WO2021189307A1

WO2021189307A1 - Methods and apparatus of control information scheduling and modification notification for multicast and broadcast service

Info

Publication number: WO2021189307A1
Application number: PCT/CN2020/081157
Authority: WO
Inventors: Xuelong Wang
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2020-03-25
Filing date: 2020-03-25
Publication date: 2021-09-30
Also published as: WO2021190596A1

Abstract

Apparatus and methods are provided to support the scheduling and modification notification of the control information for Multicast and Broadcast Service (MBS). In one novel aspect, the control information for Multicast and Broadcast Service (MBS) is transmitted by multiple MCCHs each with independent MCCH notification cycle. The MCCH notification cycle is calculated based on scaling of cell specific MBS DRX cycle via a Scaling Factor. A MCCH DCI, with CRC scrambled by M-RNTI, schedules the MCCH. The MCCH DCI indicates that only scheduling information for MCCH transmission is present in the DCI. MCCH DCI includes one bit to indicate the modification of the MCCH information comparing with last MCCH Notification cycle at the boundary of MCCH notification Cycle. The UEs that are interested in a particular MBS service or MBS service group only monitors the Notification Frames according to the MCCH notification cycle configured for the MBS service or MBS service group. The configuration of the MBS parameters for MCCH reception for MBS services are transmitted by a MBS specific SIB, which carries MCCH information containing the MBS DRX configuration of the cell and one or a plural of MBS service or MBS service group.

Description

METHODS AND APPARATUS OF CONTROL INFORMATION SCHEDULING AND MODIFICATION NOTIFICATION FOR MULTICAST AND BROADCAST SERVICE

TECHNICAL FIELD

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to enable the scheduling and modification notification for the control information of Multicast and Broadcast Service.

BACKGROUND

3GPP specified the support for MBMS transmission with group scheduling, which is based on UMTS or EUTRAN technology. MBMS technology can be used to transmit both TV broadcast, video streaming, etc. In addition, the software update can be also based on the multicast or broadcast for some mobile devices e.g. IoT devices.

For both UMTS and EUTRAN, the traditional MBMS control information is carried by MCCH logical channel. The MCCH is transmitted with a fixed Repetition Period within a Modification Period. The MCCH is repeated at each Repetition Period within a Modification Period. The Modification Period is a multiple of the Repetition Period. Changes in MCCH information is only performed at the boundary of Modification Period and is not performed in the middle of a modification period.

In LTE based MBMS transmission, the change notification of the MBMS control information is sent in the first subframe in a Repetition Period where the SC-MCCH can be scheduled. The notification is sent using the DCI format 1C with SC-N-RNTI.

For NB-IoT UEs, LTE BL UEs and LTE UEs in enhanced coverage, there are two notification mechanisms used to announce changes of SC-MCCH due to Session Start. At first, a notification is sent in the DCI with SC-RNTI scheduling SC-MCCH. When the UE receives the notification, it acquires the SC-MCCH in the same modification period. Secondly, a notification is sent in the DCI with G-RNTI scheduling SC-MTCH. When the UE receives the notification, it acquires the SC-MCCH in the next modification period. For NB-IoT UEs, LTE BL UEs and LTE UEs in enhanced coverage, the notification used to announce changes of SC-MCCH for the ongoing service is sent in the DCI with G-RNTI scheduling SC-MTCH. When the UE receives the notification, it acquires the SC-MCCH in the next modification period.

In Dec 2019, 3GPP approved a work item (WI) on the support of NR Broadcast and Multicast Services. The application of NR Broadcast and Multicast technology includes V2X use case, public safety usage, video streaming transmission, software upgrade, etc.

In this invention, it is sought to achieve more efficient scheduling and modification notification for the control information of Multicast and Broadcast Service.

SUMMARY

A method is provided to support the scheduling and modification notification of the control information for Multicast and Broadcast Service (MBS) . In one novel aspect, the control information for Multicast and Broadcast Service (MBS) is transmitted by multiple MCCHs each with independent MCCH notification cycle. The MCCH notification cycle is calculated based on scaling of cell specific MBS DRX cycle via a Scaling Factor.

The MCCH is scheduled by a MCCH DCI, with CRC scrambled by M-RNTI. The MCCH DCI indicates that only scheduling information for MCCH transmission is present in the DCI. The MCCH DCI may indicates there is no scheduling for MCCH transmission in the current present MCCH notification cycle. MCCH DCI includes one bit to indicate the modification of the MCCH information comparing with last MCCH Notification cycle. MCCH DCI includes the indicator to indicate the start of new service and the change of the ongoing services that have the same MCCH Notification cycle.

MCCH control information can be optional scheduled with a Repetition Cycle and Repetition Factor within MCCH notification Cycle. The modification notification is only indicated at the boundary of MCCH notification Cycle. A resource pool can be allocated with a number of MBS Notification Frames for MBS control information transmission and modification notification. Optionally the Notification Frames has a number of Notification Occasions for MBS control information transmission and modification notification. The UEs that are interested in a particular MBS service or MBS service group only monitors the Notification Frames according to the MCCH notification cycle configured for the MBS service or MBS service group.

The configuration of the MBS parameters for MCCH reception for MBS services are transmitted by a MBS specific SIB. MBS specific SIB is defined to carry MCCH information, which contains the MBS DRX configuration of the cell and one or a plural of MBS service or MBS service group. The MBS DRX configuration of the cell includes one or any combination of the information elements of the MBS DRX cycle, number of Notification Frames within the MBS DRX cycle, Frame Offset, the number of Notification Occasions within each Notification Frame, and the first PDCCH monitoring occasion for each NO of the NF. The MBS service group includes one or any combination of the information elements of MBS Service Group identity, MBS Scaling Factor (or MCCH notification cycle) , and corresponding MCCH LCID. Optionally the MBS service group may include the MCCH Repetition cycle and Repetition Factor for each MBS Service Group.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and therefore not to be considered limiting of its scope, for the descriptions may admit to other equally effective aspects.

Figure 1 (a) is a schematic system diagram illustrating an exemplary Base Station (i.e. BS) , in accordance with certain aspects of the present disclosure.

Figure 1 (b) is a schematic system diagram illustrating an exemplary UE , in accordance with certain aspects of the present disclosure.

Figure 2 illustrates an exemplary NR wireless communication system, in accordance with certain aspects of the present disclosure.

Figure 3 illustrates an exemplary NR MBS DRX cycle, in accordance with certain aspects of the present disclosure.

Figure 4 illustrates an exemplary MCCH notification cycle allocation within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure.

Figure 5 illustrates an exemplary NF allocation for different MCCH notification cycles within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure.

Figure 6 illustrates an exemplary repeated MCCH transmission and/or modification notification within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure.

Figure 7 illustrates another exemplary repeated MCCH transmission and/or modification notification within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure.

Figure 8 illustrates an exemplary procedure for MCCH control information transmission, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATIONS

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, such as enhanced mobile broadband targeting wide bandwidth, millimeter wave targeting high carrier frequency, massive machine type communications targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications. These services may include latency and reliability requirements. These services may also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services may co-exist in the same subframe.

Figure 1 (a) is a schematic system diagram illustrating an exemplary Base Station (i.e. BS) , in accordance with certain aspects of the present disclosure. The BS 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. The Base Station 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 functions. Memory stores program instructions and data to control the operations of Base Station.

Figure 1 (b) is a schematic system diagram illustrating an exemplary UE, in accordance with certain aspects of the present disclosure. The UE may also be referred to as a mobile station, a mobile terminal, a mobile phone, smart phone, wearable, an IoT device, a table let, a laptop, or other terminology used in the art. 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. 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.

Figure 2 illustrates an exemplary NR wireless communication system, in accordance with certain aspects of the present disclosure. Different protocol split options between Central Unit and Distributed Unit of gNB nodes may be possible. 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.

In certain systems, such as NR systems, NR multicast is transmitted in the coverage of a cell. From logical channel perspective, the MCCH (i.e. multicast control channel) and MTCH (i.e. multicast traffic channel) are mapped on DL-SCH. The scheduling for NR multicast is done by the gNB. MCCH provides the information of a list of NR multicast services with ongoing sessions transmitted on MTCH (s) . At physical layer, MTCH is scheduled by gNB in the common search space of PDCCH with G-RNTI scrambled. UE decodes the MTCH data for a multicast session in the multicast PDSCH according to the resource indicated by DCI.

The traditional MBMS control information (i.e. MCCH information) transmission obeys a fixed Repetition Period and Modification Period. The Modification of MBMS control information only occurs at the boundary of the Modification Period. The Modification Period is a plural of Repetition Period. During the Modification Period, the MCCH information is repeated until the next Modification Period. MCCH repetition is meant to handle UEs, which just started monitoring the service on this cell. Time aligning MCCH modifications would give the knowledge to the UE when it would be useful to read the MCCH. This mechanism would come at the expense of some additional delays as well as some restrictions in applying modifications on the network side.

The definition of fixed Repetition Period and Modification Period for MCCH and MCCH change notification was specified to support the TV based broadcast transmission in 3GPP. The fixed timing for transmission of MCCH is not flexible, since all MTCHs and all UEs shares one MCCH repetition period and Modification period. One notification or MCCH change will cause all UEs to read the MCCH information. However, the NR multicast and broadcast service (i.e. MBS) mechanism is supposed to support a variety of applications such as V2X application, public safety, video streaming, software update, etc. Then fixed Repetition Period and Modification Period can not cater for the scheduling and notification requirements of all of the services.

In general, different MBS application and its services require different cycle for transmitting the control information. In a cell, a number of MBS services are supported, with each carried by an independent MTCH. A single MCCH or multiple MCCHs are supported to transmit the control information of all or a group of the MTCHs. The configuration of only a single MCCH Repetition Period and Modification Period for these MBS services is not power consumption friendly and not flexible enough. On one hand, some UEs may experience delay when attempting to read the update of MCCH control information, on the other hand, some other UEs may read the MCCH control information too often to save the UE power. Both cases are not desirable to the UE and the network for NR multicast and broadcast services.

MCCH mainly carries the identities of MBS services and their scheduling information (e.g. G-RNTI) . The change of MCCH information include two cases. One case is to start one or a plural of new MBS service. The other case is to modify or stop one or a plural of ongoing MBS service.

The Principle of MCCH scheduling and Notification

In certain systems, such as NR systems, the MBS control information (i.e. MCCH information) is transmitted with variable cycles depending on the characteristics of the MBS services. Accordingly the notification of the modification of the MBS control information (i.e. MCCH information) obeys variable cycles. This means a number of MCCH logical channels are allocated within a particular cell to support different type of MBS service or MBS service groups. Each MCCH logical channel is configured with a specific MCCH notification cycle. Within the MCCH notification cycle, the MCCH transmission may be repeated. The modification of MCCH information of specific MCCH only occurs at the boundary of each MCCH notification cycle. Then, independent modification notification is sent for each specific MCCH. In practice, there may be multiple notification messages sent over the air for the cell to support the announcement of the start of new MBS service (s) or the modification notification of the ongoing MBS service (s) .

Aspecific modification notification is sent together with MCCH control information carried by a MCCH when there is modification on the MCCH control information. Both modification notification and MCCH control information are addressed by a common RNTI in order to reduce UE’s complexity for the search at PDCCH search space. The modification notification if any is piggybacked by the DCI scheduling the transmission of MCCH control information in the current MCCH notification cycle. When the transmission of MCCH information is repeated, the modification notification if any is piggybacked by the first DCI scheduling the transmission of MCCH information within the MCCH notification cycle or by all of the DCIs that schedules the transmission of MCCH information within the MCCH notification cycle.

Furthermore, the MCCH control information transmission and modification notification can be subject to DRX like operation, in order to reduce UE power saving. This means the UEs can only monitor the PDCCH at the occasions as defined by the given MCCH notification cycle to check if there is any transmitted MCCH control information and/or modification notification. The delivery of the MCCH control information by the network can be subject to Discontinuous Transmission (i.e. DTX) . Then the MCCH control information transmission by network can be stopped at some MCCH notification cycles, which can be indicated by the DCI. When there is no MCCH control information transmission by the DCI, the UE will skip the decoding of the PDSCH.

A specific MBS DRX cycle is defined for NR MBS control information transmission and modification notification within a particular cell. Within the MBS DRX cycle, a pool of transmission resources are allocated for NR MBS control information transmission and modification notification. A number of Radio Frames is defined within the resource pool. The Radio Frame for MBS control information transmission and modification notification calls Notification Frame (i.e. NF) . In some NF, there may be only MBS control information transmission and there is no modification notification. In some NF, there may be both MBS control information transmission and modification notification indicator. In one embodiment, one Radio Frames in the pool may include one, two or four MBS Notification Occasions (i.e. NO) . Then the network needs to select one of the NO within a particular NF to transmit the MBS control information transmission and/or modification notification. Accordingly, the UE needs to select the same NO to perform reception.

The UEs that are interested in a particular MBS service or MBS service group only monitors the Notification Frames according to the MCCH notification cycle configured for the MBS service or MBS service group. Different UEs that are interested in different MBS service (s) or MBS service group (s) may monitors different Notification Frames with diverse time interval. This principle applies to the PDCCH monitoring for both MCCH control information reception and MCCH modification notification.

The unit of MBS DRX cycle and MCCH notification cycle is one radio frame (i.e. 10ms) and the value of MBS DRX cycle and MCCH notification cycle can be integers of multiple radio system frames.

Figure 3 illustrates an exemplary NR MBS DRX cycle, in accordance with certain aspects of the present disclosure. In Figure 3, the MBS DRX cycle is defined as 1280ms (i.e. 128 radio frames) . For simplicity, in the example, the MBS DRX cycle starts from SFN one. In Figure 3, 16 MBS Notification Frames are included in the MBS DRX cycle, each with two independent MBS Notification Occasions configured. Then in total, there are 32 MBS Notification Occasions within one MBS DRX cycle in Figure 3. Different MBS Notification Occasions within a MBS Notification Frame (NF) may be located at different subframes or slots within the same radio frame. For simplicity, in Figure 3, the first NF starts from the first radio frame. This means the Frame Offset for NF is 0.

Within a cell, the control information and modification notification of different MBS services are scheduled with variable length of MCCH notification cycle. The concept of MCCH notification cycle is equivalent of the MBMS MCCH modification period defined by UTRAN and EUTRAN. From terminology perspective, MCCH notification cycle can be named as MCCH modification cycle or MCCH modification period. The length of a MCCH notification cycle means the shortest cycle when the MCCH modification notification can be transmitted to the UE. The length of a MCCH notification cycle also means how often the UE needs to monitor PDCCH occasion for check if there is updated MCCH information.

For the NR MBS service that changes slowly (e.g. for delay tolerant MBS service) , a long MCCH notification cycle can be configured. The longest MCCH notification cycle within a cell is the configured MBS DRX cycle. For the NR MBS service that is subject to dynamic change, a short MCCH notification cycle can be configured. A Scaling Factor (SF, which is an integer) is defined to calculate the exact length of MCCH notification cycle. The configured MBS DRX cycle (e.g. expressed by MBS-DRX-cycle) for a cell is scaled by a configured Scaling Factor (e.g. expressed by Scaling-Factor) to derive the MCCH notification cycle (e.g. expressed by MCCH-Notification-cycle) via the formulae: MCCH-Notification-cycle=MBS-DRX-cycle div Scaling-Factor. For example, the Scaling Factor can be configured as 1, 2, 4, 8 or 16. In this example, the shortest MCCH notification cycle is one-sixtieth of MBS DRX cycle for cell when the Scaling Factor is equal to 16. In practice, the MCCH notification cycle and the occupied Notification Frames of a MBS service is determined by both Scaling Factor and system frame offset for MCCH.

Figure 4 illustrates an exemplary MCCH notification cycle allocation within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure. In Figure 4, MBS DRX cycle is defined as 1280ms (i.e. 128 radio frames) . In Figure 4, 16 MBS Notification Frames are included in the MBS DRX cycle. In Figure 4, the shortest MCCH notification cycle is one-sixtieth of MBS DRX cycle and then there are 16 MCCH notification cycles within one configured MBS DRX cycle within the cell, which is not depicted in Figure 4 in details. For simplicity, the shortest MCCH notification cycle in Figure 4 is configured based on zero system frame offset. In Figure 4, the longest MCCH notification cycle is the full MBS DRX cycle, and then there is only one MCCH notification cycle within one configured MBS DRX cycle within the cell. In Figure 4, a medium-duration MCCH notification cycle is one-fourth of MBS DRX cycle and there are two MCCH notification cycles within one configured MBS DRX cycle as the system frame offset configured is five radio frames.

As depicted in Figure 4, when the control information of a MBS service is transmitted from the cell to the UEs with a shorter MCCH notification cycle within the configured MBS DRX cycle, the UEs are expected to read the MCCH more frequently. Otherwise, the UEs read the MCCH less frequently. In the end, the UEs interested in receiving different services may read different MCCHs at different time and/or with different frequency. The same principle applies to the UEs who are receiving ongoing MBS services.

Figure 5 illustrates an exemplary NF allocation for different MCCH notification cycles within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure. In Figure 5, MBS DRX cycle is defined as 1280ms (i.e. 128 radio frames) . In the example of Figure 5, the first MBS service is configured with a MCCH notification cycle 320ms and zero SFN offset. Then there are four NFs of this MBS service. In Figure 5, the second MBS service is configured with a MCCH notification cycle 640ms and 16 SFN offset. In the example of Figure 5, The 16 SFN offset means two NFs offset as there is 8-system frame interval between two consecutive NFs. There are two NFs valid for the second MBS service. In Figure 5, the third MBS service is configured with a MCCH notification cycle 1280ms and 24 SFN offset (i.e. three NFs offset) . Then there is only one NF valid for this MBS service.

Optionally, the notification of a MBS service and the transmission of the actual control information of the MBS service is repeated once or a plural of times in order to allow UEs missing the first reception to receive them in the follow-up Notification Frames within the configured MCCH notification cycle. Figure 6 illustrates an exemplary repeated MCCH transmission and/or modification notification within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure. In the example of Figure 6, the MBS service is configured with a MCCH notification cycle 320ms and zero SFN offset. Then there are four NFs valid for the initial transmission of the control information and/or notification of this MBS service. In the example of Figure 6, the MBS service is configured with a repetition cycle 80ms (i.e. eight system frames) . Then there are four repeated transmissions of the control information and/or notification for this MBS service. As depicted in Figure 6, each initial transmission is only repeated once for this MBS service. In different scenarios, depending on the configuration of the repetition cycle, the initial transmission can be repeated once or a plural of times within the configured MCCH notification cycle.

From the repeated transmission of MCCH control information and/or MCCH notification perspective, the exact repetition pattern is subject to the configuration of both Repetition Cycle and Repetition Factor. Repetition Cycle defines the time interval between the initial transmission and its repetitions. The unit of Repetition Cycle is one radio frame (i.e. 10ms) and the Repetition Cycle is an integer of multiple radio system frames. The Repetition Factor is an integer, which defines how many times the same MCCH control information and/or MCCH notification repeats at a given MCCH notification cycle repeats. It should be noted that the configuration of Repetition Cycle and Repetition Factor are correlated, since a particular Repetition Cycle may only support a limited set of Repetition Factor. As shown in Figure 6, the Repetition Cycle for the MBS service is eight radio frames (i.e. 80ms) and the Repetition Factor is one, which defines a single repeated transmission for the MCCH control information and/or MCCH notification. The configurable Repetition Factor in Figure 6 are one, two and three, since there are only three unoccupied NFs within the given MCCH notification cycle. The Scaling Factor for a particular MBS service restricts the configurable Repetition Factors, since unoccupied NFs within the given MCCH notification cycle is actually determined by the Scaling Factor.

The repeated transmission of the initial MCCH control information and/or MCCH notification can also be configured to skip one or a plural of follow-up NFs. In the example of Figure 6, the repeated transmission can occur at third NF, as shown in Figure 7. Figure 7 illustrates another exemplary repeated MCCH transmission and/or notification within an NR MBS DRX cycle, in accordance with certain aspects of the present disclosure. In Figure 7, the repetition cycle is 160ms (i.e. sixteen system frames) . In Figure 7, the Repetition Factor is one. Actually, In Figure 7, there is no additional configurable Repetition Factor other than one. The transmission pattern of MCCH transmission and/or notification as shown in Figure 7 is equaling to the transmission pattern of the MCCH control information and/or MCCH notification with a 320ms MCCH notification cycle and zero SFN offset, since 320 ms MCCH notification cycle within 1280ms configured MBS DRX cycle means eight occurrence of transmission and/or notification.

L1 Signaling of MCCH Scheduling and Notification

In certain systems, such as NR system, one cell typically support the simultaneous transmission of a large number of MBS services (e.g. 1024 services) . In reality, it would be difficult to assign a unique MCCH notification cycle to each MBS service, since the available NFs within a MBS DRX cycle are usually limited. One possibility is to utilize different Notification Occasions within the NFs to host different MBS service when they share the same MCCH notification cycle. However, the available of Notification Occasions within a Notification Frame are usually also limited. For example, in NR, the maximum configuration of Notification Occasions (NO) within a Notification Frame can be four.

It would be beneficial to group some of MBS services together to form a MBS service group to share the same MCCH notification cycle. For example, the same MBS services with same or similar QoS requirement can be grouped together. A MBS specific QCI or QFI may be defined to express the service or the flow of the service with particular QoS requirement. Then the MBS services having same or close QCI or QFI can be grouped together to share the same MCCH notification cycle. The negative point of grouping different service together is that it increases the possibility of false alarm, when the UE checks the DCI but there is no modification notification for the MBS services that the UE is interested in receiving or is receiving. This means there should be a limitation for MBS service grouping when determining the MCCH notification cycle for the MBS services within a cell.

For example, within the configured 2560ms MBS DRX cycle, it assumes there are 32 NFs, each with 4 NOs configured. The configurable MCCH notification cycle can be 2560ms (i.e. with Scaling Factor 1) , 1280ms (i.e. with Scaling Factor 2) , 640ms (i.e. with Scaling Factor 4) , 320ms (i.e. with Scaling Factor 8) , 160ms (i.e. with Scaling Factor 16) and 80ms (i.e. with Scaling Factor 32) . Then these MCCH notification cycles have 32 NFs, 16 NFs, 8 NFs, 4 NFs, 2 NFs or 1 NF respectively. It means within this cell, six unique MCCH notification cycles can be configured to different service groups. In each service group, four unique occasion can be assigned to different services when taking full advantage of all of the configured NOs. This means this cell can support the MCCH transmission and/or notification without overlapping for up to 24 MBS services. When the cell supports more MBS services, the MCCH transmission and/or notification of multiple MBS services needs to be combined together and transmit at the same NF and/or NO.

Considering the repetitions of MCCH transmission and/or notification, the MCCH transmission and/or notification of different MBS services to be combined together at a given same NF and/or NO may present a larger number than non-repetition case.

In certain systems, such as NR system, the MCCH transmission and/or notification can be addressed via a new RNTI (e.g. MBS RNTI with abbreviation M-RNTI) . In NR, DCI format 1_0 is used for the scheduling of PDSCH in one DL cell. Hence, the content of MCCH transmission and/or notification can be carried by DCI format 1_0 with CRC scrambled by M-RNTI. As an alternative, the MCCH transmission and/or notification can be addressed by P-RNTI over PDCCH.

The content of the MCCH transmission and/or notification carried by DCI format 1_0 can include Short Messages Indicator (2 bits according to Table 7.3.1.2.1-1 of 3GPP TS38.212. ) , Short Messages bits, Frequency domain resource assignment, Time domain resource assignment, VRB-to-PRB mapping, Modulation and coding scheme, TB scaling and Reserved bits. For example, within the Short Messages Indicator, the reserved code point “00” can be used to indicate that only scheduling information for MCCH transmission and/or notification is present in the DCI, if P-RNTI is used for addressing. Within the Short Messages Indicator, the code point “00” or “01” can be used to indicate that only scheduling information for MCCH transmission and/or notification is present in the DCI, if a new M-RNTI is used for addressing. The other code points of Short Messages Indicator are reserved. The Short Messages bits (8 bits, according to Subclause 6.5 of 3GPP TS38.331) is also reserved as the intention of this DCI is only to deliver MCCH transmission and/or notification. The rest bits including Frequency domain resource assignment, Time domain resource assignment, VRB-to-PRB mapping, Modulation and coding scheme and TB scaling are used to schedule the actual transmission of the content of MCCH over PDSCH. As an alternative, a new DCI format is used to carry the content of MCCH transmission and/or notification in order to reduce the reserved bits in DCI format 1_0. When the DCI format 1_0 or a new DCI format is used to carry the content of MCCH transmission and/or notification, the DCI is called MCCH DCI.

In addition, the content of MCCH DCI can include one bit to indicate the modification of the MCCH information comparing with last MCCH Notification cycle. This bit can be only toggled at the boundary of MCCH Notification cycles. Depending on if this bit is toggled, the UE determines the succeeding reception behavior. The UEs that have already read the same MCCH content will not read the MCCH content again if this bit is not toggled. This applies to the UEs that are interested in MBS reception or are receiving ongoing MBS services. With regard to the UEs that just power on or move to the current cell from neighbor cells, the UEs will read the MCCH content in any case.

In an embodiment, one or plural of MBS sercice group identity is included in the MCCH DCI to tell the UE (s) which MBS sercice group (s) is configured by this MCCH. These MBS sercice group (s) shares this MCCH. UE can skip the reception of the PDSCH if the UE (s) is not inteseted in the MBS services belonging to the MBS sercice group (s) indicated by this DCI. The length of MBS sercice group identity is configurable or fixed by network.

In an embodiment, the content of MCCH DCI can include one bit to indicate if there is any MCCH control information scheduled within this MCCH notification cycle. When this bit is transmitted, the UEs receiving this DCI is not expected to decode any follow-up PDSCH transmission for MCCH control information.

In an embodiment, the content of MCCH DCI can include two bits to indicate the modification of the MCCH. One bit is used to indicate the start of new MBS service for the current MBS service group (s) that shares the same MCCH notification cycle, or start of new MBS service for a new MBS service group that shares the same MCCH notification cycle as the current one. The other bit is used to indicate the change of the ongoing MBS services that have the same MCCH Notification cycle.

In an embodiment, the content of MCCH DCI can include multiple bits to indicate the modification of the MCCH cause by which MBS service group. MBS service group ID (s) are included to show the modification of the MCCH information for that particular MBS service group (s) .

In an embodiment, the content of MCCH DCI can include two bits to indicate the modification of the other MCCH that uses different MCCH Notification cycle. One bit is used to indicate the start of new MBS service of MBS service group that have different MCCH notification cycle from the current one. The other bit is used to indicate the change of the ongoing MBS services that have different MCCH Notification cycle.

In an embodiment, the identity information of MBS service group, and/or the identity information of the MTCH carried by the MCCH is indicated within the MCCH DCI. This helps the UEs to judge if the interested MBS service group or MBS service is scheduled by the follow-up MCCH and this judgement helps the UE to determine if there is a need to futher decode the PDSCH carrying the MCCH in order to anquire the updated information for the interested MBS service (s) or ongoing MBS service (s) . Traditionally, for a particular MTCH, the MCCH carries the identity information of MBS service corresponding to MTCH, scheduling information of MTCH and neighbouring cell information for the MTCH.

There are different ways to carry the the identity information of MBS service group, and/or the identity information of the MTCH within the MCCH DCI. One way is to use a bitmap with each bit indicating the scheduing of one MBS service group. Another bitmap is used to indicate the MBS service within the MBS service group. The identities of each MBS service group and the MBS service within each MBS service group are configured by system information at BCCH. For example, in a cell, if there are four MBS service groups each with with 8 MBS services configured. When only the first MBS service group is scheduled, bitmap “1000” or “0001” is used. When only the first two MBS services within the first MBS service group is notified in this MCCH notificaiton DCI, bitmap “1000000” or “00000001” is used.

In certain systems, such as NR system, the UEs in RRC_CONNECTED, RRC_IDLE and RRC_INACTIVE state use Discontinuous Reception (DRX) mode to monitor MCCH DCI in order to reduce power consumption. The UEs obey the MCCH notification cycle of the interested MBS service or the ongoing MBS service. If the UE intends to receive multiple types of MBS service within the same service group, the UE performs DRX reception following only one MCCH notification cycle, corresponding to the MBS service group. If the UE intends to receive multiple types of MBS service within the different service groups, the UE performs DRX reception following more than one MCCH notification cycles.

For a particular MCCH notification cycle, the UE monitors one MBS Notification Occasion (NO) per MCCH notification cycle. A MBS NO is a set of PDCCH monitoring occasions and can consist of multiple time slots (e.g. subframe or OFDM symbol) where MCCH DCI can be sent. The PDCCH monitoring occasions for MBS NO follows the same principle as that for legacy paging and are configured at BCCH. One MBS Notification Frame (NF) is one Radio Frame and may contain one or multiple MBS NO (s) or starting point of a NO. In multi-beam operations, the UE assumes that the same MCCH DCI is repeated in all transmitted beams and thus the selection of the beam (s) for the reception of the MCCH DCI is up to UE implementation.

The MBS NF and NO are determined by the following formulas. SFN for the NF is determined by: SFN mod T = NF_offset. NF_offset is the offset used for NF determination and the unit of NF offset is one rado frame. T is the MCCH notification cycle of the MBS service or MBS service group. T is determined by: T= N div S. N is the number of total NFs within a MBS DRX cycle in the cell. S is the Scaling Factor for MCCH notification cycle within the MBS DRX cycle. It means that the value T is determined by Scaling Factor of the MBS service or MBS service group and the number of total NFs within a MBS DRX cycle. The values N and NF_offset configured via in BCCH.

When Repetition cycle and Repetition Factor are configured for MCCH repeated transmission, the Repetition SFN for the NF is determined by: SFN mod T = NF_offset + m*R. R is the Repetition Cycle of the MBS service or MBS service group. Repetition Cycle is configured by RRC in system information. The integer n includes all of the integers within the set {0, 1, …, M} , where M is the configured Repetition Factor of the MBS service or MBS service group. T is determined by: T= N div S, which follows the same principle as for non-repetition case.

Index (i_s) , indicating the index of the NO is determined by: i_s= Group_ID mod Ns. Ns is the number of Notification Occasions for a NF. Parameters Ns is signaled in BCCH. Group_ID can be the identity of the MBS service group. Alternatively, the identity of the first MBS service within the MBS service group can be used as Group ID in the formula. When Repetition is configured for a particular MCCH transmission, the same NO is used in the repeated NF as the initial transmission NF.

RRC Aspects of MCCH Scheduling and Notification

In certain systems, such as NR system, the MBS related control information is transmitted by MCCH. A limited amount of MBS control information is provided on the BCCH. This primarily concerns the information needed to acquire the MCCH. The MCCH information (i.e. information transmitted in messages sent over MCCH) is transmitted periodically, using a configurable MCCH notification cycle. The MCCH may be repeated with a repetition cycle within the MCCH notification cycle.

A new SIB is defined to carry MCCH information. This SIB contains the information required to acquire the control information associated with the transmission of MBS service (s) . This SIB contains the MBS DRX configuration of the cell and one or a plural of MBS service or MBS service group. The MBS DRX configuration of the cell includes one or any combination of the information elements of the MBS DRX cycle, number of Notification Frames within the MBS DRX cycle, the MBS Notification Frame Offset, the number of Notification Occasions within each Notification Frame, and the first PDCCH monitoring occasion for each NO of the NF. Within this SIB, a list of MBS service group is included. For each MBS service group, one or any combination of the information elements of MBS Service Group identity, MBS Scaling Factor (or MCCH notification cycle) , and corresponding MCCH LCID. The Scaling Factor can be used to calculate the MCCH notification cycle based on MBS DRX cycle. Optionally, the MCCH Repetition cycle and Repetition Factor are also included for each MBS Service Group.

A cell may support one or a plural of MCCH channel. Each MCCH logical channel has a unique MCCH notification cycle. Each MCCH is responsible for the transmission of the MBS control information of one or a plural of MBS service group.

In an embodiment, within the MBS specific SIB, a list of MBS service is included. For each MBS service, one or any combination of the information elements of MBS Service identity, MBS Scaling Factor (or MCCH notification cycle) , and corresponding MCCH LCID. Optionally, the MCCH Repetition cycle and Repetition Factor are also included for each MBS Service. The MBS Service identity can be the MBS session ID, the ID of the MTCH for the MBS Service, or an index of the supported MBS service within the cell.

The principle is that the BCCH provide the overview of all of the MBS services or MBS service groups transmitted or to be transmitted in the cell. The MCCH provides a full or subset of the information of the MBS services or MBS service groups in a given MCCH notification cycle. However, looking at the whole MBS DRX cycle, a full set of the information of the MBS services or MBS service groups is provisioned by the MCCHs.

In a given MCCH notification cycle, the MCCH provides the configuration of a list of MBS service groups. The MCCH also provides a list of neighbour cells providing MBS services. For each MBS service group, the MBS service group ID and a list of MTCH are provided. For each MTCH, MBS session information, G-RNTI and MTCH scheduling information are included. Optionally, for each MTCH, a local index is provided to express the sequential number of the MBS service within current MBS service group. This index can be used to form the bitmap for purpose of modification notification in MCCH DCI. For example, if the current MBS service group has 8 MBS services in transmission, the value range of the local index is the integer of the set {0, 1, …, 7} . As an alternative, no MBS service group information is provided, only MBS service related information is provided in MCCH.

Figure 8 illustrates an exemplary procedure for MCCH control information transmission, in accordance with certain aspects of the present disclosure. In Step 1 of Figure 8, SIB1 schedules the MBS specific SIB. According to the SIB1 scheduling, the UE can read the MBS specific SIB in Step 1 of Figure 8. In Step 1 of Figure 8, the UE finds his interested MBS service group or MBS service and then determine the exact NF/NO and MCCH notification cycle to monitor the corresponding MCCH DCI for the MBS service group or MBS service. Optionally the Repetition cycle and Repetition Factor are used by the UE to find the closest upcoming MCCH transmission.

In Step 2 of Figure 8, the relevant MCCH control information is scheduled by the network following the configured MCCH notification cycle (and MCCH Repetition cycle) in a Notification Frame. The UE monitors the Notification Frame and Notification Occasion according to the local calculation and decodes the MCCH DCI by M-RNTI. After decoding the DCI, the UE decodes the corresponding PDSCH to read the MCCH in order to get the scheduling information of the MBS service that the UE is interested. The transmission of MCCH is carried by a single Transport Block (i.e. TB) , and then one-shot transmission is used for the MCCH. In one embodiment, the transmission of MCCH is carried by multiple Transport Blocks, and then the UE needs to keep monitoring the PDCCH after the reception of the first PDSCH for the first Transport Block (i.e. TB) . In this case, the legacy On-Duration-Timer, DRX-Inactivity-Timer, and Scheduling-Period-Start-Offset may be configured by BCCH for this MCCH. UE needs to monitor the PDCCH until finish reception of all the TBs for MCCH.

In Step 3 of Figure 8, the relevant MTCH transmission is scheduled by the network in light of the configured MTCH scheduling information as acquired by the UE in Step 2 of Figure 8. The UE receives the MTCH transmission, which is transmitted in multicast or broadcast manner. In Step 4 of Figure 8, the UE periodically checks the MCCH DCI in the boundary of MCCH notification cycle. When there is no modification indicated in the DCI, the UE skips the reception of the MCCH scheduled by the DCI. It should be noted that there may be some modification for other MBS service or MBS service group, which can be also included in the current MCCH DCI. In Step 5 of Figure 8, the MTCH transmission scheduled by the network is the same as Step 3, as there is no modification at Step 4 of Figure 8.

In Step 6 of Figure 8, the network broadcasts the MCCH modification indicator (i.e. change notification) within the MCCH DCI in the boundary of MCCH notification cycle. In Step 7 of Figure 8, the UE decodes the MCCH DCI, finds there is indication for the modification of the MCCH control information, and then decodes the PDSCH carrying the updated MCCH control information. In Step 8 of Figure 8, the relevant MTCH transmission is scheduled by the network in light of the updated MTCH scheduling information as acquired by the UE in Step 7 of Figure 8.

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 for wireless communications, comprising:

Scheduling the control information for Multicast and Broadcast Service (MBS) and

Performing modification notification of the control information for Multicast and Broadcast Service (MBS) .
The method of claim 1, wherein the control information for Multicast and Broadcast Service (MBS) is transmitted by multiple MCCHs each with independent MCCH notification cycle.
The method of claim 2, wherein the MCCH notification cycle is calculated based on scaling of cell specific MBS DRX cycle via a Scaling Factor.
The method of claim 2, wherein the MCCHs are scheduled by a MCCH DCI, with CRC scrambled by M-RNTI.
The method of claim 4, wherein the MCCH DCI indicates that only scheduling information for MCCH transmission and/or notification is present in the DCI.
The method of claim 4, wherein the MCCH DCI includes one bit to indicate the modification of the MCCH information comparing with last MCCH Notification cycle.
The method of claim 4, wherein the MCCH DCI includes one bit to indicate there is no MCCH information scheduled in the MCCH Notification cycle.
The method of claim 4, wherein the MCCH DCI includes the indicator to indicate the start of new service and the change of the ongoing services that have the same MCCH Notification cycle.
The method of claim 4, wherein the MCCH DCI includes the indicator to indicate the start of new service and the change of the ongoing services that have different MCCH Notification cycle.
The method of claim 4, wherein the MCCH DCI includes the identity information of MBS service group, and/or the identity information of the MTCH carried by the MCCH.
The method of claim 10, wherein the identity information of MBS service group is expressed by a bitmap.
The method of claim 10, wherein the identity information of the MTCH is expressed by a bitmap.
The method of claim 1, wherein the control information is scheduled with a Repetition Cycle and Repetition Factor within MCCH notification Cycle.
The method of claim 1, wherein the modification notification is only indicated at the boundary of MCCH notification Cycle.
A method for wireless communications, further comprising:

Allocation of specific resource pool for MBS control information and notification transmission.
The method of claim 15, wherein the resource pool has a number of MBS Notification Frames for MBS control information transmission and modification notification.
The method of claim 16, wherein the Notification Frames has a number of Notification Occasions for MBS control information transmission and modification notification.
The method of claim 16, wherein the MBS NF are determined by: SFN mod T = NF_offset. NF_offset is the offset used for NF determination. T is the MCCH notification cycle of the MBS service or MBS service group. T is determined by: T= N div S. N is the number of total NFs within a MBS DRX cycle in the cell. S is the Scaling Factor.
The method of claim 16, wherein the MBS NF are determined by: SFN mod T = NF_offset + m*R, when Repetition cycle and Repetition Factor are configured for MCCH repeated transmission. R is the Repetition Cycle. The integer n includes all of the integers within the set {0, 1, …, M} , where M is the configured Repetition Factor. T is determined by: T= N div S. N is the number of total NFs within a MBS DRX cycle in the cell. S is the Scaling Factor.
The method of claim 17, wherein the MBS NO are determined by: Index (i_s) = Group_ID mod Ns. Ns is the number of Notification Occasions for a NF. Parameters Ns is signaled in BCCH. Group_ID can be the identity of the MBS service group.
A method for wireless communications, further comprising:

Configuring the MBS parameters for MCCH reception for MBS services.
The method of claim 21, wherein the MBS parameters for MCCH reception are transmitted by a MBS specific SIB.
The method of claim 22, wherein the MBS specific SIB is defined to carry MCCH information, which contains the MBS DRX configuration of the cell and one or a plural of MBS service or MBS service group.
The method of claim 23, wherein the MBS DRX configuration of the cell includes one or any combination of the information elements of the MBS DRX cycle, number of Notification Frames within the MBS DRX cycle, Frame Offset, the number of Notification Occasions within each Notification Frame, and the first PDCCH monitoring occasion for each NO of the NF.
The method of claim 23, wherein the MBS service group includes one or any combination of the information elements of MBS Service Group identity, MBS Scaling Factor (or MCCH notification cycle) , and corresponding MCCH LCID.
The method of claim 23, wherein the MBS service group includes the MCCH Repetition cycle and Repetition Factor for each MBS Service Group.
The method of claim 23, wherein the MCCH contains the MBS service group ID and a list of MTCH.
The method of claim 27, wherein the list of MTCH include a local index for each MTCH to express the sequential number of the MBS service within current MBS service group.