User equipment and method for sidelink communication

Abstract

A UE may be provided, comprising a wireless transceiver and a controller. The wireless transceiver may perform wireless transmission and reception with one or more peer UEs. The controller may determine a SL DRX configuration set; and apply the SL DRX configuration set to enable DRX operation for SL communication with the peer UE via the wireless transceiver, wherein the SL DRX configuration set may be determined based on one of the following: one or more types of one or more SL services performed by the UE with the peer UE; one or more SL DRX configurations received from the peer UE; and control information received from a base station. By utilizing the present invention, sidelink communication may be improved.

Description

[0001] Cross-references

[0002] The present invention claims priority to international application No. PCT / CN2020 / 070580, filed on January 7, 2020, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present invention relates to mobile communications, and more particularly to an apparatus and method for supporting discontinuous reception (DRX) in sidelink (SL) communications. Background Art

[0004] In a typical mobile communication environment, a user equipment (UE) (also called a mobile station (MS)) with wireless communication capabilities, such as a phone (also called a mobile phone) or a tablet personal computer (PC), can communicate voice and / or data signals with one or more service networks. Wireless communications between UEs and a serving network may be performed using various radio access technologies (RATs), such as Global System for Mobile communications (GSM), General Packet Radio Service (GPRS), Enhanced Data rates for Global Evolution (EDGE), Wideband Code Division Multiple Access (WCDMA), Code Division Multiple Access 2000 (CDMA-2000), Time Division-Synchronous Code Division Multiple Access (TD-SCDMA), Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE), and Long Term Evolution-Advanced (LTE-A).

[0005] The above RAT technologies have been adopted in various telecommunication standards to provide a common protocol, enabling different wireless devices to communicate at a municipal, national, regional or even global level. An example of an emerging telecommunication standard is the fifth generation (5G) th 5G New Radio (NR) is a set of enhancements to the LTE mobile standard released by the Third Generation Partnership Project (3GPP). 5G NR is designed to better support mobile broadband internet access by increasing spectrum efficiency, reducing costs, and improving services.

[0006] In LTE and 5G NR, device-to-device (D2D) communication is supported to allow two or more UEs to communicate directly with each other. This D2D communication can also be called sidelink (SL) communication, which can be applied to vehicle-to-everything (V2X) services. V2X can be collectively referred to as technologies for communicating with vehicles through all interfaces, including vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-person (V2P), and vehicle-to-network (V2N).

[0007] In particular, according to Release 16 of the 3GPP specification for NR-based V2X, diverse Quality of Service (QoS) traffic can be supported and UEs can be allowed to simultaneously send / receive traffic delivered via unicast, multicast, and broadcast. Despite being a significant enhancement compared to LTE-based V2X, the current NR-based V2X design has not yet introduced any power saving-related mechanisms. Because the UE does not know when other UEs will attempt to communicate with it, even if there may not be any peer UEs nearby, the UE still needs to continuously monitor Sidelink Control Information (SCI) via the PC5 interface. Unfortunately, the constant SCI monitoring on the PC5 interface results in higher power consumption of the V2X UE.

[0008] Furthermore, in NR-based V2X, if Mode 1 resource scheduling is applied (i.e., SL resources are scheduled by the network), radio resources for new and retransmissions can be scheduled by the network. This means that when there may be upcoming SL traffic, the UE needs to continuously monitor the Uu interface to receive SL authorization scheduling from the network, ignoring the power saving rules currently in use on the Uu interface. Similarly, continuous monitoring of the Uu interface can also degrade the power saving performance of the Uu interface.

[0009] Therefore, a robust and efficient power saving mechanism is needed for NR-based V2X. Summary of the Invention

[0010] The present invention may propose a power saving mechanism for NR-based V2X, where DRX-like operations may be introduced into SL communications.

[0011] In a first aspect of the present invention, a user equipment is provided, comprising a wireless transceiver and a controller. The wireless transceiver is configured to perform wireless transmission and reception with one or more peer user equipments. The controller is configured to determine a sidelink discontinuous reception configuration set; and apply the sidelink discontinuous reception configuration set to enable discontinuous reception operation for sidelink communication with the peer user equipment via the wireless transceiver, wherein the sidelink discontinuous reception configuration set is determined based on one of the following: one or more types of one or more sidelink services performed by the user equipment with the peer user equipment; one or more sidelink discontinuous reception configurations received from the peer user equipment; and control information received from a base station.

[0012] In a second aspect of the present invention, a method is provided, comprising the following steps: determining, by a user equipment, a sidelink discontinuous reception configuration set; and applying, by the user equipment, the sidelink discontinuous reception configuration set to enable discontinuous reception operation for sidelink communication with one or more peer user equipment, wherein the sidelink discontinuous reception configuration set is determined based on one of: one or more types of one or more sidelink services performed by the user equipment with the peer user equipment; one or more sidelink discontinuous reception configurations received from the peer user equipment; and control information received from a base station.

[0013] By utilizing the present invention, sidelink communications can be better performed.

[0014] After reading the following description of specific embodiments of a UE and a method supporting DRX in SL communication, other aspects and features of the present invention will become more apparent to those skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention may be more fully understood by reading the following detailed description and examples with reference to the accompanying drawings, in which:

[0016] Figure 1 is a schematic diagram of a cellular communication network according to an embodiment of the present invention.

[0017] Figure 2 is a schematic diagram of an SL communication environment according to an embodiment of the present invention.

[0018] Figure 3 is a schematic diagram of an SL communication environment according to another embodiment of the present invention.

[0019] Figure 4 is a block diagram of a UE according to an embodiment of the present invention.

[0020] Figure 5 is a schematic diagram of determining a SL DRX configuration for a UE according to an embodiment of the present invention, wherein the UE has an aligned SL DRX offset with a peer UE.

[0021] Figure 6 is a timing diagram of fast SL communication using Internet Packet Groper (ping) messages according to an embodiment of the present invention.

[0022] Figure 7 FIG. 2 is a schematic diagram of improving SL DRX operation by using a wake-up signal according to an embodiment of the present invention.

[0023] Figure 8 is a timing diagram of improving SL DRX operation using DRX request according to an embodiment of the present invention.

[0024] Figure 9 4 is a flow chart of a method for supporting DRX in SL communication according to an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following description is intended to illustrate the general principles of the present invention and should not be construed as limiting. It will be understood that these embodiments may be implemented in software, hardware, firmware, or a combination thereof. When the words "comprise," "include," "contain," and / or "have" are used in the present invention, they indicate the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or combinations thereof.

[0026] Figure 1 is a schematic diagram of a cellular communication network according to an embodiment of the present invention.

[0027] like Figure 1 As shown, the cellular communication network 100 may include an access network 110 and a core network 120. The access network 110 may be responsible for processing radio signals, terminating radio protocols, and connecting one or more UEs (not shown) with the core network 120. The core network 120 may be responsible for performing mobility management, network-side authentication, and interfacing with public / external networks (e.g., the Internet).

[0028] In one embodiment, the cellular communication network 100 may be a 5G NR network, the access network 110 may be a Next Generation Radio Access Network (NG-RAN), and the core network 120 may be a Next Generation Core Network (NG-CN).

[0029] The NG-RAN may include one or more base stations (BSs), such as next-generation NodeBs (gNBs) that support high-frequency bands (e.g., above 24 GHz). Each gNB may also include one or more transmission reception points (TRPs). Each gNB or TRP may be referred to as a 5G base station. Some gNB functions may be distributed across different TRPs, while others may be centralized, allowing for flexibility and scope for specific deployments to meet specific needs. For example, various protocol split options may be available between the central and distributed units of a gNB node. In one embodiment, the Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) layers may be located in the central unit, while the Radio Link Control (RLC), Medium Access Control (MAC), and Physical (PHY) layers may be located in the distributed units.

[0030] A 5G BS can form one or more cells with different component carriers (CCs) to provide mobile services to UEs. For example, a UE can reside on one or more cells formed by one or more gNBs or TRPs, where the cell in which the UE resides can be called a serving cell.

[0031] NG-CN can generally support various network functions, including Access and Mobility Management Function (AMF), Session Management Function (SMF), Policy Control Function (PCF), Application Function (AF), Authentication Server Function (AUSF), User Plane Function (UPF) and User Data Management (UDM) functions, where each network function can be implemented as a network element on dedicated hardware, or as a software instance running on dedicated hardware, or as a virtual function installed on an appropriate platform (such as cloud infrastructure).

[0032] AMF can provide UE-based authentication, authorization, mobility management, etc. SMF can be responsible for session management and assigning Internet Protocol (IP) addresses to UE. SMF can also select and control UPF for data transmission. If the UE has multiple sessions, a different SMF can be assigned to each session to manage each session separately and provide different functions for each session. AF can provide information about packet flows to PCF, which is responsible for policy control, to support QoS. PCF can determine policies on mobility and session management based on the above information to enable AMF and SMF to operate normally. AUSF can store UE's authentication data, and UDM can store UE's subscription data.

[0033] It should be understood that Figure 1 The cellular communication network 100 described in the embodiments is for illustrative purposes only and is not intended to limit the scope of this disclosure. For example, the RAT used by the cellular communication network 100 may be a legacy technology such as LTE, LTE-A, or TD-LTE, or it may be a future enhancement of 5G NR technology, such as 6G technology.

[0034] Figure 2 is a schematic diagram of an SL communication environment according to an embodiment of the present invention.

[0035] like Figure 2As shown, UE1 may be within the radio coverage of the BS and can communicate with the BS via the Uu interface, while UE2 and UE3 are not within the radio coverage of the BS. In addition to supporting the Uu interface, UE1 may also support the PC5 interface for SL communication with UE2 and UE3.

[0036] In particular, UE1 can operate as a scheduler UE (or relay UE), which schedules or allocates radio resources for UE2 and UE3 (or scheduled UEs) according to the configuration received from the BS or according to the configuration predefined in the NR-based V2X 3GPP specification. UE1, as a relay, can forward traffic between UE2 and UE3, and / or forward traffic between UE2 / UE3 and the BS. For example, UE1 can be configured as a Layer 2 relay or a Layer 3 relay. Alternatively, UE1 may not operate as a relay, but may initiate direct SL communication with one or both of UE2 and UE3.

[0037] Please note that the 3GPP specifications mentioned in the present invention are only used to illustrate the spirit of the present invention, and the present invention is not limited thereto.

[0038] Figure 3 is a schematic diagram of an SL communication environment according to another embodiment of the present invention.

[0039] like Figure 3 As shown, UE1-UE3 are not within the radio coverage of the BS, but SL communication between UE1-UE3 can be performed through the PC5 interface.

[0040] In particular, UE1 can operate as a scheduler UE (or relay UE), which can schedule or allocate radio resources for UE2 and UE3 (or scheduled UEs) according to the configuration predefined in the NR-based V2X 3GPP specification or the configuration previously received from the BS when UE1 is camped on the BS. UE1, as a relay, can forward traffic between UE2 and UE3. For example, UE1 can be configured as a layer 2 relay or a layer 3 relay. Alternatively, UE1 may not operate as a relay, but may initiate direct SL communication with one or both of UE2 and UE3.

[0041] Figure 4 is a block diagram of a UE according to an embodiment of the present invention.

[0042] like Figure 4 As shown, a UE (such as a scheduler UE or a scheduled UE) may include a wireless transceiver 10 , a controller 20 , a storage device 30 , a display device 40 and an input / output (I / O) device 50 .

[0043] The wireless transceiver 10 may be configured to wirelessly transmit to and receive from other UEs and / or BSs of the access network 110 .

[0044] In particular, the wireless transceiver 10 may include a baseband processing device 11 , a radio frequency (RF) device 12 , and an antenna 13 , wherein the antenna 13 may include an antenna array for beamforming.

[0045] The baseband processing device 11 may be configured to perform baseband signal processing and control communication between a subscriber identity card (not shown) and the RF device 12. The baseband processing device 11 may include multiple hardware components to perform baseband signal processing, including analog-to-digital conversion (ADC) / digital-to-analog conversion (DAC), gain adjustment, modulation / demodulation, encoding / decoding, etc.

[0046] The RF device 12 can receive an RF wireless signal via the antenna 13 and convert the received RF wireless signal into a baseband signal, where the baseband signal is processed by the baseband processing device 11, or receive a baseband signal from the baseband processing device 11 and convert the received baseband signal into an RF wireless signal, where the RF wireless signal is then transmitted via the antenna 13. The RF device 12 can also include multiple hardware devices to perform radio frequency conversion. For example, the RF device 12 can include a mixer to multiply the baseband signal with a carrier oscillating at the radio frequency of the supported RAT. Depending on the RAT used, the radio frequency can be any radio frequency used in 5G NR technology (such as 30 GHz to 300 GHz for millimeter wave (mmWave)), or can be 900 MHz, 2100 MHz, or 2.6 GHz used in LTE / LTE-A / TD-LTE technology, or other radio frequencies.

[0047] The controller 20 can be a general-purpose processor, a microcontroller (MCU), an application processor, a digital signal processor (DSP), a graphics processing unit (GPU), a holographic processing unit (HPU) or a neural processing unit (NPU), etc. The controller 20 may include various circuits to provide the following functions: data processing and calculation, controlling wireless communication between the wireless transceiver 10 and the service network 120, storing and retrieving data (such as program code) to and from the storage device 30, sending a series of frame data (frame data) to the display device 40 (such as text messages, graphics, images, etc.), and receiving user input or output signals via the I / O device 50.

[0048] In particular, the controller 20 may coordinate operations of the wireless transceiver 10 , the storage device 30 , the display device 40 , and the I / O device 50 to perform a method for SL communication based on UE-coordinated resource allocation.

[0049] In another embodiment, the controller 20 may be incorporated into the baseband processing device 11 to serve as a baseband processor.

[0050] It will be appreciated by those skilled in the art that the circuitry of the controller 20 may typically include transistors, which may be configured to control the operation of the circuitry according to the functions and operations described herein. As will be further appreciated, the specific structure or interconnection of the transistors may typically be determined by a compiler, such as a register transfer language (RTL) compiler. An RTL compiler may be operated by a processor on a script that is very similar to assembly language code to compile the script into a form that can be used to lay out or manufacture the final circuit. In fact, RTL is widely known for its role in facilitating the design process of electronic and digital systems.

[0051] The storage device 30 may be a non-transitory machine-readable storage medium, wherein the storage medium includes a memory (such as flash memory or non-volatile random access memory (NVRAM)), or a magnetic storage device (such as a hard disk or a tape), or an optical disk, or any combination thereof for storing data, instructions and / or application program code, communication protocols and / or methods for SL communication based on UE-coordinated resource allocation.

[0052] The display device 40 may be a liquid crystal display (LCD), a light-emitting diode (LED) display, an organic light-emitting diode (OLED) display, or an electronic paper display (EPD) to provide a display function. Alternatively, the display device 40 may further include one or more touch sensors disposed thereon or thereunder to sense touch, contact, or proximity of an object (such as a finger or a stylus).

[0053] The I / O device 50 may include one or more buttons, keyboards, mice, touchpads, cameras, microphones, and / or speakers, etc., as a man-machine interface (MMI) for interacting with a user.

[0054] It is understandable that in Figure 4 The components described in the embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0055] For example, the UE may include more components, such as a power supply and / or a Global Positioning System (GPS) device, where the power supply may be a portable / replaceable battery that powers all other components of the UE, and the GPS device may provide the UE's location information for use by some location-based services or applications. Alternatively, the UE may include fewer components. For example, the UE may not include the display device 40 and / or the I / O device 50.

[0056] Traditional DRX operation for Uu interface

[0057] In NR 3GPP specification version 15 (Release 15), the DRX configuration of the Uu interface may include several timers and counters to define when the UE can turn on its radio transceiver to monitor the Physical Downlink Control Channel (PDCCH) for possible scheduling. The period during which the radio transceiver remains on may be called the DRX active time. For times that are not part of the DRX active time, the UE does not need to monitor the PDCCH, but can turn off the radio transceiver to save power. Since the DRX configuration is provided by the network, the network and the UE have the same understanding of the DRX active time, so when the UE is in the DRX active time, the network can initiate communication with the UE.

[0058] In particular, in NR Release-15, three parameters including DRX offset, DRX cycle and DRX-ON duration can be used to define the basic on-off pattern of DRX operation. The DRX cycle can refer to the period of each on-off pattern. For example, if the DRX cycle is 10 milliseconds (ms), it means that the on-off pattern is repeated every 10 ms. The start time of each DRX cycle can be determined by the DRX offset (more specifically, the start offset and the time slot offset). At the beginning of each DRX cycle, the UE can turn on its radio transceiver to monitor the PDCCH for a period of time, which can be called the DRX-ON duration (which can be defined by the DRX-ON duration timer). If no PDCCH data is received during the DRX-ON duration, the UE can turn off its radio transceiver to save power until the end of the DRX cycle and resume PDCCH monitoring at the beginning of the next DRX cycle.

[0059] In addition, if there is traffic activity when DRX is configured, the UE can still stay awake for a longer time (for example, the DRX active time can be extended) to perform possible data transmission and reception. For example, if the UE receives PDCCH data indicating that a new transmission (such as uplink (UL) / downlink (DL) transmission) is scheduled, the UE can start the DRX inactivity timer. While the DRX inactivity timer is running, the UE can continue to monitor the PDCCH. The idea is that since a new transmission is in progress, there may be more traffic after the new transmission.

[0060] In addition, DRX operation may also need to take into account Hybrid Automatic RepeatreQuest (HARQ) transmission / retransmission. In particular, when the UE sends an UL packet, the network may need some time (i.e., the UL HARQ round-trip time (RTT)) to prepare for the scheduling of HARQ retransmissions, which means that the network may not schedule any UL retransmissions for the same HARQ process. In response, the UE can sleep during the UL HARQ RTT time. When the UL HARQ RTT time elapses, the UE can wake up to monitor the PDCCH for possible HARQ retransmissions within a time period, where the time period can be controlled by the HARQ retransmission timer. If no HARQ retransmission is received while the HARQ retransmission timer is running, the UE can assume that the network does not intend to send an UL grant for HARQ retransmission for the HARQ process, and therefore, the UE can go to sleep again. For the DL direction, the DL HARQ RTT timer and DL HARQ transmission / retransmission may apply a design similar to that of the UL HARQ RTT timer and UL HARQ transmission / retransmission.

[0061] SL DRX operation for PC5 interface

[0062] To introduce a DRX-like mechanism for SL communications, a V2X UE needs to know when it is communicating with a peer UE, that is, whether the peer UE is in the SL DRX active time. Without this information, the UE may initiate SL communications with the peer UE while the peer UE is asleep (i.e., when the peer UE has turned off its radio to save power). The UE may also perform unnecessary HARQ retransmissions due to not receiving a response from the peer UE. Therefore, some coordination is required between the UEs to have a consistent understanding of each other's SL DRX configuration.

[0063] In the present invention, the DRX operation for SL communication with all peer UEs may apply the same SL DRX configuration, or the DRX operation for SL communication with each peer UE may apply a corresponding SL DRX configuration. The SL DRX configuration may include information on the SL DRX offset, the SL DRX cycle, and the SL DRX-ON duration to define the DRX switching pattern for SL channel monitoring. In addition, the SL DRX configuration may include the following information: a SL DRX inactivity timer for extending the SL DRX active time, a DRX retransmission timer for SL reception, a DRX retransmission timer for SL transmission, a HARQ RTT timer for SL reception, and a HARQ RTT timer for SL transmission, wherein the above information may also be used to manage the SL DRX active time in the HARQ process.

[0064] In one novel aspect of the present invention, the SL DRX inactivity timer may be started / restarted in response to one or more of the following conditions. For example, when the UE receives a SL-related Radio Network Temporary Identifier (RNTI) (e.g., SL-RNTI, SL Configured Scheduling (SLCS) RNTI (SLCS-RNTI), and SL Semi-Persistent Scheduling V-RNTI) from the BS for configuring SL resources for new transmissions, retransmissions, or for activation / deactivation of a SL configured grant, the SL DRX inactivity timer may be started / restarted. For example, when the UE receives an SCI associated with one of the SL services that the UE is conducting with a peer UE (e.g., the received SCI includes one of a destination identity (ID) for the UE to conduct only new transmissions or a destination ID for both new transmissions and retransmissions, or the received SCI includes a destination ID associated with a V2X service in which the UE is interested for new transmissions or retransmissions), the SL DRX inactivity timer may be started / restarted. In this example, the SL DRX inactivity timer may be started or restarted upon receipt of the first phase or second phase SCI of the relevant SCI. As another example, when SL mode 2 resource scheduling is configured for the UE (i.e., SL resources selected by the UE) and the UE performs resource selection or reselection to make only new transmissions or one of new transmissions or retransmissions, the SL DRX inactivity timer may be started or restarted.

[0065] When the SL receive HARQ RTT timer associated with a receiving HARQ process expires, the SL receive DRX retransmission timer associated with the same receive HARQ process may be started. Alternatively, the timer may be started upon receipt of an SCI for receiving a Physical Sidelink Shared Channel (PSSCH) on the same receive HARQ process, and may be stopped upon receipt of a SL MAC Protocol Data Unit (PDU) corresponding to the same receive HARQ process.

[0066] When the SL transmit HARQ RTT timer associated with a transmit HARQ process expires, the SL transmit DRX retransmission timer associated with the same transmit HARQ process may be started. Alternatively, the timer may be started when the UE receives PDCCH data from the BS indicating SL transmit resources for the transmit HARQ process (i.e., SL Mode 1 resource scheduling), or when the UE selects SL transmit resources for the transmit HARQ process (i.e., SL Mode 2 resource scheduling).

[0067] The SL receive HARQ RTT timer associated with a receive HARQ process may be started upon receiving an SCI for PSSCH reception on that receive HARQ process. Alternatively, the timer may be started upon receiving a SL MAC PDU in a dynamic SL grant and / or configured SL grant for that receive HARQ process. Alternatively, the UE may start the HARQ RTT timer for a receive SL HARQ process when it sends HARQ feedback to the transmitter UE for a SL MAC PDU (PSSCH) previously received on that receive HARQ process.

[0068] The SL transmit HARQ RTT timer associated with the transmitting HARQ process may be started when the UE receives PDCCH data indicating SL transmit resources (i.e., SL Mode 1 resource scheduling for new transmission and / or for retransmission), or when the UE selects SL transmit resources (i.e., SL Mode 2 resource scheduling). Alternatively, the timer may be started when a SL MAC PDU is transmitted on the transmitting HARQ process in a configured SL grant and / or dynamic SL grant. Alternatively, the timer may be started when the UE transmits an SCI for transmission or retransmission of a SL MAC PDU. Alternatively, for Mode 1 scheduling, the HARQ RTT timer for the transmitting SL HARQ process may be restarted when the UE sends a PUCCH to the gNB as SL HARQ feedback for the transmitting SL HARQ process to request a SL grant for retransmission or new transmission for the transmitting SL HARQ process. Alternatively, after receiving the scheduled / configured time for the UE to send HARQ feedback (eg, Physical Sidelink Feedback Channel (PSFCH)), the HARQ RTT timer for the transmit SL HARQ process may be restarted.

[0069] The SL DRX active time may be in units of absolute time (e.g., subframes, milliseconds, or time slots), or may be in units of time slots available for PSSCH monitoring. For example, the SL DRX active time may be in units of Physical Sidelink Control Channel (PSCCH) occasions. For example, the SL DRX ON duration timer may be counted down only during the monitored receive resource pool (rather than the selected transmit resource pool). Similarly, the SL DRX inactivity timer may also be in units of absolute time or in units available for receiving PSSCH. Because the HARQ RTT timer may reflect the time taken by the UE to respond, the HARQ RTT timer for transmission and reception may be in units of absolute time. The retransmission timer for receiving HARQ processing may be in units of absolute time or in units of time used to receive PSCCH / PSSCH (e.g., it may be counted down only during the receive resource pool). In contrast, the retransmission timer for transmitting the HARQ process may be in units of absolute time, or in units of time for transmitting the PSCCH / PSSCH (eg, the countdown may be performed only in the transmission resource pool).

[0070] SL DRX active time

[0071] Based on the above-mentioned SL DRX parameters and timers, the SL DRX active time (i.e., the time during which the UE remains awake (e.g., turns on the radio transceiver) to at least monitor the PSSCH during SL DRX operation) can be determined according to the SL DRX configuration set of different peer UEs. In one embodiment, the UE may be in the SL DRX active time when the SL DRX-ON duration timer is running, or when the SL DRX inactivity timer is running, or when the SL DRX retransmission timer for any transmit or receive HARQ process is running. In addition, if the UE has data or CSI reports to transmit to the peer UE, the UE may remain in the SL DRX active time. For unicast or multicast communications, if the UE has data or CSI reports to transmit to the peer UE, and the peer UE can also receive services (e.g., also in the SLDRX active time), the UE may remain in the SL DRX active time. In addition, the SL DRX active time may include a timer for the UE to sense the channel, i.e., if the UE is monitoring the PSSCH (e.g., collecting sensing results for transmission resource selection), the UE may be in the SL DRX active time.

[0072] Since a UE can apply the same or different SL DRX configurations to communicate with multiple peer UEs simultaneously, the UE can determine its SL DRX active time based on the traffic activities with the peer UEs. In particular, the UE can determine whether the peer UE is within the SL DRX active time based on the SL communication with each peer UE.

[0073] In one embodiment, the UE may maintain the SL DRX active time for each UE and may maintain the SL DRX timer for each link. When any one of the sidelink ON duration timer, SL DRX inactivity timer, and SL DRX retransmission timer for transmitting or receiving HARQ processing is running, the UE may remain in the SL active time.

[0074] In one embodiment, the UE may maintain a corresponding SL DRX active time for each SL link to the peer UE (i.e., the SL active time for each link). It can also be said that each SL link to the peer UE may have its own SL DRX active time, SL DRX-ON duration timer, SL DRX inactivity timer, HARQ RTT timer for SL transmission and reception, and DRX HARQ retransmission timer for SL transmission and reception. When any one of the SL DRX-ON duration timer, SL DRX inactivity timer, and DRX HARQ retransmission timer for SL transmission or reception of all SL links to the peer UE is running, the UE may remain in the SL DRX active time. It can also be said that the SL DRX active time of the UE (i.e., the SL active time for each UE) may be determined as the joint set of SL DRX active times of all SL links to the peer UE.

[0075] In another embodiment, the UE may maintain only one SL DRX inactivity timer, and the single SL DRX inactivity timer may be shared by all SL links to the peer UE. So no matter on which link or for which peer UE the new transmission / reception occurs, the SL DRX inactivity timer may always be started / restarted. In this embodiment, separate links to different peer UEs may share the same SL DRX-ON duration timer or use separate SL DRX-ON duration timers. The UE may remain in the SL DRX active time when the UE-specific SL DRX inactivity timer or any one of the SL DRX-ON duration timer and the DRX HARQ retransmission timer for SL transmission / reception is running.

[0076] In one embodiment, for unicast links, the SL DRX timer can be configured for each peer UE, each unicast link, or each PC5 RRC connection. For example, the SL DRX configuration can be identified by the source ID and destination ID of the SL link. For example, the SL DRX configuration can be configured for each combination of source ID, destination ID, and cast type. This means that even for the same pair of source ID and destination ID, different SL DRX configurations can be applied for different cast types.

[0077] In one embodiment, for any of unicast / multicast / broadcast, the SL DRX configuration can be associated with a destination ID. For example, for multicast and broadcast, each UE can identify a V2X service based on the multicast / broadcast destination ID, thereby understanding the SL DRX configuration associated with the V2X service. For example, the UE can understand the transmission pattern of the V2X service based on the SL DRX configuration associated with the used multicast / broadcast, and can monitor the timing of the transmission pattern to receive the multicast / broadcast service of interest.

[0078] A UE may have several SL DRX configurations to apply at the same time, for example, different peer UEs may apply different SLDRX configurations, and different broadcast / multicast services may also apply different SL DRX configurations. In this case, the UE may monitor the joint set or superposition of all SL DRX active times requested by the peer UEs and the multicast / broadcast services of interest indicated in its SLDRX configuration. For example, a UE may receive a SL DRX configuration that may indicate when a peer UE may perform SL transmission or when a multicast / broadcast service of interest may perform SL transmission. The UE may then remain awake during the transmission pattern indicated by any peer UE and any multicast / broadcast service of interest. In another example, the UE may receive a SL DRX configuration that may indicate when a peer UE wakes up for data reception. If the UE wants to communicate with a peer UE, the UE may remain awake during the SL DRX-ON duration of the peer UE.

[0079] To further clarify, the SL DRX active time can have some impact on the Uu DRX active time (i.e., the DRX active time of the Uu interface). For example, for a mode 1 UE in the RRC connected (RRC_CONNECTED) state, when the UE's PC5 interface is still in the SL DRX active time (i.e., the SL DRX active time has not passed), the UE's Uu interface can remain in the DRX active time (i.e., the Uu DRX active time can be extended even if it has passed) to receive SL authorization from the network. Alternatively, if the Uu interface is not in the DRX active time (e.g., the Uu DRX active time has passed), the PC5 interface can be configured to enter the DRX inactive time (i.e., the SL DRX active time can be stopped). It can also be said that the UE's power saving behavior related to the Uu interface will be interrupted by the SL communication on the PC5 interface. In other words, SL transmission on the PC5 interface may reduce the UE's power saving performance on the Uu interface.

[0080] In one example, if the Uu interface is in the DRX off time, only high-priority SL services can trigger the SL buffer status report (BSR) / scheduling request (SR) / random access channel (RACH) to interrupt the sleep state of the Uu interface, while low-priority SL services can be delayed or transmitted through mode 2 resource scheduling (i.e., without waking up the Uu interface).

[0081] In one example, if the Uu interface is in DRX-OFF time and the UE is configured with Mode 1 resource scheduling, low priority SL traffic may remain in the transmit buffer and the UE may wait for the next SL DRX-ON duration to start transmitting.

[0082] In one example, if the Uu interface is in DRX off time, the Mode 1 UE may autonomously fall back to Mode 2 resource scheduling to transmit SL data when the requirements for operating in Mode 2 resource scheduling are met (eg, sensing results for resource selection are available).

[0083] In one example, if the Uu interface is in the DRX off time and the UE is configured with mixed mode resource scheduling (ie, both mode 1 and mode 2 are allowed), low priority SL services can be transmitted through mode 2 resource scheduling to reduce service delay.

[0084] The network can configure Mode 1 or Mode 2 resource scheduling for the UE based on the UE's SL service priority. For example, if the SL service has a high priority, the network can configure Mode 1 resource scheduling for the UE. If all transmittable SL services have a low priority, the network can configure Mode 2 resource scheduling for the UE. Because the UE can select resources to transmit low-priority SL services, there is no need to strictly align the Uu DRX active time and the SL DRX active time in Mode 2 resource scheduling.

[0085] A Mode 1 UE may have a SL configuration grant of Type 1 (RRC configuration) or Type 2 (DCI activation / deactivation). When a Mode 1 UE enables SL DRX operation, a question arises as to whether the UE is allowed to send SL traffic outside the SL DRX active time in the configuration grant.

[0086] In one embodiment, if the configuration grant is not within the SL DRX active time, the UE may not be allowed to use the configuration grant for new transmission, but may be allowed to use the configuration grant for retransmission. This is because when SL transmission / retransmission is performed, the HARQ RTT timer for SL transmission may be started / restarted, and after the HARQ RTT timer for SL transmission expires, the HARQ retransmission timer for SL transmission may be started, so that the UE enters the SL DRX active time to perform retransmission.

[0087] In one embodiment, if the configuration grant is not within the SL DRX active time, the UE may be allowed to use the configuration grant for new transmissions so that delay-sensitive SL services (e.g., some Ultra-Reliable and Low Latency Communications (URLLC) type SL services) can be sent as soon as possible.

[0088] In one embodiment, whether the UE is allowed to use the configuration grant when it is not in the SL DRX active time may depend on the priority or type of the SL service (e.g., Enhanced Mobile Broadband (eMBB) or URLLC). If there is SL service above a priority threshold (e.g., based on a comparison of logical channel priorities), the UE may use the configuration grant to transmit high priority SL services. Note that when the UE performs SL transmission for new data, the SL DRX inactivity timer may be restarted and the UE may enter the SL DRX active time. If all SL data available for transmission is below the priority threshold, the UE may not be allowed to use the configuration grant to transmit low priority SL services. The above functionality may be achieved by introducing an improved SL Logical Channel Prioritization (LCP) process. For example, each SL configuration grant may be associated with a priority threshold so that the UE can check when the UE is in inactive time. When in inactive time, if the UE has data with a priority higher than the priority threshold of the configuration grant, the configuration grant may be used for data transmission, and the high priority data may pass the SL LCP check to be included in the configuration grant for transmission. Alternatively, each SL configuration grant may be associated with a type of SL service (eg, eMBB or URLLC), and the UE may be allowed to use the configuration grant when the type of SL service available for transmission is the type associated with the configuration grant.

[0089] Determination of SL DRX configuration

[0090] Each SL DRX configuration may be determined based on the type of SL service the UE is performing with an associated peer UE, or based on a SL DRX configuration received from the associated peer UE, or based on control information received from a BS.

[0091] In one embodiment, the UE may apply the same SL DRX configuration to communicate with all peer UEs. For example, to simplify the calculation of the SL DRX active time, the UE may notify all peer UEs of the same SL DRX configuration.

[0092] In another embodiment, the UE may apply different SL DRX configurations to communicate with different peer UEs. In particular, each SL DRX configuration may be determined based on the type of service being performed (e.g., V2X application). For example, if the type of service being performed with the peer UE is delay tolerant, a longer SL DRX cycle may be applied. Figure 5 As shown, the SL DRX offsets of different SL DRX configurations can be set to the same value (i.e., the SL DRX offsets are aligned) to reduce the union of the SL DRX active time of the peer UE. The SL DRX configuration related to the V2X application / V2X service can come from a higher layer, such as the Non-Access Stratum (NAS), the V2X layer, or the V2X application layer.

[0093] For further explanation, for a Mode 1 (i.e., Mode 1 resource scheduling) or Mode 2 (i.e., Mode 2 resource scheduling) UE in the RRC_CONNECTED state, the SL DRX configuration applied to one peer UE (per PC5 link) or all peer UEs may be controlled by the network (e.g., the cellular communication network 100) or by the UE itself. For a Mode 2 UE out of network coverage or in the RRC inactive (RRC_INACTIVE) / RRC idle (RRC_IDLE) state, the SL DRX configuration may be controlled by the network (e.g., through system information or per configuration) or the UE may select the SL DRX configuration itself.

[0094] In one example, a Mode 1 or Mode 2 UE in RRC_CONNECTED state may configure its SL DRX configuration based on dedicated signaling received from the network.

[0095] In one example, a Mode 2 UE in the RRC_CONNECTED state may configure the SL DRX configuration itself, for example, based on the ongoing SL service pattern / application.

[0096] In one example, a UE in RRC_IDLE / RRC_INACTIVE state may configure its SL DRX configuration based on system information for SL DRX configuration broadcast by the network. The system information containing the SL DRX configuration may be configured by the network for each cell or for each area (e.g., all serving cells in the same area may apply the same SL DRX configuration).

[0097] In one example, a UE in RRC_IDLE / RRC_INACTIVE state may configure its SL DRX configuration by itself, for example, based on the ongoing SL traffic pattern.

[0098] In one example, an out-of-coverage UE may configure its SL DRX configuration based on a pre-configuration of the SL.

[0099] In one example, an out-of-coverage UE may configure its SL DRX configuration itself, for example based on the ongoing SL traffic pattern.

[0100] In one example, for a Mode 1 and / or Mode 2 UE in the RRC_CONNECTED state, its SL DRX configuration may be configured by the network, wherein the BS may configure the SL DRX configuration to be aligned with the Uu DRX configuration of the UE (e.g., setting the same DRX offset, the same DRX ON duration, or the same DRX inactivity timer value in the Uu DRX configuration and the SL DRX configuration). In this way, the probability of the Uu sleep time being interrupted by the SL service activity may be reduced.

[0101] In one example, for Mode 1 and / or Mode 2 UEs, the SL DRX configuration may be configured by the network, wherein when the UE is in the same cell, the same area (which may include several cells or several Transmission and Reception Points (TRPs)), or in the same group for V2X multicast communication, the BS may configure the same SL DRX configuration for the UE. In this way, since the same SL DRX configuration is applied, the UE and its peer UE may have aligned SL DRX-ON durations. The cell / area-specific SL DRX configuration may be delivered through UE-specific dedicated signaling, system information for SL, or pre-configuration for SL.

[0102] In one example, the SL DRX configuration may be configured by the network, and the UE may send UE assistance information or SL UE information to the network to report the current SL service pattern or preferred SL DRX configuration to the network. In addition, the UE may report DRX-related statistics (e.g., the percentage of SL DRX active time in a given time period, and / or the average percentage of SL DRX active time per SL DRX cycle) or measurement results (e.g., the percentage of time that the UE monitors the SCI but does not send or receive SL transmit / receive data) to the network.

[0103] In one example, for Mode 1 and / or Mode 2 UEs, the SL DRX configuration may be network-configured, where the BS may configure the same SL DRX configuration for UEs participating in the same V2X application / service. The V2X application / service-specific SL DRX configuration may be delivered via UE-specific dedicated signaling, system information for SL, or pre-configuration.

[0104] In one example, for Mode 1 and / or Mode 2 UEs, the SL DRX configuration may be configured for each V2X application / service or for each UE ID. In other words, the UE may have a separate UE ID for transmitting / receiving different V2X applications / services, and thus the UE may apply different SL DRX configurations for different V2X applications / services.

[0105] For groupcast SL communication, all group members (i.e., UEs) in the group can apply the same or aligned SL DRX configuration to achieve power saving for group-specific SL communication. The group-specific SL DRX configuration can be configured / assigned / determined by the group leader via multicast or unicast (e.g., when a group member requests it or when a new group member joins the group), or can be configured by the network.

[0106] In one example, when a new member joins the group, the group leader may provide the new member with a group-specific SL DRX configuration to align its SL DRX active time with other members. When the group leader applies the new SL DRX configuration, the group leader may notify the new SL DRX configuration to the group members.

[0107] In one example, if a group member is in RRC_CONNECTED state, the network (e.g., gNB) can configure the same or aligned SL DRX configuration by sending dedicated signaling to the group member.

[0108] In one example, the group leader may transmit periodically or on demand to deliver the group-specific SL DRX configuration.

[0109] The group-specific SL DRX configuration may include further parameters, such as an indication of whether the group has SL DRX operation enabled, and a timestamp or version number identifying the SL DRX configuration currently applied in the group. If a group member finds that its stored or applied SL DRX configuration is out of date, the group member may send a message (e.g., to the group leader) to request the latest group-specific SL DRX configuration.

[0110] SL DRX configuration exchange

[0111] If the SL DRX configuration is determined by the UE itself, the UE can exchange the SL DRX configuration with the peer UE (for each MAC entity or each peer UE) after determining its own SL DRX configuration. In order to exchange the SL DRX configuration with the peer UE, the UE needs to know when its peer UE wakes up so that it can perform SL communication with the peer UE.

[0112] In one embodiment, the SLDRX configuration may be exchanged between UEs via an access stratum (AS) information exchange message of a PC5-RRC connection establishment procedure or a PC5-RRC connection configuration / reconfiguration procedure, for example, using an RRC reconfiguration SL message.

[0113] In another embodiment, the SL DRX configuration may be exchanged via a dedicated SL MAC control element (CE) or a dedicated PC5-RRC message. For example, a UE may send a PC5-RRC message containing one or more SL DRX configurations to its peer UE, and subsequently, the UE may send a SL MAC CE to its peer UE to adjust / select / switch the SL DRX configuration previously sent in the PC5-RRC message.

[0114] Ping for fast SL transfers

[0115] Compared to the traditional DRX operation for the Uu interface (where the UE only communicates with the BS), the UE in SL communication can receive packets from multiple peer UEs through the PC5 interface, and the UE needs to remain awake if SL communication is ongoing with at least one peer UE. This means that the UE may not be able to fully grasp the SL DRX active time of all peer UEs. For example, even though UE1 and UE2 may have exchanged their SL DRX configurations with each other, when UE2 is not in the SL DRX-ON duration of UE2, UE2 can still be in the SL DRX active time to perform SL communication with other UEs. Since UE1 does not know whether UE2 is performing SL communication with other UEs, when UE1 wants to initiate early communication with UE2 during the SL DRX-OFF period of UE2, it is unknown to UE1 whether UE2 is asleep or awake.

[0116] In one embodiment, if it is not currently in the SL DRX-ON duration of the peer UE, the UE may wait until the next SL DRX-ON duration of the peer UE begins. Alternatively, when it is not currently in the SL DRX-ON duration of the peer UE, the UE may determine whether its peer UE is still in the SL DRX active time based on the received SCI information, and if the peer UE is still in the SL DRX active time, may initiate early SL communication with the peer UE. For example, if the UE recently received an SCI from its peer UE, which SCI is used for SL communication with other UEs or the UE, the UE may be able to determine whether the peer UE is still in the SL DRX active time based on the SL DRX inactivity timer of the peer UE. It can also be said that the peer UE may remain in the SL DRX active time before the expiration of its SL DRX inactivity timer (the SL DRX inactivity timer may be started when the peer UE sends the SCI), and the value of the SL DRX inactivity timer of the peer UE may be derived from the signaling previously used for the SL DRX configuration exchange.

[0117] In another embodiment, when it is not in the SL DRX-ON duration of the peer UE, the UE may send a ping message to its peer UE to check whether the peer UE is still in the SL DRX active time.

[0118] Figure 6 FIG. 4 is a timing diagram of using a ping message to perform fast SL communication according to an embodiment of the present invention.

[0119] In step S610 , the UE may send a ping message to the peer UE to check whether the peer UE is still in the SL DRX active time.

[0120] In one embodiment, the UE may send a ping message when it wants to communicate with a peer UE but is not currently in the peer UE's SL DRX-ON duration, and the UE does not know whether the peer UE is still in the SL DRX active time.

[0121] In another embodiment, when the UE has a high priority SL service to transmit (i.e., a priority above a threshold), a ping message may be sent. Otherwise, if the priority of the SL service to be transmitted is below the threshold, the UE may not be allowed to send the ping message, and the UE may postpone the SL service transmission until the next SL DRX-ON duration of the peer UE begins or until an SCI is received from the peer UE.

[0122] In yet another embodiment, whether the UE is allowed to send a ping message may be configured or controlled by the network.

[0123] After step S610, if the peer UE successfully receives the ping message, the following steps S620A to S640A may be executed.

[0124] In particular, in step S620A, since the peer UE is still in its SL DRX active time, the peer UE successfully receives the ping message.

[0125] In step S630A, in response to the ping message, the peer UE may reply to the UE with a ping response, SL traffic, or SCI.

[0126] In step S640A, when any response to the ping message is received from the peer UE, the UE starts to perform SL communication with the peer UE.

[0127] After step S610, if the peer UE does not successfully receive the ping message, the following steps S620B to S630B may be executed.

[0128] In particular, in step S620B, the peer UE does not receive the ping message because the peer UE is not in its SL DRX active time.

[0129] In step S630B, the UE may wait until the next SL DRX-ON duration of the peer UE and then start SL communication with the peer UE.

[0130] In one embodiment, the ping message can be carried by the traditional SCI on the PSSCH, and the ping response can be a HARQ Acknowledgement (ACK). For example, if a peer UE receives an SCI on the PSSCH and finds that the indicated L2 ID matches the peer UE's own ID, the peer UE can reply to the UE with a HARQ ACK on the PSFCH. Alternatively, the ping response can be a separate message, for example, carried by a separate SCI. For example, if a UE receives any message from a peer UE, such as an SCI transmitted by the peer UE, the UE can regard the message as a received ping response regardless of whether the SL service from the peer UE is also for the UE.

[0131] In another embodiment, an indicator indicating that the message is a ping message may be carried in the SCI field, the MAC header, or the MAC sub-header, or a new SL MAC CE may be used as a ping message, or radio resources may be dedicated to ping messages. For example, a new SL MAC CE dedicated to ping messages may include a new logical channel ID in the MAC sub-header and may optionally include a zero-byte payload. Similarly, if a ping response is not carried on the PSFCH, an indicator indicating that the message is a ping response may be carried in the SCI field, the MAC header, the MAC sub-header, or the new SL MAC CE, or the ping response may be transmitted on radio resources dedicated to ping responses.

[0132] In addition, if the UE does not receive any ping response in the expected feedback channel or time-frequency radio resource, the UE may retransmit the ping message up to the maximum retransmission limit. When the maximum retransmission limit is reached, the UE may consider the peer UE to be in SL DRX inactivity time and may wait for the next SL DRX-ON duration of the peer UE.

[0133] In one embodiment, at the beginning of the next SL DRX-ON duration of the peer UE, the UE can wake up and switch to the SL DRX active time even if it is not the SL DRX-ON duration of the UE. By doing so, the pending SL traffic can be transmitted as soon as possible. During the period of time when the UE is waiting for the next SL DRX-ON duration of the peer UE, the UE can go to sleep to save power. This period of time can be modeled as a timer associated with the peer UE. For example, a new timer can be introduced to calculate the length of this period of time, and when the UE has SL traffic for the peer UE and the timer associated with the peer UE expires, the UE can enter the SL DRX active time.

[0134] Using wake-up signals to save power

[0135] According to the SL DRX configuration, even if the peer UE may not have any SL services for the UE, the UE may wake up periodically during the SL DRX-ON duration of each SL DRX cycle of each peer UE to monitor the SCI. In order to save UE power consumption associated with futile SCI monitoring, the present application may propose the concept of a wake-up signal. The wake-up signal may refer to a radio resource dedicated to the peer UE of the UE to wake up the peer UE. If the UE detects a wake-up signal from any peer UE before the upcoming SL DRX-ON duration, the UE may wake up for SCI monitoring within the SL DRX-ON duration. Otherwise, if the UE does not detect a wake-up signal from any peer UE before the upcoming SL DRX-ON duration, the UE may not wake up during the upcoming one or more SL DRX-ON durations (i.e., one or more SL DRX-ON durations may be skipped).

[0136] Figure 7 FIG. 2 is a schematic diagram of improving SL DRX operation by using a wake-up signal according to an embodiment of the present invention.

[0137] like Figure 7As shown, the UE may wake up for a short period of time (denoted as a detection window for a wake-up signal) before each SL DRX-ON duration to detect whether a wake-up signal is received. If the UE detects the presence of a wake-up signal in the detection window, the UE may wake up within the upcoming SL DRX-ON duration to receive SL services from the peer UE that sent the wake-up signal. Otherwise, if the UE does not detect the presence of a wake-up signal in the detection window, the UE may skip one or more upcoming SL DRX-ON durations. Specifically, if no wake-up signal is detected from any peer UE, the UE may be configured to skip sensing-related behaviors (such as SCI decoding) until the next wake-up signal detection resource arrives, for example.

[0138] In one embodiment, the traditional SCI used for PSSCH transmission can be used as a wake-up signal. For example, the SCI carrying the UE's destination ID can be used as a wake-up signal to notify the UE to wake up in the next SLDRX-ON duration.

[0139] In one embodiment, a special SCI may be used as a wake-up signal. The SCI / PSCCH may or may not be followed by a corresponding PSSCH.

[0140] In one embodiment, the wake-up signal may be carried by the SCI, wherein there may be a wake-up indication in the SCI field.

[0141] In one embodiment, the radio resources used for the wake-up signal may be separated from the radio resources used for SL data transmission (from a time / frequency / code domain perspective).

[0142] In one embodiment, for a Mode 1 UE, the network may configure periodic radio resources for the UE to receive a wake-up signal.

[0143] In one embodiment, if the UE does not monitor the configured time-frequency resources to obtain the wake-up signal for some reason (for example, the configured time-frequency resources overlap with the measurement gap), the UE can wake up at the upcoming SL DRX-ON duration to monitor the SCI as if the wake-up signal was detected before the SL DRX-ON duration.

[0144] In one embodiment, the detection window and periodicity of the wake-up signal may be independent of the SL DRX-ON duration.

[0145] In one embodiment, the detection window for the wake-up signal may start from an offset before each SL DRX-ON duration, or may start from the first several symbols / slots of each SL DRX-ON duration.

[0146] In one embodiment, the detection window may be configured to repeat in each SL DRX cycle or once in several SL DRX cycles.

[0147] In one embodiment, the UE may periodically broadcast its UE ID, SL DRX configuration, and / or time-frequency resources of the wake-up signal. For a new NR-V2X UE that has just activated the PC5 interface for SL communication, the NR-V2X UE may use the SL DRX configuration and wake-up signal-related information broadcast by the UE to communicate with the UE without establishing a PC5-RRC connection with the UE.

[0148] In a multicast scenario, UE-specific or group-specific wake-up signal configurations may be configured. For example, UE-specific SLDRX configurations and UE-specific wake-up signal configurations may be broadcast / multicast by the group leader (periodically or as needed) rather than by each group member themselves. In other words, when a group member wants to communicate with another group member, it is possible to determine when the target group member will monitor the wake-up signal based on the broadcast information, and therefore, the target group member may be woken up for SL communication. For example, group-specific wake-up resources may be configured so that when the group leader or group member has group-specific signaling / data to share, a wake-up signal may be sent to wake up one or more group members to monitor the next SL DRX-ON duration to receive SL services. For example, UE-specific and group-specific wake-up resources may be configured separately so that a group member may send a wake-up signal on a UE-specific resource when conducting a one-to-one unicast communication with a specific UE, or may send a wake-up signal on a group-specific resource when the group member wants to conduct a multicast communication.

[0149] In the SL relay scenario, UE-specific or group-specific wake-up signal configurations may be broadcast / multicast / delivered by the relay UE (periodically or as needed) rather than by each remote UE itself. When a remote UE wants to communicate with other remote UEs or relay UEs, it may determine when the other remote UEs or relay UEs monitor for the wake-up signal based on the wake-up signal configuration, and thus, may wake up the other remote UEs or relay UEs for SL communication. Since each remote UE follows the wake-up signal configuration received from the relay UE, the relay UE may wake up the remote UE via a wake-up signal when needed (e.g., when DL data for the remote UE arrives and waits for the relay UE to forward via the SL). If group-specific resources for the wake-up signal are configured, and the relay UE (or remote UE) has group-specific signaling / data to share, a wake-up signal may be sent to wake up one or more group members (e.g., the relay UE or other remote UEs associated with the relay UE) to monitor the next SL DRX-ON duration to receive SL services. The UE-specific resources and group-specific resources for wake-up signals can be configured separately, so that the relay UE can send the wake-up signal on the UE-specific resources when conducting one-to-one unicast communication with the remote UE (for example, transmitting SL relay data), or can send the wake-up signal on the group-specific resources when the relay UE wants to perform groupcast communication (for example, updating the SL relay configuration).

[0150] To further illustrate, it is particularly beneficial to apply the wake-up signal when the UE has SL traffic to transmit / receive every tens or hundreds of SL DRX cycles. However, applying the wake-up signal may consume more power for SCI monitoring in the following two cases. The first case is that if the UE has frequent SL traffic arriving (regardless of whether the SL traffic is from the same or different peer UEs), the UE may need to monitor each SL DRX-ON duration and may therefore consume unnecessary power to monitor the wake-up signal. The second case is that if the SL DRX cycle is relatively short (for example, to support delay-sensitive applications), the resource density of the wake-up signal may be high, i.e., the UE may need to monitor the wake-up signal frequently. Therefore, the UE may activate or deactivate the use of the wake-up signal based on the traffic arrival rate and the SL DRX cycle length.

[0151] In one embodiment, a message may be configured to inform the peer UE whether to apply the wake-up signal. The message may be delivered via a PC5-RRC message or a SL MAC CE.

[0152] In one embodiment, even during the SL DRX inactive time, the UE can still monitor some time-frequency resources to discover new peer UEs. If a new peer UE is discovered, the UE can exchange SL DRX configurations, including wake-up signal configurations, with the peer UE.

[0153] Using DRX requests to save power

[0154] In some cases, the UE may want to end the SL communication with the peer UE even if the SL DRX-ON duration timer or the SL DRX inactivity timer is still running. For example, all SL services have been transmitted (i.e., there is no data in the SL HARQ buffer for transmission), so the UE wants to enter the sleep state immediately. For example, the UE may not have a sufficient number of HARQ processes or HARQ numbers to handle simultaneous SL service transmission / reception, so the UE may want to postpone some transmissions to the next SL DRX cycle. In order to allow the UE to shorten the SL DRX active time, the present application may propose the concept of DRX request.

[0155] Figure 8 is a timing diagram of improving SL DRX operation using DRX request according to an embodiment of the present invention.

[0156] In step S810 , the UE may send a DRX request to a peer UE to request the peer UE to enter the SL DRX inactive time.

[0157] In one embodiment, a DRX request may be sent when the UE has no more SL traffic to transmit to a peer UE.

[0158] In another embodiment, the DRX request may be sent when the UE has no more high priority (eg, above a priority threshold) SL traffic to transmit to the peer UE.

[0159] After step S810 , if the peer UE accepts the DRX request, the following steps S820A to S840A may be executed.

[0160] In particular, in step S820A, the peer UE also has no more SL traffic (eg, high-priority SL traffic), so the DRX request may be accepted to enter the SL DRX inactive time.

[0161] In step S830A, the peer UE may reply a message to the UE to confirm acceptance of the DRX request.

[0162] In step S840A, the UE and the peer UE may enter the SL DRX inactive time until the next SL DRX-ON duration begins. In other words, the two UEs may regard each other as being in the SL DRX inactive time and, if necessary, may perform SL communication in a subsequent transmission opportunity when both UEs are in the SL DRX active time (e.g., the next SL DRX-ON duration).

[0163] After step S810 , if the DRX request is rejected by the peer UE, the following steps S820B to S840B may be executed.

[0164] In particular, in step S820B, the peer UE still has SL traffic (eg, high-priority SL traffic) to transmit to the UE, so the DRX request for entering the SL DRX inactive time may be rejected.

[0165] In step S830B, the peer UE may continue to transmit the remaining SL traffic to the UE.

[0166] In step S840B, SL communication between the UE and the peer UE may continue.

[0167] In one embodiment, if the peer UE still has SL traffic to transmit to the UE, the peer UE may continue to transmit the SL traffic and ignore the DRX request, or may send an acknowledgment message when transmission of the remaining SL traffic is completed.

[0168] Figure 9 4 is a flow chart of a method for supporting DRX in SL communication according to an embodiment of the present invention.

[0169] In this embodiment, the method of supporting DRX in SL communication may be applied to and performed by the UE.

[0170] Initially, the UE may determine a SL DRX configuration set based on one of: one or more types of one or more SL services performed by the UE with one or more peer UEs, one or more SL DRX configurations received from the peer UEs, and control information received from the BS (step S910).

[0171] The UE may then apply the SL DRX configuration set to enable DRX operation for SL communication with peer UEs (step S920 ).

[0172] In particular, the SL DRX configuration set may include one or more SL DRX configurations, where each SL DRX configuration may correspond to a DRX operation for SL communication with each peer UE, and each SL DRX configuration may include information of a SL DRX offset, a SL DRX cycle, a SL DRX-ON duration, and a SL DRX inactivity timer.

[0173] In one embodiment, the SL DRX configuration may be received from the peer UE via at least one of a PC5-RRC message and a SL MAC CE.

[0174] In one embodiment, the control information received from the BS may include a DRX configuration, which may be applied to enable another DRX operation for communicating with the BS.

[0175] By reading the above embodiments, it can be understood that the present application can achieve robust and efficient power saving for NR-based V2X by providing SL DRX operation for the PC5 interface. In particular, the parameters used in the SL DRX operation (e.g., SL DRX offset, SL DRX cycle, and SL DRX active time) and counters (e.g., SL DRX-ON duration timer, SL DRX inactivity timer, DRX retransmission timer for SL reception / transmission, and HARQ RTT timer for SL reception / transmission) can also be adapted to the evolution of NR-based V2X.

[0176] Although the present invention has been described in an exemplary manner according to preferred embodiments, it is to be understood that the present invention is not limited thereto. Those skilled in the art may still make various changes and modifications without departing from the scope and spirit of the present invention. Therefore, the scope of the present invention should be defined and protected by the appended claims and their equivalents.

[0177] Ordinal numbers used in the claims to modify claim elements (such as "first", "second", etc.) do not, by themselves, imply any priority, preference, or order of one claim element with respect to another claim element or with respect to the temporal order of the acts of performing the method, but serve merely as labels to distinguish one claim element having a particular name from another element having the same name (except for the use of the ordinal number) to distinguish claim elements.

Claims

1. A user equipment for sidelink communication, comprising: a wireless transceiver configured to perform wireless transmission and reception with one or more peer user devices; as well as The controller is configured as: determining one or more sidelink discontinuous reception configurations; and applying the one or more sidelink discontinuous reception configurations to enable discontinuous reception operation for sidelink communication with the peer user equipment via the wireless transceiver, Each sidelink discontinuous reception configuration includes at least one of a sidelink discontinuous reception offset, a sidelink discontinuous reception period, a sidelink discontinuous reception on duration, and a sidelink discontinuous reception inactivity timer. The user equipment is configured to perform a sidelink discontinuous reception operation during a sidelink active time to monitor sidelink control information, wherein the sidelink active time is determined according to a corresponding sidelink discontinuous reception configuration. Wherein, when multiple sidelink discontinuous reception configurations for unicast, groupcast or broadcast communications corresponding to multiple peer user equipments are applied, the user equipments maintain separate sidelink active times for different sidelink discontinuous reception configurations.

2. The user equipment according to claim 1, wherein The sidelink discontinuous reception offsets of the sidelink discontinuous reception configurations are the same.

3. The user equipment according to claim 1, wherein When the user equipment is in the sidelink discontinuous reception on-duration, the controller turns on the wireless transceiver; When the user equipment is not in the sidelink DRX on-duration, unless the inactivity timer is running, turning off the radio transceiver; and The inactivity timer is started in response to one of the following conditions: The user equipment receives a sidelink-related radio network temporary identifier from the base station for configuring sidelink resources or for activating or deactivating a sidelink configuration grant; The user equipment receives sidelink control information associated with one of the sidelink services from one of the peer user equipments; When sidelink mode 2 resource scheduling is configured for the user equipment, the user equipment selects a sidelink resource from the sidelink resources for data transmission with one of the peer user equipments.

4. The user equipment according to claim 1, wherein a first active time of the discontinuous reception operation for the sidelink communication with the peer user equipment being related to a second active time of another discontinuous reception operation for communication with a base station; as well as When the second active time has passed but the first active time has not passed, the second active time is extended or the first active time is stopped.

5. The user equipment according to claim 1, wherein The user equipment receives control information from a base station, the control information including a discontinuous reception configuration, wherein the discontinuous reception configuration is applied to enable another discontinuous reception operation for communicating with the base station.

6. The user equipment according to claim 1, wherein The sidelink discontinuous reception configuration is received from the peer user equipment via at least one of a PC5-Radio Resource Control message and a control element of a sidelink medium access control.

7. The user equipment according to claim 1, wherein In response to one of the peer user equipment not being in the sidelink discontinuous reception on-duration of the sidelink discontinuous reception configuration associated with the peer user equipment, the controller further transmitting a message to the peer user equipment via the wireless transceiver; and In response to receiving a response to the message from the peer user equipment, the sidelink communication is conducted with the peer user equipment.

8. The user equipment according to claim 1, wherein The controller turns on the wireless transceiver for a period of time before the sidelink discontinuous reception on-duration corresponding to the discontinuous reception operation of one of the peer user equipments for the sidelink communication to determine whether a signal is received from the peer user equipment; as well as In response to not receiving the signal from the peer user equipment within the period of time, turning off the wireless transceiver for a next sidelink discontinuous reception on-duration, wherein the next sidelink discontinuous reception on-duration corresponds to the discontinuous reception operation of the peer user equipment for the sidelink communication.

9. The user equipment according to claim 1, wherein: During the sidelink discontinuous reception on-duration corresponding to the discontinuous reception operation of one of the peer user devices performing the sidelink communication, the controller sends a request to the peer user device via the wireless transceiver so that the peer user device turns off its wireless transceiver until the next sidelink discontinuous reception on-duration starts.

10. A method for sidelink communication, comprising: determining, by the user equipment, one or more sidelink discontinuous reception configurations; as well as applying, by the user equipment, the one or more sidelink discontinuous reception configurations to enable discontinuous reception operation for sidelink communication with one or more peer user equipments, Each sidelink discontinuous reception configuration includes at least one of a sidelink discontinuous reception offset, a sidelink discontinuous reception period, a sidelink discontinuous reception on duration, and a sidelink discontinuous reception inactivity timer. The user equipment is configured to perform a sidelink discontinuous reception operation during a sidelink active time to monitor sidelink control information, wherein the sidelink active time is determined according to a corresponding sidelink discontinuous reception configuration. Wherein, when multiple sidelink discontinuous reception configurations for unicast, groupcast or broadcast communications corresponding to multiple peer user equipments are applied, the user equipments maintain separate sidelink active times for different sidelink discontinuous reception configurations.

11. The method for sidelink communication according to claim 10, wherein: The sidelink discontinuous reception offsets of the sidelink discontinuous reception configurations are the same.

12. The method for sidelink communication according to claim 10, wherein: Also includes: When the user equipment is in the sidelink discontinuous reception on-duration period, turning on a wireless transceiver; When the user equipment is not in the sidelink DRX on-duration, unless the inactivity timer is running, turning off the radio transceiver; and The inactivity timer is started in response to one of the following conditions: The user equipment receives a sidelink-related radio network temporary identifier from the base station for configuring sidelink resources or for activating or deactivating a sidelink configuration grant; The user equipment receives sidelink control information associated with one of the sidelink services from one of the peer user equipments; When sidelink mode 2 resource scheduling is configured for the user equipment, the user equipment selects a sidelink resource from the sidelink resources for data transmission with one of the peer user equipments.

13. The method for sidelink communication according to claim 10, wherein: a first active time of the discontinuous reception operation for the sidelink communication with the peer user equipment being related to a second active time of another discontinuous reception operation for communication with a base station; as well as When the second active time has passed but the first active time has not passed, the second active time is extended or the first active time is stopped.

14. The method for sidelink communication according to claim 10, wherein: The user equipment receives control information from a base station, the control information including a discontinuous reception configuration, wherein the discontinuous reception configuration is applied to enable another discontinuous reception operation for communicating with the base station.

15. The method for sidelink communication according to claim 10, wherein: The sidelink discontinuous reception configuration is received from the peer user equipment via at least one of a PC5-Radio Resource Control message and a control element of a sidelink medium access control.

16. The method for sidelink communication according to claim 10, wherein: Also includes: sending a message to one of the peer user equipments in response to the peer user equipment not being in the sidelink discontinuous reception on-duration of the sidelink discontinuous reception configuration associated with the peer user equipment; and In response to receiving a response to the message from the peer user equipment, the sidelink communication is conducted with the peer user equipment.

17. The method for sidelink communication according to claim 10, wherein: Also includes: Before the sidelink DRX on-duration corresponding to the DRX operation of one of the peer user equipments performing the sidelink communication, turning on the wireless transceiver of the user equipment for a period of time to determine whether a signal is received from the peer user equipment; as well as In response to not receiving the signal from the peer user equipment within the period of time, turning off the wireless transceiver for a next sidelink discontinuous reception on-duration, wherein the next sidelink discontinuous reception on-duration corresponds to the discontinuous reception operation of the peer user equipment for the sidelink communication.

18. The method for sidelink communication according to claim 10, wherein: Also includes: During the sidelink discontinuous reception on-duration corresponding to the discontinuous reception operation of one of the peer user equipments for the sidelink communication, a request is sent to the peer user equipment to cause the peer user equipment to turn off its wireless transceiver until the next sidelink discontinuous reception on-duration begins.

19. A storage device storing program instructions, wherein when the program instructions are executed by a user equipment, the user equipment is caused to perform the steps of the method for sidelink communication according to any one of claims 10 to 18.

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