KR20240043070A - Method and apparatus for channel access in sidelink communication - Google Patents

Abstract

A method and apparatus for channel access in sidelink communication are disclosed. The method of a first terminal includes the steps of initiating a COT, performing groupcast SL transmission within the COT, receiving one or more HARQ-ACK feedbacks for the groupcast SL transmission, and determining a rate threshold of the first terminal. When configured in the terminal, calculating an ACK rate based on the one or more HARQ-ACK feedbacks, and adjusting CW based on a comparison result between the ACK rate and the rate threshold.

Description

Method and apparatus for channel access in sidelink communication {METHOD AND APPARATUS FOR CHANNEL ACCESS IN SIDELINK COMMUNICATION}

The present invention relates to channel access technology in a communication system, and more specifically, to channel access technology for sidelink communication.

With the advancement of information and communication technology, various wireless communication technologies are being developed. Representative wireless communication technologies may be long term evolution (LTE), advanced (LTE-A), new radio (NR), etc. specified in the 3rd generation partnership project (3GPP) standard. LTE and/or LTE-A may be 4G (4th Generation) communication technology. NR may be a 5G (5th Generation) communication technology.

In order to process the rapid increase in wireless data after the commercialization of the 4G communication system (e.g., a communication system supporting LTE and/or LTE-A), the frequency band of the 4G communication system (e.g., a frequency band below 6 GHz) ), as well as a 5G communication system (e.g., a communication system supporting NR) that uses a higher frequency band (e.g., a frequency band of 6 GHz or higher) than the frequency band of the 4G communication system is being considered. The 5G communication system may support enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communication (URLLC), and/or massive Machine Type Communication (mMTC).

The 5G communication system can support sidelink communication. In sidelink communication, communication can be performed between terminals. For example, a first terminal may transmit signals, information, and/or data to a second terminal, and the second terminal may receive signals, information, and/or data from the first terminal. Channels for sidelink communication may be Physical Sidelink Broadcast Channel (PSBCH), Physical Sidelink Shared Channel (PSSCH), Physical Sidelink Control Channel (PSCCH), and/or Physical Sidelink Feedback Channel (PSFCH).

The 5G communication system can support unlicensed band communication. The unlicensed band can be shared by multiple communication systems. To ensure fairness in the use of unlicensed bands, channel access procedures may be necessary. The 5G communication system can support sidelink communication in unlicensed bands. In this case, a sidelink channel access procedure for the terminal to use the unlicensed band may be necessary.

Meanwhile, the technology behind the invention was written to improve understanding of the background of the invention, and may include content that is not prior art already known to those skilled in the art in the field to which this technology belongs.

The purpose of the present invention to solve the above problems is to provide a method and device for channel access in sidelink communication.

A method of a first terminal according to embodiments of the present invention for achieving the above object includes the steps of initiating a COT, performing groupcast SL transmission within the COT, and one or more HARQ for the groupcast SL transmission. - Receiving ACK feedbacks, if a rate threshold is set in the first terminal, calculating an ACK rate based on the one or more HARQ-ACK feedbacks, and based on a comparison result between the ACK rate and the rate threshold This includes the step of adjusting the CW.

The one or more HARQ-ACK feedbacks considered for adjustment of the CW may be one or more HARQ-ACK feedbacks for the groupcast SL transmission performed in the most recent COT initiated by the first terminal among COTs.

The one or more HARQ-ACK feedbacks considered for the CW adjustment may be one or more HARQ-ACK feedbacks for the groupcast SL transmission performed in the reference duration in the most recent COT initiated by the first terminal among COTs. there is.

HARQ-ACK feedback for the groupcast SL transmission may be enabled.

The one or more HARQ-ACK feedbacks may be received on PSFCH within the same slot.

Adjusting the CW may include changing the CW to the minimum CW when the ACK rate is greater than or equal to the rate threshold.

Adjusting the CW may include reducing the CW when the ACK rate is greater than or equal to the rate threshold.

Adjusting the CW may include increasing the CW when the ACK rate is less than the rate threshold.

The CW for all priority classes may be increased.

If the rate threshold is not set in the first terminal, calculating the ACK rate may not be performed, and if the one or more HARQ-ACK feedbacks include at least one ACK, the CW may be set to the minimum CW. It can be changed to .

The ACK ratio may be a ratio between “ACK(s) among the one or more HARQ-ACK feedbacks” and “the number of terminals expected to transmit HARQ-ACK feedback for the groupcast SL transmission.”

The ACK ratio may be a ratio between “ACK(s) among the one or more HARQ-ACK feedbacks” and “the number of expected HARQ-ACK feedbacks for the groupcast SL transmission.”

When the NACK-only transmission method is used, HARQ-ACK feedback that is not received by the transmitting terminal among the predicted HARQ-ACK feedbacks may be regarded as ACK.

A method of a first terminal according to embodiments of the present invention for achieving the above object includes the steps of initiating a COT, performing groupcast SL transmission within the COT, and one or more HARQ for the groupcast SL transmission. - Receiving ACK feedbacks, if a rate threshold is set in the first terminal, calculating a NACK rate based on the one or more HARQ-ACK feedbacks, and based on a comparison result between the NACK rate and the rate threshold. This includes the step of adjusting the CW.

The one or more HARQ-ACK feedbacks considered for the CW adjustment may be one or more HARQ-ACK feedbacks for the groupcast SL transmission performed in the reference duration in the most recent COT initiated by the first terminal among COTs. there is.

In the step of adjusting the CW, the first terminal may change the CW to the minimum CW if the NACK rate is less than the rate threshold, and may increase the CW if the NACK rate is greater than the rate threshold. .

The NACK ratio is the ratio between “NACK(s) among the one or more HARQ-ACK feedbacks” and “the number of terminals expected to transmit HARQ-ACK feedback for the groupcast SL transmission” or “the one or more HARQ -It may be a ratio between “NACK(s) among ACK feedbacks” and “the number of predicted HARQ-ACK feedbacks for the groupcast SL transmission.”

A first terminal according to embodiments of the present invention for achieving the above object includes at least one processor, and the at least one processor is configured to enable the first terminal to initiate a COT and set a group cast SL within the COT. Perform transmission, receive one or more HARQ-ACK feedbacks for the groupcast SL transmission, and when a rate threshold is set in the first terminal, calculate an ACK rate based on the one or more HARQ-ACK feedbacks, and causes CW to be adjusted based on a comparison result between the ACK rate and the rate threshold.

When adjusting the CW, the at least one processor may change the CW to the minimum CW when the first terminal has the ACK rate equal to or higher than the rate threshold, and when the ACK rate is less than the rate threshold, the at least one processor may change the CW to the minimum CW. This can cause CW to increase.

The ACK ratio is the ratio between “ACK(s) among the one or more HARQ-ACK feedbacks” and “the number of terminals expected to transmit HARQ-ACK feedback for the groupcast SL transmission” or “the one or more HARQ -It may be the ratio between “ACK(s) among ACK feedbacks” and “the number of predicted HARQ-ACK feedbacks for the groupcast SL transmission.”

According to the present disclosure, a transmitting terminal can receive HARQ-ACK (hybrid automatic repeat request-acknowledgement) feedback(s) for sidelink (SL) transmission, and ACK rate or NACK based on the HARQ-ACK feedback(s). (negative ACK) rate can be calculated. The transmitting terminal may adjust the content window (CW) based on the comparison result between the ACK rate (or NACK rate) and the rate threshold. Therefore, SL communication can be performed efficiently in the unlicensed band.

1 is a conceptual diagram showing a first embodiment of a communication network.
Figure 2 is a block diagram showing a first embodiment of a communication node constituting a communication network.
Figure 3 is a conceptual diagram showing a first embodiment of a system frame in a communication network.
Figure 4 is a conceptual diagram showing a first embodiment of a subframe in a communication network.
Figure 5 is a conceptual diagram showing a first embodiment of a slot in a communication network.
Figure 6 is a conceptual diagram showing a first embodiment of time-frequency resources in a communication network.
Figure 7 is a conceptual diagram showing a first embodiment of setting a resource pool, SL signal, and SL channel within SL BWP.
Figure 8 is a conceptual diagram showing a first embodiment of SL resources.
Figure 9 is a flowchart showing a first embodiment of a method for controlling the CW size.
Figure 10 is a conceptual diagram showing a first embodiment of a reference section within channel occupancy.
Figure 11 is a conceptual diagram showing a second embodiment of a reference section within channel occupancy.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be named a second component, and similarly, the second component may also be named a first component without departing from the scope of the present invention. The term “and/or” includes any of a plurality of related stated items or a combination of a plurality of related stated items.

In the present disclosure, “at least one of A and B” may mean “at least one of A or B” or “at least one of combinations of one or more of A and B.” Additionally, in the present disclosure, “one or more of A and B” may mean “one or more of A or B” or “one or more of combinations of one or more of A and B.”

In this disclosure, (re)transmit can mean “transmit,” “retransmit,” or “transmit and retransmit,” and (re)set can mean “set,” “reset,” or “set and reset.” can mean “connection,” “reconnection,” or “connection and reconnection,” and (re)connection can mean “connection,” “reconnection,” or “connection and reconnection.” It can mean.

When a component is said to be "connected" or "connected" to another component, it is understood that it may be directly connected to or connected to the other component, but that other components may exist in between. It should be. On the other hand, when it is mentioned that a component is “directly connected” or “directly connected” to another component, it should be understood that there are no other components in between.

The terms used in this disclosure are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In the present disclosure, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless clearly defined in the present disclosure, should not be interpreted in an idealized or excessively formal sense. No.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings. In order to facilitate overall understanding when describing the present invention, the same reference numerals are used for the same components in the drawings, and duplicate descriptions for the same components are omitted.

A communication network (communication system) to which embodiments according to the present invention are applied will be described. The communication networks to which the embodiments according to the present invention are applied are not limited to those described below, and the embodiments according to the present invention can be applied to various communication networks. Here, communication network may be used in the same sense as communication system. A communication network may refer to a wireless communication network, and a communication system may refer to a wireless communication system.

In the present disclosure, “setting an operation (e.g., a transmission operation)” means “setting information (e.g., information element, parameter) for the operation” and/or “performing the operation.” This may mean that “indicating information” is signaled. “An information element (eg, parameter) is set” may mean that the information element is signaled. In the present disclosure, signaling includes system information (SI) signaling (e.g., transmission of a system information block (SIB) and/or master information block (MIB)), RRC signaling (e.g., RRC parameters and/or upper layer parameters) transmission of), MAC control element (CE) signaling, or PHY signaling (e.g., transmission of downlink control information (DCI), uplink control information (UCI), and/or sidelink control information (SCI)). You can.

1 is a conceptual diagram showing a first embodiment of a communication network.

Referring to FIG. 1, the base station 110 uses cellular communication (e.g., long term evolution (LTE), LTE-A (advanced), and LTE-A Pro defined in the 3rd generation partnership project (3GPP) standard. , LTE-U (unlicensed), NR (new radio), NR-U (unlicensed), etc. The base station 110 supports multiple input multiple output (MIMO) (e.g., single user (SU)-MIMO). , MU (multi user)-MIMO, massive MIMO, etc.), CoMP (coordinated multipoint), carrier aggregation (CA), etc. can be supported.

The first terminal 120 and the second terminal 130 may perform sidelink communication. Sidelink communication can be performed based on mode 1 or mode 2. When mode 1 is used, sidelink communication between the first terminal 120 and the second terminal 130 may be performed using resource(s) allocated by the base station 110. When mode 2 is used, sidelink communication between the first terminal 120 and the second terminal 130 will be performed using the resource(s) selected by the first terminal 120 or the second terminal 130. You can.

Communication nodes (e.g., base stations, terminals, etc.) that make up the communication network described above use a communication protocol based on CDMA (code division multiple access), a communication protocol based on WCDMA (wideband CDMA), and a time division multiple access (TDMA). communication protocol based on FDMA (frequency division multiple access), communication protocol based on single carrier (SC)-FDMA, communication protocol based on orthogonal frequency division multiplexing (OFDM), orthogonal frequency division multiple access (OFDMA) based It can support communication protocols, etc.

Among communication nodes, base stations include NodeB, evolved NodeB, 5g NodeB (gNodeB), base transceiver station (BTS), radio base station, radio transceiver, and access point. It may be referred to as an access point, an access node, a transmission/reception point (Tx/Rx Point), etc. Among communication nodes, terminals include UE (user equipment), access terminal, mobile terminal, station, subscriber station, portable subscriber station, and mobile. It may be referred to as a mobile station, node, device, etc. A communication node may have the following structure.

Figure 2 is a block diagram showing a first embodiment of a communication node constituting a communication network.

Referring to FIG. 2, the communication node 200 may include at least one of at least one processor 210, a memory 220, or a transmitting and receiving device 230 that is connected to a network and performs 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 is connected by a bus 270 and can communicate with each other.

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

The processor 210 may execute a program command stored in at least one of the memory 220 and the storage device 260. The processor 210 may refer to 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 comprised of at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 220 may be comprised of at least one of read only memory (ROM) and random access memory (RAM).

Next, operating methods of a communication node in a communication network will be described. Even when a method (e.g., transmission or reception of a signal) performed in a first communication node among communication nodes is described, the corresponding second communication node is described as a method (e.g., transmitting or receiving a signal) corresponding to the method performed in the first communication node. For example, reception or transmission of a signal) can be performed. In other words, when the operation of the first terminal (e.g., the transmitting terminal) is described, the corresponding second terminal (e.g., the receiving terminal) can perform an operation corresponding to the operation with the first terminal. there is. Conversely, when the operation of the second terminal is described, the corresponding first terminal may perform an operation corresponding to the operation of the second terminal.

Figure 3 is a conceptual diagram showing a first embodiment of a system frame in a communication network.

Referring to FIG. 3, time resources in a communication network can be divided into frames. For example, in the time domain of a communication network, system frames may be set sequentially. The length of the system frame may be 10ms (millisecond). The system frame number (SFN) can be set to #0 to #1023. In this case, 1024 system frames may be repeated in the time domain of the communication network. For example, the SFN of the system frame after system frame #1023 may be #0.

One system frame may include two half frames. The length of one half frame may be 5ms. The half frame located in the start area of the system frame may be referred to as “half frame #0,” and the half frame located in the end area of the system frame may be referred to as “half frame #1.” A system frame may include 10 subframes. The length of one subframe may be 1ms. Ten subframes within one system frame may be referred to as “subframes #0-9”.

Figure 4 is a conceptual diagram showing a first embodiment of a subframe in a communication network.

Referring to FIG. 4, one subframe may include n slots, and n may be a natural number. Therefore, one subframe may consist of one or more slots.

Figure 5 is a conceptual diagram showing a first embodiment of a slot in a communication network.

Referring to FIG. 5, one slot may include one or more symbols. One slot shown in FIG. 5 may include 14 symbols. The length of a slot may vary depending on the number of symbols included in the slot and the length of the symbol. Alternatively, the length of the slot may vary depending on numerology. If the subcarrier spacing is 15 kHz (eg, μ=0), the length of the slot may be 1 ms. In this case, one system frame may include 10 slots. If the subcarrier spacing is 30 kHz (eg, μ=1), the length of the slot may be 0.5 ms. In this case, one system frame may include 20 slots.

If the subcarrier spacing is 60 kHz (eg, μ=2), the length of the slot may be 0.25 ms. In this case, one system frame may include 40 slots. If the subcarrier spacing is 120 kHz (eg, μ=3), the length of the slot may be 0.125 ms. In this case, one system frame may include 80 slots. If the subcarrier spacing is 240 kHz (eg, μ=4), the length of the slot may be 0.0625 ms. In this case, one system frame may include 160 slots.

Figure 6 is a conceptual diagram showing a first embodiment of time-frequency resources in a communication network.

Referring to FIG. 6, a resource consisting of one symbol (eg, OFDM symbol) in the time domain and one subcarrier in the frequency domain may be defined as a “resource element (RE).” Resources consisting of one OFDM symbol in the time domain and K subcarriers in the frequency domain can be defined as a “resource element group (REG).” REG may contain K REs. REG can be used as a basic unit of resource allocation in the frequency domain. K may be a natural number. For example, K could be 12. N may be a natural number. In the slot shown in FIG. 5, N may be 14. N OFDM symbols can be used as a basic unit of resource allocation in the time domain.

Methods for transmitting and receiving data in a communication network will be described. In downlink communication, downlink data may be transmitted through a physical downlink shared channel (PDSCH). In uplink communication, uplink data may be transmitted through a physical uplink shared channel (PUSCH). In the present disclosure, PDSCH may refer to downlink data or a resource through which the downlink data is transmitted and received, and PUSCH may refer to uplink data or a resource through which the uplink data is transmitted and received. The base station may transmit downlink control information (DCI) including PDSCH configuration information (e.g., resource allocation information, scheduling information) through a physical downlink control channel (PDCCH). In the present disclosure, PDCCH may mean DCI (eg, control information) or a resource on which the DCI is transmitted.

The terminal can receive DCI from the PDCCH and check the configuration information of the PDSCH included in the DCI. For example, the configuration information of the PDSCH may include time domain resource assignment (TDRA), frequency domain resource assignment (FDRA), and/or modulation and coding scheme (MCS) information. TDRA may indicate the resource area of PDSCH in the time domain. FDRA can indicate the resource area of PDSCH in the frequency domain. MCS information may be MCS level or MCS index.

Methods of SL (sidelink) communication in a communication network will be described. SL communication may be performed in licensed and/or unlicensed bands. SL communication in the unlicensed band may be referred to as sidelink-unlicensed (SL-U) communication or unlicensed-sidelink (U-SL) communication. SL resources may be used for transmission of SL signals and/or channels. SL resources can be set on a resource pool basis. The resource pool may be referred to as an SL resource pool. The resource pool may include a Tx resource pool and/or an Rx resource pool. The Tx resource pool can be used for SL transmission, and the Rx resource pool can be used for SL reception. Tx resource pool and Rx resource pool can be distinguished from each other. The Tx resource pool and Rx resource pool can be set independently.

In the time domain, a resource pool may include one or more slots, and in the frequency domain, a resource pool may include one or more subchannels. One subchannel may include N _PRB physical resource blocks (PRBs). N _PRB can be one of 10, 12, 15, 20, 25, 50, 75, or 100. Resource pools can be set up periodically. For example, a resource pool can be set to a period of 10240ms (millisecond) in the time domain. Among all slots belonging to the section corresponding to the period of 10240ms, some slots may be set as a resource pool. Depending on the time division duplex (TDD) configuration, slot(s) containing a downlink (DL) symbol may not be set to a resource pool. Slot(s) containing resources that can transmit a sidelink-synchronization signal block (S-SSB) may not be set to a resource pool. Slot(s) that can be configured as a resource pool can be defined as a bitmap. In other words, the bitmap can indicate slot(s) that can be configured as a resource pool.

The SL channel may be used for transmission and reception of traffic (e.g., data), management information, and/or control information (e.g., control information related to scheduling) related to the SL service. The SL channel may include a Physical Sidelink Broadcast Channel (PSBCH), a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Control Channel (PSCCH), and/or a Physical Sidelink Feedback Channel (PSFCH). The SL signal may be a synchronization signal (e.g., sidelink-primary synchronization signal (S-PSS), sidelink-secondary synchronization signal (S-SSS)) and/or a reference signal (e.g., demodulation reference signal (DMRS), CSI -May include channel state information-reference signal (RS), phase tracking (PT)-RS, and positioning reference signal (PRS).

PSSCH may be a channel used for transmission and reception of transport block (TB), data, and/or traffic. PSCCH may be a channel used for transmitting and receiving control information. PSFCH may be a channel used for transmission and reception of HARQ (hybrid automatic repeat request) feedback indicating the reception status of PSSCH. S-SSB may include at least one of PSBCH, S-PSS, or S-SSS. S-SSB may further include DMRS. Synchronization between terminals may be performed using synchronization signals (eg, S-PSS and/or S-SSS).

Figure 7 is a conceptual diagram showing a first embodiment of setting a resource pool, SL signal, and SL channel within an SL BWP (bandwidth part).

Referring to FIG. 7, the resource pool includes one or more slots excluding “slot(s) that do not meet the setting conditions of the resource pool” and/or “slot(s) not indicated by the bitmap” among a plurality of slots. may include. Discontinuous slots in the time domain can be interpreted as continuous slots within a resource pool. In other words, even if the slots set to the resource pool are not consecutive, the indexes of the slots within the resource pool may be consecutive.

In the present disclosure, SL resources (eg, SL transmission resources) may refer to resources within a resource pool. SL resources may refer to resources for transmission of SL signals and/or SL channels. In the present disclosure, signal transmission may mean transmission of an SL signal and/or SL channel, and signal reception may mean reception of an SL signal and/or SL channel. “Signal” can be interpreted as “signal” or “signal + channel”, and “channel” can be interpreted as “channel” or “channel + signal”. SL signal/channel can be interpreted as “SL signal”, “SL channel”, or “SL signal + SL channel”.

Figure 8 is a conceptual diagram showing a first embodiment of SL resources.

Referring to FIG. 8, the basic transmission unit of an SL signal/channel in the time domain may be one slot, and the basic transmission unit of an SL signal/channel in the frequency domain may be one subchannel. The transmission resource of the SL signal/channel may include one or more slots and/or one or more subchannels. Transmission resources may include PSCCH and/or PSSCH. Additionally, transmission resources may include PSFCH. A slot containing the PSFCH (eg, slot location) may be predefined. A slot containing PSFCH may be referred to as a PSFCH slot. The setting conditions of the PSFCH slot in the licensed band may be different from the setting conditions of the PSFCH slot in the unlicensed band. The transmission operation of HARQ feedback in the PSFCH slot of the licensed band may be different from the transmission operation of HARQ feedback in the PSFCH slot of the unlicensed band. The configuration information of the SL channel actually transmitted in the transmission resource may be transmitted through signaling (e.g., RRC message, SCI). The configuration information of the SL channel may include frequency resource information (e.g., location of the frequency resource area), time resource information (e.g., location of the time resource area), etc.

The base station may transmit configuration information (e.g., transmission resource information) of the SL channel(s) to the terminal. The terminal may receive configuration information of the SL channel(s) from the base station and transmit the SL channel(s) based on the configuration information (eg, transmission resources indicated by the configuration information). Alternatively, the terminal may select resource(s) by performing a resource sensing operation and/or a resource selection operation, and may transmit SL channel(s) on the selected resource(s). The selected resource(s) may mean transmission resource(s). Transmission resources may include one or more subchannels and one or more slots.

The transmitting terminal may transmit an SCI including transmission resource information (eg, scheduling information) of the PSSCH to the receiving terminal. Transmission resource information may be allocation information of subchannel(s) and/or slot(s) of PSSCH. A transmitting terminal may refer to a terminal that transmits PSSCH (eg, data). A receiving terminal may refer to a terminal that receives PSSCH (eg, data). Transmission resource information included in the SCI may indicate the transmission resource of PSSCH in the slot in which the SCI is transmitted. Alternatively, transmission resource information included in the SCI may indicate transmission resources of the PSSCH in a slot other than the slot in which the SCI is transmitted.

In SL-U communication, a listen-before-talk (LBT) operation may be performed for coexistence with other communication nodes (eg, communication devices). Actual transmission resources may be determined based on the results of LBT operation. The terminal can perform an LBT operation, and if the LBT operation is successful, it can use the channel for a specific time (eg, channel occupancy time (COT)). For example, if the LBT operation of the terminal is successful, COT may be initiated by the terminal, and the terminal may perform communication (eg, SL-U communication) during the COT. Depending on certain conditions, other terminals (e.g., terminals that have not initiated COT) may perform communication (e.g., SL-U communication) during COT. In other words, the COT can be shared with other terminal(s), and in this case, the other terminal(s) can perform communication within the shared COT.

Within the COT, the transmission unit (e.g., symbol setting) may vary. Within COT, transmission unit configuration information may be transmitted through signaling (eg, SCI). The symbol may refer to an OFDM symbol. In the embodiment of FIG. 8, PSCCH and PSSCH may be set together within transmission resources. PSCCH may be set starting from the PRB with the lowest index in the subchannel with the lowest index among the subchannel(s) configured for PSSCH transmission.

Operations, procedures, control information, and/or configuration information for operating channel occupancy in SL-U communication will be described. An operating channel may refer to a frequency resource having a bandwidth of a predefined size. Resources (e.g., time resources, frequency resources, carriers, subcarriers, subchannels) of unlicensed bands are used in networks other than cellular networks (e.g., 4G networks, 5G networks) (e.g., WLAN (wireless local area networks). It can be occupied by a communication node belonging to an area network). Resources in the unlicensed band may be occupied by signals/channels transmitted and received between a base station and a terminal belonging to a cellular network. Resources in the unlicensed band may be occupied by signals/channels transmitted and received between terminals belonging to the cellular network.

In the present disclosure, a communication node (e.g., base station, terminal) transmitting a signal/channel may be expressed as a transmitting node, and a communication node (e.g., base station, terminal) receiving a signal/channel may be expressed as a receiving node. It can be expressed as In the unlicensed band, communication nodes can share an operating channel. LBT operation may be performed to minimize interference between communication nodes. The LBT operation may include checking whether the operating channel is occupied by another signal before transmitting the signal/channel. If LBT operation is supported, a communication node (eg, transmitting node) may perform a random backoff procedure.

If the LBT operation is successful, the communication node can occupy the operating channel. Occupancy of an operating channel may be referred to as channel occupancy (CO). The terminal can secure CO by performing LBT operation. CO settings may vary depending on the type of LBT operation performed by the terminal. For example, the maximum length of CO may vary depending on the type of LBT operation performed by the UE. The type of LBT operation performed by the terminal may vary depending on the priority class of the data the terminal wishes to transmit within the CO.

The UE may perform an LBT operation using different parameters (eg, different LBT parameters) to obtain a CO corresponding to each priority class. When the LBT operation is performed according to the priority class, the parameters that determine the performance time of the LBT operation may vary. In LBT operation involving a random backoff procedure, the minimum and/or maximum size of the contention window (CW) may be set differently for each priority class. The UE can select a random backoff counter within the CW and perform a random backoff procedure based on the selected random backoff counter.

The fixed time interval in which the LBT operation is performed may be determined based on the type of LBT operation and/or LBT parameter(s). The length of the fixed time interval may be 16 μs or 25 μs. A communication node (e.g., transmitting node) that performed an LBT operation may transmit CO information (e.g., CO setting information) obtained by the LBT operation to another communication node (e.g., receiving node). there is. CO configuration information may include LBT parameter(s) used for LBT operation of the terminal. LBT parameter(s) may include information of priority class. CO setting information may include at least one of CO start point information, CO length information, or CO end point information. In the present disclosure, time point may be interpreted as time.

The receiving node may receive CO configuration information from the transmitting node and confirm the LBT parameter(s) used for acquisition of CO based on the CO configuration information. The receiving node may confirm the priority class for the CO initiated by the transmitting node based on the LBT parameter(s). The receiving node can confirm the CO initiated by the transmitting node based on the CO configuration information and perform communication within the CO. For example, a receiving node can transmit and receive signals/channels within a CO.

The transmitting node can set COT (channel occupancy time). COT establishment may mean COT initiation. COT may be set within time resources and/or frequency resources. COT configuration information may indicate time resources and/or frequency resources for which the COT is configured. COT may be referred to as CO or COR (channel occupancy resource). In the unlicensed band, resources can be shared by multiple communication nodes. A communication node may use discontinuous resources (eg, discontinuous time resources and/or discontinuous frequency resources). In this case, signal/channel transmission in the unlicensed band may be performed in a discontinuous burst manner. The burst method may refer to transmission performed on transmission resources including one or more slots.

Signals/channels can be transmitted in times with a length shorter than a slot. A time with a length shorter than a slot may include consecutive symbols. A time with a length shorter than a slot may be a mini slot. Consecutive transmission resources within the COT can be configured. The transmitting node may transmit an initial signal and/or a burst signal (eg, PSSCH, PSFCH, PSCCH, reference signal) within the COT. The initial signal may be a copied signal of the signal in the first symbol on which SL transmission is performed. Alternatively, the initial signal may be a signal composed of a cyclic prefix (CP).

SL resources can be allocated based on mode 1 or mode 2. Mode 1 may be referred to as resource allocation (RA)-mode 1, and mode 2 may be referred to as RA-mode 2. When RA-mode 1 is used, the base station may transmit a DCI (e.g., SL grant) containing SL resource allocation information to the terminal, and the terminal performs SL communication using the SL resources allocated by the base station. can do. When RA-mode 2 is used, the terminal can perform a resource sensing operation within the resource pool, perform a resource selection operation for the resources sensed by the resource sensing operation, and select the resource selected by the resource selection operation. SL communication can be performed using resources.

In RA-mode 1, when transmission data occurs, the terminal can transmit a scheduling request (SR) for the transmission data to the base station, and the base station uses a dynamic grant (DG) based on the SR of the terminal. Resources (eg, SL resources) can be allocated to the terminal. In RA-mode 1, the base station can allocate periodic resources to the terminal in a semi-static manner, and the terminal can perform SL communication using the periodic resources allocated by the base station.

A periodic resource allocated in a quasi-static manner may be a configured grant (CG) resource. The base station may transmit allocation information of CG resources to the terminal. Allocation information of CG resources may include at least one of location information of CG resources, time resource information of CG resources, frequency resource information of CG resources, or period information of CG resources. Depending on the release procedure or deactivate procedure of CG resources, CG methods can be classified into CG-Type 1 and CG-Type 2. In CG-Type 1, CG resources can be released by RRC signaling. In CG-Type 2, CG resources can be deactivated by DCI signaling.

In RA-mode 2, the terminal can perform a resource sensing operation during the sensing window, select resource(s) that satisfy predefined conditions among the resources sensed by the resource sensing operation, and select the selected resource(s) You can transmit SL signals/channels using . Resource sensing/selection methods according to RA-mode 2 can be classified into dynamic methods and semi-static methods. According to the quasi-static method, specific time resources can be occupied. Dynamic methods and semi-static methods can be distinguished depending on the time of selection of new resources. When the dynamic method is used, the UE can select resources for TB transmission every time it wants to transmit a new TB. TB transmission may include “new TB transmission (e.g., first TB transmission)” and/or “TB retransmission”. One or more resources (e.g., one or more transmission resources) may be used, occupied, and/or reserved for TB transmission.

If a quasi-static method is used, the counter value of TB transmission during a specific time (eg, resource reservation interval (RRI)) may be 0. Alternatively, if a quasi-static method is used, a new transmission resource may be selected under certain conditions. The counter value of TB transmission may be selected randomly. The selected counter value may be decreased by 1 when one TB transmission (e.g., new TB transmission and/or TB retransmission) is completed. When a quasi-static method is used, the terminal can continue to occupy the selected resource during a specific time. In other words, the terminal can continue to use the selected resource during a specific time. The specific time may mean a time that the terminal can exclusively occupy. A specific time can be defined as RRI.

The base station can signal the RRI list to the terminal. The RRI list may include up to 16 RRIs (eg, up to 16 RRI values). Signaling may be at least one of system information (SI) signaling, RRC signaling, MAC CE signaling, or PHY signaling. The terminal may receive an RRI list from the base station, select one RRI among RRIs belonging to the RRI list, and use the selected resource (eg, selected transmission resource) during the selected RRI. The terminal can occupy consecutive resources during RRI. Consecutive resources can be set in a logical resource area for SL.

The first terminal may transmit an SCI containing information of the selected RRI to the second terminal. The second terminal can receive the SCI from the first terminal and confirm the RRI selected by the first terminal based on the information element included in the SCI. The second terminal may not select a resource (eg, a resource selected by the first terminal) during RRI indicated by the SCI. Information on the resource selected by the first terminal may be included in the SCI.

When RA-mode 2 is used, a resource sensing window and/or a resource selection window can be set. A resource sensing window may be referred to as a sensing window (SSW), and a resource sensing operation may be performed within the SSW. The resource selection window may be referred to as a selection window (SLW), and the resource selection operation may be performed within the SLW. Resources used during RRI (eg, RRI value) indicated by the SCI can be confirmed by a resource sensing operation performed in the SSW.

Sidelink control information (SCI) may include scheduling information (e.g., scheduling information of the TB) and/or parameter(s) applicable to TB transmission. Parameter(s) applied to TB transmission can be used by demodulating/decoding the TB in the receiving terminal. SCI can be classified into level 1 SCI ( ^1st SCI) and level 2 SCI ( ^2nd SCI). Level 1 SCI can be transmitted on PSCCH, and level 2 SCI can be transmitted on PSSCH. A level 2 SCI can be linked to a level 1 SCI. Phase 1 SCI may include scheduling information for initial TB transmission and/or scheduling information for TB retransmission. Step 2 SCI may include at least one of PSSCH transmitting terminal information, PSSCH receiving terminal information, HARQ feedback information, or retransmission information.

Y transmission resources including slots in which phase 1 SCI is transmitted can be set. Y can be a natural number. For example, Y can be 2 or 3. The first transmission resource among Y transmission resources can be set in the slot where the first-level SCI is transmitted. In other words, the first transmission resource among the transmission resources may be a slot through which the first-level SCI is transmitted. The slot(s) in which (Y-1) transmission resources are configured may be defined by slot offset(s). The slot offset can be a positive integer. The maximum value of the slot offset may be 32.

The scheduled first transmission resource may include N _subchannels in the frequency domain. The first subchannel (eg, start subchannel) among the N _subchannels may be a subchannel through which the first-level SCI is transmitted. N _subchannel can be a natural number. N _subchannels can be set to less than the maximum number of subchannels set by higher layer signaling. Step 1 SCI is the frequency resource information of the second transmission resource (e.g., information of the N subchannel(s), information of the start subchannel among the N subchannel(s)) and/or the frequency of the third transmission resource. It may include resource information (e.g., information on N subchannel(s), information on a start subchannel among N subchannel(s)). The number of subchannels (N) of the second transmission resource may be the same as the number of subchannels (N _subchannel ) of the first transmission resource. The number of subchannels (N) of the third transmission resource may be the same as the number of subchannels (N _subchannel ) of the first transmission resource. The first transmission resource among Y transmission resources may be a transmission resource for the first TB transmission (eg, first TB transmission). The remaining (Y-1) transmission resource(s) may be transmission resource(s) for TB retransmission.

A level 1 SCI may include one or more information elements defined in Table 1 below.

A level 2 SCI may contain one or more information elements. Information elements included in the level 2 SCI may vary depending on the format of the level 2 SCI. A level 2 SCI may include one or more information elements defined in Table 2 below.

PSFCH may be configured periodically within the SL resource area. The slot in which the PSFCH is configured may be referred to as a PSFCH slot. PSFCH slots can be set according to the cycle. The period of the PSFCH slot may be referred to as PSFCH transmission occasion resource (TPR). PSFCH TPR can be defined on a slot basis within the resource pool. PSFCH TRP may be 1 slot, 2 slots, or 4 slots. PRB(s) capable of transmitting PSFCH in the frequency domain may be indicated by a bitmap. PRBs available for PSFCH transmission may be all PRBs or some PRBs. One PSFCH can be transmitted in one PRB. Alternatively, one PSFCH may be transmitted in one or more PRBs in the unlicensed band.

The PRB(s) through which the PSFCH is transmitted may be determined based on the location of the slot in which the PSSCH associated with the PSFCH is received. The difference (eg, slot offset, interval) between the slot in which the PSSCH is received and the slot in which the PSFCH is to be transmitted may be considered. For example, the PSFCH may be transmitted in the first PSFCH slot after K slot(s) starting from slot n in which the PSSCH was received. The PRB index (eg, the index of the PRB through which the PSFCH is transmitted) may be defined based on the function f(P _PSFCH , n, K, k _subch ). P _PSFCH may be the period of PSFCH. n may be the index of the slot in which the PSSCH was received. K may be a slot offset used to determine the PSFCH slot in which the PSFCH is transmitted. k _subch may be the index of the subchannel on which the PSCCH is configured.

In the function f(.) for determining the PRB index, at least one of a different code (q), the ID (identifier) of the transmitting terminal, or the ID of the receiving terminal transmitting the PSFCH may be considered. Code (q) may be defined by a cyclic shift or a cyclic shift pair. Cyclic shifts can be related to different Zadoff-Chu sequences. A cyclic shift pair may refer to a pair of different sequences according to acknowledgment (ACK) or negative ACK (NACK).

The PRB set through which the PSFCH is transmitted may be determined based on slot #n through which the PSSCH is transmitted and/or the index of the subchannel through which the PSSCH is transmitted. The code delivered to the PRB and PSFCH in the PRB set may be determined based on a function that considers at least one of the ID of the transmitting terminal or the ID of the receiving terminal transmitting the PSFCH.

The first terminal may transmit a signal/channel to the second terminal using the SL transmission method. The second terminal can receive a signal/channel from the first terminal using the SL reception method. The first terminal may transmit TB on PSSCH. The first terminal may transmit control information on PSSCH. Control information may include information element(s) necessary for demodulation and/or decoding of TB transmitted on PSSCH. The first terminal may transmit control information on PSCCH. The second terminal can receive control information from the first terminal and check resource usage information based on the control information. The second terminal may receive a PSSCH (eg, TB) and transmit HARQ-ACK feedback (eg, HARQ feedback, HARQ response) for the PSSCH to the first terminal. HARQ-ACK feedback for PSSCH may be transmitted on PSFCH.

In the present disclosure, a terminal performing PSCCH transmission, PSSCH transmission, and/or PSFCH reception may be referred to as a transmitting terminal or a first terminal, and a terminal performing PSCCH reception, PSSCH reception, and/or PSFCH transmission is a receiving terminal. Alternatively, it may be referred to as a second terminal.

In SL-U communication, the terminal can perform LBT operation before transmitting the signal/channel. If the result of the LBT operation is idle, the terminal can transmit a signal/channel. If the result of the LBT operation is busy, the terminal may not transmit the signal/channel. “The result of the LBT operation is children” may mean “the LBT operation is successful.” “The result of the LBT operation is busy” may mean “the LBT operation failed.” Based on the result of comparison between the energy detection level and the predefined threshold, the result of the LBT operation can be determined as idle or busy.

LBT operation can be classified into type 1 LBT operation and type 2 LBT operation. In type 1 LBT operation, channel sensing time may be variable. Channel sensing time can be changed by random variables. Type 1 LBT operation may refer to LBT operation involving a random backoff procedure. In type 2 LBT operation, the channel sensing time may be fixed. The channel sensing time may be m ㎲. m may be a natural number.

When a type 1 LBT operation is performed, the terminal can randomly select the value (N) according to equal probability within the CW. The value (N) may be an integer. Value (N) may be a random backoff counter. The terminal may perform a channel sensing operation in a predefined sensing interval (eg, sensing slot interval). A channel sensing operation may mean an energy detection operation for time and/or frequency resource(s). If the result of the channel sensing operation in one sensing period is idle, the terminal may decrease the value (N) selected in the CW by 1. If the result of the channel sensing operation in one sensing period is busy, the terminal can additionally perform the channel sensing operation. If the result of the channel sensing operation in N sensing sections is idle, the terminal can transmit a signal/channel.

In Type 1 LBT operation, CW (e.g., CW size) may be changed. The CW of the transmitting terminal may be changed based on the reception status (eg, ACK and/or NACK) of the signal/channel transmitted by the transmitting terminal. The receiving terminal may transmit HARQ-ACK feedback for the signal/channel of the transmitting terminal to the transmitting terminal. The transmitting terminal can check the reception status at the receiving terminal based on the HARQ-ACK feedback received from the receiving terminal. If the HARQ-ACK feedback received from the receiving terminal indicates ACK, the transmitting terminal may reduce the CW (eg, CW size). If the HARQ-ACK feedback received from the receiving terminal indicates NACK, the transmitting terminal can increase the CW.

CW (eg, CW size) may be individually managed according to channel access priority class (CAPC). CAPC may be related to the quality of service (QoS) of the data that the terminal wants to transmit. Different CWs may be applied for each CAPC.

The transmitting terminal may transmit data for CAPC #N, and CW (eg, CW size) may be adjusted based on HARQ-ACK feedback for the data. In this case, only the CW for CAPC #N may be changed, and the CW for other CAPCs may not be changed. In other words, CW for different CAPCs can remain the same. A change in CW may mean a change in CW size.

Alternatively, the transmitting terminal may transmit data for CAPC #N, and the CW (eg, CW size) may be adjusted based on HARQ-ACK feedback for the data. In this case, CW for all CAPCs may be changed. If it is determined to increase the CW for CAPC #N based on HARQ-ACK feedback for data, the transmitting terminal may increase the CW for all CAPCs. If it is determined to reduce or initialize the CW for CAPC #N based on HARQ-ACK feedback for data, the transmitting terminal can decrease or initialize the CW for all CAPCs.

The initial value of CW (eg, initial CW) may be predefined. The minimum value of CW (eg, minimum CW) and/or the maximum value of CW (eg, maximum CW) may be predefined. The initial CW may be equal to the minimum CW. The initial CW may be referred to as CW _initial . The minimum CW may be referred to as CW _min . The maximum CW may be referred to as CW _max . CW _initial , CW _min , and CWmax can each be set differently for each CAPC. If CW _max is used in the terminal and an increase in CW _max is required based on HARQ-ACK feedback for data, the terminal may maintain CW _max . In other words, the terminal may not increase CW _max .

CW _initial may be defined differently for each CAPC. Based on HARQ-ACK feedback for the signal/channel (e.g., data), CW may be set to CW _initial . Based on HARQ-ACK feedback for the signal/channel (e.g., data), the CW can be increased by a factor of 2. In other words, CW can be doubling. Based on the HARQ-ACK feedback for the signal/channel (e.g., data), the CW may remain the same. The terminal can use the changed CW or maintained CW in the LBT operation for the next transmission.

The transmitting terminal can transmit the PSSCH to the receiving terminal based on unicast. When the unicast method is used, one transmitting terminal can transmit a signal/channel to one receiving terminal. The receiving terminal can receive the PSSCH from the transmitting terminal. In other words, the receiving terminal can receive the TB of the transmitting terminal on PSSCH.

The transmitting terminal may transmit a first-level SCI containing the information element(s) necessary for demodulation/decoding of the TB and/or the second-level SCI. The receiving terminal can receive the first-level SCI from the transmitting terminal and check the information element(s) included in the first-level SCI. In other words, the receiving terminal can confirm the information element(s) required for demodulation/decoding of the TB and/or the second-level SCI by receiving the first-level SCI of the transmitting terminal.

The receiving terminal may receive the PSSCH from the transmitting terminal and transmit the reception result of the PSSCH (eg, HARQ-ACK feedback) to the transmitting terminal through the PSFCH. When it is instructed not to transmit HARQ-ACK feedback (for example, when a HARQ feedback disable indicator is received), the receiving terminal may not transmit HARQ-ACK feedback for the PSSCH to the transmitting terminal.

The receiving terminal can transmit HARQ-ACK feedback to the transmitting terminal using PSFCH. When the PSSCH is successfully received (for example, when the demodulation/decoding operation for the PSSCH is completed normally), the receiving terminal may transmit HARQ-ACK feedback indicating ACK. If reception of the PSSCH fails (for example, if the demodulation/decoding operation for the PSSCH fails), the receiving terminal may transmit HARQ-ACK feedback indicating NACK. Successful reception of the PSSCH may be determined depending on whether the CRC (cyclic redundancy check) code is decoded.

“If a first-level SCI is received from the transmitting terminal and a second-level SCI is not received from the transmitting terminal,” the receiving terminal may transmit HARQ-ACK feedback indicating NACK to the transmitting terminal. “If the transmitting terminal transmits a PSSCH to the receiving terminal, but does not receive HARQ-ACK feedback for the PSSCH from the receiving terminal,” the transmitting terminal may consider that the receiving terminal has transmitted a NACK.

When an ACK is received from the receiving terminal, the transmitting terminal can change CW to CW _initial or CW _min . When a NACK is received from the receiving terminal, the transmitting terminal can increase the CW. If ACK is not received from the receiving terminal, the transmitting terminal may increase the CW. In cases other than when ACK is received from the receiving terminal, the transmitting terminal may increase the CW. If the NACK is deemed to have been received from the receiving terminal, the transmitting terminal may increase the CW. When the transmitting terminal instructs the receiving terminal not to transmit HARQ-ACK feedback (for example, when the transmitting terminal transmits an SCI including a HARQ feedback disable indicator to the receiving terminal), the transmitting terminal CW can be maintained regardless of the reception status of PSSCH. In other words, when HARQ feedback is disabled, the transmitting terminal may not change the CW regardless of the reception status of the PSSCH at the receiving terminal.

Figure 9 is a flowchart showing a first embodiment of a method for controlling the CW size.

Referring to FIG. 9, the transmitting terminal may perform a channel access procedure for PSSCH transmission (e.g., data transmission, unicast SL transmission, groupcast SL transmission) (S910). The channel access procedure may include LBT operation. If the channel access procedure is successful, the transmitting terminal can transmit PSSCH to the receiving terminal (S920). The receiving terminal can receive the PSSCH from the transmitting terminal and perform demodulation/decoding operations on the PSSCH. The receiving terminal may generate HARQ-ACK feedback based on the results of the demodulation/decoding operation for the PSSCH (S930). HARQ-ACK feedback may indicate ACK or NACK. The receiving terminal may transmit HARQ-ACK feedback to the transmitting terminal (S940). HARQ-ACK feedback may be transmitted on PSFCH. The transmitting terminal can receive HARQ-ACK feedback from the receiving terminal. The transmitting terminal may adjust CW (eg, CW size) based on HARQ-ACK feedback (S950). For example, the transmitting terminal can increase or decrease CW. Alternatively, the transmitting terminal may maintain CW.

The transmitting terminal may transmit PSSCH to one or more receiving terminals (eg, receiving terminal(s) belonging to a group) based on the group cast method. The transmitting terminal may transmit the PSSCH in a group cast manner within the COT initiated or set by the transmitting terminal. PSSCH transmission(s) based on the groupcast method may be groupcast SL transmission(s). Groupcast SL transmission(s) may be transmitted in a reference duration within the COT (e.g., the latest COT) initiated by the transmitting terminal. The transmitting terminal may receive HARQ-ACK feedback(s) from one or more receiving terminals through the PSFCH. The transmitting terminal may receive HARQ-ACK feedback(s) for PSSCH(s) transmitted in the same slot from one or more receiving terminals.

The transmitting terminal may adjust CW based on HARQ-ACK feedback(s) for groupcast SL transmission(s). If one or more of the HARQ-ACK feedbacks indicate ACK, the transmitting terminal sets CW (e.g., current CW) to initial CW (e.g., CW _initial ) or minimum CW (e.g., CW _min ) can be changed. If at least one HARQ-ACK feedback among the HARQ-ACK feedbacks does not indicate ACK, the transmitting terminal may increase the CW.

Alternatively, the transmitting terminal may adjust CW based on the ACK rate and/or NACK rate.

A is “the number of ACKs received by the transmitting terminal” or “the number of ACKs received by the transmitting terminal + the number of HARQ-ACK feedback (s) considered as ACK among the HARQ-ACK feedback (s) not received by the transmitting terminal "can be indicated. When the NACK-only feedback method is used, A may indicate the number of HARQ-ACK feedbacks that the transmitting terminal did not receive. In this case, the transmitting terminal may regard the unreceived HARQ-ACK feedback as ACK. F is “total number of HARQ-ACK feedbacks received by the transmitting terminal”, “estimated number of HARQ-ACK feedbacks for groupcast SL transmission”, “number of receiving terminals participating in groupcast SL communication”, “group Number of terminals participating in cast SL communication -1", "Number of receiving terminals expected to transmit HARQ-ACK feedback", or "HARQ-ACK expected to be received from receiving terminals participating in groupcast SL communication It may be “the number of feedbacks.”

N is “the number of NACKs received by the transmitting terminal” or “the number of NACKs received by the transmitting terminal + the number of HARQ-ACK feedback (s) considered as NACK among the HARQ-ACK feedback (s) not received by the transmitting terminal "can be indicated. F is “total number of HARQ-ACK feedbacks received by the transmitting terminal”, “estimated number of HARQ-ACK feedbacks for groupcast SL transmission”, “number of receiving terminals participating in groupcast SL communication”, “group Number of terminals participating in cast SL communication -1", "Number of receiving terminals expected to transmit HARQ-ACK feedback", or "HARQ-ACK expected to be received from receiving terminals participating in group cast SL communication It may be “the number of feedbacks.”

The transmitting terminal can calculate the ACK rate based on Equation 1. If the ACK rate is greater than or equal to the rate threshold, the transmitting terminal may change the CW (eg, current CW) to the initial CW (eg, CW _initial ) or minimum CW (eg, CW _min ). Alternatively, if the ACK rate is greater than the rate threshold, the transmitting terminal may decrease the CW. If the ACK rate is less than the rate threshold, the transmitting terminal may increase the CW. The rate threshold may be referred to by other terms (eg, specific threshold, first threshold).

The transmitting terminal can calculate the NACK rate based on Equation 2. If the NACK rate is less than the rate threshold, the transmitting terminal may change the CW to the initial CW (eg, CW _initial ) or the minimum CW (eg, CW _min ). Alternatively, if the NACK rate is less than the rate threshold, the transmitting terminal may decrease the CW. If the NACK rate is higher than the rate threshold, the transmitting terminal can increase the CW.

The rate threshold can be set in the terminal(s) through signaling. For example, the base station may transmit an RRC message including a rate threshold to the terminal(s). When the rate threshold is set in the terminal(s), the transmitting terminal can adjust the CW based on the “result of comparison between the ACK rate and the rate threshold” or “the result of the comparison between the NACK rate and the rate threshold.” If the rate threshold is not set in the terminal(s), the transmitting terminal may not consider the ACK rate and/or NACK rate for CW adjustment. In this case, when at least one ACK is received, the transmitting terminal can change the CW to the initial CW or minimum CW. Alternatively, if at least one ACK is received, the transmitting terminal may decrease the CW. If at least one ACK is not received, the transmitting terminal may increase CW.

The transmitting terminal may receive HARQ-ACK feedback(s) for the PSSCH(s) (eg, groupcast SL transmission(s)) from one or more receiving terminal(s) through the PSFCH in the same slot. The transmitting terminal may adjust the CW based on the HARQ-ACK feedback(s) for the groupcast SL transmission(s) in the reference duration within the COT most recently initiated by the transmitting terminal. Alternatively, the transmitting terminal may adjust the CW based on HARQ-ACK feedback(s) for the most recently transmitted PSSCH (eg, most recent groupcast SL transmission).

If HARQ-ACK feedback #N for PSSCH transmitted in slot #N and HARQ-ACK feedback #N+M for PSSCH transmitted in slot #N+M are received on PSFCH within the same slot, the transmitting terminal performs HARQ- Among ACK feedbacks, CW can be adjusted using HARQ-ACK feedback #N+M. Each of N and M may be a natural number. For selection of HARQ-ACK feedback used for CW adjustment, the CAPC of the PSSCH transmitted in slot #N and the CAPC of the PSSCH transmitted in slot #N+M may not be considered. In other words, CW adjustment can be performed regardless of the CAPC of the PSSCH transmitted in slot #N and the CAPC of the PSSCH transmitted in slot #N+M.

The CW adjustment operation can be performed when the CAPC of the PSSCH transmitted in slot #N is the same as the CAPC of the PSSCH transmitted in slot #N+M. If the CAPC of the PSSCH transmitted in slot #N is different from the CAPC of the PSSCH transmitted in slot #N+M, CW adjustment for each CAPC can be performed based on HARQ-ACK feedback for the PSSCH corresponding to each CAPC. there is.

The transmitting terminal may receive one or more HARQ-ACK feedbacks for one or more PSSCHs from one or more receiving terminals through the PSFCH in the same slot. One or more PSSCHs for one or more HARQ-ACK feedbacks received on the PSFCH within the same slot may be continuous or discontinuous in the time domain. The transmitting terminal may individually change the CW based on one or more HARQ-ACK feedbacks for one or more discontinuous PSSCHs in the time domain. The transmitting terminal sends HARQ-ACK feedback #N for PSSCH #N transmitted in slot #N and HARQ-ACK feedback #N+M for PSSCH #N+M transmitted in slot #N+M on PSFCH within the same slot. You can receive it. In this case, the transmitting terminal can change the CW using HARQ-ACK feedback #N. Additionally, the transmitting terminal can change the CW changed based on HARQ-ACK feedback #N using HARQ-ACK feedback #N+M. Each of N and M may be a natural number.

The transmitting terminal can perform PSSCH transmissions in consecutive slots in the time domain. The transmitting terminal may receive HARQ-ACK feedback(s) for PSSCHs transmitted in consecutive slots in the time domain through the PSFCH in the same slot. The transmitting terminal can change the CW using HARQ-ACK feedback for the PSSCH transmitted first among PSSCHs transmitted in consecutive slots in the time domain. For example, "PSSCH transmissions are performed in slot #N, slot #N+1, ??, slot #N+M, and HARQ-ACK feedback(s) for the PSSCH transmissions are provided on PSFCH (e.g., When received from a PSSCH in the same slot, the transmitting terminal can change the CW using HARQ-ACK feedback for the PSSCH transmitted in slot #N.

The transmitting terminal may calculate the ACK rate and/or NACK rate based on one or more HARQ-ACK feedbacks, and may adjust the CW based on the ACK rate and/or NACK rate. The transmitting terminal may receive HARQ-ACK feedback(s) for one or more PSSCH transmissions through the PSFCH in slot #N. One or more PSSCH transmissions may be transmitted in the most recent COT initiated by the transmitting terminal (eg, reference duration within the most recent COT). The transmitting terminal can calculate the ACK rate based on Equation 1 described above. The transmitting terminal can calculate the NACK rate based on Equation 2 described above.

If the ACK rate is greater than the rate threshold, the transmitting terminal can change the CW to the initial CW or initial CW. Alternatively, if the ACK rate is greater than the rate threshold, the transmitting terminal may decrease the CW. If the ACK rate is less than the rate threshold, the transmitting terminal may increase the CW. If the NACK rate is higher than the rate threshold, the transmitting terminal can increase the CW. If the NACK rate is less than the rate threshold, the transmitting terminal may change the CW to the initial CW or initial CW. Alternatively, if the NACK rate is less than the rate threshold, the transmitting terminal may decrease the CW.

When the CW is adjusted based on the HARQ-ACK feedback received in the PSFCH, the transmitting terminal may perform the next LBT operation (eg, type 1 LBT operation) using the adjusted CW.

When the receiving terminal's HARQ-ACK feedback is received through the PSFCH, the transmitting terminal predefines the reception time of the HARQ-ACK feedback, the transmission time of the PSSCH associated with the HARQ-ACK feedback, or the transmission time of the PSCCH associated with the PSSCH. After the specified time, the CW can be adjusted based on the HARQ-ACK feedback, and the next LBT operation can be performed using the adjusted CW. Alternatively, when the CW is adjusted based on the HARQ-ACK feedback received in the PSFCH, the transmitting terminal has the reception time of the HARQ-ACK feedback, the transmission time of the PSSCH associated with the HARQ-ACK feedback, and the transmission time of the PSSCH associated with the PSSCH. The next LBT operation can be performed using the adjusted CW after a predefined time from the transmission time or the generation time of the adjusted CW. A predefined time can be set to the terminal(s) through signaling. The predefined time can be set on a slot basis. When HARQ-ACK feedback(s) is received through PSFCH in slot #N, the transmitting terminal can adjust CW based on the HARQ-ACK feedback(s) and use the adjusted CW starting from slot #N+M. Thus, the LBT operation can be performed. Each of N and M may be a natural number.

The transmitting terminal may perform SL transmission to one or more receiving terminals. The transmitting terminal may transmit PSSCH to one or more receiving terminals based on the groupcast method. In other words, the transmitting terminal can perform groupcast SL transmission(s). In groupcast SL transmission, one transmitting terminal can transmit a signal/channel to one or more receiving terminals. For groupcast SL transmission, the communication system (e.g., network node, base station, transmitting terminal) sends an ID (identifier) for groupcast SL transmission to one or more terminals (e.g., transmitting terminal and/or receiving terminal). (s)). The ID for groupcast SL transmission may be referred to as groupcast SL ID. The groupcast SL ID may be transmitted to the terminal(s) through signaling (eg, RRC signaling). The terminal(s) may receive a groupcast SL ID through signaling and may receive a signal/channel (eg, groupcast signal/channel) associated with the groupcast SL ID.

The transmitting terminal may generate a first-level SCI containing information necessary for reception of the second-level SCI and/or information necessary for demodulation/decoding of the TB, and transmit the first-level SCI on the PSCCH. The receiving terminal may receive a first-stage SCI from the transmitting terminal and check information (eg, information element(s)) included in the first-stage SCI. The transmitting terminal may transmit level 2 SCI and/or TB on PSSCH. The receiving terminal may receive level 2 SCI and/or TB from the transmitting terminal in PSSCH.

Step 2 SCI may include information indicating whether to perform groupcast SL transmission. Step 2 SCI may indicate the transmission method of HARQ-ACK feedback for PSSCH transmission (eg, data transmission). The transmission method of HARQ-ACK feedback is transmission of HARQ-ACK feedback (e.g., enabling of HARQ-ACK feedback), non-transmission of HARQ-ACK feedback (e.g., disabling of HARQ-ACK feedback), and ACK. /NACK transmission or NACK-only transmission may be indicated. In the ACK/NACK transmission method, ACK or NACK can be transmitted. In the NACK-only transmission method, only NACK can be transmitted. In other words, in the NACK-only transmission method, even if an ACK occurs, the ACK may not be transmitted. The receiving terminal can receive the second-level SCI and check whether groupcast SL transmission is performed based on the information included in the second-level SCI. Additionally, the receiving terminal can confirm the transmission method of HARQ-ACK feedback based on the information included in the second-level SCI.

The receiving terminal may receive a groupcast PSSCH (eg, groupcast SL transmission) from the transmitting terminal. If the destination ID included in the second-level SCI is set as an ID for groupcast, the receiving terminal may determine the PSSCH associated with the second-level SCI to be a groupcast PSSCH. Alternatively, if the cast type included in the level 2 SCI indicates group cast, the receiving terminal may determine the PSSCH associated with the level 2 SCI to be a group cast PSSCH.

The receiving terminal may receive the PSSCH from the transmitting terminal and transmit the reception result of the PSSCH (eg, HARQ-ACK feedback) to the transmitting terminal through the PSFCH. If the transmitting terminal instructs the receiving terminal to not transmit HARQ-ACK feedback (e.g., disable HARQ-ACK feedback), the receiving terminal will not transmit HARQ-ACK feedback for PSSCH to the transmitting terminal. You can.

HARQ-ACK feedback method can be classified into HARQ-ACK feedback method 1 and HARQ-ACK feedback method 2. In HARQ-ACK feedback method 1, when the PSSCH is successfully received, the receiving terminal can transmit ACK, and when reception of the PSSCH fails, the receiving terminal can transmit NACK. HARQ-ACK feedback method 1 may be an ACK/NACK transmission method. Successful reception of the PSSCH may be determined depending on the demodulation/decoding results of the TB. Successful reception of the PSSCH can be determined based on the CRC check result. In HARQ-ACK feedback method 1, the transmitting terminal can adjust the CW based on at least one of the number of ACKs, ACK rate, number of NACKs, or NACK rate.

In HARQ-ACK feedback scheme 2, if the PSSCH is successfully received, the receiving terminal may not transmit ACK, and if reception of the PSSCH fails, the receiving terminal may transmit NACK (e.g., HARQ-ACK feedback). You can. HARQ-ACK feedback method 2 may be a NACK-only transmission method. In HARQ-ACK feedback method 2, the transmitting terminal can adjust the CW based on at least one of the number of NACKs or the NACK ratio. HARQ-ACK feedback method 1 or HARQ-ACK feedback method 2 can be applied to groupcast SL transmission.

The HARQ-ACK feedback scheme can be set by signaling (eg, RRC signaling). The base station may transmit a signaling message containing information indicating the HARQ-ACK feedback method to the terminal. The terminal can receive a signaling message from the base station and confirm the HARQ-ACK feedback method based on the information included in the signaling message. If a signaling message indicating the HARQ-ACK feedback method is not received, the terminal may use the default HARQ-ACK feedback method. The default HARQ-ACK feedback method may be HARQ-ACK feedback method 1 or HARQ-ACK feedback method 2.

The HARQ-ACK feedback method may be indicated by control information (eg, SCI, PHY signaling). The transmitting terminal may transmit control information including information indicating the HARQ-ACK feedback method to the receiving terminal. Control information may be transmitted on PSCCH or PSSCH. Control information may be transmitted via level 1 SCI and/or level 2 SCI. The receiving terminal can receive control information from the transmitting terminal and check the HARQ-ACK feedback method based on the information included in the control information. If control information indicating the HARQ-ACK feedback method is not received, the receiving terminal may use the default HARQ-ACK feedback method. The default HARQ-ACK feedback method may be HARQ-ACK feedback method 1 or HARQ-ACK feedback method 2.

The transmitting terminal can adjust CW based on HARQ-ACK feedback for groupcast SL transmission. The HARQ-ACK feedback method for groupcast SL transmission may be HARQ-ACK feedback method 1 or HARQ-ACK feedback method 2.

The transmitting terminal can perform groupcast SL transmission(s) using PSSCH. The receiving terminal(s) may receive groupcast SL transmission(s) from the transmitting terminal. The receiving terminal(s) receiving the Groupcast SL transmission(s) may be terminal(s) participating in Groupcast SL communication. The receiving terminal(s) may transmit ACK or NACK to the transmitting terminal according to the demodulation/decoding result for the PSSCH (e.g., groupcast SL transmission(s)). The receiving terminal(s) may transmit HARQ-ACK feedback (eg, ACK or NACK) to the transmitting terminal using the PSFCH.

The transmitting terminal may receive HARQ-ACK feedback(s) from the receiving terminal(s) and may adjust CW based on the HARQ-ACK feedback(s). For example, the transmitting terminal may adjust CW based on the ACK rate or NACK rate for groupcast SL transmission(s). The transmitting terminal can determine the ACK rate based on Equation 1 described above. The transmitting terminal can determine the NACK rate based on Equation 2 described above. The transmitting terminal can adjust CW based on the ACK rate. If the ACK rate is greater than the rate threshold, the transmitting terminal may change the CW (eg, current CW) to the initial CW or minimum CW. Alternatively, if the ACK rate is greater than the rate threshold, the transmitting terminal may decrease the CW. If the ACK rate is less than the rate threshold, the transmitting terminal may increase the CW.

Information about the ACK rate (or NACK rate) and/or rate threshold may be transmitted to the terminal through signaling. Signaling may be at least one of SI signaling, RRC signaling, MAC CE signaling, or PHY signaling. The UE can determine the rate threshold used for CW adjustment based on the ACK rate information indicated by signaling. In other words, when the rate threshold is not explicitly indicated, the UE can determine the rate threshold used for CW adjustment based on the ACK rate information indicated by signaling.

If ACK rate information is not indicated by signaling, the terminal can use the default threshold for CW adjustment. The default threshold may be 0. If the default threshold is used, the UE can change the CW to the initial CW or minimum CW if even one ACK is received. Alternatively, the terminal may decrease the CW if even one ACK is received. If the default threshold is used, the terminal can increase the CW if even one ACK is not received.

The transmitting terminal may adjust the CW based on the ACK ratio or NACK ratio to the total number of HARQ-ACK feedback for PSSCH (eg, groupcast SL transmission). If the ACK rate is higher than a certain predefined threshold, the transmitting terminal can change the CW to the initial CW or minimum CW. Alternatively, if the ACK rate is higher than a certain predefined threshold, the transmitting terminal can reduce the CW. If the ACK rate is less than a certain predefined threshold, the transmitting terminal can increase the CW. If the NACK rate is higher than a certain predefined threshold, the transmitting terminal can increase the CW. If the NACK rate is less than a certain predefined threshold, the transmitting terminal can change the CW to the initial CW or the minimum CW. Alternatively, if the NACK rate is less than a certain predefined threshold, the transmitting terminal may decrease the CW.

When one or more ACKs for PSSCH (eg, groupcast SL transmission) are received, the transmitting terminal may change the CW to the initial CW or minimum CW. Alternatively, when one or more ACKs for PSSCH (eg, groupcast SL transmission) are received, the transmitting terminal may decrease the CW. If one or more ACKs for PSSCH (eg, groupcast SL transmission) are not received, the transmitting terminal may increase the CW. If one or more NACKs for PSSCH (eg, groupcast SL transmission) are received, the transmitting terminal may increase the CW.

When the transmitting terminal instructs the receiving terminal to not transmit HARQ-ACK feedback (e.g., disable HARQ-ACK feedback), the transmitting terminal transmits CW (e.g. , the current CW) can be maintained.

The transmitting terminal can perform groupcast SL transmission(s) using PSSCH. The receiving terminal(s) may receive groupcast SL transmission(s) from the transmitting terminal. When HARQ-ACK feedback method 2 (eg, NACK-only transmission method) is used, the receiving terminal(s) may transmit NACK to the transmitting terminal according to the demodulation/decoding result of the PSSCH. The receiving terminal(s) may transmit NACK to the transmitting terminal using PSFCH. Alternatively, the receiving terminal(s) may not transmit HARQ-ACK feedback (eg, ACK) to the transmitting terminal according to the demodulation/decoding result of the PSSCH.

The transmitting terminal may adjust the CW based on HARQ-ACK feedback for PSSCH (eg, groupcast SL transmission(s)). For example, the transmitting terminal may adjust the CW based on the ratio between the number of receiving terminals receiving PSSCH and the received NACK(s). The transmitting terminal can calculate the NACK rate based on Equation 2 described above.

If the NACK rate is higher than a certain predefined threshold, the transmitting terminal can increase the CW. If the NACK rate is less than a certain predefined threshold, the transmitting terminal can change the CW to the initial CW or the minimum CW. Alternatively, if the NACK rate is less than a certain predefined threshold, the transmitting terminal may decrease the CW.

If not even a single NACK for PSSCH is received, the transmitting terminal may change the CW to the initial CW or minimum CW. Alternatively, if not even a single NACK for PSSCH is received, the transmitting terminal may decrease the CW. When NACKs for PSSCH are received from all receiving terminals, the transmitting terminal can increase the CW. If the number of received NACKs is less than or equal to a predefined threshold, the transmitting terminal can change the CW to the initial CW or minimum CW. Alternatively, if the number of received NACKs is less than or equal to a predefined threshold, the transmitting terminal may decrease the CW. If the number of received NACKs exceeds a predefined threshold, the transmitting terminal may increase the CW. If not even a single NACK for PSSCH is received, the transmitting terminal may maintain CW (eg, current CW). If even one NACK for PSSCH is received, the transmitting terminal can increase the CW.

When HARQ-ACK feedback method 2 is used, the transmitting terminal can maintain CW (eg, current CW) regardless of HARQ-ACK feedback for PSSCH. The current CW may be the CW used for the most recent LBT operation (eg, the most recent type 1 LBT operation). The transmitting terminal may maintain CW (eg, current CW) for all priority classes.

If the transmitting terminal instructs the receiving terminal to non-transmit HARQ-ACK feedback (e.g., disable HARQ-ACK feedback), the transmitting terminal transmits the CW (e.g., CW) regardless of the HARQ-ACK feedback for the PSSCH. Current CW) can be maintained.

The transmission of the terminal (eg, the transmitting terminal) may not require HARQ-ACK feedback. In other words, transmission of ACK or NACK according to HARQ-ACK feedback scheme 1 may not be required. The terminal's transmission may not meet the requirements of the standard section for CW adjustment.

The terminal may perform type 1 LBT operation for transmission. The terminal can perform transmission with a specific priority class (e). The UE may perform type 1 LBT operation for the current transmission based on the CW used in the most recent transmission for priority class (e). If transmission with priority class (e) has never been performed, the terminal may perform a type 1 LBT operation using the initial CW or minimum CW defined for the priority class (e).

After transmission with priority class (e) is performed, the terminal can keep the CW of priority class (e) the same as the CW of the previous transmission. If the same CW is used more than a predefined number of times, the terminal can increase the CW. If the same CW is used r times, the terminal can increase the CW. r may be a predefined value. r may be variable depending on the settings of the communication system. r may be transmitted to the terminal through signaling (e.g., higher layer signaling). r may be a natural number. When the CW increases, the UE can increase the CW for all priority classes. In other words, if it is decided to increase the CW for one priority class, the terminal can increase the CW for all priority classes.

If the CW (e.g., maximum CW) for type 1 LBT operation for priority class (t) is used more than a predefined number (y), the terminal uses the CW for priority class (t) as the initial CW. Or you can change it to minimum CW. The predefined number of times (y) may be set differently for each priority class. y may be a predefined value. y may be variable depending on the settings of the communication system. y may be transmitted to the terminal through signaling (e.g., higher layer signaling). y may vary depending on the implementation of the terminal. y may be a natural number. For example, y may be a natural number between 1 and 8.

A terminal (eg, receiving terminal) that will transmit HARQ-ACK feedback for groupcast SL transmission may be indicated or configured. The transmitting terminal can inform the receiving terminal of the location information of the transmitting terminal. The transmitting terminal may inform the receiving terminal of the ID (identifier) of the area (eg, zone) to which the transmitting terminal belongs. The transmitting terminal may transmit an SCI containing location information of the transmitting terminal. The receiving terminal can receive location information of the transmitting terminal and confirm the location of the transmitting terminal based on the location information. The receiving terminal can confirm the location of the transmitting terminal based on the ID of the area to which the transmitting terminal belongs.

The transmitting terminal may inform the receiving terminal of the communication distance requirements for transmission of the transmitting terminal. The transmitting terminal may transmit SCI containing information on communication distance requirements. The receiving terminal can check the communication distance requirements of the transmitting terminal and check the transmission range of the sending terminal based on the communication distance requirements.

The receiving terminal can check the transmission coverage of the transmitting terminal based on the location information and communication distance requirements of the transmitting terminal. The receiving terminal can use the location information of the receiving terminal to check whether the receiving terminal is within the transmission coverage of the transmitting terminal.

The transmitting terminal may use different SCIs to determine the range of the receiving terminal to transmit HARQ-ACK feedback. The transmitting terminal may use SCI format A (eg, SCI format 1-A and/or SCI format 2-A) to transmit HARQ-ACK feedback for the PSSCH to all receiving terminals that received the PSSCH. The receiving terminal that receives the PSSCH using SCI format A can transmit HARQ-ACK feedback for the PSSCH to the transmitting terminal.

The transmitting terminal allows the receiving terminal(s) within a specific range (e.g., transmission coverage) among the receiving terminals that received the PSSCH to transmit HARQ-ACK feedback for the PSSCH in SCI format B (e.g., 2-B) can be used. The receiving terminal that received the PSSCH using SCI format B can determine whether it is within the transmission coverage of the transmitting terminal. If the receiving terminal is within the transmission coverage of the transmitting terminal, the receiving terminal may transmit HARQ-ACK feedback for the PSSCH to the transmitting terminal. If the receiving terminal is not within the transmission coverage of the transmitting terminal, the receiving terminal may not transmit HARQ-ACK feedback for the PSSCH to the transmitting terminal. To determine whether the receiving terminal is within the transmission coverage of the transmitting terminal, the receiving terminal may use at least one of location information of the transmitting terminal, communication distance requirements of the transmitting terminal, or location information of the receiving terminal. .

The receiving terminal can perform demodulation/decoding operations for PSSCH using SCI format B. If the receiving terminal is within the transmission coverage of the transmitting terminal, the receiving terminal may transmit HARQ-ACK feedback for the PSSCH to the transmitting terminal. If the receiving terminal is not within the transmission coverage of the transmitting terminal, the receiving terminal may not transmit HARQ-ACK feedback for the PSSCH to the transmitting terminal.

The transmitting terminal may receive one or more HARQ-ACK feedbacks for one or more groupcast SL transmissions from one or more receiving terminals through the PSFCH in the same slot. The transmitting terminal may adjust the CW using the HARQ-ACK feedback for the most recent groupcast SL transmission among one or more HARQ-ACK feedbacks. The transmitting terminal provides HARQ-ACK feedback #N for the PSSCH (e.g., groupcast SL transmission) transmitted in slot #N and HARQ-ACK feedback for the PSSCH (e.g., groupcast SL transmission) transmitted in slot #N+M. HARQ-ACK feedback #N+M can be received through PSFCH in the same slot. In this case, the transmitting terminal can adjust the CW using HARQ-ACK feedback #N+M among HARQ-ACK feedback #N and HARQ-ACK feedback #N+M. The CW adjustment operation can be performed when the CAPC of the PSSCH transmitted in slot #N is the same as the CAPC of the PSSCH transmitted in slot #N+M. If the CAPC of the PSSCH transmitted in slot #N is different from the CAPC of the PSSCH transmitted in slot #N+M, the transmitting terminal may adjust the CW for each CAPC based on the HARQ-ACK feedback for the PSSCH corresponding to each CAPC. You can. Each of N and M may be a natural number.

The transmitting terminal may receive one or more HARQ-ACK feedbacks for one or more groupcast SL transmissions from one or more receiving terminals through the PSFCH in the same slot. The transmitting terminal can receive HARQ-ACK feedback for discontinuous groupcast SL transmissions in the time domain on the PSFCH within the same slot. In this case, the transmitting terminal can individually adjust the CW based on each of the HARQ-ACK feedbacks for discontinuous groupcast SL transmissions in the time domain. HARQ-ACK feedback for PSSCH transmitted in slot #N (e.g., groupcast SL transmission) #N and HARQ-ACK for PSSCH transmitted in slot #N+M (e.g., groupcast SL transmission) If feedback #N+M is received through PSFCH within the same slot, the transmitting terminal can adjust the CW using HARQ-ACK feedback #N, and use the adjusted CW (e.g., HARQ-ACK feedback #N) The adjusted CW) can be adjusted again based on HARQ-ACK feedback #N+M. Each of N and M may be a natural number.

The transmitting terminal can receive HARQ-ACK feedback for consecutive groupcast SL transmissions in the time domain on the PSFCH within the same slot. Groupcast SL transmissions may be performed in consecutive slots. In this case, the transmitting terminal can adjust the CW using the HARQ-ACK feedback for the groupcast SL transmission that was performed first among the HARQ-ACK feedbacks. For example, slot #N, slot #N+1, ?? , If HARQ-ACK feedback for consecutive groupcast SL transmissions in slot #N+M is received on PSFCH in the same slot, the transmitting terminal uses HARQ-ACK feedback for groupcast SL transmission in slot #N CW can be adjusted.

The transmitting terminal may adjust the CW based on HARQ-ACK feedback(s) for PSSCH transmission (eg, groupcast SL transmission) in the reference period. The reference interval may belong to the COT initiated by the transmitting terminal. The reference interval may mean a reference duration.

The start time of the reference interval may be the start time of transmission of the transmitting terminal, which starts at the start of channel occupancy (eg, COT). The end time of the reference section may be the end time of the slot after the start time of the reference section. Alternatively, the end time of the reference section may be the end time of transmission of the transmitting terminal that starts at the start of channel occupancy.

Figure 10 is a conceptual diagram showing a first embodiment of a reference section within channel occupancy.

Referring to FIG. 10, transmission (eg, groupcast SL transmission) of the transmitting terminal may be initiated at the start time (T1) of channel occupancy (eg, COT). The starting point of the reference section may be T1. The end time of the reference section may be the end time of a slot (eg, the first slot) after the start time (T1) of the reference section. In this case, the end time of the reference section may be the end time of slot #N. “If the start time of the reference section is T1 and the end time of the reference section is the end time of slot #N,” the reference section may be slot #N. Alternatively, the end point of the reference interval may be the end point of transmission of the transmitting terminal that started at the start point of channel occupancy (T1). In this case, the end point of the reference section may be T2. Therefore, the reference section may be “Slot #N + Slot #N+1”.

Figure 11 is a conceptual diagram showing a second embodiment of a reference section within channel occupancy.

Referring to FIG. 11, transmission (eg, groupcast SL transmission) of the transmitting terminal may be initiated at the start time (T1) of channel occupancy (eg, COT). The starting point of the reference section may be T1. The end time of the reference section may be the end time of a slot (eg, the first slot) after the start time (T1) of the reference section. In this case, the end time of the reference section may be the end time of slot #N. “If the start time of the reference section is T1 and the end time of the reference section is the end time of slot #N,” the reference section may be the section from T1 to the end time of slot #N. Alternatively, the end point of the reference interval may be the end point of transmission of the transmitting terminal that started at the start point of channel occupancy (T1). In this case, the end point of the reference section may be T2. Therefore, the reference section may be the section from T1 to T2 (eg, the end point of slot #N+1).

“If one or more unicast SL transmissions are performed within a time interval, and HARQ feedback for the one or more unicast SL transmissions is enabled” and/or “If one or more groupcast SL transmissions are performed within a time interval , When HARQ feedback for the one or more groupcast SL transmissions is enabled, the time interval may be interpreted as a reference interval. The transmitting terminal may adjust CW based on HARQ-ACK feedback for transmission in the time interval (eg, reference interval). Enabling HARQ feedback may mean “activation of HARQ feedback” and/or “use of HARQ-ACK feedback scheme 1 (e.g., ACK/NACK transmission scheme).”

“If unicast SL transmission with HARQ feedback enabled within the time interval is not performed” and/or “If groupcast SL transmission with HARQ feedback enabled within the time interval is not performed”, The time interval may not be a reference interval. The transmitting terminal may not use HARQ-ACK feedback for transmission in the time interval (eg, a interval other than the standard interval) for CW adjustment.

The start time of the reference section may be the same as the start time of channel occupancy. Channel occupation time may include PSSCH transmission. The end time of the reference interval may be the end time of the first slot in which PSSCH transmission to which HARQ-ACK feedback method 1 (eg, ACK/NACK transmission method) is applied is performed. In the embodiment of FIG. 10, the start time of the reference section may be the start time (T1) of the channel occupancy time. The end point of the reference section can be determined according to the location of the first PSSCH transmission to which HARQ-ACK feedback method 1 is applied. When PSSCH transmission to which HARQ-ACK feedback method 1 is applied is performed in slot #N, the end time of the reference period may be the end time of slot #N.

"If PSSCH transmission to which HARQ-ACK feedback method 1 is applied is not performed in slot #N, and PSSCH transmission to which HARQ-ACK feedback method 1 is applied is performed in slot #N+1", the end point of the reference section is This may be the end point of slot #N+1. If PSSCH transmission to which HARQ-ACK feedback method 1 is applied does not occur within the channel occupancy time, there may not be a reference period within the channel occupancy time. If the reference section does not exist, CW can be maintained. In other words, if the reference section does not exist, CW may not be adjusted.

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. Computer-readable media may include program instructions, data files, data structures, etc., singly or in combination. Program instructions recorded on a computer-readable medium may be specially designed and constructed for the present invention or may be known and usable by those skilled in the computer software art.

Examples of computer-readable media include hardware devices specially configured to store and execute program instructions, such as ROM, RAM, flash memory, etc. Examples of program instructions include machine language 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 above-described hardware device may be configured to operate with at least one software module to perform the operations of the present invention, and vice versa.

Although the description has been made with reference to the above examples, those skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and scope of the present invention as set forth in the claims below. You will be able to.

Claims (20)

As a method of the first terminal,
Initiating channel occupancy time (COT);
Performing groupcast SL (sidelink) transmission within the COT;
Receiving one or more hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback for the groupcast SL transmission;
When a rate threshold is set in the first terminal, calculating an ACK rate based on the one or more HARQ-ACK feedbacks; and
Comprising a step of adjusting a content window (CW) based on a comparison result between the ACK rate and the rate threshold,
Method of the first terminal. In claim 1,
The one or more HARQ-ACK feedbacks considered for adjustment of the CW are one or more HARQ-ACK feedbacks for the groupcast SL transmission performed in the most recent COT initiated by the first terminal among COTs,
Method of the first terminal. In claim 1,
The one or more HARQ-ACK feedbacks considered for the CW adjustment are one or more HARQ-ACK feedbacks for the groupcast SL transmission performed in the reference duration in the most recent COT initiated by the first terminal among COTs. ACK feedbacks,
Method of the first terminal. In claim 1,
HARQ-ACK feedback for the groupcast SL transmission is enabled,
Method of the first terminal. In claim 1,
The one or more HARQ-ACK feedbacks are received on a physical sidelink feedback channel (PSFCH) within the same slot,
Method of the first terminal. In claim 1,
The step of adjusting the CW is,
When the ACK rate is greater than or equal to the rate threshold, changing the CW to the minimum CW,
Method of the first terminal. In claim 1,
The step of adjusting the CW is,
If the ACK rate is greater than or equal to the rate threshold, reducing the CW,
Method of the first terminal. In claim 1,
The step of adjusting the CW is,
If the ACK rate is below the rate threshold, increasing the CW.
Method of the first terminal. In claim 8,
The CW for all priority classes is increased,
Method of the first terminal. In claim 1,
If the rate threshold is not set in the first terminal, the step of calculating the ACK rate is not performed, and if the one or more HARQ-ACK feedbacks include at least one ACK, the CW is changed to the minimum CW. felled,
Method of the first terminal. In claim 1,
The ACK ratio is the ratio between “ACK(s) among the one or more HARQ-ACK feedbacks” and “the number of terminals expected to transmit HARQ-ACK feedback for the groupcast SL transmission.”
Method of the first terminal. In claim 1,
The ACK ratio is the ratio between “ACK(s) of the one or more HARQ-ACK feedbacks” and “the number of predicted HARQ-ACK feedbacks for the groupcast SL transmission”.
Method of the first terminal. In claim 12,
When a negative ACK (NACK)-only transmission method is used, among the predicted HARQ-ACK feedbacks, HARQ-ACK feedback that is not received at the transmitting terminal is considered ACK.
Method of the first terminal. As a method of the first terminal,
Initiating channel occupancy time (COT);
Performing groupcast SL (sidelink) transmission within the COT;
Receiving one or more hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback for the groupcast SL transmission;
When a rate threshold is set in the first terminal, calculating a negative ACK (NACK) rate based on the one or more HARQ-ACK feedbacks; and
Comprising a step of adjusting a content window (CW) based on a comparison result between the NACK rate and the rate threshold,
Method of the first terminal. In claim 14,
The one or more HARQ-ACK feedbacks considered for the CW adjustment are one or more HARQ-ACK feedbacks for the groupcast SL transmission performed in the reference duration in the most recent COT initiated by the first terminal among COTs. ACK feedbacks,
Method of the first terminal. In claim 14,
In the step of adjusting the CW,
The first terminal changes the CW to the minimum CW when the NACK rate is less than the rate threshold, and increases the CW when the NACK rate is greater than the rate threshold.
Method of the first terminal. In claim 14,
The NACK ratio is the ratio between “NACK(s) among the one or more HARQ-ACK feedbacks” and “the number of terminals expected to transmit HARQ-ACK feedback for the groupcast SL transmission” or “the one or more HARQ -The ratio between "NACK(s) among ACK feedbacks" and "number of predicted HARQ-ACK feedbacks for the groupcast SL transmission",
Method of the first terminal. As a first terminal,
Contains at least one processor,
The at least one processor is the first terminal,
initiate channel occupancy time (COT);
Perform groupcast SL (sidelink) transmission within the COT;
Receive one or more hybrid automatic repeat request-acknowledgement (HARQ-ACK) feedback for the groupcast SL transmission;
If a rate threshold is set in the first terminal, calculate an ACK rate based on the one or more HARQ-ACK feedbacks; and
causing to adjust a content window (CW) based on a comparison result between the ACK rate and the rate threshold,
1st terminal. In claim 18,
When adjusting the CW, the at least one processor is configured to:
causing the CW to be changed to the minimum CW if the ACK rate is above the rate threshold and to increase the CW if the ACK rate is below the rate threshold,
1st terminal. In claim 18,
The ACK ratio is the ratio between “ACK(s) among the one or more HARQ-ACK feedbacks” and “the number of terminals expected to transmit HARQ-ACK feedback for the groupcast SL transmission” or “the one or more HARQ -The ratio between “ACK(s) among ACK feedbacks” and “Number of predicted HARQ-ACK feedbacks for the groupcast SL transmission”,
1st terminal.

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