a factor of the subband size. Alternatively, a method of limiting the value of N^bundle_RB to only 1 and 2 may be considered.

As mentioned above, according to the current standard, CSI-RS patterns are defined only for 1, 2, 4, and 8 CSI-RS antenna ports, and 12 and 16 CSI-RS antenna ports are a plurality of component CSI-RSs. It is formed by aggregating the configuration. Meanwhile, for the number of CSI-RS antenna ports other than 1, 2, 4, and 8, a method of defining a CSI-RS pattern without depending on the resource aggregation may be considered. In this case, method Mb100 has a restriction that it cannot be applied to 64 CSI-RS antenna ports in the current CSI-RS resource pool. In addition, even if the base station wants to configure 32 CSI-RS antenna ports using method Mb100, the CSI-RS pattern cannot be defined only by combining CDM-2 and FDM within one PRB pair, and TDM or length-4 Since the CSI-RS pattern can be defined only through combination with the above CDM, at least 4 OFDM symbols are required for CSI-RS configuration and transmission. Therefore, when 32 CSI-RS antenna ports are set, the phase drift between OFDM symbols due to oscillator impairment may be relatively more exposed than when 16 or less CSI-RS antenna ports are set.

One of the advantages of the method Mb100 is that since the existing CSI-RS pattern remains the same within one PRB pair, the base station transmits the CSI-RS to the UE to which PRB bundling can be applied and the legacy to which PRB bundling cannot be applied. ) that the UE can share some REs.

5A and 5B are diagrams illustrating a method of configuring CSI-RS resources using method Mb100 according to another embodiment of the present invention.

Specifically, in FIGS. 5A and 5B, CSI-RS configuration of a new UE to which PRB bundling is applied for CSI-RS and an existing UE to which PRB bundling cannot be applied (or a new UE to which PRB bundling is not applied) share resources. A case is exemplified.

In FIG. 5A, UE-a and UE-b are configured with 8 CSI-RS antenna ports by the same CSI-RS configuration, and 2 PRBs are configured for UE-a by method Mb100. A case where bundling is applied to a pair is exemplified. For example, RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3) of slot 1 in PRB pair 0. , 5), REs (2, 4), and REs (3, 4) are configured as CSI-RS REs for UE-a. RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3, 5), RE of slot 1 in each PRB pair (2, 4) and REs (3, 4) are configured as CSI-RS REs for a UE (UE-b) to which PRB bundling is not applied. Consequently, RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3, 5) of slot 1 in PRB pair 0 ), REs (2, 4), and REs (3, 4) are configured as CSI-RS REs for UE-a and UE-b.

In FIG. 5B, the base station configures bundling of two PRB pairs to the UE (UE-a) using method Mb100, configures the CSI-RS pattern of 8 antenna ports in PRB pair 0, and configures the UE (UE-b ) is an example of configuring four CSI-RS antenna ports without PRB bundling. For example, RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3) of slot 1 in PRB pair 0. , 5), REs (2, 4), and REs (3, 4) are configured as CSI-RS REs for UE-a. RE(2, 11), RE(3, 11), RE(2, 5), and RE(3, 5) of slot 1 in each PRB pair are configured as CSI-RS REs for UE-b. do. Consequently, REs (2, 11), REs (3, 11), REs (2, 5), and REs (3, 5) of slot 1 in PRB pair 0 are the UE UE-a and the UE UE-a. It is set as the CSI-RS RE for b).

In the method illustrated in FIGS. 5A and 5B, the CSI-RS resource configuration for the UE (UE-a) and the UE (UE-b) shares some REs, so that the CSI of the two UEs (UE-a and UE-b) -Compared to a method in which there is no intersection between RS RE sets, CSI-RS transmission overhead can be reduced.

6 is a diagram illustrating a method of configuring CSI-RS resources using method Mb100 according to another embodiment of the present invention.

Specifically, FIG. 6 illustrates a method in which a base station configures CSI-RS resources for a plurality of terminals using different PRB pairs in a PRB bundle and allows a plurality of terminals to share the same RE in the frequency axis. In FIG. 6, UEs (UE-a, UE-b, UE-c, and UE-d) are UEs capable of receiving PRB bundling, and each UE (UE-a, UE-b, UE-c, UE-d) d) can be configured for bundling of two PRB pairs.

The base station commonly sets the same CSI-RS configuration and N^bundle_RB = 2 for 8 CSI-RS antenna ports to the UE (UE-a) and the UE (UE-b), and The PRB shift is set to 0, and the PRB shift for the UE (UE-b) is set to 1. For example, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6) of slot 0 in PRB pair 0 , 3), RE(5, 2), and RE(6, 2) are configured as CSI-RS REs for UE-a. RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6, 3), RE(5, 2) and RE(6, 2) are configured as CSI-RS REs for UE-b.

At this time, since the CSI-RS for the UE (UE-a) and the UE (UE-b) are transmitted through different PRB pairs, the CSI-RS for the UE (UE-a) and the UE (UE-b) It is possible to apply different virtualizations. That is, user equipment-specific CSI-RS beamforming is possible. This is useful when the channels of the terminal UE-a and the terminal UE-b have different directions within a beam space or a vector space.

The base station configures two CSI-RS antenna ports for UE (UE-c) and UE (UE-d). The principle applied to the CSI-RS configuration for UE (UE-c) and UE (UE-d) is the same as the example of UE (UE-a) and UE (UE-b). For example, REs (2, 11) and REs (3, 11) of slot 1 in PRB pair 0 are set as CSI-RS REs for the UE (UE-c). REs (2, 11) and REs (3, 11) of slot 1 in PRB pair #1 are configured as CSI-RS REs for the UE (UE-d).

Method Mb200 is a method in which an RE set of CSI-RS antenna ports included in a CSI-RS pattern is mapped in a uniform number (or a maximum uniform number) to all PRB pairs included in a PRB bundle.

In method Mb200, in order to map the same number of CSI-RS antenna ports to N^bundle_RB PRB pairs, N^bundle_RB must be a power of 2. Therefore, in method Mb100, the size of the PRB bundle may be any natural number, whereas in method Mb200, it may be effective to limit the size of the PRB bundle to a power of 2.

7 is a diagram illustrating a method of configuring resources for 16 CSI-RS antenna ports using method Mb200 according to an embodiment of the present invention.

Specifically, FIG. 7 illustrates a case in which two PRB pairs are bundled.

As illustrated in FIG. 7, the base station applies PRB bundling and antenna-port multiplexing (FDM) to the existing 8 CSI-RS patterns and extends the CSI-RS pattern by 2 times in the frequency axis to obtain 16 CSI-RS patterns. You can set the pattern of the RS antenna port.

At this time, the number of CSI-RS configurations that can be configured within one subframe is 5 (eg, 0 to 4). For example, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6) of slot 0 in PRB pair 0 , 3), RE(5, 2), and RE(6, 2) and RE(5, 9), RE(6, 9), RE(5, 8), RE( 6, 8), RE(5, 3), RE(6, 3), RE(5, 2), and RE(6, 2) are CSI-RS REs for CSI-RS configuration 0 (eg, CSI -RS antenna ports 15 to 30).

According to the embodiment illustrated in FIG. 7, as in method Mb100, the frequency axis resource density of each CSI-RS antenna port is reduced by half as much as two PRB pairs are bundled and bundled.

8A and 8B are diagrams illustrating a method of configuring resources for 12 CSI-RS antenna ports using method Mb200 according to an embodiment of the present invention.

Specifically, FIGS. 8A and 8B illustrate a case in which two PRB pairs are bundled. Unlike the case where the number of CSI-RS antenna ports is 16, when the number of CSI-RS antenna ports is 12, if the base station wants to equally divide and configure CSI-RS antenna ports in two PRB pairs, 6 within one PRB pair CSI-RS antenna ports need to be mapped. In this case, since a pattern for 6 CSI-RS antenna ports configured within one PRB pair is not defined in the existing standard, a new pattern for 6 CSI-RS antenna ports must be defined. To avoid this, a method of non-uniformly dividing and mapping 12 CSI-RS antenna ports to two PRB pairs may be considered.

8A and 8B illustrate a case in which the base station maps 8 and 4 CSI-RS antenna ports to PRB pairs 0 and 1, respectively.

A pattern for 8 CSI-RS antenna ports in the existing standard is applied to PRB pair No. 0, and a pattern for 4 CSI-RS antenna ports in the existing standard is applied to PRB pair No. 1.

At this time, the number of CSI-RS configurations that can be configured within one subframe is 5 (eg, 0 to 4). For example, in the embodiment illustrated in FIG. 8A, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE of slot 0 in PRB pair 0 (5, 3), RE(6, 3), RE(5, 2), and RE(6, 2) and RE(5, 9), RE(6, 9) of slot 0 in PRB pair #1, RE(5, 3) and RE(6, 3) are configured as CSI-RS REs (eg, CSI-RS antenna ports 15 to 26) for CSI-RS configuration 0. In the embodiment illustrated in FIG. 8B, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3) of slot 0 in PRB pair 0 ), RE(6, 3), RE(5, 2), and RE(6, 2) and RE(5, 8), RE(6, 8), RE(5, 2), and REs (6, 2) are set as CSI-RS REs (eg, CSI-RS antenna ports 15 to 26) for CSI-RS configuration No. 0.

At this time, as in the CSI-RS patterns illustrated in FIGS. 8A and 8B, the set of REs set in PRB pair 1 is included in the set of REs set in PRB pair 0, which is the ZP CSI-RS for other terminals. It can be effective for setting RS.

9 is a diagram illustrating a method of configuring resources for 32 CSI-RS antenna ports using method Mb200 according to an embodiment of the present invention.

Specifically, a case in which two PRB pairs are bundled is illustrated in FIG. 9 .

The base station applies PRB bundling and antenna-port multiplexing (FDM) to the pattern of 8 CSI-RS antenna ports on the existing standard, and expands the CSI-RS pattern by 4 times in the frequency axis, resulting in 32 CSI-RS antenna ports. Patterns can be set.

At this time, the number of CSI-RS configurations that can be set within one subframe is one (eg, number 0). For example, in the embodiment illustrated in FIG. 9 , RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE of slot 1 in PRB pair 0 (2, 9), RE(3, 9), RE(2, 8), RE(3, 8), RE(2, 5), RE(3, 5), RE(2, 4), RE( 3, 4), RE(2, 3), RE(3, 3), RE(2, 2), and RE(3, 2), and RE(2, 11) of slot 1 in PRB pair 1, RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 9), RE(3, 9), RE(2, 8), RE(3, 8), RE (2, 5), RE(3, 5), RE(2, 4), RE(3, 4), RE(2, 3), RE(3, 3), RE(2, 2), and RE (3, 2) are set as CSI-RS REs (eg, CSI-RS antenna ports 15 to 46) for CSI-RS configuration No. 0.

Meanwhile, the embodiments illustrated in FIGS. 7 to 9 are only specific examples for defining a CSI-RS pattern. The base station may define various CSI-RS patterns within the CSI-RS resource pool through the same or similar method as the above method using method Mb200.

Meanwhile, similar to method Mb100, even when method Mb200 is used, PRB bundling may be applied to 1, 2, 4, or 8 CSI-RS antenna ports.

10 is a diagram illustrating a method of configuring CSI-RS resources using method Mb200 according to another embodiment of the present invention.

Specifically, in FIG. 10, the base station bundles two PRB pairs and provides 8, 4, 2, or 1 CSI-RS antenna ports to each of the terminals (UE-a, UE-b, UE-c, and UE-d). A case of setting is exemplified.

For each CSI-RS pattern having 2, 4, or 8 antenna ports, PRB bundling and antenna-port multiplexing (FDM) are applied to the existing CSI-RS pattern of 1, 2, or 4 antenna ports, and the frequency axis It can be defined in a form in which the CSI-RS pattern is doubled. For example, RE(2, 11), RE(3, 11), RE(2, 5), and RE(3, 5) of slot 1 in PRB pair 0 and slot 1 in PRB pair 1 RE(2, 11), RE(3, 11), RE(2, 5), RE(3, 5) are CSI-RS REs for the UE (UE-a) (e.g., CSI-RS antenna port 15~ 22) is set as REs (5, 8) and REs (6, 8) of slot 1 in PRB pair No. 0 and REs (5, 8) and REs (6, 8) of slot 1 in PRB pair No. 1 are the UE (UE-b) ) for CSI-RS REs (eg, CSI-RS antenna ports 15 to 18). REs (5, 9) and REs (6, 9) of slot 0 in PRB pair 0 and REs (5, 9) and REs (6, 9) of slot 0 in PRB pair 1 are ) for the CSI-RS RE (eg, CSI-RS antenna ports 15 to 16).

In the case of CSI-RS resource configuration for UE-a and UE-b illustrated in FIG. 10, prepare for CSI-RS resource configuration of 8 or 4 antenna ports to which PRB bundling is not applied. Thus, the frequency axis density of CSI-RS resources is reduced by half. As a result, CSI-RS transmission overhead is reduced by half.

However, as can be seen through the CSI-RS resource configuration for the UE (UE-d) illustrated in FIG. 10, when the number of CSI-RS antenna ports configured in the UE is 1 and PRB bundling is used, the principle of method Mb200 cannot be applied Generalizing this, if the size of the PRB bundle is greater than the number of CSI-RS antenna ports configured in the UE, the principle of method Mb200 cannot be applied. In this case, as an exception, similar to method Mb100, a CSI-RS RE set may be mapped to only one PRB pair within a PRB bundle. At this time, the PRB pair to which the CSI-RS RE set is mapped may be predetermined. For example, in FIG. 10, REs (5, 3) and REs (6, 3) of slot 0 in PRB pair 0 are CSI-RS REs for the UE (UE-d) (e.g., CSI-RS antenna port 15) is set as

In addition, as can be seen through the CSI-RS resource configuration for the terminal (UE-c), when the number of CSI-RS antenna ports configured in the terminal is 2, there is no reduction in CSI-RS transmission overhead even if PRB bundling is used. . That is, if the size of the PRB bundle is equal to the number of CSI-RS antenna ports, method Mb200 can be used, but there is no overhead reduction effect. In consideration of this, a method of limiting the size of the PRB bundle (N^bundle_RB) to be set to a value smaller than or a multiple of the number of CSI-RS antenna ports to be configured in the UE may be used.

On the other hand, in method Mb200, if the size of the PRB bundle (N^bundle_RB) is not a divisor of the number of CSI-RS antenna ports, after all antenna ports are mapped as uniformly as possible within the PRB bundle, in a certain PRB pair, another PRB Antenna ports may be mapped to fewer REs than pair(s). At this time, in order to map the antenna ports to the same number of REs in all PRB pairs, the CSI-RS antenna ports are reset from number 15 to the remaining REs of the PRB pair(s) to which a smaller number of REs are mapped. A method of sequentially mapping may be considered. Alternatively, a method of not mapping CSI-RS to the remaining RE(s) may be considered. However, these methods are difficult to solve problems such as imbalance in resource allocation between CSI-RS antenna ports or degradation of channel estimation performance due to inefficient resource allocation. Therefore, when method Mb200 is used, the size of the PRB bundle (N^bundle_RB) is preferably a divisor of the number of CSI-RS antenna ports. Although the size of the PRB bundle (N^bundle_RB) is limited to be set only to the power of 2, in most cases it is possible to set the size of the PRB bundle (N^bundle_RB) to be a divisor of the number of CSI-RS antenna ports .

According to method Mb200, since different CSI-RS antenna ports are mapped to the same RE for each PRB pair included in a PRB bundle, it is difficult for a new terminal to which PRB bundling can be applied and an existing terminal to share NZP CSI-RS transmission resources. . On the other hand, according to method Mb200, since the number and location of CSI-RS REs are set to be the same for all PRB pairs, method Mb200 is a method for the existing UE to set the corresponding REs as ZP CSI-RS and perform PDSCH rate matching. It is more advantageous than Mb100.

Also in method Mb200, the maximum value of the size of the PRB bundle (N^bundle_RB) may be set. The size of a PRB bundle (N^bundle_RB) may be limited so as not to exceed the number of RBs in one subband. Alternatively, the size of the PRB bundle may be limited to a factor of the subband size. Alternatively, the size of the PRB bundle (N^bundle_RB) may be limited to only 1 and 2.

Method Mb201 is a modified method of method Mb200, which maps CSI-RS antenna ports in a uniform number (or as uniform as possible) to all PRB pairs on the entire system band without separately defining a PRB bundle. to be.

Method Mb201 may be interpreted as a special case of method Mb200. That is, method Mb201 is equivalent to the case where the size of the PRB bundle is set equal to the system bandwidth in method Mb200 (N^bundle_RB = N^DL_RB). However, in this case, since the number of REs generally greater than the number of CSI-RS antenna ports configured in the UE exists over the entire band, a rule for mapping each CSI-RS antenna port to a plurality of REs must be newly defined. You may. A method of repeating sequential mapping of all CSI-RS antenna ports starting from number 15 may be used. At this time, as an antenna port mapping rule within one PRB pair, a method following a pattern of 1, 2, 4, or 8 existing CSI-RS antenna ports may be used (FIG. 11a), or a new method ( 11 b) may be used. This will be described with reference to FIGS. 11A and 11B.

11A and 11B are diagrams illustrating a method of configuring resources for 6 CSI-RS antenna ports using method Mb201 according to an embodiment of the present invention. In the embodiments illustrated in FIGS. 11A and 11B , unlike the embodiments described so far, a PRB pair having a higher frequency has a lower PRB pair index.

Specifically, a case in which a method following a pattern of 1, 2, 4, or 8 existing CSI-RS antenna ports is used is illustrated in FIG. 11A. The mapping order of CSI-RS patterns for 8 antenna ports within each PRB pair is used. For example, RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3) of slot 1 in PRB pair 0. , 5), REs (2, 4), and REs (3, 4) are set as CSI-RS REs (eg, CSI-RS antenna ports 15 to 20, CSI-RS antenna ports 15 to 16) . RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3, 5), RE(2, 4) and RE(3, 4) are configured as CSI-RS REs (eg, CSI-RS antenna ports 17 to 20 and CSI-RS antenna ports 15 to 18). RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3, 5), RE(2, 4) and RE(3, 4) are configured as CSI-RS REs (eg, CSI-RS antenna ports 19 to 20 and CSI-RS antenna ports 15 to 20).

11B illustrates a case in which a new method of ignoring an existing mapping rule is used. For example, REs (2, 10) and REs (3, 10) of slot 1 in PRB pair 0 are set as CSI-RS antenna ports 17 to 18, and REs (2 of slot 1 in PRB pair 0) , 5) and REs (3, 5) are set as CSI-RS antenna ports 19 to 20.

As such, if the number of CSI-RS antenna ports is not a power of 2, as illustrated in FIGS. 11A and 11B , REs mapped to each CSI-RS antenna port number may not be arranged at equal intervals on the frequency axis. can As a result, degradation of channel estimation performance or increase in complexity may occur.

In method Mb201, like method Mb200, it is difficult to share new CSI-RS configuration resources extended by PRB bundling with NZP CSI-RS resource configuration of an existing UE, and the existing UE configures new configuration resources as ZP CSI-RS It is advantageous to perform PDSCH rate matching.

So far, methods for extending or changing the CSI-RS pattern in the frequency axis using PRB bundling have been described. A method of extending the PRB bundling to be possible for ZP CSI-RS resource configuration by equally applying the above methods to ZP CSI-RS configuration may be considered. For example, when method Mb100 is applied to the configuration of ZP CSI-RS, the base station informs the UE to which PRB pair within the PRB bundle the ZP CSI-RS RE set indicated by the bitmap is mapped, that is, , can inform the PRB shift. Alternatively, one ZP CSI-RS configuration may include a plurality of bitmaps. At this time, the number of bitmaps is equal to the size of the PRB bundle (N^bundle_RB), and the bitmap and PRB pair may be mapped one-to-one. For another example, when method Mb200 is applied to the configuration of ZP CSI-RS, the size of the PRB bundle may be 2. At this time, the length of the bitmap is twice the original length, and each bit of the bitmap is common to PRB pairs 0 and 1, and each CSI-RS in the case of two CSI-RS antenna ports in Table 1. It may correspond to the RE set indicated by the configuration. That is, each bit of the bitmap may correspond to two REs of PRB pair No. 0 and two REs of PRB pair No. 1.

As described above, since PRB bundling is applied to ZP CSI-RS configuration, inter-cell interference control or interference measurement can be easily performed. For example, when a neighboring cell transmits a PRB-bundled NZP CSI-RS, the serving cell sets the corresponding resource to the UE as a ZP CSI-RS to which the same PRB bundling is applied, so that accurate interference measurement or PDSCH resource allocation without resource waste is achieved. can make it possible.

Meanwhile, when PRB bundling is applied to the CSI-RS, the frequency domain RE density of each CSI-RS antenna port is reduced, so the number of CSI-RS symbols to be transmitted per CSI-RS antenna port is reduced. At this time, two methods may be considered for CSI-RS sequence generation and symbol mapping. The first is a method of generating a CSI-RS sequence according to the density of CSI-RS REs reduced for each antenna port, and sequentially mapping symbols constituting the sequence to set REs on the frequency axis. The second is a method of generating a CSI-RS sequence of the same length as the existing one for each antenna port, and mapping the symbols constituting the sequence to set REs in the same way as the existing mapping between symbols and PRB pairs (ie, sparsely). . The latter method has an advantage that a CSI-RS can be transmitted on the same resource by sharing a CSI-RS sequence between a new terminal to which PRB bundling can be applied and an existing terminal.

Meanwhile, in methods Mb100 and Mb200, the size of the last PRB bundle may be smaller than N^bundle_RB. For example, in the case of a system with a bandwidth of 50 RBs, if the PRB bundle size of CSI-RS is set to 3, the size of the last PRB bundle becomes 2. A method in which the same CSI-RS pattern is applied to the last PRB bundle, but mapping is omitted for a CSI-RS antenna port for which there are no resources to be mapped due to lack of PRB pairs may be considered. Alternatively, a method of not transmitting CSI-RS in the last PRB bundle may be considered.

Meanwhile, all methods of configuring CSI-RS resources by bundling a plurality of PRB pairs described above may be applied for configuring the second CSI-RS. The second CSI-RS configuration may include one or a plurality of CSI-RS configurations. In this case, the above-described methods may be applied for each CSI-RS configuration. That is, whether PRB bundling is applied, the size of the PRB bundle, and the PRB shift may be defined for each CSI-RS configuration. Alternatively, one or more of whether PRB bundling is applied, the size of the PRB bundle, and PRB shift may be commonly defined in all CSI-RS configurations constituting the second CSI-RS configuration. Alternatively, one or more of the application of PRB bundling, the size of the PRB bundle, and the PRB shift are commonly defined in a set of some CSI-RS configuration(s) among the CSI-RS configurations constituting the second CSI-RS configuration. It can be.

Hereinafter, a method of configuring CSI-RS resources for a UE by applying PRB bundling and aggregating a plurality of component CSI-RS configurations will be described.

First, a CSI-RS resource aggregation method for method Mb100 will be described. The aggregation method with the highest degree of freedom is a method of independently setting the size of a PRB bundle for each component CSI-RS configuration. In the following, only cases in which all aggregated component CSI-RS configurations have the same PRB bundle size will be considered. Even in the case of CSI-RS resource aggregation, the size of the PRB bundle may be signaled to the UE or may follow a predetermined value. At this time, it can be divided into method Mb110 to method Mb130 according to whether PRB shift signaling exists.

Method Mb110 is a method of setting a PRB shift for each component CSI-RS configuration.

Method Mb110 is a method with a higher degree of freedom in CSI-RS resource aggregation than methods Mb120 and Mb130. At this time, the parameter for CSI-RS resource aggregation includes PRB shift for each component CSI-RS configuration in addition to CSI-RS configuration information for each component CSI-RS configuration, and is common to all component CSI-RS configurations. It may additionally include the size of the PRB bundle (N^bundle_RB).

The number of CSI-RS antenna ports configurable for each component CSI-RS configuration may include only 4 or 8 of the Release 13 standard, and the number of ports other than 4 or 8, including the new number of ports described above. may further include.

When the number of antenna ports is 1, 2, 4, or 8, the component CSI-RS configuration may be a CSI-RS configuration according to the existing standard, and when the number of ports is other than that, the component CSI-RS configuration is a newly defined CSI-RS configuration. -Can be RS configuration.

As described above in method Mb100, the PRB shift may be expressed as an integer value greater than or equal to 0 and less than N^bundle_RB.

12 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations using method Mb110 according to an embodiment of the present invention.

For the UE (UE-e), two component CSI-RS configurations including 8 CSI-RS antenna ports are aggregated, and a total of 16 CSI-RS antenna ports are configured. For example, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6) of slot 0 in PRB pair 0 , 3), REs (5, 2), and REs (6, 2) are, for the UE (UE-e), component CSI-RS configuration No. 0 CSI-RS RE (eg, CSI-RS antenna port 15 ~ 22) is set as RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6, 3), REs (5, 2) and REs (6, 2) are CSI-RS REs of component CSI-RS configuration No. 1 (eg, CSI-RS antenna ports 15 to 22) for the UE (UE-e). is set

According to the parameter example described above, the parameters transmitted to the UE-e include the PRB shift for each component CSI-RS configuration in addition to the CSI-RS configuration information of each component CSI-RS configuration, and the PRB of 2 The bundle size (N^bundle_RB) may be additionally included. The PRB shift for component CSI-RS configuration No. 0 is 0, and the PRB shift for component CSI-RS configuration No. 1 is 1.

At this time, as a method of multiplexing between antenna ports of component CSI-RS configurations (Nos. 0 and 1) for the UE (UE-e), the two component CSI-RS configurations (Nos. 0 and 1) are the same OFDM. Since it is allocated on a symbol, FDM can be used.

Meanwhile, in the embodiment illustrated in FIG. 12 , a total of 10 CSI-RS antenna ports are configured for the UE (UE-f) by aggregating two component CSI-RS configurations. For example, RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3) of slot 1 in PRB pair 1. , 5), REs (2, 4), and REs (3, 4) are, for the UE (UE-f), component CSI-RS configuration No. 0 CSI-RS RE (eg, CSI-RS antenna port 15 ~ 22) is set as REs (5, 9) and REs (6, 9) of slot 1 in PRB pair No. 1 are CSI-RS REs of component CSI-RS configuration No. 1 (eg, CSI-RS antenna, for the UE (UE-f) port 15~16).

The parameters transmitted to the terminal (UE-f) include PRB shift for each component CSI-RS configuration in addition to CSI-RS configuration information of each component CSI-RS configuration, and the size of the PRB bundle of 2 (N^bundle_RB ) may be further included. Both PRB shifts for component CSI-RS configuration #0 and component CSI-RS configuration #1 are 1.

At this time, since the two component CSI-RS configurations (No. 0 and No. 1) for the UE (UE-f) are allocated to different OFDM symbols, the antenna ports of the component CSI-RS configurations (No. 0 and No. 1) As an inter-multiplexing scheme, FDM cannot be used and TDM can be used.

13 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations using method Mb110 according to another embodiment of the present invention.

Specifically, in FIG. 13, a case in which three component CSI-RS configurations (0, 1, and 2) are aggregated for one UE (UE-e) and a total of 48 CSI-RS antenna ports are set is an example. has been

The PRB bundle size (N^bundle_RB) is 2, and the number of antenna ports of each component CSI-RS configuration (0 to 2) is 16. For example, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6) of slot 0 in PRB pair 0 , 3), RE(5, 2), and RE(6, 2) and RE(2, 9), RE(3, 9), RE(2, 8), RE( 3, 8), RE(2, 3), RE(3, 3), RE(2, 2), and RE(3, 2) are, for UE-e, component CSI-RS configuration 0 It is set as a CSI-RS RE (eg, CSI-RS antenna ports 15 to 30). RE(2, 11), RE(3, 11), RE(2, 10), RE(3, 10), RE(2, 5), RE(3, 5) of slot 1 in PRB pair 0 RE(2, 4), and RE(3, 4) and RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8) of slot 1 in PRB pair 0 , RE(5, 3), RE(6, 3), RE(5, 2), and RE(6, 2), for the UE (UE-e), component CSI-RS configuration No. 1 CSI-RS It is set as an RE (eg, CSI-RS antenna ports 15 to 30). RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6, 3), RE(5, 2), and RE(6, 2) and RE(2, 9), RE(3, 9), RE(2, 8), RE(3, 8) of slot 1 in PRB pair 1 , RE(2, 3), RE(3, 3), RE(2, 2), and RE(3, 2), for the UE (UE-e), component CSI-RS configuration No. 2 CSI-RS It is set as an RE (eg, CSI-RS antenna ports 15 to 30).

Method Mb120 is a method of setting the PRB shift to the same value in all component CSI-RS configurations.

Compared to method Mb110, method Mb120 is a method that can reduce signaling overhead, instead of slightly restricting settings. According to method Mb120, since CSI-RS REs of all component CSI-RS configurations are mapped on the same PRB pair, it may be difficult to aggregate multiple CSI-RS antenna ports.

Method Mb130 is a method in which the PRB shift is not signaled to the UE and follows a predetermined rule.

Compared to methods Mb110 and Mb120, method Mb130 is a method that can reduce signaling overhead instead of slightly restricting settings. As one method for a predetermined aggregation rule, a method in which the PRB shift is determined as a function of the index of each component CSI-RS configuration may be considered. For example, the PRB shift for each component CSI-RS configuration may be determined by the result of a modulo operation of the corresponding component CSI-RS configuration index with the size of the PRB bundle (N^bundle_RB) ( hereinafter 'Method Mb130-1'). Alternatively, the size of the PRB bundle (N^bundle_RB) may be determined by the number of component CSI-RS configurations, and the PRB shift for each component CSI-RS configuration may be determined by the index of the corresponding component CSI-RS configuration (hereinafter, 'method Mb130-2').

At this time, the parameter for CSI-RS resource aggregation includes only CSI-RS configuration information of each component CSI-RS configuration, or additionally includes the size (N^bundle_RB) of a PRB bundle common to all component CSI-RS configurations. may also include

14 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations using method Mb130 according to an embodiment of the present invention.

For the UE (UE-e), a total of 10 CSI-RS antenna ports are set by aggregating three component CSI-RS configurations according to method Mb130-1. For example, REs (2, 11), REs (3, 11), REs (2, 5), and REs (3, 5) of slot 1 in PRB pair 0 are for the terminal UE-e. , component CSI-RS configuration is set as CSI-RS RE of No. 0 (eg, CSI-RS antenna ports No. 15 to 18). REs (5, 9), REs (6, 9), REs (5, 3), and REs (6, 3) of slot 1 in PRB pair No. 1 are, for the UE (UE-e), component CSI- RS configuration It is set as CSI-RS RE of No. 1 (eg, CSI-RS antenna ports No. 15 to 18). REs (5, 9) and REs (6, 9) of slot 1 in PRB pair 0 are CSI-RS REs of component CSI-RS configuration No. 2 (e.g., CSI-RS antenna for UE-e) port 15~16).

In this case, the sizes (N^bundle_RB) of PRB bundles for component CSI-RS configuration No. 0 to component CSI-RS configuration No. 2 are all 2. In addition, the PRB shift for component CSI-RS configuration No. 0 to component CSI-RS configuration No. 2 is the result of the modulo operation of the corresponding component CSI-RS configuration index with the size of the PRB bundle (N^bundle_RB), that is, 0, 1, and 0, respectively. For the UE (UE-f), by method Mb130-2, two component CSI-RS configurations including 8 CSI-RS antenna ports are aggregated, resulting in a total of 16 CSI-RS configurations. RS antenna port is set. For example, RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6) of slot 0 in PRB pair 0 , 3), REs (5, 2), and REs (6, 2) are, for the UE (UE-f), component CSI-RS configuration No. 0 CSI-RS RE (eg, CSI-RS antenna port 15 ~ 22) is set as RE(5, 9), RE(6, 9), RE(5, 8), RE(6, 8), RE(5, 3), RE(6, 3), REs (5, 2) and REs (6, 2) are CSI-RS REs of component CSI-RS configuration No. 1 (eg, CSI-RS antenna ports 15 to 22) for the UE (UE-f). is set

In this case, the size of the PRB bundle (N^bundle_RB) is set to 2, which is the number of component CSI-RS configurations. In addition, PRB shifts for component CSI-RS configuration No. 0 and component CSI-RS configuration No. 1 are determined by corresponding component CSI-RS configuration indexes, that is, 0 and 1, respectively.

Next, a CSI-RS resource aggregation method for method Mb200 will be described.

As described above, assuming that all component CSI-RS configurations to be aggregated have the same PRB bundle size, the parameter for CSI-RS resource aggregation includes only CSI-RS configuration information for each component CSI-RS configuration, or It may additionally include the size of the PRB bundle (N^bundle_RB) common to all component CSI-RS configurations.

15 is a diagram illustrating a method of aggregating a plurality of component CSI-RS configurations when PRB bundling of method Mb200 is used according to an embodiment of the present invention.

Specifically, FIG. 15 illustrates a case where the PRB bundle size (N^bundle_RB) is 2 and the number of aggregated component CSI-RS configurations is 2.

The CSI-RS pattern extended by PRB bundling of method Mb200 is applied to both component CSI-RS configurations 0 and 1, and both component CSI-RS configurations 0 and 1 have the number of CSI-RS antenna ports. . For example, REs (5, 9), REs (6, 9), REs (5, 3), and REs (6, 3) in slot 0 in PRB pair 0 and REs in slot 0 in PRB pair 1. (5, 9), RE(6, 9), RE(5, 3), and RE(6, 3) are CSI-RS REs of component CSI-RS configuration 0 for the UE (UE-e) ( For example, it is set as CSI-RS antenna ports 15 to 22). RE(2, 11), RE(3, 11), RE(2, 5), and RE(3, 5) of slot 1 in PRB pair 0 and RE(2, 11) of slot 1 in PRB pair 1 ), REs (3, 11), REs (2, 5), and REs (3, 5) are, for the UE (UE-e), component CSI-RS configuration No. 1 CSI-RS RE (eg, CSI- It is set as RS antenna port 15~22).

Meanwhile, with respect to all methods of bundling a plurality of PRB pairs described above to configure CSI-RS resources, a method of transmitting CSI-RS by periodically crossing the index of a PRB pair in different subframes is can be applied

16 is a diagram illustrating a method of transmitting a CSI-RS by temporally crossing indices of bundled PRB pairs according to an embodiment of the present invention.

As illustrated in FIGS. 8A and 8B, when the base station configures 12 CSI-RS antenna ports for the UE by bundling two PRB pairs according to method Mb200, the base station, as illustrated in FIG. 16, CSI -The CSI-RS may be transmitted by alternately changing the location of the PRB pair for each RS transmission subframe.

Specifically, assuming that the CSI-RS transmission period is T, the positions of PRB pairs 0 and 1 in the CSI-RS transmission subframe n+T are the positions of PRB pairs 0 and 1 in the CSI-RS transmission subframe n and In an inverted form, the CSI-RS may be transmitted.

Through this, since the UE can perform channel estimation for the frequency domain of all PRB pairs within the system band for each CSI-RS antenna port, CSI measurement accuracy can be improved.

Meanwhile, all methods of aggregating CSI-RS resources by bundling a plurality of PRB pairs described above may be applied for the first CSI-RS configuration. In addition, as described above, the above-described CSI-RS resource aggregation methods may be equally or similarly applied to the configuration of the number of new CSI-RS antenna ports.

Meanwhile, as a method of applying CDM-4 to method Mb100 and detailed methods of method Mb100, as in the case of existing standards to which PRB bundling is not applied, a method of applying CDM-4 within each component CSI-RS configuration. this can be used In this case, if the number of antenna ports of the component CSI-RS configuration is 4 or 8, the CDM-4 pattern of the existing standard can be equally applied. On the other hand, in order to apply CDM-4 to method Mb200 and detailed methods of method Mb200, if CDM-4 is applied within each component CSI-RS configuration, the frequency axis distance between REs constituting the CDM-4 pattern is far away, and channel estimation performance may be deteriorated. In this case, a method in which one CDM-4 pattern is defined across a plurality (eg, two) component CSI-RS configurations may be used.

3.2. CSI-RS resource configuration method applied only to TDD when a normal CP is configured

In Table 1, CSI-RS patterns and resource mapping for CSI-RS configurations 20 to 31 are designed to avoid overlap with DMRS transmission resources of antenna port 5. At this time, the CSI-RS resource pool within one PRB pair to which PRB bundling is not applied includes 24 REs. Even in this case, all the PRB bundling methods described above and their principles may be applied identically or similarly. However, it is impossible to define a pattern of more than 24 CSI-RS antenna ports or to aggregate more than 24 CSI-RS antenna ports within one PRB pair.

3.3. CSI-RS resource configuration method that can be commonly applied to FDD and TDD when an extended CP is configured

When an extended CP is set, a total of 16 CSI-RS configurations, numbered 0 to 15, are commonly applied to FDD and TDD in the existing standard. A CSI-RS resource pool in one PRB pair includes 32 REs. Even in this case, all the PRB bundling methods described above and their principles may be applied identically or similarly.

3.4. CSI-RS resource configuration method applied only to TDD when an extended CP is configured

When an extended CP is set, CSI-RS resource configurations of CSI-RS configuration No. 16 to 27 on the existing standard are designed to avoid overlap with DMRS transmission resources of antenna port No. 5 as much as possible. In this case, the CSI-RS resource pool in one PRB pair includes 24 REs. Even in this case, all the PRB bundling methods described above and their principles may be applied identically or similarly. However, it is impossible to define a pattern of more than 24 CSI-RS antenna ports or to aggregate more than 24 CSI-RS antenna ports within one PRB pair.

17 is a diagram illustrating a base station 100 according to an embodiment of the present invention.

The base station 100 includes a processor 110, a memory 120, and an RF converter 130.

Processor 110 may be configured to implement the functions, procedures, and methods described herein with respect to base stations. Also, the processor 110 may control each component of the base station 100 .

The memory 120 is connected to the processor 110 and stores various information related to the operation of the processor 110 .

The RF converter 130 is connected to the processor 110 and transmits or receives a radio signal.

18 is a diagram illustrating a terminal 200 according to an embodiment of the present invention.

The terminal 200 includes a processor 210, a memory 220, and an RF converter 230.

The processor 210 may be configured to implement the functions, procedures, and methods described herein with respect to a terminal. Also, the processor 210 may control each component of the terminal 200 .

The memory 220 is connected to the processor 210 and stores various information related to the operation of the processor 210 .

The RF converter 230 is connected to the processor 210 and transmits or receives a radio signal.

Meanwhile, the embodiment of the present invention has been described so far by taking a case where the downlink RS is a CSI-RS as an example, but this is only an example. An embodiment of the present invention can be applied even when the downlink RS is other than the CSI-RS.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims are also included in the scope of the present invention. that fall within the scope of the right.

Claims (1)

In a terminal operating in a communication system,
contains a processor;
The processor is the terminal,
Indicates information indicating the transmission density of a channel state information-reference signal (CSI-RS) in the frequency domain and one PRB to which the sequence of the CSI-RS is mapped for every N physical resource blocks (PRBs) in the frequency domain Receive setting information including information to be received from the base station;
For each antenna port of the CSI-RS, determine that the sequence is mapped to the one PRB indicated by the configuration information for every N PRBs in the frequency domain based on the transmission density; And
Causes PRBs determined to be mapped to the sequence to perform a reception operation of the CSI-RS,
Among the N PRBs, the one PRB to which the sequence is mapped is the same for antenna ports of the CSI-RS, and N is an integer greater than or equal to 2.

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