Method and apparatus for data transmission in wireless communication system supporting device to device communication

Abstract

A data transmission technology in a wireless communication system that supports communication between terminals is disclosed. A method of operation performed at a first communication node of the wireless communication system is provided, comprising: receiving data transmitted by a transmitting terminal to a receiving terminal; receiving feedback transmitted by the receiving terminal; decoding the received feedback and, if retransmission is necessary, allocating resources for retransmission; and retransmitting the data received from the transmitting terminal to the receiving terminal using the allocated resources.

Description

Technology Field

[0001] The present invention relates to a data transmission technology in a wireless communication system that supports device-to-device (D2D) communication. More specifically, it relates to a data transmission technology that enables data transmitted and received via D2D communication to be retransmitted via a sidelink under the control of a base station. Background Technology

[0002] Along with the advancement of information and communication technology, various wireless communication technologies are being developed. Representative wireless communication technologies include LTE (long term evolution) and NR (new radio), which are defined in the 3GPP (3rd generation partnership project) standards. LTE can be one of the wireless communication technologies among 4G (4th Generation) wireless communication technologies, and NR can be one of the wireless communication technologies among 5G (5th Generation) wireless communication technologies.

[0003] To handle the surge in wireless data following the commercialization of 4G communication systems (e.g., communication systems supporting LTE), 5G communication systems (e.g., communication systems supporting NR) that use frequency bands higher than those of 4G communication systems (e.g., frequency bands below 6 GHz) are being considered. 5G communication systems can support eMBB (enhanced Mobile BroadBand), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication).

[0004] Meanwhile, in LTE systems, reliability regarding the packet transmission process between a base station and a terminal can be provided through automatic repeat request (ARQ) and hybrid ARQ (HARQ) retransmissions performed at the Radio Link Control (RLC) and Medium Access Control (MAC) layers. The ARQ function can support error correction through retransmission based on RLC status messages in Layer-2 Acknowledged Mode (AM), and the HARQ function can guarantee delivery between two peer entities at Layer-1 through retransmission based on HARQ ACK / NACK feedback consisting of a single bit. In other words, both ARQ and HARQ can operate based on feedback. 5G NR systems may seek to enhance transmission reliability by performing possible repeated transmissions in the time, frequency, and spatial domains to obtain diversity gains. The problem to be solved

[0005] The objective of the present invention, which is to solve the above-mentioned problems, is to provide a data transmission technology that enables data transmitted and received via D2D communication to be retransmitted via a sidelink under the control of a base station. means of solving the problem

[0006] A data transmission method according to a first embodiment of the present invention for achieving the above-mentioned purpose may include, as an operation method performed at a first communication node of a wireless communication system, a step of receiving data transmitted by a transmitting terminal to a receiving terminal; a step of receiving feedback transmitted by the receiving terminal; a step of decoding the received feedback and, if retransmission is necessary, allocating resources for retransmission; and a step of retransmitting the data received from the transmitting terminal to the receiving terminal using the allocated resources. Effects of the invention

[0007] 5G NR systems may aim to increase transmission reliability by performing possible repeated transmissions in the time, frequency, and spatial domains to obtain diversity gains.

[0008] In a wireless communication system supporting sidelink communication to which the present invention is applied, a sidelink communication method that can provide enhanced reliability and simultaneously reduce latency by utilizing such features of a 5G NR system can be disclosed.

[0009] That is, according to the present invention, data transmitted by a transmitting terminal to a receiving terminal is received, feedback transmitted by the receiving terminal is received, the received feedback is decoded, and if retransmission is necessary, resources for retransmission are allocated, and the data received from the transmitting terminal is retransmitted to the receiving terminal using the allocated resources, thereby ensuring improved reliability and simultaneously reducing delay in a wireless communication system that supports sidelink communication. Brief explanation of the drawing

[0010] FIG. 1 is a conceptual diagram illustrating a first embodiment of a communication system. FIG. 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system. FIG. 3 is a flowchart that can explain the side-link data retransmission operation process in D2D communication of a wireless communication system to which the present invention can be applied. FIG. 4 is a configuration diagram of a data transmission device in a wireless communication system that supports communication between terminals according to the first embodiment of the present invention. FIG. 5 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a first embodiment of the present invention. FIG. 6 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a second embodiment of the present invention. FIG. 7 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a third embodiment of the present invention. FIG. 8 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a fourth embodiment of the present invention. FIG. 9 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to the fifth embodiment of the present invention. FIG. 10 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to the 6th embodiment of the present invention. FIG. 11 is a configuration diagram of a data transmission device in a wireless communication system that supports communication between terminals according to the seventh embodiment of the present invention. FIG. 12 is a conceptual diagram showing a first embodiment of the data retransmission processing method of FIG. 11. FIG. 13 is a conceptual diagram showing a second embodiment of the data retransmission processing method of FIG. 11. FIG. 14 is a conceptual diagram showing a third embodiment of the data retransmission processing method of FIG. 11. FIG. 15 is a conceptual diagram showing a fourth embodiment of the data retransmission processing method of FIG. 11. Specific details for implementing the invention

[0011] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are illustrated in the drawings and described in detail. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0012] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any of a plurality of related described items.

[0013] When it is stated that one component is "connected" or "connected" to another component, it should be understood that while it may be directly connected or connected to that other component, there may also be other components in between. On the other hand, when it is stated that one component is "directly connected" or "directly connected" to another component, it should be understood that there are no other components in between.

[0014] The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comprising" or "having" are intended to specify the presence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0015] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0016] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In order to facilitate an overall understanding of the present invention, the same reference numerals are used for identical components in the drawings, and redundant descriptions of identical components are omitted.

[0017] A communication system to which embodiments according to the present invention are applied will be described. The communication system to which embodiments according to the present invention are applied is not limited to the details described below, and embodiments according to the present invention may be applied to various communication systems. Here, the term "communication system" may be used interchangeably with "communication network."

[0018] FIG. 1 is a conceptual diagram illustrating a first embodiment of a communication system.

[0019] Referring to FIG. 1, the communication system (100) may include a plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6). The plurality of communication nodes may support 4G communication (e.g., LTE (long term evolution), LTE-A (advanced)), 5G communication (e.g., NR (new radio)), etc., as defined in the 3GPP (3rd generation partnership project) standard. 4G communication may be performed in a frequency band of 6 GHz or lower, and 5G communication may be performed not only in a frequency band of 6 GHz or lower but also in a frequency band of 6 GHz or higher.

[0020] For example, for 4G communication and 5G communication, multiple communication nodes can support communication protocols based on CDMA (code division multiple access), WCDMA (wideband CDMA), TDMA (time division multiple access), FDMA (frequency division multiple access), OFDM (orthogonal frequency division multiplexing), Filtered OFDM, CP (cyclic prefix)-OFDM, DFT-s-OFDM (discrete Fourier transform-spread-OFDM), OFDMA (orthogonal frequency division multiple access), SC (single carrier)-FDMA, NOMA (Non-orthogonal Multiple Access), GFDM (generalized frequency division multiplexing), FBMC (filter bank multi-carrier) based communication protocol, UFMC (universal filtered multi-carrier) based communication protocol, SDMA (Space Division Multiple Access) based communication protocol, etc.

[0021] Additionally, the communication system (100) may further include a core network. If the communication system (100) supports 4G communication, the core network may include an S-GW (serving-gateway), a P-GW (PDN (packet data network)-gateway), an MME (mobility management entity), etc. If the communication system (100) supports 5G communication, the core network may include a UPF (user plane function), an SMF (session management function), an AMF (access and mobility management function), etc.

[0022] Meanwhile, each of the plurality of communication nodes (110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, 130-6) constituting the communication system (100) may have the following structure.

[0023] FIG. 2 is a block diagram illustrating a first embodiment of a communication node constituting a communication system.

[0024] Referring to FIG. 2, the communication node (200) may include at least one processor (210), a memory (220), and a transceiver (230) that is connected to a network to perform communication. Additionally, the communication node (200) may further include an input interface device (240), an output interface device (250), a storage device (260), etc. Each component included in the communication node (200) may be connected by a bus (270) to communicate with one another.

[0025] However, each component included in the communication node (200) may be connected via individual interfaces or individual buses centered around the processor (210), rather than via a common bus (270). For example, the processor (210) may be connected via a dedicated interface to at least one of a memory (220), a transmission / reception device (230), an input interface device (240), an output interface device (250), and a storage device (260).

[0026] The processor (210) can execute a program command stored in at least one of the memory (220) and the storage device (260). The processor (210) may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory (220) and the storage device (260) may be composed of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory (220) may be composed of at least one of read-only memory (ROM) and random access memory (RAM).

[0027] Referring again to FIG. 1, the communication system (100) may include a plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) and a plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6). The communication system (100) including the base stations (110-1, 110-2, 110-3, 120-1, 120-2) and terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) may be referred to as an "access network". Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can form a macro cell. Each of the fourth base station (120-1) and the fifth base station (120-2) can form a small cell. The fourth base station (120-1), the third terminal (130-3), and the fourth terminal (130-4) may be located within the cell coverage of the first base station (110-1). The second terminal (130-2), the fourth terminal (130-4), and the fifth terminal (130-5) may be located within the cell coverage of the second base station (110-2). The fifth base station (120-2), the fourth terminal (130-4), the fifth terminal (130-5), and the sixth terminal (130-6) may be located within the cell coverage of the third base station (110-3). The first terminal (130-1) may be located within the cell coverage of the fourth base station (120-1). The sixth terminal (130-6) may be located within the cell coverage of the fifth base station (120-2).

[0028] Here, each of the plurality of base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be referred to as Node B, evolved Node B, gNB, base transceiver station (BTS), radio base station, radio transceiver, access point, access node, etc. Each of the plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) may be referred to as User Equipment (UE), terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, etc.

[0029] Meanwhile, each of the multiple base stations (110-1, 110-2, 110-3, 120-1, 120-2) may operate in different frequency bands or in the same frequency band. Each of the multiple base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be connected to each other via an ideal backhaul link or a non-ideal backhaul link, and may exchange information with each other via an ideal backhaul link or a non-ideal backhaul link. Each of the multiple base stations (110-1, 110-2, 110-3, 120-1, 120-2) may be connected to a core network via an ideal backhaul link or a non-ideal backhaul link. Each of the multiple base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit a signal received from the core network to the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6), and can transmit a signal received from the corresponding terminal (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) to the core network.

[0030] In addition, each of the multiple base stations (110-1, 110-2, 110-3, 120-1, 120-2) can support MIMO (Multiple Antenna Technology, Multiple Input Multiple Output) transmission (e.g., SU (single user)-MIMO, MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint) transmission, CA (carrier aggregation) transmission, transmission in an unlicensed band, device-to-device communication (D2D) (or ProSe (proximity services)), etc. Here, each of the plurality of terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) can perform an operation corresponding to the base station (110-1, 110-2, 110-3, 120-1, 120-2) and an operation supported by the base station (110-1, 110-2, 110-3, 120-1, 120-2). For example, the second base station (110-2) can transmit a signal to the fourth terminal (130-4) based on the SU-MIMO method, and the fourth terminal (130-4) can receive a signal from the second base station (110-2) based on the SU-MIMO method. Alternatively, the second base station (110-2) can transmit a signal to the fourth terminal (130-4) and the fifth terminal (130-5) based on the MU-MIMO method, and each of the fourth terminal (130-4) and the fifth terminal (130-5) can receive a signal from the second base station (110-2) by the MU-MIMO method.

[0031] Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can transmit a signal to the fourth terminal (130-4) based on the CoMP method, and the fourth terminal (130-4) can receive a signal from the first base station (110-1), the second base station (110-2), and the third base station (110-3) by the CoMP method. Each of the multiple base stations (110-1, 110-2, 110-3, 120-1, 120-2) can transmit and receive signals based on the CA method with terminals (130-1, 130-2, 130-3, 130-4, 130-5, 130-6) within its cell coverage area. Each of the first base station (110-1), the second base station (110-2), and the third base station (110-3) can control D2D between the fourth terminal (130-4) and the fifth terminal (130-5), and each of the fourth terminal (130-4) and the fifth terminal (130-5) can perform D2D by controlling each of the second base station (110-2) and the third base station (110-3).

[0032] Meanwhile, reliability for sidelink data transmission between terminals based on the LTE protocol can be provided through blind retransmission, which involves repeating transmissions a number of times set by RRC (radio resource control) regardless of HARQ ACK (Acknowledgement) / NACK (Negative Acknowledgement) feedback. Blind retransmission supports reliability by ensuring that the sidelink transmitting terminal always performs data retransmission when transmitting packets, even though the terminal receiving data via sidelink communication also performs HARQ combining just like the terminal receiving data from the base station, but HARQ feedback transmission is not supported.

[0033] To describe the blind retransmission operation more specifically, the transmitting terminal can retransmit protocol data units (MAC PDUs) transmitted as a transport block within a single subframe three times through consecutive subframes within the sidelink control period. Consequently, four transmissions of MAC PDUs occur, including the initial transmission, and each transmission may include a redundancy version value that follows a fixed pattern. Furthermore, since only the initial transmission is indicated in sidelink control information (SCI 0), the receiving terminal can use the received SCI 0 value to derive all the data necessary for demodulating subsequent retransmission packets.

[0034] Unlike LTE sidelink transmission, sidelink transmission in NR V2X (Vehicle to everything) can support HARQ / CSI (channel state information) feedback for unicast and groupcast transmissions, along with blind retransmission for transmission blocks.

[0035] NR V2X sidelink transmission is also supported by default via UM (Unacknowledged Mode) RLC, but RLC AM may also be supported for unicast transmission. The physical channels of the NR V2X sidelink may include PSCCH (physical SL control channel), PSSCH (physical SL shared channel), and PSFCH (physical sidelink feedback channel), which are improvements over LTE sidelinks. Additionally, NR V2X may support physical layer HARQ feedback and HARQ combining for sidelink unicast and groupcast.

[0036] HARQ-ACK feedback for PSSCH is transmitted in the SFCI (sidelink feedback control information) format via PSFCH according to resource allocation modes 1 and 2, and the time between the transmission of HARQ feedback on PSSCH and PSFCH can be pre-configured or configured during the resource allocation process for both resource allocation modes 1 and 2.

[0037] FIG. 3 is a flowchart that can explain the side-link data retransmission operation process in D2D communication of a wireless communication system to which the present invention can be applied.

[0038] Referring to FIG. 3, in the D2D communication of a wireless communication system to which the present invention can be applied, the side-link data retransmission operation process first involves a transmitting terminal and a receiving terminal located within the base station coverage and participating in side-link communication, which can search for other terminals through the base station (S301). Then, the transmitting terminal and the receiving terminal can establish a side-link (S302). Subsequently, the transmitting terminal and the receiving terminal can receive side-link configuration information from the base station that may be required depending on the service (S303). Here, the side-link configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the side-link configuration information may be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal.

[0039] If the transmitting terminal has data to transmit to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S304). At this time, the transmitting terminal may request resource allocation from the base station using the uplink channel PUCCH. Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data via sidelink transmission (S305), and may approve the resource allocation by creating a sidelink grant and transmitting it to the transmitting terminal (S306).

[0040] Meanwhile, the transmitting terminal can transmit data to the receiving terminal through allocated resources (S307). At this time, if retransmission is required, the receiving terminal can generate NACK feedback (S308) and transmit the generated NACK feedback to the transmitting terminal (S309). Accordingly, the transmitting terminal that receives the NACK feedback can request the base station to allocate resources for retransmission using the uplink channel PUCCH (S310).

[0041] Accordingly, the base station can schedule the relevant resources so that the transmitting terminal can retransmit data via sidelink transmission, and can approve the resource allocation by creating a sidelink grant and transmitting it to the transmitting terminal (S311). Accordingly, the transmitting terminal can retransmit data to the receiving terminal using the resources allocated from the base station for data retransmission (S312). Accordingly, the receiving terminal can generate ACK feedback (S313) and transmit the generated ACK feedback to the transmitting terminal (S314). Upon receiving the ACK feedback, the transmitting terminal can terminate the retransmission operation.

[0042] Meanwhile, a 5G NR system may aim to increase transmission reliability by performing possible repeated transmissions in the time, frequency, and spatial domains to obtain diversity gains. In a wireless communication system supporting sidelink communication to which the present invention is applied, a sidelink communication method that can reduce latency while demonstrating enhanced reliability by utilizing such characteristics of the 5G NR system can be described.

[0043] According to the present invention, when a side link is formed between terminals within a cell, the transmitting terminal can directly transmit data to a receiving terminal within a cell using resources allocated by a base station, and can directly receive a feedback signal generated and transmitted by the receiving terminal regarding the data received.

[0044] Furthermore, according to the present invention, a base station can receive data directly transmitted by a sidelink transmitting terminal to a receiving terminal together with the receiving terminal. Additionally, the base station can receive a feedback signal transmitted by a sidelink receiving terminal together with the transmitting terminal. The base station can determine whether to retransmit by decoding the received feedback, and if retransmission is necessary, it can allocate resources for retransmission and perform retransmission together with the sidelink transmitting terminal.

[0045] If the base station receives a retransmission indicator instead of feedback from the receiving terminal, the base station can use it to determine whether to retransmit, and if retransmission is required, it can perform the retransmission together with the sidelink transmitting terminal using pre-allocated retransmission resources after receiving data from the receiving terminal.

[0046] In order to achieve these technical challenges, in a wireless communication system that supports sidelink communication according to one embodiment of the present invention, data transmission can be achieved through communication composed of three main units: a base station (401 in FIG. 4, 1101 in FIG. 11), and a transmitting terminal and a receiving terminal (402, 403 in FIG. 4, 1102, 1103 in FIG. 11) that perform sidelink communication.

[0047] FIG. 4 is a configuration diagram of a data transmission device in a wireless communication system that supports communication between terminals according to the first embodiment of the present invention.

[0048] Referring to FIG. 4, a data transmission device in a wireless communication system that supports communication between terminals according to a first embodiment of the present invention may include a base station (401), a transmitting terminal (402) that performs side-link communication, and a receiving terminal (403) that performs side-link communication. The transmitting terminal (402) and the receiving terminal (403) may participate in side-link communication and may be located within the coverage of the base station (401). Furthermore, the transmitting terminal (402) and the receiving terminal (403) may search for a counterpart terminal through the base station (401) and establish a side-link between the discovered different terminals.

[0049] These transmitting terminals (402) and receiving terminals (403) can receive sidelink configuration information required according to the service from the base station (401). Here, the sidelink configuration information may be transmitted from the base station (401) to the transmitting terminal (402) and receiving terminal (403) via a System Information Block, such as frequency and bandwidth. Alternatively, the sidelink configuration information may be transmitted from the base station (401) to the transmitting terminal (402) and receiving terminal (403) via an RRC message specific to the cell or an RRC message specific to the terminal. Additionally, as an example for Sidelink RNTI (SL-RNTI), it may be a Sidelink ID or a Group ID.

[0050] The process of a transmitting terminal (402) transmitting data to a receiving terminal (403) can be largely composed of an initial transmission (S401) stage and a retransmission (S402) stage. The initial transmission process (S401) may include a step in which a transmitting terminal (402) that intends to transmit data requests resource allocation for data transmission from a base station (401), and a step in which the base station (401) schedules resources and approves resources.

[0051] Additionally, the initial transmission process (S401) may include the step of the transmitting terminal (402) transmitting data to the receiving terminal (403) using allocated resources; the step of the receiving terminal (403) transmitting feedback regarding the received data; and the step of the transmitting terminal (402) determining whether to retransmit based on the result of decoding the received feedback. At this time, the data transmitted from the transmitting terminal (402) in the data transmission step may be delivered to the base station (401) as well as the receiving terminal (403), and each may be decoded. Also, the feedback transmitted from the receiving terminal (403) in the feedback transmission step may be delivered to the base station (401) as well as the transmitting terminal (402). The transmitting terminal (402) may determine whether to retransmit after the feedback is decoded. Alternatively, the base station (401) may determine whether to retransmit based on the result of decoding the feedback. Also, as an example for Sidelink RNTI (radio network temporary identifier), SL-RNTI, it can be a Sidelink ID or a Group ID.

[0052] Next, the retransmission process (S402) is performed when the base station (401) and the transmitting terminal (402) determine that retransmission is necessary, and may include the step of the base station (401) that has decided on retransmission scheduling resources for retransmission and approving resource allocation; the step of the base station (401) retransmitting data using allocated resources; the step of the transmitting terminal (402) retransmitting data using allocated resources; and the step of the receiving terminal (403) receiving the retransmitted data from the base station (401) and the transmitting terminal (402), decoding it, and transmitting feedback. At this time, the data retransmitted from the base station (401) and the data retransmitted from the transmitting terminal (402) may be received and decoded by the receiving terminal (403) simultaneously or sequentially. Additionally, the feedback transmitted by the receiving terminal (403) in the feedback transmission step may be delivered to the base station (401) and the transmitting terminal (402) and decoded, respectively.

[0053] As such, the present invention may include a procedure for determining whether to retransmit data from a base station (401) to a receiving terminal (403), and a process for approving resource allocation for data transmission or retransmission through sidelink communication to which the present invention is applied. First, the retransmission determination process performed by the base station (401) in determining whether to retransmit data based on a retransmission indicator or new data received from a transmitting terminal (402) may be described.

[0054] FIG. 5 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a first embodiment of the present invention.

[0055] Referring to FIG. 5, a data transmission method in a wireless communication system supporting communication between terminals according to a first embodiment of the present invention can show a process in which data transmitted by a transmitting terminal via sidelink communication is retransmitted when the receiving terminal fails to receive it. First, a transmitting terminal and a receiving terminal located within the base station coverage and participating in sidelink communication can search for a counterpart terminal (S501). At this time, the search for the counterpart terminal can be performed through the base station, or it can be performed solely through signaling between the transmitting terminal and the receiving terminal. Next, the transmitting terminal and the receiving terminal can establish a sidelink (S502). Subsequently, the transmitting terminal and the receiving terminal can receive sidelink configuration information from the base station that may be required depending on the service (S503). Here, the sidelink configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the sidelink configuration information may be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal. Also, as an example for Sidelink RNTI (Sidelink RNTI, SL-RNTI), it can be a Sidelink ID or a Group ID.

[0056] Next, if the transmitting terminal has data to transmit to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S504). Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data to the receiving terminal via sidelink transmission (S505), and may create a sidelink grant and transmit it to the transmitting terminal and the receiving terminal to approve the resource allocation (S506). At this time, the sidelink grant may include allocation resource information such as (Table 1).

[0057] Types of allocated resources Target resources Transmitter receiving side Data Resource Grant Side link terminal terminal Uplink terminal base station Feedback Resource Grant Side link terminal terminal Feedback Resource Grant / Tx (or ReTx) Resource Allocation Download link base station terminal

[0058] In (Table 1), the uplink resources approved as resources for data transmission may be the same resources as the sidelink resources. Sidelink grants can be transmitted to all terminals participating in sidelink communication and decoded, and in the first embodiment, sidelink grants transmitted from the base station can be delivered to the transmitting terminal and the receiving terminal. Meanwhile, the transmitting terminal can transmit sidelink control information and data to the receiving terminal through the allocated resources, and at this time, the base station can receive the sidelink control information and data transmitted by the transmitting terminal directly or through monitoring (S507). In this way, the data transmitted by the receiving terminal can be delivered to the base station and the transmitting terminal simultaneously or sequentially and decoded respectively.

[0059] Accordingly, the receiving terminal and the base station can generate feedback by decoding the data received from the transmitting terminal. Then, the receiving terminal and the base station can transmit the feedback generated by each using resources allocated by the base station to the transmitting terminal (S508, S509). At this time, since the base station succeeded in decoding, it can transmit a sidelink grant to the transmitting terminal that includes ACK feedback and resource allocation information for transmitting (or retransmitting) the received data (S508). Here, the sidelink grant may include the configuration of (Table 1). Then, the receiving terminal can generate NACK feedback and transmit it to the transmitting terminal because it failed to decode the data received from the transmitting terminal (S509).

[0060] The transmitting terminal determines whether the feedback received from the receiving terminal is NACK feedback requiring retransmission (S310). If it is NACK feedback, it can retransmit data to the receiving terminal using resources allocated for data retransmission received from the base station via step S508 (S511). At this time, the transmitting terminal can notify the base station of whether retransmission is required by sending a retransmission indication using the uplink information of the sidelink grant (S511). Upon receiving the retransmission indication, the base station determines whether retransmission is required (S512). If it is determined that retransmission is required, it can retransmit the data received from the transmitting terminal to the receiving terminal (S513). At this time, the data retransmitted by the base station can be transmitted using the retransmission resource allocation of (Table 1). Accordingly, the receiving terminal can receive data from the transmitting terminal and the base station simultaneously or sequentially, can decode the received data to generate feedback, and can transmit the generated feedback to the transmitting terminal (S514). The base station can transmit allocation information for data transmission through the sidelink along with previous feedback information (S515).

[0061] FIG. 6 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a second embodiment of the present invention.

[0062] Referring to FIG. 6, a data transmission method in a wireless communication system supporting communication between terminals according to a second embodiment of the present invention can demonstrate a retransmission process when data transmitted from a transmitting terminal to a base station via an uplink fails to be received. To this end, a transmitting terminal and a receiving terminal located within the base station coverage and participating in sidelink communication can first search for a counterpart terminal (S601). At this time, the search for the counterpart terminal can be performed through the base station, or it can be performed solely through signaling between the transmitting terminal and the receiving terminal. Next, the transmitting terminal and the receiving terminal can establish a sidelink (S602). Subsequently, the transmitting terminal and the receiving terminal can receive sidelink configuration information from the base station that may be required depending on the service (S603). Here, the sidelink configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the sidelink configuration information may be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal.

[0063] If the transmitting terminal has data to be transmitted to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S604). Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data to the receiving terminal via sidelink transmission (S605), and may create a sidelink grant and transmit it to the transmitting terminal and the receiving terminal to approve the resource allocation (S606). At this time, the sidelink grant may include allocation resource information such as (Table 1).

[0064] Meanwhile, the transmitting terminal can transmit sidelink control information and data to the receiving terminal through allocated resources, and at this time, the base station can receive the sidelink control information and data transmitted by the transmitting terminal directly or through monitoring (S607). In this way, the data transmitted by the receiving terminal can be delivered to the base station and the transmitting terminal simultaneously or sequentially and decoded respectively.

[0065] Next, the receiving terminal and the base station can generate feedback by decoding the data received from the transmitting terminal. Then, the receiving terminal and the base station can each transmit the feedback to the transmitting terminal using resources allocated by the base station (S608, S609). At this time, the base station can transmit a sidelink grant to the transmitting terminal that includes NACK feedback and resource allocation information for transmitting (or retransmitting) the received data in the case of a decoding failure (S608). Here, the sidelink grant may include the configuration of (Table 1). Then, the receiving terminal can generate NACK feedback and transmit it to the transmitting terminal because decoding of the data received from the transmitting terminal failed (S609).

[0066] Meanwhile, the transmitting terminal determines whether the feedback received from the receiving terminal is NACK feedback requiring retransmission (S610). If it is NACK feedback, it can retransmit data to the receiving terminal using resources allocated for data retransmission received from the base station through step S608 (S611). At this time, the transmitting terminal can notify the base station of whether retransmission is required by transmitting a retransmission indication using the uplink information of the sidelink grant (S611). The base station receives the retransmission indication and determines whether retransmission is required (S612). If retransmission is required, it can transmit a sidelink grant containing NACK feedback and resource allocation information for transmitting (or retransmitting) the received data to the transmitting terminal (S613). Meanwhile, the receiving terminal can receive the data retransmitted by the transmitting terminal, can decode the received data to generate ACK feedback, and can transmit the generated ACK feedback to the transmitting terminal (S614).

[0067] FIG. 7 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a third embodiment of the present invention.

[0068] Referring to FIG. 7, a data transmission method in a wireless communication system supporting communication between terminals according to a third embodiment of the present invention can show a processing process when a receiving terminal successfully receives data transmitted by a transmitting terminal via sidelink communication. To this end, first, a transmitting terminal and a receiving terminal located within the base station coverage and participating in sidelink communication can search for a counterpart terminal (S701). At this time, the search for the counterpart terminal can be performed through the base station, or it can be performed solely through signaling between the transmitting terminal and the receiving terminal. Next, the transmitting terminal and the receiving terminal can establish a sidelink (S702). Subsequently, the transmitting terminal and the receiving terminal can receive sidelink configuration information from the base station that may be required depending on the service (S703). Here, the sidelink configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the sidelink configuration information may be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal.

[0069] Next, if the transmitting terminal has data to transmit to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S704). Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data to the receiving terminal via sidelink transmission (S705), and may create a sidelink grant and transmit it to the transmitting terminal and the receiving terminal to approve the resource allocation (S706). At this time, the sidelink grant may include allocation resource information such as (Table 1).

[0070] Meanwhile, the transmitting terminal can transmit sidelink control information and data to the receiving terminal through allocated resources, and at this time, the base station can receive the sidelink control information and data transmitted by the transmitting terminal directly or through monitoring (S707). In this way, the data transmitted by the receiving terminal can be delivered to the base station and the transmitting terminal simultaneously or sequentially and decoded respectively.

[0071] The receiving terminal and the base station can decode data received from the transmitting terminal to generate ACK or NACK feedback. Here, it can be assumed that the receiving terminal and the base station successfully decoded the data received from the transmitting terminal and generated ACK feedback. Then, the receiving terminal and the base station can each transmit the ACK feedback to the transmitting terminal using resources allocated by the base station (S708, S709). At this time, the base station can transmit a sidelink grant to the transmitting terminal that includes the ACK feedback that was successfully decoded and resource allocation information for transmitting (or retransmitting) the received data (S708). Here, the sidelink grant may include the configuration of (Table 1).

[0072] The transmitting terminal determines whether the feedback received from the receiving terminal is NACK feedback requiring retransmission (S710), and if it is ACK feedback, it can transmit new data to the receiving terminal and the base station (S711). When the base station receives new data, it determines whether retransmission is required (S712), can generate feedback for the received new data, and can generate a sidelink grant for it and deliver it to the transmitting terminal (S713). Meanwhile, the receiving terminal can receive new data from the transmitting terminal, can decode the received new data to generate ACK feedback, and can transmit the generated ACK feedback to the transmitting terminal (S714).

[0073] Meanwhile, in the third embodiment of the present invention, since the sidelink feedback received from the receiving terminal through step S709 is ACK feedback, the same operation can be performed even if the sidelink feedback transmitted from the base station in step S708 includes NACK feedback.

[0074] In the following, a procedure for determining whether to retransmit data from a base station to a receiving terminal, and a process for approving resource allocation for data transmission or retransmission through sidelink communication to which the present invention is applied, can be described, wherein feedback information regarding received data transmitted from a receiving terminal to a transmitting terminal can be transmitted using resources allocated by the base station when the base station determines retransmission, and data retransmission performed under monitoring by the base station can be described.

[0075] FIG. 8 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to a fourth embodiment of the present invention.

[0076] Referring to FIG. 8, a data transmission method in a wireless communication system supporting inter-terminal communication according to the fourth embodiment of the present invention may show a process in which data transmitted by a transmitting terminal via sidelink communication is retransmitted multiple times by monitoring of a base station when the receiving terminal fails to receive it. To this end, first, a transmitting terminal and a receiving terminal located within the base station coverage and participating in sidelink communication can search for a counterpart terminal (S801). At this time, the search for the counterpart terminal can be performed through the base station, or it can be performed solely through signaling between the transmitting terminal and the receiving terminal. Next, the transmitting terminal and the receiving terminal can establish a sidelink (S802). Subsequently, the transmitting terminal and the receiving terminal can receive sidelink configuration information from the base station that may be required depending on the service (S803). Here, the sidelink configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the sidelink configuration information may be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal. Also, as an example for Sidelink RNTI (Sidelink RNTI, SL-RNTI), it can be a Sidelink ID or a Group ID.

[0077] Next, if the transmitting terminal has data to be transmitted to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S804). Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data to the receiving terminal via sidelink transmission (S805), and may create a sidelink grant and transmit it to the transmitting terminal and the receiving terminal to approve the resource allocation (S806). At this time, the sidelink grant may include allocation resource information such as (Table 2).

[0078] In particular, the uplink resources allocated for data transmission in (Table 2) may be the same resources as the sidelink resources due to the characteristics of the sidelink that basically uses uplink resources.

[0079] Types of allocated resources Target resources Transmitter receiving side Data Resource Grant Side link terminal terminal Uplink terminal base station Feedback Resource Grant Side link terminal terminal Uplink terminal base station

[0080] Additionally, if the feedback transmitted from the receiving terminal is not transmitted to the base station, the uplink allocation for the feedback resource grant may be non-existent or have the same value. Such a sidelink grant can be transmitted to all terminals participating in the sidelink communication and decoded, and in the fourth embodiment, the sidelink grant transmitted from the base station can be delivered to both the transmitting terminal and the receiving terminal. Meanwhile, the transmitting terminal can transmit sidelink control information and data to the receiving terminal through the allocated resources, and at this time, the base station can receive the sidelink control information and data transmitted by the transmitting terminal (S807). In this way, the sidelink control information and data transmitted by the transmitting terminal can be delivered to the base station and the receiving terminal simultaneously or sequentially and decoded respectively.

[0081] The receiving terminal can decode the data received from the transmitting terminal to generate ACK or NACK feedback. Here, it can be assumed that the receiving terminal generates NACK feedback because the decoding of the received data failed. Next, the receiving terminal can transmit the feedback to the transmitting terminal and the base station using resources allocated by the base station (S808). At this time, the receiving terminal may use the uplink resources allocated for feedback in step S806 to transmit the sidelink feedback to the base station. The transmitting terminal receives the feedback from the receiving terminal, decodes it, and then determines whether it is NACK feedback (S809). If it is NACK feedback, it may be necessary to retransmit the data.

[0082] Meanwhile, the base station can determine whether data retransmission is necessary when it receives feedback from the receiving terminal (S810), and if it is NACK feedback, it can determine that retransmission is necessary. Then, if the base station succeeds in decoding the data received from the transmitting terminal in S807 and determines in S810 that retransmission to the receiving terminal is necessary, it can transmit feedback on the data received from the transmitting terminal, a sidelink grant for the retransmission data, and the retransmission data to the transmitting terminal and the receiving terminal (S811). At this time, since the sidelink grant does not require resources to transmit data from the transmitting terminal to the base station, it may include the resource configuration of (Table 3).

[0083] Types of allocated resources Target resources Transmitter receiving side Data Resource Grant Side link terminal terminal Feedback Resource Grant Side link terminal terminal Uplink terminal base station

[0084] Next, when the transmitting terminal receives resource allocation approval via a sidelink grant, it can retransmit data to the receiving terminal using the resources allocated from the base station (S812). At this time, the data retransmitted from the base station and the transmitting terminal can be delivered to the receiving terminal simultaneously or sequentially and decoded. The receiving terminal can receive one or more retransmitted data, generate feedback including the decoded result, and transmit it to the transmitting terminal, or simultaneously transmit it to the base station (S813). Of course, the base station can also receive feedback by monitoring the sidelink resources to which the feedback is transmitted.

[0085] FIG. 9 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to the fifth embodiment of the present invention.

[0086] Referring to FIG. 9, a data transmission method in a wireless communication system supporting communication between terminals according to the fifth embodiment of the present invention can show a process in which data is retransmitted through the monitoring function of the base station when the transmitting terminal fails to receive both the data transmitted to the receiving terminal and the data transmitted to the base station through sidelink communication.

[0087] To this end, first, a transmitting terminal and a receiving terminal located within the base station coverage and participating in sidelink communication can search for a counterpart terminal (S901). At this time, the search for the counterpart terminal can be performed through the base station, or it can be performed solely through signaling between the transmitting terminal and the receiving terminal. Next, the transmitting terminal and the receiving terminal can establish a sidelink (S902). Subsequently, the transmitting terminal and the receiving terminal can receive sidelink configuration information from the base station that may be required depending on the service (S903). Here, the sidelink configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the sidelink configuration information can be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal.

[0088] If the transmitting terminal has data to be transmitted to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S904). Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data to the receiving terminal via sidelink transmission (S905), and may create a sidelink grant and transmit it to the transmitting terminal and the receiving terminal to approve the resource allocation (S906). At this time, the sidelink grant may include allocation resource information such as (Table 2).

[0089] In particular, the uplink resources allocated for data transmission in (Table 2) may be the same resources as the sidelink resources due to the characteristics of the sidelink that basically uses uplink resources.

[0090] Additionally, if feedback transmitted from the receiving terminal is not transmitted to the base station, the uplink allocation for feedback resource acknowledgment may be non-existent or have the same value. Such sidelink grants can be transmitted to and decoded by all terminals participating in the sidelink communication, and in the fifth embodiment, sidelink grants transmitted from the base station can be delivered to both the transmitting terminal and the receiving terminal.

[0091] Meanwhile, the transmitting terminal can transmit sidelink control information and data to the receiving terminal through allocated resources, and at this time, the base station can receive the sidelink control information and data transmitted by the transmitting terminal (S907). In this way, the sidelink control information and data transmitted by the transmitting terminal can be delivered to the base station and the receiving terminal simultaneously or sequentially and decoded respectively.

[0092] The receiving terminal can generate ACK or NACK feedback by decoding data received from the transmitting terminal. Here, as a result of the receiving terminal decoding the received data, NACK feedback can be generated in the case where decoding fails. The receiving terminal can transmit the feedback to the transmitting terminal using resources allocated by the base station, and at this time, the base station can receive the feedback transmitted by the receiving terminal (S908). At this time, the receiving terminal can use the uplink resources allocated for feedback in step S906 to transmit the sidelink feedback to the base station.

[0093] The transmitting terminal receives feedback from the receiving terminal, decodes it, and determines whether there is NACK feedback (S909). If there is NACK feedback, the data may be retransmitted. Additionally, the base station can determine whether data retransmission is necessary when it receives feedback from the receiving terminal (S910). Here, the base station may determine that retransmission is necessary because it has received NACK feedback from the receiving terminal.

[0094] Meanwhile, if the base station fails to successfully decode the data received from the transmitting terminal in S907 and determines in S910 that retransmission to the receiving terminal is necessary, it may generate NACK feedback for the data received from the transmitting terminal and a sidelink grant for the retransmitted data and transmit them to the transmitting terminal and the receiving terminal (S911). At this time, since the sidelink grant does not require data resources transmitted from the transmitting terminal to the base station, it may include the resource configuration included in (Table 3).

[0095] Next, when the transmitting terminal receives a resource allocation approval through a sidelink grant, it can retransmit data to the receiving terminal using the resources allocated from the base station (S912). When the receiving terminal receives the retransmitted data, it can generate feedback including the decoded result and transmit it to the transmitting terminal (S913). Meanwhile, since the base station failed to decode the data received in S907 and cannot participate in the retransmission, it may not perform monitoring of the sidelink resources until a new scheduling request arrives.

[0096] FIG. 10 is a flowchart of a data transmission method in a wireless communication system that supports communication between terminals according to the 6th embodiment of the present invention.

[0097] Referring to FIG. 10, a data transmission method in a wireless communication system supporting communication between terminals according to the 6th embodiment of the present invention can show the process of transmission through the monitoring function of a base station when the decoding of data transmitted from a transmitting terminal to a receiving terminal via sidelink communication is successful.

[0098] To this end, first, a transmitting terminal and a receiving terminal located within the base station coverage and participating in sidelink communication can search for a counterpart terminal (S1001). At this time, the search for the counterpart terminal can be performed through the base station, or it can be performed solely through signaling between the transmitting terminal and the receiving terminal. Next, the transmitting terminal and the receiving terminal can establish a sidelink (S1002). Subsequently, the transmitting terminal and the receiving terminal can receive sidelink configuration information from the base station that may be required depending on the service (S1003). Here, the sidelink configuration information, such as frequency and bandwidth, can be transmitted from the base station to the transmitting terminal and the receiving terminal through a System Information Block. Additionally, the sidelink configuration information can be transmitted from the base station to the transmitting terminal and the receiving terminal through an RRC message specific to the cell or an RRC message specific to the terminal.

[0099] If the transmitting terminal has data to be transmitted to the receiving terminal via sidelink communication, it may request resource allocation from the base station (S1004). Then, the base station may schedule the corresponding resource so that the transmitting terminal can transmit data to the receiving terminal via sidelink transmission (S1005), and may create a sidelink grant and transmit it to the transmitting terminal and the receiving terminal to approve the resource allocation (S1006). At this time, the sidelink grant may include allocation resource information such as (Table 2).

[0100] Meanwhile, the transmitting terminal can transmit sidelink control information and data to the receiving terminal through allocated resources, and at this time, the base station can receive the sidelink control information and data transmitted by the transmitting terminal (S1007). In this way, the sidelink control information and data transmitted by the transmitting terminal can be delivered to the base station and the receiving terminal simultaneously or sequentially and decoded respectively.

[0101] Next, when the receiving terminal receives sidelink control information and data from the transmitting terminal, it can decode the received data and generate ACK feedback information if the decoding is successful. Then, the receiving terminal can transmit the generated feedback to the transmitting terminal using resources allocated by the base station, and at this time, the base station can receive the feedback transmitted by the receiving terminal (S1008).

[0102] The transmitting terminal receives feedback from the receiving terminal, decodes it, and determines whether it is NACK feedback (S1009). Since the receiving terminal has transmitted ACK feedback, it is determined to be ACK feedback, so there may be no need to retransmit the data.

[0103] Meanwhile, when the base station receives feedback from the receiving terminal, it can determine whether data retransmission is necessary (S1010). Here, the base station may not need to retransmit data because the receiving terminal has transmitted ACK feedback. In this case, the receiving terminal may use the uplink resources allocated for feedback in step S1006 to transmit sidelink feedback to the base station.

[0104] In this way, if the base station determines that retransmission of data to the receiving terminal is not necessary, it may transmit an ACK or NACK feedback and a sidelink grant for new data transmission to the transmitting terminal and the receiving terminal depending on whether the decoding of the data received from the transmitting terminal is successful (S1011). At this time, the sidelink grant may include allocation resource information such as (Table 2).

[0105] In particular, the uplink resources allocated for data transmission in (Table 2) may be the same resources as the sidelink resources due to the characteristics of the sidelink that basically uses uplink resources.

[0106] Additionally, if feedback transmitted from the receiving terminal is not transmitted to the base station, the uplink allocation for the feedback resource grant may be non-existent or have the same value. Such sidelink grants can be transmitted to and decoded by all terminals participating in the sidelink communication, and in the sixth embodiment, the sidelink grant transmitted from the base station can be delivered to both the transmitting terminal and the receiving terminal.

[0107] Meanwhile, the transmitting terminal can transmit sidelink control information and new data to the receiving terminal through the allocated new resources, and at this time, the base station can receive the sidelink control information and new data transmitted by the transmitting terminal (S1012). In this way, the sidelink control information and new data transmitted by the transmitting terminal can be delivered to the base station and the receiving terminal simultaneously or sequentially and decoded respectively.

[0108] When the receiving terminal receives sidelink control information and new data from the transmitting terminal, it can decode the received new data and, if the decoding is successful, generate ACK feedback information. Then, the receiving terminal can transmit the generated feedback to the transmitting terminal using new resources allocated by the base station, and at this time, the base station can receive the feedback transmitted by the receiving terminal directly or through monitoring (S1013).

[0109] FIG. 11 is a configuration diagram of a data transmission device in a wireless communication system that supports communication between terminals according to the seventh embodiment of the present invention.

[0110] Referring to FIG. 11, a data transmission device in a wireless communication system supporting inter-terminal communication according to the seventh embodiment of the present invention may include a base station (1101), a transmitting terminal (1102) existing within a cell of the base station (1101), and a receiving terminal (1103) existing within a cell of the base station (1101). Data transmitted between the base station (1101), the transmitting terminal (1102), and the receiving terminal (1103) may be denoted as RM as data for which rate matching processing has been completed. More specifically, there may be data RMn transmitted from the transmitting terminal (1102) to the receiving terminal (1103), data RMx retransmitted from the transmitting terminal (1102) to the receiving terminal (1103), and data RMy retransmitted from the base station (1101) to the receiving terminal (1103). Additionally, there may be a feedback signal transmitted from the receiving terminal (1103) to the transmitting terminal (1102). In FIG. 11, a feedback NACK signal (S1103) may be illustrated to describe a retransmission operation occurring in a side link. The transmitted data RMs may be transmitted using a resource R composed of one or more physical resource blocks (PRBs) allocated for transmission at the base station (1101).

[0111] More specifically, the rate-matching processed data transmitted from the transmitting terminal to the receiving terminal is RM n It can be denoted as, and the data with completed rate matching processing that is retransmitted from the transmitting terminal to the receiving terminal is RM x It can be denoted as, and the rate-matching processed data retransmitted from the base station to the receiving terminal is RM y It can be denoted as such. There may also be a feedback signal transmitted from the receiving terminal to the transmitting terminal, which can be denoted as NACK.

[0112] Looking at this in more detail, first, the transmitting terminal (1102) has a sidelink resource R allocated by the base station (1101). s Data RM with completed rate matching processing using n It can be initially transmitted to the receiving terminal (S1101). At this time, the base station (1101) transmits the data RM transmitted by the transmitting terminal. n It can be received and decoded through monitoring (S1102).

[0113] The receiving terminal can decode the received data and generate HARQ NACK feedback based on the decoding result, and transmit the generated HARQ NACK to the transmitting terminal (S1103). At this time, the base station can receive and decode the HARQ NACK feedback transmitted from the receiving terminal through monitoring (S1104).

[0114] The transmitting terminal that decodes the NACK feedback data RM x It can be retransmitted to the receiving terminal (S1105), and the base station also data RM y It can be retransmitted to the receiving terminal (S1106). The receiving terminal initially received the data RM but failed to decode. n , data received via multiple retransmission RM x and data RM yIt can be combined.

[0115] The method by which sidelink data RM is retransmitted can consist of four cases. In this case, the base station uses downlink resource R d It can use, and the transmitting terminal sidelink resource R s You can use .

[0116] Some or all of the configurations of the seventh embodiment of the present invention described above with reference to FIG. 11 may be applied in the same or similar way to the first embodiment of the present invention described with reference to FIG. 4 and FIG. 5.

[0117] FIG. 12 is a conceptual diagram showing a first embodiment of the data retransmission processing method of FIG. 11.

[0118] Referring to FIG. 12, in the first embodiment of the data retransmission processing method of FIG. 11, a base station (1201) that determines retransmission by the decoded NACK, at timing t, downlink resource R d Using RM to the receiving terminal (1203) p It can be retransmitted. In this case, RM p is the data RM previously transmitted by the transmitting terminal n It may be an RM that is the same as or has a different RV (Redundancy version). The transmitting terminal (1202), which determines retransmission based on the decoded NACK, uses the sidelink resource R at timing t. s Using RM to the receiving terminal (1202) p+1 It can be retransmitted. In this case, RM p+1 is the data RM that the transmitting terminal (1202) previously transmitted. n RM that is different from RV n+1 It could be.

[0119] FIG. 13 is a conceptual diagram showing a second embodiment of the data retransmission processing method of FIG. 11.

[0120] Referring to FIG. 13, in the second embodiment of the data retransmission processing method of FIG. 11, a base station (1301) that determines retransmission by the decoded NACK, at timing t, downlink resource R d Using RM to the receiving terminal (1303) p It can be retransmitted. In this case, RM p is data RM that the transmitting terminal (1302) previously transmitted. n It may be an RM that is the same as or has a different RV. The transmitting terminal (1302) that determines retransmission based on the decoded NACK, at timing t, sidelink resource R s Using RM to the receiving terminal (1303) p It can be retransmitted. In this case, RM p is the data RM previously transmitted by the transmitting terminal n It can be the same as or a different RM with RV.

[0121] FIG. 14 is a conceptual diagram showing a third embodiment of the data retransmission processing method of FIG. 11.

[0122] Referring to FIG. 14, in the third embodiment of the data retransmission processing method of FIG. 11, a base station (1401) that determines retransmission by the decoded NACK, at timing t, downlink resource R d Using RM to the receiving terminal (1403) p It can be retransmitted. In this case, RM p is the data RM that the transmitting terminal (1402) previously transmitted. n It may be an RM that is the same as or has a different RV. The transmitting terminal (1402) that determines retransmission based on the decoded NACK, at timing t+1, sidelink resource R s Using RM to the receiving terminal (1403) p It can be retransmitted. In this case, RM p is the data RM that the transmitting terminal (1402) previously transmitted. n It can be the same as or a different RM with RV.

[0123] FIG. 15 is a conceptual diagram showing a fourth embodiment of the data retransmission processing method of FIG. 11.

[0124] Referring to FIG. 15, in the fourth embodiment of the data retransmission processing method of FIG. 11, a base station (1501) that determines retransmission by the decoded NACK, at timing t, downlink resource R d Using RM to the receiving terminal (1503) x It can be retransmitted. In this case, RM x is the data RM that the transmitting terminal (1502) previously transmitted. n It may be an RM that is the same as or has a different RV. The transmitting terminal (1502) that determines retransmission based on the decoded NACK, at timing t+k, sidelink resource R s Using RM to the receiving terminal (1503) y It can be retransmitted. In this case, RM y is the data RM that the transmitting terminal (1502) previously transmitted. n It may be an RM that is the same as or different from RV. Here, the base station (1501) and the transmitting terminal (1502) may retransmit at consecutive timings t and t+1, respectively, or may retransmit at non-consecutive timings.

[0125] The process of a transmitting terminal transmitting and retransmitting data packets using sidelink communication may include resource request and resource allocation processes for data and feedback transmission through a base station. Therefore, four signal exchanges (4-way handshake) may be required for a single transmission or retransmission.

[0126] The proposed multiple retransmission operation allows the base station to allocate resources for retransmission to the transmitting terminal and simultaneously allocate downlink resources to initiate data retransmission to the receiving terminal if data transmission via the sidelink fails. This reduces signaling overhead and consequently minimizes retransmission delay. Furthermore, in situations where the channel between the transmitting and receiving terminals is poor and requires one or more retransmissions, the receiving terminal can receive retransmission data via the downlink from a base station independent of channel conditions, in addition to data from the transmitting terminal. Consequently, the number of retransmissions originating solely from the transmitting terminal can be reduced. Ultimately, this enables the provision of URLLC services through improved system latency and enhanced reliability.

[0127] The methods according to the present invention may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, etc., either alone or in combination. The program instructions recorded on the computer-readable medium may be those specifically designed and configured for the present invention, or they may be those known and available to those skilled in the art of computer software.

[0128] Examples of computer-readable media include hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, and flash memory. Examples of program instructions include machine code, such as that produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter, etc. The aforementioned hardware devices may be configured to operate as at least one software module to perform the operation of the present invention, and vice versa.

[0129] Although the invention has been described with reference to the above embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

Claims

Claim 1 A method of operation performed at a first communication node of a wireless communication system, comprising: a step of obtaining, through monitoring, first data for which rate matching processing is completed, which the first communication node transmits from a transmitting terminal to a receiving terminal using a sidelink resource; a step of obtaining, through monitoring, first feedback transmitted from the receiving terminal to the transmitting terminal by the first communication node; a step of allocating a first resource for retransmission of the first data by the first communication node based on the received first feedback indicating that retransmission of the first data is required; and a step of transmitting, through monitoring, second data for which rate matching processing is completed based on the first data obtained from the transmitting terminal by the first communication node to the receiving terminal using the allocated first resource, wherein the first resource is a downlink resource. Claim 2 A method of operation performed at a first communication node according to claim 1, wherein the second data is data identical to the first data or data having a different RV (redundancy version) from the first data. Claim 3 A method of operation performed at a first communication node according to claim 1, further comprising: a step of determining that retransmission of the first data is necessary if the first communication node fails to decode the first data; a step of the first communication node allocating a second resource for retransmission of the first data; and a step of the first communication node transmitting allocation information for the second resource to the transmitting terminal. Claim 4 A method of operation performed at a first communication node according to claim 1, further comprising: a step in which the first communication node decodes the received first feedback and allocates a third resource for transmission of the third data if retransmission is not required; and a step in which the first communication node transmits allocation information for the third resource to the transmitting terminal. Claim 5 A method of operation performed at a first communication node according to claim 1, further comprising: the step of the first communication node receiving a retransmission indicator at the transmitting terminal; and the step of the first communication node transmitting the first data to the receiving terminal according to the retransmission indicator. Claim 6 A first communication node comprising a processor, wherein the processor obtains, through monitoring, first data for which rate matching processing is completed, which the first communication node transmits from a transmitting terminal to a receiving terminal using a sidelink resource; wherein the processor obtains, through monitoring, first feedback transmitted from the receiving terminal to the transmitting terminal by the first communication node; wherein, based on the received first feedback indicating that retransmission of the first data is required, the processor allocates a first resource for the retransmission of the first data by the first communication node; and wherein the processor operates to cause the first communication node to transmit, using the allocated first resource, second data for which rate matching processing is completed based on the first data obtained from the transmitting terminal through monitoring, to the receiving terminal, wherein the first resource is a downlink resource. Claim 7 A first communication node according to claim 6, wherein the second data is data identical to the first data or data having a different RV (redundancy version) from the first data. Claim 8 In claim 6, the processor determines that if the first communication node fails to decode the first data, retransmission of the first data is required; the processor allocates a second resource to the first communication node for retransmission of the first data; and the processor operates to further cause the first communication node to transmit allocation information for the second resource to the transmitting terminal, a first communication node. Claim 9 In claim 6, the processor allocates a third resource for transmission of third data if the first communication node decodes the first feedback received and does not require retransmission; and the processor operates to further cause the first communication node to transmit allocation information for the third resource to the transmitting terminal. Claim 10 In claim 6, the processor enables the first communication node to receive a retransmission indicator from the transmitting terminal; and the processor further enables the first communication node to transmit the first data to the receiving terminal in accordance with the retransmission indicator, the first communication node.

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