Method and apparatus for supporting multicast and broadcast services (MBS) - Patents.com

Abstract

An embodiment of the present application relates to a method and apparatus for supporting multicast and broadcast services (MBS). An exemplary method includes receiving, by a user equipment (UE) via a transceiver, configuration information regarding at least one condition parameter associated with a radio resource control (RRC) state transition for multicast reception, and triggering, by the UE, an RRC connection resumption procedure to enter an RRC connected state from an RRC inactive state in response to the at least one condition parameter being satisfied when the UE is receiving multicast or is configured to receive multicast in an RRC inactive state.

Description

[Technical field]

[0001] TECHNICAL FIELD Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to a method and apparatus for supporting multicast and broadcast services (MBS). [Background technology]

[0002] In New Radio (NR) Release (R)17, MBS will focus on small area mixed mode multicast (also referred to as Objective A in TR23.757). Objective A is about enabling general MBS services over 5G systems (5GS) and the identified use cases that may benefit from this capability. These use cases include, but are not limited to, public safety and mission critical, vehicle-to-everything (V2X) applications, transparent Internet Protocol version 4 (IPv4) / Internet Protocol version 6 (IPv6) multicast distribution, Internet Protocol Television (IPTV), software distribution over wireless, group communication, and Internet of Things (IoT) applications.

[0003] Meanwhile, work items on NR support for MBS have also been agreed in R17 (e.g., RP-201038), in which MBS reception should be supported in all Radio Resource Control (RRC) states, i.e., RRC_IDLE, RRC_INACTIVE, and RRC_CONNECTED. However, various issues occur during transitions between different RRC states, such as service interruption, data loss, or significant delay. Take multicast reception as an example, it is only supported in RRC_CONNECTED in R17. When a user equipment (UE) transitions from RRC_CONNECTED to RRC_INACTIVE or RRC_IDLE, it cannot receive multicast, e.g., multicast sessions or multicast radio bearers. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] TR23.757 [Non-Patent Document 2] TS24.501

[23] Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, improved technical solutions for MBS taking into account RRC state transitions, for example, methods to support multicast reception in the RRC_INACTIVE state, should be seriously considered. [Means for solving the problem]

[0006] One objective of the present application is to provide a method and apparatus for supporting MBS, in particular for supporting multicast reception in RRC_INACTIVE state.

[0007] Some embodiments of the present application provide an example apparatus, e.g., a UE, including a transceiver and at least one processor coupled to the transceiver, wherein the at least one processor is configured to receive, via the transceiver, configuration information regarding at least one condition parameter associated with an RRC state transition for multicast reception, and, in response to the at least one condition parameter being satisfied, trigger an RRC connection resumption procedure to enter an RRC connected state from an RRC inactive state when the UE is receiving the multicast or is configured to receive the multicast in an RRC inactive state.

[0008] Certain embodiments of the present application provide an example method that includes receiving, by the UE, configuration information regarding at least one condition parameter associated with an RRC state transition for multicast reception, and, if the UE is receiving multicast or is configured to receive multicast in an RRC inactive state, triggering, by the UE, an RRC connection resumption procedure to enter an RRC connected state from an RRC inactive state in response to the at least one condition parameter being satisfied.

[0009] In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold and a state transition timer associated with the radio link quality threshold, and the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold for a time interval of the state transition timer.

[0010] In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold and at least one scaling factor associated with the radio link quality threshold, and the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold multiplied by a scaling factor of the at least one scaling factor, the scaling factor being dependent on the network load or dependent on the mobility speed of the UE.

[0011] In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold, a state transition timer, and at least one scaling factor associated with the radio link quality threshold, and the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold multiplied by a scaling factor of the at least one scaling factor for a time interval of the state transition timer, where the scaling factor depends on the network load or depends on the mobility speed of the UE.

[0012] In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold, a state transition timer, and at least one scaling factor associated with the state transition timer, and the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold multiplied by a scaling factor of the at least one scaling factor for a time interval of the state transition timer, the scaling factor being dependent on the network load or dependent on the mobility speed of the UE.

[0013] In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold, at least one first scaling factor associated with the radio link quality threshold, a state transition timer, and at least one second scaling factor associated with the state transition timer, and the RRC connection resumption procedure is triggered if the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold multiplied by a first scaling factor of the at least one first scaling factor multiplied by a second scaling factor of the at least one second scaling factor for a time interval of the state transition timer, where the first scaling factor and the second scaling factor depend on the network load or depend on the mobility speed of the UE.

[0014] In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold and at least one offset value associated with the radio link quality threshold, each of the at least one offset value being associated with a multicast session or an MRB, and the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold plus an offset value corresponding to the radio link quality threshold for one multicast session of the multicast reception or for one MRB of the multicast reception, or when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold plus an offset value corresponding to the radio link quality threshold for all multicast sessions of the multicast reception or for all MRBs of the multicast reception. According to some embodiments of the present application, the at least one condition parameter further includes a state transition timer, and the RRC connection resumption procedure is triggered if the radio link quality of the serving cell of the UE is lower than or equal to an offset value corresponding to a radio link quality threshold for one multicast session of the multicast reception or for one MRB of the multicast reception during a time interval of the state transition timer, or if the radio link quality of the serving cell of the UE is lower than or equal to an offset value corresponding to a radio link quality threshold for all MRBs of the multicast reception or for all MRBs of the multicast reception during a time interval of the state transition timer. According to some embodiments of the present application, each of the at least one offset value is a hysteresis value.

[0015] In some embodiments of the present application, the at least one condition parameter includes at least one packet loss threshold, each of the at least one packet loss threshold is associated with a multicast session or an MRB, and the RRC connection resumption procedure is triggered when a packet loss rate of the multicast session of the multicast reception or the MRB of the multicast reception is equal to or greater than the corresponding packet loss threshold. For example, the packet loss rate is the number of missing Protocol Data Convergence Protocol (PDCP) packets counted at the PDCP layer within a set time length, or the packet error over the air (PER) or block error rate (BLER) counted at the physical layer. In another example, the packet loss rate is the number of PDCP reordering timer expirations counted at the PDCP layer, and the corresponding packet loss threshold is the threshold of the number of PDCP reordering timer expirations.

[0016] In some embodiments of the present application, the at least one condition parameter is a timer, the timer being started by the UE in response to entering the RRC inactive state for multicast reception, and the RRC connection resumption procedure being triggered in response to expiration of the timer.

[0017] In some embodiments of the present application, the at least one condition parameter includes a multicast inactivity timer that is started or re-started in response to reception of a Media Access Control (MAC) Service Data Unit (SDU) on a Multicast Traffic Channel (MTCH) logical channel by the UE in an RRC inactive state, and the RRC connection resumption procedure is triggered in response to expiration of the multicast inactivity timer.

[0018] In some embodiments of the present application, the at least one condition parameter further includes a connection prohibit timer, and if the connection prohibit timer is running, triggering the RRC connection resumption procedure or evaluating whether the at least one condition parameter is satisfied is prohibited.

[0019] In some embodiments of the present application, the at least one condition parameter is configured via system information or RRC dedicated signaling.

[0020] In some embodiments of the present application, the RRC connection restart procedure is triggered by an access category defined for the RRC connection restart procedure triggered for multicast reception and an RRC cause to indicate that an RRC connection restart procedure is requested due to multicast reception.

[0021] In some embodiments of the present application, the at least one processor is configured to stop or cancel evaluating whether the at least one condition parameter is satisfied in response to the RRC connection resumption procedure being triggered by higher layers, or by a periodic Radio Access Network (RAN)-based Notification Area (RNA) update, or in response to a RAN paging, or the RRC connection setup procedure being triggered in response to a Core Network (CN) paging, or an RRC resumption message being received, or an RRC setup message being received. According to some embodiments of the present application, the at least one processor may be configured to release configuration information regarding the at least one condition parameter in response to stopping or canceling evaluating whether the at least one condition parameter is satisfied.

[0022] In some embodiments of the present application, in response to an RRC rejection message being received during the triggered RRC connection resumption procedure, the at least one processor is configured to reinitiate the RRC resumption message after a configured time interval if the at least one condition parameter is evaluated to be met. The at least one processor may be configured to reevaluate whether the at least one condition parameter is met upon receipt of the RRC rejection message or after a configured time interval from receipt of the RRC rejection message.

[0023] The embodiments of the present application solve technical problems occurring during RRC state transitions in MBS and can support multicast reception in the RRC_INACTIVE state, thus facilitating the deployment and implementation of NR.

[0024] To illustrate how the advantages and features of the present disclosure can be obtained, the present disclosure will be described with reference to specific embodiments that are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present disclosure and therefore should not be considered as limiting the scope of the disclosure. [Brief description of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram illustrating an example wireless communication system according to some embodiments of the present application. [Diagram 2] FIG. 2 is a schematic diagram illustrating an example scenario of RRC state transitions for multicast reception according to some embodiments of the present application; [Diagram 3] 1 is a flowchart illustrating an example method for supporting MBS, according to some embodiments of the present application. [Figure 4] 1 is a block diagram of an example device supporting MBS in accordance with some embodiments of the present application. [Diagram 5] 1 is a block diagram of an example device supporting MBS in accordance with some other embodiments of the present application. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application, and is not intended to represent the only form in which the present application may be practiced. It is to 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.

[0027] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as 3rd Generation Partnership Project (3GPP) 5G, 3GPP Long Term Evolution (LTE), etc. With the development of network architectures and new service scenarios, it is contemplated that all embodiments of the present application are also applicable to similar technical problems, and further, the terms listed in the present application may be changed, which should not affect the principle of the present application.

[0028] FIG. 1 illustrates a schematic diagram of an example wireless communication system 100 in accordance with some embodiments of the present application.

[0029] As shown in Figure 1, the wireless communication system 100 includes at least one base station (BS) 101 and at least one UE 102. In particular, the wireless communication system 100 includes, for illustrative purposes, one BS 101 and two UEs 102 (e.g., a first UE 102a and a second UE 102b). Although a particular number of BSs and UEs are shown in Figure 1 for simplicity, it is contemplated that, for example, in certain other embodiments of the present application, the wireless communication system 100 may include more or fewer BSs and UEs.

[0030] The wireless communication system 100 is compatible with any type of network capable of transmitting 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 communication network, a high altitude platform network, and / or other communication networks.

[0031] The BS 101 may communicate over an interface with a CN node (not shown), e.g., a Mobility Management Entity (MME) or Serving Gateway (S-GW), a Mobility Management Function (AMF) or a User Plane Function (UPF), etc. The BS may also be referred to as an access point, an access terminal, a base, a macro cell, a Node B, an enhanced Node B (eNB), a gNB, a Home Node B, a relay node, or a device, and may be described using other terms used in the art. In 5G NR, the BS may be referred to as a RAN node or a network device. Each BS may serve multiple UEs within a service area, e.g., a cell or a cell sector, via wireless communication links. Neighboring BSs may communicate with each other as needed, e.g., during a handover procedure of a UE.

[0032] The UE 102, e.g., the first UE 102a and the second UE 102b, should be understood as any type of terminal device that 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, gaming consoles, security systems (including security cameras), in-vehicle computers, network devices (e.g., routers, switches, and modems). According to an embodiment of the present application, the UE may include portable wireless communication devices, smartphones, cellular phones, flip phones, devices with subscriber identity modules, personal computers, selective call receivers, or any other devices capable of transmitting and receiving communication signals over a wireless network. In some embodiments, the UE may include wearable devices such as smart watches, fitness bands, optical head-mounted displays, etc. Furthermore, the UE may be referred to as a subscriber unit, mobile, mobile station, user, terminal, mobile terminal, wireless terminal, fixed terminal, subscriber station, user terminal, or device, and may be described using other terms used in the art.

[0033] MBS was introduced to focus on small area mixed mode multicast in NR R17, and multicast is supported only in the RRC_CONNECTED state. Multicast reception in the RRC_CONNECTED state can provide a quality of service (QoS) experience because hybrid automatic repeat request (HARQ) and point-to-multipoint (PTM) / point-to-point (PTP) dynamic switch are supported to achieve high reliability. That is, when a UE receiving multicast enters an unconnected state, e.g., RRC_CONNECTED state, into an RRC_INACTIVE state, it cannot continue to receive multicast. Multicast reception is interrupted. Therefore, one of the potential purposes of MBS in R18 is to support multicast reception in an unconnected state, e.g., RRC_INACTIVE state, so that some UEs that are in the RRC_CONNECTED state, receiving multicast, or configured to receive multicast can be released (or sent) to an unconnected state, e.g., RRC_INACTIVE state, at least to relieve network congestion.

[0034] FIG. 2 is a schematic diagram illustrating an example scenario of RRC state transitions for multicast reception according to some embodiments of the present application.

[0035] As shown in Fig. 2, for the coverage 200 provided by a BS, for example the BS 101 shown in Fig. 1, this generally includes a good coverage area 201, for example the central area of ​​the coverage 200, and a bad coverage area 203, for example the area at the edge of the coverage 200. Taking a UE, for example the first UE 102a shown in Fig. 1 as an example, it is assumed that the first UE 102a can receive multicast in both RRC_CONNECTED and RRC_INACTIVE states. If the first UE 102a is located within the good coverage area 201 and is receiving or configured to receive multicast, the first UE 102a may be released by the BS to the RRC_INACTIVE state to alleviate network congestion in the coverage 200. That is, the first UE 102a is transitioned (or switched) from the RRC_CONNECTED state to the RRC_INACTIVE state. The first UE 102a can continue to receive the multicast in the RRC_INACTIVE state. If the first UE 102a is still in a good coverage area 201 and has low mobility, the QoS experienced by the first UE 102a is likely to be similar to that in the RRC_CONNECTED state.

[0036] However, when the first UE 102a moves to a poor coverage area 203 or there is little or no network congestion in the coverage 200, it would be better for the first UE 102a to return to the RRC_CONNECTED state from the RRC_INACTIVE state for a better QoS experience of multicast reception. Paging is not a good solution for the first UE 102a to re-enter the RRC_CONNECTED state because the BS does not know the location of the first UE 102a in the RRC_INACTIVE state and a full RAN Notification Area (RNA) may be required to page the first UE 102a. Therefore, a novel technical solution is needed to support the first UE 102a, etc. to re-enter the RRC_CONNECTED state in such scenarios.

[0037] In order to solve at least the above technical problems, the embodiments of the present application propose an improved technical solution for MBS. For example, according to some embodiments of the present application, a method and an apparatus supporting MBS trigger a UE receiving a multicast to return to an RRC_CONNECTED state from an RRC_INACITVE state based on a coverage status (or a radio, link state) while avoiding a ping-pong state transition. According to some embodiments of the present application, a method and an apparatus supporting MBS trigger a UE receiving a multicast to return to an RRC_CONNECTED state from an RRC_INACITVE state based on a network congestion state or a multicast data inactivity state. According to some embodiments of the present application, a method and an apparatus supporting MBS define a new access category and a resumption cause for an RRC connection resumption procedure triggered for multicast reception.

[0038] 3 is a flowchart illustrating an example method for supporting MBS according to some embodiments of the present application, which may be performed by a UE on a remote side, such as the first UE 102a or the second UE 102b shown in FIG 1. The UE is assumed to support multicast reception in an RRC connected state and an RRC unconnected state, such as an RRC inactive state.

[0039] When network congestion occurs, the network side, e.g., a gNB, may release (or send) a UE in an RRC connected state and receiving or configured to receive multicast to an RRC inactive state, and configure the UE to continue receiving multicast in the RRC inactive state. The network side may also configure at least one condition parameter so that the UE can enter (or re-enter or return to) the RRC connected state when congestion eases or disappears. That is, at least one condition parameter associated with an RRC state transition for multicast reception may be configured in the UE, e.g., by a gNB, to trigger a UE receiving multicast or configured to receive multicast in an RRC inactive state (e.g., RRC_INACTIVE state) to re-enter an RRC connected state (e.g., RRC_CONNECTED state). As shown in FIG. 3, in 301, the UE receives configuration information regarding at least one condition parameter associated with an RRC state transition for multicast reception. For example, the UE may receive at least one condition parameter via system information, eg, system information (SIB), or RRC dedicated signaling, eg, an RRCReconfiguration message or an RRCRelease message.

[0040] At least one condition parameter associated with an RRC state transition for multicast reception may be configured in various ways. For example, in some embodiments of the present application, the at least one condition parameter associated with an RRC state transition for multicast reception may be configured according to a congestion state or a radio link state including a radio link quality threshold and a state transition timer associated with the radio link quality threshold, or including a radio link quality threshold and at least one scaling factor associated with the radio link quality threshold, etc. In some other embodiments of the present application, the at least one condition parameter associated with an RRC state transition for multicast reception may be a timer, for example, a timer started by the UE in response to entering an RRC inactive state for multicast reception, or a multicast inactive timer started or restarted in response to reception of a MAC SDU of the MTCH logical channel by the UE in the RRC inactive state.

[0041] In some embodiments of the present application, in order to avoid a ping-pong state transition, the at least one condition parameter may include a connection prohibit timer, whereby, when the connection prohibit timer is running, evaluating whether the at least one condition parameter is satisfied or triggering an RRC connection resumption procedure is prohibited.

[0042] Based on the received configuration information on the at least one condition parameter, the UE receiving or configured to receive multicast in the RRC inactive state evaluates whether the at least one condition parameter is satisfied in the RRC inactive state. If the at least one condition parameter includes a connection prohibit timer configured to prohibit evaluating whether the at least one condition parameter is satisfied, evaluating whether the at least one condition parameter is satisfied is prohibited while the connection prohibit timer is running. In response to the at least one condition parameter being satisfied, in step 303, an RRC connection resumption procedure may be triggered by the UE to enter an RRC connected state from the RRC inactive state. However, if the at least one condition parameter includes a connection prohibit timer configured to prohibit triggering the RRC connection resumption procedure, triggering the RRC connection resumption procedure is prohibited while the connection prohibit timer is running.

[0043] Evaluating whether the at least one condition parameter is met may be stopped or canceled in some scenarios. For example, evaluating whether the at least one condition parameter is met may be stopped or canceled in response to an RRC connection resumption procedure being triggered by higher layers, or by a periodic RNA update, or in response to RAN paging. In another example, evaluating whether the at least one condition parameter is met may be stopped or canceled in response to an RRC connection setup procedure being triggered in response to CN paging. In another example, evaluating whether the at least one condition parameter is met may be stopped or canceled in response to an RRC resumption message, e.g., an RRCResume message, being received. In another example, evaluating whether the at least one condition parameter is met may be stopped or canceled in response to an RRC setup message, e.g., an RRCSetup message being received. When evaluating whether the at least one condition parameter is met is stopped or canceled, configuration information regarding the at least one condition parameter is published.

[0044] In some embodiments of the present application, upon receiving an RRC reject message, e.g., an RRCReject message during a triggered RRC connection resumption procedure or after a configured time interval from receiving the RRC reject message (i.e., the configured time expires), the UE re-evaluates whether at least one condition parameter is satisfied. If the at least one condition parameter is re-evaluated as satisfied, the UE may re-initiate an RRC resume message after the configured time interval.

[0045] Based on the above general description, further details are described in the following various embodiments, and different schemes are provided in consideration of different configuration information about at least one condition parameter. Considering the consistency between the remote side and the network side, some demonstrations in this specification are mainly provided on the remote side, but those skilled in the art should clearly understand how to apply them on the network side.

[0046] Method 1 In some embodiments of the present application, the at least one condition parameter includes a radio link quality threshold and a state transition timer associated with the radio link quality threshold. For example, the radio link quality threshold may be a reference signal received power (RSRP) threshold or a reference signal received quality (RSRQ) threshold. The state transition timer is provided mainly to avoid ping-pong state transition. If the measured radio link quality, e.g., the RSRP of the UE's serving cell (or cells), is below the radio link quality threshold for the time interval of the state transition timer (i.e., the state transition timer expires), the UE triggers an RRC connection resumption procedure to enter the RRC connected state. That is, even if the radio link quality of the UE's serving cell is below the radio link quality threshold, the UE does not trigger an RRC connection resumption procedure if the state transition timer is running.

[0047] The at least one condition parameter may further include a connection prohibit timer. When the connection prohibit timer is running, the UE does not evaluate whether the radio link quality of the UE's cell is equal to or lower than the radio link quality threshold during the time interval of the state transition timer. Alternatively, when the connection prohibit timer is running, the UE does not trigger an RRC connection resumption procedure even if the radio link quality of the UE's cell is equal to or lower than the radio link quality threshold during the time interval of the state transition timer.

[0048] Method 2 In some embodiments of the present application, at least one of the radio link quality thresholds and state transition timers described in Scheme 1 may be used with a corresponding scaling factor that may be dependent on the network load or on the mobility speed of the UE.

[0049] For example, the at least one condition parameter may include a radio link quality threshold and at least one scaling factor associated with the radio link quality threshold. The UE evaluates whether the radio link quality of the UE's cell is less than or equal to the radio link quality threshold multiplied by the corresponding scaling factor. If the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold multiplied by the corresponding scaling factor, the UE triggers an RRC connection resumption procedure.

[0050] The at least one condition parameter may further include a connection prohibition timer. When the connection prohibition timer is running, the UE does not evaluate whether the radio link quality of the UE's cell is equal to or lower than the value multiplied by a scaling factor corresponding to the radio link quality threshold, or does not trigger an RRC connection resumption procedure, depending on whether it is prohibited by the connection prohibition timer. In any case, when the connection prohibition timer is running, the UE does not trigger an RRC connection resumption procedure even if the radio link quality of the UE's cell is equal to or lower than the value multiplied by a scaling factor corresponding to the radio link quality threshold.

[0051] In another example, the at least one condition parameter may include a radio link quality threshold, a state transition timer, and at least one scaling factor associated with the radio link quality threshold. The UE evaluates whether the radio link quality of the UE's cell is equal to or lower than the radio link quality threshold multiplied by the corresponding scaling factor during a time interval of the state transition timer. If the radio link quality of the UE's serving cell is equal to or lower than the radio link quality threshold multiplied by the corresponding scaling factor during a time interval of the state transition timer, the UE triggers an RRC connection resumption procedure to enter the RRC connected state. However, if the at least one condition parameter includes a connection prohibit timer and the connection prohibit timer is running, the UE does not evaluate whether the radio link quality of the UE's cell is equal to or lower than the radio link quality threshold multiplied by the corresponding scaling factor during a time interval of the state transition timer or does not trigger an RRC connection resumption procedure, which depends on whether it is prohibited by the connection prohibit timer.

[0052] In another example, the at least one condition parameter may include a radio link quality threshold, a state transition timer, and at least one scaling factor associated with the state transition timer. The UE evaluates whether the radio link quality of the UE's cell is equal to or less than the radio link quality threshold multiplied by the corresponding scaling factor for a time interval of the state transition timer. If the radio link quality of the UE's serving cell is equal to or less than the radio link quality threshold for a time interval of the state transition timer multiplied by the corresponding scaling factor, the UE triggers an RRC connection resumption procedure to enter the RRC connected state. That is, the actual time interval of the state transition timer is changed to a time interval (e.g., the original time interval) multiplied by the corresponding scaling factor. However, if the at least one condition parameter includes a connection prohibit timer and the connection prohibit timer is running, the UE does not evaluate whether the radio link quality of the UE's cell is equal to or less than the radio link quality threshold multiplied by the corresponding scaling factor for a time interval of the state transition timer or does not trigger an RRC connection resumption procedure, which depends on whether it is prohibited by the connection prohibit timer.

[0053] In another example, the at least one condition parameter may include a radio link quality threshold, at least one first scaling factor associated with the radio link quality threshold, a state transition timer, and at least one second scaling factor associated with the state transition timer. The UE evaluates that the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold multiplied by a first scaling factor of the at least one first scaling factor multiplied by a second scaling factor of the at least one second scaling factor for a time interval of the state transition timer. If the radio link quality of the serving cell is less than or equal to the radio link quality threshold multiplied by the first scaling factor for a time interval of the state transition timer multiplied by the second scaling factor, the UE triggers an RRC connection resumption procedure to enter the RRC connected state. However, if the at least one condition parameter includes a connection prohibition timer and the connection prohibition timer is running, the UE does not evaluate whether the radio link quality of the UE's cell is below the radio link quality threshold multiplied by the first scaling factor for the time interval of the state transition timer multiplied by the first scaling factor or does not trigger an RRC connection resumption procedure, which depends on whether it is prohibited by the connection prohibition timer.

[0054] Furthermore, if the scaling factor is a network load dependent scaling factor, the scaling factor can be adjusted or updated according to the network congestion state. For example, for a cell in a high load state, the scaling factor can be 1.5, and for a cell in a medium load state, the scaling factor can be 1.2. Thus, the network can control the UE to enter the RRC connected state according to the network load state, and it is assumed that the UE in a worse congestion state enters the RRC connected state with a higher priority than the UE in a better congestion state.

[0055] For example, the at least one condition parameter may include a radio link quality threshold and a network load-dependent scaling factor, e.g., 1.5. When evaluating whether the at least one condition parameter is satisfied, the UE evaluates whether the radio link quality of the UE's serving cell is equal to or less than a new threshold, which is counted by multiplying the configured radio link quality threshold by 1.5. If the radio link quality of the UE's serving cell is equal to or less than the new threshold, the UE triggers an RRC connection resumption procedure.

[0056] If the scaling factor is a UE mobility speed dependent scaling factor, the scaling factor can be adjusted or updated according to the UE mobility speed. For example, for a UE at a high mobility speed, the scaling factor can be 0.5, and for a UE at a medium mobility speed, the scaling factor can be 0.8. Therefore, it is assumed that a UE at a high mobility speed enters the RRC connected state with a higher priority than a UE at a low mobility speed.

[0057] For example, the at least one condition parameter may include a radio link quality threshold, a state transition timer, and a UE mobility speed dependent scaling factor associated with the state transition timer, e.g., 0.5. When evaluating whether the at least one condition parameter is satisfied, the UE evaluates whether the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold for a time interval of the state transition timer multiplied by 0.5. If the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold for a time interval of the state transition timer multiplied by 0.5, the UE triggers an RRC connection resumption procedure.

[0058] Method 3 In some embodiments of the present application, the radio link quality threshold described in scheme 1 can be used with a corresponding offset value that can be configured per MRB or per multicast session. That is, each MRB or multicast session has at least one corresponding condition parameter. According to some embodiments of the present application, the offset value is a hysteresis value. Similarly, if the at least one condition parameter includes a connection prohibition timer and the connection prohibition timer is running, the UE does not evaluate whether the at least one condition parameter is satisfied or does not trigger an RRC connection resumption procedure, which depends on whether it is prohibited by the connection prohibition timer.

[0059] If multiple MRBs or multiple multicast sessions exist, the UE may evaluate whether at least one condition parameter is satisfied based on the multiple MRBs or multiple multicast sessions. However, the UE may trigger an RRC connection resumption procedure to enter the RRC connected state if one of the multiple MRBs or multiple multicast sessions satisfies the requirements (or criteria) provided by the corresponding at least one condition parameter, or if all of the multiple MRBs or multiple multicast sessions satisfy the requirements (or criteria) provided by the respective at least one condition parameter.

[0060] For example, the at least one condition parameter may include a radio link quality threshold and at least one offset value associated with the radio link quality threshold, each of the at least one offset value being associated with a multicast session or MRB. For each MRB or multicast session, the UE evaluates whether a radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold plus a corresponding offset value.

[0061] In some embodiments of the present application, when there are multiple MRBs or multicast sessions in the multicast reception, if the radio link quality of the serving cell of the UE is less than or equal to the radio link quality threshold plus an offset value of one of the multiple MRBs or multiple multicast sessions, the UE triggers an RRC connection resumption procedure to enter the RRC connected state. That is, the RRC connection resumption procedure is triggered when the radio link quality of the serving cell of the UE is less than or equal to the radio link quality threshold plus an offset value corresponding to the radio link quality threshold for one multicast session of the multicast reception or for one MRB of the multicast reception (i.e., one MRB or multicast session meets the requirement).

[0062] In some other embodiments of the present application, when there are multiple MRBs or multicast sessions in the multicast reception, if for each MRB or each multicast session, the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold plus an offset value corresponding to the radio link quality threshold, the UE triggers an RRC connection resumption procedure to enter the RRC connected state. That is, the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is less than or equal to the radio link quality threshold plus an offset value corresponding to the radio link quality threshold for all multicast sessions of the multicast reception or for all MRBs of the multicast reception (that is, all MRBs or multicast sessions must meet the requirement).

[0063] Similar to Scheme 1 and Scheme 2, a state transition timer may also be used in Scheme 3. For example, the at least one condition parameter includes a state transition timer, and the RRC connection resumption procedure is triggered when the radio link quality of the UE's serving cell is equal to or lower than a radio link quality threshold plus an offset value corresponding to the radio link quality threshold for one multicast session of multicast reception or for one MRB of multicast reception during a time interval of the state transition timer, or when the radio link quality of the UE's serving cell is equal to or lower than a radio link quality threshold plus an offset value corresponding to the radio link quality threshold for all MRBs of multicast reception or for all MRBs of multicast reception during a time interval of the state transition timer.

[0064] Method 4 In some embodiments of the present application, the at least one condition parameter includes at least one packet loss threshold, and each of the at least one packet loss threshold is associated with a multicast session or an MRB. That is, the packet loss threshold is per multicast session or per MRB. In another example, the packet loss rate is counted at the PDCP layer, for example, the number of missing PDCP packets, for example, protocol data units (PDUs) or SDUs, counted at the PDCP layer within a set time length, or the number of PDCP reordering timer expirations counted at the PDCP layer. If the packet loss rate is the number of PDCP reordering timer expirations counted at the PDCP layer, the corresponding packet loss threshold is the threshold of the number of PDCP reordering timer expirations. In another example, the packet loss rate is counted at the physical layer, for example, the PER or BLER counted at the physical layer.

[0065] The UE evaluates whether the packet loss rate of the multicast session of the multicast reception or the MRB of the multicast reception is equal to or greater than the corresponding packet loss threshold. For example, the UE may evaluate whether the number of PDCP reordering timer expirations counted at the PDCP layer is equal to or greater than the threshold number of PDCP reordering timer expirations within a configured time. The RRC connection resumption procedure is triggered when the packet loss rate of the multicast session of the multicast reception or the MRB of the multicast reception is equal to or greater than the corresponding packet loss threshold.

[0066] Similarly, if the at least one condition parameter includes a connection prohibition timer and the connection prohibition timer is running, the UE does not evaluate whether the at least one condition parameter is satisfied or does not trigger an RRC connection resumption procedure, which depends on whether it is prohibited by the connection prohibition timer.

[0067] Method 5 In some embodiments of the present application, the at least one condition parameter is a timer. For example, the timer is a timer configured to be started by the UE in response to entering an RRC inactive state for multicast reception. The UE may trigger an RRC connection resumption procedure in response to expiration of the timer. In another example, the timer is a multicast inactivity timer that is started or re-started in response to reception of a MAC SDU of an MTCH logical channel by the UE in the RRC inactive state. The UE may trigger an RRC connection resumption procedure in response to expiration of the multicast inactivity timer. However, according to some embodiments of the present application, expiration of the multicast inactivity timer does not trigger an RRC connection resumption procedure and the UE enters an RRC idle state.

[0068] An exemplary procedure based on a multicast inactivity timer is proposed as follows. If dataInactivityTimer_RRC_INACTIVE is set, the UE shall: 1> When receiving multicast and in RRC_INACTIVE state: 2> Any MAC entity receives a MAC SDU for a multicast MTCH logical channel, or 3>Start or restart the dataInactivityTimer_RRC_INACTIVE. 2>If dataInactivityTimer_RRC_INACTIVE expires: 3>Indicate expiration of dataInactivityTimer_RRC_INACTIVE to higher layers. 1> If the UE receives the expiration of dataInactivityTimer_RRC_INACTIVE from the lower layers during RRC_INACTIVE, 2> Perform an RRC Resume procedure to return to the RRC_CONNECTED state, or 2> Execute the action when transitioning to RRC_IDLE.

[0069] Considering that the state transition from RRC Inactive to RRC Connected is triggered by an Access Stratum (AS) triggered request, it is up to the RRC layer to decide the access category, and the Non-Access Stratum (NAS) decides the access identity(ies). An embodiment of the present application proposes a new access category, e.g., access category 9, for the RRC Connection Resumption procedure triggered for multicast reception, and proposes to set the RRC cause (or RRC Resume Request cause) in the RRC Resume Request message to "multicast invocation" to indicate that the request is due to multicast reception.

[0070] An exemplary detailed procedure by using the new access category is as follows: At the start of the RRC resumption procedure, the UE shall: 1> If the RRC connection resumption is triggered by a response to NG-RAN paging: 2> Select "0" as the access category, 2> Execute the integrated access control procedures specified in 5.3.14 using the selected access category and one or more access IDs provided by the higher tier; 3> If the access attempt is denied, the procedure ends and 1> Otherwise, if the RRC connection resumption is triggered by higher layers, 2> If a higher layer provides an access category and one or more access IDs, 3) Execute the integrated access control procedures specified in 5.3.14 using the access categories and access IDs provided by the higher layer; 4> If the access attempt is denied, the procedure ends and 2> Set resumeCause according to information received from higher layers, 1> Otherwise, if an RRC connection restart is triggered by an RNA update as specified in 5.3.13.8, 2>If emergency services are in progress, NOTE: How the RRC layer in the UE becomes aware of ongoing emergency services is up to the UE implementation. 3> Select "2" as the access category, 3> Set resumeCause to Urgent, 2>Otherwise, 3> Select "8" as the access category, 2> Execute the integrated access control procedures specified in 5.3.14 using the selected access category and the applicable access ID or IDs as specified in TS 24.501

[23] ; 1> Otherwise, if the RRC connection resumption is triggered by multicast reception, 2> Select "9" as the access category, 2>2>Perform the integrated access control procedures specified in 5.3.14 using the selected access category and the applicable access ID or IDs as specified in TS 24.501

[23] .

[0071] Exemplary RRC resume causes are: -ResumeCause The IE ResumeCause is used in RRCResumeRequest and RRCResumeRequest1 to indicate the cause of the resume. ResumeCause information element -- ASN1START -- TAG-RESUMECAUSE-START ResumeCause::=ENUMERATED { emergency, highPriorityAccess, mt-Access, mo-Signalling, mo-Data, mo-VoiceCall, mo-VideoCall, mo-SMS, rna-Update, mps-PriorityAccess, mcs-PriorityAccess, Multicast Receive, Spare 1, Spare 2, Spare 3, Spare 4,} -- TAG-RESUMECAUSE-STOP -- ASN1STOP

[0072] The embodiments of the present application also provide a solution to stop or cancel evaluating whether at least one condition parameter is satisfied.

[0073] For example, if the RRC connection resumption procedure is triggered by higher layers, or by a periodic RNA update, or in response to RAN paging, the UE may stop or cancel evaluating whether at least one condition parameter is met.

[0074] In another example, the UE may stop or cancel evaluating whether at least one condition parameter is met if an RRC setup procedure is triggered in response to a CN paging or if a RAN or CN paging is received.

[0075] In another example, the UE may stop or cancel evaluating whether at least one condition parameter is satisfied if an RRCSetup message or an RRCResume message is received.

[0076] If an RRCReject message is received, the UE may re-initiate an RRCResume message after a configured time interval, e.g., by a configured timer, if the criteria for returning a connection state for multicast reception to RRC are still met. If an RRCReject message is received, the UE may re-evaluate the criteria in response to receiving the RRCReject message or after a configured time interval (e.g., expiration of a configured timer).

[0077] If the UE stops or cancels evaluating whether at least one condition parameter is satisfied (e.g., if an RRC connection resumption procedure is triggered by higher layers, or by a periodic RNA update, or in response to RAN paging, or if an RRC setup procedure is triggered in response to CN paging, or if a RAN paging or CN paging is received, or if an RRCSetup or RRCResume message is received), the UE may release the configuration of the at least one condition parameter.

[0078] In addition to the method, the embodiments of the present application also propose an apparatus for supporting MBS.

[0079] FIG. 4 illustrates a block diagram of a device supporting the MBS 300 according to some embodiments of the present application.

[0080] 4, the apparatus 400 may include at least one non-transitory computer-readable medium 401, at least one receiving circuit 402, at least one transmitting circuit 404, and at least one processor 406 coupled to the non-transitory computer-readable medium 401, the receiving circuit 402, and the transmitting circuit 404. The at least one processor 406 may be a CPU, a DSP, a microprocessor, etc. The apparatus 400 may be a remote device, such as a UE, configured to perform methods, such as those illustrated above.

[0081] In this drawing, elements such as at least one processor 406, the transmit circuitry 404, and the receive circuitry 402 are described in the singular, but the plural is contemplated unless limitation to the singular is explicitly stated. In some embodiments of the present application, the receive circuitry 402 and the transmit circuitry 404 may be combined into a single device, such as a transceiver. In certain embodiments of the present application, the apparatus 400 may further include an input device, a memory, and / or other components.

[0082] In some embodiments of the present application, the non-transitory computer-readable medium 401 may store computer-executable instructions to cause a processor to implement the methods with respect to the UE described above. For example, the computer-executable instructions, when executed, cause the processor 406 to interact with the receiving circuitry 402 and the transmitting circuitry 404 to perform steps with respect to the UE as shown above.

[0083] FIG. 5 is a block diagram of an apparatus supporting MBS according to some other embodiments of the present application.

[0084] 5, an apparatus 500, e.g., a UE, may include at least one processor 502 and at least one transceiver 504 coupled to the at least one processor 502. The transceiver 504 may include at least one separate receiving circuit 506 and transmitting circuit 508, or at least one integrated receiving circuit 506 and transmitting circuit 508. The at least one processor 502 may be a CPU, DSP, microprocessor, etc.

[0085] According to some embodiments of the present application, when the apparatus 500 is a UE, the processor 502 is configured to receive, via the at least one receiving circuit 506, configuration information regarding at least one condition parameter associated with an RRC state transition for multicast reception, and, when the UE is receiving the multicast or is configured to receive the multicast in an RRC inactive state, trigger an RRC connection resumption procedure to enter an RRC connected state from an RRC inactive state in response to the at least one condition parameter being satisfied.

[0086] The method according to the embodiment of the present application can also be implemented on a programmed processor. However, the controller, the flow chart, and the module can also be implemented on hardware electronic or logical circuits, such as a general-purpose or special-purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a discrete element circuit, a programmable logic device, etc. In general, any device capable of implementing the flow charts shown in the drawings can be used to implement the processor function of this application. For example, an embodiment of the present application provides an apparatus including a processor and a memory. The computer programmable instructions for implementing the method are stored in the memory, and the processor is configured to execute the computer programmable instructions for implementing the method. The method may be the method described above or other methods according to an embodiment of the present application.

[0087] An alternative embodiment preferably implements the method according to the embodiment of the present application in a non-transitory computer-readable storage medium storing computer programmable instructions. The instructions are preferably executed by a computer executable component that is preferably integrated with the network security system. The non-transitory computer-readable storage medium may be stored in any suitable computer readable medium, such as a RAM, a ROM, a flash memory, an EEPROM, an optical storage device (CD or DVD), a hard drive, a floppy drive, or any suitable device. The computer executable component is preferably a processor, but the instructions may alternatively or additionally be executed by any suitable dedicated hardware device. For example, an embodiment of the present application provides a non-transitory computer-readable storage medium having stored thereon computer programmable instructions. The computer programmable instructions are configured to implement the method described above, or other methods according to the embodiment of the present application.

[0088] Furthermore, in this disclosure, the terms "includes," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, and 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 preceded by "a," "an," etc., does not preclude the presence of additional identical elements within a process, method, article, or apparatus that includes the element, unless further constrained. Also, the term "another" is defined as at least a second, or more. Terms such as "having," as used herein, are defined as "including." [Explanation of symbols]

[0089] 100 Wireless communication system 101 Base station (BS) 102UE 102a First UE 102b Second UE 200 Coverage 201 Good coverage area 203 Poor Coverage Area 300MBS 400 equipment 401 Non-transitory computer-readable medium 402 Receiving circuit 404 Transmitting circuit 406 Processor 500 devices 502 processor 504 Transceiver 506 Receiving circuit 508 Transmitting Circuit

Claims

1. A user equipment (UE), A transceiver; at least one processor coupled to the transceiver; wherein the at least one processor: receiving, via the transceiver, configuration information regarding at least one condition parameter associated with a radio resource control (RRC) state transition for multicast reception; triggering an RRC connection resumption procedure to enter an RRC connected state from the RRC inactive state in response to the at least one condition parameter being satisfied when the UE is receiving a multicast or is configured to receive the multicast in an RRC inactive state; The UE is configured to:

2. The at least one condition parameter comprises a radio link quality threshold and a state transition timer associated with the radio link quality threshold, and the RRC connection resumption procedure further comprises: The UE of claim 1 , wherein the state transition timer is triggered when a radio link quality of a serving cell of the UE is less than or equal to the radio link quality threshold for a time interval of the state transition timer.

3. The at least one condition parameter comprises a radio link quality threshold, a state transition timer, and at least one scaling factor associated with the radio link quality threshold, and the RRC connection resumption procedure further comprises:

2. The UE of claim 1, wherein a state transition timer is triggered when a radio link quality of a serving cell of the UE is equal to or less than the radio link quality threshold multiplied by a scaling factor of the at least one scaling factor for a time interval of the state transition timer, the scaling factor being dependent on a network load or a mobility speed of the UE.

4. The at least one condition parameter comprises at least one packet loss threshold, each of the at least one packet loss threshold being associated with a multicast session or a multicast radio bearer (MRB), and the RRC connection resumption procedure further comprises: The UE of claim 1, wherein the UE is triggered when a packet loss rate of a multicast session of the multicast reception or an MRB of the multicast reception is equal to or greater than a corresponding packet loss threshold.

5. 2. The UE of claim 1, wherein the at least one condition parameter is a timer, the timer being started by the UE in response to entering the RRC inactive state for multicast reception, and the RRC connection resumption procedure being triggered in response to expiration of the timer.

6. 2. The UE of claim 1, wherein the at least one condition parameter comprises a multicast inactivity timer that is started or restarted in response to reception by the UE of a media access control (MAC) service data unit (SDU) on a multicast traffic channel (MTCH) logical channel in the RRC inactive state, and the RRC connection resumption procedure is triggered in response to expiration of the multicast inactivity timer.

7. 7. The UE of claim 2, wherein the at least one condition parameter further comprises a connection prohibition timer, and when the connection prohibition timer is running, triggering the RRC connection resumption procedure or evaluating whether the at least one condition parameter is satisfied is prohibited.

8. the at least one processor: The RRC connection resumption procedure was triggered by higher layers, or by a periodic Radio Access Network (RAN)-based Notification Area (RNA) update, or in response to RAN paging; or that the RRC connection setup procedure was triggered by a response to Core Network (CN) paging, or An RRC Resume message was received, or RRC setup message was received 13. The UE of claim 1, configured to stop or cancel evaluating whether the at least one condition parameter is satisfied in response to:

9. receiving, by a user equipment (UE), configuration information regarding at least one condition parameter associated with a radio resource control (RRC) state transition for multicast reception; triggering, by the UE, an RRC connection resumption procedure to enter an RRC connected state from the RRC inactive state in response to the at least one condition parameter being satisfied, if the UE is receiving a multicast or is configured to receive the multicast in an RRC inactive state; A method comprising:

10. The at least one condition parameter comprises a radio link quality threshold and a state transition timer associated with the radio link quality threshold, and the RRC connection resumption procedure further comprises: The method of claim 9, triggered when a radio link quality of a serving cell of the UE is below the radio link quality threshold for a time interval of the state transition timer.

11. The at least one condition parameter comprises a radio link quality threshold, a state transition timer, and at least one scaling factor associated with the radio link quality threshold, and the RRC connection resumption procedure further comprises:

10. The method of claim 9, wherein a radio link quality of a serving cell of the UE is triggered when the radio link quality threshold multiplied by a scaling factor of the at least one scaling factor for a time interval of the state transition timer, the scaling factor being dependent on a network load or a mobility speed of the UE.

12. The at least one condition parameter comprises at least one packet loss threshold, each of the at least one packet loss threshold being associated with a multicast session or a multicast radio bearer (MRB), and the RRC connection resumption procedure further comprises: The method of claim 9, wherein the method is triggered when a packet loss rate of a multicast session of a multicast reception or an MRB of a multicast reception is equal to or greater than a corresponding packet loss threshold.

13. 10. The method of claim 9, wherein the at least one condition parameter is a timer, the timer being started by the UE in response to entering the RRC inactive state for multicast reception, and the RRC connection resumption procedure being triggered in response to expiration of the timer.

14. 14. The method according to claim 10, wherein the at least one condition parameter further comprises a connection prohibit timer, and when the connection prohibit timer is running, triggering the RRC connection resumption procedure or evaluating whether the at least one condition parameter is fulfilled is prohibited.

15. The RRC connection resumption procedure was triggered by higher layers, or by a periodic Radio Access Network (RAN)-based Notification Area (RNA) update, or in response to RAN paging; or that the RRC connection setup procedure was triggered by a response to Core Network (CN) paging, or An RRC Resume message was received, or RRC setup message was received 10. The method of claim 9, further comprising: in response to stopping or canceling evaluating whether the at least one condition parameter is satisfied.

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