WO2022082340A1

WO2022082340A1 - Methods and apparatus to deliver reliable multicast services via mrb

Info

Publication number: WO2022082340A1
Application number: PCT/CN2020/121791
Authority: WO
Inventors: Yuanyuan Zhang; Xuelong Wang
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2020-10-19
Filing date: 2020-10-19
Publication date: 2022-04-28
Also published as: CN114390447A; CN114390447B

Abstract

This disclosure describes methods and apparatus to deliver multicast services via MRB. A particular radio bearer called MRB is introduced, which is associated to a multicast logical channel and a unicast logical channel to enhance the reliability. The procedures to control the MRB is required to perform MRB establishment, reconfiguration and release. UE initiates the MRB establishment, reconfiguration and release when the corresponding events occur.

Description

METHODS AND APPARATUS TO DELIVER RELIABLE MULTICAST SERVICES VIA MRB

TECHNICAL FIELD

The present disclosure relates generally to communication systems, and more particularly, the method to support reliable multicast service delivery via MRB from the wireless network to the UEs.

BACKGROUND

Various cellular systems, including both 4G/LTE and 5G/NR systems, may provide a multicast functionality, which allows user equipments (UEs) in the system to receive multicast services transported by the cellular system. A variety of applications may rely on communication over multicast transmission, such as live stream, video distribution, vehicle-to-everything (V2X) communication, public safety (PS) communication, file download, and so on. In some cases, there may be a need for the cellular system to enable reliable multicast transmission in order to ensure the reception quality at the UE side. In these cases, it may be beneficial for the receiving UE to provide the feedback on its reception of the multicast transmission, which helps the network to perform necessary retransmission of the content to the UE. A particular radio bearer (RB) should be introduced to deliver the multicast services to UE.

In this invention, apparatus and mechanisms are sought to establish, (re) configure and release the particular RB in order to support the reliable delivery for the multicast services, especially when UE moves among difference cell to guarantee the service continuity.

SUMMARY

The following presents a simplified summary of one or more aspects in order to provide a basic understanding of such aspects. This summary is not an extensive overview of all contemplated aspects, and is intended to neither identify key or critical elements of all aspects nor delineate the scope of any or all aspects. Its sole purpose is to present some concepts of one or more aspects in a simplified form as a prelude to the more detailed description that is presented later.

In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The apparatus may be a UE. The UE applies the MRB establishment procedure to start receiving a session of a multicast service. UE establish/add a MRB when one or more of the establishment conditions is met. The UE applies the MRB reconfiguration procedure to switch the transmission mode (i.e. PTM, PTP or PTM+PTP) for the on-going session of a multicast service. UE reconfigure/modify a MRB when one or more of the reconfiguration conditions is met. The UE applies the MRB release procedure to stop receiving a session. UE release/remove the MRB when one or more of the release conditions is met.

In MRB establishment procedure, for PDCP-based retransmission to enhance the reliability, UE establishes a PDCP entity for the MRB. UE establishes one or two RLC entities and configures two logical channel MTCH and DTCH for the MRB. UE configures the MAC entity to map MTCH to MCH and map DTCH to DL-SCH. For RLC-based retransmission for reliability enhancement, UE establishes a PDCP entity and a particular RLC entity for the MRB. The RLC entity is associated to one or two logical channels. For MAC-based retransmission for reliability enhancement, UE establishes a PDCP entity and a RLC entity for the MRB. UE configures the MAC entity to map MTCH to MCH and map DTCH to DL-SCH.

In MRB reconfiguration procedure, for PDCP-based retransmission to enhance the reliability, UE reconfigures the PDCP entity for MRB and performs RLC bearer addition/modification. For RLC-based retransmission for reliability enhancement, UE reconfigures the PDCP entity for MRB and performs RLC bearer reconfiguration. For MAC-based retransmission, UE reconfigures the PDCP entity for MRB and performs RLC bearer addition/modification. UE configures MAC entity for the logical channel.

In MRB release procedure, for PDCP-based retransmission to enhance the reliability, UE release the PDCP entity for MRB and release the one or two RLC entities. For RLC-based retransmission, UE release the PDCP entity for MRB and release the RLC entity and logical channels. For MAC-based retransmission, UE release the PDCP entity for MRB and release the RLC entity. UE release the MAC configuration for the MRB.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed, and this description is intended to include all such aspects and their equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 illustrates a schematic system diagram illustrating an exemplary wireless network in accordance with embodiments of the current invention.

Figure 2 illustrates an exemplary NR wireless system with centralization of the upper layers of the NR radio stacks in accordance with embodiments of the current invention.

Figure 3 illustrates an exemplary Multicast radio bearer (MRB) in accordance with embodiments of the current invention.

Figure 4 illustrates an exemplary protocol stack for a MRB with PDCP-based retransmission in accordance with embodiments of the current invention.

Figure 5 illustrates an exemplary protocol stack for a MRB with RLC-based retransmission in accordance with embodiments of the current invention.

Figure 6 illustrates an exemplary protocol stack for a MRB with MAC-based retransmission in accordance with embodiments of the current invention.

Figure 7 illustrates exemplary configurations for a MRB for different retransmission schemes in accordance with embodiments of the current invention.

Figure 8 illustrates an exemplary flowchart to control the MRB in accordance with embodiments of the current invention.

Figure 9 illustrates the exemplary flowcharts to establish/add a MRB for different retransmission schemes in accordance with embodiments of the current invention.

Figure 10 illustrates the exemplary flowcharts to reconfigure/modify a MRB for different retransmission schemes in accordance with embodiments of the current invention.

Figure 11 illustrates the exemplary flowcharts to release/remove a MRB for different retransmission schemes in accordance with embodiments of the current invention.

Figure 12 illustrates an exemplary flowchart to perform MRB reconfiguration during RRC state transmission from IDLE/INACTIVE to CONNECTED in accordance with embodiments of the current invention.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATIONS

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of telecommunication systems will now be presented with reference to various apparatus and methods. These apparatus and methods will be described in the following detailed description and illustrated in the accompanying drawings by various blocks, components, circuits, processes, algorithms, etc. (collectively referred to as “elements” ) . These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

Aspects of the present disclosure provide methods, apparatus, processing systems, and computer readable mediums for NR (new radio access technology, or 5G technology) or other radio access technology. NR may support various wireless communication services. These services may have different quality of service (QoS) requirements e.g. latency and reliability requirements.

Figure 1 illustrates a schematic system diagram illustrating an exemplary wireless network in accordance with embodiments of the current invention. Wireless system 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, a gNB, or by other terminology used in the art. As an example, base stations serve a number of mobile stations within a serving area, for example, a cell, or within a cell sector. In some systems, one or more base stations are coupled to a controller forming an access network that is coupled to one or more core networks. gNB 1and gNB 2 are base stations in NR, the serving area of which may or may not overlap with each other. As an example, UE1 or mobile station is only in the service area of gNB 1 and connected with gNB1. UE1 is connected with gNB1 only, gNB1 is connected with gNB 102 via Xn interface. UE2 is in the overlapping service area of gNB1 and gNB2. In one embodiment, both gNB1 and gNB2 provide the same MBMS services, service continuity during handover is guaranteed when UE 2 moves from gNB1 to gNB2 and vice versa.

Figure 1 further illustrates simplified block diagrams for UE2 and gNB2, respectively. UE has an antenna, which transmits and receives radio signals. A RF transceiver, coupled with the antenna, receives RF signals from antenna, converts them to baseband signal, and sends them to processor. In one embodiment, the RF transceiver may comprise two RF modules (not shown) . A first RF module is used for transmitting and receiving on one frequency band, and the other RF module is used for different frequency bands transmitting and receiving which is different from the first transmitting and receiving. RF transceiver also converts received baseband signals from processor, converts them to RF signals, and sends out to antenna. Processor processes the received baseband signals and invokes different functional modules to perform features in UE. Memory stores program instructions and data to control the operations of mobile station. UE also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention.

A RRC State controller, which controls UE RRC state according to network’s command and UE conditions. RRC supports the following states, RRC_IDLE, RRC_CONNECTED and RRC_INACTIVE. In one embodiment, UE can receive the broadcast services in RRC_IDLE/INACTIVE state. The UE applies the MRB establishment procedure to start receiving a session of a service it has an interest in. The UE applies the MRB release procedure to stop receiving a session.

A MRB controller, which controls to establish/add, reconfigure/modify and release/remove a MRB based on different sets of conditions for MRB establishment, reconfiguration and release. A protocol stack controller, which manage to add, modify or remove the protocol stack for the MRB. The protocol Stack includes RLC, MAC and PHY layers. In one embodiment, the SDAP layer is optionally configured.

In one embodiment, the PDCP layer supports the functions of transfer of data, maintenance of PDCP SN, header compression and decompression using the ROHC protocol, ciphering and deciphering, integrity protection and integrity verification, timer based SDU discard, routing for split bearer, duplication, re-ordering and in-order delivery; out of order delivery and duplication discarding.

In one embodiment, the RLC layer supports the functions of error correction through ARQ, segmentation and reassembly, re-segmentation, duplication detection, re-establishment, etc. In one embodiment, a new procedure for RLC reconfiguration is performed, which can reconfigure the RLC entity to associated to one or two logical channels.

In one embodiment, the MAC layer supports the following functions: mapping between logical channels and transport channels, multiplexing/demultiplexing, HARQ, radio resource selection, etc.

Similarly, gNB2 has an antenna, which transmits and receives radio signals. A RF transceiver, coupled with the antenna, receives RF signals from antenna, converts them to baseband signals, and sends them to processor. RF transceiver also converts received baseband signals from processor, converts them to RF signals, and sends out to antenna. Processor processes the received baseband signals and invokes different functional modules to perform features in gNB2. Memory stores program instructions and data to control the operations of gNB2. gNB2 also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention.

A RRC State controller, which performs access control for the UE.

Figure 2 illustrates an exemplary NR wireless system with centralization of the upper layers of the NR radio stacks in accordance with embodiments of the current invention. Different protocol split options between Central Unit and lower layers of gNB nodes may be possible. The functional split between the Central Unit and lower layers of gNB nodes may depend on the transport layer. Low performance transport between the Central Unit and lower layers of gNB nodes can enable the higher protocol layers of the NR radio stacks to be supported in the Central Unit, 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 central unit, while RLC, MAC and PHY layers are located in the distributed unit.

Figure 3 illustrates an exemplary Multicast radio bearer (MRB) in accordance with embodiments of the current invention. Multicast radio bearer provides multicast services, which is carried by MTCH, DTCH or both of MTCH and DTCH. In one embodiment, the MRB is configured to be associated to a MTCH. In one embodiment, the MRB is configured to be associated to a DTCH. In one embodiment, the MRB is configured to be associated to a MTCH and a DTCH. In one embodiment, the MRB is configured in PTM&PTP transmission mode. One or multiple multicast Radio Bearers (MRB) established corresponding to the multicast flows of a particular multicast session in order to support the multicast transmission in the downlink over the air. The multicast Radio Bearer (i.e. RB) can be subject to Point-to-Multiple Point (i.e. PTM) , Point-to-Point (i.e. PTP) transmission or combination of PTM and PTP transmission within a cell. In one embodiment, the MRB is configured in PTP transmission mode. In one embodiment, the MRB is configured in PTM mode. In one embodiment, the MRB is configured in PTM&PTP transmission mode.

The described invention operates in the context of multicast transmission in a cellular system. In certain systems, such as NR systems, NR multicast/broadcast is transmitted in the coverage of a cell. In one embodiment, MCCH provides the information of a list of NR multicast/broadcast services with ongoing sessions transmitted on MTCH (s) . At physical layer, MTCH is scheduled by gNB in the search space of PDCCH with G-RNTI scrambled. UE decodes the MTCH data for a multicast session in the multicast PDSCH.

In legacy system supporting MBMS/eMBMS, the radio bearer structure for multicast and broadcast transmission is modelled in an independent way from unicast transmission. Because of the unidirectional transmission for legacy MBMS/eMBMS service, RLC UM node is used for the transmission of multicast/broadcast session. In this case there is no need to make the interaction between multicast and unicast for a particular UE which is in RRC Connected state.

There is a clear requirement on the reliable transmission for NR multicast services. But the characteristics of multicast transmission does not allow the network to ensure all the UEs to make successful reception for the services. Otherwise, the network should apply very conservative link adaptation, which may impact the radio resource utilization efficiency.

In order to support the reliable transmission for NR multicast service, a feedback channel in the uplink is needed for each UE receiving the service, which can be used by the receiving UE to feedback its reception status about the service to the network. Based on the feedback, the network may perform necessary retransmission to improve the transmission reliability. From uplink feedback perspective, the feedback channel may be used for L2 feedback (e.g. RLC Status Report and/or PDCP Status Report) . In addition, the feedback channel may be used for HARQ feedback. Furthermore, the feedback should be a bidirectional channel between the UE and the network, with the assumption that the network may take that channel to perform needed packet retransmission. The said packet retransmission is L2 retransmission (e.g. RLC retransmission and/or PDCP retransmission) . In addition, the feedback channel may be used for HARQ retransmission.

Figure 4 illustrates an exemplary protocol stack for a MRB with PDCP-based retransmission in accordance with embodiments of the current invention. There is one PDCP entity per MRB. Two logical channels, i.e. MTCH and DTCH are associated to the PDCP entity. Each logical channel is corresponding to a RLC entity. From UE aspect, the PDCP status report to trigger PDCP retransmission is delivered to the RLC entity corresponding to DTCH. From network aspect, the PDCP PDUs subject to retransmission is delivered through DTCH. The MAC entity maps the logical channel MTCH to the transport channel MCH and maps the logical channel DTCH to the transport channel DL-SCH. UE monitors two independent transport channels via different RNTIs. The ROHC function and security function is optional for multicast transmission. The RLC layer includes only segmentation and the ARQ function of RLC layer is moved to PDCP layer.

Figure 5 illustrates an exemplary protocol stack for a MRB with RLC-based retransmission in accordance with embodiments of the current invention. There is one PDCP entity and one RLC entity per MRB. Each RLC entity is associated to two logical channels, i.e. MTCH and DTCH. From UE aspect, the RLC status report to trigger RLC retransmission is delivered through DTCH. From network aspect, the RLC PDUs subject to retransmission is delivered through DTCH. The MAC entity maps the logical channel MTCH to the transport channel MCH and maps the logical channel DTCH to the transport channel DL-SCH. UE monitors two independent transport channels via different RNTIs.

Figure 6 illustrates an exemplary protocol stack for a MRB with MAC-based retransmission in accordance with embodiments of the current invention. There is one PDCP entity and one RLC entity per MRB. Each RLC entity is associated to one logical channel, i.e. MTCH. The MAC entity maps the logical channel MTCH to MCH and DL-SCH. MCH is used for initial transmission and optionally retransmission. DL-SCH is used for retransmission of the TBs. From UE aspect, the HARQ feedback to trigger HARQ retransmission is delivered through UL-SCH. From network aspect, the TBs subject to retransmission is delivered through DL-SCH. UE monitors two independent transport channels via different RNTIs.

Figure 7 illustrates exemplary configurations for a MRB for different retransmission schemes in accordance with embodiments of the current invention. For PDCP-based retransmission to enhance the reliability, in one embodiment, the MRB is configured with one RLC entity, associated to MTCH; in one embodiment, the MRB is configured with one RLC entity, associated to DTCH; in one embodiment, the MRB is configured with two RLC entities, associated to MTCH and DTCH respectively. For RLC-based retransmission to enhance the reliability, in one embodiment, the RLC entity of the MRB is associated to MTCH; in one embodiment, the RLC entity of the MRB is associated to DTCH; in one embodiment, the RLC entity of the MRB is associated to two logical channels, i.e. MTCH and DTCH. For MAC-based retransmission to enhance the reliability, in one embodiment, the MAC entity maps MTCH to MCH; in one embodiment, the MAC entity maps MTCH to DL-SCH; in one embodiment, the MAC entity maps MTCH to both MCH and DL-SCH.

Figure 8 illustrates an exemplary flowchart to control the MRB in accordance with embodiments of the current invention. The UE applies the MRB establishment procedure to start receiving a session of a multicast service. UE establish/add a MRB when one of the establishment conditions is met. The establishment conditions contain at least the following events:

● upon start of the multicast session,

● upon (re-) entry of the corresponding multi-cast service area, which is one cell or multiple cells,

● upon becoming interested in the multicast service,

● upon reception of a command to establish/add the MRB.

The UE applies the MRB reconfiguration procedure to switch the transmission mode (i.e. PTM, PTP or PTM+PTP) for the on-going session of a multicast service. UE reconfigure/modify a MRB when one of the reconfiguration conditions is met. The reconfiguration conditions contain at least the following events:

● upon state transition from IDLE/INACTIVE to CONNECTED;

● upon reception of a command to modify/reconfigure the MRB.

The UE applies the MRB release procedure to stop receiving a session. UE release/remove the MRB when one of the release conditions is met. The release conditions contain at least the following events:

● upon stop of the multicast session,

● upon leaving the corresponding multi-cast service area, which is one cell or multiple cells,

● upon losing interest in the multicast service,

● upon reception of a command to release/remove the MRB,

● upon state transition from CONNECTED to IDLE/INACTIVE.

Figure 9 illustrates the exemplary flowcharts to establish/add a MRB for different retransmission schemes in accordance with embodiments of the current invention. For PDCP-based retransmission for reliability enhancement, UE establishes a PDCP entity for the MRB. In one embodiment, UE establishes an RLC entity and configures an MTCH logical channel for the MRB; in one embodiment, UE establishes an RLC entity and configures a DTCH logical channel for the MRB; in one embodiment, UE establishes two RLC entities and configures two logical channel MTCH and DTCH for the MRB. UE configures the MAC entity to map MTCH to MCH and map DTCH to DL-SCH.

For RLC-based retransmission for reliability enhancement, UE establishes a PDCP entity and a particular RLC entity for the MRB. In one embodiment, UE establishes an RLC entity and configures an MTCH logical channel for the MRB; in one embodiment, UE establishes an RLC entity and configures a DTCH logical channel for the MRB; in one embodiment, UE establishes an RLC entity and configures two logical channel MTCH and DTCH for the MRB. UE configures the MAC entity to map MTCH to MCH and map DTCH to DL-SCH.

For MAC-based retransmission for reliability enhancement, UE establishes a PDCP entity and a RLC entity for the MRB. UE configures the MAC entity to map MTCH to both MCH and DL-SCH.

Figure 10 illustrates the exemplary flowcharts to reconfigure/modify a MRB for different retransmission schemes in accordance with embodiments of the current invention. For PDCP-based retransmission for reliability enhancement, UE reconfigures the PDCP entity for MRB according to the configuration, e.g. pdcp-config. UE performs RLC bearer addition/modification based on the configuration, e.g. RLC-BearerConfig. As a result, the PDCP entity is reconfigured as one of the following three options: one RLC entity for MTCH, one RLC entity for DTCH and two RLC entities for MTCH and DTCH respectively for the MRB. In other words, for MRB reconfiguration, the change between the three options is performed. UE associates the logical channel with the PDCP entity identified by servedRadioBearer if a logical channel with the given logicalChannelIdentity is not configured before. UE configures MAC entity for the logical channel according to the configuration, e.g. mac-LogicalChannelConfig.

For RLC-based retransmission for reliability enhancement, UE reconfigures the PDCP entity for MRB according to the configuration, e.g. pdcp-config. UE performs RLC bearer reconfiguration based on the configuration, e.g. RLC-BearerConfig. As a result, the RLC entity is associated to one or two logical channels, i.e. MTCH, DTCH or both DTCH and MTCH. For RLC reconfiguration, the change between the association to MTCH, DTCH and both MTCH and DTCH is performed. UE configures MAC entity for the logical channel according to the configuration, e.g. mac-LogicalChannelConfig.

For MAC-based retransmission for reliability enhancement, UE reconfigures the PDCP entity for MRB according to the configuration, e.g. pdcp-config. UE performs RLC bearer addition/modification based on the configuration, e.g. RLC-BearerConfig. UE configures MAC entity for the logical channel according to the configuration, e.g. mac-LogicalChannelConfig. As a result, the MAC entity is associated to one or two transport channels, i.e. MCH, DL-SCH or both MCH and DL-SCH.

Figure 11 illustrates the exemplary flowcharts to release/remove a MRB for different retransmission schemes in accordance with embodiments of the current invention. For PDCP-based retransmission for reliability enhancement, UE release a PDCP entity for the MRB. UE release one or two RLC entities and the associated logical channels. UE release the MAC configuration for the MRB. For RLC-based retransmission for reliability enhancement, UE release a PDCP entity for the MRB. UE release the RLC entity and the associated one or two logical channels. UE release the MAC configuration for the MRB. For MAC-based retransmission for reliability enhancement, UE release a PDCP entity for the MRB. UE release the RLC entity and the associated logical channel, i.e. MTCH. UE release the MAC configuration for the MRB.

Figure 12 illustrates an exemplary flowchart to perform MRB reconfiguration during RRC state transmission from IDLE/INACTIVE to CONNECTED in accordance with embodiments of the current invention. UE establishes a MRB in IDLE/INACTIVE for a multicast service. Then UE transfers to CONNECTED mode for the unicast services. UE sends the multicast interest indication to the network, informing which multicast service is on-going or it is interested in. UE receives the RRC reconfiguration message to reconfigure the MRB as a response to the interest indication.

It is understood that the specific order or hierarchy of blocks in the processes /flowcharts disclosed is an illustration of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of blocks in the processes /flowcharts may be rearranged. Further, some blocks may be combined or omitted. The accompanying method claims present elements of the various blocks in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more. ” The word “exemplary” is used herein to mean “serving as an example, instance, or illustration. ” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects. Unless specifically stated otherwise, the term “some” refers to one or more. Combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” include any combination of A, B, and/or C, and may include multiples of A, multiples of B, or multiples of C. Specifically, combinations such as “at least one of A, B, or C, ” “one or more of A, B, or C, ” “at least one of A, B, and C, ” “one or more of A, B, and C, ” and “A, B, C, or any combination thereof” may be A only, B only, C only, A and B, A and C, B and C, or A and B and C, where any such combinations may contain one or more member or members of A, B, or C. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. The words “module, ” “mechanism, ” “element, ” “device, ” and the like may not be a substitute for the word “means. ” As such, no claim element is to be construed as a means plus function unless the element is expressly recited using the phrase “means for. ”

While aspects of the present disclosure have been described in conjunction with the specific embodiments thereof that are proposed as examples, alternatives, modifications, and variations to the examples may be made. Accordingly, embodiments as set forth herein are intended to be illustrative and not limiting. There are changes that may be made without departing from the scope of the claims set forth below.

Claims

A method to control a UE to receive the multicast services with enhanced reliability via multicast radio bearer, wherein the MRB is associated to a unicast channel, a multicast channel or both a unicast channel and a multicast channel and the reliability is enhanced by PDCP-based, RLC-based or MAC-based retransmission through the unicast channel, comprising the steps of:

establishing one MRB when one or more of the establishment conditions are met;

reconfigure the MRB when one or more of the reconfiguration conditions are met;

releasing the MRB when one or more of the release conditions are met.
The method of claim 1, wherein the establishment conditions comprising at least following events: upon start of the multicast session, upon (re-) entry of the corresponding multi-cast service area, which is one cell or multiple cells, upon becoming interested in the multicast service, or upon reception of a command to establish/add the MRB.
The method of claim 1, wherein the reconfiguration conditions comprising at least following events: upon state transition from IDLE/INACTIVE to CONNECTED, or upon reception of a command to modify/reconfigure the MRB.
The method of claim 1, wherein the release conditions comprising at least following events: upon stop of the multicast session, upon leaving the corresponding multi-cast service area, which is one cell or multiple cells, upon losing interest in the multicast service, upon reception of a command to release/remove the MRB, or upon state transition from CONNECTED to IDLE/INACTIVE.
The method of claim 1, wherein establish on MRB for PDCP-based retransmission further comprising:

establishing a PDCP entity for the MRB;

establishing one or two RRC entities;

configuring MTCH, DTCH or both MTCH and DTCH;

configuring the MAC entity to map MTCH to MCH and map DTCH to DL-SCH.
The method of claim 1, wherein establish on MRB for RLC-based retransmission further comprising:

establishing a PDCP entity for the MRB;

establishing one RLC entity for the MRB;

configuring MTCH, DTCH or both MTCH and DTCH;

configuring the MAC entity to map MTCH to MCH and map DTCH to DL-SCH.
The method of claim 1, wherein establish on MRB for MAC-based retransmission further comprising:

establishing a PDCP entity for the MRB;

establishing one RLC entity for the MRB;

configuring MTCH;

configuring the MAC entity to map MTCH to MCH and DL-SCH.
The method of claim 1, wherein reconfigure the MRB for PDCP-based retransmission further comprising:

reconfiguring the PDCP entity for the MRB according to the PDCP configuration;

performing RLC bearer addition/modification;

configuring MAC entity for the logical channels MTCH, DTCH or both.
The method of claim 1, wherein reconfigure the MRB for RLC-based retransmission further comprising:

reconfiguring the PDCP entity for the MRB according to the PDCP configuration;

reconfiguring RLC entity, which changes the logical channel association;

configuring MAC entity for the logical channels MTCH, DTCH or both.
The method of claim 1, wherein reconfigure the MRB for MAC-based retransmission further comprising:

reconfiguring the PDCP entity for the MRB according to the PDCP configuration;

performing RLC bearer addition/modification;

configuring MAC entity to associate MTCH to MCH, DL-SCH or both.
The method of claim 1, wherein release the MRB for PDCP-based retransmission further comprising:

releasing the PDCP entity for the MRB;

releasing one or two RLC entities and the associated logical channels;

release the MAC configuration for the MRB.
The method of claim 1, wherein release the MRB for RLC-based retransmission further comprising:

releasing the PDCP entity for the MRB;

releasing the RLC entity for the MRB and the associated logical channels;

release the MAC configuration for the MRB.
The method of claim 1, wherein release the MRB for RLC-based retransmission further comprising:

releasing the PDCP entity for the MRB;

releasing the RLC entity for the MRB and MTCH;

release the MAC configuration for the MRB.
The method of claim 1, further comprising:

establishing a MRB in IDLE/INACTIVE state;

sending interest indication to network upon RRC state transition; and

reconfiguring the MRB based on the network configuration.