WO2024007317A1

WO2024007317A1 - Wireless communication method and related devices

Info

Publication number: WO2024007317A1
Application number: PCT/CN2022/104681
Authority: WO
Inventors: Xin Zhang
Original assignee: Shenzhen Tcl New Technology Co., Ltd.
Priority date: 2022-07-08
Filing date: 2022-07-08
Publication date: 2024-01-11

Abstract

Disclosed is a wireless communication method. The method, performed by a user equipment (UE) in a network, includes receiving multicast service in an inactive state; and triggering a small data transmission (SDT) procedure to send hybrid automatic repeat request (HARQ) feedback for the multicast service during the inactive state. The method can improve the reliability of transmission of multicast services in inactive state.

Description

WIRELESS COMMUNICATION METHOD AND RELATED DEVICES

TECHNICAL FIELD

The present disclosure relates to wireless communication technologies, and more particularly, to wireless communication method, and related devices such as a user equipment (UE) and a base station (BS) (e.g., a gNB) .

BACKGROUND ART

Communication systems and networks have developed towards being a broadband and mobile system. In cellular wireless communication systems developed by the Third Generation Partnership Project (3GPP) , user equipment (UE) is connected by a wireless link to a radio access network (RAN) . The RAN includes a set of base stations (BSs) which provide wireless links to the UEs located in cells covered by the base station, and an interface to a core network (CN) which provides overall network control. As will be appreciated the RAN and CN each conduct respective functions in relation to the overall network. The 3GPP has developed the so-called Long Term Evolution (LTE) system, namely, an Evolved Universal Mobile Telecommunication System Territorial Radio Access Network (E-UTRAN) , for a mobile access network where one or more macro-cells are supported by a base station known as an eNodeB or eNB (evolved NodeB) . More recently, evolved from LTE, the so-called 5G or New radio (NR) systems where one or more cells are supported by a base station known as a gNB.

In LTE, the network may order the UE to get into an RRC_IDLE state if the UE has no activity for a while. This is done to reduce UE’s power consumption. The UE needs to transit from the RRC_IDLE state to an RRC_CONNECTED state whenever the UE needs to perform some activity. Since small amounts of data have to be sent very frequently in current mobile communication applications, frequent Idle-Connected-Idle transitions increase network signaling load and latency. Therefore, 5G NR has defined a new state called RRC_INACTIVE to reduce network signaling load and latency involved in transiting to RRC_CONNECTED state. In NR, a UE is in RRC_CONNECTED when an RRC connection has been established or in RRC_INACTIVE when the RRC connection is suspended. If this is not the case, the UE is in RRC_IDLE state, that is, no RRC connection is established. The RRC_INACTIVE and RRC_IDLE states may be referred to a power saving state. More specifically, in RRC_INACTIVE state, the UE Access Stratum (AS) context is stored at both UE and network sides so that the core network connection is maintained (i.e., the UE keeps in CM (abbreviated from Connection Management) -CONNECTED) and the radio access network (RAN) connection is released. The network can reach the inactive UE through RAN or CN Paging messages.

UE performs a random access (RA) procedure to get access to network. The RA procedure can be classified into a Contention Free Random Access (CFRA) type and a Contention-based Random Access (CBRA) type. The contention-free or contention-based RA procedure can be a four-step (4-step) procedure or a two-step (2-step) procedure. Taking 4-step contention-based Random Access RA procedure for example, the UE transmits a contention-based PRACH preamble, also known as MSG1. After detecting the preamble, the gNB responds with a random-access response (RAR) , also known as MSG2. The RAR includes an uplink grant for scheduling a PUSCH transmission from the UE known as MSG3. In response to the RAR, the UE transmits MSG3 including an ID for contention resolution. Upon receiving MSG3, the network transmits a contention resolution message, also known as MSG4, with the contention resolution ID. The UE receives MSG4, and if the UE finds its contention-resolution ID it sends an acknowledgement on a PUCCH, which completes the 4-step random access procedure. The 2-step RA procedure is to reduce latency and control signaling overhead by having a single round trip cycle between the UE and the base station. This is achieved by combining the preamble (MSG1) and the scheduled PUSCH transmission (MSG3) into a single message (MSGA) from the UE to the gNB, known as MSGA and by combining the random-access respond (MSG2) and the contention resolution message (MSG4) into a single message (MSGB) from the gNB to UE. The 2-step procedure and the 4-step procedure can be applied to the CFRA in the case that the dedicated preamble is provided to the UE.

WI “NR small data transmissions (SDT) in inactive state” is introduced and specified in R17. The motivation to have this WI is basically as the following: “NR supports RRC_INACTIVE state and UEs with infrequent (periodic and/or non-periodic) data transmission are generally maintained by the network in the RRC_INACTIVE state. Until Rel-16, the RRC_INACTIVE state doesn’t support data transmission. Hence, the UE has to resume the connection (i.e. move to RRC_CONNECTED state) for any DL (MT) and UL (MO) data. Connection setup and subsequently release to INACTIVE state happens for each data transmission however small and infrequent the data packets are. This results in unnecessary power consumption and signalling overhead. ”

To enable resource-efficient delivery of multicast/broadcast services (MBS) , 3GPP has developed NR broadcast/multicast in Rel-17, aiming to enable general MBS services over 5G system (5GS) . The use cases identified that could benefit from this feature include public safety and mission critical, V2X applications, IPTV, live video, software delivery over wireless and IoT applications, etc. Two delivery modes have been agreed for Rel-17 MBS with delivery mode 1 (only for multicast) capable of addressing higher QoS services and delivery mode 2 (only for broadcast) focusing on lower QoS services. Given that Rel-17 MBS already provides the basic function to support MBS services, the general main goal for Rel-18 should be to enable better deployment of MBS, such as improvement of resource efficiency and capacity based on Rel-17 MBS.

In Rel-17, RAN only specifies multicast for UEs in RRC_CONNECTED state, which may not fully fulfil the requirements of Mission Critical Services for example, especially for cells with a large number of UEs. Also, to always keep UEs in RRC_CONNECTED state is not power efficient. It is therefore important to support multicast for UEs in RRC_INACTIVE.

In RANP#94 meeting, the following R18 WID has been approved (RP-213568) .

- Specify support of multicast reception by UEs in RRC_INACTIVE state [RAN2, RAN3]

○ PTM configuration for UEs receiving multicast in RRC_INACTIVE state [RAN2]

○ Study the impact of mobility and state transition for UEs receiving multicast in RRC_INACTIVE. (Seamless/lossless mobility is not required) [RAN2, RAN3]

- Specify Uu signalling enhancements to allow a UE to use shared processing for MBS broadcast and unicast reception, i.e., including UE capability and related assistance information reporting regarding simultaneous unicast reception in RRC_CONNECTED and MBS broadcast reception from the same or different operators [RAN2]

- Study and if necessary, specify enhancements to improve the resource efficiency for MBS reception in RAN sharing scenarios [RAN3]

Note: collaboration with SA2 is expected in due course for the above objectives.

In R17 UEs interested in receiving multicast services are mandatory to stay in connected state when receiving services and are able to use hybrid automatic repeat request (HARQ) to ensure the reliability. However, in R18, UEs interested in receiving multicast services are allowed to stay in inactive state when receiving services. In inactive state, HARQ feedbacks are not able to be sent to gNB which lead to HARQ is allowed to be adopted. Therefore, in such case reliability cannot be ensured, especially for the multicast services with high reliability requirements.

Accordingly, there is a need to develop a mechanism to address above problem.

SUMMARY

The objective of the present disclosure is to provide a wireless communication method and related devices for improving the reliability of transmission of multicast services in inactive state.

In a first aspect, an embodiment of the present application provides a wireless communication method, performed by a user equipment (UE) in a network, the method including: receiving multicast service in an inactive state; and triggering a small data transmission (SDT) procedure to send hybrid automatic repeat request (HARQ) feedback for the multicast service during the inactive state.

In a second aspect, an embodiment of the present application provides a wireless communication method, performed by a user equipment (UE) in a network, the method including: receiving multicast service in an inactive state; and transiting to a connected state and sending hybrid automatic repeat request (HARQ) feedback for the multicast service during the connected state.

In a third aspect, an embodiment of the present application provides a wireless communication method, performed by a user equipment (UE) in a network, the method including: receiving a first multicast packet with one or more repetitions in an inactive state without sending any hybrid automatic repeat request (HARQ) feedback for the first multicast packet or the one or more repetitions during the inactive state.

In a fourth aspect, an embodiment of the present application provides a wireless communication method, performed by a base station (BS) in a network, the method including: transmitting multicast service to a user equipment (UE) in an inactive state; and receiving hybrid automatic repeat request (HARQ) feedback for the multicast service, wherein the HARQ feedback is transmitted in a small data transmission (SDT) procedure from the UE in the inactive state.

In a fifth aspect, an embodiment of the present application provides a wireless communication method, performed by a base station (BS) in a network, the method including: transmitting multicast service to a user equipment (UE) in an inactive state; and receiving hybrid automatic repeat request (HARQ) feedback for the multicast service from the UE when the UE transits from the inactive state to a connected state.

In a sixth aspect, an embodiment of the present application provides a wireless communication method, performed by a base station (BS) in a network, the method including: transmitting a first multicast packet with one or more repetitions from a user equipment (UE) in an inactive state without receiving from the UE in the inactive state any hybrid automatic repeat request (HARQ) feedback for the first multicast packet or the one or more repetitions.

In a seventh aspect, an embodiment of the present application provides a UE, including a processor and a transmitter, wherein the processor is configured to call and run program instructions stored in a memory, to cooperate with the transmitter to execute the method of any of the first, the second, or the third aspect.

In an eighth aspect, an embodiment of the present application provides a BS, including a processor and a transmitter, wherein the processor is configured to call and run program instructions stored in a memory, to cooperate with the transmitter to execute the method of any of the fourth, the fifth, or the sixth aspect.

In a ninth aspect, an embodiment of the present application provides a computer readable storage medium provided for storing a computer program, which enables a computer to execute the method of any of the first to the sixth aspects.

In a tenth aspect, an embodiment of the present application provides a computer program product, which includes computer program instructions enabling a computer to execute the method of any of the first to the sixth aspects.

In an eleventh aspect, an embodiment of the present application provides a computer program, when running on a computer, enabling the computer to execute the method of any of the first to the sixth aspects.

The non-transitory computer readable medium may include at least one from a group consisting of: a hard disk, a CD-ROM, an optical storage device, a magnetic storage device, a Read Only Memory, a Programmable Read Only Memory, an Erasable Programmable Read Only Memory, EPROM, an Electrically Erasable Programmable Read Only Memory and a Flash memory.

DESCRIPTION OF DRAWINGS

In order to more clearly illustrate the embodiments of the present disclosure or related art, the following figures that will be described in the embodiments are briefly introduced. It is obvious that the drawings are merely some embodiments of the present disclosure, a person having ordinary skill in this field can obtain other figures according to these figures without paying the premise.

FIG. 1 is a schematic block diagram illustrating a communication network system according to an embodiment of the present application.

FIG. 2 is a flowchart of a wireless communication method according to a first embodiment of the present application.

FIG. 3 is a flowchart of enabling HARQ feedback in inactive state according to an embodiment of the present application.

FIG. 4A is a flowchart of transmitting HARQ feedback in 4-step RA-SDT for multicast services according to an embodiment of the present application.

FIG. 4B is a flowchart of transmitting HARQ feedback in 2-step RA-SDT for multicast services according to an embodiment of the present application.

FIG. 4C is a flowchart of transmitting HARQ feedback in CG-SDT for multicast services according to an embodiment of the present application.

FIG. 5A is a flowchart of transmitting HARQ feedback in subsequent transmission of 4-step RA-SDT for multicast services according to an embodiment of the present application.

FIG. 5B is a flowchart of transmitting HARQ feedback in subsequent transmission of 2-step RA-SDT for multicast services according to an embodiment of the present application.

FIG. 5C is a flowchart of transmitting HARQ feedback in subsequent transmission of CG-SDT for multicast services according to an embodiment of the present application.

FIG. 6 is a flowchart of a wireless communication method according to a second embodiment of the present application.

FIG. 7 is a flowchart of transmitting HARQ feedback in connected state for multicast services according to an embodiment of the present application.

FIG. 8 is a flowchart of a wireless communication method according to a third embodiment of the present application.

FIG. 9 is a flowchart of receiving multicast packets with repetitions in inactive state without transmission of HARQ feedback according to an embodiment of the present application.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the disclosure are described in detail with the technical matters, structural features, achieved objects, and effects with reference to the accompanying drawings as follows. Specifically, the terminologies in the embodiments of the present disclosure are merely for describing the purpose of the certain embodiment, but not to limit the disclosure.

FIG. 1 illustrates that, in some embodiments, one or more user equipments (UEs) 10 and a base station (e.g., gNB or eNB) 20 for wireless communication in a communication network system 30 according to an embodiment of the present application are provided. The communication network system 30 includes the one or more UEs 10 and the base station 20. The one or more UEs 10 may include a memory 12, a transceiver 13, and a processor 11 coupled to the memory 12 and the transceiver 13. The base station 20 may include a memory 22, a transceiver 23, and a processor 21 coupled to the memory 22 and the transceiver 23. The

processor

11 or 21 may be configured to implement proposed functions, procedures and/or methods described in this description. Layers of radio interface protocol may be implemented in the

processor

11 or 21. The

memory

12 or 22 is operatively coupled with the

processor

11 or 21 and stores a variety of information to operate the

processor

11 or 21. The

transceiver

13 or 23 is operatively coupled with the

processor

11 or 21, and the

transceiver

13 or 23 transmits and/or receives a radio signal.

The

processor

11 or 21 may include application-specific integrated circuit (ASIC) , other chipset, logic circuit and/or data processing device. The

memory

12 or 22 may include read-only memory (ROM) , random access memory (RAM) , flash memory, memory card, storage medium and/or other storage device. The

transceiver

13 or 23 may include baseband circuitry to process radio frequency signals. When the embodiments are implemented in software, the techniques described herein can be implemented with modules (e.g., procedures, functions, and so on) that perform the functions described herein. The modules can be stored in the

memory

12 or 22 and executed by the

processor

11 or 21. The

memory

12 or 22 can be implemented within the

processor

11 or 21 or external to the

processor

11 or 21 in which case those can be communicatively coupled to the

processor

11 or 21 via various means as is known in the art.

FIG. 2 is a flowchart of a wireless communication method 100 according to a first embodiment of the present application. Referring to FIG. 2 in conjunction with FIG. 1, the method 100 includes the following. In Step 110, the UE 10 receives from the base station 20 multicast service in an inactive state (e.g., RRC_INACTIVE state) . In Step 120, the UE 10 sends and the base station 20 receives hybrid automatic repeat request (HARQ) feedback for the multicast service. The UE 10 triggers a small data transmission (SDT) procedure to send the HARQ feedback during the inactive state. The HARQ feedback is transmitted in the SDT procedure from the UE to the base station 20. With this method, the reliability of transmission of multicast services in inactive state is enhanced.

In an embodiment, the method further including: receiving an indication indicating that the HARQ feedback for the multicast service is enabled. HARQ feedback is allowed to be adopted and can be enabled/disabled. Please refer to FIG. 3, which is a flowchart of enabling HARQ feedback in inactive state according to an embodiment of the present application. When the UE is in inactive state (e.g., RRC_INACTIVE state) and receives multicast services (steps 1 and 2) , the base station (e.g., gNB) may transmit an indication to the UE to indicate that HARQ feedback is enabled and the UE is required to send acknowledgement (ACK/NACK) for the received multicast services in the inactive state (step 4) . Upon reception of the indication, the UE can send to the base station the HARQ feedback in the SDT procedure during the inactive state. The HARQ feedback for the multicast service may be enabled when Quality of Service (QoS) of the multicast service is higher than a threshold. When this criteria is met, the base station may decide to send the notification (Step 3) . When the QoS requirement of multicast service is high, the HARQ feedback may be enabled to ensure the reliability of transmission of multicast service. When the QoS requirement of multicast service is low, the HARQ feedback may be disabled to enhance resource efficiency.

In an embodiment, the SDT procedure is a 4-step Random Access (RA) -SDT procedure, and the HARQ feedback is carried on MSG3. The UE may transmit the HARQ feedback for the multicast service in a 4-step RA-SDT procedure. Please refer to FIG. 4A, which is a flowchart of transmitting HARQ feedback in 4-step RA-SDT for multicast services according to an embodiment of the present application. When the UE is in inactive state (e.g., RRC_INACTIVE state) and receives multicast services (steps 1 and 2) , if the HARQ feedback is enabled (e.g., multicast services requiring high QoS) , the UE may trigger a 4-step RA-SDT procedure to feed back ACK/NACK to the base station for the multicast service (step 3) . In the 4-step RA-SDT procedure, the UE sends a preamble in MSG1 to the base station (step 4) , and the base station transmits back a random access response (RAR) message in MSG2 in response to the preamble (step 5) . After that, a radio resource control (RRC) resume request is transmitted to the base station in MSG 3. The HARQ feedback for the multicast service can be carried on MSG3 (step 6) . Upon reception of the RRC resume request, the base station sends MSG 4 to the UE for contention resolution (step 7) . The UE may end the SDT procedure upon receiving RRCrelease with suspend configuration from gNB (steps 8 and 9) , and still stays in inactive state (step 10) .

In an embodiment, the SDT procedure is a 2-step Random Access (RA) -SDT procedure, and the HARQ feedback is carried on MSGA. The UE may transmit the HARQ feedback for the multicast service in a 2-step RA-SDT procedure. Please refer to FIG. 4B, which is a flowchart of transmitting HARQ feedback in 2-step RA-SDT for multicast services according to an embodiment of the present application. When the UE is in inactive state (e.g., RRC_INACTIVE state) and receives multicast services (steps 1 and 2) , if the HARQ feedback is enabled (e.g., multicast services requiring high QoS) , the UE may trigger a 2-step RA-SDT procedure to feed back ACK/NACK to the base station for the multicast service (step 3) . In the 2-step RA-SDT procedure, the UE sends a preamble and a radio resource control (RRC) resume request in MSGA to the base station, wherein the HARQ feedback for the multicast service can be carried on MSGA (step 4) , and the base station transmits back a random access response (RAR) message in MSGB in response to the preamble and sends the MSGB to the UE for contention resolution upon reception of the RRC resume request (step 5) . The UE may end the SDT procedure upon receiving RRCrelease with suspend configuration from gNB (steps 6 and 7) , and still stays in inactive state (step 8) .

In an embodiment, the SDT procedure is a Configured Grant (CG) -SDT procedure, and the HARQ feedback is transmitted on CG resources. The UE may transmit the HARQ feedback for the multicast service in a CG-SDT procedure. Please refer to FIG. 4C, which is a flowchart of transmitting HARQ feedback in CG-SDT for multicast services according to an embodiment of the present application. When the UE is in inactive state (e.g., RRC_INACTIVE state) and receives multicast services (steps 1 and 2) , if the HARQ feedback is enabled (e.g., multicast services requiring high QoS) , the UE may trigger a CG-SDT procedure to feed back ACK/NACK to the base station for the multicast service (step 3) . In the CG-SDT procedure, the UE sends a radio resource control (RRC) resume request to the base station, and the HARQ feedback for the multicast service can be transmitted on CG resources (step 4) . The UE may end the SDT procedure upon receiving RRCrelease with suspend configuration from gNB (steps 5 and 6) , and still stays in inactive state (step 7) .

Upon arrival of data only for Data Radio Bearer (s) (DRB (s) ) /Signaling Radio Bearer (s) (SRB (s) ) for which SDT is enabled, the high level procedure for selection between SDT and non SDT procedure is as follows: If CG-SDT criteria is met: UE selects CG-SDT. UE initiate CG-SDT procedure. Else if RA-SDT criteria is met: UE selects RA-SDT. UE initiate RA-SDT procedure. Else: UE initiate non SDT procedure. CG-SDT criteria is considered met, if all of the following conditions are met: 1) Available data volume <= data volume threshold; 2) Reference Symbol Received Power (RSRP) is greater than or equal to a configured threshold; and 3) CG-SDT resources are configured on the selected uplink (UL) carrier and are valid. RA-SDT criteria is considered met, if all of the following conditions are met: 1) Available data volume <= data volume threshold; 2) Reference Symbol Received Power (RSRP) is greater than or equal to a configured threshold; and 3) 4-step RA-SDT resources are configured on the selected UL carrier and criteria to select 4-step RA SDT is met; or 2-step RA-SDT resources are configured on the selected UL carrier and criteria to select 2-step RA SDT is met.

In current 3GPP specification (R17) , subsequent transmission in SDT procedure is allowed. Herein, after the first ACK/NACK is transmitted, the following ACK/NACKs for the multicast services received in the inactive state can be transmitted as well during the SDT procedure.

In an embodiment, the HARQ feedback for the multicast service may be transmitted by subsequent transmission in a 4-step RA-SDT procedure. The HARQ feedback for the multicast service may be the first HARQ feedback in the 4-step RA-SDT procedure and may also be the subsequent HARQ feedback in the 4-step RA-SDT procedure. Please refer to FIG. 5A, which is a flowchart of transmitting HARQ feedback in subsequent transmission of 4-step RA-SDT for multicast services according to an embodiment of the present application. After 4-step RA, subsequent transmission is performed on 4-step RA-SDT resources. The HARQ feedback for the multicast service can be the subsequent HARQ feedback in the 4-step RA-SDT procedure (step 8) . During the 4-step RA-SDT procedure, the subsequent HARQ feedback is sent after the first HARQ feedback.

In an embodiment, the HARQ feedback for the multicast service may be transmitted by subsequent transmission in a 2-step RA-SDT procedure. The HARQ feedback for the multicast service may be the first HARQ feedback in the 2-step RA-SDT procedure and may also be the subsequent HARQ feedback in the 2-step RA-SDT procedure. Please refer to FIG. 5B, which is a flowchart of transmitting HARQ feedback in subsequent transmission of 2-step RA-SDT for multicast services according to an embodiment of the present application. After 2-step RA, subsequent transmission is performed on 2-step RA-SDT resources. The HARQ feedback for the multicast service can be the subsequent HARQ feedback in the 2-step RA-SDT procedure (step 6) . During the 2-step RA-SDT procedure, the subsequent HARQ feedback is sent after the first HARQ feedback.

In an embodiment, the HARQ feedback for the multicast service may be transmitted by subsequent transmission in a CG-SDT procedure. The HARQ feedback for the multicast service may be the first HARQ feedback in the CG-SDT procedure and may also be the subsequent HARQ feedback in the CG-SDT procedure. Please refer to FIG. 5C, which is a flowchart of transmitting HARQ feedback in subsequent transmission of CG-SDT for multicast services according to an embodiment of the present application. After the first transmission on CG resources, subsequent transmission is also performed on CG resources. The HARQ feedback for the multicast service can be the subsequent HARQ feedback in the CG-SDT procedure (step 5) . During the CG-SDT procedure, the subsequent HARQ feedback is sent after the first HARQ feedback.

In an embodiment, the method further includes: upon a timer expires or a counter reaches a maximum value, stopping sending the subsequent HARQ feedback. Referring to FIGs. 5A to 5C, a timer or a counter can be set/configured by the base station for subsequent transmission in SDT procedure (e.g., CG-SDT, 4-step RA-SDT, 2-step RA-SDT) . When the timer expires or the counter reaches a maximum value, the UE may stop sending the subsequent HARQ feedback for the multicast services to the base station, and ACK/NACK are not allowed to be transmitted during the SDT procedure. That is, the subsequent HARQ feedback is allowed to transmit only when the timer is not expired or the counter remains within the maximum value.

FIG. 6 is a flowchart of a wireless communication method 200 according to a second embodiment of the present application. Referring to FIG. 6 in conjunction with FIG. 1, the method 200 includes the following. In Step 210, the UE 10 receives from the base station 20 multicast service in an inactive state (e.g., RRC_INACTIVE state) . In Step 220, the UE 10 transits from the inactive state to a connected state (e.g., RRC_Connected state) and then sends hybrid automatic repeat request (HARQ) feedback for the multicast service during the connected state. That is, the base station 20 receives the HARQ feedback for the multicast service from the UE when the UE is in the connected state. With this method, the reliability of transmission of multicast services in inactive state is enhanced.

Please refer to FIG. 7 in conjunction with FIG. 6. FIG. 7 is a flowchart of transmitting HARQ feedback in connected state for multicast services according to an embodiment of the present application. When the UE is in inactive state (e.g., RRC_INACTIVE state) and receives multicast services (steps 1 and 2) , the base station (e.g., gNB) may transmit an indication to the UE to indicate that HARQ feedback is enabled and the UE is required to send acknowledgement (ACK/NACK) for the received multicast services (step 3) . If UE can only be allowed to send ACK/NACK in a connected state, UE needs to go to the connected state first (step 4) . The UE sends HARQ feedback for the received multicast service during the connected state (step 5) . The base station may then disable the HARQ feedback upon reception of the HARQ feedback (step 6) . The UE may go to inactive state again if no HARQ feedback needs to be transmitted (step 7) . The UE may again receive multicast service in the inactive state (Step 8) .

FIG. 8 is a flowchart of a wireless communication method 300 according to a third embodiment of the present application. The above mechanisms focus on using HARQ feedback to ensure the reliability. There may be another way to improve the reliability. Referring to FIG. 8 in conjunction with FIG. 1, the method 300 includes the following. In Step 310, the UE 10 receives from the base station 20 a first multicast packet with one or more repetitions in an inactive state. In this case, during the inactive state, no hybrid automatic repeat request (HARQ) feedback for the first multicast packet or the one or more repetitions needs to be sent from the UE 10 to the base station 20. In some embodiments, the UE 10 may receive from the base station 20 a second multicast packet without repetition in a connected state and send to the base station 20 the HARQ feedback for the second multicast packet during the connected state. With this method, the reliability of transmission of multicast services in inactive state is ensured by transmission of the multicast packet with repetitions.

Please refer to FIG. 9 in conjunction with FIG. 8. FIG. 9 is a flowchart of receiving multicast packets with repetitions in inactive state without transmission of HARQ feedback according to an embodiment of the present application. In the case that the QoS requirement of multicast service is high and the reliability needs to be ensured even in the inactive state, when the UE is in inactive state (e.g., RRC_INACTIVE state) and receives multicast services (steps 1 and 2) , the base station (e.g., gNB) may transmit the same multicast packet more than one time (i.e., a multicast packet with one or more repetitions) while the UE is in the inactive state (step 3) . During the inactive state, the transmission of multicast packets is with repetition. When the state transits to connected state (step 5) , the legacy reliability mechanism can be adopted such as HARQ feedback. After a multicast packet N is received during the connected state (step 6) , the UE sends HARQ feedback to the base station for the multicast packet N (step 7) . After a multicast packet N+1 is received during the connected state (step 8) , the UE sends HARQ feedback to the base station for the multicast packet N+1 (step 9) . During the connected state, the transmission of multicast packets is without repetition.

Commercial interests for some embodiments are as follows. 1. Solving issues in the prior art. 2. Enhancing the reliability of transmission of multicast services in inactive state. 3. Providing a good communication performance. Some embodiments of the present application are used by 5G-NR chipset vendors, V2X communication system development vendors, automakers including cars, trains, trucks, buses, bicycles, moto-bikes, helmets, and etc., drones (unmanned aerial vehicles) , smartphone makers, communication devices for public safety use, AR/VR device maker for example gaming, conference/seminar, education purposes. Some embodiments of the present application are a combination of “techniques/processes” that can be adopted in 3GPP specification to create an end product. Some embodiments of the present application could be adopted in the 5G NR unlicensed band communications. Some embodiments of the present application propose technical mechanisms.

The embodiment of the present application further provides a computer readable storage medium for storing a computer program. The computer readable storage medium enables a computer to execute corresponding processes implemented by the UE/BS in each of the methods of the embodiment of the present application. For brevity, details will not be described herein again.

The embodiment of the present application further provides a computer program product including computer program instructions. The computer program product enables a computer to execute corresponding processes implemented by the UE/BS in each of the methods of the embodiment of the present application. For brevity, details will not be described herein again.

The embodiment of the present application further provides a computer program. The computer program enables a computer to execute corresponding processes implemented by the UE/BS in each of the methods of the embodiment of the present application. For brevity, details will not be described herein again.

Although not shown in detail any of the devices or apparatus that form part of the network may include at least a processor, a storage unit and a communications interface, wherein the processor unit, storage unit, and communications interface are configured to perform the method of any aspect of the present invention.

A person of ordinary skill in the art may be aware that, in combination with the examples described in the embodiments disclosed in this specification, units and algorithm steps may be implemented by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are performed by hardware or software depends on particular applications and design constraint conditions of the technical solutions. A person skilled in the art may use different approaches to implement the described functions for each particular application, but it should not be considered that the implementation goes beyond the scope of the present application.

Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by, for example, a single unit or processor. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to ‘a’ , ‘an’ , ‘first’ , ‘second’ , etc. do not preclude a plurality.

While the present application has been described in connection with what is considered the most practical and preferred embodiments, it is understood that the present application is not limited to the disclosed embodiments but is intended to cover various arrangements made without departing from the scope of the broadest interpretation of the appended claims.

Claims

A wireless communication method, performed by a user equipment (UE) in a network, the method comprising:

receiving multicast service in an inactive state; and

triggering a small data transmission (SDT) procedure to send hybrid automatic repeat request (HARQ) feedback for the multicast service during the inactive state.
The method of claim 1, further comprising:

receiving an indication indicating that the HARQ feedback for the multicast service is enabled.
The method of claim 2, wherein the HARQ feedback for the multicast service is enabled when Quality of Service (QoS) of the multicast service is higher than a threshold.
The method of claim 1, wherein the SDT procedure is a Configured Grant (CG) -SDT procedure, and the HARQ feedback is transmitted on CG resources.
The method of claim 1, wherein the SDT procedure is a 4-step Random Access (RA) -SDT procedure, and the HARQ feedback is carried on MSG3.
The method of claim 1, wherein the SDT procedure is a 2-step Random Access (RA) -SDT procedure, and the HARQ feedback is carried on MSGA.
The method of claim 1, wherein the HARQ feedback for the multicast service comprises first HARQ feedback and subsequent HARQ feedback after the first HARQ feedback, and wherein during the SDT procedure, the subsequent HARQ feedback is sent after first HARQ feedback.
The method of claim 7, further comprising:

upon a timer expires or a counter reaches a maximum value, stopping sending the subsequent HARQ feedback.
The method of claim 7, wherein the SDT procedure is a CG-SDT procudure, a 4-step RA-SDT procedure or a 2-step RA-SDT procedure.
A wireless communication method, performed by a user equipment (UE) in a network, the method comprising:

receiving multicast service in an inactive state; and

transiting to a connected state and sending hybrid automatic repeat request (HARQ) feedback for the multicast service during the connected state.
A wireless communication method, performed by a user equipment (UE) in a network, the method comprising:

receiving a first multicast packet with one or more repetitions in an inactive state without sending any hybrid automatic repeat request (HARQ) feedback for the first multicast packet or the one or more repetitions during the inactive state.
The method of claim 11, further comprising:

receiving a second multicast packet without repetition in a connected state; and

sending the HARQ feedback for the second multicast packet during the connected state.
A wireless communication method, performed by a base station (BS) in a network, the method comprising:

transmitting multicast service to a user equipment (UE) in an inactive state; and

receiving hybrid automatic repeat request (HARQ) feedback for the multicast service, wherein the HARQ feedback is transmitted in a small data transmission (SDT) procedure from the UE in the inactive state.
The method of claim 13, further comprising:

transmitting to the UE an indication indicating that the HARQ feedback for the multicast service is enabled.
The method of claim 14, wherein the HARQ feedback for the multicast service is enabled when Quality of Service (QoS) of the multicast service is higher than a threshold.
The method of claim 13, wherein the SDT procedure is a Configured Grant (CG) -SDT procedure, and the HARQ feedback is transmitted on CG resources.
The method of claim 13, wherein the SDT procedure is a 4-step Random Access (RA) -SDT procedure, and the HARQ feedback is carried on MSG3.
The method of claim 13, wherein the SDT procedure is a 2-step Random Access (RA) -SDT procedure, and the HARQ feedback is carried on MSGA.
The method of claim 13, wherein the HARQ feedback for the multicast service comprises first HARQ feedback and subsequent HARQ feedback after the first HARQ feedback, and wherein during the SDT procedure, the subsequent HARQ feedback is transmitted after first HARQ feedback.
The method of claim 19, further comprising:

expecting the UE to stop sending the subsequent HARQ feedback upon a timer expires or a counter reaches a maximum value.
The method of claim 19, wherein the SDT procedure is a CG-SDT procudure, a 4-step RA-SDT procedure or a 2-step RA-SDT procedure.
A wireless communication method, performed by a base station (BS) in a network, the method comprising:

transmitting multicast service to a user equipment (UE) in an inactive state; and

receiving hybrid automatic repeat request (HARQ) feedback for the multicast service from the UE when the UE transits from the inactive state to a connected state.
A wireless communication method, performed by a base station (BS) in a network, the method comprising:

transmitting a first multicast packet with one or more repetitions from a user equipment (UE) in an inactive state without receiving from the UE in the inactive state any hybrid automatic repeat request (HARQ) feedback for the first multicast packet or the one or more repetitions.
The method of claim 23, further comprising:

transmitting a second multicast packet without repetition to the UE in a connected state; and

receiving the HARQ feedback for the second multicast packet from the UE in the connected state.
A user equipment (UE) , comprising a processor and a transmitter, wherein the processor is configured to call and run program instructions stored in a memory, to cooperate with the transmitter to execute the method of any of claims 1 to 9.
A base station (BS) , comprising a processor and a transmitter, wherein the processor is configured to call and run program instructions stored in a memory, to cooperate with the transmitter to execute the method of any of claims 13 to 21.