CSI Report Based on 3-Component Codebook

Abstract

The present invention relates to a method performed by a user equipment (UE) that provides CSI feedback in the form of one or more channel state information (CSI) reports in a wireless communication system (A), the method comprising: receiving, from a network node (gNB) via a MIMO channel, one or more higher layer configurations of downlink reference signals, one or more CSI report configurations associated with the downlink reference signal configurations, and a wireless signal, the wireless signal including a downlink reference signal associated with the one or more downlink reference signal configurations; estimating a downlink MIMO channel based on measurements on the received one or more downlink reference signals, the downlink reference signals being provided via a configured number of frequency domain resources, time domain resources, and one or more ports; estimating, for each CSI report configuration, an estimated channel matrix and two codebooks, one or more spatial domain (SD) precoders. determining a precoding matrix based on two codebooks, including a spatial codebook including basis components and a delay codebook including one or more delay-domain (DD) basis components of a precoder, and one or more non-zero combining coefficients that complex-combines the one or more SD and DD basis vectors; reporting one or more CSI reports of one or more CSI report configurations to a network node, each CSI report including a selected precoding matrix in the form of a precoding matrix identifier PMI and a rank identifier RI, where the rank identifier (RI) indicates the transmission rank of the RI layer of the precoding matrix; each CSI report including two parts: CSI Part 1 and CSI Part 2, where CSI Part 1 has a fixed payload size and includes information indicating the size of the payload of CSI Part 2, and CSI Part 2 includes at least amplitude and phase information of the selected non-zero combining coefficients of the CSI report, and part or all of CSI Part 2 is available for omission from the CSI report.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication, and in particular, to a method for a user equipment to provide channel state information (CSI) feedback in the form of one or more CSI reports in a wireless communication system, a user equipment, a network node, and a computer program product.

Background Art

[0002] In a wireless communication system such as a 3GPP fifth-generation wireless communication system or New Radio, also abbreviated as 5G, downlink (DL) signals and uplink (UL) signals carry data signals, DL control information (DCI) and / or uplink control information (UCI), control signals, and several reference signals (RS) used for different purposes. A wireless network node, or a radio base station, or a g-node B (or gNB or gNB / TRP (Transmit Reception Point)) transmits data and DCI through a so-called physical downlink shared channel (PDSCH) and a physical downlink control channel (PDCCH), respectively.

[0003] The UE transmits data and UCI through the so-called physical uplink shared channel (PUSCH) and physical uplink control channel (PUCCH), respectively. Further, the DL or UL signals of the gNB, i.e., the user equipment (UE or radio device), may each include one or more types of RS including channel state information RS (CSI-RS), demodulation RS (DM-RS), and sounding RS (SRS). The CSI-RS (SRS) is transmitted in the DL (UL) system bandwidth part and is used at the UE (gNB) for CSI acquisition. The DM-RS is transmitted only in the bandwidth part of each PDSCH / PUSCH and is used by the UE / gNB for data demodulation.

[0004] One of the many key features of 5G is the use of the multi-input multi-output (MIMO) transmission method to achieve high system throughput compared to previous-generation mobile systems. In MIMO transmission, generally, the availability of accurate CSI used at the gNB is required to precode signals using a precoding matrix for data and control information. Therefore, the current 3rd Generation Partnership Project Release 15 specification (3GPP Release 15) provides a comprehensive framework for CSI reporting. CSI is obtained at the UE in a first step based on the received CSI-RS signal transmitted by the gNB. In a second step, the UE determines a precoding matrix from a predefined set of matrices called a "codebook" based on the estimated channel matrix. In a third step, the selected precoding matrix is reported to the gNB in the form of a precoding matrix identifier (PMI) and a rank identifier (RI).

[0005] Dual-stage Precoding and CSI Reporting in 3GPP Release 15 In the current Release 15 NR specification, there are two types (Type I and Type II) of CSI reports, both of which rely on dual-stage, i.e., a two-component W1W2 codebook. The first component, i.e., the first-stage precoder W1, is used to select the number of beam vectors and, if set, the rotation oversampling factors from a Discrete Fourier Transform-based (DFT-based) matrix also called a spatial codebook. The spatial codebook includes a DFT or oversampled DFT matrix of dimension N1N2×N1O1N2O2, where O1 and O2 indicate the oversampling factors for 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 subgroups, where each subgroup contains N1N2 DFT vectors and the parameters q1 and q2 are indicated as rotation oversampling factors. The second component, the so-called second-stage precoder W2, is used for combining the selected beam vectors.

[0006] Assuming rank-R transmission and a dual-polarized antenna array in a gNB with configuration (N1,N2,2), for the s-th subband and the r-th transmission layer, the Release 15 double-stage precoder disclosed in [1] (Non-Patent Document 1) is

[0007]

Equation

[0008] given by, and the precoder matrix W (r) (s) has 2N1N2 rows corresponding to the number of antenna ports and S columns for the reporting subband / PRB. The matrix

[0009]

Number

[0010] is a wideband first-stage precoder that includes 2U spatial beams in both polarization states that are identical across all S subbands, and F A is a diagonal matrix that includes 2U wideband amplitudes associated with the 2U spatial beams,

[0011]

Number

[0012] is a second-stage precoder that includes 2U subbands, subband amplitudes and phases, and complex frequency-domain coupling coefficients associated with the 2U spatial beams in the s-th subband. In the dual-stage type II CSI report of 3GPP Release 15, the second-stage precoder W2 is

[0013]

Number

[0014] The number of columns is calculated on a sub-band basis such that it depends on the number of configured sub-bands. Here, a sub-band refers to a group of adjacent physical resource blocks (PRBs). One of the main drawbacks of type II CSI feedback is the large feedback overhead for reporting the coupling coefficients on a sub-band basis. The feedback overhead increases approximately linearly with the number of sub-bands and becomes quite large when there are a large number of sub-bands. To address the high feedback overhead of the release 15 type II CSI reporting method, recently, in 3GPP RAN#81 [2] (Non-Patent Document 2) (3GPP Radio Access Network (RAN) 3GPP RAN#81), it was decided to study a feedback compression method for the second-stage precoder W2. Some contributions [3] and [4] (Non-Patent Documents 3, 4) have demonstrated that when converting W2 using a small set of DFT basis vectors to the delay domain, the number of beam coupling coefficients in W2 can be dramatically reduced. The corresponding three-stage precoder has three stages, i.e., three components

[0015]

Number

[0016] relies on a codebook. The first component represented by the matrix W1 is the same as that of release 15 NR, is independent of the layer (r), and includes several spatial domain (SD) basis vectors selected from a spatial codebook. The matrix W3 (r) The second component represented by is layer-dependent and is used to select several delay domain (DD) basis vectors from a discrete Fourier transform-based (DFT-based) matrix, also called a delay codebook. The matrix W2 (r)The third component represented by is layer-dependent and includes the number of coupling coefficients used to combine the SD basis vector and the DD basis vector respectively selected from the spatial and delay codebooks.

[0017] Assuming rank R transmission, the three-component precoder matrix or CSI matrix of the antenna / DL-RS port with a 2N1N2 configuration and the subband with an N3 configuration is for the first polarization of the antenna port and the r-th transmission layer

[0018]

Number

[0019] is represented as, and for the second polarization of the antenna port and the r-th transmission layer

[0020]

Number

[0021] is represented as, where b u =(u = 0, ···, U - 1) represents the u-th SD basis vector selected from the spatial codebook,

[0022]

Number

[0023] is the d-th DD basis vector associated with the r-th layer selected from the delay codebook, and γ (p,u,d) (r) is the complex delay-domain coupling coefficient associated with the u-th SD basis vector, the d-th DD basis vector, and the p-th polarization. U represents the number of set SD basis vectors, D represents the number of set DD basis vectors, and α (l,p) is a normalization scalar.

[0024] The main advantage of the three-component CSI reporting method in Equation (2) is that the feedback overhead for reporting the precoder matrix or the coupling coefficients of the CSI matrix no longer depends on the number of frequency-domain subbands to be set, that is, it is independent of the system bandwidth. Furthermore, the feedback overhead and performance of the precoder matrix or the CSI matrix can be included for each layer or for all layers in the third component W2 (r) and can be controlled by the gNB by setting the maximum number of non-zero coupling coefficients K reported by the UE. Since only the amplitude and phase information of the non-zero coupling coefficients are reported, an indicator such as a bitmap is required to indicate which of the 2UD coefficients for each layer is selected and reported by the UE. According to [5] (Non-Patent Document 5), the selected non-zero coefficients of the r-th layer are indicated by a bitmap, where each bit in the bitmap is associated with the polarization index (p ∈ {1, 2}), the SD basis index (0 ≤ u ≤ U - 1), and the DD basis index (0 ≤ d ≤ D - 1). A "1" in the bitmap indicates that the coupling coefficient associated with the polarization index p, the SD basis index u, and the DD basis index is non-zero and is selected and reported by the UE. A "0" in the bitmap indicates that the coupling coefficient associated with the polarization index p, the SD basis vector u, and the DD basis index d is zero, and thus is a coupling coefficient not reported by the UE.

[0025] According to [6] (Non-Patent Document 6), the strongest coupling coefficient for each layer is normalized to 1 and not reported. To indicate which of the 2UD coefficients of the layer is the strongest coupling coefficient, a strongest coefficient indicator (SCI) is reported by the UE for each layer.

[0026] According to [6] (Non-Patent Document 6), the non-zero coupling coefficient γ (p,u,d) (r) (included in W2 (r) ) is as follows:

[0027] [Number]

[0028] is quantized as, where the amplitude γ of the coupling coefficient (p,u,d) (r) is given by two amplitudes, namely P ref (r,p) and a (p,u,d) (r) by the first and second amplitudes respectively indicated by. Here, P ref (r,p) represents the polarization reference amplitude defined for each polarization common to all amplitude values associated with the polarization p (p = 1, 2). In the polarization index of U, the SD component associated with SCI(P ref (r,p) = 1) is not reported. The polarization reference amplitudes associated with other polarizations P ref (p’) , p’≠p are quantized using a’ bits. In addition, the amplitude a (p,u,d) (r) of each coupling coefficient γ (p,u,d) (r) and the phase θ (p,u,d) (r) are quantized using a bits and b bits respectively.

[0029] Configuration and Reporting of 3-Component CSI Scheme Regarding the configuration of the precoder matrix or CSI matrix, the CSI report configuration can be signaled from the gNB to the UE via the upper layer (e.g., RRC), and the upper layer CSI report configuration may include the following information [7] (Non-Patent Document 7): - Parameter U indicating the number of SD basis vectors to be selected by the UE from the spatial codebook for the calculation of W1, - W3 (r) Parameter D or its variants indicating the number of DD basis vectors to be selected by the UE layer by layer from the delay codebook for the calculation of, - Matrix W2 layer by layer or for all layers (r)A parameter K or a variant thereof that indicates the maximum number of non-zero coefficients used by the UE to combine the selected SD basis vectors and DD basis vectors included in - A parameter N3 indicating the number of frequency domain sub-bands of the CSI matrix and the dimension of the DD basis vectors in the delay codebook, and - Additional parameters for the reporting configuration of the DD basis vectors.

[0030] The CSI report may include at least a rank indicator (RI) indicating the selected number of layers of the CSI matrix, the selected number of non-zero coupling coefficients over all layers K NZ and a PMI that defines three components of the CSI matrix. The PMI may include at least the following information [7] (Non-Patent Document 7): - U SD basis vectors selected from the spatial codebook of the RI layer of the CSI matrix, and a spatial domain subset indicator (SD basis indicator) indicating the selected oversampling rotation factors, if set, - A delay domain subset indicator (DD basis indicator) indicating the selected DD basis vectors for each layer, - A strongest coefficient indicator (SCI) for each layer indicating the SD basis index or SD and DD basis indices associated with the strongest coupling coefficient that is not reported, - For each layer, K NZ,r Amplitude and phase information associated with the selected non-zero quantized delay domain coupling coefficients for each layer, - For each layer, K NZ,r A bitmap for each layer indicating the SD basis index and DD basis index associated with the non-zero coefficients for each layer, - The polarization eigenbasis amplitude for each layer, and - Additional parameters that may be associated with the DD base subset indication.

[0031] UCI Omission in CSI Reports of 3GPP Release 15 PUSCH - based resource allocation and UCI omission in CSI reports [1] (Non - Patent Document 1) were introduced in 3GPP Release 15. Thereby, when the PUSCH resource allocation is not sufficient to carry the entire content of the CSI report, the UE can drop some parts of one or more CSI reports. UCI omission can occur when the base station does not allocate the PUSCH resources accurately at the time of scheduling the CSI report. For example, the base station may allocate resources to a rank - 1 (RI = 1) CSI report, but the UE determines a rank - 2 transmission and reports a rank - 2 (RI = 2) CSI report with a size larger than the size of the allocated PUSCH resources. In such a case, the UE needs to drop some of the UCI content. In 3GPP Release 15, the drop is achieved by decomposing the UCI payload associated with the CSI report into smaller multiple parts, so - called multiple priority levels. See Table 5.2.3 - 1 in [1] (Non - Patent Document 1). In this table, priority level 0 has the highest priority, and N REP represents the total number of CSI reports configured to be carried on the PUSCH. Each priority level is associated with a part of the CSI report. The UE drops the CSI parts with lower priority so that the payload size of the CSI report matches the PUSCH resource allocation. Further, the CSI payload is divided into two parts: CSI part 1 and CSI part 2. CSI part 1 includes the RI and an indicator indicating the size of CSI part 2. The size of CSI part 1 is fixed, while the size of CSI part 2 varies depending on the RI determined by the UE and some other factors. Since the gNB needs to know CSI part 1 to decode CSI part 2, UCI omission is performed only for CSI part 2.

[0032] CSI part 2 is 2N REPIt is created by +1 CSI part. Here, 2N REP CSI parts, so-called sub-band PMI, are N REP CSI content associated with the even and odd sub-bands of N CSI reports. Further, each sub-band PMI is associated with priority levels starting from index 1 to 2N REP up to. In addition, the first CSI part associated with priority level index 0 contains all 2N REP sub-band PMIs, that is, information on the entire CSI reporting band. The motivation behind the sub-band-based CSI decomposition and omission method in Release 15 is that when the gNB omits the first sub-band PMI of CSI report n, the gNB can use the CSI content of the reported second sub-band PMI of CSI report n and estimate the CSI of the omitted first sub-band PMI by using an interpolation method. In this way, since adjacent sub-bands are typically highly correlated, a significant degradation in performance can be avoided.

Prior Art Documents

Non-Patent Documents

[0033]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Summary of the Invention

Means for Solving the Problems

[0034] Regarding the known three-component CSI reporting scheme, there is no sub-band based PMI, and it is not possible to decompose CSI part 2 into several sub-band PMIs. Therefore, the UCI omission procedure of 3GPP Release 15 cannot be reused. Thus, new UCI omission rules are required.

[0035] In addition, in the three-component CSI reporting method, the CSI payload of the CSI report can be controlled by the UE according to the number of non-zero coefficients to be reported. In the case of UCI omission, the UE can simply reduce the number of non-zero coefficients to be reported in one or more of the CSI reports based on the available PUSCH resources. However, to reduce the number of non-zero coupling coefficients, it is necessary to recalculate the coupling coefficients, the SD and DD basis vectors of the CSI matrix of one or more CSI reports, which occupies additional UE resources. Such additional UE resources are not available in the UE. Therefore, the UCI omission method should not require the recalculation of the CSI matrix of one or more CSI reports.

[0036] In the three-component CSI reporting method, the size of the payload of the CSI report is mainly determined by the bitmap of the non-zero coupling coefficients reported in the CSI report and the amplitude and phase information.

[0037] In the present invention, different segmentation methods for the bitmap of the non-zero coupling coefficients reported in the CSI report and the amplitude and phase information in the three-component CSI reporting method are proposed. In one solution of the present invention, the UCI omission method is based on dropping a part of the amplitude and phase information of the non-zero coupling coefficients of the CSI report.

[0038] In another solution of the present invention, the UCI omission method is based on dropping a part of the amplitude and / or phase information of the non-zero coupling coefficients and a part of the bitmap associated with the dropped coupling coefficients.

[0039] The present invention provides a method executed by a user equipment (UE) that provides CSI feedback in the form of one or more channel state information (CSI) reports in a wireless communication system. The method includes - Receiving, from a network node (gNB) via a MIMO channel, the higher layer configuration of one or more downlink reference signals, one or more CSI report configurations associated with the configuration of the downlink reference signals, and a radio signal, the radio signal including a downlink reference signal according to the configuration of the one or more downlink reference signals, - Estimating a downlink MIMO channel based on measurements on the received one or more downlink reference signals, the downlink reference signals being supplied via a set number of frequency domain resources, time domain resources, and one or more ports, - For each CSI report configuration, based on the estimated channel matrix and two codebooks, - A spatial codebook including one or more spatial domain (SD) basis components of a precoder, and - A delay codebook including one or more delay domain (DD) basis components of a precoder, two codebooks, and one or more non-zero coupling coefficients for complex coupling of one or more SD and DD basis vectors, determining a precoding matrix, - Reporting to the network node one or more CSI reports of one or more CSI report configurations.

[0040] Each CSI report includes a selected precoding matrix in the form of a precoding matrix identifier (PMI) and a rank identifier (RI), the rank identifier (RI) indicating the transmission rank of the RI layer of the precoding matrix, each CSI report including two parts, CSI part 1 and CSI part 2, CSI part 1 having a fixed payload size and CSI part 2 including information indicating the size of the payload of CSI part 2. CSI part 2 includes at least the amplitude and phase information of the selected non-zero coupling coefficients of the CSI report, and part or all of CSI part 2 is available for omission from the CSI report.

[0041] According to one proposed aspect of the present invention, the CSI part 1 includes at least information about a selected number of non-zero coupling coefficients across all RI layers and an indication of the transmission rank of the RI layer of the selected precoding matrix.

[0042] The CSI part 2 includes at least the following information about the RI layer of the selected precoding matrix: - When a rotation oversampling factor indicating a selected SD basis vector from the spatial codebook is set, a spatial region (SD) basis subset indicator including the rotation oversampling factor, - One or more delay region (DD) basis subset indicators indicating selected DD basis vectors from the delay codebook, - The phase and amplitude of the selected non-zero delay region coupling coefficients, - A strongest coefficient indicator SCI indicating the DD and SD vectors associated with the strongest coefficient per layer, - The polarization reference amplitude per layer, - A bitmap indicating the non-zero coupling coefficients per layer, and - Additional possible parameters associated with the DD basis subset indication It is also proposed to include.

[0043] A particular aspect of the present invention is that the part 2 of N REP CSI reports can be segmented into TN REP CSI subgroups, and it is taught that the T CSI subgroups are always associated with a single CSI report, and each CSI subgroup is associated with a priority, i.e., a priority level.

[0044] Another aspect of the present invention is that the part 2 of N REP CSI reports can be segmented into TN REP +1 CSI subgroups, the T CSI subgroups are always associated with a single CSI report, and one CSI subgroup is all N REPincluding information associated with individual CSI reports, where each CSI subgroup is associated with a priority, i.e., a priority level, and all N REP teaches that CSI subgroups including information associated with the N reports have the highest priority, i.e., a priority level of "0".

[0045] It is proposed that in case of omission, the UE may drop CSI subgroups with lower priority until the payload size of the CSI report matches the resource allocation from the gNB. When omitting a CSI subgroup of a specific priority level, the UE may omit all CSI content of that priority level.

[0046] The parameter T may indicate the number of CSI subgroups per CSI report, may be related to the granularity of the CSI content omitted from the CSI report, where a high value of T indicates high granularity and a low value of T indicates low granularity, and when the parameter T is given a value of "2", each CSI report is associated with only two CSI subgroups.

[0047] The parameter T may depend on the information content included in the CSI report in the following cases: The parameter T may depend on the RI value indicated in the CSI report, where when the RI value indicated in the CSI report is greater than a specific threshold, T = 2, and when the RI value of the CSI report is less than the specific threshold, T = 1, or The parameter T depends on the non-zero coefficient number number K NZ indicated in the CSI report, where when the number of non-zero coefficients indicated in the CSI report is greater than a specific threshold as

[0048]

Number

[0049] such, T = 2, and in other cases, T = 1. One proposed aspect of the present invention is that the first CSI subgroup associated with priority level 0 includes the CSI information of all N REP CSI reports, and the joint CSI subgroup includes the following parameters: - When the rotational oversampling factor is set, the selected SD basis subset indicator including the rotational oversampling factor and - The SCI of the RI layer is taught to include at least one piece of information.

[0050] The CSI subgroup with the highest priority of the CSI report includes at least the following parameters: - The selected DD basis subset indicator of the RI layer, - The polarization reference amplitude value of the RI layer, - K of the RI layer NZ a bitmap indicating non-zero coupling coefficients, and - Additional possible parameters associated with the DD basis subset indication is also proposed to be included.

[0051] Also, the CSI subgroup with the highest priority of the CSI report includes at least the following parameters: - The selected DD basis subset indicator of the RI layer, - The polarization reference amplitude value of the RI layer, - K of the RI layer NZ a bitmap indicating non-zero coupling coefficients, and - The window parameter M init is also proposed to be included.

[0052] Each CSI subgroup including information on a part of the coupling coefficients is the CSI report of

[0053]

Number

[0054] It is proposed that the amplitude value associated with the maximum of the individual coupling coefficients, or the phase and amplitude values, may be included, and the remaining CSI subgroups with lower priority may include the remaining amplitude values of the CSI report, or the remaining phase and amplitude values.

[0055] Each CSI subgroup having the highest priority and associated with a single CSI report may include at least a bitmap associated with all SD components of one or more DD basis vectors or one or more DD basis vector indices for the RI layer of the precoding matrix indicated in the CSI report, and the CSI subgroup may include the corresponding amplitude and / or phase information of the coupling coefficients associated with the bitmap.

[0056] Another aspect of the present invention teaches that the bitmap and coupling coefficient information for the RI layer of the CSI report are segmented into D segments, where each segment includes a sub-bitmap associated with all SD components of a single DD basis index of all RI layers of the precoding matrix, and the CSI subgroup having the highest priority and associated with a single CSI report includes one or more of the D segments.

[0057] Here, it is proposed that each segment may include the associated amplitude and / or phase information of the coupling coefficients for the RI layer associated with the sub-bitmap. The CSI subgroup associated with the highest priority of the CSI report may include at least a bitmap indicating non-zero coupling coefficients for a first subset of the RI layer, associated with the first subset of the RI layer of the precoding matrix indicated in the CSI report, and a first portion of the amplitude and phase values of the selected non-zero delay region coupling coefficients.

[0058] N REPIt is proposed that a CSI subgroup including CSI information associated with a CSI report may include, for one or more CSI reports, SCI for the RI layer, a part of the bitmap, and the amplitude and / or phase information of the combined coefficients associated with all SD components and DD basis vector index 0 for the RI layer of each CSI report.

[0059] If the bitmap of all RI layers of size 2UD×RI associated with a single CSI report is included in a single CSI subgroup, the bitmap is segmented into RI segments, each of 2UD bits is in ascending order with respect to the number of layers, and it is proposed that each segment is associated with all SD and DD basis indices of the layer.

[0060] If a CSI subgroup includes the bitmap of all RI layers, the bitmap of size 2UD×RI is segmented into D segments, each segment has size 2U×RI and is associated with a single DD basis vector index. Each segment of size 2U×RI is further segmented into RI segments, each segment has size 2U×1 and is also proposed to be associated with a single DD basis vector index and a single layer index.

[0061] It is proposed that each CSI subgroup includes the amplitude and / or phase information of the combined coefficients associated with a part of the bitmap of the RI layer or a part of the bitmap of D segments.

[0062] The bit width of a single CSI report and the CSI subgroup associated with the highest priority may be fixed and given by A + B, where A is the combined bit width of all components included in the CSI subgroup away from the number of non-zero combined coefficients, and B is the combined coefficient

[0063]

Number

[0064] It is a bit width associated with the amplitude information (a) and phase information (b) of a part of The present invention also relates to a method performed by a network node (gNB) that receives CSI feedback in the form of one or more channel state information (CSI) reports in a wireless communication system. The method includes: - Transmitting to a user equipment (UE) via a MIMO channel one or more downlink reference signal upper layer configurations, one or more CSI report configurations associated with the downlink reference signal configuration, and a wireless signal, the wireless signal including a downlink reference signal according to the downlink reference signal configuration; - Receiving from the UE one or more CSI reports of one or more CSI report configurations, the one or more CSI reports being generated by the UE by: - Estimating a downlink MIMO channel based on measurements on the received one or more downlink reference signals, the downlink reference signals being provided via a set number of frequency domain resources, time domain resources, and one or more ports; - For each CSI report, determining a precoding matrix based on the estimated channel, two codebooks including: - A spatial codebook including one or more spatial domain (SD) basis components of a precoder; and - A delay codebook including one or more delay domain (DD) basis components of a precoder, and one or more non-zero coupling coefficients that complexly couple one or more SD and DD basis vectors. Each CSI report includes a selected precoding matrix in the form of a precoding matrix identifier (PMI) and a rank identifier (RI). The rank identifier (RI) indicates the transmission rank of the RI layer of the precoding matrix. Each CSI report includes two parts: CSI part 1 and CSI part 2. Part 1 has a fixed payload size, and part 2 includes information indicating the size of the payload of part 2. Part 2 includes at least the amplitude and phase information of the selected non-zero coupling coefficients of the CSI report. Part or all of part 2 is available for omission from the CSI report.

[0065] The present invention also relates to a user equipment (UE) comprising a processor and a memory. The memory includes computer program code executable by the processor, whereby the UE is operable to perform any one of the subject matters of the method of the present invention executed by the UE.

[0066] The present invention also relates to a network node comprising a processor and a memory. The memory includes computer program code executable by the processor, whereby the network node is operable to perform any one of the subject matters of the method of the present invention executed by the network node.

[0067] The present invention also relates to a computer program product comprising computer program code. When the computer program code is executed by a processor, the processor can perform any one of the subject matters of the method of the present invention executed by the UE.

[0068] The present invention also relates to a computer program product comprising computer program code. When the computer program code is executed by a processor, the processor can perform any one of the subject matters of the method of the present invention executed by the network node.

[0069] The present invention provides a method for implementing a new UCI omission rule that enables a UE using a known three-component CSI reporting method to utilize an omission procedure without having to recalculate the coupling coefficients of the CSI matrix, SD, and DD basis vectors of one or more CSI reports.

[0070] Examples of embodiments and advantages of the embodiments in this specification will be described in more detail with reference to the accompanying drawings.

Brief Description of the Drawings

[0071]

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DETAILED DESCRIPTION OF THE INVENTION

[0072] Hereinafter, in conjunction with the drawings, detailed descriptions of exemplary embodiments in several scenarios are presented to make it easier to understand the solutions described in this specification. As described above, in the new radio system of 3GPP, the UCI omission procedure was standardized in Release 15. Since the omission procedure does not have a sub-band-based PMI and it is not possible to decompose CSI part 2 into several sub-band PMIs, it cannot be reused. Therefore, a new UCI omission rule is required.

[0073] FIG. 1 is a simplified diagram of a method executed by a user equipment (UE) and a radio base station (gNB) to provide CSI feedback in the form of a channel state information (CSI) report in a radio communication system A. The method includes - Receiving, from a network node (gNB) via a MIMO channel, a higher layer configuration of one or more downlink reference signals, one or more CSI report configurations associated with the configuration of the downlink reference signals, and a radio signal, the radio signal including a downlink reference signal according to the configuration of the one or more downlink reference signals, - Estimating a downlink MIMO channel based on measurements on the received one or more downlink reference signals, the downlink reference signals being supplied via a set number of frequency domain resources, time domain resources, and one or more ports, - For each CSI report configuration, based on the estimated channel matrix and two codebooks, - A spatial codebook including one or more spatial domain (SD) basis components of a precoder, and - A delay codebook including one or more delay domain (DD) basis components of a precoder, determining a precoding matrix based on the two codebooks and one or more non-zero coupling coefficients that complexly combine one or more SD and DD basis vectors, - Reporting to the network node one or more CSI reports of one or more CSI report configurations.

[0074] Each CSI report includes a selected precoding matrix in the form of a precoding matrix identifier (PMI) and a rank identifier (RI) indicating the transmission rank of the RI layer of the precoding matrix. Each CSI report includes two parts: a CSI part 1 and a CSI part 2. CSI part 1 has a fixed payload size and includes information indicating the size of the payload of CSI part 2. CSI part 2 includes at least the amplitude and phase information of the selected non-zero coupling coefficients of the CSI report, and part or all of CSI part 2 is available for omission from the CSI report.

[0075] According to one embodiment, the UE is configured with N CSI reports to be carried on the PUSCH, and each CSI report may include two parts: CSI part 1 and CSI part 2. CSI part 1 has a fixed payload size and is used to indicate the size of the payload of CSI part 2. CSI part 1 may include at least information about the number of coupling coefficients across all layers and the transmission rank (RI) of the RI layer of the selected precoding matrix. The CSI part 2 of the CSI report may include at least the following information about the RI layer of the CSI matrix selected for the configured antenna port and subband: REP - (if configured) a selected SD basis subset indicator including a rotation oversampling factor, - a selected DD basis subset indicator for each layer, - the phase and amplitude of the selected non-zero delay region coupling coefficients for each layer, - a strongest coefficient indicator (SCI) for each layer, - the polarization reference amplitude for each layer, - a bitmap indicating non-zero coupling coefficients for each layer, and - additional possible parameters associated with the DD basis subset indication. - DD basis subset indication and associated additional possible parameters.

[0076] Decomposition for CSI part 2 - Method 1 According to an embodiment, in the first decomposition method (Method 1), the CSI part 2 of the N CSI reports may be segmented into N CSI subgroups, and the T CSI subgroups are always associated with a single CSI report. Further, each CSI subgroup is associated with a priority level, and the first subgroup has the highest priority level 0. The remaining T N - 1 CSI subgroups have lower priority levels from 1 to T N - 1. REP The CSI part 2 of the N CSI reports can be segmented into N CSI subgroups, and the T CSI subgroups are always associated with a single CSI report. Further, each CSI subgroup is associated with a priority level, and the first subgroup has the highest priority level 0. The remaining T N REP - 1 CSI subgroups have lower priority levels from 1 to T N REP - 1, REPis associated with up to -1. The last CSI subgroup TN REP -1 is the lowest priority level TN REP can be associated with -1.

[0077] Figure 2 shows a first example of Method 1. In Figure 2, the priority levels range from (t - 1)N REP to tN REP -1 (1 ≤ t ≤ T), and the N REP CSI subgroups associated with N REP CSI reports are always grouped together.

[0078] Figure 3 shows a second example of Method 1. In Figure 3, the priority levels range from (n - 1)T to nT - t (1 ≤ n ≤ N REP ), and the T CSI subgroups associated with a single CSI report are always grouped together.

[0079] The parameter T indicates the number of CSI subgroups per CSI report and is related to the granularity of the CSI content omitted from the CSI report. A high value of T indicates high granularity, and a low value of T indicates low granularity. When the value of the parameter T is given as "2", each CSI report is associated with only two CSI subgroups.

[0080] The parameter T indicating the number of CSI subgroups per CSI report can also depend on the CSI report. In one example, the parameter T can depend on the rank indicated in the CSI report. For example, when the rank indicated in the CSI report is greater than 1 (RI > 1), T = 2, and when the rank indicated in the CSI report is 1 (RI = 1), T = 1. In another example, the parameter T can depend on the non - zero number coefficient K NZ indicated in the CSI report. For example, when the number of non - zero coefficients indicated in the CSI report is greater than a specific threshold, i.e.,

[0081]

Number

[0082] If it is the case, T = 2, and in other cases, T = 1. All of the first CSI subgroup for all N REP In contrast to the Release 15 CSI decomposition where the first CSI subgroup contains information for all N CSI reports, each subgroup in the proposed decomposition contains only information associated with a single CSI report.

[0083] In the case of UCI omission, the UE drops the lower-priority CSI subgroups until the payload size of the CSI report matches the PUSCH resource allocation. When omitting a CSI subgroup of a specific priority level, the UE omits all CSI content of that priority level.

[0084] Decomposition of CSI Part 2 - Method 2 The drawback of the above CSI decomposition method 1 shown in FIGS. 2 and 3 is that when all CSI subgroups associated with a single CSI report are dropped, the complete CSI report is dropped. To avoid a complete drop of the CSI content of a CSI report, the following embodiment enables the gNB to partially recompute the CSI matrix of all N CSI subgroups even if all CSI subgroups except the first CSI subgroup having the highest priority level 0 are dropped by the UE. REP A CSI decomposition is proposed that enables the gNB to partially recompute the CSI matrix of all N CSI subgroups even if all CSI subgroups except the first CSI subgroup having the highest priority level 0 are dropped by the UE.

[0085] According to an embodiment, REP CSI Part 2 of N CSI reports can be segmented into TN REP +1 CSI subgroups, where T CSI subgroups are always associated with a CSI report. The first subgroup of CSI contains information associated with all N REP CSI reports.

[0086] Each CSI subgroup is associated with a priority level, and the first subgroup has the highest priority level 0. The remaining TN REP CSI subgroups are associated with lower priority levels from 1 to TN REP to TN REP and the last CSI subgroup TN REP is associated with the lowest priority level TN

[0087] Parameter T indicates the number of CSI subgroups per CSI report and is related to the granularity of the CSI content omitted from the CSI report. A high value of T indicates high granularity, and a low value of T indicates low granularity. When the value 2 is given to parameter T, each CSI report is associated with only two CSI subgroups.

[0088] Parameter T, which indicates the number of CSI subgroups per CSI report, can also depend on the CSI report. In one example, parameter T can depend on the rank indicated in the CSI report. For example, when the rank indicated in the CSI report is greater than 1, i.e., RI > 1, T = 2, and when the rank indicated in the CSI report is 1, i.e., RI = 1, T = 1. In another example, parameter T can depend on the number of non-zero coefficients K NZ indicated in the CSI report. For example, when the number of non-zero coefficients indicated in the CSI report is greater than a specific threshold, i.e.,

[0089]

Number

[0090] then T = 2, and in other cases, T = 1. In the case of UCI omission, the UE drops the lower-priority CSI subgroups until the payload size of the CSI report matches the PUSCH resource allocation. When omitting a CSI subgroup of a specific priority level, the UE omits all CSI content of that priority level.

[0091] FIG. 4 shows a first example of Method 2, having priority levels (n - 1)T + 1 to nT (1 ≦ n ≦ N REP ), and the T CSI subgroups associated with a single CSI report are always grouped together.

[0092] FIG. 5 shows a second example of Method 2, in which, in FIG. 5, the priority levels are (t - 1)N REP + 1 to tN REP (1 ≦ t ≦ T), and the N REP CSI subgroups associated with N REP CSI reports are always grouped together.

[0093] Contents of CSI Subgroups According to an embodiment, if the first CSI subgroup (associated with the highest priority level 0) contains CSI information for all N REP CSI reports, the joint CSI subgroup may include at least one of the following parameters: - A selected SD basis subset indicator including a rotation oversampling factor, if set, - A selected DD basis subset indicator for the RI layer, - SCI for the RI layer, - Polarization reference amplitude value for the RI layer, - K for the RI layer NZ - A bitmap indicating K non - zero coupling coefficients for the RI layer,

[0094] For the segmentation of the phase and amplitude values of the N REP CSI reports in Method 2, two segmentation methods are proposed below. In the first method, N REPThe first part of the phase and amplitude values of the selected non-zero delay region coupling coefficients of the CSI reports is included in the first joint CSI subgroup with the highest priority. An example of the CSI content of the first joint CSI subgroup related to the first method and the CSI subgroup associated with a single CSI report with the highest priority is shown in FIG. 6.

[0095] In the second method, the first CSI subgroup with the highest priority does not include any phase and amplitude values of the selected non-zero delay region coupling coefficients of the N REP CSI reports, and only the remaining CSI subgroups contain information on non-zero coupling coefficients. An example of the CSI content of the first joint CSI subgroup related to the second method and the CSI subgroup associated with a single CSI report is shown in FIG. 7.

[0096] In addition, depending on the CSI content of the first joint CSI subgroup with priority level 0, each CSI subgroup with the highest priority and associated with a single CSI report may include the following parameters if not already listed in the first joint CSI subgroup: - The selected DD basis subset indicator of the RI layer, - The SCI of the RI layer, - The polarization reference amplitude value of the RI layer, - K of the RI layer NZ A bitmap indicating the N non-zero coupling coefficients, and - Additional possible parameters associated with the DD basis subset indication.

[0097] For the UE regarding decomposition method 1, N REPconfigured to split the CSI payload of a CSI report, and if the UE drops CSI sub-groups up to T-1 associated with a single CSI report, the gNB should still be able to recalculate the part of the CSI matrix at the RI layer based on the remaining non-dropped CSI sub-groups associated with that CSI report. In this way, even if most of the CSI content of the CSI report is dropped, a specific minimum performance can be guaranteed. To recalculate a part of the CSI matrix from the CSI report, the gNB obtains from the CSI report the selected SD and DD basis subset indicators, SCI, bitmap, and the polarization reference amplitude value and window parameter M at the RI layer init etc. It is necessary to know at least some of the parameters. This information must be included in each CSI report in the CSI sub-group with the highest priority.

[0098] According to an embodiment, N REP If the CSI payload including the CSI information of N CSI reports is split into several CSI sub-groups, and each CSI sub-group includes CSI information associated with only a single CSI report, the CSI sub-group with the highest priority of the CSI report may include at least the following parameter information: - The selected SD basis subset indicator including the rotation oversampling factor, if configured, - The selected DD basis subset indicator at the RI layer, - The SCI at the RI layer, - The polarization reference amplitude value at the RI layer, - K at the RI layer NZ A bitmap indicating the non-zero coupling coefficients of K, - Additional possible parameters associated with the DD basis subset indication.

[0099] To split the amplitude and phase values into CSI subgroups, several methods are proposed as follows. In the first method, for each CSI report, the CSI subgroup with the highest priority contains no information of any selected non-zero coupling coefficients, and only the remaining T-1 CSI subgroups with lower priority contain the amplitude and phase values of the selected non-zero coupling coefficients of the CSI report. In the second method, for each CSI report, the CSI subgroup with the highest priority may contain information of the first part of the amplitude values of the selected non-zero delay region coupling coefficients, and the remaining T-1 CSI subgroups with lower priority contain the remaining parts of the amplitude values and all phase values of the CSI report. In the third method, for each CSI report, the CSI subgroup with the highest priority may contain information of the first part of the amplitude and phase values of the selected non-zero delay region coupling coefficients, and the remaining T-1 CSI subgroups with lower priority contain the remaining parts of the amplitude and phase values of the CSI report.

[0100] FIG. 8 shows the CSI content of two CSI subgroups associated with a single CSI report and the corresponding CSI content of each CSI subgroup when splitting the amplitude and phase values for the third method.

[0101] In the case of UCI omission and CSI splitting shown in FIG. 2, the UE first drops the CSI subgroups containing CSI information related to the non-zero coupling coefficients. The remaining CSI subgroups still contain CSI content that can be used to partially recompute the CSI matrix indicated in the CSI report. Only when the UE drops all T CSI subgroups associated with a CSI report, the complete CSI report is dropped.

[0102] In the case of UCI omission and CSI splitting shown in FIG. 3, the UE first drops the CSI subgroups containing CSI information related to the non-zero delay region coupling coefficients of the CSI report with the lowest priority. When the UE drops all T CSI subgroups associated with the CSI report with the lowest priority, the complete CSI report is dropped.

[0103] According to an embodiment, each CSI subgroup including information on the coupling coefficient part may include an amplitude value or a phase and an amplitude value associated with up to

[0104]

Number

[0105] the number of coupling coefficients. The remaining CSI subgroups with lower priority may include the remaining amplitude values or the remaining phase and amplitude values of the CSI report.

[0106] For example, when T = 2 and x = 2, the phase and amplitude values of the coupling coefficients are segmented into two CSI subgroups. The first CSI subgroup includes

[0107]

Number

[0108] the phase and amplitude values associated with the number of coupling coefficients, and the second CSI subgroup includes the remaining

[0109]

Number

[0110] phase and amplitude associated with the number of coupling coefficients. Bitmap and Segmentation of Coupling Coefficients The payload of CSI part 2 is mainly determined by a bitmap and the phase and amplitude information of non-zero coupling coefficients.

[0111] In the proposed method 1, one or more bitmaps in the RI layer of the CSI report are included in the first CSI subgroup with the highest priority. Therefore, the payload size of this CSI subgroup can be larger than the payload sizes of other CSI subgroups. Due to the larger payload size, when the UCI omission rate is high, that is, when the UE has to drop most of the content of CSI part 2, the UE may, in some cases, drop the CSI subgroup including the bitmap and thus the complete CSI report.

[0112] Similarly, in the proposed method 2, all bitmaps in the RI layer of N REP CSI reports can be included in the first joint CSI subgroup, or can be included in the first CSI subgroup with the highest priority for each CSI report. The payload size of this / these CSI subgroup(s) can be large, and the UE may, in some cases, when the UCI omission rate is high, drop the CSI subgroup including the bitmap in the RI layer.

[0113] The following embodiments propose various methods to reduce the payload size of the CSI subgroup including the bitmap and thus reduce the probability of dropping this / these CSI subgroup(s) by splitting the bitmap and the phase and amplitude information of the combining coefficients into different CSI subgroups.

[0114] Segmentation regarding the DD basis subset The first segmentation method splits a plurality of bitmaps and a plurality of combining coefficients with respect to the number of DD basis vector indexes of the CSI report.

[0115] When the UE drops a CSI subgroup, the CSI content of the remaining CSI subgroups with higher priorities should enable the gNB to partially reconstruct the CSI matrix of the RI layer indicated in the CSI report. To do this, the gNB needs the knowledge of the SD and DD basis indices associated with the strongest coupling coefficients for each layer. This information can be obtained from the bitmap of the RI layer and the SCI. To correctly interpret the SCI, the first joint CSI subgroup or the first CSI subgroup associated with a single CSI report should include at least a part of the bitmap and the information of the coupling coefficients associated with the DD basis vector indices of the SCI of the RI layer.

[0116] According to one embodiment, each CSI subgroup having the highest priority and associated with a single CSI report may include at least a bitmap associated with all SD components of one or more DD basis vectors (or one or more DD basis vector indices) of the RI layer of the CSI matrix indicated in the CSI report. Additionally, the CSI subgroup may include the corresponding amplitude and / or phase information of the coupling coefficients of the RI layer of the CSI matrix.

[0117] The bitmap of the RI layer of the CSI subgroup and the corresponding amplitude and / or phase information of the coupling coefficients may be segmented into D' segments, where each segment includes one or more bitmaps of the RI layer associated with a single DD basis vector (or DD basis vector index) and the corresponding amplitude and / or phase information of the coupling coefficients. Here, D' ≤ D, and D indicates the number of DD basis vectors set for the UE for each of the RI layers of the CSI matrix.

[0118] When D' < D in the CSI subgroup, the CSI subgroups with lower priorities and / or the joint CSI subgroup if it exists may include the remaining segments associated with the remaining DD basis vectors (DD basis vector indices).

[0119] According to one embodiment, each CSI subgroup having the highest priority and associated with a single CSI report may include a part of the information of the combined coefficients associated with all SD components of the DD basis vector index associated with the bitmap and the SCI of the RI layer.

[0120] Example of segmentation According to one embodiment, the bitmap and amplitude and / or phase information included in the CSI subgroup are segmented into one or more segments, where each segment may include a sub-bitmap that is a part of the bitmap in each of the RI layers and the associated amplitude and / or phase information of the combined coefficients associated with the sub-bitmap.

[0121] In the configuration example of T = 2, the CSI contents of two CSI subgroups associated with a single CSI report are shown in FIG. 9. As observed from the figure, the sub-bitmap and the phase and amplitude information of the combined coefficients associated with all SD components and the DD basis vector index of the RI layer are always packed together in a single segment.

[0122] Note that the last segment of the CSI subgroup may include only a part of the sub-bitmap or only a part of the amplitude and / or phase information associated with the sub-bitmap. In such a case, the remaining part of the sub-bitmap not included in the CSI subgroup or the remaining part of the amplitude and / or phase information associated with the sub-bitmap may be included in a CSI subgroup with a lower priority of the same CSI report.

[0123] According to one embodiment, the bitmap and amplitude and / or phase information included in the CSI subgroup are segmented into one or more segments, where each segment may include a sub-bitmap that is a part of the bitmap in each of the RI layers and the associated amplitude and / or phase information of the combined coefficients associated with the sub-bitmap.

[0124] In one example, the k-th segment is further segmented into RI sub-segments, where each sub-segment includes a sub-bitmap associated with all SD components and DD basis vector indices of a single layer, and a coupling coefficient associated with the sub-bitmap. See Figure 10.

[0125] In one case, each sub-segment k associated with the r-th layer r can be further segmented into k r,2U sub-segments, as shown in Figure 11. Each k r,u sub-segment includes a single bit from the sub-bitmap and the corresponding amplitude and phase information of the coupling coefficient. Note that when k r,u is "0", sub-segment k r,u follows immediately after bit k r,u+1 . This is due to the absence of amplitude and phase information associated with bit k r,u .

[0126] According to one embodiment, the bitmap and coupling coefficient information of the RI layer of the CSI report are segmented into D segments, where each segment includes a bitmap, i.e., a sub-bitmap, associated with all SD components of a single DD basis index of all RI layers. In addition, each segment may include associated amplitude and / or phase information of the coupling coefficients of the RI layer associated with the sub-bitmap. A CSI subgroup having the highest priority and associated with a single CSI report may include one or more of the D segments.

[0127] Each CSI subgroup having the highest priority may further include a parameter set required from the CSI report such that the gNB can recalculate the CSI matrix based on a portion of the bitmap of the RI layer, and the amplitude and / or phase information of the coupling coefficients included in the CSI subgroup.

[0128] According to one embodiment, N REPThe CSI payload containing the CSI information of the CSI reports is decomposed into several CSI subgroups, each CSI subgroup containing CSI information associated with only a single CSI report. Additionally, if the UE is configured to perform segmentation of the bitmap and the amplitude and / or phase information of the combining coefficients into CSI subgroups with respect to the DD basis vector index, each CSI subgroup with the highest priority may additionally include at least the following parameters: - A selected SD basis subset indicator including a rotation oversampling factor, - A selected DD basis subset indicator for the RI layer, - The SCI of the RI layer, - The polarization reference amplitude value of the RI layer, - Additional possible parameters associated with the DD basis subset indication.

[0129] According to an embodiment, N REP The CSI payload containing the CSI information of the CSI reports is decomposed into several CSI subgroups. The first CSI subgroup contains CSI information associated with N REP CSI reports. Additionally, if the UE is configured to perform segmentation of the bitmap and the amplitude and / or phase information of the combining coefficients into CSI subgroups with respect to the DD basis vector index, the joint CSI subgroup may include at least the following parameters: - A selected SD basis subset indicator including a rotation oversampling factor (if configured), - A selected DD basis subset indicator for the RI layer, - The SCI of the RI layer, - The polarization reference amplitude value of the RI layer, - Additional possible parameters associated with the DD basis subset indication.

[0130] The remaining CSI subgroups include at least CSI content associated with the bitmap of the RI layer and phase and amplitude information of the coupling coefficients. Each CSI subgroup with the highest priority and associated with a single CSI report includes at least a portion of the bitmap of the RI layer and NZ phase and amplitude information of a portion of K

[0131] Depending on the structure of the joint CSI subgroup with priority level 0 which is the highest priority, each CSI subgroup associated with a single CSI report and having the highest priority may also include the following parameters if not already listed in the joint CSI subgroup: - Selected DD basis subset indicator of the RI layer, - SCI of the RI layer, - Polarization reference amplitude value of the RI layer, - Additional possible parameters associated with the DD basis subset indication.

[0132] If the UE is implemented to perform a cyclic shift operation on the selected DD basis vectors for each layer with respect to the DD basis vector index associated with the selected coupling coefficients and SCI, after the cyclic shift operation, only a portion of the bitmap associated with all SD basis vectors and the DD basis vector index 0 which is the first DD basis vector is required for each RI layer to identify the SD and DD basis indices associated with the strongest coupling coefficients. To correctly interpret the SCI, the first CSI subgroup should include the portion of the bitmap associated with the DD basis vector index 0 and the information of the coupling coefficients.

[0133] Note that the SCI is

[0134]

Number

[0135] When given by a bit indicator, the SCI may not be indicated by a sub-bitmap associated with the DD base vector index 0, and thus the per-layer sub-bitmap may have a size of 2U - 1×1 instead of 2U×1.

[0136] According to one embodiment, when the UE is configured to perform a cyclic shift operation on the selected coupling coefficients and the selected DD base vectors per layer with respect to the DD base vector index associated with the SCI for a CSI report, the CSI subgroup having the highest priority associated with the CSI report includes the sub-bitmap associated with the DD base vector index 0 and the corresponding amplitude and / or phase information of the coupling coefficients associated with the sub-bitmap of the RI layer. For example, the first segment of the CSI subgroup having the highest priority may be associated with the DD base vector index 0.

[0137] When the UE is not implemented to perform a cyclic shift on the selected coupling coefficients and the selected DD base vectors per layer with respect to the DD base vector index associated with the SCI, in order to identify the SD and DD base vector indices associated with the strongest coupling coefficients, a complete bitmap of all the selected SD and DD base vectors per layer may be required by the gNB. Thus, the above segmentation of the bitmap and the coupling coefficients with respect to the DD base vector index may not be possible.

[0138] According to one embodiment, when the UE is not implemented to perform a cyclic shift operation on the selected coupling coefficients and the selected DD basis vectors for each layer with respect to the DD basis vector index associated with the SCI for the CSI report, the CSI subgroup of the CSI report with the highest priority may include at least the bitmap of the RI layer and all or part of the phase and / or amplitude information of the coupling coefficients of the CSI matrix of the CSI report. When the CSI subgroup includes only part of the phase and / or amplitude information of the coupling coefficients, the remaining CSI subgroups of the CSI reports with lower priority may include the remaining part of the phase and / or amplitude information of the coupling coefficients of the CSI matrix.

[0139] According to one embodiment, the UE is not implemented to perform a cyclic shift operation on the selected coupling coefficients and the selected DD basis vectors for each layer with respect to the DD basis vector index associated with the SCI for the CSI report, and REP when the CSI payload including the CSI information of N REP CSI reports is decomposed into several CSI subgroups that constitute a joint CSI subgroup including the CSI information associated with the N

[0140] Segmentation for multiple layers The second segmentation method divides the bitmap and the coupling coefficients with respect to the RI layer of the CSI matrix indicated by the CSI report for the CSI report.

[0141] According to an embodiment, the CSI subgroup associated with the highest priority of the CSI report may include at least the bitmap indicating the non-zero coupling coefficients of the first subset of the RI layer, and the first subset of the RI layer of the CSI matrix indicated by the CSI report, and the first part of the amplitude and phase values of the selected non-zero delay region coupling coefficients.

[0142] The remaining CSI subgroups with lower priorities associated with the same CSI report may include at least the bitmap of the remaining (second subset) of the RI layer and the remaining amplitude and phase values associated with the second subset of the RI layer of the CSI report.

[0143] When the UE is configured to decompose the CSI payload according to the above method 1, the CSI subgroup with the highest priority for each CSI report may additionally include the following parameters: - A selected SD basis subset indicator including a rotation oversampling factor (if configured), - A selected DD basis subset indicator for the first subset of the RI layer, - The SCI of the first subset of the RI layer, - The polarization reference amplitude value of the first subset of the RI layer, - A bitmap indicating non-zero coupling coefficients of the first subset of the RI layer, - Additional possible parameters associated with the DD basis subset indication.

[0144] When the UE is configured to decompose the CSI payload according to the above method 2, the CSI subgroup with the highest priority for each CSI report of the CSI report may additionally include (if not already listed in the joint CSI subgroup) the following parameters: - A selected DD basis subset indicator for the RI layer, - The SCI of the RI layer, - The polarization reference amplitude value of the RI layer, - Additional possible parameters associated with the DD basis subset indication.

[0145] Wideband CSI information In 3GPP Release 15, the decomposition of CSI part 2 is to the first CSI part with priority level 0, N REPincludes the so-called wideband amplitudes of the CSI reports. Based on these wideband amplitudes in the first CSI part, the gNB can reconstruct the wideband CSI matrix of the configured subbands for each CSI report even when dropping all parts except the first CSI part for which the UE has priority level 0. When applying the second CSI decomposition method described above, similar wideband CSI matrices can be defined with two codebook-based CSI reporting methods. The gNB can derive the wideband CSI matrix of the CSI report if it has knowledge about a part of the bitmap associated with the amplitude information of the coupling coefficients and the "strongest" DD basis vector index of each of the RI layers. In many cases, the "strongest" DD basis vector index per layer corresponds to the DD basis vector index associated with the SCI. Therefore, based on the SCI, the bitmap associated with the DD basis vector index associated with the SCI, and the amplitude information of the coupling coefficients, the gNB can reconstruct the wideband CSI matrix as proposed in the following embodiments.

[0146] According to one embodiment, N REP the CSI payload including the CSI information of the CSI reports is decomposed into several CSI subgroups, and when the first CSI subgroup includes the CSI information associated with N REP CSI reports, the joint CSI subgroup may include the SCI of the RI layer, a part of the bitmap, and the amplitude and / or phase information of the coupling coefficients associated with all SD components of the DD basis vector index associated with the SCI of the RI layer of one or more CSI reports. Based on the information included in the joint CSI subgroup, the gNB can recalculate the wideband CSI matrix of each of the one or more CSI reports.

[0147] Similar to the consideration of the above cyclic shift operation, when the UE is configured to perform a cyclic shift operation on the selected DD basis vectors for each layer with respect to the selected combination coefficients and the DD basis vectors associated with the SCI for the CSI report, the DD basis vector index 0 is associated with the SCI.

[0148] According to one embodiment, N REP CSI payloads including CSI information of N REP CSI reports are decomposed into several CSI subgroups. When the first CSI subgroup includes CSI information associated with N

[0149] CSI reports, the joint CSI subgroup may include, for one or more CSI reports, the SCI of the RI layer, a part of the bitmap, and the amplitude and / or phase information of the combination coefficients associated with all SD components and the DD basis vector index 0 of the RI layer for each CSI report.

[0150] According to one embodiment, N REP CSI payloads including CSI information of N REPIf it includes CSI information associated with a CSI report and the UE is not implemented to perform a cyclic shift operation on the selected coupling coefficient of the CSI report, the joint CSI subgroup may include a complete bitmap of all selected SD and DD basis vector indices for each layer, and at least the amplitude and / or phase information of the coupling coefficients associated with the DD basis vector indices related to the SCI of the RI layer of that CSI report.

[0151] The size of the joint CSI subgroup depends on the number of non-zero coupling coefficients associated with the DD basis vector indices of the SCI of one or more CSI reports. Therefore, the gNB may not know the payload size of the joint CSI subgroup even after decoding the CSI part 1 of the CSI payload. Hereinafter, a method for fixing the payload size of the joint CSI subgroup is presented.

[0152] According to one embodiment, the joint CSI subgroup includes at least the SCI of the RI layer, a part of the bitmap, and the amplitude and / or phase information of the coupling coefficients associated with all SD components and DD basis vector indices of the SCI of the RI layer in the N CSI reports with the highest priority.

[0153] The value of the parameter N may be in the upper layer set by the gNB, may be pre-known by the UE, for example fixed by the specification, or may be determined by the UE. For example, the UE may determine the value of the parameter N, that is, the number of CSI reports with the highest priority, so that the payload size of the joint CSI subgroup is fixed.

[0154] Readout / Packing Rules When the RI Layer Bitmap is Included in a Single CSI Subgroup As described above, a CSI subgroup having the highest priority and associated with a single CSI report may include all RI layer bitmaps and only a portion of the phase and / or amplitude information of the coupling coefficients.

[0155] The following embodiments present a decomposition method for the phase and / or amplitude information of the coupling coefficients with respect to the number of CSI subgroups. The decomposition of the phase and / or amplitude information of the coupling coefficients may depend on the ordering of the bit sequences of the associated bitmaps of the RI layers of the CSI report.

[0156] According to an embodiment, when all RI layer bitmaps of size 2UD×RI associated with a single CSI report are included in a single CSI subgroup, the bitmap is segmented into RI segments, and each of the 2UD bits is in ascending order with respect to the number of layers. Each segment is associated with all SD and DD base indices of the layer. See FIG. 12. In the case of UCI omission, the UE first drops the CSI content associated with one or more upper layers, and then drops the CSI content associated with one or more lower layers. For example, when RI = 4 and T = 2, the UE may first drop the CSI content associated with the CSI subgroups of layers 3 and 4 with lower priority, and then may drop the CSI content associated with the CSI subgroups of layers 1 and 2 with high priority of the CSI report.

[0157] The bit sequences within each segment can be ordered with respect to one of the following two schemes. In the first ordering scheme (Scheme 1), the bits within each segment of size 2UD×1 are ordered such that the first 2U bits are associated with all 2U SD components of the first DD base index, followed by 2U bits associated with all 2U SD components of the second DD base index, and so on. See Figure 13. In the second ordering scheme (Scheme 2), the bits within each segment of size 2UD×1 are ordered such that the first D bits are associated with all D DD base indices of the first SD base index, followed by D bits associated with all D DD base indices of the second SD base index, and so on. See Figure 14 or Figure 15.

[0158] When the bitmap is ordered as shown in Figure 13, Figure 14, or Figure 15, the portion of the phase and / or amplitude information of the combined coefficients included in the CSI subgroup is always associated with only a subset of the RI layer of the CSI report. Such ordering / packing can lead to a significant performance loss compared to dropping only the portion of the phase and / or amplitude information of the combined coefficients of all RI layers. The following embodiments present alternative orderings / segmentations of the bitmap and combined coefficients that avoid dropping the combined coefficients of one or more layers of the CSI report.

[0159] According to an embodiment, when the CSI subgroup includes the bitmaps of all RI layers, the bitmap of size 2UD×RI is segmented into D segments, each segment having a size of 2U×RI and being associated with a single DD base vector index. Refer to FIG. 16. In the case of UCI omission, the UE first drops the CSI content associated with one or more DD base indexes of all RI layers, and then drops the CSI content associated with the remaining DD base indexes of all RI layers. For example, when D = 4, the UE may first drop the CSI content associated with DD base indexes 3 and 4, and then may drop the CSI content associated with DD base indexes 1 and 2 of the CSI report.

[0160] The bit sequences within each segment can be ordered with respect to one of the following two methods. In the first ordering method (Method 1), the bits within each segment of size 2U×RI are ordered such that the first RI bit is associated with the first SD base vector index of all RI layers, followed by the next RI bit associated with the second SD base index of all RI layers, and so on. Refer to FIGS. 17 and 18. In the second ordering method (Method 2), the bits within each segment of size 2U×RI are ordered such that the first 2U bits are associated with all 2U SD components of the DD base index associated with the first layer, followed by 2U bits associated with all 2U SD components of the DD base index associated with the second layer, and so on. Refer to FIG. 19.

[0161] Packing / Ordering Rules for Combining Coefficients As described in one embodiment, the CSI subgroup associated with the CSI report may include the amplitude and phase information of a part of the combining coefficients, where different ordering methods for the amplitude and phase values may be applied.

[0162] According to one embodiment, the amplitude and phase information of a plurality of coupling coefficients within a CSI subgroup can be ordered by one of the following methods. In Method 1, for each coupling coefficient within the CSI subgroup, b bits of phase information follow a bits of amplitude information. Refer to FIG. 20. Here, X represents the number of coupling coefficients included in the CSI subgroup. In Method 2, Xb bits of phase information of the X coupling coefficients follow Xa bits of amplitude information of the X coupling coefficients. Refer to FIG. 21. In Method 3, Xa bits of amplitude information of the X coupling coefficients follow Xb bits of phase information of the X coupling coefficients. Refer to FIG. 22.

[0163] Bit width of the subgroup According to an embodiment, the bit width of a first CSI subgroup associated with a single CSI report and the highest priority can be fixed and can be given by A + B, where A is the combined bit width of all components included in the first subgroup apart from the number of non-zero coupling coefficients, and B is the bit width associated with the amplitude information (a) and phase information (b) of a portion of the coupling coefficients.

[0164]

Number

[0165] which is associated with the amplitude information (a) and phase information (b) of a portion of the coupling coefficients. For example, when T = 2 and the first subgroup has only a portion of the bitmaps and coupling coefficients of all layers

[0166]

Number

[0167] the bit widths of the first CSI subgroup and the second CSI subgroup 2 are respectively given by

[0168]

Number

[0169] respectively. In one example, x = T. Another proposed aspect of the present invention will be described again with reference to FIG. 1 showing a method performed by a network node (gNB). The present invention proposes that a network node (gNB) receives CSI feedback in the form of one or more channel state information (CSI) reports in a wireless communication system.

[0170] The method comprises - transmitting, via a MIMO channel, to a user equipment (UE), an upper layer configuration of one or more downlink reference signals, one or more CSI report configurations associated with the configuration of the downlink reference signals, and a wireless signal, the wireless signal including a downlink reference signal according to the configuration of the one or more downlink reference signals, - receiving, from the UE, one or more CSI reports of the one or more CSI report configurations.

[0171] The one or more CSI reports are generated by the UE performing - estimating a downlink MIMO channel based on measurements on the received one or more downlink reference signals, the downlink reference signals being provided via a set number of frequency domain resources, time domain resources, and one or more ports, - for each CSI report, determining a precoding matrix based on the estimated channel and two codebooks, - a spatial codebook including one or more spatial domain (SD) basis components of a precoder, and - a delay codebook including one or more delay domain (DD) basis components of a precoder, and one or more non-zero coupling coefficients for complex coupling one or more SD and DD basis vectors.

[0172] Each CSI report includes a selected precoding matrix in the form of a precoding matrix identifier (PMI) and a rank identifier (RI), where the rank identifier (RI) indicates the transmission rank of the RI layer of the precoding matrix. Each CSI report may include two parts, CSI part 1 and CSI part 2. Part 1 has a fixed payload size and includes information indicating the size of the payload of part 2. Part 2 includes at least the amplitude and phase information of the selected non-zero coupling coefficients of the CSI report, and part or all of part 2 is available for omission from the CSI report.

[0173] To perform the method steps and UE operations described above, a UE 30 is also provided as shown in FIG. 23. The UE 30 includes a processor 31, a processing circuit, a processing module, a processor, or means; a receiver circuit or receiver module 34; a transmitter circuit or transmitter module 35; a memory module 32; and a transceiver circuit or transceiver module 33 that may include the transmitter circuit 35 and the receiver circuit 34. The UE 30 further includes an antenna system 36 that includes an antenna circuit for transmitting and receiving signals at least between the UE 30.

[0174] To perform the method steps and operations of the network node described above, a network node (gNB) is also provided as shown in FIG. 1. The network node (gNB) includes a processor or processing circuit or processing module or processor or means, a receiver circuit or receiver module, a transmitter circuit or transmitter module, a memory module, and a transceiver circuit or transceiver module that may include the transmitter circuit and the receiver circuit. The network node (gNB) further includes an antenna system that includes an antenna circuit for transmitting and receiving signals at least between the network node gNB.

[0175] The present invention also relates to a computer program product 37, which is stored in a memory module 32 in the figure. The computer program product 37 includes computer program code 38 that enables a processor 31 to execute any one of the subject matters of the method of the present invention executed by a UE when executed by the processor 31.

[0176] The present invention also relates to a computer program product. When the computer program product is executed by a processor of a network node (gNB), the computer program product includes computer program code that enables the processor to execute any one of the subject matters of the method of the present invention executed by the network node (gNB).

[0177] References [1] 3GPP TS 38.214 V15.3.0: "3GPP; TSGRAN; NR; Physical Layer Procedures for Data (Release 15) (3GPP; TSGRAN; NR; Physical layer procedures for data (Rel. 15)).", September 2018 [2] Samsung, "Revised WID: Enhancements on MIMO for NR", RP-182067, 3GPP RAN#81, Gold Coast, Australia, September 10 - 13, 2018 [3] R1-1806124, Fraunhofer IIS, Fraunhofer HHI, Enhancements on Type-II CSI reporting scheme, RAN1#93, Busan, Korea, May 21 - 25, 2018 [4] R1-1811088, Fraunhofer IIS, Fraunhofer HHI, Enhancements on Type-II CSI reporting scheme, RAN1#94-Bis, Chengdu, China, October 8 - 12, 2018 [5] Chairman’s Notes, RAN1#96, Athens, Greece, February 25 - March 1, 2019 [6] R1-1902304, Samsung, Summary of CSI enhancement for MU-MIMO, RAN1#96, February 25 - March 1, 2019 [7] R1-1905629, Samsung, Feature lead summary for MU-CSI - revision on selected issues, Xi'an, China, April 12 - 16, 2019

Claims

Claim 1 A method performed by a user equipment (UE) that provides CSI feedback in the form of one or more channel state information (CSI) reports in a wireless communication system (A), comprising: receiving, from a network node (gNB), a higher layer configuration of one or more downlink reference signals, one or more CSI report configurations associated with the configuration of the one or more downlink reference signals, and a wireless signal, the wireless signal including the one or more downlink reference signals according to the configuration of the one or more downlink reference signals, the one or more downlink reference signals being supplied via a set number of frequency domain resources, time domain resources, and one or more ports; for each CSI report, determining a precoding matrix based on the one or more downlink reference signals and two codebooks, a spatial codebook including one or more spatial domain (SD) basis components of a precoder, and the two codebooks including a delay codebook including one or more delay domain (DD) basis components of the precoder, and one or more non-zero coupling coefficients that complexly couple the one or more SD and DD basis vectors; reporting the one or more CSI reports of the one or more CSI report configurations to the network node. Each CSI report includes the selected precoding matrix in the form of a precoding matrix identifier (PMI) and a rank identifier (RI), where the rank identifier (RI) indicates the transmission rank of the RI layer of the precoding matrix. Each CSI report includes two parts: CSI part 1 and CSI part 2. Part 1 has a fixed payload size and includes information indicating the size of the payload of part 2. Part 2 includes at least the amplitude and phase information of the selected non-zero coupling coefficients of the CSI report. The amplitude and phase information of the non-zero coupling coefficients within the CSI subgroup related to the CSI report are ordered. The CSI subgroup includes the amplitude and phase information of some of the non-zero coupling coefficients. After the amplitude information (Xa bits) of X coupling coefficients, the phase information (Xb bits) of X coupling coefficients follows, where X indicates the number of coupling coefficients included in the CSI subgroup. A part or all of part 2 can be used for omission from the CSI report. Claim 2 The method according to claim 1, wherein CSI part 1 includes at least information about a selected number of non-zero coupling coefficients across all RI layers and an indication of the transmission rank of the RI layer of the selected precoding matrix. Claim 3 CSI part 2 includes at least, for the RI layer of the selected precoding matrix, when a rotation oversampling factor indicating the selected SD basis vector from the spatial codebook is set, a spatial domain (SD) basis subset indicator including the rotation oversampling factor, one or more delay domain (DD) basis subset indicators indicating the selected DD basis vector from the delay codebook, the phase and amplitude of the selected non-zero coupling coefficients, a strongest coefficient indicator (SCI) indicating the DD and SD vectors associated with the strongest coefficient per layer, the polarization reference amplitude per layer, a bitmap indicating the non-zero coupling coefficients per layer, and an additional possible parameter associated with the DD basis subset indicator. The method according to claim 1. Claim 4 N ＲＥＰ The CSI part 2 of the N CSI reports is segmented into TN ＲＥＰ +1 CSI subgroups, and the T CSI subgroups are always associated with a single CSI report. One CSI subgroup contains information associated with all N ＲＥＰ CSI reports, and each CSI subgroup is associated with a priority (priority level). The method according to claim 1 or 3 Claim 5 All N ＲＥＰ The CSI subgroup containing information associated with the CSI reports of all N has the highest priority (priority level 0), and the remaining TN ＲＥＰ CSI subgroups of the individual CSI reports are associated with lower priority levels from 1 to TN ＲＥＰ up to, and the last CSI subgroup TN ＲＥＰ is associated with the lowest priority level TN ＲＥＰ associated with, the method according to claim 4. Claim 6 The CSI subgroup includes the bitmaps of all RI layers. The bitmap of size 2UD×RI is segmented into D segments, each segment having a size of 2U×RI and being associated with a single DD base vector index. U represents the number of set SD base vectors, and D represents the number of set DD base vectors. The method according to claim 4 or 5, which is dependent on claim 3.

7. The bits within each segment of size 2UD×RI are ordered such that the first RI bits are associated with the first SD base vector index of all RI layers, followed by the next RI bits associated with the second SD base vector index, and so on. The method according to claim 6.

8. Each CSI subgroup having the highest priority and associated with a single CSI report can include at least a part of the bitmap of the RI layer and the phase and amplitude information of a part of the K ＮＺ phase and amplitude information of a part of the binding coefficients, and the method according to claim 6 or 7.

9. Each CSI subgroup having the highest priority associated with a single CSI report includes at least a portion of the bitmap and the information of the combined coefficients associated with the DD base vector index of the strongest coefficient indicator (SCI) of the RI layer. The method according to claim 6 or 7.

10. Each CSI subgroup including information of a portion of the combined coefficients includes the phase and amplitude values associated with the maximum of 【Number 1】 the number of combined coefficients of the CSI report. The remaining CSI subgroups with lower priority include the remaining phase and amplitude values of the CSI report. KNZ is the number of non-zero combined coefficients for the RI layer. The method according to claim 8 or 9.

11. A method performed by a network node (gNB) that receives CSI feedback in the form of one or more channel state information (CSI) reports in a wireless communication system (A), transmitting to the user equipment (UE) one or more upper layer configurations of downlink reference signals, one or more CSI report configurations associated with the configurations of the one or more downlink reference signals, and a wireless signal that includes the one or more downlink reference signals according to the configurations of the one or more downlink reference signals, the transmitting, receiving from the UE one or more CSI reports of one or more CSI report configurations, comprising, each CSI report is the one or more downlink reference signals and two codebooks, A spatial codebook including one or more spatial domain (SD) basis components of a precoder, and a delay codebook including one or more delay domain (DD) basis components of the precoder, the two codebooks including, and one or more non-zero coupling coefficients for complex coupling the one or more SD and DD basis vectors, a precoding matrix determined based on, each CSI report includes the selected precoding matrix in the form of a precoding matrix identifier (PMI) and a rank identifier (RI), the rank identifier (RI) indicates the transmission rank of the RI layer of the precoding matrix, each CSI report includes two parts, CSI part 1 and CSI part 2, part 1 has a fixed payload size, part 2 includes information indicating the size of the payload of part 2, part 2 includes at least the amplitude and phase information of the selected non-zero coupling coefficients of the CSI report, the amplitude and phase information of the non-zero coupling coefficients within the CSI subgroup related to the CSI report are ordered, the CSI subgroup includes the amplitude and phase information of some of the non-zero coupling coefficients, after the amplitude information (Xa bits) of X coupling coefficients, the phase information (Xb bits) of X coupling coefficients follows, X indicates the number of coupling coefficients included in the CSI subgroup, part 2 or all of part 2 is available for omission from the CSI report, method.

12. A user equipment (UE) (30) comprising a processor (31) and a memory (32), the memory (32) including computer program code (38) executable by the processor (31), whereby the UE (30) is operable to perform the method according to any one of claims 1 to 10, user equipment.

13. A network node comprising a processor and a memory, the memory including computer program code executable by the processor, whereby the network node is operable to perform the method according to claim 11, network node.

14. A computer program (37) comprising computer program code which, when executed by a processor (31) of a user equipment (UE), enables the processor (31) to execute the method according to any one of claims 1 to 10.

15. A computer program comprising computer program code which, when executed by a processor of a network node (gNB), enables the processor to execute the method according to claim 11.

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