Method and apparatus for reducing peak-to-average power ratio in wireless communication system supporting multiple input multiple output

Abstract

The present disclosure relates to a method and an apparatus for efficiently reducing a PAPR in a wireless communication system supporting MIMO. A PAPR reduction method performed by a base station in a wireless communication system supporting MIMO, according to an embodiment of the present disclosure, comprises the steps of: identifying an operation mode for generating a peak cancellation signal (PCS) for reducing the PAPR; identifying a null space which is a spatial resource in a MIMO channel and in which the PCS is placed, during generation of the PCS on the basis of the operation mode; applying the PCS for PAPR reduction to a signal to be transmitted; and transmitting, to a UE, the transmission signal to which the PCS is applied.

Description

Method and device for reducing peak power to average power ratio in a wireless communication system supporting multiple inputs and multiple outputs

[0001] The present disclosure relates to a method and apparatus for reducing PAPR in a wireless communication system.

[0002] Looking back at the evolution of wireless communication over successive generations, technologies have primarily been developed for human-facing services such as voice, multimedia, and data. With the commercialization of 5G (5th-generation) communication systems, an explosive increase in connected devices is expected to be connected to communication networks. Examples of networked objects include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction equipment, and factory equipment. Mobile devices are expected to evolve into diverse form factors, including augmented reality glasses, virtual reality headsets, and holographic devices. In the 6th-generation (6G) era, efforts are being made to develop improved 6G communication systems to connect hundreds of billions of devices and objects and provide diverse services. For this reason, 6G communication systems are often referred to as "beyond 5G."

[0003] The 6G communication system, expected to be realized around 2030, will have a maximum transmission speed of terabytes per second (i.e., 1,000 gigabits per second) and a wireless latency of 100 microseconds (μsec). In other words, compared to 5G, the transmission speed in a 6G communication system will be 50 times faster, while the wireless latency will be reduced to one-tenth.

[0004] To achieve these high data rates and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz band (e.g., from 95 gigahertz (GHz) to 3 terahertz (THz)). Compared to the millimeter wave (mmWave) band introduced in 5G, the terahertz band is expected to experience more severe path loss and atmospheric absorption, making it more crucial to ensure signal reach, or coverage, in this band. Key technologies to ensure coverage include radio frequency (RF) components, antennas, new waveforms that offer better coverage than OFDM (orthogonal frequency division multiplexing), beamforming, and multiple antenna transmission technologies such as massive multiple-input and multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing using orbital angular momentum (OAM), and reconfigurable intelligent surfaces (RIS) are being discussed to improve the coverage of terahertz band signals.

[0005] In addition, in order to improve frequency efficiency and system network, 6G communication systems are developing full duplex technology that utilizes the same frequency resources for uplink and downlink at the same time; network technology that integrates satellites and high-altitude platform stations (HAPS); network structure innovation technology that supports mobile base stations and enables optimization and automation of network operation; dynamic spectrum sharing technology through collision avoidance based on spectrum usage prediction; AI-based communication technology that utilizes artificial intelligence (AI) from the design stage and internalizes end-to-end AI support functions to realize system optimization; and next-generation distributed computing technology that realizes services with complexity that exceeds the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources (mobile edge computing (MEC), cloud, etc.). In addition, efforts are being made to further strengthen connectivity between devices, further optimize networks, promote softwareization of network entities, and increase the openness of wireless communications through the design of new protocols to be used in 6G communication systems, the implementation of hardware-based security environments, the development of mechanisms for the safe use of data, and the development of technologies for maintaining privacy.

[0006] Research and development of these 6G communication systems are expected to enable a new level of hyper-connected experience through the hyper-connectivity of 6G communication systems, which encompass not only connections between things but also connections between people and things. Specifically, 6G communication systems are expected to enable services such as truly immersive extended reality (Truly Immersive XR), high-fidelity mobile holograms, and digital replicas. Furthermore, services such as remote surgery, industrial automation, and emergency response, which are provided through 6G communication systems through enhanced security and reliability, will find application in diverse fields such as industry, medicine, automobiles, and home appliances.

[0007] The present disclosure provides a method and device for efficiently reducing PAPR in a wireless communication system supporting MIMO.

[0008] In addition, the present disclosure provides a method and device for efficiently reducing PAPR by using null space in a wireless communication system supporting MIMO.

[0009] In addition, the present disclosure provides a method and device for efficiently reducing PAPR by using feedback information from a UE in a wireless communication system supporting MIMO.

[0010] According to an embodiment of the present disclosure, a method for reducing a peak-to-average power ratio (PAPR) performed by a base station in a wireless communication system supporting multiple input multiple output (MIMO) includes: a process of identifying an operation mode for generating a peak cancelling signal (PCS) for reducing the PAPR; a process of identifying a null space, which is a spatial resource in which the PCS is placed in a MIMO channel, when generating the PCS based on the operation mode; a process of applying the PCS for reducing the PAPR to a signal to be transmitted; and a process of transmitting a transmission signal to which the PCS is applied to a UE (user equipment).

[0011] In addition, according to an embodiment of the present disclosure, in a wireless communication system supporting MIMO, a base station includes a processor configured to identify an operation mode for generating a peak cancellation signal (PCS) for reducing PAPR, a transceiver, and, when generating the PCS based on the operation mode, identify a null space, which is a spatial resource in which the PCS is arranged in a MIMO channel, apply the PCS for reducing the PAPR to a signal to be transmitted, and transmit a transmission signal to which the PCS is applied to a UE through the transceiver.

[0012] Also, according to an embodiment of the present disclosure, in a wireless communication system supporting MIMO, a UE includes a transceiver, and a processor configured to receive, from a base station through the transceiver, configuration information for transmitting feedback information related to generation of a peak cancellation signal (PCS) for reducing PAPR by using a null space in a MIMO channel, transmit the feedback information related to generation of the PCS to the base station through the transceiver based on the configuration information, and receive, from the base station through the transceiver, a signal to which the PCS is applied based on the feedback information.

[0013] Figure 1 is a diagram showing the basic structure of the time-frequency domain, which is a radio resource domain in which data or control channels are transmitted in the LTE system.

[0014] Figure 2 is a diagram illustrating a PDCCH, a downlink physical channel through which DCI is transmitted in an LTE system.

[0015] Figure 3 is a diagram showing an example of a basic unit of time and frequency resources that constitute a downlink control channel that can be used in a 5G system.

[0016] Figure 4 is a diagram illustrating an example of a control area (CORESET) in which a downlink control channel is transmitted in a 5G system.

[0017] FIG. 5 is a diagram illustrating an example of a configuration for a downlink RB structure in a 5G system.

[0018] FIG. 6a is a diagram showing an example of a DL MU-MIMO environment in a wireless communication system.

[0019] Figure 6b is a diagram showing an example of a DL SU-MIMO environment in a wireless communication system.

[0020] FIG. 6c is a diagram for explaining a method for reducing PAPR in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0021] FIG. 7 is a diagram illustrating a method in which a base station uses an SRS received from a UE for PCS generation in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0022] FIG. 8 is a diagram illustrating a method in which a base station uses feedback information received from a UE to generate a PCS in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0023] FIG. 9 is a diagram illustrating a method for a base station to generate a PCS in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0024] FIG. 10 is a diagram illustrating an operation mode control in which a base station applies PCS to a transmission signal in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0025] FIG. 11 is a diagram illustrating a method for a base station to generate a precoding signal with PCS applied in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0026] FIG. 12 is a diagram illustrating the operation of a base station for generating PCS when the base station receives a Persistent SRS or Semi-persistent SRS from a terminal in a wireless communication system supporting MIMO according to an embodiment of the present disclosure.

[0027] Fig. 13 is a diagram showing the timing for transmitting and receiving signals of the time axis required in the base station operation of Fig. 12.

[0028] FIG. 14 is a diagram illustrating the operation of a base station for generating PCS when the base station receives an Aperiodic SRS from a terminal in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0029] FIG. 15 is a diagram showing an example of a method for applying PCS based on periodic NI feedback in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0030] FIG. 16 is a diagram showing an example of a method for applying PCS based on aperiodic NI feedback in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0031] FIG. 17 is a diagram showing UE operation in a PCS application method based on NI feedback in a wireless communication system supporting MIMO according to an embodiment of the present disclosure;

[0032] FIG. 18 is a diagram illustrating a method in which a UE performs NI Feedback based on a PMI codebook for PCS generation at a base station of a wireless communication system according to an embodiment of the present disclosure;

[0033] FIG. 19 is a diagram illustrating a method for performing NI Feedback based on rules for Quantization and Compression by a UE for PCS generation at a base station of a wireless communication system according to an embodiment of the present disclosure;

[0034] FIG. 20 is a diagram showing an example configuration of a base station in a wireless communication system according to an embodiment of the present disclosure; and

[0035] FIG. 21 is a diagram showing an example configuration of a UE in a wireless communication system according to an embodiment of the present disclosure.

[0036] The operating principles of the present disclosure are described in detail below with reference to the attached drawings. In the following description of the present disclosure, detailed descriptions of related known functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, the terms described below are defined based on the functions of the present disclosure and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the overall content of this specification.

[0037] For the same reason, some components in the attached drawings are omitted or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect its actual size. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0038] The advantages and features of the present disclosure, and methods for achieving them, will become clearer with reference to the embodiments described below in detail with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. The various embodiments are provided to ensure that the present disclosure is complete and to fully convey the scope of the present disclosure to those skilled in the art, and the present disclosure is defined solely by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0039] At this time, it will be understood that each block of the processing flow diagrams and combinations of the flow diagrams can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flow diagram block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flow diagram block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0040] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0041] The term "~unit" used in various embodiments of the present disclosure refers to a software or hardware component, and the "~unit" performs certain roles. However, the "~unit" is not limited to software or hardware. The "~unit" may be configured to reside on an addressable storage medium and may be configured to regenerate one or more processors. Thus, as an example, the "~unit" includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functionality provided within the components and "~units" may be combined into a smaller number of components and "~units" or further separated into additional components and "~units." In addition, the components and "~units" may be implemented to regenerate one or more CPUs within a device or a secure multimedia card. Additionally, in various embodiments of the present disclosure, '~bu' may include one or more processors.

[0042] In this disclosure, phrases such as "A and / or B", "A or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", and "at least one of A, B, or C" can each include any one of the items listed together in that phrase, or all possible combinations thereof. Terms such as "first", "second", or "first" or "second" may be used merely to distinguish the corresponding component from other corresponding components and do not limit the corresponding components in any other respect (e.g., importance or order).

[0043] In embodiments of the present disclosure, a user equipment (UE) may be a terminal, a mobile station (MS), a cellular phone, a smartphone, a computer, or any other electronic device capable of performing a communication function. In addition, a base station (BS) is a network entity that performs resource allocation to a UE, and may be at least one of a Node B, an eNB (eNode B), a gNB (gNode B), a wireless access unit, a base station controller, or a node on a network.

[0044] Furthermore, the various embodiments of the present disclosure described below may be applied to other communication systems having similar technical backgrounds or channel configurations. Furthermore, the various embodiments of the present disclosure may be applied to other communication systems with some modifications, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure.

[0045] In specifically describing various embodiments of the present disclosure, the communication system may utilize a wireless communication system, for example, the LTE system proposed by 3GPP (3rd generation partnership project long term evolution), a wireless communication standard standardization organization, or the 5G communication system based on NR (New RAN) communication standard. In addition, it may be applied to other communication systems with similar technical backgrounds with slight modifications within a range that does not significantly deviate from the scope of the present disclosure, and this will be possible at the discretion of a person skilled in the technical field of the present disclosure. For the convenience of the following description, some terms and names defined in the 3GPP standard may be used. However, the present disclosure is not limited to the above terms and names, and can be equally applied to systems that comply with other standards. Wireless communication systems have evolved from providing initial voice-oriented services to broadband wireless communication systems that provide high-speed, high-quality packet data services, such as communication standards such as 3GPP's HSPA (High Speed ​​Packet Access), LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2's HRPD (High Rate Packet Data), UMB (Ultra Mobile Broadband), and IEEE's 802.16e.

[0046] As a representative example of the above broadband wireless communication system, the LTE system adopts the OFDM (Orthogonal Frequency Division Multiplexing) method in the downlink (DL; DownLink) and the SC-FDMA (Single Carrier Frequency Division Multiple Access) method in the uplink (UL; UpLink). The uplink refers to a wireless link in which a terminal (UE; User Equipment or MS; Mobile Station) transmits data or control signals to a base station (eNode B or BS; Base Station), and the downlink refers to a wireless link in which a base station transmits data or control signals to a terminal. The above multiple access method typically distinguishes the data or control information of each user by allocating and operating the time-frequency resources to be used to transmit data or control information to each user so that they do not overlap, that is, so as to achieve orthogonality.

[0047] As the future communications system beyond LTE, 5G communication systems must be able to freely reflect the diverse needs of users and service providers. Therefore, they must support services that simultaneously satisfy these diverse requirements. Services being considered for 5G communication systems include enhanced Mobile Broadband (eMBB), massive Machine Type Communication (mNTC), and Ultra Reliability Low Latency Communication (URLLC).

[0048] eMBB aims to provide data transmission rates that are significantly higher than those supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, eMBB must be able to support a peak data rate of 20 Gbps in the downlink and a peak data rate of 10 Gbps in the uplink from the perspective of a single base station. Furthermore, 5G communication systems must provide not only the peak data rate but also the increased user-perceived data rate for terminals. To meet these requirements, improvements in various transmission and reception technologies, including improved multi-antenna (MIMO) transmission technology, are required. Furthermore, while current LTE transmits signals using a maximum transmission bandwidth of 20 MHz in the 2 GHz band, 5G communication systems can meet the data transmission rates required by 5G communication systems by utilizing a wider frequency bandwidth than 20 MHz in the 3-6 GHz or higher 6 GHz band.

[0049] At the same time, mMTC is being considered to support application services such as the Internet of Things (IoT) in 5G communication systems. To efficiently provide the Internet of Things, mMTC requires support for large-scale terminal connection within a cell, improved terminal coverage, improved battery life, and reduced terminal costs. The Internet of Things provides communication functions by attaching various sensors and various devices, so a large number of terminals (e.g., 1,000,000 terminals / km) are required within a cell. 2) must be able to support. Furthermore, terminals supporting mMTC are likely to be located in shadow areas not covered by cells, such as basements of buildings, due to the nature of the service, and therefore require wider coverage than other services provided by 5G communication systems. Terminals supporting mMTC must be composed of low-cost terminals, and since it is difficult to frequently replace the terminal's battery, a very long battery life time, such as 10 to 15 years, is required.

[0050] Finally, URLLC refers to a cellular-based wireless communication service used for a specific purpose (mission-critical). For example, services such as remote control of robots or machinery, industrial automation, unmanned aerial vehicles, remote health care, and emergency alerts can be considered. Therefore, the communication provided by URLLC must provide very low latency and very high reliability. For example, a service supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds and, at the same time, must have a 10 -5 The following packet error rate (PER) requirements apply. Therefore, for services supporting URLLC, 5G systems must provide a smaller Transmit Time Interval (TTI) than other services, while simultaneously allocating a wide range of resources in the frequency band to ensure communication link reliability.

[0051] The three 5G services—eMBB, URLLC, and mMTC—can be multiplexed and transmitted within a single system. To meet the diverse requirements of each service, different transmission and reception techniques and parameters can be used.

[0052] Below, the frame structure of the LTE and LTE-A systems will be described in more detail with reference to drawings.

[0053] Figure 1 is a diagram showing the basic structure of the time-frequency domain, which is a radio resource domain in which data or control channels are transmitted in an LTE system.

[0054] In Figure 1, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM symbol. (101) OFDM symbols are grouped to form one slot (102), and two slots are grouped to form one subframe (103). The length of the slot is 0.5 ms, and the length of the subframe is 1.0 ms. In addition, the radio frame (104) is a time domain unit consisting of 10 subframes. The minimum transmission unit in the frequency domain is a subcarrier, and the bandwidth of the entire system transmission bandwidth is the total It consists of (105) subcarriers. The basic unit of resources in the time-frequency domain is the resource element (RE; Resource Element, 106), which can be expressed by the OFDM symbol index and subcarrier index. The resource block (RB; Resource Block or PRB; Physical Resource Block, 107) is a resource block in the time domain. (101) consecutive OFDM symbols in the frequency domain. It is defined as (108) consecutive subcarriers. Therefore, one RB (108) is x It consists of RE(106). In general, the minimum transmission unit of data is the RB unit. In LTE system, the above is generally =7, =12, and and is proportional to the bandwidth of the system transmission band.

[0055] Next, we will specifically explain downlink control information (DCI) in LTE and LTE-A systems.

[0056] In the LTE system, scheduling information for downlink or uplink data is transmitted from the base station to the terminal via DCI. DCI defines various formats, and the DCI format is applied and operated according to various factors such as whether the scheduling information is for uplink or downlink data, whether it is compact DCI with small control information, whether it applies spatial multiplexing using multiple antennas, and whether it is DCI for power control. For example, DCI format 1, which is scheduling control information for downlink data, is configured to include at least the following control information.

[0057] - Resource allocation type 0 / 1 flag: Notifies whether the resource allocation method is type 0 or type 1. Type 0 allocates resources in units of RBG (resource block group) using a bitmap method. In the LTE system, the basic unit of scheduling is an RB (resource block) expressed as a time and frequency domain resource, and an RBG consists of multiple RBs and becomes the basic unit of scheduling in the type 0 method. Type 1 allows a specific RB to be allocated within an RBG.

[0058] Resource block assignment: Notifies the RBs allocated for data transmission. The resources represented are determined based on system bandwidth and resource allocation method.

[0059] - Modulation and Coding Scheme (MCS): Notifies the modulation method used for data transmission and the size of the transport block, which is the data to be transmitted.

[0060] - HARQ process number: Notifies the HARQ process number.

[0061] - New data indicator: Notifies whether this is a HARQ initial transmission or a retransmission.

[0062] - Redundancy version: Notifies the redundancy version of HARQ.

[0063] - Transmit Power Control command for PUCCH (Physical Uplink Control CHannel) (TPC): Notifies a transmit power control command for PUCCH, which is an uplink control channel.

[0064] The above DCI is transmitted through the PDCCH (Physical Downlink Control CHannel), a downlink physical control channel, after going through channel coding and modulation processes.

[0065] The DCI message payload is accompanied by a CRC (Cyclic Redundancy Check), which is scrambled with an RNTI (Radio Network Temporary Identifier), which corresponds to the terminal's identification information. Different RNTIs are used depending on the purpose of the DCI message, such as UE-specific data transmission, power control command, or random access response. In other words, the RNTI is not transmitted explicitly, but is included in the CRC calculation process. When the terminal receives a DCI message transmitted on the PDCCH, it verifies the CRC using the assigned RNTI. If the CRC verification result is correct, it can be determined that the message was transmitted to that terminal.

[0066] Figure 2 is a diagram illustrating PDCCH (201), a downlink physical channel through which DCI is transmitted in an LTE system.

[0067] According to Fig. 2, PDCCH (201) is time-multiplexed with PDSCH (202), which is a data transmission channel, and transmitted across the entire system bandwidth. The area of ​​PDCCH (201) is expressed by the number of OFDM symbols, which is indicated to the terminal by CFI (Control Format Indicator) transmitted through PCFICH (Physical Control Format Indicator CHannel). By allocating PDCCH (201) to OFDM symbol at the beginning of subframe, it is possible to enable the terminal to decode the downlink scheduling assignment as quickly as possible, thereby reducing the decoding delay for DL-SCH (Downlink Shared CHannel), i.e., the overall downlink transmission delay. Since one PDCCH carries one DCI message and multiple terminals can be scheduled simultaneously for downlink and uplink, multiple PDCCHs are transmitted simultaneously within each cell. A cell-specific reference signal (CRS, 203) is used as a reference signal for decoding the PDCCH (201). The CRS (203) is transmitted in every subframe across the entire bandwidth, and scrambling and resource mapping vary depending on the cell ID. Since the CRS (203) is a reference signal commonly used by all terminals, terminal-specific beamforming cannot be used. Therefore, the multi-antenna transmission method for the LTE PDCCH is limited to open-loop transmit diversity. The number of CRS ports is implicitly known to the terminal through the decoding of the PBCH (Physical Broadcast Channel).

[0068] Resource allocation of PDCCH (201) is based on CCE (Control-Channel Element), and one CCE consists of 9 REG (Resource Element Group), i.e., a total of 36 RE (Resource Elements). The number of CCEs required for a specific PDCCH (201) can be 1, 2, 4, or 8, and this varies depending on the channel coding rate of the DCI message payload. These different numbers of CCEs are used to implement link adaptation of PDCCH (201). The UE must detect a signal without knowing information about the PDCCH (201). In LTE, a search space representing a set of CCEs is defined for blind decoding. The search space consists of multiple sets at the aggregation level (AL) of each CCE, and this is implicitly defined through a function based on the UE identity and subframe number without being explicitly signaled. Within each subframe, the terminal decodes the PDCCH (201) for all possible resource candidates that can be created from CCEs within the configured search space, and processes information declared to be valid for the terminal through CRC verification.

[0069] The search space is divided into terminal-specific search space and common search space. A certain group of terminals or all terminals can search the common search space of the PDCCH (201) to receive cell-common control information, such as dynamic scheduling or paging messages for system information. For example, scheduling allocation information for the DL-SCH for transmission of the SIB (System Information Block)-1, which includes the cell's operator information, can be received by searching the common search space of the PDCCH (201).

[0070] In the LTE system, the entire PDCCH region consists of a set of CCEs in the logical domain, and a search space exists consisting of these sets of CCEs. The search space is divided into a common search space and a terminal-specific search space. The search space for the LTE PDCCH is defined as shown in [Table 1] below.

[0071] [Table 1]

[0072]

[0073]

[0074] According to the definition of the search space for the PDCCH described in [Table 1] above, the UE-specific search space is not explicitly signaled, but is implicitly defined through a function based on the UE's identification information and subframe number. In other words, since the UE-specific search space can change based on the subframe number, this means that it can change over time, which solves the problem of a specific UE being blocked from using the search space by other UEs among UEs (the blocking problem). If a UE is prevented from being scheduled in a subframe because all of the CCEs it is searching are already being used by other UEs scheduled in the same subframe, this problem can be avoided in the subsequent subframe because the search space changes over time. For example, even if a portion of the UE-specific search spaces of UE #1 and UE #2 overlap in a specific subframe, the overlap in the subsequent subframe can be expected to be different because the UE-specific search space changes from subframe to subframe.

[0075] According to the definition of the search space for the PDCCH described above, the common search space is defined as a pre-arranged set of CCEs, since a certain group of terminals or all terminals must receive the PDCCH. In other words, the common search space does not change based on terminal identity or subframe number. Although the common search space exists for the transmission of various system messages, it can also be used to transmit control information for individual terminals. This allows the common search space to be used as a solution to the phenomenon of terminals not being scheduled due to insufficient resources in the terminal-specific search space.

[0076] A search space is a set of candidate control channels, consisting of CCEs, that a UE must attempt to decode at a given aggregation level. Since there are multiple aggregation levels, each of which creates a single bundle of 1, 2, 4, or 8 CCEs, a UE has multiple search spaces. The number of PDCCH candidates that a UE must monitor within a search space defined by the aggregation level in the LTE PDCCH is defined in [Table 2] below.

[0077] [Table 2]

[0078]

[0079] According to the above [Table 2], in the case of the terminal-specific search space, aggregation levels {1, 2, 4, 8} are supported, and in this case, there are {6, 6, 2, 2} PDCCH candidates. In the case of the common search space (302), aggregation levels {4, 8} are supported, and in this case, there are {4, 2} PDCCH candidates. The reason why the common search space supports only aggregation levels {4, 8} is to improve the coverage characteristics, since system messages generally have to reach the cell edge.

[0080] DCI transmitted in the common search space is defined only for specific DCI formats, such as 0 / 1A / 3 / 3A / 1C, which are used for system messages or power control for a group of terminals. DCI formats with spatial multiplexing are not supported within the common search space. The downlink DCI format to be decoded in the terminal-specific search space depends on the transmission mode configured for the terminal. Since the transmission mode is configured via RRC (Radio Resource Control) signaling, the exact subframe number for which the configuration takes effect for the terminal is not specified. Therefore, the terminal can operate without losing communication by always performing decoding for DCI format 1A regardless of the transmission mode.

[0081] The above describes the method and search space for transmitting and receiving downlink control channels and downlink control information in conventional LTE and LTE-A.

[0082] Below, the downlink control channel in the 5G communication system currently being discussed will be described in more detail with reference to drawings.

[0083] FIG. 3 is a diagram showing an example of a basic unit of time and frequency resources that constitute a downlink control channel that can be used in a 5G system.

[0084] According to FIG. 3, the basic unit of time and frequency resources (Resource Element Group: REG) constituting the control channel is composed of 1 OFDM symbol (301) on the time axis and 12 subcarriers (302), i.e., 1 RB, on the frequency axis. By assuming that the basic unit of the time axis is 1 OFDM symbol (301) in constituting the basic unit of the control channel, the data channel and the control channel can be time multiplexed within one subframe. By positioning the control channel before the data channel, the processing time of the user can be reduced, making it easy to satisfy the delay time requirement. By setting the basic unit of the frequency axis of the control channel to 1 RB (302), frequency multiplexing between the control channel and the data channel can be performed more efficiently.

[0085] By concatenating REGs (303) illustrated in FIG. 3, control channel areas of various sizes can be set. For example, if the basic unit to which a downlink control channel is allocated in 5G is called CCE (304), 1 CCE (304) can be composed of multiple REGs (303). Taking REG (304) illustrated in FIG. 3 as an example, if REG (303) can be composed of 12 REs and 1 CCE (304) is composed of 6 REGs (303), it means that 1 CCE (304) can be composed of 72 REs. When a downlink control area is set, the area can be composed of multiple CCEs (304), and a specific downlink control channel can be mapped to one or multiple CCEs (304) and transmitted according to the aggregation level (AL) within the control area. CCEs (304) within the control area are distinguished by numbers, and the numbers can be assigned according to a logical mapping method.

[0086] The basic unit of the downlink control channel illustrated in FIG. 3, that is, the REG (303), may include both REs to which DCI is mapped and areas to which the DMRS (Demodulation Reference Signal, 305), which is a reference signal for decoding the REs, is mapped. As shown in FIG. 3, the DMRS (305) may be transmitted in six REs within one REG (303). For reference, since the DMRS (303) is transmitted using the same precoding as the control signal mapped within the REG (303), the terminal can decode the control information even without information on what precoding the base station applied.

[0087] FIG. 4 is a diagram illustrating an example of a control area (CORESET; Control Resource Set) in which a downlink control channel is transmitted in a 5G system.

[0088] FIG. 4 shows an example in which two control regions (Control Region #1 (401), Control Region #2 (402)) are set within a system bandwidth (410) in the frequency axis and 1 slot (420) in the time axis (in the example of FIG. 4, 1 slot is assumed to be 7 OFDM symbols). The control regions (401, 402) can be set to a specific subband (403) within the entire system bandwidth (410) in the frequency axis. The time axis can be set to one or more OFDM symbols, which can be defined as the control region length (Control Resource Set Duration, 404). In the example of FIG. 4, Control Region #1 (401) is set to a control region length of 2 symbols, and Control Region #2 (402) is set to a control region length of 1 symbol.

[0089] The control region in 5G described above can be configured by the base station to the terminal via higher-layer signaling (e.g., system information, Master Information Block (MIB), RRC signaling). Configuring a control region for the terminal means providing information such as the control region's location, subbands, control region resource allocation, and control region length. For example, this information may include the information in [Table 3] below.

[0090] [Table 3]

[0091]

[0092] In addition to the setting information in [Table 3] above, various information required for transmitting a downlink control channel can be set to the terminal.

[0093] Next, we will explain in detail the downlink control information (DCI) in the 5G system.

[0094] In a 5G system, scheduling information for uplink data (PUSCH; Physical Uplink Shared Channel) or downlink data (PDSCH; Physical Downlink Shared Channel) is transmitted from the base station to the terminal via DCI. The terminal can monitor the fallback DCI format and the non-fallback DCI format for the PUSCH or PDSCH. The fallback DCI format can consist of fixed fields between the base station and the terminal, while the non-fallback DCI format can include configurable fields.

[0095] The DCI for scheduling PUSCH may include, for example, information as shown in [Table 4] below.

[0096] [Table 4]

[0097]

[0098] The DCI for scheduling PUSCH may include, for example, information as shown in [Table 5] below.

[0099] [Table 5]

[0100]

[0101]

[0102] The DCI for scheduling PDSCH may include, for example, information as shown in [Table 6] below.

[0103] [Table 6]

[0104]

[0105] The DCI for scheduling PDSCH may include, for example, information as shown in [Table 7] below.

[0106] [Table 7]

[0107]

[0108]

[0109] The above DCI can be transmitted through the Physical Downlink Control CHannel (PDCCH) after going through the channel coding and modulation process. The DCI message payload is accompanied by a Cyclic Redundancy Check (CRC), and the CRC is scrambled with a Radio Network Temporary Identifier (RNTI) corresponding to the identity of the terminal. Different RNTIs are used depending on the purpose of the DCI message, such as UE-specific data transmission, power control command, or random access response. In other words, the RNTI is not transmitted explicitly, but is included in the CRC calculation process and transmitted. When the terminal receives the DCI message transmitted on the PDCCH, it verifies the CRC using the assigned RNTI. If the CRC verification result is correct, it can be determined that the message was transmitted to the terminal.

[0110] For example, a DCI scheduling a PDSCH for system information (SI) may be scrambled with SI-RNTI. A DCI scheduling a PDSCH for a Random Access Response (RAR) message may be scrambled with RA-RNTI. A DCI scheduling a PDSCH for a paging message may be scrambled with P-RNTI. A DCI notifying a Slot Format Indicator (SFI) may be scrambled with SFI-RNTI. A DCI notifying a Transmit Power Control (TPC) may be scrambled with TPC-RNTI. A DCI scheduling a UE-specific PDSCH or PUSCH may be scrambled with C-RNTI (Cell RNTI).

[0111] When a specific terminal is scheduled for a data channel, i.e., a PUSCH or PDSCH, through the PDCCH, data is transmitted and received together with DMRS within the scheduled resource region. FIG. 5 illustrates a case where a specific terminal uses 14 OFDM symbols as one slot (or subframe) in downlink, the PDCCH is transmitted in the first two OFDM symbols, and the DMRS is transmitted in the third symbol. In the case of FIG. 5, within a specific RB where the PDSCH is scheduled, the PDSCH is transmitted by mapping data to REs where the DMRS is not transmitted in the third symbol and REs from the fourth to the last symbol thereafter. In the example of FIG. 5, reference numeral 501 represents REs where the PDCCH is transmitted, 502 represents REs where the DMRS is transmitted, and 503 represents REs where the PDSCH is transmitted. The subcarrier spacing Δf expressed in Fig. 5 is 15 kHz for the LTE / LTE-A system and one of {15, 30, 60, 120, 240, 480} kHz is used for the 5G system.

[0112] Meanwhile, as described above, in order to measure the downlink channel status in a cellular system, the base station must transmit a reference signal. In the case of the 3GPP LTE-A (Long Term Evolution Advanced) system, the terminal can measure the channel status between the base station and the terminal using the CRS or CSI-RS transmitted by the base station. The channel status must be measured by considering various factors, which may include the amount of interference in the downlink. The amount of interference in the downlink includes interference signals and thermal noise generated by antennas belonging to adjacent base stations, and the amount of interference in the downlink is important for the terminal to determine the channel status of the downlink. For example, when a signal is transmitted from a base station using one transmitting antenna to a terminal using one receiving antenna, the terminal can determine Es / Io by judging the energy per symbol (Es) that can be received in the downlink from the reference signal received from the base station and the amount of interference (Io) that will be simultaneously received in the section in which the corresponding symbol is received. The determined Es / Io is converted into a data transmission rate or a value corresponding thereto and transmitted to the base station in the form of a channel quality indicator (CQI), and can be used by the base station to determine at what data transmission rate to perform transmission to the terminal.

[0113] In the LTE-A system, the terminal feeds back information about the downlink channel status to the base station, allowing it to be utilized in the base station's downlink scheduling. Specifically, the terminal measures the reference signal transmitted by the base station on the downlink and feeds back the extracted information to the base station in a format defined by the LTE / LTE-A standard. As described above, the information fed back by the terminal in LTE / LTE-A can be referred to as channel status information, and this channel status information can include the following three types of information.

[0114] - Rank Indicator (RI): The number of spatial layers that the terminal can receive in the current channel state.

[0115] - Precoding Matrix Indicator (PMI): An indicator of the precoding matrix preferred by the terminal in the current channel condition.

[0116] - Channel Quality Indicator (CQI): The maximum data rate that the terminal can receive in the current channel condition.

[0117] CQI can also be replaced by signal-to-interference plus noise ratio (SINR), maximum error correction code rate and modulation scheme, and data efficiency per frequency, which can be utilized similarly to maximum data rate.

[0118] The above RI, PMI, and CQI are interrelated and have different meanings. For example, the precoding matrix supported by LTE / LTE-A is defined differently for each rank. Therefore, for example, the PMI value X when RI has a value of 1 and the PMI value X when RI has a value of 2 may be interpreted differently. In addition, when the terminal determines the CQI, it is assumed that the PMI value X that the terminal notified to the base station has been applied by the base station. In other words, when the terminal reports RI_X, PMI_Y, and CQI_Z to the base station, it is the same as reporting that the terminal can receive the data rate corresponding to CQI_Z when the rank is RI_X and the PMI is PMI_Y. In this way, when the terminal calculates the CQI, it assumes which transmission method the base station will perform so that it can obtain optimized performance when actually performing transmission with the corresponding transmission method.

[0119] In the LTE / LTE-A system, the channel state information (RI, PMI, CQI) fed back by the terminal can be fed back in a periodic or aperiodic form. If the base station wishes to aperiodically obtain the channel state information of a specific terminal, the base station can configure to perform aperiodic feedback (or aperiodic channel state information reporting) using an aperiodic feedback indicator (or channel state information request field, channel state information request information) included in the downlink control information (DCI) for the terminal. In addition, if the terminal receives an indicator configured to perform aperiodic feedback in the nth subframe, the terminal can perform uplink transmission by including the aperiodic feedback information (or channel state information) in the data transmission in the (n+k)th subframe. Here, k is a parameter defined in the 3GPP LTE Release 11 standard, for example, and can be defined as 4 in FDD (Frequency Division Duplexing) and as shown in [Table 8] below in TDD (Time Division Duplexing). [Table 8] below shows the k value for each subframe number n in the TDD UL / DL configuration.

[0120] [Table 8]

[0121]

[0122] When aperiodic feedback is set, feedback information (or channel state information) includes RI, PMI, and CQI, and depending on the feedback setting (or channel state reporting setting), RI and PMI may not be fed back.

[0123] In an embodiment of the present disclosure, in a downlink environment using multiple antennas in an OFDM-based wireless communication system, a method for transmitting and operating a peak-canceling signal (PCS) by adding it to a transmission signal in order to reduce the peak-to-average power ratio (PAPR) of a signal transmitted by each transmitter antenna port of a base station is proposed. The present disclosure proposes a method for determining whether a base station determines to generate a PCS, a method for generating a PCS, and a method for transmitting related information to a terminal for generating a PCS. In addition, the present disclosure proposes a method for transmitting information required for the base station to generate a PCS by signaling / feedback from a terminal to the base station.

[0124] Figure 6a is a downlink of a wireless communication system considered in the present disclosure. A base station (61) using multiple antennas and a single receiving antenna An example of a DL MU (multi-user)-MIMO environment including UEs (62, 63, 64) is shown. Also, as in the example of FIG. 6b, the present disclosure provides a method for A base station (61) using multiple antennas It can also be applied to a DL SU (single user)-MIMO environment including a single UE (65) using multiple receive antennas. In the embodiment of the present disclosure, for convenience of explanation, a situation such as FIG. 6a will be considered and described, but the present disclosure can also be applied to a MIMO environment in which each UE uses multiple antennas. The embodiment of the present disclosure can be applied to various MIMO environments in which the number of transmit antennas of a base station is greater than the number of receive antennas of a terminal.

[0125] FIG. 6c is a diagram illustrating a method for reducing PAPR in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. The MIMO may be, for example, massive MIMO. For convenience of explanation, two UEs are illustrated, but multiple UEs may exist.

[0126] In the example of Fig. 6c, it is assumed that the number of transmitting antennas of the base station (601) is greater than the number of receiving antennas of each UE (602, 603). The base station (601) transmits signals to multiple UEs (602, 603). can be generated. Reference numbers 604 and 605 represent channel components (H) of UEs (602 and 603), respectively. (1) , H (2) ) represents a transmission signal to which PAPR is applied. Here, s is a matrix composed of symbol vectors modulated for transmission, W is a precoding matrix, and superscripts (1) and (2) represent signal / channel components for UE (602) and UE (603), respectively. And r (606) is a matrix of a peak cancelling signal added to reduce PAPR in a signal x to be transmitted according to the present disclosure. In the present disclosure, the peak cancelling signal (r) (606) can be placed / allocated in a null space, which is a spatial resource not used for data transmission and reception in a MIMO environment. For example, in a MIMO environment where the number of transmit antennas of a base station is 32 and the number of receive antennas of a UE is 4, the null space can use 28, which is the number of transmit antennas minus the number of receive antennas. By the peak cancelling signal (r) (606), the UEs (602, 603) can receive a signal with reduced PAPR. For example, reference number 607 represents a received signal when the peak removal signal (r) (606) is not applied, and 608 represents a received signal when the peak removal signal (r) (606) is applied.

[0127] In the present disclosure, as in the above-described embodiment, since the PAPR is reduced by using the null space, which is a spatial resource that is not used for data transmission and reception in a MIMO channel, additional resources for PAPR reduction are not required, unlike the existing PAPR reduction method that uses a clipping method. In the PAPR reduction method of the present disclosure, signal distortion occurring in the reception signal of the UE can be prevented by projecting the clipped signal to the null space for PAPR reduction. In addition, the efficiency of the power amplifier (PA) in the base station can be improved by the PAPR reduction method of the present disclosure. For example, Tx ant. / UEs / N=128 subcarriers / FFT size = 512 (oversampling factor of 4) / TDL(tapped delay line)-C channel model / Modulation 16 QAM(quadrature amplitude modulation) According to the simulation results in an OFDM environment, the PAPR reduction method according to the present disclosure can have a PAPR gain of about 3 dB compared to the existing ZF(zero forcing) method.

[0128] In the present disclosure, the generation of a peak cancelling signal r for reducing the null space and PAPR of a MIMO channel can be defined as shown in [Table 9] below.

[0129] [Table 9]

[0130]

[0131] As an optional embodiment, the PAPR reduction method of the present disclosure may be used in combination with known power reduction methods. The known power reduction methods may be, for example, clipping and filtering (CFR), digital pre-distortion (DPD), envelope tracking (ET), etc.

[0132] Hereinafter, in the embodiments of the present disclosure, a peak cancelling signal (PCS) may be simply referred to as PCS. The embodiments of the present disclosure will describe a method in which a base station controls / adjusts the PCS mode on or off according to predetermined conditions to be described later, and generates a PCS when the PCS mode is on. In addition, in the embodiments of the present disclosure, the base station may utilize a Sounding Reference Signal (SRS) or feedback information received from a UE to generate a PCS.

[0133] FIG. 7 is a diagram illustrating a method in which a base station uses a sounding reference signal (SRS) received from a UE to generate a PCS in a wireless communication system supporting MIMO according to an embodiment of the present disclosure.

[0134] Referring to FIG. 7, in step 701, the base station (71) receives an SRS from the UE (72). In step 702, the base station (71) can estimate a downlink channel (i.e., a MIMO channel) based on the received SRS, and can confirm a null space in the estimated MIMO channel. Since the SRS is received in an uplink channel and the estimated MIMO channel is a downlink channel, the two channels are reversible, and it is assumed that they are applied in a TDD (Time Division Duplexing) method. The null space can be confirmed using the definition of [Table 9]. The base station (71) can generate a PCS for PAPR reduction using the confirmed null space, and can transmit the PCS by adding / including it to a signal to be transmitted in the downlink channel (e.g., a PDSCH signal).

[0135] FIG. 8 is a diagram illustrating a method in which a base station uses feedback information received from a UE to generate a PCS in a wireless communication system supporting MIMO according to an embodiment of the present disclosure.

[0136] Referring to FIG. 8, in step 801, the base station (81) can transmit a CSI-RS (channel state information-reference signal) to the UE (82) in a downlink channel. In step 802, the UE (82) can acquire / configure / generate feedback information related to PCS generation based on the received CSI-RS. In the present disclosure, the feedback information can use a NI (Null Space Indicator), and a specific method of acquiring / configuring / generating the NI feedback information will be described later. The base station (81) can receive the NI feedback information from the UE (82) to confirm a null space in a MIMO channel. Thereafter, the base station (81) can generate a PCS for PAPR reduction using the confirmed null space, and transmit the PCS by adding / including it to a signal to be transmitted in the downlink channel (e.g., a PDSCH signal).

[0137] FIG. 9 is a diagram illustrating a method for a base station to generate a PCS in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. FIG. 9 illustrates an example of a transmission structure in which a PCS is added / included for PAPR reduction in a transmission signal to which precoding and OFDM modulation are applied.

[0138] Referring to FIG. 9, the base station includes N precoders (901-1, …901-n, …, 901-N) for precoding symbols to be transmitted, N adders (902-1, …902-n, …, 902-N) for adding / including a peak-canceling signal (PCS) to the outputs of the N precoders (901-1, …901-n, …, 901-N), and a mapper (903) for mapping the outputs of the adders (902-1, …902-n, …, 902-N) to antenna ports, which converts the outputs from the frequency domain to the time domain. It includes L-point IFFT (inverse fast Fourier transform). The base station's transmission signal is transmitted to the MIMO channel by applying (adding / including) PCS through the configuration of FIG. 9, and the PAPR can be reduced through PCS. For convenience, the description of FIG. 9 below will explain how PCS is applied by taking the Modulated symbol vector mapped to the n-th subcarrier as an example, but the way PCS is applied to the Modulated symbol vector mapped to the 1st to N-th subcarriers is the same as in the case of the n-th subcarrier. In the example of FIG. 9, the superscript t of variables x and a means transpose in the transpose matrix.

[0139] first, (where N is the number of subcarriers) is the modulated symbol vector mapped to the nth subcarrier to be transmitted, It is a vector of size. Each element of It means the signal to be transmitted to the UE of the dog. After that, silver Precoding matrix of size Multiplying by (901-n), the precoded signal is printed. Here silver It is a vector of size. The signal to which precoding is applied. There is a peak-canceling signal (PCS). is a vector of is added / included (902-n), is printed. Currently corresponds to each nth subcarrier. It is a vector. The base station maps the transmission signal to each antenna port and transmits it. Stack them in rows procession , and each row vector of the obtained matrix is It is called. silver It means vector, It refers to the frequency domain signal that is mapped to the th antenna port. That is, the matrix created through each row vector is this relationship is satisfied. After that, Vectorin By filling the remaining LN elements with 0s and performing L-point IFFT to match the assigned frequency positions, Vectorin and obtain, cast is transmitted by mapping to the nth antenna port. Here, the multi-antenna channel of the nth subcarrier is Modeled as, The size of am.

[0140] FIG. 10 is a diagram illustrating an operation mode control for applying PCS to a transmission signal by a base station in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. In the present disclosure, the base station can control the operation mode for applying / generating PCS on or off according to predetermined conditions. The PCS operation mode control of FIG. 10 can be performed selectively.

[0141] Referring to FIG. 10, in step 1001, the base station checks whether the current communication environment satisfies at least one of the On conditions of the PCS operation mode. If the condition is satisfied in step 1001, the base station can turn on the PCS operation mode in step 1002, and if the PCS On condition is not satisfied in step 1001, the base station can turn off the PCS operation mode in step 1003.

[0142] The On conditions of the above PCS operation mode are as shown in examples of conditions 1 to 5 below, and the On conditions are not limited to the examples below, and may be determined by various condition(s) or combinations thereof related to the capability / load / efficiency of the base station. Referring to the examples of the conditions below, if the capability of the base station is good, the load is light, or the efficiency of the power amplifier of the base station needs to be improved, the PCS operation mode is turned on, and if feedback information is received from the UE to generate PCS, the uplink traffic of the UE increases, so the PCS operation mode can be turned on when the amount of uplink traffic of the UE is small.

[0143] - Condition 1: When the computing capability of the base station's processor (CPU (central processing unit), GPU (graphic processing unit), etc.) exceeds a certain standard.

[0144] - Condition 2: When the computing load of the base station processor (CPU, GPU, etc.) is below a certain value.

[0145] - Condition 3: When the UE's uplink traffic is below a certain value

[0146] - Condition 4: When the efficiency of the base station's power amplifier (PA) is lower than a certain value.

[0147] - Condition 5: When base station coverage improvement is required

[0148] FIG. 11 is a diagram illustrating a method for a base station to generate a precoded signal with PCS applied in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. In other words, the example of FIG. 11 relates to the operation of a base station that outputs a frequency domain signal with PCS and precoding applied as proposed in the present disclosure. The embodiment of FIG. 11 can be performed in a base station having the transmission structure of FIG. 9.

[0149] Referring to Figure 11, first, in step 1101, the base station transmits each nth subcarrier signal The initial precoded signal is multiplied by a precoding matrix such as ZF (zero forcing) precoding. Then, in step 1102, the base station generates a matrix that spans the subspace of the null space of the subband s(n) including the nth subcarrier. Creates. Here The size of , and when the UE reports SRS to the base station. (Here, K is the number of Singular Vectors that constitute the Null Space.) Or, when the UE receives the CSI-RS and reports NI feedback information to the base station, the base station can determine the K value for reporting NI. When the number of iterations for applying the PCS is maxIter, the base station in step 1103 In this case, the precoded signal is 1104. First, convert it into a time domain signal. . Afterwards, at step 1105, the base station receives the time domain signal For each element, a clipping operation as in [Mathematical Formula 1] is performed.

[0150] [Mathematical Formula 1]

[0151]

[0152] Here, i=1,… represents the time domain sample index, refers to the Target PAPR threshold value set by the system. The base station performs the clipping operation defined above. Clipping signals in the time domain by applying . After that, the base station at After subtracting the frequency domain, FFT is taken to generate a clipping signal (Freq.-domain clipping noise signal) in the frequency domain. The frequency domain clipping noise signal is can be expressed as follows. At step 1106, the base station clips the signal in the frequency domain. Obtained by performing coordinate axis transformation (axis change) on is the null space matrix obtained in step 1102 above. Projection and counting ( )cast can be obtained as follows. Afterwards, in step 1107, the base station applies a power scaling factor to the transmitted signal, can be obtained by calculating the power scaling factor p n In the formula of corresponds to PCS. In step 1108, the base station calculates the Precoded signal using Update the precoded signal can be expressed as . Afterwards, the base station increases the count of the number of repetitions by 1 in step 1109. And do it, The operations of steps 1104 to 1109 are repeated within the above conditions.

[0153] After repeating the above operations, in step 1103, if the number of repetitions exceeds the maximum number of repetitions, the base station ) In this case, at step 1110, the time domain signal corresponding to that point in time is transmitted to the RF terminal of the base station and mapped to each antenna port for transmission.

[0154] The algorithm for generating a precoding signal with PCS applied at the base station described in the above-described Figure 11 is as shown in the example in [Table 10] below.

[0155] [Table 10]

[0156]

[0157] FIG. 12 is a diagram showing the operation of a base station for generating PCS when the base station receives a Persistent SRS or Semi-persistent SRS from a terminal in a wireless communication system supporting MIMO according to an embodiment of the present disclosure, and FIG. 13 is a diagram showing the timing for transmitting and receiving a signal on a time axis required in the operation of the base station of FIG. 12.

[0158] Referring to FIGS. 12 and 13, in step 1201, the base station receives PDSCH data signals (FDM (frequency division multiplexing) signals) for multiple UEs to transmit at Slot n time from a higher layer (1303). Thereafter, in step 1202, if the PCS operation mode described in FIG. 10 is On and the SRS received from each UE is received after nq slots (1304) (which may be referred to as “critical slots”) (1302), the base station generates the PCS described in FIG. 9 by utilizing the channel matrix estimated through the SRS transmitted from the UE in step 1203 and applies the PCS to the transmission signal to the UE to reduce PAPR. In step 1202, if the PCS operation mode of the base station is On and the SRS received from the UE is received before the nq slot (1301), in step 1204, the base station determines that the channel estimated by the SRS received before the nq slot (1304) is outdated and does not use the channel when generating a PCS. In the example of Fig. 12, the q value can be understood as a threshold value for determining whether the channel information obtained by the base station through SRS reception is available for use when generating a PCS. In other words, the q value can be predetermined so that when the base station generates a PCS, an outdated channel received before exceeding the threshold value is not used when generating a PCS.

[0159] FIG. 14 is a diagram illustrating the operation of a base station for generating PCS when the base station receives an Aperiodic SRS from a terminal in a wireless communication system supporting MIMO according to an embodiment of the present disclosure.

[0160] Referring to FIG. 14, in step 1401, if the PCS operation mode is On and the most recently received SRS from a UE in an RRC Connected state is received before a first time (q1 time), then in step 1402, the base station may request the UE to transmit an Aperiodic SRS on a specific frequency and time resource through a MAC CE (MAC Control Element). Thereafter, in step 1403, the base station may utilize the channel information acquired through Aperiodic SRS reception from the UE when generating PCS until a second time (q2 time) after receiving the SRS. The first time (q1 time) and the second time (q2 time) may be set / determined to be the same or different. The second time (q2 time) may be understood as an effective time during which the channel information acquired through Aperiodic SRS reception can be utilized for PCS generation.

[0161] FIG. 15 is a diagram illustrating an example of a method for applying PCS based on periodic NI feedback in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. The example of FIG. 15 specifically illustrates a procedure related to NI feedback transmission in the embodiment of FIG. 8, in which a base station transmits a CSI-RS to a UE on a downlink channel, and the UE transmits NI feedback information related to PCS generation to the base station based on the CSI-RS, from a periodic transmission perspective. The PCS generation method using NI feedback based on CSI-RS in the present disclosure can be applied to both time division duplexing (TDD) and frequency division duplexing (FDD) schemes.

[0162] Referring to FIG. 15, at step 1501, the base station may provide the UE with configuration information including at least one parameter for NI (Null Space Indicator) feedback via RRC and / or MAC-CE. Although not illustrated, control information for periodic transmission of the NI feedback information may also be transmitted to the UE via DCI. That is, the configuration / control information for periodic transmission of the NI feedback information may be transmitted to the UE via various combinations of RRC, MAC-CE, and / or DCI. In an optional embodiment, the configuration / control information may be provided to the UE when the PCS operation mode is turned on at the base station.

[0163] In the above step 1501, the configuration information related to the transmission of NI feedback information may include at least one of the following parameters: NumDimNullLayers K indicating the number of Null Space Layers to be transmitted, NIType distinguishing according to the quantization level and compression level or distinguishing Type 1, Type 2, eType 2, etc. used in the existing NR, NIFreqLoc indicating the frequency resource location of NI feedback, NITimeLoc indicating the time resource location of NI feedback, NIReportPeriod determining the NI Feedback period, N_Amp_Level, N_Phase_Level, N_Round_Level determining the Quantization level for NI feedback, etc.

[0164] The configuration information related to the periodic transmission of the above NI feedback information can be exemplified as shown in [Table 11] below.

[0165] [Table 11]

[0166]

[0167] In step 1502, the UE acquires channel information from the CSI-RS, and can acquire / configure / generate NI feedback information related to PCS generation based on the acquired channel information and the configuration information and / or control information. The UE transmits the acquired NI feedback information to the base station via PUSCH or PUCCH. The example of FIG. 15 illustrates a case where the UE periodically transmits NI feedback information to the base station. For example, the UE can periodically perform NI feedback in time and frequency resources specified by the corresponding NI feedback parameters in the configuration information. Thereafter, in step 1503, the base station can receive the NI feedback information from the UE and identify the null space in the MIMO channel. The base station can generate a PCS for PAPR reduction using the identified null space, and can transmit the PCS by adding / including it to a signal to be transmitted on a downlink channel (e.g., a PDSCH signal).

[0168] FIG. 16 is a diagram illustrating an example of a method for applying PCS based on aperiodic NI feedback in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. The example of FIG. 16 specifically illustrates, from an aperiodic transmission perspective, the procedure related to NI feedback transmission in the embodiment of FIG. 8, in which a base station transmits a CSI-RS to a UE on a downlink channel, and the UE transmits NI feedback information related to PCS generation to the base station based on the CSI-RS.

[0169] Referring to FIG. 16, in step 1601, the base station may provide the UE with configuration information including at least one parameter for NI (Null Space Indicator) feedback via RRC and / or MAC-CE. Furthermore, in step 1602, the base station may transmit control information for aperiodic transmission of the NI feedback information to the UE via DCI. That is, the configuration / control information for aperiodic transmission of the NI feedback information may be transmitted to the UE via various combinations of RRC, MAC-CE, and / or DCI. In an optional embodiment, the configuration / control information may be provided to the UE when the PCS operation mode is turned on at the base station.

[0170] In the above step 1601, the configuration information related to the transmission of NI feedback information may include at least one of the following parameters: NumDimNullLayers K indicating the number of Null Space Layers to be transmitted; NIType distinguishing according to Quantization level and Compression level or distinguishing Type 1, Type 2, eType 2 used in existing NR; NIFreqLoc indicating the frequency resource location of NI feedback; NITimeLoc indicating the time resource location of NI feedback; NIReportPeriod determining the NI Feedback period; N_Amp_Level, N_Phase_Level, N_Round_Level determining the Quantization level for NI feedback.

[0171] The configuration / control information related to the aperiodic transmission of the above NI feedback information can be exemplified as shown in [Table 12] below.

[0172] [Table 12]

[0173]

[0174] In step 1603, the UE can obtain channel information from the CSI-RS, and obtain NI feedback information related to PCS generation based on the obtained channel information and the configuration information and / or control information. The UE transmits the obtained NI feedback information to the base station via the PUSCH or PUCCH. The example of FIG. 16 illustrates a case where the UE aperiodically transmits the NI feedback information to the base station. For example, the UE can aperiodically perform NI feedback in time and frequency resources specified by the corresponding NI feedback parameter in the configuration information. Thereafter, in step 1604, the base station can receive the NI feedback information from the UE and identify the null space in the MIMO channel. The base station can generate a PCS for PAPR reduction using the identified null space, and transmit the PCS by adding / including it to a signal to be transmitted on the downlink channel (e.g., a PDSCH signal).

[0175] FIG. 17 is a diagram illustrating UE operation in a method for applying NI feedback-based PCS in a wireless communication system supporting MIMO according to an embodiment of the present disclosure. In the example of FIG. 17, a base station transmits a CSI-RS to a UE on a downlink channel, and the UE can obtain NI feedback information related to PCS generation based on the CSI-RS.

[0176] Referring to FIG. 17, in step 1701, the UE may receive configuration information including at least one parameter for NI feedback from the base station via RRC and / or MAC-CE. In addition, in step 1702, the UE may receive control information for aperiodic transmission of NI feedback information (e.g., time and frequency resource information for NI feedback transmission, etc.) via DCI. Step 1702 may be optionally performed. That is, the configuration / control information for periodic / aperiodic transmission of NI feedback information may be received by the UE from the base station via various combinations of RRC, MAC-CE, and / or DCI. In an optional embodiment, the configuration / control information may be received by the UE when the PCS operation mode is turned on at the base station. In step 1703, the UE may obtain channel information from the CSI-RS, and obtain NI feedback information related to PCS generation based on the obtained channel information and the configuration information and / or control information. The UE can transmit the acquired NI feedback information to the base station via PUSCH or PUCCH in the time and frequency resources specified by the NI parameters in the above configuration information and / or control information.

[0177] FIG. 18 is a diagram illustrating a method for a UE to receive a CSI-RS and perform NI Feedback based on a PMI codebook for PCS generation at a base station of a wireless communication system according to an embodiment of the present disclosure. Here, the PMI codebook can be used in the same manner as in a conventional NR system in which the UE receives a CSI-RS and provides PMI feedback.

[0178] Referring to FIG. 18, in step 1801, first, the UE estimates a channel using the received CSI-RS and then estimates the channel. Null space consisting of Null layer vectors( ) is calculated. At step 1802, the UE calculates each vector ( ) PMI-based codebooks such as Type 1 and Type 2 used in existing NR systems Find the closest vector among them. Then, in step 1803, the UE calculates the similarity value between the null layer vector and the corresponding codebook vector pair. In step 1804, the UE selects the codebook index corresponding to the top K among the calculated similarity values ​​as NI. Then, in step 1805, the UE transmits the selected K NI feedback through PUSCH or PUCCH on the designated frequency and time resources.

[0179] FIG. 19 is a diagram illustrating a method for a UE to receive a CSI-RS and perform NI Feedback based on separate Quantization and Compression rules for PCS generation at a base station of a wireless communication system according to an embodiment of the present disclosure.

[0180] Referring to FIG. 19, in step 1901, first, the UE estimates a channel using the received CSI-RS and then estimates the channel. Null space consisting of Null layer vectors( ) is calculated. At step 1902, the UE calculates each vector ( ) can perform compression (e.g., quantization) according to established rules. In step 1903, the UE calculates the similarity value between each Null layer vector and the compressed (quantized) Amplitude and Phase for each Subband.

[0181] [Table 13] below shows an example of rules for quantizing null space into amplitude and phase.

[0182] [Table 13]

[0183]

[0184] Specifically, to store Amplitude information, Amplitude can be divided into N_Amp_Level levels as in the example in [Table 13], and Phase can be divided into N_Phase_Level levels to store Phase information. In addition, [Mathematical Formula 2] below is an example of quanization by rounding each Null space information to a decimal point.

[0185] [Equation 2]

[0186]

[0187] As in the example of [Mathematical Formula 2] above, the number of bits for NI feedback can be reduced by quanizing up to the second decimal place. Each UE is a vector ( ) for each given Subband and Tx antenna port as exemplified in [Table 13] above, the closest index among the indices representing N_Amp_Level levels can be selected, and the closest index among the indices representing N_Phase_Level phases can be selected. Alternatively, the UE can select each vector as exemplified in [Mathematical Formula 2] above. ( ) can be rounded to the N_Round_Level digit below the decimal point to obtain a vector to be fed back. The UE can calculate the similarity value between the Null layer vector and the corresponding quantized vector pair in step 1903 in the above-described manner. In step 1904, the UE selects the index corresponding to the top K among the calculated similarity values ​​as NI. Then, in step 1905, the UE transmits the selected K NIs as feedback through PUSCH or PUCCH in the designated frequency and time resources.

[0188] FIG. 20 is a diagram showing an example configuration of a base station in a wireless communication system according to an embodiment of the present disclosure.

[0189] The base station of FIG. 20 may operate by each of the embodiments of FIGS. 6 to 19 described above, as well as by a combination of two or more embodiments. The base station of FIG. 20 may include a processor (2001), a transceiver (2003), and a memory (2005). The processor (2001), the transceiver (2003), and the memory (2005) of the base station may operate according to the methods described in the embodiments of FIGS. 6 to 19. However, the components of the base station are not limited to the examples described above. For example, the base station may include more or fewer components than the components described above. In addition, the processor (2001), the transceiver (2003), and the memory (2005) may be implemented in the form of a single chip.

[0190] The transceiver (2003) is a general term for the base station receiver and the base station transmitter, and can transmit and receive signals with the UE. At this time, the transmitted and received signals may include at least one of control information and data. In addition, the transceiver (2003) may receive a signal, output it to the processor (2001), and transmit the signal output from the processor (2001). In addition, the transceiver (2003) of FIG. 20 may include an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and frequency-downconverts the received signal. In addition, the transceiver (2003) may receive a signal, output it to the processor (2001), and transmit the signal output from the processor (2001) to the UE via a network. The memory (2005) may store programs and data necessary for the operation of the base station according to at least one of the embodiments of FIGS. 6 to 19. Additionally, the memory (2005) can store control information or data included in a signal acquired from the base station. The memory (2005) can be configured as a storage medium or a combination of storage media, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD.

[0191] In addition, the processor (2001) may control a series of processes so that the base station can operate according to at least one of the embodiments of FIGS. 6 to 19. The processor (2001) may include at least one processor. The processor (2001) may control, for example, a process of turning on / off the Peak Canceling Signal generation mode of the present disclosure, a process of generating a Peak Canceling Signal based on SRS or NI feedback information, a process of transmitting parameters for NI feedback to the UE, etc.

[0192] FIG. 21 is a diagram showing an example configuration of a UE in a wireless communication system according to an embodiment of the present disclosure.

[0193] The UE of FIG. 21 may operate by each of the embodiments of FIGS. 6 to 19 described above, as well as by a combination of two or more embodiments. The UE of FIG. 21 may include a processor (2101), a transceiver (2103), and a memory (2105). The processor (2101), the transceiver (2103), and the memory (2105) of the UE may operate according to the methods described in the embodiments of FIGS. 6 to 19. However, the components of the UE are not limited to the examples described above. For example, the UE may include more or fewer components than the components described above. In addition, the processor (2101), the transceiver (2103), and the memory (2105) may be implemented in the form of a single chip.

[0194] The transceiver (2103) is a general term for the UE's receiver and the UE's transmitter, and can transmit and receive signals with the base station. At this time, the transmitted and received signals may include at least one of control information and data. In addition, the transceiver (2103) may receive a signal, output it to the processor (2101), and transmit the signal output from the processor (2101). In addition, the transceiver (2103) of FIG. 21 may include an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and frequency-downconverts the received signal. In addition, the transceiver (2103) may receive a signal, output it to the processor (2101), and transmit the signal output from the processor (2101) to the UE via a network. The memory (2105) may store programs and data necessary for the operation of the UE according to at least one of the embodiments of FIGS. 6 to 19. Additionally, the memory (2105) can store control information or data included in a signal acquired from the UE. The memory (2105) can be configured as a storage medium or a combination of storage media, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD.

[0195] In addition, the processor (2101) may control a series of processes so that the UE can operate according to at least one of the embodiments of FIGS. 6 to 19. The processor (2101) may include at least one processor. The processor (2101) may control, for example, a process of receiving NI Feedback-related parameters designated through RRC or the like from a base station of the present disclosure, a process of performing NI Feedback at specific time and frequency resources designated by the base station in accordance with the NI Feedback parameters, etc.

[0196] 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. If 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 the methods according to the embodiments described in the claims or specification of the present disclosure.

[0197] 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-ROMs (CD-ROMs), 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. The above 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. This storage device may be connected to a device performing 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 performing an embodiment of the present disclosure.

[0198] In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed in the singular or plural form, 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 the plural form may be composed of singular elements, or components expressed in the singular form may be composed of plural elements.

Claims

1. In a method for reducing PAPR (peak-to-average power ratio) performed by a base station in a wireless communication system supporting MIMO (multiple input multiple output), A process for identifying an operation mode for generating a peak cancelling signal (PCS) to reduce the above PAPR; A process of confirming a null space, which is a space resource where the PCS is placed in a MIMO channel, when generating the PCS based on the above operation mode; A process of applying the PCS to a signal to be transmitted for reducing the PAPR; and A method including a process of transmitting a transmission signal to which the above PCS is applied to a UE (user equipment).

2. In paragraph 1, A method wherein the process of applying the above PCS to a signal to be transmitted includes a process of projecting a clipped signal to the null space for reducing the PAPR.

3. In paragraph 1, The process of applying the above PCS to a signal to be transmitted includes: a process of adding the PCS for each subcarrier to a first signal vector in which a modulated symbol vector mapped to each of a plurality of subcarriers is precoded to output a second signal vector; and A method comprising a process of mapping the second signal vector to each antenna port.

4. In paragraph 1, A method in which the operation mode for generating the PCS is controlled to be on when at least one of the conditions 1 to 4 below is satisfied. Condition 1: If the computing capability of the above base station exceeds a certain standard, Condition 2: If the computing load of the above base station is below a certain value, Condition 3: If the uplink traffic of the above UE is below a certain value, Condition 4: If the efficiency of the power amplifier of the base station is lower than a specific value, and Condition 5: If the coverage of the above base station needs to be improved.

5. In paragraph 1, A process of receiving a sounding reference signal (SRS) from the UE; and It further includes a process of estimating a MIMO channel for confirming the null space based on the received SRS. A method in which the above SRS is received periodically or aperiodically.

6. In paragraph 5, If the above SRS is a periodic transmission, the estimated channel information based on the received SRS after a set threshold slot is used when generating the PCS. A method of using channel information estimated based on the received SRS when generating the PCS for a set time after receiving the SRS, when the above SRS is an aperiodic transmission.

7. In paragraph 1, A process of transmitting a CSI-RS (channel state information-reference signal) to the UE; and A method further comprising a step of receiving feedback information for generation of the PCS from the UE based on the transmitted CSI-RS.

8. In paragraph 7, It further includes a process of transmitting setting information for receiving the above feedback information to the UE, The above setting information is, Information indicating whether the transmission type of the above feedback information is periodic or aperiodic; If the above transmission type is periodic, information indicating the transmission period of the above feedback information, Information indicating the time and frequency resources at which the above feedback information is transmitted; A method comprising at least one piece of information indicating a quantization level of the above feedback information.

9. In paragraph 7, The above feedback information is obtained based on a similarity value between a null layer vector corresponding to the null space and a PMI (precoding matrix indicator) codebook vector.

10. In paragraph 7, A method in which the above feedback information is obtained based on a similarity value between a null layer vector corresponding to the null space and a quantized magnitude and phase for a given subband and antenna port.

11. In a wireless communication system supporting MIMO (multiple input multiple output), at the base station, Transmitter and receiver; and Verify the operation mode for generating a peak cancelling signal (PCS) to reduce the PAPR (peak-to-average power ratio). When generating the PCS based on the above operation mode, the null space, which is a space resource where the PCS is placed in the MIMO channel, is checked, Applying the PCS for reducing the PAPR to the signal to be transmitted, A base station including a processor configured to transmit a transmission signal to which the PCS is applied to a UE (user equipment) through the transceiver.

12. In paragraph 11, A base station according to claim 11, adapted to operate according to any one of the methods of claims 2 to 10.

13. In a wireless communication system supporting MIMO (multiple input multiple output), in the UE (user equipment), Transmitter and receiver; and Receive configuration information for transmission of feedback information related to generation of a peak cancelling signal (PCS) for reducing PAPR (peak-to-average power ratio) by using null space in a MIMO channel through the transceiver from the base station, Transmitting the feedback information related to the generation of the PCS based on the setting information to the base station through the transceiver, and A UE including a processor configured to receive a signal to which the PCS is applied based on the feedback information from the base station through the transceiver.

14. In paragraph 13, The above setting information is, Information indicating whether the transmission type of the above feedback information is periodic or aperiodic; If the above transmission type is periodic, information indicating the transmission period of the above feedback information, Information indicating the time and frequency resources at which the above feedback information is transmitted; A UE including at least one piece of information indicating a quantization level of the above feedback information.

15. In paragraph 13, The above processor, A UE further configured to receive DCI (downlink control information) including information requesting transmission of the feedback information from the base station through the transceiver, when the transmission type of the feedback information is aperiodic.

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