KR20220137430A - Apparatus and method for uplink demodulation reference signal in wireless communication system - Google Patents

Abstract

The present disclosure relates to a 5^th generation (5G) or pre-5G communication system for supporting a data transmission rate higher than a 4^th generation (4G) communication system such as long term evolution (LTE). A method performed by a terminal in a wireless communication system, includes the following steps of: receiving control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot from a base station; identifying uplink DMRS allocation based on the control information; and transmitting at least one uplink DMRS symbol, based on the uplink DMRS allocation, wherein the uplink DMRS allocation can include the number of the at least one uplink DMRS symbol and a position resource position of each of the at least one uplink DMRS symbol. Therefore, the present invention is capable of improving reception performance and cell coverage.

Description

Apparatus and method for uplink DMRS in wireless communication system {APPARATUS AND METHOD FOR UPLINK DEMODULATION REFERENCE SIGNAL IN WIRELESS COMMUNICATION SYSTEM}

The present disclosure generally relates to a wireless communication system, and more particularly, to an apparatus and method for an uplink demodulation reference signal (DMRS) in a wireless communication system.

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

In order to achieve a high data rate, the 5G communication system is being considered for implementation in a very high frequency (mmWave) band (eg, such as a 60 gigabyte (60 GHz) band). In order to alleviate the path loss of radio waves and increase the propagation distance of radio waves in the ultra-high frequency band, in the 5G communication system, beamforming, massive MIMO, and Full Dimensional MIMO (FD-MIMO) are used. ), array antenna, analog beam-forming, and large scale antenna technologies are being discussed.

In addition, for network improvement of the system, in the 5G communication system, an evolved small cell, an advanced small cell, a cloud radio access network (cloud radio access network, cloud RAN), an ultra-dense network (ultra-dense network) , Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and reception interference cancellation (interference cancellation) Technology development is underway.

In addition, in the 5G system, Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation (FQAM) and Sliding Window Superposition Coding (SWSC), which are advanced coding modulation (Advanced Coding Modulation, ACM) methods, and Filter Bank Multi Carrier (FBMC), an advanced access technology, ), Non Orthogonal Multiple Access (NOMA), and Sparse Code Multiple Access (SCMA) are being developed.

In a wireless communication system, a terminal may transmit an uplink signal to a base station. An uplink reference signal for demodulating an uplink signal may be defined. The base station may allocate the uplink reference signal of the terminal. For coverage enhancement, a more efficient uplink reference signal operation method is required.

Based on the above discussion, the present disclosure provides an apparatus and method for allocating an uplink demodulation reference signal (DMRS) in a wireless communication system.

In addition, the present disclosure provides an apparatus and method for determining the number of uplink DMRS symbols in a slot in a wireless communication system.

In addition, the present disclosure provides an apparatus and method for indicating an interval (interval) of uplink DMRS symbols within a slot in a wireless communication system.

According to various embodiments of the present disclosure, in a wireless communication system, a method performed by a terminal includes receiving control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot from a base station. a process of identifying an uplink DMRS assignment based on the control information; and transmitting one or more uplink DMRS symbols based on the uplink DMRS assignment, wherein the uplink DMRS assignment comprises: The number of one or more uplink DMRS symbols and a location resource location of each of the one or more uplink DMRS symbols may be included.

According to various embodiments of the present disclosure, in a wireless communication system, a method performed by a base station transmits control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot to the terminal. and receiving one or more uplink DMRS symbols from the terminal, wherein the number of the one or more uplink DMRS symbols and the location resource location of each of the one or more uplink DMRS symbols are based on the symbol interval can be assigned.

According to various embodiments of the present disclosure, in a wireless communication system, a terminal includes at least one transceiver and at least one processor, and the at least one processor includes an uplink demodulation reference signal (DMRS) in a slot. ) receive control information related to a symbol interval between symbols from a base station, identify an uplink DMRS assignment based on the control information, and transmit one or more uplink DMRS symbols based on the uplink DMRS assignment and, the uplink DMRS allocation may include the number of the one or more uplink DMRS symbols and a location resource location of each of the one or more uplink DMRS symbols.

According to various embodiments of the present disclosure, in a wireless communication system, a base station includes at least one transceiver and at least one processor, and the at least one processor includes an uplink demodulation reference (DMRS) in a slot. signal) is configured to transmit control information related to a symbol interval between symbols to a terminal and receive one or more uplink DMRS symbols from the terminal, the number of the one or more uplink DMRS symbols and the one or more uplink DMRS symbols Each of the location resource locations may be allocated based on the symbol interval.

According to various embodiments of the present disclosure, in a wireless communication system, a method performed by a base station includes a process of estimating an uplink channel, and a channel variation metric and a signal strength metric based on a result of estimating the uplink channel. a process of obtaining , the process of determining the number of uplink demodulation reference signal (DMRS) symbols based on the channel variation metric and the signal strength metric, and transmitting DMRS allocation information according to the number of uplink DMRS symbols to the terminal process may include.

According to various embodiments of the present disclosure, in a wireless communication system, a base station includes at least one transceiver and at least one processor, wherein the at least one processor estimates an uplink channel, and Based on the estimation result, a channel variation metric and a signal strength metric are obtained, and based on the channel variation metric and the signal strength metric, the number of uplink demodulation reference signal (DMRS) symbols is determined, and the number of uplink DMRS symbols It may be configured to transmit DMRS allocation information according to .

The apparatus and method according to various embodiments of the present disclosure provide improved reception performance and improved cell coverage by adaptively indicating the number of uplink demodulation reference signals (DMRS) or an interval between DMRS symbols based on a channel condition. do.

1 illustrates an example of a wireless communication environment according to various embodiments of the present disclosure.
2 illustrates an example of a radio resource area in a wireless communication system according to various embodiments of the present disclosure.
3 illustrates an example of an uplink demodulation reference signal (DMRS) in long term evolution (LTE) according to an embodiment of the present disclosure.
4 illustrates an example of an uplink DMRS in new radio (NR) according to an embodiment of the present disclosure.
5 illustrates an example of allocation of uplink DMRS symbols in a base station according to an embodiment of the present disclosure.
6 illustrates an example of signaling between a base station and a terminal for DMRS symbol allocation according to an embodiment of the present disclosure.
7 illustrates an example of DMRS allocation according to embodiments of the present disclosure.
8 illustrates an example of frequency division multiplexing (FDM) according to embodiments of the present disclosure.
9 illustrates a relationship between channel quality and reception probability according to embodiments of the present disclosure.
10 illustrates a functional configuration of a base station in a wireless communication system according to various embodiments of the present disclosure.
11 illustrates a functional configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure.

Terms used in the present disclosure are used only to describe specific embodiments, and may not be intended to limit the scope of other embodiments. The singular expression may include the plural expression unless the context clearly dictates otherwise. Terms used herein, including technical or scientific terms, may have the same meanings as commonly understood by one of ordinary skill in the art described in the present disclosure. Among the terms used in the present disclosure, terms defined in a general dictionary may be interpreted with the same or similar meaning as the meaning in the context of the related art, and unless explicitly defined in the present disclosure, ideal or excessively formal meanings is not interpreted as In some cases, even terms defined in the present disclosure cannot be construed to exclude embodiments of the present disclosure.

In various embodiments of the present disclosure described below, a hardware access method will be described as an example. However, since various embodiments of the present disclosure include technology using both hardware and software, various embodiments of the present disclosure do not exclude a software-based approach.

Hereinafter, the present disclosure relates to an apparatus and method for allocating an uplink demodulation signal (DMRS), which is an uplink reference signal, in a wireless communication system. Specifically, the present disclosure proposes a method for improving uplink communication performance and cell coverage by determining the number of DMRS symbols according to a channel in a wireless communication system and adaptively allocating them to a terminal.

Terms related to time resources (eg, symbols, slots, subframes, radio frames) used in the following description, terms related to frequency resources (eg, resource element (RE), resource block (RB), bandwidth part (BWP) BW (bandwidth), carrier (carrier), terms related to signals (eg, RS, symbol, information), terms related to signal processing (eg, encoding/decoding, channel coding, scrambling) , modulation, IFFT/FFT, and cyclic prefix (CP) insertion/deletion have been described based on the terms defined in the LTE or NR standards of the current 3GPP, but other terms with equivalent technical meanings may be used. In addition, terms (eg, format name, parameter name) that refer to parameters used in the following description, terms that indicate variables (eg, c, f, i, j, etc.), and terms that refer to channels (eg, uplink) link control channel), control information (eg, MAC (medium access control) CE (control element)), uplink control information (UCI), SR (scheduling request), HARQ-ACK (hybrid acknowledge repetition request-) acknowledge), a term referring to channel state information (CSI), a term referring to network entities (eg, a transmission device, a reception device, a transmission end, a reception) end), base station, terminal, communication node (communication node), radio node (radio node), radio unit (radio unit), network node (network node), master node (master n) ode, MN), sub-node (secondary node, SN), transmission/reception point (transmission/reception point, TRP), DU (digital unit), RU (radio unit), MMU (Massive MIMO unit), etc. for convenience of explanation it is exemplified Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

In addition, various embodiments of the present disclosure are described using terms used in some communication standards (eg, long term evolution (LTE) and new radio (NR) defined in 3rd Generation Partnership Project (3GPP)). The 3GPP mobile communication system dealt with here may include both 4G (Long Term Evolution (LTE)) and 5G (5G, hereinafter NR (New Radio)). However, the embodiments of the present disclosure may be easily modified and applied not only in the 3GPP mobile communication system, but also in other communication systems. Although uplink transmission is described as an example of the transmission or reception operation according to embodiments of the present disclosure, the same or similar technical principles may be applied to downlink transmission or sidelink transmission.

In addition, in the present disclosure, in order to determine whether a specific condition is satisfied or fulfilled, an expression of more than or less than is used, but this is only a description to express an example, and more or less description is excluded. not to do Conditions described as 'more than' may be replaced with 'more than', conditions described as 'less than', and conditions described as 'more than and less than' may be replaced with 'more than and less than'.

1 illustrates an example of a wireless communication environment according to various embodiments of the present disclosure. Referring to FIG. 1 , a base station 110 and a terminal 120 are illustrated as some of nodes using a wireless channel in a wireless communication system. The terminal 120 may also be connected to a plurality of base stations. Although not shown in FIG. 1 , the base stations may be connected to the terminal 120 through multiple connectivity (eg, dual connectivity, DC).

The base station 110 is a network infrastructure that provides a wireless connection to the terminal 120 . The base station 110 has coverage defined as a certain geographic area based on a distance capable of transmitting a signal. Hereinafter, the term 'coverage' used may refer to a service coverage area in the base station 110 . The base station 110 may cover one cell or may cover multiple cells. Here, a plurality of cells may be divided by a supported frequency and a covered sector area.

In addition to the base station, the base station 110 includes an 'access point (AP)', an 'eNodeB (eNodeB)', a '5G node (5th generation node)', a '5G node ratio (5G NodeB, NB)', 'gNB (next generation node B)', 'wireless point', 'transmission/reception point (TRP)', 'distributed unit (DU)', 'wireless unit (radio unit, RU), remote radio equipment (remote radio head, RRH), or may be referred to as another term having an equivalent technical meaning. According to various embodiments, the base station 110 may be connected to one or more 'transmission/reception points (TRP)'. The base station 110 may transmit a downlink signal to the terminal 120 or receive an uplink signal through one or more TRPs.

The terminal 120 is a device used by a user and performs communication with the base station 110 through a wireless channel. In some cases, the terminal 120 may be operated without the user's involvement. That is, at least one of the terminals 120 is a device that performs machine type communication (MTC) and may not be carried by the user. The terminal 120 includes 'user equipment (UE)', 'mobile station', 'subscriber station', 'customer premises equipment' (CPE) other than a terminal. , 'remote terminal', 'wireless terminal', 'electronic device', or 'vehicle (vehicle) terminal', 'user device' or equivalent technical It may be referred to by other terms that have a meaning.

Carrier aggregation (CA) technology is a technology introduced in 3GPP Standard Release 10. In CA, the UE is connected to a group of homogeneous radio communication cells having a common radio resource control entity and simultaneously uses frequency resources on component carriers of each cell located in different frequency bands for signal transmission and reception. It is a technology that increases the frequency use efficiency. Dual connectivity (DC) technology, a type of multiple connectivity, was introduced from the 3rd Generation Partnership Project (3GPP) standard release 12. In dual connectivity, the terminal is simultaneously connected with two independent heterogeneous or homogeneous wireless communication cell groups having a separate radio resource control entity, and a component carrier of a cell in each cell group located in a different frequency band It is a technology for increasing frequency use efficiency of a terminal and a base station by using a frequency resource on a component carrier for signal transmission and reception. In the dual connection, a control plane is directly connected to a core network to manage a radio resource control state of a terminal and is linked to a master cell group and a main cell group. It is composed of a secondary cell group.

Due to the technical advantages of increasing the efficiency in using the limited wireless communication resources of the terminal and the wireless communication resources of the base station, the dual connectivity technology and the carrier aggregation technology have been actively studied in academic terms. In particular, the 5G mobile communication system uses a non-stand alone operation as a basic operation method in conjunction with the 4G core network, so it is being used as a core technology in commercial services supporting the 5G mobile communication system.

A communication node (eg, a terminal, a base station, and an entity of a core network) according to various embodiments of the present disclosure may operate in an NR system. Also, communication nodes (eg, terminals, base stations, and entities of a core network) according to various embodiments of the present disclosure may operate together in an LTE system. Hereinafter, the structure shown in FIG. 2 is described as an example of an NR communication system, but these are exemplary and are not to be construed as excluding other communication systems.

2 illustrates an example of a radio resource area in a wireless communication system according to various embodiments of the present disclosure. In various embodiments, the radio resource region may include a structure of a time-frequency region. According to an embodiment, the wireless communication system may include an NR communication system.

Referring to FIG. 2 , in the radio resource domain, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The length of the radio frame 204 is 10 ms. The radio frame 204 may be a time domain interval consisting of 10 subframes. The length of the subframe 203 is 1 ms. A structural unit in the time domain may be orthogonal frequency division multiplexing (OFDM) and/or discrete fourier transform (DFT)-spread-OFDM (DFT-s-OFDM) symbols, and N _symb OFDM and/or DFT-s- OFDM symbols 201 may be gathered to configure one slot 202 . In various embodiments, the OFDM symbol may include a symbol for transmitting and receiving a signal using an OFDM multiplexing scheme, and the DFT-s-OFDM symbol is DFT-s-OFDM or single carrier frequency division multiple (SC-FDMA). access) may include a symbol for transmitting and receiving a signal using a multiplexing method. A minimum transmission unit in the frequency domain is a subcarrier, and a carrier bandwidth constituting a resource grid may be composed of a total of N _sc ^BW subcarriers 205 . Also, in the present disclosure, an embodiment of downlink signal transmission/reception is described for convenience of description, but this is also applicable to an embodiment related to uplink signal transmission/reception.

)로 지칭될 수 있다. 즉, 서브캐리어 간격, 서브프레임에 포함되는 슬롯의 개수, 슬롯의 길이, 서브프레임의 길이는 가변적으로 구성될 수 있다. 예를 들어, NR 통신 시스템에서 서브캐리어 간격(subcarrier spacing, SCS)이 15kHz인 경우, 1개의 슬롯(202)이 하나의 서브프레임(203)을 구성하며, 슬롯(202) 및 서브프레임(203)의 길이는 각각 1ms일 수 있다. 또한, 예를 들어, 서브캐리어 간격이 30kHz인 경우, 2개의 슬롯이 하나의 서브프레임(203)을 구성할 수 있다. 이 때, 슬롯의 길이는 0.5ms이며 서브프레임의 길이는 1ms이다. In some embodiments, the number of slots 202 and the length of the slots 202 constituting one subframe 203 may vary according to a subcarrier interval. This sub-carrier spacing is based on numerology (

) can be referred to as That is, the subcarrier interval, the number of slots included in the subframe, the length of the slot, and the length of the subframe may be variably configured. For example, when the subcarrier spacing (SCS) is 15 kHz in the NR communication system, one slot 202 constitutes one subframe 203, and the slot 202 and the subframe 203). may have a length of 1 ms, respectively. Also, for example, when the subcarrier interval is 30 kHz, two slots may constitute one subframe 203 . In this case, the length of the slot is 0.5 ms and the length of the subframe is 1 ms.

)은 15kHz, 30kHz, 60kHz, 120kHz, 240kHz 중 하나일 수 있고, 서브캐리어 간격(

)에 따라 하나의 서브프레임에 포함되는 슬롯의 개수는, 1, 2, 4, 8, 16 일 수 있다. In some embodiments, a subcarrier interval, the number of slots included in a subframe, a length of a slot, and a length of a subframe may be variably applied according to a communication system. For example, in the case of an LTE system, the subcarrier interval is 15 kHz, and two slots constitute one subframe. In this case, the length of the slot may be 0.5 ms and the length of the subframe may be 1 ms. For another example, in the case of an NR system, the subcarrier spacing (

) can be one of 15 kHz, 30 kHz, 60 kHz, 120 kHz, 240 kHz, and the subcarrier spacing (

), the number of slots included in one subframe may be 1, 2, 4, 8, or 16.

A basic unit of a resource in the time-frequency domain may be a resource element (RE) 206 , and the resource element 206 may be expressed by an OFDM symbol index and a subcarrier index. A resource block may include a plurality of resource elements. In an NR system, a resource block (Resource Block, RB) (or a physical resource block (PRB)) 207 is N _SC ^RB consecutive in the frequency domain. may be defined as subcarriers. The number of subcarriers may be N _SC ^RB =12. The frequency domain may include common resource blocks (CRBs). A physical resource block (PRB) may be defined in a bandwidth part (BWP) in the frequency domain. CRB and PRB numbers may be determined differently according to subcarrier spacing. In the LTE system, an RB may be defined as N _symb consecutive OFDM symbols in the time domain and N _SC ^RB consecutive subcarriers in the frequency domain.

In the NR and/or LTE system, scheduling information for downlink data or uplink data may be transmitted from the base station to the terminal through downlink control information (DCI). In various embodiments, DCI may be defined according to various formats, and each format indicates whether the DCI includes scheduling information (eg, UL grant) for uplink data, scheduling information for downlink data (DL resource allocation) It may indicate whether it includes, whether it is compact DCI having a small size of control information, whether it is fall-back DCI, whether spatial multiplexing using multiple antennas is applied, and/or whether it is DCI for power control. For example, NR DCI format 1_0 or NR DCI format 1_1 may include scheduling for downlink data. Also, for example, NR DCI format 0_0 or NR DCI format 0_1 may include scheduling for uplink data.

Various embodiments of the present disclosure are described based on an LTE communication system or an NR communication system, but the contents of the present disclosure are not limited thereto and may be applied in various wireless communication systems for transmitting uplink control information. In addition, it goes without saying that the contents of the present disclosure may be applied as needed in an unlicensed band in addition to the licensed band.

Hereinafter, in the present disclosure, higher layer signaling or higher signal is signal transmitted from the base station to the terminal using the downlink data channel of the physical layer, or from the terminal to the base station using the uplink data channel of the physical layer. it could be a way According to an embodiment, higher layer signaling is radio resource control (RRC) signaling, signaling according to the F1 interface between a centralized unit (CU) and a distributed unit (DU), or a MAC control element (media access control (MAC)) control element, MAC CE). Also, according to an embodiment, the higher layer signaling or the higher signal may include system information commonly transmitted to a plurality of terminals, for example, a system information block (SIB).

3 illustrates an example of an uplink demodulation reference signal (DMRS) in long term evolution (LTE) according to an embodiment of the present disclosure.

Referring to FIG. 3 , the resource grid 300 shows an example of DMRS allocation in one subframe and one PRB in an LTE communication system. One subframe may be 1 ms. One sub-carrier may include 12 sub-carriers. One subframe may include two slots. One slot may include 7 symbols in the time domain. A DMRS symbol may be located in the center of each slot. In other words, a DMRS symbol may be allocated to a symbol located at the 4th position among the 7 symbols (0, 1, 2, ..., 5, 6). In the LTE communication system, two DMRS symbols are allocated to one subframe. A sounding reference signal (SRS) may be allocated to the last symbol of the subframe.

In the LTE communication system, the positions of DMRS symbols in the subframe are fixed. However, in the current NR communication system, for more flexible allocation, the number of DMRS symbols may be one of 1 to 4, and the position of each DMRS symbol may vary according to a configuration. Hereinafter, an example of DMRS symbol mapping in an NR communication system will be described with reference to FIG. 4 .

4 illustrates an example of an uplink DMRS in new radio (NR) according to an embodiment of the present disclosure. The uplink DMRS may be transmitted for demodulation of uplink transmission. Uplink transmission in the NR communication system may include physical uplink shared channel (PUSCH) transmission or physical uplink shared channel (PUCCH) transmission. PUSCH transmission may include transmission of data along an uplink (UL)-shared channel (SCH). PUCCH transmission may include transmission of uplink control information (UCI). The UCI may include at least one of a scheduling request (SR), a hybrid acknowledge repetition request-acknowledgment (HARQ-ACK), and a channel state information (CSI). UCI may be transmitted in PUSCH.

It is assumed that the radio channel experienced by the DMRS is the same as or similar to the radio channel experienced by the signal of uplink transmission. That is, the precoding applied to the uplink signal may be equally applied to the DMRS. Likewise, the antenna port used by the uplink signal may be used by the DMRS. The base station may know in advance the sequence of the DMRS to be used by the terminal for the uplink signal. A DMRS sequence may be predefined according to communication settings (eg, whether transform precoding is performed, cell ID (identity), scrambling ID, DMRS configuration). In the uplink, the base station can estimate the channel by comparing the DMRS to be transmitted by the terminal and the received DMRS. The base station may demodulate the received uplink signal through channel estimation. Hereinafter, uplink transmission is described using PUSCH as an example, but embodiments of the present disclosure may be applied to PUCCH in the same or similar manner.

Referring to FIG. 4 , the first slot structure 401 may include a data area and an RS area. In the data region, PUSCH symbols may be mapped for payload delivery. The PUSCH may include data according to the UL-SCH. In the RS region, uplink DMRS symbols may be mapped for coherent demodulation of a channel. The first slot structure 401 may include 4 DMRS symbols in the time domain. According to an embodiment, the base station may notify the terminal of the number of DMRS symbols in the slot through higher layer signaling (eg, RRC signaling). A slot includes a total of 14 symbols. For example, the number of DMRS symbols indicated by higher layer signaling may be 4. Meanwhile, according to an embodiment of the present disclosure, in addition to RRC, a parameter in MAC CE or DCI may explicitly or implicitly indicate that the number of DMRS symbols is four.

The second slot structure 403 may include a data area and an RS area. In the RS region, uplink DMRS symbols may be mapped. The second slot structure 403 may include three DMRS symbols in the time domain. According to an embodiment, the base station may notify the terminal of the number of DMRS symbols in the slot through higher layer signaling (eg, RRC signaling). A slot includes a total of 14 symbols. For example, the number of DMRS symbols indicated by higher layer signaling may be three. Meanwhile, according to an embodiment of the present disclosure, a parameter in MAC CE or DCI other than RRC may explicitly or implicitly indicate that the number of DMRS symbols is three.

The third slot structure 405 may include a data area and an RS area. In the RS region, uplink DMRS symbols may be mapped. The third slot structure 405 may include two DMRS symbols in the time domain. According to an embodiment, the base station may notify the terminal of the number of DMRS symbols in the slot through higher layer signaling (eg, RRC signaling). A slot includes a total of 14 symbols. For example, the number of DMRS symbols indicated by higher layer signaling may be two. Meanwhile, according to an embodiment of the present disclosure, a parameter in MAC CE or DCI other than RRC may explicitly or implicitly indicate that the number of DMRS symbols is two.

The fourth slot structure 407 may include a data area and an RS area. In the RS region, an uplink DMRS symbol may be mapped. The fourth slot structure 407 may include one DMRS symbol in the time domain. According to an embodiment, the base station may notify the terminal of the number of DMRS symbols in the slot through higher layer signaling (eg, RRC signaling). A slot includes a total of 14 symbols. For example, the number of DMRS symbols indicated by higher layer signaling may be 1. Meanwhile, according to an embodiment of the present disclosure, in addition to RRC, a parameter in MAC CE or DCI may explicitly or implicitly indicate that the number of DMRS symbols is 1.

In FIG. 4, DMRS symbol allocation according to single symbol DMRS has been described as an example, but this is only an example of DMRS symbol allocation. The drawings or descriptions shown in FIG. 4 are not to be construed as limiting the embodiments of the present disclosure. Of course, embodiments of the present disclosure may be applied to double symbol DMRS for MU-MIMO.

DMRS symbol assignment

As described with reference to FIG. 2 , a slot may include 14 symbols. DMRS allocated in the slot is used for channel estimation and tuning demodulation. Additional allocation of DMRS may increase channel estimation performance in the base station. For example, if PUSCH transmission includes two DMRS transmissions, the base station may estimate a channel in each of two time intervals (eg, symbols). The base station may perform interpolation between each time interval based on the estimated channel result. As the number of DMRS symbols increases, a gap between channel estimation results decreases. The reduced gap reduces the requirement for interpolation. In an environment in which a channel changes rapidly, such as in a high-speed movement scenario, it is required to increase demodulation performance by allocating additional DMRS symbols. On the other hand, when the number of DMRS symbols allocated in the slot is increased, the area to which data symbols (UL-SCH data of PUSCH transmission or UCI of PUCCH transmission) is to be allocated is relatively decreased. That is, when the number of RSs increases, transmission overhead increases. Therefore, the base station is required to allocate the number of DMRS symbols more suitable for the channel environment to the terminal.

5 illustrates an example of allocation of uplink DMRS symbols in a base station according to an embodiment of the present disclosure. In FIG. 5, a method for how the base station determines the number of DMRS symbols allocated to the terminal is described. Meanwhile, the method illustrated in FIG. 5 is an example, and the functional block or description illustrated in FIG. 5 is not construed as limiting another embodiment of the present disclosure.

Referring to FIG. 5 , the base station may include an FFT block 510 , a Doppler estimation block 521 , an SNR estimation block 523 , and a DMRS allocation block 530 . The base station may receive an uplink signal. The uplink signal may include one or more DMRSs. The base station may obtain DMRS signals through the FFT block 510 . The base station may identify DMRS symbols mapped to one or more REs. The base station may acquire the received DMRS signal. The base station may estimate the channel from the received DMRS. According to an embodiment, a DMRS sequence according to communication settings (eg, whether transform precoding is performed, cell ID (identity), scrambling ID, DMRS configuration) may be predefined. . The base station can estimate the channel by comparing the DMRS sequence with the actually received MRS.

The base station may obtain the channel variation TD_H_Variation in the time domain through the Doppler estimation block 521 . Communication channels vary in time. Doppler spread is a measure of how quickly a received signal changes by a time-varying channel. As the channel changes rapidly, the amount of channel change increases. As described above, in order to increase demodulation performance as the channel changes rapidly, it may be required to allocate a large number of DMRS symbols. The base station may transmit the acquired channel change amount to the DMRS allocation block 530 .

The base station may obtain an SNR value (SNR_Value) through the SNR estimation block 523 . A high SNR value may indicate that the terminal is in a strong electric field. A low SNR value may indicate that the terminal is in a weak electric field. That is, the better the channel quality, the less DMRS may be required. The base station may transmit the obtained SNR value to the DMRS allocation block 530 .

The base station may determine the number of DMRS symbols allocated based on the channel estimation result. The base station may determine the number of DMRS symbols to be allocated in the slot through the DMRS allocation block 530 . According to an embodiment, the base station may determine the number of DMRSs to be allocated to the terminal based on the time variation or SNR of the fading channel. The DMRS allocation block 530 may perform DMRS allocation based on the channel variation obtained from the Doppler estimation block 521 and the SNR value obtained from the SNR estimation block 523 .

According to an embodiment, the DMRS allocation block 530 may allocate one or more DMRS symbols based on the amount of time variation of the fading channel. A large amount of time variation means that the channel is relatively unstable. In this case, in order to expect stable demodulation performance for uplink transmission, a larger number of DMRS symbols are required to be allocated. For example, the DMRS allocation block 530 may perform DMRS allocation based on the following equation.

<Equation 2>

if( Metric_SNR < SNR_TH1) Num_DMRS_SNR = 4;

else if( Metric_ SNR < SNR _TH2) Num_DMRS_SNR = 3;

else if( Metric_ SNR < SNR _TH3) Num_DMRS_SNR = 2;

else Num_DMRS_SNR = 1;

Here, Metric_SNR denotes a measured SNR value, and SNR_TH1, SNR_TH2, and SNR_TH3 denote a first threshold value, a second threshold value, and a third threshold value, respectively. Num_DMRS_SNR indicates the number of DMRS symbols in a slot.

According to an embodiment, the first threshold value, the second threshold value, and the third threshold value may be predefined values. According to another embodiment, the first threshold, the second threshold, and the third threshold are the types of uplink transmission (eg, PUSCH, PUCCH, Msg A of 2-step RACH, CP-OFDM, or DFT-S OFDM). recognition, etc.) may be determined. According to another embodiment, the first threshold value, the second threshold value, and the third threshold value may be determined based on a channel state. For example, a first threshold value, a second threshold value, and a third threshold value may be determined based on the channel state information reported by the terminal. In addition, as an example, the first threshold, the second threshold, and the third threshold are beam information (eg, SS/PBCH index) associated with a cell, BWP, or uplink transmission in which the base station currently serves the terminal. , CSI-RS resource, SRS resource) may be determined based on at least one.

According to an embodiment, the DMRS allocation block 530 may allocate one or more DMRS symbols based on both the SNR and the time variation of the fading channel. For example, the DMRS allocation block 530 may perform DMRS allocation based on both Equations 1 and 2 above.

<Equation 3>

if( Metric_DOP < DOP_TH1) Num_DMRS_DOP = 1;

else if( Metric_DOP < DOP_TH2) Num_DMRS_DOP = 2;

else if( Metric_DOP < DOP_TH3) Num_DMRS_DOP = 3;

else Num_DMRS_DOP = 4;

if( Metric_SNR < SNR_TH1) Num_DMRS_SNR = 4;

else if( Metric_ SNR < SNR _TH2) Num_DMRS_SNR = 3;

else if( Metric_ SNR < SNR _TH3) Num_DMRS_SNR = 2;

else Num_DMRS_SNR = 1;

Num_DMRS = max(Num_DMRS_DOP, Num_DMRS_SNR)

Here, Num_DMRS indicates the finally determined number of DMRS symbols in the slot. In Equation 3, the number of DMRS symbols to be allocated is determined through the max function, but the embodiment of the present disclosure is not limited thereto. In addition to the max function, at least one of various functions for specifying a result value, such as a min function, an average function, and a weight function, may be used for DMRS symbol allocation. In addition, various methods may be used for a calculation function for finally determining the number of DMRS symbols based on each metric. The calculation function may be a predefined function, or a type of uplink transmission or an uplink channel state may be used.

The base station may determine the number of DMRS symbols allocated based on the channel estimation result. Although DMRS is referred to as a signal for channel estimation in the present disclosure, other signals may be used as a reference signal for channel estimation. According to an embodiment, a sounding reference signal (SRS) transmitted from the terminal to the base station may be used for channel estimation. The base station may perform channel estimation based on the SRS received from the terminal. According to an embodiment, channel state information (CSI) reported by the terminal to the base station may be used for channel estimation. If a time division duplex (TDD) communication system is assumed, channel reciprocity is satisfied. Based on the CSI-RS transmitted by the base station to the terminal, the terminal may generate CSI. CSI is channel information for a downlink channel, but since channel reciprocity is satisfied, CSI may be used to obtain uplink channel information. The CSI may include at least one of a rank indicator (RI), a precoding matrix indicator (PMI), and a channel quality indicator (CQI). For example, the CQI may be used to determine a channel quality for determining a strong electric field or a weak electric field.

In FIG. 5 , SNR is used as a metric for determining whether a channel is a fast fading channel, and a metric for determining whether a channel change amount in the time domain and a weak electric field are used. However, the metric shown in FIG. 5 is only an example, and it goes without saying that other parameters may be used as a metric for determining a fading channel or an electric field. According to an embodiment, at least one of Doppler spread, frequency spread, delay spread, movement speed, and the number of beam changes per unit time may be used instead of the amount of channel change in the time domain. have. As an example, the base station may allocate more DMRS symbols because it time-varying rapidly as the size of the Doppler spread increases. According to an embodiment, instead of SNR, reference signal received power (RSRP), reference signal received quality (RSRQ), beam reference signal received power (BRSRP), received signal strength indicator (RSRI), signal to interference and noise ratio (SINR) , at least one of carrier to interference and noise ratio (CINR), error vector magnitude (EVM), bit error rate (BER), and block error rate (BLER) may be used. In addition to the above-described examples, of course, other terms having an equivalent technical meaning or other metrics indicating channel quality may be used. On the other hand, high SNR means high channel quality and low SNR means low channel quality. In Equation 2 or 3, the inequality relationship in Equation 2 or 3 may be reversed when using a metric related to an error rate.

As a DMRS allocation scheme related to coverage enhancement that is being discussed as a study item for Release 17, a greater number of DMRSs than the maximum of four DMRSs defined in the current standard may be allocated. The higher the number of DMRSs, the higher the demodulation performance in the weak field. Because high demodulation performance means a high transmission probability of data, coverage is improved. Hereinafter, in order to improve cell coverage, a method for operating a larger number of DMRSs will be described.

6 illustrates an example of signaling between a base station and a terminal for DMRS symbol allocation according to an embodiment of the present disclosure. The base station illustrates the base station 110 of FIG. 1 , and the terminal illustrates the terminal 120 of FIG. 1 .

Referring to FIG. 6 , in step 601 , the base station may transmit DMRS configuration information to the terminal. The terminal may receive DMRS configuration information from the base station. According to an embodiment, the DMRS configuration information may be transmitted through radio resource control (RRC) signaling. The DMRS configuration information may include information for configuring uplink DMRSs for an uplink signal (eg, PUSCH). The DMRS configuration information may include at least one of a mapping type, an additional DMRS location, whether a phase tracking reference signal (PTRS), a maximum symbol length for front loaded, and information indicating whether or not transform precoding is performed. According to an embodiment, the DMRS configuration information may include indication information for indicating whether to support the coverage extension DMRS mode according to embodiments of the present disclosure. When the corresponding indication information is enabled, the UE can know that, according to embodiments to be described later, a setting for operation of a DMRS symbol greater than the four DMRS symbols of the existing standard is applied to the UE. Although not shown in FIG. 6 , the terminal may transmit capability information indicating support of the coverage extension DMRS mode to the base station.

The DMRS configuration information may include DMRS allocation information. DMRS allocation information may indicate a position to which DMRS symbols are allocated and the number of DMRS symbols. In some embodiments, the DMRS configuration information may include information about the number of DMRSs. According to an embodiment, the DMRS symbol positions may be predefined for each number of DMRSs to be spread to an appropriate position among 14 symbols. Also, according to an embodiment, the DMRS symbol position may be determined according to a pattern predefined for each DMRS number. In the future, even if DMRS symbols partially configured by DCI are not used, DMRS symbol positions available as candidates may be indicated in advance.

In some embodiments, the DMRS configuration information may include a bitmap. The size of the bitmap may be 14. The DMRS configuration information may indicate whether a DMRS symbol is allocated to each symbol through a bitmap. According to an embodiment, when the PUSCH mapping type is B, the UE may ignore the bitmap region to which data is allocated. Alternatively, according to another embodiment, when the PUSCH mapping type is B, the size of the bitmap may be reduced based on the area to which the actual PUSCH is allocated.

In some embodiments, the DMRS configuration information may include information on a DMRS symbol interval (or density). The information on the DMRS symbol interval may indicate the interval between two DMRS symbols among 14 symbols. As the DMRS symbol interval increases, the number of DMRS symbols allocated for a predetermined period decreases. The better the channel condition, the less interpolation is required, so the DMRS symbol interval can be increased. Meanwhile, the DMRS configuration information may not indicate the DMRS symbol interval as an explicit value, but may implicitly indicate the DMRS symbol interval through association with an IE (information element) for uplink resource allocation of the UE. For example, when uplink resources are allocated through RRC as in Configured Grant Type 1, a DMRS symbol interval may be indicated based on a parameter of Configured Grant configuration information.

In some embodiments, the DMRS configuration information may include one or more threshold values. Here, the threshold value may be a threshold value for determining the range of TBS when determining the DMRS symbol interval according to TBS in Equation 4 to be described later. For example, the DMRS configuration information may include three threshold values. A DMRS symbol interval may be specified through comparison between a threshold value indicated by DMRS configuration information and TBS of DCI, which will be described later. Meanwhile, since TBS is one parameter for indicating a weak electric field or a strong electric field among DCI parameters, the threshold value included in the DMRS configuration information may be a threshold value defined for another parameter instead of the TBS. For example, the DMRS configuration information may include a threshold for the MCS level. This is because the lower the MCS level, the worse the channel state, so a larger number of DMRS symbols may be required. On the other hand, the conditional expression may be configured to increase the number of DMRS symbols required to more accurately perform channel estimation as the MCS level is higher.

In step 603, the base station may transmit DCI to the terminal. DCI may include uplink resource allocation. As an example, DCI may be configured according to one of DCI format 0_0, DCI format 0_1, or DCI format 0_2. The terminal may receive DCI from the base station. The UE may identify uplink resource allocation from DCI. At least one parameter indicating uplink resource allocation may include a frequency domain resource assignment, a time domain resource assignment, a modulation and coding scheme (MCS), a BWP indicator, and an antenna port. can The UE may identify the position of the uplink DMRS symbol or the number of uplink DMRS symbols based on at least one parameter indicating uplink resource allocation. According to an embodiment, the UE may identify an interval between DMRS symbols in a slot. According to an embodiment, the UE may identify the positions of DMRS symbols based on uplink resource allocation. According to an embodiment, the UE may identify the DMRS symbol interval based on the TBS size indicated by the DCI. The TBS size may be determined based on at least one parameter indicating the uplink resource allocation.

A slot may include 14 symbols. At least some of the 14 symbols may be used for DMRS. For coverage enhancement, the base station may allocate a larger number of DMRS symbols than the four DMRS symbols indicated by RRC of the existing NR standard. According to an embodiment, the base station may indicate the DMRS that is additionally defined through DCI. As in the existing standard, additional DMRS symbols in addition to the four DMRSs indicated by RRC signaling may be allocated through DCI. According to another embodiment, in order to dynamically indicate the number of DMRS symbols in a rapidly changing channel, the base station may allocate DMRS symbols using DCI.

Instead of using the existing DCI, a new DCI may be used. A DCI format for a new field may be newly defined. In some embodiments, DCI may include information on DMRS symbol interval (or density). As an example, an index indicating a specific DMRS symbol interval among DMRS symbol intervals configured in RRC may be delivered to the UE by DCI. In this case, a DCI format for transferring a new index may be newly defined. In some other embodiments, the DCI may include a bitmap. A bitmap for indicating whether to use a DMRS symbol for each symbol in a slot may be defined. Depending on whether each bit is 0 or 1, whether the corresponding symbol is a DMRS symbol may be indicated.

In step 605, the UE may identify a DMRS symbol. The UE may identify at least one DMRS symbol allocated to the UE based on at least one of the DMRS configuration information of step 601 and the DCI of step 603. Although RRC and DCI have been described as examples in FIG. 6 , it may also be understood as an embodiment of the present disclosure that some symbols are activated through MAC CE and whether actual transmission is indicated through DCI.

According to an embodiment, the UE may identify the DMRS symbol interval. DMRS symbol interval is related to good or bad channel condition. A good channel state may mean a high channel quality. When the channel quality is high, a larger number of bits may be mapped to one symbol (or resource element (RE)). If the channel condition is good, a strong electric field is likely and a requirement for interpolation is low, so a relatively small number of DMRSs may be required. As the channel condition is good, the DMRS symbol interval may be increased. In the present disclosure, the DMRS symbol interval is described, but the interval may be replaced with other technical terms having the same or similar meaning. As an example, the DMRS symbol interval may be referred to as a DMRS density. The base station may transmit an index indicating one density among a plurality of predefined densities to the terminal. The UE may check the DMRS density in the slot from the corresponding index and identify the DMRS location in the slot. Also, as an example, the DMRS symbol interval may be referred to as a DMRS pattern. The base station may notify the terminal of a specific predefined pattern among a plurality of predefined patterns. The UE may identify the DMRS position in the slot according to the indicated pattern number.

According to an embodiment, the UE may identify the DMRS symbol allocation position within the slot. According to an embodiment, the UE may identify the number of DMRS symbols in the slot. The number of DMRS symbols may be an integer of 14 or less. The UE may identify the number of DMRS symbols based on the symbol interval. For example, when the symbol interval is 0, a DMRS symbol may be mapped to each symbol of a slot. In this case, the uplink data may be frequency division multiplexed (FDM) with the DMRS symbol. Also, for example, when the symbol interval is 1, one data symbol may be located between a DMRS symbol and a DMRS symbol in the time domain.

According to an embodiment, the UE may identify whether DMRS symbols and data are FDM. When the DMRS symbol interval is narrowed, data allocation within a predetermined slot may not be easy. Thus, FDM can be used. The UE may identify whether FDM is activated according to the DMRS symbol interval.

In step 607, the terminal may perform uplink transmission. The terminal may transmit an uplink signal to the base station. Uplink transmission may include at least one of PUSCH transmission, PUCCH transmission, or PUSCH transmission of Msg A in 2-step RACH. Uplink transmission may include uplink DMRS transmission for demodulation of PUSCH or PUCCH. The UE may transmit the DMRS symbol according to the allocation position of the DMRS symbol identified in step 605 . The base station may receive an uplink signal from the terminal. The base station may receive a DMRS symbol from the terminal. The base station may estimate the channel through the DMRS symbol. The base station may acquire uplink data (eg, UL-SCH data of PUSCH) or uplink control information (UCI) based on the estimated channel result.

Although several embodiments have been described in FIG. 6 , each of the embodiments may be used in combination with each other. For example, two embodiments of DMRS configuration information may be transmitted by one RRC signaling. Also, for example, the embodiment of DMRS configuration information and the embodiment of DCI are combined with each other, and the two embodiments may be used to deliver specific information (eg, DMRS symbol interval, DMRS symbol allocation position) to the UE. . In addition, information according to embodiments of the DMRS configuration information mentioned with reference to FIG. 6 is indicated through DCI may also be understood as an embodiment of the present disclosure. In other words, the embodiments mentioned through FIG. 6 may not only be used in combination within the corresponding step, but also be used in combination with other steps may be included in the scope of the present disclosure.

Omitting some steps of the procedures shown in FIG. 6 may also be included in the scope of the present disclosure. For example, the uplink DMRS symbol allocation indicated only by the DCI in step 603 may also be understood as an embodiment of the present disclosure.

7 illustrates an example of DMRS allocation according to embodiments of the present disclosure. In FIG. 7, an example in which the symbol interval is indicated by DCI is described. A mode indicator ('Coverage_Enhancement_DMRS_Mode') may be defined. According to an embodiment, the DCI may include a mode indicator. When the mode indicator is OFF, DMRS may be transmitted as in the current standard. DMRS transmission according to the current standard (Release 16 or less) may include a configuration of up to four DMRS symbols through RRC and transmission of DMRS symbols in a valid region according to an allocation type of PUSCH among the configured symbols. Meanwhile, DMRS transmission according to the current standard (Release 16 or less) may not include 5 or more DMRS transmissions or DCI-based transmission according to a defined symbol interval. DMRS transmission according to the current standard (Release 16 or less) may not include 5 or more DMRS transmissions or DCI-based transmission according to a defined symbol interval. On the other hand, according to an embodiment, when the mode indicator is ON, the UE may identify a DMRS interval based on assignment information of DCI, and may perform DMRS transmission at a DMRS symbol assignment position according to the DMRS interval. Hereinafter, an example of DMRS allocation according to the DMRS interval is described with reference to FIG. 7 .

Referring to FIG. 7 , when the DMRS symbol interval is 0, the first slot structure 701 indicates symbols within the slot. A DMRS symbol may be located in every symbol. At this time, although not shown in FIG. 7, the PUSCH data symbol for uplink transmission may be multiplexed with the DMRS symbol in the frequency domain. In a weak field channel such as a cell boundary, a larger number of DMRS symbols may be allocated to improve communication performance. In particular, when a requirement for interpolation increases, communication performance can be improved by reducing the interval between symbols.

The second slot structure 703 indicates symbols within a slot when the DMRS symbol interval is 1. A DMRS symbol may be located in every two symbols. At this time, although not shown in FIG. 7 , in some embodiments, a PUSCH data symbol for uplink transmission may be multiplexed with a DMRS symbol in the frequency domain. According to an embodiment, when the PUSCH mapping type is B, the position of the start DMRS symbol may be separately indicated or determined, or may be defined as a fixed position (eg, the start of the PUSCH). The third slot structure 705 indicates the symbols in the slot when the DMRS symbol interval is 2. A DMRS symbol may be located every three symbols in the slot. At this time, although not shown in FIG. 7 , in some embodiments, a PUSCH data symbol for uplink transmission may be multiplexed with a DMRS symbol in the frequency domain. According to an embodiment, when the PUSCH mapping type is B, the position of the start DMRS symbol may be separately indicated or determined, or may be defined as a fixed position (eg, the start of the PUSCH). The fourth slot structure 707 indicates symbols within the slot when the DMRS symbol interval is 3 . A DMRS symbol may be located in every 4 symbols in the slot. At this time, although not shown in FIG. 7 , in some embodiments, a PUSCH data symbol for uplink transmission may be multiplexed with a DMRS symbol in the frequency domain. According to an embodiment, when the PUSCH mapping type is B, the position of the start DMRS symbol may be separately indicated or determined, or may be defined as a fixed position (eg, the start of the PUSCH).

According to embodiments of the present disclosure, the terminal may determine the TBS allocated for uplink transmission. According to an embodiment, the UE may determine the TBS based on DCI. For example, the UE may determine the TBS based on the number of resource blocks indicated through DCI and the modulation order. A large TBS means that a large number of bits are transmitted within a limited resource. A large TBS may indicate that the channel state is relatively good. If TBS is small, it means that the current channel is a weak electric field. By transmitting a larger number of DMRS symbols, the UE can improve communication performance. By improving the channel estimation performance in the weak field, the reception performance may be increased to improve cell coverage. Since the number of DMRS symbols is not limited to four, a DMRS symbol interval may be used as a method for indicating the number or position of DMRS symbols. For example, the DMRS symbol interval may be determined based on the following equation.

<Equation 4>

if( TBS_Size < TBS_TH1) DMRS_Interval = 0;

else if( TBS_Size < TBS_TH2) DMRS_Interval = 1;

else if( TBS_Size < TBS_TH3) DMRS_Interval = 2;

else DMRS_Interval = 3;

TBS_Size means a transport block size (TBS) according to DCI, and DMRS_Interval means a symbol interval between DMRS symbols in a slot.

8 illustrates an example of frequency division multiplexing (FDM) according to embodiments of the present disclosure. DMRS may not be mapped over all frequency domains within a slot, but may be mapped over some frequency domains. In other words, the UL-SCH data symbol and the DMRS symbol may be FMD.

Referring to FIG. 8 , the resource mapping 800 shows an example in which data and DMRS are mapped. One RB may include 12 subcarriers. An uplink DMRS symbol may be mapped for every two subcarriers. A data symbol may be mapped to the blank area. That is, the base station may map the DMRS symbol and the data symbol in the FDM scheme.

In each of the embodiments described above with reference to FIGS. 1 to 7 , the FDM may be additionally operated. According to an embodiment, the base station may enable FDM. When FDM is enabled, the base station can allocate data symbols and RS symbols in the same symbol interval (meaning a symbol interval in the time domain) in units of subcarriers. Although not shown in FIG. 8 , when FDM is disabled according to the configuration of the base station, the data symbol may not be mapped to the frequency domain within the symbol to which the DMRS symbol is allocated. For example, when DMRS_interval is 0 as in the first slot structure 701 of FIG. 7 , the uplink data symbols may be required to be mapped through FDM due to the allocation of DMRS symbols. As the number of DMRS symbols increases, that is, as the DMRS interval decreases, the actual benefit of the FDM function may increase.

9 illustrates a relationship between channel quality and reception probability according to embodiments of the present disclosure. If the number of DMRS symbols increases, noise in channel estimation may be reduced. For example, when the number of symbols of the DMRS is doubled, a noise reduction effect increases by 3 dB during channel estimation. If the number of DMRS symbols allocated is increased, the coverage is also increased as well as the performance improvement of the channel estimation. A specific example is described with reference to FIG. 9 . In FIG. 9 , signal to noise ratio (SNR) is used as an example of channel quality, but the principle described in FIG. 9 uses other channel quality metrics (eg, reference signal received power (RSRP), reference signal received quality (RSRQ), RSRI). (received signal strength indicator), SINR (signal to interference and noise ratio), CINR (carrier to interference and noise ratio) can also be applied, of course.

Referring to FIG. 9 , a graph 900 shows a relationship between a reception SNR and a reception probability. -16dB, 15dB, -14dB, and -13dB represent the transmission SNR, respectively. The horizontal axis represents the reception SNR, and the vertical axis represents the reception probability. As a retransmission algorithm to improve communication performance, a hybrid automatic repeat request (HARQ) method in which forward error control (FEC) and automatic repeat request (ARQ) are combined may be used. In the HARQ method, a receiving end (eg, a base station) combines and decodes retransmission data received in the same HARQ process with data in a soft buffer (data received in the corresponding HARQ process), thereby obtaining a combined gain. have. On the other hand, a signal with a low SNR is subjected to DTX determination. That is, the base station determines that a signal having a low SNR, that is, a signal having a signal strength equal to or less than a threshold value, is not transmitted. The base station excludes the LLR of the corresponding signal. As the LLR of the corresponding signal is excluded, the base station cannot obtain a gain for soft combining in the HARQ process. According to an embodiment, when the number of DMRS symbols increases, the threshold for DTX determination is lowered. For example, when the DTX threshold is set to -9 dB, the LLR of the slot measured to be less than -9 dB is excluded from the HARQ combining process. As it is excluded from HARQ combining, the HARQ process does not work smoothly. On the other hand, if the number of DMRS symbols is increased, channel estimation performance is improved in a weak electric field situation. Therefore, since more samples have a relatively high SNR, it becomes possible to set the DTX threshold lower. As a result, the probability of excluding valid LLRs decreases, and overall performance may be improved.

10 illustrates a functional configuration of a base station in a wireless communication system according to various embodiments of the present disclosure. Terms such as '... unit' and '... group' used below mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. have.

Referring to FIG. 10 , the base station includes a communication unit 1001 , a backhaul communication unit 1003 , a storage unit 1005 , and a control unit 1007 .

The communication unit 1001 performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit 1001 performs a function of converting between a baseband signal and a bit stream according to a physical layer standard of a system. For example, when transmitting data, the communication unit 1001 generates complex symbols by encoding and modulating the transmitted bit stream. In addition, when receiving data, the communication unit 1001 restores the received bit stream by demodulating and decoding the baseband signal. The communication unit 1001 may be configured to perform at least one of the operations of the transmitting end and the operations of the receiving end described with reference to FIGS. 1 to 6 . According to an embodiment, the communication unit 1001 may transmit the allocation of the uplink DMRS to the terminal. According to an embodiment, the communication unit 1001 may be configured to receive an uplink DMRS from the terminal.

The communication unit 1001 up-converts the baseband signal into a radio frequency (RF) band signal, transmits the signal through the antenna, and downconverts the RF band signal received through the antenna into a baseband signal. To this end, the communication unit 1001 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. Also, the communication unit 1001 may include a plurality of transmission/reception paths. Furthermore, the communication unit 1001 may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit 1001 may be composed of a digital unit and an analog unit, and the analog unit is divided into a plurality of sub-units according to operating power, operating frequency, etc. can be configured. According to an embodiment, the communication unit 1001 may include a beam forming unit, that is, a beamforming unit. For example, the communication unit 1001 may include a massive MIMO unit (MMU) for beamforming.

The communication unit 1001 may transmit and receive signals. To this end, the communication unit 1001 may include at least one transceiver. For example, the communication unit 1001 may transmit a synchronization signal, a reference signal, system information, a message, control information, or data. Also, the communication unit 1001 may perform beamforming. The communication unit 1001 may apply a beamforming weight to a signal to be transmitted/received in order to give a direction according to the setting of the control unit 1007 to the signal. According to an embodiment, the communication unit 1001 may generate a baseband signal according to a scheduling result and a transmission power calculation result. In addition, the RF unit in the communication unit 1001 may transmit the generated signal through the antenna.

The communication unit 1001 transmits and receives signals as described above. Accordingly, all or part of the communication unit 1001 may be referred to as a 'transmitter', 'receiver', or 'transceiver'. In addition, in the following description, transmission and reception performed through a wireless channel are used in the meaning including the processing as described above by the communication unit 1001 being performed.

The backhaul communication unit 1003 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 1003 converts the bit string transmitted from the base station to another node, for example, another access node, another base station, upper node, core network, etc. into a physical signal, and converts the physical signal received from the other node. Convert to bit string.

The storage unit 1005 stores data such as a basic program, an application program, and setting information for the operation of the base station. The storage unit 1005 may include a memory. The storage unit 1005 may be configured as a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. Then, the storage unit 1005 provides the stored data according to the request of the control unit 1007 .

The controller 1007 controls overall operations of the base station. For example, the control unit 1007 transmits and receives signals through the communication unit 1001 or through the backhaul communication unit 1003 . In addition, the control unit 1007 writes and reads data in the storage unit 1005 . In addition, the control unit 1007 may perform functions of a protocol stack required by the communication standard. To this end, the controller 1007 may include at least one processor. According to various embodiments, the controller 1007 may control the base station to perform operations according to the various embodiments described above. According to an embodiment, the controller 1007 may estimate an uplink channel. The controller 1007 may generate uplink DMRS allocation information based on an estimation result of the uplink channel.

The configuration of the base station 110 shown in FIG. 10 is only an example of the base station, and the example of the base station performing various embodiments of the present disclosure from the configuration shown in FIG. 10 is not limited. That is, according to various embodiments, some configurations may be added, deleted, or changed.

Although the base station is described as one entity in FIG. 10, as described above, the present disclosure is not limited thereto. The base station according to various embodiments of the present disclosure may be implemented to form an access network having a distributed deployment as well as an integrated deployment (eg, an eNB of LTE). As exemplified to describe the embodiments of FIGS. 1 to 6 , the base station is divided into a central unit (CU) and a digital unit (DU), and the CU is an upper layer function (eg, packet data (PDCP)). Convergence protocol (RRC)) DU may be implemented to perform lower layers (eg, medium access control (MAC), physical (PHY)).

In this way, the base station having the separate arrangement may further include a configuration for fronthaul interface communication. According to an embodiment, the base station, as a DU, may perform functions for transmitting and receiving signals in a wired communication environment. The DU may include a wired interface for controlling a direct connection between the device and the device via a transmission medium (eg, copper wire, optical fiber). For example, the DU may transmit an electrical signal to another device through a copper wire or perform conversion between an electrical signal and an optical signal. A DU may be connected to a CU in a distributed deployment. However, this description is not to be construed as excluding a scenario in which the DU is connected to the CU through a wireless network. In addition, the DU may be additionally connected to a radio unit (RU). However, this description is not to be construed as excluding a radio environment consisting only of CUs and DUs.

11 illustrates a functional configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure. Terms such as '... unit' and '... group' used below mean a unit that processes at least one function or operation, which may be implemented as hardware or software, or a combination of hardware and software. have.

Referring to FIG. 11 , the terminal includes a communication unit 1101 , a storage unit 1103 , and a control unit 1105 .

The communication unit 1101 performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit 1101 performs a function of converting between a baseband signal and a bit stream according to a physical layer standard of a system. For example, when transmitting data, the communication unit 1101 generates complex symbols by encoding and modulating the transmitted bit stream. In addition, when receiving data, the communication unit 1101 restores the received bit stream by demodulating and decoding the baseband signal. The communication unit 1101 upconverts the baseband signal into an RF band signal, transmits the signal through the antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the communication unit 1101 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like.

Also, the communication unit 1101 may include a plurality of transmission/reception paths. Furthermore, the communication unit 1101 may include an antenna unit. The communication unit 1101 may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit 1101 may include a digital circuit and an analog circuit (eg, a radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented as one package. In addition, the communication unit 1101 may include a plurality of RF chains. The communication unit 1101 may perform beamforming. The communication unit 1101 may apply a beamforming weight to the signal to give a signal to be transmitted/received with directionality according to the setting of the control unit 1105 .

Also, the communication unit 1101 may transmit/receive a signal. To this end, the communication unit 1101 may include at least one transceiver. The communication unit 1101 may receive a downlink signal. The downlink signal includes a synchronization signal (SS), a reference signal (RS) (eg, cell-specific reference signal (CRS), demodulation (DM)-RS), system information (eg, MIB, SIB, It may include remaining system information (RMSI), other system information (OSI), a configuration message, control information, or downlink data. Also, the communication unit 1101 may transmit an uplink signal. The uplink signal includes uplink control information (UCI), a random access-related signal (eg, a random access preamble (RAP) (or Msg1 (message 1)), Msg3 (message 3)), a reference It may include a signal (eg, a sounding reference signal (SRS), DM-RS), or a buffer status report (BSR). For example, the uplink control information may include at least one of a scheduling request (SR), ACK/NACK information of a hybrid acknowledge (HARQ) procedure, or channel state information (CSI). According to an embodiment, the communication unit 1101 may receive uplink DMRS allocation information. Also, according to an embodiment, the communication unit 1101 may transmit an uplink DMRS symbol.

Specifically, the communication unit 1101 may include an RF processing unit and a baseband processing unit. The RF processing unit performs a function for transmitting and receiving a signal through a wireless channel, such as band conversion and amplification of the signal. That is, the RF processor up-converts the baseband signal provided from the baseband processor into an RF band signal, transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital to analog converter (DAC), an analog to digital converter (ADC), and the like. The terminal may include one or more antennas. The RF processing unit may include multiple RF chains. Furthermore, the RF processing unit may perform beamforming. For the beamforming, the RF processing unit may adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements.

The baseband processing unit performs a conversion function between the baseband signal and the bit stream according to the physical layer standard of the system. For example, when transmitting data, the baseband processing unit generates complex symbols by encoding and modulating the transmitted bit stream. In addition, when receiving data, the baseband processing unit restores the received bit stream by demodulating and decoding the baseband signal provided from the RF processing unit. For example, in the case of orthogonal frequency division multiplexing (OFDM), when data is transmitted, the baseband processing unit generates complex symbols by encoding and modulating a transmission bit stream, maps the complex symbols to subcarriers, and then IFFT OFDM symbols are constructed through an inverse fast Fourier transform operation and cyclic prefix (CP) insertion. In addition, upon data reception, the baseband processor divides the baseband signal provided from the RF processor into OFDM symbol units, restores signals mapped to subcarriers through a fast Fourier transform (FFT) operation, and then demodulates and decodes them. recovers the received bit string through

The communication unit 1101 transmits and receives signals as described above. Accordingly, all or part of the communication unit 1101 may be referred to as a transmitter, a receiver, or a transceiver. Furthermore, the communication unit 1101 may include a plurality of communication modules to support a plurality of different wireless access technologies. Also, the communication unit 1101 may include different communication modules to process signals of different frequency bands. For example, the different radio access technologies may include a wireless LAN (eg, IEEE 802.1x), a cellular network (eg, LTE, NR), and the like. In addition, the different frequency bands may include a super high frequency (SHF) (eg, 2.5 GHz, 5 GHz) band and a millimeter wave (eg, 60 GHz) band. In addition, the communication unit 1101 performs the same method of radio on different frequency bands (eg, licensed assisted access (LAA) or unlicensed band for NR-U, citizens broadband radio service (CBRS) (eg, 3.5 GHz))). Connection technology may also be used.

The storage unit 1103 stores data such as a basic program, an application program, and setting information for the operation of the terminal. The storage unit 1103 may be configured as a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. The storage unit 1103 stores data such as a basic program, an application program, and setting information for the operation of the terminal.

The controller 1105 controls overall operations of the terminal. For example, the control unit 1105 transmits and receives signals through the communication unit 1101 . In addition, the control unit 1105 writes and reads data in the storage unit 1103 . In addition, the control unit 1105 may perform the functions of the protocol stack required by the communication standard. To this end, the controller 1105 may include at least one processor. The controller 1105 may include at least one processor or microprocessor, or may be a part of the processor. In addition, a part of the communication unit 1101 and the control unit 1105 may be referred to as a CP. The control unit 1105 may include various modules for performing communication. According to various embodiments, the controller 1105 may control the terminal to perform operations according to various embodiments to be described later.

The controller 1105 controls overall operations of the terminal. For example, the control unit 1105 transmits and receives signals through the communication unit 1101 . In addition, the control unit 1105 writes and reads data in the storage unit 1103 . To this end, the controller 1105 may include at least one processor. For example, the controller 1105 may include a communication processor (CP) that controls for communication and an application processor (AP) that controls an upper layer such as an application program. According to various embodiments of the present disclosure, the controller 1105 may be configured to perform a function of dynamic spectrum sharing. According to an embodiment, the control unit 1105 may be configured so that the terminal 120 dynamically uses a cell of LTE and a cell of NR in an EN-DC environment. Also, according to an embodiment, the controller 1105 may be configured so that the terminal 120 dynamically uses cells by two nodes in an EN-DC environment as well as an MR-DC environment. In addition, the controller 1105 may control the terminal to perform operations according to the various embodiments described above. According to an embodiment, the controller 1105 may identify uplink DMRS allocation information received from the base station. According to an embodiment, the controller 1105 may identify the number of uplink DMRS symbols. According to an embodiment, the controller 1105 may identify an interval between uplink DMRS symbols. According to an embodiment, the controller 1105 may identify positions of uplink DMRS symbols within a slot.

Methods according to the embodiments described in the claims or specifications of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium are configured to be executable by one or more processors in an electronic device (device). One or more programs include instructions for causing an electronic device to execute methods according to embodiments described in a claim or specification of the present disclosure.

Such programs (software modules, software) include random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable ROM (electrically erasable programmable read only memory, EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), or other It may be stored in an optical storage device or a magnetic cassette. Alternatively, it may be stored in a memory composed of a combination of some or all thereof. In addition, each configuration memory may be included in plurality.

In addition, the program is transmitted through a communication network consisting of a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. It may be stored on an attachable storage device that can be accessed. Such a storage device may be connected to a device implementing an embodiment of the present disclosure through an external port. In addition, a separate storage device on the communication network may be connected to the device implementing the embodiment of the present disclosure.

In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed in the singular or plural according to the specific embodiments presented. However, the singular or plural expression is appropriately selected for the context presented for convenience of description, and the present disclosure is not limited to the singular or plural component, and even if the component is expressed in plural, it is composed of a singular or singular. Even an expressed component may be composed of a plurality of components.

Meanwhile, although specific embodiments have been described in the detailed description of the present disclosure, various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments and should be defined by the claims described below as well as the claims and equivalents.

Claims (26)

In a wireless communication system, a method performed by a terminal,
A process of receiving, from a base station, control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot;
The process of identifying an uplink DMRS allocation based on the control information;
Transmitting one or more uplink DMRS symbols based on the uplink DMRS assignment;
The uplink DMRS allocation includes the number of the one or more uplink DMRS symbols and a location resource location of each of the one or more uplink DMRS symbols.
The method according to claim 1,
The control information includes downlink control information (DCI),
The symbol interval is determined based on a transport block size (TBS) obtained by the DCI.
3. The method according to claim 2,
If the TBS is less than the threshold, the symbol interval is a first value,
If the TBS is greater than or equal to the threshold, the symbol interval is a second value,
The second value is greater than the first value.
The method according to claim 1,
The control information includes downlink control information (DCI),
The symbol interval is obtained based on an MCS index of a modulation and coding scheme (MCS) field of the DCI.
The method according to claim 1, wherein when the symbol interval is a specific value, the number of the one or more uplink DMRS symbols is greater than 4.
In a wireless communication system, a method performed by a base station comprising:
A process of transmitting control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot to a terminal;
Receiving one or more uplink DMRS symbols from the terminal,
The number of the one or more uplink DMRS symbols and the location resource position of each of the one or more uplink DMRS symbols are allocated based on the symbol interval.
7. The method of claim 6,
The control information includes downlink control information (DCI),
The symbol interval is determined based on a transport block size (TBS) obtained by the DCI.
8. The method of claim 7,
If the TBS is less than the threshold, the symbol interval is a first value,
If the TBS is greater than or equal to the threshold, the symbol interval is a second value,
The second value is greater than the first value.
7. The method of claim 6,
The control information includes downlink control information (DCI),
The symbol interval is obtained based on an MCS index of a modulation and coding scheme (MCS) field of the DCI.
The method of claim 6, wherein when the symbol interval is a specific value, the number of the one or more uplink DMRS symbols is greater than 4.
In a wireless communication system, in a terminal,
at least one transceiver;
at least one processor;
the at least one processor,
Receive control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot from a base station,
Identifies an uplink DMRS allocation based on the control information,
configured to transmit one or more uplink DMRS symbols based on the uplink DMRS assignment;
The uplink DMRS allocation includes the number of the one or more uplink DMRS symbols and a location resource location of each of the one or more uplink DMRS symbols.
12. The method of claim 11,
The control information includes downlink control information (DCI),
The symbol interval is determined based on a transport block size (TBS) obtained by the DCI.
13. The method of claim 12,
If the TBS is less than the threshold, the symbol interval is a first value,
If the TBS is greater than or equal to the threshold, the symbol interval is a second value,
The second value is greater than the first value.
12. The method of claim 11,
The control information includes downlink control information (DCI),
The symbol interval is obtained based on an MCS index of a modulation and coding scheme (MCS) field of the DCI.
The terminal of claim 11, wherein when the symbol interval is a specific value, the number of the one or more uplink DMRS symbols is greater than 4.
In a wireless communication system, in a base station,
at least one transceiver;
at least one processor;
the at least one processor,
Transmitting control information related to a symbol interval between uplink demodulation reference signal (DMRS) symbols in a slot to the terminal,
configured to receive one or more uplink DMRS symbols from the terminal;
The number of the one or more uplink DMRS symbols and the location resource position of each of the one or more uplink DMRS symbols are allocated based on the symbol interval.
17. The method of claim 16,
The control information includes downlink control information (DCI),
The symbol interval is determined based on a transport block size (TBS) obtained by the DCI.
18. The method of claim 17,
If the TBS is less than the threshold, the symbol interval is a first value,
If the TBS is greater than or equal to the threshold, the symbol interval is a second value,
The second value is greater than the first value.
17. The method of claim 16,
The control information includes downlink control information (DCI),
The symbol interval is obtained based on an MCS index of a modulation and coding scheme (MCS) field of the DCI.
The base station according to claim 6, wherein when the symbol interval is a specific value, the number of the one or more uplink DMRS symbols is greater than 4.
In a wireless communication system, a method performed by a base station comprising:
The process of estimating an uplink channel;
obtaining a channel variation metric and a signal strength metric based on the estimation result of the uplink channel;
determining the number of uplink demodulation reference signal (DMRS) symbols based on the channel variation metric and the signal strength metric;
and transmitting DMRS allocation information according to the number of uplink DMRS symbols to the terminal.
The method of claim 21, wherein the determining of the number of DMRS symbols comprises:
determining whether the channel variation metric is greater than a specified channel variation threshold;
determining a first value as the number of DMRS symbols when the channel variation metric is greater than the channel variation threshold;
determining a second value as the number of DMRS symbols when the channel variation metric is not greater than the channel variation threshold;
wherein the first value is greater than the second value.
The method of claim 21, wherein the determining of the number of DMRS symbols comprises:
determining whether the signal strength metric is greater than a specified signal strength threshold;
determining a first value as the number of DMRS symbols when the signal strength metric is greater than the signal strength threshold;
if the signal strength metric is not greater than the signal strength threshold, determining a second value as the number of DMRS symbols;
wherein the first value is less than the second value.
In a wireless communication system, in a base station,
at least one transceiver;
at least one processor;
the at least one processor,
Estimating an uplink channel,
obtaining a channel variation metric and a signal strength metric based on the estimation result of the uplink channel;
Determine the number of uplink demodulation reference signal (DMRS) symbols based on the channel variation metric and the signal strength metric,
A base station configured to transmit DMRS allocation information according to the number of uplink DMRS symbols to a terminal.
25. The method of claim 24, wherein the at least one processor is configured to: determine the number of DMRS symbols;
It is determined whether the channel variation metric is greater than a specified channel variation threshold,
When the channel variation metric is greater than the channel variation threshold, a first value is determined as the number of DMRS symbols;
and if the channel variation metric is not greater than the channel variation threshold, determine a second value as the number of DMRS symbols;
wherein the first value is greater than the second value.
25. The method of claim 24, wherein the at least one processor is configured to: determine the number of DMRS symbols;
determine whether the signal strength metric is greater than a specified signal strength threshold;
If the signal strength metric is greater than the signal strength threshold, determining a first value as the number of DMRS symbols,
if the signal strength metric is not greater than the signal strength threshold, determine a second value as the number of DMRS symbols;
The first value is less than the second value.

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