Patent Description:
New Radio (NR) uses CP-OFDM (Cyclic Prefix Orthogonal Frequency Division Multiplexing) in both downlink (DL) (i.e., from a network node, gNB, or base station, to a user equipment or UE) and uplink (UL) (i.e., from UE to gNB). Discrete Fourier Transform (DFT) spread OFDM is also supported in the uplink. In the time domain, NR downlink and uplink are organized into equally sized subframes of <NUM> each. A subframe is further divided into multiple slots of equal duration. The slot length depends on subcarrier spacing. For subcarrier spacing of Δf = <NUM>kHz, there is only one slot per subframe, and each slot consists of <NUM> OFDM symbols.

Data scheduling in NR is typically in slot basis, an example is shown in <FIG> with a <NUM>-symbol slot, where the first two symbols contain physical downlink control channel (PDCCH) and the rest contains physical shared data channel, either physical downlink shared channel (PDSCH) or physical uplink shared channel (PUSCH).

Different subcarrier spacing values are supported in NR. The supported subcarrier spacing values (also referred to as different numerologies) are given by Δf = (<NUM> × <NUM>µ) kHz where µ ∈ {<NUM>, <NUM>, <NUM>, <NUM>,<NUM>}. Δf = <NUM>kHz is the basic subcarrier spacing. The slot durations at different subcarrier spacings is given by <MAT>.

In the frequency domain, a system bandwidth is divided into resource blocks (RBs), each corresponds to <NUM> contiguous subcarriers. The RBs are numbered starting with <NUM> from one end of the system bandwidth. The basic NR physical time-frequency resource grid is illustrated in <FIG>, where only one resource block (RB) within a <NUM>-symbol slot is shown. One OFDM subcarrier during one OFDM symbol interval forms one resource element (RE).

In NR, uplink and downlink data transmissions can be either dynamically scheduled using various Downlink Control Information (DCI) formats or semi-statically configured through Radio Resource Control (RRC) signaling. A DCI is carried on a Physical Downlink Control Channel (PDCCH). A UE first decodes a DCI in a PDCCH and then receives data in the scheduled PDSCH or transmits data over the scheduled PUSCH based the decoded DCI. A DCI contains all the necessary information which contains information such as modulation order, coding rate, resource allocation, etc. for a UE to decode a PDSCH or encode and modulate a PUSCH. For semi-statically configured PUSCH transmission, also referred to as Configured Grant (CG).

In NR, there are two PUSCH mapping types supported, Type A and Type B. Type A is usually referred to as slot-based while Type B may be referred to as non-slot-based or mini-slot-based. A slot based transmission typically start in the first OFDM symbol and use the whole slot, i.e., all <NUM> OFDM symbols, or part of a slot. Mini-slot based PUSCH transmissions can be of any length (i.e., number of OFDM symbols) and can thus start and end in any symbol within a slot. Note that slot or particularly mini-slot transmissions in NR Rel-<NUM> may not cross the slot-border.

In NR release <NUM> (Rel-<NUM>), it is possible to schedule a PUSCH with repetition over multiple slots. The number of repetitions are configured by a RRC parameter pusch-AggregationFactor, which can have a value of <NUM>, <NUM>, or <NUM>. In this case, a PUSCH is repeated in multiple adjacent slots (if the slot is available for UL) up until the number of repetitions configured. This also referred to as slot based PUSCH repetition or PUSCH repetition Type A.

In NR Rel-<NUM>, PUSCH repetition type A was enhanced so that the number of repetitions can instead be dynamically indicated, i.e., change from one PUSCH scheduling occasion to the next. The dynamic number of repetitions is configured as part of the time-domain resource allocation (TDRA) for PUSCH. That is, in addition to the starting symbol, S, and the length, L, of the PUSCH in a slot, a number of nominal repetitions, K, can be added to the TDRA. A list of TDRAs can be configured to a UE, different TDRAs can be configured with different K values. By selecting different TDRAs from the list by using the time-domain resource assignment field in DCI signaled from gNB to UE, different number of repetitions can be used. Note that K is the nominal number of repetitions. Some of these repetitions are not valid, for example if the slot is pre-configured as a DL slot, hence the actual number of repetitions may be smaller than the indicated value K. Furthermore, the maximum number of aggregated slots in Rel. <NUM> has been increased to K=<NUM> to account for DL heavy Time Division Duplexing (TDD) patterns (i.e., where majority of slots are DL slots), otherwise the actual number of repetitions would be too small in these cases.

In addition, PUSCH repetition Type B was introduced in NR Rel-<NUM>, in which a PUSCH may be repeated multiple times within a slot or across two adjacent slots. When scheduling a transmission with PUSCH repetition Type B, in addition to the starting symbol, S, and the length, L, of the PUSCH, a number of nominal repetitions K is also signaled as part of the time-domain resource allocation (TDRA) in NR Rel-<NUM>. The actual number of transmission can be different from the number of nominal repetitions due to reasons such as collision with DL symbols. To determine the actual time domain allocation of PUSCH repetition Type B, a two-step process is used:.

Physical Uplink Control Channel (PUCCH) is used in NR to carry UL control information (UCI) such as Hybrid Automatic Repeat reQuest Acknowledgement (HARQ-ACK), Scheduling Request (SR), or Channel State Information (CSI). There are five PUCCH Formats supported in NR, i.e., PUCCH Formats <NUM> to <NUM>. PUCCH Formats <NUM> and <NUM> can be one or two OFDM symbols within a slot and referred to as short PUCCHs, while PUCCH Formats <NUM>,<NUM> and <NUM> can be <NUM> to <NUM> OFDM symbols long and are referred to as long PUCCHs. PUCCH repetition over adjacent slots is supported in NR for long PUCCHs. The number of PUCCH repetitions can be configured by RRC.

Spatial relation is used in NR to refer to a relationship between an UL reference signal (RS) to be transmitted such as PUCCH/PUSCH DMRS (demodulation reference signal) and another previously transmitted or received RS, which can be either a DL RS (e.g., CSI-RS (channel state information RS) or SSB (synchronization signal block)) or an UL RS (i.e., SRS (sounding reference signal)). This is also defined from a UE perspective.

If the UE is configured to transmit an UL RS which is configured or indicated as spatially related to a previously received DL RS, it means that the UE should transmit the UL RS in the opposite (reciprocal) direction from which it received the DL RS previously. More precisely, the UE should apply the "same" Transmit (Tx) spatial filtering configuration for the transmission of the UL RS as the Rx spatial filtering configuration it used to receive the spatially related DL RS previously. Here, the terminology 'spatial filtering configuration' may refer to the antenna weights that are applied at either the transmitter or the receiver for data/control transmission/reception. Another way to describe this is that the same antenna "beam" should be used to transmit the signal from the UE as the beam that was used to receive the previous DL RS signal. The DL RS is also referred as the spatial filter reference signal.

On the other hand, if a first UL RS is spatially related to a second UL RS, then the UE should apply the same Tx spatial filtering configuration for the transmission for the first UL RS as the Tx spatial filtering configuration it used to transmit the second UL RS previously. In other words, same beam is used to transmit the first and second UL RS in two different points in time, respectively.

Since the UL RS is associated with a layer of PUSCH or PUCCH transmission (if the UL RS is the DMRS), it is understood that the PUSCH/PUCCH is also transmitted with the same TX spatial filter as the associated UL RS since the PUSCH/PUCCH shall be transmitted with the same filter as the associated DMRS.

Below is an example of spatial relation configuration for PUCCH. It contains a serving cell ID, a spatial relation ID, a reference signal, a pathloss reference signal, and power control parameters for the PUCCH.

For PUSCH, the spatial relation information is indicated by a Sounding Reference Resource (SRS) Indicator (SRI) which is included in DCI for dynamically scheduled PUSCH and is configured by higher layer signaling for semi-statically configured PUSCH. A SRI indicates an SRS resource associated with a PUSCH transmission.

A core component in LTE and NR is the support of MIMO antenna deployments using antenna arrays and Multiple Input Multiple Output (MIMO) related techniques. Spatial multiplexing is one of the MIMO techniques used to achieve high data rates in favorable channel conditions.

For an antenna array with NT antenna ports at the gNB for transmitting r DL symbols s = [s<NUM>, s<NUM>,. , sr]T, the received signal at a UE with NR receive antennas at a certain RE n can be expressed as: <MAT> where yn is a NR × <NUM> received signal vector; Hn a NR × NT channel matrix at the RE between the gNB and the UE; W is an NT x r precoder matrix; en is a NR × <NUM> noise plus interference vector received at the RE by the UE. The precoder W can be a wideband precoder, i.e., constant over a whole bandwidth part (BWP), or a subband precoder, i.e., constant over each subband.

The precoder matrix is typically selected from a codebook of possible precoder matrices, and typically indicated by means of a precoder matrix indicator (PMI), which specifies a unique precoder matrix in the codebook for a given number of symbol streams. The r symbols in s each corresponds to a spatial layer and r is referred to as the transmission rank.

For a given block error rate (BLER), the modulation level and coding scheme (MCS) is determined by the Signal to Interference Plus Noise Ratio (SINR), or channel quality. The preceding matrix, the transmission rank, and the channel quality are part of channel state information (CSI), which is typically measured by a UE and fed back to a network node or gNB.

Like in LTE, NR has adopted an implicit CSI mechanism where a UE feeds back the downlink CSI comprising one or more of a transmission rank indicator (RI), a precoder matrix indicator (PMI), and one or two channel quality indicator(s) (CQI). NR supports transmission of either one or two transport blocks (TBs) to a UE in a slot, depending on the rank. One TB is used for ranks <NUM> to <NUM>, and two TBs are used for ranks <NUM> to <NUM>. A CQI is associated to each TB. The CQI/RI/PMI report can be either wideband or subband based on configuration.

Similar to LTE, CSI-RS was introduced in NR for channel measurement in the downlink. A CSI-RS is transmitted on each transmit antenna port and is used by a UE to measure downlink channel associated with each of antenna ports. The antenna ports are also referred to as CSI-RS ports. The supported number of antenna ports in NR are {<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>,<NUM>}. By measuring the received CSI-RS, a UE can estimate the channel the CSI-RS is traversing, including the radio propagation channel and antenna gains. CSI-RS for channel measurement purpose is also referred to as Non-Zero Power (NZP) CSI-RS. NZP CSI-RS can be configured to be transmitted in certain REs in a PRB.

CSI resource for interference measurement, CSI-IM, is used in NR for a UE to measure noise and interference, typically from other cells. Typically, gNB does not transmit any signal in the CSI-IM resource so that what is observed in the resource is noise and interference from other cells.

By measuring the channel based on a NZP CSI-RS resource and interference based on a CSI-IM resource, a UE can estimate the CSI, i.e., RI, PMI, and CQI(s).

In NR, a UE can be configured with one or multiple CSI Report Settings, each configured by a higher layer parameter CSI-ReportConfig. Each CSI-ReportConfig is associated with a BWP and contains one or more of the followings.

A UE can be configured with one or multiple CSI resource configurations for channel measurement and one or more CSI-IM resources for interference measurement. Each CSI resource configuration for channel measurement can contain one or more Non-Zero Power (NZP) CSI-RS resource sets. For each NZP CSI-RS resource set, it can further contain one or more NZP CSI-RS resources. A NZP CSI-RS resource can be periodic, semi-persistent, or aperiodic.

Similarly, each CSI-IM resource configuration for interference measurement can contain one or more CSI-IM resource sets. For each CSI-IM resource set, it can further contain one or more CSI-IM resources. A CSI-IM resource can be periodic, semi-persistent, or aperiodic.

A UE performs SP CSI reporting on PUSCH upon successful decoding of a DCI format 0_1 or DCI format 0_2 which activates a SP CSI trigger state. DCI format 0_1 and DCI format 0_2 contains a CSI request field which indicates the SP CSI trigger state to activate or deactivate the reporting. For SP CSI reporting on PUSCH, a set of trigger states are higher layer configured by CSI-SemiPersistentOnPUSCH-TriggerStateList, where the CSI request field in DCI activates one of the trigger states. Each SP CSI trigger state contains a CSI-ReportConfigld which points to a CSI-ReportConfig with reportConfigType set to semiPersistentOnPUSCH. An example of semiPersistentOnPUSCH configuration is shown below, where the Semi-Persistent CSI (SP-CSI) period is configured by reportSlotConfig to one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> slots and a list of slot offsets, one of which is indicated in the activating DCI. p0alpha is a power control parameter.

<FIG> is an example of SP CSI reporting on PUSCH, where the first SP CSI report is sent three slots (the slot offset) after receiving the activation DCI (SP-CSI activation trigger). The SP CSI is then in this example reported every five slots (the period) until a deactivation DCI is received (SP-CSI deactivation trigger).

A codepoint of the CSI request field in the DCI is mapped to a SP-CSI triggering state according to the order of the positions of the configured trigger states in CSI-SemiPersistentOnPUSCH-TriggerStateList, with codepoint '<NUM>' mapped to the triggering state in the first position.

A UE validates, for SP CSI activation or release, a DL semi-persistent assignment PDCCH on a DCI only if both of the following conditions are met:.

If validation is achieved, the UE considers the information in the DCI format as a valid activation or valid release of SP CSI transmission on PUSCH, and the UE activates or deactivates a CSI Reporting Setting indicated by CSI request field in the DCI.

Note that SP CSI reporting on PUSCH activated by a DCI format is not expected to be multiplexed with uplink data on the PUSCH.

For SP CSI reporting on PUCCH, a UE is configured with CSI report setting(s) where the higher layer parameter reportConfigType is set to 'semiPersistentOnPUCCH" as shown below:
<IMG>
<IMG>.

For SP CSI reporting on PUCCH, the PUCCH resource in each BWP used for transmitting the CSI report is configured by PUCCH-CSI-Resource in semiPersistentOnPUCCH. SP CSI reporting on PUCCH is activated (or deactivated) by an activation (or deactivation) command carried on a Medium Access Control (MAC) Control Element (CE), which selects one of the semi-persistent Reporting Settings for use by the UE on the PUCCH.

The MAC CE is shown in <FIG>. It contains the following fields:.

When the UE would transmit a PUCCH with HARQ-ACK information in slot n corresponding to the PDSCH carrying the activation (or deactivated) command, the indicated SP CSI Reporting Setting is activated starting from the first slot that is after slot <MAT> where <MAT> is the number of slots per subframe and µ is the Sub-Carrier Spacing (SCS) configuration for the PUCCH.

Periodic CSI is always transmitted on PUCCH. Similar to SP-CSI on PUCCH, the PUCCH resource(s) for carrying periodic CSI is configured in the associated CSI-ReportConfig as shown below, where a PUCCH resource carrying the periodic CSI is configured for each BWP:
<IMG>.

There currently exist certain challenge(s). In NR up to Release <NUM>, for SP-CSI on PUSCH, there is no repetition supported which is a problem. The number of transmissions in each reporting period is always assumed to be one, regardless of the value of the high layer parameter pusch-AggregationFactor or numberOfRepetitions-rl6 configured in a TDRA row indicated by the TDRA field of a DCI activating the SP-CSI. The same is true for periodic CSI and SP-CSI on PUCCH, where a single transmission is always assumed regardless whether PUCCH repetition is configured or not.

In addition, in frequency range <NUM> (FR2), channel blocking is a particular problem that needs to be overcome. If a SP-CSI or periodic CSI is transmitted by the UE in a slot when the channel between the UE and the TRP is blocked, then the SP CSI or periodic CSI may not be decoded correctly at the gNB.

Deploying multiple TRPs is one efficient way to combat channel blocking, particular in FR2. However, with current SP CSI or periodic CSI reporting in NR, CSI is only sent to one TRP by the UE. How to ensure reliability of SP CSI or periodic CSI in FR2 is an open problem that needs to be solved. <CIT> discloses a user equipment having (i) a transmission unit for transmitting multiple uplink shared channels associated with multiple transmission/reception points and (ii) a control unit for multiplexing multiple pieces of channel state information associated with the multiple transmission/reception points into the multiple uplink shared channels. According to this document, when repeatedly transmitting the uplink shared channels to the multiple TRPs, the pieces of CSI are properly reported.

Systems and methods for reliable Channel State Information (CSI) feedback towards multiple Transmission/Reception Points (TRPs) are provided. The present disclosure in particular provides a method performed by a wireless device, a method performed by a base station, a wireless device and a base station as defined in the independent claims.

In some embodiments, a wireless device receives a configuration for one or more of: Semi-Persistent CSI (SP-CSI) reporting on PUCCH comprising a first PUCCH resource; SP-CSI reporting on PUSCH comprising a reporting periodicity and slot offset; and periodic CSI reporting on PUCCH comprising a second PUCCH resource activated with a third and a fourth spatial relations or uplink TCI states, and a reporting periodicity and slot offset. The wireless device also receives an appropriate activation command and transmits SP-CSI in a PUCCH resource; a periodic CSI in a PUCCH resource; and/or a SP-CSI in a PUSCH resource. In this way, reliability of SP-CSI on PUSCH, or SP-CSI on PUCCH, or periodic CSI on PUCCH can be improved by repeating the SP-CSI or periodic CSI over multiple TRPs.

Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. A method is proposed to enable repeating a CSI feedback towards multiple TRPs for SP-CSI on PUSCH, SP-CSI on PUCCH, and periodic CSI on PUCCH.

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. Certain embodiments may provide one or more of the following technical advantage(s). The proposed solution improves reliability of SP-CSI on PUSCH, or SP-CSI or periodic CSI on PUCCH by repeating the SP-CSI or periodic CSI over multiple TRPs. The solution is particularly beneficial in FR2 scenarios as at least one TRP can receive the SP-CSI or periodic CSI when the one of the TRPs is blocked.

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.

Transmission/Reception Point (TRP): In some embodiments, a TRP may be either a network node or a radio head. A TRP may be represented by a spatial relation or a TCI state in some embodiments. In some embodiments, a TRP may be using multiple TCI states. In some embodiments, each TRP intended for reception of a signal that the UE transmits in the UL is represented in specification text by a SRS Resource Indicator (SRI), a spatial relation, or a TCI state for example an UL TCI state.

<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 Next Generation RAN (NG-RAN) and a <NUM> Core (5GC). In this example, the RAN includes base stations <NUM>-<NUM> and <NUM>-<NUM>, which in the 5GS include NR base stations (gNBs) and optionally next generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC), 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 <NUM> System (5GS) is referred to as the 5GC. The base stations <NUM> (and optionally the low power nodes <NUM>) are connected to the core network <NUM>.

In the following embodiments, the term TRP is used. Note however that in 3GPP specifications, the term TRP may not be captured. Instead each TRP intended for reception of a signal that the UE transmits in the UL is represented in specification text by a SRS resource set, a SRS Resource Indicator (SRI), a spatial relation, or a TCI state for example an UL TCI state.

A method is proposed to enable repeating a CSI feedback towards multiple TRPs for Semi-Persistent CSI (SP-CSI) on PUSCH, SP-CSI on PUCCH, and periodic CSI on PUCCH. Systems and methods for reliable CSI feedback towards multiple TRPs are provided. <FIG> illustrates a method performed by a wireless device for reliable CSI feedback. The method includes one or more of: receiving (step <NUM>) a configuration for one or more of: SP-CSI reporting on PUCCH comprising a first PUCCH resource activated with a first and a second spatial relation or uplink TCI states, a reporting periodicity, and/or slot offset; SP-CSI reporting on PUSCH comprising a reporting periodicity and slot offset; and periodic CSI reporting on PUCCH comprising a second PUCCH resource activated with a third and a fourth spatial relations or uplink TCI states, and a reporting periodicity and slot offset. The method might also include receiving (step <NUM>) one or more of: an activation command activating the SP-CSI on PUCCH; an activation Downlink Control Information, DCI, activating the SP-CSI on PUSCH, wherein the DCI comprising a first and a second SRS Resource Indicators, SRIs, and a PUSCH resource. Additionally, the method might include transmitting (step <NUM>) one or more of: a SP-CSI in the first PUCCH resource in a first transmission occasion according to the first spatial relation and in a second transmission occasion according to the second spatial relation activated for the first PUCCH resource; a periodic CSI in the second PUCCH resource in a third transmission occasion according to the third spatial relation and in a fourth transmission occasion according to the fourth spatial relation configured for the second PUCCH resource; and a SP-CSI in the PUSCH resource in a fifth transmission occasion according to the first SRI and in a sixth transmission occasion according to the second SRI.

<FIG> illustrates a method performed by a base station for reliable CSI feedback. The method includes one or more of: transmitting (step <NUM>), to a wireless device, a configuration for one or more of: SP-CSI reporting on PUCCH comprising a first PUCCH resource activated with a first and a second spatial relation or uplink TCI states, a reporting periodicity, and/or slot offset; a SP-CSI reporting on PUSCH comprising a reporting periodicity and slot offset; and periodic CSI reporting on PUCCH comprising a second PUCCH resource activated with a third and a fourth spatial relations or uplink TCI states, and a reporting periodicity and slot offset.

The method might also include transmitting (step <NUM>), to the wireless device, one or more of: an activation command activating the SP-CSI on PUCCH; an activation DCI activating the SP-CSI on PUSCH, wherein the DCI comprising a first and a second SRIs and a PUSCH resource.

The method might also include receiving (step <NUM>), from the wireless device, one or more of: a SP-CSI in the first PUCCH resource in a first transmission occasion according to the first spatial relation and in a second transmission occasion according to the second spatial relation activated for the first PUCCH resource; a periodic CSI in the second PUCCH resource in a third transmission occasion according to the third spatial relation and in a fourth transmission according to the fourth spatial relation configured for the second PUCCH resource; and a SP-CSI in the PUSCH resource in a fifth transmission occasion according to the first SRI and in a sixth transmission occasion according to the second SRI.

The proposed solution improves reliability of SP-CSI on PUSCH, or SP-CSI or periodic CSI on PUCCH by repeating the SP-CSI or periodic CSI over multiple TRPs. The solution is particularly beneficial in FR2 scenarios as at least one TRP can receive the SP-CSI or periodic CSI when the one of the TRPs is blocked.

For PUSCH and PUCCH transmission toward multiple TRPs, a PUSCH or a PUCCH may be repeated towards to different TRPs as shown in <FIG>. Here the transmission in the <NUM>st occasion is directed toward TRP1 and the transmission in the <NUM>nd occasion is directed toward TRP2. More reliable PUSCH or PUCCH transmission can thereby be achieved, for example when the path towards one of the TRPs is blocked due to objects along the transmission path, since the PUSCH can reach the second TRP in this case.

The SRI, spatial relation, or UL TCI state essentially provides an indicator of a spatial filter or beam that the UE should use to target an uplink transmission towards a given TRP. Furthermore, although the below embodiments are discussed using SRIs and spatial relations, the embodiments are non-limiting and can be equally applicable to cases where SRIs are replaced by UL TCI states, DL CSI-RS resources, or TCI states in general. In the following discussion, CSI reporting in a BWP of a serving cell is considered.

Basically, the UE is indicated multiple SRIs {SRI1, SRI2,. ) (or spatial relations) and for each SP-CSI transmission, a rule is specified to determine which of the SRI (or spatial relation) that applies for the actual SP-CSI transmission. The simplest rule is that SRI1 (or a first spatial relation) is used for the first transmission and SRI2 (or a second spatial relation) is used for the second transmission etc. SRI1 indicates a first SRS resource from a first SRS resource set which is used to transmit the spatial relation source RS for PUSCH transmission carrying SP-CSI towards TRP1. SRI2 indicates a second SRS resource from a second SRS resource set which is used to transmit the spatial relation source RS for PUSCH transmission carrying SP-CSI towards TRP1.

In this embodiment, when repetition for PUSCH Type A scheduling is configured and two or more SRIs (or UL TCI states) are indicated in a DCI activating a SP-CSI report carried on PUSCH , the SP-CSI is repeated in two or more slots within a SP-CSI reporting period.

Each repetition within a SP-CSI reporting period is intended to be received by a different TRP, i.e., transmission is directed toward a different TRP. When using a number of repetitions larger than the number of TRPs, the SP-CSI repetitions can cycle among the different TRPs.

An example is shown in <FIG>, where a SP-CSI report is repeated twice in two slots towards two TRPs in each reporting period. In this example, the SP-CSI reporting period equals to P slots. The benefit is that in case of the channel to one TRP is blocked, the SP-CSI can still be received by the other TRP, thus the reliability of SP-CSI transmission is increased.

In one embodiment, the number of repetitions the UE is transmitting within a SP-CSI reporting period is equal to the number of SRIs (or UL TCI states) indicated in the DCI activating the SP-CSI. In other words, the number of repetitions in the SP-CSI reporting period is always assumed to be equal to the number of SRIs indicated via the DCI regardless of the number of repetitions indicated by the TDRA field in the activation DCI. In this case, SP-CSI report on PUSCH is repeated on time for each SRI value indicated. In one example, when two SRIs are indicated to the UE via the activation DCI for SP-CSI on PUSCH, the UE assumes two repetitions in each SP-CSI reporting period and ignores the number of repetitions indicated by the TDRA field in the activation DCI. Stated in other words, in this embodiment, the number of SRIs indicated in the activation DCI for SP-CSI on PUSCH overrides the number of repetitions indicated by the TDRA field in the activation DCI.

In another alternative embodiment, when more than one SRI are indicated to the UE via the activation DCI for SP-CSI on PUSCH, SP-CSI report on PUSCH is transmitted using the spatial relation indicated by one of the SRIs in each SP-CSI periodicity. The SRI that is used to derive the spatial relation for a SP-CSI on PUSCH is cycled through the more than one SRIs indicated to the UE in different SP-CSI periodicities. For example, when two SRIs are indicated to the UE via the activation DCI, the first indicated SRI is used to derive the spatial relation for a SP-CSI on PUSCH on odd SP-CSI periodicities, and the second indicated SRI is used to derive the spatial relation for a SP-CSI on PUSCH on even SP-CSI periodicities.

In another embodiment, the number of repetitions the UE is transmitting within a SP-CSI reporting period is determined by both the number of SRIs as indicated in the activation DCI and the number of repetitions. The number of repetitions may be semi-statically configured via RRC, or dynamically indicated by a DCI. In a preferred example, the number of repetitions is provided by an element of the TDRA (time domain resource allocation) as indicated in the activation DCI. Hence, the content of both these fields in the activation DCI are used, together with specified rules, to determine how and how many times the UE shall transmit the repeated SP-CSI report.

The number of repetitions is in this case configured in the PUSCH TDRA row, which is selected by the TDRA field in the activation DCI. The TDRA table containing multiple rows are provided by RRC signaling to the UE.

In one embodiment A1, the value indicated by TDRA row is the total number of transmissions (across all values of SRIs) of SP-CSI in the SP-CSI reporting period. For example, the number of repetitions configured in the selected TDRA row as indicated by DCI applies only if more than one SRI are indicated in the DCI. Moreover, in case the total number of repetitions is indicated by the TDRA row, and if the number of repetitions are more than the number of SRIs ( or UL TCI states) indicated, the repetition may be cycled over the TRPs so that at least one of the SRI values is utilized for more than one transmission. That TRP thus receives the SP-CSI report more than one time during the SP-CSI reporting period.

In an alternative embodiment A2, the value indicated by TDRA row is the number of transmissions of the SP-CSI for each SRI value. If the value indicated by TDRA row is two or larger, the repetition may be cycled over the TRPs so that at least one of the SRI values is utilized for more than one transmission.

An example of the former embodiment A1 is shown in <FIG>, where a total of four repetitions are indicated in the TDRA while two SRIs (or UL TCI states) are indicated. The SP-CSI is repeated <NUM> times in <NUM> slots to the two TRPs in a cyclic manner. Alternatively, it may be specified that the order of these transmissions are arranged differently, e.g., the first two repetitions in slots n and n+<NUM> may be sent towards TRP1 (i.e., associated with the first SRI) and the next two repetitions in slot n+<NUM> and n+<NUM> may be sent towards TRP2 (associated with the second SRI).

In yet another embodiment, the order of transmissions towards different TRPs are configured to the UE from the network using e.g., higher layer RRC signaling. For example, the order {SRI1, SRI1, SRI2, SRI2,. } or the order {SRI1, SRI2, SRI1, SRI2,. ) may be configured, where these have different advantages depending on whether blocking probability is the same for the two links or if one link have a smaller blocking probability than the other.

For both embodiment A1 and A2, the same pattern may be repeated in each SP-CSI reporting period.

In this embodiment, when PUSCH repetition Type B and two or more SRIs ( or UL TCI states) are indicated in a DCI activating a SP-CSI on PUSCH , the SP-CSI is repeated in two or more mini-slots within a SP-CSI reporting period, where a mini-slot contains a number of OFDM symbols and is the same as a nominal repetition with a starting symbol and length. Each repetition is toward a different TRP. An example is shown in <FIG>, where a SP-CSI report is repeated twice in two mini-slots towards two TRPs in each reporting period.

Similar to PUSCH repetition Type A, in one embodiment, the number of repetitions may equal to the number of SRIs (or UL TCI Fstates) indicated in the DCI activating the SP-CSI. In another embodiment, the number of repetitions may be determined by both the number of SRIs and the number of repetitions configured in the PUSCH TDRA row selected by the TDRA field in the activation DCI. The Embodiments A1 and A2 in the previous section on how to use the DCI fields of TDRA row and SRI to determine the repetitions applies equally well to SP-CSI on PUSCH with PUSCH repetition type B. In one example, the number of repetitions configured in the selected TDRA row applies only if more than one SRI are indicated in the DCI.

The SP CSI may be sent in a nominal repetition occasion only if it is the same as the actual repetition occasion, i.e., the nominal repetition is not segmented or omitted.

In some embodiments, when SP CSI on PUSCH is transmitted towards to different TRPs, two different power control parameter sets may be provided to the UE so that each of the set of power control parameters may be used by the UE when transmitting to each of the TRPs. The two different sets of power control parameters may be provided as part of the CSI-ReportConfig information element in 3GPP TS <NUM>. An example of this embodiment is shown below, where pOalphaList provides up to two sets of power control parameters.

<FIG> illustrates a method performed by a wireless device for reliable CSI feedback, according to some embodiments of the present disclosure. The wireless device receives the configuration for SP-CSI reporting on PUSCH comprising a reporting periodicity and slot offset (step <NUM>). The wireless device receives the activation DCI activating the SP-CSI on PUSCH, where the DCI comprises the first and the second SRIs and the PUSCH resource (step <NUM>). The wireless device transmits the SP-CSI in the PUSCH resource in the fifth transmission occasion according to the first SRI and in the sixth transmission occasion according to the second SRI (step <NUM>).

Similar to SP CSI on PUSCH, when a PUCCH resource for a SP CSI on PUCCH is activated with two or more spatial relations (or UL TCI states), the SP-CSI is repeated in two or more slots within a SP-CSI reporting period. Each repetition is toward a different TRP over the same PUCCH resource. Each TRP is associated with a spatial relation or a UL TCI state. An example is shown in <FIG>, where a SP-CSI report is repeated in two slots towards two TRPs in each reporting period. In this example, the SP-CSI reporting period equals to P slots. The activation of two or more spatial relations (or UL TCI states) for a PUCCH resource to be used for SP-CSI reporting is achieved via a MAC CE that is separate from the MAC CE that activates the SP-CSI reporting on PUCCH. The benefit of using different MAC CEs for activating the SP-CSI reporting on PUCCH and for activating two or more spatial relations (or UL TCI states) for a PUCCH resource is that it allows independent control of when to activate the SP-CSI reporting on PUCCH and how many TRPs to transmit the SP-CSI towards.

In one embodiment, the number of repetitions is equal to the number of spatial relations or UL TCI states activated. In another embodiment, the number of repetitions may be explicitly configured in the associated PUCCH resources.

As an example, the PUCCH resource configuration can be enhanced as illustrated below, to provide multi-TRP indication (via SpatialRelationList) and the number of repetitions for this PUCCH resource (via NrRepetitions).

Alternatively, when two or more PUCCH resources each with an associated spatial relation or UL TCI state are configured for a SP CSI on PUCCH in a BWP, the SP-CSI is repeated in two or more slots within a SP-CSI reporting period. Each repetition is toward a different TRP associated with one of the two or more spatial relations or UL TCI states. The number of repetitions is equal to the number of PUCCH resources.

In yet another embodiment, instead of repetition in different slots, the SP CSI repetition may be within a slot, i.e., intra-slot repetition.

In a further embodiment, instead of intra-slot repetition, the SP CSI may be hopped between TRPs in a slot in which some PUCCH symbols carrying the SP CSI are transmitted to one TRP while the rest of the symbols are sent to a different TRP. An example is shown in <FIG>, where the <NUM>st four symbols of an <NUM>-symbol PUCCH carrying SP CSI are sent toward TRP1 and the rest sent to TRP2.

In the above discussion, the DCI-based activation and deactivation mechanism of SP-CSI on PUSCH is assumed to be an UE-specific DCI that schedules PUSCH (aka, UL DCI), e.g., DCI format 0_1 and 0_2. For SP-CSI on PUCCH, the activation and deactivation is via the mechanism of MAC CE.

Alternatively or additionally, other DCI-based activation and deactivation mechanisms can be used, as discussed below.

In one embodiment, the activation mechanism is a UE-specific DCI that schedules PDSCH (aka, DL DCI), e.g., DCI format 1_1 and 1_2. A DL DCI can trigger SP-CSI report on PUCCH, although not on PUSCH. To indicate that the DL DCI is sent for activation of SP-CSI report, CRC parity bits of the DCI format are scrambled with a SP-CSI-RNTI.

The deactivation mechanism can also be a UE-specific DCI, where the CRC parity bits of the DCI formats 1_0,1_1 or 1_2 are scrambled with a SP-CSI-RNTI.

When using the DL DCI to activate and deactivate, special field values in the DCI are used to validate the SP-CSI activation and deactivation. As an example, the fields shown in Table <NUM> can be used to validate the activation, and the fields shown in Table <NUM> can be used to validate the deactivation.

In another embodiment, a group common DCI can be used to activate and/or deactivate SP-CSI on PUCCH.

For example, a modified DCI format 2_3, or a new DCI format (e.g., DCI format 2_7) can be used for SP-CSI activation/deactivation. To indicate that the DL DCI is sent for activation/activation of SP-CSI report, CRC parity bits of the DCI format are scrambled with the corresponding group-common RNTI, e.g., TPC-SRS-RNTI for DCI format 2_3.

The DCI can carry a SP-CSI field for each UE, where the SP-CSI is composed of one or more bits. For example, four bits of {S0, S1, S2, S3} are sent to a UE, for activation/deactivation of SP-CSI in the same BWP of the same serving cell where the DCI is sent. The Si (i=<NUM>, <NUM>, <NUM>, <NUM>) indicates the activation/deactivation status of the Semi-Persistent CSI report configuration within a list of CSI-ReportConfigs. S<NUM> refers to the report configuration which includes PUCCH resources for SP CSI reporting in the indicated BWP and has the lowest CSI-ReportConfigId within the list with type set to semiPersistentOnPUCCH, S<NUM> to the report configuration which includes PUCCH resources for SP CSI reporting in the indicated BWP and has the second lowest CSI-ReportConfigld and so on. The Si is set to <NUM> to indicate that the corresponding Semi-Persistent CSI report configuration shall be activated. The Si is set to <NUM> to indicate that the corresponding Semi-Persistent CSI report configuration i shall be deactivated;.

Parts of the embodiments covered above for SP-CSI on PUCCH can also be extended to P-CSI on PUCCH. In this case, when a PUCCH resource for a P-CSI on PUCCH is configured with two or more spatial relations (or UL TCI states), the P-CSI is repeated in two or more slots within a P-CSI reporting period. Each repetition is toward a different TRP over the same PUCCH resource. Each TRP is associated with a spatial relation or a UL TCI state. The example in <FIG> is equally valid for this case where SP-CSI in the figure is replaced by P-CSI. In this example, a P-CSI report is repeated in two slots towards two TRPs in each reporting period. In this example, the P-CSI reporting period equals to P slots. The activation of two or more spatial relations (or UL TCI states) for a PUCCH resource to be used for P-CSI reporting is achieved via a MAC CE. Note that one difference from the SP-CSI on PUCCH case here is that since the CSI is periodic, there is no MAC CE for activating the CSI reporting on PUCCH (i.e., CSI reporting on PUCCH is periodic).

In one embodiment, the number of repetitions is equal to the number of spatial relations or UL TCI states activated for the PUCCH resource carrying the P-CSI. In another embodiment, the number of repetitions may be explicitly configured in the associated PUCCH resources.

In another embodiment, when more than one spatial relation (or UL TCI state) is activated for the PUCCH resource carrying P-CSI, P-CSI report on PUCCH is transmitted using one of the activated spatial relations (or UL TCI states) in each P-CSI periodicity. The spatial relation (or UL TCI state) that is used for a P-CSI on PUCCH is cycled through the more than one spatial relation (or UL TCI states) indicated to the UE in different P-CSI periods. For example, when two spatial relations (or two UL TCI states) are activated, the first activated spatial relation (or UL TCI state) is used for a P-CSI in odd SP-CSI periods, and the second activated spatial relation (or UL TCI state) is used for a P-CSI in even P-CSI periods.

<FIG> is a schematic block diagram of a radio access node <NUM> according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The radio access node <NUM> may be, for example, a base station <NUM> or <NUM> or a network node that implements all or part of the functionality of the base station <NUM> or gNB described herein. As illustrated, the radio access 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 radio access 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 radio access 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>.

As used herein, a "virtualized" radio access node is an implementation of the radio access node <NUM> in which at least a portion of the functionality of the radio access 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 radio access 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 radio access 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 radio access 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 radio access 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).

<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..

With reference to <FIG>, in accordance with an embodiment, a communication system includes a telecommunication network <NUM>, such as a 3GPP-type cellular network, which comprises an access network <NUM>, such as a RAN, and a core network <NUM>. The access network <NUM> comprises a plurality of base stations 2006A, 2006B, 2006C, such as Node Bs, eNBs, gNBs, or other types of wireless Access Points (APs), each defining a corresponding coverage area 2008A, 2008B, 2008C. Each base station 2006A, 2006B, 2006C is connectable to the core network <NUM> over a wired or wireless connection <NUM>. A first UE <NUM> located in coverage area 2008C is configured to wirelessly connect to, or be paged by, the corresponding base station 2006C. A second UE <NUM> in coverage area 2008A is wirelessly connectable to the corresponding base station 2006A.

It is noted that the host computer <NUM>, the base station <NUM>, and the UE <NUM> illustrated in <FIG> may be similar or identical to the host computer <NUM>, one of the base stations 2006A, 2006B, 2006C, and one of the UEs <NUM>, <NUM> of <FIG>, respectively.

The wireless connection <NUM> between the UE <NUM> and the base station <NUM> is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE <NUM> using the OTT connection <NUM>, in which the wireless connection <NUM> forms the last segment. More precisely, the teachings of these embodiments may improve the e.g., data rate, latency, power consumption, etc. and thereby provide benefits such as e.g., reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc..

Claim 1:
A method performed by a wireless device for reliable Channel State Information, CSI, feedback, the method comprising:
receiving (<NUM>) a configuration for Semi-Persistent CSI, SP-CSI, reporting on a Physical Uplink Shared Channel, PUSCH, comprising a reporting periodicity and a list of slot offsets, and a first and a second Sounding Reference Signal, SRS, Resource sets;
receiving (<NUM>) an activation Downlink Control Information, DCI, activating the SP-CSI on the PUSCH, wherein the DCI comprising a first and a second SRS Resource Indicators, SRIs, indicating a first and a second SRS resources in the first and the second SRS resource sets, respectively, a slot offset from the list of slot offsets, and a PUSCH resource allocation including a number of transmission occasions configured or indicated in the Time Domain Resource Allocation, TDRA, field of the activation DCI;
determining the number of transmission occasions in which SP-CSI is to be transmitted according to the number of SRS resource sets from which SRIs are indicated in the DCI, regardless of the number of transmission occasions configured or indicated in the TDRA field of the activation DCI; and
transmitting (<NUM>) an SP-CSI report in the PUSCH resource in a first transmission occasion according to the first or the second SRI and in a second transmission occasion according to the second or the first SRI in each reporting period specified by the reporting periodicity and the slot offset.