Method and device for processing retransmission for controlling interference in wireless communication system

Abstract

The present disclosure relates to a method and device for processing retransmission for controlling interference between a base station and a terminal in a wireless communication system. According to one embodiment of the present disclosure, the method comprises the steps of: transmitting, from a base station to a terminal, first downlink control information (DCI) and a transport block (TB); transmitting, to the terminal, a transport block (TB) on the basis of the first DCI; receiving hybrid automatic repeat request (HARQ) feedback from the terminal when the transmission of the transport block fails; and retransmitting, to the terminal, the transport block on the basis of the HARQ feedback.

Description

Method and device for handling retransmission to control interference in a wireless communication system

[0001] The present disclosure relates to a wireless communication system. More specifically, the present invention relates to a method and apparatus for processing retransmission to control interference between a base station and a terminal in a wireless communication system.

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

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

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

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

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

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

[0008] Additionally, sidelink communication using 5G communication systems is being studied, and it is expected that direct communication between terminals will be applied to, for example, vehicle-to-everything (V2X) communication and public safety networks, and will be able to provide various services to users.

[0009] In particular, there is a need for a method that utilizes sidelink relays that can support expansion of service coverage, increased reliability of data transmission, and reduced power consumption of terminals.

[0010] The purpose of the present invention is to provide a device and method capable of providing retransmission that effectively controls interference by reflecting different channel characteristics for each slot in a wireless communication system.

[0011] The technical problems to be achieved in the present disclosure are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by a person having ordinary skill in the technical field to which the present disclosure belongs from the description below.

[0012] The present invention for solving the above-mentioned problem is a method performed by a base station in a wireless communication system, the method comprising: a step of transmitting first downlink control information (DCI) and a transport block (TB) to a terminal; a step of transmitting a transport block (TB) to the terminal based on the first DCI; a step of receiving HARQ (Hybrid automatic repeat request) feedback from the terminal when transmission of the transport block fails; and a step of retransmitting the transport block to the terminal based on the HARQ feedback, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource coefficient, and Redundancy version (RV) information for retransmission.

[0013] In one embodiment, the method further comprises a step of transmitting an RRC (Radio Resource Control) message including a maximum number of retransmissions and an RV order according to the number of retransmissions related to the RV information for the retransmission.

[0014] In one embodiment, the method further comprises the step of transmitting the second downlink control information based on the HARQ feedback to the terminal, wherein the second downlink control information includes only time domain resource allocation and frequency domain resource allocation.

[0015] In one embodiment, slots having similar channel conditions are grouped based on at least one of SINR (Signal to Interference plus Noise Ratio), CQI (Channel Quality Information), and MCS (Modulation Coding Scheme), and the transmission block is retransmitted within the same group.

[0016] In one embodiment, the first downlink control information is characterized in that it further includes group information and slot information for the group.

[0017] In addition, in another embodiment of the present invention, a method performed by a terminal in a wireless communication system, the method includes the steps of: receiving first downlink control information (DCI) from a base station; receiving a transport block (TB) from the base station based on the first DCI; transmitting, to the base station, a hybrid automatic repeat request (HARQ) feedback when reception of the transport block fails; and re-receiving, from the base station, the transport block based on the HARQ feedback, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource coefficient, and Redundancy version (RV) information for retransmission.

[0018] In addition, in another embodiment of the present invention, in a wireless communication system, a base station includes a transceiver capable of transmitting and receiving at least one signal; and a control unit coupled to the transceiver, wherein the control unit is configured to: transmit first downlink control information (DCI) and a transport block (TB) to a terminal, transmit a transport block (TB) to the terminal based on the first DCI, receive hybrid automatic repeat request (HARQ) feedback from the terminal when transmission of the transport block fails, and retransmit the transport block to the terminal based on the HARQ feedback, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource coefficient, and redundancy version (RV) information for retransmission.

[0019] In addition, in another embodiment of the present invention, in a wireless communication system, a terminal includes a transceiver capable of transmitting and receiving at least one signal; and a control unit coupled to the transceiver, wherein the control unit is configured to: receive first downlink control information (DCI) from a base station, receive a transport block (TB) from the base station based on the first DCI, transmit a hybrid automatic repeat request (HARQ) feedback to the base station when reception of the transport block fails, and re-receive the transport block from the base station based on the HARQ feedback, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource coefficient, and Redundancy version (RV) information for retransmission.

[0020] According to one embodiment of the present disclosure, a device and method can be provided that can provide retransmission that effectively controls interference by reflecting different channel characteristics for each slot in a wireless communication system.

[0021] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0022] Figure 1 is a diagram illustrating the basic structure of the time-frequency domain in LTE.

[0023] Figure 2 is a diagram illustrating a downlink control channel of LTE.

[0024] Figure 3 is a diagram illustrating transmission resources of a downlink control channel in 5G.

[0025] Figure 4 is a diagram illustrating an example of settings for a control area in 5G.

[0026] FIG. 5 is a diagram illustrating an example of a configuration for a downlink RB structure in 5G.

[0027] Figure 6 is a diagram showing a slot structure according to an example of a TDD setting.

[0028] FIG. 7 is an example diagram showing the average channel situation for each slot number when there is a transmission restriction according to one embodiment of the present invention.

[0029] Figure 8 is a diagram illustrating an example of a conventional retransmission process.

[0030] FIG. 9 is a diagram showing an example of an average channel situation and a similar channel situation for each slot number according to one embodiment of the present invention.

[0031] Figure 10 is a drawing illustrating another embodiment of the present invention.

[0032] Figure 11 is a drawing illustrating another embodiment of the present invention.

[0033] Figure 12 is a drawing illustrating another embodiment of the present invention.

[0034] Figure 13 is a drawing illustrating another embodiment of the present invention.

[0035] Figure 14 is a drawing illustrating another embodiment of the present invention.

[0036] Figure 15 is a drawing illustrating another embodiment of the present invention.

[0037] FIG. 16 is a diagram illustrating the structure of a terminal according to one embodiment of the present invention.

[0038] FIG. 17 is a diagram illustrating the structure of a base station according to one embodiment of the present invention.

[0039] As described above, advancements in wireless communication systems have enabled the provision of a variety of services, creating a need for methods to seamlessly deliver these services. In particular, communication methods that conserve terminal power and channel status information reporting methods that take this into account are needed to provide services to users for longer periods of time.

[0040] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

[0041] In describing the embodiments, descriptions of technical details that are well-known in the technical field to which the present disclosure pertains and are not directly related to the present disclosure will be omitted. This is to avoid obscuring the gist of the present disclosure by omitting unnecessary explanations and to convey it more clearly. Furthermore, the terms described below are defined based on their functions in the present invention and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the contents throughout this specification.

[0042] For the same reason, some components in the attached drawings are exaggerated, 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.

[0043] 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 together 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 embodiments of the present disclosure are provided only to make the present disclosure complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0044] At this time, it will be understood that each block of the processing flowchart drawings and combinations of the flowchart drawings 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 flowchart 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 flowchart 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, so that 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 be able to provide steps for performing the functions described in the flowchart block(s).

[0045] 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.

[0046] Here, the term '~ unit' used in the present embodiment means software or hardware components such as FPGA (Field Programmable Gate Array) or ASIC (Application Specific Integrated Circuit), and the '~ unit' performs certain roles. However, the '~ unit' is not limited to software or hardware. The '~ unit' may be configured to be on an addressable storage medium and may be configured to play one or more processors. Accordingly, according to some embodiments, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions 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'. Additionally, the components and '~parts' may be implemented to activate one or more CPUs within the device or secure multimedia card. Furthermore, according to some embodiments, the '~parts' may include one or more processors.

[0047] Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the attached drawings. In the following description of the present disclosure, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present disclosure, the detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of the functions of the present disclosure, and these may vary depending on the intention or custom of the user or operator. Therefore, the definitions should be made based on the contents throughout this specification. Hereinafter, a base station is an entity that performs resource allocation of a terminal, and may be at least one of a gNode B, an eNode B, a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. Of course, the present disclosure is not limited to the above examples. Hereinafter, the present disclosure describes a technology for a terminal to receive broadcast information from a base station in a wireless communication system. The present disclosure is a 4G (4G) th 5G (5 generation) system to support higher data rates th The present disclosure relates to a communication technique and system that fuses a 5G communication system with IoT (Internet of Things) technology. The present disclosure can be applied to intelligent services (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail, security and safety-related services, etc.) based on 5G communication technology and IoT-related technologies.

[0048] In the following description, terms referring to broadcast information, terms referring to control information, terms related to communication coverage, terms referring to state changes (e.g., events), terms referring to network entities, terms referring to messages, terms referring to device components, etc. are examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0049] For convenience of explanation, some terms and names defined in the 3GPP LTE (3rd generation partnership project long term evolution) standard may be used. However, the present disclosure is not limited to these terms and names, and can be equally applied to systems conforming to other standards.

[0050] Wireless communication systems are evolving from providing voice-oriented services in the early days 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.

[0051] As a representative example of a broadband wireless communication system, the LTE system adopts the Orthogonal Frequency Division Multiplexing (OFDM) method in the downlink (DL) and the Single Carrier Frequency Division Multiple Access (SC-FDMA) method in the uplink (UL). The uplink refers to a wireless link in which a terminal (User Equipment (UE) or Mobile Station (MS)) transmits data or control signals to a base station (eNode B or base station (BS)), 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 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.

[0052] As a future communications system beyond LTE, 5G communication systems must be able to freely reflect the diverse needs of users and service providers, and thus support services that satisfy these diverse requirements. Services being considered for 5G communication systems include Enhanced Mobile Broadband (eMBB), Massive Machine Type Communication (mMTC), and Ultra Reliability Low Latency Communication (URLLC).

[0053] In some embodiments, eMBB aims to provide data rates that are significantly higher than those supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, eMBB should be able to provide 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. At the same time, it should provide an increased user-perceived data rate for the terminal. To meet these requirements, improvements in transmission and reception technologies, including further enhanced Multi-Input Multi-Output (MIMO) transmission technology, are required. In addition, the data rates required by 5G communication systems can be met by using a wider frequency bandwidth than 20 MHz in the 3-6 GHz or higher 6 GHz frequency band instead of the 2 GHz band used by the current LTE.

[0054] 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 IoT, mMTC may require support for large-scale terminal connections within a cell, improved terminal coverage, improved battery life, and reduced terminal costs. The IoT requires the ability to support a large number of terminals (e.g., 1,000,000 terminals / km2) within a cell, as it provides communication capabilities through the attachment of various sensors and devices. Furthermore, terminals supporting mMTC are likely to be located in shadow areas not covered by cells, such as basements, due to the nature of the service. This may require broader coverage compared to other services provided by 5G communication systems. Terminals supporting mMTC should be comprised of low-cost terminals, and since frequent battery replacement is difficult, very long battery life may be required.

[0055] Finally, URLLC, a cellular-based wireless communication service used for specific mission-critical purposes such as remote control of robots or machinery, industrial automation, unmanned aerial vehicles, remote health care, and emergency alerts, must provide ultra-low latency and ultra-reliable communication. For example, a service supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds and simultaneously have a packet error rate (PER) of 10-5 or less. Therefore, for a service supporting URLLC, the 5G system must provide a smaller transmit time interval (TTI) than other services, and at the same time, the design requires allocation of wide resources in the frequency band. However, the above-mentioned mMTC, URLLC, and eMBB are merely examples of different service types, and the service types to which the present disclosure applies are not limited to the above-mentioned examples.

[0056] The services considered in the aforementioned 5G communication system should be integrated and provided based on a single framework. In other words, for efficient resource management and control, it is desirable for each service to be integrated, controlled, and transmitted as a single system, rather than operated independently.

[0057] Furthermore, while embodiments of the present disclosure are described below using LTE, LTE-A, LTE Pro, or NR systems as examples, the embodiments of the present disclosure may also be applied to other communication systems with similar technical backgrounds or channel types. Furthermore, the 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.

[0058] Below, the frame structure of the LTE and LTE-A systems will be described in more detail with reference to drawings.

[0059] Figure 1 is a diagram illustrating the basic structure of the time-frequency domain in LTE. Specifically, Figure 1 is a diagram illustrating the basic structure of the time-frequency domain, which is the radio resource domain where data or control channels are transmitted in the LTE system.

[0060] 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), and N symb OFDM symbols (101) are grouped to form one slot (102), and two slots are grouped to form one subframe (103). The length of the slot (102) is 0.5 ms, and the length of the subframe (103) is 1.0 ms. In addition, a radio frame (104) is a time domain unit composed of 10 subframes (103). The minimum transmission unit in the frequency domain is a subcarrier (105), and the bandwidth of the entire system transmission bandwidth is a total of N BW It consists of a subcarrier (105).

[0061] The basic unit of resources in the time-frequency domain is a resource element (RE) (106), which can be represented by an OFDM symbol index and a subcarrier index. A resource block (RB; Resource Block or PRB; Physical Resource Block) (107) is N in the time domain. symb N consecutive OFDM symbols (101) in the frequency domain RB is defined as a series of consecutive subcarriers (108). Therefore, one RB (107) is N symb x N RB It consists of RE(106). In general, the minimum transmission unit of data is the RB unit. In LTE system, the N symb = 7, N RB =12, and N BW and N RB is proportional to the bandwidth of the system transmission band.

[0062] Next, we will specifically explain downlink control information (DCI) in LTE and LTE-A systems.

[0063] In the LTE system, scheduling information for downlink or uplink data is transmitted from the base station to the terminal via DCI. The DCI may include information such as whether the scheduling information is for uplink or downlink data, whether it is compact DCI with small control information size, whether it applies spatial multiplexing using multiple antennas, and whether it is DCI for power control. In addition, a DCI format defined according to the above-described information may be applied and operated. For example, DCI format 1, which is scheduling control information for downlink data, is configured to include at least the following control information.

[0064] - 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 the 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.

[0065] Resource block assignment: Notifies the RBs allocated for data transmission. The resources represented are determined based on system bandwidth and resource allocation method.

[0066] - 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.

[0067] - HARQ process number: Notifies the process number of HARQ (Hybrid Automatic Repeat and request).

[0068] - New data indicator: Notifies whether this is a HARQ initial transmission or a retransmission.

[0069] - Redundancy version (RV): Notifies the redundancy version of HARQ.

[0070] - 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.

[0071] 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.

[0072] The DCI message payload is accompanied by a CRC (Cyclic Redundancy Check), which is scrambled with an RNTI (Radio Network Temporary Identifier) ​​that identifies the UE. 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 a DCI message transmitted on the PDCCH is received, the UE 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 UE.

[0073] Figure 2 is a diagram illustrating the downlink control channel of LTE. Specifically, Figure 2 is a diagram illustrating the PDCCH, a downlink physical channel through which LTE DCI is transmitted.

[0074] According to Fig. 2, the PDCCH (201) is time-multiplexed with the PDSCH (Physical Downlink Shared Channel) (202), which is a data transmission channel, and is transmitted across the entire system bandwidth. The area of ​​the PDCCH (201) is expressed by the number of OFDM symbols, and this is indicated to the terminal by the CFI (Control Format Indicator) transmitted through the PCFICH (Physical Control Format Indicator CHannel).

[0075] By allocating PDCCH (201) to the OFDM symbol at the beginning of the subframe, the terminal can decode the downlink scheduling assignment as quickly as possible, thereby reducing the decoding delay for the DL-SCH (Downlink Shared CHannel), i.e., the overall downlink transmission delay.

[0076] A single PDCCH carries a single DCI message, and since multiple terminals can be scheduled simultaneously on downlink and uplink, multiple PDCCH transmissions occur 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 (IDentity). 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 PDCCH in LTE is limited to open-loop transmit diversity. The number of ports of the CRS is implicitly known to the terminal through the decoding of the PBCH (Physical Broadcast CHannel).

[0077] Resource allocation for PDCCH (201) is based on Control-Channel Elements (CCEs), and each CCE consists of nine Resource Element Groups (REGs), for a total of 36 Resource Elements (REs). The number of CCEs required for a specific PDCCH (201) can be 1, 2, 4, or 8, depending on the channel coding rate of the DCI message payload. These different numbers of CCEs are used to implement link adaptation for PDCCH (201).

[0078] The terminal 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 terminal 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 the CCEs within the configured search space, and processes information declared valid for the terminal through CRC verification.

[0079] 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).

[0080] In LTE, the entire PDCCH region is composed of a set of CCEs in the logical domain, and a search space exists consisting of these 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 follows.

[0081]

[0082] According to the definition of search space for the PDCCH described above, the terminal-specific search space is not explicitly signaled, but is implicitly defined through a function based on terminal identity and subframe number. In other words, since the terminal-specific search space can change based on subframe number, this implies that it can change over time, thereby resolving the problem of certain terminals being blocked from using the search space by other terminals (blocking problem).

[0083] In one embodiment, if a particular terminal is not scheduled in a subframe because all the CCEs it is searching for are already being used by other terminals scheduled in the same subframe, this problem may not occur in the next subframe because this search space changes over time. For example, even if a portion of the terminal-specific search spaces of terminal #1 and terminal #2 overlap in a particular subframe, the overlap in the next subframe can be expected to be different because the terminal-specific search space changes from subframe to subframe.

[0084] 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.

[0085] 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 the table below.

[0086] [Table 1]

[0087]

[0088] According to [Table 1], the terminal-specific search space supports aggregation levels {1, 2, 4, 8}, with each having {6, 6, 2, 2} PDCCH candidates. The common search space supports aggregation levels {4, 8}, with each having {4, 2} PDCCH candidates. The reason the common search space only supports aggregation levels {4, 8} is to improve coverage characteristics, as system messages generally need to reach the cell edge.

[0089] 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.

[0090] 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.

[0091] Below, the downlink control channel in the 5G communication system currently being discussed will be described in more detail with reference to drawings.

[0092] Figure 3 is a diagram illustrating transmission resources for a downlink control channel in 5G. Specifically, Figure 3 is a diagram showing an example of the basic units of time and frequency resources that constitute a downlink control channel in 5G.

[0093] According to FIG. 3, the REG (Resource Element Group) (303), which is the basic unit of time and frequency resources constituting the control channel, is composed of 1 OFDM symbol (301) on the time axis and 12 subcarriers (302), i.e., 1 RB (Resource Block) 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.

[0094] 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 a Control Channel Element (CCE) (304), 1 CCE (304) can be composed of multiple REGs (303). Taking REG (303) 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.

[0095] 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 REs to which a DMRS (Demodulation Reference Signal) (305), which is a reference signal for decoding the same, is mapped. As shown in FIG. 3, the DMRS (305) may be transmitted in three REs within one REG (303). For reference, since the DMRS (305) 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.

[0096] Figure 4 is a diagram illustrating an example of a control region configuration in 5G. Specifically, Figure 4 is a diagram illustrating an example of a control region (CORESET; Control Resource Set) through which a downlink control channel is transmitted in a 5G wireless communication system.

[0097] An example of Fig. 4 is a case where 1 slot is assumed to be 7 OFDM symbols. Fig. 4 shows an example in which two control regions (control region #1 (401), control region #2 (402)) are set within 1 slot (420) on the time axis and the system bandwidth (410) on the frequency axis. The frequency of the control regions (401, 402) can be set to a specific subband (403) within the entire system bandwidth (410). The time length of the control regions (401, 402) can be set to one or more OFDM symbols, and further, the time length of the control regions (401, 402) can be defined as the control region length (Control Resource Set Duration) (404). In an 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.

[0098] The control region in 5G, as described above, can be established by the base station to the terminal via higher-layer signaling (e.g., system information, Master Information Block (MIB), RRC signaling). Establishing 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 2].

[0099] [Table 2]

[0100]

[0101] The configuration information in [Table 2] is an example of the present disclosure, and in addition to the configuration information in [Table 2], various pieces of information required for transmitting a downlink control channel can be set in the terminal.

[0102] Next, we will explain in detail the downlink control information (DCI) in 5G.

[0103] 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 through DCI.

[0104] A terminal can monitor a fallback DCI format and a non-fallback DCI format for PUSCH or PDSCH. The fallback DCI format may consist of fixed fields between the base station and the terminal, and the non-fallback DCI format may include configurable fields.

[0105] According to one embodiment of the present disclosure, a DCI for scheduling a PUSCH may include information of [Table 3].

[0106] [Table 3]

[0107]

[0108] According to one embodiment of the present disclosure, DCI for non-contingent scheduling of PUSCH may include information of [Table 4].

[0109] [Table 4]

[0110]

[0111]

[0112] According to one embodiment of the present disclosure, a DCI for scheduling a PDSCH may include information of [Table 5].

[0113] [Table 5]

[0114]

[0115] According to one embodiment of the present disclosure, a DCI for non-contingent scheduling of a PDSCH may include information of [Table 6].

[0116] [Table 6]

[0117]

[0118]

[0119] The above DCI can be transmitted through the Physical Downlink Control CHannel (PDCCH) after going through channel coding and modulation processes. The DCI message payload includes a CRC (Cyclic Redundancy Check), which is scrambled with an RNTI (Radio Network Temporary Identifier), which corresponds to the terminal's identity.

[0120] Different RNTIs are used depending on the purpose of the DCI message, such as UE-specific data transmission, power control commands, or random access responses. In other words, the RNTI is not explicitly transmitted but is included in the CRC calculation process. When a UE receives a DCI message transmitted on the PDCCH, it can verify the CRC using the assigned RNTI. If the CRC verification result is correct, the UE knows that the message was sent to that UE.

[0121] 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).

[0122] When a specific terminal is scheduled for a data channel, i.e., PUSCH or PDSCH, through the PDCCH, data is transmitted and received together with DMRS within the scheduled resource region.

[0123] FIG. 5 is a diagram illustrating an example of a configuration for a downlink RB structure in 5G.

[0124] In more detail, Fig. 5 illustrates a case where a specific terminal uses 14 OFDM symbols as one slot (or subframe) in the downlink, PDCCH is transmitted in the first two OFDM symbols, and 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 DMRS is not transmitted in the third symbol and REs from the fourth to the last symbol thereafter. The subcarrier spacing expressed in Fig. 5 For LTE / LTE-A systems, it is 15 kHz, and for 5G systems, one of {15, 30, 60, 120, 240, 480} kHz is used.

[0125] Meanwhile, as described above, to measure downlink channel conditions in a cellular system, the base station must transmit a reference signal. In the 3GPP's LTE-A (Long Term Evolution Advanced) system, the terminal can measure the channel conditions between the base station and the terminal using the CRS or CSI-RS transmitted by the base station.

[0126] The above channel condition 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 condition of the downlink. For example, when a base station with one transmit antenna transmits a signal to a terminal with one receive antenna, the terminal must determine the energy per symbol that can be received in the downlink from the reference signal received from the base station and the amount of interference that will be simultaneously received during the period of receiving the corresponding symbol to determine Es / Io. The determined Es / Io is converted into a data transmission rate or an equivalent value and transmitted to the base station in the form of a channel quality indicator (CQI), which can be used by the base station to determine at what data transmission rate to perform transmission to the terminal.

[0127] More specifically, in the LTE-A system, the terminal feeds back information about the downlink channel status to the base station so that it can be utilized for the base station's downlink scheduling. That is, the terminal measures the reference signal transmitted by the base station in 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.

[0128] - Rank Indicator (RI): The number of spatial layers that the terminal can receive in the current channel state.

[0129] - Precoding Matrix Indicator (PMI): An indicator of the precoding matrix preferred by the terminal in the current channel condition.

[0130] - Channel Quality Indicator (CQI): The maximum data rate that the terminal can receive in the current channel condition.

[0131] 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.

[0132] 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, 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.

[0133] Also, as an example, when a terminal determines the CQI, it assumes that the PMI value X that it notified to the base station is applied at 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 using the transmission method.

[0134] In LTE / LTE-A, channel state information (RI, PMI, CQI) fed back by a terminal can be fed back in a periodic or aperiodic form. If a base station wishes to aperiodically acquire channel state information of a specific terminal, the base station can configure 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, and can be defined as 4 for FDD (Frequency Division Duplexing) and as shown in [Table 7] for TDD (Time Division Duplexing).

[0135] [Table 7] k value for each subframe number n in TDD UL / DL configuration

[0136]

[0137] 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.

[0138] Figure 6 is a diagram showing a slot structure according to an example of a TDD setting.

[0139] More specifically, when the ratio of the number of DL Slots to the number of UL Slots is approximately 4:1, it can be expressed as in Fig. 6. However, in the case of a DL Slot located immediately before a UL Slot, not all symbols may be DL symbols, and at least there is a Guard symbol that takes into account the propagation delay time of the radio wave, but for convenience, it is classified as a DL Slot in the example.

[0140] Also, as an example, when DL Slots are consecutive, each slot can be distinguished by assigning a number, such as D#1 to D#4, as shown in FIG. 6. Similarly, when UL Slots are consecutive, each consecutive slot can be distinguished by assigning a number, etc. For convenience of explanation, the present disclosure will focus on downlink transmission.

[0141] Base station resource allocation is not fixed and is implementation-dependent. Specifically, transmission constraints or rules can be internally defined for interference control. For example, consider the following transmission constraints:

[0142] Each base station can apply transmission constraints so that resource allocation does not start immediately when data arrives in its buffer, but rather starts from a specific slot.

[0143] Figure 7 is a diagram showing the average channel conditions for each slot number when there are transmission constraints such as the example above. The average channel conditions indicated on the Y-axis can be the average SINR, the average CQI value reported by the terminal to the base station, or the average MCS value, which is the channel condition of the terminal as perceived by the base station. The number of slots for resource allocation is determined based on the amount of traffic requested by the terminal, and resource allocation is performed sequentially starting from a specific slot. Therefore, as shown in the diagram, the slots further away from the slot where resource allocation begins often have less interference, resulting in a better average channel condition. In other words, a better average channel condition means a higher possibility of assigning a higher MCS.

[0144] Figure 8 is a diagram illustrating an example of a conventional retransmission process. Specifically, Figure 8 is a simplified diagram illustrating the retransmission process when a specific transmission fails. For convenience, this diagram assumes that a TB is transmitted using the PDSCH in the same slot after a DCI transmission via the PDCCH. As shown in Figure 8, if the transmission of the third TB fails and a HARQ NACK is received from the UE, the base station performs a retransmission of the corresponding TB. At this time, the base station can transmit in any slot, regardless of the specific slot. When the transmission in Figure 8 is performed, it is assumed that the channel conditions as in Figure 7 are present. The transmission in D#3 may have been assigned a high MCS because it exhibits an average good channel condition. However, if the transmission fails, retransmission provides a combining gain, which increases the probability of success. In other words, the channel conditions during retransmission are also important for achieving the combining gain. However, in channel conditions such as those in Figure 7, the average channel condition in D#2 is worse than that in D#3, so even if combining gains are achieved, the average channel condition is likely to still be worse than that in D#3. Consequently, even if retransmissions are performed, there is a high probability that transmissions will still fail. However, if retransmissions were performed in D#3, which has similar channel conditions, the combining gains would increase the probability of success.

[0145] In order to solve the problem described above, this patent proposes a technique for retransmitting in slots with similar channel conditions.

[0146] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Although embodiments of the present disclosure will be described below using LTE or LTE-A systems as examples, embodiments of the present disclosure may also be applied to other communication systems with similar technical backgrounds or channel types. For example, communication systems to which embodiments of the present disclosure are applicable may also include fifth-generation mobile communication technology (5G, new radio, NR) developed after LTE-A. Therefore, embodiments of the present disclosure may be applied to other communication systems with some modifications within a scope that does not significantly deviate from the scope of the present disclosure, as determined by a person having skilled technical knowledge.

[0147] Additionally, when describing the present disclosure, detailed descriptions of related 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 contents of this specification.

[0148] <Example 1>

[0149] Example 1 describes a method for performing retransmission in a slot having a channel condition similar to that of the initial transmission when a failed transmission is retransmitted.

[0150] FIG. 9 is a diagram illustrating an example of an average channel situation and a similar channel situation for each slot number according to an embodiment of the present invention. FIG. 9 is a diagram illustrating a channel situation for each slot number, similar to FIG. 7. In this diagram, for convenience, it is assumed that slots are managed in units of eight. As shown in FIG. 9, slots exhibiting similar average channel situations can be expressed in a similar pattern. In addition, if the average channel situation is considered to be the average MCS used by the base station when allocating resources to the corresponding terminal, it can be considered as shown in the illustrated example.

[0151] In this embodiment, if a failed transmission is retransmitted, the retransmission is assigned in a channel situation similar to that of the initial transmission. For example, if a transmission in D#3 fails, the retransmission for the corresponding data can be performed in the same slot number D#3. This example will be described in more detail in Embodiment 2. As another example, if a transmission in D#3 fails, the retransmission for the corresponding data can be performed in other slots D#5 or D#7 that have similar channel conditions to the corresponding slot including D#3. This example will also be described in more detail in Embodiment 5.

[0152] <Example 2>

[0153] Example 2 describes a method of retransmitting while maintaining the slot number the same as in Example 1.

[0154] FIG. 10 is a diagram illustrating another embodiment of the present invention. Specifically, FIG. 10 is an example diagram showing that, when transmission in slot D#1 fails in performing Embodiment 2, retransmission is performed in slot D#1 having the same slot number. As in FIG. 10, the numbering of slots varies depending on the number of units in which slots are managed. In order to manage D#1 to D#4 as in FIG. 10, a cycle for counting slot numbers (expressed as T in the diagram, T = 5) is required. The slots in which retransmission can be performed may vary depending on the value of the cycle for counting slot numbers.

[0155] <Example 3>

[0156] Example 3 describes a method of performing retransmission without retransmission scheduling via DCI in accordance with Example 2.

[0157] FIG. 11 is a diagram illustrating another embodiment of the present invention. Specifically, FIG. 11 is an example diagram showing that when transmission in slot D#1 fails in performing Embodiment 3, when retransmission is performed in slot D#1 with the same slot number, PDSCH transmission is performed without DCI in the retransmission using only the DCI transmitted in the initial transmission. In FIG. 11, the DCI proposed in the present invention is indicated as proposed DCI, and it is assumed to be classified in a separate format from the existing DCI.

[0158] In this embodiment, when the base station allocates resources for retransmission, it is assumed that the resource allocation in the time axis and frequency axis is the same as that of the initial transmission. When the base station receives a NACK from the uplink resource where the terminal transmits HARQ ACK / NACK information, or when the base station fails to receive a HARQ ACK / NACK, it performs an operation of allocating a retransmission from the announced resource.

[0159] In order for the terminal to operate as in this embodiment, the following information is required.

[0160] a. Slot count period (for example, T = 5 in the example of Fig. 10)

[0161] b. If the initial transmission fails, the location of the slot to which retransmission will be allocated.

[0162] c. Redundancy version (RV) to be used when retransmitting.

[0163] The above information can be set using RRC or DCI. Furthermore, some of the above information can be set via RRC, while others can be set via DCI. For convenience, this embodiment will only describe the cases where all information is set via RRC and the cases where all information is set via DCI.

[0164] - When set via RRC

[0165] When set via RRC, information corresponding to a, b, and c can be set.

[0166] The b information can be expressed in various ways. It can indicate the location where the retransmission will be allocated based on the DCI transmission location, and the length of the entire slot. This is expressed as AT in Fig. 10. Alternatively, since the location where the retransmission will be allocated will be a multiple of the a information, there is a method of setting a coefficient so that the terminal can calculate it by combining it with the a information. This corresponds to A in Fig. 10. In addition, similar to the example in Fig. 10, it is possible to set that there will be a retransmission allocation after the BT slot based on the location of the HARQ ACK / NACK, and only the coefficient B can be set.

[0167] c information can preset the order of RVs when retransmission occurs. For example, if the retransmission RV is set to 0231, the terminal can identify the RV of the retransmitted TB by looking at the information.

[0168] When configured via RRC, an additional field is required in the DCI indicating that the DCI operates as in this embodiment. Alternatively, it may operate in the same manner as in this embodiment only when the RRC value proposed in this embodiment is configured.

[0169] - When set through DCI

[0170] As with the case where it is set via the RRC, if the information of a and b is set via DCI, additional fields must be newly defined. If the information of c is set in advance for all retransmissions in RRC, it can only indicate the RV value corresponding to the immediately next retransmission in the newly defined field via DCI, or it can set all RVs in advance and notify them like RRC.

[0171] To use the proposed DCI as in this embodiment, additional RRC settings are required. Specifically, the additional RRC settings for the redundancy version order for retransmission may be as follows.

[0172]

[0173] In the above description, repK may refer to the maximum number of configured retransmissions, and repK-RV may refer to the RV order according to the number of retransmissions. The proposed DCI must define a new DCI format, and must notify the terminal through RRC configuration that the format can be transmitted through Search Space configuration. If a new DCI format is not defined in order to use the proposed DCI, there is a method to utilize the existing format in terms of Search Space, but define an indicator to use the form of the proposed DCI format, and notify the terminal through RRC.

[0174] <Example 4>

[0175] Example 4 describes a retransmission method using reduced DCI in accordance with Example 2.

[0176] FIG. 12 is a diagram illustrating another embodiment of the present invention. Specifically, FIG. 12 is an example diagram showing that when transmission in slot D#1 fails in performing Embodiment 3, when retransmission is performed in slot D#1 having the same slot number, the proposed DCI is used for the initial transmission, and PDSCH transmission is performed through reduced DCI for the retransmission. In FIG. 12, the DCI used for the initial transmission allocation proposed in the present invention is indicated as proposed DCI, and the DCI used for the retransmission allocation is indicated as reduced DCI. It is assumed that both proposed DCIs are classified in a separate format from the existing DCI to be transmitted, and for convenience, they are named in the above format.

[0177] In this embodiment, the base station can utilize resources for retransmission even when the resource allocation along the time axis and frequency axis differs from the initial transmission. When the base station receives a NACK from the uplink resource where the terminal transmits HARQ ACK / NACK information, or when the base station fails to receive a HARQ ACK / NACK, it performs an operation of allocating retransmission from the announced resource.

[0178] In order for the terminal to operate as in this embodiment, the following information is required as in Example 3, and the terminal can also recognize that reduced DCI will be transmitted at the corresponding location.

[0179] a. The cycle for counting slot numbers (T = 5 in the example of Fig. 10)

[0180] b. If the initial transmission fails, the location of the slot to which retransmission will be allocated.

[0181] c. Redundancy version (RV) to be used when retransmitting.

[0182] The above information can be set using RRC or DCI. Furthermore, some of the above information can be set via RRC, while others can be set via DCI. For convenience, this embodiment will only describe the cases where all information is set via RRC and the cases where all information is set via DCI.

[0183] - When set via RRC

[0184] When set via RRC, information corresponding to a, b, and c can be set.

[0185] The b information can be expressed in various ways. It can indicate the location where the retransmission will be allocated based on the DCI transmission location, and the length of the entire slot. This is expressed as AT in Fig. 10. Alternatively, since the location where the retransmission will be allocated will be a multiple of the a information, there is a method of setting a coefficient so that the terminal can calculate it by combining it with the a information. This corresponds to A in Fig. 10. In addition, similar to the example in Fig. 10, it is possible to set that there will be a retransmission allocation after the BT slot based on the location of the HARQ ACK / NACK, and only the coefficient B can be set.

[0186] c information can preset the order of RVs when retransmission occurs. For example, if the retransmission RV is set to 0231, the terminal can identify the RV of the retransmitted TB by looking at the information.

[0187] When configured via RRC, an additional field is required in the DCI indicating that the DCI operates as in this embodiment. Alternatively, it may operate in the same manner as in this embodiment only when the RRC value proposed in this embodiment is configured.

[0188] - When set through DCI

[0189] As with the case where it is set via the RRC, if the information of a and b is set via DCI, additional fields must be newly defined. If the information of c is set in advance for all retransmissions in RRC, it can only indicate the RV value corresponding to the immediately next retransmission in the newly defined field via DCI, or it can set all RVs in advance and notify them like RRC.

[0190] To use the proposed DCI as in this embodiment, additional RRC configuration is required. Specifically, the additional RRC configuration for the redundancy version order for retransmission may be as follows.

[0191]

[0192] In the above description, repK may refer to the maximum number of configured retransmissions, and repK-RV may refer to the RV order according to the number of retransmissions. The proposed DCI must define a new DCI format, and must notify the terminal through RRC configuration that the format can be transmitted through Search Space configuration. If a new DCI format is not defined in order to use the proposed DCI, there is a method of utilizing the existing format in terms of Search Space, but defining an indicator to use the form of the proposed DCI format, and notifying the terminal through RRC.

[0193] In the case of reduced DCI, only time-domain resource allocation information and frequency-domain resource allocation information may be included. It is assumed that the terminal has received the necessary information in the proposed DCI, as in the previous embodiment 3. At this time, in order to perform retransmission as in this embodiment, the terminal can know the reduced DCI and the location of the slot where retransmission will occur through the proposed DCI. In order to check the reduced DCI at the corresponding location, a new format must be defined in RRC. In addition, it is necessary to notify the terminal through RRC that the newly defined format can be transmitted through the PDCCH through the Search Space configuration.

[0194] At this time, since reduced DCI contains less information than existing technology, transmission is possible using minimal PDCCH resources. For example, if existing DCI transmission requires N CCE, reduced DCI requires M CCE (M < N), so the resource requirement becomes M / N, and the PDCCH capacity increases by approximately N / M times.

[0195] <Example 5>

[0196] Example 5 describes a method for defining a group of slots with similar channel conditions and retransmitting them while maintaining the group as the same as in Example 1.

[0197] FIG. 13 is a diagram illustrating another embodiment of the present invention. Specifically, FIG. 13 is an example diagram showing that, when transmission in slot D#1 fails during embodiment 5, retransmission is performed in slot D#1 or D#3 having the same slot number or the same channel conditions. As in FIG. 13, the slot number assignment varies depending on the number of units in which slots are managed. In addition, it also varies depending on the number of slots and each slot having similar channel conditions. Similar to FIG. 10, in FIG. 13, in order to manage slots D#1 to D#4, a slot number counting cycle (represented as T in the drawing, T = 5) is required. The slots in which retransmission can be performed can vary depending on the value of the slot number counting cycle. In addition, the slots in which retransmission can be performed vary depending on slots having similar channel conditions, and for convenience, slots having similar channel conditions are represented in the same format in FIG. 13.

[0198] <Example 6>

[0199] Example 6 describes a method of performing retransmission without retransmission scheduling via DCI in accordance with Example 5.

[0200] FIG. 14 is a diagram illustrating another embodiment of the present invention. Specifically, FIG. 14 is an example diagram showing that when transmission in slot D#1 fails in performing Embodiment 6, when retransmission is performed in slot D#1 or D#3 having the same slot number or the same channel conditions, PDSCH transmission is performed without DCI in the retransmission using only the DCI transmitted in the initial transmission. In FIG. 14, the DCI proposed in the present invention is indicated as proposed DCI, and it is assumed to be classified in a separate format from the existing DCI. In addition, for convenience, slots having similar channel conditions are named the same group.

[0201] In this embodiment, similar to Embodiment 3, the base station assumes that when allocating resources for retransmission, the resource allocation in the time axis and frequency axis is the same as that of the initial transmission. When the base station receives a NACK in the uplink resource where the terminal transmits HARQ ACK / NACK information, or when the base station fails to receive a HARQ ACK / NACK, it performs an operation of allocating a retransmission in a slot within the announced group.

[0202] In order for the terminal to operate as in this embodiment, the following information is required.

[0203] a. The cycle for counting slot numbers (T = 5 in the example of Fig. 10)

[0204] b. If the initial transmission fails, the location of the slot to which retransmission will be allocated.

[0205] c. Redundancy version (RV) to be used when retransmitting.

[0206] d. Group information of slots with similar channel conditions

[0207] The above information can be set using RRC or DCI. Furthermore, some of the above information can be set via RRC, while others can be set via DCI. For convenience, this embodiment will only describe the cases where all information is set via RRC and the cases where all information is set via DCI.

[0208] - When set via RRC

[0209] When set via RRC, information corresponding to a, b, and c can be set.

[0210] The b information can be expressed in various ways. It can indicate the location where the retransmission will be allocated based on the DCI transmission location, and the length of the entire slot. This is expressed as AT in Fig. 10. Alternatively, since the location where the retransmission will be allocated will be a multiple of the a information, there is a method of setting a coefficient so that the terminal can calculate it by combining it with the a information. This corresponds to A in Fig. 10. In addition, similar to the example in Fig. 10, it is possible to set that there will be a retransmission allocation after the BT slot based on the location of the HARQ ACK / NACK, and only the coefficient B can be set.

[0211] c information can preset the order of RVs when retransmission occurs. For example, if the retransmission RV is set to 0231, the terminal can identify the RV of the retransmitted TB by looking at the information.

[0212] d information can set information for each group based on a information. The information set may vary for each terminal depending on the number of groups and the slots belonging to each group.

[0213] When configured via RRC, an additional field is required in the DCI indicating that the DCI operates as in this embodiment. Alternatively, it may operate in the same manner as in this embodiment only when the RRC value proposed in this embodiment is configured.

[0214] - When set through DCI

[0215] As with the case where it is set via the RRC, if the information of a and b is set via DCI, additional fields must be newly defined. If the information of c is set in advance for all retransmissions in RRC, it can only indicate the RV value corresponding to the immediately next retransmission in the newly defined field via DCI, or it can set all RVs in advance and notify them like RRC.

[0216] Additionally, information for d can be configured in a newly defined field via DCI, and can be configured in various ways. For example, it can be configured to report all slots that make up the same group as the initial transmission. Since the terminal cannot know where its retransmission data will arrive within the group, it must perform decoding after receiving the PDSCH in every slot, which is inefficient. Alternatively, it is also possible to pre-configure specific slots within the group.

[0217] To use the proposed DCI as in this embodiment, additional RRC settings are required. Specifically, the additional RRC settings for the redundancy version order for retransmission may be as follows.

[0218]

[0219] In the above description, repK may refer to the maximum number of configured retransmissions, and repK-RV may refer to the RV order according to the number of retransmissions. The proposed DCI must define a new DCI format, and must notify the terminal through RRC configuration that the format can be transmitted through Search Space configuration. If a new DCI format is not defined in order to use the proposed DCI, there is a method to utilize the existing format in terms of Search Space, but define an indicator to use the form of the proposed DCI format, and notify the terminal through RRC.

[0220] <Example 7>

[0221] Example 7 describes a retransmission method using reduced DCI in accordance with Example 5.

[0222] FIG. 15 is a diagram illustrating another embodiment of the present invention. Specifically, FIG. 15 is an example diagram showing that when transmission in slot D#1 fails in performing Embodiment 7, when retransmission is performed in slot D#1 or D#3 having the same slot number or the same channel condition, PDSCH transmission is performed through reduced DCI for retransmission. In FIG. 15, the DCI used for initial transmission allocation proposed in the present invention is indicated as proposed DCI, and the DCI used for retransmission allocation is indicated as reduced DCI. It is assumed that both proposed DCIs are classified in a separate format from the existing DCI to be transmitted, and for convenience, they are named in the above format.

[0223] In this embodiment, similar to Embodiment 4, the base station assumes that when allocating resources for retransmission, the resource allocation in the time axis and frequency axis is the same as that of the initial transmission. When the base station receives a NACK in the uplink resource where the terminal transmits HARQ ACK / NACK information, or when the base station fails to receive a HARQ ACK / NACK, it performs an operation of allocating a retransmission in a slot within the announced group.

[0224] In order for the terminal to operate as in this embodiment, the following information is required.

[0225] a. The cycle for counting slot numbers (T = 5 in the example of Fig. 10)

[0226] b. If the initial transmission fails, the location of the slot to which retransmission will be allocated.

[0227] c. Redundancy version (RV) to be used when retransmitting.

[0228] d. Group information of slots with similar channel conditions

[0229] The above information can be set using RRC or DCI. Furthermore, some of the above information can be set via RRC, while others can be set via DCI. For convenience, this embodiment will only describe the cases where all information is set via RRC and the cases where all information is set via DCI.

[0230] - When set via RRC

[0231] When set via RRC, information corresponding to a, b, and c can be set.

[0232] The b information can be expressed in various ways. It can indicate the location where the retransmission will be allocated based on the DCI transmission location, and the length of the entire slot. This is expressed as AT in Fig. 10. Alternatively, since the location where the retransmission will be allocated will be a multiple of the a information, there is a method of setting a coefficient so that the terminal can calculate it by combining it with the a information. This corresponds to A in Fig. 10. In addition, similar to the example in Fig. 10, it is possible to set that there will be a retransmission allocation after the BT slot based on the location of the HARQ ACK / NACK, and only the coefficient B can be set.

[0233] c information can preset the order of RVs when retransmission occurs. For example, if the retransmission RV is set to 0231, the terminal can identify the RV of the retransmitted TB by looking at the information.

[0234] d information can set information for each group based on a information. The information set may vary for each terminal depending on the number of groups and the slots belonging to each group.

[0235] When configured via RRC, an additional field is required in the DCI indicating that the DCI operates as in this embodiment. Alternatively, it may operate in the same manner as in this embodiment only when the RRC value proposed in this embodiment is configured.

[0236] - When set through DCI

[0237] As with the case where it is set via the RRC, if the information of a and b is set via DCI, additional fields must be newly defined. If the information of c is set in advance for all retransmissions in RRC, it can only indicate the RV value corresponding to the immediately next retransmission in the newly defined field via DCI, or it can set all RVs in advance and notify them like RRC.

[0238] Additionally, information for d can be configured in a newly defined field via DCI, and can be configured in various ways. For example, it can be configured to report all slots that make up the same group as the initial transmission. Since the terminal cannot know where its retransmission data will arrive within the group, it must perform decoding after receiving the PDSCH in every slot, which is inefficient. Alternatively, it is also possible to pre-configure specific slots within the group.

[0239] To use the proposed DCI as in this embodiment, additional RRC settings are required. Specifically, the additional RRC settings for the redundancy version order for retransmission may be as follows.

[0240]

[0241] In the above description, repK may refer to the maximum number of configured retransmissions, and repK-RV may refer to the RV order according to the number of retransmissions. The proposed DCI must define a new DCI format, and must notify the terminal through RRC configuration that the format can be transmitted through Search Space configuration. If a new DCI format is not defined in order to use the proposed DCI, there is a method to utilize the existing format in terms of Search Space, but define an indicator to use the form of the proposed DCI format, and notify the terminal through RRC.

[0242] In the case of reduced DCI, only time-domain resource allocation information and frequency-domain resource allocation information may be included. The terminal operates as if it had received the necessary information from the proposed DCI, as in the previous embodiment 3. At this time, in order to perform retransmission as in the present embodiment, the terminal can know the reduced DCI and the location of the slot where the retransmission will occur through the proposed DCI. In order to confirm the reduced DCI at that location, a new format must be defined in RRC. In addition, it must be notified to the terminal through RRC that the newly defined format can be transmitted via the PDCCH through the Search Space configuration.

[0243] At this time, since reduced DCI contains less information than existing technology, transmission is possible using minimal PDCCH resources. For example, if existing DCI transmission requires N CCE, reduced DCI requires M CCE (M < N), so the resource requirement becomes M / N, and the PDCCH capacity increases by approximately N / M times.

[0244] <Example 8>

[0245] Example 8 describes the case where the terminal fails to decode DCI.

[0246] In this embodiment, the case where the terminal fails DCI can be divided into 1) cases where there is only one transmission during a given period, and 2) cases where there are multiple transmissions.

[0247] 1) If there is only one transmission within a cycle, and the ACK / NACK itself is not received when the terminal transmits HARQ ACK / NACK, the base station can determine that the terminal has failed to decode DCI and, rather than entering the retransmission process, can operate to restart from the DCI transmission for the corresponding TB.

[0248] 2) When there are multiple transmissions within a cycle, the terminal usually transmits multiple TBs at once as HARQ ACK / NACK, which is usually called an ACK codebook. At this time, even if there is a transmission that failed in the middle or a transmission where DCI decoding failed, the terminal can record and transmit a NACK because it knows the total number of transmissions and the current TB. To solve this, two methods are possible. First, for all transmissions determined to be NACKs, transmission can be restarted from the DCI transmission for the corresponding TB, as if there was only one transmission within the cycle. Second, the terminal can provide additional information about the NACK portion of the ACK codebook, to transmit information on whether the NACK is due to a DCI failure or whether the DCI was successful but TB decoding failed. In this case, the base station only needs to restart transmission from the DCI for the corresponding transmission, which is more efficient than the first method.

[0249] FIG. 16 is a diagram illustrating the structure of a terminal according to one embodiment of the present invention.

[0250] Referring to FIG. 16, the terminal may include a transceiver (1610), a control unit (1620), and a storage unit (1630). In the present invention, the control unit may be defined as a circuit or an application-specific integrated circuit or at least one processor.

[0251] The transceiver (1610) can transmit and receive signals with other network entities. The transceiver (1610) can receive system information from a base station, for example, and can receive a synchronization signal or a reference signal.

[0252] The control unit (1620) can control the overall operation of the terminal according to the embodiment proposed in the present invention. For example, the control unit (1620) can control the signal flow between each block to perform operations according to the flowchart described above.

[0253] The storage unit (1630) can store at least one of the information transmitted and received through the transmission and reception unit (1610) and the information generated through the control unit (1620).

[0254] FIG. 17 is a diagram illustrating the structure of a base station according to one embodiment of the present invention.

[0255] Referring to FIG. 17, the base station may include a terminal, a transceiver (1710), a control unit (1720), and a storage unit (1730). In the present invention, the control unit may be defined as a circuit or an application-specific integrated circuit or at least one processor.

[0256] The transceiver (1710) can transmit and receive signals with other network entities. The transceiver (1710) can transmit system information to a terminal, for example, and can transmit a synchronization signal or a reference signal.

[0257] The control unit (1720) can control the overall operation of the base station according to the embodiment proposed in the present invention. For example, the control unit (1720) can control the signal flow between each block to perform operations according to the flowchart described above. Specifically, the control unit (1720) can control the operation proposed in the present invention to transmit residual system information (RMSI) in a multi-beam-based system according to the embodiment of the present invention.

[0258] The storage unit (1730) can store at least one of the information transmitted and received through the transmission and reception unit (1710) and the information generated through the control unit (1720).

Claims

1. A method performed by a base station in a wireless communication system, the method comprising: A step of transmitting first downlink control information (DCI) and a transport block (TB) to a terminal; A step of transmitting a transport block (TB) based on the first DCI to the terminal; If the transmission of the above transmission block fails, a step of receiving HARQ (Hybrid automatic repeat request) feedback from the terminal; and Including a step of retransmitting the transmission block based on the HARQ feedback to the terminal, A method, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource count, and redundancy version (RV) information for retransmission.

2. In paragraph 1, A method characterized by further comprising the step of transmitting an RRC (Radio Resource Control) message including a maximum set number of retransmissions and an RV order according to the number of retransmissions related to RV information for the above retransmission.

3. In paragraph 1, Further comprising a step of transmitting the second downlink control information based on the HARQ feedback to the terminal, A method, characterized in that the second downlink control information includes only time domain resource allocation and frequency domain resource allocation.

4. In the first paragraph, the step of retransmitting the transmission block is: A step of grouping slots with similar channel conditions and retransmitting the transmission block within the same group, A method, characterized in that the first downlink control information further includes group information and slot information for the group.

5. In a method performed by a terminal in a wireless communication system, the method comprises: A step of receiving first downlink control information (DCI) from a base station; A step of receiving a transport block (TB) based on the first DCI from the base station; If reception of the above transmission block fails, a step of transmitting HARQ (Hybrid automatic repeat request) feedback to the base station; and comprising a step of re-receiving the transmission block based on the HARQ feedback from the base station; A method, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource count, and redundancy version (RV) information for retransmission.

6. In paragraph 5, A method characterized by further comprising the step of receiving an RRC (Radio Resource Control) message including a maximum set number of retransmissions and an RV order according to the number of retransmissions related to RV information for the above retransmission.

7. In paragraph 5, Further comprising a step of receiving the second downlink control information based on the HARQ feedback from the base station, A method, characterized in that the second downlink control information includes only time domain resource allocation and frequency domain resource allocation.

8. In paragraph 5, the step of re-receiving the transmission block comprises: A step of grouping slots with similar channel conditions and re-receiving the transmission block within the same group, A method, characterized in that the first downlink control information further includes group information and slot information for the group.

9. In a base station in a wireless communication system, A transceiver capable of transmitting and receiving at least one signal; and Including a control unit coupled with the above transmitter and receiver, The above control unit: To the terminal, the first downlink control information (DCI) and transport block (TB) are transmitted, To the above terminal, a transport block (TB) is transmitted based on the first DCI, If the transmission of the above transmission block fails, HARQ (Hybrid automatic repeat request) feedback is received from the terminal, and The terminal is configured to retransmit the transmission block based on the HARQ feedback, A base station, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource count, and redundancy version (RV) information for retransmission.

10. In paragraph 9, the control unit: A base station, characterized in that it is further configured to transmit an RRC (Radio Resource Control) message including a maximum set number of retransmissions and an RV order according to the number of retransmissions related to RV information for the above retransmission.

11. In paragraph 9, the control unit: The terminal is further configured to transmit the second downlink control information based on the HARQ feedback, A base station, characterized in that the second downlink control information includes only time domain resource allocation and frequency domain resource allocation.

12. In paragraph 9, the control unit: Group slots with similar channel conditions and retransmit the transmission block within the same group, A base station, characterized in that the first downlink control information further includes group information and slot information for the group.

13. In a wireless communication system, at a terminal, A transceiver capable of transmitting and receiving at least one signal; and Including a control unit coupled with the above transmitter and receiver, The above control unit: Receive first downlink control information (DCI) from the base station, From the above base station, a transport block (TB) is received based on the first DCI, If the reception of the above transmission block fails, HARQ (Hybrid automatic repeat request) feedback is transmitted to the base station, and configured to re-receive the transmission block from the base station based on the HARQ feedback, A terminal, wherein the first downlink control information includes at least one of a slot number counting period, a retransmission time domain resource count, and redundancy version (RV) information for retransmission.

14. In paragraph 13, the control unit A terminal further characterized by being configured to receive an RRC (Radio Resource Control) message including a maximum set number of retransmissions and an RV order according to the number of retransmissions related to RV information for the above retransmission.

15. In paragraph 13, the control unit Further configured to receive the second downlink control information based on the HARQ feedback from the base station, The above second downlink control information includes only time domain resource allocation and frequency domain resource allocation, Group slots with similar channel conditions and re-receive the transmission block within the same group, A terminal, characterized in that the first downlink control information further includes group information and slot information for the group.

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