Managing transmission and reception of multicast data in a distributed base station environment

Abstract

A method for managing transmission of multicast and / or broadcast services (MBS) is implemented in a central unit (CU) of a distributed base station including a CU and a distributed unit (DU). The method includes receiving a request from a core network (CN) for configuring CN-to-BS resources for transmitting downlink (DL) MBS data related to an MBS session from the CN for a plurality of user equipment units (UEs) via the distributed base station (602), obtaining a configuration for a downlink (DL) tunnel for transmitting the DL MBS data from the CU to the DU (606), and communicating the DL MBS data between the CN and the DU using the CN-to-BS resources and the configuration for the DL tunnel (614, 616).

Description

[Technical Field]

[0001] The present disclosure relates to wireless communications, and more particularly to managing multicast and / or broadcast communications in a distributed base station environment. [Background technology]

[0002] The background discussion provided herein is intended to provide an overall context for the present disclosure. To the extent described in this Background section, the work of the inventors named herein, as well as aspects of the description that may not qualify as prior art at the time of filing, are not expressly or implicitly admitted as prior art to the present disclosure.

[0003] In telecommunications systems, the Packet Data Convergence Protocol (PDCP) layer of a radio protocol stack provides services such as user plane data transport, encryption, and integrity protection. For example, the PDCP sublayer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) air interface (see 3rd Generation Partnership Project (3GPP) specification TS 36.323 ("3GPP" is a registered trademark)) and New Radio (NR) (see 3GPP specification TS 38.323) provides protocol data unit (PDU) ordering in the uplink direction from a user device (also known as user equipment or "UE") to a base station and in the downlink direction from a base station to a UE. The PDCP sublayer also provides services for signaling radio bearers (SRBs) to the Radio Resource Control (RRC) sublayer. Furthermore, the PDCP sublayer provides services for data radio bearers (DRBs) to protocol layers such as the Service Data Adaptation Protocol (SDAP) sublayer or the Internet Protocol (IP) layer, the Ethernet protocol layer, and the Internet Control Message Protocol (ICMP) layer. In general, the UE and the base station can exchange RRC messages and non-access stratum (NAS) messages using SRBs, and can transport data in the user plane using DRBs.

[0004] In some scenarios, a UE can simultaneously utilize resources from multiple nodes of a radio access network (RAN) (e.g., base stations or components of a distributed base station, also known as a separated base station) interconnected by a backhaul. When these network nodes support different radio access technologies (RATs), this type of connection is called multi-radio dual connectivity (MR-DC). When operating in MR-DC, cells associated with a base station operating as a master node (MN) define a master cell group (MCG), and cells associated with a base station operating as a secondary node (SN) define a secondary cell group (SCG). The MCG covers a primary cell (PCell) and zero, one, or more secondary cells (SCells), and the SCG covers a primary secondary cell (PSCell) and zero, one, or more SCells. The UE communicates with the MN (via the MCG) and with the SN (via the SCG). In other scenarios, the UE utilizes resources from one base station at a time, in single connectivity (SC). A UE in an SC only communicates with the MN via the MCG. The base station and / or the UE decide when the UE should establish a radio connection with another base station. For example, the base station may decide to hand over the UE to another base station and initiate a handover procedure. In other scenarios, the UE may simultaneously utilize resources of another RAN node (e.g., a base station or a component of a distributed or separated base station) interconnected by a backhaul.

[0005] A UE can use several types of SRBs and DRBs. So-called "SRB1" resources carry RRC messages, which in some cases include NAS messages on a dedicated control channel (DCCH), and "SRB2" resources support RRC messages including recorded measurement information or NAS messages, also on the DCCH but with lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange RRC messages related to the MN to embed RRC messages related to the SN and may also be referred to as MCG SRBs. "SRB3" resources allow the UE and SN to exchange RRC messages related to the SN and may also be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via the MN's and the SN's lower layer resources. Furthermore, a DRB that terminates in an MN and uses lower layer resources only in the MN can be called an MCG DRB, a DRB that terminates in an SN and uses lower layer resources only in the SN can be called an SCG DRB, and a DRB that terminates in an MN or an SN but uses lower layer resources only in the MN and SN can be called a split DRB. A DRB that terminates in an MN but uses lower layer resources only in the SN can be called an MN-terminated SCG DRB. A DRB that terminates in an SN but uses lower layer resources only in the MN can be called an SN-terminated MCG DRB.

[0006] Base stations operating in accordance with fifth-generation (5G) New Radio (NR) requirements support much wider bandwidths than fourth-generation (4G) base stations. Accordingly, in Release 15, the Third Generation Partnership Project (3GPP) proposed that user equipment units (UEs) should support a 100 MHz bandwidth in Frequency Range 1 (FR1) and a 400 MHz bandwidth in Frequency Range 2 (FR2). Because the bandwidth of a typical carrier in 5G NR is relatively wide, 3GPP proposed in Release 17 that 5G NR base stations should be capable of providing multicast and / or broadcast services (MBS) to UEs. MBS can be useful in many content distribution applications, such as transparent IPv4 / IPv6 multicast distribution, IPTV, wireless software distribution, group communications, Internet of Things (IoT) applications, V2X applications, and public safety emergency messages.

[0007] 5G NR provides both point-to-point (PTP) and point-to-multipoint (PTM) delivery methods for transmitting MBS packet flows over the air interface. In PTP communication, a RAN node transmits different copies of each MBS data packet to different UEs over the air interface. In PTM communication, a RAN node transmits a single copy of each MBS data packet to multiple UEs over the air interface. However, in some scenarios, especially when base stations are implemented in a distributed manner, it is unclear how base stations receive MBS data packets from the core network and how they transmit each MBS data packet to UEs. Summary of the Invention [Means for solving the problem]

[0008] One exemplary embodiment of the techniques of this disclosure is a method for managing MBS transmission, implemented in a CU of a distributed base station including a CU and a DU. The method is executed by processing hardware and includes receiving a request from a core network (CN) to configure CN-to-BS resources for transmitting downlink (DL) MBS data associated with an MBS session for multiple UEs via the distributed base station, obtaining a configuration for a downlink (DL) tunnel for transmitting the DL MBS data from the CU to the DU, and communicating the DL MBS data between the CN and the DU using the CN-to-BS resources and the configuration for the DL tunnel.

[0009] Another exemplary embodiment of these techniques is a method for managing transmission of MBS data, implemented in a DU of a distributed base station including a CU and a DU. The method is executed by processing hardware and includes receiving, for a plurality of UEs, a request for configuration of a DL tunnel for receiving MBS data associated with an MBS session, from the CU, transmitting the configuration of the DL tunnel to the CU, receiving DL MBS data from the CU via the DL tunnel, and transmitting the DL MBS data to the plurality of UEs via an air interface.

[0010] Yet another exemplary embodiment of these techniques is a network node that includes processing hardware and is configured to perform one of the above methods. [Brief explanation of the drawings]

[0011] [Figure 1A] FIG. 1 is a block diagram of an example wireless communication system in which a core network (CN), base stations (BSs), and user equipments (UEs) can implement techniques of the present disclosure for managing multicast and / or broadcast service (MBS) communications in a distributed base station environment. [Figure 1B]1B is a block diagram of an exemplary base station (BS) including a central unit (CU) and a distributed unit (DU) that can operate in the system of FIG. 1A. [Figure 2A] 1B is a block diagram of an example protocol stack according to which the UE of FIG. 1A can communicate with the base station of FIG. 1A. [Figure 2B] 1B is a block diagram of an example protocol stack according to which the UE of FIG. 1A can communicate with the DU and CU of the base station. [Figure 2C] FIG. 1B is a block diagram of another example protocol stack according to which the UE of FIG. 1A can communicate with the DU and CU of the base station, including support for the F1AP protocol between the CU and DU. [Figure 2D] FIG. 10 is a block diagram of an example protocol stack according to which a CU and a DU can communicate user plane traffic. [Figure 2E] FIG. 10 is a block diagram of an example protocol stack according to which a CU and a DU can communicate control plane traffic. [Figure 3] FIG. 1 is a block diagram illustrating an example tunnel architecture for MBS and PDU sessions. [Figure 4] A block diagram illustrating example MRBs and DRBs that a distributed base station can configure to communicate multicast, broadcast, and / or unicast traffic with UEs. [Figure 5A] FIG. 10 is a messaging diagram of an example scenario in which a CN and a distributed base station configure resources for transmitting MBS data of an MBS session to multiple UEs. [Figure 5B] 5B is a messaging diagram for a scenario similar to that of FIG. 5A, but in which the CN provides a list of UEs participating in the MBS session before, rather than after, configuring a CN-to-BS tunnel for the MBS. [Figure 6]FIG. 10 is a flowchart of an exemplary method, which may be implemented in a CU of the present disclosure, for configuring a transport layer of a CN-to-BS tunnel for receiving MBS data from a core network and a CU-to-DU link for transmitting MBS data to a DU, and for providing a radio interface configuration to a UE via the DU. [Figure 7] 10 is a flow diagram of another method for configuring an MBS session in a CU, including multiple instances of a UE context setup procedure and multiple transmissions of air interface configuration to respective UEs. [Figure 8] 10 is a flow diagram of another method for configuring an MBS session in a CU, including configuring multiple CU-to-DU links for each DU connected to the CU. [Figure 9] 10 is a flow diagram of a method for configuring an MBS session in a CU, including providing a common DU configuration to multiple UEs. [Figure 10A] 10 is a flow diagram of an example method for configuring a transport layer of a CU-to-DU link to receive MBS data from a CU and generate a DU configuration for a UE, which may be implemented in a DU of the present disclosure. [Figure 10B] FIG. 10 is a flow chart of another exemplary method for configuring an MBS session at a DU, where the DU provides the transport layer configuration to the CU during a first UE context procedure, rather than separately after establishing the MBS context. [Figure 11] 10 is a flow diagram of another method for configuring an MBS session in a DU, including multiple instances of a UE context setup procedure and multiple transmissions of air interface configuration to respective UEs. [Figure 12] 10 is a flow diagram of another method for configuring an MBS session in a DU, including configuring a DL tunnel on a CU-to-DU interface and configuring a logical channel on the radio interface for the MBS session. [Figure 13]10 is a flow diagram of another method for configuring an MBS session in a DU, including configuring one or more QoS flows on a CU-to-DU interface and configuring one or more corresponding logical channels on the radio interface for the MBS session. [Figure 14] 10 is a flow diagram of an example method for determining an uplink transport layer configuration for a CU-to-DU link depending on whether a radio bearer is a DRB or an MRB, which may be implemented in a CU of the present disclosure. [Figure 15] 10 is a flow diagram of an example method in a CU for determining whether to include one or more identifications of an SRB, DRB, or MRB in a CU-to-DU message requesting radio resources for an MBS session or another data session. [Figure 16] 10 is a flow diagram of an example method in a DU for determining whether a CU has requested one or more of an SRB, a DRB, or an MRB for an MBS session or another data session. [Figure 17A] 1 is a flow diagram of an example method for a DU to determine which logical channel the DU should use to transmit a data packet based on whether the DL tunnel through which the data packet arrived is associated with an MBS session or a UE-specific PDU session. [Figure 17B] 1 is a flow diagram of an example method for a DU to determine which logical channel the DU should use to transmit a data packet depending on whether the DL tunnel through which the data packet arrived is a common DL tunnel or a UE-specific DL tunnel. [Figure 17C] 10 is a flow diagram of an example method for a DU to determine which logical channel the DU should use to transmit a data packet depending on which DL tunnel the CU used to transmit the data packet. [Figure 18]10 is a flow diagram of an example method in a DU for determining whether the DU should generate a transport layer configuration for an MBS session or whether to include a previously generated transport configuration in a message to a CU. [Figure 19] 1 is a flow diagram of an example method for managing MBS transmission that may be implemented in a DU of the present disclosure. [Figure 20] 10 is a flow diagram of an example method for managing MBS transmission that may be implemented in a CU of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0012] As discussed in more detail below, a node in the distributed base station of the present disclosure manages MBS transmissions over the CU-to-DU interface and the air interface between one or more DUs and multiple UEs participating in the MBS session. More specifically, the CU can configure a common DL tunnel on the CU-to-DU link for transmitting MBS data packets received from the CN to multiple UEs. One or more DUs can configure logical channels (e.g., MTCH, DTCH) over the air interface for the MBS session. The CU can further configure a multicast radio bearer (MRB) including a DL tunnel on the CU-to-DU link, optionally a UL tunnel on the CU-to-DU link, one or more DL logical channels, and optionally one or more uplink logical channels. Furthermore, the CU can in some cases configure multiple QoS flows for the MBS session, and the DU can map these to different logical channels.

[0013] 1A illustrates an example wireless communication system 100 in which techniques of the present disclosure for managing transmission and reception of multicast and / or broadcast service (MBS) information may be implemented. The wireless communication system 100 includes user equipment (UE) 102A, 102B and base stations 104, 106 in a radio access network (RAN) 105 connected to a core network (CN) 110. In other implementations or scenarios, the wireless communication system 100 may instead include more or fewer UEs and / or more or fewer base stations than shown in FIG. 1A. The base stations 104, 106 may be any suitable type or types of base stations, such as, for example, an evolved node B (eNB), a next-generation eNB (ng-eNB), or a 5G Node B (gNB). As a more specific example, the base station 104 may be an eNB or a gNB, and the base station 106 may be a gNB.

[0014] The base station 104 supports a cell 124, and the base station 106 supports a cell 126. Because the cell 124 partially overlaps with the cell 126, the UE 102A can be within communication range of the base station 104 and simultaneously within communication range of the base station 106 (or within range to detect or measure a signal from the base station 106). This overlap can enable the UE 102A to handover between cells (e.g., from the cell 124 to the cell 126) or between base stations (e.g., from the base station 104 to the base station 106) before the UE 102A experiences a radio link failure. Moreover, this overlap enables various dual connectivity (DC) scenarios. For example, the UE 102A can communicate in DC with the base station 104 (acting as a master node (MN)) and the base station 106 (acting as a secondary node (SN)). When the UE 102A is in a DC state with the base station 104 and the base station 106, the base station 104 operates as a master eNB (MeNB), a master ng-eNB (Mng-eNB), or a master gNB (MgNB), and the base station 106 operates as a secondary gNB (SgNB) or a secondary ng-eNB (Sng-eNB).

[0015] In non-MBS (unicast) operation, the UE 102A may use radio bearers (e.g., DRBs or SRBs) that terminate at different times at the MN (e.g., base station 104) or the SN (e.g., base station 106). For example, after a handover to the base station 106 or an SN change, the UE 102A may use radio bearers (e.g., DRBs or SRBs) that terminate at the base station 106. The UE 102A may apply one or more security keys in the uplink (UE 102A to base station) and / or downlink (base station to UE 102A) directions when communicating on the radio bearers. In non-MBS operation, the UE 102A transmits data to a base station via radio bearers on (i.e., within) the uplink (UL) bandwidth part (BWP) of a cell and / or receives data from a base station via radio bearers on the downlink (DL) BWP of a cell. The UL BWP may be an initial UL BWP or a dedicated UL BWP, and the DL BWP may be an initial DL BWP or a dedicated DL BWP. The UE 102A can receive paging, system information, public warning messages, or random access responses over the DL BWP. In this non-MBS operation, the UE 102A may be in a connected state. Alternatively, if the UE 102A supports small amounts of data transmission in the idle or inactive state, the UE 102A may be in an idle or inactive state.

[0016] In MBS operation, the UE 102A may use an MBS radio bearer (e.g., MRB) that terminates at a MN (e.g., base station 104) or an SN (e.g., base station 106) at different times. For example, after a handover or SN change, the UE 102A may use an MRB that terminates at the base station 106, which may be operating as an MN or an SN. In some scenarios, the base station (e.g., MN or SN) may transmit MBS data to the UE 102A via an MRB over unicast radio resources (i.e., radio resources dedicated to the UE 102A). In other scenarios, the base station (e.g., MN or SN) may transmit MBS data from the base station to the UE 102A via an MRB over multicast radio resources (i.e., radio resources common to the UE 102A and one or more other UEs) or over a cell's DL BWP. The DL BWP may be an initial DL BWP, a dedicated DL BWP, or an MBS DL BWP (i.e., a DL BWP specific to the MBS or not for unicast).

[0017] The base station 104 includes processing hardware 130, which may include one or more general-purpose processors (e.g., central processing units (CPUs)) and computer-readable memory that stores machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. The processing hardware 130 in the example implementation of FIG. 1A includes an MBS controller 132 configured to manage or control transmission of MBS information received from the CN 110 or edge server. For example, as discussed below, the MBS controller 132 may be configured to support radio resource control (RRC) configurations, procedures and messaging related to MBS procedures, and / or other operations related to those configurations and / or procedures. The processing hardware 130 may also include a non-MBS controller 134 configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 104 operates as an MN or SN during non-MBS operation.

[0018] The base station 106 includes processing hardware 140, which may include one or more general-purpose processors (e.g., CPUs) and computer-readable memory that stores machine-readable instructions executable on the general-purpose processor(s), and / or special-purpose processing units. The processing hardware 140 in the example implementation of FIG. 1A includes an MBS controller 142 and a non-MBS controller 144, which may be similar to the controllers 132 and 134, respectively, of the base station 130. Although not shown in FIG. 1A, the RAN 105 may include additional base stations with processing hardware similar to the processing hardware 130 of the base station 104 and / or the processing hardware 140 of the base station 106.

[0019] The UE 102A includes processing hardware 150, which may include one or more general-purpose processors (e.g., CPUs), computer-readable memory storing machine-readable instructions executable on the general-purpose processors, and / or dedicated processing units. The processing hardware 150 in the example implementation of FIG. 1A includes an MBS controller 152 configured to manage or control reception of MBS information. For example, as discussed below, the UE MBS controller 152 may be configured to support RRC configuration, procedures and messaging related to MBS procedures, and / or other operations related to those configurations and / or procedures. The processing hardware 150 may also include a non-MBS controller 154 configured to manage or control one or more RRC configurations and / or RRC procedures according to any of the implementations discussed below when the UE 102A communicates with the MN and / or SN during non-MBS operation. Although not shown in FIG. 1A, the UE 102B may include processing hardware similar to the processing hardware 150 of the UE 102A.

[0020] The CN 110 may be an evolved packet core (EPC) 111 or a fifth-generation core (5GC) 160, both of which are shown in FIG. 1A . The base station 104 may be an eNB supporting an S1 interface for communicating with the EPC 111, an ng-eNB supporting an NG interface for communicating with the 5GC 160, or a gNB supporting an NR air interface and an NG interface for communicating with the 5GC 160. The base station 106 may be a EUTRA-NR DC (EN-DC) gNB (en-gNB) with an S1 interface to the EPC 111, an en-gNB that does not connect to the EPC 111, a gNB supporting an NR air interface and an NG interface to the 5GC 160, or an ng-eNB supporting a EUTRA air interface and an NG interface to the 5GC 160. The base stations 104 and 106 may support an X2 interface or an Xn interface to directly exchange messages with each other during the scenarios discussed below.

[0021] Among other components, the EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. The SGW 112 is generally configured to forward user plane packets related to voice calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides connectivity from a UE (e.g., UE 102A or 102B) to one or more external packet data networks, e.g., an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC 160 may include a user plane function (UPF) 162 and an access and mobility management function (AMF) 164, and / or a session management function (SMF) 166. The UPF 162 is generally configured to forward user plane packets related to voice calls, video calls, Internet traffic, etc., the AMF 164 is generally configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is generally configured to manage PDU sessions.

[0022] The UPF 162, the AMF 164, and / or the SMF 166 may be configured to support MBS. For example, the SMF 166 may be configured to manage or control MBS transport, configure the UPF 162 and / or the RAN 105 for MBS flows, and / or manage or configure one or more MBS or PDU sessions for MBS for a UE (e.g., UE 102A or 102B). The UPF 162 is configured to forward MBS data packets for audio, video, Internet traffic, etc. to the RAN 105. As indicated by the prefix “(MB-)” shown in FIG. 1A , the UPF 162 and / or the SMF 166 may be configured for both non-MBS unicast services and MBS services, or for only MBS services.

[0023] In general, the wireless communication system 100 may include any suitable number of base stations supporting NR and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations supporting NR and / or EUTRA cells. While the following examples specifically reference particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques of this disclosure may also apply to other suitable radio access and / or core network technologies, such as, for example, sixth generation (6G) radio access and / or 6G core network or 5G NR-6G DC.

[0024] In different configurations or scenarios of the wireless communication system 100, the base station 104 may operate as an MeNB, an Mng-eNB, or an MgNB, and the base station 106 may operate as an SgNB or an Sng-eNB. The UE 102A may communicate with the base station 104 and the base station 106 via the same radio access technology (RAT), such as EUTRA or NR, or via different RATs.

[0025] When the base station 104 is an MeNB and the base station 106 is an SgNB, the UE 102A may be in an EN-DC state with the MeNB 104 and the SgNB 106. When the base station 104 is an Mng-eNB and the base station 106 is an SgNB, the UE 102A may be in a next generation (NG) EUTRA-NR DC (NGEN-DC) state with the Mng-eNB 104 and the SgNB 106. When the base station 104 is an MgNB and the base station 106 is an SgNB, the UE 102A may be in an NR-NR DC (NR-DC) state with the MgNB 104 and the SgNB 106. When the base station 104 is an MgNB and the base station 106 is an Sng-eNB, the UE 102A may be in an NR-EUTRA DC (NE-DC) state with the MgNB 104 and the Sng-eNB 106.

[0026] 1B illustrates any one or more exemplary distributed implementations of base stations 104 and 106. In this implementation, base stations 104, 106 include a central unit (CU) 172 and one or more distributed units (DUs) 174. CU 172 includes processing hardware, such as one or more general-purpose processors (e.g., CPUs) and computer-readable memory that stores machine-readable instructions executable on the general-purpose processors, and / or dedicated processing units. For example, CU 172 may include some or all of processing hardware 130 or 140 of FIG. 1A.

[0027] Each of the DUs 174 also includes processing hardware, which may include one or more general-purpose processors (e.g., CPUs) and computer-readable memory that stores machine-readable instructions executable on the one or more general-purpose processors, and / or special-purpose processing units. For example, the processing hardware may include a MAC controller configured to manage or control one or more medium access control (MAC) operations or procedures (e.g., random access procedures), and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station (e.g., base station 104) operates as an MN or SN. The processing hardware may also include a PHY layer controller configured to manage or control one or more PHY layer operations or procedures.

[0028] In some implementations, the CU 172 may include one or more logical nodes (CU-CP 172A) that host the control plane portion of the Packet Data Convergence Protocol (PDCP) protocol and / or the Radio Resource Control (RRC) protocol of the CU 172. The CU 172 may also include one or more logical nodes (CU-UP 172B) that host the user plane portion of the PDCP protocol and / or the Service Data Adaptation Protocol (SDAP) protocol of the CU 172. As described herein, the CU-CP 172A can transmit non-MBS control information and MBS control information, and the CU-UP 172B can transmit non-MBS data packets and MBS data packets.

[0029] The CU-CP 172A may be connected to multiple CU-UPs 172B through an E1 interface. The CU-CP 172A selects an appropriate CU-UP 172B for a requested service for the UE 102A. In some implementations, a single CU-UP 172B may be connected to multiple CU-CPs 172A through an E1 interface. The CU-CP 172A may be connected to one or more DUs 174 through an F1-C interface. The CU-UP 172B may be connected to one or more DUs 174 through an F1-U interface under the control of the same CU-CP 172A. In some embodiments, one DU 174 may be connected to multiple CU-UPs 172B under the control of the same CU-CP 172A. In such implementations, the connection between the CU-UP 172B and the DU 174 is established by the CU-CP 172A using a bearer context management function.

[0030] 2A illustrates, in a simplified manner, an exemplary protocol stack 200 according to which a UE (e.g., UE 102A or 102B) can communicate with an eNB / ng-eNB or gNB (e.g., one or more of base stations 104, 106). In the exemplary protocol stack 200, the EUTRA PHY sublayer 202A provides transport channels to the EUTRA MAC sublayer 204A, which then provides logical channels to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides RLC channels to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides transport channels to the NR MAC sublayer 204B, which then provides logical channels to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides RLC channels to the NR PDCP sublayer 210. In some implementations, the UE 102A or 102B supports both the EUTRA and NR stacks as shown in FIG. 2A to support handover between EUTRA and an NR base station and / or to support DC over the EUTRA and NR interfaces. Additionally, as shown in FIG. 2A, the UE 102A or 102B can support layering of the NR PDCP 210 over the EUTRA RLC 206A and the SDAP sublayer 212 over the NR PDCP sublayer 210. In this specification, the sublayers are also referred to simply as "layers."

[0031] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets that may be referred to as service data units (SDUs) (e.g., from an IP layer layered directly or indirectly on the PDCP layer 208 or 210) and output packets that may be referred to as protocol data units (PDUs) (e.g., to the RLC layer 206A or 206B). For brevity, this disclosure refers to both SDUs and PDUs as "packets" unless the distinction between SDUs and PDUs is important. Packets may be MBS packets or non-MBS packets. MBS packets may, for example, include application content for MBS services (e.g., IPv4 / IPv6 multicast distribution, IPTV, wireless software distribution, group communication, IoT applications, V2X applications, and / or public safety emergency messages). As another example, MBS packets may include application control information for MBS services.

[0032] On the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide SRBs, for example, to exchange RRC messages or non-access stratum (NAS) messages. On the user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide DRBs to support data exchange. The data exchanged on the NR PDCP sublayer 210 can be, for example, SDAP PDUs, IP packets, or Ethernet packets.

[0033] In a scenario where the UE 102A or 102B operates in an EN-DC with the base station 104 acting as an MeNB and the base station 106 acting as an SgNB, the wireless communication system 100 can provide the UE 102A or 102B with an MN-terminated bearer using the EUTRA PDCP sublayer 208 or an MN-terminated bearer using the NR PDCP sublayer 210. In various scenarios, the wireless communication system 100 can also provide the UE 102A or 102B with an SN-terminated bearer using only the NR PDCP sublayer 210. The MN-terminated bearer can be an MCG bearer, a split bearer, or an MN-terminated SCG bearer. The SN-terminated bearer can be an SCG bearer, a split bearer, or an SN-terminated MCG bearer. The MN-terminated bearer can be an SRB (e.g., SRB1 or SRB2) or a DRB. The SN-terminated bearer can be an SRB or a DRB.

[0034] In some implementations, a base station (e.g., base station 104, 106) broadcasts MRB data packets over one or more MBS radio bearers (MRBs), and the UE 102A or 102B receives the MBS data packets over the MRBs. The base station may include a configuration for the MRB in multicast configuration parameters (which may also be referred to as MBS configuration parameters), described below. In some implementations, the base station broadcasts the MBS data packets over the RLC sublayer 206, the MAC sublayer 204, and the PHY sublayer 202, and correspondingly, the UE 102A or 102B uses the PHY sublayer 202, the MAC sublayer 204, and the RLC sublayer 206 to receive the MBS data packets. In such implementations, the base station and the UE 102A or 102B may not use the PDCP sublayer 208 and the SDAP sublayer 212 to communicate the MBS data packets. In other implementations, the base station transmits MBS data packets via the PDCP sublayer 208, the RLC sublayer 206, the MAC sublayer 204, and the PHY sublayer 202, and correspondingly, the UE 102A or 102B uses the PHY sublayer 202, the MAC sublayer 204, the RLC sublayer 206, and the PDCP sublayer 208 to receive the MBS data packets. In such implementations, the base station and UE 102A or 102B may not use the SDAP sublayer 212 to communicate the MBS data packets. In yet another implementation, the base station transmits MBS data packets via the SDAP sublayer 212, the PDCP sublayer 208, the RLC sublayer 206, the MAC sublayer 204, and the PHY sublayer 202, and correspondingly, the UE 102A or 102B uses the PHY sublayer 202, the MAC sublayer 204, the RLC sublayer 206, the PDCO sublayer 208, and the SDAP sublayer 212 to receive the MBS data packets.

[0035] FIG. 2B illustrates, in a simplified manner, an exemplary protocol stack 250 through which the UE 102A or 102B may communicate with a DU (e.g., DU 174) and a CU (e.g., CU 172). The radio protocol stack 200 is functionally divided as illustrated by the radio protocol stack 250 of FIG. 2B. The CU may retain all control and higher layer functions (e.g., RRC 214, SDAP 212, NR PDCP 210) in either the base station 104 or 106, while lower layer operations (e.g., NR RLC 206B, NR MAC 204B, and NR PHY 202B) are delegated to the DU. To support connectivity to 5GC, the NR PDCP 210 provides SRBs to the RRC 214, which in turn provides DRBs to the SDAP 212 and provides SRBs to the RRC 214.

[0036] 2C shows, in simplified form, an exemplary protocol stack 260 that the UE 102A or 102B may use to communicate with a DU (e.g., DU 174) and a CU (e.g., CU 172). Protocol stack 260 is generally similar to protocol stack 250, except that here, an RRC layer 214 is layered on top of the PDCP layer 210 to carry RRC messages between the UE and the CU 172, transparent to the DU 174.

[0037] 2D is a block diagram of an example protocol stack 270 according to which the CU 172 and DU 174 can communicate user plane traffic. A GTP-U layer 278 is layered on top of UDP 276, which is layered on top of IP 274. The UDP / IP layer is layered on top of a data link layer 272 and a PHY layer 271. The PHY layer 271 may be, for example, a wired link.

[0038] 2E is a block diagram of an example protocol stack 280 according to which the CU 172 and the DU 174 may communicate control plane traffic. The stack 280 is generally similar to the stack 270, but here a Stream Control Transmission Protocol (SCTP) layer 282 sits above the IP layer 274 to carry control messages.

[0039] 3, an MBS session 302A may include a tunnel 312A with endpoints at the CN 110 and the base station 104 / 106. The MBS session 302A may correspond to a session ID, such as, for example, a Temporary Mobile Group Identity (TMGI). The MBS data may include, for example, IP packets, TCP / IP packets, UDP / IP packets, Real-Time Transport Protocol (RTP) / UDP / IP packets, or RTP / TCP / IP packets.

[0040] In some cases, the CN 110 and / or base station 104 / 106 configure the tunnel 312A only for MBS traffic directed from the CN 110 to the base station 104 / 106, and the tunnel 312A may be referred to as a downlink (DL) tunnel. However, in other cases, the CN 110 and base station 104 / 106 use the tunnel 312A for downlink as well as uplink (UL) MBS traffic, for example, to support commands or service requests from a UE. Furthermore, because the base station 104 / 106 can direct MBS traffic arriving via the tunnel 312A to multiple UEs, the tunnel 312A may be referred to as a common tunnel or a common DL tunnel.

[0041] The tunnel 312A may operate at the transport layer or sublayer of, for example, the User Datagram Protocol (UDP) protocol layered on the Internet Protocol (IP). As a more specific example, the tunnel 312A may be associated with the General Packet Radio System (GPRS) Tunneling Protocol (GTP). The tunnel 312A may correspond, for example, to an IP address (e.g., the IP address of the base station 104 / 106) and a Tunnel Endpoint Identifier (TEID) (e.g., assigned by the base station 104 / 106). More generally, the tunnel 312A may have any suitable transport layer configuration. The CN 110 may specify the IP address and the TEID address in the header of a tunnel packet containing the MBS data packet and transmit the tunnel packet downstream to the base station 104 / 106 via the tunnel 312A. The header may include the IP address and / or the TEID. For example, the headers include an IP header and a GTP header, which include an IP address and a TEID, respectively. Thus, the base station 104 / 106 can use the IP address and / or the TEID to identify data packets traveling through the tunnel 312A.

[0042] As shown in FIG. 3, the base station 104 / 106 maps traffic in the tunnel 312A to N radio bearers 314A-1, 314A-2, ..., 314A-N, which may be configured as MBS radio bearers or MRBs, where N >= 1. Each MRB may correspond to a respective logical channel. As discussed above, the PDCP sublayer supports radio bearers such as SRBs, DRBs, and MRBs, and the EUTRA or NR MAC sublayer provides logical channels to the EUTRA or NR RLC sublayer. For example, each of the MRBs 314A may correspond to a respective MBS traffic channel (MTCH). The base station 104 / 106 and the CN 110 may also maintain another MBS session 302B, which may similarly include a tunnel 312B corresponding to MRBs 314B-1, 314B-2, ..., 314B-N, where N >= 1. Each of the MRBs 314B may correspond to a respective logical channel.

[0043] MBS traffic may include one or more quality-of-service (QoS) flows for each of tunnels 312A, 312B, etc. For example, MBS traffic on tunnel 312B may include a set of flows 316 including QoS flows 316A, 316B, ..., 316L. Furthermore, a logical channel of an MRB can support a single QoS flow or multiple QoS flows. In the example configuration of FIG. 3, base station 104 / 106 maps QoS flows 316A and 316B to the MTCH of MRB 314B-1 and QoS flow 316L to the MTCH of MRB 314B-N.

[0044] In various scenarios, the CN 110 can assign different types of MBS traffic to different QoS flows. For example, a flow with a relatively high QoS value may correspond to audio packets, while a flow with a relatively low QoS value may correspond to video packets. As another example, a flow with a relatively high QoS value may correspond to I-frames or full images used in video compression, while a flow with a relatively low QoS value may correspond to P-frames or predicted pictures that contain only changes to I-frames.

[0045] Continuing with reference to FIG. 3, the base station 104 / 106 and the CN 110 can maintain one or more PDU sessions to support unicast traffic between the CN 110 and a particular UE. The PDU session 304A may include a UE-specific DL tunnel and / or a UE-specific UL tunnel 322A corresponding to one or more DRBs 324A, such as DRBs 324A-1, 324A-2, ..., 324A-N. Each of the DRBs 324A may correspond to a respective logical channel, such as a Dedicated Traffic Channel (DTCH). The base station 104 / 106 and the CN 110 may also maintain one or more other PDU sessions to support unicast traffic between the CN 110 and a particular UE. For example, the PDU session 304B may include a UE-specific DL tunnel and / or a UE-specific UL tunnel 322B corresponding to one or more DRBs 324B, such as DRBs 324B-1, 324B-2, ..., 324B-N. Each of the DRBs 324B may correspond to a respective logical channel, such as a DTCH.

[0046] Referring now to FIG. 4 , when the base stations 104 / 106 are implemented in a distributed manner, one or more DUs 174A / 174B may be associated with the CU 172. The CU 172 and the DUs 174A / 174B may establish tunnels for downlink and / or uplink data associated with an MRB or DRB. The MRB 314A-1 discussed above may be implemented as an MRB 402A connecting the CU 172 to multiple UEs, such as the UE 102A and the UE 102B. The MRB 402A may include a DL tunnel 412A connecting the CU 172 and the DUs 174A / 174B and a DL logical channel 422A corresponding to the DL tunnel 412A. In particular, the DUs 174A / 174B may map downlink traffic received via the DL tunnel 412A to the DL logical channel 422A, which may be, for example, an MTCH or a DTCH. The DL tunnel 412A may be a common DL tunnel through which the CU 172 transmits MBS data packets to multiple UEs, or alternatively, the DL tunnel 412A may be a UE-specific DL tunnel through which the CU 172 transmits MBS data packets to a specific UE.

[0047] Optionally, the MRB 402A includes a UL tunnel 413A connecting the CU 172 and the DU 174A / 174B, and a UL logical channel 423A corresponding to the UL tunnel 413A. For example, the UL logical channel 423A may be a DTCH. The DU 174A / 174B can map uplink traffic received via the UL logical channel 423A to the UL tunnel 413A.

[0048] Tunnels 412A and 413A can operate at the transport layer or sublayer of the F1-U interface. As a more specific example, CU 172 and DU 174A / 174B can utilize F1-U for user plane traffic, and tunnels 412A and 413A may be associated with the GTP-U protocol layered over UDP / IP, with IP layered over the appropriate data link and physical (PHY) layer. Furthermore, MRB 402 and / or DRB 404 additionally support control plane traffic, at least in some instances. More specifically, CU 172 and DU 174A / 174B can exchange F1-AP messages over the F1-C interface relying on Stream Control Transmission Protocol (SCTP) layered over IP, with IP layered over the appropriate data link and PHY layer, similar to F1-U.

[0049] Similarly, MRB 402B may include DL tunnel 412B and, optionally, UL tunnel 413B. DL tunnel 412B may correspond to DL logical channel 422B, and UL tunnel 413B may correspond to UL logical channel 423B.

[0050] In some cases, the CU 172 uses the DRB 404A to transmit MBS data packets or unicast data packets associated with a PDU session to a specific UE (e.g., the UE 102A or 102B). The DRB 404A may include a UE-specific DL tunnel 432A connecting the CU 172 and the DU 174A / 174B and a DL logical channel 442A corresponding to the DL tunnel 432A. In particular, the DU 174A / 174B can map downlink traffic received via the DL tunnel 432A to the DL logical channel 442A, which may be, for example, a DTCH. The DRB 404A further includes a UE-specific UL tunnel 433A connecting the CU 172 and the DU 174A / 174B and a UL logical channel 443A corresponding to the UL tunnel 433A. For example, the UL logical channel 443A may be a PUSCH. The DU 174A / 174B can map uplink traffic received via the UL logical channel 443A to the UL tunnel 433A.

[0051] Similarly, the DRB 404B may include a UE-specific DL tunnel 432B corresponding to the DL logical channel 442B and a UE-specific UL tunnel 433B corresponding to the UL logical channel 443B.

[0052] 5A , in scenario 500A, UE 102A first performs an MBS session join procedure with CN 110 via base station 104 to join an MBS session (502). In some scenarios, UE 102A subsequently performs one or more additional MBS join procedures, making event 502 the first of multiple MBS join procedures. When base station 104 configures a common DL tunnel for MBS traffic rather than a UE-specific tunnel, procedures 502 and 586 can occur in either order. In other words, base station 104 can configure a common DL tunnel even if no UEs yet participate in the MBS session.

[0053] To perform the MBS session join procedure (event 502), in some implementations, the UE 102A sends an MBS session join request message to the CN 110 via the base station 104. In response, the CN 110 can send an MBS session join response message to the UE 102A via the base station 104 to grant the UE 102A access to the first MBS session. In some implementations, the UE 102A can include an MBS session ID of the MBS session in the MBS session join request message. In some cases, the CN 110 includes the MBS session ID in the MBS session join response message. In some implementations, the UE 102A can send an MBS session join complete message to the CN 110 via the base station 104 in response to the MBS session join response message.

[0054] In some cases, the UE 102A performs an additional MBS session join procedure with the CN 110 via the RAN 105 (e.g., the base station 104 or the base station 106) to join the additional MBS session. For example, the UE 102A can perform a second MBS session join procedure with the CN 110 via the RAN 105 to join the second MBS session. Similar to event 502, in some implementations, the UE 102A can send a second MBS session join request message to the CN 110 via the base station 104, and the CN 110 can respond with a second MBS session join response message to grant the UE 102A access to the second MBS session. In some implementations, the UE 102A can send a second MBS session join complete message to the CN 110 via the base station 104 in response to the second MBS session join response message. In some implementations, the UE 102A may include a second MBS session ID of the second MBS session in the second MBS session join request message. Optionally, the CN 110 includes the second MBS session ID in the second MBS session join response message. In some implementations, the UE 102A may include the first MBS session ID and the second MBS session ID in the MBS session join request message (e.g., the first MBS session join request message) to request to join the first MBS session and the second MBS session simultaneously. In such a case, the CN 110 may send an MBS session response message to admit either the first MBS session or the second MBS session, or both the first MBS session and the second MBS session.

[0055] In some implementations, the MBS session join request message, the MBS session join response message, and the MBS session join complete message may be session initiation protocol (SIP) messages. In other implementations, the MBS session join request message, the MBS session join response message, and the MBS session join complete message may be NAS messages such as 5G mobility management (5GMM) messages or 5G session management (5GSM) messages. In the case of 5GSM messages, the UE 102A may send a (first) UL container message including the MBS session join request message to the CN 110 via the base station 104, the CN 110 may send a DL container message including the MBS session join response message to the UE 102A via the base station 104, and the UE 102A may send a (second) UL container message including the MBS session join complete message to the CN 110 via the base station 104. These container messages may alternatively be 5GMM messages. In some implementations, the MBS Session Join Request message, the MBS Session Join Response message, and the MBS Session Join Complete message may be a PDU Session Modification Request message, a PDU Session Modification Command message, and a PDU Session Modification Complete message, respectively. For simplicity of the following description, the MBS Session Join Request message, the MBS Session Join Response message, and / or the MBS Session Join Complete message may also represent their respective container messages.

[0056] In some implementations, to perform the (first) MBS session join procedure, the UE 102A may perform a PDU session establishment procedure (not shown) with the CN 110 via the base station 104 to establish a PDU session. During the PDU session establishment procedure, the UE 102A may communicate a PDU session ID of the PDU session with the CN 110 via the base station 104.

[0057] Before, during, or after the first MBS session join procedure (event 502), the CN 110 may send a (first) CN-to-BS message including a first MBS session ID and / or PDU session ID to the CU 172 to request the CU 172 to configure resources for the (first) MBS session (504). In response to receiving the first CN-to-BS message (504), the CU 172 sends a CU-to-DU message to the DU 174 to request setup for an MBS context and / or a common DL tunnel for the first MBS session (506). In response to receiving the CU-to-DU message (506), the DU 174 sends a DU-to-CU message including a first DU DL transport layer configuration to the CU 172 to configure a common CU-to-DU DL tunnel for the first MBS session (e.g., for an MRB identified by one of the MRB IDs) (508). The DU 174 can include additional DL transport layer configurations in the DU-to-CU message to configure additional common CU-to-DU DL tunnels for additional MRBs identified by additional MRB IDs in the MRB IDs. In some implementations, the DU 174 can include MRB IDs associated with the first DL transport layer configuration and / or the additional DL transport layer configurations in the DU-to-CU message. In some implementations, the CU-to-DU message is a generic F1AP message or a dedicated F1AP message specifically defined for carrying this type of request (e.g., an MBS context setup request message). In some implementations, the DU-to-CU message of event 508 is a generic F1AP message or a dedicated F1AP message specifically defined for this purpose (e.g., an MBS context setup response message). The CN 110 can additionally include quality of service (QoS) configurations for the first MBS session in the first CN-to-BS message. In such a case, the CU 172 can include the QoS configuration in the CU-to-DU message (event 506).

[0058] The CU 172 sends 510 a first BS-to-CN message (e.g., an MBS session resource setup response message) in response to the message of event 504. The CU 172 can include a first MBS session ID and / or a PDU session ID in the first BS-to-CN message. The first BS-to-CN message can include a DL transport layer configuration to configure a common DL tunnel for the CN 110 to transmit MBS data to the CU 172. The DL transport layer configuration includes a transport layer address (e.g., an IP address and / or a TEID) to identify the common DL tunnel. In some implementations, the CN-to-BS message of event 504 is a generic NGAP message or a dedicated NGAP message (e.g., an MBS session resource setup request message) specifically defined to request resources for an MBS session. In some implementations, the BS-to-CN message of event 510 is a generic NGAP message or a dedicated NGAP message (e.g., an MBS session resource setup response message) specifically defined to carry resources for an MBS session. In such a case, the CN-to-BS message of event 504 and the BS-to-CN message of event 510 may be non-UE specific messages.

[0059] In some implementations, the QoS configuration includes QoS parameters for the MBS session. In some implementations, the QoS configuration includes configuration parameters for configuring one or more QoS flows for the MBS session (see FIG. 3). In some implementations, the configuration parameters include one or more QoS flow IDs that identify the QoS flows. Each of the QoS flow IDs identifies a particular QoS flow of the QoS flows. In some implementations, the configuration parameters include QoS parameters for each QoS flow. The QoS parameters may include a 5G QoS identifier (5QI), a priority level, a packet delay budget, a packet error rate, an average duration, and / or a maximum data burst amount. The CN 110 can specify different values ​​of the QoS parameters for the QoS flows.

[0060] Events 504, 506, 508, and 510 are collectively referred to as MBS session resource setup procedure 586 in FIG. 5A.

[0061] When the CN 110 admits the UE 102A to an additional MBS session in an additional MBS session join procedure, the CN 110 may include the additional MBS session ID and, optionally, the QoS configuration for the additional MBS session ID in the first CN-to-BS message, a subsequent CN-to-BS message, or an additional CN-to-BS message similar to the first or subsequent CN-to-BS message. In such a case, the CU 172 includes additional transport layer configurations for the additional MBS session to configure additional common DL tunnels in the first BS-to-CN message, a subsequent BS-to-CN message, or an additional BS-to-CN message similar to the first or subsequent BS-to-CN message. Each of the transport layer configurations configures a specific common DL tunnel of the common DL tunnel and may be associated with a specific MBS session of the additional MBS session. Alternatively, the CN 110 may perform an additional MBS session resource setup procedure with the CU 172 to obtain the additional transport layer configurations from the CU 172, similar to the single-session MBS session resource setup procedure 586 shown in FIG. 5A. To distinguish different common DL tunnels, the transport layer configurations may be different. In particular, any pair of transport layer configurations may have different IP addresses, different DL TEIDs, or different IP addresses and different DL TEIDs.

[0062] In some implementations, the CN 110 may indicate a list of UEs participating in the first MBS session in the first CN-to-BS message. In other implementations, the CN 110 may send a second CN-to-BS message to the CU 172 indicating a list of UEs participating in the first MBS session (512). The CN 110 may include the first MBS session ID and / or PDU session ID in the second CN-to-BS message. The CU 172 may send a second BS-to-CN message to the CN 110 in response to the second CN-to-BS message 512 (519). In such a case, the second CN-to-BS message may be a non-UE-specific message, i.e., a message that is not specific to the UE 102A or the UE 102B. The CU 172 may include the first MBS session ID and / or PDU session ID in the second BS-to-CN message. For example, the list of UEs includes the UE 102A and / or the UE 102B. To indicate the list of UEs, the CN 110 may include a list of (CN UE interface ID, RAN UE interface ID) pairs, each identifying a specific UE of the UE. The CN 110 assigns the CN UE interface ID, and the CU 172 assigns the RAN UE interface ID. The CN 110 sends the list of (CN UE interface ID, RAN UE interface ID) pairs in a second CN-to-BS message (512), the CU 172 sends a BS-to-CN message (e.g., an NGAP message, an INITIAL UE MESSAGE, or a PATH SWITCH REQUEST message) including the RAN UE interface ID to the CN 110 for each of the UEs (not shown), and the CN 110 sends a CN-to-BS message (e.g., an NGAP message, an INITIAL CONTEXT SETUP REQUEST message, or a PATH SWITCH REQUEST ACKNOWLEDGE message) including the CN UE interface ID to the CU 172 for each of the UEs (not shown).In one example, the list of pairs includes a first pair (first CN UE interface ID and first RAN UE interface ID) identifying the UE 102A and a second pair (second CN UE interface ID, second RAN UE interface ID) identifying the UE 102B. In some implementations, the "CN UE interface ID" may be an "AMF UE NGAP ID," and the "RAN UE interface ID" may be a "RAN UE NGAP ID." In other implementations, the CN 110 may include a list of UE IDs, each identifying a specific UE of the UEs. In some implementations (not shown), the CN 110 may assign the UE IDs and transmit each of the UE IDs to a specific UE of the UEs in a NAS procedure (e.g., a registration procedure) that the CN 110 performs with the specific UE. For example, the list of UE IDs may include a first UE ID of the UE 102A and a second UE ID of the UE 102B. In some implementations, the UE IDs are S-Temporary Mobile Subscriber Identities (S-TMSIs) (e.g., 5G-S-TMSI). Before the CN 110 sends (512) the list of UE IDs, the CU 172 may receive (not shown) the UE IDs from the UE 102 or the CN 110 for each of the UEs. For example, the CU 172 may receive (not shown) an RRC message (e.g., an RRCSetupComplete message) from the UE 102 during an RRC connection establishment procedure that includes the UE IDs. In another example, the CU 172 may receive (not shown) a CN-to-BS message (e.g., an NGAP message, an INITIAL CONTEXT SETUP REQUEST message, or a UE INFORMATION TRANSFER message) from the CN 110 that includes the UE IDs.

[0063] In other implementations, the CN 110 may send a second CN-to-BS message to the CU 172 indicating (only) the UE 102 (e.g., either UE 102A or UE 102B) that will participate in the first MBS session (512). The second CN-to-BS message may be a UE-related message for the UE 102. That is, the second CN-to-BS message is specific to the UE 102. In response to receiving the second CN-to-BS message, the CU 172 may send a UE context request message for the UE 102 to the DU 174 (514). In some implementations, the CU 172 may include the first MBS session ID and / or an MRB ID of an MRB associated with the first MBS session (ID) in the UE context request message. In response to the UE context request message, the DU 174 sends a UE context response message to the CU 172 that includes configuration parameters for the UE 102A to receive MBS data of the first MBS session (516). In some implementations, the CU 172 can include the QoS configuration in the UE context request message. In such a case, the CU 172 may or may not include the QoS configuration in the CU-to-DU message sent (506) during the MBS session resource setup procedure 586. (Part of) the configuration parameters may be associated with the MRB / MRB ID. In some implementations, the DU 174 generates a DU configuration to include the configuration parameters and includes the DU configuration in the UE context response message. In some implementations, the DU configuration may be a CellGroupConfig IE. In other implementations, the DU configuration may be an MBS-specific IE. In some implementations, the configuration parameters configure one or more logical channels (LCs). For example, the configuration parameters may include one or more logical channel IDs (LCIDs) for configuring one or more logical channels. Each LCID identifies a specific logical channel of the one or more logical channels.

[0064] In some implementations, the second CN-to-BS message and the second BS-to-CN message may be a PDU session resource modification request message and a PDU session resource modification response message, respectively. In some implementations, the second CN-to-BS message and the second BS-to-CN message may be UE-related messages, i.e., the messages are associated with a particular UE (e.g., UE 102A or 102B).

[0065] If the CN 110 admits an additional MBS session for the UE 102A in the additional MBS session join procedure, the CN 110 can include an additional MBS session ID and / or QoS configuration for the additional MBS session ID in the first CN-to-BS message or the second CN-to-BS message. In such a case, the CU 172 can include an additional MBS session ID and MRB ID in the CU-to-DU message, and the DU 174 includes an additional DU transport layer configuration for configuring an additional CN-to-BS DL tunnel for the additional MBS session in the DU-to-CU message. Alternatively, the CU 172 can perform an additional MBS session resource setup procedure with the DU 174 to obtain the additional DU DL transport layer configuration, similar to events 506 and 508. In some implementations, the CU 172 includes an additional CU DL transport layer configuration for the additional MBS session in the first BS-to-CN message for configuring an additional CN-to-BS common DL tunnel. Each transport layer configuration configures a specific DL tunnel of the common CN-to-BS DL tunnel and may be associated with a specific MBS session of the additional MBS sessions. Alternatively, the CN 110 can perform additional MBS session resource setup procedures with the CU 172, similar to the MBS session resource setup procedure 586, to obtain additional CU DL transport layer configurations from the CU 172. The transport layer configurations may be different to distinguish between different common DL tunnels. In particular, any pair of transport layer configurations may have different IP addresses, different DL TEIDs, or different IP addresses and different DL TEIDs.

[0066] In some implementations, the CN 110 includes the QoS configuration in the second CN-to-BS message. In such a case, the CN 110 may include the QoS configuration in the first CN-to-BS message or may omit the QoS configuration. In some implementations, the DU 174 generates configuration parameters for the UE 102A to receive MBS data of the first MBS session in response to receiving the CU-to-DU message (506) or receiving the UE context request message (514). In some implementations, the CU 172 includes the QoS configuration in the UE context request message and / or the CU-to-DU message. The DU 174 can determine the content of the configuration parameters according to the QoS configuration. When the CU 172 does not include the QoS configuration in either the CU-to-DU message or the UE context request message, the DU 174 can determine the value of the configuration parameter according to a predetermined (default) QoS configuration.

[0067] In some implementations, the UE context request message and the UE context response message are UE Context Setup Request and UE Context Setup Response messages, respectively. In other implementations, the UE context request message and the UE context response message are UE Context Modification Request and UE Context Modification Response messages, respectively.

[0068] After receiving the UE context response message (516), the CU 172 generates an RRC reconfiguration message including the configuration parameters and one or more MRB configurations and sends the RRC reconfiguration message to the DU 174 (518). The DU 174 then sends the RRC reconfiguration message to the UE 102 (520). The UE 102 then sends an RRC reconfiguration complete message to the DU 174 (522), and the DU 174 sends the RRC reconfiguration complete message to the CU 172 (523).

[0069] Events 512, 514, 516, 518, 519, 520, 522, and 523 are collectively referred to in Figure 5A as MBS radio connection reconfiguration procedure 588. Events 514, 516, 518, 520, 522, and 523 are collectively referred to in Figure 5A as MBS radio connection reconfiguration procedure 589.

[0070] In some implementations, the CU 172 generates a PDCP PDU including the RRC reconfiguration message and transmits a CU-to-DU message including the PDCP PDU to the DU 174 (518), and the DU 174 extracts the PDCP PDU from the CU-to-DU message and transmits the PDCP PDU to the UE 102 via the RLC layer 206B, the MAC layer 204B, and the PHY layer 202B (520). The UE 102 receives the PDCP PDU from the DU 174 via the PHY layer 202B, the MAC layer 204B, and the RLC layer 206B (520). In some implementations, the UE 102 generates a PDCP PDU including the RRC reconfiguration complete message and transmits the PDCP PDU to the DU 174 via the RLC layer 206B, the MAC layer 204B, and the PHY layer 202B (522). The DU 174 receives PDCP PDUs from the UE 102 via the PHY layer 202B, the MAC layer 204B, and the RLC layer 206B (522) and sends DU-to-CU messages containing the PDCP PDUs to the CU 172 (523). The CU 172 extracts the PDCP PDUs from the DU-to-CU messages and extracts the RRC reconfiguration complete message from the PDCP PDUs.

[0071] Before or after receiving the UE context response message (516), the CU 172 can send a second BS-to-CN message to the CN 110 in response to the second CN-to-BS message 512 (519). In some implementations, the CU 172 sends the second BS-to-CN message to the CN 110 (519) before receiving the RRC reconfiguration complete message (523). In other implementations, the CN 110 sends the second BS-to-CN message to the CN 110 (519) after receiving the RRC reconfiguration complete message (523). The CU 172 can include the first CN UE interface ID and the first RAN UE interface ID in the second BS-to-CN message. Alternatively, the CU 172 can include the first UE ID in the second BS-to-CN message.

[0072] In some implementations, a respective instance of the MBS radio connection reconfiguration procedure 588 exists for each of the UE 102A and the UE 102B. The configuration parameters for the UE 102A and the UE 102B to receive MBS data of the first MBS session may be the same.

[0073] In some implementations, the CU 172 includes the CU DL transport layer configuration in the second BS-to-CN message and / or a subsequent BS-to-CN message. In other words, the CU 172 can send the same CU DL transport layer configuration in a BS-to-CN message in response to the CN-to-BS message indicating that the UE will participate in the same MBS session. In such implementations, the CN 110 can blend the MBS resource setup procedure 586 and the MBS radio connection reconfiguration procedure 588 into a single procedure.

[0074] When the CU 172 performs the MBS resource setup procedure 586 (e.g., events 504, 510) with the CN 110 to establish a common CN-to-BS DL tunnel for the first MBS session, the CU 172 may refrain from including the DL transport layer configuration for the first MBS session in the second BS-to-CN message. In such a case, the CN 110 may refrain from including the UL transport layer configuration for the first MBS session in the second CN-to-BS message. When the DU 174 performs the MBS resource setup procedure 586 (e.g., events 506, 508) with the CU 172 to establish a common CU-to-DU DL tunnel for the first MBS session, the DU 174 may refrain from including the DL transport layer configuration for the first MBS session in the UE context response message. In such a case, the CU 172 may refrain from including the UL transport layer configuration for the first MBS session in the UE context request message.

[0075] After receiving the first BS-to-CN message (510) or the second BS-to-CN message (519), the CN 110 can transmit MBS data (e.g., one or more MBS data packets, also interchangeably referred to herein as “MBS content data” or “MBS payload data”) to the CU 172 via the common CN-to-BS DL tunnel (524), and the CU 172 transmits the MBS data to the DU 174 via the common CU-to-DU tunnel (526). The DU 174 transmits (e.g., multicast or unicast) the MBS data to the UE 102 (i.e., UE 102A and UE 102B) via one or more logical channels (528). The UE 102 receives the MBS data via one or more logical channels (528). For example, the CU 172 receives the MBS data packet (524), generates a PDCP PDU including the MBS data packet, and transmits the PDCP PDU to the DU 174 (526). The DU 174 then generates a MAC PDU including the logical channel ID and the PDCP PDU and transmits the MAC PDU to the UE 102 via multicast or unicast (528). The UE 102 receives the MAC PDU via multicast or unicast (528), extracts the PDCP PDU and the logical channel ID from the MAC PDU, identifies the PDCP PDU associated with the MRB according to the logical channel ID, and extracts the MBS data packet from the PDCP PDU according to the PDCP configuration in the MRB configuration.

[0076] In some implementations, the CU 172 may configure (determine) a UE-specific CN-to-BS DL tunnel for the UE 102 in response to receiving the first CN-to-BS message (504) or the second CN-to-BS message (512). In such a case, the CU 172 may omit event 506 and may include in the second BS-to-CN message a DL transport layer configuration for configuring the UE-specific DL tunnel. The CN 110 may transmit MBS data to the CU 172 via the UE-specific CN-to-BS DL tunnel (524). In some implementations, the CU 172 may configure (determine) a UE-specific CU-to-DU DL tunnel for the UE 102 in response to receiving the first CN-to-BS message (504) or the second CN-to-BS message (512). In such a case, the CU 172 may omit event 510 and the DU 174 may include in the UE context response message a DL transport layer configuration for configuring the UE-specific CU-to-DU DL tunnel. In such a case, the CU 174 may transmit the MBS data to the DU 174 via the UE-specific CU-to-DU DL tunnel (526).

[0077] In some implementations, one or more MRB configurations constituting one or more MRBs are associated with the first MBS session. In some implementations, the configuration parameters also include one or more RLC bearer configurations, each associated with a particular MRB. Each of the MRB configurations may include an MRB ID, a PDCP configuration, a first MBS session ID, a PDCP reestablishment indication (e.g., reestablishPDCP), and / or a PDCP recovery indication (e.g., recoveryPDCP). In some implementations, the PDCP configuration may be a PDCP-Config IE for the DRB. In other implementations, the RLC bearer configuration may be an RLC-BearerConfig IE. In some implementations, the RLC bearer configuration may include a logical channel (LC) ID constituting a logical channel. In some implementations, the logical channel may be a multicast traffic channel (MTCH). In other implementations, the logical channel may be a dedicated traffic channel (DTCH). In some implementations, the configuration parameters may include a logical channel configuration (e.g., a LogicalChannelConfig IE) constituting a logical channel. In some implementations, the RLC bearer configuration may include an MRB ID.

[0078] In some implementations, the CU 172 can configure the MRB as a DL-only RB in the MRB configuration. For example, to configure the MRB as a DL-only RB, the CU 172 refrains from including UL configuration parameters in the PDCP configuration in the MRB configuration. The CU 172 includes only DL configuration parameters in the MRB configuration, for example, as described above. In such a case, the CU 172 configures the UE 102 not to transmit UL PDCP data PDUs to the DU 174 and / or CU 172 via the MRB by not including UL configuration parameters for the MRB in the PDCP configuration in the MRB configuration. In another example, the DU 174 refrains from including UL configuration parameters in the RLC bearer configuration. In such a case, the DU 174 configures the UE 102 not to transmit control PDUs to the base station 104 via logical channels by not including UL configuration parameters in the RLC bearer configuration.

[0079] If the DU 174 includes an UL configuration parameter in the RLC bearer configuration, the UE 102 may transmit a control PDU (e.g., a PDCP control PDU and / or an RLC control PDU) to the DU 174 via a logical channel using the UL configuration parameter. If the control PDU is a PDCP control PDU, the DU 174 may transmit the PDCP control PDU to the CU 172. For example, the CU 172 may configure the UE to receive MBS data using a compression (decompression) protocol (e.g., a robust header compression (ROHC) protocol), for example, in the MRB configuration. In this case, when the CU 172 receives an MBS data packet from the CN 110 (524), the CU 172 compresses the MBS data packet using the compression protocol to obtain a compressed MBS data packet and transmits a PDCP PDU including the compressed MBS data packet to the DU 174 via a common CU-to-DU DL tunnel (526). The DU 174 then transmits (e.g., multicast or unicast) the PDCP PDU to the UE 102 via the logical channel (528). When the UE 102 receives the PDCP PDU via the logical channel, the UE 102 extracts the compressed MBS data packet from the PDCP PDU. The UE 102 decompresses the compressed MBS data packet using a compression (decompression) protocol to obtain the original MBS data packet. In such a case, the UE 102 may transmit a PDCP control PDU including header compression protocol feedback (e.g., interspersed ROHC feedback) for the operation of the header compression (decompression) protocol to the DU 174 via the logical channel. The DU 174 then transmits the PDCP control PDU to the CU 172 via a UE-specific UL tunnel, i.e., the UL tunnel is specific to the UE 102 (e.g., UE 102A). In some implementations, the CU 172 can include a CU UL transport layer configuration for configuring the UE-specific UL tunnel in the UE context request message.The CU UL transport layer configuration includes a CU transport layer address (eg, an Internet Protocol (IP) address) and a CU UL TEID to identify a UE-specific UL tunnel.

[0080] In some implementations, the MRB configuration may be an MRB-ToAddMod IE (e.g., mrb-Identity or MRB-Identity) that includes an MRB ID. The MRB ID identifies a particular MRB of the MRBs. The base station 104 sets the MRB ID to a different value. When the CU 172 configures a DRB for the UE 102 for unicast data communication, in some implementations, the CU 172 may set one or more of the MRB IDs to a value different from the DRB ID of the DRB. In such a case, the UE 102 and the CU 172 may distinguish whether an RB is an MRB or a DRB according to the RB ID of the RB. In other implementations, the CU 172 may set one or more of the MRB IDs to a value that may be the same as the DRB ID. In such a case, the UE 102 and the CU 172 may distinguish whether an RB is an MRB or a DRB according to the RB ID of the RB and the RRC IE that configures the RB. For example, a DRB configuration that configures a DRB is a DRB-ToAddMod IE that includes DRB identification information (e.g., drb-Identity or DRB-Identity) and a PDCP configuration. Thus, the UE 102 can determine that an RB is a DRB if it receives a DRB-ToAddMod IE that configures an RB, and can determine that an RB is an MRB if it receives an MRB-ToAddMod IE that configures an RB. Similarly, the CU 172 can determine that an RB is a DRB if it sends a DRB-ToAddMod IE that configures an RB to the UE 102, and can determine that an RB is an MRB if it sends an MRB-ToAddMod IE that configures an RB to the UE 102.

[0081] In some implementations, the configuration parameters for receiving MBS data of the first MBS session include one or more logical channel (LC) IDs for configuring one or more logical channels. In some implementations, the logical channel may be a dedicated traffic channel (DTCH). In other implementations, the logical channel may be a multicast traffic channel (MTCH). In some implementations, the configuration parameters may or may not include a group radio network temporary identifier (G-RNTI). An RRC reconfiguration message for UEs (e.g., UE 102A and UE 102B) participating in the first MBS session includes the same configuration parameters as for receiving MBS data of the first MBS session. In some implementations, the RRC reconfiguration message for the UEs may include the same or different configuration parameters as for receiving non-MBS data.

[0082] In some implementations, the CU 172 can include an MBS session join response message in an RRC reconfiguration message. The UE 102 can include an MBS session join complete message in an RRC reconfiguration complete message. Alternatively, the UE 102 can send an UL RRC message including the MBS session join complete message to the CU 172 via the DU 174. The UL RRC message can be any appropriate RRC message that can include a UL information transfer message or a UL NAS PDU. The CU 172 can include the MBS session join complete message in a second BS-to-CN message. Alternatively, the CU 172 can send a BS-to-CN message (e.g., an UPLINK NAS TRANSPORT message) including the MBS session join complete message to the CN 110.

[0083] In another implementation, the CU 172 sends a DL RRC message including an MBS Session Join Response message to the UE 102. The DL RRC message may be a DL Information Transfer message, another RRC Reconfiguration message, or any suitable RRC message that may include a DL NAS PDU. The UE 102 may send a UL RRC message including an MBS Session Join Complete message to the CU 172 via the DU 174. The UL RRC message may be a UL Information Transfer message, another RRC Reconfiguration Complete message, or any suitable RRC message that may include a UL NAS PDU.

[0084] Continuing with reference to FIG. 5A, the UE 102B may perform an MBS session join procedure similar to procedure 502 discussed above (530). The UE 102B may perform a PDU session establishment procedure with the CN 110 via the base station 104, as described with reference to procedure 502. The UE 102B may communicate a PDU session ID with the CN 110 in the PDU session establishment procedure. The UE 102B may join the same MBS session as the UE 102A by sending an MBS session join request and specifying the same MBS session ID. In this example scenario, the UE 102B joins the MBS session after the base station 104 begins transmitting MBS data packets to the UE 102A (528). The CN 110 sends a CN-to-BS message including the MBS session ID and / or PDU session ID to the CU 172 to indicate that the UE 102B should begin receiving MBS data for the MBS session corresponding to the MBS session ID (532).

[0085] In some scenarios, the CU 172 or the CN 110 determines that a DL tunnel already exists for the MBS session identified in event 532 and that there is no need to perform procedure 586. However, optionally, the CU 172 sends a CU-to-DU message to the DU 174 to trigger an MBS radio connection reconfiguration procedure for the first MBS session similar to event 589 (534), and the DU 174 responds with a DU configuration (536).

[0086] The CU 172 sends an RRC reconfiguration message to the DU 174 (538), and the DU 174 sends an RRC reconfiguration message to the UE 102B to configure the UE 102B to receive MBS traffic (540). The RRC reconfiguration message may include the same LCID (value), MRB configuration, and RLC bearer configuration as in event 520 when the UEs 102A and 102B operate in the same cell. When the UEs 102A and 102B operate in different cells, the RRC reconfiguration message may have, for example, different G-RNTI, LCID, and / or RLC bearer configuration. The RRC reconfiguration message may include the same MRB configuration as in event 520 when the UEs 102A and 102B operate in different cells. As shown in FIG. 3, the CU 172 can map data packets arriving via the common CN-to-BS DL tunnel to one or more MRBs, each corresponding to a common CU-to-DU DL tunnel and / or a respective logical channel.

[0087] In response to the RRC reconfiguration message of event 540, which may be received by the DU 174 (542), the UE 102B transmits an RRC reconfiguration complete message (e.g., an RRCReconfigurationComplete message) to the base station 104 (542). In response to the DU 174 of the base station 104 receiving the RRC reconfiguration complete message (542), the DU 174 transmits an RRC reconfiguration complete message to the CU 172 (543). Before or after receiving the RRC reconfiguration complete message (542), the base station 104 may, in some cases, transmit another BS-to-CN message to the CN 110 (539), e.g., in a manner generally similar to event 519. The BS-to-CN message may indicate, for example, an updated list of UEs associated with the MBS session specified in event 532. After the UE 102B joins the MBS session (530) and obtains the required RRC configuration (540), the CU 172 continues to receive MBS data via the common CN-to-BS DL tunnel (544) and transmits the MBS data to the DU 174 via the common CU-to-DU DL tunnel (546). In some implementations, the DU 174 transmits the MBS data to the UE 102A and the UE 102B via multicast (548). The UE 102A and the UE 102B can receive the MBS data similar to event 528 (548). Alternatively, the base station 104 can transmit the MBS data to the UE 102A and the UE 102B separately via unicast (548).

[0088] Referring now to Figure 5B, a scenario 500B is illustrated that is generally similar to scenario 500A. Events in this scenario similar to those discussed above are labeled with the same reference numbers, and the examples and implementations of Figure 5A may apply to Figure 5B. Differences between the scenarios of Figure 5A and 5B are discussed below.

[0089] In some implementations, the CU 172 can perform an MBS session resource setup procedure and a UE-specific MBS session configuration procedure 587 (e.g., a combination of events 586 and 589) with the CN 110 in response to receiving (512) a second CN-to-BS message that specifies a UE ID and a session ID for the UE 102A. In such implementations, the CU 172 sends (510) a first BS-to-CN message to the CN 110 in response to receiving (512) the second CN-to-BS message. The CN 110 then sends (504) a first CN-to-BS message to the CU 172 in response to receiving (510) the first BS-to-CN message. In such cases, the CN 110 may or may not include an MBS session ID (i.e., the first MBS session ID) in the first CN-to-BS message. The CN 110 may transmit a second BS-to-CN message (519) in response to or after receiving the second CN-to-BS message (512) or the first CN-to-BS message (504). After or in response to receiving the second CN-to-BS message (512), transmitting the first BS-to-CN message (510), or receiving the first CN-to-BS message (504), the CU 172 may transmit a CU-to-DU message to the DU 174 (506).

[0090] Instead of sending a CU-to-DU message to request that the CU 172 configure a common CU-to-DU DL tunnel (506), the DU 174, in some implementations, may send a DU-to-CU message (508) in response to receiving the UE context request message (514) in addition to sending a UE context response message (516). The CU 172 may then send a CU-to-DU response message to the DU 174 in response to receiving the DU-to-CU message (506) (508). In such cases, the DU-to-CU message and the CU-to-DU response message may be non-UE-associated messages, i.e., the messages are not associated with a particular UE.

[0091] 5B as an MBS resource setup and UE-specific MBS session configuration procedure 587. If the CN 110 admits an additional MBS session for the UE 102A in an additional MBS session join procedure, the CN 110 may perform the MBS resource setup and UE-specific MBS session configuration procedure with the base station 104 and the UE 102A, similar to procedure 587. In such a case, the CN 110 may include the additional MBS session ID, and optionally a QoS configuration for the additional MBS session ID, in the CN-to-BS message in the MBS resource setup and UE-specific MBS session configuration procedure, similar to the first or second CN-to-BS message. In such a case, the CU 172 includes additional transport layer configurations for the additional MBS sessions to configure the additional common DL tunnels in the BS-to-CN message in the MBS resource setup and UE-specific MBS session configuration procedure, similar to the first or second BS-to-CN message. Each of the transport layer configurations configures a specific common DL tunnel of the common DL tunnels and may be associated with a specific MBS session of the additional MBS session. The transport layer configurations may be different to distinguish between different common DL tunnels. In particular, any pair of transport layer configurations may have different IP addresses, different DL TEIDs, or different IP addresses and different DL TEIDs.

[0092] Although not fully illustrated in FIGS. 5A and 5B to avoid confusion, an exemplary procedure for indicating interest in an MBS will now be briefly discussed.

[0093] A UE that is receiving or interested in receiving MBS can send an MBS interest indication to the network (e.g., to the CN 110). Based on the MBS interest indication, the network attempts to enable the UE to receive MBS and unicast services, subject to the UE's capabilities, e.g., the UE's radio capabilities. In the MBS interest indication, the UE can indicate a set of frequencies (including one or more frequencies) on which the UE is receiving or interested in receiving MBS. The MBS interest indication can also indicate a list of MBS services that the UE is receiving or interested in receiving on the indicated one or more frequencies. Furthermore, the UE can send an MBS interest indication regardless of whether the serving cell supports MBS. In some cases, the UE can send a first MBS interest indication to the network and later send a second, updated MBS interest indication.

[0094] Generally, the UE and / or the RAN manage information related to multicast and / or broadcast services (MBS). In response to determining that the radio connection between the UE and the RAN should be modified, the UE can decide to either maintain or release the MBS interest indication. If the UE maintains the MBS interest indication, the UE can later send an MBS interest indication update to the RAN. If the UE releases the MBS interest indication, the UE can send another MBS interest indication to the RAN after modifying the radio connection.

[0095] Similarly, a node of the RAN may also receive an MBS interest indication from a UE and, in response to determining that the radio connection between the UE and the RAN should be modified, either maintain or release the configuration included in the MBS interest indication. Triggering events that may cause the UE and / or RAN to decide to release or maintain the MBS interest indication include the UE detecting a failure in the radio connection or the UE suspending, resuming, or re-establishing the radio connection with the RAN.

[0096] Additionally, the MBS interest indication may be stored in the receiving RAN node, in other RAN nodes, and / or in one or more CNs of the wireless communications system. For example, a RAN node that receives the MBS interest indication from the UE may forward the received UE MBS interest indication to another RAN node, a CN, etc., any of which may forward the UE MBS interest indication to other RAN nodes and / or CNs.

[0097] Some example methods for configuring and utilizing resources to facilitate MBS communications will now be discussed with respect to Figures 6 through 20. For example, the methods in the CU may be implemented in the CU 172, and the methods in the DU may be implemented in the DU 174. These methods may be implemented as a set of instructions stored on a non-transitory computer-readable medium and executable by processing hardware such as, for example, one or more CPUs.

[0098] 6, for example, an exemplary method 600 for configuring the transport layer of the CN-to-BS tunnel and the CU-to-DU link may be implemented in a CU. When the CU receives a request from the CN and does not already have the necessary configuration for an MBS session over the CU-to-DU interface, the CU may execute this method to configure CU-to-DU communication for that MBS session.

[0099] Method 600 begins at block 602, where a CU receives a CN-to-BS message requesting the CU to set up an MBS session for an MBS session ID (e.g., event 504). Next, at block 604, the CU sends a CU-to-DU message requesting the DU to establish an MBS session context for the MBS session (e.g., event 506). This CU-to-DU message may be referred to as a first CU-to-DU message. The CU may execute block 604 directly in response to receiving the CN-to-BS message at block 602 or thereafter.

[0100] In block 606, in response to the first CU-to-DU message, the CU receives a (first) DU-to-CU message including a (first) transport layer configuration (e.g., event 508). Then, in block 608, the CU sends a (second) CU-to-DU message to the DU to request configuration parameters for UEs operating in the DU's cell and that have expressed interest in and / or joined the MBS session (e.g., events 514, 534). In response, in block 610, the CU may receive a (second) DU-to-CU message from the DU. This message may include a DU configuration that the UE can apply to receive MBS data of the MBS session (e.g., events 516, 536). In block 612, the CU sends the DU configuration and MRB configuration to the UE via the DU (e.g., events 520, 540).

[0101] In block 614, the CU receives MBS data associated with the MBS session from the CN (e.g., event 524). The CU then, in block 616, transmits the MBS data to the UE via the DU in accordance with the transport layer configuration for the CU-to-DU link received in block 606.

[0102] 7, a method 700 is also for configuring an MBS session at a CU, where the CU performs a UE context procedure for multiple UEs. At block 702, the CU receives a CN-to-BS message requesting the CU to set up an MBS session for an MBS session ID (e.g., event 504).

[0103] In block 704, in response to or after receiving the CN-to-BS message, the CU performs an MBS context setup procedure with the DU to obtain at least one transport layer configuration for transmitting MBS data for the MBS session to UE1, ..., N, where N > 0 (e.g., events 506, 508). However, in some implementations, the CU can obtain at least one transport layer configuration during the UE context procedure discussed below, in which case the CU need not perform the MBS context setup procedure in block 704.

[0104] Next, in block 706, the CU performs UE context procedures 1, ..., N with the DUs to obtain DU configurations 1, ..., N for UEs 1, ..., N, respectively (e.g., events 514, 516, 534, 536). The UEs use the corresponding DU configurations to receive MBS data for the MBS session.

[0105] In some implementations, the CU connects to UE1,...,N and UE(N+1),...,Z, where Z>N>0, and / or stores UE context 1,...,Z for UE1,...,Z. The CU determines that only UE1,...,N participated in the MBS session, and UE(N+1),...,Z did not participate in the MBS session. In such a scenario, the CN-to-BS message may include MBS session information indicating that UE1,...,N participated in the MBS session and indicating (explicitly or implicitly) that UE(N+1),...,Z did not participate in the MBS session. In other scenarios, rather than receiving a list of UEs, the CU receives a separate CN-to-BS message from the CN for each of UE1,...,N, where each CN-to-BS message indicates that a UE has joined the MBS session.

[0106] In block 708, the CU transmits corresponding DU configurations to UE1, ..., N via the DU (e.g., events 520, 540). In block 710, the CU receives MBS data associated with an MBS session from the CN (e.g., events 524, 544). The CU then transmits the MBS data to UE1, ..., N in accordance with the at least one transport layer configuration in block 712 (e.g., events 526, 528, 546, 548). More specifically, the CU can generate and transmit transport layer data packets, such as PDCP PDUs.

[0107] Furthermore, when the base station includes multiple DUs, the CU can perform blocks 704 to 712 for another (second DU) to transmit MBS data to UE1, ..., P, where P>0.

[0108] Next, Figure 8 shows another method 800 for configuring an MBS session in a CU. The CU can perform this method to configure multiple CU-to-DU links for each DU connected to the CU, with different sets of UEs communicating with the corresponding DUs (e.g., a first set of UEs communicating with the CU via a first DU, and a second set of UEs communicating with the CU via a second DU). In the following discussion of Figure 8, transport layer configuration refers to CU-to-DU links (e.g., rather than CN-to-BS links or air interfaces).

[0109] In block 802, the CU receives a CN-to-BS message including an MBS session ID from the CN to request the CU to set up resources for the MBS session (e.g., event 504). Method 800 optionally includes block 804, in which the CU performs a (first) MBS context setup procedure with a first DU to obtain a first transport layer configuration (e.g., event 586) so that the CU can transmit MBS data to UEs in the first set. In block 806, the CU performs a UE context procedure with the first DU to obtain a first DU configuration for each UE in the first set (e.g., events 514, 516, 534, 536). In optional block 808, the CU performs a second MBS context procedure with a second DU to obtain a second transport layer configuration so that the CU can transmit MBS data for the MBS session to UEs in the second set. Then, in block 810, the CU performs a UE context procedure with the second DU to obtain a second DU configuration for each UE in the second set.

[0110] In block 812, the CU sends at least one first DL message to at least one UE in the first set via a first DU, each DL message including a specific DU configuration of the at least one first DU configuration (e.g., events 520, 540). In block 814, the CU sends at least one second DL message to at least one UE in the second set via a second DU, each DL message including a specific DU configuration of the at least one second DU configuration. Next, in block 816, the CU receives MBS data for the MBS session from the CN. In block 818, the CU sends the MBS data to at least one UE in the first set and at least one UE in the second set via the first DU and the second DU, respectively. For this purpose, the CU uses the first transport layer configuration and the second transport layer configuration, respectively.

[0111] Referring now to FIG. 9, a CU may perform a method 900 to configure an MRB session and provide a shared or common MRB configuration to multiple UEs.

[0112] In block 902, the CU determines to configure at least one MRB for one or more UEs through which the UEs will receive MBS data for an MBS session. In block 904, the CU may assign MRB IDs to the MRBs. When the CU configures multiple MRBs, the CU assigns different MRB IDs to the corresponding MRBs. Next, in block 906, the CU may send a CU-to-DU message to the DU that includes the MRB ID for each of the UEs (e.g., events 514, 534). When the CU is connected to multiple DUs, the CU may send a separate CU-to-DU message to each of the DUs.

[0113] At block 908, the CU may receive a DU-to-CU message including configuration parameters associated with the MRB ID from the DU in response to the corresponding CU-to-DU message (e.g., events 516, 536). Then, at block 910, the CU may generate an MRB configuration for at least one MRB (e.g., events 520, 540). The CU may also generate a DL message including the MRB configuration and configuration parameters for each of the UEs. At block 912, the CU transmits the DL message to the UE via the corresponding DU (e.g., events 520, 540). At block 914, the CU receives MBS data for the MBS session from the CN (e.g., events 524, 544), and at block 916, the CU transmits the MBS data for the MBS session to one or more DUs (e.g., events 526, 546).

[0114] Next, FIG. 10A illustrates an example method 1000A in a DU for configuring the transport layer of a CU-to-DU link for receiving MBS data from a CU and generating a DU configuration for a UE.

[0115] In block 1002, the DU performs an MBS context setup procedure with the CU to provide at least one transport layer configuration for the MBS session from the CU (e.g., event 586). In block 1004, the DU performs UE context procedures 1, ..., N with the CU to provide the CU with DU configurations 1, ..., N for UEs 1, ..., N, respectively, where N>0, so that the UEs can receive MBS data for the MBS session (e.g., events 514, 516, 534, 536). In block 1006, the DU can receive MBS data for the MBS session from the CU using at least the transport layer configurations (e.g., events 526, 546). In block 1008, the DU transmits MBS data to UEs 1, ..., N using DU configurations 1, ..., N (e.g., events 526, 528, 546, 548).

[0116] FIG. 10B illustrates a generally similar method 100B in which the DU provides the transport layer configuration to the CU during the first UE context procedure, rather than separately after establishing the MBS context.

[0117] Specifically, in block 1003, the DU performs UE context procedure 1 with the CU to provide the CU with at least one transport layer configuration for the MBS session and DU configuration 1 for UE1 to receive MBS data of the MBS session (e.g., events 514, 516). In block 1005, the DU performs UE context procedure 2, ..., N with the DU to provide the CU with DU configurations 2, ..., N for UE1, ..., N, respectively, where N>1 (e.g., events 534, 536). Flow then proceeds to blocks 1006 and 1008, discussed above.

[0118] 11 is a flow diagram of another method 1100 in a DU for configuring an MBS session. The method 1100 includes multiple instances of a UE context setup procedure and multiple transmissions of air interface configuration to respective UEs.

[0119] Specifically, in block 1102, the DU receives a first CU-to-DU message from the CU, the first CU-to-DU message including an MBS session ID and / or an MRB configuration (e.g., events 506, 514). The first CU-to-DU message requests the DU to set up an MBS session context for the MBS session. In some implementations, the MRB information may include MRB IDs with different values. For each MRB ID, the DU may assign a specific logical channel ID among the logical channel IDs. For each MRB ID, the DU may generate a specific transport layer configuration. Each transport layer configuration may include a transport layer address and / or a DL tunnel ID. The transport layer configurations are different. In some implementations, the DU may include the transport layer configuration in the first DU-to-CU message and / or other DU-to-CU messages. The DU may receive MBS data for the MBS session from the CU according to the transport layer configuration.

[0120] In block 1104, the DU establishes an MBS session context according to the first CU-to-DU message. In block 1106, the DU sends a first DU-to-CU message to the CU in response to the first CU-to-DU message (e.g., events 508, 516). In block 1108, the DU receives other CU-to-DU messages 1, ..., N from the CU, each containing an MBS session ID and / or MRB information for UE 1, ..., N (e.g., events 514, 534).

[0121] In block 1110, the DU sends other DU-to-CU messages 1, ..., N to the CU, each including DU configurations 1, ..., N, where N>0, in response to the other CU-to-DU messages 1, ..., N (e.g., events 516, 536). In some implementations, the DU includes logical channel IDs, each identifying a logical channel within each of the DU configurations 1, ..., N. Next, in block 112, the DU receives MBS data for the MBS session from the CU (e.g., events 526, 546). In block 114, the DU transmits MBS data to UEs 1, ..., N using DU configurations 1, ..., N (e.g., events 528, 548).

[0122] Referring to FIG. 12, a DU may perform a method 1200 to configure a DL tunnel on the CU-to-DU interface and a logical channel on the radio interface for an MBS session.

[0123] Method 1200 begins at block 1202, where the DU performs a procedure with the CU to set up at least one DL tunnel for one or more MBS sessions and assign at least one DL tunnel ID associated with the at least one DL tunnel (e.g., events 506, 508, 514, 516). At block 1204, the DU configures at least one logical channel (ID) associated with the at least one DL tunnel (ID). At block 1206, the DU sends DU configurations to the UE, each configuring at least one logical channel (ID) (e.g., events 516, 518, 520, 536, 538, 540). Next, at block 1208, the DU receives MBS data for the MBS session from the CU via the at least one DL tunnel (e.g., events 526, 546). At block 1210, the DU transmits the MBS data to the UE via the at least one logical channel tunnel (events 528, 548).

[0124] FIG. 13 shows a method 1300 for configuring an MBS session in a DU, where the setup includes configuring one or more QoS flows on the CU-to-DU interface and one or more corresponding logical channels on the radio interface for the MBS session.

[0125] More specifically, in block 1302, the DU performs procedures with the CU to set up at least one DL tunnel for one or more MBS QoS flows associated with the MBS session (e.g., events 506, 508, 513, 515). In block 1304, the DU configures at least one logical channel (ID) associated with the MBS QoS flow (ID). In block 1306, the DU sends a DL message to one or more UEs configuring at least one logical channel (ID) (e.g., events 520, 540). In block 1308, the DU receives MBS data for the MBS QoS flow from the CU via the at least one DL tunnel (e.g., events 542, 544). In block 1310, the DU transmits the MBS data to one or more UEs via the at least one logical channel tunnel (events 526, 528, 546, 548).

[0126] Now, referring to FIG. 14, in some cases, the CU may generate an uplink transport layer configuration for the DU-to-CU link differently depending on whether the radio bearer is a DRB or an MRB.

[0127] Method 1400 begins at block 1402, where the CU determines to request radio resources for a radio bearer. In block 1404, the CU determines whether the radio bearer is a DRB or an MRB. If the CU determines that the radio bearer is a DRB, flow proceeds to block 1406, where the CU includes a DRB ID of the DRB in a first CU-to-DU message. In block 1408, the CU includes a first uplink transport layer configuration in the first CU-to-DU message. In block 1410, the CU sends the first CU-to-DU message to the DU. However, if the CU determines in block 1404 that the radio bearer is an MRB, flow proceeds to block 1412, where the CU includes an MRB ID of the MRB in a second CU-to-DU message (e.g., 514, 534). The flow proceeds to optional block 1414, where the CU can include the second uplink transport layer configuration in a second CU-to-DU message (e.g., 514, 534), and then the flow proceeds to block 1416, where the CU sends the second CU-to-DU message to one or more DUs (e.g., events 514, 534).

[0128] 15, the CU may also perform method 1500 to determine whether to include one or more identifications of an SRB, DRB, or MRB in a CU-to-DU message requesting radio resources for an MBS session or another data session. The method begins at block 1502, where the CU determines to send a CU-to-DU message to request radio resources for at least one radio bearer. In block 1504, the CU determines whether the at least one radio bearer includes an SRB. If so, the CU includes the SRB ID of the SRB in the CU-to-DU message (e.g., 514, 534) in block 1506. Otherwise, flow proceeds directly from block 1504 to block 1508.

[0129] In block 1508, the CU determines whether at least one radio bearer includes a DRB. If so, in block 1510, the CU includes the DRB ID of the DRB in the CU-to-DU message (e.g., 514, 534), and in block 1512, the CU includes the first uplink transport layer configuration in the CU-to-DU message (e.g., 514, 534). Otherwise, flow proceeds directly from block 1508 to block 1514.

[0130] In block 1514, the CU determines whether at least one radio bearer includes an MRB. If so, the CU includes the MRB ID of the MRB in the CU-to-DU message in block 1516 (e.g., 514, 534). Otherwise, method 1500 is complete (block 1522). Optionally, in block 1518, the CU includes the second uplink transport layer configuration in the CU-to-DU message (e.g., 514, 534). In block 1520, the CU sends the CU-to-DU message to the DU (e.g., 514, 534).

[0131] 16 illustrates an example method 1600 for determining, at a DU, whether a CU has requested one or more of an SRB, a DRB, or an MRB for an MBS session or another data session. The DU may perform method 1600 in response to the CU performing method 1500 discussed above with respect to FIG.

[0132] In block 1602, the DU receives a CU-to-DU message from the CU (e.g., 514, 534). In block 1604, the DU determines whether the CU-to-DU message requested radio resources for an SRB. If so, flow proceeds to block 1606, where the DU includes the SRB ID of the SRB and radio resource configuration parameters for the SRB in the DU-to-CU message (e.g., 516, 536). Otherwise, flow proceeds to block 1608, where the DU determines whether the CU-to-DU message requested radio resources for a DRB. If so, flow proceeds to block 1610 and then to block 1612. In block 1610, the DU includes the DRB ID of the DRB and configuration parameters for the DRB in the DU-to-CU message (e.g., 516, 536). In block 1612, the DU includes a first downlink transport layer configuration in the DU-to-CU message (e.g., 516, 536).

[0133] In block 1614, the DU determines whether the CU-to-DU message requested radio resources for the MRB. If the CU-to-DU message did not request radio resources for the MRB, method 1600 is complete. Otherwise, the flow proceeds to block 1616, where the DU includes the MRB ID of the MRB and / or configuration parameters for the MRB in the DU-to-CU message (e.g., 516, 536). In optional block 1618, the DU includes a second uplink transport layer configuration in the DU-to-CU message (e.g., 516, 536). In block 1620, the DU sends a DU-to-CU message to the CU in response to the CU-to-DU message (e.g., 516, 536).

[0134] Referring generally to method 1600, in some implementations, the DU generates configuration parameters for an SRB, a DRB, and / or an MRB. The configuration parameters for the SRB include a first RLC bearer configuration (e.g., an RLC-BearerConfig IE) and an SRB configuration (e.g., an SRB-ToAddMod IE). The first RLC bearer configuration may include an SRB ID and a first logical channel ID identifying a first logical channel. The configuration parameters for the DRB include a second RLC bearer configuration (e.g., an RLC-BearerConfig IE) and a DRB configuration (e.g., a DRB-ToAddMod IE). The second RLC bearer configuration may include a DRB ID and a second logical channel ID identifying a second logical channel. The configuration parameters for the MRB include a third RLC bearer configuration (e.g., an RLC-BearerConfig IE) and an MRB configuration (e.g., an MRB-ToAddMod IE). The third bearer RLC configuration may include an MRB ID and a third logical channel ID that identifies the third logical channel. In some implementations, in addition to the third RLC bearer configuration, the configuration parameters may include a fourth RLC bearer configuration (e.g., an RLC-BearerConfig IE). In such a case, the fourth RLC bearer configuration may include an MRB ID and a fourth logical channel ID that identifies the fourth logical channel. In some implementations, the DU assigns different values ​​to the logical channel IDs.

[0135] Each RLC bearer configuration may include RLC configuration parameters for operating an RLC entity, such as an RLC mode (e.g., acknowledged mode or unacknowledged mode), an RLC sequence number length, and / or a timer value.

[0136] Referring now to FIG. 17A, a DU may perform method 1700A to determine which logical channel the DU should use to transmit a data packet based on whether the DL tunnel through which the data packet arrived is an MBS session or a UE-specific PDU session.

[0137] In block 1702, the DU receives a DL data packet from the CU via the DL tunnel (e.g., events 526, 546). If, in block 1704, the DU determines that the DL tunnel is associated with an MBS session, flow proceeds to block 1706. Otherwise, flow proceeds to block 1708. In block 1706, the DU transmits the DL data packet to multiple UEs via a first logical channel (e.g., MTCH or DTCH) (e.g., events 528, 548), and method 1700 is complete. Otherwise, in block 1708, the DU transmits the DL packet to a specific UE via a second logical channel (e.g., DTCH).

[0138] Instead of or in addition to method 1700A, the DU can perform method 1700B. According to this method, in block 1703, the DU determines which logical channel the DU should use to transmit a data packet depending on whether the DL tunnel through which the data packet arrived is a common DL tunnel or a UE-specific DL tunnel. When the DL tunnel is a common DL tunnel, flow proceeds to block 1706 discussed above, and when the DL tunnel is a UE-specific DL tunnel, flow proceeds to block 1708. In some implementations, the DU performs both the determination of block 1704 and the determination of block 1703, such that, for example, when the session is an MBS session and the tunnel is a common DL tunnel, flow proceeds to block 1706.

[0139] 17A and 17B, in some cases, the DU assigns a first LCID and a second LCID to identify a first LC and a second LC, respectively. To transmit a DL data packet via the first LC, the DU generates a DL MAC PDU including the first LCID and the DL data packet and transmits (i.e., multicast or unicast) the DL MAC PDU to multiple UEs. To transmit a DL data packet via the second LC, the DU generates a DL MAC PDU including the second LCID and the DL data packet and transmits (i.e., unicast) it to a specific UE. The DU transmits DL messages (e.g., 1, ..., N) including the first LCID to multiple UEs (e.g., 1, ..., N), respectively. The DU transmits DL messages including the second LCID to a specific UE.

[0140] As another alternative to method 1700A, or in addition to methods 1700A and / or 1700B, the DU can perform method 1700C as shown in Figure 17C. According to this method, the DU determines whether the DL data packet was received via the first DL tunnel or the second DL tunnel in block 1705. If the DL tunnel is the first DL tunnel, flow proceeds to block 1706, discussed above, and if the DL tunnel is the second DL tunnel, flow proceeds to block 1708.

[0141] In some implementations, the DU assigns a first transport layer configuration and a second transport layer configuration to identify a first DL tunnel and a second DL tunnel, respectively. The first transport layer configuration includes a first transport layer address and a first TEID, and the second transport layer configuration includes a second transport layer address and a second TEID. At least one of the first transport layer address (value) and the first TEID (value) is different from at least one of the second transport layer address (value) and the second TEID (value). The DU receives a DL tunnel packet including the transport layer address, the TEID, and the DL data packet. If the transport layer address and the TEID are the first transport layer address and the first DL TEID, respectively, the DU determines that the DL data packet is received via the first DL tunnel. If the transport layer address and the TEID are the second transport layer address and the second DL TEID, respectively, the DU determines that the DL data packet is received via the second DL tunnel.

[0142] In some implementations, the DU assigns a first LCID and a second LCID to identify the first LC and the second LC. The DU can associate the first LCID and the second LCID with a first transport layer configuration and a second transport layer configuration, respectively. To transmit a DL data packet over the first LC, the DU generates a DL MAC PDU including the first LCID and the DL data packet and transmits (i.e., multicast or unicast) the DL MAC PDU to multiple UEs. To transmit a DL data packet over the second LC, the DU generates a DL MAC PDU including the second LCID and the DL data packet and transmits (i.e., unicast) it to a specific UE. The DU transmits DL messages (e.g., 1, ..., N) including the first LCID to multiple UEs (e.g., 1, ..., N), respectively. The DU transmits DL messages including the second LCID to a specific UE.

[0143] FIG. 18 is a flow diagram of an example method 1800 in a DU for determining whether the DU should generate a transport layer configuration for an MBS session or whether to include a previously generated transport configuration in a message to the CU.

[0144] In block 1802, the DU receives a CU-to-DU message from the CU, including an ID of the MBS session. In block 1804, the DU determines whether it already has a transport layer configuration for the MBS session. If so, the flow proceeds to block 1810. Otherwise, the DU generates a transport layer configuration for the MBS session in block 1806, includes the corresponding configuration parameters in a DU-to-CU message in block 1808, and proceeds to block 1812, where the DU sends the DU-to-CU message to the CU. In block 1814, the DU receives MBS data for the MBS session from the CU and can multicast the MBS data to one or more UEs in block 1816.

[0145] 19 , a DU can perform an example method 1900 to manage MBS transmissions. In block 1902, the DU establishes a common DL tunnel with a CU for an MBS session (e.g., events 508, 536). In block 1904, the DU transmits (identical) configuration parameters to (each of) multiple UEs to configure the multiple UEs to receive MBS data of the MBS session via the CU (e.g., events 516, 518, 520, 536, 538, 540). In block 1906, the DU receives MBS data of the MBS session from the CU via the common DL tunnel (e.g., events 526, 546). In block 1908, the DU transmits MBS data to the UEs using the configuration parameters (e.g., events 528, 548).

[0146] Finally, Figure 20 shows an example method 2000 for managing MBS transmissions that may be implemented in a CU. In block 2002, the CU establishes a common DL tunnel with the DU for an MBS session (e.g., events 508, 536). In block 2004, the CU sends (identical) configuration parameters to (each of) multiple UEs to configure the multiple UEs to receive MBS data of the MBS session via the DU (e.g., events 518, 520, 538, 540). In block 2006, the CU receives MBS data for the MBS session from the CN (e.g., events 524, 544). In block 2008, the CU transmits the MBS data to the multiple UEs via the common DL tunnel and the DU (e.g., events 526, 528, 546, 548).

[0147] The following list of examples reflects various embodiments specifically contemplated by this disclosure.

[0148] Example 1. A method for managing transmission of multicast and / or broadcast service (MBS) data, implemented in a central unit (CU) and distributed units (DUs) of a distributed base station, comprising: receiving, by processing hardware, a request from a core network (CN) to configure CN-to-BS resources for transmitting downlink (DL) MBS data associated with an MBS session from the CN for a plurality of user equipment units (UEs) via the distributed base station; obtaining, by the processing hardware, a configuration for a downlink (DL) tunnel for transmitting the DL MBS data from the CU to the DU; and communicating, by the processing hardware, the DL MBS data between the CN and the DU using the CN-to-BS resources and the configuration for the DL tunnel.

[0149] Example 2. The method of Example 1, wherein the obtaining step includes configuring the DL tunnel as a common DL tunnel through which the CU is configured to transmit common data packets included in the DL MBS data to two or more of the plurality of UEs via the DU.

[0150] Example 3. The method of Example 2, wherein the DU is one of a plurality of DUs included in a distributed base station, and the obtaining step includes configuring a respective common DL tunnel for each of the plurality of DUs.

[0151] Example 4. The method of Example 2, wherein configuring the DL tunnel includes sending a CU-to-DU message to the DU, the CU-to-DU message including a session identifier for the MBS session, and receiving a DU-to-CU message in response to the CU-to-DU message, the DU-to-CU message including a transport layer configuration for the common DL tunnel.

[0152] Example 5. The method of Example 4, wherein the transport layer configuration for the common DL tunnel includes at least one of an Internet Protocol (IP) address or a tunnel endpoint identifier (TEID).

[0153] Example 6. The method of any of the preceding examples, further comprising: transmitting, by the processing hardware to the DU, a request for radio resources for transmitting DL MBS data to the DU; and receiving, by the processing hardware in response to the request, from the DU a DU configuration including at least one logical channel associated with the radio interface of the DU.

[0154] Example 7. The method of Example 6, wherein transmitting the request for radio resources includes transmitting a request for one context of a plurality of UEs.

[0155] Example 8. The method of Example 7, further comprising transmitting, in each of a plurality of instances, a request for radio resources for each of a plurality of UEs.

[0156] Example 9. The method of Example 6, further comprising transmitting a DU configuration to a plurality of UEs via the DU.

[0157] Example 10. The method of Example 9, wherein transmitting the DU configuration includes transmitting, to each of the plurality of UEs, a respective reconfiguration command associated with a protocol for controlling radio resources.

[0158] Example 11. The method of any of Examples 6 to 10, further comprising: determining, by the processing hardware, a multicast radio bearer (MRB) that includes at least one logical channel; and sending, by the processing hardware, to the DU, an indication that the MRB corresponds to an MBS session.

[0159] Example 12. The method of any of Examples 1 to 10, further comprising: generating, by processing hardware, a configuration for an uplink (UL) tunnel for the MBS session; and transmitting, by the processing hardware, the configuration for the UL tunnel to the DU.

[0160] Example 13. The method of Example 12, wherein generating the configuration for the UL tunnel includes configuring the UL tunnel as a common UL tunnel for use by a plurality of UEs in response to determining that the radio bearer corresponding to the MBS session is an MRB.

[0161] Example 14. The method of Example 12, wherein generating the configuration for the UL tunnel includes configuring the UL tunnel as a UE-specific DL tunnel for one of the plurality of UEs in response to determining that the radio bearer corresponding to the MBS session is a data radio bearer (DRB).

[0162] Example 15. The method of any of Examples 1 to 10, further comprising, in response to determining that the radio bearer corresponding to the MBS session is an MRB, refraining from configuring a UL tunnel for the MBS session.

[0163] Example 16. The method of any of the preceding examples, further comprising receiving, from the CN, a list specifying a plurality of UEs to participate in the MBS session following the request to configure CN-to-BS resources.

[0164] Example 17. The method of any of Examples 1 to 15, further comprising receiving, from the CN, a list specifying a plurality of UEs to participate in the MBS session prior to the request to configure CN-to-BS resources.

[0165] Example 18. The method of any of the preceding examples, further comprising receiving, by the processing hardware, a quality of service (QoS) configuration for the MBS session from the CN; and transmitting, by the processing hardware, the QoS configuration to the DU.

[0166] Example 19. The method of Example 18, wherein receiving a QoS configuration includes receiving a configuration for a plurality of QoS flows.

[0167] Example 20. A method for managing transmission of multicast and / or broadcast service (MBS) data, implemented in a DU of a distributed base station including a CU and a DU, comprising: receiving, by processing hardware, from the CU a request for configuration of a DL tunnel for receiving MBS data from the CU associated with an MBS session for a plurality of UEs; transmitting, by the processing hardware, the configuration of the DL tunnel to the CU; receiving, by the processing hardware, the DL MBS data from the CU via the DL tunnel; and transmitting, by the processing hardware, the DL MBS data to the plurality of UEs via an air interface.

[0168] Example 21. The method of Example 20, further comprising the step of the DU receiving data packets associated with the MBS session and configuring the DL tunnel as a common DL tunnel through which the data packets are transmitted over the air interface to a plurality of UEs.

[0169] Example 22. The method of Example 21, wherein configuring the DL tunnel includes receiving, from the CU, a CU-to-DU message including a session identifier for the MBS session, and sending, in response to the CU-to-DU message, a DU-to-CU message including a transport layer configuration for the common DL tunnel.

[0170] Example 23. The method of Example 22, wherein the transport layer configuration for the common DL tunnel includes at least one of an Internet Protocol (IP) address and a tunnel endpoint identifier (TEID).

[0171] Example 24. The method of any of Examples 20 to 23, further comprising receiving, by the processing hardware, from the CU a request for radio resources for the MBS session; allocating, by the processing hardware, at least one logical channel associated with the radio interface of the DU; and transmitting, by the processing hardware in response to the request, to the CU a DU configuration including the at least one logical channel.

[0172] Example 25. The method of Example 24, wherein receiving a request for radio resources includes receiving a request for a context of a plurality of UEs.

[0173] Example 26. The method of Example 25, further comprising receiving, in each of a plurality of instances, a request for radio resources for each of a plurality of UEs.

[0174] Example 27. The method of any of Examples 24 to 26, further comprising receiving, by processing hardware, from the CU, an indication of an MRB corresponding to an MBS session and including at least one logical channel.

[0175] Example 28. The method of any of Examples 24 to 27, further comprising transmitting an indication of the at least one logical channel to each of a plurality of UEs.

[0176] Example 29. The method of any of Examples 24 to 28, wherein at least one logical channel is a multicast traffic channel (MTCH).

[0177] Example 30. The method of any of Examples 20 to 29, wherein receiving DL MBS data from the CU via the DL tunnel includes receiving a data packet, and determining, by processing hardware, in response to determining that the DL tunnel is associated with an MBS session, to transmit the data packet to the plurality of UEs.

[0178] Example 31. The method of any of Examples 20 to 29, wherein receiving DL MBS data from the CU via the DL tunnel includes receiving a data packet, and determining, by the processing hardware, to transmit the data packet to the plurality of UEs in response to determining that the DL tunnel is a common tunnel configured for more than one UE.

[0179] Example 32. A network node comprising processing hardware and configured to perform a method according to any of the preceding examples.

[0180] The following additional considerations apply to the above discussion:

[0181] In some implementations, "message" is used and may be replaced by "information element (IE)". In some implementations, "IE" is used and may be replaced by "field". In some implementations, "configuration" may be replaced by "configurations" or configuration parameters. In some implementations, "MBS" may be replaced by "multicast" or "broadcast".

[0182] A user device (e.g., UE 102A or 102B) on which the techniques of this disclosure may be implemented may be any suitable device capable of wireless communication, such as a smartphone, a tablet computer, a laptop computer, a mobile game console, a point-of-sale (POS) terminal, a health management device, a drone, a camera, a media streaming dongle or another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Furthermore, a user device may in some cases be integrated into an electronic system such as a vehicle head unit or an advanced driver assistance system (ADAS). Furthermore, a user device may operate as an internet-of-things (IoT) device or a mobile internet device (MID). Depending on the type, a user device may include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0183] Some embodiments are described in this disclosure as including logic or several components or modules. The modules may be software modules (e.g., code stored on a non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing several operations and may be configured or arranged in a certain manner. A hardware module may comprise dedicated circuitry or logic that is permanently configured to perform several operations (e.g., as a field programmable gate array (FPGA) or a dedicated processor such as an application-specific integrated circuit (ASIC)). A hardware module may also comprise programmable logic or circuitry (e.g., as contained in a general-purpose processor or other programmable processor) that is temporarily configured by software to perform several operations. The decision to implement a hardware module in dedicated, permanently configured circuitry or in temporarily configured circuitry (e.g., configured by software) may depend on cost and time considerations.

[0184] When implemented in software, the techniques may be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software may be executed by one or more general-purpose processors or one or more special-purpose processors.

[0185] Upon reading this disclosure, those skilled in the art will recognize still further alternative structural and functional designs for communicating MBS information through the principles disclosed herein. Accordingly, while particular embodiments and applications have been shown and described, it should be understood that the disclosed embodiments are not limited to the precise structure and components disclosed herein. [Explanation of symbols]

[0186] 100 Wireless Communication System 101UE 102UE 104 Base station 105 Radio Access Network (RAN) 106 Base Station 110 Core Network 111 Evolved Packet Core (EPC) 112 Serving Gateway (SGW) 114 Mobility Management Entity (MME) 116 Packet Data Network Gateway (PGW) 124 cells 126 cells 130 Processing Hardware 132 MBS Controller 134 Non-MBS Controller 140 Processing Hardware 142 MBS Controller 144 Non-MBS Controller 150 Processing Hardware 152 MBS Controller 154 Non-MBS Controller 160 5th Generation Core (5GC) 162 (MB-)UPF, User Plane Functions 164 Access and Mobility Management Function (AMF) 166 (MB-)SMF, Session Management Function (SMF) 172 Central Unit (CU) 174 Distributed Unit (DU) 202 PHY Sublayer 204 MAC Sublayer 206 RLC Sublayer 208 EUTRA PDCP Sublayer 210 NR PDCP Sublayer 212 SDAP Sublayer 214 RRC Layer 220 Transport Network Layer 222 PHY 224 Data Link Layer 226 IP 228 UDP 230 GTP-U 232 F1AP 240 Transport Network Layer 242 SCTP 250 Protocol Stack 260 Protocol Stack 270 Protocol Stack 271 PHY Layer 272 Data Link Layer 274 IP, IP layer 276 UDP 278 GTP-U Layer 280 Protocol Stack 282 Stream Control Transmission Protocol (SCTP) Layer 302 MBS Sessions 304 PDU sessions 312 DL Tunnel 314 MRB 316 QoS Flows 322 UE-specific DL tunnel and / or UL tunnel 324 DRB 402 MRB 404 DRB 412 DL Tunnel 413 UL Tunnel 422 DL logical channels 423 UL logical channels 432 UE-specific DL tunnel 433 UE-specific UL tunnel 442 DRB / DL logical channels 443 DRB / UL logical channels

Claims

1. 1. A method for managing transmission of multicast and / or broadcast service (MBS) data, implemented in a central unit (CU) of a distributed base station including a CU and distributed units (DUs), comprising: receiving, by the CU, from a core network (CN), a first CN-to-BS message including a request to configure CN-to-BS resources for transmitting downlink (DL) MBS data associated with an MBS session from the CN for a plurality of user equipment units (UEs) via the distributed base station; sending, by the CU to the DU, a first CU-to-DU message requesting the DU to establish an MBS session context for the MBS session; receiving, by the CU, from the DU, a configuration for a downlink (DL) tunnel for transmitting the DL MBS data from the CU to the DU; receiving, by the CU, from the CN, a second CN-to-BS message indicating UEs among the plurality of UEs that will participate in the MBS session; sending, by the CU to the DU after the second CN-to-BS message, a second CU-to-DU message requesting radio resources for transmitting the DL MBS data from the DU to UEs participating in the MBS session; receiving, by the CU, from the DU in response to the second CU-to-DU message, a DU configuration that UEs participating in the MBS session can utilize to communicate the DL MBS data with the DU; and communicating, by the CU, the DL MBS data between the CN and the DU using the CN-to-BS resources and the configuration for the DL tunnel.

2. The method of claim 1 , wherein a DU configuration includes at least one logical channel associated with an air interface of the DU.

3. determining, by the CU, a multicast radio bearer (MRB) including the at least one logical channel; and sending, by the CU to the DU, an indication that the MRB corresponds to the MBS session.

4. The method of claim 1 , wherein transmitting the second CU-to-DU message includes transmitting a request for a context of one of the plurality of UEs.

5. The method of claim 4, further comprising the step of transmitting the request for a context for each of the plurality of UEs.

6. The method of claim 4 , wherein transmitting the request for a context comprises transmitting at least one of a UE context setup request message or a UE context modification request message.

7. The method of claim 1 , further comprising transmitting the DU configuration to the plurality of UEs via the DU.

8. the step of transmitting the DU configuration comprises:

8. The method of claim 7, comprising sending to each of the plurality of UEs a respective reconfiguration command associated with a protocol for controlling radio resources.

9. generating, by the CU, a configuration for an uplink (UL) tunnel for the MBS session; and transmitting, by the CU, the configuration for the UL tunnel to the DU.

10. 1. A method for managing transmission of multicast and / or broadcast service (MBS) data, implemented in a central unit (CU) and distributed units (DUs) of a distributed base station, the method comprising: receiving, by the DU from the CU, a first CU-to-DU message requesting the DU to establish an MBS session context for an MBS session, the MBS session being for communicating downlink (DL) MBS data to a plurality of user equipment units (UEs); sending, by the DU to the CU, a configuration of a DL tunnel for receiving the DL MBS data from the CU at the DU; receiving, by the DU, from the CU, a second CU-to-DU message requesting radio resources for transmitting the DL MBS data from the DU to UEs participating in the MBS session among the plurality of UEs; sending, by the DU to the CU, a DU configuration that can be used by UEs participating in the MBS session to communicate the DL MBS data with the DU; receiving, by the DU, the DL MBS data from the CU via the DL tunnel; and transmitting, by the DU, the DL MBS data to the plurality of UEs.

11. allocating, by the DU, at least one logical channel associated with the radio interface of the DU; and b. including the at least one logical channel in the DU configuration.

12. The method of claim 10 , wherein receiving the second CU-to-DU message comprises receiving a request for a context for one of the plurality of UEs.

13. The method of claim 12, further comprising receiving the request for a context for each of the plurality of UEs.

14. 13. The method of claim 12, wherein receiving the request for a context comprises receiving at least one of a UE context setup request message or a UE context modification request message.

15. A network node comprising processing hardware and configured to perform the method of any one of claims 1 to 9.

16. A network node comprising processing hardware and configured to carry out the method of any one of claims 10 to 14.

Images