APPARATUS AND METHOD FOR PROCESSING SIDELINK HARQ RETRANSMISSION PROCEDURE IN WIRELESS COMMUNICATION SYSTEM

The present disclosure relates to a technique for a sensor network, machine to machine (M2M) communication, machine-type communication (MTC) and the Internet of things (IoT). The present disclosure can be utilized in intelligent services (smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail business, security- and safety-related services, etc.) based on the technique. According to an embodiment of the present disclosure, provided is a method for a sidelink transmission UE in a communication system. The method comprises the steps of: receiving, from a base station, configuration information regarding a sidelink logical channel, the configuration information comprising information indicating to use hybrid automatic repeat request (HARQ) feedback-based retransmission and blind retransmission for the sidelink logical channel; when a medium access control (MAC) protocol data unit (PDU) to be transmitted is associated with the sidelink logical channel, determining any one of the HARQ feedback-based retransmission and the blind retransmission as a retransmission mode for the MAC PDU; verifying whether to retransmit the MAC PDU after transmitting the MAC PDU according to the retransmission mode; when it is verified to retransmit the MAC PDU, verifying whether to change the retransmission mode, on the basis of the configuration information; and when it is verified to change the retransmission mode, transmitting the MAC PDU, on the basis of the changed retransmission mode.

TECHNICAL FIELD

The disclosure relates to a wireless communication system and, more particularly, to a method and apparatus for a terminal to apply hybrid automatic repeat request (HARQ) feedback-based retransmission and blind retransmission in a mixed manner for the same sidelink logical channel in a wireless communication system.

BACKGROUND ART

To meet the ever increasing demand for wireless data traffic since the commercialization of 4th generation (4G) communication systems, efforts have been made to develop improved 5th generation (5G) or pre-5G communication systems. As such, 5G or pre-5G communication systems are also called “beyond 4G network system” or “post Long Term Evolution (LTE) system”.

To achieve high data rates, 5G communication systems are being considered for implementation in the extremely high frequency (mmWave) band (e.g., 60 GHz band). To decrease path loss of radio waves and increase the transmission distance in the mmWave band, various technologies including beamforming, massive multiple-input multiple-output (massive MIMO), full dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large scale antennas are considered for 5G communication systems.

To improve system networks in 5G communication systems, technology development is under way regarding evolved small cells, advanced small cells, cloud radio access networks (cloud RANs), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, moving networks, cooperative communication, coordinated multi-points (CoMP), interference cancellation, and the like.

Additionally, advanced coding and modulation (ACM) schemes such as hybrid frequency shift keying and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC), and advanced access technologies such as filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) are also under development for 5G systems.

Meanwhile, the Internet is evolving from a human centered network where humans create and consume information into the Internet of Things (IoT) where distributed elements such as things exchange and process information. There has also emerged the Internet of Everything (IoE) technology that combines IoT technology with big data processing technology through connection with cloud servers. To realize IoT, technology elements related to sensing, wired/wireless communication and network infrastructure, service interfacing, and security are needed, and technologies interconnecting things such as sensor networks, machine-to-machine (M2M) or machine type communication (MTC) are under research in recent years. In IoT environments, it is possible to provide intelligent Internet technology services, which collect and analyze data created by interconnected things to add new values to human life. Through convergence and combination between existing information technologies and various industries, IoT technology may be applied to various areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, health-care, smart consumer electronics, and advanced medical services.

Accordingly, various attempts are being made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks and machine-to-machine (M2M) or machine type communication (MTC) are being realized by use of 5G communication technologies including beamforming, MIMO, and array antennas. Application of cloud RANs as a big data processing technique described above may be an instance of convergence of 5G technology and IoT technology.

In addition, terminal-to-terminal communication (sidelink communication) using 5G communication system is being studied, and the sidelink communication is applied to, for example, vehicle-to-everything (V2X) and is expected to provide various services to users.

DISCLOSURE OF INVENTION

Technical Problem

The disclosure is to provide an apparatus and method for a terminal to process HARQ feedback-based retransmission and blind retransmission (performing retransmission based on retransmission configuration values without HARQ feedback from receiving terminal) in a mixed manner for the same sidelink logical channel in a wireless communication system.

Solution to Problem

According to an embodiment of the disclosure, there is provided a method of a first terminal in a communication system. The method may include: receiving configuration information, for a sidelink logical channel, including information indicating utilization of hybrid automatic repeat request (HARQ) feedback-based retransmission and blind retransmission for the sidelink logical channel from a base station; determining, in case that a medium access control (MAC) protocol data unit (PDU) to be transmitted is associated with the sidelink logical channel, one of HARQ feedback-based retransmission and blind retransmission as a retransmission mode for the MAC PDU; determining, after transmitting the MAC PDU according to the retransmission mode, whether to retransmit the MAC PDU; determining, in case of determining to retransmit the MAC PDU, whether to change the retransmission mode based on the configuration information; and transmitting, in case of determining to change the retransmission mode, the MAC PDU based on the changed retransmission mode.

According to an embodiment of the disclosure, there is provided a first terminal in a communication system. The first terminal may include: a transceiver; and a controller that is configured to: control the transceiver to receive configuration information, for a sidelink logical channel, including information indicating utilization of hybrid automatic repeat request (HARQ) feedback-based retransmission and blind retransmission for the sidelink logical channel from a base station; determine, in case that a medium access control (MAC) protocol data unit (PDU) to be transmitted is associated with the sidelink logical channel, one of HARQ feedback-based retransmission and blind retransmission as a retransmission mode for the MAC PDU; determine, after transmitting the MAC PDU according to the retransmission mode, whether to retransmit the MAC PDU; determine, in case of determining to retransmit the MAC PDU, whether to change the retransmission mode based on the configuration information; and control, in case of determining to change the retransmission mode, the transceiver to transmit the MAC PDU based on the changed retransmission mode.

Advantageous Effects of Invention

According to various embodiments of the disclosure, the terminal can apply various HARQ retransmission modes such as HARQ feedback-based retransmission and blind retransmission for the same sidelink logical channel, which can produce the effect of efficiently supporting the sidelink flow configured for services with various quality of service (QoS) profiles and mixed QoS profiles.

The effects that can be obtained in the disclosure are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those of ordinary skill in the art to which the disclosure belongs from the following description.

MODE FOR THE INVENTION

Hereinafter, exemplary embodiments of the disclosure will be described in detail with reference to the accompanying drawings. Here, it should be noted that the same components are denoted by the same reference symbols as much as possible in the accompanying drawings. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the disclosure will be omitted.

In the following description of embodiments of the present specification, descriptions of technical details well known in the art and not directly related to the disclosure may be omitted. This is to more clearly convey the subject matter of the disclosure without obscurities by omitting unnecessary descriptions.

Likewise, in the drawings, some elements are exaggerated, omitted, or only outlined in brief. Also, the size of each element does not necessarily reflect the actual size. The same or similar reference symbols are used throughout the drawings to refer to the same or like parts.

Advantages and features of the disclosure and methods for achieving them will be apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings. However, the disclosure is not limited to the embodiments disclosed below but may be implemented in various different ways, the embodiments are provided only to complete the disclosure and to fully inform the scope of the disclosure to those skilled in the art to which the disclosure pertains, and the disclosure is defined only by the scope of the claims. The same reference symbols are used throughout the description to refer to the same parts.

Meanwhile, it will be appreciated that blocks of a flowchart and a combination of flowcharts may be executed by computer program instructions. These computer program instructions may be loaded on a processor of a general purpose computer, special purpose computer, or programmable data processing equipment, and the instructions executed by the processor of a computer or programmable data processing equipment create a means for carrying out functions described in blocks of the flowchart. To implement the functionality in a certain way, the computer program instructions may also be stored in a computer usable or readable memory that is applicable in a specialized computer or a programmable data processing equipment, and it is possible for the computer program instructions stored in a computer usable or readable memory to produce articles of manufacture that contain a means for carrying out functions described in blocks of the flowchart. As the computer program instructions may be loaded on a computer or a programmable data processing equipment, when the computer program instructions are executed as processes having a series of operations on a computer or a programmable data processing equipment, they may provide steps for executing functions described in blocks of the flowchart.

Further, each block of a flowchart may correspond to a module, a segment or a code containing one or more executable instructions for executing one or more logical functions, or to a part thereof. It should also be noted that functions described by blocks may be executed in an order different from the listed order in some alternative cases. For example, two blocks listed in sequence may be executed substantially at the same time or executed in reverse order according to the corresponding functionality.

Here, the word “unit”, “module”, or the like used in the embodiments may refer to a software component or a hardware component such as an FPGA or ASIC capable of carrying out a function or an operation. However, “unit” or the like is not limited to hardware or software. A unit or the like may be configured so as to reside in an addressable storage medium or to drive one or more processors. For example, units or the like may refer to components such as a software component, object-oriented software component, class component or task component, processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, or variables. A function provided by a component and unit may be a combination of smaller components and units, and it may be combined with others to compose larger components and units. Further, components and units may be implemented to drive one or more processors in a device or a secure multimedia card.

In describing the embodiments of the disclosure in detail, the main focus is placed on the radio access network (new RAN (NR)) and the packet core (5G system, 5G core network, or next generation core (NG core)) being the core network according to the 5G mobile communication standards specified by 3GPP being a mobile communication standardization organization, but it should be understood by those skilled in the art that the subject matter of the disclosure is applicable to other communication systems having similar technical backgrounds without significant modifications departing from the scope of the disclosure.

In the 5G system, to support network automation, a network data collection and analysis function (NWDAF), which is a network function that provides a function to analyze and provide data collected from a 5G network, can be defined. The NWDAF can collect/store/analyze information from the 5G network and provide results to unspecified network functions (NFs), and the analysis results can be used independently by each NF.

For convenience of description, some terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP) standards (standards of 5G, NR, LTE, or similar systems) may be used. However, the disclosure is not limited by these terms and names, and may be equally applied to systems conforming to other standards.

Hereinafter, the disclosure relates to an apparatus and method for a UE to process a sidelink operation in a wireless communication system when HARQ feedback-based retransmission is applied, when blind retransmission is applied, and when both HARQ feedback-based retransmission and blind retransmission are applied. Specifically, in the disclosure, the UE may identify the HARQ retransmission mode configuration for a sidelink logical channel, and process HARQ feedback-based retransmission, blind retransmission, or HARQ feedback-based retransmission and blind retransmission according to HARQ retransmission mode of the sidelink logical channel included in a medium access control (MAC) protocol data unit (PDU), configuration information determining the HARQ retransmission mode (packet delay budget (PDB) or latency), or the feedback mode or feedback transmission resource configuration indicated by the base station.

According to an embodiment of the disclosure, the UE can produce the effect of effectively supporting the sidelink flow set for serving various QoS profiles and mixed QoS profiles by operating various HARQ retransmission modes.

Those terms used in the following description for indicating a signal, indicating a channel, indicating control information, indicating a network entity, and indicating a component of an equipment are taken as illustration for ease of description. Accordingly, the disclosure is not limited by the terms used herein, and other terms referring to objects having an equivalent technical meaning may be used.

In the following description, a physical channel and a signal may be used interchangeably with data or a control signal. For example, a physical downlink shared channel (PDSCH) is a term referring to a physical channel through which data is transmitted, but the PDSCH may also be used to refer to data. That is, in the disclosure, an expression “transmitting a physical channel” may be interpreted equivalently to an expression “transmitting data or a signal through a physical channel”.

In the disclosure, higher signaling indicates a method of transmitting a signal from the base station to the UE by using a downlink data channel of the physical layer, or from the UE to the base station by using an uplink data channel of the physical layer. Higher signaling may be understood as radio resource control (RRC) signaling or medium access control (MAC) control element (CE).

Also, in the disclosure, to determine whether a specific condition is satisfied or fulfilled, an expression such as ‘greater than’ or ‘less than’ may be used, but this is illustrative and does not exclude the use of ‘greater than or equal to’ or ‘less than or equal to’. ‘Greater than or equal to’, ‘less than or equal to’, and ‘greater than or equal to and less than’ may be replaced with ‘greater than’, ‘less than’, and ‘greater than and greater than or equal to’, respectively.

Further, in the disclosure, performing HARQ retransmission may mean retransmission of data (MAC PDU or transport block including the same) when receiving a negative acknowledgement (NACK) from the receiving UE in the case of HARQ feedback-based retransmission, and may mean retransmission of data (MAC PDU or transport block including the same) according to a configured retransmission value without relying on HARQ feedback from the receiving UE in the case of blind retransmission.

Further, in the disclosure, processing retransmission may mean performing retransmission of data (MAC PDU or transport block including the same).

In addition, although the disclosure describes embodiments using terms used in some communication standards (e.g., 3rd generation partnership project (3GPP)), this is only an example for description. The embodiments of the disclosure may be applied to other communication systems with easy modifications.

FIG.1is a diagram illustrating a wireless communication system according to an embodiment of the disclosure.

FIG.1illustrates a base station110, a UE120, and a UE130as a node using a radio channel in a wireless communication system. Although only one base station is illustrated inFIG.1, other base stations that are the same as or similar to the base station110may be further included.

The base station110is a network infrastructure that provides radio access to the UEs120and130. The base station110has a coverage defined as a specific geographic area based on the signal transmission distance. The base station110may also be referred to as “access point (AP)”, “eNodeB (eNB)”, “5th generation node (5G node)”, “next generation nodeB (gNB)”, “wireless point”, “transmission/reception point (TRP)”, or another term having an equivalent technical meaning.

Each of the first UE120and the second UE130is a device used by a user, and performs communication with the base station110through a radio channel. The link from the base station110to the first UE120or the second UE130is referred to as downlink (DL), and the link from the first UE120or the second UE130to the base station110is referred to as uplink (UL). Further, the first UE120and the second UE130may perform communication with each other through a radio channel. Here, the link between the first UE120and the second UE130is referred to as sidelink, and the sidelink may also be referred to as a PC5 interface. In some cases, at least one of the first UE120or the second UE130may be operated without user's involvement. That is, at least one of the first UE120or the second UE130is a device that performs machine type communication (MTC), and may be not carried by the user. Each of the first UE120and the second UE130may be referred to as “user equipment (UE)”, “UE”, “subscriber station”, “remote UE”, “wireless UE”, “user device”, or another term having an equivalent technical meaning.

The base station110, the first UE120, and the second UE130may transmit and receive radio signals in the millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, and 60 GHz). In this case, to improve the channel gain, the base station110, the first UE120, and the second UE130may perform beamforming. Here, beamforming may include transmit beamforming and receive beamforming. That is, the base station110, the first UE120, and the second UE130may give directivity to a transmission signal or a reception signal. To this end, the base station110and the UEs120and130may select serving beams112,113,121and131through a beam search or beam management procedure. After the serving beams112,113,121and131are selected, subsequent communication may be performed through resources having a quasi co-located (QCL) relationship with the resources having transmitted the serving beams112,113,121and131.

If large-scale characteristics of the channel carrying a symbol on a first antenna port can be inferred from the channel carrying a symbol on a second antenna port, the first antenna port and the second antenna port may be evaluated to be in a QCL relationship. For example, the large-scale characteristics may include at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, or spatial receiver parameter.

The first UE120and the second UE130illustrated inFIG.1may support vehicular communication. In the case of vehicular communication, standardization for vehicle-to-everything (V2X) technology based on the device-to-device (D2D) communication structure has been completed in 3GPP Release 14 and Release 15 for the LTE system, and currently, efforts are underway to develop V2X technology based on 5G NR. NR V2X will support unicast communication between UEs, groupcast (or multicast) communication, and broadcast communication. Further, unlike LTE V2X which aims to transmit and receive basic safety information necessary for the vehicle to drive on the road, NR V2X aims to provide more advanced services such as platooning, advanced driving, extended sensor, and remote driving.

V2X services can be divided into basic safety services and advanced services. The basic safety services may include vehicle notification (cooperative awareness message (CAM) or basic safety message (BSM)) services, and detailed services such as left turn notification, forward collision warning, emergency vehicle approaching, forward obstacle warning, and intersection movement information; and V2X information may be transmitted and received by using broadcast, unicast, or groupcast transmission. The advanced services not only have enhanced quality of service (QoS) requirements compared to the basic safety services but also require a method for transmitting and receiving V2X information by using unicast and groupcast in addition to broadcast so that V2X information can be transmitted and received within a specific vehicle group or between two vehicles. The advanced services may include detailed services such as platooning, autonomous driving, remote driving, and extended sensor-based V2X service.

In the following description, the sidelink (SL) refers to a signal transmission/reception path between UEs, and may be used interchangeably with PC5 interface. Also, the base station is a main agent that allocates resources to the UE, and it may be a base station that supports both V2X communication and regular cellular communication or a base station that supports only V2X communication. That is, the base station may mean an NR base station (e.g., gNB), an LTE base station (e.g., eNB), or a road site unit (RSU). The UE may include not only a general user equipment and a mobile station but also include a vehicle supporting vehicle-to-vehicle (V2V) communication, a vehicle or pedestrian handset (i.e., smartphone) supporting vehicle-to-pedestrian (V2P) communication, a vehicle supporting vehicle-to-network (V2N) communication, a vehicle supporting vehicle-to-infrastructure (V2I) communication, an RSU equipped with UE functionality, an RSU equipped with base station functionality, and an RSU equipped with some of base station functionality and some of UE functionality. Further, the following description, the V2X UE may be referred to as a UE. That is, in relation to V2X communication, the UE may be used as a V2X UE.

The base station and the UE may be connected through a Uu interface. Uplink (UL) means a radio link through which the UE transmits data or a control signal to the base station, and downlink (DL) refers to a radio link through which the base station transmits data or a control signal to the UE.

FIG.2is a diagram illustrating the configuration of a base station in a wireless communication system according to an embodiment of the disclosure.

The configuration shown inFIG.2may be understood as a configuration of the base station110. A term such as “ . . . unit” or “ . . . device” used herein means a unit that processes at least one function or operation, and may be implemented with hardware, software, or a combination thereof.

With reference toFIG.2, the base station110may include a wireless communication unit210, a backhaul communication unit220, a storage230, and a controller240.

The wireless communication unit210performs functions for transmitting and receiving signals through a radio channel. For example, the wireless communication unit210performs conversion between a baseband signal and a bit stream in accordance with the physical layer specification of the system. For instance, for data transmission, the wireless communication unit210generates complex symbols by encoding and modulating a transmission bit stream. Further, for data reception, the wireless communication unit210restores a reception bit stream by demodulating and decoding a baseband signal.

In addition, the wireless communication unit210performs up-conversion of a baseband signal into a radio frequency (RF) band signal and transmits the converted signal through an antenna, and performs down-conversion of an RF-band signal received through an antenna into a baseband signal. To this end, the wireless communication unit210may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), and an analog-to-digital converter (ADC). Also, the wireless communication unit210may include a plurality of transmission and reception paths. Further, the wireless communication unit210may include at least one antenna array composed of plural antenna elements.

In terms of hardware, the wireless communication unit210may be composed of a digital unit and an analog unit, and the analog unit may include of a plurality of sub-units according to the operating power, operating frequency, and the like. The digital unit may be implemented with at least one processor (e.g., digital signal processor (DSP)).

The wireless communication unit210transmits and receives signals as described above. Hence, the whole or a part of the wireless communication unit210may be referred to as ‘transmitter’, ‘receiver’, or ‘transceiver’. Also, in the following description, transmission and reception performed through a radio channel is used as having a meaning of processing performed by the wireless communication unit210as described above.

The backhaul communication unit220provides an interface for performing communication with other nodes on the network. That is, the backhaul communication unit220converts a bit stream to be transmitted from the base station110to another node, for example, another access node, another base station, higher node, or core network, into a physical signal, and converts a physical signal received from another node into a bit stream.

The storage230stores data such as basic programs, application programs, and configuration information for the operation of the base station110. The storage230may be configured as a volatile memory, a non-volatile memory, or a combination thereof. In addition, the storage230provides stored data in response to a request from the controller240.

The controller240controls the overall operation of the base station110. For example, the controller240transmits and receives a signal through the wireless communication unit210or through the backhaul communication unit220. Also, the controller240writes and reads data to and from the storage230. In addition, the controller240may perform functions of a protocol stack required by the communication standard. According to another implementation example, the protocol stack may be included in the wireless communication unit210. To this end, the controller240may include at least one processor. According to an embodiment, the controller240may control the base station110to perform operations according to embodiments to be described later.

FIG.3is a diagram illustrating the configuration of a UE in a wireless communication system according to an embodiment of the disclosure.

The configuration shown inFIG.3may be understood as a configuration of the UE120. A term such as “ . . . unit” or “ . . . device” used herein means a unit that processes at least one function or operation, and may be implemented with hardware, software, or a combination thereof.

With reference toFIG.3, the UE120may include a communication unit310, a storage320, and a controller330.

The communication unit310performs functions for transmitting and receiving signals through a radio channel. For example, the communication unit310performs conversion between a baseband signal and a bit stream in accordance with the physical layer specification of the system. For instance, for data transmission, the communication unit310generates complex symbols by encoding and modulating a transmission bit stream. Further, for data reception, the communication unit310restores a reception bit stream by demodulating and decoding a baseband signal. In addition, the communication unit310performs up-conversion of a baseband signal into an RF band signal and transmits the converted signal through an antenna, and performs down-conversion of an RF-band signal received through an antenna into a baseband signal. For example, the communication unit310may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.

In addition, the communication unit310may include a plurality of transmission and reception paths. Further, the communication unit310may include at least one antenna array composed of plural antenna elements. In terms of hardware, the communication unit310may be composed of a digital circuit and an analog circuit (e.g., radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented as a single package. Also, the communication unit310may include a plurality of RF chains. Further, the communication unit310may perform beamforming.

The communication unit310transmits and receives signals as described above. Hence, the whole or a part of the communication unit310may be referred to as ‘transmitter’, ‘receiver’, or ‘transceiver’. Also, in the following description, transmission and reception performed through a radio channel is used as having a meaning of processing performed by the communication unit310as described above.

The storage320stores data such as basic programs, application programs, and configuration information for the operation of the UE210. The storage320may be configured as a volatile memory, a non-volatile memory, or a combination thereof. In addition, the storage320provides stored data in response to a request from the controller330.

The controller330controls the overall operation of the UE120. For example, the controller330transmits and receives signals through the communication unit310. Also, the controller330writes and reads data to and from the storage320. In addition, the controller330may perform the functions of a protocol stack required by the communication standard. To this end, the controller330may include at least one processor or microprocessor, or may be a part of a processor. Further, a part of the communication unit310and the controller330may be referred to as a communication processor (CP). According to an embodiment, the controller330may control the UE120to perform operations according to embodiments to be described later.

FIG.4is a diagram illustrating the constitution of a communication unit in a wireless communication system according to an embodiment of the disclosure.

FIG.4illustrates a detailed constitution of the wireless communication unit210inFIG.2or the communication unit310inFIG.3. Specifically,FIG.4shows components for performing beamforming as a part of the wireless communication unit210inFIG.2or the communication unit310inFIG.3.

With reference toFIG.4, the wireless communication unit210or the communication unit310may include an encoder and modulator402, a digital beamformer404, a plurality of transmission paths406-1to406-N, and an analog beamformer408.

The encoder and modulator402performs channel encoding. For channel encoding, at least one of a low density parity check (LDPC) code, a convolution code, or a polar code may be used. The encoder and modulator402generates modulation symbols by performing constellation mapping.

The digital beamformer404performs beamforming on a digital signal (e.g., modulation symbols). To this end, the digital beamformer404multiplies the modulation symbols by beamforming weights. Here, the beamforming weights are used to change the magnitude and phase of a signal, and may be referred to as ‘precoding matrix’ or ‘precoder’. The digital beamformer404outputs the digitally beamformed modulation symbols to the plural transmission paths406-1to406-N. Here, according to the multiple input multiple output (MIMO) transmission scheme, the modulation symbols may be multiplexed, or the same modulation symbols may be provided to multiple transmit paths406-1to406-N.

The plural transmission paths406-1to406-N convert digitally beamformed digital signals into an analog signal. To this end, each of the plural transmission paths406-1to406-N may include an inverse fast Fourier transform (IFFT) calculator, a cyclic prefix (CP) inserter, a DAC, and an up converter. The CP inserter is for orthogonal frequency division multiplexing (OFDM), and may be omitted when another physical layer scheme (e.g., filter bank multi-carrier (FBMC)) is applied. That is, the plural transmission paths406-1to406-N provide independent signal processing processes for a plurality of streams generated through digital beamforming. However, depending on the implementation scheme, some of the components of the plural transmission paths406-1to406-N may be used in common.

The analog beamformer408performs beamforming on an analog signal. To this end, the digital beamformer404multiplies analog signals by beamforming weights. Here, the beamforming weights are used to change the magnitude and phase of a signal. Specifically, the analog beamformer408may be configured in various ways according to the connection structure between the plural transmission paths406-1to406-N and antennas. For example, each of the plural transmission paths406-1to406-N may be connected to one antenna array. As another example, the plural transmission paths406-1to406-N may be connected to one antenna array. As another example, the plural transmission paths406-1to406-N may be adaptively connected to one antenna array or to two or more antenna arrays.

FIG.5is a diagram illustrating the structure of radio time-frequency resources in a wireless communication system according to an embodiment of the disclosure.

With reference toFIG.5, in the radio resource region, the horizontal axis represents the time domain and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is OFDM or DFT-S-OFDM symbols, and Nsymb OFDM or DFT-S-OFDM symbols530may be included in one slot505. In the NR system, unlike the slot, the length of a subframe may be defined as 1.0 ms, and the length of a radio frame500may be defined as 10 ms. The minimum transmission unit in the frequency domain is subcarriers, and the entire system transmission bandwidth may include a total of NBW subcarriers525. Specific values such as Nsymb and NBW may be variably applied depending on the system.

The basic unit of the time-frequency resource region is a resource element (RE)510, which may be represented by an OFDM or DFT-S-OFDM symbol index and a subcarrier index. A resource block (RB)515may be defined as NRB consecutive subcarriers520in the frequency domain. In general, the minimum transmission unit of data is an RB, and Nsymb=14 and NRB=12 in the NR system.

The structure of radio time-frequency resources as shown inFIG.5may be applied to the Uu interface. In addition, the radio time-frequency resource structure as shown inFIG.5may be similarly applied to the sidelink.

FIG.6Ais a diagram illustrating a scenario for sidelink communication according to an embodiment of the disclosure.

Referring toFIG.6A,FIG.6Aillustrates an in-coverage scenario in which sidelink UEs620aand620bare located within the coverage of a base station610. The sidelink UEs620aand620bmay receive data and control information through a downlink (DL) from the base station610, or may transmit data and control information to the base station through an uplink (UL). In this case, the data and control information may be data and control information for sidelink communication or data and control information for regular cellular communication other than sidelink communication. Also, inFIG.6A, the sidelink UEs620aand620bmay transmit and receive data and control information for sidelink communication through a sidelink (SL).

FIG.6Bis a diagram illustrating a scenario for sidelink communication according to an embodiment of the disclosure.

FIG.6Billustrates a partial coverage case in which a first UE620aamong sidelink UEs is located within the coverage of the base station610and a second UE620bis located outside the coverage of the base station610. The first UE620alocated within the coverage of the base station610may receive data and control information from the base station through the downlink or transmit data and control information to the base station through the uplink. The second UE620blocated outside the coverage of the base station610cannot receive data and control information from the base station through the downlink, and cannot transmit data and control information to the base station through the uplink. The second UE620bmay transmit or receive data and control information for sidelink communication to or from the first UE620athrough the sidelink SL.

FIG.6Cis a diagram illustrating a scenario for sidelink communication according to an embodiment of the disclosure.

FIG.6Cillustrates a case in which sidelink UEs (e.g., first UE620aand second UE620b) are located outside the coverage of the base station. Hence, neither the first UE620anor the second UE620bcan receive data and control information from the base station through the downlink, and can transmit data and control information to the base station through the uplink. The first UE620aand the second UE620bmay transmit or receive data and control information for sidelink communication through the sidelink SL.

FIG.6Dis a diagram illustrating a scenario for sidelink communication according to an embodiment of the disclosure.

With reference toFIG.6D, for sidelink communication, the first UE620aand the second UE620b, in connected state (e.g., RRC connected state) or camping state (e.g., RRC disconnected state, i.e., RRC idle state) with different base stations (e.g., first base station610aand second base station610b), may perform inter-cell sidelink communication. Here, the first UE620amay be a sidelink transmitting UE, and the second UE620bmay be a sidelink receiving UE. Alternatively, the first UE620amay be a sidelink receiving UE, and the second UE620bmay be a sidelink transmitting UE. The first UE620amay receive a sidelink dedicated system information block (SIB) from the base station610ato which it is connected (or on which it is camping), and the second UE620bmay receive a sidelink dedicated SIB from another base station620bto which it is connected (or on which it is camping). In this case, the information of the sidelink dedicated SIB received by the first UE620aand the information of the sidelink dedicated SIB received by the second UE620bmay be different from each other. Hence, it is necessary to unify information for sidelink communication between UEs located in different cells.

In the above-described examples ofFIGS.6A to6D, a sidelink system composed of two UEs (e.g., first UE610aand second UE620b) has been described for convenience of explanation, but the disclosure is not limited thereto and may also be applied to a sidelink system composed of two or more UEs. In addition, the uplink and downlink between the base station610,610aor610band the sidelink UE620aor620bmay be referred to as a Uu interface, and the sidelink between sidelink UEs may be referred to as a PC-5 interface. In the following description, uplink or downlink and Uu interface may be used interchangeably, and sidelink and PC-5 may be used interchangeably.

Meanwhile, in the disclosure, the UE may refer to a vehicle supporting vehicle-to-vehicle (V2V) communication, a vehicle or pedestrian handset (i.e., smartphone) supporting vehicle-to-pedestrian (V2P) communication, a vehicle supporting vehicle-to-network (V2N) communication, or a vehicle supporting vehicle-to-infrastructure (V2I) communication. Further, in the disclosure, the UE may refer to a road side unit (RSU) equipped with UE functionality, an RSU equipped with base station functionality, or an RSU equipped with some of base station functionality and some of UE functionality.

FIGS.7A and7Bare a diagram for explaining a transmission scheme for sidelink communication according to an embodiment of the disclosure.

With reference toFIG.7A, a transmitting UE720aand a receiving UE720bmay perform one-to-one communication. The transmission scheme as shown inFIG.7Amay be referred to as unicast communication.

With reference toFIG.7B, the transmitting UE720aor720dand the receiving UEs720band720c, or720e,720fand720gmay perform one-to-many communication. The transmission scheme as shown inFIG.7Bmay be referred to as groupcast or multicast. InFIG.7B, a first UE720a, a second UE720b, and a third UE720cform one group to perform groupcast communication; a fourth UE720d, a fifth UE720e, a sixth UE720f, and a seventh UE720gform another group to perform groupcast communication. One UE may perform groupcast communication in the group to which it belongs, and may perform unicast, groupcast, or broadcast communication with at least one other UE belonging to a different group. Although two groups are illustrated inFIG.7Bfor convenience of explanation, the disclosure is not limited thereto, and may also be applied to a case where a larger number of groups is formed.

Meanwhile, although not shown inFIG.7AorFIG.7B, sidelink UEs may perform broadcast communication. Broadcast communication refers to a scheme in which all sidelink UEs receive data and control information transmitted by a sidelink transmitting UE through the sidelink. For example, inFIG.7B, if the first UE720ais a transmitting UE, the remaining UEs720b,720c,720d,720e,720fand720gmay receive data and control information transmitted by the first UE720a.

The aforementioned sidelink unicast communication, groupcast communication, and broadcast communication may be supported in an in-coverage scenario, a partial-coverage scenario, or an out-of-coverage scenario.

In the case of NR sidelink, unlike in LTE sidelink, support of a transmission type in which a vehicle UE transmits data to only one specific UE through unicast and a transmission type in which data is transmitted to a plurality of specific UEs through groupcast may be considered. For example, when considering a service scenario such as platooning, which is a technology that connects two or more vehicles on one network and moves in a cluster form, these unicast and groupcast techniques may be usefully utilized. Specifically, the leader UE of the group connected through platooning may use unicast communication to control one specific UE, and may use groupcast communication to simultaneously control the group composed of many specified UEs.

Resource allocation in the V2X system can be performed in the following way.

Scheduled resource allocation is a method in which the base station allocates resources used for sidelink transmission to RRC-connected UEs in a dedicated scheduling manner. The scheduled resource allocation can be effective for interference management and resource pool management (dynamic allocation and/or semi-persistent transmission) because the base station can manage sidelink resources. When there is data to be transmitted to other UE(s), the RRC connected mode UE may transmit information notifying that there is data to be transmitted to other UE(s) to the base station by using an RRC message or a MAC control element (CE). For example, the RRC message transmitted by the UE to the base station may be a sidelink UE information (e.g., SidelinkUEInformation) message or a UE assistant information (e.g., UEAssistanceInformation) message, and the MAC CE may correspond to a BSR MAC CE including at least one of an indication indicating that it is a buffer status report (BSR) for V2X communication or information on the size of data buffered for sidelink communication, or a scheduling request (SR).

Second, UE autonomous resource selection is a method in which sidelink transmission/reception resource pools for V2X are provided to the UE by use of system information or an RRC message (e.g., RRCReconfiguration message, PC5-RRC message) and the UE selects a resource pool and a resource according to a preset rule. The UE autonomous resource selection may correspond to one or more of the following resource allocation schemes.The UE autonomously selects a sidelink resource for transmission.The UE assists sidelink resource selection for other UEs.The UE is configured with NR configured grant for sidelink transmission.The UE may schedule sidelink transmission of other UEs.The resource selection method of the UE may include zone mapping, sensing-based resource selection, random selection, and the like.Additionally, even if the UE is located in the coverage of the base station, resource allocation or resource selection may be not performed in scheduled resource allocation or UE autonomous resource selection mode, in which case the UE may perform V2X sidelink communication through a preconfigured sidelink transmission/reception resource pool.In addition, when UEs for V2X communication are located outside the coverage of the base station, the UE may perform V2X sidelink communication through a preconfigured sidelink transmission/reception resource pool.

When the UE performs sidelink-based data transmission/reception, HARQ retransmission may be processed. The sidelink HARQ retransmission may include HARQ feedback-based retransmission and blind retransmission. In the case of HARQ feedback-based retransmission, the transmitting UE may determine that retransmission is necessary by obtaining HARQ feedback from the receiving UE. According to an embodiment, HARQ feedback-based retransmission may be configured for each logical channel corresponding to a sidelink radio bearer (SLRB) of the UE. For a logical channel configured with HARQ feedback-based retransmission, the transmitting UE may instruct the receiving UE to transmit HARQ feedback, and may determine retransmission based on the HARQ feedback from the receiving UE. Here, the transmitting UE may instruct the receiving UE to transmit HARQ feedback by including information on whether to transmit HARQ feedback in control information (e.g., sidelink control information (SCI)) delivered to the receiving UE. On the other hand, for a logical channel not configured with HARQ feedback-based retransmission, the transmitting UE does not instruct the receiving UE to transmit HARQ feedback, and if a retransmission value is set, it may determine whether to perform retransmission based on this. Here, the latter case may be referred to as blind retransmission. The retransmission value may be set by the base station or set in advance. The retransmission value may be set to a value of 0 (no retransmission) or higher.

As described above, HARQ feedback-based retransmission or blind retransmission may be configured for one logical channel.

Meanwhile, to support more improved reliability and low-latency in the sidelink communication system, the disclosure proposes a method for applying (or using) both HARQ feedback-based retransmission and blind retransmission for one logical channel.

In various embodiments proposed in the disclosure, when configuring a sidelink radio bearer (SLRB), for one or more logical channels, HARQ feedback-based retransmission and blind retransmission may be configured to be used in a mixed manner. For example, HARQ feedback-based retransmission and blind retransmission may be used in a mixed manner in the following cases. On the other hand, the disclosure is not limited to the following examples; some of the following examples may be combined, or HARQ feedback-based retransmission and blind retransmission may be used in a mixed manner according to various schemes or conditions.Configure HARQ feedback-based retransmission to satisfy the reliability requirement of the QoS profile of a sidelink flow corresponding to a specific SLRB, but if it is determined that HARQ feedback-based retransmission is not suitable to satisfy the latency requirement of the QoS profile of the corresponding sidelink flow, blind retransmission may be applied.

If it is determined that HARQ feedback resource allocation is not available while processing HARQ feedback-based retransmission for a logical channel configured with HARQ feedback-based retransmission, blind retransmission may be applied (e.g., a case where the configuration is changed to use a resource pool without a PSFCH resource, a case where it is determined that the base station does not allocate a PSFCH resource).When a logical channel configured with HARQ feedback-based retransmission and a logical channel configured with blind retransmission are allowed to be multiplexedWhen the base station instructs to perform blind retransmission for a logical channel configured with HARQ feedback-based retransmission for operational reasons

FIG.8is a diagram illustrating operations of the UE to handle sidelink HARQ retransmission according to an embodiment of the disclosure.

With reference toFIG.8, at step800, the UE may construct a sidelink medium access control (MAC) protocol data unit (PDU) to be transmitted, and identify HARQ configuration information applicable to a transport block including the MAC PDU. The HARQ configuration information may include at least one of HARQ feedback configuration information (e.g., HARQ feedback enabled or disabled setting) for a logical channel corresponding to the MAC PDU, or a maximum transmission value when blind retransmission is configured. When constructing a MAC PDU, a logical channel to be included in the MAC PDU may be determined according to the transmission priority of logical channels, and the HARQ feedback configuration to be applied to the MAC PDU may be determined based on the HARQ feedback configuration of the highest priority logical channel included in the MAC PDU.

At step802, the UE may determine whether HARQ feedback-based retransmission is configured (e.g., HARQ feedback enabled setting) for the MAC PDU. Upon determining that HARQ feedback-based retransmission is configured based on the determination at step802, at step804, the UE may perform HARQ retransmission based on the feedback obtained from the receiving UE. Upon determining that HARQ feedback-based retransmission is not configured for the MAC PDU based on the determination at step802, at step806, the UE may perform HARQ retransmission based on the configuration for blind retransmission. For example, at step806, the UE may identify the number of retransmissions based on the MaxTxTransNumPSSCH configuration value in Table 1.

FIG.9is a diagram illustrating operations of the UE to handle sidelink HARQ retransmission according to an embodiment of the disclosure.

With reference toFIG.9, at step900, the UE may start the operation of sidelink HARQ processing. At step902, the UE may construct a sidelink MAC PDU to be transmitted, and identify HARQ configuration information applicable to a transport block including the MAC PDU. The HARQ configuration information may include at least one of configuration information for a mode in which both HARQ feedback-based retransmission and blind retransmission are applied to a logical channel corresponding to the MAC PDU, configuration information for HARQ feedback-based retransmission mode, configuration information for blind retransmission mode, the maximum transmission value, or a combination thereof. Here, the configuration information about the mode in which both HARQ feedback-based retransmission and blind retransmission are applied may mean information indicating whether the mode applying both HARQ feedback-based retransmission and blind retransmission is enabled or disabled for a logical channel. Also, the configuration information about the HARQ feedback-based retransmission mode may mean information indicating whether the HARQ feedback-based retransmission mode is enabled or disabled for a logical channel. In addition, the configuration information about the blind retransmission mode may refer to information indicating whether the blind retransmission mode is enabled or disabled for a logical channel. On the other hand, information (e.g., indication) indicating one of HARQ feedback-based retransmission mode, blind retransmission mode, and mode in which both HARQ feedback-based retransmission and blind retransmission are applied may be included. At step904, the UE may determine whether the mode applying both HARQ feedback-based retransmission and blind retransmission is configured for the MAC PDU to be transmitted. If it is determined at step904that the mode applying both HARQ feedback-based retransmission and blind retransmission is not configured, the UE may proceed to step905. At step905, the UE may perform the same procedure (step906or step907) as the procedure of step802and subsequent steps inFIG.8(step804or step806). Here, the UE may process MAC PDU transmission/retransmission according to the HARQ feedback configuration during HARQ feedback-based retransmission (step907) or blind retransmission (step906).

If it is determined at step904that the mode applying both HARQ feedback-based retransmission and blind retransmission is configured, at step908, the UE may determine whether it is necessary to retransmit the transport block including the MAC PDU. The UE operation for determining retransmission at step908may include at least one the following operations or a combination thereof.When HARQ feedback-based retransmission is configured for the corresponding HARQ process at the transmission time of the most recent MAC PDU, and it is determined that the HARQ feedback obtained from the receiving UE is non-acknowledgement (e.g., when reception of HARQ ACK is expected but HARQ ACK is not received, when reception of HARQ ACK is expected but HARQ NACK is received, when HARQ NACK is received)When it is determined that blind retransmission is configured for the corresponding HARQ process and the maximum retransmission configuration value is not reachedWhen it is determined that the maximum retransmission configuration value for the HARQ process is not reachedWhen it is determined that retransmission is indicated for the corresponding HARQ process over the transmission resource allocated by the base station

If it is determined at step908that it is not necessary to retransmit the MAC PDU, the UE may proceed to step900. If it is determined at step908that it is necessary to retransmit the MAC PDU, the UE may proceed to step910. At step910, the UE may identify the HARQ retransmission mode to be applied to the transport block including the MAC PDU. That is, the UE may select one of HARQ feedback-based retransmission and blind retransmission to be applied to the transport block including the MAC PDU. At step912, the UE may transmit the transport block including the MAC PDU by applying the selected retransmission mode, and then proceed to step908. For example, if the HARQ feedback-based retransmission mode is selected, the terminal may instruct the receiving UE to transmit HARQ feedback in response to the MAC PDU transmitted at step912. As another example, if the blind retransmission mode is selected, the UE may transmit the MAC PDU without an HARQ feedback transmission instruction at step912, and in this case, the IE may determine whether the preset maximum number of transmissions is not exceeded. On the other hand, when the mode applying both HARQ feedback-based retransmission and blind retransmission is configured, the maximum number of transmissions used by the UE for blind retransmission may be the same configuration value as the maximum number of transmissions (e.g., sl-MaxTxTransNumPSSCH) set in the case of applying only the blind retransmission mode, or may correspond to a configuration value for the maximum number of transmissions (eg, sl-MaxTxTransNumPSSCHMixed) set in the mixed mode.

Next, as an embodiment of the disclosure, a detailed description will be given of the operation in which the UE selects one of HARQ feedback-based retransmission and blind retransmission at step910.

If the mode applying both HARQ feedback-based retransmission and blind retransmission is configured for a logical channel, upon determining that retransmission is necessary for the MAC PDU, the UE may determine whether to apply HARQ feedback-based retransmission or blind retransmission according to at least one of the following (1), (2), (3), (4), (5) and (6) or a combination thereof. As an embodiment, when at least one of (1), (2), (3), (4), (5) and (6) or a combination thereof is satisfied, the UE under HARQ feedback-based retransmission may transmit the MAC PDU by applying blind retransmission. Alternatively, as an embodiment, when at least one of (1), (2), (3), (4), (5) and (6) or a combination thereof is satisfied, the UE under blind retransmission may transmit the MAC PDU by applying HARQ feedback-based retransmission.

(1) If it is determined that a logical channel cannot satisfy the latency requirement of a corresponding SL flow (SLRB) (if transmission(s) with the configured sidelink grant cannot fulfil the latency requirement of the SL data in a logical channel)

(2) If it is determined that a logical channel cannot satisfy the PDB requirement of a corresponding SL flow (SLRB) (if transmission(s) with the configured sidelink grant cannot fulfil the PDB requirement of SL data available in a logical channel)

(3) If a resource is selected from the resource pool that does not include a physical sidelink feedback channel (PSFCH) resource (if the configured sidelink grant is (re-)selected from the pool of resource without PSFCH)

(4) If the base station indicates feedback enablement or disablement in an allocated resource in the case of mode 1 resource allocation where the base station allocates sidelink transmission resources (if the configured sidelink grant scheduled by gNB(ng-eNB) indicates HARQ feedback enabled or HARQ feedback disabled for a logical channel)

(5) In the case of mode 1 resource allocation where the base station allocates sidelink transmission resources, in the case of mode 2 resource allocation where the base station does not allocate feedback resources, if a sidelink transmission resource pool in which no PSFCH resource is configured (if the configured sidelink grant for a logical channel has no corresponding resource for PSFCH)

(6) If a logical channel configured with HARQ feedback-based retransmission and a logical channel configured with blind retransmission are allowed to be multiplexed into the same MAC PDU, if a logical channel configured with both HARQ feedback-based retransmission and blind retransmission and a logical channel configured with blind retransmission are allowed to be multiplexed into the same MAC PDU, or if a logical channel configured with both HARQ feedback-based retransmission and blind retransmission and a logical channel configured with HARQ feedback are allowed to be multiplexed into the same MAC PDU

The operation of the UE according to the embodiment ofFIG.9may be the same as the procedure of Table 2.

Next, as an embodiment of the disclosure, a detailed description will be given of an operation in which the UE selects one of HARQ feedback-based retransmission or blind retransmission at step910.

(1) A HARQ transmission configuration value allowing blind transmissions without HARQ feedback (number of blind transmissions) and a configuration value for the maximum number of transmissions may be set in the UE. The UE may perform retransmission as many times as the number of HARQ transmissions allowing blind transmissions without HARQ feedback. For example, when the HARQ transmission configuration value allowing blind transmissions without feedback is set to 2, the operation of the UE is as follows. The UE may perform transmission twice according to blind transmission/retransmission and then perform HARQ feedback-based retransmission. According to HARQ feedback-based retransmission, if the UE determines that retransmission is necessary (that is, when it is determined that a NACK is received from the receiving UE, the transmitting UE may determine that retransmission is necessary) the UE may perform transmission twice according to blind retransmission. The UE may repeat this operation until it is determined that a HARQ NACK has not been received from the receiving UE or until it is determined that the preset maximum number of transmissions is reached.

(2) A transmission configuration value based on HARQ feedback (number of transmissions based on HARQ feedback) and a configuration value for the maximum number of transmissions may be set in the UE. When the UE performs initial transmission and then performs retransmission upon determining that a HARQ NACK is obtained from the receiving UE, the number of transmissions based on HARQ feedback may correspond to a total of the number of initial transmission and the number of retransmissions. As another example, when the UE performs retransmission upon determining that a HARQ NACK is obtained from the receiving UE, the number of transmissions based on HARQ feedback may correspond to the total number of retransmissions. After transmission/retransmission is performed for a preset number of HARQ feedback-based transmissions, if it is determined that retransmission is still necessary, the UE may perform blind retransmission until it is determined that the configuration value for the maximum number of transmissions is reached. For example, assuming that the transmission configuration value based on HARQ feedback corresponds to the total of initial transmission and retransmissions, when this value is set to 3, the operation of the UE is as follows. The UE may initially transmit a MAC PDU based on HARQ feedback, and if it is determined that a HARQ NACK is obtained from the receiving UE, the UE may perform HARQ feedback based retransmission. If it is determined that a HARQ NACK is obtained from the receiving UE for the retransmission, the UE may determine that retransmission is necessary; since transmission is performed three times with the configuration value of 3 for HARQ feedback-based transmission, the UE may determine that subsequent retransmission should be performed on a blind basis. Thereafter, the UE may perform HARQ transmission as many times as a number obtained by subtracting the number of already performed transmissions from the configuration value for the maximum number of transmissions. In the above example, if it is determined that an ACK is obtained from the receiving UE before the preset value of 3 times for HARQ feedback-based transmissions is reached, the UE may stop transmitting the MAC PDU.

(3) While the base station allocates initial transmission resources and retransmission resources, it may inform the UE whether HARQ feedback-based retransmission is required or blind retransmission is required. When the UE receives transmission resource allocation control signaling from the base station and determines that HARQ feedback-based transmission is indicated, it may instruct the receiving UE to transmit HARQ feedback when transmitting the MAC PDU through the corresponding resource. Or, when the UE receives transmission resource allocation control signaling from the base station and determines that blind transmission is indicated (i.e., HARQ feedback is disabled and the maximum number of retransmissions is non-zero), it transmits the MAC PDU through the corresponding resource, in which case there is no need to instruct the receiving UE to transmit HARQ feedback.

According to various embodiments of the disclosure, configuration information for the UE to determine whether to apply HARQ retransmission mode and blind retransmission mode in a mixed manner may include Table 3 below. The configuration information may be configured for a logical channel of the corresponding SLRB when configuring the SLRB based on the QoS profile of the sidelink flow reported by the UE to the base station. Or, the configuration information may be configured for the SLRB logical channel corresponding to the QoS profile in the SLRB configuration of the SIB transmitted by the base station. Or, the configuration information may be configured for the SLRB logical channel corresponding to the QoS profile in the pre-configured SLRB configuration. Or, the configuration information may be configured for each sidelink logical channel, for each UE, or for each cell. For example, the configuration information may be configured in the UE by being included in the SL-LogicalChannelConfig information element and the SL-PSSCH-TxParameters information element.

TABLE 3- Maximum transmission configuration value when using blindretransmission mode in mixed mode (sl-MaxTxTransNumPSSCHMixed)- PDB requirement (Required delay budget, sl-DelayBudget)- Latency requirement (Required latency bound, sl-LatencyBound)- Indication of whether to apply mixed mode for corresponding logicalchannel (sl- HARQMixedEnabled- HARQ retransmission mode configuration applied to correspondinglogical channel (sl-HARQ-FeedbackMode: FeedbackandBlindEnabled,BlindEnabled, FeedbackEnabled)

A logical channel configured with HARQ feedback-based retransmission and a logical channel configured with blind retransmission cannot be multiplexed into the same MAC PDU. On the other hand, a logical channel configured with both HARQ feedback-based retransmission and blind retransmission and a logical channel configured with HARQ feedback-based retransmission may be allowed to be multiplexed into the same MAC PDU. This may be configured for a logical channel of the UE. Also, a logical channel configured with both HARQ feedback-based retransmission and blind retransmission and a logical channel configured with blind retransmission may be allowed to be multiplexed into the same MAC PDU. This may be configured for a logical channel of the UE. The UE operation for determining multiplexing based on the HARQ transmission (retransmission) mode of a logical channel is shown as a procedure of Table 4 below.

TABLE 4Allocation of sidelink resourcesThe MAC entity shall for each SCI corresponding to a new transmission:- A logical channel configured with sl-HARQ-FeedbackMode setto FeedbackEnabled and a logical channel configured with sl-HARQ-FeedbackMode set to BlindEnabled cannot be multiplexed into the sameMAC PDU.- A logical channel configured with sl-HARQ-FeedbackMode setto FeedbackEnabled and a logical channel configured with sl-HARQ-FeedbackMode set to FeedbackAndBlindEnabled can be multiplexedinto the same MAC PDU if multiplexallowedMixed is configured.- A logical channel configured with sl-HARQ-FeedbackMode setto BlindEnabled and a logical channel configured with sl-HARQ-FeedbackMode set to FeedbackAndBlindEnabled can be multiplexedinto the same MAC PDU if multiplexallowedMixed is configured.

A scheme for the UE to select a logical channel when constructing a MAC PDU for initial transmission is shown as a procedure of Table 5. When a logical channel supporting both HARQ feedback-based retransmission and blind retransmission is multiplexed with a logical channel of HARQ feedback-based retransmission mode or a logical channel of blind retransmission mode as in embodiment 2 or embodiment 3 of Table 5, if the UE determines that retransmission of the MAC PDU is necessary, as in various embodiments of the disclosure, the UE may determine the retransmission mode based on the retransmission condition for a logical channel supporting both HARQ feedback-based retransmission and blind retransmission (e.g., determination at step910).

TABLE 5Selection of logical channels, embodiment 1 (a logical channel determined to havethe highest priority and a logical channel of the same sl-HARQ-FeedbackMode asthat may be multiplexed)Embodiment 1 may be, for example, as follows.The MAC entity shall for each SCI corresponding to a new transmission:-1> if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to FeedbackEnabled.--2>exclude the logical channels configured with sl-HARQ-FeedbackMode set toBlindEnabled and the logical channels configured with sl-HARQ-FeedbackMode setto FeedbackAndBlindEnabled, if any.-1> else if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to FeedbackAndBlindEnabled.--2> exclude the logical channels configured with sl-HARQ-FeedbackMode set toBlindEnabled and the logical channels configured with sl-HARQ-FeedbackMode setto FeedbackEnabled, if any.-1> else if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to BlindEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode set toFeedbackAndBlindEnabled and the logical channels configured with sl-HARQ-FeedbackMode set to FeedbackEnabled, if any.Selection of logical channels, Embodiment 2 (when the logical channel determinedto have the highest priority corresponds to the HARQ feedback-based retransmissionmode or the blind retransmission mode, a logical channel of the same mode (HARQfeedback-based retransmission mode or blind retransmission mode) and a logicalchannel configured to use both HARQ feedback-based retransmission and blindretransmission may be multiplexed. When the logical channel determined to have thehighest priority is a logical channel configured to use both HARQ feedback-basedretransmission and blind retransmission, logical channels having the sameconfiguration may be multiplexed.) Embodiment 2 may be, for example, as follows.The MAC entity shall for each SCI corresponding to a new transmission:-1> if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to FeedbackEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode set toBlindEnabled, if any.-1> else if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to BlindEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode setto FeedbackEnabled, if any.-1> else if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to FeedbackAndBlindEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode set toBlindEnabled and the logical channels configured with sl-HARQ-FeedbackMode setto FeedbackEnabled, if any.Selection of logical channels, Embodiment 3 (when the logical channel determinedto have the highest priority corresponds to the HARQ feedback-based retransmissionmode or the blind retransmission mode, a logical channel of the same mode (HARQfeedback-based retransmission mode or blind retransmission mode) and a logicalchannel configured to use both HARQ feedback-based retransmission and blindretransmission may be multiplexed. When the logical channel determined to have thehighest priority is a logical channel configured to use both HARQ feedback-basedretransmission and blind retransmission, a logical channel of the same mode as thatand a logical channel configured with blind retransmission may be multiplexed.)Embodiment 3 may be, for example, as follows.The MAC entity shall for each SCI corresponding to a new transmission:-1> if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to FeedbackEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode set toBlindEnabled, if any.-1> else if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to BlindEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode setto FeedbackEnabled, if any.-1> else if the selected logical channel with the highest priority has been configuredwith sl-HARQ-FeedbackMode set to FeedbackAndBlindEnabled:--2> exclude the logical channels configured with sl-HARQ-FeedbackMode setto FeedbackEnabled, if any.

The methods according to the embodiments described in the claims or specification of the disclosure may be implemented in the form of hardware, software, or a combination thereof.

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

Such a program (software module, software) may be stored in a random access memory, a nonvolatile memory such as a flash memory, a read only memory (ROM), an electrically erasable programmable read only memory (EEPROM), a magnetic disc storage device, a compact disc ROM (CD-ROM), a digital versatile disc (DVD), other types of optical storage devices, or a magnetic cassette. Or, such a program may be stored in a memory composed of a combination of some or all of them. In addition, a plurality of component memories may be included.

In addition, such a program may be stored in an attachable storage device that can be accessed through a communication network such as the Internet, an intranet, a local area network (LAN), a wide LAN (WLAN), or a storage area network (SAN), or through a communication network composed of a combination thereof. Such a storage device may access the device that carries out an embodiment of the disclosure through an external port. In addition, a separate storage device on a communication network may access the device that carries out an embodiment of the disclosure.

In the specific embodiments of the disclosure, the elements included in the disclosure are expressed in a singular or plural form according to the proposed specific embodiment. However, the singular or plural expression is appropriately selected for ease of description according to the presented situation, and the disclosure is not limited to a single element or plural elements. Those elements described in a plural form may be configured as a single element, and those elements described in a singular form may be configured as plural elements.

On the other hand, although specific embodiments have been described in the detailed description of the disclosure, various modifications are possible without departing from the scope of the disclosure. Therefore, the scope of the disclosure should not be limited to the described embodiments but should be defined by both the claims described below and their equivalents.