CN115988427A - Method and user equipment for setting initial PDCP state variable for multicast - Google Patents

Abstract

The invention provides a method and user equipment for setting an initial PDCP state variable for multicast, wherein the method comprises the following steps: configuring, by a user equipment, an MRB for one or more MBS in a wireless network, wherein the MRB configuration enables feedback to the one or more MBS; initiating a joining process to join an MBS session, wherein the MBS session is in an active state; receiving one or more configuration values of a PDCP state variable from the wireless network, wherein the PDCP state variable controls PDCP transceiving for the MBS session; and configuring the PDCP state variable based on the received one or more configuration values. By using the present invention, the PDCP state variable of the multicast service can be initialized.

Description

Method and user equipment for setting initial PDCP state variable for multicast

Technical Field

The present invention relates to wireless communications, and more particularly, to a method and apparatus for setting a state variable (state variable) of a Packet Data Convergence Protocol (PDCP) for multicast (multicast).

Background

With the exponential growth of wireless data services, content delivery to large mobile user groups is rapidly evolving. Various cellular systems, including 4G/Long Term Evolution (LTE) systems and 5G/New Radio (NR) systems, may provide multicast functionality, allowing User Equipments (UEs) in the system to receive multicast services transmitted by the cellular systems. Various applications may rely on multicast transport communications such as live streaming, video distribution, vehicle-to-internet (V2X) communications, public safety communications, file downloads, and the like. When a UE establishes a Multicast Radio Bearer (MRB), a Hyper Frame Number (HFN) is required between the radio network and the UE. It is also necessary to set an initial value of the PDCP reception window. In the existing system, since data transmission/reception is started after the UE is in the RRC connected state, initial values of transmission and reception operation variables of the PDCP layer are determined and generally started from zero. In NR multicast, a UE may join a Multicast and Broadcast Service (MBS) session after the MBS session is activated, which means that PDCP packet transmission over the air interface has been in progress for some time. Therefore, the UE cannot initialize PDCP variables for MBS sessions as usual.

Improvements and enhancements are needed to initialize PDCP state variables for multicast services.

Disclosure of Invention

An embodiment of the present invention provides a method for setting an initial PDCP status variable for multicast, including: configuring, by a user equipment, an MRB for one or more MBS in a wireless network, wherein the MRB configuration enables feedback to the one or more MBS; initiating a join process to join an MBS session, wherein the MBS session is in an active state; receiving one or more configuration values of a PDCP state variable from the wireless network, wherein the PDCP state variable controls PDCP transceiving for the MBS session; and configuring the PDCP state variable based on the received one or more configuration values.

Another embodiment of the present invention provides a method for setting an initial PDCP status variable for multicast, including: a base station in a wireless network receiving a join request from a user equipment to join an active MBS session, wherein the MBS session is served by an MRB, and wherein the base station and the user equipment have a unicast connection for feedback; the base station sends one or more configuration values of a PDCP state variable to the user equipment, wherein the PDCP state variable controls PDCP transceiving for the MBS session; and receiving feedback on the receipt information of the MBS session from the user equipment.

Another embodiment of the present invention provides a user equipment, including: a transceiver to transmit and receive radio frequency signals in a wireless network; a configuration module, configured to configure an MRB for one or more MBS in the wireless network, wherein the MRB configuration enables feedback to the one or more MBS; the joining module is used for initiating a joining process to join the MBS conversation, wherein the MBS conversation is in an active state; a receiving module to receive one or more configuration values of packet data convergence protocol, PDCP, state variables from the wireless network, wherein the PDCP state variables control PDCP transceiving for the MBS session; and a state variable module to configure the PDCP state variable based on the received one or more configuration values.

Another embodiment of the present invention provides a storage medium storing a program that, when executed, causes a user equipment to perform the steps of the method of setting initial PDCP state variables for multicast of the present invention.

By using the present invention, the PDCP state variable of the multicast service can be initialized.

Drawings

The drawings illustrate embodiments of the present invention, wherein like numerals refer to like elements throughout.

Fig. 1 is a system diagram of an exemplary wireless communication network that initializes PDCP state variables for multicast based on configuration UEs received from the wireless network in accordance with an embodiment of the present invention.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of the NR radio interface stack in accordance with an embodiment of the present invention.

FIG. 3 is a schematic diagram of an exemplary MRB configuration in accordance with an embodiment of the present invention.

Fig. 4 is a schematic diagram of a protocol stack for MRB configuration with PDCP based retransmission according to an embodiment of the present invention.

Fig. 5 is an exemplary flowchart of UE RRC state conditions when an MBS session is active according to an embodiment of the present invention.

Fig. 6 is an exemplary flowchart for setting conditions of PDCP state variables based on network information of a multicast service according to an embodiment of the present invention.

Fig. 7 is an exemplary message diagram for setting PDCP status variables based on received network information for a multicast service according to an embodiment of the present invention.

Fig. 8 is an exemplary diagram for setting a UE PDCP status variable indicated by a network according to an embodiment of the present invention.

Fig. 9 is an exemplary flowchart for a UE to receive one or more configuration values of UE PDCP state variables for an MBS session from a network and to set the PDCP state variables according to an embodiment of the present invention.

FIG. 10 is an exemplary flowchart of a base station transmitting one or more configuration values of UE PDCP status variables for an MBS session according to an embodiment of the present invention.

Detailed Description

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Methods, apparatuses, processing systems, and computer readable media are provided for NR (new radio access technology or 5G technology) or other radio access technologies. The NRs may support various wireless communication services such as enhanced mobile broadband for wide bandwidths, millimeter waves for high carrier frequencies, large MTC for non-backward compatible Machine Type Communication (MTC) technologies, and/or mission critical for ultra-reliable low latency communication. These services may have delay and reliability requirements. These services may also have different Transmission Time Intervals (TTIs) to meet respective quality of service (QoS) requirements. Furthermore, these services may coexist in the same subframe. Several aspects of a telecommunications system will now be described with reference to various apparatus and methods, which will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc., which are collectively referred to as "elements". These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

Fig. 1 is a system diagram of an exemplary wireless communication network that initializes PDCP state variables for multicast based on configuration UEs received from the wireless network in accordance with an embodiment of the present invention. The wireless communication network 100 includes one or more fixed infrastructure elements that form a network distributed over a geographic area. These base units may also be referred to as access points, access terminals, base stations, node bs, evolved node bs (eNode-bs), next generation node bs (gnbs), or other terminology used in the art. For example, a base station may serve multiple mobile stations within a service area (e.g., a cell or cell sector). In some systems, one or more base stations are coupled to a controller forming an access network that is coupled to one or more core networks. The gnbs 106, 107, and 108 are base stations in a wireless network, and their service areas may or may not overlap with each other. In an example, UE 101 or mobile station 101 is in a service area covered by gNB106 and gNB 107. In an example, UE 101 or mobile station 101 is only in the service area of gNB106 and connected to gNB106, and UE 102 or mobile station 102 is only in the service area of gNB107 and connected to gNB 107. The gNB106 is connected to the gNB107 through an Xn interface 121. The gNB106 is connected to the gNB 108 through an Xn interface 122. The 5G network entity 109 is connected to the gnbs 106, 107 and 108 via NG connections 131, 132 and 133, respectively. In an embodiment, gNB106 and gNB107 provide the same MBMS service. Service continuity during handover is guaranteed when UE 101 moves from gNB106 to gNB107 and vice versa. The area covered by the gnbs 106 and 107 having the same MBMS service is the multicast service area of the MBMS service.

Fig. 1 further shows a simplified block schematic diagram of a base station and a mobile device/UE for multicast transmission. The gNB106 has an antenna 156 that transmits and receives radio signals. RF transceiver circuitry 153 coupled to the antenna receives RF signals from antenna 156, converts the RF signals to baseband signals, and sends the baseband signals to processor 152. The RF transceiver 153 also converts a baseband signal received from the processor 152 into an RF signal and transmits to the antenna 156. Processor 152 processes the received baseband signals and invokes different functional modules to perform functional features in gNB 106. Memory 151 stores program instructions and data 154 to control the operation of gNB 106. The gNB106 also includes a set of control modules 155 for performing functional tasks for communicating with mobile stations. These control modules may be implemented in circuitry, software, firmware, or a combination thereof.

FIG. 1 also shows a simplified block diagram of a UE (e.g., UE 101). The UE has an antenna 165 for transmitting and receiving radio signals. The RF transceiver circuit 163, which is coupled to the antenna, receives RF signals from the antenna 165, converts the RF signals to baseband signals, and sends the baseband signals to the processor 162. In one embodiment, the RF transceiver may include two RF modules (not shown) for transmission and reception of different frequency bands. The RF transceiver 163 also converts a baseband signal received from the processor 162 into an RF signal and transmits to the antenna 165. The processor 162 processes the received baseband signals and invokes different functional modules to perform functional features in the UE 101. The memory 161 stores program instructions and data 164 to control the operation of the UE 101. Uplink transmission and downlink reception between antenna 165 and antenna 156 of gNB 106.

The UE also includes a set of control modules for performing functional tasks. These functional blocks may be implemented by circuitry, software, firmware, or a combination thereof. The configuration module 191 configures an MRB for one or more Multicast Broadcast Services (MBS) in a wireless network, where the MRB configuration enables feedback to the one or more MBS. The join module 192 initiates a join process to join the MBS session, where the MBS session is in an active state (active). The receiving module 193 receives one or more configuration values of PDCP state variables from the radio network, wherein the PDCP state variables control PDCP transceiving of MBS sessions. The state variable module 194 configures PDCP state variables based on the received one or more configuration values. The PDCP processing module 195, upon receiving one or more PDCP Packet Data Units (PDUs) before receiving one or more configuration values of the PDCP status variable from the radio network, stores the one or more PDCP PDUs in the receive buffer.

In an embodiment, the UE further includes a Radio Resource Control (RRC) state controller, an MBS controller, and a protocol stack controller. The RRC state controller controls the UE RRC state according to a command from the network and the UE condition. RRC supports the following states: RRC idle state, RRC connected state, and RRC inactive state. In an embodiment, the UE may receive MBS in an RRC idle/inactive state. The UE may apply the MRB setup procedure to start a session to receive the service of interest to it. The UE may apply an MRB release procedure to stop the reception session. The MBS controller controls the establishment/addition, reconfiguration/modification and release/deletion of MRBs based on different sets of conditions for MRB establishment, reconfiguration and release. The protocol stack controller may add, modify, or delete protocol stacks for the MRB. The protocol stack includes a PDCP layer 182, a Radio Link Control (RLC) layer 183, a Medium Access Control (MAC) layer 184, and a Physical (PHY) layer 185. In an embodiment, a Service Data Adaptation Protocol (SDAP) layer 181 is an optional configuration.

In one embodiment, the PDCP layer supports data transmission, PDCP Sequence Number (SN) maintenance, header compression and decompression using robust header compression (ROHC) protocol, ciphering and deciphering, integrity protection and integrity verification functions, timer-based Service Data Unit (SDU) discard, bearer splitting routing, replication, reordering, in-order delivery, out-of-order delivery, and duplicate discard. The PDCP entity includes a reordering buffer 188 and a status reporter 189. In an embodiment, the receiving PDCP entity sends a PDCP status report when a reordering timer (t-reordering) expires. In an embodiment, the PDCP status report triggers a PDCP retransmission at the network side peer sending PDCP entity.

In one embodiment, the RLC layer 183 supports error correction by ARQ, segmentation and reassembly, re-segmentation, duplicate detection, re-establishment, and the like. In an embodiment, a new procedure for RLC reconfiguration is performed, which may reconfigure the RLC entity to be associated to one or two logical channels. In another embodiment, the MAC layer 184 supports mapping, multiplexing, demultiplexing, HARQ, radio resource selection, etc., between logical channels and transport channels.

Fig. 2 is a schematic diagram of an exemplary NR wireless system with a centralized upper layer of the NR radio interface stack in accordance with an embodiment of the present invention. Different protocol partitioning options are possible between Central Units (CUs) and Distributed Units (DUs) of the gNB node. The functional division between CUs and DUs of the gNB node may depend on the transport layer. Since higher protocol layers have lower performance requirements on the transport layer in terms of bandwidth, delay, synchronization and jitter, low performance transmission between CUs and DUs of the gNB node may enable the higher protocol layers of the NR radio stack to be supported in the CUs. In one embodiment, the SDAP and PDCP layers are located in the CU, while the RLC, MAC, and PHY layers are located in the DU. The core unit (core unit) 201 is connected to a central unit 211 having a gNB upper layer (upper layer) 252. In an embodiment 250, the gNB upper layers 252 include a PDCP layer and an optional SDAP layer. CU 211 is connected to DUs 221, 222, and 223, wherein DUs 221, 222, and 223 correspond to cells 231, 232, and 233, respectively. The DUs such as 221, 222 and 223 include a lower layer 251 of the gNB. In an embodiment, the gbb lower layer 251 includes PHY, MAC, and RLC layers. In another embodiment 260, each gNB has a protocol stack 261 that includes SDAP, PDCP, RLC, MAC, and PHY layers.

FIG. 3 is a schematic diagram of an exemplary MRB configuration in accordance with an embodiment of the present invention. The MRB 305 provides multicast services, which are carried by Multicast Traffic Channels (MTCHs) of a point-to-multipoint (PTM) 306, dedicated Traffic Channels (DTCHs) 307 of a point-to-point (PTP), or both MTCHs 306 and DTCHs 307 through the UE protocol stack 301. In an embodiment 320, an MRB is configured to be associated with an MTCH. In another embodiment 330, the MRB is configured to be associated with a DTCH. In yet another embodiment 310, an MRB is configured to be associated with an MTCH as well as a DTCH. In embodiment 310, the MRB is configured in PTM & PTP transmission mode. One or more MRBs of a multicast stream corresponding to a particular multicast session may be established to support multicast transmission in the over-the-air downlink. MRB may be used for PTM and/or PTP transmissions in many cells. In embodiment 320, the MRB is configured for PTM transmission mode. In an embodiment 330, the MRB is configured for PTP mode. In embodiment 310, the MRB is configured for PTM & PTP transmission mode.

In some systems, such as NR systems, NR multicast/broadcast is transmitted within the coverage of a cell. In an embodiment, the MCCH provides information with the NR MBS list of ongoing sessions transmitted on MTCH. In the physical layer, MTCH is scheduled by the gNB in a search space of a Physical Downlink Control Channel (PDCCH) scrambled by a group radio network temporary identifier (G-RNTI). The UE decodes the MTCH data for a multicast session in a multicast Physical Downlink Shared Channel (PDSCH). In legacy systems that support MBMS/eMBMS, the radio bearer structure for multicast and broadcast transmissions is modeled independently of unicast transmissions. Since the conventional MBMS/eMBMS service is unidirectional transmission, an RLC Unacknowledged Mode (UM) node may be used to transmit the MBS session. In this case, no interaction between multicast and unicast is required for a particular UE in RRC connected state. In NR networks providing new services over MBS, reliable transmission is required. Conventional multicast transmission does not guarantee successful reception for all UEs unless very conservative link adaptation is implemented, which greatly reduces resource efficiency. In order to support reliable transmission of the NR multicast service, each UE receiving the service requires a feedback channel in the uplink, through which the receiving UE can feed back the reception status of its service to the network. Based on the feedback, the network may perform the necessary retransmissions to improve transmission reliability. From an uplink feedback perspective, the feedback channel may be used for layer 2 (L2) feedback (e.g., RLC status report and/or PDCP status report). The feedback channel may also be used for HARQ feedback. Furthermore, the feedback should be a bi-directional channel between the UE and the network, and it is assumed that the network can use this channel to perform the required packet retransmissions. The packet retransmission is an L2 retransmission (e.g., an RLC retransmission and/or a PDCP retransmission). In addition, the feedback channel may be used for HARQ retransmissions.

Fig. 4 is a schematic diagram of a protocol stack for MRB configuration with PDCP based retransmission according to an embodiment of the present invention. In PDCP based retransmission 490, there is one PDCP entity 491 per MRB. Two logical channels (MTCH and DTCH) are associated with the PDCP entity. Each logical channel corresponds to one RLC entity, RLC 492 corresponds to MTCH, and RLC 493 corresponds to DTCH. From the UE perspective, the PDCP status report that triggers the PDCP retransmission is delivered to the RLC entity 493 corresponding to the DTCH. From the network perspective, the retransmitted PDCP Protocol Data Unit (PDU) is delivered through DTCH. The MAC entity maps a logical channel MTCH to a transport channel 1 (e.g., multicast Channel (MCH), downlink shared channel (DL-SCH)) and a logical channel DTCH to a transport channel 2 (e.g., MCH, DL-SCH). The UE monitors two independent transport channels through different Radio Network Temporary Identifiers (RNTIs). The ROHC function and security function are optional for multicast transmission.

A network entity, such as a base station/gNB, transmits MBS data packets to the N UEs over the PTM link and retransmits the MBS data packets over the PTP link associated with the PDCP protocol stack based on the feedback. And correspondingly configuring the UE based on the PDCP protocol stack to receive the MBS data packet from the base station on the PTM RB and send feedback to the base station. The scheduling of the multicast is independent of the PTP transmission. The protocol stack of the base station and the UE includes an SDAP layer 401, a PDCP layer 402, an RLC layer 403, and a MAC layer 404.SDAP layer 401 processes QoS flows 481, including QoS flow processing 411 for UE-1 and QoS flow processing 412 for UE-N at the base station, and QoS flow processing 413 for the UE at the UE. The PDCP layer 402 includes an ROHC function and a security function. The ROHC function and the security function are optional for multicast transmission. The PDCP layer 402 includes the functions of ROHC 421 and security 424 for UE-1 multicast, ROHC 4212 and security 4242 for UE-1 unicast, ROHC422 and security 425 for UE-N multicast, ROHC4222 and security 4252 for UE-N unicast, and ROHC 423 and security 426 at the UE. RB 482 is processed in the PDCP layer 402. RLC layer 403 includes segmentation and ARQ431 for UE-1 multicast at base station, segmentation and ARQ 432 for UE-1 unicast at base station, segmentation and ARQ 433 for UE-N multicast at base station, segmentation and ARQ 434 for UE-N unicast at base station; and segmentation and ARQ 435 for unicast channel at the UE, and segmentation and ARQ 436 for multicast channel at the UE. RLC channel 483 is processed in RLC layer 403. The MAC layer 404 includes scheduling and prioritization 441 at the base station, multiplexing 443 and HARQ 446 for UE-1 at the base station, multiplexing 444 and HARQ447 for UE-N at the base station; as well as scheduling and prioritization 442 at the UE for the UE, multiplexing 445 and HARQ 448 at the UE for the UE. Logical channel 484 and transport channel 485 are processed at MAC layer 404.

Fig. 5 is an exemplary flowchart of a UE RRC state condition when an MBS session is active according to an embodiment of the present invention. The UE is configured with one or more MBS services. In step 501, the UE joins a multicast/MBS session. In an embodiment, a UE sends a request to join an MBS session. After the UE joins the multicast session, in one embodiment, the UE joins the active MBS session, i.e., the MBS session is active at step 502 when the UE joins. In other scenarios, the MBS session is not activated, and when the MBS session is activated, the UE will receive the session activation notification. In some scenarios, when the MBS session is not active, the UE may transition to the RRC idle/inactive state to save power. In other scenarios, when the MBS session is not active, the UE may stay in the RRC connected state for other reception. If the MBS session is not activated, the RRC connected state UE can stay in the RRC connected state and also can be converted to the RRC idle/inactive state. When the multicast session is active, the UE receives the session activation notification and detects that the MBS session is active in step 502. If it is detected that the MBS session is in an active state, the UE determines whether the UE is in an RRC connected state in step 510. If the determination in step 510 is negative, the UE transitions to the RRC connected state in step 512. If the result of the determination in step 510 is yes, the UE in the RRC connected state receives RRC signaling to set an initial PDCP state variable in step 511.

Fig. 6 is an exemplary flowchart of setting a condition of a PDCP state variable based on network information of a multicast service according to an embodiment of the present invention. In step 601, the ue is in an RRC connected state. In one embodiment, the MBS session is activated. In step 602, the ue receives a message for detailed RRC configuration from the network. In one embodiment, the network message is an RRC message. According to some embodiments, the RRC message may be an RRC reconfiguration (RRCReconfiguration) message, an RRC recovery (rrcreesume) message, or an RRC setup (RRCSetup) message, etc. The radio network indicates the SN (e.g., next-SN) and corresponding HFN value (e.g., initial _ HFN) of the first PDU to be sent to the UE. In an embodiment 621, the indication is provided by an RRC reconfiguration message, wherein initial _ HFN and next _ SN information is added to the RRC message. In one embodiment, the indication is provided by an RRC setup/recovery signal according to the RRC state of the UE (not shown). In step 603, the ue sets the HFN to the value of the network indicated HFN, i.e., initial _ HFN in the RRC message; and sets the SN of RX _ DELIV and/or RX _ NEXT to the SN of the first PDU the network will transmit, i.e., the NEXT _ SN in the RRC message. After the UE applies the RRC configuration, the UE transmits an RRC message, such as an RRC reconfiguration complete (rrcconfigurationcomplete) message, to the radio network in step 604.

Fig. 7 is an exemplary message diagram for setting PDCP status variables based on received network information for a multicast service according to an embodiment of the present invention. UE701 is configured with one or more MBS in a wireless network with a gNB 702. Different scenarios should be considered before the UE receives data packets from the configured MBS. In one scenario 711, the UE701 is in an RRC idle/inactive state. In another scenario, the MBS session is not active. In step 721, the network notifies the activation of the MBS session. In an embodiment, gNB 702 sends an MBS session activation notification to one or more UEs (including UE 701). In one embodiment, an MBS session activation notification is broadcast. In an embodiment, the MBS session activation notification may be unicast to each UE. In some scenarios, the MBS session is activated when the UE701 is in an RRC idle/inactive state, while in other scenarios the UE701 is in an RRC connected state. The MBS session is activated before or after the UE701 determines to join the session. In an embodiment, the UE701 is in an RRC connected state prior to session activation. The UE701 receives the unicast service at the same time. In this case, the network will send an RRC reconfiguration message without an additional session activation notification. In an embodiment, the UE is in an RRC idle/inactive state prior to session activation. The UE needs to listen for the session activation notification. After the network notification session is activated, the UE transitions to the RRC connected state to receive the multicast service. In one scenario, at step 712, ue 712 enters an RRC connected state. In step 722, the MBS session is activated.

When an MBS session is activated and the UE701 is in an RRC connected state, the UE receives HFN and SN values for the UE PDCP state variables for the active MBS session from the network. In an embodiment, in step 731, the ue701 receives RRC signaling for detailed RRC configuration. The RRC signaling from the network includes one or more configuration values for UE PDCP state variables for MBS sessions, including HFN values (e.g., initial _ HFN) and SN values (e.g., next _ SN). In an embodiment, the network utilizes an RRC reconfiguration message to indicate the HFN and the SN of the next PDCP PDU to be sent. In step 713, the ue701 sets an HFN to an initial _ HFN included in an RRC message from the network. In step 718, the ue701 sets HFN to initial _ HFN. In step 719, UE701 sets the SN portion of RX _ DELIV to next _ SN. Optionally, UE701 sets the SN portion of RX _ NEXT to NEXT _ SN. After completing the RRC reconfiguration including the PDCP state variable initialization, the ue701 transmits an RRC reconfiguration complete message to the network in step 732.

Fig. 8 is an exemplary diagram for setting a UE PDCP status variable indicated by a network according to an embodiment of the present invention. UE 802 is configured with one or more MBS in a wireless network with a gNB 801. When the UE 802 establishes the MRB, the initial values of the PDCP state variables will be transmitted in RRC signaling. In step 811, the gnb 801 sends RRC messages/signaling with configured values of PDCP state variables, including HFN values and SN values. In step 821, the ue 802 sets a PDCP state variable based on the configuration value received from the RRC message. Assuming that the initial HFN indicated by the network has a value of X and the SN of the next PDCP PDU to be transmitted is N, the network sends data packet 810 with SN N, N +1, N +2, N +3, etc.

In an embodiment, the UE may receive subsequent data PDUs earlier than RRC signaling (not shown). The UE receives the MBS data packet 820 and processes the received packet based on the network configuration value of the UE PDCP state variable. In an embodiment, the UE must receive MBS data PDUs after receiving RRC signaling. When one or more PDCP PDUs are received before the one or more configuration values for the PDCP status variable are received from the wireless network, the UE stores the one or more PDCP PDUs in a receive buffer. The UE then processes the stored PDCP PDUs upon receiving and applying the one or more configuration values from the wireless network. Upon receiving RRC signaling with configured values of UE PDCP status variables, the UE sets HFN = X, SN part = N of RX _ DELIV. As shown, the SN portion of RX _ NEXT will be updated based on the SN of the received PDU. In step 831, if some PDUs are missing (assuming [ X, N ] and [ X, N +1] are missing), the UE will update RX _ NEXT to SN +1 of the NEXT received PDU. At step 832, RX _NEXTis updated to N +3. In step 833, the UE starts reordering when processing the stored PDCP PDUs when it is determined that RX _ NEXT is not equal to RX _ DELIV. At step 834, RX _NEXTis updated to N +4. In subsequent receptions, if a PDCP PDU with COUNT [ X, N ] is successfully received, the SN portions of RX _ NEXT and RX DELIV will be updated to N +1.

Fig. 9 is an exemplary flowchart for a UE to receive one or more configuration values of UE PDCP state variables for an MBS session from a network and to set the PDCP state variables according to an embodiment of the present invention. In step 901, the UE configures an MRB for one or more MBS in the wireless network, wherein the MRB configuration enables feedback to the one or more MBS. In step 902, the UE initiates a join procedure to join the MBS session, wherein the MBS session is in an active state. In step 903, the UE receives one or more configuration values of PDCP state variables from the wireless network, wherein the PDCP state variables control PDCP transceiving for the MBS session. In step 904, the ue configures PDCP state variables based on the received one or more configuration values.

FIG. 10 is an exemplary flowchart of a base station transmitting one or more configuration values of UE PDCP State variables for an MBS session, according to an embodiment of the present invention. In step 1001, the base station/gNB receives a join request from the UE to join an active MBS session, wherein the MBS session is served by the MRB, and wherein the base station/gNB and the UE have a unicast connection for feedback. In step 1002, the base station/gNB sends one or more configuration values of PDCP status variables controlling PDCP transceiving for MBS sessions to the UE. In step 1003, the base station/gNB receives feedback on the reception information of the MBS session from the UE.

In one embodiment, a storage medium (e.g., a computer-readable storage medium) stores a program that, when executed, causes a UE to perform various embodiments of the present invention.

Although the present invention has been described in connection with the specified embodiments for the purpose of illustration, the present invention is not limited thereto. Thus, various modifications, adaptations, and combinations of the various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims (21)

1. A method for setting initial PDCP state variables for multicast, comprising:

configuring, by a user equipment, a multicast radio bearer, MRB, for one or more multicast broadcast services, MBS, in a wireless network, wherein the MRB configuration enables feedback to the one or more MBS;

initiating a join process to join an MBS session, wherein the MBS session is in an active state;

receiving one or more configuration values of a packet data convergence protocol, PDCP, state variable from the wireless network, wherein the PDCP state variable controls PDCP transceiving for the MBS session; and

configuring the PDCP state variable based on the received one or more configuration values.

2. The method of setting an initial PDCP state variable for multicast according to claim 1, wherein the one or more configuration values of the PDCP state variable are received from a radio resource control, RRC, message.

3. The method of setting initial PDCP state variable for multicast according to claim 2, wherein the RRC message is an RRC reconfiguration message, an RRC recovery message, or an RRC setup message.

4. The method of setting initial PDCP state variable for multicast according to claim 1, wherein the one or more configuration values include a hyper frame number and a sequence number.

5. The method of setting an initial PDCP state variable for multicast according to claim 1, wherein configuring the PDCP state variable comprises initializing an RX DELIV value based on a configuration value of a hyper frame number and a sequence number received from the radio network.

6. The method of setting initial PDCP state variable for multicast according to claim 1, wherein configuring the PDCP state variable comprises setting an RX _ NEXT value based on a configuration value of a hyper-frame number and a sequence number received from a radio network.

7. The method of setting initial PDCP state variables for multicast according to claim 1, further comprising:

storing one or more PDCP packet data units in a receive buffer when the one or more PDCP packet data units are received before the one or more configuration values for the PDCP status variables are received from the wireless network.

8. The method of setting initial PDCP state variables for multicast according to claim 7, further comprising:

processing the stored one or more PDCP packet data units when the one or more configuration values are received and applied from the wireless network.

9. A method for setting initial PDCP state variables for multicast, comprising:

a base station in a wireless network receiving a join request from a user equipment to join an active multicast broadcast service, MBS, session, wherein said MBS session is served over a multicast radio bearer, MRB, and wherein said base station and said user equipment have a unicast connection for feedback;

the base station sends one or more configuration values of a Packet Data Convergence Protocol (PDCP) state variable to the user equipment, wherein the PDCP state variable controls PDCP transceiving for the MBS session; and

receiving feedback from the user equipment regarding reception information of the MBS session.

10. The method of setting initial PDCP state variable for multicast according to claim 9, wherein the one or more configuration values of the PDCP state variable are sent through a radio resource control, RRC, message.

11. The method of setting initial PDCP state variable for multicast according to claim 10, wherein the RRC message is an RRC reconfiguration message, an RRC recovery message, or an RRC setup message.

12. The method of setting initial PDCP state variable for multicast according to claim 9, wherein the one or more configuration values include a hyper frame number and a sequence number.

13. A user device, comprising:

a transceiver to transmit and receive radio frequency signals in a wireless network;

a configuration module to configure a multicast radio bearer, MRB, for one or more multicast broadcast services, MBS, in the wireless network, wherein MRB configuration enables feedback to one or more MBS;

the joining module is used for initiating a joining process to join the MBS conversation, wherein the MBS conversation is in an active state;

a receiving module, configured to receive one or more configuration values of a packet data convergence protocol, PDCP, state variable from the wireless network, wherein the PDCP state variable controls PDCP transceiving for the MBS session; and

a state variable module to configure the PDCP state variables based on the received one or more configuration values.

14. The user equipment of claim 13, wherein the one or more configuration values of the PDCP state variable are received from a radio resource control, RRC, message.

15. The user equipment of claim 14, wherein the RRC message is an RRC reconfiguration message, an RRC recovery message, or an RRC setup message.

16. The user equipment of claim 13, wherein the one or more configuration values include a hyper frame number and a sequence number.

17. The user equipment of claim 13, wherein configuring the PDCP state variable comprises initializing an RX DELIV value based on a configuration value of a hyper frame number and a sequence number received from the wireless network.

18. The user equipment of claim 13, wherein configuring the PDCP state variable comprises setting an RX _ NEXT value based on a configured value of a hyper frame number and a sequence number received from a wireless network.

19. The user equipment of claim 13, further comprising:

a PDCP processing module to store one or more PDCP packet data units in a receive buffer when the one or more PDCP packet data units are received before the one or more configuration values of the PDCP status variable are received from the wireless network.

20. The user equipment of claim 19, wherein the PDCP processing module processes the one or more stored PDCP packet data units when receiving and applying the one or more configuration values from the wireless network.

21. A storage medium storing a program that, when executed, causes a user equipment to perform the steps of the method of setting initial PDCP state variables for multicast according to any of claims 1-8.

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