WO2021184201A1

WO2021184201A1 - Methods and apparatus of csi report to support reliable multicast transmission

Info

Publication number: WO2021184201A1
Application number: PCT/CN2020/079729
Authority: WO
Inventors: Xuelong Wang
Original assignee: Mediatek Singapore Pte. Ltd.
Priority date: 2020-03-17
Filing date: 2020-03-17
Publication date: 2021-09-23
Also published as: WO2021185267A1

Abstract

Apparatus and methods are provided to support CSI report for multicast transmission. The CSI physical layer signals are configured via RRC message to the concerned UEs for measurements related to multicast transmission. In one novel aspect, the multicast MAC CE is multiplexed with multicast data and the multicast MAC CE includes concantenated mutliple UE information related to the configuration of the CSI physical layer signals. Uplink resource for multicast CSI report related to multicast transmission can be PUCCH resource configured by the Base Station, which may span over a consective slots or PUCCH resource allocation periods. The CSI feedback can also be reported via specific MAC CE, which may consist of UE specific ID (e.g. C-RNTI) and multicast specific ID.

Description

METHODS AND APPARATUS OF CSI REPORT TO SUPPORT RELIABLE MULTICAST TRANSMISSION

TECHNICAL FIELD

Aspects of the present disclosure relate generally to wireless communication systems, and more particularly, to enable CSI report for reliable multicast based transmission.

BACKGROUND

3GPP specified the support for MBMS transmission with group scheduling, which is based on UMTS or EUTRAN technology.

The group scheduling for multicast transmission specified by 3GPP has no Uplink feedback support so far. At Rel-13, there is a discussion at 3GPP to support physical layer feedback (e.g. CSI feedback) in the context of SC-PTM transmission. However, eventually it is not specified.

In both LTE and NR, CSI report is supported for unicast-based transmission. In NR, CSI-RS has the main functionalities of CSI acquisition, Beam management and CONNECTED mode RRM measurement (for L3 mobility) . The CSI framework is designed to support the following application scenarios, Beam management, operation with codebook for NP CSI-RS or BF CSI-RS, Multi-TRP operation, Multi-CC operation, Hybrid CSI operation, NZP CSI-RS based interference measurement. LTE and NR supports periodic, semi-persistent and aperiodic CSI reporting and CSI-RS configuration.

In Dec 2019, 3GPP approved a work item (WI) on the support of NR Broadcast and Multicast Services. Within the scope of the WI, the reliable transmission of the NR Multicast services with uplink feedback is the key objective. The CSI report based uplink feedback for NR multicast is to be studied.

In this invention, it is sought to achieve reliable multicast transmission via CSI report based uplink feedback.

SUMMARY

A method is provided to support the CSI report for multicast transmission. The CSI physical layer signals are configured via RRC message to the concerned UEs for measurements related to multicast transmission. The configuration of the CSI physical layer signals may be activated via multicast L1 signaling or multicast MAC CE. In one novel aspect, the multicast MAC CE is multiplexed with multicast data and the multicast MAC CE includes concantenated mutliple UE information related to the configuration of the CSI physical layer signals.

Uplink resource for multicast CSI report related to multicast transmission can be PUSCH resource or PUCCH resource. In case of PUSCH resource for CSI feedback, it can be configured by Configured Grant or scheduled by Dynamic Grant.

In case of PUCCH resource for CSI feedback, it can be as configured by the Base Station via RRC Reconfiguration during multicast Radio Bearer establishment. The PUCCH resource as configured by the Base Station may span over a consective slots or PUCCH resource allocation periods in order to present enough PUCCH resources for CSI feedback to support reliable multicast transmission.

The CSI feedback can also be reported via specific MAC CE, which may consist of UE specific ID (e.g. C-RNTI) and multicast specific ID (e.g. multicast session ID, DL MTCH logical channel ID, etc) . The multicast CSI reporting may trigger a SR according to the preconfigured SR configuration.

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 Periodic multicast CSI reporting procedure, in accordance with certain aspects of the present disclosure.

Figure 4 illustrates an exemplary Semi-Persistent multicast CSI reporting procedure, in accordance with certain aspects of the present disclosure.

Figure 5 illustrates an exemplary Aperiodic multicast CSI reporting procedure, in accordance with certain aspects of the present disclosure.

Figure 6 illustrates an exemplary PUCCH resource assignment for multicast CSI reporting, in accordance with certain aspects of the present disclosure.

Figure 7 illustrates an exemplary multicast CSI Reporting MAC CE structure for NR multicast, in accordance with certain aspects of the present disclosure.

DETAILED DESCRIPTION

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, one MCCH (i.e. multicast control channel) and one or more MTCH (s) (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 the list of all NR multicast services with ongoing sessions transmitted on MTCH (s) . At physical layer, the MCCH is scheduled by gNB in the common search space of PDCCH with MB-RNTI scrambled. MB-RNTI is MCCH logical channel specific RNTI, with fixed value specified in MAC (e.g., the value can be FFFD) . 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.

In order to support reliable DL multicast transmission, the UEs that participate the reception of DL multicast transmission is expected to provide Uplink CSI Feedback to the Base Station. In this disclosure, this type of Uplink CSI Feedback is called multicast CSI Feedback, multicast CSI Report, or multicast CSI reporting.

Framework for multicast CSI Feedback

In NR, the legacy resource settings for CSI acquisition, beam management and interference measurement is configured in UE specific way. In the context of multicast transmission, multiple UEs that receive the multicast PDSCH can perform the measurement based on the same CSI-RS or SSB resources. This means the resource settings are shared by the concerned UEs. There are two options to configure the said resource settings to the UEs. In the first option, the pool of resource settings for unicast and multicast transmission within a cell are shared. In case of multicast transmission (i.e. when a multicast radio bearer is configured to the concerned UEs) , a legacy resource setting is allocated in the same way as for unicast transmission. In the second option, a specific pool of resource settings for multicast transmission within a cell is reserved. In case of multicast transmission (i.e. when a multicast radio bearer is configured to the concerned UEs) , a subset of the pool of the reserved resource setting is allocated. The said resource settings includes one or a plural of CSI-RS or SSB resource set. Each CSI-RS resource set consists of the configuration of one or a plural of CSI-RS or SSB resources.

When a multicast radio bearer is configured to the concerned UEs, the specific multicast CSI measurement setting is configured to the UEs. The multicast CSI measurement setting includes resource settings indication, multicast CSI reporting setting indication, the Quantities to be measured (either for channel measurement or for interference measurement) , etc. The content of Multicast CSI report consists of a combination of Channel Quality Indicator (CQI) , Precoding matrix indicator (PMI) , CSI-RS resource indicator (CRI) , SSBRI, Layer Indication (LI) , Rank Indication (RI) , and L1-RSRP, according to the dependency as defined by NR legacy CSI report in section 5.2.1.4 of TS 38.214. LI is calculated conditioned on the reported CQI, PMI, RI and CRI. CQI is calculated conditioned on the reported PMI, RI and CRI. PMI is calculated conditioned on the reported RI and CRI. RI is calculated conditioned on the reported CRI.

The CSI-RS transmission for purpose of multicast CSI reporting can be Periodic, Aperiodic or Semi-Persistent depending on the configuration. Correspondingly, when the Resource Configuration (e.g. CSI-RS Configuration) is periodic, the multicast CSI Report Configuration can be set to one of the types including Periodic, Semi-Persistent and Aperiodic. When the Resource Configuration (e.g. CSI-RS Configuration) is Semi-Periodic, the multicast CSI Report Configuration can be set to Semi-Persistent or Aperiodic. When the Resource Configuration (e.g. CSI-RS Configuration) is Aperiodic, the multicast CSI Report Configuration can only be Aperiodic.

In case of Semi-Persistent multicast CSI-RS transmission, the configured Semi-Persistent CSI-RS resource sets for multicast transmission are initially deactivated upon RRC configuration. The network may activate and deactivate the configured Semi-Persistent CSI-RS resource sets of a Serving Cell by sending a specific multicast MAC CE to the concerned UEs. In case of Semi-Persistent multicast CSI reporting on PUCCH, it is initially deactivated upon RRC configuration. The network may activate and deactivate the configured Semi-Persistent CSI reporting on PUCCH of a Serving Cell by sending a specific multicast MAC CE to the concerned UEs. In case of Aperiodic multicast CSI triggering, the network may select among the configured Aperiodic CSI trigger states of a Serving Cell by sending a multicast Aperiodic CSI Trigger State Subselection MAC CE to the concerned UEs. The multicast DCI that schedules the multicast PDSCH transmission controls the Aperiodic multicast CSI report. In addition, the Periodic multicast CSI-RS transmission triggering and Periodic multicast CSI reporting for multicast follows the NR legacy operation for unicast transmission.

As a clear difference from the legacy MAC CE, the abovementioned multicast MAC CEs are sent in a multicast manner with the aim to reach all of the UEs participated in the multicast reception. The intention is to improve the transmission efficiency. This puts a restriction for the transmission of the said multicast MAC CE from the perspective of multiplexing for downlink transmission from the BS to the UEs. The said multicast MAC CE is multiplexed with the multicast MAC PDU data and then is mapped to the multicast PDSCH for downlink transmission. The priority of said MAC CE is higher than the priority of the logical channel that carries the multicast data. The contents of these multicast MAC CEs in principle follows the content as defined in TS38.321 for the corresponding MAC CEs defined for unicast transmission. The difference is that for unicast transmission there is only information for one UE. Within these multicast MAC CEs, multiple UE’s information is concatenated together, which can be shown in the following examples.

For example, the multicast SP CSI-RS/CSI-IM Resource Set Activation/Deactivation MAC CE is identified by a MAC subheader with a specific LCID. It can include an A/D field to indicate whether to activate or deactivate the indicated SP CSI-RS and/or CSI-IM resource set (s) . It can include a Serving Cell ID field to indicate the identity of the Serving Cell for which the MAC CE applies. It can include a BWP ID field to indicate a DL BWP for which the MAC CE applies. It can include multiple combinations of {UE ID, SP CSI-RS resource set ID, SP CSI-IM resource set ID, TCI State ID} to indicate the concerned UEs the exact CSI-RS and/or CSI-IM resource set to activate or deactivate. The UE ID can be expressed by C-RNTI.

For example, the multicast Aperiodic CSI Trigger State Subselection MAC CE is identified by a MAC subheader with a specific LCID. It can include a Serving Cell ID field to indicate the identity of the Serving Cell for which the MAC CE applies. It can include a BWP ID field to indicate a DL BWP for which the MAC CE applies. It can include multiple combinations of {UE ID, List of Selection status} to indicate the concerned UEs the exact selection status of the Aperiodic Trigger States configured within CSI-aperiodicTriggerStateList, as specified in TS 38.331. The UE ID can be expressed by C-RNTI.

For example, the multicast SP CSI reporting on PUCCH Activation/Deactivation MAC CE is identified by a MAC subheader with a specific LCID. It can include a Serving Cell ID field to indicate the identity of the Serving Cell for which the MAC CE applies. It can include a BWP ID field to indicate a DL BWP for which the MAC CE applies. It can include multiple combinations of {UE ID, List of Activation status} to indicate the concerned UEs the exact activation/deactivation status of the Semi-Persistent CSI report configuration within csi-ReportConfigToAddModList, as specified in TS 38.331. The UE ID can be expressed by C-RNTI.

Higher layer (i.e. RRC) may configure Periodic multicast CSI-RS. In addition, Periodic multicast CSI reporting is carried at least on Short PUCCH or Long PUCCH. Different from the uncast transmission, the unique PUCCH resource for Periodic multicast CSI reporting specific to multicast transmission needs to be allocated to each UE participating the multicast PDSCH transmission.

Figure 3 illustrates an exemplary Periodic multicast CSI reporting procedure, in accordance with certain aspects of the present disclosure. In Step1 of Figure 3, the CSI related physical layer signal (s) is configured via RRC Reconfiguration message to each UE (i.e. UE1 and UE2 in Figure 3) during the establishment of multicast radio bearer. In Step 2 and Step 4 of Figure 3, the CSI related physical layer signal (s) is transmitted periodically from the Base Station to each concerned UE. In Step 3 and Step 5 of Figure 3, the multicast CSI report is sent periodically from each concerned UE to the Base Station over different PUCCH resource. The periodicity is expressed by slots in the configuration.

Higher layer (i.e. RRC) may configure Semi-Persistent (SP) multicast CSI-RS transmission. Semi-Persistent (SP) multicast CSI reporting can be carried by PUCCH. In this case, it is activated by multicast MAC CE. One of the Semi-Persistent (SP) CSI Report Setting for PUCCH is selected by the same MAC CE. Each SP multicast CSI Report Setting for PUCCH is configured in RRC with the PUCCH resource used for transmitting the multicast CSI report. The unique PUCCH resource for SP multicast CSI reporting specific to multicast transmission needs to be allocated to each UE participating the multicast PDSCH transmission. Depending on the high layer (i.e. RRC) configuration, Semi-Persistent (SP) multicast CSI reporting can be also carried by PUSCH. In this case, a set of SP-CSI report settings for PUSCH are RRC configured and the CSI request field in multicast DCI scrambled with SP-CSI C-RNTI activates one of the SP-CSI reports.

Figure 4 illustrates an exemplary Semi-Persistent multicast CSI reporting procedure, in accordance with certain aspects of the present disclosure. In Step1 of Figure 4, the Semi-Persistent CSI related physical layer signal (s) (e.g. NZP CSI-RS) is configured via RRC Reconfiguration message to each UE (i.e. UE1 and UE2 in Figure 4) during the establishment of multicast radio bearer. In Step 2 of Figure 4, a specific MAC CE is transmitted to all of the concerned UEs in multicast manner to activate the configured Semi-Persistent CSI related physical layer signal (s) .

In Step 3 and Step 5 of Figure 4, the CSI related physical layer signal (s) is transmitted periodically from the Base Station to each concerned UE. In Step 4 and Step 6 of Figure 4, the multicast CSI report is sent periodically from each concerned UE to the Base Station over different PUCCH resource. The periodicity is expressed by slots in the configuration. In Step 7 of Figure 4, a specific MAC CE is transmitted to all of the concerned UEs in multicast manner to deactivate the configured Semi-Persistent CSI related physical layer signal (s) . Then transmission of Semi-Persistent CSI related physical layer signal (s) is stopped by the Base Station. And the multicast CSI report is also stopped accordingly by both UE1 and UE2.

In Step 8 of Figure 4, a specific MAC CE is transmitted to all of the concerned UEs in multicast manner to activate the configured Semi-Persistent CSI related physical layer signal (s) . The gap between Step 7 and Step 8 of Figure 4 can be any number of slots. In Step 9 and Step 11 of Figure 4, the CSI related physical layer signal (s) is again transmitted periodically from the Base Station to each concerned UE. In Step 10 and Step 12 of Figure 4, the multicast CSI report is sent again periodically from each concerned UE to the Base Station over different PUCCH resource.

Higher layer (i.e. RRC) may configure Aperiodic multicast CSI triggering. The Aperiodic CSI triggering state is configured by RRC and activated by multicast MAC CE or L1 DCI (scheduling multicast transmission) depending on the number of RRC configured multicast CSI triggering states. When the number of RRC configured multicast CSI triggering states is smaller than the 2N (N is the bitwidth of a CSI request field in multicast DCI) , L1 DCI is used for its activation. Otherwise the combination of multicast MAC CE and L1 DCI is used for its activation. Aperiodic multicast CSI reporting is carried by PUSCH.

Figure 5 illustrates an exemplary Aperiodic multicast CSI reporting procedure, in accordance with certain aspects of the present disclosure. In Step1 of Figure 5, the CSI related physical layer signal (s) is configured via RRC Reconfiguration message to each UE (i.e. UE1 and UE2 in Figure 5) during the establishment of multicast radio bearer. In Step 2 and Step 2a of Figure 5, a specific MAC CE or L1 DCI is transmitted to all of the concerned UEs in multicast manner to activate the configured Aperiodic CSI related physical layer signal (s) . In Step 3 of Figure 5, the CSI related physical layer signal (s) is transmitted from the Base Station to each concerned UE after a configured number of slots (e.g. X slots) . In Step 4 of Figure 5, the multicast CSI report is sent from each concerned UE to the Base Station after a configured number of slots (e.g. Y slots) .

Resource Allocation for multicast CSI Feedback

When the multicast CSI reporting is carried by PUSCH for Semi-Persistent (SP) multicast CSI reporting and/or Aperiodic multicast CSI reporting, there are different options for PUSCH resource allocation. In the first option, the said multicast CSI reporting is piggybacked by each UE’s uplink data transmission (i.e. normal PUSCH) according to the timing configuration (e.g. via slot and slot offset configuration) required by the multicast CSI reporting. This case means the UE has a UL grant at the time duration (e.g. expressed by slots) required by the multicast CSI reporting. In the second option, one or a plural of SR configuration is configured for the said multicast CSI reporting. Then the said multicast CSI reporting triggers a SR according to the preconfigured SR configuration. The network schedules a specific UL grant to each UE participating the multicast reception for multicast CSI reporting. The network may explicitly indicate to UE that the particular UL grant is used for multicast CSI reporting. The UE send the multicast CSI reporting over the granted uplink resource to the network. In the third option, since network schedules the multicast transmission and configures the multicast CSI reporting, the network can configures or schedules the appropriate UL resources for the UEs to report CSI information. During or ahead of a particular multicast transmission, the network may provide the UE a special Configured Grant (CG) or Dynamic Grant to the UE via unicast L1 DCI, MAC CE or RRC signaling for each UE to perform the said multicast CSI reporting.

As an alternative, in case of PUSCH carrying Semi-Persistent (SP) multicast CSI reporting, this multicast CSI reporting can be dropped when there is already a unicast CSI reporting carrying by the same PUSCH serving the same purpose.

In certain systems, such as NR system, specific PUCCH Resource for downlink unicast transmission is configured for each CSI report configuration. Specific to CSI report configuration, PUCCH Resource is configured per uplink BWP. When the multicast CSI reporting is carried by PUCCH for Semi-Persistent (SP) multicast CSI reporting and/or Periodic multicast CSI reporting, unique PUSCH resource needs to be allocated to each UE participating the multicast reception. A new set of PUCCH resource set for NR multicast feedback can be defined in physical layer and needs to be added into TS38.213. Alternatively, the existing PUCCH resource set for unicast based feedback can be applicable to multicast CSI feedback.

The legacy PUCCH resource is identified by a PUCCH-Resource-ID, which expresses a unique PUCCH resource within a slot or a PUCCH resource allocation period. Considering the large number of UEs that are required to report CSI for multicast transmission, the current available PUCCH resource (or extended allocation of PUCCH resource) within one slot or one PUCCH resource allocation period may be not enough to support unique allocation of PUCCH to the all of the UEs that receive the multicast transmission in a cell. If the legacy method to allocate the PUCCH resource to unicast CSI report is used to allocate PUCCH resource to multicast CSI report, it may cause unnecessary PUCCH collision.

From network (i.e. gNB) perspective, the expected multicast CSI feedback from multiple UEs can span over a number of consecutive slots or PUCCH resource allocation periods. The sum of the consecutive slots is restricted by the timeliness of CSI in order to not produce out of date CSI report over the air interface. Correspondingly, the network can configure the PUCCH resources within consecutive number of slots of PUCCH resource allocation periods to the UEs participating the multicast reception for one multicast session or multiple multicast sessions. Hence, a slot offset, or an offset of PUCCH resource allocation period, is indicated to each UE that is expected to use the PUCCH resource for multicast CSI report. When the offset is configured as zero, the UE uses the PUCCH resource of the current slot or PUCCH resource allocation period according to the PUCCH-Resource-ID. When the offset is configured as k, the UE uses the PUCCH resource of the “t+k” slot or PUCCH resource allocation period according to the PUCCH-Resource-ID, where “t” is the current slot index.

Figure 6 illustrates an exemplary PUCCH resource assignment for multicast CSI reporting, in accordance with certain aspects of the present disclosure. As depicted in Figure 6, there are 16 PUCCH resources defined for each slot (i.e. slot n and slot n+1) . The PUCCH resource with ID 11 in slot n is allocated to UE-X. The PUCCH resource with ID 14 in slot n+1 is allocated to UE-Y. Both UE-X and UE-Y are receiving the same multicast transmission. UE-X and UE-Y are using the PUCCH resources in consecutive slots (i.e. slot n and slot n+1) to transmit the CSI report to the Base Station.

From example, in order to ensure the uniqueness of the PUCCH resource allocated to each UE, PUCCH-Resource-ID, Slot-Offset (or PUCCH resource allocation period Offset) and UL BWP-ID as a combination needs to be configured to each UE e.g. during RRC reconfiguration for multicast radio bearer establishment.

The resource allocation described in this disclosure can also be used to allocate the Uplink resource (e.g. PUCCH resource) for HARQ feedback from each UE to the network.

MAC CE based CSI Report

In certain systems, such as NR system, the legacy Uplink CSI report for unicast transmission is transmitted by the UE over PUCCH resources configured by the Base Station. One alternative way is support multicast CSI report via a specific uplink MAC CE from the UE to the Base Station.

This multicast CSI report MAC CE is multiplexed with other uplink MAC PDU data at MAC layer and then is carried by PUSCH. The Base station may indicate to the UE the required timing (e.g. counted by slots or subframes) for the UE to report the CSI via MAC CE. When a mulitcast CSI reporting is triggered and there is available UL grant in the time duration (e.g. counted by slots or subframes) as defined by the timing requirement of the CSI reporting, the CSI reporting may be prioritized during LCP procedure at the UE. The multicast CSI report MAC CE is assembled by MAC layer to general MAC PDU. MAC layer further delivers the multicast CSI report as part of MAC PDU to physical layer for transmission. The multicast CSI report event is cancelled if the multicast CSI report has been transmitted. When there is no UL grant available, the said multicast CSI reporting triggers a SR according to the preconfigured SR configuration. One or a plural of SR configuration is configured for the said multicast CSI reporting. The network may schedule a specific UL grant to each UE participating the multicast reception for multicast CSI reporting. The UE sends the MAC CE carrying multicast CSI reporting over the granted uplink resource to the network.

A MAC subheader with a specific LCID identifies the CSI Reporting MAC CE. The priority of the multicast CSI Reporting MAC CE can be fixed and is prioritized over UL normal data. For example, the priority of multicast CSI Reporting MAC CE can be set up to be the highest priority. The content of multicast CSI report (i.e. Report Quantity) consists of a combination of Channel Quality Indicator (CQI) , Precoding matrix indicator (PMI) , CSI-RS resource indicator (CRI) , SSBRI, Layer Indication (LI) , Rank Indication (RI) , and L1-RSRP, according to the dependency defined by NR legacy CSI report. The allowed combination for multicast CSI report follows the legacy definition as defined by the parameter reportQuantity within CSI-ReportConfig (in 3GPP TS 38.331) : {none} , {CRI, RI, PMI, CQI} , {CRI, RI, i1} , {CRI, RI, i1, CQI} , {CRI, RI, CQI} , {CRI, RSRP} , {ssb-Index-RSRP} , and {CRI, RI, LI, PMI, CQI} , where “il” expresses the wideband PMI index. The IE CSI-ReportConfig is configured to UE from the network during RRC Reconfiguration. Different Report Quantity combinations have different sizes for multicast CSI MAC CE. So then in general, one MAC CE format can be used to host one Report Quantity combination based multicast CSI report.

The IE CSI-ReportConfig configures the exact Report Quantity and their detailed restriction for UE to determine the exact report length of the CSI report. For example, when the cqi-FormatIndicator within CSI-ReportConfig indicates wideband-CQI, only a single wideband CQI index is reported. When wideband PMI reporting is configured, a wideband PMI (e.g. “il” ) is reported for the entire CSI reporting band. In case of subband CQI/PMI, more bits are used to for CQI/PMI report. Hence, the detailed configuration within CSI-ReportConfig leads to a variable size for multicast CSI MAC CE for the same Report Quantity combination.

One combination of the said Report Quantity within multicast CSI report requires one MAC CE format, since different combinations may require different byte lengths at the MAC CE. One format field may be included in the MAC CE to tell the exact format being used during multicast CSI report via MAC CE. There are 8 Report Quantity combinations and there are 7 valid Report Quantity combinations. Then 3 bits can be used to tell the format.

In order to distinguish the UE, each UE can include UE specific ID (e.g. C-RNTI) into the content of mutlicast CSI Reporting MAC CE. In order to distinguish different multicast transmission, each UE can include multicast specific ID (e.g. multicast session ID, DL MTCH logical channel ID, etc) into the content of mutlicast CSI Reporting MAC CE. With UE specific ID and multicast specific ID, the Base Station can tell which UE reports the CSI feedback for which multicast transmission.

In one embodiment, in order to desribe the length of the MAC CE, a Length Indicator field is used to tell the varaible size for a particular MAC CE format (i.e. a particular Report Quantity combination) of mutlicast CSI Reporting MAC CE.

As an example, the UE’s Report Quantity is configured as {CRI, RI, PMI, CQI} . And the cqi-FormatIndicator indicates single CQI reporting (i.e. wideband-CQI) and pmi-FormatIndicator indicates single PMI reporting (i.e. wideband-PMI) , then only CRI, RI, wideband CQI and wideband PMI is reported within multicast CSI Report MAC CE as Report Quantities. The CQI indices and their interpretations are given in section 5.2.2.1 of 3GPP TS38.214. Four bits are used to express CQI index. In this example, it is further assumed that the UE’s codebookType for CSI report is set as 'typeI-SinglePanel'for 2 antenna ports {3000, 3001} within CSI-ReportConfig. Then each PMI value corresponds to a codebook index given in Table 5.2.2.2.1-1 of 3GPP TS38.214. Hence, two bits are used to express PMI index. For simplicity, the CRI indicating the CSI-RS resource is assumed to be 4 bits and the RI indicating the Rank is assumed to be 2 bits. In summary, in this example, there are 12 bits in total used to express the Report Quantities of the CSI report within the multicast CSI report MAC CE.

Figure 7 illustrates an exemplary multicast CSI Reporting MAC CE structure for NR multicast, in accordance with certain aspects of the present disclosure. The exemplary multicast CSI Reporting MAC CE in Figure 7 includes the following fields. The field F indicates the format of the MAC CE (i.e. the Report Quantity combination) and this CSI Report MAC CE only provide CQI, PMI, RI and CRI information. The field F is 3 bits. The field CRI indicates the CSI-RS resource and the length of the field is 4 bits. The field R is Reserved bits, which is set to 0.

In Figure 7, the field RI indicates the derived value of the Rank Indicator for CSI reporting and the length of the field is 2 bits. The field CQI indicates the derived value of the Channel Quality Indicator for CSI reporting and the length of the field is 4 bit.

In Figure 7, the field MTCH-ID indicates the identity of the multicast logical channel (i.e. MTCH) that carries the traffic of multicast flow that maps to Downlink multicast PDSCH transmission. The length of MTCH-ID is 16 bits. Alternatively, the Network may configure a short format of MTCH-ID for CSI report MAC CE in order to reduce the overhead. The field C-RNTI indicates the identity of the UE that reports the CSI information and the length is 16 bits. Alternatively, the Network may configure a short format of UE ID for CSI report MAC CE in order to reduce the overhead. In addition, the field C-RNTI can be omitted if BS can identify the CSI report from which UE via additional way.

The description in this invention can be also applicable to the Uplink feedback procedure for NR broadcast services.

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:

Configuring CSI physical layer signals for measurements related to multicast transmission; and

Activating the configuration of the CSI physical layer signals related to multicast transmission.
The method of claim 1, wherein the CSI physical layer signals are configured to the UE participating the multicast reception via RRC Reconfiguration by the Base Station during multicast Radio Bearer establishment.
The method of claim 1, wherein the configuration of the CSI physical layer signals can be activated by the Base Station via multicast MAC CE.
The method of claim 3, wherein the multicast MAC CE is multiplexed with multicast data.
The method of claim 3, wherein the multicast MAC CE includes concantenated mutliple UE information related to the configuration of the CSI physical layer signals.
The method of claim 3, wherein the multicast MAC CE includes UE ID for UE to identify the information.
A method for wireless communications, further comprising:

Allocating the Uplink resource for multicast CSI report related to multicast transmission.
The method of claim 7, wherein the Uplink resource can be PUSCH resource as configured by Configured Grant or as scheduled by Dynamic Grant.
The method of claim 7, wherein the multicast CSI report triggers SR.
The method of claim 9, wherein the SR is sent via preconfigured SR configuration for multicast CSI reporting.
The method of claim 7, wherein the Uplink resource can be PUCCH resource as configured by the Base Station via RRC Reconfiguration during multicast Radio Bearer establishment.
The method of claim 11, wherein PUCCH resource as configured by the Base Station span over a consective slots or PUCCH resource allocation periods.
The method of claim 11, wherein the PUCCH resource is configured via a combination of PUCCH-Resource-ID, Slot-Offset (or PUCCH resource allocation period Offset) and UL BWP-ID.
A method for wireless communications, further comprising:

Performing multicast CSI report to support multicast transmission.
The method of claim 14, wherein the multicast CSI report can be sent at L1.
The method of claim 14, wherein the multicast CSI report can be sent via specific multicast CSI report MAC CE.
The method of claim 14, wherein the multicast CSI reporting triggers a SR according to the preconfigured SR configuration.
The method of claim 16, wherein the multicast CSI report MAC CE consists of a Report Quantity combination of Channel Quality Indicator (CQI) , Precoding matrix indicator (PMI) , CSI-RS resource indicator (CRI) , SSBRI, Layer Indication (LI) , Rank Indication (RI) , and L1-RSRP, according to the dependency defined by NR legacy CSI report.
The method of claim 16, wherein the multicast CSI report MAC CE consists of F field to indicate a particular Report Quantity combination.
The method of claim 16, wherein the multicast CSI report MAC CE consists of UE specific ID (e.g. C-RNTI)
The method of claim 16, wherein the multicast CSI report MAC CE consists of multicast specific ID (e.g. multicast session ID, DL MTCH logical channel ID, etc) .