Method and user equipment for performing sidelink communication

Abstract

A method and a user equipment (UE) for performing sidelink (SL) communication are provided. The method includes performing SL transmission based on a first set of timers configured for controlling SL discontinuous transmission (DTX) behavior of the UE, and performing SL reception based on a second set of timers configured for controlling SL discontinuous reception (DRX) behavior of the UE, wherein at least one first timer value in the first set of timers and at least one second timer value in the second set of timers are independently configured.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Patent Application No. 63 / 031,510, entitled “INTER-UE SIDELINK CONTINUOUS TRANSMISSION AND RECEPTION OPERATI ON”, filed May 28, 2020 (hereinafter referred to as “'510 Provisional Case”), and U.S. Provisional Patent Application No. 63 / 028,502, entitled “ADAPTATION OF RESOURED SELECTION METHODS FOR SIDELINK COMMUNICATION”, filed May 21, 2020 (hereinafter referred to as “'510 Provisional Case”). For all purposes, the disclosures of '510 Provisional Case and '502 Provisional Case are hereby incorporated herein by reference in their entirety. Technical Field

[0003] This disclosure generally relates to wireless communication, and more specifically, to methods and user equipment (UE) for performing sidelink (SL) communication. Background Technology

[0004] With the massive growth in the number of connected devices and the rapid increase in user / network traffic, various efforts have been made to improve different aspects of wireless communication in next-generation wireless communication systems, such as fifth-generation (5G) New Radio (NR), by increasing data rates, latency, reliability, and mobility.

[0005] 5G NR systems are designed to provide flexibility and configurability to optimize network services and types to adapt to different use cases, such as enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliable and low-latency communication (URLLC).

[0006] However, with the continued increase in demand for radio access, there is a need to further improve wireless communication in next-generation wireless communication systems. Summary of the Invention

[0007] This disclosure relates to methods and user equipment (UE) for adaptive resource selection methods.

[0008] According to one aspect of this disclosure, a method for performing side-link (SL) communication is provided. The method includes: performing SL transmission based on a first timer set configured to control SL discontinuous transmission (DTX) behavior of the UE; and performing SL reception based on a second timer set configured to control SL discontinuous reception (DRX) behavior of the UE, wherein at least one first timer value in the first timer set and at least one second timer value in the second timer set are independently configured.

[0009] According to another aspect of the present invention, a UE for performing SL communication is provided. The UE includes a transceiver and at least one hardware processor coupled to the transceiver. The at least one hardware processor is configured to: control the transceiver to perform SL transmission based on a first timer set, the first timer set being configured to control the UE's SLDTX behavior; and control the transceiver to perform SL reception based on a second timer set, the second timer set being configured to control the UE's SL DRX behavior, wherein at least one first timer value in the first timer set and at least one second timer value in the second timer set are independently configured. Attached Figure Description

[0010] When with attachment Figure 1 When reading this document, it is best to understand the various aspects of the embodiments from the following detailed description. The features are not drawn to scale. For clarity of discussion, the sizes of the features may be arbitrarily increased or decreased.

[0011] Figure 1 A process for fully sensing-based resource selection according to an embodiment of this disclosure is illustrated.

[0012] Figure 2 An exemplary scenario is shown where the SL discontinuous transmission and / or reception (DTRX) cyclic coordination problem occurs between different broadcast groups for an SL UE.

[0013] Figure 3 An SL DTRX operation for a multicast group operating in a negative acknowledgment only (NACK) feedback mode, according to an embodiment of this disclosure, is illustrated.

[0014] Figure 4 The process of independent SL transmission and SL reception control according to an embodiment of this disclosure is illustrated.

[0015] Figure 5 The temporal relationship between the SL DRX activation duration and the transport resource pool according to an embodiment of the present disclosure is shown.

[0016] Figure 6 This is a schematic diagram illustrating the temporal relationship between the SL DRX activation duration and the transmission resource pool according to an embodiment of the present disclosure.

[0017] Figure 7 A flowchart of a method for SL communication according to an embodiment of the present disclosure is shown.

[0018] Figure 8 An exemplary DRX operation according to an embodiment of this disclosure is shown.

[0019] Figure 9 This is a block diagram illustrating a node for wireless communication according to an embodiment of the present disclosure. Detailed Implementation

[0020] The following contains specific information relating to embodiments described in this disclosure. The accompanying drawings and their descriptions are for illustrative purposes only. However, this disclosure is not limited to these embodiments. Other variations and embodiments of this disclosure will be apparent to those skilled in the art.

[0021] Unless otherwise stated, the same or corresponding elements in the accompanying drawings may be indicated by the same or corresponding reference numerals. Furthermore, the figures and illustrations in this disclosure are generally not drawn to scale and are not intended to correspond to actual relative dimensions.

[0022] For the purposes of consistency and ease of understanding, similar features may be identified by the same numbers in the accompanying drawings (although not shown in some examples). However, features in different embodiments may differ in other respects and should not be narrowly limited to what is shown in the accompanying drawings.

[0023] The phrases “in one embodiment” or “in some embodiments” may each refer to one or more of the same or different embodiments. The term “coupled” is defined as a connection, whether direct or indirect through intermediate components, and is not necessarily limited to a physical connection. The term “comprising” means “including but not limited to”; it specifically indicates an open inclusion or membership in a disclosed combination, group, series, or equivalent. The expression “at least one of A, B, and C” or “at least one of A, B, and C” means: “only A, or only B, or only C, or any combination of A, B, and C.”

[0024] The terms "system" and "network" are used interchangeably. The term "and / or" is used only to disclose the relationships between related objects and indicates that three relationships may exist: A and / or B can mean A exists alone, A and B exist simultaneously, or B exists alone. "A and / or B and / or C" can mean that at least one of A, B, and C exists. The character " / " generally indicates that related objects are in an "or" relationship.

[0025] For purposes of explanation and non-limitation, specific details such as functional entities, technologies, protocols, and standards are described to provide an understanding of the disclosed technologies. In other examples, detailed descriptions of well-known methods, technologies, systems, architectures, etc., are omitted to avoid unnecessary ambiguity.

[0026] Those skilled in the art will readily recognize that any disclosed network function or algorithm can be implemented by hardware, software, or a combination of both. The described functions may correspond to modules, which can be software, hardware, firmware, or any combination thereof.

[0027] Software implementations may include computer-executable instructions stored on a computer-readable medium such as memory or other types of storage devices. One or more microprocessors or general-purpose computers with communication processing capabilities may be programmed using the corresponding computer-executable instructions to perform the disclosed network functions or algorithms.

[0028] These microprocessors or general-purpose computers may include application-specific integrated circuits (ASICs), programmable logic arrays, and / or use one or more digital signal processors (DSPs). While some of the disclosed embodiments are geared toward software installed and executed on computer hardware, alternative embodiments implemented as firmware or hardware or a combination of hardware and software are also fully within the scope of this disclosure. Computer-readable media include, but are not limited to, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, compact disc read-only memory (CD-ROM), magnetic tape, magnetic tape, disk storage, or any other equivalent medium capable of storing computer-readable instructions.

[0029] Radio communication network architectures such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), LTE-Advanced Pro, or 5G NR Radio Access Networks (RANs) typically include at least one base station (BS), at least one user equipment (UE), and one or more optional network elements providing network connectivity. The UE can communicate with networks such as the Core Network (CN), Evolved Packet Core (EPC), Evolved Universal Terrestrial Radio Access Network (E-UTRAN), Next-Generation Core (NGC), 5G Core (5GC), or the Internet through the RAN established by one or more BSs.

[0030] The UE may include, but is not limited to, a mobile station, a mobile terminal or device, or a user communication radio terminal. The UE may be a portable wireless device, including but not limited to mobile phones, tablets, wearable devices, sensors, vehicles, or personal digital assistants (PDAs) with wireless communication capabilities. The UE may be configured to receive signals via an air interface and transmit signals to one or more cells in the RAN.

[0031] The BS can be configured to provide communication services based on at least one of the following radio access technologies (RATs): Worldwide Interoperability for Microwave Access (WiMAX), Global System for Mobile Communications (GSM), commonly referred to as 2G, GSM Enhanced Data Rate Radio Access Network (GERAN) for GSM evolution, General Packet Radio Service (GPRS), Universal Mobile Telecommunication System (UMTS), commonly referred to as 3G, based on Basic Wideband Code Division Multiple Access (W-CDMA), High-Speed ​​Packet Access (HSPA), LTE, LTE-A, Evolved / Enhanced LTE (eLTE), i.e., LTE connected to 5GC, NR (commonly referred to as 5G), and / or LTE-A Pro. However, the scope of this disclosure is not limited to these protocols.

[0032] A BS may include, but is not limited to: Node B (NB) in UMTS, Evolved Node B (eNB) in LTE or LTE-A, Radio Network Controller (RNC) in UMTS, BS Controller (BSC) in GSM / GERAN, next-generation eNB (ng-eNB) in an Evolved Universal Terrestrial Radio Access (E-UTRA) BS connected to 5GC, next-generation Node B (gNB) in 5G-RAN (or 5G Access Network (5G-AN)), and any other device capable of controlling radio communications and managing radio resources within the cell. A BS can serve one or more UEs through its radio interface.

[0033] A BS can use multiple cells included in the RAN to provide radio coverage to a specific geographic area. The BS can support cell operation. Each cell can operate to provide service to at least one UE within its radio coverage area.

[0034] Each cell (usually referred to as the serving cell) can provide services to one or more UEs within its radio coverage area, such that each cell schedules downlink (DL) and optional uplink (UL) resources to at least one UE within its radio coverage area for DL ​​and optional UL packet transmissions. A BS can communicate with one or more UEs in a radio communication system through multiple cells.

[0035] A cell can allocate sidelink (SL) resources to support Proximity Service (ProSe), LTE SL service, and / or LTE / NR Vehicle to Everything (V2X) service. Each cell can have coverage areas that overlap with other cells.

[0036] In Multi-RAT Dual Connectivity (MR-DC) scenarios, the primary cell of either the Master Cell Group (MCG) or Secondary Cell Group (SCG) can be referred to as a Special Cell (SpCell). A Primary Cell (PCell) can refer to the SpCell of the MCG. A Primary SCG Cell (PSCell) can refer to the SpCell of the SCG. An MCG can refer to the serving cell group associated with the Master Node (MN), including SpCells and one or more optional Scells. An SCG can refer to the serving cell group associated with the Secondary Node (SN), including SpCells and one or more optional Scells.

[0037] As previously mentioned, the frame structure for NR supports flexible configuration to accommodate various next-generation (e.g., 5G) communication requirements, such as eMBB, mMTC, and URLLC, while meeting high reliability, high data rate, and low latency requirements. Orthogonal Frequency Division Multiplexing (OFDM) technology in 3GPP can be used as the baseline for NR waveforms. Scalable OFDM digital schemes, such as adaptive subcarrier spacing, channel bandwidth, and cyclic prefix (CP), can also be used.

[0038] For NR, two coding schemes are considered: Low-Density Parity-Check (LDPC) codes and polar codes. Coding scheme adaptation can be configured based on channel conditions and / or the serving application.

[0039] At least DL transmission data, guard period, and UL transmission data should be included in the transmission time interval (TTI) of a single NR frame. The individual portions of the DL transmission data, guard period, and UL transmission data should also be configurable, based on, for example, NR network dynamics. SL resources can also be provided in NR frames to support ProSe or V2X services. In LTE systems, TTI is a time-domain scheduling unit and equals one subframe, with a subframe length of 1 millisecond (ms). Depending on the cyclic prefix (CP) length, a TTI consists of 12 or 14 symbols. In NR systems, TTI is represented as a time slot, which consists of 12 or 14 symbols depending on the cyclic prefix (CP). The time slot length can vary depending on a set of parameters (e.g., subcarrier spacing and / or CP length). For example, for a 15 kHz subcarrier spacing, one time slot = 1 ms = 1 subframe. However, for 30 kHz, one time slot = 0.5 ms.

[0040] Power consumption on the UE side is a primary design consideration for many wireless communication systems. This need has spurred various innovative techniques to achieve power-saving gains in scenarios such as cellular communication and vehicle-to-everything (V2X) communication. For example, Connected Mode Discontinuous Reception (C-DRX) has been implemented in the LTE / NR Uu interface as one of the enablers for power saving on the UE side. In LTE sidelink (SL) communication, partially sense-based resource selection and random resource selection are introduced to reduce power consumption for devices such as pedestrian UEs. Unfortunately, no power-saving mechanisms have yet been introduced for NR (V2X) SL communication.

[0041] In LTE-based V2X SL communication, the transport (TX) UE is allowed to select transport resources from a (pre)configured transport resource pool, such as SL transport mode 4 as specified in TS 36.213, e.g., V16.0.0. Sensing-based resource selection and random resource selection methods are supported. For sensing-based resource selection methods, both fully sensing-based and partially sensing-based methods are specified.

[0042] Random resource selection method: The UE identifies a set of candidate resources within the resource selection window. These candidate resources are called Candidate Single-Subframe Resources (CSRs). A CSR defines the time-frequency resources that can be used for SL data transmission. As long as the CSR does not violate the UE's transmission capacity constraints, the UE randomly selects a CSR for SL data transmission. As an example of UE transmission capacity constraints, the UE may not be able to transmit simultaneously on two specific carriers.

[0043] The fully sensing-based resource selection method involves the UE identifying a set of CSRs, such as the valid CSR set, within a resource selection window. Furthermore, sensing operations are performed within the sensing window. During the sensing operation, the UE can successfully decode one or more SL Control Information (SCIs) from one or more other SL UEs. The received SCIs can indicate their future transmission modes. If a CSR and / or its future resource reservation conflicts with the future transmission mode indicated by the received SCI, the CSR can be excluded from the valid CSR set. For subframes not listened to within the sensing window, hypothetical SCIs from the subframes can be assumed to be received. Hypothetical SCIs (SC1) are used to derive potential future transmission modes based on the transmission modes configured by Radio Resource Control (RRC). If a CSR or its associated future resource reservation conflicts with a potential future transmission mode associated with hypothetical SCIs (SC1), the CSR can also be excluded from the valid CSR set. The UE can randomly select a CSR from the valid CSR set.

[0044] Partial sensing-based resource selection method: Within the resource selection window, the UE can select Y subframes. The value of Y can be equal to or greater than the (pre)configured number. The CSRs associated with the selected Y subframes can constitute a valid CSR set. Furthermore, sensing operations are performed within the sensing window. The sensing operations ensure that at least a subset of the subframes in the sensing window, derived from at least Y subframes and information signals from the Network (NW), will be sensed. During the sensing operations, the UE can successfully decode one or more SCIs from one or more other SL UEs. The received SCIs can indicate their future transmission modes. If 1) a CSR and its future resource reservation conflict with the future transmission mode indicated by the received SCI, the CSR is excluded from the valid CSR set. The UE can randomly select CSRs from the valid CSR set.

[0045] Figure 1 A process for fully sensing-based resource selection according to an embodiment of this disclosure is illustrated. Assume that in time slot t... n(Time point n is located within) Resource selection triggered by the upper layer of the UE (e.g., RRC layer or MAC sublayer), the (resource) selection window 104 is defined as the duration [n+T1, n+T2] and the sensing window 102 is defined as the duration [n-T0, nT] proc,0 ],in

[0046] T0 is a time point configured via, for example, RRC signaling;

[0047] T proc,0 It is specified in the TS 38 series specifications to take UE processing time into account;

[0048] T1 can vary depending on the UE implementation, but is subject to the constraint: 0 ≤ T1 ≤ T proc,1 T proc,1 It is specified in the TS 38 series specifications to take into account UE processing time; and

[0049] T2 may vary depending on the UE implementation, but is subject to the following constraints:

[0050] If the remaining PDB > T 2min (prio TX ), then T 2min (prio TX ) ≤ T2 ≤ Remaining Packet Delay Budget (PDB), where T 2min (prio TX This can be indicated by NW and can be associated with a priority level that triggers resource selection. There may be only one priority, and therefore T... 2min It is merely a scalar, not a vector; and

[0051] If the remaining PDB < T 2min (prio TX If ), then T2 = remaining PDB.

[0052] Similar to the full sensing principle of LTE V2X, a valid set of candidate single-slot resources (CSRs) can be derived for resource selection / reservation in NR. As a result of resource selection, it can be... Figure 1 The selection of a set of half-persistent resources is shown, where the interval between the half-persistent resources is represented as resource reservation interval 106. For each half-persistent resource (e.g., each of half-persistent resource 110, half-persistent resource 120, and half-persistent resource 130), a number of associated retransmission resources of the same size may also be reserved during the selection period. The retransmission resources are used for retransmission of transport blocks (TBs).

[0053] DRX operation in NR Uu interference

[0054] The UE can be configured with DRX functionality, which controls the UE's PDCCH listening activity. When in RRC_CONNECTED mode, the UE does not need to continuously listen to the PDCCH when DRX is configured.

[0055] DRX operation can be determined by the following factors (1) through (4):

[0056] (1) On-duration: The duration during which the UE waits to receive the PDCCH after being woken up. If the UE successfully decodes the PDCCH, the UE remains awake and (re)starts the deactivation timer;

[0057] (2) Inactivity-timer: The UE waits for the duration of a successful PDCCH decoding, starting from the last successful decoding of the PDCCH. If the decoding fails, the UE can return to sleep. The UE should restart the inactivity-timer after a single successful decoding of the PDCCH used only for the first transmission (i.e., not for retransmission).

[0058] (3) Retransmission timer: The duration until a (HARQ) retransmission can be expected;

[0059] cycle: Specifies the periodic repetition of an on-time duration followed by a possible deactivation cycle;

[0060] (4) Active-Time: The total duration for which the UE listens to the PDCCH. For example... Figure 8 As shown, this includes the "on duration" of the DRX cycle, the time the UE is performing continuous reception while the deactivation timer has not expired, and the time the UE is performing continuous reception while waiting for a retransmission opportunity.

[0061] Table 1 shows exemplary UE behavior for DRX operation.

[0062] Table 1

[0063]

[0064]

[0065]

[0066] Regarding the DRX command MAC CE, it can be identified by a MAC subheader with LCID. It has a fixed size of zero bits.

[0067] The long DRX command MAC CE can be identified by a MAC subheader with an LCID. It has a fixed size of zero bits.

[0068] DRX configuration can refer to an information element (IE) represented as, for example, DRX-Config, which can be used to configure one or more DRX-related parameters. An example of an IE DRX-Config represented by Abstract Syntax Mark-1 (ASN.1) is shown in Table 2.

[0069] Table 2

[0070]

[0071]

[0072]

[0073] The definitions of the parameters described in Table 2 are shown in Table 3.

[0074] Table 3

[0075]

[0076] The following content may be used to further disclose terminology, examples, embodiments, implementation methods, actions, and / or behaviors:

[0077] Beam: The term "beam" can be replaced by a spatial filter. For example, when a UE reports a preferred gNB TX beam, the UE essentially selects the spatial filter used by the gNB. The term "beam information" is used to provide information about which beam / spatial filter is being used / selected. In one embodiment, separate reference signals are transmitted by applying individual beams (spatial filters). Thus, the term beam or beam information can be represented by one or more reference signal resource indices.

[0078] Antenna panel: A conceptual term for UE antenna implementations. A panel can be assumed to be an operational unit for controlling the transmit spatial filter (beam). A panel typically consists of multiple antenna elements. In one implementation, the beam can be formed by the panel, and two panels are required to form two beams simultaneously. This simultaneous beamforming from multiple panels is limited by UE capabilities. A similar definition of "panel" can be applied by considering spatial receive filtering characteristics.

[0079] HARQ: A function that ensures delivery between peer entities at Layer 1 (i.e., the physical layer). When the physical layer is not configured for downlink / uplink spatial multiplexing, a single HARQ process supports one Transport Block (TB). When the physical layer is configured for downlink / uplink spatial multiplexing, a single HARQ process supports one or more TBs. There is one HARQ entity per serving cell. Each HARQ entity supports a parallel (number) number of DL and UL HARQ processes.

[0080] Timers: A MAC entity can set one or more timers for a single purpose, such as triggering some uplink signaling retransmissions or limiting some uplink signaling retransmission cycles. Once started, a timer begins running and continues until stopped or expires; otherwise, it does not run. If a timer is not running, it can be started, or if it is running, it can be restarted. Timers always start or restart from their initial value. The initial value can be configured by the gNB via downlink RRC signaling, but is not limited to this.

[0081] BWP: A subset of the total cell bandwidth is called a Bandwidth Part (BWP), and Bandwidth Part adaptation is achieved by configuring BWPs for the UE and informing the UE which configured BWPs are currently active. To achieve Bandwidth Adaptation (BA) on a PCell, the gNB configures UL and DL BWPs for the UE. To enable BA on a SCell in the case of CA, the gNB configures the UE to have at least a DL BWP (i.e., there may be no DL BWP in the UL). For a PCell, the initial BWP is the BWP used for initial access. For a SCell, the initial BWP is the BWP configured for the UE that first operates under SCell activation. The UE can configure a first active uplink BWP via the firstActiveUplinkBWP IE. If the first active uplink BWP is configured for the SpCell, the firstActiveUplinkBWP IE field contains the ID of the UL BWP that will be activated during RRC (re)configuration. If this field is not present, RRC (re)configuration does not apply BWP handover. If the first active uplink BWP is configured for SCell, the firstActiveUplinkBWP IE field contains the ID of the portion of uplink bandwidth that will be used when the SCell is MAC activated.

[0082] Quasi-co-location (QCL): Two antenna ports are said to be quasi-co-located if the properties of the channel transmitting symbols on one antenna port can be inferred from the properties of the channel transmitting symbols on the other antenna port. The aforementioned "channel properties" may include Doppler shift, Doppler spread, average delay, delay spread, and spatial RX parameters. These properties are categorized into different QCL types in the NR specification. For example, QCL-Type D refers to spatial RX parameters. QCL-Type D is also referred to as "beaming" in this document.

[0083] Transmission Configuration Indication (TCI) Status: The TCI status contains parameters used to configure the QCL relationship between one or two DL reference signals and a target reference signal set. For example, the target reference signal set can be the DM-RS port of a PDSCH or PDCCH.

[0084] A sidelink (SL) communication link includes at least an SL TX UE and an SL receive (RX) UE. For power saving purposes, when an SL RX UE is not requested to listen for SL channel activation, its associated SL TX UE may not be requested / permitted to perform a transmission. In this sense, SL power saving mechanisms based on discontinuous operation (e.g., discontinuous transmission and / or receive (DTRX) operation) can involve both transmission and / or receive behaviors.

[0085] Unlike Uu DRX, SL DTRX operation can define both listening and transmitting behavior for the SL control / data / feedback channels based on timers similar to those defined for Uu DRX. To adapt to the purposes of defining SL transmission behavior, some timers may need to be modified to command transmit / receive behavior instead of the UL / DL in their Uu counterparts.

[0086] For example, in SL DTRX operation, more HARQ feedback options may be used compared to Uu DRX operation. Specifically, for multicast transmissions, both ACK / NACK feedback and NACK-only feedback are supported. It should be noted that, unless otherwise specified, the HARQ protocol in this disclosure is referred to as the SL HARQ protocol. Additionally or alternatively, in SL DTRX operation, a single SCI (or “single SCI message”) may indicate a retransmission resource in addition to the current transmission resource.

[0087] In addition, during SL DTRX operations, there may be inter-cast SL DTRX coordination issues and / or intra-cast SL DTRX coordination issues.

[0088] Inter-cast group SL DTRX coordination issue: Running timers can cause extended activation times triggered by specific broadcast groups, while other broadcast groups may remain in a shutdown state for extended periods. This can result in different SL DTRX states between different broadcast groups.

[0089] Intra-cast group SL DTRX coordination problem: By introducing only SL HARQ NACK feedback, members within the same broadcast group can experience different SL DTRX states.

[0090] Therefore, at least some embodiments of this disclosure provide control mechanisms for discontinuous SL operations to address the previously described coordination problems.

[0091] SL Discontinuous Transmission and / or Receive (DTRX) Operation

[0092] The SL DTRX control mechanism may involve at least one of the following timers (1) to (6):

[0093] (1) The SL on-duration timer (or “OnDurationTimer-SL timer”) defines the DTRX on-duration of the SL DTRX cycle. The OnDurationTimer-SL timer can be started periodically based on configuration. The OnDurationTimer-SL timer can be a timer per Medium Access Control (MAC) entity. The OnDurationTimer-SL timer can be started at the beginning of the DTRX cycle. For example, the OnDurationTimer-SL timer can be started after an offset from the start of the timeslot (of the DTRX cycle) (e.g., timeslot offset). Whether the timer should be started can be controlled by specific indications (e.g., specific downlink control information (DCI) for power saving).

[0094] (2) The deactivation timer for SL (or "InactivityTimer-SL timer") is defined as an additional activation time following the sensing of SL activation during the DTRX activation period. SL activation can refer to one or a combination of the following events (i) to (vi):

[0095] (i) Physical Sidelink Control Channel (PSCCH) monitoring.

[0096] (ii) PSCCH transmission and / or reception.

[0097] (ii) Transmission and / or reception of the Physical Sidelink Shared Channel (PSSCH).

[0098] (iv) Transmission and / or reception of the Physical Sidelink Feedback Channel (PSFCH).

[0099] (v) SL Synchronization Signal (SS) / (Physical Broadcast Channel (PBCH) block transmission, if the relevant UE is the synchronization source for repeated transmission of SL SS / PBCH blocks.

[0100] (vi)SL SS / PBCH block listener / receiver.

[0101] In one implementation, SL activation can be defined by PSCCH transmission and / or PSCCH listening.

[0102] In one implementation, the InactivityTimer-SL timer can be a per-MAC entity timer. The InactivityTimer-SL timer can be started when an SL activation associated with the corresponding MAC entity is identified. In one implementation, the InactivityTimer-SL timer can be started when an SL activation associated with the first / initial transmission of a TB is identified. In one implementation, a Transport Block (TB) can be (re)transmitted across multiple resource reservation periods. The first transmission of a TB corresponds to the first resource reservation period among multiple resource reservation periods. In one implementation, a TB can be (re)transmitted across multiple resource reservation periods. The first transmission of a TB corresponds to all first transmissions across multiple resource reservation periods. In one implementation, the InactivityTimer-SL timer can be started in the first symbol after SL activation has ended. In one implementation, the InactivityTimer-SL timer can be started when resources for SL activation are provided. For example, the InactivityTimer-SL timer can be started when an SL authorization is received via UuDCI signaling.

[0103] (3) A Hybrid Automatic Repeat Request (HARQ) Round Trip Time (RTT) timer (or “HARQ-RTT-Timer-SL-TX timer”) for SL transmissions, which defines the minimum duration prior to an executable retransmission, or the retransmission resources associated with an earlier SL transmission of the SL-TX UE, are authorized. The RTT-TX timer may herein be a timer per HARQ process (or “HARQ-process-specific timer”, which may be used interchangeably in this disclosure).

[0104] In one implementation, the HARQ-RTT-Timer-SL-TX timer may be started after an expected / received SLHARQ-ACK transmission from the peer SL RX UE corresponding to the SL transmission. In one implementation, the HARQ-RTT-Timer-SL-TX timer may be (re)started after the corresponding SL transmission ends. In one implementation, the HARQ-RTT-Timer-SL-TX timer may be started after the SL transmission on the PSCCH or PSSCH ends. In one implementation, the HARQ-RTT-Timer-SL-TX timer may be started at the first symbol after the SL transmission on the PSCCH or PSSCH ends. In one implementation, the HARQ-RTT-Timer-SL-TX timer may be started after the SL HARQ-ACK transmission ends. In one implementation, the timer may be started at the first symbol after the SL HARQ-ACK transmission ends. In one implementation, the HARQ-RTT-Timer-SL-TX timer may be started if SL HARQ feedback is enabled / indicated for the SL transmission. In one implementation, the indication may be included in the SL control channel associated with the SL transmission. In one implementation, the SL HARQ feedback option can be ACK / NACK or NACK only. In one implementation, the SL transmission associated with TB can span one or more resource reservation periods for (retransmission) transmission. The end time of the SL transmission can be determined based on the first transmission. The first transmission can be associated with the first / initial transmission in each resource reservation period. In one implementation, when HARQ-RTT-Timer-SL-TX expires, the TX UE can (begin) performing retransmission to the RX UE. The previously described SL transmissions may include transmissions of PSCCH and / or PSSCH.

[0105] (4) A HARQ RTT timer (or “HARQ-RTT-Timer-SL-RX timer”) for SL reception, which defines the minimum duration prior to a retransmission by the SL RX UE for an earlier SL transmission by the peer SL TX UE that may be expected / received. The HARQ-RTT-RX timer may be a timer per HARQ process. In one embodiment, the HARQ-RTT-Timer-SL-RX timer may be started at the end of SL reception from the peer SL TX UE. In one embodiment, the timer may be started after an SL HARQ-ACK transmission from the peer SL TX UE. In one embodiment, the HARQ-RTT-Timer-SL-RX timer may be started at the first symbol after the end of SL reception. The HARQ-RTT-Timer-SL-RX timer may be started when an SL HARQ ACK / NACK feedback is indicated, for example, by the SL control channel, or when a (SL) HARQ NACK feedback mode is indicated, for example, by the SL control channel. In one implementation, the activation of the HARQ-RTT-Timer-SL-RX timer may further require that the SL decoding result associated with SL reception is unsuccessful. The HARQ-RTT-Timer-SL-RX timer may not be activated if SL HARQ feedback is disabled via, for example, the SL control channel or SCI, or when HARQ feedback for SL NACK is indicated and the SL decoding result associated with SL reception is successful. The minimum configurable value of the RTT-RX timer guarantees the decoding time required for SL reception. The minimum configurable value may be related to the SL RX UE capability. The minimum configurable value of the RTT-RX timer guarantees the round-trip time between the TX and RX UEs.

[0106] SL transmissions from a peer SL TX UE may involve one or more (retransmission) transmissions. These (retransmission) transmissions may span one or more resource reservation periods. The end time of SL reception is determined based on the first transmission. The first transmission may be associated with the first transmission in each resource reservation period.

[0107] (5) A retransmission timer (or “RetransmissionTimer-SL-TX timer”) for SL transmissions, which defines the maximum duration until a retransmission is performed or a retransmission resource is authorized. The RetransmissionTimer-SL-TX timer can be a timer per HARQ process. The RetransmissionTimer-SL-TX timer can be started when its associated RTT-TX timer expires. The TX retransmission timer can be started when the earliest PSDCH associated with the latest SL (retransmission) transmission of the relevant HARQ process is expected / received. The RetransmissionTimer-SL-TX timer can be started if, for example, a subsequent retransmission of a TB associated with the most recent SL (retransmission) transmission of the HARQ process of interest is indicated by a higher layer. The start of the RetransmissionTimer-SL-TX timer may also require HARQ feedback to be disabled for, for example, the HARQ process of interest.

[0108] In one implementation, the RetransmissionTimer-SL-TX timer can be started at an offset after a new transmission has been performed. In one implementation, the RetransmissionTimer-SL-TX timer can be stopped while a RetransmissionTimer-SL-TX timer associated with the same HARQ process number is running. In one implementation, the RetransmissionTimer-SL-TX timer can be stopped when an acknowledgment (ACK) is received from the RX UE. When the RetransmissionTimer-SL-TX timer is running, the TX UE can perform retransmissions to the RX UE. When the RetransmissionTimer-SL-TX timer is not running, the TX UE may not perform retransmissions to the RX UE.

[0109] (6) A retransmission timer (or “RetransmissionTimer-SL-RX timer”) for SL reception, which defines the maximum duration until a retransmission is expected / received by the UE via SL RX. The RetransmissionTimer-SL-RX timer may be a timer per HARQ process. The RetransmissionTimer-SL-RX timer may be started when its associated RTT-RX timer expires and / or when the SL decoding result associated with the most recent SL reception of the relevant HARQ process is unsuccessful. The RetransmissionTimer-SL-RX timer may be started when the earliest PSDCH associated with the latest SL reception of the relevant HARQ process is expected / transmitted. The RetransmissionTimer-SL-RX timer may also be started if a subsequent retransmission of the TB associated with the latest SL reception of the relevant HARQ process is indicated, for example, by the SL control channel associated with the latest SL reception. The start of the RetransmissionTimer-SL-RX timer may also require HARQ feedback to be disabled for, for example, the relevant HARQ process. The RetransmissionTimer-SL-RX timer can be stopped while the HARQ-RTT-Timer-SL-RX associated with the same HARQ process number is running.

[0110] The timers per HARQ process described above can be configured with a set of specific timer values, where the timers per HARQ process can refer to the HARQ-RTT-Timer-SL-TX timer, the HARQ-RTT-Timer-SL-RX timer, the RetransmissionTimer-SL-TX timer, or the RetransmissionTimer-SL-RX timer.

[0111] Figure 2 This illustrates an exemplary scenario where the SL DTRX loop coordination problem occurs between different broadcast groups for SL UEs. For example... Figure 2As shown, SL UE#1202 is configured with four broadcast groups: unicast #1 (where SL UE#1202 communicates with SL UE 204 via unicast), unicast #2 (where SL UE#1202 communicates with SL UE 206 via unicast), multicast #1208 (where SL UE#1202 communicates with SL UE via multicast), and multicast #2210 (where SL UE#1202 communicates with SL UE via multicast). For each broadcast group, a subset of the HARQ process can be used for service switching on the broadcast group, resulting in four subsets of the HARQ process. For each subset of HARQ processes, the associated timer value for each HARQ process is provided / configured for each group, such that the first timer value of the HARQ-RTT-Timer-SL-TX timer associated with multicast #1208 can be different from the second timer value of the HARQ-RTT-Timer-SL-TX timer associated with multicast #2 210. Note that although in Figure 2 In this disclosure, the timer per HARQ process is presented as the HARQ-RTT-Timer-SL-TX timer; however, in other implementations, different types of timers per HARQ process, such as a deactivation timer per HARQ process, may be applied. In this disclosure, SL UE refers to a UE participating in SL communication.

[0112] For the SL UE, the SL UE is either active or OFF when the SL DTRX configuration is configured and / or activated. The SL UE may be active during at least one of the following timers: the onDuration-Timer, the InactivityTimer-SL timer, the RetransmissionTimer-SL-TX timer, and the RetransmissionTimer-SL-RX timer. Otherwise, the SL UE may be OFF. During the SL DTRX active period, the SL UE may need to listen for / receive or transmit the PSCCH and / or PSSCH. In another example, the SL UE may need to listen for / receive or transmit the PSCCH and / or PSFCH during the SL DTRX active period.

[0113] Inter-cast SL DTRX Coordination

[0114] High-level inter-cast group SL DTRX coordination can refer to the coordination of SL DTRX behavior between SL UEs in different broadcast groups associated with an SL UE. Figure 2The diagram illustrates an inter-multicast group SL DTRX coordination issue, where SL UE#1202 is configured with two multicast links and two unicast links. From the perspective of SL UE#1202, SL UE#1202 is in an active period due to transmit / receive activation in the unicast #1 link. The active period can be a result of a retransmission timer or a deactivation timer running in the SL. However, from the perspective of the SL UEs in multicast #1208, multicast #2210, and unicast #2206, they may have entered the SLDTRX off period before the SLDTRX on duration timer expires due to a lack of transmit / receive activation. Any transmit / receive through SL UE#1202 to / from multicast #1208, multicast #2210, or unicast #2206 may not be monitored / responded to.

[0115] To prevent SL UE from transmitting to broadcast groups that may not be active, a specific group's disabler and / or SL can be used to activate the timer.

[0116] Group-specific disablers can be used, for example, for (UE's) configured groups. For instance, group G_i can be disabled when no timer associated with G_i is running, or enabled when at least one timer associated with G_i is running. In one implementation, the timer associated with G_i is a per-HARQ process timer. In another implementation, the timer associated with G_i is timer-specific per group.

[0117] The timer for each HARQ process can be a RetransmissionTimer-SL-TX timer and / or a RetransmissionTimer-SL-RX timer. The SL UE can be active while one of the onDuration-Timer, InactivityTimer-SL, RetransmissionTimer-SL-TX, and RetransmissionTimer-SL-RX timers is running. However, the group G_i of the SL UE can be active while the SL UE is also in an enabled state. Otherwise, the group G_i of the SL UE can be inactive (e.g., when it is in {onDuration-Timer, InactivityTimer-SL, RetransmissionTimer-SL-TX, RetransmissionTimer-SL-RX}).

[0118] If the SL UE is in an active period, but group G_j is in a disabled state, then SL activation associated with G_j may not occur. The SL deactivation timer can be used to define an additional activation period after SL activation is sensed during the active period.

[0119] As described above, SL activation may include one or a combination of the following events (i) to (vi):

[0120] (i) PSCCH monitoring.

[0121] (ii) PSCCH transmission and / or reception.

[0122] (iii) PSSCH transmission and / or reception.

[0123] (iv) PSFCH transmission and / or reception.

[0124] (v) SL SS / PBCH block transmission, if the UE of interest is the synchronization source for repeated transmission of SL SS / PBCH blocks.

[0125] (vi)SL SS / PBCH block listener / receiver.

[0126] (vii) In one implementation, the PSCCH listener, transmit and / or receive are considered SL active.

[0127] The SL deactivation timer can be a per-cast group timer, such as the InactivityTimer-SL-perGroup timer. The InactivityTimer-SL-perGroup timer can be started when an SL activation associated with the corresponding broadcast group of a MAC entity is identified. For example, in Figure 2 In this context, separate deactivation timers can be applied for multicast #1 208, multicast #2 210, unicast #1 (including SL UE204), and unicast #2 (including SL UE206). In one implementation, the broadcast group can be identified by its destination ID. The destination ID can be a Layer 2 ID or a Layer 1 ID derived from a Layer 2 ID provided by RRC signaling. In this sense, a timer for each group is dedicated to the corresponding destination ID.

[0128] In one implementation, the InactivityTimer-SL-perGroup timer can replace the aforementioned InactivityTimer-SL timer. The InactivityTimer-SL-perGroup timer and the InactivityTimer-SL timer may not coexist.

[0129] In one implementation, the additional activation time, as a result of the InactivityTimer-SL-perGroup timer, may only apply to the corresponding broadcast group.

[0130] For SL UE, the activation times for different broadcast groups can be different. S_HARQ_i represents the set of HARQ process numbers for SL transmission / reception for broadcast group G_i. Broadcast group G_i can be in the activation time when one of the following timers (1) to (4) is running.

[0131] (2)InactivityTimer-SL-perGroup_G_i, which is the deactivation timer associated with the broadcast group G_i.

[0132] (3) RetransmissionTimer-SL-TX_G_i, which includes one or more SL TX retransmission timers associated with the HARQ process set S_HARQ_i.

[0133] (4) RetransmissionTimer-SL-RX_G_i, which includes one or more SL RX retransmission timers associated with the HARQ process set S_HARQ_i.

[0134] The SL deactivation timer can be a timer per HARQ process, or InactivityTimer-SL-perHARQ. InactivityTimer-SL-perHARQ can be started when the SL activation associated with the corresponding HARQ process number of the MAC entity is identified.

[0135] In one implementation, InactivityTimer-SL-perHARQ can replace InactivityTimer-SL.

[0136] For SL UEs, the activation time can be different for different broadcast groups. S_HARQ_k represents the set of HARQ process numbers for SL transmission / reception for broadcast group G_k. Broadcast group G_i can be in the activation time when one of the following timers (1) to (4) is running:

[0137] (1) onDuration-Timer;

[0138] (2) InactivityTimer-SL-perGroup_G_k, which includes one or more deactivation timers associated with the HARQ process set S_HARQ_k.

[0139] (3) RetransmissionTimer-SL-TX_G_k, which includes one or more SL TX retransmission timers associated with the HARQ process set S_HARQ_k.

[0140] (4) RetransmissionTimer-SL-RX_G_k, which includes one or more SL RX retransmission timers associated with the HARQ process set S_HARQ_k.

[0141] Intra-cast SL DTRX Coordination

[0142] Intra-cast group SL DTRX coordination can refer to the coordination of SL DTRX behaviors between SL UEs within the same broadcast group.

[0143] Figure 3 The SL DTRX operation for a multicast group 310 operating in NACK-only feedback mode, according to an embodiment of this disclosure, is illustrated. Implementation details depend on, for example, the timer previously described. Figure 3 The DTRX states of the SL UEs shown (e.g., SLUE#1 302, SL UE#2 304, SL UE#3 306, and SL UE#4 308) may be inconsistent. The following example illustrates one possible such case:

[0144] -(SL) Only HARQ NACK feedback mode is indicated for use with respect to the TB of interest.

[0145] - The relevant TB decoding results were successful for SL UE#3 306 and SL UE#4 308, but unsuccessful for SL UE#2 304.

[0146] -SL UE#2 starts its HARQ-RTT-Timer-RX timer after indicating NACK in the associated PSDCH timing / transmission. SL UE#3 306 and SL UE#4 308 do not indicate ACK in the associated PSDCH timing / transmission, and therefore, their respective HARQ-RTT-Timer-RX timers do not start.

[0147] -SL UE#1302 starts its HARQ-RTT-Timer-TX timer after receiving a NACK from SL UE#2 in the associated PSDCH timing / reception.

[0148] - After the corresponding RTT timer expires, SL UE#1302 and SL UE#2304 start their RetransmissionTimer-SL-TX timer and RetransmissionTimer-SL-RX timer.

[0149] As a result, the activation times of SL UE#1302 and SL UE#2304 can be extended due to the running of their respective retransmission timers, while SL UE#3306 and SL UE#4308 can be in the OFF time because their retransmission timers are not started or stopped. It should be noted that here, it is assumed that the deactivation timer value for the SL multicast UEs is not configured or can be configured to a very small value. If supported, the transmission of PSSCH associated with the relevant TB may also not be accompanied by the associated PSCCH, causing the deactivation timers of the SL group UEs not to (re)start. Therefore, further multicast transmissions initiated by SL UE#1 302 or SL UE#2 304 may not be listened to by SL UE#3 306 and SL UE#4 308.

[0150] In one implementation, the SL UE can perform a retransmission associated with the failed TB if the retransmission timer associated with it is running. The retransmission timer can be a RetransmissionTimer-SL-TX timer. A new TB transmission can also be performed if the deactivation timer and / or the enable duration timer are running. If the enable time is extended solely due to the running of the retransmission timer associated with the failed TB of the SL UE, the SL UE may not expect to perform transmissions and / or receptions associated with the new TB. In one implementation, at least the deactivation timer and the enable duration timer are not running. In one implementation, the deactivation timer can be a group-specific timer associated with the listener broadcast group where the failed TB occurred. In one implementation, the deactivation timer can be a per-HARQ process timer associated with the HARQ process corresponding to the failed TB.

[0151] The above may be applicable when the running retransmission timer is associated with a HARQ process with a feedback option of NACK only.

[0152] Independent transmission and reception control

[0153] NR Uu DRX can be used to define the receive / listen requirements for DL ​​control channels (e.g., PDCCH). For SL, power savings can be achieved by applying separate controls to discontinuous reception (DRX) and discontinuous transmission (DTX).

[0154] For an SL UE with separate DRX / DTX control, its operation may include one or more of the following features (1) and (2):

[0155] (1) SL DRX can set behavioral restrictions for one or more of the following channels (i) to (iii):

[0156] (i) PSCCH monitoring.

[0157] (ii) PSSCH reception associated with PSCCH detection; and

[0158] (ii) PSFCH transmission associated with PSCCH / PSSCH detection.

[0159] (2) The SL DRX behavior restrictions for the above channels can be implemented based on the following timers (i) to (v):

[0160] (i) An on-duration timer (or “OnDurationTimer-SL-DRX timer”) for SL DRX that behaves similarly to the description of the OnDurationTimer-SL timer. For example, the OnDurationTimer-SL-DRX timer can define the DRX on-duration of an SL DRX cycle. The OnDurationTimer-SL-DRX timer can start periodically. The OnDurationTimer-SL-DRX timer can be a timer per MAC process. The OnDurationTimer-SL timer can start at the beginning of a DRX cycle. For example, the OnDurationTimer-SL-DRX timer can start after an offset from the start of a timeslot (e.g., a timeslot offset). Whether the timer should start can be controlled by specific indications (e.g., specific DCIs for power saving).

[0161] (ii) A deactivation timer (or “InactivityTimer-SL-DRX timer”) for SL DRX that behaves similarly to the descriptions of the InactivityTimer-SL timer, Inactivity-SL-perGroup timer, or Inactivity-SL-perHARQ timer. For example, after SL activation is sensed during the DRX activation period, the InactivityTimer-SL-DRX timer can define an additional activation period.

[0162] (iii) A HARQ RTT timer (e.g., "HARQ-RTT-Timer-SL-DRX timer") for SL DRX that behaves similarly to the description of the HARQ-RTT-Timer-SL-RX timer. For example, the HARQ-RTT-Timer-SL-DRX timer may be defined as the minimum duration prior to the expected / received retransmission of an earlier SL transmission by the SL RX UE for a peer SL TX UE.

[0163] (iv) A retransmission timer (or “RetransmissionTimer-SL-DRX timer”) for SL DRX that behaves similarly to the description of the RetransmissionTimer-SL-RX timer. For example, the RetransmissionTimer-SL-DRX timer can be defined to have a maximum duration until the SL RX Ue expects / receives a retransmission.

[0164] (v) A group-specific prohibitor for RX that behaves similarly to the description of a group-specific prohibitor, but may be further limited to the channel behavior mentioned in the preceding items, such as PSCCH listening instead of PSCCH transmission.

[0165] It should be noted that the analogy between the timers described in this disclosure is applicable to SL DRX behavior constraints.

[0166] The limitations set by the SL DRX timer as described in the previously described implementation (independent transmission and reception control) can be applied to PSCCH listening, PSSCH reception, or PSFCH transmission. The limitations set by the SL DRX timer as described in the previously described implementation (independent transmission and reception control) may not apply to PSCCH transmission, PSSCH transmission, or PSFCH reception.

[0167] For an SL UE with separate DRX / DTX control, DTX operation (or “SL DTX behavior”, which may be used interchangeably in this disclosure) may include one or more of the following features (1) and (2):

[0168] (1) The SL DTX operation can set behavioral restrictions (e.g., timing for activating / deactivating channel transmission or reception) for one or more of the following channels (i) to (iii):

[0169] (i) PSCCH transmission;

[0170] (ii) PSSCH transmissions associated with PSCCH transmissions; and

[0171] (iii) PSDCH reception / listening related to PSCCH / PSSCH transmission.

[0172] (2) The SL DTX behavior restrictions for the above channels can be implemented based on the following timers (i) to (iv):

[0173] (i) An on-duration timer (or “OnDurationTimer-SL-DTX timer”) for SL DTX behaves similarly to the OnDurationTimer-SL timer described. In one example, there is a single OnDurationTimer used to control the on-duration of DTX and DRX, i.e., the OnDurationTimer-SL-DTX timer can be the same as the OnDurationTimer-SL-DRX timer.

[0174] (ii) A deactivation timer (or “InactivityTimer-SL-DTX timer”) for SL DTX that behaves similarly to the descriptions of the InactivityTimer-SL timer, Inactivity-SL-perGroup timer, or Inactivity-SL-perHARQ timer.

[0175] (iii) A HARQ RTT timer (or “HARQ-RTT-Timer-SL-DTX timer”) for SL DTX, which behaves similarly to the description of the HARQ-RTT-Timer-SL-TX timer.

[0176] (iv) A retransmission timer (or “RetransmissionTimer-SL-DTX timer”) for SL DTX, which behaves similarly to the description of the RetransmissionTimer-SL-TX timer. A group-specific-prohibitor-TX, which behaves similarly to the description of a group-specific prohibitor, but may be further limited to the channel behavior mentioned in the preceding items, such as PSCCH transmission, rather than PSCCH reception.

[0177] Note that the analogy between the timer here and the timer described earlier applies to SL DTX behavior constraints.

[0178] The limitations on the SL DTX timer settings described in the previously described implementation (independent transmission and reception control) may not apply to PSCCH listening, PSSCH reception, or PSDCH transmission. The limitations on the SLDTX timer settings described in the previously described implementation (independent transmission and reception control) may apply to PSCCH transmission, PSSCH transmission, or PSFCH reception.

[0179] Figure 4 The process of independent SL transmission and SL reception control according to an embodiment of this disclosure is illustrated. For example... Figure 4 As shown, SL UE#1 420 and SL UE#2 440 communicate with each other, wherein SL UE#1 420 performs discontinuous operations (e.g., DTRX operations) based on independent transmit and receive control.

[0180] In action 402, at time t1, SL UE#1 420 initiates the first / initial transmission of TB#1 via PSSCH, which may be accompanied by an associated PSCCH. During the TB#1 transmission, a first RTT timer associated with the HARQ process occupied by TB#1, such as the HARQ-RTT-Timer-SL-DTX timer, may be started.

[0181] In action 404, at time t2, SL UE#1 420 receives the first transmission of TB#2 from SL UE#2 440.

[0182] In action 406, at time t3, SL UE#1 420 receives a NACK feedback via PSDCH associated with the first transmission of TB#1.

[0183] In action 408, at time t4, a NACK feedback is transmitted via SLUE#1 420 through the PSDCH associated with the first transmission of TB#2. A second RTT timer, such as the HARQ-RTT-timer-SL-DRX timer, associated with the HARQ process occupied by TB#2 can be started.

[0184] Before or at time t5, the first RTT timer expires, and the first reTX timer can be started.

[0185] In action 410, at time t5, the second transmission of TB#1 is transmitted by SL UE#1 420.

[0186] Before or at time t6, the second RTT timer expires, and the second retransmission timer can be started.

[0187] In action 412, at time t6, SL UE#1 420 receives the second transmission of TB#2.

[0188] In action 414, at time t7, SL UE#1 420 receives ACK feedback for the second transmission of TB#1.

[0189] In action 416, at time t8, SL UE#1 420 transmits an ACK feedback for the second transmission of TB#2.

[0190] Impact of SL DRX Operation on Sensing-Based Resource Selection

[0191] Uu interface DRX operation can, in principle, set requirements for DL ​​receive behavior (e.g., PDCCH snooping), but not at the transmit end. Using this operation, the UE can perform power savings by shutting down a portion of its circuitry. In SL, DRX operation may require setting requirements for both transmit and receive directions. In this sense, restrictions can be imposed on both the transmit and receive resource pools. In the following, it is assumed that UE sensing behavior is unaffected during the DRX activation period.

[0192] Sensing operations may include listening for SL sidelink control information (SCI) in the configured transport resource pool to determine whether certain future resources are reserved by other SL UEs. Since SL DRX operations may not require SL UEs to listen for / decode SL SCI during the DRX off duration, sensing results may be incomplete based on sensing operation requirements. Due to incomplete sensing results, resource selection restrictions from the transport resource pool may exist during SL DRX operations.

[0193] Sensing operation during SL DRX

[0194] For SL UEs, sensing operations are associated with the transport resource pool. From the perspective of NW configuration, the transport resource pool is a subset of the receive resource pool. Ideally, if the execution of the DRX and transport resource pool configurations ensures that the transport resource pool resides within the period defined by the DRX onDuration timer used for SL, then the sensing results will be complete, regardless of whether a full or partial sensing method is used.

[0195] Figure 5 The temporal relationship between the SL DRX on-time duration and the transport resource pool according to an embodiment of this disclosure is shown. For example... Figure 5 As shown, the SL DRX on durations 502, 504, and 506 completely cover the timing of the transmission resources in the transmission resource pool in the time domain (in Figure 5 (represented as "TX" in the original text). Therefore, the UE's sensing operations will not be affected.

[0196] However, Figure 5 The scenarios illustrated may be difficult to implement because time-domain resources (e.g., at the time slot granularity) may be provided in a periodic manner. For example, the period indicated in the LTE V2X resource pool indication is 10ms, which makes the task of limiting the transmission resource pool to the DRX-enabled duration very challenging for DRX operations with long period durations.

[0197] Figure 6 This is a schematic diagram illustrating the time-domain relationship between the SL DRX activation duration and the transmission resource pool according to an embodiment of this disclosure. For example... Figure 6 As shown, at least a portion of the transmission opportunities in the cycle of the transmission resource pool (i.e., in) Figure 6 The timing of the transfer resource (represented as "TX") may miss (or not occur) the SL DRX on-times 602, 604, and 606. It should be noted that although in Figure 6 The image only shows the duration of DRX activation, but in principle, sensing operations can function normally during the DRX activation period.

[0198] To ensure that the sensing operation works properly with the SLDRX, one or a combination of the following methods can be applied.

[0199] In one approach, sensing operations may not be required during the DRX off-duty period. If a time slot is not monitored due to the DRX off-duty period, a hypothetical SL SCI is assumed to be received. All possible resource reservation patterns configured by RRC signaling are assumed to be possible resource reservations for deriving the hypothetical SL SCI and are excluded from the candidate set used for resource selection.

[0200] In one approach, sensing operations may not be required during the DRX off duration. The UE can be provided with a threshold priority through (pre)configuration. If the TX priority associated with the resource trigger has a higher priority than the threshold priority, a hypothetical SL SCI may not be assumed for a time slot not being listened to due to the DRX off duration. There may be no application restrictions for resource selection associated with the resource trigger. The resource trigger is associated with a sensing window used for sensing operations. If the TX priority associated with the resource trigger has a lower priority than the threshold priority, a hypothetical SL SCI can be assumed for a time slot not being listened to due to the DRX off duration. All possible resource reservation modes configured by RRC signaling are assumed for possible resource reservations used to derive the hypothetical SL SCI and are excluded from the candidate set used for resource selection. When RRC enables preemption, the threshold priority can be the preemption priority.

[0201] In one approach, sensing operations on a transport resource pool may need to be performed during the DRX shutdown duration. In one implementation, transmission on the transport resource pool is not required during the DRX shutdown duration. In one implementation, a sensing timer may be introduced in the SL DRX operation. When the sensing timer runs, sensing operations on the transport resource pool are required. Depending on the implementation example, the sensing timer may be per MAC entity or per transport resource pool. The sensing timer may be started at the first transport resource in a transport resource pool within a cycle. When a DRX cycle is configured, the DRXC activation time includes the time during which the sensing timer is running. The length or duration of the sensing timer may be the same as or shorter than the length / duration of the sensing window.

[0202] In one approach, when DRX cycling is configured, from the UE's perspective, the time of sensing operation (e.g., configured by NW) is considered the DRX activation time.

[0203] Resource selection restrictions during SL DRX

[0204] During SL DRX, once an initial SL transfer occurs, retransmission opportunities can be guaranteed by utilizing retransmission timers and / or RTT timers, as in Uu DRX. In one implementation, the resource for the initial transfer of TB may reside during the active time in order to select a resource within a resource selection window associated with resource selection triggering. In one implementation, the initial transfer resource may be further restricted to the DRX enable duration, i.e., while the DRX enable duration timer is running.

[0205] Resource reservations triggered by resource selection may include periodic resources for, for example, initial transmissions and associated resources for retransmissions. The periodicity of periodic resources is represented as a Resource Reservation Period (RRP). To ensure transmission within each RRP, in one example, the RRP is aligned with the SL DRX cycle. In one implementation, the RRP may be the same as the SL DRX cycle. In another example, the RRP may be a multiple of the SL DRX cycle.

[0206] Figure 7 A flowchart of a method 700 for SL communication according to an embodiment of the present disclosure is shown. Although actions 702 and 704 are... Figure 7 In the text, actions are represented as individual actions within independent boxes, but these individually depicted actions should not be interpreted as necessarily depending on the order. Figure 7 The order in which actions are performed is not intended to be construed as a limitation, and any number of the exposed boxes can be combined in any order to implement the method or alternative methods.

[0207] In action 702, the UE may perform SL transmission based on a first set of timers configured to control the UE's SL DTX behavior.

[0208] In action 704, the UE can perform SL reception based on a second set of timers configured to control the UE's SL DRX behavior, wherein at least one first timer value in the first timer set and at least one second timer value in the second timer set are configured independently. By configuring at least two sets of timers for the UE, independent DTX and DRX control can be achieved, which can realize power saving effects from both the transmission and reception perspectives.

[0209] In one implementation, the first timer set may include a first on-duration timer (e.g., onDurationTimer-SL timer), a first deactivation timer (e.g., InactivityTimer-SL timer), a first HARQ RTT timer (e.g., HARQ-RTT-Timer-SL-TX timer), and a first retransmission timer (e.g., retransmissionTimer-SL-TX timer). The second timer set may include a second on-duration timer (e.g., another onDurationTimer-SL timer), a second deactivation timer (e.g., another InactivityTimer-SL timer), a second HARQ RTT timer (e.g., HARQ-RTT-Timer-SL-RX timer), and a second retransmission timer (e.g., retransmissionTimer-SL-RX timer).

[0210] In one implementation, the UE can determine whether a specific timer included in a first timer set is running, wherein the UE is only permitted to initiate a new TB transmission to a group of UEs operating in HARQ NACK-only feedback mode if the specific timer is running. The specific timer can be one of a first enable duration timer and a first deactivation timer. Figure 3 For example, in the scenario where SL UE communicates with multicast group 310 in NACK-only feedback mode, if new SL TB transmissions are only allowed when the deactivation timer or the enable duration timer is running, the problem of inconsistent deactivation / activation times among SLUE#2 304, SL UE#3 306, and SL UE#4 308 can be resolved.

[0211] In one implementation, the UE can determine the DRX state based on a first set of timers, and determine the state of the inhibit for the UE group based on at least one HARQ-process-specific timer in the first set of timers; after determining that the DRX state is active and the inhibit is enabled, SL transmission to the UE group is performed, and SL transmission is prohibited if the inhibit is disabled.

[0212] In one implementation, each of the at least one HARQ process-specific timer may be a HARQRTT timer or a retransmission timer.

[0213] In one implementation, each of the at least one HARQ process-specific timer belongs to a HARQ process group.

[0214] Figure 9 This is a block diagram illustrating a node 900 for wireless communication according to an embodiment of the present disclosure. Figure 9 As shown, node 900 may include a transceiver 920, a processor 928, a memory 934, one or more presentation components 938, and at least one antenna 936. Node 900 may also include a radio frequency (RF) spectrum module, a base station communication module, a network communication module, a system communication management module, input / output (I / O) ports, I / O components, or a power supply (in [the context of the previous sentence]). Figure 9 (Not shown in the image).

[0215] Each component can communicate with each other directly or indirectly via one or more buses 940. Node 900 can be an execution reference. Figures 1 to 8 The various functions of the UE or BS are publicly available.

[0216] A transceiver 920, having a transmitter 922 (e.g., transmitting / transmission circuitry) and a receiver 924 (e.g., receiving / reception circuitry), can be configured to transmit and / or receive time and / or frequency resource allocation information. The transceiver 920 can be configured to transmit in different types of subframes and time slots, including but not limited to usable, unusable, and flexibly usable subframe and time slot formats. The transceiver 920 can be configured to receive data and control channels.

[0217] Node 900 may include a variety of computer-readable media. Computer-readable media may be any available media that can be accessed by Node 900, and includes volatile (and / or non-volatile) media, removable (and / or non-removable) media.

[0218] Computer-readable media can include computer storage media and communication media. Computer storage media include both volatile (and / or non-volatile) and removable (and / or non-removable) media, and can be implemented in any way or by any technique for use with information such as computer-readable instructions, data structures, program modules, or data.

[0219] Computer storage media include RAM, ROM, EEPROM, flash memory (or other storage technologies), CD-ROM, Digital Versatile Disk (DVD) (or other optical disc storage devices), magnetic tape cartridges, magnetic tape, disk storage, or other magnetic storage devices. Computer storage media may not include the transmission of data signals. Communication media may typically contain computer-readable instructions, data structures, program modules, or other data in modulated data signals (such as carrier waves or other transmission mechanisms), and include any information transmission medium.

[0220] The term "modulated data signal" can refer to a signal having one or more characteristics set or altered in a manner that encodes information in the signal. Communication media include wired media (such as wired networks or direct wired connections) and wireless media (such as acoustic, RF, infrared, and other wireless media). Any combination of the components listed above should also be included within the scope of computer-readable media.

[0221] Memory 934 may include computer storage media in the form of volatile and / or non-volatile memory. Memory 934 may be removable, non-removable, or a combination thereof. For example, memory may include solid-state memory, hard disk drive, optical disk drive, etc. Figure 9 As shown, memory 934 may store computer-readable, computer-executable program 932 (e.g., software code), which, when executed, causes processor 928 (e.g., processing circuitry) to perform various functions disclosed herein, for example, referring to... Figures 1 to 8 Alternatively, program 932 may not be executed directly by processor 928, but may be configured to cause node 900 (e.g., when compiled and executed) to perform the various functions disclosed herein.

[0222] Processor 928 (e.g., having processing circuitry) may include intelligent hardware devices, such as a central processing unit (CPU), microcontroller, ASIC, etc. Processor 928 may include memory. Processor 928 can process data 930 and program 932 received from memory 934, as well as information transmitted and received via transceiver 920, baseband communication module, and / or network communication module. Processor 928 can also process information to be sent to transceiver 920 for transmission via antenna 936 to NW communication module for transmission to CN.

[0223] One or more presentation components 938 may present data indications to a person or other device. Examples of presentation components 938 may include display devices, speakers, printing components, and vibrating components.

[0224] According to this disclosure, it will be apparent that various techniques can be used to implement the concepts of this disclosure without departing from the scope of these concepts. Furthermore, although the concepts have been disclosed by specific reference to certain embodiments, those skilled in the art will recognize that changes in form and detail can be made without departing from the scope of these concepts. Therefore, the disclosed embodiments are to be considered illustrative rather than restrictive in all respects. It should also be understood that this application is not limited to the specific embodiments disclosed, but many rearrangements, modifications, and substitutions are possible without departing from the scope of this disclosure.

Claims

1. A method performed by a user equipment (UE) for sidelink (SL) communication, the method comprising: performing SL transmission based on a first set of timers configured for controlling SL discontinuous transmission (DTX) behavior of the UE; and performing SL reception based on a second set of timers configured for controlling SL discontinuous reception (DRX) behavior of the UE, wherein at least one first timer value in the first set of timers and at least one second timer value in the second set of timers are independently configured, the first set of timers comprises: a first on-duration timer, a first deactivation timer, a first hybrid automatic repeat request (HARQ) round trip time (RTT) timer, and a first retransmission timer, and the second set of timers comprises: a second on-duration timer, a second deactivation timer, a second HARQ RTT timer, and a second retransmission timer. 2.The method of claim 1, further comprising: determining that a particular timer included in the first set of timers is running, wherein the UE is allowed to initiate a new transport block (TB) transmission to a group of UEs operating in a HARQ negative acknowledgement (NACK) only feedback mode only when the particular timer is running. 3.The method of claim 2, wherein the particular timer is one of the first on-duration timer and the first deactivation timer. 4.The method of claim 1, further comprising: determining a DRX state according to the first set of timers; determining a state of a prohibit for a group of UEs according to at least one HARQ process specific timer in the first set of timers; performing the SL transmission for the group of UEs after determining that the DRX state is an active state and the prohibit is in an allowed state; and prohibiting performing the SL transmission in a case that the prohibit is in a prohibited state. 5.The method of claim 4, wherein each of the at least one HARQ process specific timer is a HARQ RTT timer or a retransmission timer. 6.The method of claim 4, wherein each of the at least one HARQ process specific timer belongs to a group of HARQ processes. 7.A user equipment (UE) for performing sidelink (SL) communication, the UE comprising: a transceiver; and at least one hardware processor coupled to the transceiver, the at least one hardware processor configured to: control the transceiver to perform SL transmission based on a first set of timers configured for controlling SL discontinuous transmission (DTX) behavior of the UE; and control the transceiver to perform SL reception based on a second set of timers configured for controlling SL discontinuous reception (DRX) behavior of the UE, wherein at least one first timer value in the first set of timers and at least one second timer value in the second set of timers are independently configured, the first set of timers comprises: ​ ​ ​ a first on-duration timer, a first inactivity timer, a first hybrid automatic repeat request (HARQ) round trip time (RTT) timer, and a first retransmission timer, and the second set of timers includes: a second on-duration timer, a second inactivity timer, a second HARQ RTT timer, and a second retransmission timer.

8. The UE of claim 7, wherein, the at least one hardware processor is further configured to: determine that a particular timer included in the first set of timers is running, wherein the UE is allowed to initiate a new transport block (TB) transmission to a group of UEs operating in a HARQ negative-acknowledgement (NACK) only feedback mode only when the particular timer is running.

9. The UE of claim 8, wherein: the particular timer is one of the first on-duration timer and the first inactivity timer.

10. The UE of claim 7, wherein, the at least one hardware processor is further configured to: determine a DRX state from the first set of timers; determine a state of a prohibitor for a group of UEs from at least one HARQ process specific timer of the first set of timers; control the transceiver to perform the SL transmission for the group of UEs after determining that the DRX state is an active state and the prohibitor is in an allowed state; and prohibit performing the SL transmission in a case where the prohibitor is in a prohibited state.

11. The UE of claim 10, wherein: each of the at least one HARQ process specific timer is a HARQ RTT timer or a retransmission timer.

12. The UE of claim 10, wherein: each of the at least one HARQ process specific timer belongs to a group of HARQ processes.

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