Patent Description:
With the exponential growth of wireless data services, the content delivery to large mobile user groups has grown rapidly. Various cellular systems, including both <NUM>/long term evolve (LTE) system and <NUM>/ new radio (NR) systems, may provide a multicast functionality, which allows user equipments (UEs) in the system to receive multicast services transported by the cellular system. A variety of applications may rely on communication over multicast transmission, such as live stream, video distribution, vehicle-to-everything (V2X) communication, public safety (PS) communication, file download, and so on. When UE establishes multicast radio bearer (MRB), hyper frame number (HFN) needs to be synchronized between the wireless network and the UE. It is also necessary to set initial value of packet data convergence protocol (PDCP) receiving window. In the legacy system, the initial values of the variables for transmit and receive operation at the PDCP layer are deterministic and usually starts from zero because data transmission/reception starts after UE is in the RRC CONNECTED state. In the NR multicast, the UE may join the multicast and broadcast service (MBS) session after the MBS session activation, which implies that the PDCP packets transmission over the air interface has been on-going for a while. Therefore, the UE cannot initialize the PDCP variables as usual for the MBS session. 3GPP Draft R2-<NUM>, 3GPP Draft R2-<NUM>, 3GPP Draft R2-<NUM>, and <CIT> disclose corresponding background art.

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

Apparatus and methods are provided for setting initial PDCP state variables for multicast services and are defined in the independent claims. The dependent claims define preferred embodiments thereof. In one novel aspect, the UE sets initial PDCP state variables for the MBS session based on configuration values received from the network. Preferably, the UE receives dedicated RRC signaling from the network, which contains initial HFN value and the SN of the next PDCP PDU to be transmitted. Preferably, the one or more configuration values are provided in RRC Reconfiguration message. Preferably, the one or more configuration values are provided in RRCResume, or RRCSetup message, according to different RRC states of UE. Preferably, the UE initializes the RX_DELIV value based on the configuration value of HFN and SN received from the wireless network. When receiving the one or more configuration values of initial PDCP state variables, UE sets HFN to initial HFN value and sets RX_DELIV to the COUNT value of next PDCP PDU to be transmitted by network. Preferably, the UE stores one or more PDCP packet data units (PDUs) in a reception buffer when the one or more PDCP PDUs are received before receiving one or more configuration values for PDCP state variables from the wireless network.

In another embodiment, the gNB receives a join request from a UE to join an active MBS session, wherein the MBS session is served with an MRB, and wherein the gNB and the UE has a unicast connection for feedback; sends one or more configuration values for PDCP state variables to the UE, wherein the PDCP state variables control PDCP transceiving for the MBS session; and receives feedback from the UE regarding reception information of the MBS session.

This summary does not purport to define the invention.

The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

Aspects of the present disclosure provide methods and an apparatus for NR (new radio access technology, or <NUM> technology) or other radio access technologies. NR may support various wireless communication services, such as enhanced mobile broadband targeting wide bandwidth, millimeter wave targeting high carrier frequency, massive machine type communications targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc., collectively referred to as "elements".

<FIG> is a schematic system diagram illustrating an exemplary wireless communication network where the UE initializes the PDCP state variables for multicast based on configurations received from the wireless network. Wireless communication network <NUM> includes one or more fixed base infrastructure units forming a network distributed over a geographical region. The base unit may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B (eNB), a gNB, or by other terminology used in the art. As an example, base stations serve a number of mobile stations within a serving area, for example, a cell, or within a 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. gNB <NUM>, gNB <NUM> and gNB <NUM> are base stations in the wireless network, the serving area of which may or may not overlap with each other. As an example, user equipment (UE) <NUM> or mobile station <NUM> is in the serving area covered by gNB <NUM> and gNB <NUM>. As an example, UE <NUM> or mobile station <NUM> is only in the service area of gNB <NUM> and connected with gNB <NUM>. UE <NUM> or mobile station <NUM> is only in the service area of gNB <NUM> and connected with gNB <NUM>. gNB <NUM> is connected with gNB <NUM> via Xn interface <NUM>. gNB <NUM> is connected with gNB <NUM> via Xn interface <NUM>. A <NUM> network entity <NUM> connects with gNB <NUM>, <NUM>, and <NUM> via NG connection <NUM>, <NUM>, and <NUM>, respectively. Preferably, gNB <NUM> and gNB <NUM> provide the same MBMS services. The service continuity during handover is guaranteed when UE <NUM> moves from gNB <NUM> to gNB <NUM> and vice versa. The area covered by gNB <NUM> and <NUM> with the same MBMS services is a multi-cast service area for the MBMS services.

<FIG> further illustrates simplified block diagrams of a base station and a mobile device/UE for multicast transmission. gNB <NUM> has an antenna <NUM>, which transmits and receives radio signals. An RF transceiver circuit <NUM>, coupled with the antenna <NUM>, receives RF signals from antenna <NUM>, converts them to baseband signals, and sends them to processor <NUM>. RF transceiver <NUM> also converts received baseband signals from processor <NUM>, converts them to RF signals, and sends out to antenna <NUM>. Processor <NUM> processes the received baseband signals and invokes different functional modules to perform features in gNB <NUM>. Memory <NUM> stores program instructions and data <NUM> to control the operations of gNB <NUM>. gNB <NUM> also includes a set of control modules <NUM> that carry out functional tasks to communicate with mobile stations. These control modules can be implemented by circuits, software, firmware, or a combination of them.

<FIG> also includes simplified block diagrams of a UE, such as UE <NUM>. The UE has an antenna <NUM>, which transmits and receives radio signals. An RF transceiver circuit <NUM>, coupled with the antenna, receives RF signals from antenna <NUM>, converts them to baseband signals, and sends them to processor <NUM>. Preferably, the RF transceiver <NUM> may comprise two RF modules (not shown) which are used for different frequency bands transmitting and receiving. RF transceiver <NUM> also converts received baseband signals from processor <NUM>, converts them to RF signals, and sends out to antenna <NUM>. Processor <NUM> processes the received baseband signals and invokes different functional modules to perform features in UE <NUM>. Memory <NUM> stores program instructions and data <NUM> to control the operations of UE <NUM>. Antenna <NUM> sends uplink transmission and receives downlink transmissions to/from antenna <NUM> of gNB <NUM>.

The UE also includes a set of control modules that carry out functional tasks. These control modules can be implemented by circuits, software, firmware, or a combination of them. A configuration module <NUM> configures an MRB for one or more multicast and broadcast services (MBSs) in a wireless network, wherein an MRB configuration enables feedback for the one or more MBSs. A joining module <NUM> initiates a join procedure to join an MBS session, wherein the MBS session is active. A reception module <NUM> receives one or more configuration values for packet data convergence protocol (PDCP) state variables from the wireless network, wherein the PDCP state variables control PDCP transceiving for the MBS session. A state variable module <NUM> configures PDCP state variables based on the received one or more configuration values. A PDCP processing module <NUM> stores one or more PDCP packet data units (PDUs) in a reception buffer when the one or more PDCP PDUs are received before receiving one or more configuration values for PDCP state variables from the wireless network.

Preferably, the UE further has an RRC state controller, an MBS controller, and a protocol stack controller. RRC state controller controls UE RRC state according to commands from the network and UE conditions. RRC supports the following states, RRC_IDLE, RRC_CONNECTED and RRC_INACTIVE. Preferably, UE can receive the multicast and broadcast services in RRC_IDLE/INACTIVE state. The UE applies the MRB establishment procedure to start receiving a session of a service it has an interest in. The UE applies the MRB release procedure to stop receiving a session. MBS controller controls to establish/add, reconfigure/modify and release/remove a MRB based on different sets of conditions for MRB establishment, reconfiguration, and release. A protocol stack controller manages to add, modify, or remove the protocol stack for the MRB. The protocol Stack includes the packet data convergence protocol (PDCP) layer <NUM>, the radio link control (RLC) <NUM>, the MAC layer <NUM> and the PHY layer <NUM>. Preferably, the service data adaptation protocol (SDAP) layer <NUM> is optionally configured.

Preferably, the PDCP layer supports the functions of transfer of data, maintenance of PDCP sequence number (SN), header compression and decompression using the robust header compression (ROHC) protocol, ciphering and deciphering, integrity protection and integrity verification, timer based SDU discard, routing for split bearer, duplication, re-ordering, in-order delivery, out of order delivery and duplication discarding. The PDCP entity includes a reordering buffer <NUM> and a status reporter <NUM>. Preferably, the receiving PDCP entity sends PDCP status report upon t-Reordering expiry. Preferably, the PDCP status reports triggers PDCP retransmission at the peer transmitting PDCP entity at the network side.

Preferably, the RLC layer <NUM> supports the functions of error correction through ARQ, segmentation and reassembly, re-segmentation, duplication detection, reestablishment, etc. Preferably, a new procedure for RLC reconfiguration is performed, which can reconfigure the RLC entity to associated to one or two logical channels. Preferably, the MAC layer <NUM> supports mapping between logical channels and transport channels, multiplexing, demultiplexing, HARQ, radio resource selection, and etc..

<FIG> illustrates an exemplary NR wireless system with centralized upper layers of the NR radio interface stacks. Different protocol split options between central unit (CU) and distributed unit (DU) of gNB nodes may be possible. The functional split between the CU and DU of gNB nodes may depend on the transport layer. Low performance transport between the CU and DU of gNB nodes can enable the higher protocol layers of the NR radio stacks to be supported in the CU, since the higher protocol layers have lower performance requirements on the transport layer in terms of bandwidth, delay, synchronization, and jitter. Preferably, SDAP and PDCP layer are located in the CU, while RLC, MAC and PHY layers are located in the DU. A core unit <NUM> is connected with one central unit <NUM> with gNB upper layer <NUM>. In one embodiment <NUM>, gNB upper layer <NUM> includes the PDCP layer and optionally the SDAP layer. Central unit <NUM> connects with distributed units <NUM>, <NUM>, and <NUM>. Distributed units <NUM>, <NUM>, and <NUM> each corresponds to a cell <NUM>, <NUM>, and <NUM>, respectively. The DUs, such as <NUM>, <NUM> and <NUM> includes gNB lower layers <NUM>. Preferably, gNB lower layers <NUM> include the PHY, MAC and the RLC layers. In another embodiment <NUM>, each gNB has the protocol stacks <NUM> including SDAP, PDCP, RLC, MAC and PHY layers.

<FIG> illustrates exemplary MRB configuration in accordance with embodiments of the current invention. Multicast radio bearer <NUM> provides multicast service, which is carried by multicast traffic channel (MTCH) of a point to multipoint (PTM) <NUM>, a dedicated traffic channel (DTCH) of a point to point(PTP) <NUM>, or both MTCH <NUM> and DTCH <NUM> with a UE protocol stack <NUM>. In one embodiment <NUM>, the MRB is configured to be associated to a MTCH. In another embodiment <NUM>, the MRB is configured to be associated to a DTCH. In yet another embodiment <NUM>, the MRB is configured to be associated to a MTCH and a DTCH. In embodiment <NUM>, the MRB is configured in PTM&PTP transmission mode. One or multiple MRBs are established corresponding to the multicast flows of a particular multicast session in order to support the multicast transmission in the downlink over the air. The multicast Radio Bearer (i.e., RB) can be subject to PTM and/or PTP transmission within a cell. In embodiment <NUM>, the MRB is configured in PTM transmission mode. In embodiment <NUM>, the MRB is configured in PTM mode. In embodiment <NUM>, the MRB is configured in PTM&PTP transmission mode.

In certain systems, such as NR systems, NR multicast/broadcast is transmitted in the coverage of a cell. Preferably, MCCH provides the information of a list of NR multicast/broadcast services with ongoing sessions transmitted on MTCH(s). At physical layer, MTCH is scheduled by gNB in the search space of PDCCH with G-RNTI scrambled. UE decodes the MTCH data for a multicast session in the multicast PDSCH. In legacy system supporting MBMS/eMBMS, the radio bearer structure for multicast and broadcast transmission is modelled in an independent way from unicast transmission. Because of the unidirectional transmission for legacy MBMS/eMBMS service, RLC unacknowledged mode (UM) node is used for the transmission of MBS session. In this case there is no need to make the interaction between multicast and unicast for a particular UE which is in RRC CONNECTED state. For the NR network, with new services provided through MBS, reliable transmission is required. The traditional multicast transmission does not ensure successful reception for all UEs, unless very conservative link adaptations are implemented, which greatly degrades the resource efficiency. To support the reliable transmission for NR multicast service, a feedback channel in the uplink is needed for each UE receiving the service, which can be used by the receiving UE to feedback its reception status about the service to the network. Based on the feedback, the network may perform necessary retransmission to improve the transmission reliability. From uplink feedback perspective, the feedback channel may be used for L2 feedback (e.g., RLC Status Report and/or PDCP Status Report). In addition, the feedback channel may be used for HARQ feedback. Furthermore, the feedback should be a bidirectional channel between the UE and the network, with the assumption that the network may take that channel to perform needed packet retransmission. The said packet retransmission is L2 retransmission (e.g., RLC retransmission and/or PDCP retransmission). In addition, the feedback channel may be used for HARQ retransmission.

<FIG> illustrates an exemplary protocol stack for a MRB configuration with PDCP-based retransmission. In the PDCP-based retransmission <NUM>, there is one PDCP entity <NUM> per MRB. Two logical channels, i.e., MTCH and DTCH are associated to the PDCP entity. Each logical channel is corresponding to a RLC entity, RLC <NUM> corresponding to the MTCH and RLC <NUM> corresponding to the DTCH. From UE aspect, the PDCP status report to trigger PDCP retransmission is delivered to the RLC entity <NUM> corresponding to DTCH. From network aspect, the PDCP protocol data units (PDUs) subject to retransmission are delivered through DTCH. The MAC entity maps the logical channel MTCH to the transport channel <NUM> (e.g., MCH, DL-SCH) and maps the logical channel DTCH to the transport channel <NUM> (e.g., MCH, DL-SCH). UE monitors two independent transport channels via different radio network temporary identifiers (RNTIs). The ROHC function and security function are optional for multicast transmission. The RLC layer includes only segmentation and the ARQ function of RLC layer is moved to PDCP layer. RLC <NUM> and RLC <NUM> maps to MAC <NUM> and send the data packets to PHY <NUM>.

A network entity, such as a base station/gNB, transmits MBS data packets with PTM link to a number N of UEs and retransmits MBS data packets based on feedbacks through associated PTP link with the PDCP-based protocol stack. An exemplary UE, correspondingly configured with PDCP-based protocol stack receives MBS data packets on the PTM RB from the bases station and sends feedback to the base station. The multicast is scheduled independently from PTP transmission. The protocol stack for both the base station and the UE includes SDAP layer <NUM>, PDCP layer <NUM>, RLC layer <NUM>, and MAC layer <NUM>. SDAP layer <NUM> handles QoS flows <NUM>, including functions at the base station of QoS flow handling <NUM> for UE-<NUM> and QoS flow handling <NUM> for UE-N, and functions at the UE of QoS flow handling <NUM> for the UE. The PDCP layer <NUM> includes ROHC functions and security functions. The ROHC function and security function are optional for multicast transmission. PDCP layer <NUM> includes base station functions of ROHC <NUM> and security <NUM> for UE-<NUM> multicast, ROHC <NUM> and security <NUM> for UE-<NUM> unicast, ROHC <NUM> and security <NUM> for UE-N multicast, ROHC <NUM> and security <NUM> for UE-N unicast, and functions at the UE of ROHC <NUM> and security <NUM>. RBs <NUM> are handled in PDCP layer <NUM>. The RLC layer <NUM> includes both segmentation and ARQ function at base Station of segmentation and ARQ <NUM> for UE-<NUM> multicast, segmentation and ARQ <NUM> for UE-<NUM> unicast, segmentation and ARQ <NUM> for UE-N multicast, segmentation and ARQ <NUM> for UE-N unicast, as well as UE functions of segmentation and ARQ <NUM> for the unicast channel of the UE, and segmentation and ARQ <NUM> for the multicast channel. RLC channels <NUM> are handled in RLC layer <NUM>. MAC layer <NUM> includes functions of scheduling and priority handling <NUM> at the base station, multiplexing <NUM> and HARQ <NUM> for UE-<NUM> at the base station, multiplexing <NUM> and HARQ <NUM> for UE-N at the base station; and functions for the UE of scheduling and priority handling <NUM> of the UE, multiplexing <NUM> of the UE and HARQ <NUM> of the UE. Logic channels <NUM> and transport channels <NUM> are handled at MAC layer <NUM>.

<FIG> illustrates an exemplary flow diagram of conditions for UE RRC states when MBS sessions are active in accordance with embodiments of the current invention. The UE is configured with one or more MBS services. At step <NUM>, the UE joins a multicast/MBS session. Preferably, a request is sent from the UE to join the MBS session. After UE joined multicast session, preferably, the UE joins an active MBS session, i.e., the MBS session is active at step <NUM> when the UE joins. In other scenarios, the MBS session is not active and when the MBS session activates, the UE will receive a session activation notification. In some scenarios, the UE transit to RRC IDLE / INACTIVE states for power saving when the MBS session was not active. In other scenarios, the UE may stay in RRC CONNECTED state for other receptions when the MBS session was not active. The RRC CONNECTED state UE may stay in the RRC CONNECTED state or transits to RRC IDLE / INACTIVE state if the MBS session is not active. When multicast session activates, UE receives session activation notification and detected that the MBS session is active at step <NUM>. Upon detecting the MBS session is active, at step <NUM>, the UE determines if the UE is in the RRC CONNECTED state. If step <NUM> determines no, the UE transits to RRC CONNECTED state at step <NUM>. If step <NUM> determines yes, at step <NUM>, the UE in the RRC CONNECTED state receives RRC signaling to set initial PDCP state variables.

<FIG> illustrates an exemplary flow diagram of conditions for setting the PDCP state variables based on network information for multicast services in accordance with embodiments of the current invention. At step <NUM>, the UE is in the RRC CONNECTED state. Preferably, the MBS session is activated. At step <NUM>, the UE receives message from network for detailed RRC configuration. Preferably, the network message is an RRC message. Preferably, the RRC message is a RRCReconfiguration message, a RRCResume message, or a RRCSetup message. The wireless network indicates the SN of the first PDU will be transmitted to UE (e.g., next_SN) and corresponding HFN value (e.g., initial_HFN). In one embodiment <NUM>, the indicator is provided by RRC Reconfiguration message, with the initial _HFN and next_SN information added to the RRC message. Preferably, the indicator is provided by RRC Setup/Resume signal according to RRC states of UE (not shown). At step <NUM>, the UE sets HFN to the value of the HFN indicated by the network, which is the initial_HFN in the RRC message; and set SN of RX_DELIV and/or RX_ NEXT to the SN of the first PDU will be transmitted by the network, which is the next_SN in the RRC message. After the UE applies the RRC configurations, at step <NUM>, the UE transmits a RRC message, such as RRCReconfigurationComplete message to the wireless network.

<FIG> illustrates an exemplary message diagram of setting the PDCP state variables based on the received network information for multicast services in accordance with embodiments of the current invention. A UE <NUM> is configured with one or more MBSs in a wireless network with a gNB <NUM>. Considering different scenarios before the UE receiving data packets from a configured MBS. In one scenario <NUM>, UE <NUM> is in the RRC IDLE/INACTIVE state. In another scenario, the MBS session is not activated. At step <NUM>, the network notifies to activate MBS session. Preferably, gNB <NUM> sends an MBS session activation notification to one or more UEs, including UE <NUM>. Preferably, the MBS session activation notification is broadcasted. Alternatively or additionally preferably, the MBS session activation notification is unicasted to each UE. In some scenarios, the MBS session becomes activated when UE <NUM> is the RRC IDLE /INACTIVE state, while in other scenarios, UE <NUM> is in the RRC CONNECTED state. The MBS session becomes activated before or after UE <NUM> determines to join the session. Preferably, UE <NUM> is in RRC CONNECTED before session activate. UE <NUM> receives unicast services simultaneously. In this case, network will transmit RRC reconfiguration message without additional session activation notification. Preferably, UE is in RRC IDLE/INACTIVE state before session activate. The UE needs to monitor session activation notification. After network notify session activation, UE transits to RRC CONNECTED states to receive multicast service. In one scenario, at step <NUM>, UE <NUM> enters RRC CONNECTED state. At step <NUM>, the MBS session is activated.

When the MBS session is activated and UE <NUM> is in the RRC CONNECTED state, the UE receives from the network the HFN and SN values for the UE PDCP state variables for the active MBS session. Preferably, at step <NUM>, UE <NUM> receives RRC signaling for detailed RRC configuration. The RRC signaling from the network includes one or more configuration values for the UE PDCP state variables of the MBS session, including an HFN value, such as the initial_HFN, and an SN value, such as the next_SN. Preferably, RRC Reconfiguration message is used from network with the indicator of HFN and the SN of the next PDCP PDU to be transmitted. At step <NUM>, UE <NUM> sets HFN to initial _HFN included in the RRC message from the network. At step <NUM>, UE <NUM> sets HFN to initial _HFN. At step <NUM>, UE <NUM> sets SN parts of RX_DELIV to next_SN. Optionally, UE <NUM> sets SN parts of RX_NEXT to next_SN. After finishing RRC reconfiguration including PDCP state variables initialization, at step <NUM>, UE <NUM> submits RRCReconfigurationComplete message to the network.

<FIG> illustrates an exemplary diagram for setting the UE PDCP state variables indicated by the network in accordance with embodiments of the current invention. A UE <NUM> is configured with one or more MBSs in a wireless network with a gNB <NUM>. When UE <NUM> establish an MRB, initial value of PDCP state variables will be transmitted in RRC signaling. At step <NUM>, gNB <NUM> sends an RRC message/signal with configuration values for PDCP state variables, including an HFN value and an SN value. At step <NUM>, UE <NUM> sets PDCP state variables based on the configuration values received from the RRC message. Assuming that the value of the initial HFN indicated by the network is X and the SN of the next PDCP PDU to be transmitted is N. The network sends data packets <NUM> with SN of N, N+<NUM>, N+<NUM>, N+<NUM>, and etc..

Preferably, UE may receive subsequent data PDUs earlier than RRC signaling (not shown). The UE receives MBS data packets <NUM> and processes the received packets based on the network configuration values for the UE PDCP state variables. Preferably, UE have to receive MBS data PDUs after receiving RRC signaling. The UE stores one or more PDCP PDUs in reception buffer when the one or more PDCP PDUs are received before receiving one or more configuration values for PDCP state variables from the wireless network. Subsequently, the UE processes the stored PDCP PDUs when one or more configuration values from the wireless network are received and applied. Upon receiving the RRC signal with the configuration values for the UE PDCP state variables, the UE sets HFN=X, SN parts of RX_DELIV=N. As illustrated, SN part of RX_NEXT will be updated according to the SN of received PDUs. At step <NUM>, if some PDUs is lost (assume[X,N] and [X,N+<NUM>] is lost), UE will update RX_NEXT to the SN of the next received PDU +<NUM>. At step <NUM>, the RX_NEXT is updated to N+<NUM>. At step <NUM>, upon determining that RX_NEXT is not equal to RX_DELIV, the UE start reordering when processing the stored PDCP PDUs. At step <NUM>, the RX_NEXT is update to N+<NUM>. In subsequent reception, if PDCP PDU with COUNT [X,N] is successfully received, SN parts of RX_NEXT and RX DELIV will be updated to N+<NUM>.

<FIG> illustrates an exemplary flow chart for the UE receiving one or more configuration values for UE PDCP state variables for an MBS session from the network and setting the PDCP state variables in accordance with embodiments of the current invention. At step <NUM>, the UE configures an MRB for one or more MBSs in a wireless network, wherein an MRB configuration enables feedback for the one or more MBSs. At step <NUM>, the UE initiates a join procedure to join an MBS session, wherein the MBS session is active. At step <NUM>, the UE receives one or more configuration values for PDCP state variables from the wireless network, wherein the PDCP state variables control PDCP transceiving for the MBS session. At step <NUM>, the UE configures PDCP state variables based on the received one or more configuration values.

<FIG> illustrates an exemplary flow chart for the base station sending one or more configuration values for UE PDCP state variables for an MBS session in accordance with embodiments of the current invention. At step <NUM>, the base station/gNB receives a join request from a UE to join an active MBS session, wherein the MBS session is served with an MRB, and wherein the base station/gNB and the UE has a unicast connection for feedback. At step <NUM>, the base station/gNB sends one or more configuration values for PDCP state variables to the UE, wherein the PDCP state variables control PDCP transceiving for the MBS session. At step <NUM>, the base station/gNB receives feedback from the UE regarding reception information of the MBS session.

Claim 1:
A method comprising:
establishing, by a user equipment, in the following also referred to as UE, a multicast radio bearer, in the following also referred to as MRB, with a base station in a wireless network for one or more multicast and broadcast services, in the following also referred to as MBSs, wherein an MRB configuration enables feedback for the one or more MBSs (<NUM>) and wherein the base station and the UE has a unicast connection for feedback;
initiating, by the UE, a join procedure to join an MBS session, wherein the MBS session is active (<NUM>);
receiving, by the UE, one or more configuration values for packet data convergence protocol, in the following also referred to as PDCP, state variables from the base station in the wireless network after the UE initiates the join procedure, wherein the PDCP state variables control PDCP transceiving for the MBS session (<NUM>; <NUM>);
configuring, by the UE, PDCP state variables based on the received one or more configuration values (<NUM>, <NUM>; <NUM>); and
transmitting, by the UE, feedback to the base station regarding reception of information of the MBS session.