Patent Description:
The present disclosure is related to Tracking Reference Signal (TRS) configuration in wireless communication systems.

The Third Generation Partnership Project (3GPP) is defining technical specifications for New Radio (NR) (e.g., Fifth Generation (<NUM>)). In Release <NUM> (Rel-<NUM>) NR, a User Equipment (UE) can be configured with up to four carrier Bandwidth (BW) Parts (BWPs) in the Downlink (DL) with a single DL carrier BWP being active at a given time. A UE can be configured with up to four carrier BWPs in the Uplink (UL) with a single UL carrier BWP being active at a given time. If a UE is configured with a supplementary UL, the UE can additionally be configured with up to four carrier BWPs in the supplementary UL with a single supplementary UL carrier BWP being active at a given time.

For a carrier BWP with a given numerology µ<NUM>, a contiguous set of Physical Resource Blocks (PRBs) are defined and numbered from <NUM> to <MAT>, where i is the index of the carrier BWP. A Resource Block (RB) is defined as <NUM> consecutive subcarriers in the frequency domain.

Multiple Orthogonal Frequency-Division Multiplexing (OFDM) numerologies, µ, are supported in NR as given by Table <NUM>, where the subcarrier spacing, Δf, and the cyclic prefix for a carrier BWP are configured by different higher layer parameters for DL and UL, respectively.

A DL physical channel corresponds to a set of resource elements carrying information originating from higher layers. The following DL physical channels are defined:.

PDSCH is the main physical channel used for unicast DL data transmission, but also for transmission of Random Access Response (RAR), certain system information blocks, and paging information. PBCH carries the basic system information, required by the UE to access the network. PDCCH is used for transmitting DL Control Information (DCI), mainly scheduling decisions, required for reception of PDSCH, and for UL scheduling grants enabling transmission on PUSCH.

An UL physical channel corresponds to a set of resource elements carrying information originating from higher layers. The following UL physical channels are defined:.

PUSCH is the UL counterpart to the PDSCH. PUCCH is used by UEs to transmit UL control information, including HARQ acknowledgements, channel state information reports, etc. PRACH is used for random access preamble transmission.

The ultra-lean design principle in NR aims to minimize the always-on transmissions that exist in earlier systems (e.g., Long Term Evolution (LTE) Cell-Specific Reference Signal (CRS) reference symbols). Instead, NR provides reference symbols such as Synchronization Signal (SS) Blocks (SSBs) on a periodic basis, by default once every <NUM> milliseconds (ms). In addition, for connected mode UEs, typically a set of reference symbols are provided for optimal link performance. Some of these reference symbols are clarified below.

A UE in Radio Resource Control (RRC) connected mode is expected to receive from the network the RRC layer UE specific configuration of a NZP-CSI-RS-ResourceSet configured including the parameter trs-Info (e.g., a parameter for a Tracking Reference Signal (TRS)). For a NZP-CSI-RS-ResourceSet configured with the higher layer parameter trs-Info set to "true", the UE shall assume the antenna port with the same port index of the configured Non-Zero Power (NZP) CSI-RS resources in the NZP-CSI-RS-ResourceSet is the same.

A UE configured with NZP-CSI-RS-ResourceSet(s) configured with higher layer parameter trs-Info may have the CSI-RS resources configured as:.

A UE does not expect to be configured with a CSI-ReportConfig that is linked to a CSI-ResourceConfig containing an NZP-CSI-RS-ResourceSet configured with trs-Info and with the CSI-ReportConfig configured with the higher layer parameter timeRestrictionForChannelMeasurements set to 'configured'.

A UE does not expect to be configured with a CSI-ReportConfig with the higher layer parameter reportQuantity set to other than 'none' for aperiodic NZP CSI-RS resource set configured with trs-Info.

A UE does not expect to be configured with a CSI-ReportConfig for periodic NZP CSI-RS resource set configured with trs-Info.

A UE does not expect to be configured with a NZP-CSI-RS-ResourceSet configured both with trs-Info and repetition.

Each CSI-RS resource, defined in Clause <NUM>. <NUM> of Technical Specification (TS) <NUM>, is configured by the higher layer parameter NZP-CSI-RS-Resource with the following restrictions:.

The UE can be configured with one or more 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 ≥ <NUM> NZP CSI-RS resource(s).

The following parameters for which the UE shall assume non-zero transmission power for CSI-RS resource are configured via the higher layer parameter NZP-CSI-RS-Resource, CSI-ResourceConfig, and NZP-CSI-RS-ResourceSet for each CSI-RS resource configuration:.

All CSI-RS resources within one set are configured with same density and same nrofPorts, except for the NZP CSI-RS resources used for interference measurement. The UE expects that all the CSI-RS resources of a resource set are configured with the same starting RB and number of RBs and the same cdm-type.

The bandwidth and initial CRB index of a CSI-RS resource within a BWP, as defined in Clause <NUM>. <NUM> of TS <NUM>, are determined based on the higher layer parameters nrofRBs and startingRB, respectively, within the CSI-FrequencyOccupation Information Element (IE) configured by the higher layer parameter freqBand within the CSI-RS-ResourceMapping IE. Both nrofRBs and startingRB are configured as integer multiples of <NUM> RBs, and the reference point for startingRB is CRB <NUM> on the CRB grid. If <MAT>, the UE shall assume that the initial CRB index of the CSI-RS resource is <MAT>, otherwise Ninitial RB = startingRB. If <MAT>, the UE shall assume that the bandwidth of the CSI-RS resource is <MAT>, otherwise <MAT>. In all cases, the UE shall expect that <MAT>.

<FIG> illustrates the NZP-CSI-RS-Resource IE. The NZP-CSI-RS-Resource IE is used to configure NZP CSI-RS transmitted in the cell where the IE is included, which the UE may be configured to measure on (see TS <NUM>, clause <NUM>. Fields for the NZP-CSI-RS-Resource IE are further described in Table <NUM> below.

<FIG> illustrates the NZP-CSI-RS-ResourceId IE. The NZP-CSI-RS-ResourceId IE is used to identify one NZP-CSI-RS-Resource.

<FIG> illustrates the NZP-CSI-RS-ResourceSet IE. The NZP-CSI-RS-ResourceSet IE is a set of NZP CSI-RS resources (their IDs) and set-specific parameters. Fields for the NZP-CSI-RS-ResourceSet IE are further described in Table <NUM> below.

<FIG> illustrates the NZP-CSI-RS-ResourceSetId IE. The NZP-CSI-RS-ResourceSetId IE is used to identify one NZP-CSI-RS-ResourceSet.

<FIG> illustrates the CSI-ResourceConfig IE. The CSI-ResourceConfig IE defines a group of one or more NZP-CSI-RS-ResourceSet, CSI-IM-ResourceSet and/or CSI-SSB-ResourceSet. Fields for the CSI-ResourceConfig IE are further described in Table <NUM> below.

<FIG> illustrates the CSI-ResourceConfigId IE. The CSI-ResourceConfigId IE is used to identify a CSI-ResourceConfig.

<FIG> illustrates the CSI-ResourcePeriodicityAndOffset IE. The CSI-ResourcePeriodicityAndOffset IE is used to configure a periodicity and a corresponding offset for periodic and semi-persistent CSI resources, and for periodic and semi-persistent reporting on PUCCH. Both the periodicity and the offset are given in number of slots. The periodicity value slots4 corresponds to <NUM> slots, slots5 corresponds to <NUM> slots, and so on.

<FIG> illustrates the CSI-RS-ResourceMapping IE. The CSI-RS-ResourceMapping IE is used to configure the resource element mapping of a CSI-RS resource in time- and frequency domain. Fields for the CSI-RS-ResourceMapping are further described in Table <NUM> below.

<FIG> illustrates the CSI-FrequencyOccupation IE. The CSI-FrequencyOccupation IE is used to configure the frequency domain occupation of a channel state information measurement resource (e.g., NZP-CSI-RS-Resource, CSI-IM-Resource). Fields for the CSI-FrequencyOccupation IE are further described in Table <NUM> below.

There currently exist certain challenge(s). In NR, in connected mode, a UE is provided either with periodic, semi-periodic or aperiodic CSI-RS/TRS (TRS or CSI RS for tracking) so it can measure the channel qualities, and/or track the reference signal in order to fine tune its time and frequency synchronization. Such RSs may also not be turned off despite some individual UEs may be in Idle/Inactive states. Nevertheless, the UE is not aware of the potential existence of such RSs during the RRC_Idle/Inactive. As such the UE conventionally relies on SSB signals during RRC_Idle/Inactive for, e.g., Automatic Gain Control (AGC) setting, synchronization, and/or cell quality measurements.

The problem with SSB measurements is that SSBs come in long time intervals (e.g., <NUM>) and sometimes the UE may need to stay out of deep sleep for an extended time before it is able to, e.g., read its paging message after the previous available SSB reception, which leads to a waste of UE energy.

Exposing CSI-RSs for tracking or TRSs that are available during RRC_Connected to RRC_Idle is considered as a solution to help the UE reduce the power consumption during RRC_Idle/Inactive. In particular, provision of such information via System Information (SI) (e.g., a SI Block (SIB), such as SIB1, SIB2,. SIBn) is considered as a viable mechanism. Nevertheless, this involves a large overhead on the network side and also occupies a large part of the SI if the TRS configuration follows the same approach as Rel-<NUM>/<NUM>. In general, TRS configuration in the current versions of Rel-<NUM>/<NUM> includes several parameters having configurations which are always the same. Nevertheless, TRS configuration needs to be explicitly configured, since it follows the same approach as other types of CSI-RSs for configuration.

Documents <NPL>), <CIT> and <CIT> represent relevant prior-ar.

Methods of compact Tracking Reference Signal (TRS) configuration for New Radio (NR) User Equipment (UE) are provided. The Channel State Information Reference Signal (CSI-RS) configuration framework through which the TRS is traditionally configured in connected mode is quite hefty in terms of number of possibilities and Information Elements (IEs) included in its structures. It entails IEs that can be used for configuration of multiple sets (up to <NUM>) of both Zero Power (ZP) and Non-zero Power (NZP) CSI-RSs. Each of these sets can itself include configuration of up to <NUM> resources.

In order to be able to provide TRS configuration and availability information to the UEs in Radio Resource Control (RRC) Idle/Inactive states, a compact TRS mechanism is disclosed through which the network can configure the UE with specific TRSs. Further, this approach can indicate to the UE if the configured RS is applicable to all RRC states (e.g., connected, idle, or inactive), or to specific RRC states. Specifically, the present disclosure provides mechanisms with which different configuration parameters are needed to be set to configure the UE with a compact TRS. Furthermore, the disclosure provides methods and mechanisms with which the UE can communicate its capabilities or provide assistance information to the network, in order to configure the UE with a proper compact TRS.

In this regard, embodiments described herein provide UEs with a mechanism to be configured efficiently with a compact TRS. The compact TRS removes the redundant parts of a traditional TRS while providing flexibility for the network to further expose the TRS to idle UEs. Embodiments exploit the compact TRS to achieve power savings particularly during RRC_Idle/Inactive modes. Furthermore, the compact TRS significantly reduces the network overhead in configuring the TRS.

The present invention is defined by the attached independent claims. Other preferred embodiments may be found in the dependent claims.

Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing a Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

<FIG> illustrates one example of a cellular communications system <NUM> in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system <NUM> is a <NUM> System (5GS) including a NR RAN or LTE RAN (i.e., Evolved Universal Terrestrial Radio Access (E-UTRA) RAN) or an Evolved Packet System (EPS) including a LTE RAN. In this example, the RAN includes base stations <NUM>-<NUM> and <NUM>-<NUM>, which in LTE are referred to as eNBs (when connected to Evolved Packet Core (EPC)) and in <NUM> NR are referred to as gNBs (e.g., LTE RAN nodes connected to <NUM> Core (5GC), which are referred to as gn-eNBs), controlling corresponding (macro) cells <NUM>-<NUM> and <NUM>-<NUM>. The base stations <NUM>-<NUM> and <NUM>-<NUM> are generally referred to herein collectively as base stations <NUM> and individually as base station <NUM>. Likewise, the (macro) cells <NUM>-<NUM> and <NUM>-<NUM> are generally referred to herein collectively as (macro) cells <NUM> and individually as (macro) cell <NUM>. The RAN may also include a number of low power nodes <NUM>-<NUM> through <NUM>-<NUM> controlling corresponding small cells <NUM>-<NUM> through <NUM>-<NUM>. The low power nodes <NUM>-<NUM> through <NUM>-<NUM> can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells <NUM>-<NUM> through <NUM>-<NUM> may alternatively be provided by the base stations <NUM>. The low power nodes <NUM>-<NUM> through <NUM>-<NUM> are generally referred to herein collectively as low power nodes <NUM> and individually as low power node <NUM>. Likewise, the small cells <NUM>-<NUM> through <NUM>-<NUM> are generally referred to herein collectively as small cells <NUM> and individually as small cell <NUM>. The cellular communications system <NUM> also includes a core network <NUM>, which in the 5GS is referred to as the <NUM> Core (5GC). The base stations <NUM> (and optionally the low power nodes <NUM>) are connected to the core network <NUM>.

In embodiments described herein, methods and mechanisms are provided with which a network (e.g., a NR RAN of the cellular communications system <NUM>) can configure a UE (e.g., the wireless communication devices <NUM>) with one or multiple Tracking Resource Signals (TRSs) in a compact way. The underlying configuration can be performed through different mechanisms, such as a System Information (SI) update, Radio Resource Control (RRC) configuration, or RRC release command.

Furthermore, the compact TRS mechanisms described herein do not require reporting from the UE. For example, the UE can employ them for measurement and tracking purposes and do not need to provide feedback to the network.

Configuring a UE with a compact TRS involves several parameters. In one example, a specific NZP-CSI-RS-Resource can be configured for compact TRS (e.g., a TRS-config Information Element (IE) which includes the most relevant fields from CSI-RS-ResourceMapping as well as NZP-CSI-RS-Resourceset). Below, example embodiments are described on how the relevant parameters can be configured in a compact way.

In one example, this IE can be simply called as a CSI-RS-for-tracking-Resource IE, or TRS-config IE clarifying that this is a compact TRS configuration.

In one example, this parameter does not need to be explicitly configured, particularly if the compact TRS IE is configured as an independent NZP-CSI-RS-Resource IE as described above.

In another example, the parameter can be simply called in a relation to compact TRS configuration, clarifying that this is different from other types of Channel State Information Reference Signal (CSI-RS) configuration (e.g., TRS-config, or compact CSI-RS for tracking and so on).

In one example, an independent CSI-RS-ResourceMapping IE for compact TRS can be configured. In another preferred approach, all the related resource mapping fields can be moved to the compact TRS IE.

Power offset of Physical Downlink Shared Channel (PDSCH) Resource Element (RE) to Non-Zero Power (NZP) CSI-RS RE. In one example, this field is removed from compact TRS configuration, since the UE is not expected to report anything after receiving TRS.

Power control offset SS is the ratio of NZP CSI-RS Energy Per Resource Element (EPRE) to the Secondary Synch Signal of SS/ Physical Broadcast Channel (PBCH) block EPRE.

In one example, the ratio can be configured as <NUM> or <NUM> decibels (dB). In this case, in one approach the compact TRS may not include this IE indicating that the power control offset SS is configured as <NUM> to reduce the size. For example, if the compact TRS is present in idle mode, the network may wish to configure this parameter as <NUM> and thus do not explicitly configure it in compact TRS.

In another example, the value can be explicitly configured, or the value can be configured explicitly only when it is not <NUM>. In yet another example, the UE may be configured differently for connected and idle modes (e.g., a higher or lower value for the connected mode, and <NUM> for idle mode).

In one example, the scrambling ID of compact TRS can be configured in the same way as in Rel-<NUM>/<NUM>.

In another example, the scrambling ID of compact TRS can be associated with the RRC state (e.g., for connected mode a different ID can be employed with respect to the one used in the idle mode).

In one aspect, the scrambling ID can be the same or based on Cell identity; in this case the field of scrambling ID can be omitted.

In one example, the compact TRS periodicity and offset is configured as in Rel-<NUM>/<NUM>, however, with a reduced number of possibilities (e.g., only the ones associated with periodicities of <NUM>, <NUM>, <NUM>, or <NUM> or other values in terms of the number of slots). In another example, the periodicity can be configured explicitly from a set of values in terms of milliseconds (ms).

In another example, the compact TRS periodicity can be associated with a specific SS Block (SSB) periodicity, e.g., the same periodicity as SSB, or a fraction of SSB periodicity, or multiples of SSB periodicity. Furthermore, an offset indicator can indicate the offset between the compact TRS and SSB.

In another example, the compact TRS periodicity can be associated with a Paging Occasion (PO), or a number of POs. For example, the compact TRS periodicity may be configured to be every PO, or multiples of PO periodicity, or a fraction of it. Furthermore, an offset indicator can indicate the offset between the compact TRS and the PO.

In another example, the compact TRS periodicity can be associated with a Discontinuous Reception (DRX) cycle (e.g., Connected Mode DRX (C-DRX), Idle Mode DRX (I-DRX)), or a fraction of it, or multiple of it. Furthermore, an offset indicator can indicate the offset between the compact TRS and a specific part of the DRX cycle (e.g., the end of the cycle, the beginning of the cycle, or ON duration of C-DRX).

In another example, the compact TRS may be configured with separate periodicities for different RRC states. For example, the compact TRS periodicity may be shorter for connected mode, and longer for the idle mode, or vice-versa. Or it can be configured in a different way for the connected mode and idle mode. For example, the UE may be configured with a TRS of <NUM> periodicities for connected mode, but periodicity equivalence of a PO in idle mode.

This parameter typically contains a reference to a TCI-State indicating Quasi Co-Location (QCL) source Reference Signal(s) (RS(s)) and QCL type(s). In one example, the same procedure as in Rel-<NUM>/<NUM> can be employed for compact TRS.

In another example, particularly when the compact TRS is configured as part of SI update, or that the compact TRS is employed during idle mode, the QCL information can be configured in association with one or more specific SSBs. That is, the UE is configured to receive TRS in the same QCLs which are configured for the associated SSBs. Hence, there might be several TRSs provided in the cell, each associated with one/several of the SSBs provided in the cell.

In one example, this field remains in the same way as in Rel-<NUM>/<NUM>. That is, it can be present if the compact TRS configuration is periodic and absent if not or if there is also an aperiodic element (e.g., as in the case of Frequency Range <NUM> (FR2)).

In another example, this field is not configured at all in compact TRS, since there is a periodic element in all types of TRS configuration, and if the field aperiodicTriggeringOffset is also additionally configured, it indicates presence of the aperiodic element as well (e.g., as in the case of FR2).

In another example, this field can additionally indicate that the compact TRS configuration is applicable to which RRC states. For example, this field can indicate if the compact TRS configuration is applicable to both connected mode (e.g., RRC_Connected UEs) and idle mode UEs (e.g., RRC_Idle/Inactive UEs), or only applicable to connected mode UEs, or only applicable to an individual state or set of specific states. In a related realization, this part is only configured if the TRS configuration is applicable to Idle UEs as well, or in an alternative solution, if the field is absent, it is available to all RRC states. Furthermore, this field can also be configured with its different possibilities with regard to different RRC states as an independent field in compact TRS configuration IE.

In one example, all the fields in this IE can be moved to the generic compact TRS configuration. Otherwise, it can become an independent compact TRS set configuration IE (e.g., TRS-config-set IE).

In another example, the parameter can be simply called in a relation to compact TRS configuration, clarifying that this is different from other types of CSI-RS configuration (e.g., TRS-config, or compact CSI-RS for tracking and so on).

In one example, this field is removed and not configured for compact TRS configuration as there is no reporting expected for TRS.

In one example, this field is not configured for compact TRS configuration, since it is clear that the configuration is related to TRS.

In one example, this field is only configured if the compact TRS involves an aperiodic component as in the case of TRS for FR2. The configuration can be as in the case of Rel-<NUM>/<NUM>. If the field is not present, the UE assumes that all the parameters are periodic.

In case the compact TRS is only provided for idle UEs, the aperiodicTriggeringOffset is completely omitted for the structure pointed out in compact TRS configuration.

bwp-Id is currently configured as part of the CSI-ResourceConfig IE in Rel-<NUM>/<NUM>. In one example, the bwp-Id and Bandwidth (BW) related configurations can be moved under the compact TRS configuration IE. Another option is to make a specific compact TRS resource configuration, and include this field there. The following examples can be adapted to both possibilities.

In one example, the TRS is configured with a specific Bandwidth Part (BWP) among the ones which are configured for a specific cell. In such case, through a bwp-Id, the BWP (and associated subcarrier spacing) in which the TRS is provided is identified by the UE. In another example, particularly if the TRS is intended to be employed during idle mode, the UE can be configured with the same BWP as it is supposed to employ during idle mode. For example, the UE may be configured with the initial BWP during idle mode, and the same BWP can be configured for the compact TRS. As such, in one approach, the associated IE related to BWP configuration (e.g., bwp-Id) can remain optional, meaning if omitted the UE should assume the same BWP as idle mode for the TRS.

Similarly, the information about BW of the TRS available in a BWP can optionally be provided to the UE. The reason for the optionality of this IE is that typically the TRS is intended for wideband transmission and covers the whole BWP (e.g., <NUM> Resource Blocks (RBs) as described above). However, in case the initial BWP accommodates more than <NUM> RBs (e.g., <NUM> RBs in <NUM> subcarrier spacing case) such optional indicator can be used to inform the UE whether the TRS covers the whole BWP (in this case <NUM> RBs) or only the default <NUM> RBs, or potentially an even smaller number of resource blocks (e.g., corresponding to SSB bandwidth).

Yet in another example, the UE may be configured with the same BWP or a subset of BWP for TRS which is configured for SSB. For example, an IE can be added to the compact TRS configuration related to BWP which indicates the BWP is associated with a specific SSB meaning it is the same BWP as the specific SSB.

UEs in Idle/Inactive mode may not need to operate on bandwidth larger than the bandwidth corresponding to initial BWP or the bandwidth of Coreset <NUM> (e.g., if there is no initial DL BWP). Thus, in yet another example, the UE may assume the TRS is transmitted in Physical RBs (PRBs) corresponding to a reference bandwidth or set of PRBs. The reference bandwidth can be the SSB bandwidth, the bandwidth corresponding to Coreset <NUM> or the bandwidth corresponding to initial BWP. In cases where the network may indicate an initial BWP in SI (e.g., a SI Block (SIB) such as SIB1), UEs in Idle/Inactive mode can assume that the TRS are present only in a subset of PRBs of the initial BWP - this subset of PRBs can be explicitly indicated via the BW field in the TRS configuration, or implicit indication (default can be the PRBs to the bandwidth corresponding to Coreset <NUM>). This enables the network to keep the frequency span of the TRS to be as small as possible for the purpose of aiding the Idle/Inactive mode UEs. The frequency location and span of the TRS as well as the starting RB and the number of RBs can be provided as part of the configuration (e.g., in the element freqBand as part of an independent compact TRS resource mapping IE) or directly as part of the compact TRS configuration IE.

In one example, all the fields in this IE can be moved to the generic compact TRS configuration. Otherwise, it can become an independent compact TRS set resource mapping configuration IE (e.g., TRS-config-ResourceMapping IE).

In one example, this field is not configured as part of compact TRS IE, or in another word is not included, since for TRS, it is always related to Rel-<NUM>/<NUM> specifications associated with a case of no-Consolidated Data Model (CDM), number of ports <NUM> and density of <NUM> (e.g., row <NUM> of 3GPP Technical Specification TS <NUM> of Table <NUM>. <NUM>-<NUM>).

In one example, the compact TRS does not include the number of ports, since TRS is only associated with one port, and it is the same among all the underlying RS resources.

In one example, for compact TRS, there is no CDM and thus this line is not configured for the compact TRS. In other words, there is no need to consider CDM-type as part of the compact TRS configuration, and the UE by default assumes there is no CDM type configured.

density defines CSI-RS frequency density of each CSI-RS port per PRB, and CSI-RS PRB offset in case of the density value of ½. For the compact TRS, in one example, the density is always the same, and determined by the specification (e.g., density of <NUM>), and thus this field does not need to be explicitly configured for the compact TRS.

When it comes to density in time, the TRS resources are always separated by <NUM> symbols and do not need to be signaled. However, the starting symbol in time indicated by firstOFDMSymbolInTimeDomain can be configured (e.g., it can be one of the values {<NUM>, <NUM>, <NUM>} for Frequency Range <NUM> (FR1) and FR2, or additional values for starting symbol can be included for FR2 {<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>}).

This parameter is responsible for determining the number of RBs as well as the starting RB.

<FIG> and <FIG> provide examples of how a compact TRS configuration IE can appear, with its elements as described in Aspect <NUM>. <FIG> illustrates an example of the TRS-Config IE. <FIG> illustrates a more compact example of the TRS-Config IE when the BWP is the same as the initial BWP for the UE.

In one example, the UE indicates to the network through capability signaling that it can support compact TRS. In another approach, the UE indicates to the network that it can exploit TRS for other purposes than tracking, such as to achieve power savings (e.g., in the idle mode).

The network then decides to configure or not the UE with a compact TRS as disclosed in Aspect <NUM>.

In one example, the UE provides additional assistance information than just capability. For example, the UE provides preferences with regard to the underlaying parameters of compact TRS discussed in Aspect <NUM>, or a subset of them. In a related realization, the UE may decide to even communicate a specific preferred compact TRS configuration or a set of specific TRS configurations.

The network can then decide to consider the UE preferences and configure the UE with one or more compact TRSs as such. In a related realization, particularly when the compact TRS is configured through SI, or when TRS is broadcasted to all the UEs, the network can consider the most common preferred parameter configurations from the UEs.

<FIG> is a flowchart illustrating a method for compactly configuring a TRS in accordance with one embodiment. The method may be implemented in a wireless device. Optional steps are indicated with dashed lines. In optional step <NUM>, the wireless device provides capability signaling indicating a capability of the wireless device to exploit a compact TRS IE. In optional step <NUM>, the wireless device provides compact TRS configuration assistance information. In step <NUM>, the wireless device receives the compact TRS IE from a network. In an exemplary aspect, the compact TRS IE is received without a CSI-RS configuration. In step <NUM>, the wireless device configures at least one TRS in accordance with the compact TRS IE. In optional step <NUM>, the wireless device deploys the at least one TRS for a measurement and/or tracking purpose.

<FIG> is a flowchart illustrating a method for providing a compact TRS configuration in accordance with one embodiment. The method may be implemented in a base station. Optional steps are indicated with dashed lines. In optional step <NUM>, the base station receives capability signaling indicating a capability of a wireless device to exploit a compact TRS IE. In optional step <NUM>, the base station receives compact TRS configuration assistance information. In step <NUM>, the base station determines at least one TRS configuration for the wireless device. In step <NUM>, the base station provides the compact TRS IE to the wireless device in accordance with the at least one TRS configuration. In an exemplary aspect, the compact TRS IE is provided without providing a CSI-RS configuration.

<FIG> is a schematic block diagram of a network node <NUM> according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node <NUM> may be, for example, a base station <NUM> or <NUM> or another network node that implements all or part of the functionality of the base station <NUM> or gNB described herein. As illustrated, the network node <NUM> includes a control system <NUM> that includes one or more processors <NUM> (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory <NUM>, and a network interface <NUM>. The one or more processors <NUM> are also referred to herein as processing circuitry. In addition, the network node <NUM> may include one or more radio units <NUM> that each includes one or more transmitters <NUM> and one or more receivers <NUM> coupled to one or more antennas <NUM>. The radio units <NUM> may be referred to or be part of radio interface circuitry. In some embodiments, the radio unit(s) <NUM> is external to the control system <NUM> and connected to the control system <NUM> via, e.g., a wired connection (e.g., an optical cable). However, in some other embodiments, the radio unit(s) <NUM> and potentially the antenna(s) <NUM> are integrated together with the control system <NUM>. The one or more processors <NUM> operate to provide one or more functions of a network node <NUM> as described herein. In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory <NUM> and executed by the one or more processors <NUM>.

<FIG> is a schematic block diagram that illustrates a virtualized embodiment of the network node <NUM> according to some embodiments of the present disclosure. This discussion is equally applicable to radio access nodes and other types of network nodes.

As used herein, a "virtualized" network node is an implementation of the network node <NUM> in which at least a portion of the functionality of the network node <NUM> is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the network node <NUM> may include the control system <NUM> and/or the one or more radio units <NUM>, as described above. The control system <NUM> may be connected to the radio unit(s) <NUM> via, for example, an optical cable or the like. The network node <NUM> includes one or more processing nodes <NUM> coupled to or included as part of a network(s) <NUM>. If present, the control system <NUM> or the radio unit(s) are connected to the processing node(s) <NUM> via the network <NUM>. Each processing node <NUM> includes one or more processors <NUM> (e.g., CPUs, ASICs, FPGAs, and/or the like), memory <NUM>, and a network interface <NUM>.

In this example, functions <NUM> of the network node <NUM> described herein are implemented at the one or more processing nodes <NUM> or distributed across the one or more processing nodes <NUM> and the control system <NUM> and/or the radio unit(s) <NUM> in any desired manner. In some particular embodiments, some or all of the functions <NUM> of the network node <NUM> described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) <NUM>. As will be appreciated by one of ordinary skill in the art, additional signaling or communication between the processing node(s) <NUM> and the control system <NUM> is used in order to carry out at least some of the desired functions <NUM>. Notably, in some embodiments, the control system <NUM> may not be included, in which case the radio unit(s) <NUM> communicate directly with the processing node(s) <NUM> via an appropriate network interface(s).

In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node <NUM> or a node (e.g., a processing node <NUM>) implementing one or more of the functions <NUM> of the network node <NUM> in a virtual environment according to any of the embodiments described herein is provided.

<FIG> is a schematic block diagram of the network node <NUM> according to some other embodiments of the present disclosure. The network node <NUM> includes one or more modules <NUM>, each of which is implemented in software. The module(s) <NUM> provide the functionality of the network node <NUM> described herein.

<FIG> is a schematic block diagram of a wireless communication device <NUM> according to some embodiments of the present disclosure. As illustrated, the wireless communication device <NUM> includes one or more processors <NUM> (e.g., CPUs, ASICs, FPGAs, and/or the like), memory <NUM>, and one or more transceivers <NUM> each including one or more transmitters <NUM> and one or more receivers <NUM> coupled to one or more antennas <NUM>. The transceiver(s) <NUM> includes radio-front end circuitry connected to the antenna(s) <NUM> that is configured to condition signals communicated between the antenna(s) <NUM> and the processor(s) <NUM>, as will be appreciated by on of ordinary skill in the art. The processors <NUM> are also referred to herein as processing circuitry. The transceivers <NUM> are also referred to herein as radio circuitry. In some embodiments, the functionality of the wireless communication device <NUM> described above may be fully or partially implemented in software that is, e.g., stored in the memory <NUM> and executed by the processor(s) <NUM>. Note that the wireless communication device <NUM> may include additional components not illustrated in <FIG> such as, e.g., one or more user interface components (e.g., an input/output interface including a display, buttons, a touch screen, a microphone, a speaker(s), and/or the like and/or any other components for allowing input of information into the wireless communication device <NUM> and/or allowing output of information from the wireless communication device <NUM>), a power supply (e.g., a battery and associated power circuitry), etc..

Claim 1:
A method performed by a wireless device (<NUM>) for compactly configuring a Tracking Reference Signal, TRS, Information Element, IE, the method comprising:
receiving (<NUM>) a compact TRS IE from higher layer signaling of a network, wherein the compact TRS IE is received without a Channel State Information Reference Signal, CSI-RS, configuration, and wherein the compact TRS IE is received when the wireless device is in one of an idle mode or an inactive mode; and
configuring (<NUM>) at least one TRS in accordance with the compact TRS IE, wherein configuring the at least one TRS in accordance with the compact TRS IE comprises configuring a frequency location of TRS occasions within an initial bandwidth part, BWP, of the idle mode or the inactive mode.