WO2021160123A1

WO2021160123A1 - Methods and apparatus of multicast radio bearer establishment for nr multicast and broadcast services

Info

Publication number: WO2021160123A1
Application number: PCT/CN2021/076245
Authority: WO
Inventors: Xuelong Wang
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2020-02-10
Filing date: 2021-02-09
Publication date: 2021-08-19
Also published as: WO2021159229A1

Abstract

Apparatus and methods are provided to support the establishment of radio bearers at the base station and the UE to support multicast data transmission for a multicast session modified or established as requested by the 5GC in the NR wireless network. In one novel aspect, the UE establishes one SDAP entity for one multicast session established. The base station establishes one SDAP entity for one multicast session when the base station determines to use point-to-multipoint (PTM) RB to transmit the multicast data. The base station established one or more SDAP entities for one multicast session when the base station determines to use point-to-point (PTT) RB/unicast RB to transmit the multicast data. The RRC message, such as RRC Reconfiguration message including RadioBearerConfig structure or new defined MulticastRadioBearerConfig structure carrying one or a plural of DRB-ToAddMod structure and Multicast-securityConfig structure, is used to set up the RBs for the multicast services.

Description

METHODS AND APPARATUS OF MULTICAST RADIO BEARER ESTABLISHMENT FOR NR MULTICAST AND BROADCAST SERVICES

CROSS REFERENCE TO RELATED APPLICATIONS

This application is filed under 35 U.S.C. §111 (a) and is based on and hereby claims priority under 35 U.S.C. §120 and §365 (c) from International Application No. PCT/CN2020/074602, titled “Methods and Apparatus of Multicast Radio Bearer Establishment for NR Multicast and Broadcast Services, ” with an international filing date of Feb. 10, 2020. The disclosure of each of the foregoing documents is incorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally towireless communication, and, more particularly, tomulticast radio bearer establishment for new radio (NR) multicast and broadcast services.

BACKGROUND

With the exponential growth of wireless data services, the content delivery to large mobile user groups has grown rapidly. Initial wireless multicast/broadcast services include streaming services such as mobile TV and IPTV. With the growing demand for large group content delivery, recent application development for mobile multicast services requires highly robust and critical communication services such as group communication in disaster situations and the necessity of public safety network-related multicast services. The early 3GPP in the LTE standard defines enhanced multimedia broadcast multicast services eMBMS. The single-cell point to multipoint (SC-PTM) services and multicast-broadcast single-frequency network (MBSFN) are defined. The fifth generation (5G) multicast and broadcast services (MBS) are defined based on the unicast 5G core (5GC) architecture. The support for NR multicast and broadcast services need to be defined. In particular the radio bearer establishment procedure using either a multicast radio bearer or unicast radio bearer in the NR network needs to be defined. To align with the unicast 5GC based on the 5G MBS architecture, the protocol for the delivery of data of NR MBS needs to be defined.

Improvements and enhancements are required to support multicast radio bearer (RB) establishment for NR multicast and broadcast services in the context of the unicast 5GC based 5G MBS architecture.

SUMMARY

Apparatus and methods are providedto support the establishment of radio bearers at the base station and the UE to support multicast data transmission for a multicast session modified or established as requested by the 5GC in the NR wireless network. In one novel aspect, the UE establishes one SDAP entity for one multicast session established. The base station establishes one SDAP entity for one multicast session when the base station determines to use point-to-multipoint (PTM) RB to transmit the multicast data. The base station established one or more SDAP entities for one multicast session when the base station determines to use point-to-point (PTT) RB/unicast RB to transmit the multicast data. The RRC message, such as RRC Reconfiguration message including RadioBearerConfig structure or new defined MulticastRadioBearerConfig structure carrying one or a plural of DRB-ToAddMod structure and Multicast-securityConfig structure, is used to set up the RBs for the multicast services.

In one embodiment, the base station sends a multicast configuration to configure one or more multicast sessions to a user equipment (UE) in a wireless network, establishes one or more corresponding radio bearers for each of the one or more multicast sessions, wherein each radio bearer is a multicast radio bearer or a unicast radio bearer, establishes one or more service data adaptation protocol (SDAP) entities for each multicast session based on a multicast configuration from a 5G core (5GC) entity of the wireless network, and transmits multicast data for each of the one or more multicast sessions. In one embodiment, a multicast radio bearer is established for a first multicast session, and wherein one service data adaptation protocol (SDAP) entity is established for the first multicast session. In another embodiment, N number of unicast radio bearers are established for a first multicast session, and wherein N number of SDAP entities are established for the first multicast session.

This summary does not purport to define the invention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

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

Figure 1 is a schematic system diagram illustrating an exemplary NR wireless network that supports multicast radio bearer establishmentfor multicast services in a NR network in accordance with embodiments of the current invention.

Figure 2 illustrates an exemplary NR wireless system with centralized upper layers of the NR radio interface stacks and UE stack with multicast protocol and unicastprotocol in accordance with embodiments of the current invention.

Figure 3 illustrates an exemplary user plane protocol stack for 5G MBS data transmission in accordance with embodiments of the current invention.

Figure 4 illustrates exemplary mapping scenarios between PDU session and multicast radio bearer for 5G MBS transmission in accordance with embodiments of the current invention.

Figure 5A illustrates an exemplary flow diagram for the multicast radio bearer establishment for 5G MBS transmission in accordance with embodiments of the current invention.

Figure 5B illustrates exemplary diagrams of information structures for the radio bearer establishment during the setup procedure in accordance with embodiments of the current invention.

Figure 6 illustrates exemplary diagrams for SDAP and PDCP model for one multicast session of 5G MBS transmission in accordance with embodiments of the current invention.

Figure 7 illustrates an exemplary flow chart for the UE to perform the radio bearer establishment for multicast services in the NR wireless network.

Figure 8 illustrates an exemplary flow chart for the base station to perform the radio bearer establishment for multicast services in the NR wireless network.

DETAILED DESCRIPTION

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

Figure 1 is a schematic system diagram illustrating an exemplary NR wireless network that supports multicast radio bearer establishment for multicast services in a NR network in accordance with embodiments of the current invention. NR wireless system 100 includes one or more fixed base infrastructure units forming a network distributed over a geographical region. The base unit may also be referred to as an access point, an access terminal, a base station, a Node-B, an eNode-B (eNB) , a gNB, or by other terminology used in the art. The network can be homogeneous network or heterogeneous network, which can be deployed with the same frequency or different frequency. gNB 101 and gNB 102are base stations in the NR network, the serving area of which may or may not overlap with each other. The backhaul connection such as 136, connects the non-co-located receiving base units, such as gNB 101 and gNB 102. These backhaul connections, such as connection 136, can be either ideal or non-ideal. gNB 101 connects with gNB 102 via Xnr interface. The base stations, such as gNB 101 and gNB 102, connects to the 5G core (5GC) network 103 through network interfaces, such as N2 interface for the control plane and N3 interface for the user plane.

NR wireless network 100 also includes multiple communication devices or mobile stations, such user equipments (UEs) such as UEs 111, 112, 113, 114, 116, 117, 118, 121 and 122. The mobile devices can establish one or more unicast connections with one or more base stations. For example, UE 115 has unicast connection 133 with gNB 101. Similarly, UEs 121 connects with gNB 102 with unicast connection 132.

In one novel aspect, one or more radio bearers are established for one or more multicast sessions/services. A multicast service-1 is provided by gNB 101 and gNB 102. UEs 111, 112 and 113 receive multicast services from gNB 101. UEs 121 and 122 receive multicast services from gNB 102. Multicast service-2 is provided by gNB 101 to the UE group of UEs 116, 117, and 118. Multicast service-1 and multicast service-2 are delivered in multicast mode with a multicast radio bearer (MRB) configured by the NR wireless network. The receiving UEs receives data packets of the multicast service through corresponding MRB configured. UE 111 receives multicast service-1 from gNB 101. gNB 102 provides multicast service-1as well. In one embodiment, multicast services are configured with unicast radio bearers. A multicast service-3 is delivered to UE 113 and UE 114 via

unicast radio link

131 and 134, respectively. In one embodiment, the UE receives a plurality of multicast services. Some of the multicast services are configured with multicast RBs and some of the multicast services are configured with unicast RBs. UE 113 receives multicast service-1 through an established multicast RB. UE 113 also receives multicast service-3 through an established unicast RB.

Figure 1 further illustrates simplified block diagrams of a base station and a mobile device/UE forradio bearer establishment. gNB 102 has an antenna 156, which transmits and receives radio signals. An RF transceiver circuit 153, coupled with the antenna, receives RF signals from antenna156, converts them to baseband signals, and sends them to processor 152. RF transceiver 153 also converts received baseband signals from processor152, converts them to RF signals, and sends out to antenna 156. Processor 152 processes the received baseband signals and invokes different functional modules to perform features in gNB 102. Memory 151 stores program instructions and data 154 to control the operations of gNB 102. gNB 102 also includes a set of control modules 155 that carry out functional tasks to communicate with mobile stations.

Figure 1 also includes simplified block diagrams of a UE, such as UE 111. The UE has an antenna 165, which transmits and receives radio signals. An RF transceiver circuit 163, coupled with the antenna, receives RF signals from antenna165, converts them to baseband signals, and sends them to processor 162. In one embodiment, the RF transceiver may comprise two RF modules (not shown) . A first RF module is used for HF transmitting and receiving, and the other RF module is used for different frequency bands transmitting and receiving which is different from the HF transceiver. RF transceiver 163 also converts received baseband signals from processor162, converts them to RF signals, and sends out to antenna 165. Processor 162 processes the received baseband signals and invokes different functional modules to perform features in UE 111. Memory 161 stores program instructions and data 164 to control the operations of UE 111. Antenna 165 sends uplink transmission and receives downlink transmissions to/from antenna 156 of gNB 102.

The UEalso includes a set of control modules that carry out functional tasks. These control modules can be implemented by circuits, software, firmware, or a combination of them. Aconfiguration module 191 receives a multicast configuration for one or more multicast sessions from a 5G core (5GC) entity in the wireless network. A radio bearer module 192 establishes one or more corresponding radio bearers with a base station for each of the one or more multicast sessions, wherein each radio bearer is a multicast radio bearer or a unicast radio bearer. A service data adaptation protocol (SDAP) module 193 establishes one SDAP entity for each multicast session based on the multicast configuration. A multicast module 194 receives multicast data for each of the one or more multicast sessions.

Figure 2 illustrates an exemplary NR wireless system with centralized upper layers of the NR radio interface stacks and UE stack with multicast protocol and unicastprotocol in accordance with embodiments of the current invention. Different protocol split options between central unit (CU) and distributed unit (DU) of gNB nodes may be possible. The functional split between the CU and DU of gNB nodes may depend on the transport layer. Low performance transport between the CU and DU of gNB nodes can enable the higher protocol layers of the NR radio stacks to be supported in the CU, since the higher protocol layers have lower performance requirements on the transport layer in terms of bandwidth, delay, synchronization, and jitter. In one embodiment, SDAP and PDCP layer are located in the CU, while RLC, MAC and PHY layers are located in the DU. Acore unit 201 is connected with one central unit 211 with gNB upper layer 252. In one embodiment 250, gNB upper layer 252 includes the PDCP layer and optionally the SDAP layer. Central unit 211 connects with distributed

units

221, 222, and 221. Distributed

units

221, 222, and 223 each corresponds to a

cell

231, 232, and 233, respectively. The DUs, such as 221, 222 and 223 includes gNB lower layers 251. In one embodiment, gNB lower layers 251 include the PHY, MAC and the RLC layers. In another embodiment 260, each gNB has the protocol stacks 261 including SDAP, PDCP, RLC, MAC and PHY layers.

Figure 3 illustrates an exemplary user plane protocol stack for 5G MBS data transmission in accordance with embodiments of the current invention. AUE 310 receives 5G MBS from an application server 340 in a NR wireless network. Data packets are transmitted through network entities, such as the user plane function (UPF) entity 330 and application server 340, and base station 320. At base station 320, the MBS data packets are transmitted to UE 310 through established downlink radio bearers. For the multicast transmission at downlink, the data goes to the SDAP layer of gNB, and then reaches one radio bearer’s specific PDCP entity for further data delivery. The SDAP is responsible for the mapping between multicast flow (s) and radio bearer. The radio bearer carrying the multicast flow (s) can be point-to-point (PTP) radio bearer (i.e. unicast RB) or point-to-multipoint (PTM) radio bearer (i.e. multicast RB, or MRB) . The PDCP entity performs functions, such as sequence numbering, ROHC, security handling etc. PDCP packets further goes to RLC, MAC and PHY for air interface transmission. In one embodiment, the unicast PDU session applies for 5G MBS session. Each PDU session context for the UE is associated with one multicast session context. At the session management level for a partricular UE, the multicast session context may exist in association with at least one PDU session. The multicast session context is identified by a multicast session context ID and is used to represent information about the group of UEs receiving multicast flows with the same multicast session context ID. Multicast session context is common to all UEs receiving the corresponding multicast services. In one embodiment, shared tunnel 351 is established between tunnel 321 of base station 320 and tunnel 331 of UPF 330. In one embodiment, multicast radio bearer is established for the multicast service to UE 310. Tunnel 351 is a PTM GPRS tunneling protocol (GTP) -user plane (GTP-U) tunnel. The multicast service to UE 301 can also use unicast radio bearer, where tunnel 351 is a PTP GTP-U tunnel. Multicast flows within one multicast session context use the same shared tunnel between the UPF entity and the gNB. At the gNB, the multicast flow identifier maps to a radio bearer. In one embodiment, if the QoS characteristics of multicast flows allow, the gNB maps several multicast flows within a multicast session context to one radio bearer.

Figure 4 illustrates exemplary mapping relations between PDU session and multicast radio bearer for 5G MBS transmission in accordance with embodiments of the current invention. Three UEs, UE1 401, UE2 402, and UE3 403, receive one or more multicast services in the NR wireless network. UE1 401, UE2 402, and UE3 403 each has one or more corresponding PDU sessions, PDU session-UE1 405, PDU session-UE2 406, and PDU session-UE3 407, respectively. UE1 has two PDU sessions, PDU session-A 411, and PDU-session-B 412. UE2 has two PDU sessions, PDU session-C 413, and PDU-session-D 414. UE3 has one PDU session, PDU session-E 415. One or more UE PDU sessions map to one multicast session. Multicast session-1 421 is common or shared by UE1 401, UE2 402, and UE3 403. PDU session-A 411, PDU-session-C 413, and PDU session-E 415 map to multicast session-1 421. Multicast session-2 422 is common or shared by UE1 401, and UE2 402. PDU session-B 412, and PDU-session-D 414 map to multicast session-2 422.

In one embodiment, one multicast session has one or moremulticast flows. Multicast session-1 421 has two multicast

flows

431 and 432. Multicast session-2 422 has three multicast

flows

434, 435, and 436. In one embodiment, one multicast session includes different PDU session with different number of multicast flows. For example, PDU session-B 412 mapped to multicast session-2 422has different multicast flows than PDU session-D 414. The characteristics of PDU session-B 412 may be the same as PDU session-D or be different from PDU session-D 414. Multicast flows are mapped by gNB to radio bearers including both point-to-point (PTP) RBs (i.e. unicast RB) and point-to-multipoint (PTM) RBs (MRBs) . Flow to RB mapping 441 maps multicast flow-1 431 and multicast flow-2 432 to RB-1 451, which is a multicast RB. RB-1 451 is transmitted over the air interface via PTM transmission to UE1 401, UE2 402, and UE3 403. Flow to RB mapping 442 maps multicast flow-X 434 and multicast flow-Y 435 to RB-2 453, which is a multicast RB, transmitted over the air interface via PTM transmission to UE1 401 and UE2 402. Multicast flow-Z 436 is mapped to two unicast RBs, RB-3 455 via PTP to UE1 401 and RB-4 456 via PTP to UE2 402.

Figure 5A illustrates an exemplary flow diagram for the multicast radio bearer establishment for 5G MBS transmission in accordance with embodiments of the current invention. A UE 501 receives one or more multicast services in a NR wireless network through a base station/gNB 502 and network entities 503. At step 510, the content provider announces the availability of multicast using higher layer (e.g. application layer) . The announcement includes at least a multicast address of multicast group that UE can join. At step 511, UE 501 registers in the PLMN and requests the establishment of a PDU session for unicast service or 5G MBS service. At step 512, UE 501 joins a multicast group via user plane signaling or control plane signaling. At step 521, a network entity of 5GC 503 sends a message for the multicast service to gNB 502. In one embodiment, step 521 sends a Multicast Session Establishment message or a Modification Request over the N2 interface to gNB 502. The message includes UE information and multicast related information. Multicast related information includes multicast session context ID, multicast group identity, and/or multicast flow information such as multicast QoS Flow ID (s) and associating QoS information. UE information may include one or multiple UE (s) that join the multicast group corresponding to the multicast session. In one embodiment, a list of PDU Session IDs identifying one or more PDU sessions that map to the multicast session for the UE is also included in the message. In one embodiment, the security configuration of the multicast session is also included in the multicast session establishment message.

At step 522, gNB 502 uses UE information and multicast related information to determine that the session establishment or modification procedures of one or more UEs correspond to one particular multicast group. gNB 502 determines which UEs intend to receive the same multicast service.gNB 502 determineswhether to use a PTM MRB for the upcoming multicast data transmission. When gNB 502 decides to use PTM MRB to transmit the upcoming multicast data of the established or modified multicast session, gNB 502 reconfigures an existing PTM MRB or configures a new PTM MRB to transmit the upcoming multicast data. When gNB 502 decides to use unicast RB to transmit the upcoming multicast data of the established or modified multicast session to one or a plural of UE (s) , gNB 502 reconfigures an existing unicast RB or configures a new unicast RB to transmit the upcoming multicast data for each UE in the multicast group within the coverage of gNB 502.

At step 531, gNB 502 sends a RRC message e.g. RRC Reconfiguration to the UE to perform RB configuration or reconfiguration to prepare the transmission of the multicast data corresponding to the established or modified multicast session. gNB 502 configures the PHY, MAC, RLC, PDCP and/or SDAP configurations to the UE for multicast data transmission.

In one embodiment, gNB 502 is configured with the necessary security configuration for a particular multicast session according to the interaction between gNB 502 and CN in 5GC 503. gNB 502 interacts with UE 501 to add the additional cipher and/or integrity configuration to the UE context specific to the multicast data corresponding to the multicast session. The security configuration of a particular multicast session can be UE or non-UE specific. In case of non-UE specific, it can be session, cell, or RB specific. gNB 502 derives the security key at the AS layer via the session ID, cell ID or RB ID based on a general security key setting specific to one multicast session defined by NAS layer. UE 501 gets the general security key setting via NAS message interaction with the 5GC before the establishment of multicast session. During RRC Reconfiguration, the specific security key setting specific to the multicast data is activated for the RB for transmitting themulticast data corresponding to one multicast session. In one embodiment, during the RRC Reconfiguration, gNB 502 notifiesUE 501 the additional parameters used to derive the AS layer security key. The said security key includes both cipher key and integrity key for RB.

Upon receiving the RRC message, such as the RRC reconfiguration message, UE 501 establishes one SDAP entity for each multicast session. One or more PDCP entities are established based on the number of RBs used to deliver the multicast data for the multicast session. The number of RBs used are determined by gNB 502. The corresponding SDAP entity can be modified if it is a modified message within RRC Reconfiguration. One or more new PDCP entitiesare established if the established or modified multicast session message within RRC Reconfiguration requires establishing new RB (s) following the gNB decision. This principle applies to both PTM RB and PTP RB. UE 501 is scheduled by a multicast RNTI at PDCCH to receive multicast control information including group RNTI (G-RNTI) for PTM RB. UE 501 is scheduled by a G-RNTI to receive traffic of PTM RB.According to the RRC Reconfiguration message received, UE 501, in the AS layer, creates and maintains one or more mappings including the mapping relationship between PDU session and Multicast session, the mapping relationship between Multicast session and multicast flow, the mapping relationship multicast flow and RB for the established or modified multicast session. The relationship helps the UE to find the right flow, the multicast session, and/or the PDU session a multicast data PDU is received from PDCP entity. At step 532, in response to the RRC Reconfiguration message, UE 501 sends RRC reconfiguration complete message to gNB 502.

At step 533, gNB 502 sends multicast establishment response or modification response message to 5GC 503 via N2 interface. At step 541, 5GC 503 entity starts multicast data transmission to gNB 502. At step 551, gNB 502 selects corresponding established RBs for the received multicast data from 5GC 503 entity. At step 552, gNB 502 transmits the multicast data to the corresponding one or more UEs through the established PTP RB or PTM RB. For a particular UE, one or multiple PDU session (s) can be mapped to one multicast session and one multicast session is mapped to one SDAP entity. In one embodiment, there is a need to put an identity of the PDU session into the header of the multicast data by the network in order for the UE classify the data when delivering the data to PDU session level. The identity information can be put into the IP header or SDAP header of the DL multicast data PDU.

In one embodiment, one or more SDAP entities are established at the base station for multicast services. There are different cases for the establishment of corresponding PDCP and SDAP entities.

Figure 5B illustrates exemplary diagrams of information structures for the radio bearer establishment during the setup procedure in accordance with embodiments of the current invention. In one embodiment, the PTM MRB is established for the multicast service. In another embodiment, PTP RB, or the unicast RB, is established for the multicast service. The selected RB configuration is sent to the UE by the base station in an RRC message. In one embodiment, RRC reconfiguration message 560 is sent to the UE to configure and establish the RB for the multicast service. If gNB determines to use a PTM MRB to transmit the upcoming Multicast data, the the existing RadioBearerConfig structurewithin RRC Reconfiguration message, or a new defined MulticastRadioBearerConfig structure in theRRC Reconfiguration message560 is used to hold all of the RB configuration for multicast. RadioBearerConfig structure includes a RadioBearerConfigsub structure 561 and multicast sub structure 580. MulticastRadioBearerConfig structure includes a MulticastRadioBearerConfig sub structure 562 and multicast sub structure 580. Multicast sub structure 580 includes one or more structures including DRB-ToAdd 581, Multicast-securityConfig 582. If the existing RadioBearerConfig structureis used to express the multicast RB configuration, RadioBearerConfigsub structure 561 includes one or more additional fields, such asmulticast RB indicator, index of multicast RB, multicast group, multicast session context ID. RadioBearerConfigsub structure 561 distinguishesmulticast RB from normal RBand distinguishes different multicast RBs for different multicast sessions. If a new defined MulticastRadioBearerConfig structure is used to express the multicast RB configuration, MulticastRadioBearerConfigsub structure 562 includes one or more additional fields, such as index of multicast RB, multicast session context ID. MulticastRadioBearerConfig sub structure 562 distinguishes different multicast RBs for each multicast session. In one embodiment, the existing RadioBearerConfig structure or newly defined MulticastRadioBearerConfig structure used to configure multicast RB (s) includes one or moreof DRB-ToAddMod structure 581 and Multicast-securityConfig structure 582. The DRB-ToAddMod structure 581 includes Multicast-SDAP-Config 591, Multicast-DRB-Identity, Multicast-PDCP-Config, etc. In one embodiment, Multicast-securityConfig structure 582 within the RB configuration for multicast data requires that separate security configuration applies to multicast data from unicast data for the UE. Alternatively, the Multicast-securityConfig structure is put into the DRB-ToAddMod structure 581. In this case, different security configuration applies to different multicast RB. The set of multicast RB serving the same multicast session can use the same Multicast-securityConfig. All UEs that join the multicast group use the same Multicast-securityConfig for the corresponding multicast session. The Multicast-PDCP-Config structure, legacy fields of PDCP-Config structure are adopted with only DL information elements included. Specific to ROHC configuration, unidirectional mode (U-mode) is adopted. The Multicast-SDAP-Config structure 591 includes the information elements of Multicast-SessionID, sdap-HeaderDL, mappedQoS-FlowsToAdd, mappedQoS-FlowsToRelease, or any combination among them. The information elements sdap-HeaderDL, mappedQoS-FlowsToAdd and mappedQoS-FlowsToRelease follow the legacy configuration for uncast. The Multicast-SessionID is the multicast session context ID, or other identical ID (e.g. multicast group ID) that identifies the multicast session or multicast group. In one embodiment, the information element PDU-SessionID-List is also included in Multicast-SDAP-Config structure. The PDU-SessionID-List identifies one or a plural of PDU Sessions that map to the multicast session for the UE. gNB 502 receives the information of PDU session ID list mapped to the multicast session in step 521. If gNB decides to use a unicast RB /PTP RB to transmit the upcoming multicast data, the similar principle of the configuration of PTM RB is adopted with the following difference. First, the gNB delivers the PTP data via dedicated physical resources. Second, this special PTP RB to deliver multicast data can use UE specific security configuration or a common security configuration as PTM RB during PDCP layer handling, as required by upper layer. When multiple PTP RB between gNB and UE is established to transmit the multicast data corresponding to one multicast session, the common or different security configuration is used.

Figure 6 illustrates exemplary diagrams for SDAP and PDCP model for one multicast session of 5G MBS transmission in accordance with embodiments of the current invention. In one embodiment, the base station /gNB establishes one SDAP entity for each multicast session. The SDAP is shared for all UEs joining the multicast group corresponding to the multicast session. One or more PDCP entities are established for the corresponding one SDAP entity to deliver the multicast data for DL transmission. The number of PDCP entities depends on the number of RBs determined by the gNB to transmit the multicast flows within the multicast session.

In one embodiment 610, one SDAP entity 611 and one PDCP entity 615 are established to deliver the data of the Multicast flows within the multicast session 601. A shared RB, the PTM RB, transmits the multicast flows 613 within the multicast session 601. In one embodiment 620, one SDAP entity 621 and two PDCP entities 625 and 626 are established to deliver the data of the multicast flows 623 and 624 within the multicast session 602. Two shared RBs, the PTM RBs, transmit the multicast flows within the multicast session 602 with each shared RB carrying different multicast QoS flows with different QoS characteristics. In one embodiment 630, one SDAP entity 631 and one PDCP entity 633 are established to deliver the data of the multicast flows 633 within the multicast session 603. One unicast RB, the PTP RB, transmits the multicast flows within the multicast session to the UE. This means only one UE joined the multicast group. In one embodiment 640, one SDAP entity 641 and two

PDCP entities

645 and 646 are established to deliver the data of the multicast flows 643 and 544 within the multicast session 604. Two unicast RBs, the PTP RB, transmit the multicast flows within the multicast session to the UE. Two UEs joined the multicast group.

In one embodiment, the gNB establishes the number N of entities for both SDAP and PDCP when the gNB uses unicast RBs to transmit the multicast flows within the multicast session. The number N of SDAP/PDCP entities to be established depends on the number of unicast RBsdetermined by the gNB to transmit the multicast flows within the multicast session. In one embodiment 650, two

SDAP entities

651 and 652 and two

PDCP entities

655 and 656 are established to deliver the data of the multicast flows 653 and 654 within the multicast session 605. Two unicast RBs, the PTP RBs, transmits the multicast flows within the multicast session to the UE. Two UEs joined the multicast group.

Figure 7 illustrates an exemplary flow chart for the UE to perform the radio bearer establishment for multicast services in the NR wireless network. At step 701, the UE receives a multicast configuration for one or more multicast sessions from a 5G core (5GC) entity in a wireless network. At step 702, the UE establishes one or more corresponding radio bearers with a base station for each of the one or more multicast sessions, wherein each radio bearer is a multicast radio bearer or a unicast radio bearer. At step 703, the UE establishes one service data adaptation protocol (SDAP) entity for each multicast session based on the multicast configuration. At step 704, the UE receives multicast data for each of the one or more multicast sessions.

Figure 8 illustrates an exemplary flow chart for the base station to perform the radio bearer establishment for multicast services in the NR wireless network. At step 801, the base station sends a multicast configuration to configure one or more multicast sessions to a user equipment (UE) in a wireless network. At step 802, the base station establishes a multicast configuration to configure one or more multicast sessions to a user equipment (UE) in a wireless network. At step 803, the base station establishes one or more service data adaptation protocol (SDAP) entities for each multicast session based on a multicast configuration from a 5G core (5GC) entity of the wireless network. At step 804, the base station transmits multicast data for each of the one or more multicast sessions.

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

Claims

A method comprising:

receiving, by a user equipment (UE) , a multicast configuration for one or more multicast sessions from a 5G core (5GC) entity in a wireless network;

establishingone or more corresponding radio bearers with a base station for each of the one or more multicast sessions, wherein each radio bearer is a multicast radio bearer or a unicast radio bearer;

establishing one service data adaptation protocol (SDAP) entity for each multicast session based on the multicast configuration; and

receiving multicast data for each of the one or more multicast sessions.
The method of claim 1, wherein the multicast configuration is carried in a radio resource control (RRC) message.
The method of claim 2, wherein the RRC message carrying the multicast configuration is an RRC Reconfiguration message that includes one configuration structure selecting from a RadioBearerConfig and a MulticastRadioBearerConfig, and wherein the configuration structure comprising one or more DRB-ToAddMod structure and Multicast-securityConfig structure.
The method of claim 3, wherein the Multicast-securityConfig structure is common to all multicast radio bearers serving a same multicast session.
The method of claim 3, wherein the Multicast-securityConfig structure is common to all UEs joining a same multicast group corresponding to one multicast session.
The method of claim 3, wherein the DRB-ToAddMod structure includes a Multicast-PDCP-Config structure and a Multicast-SDAP-Config structure.
The method of claim 6, wherein the Multicast-SDAP-Config includes one or more information elements comprising a Multicast-SessionID, an sdap-HeaderDL, a mappedQoS-FlowsToAdd, and a mappedQoS-FlowsToRelease.
A method comprising:

sending, by a base station, a multicast configuration to configure one or more multicast sessions to a user equipment (UE) in a wireless network;

establishing one or more corresponding radio bearers for each of the one or more multicast sessions, wherein each radio bearer is a multicast radio bearer or a unicast radio bearer;

establishing one or more service data adaptation protocol (SDAP) entities for each multicast session based on a multicast configuration from a 5G core (5GC) entity of the wireless network; and

transmitting multicast data for each of the one or more multicast sessions.
The method of claim 8, wherein a multicast radio bearer is established for a first multicast session, and wherein one service data adaptation protocol (SDAP) entity is established for the first multicast session.
The method of claim 8, wherein N number of unicast radio bearers are established for a first multicast session, and wherein N number of SDAP entities are established for the first multicast session.
The method of claim 8, wherein the multicast configuration is carried in a radio resource control (RRC) message.
The method of claim 11, wherein the RRC message carrying the multicast configuration is an RRC Reconfiguration message that includes one configuration structure selecting from a RadioBearerConfig and a MulticastRadioBearerConfig, and wherein the configuration structure comprising one or more DRB-ToAddMod structure and Multicast-securityConfig structure.
The method of claim 12, wherein the DRB-ToAddMod structure includes a Multicast-PDCP-Config structure and a Multicast-SDAP-Config structure.
A user equipment (UE) , comprising:

a transceiver that transmits and receivesradio frequency (RF) signal in a new radio (NR) wireless network;

a configuration module that receives a multicast configuration for one or more multicast sessions from a 5G core (5GC) entity in the wireless network;

a radio bearer module that establishes one or more corresponding radio bearers with a base station for each of the one or more multicast sessions, wherein each radio bearer is a multicast radio bearer or a unicast radio bearer;

a service data adaptation protocol (SDAP) module that establishes one SDAP entity for each multicast session based on the multicast configuration; and

a multicast module that receives multicast data for each of the one or more multicast sessions.
The UE of claim 14, wherein the multicast configuration is carried in a radio resource control (RRC) message.
The UE of claim 15, wherein the RRC message carrying the multicast configuration is an RRC Reconfiguration message that includes one configuration structure selecting from a RadioBearerConfig and a MulticastRadioBearerConfig, and wherein the configuration structure comprising one or more DRB-ToAddMod structure and Multicast-securityConfig structure.
The UE of claim 16, wherein the Multicast-securityConfig structure is common to all multicast radio bearers serving a same multicast session.
The UE of claim 16, wherein the Multicast-securityConfig structure is common to all UEs joining a same multicast group corresponding to one multicast session.
The UE of claim 16, wherein the DRB-ToAddMod structure includes a Multicast-PDCP-Config structure and a Multicast-SDAP-Config structure.
The UE of claim 19, wherein the Multicast-SDAP-Config includes one or more information elements comprising a Multicast-SessionID, an sdap-HeaderDL, a mappedQoS-FlowsToAdd, and a mappedQoS-FlowsToRelease.