Doppler-based enhanced type II csi reporting in 5G nr systems

Abstract

The invention relates to a method and apparatus for generating and reporting a CSI report. The method performed by the UE comprises: receiving (400) a CSI report configuration from a network node (600); determining (401) one or more frequency domain, FD, components of the set of linearly combined coefficients; determining (402) one or more time domain (TD) components of the set of linear combination coefficients; determining (403) one or more spatial domain SD components of the set of linearly combined coefficients; determining (404) a set of frequency domain FD / time domain TD component pairs, each component pair comprising one FD component and one TD component, and the component pairs being common in a subset of spatial domain components of the set of linear combination coefficients; and generating and transmitting or reporting (405) a CSI report to the network node (600), the CSI report comprising the determined SD component, FD component and TD component, FD / TD component pairs and an indication of combined coefficients of precoder vectors or matrices.

Description

Technical Field

[0001] The present disclosure relates to the field of wireless communications, and more particularly, to a method and apparatus for channel state information (CSI) feedback reporting based on codebook precoding in a wireless communication network (such as an advanced 5G network). Background Art

[0002] The fifth generation (5G) mobile communication system, also known as New Radio (NR), provides a higher level of performance than previous generations of mobile communication systems. The development of 5G mobile communications stems from the need to provide ubiquitous connectivity for a variety of applications, including automotive communications, remote control with feedback, video downloads, and data applications for Internet of Things (IoT) devices, machine type communication (MTC) devices, etc. 5G wireless technology brings several major advantages, such as faster speeds, shorter latency, and higher connectivity. The 3rd Generation Partnership Project (3GPP) provides a complete system specification for the 5G network architecture, which includes at least a radio access network (RAN), a core transmission network (CN), and service capabilities.

[0003] Figure 1 A simplified schematic diagram illustrating an example of a wireless communication network 100 is shown. The wireless communication network 100 includes a core network (CN) 110 and a radio access network (RAN) 120. As shown, the RAN 120 includes a plurality of network nodes or radio base stations, which are referred to as gNBs in 5G. Three radio base stations, namely gNB1, gNB2, and gNB3, are depicted in the figure. Each gNB serves an area referred to as a coverage area or cell. Figure 1 Three cells, cell 121, cell 122, and cell 123, are illustrated, and each cell is served by its respective gNB1, gNB2, and gNB3. It should be noted that the network 100 may include any number of cells and gNBs. The radio base station or network node serves users within the cell. In 4G or Long Term Evolution (LTE), the radio base station is referred to as an eNB; in 3G or Universal Mobile Telecommunications System (UMTS), the radio base station is referred to as an eNodeB; in other radio access technologies, it is referred to as a base station (BS). A user or user equipment (UE) may be a wireless or mobile terminal device, or a fixed communication device. The mobile terminal device or UE may also be an IoT device, an MTC device, etc. IoT devices may include wireless sensors, software, actuators, and computer devices. They can be embedded in mobile devices, motor vehicles, industrial equipment, environmental sensors, medical devices, aircraft, etc., and have network connection capabilities to collect and exchange data through existing network infrastructures.

[0004] Return to Figure 1, each cell is shown to contain a UE and an IoT device. gNB1 in cell 121 serves UE1 121A, UE2 121B, and IoT device 121C. Similarly, gNB2 in cell 122 serves UE3 122A, UE4 122B, and IoT device 122C, and gNB3 in cell 123 serves UE5 123A, UE6 123B, and IoT device 123C. Network 100 may include any number of user devices, IoT devices, or any other type of devices. These devices communicate with the serving gNB in the uplink, while the gNB communicates with these devices in the downlink. Each of the base stations gNB1 to gNB3 may be connected to CN120 via, for example, the S1 interface, via their respective backhaul links 111, 121D, 122D, 123D, which are schematically represented by arrows pointing to the "core" in Figure 1 . The core network 120 may be connected to one or more external networks, such as the Internet. The gNBs may be interconnected with each other via the S1 interface, X2 interface, or XN interface in 5G, via their respective interface links 121E, 122E, and 123E, as shown by the arrows pointing to the gNBs in the figure.

[0005] In terms of data transmission, a physical resource grid can be used. The physical resource grid can include a set of resource elements (REs), to which various physical channels and physical signals are mapped. For example, physical channels can include physical downlink, uplink, and / or sidelink (SL) shared channels (PDSCH, PUSCH, PSSCH) (these channels carry specific user data and are also referred to as downlink, uplink, or sidelink payload data); physical channels can include physical broadcast channels (PBCH) (carrying, for example, master information blocks (MIBs) and system information blocks (SIBs)); physical channels can include physical downlink, uplink, and / or sidelink control channels (PDCCH, PUCCH, PSCCH) (carrying, for example, downlink control information (DCI), uplink control information (UCI), or sidelink control information (SCI)). In the uplink, physical channels can also include physical random access channels (PRACH or RACH), which UEs can use to access the network after completing synchronization and obtaining the MIB and SIB. Physical signals can include reference signals (RSs), synchronization signals (SSs), etc. The resource grid can include frames or radio frames that have a specific duration (e.g., 10 milliseconds) in the time domain and a given bandwidth in the frequency domain. A radio frame can have a certain number of subframes of predefined length, for example, two subframes of length 1 millisecond. Each subframe can contain two time slots with multiple OFDM symbols, depending on the length of the cyclic prefix (CP). In 5G, based on normal CP and extended CP, each time slot consists of 14 OFDM symbols or 12 OFDM symbols, respectively. When using a shortened transmission time interval (TTI) or a micro-slot / non-slot frame structure that includes only a few OFDM symbols, a frame can also consist of a smaller number of OFDM symbols. 5G NR supports time slot aggregation, so data transmission can be scheduled to span one or more time slots. The time slot format indication notifies the UE whether an OFDM symbol is downlink, uplink, or flexible.

[0006] A wireless communication network system can be a single-tone or multi-carrier system using frequency division multiplexing, such as an orthogonal frequency division multiplexing (OFDM) system, an orthogonal frequency division multiple access (OFDMA) system, or any other IFFT-based signal with or without CP, such as DFT-OFDM. Other waveforms can also be used, such as non-orthogonal waveforms for multiple access, such as filter bank multi-carrier (FBMC), generalized frequency division multiplexing (GFDM), or universal filtered multi-carrier (UFMC). The wireless communication system can operate, for example, according to the LTE-Advanced pro standard or the 5G or NR (New Radio) standard.

[0007] Figure 1The wireless communication network system shown can be a heterogeneous network having two different overlapping networks, one being a macro cell network where each macro cell contains a macro base station such as base stations gNB1 to gNB3, and the other being a small cell base station network ( Figure 1 not shown in) such as femto base stations or pico base stations. In addition to the above wireless networks, there also exists a non-terrestrial wireless communication network including spaceborne transceivers (such as satellites) and / or airborne transceivers (such as unmanned aerial vehicle systems). The non-terrestrial wireless communication network or system can operate in a manner similar to the terrestrial system described above Figure 1 , for example, operating according to the LTE-Advanced pro standard or the 5G or NR standard.

[0008] In a wireless communication network system schematically depicted as Figure 1 , multi-antenna techniques (e.g., according to LTE, NR, or other communication systems) can be used to improve user data rate, link reliability, cell coverage, and network capacity. To support multi-stream or multi-layer transmission, the physical layer of the communication system uses linear precoding. Linear precoding is achieved through a precoder matrix that maps data layers to antenna ports. Precoding can be regarded as an extension of beamforming, which is a technique for spatially directing or focusing data to the intended receiver. The precoder matrix used by the gNB to map data to the transmit antenna ports is determined based on the channel state information (CSI).

[0009] In the above wireless communication network systems (such as LTE or New Radio (5G)), the downlink signals transmit data signals, control signals including downlink (DL) control information (DCI), and multiple reference signals or symbols (RS) for different purposes. The 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. In addition, the downlink signals of the gNB may include one or more types of reference signals (RS), including common RS (CRS), channel state information RS (CSI-RS), demodulation RS (DM-RS), and phase tracking RS (PT-RS) in LTE. The CRS is transmitted over the DL system bandwidth part, and the user equipment (UE) uses it to obtain channel estimation for demodulating data or control information. Compared with the CRS, the CSI-RS has a lower transmission density in the time domain and frequency domain, and the UE uses it for channel estimation or obtaining channel state information (CSI). The DM-RS is only transmitted over the bandwidth part of the respective PDSCH, and the UE uses it for data demodulation. For signal precoding at the gNB, several CSI-RS reporting mechanisms are used, such as non-precoded CSI-RS and beamforming CSI-RS reporting. For the non-precoded CSI-RS, a one-to-one mapping is adopted between the CSI-RS ports of the gNB's antenna array and the transceiver unit (TXRU). Therefore, the non-precoded CSI-RS provides cell-wide coverage, where different CSI-RS ports have the same beam direction and beam width. For the UE-specific or non-UE-specific CSI-RS for beamforming / precoding, beamforming operations are applied on a single antenna port or multiple antenna ports to generate several narrow beams with high gain in different directions, so it does not provide cell-wide coverage.

[0010] In a wireless communication network system adopting time division duplex (TDD), due to channel reciprocity, the base station (gNB) can obtain CSI. However, when adopting frequency division duplex (FDD), due to the lack of channel reciprocity, channel estimation is performed at the UE side and the estimation result is fed back to the gNB. Figure 2 Shows a block-based model of multi-input multi-output (MIMO) DL transmission using codebook-based precoding according to LTE Release 8. Figure 2 Schematically shows a base station 200 (gNB), a user equipment (UE) 202, and a channel 204, such as a wireless channel for wireless data communication between the base station 200 and the user equipment 202. The base station includes an antenna array ANT having a plurality of antennas or antenna elements T, and a precoder 206 that receives a data vector 208 and a precoder matrix F from a codebook 210. The channel 204 can be described by an available channel tensor / matrix 212. The user equipment 202 receives a data vector 214 via an antenna or an antenna array ANT having a plurality of antennas or antenna elements. A feedback channel 216 is provided between the user equipment 202 and the base station 200 for transmitting feedback information. Previous versions of 3GPP (up to version 15) supported the UE to use multiple downlink reference symbols (such as CSI-RS) for CSI estimation. R The user equipment 202 receives a data vector 214. A feedback channel 216 is provided between the user equipment 202 and the base station 200 for transmitting feedback information. Previous versions of 3GPP (up to version 15) supported the UE to use multiple downlink reference symbols (such as CSI-RS) for CSI estimation.

[0011] In an FDD system (up to version 15), the channel estimated by the UE is implicitly reported to the gNB, where the CSI report transmitted by the UE via the feedback channel includes a rank index (RI), a precoding matrix index (PMI), and a channel quality indicator (CQI) (and a CRI starting from version 13), such that the gNB can determine the precoding matrix, as well as the modulation order and coding scheme (MCS) of the symbols to be transmitted. The PMI and RI are used to determine the precoding matrix from a set of predefined matrices Ω (also called a codebook). For example, according to LTE, the codebook can be a look-up table, and each entry in the table has a matrix. The PMI and RI of the UE determine which row and column in the table to obtain the precoder matrix to be used. Up to version 15, the precoder and the codebook were designed for a gNB equipped with a one-dimensional uniform linear array (ULA) having N1 dual-polarized antennas (a total of N t = 2N1 antennas), or a two-dimensional uniform planar array (UPA) having dual-polarized antennas at N1N2 positions. The ULA only allows controlling radio waves in the horizontal (azimuth) direction, such that the gNB can perform only azimuth beamforming, while the UPA supports transmitting beamforming in both the vertical (elevation) and horizontal (azimuth) directions, which is also called full-dimension (FD) MIMO. For example, in the case of a large-scale antenna array (such as FD-MIMO), the codebook can be a set of beamforming weights, and the array response vectors of the array are used to form spatially separated electromagnetic transmit / receive beams. The beamforming weights of the array (also called the array steering vector) are the amplitude gain and phase adjustment applied to the signal fed to the antenna (or the signal received from the antenna) to transmit (or obtain) radiation in (or from) a specific direction. The components of the precoder matrix are obtained from the codebook, and the PMI and RI are used to read the codebook and obtain the precoder. When using the ULA or UPA for signal transmission, the array steering vector can be described by the columns of a two-dimensional discrete Fourier transform (DFT) matrix.

[0012] The precoder matrices used in Type I, Type I multi-panel, and Type II CSI reporting schemes in 3GPP New Radio Release 15 are defined in the frequency domain and have a two-level structure (i.e., two component codebooks): F(s) = F1F2(s), s = 0…, S-1, where S represents the number of subbands. The first component or the so-called first-level precoder F1 is used to select multiple beam vectors from a Discrete Fourier Transform (DFT)-based matrix (also known as the spatial codebook). In addition, the first-level precoder F1 corresponds to a wideband matrix, independent of the subband index s, and contains L spatial beamforming vectors (i.e., the so-called spatial beams) l = 0,.., L-1, and these vectors are selected from the DFT-based codebook matrices for the two polarizations of the antenna array.

[0013]

[0014] For the Type I codebook, L = 1, so F1 is simply given by:

[0015]

[0016] The spatial codebook includes an oversampled DFT matrix of dimension N1N2×N1O1N2O2, where O1 and O2 represent the oversampling factors with respect to the first and second dimensions of the codebook, respectively. The DFT vectors in the codebook are grouped into (q1,q2), (0 ≤ q1 ≤ O1-1, 0 ≤ q2 ≤ O2-1) subsets, each subset containing N1N2 DFT-based vectors, and the parameters q1 and q2 represent the rotational oversampling factors with respect to the first and second dimensions of the antenna array, respectively.

[0017] The second component or the so-called second-level precoder F2(s) is used to combine the selected beam vectors. This means that the second-level precoder F2(s) corresponds to a selection / combination / in-phase matrix for selecting / combining / in-phasing the beams defined in F1 for the sth configured subband. For example, for rank-1 transmission and Type I CSI reporting, for a dual-polarized antenna array, F2(s) is given by:

[0018]

[0019] is the quantization in-phase factor (phase adjustment) between the two orthogonal polarizations of the antenna array. Thus, for the Type I codebook, a single DFT beam is selected in each transmit layer of precoding such that the transmission is directed towards the strongest path component of the radio channel.

[0020] For rank-1 transmission and Type II CSI reporting, for a dual-polarized antenna array, F2(s) is given by:

[0021]

[0022] where p l and l = 0, 2, …, 2L-1 are the quantized amplitude and phase beam combining coefficients, respectively. For a transmission with rank R, F2(s) contains R vectors, where R represents the transmission rank, and the entries of each vector are selected to combine single or multiple beams within each polarization.

[0023] The selection of matrices F1 and F2(s) is performed by the UE based on knowledge of reference signals (such as CSI-RS) and channel conditions. The selected matrices are indicated in the CSI report in the form of RI (where RI represents the rank of the precoding matrix) and PMI, and are used at the gNB to update the multi-user precoder for the next transmission time interval.

[0024] In addition to the type-I codebook, the 3GPP Release 15 specification also defines a type-I multi-panel (multi-antenna array) codebook for the case where the gNB is equipped with multiple (co-located) antenna panels or antenna arrays (which may not be calibrated). The precoder of this codebook is similar to the type-I codebook, applying a single DFT beam in each transmission layer of the precoding matrix. To account for different spacings between antenna panels and / or possible phase calibration errors between antenna panels (e.g., due to different local oscillators), a panel-specific in-phase factor is applied to each panel. For example, for a transmission with rank 1 and a gNB equipped with N g = 2 antenna panels, the type-I multi-panel CSI report is defined as:

[0025]

[0026] where and are the quantized in-phase factors, is the panel-specific in-phase factor applied to the second panel.

[0027] For the two-stage type-II CSI report of 3GPP Release 15, the second-stage precoder F2(s) is calculated based on sub-bands such that for the r-th transmission layer, The number of columns depends on the configured number of CQI subbands S. Here, a subband refers to a group of adjacent physical resource blocks (PRBs). One drawback of type II CSI feedback is that the feedback overhead is large when reporting combining coefficients based on subbands. The feedback overhead approximately increases linearly with the number of subbands, and when the number of subbands is large, the feedback overhead becomes quite large. To overcome the high feedback overhead problem of the type II CSI reporting scheme in Release 15, 3GPP RAN#81 decided to study a feedback compression scheme for the second-stage precoder F2. Some research results show that when using a small number of DFT-based basis vectors to transform F2 into a transform domain called the delay domain, the number of beam combining coefficients in F2 can be significantly reduced. The corresponding three-stage precoder depends on a three-stage (i.e., three components) codebook. The first component is represented by the matrix F1, which is the same as the NR component in Release 15, independent of the transmit layer (r), and contains multiple spatial domain (SD) basis vectors selected from the spatial codebook. The second component is represented by the matrix and is layer-dependent, used to select multiple delay domain (DD) basis vectors from a discrete Fourier transform (DFT)-based matrix (also called the delay codebook). The third component is represented by the matrix and contains multiple combining coefficients for combining the SD basis vectors and DD basis vectors selected from the spatial codebook and the delay codebook, respectively.

[0028] Assuming transmission with rank R, for the configured 2N1N2 antennas / CSI-RS ports and the configured S subbands, for the first polarization of the antenna port and the r-th transmit layer, the precoding matrix or CSI matrix consisting of three components is represented as:

[0029]

[0030] And is represented for the second polarization of the antenna port, and the r-th transmit layer is represented as:

[0031]

[0032] where b u (l = 0,…, L-1) represents the u-th SD basis vector selected from the spatial codebook, is the d-th DD basis vector associated with the r-th layer and selected from the delay codebook, is the complex delay domain combining coefficient associated with the u-th SD basis vector, the d-th DD basis vector, and the p-th polarization, D represents the number of configured DD basis vectors, and α (r) is the normalization scalar.

[0033] The advantage of the three-component CSI reporting scheme in the above equation is that the feedback overhead for reporting the combined coefficients of the precoder matrix or the CSI matrix is no longer related to the number of configured CQI subbands (i.e., independent of the system bandwidth). Therefore, the above three-component codebook has recently been used in the two-stage type-II CSI reporting specification of 3GPP Release 16.

[0034] There is an inherent drawback in the current type-II CSI-based CSI reporting scheme, that is, the RI and PMI only contain information about the current channel condition. Therefore, the CSI reporting rate is related to the channel coherence time, which defines the time period during which the channel is considered unchanged. This means that in a quasi-static channel scenario where the wireless device does not move or moves slowly, the channel coherence time is long and the CSI does not need to be updated frequently. However, if the channel condition changes rapidly, for example, due to the high-speed or fast movement of the wireless device (or UE) in a multipath channel environment, the channel coherence time will be very short and the transmitted signal will experience severe fading due to Doppler frequency-domain spreading. For such channel conditions, the CSI needs to be updated frequently, which will result in a high feedback overhead. Especially for the NR system (Release 16) that may be more focused on multi-user centricity, multiple CSI reports from users (or UEs) in a high-dynamic channel scenario will significantly reduce the overall efficiency of the communication system.

[0035] Therefore, the above-known solutions have defects, and the present invention according to the present disclosure solves these defects. Summary of the Invention

[0036] The object of the embodiments herein is to provide a method and apparatus for codebook-based precoding CSI feedback reporting in a wireless communication network (such as an advanced 5G network).

[0037] According to one aspect of some embodiments herein, a method performed by a wireless device (or user equipment) is provided for generating and reporting or transmitting a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as a linear combination of a spatial domain (SD) component, a frequency domain (FD) component, and a time domain (TD) component, and a set of linear combination coefficients for combining the spatial domain component, the frequency domain component, and the time domain component, the method comprising:

[0038] Receiving a CSI report configuration from a network node;

[0039] Determining one or more frequency domain (FD) components of the set of linear combination coefficients;

[0040] Determining one or more time domain (TD) components of the set of linear combination coefficients;

[0041] Determine one or more spatial domain (SD) components of the set of linear combination coefficients;

[0042] Determine a set of frequency domain FD / time domain TD component pairs, each component pair including an FD component and a TD component, and the component pairs being shared in a subset of the spatial domain components of the set of linear combination coefficients;

[0043] Generate and transmit or report a CSI report to the network node, the CSI report including an indication of the determined spatial domain components, frequency domain components, and time domain components, frequency domain / time domain component pairs, and combination coefficients of the precoder vector or matrix.

[0044] According to one aspect of some embodiments herein, another method performed by a wireless device (or user equipment) is provided for generating and reporting or transmitting a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as linear combinations of spatial domain components, frequency domain components, and time domain components, and a set of linear combination coefficients for combining the spatial domain components, the frequency domain components, and the time domain components, the method comprising:

[0045] Receive a CSI report configuration from a network node;

[0046] Determine one or more frequency domain (FD) components of the set of linear combination coefficients;

[0047] Determine one or more time domain (TD) components of the set of linear combination coefficients;

[0048] Determine one or more spatial domain (SD) components of the set of linear combination coefficients;

[0049] Determine a set of spatial domain SD / time domain TD component pairs, each component pair including an SD component and a TD component, and the component pairs being shared in a subset of the frequency domain components or all of the frequency domain components of the set of linear combination coefficients;

[0050] Generate and transmit or report a CSI report to the network node, the CSI report including an indication of the determined spatial domain components, frequency domain components, and time domain components, spatial domain / time domain component pairs, and combination coefficients of the precoder vector or matrix.

[0051] According to another aspect of some embodiments herein, a method performed by a network node is provided for receiving a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as a linear combination of spatial-domain components, frequency-domain components, and time-domain components, and a set of linear combination coefficients for combining the spatial-domain components, the frequency-domain components, and the time-domain components, the method comprising: transmitting a CSI report configuration to a wireless device, and receiving a CSI report from the wireless device, the CSI report including an indication of the determined spatial-domain components, frequency-domain components, and time-domain components, frequency-domain / time-domain component pairs, and combination coefficients of the precoder vectors or matrices; wherein the content of the CSI report is determined by the wireless device according to the present disclosure.

[0052] According to another aspect of some embodiments herein, a method performed by a network node is provided for receiving a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as a linear combination of spatial-domain components, frequency-domain components, and time-domain components, and a set of linear combination coefficients for combining the spatial-domain components, the frequency-domain components, and the time-domain components, the method comprising: transmitting a CSI report configuration to a wireless device, and receiving a CSI report from the wireless device, the CSI report including an indication of the determined spatial-domain components, frequency-domain components, and time-domain components, spatial-domain / time-domain component pairs, and combination coefficients of the precoder vectors or matrices; wherein the content of the CSI report is determined by the wireless device according to the present disclosure.

[0053] According to another aspect of some embodiments herein, a wireless device (or UE) is provided, comprising a processor and a memory, the memory containing instructions executable by the processor such that the wireless device is operable or configured to perform any one of the embodiments related to the actions performed by the wireless device described in the detailed description of the present disclosure.

[0054] According to another aspect of embodiments herein, a network node is provided, comprising a processor and a memory, the memory containing instructions executable by the processor such that the network node is operable or configured to perform any one of the embodiments presented in the detailed description related to the network node.

[0055] A computer program is also provided, the computer program comprising instructions that, when executed on at least one processor of a wireless device, cause the at least one processor to perform the actions or method steps described herein.

[0056] There is also provided a computer program comprising instructions which, when executed on at least one processor of a network node, cause the at least one processor to perform the method steps described herein.

[0057] There is also provided a carrier containing the computer program, wherein the carrier is one of a computer-readable storage medium, an electronic signal, an optical signal or a radio signal.

[0058] The advantages achieved by the embodiments of the present invention include significantly reducing the feedback overhead and computational complexity of wireless devices in codebook-based CSI reporting. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, in which:

[0060] Figure 1 A schematic diagram of a wireless communication system is shown;

[0061] Figure 2 A block-based model of MIMO DL transmission using codebook-based precoding according to LTE Release 8 is shown;

[0062] Figure 3 is a schematic diagram of a wireless communication system for communicating information between a transmitter and a plurality of receivers, in which embodiments of the present application can be applied;

[0063] Figure 4 A flowchart of a method performed by a wireless device (or UE) according to some embodiments of the present application is illustrated;

[0064] Figure 5 A bitmap for non-zero combination coefficient indication in CSI reporting is illustrated;

[0065] Figure 6 is a block diagram depicting a wireless device according to some embodiments of the present application;

[0066] Figure 7 is a block diagram depicting a network node according to some embodiments of the present application;

[0067] Figure 8 A bitmap for non-zero combination coefficient indication in CSI reporting is illustrated;

[0068] Figure 9 A flowchart of a method performed by a wireless device (or UE) according to some embodiments of the present application is illustrated. DETAILED DESCRIPTION

[0069] Exemplary embodiments will be described in detail below in conjunction with the accompanying drawings, through various scenarios to facilitate understanding of the solutions described herein.

[0070] The invention of this embodiment solves the defects described above. Specifically, a method is proposed that can significantly reduce the feedback overhead and computational complexity of user equipment in codebook-based CSI reporting.

[0071] In addition, to overcome the problems mentioned in the prior art above, the invention of the present disclosure proposes an extension to the NR type-II CSI report to allow for time-domain based downlink precoding for time-varying multipath propagation channels. Compared with the prior art CSI reporting scheme, it is proposed to extend the CSI reporting scheme by Doppler components, which allow for time-domain based channel prediction and downlink signal precoding. Moreover, such Doppler components in the CSI report significantly reduce the CSI overhead over time, as the CSI describes the evolution of the channel over time in a compact manner.

[0072] Refer to Figure 3 , which depicts a schematic diagram of a wireless communication system for communicating information between a transmitter 200 (such as a base station or gNB) and a plurality of communication devices 2021 to 202 n (such as wireless devices or UEs served by the base station 200). The base station 200 and the UE 202 can communicate via a wireless communication link or channel 204 (such as a wireless link). The base station 200 includes one or more antennas ANT T or an antenna array having a plurality of antenna elements, and a signal processor 200a. The UE 202 includes one or more antennas ANT R or an antenna array having a plurality of antennas, signal processors 202a1, 202a n , and transceivers 202b1, 202b n . The base station 200 and each UE 202 can operate according to the teachings of the invention described herein.

[0073] Precoder Structure and CSI Reporting

[0074] It should be noted that the terms "precoding" and "precoder" have the same meaning. Therefore, in the present disclosure, precoding and precoder can be used interchangeably.

[0075] The term "beam" is used to represent the precoding / filtering of a signal at the antenna port of a device (UE or gNB) by using a specific set of coefficients, so as to achieve the spatially selective / directional transmission of the outgoing signal, or the spatially selective / directional reception of the incoming signal. The terms precoding, precoder, or filtering may refer to the processing of a signal in the analog domain or the digital domain. The set of coefficients used for spatially directional transmission / reception in a specific direction may vary depending on the direction. The term "Tx beam" represents spatially selective / directional transmission, and the term "Rx beam" represents spatially selective / directional reception. The set of coefficients used for precoding / filtering the transmission or reception is represented by the term "spatial filter". In this document, the terms "spatial filter" and "beam direction" are used interchangeably because the spatial filter coefficients determine the direction in space to which the transmission / reception refers.

[0076] In some embodiments, each of the multiple precoder vectors or matrices is represented by a linear combination of a spatial domain (SD) component, a frequency-domain (FD) component, and a time-domain (TD) component, and a set of combining / combining coefficients for combining the spatial domain component, the frequency-domain component, and the time-domain component. The multiple precoder vectors or matrices can be indicated in the CSI report by indicating the spatial domain component, the frequency-domain component, and the time-domain component, and the set of linear combination coefficients.

[0077] In this disclosure, the terms "combining coefficient" and "merging coefficient" are used interchangeably.

[0078] In general, some non-limiting exemplary effects implemented according to the embodiments of the present disclosure include: A wireless device receives a CSI report configuration from a network node or gNB via a higher layer (e.g., RRC), the configuration indicating one or more antenna port groups or CSI-RS resources associated with one or more antenna ports or CSI-RS ports used by the wireless device for CSI measurement. An antenna port group may include or indicate multiple antennas or CSI-RS ports, and is associated with a specific set of time-domain and frequency-domain resources of a DL channel. In some examples, an antenna port group is a CSI-RS resource that includes or indicates multiple antennas or CSI-RS ports. The wireless device may be configured (via the CSI report configuration) with multiple antenna port groups (e.g., multiple CSI-RS resources). In the following, such a configuration is referred to as a CSI-RS burst. It should be noted that in some examples, the wireless device may be configured with multiple antenna port groups, where each antenna port group indicates one or more antennas or CSI-RS ports, and all antenna port groups are associated with or included in a single CSI-RS resource. In some examples, the wireless device may be configured with N antenna port groups associated with a single CSI-RS resource, where N = 2 or N > 2. The CSI-RS ports of the configured antenna port groups may be the same or different. In certain embodiments, the antenna port groups configured for the wireless device are associated with different time-domain resources of the DL channel. The CSI report configuration may also include parameters N1 and N2, indicating the number of antennas or CSI-RS ports in the first and second dimensions, respectively.

[0079] The precoder vector or matrix may be defined over multiple subbands N3 and time instances N4. The bandwidth of the DL channel may be divided into multiple subbands, where each precoder vector or matrix is associated with one subband. In certain embodiments, the number of subbands of the precoder is an integer multiple (or a real multiple less than 1) of the number of CQI subbands configured for the wireless device. The number of CQI subbands may be indicated to the wireless device via the CSI report configuration.

[0080] Each precoder vector or matrix may also be associated with a time instance of the DL channel. In some examples, the number of time instances N4 associated with the precoder may be the same as the number of antenna port groups configured for the wireless device. In certain embodiments, the number of time instances is an integer multiple of the number of antenna port groups Z configured for the wireless device. This means that N4 = u·Z, where u = 1 or u is any number greater than 1. In some examples, N4 is configured for the wireless device by the network node via a higher layer (e.g., RRC).

[0081] The precoder vector or matrix is determined by the wireless device based on measurements of received reference signals (e.g., CSI-RS), where the reference signals are provided by another wireless device or network node. The reference signals are configured to the wireless device via a CSI reporting configuration. The wireless device is configured to perform CSI measurements on an antenna port group (i.e., on a CSI-RS burst), and to determine a precoder vector or matrix for a plurality of future time slots or time instances based on the CSI measurements, and to indicate these precoder vectors or matrices in a CSI report. The number of future time slots or time instances can be configured to the wireless device by the network node.

[0082] The wireless device can measure the CSI-RS ports over a plurality of time instances (e.g., OFDM symbols, time slots or frames). In some embodiments, the number of time instances can correspond to the size (or length) of a third set of basis vectors (see below). In some embodiments, the number of time instances can correspond to the number of antenna port groups or CSI-RS resources configured to the wireless device to determine the precoder vector or matrix. In some embodiments, the number of time slots or time instances is indicated to the wireless device, for example, via a higher layer, or is fixed in the NR specification and known to the wireless device, or is selected by the wireless device and indicated in the CSI report. The wireless device generates a CSI report indicating the precoder vector or matrix and transmits it to the network node, gNB or another wireless device via an uplink channel.

[0083] Spatial domain components of the precoder

[0084] In some embodiments, the wireless device is configured to determine one or more spatial domain components of the set of linear combination coefficients of the precoder. Each spatial domain component corresponds to a basis vector. The set of spatial domain components may correspond to a first set of basis vectors. To determine the precoder vector or matrix, the wireless device is configured to select one or more spatial domain components from the first set of basis vectors. One basis vector in the first set of basis vectors is associated with a set of antenna ports or CSI-RS ports of an antenna port group. The set of antenna ports or CSI-RS ports may be associated with first and second polarizations. The first set of antenna or CSI-RS ports may be associated with the first polarization, and the second set of antenna or CSI-RS ports may be associated with the second polarization. The selection of one or more basis vectors (one or more spatial domain components) from the first set of basis vectors may be polarization-common or polarization-specific. In the case of polarization-common selection, the basis vectors selected from the first set of basis vectors are common to both polarizations of the antenna or CSI-RS ports configured for the wireless device. In the case of polarization-specific selection, the wireless device independently selects the basis vectors selected from the first set for both polarizations of the antenna or CSI-RS ports configured on the wireless device. In an exemplary embodiment, the wireless device selects L basis vectors of the precoding vector or matrix from the first set of basis vectors and indicates the selected L basis vectors in the CSI report. In some examples, the selected L basis vectors are polarization-common, so the L basis vectors selected for the first and second sets of antenna or CSI-RS ports are the same. In some examples, the selected L basis vectors are polarization-dependent, so the L basis vectors selected for the first or second set of antenna or CSI-RS ports may be different. In some examples, the selected L basis vectors are layer-dependent and are different for a subset of the transmit layers of the precoder or for each transmit layer. In this case, each subset or each layer of the precoder independently selects basis vectors. In some other examples, the selected L basis vectors are layer-independent and are the same for all layers of the precoder.

[0085] In some embodiments, the first set of basis vectors is a set of orthogonal basis vectors, i.e., the set of basis vectors includes a plurality of orthogonal basis vectors. For example, the first set of basis vectors is a DFT- or DCT-based set of basis vectors. In some embodiments, the first set of basis vectors is defined by a DFT or IDFT set of basis vectors, or by an oversampled DFT or IDFT set of basis vectors. In some embodiments, the first set of basis vectors includes a set of vectors based on the discrete cosine transform (DCT). When the first set of basis vectors is defined by a DFT (DFT or IDFT)-based set of basis vectors, the first set of basis vectors is represented by a DFT or IDFT matrix. In some embodiments, the first set of basis vectors is defined by rotated DFT-based basis vectors, where the index of the DFT-based vector is given by i1 = O1i 11 +q1,i11 = 0, …, N1 - 1, i2 = O2i 22 + q2,i 22 = 0, …, N2 - 1 are defined, where q1 = 0, …, O1 - 1 and q2 = 0, …, O2 - 1 are rotation factors of the rotated DFT - based basis vectors. N1 and N2 respectively represent the number of antenna ports in the first and second dimensions, and O1 and O2 respectively represent the oversampling factors in the first and second dimensions. In this case, the rotated DFT - based basis vectors are selected from the oversampled DFT - based basis vectors that contain O1O2N1N2 DFT - based vectors. The rotation factors can be selected by the wireless device, or configured for the wireless device, or reported by the wireless device as part of the CSI report. The oversampling factors can be configured for the wireless device.

[0086] In some embodiments, the first set of basis vectors is an orthogonal basis vector group, that is, the basis vector group contains a plurality of orthogonal basis vectors, including an identity matrix. Each vector of size P CSI-RS or P CSI-RS / 2 in the basis vector group is associated with a CSI - RS port and contains P CSI-RS - 1 or zeros and one 1, where P CSI-RS or P CSI-RS / 2 (e.g., each antenna port polarization) is the number of antenna ports of one or more antenna port groups.

[0087] The frequency - domain components of the precoder

[0088] In some embodiments, the wireless device is configured to determine one or more frequency - domain components of a set of linear combination coefficients of the precoder. Each frequency - domain component of the precoder corresponds to a basis vector. The set of frequency - domain components corresponds to a second set of basis vectors. To determine the precoder vector or matrix, the wireless device is configured to select one or more frequency - domain components (i.e., basis vectors) from the second set of basis vectors. One basis vector in the second set of basis vectors is associated with a plurality of sub - bands N3 of the DL channel bandwidth. One sub - band can contain a plurality of physical resource blocks (PRBs). In some embodiments, the number of sub - bands N3 depends on the number of CQI sub - bands, or on the CQI sub - band size configured for the wireless device.

[0089] In some embodiments, the second set of basis vectors is defined by an orthogonal basis vector set, i.e., the basis vector set includes a plurality of orthogonal vectors. For example, the second set of basis vectors is DFT- or DCT-based basis vectors. In some embodiments, the second set of basis vectors is defined by DFT or IDFT basis vectors, or by oversampled DFT or IDFT basis vectors. In some embodiments, the second set of basis vectors includes a set of discrete cosine transform (DCT)-based vectors. When the second set of basis vectors is defined by DFT (DFT or IDFT)-based basis vectors, the second set of basis vectors can be represented by a DFT or IDFT matrix. In some embodiments, the second set of basis vectors is defined by rotated DFT-based basis vectors, where the index of the DFT-based vectors is defined by d3 = O3i3 + q3, i3 = 0, …, N3−1, where q3 = 0, …, O3−1 is the rotation factor of the rotated DFT-based basis vectors. In this case, the rotated DFT-based basis vectors are selected from an oversampled DFT-based basis vector including O3N3 DFT-based vectors. This means that the basis vector set corresponding to the frequency domain components is an oversampled DFT- or DCT-based matrix including O3 orthogonal DFT- or DCT-based matrices. The rotation factor can be selected by the wireless device, or configured for the wireless device, or reported by the wireless device as part of the CSI report. In some embodiments, the number of frequency domain subbands defines the length (N3) of the basis vectors of the second set of basis vectors. The number of frequency domain subbands can be indicated to the wireless device via higher layers, for example, or can be fixed in the NR specification and known to the wireless device, or selected by the wireless device and indicated in the CSI report.

[0090] In some embodiments, the set of frequency domain components is a basis vector set represented by a DFT- or DCT-based matrix or an oversampled DFT- or DCT-based matrix, and the basis vector set includes a plurality of basis vectors representing frequency domain components, and each basis vector is a DFT- or DCT-based vector.

[0091] In some embodiments, the basis vector set of the frequency domain components is an oversampled DFT- or DCT-based matrix that includes O3 orthogonal DFT- or DCT-based matrices.

[0092] Time domain components of the precoder

[0093] In some embodiments, the wireless device is configured to determine one or more time-domain components of the set of linear combination coefficients of the precoder. Each time-domain component of the precoder corresponds to a basis vector. The set of time-domain components corresponds to a third set of bases (vectors) that includes a plurality of basis vectors. To determine the precoder vector or matrix, the wireless device is configured to select one or more time-domain components (i.e., basis vectors) from the third set of basis vectors. In some examples, the length of the basis vector (i.e., the number of entries in each basis vector) is defined as an integer multiple of the number of antenna port groups configured for the wireless device (as described above). In some examples, the length of the basis vector (i.e., the number of entries in each basis vector) is configured for the wireless device by a network node.

[0094] The wireless device is configured to perform measurements on reference signals received over N4 time instances (i.e., for the configured antenna port group). Note that one time instance of the DL channel can be associated with one OFDM symbol, a set of symbols, one time slot, or one radio frame.

[0095] In some embodiments, the third set of basis vectors comprises a plurality of basis vectors. The third set of basis vectors can be defined by DFT or IDFT basis vectors, or by oversampled DFT or IDFT basis vectors. In some embodiments, the third set of basis vectors comprises a set of discrete cosine transform (DCT)-based vectors. When the third set of basis vectors is defined by DFT (DFT or IDFT)-based basis vectors, the third set of basis vectors can be represented by a DFT or IDFT matrix. In some embodiments, the third set of basis vectors is defined by rotated DFT-based basis vectors, where the indices of the DFT-based vectors are defined by d4 = O4i4 + q4, i4 = 0, …, N4 - 1, where q4 = 0, …, O4 - 1 is the rotation factor of the rotated DFT-based basis vectors. In this case, the rotated DFT-based basis vectors are selected from an oversampled DFT-based basis vector comprising O4N4 DFT-based vectors. This means that the set of basis vectors corresponding to the time domain components is an oversampled DFT- or DCT-based matrix that comprises O4 orthogonal matrices of DFT or DCT. The rotation factor can be selected by the wireless device, or configured for the wireless device, or reported by the wireless device as part of a CSI report. In some embodiments, the number of time instances defines the length (N4) of the basis vectors of the third set of basis vectors, and each entry of the basis vectors is associated with one time instance of the precoder vector or matrix. When the third set of basis vectors is defined by an N4×N4 DFT (DFT or IDFT)-based matrix, the phase of each basis vector element increases (or decreases) with respect to the element index. Thus, each basis vector in the third set of basis vectors is associated with a Doppler frequency in the transform domain. Thus, the N4 basis vectors of the third set of basis vectors are associated with N4 different Doppler frequencies. The wireless device selects a basis vector (i.e., a Doppler frequency) for the precoder based on the measured reference signal.

[0096] Selection of Basis Vectors and Indication in CSI Report

[0097] In some embodiments, the wireless device receives a CSI report configuration from a network node, gNB, or another wireless device. The wireless device is configured with a set of spatial domain components (first set of basis vectors) and determines a subset of one (i.e., one or more) spatial domain components of the precoder from the set of spatial domain components. The subset of the spatial domain components is smaller than the set of spatial domain components. The wireless device selects a plurality of basis vectors (e.g., L basis vectors) from the first set of basis vectors, where the first set of basis vectors corresponds to the set of spatial domain components, and the number of selected basis vectors is smaller than the number of the first set of basis vectors. The selected basis vectors are indicated in the CSI report. In some examples, the selected basis vectors are indicated by a bitmap or a combined bit indicator (e.g., by a bit indicator or a similar indicator).

[0098] In some embodiments, a wireless device configured with a set of frequency-domain components (a second set of basis vectors) determines a subset of frequency-domain components (i.e., one or more frequency-domain components) from the set of frequency-domain components, where the subset of frequency-domain components is less than the set of frequency-domain components. The wireless device selects a plurality of basis vectors (i.e., M basis vectors) from the second set of basis vectors, where the number of selected basis vectors is less than the number of the second set of basis vectors. In some embodiments, the M selected basis vectors (or delays) are indicated in the CSI report. In some examples, the selected basis vectors are indicated by a bitmap or a combined bit indicator (e.g., a or bit indicator).

[0099] In some embodiments, a wireless device configured with a set of time-domain components (a third set of basis vectors) determines a subset of time-domain components from the set of time-domain components, where the subset of time-domain components is less than the set of time-domain components. The wireless device selects a plurality of basis vectors (i.e., Q basis vectors) from the third set of basis vectors, where the number of selected basis vectors is less than the number of the third set of basis vectors. In some embodiments, the Q selected basis vectors (or Doppler frequencies) are indicated in the CSI report. In some examples, the selected basis vectors are indicated by a bitmap or a combined bit indicator (e.g., by a or bit indicator).

[0100] In some embodiments, the wireless device determines a space-domain specific subset for each selected space-domain component, the subset including one or more time-domain components selected from the selected time-domain components and one or more frequency-domain components selected from the selected frequency-domain components. The wireless device also determines a set of combining coefficients for combining the space-domain components, time-domain components, and frequency-domain components selected from the space-domain specific subset. The wireless device generates and reports a CSI report to a network node or another wireless device, the CSI report including an indication of the selected one or more space-domain components, an indication of the one or more time-domain components selected from the space-domain specific subset, an indication of the one or more frequency-domain components selected from the space-domain specific subset, and an indication of the combining coefficients of the precoder vector or matrix.

[0101] In some embodiments, the set of spatial domain components corresponding to the first set of basis vectors includes O1O2N1N2 basis vectors, the set of frequency domain components corresponding to the second set of basis vectors includes N3 or N3O3 basis vectors, and the set of time domain components corresponding to the third set of basis vectors includes N4 or N4O4 basis vectors. The wireless device selects L basis vectors from the O1O2N1N2 basis vectors, from the first set of basis vectors, where L < O1O2N1N2. The wireless device selects M basis vectors from the N3 or N3O3 basis vectors, from the second set of basis vectors, where M < N3 or M < N3O3. The wireless device selects Q basis vectors from the N4 or N4O4 basis vectors, from the third set of basis vectors, where N < N4 or N < N4O4.

[0102] In some embodiments, a subset of the selected time domain and frequency domain components (e.g., M and N basis vectors selected from the second and third sets of basis vectors, respectively) has common basis vectors for the selected spatial domain components (e.g., L selected basis vectors selected from the first set of basis vectors) for each transmit layer, subset of transmit layers, or all transmit layers of the precoder. The common basis vectors (for each transmit layer, subset of transmit layers, or all transmit layers) are indicated in the CSI report. In some examples, the wireless device indicates the common basis vectors for the selected subset of time domain components and the selected subset of frequency domain components via the bitmap or combined indicator explained above.

[0103] Indication of spatial / time / frequency components in the CSI report

[0104] In some embodiments, the wireless device determines a spatially specific subset for each selected spatial domain component from the subset of spatial domain components, where the spatially specific subset includes one or more time domain components selected from the subset of time domain components and one or more frequency domain components selected from the subset of frequency domain components. One or more time domain components and one or more frequency domain components in the spatially specific subset are indicated in the CSI report. In some examples, the wireless device determines a spatially specific subset for each selected basis vector from the first set of basis vectors, the subset including M' basis vectors selected from the M basis vectors (representing the subset of frequency domain components) selected from the second set of basis vectors, and Q' basis vectors selected from the N basis vectors (representing the subset of time domain components) selected from the third set of basis vectors, where M' ≤ M and Q ′ ≤ Q. The selected M' basis vectors are a subset of the M selected basis vectors and are indicated in the CSI report. The selected Q' basis vectors are a subset of the selected Q basis vectors and are indicated in the CSI report for each selected basis vector (i.e., each selected spatial domain component) from the first set of basis vectors.

[0105] In some embodiments, M′ and Q′ basis vectors selected from the second and third sets of basis vectors, respectively, are indicated via a bitmap for each selected spatial component in the CSI report. In another embodiment, M′ and Q′ basis vectors selected from the second and third sets of basis vectors, respectively, are indicated via bit indicators for each selected spatial component in the CSI report. In some examples, the combined bit indicator is given by a or bit indicator.

[0106] In some embodiments, one or more basis vectors selected from the first, second, and third sets of basis vectors of a precoder are indicated via a bitmap in the CSI report, where each bit is associated with a basis vector selected from the first, second, and third sets of basis vectors and a combining coefficient of the precoder. In some embodiments, each selected frequency component, time component, and spatial component is associated with a non-zero combining coefficient of a precoder vector or matrix.

[0107] In some embodiments, each frequency component and time component in a spatially specific subset are associated with a non-zero combining coefficient of a precoder vector or matrix.

[0108] In some embodiments, a subset of time domain components is configured for a wireless device by, for example, a network node, gNB, or other wireless device.

[0109] In some embodiments, the number of time domain components in a subset of time domain components (e.g., a parameter Q indicating the subset size) is configured for a wireless device by, for example, a network node, gNB, or other wireless device.

[0110] In some embodiments, a subset of frequency domain components is configured for a wireless device by, for example, a network node, gNB, or other wireless device.

[0111] In some embodiments, the number of frequency domain components in a subset of frequency domain components (e.g., a parameter M indicating the subset size) is configured for a wireless device by, for example, a network node, gNB, or other wireless device.

[0112] In some embodiments, a spatially specific subset for a selected spatial domain component is the same for two polarizations, where the spatially specific subset includes one or more time domain components selected from a subset of time domain components and one or more frequency domain components selected from a subset of frequency domain components. One or more time domain components and one or more frequency domain components in the spatially specific subset specific to two polarizations are indicated in the CSI report.

[0113] In some embodiments, a spatial-domain specific subset for a selected spatial-domain component is the same for a part of the emission layer, where the spatial-domain specific subset includes one or more time-domain components selected from a time-domain component subset and one or more frequency-domain components selected from a frequency-domain component subset. One or more time-domain components and one or more frequency-domain components in the spatial-domain specific subset specific to a layer subset are indicated in the CSI report.

[0114] In some embodiments, a spatial-domain specific subset for a selected spatial-domain component is the same for two polarizations and a layer subset, where the spatial-domain specific subset includes one or more time-domain components selected from a time-domain component subset and one or more frequency-domain components selected from a frequency-domain component subset. One or more time-domain components and one or more frequency-domain components in the spatial-domain specific subset specific to two polarizations and a layer subset are indicated in the CSI report.

[0115] Precoder matrix

[0116] In some embodiments, the precoder vector or matrix of the emission layer associated with two polarizations of an antenna port is given by:

[0117]

[0118] Where:

[0119] -v l represents a basis vector selected from a first set of basis vectors (the set of spatial-domain components) and corresponds to the spatial-domain component of the precoder;

[0120] -c l,f,n represents the combined coefficient associated with the l-th selected spatial-domain component, the f-th frequency-domain component, and the n-th time-domain component of the precoder vector or matrix;

[0121] or is the t-th (t = 0, 1, …, N3 - 1) component / entry of the -th basis vector / frequency-domain component selected from a second set of basis vectors associated with the frequency-domain component of the precoder; and

[0122] or is the h-th (h = 0, 1, …, N4 - 1) component / entry of the -th basis vector / time-domain component selected from a third set of basis vectors associated with the time-domain component of the precoder.

[0123] Method for reducing CSI report feedback overhead

[0124] In some embodiments, the wireless device is configured to select M FD components for a precoding matrix and indicate the selected M FD components in a CSI report.

[0125] In some embodiments, the wireless device is configured to select Q TD components for a precoding matrix and indicate the selected Q FD components in a CSI report.

[0126] In some embodiments, the wireless device is configured to select L SD components for a precoding matrix and indicate the selected L SD components in a CSI report. Note that the SD components are the same for both polarizations of an antenna port. Thus, the precoding matrix is associated with 2L SD components, where L SD components are the same for both polarizations.

[0127] In some embodiments, the wireless device selects 2LMQ combining coefficients, where L is the number of spatial domain (SD) components, M is the number of frequency domain (FD) components, and Q is the number of time domain (TD) components. The number of SD components, FD components, and TD components is either selected and reported by the wireless device, or configured for the UE by a higher layer (e.g., via RRC), or fixed in the specification and known to the wireless device.

[0128] To reduce the feedback overhead, the wireless device may be configured to determine K or fewer non-zero combined coefficients from the 2LMQ combining coefficients. The wireless device reports the K non-zero combined coefficients (as part of the CSI report) to a network node (e.g., gNB).

[0129] In some embodiments, the wireless device determines a bitmap of size 2LMQ to indicate the selected non-zero combined coefficients. The bitmap consists of 1s and 0s. A "1" is associated with a selected non-zero combined coefficient, and a "0" is associated with a zero or unselected combining coefficient, and vice versa. In some examples, the bitmap is selected for each layer of the precoding matrix. The bitmap is part of the CSI report. In some embodiments, the wireless device is configured to use a bitmap of size 2LMQ bits or use a bit indicator to indicate the positions of the selected non-zero coefficients in the CSI report.

[0130] Since the feedback overhead increases as the values of L, M, and Q increase, methods for reducing the feedback overhead of CSI reports (non-zero coefficient position reports) will be described in more detail below.

[0131] In some embodiments, the wireless device is configured to determine R FD / TD component pairs that are common across the SD component subset or all SD components of a precoding matrix. An FD / TD component pair is defined as a pair that includes one FD component and one TD component. In some examples, the R FD / TD component pairs are selected for common use across all SD components in each layer, layer subset, or all layers of the precoding matrix. The number of per-layer combining coefficients (zero and non-zero combination coefficients) is equal to 2LR. Note that multiple combining coefficients associated with different SD components can be associated with the same FD / TD component pair.

[0132] Furthermore, the wireless device is configured to determine K or fewer non-zero combination coefficients from the 2LR combining coefficients. The wireless device reports these non-zero combination coefficients as part of a CSI report to a network node (e.g., gNB). To indicate the non-zero combination coefficients selected from the 2LR combining coefficients, in the case of polarization-specific combining coefficient selection, the wireless device reports a bitmap of size 2LR for each layer, layer subset, or all layers of the precoding matrix. Since the bitmap size is only 2LR instead of 2LMQ, the CSI reporting overhead is significantly reduced.

[0133] In the case of polarization-common combining coefficient selection, the wireless device is configured to determine K or fewer non-zero combination coefficients from the 2LR combining coefficients. The wireless device reports these non-zero combination coefficients as part of a CSI report to a network node (e.g., gNB). To indicate the non-zero combination coefficients selected from the 2LR combining coefficients, in the case of polarization-common combining coefficient selection, the wireless device reports a bitmap of size LR bits for each layer, layer subset, or all layers of the precoding matrix. Since the bitmap size is only LR instead of 2LMQ, the CSI reporting overhead is significantly reduced.

[0134] Reference Figure 5 , which depicts a schematic diagram of a bitmap of size 2L×R used to indicate non-zero coefficients of a precoder matrix in a CSI report. Each column of the bitmap is associated with a selected FD / TD component pair. There are a total of R FD / TD component pairs. The bitmap entries indicate the combining coefficients associated with a particular SD component and FD / TD component pair. A "1" represents a non-zero coefficient of the precoding matrix, and a "0" represents a zero-valued combining coefficient of the precoding matrix.

[0135] In some embodiments, the number R of FD / TD component pairs is configured by a network node to a wireless device via higher layer signaling (e.g., RRC). The value of R can be configured jointly for each layer, layer subset, or all layers of the precoding matrix. In some embodiments, the number R of FD / TD component pairs is derived from one or more other parameters that are either configured to the wireless device or fixed in the 3GPP specifications. In one example, R is derived from the parameter M, where M is the number of configured FD components of the precoding matrix. In another example, R is derived from the parameter Q, where Q is the number of configured TD components of the precoding matrix. In another example, R is derived from the parameters M and Q, where M is the number of FD components and Q is the number of TD components. In some examples, M is configured by the network node to the wireless device, or M and Q are configured by the network node to the wireless device. In some examples, the value of R is reported by the wireless device to the network node as part of a CSI report for each layer, layer subset, or all layers of the precoding matrix. In some examples, the value of R is reported by the wireless device using bit indicators.

[0136] In some embodiments, the wireless device is configured to indicate the selected FD / TD component pair index in a CSI report. In some examples, the CSI report may include an FD indicator for indicating the FD component index selected from a set of FD components of size N3, and a TD indicator for indicating the TD component index selected from a set of TD components of size N4.

[0137] In some examples, each FD component associated with each FD-TD component pair is indicated using a bit indicator or a bit indicator. For R component pairs, the total feedback for reporting the FD components is thus given by bits or bits or bits or bits.

[0138] In some examples, each TD component associated with each FD-TD component pair is indicated using a bit indicator or a bit indicator. For R component pairs, the total feedback for reporting the TD components is thus given by bits or bits or bits or bits.

[0139] In some embodiments, each TD component associated with an FD / TD component pair is indicated in a CSI report by a first indicator and a second indicator. The first indicator indicates Q selected TD components shared for R FD / TD component pairs. The second indicator indicates one TD component selected from the Q selected TD components for each specific FD / TD component pair.

[0140] In some embodiments, each FD component associated with an FD / TD component pair is indicated in a CSI report by a first indicator and a second indicator. The first indicator indicates M selected FD components shared for R FD / TD component pairs. The second indicator indicates one FD component selected from the M selected FD components for each specific FD / TD component pair.

[0141] In some embodiments, the association between the FD component and the TD component of each FD-TD component pair is fixed in the specification or known to the UE.

[0142] In some embodiments, for M selected FD components and Q selected TD components, there are MQ FD / TD component pairs. In some examples, R FD / TD component pairs selected from the MQ FD / TD component pairs are indicated in a CSI report. In some examples, they are indicated by a bitmap of MQ bits or an indicator of bits. There is a mapping between each FD / TD component pair and the associated FD and TD components. Examples of such a mapping are given below.

[0143] In the first example, the mapping between the associated FD and TD components and the r-th FD / TD component pair is given by r = Qm + q, where q ∈ {0,..., Q - 1} is the TD component index and m ∈ {0,…, M - 1} is the FD component index.

[0144] In the second example, the mapping between the associated FD and TD components and the r-th FD / TD component pair is given by r = Mq + m, where q ∈ {0,..., Q - 1} is the TD component index and m ∈ {0,…, M - 1} is the FD component index.

[0145] Scheme 1 for indicating selected FD / TD component pairs

[0146] In some embodiments, the number R of TD / FD component pairs is equal to the number M of configured FD components. The M FD components are selected from a set of FD components of size N3. The Q TD components are selected from a set of TD components of size N4. Each TD / FD component pair is associated with a single FD component selected from a set of FD components of size N3 and a single TD component selected from a set of TD components of size N4. The R component pair indices are given by (m0,q0)(m1,q1)…(m M-2 ,q M-2 )(m M-1 ,q M-1 ), where m i ∈ {0, …, N3−1}, and q i ∈ {0, …, N4−1}. For the FD component indices, when i ≠ j, m i ≠ m j . Further, the FD component indices are sorted in ascending order, where m0 < m1 < … < m M-1 . In some examples, the M FD components selected among the M FD-TD component pairs are indicated in the CSI report using a -bit indicator or a -bit indicator.

[0147] The CSI report includes an indication of each TD component index for each FD / TD component pair included in the CSI report. Examples of such indicators are presented below. In one example, each TD component associated with each FD-TD component pair is indicated using a -bit indicator or a -bit indicator. For the M component pairs, the total feedback reporting the TD components is thus given by bits or bits or bits or (M - bits. In some embodiments, each TD component associated with an FD / TD component pair is indicated in the CSI report by a first indicator and a second indicator. The first indicator indicates the Q selected TD components common to the M FD / TD component pairs. The second indicator indicates one TD component selected from the Q selected TD components for each particular FD / TD component pair. In some examples, the first indicator can be a -bit indicator or a -bit indicator or a bitmap of size N4. The second indicator can be a -bit indicator or a bitmap of size Q. Thus, for the M FD / TD component pairs, the total feedback reporting the TD components is bit or M·Q bits or bit or (M - 1)·Q bits.

[0148] In some embodiments, the association between the FD component and the TD component of each FD-TD component pair is fixed in the specification or known to the UE.

[0149] Scheme II for indicating the selected FD / TD component pair

[0150] In some embodiments, the number R of TD / FD component pairs is equal to the number Q of configured TD components. M FD components are selected from a set of FD components of size N3. Q TD components are selected from a set of TD components of size N4. Each TD / FD component pair is associated with a single FD component selected from a set of FD components of size N3 and a single TD component selected from a set of TD components of size N4. The R component pair indices are given by (m0,q0)(m1,q1)…(m Q-2 ,q Q-2 )(m Q-1 ,q Q-1 ), where m i ∈{0,…,N3 - 1}, and q i ∈{0,…,N4 - 1}. For the TD component indices, when i≠j, q i ≠q j . Further, the TD component indices are sorted in ascending order, where q0 < q1 < … < q Q-1 . In some examples, the Q TD components selected from the Q FD-TD component pairs are indicated in the CSI report using a bit indicator or a bit indicator.

[0151] The CSI report includes an indication of each FD component index of each FD / TD component pair included in the CSI report. Examples of such indicators are presented below. In one example, each FD component associated with each FD-TD component pair is indicated using a bit indicator or a bit indicator. For the Q component pairs, the total feedback reporting the FD components is thus by bits or bits or bits or Bits are given. In some embodiments, each FD component associated with an FD / TD component pair is indicated in the CSI report by a first indicator and a second indicator. The first indicator indicates M selected FD components shared among Q FD / TD component pairs. The second indicator indicates one FD component selected from the M selected FD components for each specific FD / TD component pair. In some examples, the first indicator can be a -bit indicator or a -bit indicator or a bitmap of size N3. The second indicator can be a -bit indicator or a bitmap of size M. Thus, for Q FD / TD component pairs, the total feedback for reporting FD components is bits or Q·M bits or bits or (Q - 1)·M bits.

[0152] In some embodiments, the association between the FD component and the TD component of each FD-TD component pair is fixed in the specification or known to the UE.

[0153] In some embodiments, the wireless device is configured to determine T SD / TD component pairs shared among the FD subset or all FD components of the precoding matrix. An SD / TD component pair is defined as a pair containing one SD component and one TD component. In some examples, the T SD / TD component pairs are selected for sharing among all FD components in each layer, layer subset, or all layers of the precoding matrix. The number of combining coefficients (zero and non-zero combination coefficients of the precoder) for each layer is equal to MT. It should be noted that multiple combining coefficients associated with different FD components can be associated with the same SD / TD component pair.

[0154] Furthermore, the wireless device is configured to determine K or fewer non-zero combination coefficients from the MT combining coefficients. The wireless device reports these non-zero combination coefficients to a network node (such as a gNB) as part of the CSI report. To indicate the non-zero combination coefficients selected from the MT combining coefficients, the wireless device reports a bitmap of size MT for each layer, layer subset, or all layers of the precoding matrix. Since the bitmap size is only MT instead of 2LMQ, the CSI report overhead is significantly reduced.

[0155] Refer to Figure 8, which depicts a schematic diagram of a bitmap used to indicate the size of non-zero coefficients of a precoder matrix as M×T in a CSI report. Each column of the bitmap is associated with a selected SD / TD component pair. There are a total of T FD / TD component pairs. The bitmap entry indicates the combining coefficient associated with a particular FD component and SD / TD component pair. "1" indicates a non-zero coefficient of the precoding matrix, and "0" indicates a zero-valued combining coefficient of the precoding matrix.

[0156] In some embodiments, the parameter T of the SD / TD component pair is configured by a network node to a wireless device via a higher layer (e.g., RRC). The parameter T can be configured commonly for each layer, a subset of layers, or all layers of the precoding matrix. In some embodiments, the number T of SD / TD component pairs is derived from one or more other parameters, which are either configured to the wireless device or fixed in the 3GPP specification. In one example, T is derived from the parameter L, where L is the number of configured SD components of the precoding matrix (the same for two polarizations of an antenna port). In another example, T is derived from the parameter Q, where Q is the number of configured TD components of the precoding matrix. In another example, T is derived from the parameters L and Q, where L is the number of SD components and Q is the number of TD components. In some examples, L is configured by the network node to the wireless device, or L and Q are configured by the network node to the wireless device. In some examples, the value of T is reported by the wireless device to the network node as part of a CSI report for each layer, a subset of layers, or all layers of the precoding matrix. In some examples, the value of T is reported by the wireless device using a bit indicator. In some examples, the value of T is reported by the wireless device using a bit indicator.

[0157] In some embodiments, the wireless device is configured to indicate a selected SD / TD component pair index in a CSI report. In some examples, the CSI report may include an SD indicator for indicating the SD component index selected from a set of SD components of size N1N2, and a TD indicator for indicating the TD component index selected from a set of TD components of size N4.

[0158] In some examples, each SD component associated with each SD / TD component pair is indicated using a bit indicator. For T component pairs, the total feedback for reporting the SD components is thus given by bits.

[0159] In some examples, each TD component associated with each SD / TD component pair is indicated using a bit indicator or a Indicated by an indicator of bits. For T component pairs, the total feedback reporting the TD component is thus given by bits or bits.

[0160] In some embodiments, each TD component associated with an SD / TD component pair is indicated in the CSI report by a first indicator and a second indicator. The first indicator indicates Q selected TD components shared for T SD / TD component pairs. The second indicator indicates one TD component selected from the Q selected TD components for each specific SD / TD component pair.

[0161] In some embodiments, each SD component associated with an SD / TD component pair is indicated in the CSI report by a first indicator and a second indicator. The first indicator indicates L selected SD components shared for T SD / TD component pairs. The second indicator indicates one SD component selected from the L selected SD components for each specific SD / TD component pair.

[0162] For the L selected SD components and the Q selected TD components, there are 2LQ SD / TD component pairs for the two polarizations of the antenna port / precoding matrix. In some examples, T SD / TD component pairs selected from the 2LQ SD / TD component pairs are indicated using a bitmap of size 2LQ bits or an indicator of bits. In some examples, assuming that the SD / TD component pairs are shared for the two polarization modes of the antenna port / precoding matrix, T SD / TD component pairs selected from the 2LQ SD / TD component pairs are indicated using an LQ-bit indicator or an indicator of bits.

[0163] In some embodiments, for the L selected SD components and the Q selected TD components, when the SD / TD component pair selection is polarization-shared (i.e., the two polarizations of the precoder matrix have the same SD / TD component pairs), there are LQ SD / TD component pairs. In some examples, T SD / TD component pairs selected from the LQ SD / TD component pairs are indicated using a bitmap of size LQ bits or an indicator of bits. There is a mapping between each SD / TD component pair and the SD component and the TD component. Examples of such a mapping are given below.

[0164] In some examples, assuming a polarization - shared SD / TD component pair selection method (assuming that the SD / TD component pair is the same for two polarization modes of the antenna port), the mapping between the associated SD component and TD component and the t - th SD / TD component pair is given by t = Ql+q, where q ∈ {0,...,Q - 1} is the TD component index, and l ∈ {0,…,L - 1} is the SD component index.

[0165] In some examples, assuming a polarization - shared SD / TD component pair selection method (assuming that the SD / TD component pair is the same for two polarization modes of the antenna port), the mapping between the associated SD component and TD component and the t - th SD / TD component pair is given by t = Lq + l, where q ∈ {0,...,Q - 1} is the TD component index, and l ∈ {0,…,L - 1} is the SD component index.

[0166] In certain embodiments, for the selected L SD components and the selected Q TD components, for polarization - specific SD / TD component pair selection (i.e., the SD / TD component pairs of two polarizations of the precoder matrix can be different), there are 2LQ SD / TD component pairs. In some examples, T SD / TD component pairs selected from the 2LQ SD / TD component pairs are indicated using a 2LQ - bit bitmap or a bit indicator. There is a mapping between each SD / TD component pair and the SD component and TD component. Examples of such mapping are given below.

[0167] In some examples, the mapping between the associated SD component and TD component and the t - th SD / TD component pair is given by t = Ql+q, where q ∈ {0,...,Q - 1} is the TD component index, and l ∈ {0,…,2L - 1} is the SD component index.

[0168] In some examples, the mapping between the associated SD component and TD component and the t - th SD / TD component pair is given by t = 2Lq + l, where q ∈ {0,...,Q - 1} is the TD component index, and l ∈ {0,…,2L - 1} is the SD component index.

[0169] Scheme 1 for indicating the selected SD / TD component pairs

[0170] In some embodiments, the number T of SD / TD component pairs is equal to the number L of configured SD components. The L SD components are selected from a set of SD components of size N1N2. Q = L TD components are selected from a set of TD components of size N4. Each SD / TD component pair is associated with a single SD component selected from a set of SD components of size N1N2 and a single TD component selected from a set of TD components of size N4. For polarization-shared SD / DD pair selection, the L SD / DD component pair indices are shared for the two polarizations of the precoder matrix and are given by (l0,q0),(l1,q1),…,(l L-1 ,q L-1 ),(l L ,q0),(l L+1 ,q1),…,(l 2L-1 ,q L-1 ), where l i ∈ {0,…,N1N2 - 1}, and q i ∈ {0,…,N4 - 1}. In some examples, for the SD component indices, when i ≠ j, l i ≠ l j , where i,j ∈ {0,…,L - 1}. In some examples, the SD component indices are sorted in ascending order, where l0 < l1 < … < l L-1 , and l i = l L+i , In some examples, the L SD components selected among the L SD / TD component pairs are indicated in the CSI report using a -bit indicator.

[0171] In some embodiments, the number T of SD / TD component pairs is equal to 2L, where L is the number of configured SD components. The L SD components are selected from a set of SD components of size N1N2. Q = 2L TD components are selected from a set of TD components of size N4. Each SD / TD component pair is associated with a single SD component selected from a set of SD components of size N1N2 and a single TD component selected from a set of TD components of size N4. For polarization-shared SD / TD pair selection, the 2L SD / TD component pair indices are given by (l0,q0),(l1,q1)…(l L-1 ,q L-1 ),(l L ,q L ),…,(l 2L-2 ,q 2L-2 ),(l 2L-1 ,q 2L-1 ), where l i ∈ {0,…,N1N2 - 1}, and qi ∈ {0, …, N4 - 1}. In some examples, for the SD component index, when i ≠ j, there is l i ≠ l j , where i, j ∈ {0, …, L - 1}. In some examples, the SD component indices are sorted in ascending order, where l0 < l1 < … < l L-1 , and l i = l L+i , In some examples, among the 2L SD / TD component pairs, the L selected SD components are indicated in the CSI report using a bit indicator.

[0172] In certain embodiments, the CSI report includes an indication of each TD component index for each SD / TD component pair. Examples of such indicators are presented below. In one example, each TD component associated with each SD / TD component pair uses a bit indicator or a bit indicator for indication. For the polarization - shared SD / TD component selection among the L SD / TD component pairs, the total feedback for reporting the TD components is thus given by bits or bits. For the polarization - specific SD / TD component selection among the 2L component pairs, the total feedback for reporting the TD components is thus given by bits or bits. In certain embodiments, each TD component associated with an SD / TD component pair is indicated in the CSI report by a first indicator and a second indicator. The first indicator indicates the sharing for the Q selected TD components common to the L or 2L SD / TD component pairs. The second indicator indicates one TD component selected from the Q selected TD components for each SD / TD component pair. In some examples, the first indicator can be a bit indicator or a bit indicator or a bitmap of size N4. The second indicator can be a bit indicator or a bitmap of size Q. Thus, for the polarization - shared SD / TD component selection, for T = L SD / TD component pairs, the total feedback for reporting the TD components is bits or L·Q bits. Thus, for the polarization - specific SD / TD component selection, for T = 2L SD / TD component pairs, the total feedback for reporting the TD components is bits or 2L·Q bits.

[0173] Scheme II for indicating the selected SD / TD component pairs

[0174] In some embodiments, the number T of SD / TD component pairs is equal to the number Q of configured TD components. The L SD components are selected from a set of SD components of size N1N2. The Q TD components are selected from a set of TD components of size N4. Each SD / TD component pair is associated with a single SD component selected from a set of SD components of size N1N2 and a single TD component selected from a set of TD components of size N4. For polarization-shared SD / TD pairs, the Q SD / TD component pair indices are given by (l0,q0)(l1,q1)…(l Q-2 ,q Q-2 )(l Q-1 ,q Q-1 ), where l i ∈ {0,…,N1N2 - 1}, and q i ∈ {0,…,N4 - 1}. For polarization-specific SD / TD pairs, the Q SD / TD component pair indices are given by (l0,q0)(l1,q1)…(l Q-2 ,q Q-2 )(l Q-1 ,q Q-1 ), where l i ∈ {0,…,N1N2 - 1}, and q i ∈ {0,…,N4 - 1}. For TD component indices, when i ≠ j, q i ≠ q j . The TD component indices are sorted in ascending order, where q0 < q1 < … < q Q-1 . In some examples, the Q TD components selected from the Q SD / TD component pairs are indicated in the CSI report using a -bit indicator or a -bit indicator or a bitmap of size N4.

[0175] The CSI report includes an indication of each SD component index for each SD / TD component pair. Examples of such indicators are presented below. In one example, each SD component associated with each SD / TD component pair is indicated using a -bit indicator. For Q component pairs, the total feedback reporting the SD components is thus given by bits. In some embodiments, each SD component associated with an SD / TD component pair is indicated in the CSI report by a first indicator and a second indicator. The first indicator indicates the L selected SD components shared for the Q SD / TD component pairs. The second indicator indicates one SD component selected from the L selected SD components for each specific SD / TD component pair. In some examples, the first indicator can be a An indicator of bits or a bitmap of size N1N2. For polarization-specific SD / TD component selection, the second indicator can be an indicator of bits or a bitmap of size L. Thus, for Q SD / TD component pairs, the total feedback for reporting the SD component is bits or Q·L bits. For polarization-specific SD / TD component indication, the second indicator can be an indicator of bits or a bitmap of size 2L. Thus, for Q SD / TD component pairs, the total feedback for reporting the SD component for polarization-specific SD / TD component pairs is bits or Q·2L bits.

[0176] Reference Figure 4 illustrates a method performed by a wireless device according to some of the embodiments described above. The method is performed by a wireless device (or UE) for generating and transmitting a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as a linear combination of spatial domain components, frequency domain components, and time domain components, and a set of linear combination coefficients for combining the spatial domain components, the frequency domain components, and the time domain components. As shown, the method includes:

[0177] Receiving (400) a CSI report configuration from a network node;

[0178] Determining (401) one or more frequency domain FD components of the set of linear combination coefficients;

[0179] Determining (402) one or more time domain TD components of the set of linear combination coefficients;

[0180] Determining (403) one or more spatial domain SD components of the set of linear combination coefficients;

[0181] Determining (404) a set of frequency domain FD / time domain TD component pairs, each component pair including an FD component and a TD component, and the component pairs being shared among a subset of the spatial domain components or all of the spatial domain components of the set of linear combination coefficients, and generating and transmitting or reporting (405) a CSI report to the network node (600), the CSI report including an indication of the determined SD components, FD components, and TD components, FD / TD component pairs, and combination coefficients of the precoder vector or matrix.

[0182] According to one embodiment, the wireless device is configured to determine or select a plurality of common FD / TD component pairs on all selected SD components of the precoding matrix.

[0183] According to one embodiment, the combining coefficients associated with the same FD / TD component pair are associated with different SD components.

[0184] According to one embodiment, the TD component associated with the FD / TD component pair is indicated in the CSI report using a first indicator and a second indicator.

[0185] According to one embodiment, the first indicator indicates Q selected TD components shared by all FD / TD component pairs, and the second indicator indicates one TD component selected from the Q TD components for one FD / TD component pair.

[0186] According to one embodiment, the FD component associated with the FD / TD component pair is indicated in the CSI report using a first indicator and a second indicator.

[0187] According to one embodiment, the first indicator indicates M selected FD components shared by all FD / TD component pairs, and the second indicator indicates one FD component selected from the M FD components for one FD / TD component pair.

[0188] Reference Figure 9 , a method performed by a wireless device according to some of the embodiments described above is illustrated. The method is performed by a wireless device (or UE) for generating and transmitting a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices represented as linear combinations of spatial domain components, frequency domain components, and time domain components, and a set of linear combination coefficients for combining the spatial domain components, the frequency domain components, and the time domain components. As shown, the method includes:

[0189] Receiving (700) a CSI report configuration from a network node;

[0190] Determining (701) one or more frequency domain FD components of the set of linear combination coefficients;

[0191] Determining (702) one or more time domain TD components of the set of linear combination coefficients;

[0192] Determining (703) one or more spatial domain SD components of the set of linear combination coefficients;

[0193] Determine (704) a set of spatial domain SD / time domain TD component pairs, each component pair including an SD component and a TD component, and the component pairs being shared among a subset of the frequency domain components or all of the frequency domain components of the set of linear combination coefficients, and generate and transmit or report (705) a CSI report to the network node (600), the CSI report including an indication of the determined SD components, FD components, and TD components, SD / TD component pairs, and combination coefficients of the precoder vector or matrix.

[0194] To perform the processes or method steps described above performed by a wireless device or UE, a wireless device is also provided. Figure 6 A block diagram depicting a wireless device 500 or UE is illustrated. The wireless device 500 includes a processor 510 or processing circuitry or processing module or processor component 510; a receiver circuit or receiver module 540; a transmitter circuit or transmitter module 550; a storage module 520, a transceiver circuit or transceiver module 530, and the transceiver circuit or transceiver module 530 may include the transmitter circuit 550 and the receiver circuit 540. The wireless device 500 further includes an antenna system 560, and the antenna system 560 includes antenna circuitry for transmitting signals to and receiving signals from at least a network node or other wireless devices. The antenna system employs the beamforming techniques described above.

[0195] The wireless device 500 may belong to any wireless access technology that supports beamforming techniques, including 4G or LTE, LTE-A, 5G, advanced 5G, or combinations thereof. The wireless device includes a processor and a memory, and the memory contains instructions executable by the processor such that the wireless device 500 is operable or configured to perform any one of the embodiments related to the wireless device described above.

[0196] The processing module / circuit 510 includes a processor, a microprocessor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc., and may be referred to as a "processor". The processor 510 controls the operation of the wireless device and its components. The memory (circuit or module) 520 includes random access memory (RAM), read only memory (ROM), and / or other types of memory for storing data and instructions that may be used by the processor 510. Generally, it can be understood that in one or more embodiments, the wireless device 500 includes fixed or programmable circuitry configured to perform the operations in any of the embodiments disclosed herein.

[0197] In at least one such example, the processor 510 includes a microprocessor, a microcontroller, a DSP, an ASIC, an FPGA, or other processing circuitry, and the processor 510 is configured to execute computer program instructions from a computer program stored in a non-transitory computer-readable medium, where the non-transitory computer-readable medium is located within or accessible by the processing circuitry. Here, "non-transitory" does not necessarily mean permanent or immutable storage, and can include storage in working or volatile memory, but the term does mean storage with at least some persistence. The execution of the program instructions is specifically adapted to the processing circuitry or configures the processing circuitry to perform operations related to the wireless device in this disclosure. Additionally, it can be understood that the wireless device 500 may include other components.

[0198] The wireless device 500 executes instructions contained in the memory 520 via the processor 510, enabling the wireless device to be operable to perform any one of the embodiments related to the actions performed by the wireless device described previously, some of which are presented in this disclosure.

[0199] A computer program is also provided, which includes instructions that, when executed by the processor 510 of the wireless device, cause the processor 510 to perform the methods described herein.

[0200] A method performed by a network node is also provided for receiving a CSI report in a wireless communication system, where the CSI report indicates a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as a linear combination of spatial-domain components, frequency-domain components, and time-domain components, and a set of linear combination coefficients for combining the spatial-domain components, the frequency-domain components, and the time-domain components. The method includes:

[0201] Transmitting a CSI report configuration to a wireless device (500) so that the wireless device (500) can determine one or more frequency-domain FD components of the set of linear combination coefficients; determining one or more time-domain TD components of the set of linear combination coefficients; determining one or more spatial-domain SD components of the set of linear combination coefficients; determining a set of frequency-domain / time-domain (FD / TD) component pairs, each component pair including an FD component and a TD component, and the component pairs being shared among a subset or all of the spatial-domain components of the set of linear combination coefficients, and generating and transmitting or reporting to the network node (600) a CSI report that includes an indication of the determined SD components, FD components, and TD components, the FD / TD component pairs, and the combination coefficients of the precoder vector or matrix; and

[0202] Receiving a CSI report from the wireless device (500), the CSI report including an indication of the determined spatial domain components, frequency domain components, and time domain components, frequency domain / time domain component pairs, and combination coefficients of a precoder vector or matrix; wherein the content of the CSI report is determined by the wireless device (500) according to this specification.

[0203] There is also provided a method performed by a network node for receiving a CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices represented as linear combinations of spatial domain components, frequency domain components, and time domain components, and a set of linear combination coefficients for combining the spatial domain components, the frequency domain components, and the time domain components, the method comprising:

[0204] Transmitting a CSI report configuration to the wireless device (500); such that the wireless device (500) can determine one or more frequency domain (FD) components of the set of linear combination coefficients; determining one or more time domain (TD) components of the set of linear combination coefficients; determining one or more spatial domain (SD) components of the set of linear combination coefficients; determining a set of spatial domain / time domain (SD / TD) component pairs, each component pair including an SD component and a TD component, and the component pairs being shared among a subset of the frequency domain components or all of the frequency domain components of the set of linear combination coefficients, and generating and transmitting or reporting to the network node (600) a CSI report, the CSI report including an indication of the determined SD components, FD components, and TD components, SD / TD component pairs, and combination coefficients of the precoder vector or matrix; and

[0205] Receiving a CSI report from the wireless device (500), the CSI report including an indication of the determined spatial domain components, frequency domain components, and time domain components, spatial domain / time domain component pairs, and combination coefficients of a precoder vector or matrix; wherein the content of the CSI report is determined by the wireless device (500) according to this specification.

[0206] The actions performed by the wireless device for determining the CSI report to be transmitted to the network node have been described above and will not be elaborated here.

[0207] To perform the processes or method steps performed by the network node described above, there is also provided a network node. Figure 7A block diagram depicting network node 600 is illustrated. Network node 600 includes a processor 610 or processing circuitry or processing module or processor component 610; a receiver circuit or receiver module 640; a transmitter circuit or transmitter module 650; a storage module 620, and a transceiver circuit or transceiver module 630, where the transceiver circuit or transceiver module 630 may include the transmitter circuit 650 and the receiver circuit 640. Network node 600 further includes an antenna system 660, and the antenna system 660 includes antenna circuitry for transmitting signals to and receiving signals from at least wireless devices. The antenna system employs the beamforming techniques described above.

[0208] Network node 600 may belong to any wireless access technology that supports beamforming techniques, including 4G or LTE, LTE-A, 5G, advanced 5G, or combinations thereof. The network node includes a processor and a memory that contains instructions executable by the processor such that network node 600 is operable or configured to perform any one of the embodiments related to network node 600 described above.

[0209] Processing module / circuit 610 includes a processor, a microprocessor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), etc., and processing module / circuit 610 may be referred to as a "processor". Processor 610 controls the operation of network node and its components. Memory (circuit or module) 620 includes random access memory (RAM), read only memory (ROM), and / or other types of memory for storing data and instructions that may be used by processor 610. Generally, it can be understood that in one or more embodiments, the network node includes fixed or programmable circuitry configured to perform the operations in any of the embodiments disclosed herein.

[0210] In at least one such example, processor 610 includes a microprocessor, a microcontroller, a DSP, an ASIC, an FPGA, or other processing circuitry, and processor 610 is configured to execute computer program instructions from a computer program stored in a non-transitory computer-readable medium, where the non-transitory computer-readable medium is within or accessible by the processing circuitry. Here, "non-transitory" does not necessarily mean permanent or immutable storage and may include storage in working or volatile memory, but the term does mean storage with at least some persistence. Execution of the program instructions is specifically adapted to the processing circuitry or configures the processing circuitry to perform the operations related to the network node in this disclosure. Additionally, it can be understood that network node 600 may include other components. Network node 600 may also be regarded as a transmitter and receiver point (TRP).

[0211] The network node 600 executes instructions included in the memory 620 via the processor 610, enabling the network node 600 to be operable to execute any of the foregoing embodiments related to the actions performed by the network node.

[0212] A computer program is also provided, which includes instructions that, when executed by the processor 610 of the network node, cause the processor 610 to execute the methods described in this specification.

[0213] As described above, the embodiments described in the present disclosure achieve several advantages, including significantly reducing the feedback overhead and computational complexity of wireless devices in codebook-based CSI reporting. Another advantage is reducing the latency in CSI reporting.

[0214] Note: The combining coefficient or the combined coefficients represent the same technical feature, that is, they can be used interchangeably.

[0215] The following is a summary of the embodiments of the present invention. A method performed by a wireless device (500) for generating and reporting or transmitting a channel state information CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as linear combinations of spatial domain components, frequency domain components, and time domain components, and a set of linear combination coefficients for combining the spatial domain components, the frequency domain components, and the time domain components, the method comprising:

[0216] The network node (600) receives (700) a CSI report configuration;

[0217] Determine (701) one or more frequency domain FD components of the set of linear combination coefficients;

[0218] Determine (702) one or more time domain TD components of the set of linear combination coefficients;

[0219] Determine (703) one or more spatial domain SD components of the set of linear combination coefficients;

[0220] Determine (704) a set of spatial domain SD / time domain TD component pairs, each component pair including an SD component and a TD component, and the component pairs being shared in a subset of the FD components or all of the FD components of the set of linear combination coefficients;

[0221] Generate and transmit or report (705) a CSI report to the network node (600), the CSI report including an indication of the determined SD components, FD components, and TD components, SD / TD component pairs, and the combination coefficients of the precoder vectors or matrices.

[0222] According to one embodiment, a wireless device (500) is provided, including a processor (510) and a memory (520), the memory (520) containing instructions executable by the processor (510) such that the wireless device (500) is operable to perform the above method.

[0223] According to another embodiment, a method performed by a network node is provided for receiving a channel state information CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices represented as linear combinations of spatial domain components, frequency domain components, and time domain components, and a set of linear combination coefficients for combining the spatial domain components, the frequency domain components, and the time domain components, the method including: transmitting a CSI report configuration to a wireless device (500); determining one or more frequency domain FD components of the set of linear combination coefficients such that the wireless device (500) is able to determine the set of linear combination coefficients; determining one or more time domain TD components of the set of linear combination coefficients; determining one or more spatial domain SD components of the set of linear combination coefficients; determining a set of spatial domain SD / time domain TD component pairs, each component pair including an SD component and a TD component, and the component pairs being common among a subset of the frequency domain components or all of the frequency domain components of the set of linear combination coefficients, and generating and transmitting or reporting a CSI report to the network node (600), the CSI report including an indication of the determined SD components, FD components, and TD components, SD / TD component pairs, and combination coefficients of the precoder vector or matrix; and receiving the CSI report from the wireless device (500), the CSI report including an indication of the determined spatial domain components, frequency domain components, and time domain components, frequency domain / time domain component pairs, and combination coefficients of the precoder vector or matrix; wherein the content of the CSI report is determined by the wireless device (500) according to the present disclosure.

[0224] According to one embodiment, a network node (600) includes a processor (610) and a memory (620), the memory (620) containing instructions executable by the processor (610) such that the network node (600) is operable to perform the above method.

[0225] The wireless device is configured to determine or select a plurality of SDTD component pairs that are common over all selected FD components of the precoding matrix.

[0226] The method / procedure further includes that the combining coefficients associated with the same SD / TD component pair are associated with different FD components. The FD components associated with the SD / TD component pair are indicated in the CSI report using a first indicator and a second indicator. The first indicator indicates M or M - 1 selected FD components shared by all SD / TD component pairs, and the second indicator indicates one FD component selected from the M or M - 1 FD components for one SD / TD component pair. The SD components associated with the SD / TD component pair are indicated in the CSI report using a first indicator and a second indicator. The first indicator may indicate L selected SD components shared by all SD / TD component pairs, and the second indicator indicates one SD component selected from the L SD components for one SD / TD component pair. R FD / TD component pairs selected from MQ FD / TD component pairs are indicated in the CSI report. The selected R FD / TD component pairs are indicated by a bitmap of MQ bits or a bit indicator. T SD / TD component pairs selected from 2LQ SD / TD component pairs are indicated in the CSI report. The selected T SD / TD component pairs may be indicated by a bitmap of size 2LQ bits or a bit indicator.

[0227] The SD / TD component pair selection may be shared on two polarizations of the precoding matrix, and T SD / TD component pairs selected from the LQ SD / TD component pairs with polarization sharing are indicated in the CSI report. The selected T SD / TD component pairs may be indicated by a bitmap of size LQ bits or a bit indicator.

[0228] In this specification, the reference to "an example" or "exemplary" means that the particular features, structures, or characteristics described in connection with the example are included in at least one embodiment of the present technology. Thus, the appearances of the phrases "in an example" or "exemplary" throughout this specification are not necessarily all referring to the same embodiment.

[0229] In this disclosure, the term "comprise (or comprising)" is used in a non - restrictive sense, meaning "consisting at least of...". Although specific terms may be adopted herein, they are used only in a general and descriptive sense and not for limiting purposes. The embodiments herein can be applied to any wireless system, including LTE or 4G, LTE - A (or LTE - Advanced), 5G, advanced 5G, WiMAX, WiFi, satellite communication, television broadcasting, etc.

Claims

1. A method performed by a wireless device (500) for generating and reporting or transmitting a Channel State Information (CSI) report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices being represented as linear combinations of spatial domain (SD) components, frequency domain (FD) components, and time domain (TD) components, and a set of linear combination coefficients for combining the SD components, the FD components, and the TD components, the method comprising: Receive (400) a CSI report configuration from a network node (600); Determine (401) one or more FD components of the set of linear combination coefficients; Determine (402) one or more TD components of the set of linear combination coefficients; Determine (403) one or more SD components of the set of linear combination coefficients; Determine (404) a set of frequency-domain FD / time-domain TD component pairs, each component pair including an FD component and a TD component, and the component pairs being shared in an SD subset of the set of linear combination coefficients; Generate and transmit or report (405) a CSI report to the network node (600), the CSI report including an indication of the determined SD components, FD components, and TD components, FD / TD component pairs, and combination coefficients of a precoder vector or matrix.

2. The method according to claim 1, wherein the wireless device determines a spatially specific subset for each selected SD component from a subset of the SD components, the spatially specific subset including one or more TD components selected from a subset of the TD components, one or more FD components selected from a subset of the FD components, and a set of combination coefficients for combining the SD components, TD components, and FD components selected from the spatially specific subset.

3. The method according to claim 1 or 2, for M selected FD components and Q selected TD components, there are MQ FD / TD component pairs, and wherein, Use a bitmap of size MQ bits to indicate the FD / TD component pairs selected in each space-domain specific subset.

4. The method according to any one of claims 1 - 3, wherein each FD component and TD component in the spatially specific subset is associated with a non - zero combination coefficient of the precoder vector or matrix.

5. The method according to any one of claims 1 - 4, wherein the mapping between the associated FD component and TD component and the r - th FD / TD component pair is given by: r = Mq + m, where q ∈ {0, …, Q - 1} is the TD component index, and m ∈ {0, …, M - 1} is the FD component index.

6. The method according to any one of claims 1 - 5, wherein the wireless device is configured to determine or select a plurality of common FD / TD component pairs over all selected SD components of the precoding matrix.

7. The method according to any one of claims 1 - 6, wherein the combining coefficients associated with the same FD / TD component pair are associated with different SD components.

8. The method according to any one of claims 1 - 7, wherein the TD component associated with the FD / TD component pair is indicated in the CSI report using a first indicator and a second indicator.

9. The method according to claim 8, wherein the first indicator indicates Q selected TD components common to all FD / TD component pairs, and the second indicator indicates one TD component selected from the Q TD components for one FD / TD component pair.

10. The method according to any one of claims 1 - 7, wherein the FD component associated with the FD / TD component pair is indicated in the CSI report using a first indicator and a second indicator.

11. The method according to claim 10, wherein the first indicator indicates M selected FD components common to all FD / TD component pairs, and the second indicator indicates one FD component selected from the M FD components for one FD / TD component pair.

12. A wireless device (500) comprising a processor (510) and a memory (520), the memory (520) containing instructions executable by the processor (510) such that the wireless device (500) is operable to perform the method according to any one of claims 1 - 11.

13. A method performed by a network node (600) for receiving a channel state information CSI report in a wireless communication system, the CSI report indicating a plurality of precoder vectors or matrices, the precoder vectors or matrices represented as linear combinations of SD components, FD components, and TD components, and a set of linear combination coefficients for combining the SD components, the FD components, and the TD components, the method comprising: Transmit a CSI report configuration to a wireless device (500); such that the wireless device (500) can determine one or more FD components of the set of linear combination coefficients; determine one or more TD components of the set of linear combination coefficients; determine one or more SD components of the set of linear combination coefficients; determine a set of FD / TD component pairs, each component pair including an FD component and a TD component, and the component pairs being shared in an SD subset of the set of linear combination coefficients, and generate and transmit or report a CSI report to the network node (600), the CSI report including an indication of the determined SD components, FD components, and TD components, FD / TD component pairs, and combination coefficients of a precoder vector or matrix; and Receive a CSI report from the wireless device (500), the CSI report including an indication of the determined SD components, FD components, and TD components, FD / TD component pairs, and combination coefficients of a precoder vector or matrix; wherein the content of the CSI report is determined by the wireless device (500) according to claim 1.

14. A network node (600) comprising a processor (610) and a memory (620), the memory (620) containing instructions executable by the processor (610) such that the network node (600) is operable to perform the method according to claim 13.

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