Method and apparatus for feedback reporting for wireless communications

Abstract

Methods and apparatuses for a wireless communications networks are presented According to an aspect of some embodiments, there is provided a method performed by a wireless device. The method comprises receiving (401) from a network node an indication or a configuration of at least two sets of Channel State Information Reference Signal, CSI-RS, resources. The method further comprises determining (402) a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources received from the network node. The method further comprises determining (403) a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources received from the network node. The method further comprises generating (404) a feedback based on the first and the second CSI, and reporting (405) the feedback to the network node.

Description

[0001] Method and Apparatus for feedback reporting for Wireless Communications

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of wireless communications, and in particular to methods and apparatuses for feedback reporting in an Uplink Control Channel (UCI) in a wireless communications network such as advanced 5G or 6G networks.

[0004] BACKGROUND

[0005] The radio access technology (RAT) in fifth generation (5G) mobile communications system, also known as 5G new radio (NR), provides a higher level of performance and flexibility than the previous generations of mobile communications systems. 5G mobile communications has been driven by the need to provide ubiquitous connectivity for applications as diverse automotive communications, remote control with feedback, video downloads, as well as data applications for Internet-of-Things (loT) devices, machine type communication (MTC) devices, etc. 5G wireless technology brings several main benefits, such as faster speed, shorter delays and increased connectivity. 5G mobile communications supports massive multiple-input multiple-output antenna technologies from sub-6 GHz up to mm Wave-frequencies, new beamforming management procedures to provide increased beamforming gain and link reliability, new waveforms, etc. The third-generation partnership project (3GPP) provides the complete system specification for the 5G network architecture, which includes at least a radio access network (RAN), core transport networks (CN) and service capabilities. Due to the amount of traffic that needs to be handled by the network is growing significantly, there exists a need to further improve downlink performance.

[0006] SUMMARY

[0007] In Release 18 of 3GPP New Radio, a new codebook design has been standardized to facilitate a wireless device to perform Channel State Information (CSI) prediction and reporting of the predicted CSI. As the CSI prediction accuracy is crucial for optimizing or enhancing the downlink performance, this invention focuses on solutions related to the reporting of the accuracy measure(s) of the CSI prediction to the network node. It is an objective of the embodiments herein to provide methods and apparatuses for feedback reporting in a wireless communications network such as advanced 5G networks.

[0008] According to an aspect of some embodiments herein, there is provided a method performed by a wireless device (e.g., a UE) in a wireless communications network, the method comprising:

[0009] • receiving from a network node an indication or a configuration of at least two sets of Channel State Information Reference Signal, CSI-RS, resources,

[0010] • determining a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources received from the network node,

[0011] • determining a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources received from the network node,

[0012] • generating a feedback based on the first and the second CSI, and

[0013] • reporting the feedback to the network node.

[0014] According to another aspect of some embodiments herein, there is provided a method performed by a network node (e.g., a gNB), for receiving, from a wireless device, a feedback in a wireless communications network, the method comprising:

[0015] - transmitting to a wireless device, an indication or a configuration of a number of CSI-RS resources,

[0016] - providing a first and second set of CSI-RS resources, for enabling the wireless device to: o determining a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources provided by the network node, o determining a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources provided by the network node, o generating a feedback based on the first and second CSI, and

[0017] - receiving the feedback from the wireless device.

[0018] According to another aspect of embodiments herein, there is also provided a wireless device (e.g., a UE) comprising a processor and a memory containing instructions executable by the processor, whereby said wireless device is operative or configured to perform any one of the embodiments presented in the detailed description related to the actions performed by the wireless device.

[0019] According to yet another aspect of embodiments herein, there is provided a network node comprising a processor and a memory containing instructions executable by the processor, whereby said network node is operative or configured to perform any one of the embodiments presented in the detailed description related to the actions performed by the network node.

[0020] There is also provided a computer program comprising instructions which when executed on at least one processor of the wireless device (e.g., a UE), cause the at least said one processor to carry out the actions or method steps presented herein.

[0021] There is also provided a computer program comprising instructions which when executed on at least one processor of the network node, cause the at least said one processor to carry out the method steps presented herein.

[0022] A carrier is also provided containing the computer program, wherein the carrier is one of a computer readable storage medium, an electronic signal, optical signal, or a radio signal.

[0023] An advantage of the embodiments herein is to improve the performance of precoded downlink transmissions in 5G systems. In detail, the CSI report that carries information related to a predicted CSI, e.g., a precoder matrix or a CQI, for one or more future slots is reported from the wireless device to the network node. In some cases, the predicted CSI reported from the wireless device may be not well aligned, or not correctly be adapted to the radio channel associated with the one or more future slots. Obviously, this may lead to a performance degradation. In one example, when an AI / ML model or a filtering approach is used at the wireless device for the calculation of the predicted CSI, it may happen that the AI / ML model itself or the filter, or parameters of the AI / ML model, are not well aligned with the radio channel environment. In such a case, the wireless device should perform a model update of the AI / ML-based or filtering-based CSI prediction algorithm to improve the accuracy of the predicted CSI, where improving the prediction performance results in improved downlink performance. In this invention, several feedback schemes are proposed to inform a network node about the accuracy or quality of a CSI predicted at the wireless device. Additional advantages of the embodiments herein are provided in the detailed description of this disclosure.

[0024] BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Embodiments of the present invention are now described in further detail with reference to the accompanying drawings, in which:

[0026] Fig. 1 shows a schematic representation of a wireless communications system;

[0027] Fig. 2 shows a block-based model of a MIMO DL transmission using codebook- based-precoding in accordance with LTE Release 8;

[0028] Fig. 3 illustrates a flowchart of a method performed by a wireless device (e.g., a UE) according to some embodiments herein;

[0029] Fig. 4 illustrates a flowchart of a method performed by a network node (e.g., a gNB) according to some embodiments herein;

[0030] Fig. 5 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I, and when the slots of the first and second window are identical;

[0031] Fig. 6 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I, where the second set of CSI-RS resources comprises only a single CSI-RS resource, and where the second window comprises only a single slot;

[0032] Fig. 7 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I, where the second set of CSI-RS resources comprises only a single CSI-RS resource, and where the second window comprises at least two slots;

[0033] Fig. 8 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I, where the second set of CSI-RS resources comprises two CSI-RS resources, and where the second window comprises two non-consecutive slots; Fig. 9 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k = I, and when the slots of the first and second window are identical;

[0034] Fig. 10 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k = I, where the second set of CSI-RS resources comprises only a single CSI-RS resource, and where the second window comprises only a single slot;

[0035] Fig. 11 illustrates a schematic representation of the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k = I, where the second set of CSI-RS resources comprises two CSI-RS resources, and where the second window comprises two non-consecutive slots;

[0036] Fig. 12 is a block diagram depicting a wireless device (e.g., a UE) according to exemplary embodiments herein;

[0037] Fig. 13 is a block diagram depicting a network node (e.g., a gNB) according to exemplary embodiments herein.

[0038] DETAILED DESCRIPTION

[0039] In the following, a detailed description of the exemplary embodiments is described in conjunction with the drawings, in several scenarios to enable easier understanding of the solution(s) described herein.

[0040] Figure 1 illustrates a simplified schematic view of an example of a wireless communications network 100 including a core network (CN) 110 and a radio access network (RAN) 120. The RAN 120 is shown including a plurality of network nodes or radio base stations, which in 5G are called gNBs. Three radio base stations are depicted gNB1 , gNB2 and gNB3. Each gNB serves an area called a coverage area or a cell. Figure 1 illustrates 3 cells 121 , 122 and 123, each served by its own gNB, gNB1 , gNB2 and gNB3, respectively. It should be mentioned that the network 100 may include any number of cells and gNBs. The radio base stations, or network nodes serve users within a cell. In 4G or LTE, a radio base station is called an eNB, in 3G or UMTS, a radio base station is called an eNodeB, and BS in other radio access technologies. A user or a user equipment (UE) may be a wireless or a mobile terminal device or a stationary communication device. A mobile terminal device or a UE may also be an loT device, an MTC device, etc. loT devices may include wireless sensors, software, actuators, and computer devices. They can be imbedded into mobile devices, motor vehicle, industrial equipment, environmental sensors, medical devices, aerial vehicles and more, as well as network connectivity that enables these devices to collect and exchange data across an existing network infrastructure.

[0041] Referring back to Figure 1 , each cell is shown including UEs and loT devices. gNB1 in cell 121 serves UE1 121 A, UE2 121 B and loT device 121 C. Similarly, gNB2 in cell 121 serves UE3 122A, UE4 122B and loT device 122C, and gNB3 in cell 123 serves UE5 123A, UE6 123B and loT device 123C. The network 100 may include any number of UEs and loT devices or any other types of devices. The devices communicate with the serving gNB(s) in the uplink and the gNB(s) communicate with the devices in the downlink. The respective base station gNB1 to gNB3 may be connected to the CN 120, e.g., via the S1 interface, via respective backhaul links 111 , 121 D, 122D, 123D, which are schematically depicted in Fig. 1 by the arrows pointing to “core”. The core network 120 may be connected to one or more external networks, such as the Internet. The gNBs may be connected to each other via the S1 interface or the X2 interface or the XN interface in 5G, via respective interface links 121 E, 122E and 123E, which is depicted in the figure by the arrows pointing to gNBs.

[0042] For data transmission, a physical resource grid may be used. The physical resource grid may comprise a set of resource elements (REs) to which various physical channels and physical signals are mapped. For example, the physical channels may include the physical downlink, uplink and / or sidelink (SL) shared channels (PDSCH, PUSCH, PSSCH) carrying user specific data, also referred to as downlink, uplink or sidelink payload data, the physical broadcast channel (PBCH) carrying for example a master information block (MIB) and a system information block (SIB), the physical downlink, uplink and / or sidelink control channels (PDCCH, PUCCH, PSCCH) carrying for example the downlink control information (DCI), the uplink control information (UCI) or the sidelink control information (SCI). For the uplink, the physical channels may further include the physical random-access channel (PRACH or RACH) used by UEs for accessing the network once a UE is synchronized and obtains the MIB and SIB. The physical signals may comprise reference signals (RS), synchronization signals (SSs) and the like. The resource grid may comprise a frame or radio frame having a certain duration, like 10 milliseconds, in the time domain and having a given bandwidth in the frequency domain. The radio frame may have a certain number of subframes of a predefined length, e.g., 2 subframes with a length of 1 millisecond. Each subframe may include two slots of a number of OFDM symbols depending on the cyclic prefix (CP) length. IN 5G, each slot consists of 14 OFDM symbols or 12 OFDM symbols based on normal CP and extended CP respectively. A frame may also consist of a smaller number of OFDM symbols, e.g., when utilizing shortened transmission time intervals (TTIs) or a mini-slot / non-slot-based frame structure comprising just a few OFDM symbols. Slot aggregation is supported in 5G NR, and hence data transmission can be scheduled to span over one or multiple slots. Slot format indication informs a wireless device or UE whether an OFDM symbol is downlink, uplink or flexible.

[0043] In some examples, the wireless communication network system may be any singletone or multicarrier system using frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system, or any other Discrete Fourier Transform (DFT) based signal with or without CP, e.g., DFT-spread OFDM (DFT-s-OFDM). Other waveforms, like non-orthogonal waveforms for multiple access, e.g., filter-bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM) or universal filtered multi carrier (LIFMC), may also be used. The wireless communication system may operate, e.g., in accordance with the LTE-Advanced Pro standard, the 5G or NR (New Radio) standard or any other standard using any of the aforementioned waveforms.

[0044] The wireless communications network system depicted in Figure 1 may be a heterogeneous network having two distinct overlaid networks, a network of macro cells with each macro cell including a macro base station, like base station gNB1 to gNB3, and a network of small cell base stations (not shown in Figure 1 ), like femto- or picobase stations. In addition to the above described wireless network also non-terrestrial wireless communication networks exist including spaceborne transceivers, like satellites, and / or airborne transceivers, like unmanned aircraft systems. The nonterrestrial wireless communication network or system may operate in a similar way as the terrestrial system described above with reference to Figure 1 , for example in accordance with the LTE-advanced pro standard or the 5G or NR, standard. In the wireless communications network system such as the one depicted schematically in Figure 1 , multi-antenna techniques may be used, e.g., in accordance with LTE, NR or any other communication system, to improve user data rates, link reliability, cell coverage and network capacity. To support multi-stream or multi-layer transmissions, linear precoding is used in the physical layer of the communication system. Linear precoding is performed by a precoder matrix which maps layers of data to antenna ports. The precoding may be seen as a generalization of beamforming, which is a technique to spatially direct or focus a data transmission towards an intended receiver. The precoder matrix to be used at the gNB to map the data to the transmit antenna ports is decided using channel state information, CSI.

[0045] In the wireless communications network system as described above, such as LTE or New Radio (5G), downlink signals convey data signals, control signals containing downlink, DL, control information (DCI), and a number of reference signals or symbols (RS) used for different purposes. A gNodeB (or gNB or base station) transmits data and downlink control information (DCI) through the so-called physical downlink shared channel (PDSCH) and physical downlink control channel (PDCCH) or enhanced PDCCH (ePDCCH), respectively. Moreover, the downlink signal(s) of the gNB may contain one or multiple types of reference signals (RSs) including a common RS (CRS) in LTE, a channel state information RS (CSI-RS), a demodulation RS (DM-RS), and a phase tracking RS (PT-RS). The CRS is transmitted over a DL system bandwidth part and used at the user equipment (UE) to obtain a channel estimate to demodulate the data or control information. The CSI-RS is transmitted with a reduced density in the time and frequency domain compared to CRS and used at the UE for channel estimation or for channel state information (CSI) acquisition. The DM-RS is transmitted only in a bandwidth part of the respective PDSCH and used by the UE for data demodulation. For signal precoding at the gNB, several CSI-RS reporting mechanisms are used such as non-precoded CSI-RS and beamformed CSI-RS reporting. For a non-precoded CSI-RS, a one-to-one mapping between a CSI-RS port and a transceiver unit, TXRU, of the antenna array at the gNB is utilized. Therefore, non- precoded CSI-RS provides a cell-wide coverage where the different CSI-RS ports have the same beam direction and beam width. For beamformed / precoded UE-specific or non-UE-specific CSI-RS, a beamforming operation is applied over a single antenna port or over multiple antenna ports to have several narrow beams with high gain in different directions and, therefore, no cell-wide coverage.

[0046] In a wireless communications network system employing time division duplexing, TDD, due to channel reciprocity, the CSI is available at the base station (gNB). However, when employing frequency division duplexing, FDD, due to the absence of channel reciprocity, the channel is estimated at the UE and the estimate is fed back to the gNB.

[0047] Figure 2 shows a block-based model of a Multiple Input Multiple Output (MIMO) DL transmission using codebook-based-precoding in accordance with LTE release 8. Fig. 2 shows schematically the base station 200, gNB, the user equipment, UE, 202 and the channel 204, like a radio channel for a wireless data communication between the base station 200 and the user equipment 202. The base station includes an antenna array ANTT having a plurality of antennas or antenna elements, and a precoder 206 receiving a data vector 208 and a precoder matrix F from a codebook 210. The channel 204 may be described by the channel tensor / matrix 212. The user equipment 202 receives the data vector 214 via an antenna or an antenna array ANTR having a plurality of antennas or antenna elements. A feedback channel 216 between the user equipment 202 and the base station 200 is provided for transmitting feedback information. The previous releases of 3GPP up to Release 15 support the use of several downlink reference symbols (such as CSI-RS) for CSI estimation at the UE.

[0048] In FDD systems (up to Rel. 15), the estimated channel at the UE is reported to the gNB implicitly where the CSI report transmitted by the UE over the feedback channel includes the rank index (Rl), the precoding matrix index (PMI) and the channel quality index (CQI) (and the CRI from Rel. 13) allowing, at the gNB, to decide the precoding matrix, and the modulation order and coding scheme (MCS) of the symbols to be transmitted. The PMI and the Rl are used to determine the precoding matrix from a predefined set of matrices 1 also referred to as codebook. The codebook, e.g., in accordance with LTE, may be a look-up table with matrices in each entry of the table, and the PMI and Rl from the UE decide from which row and column of the table the precoder matrix to be used is obtained. The precoders and codebooks are designed up to Rel. 15 for gNBs equipped with one-dimensional Uniform Linear Arrays (ULAs) having N dual-polarized antennas (in total Nt= 2N antennas or antenna ports), or with two-dimensional Uniform Planar Arrays (UPAs) having dual-polarized antennas at N N2positions (in total Nt= 2N N2antennas or antenna ports). The ULA allows controlling the radio wave in the horizontal (azimuth) direction only, so that azimuth- only beamforming at the gNB is possible, whereas the UPA supports transmit beamforming on both vertical (elevation) and horizontal (azimuth) directions, which is also referred to as full-dimension (FD) MIMO. The codebook, e.g., in the case of massive antenna arrays such as FD-MIMO, may be a set of beamforming weights that forms spatially separated electromagnetic transmit / receive beams using the array response vectors of the array. The beamforming weights (also referred to as the array steering vectors) of the array are amplitude gains and phase adjustments that are applied to the signal fed to the antennas (or the signal received from the antennas) to transmit (or obtain) a radiation towards (or from) a particular direction. The components of the precoder matrix are obtained from the codebook, and the PM I and the Rl are used to read the codebook and obtain the precoder. The array steering vectors may be described by the columns of a two-dimensional Discrete Fourier Transform (DFT) matrix when ULAs or UPAs are used for signal transmission.

[0049] The precoder matrices used in the Type-1, Type-1 multi-panel and Type-ll CSI reporting schemes in 3GPP NR standards are defined by a dual-stage structure (i.e., two components codebook), F = F1F2. The first component or the so-called first stage precoder or matrix, Fl tis used to select a number of beam vectors from a Discrete Fourier Transform -based (DFT-based) matrix, which is also called the spatial codebook. Moreover, the first stage precoder, F , corresponds to a wide-band matrix and contains a number of spatial beamforming vectors (the so-called spatial beams) selected from a DFT-based codebook matrix for the two polarizations of the antenna array. The second component or the so-called second stage precoder is used to combine the selected beam vectors. This means the second stage precoder or matrix, F2, corresponds to a selection / combining / co-phasing matrix to select / combine / co- phase the beams defined in F . For rank- / ? transmission, F contains v vectors, wherein v denotes the transmission rank, where the entries of each vector are chosen to combine single or multiple beams within each polarization. The selection of the matrices Frand F2is performed by the UE based on reference signals such as CSI- RS and the knowledge of the channel conditions. The selected matrices are indicated in a CSI report in the form of a Rl (the Rl is the rank indicator and denotes the rank of the precoding matrix) and a PMI and are used at the gNB to update the multi-user precoder for the next transmission time interval.

[0050] The term ‘higher layer’ in the following, when used in isolation, denotes any communication layer above the physical layer in the protocol stack. When the term is used in connection with a specific layer, it denotes any communication in the protocol stack above said layer.

[0051] The term serving cell and carrier component (CC) may be used interchangeably in this disclosure as a serving cell configured for a UE and is usually a separate physical carrier centered around a particular carrier frequency. Depending on the frequency of a component carrier / serving cell, the size of the cell and the beamformed reference signals may vary.

[0052] The term ‘PDxCH’ or ‘PDXCH’ may indicate either the physical downlink shared channel (PDSCH) or the physical downlink control channel (PDCCH), while ‘PUxCH’ or ‘PUXCH’ may indicate either the physical uplink shared channel (PUSCH) or the physical uplink control channel (PUCCH). The term ‘PxxCH’ or ‘PXXCH’ may denote a PDSCH, a PDCCH, a PUSCH, a PRACH, a PBCH, a PSSCH, or a PSCCH.

[0053] The phrase ‘fixed / predetermined / provided in the specifications’ in this invention disclosure may mean the following: one or more rules and / or methods and / or particulars regarding certain parameter(s) are provided in the standard specifications that the UE and / or any network node is supposed to follow or implement.

[0054] The term ‘configured’ may mean the following: one or more rules and / or methods and / or particulars, regarding one or more parameters as provided in the standard specifications that the UE is supposed to follow or implement, are provided to the UE by one or more network entities, e.g., via higher layer signaling, like radio resource control, RRC, signaling.

[0055] The AI / ML Model utilizes one or more modules to generate the predicted CSI based on one or more input parameters. The one or more input parameters include but not limited to the present and past channel frequency response, present and past channel impulse response, noise levels, SNR, interference information, CSI-RS periodicity etc., The AI / ML model for the predicted CSI is based on the following architectures. In one example, the AI / ML model architecture includes Recurrent Neural Networks (RNNs). In another example, the AI / ML model architecture includes Convolutional Neural Networks (CNNs). In another example, the AI / ML architecture include both RNNs and CNNs. Examples of RNNs types include but not limited to long-short term memory (LSTM), Gated Recurrent units, bidirectional LSTM, convolutional LSTM etc. Examples of CNNs include but not limited to temporal convolutional networks, 1 D CNNs etc.

[0056] In certain embodiments, a method performed by a wireless device in a wireless communications network is proposed, the method comprising:

[0057] • receiving from a network node an indication or a configuration of at least two sets of Channel State Information Reference Signal, CSI-RS, resources,

[0058] • determining a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources received from the network node,

[0059] • determining a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources received from the network node,

[0060] • determining a feedback based on the first and the second CSI, and

[0061] • reporting the feedback to the network node.

[0062] CSI-RS configuration

[0063] The wireless device determines the first CSI and second CSI using the CSI-RS resource(s) of the first and second set of CSI-RS resources, respectively. The CSI-RS resource(s) of the first and second set may be received from a network node. In some examples, the first and / or second set of CSI-RS resources may comprise one or more periodic or semi-persistent CSI-RS resource(s). For the case of a periodic or semi- persistent CSI-RS resource, the CSI-RS resource is associated with a periodicity which is semi-statically configured to the wireless device. The periodic or semi-persistent CSI-RS resource is transmitted by the network node with the configured periodicity (e.g., the CSI-RS resource is transmitted once on every K slots). For a periodic CSI- RS, the wireless device may assume that the periodic CSI-RS is available once the periodic CSI-RS resource is configured. In contrast, the wireless device may assume that the semi-persistent CSI-RS is available once it received a MAC-CE command for its activation from the network node.

[0064] In certain embodiments, the first set of CSI-RS resources comprises M > 1 CSI-RS resources received from the network node in slot(s) from n to n + k, wherein n is a slot index, and k > 0 is an integer variable. In some examples, the M CSI-RS resources are provided in M slot(s) n + mA, , m = 0, ... , M - 1, wherein n is a slot index, and A, is a gap in terms of number of slots or any other unit of duration (frame / subframe / seconds). In some examples, M = 1 such that the first set of CSI-RS resources comprises only a single CSI-RS resource. In certain embodiments, the M CSI-RS resource(s) of the first set is / are configured to the UE via higher layer signaling from a network node. For example, the M CSI-RS resource(s) are provided via a higher layer configuration, e.g., CSI report configuration, from a network node to the UE. Similarly, the gap, Ax, can be provided to the UE via layer signaling from the network node, or the value(s) of A, are predetermined, such as being provided in the NR specifications, and hence known to the UE. Examples for possible values of M are (1 ,2, 3, 4, 8, 16). Examples for possible values for A, are (0, 1 ,2, 3, 4, 8).

[0065] In certain embodiments, the second set of CSI-RS resources comprises P > 1 CSI-RS resources provided in slot(s) n + I to n + I + t, t e Z+ or t > 0 is an integer variable, wherein n + I is a slot index. In some examples, the P CSI-RS resources of the second set are provided in P slot(s) n + I + pA2, p = 0, ... , P - 1, wherein n is a slot index, and A2is a gap in terms of number of slots or any other unit of duration (frame / subframe / seconds). In one option, the P CSI-RS resource(s) from the second set is / are configured to the UE via higher layer signaling from a network node. For example, the P CSI-RS resource(s) are provided via a higher layer configuration (e.g., a CSI report configuration) from a network node to the UE. Similarly, the gap, A2, can be provided to the UE via higher layer signaling from a network node, or the value(s) of A2are provided in the NR specifications, and hence known to the UE. Examples for possible values of P are (1 ,2,3,4,8,16). Examples for possible values for A2are (0,1 , 2, 3, 4, 8). In certain embodiments, the second set of CSI-RS resources comprises only a single CSI-RS resource. In one example, the single CSI-RS resource of the second set is received by the wireless device in a slot later in time than the CSI-RS resources of the first set. In some examples, I = k, and there is an overlap of at most one CSI-RS resource between the first set and the second set. In some other examples, I < k, and there is an overlap of at least one CSI-RS resource between the first set and the second set. In some other examples, I > k and there is no overlap of the CSI-RS resources of the first set and the second set. In some examples, M > P, or M = P. In some examples, P = 1 and M > 1.

[0066] In certain embodiments, the first and / or second set of CSI-RS resources comprises an a-periodic CSI-RS resource, or a CSI-RS burst (comprising an a-periodic CSI-RS resource set comprising a number of CSI-RS resources). For an a-periodic CSI-RS or a CSI-RS burst, the wireless device may assume that the a-periodic CSI-RS or CSI- RS burst is available / triggered once it is received a higher-layer or a physical layer indication indicating the a-periodic CSI-RS or CSI-RS burst.

[0067] In certain embodiments, the configuration comprises one CSI-RS resource set or two CSI-RS resource sets, or at least two CSI-RS resource sets.

[0068] In some examples, the first set of CSI-RS resources is a CSI-RS resource set comprising one or more periodic or semi-persistent CSI-RS resource(s) and the second set is a different CSI-RS resource set comprising one or more periodic or semi- persistent CSI-RS resource(s).

[0069] In some examples, the first set of CSI-RS resources is a CSI-RS resource set comprising one or more periodic CSI-RS resource(s) and the second set is from the same CSI-RS resource set comprising one or more periodic CSI-RS resource(s).

[0070] In some examples, the first set of CSI-RS resources is a CSI-RS resource set comprising one or more semi-persistent CSI-RS resource(s) and the second set is from the same CSI-RS resource set comprising one or more semi-persistent CSI-RS resource(s).

[0071] In some examples, the first set of CSI-RS resources is a CSI-RS resource set comprising one or more periodic or semi-persistent CSI-RS resource(s) and the second set is a CSI-RS resource set comprising one or more a-periodic CSI-RS resource(s).

[0072] In some examples, the first set of CSI-RS resources is a CSI-RS resource set comprising one or more a-periodic CSI-RS resource(s) and the second set is a CSI- RS resource set comprising one or more a-periodic CSI-RS resource(s). In some examples, the first set of CSI-RS resources and the second set of CSI-RS resources are from the same CSI-RS resource set. The CSI-RS resource set may - comprise one or more periodic, semi-persistent or a-periodic CSI-RS resource(s).

[0073] In some examples, the first set of CSI-RS resources and the second set of CSI-RS resources are identical, i.e. , they are the same CSI-RS resource set.

[0074] In certain embodiments, the first set of CSI-RS resources are a subset of a CSI-RS resource set. The CSI-RS resource set can be configured to the wireless device from the network node.

[0075] In certain embodiments, the second set of CSI-RS resources are a subset of a CSI- RS resource set. The CSI-RS resource set can be configured to the wireless device from the network node.

[0076] In certain embodiments, a CSI-RS resource set comprising a first set of CSI-RS resources is different to a CSI-RS resource set comprising a second set of CSI-RS resources.

[0077] In certain embodiments, the CSI-RS resources of the first and / or second set are configured for channel measurement.

[0078] In certain embodiments, each CSI-RS resource comprises a number of antenna or CSI-RS ports. The antenna or CSI-RS ports are used by the wireless device for the CSI measurements. In some examples, a CSI-RS resource may comprise / V antenna or CSI-RS ports where / V is an integer value (e.g., N = 2, 4, 8, 12, 16, 32, 64,128).

[0079] In certain embodiments, at least one CSI-RS resource in the second set is identical to one CSI-RS resource in the first set. Such a CSI-RS resource may be referred to as reference CSI-RS resource. The reference CSI-RS resource may be the latest CSI-RS resource of the first set and the first CSI-RS resource of the second set used by the wireless device for determining the first and second CSI.

[0080] In certain embodiments, a CSI-RS reference resource is on the latest or the last slot on which a wireless device can receive and measure the CSI-RS resource. In some examples, the CSI or PMI determined by the wireless device on the latest or the last slot is included in the next available uplink slot. In some examples, for the CSI-RS resources in the first set, the CSI reference resource is given by the last slot, n + (M -

[0081] 1)A-L, wherein n is the slot index, and Axis a gap in terms of number of slots or any other unit of duration (frame / subframe / seconds) on which the last CSI-RS resource is measured. For periodic and semi-persistent CSI-RS, when a single CSI-RS resource is configured for channel measurement, the CSI reference resource slot is the smallest value greater than or equal to 4 • 2^DLsuch that it corresponds to a valid downlink slot, where [iDLis the downlink subcarrier spacing. When multiple CSI-RS resources are configured for channel measurement, the CSI reference resource slot is the smallest value greater than or equal to 5 • 2^DL, such that it corresponds to a valid downlink slot, where [iDLis the downlink subcarrier spacing. For a-periodic CSI-RS, if the wireless device is indicated by a downlink control indicator, DCI, to report the feedback in the same slot as the feedback request, the CSI reference resource is in the slot in which the feedback is requested, otherwise the CSI reference resource index is the smallest value greater than or equal to where Z’ is the minimum number of OFDM symbols between the last symbol on which the a-periodic CSI-RS is used to calculate the first CSI and the first symbol of the PUSCH which carries the feedback, and N^bis the number of OFDM symbols in a slot.

[0082] In certain embodiments, the CSI-RS resources of the first set comprises a CSI reference resource index associated with a downlink slot k and the CSI-RS resources of the second set comprises a CSI reference resource index associated with a downlink slot k2. In some examples, k = k2. In some examples, k < k2, or k > k2. In some options, k = k2and the CSI reference resource of the first set of CSI-RS resources is present on the same slot as the CSI reference resource of the second set of CSI-RS resource(s). In some examples, the feedback of the wireless device is associated with the one or more of the future slots n + (M - 1)AX+ ri + 6, wherein n is a slot index, and Axis a gap in terms of number of slots or any other unit of duration (frame / subframe / seconds) on which the last CSI-RS resource is measured. Here, M is the total number of CSI-RS resources in the first set, n’ is the CSI processing delay, and 6 e {- / , 0,1, 2,3,4, ... } is a higher layer configured parameter or a parameter determined by the UE and reported in the feedback.

[0083] In some examples, for periodic or semi-persistent feedback reporting by the wireless device, the difference between the downlink slots k and k2is given by the smallest value greater than or equal to 4 • 2^DL, such that the difference corresponds to a valid downlink slot, where jiDLis the downlink subcarrier spacing.

[0084] In some examples, for periodic or semi-persistent feedback reporting, the difference between the downlink slots krand k2is given by the smallest value greater than or equal to 5 • 2^DL, such that the difference corresponds to a valid downlink slot, where jiDLis the downlink subcarrier spacing.

[0085] In some examples, the difference between the downlink slots k and k2is given by the smallest value greater than or equal to where Z' is the minimum number of

[0086] OFDM symbols between the last symbol on which the a-periodic CSI-RS is used to calculate the first and / or the second CSI and the first symbol of the PUSCH which carries the feedback and N^bis the number of OFDM symbols in a slot.

[0087] CSI quantities

[0088] The first and / or second CSI may comprise a number of quantities (i.e. , parameters or types), wherein a quantity is one of the following:

[0089] - a CSI-RS resource indicator (CRI) or SSB resource indicator (SSBRI) indicating a channel measurement resource (CSI-RS or SSB resource) with which the other parameters in the CSI feedback are associated. The network may configure one or more resources that the wireless device may measure. From the measurements of those resource(s), the wireless device may choose to associate one of the resources for PDSCH transmission. Said resource is indicated via the CRI / SSBRI.

[0090] - a precoding matrix identifier, PMI, indicating a precoding matrix for a corresponding downlink transmission,

[0091] - a channel quality indicator, CQI, indicating a modulation and coding scheme (MCS) conditioned on the PMI and the Rl for a corresponding downlink transmission such that the PDSCH transport block with said MCS, PMI and Rl would have a block error rate of at most , where is either a value known apriori to the wireless device or is received from the network node. In some examples, when there is no PMI computed by the UE, the CQI is conditioned on the Rl, but not the PMI. In some other examples, the CQI may be computed conditioned directly on the reference signal measurements, and

[0092] - a rank indicator indicating the rank of the transmission (number of spatial layers of transmission) for a corresponding downlink transmission.

[0093] In certain embodiments, the one or more slots of the first window of slot(s) associated with the first CSI may occur later in time than the one or more slot(s) on which the CSI- RS resources of the first set are received by the wireless device. This means the wireless device may apply predictive signal processing techniques based on the received or measured CSI-RS resources of the first set for determining the quantities of the first CSI for the one or more slot(s) which occur later in time than the received or measured CSI-RS resources. In some examples, the wireless device calculates an explicit estimate of the radio channel (e.g., a channel matrix) between the antenna ports of the wireless device and the antenna ports of the network node for the one or more slot(s) associated with the CSI-RS resource(s) of the first set. The channel estimates are provided by the wireless device in time or frequency domain. Based on the channel estimates, the wireless device may apply predictive signal processing techniques (e.g., Kalman filtering, etc.) to predict the radio channel(s) (e.g., channel matrices) for the one or more slot(s) associated with the first window. The predicted radio channel(s) are further used to determine the quantities of the first CSI. In another example, the wireless device may determine the quantities of the first CSI directly using the measured CSI-RS resources of the first set and applying advanced signal processing techniques such as AI / ML-models or algorithms for CSI prediction. In such a case, the input of the AI / ML-model is the received or measured CSI-RS resource(s), or a pre-processed version of the received or measured CSI-RS resource(s), or a computed CSI, and the output is one or more predicted quantities which is then included in the first CSI. The first CSI may comprise one or more ‘legacy’ CSI quantities (e.g., the PMI, Rl, and / or CQI) or a compressed version / format of a CSI computed by the AI / ML model or algorithm. A wireless device can be configured to generate the CSI using an AI / ML-based algorithm, model or technique, or a temporal AI / ML-based algorithm, model or technique in combination with a pre-defined codebook. The AI / ML- based technique can utilize machine learning, a neural network, a convolutional autoencoder, a recurrent autoencoder, a transformer neural network, etc. to generate the CSI. In certain embodiments, the first CSI is associated with one or more slot(s) of a first window of slot(s). In some examples, the first CSI may comprise one or more PMIs, and / or one or more CQIs, wherein a PMI and / or CQI is associated with one or multiple slot(s) within the first window of slot(s). In some examples, the first window comprises a single slot. In some examples, the first window comprises WCSIslots. In one option, the first CSI comprises K PMIs, and Q CQIs, wherein a PMI and / or CQI is associated with a single slot, two slots, or WCSI / K consecutive or non-consecutive slots and WCSI / Q consecutive or non-consecutive slots, respectively, of the first window. In some examples, the i-th PMI (i = 0, 1) is associated with slots + 1, (i + l)WCSi / K. In some examples, the j-th CQI (j = 0, ..., Q - 1) is associated with slots The K PMIs can be identified by multiple variables / indicators in the first CSI. In another option, the first CSI comprises at least a single PMI indicating K precoding matrices, wherein each precoding matrix is associated with one or more slot(s) of the first window, and wherein K > 1 or K > 1.

[0094] In certain embodiments, the second CSI is associated with one or more slot(s) of a second window of slot(s). The second CSI comprises at least one PMI and / or CQI and / or Rl. In certain embodiments, the one or more slot(s) of the second window for which the second CSI is determined by the wireless device occur(s) not later in time than the received or measured CSI-RS resource(s) of the second set. The one or more slots of the second window can be identical to the one or more slot(s), or may comprise the one or more slot(s), on which the CSI-RS resource(s) of the second set are received by the wireless device. The wireless device may perform the CSI measurements on the CSI-RS resource(s) of the second set and may apply non- predictive signal processing techniques to determine the second CSI for one or more slot(s) of the second window.

[0095] In some examples, the second set comprises only a single CSI-RS resource. In such a case, the second CSI comprises only a single PMI and / or CQI and / or Rl. The PMI and / or CQI and / or Rl is / are associated with at least a single slot of the second window.

[0096] In some examples, the second window comprises only a single slot, wherein the single slot comprises the CSI-RS resource of the second set. This means the slot for which the second CSI is determined comprises the CSI-RS resource. In some examples, the second window comprises the same slot(s) as the first window. One or more slot(s) of the second window may comprise the one or more CSI-RS resource(s) of the second set.

[0097] In certain embodiments, one or more slots of the second window of slot(s) associated with the second CSI occur later in time than one or more slot(s) on which the CSI-RS resources of the second set are received by the wireless device.

[0098] The difference between the slot index of the last CSI-RS occasion of the first set and the first slot of the first window is given by m1. The difference between the slot index of the last CSI-RS occasion of the second set and the first slot of the second window is given by m2. In some examples, when > m2, the prediction ability or accuracy for two different prediction lengths (i.e. , and m2) may be determined by the wireless device. Reporting the accuracy measure to the network node in such a case facilitates the network node to adapt to the wireless device ability to perform prediction. In some examples, and m2are CSI processing delays and may be related to a wireless device capability.

[0099] In the following, some examples of the CSI-RS resource occasions of the CSI-RS resources of the first and second set and corresponding slot(s) of the first window and second window associated with the first CSI and second CSI, respectively, are proposed.

[0100] A first example is illustrated in Figure 5, where the CSI-RS occasions (slots) of the CSI- RS resources of the first and second set for the case k < I are shown. In this example, the first and second window are later in time than the CSI-RS resource occasions from the first set. Moreover, the first and second window are identical and comprise at least one slot.

[0101] A second example is illustrated in Figure 6, where the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I are shown. As the second set of CSI-RS resources comprises only a single CSI-RS resource, only a single CSI-RS resource occasion is shown. In this example, the first and second window are later in time than the CSI-RS resource occasions from the first set. Moreover, the first window comprises the second window, and the second window comprises only a single slot. A third example is illustrated in Figure 7, where the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I are shown. The second set of CSI-RS resources comprises a single CSI-RS resource, and hence, only a single CSI-RS resource occasion is shown. In this example, the first and second window are later in time than the CSI-RS resource occasions from the first set. Moreover, the first window comprises the second window, and the second window comprises two consecutive slots.

[0102] A fourth example is illustrated in Figure 8, where the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k < I are shown. The second set of CSI-RS resources comprises two CSI-RS resources shown by the two CSI-RS occasions. In this example, the first and second window are also later in time than the CSI-RS resource occasions from the first set. Moreover, the first window comprises the second window, and the second window comprises two non-consecutive slots.

[0103] A fifth example is illustrated in Figure 9, where the CSI-RS occasions (slots) of the CSI- RS resources of the first and second set for the case k = I are shown. There is one CSI-RS resource which is present in the first and second set of CSI-RS resources. In this example, the first and second window are not later in time than the last CSI-RS resource occasion from the first set. There is at least one overlapping slot between the last CSI-RS occasion of the CSI-RS resources from the first set, the first CSI-RS occasion of the CSI-RS resources of the second set and the first and second window. Moreover, the first and second window are identical and comprise multiple slots.

[0104] A sixth example is illustrated in Figure 10, where the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k = I are shown. There is one CSI-RS resource which is present in the first and second set of CSI-RS resources. In this example, the first and second window are not later in time than the last CSI-RS resource occasion from the first set. There is one overlapping slot between the last CSI-RS occasion of the CSI-RS resources from the first set, the first CSI-RS occasion of the CSI-RS resources of the second set and the first and second window. Moreover, the second window is contained in the first window and comprises a single slot, whereas the first window comprises multiple slots.

[0105] A seventh example is illustrated in Figure 11 , where the CSI-RS occasions (slots) of the CSI-RS resources of the first and second set for the case k = I are shown. There is one CSI-RS resource which is present in the first and second set of CSI-RS resources. In this example, the first and second window are not later in time than the last CSI-RS resource occasion from the first set. The second set of CSI-RS resources comprises two CSI-RS resources. There is one overlapping slot between the last CSI- RS occasion of the CSI-RS resources from the first set, the first CSI-RS occasion of the CSI-RS resources of the second set and the first and second window. Moreover, the second window is contained in the first window and comprises two slots. The first window comprises two non-consecutive slots.

[0106] In some examples, the second set of CSI-RS resources comprises at least two CSI- RS resources. In such a case, the second CSI may comprise at least two PMIs, and / or one CQI or two CQIs. Each PMI may be associated with at least a single slot of the second window. In some examples, the second window comprises two slots, wherein each slot is associated with a PMI of the second CSI, and each slot comprises a CSI- RS resource of the second set. In some examples, the second window comprises one or more slots, wherein the one or more slots comprise one or more CSI-RS resource(s) of the second set.

[0107] In some examples, the second window comprises N slots, wherein the first N / 2 slot(s) are associated with a first PMI and / or CQI and at least one slot of first N / 2 slot(s) is associated with a first CSI-RS resource of the second set and the second N / 2 slot(s) are associated with a second PMI and / or second CQI and at least one slot of the second N / 2 slot(s) is associated with a second CSI-RS resource of the second set.

[0108] In certain embodiments, a PMI in the first or second CSI indicates a precoding matrix defined by a linear combination of basis vectors which are selected from one, two or three basis sets. The precoding matrix can be identical for one, two, or multiple slot(s) within the first window. In some examples, the precoding matrix may be identified by amplitude and phase information related to a set of combining coefficients and a set of basis vectors selected from the first and second basis set. The first basis set may comprise spatial domain, SD, components, or vectors which are defined across antenna or CSI-RS ports. The second basis set may comprise frequency domain, FD, components, or vectors which are defined across multiple frequency units, or physical resource blocks, PRBs, or subbands in the frequency domain. In some examples, the first and / or second basis set is / are discrete Fourier transform, DFTbasis set(s) or oversampled DFT- basis set(s) comprising DFT-based or oversampled DFT-based vectors.

[0109] In some examples, the single PMI, indicating K precoding matrices, or a single precoding matrix, comprising the K precoding matrices (e.g., K precoding submatrices), is defined by a linear combination of basis vectors which are selected from multiple basis sets. The precoding matrix is defined across multiple time units or slots of the first window and comprises K precoding sub-matrices, wherein each precoding sub-matrix is associated with a time unit or one or more slot(s) of the first window. Moreover, the precoding matrix may be identified by amplitude and phase information related to a set of combining coefficients and set of indices identifying the basis vectors of a first, second, and / or third basis set. The first basis set may comprise spatial domain, SD, components, or vectors which are defined across antenna or CSI-RS ports. The second basis set may comprise frequency domain, FD, components, or vectors which are defined across multiple frequency units, or physical resource blocks, PRBs, or subbands in the frequency domain. The third basis set, if available, may comprise time domain, TD, components, or vectors which are defined across multiple time units, or slot(s) in the time domain. In some examples, the first and / or second and / or third basis set is / are DFT-basis set(s) or oversampled DFT-basis set(s) comprising DFT-based or oversampled DFT based vectors.

[0110] In certain embodiments, the second CSI comprises at least one PMI. The PMI may indicate a precoding matrix defined by a linear combination of basis vectors which are selected from multiple basis sets. The precoding matrix may be identified by amplitude and phase information related to a set of combining coefficients and set of indices identifying the basis vectors of a first and / or second basis set. A first basis set may comprise spatial domain, SD, components or vectors which are defined across antenna or CSI-RS ports. A second basis set may comprise frequency domain, FD, components or vectors which are defined across multiple frequency units, or physical resource blocks, PRBs, or subbands in the frequency domain. In some examples, the first and / or second basis set is / are DFT-basis set(s) or oversampled DFT-basis set(s) comprising DFT-based or oversampled DFT based vectors. In some examples, the second CSI comprises two PMIs. In certain embodiments, the slot(s) on which the CSI-RS resource(s) of the second set are received by the wireless device are contained in the first window. In such a case, the slot(s) of the second window can partially or completely identical to one or more slot(s) of the first window.

[0111] Reporting

[0112] In certain embodiments, the wireless device may determine feedback using the first CSI and second CSI and report the feedback to the network node. In some cases, the feedback is a CSI report. The feedback may be transmitted by the wireless device via an uplink channel to the network node. In one example, the feedback or CSI report comprises the first CSI, the second CSI, or the first and second CSI. In another example, the wireless device may compare the first CSI and the second CSI with respect to a certain quality parameter or metric and may report the result of the comparison via the feedback to the network node. In some examples, the first CSI is a predicted CSI and the second CSI is a non-predicted CSI. In some other examples, the first CSI is a non-predicted CSI, and the second CSI is a non-predicted CSI. In some other examples, the first CSI is a predicted CSI and the second CSI is a predicted CSI. For example, the wireless device may determine the prediction quality by determining a similarity or correlation between the predicted CSI (e.g., PMI), contained in the first CSI, and the non-predicted CSI (e.g., PMI), contained in the second CSI, using an error, similarity or correlation metric. In some examples, the wireless device may calculate the metric using the precoding matrix / matrices of the first CSI and the precoding matrix / matrices of the second CSI for each slot of the first and second window. In some examples, the wireless device may calculate the metric using

[0113] - the precoding matrix / matrices of the first CSI and the channel information calculated using the CSI-RS resources of the second set, and

[0114] - the precoding matrix / matrices of the second CSI and the channel information calculated using the CSI-RS resources of the second set for each slot of the first and second window.

[0115] Examples of such metrics are the squared generalized cosine similarity, SGCS, or the mean-squared error, MSE, the normalized mean-squared error, NMSE, or the difference between the precoding matrix / matrices of the first CSI and the channel information calculated using the CSI-RS resources of the second set and the precoding matrix / matrices of the second CSI and the channel information calculated using the CSI-RS resources of the second set for each slot of the first and second window. Note that the feedback can also comprise the quality or error metric as described above. In another example, the feedback is binary. In such a case, the feedback may indicate that the quality parameter or metric is above or below a certain threshold, e.g., when the error between the predicted CSI, contained in the first CSI, and the non-predicted CSI, contained in the second CSI, is large. When an AI / ML-based model is used at the wireless device to determine the first CSI, the feedback reported by the wireless device indicates to the network node about the accuracy of the AI / ML-based CSI prediction. In case that the accuracy is below a certain threshold, the network may trigger the wireless device to perform a model update of the AI / ML-based CSI prediction algorithm. In another example, the feedback comprises one or more PMIs of the first CSI, and a PMI of the second CSI. In another example, the feedback comprises one or two PMIs of the first CSI and two PMIs of the second CSI. In another example, the feedback comprises the first CSI or the second CSI and the quality parameter or metric of the first CSI.

[0116] In certain embodiments, the wireless device determines the feedback using the first CSI and second CSI and report the feedback to the network node. In some cases, the feedback is a CSI report, included in a CSI report or included in a PHY-layer (e.g., PUSCH / PUCCH) or a higher layer signaling (e.g., MAC-CE or RRC message) to the network node.

[0117] In some cases, the first CSI indicates or is associated with a first precoder matrix and the second CSI indicates or is associated with a second precoder matrix. The wireless device may determine a first channel quality indicator, CQI, using the first precoder matrix and a second CQI using the second precoder matrix. In some examples, the wireless device may provide the first and second CQI in the feedback or CSI report. In another example, the wireless device may indicate at least a difference between the first and the second CQI, along with the first or the second CQI, in the feedback or CSI report. In a third example, the wireless device may indicate at least a difference between the first and the second CQI in the feedback or CSI report.

[0118] In certain examples, the wireless device may report a differential CQI in the feedback or the CSI report. A differential CQI is a value / index that indicates the difference between the first and the second CQI values or indicates the range in which the difference between the first and the second CQI values lie, wherein the difference is either [first CQI - second CQI], or [second CQI - first CQI].

[0119] In some examples, the wireless device may report a differential CQI in the feedback wherein the difference indicated by the differential CQI is the following:

[0120] - [first CQI - second CQI] if the second CQI is greater than the first CQI, or

[0121] - [second CQI - first CQI] if the first CQI is greater than the second CQI.

[0122] In some cases, the wireless device may provide at least one of the following information in the feedback if a differential CQI is reported:

[0123] - An absolute CQI value which may be the first CQI or the second CQI,

[0124] - An indication of whether the absolute CQI value provided in the report corresponds to the first or the second CQI value,

[0125] - An indication if the differential CQI is computed with respect to the first CQI or the second CQI,

[0126] - The greater CQI value among the first and the second CQI values.

[0127] The above information would be required if both the first and second CQI values are not reported. This differential CQI reporting helps the network node to gauge the accuracy of the precoding prediction algorithms with reduced feedback overhead.

[0128] In some cases, the first CSI indicates or is associated with a first precoder matrix and a first rank, and the second CSI indicates or is associated with a second precoder matrix and a second rank. The first rank may indicate the number of layers associated with the first precoder matrix and the second rank may indicate the number of layers associated with the second precoder matrix. The wireless device may indicate the first and second rank in the feedback or CSI report. In some examples, the wireless device may indicate the first rank or the second rank, and a difference between the first rank and the second rank in the feedback or CSI report. In some other examples, the wireless device may indicate only the difference between the first rank and the second rank, without including the first rank or the second rank, in the feedback or CSI report.

[0129] The difference between the first rank and the second rank may denote either the value [first rank - second rank] or the value [second rank - first rank]. The feedback may be transmitted by the wireless device via a physical layer uplink channel such as PUSCH or PUCCH to the network node, or via a higher layer signaling such as a MAC-CE or an RRC message. In one example, the feedback or CSI report comprises the first CSI, or the second CSI, or the first and second CSI. In another example, the wireless device may compare the first CSI and the second CSI with respect to a certain quality parameter or metric and may report the result of the comparison via the feedback to the network node. In some examples, the feedback or CSI report may comprise the first CSI or the second CSI and some additional information. Such additional information can be related to the CQI and / or rank as described above.

[0130] In certain embodiments, the wireless device determines multiple first CQIs, wherein each first CQI is associated with one or multiple different slot(s) of the first window of slot(s). The wireless device may determine one or multiple second CQI(s), wherein each second CQI is associated with one or multiple slot(s) of the second window of slot(s). In some options, the first and second window are overlapping or partly overlapping (i.e. , one or more slot(s) or all slot(s) of the first window is / are identical to one or more slot(s) of the second window of slot(s)). Note that a first CQI is associated with the first CSI, or a precoder matrix of the first CSI. A second CQI is associated with the second CSI, or a precoder matrix of the second CSI.

[0131] In a first option, the wireless device may determine multiple first CQIs associated with multiple different slot(s) or groups of slots of the first window of slot(s). The wireless device may also determine a single second CQI associated with one or multiple different slot(s) or groups of slots of the second window of slot(s). It may be assumed that a slot or multiple slots or groups of slots of the first and second window are identical and associated with a first CQI and a second CQI. Each group of slots is associated with a single CQI value. The wireless device may indicate the multiple first CQIs and the second CQI explicitly or implicitly in the feedback or CSI report. In some examples, the wireless device indicates directly the multiple first CQIs and the second CQI in the feedback or CSI report. In some examples, the wireless device indicates the second CQI and one or more differences between the second CQI and the first CQIs in the feedback or CSI report. This means that the wireless device may determine for a 1 second CQI, the difference between a second CQI and a first CQI and may indicate the difference or information related to the difference in the feedback or CSI report. In some cases, the number of first CQIs is two. In some cases, the number of slots of the second window is one.

[0132] In a second option, the wireless device may determine multiple first CQIs associated with multiple different slot(s) or groups of slots of the first window and multiple second CQIs associated with multiple different slot(s) or groups of slots of the second window. It is assumed that a slot or multiple slots or groups of slots of the first and second window of slot(s) are identical and associated with a first CQI and a second CQI. Each group of slots is associated with a single CQI value. In some examples, the wireless device indicates the multiple first CQIs and second CQIs in the feedback or CSI report. In some examples, the wireless device indicates the second CQIs or first CQIs and the differences between the second CQI and the first CQIs in the feedback or CSI report.

[0133] In certain embodiments, the wireless device determines a first rank associated with one or multiple different slot(s) or groups of slots of the first window. The wireless device may determine one or multiple second rank(s), wherein each second rank is associated with one or multiple slot(s) or groups of slots of the second window. In some options, the first and second window are overlapping or partly overlapping (i.e. , one or more slot(s) or all slot(s) of the first window is / are identical to one or more slot(s) of the second window of slot(s)). Note that the first rank is associated with the first CSI, or the precoder matrix of the first CSI. A second rank is associated with the second CSI, or a precoder matrix of the second CSI.

[0134] In a first option, the wireless device may determine a first rank associated with the precoder of the first CSI and one or multiple different slot(s) or groups of slots of the first window. The wireless device may also determine a single second rank associated with a precoder matrix of the second CSI and one or multiple different slot(s) or groups of slots of the second window of slot(s). It may be assumed that a slot or multiple slots or groups of slots of the first and second window can be identical. The wireless device may indicate the first rank and the second rank explicitly or implicitly in the feedback or CSI report. In some examples, the wireless device indicates directly the first rank and the second rank in the feedback or CSI report. In some examples, the wireless device indicates the first or the second rank and the difference or information related to the difference between the first and the second rank in the report.

[0135] In a second option, the wireless device may determine a first rank associated with the precoder of the first CSI and one or multiple different slot(s) or groups of slots of the first window. The wireless device may also determine multiple second ranks associated with multiple precoder matrices of the second CSI and multiple different slot(s) or groups of slots of the second window of slot(s). It may be assumed that a slot or multiple slots of the first and second window can be identical. The wireless device may indicate the first rank and the multiple second ranks explicitly or implicitly in the feedback or CSI report. In some examples, the wireless device indicates directly the first rank and the multiple second ranks in the report. In some examples, the wireless device indicates the first rank and the differences or information related to the differences between the first and multiple second ranks in the feedback or CSI report. Note that differences or difference values here may mean differential values. In another example, the wireless device indicates at least the differences or information related to the differences between the first and the multiple second ranks in the feedback or CSI report.

[0136] In this disclosure, any information that is mentioned to be provided or reported in a CSI report or a feedback by a wireless device is information that is transmitted by the wireless device via the PHY-layer (e.g., the PUSCH or the PUCCH) or a higher layer (e.g., a MAC-CE message or a RRC message). In certain embodiments, the wireless device reports a CSI report to the network node, wherein the CSI report comprises the first CSI. Note that the CSI report can be a separate report from the feedback reported to the network node.

[0137] Referring to Figure 3, there is illustrated a method performed by a wireless device (700) according to some of the previously described embodiments. The method is performed by the wireless device (700) in a wireless communications network. The method comprises:

[0138] - receiving (401 ) from a network node (800) an indication or a configuration of at least two sets of CSI-RS resources,

[0139] - determining (402) a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources received from the network node (800), - determining (403) a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources received from the network node (800),

[0140] - generating (404) a feedback based on the first and second CSI, and

[0141] - reporting (405) the feedback to the network node (800).

[0142] In certain embodiments, the first set of CSI-RS resources comprises one or more periodic or semi-persistent CSI-RS resource(s), or a CSI-RS burst, and the second set of CSI-RS resources comprises one or more a-periodic CSI-RS resources.

[0143] In certain embodiments, the first and second set of CSI-RS resources are a subset of a same CSI-RS resource set.

[0144] In certain embodiments, one CSI-RS resource in the first set is identical to one CSI- RS resource in the second set, and wherein the identical CSI-RS resource is referred to as a CSI-RS reference resource, and wherein the CSI-RS reference resource is received on the latest or the last slot on which the wireless device can receive or measure a CSI-RS resource of the first set.

[0145] In certain embodiments, the CSI-RS reference resource is a CSI-RS resource of the second set and used by the wireless device for determining the second CSI.

[0146] In certain embodiments, the first set of CSI-RS resources are received in slot(s) from n to n + k, wherein n is a slot index, and k > 0 is an integer variable, and the second set of CSI-RS resources are provided in slot(s) n + I to n + I + t, wherein t > 0 is an integer variable, and wherein I = k, or I < k, or I > k.

[0147] In certain embodiments, the one or more slots of the first window of slot(s) associated with the first CSI occur later in time than the one or more slot(s) on which the CSI-RS resources of the first set are received by the wireless device.

[0148] In certain embodiments, the first CSI is a predicted CSI.

[0149] In certain embodiments, the second CSI is a non-predicted CSI.

[0150] In certain embodiments, at least one slot of the first window of slot(s) associated with the first CSI does not occur later in time than at least one slot on which a CSI-RS resource of the first set is received by the wireless device. In certain embodiments, the one or more slots of the second window of slot(s) associated with the second CSI occur later in time than one or more slot(s) on which the CSI-RS resources of the second set are received by the wireless device.

[0151] In certain embodiments, the first CSI comprises one or more precoding matrix identifiers, PMIs, and / or one or more channel quality indicators, CQIs, and wherein a PMI and / or CQI is associated with one or more slot(s) of the first window of slot(s).

[0152] In certain embodiments, the first window comprises WCSIslots, and the first CSI comprises at least one PMI indicating K precoding matrices, wherein an indicated precoding matrix is associated with WCSI / K consecutive or non-consecutive slots of the first window, and wherein K > 1.

[0153] In certain embodiments, the one or more slot(s) of the second window for which the second CSI is determined by the wireless device occur(s) in the same slot(s) as the received or measured CSI-RS resource(s) of the second set.

[0154] In certain embodiments, the one or more slots of the second window are identical to the one or more slot(s), or comprise the one or more slot(s), on which the CSI-RS resource(s) of the second set are received by the wireless device.

[0155] In certain embodiments, the one or more slot(s) of the second window are contained in the one or more slot(s) of the first window. That is, there is an overlap of at least one slot associated with both the first CSI and the second CSI.

[0156] In certain embodiments, the one or more slot(s) of the second window are identical to the one or more slot(s) of the first window.

[0157] In certain embodiments, the first window comprises the one or more slot(s) of the second window.

[0158] In certain embodiments, the second CSI comprises at least two PMIs, and / or one CQI or two CQIs, and wherein each PMI and / or CQI is associated with one or more slot(s) of the second window.

[0159] In certain embodiments, the second window comprises N slots, wherein the first / V / 2 slot(s) are associated with a first PMI and / or CQI and at least one slot of first / V / 2 slot(s) is associated with a first CSI-RS resource of the second set and the second / V / 2 slot(s) are associated with a second PMI and / or second CQI and at least one slot of the second / V / 2 slot(s) is associated with a second CSI-RS resource of the second set.

[0160] In certain embodiments, the second CSI is associated with one or more slot(s) of the second window of slot(s) and comprises at least one PMI and / or CQI and / or Rl.

[0161] In certain embodiments, the feedback is a CSI report.

[0162] In certain embodiments, the feedback comprises the first CSI, the second CSI, or the first and second CSI.

[0163] In certain embodiments, the feedback indicates that a quality parameter or metric based on the first CSI and the second CSI is above or below a certain threshold.

[0164] In certain embodiments, the feedback comprises a quality parameter or metric based on the first CSI and second CSI. Optionally, the feedback indicates that the quality parameter or metric is above or below a certain threshold.

[0165] In certain embodiments, the quality parameter or metric is determined using the precoding matrix / matrices of the first CSI and the precoding matrix / matrices of the second CSI for each slot of the first and second window of slot(s).

[0166] In certain embodiments, the metric is a squared generalized cosine similarity (SGCS) or a normalized mean-squared error (NMSE).

[0167] In order to perform the previously described process or method steps performed by the wireless device or UE, there is also provided a wireless device. Figure 12 illustrates a simplified block diagram depicting a wireless device 700. The wireless device 700 comprises a processor 710 or processing circuit or a processing module or a processor means 710; a receiver circuit or receiver module 740; a transmitter circuit or transmitter module 750; a memory module 720, a transceiver circuit or transceiver module 730 which may include the transmitter circuit 750 and the receiver circuit 740. The wireless device 700 further comprises an antenna system 760 which includes antenna circuitry for transmitting and receiving signals to / from at least the network node or other wireless device(s). The antenna system employs beamforming as previously described.

[0168] The wireless device may be a UE or an loT device. The wireless device 700 may belong to any radio access technology including 4G or LTE, LTE-A, 5G, advanced 5G or a combination thereof that support beamforming technology. The wireless device comprising the processor and the memory contains instructions executable by the processor, whereby the wireless device 700 is operative or is configured to perform any one of the embodiments related to the wireless device as previously described.

[0169] The processing module / circuit 710 includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like, and may be referred to as the “processor.” The processor 710 controls the operation of the wireless device and its components. Memory (circuit or module) 720 includes a random-access memory (RAM), a read only memory (ROM), and / or another type of memory to store data and instructions that may be used by processor 710. In general, it will be understood that the wireless device 700 in one or more embodiments includes fixed or programmed circuitry that is configured to carry out the operations in any of the embodiments disclosed herein.

[0170] In at least one such example, the processor 710 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry that is configured to execute computer program instructions from a computer program stored in a non- transitory computer-readable medium that is in or is accessible to the processing circuitry. Here, “non-transitory” does not necessarily mean permanent or unchanging storage, and may include storage in working or volatile memory, but the term does connote storage of at least some persistence. The execution of the program instructions specially adapts or configures the processing circuitry to carry out the operations disclosed in this disclosure relating to the wireless device. Further, it will be appreciated that the wireless device 700 may comprise additional components.

[0171] The wireless device 700 by means of processor 710 executes instructions contained in the memory 720 whereby the wireless device is operative to perform any one of the previously described embodiments related to the actions performed by the wireless device, some of which are presented in appended claims.

[0172] There is also provided a computer program comprising instructions which when executed by the processor 710 of the wireless device cause the processor 710 to carry out the method according to any one of the previously described embodiments.

[0173] Referring to Figure 4, there is illustrated a method performed by a network node (800) according to some of the previously described embodiments. The method performed by the network node (800) is used for receiving, from a wireless device (700), a feedback, the method comprises:

[0174] • transmitting (501 ) to a wireless device, an indication or a configuration of a number of CSI-RS resources,

[0175] • providing (502) a first and second set of CSI-RS resources, for enabling the wireless device to: o determining a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources provided by the network node, o determining a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources provided by the network node, o generating a feedback based on the first and second CSI, and

[0176] - receiving (503) the feedback from the wireless device.

[0177] To perform the previously described process or method steps performed by the network node there is also provided a network node. Figure 13 illustrates a block diagram depicting a network node 800. The network node 800 comprises a processor 810 or processing circuit or a processing module or a processor means 810; a receiver circuit or receiver module 840; a transmitter circuit or transmitter module 850; a memory module 820, a transceiver circuit or transceiver module 830 which may include the transmitter circuit 850 and the receiver circuit 840. The network node 800 further comprises an antenna system 860 which includes antenna circuitry for transmitting and receiving signals to / from at least the wireless device. The antenna system employs beamforming as previously described.

[0178] The network node 800 may belong to any radio access technology including 4G or LTE, LTE-A, 5G, advanced 5G or a combination thereof that support beamforming technology. The network node may be a gNB. The network device comprising the processor and the memory contains instructions executable by the processor, whereby the network node 800 is operative or is configured to perform any one of the embodiments related to the network node 800 as previously described. The processing module / circuit 810 includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like, and may be referred to as the “processor.” The processor 810 controls the operation of the network node and its components. Memory (circuit or module) 820 includes a random-access memory (RAM), a read only memory (ROM), and / or another type of memory to store data and instructions that may be used by processor 810. In general, it will be understood that the network node in one or more embodiments includes fixed or programmed circuitry that is configured to carry out the operations in any of the embodiments disclosed herein.

[0179] In at least one such example, the processor 810 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry that is configured to execute computer program instructions from a computer program stored in a non- transitory computer-readable medium that is in or is accessible to the processing circuitry. Here, “non-transitory” does not necessarily mean permanent or unchanging storage, and may include storage in working or volatile memory, but the term does connote storage of at least some persistence. The execution of the program instructions specially adapts or configures the processing circuitry to carry out the operations disclosed in this disclosure relating to the wireless device. Further, it will be appreciated that the wireless device 800 may comprise additional components. The network node 800 may also be viewed as a Transmitter and Receiver Point (TRP).

[0180] The network node 800 by means of processor 810 executes instructions contained in the memory 820 whereby the network node 800 is operative to perform any one of the previously described embodiments related to the actions performed by the network node.

[0181] There is also provided a computer program comprising instructions which when executed by the processor 810 of the network node cause the processor 810 to carry out the method according to some embodiments.

[0182] Reference throughout this specification to “an example” or “exemplary” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present technology. Thus, appearances of the phrases “in an example” or the word “exemplary” in various places throughout this specification are not necessarily all referring to the same embodiment.

[0183] Throughout this disclosure, the word "comprise" or “comprising” has been used in a non-limiting sense, i.e. meaning "consist at least of". Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. The embodiments herein may be applied in any wireless systems including LTE or 4G, LTE-A (or LTE-Advanced), 5G, advanced 5G, WiMAX, WiFi, satellite communications, TV broadcasting etc.

Claims

CLAIMS1. A method performed by a wireless device (700) in a wireless communications network, the method comprising:• receiving (401 ) from a network node an indication or a configuration of at least two sets of Channel State Information Reference Signal, CSI-RS, resources,• determining (402) a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources received from the network node,• determining (403) a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources received from the network node,• generating (404) a feedback based on the first and the second CSI, and• reporting (405) the feedback to the network node.

2. The method of claim 1 , wherein the first set of CSI-RS resources comprises one or more periodic or semi-persistent CSI-RS resource(s), or a CSI-RS burst, and the second set of CSI-RS resources comprises one or more a-periodic CSI-RS resources.

3. The method of claim 1 , wherein the first and second set of CSI-RS resources are a subset of a same CSI-RS resource set.

4. The method of any of claims 1-3, wherein one CSI-RS resource in the first set is identical to one CSI-RS resource in the second set, and wherein the identical CSI- RS resource is referred to as a CSI-RS reference resource, and wherein the CSI- RS reference resource is received on the latest or the last slot on which the wireless device receives or measures a CSI-RS resource of the first set.

5. The method of claims 4, wherein the CSI-RS reference resource is a CSI-RS resource of the second set and used by the wireless device for determining the second CSI.

6. The method of any of claim 1 -3, wherein the first set of CSI-RS resources are received in slot(s) from n to n + k, wherein n is a slot index, and k > 0 is an integer variable, and the second set of CSI-RS resources are provided in slot(s) n + 1 ton + I + t, wherein t > 0 is an integer variable, and wherein I = k, or I < k, or I > k.

7. The method of claim 1 , wherein the one or more slots of the first window of slot(s) associated with the first CSI occur later in time than the one or more slot(s) on which the CSI-RS resources of the first set are received by the wireless device.

8. The method of claim 1 , wherein the first CSI is a predicted CSI.

9. The method of claim 1 , wherein the second CSI is a non-predicted CSI.

10. The method of claim 1 , wherein at least one slot of the first window of slot(s) associated with the first CSI does not occur later in time than at least one slot on which a CSI-RS resource of the first set is received by the wireless device.11 . The method of claim 1 , wherein one or more slots of the second window of slot(s) associated with the second CSI occur later in time than one or more slot(s) on which the CSI-RS resources of the second set are received by the wireless device.

12. The method of claim 1 , wherein the first CSI comprises one or more precoding matrix identifiers, PMIs, and / or one or more channel quality indicators, CQIs, and wherein a PMI and / or CQI is associated with one or more slot(s) of the first window of slot(s).

13. The method of claim 1 , wherein the first window comprises WCSIslots, and the first CSI comprises at least one PMI indicating K precoding matrices, wherein an indicated precoding matrix is associated with WCSI / K consecutive or non- consecutive slots of the first window, and wherein K > 1.

14. The method of claim 1 , wherein the one or more slot(s) of the second window for which the second CSI is determined by the wireless device occur(s) in the same slot(s) as the received or measured CSI-RS resource(s) of the second set.

15. The method of claim 1 , wherein the one or more slots of the second window are identical to the one or more slot(s), or comprise the one or more slot(s), on which the CSI-RS resource(s) of the second set are received by the wireless device.

16. The method of claim 1 , wherein the one or more slot(s) of the second window are contained in the one or more slot(s) of the first window.

17. The method of claim 1 , wherein the one or more slot(s) of the second window are identical to the one or more slot(s) of the first window.

18. The method of claim 1 , wherein the first window comprises the one or more slot(s) of the second window.

19. The method of claim 1 , wherein the second CSI comprises at least two PMIs, and / or one CQI or two CQIs, and wherein each PMI and / or CQI is associated with one or more slot(s) of the second window.

20. The method of claim 1 , wherein the second window comprises N slots, wherein the first N / 2 slot(s) are associated with a first PMI and / or CQI and at least one slot of the first N / 2 slot(s) is associated with a first CSI-RS resource of the second set, and the second N / 2 slot(s) are associated with a second PMI and / or second CQI and at least one slot of the second N / 2 slot(s) is associated with a second CSI-RS resource of the second set.21 . The method of claim 1 , wherein the second CSI is associated with one or more slot(s) of the second window of slot(s) and comprises at least one PMI and / or CQI and / or Rl.

22. The method of claim 1 , wherein the feedback is a CSI report.

23. The method of claim 1 , wherein the feedback comprises the first CSI, the second CSI, or the first and second CSI.

24. The method of claim 1 , wherein the feedback indicates that a quality parameter or metric based on the first CSI and the second CSI is above or below a certain threshold.

25. The method of claim 1 , wherein the feedback comprises a quality parameter or metric based on the first CSI and second CSI.

26. The method of claim 24 or 25, wherein the quality parameter or metric is determined using the precoding matrix / matrices of the first CSI and the precoding matrix / matrices of the second CSI for each slot of the first and second window of slot(s).

27. The method of any of claims 24-26, wherein the metric is a squared generalized cosine similarity, SGCS, or a normalized mean-squared error, NMSE.

28. The method of claim 25, wherein the feedback indicates that the quality parameter or metric is above or below a certain threshold.

29. A method performed by a network node (800), for receiving, from a wireless device (700), a feedback in a wireless communications network, the method comprising:- transmitting (501 ) to a wireless device, an indication or a configuration of a number of Channel State Information Reference Signal, CSI-RS, resources,- providing (502) a first and second set of CSI-RS resources, for enabling the wireless device to: o determining a first CSI for one or more slot(s) of a first window of slot(s) using a first set of CSI-RS resources provided by the network node, o determining a second CSI for one or more slot(s) of a second window of slot(s) using a second set of CSI-RS resources provided by the network node, o generating a feedback based on the first and second CSI, and- receiving (503) the feedback from the wireless device.

30. A network node (800) comprising a processor (810) and a memory (820) containing instructions executable by said processor (810), whereby the network node (800) is operative to perform the method according to claim 29.31 . The network node (800) of claim 30, wherein the network node (800) is a gNB.

32. A wireless device (700) comprising a processor (710) and a memory (720) containing instructions executable by said processor (710), whereby the wireless device (700) is operative to perform the method according to any of claims 1 -28.

33. The wireless device (700) of claim 32, wherein the wireless device (700) is a User Equipment, UE.

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