WO2023004637A1

WO2023004637A1 - Methods and apparatuses for maintaining an uu interface associated timer with a sl drx scheme

Info

Publication number: WO2023004637A1
Application number: PCT/CN2021/108997
Authority: WO
Inventors: Jing HAN; Mingzeng Dai; Ran YUE; Lianhai WU; Congchi ZHANG; Haiming Wang
Original assignee: Lenovo (Beijing) Limited
Priority date: 2021-07-28
Filing date: 2021-07-28
Publication date: 2023-02-02

Abstract

Embodiments of the present disclosure relate to methods and apparatuses for maintaining a timer associated with an Uu interface with a sidelink (SL) discontinuous reception (DRX) scheme in 3GPP (3rd Generation Partnership Project) 5G networks. According to an embodiment of the present disclosure, a method may be performed by a user equipment (UE) and may include: determining a data transmission status on a SL with a further UE; and maintaining a plurality of timers according to the data transmission status on the SL, wherein the timers are associated with an Uu interface with a network device, and the timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu hybrid automatic repeat request (HARQ) timer.

Description

METHODS AND APPARATUSES FOR MAINTAINING AN UU INTERFACE ASSOCIATED TIMER WITH A SL DRX SCHEME

TECHNICAL FIELD

Embodiments of the present application are related to wireless communication technology, and more particularly, related to methods and apparatuses for maintaining or configuring a timer associated with an Uu interface with a sidelink (SL) discontinuous reception (DRX) scheme in 3GPP (3rd Generation Partnership Project) 5G networks.

BACKGROUND

A sidelink is a long-term evolution (LTE) feature introduced in 3GPP Release 12, and enables a direct communication between proximal UEs, and data does not need to go through a base station (BS) or a core network. A sidelink communication system has been introduced into 3GPP 5G wireless communication technology, in which a direct link between two user equipments (UEs) is called a sidelink (SL) .

3GPP 5G networks are expected to increase network throughput, coverage, and robustness and reduce latency and power consumption. With the development of 3GPP 5G networks, various aspects need to be studied and developed to perfect the 5G technology. Currently, details regarding how to maintain or configure an Uu interface associated timer with a SL DRX scheme have not been discussed in 3GPP 5G technology yet.

SUMMARY

Some embodiments of the present application provide a method, which may be performed by a user equipment (UE) . The method includes: determining a data transmission status on a SL with a further UE; and maintaining a plurality of timers according to the data transmission status on the SL, wherein the timers are associated with an Uu interface with a network device, and the timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu hybrid automatic repeat request (HARQ) timer.

Some embodiments of the present application also provide a UE using a SL. The UE includes a processor and a wireless transceiver coupled to the processor; and the processor is configured: to determine a data transmission status on a SL with a further UE; and to maintain a plurality of timers according to the data transmission status on the SL, wherein the timers are associated with an Uu interface with a network device, and the timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu HARQ timer.

Some embodiments of the present application provide an apparatus. The apparatus includes: a non-transitory computer-readable medium having stored thereon computer-executable instructions, a receiving circuitry; a transmitting circuitry; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry and the transmitting circuitry, wherein the computer-executable instructions cause the processor to implement the abovementioned method performed by a UE.

The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which advantages and features of the present application can be obtained, a description of the present application is rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. These drawings depict only exemplary embodiments of the present application and are not therefore intended to limit the scope of the present application.

FIG. 1 illustrates an exemplary sidelink wireless communication system in accordance with some embodiments of the present application;

FIG. 2 illustrates a flow chart of a method for maintaining a timer associated with an Uu interface according to some embodiments of the present application; and

FIG. 3 illustrates an exemplary block diagram of an apparatus according to some embodiments of the present application.

DETAILED DESCRIPTION

The detailed description of the appended drawings is intended as a description of preferred embodiments of the present application and is not intended to represent the only form in which the present application may be practiced. It should be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architecture and new service scenarios, such as 3GPP LTE and LTE advanced, 3GPP 5G NR, B5G, 6G, and so on. It is contemplated that along with developments of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and moreover, the terminologies recited in the present application may change, which should not affect the principle of the present application.

FIG. 1 illustrates an exemplary sidelink wireless communication system in accordance with some embodiments of the present application.

As shown in FIG. 1, a wireless communication system 100 includes at least one user equipment (UE) 101 and at least one base station (BS) 102. In particular, the wireless communication system 100 includes two UEs 101 (e.g., UE 101a and UE 101b) and one BS 102 for illustrative purpose. Although a specific number of UEs 101 and BS 102 are depicted in FIG. 1, it is contemplated that any number of UEs 101 and BSs 102 may be included in the wireless communication system 100.

UE (s) 101 may include computing devices, such as desktop computers, laptop computers, personal digital assistants (PDAs) , tablet computers, smart televisions (e.g., televisions connected to the Internet) , set-top boxes, game consoles, security systems (including security cameras) , vehicle on-board computers, network devices (e.g., routers, switches, and modems) , or the like. According to some embodiments of the present application, UE (s) 101 may include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiver, or any other device that is capable of sending and receiving communication signals on a wireless network.

In some embodiments of the present application, a UE is a pedestrian UE (P-UE or PUE) or a cyclist UE. In some embodiments of the present application, UE (s) 101 includes wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, UE (s) 101 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described using other terminology used in the art. UE (s) 101 may communicate directly with BSs 102 via LTE or NR Uu interface.

In some embodiments of the present application, each of UE (s) 101 may be deployed an IoT application, an eMBB application and/or a URLLC application. For instance, UE 101a may implement an IoT application and may be named as an IoT UE, while UE 101b may implement an eMBB application and/or a URLLC application and may be named as an eMBB UE, an URLLC UE, or an eMBB/URLLC UE. It is contemplated that the specific type of application (s) deployed in UE (s) 101 may be varied and not limited.

In a sidelink communication system, a transmission UE may also be named as a transmitting UE, a Tx UE, a sidelink Tx UE, a sidelink transmission UE, or the like. A reception UE may also be named as a receiving UE, a Rx UE, a sidelink Rx UE, a sidelink reception UE, or the like.

According to some embodiments of FIG. 1, UE 101a functions as a Tx UE, and UE 101b functions as a Rx UE. UE 101a may exchange sidelink messages with UE 101b through a sidelink, for example, PC5 interface as defined in 3GPP TS 23.303. UE 101a may transmit information or data to other UE (s) within the sidelink communication system, through sidelink unicast, sidelink groupcast, or sidelink broadcast. For instance, UE 101a transmits data to UE 101b in a sidelink unicast session. UE 101a may transmit data to UE 101b and other UEs in a groupcast group (not shown in FIG. 1) by a sidelink groupcast transmission session. Also, UE 101a may transmit data to UE 101b and other UEs (not shown in FIG. 1) by a sidelink broadcast transmission session.

Alternatively, according to some other embodiments of FIG. 1, UE 101b functions as a Tx UE and transmits sidelink messages, UE 101a functions as a Rx UE and receives the sidelink messages from UE 101b.

Both UE 101a and UE 101b in the embodiments of FIG. 1 may transmit information to BS (s) 102 and receive control information from BS (s) 102, for example, via LTE or NR Uu interface. BS (s) 102 may be distributed over a geographic region. In certain embodiments of the present application, each of BS (s) 102 may also be referred to as an access point, an access terminal, a base, a base unit, a macro cell, a Node-B, an evolved Node B (eNB) , a gNB, a Home Node-B, a relay node, or a device, or described using other terminology used in the art. BS (s) 102 is generally a part of a radio access network that may include one or more controllers communicably coupled to one or more corresponding BS (s) 102.

The wireless communication system 100 may be compatible with any type of network that is capable of sending and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with a wireless communication network, a cellular telephone network, a Time Division Multiple Access (TDMA) -based network, a Code Division Multiple Access (CDMA) -based network, an Orthogonal Frequency Division Multiple Access (OFDMA) -based network, an LTE network, a 3GPP-based network, a 3GPP 5G network, a satellite communications network, a high altitude platform network, and/or other communications networks.

In some embodiments of the present application, the wireless communication system 100 is compatible with the 5G NR of the 3GPP protocol, wherein BS (s) 102 transmit data using an OFDM modulation scheme on the downlink (DL) and UE (s) 101 transmit data on the uplink (UL) using a Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) or cyclic prefix-OFDM (CP-OFDM) scheme. More generally, however, the wireless communication system 100 may implement some other open or proprietary communication protocols, for example, WiMAX, among other protocols.

In some embodiments of the present application, BS (s) 102 may communicate using other communication protocols, such as the IEEE 802.11 family of wireless communication protocols. Further, in some embodiments of the present application, BS (s) 102 may communicate over licensed spectrums, whereas in other embodiments, BS (s) 102 may communicate over unlicensed spectrums. The present application is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol. In yet some embodiments of present application, BS (s) 102 may communicate with UE (s) 101 using the 3GPP 5G protocols.

In general, in 3GPP RAN#86 meeting, a sidelink enhancement work item has been agreed. The necessity of NR sidelink enhancement has been identified. For V2X and public safety, the service requirements and operation scenarios are not fully supported in 3GPP Rel-16 due to the time limitation. Power saving enables UEs with battery constraint to perform sidelink operations in a power efficient manner. 3GPP Rel-16 NR sidelink is designed based on the assumption of “always-on” when a UE operates a sidelink, e.g., only focusing on UEs installed in vehicles with sufficient battery capacity. Solutions for power saving in3GPP Rel-17 are required for vulnerable road users (VRUs) in V2X use cases and for UEs in public safety and commercial use cases where power consumption in the UEs needs to be minimized.

As one mechanism of power saving, a sidelink (SL) DRX scheme is expected to be introduced for a sidelink operation. As in Uu, a SL DRX scheme is used for a non-continuously reception for a SL UE, and is controlled by several timers. One of them is inactivity timer, which is used to extend active time for a reception of continuously data, especially for aperiodic data transmission.

In particular, in 3GPP RAN2#114-e meeting, following agreements are made for Uu DRX timers with a SL DRX scheme. Following agreements mean that on an Uu interface, on-duration timer and inactivity timer are shared by Uu activity and SL activity.

(1) On duration timer and inactivity timer

a) SL-specific drx-onDurationTimer is not introduced in Uu.

b) SL-specific drx-InactivityTimer is not introduced in Uu.

c) For Tx UE configured with sidelink resource allocation mode 1, it should start or restart the Uu drx-InactivityTimer if the UE receives a PDCCH indicating a new SL transmission.

(2) HARQ timers

a) SL-specific drx-HARQ-RTT-Timer and SL-specific drx-RetransmissionTimer should be introduced in Uu, which are configured or maintained based on sidelink process.

b) When sl-PUCCH-Config is configured, SL-specific drx-HARQ-RTT-Timer and SL-specific drx-RetransmissionTimer should be configured or maintained for UE configured with sidelink resource allocation mode 1.

c) Adopt the following definitions of SL-specific drx-HARQ-RTT-Timer and drx-RetransmissionTimer:

– drx-RetransmissionTimerSL (per Sidelink process) : the maximum duration until a grant for SL retransmission is received;

– drx-HARQ-RTT-TimerSL (per Sidelink process) : the minimum duration before a SL retransmission grant is expected by the MAC entity.

d) When sl-PUCCH-Config is configured (and the PUCCH is transmitted) , the UE should start the SL-specific drx-HARQ-RTT-Timer in Uu for the corresponding SL HARQ process in the first slot after the end of the corresponding transmission carrying the SL HARQ feedback via the PUCCH.

Also, 3GPP RAN2 has agreed SL timer on PC5 interface as following, which means for some SL transmission, there does not support SL inactivity timer.

(1) At least, On-duration timer and Inactivity timer are supported in SL unicast.

(2) SL Inactivity timer is supported for groupcast.

(3) SL Inactivity timer is not supported for broadcast transmissions.

Currently, an Uu DRX command is used to indicate to a UE that there is no following Uu data. Then, the UE can go to “sleep” . But now, a SL UE is possible to have SL data, and then, the UE behavior may be different. In addition, an Uu inactivity timer is agreed to be started or restarted if the UE receives a PDCCH indicating a new SL transmission. Starting or restarting the Uu drx-InactivityTimer is to monitor followed potential SL scheduling grant. However, if there has no followed potential SL scheduling grant, there has no need to start or restart Uu drx-InactivityTimer. Given the above, several issues need to be solves, e.g., whether a UE shall stop Uu interface associated timer (s) after receiving a Uu DRX command; how to judge whether a retransmission of the corresponding sidelink process is necessary to start a SL specific HARQ timer on Uu interface; and an Uu inactivity timer is always (re) started when receiving a SL grant for a new transmission, which is not necessary sometimes for SL transmission without a SL inactivity timer.

Some embodiments of the present application propose a UE’s new behavior when the UE receives an Uu DRX command. Some embodiments of the present application provide solutions of how to determine whether a retransmission is needed to start a HARQ timer. Some embodiments of the present application provide new condition (s) to start or stop an Uu inactivity timer. More details will be illustrated in the following text in combination with the appended drawings.

FIG. 2 illustrates a flow chart of a method for maintaining a timer associated with an Uu interface according to some embodiments of the present application. The embodiments of FIG. 2 may be performed by a UE (e.g., UE 101a or UE 101b illustrated and shown in FIG. 1) . Although described with respect to a UE, it should be understood that other devices may be configured to perform a method similar to that of FIG. 2.

In the exemplary method 200 as shown in FIG. 2, in operation 201, a UE (e.g., UE 101a illustrated and shown in FIG. 1) determines a data transmission status on a SL with a further UE. In some embodiments, the UE is a transmission UE, i.e., a TX UE (e.g., UE 101a) , and the further UE is a reception UE, i.e., a RX UE (e.g., UE 101b) .

In operation 202, the UE maintains or configures a plurality of timers according to the data transmission status on the SL. The timers are associated with an Uu interface with a network device (e.g., BS 102 illustrated and shown in FIG. 1) . The timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu HARQ timer. In some embodiments, the Uu HARQ timer includes a HARQ round trip time (RTT) timer and/or a HARQ retransmission timer. For example, UE 101a maintains or configures at least an Uu on-duration timer, an Uu inactivity timer, and an Uu HARQ timer.

According to some embodiments, the UE receives an Uu DRX command from the network device. For example, the Uu DRX command is received in response to: (1) the UE is configured with sidelink resource allocation mode 1 (i.e., Mode 1, which may also be named as a BS scheduled resource mode or the like) ; (2) the UE is configured with a DRX scheme/function related to the Uu interface; and (3) the UE is configured with a DRX scheme/function related to the SL. In this example, if the UE does not successfully receive HARQ feedback information, the UE may start a HARQ retransmission timer, to monitor a potential retransmission scheduling from the network device (e.g., BS 102 illustrated and shown in FIG. 1) .

In an embodiment, in response to receiving the Uu DRX command, the UE transmits a SL DRX command to the further UE via an unicast mode or a broadcast mode. In a further embodiment, in response to receiving the Uu DRX command from the network device and in response to available data to be transmitted on the SL, the UE triggers a buffer status report (BSR) for the SL, e.g., a regular SL-BSR.

In another embodiment, after receiving the Uu DRX command, if the SL is in an activated state (i.e., SL activity) and if the Uu on-duration timer and the Uu inactivity timer are running, the UE may stop the Uu on-duration timer and the Uu inactivity timer. In yet another embodiment, after receiving the Uu DRX command, if the SL is in an un-activated state and if the Uu on-duration timer and the Uu inactivity timer are running, the UE may allow the on-duration timer and the inactivity timer to continue running.

According to some embodiments, the SL may be activated based on at least one of:

(1) the UE is configured with configuration information regarding the SL;

(2) the SL has one or more interest destinations;

(3) a medium access control (MAC) entity of the UE has been configured with sidelink resource allocation mode 1 (i.e., Mode 1) ;

(4) the UE is configured with a radio network temporary identifier (RNTI) of the SL, e.g., SL-RNTI;

(5) the UE is configured with a configured scheduling radio network temporary identifier (CS-RNTI) of the SL, e.g., SL-CSRNTI;

(6) the UE receives a grant on a PDCCH for data to be transmitted on the SL, and the UE starts or restarts an inactivity timer associated with the SL;

(7) the UE has data to be transmitted on the SL;

(8) data to be transmitted by the UE on the SL; and

(9) data to be received by the UE on the SL.

For instance, after receiving the Uu DRX command, if an on-duration timer associated with the SL (i.e., SL on-duration timer) is running, the UE may stop the on-duration timer associated with the SL; if an inactivity timer associated with the SL (i.e., SL inactivity timer) is running, the UE may stop the inactivity timer associated with the SL; and the UE may use a cycle of a DRX function related to the SL. In an embodiment, the UE stops the SL on-duration timer or the SL inactivity timer if there is no data for all data radio bearers (DRBs) of the SL to be transmitted to the further UE. In a further embodiment, the UE stops the SL on-duration timer or the SL inactivity timer if the UE is switched from sidelink resource allocation mode 1 (i.e., Mode 1) to sidelink resource allocation mode 2 (i.e., Mode 2) in one DRX cycle, e.g., the same long DRX cycle.

According to some embodiments, in response to receiving, on the Uu interface, configuration information regarding a physical uplink control channel (PUCCH) of the SL (e.g., sl-PUCCH-Config) , the UE generates negative acknowledgement (NACK) for a physical uplink control channel (PUCCH) and instructs a physical layer of the UE to signal a negative acknowledgement corresponding to the transmission on the PUCCH. If a time alignment (TA) is not expired, the UE determines that a retransmission on the SL is needed and there is a need to start a HARQ retransmission timer.

According to some embodiments, in response to not receiving configuration information regarding a PUCCH of the SL, the UE determines that a retransmission on the SL is necessary. In some embodiments, in response to determining that the retransmission on the SL is necessary, the UE may transmit, to the network device, an indicator to start or restart the Uu HARQ timer at the network device. The indicator may be transmitted in a scheduling request (SR) . In an embodiment, after the UE transmits the indicator, e.g., in the SR, both the Uu HARQ timer at the network device and the Uu HARQ timer at the UE are started or restarted.

For instance, the UE may determine that the retransmission on the SL is necessary when fulfilling at least one condition of:

(1) a most recent transmission of a medium access control (MAC) protocol data unit (PDU) is not prioritized;

(2) a HARQ feedback scheme has been disabled for the MAC PDU, and no sidelink grant is available for a next retransmission of the MAC PDU;

(3) the HARQ feedback scheme has been enabled, and the UE receives NACK on a physical sidelink feedback channel (PSFCH) of the most recent transmission; and

(4) the HARQ feedback scheme has been enabled, and the UE receives a discontinuous transmission (DTX) for the HARQ feedback scheme of the most recent transmission.

According to some embodiments, if the UE is switched from sidelink resource allocation mode 1 (i.e., Mode 1) to sidelink resource allocation mode 2 (i.e., Mode 2) and if the Uu HARQ timer is running, the UE may stop the Uu HARQ timer.

According to some embodiments, the plurality of timers further include an Uu DRX inactivity timer, and the UE may further start or restart the Uu DRX inactivity timer. In an embodiment, the UE may starts or restart the Uu DRX inactivity timer in response to: (1) the UE is configured with Mode 1; (2) the UE is configured with a DRX function related to the Uu interface, e.g., an Uu DRX function; and (3) the UE is configured with a DRX function related to the SL, e.g., SL DRX function.

In a further embodiment, the UE may starts or restart the Uu DRX inactivity timer further in response to:

(1) receiving a PDCCH indicating an initial transmission on the SL; or

(2) receiving the PDCCH indicating the initial transmission on the SL, and a transmission on the SL supporting or being configured with an inactivity timer associated with the SL.

According to some embodiments, the UE further stops the Uu inactivity timer, in response to: (1) a transmission on the SL not supporting an inactivity timer associated with the SL; (2) the UE entering a DRX function related to the SL; and (3) the Uu inactivity timer being running. For instance, the UE may determine that the transmission on the SL does not support the inactivity timer associated with the SL when fulfilling at least one of:

(1) only a broadcast service is supported on the SL;

(2) a groupcast service is supported on the SL, and the inactivity timer associated with the SL is not supported;

(3) an unicast service is not supported on the SL;

(4) a logical channel (LCH) priority of the unicast service is lower than a LCH priority of the broadcast service and the groupcast service; and

(5) the inactivity timer associated with the SL is not configured to the transmission on the SL.

Details described in all other embodiments of the present application (for example, details of configuring or maintaining an Uu interface associated timer with a SL DRX scheme) are applicable for the embodiments of FIG. 2. Moreover, details described in the embodiments of FIG. 2 are applicable for all embodiments of FIGS. 1 and 3.

The following texts describe specific Embodiments 1-3 of the methods as shown and illustrated in FIG. 2. According to Embodiments 1-3, a SL UE and a BS may perform following operations. The SL UE may be UE 101a or UE 101b illustrated and shown in FIG. 1. The BS may be BS 102 illustrated and shown in FIG. 1.

Embodiment 1: this embodiment aims to solve an issue of whether a UE stops Uu interface associated timer (s) after receiving an Uu DRX command, i.e., an Uu DRX CMD.

In Embodiment 1, if a SL UE (which may be a TX UE, e.g., UE 101a illustrated and shown in FIG. 1) is configured with sidelink resource allocation mode 1 (i.e., Mode 1) , and configured with an Uu DRX function and a SL DRX function. When the UE receives an Uu DRX CMD from the BS (e.g., BS 102 illustrated and shown in FIG. 1) , the UE behaviors may be different as legacy procedure.

In sub-embodiment (1) of Embodiment 1, the BS sends an Uu DRX CMD to the UE after both the Uu interface and the SL has no new data. For example, if the BS has scheduled all SL data according to SL-BSR and if the BS does not receive any signaling indicating that there has any SL data, e.g., SR/BSR, the BS may determine that there is no new SL data. Then, the BS may send the Uu DRX CMD to the UE. After the UE receives the Uu DRX CMD from the BS, the UE will stop an on-duration timer and an inactivity timer on the Uu interface.

(1) In one example, the UE stops SL on-duration timer and SL inactivity timer (if any) and uses a SL DRX cycle.

(2) In a further example, after the UE receives the Uu DRX CMD from the BS, the UE is triggered to send SL DRX CMD to unicast peer UE (which may be a RX UE, e.g., UE 101b illustrated and shown in FIG. 1) , or via groupcast to other group members. Then, the UE stops SL on-duration timer and SL inactivity timer and uses a SL DRX cycle.

(3) In another example, after the UE receives the Uu DRX CMD from the BS, if there still is SL data available for transmission, the UE is triggered a regular SL-BSR.

In sub-embodiment (2) of Embodiment 1, after the UE receives the Uu DRX CMD from the BS, if there still has SL activity, the UE will not stop an Uu on-duration timer and inactivity timer. On the other word, the UE only stops an Uu on-duration timer and an Uu inactivity timer when receiving the Uu DRX CMD and there is no SL activity. The UE determines that there is SL activity according to following one or more conditions; else, the UE determines that there has no SL activity:

(1) If the UE is configured with SL configuration (no matter if has SL communication) .

(2) If a SL of the UE has interest destinations.

(3) If the MAC entity of the UE has been configured with sidelink resource allocation mode 1 (i.e., Mode 1) .

(4) If the UE is configured with SL-RNTI/SL-CSRNTI (only when the UE is a Tx UE) .

(5) If the UE receives a SL grant on PDCCH for a new SL transmission (re) start the inactivity timer (only when the UE is a Tx UE) .

(6) If the UE has SL data for transmission (only when the UE is a Tx UE) .

(7) If the UE has any activity of SL transmission/reception.

In Embodiment 1, the UE may stop an Uu on-duration timer and an Uu inactivity timer when following one or more conditions are fulfilled:

(1) After the UE receives the Uu DRX CMD from the BS, if in the same long DRX cycle, the UE has no SL data available for all SL DRBs, the UE stops an Uu on-duration timer and an Uu inactivity timer, and stops a SL on-duration timer and a SL inactivity timer.

(2) After the UE receives the Uu DRX CMD from the BS, if in the same long DRX cycle, the UE is switched from Mode 1 to Mode 2, the UE stops an Uu on-duration timer and an Uu inactivity timer, and stops a SL on-duration timer and a SL inactivity timer.

Embodiment 2: this embodiment aims to solve an issue of how to judge whether the retransmission of the corresponding sidelink process is necessary to start SL specific HARQ timer on an Uu interface. Embodiment 2 introduces new conditions for a UE to determine whether SL retransmission is necessary, e.g., for sl-PUCCH-Config configured case and sl-PUCCH-Config not configured case separately.

In Embodiment 2, if a SL UE (which may be a TX UE, e.g., UE 101a illustrated and shown in FIG. 1) is configured with Mode 1, and configured with an Uu DRX function and a SL DRX function, if the data of the corresponding HARQ scheme was not successfully received by a peer UE (which may be a RX UE, e.g., UE 101b illustrated and shown in FIG. 1) in a sidelink, the UE needs to start a HARQ retransmission timer to monitor potential retransmission scheduling from a BS (e.g., BS 102 illustrated and shown in FIG. 1) . The UE needs to determine which case represents that the Rx UE does not successfully receive SL data.

In sub-embodiment (1) of Embodiment 2, if sl-PUCCH-Config is configured, if the UE generates NACK for a physical uplink control channel (PUCCH) and instructs the physical layer to signal a negative acknowledgement corresponding to the transmission on the PUCCH, and if TA is not expired, the UE determines that a retransmission is needed and needs to start a HARQ retransmission timer.

In sub-embodiment (2) of Embodiment 2, if sl-PUCCH-Config is not configured, the UE determine that a retransmission is necessary when one or more following conditions fulfilled:

(1) if the most recent transmission of the MAC PDU was not prioritized.

(2) if HARQ feedback has been disabled for the MAC PDU and no sidelink grant is available for next retransmission (s) of the MAC PDU, if any.

(3) If HARQ feedback has been enabled and receive NACK on PSFCH of most recent transmission.

(4) If HARQ feedback has been enabled and receive DTX for A/N scheme of most recent transmission.

In Embodiment 2, if the UE determines that a retransmission is necessary, the UE indicates to the BS to (re) start a HARQ timer at the BS side by the UL signal or UL MAC CE. One example is to use a scheduling request (SR) to indicate the BS and the HARQ timer will be (re) started at the BS side. Both the BS and the UE will (re) start their HARQ timers after a transmission of the SR.

In Embodiment 2, if the UE is switched from Mode 1 to Mode 2, the UE stops all HARQ timers (E. G., HARQ RTT timer or HARQ retransmission timer) on an Uu interface.

Embodiment 3: this embodiment aims to provide new start conditions and new stop condition of an Uu inactivity timer.

In sub-embodiment (1) of Embodiment 3, if the SL UE is configured with Mode 1, and configured with an Uu DRX function and a SL DRX function, if the UE receives a PDCCH indicating a new SL transmission, and if any SL transmission support/activate SL inactivity timer, the UE should start or restart the Uu drx-InactivityTimer.

In sub-embodiment (2) of Embodiment 3, if the SL UE is configured with BS scheduled mode (e.g., Mode 1) , and configured with an Uu DRX function and a SL DRX function, and if the UE receives a PDCCH indicating a new SL transmission, the UE should start or restart the Uu drx-InactivityTimer.

In Embodiment 3, if a SL transmission does not support/activate the inactivity timer, and the UE enters DRX (or on-duration timer expires, or offset before on-duration timer expires) on PC5 interface, the UE stops an Uu inactivity timer.

In Embodiment 3, the UE determines that a SL transmission does not support SL inactivity timer if one or more following conditions fulfilled:

(1) If the UE only has a SL broadcast service.

(2) If the UE has SL groupcast but not support the inactivity timer.

(3) If the UE has no unicast service.

(4) If a logical channel (LCH) priority of an unicast service is lower than that of broadcast and groupcast services.

(5) If the SL transmission does not support or configure the inactivity timer.

FIG. 3 illustrates an exemplary block diagram of an apparatus according to some embodiments of the present application. As shown in FIG. 3, the apparatus 300 may include at least one processor 304 and at least one transceiver 302 coupled to the processor 304. The apparatus 300 may be a UE or a network device (e.g., a BS) .

Although in this figure, elements such as the at least one transceiver 302 and processor 304 are described in the singular, the plural is contemplated unless a limitation to the singular is explicitly stated. In some embodiments of the present application, the transceiver 302 may be divided into two devices, such as a receiving circuitry and a transmitting circuitry. In some embodiments of the present application, the apparatus 300 may further include an input device, a memory, and/or other components.

In some embodiments of the present application, the apparatus 300 may be a UE using a SL. The processor 304 in the UE may be configured: to determine a data transmission status on a SL with a further UE; and to maintain a plurality of timers according to the data transmission status on the SL, wherein the timers are associated with an Uu interface with a network device, and the timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu HARQ timer.

In some embodiments of the present application, the apparatus 300 may further include at least one non-transitory computer-readable medium. In some embodiments of the present disclosure, the non-transitory computer-readable medium may have stored thereon computer-executable instructions to cause a processor to implement the method with respect to a UE or a network device (e.g., a BS) as described above. For example, the computer-executable instructions, when executed, cause the processor 304 interacting with transceiver 302, so as to perform operations of the methods, e.g., as described in view of FIG. 2.

While this disclosure has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in the other embodiments. Also, all of the elements of each figure are not necessary for operation of the disclosed embodiments. For example, those having ordinary skills in the art would be enabled to make and use the teachings of the disclosure by simply employing the elements of the independent claims. Accordingly, embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure.

In this document, the terms "includes, " "including, " or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "a, " "an, " or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least a second or more. The term "having" and the like, as used herein, are defined as "including.

Claims

A method performed by a first user equipment (UE) , comprising:

determining a data transmission status on a sidelink (SL) with a second UE; and

maintaining a plurality of timers according to the data transmission status on the SL, wherein the timers are associated with an Uu interface with a network device, and the timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu hybrid automatic repeat request (HARQ) timer.
The method of Claim 1, further comprising:

receiving an Uu discontinuous reception (DRX) command from the network device.
The method of Claim 2, further comprising:

in response to receiving the Uu DRX command, transmitting a SL DRX command to the second UE via an unicast mode or a broadcast mode.
The method of Claim 2, further comprising:

in response to receiving the Uu DRX command from the network device and in response to available data to be transmitted on the SL, triggering a buffer status report (BSR) for the SL.
The method of Claim 2, further comprising:

in response to an activated state of the SL and if the Uu on-duration timer and the Uu inactivity timer are running, stopping the Uu on-duration timer and the Uu inactivity timer; or

in response to an un-activated state of the SL and if the Uu on-duration timer and the Uu inactivity timer are running, allowing the on-duration timer and the inactivity timer to continue running.
The method of Claim 2, wherein the SL is activated based on at least one of:

the first UE is configured with configuration information regarding the SL;

the SL has one or more interest destinations;

a medium access control (MAC) entity of the first UE has been configured with sidelink resource allocation mode 1;

the first UE is configured with a radio network temporary identifier (RNTI) of the SL;

the first UE is configured with a configured scheduling radio network temporary identifier (CS-RNTI) of the SL;

the first UE receives a grant on a physical downlink control channel (PDCCH) for data to be transmitted on the SL, and the first UE starts or restarts an inactivity timer associated with the SL;

the first UE has data to be transmitted on the SL;

data to be transmitted by the first UE on the SL; and

data to be received by the first UE on the SL.
The method of Claim 1, further comprising:

in response to receiving, on the Uu interface, configuration information regarding a physical uplink control channel (PUCCH) of the SL, generating negative acknowledgement (NACK) for a physical uplink control channel (PUCCH) and instructing a physical layer of the first UE to signal a negative acknowledgement corresponding to the transmission on the PUCCH; and

in response to an non-expiry of a time alignment (TA) , determining that a retransmission on the SL is needed and there is a need to start a HARQ retransmission timer.
The method of Claim 1, further comprising:

in response to not receiving configuration information regarding a physical uplink control channel (PUCCH) of the SL, determining that a retransmission on the SL is necessary.
The method of Claim 8, wherein the retransmission on the SL is determined as necessary in response to fulfilling at least one of:

a most recent transmission of a medium access control (MAC) protocol data unit (PDU) is not prioritized;

a HARQ feedback scheme has been disabled for the MAC PDU, and no sidelink grant is available for a next retransmission of the MAC PDU;

the HARQ feedback scheme has been enabled, and the first UE receives NACK on a physical sidelink feedback channel (PSFCH) of the most recent transmission; and

the HARQ feedback scheme has been enabled, and the first UE receives a discontinuous transmission (DTX) for the HARQ feedback scheme of the most recent transmission.
The method of Claim 8 or Claim 9, further comprising:

in response to switching the first UE from sidelink resource allocation mode 1 to sidelink resource allocation mode 2 and if the Uu HARQ timer is running, stopping the Uu HARQ timer.
The method of Claim 1, wherein the timers further include an Uu discontinuous reception (DRX) inactivity timer, wherein the method further comprises starting or restarting the Uu DRX inactivity timer, and wherein the Uu DRX inactivity timer is started or restarted in response to:

the first UE being configured with sidelink resource allocation mode 1;

the first UE being configured with a DRX function related to the Uu interface; and

the first UE being configured with a DRX function related to the SL.
The method of Claim 11, wherein the Uu DRX inactivity timer is started or restarted further in response to:

receiving a physical downlink control channel (PDCCH) indicating an initial transmission on the SL; or

receiving the PDCCH indicating the initial transmission on the SL, and a transmission on the SL supporting or being configured with an inactivity timer associated with the SL.
The method of Claim 1, further comprising stopping the Uu inactivity timer, in response to:

a transmission on the SL not supporting an inactivity timer associated with the SL;

the first UE entering a DRX function related to the SL; and

the Uu inactivity timer being running.
The method of Claim 13, further comprising determining that the transmission on the SL does not support the inactivity timer associated with the SL in response to fulfilling at least one of:

only a broadcast service is supported on the SL;

a groupcast service is supported on the SL, and the inactivity timer associated with the SL is not supported;

an unicast service is not supported on the SL;

a logical channel (LCH) priority of the unicast service is lower than a LCH priority of the broadcast service and the groupcast service; and

the inactivity timer associated with the SL is not configured to the transmission on the SL.
A user equipment (UE) , comprising:

a processor; and

a wireless transceiver coupled to the processor,

wherein the processor is configured:

to determine a data transmission status on a sidelink (SL) with a second UE; and

to maintain a plurality of timers according to the data transmission status on the SL, wherein the timers are associated with an Uu interface with a network device, and the timers include at least an Uu on-duration timer, an Uu inactivity timer, and an Uu hybrid automatic repeat request (HARQ) timer.