Patent Description:
Sidelink (SL) communication is a communication scheme in which a direct link is established between User Equipments (UEs) and the UEs exchange voice and data directly with each other without intervention of an evolved Node B (eNB). SL communication is under consideration as a solution to the overhead of an eNB caused by rapidly increasing data traffic. Vehicle-to-everything (V2X) refers to a communication technology through which a vehicle exchanges information with another vehicle, a pedestrian, an object having an infrastructure (or infra) established therein, and so on. The V2X may be divided into <NUM> types, such as vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P). The V2X communication may be provided via a PC5 interface and/or Uu interface.

Regarding V2X communication, a scheme of providing a safety service, based on a V2X message such as Basic Safety Message (BSM), Cooperative Awareness Message (CAM), and Decentralized Environmental Notification Message (DENM) is focused in the discussion on the RAT used before the NR. The V2X message may include position information, dynamic information, attribute information, or the like. For example, a UE may transmit a periodic message type CAM and/or an event triggered message type DENM to another UE.

Thereafter, regarding V2X communication, various V2X scenarios are proposed in NR. For example, the various V2X scenarios may include vehicle platooning, advanced driving, extended sensors, remote driving, or the like.

<NPL>, discusses remaining MAC issues. In particular, a proposal is disclosed for the situation when both DRX and PUCCH sending HARQ-ACK are configured. In this case, drx-RetransmissionTimerSL and drx-HARQ-TimerSL can be configured and included in the Acitve Time, according to a specific definition. Further, a proposal is disclosed for the situation when to start/stop drx-RetransmissionTimerSL and drx-HARQ-RTT-TimerSL are specified based on when to start/stop drx-RetransmissionTimerDL/UL and drx-HARQ-RTT-TimerDL/UL.

An object of the present disclosure is to provide a sidelink (SL) communication method between devices (or UEs) and a device (or UE) for performing the same.

Another technical object of the present disclosure is to provide a method for receiving a sidelink retransmission packet in NR V2X and a device (or UE) for performing the same.

A UE can efficiently perform SL communication.

In addition, it is possible to efficiently save power for sidelink communication in NR V2X.

In the present specification, "A or B" may mean "only A", "only B" or "both A and B. " In other words, in the present specification, "A or B" may be interpreted as "A and/or B". For example, in the present specification, "A, B, or C" may mean "only A", "only B", "only C", or "any combination of A, B, C".

A slash (/) or comma used in the present specification may mean "and/or". For example, "A, B, C" may mean "A, B, or C".

In the present specification, "at least one of A and B" may mean "only A", "only B", or "both A and B". In addition, in the present specification, the expression "at least one of A or B" or "at least one of A and/or B" may be interpreted as "at least one of A and B".

In addition, in the present specification, "at least one of A, B, and C" may mean "only A", "only B", "only C", or "any combination of A, B, and C". In addition, "at least one of A, B, or C" or "at least one of A, B, and/or C" may mean "at least one of A, B, and C".

In addition, a parenthesis used in the present specification may mean "for example". Specifically, when indicated as "control information (PDCCH)", it may mean that "PDCCH" is proposed as an example of the "control information". In other words, the "control information" of the present specification is not limited to "PDCCH" and "PDDCH" may be proposed as an example of the "control information". In addition, when indicated as "control information (i.e., PDCCH)", it may also mean that "PDCCH" is proposed as an example of the "control information".

A technical feature described individually in one figure in the present specification may be individually implemented, or may be simultaneously implemented.

<FIG> shows a structure of an NR system, in accordance with an embodiment of the present disclosure.

Layers of a radio interface protocol between the UE and the network can be classified into a first layer (layer <NUM>, L1), a second layer (layer <NUM>, L2), and a third layer (layer <NUM>, L3) based on the lower three layers of the open system interconnection (OSI) model that is well-known in the communication system. Among them, a physical (PHY) layer belonging to the first layer provides an information transfer service by using a physical channel, and a radio resource control (RRC) layer belonging to the third layer serves to control a radio resource between the UE and the network. For this, the RRC layer exchanges an RRC message between the UE and the BS.

<FIG> shows a radio protocol architecture, in accordance with an embodiment of the present disclosure. Specifically, (a) of <FIG> shows a radio protocol stack of a user plane for Uu communication, and (b) of <FIG> shows a radio protocol stack of a control plane for Uu communication. (c) of <FIG> shows a radio protocol stack of a user plane for SL communication, and (d) of <FIG> shows a radio protocol stack of a control plane for SL communication.

A radio resource control (RRC) layer is defined only in the control plane. The RRC layer serves to control the logical channel, the transport channel, and the physical channel in association with configuration, reconfiguration and release of RBs. The RB is a logical path provided by the first layer (i.e., the physical layer or the PHY layer) and the second layer (i.e., a MAC layer, an RLC layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer) for data delivery between the UE and the network.

<FIG> shows a structure of a radio frame of an NR, in accordance with an embodiment of the present disclosure.

A subframe (SF) may be divided into one or more slots, and the number of slots within a subframe may be determined in accordance with subcarrier spacing (SCS).

Table <NUM> shown below represents an example of a number of symbols per slot (Nslotsymb), a number slots per frame (Nframe,uslot), and a number of slots per subframe (Nsubframe,uslot) in accordance with an SCS configuration (u), in a case where a normal CP is used.

Table <NUM> shows an example of a number of symbols per slot, a number of slots per frame, and a number of slots per subframe in accordance with the SCS, in a case where an extended CP is used.

<FIG> shows a structure of a slot of an NR frame, in accordance with an embodiment of the present disclosure.

The BWP may be a set of consecutive physical resource blocks (PRBs) in a given numerology. The PRB may be selected from consecutive sub-sets of common resource blocks (CRBs) for the given numerology on a given carrier.

Meanwhile, the BWP may be defined for SL. The same SL BWP may be used in transmission and reception. For example, a transmitting UE may transmit an SL channel or an SL signal on a specific BWP, and a receiving UE may receive the SL channel or the SL signal on the specific BWP. In a licensed carrier, the SL BWP may be defined separately from a Uu BWP, and the SL BWP may have configuration signaling separate from the Uu BWP. For example, the UE may receive a configuration for the SL BWP from the BS/network. For example, the UE may receive a configuration for the Uu BWP from the BS/network. The SL BWP may be (pre-)configured in a carrier with respect to an out-of-coverage NR V2X UE and an RRC_IDLE UE. For the UE in the RRC_CONNECTED mode, at least one SL BWP may be activated in the carrier.

<FIG> shows an example of a BWP, in accordance with an embodiment of the present disclosure.

A sidelink synchronization signal (SLSS) may include a primary sidelink synchronization signal (PSSS) and a secondary sidelink synchronization signal (SSSS), as an SL-specific sequence. The PSSS may be referred to as a sidelink primary synchronization signal (S-PSS), and the SSSS may be referred to as a sidelink secondary synchronization signal (S-SSS). For example, length-<NUM>-sequences may be used for the S-PSS, and length-<NUM> gold sequences may be used for the S-SSS. For example, a UE may use the S-PSS for initial signal detection and for synchronization acquisition. For example, the UE may use the S-PSS and the S-SSS for acquisition of detailed synchronization and for detection of a synchronization signal ID.

A physical sidelink broadcast channel (PSBCH) may be a (broadcast) channel for transmitting default (system) information which must be first known by the UE before SL signal transmission/reception. For example, the default information may be information related to SLSS, a duplex mode (DM), a time division duplex (TDD) uplink/downlink (UL/DL) configuration, information related to a resource pool, a type of an application related to the SLSS, a subframe offset, broadcast information, or the like. For example, for evaluation of PSBCH performance, in NR V2X, a payload size of the PSBCH may be <NUM> bits including <NUM>-bit cyclic redundancy check (CRC).

<FIG> shows a UE performing V2X or SL communication, in accordance with an embodiment of the present disclosure.

Referring to <FIG>, in V2X or SL communication, the term 'UE' may generally imply a UE of a user. However, if a network equipment such as a BS transmits/receives a signal according to a communication scheme between UEs, the BS may also be regarded as a sort of the UE. For example, a UE <NUM> may be a first apparatus <NUM>, and a UE <NUM> may be a second apparatus <NUM>.

<FIG> shows a procedure of performing V2X or SL communication by a UE based on a transmission mode, in accordance with an embodiment of the present disclosure. In various embodiments of the present disclosure, the transmission mode may be called a mode or a resource allocation mode. Hereinafter, for convenience of explanation, in LTE, the transmission mode may be called an LTE transmission mode. In NR, the transmission mode may be called an NR resource allocation mode.

For example, (a) of <FIG> shows a UE operation related to an LTE transmission mode <NUM> or an LTE transmission mode <NUM>. Alternatively, for example, (a) of <FIG> shows a UE operation related to an NR resource allocation mode <NUM>. For example, the LTE transmission mode <NUM> may be applied to general SL communication, and the LTE transmission mode <NUM> may be applied to V2X communication.

For example, (b) of <FIG> shows a UE operation related to an LTE transmission mode <NUM> or an LTE transmission mode <NUM>. Alternatively, for example, (b) of <FIG> shows a UE operation related to an NR resource allocation mode <NUM>.

Referring to (a) of <FIG>, in the LTE transmission mode <NUM>, the LTE transmission mode <NUM>, or the NR resource allocation mode <NUM>, a BS may schedule an SL resource to be used by the UE for SL transmission. For example, the BS may perform resource scheduling to a UE <NUM> through a PDCCH (e.g., downlink control information (DCI)) or RRC signaling (e.g., Configured Grant Type <NUM> or Configured Grant Type <NUM>), and the UE <NUM> may perform V2X or SL communication with respect to a UE <NUM> according to the resource scheduling. For example, the UE <NUM> may transmit a sidelink control information (SCI) to the UE <NUM> through a physical sidelink control channel (PSCCH), and thereafter transmit data based on the SCI to the UE <NUM> through a physical sidelink shared channel (PSSCH).

Referring to (b) of <FIG>, in the LTE transmission mode <NUM>, the LTE transmission mode <NUM>, or the NR resource allocation mode <NUM>, the UE may determine an SL transmission resource within an SL resource configured by a BS/network or a pre-configured SL resource. For example, the configured SL resource or the pre-configured SL resource may be a resource pool. For example, the UE may autonomously select or schedule a resource for SL transmission. For example, the UE may perform SL communication by autonomously selecting a resource within a configured resource pool. For example, the UE may autonomously select a resource within a selective window by performing a sensing and resource (re)selection procedure. For example, the sensing may be performed in unit of subchannels. In addition, the UE <NUM> which has autonomously selected the resource within the resource pool may transmit the SCI to the UE <NUM> through a PSCCH, and thereafter may transmit data based on the SCI to the UE <NUM> through a PSSCH.

<FIG> shows three cast types, in accordance with an embodiment of the present disclosure. Specifically, <FIG> shows broadcast-type SL communication, <FIG> shows unicast type-SL communication, and <FIG> shows groupcast-type SL communication. In case of the unicast-type SL communication, a UE may perform one-to-one communication with respect to another UE. In case of the groupcast-type SL transmission, the UE may perform SL communication with respect to one or more UEs in a group to which the UE belongs. In various embodiments of the present disclosure, SL groupcast communication may be replaced with SL multicast communication, SL one-to-many communication, or the like.

On the other hand, in NR V2X communication or NR sidelink communication, a transmitting UE may reserve/select one or more transmission resources for sidelink transmission (e.g., initial transmission and/or retransmission), a transmitting UE may inform the receiving UE of information on the location of the one or more transmission resources.

Meanwhile, when performing sidelink communication, a method for a transmitting UE to reserve or pre-determine transmission resource(s) for receiving UE(s) may be representatively as follows.

For example, the transmitting UE may perform a reservation of transmission resource(s) based on a chain. Specifically, for example, if the transmitting UE reserves K transmission resources, the transmitting UE may transmit location information for less than K transmission resources to receiving UE(s) through a SCI transmitted to the receiving UE(s) at any (or specific) transmission time or a time resource. That is, for example, the SCI may include location information for less than the K transmission resources. Alternatively, for example, if the transmitting UE reserves K transmission resources related to a specific TB, the transmitting UE may transmit location information for less than K transmission resources to receiving UE(s) through a SCI transmitted to the receiving UE(s) at any (or specific) transmission time or a time resource. That is, the SCI may include location information for less than the K transmission resources. In this case, for example, it is possible to prevent performance degradation due to an excessive increase in payloads of the SCI, by signaling only the location information for less than K transmission resources to the receiving UE(s) through one SCI transmitted at any (or specific) transmission time or the time resource by the transmitting UE.

<FIG> shows a method in which a UE that has reserved transmission resource(s) informs another UE of the transmission resource(s), based on an embodiment of the present disclosure.

Specifically, for example, (a) of <FIG> shows a method for performing by a transmitting UE chain-based resource reservation by transmitting/signaling location information of (maximum) <NUM> transmission resources to receiving UE(s) through one SCI, in the case of a value of K = <NUM>. For example, (b) of <FIG> shows a method for performing by a transmitting UE chain-based resource reservation by transmitting/signaling location information of (maximum) <NUM> transmission resources to receiving UE(s) through one SCI, in the case of a value of K = <NUM>. For example, referring to (a) and (b) of <FIG>, the transmitting UE may transmit/signal only location information of the fourth transmission-related resource to the receiving UE(s) through the fourth (or last) transmission-related PSCCH. For example, referring to (a) of <FIG>, the transmitting UE may transmit/signal to the receiving UE(s) not only location information of the fourth transmission-related resource but also location information of the third transmission-related resource additionally through the fourth (or last) transmission-related PSCCH. For example, referring to (b) of <FIG>, the transmitting UE may transmit/signal to the receiving UE(s) not only location information of the fourth transmission-related resource but also location information of the second transmission-related resource and location information of the third transmission-related resource additionally through the fourth (or last) transmission-related PSCCH. In this case, for example, in (a) and (b) of <FIG>, if the transmitting UE may transmit/signal to the receiving UE(s) only location information of the fourth transmission-related resource through the fourth (or last) transmission-related PSCCH, the transmitting UE may configure or designate a field/bit of location information of unused or remaining transmission resource(s) to a pre-configured value (e.g., <NUM>). For example, in (a) and (b) of <FIG>, if the transmitting UE may transmit/signal to the receiving UE(s) only location information of the fourth transmission-related resource through the fourth (or last) transmission-related PSCCH, the transmitting UE may be configured or designate a field/bit of location information of unused or remaining transmission resource(s) to a pre-configured status/bit value indicating/representing the last transmission (among <NUM> transmissions).

Meanwhile, for example, the transmitting UE may perform a reservation of transmission resource(s) based on a block. Specifically, for example, if the transmitting UE reserves K transmission resources, the transmitting UE may transmit location information for K transmission resources to receiving UE(s) through a SCI transmitted to the receiving UE(s) at any (or specific) transmission time or a time resource. That is, the SCI may include location information for K transmission resources. For example, if the transmitting UE reserves K transmission resources related to a specific TB, the transmitting UE may transmit location information for K transmission resources to receiving UE(s) through a SCI transmitted to the receiving UE(s) at any (or specific) transmission time or a time resource. That is, the SCI may include location information for K transmission resources. For example, (c) of <FIG> shows a method for performing by the transmitting UE block-based resource reservation, by signaling location information of <NUM> transmission resources to receiving UE(s) through one SCI, in the case of a value of K = <NUM>.

<FIG> shows a method for a first device and a second device to perform sidelink communication, according to an embodiment of the present disclosure.

In step S1010, a first device according to an embodiment may receive SCI from a second device. In step S1020, a first device according to an embodiment may receive SCI-related data from a second device through a PSSCH. In step S1030, a first device according to an embodiment may determine a PSFCH resource for transmitting sidelink HARQ feedback information related to data to a second device based on an index of a slot and an index of a subchannel related to a PSSCH. In step S1040, a first device according to an embodiment may start a first timer related to a PSFCH resource based on sidelink HARQ feedback information being not transmitted to a second device through the PSFCH resource. In step S1050, the first device according to an embodiment may start a second timer related to a sidelink HARQ retransmission packet for SCI or PSSCH based on that the first timer has expired. In step S1060, a first device according to an embodiment may receive a sidelink HARQ retransmission packet after a second timer is started.

Hereinafter, embodiments and/or examples that may be directly or indirectly related to at least one of steps S1010 to S1060 will be reviewed. On the other hand, the following embodiments and/or examples are only related to at least one of steps S1010 to S1060, so a somewhat different feature should not be construed as deviating from the scope of the present specification, even if at least one of the following embodiments and/or examples and steps S1010 to S1060 is somewhat different in content.

On the other hand, NR V2X of Release <NUM> did not support a power saving operation of a user equipment (UE), and it is planned to support a power saving operation of the UE from NR V2X of Release <NUM>.

Meanwhile, in a Uu discontinuous reception (DRX) operation according to an embodiment, Timers such as drx-HARQ-RTT-TimerDL, drx-HARQ-RTT-TimerUL, drx-RetransmissionTimerDL, and drx-RetransmissionTimerUL are defined, so that in case of performing UE HARQ retransmission, a UE transitions to a sleep mode while a round trip time (RTT) timer (drx-HARQ-RTT-TimerDL, drx-HARQ-RTT-TimerUL) or maintain an active state while a retransmission timer (drx-RetransmissionTimerDL, drx-RetransmissionTimerUL) operates.

On the other hand, in some embodiments according to the present disclosure below, a method in which an RX UE receives a transport block (TB) for sidelink communication from a TX UE and performs a power saving operation according to the state of HARQ feedback (HARQ ACK, HARQ NACK, HARQ DTX) for the received transport block in NR V2X is proposed.

Table <NUM> below shows an example of sidelink DRX configuration.

Referring to Table <NUM>, SL drx-RetransmissionTimer-RX according to an embodiment may indicate a maximum time interval until PSCCH (sidelink control information) and PSSCH for SL HARQ retransmission are received. For example, SL drx-RetransmissionTimer-RX may be defined as a time for an RX UE to monitor a PSCCH and/or PSSCH to receive an SL HARQ retransmission transmitted by a TX UE. An RX UE may start operation of receiving a PSCCH and/or PSSCH for SL HARQ retransmission transmitted by a TX UE by transitioning to an active state when an SL drx-HARQ-RTT-Timer-RX timer expires and starting the SL drx-RetransmissionTimer-RX timer. When an SL HARQ retransmission transmitted by a TX UE is received while an SL drx-RetransmissionTimer-RX timer is running, an RX UE may stop the SL drx-RetransmissionTimer-RX timer.

Referring to Table <NUM>, SL drx-HARQ-RTT-Timer-RX according to an embodiment may represent a minimum time interval before PSCCH (sidelink control information) and/or PSSCH for SL HARQ retransmission is expected by a MAC entity of an RX UE. For example, SL drx-HARQ-RTT-Timer-RX may be defined as a minimum time required to monitor PSCCH and/or PSSCH for sidelink HARQ retransmission packet transmitted by a TX UE, when a MAC entity of an RX UE receives and successfully decodes the PSCCH (sidelink control information) transmitted by a TX UE, and fails to decode the received PSSCH (sidelink data) and transmits the HARQ NACK to the TX UE. That is, it may mean that a PSCCH and/or PSSCH for SL HARQ retransmission is not transmitted from a TX UE before an SL drx-HARQ-RTT-Timer-RX expires. RX UE may operate in sleep mode while SL drx-HARQ-RTT-Timer-RX is operating, and if SL drx-HARQ-RTT-Timer-RX is expired, may transition to an active state and start an SL drx-Retransmission-Timer-RX timer.

In some embodiments below, a method of power saving based on operations of SL drx-HARQ-RTT-Timer-RX and SL drx-retransmissionTimer-RX of an RX UE performing sidelink communication may be provided.

In an embodiment, with respect to an operation of SL drx-HARQ-RTT-Timer-RX and SL drx-retransmissionTimer-RX of an RX UE, in a HARQ feedback disabled mode, a Tx UE may transmit SL packets to an Rx UE through blind retransmission. At this time, since an Rx UE does not transmit SL HARQ feedback, it may not be able to operate the RTT/retransmission timer based on PSFCH transmission as in HARQ feedback enabled. Therefore, when an Rx UE receives a PSSCH transmitted by a Tx UE, it is necessary to start a retransmission timer to ensure reception of blind retransmission (including additional transmission) packets transmitted by the Tx UE.

In an embodiment, an inactivity timer, a HARQ RTT timer, and/or a retransmission timer may each independently operate. an inactivity timer is a common DRX timer, when an Rx UE receives a new TB from a Tx UE, the Rx UE may start an inactivity timer and monitor whether there is additional SL data transmitted by the Tx UE. When an Rx UE receives a PSSCH (new TB) transmitted by a Tx UE and operates an inactivity timer, and HARQ NACK occurs at the same time, the Rx UE may operate a HARQ RTT timer/retransmission timer independently of an inactivity timer. Meanwhile, an SL HARQ RTT timer/retransmission timer may be a timer operated per sidelink process or per HARQ process. Therefore, a TX UE and an RX UE may operate according to the following process. i) A transmitting UE may transmit a PSSCH (new TB) to a receiving UE (e.g., HARQ disabled). ii) A receiving UE may start an SL DRX inactivity timer based on a reception of a PSSCH and monitor a new additional PSSCH. iii) A receiving UE may start a HARQ RTT/retransmission timer and monitor blind retransmission packets. iv) A transmitting UE may transmit a new PSSCH (new TB). v) A transmitting UE may transmit a blind retransmission packet for i) to a receiving UE. vi) A transmitting UE may transmit a blind retransmission packet for i) back to a receiving UE. Thereafter, it may be expired/terminated after an inactivity timer is started, and after that, it may be expired/terminated after a HARQ RTT/retransmission timer is started.

In some embodiments of the present disclosure below, it describes an operation of receiving a sidelink DRX operation of an RX UE and/or a sidelink HARQ retransmission of the RX UE.

In one embodiment (or in a first embodiment), when an RX UE successfully decodes a PSCCH (Sidelink Control Information) transmitted by a TX UE, but fails to decode the PSSCH and transmits a HARQ NACK to the TX UE, the RX UE may start a Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode. When an SL drx-HARQ-RTT-Timer-RX timer expires, an RX UE transitions to an active mode to receive a PSCCH and PSSCH for a SL HARQ retransmission packet transmitted by a TX UE, starts an SL drx-RetransmissionTimer-RX timer, and may receive the PSCCH and PSSCH transmitted by the TX UE. Upon receiving a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, an RX UE may stop an SL drx-RetransmissionTimer-RX timer. If an RX UE receives a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, but the decoding of the PSSCH fails again (PSCCH decoding succeeds, PSSCH decoding fails) and transmits a HARQ NACK to the TX UE, the RX UE may restart a Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode until the Sidelink HARQ-RTT-Timer-RX expires. When a Sidelink HARQ-RTT-Timer-RX timer expires, an RX UE may start an SL drx-RetransmissionTimer-RX timer by transitioning back to the active state to receive a PSCCH and PSSCH for SL HARQ retransmission retransmitted by a TX UE. When an RX UE receives a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, the RX UE may stop an SL drx-RetransmissionTimer.

In one embodiment (or in the second embodiment), when a TX UE transmits by setting a HARQ feedback option to HARQ feedback Disable (even if PSSCH decoding fails, HARQ NACK is not transmitted to a TX UE. The TX UE performs retransmission with blind retransmission) to an RX UE through PSCCH (SCI), the TX UE may perform an operation for an RX UE to receive sidelink DRX and sidelink HARQ retransmission as follows. That is, when an RX UE successfully decodes SCI transmitted by a TX UE but fails to decode a PSSCH, the sidelink retransmission packet transmitted by the TX UE through blind retransmission without transmitting HARQ NACK feedback to the TX UE may be received. Therefore, when an RX UE successfully decodes SCI (including information indicating HARQ feedback Disabled) transmitted by a TX UE, but fails to decode a PSSCH, the RX UE may start an Sidelink HARQ-RTT-Timer-RX timer and transition to a sleep mode. That is, an RX UE may determine that a TX UE does not perform blind retransmission until an SL drx-HARQ-RTT-Timer-RX timer expires and may transition to a sleep mode. When an SL drx-HARQ-RTT-Timer-RX timer expires, an RX UE may transition to an active mode to receive a packet retransmitted by a TX UE in blind retransmission, start SL drx-RetransmissionTimer-RX, and receive the retransmission packet transmitted by the TX UE. When an RX UE receives a PSCCH and a PSSCH for blind retransmission transmitted by a TX UE, the RX UE may stop an SL drx-RetransmissionTimer-RX timer. If an RX UE fails again to decode a PSSCH for blind retransmission transmitted by a TX UE (decoding for PSCCH indicating HARQ feedback Disabled is successful, PSSCH decoding fails), the TX UE, the RX UE may restart an Sidelink HARQ-RTT-Timer-RX timer and operate in sleep mode while the timer is running. When an Sidelink HARQ-RTT-Timer-RX timer expires, an RX UE may start an SL drx-RetransmissionTimer-RX by transitioning back to an active state to receive a PSCCH and PSSCH for blind retransmission that a TX UE retransmits. When an RX UE receives a PSCCH and a PSSCH for blind retransmission transmitted by a TX UE, the RX UE may stop an SL drx-RetransmissionTimer.

In one embodiment (or in a third embodiment), when a TX UE transmits by setting the HARQ feedback option to HARQ feedback disable (HARQ ACK is not transmitted to the TX UE even if a PSSCH decoding is successful. The TX UE performs retransmission by blind retransmission. An RX UE receives the retransmission packet that the TX UE blindly retransmits) through PSCCH (SCI) to the RX UE, the RX UE may perform a reception operation of sidelink DRX and sidelink HARQ retransmission. That is, when an RX UE successfully decodes a PSCCH (SCI) transmitted by a TX UE and also succeeds in decoding the PSSCH, the RX UE may not transmit a HARQ ACK feedback to the TX UE. And the RX UE may receive a retransmission packet transmitted by the TX UE through blind retransmission. Therefore, even if an RX UE successfully decodes SCI (including information indicating HARQ feedback Disabled) transmitted by a TX UE and succeeds in decoding a PSSCH, when the RX UE is indicated as HARQ feedback Disabled by the HARQ feedback option through the PSCCH (e.g., sidelink control information), the RX UE may transition to a sleep mode while successfully receiving a PSCCH and PSSCH and starting an Sidelink HARQ-RTT-Timer-RX timer. When an SL drx-HARQ-RTT-Timer-RX timer expires, an RX UE may transition to an active mode, start an SL drx-RetransmissionTimer-RX timer in order to receive the PSCCH and PSSCH for the packet retransmitted by the TX UE in blind retransmission, and receive a PSCCH and PSSCH for sidelink blind retransmission transmitted by a TX UE. Upon receiving a PSCCH and PSSCH for blind retransmission transmitted by a TX UE, an RX UE may stop SL drx-RetransmissionTimer-RX. In addition, if the decoding of the blind retransmission packet transmitted by a TX UE succeeds or fails (decoding for the PSCCH including information indicating HARQ feedback Disabled is successful, PSSCH decoding fails), an RX UE may start an Sidelink HARQ-RTT-Timer-RX timer and operate in sleep mode until it monitors a PSCCH and PSSCH for the next blind retransmission. When an Sidelink HARQ-RTT-Timer-RX timer expires, an RX UE may transition to an active mode and start an SL drx-RetransmissionTimer-RX timer to receive a PSCCH and PSSCH for blind retransmission that a TX UE retransmits.

In relation to the second embodiment or the third embodiment, when an RX UE according to an embodiment receives HARQ disabled (packet) transmission from a TX UE may start an SL drx-RetransmissionTimer-RX timer on the corresponding HARQ disabled packet. For example, an RX UE may start a Sidelink (SL) HARQ-RTT-Timer-RX timer for the corresponding HARQ disabled packet.

In an embodiment, an RX UE may start Sidelink (SL) HARQ-RTT-Timer-RX and/or SL drx-RetransmissionTimer-RX based on the success/failure of decoding for a PSSCH related to the corresponding HARQ disabled packet.

In one example, an RX UE may not transmit an ACK to a TX UE even if decoding for a PSSCH related to a HARQ disabled packet is successful, and may start Sidelink (SL) HARQ-RTT-Timer-RX and/or SL drx-RetransmissionTimer-RX related to the HARQ disabled packet.

In one example, an RX UE may not transmit a NACK to a TX UE even if decoding for a PSSCH related to a HARQ disabled packet fails, and may start Sidelink (SL) HARQ-RTT-Timer-RX and/or SL drx-RetransmissionTimer-RX related to the HARQ disabled packet.

In one embodiment (or in the fourth embodiment), when an RX UE successfully decodes a PSCCH (sidelink control information) regardless of the success/failure of decoding for a PSSCH (sidelink data) transmitted by a TX UE, the RX UE may start an Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode. When an SL drx-HARQ-RTT-Timer-RX timer expires, an RX UE may transition to an active mode to receive a PSCCH and PSSCH for an SL HARQ retransmission packet transmitted by a TX UE, may start an SL drx-RetransmissionTimer-RX timer, and may receive a PSCCH and PSSCH transmitted by the TX UE. Upon receiving a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, an RX UE may stop an SL drx-RetransmissionTimer-RX timer. If the decoding of a PSCCH for SL HARQ retransmission transmitted by a TX UE is successful, an RX UE may restart an Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode until an Sidelink HARQ-RTT-Timer-RX timer expires. When an Sidelink HARQ-RTT-Timer-RX timer expires, an RX UE transitions back to the active state to receive a PSCCH and PSSCH for SL HARQ retransmission retransmitted by a TX UE, and may start an SL drx-RetransmissionTimer-RX timer. When an RX UE receives a PSCCH and a PSSCH for SL HARQ retransmission transmitted by a TX UE, the RX UE may stop an SL drx-RetransmissionTimer.

In one embodiment (or in a fifth embodiment), when an RX UE succeeds in decoding a PSCCH (SCI) transmitted by a TX UE and fails to decode a PSSCH (SL data), the RX UE should transmit SL HARQ NACK to the TX UE, but if it cannot transmit due to the following reasons, it may start an Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode (since the TX UE can send the SL HARQ retransmission packet to the RX UE even if the SL HARQ NACK is not transmitted to the TX UE, the Sidelink HARQ-RTT-Timer-RX timer must be started).

(Reason) When an RX UE also has SL data (e.g., SL HARQ feedback) to be transmitted to the counterpart UE and UL data to be transmitted to a base station occurs at the same time, the RX UE may compare the SL data and the UL data with priority, and may transmit data having a higher priority first. If the priority of UL data is high in the priority comparison, there may be a problem in that an SL HARQ feedback cannot be transmitted to a TX UE and UL data must be transmitted to a base station.

When an SL drx-HARQ-RTT-Timer-RX timer expires, an RX UE may start an SL drx-RetransmissionTimer-RX timer by transitioning to an active mode to receive a PSCCH and PSSCH for an SL HARQ retransmission packet transmitted by a TX UE, and may receive the PSCCH and PSSCH the TX UE transmits. When an RX UE receives a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, the RX UE may stop an SL drx-RetransmissionTimer-RX timer. If PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE are received, but decoding of PSSCH fails again (decoding of PSCCH succeeds, decoding of PSSCH fails), and HARQ NACK is transmitted to the TX UE, an RX UE may restart an Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode until an Sidelink HARQ-RTT-Timer-RX timer expires. When an Sidelink HARQ-RTT-Timer-RX timer expires, an RX UE may start an SL drx-RetransmissionTimer-RX timer by transitioning back to an active state to receive a PSCCH and PSSCH for SL HARQ retransmission that a TX UE retransmits. When an RX UE receives a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, the RX UE may stop an SL drx-RetransmissionTimer.

In an embodiment, an operation of an RTT/Retransmission Timer (or SL DRX operation) due to PSFCH dropping of an Rx UE (due to prioritization between SL and UL or prioritization between LTE SL and NR SL) may be proposed. In one example, in case of HARQ feedback Enabled MAC PDU, i) (in the case of successful decoding) a receiving UE should be able to monitor a reception of a retransmission packet of a Tx UE by starting an RTT/Retransmission timer if SL data is successfully received (decoding succeeded), since the transmitting UE may misjudgment it as a decoding failure even though a PSFCH has not actually been transmitted. ii) (In the case of decoding failure) if a receiving UE fails to receive SL data (decoding failure), it should be able to monitor whether a Tx UE's retransmission packet is received by starting an RTT/Retransmission timer, since the transmitting UE may misjudgment it as a decoding failure even though a PSFCH has not actually been transmitted.

In an embodiment, an SL DRX operation of an Rx UE when a HARQ feedback Disabled MAC PDU is transmitted from a TX UE may be provided. In one example, a receiving UE may start an RTT/Retransmission timer when receiving SL data (decoding success or decoding failure), so that the RX UE can monitor the next HARQ feedback Disabled MAC PDU (blind transmission) transmitted by a Tx UE.

In an embodiment, an SL drx-HARQ-RTT-Timer-RX and/or an SL drx-RetransmissionTimer-RX may operate based on the contents of Table <NUM> below.

<FIG> shows an example of when a first timer is started.

In an embodiment, an RX UE (in an example, may correspond to a first device to be described later in <FIG> and <FIG>) that has received sidelink data through a PSSCH from a TX UE (in an example, may correspond to a second device to be described later in <FIG> and <FIG>) may determine a PSFCH resource <NUM> for transmitting sidelink HARQ feedback information related to the data to the second device, based on an index of a slot and an index of a subchannel related to a PSSCH.

An RX UE according to an embodiment may start an SL DRX HARQ RTT timer (or a first timer), at a slot and/or symbol <NUM> following the end time <NUM> of a PSFCH resource <NUM>. In one example, an RX UE may start an SL DRX HARQ RTT timer (or first timer) related to the PSFCH resource <NUM>, based on sidelink HARQ feedback information being not transmitted from (RX UE) to TX UE through the PSFCH resource <NUM>.

For example, sidelink HARQ feedback information may not be transmitted to the TX UE through the PSFCH resource <NUM> based on a first priority value related to the sidelink HARQ feedback information. In a more specific example, the sidelink HARQ feedback information may not be transmitted to the TX UE, based on the first priority value being greater than a second priority value related to an uplink transmission to a base station.

The RX UE according to an embodiment may start an SL DRX Retransmission timer (or a second timer), after a time point <NUM> when an SL DRX HARQ RTT timer (or a first timer) expires after the operation period <NUM> of the SL DRX HARQ RTT timer (or the first timer) has elapsed. In one example, an RX UE may receive a sidelink HARQ retransmission packet from a TX UE after the SL DRX Retransmission timer (or second timer) is started.

<FIG> shows an example of a method for an RX UE to save power consumption for sidelink communication according to an embodiment.

More specifically, <FIG> shows an embodiment of a method for an RX UE to save power based on an operation of an RX SL HARQ RTT Timer-RX operation and an SL DRX retransmission timer-RX operation proposed by some of the embodiments of the present disclosure.

As in <FIG>, when an RX UE successfully decodes a PSCCH (sidelink control information) transmitted by a TX UE, but fails to decode the PSSCH and transmits a HARQ NACK to the TX UE, an RX UE may start a Sidelink HARQ-RTT-Timer-RX timer and transition to sleep mode. When an SL drx-HARQ-RTT-Timer-RX timer expires, an RX UE may transition to the active mode to receive a PSCCH and PSSCH for an SL HARQ retransmission packet transmitted by a TX UE, may start an SL drx-RetransmissionTimer-RX timer, and may receive the PSCCH and PSSCH transmitted by the TX UE. Upon receiving a PSCCH and PSSCH for SL HARQ retransmission transmitted by a TX UE, an RX UE may stop an SL drx-RetransmissionTimer-RX timer.

Some of the various embodiments of the present disclosure provide a method for enabling an RX UE operating in sidelink DRX to efficiently receive a PSCCH and a PSSCH for sidelink HARQ retransmission transmitted by a TX UE through switching between sleep mode and active mode. That is, it was intended to ensure that an RX UE receives a PSCCH and a PSSCH transmitted by a TX UE while operating in a power saving mode.

Various embodiments of the present disclosure may be combined with at least one of a power control operation of a UE, a congestion control operation of a UE, a channel coding operation of a UE, and/or an SL HARQ feedback operation of a UE.

<FIG> is a flowchart showing a method for a first device to perform sidelink communication according to an embodiment of the present disclosure.

Operations disclosed in the flowchart of <FIG> may be performed in combination with various embodiments of the present disclosure. In one example, the operations disclosed in the flowchart of <FIG> may be performed based on at least one of the devices illustrated in <FIG>. In one example, the first device of <FIG> may correspond to the first wireless device <NUM> of <FIG> to be described later, and the second device may correspond to the second wireless device <NUM> of <FIG>. In another example, the first device of <FIG> may correspond to the second wireless device <NUM> of <FIG> to be described later, and the second device may correspond to the first wireless device <NUM>.

In step S1310, a first device according to an embodiment receives sidelink control information, SCI, from a second device.

In step S1310, a first device according to an embodiment receives data related to the SCI, from the second device, through a physical sidelink shared channel, PSSCH.

In step S1330, a first device according to an embodiment determines a physical sidelink feedback channel, PSFCH, resource for transmitting sidelink hybrid automatic repeat request, HARQ, feedback information related to the data to the second device, based on an index of a slot and an index of a subchannel related to the PSSCH.

In step S1340, a first device according to an embodiment starts a first timer related to the PSFCH resource, based on the sidelink HARQ feedback information not being transmitted to the second device through the PSFCH resource.

In step S1350, a first device according to an embodiment starts a second timer related to a sidelink HARQ retransmission packet for the SCI or the PSSCH, based on the first timer being expired.

In step S1360, a first device according to an embodiment receives the sidelink HARQ retransmission packet from the second device, after the second timer is started.

In an embodiment, the first timer may correspond/be same/be similar to the above-described SL drx-HARQ-RTT-Timer-RX, and the second timer may correspond/be same/be similar to the above-described SL drx-RetransmissionTimer-RX.

In an embodiment, the sidelink HARQ feedback information may be not transmitted to the second device through the PSFCH resource, based on a first priority related to the sidelink HARQ feedback information.

In an embodiment, the sidelink HARQ feedback information may be not transmitted to the second device, based on the first priority being lower than a second priority related to an uplink transmission to a base station.

In an example, the first device may give priority to UL when the priority value of UL data is less than a UL threshold, by comparing a priority value of UL data for uplink transmission to the base station with a UL threshold value for prioritization. In other words, it may be determined that the second priority is higher than the first priority. In this case, SL transmission for transmitting the sidelink HARQ feedback information may be dropped and UL transmission may be performed.

In another example, by comparing the priority value of the UL data with the UL threshold, if the priority value of the UL data is greater than the UL threshold, the first device may compare the priority of the SL data and the SL threshold for prioritization. By comparing the priority of the SL data regarding the transmission of the sidelink HARQ feedback information and the SL threshold, if the priority value of the SL data is less than the SL threshold, the first device may give priority to SL. In other words, it may be determined that the first priority is higher than the second priority. In this case, the UL transmission may be dropped and SL transmission may be performed. Conversely, if the priority value of the SL data is greater than the SL threshold, priority may be given to the UL (In other words, it may be determined that the second priority is higher than the first priority.

In an embodiment, the first timer may be started at a symbol or a slot following the end time of the PSFCH resource.

The first device according to an embodiment may start the first timer based on the sidelink HARQ feedback information being transmitted to the second device through the PSFCH resource.

In an embodiment, the first timer may be started at a symbol or slot subsequent to the end time of PSFCH transmission based on the sidelink HARQ feedback information.

In an embodiment, the first timer and the second timer are maintained per sidelink HARQ process of the first device.

In an embodiment, the sidelink HARQ feedback information may not be transmitted to the second device, based on the first priority being lower than a third priority related to a sidelink transmission to a third device or a sidelink reception from the third device.

In an embodiment, sidelink communication based on a first wireless radio access technology, RAT, may be performed between the first device and the second device, sidelink communication based on a second wireless RAT may be performed between the first device and the third device.

In an embodiment, at least one of the third wireless RAT or the second wireless RAT may be new radio, NR, or long-term evolution, LTE.

In an embodiment, monitoring for receiving the sidelink HARQ retransmission packet from the second device may not be performed in a time interval in which the first timer operates.

In an embodiment, monitoring for receiving the sidelink HARQ retransmission packet from the second device may be performed in a time interval in which the second timer operates.

In an embodiment, the first device may be in a discontinuous reception, DRX, active state capable of receiving a signal from the second device, in the time interval in which the second timer operates.

In an embodiment, the second timer may be stated by the first device, based on the data being received through a HARQ disabled transmission of the second device.

According to an embodiment of the present disclosure, a first device for performing sidelink communication may be proposed. The first device may comprise: one or more memories storing instructions; one or more transceivers; and one or more processors connected to the one or more memories and the one or more transceivers, wherein the one or more processors may execute the instructions to: receive sidelink control information, SCI, from a second device; receive data related to the SCI, from the second device, through a physical sidelink shared channel, PSSCH; determine a physical sidelink feedback channel, PSFCH, resource for transmitting sidelink hybrid automatic repeat request, HARQ, feedback information related to the data to the second device, based on an index of a slot and an index of a subchannel related to the PSSCH; start a first timer related to the PSFCH resource, based on the sidelink HARQ feedback information not being transmitted to the second device through the PSFCH resource; start a second timer related to a sidelink HARQ retransmission packet for the SCI or the PSSCH, based on the first timer being expired; and receive the sidelink HARQ retransmission packet from the second device, after the second timer is started, wherein the sidelink HARQ feedback information may be not transmitted to the second device through the PSFCH resource, based on a first priority related to the sidelink HARQ feedback information.

According to an embodiment of the present disclosure, a device (or a chip(set)) adapted to control a first user equipment, UE, may be proposed. The device may comprise: one or more processors; and one or more memories operably connectable to the one or more processors and storing instructions, wherein the one or more processors execute the instructions to: receive sidelink control information, SCI, from a second UE; receive data related to the SCI, from the second UE, through a physical sidelink shared channel, PSSCH; determine a physical sidelink feedback channel, PSFCH, resource for transmitting sidelink hybrid automatic repeat request, HARQ, feedback information related to the data to the second UE, based on an index of a slot and an index of a subchannel related to the PSSCH; start a first timer related to the PSFCH resource, based on the sidelink HARQ feedback information not being transmitted to the second UE through the PSFCH resource; start a second timer related to a sidelink HARQ retransmission packet for the SCI or the PSSCH, based on the first timer being expired; and receive the sidelink HARQ retransmission packet from the second UE, after the second timer is started, wherein the sidelink HARQ feedback information may be not transmitted to the second UE through the PSFCH resource, based on a first priority related to the sidelink HARQ feedback information.

In one example, the first UE of the embodiment may refer to the first device described in the present disclosure. In one example, the at least one processor, the at least one memory, and the like in the device for controlling the first UE may be implemented as a separate sub-chip respectively, or at least two or more components may be implemented through one sub-chip.

According to an embodiment of the present disclosure, a non-transitory computer-readable storage medium storing instructions may be proposed. The instructions, when executed, may cause a first device to: receive sidelink control information, SCI, from a second device; receive data related to the SCI, from the second device, through a physical sidelink shared channel, PSSCH; determine a physical sidelink feedback channel, PSFCH, resource for transmitting sidelink hybrid automatic repeat request, HARQ, feedback information related to the data to the second device, based on an index of a slot and an index of a subchannel related to the PSSCH; start a first timer related to the PSFCH resource, based on the sidelink HARQ feedback information not being transmitted to the second device through the PSFCH resource; start a second timer related to a sidelink HARQ retransmission packet for the SCI or the PSSCH, based on the first timer being expired; and receive the sidelink HARQ retransmission packet from the second device, after the second timer is started, wherein the sidelink HARQ feedback information may be not transmitted to the second device through the PSFCH resource, based on a first priority related to the sidelink HARQ feedback information.

<FIG> is a flowchart showing a method for a second device to perform sidelink communication according to an embodiment of the present disclosure.

Operations disclosed in the flowchart of <FIG> may be performed in combination with various embodiments of the present disclosure. In one example, the operations disclosed in the flowchart of <FIG> may be performed based on at least one of the devices illustrated in <FIG>. In one example, the second device of <FIG> may correspond to the second wireless device <NUM> of <FIG> to be described later, and the first device may correspond to the first wireless device <NUM> of <FIG>. In another example, the second device of <FIG> may correspond to the first wireless device <NUM> of <FIG> to be described later, and the first device may correspond to the second wireless device <NUM> of <FIG>.

In step S1410, a second device according to an embodiment may transmit SCI to a first device.

In step S1420, a second device according to an embodiment may transmit, to a first device, data related to SCI through a PSSCH.

In step S1430, a second device according to an embodiment may determine a PSFCH resource for receiving sidelink HARQ feedback information based on an index of a slot and an index of a subchannel related to the PSSCH.

A first device according to an embodiment may start a first timer related to the PSFCH resource, based on the sidelink HARQ feedback information not being transmitted to the second device through the PSFCH resource.

A first device according to an embodiment may start a second timer related to a sidelink HARQ retransmission packet for the SCI or the PSSCH, based on the first timer being expired.

A first device according to an embodiment may receive the sidelink HARQ retransmission packet from the second device, after the second timer is started.

In an embodiment, the first timer and the second timer may be maintained per sidelink HARQ process of the first device.

According to an embodiment of the present disclosure, a second device for performing sidelink communication may be proposed. The second device may comprise: one or more memories storing instructions; one or more transceivers; and one or more processors connected to the one or more memories and the one or more transceivers, wherein the one or more processors may execute the instructions to: transmit SCI to the first device; transmit data related to SCI to through a PSSCH to the first device; determine a PSFCH resource for receiving sidelink HARQ feedback information, based on an index of a slot and an index of a subchannel related to PSSCH.

Various embodiments of the present disclosure may be combined with each other.

<FIG> shows a communication system <NUM>, in accordance with an embodiment of the present disclosure.

Referring to <FIG>, a communication system <NUM> to which various embodiments of the present disclosure are applied includes wireless devices, Base Stations (BSs), and a network. Herein, the wireless devices represent devices performing communication using Radio Access Technology (RAT) (e.g., <NUM> New RAT (NR)) or Long-Term Evolution (LTE)) and may be referred to as communication/radio/<NUM> devices. The wireless devices may include, without being limited to, a robot 100a, vehicles 100b-<NUM> and 100b-<NUM>, an eXtended Reality (XR) device 100c, a hand-held device 100d, a home appliance 100e, an Internet of Things (IoT) device 100f, and an Artificial Intelligence (AI) device/server <NUM>. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous vehicle, and a vehicle capable of performing communication between vehicles. Herein, the vehicles may include an Unmanned Aerial Vehicle (UAV) (e.g., a drone). The XR device may include an Augmented Reality (AR)/Virtual Reality (VR)/Mixed Reality (MR) device and may be implemented in the form of a Head-Mounted Device (HMD), a Head-Up Display (HUD) mounted in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), and a computer (e.g., a notebook). For example, the BSs and the network may be implemented as wireless devices and a specific wireless device 200a may operate as a BS/network node with respect to other wireless devices.

Here, wireless communication technology implemented in wireless devices 100a to 100f of the present disclosure may include Narrowband Internet of Things for low-power communication in addition to LTE, NR, and <NUM>. In this case, for example, NB-IoT technology may be an example of Low Power Wide Area Network (LPWAN) technology and may be implemented as standards such as LTE Cat NB1, and/or LTE Cat NB2, and is not limited to the name described above. Additionally or alternatively, the wireless communication technology implemented in the wireless devices 100a to 100f of the present disclosure may perform communication based on LTE-M technology. In this case, as an example, the LTE-M technology may be an example of the LPWAN and may be called by various names including enhanced Machine Type Communication (eMTC), and the like. For example, the LTE-M technology may be implemented as at least any one of various standards such as <NUM>) LTE CAT <NUM>, <NUM>) LTE Cat M1, <NUM>) LTE Cat M2, <NUM>) LTE non-Bandwidth Limited (non-BL), <NUM>) LTE-MTC, <NUM>) LTE Machine Type Communication, and/or <NUM>) LTE M, and is not limited to the name described above. Additionally or alternatively, the wireless communication technology implemented in the wireless devices 100a to 100f of the present disclosure may include at least one of Bluetooth, Low Power Wide Area Network (LPWAN), and ZigBee considering the low-power communication, and is not limited to the name described above. As an example, the ZigBee technology may generate personal area networks (PAN) related to small/low-power digital communication based on various standards including IEEE <NUM>. <NUM>, and the like, and may be called by various names.

Wireless communication/connections 150a, 150b, or 150c may be established between the wireless devices 100a to 100f/BS <NUM>, or BS <NUM>/BS <NUM>. Herein, the wireless communication/connections may be established through various RATs (e.g., <NUM> NR) such as uplink/downlink communication 150a, sidelink communication 150b (or, D2D communication), or inter BS communication (e.g. relay, Integrated Access Backhaul (IAB)). The wireless devices and the BSs/the wireless devices may transmit/receive radio signals to/from each other through the wireless communication/connections 150a and 150b. For example, the wireless communication/connections 150a and 150b may transmit/receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, and resource mapping/demapping), and resource allocating processes, for transmitting/receiving radio signals, may be performed based on the various proposals of the present disclosure.

<FIG> shows wireless devices, in accordance with an embodiment of the present disclosure.

<FIG> shows a signal process circuit for a transmission signal, in accordance with an embodiment of the present disclosure.

<FIG> shows another example of a wireless device, in accordance with an embodiment of the present disclosure.

<FIG> shows a hand-held device, in accordance with an embodiment of the present disclosure. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), or a portable computer (e.g., a notebook). The hand-held device may be referred to as a mobile station (MS), a user terminal (UT), a Mobile Subscriber Station (MSS), a Subscriber Station (SS), an Advanced Mobile Station (AMS), or a Wireless Terminal (WT).

<FIG> shows a vehicle or an autonomous vehicle, in accordance with an embodiment of the present disclosure. The vehicle or autonomous vehicle may be implemented by a mobile robot, a car, a train, a manned/unmanned Aerial Vehicle (AV), a ship, etc..

For example, the communication unit <NUM> may receive map data, traffic information data, etc. from an external server. The autonomous driving unit 140d may generate an autonomous driving path and a driving plan from the obtained data. The control unit <NUM> may control the driving unit 140a such that the vehicle or the autonomous vehicle <NUM> may move along the autonomous driving path according to the driving plan (e.g., speed/direction control). In the middle of autonomous driving, the communication unit <NUM> may aperiodically/periodically acquire recent traffic information data from the external server and acquire surrounding traffic information data from neighboring vehicles. In the middle of autonomous driving, the sensor unit 140c may obtain a vehicle state and/or surrounding environment information. The autonomous driving unit 140d may update the autonomous driving path and the driving plan based on the newly obtained data/information. The communication unit <NUM> may transfer information about a vehicle position, the autonomous driving path, and/or the driving plan to the external server. The external server may predict traffic information data using AI technology, etc., based on the information collected from vehicles or autonomous vehicles and provide the predicted traffic information data to the vehicles or the autonomous vehicles.

Claim 1:
A method for performing, by a first device (<NUM>), sidelink communication, the method comprising:
receiving (S1310), from a second device, first sidelink control information, SCI, for scheduling of a physical sidelink shared channel, PSSCH, through a physical sidelink control channel, PSCCH;
receiving (S1320), from the second device, sidelink data related to the first SCI through the PSSCH;
determining (S1330) a physical sidelink feedback channel, PSFCH, resource for transmitting sidelink hybrid automatic repeat request, HARQ, feedback information related to the received sidelink data through the PSSCH, based on a slot index and an index of a subchannel related to the PSSCH;
starting (S1340) a first timer, based on the sidelink HARQ feedback information being not transmitted through the PSFCH resource;
starting (S1350) a second timer for a retransmission of the first SCI or the sidelink data based on expiry of the first timer; and
receiving (S1360) the sidelink retransmission from the second device based on the second timer being running.