WO2023096547A1

WO2023096547A1 - Implicit reconfiguration of csi-rs enhancements for nr ue

Info

Publication number: WO2023096547A1
Application number: PCT/SE2022/050991
Authority: WO
Inventors: Niklas Andgart; Ilmiawan SHUBHI; Sina MALEKI; Andres Reial; Ali Nader
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-11-24
Filing date: 2022-10-31
Publication date: 2023-06-01

Abstract

Methods, systems, and apparatuses for switching channel state information (CSI)-reference signal (RS) configurations without receiving explicit instructions or commands. A user equipment (UE) may be configured with at least a first and second CSI-RS configurations. The UE may determine that determining that a CSI-RS configuration switching condition is met and, if the CSI-RS configuration switching condition is determined to be met, switch from the first CSI-RS configuration to the second CSI-RS configuration. In some aspects, the CSI-RS configuration switching condition may be a pre-defined delay, an occurrence of a quantized timing, expiration of a validity timer, an occurrence of a scheduled switching instance, a cell being actively operational, a radio resource management (RRM) configuration in which multi-layer transmission is not possible or lower than a certain number of layers is used, or the UE is operating in a relaxed measurement and/or radio link monitoring mode.

Description

IMPLICIT RECONFIGURATION OF CSI-RS ENHANCEMENTS FOR NR UE

TECHNICAL FIELD

[001] The present disclosure generally relates to the technical field of telecommunication, and particularly to methods and the apparatus for transitioning between channel state information (CSI)-reference signal (RS) configurations.

BACKGROUND

[002] 1.1 Network energy consumption

[003] The network power consumption for New Radio (NR) is said to be less than Long- Term Evolution (LTE) because of NR’s lean design. In the current implementation, however, NR will most likely consume more power than LTE (e.g., due to the higher bandwidth and/or due to introduction of additional elements such as 64 transmit (TX)/receive (RX) ports with several digital radio frequency (RF) chains. As the network is expected to be able to support user equipment (UE) with its maximum capability (e.g., throughput, coverage, etc.), the network may need to use full configuration even when the maximum network support is actually rarely needed by the UEs.

[004] In addition, an increased number of TX/RX ports also leads to an increase to the number of reference signals (e.g., channel state information (CSI)-reference signal (RS)) needed to be transmitted by the network (and to be measured by the UE) for proper signal detection. Thus, the additional TX/RX ports may result in additional power consumption (e.g., to transmit a larger number of CSLRS to the UEs). Furthermore, the larger number of CSLRS transmissions may also consume the valuable network resources.

[005] 1.2 CSLRS configuration

[006] In NR, the CSI-RS generation procedures are defined in the 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 38.211 Section 7.5.1.5. The CSI-RS is used for time/frequency tracking, CSI computation, Layer 1 (Ll)-Reference Signal Received Power (RSRP) computation, Ll-Signal to Interference & Noise Ratio (SINR) computation, and mobility. Configured with CSI-RS, the UE then needs to follow the procedures described in 3GPP TS 38.214 Section 5.1.6.1.

[007] For a CSI-RS resource associated with an NZP-CSI-RS-ResourceSet with the higher layer parameter repetition set to 'on', the UE shall not expect to be configured with CSI-RS over the symbols during which the UE is also configured to monitor the Control Resource Set (CORESET). For other NZP-CSI-RS-ResourceSet configurations, if the UE is configured with a CSI-RS resource and a search space set associated with a CORESET in the same orthogonal frequency-division multiplexing (OFDM) symbol(s), the UE may assume that the CSI-RS and a physical downlink control channel (PDCCH) demodulation reference signal (DM-RS) transmitted in all the search space sets associated with CORESET are quasi co-located with 'typeD', if 'typeD' is applicable. This also applies to the case when CSI-RS and the CORESET are in different intra-band component carriers, if 'typeD' is applicable. Furthermore, the UE shall not expect to be configured with the CSI-RS in physical resource blocks (PRBs) that overlap those of the CORESET in the OFDM symbols occupied by the search space set(s).

[008] The UE is not expected to receive CSI-RS and System Information Block #1 (SIB J) message in the overlapping PRBs in the OFDM symbols where SIB1 is transmitted.

[009] If the UE is configured with Discontinuous Reception (DRX): if the UE is configured to monitor downlink control information (DCI) format 2 6 and configured by higher layer parameter ps-TransmitOtherPeriodicCSI to report CSI with the higher layer parameter reportConfigType set to 'periodic' and reportQuantity set to quantities other than CSI-RS Resources Indicator (CRI)-RSRP (‘cri-RSRP’) and Synchronization Signal Block (SSB) Index RSRP ('ssb-Index-RSRP') when drx-onDurationTimer in DRX-Config is not started, the most recent CSI measurement occasion occurs in DRX active time or during the time duration indicated by drx-onDurationTimer in DRX-Config also outside DRX active time for CSI to be reported; if the UE is configured to monitor DCI format 2 6 and configured by higher layer parameter ps-TransmitPeriodicLl-RSRP to report LI -RSRP with the higher layer parameter reportConfigType set to 'periodic' and reportQuantity set to cri-RSRP when drx- onDurationTimer in DRX-Config is not started, the most recent CSI measurement occasion occurs in DRX active time or during the time duration indicated by drx-onDurationTimer in DRX-Config also outside DRX active time for CSI to be reported; otherwise, the most recent CSI measurement occasion occurs in DRX active time for CSI to be reported.

[0010] According to the specification ofNR (i.e., 3GPP TS 38.214 Section 5.2.2.3.1), a UE can be configured with one or more non-zero power (NZP) CSI-RS resource set configuration(s) as indicated by the higher layer parameters CSI-ResourceConfig, and NZP-CSI-RS-ResourceSet. Each NZP CSI-RS resource set consists of K>1 NZP CSI-RS resource(s). TS 38.331 states the following regarding CSI-ResourceConfig'.

- ASN1 START

- TAG-CSI-RESOURCECONFIG-START

CSI-ResourceConfig ::= SEQUENCE { csi-ResourceConfigld CSI-ResourceConfigld. csi-RS-ResourceSetList CHOICE { nzp-CSI-RS-SSB SEQUENCE { nzp-CSI-RS-ResourceSetList SEQUENCE (SIZE (1..maxNrotNZP-CSI-RS-

ResourceSetsPerConfig)) OF NZP-CSI-RS-ResourceSetld OPTIONAL, — Need R csi-SSB-ResourceSetList SEQUENCE (SIZE (1..maxNrofCSLSSB-

ResourceSetsPerConfig)) OF C SI- S SB -Resources etld OPTIONAL — Need R

}, csi-IM-ResourceSetList SEQUENCE (SIZE (L.maxNrofCSI-IM-

ResourceSetsPerConfig)) OF CSLIM-ResourceSetld

}, bwp-Id BWP-Id, resourceType ENUMERATED { aperiodic, semiPersistent, periodic },

- TAG-CSI-RESOURCECONFIG-STOP

- ASN1STOP

[0011] TS 38.331 states the following regarding the NZP-CSI-RS-ResourceSe .

- ASN1 START

- TAG-NZP-CSI-RS-RESOURCESET-START

NZP-CSI-RS-ResourceSet ::= SEQUENCE { nzp-CSI-ResourceSetld NZP-CSI-RS-ResourceSetld, nzp-CSI-RS-Resources SEQUENCE (SIZE ( I ..maxNrofNZP-CSI-RS-

ResourcesPerSet)) OF NZP-CSI-RS-Resourceld, repetition ENUMERATED { on, off }

OPTIONAL, - Need S aperiodicTriggeringOffset INTEGER(0..6)

OPTIONAL, - Need S trs-Info ENUMERATED {true}

OPTIONAL, — Need R

[[ aperiodicTriggeringOffset-r 16 INTEGER(0..31)

OPTIONAL - Need S

]]

}

- TAG-NZP-CSI-RS-RESOURCESET-STOP

- ASN1STOP

[0012] In each of the NZP CSI-RS resources, the network can set the CSI-RS resource with different powerControlOffset, scramblingID, etc. TS 38.331 states the following:

- ASN1 START

- TAG-NZP-CSI-RS-RESOURCE-START

NZP-CSI-RS-Resource ::= SEQUENCE { nzp-CSI-RS-Resourceld NZP-CSI-RS-Resourceld, resourceMapping CSI-RS-ResourceMapping, powerControlOffset INTEGER (-8 .15), powerControlOffsetSS ENUMERATED{db-3, dbO, db3, db6} OPTIONAL, -

Need R scramblingID Scramblingld, periodicityAndOffset CSI-ResourcePeriodicityAndOffset OPTIONAL, —

Cond PeriodicOrSemiPersistent qcl-InfoPeriodicCSI-RS TCI-Stateld OPTIONAL, -

Cond Periodic

}

- TAG-NZP-CSI-RS-RESOURCE-STOP

- ASN1STOP

[0013] Before transmitting, the CSI-RS is mapped according to the configured CSI-RS- Re sour c eMapping. There, the network could set the configuration of the cdm-Type, frequencyDomainAllocation, nrofPorts, etc.

- ASN1 START

- TAG-CSI-RS-RESOURCEMAPPING-START CSI-RS-ResourceMapping ::= SEQUENCE { frequencyDomainAllocation CHOICE { rowl BIT STRING (SIZE (4)), row2 BIT STRING (SIZE (12)), row4 BIT STRING (SIZE (3)), other BIT STRING (SIZE (6)) nrofPorts ENUMERATED {pl,p2,p4,p8,pl2,pl6,p24,p32}, firstOFDMSymbolInTimeDomain INTEGER (0 .13), firstOFDMSymbolInTimeDomain2 INTEGER (2 .12)

OPTIONAL, — Need R cdm-Type ENUMERATED {noCDM, fd-CDM2, cdm4-FD2-TD2, cdm8-FD2-TD4}, density CHOICE { dot5 ENUMERATED {evenPRBs, oddPRBs}, one NULL, three NULL, spare NULL freqBand CSI-FrequencyOccupation,

- TAG-CSI-RS-RESOURCEMAPPING-STOP

- ASN1STOP

[0014] TS. 38.214 section 5.2.2.3.1 provides the following explanation of the CSI-RS parameters: nzp-CSI-RS-Resourceld determines CSI-RS resource configuration identity.

- periodicityAndOjfset defines the CSI-RS periodicity and slot offset for periodic/semi- persi stent CSI-RS . All the CSI-RS resources within one set are configured with the same periodicity, while the slot offset can be same or different for different CSI-RS resources. resourceMapping defines the number of ports, CDM-type, and OFDM symbol and subcarrier occupancy of the CSI-RS resource within a slot that are given in Clause 7.4.1.5 of [4, TS 38.211], nrofPorts in resourceMapping defines the number of CSI-RS ports, where the allowable values are given in Clause 7.4.1.5 of [4, TS 38.211], density in resourceMapping defines CSI-RS frequency density of each CSI-RS port per PRB, and CSI-RS PRB offset in case of the density value of 1/2, where the allowable values are given in Clause 7.4.1.5 of [4, TS 38.211], For density 1/2, the odd/even PRB allocation indicated in density is with respect to the common resource block grid. cdm-Type in resourceMapping defines CDM values and pattern, where the allowable values are given in Clause 7.4.1.5 of [4, TS 38.211],

- powerControlOffset. which is the assumed ratio of PDSCH EPRE to NZP CSI-RS EPRE when UE derives CSI feedback and takes values in the range of [-8, 15] dB with 1 dB step size.

- powerControlOffsetSS'. which is the assumed ratio of NZP CSI-RS EPRE to SS/PBCH block EPRE. scramblingID defines scrambling ID of CSI-RS with length of 10 bits.

BWP -Id in CSI-ResourceConfig defines which bandwidth part the configured CSI-RS is located in. qcl-InfoPeriodicCSI-RS contains a reference to a TCI-State indicating QCL source RS(s) and QCL type(s). If the TCI-State is configured with a reference to an RS configured with qcl-Type set to 'typeD' association, that RS may be an SS/PBCH block located in the same or different CC/DL BWP or a CSI-RS resource configured as periodic located in the same or different CC/DL BWP.

[0015] The CSI-RS resource (or the CSI-RS resource-set) that the UE needs to measure is configured in Radio Resource Control (RRC) configuration (e.g., in the CSI-MeasConfig information element (IE)). In the CSI-MeasConfig IE, the network, based on its certain consideration, may add, or remove (release) the CSI-RS or the (CSI-RS resource-set) that UE needs to measure. 3GPP TS 38.331 states the following:

- ASN1 START

- TAG-CSI-MEASCONFIG-START

CSI-MeasConfig ::= SEQUENCE { nzp-CSLRS-ResourceToAddModList SEQUENCE (SIZE (L.maxNrofNZP-CSI-RS-

Resources)) OF NZP-CSLRS-Resource OPTIONAL, - Need N nzp-CSLRS-ResourceToReleaseList SEQUENCE (SIZE ( I ..maxNrofNZP-CSI-RS-

Resources)) OF NZP-CSLRS-Resourceld OPTIONAL, - Need N nzp-CSLRS-ResourceSetToAddModList SEQUENCE (SIZE (1..maxNrotNZP-CSI-RS-

ResourceSets)) OF NZP-CSI-RS-ResourceSet OPTIONAL, - Need N nzp-CSLRS-ResourceSetToReleaseList SEQUENCE (SIZE (1..maxNrotNZP-CSI-RS-

ResourceSets)) OF NZP-CSI-RS-ResourceSetld csi-IM-ResourceT o AddModLi st SEQUENCE (SIZE (L.maxNrofC SLIM- Resources)) OF CSI-IM-Resource OPTIONAL, - Need N c si -IM-ResourceT oRel easeLi st SEQUENCE (SIZE (L.maxNrofCSI-IM-

Resources)) OF CSI-IM-Resourceld OPTIONAL, - Need N csi-IM-ResourceSetToAddModList SEQUENCE (SIZE (L.maxNrofCSI-IM-

ResourceSets)) OF CSI-IM-ResourceSet OPTIONAL, - Need N csi-IM-ResourceSetToReleaseList SEQUENCE (SIZE (L.maxNrofCSI-IM-

ResourceSets)) OF CSI-IM-ResourceSetld OPTIONAL, — Need N csi-SSB-ResourceSetToAddModList SEQUENCE (SIZE (1..maxNrofCSI-SSB-

ResourceSets)) OF CSI-SSB-ResourceSet OPTIONAL, — Need N csi-SSB-ResourceSetToReleaseList SEQUENCE (SIZE (1. maxNrofCSI-SSB-

ResourceSets)) OF CSI-SSB-ResourceSetld OPTIONAL, — Need N csi-ResourceConfigToAddModList SEQUENCE (SIZE (1..maxNrofCSL

ResourceConfigurations)) OF CSI-ResourceConfig

OPTIONAL, - Need N csi-ResourceConfigToReleaseList SEQUENCE (SIZE (1..maxNrofCSI-

ResourceConfigurations)) OF CSI-ResourceConfigld

OPTIONAL, - Need N csi-ReportConfigToAddModList SEQUENCE (SIZE (1..maxNrofCSI-

ReportConfigurations)) OF CSI-ReportConfig OPTIONAL, — Need N csi-ReportConfigToReleaseList SEQUENCE (SIZE (L.maxNrofCSI-

ReportConfigurations)) OF CSI-ReportConfigld

OPTIONAL, - Need N reportTriggerSize INTEGER (0..6)

OPTIONAL, - Need M aperiodicTriggerStateList SetupRelease { CSLAperiodicTriggerStateList }

OPTIONAL, - Need M semiPersistentOnPUSCH-TriggerStateList SetupRelease { CSI-SemiPersistentOnPUSCH- TriggerStateList } OPTIONAL, — Need M

[[ reportTriggerSizeDCI-0-2-rl6 INTEGER (0..6)

OPTIONAL - Need R

]]

}

- TAG-CSI-MEASCONFIG-STOP

- ASN1STOP

[0016] FIG. 1 shows an overview of the CSLRS parameters that were discussed above. Each parameter is composed of several configurations (e.g., CSI-RS-ResourceMapping is composed of nofPorts. or NZP-CSI-RS-Resource is composed of ResourceMapping and powerControlOffsetsSS parameters). For simplicity, FIG. 1 does not include all the configurations for each parameter. As shown in FIG. 1, parameters are simply a mapping with each other using its different configurations. Most of the parameters are mapped to CSI- MeasConfig. [0017] After receiving the CSI-RS, the UE then reports its measurement back to the network. The reporting configuration for CSI can be aperiodic (e.g., using the Physical Uplink Shared Channel (PUSCH)), periodic (e.g., using the Physical Uplink Control Channel (PUCCH)), or semi-persistent (e.g., using PUCCH, and DCI activated PUSCH). The CSI-RS Resources can be periodic, semi-persistent, or aperiodic. Table 5.2.1.4-1 in TS 38.214 (rewritten below as Table 1) shows the supported combinations of CSI Reporting configurations and CSI-RS Resource configurations and how the CSI Reporting is triggered for each CSI-RS Resource configuration.

Table 1. Triggering/ Activation of CSI Reporting for the Possible CSI-RS Configurations SUMMARY

[0018] Aspects of the invention may relate to a user equipment (UE) that switches between multiple channel state information (CSI)-reference signal (RS) configurations without receiving explicit instructions or commands. In some aspects, the UE may switch between CSI-RS configurations based on predetermined rules (e.g., expiry of a timer, cell states, radio resource management (RRM) configurations, and/or measurements). In some aspects, the switching may be aligned with similar switching on the network node, which may apply the same criteria for transitioning between CSI-RS configurations.

[0019] In some aspects, the implicit reconfiguration mechanisms may be used when the network node has configured multiple resource mappings, or multiple configurations per parameter within a CSI-RS resource (e.g., different number of ports, power control offset, quasi-colocation (QCL) information). In some aspects, medium access control (MAC) control element (CE) or downlink control information (DCI) may be used to activate/deactivate a certain configuration (or switch between those configurations).

[0020] Some aspects of the invention may relate to a UE configured with multiple CSI-RS configurations. In some aspects, the UE may switch between one or more CSI-RS configurations based on a set of one or more conditions. In some aspects, the multiple configurations are achieved through: (i) setting multiple configurations for a parameter in a CSI- RS resource, (ii) setting multiple CSI-RS resources where each of the CSI-RS resource differs in at least one parameter, and/or (iii) setting multiple CSI-RS resource sets where each of the CSI resource set differs in at least one CSI-RS resource parameter. In some aspects, one of the multiple CSI-RS configurations may be a default configuration. In some aspects, the switching may be triggered by expiry of a timer. In some aspects, the switching may be triggered by channel or traffic properties. In some aspects, the switching may take place after a specified delay or a quantized time.

[0021] Some aspects of the invention may provide the advantage of reducing transmission overhead when a UE switches between CSI-RS configurations without explicit signaling. Some aspects of the invention may provide reduced transmission overhead compared to legacy operation where the UE requires a full Radio Resource Control (RRC) reconfiguration to dynamically change the CSI-RS configuration. Some aspects of the invention may provide reduced transmission overhead compared to signaling the UE for each transition between CSI- RS configurations.

[0022] One aspect of the invention may provide a method performed by a user equipment (UE) configured with at least a first channel state information (CSI)-reference signal (RS) configuration and a second CSI-RS configuration. The method may include determining that a CSI-RS configuration switching condition is met. The method may include, if the CSI-RS configuration switching condition is determined to be met, switching from the first CSI-RS configuration to the second CSI-RS configuration.

[0023] Another aspect of the invention may provide a user equipment (UE) configured with at least a first channel state information (CSI)-reference signal (RS) configuration and a second CSI-RS configuration. The UE may be adapted to determine that a CSI-RS configuration switching condition is met. The UE may be adapted to, if the CSI-RS configuration switching condition is determined to be met, switch from the first CSI-RS configuration to the second CSI- RS configuration.

[0024] Still another aspect of the invention may provide a computer program including instructions for adapting an apparatus to perform any of the methods set forth above. Yet another aspect of the invention may provide a carrier containing the computer program, and the carrier may be one of an electronic signal, optical signal, radio signal, or compute readable storage medium.

[0025] Still another aspect of the invention may provide a user equipment (UE) including processing circuitry and a memory. The memory may contain instructions executable by the processing circuitry, whereby the apparatus is operative to perform any of the methods set forth above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0027] FIG. 1 provides an overview of the channel state information (CSI)-reference signal (RS) parameter and its configurations.

[0028] FIG. 2 illustrates a UE according to some aspects. [0029] FIG. 3 illustrates a network node according to some aspects.

[0030] FIG. 4 is a flowchart illustrating a process according to some aspects.

[0031] FIG. 5 is a flowchart illustrating a process according to some aspects.

DETAILED DESCRIPTION

[0032] In this application, the term “node” can be a network node or a user equipment (UE). Examples of network nodes include, but are not limited to, a NodeB, a base station (BS), a multistandard radio (MSR) radio node such as a MSR BS, an eNodeB, a gNodeB, a Master eNB (MeNB), a Secondary eNB (SeNB), integrated access backhaul (IAB) node, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), Central Unit (e.g. in a gNB), Distributed Unit (e.g. in a gNB), Baseband Unit, Centralized Baseband, C-RAN, access point (AP), transmission points, transmission nodes, remote radio unit (RRU), remote radio head (RRH), nodes in distributed antenna system (DAS), core network node (e.g. MSC, MME, etc.), O&M, OSS, SON, positioning node (e.g. E-SMLC).

[0033] In this application, the term “user equipment” or “UE” is a non-limiting term that refers to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UEs include, but are not limited to, a target device, a device to device (D2D) UE, a vehicular to vehicular (V2V), a machine type UE, an machine type communication (MTC) UE, a UE capable of machine to machine (M2M) communication, a PDA, a Tablet, a mobile terminal(s), a smart phone, laptop embedded equipment (LEE), laptop mounted equipment (LME), and USB dongles.

[0034] In this application, the terms “radio network node,” “network node,” and “NW node” is generic terminology that refers to any kind of network node including but not limited to a base station, a radio base station, a base transceiver station, a base station controller, a network controller, an evolved Node B (eNB), a Node B, a gNodeB (gNB), a relay node, an access point (AP), a radio access point, a Remote Radio Unit (RRU), a Remote Radio Head (RRH), a Central Unit (e.g., in a gNB), a Distributed Unit (e.g., in a gNB), a Baseband Unit, a Centralized Baseband, a C-RAN, a Mobile Management Entity (MME), and a PDN Gateway (PGW). [0035] In this application, the term “radio access technology” or “RAT” may refer to any RAT including, for example and without limitation, UTRA, E-UTRA, narrow band internet of things (NB-IoT), WiFi, Bluetooth, next generation RAT, New Radio (NR), 4G, and 5G. Any of the equipment denoted by the terms “node,” “network node,” or “radio network node” may be capable of supporting a single or multiple RATs.

[0036] FIG. 2 is a block diagram of a UE 102 according to some aspects. As shown in FIG. 2, the UE 102 may include: processing circuitry (PC) 202, which may include one or more processors (P) 255 (e.g., one or more general purpose microprocessors and/or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like); communication circuitry 248, which is coupled to an antenna arrangement 249 comprising one or more antennas and which comprises a transmitter (Tx) 245 and a receiver (Rx) 247 for enabling UE 102 to transmit data and receive data (e.g., wirelessly transmit/receive data); and a local storage unit (a.k.a., “data storage system”) 208, which may include one or more non-volatile storage devices and/or one or more volatile storage devices. In some aspects where PC 202 includes a programmable processor, a computer program product (CPP) 241 may be provided. In some aspects, the CPP 241 may include a computer readable medium (CRM) 242 storing a computer program (CP) 243 comprising computer readable instructions (CRI) 244. CRM 242 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some aspects, the CRI 244 of computer program 243 is configured such that when executed by PC 202, the CRI causes UE 102 to perform steps described herein (e.g., steps described herein with reference to the processes 400 and 500). In other aspects, the UE 102 may be configured to perform steps described herein without the need for code. That is, for example, the PC 202 may consist merely of one or more ASICs. Hence, the features of the aspects described herein may be implemented in hardware and/or software.

[0037] FIG. 3 is a block diagram of a network node 104, according to some aspects. As shown in FIG. 3, the network node 104 may comprise: processing circuitry (PC) 302, which may include one or more processors (P) 355 (e.g., one or more general purpose microprocessors and/or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like), which processors may be co-located in a single housing or in a single data center or may be geographically distributed (i.e., the network node 104 may be a distributed computing apparatus); a network interface 368 comprising a transmitter (Tx) 365 and a receiver (Rx) 367 for enabling the network node 104 to transmit data to and receive data from other nodes connected to a network 110 (e.g., an Internet Protocol (IP) network) to which network interface 368 is connected; communication circuitry 348, which is coupled to an antenna arrangement 349 comprising one or more antennas and which comprises a transmitter (Tx) 345 and a receiver (Rx) 347 for enabling the network node 104 to transmit data and receive data (e.g., wirelessly transmit/receive data); and a local storage unit (a.k.a., “data storage system”) 308, which may include one or more non-volatile storage devices and/or one or more volatile storage devices. In aspects where PC 302 includes a programmable processor, a computer program product (CPP) 341 may be provided. CPP 341 includes a computer readable medium (CRM) 342 storing a computer program (CP) 343 comprising computer readable instructions (CRI) 344. CRM 342 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some aspects, the CRI 344 of computer program 343 may be configured such that when executed by PC 302, the CRI causes the network node 104 to perform steps described herein. In other aspects, the network node 104 may be configured to perform steps described herein without the need for code. That is, for example, PC 302 may consist merely of one or more ASICs. Hence, the features of the aspects described herein may be implemented in hardware and/or software.

[0038] Aspects of the present invention may enable a fast and/or resource efficient dynamic CSI-RS configuration adaption. In some aspects, the dynamic CSI-RS configuration adaption may be enabled by:

(a) configuring multiple resource mappings, or multiple configurations per parameter within a channel state information (CSI)-reference signal (RS) resource (e.g., different number of ports, power control offset, and/or quasi-colocation (QCL) information, etc.) and using medium access control (MAC) control element (CE) or downlink control information (DCI) to activate or deactivate a certain configuration (and/or to switch between those configurations); (b) configuring multiple CSI-RS resources within one CSI-RS resource set and using MAC CE or DCI to activate or deactivate the configured CSI-RS resources (and/or to switch between CSI-RS resources);

(c) configuring multiple CSI-RS resource sets and using MAC CE or DCI to activate or deactivate one or more configured CSI-RS resource set (or switch between CSI-RS resource sets); and/or

(d) other CSI-RS parameters included in CSI-Measconfig can have multiple CSI-RS configurations and using MAC CE or DCI to activate or deactivate one or more configured CSI-RS resource set (and/or to switch between CSI-RS resource sets).

[0039] In some aspects, the UE 102 may be configured with more than one CSI-RS configuration. Aspects of the invention may provide a fast dynamic adaptation mechanism in which the UE 102 is capable of being caused (e.g., indicated) to switch between different CSI- RS configurations. In some aspects, the switching may be, for example, done by the network node 104 during the port adaptation (e.g., port adaptation in which the network node 104 determines to change the number of ports that will be used to serve the UE 102).

[0040] In some aspects, the term “multiple CSI-RS configurations” may refer to multiple CSI-RS configurations that can be activated or deactivated or switched through MAC-CE or DCI signaling. That is, the multiple CSI-RS confirmations are different than existing CSI-RS configurations in which multiple CSI-RS configurations are added or released through RRC (re)configuration.

[0041] In some aspects, the bit field in the DCI may indicate whether the default configuration or another configuration is activated. In some aspects, the UE 102 may be configured with a first CSI-RS configuration and a second CSI-RS configuration with one of the first and second configurations being the default. In some aspects, an additional bit in the DCI (e.g., DCI 1-1/2) may be configured. In some aspects, if the UE 102 receives the additional bit in the DCI, and the additional bit has a first bit status (e.g., a bit status of “1”), the UE 102 may consider the non-default CSI-RS configuration as activated and may consider the default CSI-RS configuration as deactivated. In some aspects, if the UE 102 receives the additional bit in the DCI, and the additional bit has a second bit status (e.g., a bit status of “0”), which may be considered reserved, the UE 102 may consider the default CSI-RS configuration as the active configuration. In some alternative aspects, the DCI may include two or more additional bits, and the number of additional bits in the DCI may depend on the number of CSI-RS configurations (e.g., the DCI may include two additional bits to specify one of up to four CSI-RS configurations, and 00 may indicate the default CSI-RS configuration).

[0042] In some aspects, when multiple configurations are not set for the UE 102, a legacy behavior may apply. For example, in some aspects, if multiple CSI-RS configurations are not set for the UE 102, the UE 102 may need to monitor all of the CSI-RS, which may be included in, for example, CSI-MeasConfig. In another example, in some aspects, the additional bit field in the DCI used for the adaptation indication may not be included in the DCI transmitted to the UE 102.

[0043] In some aspects, by configuring the UE 102 with multiple CSI-RS configurations that can be activated/deactivated or switched (e.g., through MAC-CE or DCI), the network node 104 may have flexibility on which CSI-RS should be used at one time instance. In some aspects, the network node 104 may select the active CSI-RS configurations based on, for example, the state of the port adaptation. For example, in some aspects, the network node 104 may use the following process to exploit the multiple CSI-RS configurations.

[0044] In some aspects, the process may include a first step in which the network node 104 configures the UE 102 with multiple CSI-RS configurations (e.g., including at least first and second CSI-RS configurations). In some aspects, in the first step, the network node 104 configures the UE 102 with multiple CSI-RS configurations by, for example, configuring the UE 102 to have more than one parameter configuration (e.g., parameters inside the CSI-RS- ResourceMapping IE).

[0045] In some aspects, the process may include a second step in which the network node 104 causes (e.g., indicates) the UE 102 to switch from the first CSI-RS configuration to the second CSI-RS configuration. In some aspects, the network node 104 may decide to change the CSI-RS configuration, for example, when there are no more UEs 102 active in the cell, or when no UEs 102 are active that require or can take advantage of transmission with a large number of ports (e.g., sustained transmission with multiple layers and narrow beams). In some aspects, in this situation, the network node 104 may decide to switch from the first CSI-RS configuration suitable for a larger number of ports transmission to the second CSI-RS configuration suitable for a smaller number of ports transmission. In some aspects, as described above, the network node 104 may cause (e.g., indicate) the UE 102 to switch CSI-RS configurations, for example, via DCI or MAC-CE.

[0046] In some aspects, the process may include a third step in which, after sending the switching indication, the network node 104 transmits the CSI-RS according to the second CSI- RS configuration.

[0047] In some aspects, the network node 104 may configure the UE 102 through higher layer signaling (e.g., Radio Resource Control (RRC) signaling if the activation/deactivation mechanism is DCI based), MAC CE based, and also the underlying configuration (e.g., additional bit field and its interpretation in the DCI). In some alternative aspects, the UE 102 may be pre-configured (e.g., as in standardization documentations). For example, in some aspects, if there are two fields configured for a parameter (e.g., number of ports), then the UE 102 may automatically expect a MAC CE or DCI to be able to activate or deactivate the configurations (e.g., as determined in the standards).

[0048] In some aspects, on the UE 102 side, the UE 102 may receive multiple CSI-RS configurations (e.g., including at least first and second CSI-RS configurations). In some aspects, the UE 102 may receive the multiple CSI-RS configurations, for example, through RRC signaling. In some aspects, the UE 102 may measure or report based on one of the first and configurations as the default configuration, and the UE 102 may measure and report based on the other of the first and second configurations as a non-default configuration. In some aspects, the UE 102 may, in one time instant, receive a MAC CE command or a DCI indicating that the UE 102 should perform measurements or reporting based on the second configuration. In some aspects, the UE 102 may measure the CSI-RS based on the second CSI-RS configuration or report CSI based on measuring the second CSI-RS configuration.

[0049] In some aspects, a group of UEs 102 may receive command to switch to a second CSI-RS configuration. In some aspects, this may be implemented, for example, as a group MAC or a DCI using group common search space. In some aspects, a group of UEs 102 can be configured to, using low signaling overhead and low latency, switch CSI-RS configurations. In some aspects, the individual CSI-RS configurations may still be configured per-UE. In some aspects, the group switching command may be, for example, formulated as: (a) all UEs 102 in group switch to specific configuration index (e.g., switch to nzp-CSI-RS-ResourcesDefault or nzp-CSI-RS-ResourcesB), or (b) all UEs 102 in group switch to an implicitly indicated configuration (e.g., switch to CSI-RS configuration with shortest periodicity, densest allocation in time/frequency, largest number of ports, etc.).

[0050] Implicit timing of transitions between configurations

[0051] In some aspects, the UE 102 may switch from one CSI-RS confirmation to another CSI-RS configuration after having received a CSI-RS confirmation transition instruction. In some aspects, the switch to the other CSI-RS configuration may take effect after a certain predefined time. In some aspects, the predefined time may be potentially quantized to certain possible timings (e.g., the other CSI-RS configuration may take effect the next slot fulfilling slot no mod M = 0, where mod is the modulo operation). In some other aspects, the predefined time may be specified in a symbol basis, and the UE 102 may switch to the other CSI-RS configuration at the first symbol of the first slot after the predefined time. In some aspects, the time until the CSI-RS configuration change takes effect may be configured by higher layers or included by adding additional bit fields in the DCI. In some aspects, the standard may define the maximum or minimum time that is allowed for the switching between CSI-RS configurations. In some aspects, the predefined time may be different (e.g., based on the capability of the UE 102 and/or subcarrier spacing (SCS)).

[0052] In some aspects, the transition back to a CSI-RS configuration (e.g., to a default CSI- RS configuration) may be triggered by a timer. In some aspects, when in a non-default CSI-RS configuration and the timer expires, the UE 102 may switch back to the default configuration.

[0053] In some aspects, one or more validity timer durations may be assigned. In some aspects, the one or more validity timer durations may be configured by higher layers (e.g., RRC signaling). In some aspects, the one or more timers may be configured in, for example, milliseconds (ms) or in slots. For example, in some aspects, a UE 102 in slot n indicated with a validity timer of t slots may apply the current CSI-RS configuration until slot n+t. For another example, in some aspects, the validity timer may be in units of certain events (e.g., a number of discontinuous reception (DRX) cycles). For yet another example, in some aspects, the timer may be set in a grid-based manner (e.g., subframe number). In some aspects, if the UE 102 is configured with a timer of, for example, 1 subframe, the UE 102 may apply the current CSI-RS configuration until the last slot of the current subframe. In some aspects, if the UE 102 is configured with a timer of, for example, 2 subframes, the UE 102 may apply the current CSI-RS configuration until the last slot of the next subframe. In some aspects, the value (e.g., subframe number) may be an integer and/or a fraction (e.g., U, 14, 14, etc.).

[0054] In some aspects in which two or more timers are configured for the UE 102, the DCI may include a validity timer bit field (e.g., an additional bit field) that indicates a timer of the two or more timers. For example, in some aspects, a bit with a value of 0 may correspond to a first value of the timer, and a bit with a value of 1 may correspond to a second value of the timer. In some aspects, if a UE 102 receives an indication to switch to a second CSI-RS state (e.g., through a bit field in the DCI) and an indication of a second value of the timer (e.g., through a validity timer bit field in the DCI having a value of 1), the UE 101 may switch to the second CSI-RS configuration and will stay in the second CSI-RS configuration for a duration according to the second value configured to the timer.

[0055] In some aspects, the timer may be started when the UE 102 enters a non-default CSI- RS configuration (e.g., by receiving a Layer 1 (LI) (e.g., DCI), Layer 2 (L2) (e.g., MAC CE), or Layer 3 (L3) (e.g., RRC) configuration command or by any other implicit means described below). In some aspects, the timer may count down while a predetermined set of one or more conditions hold. In some aspects, the set of one or more conditions include one or more of the following conditions: (i) no CSI-RS transmission instances according to the configuration are signaled to the UE 102 by the network node 104, (ii) no CSI-RS transmissions according to the configuration are detected by the UE 102, (iii) no CSI-RS measurement reports on the corresponding resources are requested by the network node 104, (iv) no data has been scheduled for the UE 102 on a specific channel or in relation to a specific transmission (e.g., a multicast transmission), and/or (v) no multiple-input multiple-output (MIMO) layer transmissions, or fewer layers than a certain level. In some aspects, if at any time instance a condition of the set of one or more conditions does not hold (e.g., because a CSI-RS transmission is signaled or detected), the validity timer may be restarted. In some aspects, multiple sets of conditions may be predefined by RRC signaling. In some aspects, the non-default CSI-RS configuration or CSI- RS transmission instance signaling may include a bit field indicating which set of conditions should be applied by the UE 102. [0056] In some aspects, the timers may additionally or alternatively be restarted (and the resulting time at the CSI-RS configuration will be prolonged) based on certain events (e.g., when the UE 102 has been scheduled in downlink (DL), when the UE 102 has been scheduled in uplink (UL), or by reception of a certain DCI format). In some aspects, the network node 104 may transmit a special DCI (e.g., separately to individual UEs 102 using Cell Radio Network Temporary Identifiers (C-RNTIs) or as group-common signaling using a predetermined group Radio Network Temporary Identifiers (RNTI)) indicating that the CSI-RS validity timer should be restarted. In some aspects, to restart the validity timer, the network node 104 may additionally or alternatively may resend a LI -2 command to start (or restart) the same nondefault CSI-RS configuration.

[0057] In some aspects, the UE 102 may be configured with a default CSI-RS configuration and with a non-default CSI-RS configuration. In some aspects, the UE 102 may start with performing CSI-RS related measurements or reporting based on the default CSI-RS configuration. In some aspects, the default CSI-RS configuration may be pre-configured, or, alternatively, higher layer signaling may be used to define the starting CSI-RS configuration, which would be the default configuration. In some aspects, the UE 102 may then receive an indication (e.g., through a DCI or MAC CE signaling) to perform CSI-RS measurements based on the non-default CSI-RS configuration. In some aspects, the non-default CSI-RS configuration may be time-limited based on the configured or pre-configured timer values. In some aspects, while the timer is running, the UE 102 may be indicated again to perform CSI-RS measurements based on the non-default configuration and provide a new timer value. In some aspects, the UE 102 may, in response, stop the currently running timer and start the new timer (or, alternatively, the UE 102 may add the new timer to the remaining duration of the existing timer).

[0058] In some aspects, the UE 102 may be configured additionally with a Connected Mode DRX (C-DRX) configuration. In some aspects, the indicated non-default CSI-RS configuration with the timer is only applicable as long as the UE 102 is in active time (e.g., onDurationTimer or inactivityTimer are running). In some alternative aspects, the timer may keep running even if the UE 102 is not in active time. [0059] Predetermined CSI-RS configuration switching

[0060] In some aspects, the network node 104 may pre-define a schedule for switching to a non-default CSI-RS configuration. For example, in some aspects, in the beginning of frame numbers System Frame Number (SFN) mod K = 0, the configuration may be switched to a nondefault configuration. In some aspects, the non-default CSI-RS configuration may support a larger number of ports to allow higher-efficiency multi-antenna transmissions. In some aspects, once the non-default configuration is in effect, the validity timer may be started, and the procedure described above may be applied. In some aspects, when the timer expires (e.g., after zero, one, or more restarts), the CSI-RS configuration may revert to the default configurations. In some aspects, after reverting to the default CSI-RS configuration, at the next instance of SFN mod K = 0, the switching to the non-default configuration will be repeated.

[0061] In some aspects, the value of K may correspond to time scales of seconds or tens of seconds. In some aspects, the schedule (e.g., the value of K or other ways to define the switching instances) may be provided to the UE 102 in system information (SI) or via RRC signaling.

[0062] Other implicit means for switching

[0063] In some aspects, the UE 102 (if allowed by network configuration) may implicitly switch to a non-default configuration based on the state of the cell. For example, in some aspects, in case of carrier aggregation, the UE 102 may switch to a non-default CSI-RS configuration during the time the cell (SCell) is actively operational and switch to a default CSI- RS configuration when the SCell is dormant or deactivated. In some aspects, when the SCell is dormant or deactivated, a lower rate of CSI-RS transmission measurement and reporting may suffice.

[0064] In some aspects, the UE 102 (if allowed by network configuration) may implicitly switch to a non-default configuration based on a specific RRM configuration. In some aspects, if the RRM configuration provided to the UE 102 is such that multi-layer transmission is not possible or lower than a certain number of layers, the UE 102 may implicitly during such configuration switch to another (e.g., non-default) CSI-RS configuration. Example of such RRM configurations are bandwidth parts (BWPs) in which maximum number of layers are configured, or if the UE 102 is configured with discrete Fourier transform (DFT) spread orthogonal frequency division multiplexing (OFDM) (DFT-s-OFDM) in which case only single layer transmission may be allowed.

[0065] In some aspects, the UE 102 (if allowed by network configuration) may implicitly switch to a non-default configuration based on a Measurement Relaxation state. In some aspects, during the time the UE 102 is operating in a relaxed measurement/radio link monitoring mode, the UE 102 may switch to a non-default CSI-RS configuration. In some aspects, a new mechanism may be used for the UE 102 to announce the relaxed measurement/radio link monitoring mode to the network node 104 (e.g., the UE 102 may assist the network node 104), so that the network node 104 and the UE 102 are aligned on CSI-RS configuration change. In some aspects, the relaxed measurement/radio link monitoring mode announcement may be done via an explicit UL message or piggy -backed on an UL message (e.g., on PUSCH, or as part of CSI report on Physical Uplink Control Channel (PUCCH)/ Physical Uplink Shared Channel (PUSCH)).

[0066] FIG. 4 illustrates a process 400 performed by the user equipment (UE) 102 according to some aspects. In some aspects, the UE 102 may be configured with at least a first channel state information (CSI)-reference signal (RS) configuration and a second CSI-RS configuration. In some aspects, the UE 102 may be configured with additional CSI-RS configurations. In some aspects, the first CSI-RS configuration may include a configuration (e.g., value) for a parameter (e.g., number of ports, power control offset, quasi-colocation (QCL) information) in a CSI-RS resource, and the second CSI-RS configuration may include a different configuration for the parameter in the CSI-RS resource. In some aspects, the first CSI-RS configuration may include a CSI-RS resource, and the second CSI-RS configuration may include a different CSI-RS resource. In some aspects, the first CSI-RS configuration may include a CSI-RS resource set, and the second CSI-RS configuration may include a different CSI-RS resource set.

[0067] In some aspects, the first CSI-RS configuration may be a default CSI-RS configuration, and the second CSI-RS configuration may be a non-default CSI-RS configuration. In some alternative aspects, the first CSI-RS configuration may be a non-default CSI-RS configuration, and the second CSI-RS configuration may be a default CSI-RS configuration. [0068] In some aspects, the process 400 may include an optional step 402 in which the UE 102 receives the first and second CSI-RS configurations. In some aspects, the network node 104 may transmit the first and second CSI-RS configurations received by the UE 102.

[0069] In some aspects, the process 400 may include an optional step 404 in which the UE 102 receives an instruction to switch to the second CSI-RS configuration. In some aspects, the instruction to switch to the second CSI-RS configuration may include an indication of the second CSI-RS configuration. In some aspects, the instruction to switch to the second CSI-RS configuration may be received via a downlink control information (DCI). In some aspects, the instruction to switch to the second CSI-RS configuration may be received via a medium access control (MAC) control element (CE).

[0070] In some aspects, the process 400 may include a step 406 in which the UE 102 determines that a CSI-RS configuration switching condition is met. In some aspects, the process 400 may include a step 408 in which the UE 102, if the CSI-RS configuration switching condition is determined to be met, switches from the first CSI-RS configuration to the second CSI-RS configuration. In some aspects, the CSI-RS switching may be aligned with similar switching on the network node 104, which may apply the same criteria for transitioning between CSI-RS configurations.

[0071] In some aspects, the CSI-RS configuration switching condition in step 406 may be a delay following receipt in step 404 of the instruction to switch to the second CSI-RS configuration. In some aspects, the CSI-RS configuration switching condition may be an occurrence of a quantized timing. In some aspects, the quantized timing may be a slot having a slot number (slot no), and slot no mod M may equal zero (i.e., slot no mod M = 0). In some aspects, the quantized timing may be a first symbol of a first slot after a delay following receipt in step 404 of the instruction to switch to the second CSI-RS configuration. In some aspects, the delay and/or the quantized timing may be configured by higher layers (e.g., radio resource control (RRC) signaling). In some aspects, the process 400 may include receiving downlink control information (DCI) that includes one or more additional bit fields that configure the delay and/or the quantized timing.

[0072] In some aspects, the CSI-RS configuration switching condition in step 406 may be expiration of a validity timer. In some aspects, a duration of the validity timer may be a number of milliseconds, a number of slots, a number of events (e.g., Discontinuous Reception (DRX) cycles), or a subframe number. In some aspects, a duration of the validity timer may be configured by higher layers (e.g., radio resource control (RRC) signaling). In some aspects, the UE 102 may be configured with two or more validity timers, and one or more bit fields in downlink control information (DCI) (e.g., DCI that provides an instruction to switch to the first CSI-RS configuration) may select a validity timer of the two or more validity timers as the validity timer.

[0073] In some aspects, the process 400 may include an optional step in which the UE 102 starts the validity timer. In some aspects, the UE 102 may start the validity timer when the UE 102 enters the first CSI-RS configuration. In some aspects, the process 400 may include an optional step in which the UE 102 restarts the validity timer (e.g., to extend the amount of time before the validity timer expires). In some aspects, the UE 102 may restart the validity timer if a CSI-RS transmission instance according to the first CSI-RS configuration is signaled to the UE 102. In some aspects, the UE 102 may restart the validity timer if the UE 102 detects a CSI-RS transmission according to the first CSI-RS configuration. In some aspects, the UE 102 may restart the validity timer if a network node 104 requests CSI-RS measurement reports on resources corresponding to the first CSI-RS configuration. In some aspects, the UE 102 may restart the validity timer if data has been scheduled for the UE 102 on a specific channel or in relation to a specific transmission (e.g., a multicast transmission). In some aspects, the UE 102 may restart the validity timer if the UE 102 has been scheduled in downlink or uplink. In some aspects, the UE 102 may restart the validity timer if the UE 102 receives a downlink control information (DCI) format indicating that the validity timer should be restarted or an instruction to switch to the first CSI-RS configuration.

[0074] In some aspects, the CSI-RS configuration switching condition in step 406 may be an occurrence of a scheduled switching instance. In some aspects, the scheduled switching instance may be a frame having a system frame number (SFN) where SFN mod K equals zero (i.e., SFN mod K = 0). In some aspects, the process 400 may include an optional step in which the UE 102 receives the scheduled switching instance (e.g., the value of K) in system information (SI) or via RRC signaling. [0075] In some aspects, the CSI-RS configuration switching condition in step 406 may be a cell (e.g., secondary cell (SCell)) being actively operational. In some aspects, the process 400 may include an optional step (e.g., step 412) in which the UE 102 determines that the cell is dormant or deactivated and, if the cell is determined to be dormant or deactivated, transitioning (e.g., in step 414) to the first CSI-RS configuration.

[0076] In some aspects, the CSI-RS configuration switching condition in step 406 may be a radio resource management (RRM) configuration in which multi-layer transmission is not possible. In some aspects, the CSI-RS configuration switching condition in step 406 may be a radio resource management (RRM) configuration in which a maximum number of layers in which multi-layer transmission is possible is lower than or equal to a threshold number of layers.

[0077] In some aspects, the CSI-RS configuration switching condition in step 406 may be the UE 102 operating in a relaxed measurement and/or radio link monitoring mode. In some aspects, the process 400 may include an optional step in which the UE 102 transmits a relaxed measurement and/or radio link monitoring mode announcement to a network node 104. In some aspects, the relaxed measurement and/or radio link monitoring mode announcement may be transmitted via an explicit uplink message. In some aspects, the relaxed measurement and/or radio link monitoring mode announcement may be piggy -backed on an uplink message.

[0078] In some aspects, the process 400 may include a step (e.g., step 412) in which the UE 102 determines that the UE 102 is not operating in the relaxed measurement and/or radio link monitoring mode and, if the UE 102 is determined to not be operating in the relaxed measurement and/or radio link monitoring mode, transitioning (e.g., in step 414) to the first CSI- RS configuration. In some aspects, the process 400 may include an optional step in which the UE 102 transmits an end of relaxed measurement and/or radio link monitoring mode announcement to a network node 104.

[0079] In some aspects, the process 400 may include an optional step 410 in which the UE performs CSI-RS measurements and/or reporting based on the second CSI-RS configuration.

[0080] In some aspects, the process 400 may include an optional step 414 in which the UE 102 switches from the second CSI-RS configuration to the first CSI-RS configuration. [0081] In some aspects, the CSI-RS configuration switching condition may be a first CSI-RS configuration switching condition, the process 400 may include an optional step 412 in which the UE 102 determines that a second CSI-RS configuration switching condition is met. In some aspects, the second CSI-RS configuration switching condition may be expiration of a second CSI-RS configuration validity timer. In some alternative aspects, the second CSI-RS configuration switching condition may be, for example, an occurrence of a scheduled switching instance, the cell (e.g., SCell) being dormant or deactivated, a radio resource management (RRM) configuration in which multi-layer transmission is possible, an RRM configuration in which a maximum number of layers in which multi-layer transmission is possible is not lower than or equal to a threshold number of layers, or the UE 102 not operating in a relaxed measurement and/or radio link monitoring mode.

[0082] In some aspects in which the second CSI-RS configuration switching condition is the expiration of a second CSI-RS configuration validity timer, the process 400 may include an optional step in which the UE 102 starts the second CSI-RS configuration validity timer. In some aspects, the UE 102 may start the second CSI-RS configuration validity timer when the UE 102 enters the second CSI-RS configuration (e.g., in step 408). In some aspects, the process 400 may include an optional step in which the UE 102 restarts the second CSI-RS configuration validity timer (e.g., to extend the amount of time before the second CSI-RS configuration validity timer expires). In some aspects, the UE 102 may restart the second CSI-RS configuration validity timer if a CSI-RS transmission instance according to the second CSI-RS configuration is signaled to the UE 102. In some aspects, the UE 102 may restart the second CSI-RS configuration validity timer if the UE 102 detects a CSI-RS transmission according to the second CSI-RS configuration. In some aspects, the UE 102 may restart the second CSI-RS configuration validity timer if a network node 104 requests CSI-RS measurement reports on resources corresponding to the second CSI-RS configuration. In some aspects, the UE 102 may restart the second CSI-RS configuration validity timer if data has been scheduled for the UE 102 on a specific channel or in relation to a specific transmission (e.g., a multicast transmission). In some aspects, the UE 102 may restart the second CSI-RS configuration validity timer if the UE 102 has been scheduled in downlink or uplink. In some aspects, the UE 102 may restart the second CSI-RS configuration validity timer if the UE 102 receives a downlink control information (DCI) format indicating that the validity timer should be restarted or an instruction to switch to the second CSI-RS configuration.

[0083] In some aspects, the process 400 may include a step 414 in which the UE 102 switches from the second CSI-RS configuration to the first CSI-RS configuration if the second CSI-RS configuration switching condition is determined to be met.

[0084] In some aspects, the process 400 may include an optional step 416 in which the UE 102 performs CSI-RS measurements and/or reporting based on the first CSI-RS configuration.

[0085] FIG. 5 illustrates a process 500 performed by the user equipment (UE) 102 according to some aspects. In some aspects, the UE 102 may be configured with at least a first CSI-RS configuration and a second CSI-RS configuration. In some aspects, the UE 102 may be configured with additional CSI-RS configurations. In some aspects, the first CSI-RS configuration may be a default CSI-RS configuration, and the second CSI-RS configuration may be a non-default CSI-RS configuration. In some alternative aspects, the first CSI-RS configuration may be a non-default CSI-RS configuration, and the second CSI-RS configuration may be a default CSI-RS configuration.

[0086] In some aspects, the process 500 may include an optional step 502 in which the UE 102 receives the first and second CSI-RS configurations. In some aspects, the network node 104 may transmit the first and second CSI-RS configurations received by the UE 102.

[0087] In some aspects, the process 500 may include an optional step 504 in which the UE 102 receives an instruction to switch to the first CSI-RS configuration. In some aspects, the instruction to switch to the first CSI-RS configuration may include an indication of the first CSI- RS configuration. In some aspects, the instruction to switch to the first CSI-RS configuration may be received via a downlink control information (DCI). In some aspects, the instruction to switch to the first CSI-RS configuration may be received via a medium access control (MAC) control element (CE). In some aspects, the instruction to switch to the first CSI-RS configuration may be received via a downlink control information (DCI). In some aspects, the instruction to switch to the first CSI-RS configuration may be received via a medium access control (MAC) control element (CE). [0088] In some aspects, the process 500 may include an optional step 506 in which the UE 102 switches from the second CSI-RS configuration to the first CSI-RS configuration. In some aspects in which the UE 102 receives an instruction to switch to the first CSI-RS configuration (e.g., in step 504), the switch from the second CSI-RS configuration to the first CSI-RS configuration may occur immediately. In some alternative aspects in which the UE 102 receives an instruction to switch to the first CSI-RS configuration (e.g., in step 504), the switch from the second CSI-RS configuration to the first CSI-RS configuration may occur after the UE 102 determines that a CSI-RS configuration switching condition is met. In some aspects, the CSI-RS configuration switching condition may be, for example, a delay following receipt of the instruction to switch to the first CSI-RS configuration in step 504 and/or an occurrence of a quantized timing (e.g., slot no mod M = 0). In some alternative aspects in which the switch to the first CSI-RS configuration occurs without receipt of an instruction to switch to the first CSI- RS configuration, the CSI-RS configuration switching condition may be, for example, expiration of a validity timer, an occurrence of a scheduled switching instance, the cell (e.g., SCell) being actively operational, a radio resource management (RRM) configuration in which multi-layer transmission is not possible, an RRM configuration in which a maximum number of layers in which multi-layer transmission is possible is lower than or equal to a threshold number of layers, or the UE 102 operating in a relaxed measurement and/or radio link monitoring mode.

[0089] In some aspects, the process 500 may include an optional step 508 in which the UE 102 performs CSI-RS measurements and/or reporting based on the first CSI-RS configuration.

[0090] In some aspects, the process 500 may include an optional step in which the UE 102 starts a validity timer. In some aspects, the UE 102 may start the validity timer when the UE 102 enters the first CSI-RS configuration (e.g., in step 506). In some aspects, the process 500 may include an optional step 510 in which the UE 102 restarts the validity timer. In some aspects, the UE 102 may restart the validity timer if a CSI-RS transmission instance according to the first CSI-RS configuration is signaled to the UE 102. In some aspects, the UE 102 may restart the validity timer if the UE 102 detects a CSI-RS transmission according to the first CSI-RS configuration. In some aspects, the UE 102 may restart the validity timer if a network node 104 requests CSI-RS measurement reports on resources corresponding to the first CSI-RS configuration. In some aspects, the UE 102 may restart the validity timer if data has been scheduled for the UE 102 on a specific channel or in relation to a specific transmission (e.g., a multicast transmission). In some aspects, the UE 102 may restart the validity timer if the UE 102 has been scheduled in downlink or uplink. In some aspects, the UE 102 may restart the validity timer if the UE 102 receives a downlink control information (DCI) format indicating that the validity timer should be restarted or an instruction to switch to the first CSI-RS configuration.

[0091] In some aspects, a duration of the validity timer may be a number of milliseconds, a number of slots, a number of events (e.g., Discontinuous Reception (DRX) cycles), or a subframe number. In some aspects, a duration of the validity timer may be configured by higher layers (e.g., radio resource control (RRC) signaling). In some aspects, the UE 102 may be configured with two or more validity timers, and one or more bit fields in downlink control information (DCI) (e.g., the DCI that provides the instruction to switch to the first CSI-RS configuration, which may be received in step 504) may select a validity timer of the two or more validity timers as the validity timer.

[0092] In some aspects, the process 500 may include a step 512 in which the UE 102 determines that a CSI-RS configuration switching condition is met. In some aspects, the CSI-RS configuration switching condition in step 512 may be expiration of the validity timer. In some aspects, a duration of the validity timer may be a number of milliseconds, a number of slots, a number of events (e.g., DRX cycles), or a subframe number. In some aspects, a duration of the validity timer may be configured by higher layers (e.g., radio resource control (RRC) signaling). In some aspects, the UE 102 may be configured with two or more validity timers, and one or more bit fields in downlink control information (DCI) may select a validity timer of the two or more validity timers as the validity timer.

[0093] In some alternative aspects, the CSI-RS configuration switching condition in step 512 may be, for example, an occurrence of a scheduled switching instance, the cell (e.g., SCell) being dormant or deactivated, a radio resource management (RRM) configuration in which multi-layer transmission is possible, an RRM configuration in which a maximum number of layers in which multi-layer transmission is possible is not lower than or equal to a threshold number of layers, or the UE 102 not operating in a relaxed measurement and/or radio link monitoring mode.

[0094] In some aspects, the process 500 may include a step 514 in which the UE 102, if the CSI-RS configuration switching condition is determined to be met, switches from the first CSI- RS configuration to the second CSI-RS configuration. [0095] In some aspects, the process 500 may include an optional step 516 in which the UE 102 performs CSI-RS measurements and/or reporting based on the second CSI-RS configuration.

[0096] Examples

Al . A method (400, 500) performed by a user equipment (UE) (102) configured with at least a first channel state information (CSI)-reference signal (RS) configuration and a second CSI-RS configuration, the method comprising: determining (s406, s512) that a CSI-RS configuration switching condition is met; and if the CSI-RS configuration switching condition is determined to be met, switching (s408, S512) from the first CSI-RS configuration to the second CSI-RS configuration.

A2. The method of example Al, wherein the first CSI-RS configuration is a default CSI-RS configuration, and the second CSI-RS configuration is a non-default CSI-RS configuration.

A3. The method of example Al, wherein the first CSI-RS configuration is a non-default CSI- RS configuration, and the second CSI-RS configuration is a default CSI-RS configuration.

A4. The method of any one of examples Al -A3, further comprising receiving (s404) an instruction to switch to the second CSI-RS configuration.

A5. The method of example A4, wherein the instruction to switch to the second CSI-RS configuration comprises an indication of the second CSI-RS configuration.

A6. The method of example A4 or A5, wherein the instruction to switch to the second CSI- RS configuration is received via a downlink control information (DCI).

A7. The method of example A4 or A5, wherein the instruction to switch to the second CSI- RS configuration is received via a medium access control (MAC) control element (CE).

A8. The method of any one of examples A4-A7, wherein the CSI-RS configuration switching condition is a delay following receipt of the instruction to switch to the second CSI-RS configuration.

A9. The method of any one of examples A4-A7, wherein the CSI-RS configuration switching condition is an occurrence of a quantized timing. A10. The method of example A9, wherein the quantized timing is a slot having a slot number (slot no), wherein slot no mod M equals zero (i.e., slot no mod M = 0).

Al 1. The method of example A9, wherein the quantized timing is a first symbol of a first slot after a delay following receipt of the instruction to switch to the second CSI-RS configuration.

A12. The method of any one of examples A8-A11, wherein the delay and/or the quantized timing is configured by higher layers (e.g., radio resource control (RRC) signaling).

Al 3. The method of any one of examples A8-A11, further comprising receiving downlink control information (DCI) that includes one or more additional bit fields that configure the delay and/or the quantized timing.

A14. The method of any one of examples A1-A7, wherein the CSI-RS configuration switching condition is expiration of a validity timer.

A15. The method of example A14, wherein a duration of the validity timer is a number of milliseconds, a number of slots, a number of events (e.g., Discontinuous Reception (DRX) cycles), or a subframe number.

A16. The method of example A14 or A15, wherein a duration of the validity timer is configured by higher layers (e.g., radio resource control (RRC) signaling).

A17. The method of any one of examples A14-A16, wherein the UE is configured with two or more validity timers, and one or more bit fields in downlink control information (DCI) selects a validity timer of the two or more validity timers as the validity timer.

A18. The method of any one of examples A14-A17, further comprising restarting (s510) the validity timer if a CSI-RS transmission instance according to the first CSI-RS configuration is signaled to the UE.

A19. The method of any one of examples A14-A18, further comprising restarting (s510) the validity timer if the UE detects a CSI-RS transmission according to the first CSI-RS configuration.

A20. The method of any one of examples A14-A19, further comprising restarting (s510) the validity timer if a network node (104) requests CSI-RS measurement reports on resources corresponding to the first CSI-RS configuration. A21. The method of any one of examples A14-A20, further comprising restarting (s510) the validity timer if data has been scheduled for the UE on a specific channel or in relation to a specific transmission (e.g., a multicast transmission).

A22. The method of any one of examples A14-A21, further comprising restarting (s510) the validity timer if the UE has been scheduled in downlink or uplink.

A23. The method of any one of examples A14-A22, further comprising restarting (s510) the validity timer if the UE receives a downlink control information (DCI) format indicating that the validity timer should be restarted or an instruction to switch to the first CSI-RS configuration.

A24. The method of any one of examples A1-A7, wherein the CSI-RS configuration switching condition is an occurrence of a scheduled switching instance.

A25. The method of example A24, wherein the scheduled switching instance is a frame having a system frame number (SFN) where SFN mod K equals zero (i.e., SFM mod K = 0).

A26. The method of example A24 or A25, further comprising receiving the scheduled switching instance (e.g., the value of K) in system information (SI) or via RRC signaling.

A27. The method of any one of examples A1-A7, wherein the CSI-RS configuration switching condition is a cell (e.g., secondary cell (SCell)) being actively operational.

A28. The method of example A27, further comprising: determining that the cell is dormant or deactivated; and if the cell is determined to be dormant or deactivated, transitioning to the first CSI-RS configuration.

A29. The method of any one of examples A1-A7, wherein the CSI-RS configuration switching condition is a radio resource management (RRM) configuration in which multi-layer transmission is not possible.

A30. The method of any one of examples A1-A7, wherein the CSI-RS configuration switching condition is a radio resource management (RRM) configuration in which a maximum number of layers in which multi-layer transmission is possible is lower than or equal to a threshold number of layers. A31. The method of any one of examples Al -A7, wherein the CSI-RS configuration switching condition is the UE operating in a relaxed measurement and/or radio link monitoring mode.

A32. The method of example A31, further comprising transmitting a relaxed measurement and/or radio link monitoring mode announcement to a network node (104).

A33. The method of example A32, wherein the relaxed measurement and/or radio link monitoring mode announcement is transmitted via an explicit uplink message.

A34. The method of example A32, wherein the relaxed measurement and/or radio link monitoring mode announcement is piggy-backed on an uplink message.

A35. The method of anyone of examples A31-A34, further comprising: determining that the UE is not operating in the relaxed measurement and/or radio link monitoring mode; and if the UE is determined to not be operating in the relaxed measurement and/or radio link monitoring mode, transitioning to the first CSI-RS configuration.

A36. The method of example A35, further comprising transmitting an end of relaxed measurement and/or radio link monitoring mode announcement to a network node (104).

A37. The method of any one of examples A1-A36, further comprising performing (s408, s516) CSI-RS measurements and/or reporting based on the second CSI-RS configuration.

A38. The method of any one of examples A1-A37, further comprising switching (s414, s506) from the second CSI-RS configuration to the first CSI-RS configuration.

A39. The method of example A38, wherein the CSI-RS configuration switching condition is a first CSI-RS configuration switching condition, the method further comprises determining (s412) that a second CSI-RS configuration switching condition is met, and switching from the second CSI-RS configuration to the first CSI-RS configuration if the second CSI-RS configuration switching condition is determined to be met.

A40. The method of example A39, wherein the second CSI-RS configuration switching condition is expiration of a second CSI-RS configuration validity timer.

A41. The method of any one of examples A1-A40, further comprising performing (s416, s508) CSI-RS measurements and/or reporting based on the first CSI-RS configuration. A42. The method of any one of examples A1-A41, further comprising receiving (s402, s502) the first and second CSI-RS configurations.

Bl. A user equipment (UE) (102) configured with at least a first channel state information (CSI)-reference signal (RS) configuration and a second CSI-RS configuration, the UE being adapted to: determine that a CSI-RS configuration switching condition is met; and if the CSI-RS configuration switching condition is determined to be met, switch from the first CSI-RS configuration to the second CSI-RS configuration.

Cl . A computer program comprising instructions for adapting an apparatus to perform the method of any one of examples A1-A42.

DI . A carrier containing the computer program of example Cl, wherein the carrier is one of an electronic signal, optical signal, radio signal, or compute readable storage medium.

El. A user equipment (UE) ( 102) compri sing : processing circuitry (202); and a memory (242), said memory containing instructions (244) executable by said processing circuitry, whereby said apparatus is operative to perform the method of any one of the examples A1-A42.

Fl . An apparatus (102) adapted to perform the method of any one of examples A1-A42. G1. Any combination of the examples set forth above.

[0097] While various embodiments are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0098] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.

Claims

1. A method (400, 500) performed by a user equipment, UE, (102) configured with at least a first channel state information-reference signal, CSI-RS, configuration and a second CSI-RS configuration, the method comprising: determining (s406, s512) that a CSI-RS configuration switching condition is met; and if the CSI-RS configuration switching condition is determined to be met, switching (s408, S512) from the first CSI-RS configuration to the second CSI-RS configuration.

2. The method of claim 1, further comprising receiving (s404) an instruction to switch to the second CSI-RS configuration, wherein the CSI-RS configuration switching condition is after a delay following receipt of the instruction to switch to the second CSI-RS configuration.

3. The method of claim 2, wherein the instruction to switch to the second CSI-RS configuration is received via a downlink control information, DCI, or a medium access controlcontrol element, MAC-CE.

4. The method of any one of claims 2-3, wherein the delay is configured by higher layers.

5. The method of claim 3, wherein the instruction to switch to the second CSI-RS configuration is received via a DCI, and wherein the DCI includes one or more bit fields that configure the delay.

6. The method of claim 1, wherein the CSI-RS configuration switching condition is expiration of a validity timer.

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7. The method of claim 6, wherein the validity timer is started after receiving an indication to switch from a default CSI-RS configuration to a non-default CSI-RS configuration.

8. The method of claim 6 or 7, wherein a duration of the validity timer is configured by higher layers.

9. The method of any one of claims 6-8, wherein the UE is configured with two or more validity timers, and one or more bit fields in downlink control information, DCI, selects a validity timer of the two or more validity timers as the validity timer.

10. The method of any one of claims 6-9, further comprising restarting (s510) the validity timer if: a CSI-RS transmission instance according to the first CSI-RS configuration is signaled to the UE, the UE detects a CSI-RS transmission according to the first CSI-RS configuration, a network node (104) requests CSI-RS measurement reports on resources corresponding to the first CSI-RS configuration, data has been scheduled for the UE on a specific channel or in relation to a specific transmission, the UE has been scheduled in downlink or uplink, or the UE receives a downlink control information, DCI, format indicating that the validity timer should be restarted or an instruction to switch to the first CSI-RS configuration.

11. The method of claim 1, wherein the CSI-RS configuration switching condition is an occurrence of a scheduled switching instance.

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12. The method of claim 1, wherein the CSI-RS configuration switching condition is a cell being actively operational.

13. The method of claim 12, further comprising: determining that the cell is dormant or deactivated; and if the cell is determined to be dormant or deactivated, transitioning to the first CSI-RS configuration.

14. The method of claim 1, wherein the CSI-RS configuration switching condition is a radio resource management, RRM, configuration in which multi-layer transmission is not possible.

15. The method of claim 1, wherein the CSI-RS configuration switching condition is the UE operating in a relaxed measurement and/or radio link monitoring mode.

16. The method of claim 15, further comprising: determining that the UE is not operating in the relaxed measurement and/or radio link monitoring mode; and if the UE is determined to not be operating in the relaxed measurement and/or radio link monitoring mode, transitioning to the first CSI-RS configuration.

17. The method of any one of claims 1-16, further comprising performing (s408, s516) CSI- RS measurements and/or reporting based on the second CSI-RS configuration.

18. The method of any one of claims 1-17, further comprising switching (s414, s506) from the second CSI-RS configuration to the first CSI-RS configuration.

19. The method of claim 17, wherein the CSI-RS configuration switching condition is a first CSI-RS configuration switching condition, the method further comprises determining (s412) that a second CSI-RS configuration switching condition is met, and switching from the second CSI- RS configuration to the first CSI-RS configuration if the second CSI-RS configuration switching condition is determined to be met.

20. The method of any one of claims 18-19, further comprising performing (s416, s508) CSI- RS measurements and/or reporting based on the first CSI-RS configuration.

21. The method of any one of claims 1-20, wherein the first CSI-RS configuration is a default CSI-RS configuration, and the second CSI-RS configuration is a non-default CSI-RS configuration.

22. The method of any one of claims 1-21, wherein the first CSI-RS configuration is a nondefault CSI-RS configuration, and the second CSI-RS configuration is a default CSI-RS configuration.

23. The method of any one of claims 1-22, further comprising receiving (s402, s502) the first and second CSI-RS configurations.

24. A user equipment, UE, (102) configured with at least a first channel state informationreference signal, CSI-RS, configuration and a second CSI-RS configuration, the UE being adapted to: determine that a CSI-RS configuration switching condition is met; and if the CSI-RS configuration switching condition is determined to be met, switch from the first CSI-RS configuration to the second CSI-RS configuration.

25. The UE of claim 24, the UE further being adapted to perform the method of any one of claims 2-23.

26. A computer program comprising instructions for adapting an apparatus to perform the method of any one of the claims 1-23.

27. A carrier containing the computer program of claim 26, wherein the carrier is one of an electronic signal, optical signal, radio signal, or computer readable storage medium.

28. A user equipment, UE, (102) comprising: processing circuitry (202); and a memory (242), said memory containing instructions (244) executable by said processing circuitry, whereby said apparatus is operative to perform the method of any one of the claims 1-23.

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