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

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate.

Description

Technical Field

[0001] This disclosure relates to wireless communication systems. More specifically, this disclosure relates to a method and apparatus for handling retransmissions between a base station and a terminal in a wireless communication system to control interference. Background Technology

[0002] 5G mobile communication technology defines a wide frequency band, enabling high transmission rates and new services. It can be implemented not only in the "below 6 GHz" band, such as 3.5 GHz, but also in the "above 6 GHz" band, including 28 GHz and 39 GHz, known as mmWave. Furthermore, 6G mobile communication technology (called Super 5G systems) has been considered for implementation in terahertz bands (e.g., the 95 GHz to 3 THz band) to achieve transmission rates fifty times faster than 5G and ultra-low latency one-tenth that of 5G.

[0003] At the outset of 5G mobile communication technology development, standardization was underway regarding beamforming and massive MIMO to support services and meet performance requirements associated with enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC). This standardization aimed to mitigate radio wave path loss in millimeter waves and increase transmission distance, support parameter sets for dynamic operation (e.g., operating multiple subcarrier spacings) to efficiently utilize millimeter wave resources and time slot formats, initial access technologies to support multi-beam transmission and broadband, the definition and operation of bandwidth portions (BWP), new channel decoding methods (such as low-density parity-check (LDPC) codes for large data transmissions and polar codes for highly reliable transmission of control information), L2 preprocessing, and network slicing for providing dedicated networks for specific services.

[0004] Currently, given the services supported by 5G mobile communication technology, discussions are underway regarding improvements and performance enhancements to the initial 5G mobile communication technology. Physical layer standardization for technologies such as Vehicle-to-Everything (V2X) is also in place. This standardization aims to assist autonomous vehicle driving decisions based on information about the vehicle's location and status transmitted by the vehicle, enhancing user convenience. Additionally, there is NR-U (New Radio Unlicensed) and NR UE Energy Saving, Non-Terrestrial Network (NTN), which provides UE-satellite direct communication for coverage and positioning in areas where communication with terrestrial networks is unavailable.

[0005] Furthermore, standardization is ongoing for technologies within the air interface architecture / protocol, such as the Industrial Internet of Things (IIoT) for supporting new services through interoperability and convergence with other industries, Integrated Access and Backhaul (IAB) for providing nodes for network service area extension by supporting wireless backhaul and access links in an integrated manner, mobility enhancements including conditional handover and Dual Active Protocol Stack (DAPS) handover, and two-step random access (two-step RACH for NR) for simplifying the random access process. Standardization is also underway for 5G baseline architectures (e.g., service-based architectures or service-based interfaces) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, as well as system architectures / services for Mobile Edge Computing (MEC) based on UE location reception services.

[0006] With the commercialization of 5G mobile communication systems, the already exponentially growing number of connected devices will be connected to the communication network, thus necessitating enhanced functionality and performance of 5G mobile communication systems as well as integrated operation of connected devices. To this end, new research related to extended reality (XR) has been arranged to effectively support augmented reality (AR), virtual reality (VR), mixed reality (MR), etc., by leveraging artificial intelligence (AI) and machine learning (ML), AI service support, metaspace service support, and drone communication to improve 5G performance and reduce complexity.

[0007] Furthermore, this development of 5G mobile communication systems will not only serve as the foundation for developing new waveforms for providing terahertz band coverage in 6G mobile communication technologies, such as multi-antenna transmission technologies like full-dimensional MIMO (FD-MIMO), array antennas, and massive MIMO; metamaterial-based lenses and antennas for improving terahertz band signal coverage; high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM); and reconfigurable smart surfaces (RIS); it will also serve as the foundation for developing full-duplex technologies to improve the frequency efficiency of 6G mobile communication technologies and enhance system networks; AI-based communication technologies to achieve system optimization by leveraging satellites and AI from the design phase and internalizing end-to-end AI support functions; and next-generation distributed computing technologies to achieve services with complexity levels exceeding the operational capabilities of UEs by utilizing ultra-high-performance communication and computing resources.

[0008] In addition, sidelink communication using 5G communication systems is being studied. It is anticipated that sidelink communication will be applied to applications such as vehicle-to-everything (V2X) and public safety networks, thereby providing users with various services.

[0009] In particular, there is a need to utilize sidelink relay technology that can support expanded service coverage, improved data transmission reliability, and reduced terminal power consumption. Summary of the Invention

[0010] [Technical Issues]

[0011] This disclosure relates to an apparatus and method for providing retransmissions with effective interference control by reflecting the different channel characteristics of each time slot in a wireless communication system.

[0012] The technical problems to be solved by this disclosure are not limited to those described above. In other words, those skilled in the art will readily understand from the following description other technical problems not described herein.

[0013] Solution to the problem

[0014] To address the aforementioned problems, according to one aspect of this disclosure, a method performed by a base station in a wireless communication system includes: sending first downlink control information (DCI) and a transport block (TB) to a terminal; sending the transport block (TB) to the terminal based on the first DCI; receiving Hybrid Automatic Repeat Request (HARQ) feedback from the terminal when the transmission of the transport block fails; and 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.

[0015] In an embodiment, the method further includes sending a Radio Resource Control (RRC) message, which includes a maximum configured number of retransmissions associated with RV information for retransmission and an RV sequence based on the number of retransmissions.

[0016] In an embodiment, the method further includes sending second downlink control information to the terminal based on HARQ feedback, wherein the second downlink control information includes only time-domain resource allocation and frequency-domain resource allocation.

[0017] In the embodiments, time slots with similar channel conditions are grouped based on at least one of signal-to-interference-plus-noise ratio (SINR), channel quality information (CQI), and modulation and coding scheme (MCS), and transport blocks are retransmitted within the same group.

[0018] In this embodiment, the first downlink control information also includes group information and group time slot information.

[0019] Additionally, according to another embodiment of this disclosure, a method performed by a terminal in a wireless communication system includes: receiving first downlink control information (DCI) from a base station; receiving a transport block (TB) from the base station based on the first DCI; sending a Hybrid Automatic Repeat Request (HARQ) feedback to the base station when the reception of the transport block fails; and re-receiving 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] In another embodiment of this disclosure, a base station in a wireless communication system includes: a transceiver capable of transmitting and receiving at least one signal; and a control unit connected 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 the transport block (TB) to the terminal based on the first DCI; receive Hybrid Automatic Repeat Request (HARQ) feedback from the terminal when the 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.

[0021] In another embodiment of this disclosure, a terminal in a wireless communication system includes: a transceiver that transmits and receives at least one signal; and a control unit connected 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; send a Hybrid Automatic Repeat Request (HARQ) feedback to the base station when the reception of the TB fails; and re-receive the TB 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.

[0022] [Beneficial effects of the invention]

[0023] According to embodiments of this disclosure, an apparatus and method can be provided that can provide retransmissions with effective interference control by reflecting the different channel characteristics of each time slot in a wireless communication system.

[0024] The effects achievable by this disclosure are not limited to those described above. In other words, those skilled in the art will readily understand from the following description other effects not mentioned. Attached Figure Description

[0025] Figure 1 This is a diagram illustrating the basic structure of the time-frequency domain in LTE.

[0026] Figure 2 This is a diagram illustrating the downlink control channel in LTE.

[0027] Figure 3 This is a diagram illustrating the transmission resources of the downlink control channel in 5G.

[0028] Figure 4 This is a diagram illustrating an example of the configuration of the control resource set in 5G.

[0029] Figure 5 This is a diagram illustrating an embodiment of the downlink RB structure configuration in 5G.

[0030] Figure 6 This is a diagram showing an example time slot structure based on a TDD configuration.

[0031] Figure 7 This is a diagram illustrating an example of the average channel conditions for each time slot number when transmission constraints exist, according to an embodiment of the present disclosure.

[0032] Figure 8 This is a diagram illustrating an example of a standard retransmission process.

[0033] Figure 9 This is a diagram illustrating an example of average channel conditions and similar channel conditions for each time slot number according to an embodiment of the present disclosure.

[0034] Figure 10 This is a diagram illustrating another embodiment of the present disclosure.

[0035] Figure 11 This is a diagram illustrating another embodiment of the present disclosure.

[0036] Figure 12 This is a diagram illustrating another embodiment of the present disclosure.

[0037] Figure 13 This is a diagram illustrating another embodiment of the present disclosure.

[0038] Figure 14 This is a diagram illustrating another embodiment of the present disclosure.

[0039] Figure 15 This is a diagram illustrating another embodiment of the present disclosure.

[0040] Figure 16 This is a diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0041] Figure 17 This is a diagram illustrating the structure of a base station according to an embodiment of the present disclosure. Detailed Implementation

[0042] With the advancement of the aforementioned wireless communication systems, various services can be provided. Therefore, measures are needed to ensure the smooth delivery of these services. In particular, a communication method that saves terminal power and a channel state information reporting method that takes into account this power saving are needed to provide services to users over longer periods.

[0043] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0044] In describing embodiments, descriptions of technical content known in the art to which this disclosure pertains and not directly related to this disclosure will be omitted. This is to convey the essence of this disclosure more clearly and unambiguously by omitting unnecessary explanations. Furthermore, the following terms are those defined in consideration of the functions of this disclosure and may vary depending on the intentions, practices, etc., of the user and operator. Therefore, the definitions of the terms should be interpreted based on the content of this specification.

[0045] For the same reasons, some components in the accompanying drawings are enlarged, omitted, or shown schematically. Additionally, the size of each component does not perfectly reflect its actual size. In each drawing, the same reference numerals are assigned to the same or corresponding components.

[0046] The advantages and features of this disclosure and its implementation methods will become apparent from the following detailed description of embodiments with reference to the accompanying drawings. However, this disclosure is not limited to the embodiments described below, but can be implemented in various different forms. These embodiments of this disclosure are provided only to complete the disclosure and to enable those skilled in the art to fully appreciate its scope, which is defined by the scope of the claims. Throughout this specification, the same reference numerals denote the same parts.

[0047] In this context, it will be understood that each block and combination of blocks in the flowchart can be executed by computer program instructions. Since these computer program instructions can be mounted on the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, these computer program instructions, executed by the processor of the computer or other programmable data processing device, create means for performing the functions described in the blocks of the flowchart. These computer program instructions can also be stored in a computer-usable or computer-readable storage device that can instruct the computer or other programmable data processing device to operate in a particular manner, thereby causing the instructions stored in the computer-usable or computer-readable storage device to produce an article of art including instruction means that implement the functions described in the blocks of the flowchart. Since the computer program instructions can also be mounted on a computer or other programmable data processing device, performing a series of operational steps on the computer or other programmable data processing device to create a process executed by the computer, thereby executing the instructions of the computer or other programmable data processing device, can also provide steps for performing the functions described in the blocks of the flowchart.

[0048] Additionally, each box may represent a module, segment, or some of the code including one or more executable instructions for performing a specified logical function. Furthermore, it should be noted that in some alternative embodiments, the functions described in the boxes may occur out of order. For example, two boxes shown consecutively may actually be executed simultaneously, or in reverse order according to their corresponding functions.

[0049] In this context, the term "~unit" as used in this embodiment refers to a software or hardware component such as a Field-Programmable Gate Array (FPGA) or Application-Specific Integrated Circuit (ASIC), and the "~unit" performs a specific role. However, "~unit" is not intended to be limited to software or hardware. A "~unit" can be configured to be stored in an addressable storage medium or can be configured to reproduce one or more processors. Therefore, according to some embodiments, a "~unit" includes components such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. Components and functions provided in a "~unit" can be combined into a smaller number of components and / or "~units," or can be divided into additional components and "~units." Furthermore, components and "~units" can be implemented to reproduce one or more CPUs in a device or secure multimedia card. Additionally, according to some embodiments, a "~unit" can include one or more processors.

[0050] The operating principles of this disclosure will be described in detail below with reference to the accompanying drawings. Detailed descriptions of known technologies or configurations related to this disclosure will be omitted where it is determined that such descriptions may unnecessarily obscure the main points of this disclosure. Furthermore, the following terms are functional definitions of this disclosure and may vary depending on the intent and practice of the user and operator. Therefore, the definitions of the terms should be interpreted based on the content of this specification. Below, a base station is an entity that performs resource allocation for a terminal and may be at least one of a gNode B, eNode B, Node B, base station (BS), radio access unit, base station controller, or node on a network. A terminal may include a user equipment (UE), mobile station (MS), cellular phone, smartphone, computer, or multimedia system capable of performing communication functions. Of course, this disclosure is not limited to the examples above. Below, this disclosure describes a technique for a terminal to receive broadcast information from a base station in a wireless communication system. This disclosure relates to a communication technology and system for integrating 5G communication systems with Internet of Things (IoT) technology to support higher data transmission rates than 4G systems. This disclosure can be applied to smart services based on 5G communication technology and IoT-related technologies (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail, security and safety-related services, etc.).

[0051] The terms used in the following description are presented as examples, such as those referring to broadcast information, control information, communication coverage, state changes (e.g., events), network entities, messages, and components of a device, for ease of description. Therefore, this disclosure is not limited to the terms described below, and other terms with equivalent technical meanings may be used.

[0052] For ease of explanation, some terms and names defined in the 3GPP LTE standard may be used below. However, this disclosure is not limited to these terms and names and may be applied equally to systems conforming to other standards.

[0053] Wireless communication systems have evolved from their initial voice-centric services to broadband wireless communication systems that provide high-speed, high-quality packet data services, such as communication standards including 3GPP High Speed ​​Packet Access (HSPA), Long Term Evolution (LTE) (or Evolved Universal Terrestrial Radio Access (E-UTRA)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2 High Rate Packet Data (HRPD), Ultra Mobile Broadband (UMB), IEEE 802.16e, etc.

[0054] As a representative example of these broadband wireless communication systems, the LTE system employs Orthogonal Frequency Division Multiplexing (OFDM) in the downlink (DL) and Single-Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink (UL). The uplink refers to the radio link through 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 the radio link through which the base station transmits data or control signals to the terminal. The multiple access scheme described above allocates and operates time-frequency resources to carry and transmit data or control information to each user, ensuring that the time-frequency resources do not overlap, i.e., ensuring orthogonality, thereby allowing the differentiation of data or control information for each user.

[0055] Future communication systems following LTE (i.e., 5G communication systems) should be able to freely reflect the diverse requirements of users and service providers. Therefore, they should support services that meet a wide range of needs. Services being considered for 5G communication systems include enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable low-latency communications (URLLC), among others.

[0056] According to some embodiments, eMBB is designed to provide data transmission rates even higher than those supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, from the perspective of a base station, 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. Simultaneously, the 5G communication system should provide the UE with an increased real-world user-perceived data rate. To meet these requirements, improved transmission and reception technologies are needed, including more enhanced multiple-input multiple-output (MIMO) transmission technologies. Additionally, the data transmission rates required by 5G communication systems can be met by using a wider bandwidth than 20 MHz in the 3 GHz to 6 GHz, or 6 GHz or higher frequency bands instead of the 2 GHz band currently used by LTE.

[0057] Meanwhile, mMTC is seen as supporting application services such as the Internet of Things (IoT) in 5G communication systems. To efficiently deliver IoT, mMTC may need to support a large number of UEs within a cell, enhance UE coverage, extend battery life, and reduce UE costs. IoT attaches to various sensors and devices to provide communication capabilities, and therefore should be able to support a large number of UEs within a cell (e.g., 1,000,000 UEs / km). 2Additionally, due to the nature of the service, mMTC-enabled UEs are likely to be located in shadowed areas, such as basements of buildings where the cell may not be covered. Therefore, the UE may require even wider coverage than other services provided by 5G communication systems. mMTC-enabled UEs should be configured as low-cost UEs, and due to the difficulty in frequently replacing the UE's battery, they may require very long battery life.

[0058] Finally, URLLC is a cellular-based wireless communication service for mission-critical purposes, such as remote control of robots or machinery, industrial automation, drones, remote healthcare, and emergency alerts, and should provide ultra-low latency and ultra-reliable communication. For example, services supporting URLLC should meet an air interface latency of less than 0.5 milliseconds and simultaneously have 10 -5 Or a lower packet error rate (PER). Therefore, for services supporting URLLC, 5G systems should provide shorter transmission time intervals (TTIs) than other services, and at the same time, design specifications for allocating wider resources in the frequency band are required. However, the above-described mMTC, URLLC, and eMBB are merely examples of different service types, and the service types to which this disclosure applies are not limited to the examples described above.

[0059] The services considered in the aforementioned 5G communication system should be provided when they are integrated with each other based on a framework. That is, for efficient resource management and control, it is preferable to integrate each service into a single system for control and transmission, rather than operating them separately.

[0060] Furthermore, although LTE, LTE-A, LTE Pro, or NR systems are used below as examples to describe embodiments of this disclosure, embodiments of this disclosure can also be applied to other communication systems with similar technical backgrounds or channel types. Additionally, embodiments of this disclosure can be applied to other communication systems with certain modifications as determined by those skilled in the art, without significantly departing from the scope of this disclosure.

[0061] The frame structure of LTE and LTE-A systems will be described in more detail below with reference to the accompanying drawings.

[0062] Figure 1 This is a diagram illustrating the basic structure of the time-frequency domain in LTE. Specifically, Figure 1 This is a diagram illustrating the basic structure of the time-frequency domain of the radio resource domain, which serves as the data or control channel in an LTE system.

[0063] exist Figure 1 In the diagram, the horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The smallest transmission unit in the time domain is OFDM symbol 101, where N... symbOFDM symbols 101 are combined to form a time slot 102, and two time slots are combined to form a subframe 103. The duration of time slot 102 is 0.5 ms, and the duration of subframe 103 is 1.0 ms. Radio frame 104 is a time-domain unit consisting of 10 subframes 103. The smallest transmission unit in the frequency domain is a subcarrier 105, and the bandwidth of the entire system transmission is determined by a total of N... BW It consists of 105 subcarriers.

[0064] In the time-frequency domain, the basic unit of a resource is a resource element (RE) 106, and a resource element can be represented by an OFDM symbol index and a subcarrier index. A resource block (RB or physical resource block (PRB)) 107 is defined as N in the time domain. symb A consecutive OFDM symbol 101 and N in the frequency domain RB 108 consecutive subcarriers. Therefore, an RB 107 consists of N symb N RB It consists of 106 REs. Generally, the smallest unit of data transmission is the aforementioned RB unit. In LTE systems, generally, N symb =7, N RB =12, and N BW and N RB It is proportional to the bandwidth of the system transmission.

[0065] Next, we will describe the downlink control information (DCI) in LTE and LTE-A systems in detail.

[0066] In an LTE system, scheduling information for downlink or uplink data is delivered from the base station to the UE via a DCI (Distributed Control Information Center). The DCI may include information such as whether it is scheduling information for uplink or downlink data, whether it is a compact DCI with a small control information size, whether spatial multiplexing using multiple antennas is applied, and whether it is a DCI for power control. Furthermore, a DCI format defined based on the above information can be applied and operated. For example, DCI format 1, as scheduling control information for downlink data, is configured to include at least the following control information: - Resource allocation type 0 / 1 flag: This indicates whether the resource allocation scheme is type 0 or type 1. Type 0 allocates resources in units of resource block groups (RBGs) by applying a bitmap scheme. In LTE systems, the basic unit of scheduling is a resource block (RB), represented as time-domain and frequency-domain resources, and an RBG consists of multiple RBs. In the type 0 scheme, the RBG becomes the basic unit of scheduling. Type 1 causes specific RBs to be allocated within an RBG.

[0067] - Resource Block Allocation: This notifies the Resource Blocks (RBs) allocated for data transmission. The resources represented are determined based on system bandwidth and the resource allocation scheme.

[0068] - Modulation and coding scheme (MCS): It informs the modulation scheme used for data transmission and the transport block size of the data to be transmitted.

[0069] -HARQ process number: It is the process number that informs the Hybrid Automatic Repeat and Request (HARQ).

[0070] - New data indicator: It indicates whether it is an initial HARQ transmission or a retransmission.

[0071] - Redundant Version (RV): It notifies HARQ of the redundant version.

[0072] - Transmission Power Control (TPC) command for Physical Uplink Control Channel (PUCCH): It informs the PUCCH, which acts as the uplink control channel, of the transmission power control command.

[0073] The DCI undergoes channel coding and modulation processes and is transmitted on the Physical Downlink Control Channel (PDCCH), which serves as the downlink physical control channel.

[0074] Cyclic Redundancy Check (CRC) is appended to the DCI message payload, and the CRC is scrambled by a Radio Network Temporary Identifier (RNTI) corresponding to the UE's identifier. 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 sent, but is included in the CRC calculation process and sent accordingly. When a DCI message is received on the PDCCH, the UE uses the assigned RNTI to confirm the CRC. If the CRC confirmation result is correct, the UE knows that the corresponding message has been sent.

[0075] Figure 2 This is a diagram illustrating the downlink control channel in LTE. Specifically, Figure 2 This is a diagram showing the PDCCH as the downlink physical channel through which LTE DCI is transmitted.

[0076] refer to Figure 2 The PDCCH 201 is time-multiplexed with the Physical Downlink Shared Channel (PDSCH) 202, which serves as a data transmission channel, and is transmitted over the entire system bandwidth. The area of ​​the PDCCH 201 is represented by the number of OFDM symbols, which is indicated to the UE by the Control Format Indicator (CFI) transmitted on the Physical Control Format Indicator Channel (PCFICH).

[0077] By assigning PDCCH 201 to the OFDM symbol located at the beginning of the subframe, the UE can decode the downlink scheduling allocation as quickly as possible. This has the advantage of reducing the decoding latency of the downlink shared channel (DL-SCH) (i.e., the overall downlink transmission latency).

[0078] Since one PDCCH carries one DCI message, and multiple UEs can be scheduled simultaneously on both the downlink and uplink, multiple PDCCH transmissions occur concurrently within each cell. Cell-Specific Reference Signal (CRS) 203 is used as a reference signal for decoding PDCCH 201. CRS 203 is transmitted across the entire frequency band in each subframe, and scrambling and resource mapping vary according to the cell identifier (ID). Because CRS 203 is a reference signal commonly used by all UEs, UE-specific beamforming may not be possible. Therefore, multi-antenna transmission techniques for LTE PDCCH are limited to open-loop transport diversity. The number of CRS ports is implicitly known to the UE from decoding the Physical Broadcast Channel (PBCH).

[0079] Resource allocation for PDCCH 201 is based on Control Channel Elements (CCEs), and one CCE consists of 9 Resource Element Groups (REGs), for a total of 36 Resource Elements (REs). The number of CCEs required for a particular PDCCH 201 can be 1, 2, 4, or 8, depending on the channel coding rate of the DCI message payload. This varying number of CCEs is used to implement link adaptation for PDCCH 201.

[0080] The UE should detect the signal without knowing the information in PDCCH 201. For blind decoding in LTE, a search space representing a set of CCEs is defined. The search space consists of multiple groups at the aggregation level of each CCE, which are not explicitly signaled but implicitly defined based on the UE identifier via a function and subframe number. Within each subframe, the UE decodes PDCCH 201 against all possible resource candidates that can be generated from the CCEs within the configured search space, and can process information declared valid for the UE via CRC checksum.

[0081] The search space is categorized into UE-specific search space and common search space. A specific group of UEs or all UEs can search the common search space of PDCCH 201 to receive cell common control information, such as dynamic scheduling or paging messages for system information. For example, the scheduling allocation information for DL-SCH used for the transmission of System Information Block (SIB)-1, including cell operator information, can be received by searching the common search space of PDCCH 201.

[0082] In LTE, the entire PDCCH area consists of a set of CCEs within a logical area, and there exists a search space comprised of this set of CCEs. The search space is divided into a common search space and a UE-specific search space, and the search space used for the LTE PDCCH is defined as follows:

[0083] According to the definition of the search space used for PDCCH, the UE-specific search space is not explicitly signaled, but implicitly defined based on the UE identifier through a function and subframe number. In other words, since the UE-specific search space can change according to the subframe number, this means that the UE-specific search space may change over time, thereby solving the problem of a specific UE being unable to use the search space due to other UEs among multiple UEs (the blocking problem).

[0084] According to an embodiment, when no UE is scheduled in a corresponding subframe because all CCEs being searched by a particular UE have already been used by other UEs scheduled within the same subframe, this problem may not occur in the next subframe because the search space changes over time. For example, even if a portion of the UE-specific search space of UE #1 and UE #2 overlaps in a particular subframe, the overlap in the next subframe can be expected to be different because the UE-specific search space changes based on each subframe.

[0085] Based on the definition of the search space for PDCCH described above, the common search space is defined as a set of pre-arranged CCEs because a specific group of UEs or all UEs should receive the PDCCH. In other words, the common search space does not change based on the UE's identifier, subframe number, etc. Although a common search space exists for transmitting various system messages, it can also be used to transmit control information for individual UEs. In this way, the common search space can also be used as a solution to the phenomenon where a terminal is not scheduled due to a lack of available resources in a UE's specific search space.

[0086] The search space is a set of candidate control channels consisting of CCEs that the UE should attempt to decode at a given aggregation level. Since there are various aggregation levels that group 1, 2, 4, or 8 CCEs together, the UE has multiple search spaces. The number of PDCCH candidates that the UE should monitor within the search space (defined by the aggregation level in the LTE PDCCH) is defined in the following table.

[0087] [Table 1]

[0088] According to [Table 1], the UE-specific search space supports aggregation levels {1, 2, 4, 8}. In this case, each aggregation level has {6, 6, 2, 2} PDCCH candidates. The common search space supports aggregation levels {4, 8}. In this case, each aggregation level has {4, 2} PDCCH candidates. The reason why the common search space only supports aggregation levels {4, 8} is to improve coverage characteristics, since system messages typically need to reach the cell edge.

[0089] DCIs transmitted to the common search space are defined only for specific DCI formats (such as 0 / 1A / 3 / 3A / 1C), corresponding to purposes such as system messages or power control of UE groups. DCI formats with spatial multiplexing are not supported within the common search space. The downlink DCI format to be decoded in the UE-specific search space varies depending on the transmission mode configured for the corresponding UE. Since the transmission mode is configured via Radio Resource Control (RRC) signaling, no precise subframe number is specified to determine whether the corresponding configuration is valid for the corresponding UE. Therefore, the UE can prevent communication loss by always performing decoding of DCI format 1A regardless of the transmission mode.

[0090] The above describes the downlink control channel in conventional LTE and LTE-A, the methods for sending and receiving downlink control information, and the search space.

[0091] The downlink control channel in the 5G communication system currently under discussion will be described in more detail below with reference to the accompanying drawings.

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

[0093] refer to Figure 3 As the basic unit of time and frequency resources constituting the control channel, the resource element group (REG) 303 consists of one OFDM symbol 301 on the time axis and 12 subcarriers 302 on the frequency axis (i.e., one resource block (RB)). By assuming an OFDM symbol 301 as the basic unit of the time axis when constituting the basic unit of the control channel, the data channel and the control channel can be time-multiplexed within a subframe. By positioning the control channel before the data channel, user processing time can be reduced, making it easier to meet latency requirements. By configuring the basic unit of the control channel's frequency axis as an RB 302, frequency multiplexing between the control channel and the data channel can be performed more efficiently.

[0094] Through links Figure 3 The REG 303 shown can be configured with control channel regions of various sizes. For example, when the basic unit for allocating downlink control channels in 5G is called a Control Channel Element (CCE) 304, a CCE 304 can consist of multiple REG 303s. (Description) Figure 3 The REG 303 shown is an example; a REG 303 can consist of 12 REs. When a CCE 304 consists of six REG 303s, it means that the CCE 304 can consist of 72 REs. When configuring a downlink control resource set, the corresponding area can consist of multiple CCE 304s, and a specific downlink control channel can be mapped to one or more CCE 304s and transmitted according to the aggregation level (AL) within the control resource set. CCE 304s within the control resource set are identified by numbers. In this case, numbers can be allocated according to a logical mapping scheme.

[0095] Figure 3 The basic unit of the downlink control channel shown (i.e., REG 303) can include both the RE mapped to by the DCI and the region mapped to by the demodulation reference signal (DMRS) 305 (a reference signal used to decode the RE). Figure 3 As shown, DMRS 305 can be transmitted from three REs within one REG 303. For reference, since DMRS 305 is transmitted using the same precoding as the control signals mapped within REG 303, the UE can decode the control information without information about which precoding the base station applies.

[0096] Figure 4 This is a diagram illustrating an example configuration of the control resource set in 5G. Specifically, Figure 4 This is a diagram illustrating an example of a control resource set (CORESET) in a 5G wireless communication system in which downlink control channels are transmitted.

[0097] Figure 4 The example in the example assumes that a time slot has seven OFDM symbols. Figure 4 An example is shown of configuring two control resource sets (control resource set #1 401 and control resource set #2 402) within a system bandwidth 410 on the frequency axis and a time slot 420 on the time axis. The frequencies of control resource sets 401 and 402 can be configured as specific subbands 403 within the overall system bandwidth 410. The durations of control resource sets 401 and 402 can be configured as one or more OFDM symbols, and the durations of control resource sets 402 and 401 can also be defined as control resource durations 404. Figure 4In the example, control resource set #1 401 is configured with a control resource set duration of two symbols, and control resource set #2 402 is configured with a control resource set duration of one symbol.

[0098] In the aforementioned 5G architecture, the base station can configure a control resource set for the UE via higher-layer signaling (e.g., system information, Master Information Block (MIB), RRC signaling). Configuring a control resource set for the UE involves providing information such as the location, subband, resource allocation, and duration of the control resource set. For example, the information entries in Table 2 may include...

[0099] [Table 2]

[0100] The configuration information in [Table 2] is an example of this disclosure, and in addition to the configuration information in [Table 2], various types of information necessary for the UE to transmit the downlink control channel can also be configured.

[0101] Next, we will describe downlink control information (DCI) in 5G in detail.

[0102] In 5G systems, scheduling information for uplink data (Physical Uplink Shared Channel (PUSCH)) or downlink data (Physical Downlink Shared Channel (PDSCH)) is delivered from the base station to the UE via DCI.

[0103] The UE can monitor the back-off and non-back-off DCI formats of PUSCH or PDSCH. The back-off DCI format can consist of fixed fields between the base station and the UE, while the non-back-off DCI format can include configurable fields.

[0104] According to embodiments of this disclosure, the fallback DCI used to schedule PUSCH may include the information in [Table 3].

[0105] [Table 3]

[0106] According to embodiments of this disclosure, the non-back-off DCI used for scheduling PUSCH may include the information in [Table 4].

[0107] [Table 4]

[0108] According to embodiments of this disclosure, the fallback DCI used to schedule PDSCH may include the information in [Table 5].

[0109] [Table 5]

[0110] According to embodiments of this disclosure, the non-back-off DCI used for scheduling PDSCH may include the information in [Table 6].

[0111] [Table 6]

[0112] The DCI can undergo channel coding and modulation processes and can be transmitted on the Physical Downlink Control Channel (PDCCH), which serves as the downlink physical control channel. Cyclic Redundancy Check (CRC) is appended to the DCI message payload, and the CRC is scrambled by a Radio Network Temporary Identifier (RNTI) corresponding to the UE's identifier.

[0113] 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 sent, but rather included in the CRC calculation process and sent accordingly. When the UE receives a DCI message sent on the PDCCH, the UE can use the assigned RNTI to check the CRC. If the CRC check result is correct, the UE knows that the corresponding message has been sent.

[0114] For example, the DCI for scheduling PDSCH for System Information (SI) can be scrambled by SI-RNTI. The DCI for scheduling PDSCH for Random Access Response (RAR) messages can be scrambled by RA-RNTI. The DCI for scheduling PDSCH for paging messages can be scrambled by P-RNTI. The DCI for notifying Slot Format Indicator (SFI) can be scrambled by SFI-RNTI. The DCI for notifying Transmission Power Control (TPC) can be scrambled by TPC-RNTI. The DCI for scheduling UE-specific PDSCH or PUSCH can be scrambled by Cell RNTI (C-RNTI).

[0115] When a specific UE receives a scheduling for a data channel (i.e., PUSCH or PDSCH) on the PDCCH, it transmits and receives data together with the DMRS in the corresponding scheduled resource domain.

[0116] Figure 5 This is a diagram illustrating an example configuration of the downlink RB structure in 5G.

[0117] More specifically, Figure 5 This illustrates a scenario where a specific UE uses 14 OFDM symbols as a single time slot (or subframe) in the downlink and is configured to transmit the PDCCH using the first two OFDM symbols and the DMRS using the third symbol. Figure 5 In the case where PDSCH is scheduled within a specific RB, PDSCH is transmitted by mapping data to REs in the third symbol where DMRS is not transmitted, and to REs from the fourth symbol to the last symbol. For LTE / LTE-A systems, Figure 5 The subcarrier spacing Δf shown is 15 kHz, and for 5G systems, one of {15, 30, 60, 120, 240, 480} kHz is used.

[0118] As mentioned above, in order to measure the downlink channel state in a cellular system, the base station should transmit a reference signal. In the case of a 3GPP Long Term Evolution Advanced (LTE-A) system, the UE can use the CRS or CSI-RS transmitted by the base station to measure the channel state between the base station and the UE.

[0119] Channel state should be measured by considering various factors, including the amount of interference in the downlink. Downlink interference includes interference signals generated by antennas belonging to neighboring base stations, thermal noise, etc., and is important for the UE to determine the channel state of the downlink. For example, when transmitting a signal from a base station with one transmit antenna to a UE with one receive antenna, the UE should determine Es / Io by determining 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 received simultaneously during the reception of the corresponding symbol. The determined Es / Io is converted into a data transmission rate or equivalent value and sent to the base station in the form of a Channel Quality Indicator (CQI), which the base station can use to determine at what data transmission rate to perform the transmission to the UE.

[0120] More specifically, in the LTE-A system, the UE feeds back information about the downlink channel state to the base station, enabling this information to be used for downlink scheduling by the base station. That is, the UE measures the reference signal transmitted by the base station via the downlink and feeds back information extracted from the reference signal to the base station in the form defined by the LTE / LTE-A standard. As mentioned above, the information fed back by the UE in LTE / LTE-A can be called channel state information, and channel state information can include the following three types of information: - Rank Indicator (RI): The number of spatial layers that the UE can receive in the current channel state. - Precoding Matrix Indicator (PMI): An indicator of the precoding matrix preferred by the UE in the current channel state.

[0121] - Channel Quality Indicator (CQI): The maximum data rate that the UE can receive under the current channel conditions.

[0122] CQI can be replaced by signal-to-interference-plus-noise ratio (SINR), maximum error correction code rate and modulation scheme, data efficiency per frequency, etc., which can be used similarly to the maximum data rate.

[0123] RI, PMI, and CQI have related meanings. For example, the precoding matrix supported in 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 can be interpreted differently.

[0124] Furthermore, as an example, even when the UE determines the CQI, it assumes that the PMI value X reported by the UE to the base station has already been applied by the base station. That is, the UE reporting RI_X, PMI_Y, and CQI_Z to the base station is equivalent to reporting that when the rank is set to RI_X and the PMI is set to PMI_Y, the UE can receive the data transmission rate corresponding to CQI_Z. In this way, when calculating the CQI, the UE assumes which transmission scheme the base station will implement, thereby ensuring optimized performance when using the corresponding transmission scheme for actual transmission.

[0125] In LTE / LTE-A, RI, PMI, and CQI, which are channel state information fed back by the UE, can be provided periodically or aperiodically. When a base station intends to obtain channel state information from a specific UE aperiodically, it can be configured to perform aperiodic feedback (or aperiodic channel state information reporting) using an aperiodic feedback indicator (or channel state information request field, channel state information request information) included in the downlink control information (DCI) for the UE. Alternatively, when the UE receives an indicator configured for aperiodic feedback in the nth subframe, it can perform uplink transmission by including the aperiodic feedback information (or channel state information) in the data transmission in the n+kth subframe. Here, k is a parameter defined in 3GPP LTE Release 11, which is 4 for Frequency Division Duplex (FDD) and can be defined as shown in [Table 7] for Time Division Duplex (TDD).

[0126] [Table 7] k values ​​for each subframe number n in the TDD UL / DL configuration

[0127] When non-periodic feedback is configured, the feedback information (or channel state information) includes RI, PMI, and CQI, and depending on the feedback configuration (or channel state report configuration), RI and PMI may not be fed back.

[0128] Figure 6 This is a diagram showing an example time slot structure based on a TDD configuration.

[0129] More specifically, when the ratio of DL time slots to UL time slots is approximately 4:1, it can be as follows: Figure 6 As shown. However, in the case of the DL time slot immediately preceding the UL time slot, not all symbols are DL symbols, and the DL time slot has at least a protection symbol that takes into account the propagation and delivery delay, but for convenience, it is referred to as the DL time slot in this example.

[0130] Additionally, as an example, when DL time slots are consecutive, each time slot can be distinguished by assigning numbers such as D#1 to D#4, as follows: Figure 6 As shown. Similarly, even if UL time slots are consecutive, they can be assigned numbers, etc., to distinguish each consecutive time slot. For ease of description, this disclosure will focus on downlink transmissions.

[0131] Resource allocation at the base station is not based on a fixed scheme, but rather depends on the implementation. Specifically, transmission constraints or rules can be defined internally for interference control. As an example, consider the following transmission constraints.

[0132] Each base station can apply transmission constraints so that it does not perform resource allocation immediately after data enters its buffer, but instead begins resource allocation from a specific time slot.

[0133] Figure 7 This is a graph illustrating the average channel conditions for each time slot number when the transmission constraints in the example above exist. The average channel conditions represented on the Y-axis can be the average SINR, the average CQI value reported by the UE to the base station, the average MCS value indicating the channel conditions of the UE as perceived by the base station, etc. The number of time slots used for resource allocation is determined based on the traffic volume requested by the UE, and resource allocation is performed sequentially starting from a specific time slot. Therefore, as shown in the figure, time slots further away from the start of resource allocation tend to experience less interference, thus generally resulting in better channel conditions. In other words, better average channel conditions mean a higher probability of being allocated a higher MCS.

[0134] Figure 8 This is a diagram illustrating an example of a typical retransmission process. Specifically, Figure 8 This diagram schematically illustrates the process of retransmission when a specific transmission fails. For simplicity, in this diagram, it is assumed that a TB is transmitted using PDSCH in the same time slot after a DCI transmission on PDCCH. Figure 8 As shown, when 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. In this case, the base station can perform transmission in any time slot, regardless of the specific time slot. Assume that when... Figure 8 When performing a transmission, such as Figure 7The channel conditions are indicated as shown. Since the transmission in D#3 typically exhibits good channel conditions, it may have been allocated a high MCS. However, when the corresponding transmission fails, a combined gain is obtained through retransmission, and this gain increases the probability of success. In other words, the channel conditions under which retransmission is performed are also important for obtaining the combined gain. However, in cases such as... Figure 7 Under the channel conditions shown, since the average channel conditions in D#2 are worse than those in D#3, even with the combined gain, it is likely that the average channel conditions in D#2 will still be worse than those in D#3. Therefore, even if a retransmission is performed, the probability of transmission failure remains high. However, when a retransmission is performed in D#3 with similar channel conditions, the probability of success increases by obtaining the combined gain.

[0135] To address the aforementioned issues, this patent proposes a technique for performing retransmissions in time slots with similar channel conditions.

[0136] In the following, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Although LTE or LTE-A systems are used as examples in the description of the present disclosure, embodiments of the present disclosure can also be applied to other communication systems with similar technical backgrounds or channel types. For example, a communication system to which embodiments of the present disclosure are applied may include fifth-generation mobile communication technologies (5G, New Radio, NR) developed after LTE-A. Therefore, embodiments of the present disclosure can be applied to other communication systems with certain modifications as determined by those skilled in the art, without significantly departing from the scope of the present disclosure.

[0137] Furthermore, in describing this disclosure, detailed descriptions of functions or configurations related to this disclosure will be omitted where it is determined that such detailed descriptions might unnecessarily obscure the essence of this disclosure. Additionally, the following terms are those used to define the functions of this disclosure and may vary depending on the intent and practice of the user and operator. Therefore, the definitions of the terms should be interpreted based on the content of this specification.

[0138] <Example 1>

[0139] Example 1 describes a method for performing retransmission in a time slot with channel conditions similar to the initial transmission when a failed transmission is retransmitted.

[0140] Figure 9 This is a diagram illustrating an example of average channel conditions and similar channel conditions for each time slot number according to an embodiment of the present disclosure. Figure 9 Is with Figure 7 A similar diagram illustrates the channel conditions for each time slot number. For simplicity, this diagram assumes that time slots are managed in 8 units. Figure 9As shown, time slots exhibiting similar average channel conditions can be represented in a similar pattern. Furthermore, when the average channel condition is considered as the average MCS used by the base station when allocating resources to the corresponding UE, it can be viewed as shown in the example illustrated.

[0141] In this embodiment, when a failed transmission is retransmitted, the retransmission is allocated under channel conditions similar to the initial transmission. For example, when a transmission in D#3 fails, the corresponding data can be retransmitted in D#3 with the same timeslot number. This example will be described in more detail in Embodiment 2. As another example, when a transmission in D#3 fails, the corresponding data can be retransmitted in another timeslot, D#5 or D#7, with channel conditions similar to those of the corresponding timeslot including D#3. This example will also be described in more detail in Embodiment 5.

[0142] <Example 2>

[0143] Example 2 describes a method for performing retransmission while maintaining the same slot number as when performing Example 1.

[0144] Figure 10 This is a diagram illustrating another embodiment of the present disclosure. Specifically, Figure 10 This diagram illustrates an example of retransmission being performed in slot D#1 with the same slot number when transmission fails in slot D#1 during implementation of Example 2. To allocate slot numbers, as in... Figure 10 In this context, the time slot number varies depending on the number of units managing the time slots. For example... Figure 10 As shown, a slot counting period (denoted as T in the diagram, T=5) is required to manage slots D#1 through D#4. The slots that can be retransmitted can vary depending on the value of the slot counting period.

[0145] <Example 3>

[0146] Example 3 describes a method for performing retransmissions without retransmission scheduling via DCI when executing Example 2.

[0147] Figure 11 This is a diagram illustrating another embodiment of the present disclosure. Specifically, Figure 11 This diagram illustrates an example of retransmission of PDSCH transmission without the need for DCI, where a transmission in time slot D#1 fails during the execution of Embodiment 3 and a retransmission is performed in D#1 with the same time slot number, only the DCI sent for the initial transmission is used. Figure 11 In this disclosure, the proposed DCI is referred to as "the proposed DCI" and is assumed to be classified as a different format from existing DCIs.

[0148] In this embodiment, when the base station allocates resources for retransmission, it is assumed that the resource allocation on the time and frequency axes is the same as the resource allocation for the initial transmission. When the UE receives a NACK from the uplink resources that sent HARQ ACK / NACK information, or when the UE fails to receive HARQ ACK / NACK, the base station performs the retransmission allocation operation according to the announced resources.

[0149] The following information is required for the UE to operate as described in this embodiment.

[0150] a. Time slot counting period (e.g., in Figure 10 In the example, T=5)

[0151] b. Location for allocating retransmission time slots in the event of initial transmission failure.

[0152] c. Redundant Version (RV) to be used during retransmission

[0153] The information items described above can be configured using RRC or via DCI. Additionally, some of the information items can be configured via RRC, and some can be configured via DCI. For simplicity, this embodiment will only describe the cases where all information is configured via RRC and the cases where all information is configured via DCI.

[0154] - When configured via RRC

[0155] When configured via RRC, information corresponding to a, b, and c can be configured.

[0156] Information b can be represented by various schemes. Based on the DCI transmission location, it can inform the total time slot duration of the location to be allocated for retransmission. This is in Figure 10 This is represented as AT. Alternatively, since the location for retransmission will be a multiple of information a, there exists a method for configuring a coefficient that allows the UE to incorporate information a into the calculation. This corresponds to Figure 10 In A. Additionally, based on the HARQ ACK / NACK position, similar to... Figure 10 The example in the example can be configured to allocate retransmissions after the BT time slot, or only the coefficient B can be configured.

[0157] When a retransmission is performed, information c can be pre-configured with the RV sequence. For example, when the retransmission RV is configured as 0231, the UE can identify the RV of the TB being retransmitted by checking the corresponding information.

[0158] When configured via RRC, the DCI needs to include additional fields indicating that the corresponding DCI operates as described in this embodiment. Alternatively, operation in the same manner as in this embodiment can only be performed when the RRC value presented in this embodiment is configured.

[0159] - When configured via DCI

[0160] Similar to the configuration via RRC, when configuring information a and b via DCI, additional fields should be defined. If RRC has already pre-configured RV values ​​for all retransmissions, information c can simply refer to the RV value in the newly defined field via DCI corresponding to the immediate next retransmission, and all RVs can be pre-configured and provided as in RRC.

[0161] Additional RRC configuration is required to use the DCI as presented in this embodiment. Specifically, the additional RRC configuration for the redundant version sequence used for retransmission can be as follows.

[0162]

[0163] In the above description, repK can refer to the maximum number of retransmissions configured, and repK-RV can refer to the RV sequence based on the number of retransmissions. The proposed DCI should define a new DCI format, and the corresponding format can be sent to the UE via RRC configuration, which can be configured to be transmitted via the search space. When no new DCI format is defined to use the proposed DCI, there is also a method for utilizing existing formats in the search space but defining an indicator in the form of using the proposed DCI format and delivering the indicator to the UE via RRC.

[0164] <Example 4>

[0165] Example 4 describes a retransmission method using reduced DCI when performing Example 2.

[0166] Figure 12 This is a diagram illustrating another embodiment of the present disclosure. Specifically, Figure 12 This diagram illustrates an example of performing PDSCH transmission using the proposed DCI for initial transmission and the reduced DCI for retransmission when transmission fails in time slot D#1 during implementation of Example 3 and a retransmission is performed in D#1 with the same time slot number. Figure 12 In this disclosure, the DCI used for initial transmission allocation is denoted as the proposed DCI, and the DCI used for retransmission allocation is denoted as the reduced DCI. It is assumed that the two proposed DCIs are classified as having a different format from the existing DCIs being transmitted, and for convenience, they are named in the above form.

[0167] In this embodiment, when the base station allocates resources for retransmission, the proposed scheme can be used even if the resource allocation on the time and frequency axes differs from the resource allocation of the initial transmission. When the UE receives a NACK from the uplink resources that sent HARQ ACK / NACK information, or when the UE fails to receive HARQ ACK / NACK, the base station performs a retransmission operation based on the announced resource allocation.

[0168] In order for the UE to operate as in this embodiment, the following information is required, as in embodiment 3, and the UE can identify that a reduced DCI will be sent at the corresponding location.

[0169] a. Time slot counting period (in) Figure 10 In the example, T=5)

[0170] b. Location for allocating retransmission time slots in the event of initial transmission failure.

[0171] c. Redundant Version (RV) to be used during retransmission

[0172] The information items described above can be configured using RRC or via DCI. Additionally, some of the information items can be configured via RRC, and some can be configured via DCI. For simplicity, this embodiment will only describe the cases where all information is configured via RRC and the cases where all information is configured via DCI.

[0173] - When configured via RRC

[0174] When configured via RRC, information corresponding to a, b, and c can be configured.

[0175] Information b can be represented by various schemes. Based on the DCI transmission location, it can inform the total time slot duration of the location to be allocated for retransmission. This is in Figure 10 This is represented as AT. Alternatively, since the location for retransmission will be a multiple of information a, there exists a method for configuring a coefficient that allows the UE to incorporate information a into the calculation. This corresponds to Figure 10 In A. Additionally, based on the HARQ ACK / NACK position, similar to... Figure 10 The example in the example can be configured to allocate retransmissions after the BT time slot, or only the coefficient B can be configured.

[0176] When a retransmission is performed, information c can be pre-configured with the RV sequence. For example, when the retransmission RV is configured as 0231, the UE can identify the RV of the TB being retransmitted by checking the corresponding information.

[0177] When configured via RRC, an additional field indicating how the corresponding DCI operates as in this embodiment is required in the DCI. Alternatively, the operation can be performed in the same scheme as in this embodiment only when the RRC values proposed in this embodiment are configured.

[0178] - When configured via DCI

[0179] Similar to the case of RRC configuration, when information a and b are configured via DCI, additional fields should be newly defined. When the RV values for all retransmissions have been preconfigured by RRC, information c can only refer to the RV value corresponding to the next immediate retransmission in the fields newly defined via DCI, and all RVs can be preconfigured and provided as in RRC.

[0180] Additional RRC configuration is required to use the DCI proposed in this embodiment. Specifically, the additional RRC configuration for the redundancy version sequence for retransmission can be as follows.

[0181]

[0182] In the above description, repK can refer to the configured maximum number of retransmissions, and repK-RV can refer to the RV sequence according to the number of retransmissions. The proposed DCI should newly define the DCI format and deliver it to the UE via RRC configuration: the corresponding format can be sent via search space configuration. When no new DCI format is defined to use the proposed DCI, there is also a method of using an existing format of the search space but defining an indicator in the form of using the proposed DCI format and delivering this indicator to the UE via RRC.

[0183] The reduced DCI can only include time-axis resource allocation information and frequency-axis resource allocation messages. Assume that the UE has received the necessary information from the proposed DCI as in the previous Embodiment 3. In this case, in order to perform retransmission as in this embodiment, the UE can identify the positions of the time slots where the reduced DCI and retransmission will occur via the proposed DCI. In order to check the reduced DCI at the corresponding positions, a new format should be defined in RRC. Additionally, it should be delivered to the UE via RRC: the newly defined format configured via the search space can be delivered on the PDCCH.

[0184] In this case, since the reduced DCI includes less information compared to the prior art, the transmission can be performed using the least amount of PDCCH resources. For example, when the existing DCI transmission requires N CCEs, the reduced DCI requires M CCEs (M < N), so the required resource amount becomes M / N, and the PDCCH capacity increases by approximately N / M.

[0185] <Embodiment 5>

[0186] Example 5 describes a method for performing retransmission by defining and maintaining a set of time slots with similar channel conditions as in Example 1.

[0187] Figure 13 This is a diagram illustrating another embodiment of the present disclosure. Specifically, Figure 13 This diagram illustrates an example of retransmission being performed in D#1 or D#3 with the same time slot number or the same channel conditions when transmission fails in time slot D#1 during implementation of Example 5. To allocate time slot numbers, as in... Figure 13 In this context, the time slot number varies depending on the number of units managing the time slots. Additionally, the total number of time slots varies based on the number of time slots with similar channel conditions and the number of time slots per slot. Figure 10 Similarly, even in Figure 13 In this context, a time slot counting period (denoted as T in the diagram, T=5) is needed to manage D#1 to D#4. The time slots eligible for retransmission can vary depending on the value of the time slot counting period. Furthermore, the time slots eligible for retransmission vary based on time slots with similar channel conditions, and for convenience, in... Figure 13 The same form is used to represent time slots with similar channel conditions.

[0188] <Example 6>

[0189] Example 6 describes a method for performing retransmissions without retransmission scheduling via DCI when executing Example 5.

[0190] Figure 14 This is a diagram illustrating another embodiment of the present disclosure. Specifically, Figure 14 This diagram illustrates an example of a PDSCH transmission retransmission performed without the need for a DCI, using only the DCI sent for the initial transmission, when a transmission fails in time slot D#1 during the execution of Embodiment 6 and a retransmission is performed in D#1 or D#3 with the same time slot number or the same channel conditions. Figure 14 In this disclosure, the proposed DCI is referred to as "the proposed DCI" and is assumed to be classified as a different format from existing DCIs. Additionally, for convenience, time slots with similar channel conditions are named in the same group.

[0191] Similar to Example 3, in this example, when the base station allocates resources for retransmission, it is assumed that the resource allocation on the time and frequency axes is the same as the resource allocation for the initial transmission. When the UE receives a NACK from the uplink resources that sent HARQ ACK / NACK information, or when the UE fails to receive HARQ ACK / NACK, the base station performs the retransmission allocation operation in the time slots within the announced group.

[0192] The following information is required for the UE to operate as described in this embodiment.

[0193] a. Time slot counting period (in) Figure 10 In the example, T=5)

[0194] b. Location for allocating retransmission time slots in the event of initial transmission failure.

[0195] c. Redundant Version (RV) to be used during retransmission

[0196] d. Group information of time slots with similar channel conditions

[0197] The information items described above can be configured using RRC or via DCI. Additionally, some of the information items can be configured via RRC, and some can be configured via DCI. For simplicity, this embodiment will only describe the cases where all information is configured via RRC and the cases where all information is configured via DCI.

[0198] - When configured via RRC

[0199] When configured via RRC, information corresponding to a, b, and c can be configured.

[0200] Information b can be represented by various schemes. Based on the DCI transmission location, it can inform the total time slot duration of the location to be allocated for retransmission. This is in Figure 10 This is represented as AT. Alternatively, since the location for retransmission will be a multiple of information a, there exists a method for configuring a coefficient that allows the UE to incorporate information a into the calculation. This corresponds to Figure 10 In A. Additionally, based on the HARQ ACK / NACK position, similar to... Figure 10 The example in the example can be configured to allocate retransmissions after the BT time slot, or only the coefficient B can be configured.

[0201] When a retransmission is performed, information c can be pre-configured with the RV sequence. For example, when the retransmission RV is configured as 0231, the UE can identify the RV of the TB being retransmitted by checking the corresponding information.

[0202] Information d can be configured with information corresponding to each group based on information a. The configuration information for each UE can vary depending on the number of groups and the time slot belonging to each group.

[0203] When configured via RRC, the DCI needs to include additional fields indicating that the corresponding DCI operates as described in this embodiment. Alternatively, operation in the same manner as in this embodiment can only be performed when the RRC value presented in this embodiment is configured.

[0204] - When configured via DCI

[0205] Similar to the configuration via RRC, when configuring information a and b via DCI, additional fields should be defined. If RRC has already pre-configured RV values ​​for all retransmissions, information c can simply refer to the RV value in the newly defined field via DCI corresponding to the immediate next retransmission, and all RVs can be pre-configured and provided as in RRC.

[0206] Additionally, information d can be configured in a newly defined field via DCI, and can be configured using various schemes. Information d can be configured by notifying all time slots of the same group that performed the initial transmission. Since the UE does not know where its retransmitted data will arrive within the group, there is an inefficiency where the UE must attempt to decode the PDSCH in every time slot after receiving it. Alternatively, different schemes can be used to pre-configure specific time slots within the corresponding group.

[0207] Additional RRC configuration is required to use the DCI as presented in this embodiment. Specifically, the additional RRC configuration for the redundant version sequence used for retransmission can be as follows.

[0208]

[0209] In the above description, repK can refer to the maximum number of retransmissions configured, and repK-RV can refer to the RV sequence based on the number of retransmissions. The proposed DCI should define a new DCI format and be delivered to the UE via RRC configuration: the corresponding format can be sent via search space configuration. When no new DCI format is defined to use the proposed DCI, there is also a method for utilizing existing formats in the search space but defining an indicator to use the proposed DCI format and delivering the indicator to the UE via RRC.

[0210] <Example 7>

[0211] Example 7 describes a retransmission method using reduced DCI when performing Example 5.

[0212] Figure 15 This is a diagram illustrating another embodiment of the present disclosure. Specifically, Figure 15 This diagram illustrates an example of PDSCH transmission retransmission performed via reduced DCI when a transmission fails in time slot D#1 during implementation of Example 7 and a retransmission is performed in D#1 or D#3 with the same time slot number or the same channel conditions. Figure 15In this disclosure, the DCI proposed for initial transmission allocation is denoted as the proposed DCI, and the DCI proposed for retransmission allocation is denoted as the reduced DCI. It is assumed that the two proposed DCIs are classified as having a different format from the existing DCIs being transmitted, and for convenience, they are named in the above form.

[0213] Similar to Example 4, in this example, when the base station allocates resources for retransmission, it is assumed that the resource allocation on the time and frequency axes is the same as the resource allocation for the initial transmission. When the UE receives a NACK from the uplink resources that sent HARQ ACK / NACK information, or when the UE fails to receive HARQ ACK / NACK, the base station performs the retransmission allocation operation in the time slots within the announced group.

[0214] The following information is required for the UE to operate as described in this embodiment.

[0215] a. Time slot counting period (in) Figure 10 In the example, T=5)

[0216] b. Location for allocating retransmission time slots in the event of initial transmission failure.

[0217] c. Redundant Version (RV) to be used during retransmission

[0218] d. Group information of time slots with similar channel conditions

[0219] The information items described above can be configured using RRC or via DCI. Additionally, some of the information items can be configured via RRC, and some can be configured via DCI. For simplicity, this embodiment will only describe the cases where all information is configured via RRC and the cases where all information is configured via DCI.

[0220] - When configured via RRC

[0221] When configured via RRC, information corresponding to a, b, and c can be configured.

[0222] Information b can be represented by various schemes. Based on the DCI transmission location, it can inform the total time slot duration of the location to be allocated for retransmission. This is in Figure 10 This is represented as AT. Alternatively, since the location for retransmission will be a multiple of information a, there exists a method for configuring a coefficient that allows the UE to incorporate information a into the calculation. This corresponds to Figure 10 In A. Additionally, based on the HARQ ACK / NACK position, similar to... Figure 10 The example in the example can be configured to allocate retransmissions after the BT time slot, or only the coefficient B can be configured.

[0223] When a retransmission is performed, information c can be pre-configured with the RV sequence. For example, when the retransmission RV is configured as 0231, the UE can identify the RV of the TB being retransmitted by checking the corresponding information.

[0224] Information d can be configured with information corresponding to each group based on information a. The configuration information for each UE can vary depending on the number of groups and the time slot belonging to each group.

[0225] When configured via RRC, the DCI needs to include additional fields indicating that the corresponding DCI operates as described in this embodiment. Alternatively, operation in the same manner as in this embodiment can only be performed when the RRC value presented in this embodiment is configured.

[0226] - When configured via DCI

[0227] Similar to the configuration via RRC, when configuring information a and b via DCI, additional fields should be defined. If RRC has already pre-configured RV values ​​for all retransmissions, information c can simply refer to the RV value in the newly defined field via DCI corresponding to the immediate next retransmission, and all RVs can be pre-configured and provided as in RRC.

[0228] Additionally, information d can be configured in a newly defined field via DCI, and can be configured using various schemes. Information d can be configured by notifying all time slots of the same group that performed the initial transmission. Since the UE does not know where its retransmitted data will arrive within the group, there is an inefficiency where the UE must attempt to decode the PDSCH in every time slot after receiving it. Alternatively, different schemes can be used to pre-configure specific time slots within the corresponding group.

[0229] Additional RRC configuration is required to use the DCI as presented in this embodiment. Specifically, the additional RRC configuration for the redundant version sequence used for retransmission can be as follows.

[0230]

[0231] In the above description, repK can refer to the maximum number of retransmissions configured, and repK-RV can refer to the RV sequence based on the number of retransmissions. The proposed DCI should define a new DCI format and be delivered to the UE via RRC configuration: the corresponding format can be sent via search space configuration. When no new DCI format is defined to use the proposed DCI, there is also a method for utilizing existing formats in the search space but defining an indicator to use the proposed DCI format and delivering the indicator to the UE via RRC.

[0232] The reduced DCI may only include the time-axis resource allocation information and the frequency-axis resource allocation message. The UE operates based on the assumption that the UE has received the necessary information from the proposed DCI, as in the previous Embodiment 3. In this case, in order to perform retransmission as in this embodiment, the UE may identify the positions of the time slots where the reduced DCI and retransmission will occur via the proposed DCI. In order to check the reduced DCI at the corresponding positions, a new format should be defined in the RRC. Additionally, it should be delivered to the UE via the RRC that the newly defined format can be delivered on the PDCCH via the search space configuration.

[0233] In this case, since the reduced DCI includes less information compared to the prior art, the transmission can be performed using the minimum amount of PDCCH resources. For example, when the existing DCI transmission requires N CCEs, the reduced DCI requires M CCEs (M < N), so the amount of resources required becomes M / N, and the PDCCH capacity increases by approximately N / M.

[0234] <Embodiment 8>

[0235] Embodiment 8 describes the case where the UE fails to decode the DCI.

[0236] In this embodiment, the case where the UE fails to decode the DCI during a given period can be classified into 1) the case of only one transmission, and 2) the case of multiple transmissions.

[0237] 1) When there is only one transmission within a period, if the ACK / NACK itself is not received when the UE sends the HARQ ACK / NACK, the base station may determine that the UE fails to decode the DCI and operate to restart from the DCI transmission for the corresponding TB instead of entering the retransmission process.

[0238] 2) When there are multiple transmissions within a time period, the UE typically sends multiple TBs as HARQ ACK / NACK at once, which is usually referred to as the ACK codebook. In this case, even if there are intermediate failed transmissions or transmissions with DCI decoding failures, the UE can still determine the total number of transmissions and which transmission the current TB corresponds to. Therefore, even if DCI decoding fails, the UE may still record and send a NACK. To solve this problem, two solutions are possible. First, for all transmissions determined to be NACKs, there is a solution to restart transmission from the DCI transmission for the corresponding TB, as if there were only one transmission in that time period. Second, there is a method for the UE to provide additional information for the NACK entries in the ACK codebook, to send information about whether the NACK is due to DCI decoding failure or TB decoding failure (even though DCI decoding was successful). In this case, the base station only needs to restart transmission from the DCI for the corresponding transmission. Therefore, this method achieves more efficient operation compared to the first method.

[0239] Figure 16 This is a diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0240] refer to Figure 16 The terminal may include a transceiver 1610, a control unit 1620, and a storage unit 1630. In this disclosure, the control unit may be defined as a circuit, an application-specific integrated circuit, or at least one processor.

[0241] Transceiver 1610 can transmit signals to and receive signals from other network entities. Transceiver 1610 can, for example, receive system information from a base station and receive synchronization signals or reference signals.

[0242] According to the embodiments presented in this disclosure, the control unit 1620 can control the overall operation of the terminal. For example, the control unit 1620 can control the signal flow between each block to perform operations according to the flowchart described above.

[0243] The storage unit 1630 can store at least one of the information sent and received by the transceiver 1610 and the information generated by the control unit 1620.

[0244] Figure 17 This is a diagram illustrating the structure of a base station according to an embodiment of the present disclosure.

[0245] refer to Figure 17 The base station may include a transceiver 1710, a control unit 1720, and a storage unit 1730. In this disclosure, the control unit may be defined as a circuit, an application-specific integrated circuit, or at least one processor.

[0246] Transceiver 1710 can transmit signals to and receive signals from other network entities. Transceiver 1710 can send, for example, system information to terminals and send synchronization signals or reference signals.

[0247] According to embodiments of this disclosure, control unit 1720 can control the overall operation of the base station. For example, control unit 1720 can control the signal flow between each block to perform operations according to the flowchart above. Specifically, according to embodiments of this disclosure, control unit 1720 can control the operations proposed in this disclosure to transmit Residual Minimum System Information (RMSI) in a multi-beam-based system.

[0248] The storage unit 1730 can store at least one of the information sent and received by the transceiver 1710 and the information generated by the control unit 1720.

Claims

1. A method performed by a base station in a wireless communication system, the method comprising: Send the first downlink control information (DCI) and transport block (TB) to the terminal; Based on the first DCI, the transport block TB is sent to the terminal; In the event of a failure to transmit the TB, a Hybrid Automatic Repeat Request (HARQ) feedback is received from the terminal. as well as Based on the HARQ feedback, the TB is retransmitted to the terminal. The first DCI includes at least one of the following: time slot number counting period, retransmission time domain resource coefficient, and redundant version RV information for retransmission.

2. The method according to claim 1, further comprising: Send a Radio Resource Control (RRC) message, the RRC message including a maximum configured number of retransmissions associated with the RV information for retransmission and an RV sequence based on the number of retransmissions.

3. The method according to claim 1, further comprising: Based on the HARQ feedback, a second DCI is sent to the terminal. The second DCI includes only time-domain resource allocation and frequency-domain resource allocation.

4. The method according to claim 1, wherein, The TB mentioned in the retransmission also includes: Grouping multiple time slots with similar channel conditions into a single group; and Retransmit the TB in a time slot belonging to the same group as the time slot that sent the TB, and The first DCI also includes group information and group time slot information.

5. A method performed by a terminal in a wireless communication system, the method comprising: Receive first downlink control information (DCI) from base station (BS); Based on the first DCI, a transport block TB is received from the base station; In the event of a failure to receive the TB, a Hybrid Automatic Repeat Request (HARQ) feedback is sent to the base station. as well as Based on the HARQ feedback, the TB is re-received from the base station. The first DCI includes at least one of the following: time slot number counting period, retransmission time domain resource coefficient, and redundant version RV information for retransmission.

6. The method according to claim 5, further comprising: Receive a Radio Resource Control (RRC) message, the RRC message including a maximum configured number of retransmissions associated with the RV information used for retransmission and an RV sequence based on the number of retransmissions.

7. The method according to claim 5, further comprising: Based on the HARQ feedback, a second DCI is received from the base station. The second DCI includes only time-domain resource allocation and frequency-domain resource allocation.

8. The method according to claim 5, wherein, Re-receiving the TB also includes: Grouping multiple time slots with similar channel conditions into a single group; and Re-receive the TB in a time slot belonging to the same group as the time slot in which the TB was received, and The first DCI also includes group information and group time slot information.

9. A base station in a wireless communication system, comprising: A transceiver that transmits and receives at least one signal; as well as The control unit is connected to the transceiver. The control unit is configured to: Send the first downlink control information (DCI) and transport block (TB) to the terminal; Based on the first DCI, the transport block TB is sent to the terminal; In the event of a failure to transmit the TB, a Hybrid Automatic Repeat Request (HARQ) feedback is received from the terminal; and Based on the HARQ feedback, the TB is retransmitted to the terminal, and The first DCI includes at least one of the following: slot number counting period, retransmission time domain resource coefficient, and redundant version RV information for retransmission.

10. The base station according to claim 9, wherein, The control unit is further configured to send a Radio Resource Control (RRC) message, the RRC message including a maximum configured number of retransmissions associated with the RV information for retransmission and an RV sequence based on the number of retransmissions.

11. The base station according to claim 9, wherein, The control unit is also configured to: send a second DCI to the terminal based on the HARQ feedback. The second DCI includes only time-domain resource allocation and frequency-domain resource allocation.

12. The base station according to claim 9, wherein, The control unit is also configured to: Grouping multiple time slots with similar channel conditions into a single group; and Retransmit the TB in a time slot belonging to the same group as the time slot that sent the TB, and The first DCI also includes group information and group time slot information.

13. A terminal in a wireless communication system, comprising: A transceiver that transmits and receives at least one signal; as well as The control unit is connected to the transceiver. The control unit is configured to: Receive first downlink control information (DCI) from base station (BS); Based on the first DCI, a transport block TB is received from the base station; In the event of a failure to receive the TB, a Hybrid Automatic Repeat Request (HARQ) feedback is sent to the base station; and Based on the HARQ feedback, the TB is re-received from the base station, and The first DCI includes at least one of the following: slot number counting period, retransmission time domain resource coefficient, and redundant version RV information for retransmission.

14. The terminal according to claim 13, wherein, The control unit is further configured to receive a Radio Resource Control (RRC) message, the RRC message including a maximum configured number of retransmissions associated with the RV information for retransmission and an RV sequence based on the number of retransmissions.

15. The terminal according to claim 13, wherein, The control unit is further configured to receive a second DCI from the base station based on the HARQ feedback. The second DCI includes only time-domain resource allocation and frequency-domain resource allocation. The control unit is further configured to: group multiple time slots with similar channel conditions into a group, and re-receive the TB in a time slot belonging to the same group as the time slot used to receive the TB. The first DCI also includes group information and group time slot information.

Images