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 the like. 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.

As a wider range of communication devices require larger communication capacities, the need for mobile broadband communication that is more enhanced than the existing radio access technology (RAT) is rising. A next-generation radio access technology that is based on the enhanced mobile broadband communication, massive machine-type communication (MTC), ultra-reliable and low latency communication (URLLC), and the like, may be referred to as a new radio access technology (RAT) or new radio (NR). Here, the NR may also support vehicle-to-everything (V2X) communication.

Regarding V2X communication, a scheme of providing a safety service, based on a V2X message, such as a basic safety message (BSM), a cooperative awareness message (CAM), and a 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.

For example, the CAM may include dynamic state information of the vehicle such as direction and speed, static data of the vehicle such as a size, and basic vehicle information such as an exterior illumination state, route details, or the like. For example, the UE may broadcast the CAM, and latency of the CAM may be less than <NUM>. For example, the UE may generate the DENM and transmit it to another UE in an unexpected situation such as a vehicle breakdown, accident, or the like. For example, all vehicles within a transmission range of the UE may receive the CAM and/or the DENM. In this case, the DENM may have a higher priority than the CAM.

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.

For example, based on the vehicle platooning, vehicles may move together by dynamically forming a group. For example, in order to perform platoon operations based on the vehicle platooning, the vehicles belonging to the group may receive periodic data from a leading vehicle. For example, the vehicles belonging to the group may decrease or increase an interval between the vehicles by using the periodic data.

For example, based on the advanced driving, the vehicle may be semi-automated or fully automated. For example, each vehicle may adjust trajectories or maneuvers, based on data obtained from a local sensor of a proximity vehicle and/or a proximity logical entity. In addition, for example, each vehicle may share driving intention with proximity vehicles.

For example, based on the extended sensors, raw data, processed data, or live video data obtained through the local sensors may be exchanged between a vehicle, a logical entity, a UE of pedestrians, and/or a V2X application server. Therefore, for example, the vehicle may recognize a more improved environment than an environment in which a self-sensor is used for detection.

For example, based on the remote driving, for a person who cannot drive or a remote vehicle in a dangerous environment, a remote driver or a V2X application may operate or control the remote vehicle. For example, if a route is predictable such as public transportation, cloud computing based driving may be used for the operation or control of the remote vehicle. In addition, for example, an access for a cloud-based back-end service platform may be considered for the remote driving.

Meanwhile, a scheme of specifying service requirements for various V2X scenarios such as vehicle platooning, advanced driving, extended sensors, remote driving, or the like is discussed in NR-based V2X communication.

In <NPL>", time/frequency resource determination for PSFCH and indication for retransmission are discussed.

In <NPL>", the following design aspects on sidelink physical layer procedures are discussed: sidelink HARQ operations, sidedlink CSI acquisitions, and sidelink power control.

In <NPL>", QoS design issues for communication types used in NR V2X sidelink communication are discussed.

The technical problem of the present disclosure is to provide a side link communication method between devices (or terminals) and a device (or terminal) performing the same.

Features of certain embodiments are defined in the dependent claims.

According to the present disclosure, a UE (or apparatus) may efficiently perform SL communication.

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.

The technology described below may be used in various wireless communication systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and the like. The OFDMA may be implemented with a radio technology, such as institute of electrical and electronics engineers (IEEE) <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, evolved UTRA (E-UTRA), and the like.

<NUM> NR is a successive technology of LTE-A corresponding to a new Clean-slate type mobile communication system having the characteristics of high performance, low latency, high availability, and the like. <NUM> NR may use resources of all spectrum available for usage including low frequency bands of less than <NUM>, middle frequency bands ranging from <NUM> to <NUM>, high frequency (millimeter waves) of <NUM> or more, and the like.

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

For example, the UE <NUM> may be fixed or mobile and may be referred to as other terms, such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, and the like. For example, the BS may be referred to as a fixed station which communicates with the UE <NUM> and may be referred to as other terms, such as a base transceiver system (BTS), an access point (AP), and the like.

<FIG> shows a functional division between an NG-RAN and a 5GC in accordance with an embodiment of the present disclosure.

Referring to <FIG>, the gNB may provide functions, such as Inter Cell Radio Resource Management (RRM), Radio Bearer (RB) control, Connection Mobility Control, Radio Admission Control, Measurement Configuration & Provision, Dynamic Resource Allocation, and the like. An AMF may provide functions, such as non access stratum (NAS) security, idle state mobility processing, and the like. A UPF may provide functions, such as mobility anchoring, protocol data unit (PDU) processing, and the like. A session management function (SMF) may provide functions, such as user equipment (UE) Internet protocol (IP) address allocation, PDU session control, and the like.

Layers of a radio interface protocol between the UE and the network can be classified into a first layer (L1), a second layer (L2), and a third layer (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> show a radio protocol architecture in accordance with an embodiment of the present disclosure.

The embodiments of <FIG> may be combined with various embodiments of the present disclosure. Specifically, <FIG> shows a radio protocol architecture for a user plane, and <FIG> shows a radio protocol architecture for a control plane. The user plane corresponds to a protocol stack for user data transmission, and the control plane corresponds to a protocol stack for control signal transmission.

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., the MAC layer, the RLC layer, and the packet data convergence protocol (PDCP) layer) for data delivery between the UE and the network.

Examples of logical channels belonging to a higher channel of the transport channel and mapped onto the transport channels include a broadcast channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), a multicast traffic channel (MTCH), or the like.

The physical channel includes several OFDM symbols in a time domain and several sub-carriers in a frequency domain. One sub-frame includes a plurality of OFDM symbols in the time domain. A resource block is a unit of resource allocation, and consists of a plurality of OFDM symbols and a plurality of sub-carriers. Further, each subframe may use specific sub-carriers of specific OFDM symbols (e.g., a first OFDM symbol) of a corresponding subframe for a physical downlink control channel (PDCCH), i.e., an L1/L2 control channel. A transmission time interval (TTI) is a unit time of subframe transmission.

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).

Here, a symbol may include an OFDM symbol (or CP-OFDM symbol) and a Single Carrier-FDMA (SC-FDMA) symbol (or Discrete Fourier Transform-spread-OFDM (DFT-s-OFDM) symbol).

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.

In an NR system, OFDM(A) numerologies (e.g., SCS, CP length, and the like) between multiple cells being integrate to one UE may be differently configured.

The values of the frequency ranges may be changed (or varied), and, for example, the two different types of frequency ranges may be as shown below in Table A3.

For example, as shown below in Table A4, FR1 may include a band within a range of <NUM> to <NUM>. More specifically, FR1 may include a frequency band of <NUM> (or <NUM>, <NUM>, <NUM>, and the like) and higher. For example, a frequency band of <NUM> (or <NUM>, <NUM>, <NUM>, and the like) and higher being included in FR1 mat include an unlicensed band.

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

A bandwidth part (BWP) may be defined as a plurality of consecutive (physical) resource blocks ((P)RBs) in the frequency domain, and the BWP may correspond to one numerology (e.g., SCS, CP length, and the like).

Meanwhile, a radio interface between a UE and another UE or a radio interface between the UE and a network may consist of an L1 layer, an L2 layer, and an L3 layer. In various embodiments of the present disclosure, the L1 layer may imply a physical layer. In addition, for example, the L2 layer may imply at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. In addition, for example, the L3 layer may imply an RRC layer.

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.

When using bandwidth adaptation (BA), a reception bandwidth and transmission bandwidth of a UE are not necessarily as large as a bandwidth of a cell, and the reception bandwidth and transmission bandwidth of the BS may be adjusted. For example, a network/BS may inform the UE of bandwidth adjustment. For example, the UE receive information/configuration for bandwidth adjustment from the network/BS. In this case, the UE may perform bandwidth adjustment based on the received information/configuration. For example, the bandwidth adjustment may include an increase/decrease of the bandwidth, a position change of the bandwidth, or a change in subcarrier spacing of the bandwidth.

For example, the bandwidth may be decreased during a period in which activity is low to save power. For example, the position of the bandwidth may move in a frequency domain. For example, the position of the bandwidth may move in the frequency domain to increase scheduling flexibility. For example, the subcarrier spacing of the bandwidth may be changed. For example, the subcarrier spacing of the bandwidth may be changed to allow a different service. A subset of a total cell bandwidth of a cell may be called a bandwidth part (BWP). The BA may be performed when the BS/network configures the BWP to the UE and the BS/network informs the UE of the BWP currently in an active state among the configured BWPs.

For example, the UE may not receive PDCCH, PDSCH, or CSI-RS (excluding RRM) outside the active DL BWP. For example, the UE may not transmit PUCCH or PUSCH outside an active UL BWP. For example, in a downlink case, the initial BWP may be given as a consecutive RB set for an RMSI CORESET (configured by PBCH). For example, in an uplink case, the initial BWP may be given by SIB for a random access procedure. For energy saving, if the UE fails to detect DCI during a specific period, the UE may switch the active BWP of the UE to the default BWP.

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. 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.

<FIG> and <FIG> show a radio protocol architecture for a SL communication in accordance with an embodiment of the present disclosure.

The embodiments of <FIG> and <FIG> may be combined with various embodiments of the present disclosure. More specifically, <FIG> shows a user plane protocol stack, and <FIG> shows a control plane protocol stack.

Hereinafter, a sidelink synchronization signal (SLSS) and synchronization information will be described.

The 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 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> and <FIG> show 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.

The embodiments of <FIG> and <FIG> may be combined with various embodiments 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, <FIG> shows a UE operation related to an LTE transmission mode <NUM> or an LTE transmission mode <NUM>. Alternatively, for example, <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, <FIG> shows a UE operation related to an LTE transmission mode <NUM> or an LTE transmission mode <NUM>. Alternatively, for example, <FIG> shows a UE operation related to an NR resource allocation mode <NUM>.

Referring to <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 (more specifically, downlink control information (DCI)), and the UE 1may 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 <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> show three cast types in accordance with an embodiment of the present disclosure.

The embodiments of <FIG> may be combined with various embodiments 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.

Meanwhile, in sidelink communication, a UE may need to effectively select a resource for sidelink transmission. Hereinafter, a method in which a UE effectively selects a resource for sidelink transmission and an apparatus supporting the method will be described according to various embodiments of the present disclosure. In various embodiments of the present disclosure, the sidelink communication may include V2X communication.

At least one scheme proposed according to various embodiments of the present disclosure may be applied to at least any one of unicast communication, groupcast communication, and/or broadcast communication.

At least one method proposed according to various embodiment of the present embodiment may apply not only to sidelink communication or V2X communication based on a PC5 interface or an SL interface (e.g., PSCCH, PSSCH, PSBCH, PSSS/SSSS, or the like) or V2X communication but also to sidelink communication or V2X communication based on a Uu interface (e.g., PUSCH, PDSCH, PDCCH, PUCCH, or the like).

In various embodiments of the present disclosure, a receiving operation of a UE may include a decoding operation and/or receiving operation of a sidelink channel and/or sidelink signal (e.g., PSCCH, PSSCH, PSFCH, PSBCH, PSSS/SSSS, or the like). The receiving operation of the UE may include a decoding operation and/or receiving operation of a WAN DL channel and/or a WAN DL signal (e.g., PDCCH, PDSCH, PSS/SSS, or the like). The receiving operation of the UE may include a sensing operation and/or a CBR measurement operation. In various embodiments of the present disclosure, the sensing operation of the UE may include a PSSCH-RSRP measurement operation based on a PSSCH DM-RS sequence, a PSSCH-RSRP measurement operation based on a PSSCH DM-RS sequence scheduled by a PSCCH successfully decoded by the UE, a sidelink RSSU (S-RSSI) measurement operation, and an S-RSSI measurement operation based on a V2X resource pool related subchannel. In various embodiments of the disclosure, a transmitting operation of the UE may include a transmitting operation of a sidelink channel and/or a sidelink signal (e.g., PSCCH, PSSCH, PSFCH, PSBCH, PSSS/SSSS, or the like). The transmitting operation of the UE may include a transmitting operation of a WAN UL channel and/or a WAN UL signal (e.g., PUSCH, PUCCH, SRS, or the like). In various embodiments of the present disclosure, a synchronization signal may include SLSS and/or PSBCH.

In various embodiments of the present disclosure, a configuration may include signaling, signaling from a network, a configuration from the network, and/or a pre-configuration from the network. In various embodiments of the present disclosure, a definition may include signaling, signaling from a network, a configuration form the network, and/or a pre-configuration from the network. In various embodiment of the present disclosure, a designation may include signaling, signaling from a network, a configuration from the network, and/or a pre-configuration from the network.

In various embodiments of the present disclosure, a ProSe per packet priority (PPPP) may be replaced with a ProSe per packet reliability (PPPR), and the PPPR may be replaced with the PPPP. For example, it may mean that the smaller the PPPP value, the higher the priority, and that the greater the PPPP value, the lower the priority. For example, it may mean that the smaller the PPPR value, the higher the reliability, and that the greater the PPPR value, the lower the reliability. For example, a PPPP value related to a service, packet, or message related to a high priority may be smaller than a PPPP value related to a service, packet, or message related to a low priority. For example, a PPPR value related to a service, packet, or message related to a high reliability may be smaller than a PPPR value related to a service, packet, or message related to a low reliability.

In various embodiments of the present disclosure, a session may include at least any one of a unicast session (e.g., unicast session for sidelink), a groupcast/multicast session (e.g., groupcast/multicast session for sidelink), and/or a broadcast session (e.g., broadcast session for sidelink).

In various embodiments of the present disclosure, a carrier may be interpreted as at least any one of a BWP and/or a resource pool. For example, the carrier may include at least any one of the BWP and/or the resource pool. For example, the carrier may include one or more BWPs. For example, the BWP may include one or more resource pools.

In an embodiment, according to TR <NUM>, the minimum required range is a physical layer parameter in meters (defined by upper layers) useful for QoS management.

RAN1#96bis had discussed this issue in the context of sidelink HARQ feedback. The so called "distance-based HARQ feedback" was discussed and the following working assumption described below in Table <NUM> was made in the last RAN1#96bis meeting:.

The main idea is that, if an RX UE is outside the minimum communication range, it does not need to send HARQ feedback because reliable packet delivery to that specific RX UE is not essential (may cause unnecessary interference). An example of agreements related to SL HARQ feedback for groupcast is disclosed in below Table <NUM>.

An example of SA2 Proposal is as follows. The range also determines whether a particular QoS parameter can be applied, otherwise SL communication is best effort [R2-<NUM>]. - QoS parameter <NUM> is applicable when destination (receiver) UE < X meters , QoS parameter <NUM> is applicable when destination (receiver) UE < Y meters, etc. Currently, there are no mechanisms specified for location-based blind retransmissions.

Due to the short-range communication nature of the PC5 (sidelink, SL) communications, the varying geographical distance between a source (transmitting) UE and destination (receiving) UE can impact the performance of SL communications. This high mobility variation of vehicular UEs (e.g. travelling in same or opposite directions with different speeds), can result in frequent variations in the geographical distance, which can impact the reliability, and therefore the quality of a particular V2X service.

This disclosure provides details on enabling and adapting the number of blind retransmissions based on location information provided by a node.

The embodiments of the following disclosure are as follows:
In one embodiment, a method of performing retransmission in a UE is provided. The method includes: determining distance between the UE and a node; wherein the distance is determined based on location information received from the node, wherein the node is the other UE or the base station, performing a new transmission of a data unit to the node; determining a retransmission of the data unit based on the distance; wherein the maximum number of retransmissions is determined based on the distance.

In one embodiment, a method of performing retransmission in a UE is provided. The method includes: determining CSI-RSRP/SSB-RSRP/Other RSRP between the UE and a node; wherein the CSI-RSRP/SSB-RSRP/Other RSRP values is measured based on a report received from the node, wherein the node is the other UE or the base station, performing a new transmission of a data unit to the node; determining a retransmission of the data unit based on the CSI-RSRP/SSB-RSRP/Other RSRP; wherein the maximum number of retransmissions is determined based on the CSI-RSRP/SSB-RSRP/Other RSRP values.

In one embodiment, a method according to the above embodiments is provided. Wherein the following physical layer parameters may be adapted: UE transmit power (maximum or minimum), MCS (Modulation Coding Scheme) level, MIMO transmission modes and number of layers.

One of the main applications of the proposed embodiments are intended for enhancing the reliability of UEs involved in sidelink communications. The procedures of the embodiment pertaining to a method of performing a retransmission can be described as follows: determining parameters such as the distance estimate/ CSI-RSRP/SSB-RSRP/Other RSRP between a UE and a node.

A transmitting UE may receive the distance information with respect to another node which may be a: base station, UE or Road Side Unit (RSU).

The distance estimate is either computed using Radio Access Terminal (RAT) dependent or independent positioning techniques. Additional assistance data may be used to compute the distance estimate and this may include a node's location and timing-related information.

The CSI-RSRP/SSB-RSRP/Other RSRP values are normally determined using layer-<NUM> measurements.

<FIG> shows an example of adaptive blind retransmissions when HARQ is enabled.

In an embodiment, a method of performing a new transmission is provided. This method may be used in conjunction with HARQ to reduce the overhead signaling from HARQ feedback. The following case is considered:.

NOTE: In Step <NUM>), the transmitting UE may also configure the initial transmissions with K<NUM> retransmission based on distance, CSI-RSRP/SSB-RSRP/Other RSRP measurements.

The distance estimate between a UE and a node along with other parameters such as channel state information (CSI) reference signal received power (RSRP), synchronization signal block (SSB) RSRP or any other RSRP measurements may also aid the transmitting UE in determining whether retransmissions are required. This can be determined before a new data unit/packet is ready for transmission.

In description of <FIG> below, case <NUM> regarding when HARQ is disabled is followed.

<FIG> shows an example of adaptive blind retransmissions when HARQ is disabled.

The mechanism can be directly applied with a single step and application of Table <NUM> as shown below.

In one embodiment, a method for performing K<NUM> blind retransmissions is provided. Upon enabling blind retransmissions, the distance estimate, CSI-RSRP/SSB-RSRP/Other RSRP may also assist the UE in selecting the required number of retransmissions. Example, if the distance estimate falls within a specified distance interval, then the UE can determine the appropriate number of retransmissions. Table <NUM> shows an exemplary mapping of the possible link parameters to the number of retransmissions (K<NUM>). In one embodiment, mapping information of Table <NUM> may be applied to both case <NUM> and case <NUM> described above.

If either of the above link parameters are unavailable, the UE may fallback to the normal HARQ feedback procedure or default number of K<NUM> (or K<NUM>)blind retransmissions. Furthermore, the example shows a basic categorization CSI-RS and SSB RSRP measurement intervals (low, medium and high) which are mapped to the required number of retransmissions. The parameters rMax, CSI-RSRP Max and SSB-RSRP Max are upper bounded values where if exceeded, the maximum number of retransmissions (KMax) are selected. In order to cater for UE flexibility, the number of retransmissions (K<NUM> or K<NUM>) can be chosen from a set of a predefined size (e.g. Table <NUM> shows the K<NUM> (or K<NUM>)-values with set size of <NUM> corresponding to each interval).

The above proposals can be combined. The proposed method can be implemented by various devices described below.

Data unit(s) (e.g. PDCP SDU, PDCP PDU, RLC SDU, RLC PDU, RLC SDU, MAC SDU, MAC CE, MAC PDU) in the present disclosure is(are) transmitted/received on a physical channel (e.g. PDSCH, PUSCH) based on resource allocation (e.g. UL grant, DL assignment). In the present disclosure, uplink resource allocation is also referred to as uplink grant, and downlink resource allocation is also referred to as downlink assignment. The resource allocation includes time domain resource allocation and frequency domain resource allocation. In the present disclosure, an uplink grant is either received by the UE dynamically on PDCCH, in a Random Access Response, or configured to the UE semi-persistently by RRC. In the present disclosure, downlink assignment is either received by the UE dynamically on the PDCCH, or configured to the UE semi-persistently by RRC signaling from the BS.

In one embodiment, location information is exploited to enable and adapt the number of re-transmissions for efficient and reliable transmissions.

In one embodiment, UEs with higher reported range may dynamically increase the number of blind re-transmissions to enhance the reliability of transmissions.

In one embodiment, excessive HARQ feedback signaling overhead can be avoided by switching to distance-based blind retransmissions.

<FIG> is a flowchart illustrating the operation of a first apparatus in accordance with 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 another example, the operations disclosed in the flowchart of <FIG> may be performed in combination with the individual operations of the embodiments disclosed in <FIG> and <FIG> by various methods.

In one example, the first apparatus and/or a second apparatus of <FIG> may correspond to a first wireless device <NUM> of <FIG> described below. In another example, the first apparatus and/or the second apparatus of <FIG> may correspond to a second wireless device <NUM> of <FIG> described below.

In operation S1410, the first apparatus according to an embodiment may perform initial transmission to a second apparatus based on transmission of first physical sidelink control channel (PSCCH) and first physical sidelink shared channel (PSSCH) related to the PSCCH.

In operation S1420, the first apparatus according to an embodiment may perform at least one of first retransmission to the second apparatus based on at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH.

In operation S1430, the first apparatus according to an embodiment may receive hybrid automatic repeat request negative acknowledgement (HARQ NACK) related to the initial transmission and the at least one of first retransmission from the second apparatus based on physical sidelink feedback channel (PSFCH).

In operation S1440, the first apparatus according to an embodiment may perform at least one of second retransmission to the second apparatus based on the reception of the HARQ NACK.

In one embodiment, the first apparatus may receive information on distance estimate between the first apparatus and the second apparatus from the second apparatus. The first apparatus may determine distance between the first apparatus and the second apparatus based on the information on distance estimate.

In one embodiment, number of the at least one of second retransmission is determined based on the distance between the first apparatus and the second apparatus.

In an example, the number of the at least one of the second retransmission may correspond to the K<NUM> disclosed in <FIG> and <FIG>.

In one embodiment, maximum number of the at least one of second retransmission is determined based on the distance between the first apparatus and the second apparatus.

In one embodiment, number range of the at least one of second retransmission is determined based on the distance between the first apparatus and the second apparatus.

In one embodiment, the first apparatus may receive at least one of information on reference signal received power (RSRP) for channel state information - reference signal (CSI-RS) or information on RSRP for synchronization signal block (SSB) from the second apparatus. And the first apparatus may determine at least one of the RSRP for the CSI-RS or the RSRP for the SSB based on the at least one of the information on the RSRP for the CSI-RS or the information on the RSRP for the SSB.

In one embodiment, number of the at least one of second retransmission is determined based on the at least one of the RSRP for the CSI-RS or the RSRP for the SSB.

In one embodiment, maximum number of the at least one of second retransmission is determined based on the at least one of the RSRP for the CSI-RS or the RSRP for the SSB.

In one embodiment, number range of the at least one of second retransmission is determined based on the at least one of the RSRP for the CSI-RS or the RSRP for the SSB.

In one embodiment, the second apparatus is one of user equipment (UE), a node or a base station.

In one embodiment, number of the at least one of first retransmission is determined based on the distance between the first apparatus and the second apparatus.

In an example, the number of the at least one of the first retransmission may correspond to the K<NUM> disclosed in <FIG> and <FIG>.

In one embodiment, number of the at least one of first retransmission is determined based on the at least one of the RSRP for the CSI-RS or the RSRP for the SSB.

In one embodiment, number of the at least one of first retransmission is determined based on configuration from a base station.

According to an embodiment of the present disclosure, a first apparatus for performing sidelink communication is provided. The first apparatus may include at least one memory to store instructions, at least one transceiver, and at least one processor to connect the at least one memory and the at least one transceiver, wherein the at least one processor may control the at least one transceiver to perform initial transmission to a second apparatus based on transmission of first physical sidelink control channel (PSCCH) and first physical sidelink shared channel (PSSCH) related to the PSCCH, control the at least one transceiver to perform at least one of first retransmission to the second apparatus based on at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH, control the at least one transceiver to receive hybrid automatic repeat request negative acknowledgement (HARQ NACK) related to the initial transmission and the at least one of first retransmission from the second apparatus based on physical sidelink feedback channel (PSFCH), and control the at least one transceiver to perform at least one of second retransmission to the second apparatus based on the reception of the HARQ NACK.

According to an embodiment of the present disclosure, an apparatus (or chip) configured to control a first UE is provided. The apparatus may include at least one processor and at least one computer memory that is connected to be executable by the at least one processor and stores instructions, wherein the at least one processor executes the instructions to cause the first UE to perform initial transmission to a second apparatus based on transmission of first physical sidelink control channel (PSCCH) and first physical sidelink shared channel (PSSCH) related to the PSCCH, perform at least one of first retransmission to the second apparatus based on at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH, receive hybrid automatic repeat request negative acknowledgement (HARQ NACK) related to the initial transmission and the at least one of first retransmission from the second apparatus based on physical sidelink feedback channel (PSFCH), and perform at least one of second retransmission to the second apparatus based on the reception of the HARQ NACK.

In one example, the first UE of the embodiment may indicate the first apparatus described throughout the present disclosure. In one example, each of the at least one processor, the at least one memory, and the like in the apparatus for controlling the first UE may be configured as a separate sub-chip, or at least two components thereof may be configured through a single sub-chip.

According to an embodiment of the present disclosure, a non-transitory computer-readable storage medium that stores instructions (or indications) is provided. When the instructions are executed, the instructions cause a first apparatus to: perform initial transmission to a second apparatus based on transmission of first physical sidelink control channel (PSCCH) and first physical sidelink shared channel (PSSCH) related to the PSCCH, perform at least one of first retransmission to the second apparatus based on at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH, receive hybrid automatic repeat request negative acknowledgement (HARQ NACK) related to the initial transmission and the at least one of first retransmission from the second apparatus based on physical sidelink feedback channel (PSFCH), and perform at least one of second retransmission to the second apparatus based on the reception of the HARQ NACK.

<FIG> is a flowchart illustrating the operation of a second apparatus in accordance with an embodiment of the present disclosure.

In one example, the first apparatus and/or a second apparatus of <FIG> may correspond to a second wireless device <NUM> of <FIG> described below. In another example, the first apparatus and/or the second apparatus of <FIG> may correspond to a first wireless device <NUM> of <FIG> described below.

In operation S1510, the second apparatus may receive initial transmission from a first apparatus based on first physical sidelink control channel (PSCCH) and first physical sidelink shared channel (PSSCH) related to the PSCCH.

In operation S1520, the second apparatus may receive at least one of first retransmission from the first apparatus based on at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH.

In operation S1530, the second apparatus may transmit hybrid automatic repeat request negative acknowledgement (HARQ NACK) related to the initial transmission and the at least one of first retransmission to the first apparatus based on physical sidelink feedback channel (PSFCH).

In operation S1540, the second apparatus may receive at least one of second retransmission from the first apparatus based on the transmitted HARQ NACK.

According to an embodiment of the present disclosure, a second apparatus for performing sidelink communication is provided. The second apparatus may include at least one memory storing instructions, at least one transceiver and at least one processor connected to the at least one memory and the at least one transceiver, wherein the at least one processor is configured to: control the at least one transceiver to receive initial transmission from a first apparatus based on first physical sidelink control channel (PSCCH) and first physical sidelink shared channel (PSSCH) related to the PSCCH, control the at least one transceiver to receive at least one of first retransmission from the first apparatus based on at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH, control the at least one transceiver to transmit hybrid automatic repeat request negative acknowledgement (HARQ NACK) related to the initial transmission and the at least one of first retransmission to the first apparatus based on physical sidelink feedback channel (PSFCH) and control the at least one transceiver to receive at least one of second retransmission from the first apparatus based on the transmitted HARQ NACK.

Various embodiments of the present disclosure may be independently implemented. Alternatively, the various embodiments of the present disclosure may be implemented by being combined or merged. For example, although the various embodiments of the present disclosure have been described based on the 3GPP LTE system for convenience of explanation, the various embodiments of the present disclosure may also be extendedly applied to another system other than the 3GPP LTE system. For example, the various embodiments of the present disclosure may also be used in an uplink or downlink case without being limited only to direct communication between terminals. In this case, a base station, a relay node, or the like may use the proposed method according to various embodiments of the present disclosure. For example, it may be defined that information on whether to apply the method according to various embodiments of the present disclosure is reported by the base station to the terminal or by a transmitting terminal to a receiving terminal through pre-defined signaling (e.g., physical layer signaling or higher layer signaling). For example, it may be defined that information on a rule according to various embodiments of the present disclosure is reported by the base station to the terminal or by a transmitting terminal to a receiving terminal through pre-defined signaling (e.g., physical layer signaling or higher layer signaling). For example, some embodiments among various embodiments of the present disclosure may be applied limitedly only to a resource allocation mode <NUM>. For example, some embodiments among various embodiments of the present disclosure may be applied limitedly only to a resource allocation mode <NUM>.

Hereinafter, an apparatus to which various embodiments of the present disclosure can be applied will be described.

<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, or the like 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.

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.

The first wireless device <NUM> may include one or more processors <NUM> and one or more memories <NUM> and additionally further include one or more transceivers <NUM> and/ or one or more antennas <NUM>. Herein, the processor(s) <NUM> and the memory(s) <NUM> may be a part of a communication modem/ circuit/chip designed to implement RAT (e.g., LTE or NR).

The second wireless device <NUM> may include one or more processors <NUM> and one or more memories <NUM> and additionally further include one or more transceivers <NUM> and/ or one or more antennas <NUM>. Herein, the processor(s) <NUM> and the memory(s) <NUM> may be a part of a communication modem/ circuit/chip designed to implement RAT (e.g., LTE or NR).

The one or more processors <NUM> and <NUM> may generate one or more protocol data units (PDUs) and/or one or more Service Data Unit (SDUs) according to the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document.

As an example, one or more application-specific integrated Circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field programmable gate arrays (FPGAs) may be included in the one or more processors <NUM> and <NUM>.

The one or more transceivers <NUM> and <NUM> may transmit user data, control information, and/or radio signals/channels, mentioned in the methods and/or operational flowcharts of this document, to one or more other apparatuses. The one or more transceivers <NUM> and <NUM> may receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document, from one or more other apparatuses. For example, the one or more processors <NUM> and <NUM> may perform control so that the one or more transceivers <NUM> and <NUM> may transmit user data, control information, or radio signals to one or more other apparatuses. In addition, the one or more processors <NUM> and <NUM> may perform control so that the one or more transceivers <NUM> and <NUM> may receive user data, control information, or radio signals from one or more other apparatuses. In addition, the one or more transceivers <NUM> and <NUM> may be connected to the one or more antennas <NUM> and <NUM> and the one or more transceivers <NUM> and <NUM> may be configured to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, proposals, methods, and/or operational flowcharts disclosed in this document, through the one or more antennas <NUM> and <NUM>. The one or more transceivers <NUM> and <NUM> may convert received radio signals/ channels or the like from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, or the like using the one or more processors <NUM> and <NUM>. The one or more transceivers <NUM> and <NUM> may convert the user data, control information, radio signals/channels, or the like processed using the one or more processors <NUM> and <NUM> from the base band signals into the RF band signals.

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

An operation/function of <FIG> may be performed by, without being limited to, the processors <NUM> and <NUM> and/or the transceivers <NUM> and <NUM> of <FIG>.

A modulation scheme may include pi/<NUM>-binary phase shift keying (pi/<NUM>-BPSK), m-phase shift keying (m-PSK), and m-quadrature amplitude modulation (m-QAM).

For this purpose, the signal generators <NUM> may include inverse fast Fourier transform (IFFT) modules, cyclic prefix (CP) inserters, digital-to-analog converters (DACs), and frequency up-converters.

To this end, the signal restorers may include frequency downlink converters, analog-to-digital converters (ADCs), CP remover, and fast Fourier transform (FFT) modules.

<FIG> shows a wireless device in accordance with an embodiment of the present disclosure. The wireless device may be implemented in various forms according to a use-case/service (see <FIG>).

For example, the control unit <NUM> may control an electric/mechanical operation of the wireless device based on programs/ code/commands/information stored in the memory unit <NUM>. In addition, the control unit <NUM> may transmit the information stored in the memory unit <NUM> to the exterior (e.g., other communication devices) via the communication unit <NUM> through a wireless/wired interface or store, in the memory unit <NUM>, information received through the wireless/wired interface from the exterior (e.g., other communication devices) via the communication unit <NUM>.

The wireless device may be implemented in the form of, without being limited to, the robot (100a of <FIG>), the vehicles (100b-<NUM> and 100b-<NUM> of <FIG>), the XR device (100c of <FIG>), the hand-held device (100d of <FIG>), the home appliance (100e of <FIG>), the IoT device (100f of <FIG>), a digital broadcast terminal, a hologram device, a public safety device, an MTC device, a medicine device, a fintech device (or a finance device), a security device, a climate/environment device, the AI server/device (<NUM> of <FIG>), the BSs (<NUM> of <FIG>), a network node, or the like The wireless device may be used in a mobile or fixed place according to a use-example/service.

As an example, the control unit <NUM> may be configured by a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphical processing unit, and a memory control processor. As another example, the memory <NUM> may be configured by a random access memory (RAM), a dynamic RAM (DRAM), a read-only memory (ROM)), a flash memory, a volatile memory, a non-volatile memory, and/or a combination thereof.

<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).

Blocks <NUM> to <NUM>/140a to 140c correspond to the blocks <NUM> to <NUM>/<NUM> of <FIG>, respectively.

The control unit <NUM> may include an application processor (AP). In addition, the memory unit <NUM> may store input/output data/information. The power supply unit 140a may supply power to the hand-held device <NUM> and include a wired/wireless charging circuit, a battery, or the like. The interface unit 140b may support connection of the hand-held device <NUM> to other external devices.

The communication unit <NUM> may receive radio signals from other wireless devices or the BS and then restore the received radio signals into original information/ signals.

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

Referring to <FIG>, a car or autonomous vehicle <NUM> may include an antenna unit <NUM>, a communication unit <NUM>, a control unit <NUM>, a driving unit 140a, a power supply unit 140b, a sensor unit 140c, and an autonomous driving unit 140d.

The control unit <NUM> may include an electronic control unit (ECU). The driving unit 140a may include an engine, a motor, a powertrain, a wheel, a brake, a steering device, or the like The power supply unit 140b may supply power to the vehicle or the autonomous vehicle <NUM> and include a wired/wireless charging circuit, a battery, or the like The sensor unit 140c may acquire a vehicle state, ambient environment information, user information, or the like. The sensor unit 140c may include an inertial measurement unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, a slope sensor, a weight sensor, a heading sensor, a position module, a vehicle forward/backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illumination sensor, a pedal position sensor, or the like. The autonomous driving unit 140d may implement technology for maintaining a lane on which a vehicle is driving, technology for automatically adjusting speed, such as adaptive cruise control, technology for autonomously driving along a determined path, technology for driving by automatically setting a path if a destination is set, and the like.

For example, the communication unit <NUM> may receive map data, traffic information data, or the like 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 addition, 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, or the like, 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 sidelink communication (150b) by a first apparatus (<NUM>, <NUM>), the method comprising:
receiving information on reference signal received power, RSRP, for channel state information - reference signal, CSI-RS, from a second apparatus;
determining the RSRP for the CSI-RS, based on the information on the RSRP for the CSI-RS;
performing (S1410) initial transmission to the second apparatus through first physical sidelink control channel, PSCCH, and first physical sidelink shared channel, PSSCH, related to the PSCCH;
performing (S1420) at least one of first retransmission to the second apparatus through at least one of second PSCCH and at least one of second PSSCH related to the at least one of second PSCCH;
receiving (S1430) hybrid automatic repeat request negative acknowledgement, HARQ NACK, related to the initial transmission and the at least one of first retransmission from the second apparatus through physical sidelink feedback channel, PSFCH; and
performing (S1440) at least one of second retransmission to the second apparatus based on the reception of the HARQ NACK,
wherein a number of the at least one of second retransmission is determined based on mapping information between a number of retransmissions and the RSRP for the CSI-RS.