Method and device for supporting continuity of MRB

Abstract

The invention relates to a method and apparatus for supporting continuity of multicast radio bearers (MRBs). One embodiment of the present disclosure provides a user equipment (UE) comprising: a transceiver; and a processor coupled with the transceiver and configured to: receive, via the transceiver, information associated with a Packet Data Convergence Protocol (PDCP) of an MRB via Radio Resource Control (RRC) dedicated signaling, where the PDCP includes one or more PDCP variables; transitioning to an RRC non-connected state; and determining whether to use the one or more PDCP variables for continuity of the MRB while the UE is in the RRC non-connected state based on the information associated with the PDCP of the MRB.

Description

Technical Field

[0001] The present disclosure relates to wireless communication, and in particular, to methods and apparatuses for supporting the continuity of multicast / multicast radio bearers (MRBs) for multicast / broadcast services (MBS). Background Art

[0002] Support multicast reception by a user equipment (UE) in a radio resource control (RRC) disconnected state (e.g., RRC inactive state or RRC idle state). In cases where it is necessary to indicate a point-to-multipoint (PTM) configuration or a change in the PTM configuration, or during mobility outside a serving cell or base station (BS), an MBS control channel (MCCH) can be used to provide a PTM configuration for the UE to receive multicast in the RRC inactive state. Currently, the MCCH can be provided per cell only for broadcast services. The MCCH can support only an MRB join list and an MRB release list. That is, there is no MRB modification list because differential configuration is not feasible as the PTM configuration may vary between different cells.

[0003] Therefore, it is advantageous to provide methods and apparatuses for supporting the continuity of multicast MRBs. Summary of the Invention

[0004] Embodiments of the present disclosure provide a UE including: a transceiver; and a processor coupled to the transceiver and configured to: receive, via the transceiver, information associated with the packet data convergence protocol (PDCP) of an MRB via RRC dedicated signaling, where the PDCP includes one or more PDCP variables; transition to an RRC disconnected state; and determine, based on the information associated with the PDCP of the MRB, whether to use the one or more PDCP variables for the continuity of the MRB while the UE is in the RRC disconnected state.

[0005] In some embodiments, the information associated with the PDCP of the MRB includes a list of areas or cells in which the continuity of the MRB is supported.

[0006] In some embodiments, the processor is further configured to: perform cell reselection from a first cell to a second cell; and use the one or more PDCP variables for the continuity of the MRB when the first cell and the second cell are within the area or in the cell list.

[0007] In some embodiments, the processor is configured to: release a first radio link control (RLC) bearer of the MRB in the first cell when leaving the first cell; obtain an RLC bearer configuration of the MRB via an MCCH in the second cell when entering the second cell; and establish a second RLC bearer of the MRB in the second cell according to the RLC bearer configuration of the MRB.

[0008] In some embodiments, the information associated with the PDCP of the MRB indicates an identifier (ID) of a first RLC bearer in the first cell, and the processor is further configured to: associate the same PDCP entity in the first cell with the second RLC bearer in the second cell if the same ID of the second RLC bearer is also received via the MCCH in the second cell.

[0009] In some embodiments, the information associated with the PDCP of the MRB indicates a first ID of the MRB in the first cell and a second ID of the MRB in the second cell, and wherein the processor is further configured to: associate the MRB in the second cell with the PDCP entity of the MRB in the first cell.

[0010] In some embodiments, the information associated with the PDCP of the MRB indicates one or more indexes of a PDCP configuration.

[0011] In some embodiments, the one or more indexes include a first index of a PDCP configuration, and the processor is further configured to: perform cell reselection from a first cell to a second cell; receive a second index of the PDCP configuration in the second cell from the MCCH; and use the one or more PDCP variables for continuity of the MRB if the first index is the same as the second index.

[0012] In some embodiments, the information associated with the PDCP of the MRB further includes a corresponding PDCP configuration for each index.

[0013] In some embodiments, the corresponding PDCP configuration for each index is predefined.

[0014] In some embodiments, to use the one or more PDCP variables for the continuity of the MRB, the processor is further configured to: store the one or more PDCP variables of the PDCP entity for the MRB in the first cell; release the PDCP entity of the MRB and establish a new PDCP entity for a new MRB in the second cell; and set the one or more PDCP variables of the new PDCP entity of the new MRB with the one or more PDCP variables of the stored PDCP entity.

[0015] In some embodiments, to use the one or more PDCP variables for the continuity of the MRB, the processor is further configured to: maintain the same PDCP entity for the MRB in the second cell; and continue to use the most recent PDCP variables of the PDCP entity for the MRB in the second cell.

[0016] In some embodiments, to use the one or more PDCP variables for the continuity of the MRB, the processor is further configured to: reconstruct the PDCP entity for the MRB in the second cell; and continue to use the most recent PDCP variables of the PDCP entity for the MRB in the second cell.

[0017] In some embodiments, the processor is further configured to: trigger a PDCP status report and an RRC resume procedure in the second cell when the PDCP variables of a first received packet in the second cell are greater or smaller than a threshold than the corresponding stored PDCP variables.

[0018] Another embodiment of the present disclosure provides a BS, comprising: a transceiver; and a processor coupled to the transceiver and configured to: determine information associated with the PDCP of an MRB, where the PDCP includes one or more PDCP variables; and transmit, via the transceiver, the information associated with the PDCP of the MRB to a UE via RRC dedicated signaling.

[0019] In some embodiments, the information associated with the PDCP of the MRB includes a list of regions or cells in which the continuity of the MRB is supported.

[0020] In some embodiments, the information associated with the PDCP of the MRB indicates the ID of the RLC bearer in the first cell.

[0021] In some embodiments, the information associated with the PDCP of the MRB indicates a first ID of the MRB in the first cell and a second ID of the MRB in the second cell.

[0022] In some embodiments, the information associated with the PDCP of the MRB indicates one or more indexes of the PDCP configuration.

[0023] In some embodiments, the one or more indexes include a first index of the PDCP configuration in the first cell.

[0024] In some embodiments, the BS includes a Central Unit (CU) and a Distributed Unit (DU), the CU being configured to determine the information associated with the PDCP of the MRB and transmit the information associated with the PDCP of the MRB to the DU.

[0025] Another embodiment of the present disclosure provides a method performed by a UE, comprising: receiving, via RRC dedicated signaling, information associated with the PDCP of an MRB, wherein the PDCP includes one or more PDCP variables; transitioning to the RRC idle state; and determining, based on the information associated with the PDCP of the MRB, whether to use the one or more PDCP variables for the continuity of the MRB while the UE is in the RRC idle state.

[0026] Yet another embodiment of the present disclosure provides a method performed by a BS, comprising: determining information associated with the PDCP of an MRB, wherein the PDCP includes one or more PDCP variables; and transmitting, via RRC dedicated signaling, the determined information associated with the PDCP of the MRB to a UE. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] To describe the manner in which the advantages and features of the present application can be obtained, the description of the present application is presented by reference to specific embodiments of the present application illustrated in the drawings. These drawings only depict example embodiments of the present application and should not be considered as limiting its scope.

[0028] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure.

[0029] Figure 2 A method performed by a UE for wireless communication according to some embodiments of the present disclosure is illustrated.

[0030] Figure 3 A method performed by a BS for wireless communication according to some embodiments of the present disclosure is illustrated.

[0031] Figure 4 Per-region PDCP and per-cell RLC or lower layer of an MRB according to some embodiments of the present disclosure are illustrated.

[0032] Figure 5Flowchart illustrating support for MRB continuity according to some embodiments of the present disclosure.

[0033] Figure 6 Flowchart illustrating support for MRB continuity according to some embodiments of the present disclosure.

[0034] Figure 7 Simplified block diagram of a device according to some embodiments of the present disclosure. Detailed Description of the Invention

[0035] The detailed description of the drawings is intended as a description of the currently preferred embodiments of the invention and is not intended to represent the only form in which the invention 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 covered within the spirit and scope of the invention.

[0036] Although the operations are depicted in the drawings in a particular order, those skilled in the art will readily recognize that such operations need not be performed in the particular order shown or in a sequential order, or that all of the illustrated operations may be required to achieve the desired result; in some cases, one or more operations may be skipped. Additionally, the drawings may schematically depict one or more example processes in the form of a flowchart. However, other operations not depicted may be incorporated into the example processes schematically illustrated. For example, one or more additional operations may be performed before, after, simultaneously with, or between any of the illustrated operations. In some cases, multitasking and parallel processing may be advantageous.

[0037] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. For the purpose of promoting understanding, embodiments are provided in the context of specific network architectures and new service scenarios (such as cellular telephone networks, time division multiple access (TDMA)-based networks, code division multiple access (CDMA)-based networks, orthogonal frequency division multiple access (OFDMA)-based networks, LTE networks, 3rd Generation Partnership Project (3GPP)-based networks, LTE, Long Term Evolution-Advanced (LTE-A), 3GPP 4G, 3GPP 5G NR, 3GPP Release 16 and above, satellite communication networks, high altitude platform networks, etc.). It is contemplated that as the network architectures and new service scenarios evolve, all embodiments in the present disclosure are also applicable to similar technical problems; and furthermore, the terms cited in the present disclosure may change, which should not affect the principles of the present disclosure.

[0038] Figure 1 Schematic diagram of a wireless communication system according to some embodiments of the present disclosure.

[0039] As Figure 1 shown, the wireless communication system includes UE 101, BS102-A, base station 102-B, and base station 102-C. Even though Figure 1depicts a specific number of UEs and BSs, but those skilled in the art should recognize that any number of UEs and BSs can be included in a wireless communication system.

[0040] UE 101 may include a computing device, such as a desktop computer, laptop computer, personal digital assistant (PDA), tablet computer, smart TV (e.g., a TV connected to the Internet), set-top box, gaming console, security system (including security cameras), in-vehicle computer, network device (e.g., router, switch, modem), or the like. According to an embodiment of the present disclosure, UE 101 may include a portable wireless communication device, smart phone, cellular phone, flip phone, device with a subscriber identity module, personal computer, pager, or any other device capable of transmitting and receiving communication signals over a wireless network. In some embodiments, UE 101 includes a wearable device, such as a smart watch, fitness band, optical head-mounted display, or the like. Additionally, UE 101 may be referred to as a subscriber unit, mobile device, mobile station, user, terminal, mobile terminal, wireless terminal, fixed terminal, subscriber station, UE 101, user terminal, device, or other terms used in the art. UE101 may communicate directly with the BS via an uplink (UL) communication signal.

[0041] BSs may be distributed throughout a geographical area. In certain embodiments, a BS may also be referred to as an access point, access terminal, base, base station, macro cell, Node B, evolved Node B (eNB), BS, home Node B, relay node, device, or any other term used in the art. A BS is generally part of a radio access network that may include one or more controllers communicatively coupled to one or more corresponding BSs.

[0042] The wireless communication system is compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system is compatible with wireless communication networks, cellular phone networks, time division multiple access (TDMA)-based networks, code division multiple access (CDMA)-based networks, orthogonal frequency division multiple access (OFDMA)-based networks, LTE networks, 3GPP-based networks, 3GPP 5G networks, satellite communication networks, high altitude platform networks, and / or other communication networks.

[0043] In an embodiment, the wireless communication system is compatible with NR of the 3GPP protocol, where the BS transmits on the DL using an orthogonal frequency division multiplexing (OFDM) modulation scheme, and UE 101 transmits on the uplink using a single carrier frequency division multiple access (SC-FDMA) scheme or an OFDM scheme. However, more generally, the wireless communication system may implement some other open or proprietary communication protocols, such as WiMAX and other protocols.

[0044] In other embodiments, the BS may communicate using other communication protocols, such as wireless communication protocols of the IEEE 802.11 series. Additionally, in some embodiments, the BS may communicate via licensed spectrum, while in other embodiments, the BS may communicate via unlicensed spectrum. The present disclosure is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol. In another embodiment, the BS may communicate with the UE 101 using the 3GPP 5G protocol.

[0045] As Figure 1 shown, the UE 101 is currently located in cell 1 and may be in the RRC disconnected state, such as the RRC inactive state. The UE may receive MBS services in the RRC inactive state and may reselect cell 2 and enter cell 2.

[0046] Currently, the MRB served by cell 1 may be released, and a new MRB may be established in cell 2:

[0047] - For broadcasting, the MRB is released when leaving the cell of the MBS session that the broadcast UE is interested in.

[0048] - For broadcasting, the MRB is established when entering the cell that provides the MBS broadcast service that the UE is interested in.

[0049] Next, when the UE moves to an adjacent cell, the current MCCH scheme cannot support service continuity. Different from broadcast services, multicast services require high reliability and service continuity. The present disclosure proposes some solutions to support the mobility and service continuity of MCCH for multicast reception of UEs in the RRC disconnected state when the UE moves from one cell to another. More specifically, solutions for supporting the continuity of the MRB for multicast services.

[0050] Figure 2 Describe a method for wireless communication performed by a UE according to some embodiments of the present disclosure.

[0051] In operation 201, the UE may receive information associated with the PDCP of the MRB via RRC dedicated signaling via a transceiver, where the PDCP may include one or more PDCP variables, such as RX_NEXT, RX_DELIV, or the like. In operation 202, the UE may transition to the RRC disconnected state, such as the RRC inactive state. In operation 203, the UE may determine whether to use one or more PDCP variables for the continuity of the MRB while the UE is in the RRC disconnected state based on the information associated with the PDCP of the MRB.

[0052] In some embodiments, the information associated with the PDCP of the MRB includes a list of regions or cells where the continuity of the MRB is supported. For example, including Figure 1The areas of Cell 1, Cell 2, and Cell 3 shown in or include Figure 1 The cell list of Cell 1, Cell 2, and Cell 3 shown in .

[0053] In some embodiments, the UE may perform cell reselection from a first cell to a second cell; and may use one or more PDCP variables for the continuity of the MRB when the first cell and the second cell are within the area or in the cell list.

[0054] In some embodiments, the UE may release the first RLC bearer of the MRB in the first cell when leaving the first cell; obtain the RLC bearer configuration of the MRB via the MCCH in the second cell when entering the second cell; and establish the second RLC bearer of the MRB in the second cell according to the RLC bearer configuration of the MRB.

[0055] In some embodiments, the information associated with the PDCP of the MRB indicates the ID of the first RLC bearer in the first cell, and the UE may associate the same PDCP entity in the first cell with the second RLC bearer in the second cell if the same ID of the second RLC bearer is also received via the MCCH in the second cell.

[0056] In some embodiments, the information associated with the PDCP of the MRB indicates the first ID of the MRB in the first cell (e.g., MRB#1) and the second ID of the MRB in the second cell (e.g., MRB#2), and the UE may associate the MRB in the second cell (e.g., MRB#2) with the PDCP entity of the MRB in the first cell (e.g., MRB#1).

[0057] In some embodiments, the information associated with the PDCP of the MRB indicates one or more indexes of the PDCP configuration. For example, Index: PDCP Configuration 1; Index 1: PDCP Configuration 2;... etc.

[0058] In some embodiments, one or more indexes include the first index of the PDCP configuration, and the UE may perform cell reselection from the first cell to the second cell, receive the second index of the PDCP configuration in the second cell from the MCCH, and use one or more PDCP variables for the continuity of the MRB when the first index and the second index are the same. For example, PDCP Configuration 1 and PDCP Configuration 2 have the same index, such as Index 1. Therefore, the UE may use one or more PDCP variables for the continuity of the MRB in the second cell.

[0059] In some embodiments, the information associated with the PDCP of the MRB further includes the corresponding PDCP configuration for each index. For example, the MCCH also indicates the PDCP configuration for index 1. In some embodiments, the corresponding PDCP configuration for each index is predefined.

[0060] In some embodiments, to use one or more PDCP variables for the continuity of the MRB, the UE may store one or more PDCP variables of the PDCP entity for the MRB in the first cell; release the PDCP entity of the MRB and establish a new PDCP entity for the new MRB in the second cell; and set one or more PDCP variables of the new PDCP entity for the new MRB with the one or more PDCP variables of the stored PDCP entity. For example, store the latest value of the PDCP variable of the PDCP entity in the first cell, such as RX_NEXT, RX_DELIV, or the like. After establishing the new PDCP entity, the value of the PDCP variable of the new PDCP entity is set to the stored value of the PDCP variable.

[0061] In some embodiments, to use one or more PDCP variables for the continuity of the MRB, the UE may maintain the same PDCP entity for the MRB in the second cell and continue to use the latest PDCP variables of the PDCP entity for the MRB in the second cell. In some embodiments, to use one or more PDCP variables for the continuity of the MRB, the UE may re - establish the PDCP entity for the MRB in the second cell and continue to use the latest PDCP variables of the PDCP entity for the MRB in the second cell.

[0062] In some embodiments, the UE may trigger a PDCP status report and an RRC resume procedure in the second cell if the PDCP variable of the first received packet in the second cell is greater or smaller than the corresponding stored PDCP variable by a threshold.

[0063] Figure 3 Describe a method performed by a BS for wireless communication according to some embodiments of the present disclosure.

[0064] In operation 301, the BS may determine information associated with the PDCP of the MRB, where the PDCP may include one or more PDCP variables; and in operation 302, the BS may transmit, via a transceiver, the information associated with the PDCP of the MRB to the UE via RRC dedicated signaling.

[0065] In some embodiments, the BS may include a CU and a DU, where the CU is configured to determine information associated with the PDCP of the MRB and transmit the information associated with the PDCP of the MRB to the DU.

[0066] Figure 4Describe the per-region PDCP and per-cell RLC or lower layers of the MRB according to some embodiments of the present disclosure.

[0067] In Figure 4 there may be three cells, such as Cell 1, Cell 2, and Cell 3. The PDCP entity of the MRB is per-region. The RLC bearers associated with the PDCP entity are per-cell, and thus, there are three RLC bearers, such as RLC bearer 1, RLC bearer 2, and RLC bearer 3. Each RLC bearer of the MRB may include an RLC entity and other lower-layer entities of the MRB (medium access control (MAC) entity and physical (PHY) entity). RLC bearer 1 may be associated with a group radio network temporary identifier (G-RNTI), such as G-RNTI 1 in Cell 1, RLC bearer 2 may be associated with G-RNTI 2 in Cell 2, and RLC bearer 3 may be associated with G-RNTI 3 in Cell 3.

[0068] To support service continuity between cells for PTM reception of UEs in the RRC idle state (e.g., RRC idle state or RRC inactive state), the PDCP of the MRB may be continuous within a specific region. The present disclosure proposes a solution for supporting service continuity using one or more PDCP variables for the continuity of the MRB.

[0069] The PDCP variables may at least include the following: 1) RX_NEXT; and 2) RX_DELIV. The first variable (e.g., RX_NEXT) may indicate the count value of the next PDCP service data unit (SDU) or protocol data unit (PDU) expected to be received (e.g., the latest count value received currently plus 1). The second variable (e.g., RX_DELIV) may indicate the count value of the SDU or PDU that is still waiting and is the first SDU or PDU not delivered to the upper layer. In some other embodiments, other PDCP variables may also be applied.

[0070] The present disclosure proposes that when the UE moves within a region that supports the continuity of the MRB (i.e., the UE may perform a cell reselection procedure from an old cell to a new cell, and both the old cell and the new cell are within the region), the UE may use one or more PDCP variables for the continuity of the MRB. More specifically, the following options may be adopted:

[0071] - Option 1: The PDCP entity may be maintained. In other words, the PDCP entity may not be released or re-established. Since the PDCP entity is not released or re-established when the UE moves within the region, the PDCP variables (e.g., RX_NEXT and RX_DELIV) are continuous. Thus, the continuity of the MRB is achieved.

[0072] - Option 2: The old PDCP entity served by the old cell (the cell before cell reselection) can be released, and the latest PDCP variables of the old PDCP entity can be stored when the old PDCP entity is released. After a new PDCP entity is established in the new cell (the cell after cell reselection), the initial values of the PDCP variables of the new PDCP entity can be configured with the stored PDCP variables of the old PDCP entity in the old cell. In this way, the PDCP variables are continuous, and the continuity of the MRB is achieved. The release of the old PDCP entity can be realized by releasing the old MRB. The establishment of the new PDCP entity can be realized by establishing a new MRB in the new cell.

[0073] - Option 3: The PDCP entity can be reconstructed (e.g., the old PDCP entity in the old cell is reconstructed), and the PDCP variables of the PDCP entity can be maintained. More specifically, the PDCP variables of the reconstructed PDCP entity may not be reset to the initial values. In some embodiments, the stored PDCP variables of the PDCP entity in the old cell can be used as the initial values of the PDCP variables of the reconstructed PDCP entity in the new cell. In this way, the PDCP variables are continuous, and the continuity of the MRB is achieved.

[0074] For the above options, service continuity will be maintained. For example, the continuity of the MBS will be maintained.

[0075] In some other cases, the new cell can be the same cell as the old cell. For example, the UE can perform a cell selection or reselection procedure, but the target cell is the current serving cell, and the above options can also be applied.

[0076] Some examples of 3GPP files are presented in this disclosure, where the underlined expressions are presented by this disclosure.

[0077] When releasing the PDCP entity, the 3GPP file can be as follows:

[0078]

[0079] When establishing the PDCP entity, the 3GPP file can be as follows:

[0080] When establishing the PDCP entity, the 3GPP file can also be as follows:

[0081]

[0082] In some embodiments, the UE can move out of the area that supports the continuity of the MRB, and the UE can take the following options:

[0083] - Release the PDCP entity of the MRB and obtain the MCCH from the new cell. The UE may perform the PDCP establishment procedure according to the MRB configuration received in the MCCH. In some embodiments, releasing the PDCP entity of the MRB means releasing the MRB. The PDCP establishment procedure is performed during the establishment of the new MRB.

[0084] - Release the PDCP entity of the MRB and trigger the RRC resume procedure for the new PDCP configuration by returning to the RRC connected state. When the UE returns to the RRC connected state, the new PDCP configuration is provided by RRC dedicated signaling.

[0085] The present disclosure further proposes some solutions for supporting the continuity of the MRB as follows:

[0086] Solution 1

[0087] Figure 5 A flowchart showing the support for the continuity of the MRB according to some embodiments of the present disclosure.

[0088] Figure 5 It includes the UE, BS1, and BS2. The UE may be Figure 1 the UE 101 shown in Figure 1 ; BS1 may be Figure 1 the BS102-A shown in

[0089] and may manage cell 1; and BS2 may be

[0090] the BS102-B shown in Figure 1 and may manage cell 2.

[0091] Alternatively, the area information may indicate (or include) a cell list. For example, referring to Figure 1 , the area information may indicate a cell list that includes Cell 1, Cell 2, and Cell 3.

[0092] In operation 502, the UE may receive MBS services in the RRC idle state.

[0093] In operation 503, due to mobility, the UE may perform cell reselection to an adjacent cell. The UE may preferentially select a cell in the area or cell list that supports the continuity of the MRB. In other words, in the case where the area information indicates Cell 1, Cell 2, or Cell 3, the UE may preferably select Cell 1, Cell 2, or Cell 3. The UE may reselect a cell in the area that supports the continuity of the MRB, such as Cell 2, and the UE may release the old RLC bearer for Cell 1.

[0094] In operation 504, the UE may receive the MCCH from BS2, and the MCCH may provide services to the UE in Cell 2. The MCCH may indicate the RLC bearer and the lower layer configuration of the MRB. The MCCH may also provide an indication, such as a PDCP reestablishment indication, and the UE may perform PDCP reestablishment as options 1 to 3 described above.

[0095] In operation 505, for example, the UE may maintain the PDCP entity used in Cell 1 (such as option 1 described above) and establish a new RLC entity according to the RLC bearer and the lower layer configuration of the MRB.

[0096] Alternatively, the UE may apply option 2 or 3 described above. For example, the MCCH may provide other indications to indicate that the UE releases the old PDCP entity and establishes a new PDCP entity (such as option 2 described above) or indicates that the UE reestablishes the PDCP entity with the maintained PDCP variables (such as option 3 described above).

[0097] In some embodiments, the information associated with the PDCP of the MRB transmitted to the UE in Cell 1 in operation 501 may further include one or more associated MRB IDs. For example, the information associated with the PDCP of the MRB may include the associated MRB ID in each cell of the MRB.

[0098] The MRB ID may be different among different cells. For example, Figure 1 the MRB ID of the MRB in Cell 1 in Figure 1 is MRB#1, Figure 1The MRB ID of the same MRB in cell 3 in [[]] is MRB#3. Therefore, the information associated with the PDCP of the MRB may include MRB#1 in cell 1, MRB#2 in cell 2, and MRB#3 in cell 3 or the like.

[0099] After the UE reselects to another cell (such as cell 2) within the area, the UE can identify the MRB with the associated MRB ID (such as MRB#2 in cell 2) and associate the MRB in the second cell with the PDCP entity of MRB#1 in the first cell, that is, associate MRB#2 with the PDCP entity. In this way, the continuity of the MRB is achieved.

[0100] Return Figure 5 , in operation 504, the UE can obtain the MCCH to obtain the RLC configuration of the MRB in the neighboring cell (such as cell 2). The UE can identify the MRB with the associated MRB ID (such as MRB#2 in cell 2), associate MRB#2 with the PDCP entity, and reuse the value of the PDCP variable in the old cell (such as cell 1).

[0101] In some other embodiments, the information associated with the PDCP of the MRB transmitted to the UE in cell 1 in operation 501 may further include the associated RLC bearer ID.

[0102] Still referring to Figure 5 , in operation 504, the received MCCH can indicate the RLC bearer configuration of the MRB, and the UE can establish a second RLC bearer for the MRB in the second cell based on the RLC bearer configuration of the MRB. The UE can associate the same PDCP entity in the first cell (such as cell 1) with the second RLC bearer in the second cell (such as cell 2).

[0103] In the case where the wireless communication system includes a CU and a DU (such as gNB-CU and gNB-DU), the CU can determine the area where the continuity of MBS is supported and send the area information to the DU, so that the gNB-DU can know the area information and set the parameters of the PDCP configuration in the MCCH, such as PDCP-Config.

[0104] Similarly, the BS can also send the area information and the corresponding PDCP configuration to the neighboring BS through the interface between the BSs (such as the Xn interface) to achieve the continuity of MBS coordination between the BSs.

[0105] Solution 2

[0106] Still referring to Figure 5In operation 501, BS1 may transmit an RRC dedicated message, such as an RRC Release message, to the UE. Additionally, the information associated with the continuity of the MBS may include one or more indices of PDCP configurations, such as a list of indices of PDCP configurations. Each index may correspond to one or more PDCP configurations. For example, the list may be as follows:

[0107] Index 1:

[0108] PDCP Configuration 1;

[0109] PDCP Configuration 2;

[0110] Index 2:

[0111] PDCP Configuration 3;

[0112] PDCP Configuration 4;

[0113] PDCP Configuration 5;

[0114] Index 3:

[0115] PDCP Configuration 6;

[0116] etc

[0117] For example, the index included in the message from BS1 may be Index 1. The BS may further indicate the index of the PDCP configuration of the MRB currently used by the UE (e.g., the PDCP configuration of the MRB currently used by the UE in Cell 1), such as Index 1.

[0118] In some embodiments, the information associated with the continuity of the MBS may further include the PDCP configurations corresponding to each index. In some other embodiments, the PDCP configurations corresponding to each index may be predefined, preconfigured, and specified in the specification, and the information associated with the continuity of the MBS may not include the PDCP configurations. In this way, the network may only configure the reference indices to the UE, and the UE may know the corresponding PDCP configurations according to the reference indices predefined by the specification.

[0119] In some embodiments, the message may further indicate the area information associated with the continuity of the MBS described in Solution 1.

[0120] The UE may perform operations 502 and 503 in a similar manner to Solution 1.

[0121] In operation 504, the UE may acquire the MCCH and obtain the PTM configuration of the MRB. In the PTM configuration of the MRB, the index of the PDCP configuration of Cell 2 may be provided.

[0122] When the index of the PDCP configuration in cell 2 is the same as the index of the PDCP configuration currently used by the UE, the UE can use one or more PDCP variables for the continuity of the MRB. For example, the index included in the message from BS2 (which controls cell 2) can also be index 1, so the UE can use one or more PDCP variables for the continuity of the MRB.

[0123] When the index provided by the MCCH is different from the index of the PDCP configuration currently used by the UE, for example, the index included in the message from BS2 (which controls cell 2) can also be index 2, the UE can release the old PDCP entity and apply the PDCP configuration indicated by the index, such as PDCP configuration 2 for establishing a new MRB.

[0124] In some embodiments, after reselection to a second cell in an area where the continuity of the MRB is supported or the reference index of the PDCP configuration is the same as the one being used, PDCP variables (such as RX_NEXT, RX_DELIV, or the like) may be discontinuous. For example, the stored PDCP variable RX_NEXT can be 3, while the first received packet can be 10. Assume a configurable threshold, such as 5, and the difference between the value of the first received packet and the stored PDCP variable is 7, which is greater than the threshold. The UE can determine that the continuity of the MRB is not achieved. In this case, the UE can trigger a PDCP status report and an RRC resume procedure in the second cell. The report can indicate the gap in the PDCP variables.

[0125] In some other cases, the trigger condition can be that the PDCP SN of the first received packet in the new cell is less than the configured threshold of the previously stored PDCP variable, such as RX_DELIV. Other trigger conditions can also be defined to indicate to the network that the continuity of the MRB is not achieved.

[0126] Solution 3

[0127] Figure 6 A flowchart supporting the continuity of the MRB according to some embodiments of the present disclosure is described.

[0128] Figure 6 It includes a UE and BS1. The UE can be Figure 1 the UE 101 shown in Figure 1 and BS1 can be

[0129] The operations 601 and 602 are respectively similar to Figure 5 the operations 501 and 502 described in

[0130] In operation 603, the UE obtains the MCCH in cell 1 for updating the PTM configuration. In the updated configuration of the MRB, an index of the PDCP configuration may be provided.

[0131] In operation 604, in the case where the index of the updated PDCP configuration is the same as the index of the PDCP configuration currently used by the UE, the UE may use one or more PDCP variables for the continuity of the MRB. For example, the index included in the MCCH may also be index 1, so the UE may use one or more PDCP variables for the continuity of the MRB.

[0132] In operation 605, the UE may receive the MCCH for updating the PTM configuration. The MCCH may indicate the RLC bearer and the lower layer configuration of the MRB. The MCCH may also provide an indication, such as a PDCP re-establishment indication, and the UE may perform PDCP re-establishment as options 1 to 3 described above.

[0133] Figure 7 A simplified block diagram of a device according to some embodiments of the present disclosure is illustrated.

[0134] As Figure 7 shown, an example of the device 700 may include at least one processor 704 and at least one transceiver 702 coupled to the processor 704. The device 700 may be a UE, a BS, a CU, a DU, or any other device with similar functions.

[0135] Although elements such as at least one transceiver 702 and processor 704 are described in the singular in this figure, the plural form is contemplated unless explicitly stated to be limited to the singular form. In some embodiments of the present disclosure, the transceiver 702 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present disclosure, the device 700 may further include an input device, a memory, and / or other components.

[0136] In some embodiments of the present disclosure, the device 700 may be a UE. The transceiver 702 and the processor 704 may interact with each other to perform the operations of the UE described in any one of Figures 1 to 6 In some embodiments of the present disclosure, the device 700 may be a node. The transceiver 702 and the processor 704 may interact with each other to perform the operations of the node described in any one of Figures 1 to 6 The operations of the node described in any one of them.

[0137] In some embodiments of the present disclosure, the device 700 may further include at least one non-transitory computer-readable medium.

[0138] For example, in some embodiments of the present disclosure, a non-transitory computer-readable medium may have computer-executable instructions stored thereon to cause a processor 704 to implement the methods described above with respect to the UE. For example, the computer-executable instructions, when executed, cause the processor 704 to interact with a transceiver 702 to perform Figures 1 to 6 the operations of the UE described in any of

[0139] In some embodiments of the present disclosure, a non-transitory computer-readable medium may have computer-executable instructions stored thereon to cause a processor 704 to implement the methods described above with respect to the node. For example, the computer-executable instructions, when executed, cause the processor 704 to interact with a transceiver 702 to perform Figures 1 to 6 the operations of the node described in any of

[0140] The methods of the present disclosure may be implemented on a programmed processor. However, the controllers, flowcharts, and modules may also be implemented on a general or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit (such as a discrete element circuit), a programmable logic device, or the like. Generally, any device having a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processing functions of the present disclosure.

[0141] Although the present disclosure has been described in terms of its specific embodiments, it is obvious that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, the various components of the embodiments may be interchanged, added, or substituted in other embodiments. Also, the operations of the disclosed embodiments do not necessarily require all of the elements shown in each figure. For example, those skilled in the art of the disclosed embodiments will be able to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Therefore, the embodiments of the present disclosure set forth herein are intended to be illustrative rather than restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0142] In this disclosure, relational terms such as "first", "second", and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms "includes", "including", or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element that begins with "a", "an", or the like does not, without further limitation, preclude the presence of additional, identical elements in the process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least a second or more. As used herein, the terms "comprises", "has", and the like are defined as "includes".

Claims

1. A user equipment (UE), comprising: a transceiver; and a processor coupled to the transceiver and configured to: receive, via the transceiver, via radio resource control (RRC) dedicated signaling, information associated with the packet data convergence protocol (PDCP) of a multicast radio bearer (MRB), wherein the PDCP includes one or more PDCP variables; transition to the RRC idle state; and determine, based on the information associated with the PDCP of the MRB, whether to use the one or more PDCP variables for the continuity of the MRB while the UE is in the RRC idle state.

2. The UE according to claim 1, wherein the information associated with the PDCP of the MRB includes a list of areas or cells in which the continuity of the MRB is supported.

3. The UE according to claim 2, wherein the processor is further configured to: perform cell reselection from a first cell to a second cell; and use the one or more PDCP variables for the continuity of the MRB when the first cell and the second cell are within the area or in the cell list.

4. The UE according to claim 3, wherein the processor is configured to: release a first radio link control (RLC) bearer of the MRB in the first cell when leaving the first cell; obtain an RLC bearer configuration of the MRB via a multicast / broadcast service control channel (MCCH) in the second cell when entering the second cell; and establish a second RLC bearer of the MRB in the second cell according to the RLC bearer configuration of the MRB.

5. The UE according to claim 3, wherein the information associated with the PDCP of the MRB indicates a first identifier (ID) of the MRB in the first cell and a second ID of the MRB in the second cell, and wherein the processor is further configured to: associate the MRB in the second cell with the PDCP entity of the MRB in the first cell.

6. The UE according to claim 1, wherein the information associated with the PDCP of the MRB indicates one or more indices of a PDCP configuration.

7. The UE according to claim 7, wherein the one or more indices include a first index of a PDCP configuration, and the processor is further configured to: perform cell reselection from a first cell to a second cell; receive a second index of the PDCP configuration in the second cell from a multicast / broadcast service control channel (MCCH); and use the one or more PDCP variables for the continuity of the MRB when the first index is the same as the second index.

8. The UE according to claim 3 or 7, wherein, in order to use the one or more PDCP variables for the continuity of the MRB, the processor is further configured to: store the one or more PDCP variables of the PDCP entity of the MRB in the first cell; Release the PDCP entity of the MRB and establish a new PDCP entity for the new MRB in the second cell; and Set one or more PDCP variables of the new PDCP entity of the new MRB with the stored one or more PDCP variables of the PDCP entity.

9. The UE according to claim 3 or 7, wherein in order to use the one or more PDCP variables for the continuity of the MRB, the processor is further configured to: Maintain the same PDCP entity of the MRB in the second cell; and Continue to use the latest PDCP variables of the PDCP entity of the MRB in the second cell.

10. The UE according to claim 3 or 7, wherein in order to use the one or more PDCP variables for the continuity of the MRB, the processor is further configured to: Reconstruct the PDCP entity of the MRB in the second cell; and Continue to use the latest PDCP variables of the PDCP entity of the MRB in the second cell.

11. The UE according to claim 3 or 7, wherein the processor is further configured to: Trigger a PDCP status report and an RRC resume procedure in the second cell when the PDCP variable of the first received packet in the second cell is greater or smaller than a corresponding stored PDCP variable by a threshold.

12. A base station BS, comprising: A transceiver; And A processor coupled to the transceiver and configured to: Determine information associated with the packet data convergence protocol PDCP of a multicast radio bearer MRB, wherein the PDCP includes one or more PDCP variables; And Transmit, via the transceiver, via radio resource control RRC dedicated signaling, the information associated with the PDCP of the MRB to a user equipment UE.

13. The BS according to claim 12, wherein the information associated with the PDCP of the MRB includes a list of areas or cells in which the continuity of the MRB is supported.

14. The BS according to claim 12, wherein the information associated with the PDCP of the MRB indicates one or more indexes of the PDCP configuration.

15. A method performed by a user equipment UE, comprising: Receiving, via radio resource control RRC dedicated signaling, information associated with the packet data convergence protocol PDCP of a multicast radio bearer MRB, wherein the PDCP includes one or more PDCP variables; Transitioning to the RRC idle state; And Determining, based on the information associated with the PDCP of the MRB, whether to use the one or more PDCP variables for the continuity of the MRB while the UE is in the RRC idle state.

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