Method and apparatus for supporting two-dimensional precoding in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate than a 4G communication system such as LTE. Particularly, according to various embodiments of the present disclosure, a method performed by a base station in a wireless communication system comprises the steps of: identifying capability information of a user equipment regarding 2D precoding; if the user equipment supports the 2D precoding, selecting the 2D precoding on the basis of channel information associated with the user equipment; and transmitting, to the user equipment, an index indicating the 2D precoding.

Description

Method and device for supporting two-dimensional precoding in a wireless communication system

[0001] The present disclosure relates generally to wireless communication systems, and more particularly to devices and methods for selecting and signaling two-dimensional precoding in wireless communication systems.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz (THz) band (for example, 3 THz band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

[0003] In the early stages of 5G mobile communication technology, the goal is to support services and satisfy performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

[0004] Currently, discussions are underway to improve and enhance the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology was intended to support, and physical layer standardization is in progress for technologies such as V2X (Vehicle-to-Everything) to help autonomous vehicles make driving decisions and increase user convenience based on their own location and status information transmitted by vehicles, NR-U (New Radio Unlicensed) for the purpose of system operation that complies with various regulatory requirements in unlicensed bands, NR terminal low power consumption technology (UE Power Saving), Non-Terrestrial Network (NTN), which is direct terminal-satellite communication to secure coverage in areas where communication with terrestrial networks is impossible, and Positioning.

[0005] In addition, standardization of wireless interface architecture / protocols is in progress for technologies such as intelligent factories (Industrial Internet of Things, IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) that provides nodes for expanding network service areas by integrating wireless backhaul links and access links, Mobility Enhancement technology including Conditional Handover and Dual Active Protocol Stack (DAPS) handover, and 2-step random access channel (RACH) for NR to simplify random access procedures. Standardization is also in progress for system architecture / services such as 5G baseline architecture (e.g., Service-based Architecture, Service-based Interface) for grafting Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) that provides services based on the location of the terminal.

[0006] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0008] Meanwhile, the requirements for NR communication systems have significantly increased compared to previous-generation LTE communication systems. These requirements include user-perceived speed, maximum data rate, spectral efficiency, delay, mobility, network energy efficiency, and connectivity. To support mobility, the orthogonal time-frequency space (OTFS) system has been proposed as a waveform study. The orthogonal frequency division multiplexing (OFDM) used in LTE and NR can be highly vulnerable to the Doppler effect, which occurs when the receiver moves. To handle the frequency shift caused by the Doppler effect in OFDM, complex Doppler compensation algorithms may be required at the receiver. However, complex Doppler compensation algorithms can increase complexity. Meanwhile, OTFS uses the symplectic finite Fourier transform (SFFT) to process signals in the delay-Doppler domain, effectively handling the Doppler-induced frequency shift with low complexity. Therefore, a method to support OTFS is needed.

[0009] Various embodiments of the present disclosure are intended to provide a device and method capable of effectively providing a service in a wireless communication system.

[0010] According to various embodiments of the present disclosure, a method performed by a base station in a wireless communication system comprises the steps of: identifying capability information regarding 2D (dimensional) precoding of a terminal; selecting the 2D precoding based on channel information with the terminal when the terminal supports the 2D precoding; and transmitting an index indicating the 2D precoding to the terminal, wherein the 2D precoding may be applied to at least one of an uplink signal or a downlink signal.

[0011] According to various embodiments of the present disclosure, a method performed by a terminal of a wireless communication system comprises the steps of: identifying capability information regarding 2D (dimensional) precoding of a base station; selecting a first 2D precoding based on channel information with the base station when the base station supports the 2D precoding; transmitting information regarding the first 2D precoding to the base station; and receiving an index indicating a second 2D precoding from the base station, wherein the 2D precoding may be applied to at least one of an uplink signal and a downlink signal.

[0012] According to various embodiments of the present disclosure, a base station of a wireless communication system comprises a transceiver and at least one control unit connected to the transceiver, wherein the at least one control unit is configured to identify capability information regarding 2D (dimensional) precoding of a terminal, select the 2D precoding based on channel information with the terminal when the terminal supports the 2D precoding, and transmit an index indicating the 2D precoding to the terminal, wherein the 2D precoding is applied to at least one of an uplink signal and a downlink signal, and the second 2D precoding may be determined based on the first 2D precoding.

[0013] According to various embodiments of the present disclosure, a terminal of a wireless communication system comprises a transceiver and at least one control unit connected to the transceiver, wherein the at least one control unit is configured to identify capability information regarding 2D (dimensional) precoding of a base station, select a first 2D precoding based on channel information with the base station when the base station supports the 2D precoding, transmit information regarding the first 2D precoding to the base station, and receive an index indicating a second 2D precoding from the base station, wherein the 2D precoding is applied to at least one of an uplink signal and a downlink signal, and the second 2D precoding may be determined based on the first 2D precoding.

[0014] Various embodiments of the present disclosure aim to provide devices and methods capable of effectively providing services in a wireless communication system. More specifically, according to various embodiments of the present disclosure, a base station or terminal can select an appropriate 2D precoding considering channel characteristics when transmitting or receiving uplink or downlink data.

[0015] Additionally, selecting an appropriate 2D (dimensional) precoding can reduce the channel sparsity experienced by the data. Therefore, this can lead to gains in channel estimation and reduced receiver complexity.

[0016] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0017] FIG. 1 illustrates an example of a wireless communication environment according to embodiments of the present disclosure.

[0018] FIG. 2 illustrates an example of a configuration of a base station in a wireless communication system according to embodiments of the present disclosure.

[0019] FIG. 3 illustrates an example of a configuration of a terminal in a wireless communication system according to embodiments of the present disclosure.

[0020] FIG. 4 illustrates the sparsity of a channel according to 2D (dimensional) precoding in accordance with embodiments of the present disclosure.

[0021] FIG. 5 illustrates an example of an orthogonal time frequency space (OTFS) related to embodiments of the present disclosure.

[0022] FIG. 6 illustrates a 2D precoding selection procedure of a base station according to embodiments of the present disclosure.

[0023] FIG. 7 illustrates a procedure for identifying 2D precoding capability information of a terminal according to embodiments of the present disclosure.

[0024] FIG. 8 illustrates an example of information regarding a 2D precoding combination according to embodiments of the present disclosure.

[0025] FIG. 9 illustrates a 2D precoding selection procedure using a pilot symbol according to embodiments of the present disclosure.

[0026] FIG. 10 illustrates the operation sequence of 2D precoding selection according to embodiments of the present disclosure.

[0027] FIG. 11 illustrates a procedure for receiving a downlink signal according to embodiments of the present disclosure.

[0028] FIG. 12 illustrates a procedure for transmitting an uplink signal according to embodiments of the present disclosure.

[0029] FIG. 13 illustrates a 2D precoding selection procedure of a terminal according to embodiments of the present disclosure.

[0030] FIG. 14 illustrates the operation sequence of 2D precoding selection according to embodiments of the present disclosure.

[0031] FIG. 15 illustrates a 2D precoding selection procedure of a base station according to embodiments of the present disclosure.

[0032] In connection with the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0033] The terms used in this 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 plural expressions unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as commonly understood by those of ordinary skill in the art described in this disclosure. Terms defined in general dictionaries among the terms used in this disclosure may be interpreted as having the same or similar meaning in the context of the relevant technology, and shall not be interpreted in an idealized or overly formal sense unless explicitly defined in this disclosure. In some cases, even if a term is defined in this disclosure, it cannot be interpreted to exclude embodiments of the present disclosure.

[0034] The various embodiments of the present disclosure described below illustrate a hardware-based approach as an example. However, since the various embodiments of the present disclosure include techniques utilizing both hardware and software, the various embodiments of the present disclosure do not exclude a software-based approach.

[0035] In the following description, terms referring to components of the device (control unit, processor, artificial intelligence (AI) model, encoder, decoder, autoencoder (AE), neural network (NN) model, etc.) and terms referring to data (signal, feedback, report, reporting, information, parameter, value, bit, codeword, etc.) are examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms having similar or equivalent technical meanings may be used.

[0036] Additionally, while this disclosure describes various embodiments using terminology used in certain communication standards (e.g., 3rd Generation Partnership Project (3GPP)), these are merely illustrative examples. The various embodiments of this disclosure can be easily modified and applied to other communication systems.

[0037] Hereinafter, in the present disclosure, the downlink channel may be one of a physical downlink control channel (PDCCH) or a physical downlink shared channel (PDSCH). In the present disclosure, the uplink channel may be one of a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH). In addition, in the present disclosure below, uplink data may be data transmitted and / or received on the above-described uplink channel, and downlink data may be data transmitted and / or received on the above-described downlink channel.

[0038] FIG. 1 illustrates a wireless communication system according to various embodiments of the present disclosure. FIG. 1 illustrates a base station (110), a terminal (120), and a terminal (130) as some of the nodes utilizing a wireless channel in the wireless communication system. While FIG. 1 illustrates only one base station, other base stations identical to or similar to base station (110) may be included.

[0039] The base station (110) is a network infrastructure that provides wireless access to terminals (120, 130). The base station (110) has coverage defined as a certain geographical area based on the distance at which a signal can be transmitted. In addition to the base station, the base station (110) may be referred to as an 'access point (AP)', 'eNodeB (eNB)', 'gNodeB (gNB)', '5th generation node', '6th generation node', 'wireless point', 'transmission / reception point (TRP)', or other terms having equivalent technical meanings.

[0040] Each of the terminals (120) and (130) is a device used by a user and communicates with the base station (110) via a wireless channel. In some cases, at least one of the terminals (120) and (130) may be operated without the user's intervention. That is, at least one of the terminals (120) and (130) is a device that performs machine type communication (MTC) and may not be carried by the user. Each of the terminal (120) and the terminal (130) may be referred to as a 'terminal', 'user equipment (UE),' 'mobile station,' 'subscriber station,' 'customer premises equipment (CPE),' 'remote terminal,' 'wireless terminal,' 'electronic device,' or 'user device,' or other terms having similar or equivalent technical meanings thereto.

[0041] The base station (110), the terminal (120), and the terminal (130) can transmit and receive wireless signals in the millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, 60 GHz, over 60 GHz, etc.). At this time, in order to improve the channel gain, the base station (110), the terminal (120), and the terminal (130) can perform beamforming. Here, the beamforming can include transmission beamforming and reception beamforming. That is, the base station (110), the terminal (120), and the terminal (130) can provide directionality to the transmission signal or the reception signal. To this end, the base station (110) and the terminals (120, 130) can select serving beams (112, 113, 121, 131) through a beam search or beam management procedure. After serving beams (112, 113, 121, 131) are selected, subsequent communication can be performed through resources that are in a QCL (quasi co-located) relationship with the resources that transmitted the serving beams (112, 113, 121, 131).

[0042] FIG. 2 illustrates an example of a configuration of a base station in a wireless communication system according to embodiments of the present disclosure. According to various embodiments of the present disclosure, the base station (110) may be conveniently referred to as a network. The configuration illustrated in FIG. 2 can be understood as the configuration of the base station (110). Terms such as "unit" and "unit" used hereinafter mean a unit that processes at least one function or operation, and this can be implemented by hardware, software, or a combination of hardware and software.

[0043] Referring to FIG. 2, the base station (110) may include a wireless communication unit (210), a backhaul communication unit (220), a storage unit (230), and a control unit (240).

[0044] The wireless communication unit (210) performs functions for transmitting and receiving signals through a wireless channel. For example, the wireless communication unit (210) performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the system. For example, when transmitting data, the wireless communication unit (210) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the wireless communication unit (210) restores a reception bit stream by demodulating and decoding a baseband signal. In addition, the wireless communication unit (210) upconverts a baseband signal into an RF (radio frequency) band signal and transmits it through an antenna, and downconverts an RF band signal received through the antenna into a baseband signal.

[0045] To this end, the wireless communication unit (210) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital to analog convertor (DAC), an analog to digital convertor (ADC), etc. In addition, the wireless communication unit (210) may include a plurality of transmission and reception paths. Furthermore, the wireless communication unit (210) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the wireless communication unit (210) may be composed of a digital unit and an analog unit, and the analog unit may be composed of a plurality of sub-units according to operating power, operating frequency, etc.

[0046] The wireless communication unit (210) can transmit and receive signals. To this end, the wireless communication unit (210) may include at least one transceiver. For example, the wireless communication unit (210) may transmit a synchronization signal, a reference signal, system information, messages, control information, or data. In addition, the wireless communication unit (210) may perform beamforming.

[0047] The wireless communication unit (210) transmits and receives signals as described above. Accordingly, all or part of the wireless communication unit (210) may be referred to as a "transmitter," a "receiver," or a "transmitting and receiving unit." Furthermore, in the following description, transmission and reception performed via a wireless channel are used to mean processing performed by the wireless communication unit (210) as described above.

[0048] The backhaul communication unit (220) provides an interface for performing communication with other nodes within the network. That is, the backhaul communication unit (220) converts a bit string transmitted from the base station (110) to another node, such as another access node, another base station, an upper node, a core network, etc., into a physical signal, and converts a physical signal received from another node into a bit string.

[0049] The storage unit (230) stores data such as basic programs, application programs, and setting information for the operation of the base station (110). The storage unit (230) may include a memory. The storage unit (230) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. In addition, the storage unit (230) may provide stored data upon request from the control unit (240).

[0050] The control unit (240) controls the overall operations of the base station (110). For example, the control unit (240) transmits and receives signals through the wireless communication unit (210) or the backhaul communication unit (220). In addition, the control unit (240) records and reads data from the storage unit (230). In addition, the control unit (240) can perform the functions of the protocol stack required by the communication standard. To this end, the control unit (240) can include at least one processor.

[0051] Although not illustrated in FIG. 2, the base station (110) may further include a receiving device that performs embodiments of the present disclosure according to various embodiments of the present disclosure. Specifically, the receiving device may be included in the wireless communication unit (210), or may be included in the base station (110) separately from the wireless communication unit (210). Alternatively, the receiving device may be located outside the base station (110) and may be connected to the base station (110) wirelessly or by wire. In this case, the receiving device may include at least one receiver. In addition, the control unit (240) may control the receiving device to perform the embodiments of the present disclosure below.

[0052] The configuration of the base station (110) illustrated in FIG. 2 is merely an example of a base station, and examples of base stations that perform various embodiments of the present disclosure are not limited to the configuration illustrated in FIG. 2. That is, some configurations may be added, deleted, or changed according to various embodiments.

[0053] Although the base station is described as a single entity in FIG. 2, 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 not only an integrated deployment but also a distributed deployment. According to one embodiment, the base station may be divided into a central unit (CU) and a digital unit (DU), and the CU may be implemented to perform upper layer functions (e.g., radio link control (RLC), packet data convergence protocol (PDCP), and radio resource control (RRC)) and the DU may be implemented to perform lower layer functions (e.g., medium access control (MAC), physical (PHY)). The DU of the base station may form beam coverage on a wireless channel.

[0054] FIG. 3 illustrates the configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure. The configuration illustrated in FIG. 3 can be understood as the configuration of a terminal (120). Terms such as "~unit" and "~unit" used hereinafter refer to a unit that processes at least one function or operation, which can be implemented using hardware, software, or a combination of hardware and software.

[0055] Referring to FIG. 3, the terminal includes a communication unit (310), a storage unit (320), and a control unit (330).

[0056] The communication unit (310) performs functions for transmitting and receiving signals via a wireless channel. For example, the communication unit (310) performs a conversion function between a baseband signal and a bit stream according to the physical layer specifications of the system. For example, when transmitting data, the communication unit (310) generates complex symbols by encoding and modulating a transmission bit stream. In addition, when receiving data, the communication unit (310) restores a reception bit stream by demodulating and decoding the baseband signal. In addition, the communication unit (310) upconverts a baseband signal to an RF band signal and transmits it through an antenna, and downconverts an RF band signal received through the antenna to a baseband signal. For example, the communication unit (310) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0057] In addition, the communication unit (310) may include a plurality of transmission and reception paths. Furthermore, the communication unit (310) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit (310) may be composed of digital circuits and analog circuits (e.g., radio frequency integrated circuits (RFIC)). Here, the digital circuits and analog circuits may be implemented in a single package. In addition, the communication unit (310) may include a plurality of RF chains. Furthermore, the communication unit (310) may perform beamforming.

[0058] The communication unit (310) transmits and receives signals as described above. Accordingly, all or part of the communication unit (310) may be referred to as a "transmitter," a "receiver," or a "transmitting and receiving unit." Furthermore, in the following description, transmission and reception performed via a wireless channel are used to mean processing performed by the communication unit (310) as described above.

[0059] The storage unit (320) stores data such as basic programs, application programs, and setting information for the operation of the terminal. The storage unit (320) may be composed of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. In addition, the storage unit (320) provides stored data upon request from the control unit (330).

[0060] The control unit (330) controls the overall operations of the terminal. For example, the control unit (330) transmits and receives signals through the communication unit (310). In addition, the control unit (330) records and reads data from the storage unit (320). In addition, the control unit (330) can perform the functions of the protocol stack required by the communication standard. To this end, the control unit (330) may include at least one processor or microprocessor, or may be a part of a processor. In addition, a part of the communication unit (310) and the control unit (330) may be referred to as a CP (communication processor).

[0061] According to various embodiments, the control unit (330) can control the terminal to perform operations according to various embodiments described below.

[0062] The terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, and terms referring to various identification information are provided as examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms referring to objects with equivalent technical meanings may be used.

[0063] The configuration of the terminal (120) illustrated in FIG. 3 is merely an example of a terminal, and examples of terminals performing various embodiments of the present disclosure are not limited to the configuration illustrated in FIG. 3. That is, some configurations may be added, deleted, or changed according to various embodiments.

[0064] Meanwhile, the 3GPP LTE (long-term evolution) standard for mobile communications (or wireless communications) adopted the orthogonal frequency division multiplexing (OFDM) waveform. In the early stages of NR (new radio) standardization, new waveforms that could complement the various shortcomings of the existing OFDM were proposed as candidates, but 3GPP selected OFDM as the waveform for NR as well. With the recent standardization of the 6th generation mobile communication system (hereinafter referred to as 6G communication system), the key performance indicators (KPIs) used in the standardization of NR communication systems are expected to change to more challenging values. Furthermore, 6G communication networks are expected to support a wider range of use cases than NR communication systems. Therefore, the waveform may need to be highly flexible to support these diverse use cases. Therefore, new waveforms or modified OFDM waveforms that are compatible with OFDM waveforms may be adopted to support these diverse use cases.

[0065] In particular, in the standards for NR and 6G communication systems, supporting not only high-speed train channels at speeds of hundreds of km / h, but also non-terrestrial networks (NTNs) with higher mobility, along with terrestrial networks (TNs), is emerging as a critical issue. A novel waveform to address these issues could be the orthogonal time-frequency-space (OTFS) waveform. In high-speed mobile environments, conventional OFDM waveforms, which are robust to frequency-selective fading, may not be robust to time-selective fading, resulting in significant performance degradation. For example, conventional OFDM waveforms can be highly susceptible to the Doppler effect that occurs when a receiver moves. Furthermore, for OFDM waveforms, receivers may require complex Doppler compensation algorithms to handle frequency shifts due to the Doppler effect. Furthermore, Doppler compensation algorithms can increase the complexity of the receiver. In OTFS, signals can be processed in the delay-Doppler domain using the simple finite Fourier transform (SFFT). Furthermore, OTFS can effectively handle frequency shifts due to Doppler with low complexity. In the following embodiments of the present disclosure, the characteristics of OTFS as a new waveform using two-dimensional precoding and methods for selecting and applying OTFS will be described.

[0066] FIG. 4 illustrates the sparsity of a channel according to 2D (dimensional) precoding in accordance with embodiments of the present disclosure.

[0067] Referring to FIG. 4, the characteristics of graphs for OTFS waveforms and OTSM (orthogonal time sequence multiplexing) waveforms can be explained. Two-dimensional precoding (hereinafter referred to as 2D precoding) can be applied to existing OFDM waveforms. Therefore, when 2D precoding is applied, it can be represented as the (a) OTFS and (b) OTSM graphs in FIG. 4. In this case, the 2D precoding can be an inverse fast Fourier transform (IFFT), a Walsh Hadamard (WHT), or a sparse Walsh Hadamard (SWH). The 2D precoding can have different complexities. For example, an IFFT can have high complexity because it includes complex numbers. In contrast, a WHT consists of only -1 and 1, and can have lower complexity than an IFFT. Additionally, SWH may have lower complexity compared to WHT, as it consists only of 0s and 1s. However, the types of 2D precoding are not limited to the examples described above. Furthermore, in the embodiments of the present disclosure below, 2D precoding is not limited to any one, and may be a method for selecting any 2D precoding, such as the examples described above.

[0068] More specifically, depending on the type of 2D precoding, the channel shape of the converted domain (e.g., delay-Doppler domain) in the time-frequency (TF) domain channel can be represented as in Fig. 4. For example, in the delay-Doppler domain, OTFS may exhibit less sparsity (or a higher degree of localization) than OTSM. In this case, the smaller the sparsity, the more advantageous it may be for channel estimation. In addition, even if the sparsity is small, if each element is a unitary matrix with a constant modulus characteristic, there may be no difference in the error rate, but the complexity during equalization may be reduced. In addition, OTFS may have advantages in terms of separability or channel degrees of freedom (DoF). In addition, OTFS may have advantages in terms of stability due to its characteristic of changing very slowly compared to the time-frequency domain. As described above, the advantages of OTFS can ultimately result in reduced receiver complexity. In the following embodiments of the present disclosure, the operations of a base station and a terminal for adaptively selecting and operating 2D precoding for OTFS will be described.

[0069] FIG. 5 illustrates an example of OTFS in accordance with embodiments of the present disclosure.

[0070] Referring to Fig. 5, a method for applying 2D precoding to OFDM can be described by mathematical expression. As an example of generating a transmission signal in the form of an OTFS waveform, an OTFS transmitter can generate a continuous-time signal on a frame-by-frame basis. In this case, a design requirement may be that the channel remains largely unchanged in the delay-Doppler domain during one frame. For example, if a transmitter transmits J frames, the transmission signal can be expressed as in the following mathematical expression 1.

[0071]

[0072] In mathematical expression 1, s (j) (t) may be a component of the jth frame signal among the transmitted signals, and T F may be a common frame period. Since the generation method of each frame signal is the same, for convenience, the following description of the signal generation method of the 0th frame can also be applied to the description of the signal of the jth frame. Therefore, (j) can be omitted in the following description, and the generation method of s(t) can be described. A general model of an OTFS transmitter and receiver signal can be given as in Fig. 5, and Fig. 5 can represent three essential transformations used when transmitting one frame.

[0073] First, the transmitter can convert the data symbol sequence x[n] into S / P (serial-to-parallel) and place pilot symbols to generate an M-by-N (or MxN) matrix X in the delay-Doppler domain (DD domain). dd can generate a matrix X dd is a 2D information symbol matrix (quadrature amplitude modulation (QAM) symbols) that can contain actual data. And the transmitter uses the delay-Doppler domain symbol matrix X ddBy inverse symplectic finite Fourier transform (ISFFT), we obtain a time-frequency domain sample matrix X of the same size. tf can generate a time-frequency domain sample matrix X tf The process of generating the delay-Doppler domain matrix X dd Multiply the M-point DFT (discrete Fourier transform) matrix on the left side and the N-point IDFT (inverse DFT) matrix on the right side to obtain the MxN sample matrix X tf It can be a two-dimensional orthogonal transformation that obtains X. For example, X dd X is the (m,n) component of dd [m,n] and X tf X is the (l,k) component of tf The relationship between [l,k] can be expressed as the following mathematical expression 2.

[0074]

[0075] The Heisenberg transform is a time-frequency domain matrix X tf This can be mathematically equivalent to applying a pulse-shaped orthogonal frequency-division multiplexing (P / P) modulation process to an OFDM transmitter after the symbol sequence has been S / P-converted. For example, in the Heisenberg transform, a continuous-time signal s(t) can be generated through the following mathematical expression 3.

[0076]

[0077] The process of mathematical formula 3 is X tf It can be viewed as a generalized pulse-shaped OFDM modulation process that assigns the l-row symbols to the first sub-carrier and generates the k-th OFDM symbol with the k-th symbols. At this time, f can be a subcarrier spacing, can be the transmit pulse of the kth OFDM symbol, and T (k) can be the delay time of the kth transmission pulse. If, And, The mathematical expression 3 described above can be simplified as shown in the mathematical expression 4 below.

[0078]

[0079] Mathematical expression 4 is the time-frequency domain sample matrix X tf It may be a method of converting a continuous-time signal s(t) through the Heisenberg transform.

[0080] The transmitter is in the mathematical expression 3 described above. Wow T (k) By appropriately selecting k, the symbol CP (cyclic prefix) is X tf It can also have the effect of adding to each column of . Also, the transmitter can have X without symbol CP in Equation 3 tf After converting to P / S (parallel-to-serial), the effect of adding only one frame CP (frame cyclic prefix) can be achieved, and both effects can be achieved by combining the two methods described above. For convenience, the following description is described using mathematical expression 4.

[0081] When the generated OTFS signal s(t) passes through the channel, it can be received as a continuous-time signal r(t). In particular, when s(t) is received after passing through a narrowband doubly-selective fading channel, and then the transmitter performs Wigner transform on r(t) and then performs SFFT, the delayed-Doppler domain symbol matrix X ddWhen a 2D channel matrix having a sparse impulse response in the delay-Doppler domain is subjected to a 2D circular convolution, the delay-Doppler domain matrix obtained can be obtained as the output Y. Therefore, the OTFS receiver can estimate data symbols in the delay-Doppler domain using existing and novel equalization techniques that can perform 2D deconvolution in the delay-Doppler domain as long as the parameters of the channel impulse response can be well estimated.

[0082] Meanwhile, X in mathematical formula 2 below dd Expand X xy It is named as follows. If the signaling used in OTFS is generalized and expressed in the form of a matrix, X tf =U F X dd U T can be expressed as . At this time, X dd Wow X xy can all be M×N matrices, and U F can be an M×M matrix, and in OTFS, an M-point DFT matrix can be used. And U T is an N×N matrix, and an N-point IDFT matrix can be used in OTFS. Also, in OTSM, U F The existing DFT matrix can be used, and U T WHT can be used. In addition to that, U F Wow U T may have constant modulus characteristics, and if it is a single matrix, the error rate performance of the receiver may be the same.

[0083] FIG. 6 illustrates a 2D precoding selection procedure of a base station according to embodiments of the present disclosure.

[0084] Referring to FIG. 6, a 2D precoding configuration and signaling method can be described when a base station triggers a 2D precoding selection procedure.

[0085] In step 610, the base station can check whether the terminal has 2D precoding capability through a higher layer message (e.g., a radio resource control (RRC) message). For example, the terminal's 2D precoding capability may indicate whether the terminal supports 2D precoding. Step 610 may include a process in which the base station transmits a message to the terminal to inquire about the terminal's capability, and a process in which the terminal transmits a message to the base station to respond with its capability.

[0086] In step 620, the base station may transmit information about possible 2D precoding combinations to the terminal. This information about the 2D precoding combination may include at least one of the available 2D precoding combinations, based on whether the terminal supports 2D precoding. Furthermore, this information about the 2D precoding combination may be generated based on the capabilities of the terminal identified in step 610.

[0087] At step 630, the base station can determine whether a 2D precoding trigger condition is satisfied. For example, the selection operation of 2D precoding (e.g., step 640 below) may be performed periodically, in which case the 2D precoding trigger condition may include whether a predetermined period of time has elapsed since the last trigger. Additionally, the selection operation of 2D precoding may be performed when a specific condition is satisfied based on a preset value, in which case the 2D precoding trigger condition may include whether the value is satisfied (e.g., whether a predetermined measurement value is greater than or less than a threshold value, etc.).

[0088] At step 640, the base station can select the optimal 2D precoding if the 2D precoding trigger condition is satisfied. At this time, the base station can select the optimal 2D precoding based on the pilot symbol received from the terminal.

[0089] In step 650, the base station can transmit the index of the selected 2D precoding to the terminal. At this time, the index value transmitted to the terminal may be one of the index values ​​included in the information regarding the combination of 2D precodings transmitted to the terminal in step 620.

[0090] The operations of each step described above can be specifically described in FIGS. 7 to 12 below. Furthermore, the present invention is not limited to the examples described above. Accordingly, at least one of the above-described operations may be omitted, or at least one new operation may be added and organically combined with the above-described operations to perform the operations. Furthermore, some of the above-described operations may be combined into at least one operation or divided into two or more operations.

[0091] FIG. 7 illustrates a procedure for identifying 2D precoding capability information of a terminal according to embodiments of the present disclosure.

[0092] Referring to FIG. 7, the operation of checking whether the terminal has 2D precoding capability in step 610 described above can be specifically described.

[0093] In step 710, the base station may request capability information (e.g., UE_2DPrecoding_Capability) regarding the terminal's 2D precoding capabilities from the terminal. For example, the base station may transmit a UECapabilityEnquiry message to the terminal to request capability information regarding the terminal's 2D precoding capabilities. At this time, the request for capability information regarding the terminal's 2D precoding capabilities may be included in a higher layer message (e.g., an RRC message).

[0094] At step 720, the terminal may transmit a response to the request for capability information received from the base station to the base station. For example, the terminal may transmit a UECapabilityResponse message to the terminal to convey capability information regarding 2D precoding to the base station. In addition, the response of the terminal may be included in the form of UE_2DPrecoding_Capability = BOOLEAN {Enabled, Disabled} or may be included in the form of UE_2DPrecoding_Capability = ENUMERATED {true}. In addition, the response of the terminal may be included in a higher layer message (e.g., an RRC message). In one embodiment, the terminal may transmit the response to the base station based on 2D precoding support information that is pre-configured (or installed) in the terminal. For example, if the terminal does not support 2D precoding (e.g., UE_2DPrecoding_Capability = {Disabled} or UE_2DPrecoding_Capability is not included), the base station may stop the 2D precoding selection procedure based on the terminal's response and transmit and / or receive data based on the existing OFDM. For example, if the terminal supports 2D precoding (e.g., UE_2DPrecoding_Capability = {Enabled} or UE_2DPrecoding_Capability = {true}), the base station may perform the 2D precoding selection procedure according to an embodiment of the present disclosure. Thereafter, depending on the selection of 2D precoding, the base station may transmit and / or receive data to and / or from the terminal based on OTFS.

[0095] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0096] FIG. 8 illustrates an example of information regarding a 2D precoding combination according to embodiments of the present disclosure.

[0097] Referring to FIG. 8, information regarding the combination of 2D precodings transmitted by the base station to the terminal in step 620 described above can be explained. The combination information of available 2D precodings can be in the form of a table of FIG. 8. For example, the combination information of available 2D precodings can be 2DPreIndex, U T , and U F Each combination can be included. At this time, 2DPreIndex is U T and U F can mean the index of combinations of U. And T can mean a precoding matrix (single matrix) according to the frequency domain, and U F can mean a precoding matrix (single matrix) according to the time domain. The combination information of available 2D precodings can be composed of N_2D_Precoding elements, and N_2D_Precoding is N_2D_Precoding U T and U F This may mean that a combination of may be possible. For example, in Fig. 8, U T and U Fcan be one of a unit matrix, an identity matrix, a DFT, a WH, or a SWH. However, Fig. 8 is only an example of the combination information of available 2D precodings, and the combination information of available 2D precodings is not limited to the example of Fig. 8.

[0098] In one embodiment, the base station may transmit to the terminal a combination of available 2D precodings based on the 2D precoding capability information received from the terminal in FIG. 7 described above. For example, if the terminal supports 2D precoding, the base station may transmit to the terminal a combination of available 2D precodings. The table in FIG. 8 may be included in a higher layer message (e.g., an RRC message).

[0099] In one embodiment, the combination information of available 2D precodings may be preset (or installed) in the terminal. Accordingly, the base station may not need to transmit the combination information of available 2D precodings to the terminal.

[0100] FIG. 9 illustrates a 2D precoding selection procedure using pilot symbols according to embodiments of the present disclosure.

[0101] Referring to FIG. 9, the operation of selecting the optimal 2D precoding when the base station satisfies the 2D precoding trigger condition in step 640 described above can be specifically described.

[0102] First, the base station can identify whether the 2D precoding trigger condition is satisfied. In one embodiment, the selection operation of 2D precoding (e.g., step 640) can be set to be performed periodically. For example, the base station can perform the selection operation of 2D precoding every 10 ms. At this time, the value (e.g., N_Period_2Dprecoding) regarding the 2D precoding selection operation period of the base station can be set or indicated from a higher layer (e.g., RRC layer or MAC layer) or can be a value preset (or fixed) to the base station. In one embodiment, the selection operation of 2D precoding (e.g., step 640) can also be set to be performed when a specific event occurs. For example, the base station can estimate a Doppler shift value (e.g., f) based on a pilot symbol received from a terminal. D ) is the threshold (e.g., f D,Th ) is greater than or equal to 2D, a 2D precoding selection operation can be performed. For example, f D >f D,Th In this case, a 2D precoding selection operation can be performed. At this time, a threshold value (e.g., f D,Th ) can be calculated based on the carrier frequency and target velocity. In addition, a threshold value (e.g., f D,Th ) may be set or indicated from a higher layer (e.g., RRC layer or MAC layer) or may be a value preset (or installed) in the base station. When the above-described 2D precoding trigger condition is satisfied, the base station may perform operations to select the optimal 2D precoding.

[0103] In step 910, the base station may request the terminal to transmit pilot symbols to determine the characteristics of the channel with the terminal. The pilot symbol request operation may be intended to determine statistical channel characteristics, rather than instantaneous channel characteristics. Furthermore, since the pilot symbol request is not intended for data decoding, overhead may not occur even if transmitted in units of hundreds of milliseconds to seconds. At this time, the pilot symbol request may be transmitted via a control channel (e.g., PDCCH). For example, the pilot symbol request may be included in control information (e.g., downlink control information, DCI), and the pilot symbol request may include at least one of information regarding the transmission time of the pilot symbol or frequency resources for transmitting the pilot symbol. Furthermore, the pilot symbol may be an existing reference signal (e.g., including at least one of channel state information (CSI)-RS or demodulation (DM)-RS) or a newly defined pilot. For example, a newly defined pilot may include a guard band (or guard frequency) and may include consecutive pilot symbols in the time domain. Consecutive pilot symbols in the time domain may enable the base station to achieve more accurate channel estimation.

[0104] In step 920, the terminal may transmit pilot symbols to the base station based on a request for pilot symbols received from the base station. For example, after receiving a request for transmission of pilot symbols from the base station, the terminal may decode control information (e.g., DCI). Then, the terminal may transmit the pilot symbols to the base station based on the transmission time and / or frequency resources included in the control information (e.g., DCI).

[0105] At step 930, the base station can select the optimal 2D precoding by understanding the characteristics and complexity of the channel through the pilot symbols received from the terminal. For example, the base station can select the optimal 2D precoding by receiving the pilot symbols from the terminal and selecting the channel H. ft can be estimated. And the base station can estimate the estimated channel H ft Or, based on at least one of the computational complexities of each precoder, the optimal 2D precoding (U T ,U F ) can be selected.

[0106] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0107] FIG. 10 illustrates the operation sequence of 2D precoding selection according to embodiments of the present disclosure.

[0108] Referring to FIG. 10, a procedure for selecting an optimal 2D precoding based on a pilot symbol received by the base station from the terminal in step 930 described above can be specifically described.

[0109] At step 1010, the base station receives a pilot symbol from the terminal and transmits it on channel H. ft can be estimated. For example, the base station is H ft For estimation, channel estimation using the least square (LS) or minimum mean square error (MMSE) method can be performed on the REs (resource elements) containing pilot symbols. The base station can perform interpolation on the remaining REs. Therefore, as described above in Fig. 9, newly defined pilot symbols can be used to improve the accuracy of channel estimation.

[0110] At step 1020, the base station transmits the time-frequency domain channel H ft Inverse 2D precoding can be performed for each 2D precoding combination. The base station can perform H, which is the channel transfer function (or function) of the xy domain channel. xy can be obtained. For example, H xy can be expressed as in mathematical formula 5 below.

[0111]

[0112] For example, as in the case of OTFS, M-point DFT U F =F M and N-point IDFT If , the estimated H ft When SFFT is applied to , it is transformed into a delay-Doppler grid and channels in the delay-Doppler domain (e.g., H DD ) can be calculated. For example, the estimated H ft When IFFT (left) and IWHT (right) are applied to , it is transformed into a delay-sequency grid and channels in the delay-sequency domain (e.g., H DS ) can be calculated.

[0113] At step 1030, the base station has an M×N matrix H xy Clustering can be performed to calculate the number of clusters and the variance of each cluster. For example, a base station is an M×N matrix H xy Up to M data groups can be identified based on the x-axis. In addition, the base station is an M×N matrix H xyUp to N data groups can be identified based on the y-axis. The base station can then calculate the variance for each of the multiple data groups. The base station can measure the sparseness of each of the x-axis and y-axis based on the number of clusters and the variance of each cluster.

[0114] At step 1040, the base station selects the optimal 2D precoding (U) by taking a weighted average of the number of clusters, the variance of each cluster, and the computational complexity according to each precoder among the N_2D_Precoding candidates (e.g., the combinations of the available 2D precodings of step 620 described above). T ,U F ) can be selected. At this time, the optimal 2D precoding may be a 2D precoding with a small number of clusters among the N_2D_Precoding candidates and low sparsity and complexity.

[0115] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0116] FIG. 11 illustrates a procedure for receiving a downlink signal according to embodiments of the present disclosure.

[0117] Referring to FIG. 11, an operation in which a base station transmits an index of a selected 2D precoding to a terminal (e.g., step 650) and transmits downlink data to the terminal based on the 2D precoding corresponding to the index can be specifically described.

[0118] In step 1110, the base station can transmit to the terminal the index of the optimal 2D precoding selected in step 640 described above. Information about the index of the 2D precoding selected by the base station can be included in at least one of upper layer signaling (e.g., RRC message or MAC CE (control element)) or control information (e.g., DCI). In one embodiment, the base station can include a method for indicating 2D precoding to be used for transmission of downlink data in the RRC message (e.g., Indication_PDSCH_2D_precoding). The base station can configure a method for indicating the 2D precoding index to the terminal through the RRC message.

[0119] In one embodiment, when the base station instructs the terminal to select 2D precoding through DCI (e.g., when Indication_PDSCH_2D_precoding = {DCI}), the base station may transmit DCI including index information of the selected 2D precoding (e.g., Index_PDSCH_2D_precoding_DCI = {1, ..., N_2D_Precoding}) to the terminal. After receiving the DCI from the base station, the terminal may decode the Index_2D_precoding_DCI value to confirm the index of the 2D precoding selected by the base station. In addition, when the base station instructs the terminal to select 2D precoding through DCI, dynamic switching may be possible between OFDM and OTFS applying the 2D precoding selected by the base station. The base station can configure which mode (e.g., OFDM or OTFS with 2D precoding selected by the base station) it will switch to via an RRC message (e.g., Cont_Util_PDSCH_2D_precoding = {Enabled, Disabled}). For example, if Cont_Util_PDSCH_2D_precoding = Enabled, it can mean that the index of the selected 2D precoding is used until a newly updated index of 2D precoding is received via the next DCI. On the other hand, if Cont_Util_PDSCH_2D_precoding = Disabled, it can mean that the index of the selected 2D precoding is valid during a valid time (e.g., N_valid_time=10ms) after receiving the DCI, and after the valid time, it can change to the previously used OFDM.

[0120] In one embodiment, when the base station indicates the index of the selected 2D precoding to the terminal via MAC signaling (e.g., MAC CE (control element)) (e.g., when Indication_PDSCH_2D_precoding = {MAC}), the base station may select one of N_2D_Precoding indices and transmit information about the index of the selected 2D precoding to the terminal via MAC signaling (e.g., Index_PDSCH_2D_precoding_MAC={1, ..., N_2D_Precoding}). In addition, when the base station indicates the selected 2D precoding to the terminal via MAC signaling, the MAC CE may be used to semi-statically switch between OFDM and OTFS applying the 2D precoding selected by the base station.

[0121] In one embodiment, when the base station transmits the index of the selected 2D precoding to the terminal via an RRC message (e.g., when Indication_PDSCH_2D_precoding = {RRC}), the base station may inform the terminal of information about the index of the selected 2D precoding via an RRC message (e.g., PDSCH-Config.2DPrecoding ={1, 2, ..., N_2D_Precoding}). For example, the base station may set the index of the 2D precoding to be used at the time of initial access (e.g., Msg 3 in a random access procedure) to the terminal via an RRC message (e.g., RACH-ConfigCommon.msg3-2DPrecoding ={1, 2, ..., N_2D_Precoding}). In addition, the base station can set the index of the 2D precoding to be used in the PUSCH to the terminal via an RRC message (e.g., PUSCH-Config.2DPrecoding ={1, 2, ..., N_2D_Precoding}). In one embodiment, when the index of the selected 2D precoding is indicated to the terminal via the RRC message, OFDM can be indicated if the index value is 1, and in other cases, 2D precoding can be indicated to be applied. In addition, when the base station indicates the selected 2D precoding to the terminal via the RRC message, it can be statically switched between OFDM and OTFS applying the 2D precoding selected by the base station via the RRC message.

[0122] At step 1120, the terminal can receive downlink data (e.g., data received on PDSCH) from the base station. When decoding the received downlink data, the terminal can utilize information about the index of the 2D precoding received from the base station at step 1110. For example, the terminal can use the 2D precoding (U) corresponding to the index value of the 2D precoding selected by the base station. T , UF ) can be used to decode downlink data through the reverse process.

[0123] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0124] FIG. 12 illustrates a procedure for transmitting an uplink signal according to embodiments of the present disclosure.

[0125] Referring to FIG. 12, when a base station transmits an index of a selected 2D precoding to a terminal (e.g., step 650 described above), an operation in which the terminal transmits uplink data to the base station based on the 2D precoding corresponding to the index can be specifically described. In the following embodiments of the present disclosure, any description overlapping with FIG. 11 may be omitted.

[0126] In step 1210, the base station can transmit to the terminal the index of the optimal 2D precoding selected in step 640 described above. Information about the index of the 2D precoding selected by the base station can be included in at least one of upper layer signaling (e.g., RRC message or MAC signaling) or control information (e.g., DCI). In one embodiment, the base station can include a method for indicating the 2D precoding to be used for transmission of downlink data (e.g., Indication_PDSCH_2D_precoding) in the RRC message. The base station can configure how to indicate the 2D precoding index to the terminal through the RRC message.

[0127] In one embodiment, when the base station instructs the terminal to select 2D precoding through DCI (e.g., when Indication_PDSCH_2D_precoding = {DCI}), the base station may transmit DCI including index information of the selected 2D precoding (e.g., Index_PDSCH_2D_precoding_DCI = {1, ..., N_2D_Precoding}) to the terminal. After receiving the DCI from the base station, the terminal may decode the Index_2D_precoding_DCI value to confirm the index of the 2D precoding selected by the base station. In addition, when the base station instructs the terminal to select 2D precoding through DCI, dynamic switching may be possible between OFDM and OTFS applying the 2D precoding selected by the base station. The base station can configure which mode (e.g., OFDM or OTFS with 2D precoding selected by the base station) it will switch to via an RRC message (e.g., Cont_Util_PDSCH_2D_precoding = {Enabled, Disabled}). For example, if Cont_Util_PDSCH_2D_precoding = Enabled, it can mean that the index of the selected 2D precoding is used until a newly updated index of 2D precoding is received via the next DCI. On the other hand, if Cont_Util_PDSCH_2D_precoding = Disabled, it can mean that the index of the selected 2D precoding is valid during a valid time (e.g., N_valid_time=10ms) after receiving the DCI, and after the valid time, it can change to the previously used OFDM.

[0128] In one embodiment, when the base station indicates the index of the selected 2D precoding to the terminal via MAC signaling (e.g., MAC CE) (e.g., when Indication_PDSCH_2D_precoding = {MAC}), the base station may select one of the N_2D_Precoding indices and transmit information about the index of the selected 2D precoding to the terminal via MAC signaling (e.g., Index_PDSCH_2D_precoding_MAC={1, ..., N_2D_Precoding}). In addition, when the base station indicates the selected 2D precoding to the terminal via MAC signaling, the MAC CE may be used to semi-statically switch between OFDM and OTFS applying the 2D precoding selected by the base station.

[0129] In one embodiment, when the base station transmits the index of the selected 2D precoding to the terminal via an RRC message (e.g., when Indication_PDSCH_2D_precoding = {RRC}), the base station may inform the terminal of information about the index of the selected 2D precoding via an RRC message (e.g., PDSCH-Config.2DPrecoding = {1, 2, ..., N_2D_Precoding}). For example, the base station may configure the index of the 2D precoding to be used at the time of initial access (e.g., Msg 3 in a random access procedure) to the terminal via an RRC message (e.g., RACH-ConfigCommon.msg3-2DPrecoding ={1, 2, ..., N_2D_Precoding}). In addition, the base station can set the index of the 2D precoding to be used in the PUSCH to the terminal via an RRC message (e.g., PUSCH-Config.2DPrecoding ={1, 2, ..., N_2D_Precoding}). In one embodiment, when the index of the selected 2D precoding is indicated to the terminal via the RRC message, OFDM can be indicated if the index value is 1, and in other cases, 2D precoding can be indicated to be applied. In addition, when the base station indicates the selected 2D precoding to the terminal via the RRC message, static switching can be performed between OFDM and OTFS to which the 2D precoding selected by the base station is applied via the RRC message.

[0130] In step 1220, the terminal generates uplink data (e.g., data transmitted on PUSCH), and then utilizes information about the index of the 2D precoding specified through step 1210 described above to generate U corresponding to the index. T Wow U F can be applied to uplink data (e.g., data transmitted on PUSCH). The terminal transmits U to the base station. T Wow U FUplink data (e.g., data transmitted on PUSCH) to which the precoding is applied can be transmitted. The index of the 2D precoding specified by the base station can be applied not only to uplink data but also to Msg3 transmission of the random access procedure.

[0131] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0132] FIG. 13 illustrates a 2D precoding selection procedure of a terminal according to embodiments of the present disclosure.

[0133] Referring to FIG. 13, a 2D precoding configuration and signaling method can be described when a terminal triggers a 2D precoding selection procedure.

[0134] At step 1310, the terminal can check whether the base station has a 2D precoding capability through a higher layer message (e.g., an RRC message). For example, the 2D precoding capability of the base station can indicate whether the base station supports 2D precoding. In one embodiment, the base station can transmit an RRC message to the terminal to convey capability information regarding 2D precoding to the terminal. The capability information regarding 2D precoding can be included in the form of UE_2DPrecoding_Capability = {Enabled, Disabled}. The base station can transmit the capability information regarding 2D precoding to the terminal based on preset (or installed) 2D precoding support information. For example, if the base station does not support 2D precoding (e.g., BS_2DPrecoding_Capability = {Disabled}), the terminal can stop the 2D precoding selection procedure according to the response from the base station and transmit and / or receive data based on the existing OFDM. For example, if the base station supports 2D precoding (e.g., BS_2DPrecoding_Capability = {Enabled}), the terminal may perform a 2D precoding selection procedure according to an embodiment of the present disclosure. Thereafter, based on the selection of 2D precoding, the terminal may transmit and / or receive data with the terminal based on OTFS.

[0135] And the base station can transmit information about the combination of possible 2D precodings to the terminal. At this time, the information about the combination of 2D precodings can include combinations of available 2D precodings based on whether the base station supports 2D precoding. In one embodiment, the combination information of available 2D precodings can be transmitted in the form of a table identical or similar to that of FIG. 8 described above. For example, the combination information of available 2D precodings can be 2DPreIndex, U T , and U FEach combination can be included. At this time, 2DPreIndex is U T and U F It can mean the index of combinations of . The combination information of available 2D precodings can be composed of N_2D_Precoding elements, and N_2D_Precoding is N_2D_Precoding U T and U F This may mean that a combination of U is possible. For example, U T and U F can be one of the identity matrix, the DFT, the WH, or the SWH. The combination information of the available 2D precodings can be included in a higher layer message (e.g., an RRC message). The combination information of the available 2D precodings may be preset (or installed) in the terminal. Therefore, the base station may not need to transmit the combination information of the available 2D precodings to the terminal. However, the above-described example is only one example of the combination information of the available 2D precodings, and the combination information of the available 2D precodings is not limited to the above-described example.

[0136] In step 1320, the terminal can identify whether the 2D precoding trigger condition is satisfied. For example, the selection operation of 2D precoding (e.g., step 1330 below) may be performed periodically or may be performed when a specific condition is satisfied based on a preset value. In one embodiment, the selection operation of 2D precoding of the terminal may be set to be performed periodically. For example, the terminal may perform the selection operation of 2D precoding every 10 ms. At this time, the value (e.g., N_Period_2Dprecoding) regarding the 2D precoding selection operation period of the terminal may be set or indicated from a higher layer (e.g., RRC layer or MAC layer) or may be a value preset (or installed) in the terminal. In one embodiment, the selection operation of the terminal 2D precoding may be set to be performed when a specific event occurs. For example, the terminal may estimate a Doppler shift value (e.g., f) based on a pilot symbol received from a base station. D ) is the threshold (e.g., f D,Th ) is greater than or equal to 2D, a 2D precoding selection operation can be performed. For example, f D >f D,Th In this case, a 2D precoding selection operation can be performed. At this time, a threshold value (e.g., f D,Th ) can be calculated based on the carrier frequency and target velocity. In addition, a threshold value (e.g., f D,Th) may be set or indicated from a higher layer (e.g., RRC layer or MAC layer) or may be a value preset (or installed) in the terminal. In one embodiment, the terminal may request the base station to transmit pilot symbols in order to determine the characteristics of the channel with the base station. The operation of requesting pilot symbols may be for determining statistical channel characteristics rather than instantaneous channel characteristics. In addition, since the request for pilot symbols is not for data decoding, overhead may not occur even if transmitted in units of hundreds of milliseconds to seconds. In this case, the request for pilot symbols may be transmitted through a control channel (e.g., PUCCH). In addition, the pilot symbols may be existing reference signals (e.g., including at least one of CSI-RS or DM-RS) or newly defined pilots. For example, the newly defined pilot may include guard bands and may include consecutive pilot symbols in the time domain. Through consecutive pilot symbols in the time domain, the terminal may be able to perform more accurate channel estimation. The base station can transmit pilot symbols to the terminal based on a request for pilot symbols received from the terminal.

[0137] At step 1330, the terminal may select the optimal 2D precoding if the 2D precoding trigger condition is satisfied. At this time, the terminal may select the optimal 2D precoding based on the pilot symbol received from the base station. In one embodiment, the terminal may select the optimal 2D precoding by identifying the characteristics and complexity of the channel through the pilot symbol received from the base station. For example, the terminal may receive a pilot symbol from the base station and select the optimal 2D precoding for channel H. ft can be estimated. And the terminal can estimate the estimated channel H ft Alternatively, a preferred 2D precoding can be selected based on at least one of the computational complexities of each precoder.

[0138] In step 1340, the base station may transmit the index of the selected 2D precoding to the terminal. When the base station selects the 2D precoding, it may consider information reported by the terminal (e.g., the index of the optimal 2D precoding selected by the terminal in step 1330 described above or the index of the 2D precoding preferred by the terminal). Therefore, step 1340 may further include a procedure, after step 1330, in which the terminal reports information about the index of the 2D precoding selected by the terminal to the base station. At this time, the index value transmitted by the base station may be one of the index values ​​included in the information about the combination of 2D precodings received from the base station at step 1310. At this time, the information about the index of the 2D precoding selected by the base station may be included in at least one of upper layer signaling (e.g., RRC message or MAC signaling) or control information (e.g., DCI).

[0139] In one embodiment, the base station may include a method for indicating the 2D precoding to be used for transmission of downlink data (e.g., Indication_PDSCH_2D_precoding) in an RRC message. The base station may configure how to indicate the 2D precoding index to the terminal through the RRC message.

[0140] In one embodiment, when the base station instructs the terminal to select 2D precoding through DCI (e.g., when Indication_PDSCH_2D_precoding = {DCI}), the base station may transmit DCI including index information of the selected 2D precoding (e.g., Index_PDSCH_2D_precoding_DCI = {1, ..., N_2D_Precoding}) to the terminal. After receiving the DCI from the base station, the terminal may decode the Index_2D_precoding_DCI value to confirm the index of the 2D precoding selected by the base station. In addition, when the base station instructs the terminal to select 2D precoding through DCI, dynamic switching may be possible between OFDM and OTFS applying the 2D precoding selected by the base station. The base station can configure which mode (e.g., OFDM or OTFS with 2D precoding selected by the base station) it will switch to via an RRC message (e.g., Cont_Util_PDSCH_2D_precoding = {Enabled, Disabled}). For example, if Cont_Util_PDSCH_2D_precoding = Enabled, it can mean that the index of the selected 2D precoding is used until a newly updated index of 2D precoding is received via the next DCI. On the other hand, if Cont_Util_PDSCH_2D_precoding = Disabled, it can mean that the index of the selected 2D precoding is valid during a valid time (e.g., N_valid_time=10ms) after receiving the DCI, and after the valid time, it can change to the previously used OFDM.

[0141] In one embodiment, when the base station indicates the index of the selected 2D precoding to the terminal via MAC signaling (e.g., MAC CE) (e.g., when Indication_PDSCH _2D_precoding = {MAC}), the base station may select one of the N_2D_Precoding indices and transmit information about the index of the selected 2D precoding to the terminal via MAC signaling (e.g., Index_PDSCH_2D_precoding_MAC={1, ..., N_2D_Precoding}). In addition, when the base station indicates the selected 2D precoding to the terminal via MAC signaling, the MAC CE may be used to semi-statically switch between OFDM and OTFS applying the 2D precoding selected by the base station.

[0142] In one embodiment, when the base station transmits the index of the selected 2D precoding to the terminal via an RRC message (e.g., when Indication_PDSCH_2D_precoding = {RRC}), the base station may inform the terminal of information about the index of the selected 2D precoding via an RRC message (e.g., PDSCH-Config.2DPrecoding ={1, 2, ..., N_2D_Precoding}). For example, the base station may set the index of the 2D precoding to be used at the time of initial access (e.g., Msg 3 in a random access procedure) to the terminal via an RRC message (e.g., RACH-ConfigCommon.msg3-2DPrecoding ={1, 2, ..., N_2D_Precoding}). In addition, the base station can set the index of the 2D precoding to be used in the PUSCH to the terminal via an RRC message (e.g., PUSCH-Config.2DPrecoding ={1, 2, ..., N_2D_Precoding}). In one embodiment, when the index of the selected 2D precoding is indicated to the terminal via the RRC message, OFDM can be indicated if the index value is 1, and in other cases, 2D precoding can be indicated to be applied. In addition, when the base station indicates the selected 2D precoding to the terminal via the RRC message, it can be statically switched between OFDM and OTFS applying the 2D precoding selected by the base station via the RRC message.

[0143] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0144] FIG. 14 illustrates the operation sequence of 2D precoding selection according to embodiments of the present disclosure.

[0145] Referring to FIG. 14, the procedure for selecting a preferred 2D precoding based on the pilot symbol received by the terminal from the base station in step 1330 described above can be specifically described. However, in the following embodiments, the operation of the terminal may include the same or similar terminal operation as the operation of the base station in FIG. 10 described above.

[0146] At step 1410, the terminal receives a pilot symbol from the base station on channel H. ft can be estimated. For example, the terminal is H ft Channel estimation using the LS or MMSE method can be performed on REs containing pilot symbols for estimation. The terminal can perform interpolation on the remaining REs. Therefore, as described above in Figure 9, newly defined pilot symbols can be used to improve the accuracy of channel estimation.

[0147] At step 1420, the terminal transmits the time-frequency domain channel H ft For each 2D precoding combination (e.g., step 1310) received from the base station, inverse 2D precoding can be performed for each 2D precoding combination. The terminal can perform inverse 2D precoding for each 2D precoding combination. The terminal can perform H, which is a channel transfer function (or function) of the xy domain channel. xy can be obtained. H, which is the channel transfer function (or function) of the xy domain channel. xy Is It can be expressed as follows. For example, as in the case of OTFS, M-point DFT U F =F M , and N-point IDFT U F = If , the estimated H ft When SFFT is applied to , it is transformed into a delayed-Doppler grid and channels in the delayed-Doppler domain (e.g., HDD ) can be calculated. For example, the estimated H ft When IFFT (left) and IWHT (right) are applied to , it is transformed into a delay-sequence grid and channels in the delay-sequence domain (e.g., H DS ) can be calculated.

[0148] At step 1430, the terminal is an M×N matrix H xy By performing clustering on , the number of clusters and the variance of each cluster can be calculated. For example, the terminal is an M×N matrix H xy Up to M data groups can be identified based on the x-axis. In addition, the terminal is an M×N matrix H xy Up to N data groups can be identified based on the y-axis. And the terminal can calculate the variance for each of the multiple data groups.

[0149] At step 1440, the terminal can measure the sparsity of the x-axis and y-axis respectively through the number of clusters and the dispersion of each cluster. The terminal selects the optimal 2D precoding (U) by weighting the number of clusters, the dispersion of each cluster, and the computational complexity according to each precoder among the N_2D_Precoding candidates (e.g., the combinations of the available 2D precodings of step 1310 described above). T ,U F ) can be selected. At this time, the optimal 2D precoding may be a 2D precoding with a small number of clusters among the N_2D_Precoding candidates and a low sparsity and complexity, which may be a 2D precoding preferred by the terminal.

[0150] At step 1450, the terminal can transmit information about the index of the selected 2D precoding to the base station via PUSCH or PUCCH. The base station can select an optimal 2D precoding by considering the information about the index of the 2D precoding preferred by the terminal. In one embodiment, if the base station has a preferred 2D precoding index that has already been calculated for the terminal within a specific time period, the base station can indicate to the terminal that it prefers the index of the 2D precoding preferred by the base station instead of the index of the 2D precoding preferred by the terminal. On the other hand, if the base station has not already calculated the index of the 2D precoding for the terminal within a specific time period, the base station can select the index of the 2D precoding preferred by the terminal and indicate it to the terminal.

[0151] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0152] FIG. 15 illustrates a 2D precoding selection procedure of a base station according to embodiments of the present disclosure.

[0153] Referring to FIG. 15, a 2D precoding configuration and signaling method may be described when a base station triggers a 2D precoding selection procedure according to the above-described embodiments. Accordingly, in the following embodiments, the base station may further perform the operations described in the above-described embodiments (e.g., FIGS. 6 to 12 ), and redundant descriptions may be omitted.

[0154] At step 1510, the base station can identify the terminal's 2D precoding capability information. For example, the base station can confirm the terminal's 2D precoding capability through a higher-layer message (e.g., an RRC message). At this time, the terminal's 2D precoding capability can indicate whether the terminal supports 2D precoding.

[0155] At step 1520, if the terminal supports 2D precoding, the base station can select 2D precoding based on channel information with the terminal. For example, the 2D precoding selection operation can be performed periodically or when a specific condition is satisfied based on a preset value. The base station can select the optimal 2D precoding if the 2D precoding trigger condition is satisfied. At this time, the base station can estimate the channel with the terminal based on the pilot symbol received from the terminal. Therefore, the base station can select the optimal 2D precoding based on the estimated channel.

[0156] At step 1530, the base station can transmit an index indicating 2D precoding to the terminal. At this time, the index value transmitted to the terminal can be included in at least one of upper layer signaling (e.g., RRC message or MAC signaling) or control information (e.g., DCI). Then, the base station can transmit downlink data with 2D precoding corresponding to the index to the terminal. Alternatively, the base station can receive uplink data with 2D precoding corresponding to the index from the base station.

[0157] According to the embodiments described above, the base station can reduce the channel sparsity experienced by data (e.g., uplink data or downlink data) by selecting an appropriate 2D precoding. Therefore, there may be benefits in terms of channel estimation and the advantage of reducing receiver complexity. Furthermore, the embodiments of the present disclosure consider not only channel characteristics but also the complexity resulting from multiplying 2D precodings, and thus, if the channel characteristics are similar, it may be possible to select a 2D precoding that can further reduce complexity.

[0158] Of course, the above examples are not limited. Accordingly, at least one of the above-described actions may be omitted, or at least one new action may be added and organically combined with the above-described actions to perform the above-described actions. Furthermore, some of the above-described actions may be combined into at least one action or separated into two or more actions.

[0159] According to various embodiments of the present disclosure, a method performed by a base station of a wireless communication system comprises the steps of: identifying capability information regarding 2D (dimensional) precoding of a terminal; selecting the 2D precoding based on channel information with the terminal when the terminal supports the 2D precoding; and transmitting an index indicating the 2D precoding to the terminal, wherein the 2D precoding may be applied to at least one of an uplink signal and a downlink signal.

[0160] In one embodiment, the step of identifying capability information regarding the 2D precoding includes the step of transmitting an RRC (radio resource control) message for requesting the capability information to the terminal, and the step of receiving the capability information from the terminal, wherein the capability information may include information regarding whether the terminal supports the 2D precoding.

[0161] In one embodiment, the method further comprises a step of transmitting information about a combination of 2D precodings to the terminal, wherein the information about the combination of 2D precodings may include information about a combination of a precoding matrix according to a frequency domain and a precoding matrix according to a time domain.

[0162] In one embodiment, the method may further include the steps of transmitting downlink control information (DCI) for requesting a pilot symbol to the terminal, receiving the pilot symbol from the terminal based on the DCI, and estimating a channel with the terminal based on the pilot symbol.

[0163] In one embodiment, the selection of the 2D precoding may be performed periodically or when a Doppler shift value associated with the terminal is greater than or equal to a threshold value.

[0164] In one embodiment, the method further comprises a step of transmitting information on an application method of the 2D precoding to the terminal, wherein a first method of the application methods is that the 2D precoding is applied until downlink control information (DCI) including an index indicating 2D precoding to be applied after the 2D precoding is received, and a second method of the application methods is that the 2D precoding can be applied only within a valid time of the 2D precoding.

[0165] According to various embodiments of the present disclosure, a method performed by a terminal of a wireless communication system comprises the steps of: identifying capability information regarding 2D (dimensional) precoding of a base station; selecting a first 2D precoding based on channel information with the base station when the base station supports the 2D precoding; transmitting information regarding the first 2D precoding to the base station; and receiving an index indicating a second 2D precoding from the base station, wherein the 2D precoding may be applied to at least one of an uplink signal and a downlink signal.

[0166] In one embodiment, the method further comprises the step of receiving information about a combination of 2D precodings from the base station, wherein the information about the combination of 2D precodings may include information about a combination of a precoding matrix according to a frequency domain and a precoding matrix according to a time domain.

[0167] In one embodiment, the method may further include the steps of receiving a pilot symbol from the base station, and estimating a channel with the base station based on the pilot symbol.

[0168] In one embodiment, the selection of the 2D precoding may be performed periodically or when a Doppler shift value associated with the terminal is greater than or equal to a threshold value.

[0169] According to various embodiments of the present disclosure, a base station of a wireless communication system comprises a transceiver, and at least one control unit connected to the transceiver, wherein the at least one control unit is configured to identify capability information regarding 2D (dimensional) precoding of a terminal, select the 2D precoding based on channel information with the terminal when the terminal supports the 2D precoding, and transmit an index indicating the 2D precoding to the terminal, wherein the 2D precoding is applied to at least one of an uplink signal and a downlink signal, and the second 2D precoding may be determined based on the first 2D precoding.

[0170] In one embodiment, the at least one control unit is configured to transmit an RRC (radio resource control) message for requesting the capability information to the terminal and to receive the capability information from the terminal, wherein the capability information may include information regarding whether the terminal supports the 2D precoding.

[0171] In one embodiment, the at least one control unit is further configured to transmit information regarding a combination of 2D precodings to the terminal, wherein the information regarding the combination of 2D precodings may include information regarding a combination of a precoding matrix according to a frequency domain and a precoding matrix according to a time domain.

[0172] In one embodiment, the at least one control unit may be further configured to transmit downlink control information (DCI) for requesting a pilot symbol to the terminal, receive the pilot symbol from the terminal based on the DCI, and estimate a channel with the terminal based on the pilot symbol.

[0173] In one embodiment, the selection of the 2D precoding may be performed periodically or when a Doppler shift value associated with the terminal is greater than or equal to a threshold value.

[0174] In one embodiment, the at least one control unit further includes a step of transmitting information on an application method of the 2D precoding to the terminal, wherein a first method of the application methods is that the 2D precoding is applied until downlink control information (DCI) including an index indicating 2D precoding to be applied after the 2D precoding is received, and a second method of the application methods is that the 2D precoding can be applied only within a valid time of the 2D precoding.

[0175] According to various embodiments of the present disclosure, a terminal of a wireless communication system comprises a transceiver, and at least one control unit connected to the transceiver, wherein the at least one control unit is configured to identify capability information regarding 2D (dimensional) precoding of a base station, select a first 2D precoding based on channel information with the base station when the base station supports the 2D precoding, transmit information regarding the first 2D precoding to the base station, and receive an index indicating a second 2D precoding from the base station, wherein the 2D precoding is applied to at least one of an uplink signal and a downlink signal, and the second 2D precoding may be determined based on the first 2D precoding.

[0176] In one embodiment, the at least one control unit is further configured to receive information about a combination of 2D precodings from the base station, wherein the information about the combination of 2D precodings may include information about a combination of a precoding matrix according to a frequency domain and a precoding matrix according to a time domain.

[0177] In one embodiment, the at least one control unit may be further configured to receive a pilot symbol from the base station and estimate a channel with the base station based on the pilot symbol.

[0178] In one embodiment, the selection of the 2D precoding may be performed periodically or when a Doppler shift value associated with the terminal is greater than or equal to a threshold value.

[0179] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0180] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

[0181] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage devices, compact disc-ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage devices, magnetic cassettes, or may be stored in memories formed by a combination of some or all of these. In addition, each configuration memory may include multiple copies.

[0182] Additionally, the program may be stored on an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present disclosure.

[0183] In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed singularly or plurally, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in plural may be composed of singular elements, or components expressed in singular may be composed of plural elements.

[0184] While the detailed description of this disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the described embodiments, but should be defined not only by the scope of the claims described below, but also by equivalents thereof.

Claims

1. A method performed by a base station of a wireless communication system, A step of identifying capability information regarding 2D (dimensional) precoding of a terminal; If the terminal supports the 2D precoding, a step of selecting the 2D precoding based on channel information with the terminal; and A step of transmitting an index indicating the above 2D precoding to the terminal, A method wherein the above 2D precoding is applied to at least one of an uplink signal or a downlink signal.

2. In the first paragraph, the step of identifying capability information regarding the 2D precoding is: A step of transmitting an RRC (radio resource control) message to the terminal to request the above capability information; and A step of receiving the capability information from the terminal is included, A method wherein the above capability information includes information regarding whether the terminal supports the 2D precoding.

3. In the first paragraph, the method, Further comprising a step of transmitting information about a combination of 2D precoding to the terminal, A method wherein the information regarding the combination of the above 2D precoding includes information regarding the combination of a precoding matrix according to the frequency domain and a precoding matrix according to the time domain.

4. In the first paragraph, the method, A step of transmitting DCI (downlink control information) for requesting a pilot symbol to the terminal; A step of receiving the pilot symbol from the terminal based on the DCI; and Further comprising a step of estimating a channel with the terminal based on the pilot symbol, A method wherein the selection of the above 2D precoding is performed periodically or when a Doppler shift value associated with the terminal is greater than a threshold value.

5. In the first paragraph, the method, Further comprising a step of transmitting information on a method of applying the above 2D precoding to the terminal, A first method among the above application methods is that the 2D precoding is applied until a DCI including an index indicating 2D precoding to be applied after the 2D precoding is received, A second method among the above application methods is a method in which the 2D precoding is applied only within the effective time of the 2D precoding.

6. In a method performed by a terminal of a wireless communication system, A step of identifying capability information regarding 2D (dimensional) precoding of a base station; A step of selecting a first 2D precoding based on channel information with the base station when the base station supports the 2D precoding; a step of transmitting information about the first 2D precoding to the base station; and A step of receiving an index indicating a second 2D precoding from the base station, The above 2D precoding is applied to at least one of the uplink signal or the downlink signal, A method wherein the second 2D precoding is determined based on the first 2D precoding.

7. In the 6th paragraph, the method, Further comprising a step of receiving information about a combination of 2D precoding from the base station, A method wherein the information regarding the combination of the above 2D precoding includes information regarding the combination of a precoding matrix according to the frequency domain and a precoding matrix according to the time domain.

8. In paragraph 6, the method, A step of receiving a pilot symbol from the base station; and Further comprising a step of estimating a channel with the base station based on the pilot symbol, A method wherein the selection of the above 2D precoding is performed periodically or when a Doppler shift value associated with the terminal is greater than a threshold value.

9. In the base station of a wireless communication system, Transmitter and receiver; and At least one control unit connected to the above transceiver unit, At least one control unit: Identify the capability information regarding the 2D (dimensional) precoding of the terminal, If the terminal supports the 2D precoding, the 2D precoding is selected based on channel information with the terminal, and It is set to transmit an index indicating the above 2D precoding to the terminal, A base station, wherein the above 2D precoding is applied to at least one of an uplink signal or a downlink signal.

10. In the 9th paragraph, at least one control unit, Transmitting an RRC (radio resource control) message to the private terminal to request the above capability information, and It is set to receive the above capability information from the above terminal, A base station, wherein the above capability information includes information regarding whether the terminal supports the 2D precoding.

11. In the 9th paragraph, at least one control unit, It is further set to transmit information about the combination of 2D precoding to the terminal, A base station, wherein the information regarding the combination of the above 2D precoding includes information regarding the combination of a precoding matrix according to the frequency domain and a precoding matrix according to the time domain.

12. In the 9th paragraph, at least one control unit, Transmitting DCI (downlink control information) to the terminal to request a pilot symbol, Receive the pilot symbol from the terminal based on the DCI, and It is further set to estimate a channel with the terminal based on the above pilot symbol, A base station, wherein the selection of the above 2D precoding is performed periodically or when a Doppler shift value related to the terminal is greater than a threshold value.

13. In the 9th paragraph, at least one control unit, It is further set to transmit information on the method of applying the above 2D precoding to the terminal, A first method among the above application methods is that the 2D precoding is applied until a DCI including an index indicating 2D precoding to be applied after the 2D precoding is received, A second method among the above application methods is a base station in which the 2D precoding is applied only within the effective time of the 2D precoding.

14. In the terminal of a wireless communication system, Transmitter and receiver; and At least one control unit connected to the above transceiver unit, At least one control unit: Identify the capability information regarding the 2D (dimensional) precoding of the base station, If the base station supports the 2D precoding, the first 2D precoding is selected based on channel information with the base station, Transmitting information about the first 2D precoding to the base station, and It is set to receive an index indicating a second 2D precoding from the base station, The above 2D precoding is applied to at least one of the uplink signal or the downlink signal, A terminal wherein the second 2D precoding is determined based on the first 2D precoding.

15. In paragraph 14, at least one control unit, It is further configured to receive information about the combination of 2D precoding from the base station, A terminal, wherein the information regarding the combination of the above 2D precoding includes information regarding the combination of a precoding matrix according to the frequency domain and a precoding matrix according to the time domain.

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