Reciprocity-based CSI Report Configuration

Abstract

Measure the UL channel of the UE based on a reference signal to determine UL channel information. Infer DL channel information based on UL-DL channel reciprocity and the determined UL channel information. Configure the reporting of channel state information for the user equipment based on the inferred DL channel information, and allocate resources for the UE to report CSI. Signal to the UE information indicating the configuration and resources of the CSI report. Send a DL reference signal to the UE for CSI determination. Receive the CSI report on the allocated resources. The UE receives the configuration, uses the configuration and the received DL reference signal to determine CSI, and places the determined CSI in the allocated resources. The UE sends the determined CSI on the allocated resources.

Description

Technical Field

[0001] The present invention generally relates to cellular radio implementations, and more particularly to channel state information (CSI) reporting and configuration for cellular radio implementations, such as 2G, 3G, 4G, 5G radio access networks (RANs), cellular IoT RANs, and / or cellular radio HW. Background Art

[0002] This section is intended to provide background or context for the present invention disclosed below. The description herein may include concepts that may be pursued, but are not necessarily concepts that have been previously conceived, implemented, or described. Thus, unless explicitly stated otherwise herein, the content described in this section is not prior art to the description in this application and is not considered prior art by virtue of being included in this section. Abbreviations that can be found in the specification and / or drawings are defined after the main part of the "Detailed Description" section below.

[0003] Channel state information (CSI) is used to determine the attributes of a communication link. Such CSI and its reporting are used by both a base station (e.g., an eNB or a gNB) and a wireless, typically mobile, device (commonly referred to as a user equipment UE) to adapt transmissions to the current channel conditions. As cellular radio implementations become increasingly complex (due to the demand for bandwidth), CSI becomes increasingly important.

[0004] In 3GPP NR MIMO discussions, type-II CSI reporting uses linear combination codebooks to achieve high-resolution beamforming in the single-user case and high multi-user order transmissions in the multi-user case. When configured with type-II CSI reporting, the UE reports several orthogonal beams and their combination coefficients (e.g., amplitude and phase), through which an accurate beamformer can be formed at the gNB side to precode the DL transmission to the UE.

[0005] One problem with type-II CSI reporting is that the number of reported orthogonal beams varies with the UE transmission scenario and thus with the size of the reported CSI payload. It is not possible to non-causally predict and allocate resources for type-II CSI reporting before the UE is ready to report CSI. Simple solutions such as fixed resource allocation may result in waste or insufficiency of signaling resources. Therefore, this degrades system performance. Summary of the Invention

[0006] This section is intended to include examples, not limitations.

[0007] In an exemplary embodiment, a method includes: measuring an uplink channel for a user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information. The method includes: inferring downlink channel information for the user equipment based on uplink-downlink channel reciprocity and the determined uplink channel information. The method includes: configuring a report of channel state information for the user equipment based on the inferred downlink channel information, and allocating one or more resources for the user equipment to report the channel state information. The method includes: signaling to the user equipment information indicating the configuration of the report of the channel state information and information on the one or more allocated resources. The method includes: sending one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for the determination of the channel state information. The method includes: receiving one or more reports of the channel state information from the user equipment on the one or more allocated resources.

[0008] An additional exemplary embodiment includes a computer program that includes code for performing the method of the above paragraph when the computer program is run on a processor. According to the computer program of the above paragraph, wherein the computer program is a computer program product that includes a computer-readable medium that bears computer program code for use by a computer.

[0009] An exemplary apparatus includes one or more processors and one or more memories that include computer program code. The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to at least perform the following: measuring an uplink channel for a user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information; inferring downlink channel information for the user equipment based on uplink-downlink channel reciprocity and the determined uplink channel information; configuring a report of channel state information for the user equipment based on the inferred downlink channel information, and allocating one or more resources for the user equipment to report the channel state information; signaling to the user equipment information indicating the configuration of the report of the channel state information and information on the one or more allocated resources; sending one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for the determination of the channel state information; and receiving one or more reports of the channel state information from the user equipment on the one or more allocated resources.

[0010] An exemplary computer program product includes a computer-readable storage medium having computer program code embodied therein for use by a computer. The computer program code includes: code for measuring an uplink channel for a user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information; code for inferring downlink channel information for the user equipment based on uplink-downlink channel reciprocity and the determined uplink channel information; code for configuring a report of channel state information for the user equipment based on the inferred downlink channel information and allocating one or more resources for the user equipment to report the channel state information; code for signaling to the user equipment information indicating the configuration of the report of the channel state information and the one or more allocated resources; code for transmitting one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for determining the channel state information; and code for receiving one or more reports of the channel state information from the user equipment on the one or more allocated resources.

[0011] In another exemplary embodiment, an apparatus includes components for performing the following: measuring an uplink channel for a user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information; inferring downlink channel information for the user equipment based on uplink-downlink channel reciprocity and the determined uplink channel information; configuring a report of channel state information for the user equipment based on the inferred downlink channel information and allocating one or more resources for the user equipment to report the channel state information; signaling to the user equipment information indicating the configuration of the report of the channel state information and the one or more allocated resources; transmitting one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for determining the channel state information; and receiving one or more reports of the channel state information from the user equipment on the one or more allocated resources.

[0012] Another exemplary embodiment is a method that includes: sending one or more reference signals to a base station; the method includes: receiving signaling from the base station partially based on the one or more reference signals sent, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for reporting; the method includes: receiving one or more downlink reference signals from the base station; the method includes: using the configuration of the report of channel state information and the one or more received downlink reference signals to determine the channel state information; the method includes: putting the determined channel state information into one or more allocated resources; and the method includes: sending one or more reports of the channel state information to the base station on the one or more allocated resources.

[0013] An additional exemplary embodiment includes a computer program that includes code for performing the method of the above paragraph when the computer program runs on a processor. According to the computer program of the above paragraph, wherein the computer program is a computer program product including a computer-readable medium, the computer-readable medium carrying the computer program code for use by a computer.

[0014] An exemplary apparatus includes one or more processors and one or more memories including computer program code. The one or more memories and the computer program code are configured to, together with the one or more processors, cause the apparatus to at least perform the following: send one or more reference signals to a base station; receive signaling from the base station partially based on the one or more reference signals sent, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for reporting; receive one or more downlink reference signals from the base station; use the configuration of the report of channel state information and the one or more received downlink reference signals to determine the channel state information; put the determined channel state information into one or more allocated resources; and send one or more reports of the channel state information to the base station on the one or more allocated resources.

[0015] An exemplary computer program product includes a computer-readable storage medium having computer program code embodied therein for use by a computer. The computer program code includes: code for sending one or more reference signals to a base station; code for receiving, from the base station, signaling based in part on the one or more reference signals sent, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report; code for receiving one or more downlink reference signals from the base station; code for determining channel state information using the configuration of the report of channel state information and the one or more downlink reference signals received; code for placing the determined channel state information into the one or more allocated resources; and code for sending, on the one or more allocated resources, one or more reports of the channel state information to the base station.

[0016] Another exemplary embodiment is an apparatus that includes modules for performing the following operations: sending one or more reference signals to a base station; receiving, from the base station, signaling based in part on the one or more reference signals sent, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report; receiving one or more downlink reference signals from the base station; determining channel state information using the configuration of the report of channel state information and the one or more downlink reference signals received; placing the determined channel state information into the one or more allocated resources; and sending, on the one or more allocated resources, one or more reports of the channel state information to the base station. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In the drawings:

[0018] Figure 1 is a block diagram of one possible and non-limiting exemplary system in which exemplary embodiments may be practiced;

[0019] Figure 2 is a table that can be used for example payload calculations for WB+SB magnitudes, where for K major coefficients, (N1, N2) = (4, 4), Z = 3 (8-PSK phase);

[0020] Figure 3 and 4 are respectively logic flowcharts executed by a base station or a UE for reciprocity-based CSI reporting configurations, and illustrate operations of an exemplary method according to exemplary embodiments, execution results of computer program instructions embodied on a computer-readable memory, functions executed by logic implemented in hardware, and / or interconnected modules for performing functions; and

[0021] Figure 5shows the values of (N 1，2 ) and (O1, O2) that support beam selection and the parameters for a type-II single-panel (SP) codebook. DETAILED DESCRIPTION

[0022] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. All embodiments described in this detailed description are exemplary embodiments provided to enable a person skilled in the art to make or use the invention, and not to limit the scope of the invention defined by the claims.

[0023] Exemplary embodiments herein describe techniques for reciprocity-based CSI reporting configuration. After describing a system in which the exemplary embodiments can be used, additional descriptions of these techniques are presented.

[0024] Turning Figure 1 , the figure shows a block diagram of one possible and non-limiting exemplary system in which the exemplary embodiments can be practiced. In Figure 1In this case, a user equipment (UE) 110 wirelessly communicates with a wireless network 100. A UE is a wireless, typically mobile device that can access a wireless network. The UE 110 includes one or more processors 120, one or more memories 125, and one or more transceivers 130 interconnected by one or more buses 127. Each of the one or more transceivers 130 includes a receiver Rx 132 and a transmitter Tx 133. The one or more buses 127 can be address, data, or control buses and can include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optic, or other optical communication devices, etc. The one or more transceivers 130 are connected to one or more antennas 128. The one or more memories 125 include computer program code 123. The UE 110 includes a CSI module 140, and the CSI module 140 includes one or both of parts 140-1 and / or 140-2 and can be implemented in various ways. The CSI module 140 can be implemented as a circuit system as the CSI module 140-1, such as being implemented as part of one or more processors 120. The CSI module 140-1 can also be implemented as an integrated circuit or by other circuit systems such as programmable gate arrays. In another example, the CSI module 140 can be implemented as the CSI module 140-2, and the CSI module 140-2 is implemented as computer program code 123 and executed by the circuit system of one or more processors 120. For example, the one or more memories 125 and the computer program code 123 can be configured to cause the user equipment 110 to perform one or more operations described herein together with one or more processors 120. The UE 110 communicates with the gNB 170 via a wireless link 111.

[0025] gNB 170 is a base station (e.g., for 5G / NR) that provides access to a wireless network 100 for wireless devices such as UE 110. gNB 170 is one example of a suitable base station, but the base station can also be an eNB (for LTE) or other base stations for, e.g., 2G or 3G. gNB 170 includes one or more processors 152, one or more memories 155, one or more network interfaces (N / WI / F) 161, and one or more transceivers 160 interconnected by one or more buses 157. Each of the one or more transceivers 160 includes a receiver Rx 162 and a transmitter Tx 163. The one or more transceivers 160 are connected to one or more antennas 158. The one or more memories 155 include computer program code 153. gNB 170 includes a CSI module 150, which includes one or both of parts 150-1 and / or 150-2 and can be implemented in a variety of ways. The CSI module 150 can be implemented as a circuit system as CSI module 150-1, such as being implemented as part of one or more processors 152. The CSI module 150-1 can also be implemented as an integrated circuit or implemented by other circuit systems such as programmable gate arrays. In another example, the CSI module 150 can be implemented as CSI module 150-2, which is implemented as computer program code 153 and executed by the circuit system of one or more processors 152. For example, the one or more memories 155 and the computer program code 153 are configured to cause gNB 170 to perform one or more operations described herein together with one or more processors 152. The one or more network interfaces 161 communicate over a network, e.g., via links 176 and 131. Two or more gNBs 170 communicate using, e.g., link 176. Link 176 can be wired or wireless or both and can implement, e.g., the X2 interface.

[0026] One or more buses 157 can be an address, data, or control bus and can include any interconnection mechanism, such as a series of lines on a motherboard or integrated circuit, fiber optic or other optical communication devices, wireless channels, etc. For example, one or more transceivers 160 can be implemented as a remote radio head (RRH) 195, where other elements of gNB 170 are physically located at a different location from the RRH, and one or more buses 157 can be partially implemented as a fiber optic cable for connecting other elements of gNB 170 to the RRH 195.

[0027] The wireless network 100 may include a network control element (NCE) 190, which may include MME (Mobility Management Entity) / SGW (Serving Gateway) functions and provide connections to other networks such as a telephone network and / or a data communication network (e.g., the Internet). The gNB 170 is coupled to the NCE 190 via a link 131. The link 131 may be implemented as, for example, an S1 interface. The NCE 190 includes one or more processors 175, one or more memories 171, and one or more network interfaces (N / WI / F) 180 interconnected by one or more buses 185. The one or more memories 171 include computer program code 173. The one or more memories 171 and the computer program code 173 are configured to, together with the one or more processors 175, cause the NCE 190 to perform one or more operations.

[0028] The wireless network 100 may implement network virtualization, which is a process of combining hardware and software network resources and network functions into a single software-based management entity (virtual network). Network virtualization involves platform virtualization, which is typically combined with resource virtualization. Network virtualization is classified as external (combining many networks or network parts into virtual units) or internal (providing network-like functions to software containers on a single system). Note that to some extent, the virtualized entities resulting from network virtualization can still be implemented using hardware such as processors 152 or 175 and memories 155 and 171, and such virtualized entities also produce technical effects.

[0029] The computer-readable memories 125, 155, and 171 may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory, and removable memory. The computer-readable memories 125, 155, and 171 may be means for performing storage functions. The processors 120, 152, and 175 may be of any type suitable for the local technical environment and, by way of non-limiting example, may include one or more of the following: general-purpose computers, special-purpose computers, microprocessors, digital signal processors (DSPs), and processors based on multi-core processor architectures. The processors 120, 152, and 175 may be means for performing functions such as controlling the UE 110, the gNB 170, and other functions described herein.

[0030] Generally, various embodiments of the user equipment 110 may include, but are not limited to, cellular phones (such as smart phones), tablet computers, personal digital assistants (PDAs) with wireless communication capabilities, portable computers with wireless communication capabilities, image capture devices with wireless communication capabilities (such as digital cameras), game devices with wireless communication capabilities, music storage and playback devices with wireless communication capabilities, Internet devices that allow wireless Internet access and browsing, tablet computers with wireless communication capabilities, and portable devices or terminals that incorporate combinations of such functions.

[0031] Accordingly, a suitable but non-limiting technical context has been introduced for the practice of the exemplary embodiments of the present invention, and the exemplary embodiments will now be described more specifically.

[0032] As previously mentioned, a problem with a type of CSI report known as type II CSI report is that the number of reported orthogonal beams varies with the UE transmission scenario and thus with the size of the reported CSI payload. More specifically, the linear combination codebook (LCC) is used for type II CSI report in NR and is also used as an advanced CSI codebook in R14 LTE. When using the LCC, the UE reports the indices of multiple predefined DFT beams and their combination coefficients. Using the reported DFT beams and combination coefficients, the gNB reconstructs the UE's channel vector, and based on this channel vector, MIMO transmission is applied in the DL. Type II CSI report is a version of the linear combination codebook (LCC) report. Other details regarding type II CSI report are outlined in the section entitled "Type II single-panel (SP) codebook" in "WF on Type I and II CSI codebooks" (R1-1709232) presented by companies such as Samsung at the 3GPP TSG-RAN WG1 #89 meeting held in Hangzhou, China from May 15th to 19th, 2017.

[0033] Omission rules for class II CSI report are defined in the 3GPP NR R15 MIMO discussion. See, for example, Table 5.2.3-1 in Section 5.2.3 of 3GPP TS38.214 (e.g., 3GPP TS 38.214 V15.0.0 (2017-12)). When the pre-allocated / allocated signaling resources (e.g., CSI report container) are not sufficient to carry the class II CSI report, priority rules based on component carrier index and frequency domain decimation are applied, and the CSI report part is discarded to fit the container. The motivation for type II CSI report is for high-resolution beamforming and high-order multi-user transmission, and partial omission of the CSI report will significantly degrade the system performance of type II CSI report.

[0034] To solve these problems, in an exemplary embodiment, we provide a method that predicts and allocates signaling resources for type-II CSI reporting by exploring the channel reciprocity between UL and DL in, for example, an NR MIMO system. In UL, the gNB 170 can estimate the number of orthogonal beams and the rank of the UL channel of the UE 110, and use this information to configure type-II CSI reporting for DL channel estimation and accordingly allocate signaling resources for the UE 110. The UE 110 will estimate type-II CSI based on this configuration and fit the report to the allocated signaling resources. Since partial omission of CSI reports or waste of signaling resources is avoided, improved signaling overhead efficiency is achieved while ensuring the performance of type-II CSI reports in this way.

[0035] For ease of reference, the remainder of this document is divided into sections by title. This title is for introducing this section only and does not constitute a limitation.

[0036] A. Type-II CSI Reporting

[0037] The following is an overview of type-II single-panel (SP) codebooks and related reports. NR supports type-II Cat1 CSI with rank 1 and rank 2. The PMI is used for spatial channel information feedback. The PMI codebook adopts the following precoder structures:

[0038] For rank 1, W is normalized to 1; and

[0039] For rank 2: The columns of W are normalized to

[0040] The weighted combination of L beams is as follows: Where:

[0041] The value of L is configurable: L ∈ {2, 3, 4};

[0042] is the oversampled 2D DFT beam;

[0043] R = 0, 1 (polarization), 1 = 0, 1 (layer);

[0044] is the wideband (WB) beam amplitude scaling factor for beam i and at polarization r and layer 1;

[0045] is the subband (SB) beam amplitude scaling factor for beam i and at polarization r and layer l; and

[0046] c r，l，iis the beam combining coefficient (phase) for beam i and on polarization r and layer 1, and is configurable between QPSK (2 bits) and 8PSK (3 bits).

[0047] There is a configurable amplitude scaling mode between WB+SB (with unequal bit allocation) and WB only.

[0048] Regarding beam selection and parameters for the type-II SP codebook, beam selection is only wideband. Unrestricted beam selection can be performed from an orthogonal basis as follows:

[0049]

[0050]

[0051] q1 = 0,..., O1-1, q2 = 0,..., O2-1 (rotation factors); and

[0052] (orthogonal beam index).

[0053] Figure 5 Shows the supported values of (N 1，2 ) and (N 1，2 ). (*) is expressed as follows: for 4 ports, L = 2 (L = 3, 4 is not supported); for 8 ports, L = 4.

[0054] Regarding the amplitude and combining coefficients for the type-II SP codebook, the amplitude scaling and phase for the combining coefficients are described below.

[0055] Amplitude scaling is selected independently for each beam, polarization, and layer. The UE is configured to report wideband amplitude with or without subband amplitude:

[0056] and are both possible.

[0057] Only wideband is possible.

[0058] The set of wideband amplitude values (3 bits) is as follows:

[0059] The PMI payload can vary depending on whether the amplitude is zero. Most of the details of the payload have been completed. What remains to be determined is what will be done with the spare resources not used for the payload when the payload is less than the allocated resources. This has not been completed.

[0060] The set of subband amplitude values (1 bit) is as follows:

[0061] For the phase of the combined coefficients, the phase is selected independently for each beam, polarization, and layer, and the phase is only used for sub-bands.

[0062] The set of phase values is (2 bits) or (3 bits).

[0063] Regarding the bit allocation for the amplitude scaling and phase of the type-II SP codebook, (WB amplitude, SB amplitude, SB phase) are quantized and reported (X, Y, Z bits) respectively, as follows. It should be noted that for each layer, for the dominant (strongest) coefficient among the 2L coefficients, (X, Y, Z) = (0, 0, 0). Dominant (strongest) coefficient = 1.

[0064] For the WB+SB amplitude, the following conditions apply.

[0065] For the first (K-1) dominant (strongest) coefficients among the (2L-1) coefficients, (X, Y) = (3, 1) and Z ∈ {2, 3}, and for the remaining (2L-K) coefficients, (X, Y, Z) = (3, 0, 2). For L = 2, 3, and 4, the corresponding values of K are 4 (=2L), 4, and 6 respectively.

[0066] Report the following coefficient index information in the WB manner:

[0067] 1) The index of the strongest coefficient among the 2L coefficients (per layer); and

[0068] 2) Without additional signaling, each layer implicitly determines the (K-1) dominant coefficients based on the reported (2L-1) WB amplitude coefficients.

[0069] For the WB amplitude only, i.e., Y = 0, the following conditions apply.

[0070] (X, Y) = (3, 0) and Z ∈ {2, 3}.

[0071] Report the index of the strongest coefficient among the 2L coefficients per layer in the WB manner.

[0072] To configure the type-II CSI report using a specific antenna port layout and beam oversampling rate, the gNB 170 typically signals the following parameters to the UE 110:

[0073] L: The number of orthogonal beams reported;

[0074] WB or WB+SB: Coefficient amplitude reporting mode;

[0075] QPSK or 8PSK: Coefficient phase reporting quantization; and / or

[0076] K: The bit allocation parameter, where the first K principal coefficients are reported at a higher resolution.

[0077] All of these parameters may affect the reported payload size. For the K principal coefficients, Figure 2 an exemplary table is shown in where (N1, N2) = (4, 4),

[0078] and Z = 3 (8-PSK phase). This figure is a revised version of the table of "WFon Type I and II CSI codebooks" (R1-1709232) presented by Samsung and other companies at the 3GPP TSG-RAN WG1 #89 meeting in Hangzhou, China from May 15th to 19th, 2017. The variable Z indicates the number of bits used to quantize the SB phase. In this case, 3 bits are used for the 8-PSK phase.

[0079] B. Parameters and Rank Estimation at gNB 170

[0080] To predict the type-II CSI report payload size, gNB 170 first measures the UE's UL channel based on the UL reference signal (e.g., SRS), and then uses the UL channel information to infer the DL channel based on UL-DL channel reciprocity. Using the DL channel information, gNB 170 configures the type-II CSI report (e.g., L, K, WB or WB+SB for amplitude reporting, QPSK or 8PSK for phase quantization), and configures the CSI report payload size (i.e., UL resource allocation for CSI reporting) together with the channel rank information. Although the implementation details of inferring the DL channel based on UL-DL reciprocity are determined by the gNB design, an exemplary method using eigenvalue decomposition and thresholding is described below.

[0081] i) Rank Estimation

[0082] Assume that the channel vector of PRB i estimated from the UL SRS is represented as h i , then the spatial channel covariance matrix for the current subframe n is calculated by averaging over all used PRBs:

[0083]

[0084] where R(n) is the spatial channel covariance matrix at the current subframe n, h i is the i-th channel matrix h, is the Hermitian transpose (also known as conjugate transpose) of the i-th channel matrix h, and the dot represents matrix multiplication.

[0085] Perform eigenvalue decomposition on the spatial channel covariance matrix R(n) to obtain:

[0086] R(n) = UΛU H ,

[0087] where U is a square matrix, and its j-th column is the eigenvector q of R(n) j , and Λ is a diagonal matrix, and its diagonal elements are the corresponding eigenvalues, that is, Λ jj = λ j .

[0088] Generally, the eigenvalues are sorted in descending order λ1 ≥ λ2 ≥ …, and a method for estimating the rank is to set a threshold t for the eigenvalues, and if the j-th eigenvalue is greater than the threshold, then add the j-th layer to the transmission:

[0089] rank

[0090] In NR R15, type II CSI reporting supports a maximum rank 2 transmission. Therefore, another simple method to determine the transmission rank is to measure the difference between the first two eigenvalues,

[0091] λ0 - λ1 > t.

[0092] If the difference is greater than the threshold, then rank 1 (one layer) transmission will be used (i.e., the rank is 1), otherwise rank 2 transmission (two-layer transmission) (i.e., the rank is 2) will be used.

[0093] ii) Parameter L

[0094] In type II CSI reporting, orthogonal beams are reported in a broadband manner, where the channel vectors from different polarizations and different layers can be combined based on maximum ratio combining (MRC), and then the combined channel vectors are used to derive the orthogonal beams. On the other hand, a simple method to derive the parameter L is to obtain the channel vector associated with the main polarization and the main layer, and then derive the number of orthogonal beams based on this channel vector. The basic principle is usually that co-located orthogonal polarization antennas are assumed to be independent and identically distributed (i.i.d.). That is, the channel vectors from different polarizations have experienced very similar channels in a long-term broadband manner.

[0095] Assume that the channel of PRB i from one polarization is represented as Then the spatial channel covariance matrix averaged over all PRBs is as follows:

[0096]

[0097] Perform eigen - decomposition on the spatial channel covariance and remove the polarization symbols, obtaining:

[0098] R(n)=UΛU H ,

[0099] where U is a square matrix, whose j - th column is the eigen - vector q of R(n) j , and Λ is a diagonal matrix, whose diagonal elements are the corresponding eigenvalues, i.e., Λ jj =λ j . Represent the main eigen - vector as U * , one way to estimate the parameter L is to calculate its correlation with the candidate orthogonal beam. If the correlation with a candidate beam b is greater than the predefined threshold γ, then beam b is considered in the reported beams:

[0100] Corr(U * , b)>γ.

[0101] This is because, in the NR R15 Class II CSI report, where L = {2, 3, 4}, the threshold γ can be adjusted based on simulation, so the parameter L can be appropriately selected within its range.

[0102] iii) Parameters K and quantization bit width

[0103] (WB amplitude, SB amplitude, SB phase) are quantized and reported in (X, Y, Z) bits respectively. This is described in more detail in "WF on Type I and II CSI codebooks" (R1 - 1709232) proposed by Samsung et al. at the 3GPP TSG - RAN WG1#89 meeting in Hangzhou, China from May 15th to 19th, 2017.

[0104] The amplitude of the combined coefficient can be reported in WB mode or WB + SB mode (along with its corresponding quantization bit width). To determine whether SB reporting is required, the channel frequency selectivity of the UE can be measured. The same principle applies to the determination of the parameter K (bit - allocation parameter), where the first K main coefficients are reported with higher resolution. An extreme example case is that when the UE channel is completely flat, no SB reporting of amplitude or phase is required, so K can be set to 1 (one), and only the wide - band combined coefficient is reported.

[0105] For most NLOS scenarios, the UE channel is quite frequency selective, and the SB report can enhance system performance by providing additional channel information. In this case, the parameter K can be used to adjust the overhead by allowing more bits for the "primary" beam (e.g., the beam associated with the higher value eigenvector) and allowing fewer bits for the "less important" beams (e.g., the beam associated with the lower value eigenvector relative to the higher value eigenvector).

[0106] To measure the UE channel frequency selectivity, we can calculate the spatial channel covariance for each PRB i as follows:

[0107]

[0108] Then, perform eigenvalue decomposition and obtain the principal eigenvector of the PRB as follows:

[0109]

[0110] Measure the principal eigenvector of PRB i with the wideband principal eigenvector and compare the average correlation between them with a predetermined threshold η as follows:

[0111]

[0112] It can be determined whether the UE channel is flat enough in frequency for only WB amplitude reporting or whether SB amplitude reporting is necessary. That is, correlation is a measure of the "similarity" between vectors, and a high correlation between eigenvectors over a wide frequency range indicates high "similarity". Therefore, since the wideband eigenvector is sufficiently representative for the entire frequency range, narrowband reporting can be omitted. Vice versa: low correlation indicates that SB phase reporting should also be used.

[0113] In the same way, we can also determine whether the SB amplitude report requires more bits. In other words, if the correlation is low, the SB amplitude report requires more bits. That is, poor / low correlation means that the SB amplitude report requires more bits, while good / high correlation means that the SB amplitude report requires fewer bits. The WB amplitude report and the SB amplitude report (if used) and the SB phase report (if used) affect the number of quantization bit widths.

[0114] It should be noted that for the SB phase, the quantization bit width depends on the resolution of the phase that will be used to describe the coefficient. That is, for amplitude reporting, we can say that since the bit width of amplitude reporting can be adjusted once SB reporting is required, which may be the result of the above-mentioned correlation comparison. However, for phase reporting, since it is always SB, the bit width reflects the resolution of the phase reporting rather than the channel correlation comparison.

[0115] C. Other Considerations and Additional Examples

[0116] When configuring type-II CSI reporting, several factors can also be considered, such as UE speed and system capacity. For example, when the UE speed is very high and the CSI reporting resource allocation is close to the system capacity limit, fewer beams with only WB amplitude reporting can be configured to reduce the reporting overhead while keeping the performance of type-II CSI reporting acceptable.

[0117] The exemplary methods proposed above can also be applied to the following situations:

[0118] a) For the beamformed CSI codebook in NR R15 that adopts the type-II CSI reporting principle, the parameter L can be determined similarly as described above.

[0119] b) For FDD systems, reciprocity is not as good as that in TDD systems. However, since the proposed exemplary methods rely on long-term wideband average spatial channel information, these methods are also applicable to FDD systems.

[0120] c) For UE transmit antenna switching, UE transmit antenna switching can be enabled to ensure that the complete UL channel can be obtained at the gNB side. When only part of the UL channel is available, for example, only one transmit antenna associated with one polarization in UL is available (e.g., the case of a single UE transmit antenna), the above methods also work.

[0121] d) CBSR (Codebook Subset Restriction) can be applied together with the proposed exemplary methods to ensure correct UE CSI reporting behavior. For example, when the UE principal eigenvector U * is associated with multiple beams and the gNB 170 sets L = 2, CBSR can be enabled and appropriately set to prevent the reporting of less preferred orthogonal beams.

[0122] In an exemplary embodiment, new parameters are introduced for use in, for example, the specification. Specifically, the base station should signal the parameter L (i.e., the number of selected beams) to guide the UE in preparing the CSI reporting content. The signaling of the parameter L can be implemented, for example, by MAC-CE or DCI based on a trade-off between dynamicity and overhead control. Generally speaking, for control signaling, the dynamicity is RRC < MAC-CE < DCI.

[0123] In addition, modifications to existing parameters can be used to implement the exemplary embodiments herein. Specifically, in NR R15, the parameters regarding type II CSI reporting are RRC-configured, including WB or WB+SB amplitude reporting, the quantization bit width for phase reporting, and the parameter K. To increase the dynamicity, these parameters can be modified to be signaled via MAC-CE or DCI. In this way, the type II CSI reporting configuration can follow the UE channel changes and achieve better signaling resource utilization efficiency.

[0124] Figure 3 and 4 Additional examples of possible procedures that can be used in certain exemplary embodiments are provided. Turning to Figure 3 , this figure is a logic flow diagram for reciprocity-based CSI reporting configuration performed by a base station. This figure further shows the operations of one or more exemplary methods according to the exemplary embodiments, the execution results of computer program instructions embodied on a computer-readable memory, the functions executed by logic implemented in hardware, and / or the interconnected modules for performing the functions. For example, the CSI module 150 can include Figure 3 a plurality of boxes in Figure 3 , where each included box is an interconnected module for performing the function in that box. It is assumed that

[0125] the steps in

[0126] At block 320, gNB 170 configures a type-II CSI report for the UE using the inferred DL channel information and allocates one or more signaling resources for CSI reporting for the UE. The allocation of one or more signaling resources may include the CSI report payload size. Note that gNB 170 may determine the CSI report payload size based on the inference made at block 315. For example, once some or all of the inferred DL channel information 350 is known to gNB 170, a table (or other information) as shown in Figure 2 may be used to determine (e.g., infer) the total payload 210. This allows gNB 170 to allocate resources for type-II CSI reporting.

[0127] At block 325, gNB 170 signals to UE 110 information indicating the configuration for type-II CSI reporting and the one or more allocated signaling resources for CSI reporting (e.g., the CSI report payload size). This configuration is signaled dynamically, and UE 110 should follow the new configuration dynamically and estimate and report CSI accordingly. As described above and also shown in block 360, the configuration 360 may include one or more of the following configuration elements: 360-1) the number of orthogonal beams, parameter L; 360-2) WB or WB+SB amplitude reporting; 360-3) coefficient phase report quantization, e.g., QPSK or 8PSK; and / or 360-4) bit allocation parameter K. Thus, this configuration 360 allows UE 110 to determine the total payload 210 that UE 110 uses for type-II CSI reporting (see Figure 2 ), and the signaling in block 325 allows UE 110 to know the allocated resources to which the report should fit.

[0128] Note that signaling the number of orthogonal beams and parameter L dynamically in configuration element 360 provides several benefits. For example, sometimes the gNB cannot signal the correct configuration because the UE channel has changed while the configuration parameters are fixed. For example, the gNB signals L = 2 at the start of RRC configuration, and then at a later time, the UE channel changes and L = 4 is required to form beams better, but the gNB cannot (in the current scenario) signal the new L to the UE dynamically. Instead, the only way is through RRC reconfiguration, which typically takes several hundred milliseconds. Further UE channel changes, addition / removal of component cells, other gNB scheduling decisions, etc. will all affect the allocated resources, such that sometimes the gNB will actually deliberately allocate fewer resources because the gNB170 has to do so. This is because, from the overall system perspective, the gNB170 has to "sacrifice" some performance. All these sacrifices and inadequacies are due to the mismatch / conflict between the fixed configuration and the dynamic resource allocation. These problems can be solved by, for example, the dynamic signaling of parameter L as described in this document. Once the parameter L can be signaled dynamically (e.g., for the case of using two bits, we can have L = 1, 2, 3, 4), the flexibility of the dynamic signaling and the range of L will help solve this problem. According to the contract, the current fixed configuration follows a completely different principle, where UE channel information cannot be used during RRC configuration, and using UE channel information to accurately predict the payload and then configure the codebook parameters is part of the exemplary embodiments in this document. Additionally, if L = 4 is configured for all cases and the maximum resources are allocated as much as possible, the omission can be completely eliminated. However, this leads to the opposite direction and is a huge waste of system resources. Using UE channel-based prediction and system scheduling to dynamically signal parameter L is a way to avoid underallocation and waste. The rank and bit quantization are determined by the gNB, the rank is signaled dynamically, and its cost is much lower than RRC reconfiguration.

[0129] The gNB 170 sends a DL reference signal to the UE 110 for type-II CSI determination. This occurs at block 330. At block 340, the gNB 170 receives a type-II CSI report from the UE on one or more allocated signaling resources. At block 345, the gNB 170 adjusts the transmission to the UE based on the received type-II CSI report.

[0130] Figure 3 The main focus in [document name] is on type-II CSI reports. However, the exemplary embodiments in this document apply to other linear combination codebook-based reports, of which type-II CSI reports are one type. See Figure 3The frame 370. That is, the type-II CSI report is a type of linear combination codebook-based report, but the exemplary embodiments are not limited to the type-II CSI report.

[0131] Reference Figure 4 , which is a logical flow diagram executed by the UE for the reciprocity-based CSI report configuration. This figure further shows the operations of one or more exemplary methods according to the exemplary embodiments, the execution results of computer program instructions embodied on a computer-readable memory, the functions executed by logic implemented in hardware, and / or the interconnected devices for executing the functions. For example, the CSI module 140 may include Figure 4 multiple frames in, where each included frame is an interconnected device for performing the function in that frame. Assume Figure 4 the steps in are at least partially executed by the UE 110 under the control of, for example, the CSI module 140.

[0132] At block 405, the UE 110 transmits a UL reference signal to the base station. At block 425, the UE 110 receives signaling-informed information from the base station based on the UL reference signal, which indicates the configuration of the type-II CSI report and one or more allocated signaling resources for CSI reporting (e.g., the CSI report payload size). As described above, this configuration (e.g., configuration 360) is signaled dynamically by the gNB 170, and the UE 110 should dynamically follow the new configuration and accordingly estimate and report CSI. At block 430, the UE 110 receives a DL reference signal from the base station to be used for type-II CSI determination.

[0133] At block 435, UE 110 estimates type-II CSI based on the type-II CSI report configuration (e.g., configuration 360) and the received DL reference signals. Configuration 360 tells the UE what will be reported and how it will be reported, and thus the UE determines the reporting payload (e.g., number of bits). At block 437, UE 110 places the estimated type-II CSI into one or more reports on one or more allocated signaling resources. UE 110 determines that the actual type-II CSI report to be reported may be different from the report inferred by gNB 170. In other words, one or more of the allocated signaling resources to be used by UE 110 may be too small to fit the actual type-II CSI report that UE 110 determines should be reported. In such a case, UE 110 makes a decision on which type-II CSI report information to omit in the one or more allocated signaling resources. This decision is based on the predefined omission rules (as described above) agreed upon between the gNB and the UE. It should be noted that the type-II CSI report information determined by UE 110 to be sent may also occupy fewer resources than those allocated by gNB 170. In such a case, many options are possible, such as adding padding type-II CSI report information.

[0134] At block 440, UE 110 sends the type-II CSI report that has been placed into one or more allocated signaling resources for transmission to the base station. At block 445, UE 110 receives a transmission from the base station that is adjusted based on the previously sent type-II CSI report.

[0135] As Figure 3 , Figure 4 in, the main focus is on type-II CSI reports. However, the exemplary embodiments herein are applicable to other linear combination codebook-based reports, of which type-II CSI reports are one type. See Figure 4 block 470 of. In other words, type-II CSI reports are one type of linear combination codebook-based reports, but the exemplary embodiments are not limited to type-II CSI reports.

[0136] Other exemplary embodiments are as follows.

[0137] Example 1. A method includes:

[0138] Measuring an uplink channel for a user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information;

[0139] Inferring downlink channel information for the user equipment based on uplink-downlink channel reciprocity and the determined uplink channel information;

[0140] Configure the reporting of channel state information for the user equipment based on the inferred downlink channel information, and allocate one or more resources for the user equipment to report the channel state information;

[0141] Signal to the user equipment the configuration of the report indicating the channel state information and the information of one or more allocated resources;

[0142] Send one or more downlink reference signals to the user equipment, which will be used by the user equipment for the determination of the channel state information; and

[0143] Receive one or more reports of the channel state information from the user equipment on the one or more allocated resources.

[0144] Example 2. The method according to Example 1, wherein inferring the downlink channel information further includes inferring one or more of the following downlink channel information:

[0145] Rank estimation;

[0146] The number parameter L of orthogonal beams;

[0147] The bit allocation parameter K, where the first K main coefficients will be reported with higher resolution; quantization bit width; and

[0148] Wideband amplitude report or wideband and subband amplitude report.

[0149] Example 3. The method according to Example 2, wherein inferring the rank estimation includes:

[0150] Calculate the spatial channel covariance matrix at the current subframe n by averaging over all used physical resource blocks;

[0151] Perform eigenvalue decomposition on the spatial channel covariance matrix;

[0152] Sort the eigenvalues generated by the eigenvalue decomposition in descending order; and

[0153] Perform one of the following:

[0154] Determine the rank as the maximum number of eigenvalues greater than a threshold; or

[0155] Measure the difference between the two highest ranked eigenvalues, and if the difference is greater than the threshold, the rank is 1, otherwise the rank is 2.

[0156] Example 4. The method according to any one of Examples 2 or 3, wherein inferring the number parameter L of orthogonal beams includes:

[0157] Calculate the spatial channel covariance matrix at the current subframe n by averaging over all used physical resource blocks;

[0158] Perform an eigen - decomposition on the spatial channel covariance matrix;

[0159] Calculate the correlation of the dominant eigen - vector from the eigen - decomposition with a candidate orthogonal beam, compare the correlation with a threshold, and if the correlation of the beam is higher than the threshold, consider the beam as the reported beam, where the parameter L is set to the number of reported beams.

[0160] Example 5. The method according to Example 4, wherein in response to the dominant eigen - vector being correlated with multiple beams, but the parameter L is set to less than the number of reported beams among the multiple beams, the method further includes enabling and setting a codebook subset limit to prevent less preferred orthogonal beams from being reported, the less preferred orthogonal beams being among the multiple beams but not among the number of reported beams.

[0161] Example 6. The method according to Example 4, wherein configuring the reporting of the channel state information for the user equipment further includes configuring the reporting of the channel state information using a beam - formed channel state information codebook, and wherein the parameter L is set to the number of reported beams and the beams conform to the beam - formed channel state information codebook.

[0162] Example 7. The method according to any one of Examples 2 to 6, wherein inferring the wide - band amplitude report or the wide - band and sub - band amplitude reports includes:

[0163] Measure the channel frequency selectivity of the channel of the user equipment by at least performing the following:

[0164] Calculate the spatial channel covariance for each of all used physical resource blocks;

[0165] Perform an eigen - decomposition on the spatial channel covariance and obtain the dominant eigen - vector for each physical resource block;

[0166] Measure the average correlation between the dominant eigen - vector for each physical resource block and the wide - band dominant eigen - vector for all used physical resource blocks;

[0167] Compare the average correlation with a threshold, where an average correlation above the threshold indicates that the channel for the user equipment is not frequency - selective, while an average correlation below the threshold indicates that the channel for the user equipment is frequency - selective;

[0168] Use the result of the average correlation comparison to determine whether to use only the wideband amplitude report or both the wideband amplitude report and the subband amplitude report.

[0169] Example 8. The method according to Example 7, wherein inferring the quantization bit width further comprises using the result of the average correlation comparison as one element to adjust the quantization bit width.

[0170] Example 9. The method according to Example 8, wherein it is determined to use the subband amplitude report, and wherein inferring the quantization bit width further comprises determining whether more or fewer bits should be used for the subband amplitude report.

[0171] Example 10. The method according to any one of Examples 7 to 9, wherein inferring the bit allocation parameter K further comprises:

[0172] Adjusting the parameter K to adjust the overhead by allowing more bits for beams associated with higher value eigenvectors and fewer bits for beams associated with lower value eigenvectors.

[0173] Example 11. A method comprising:

[0174] Transmitting one or more reference signals to a base station;

[0175] Receiving signaling from the base station based in part on the one or more transmitted reference signals, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report;

[0176] Receiving one or more downlink reference signals from the base station;

[0177] Using the configuration of the report of channel state information and the one or more received downlink reference signals to determine the channel state information;

[0178] Placing the determined channel state information into the one or more allocated resources; and

[0179] Transmitting one or more reports of the channel state information to the base station on the one or more allocated resources.

[0180] Example 12. The method according to Example 11, wherein placing further comprises placing the determined channel state information into the one or more allocated resources by omitting at least some of the determined channel state information according to one or more rules previously agreed upon between the user equipment and the base station.

[0181] Example 13. The method according to any one of the foregoing examples, wherein the configuration comprises one or more of the following:

[0182] The number parameter L of orthogonal beams;

[0183] Wideband amplitude report or wideband and sub - band amplitude reports;

[0184] Coefficient phase report quantization; and

[0185] The bit - allocation parameter K, where the first K leading coefficients will be reported at a higher resolution.

[0186] Example 14. The method according to any one of the foregoing examples, wherein the configuration of the reporting of the channel state information conforms to a configuration based on a linear - combination codebook.

[0187] Example 15. The method according to any one of the foregoing examples, applied to a frequency - division duplex system.

[0188] Example 16. The method according to any one of the foregoing examples, wherein only a part of the uplink channel from the user equipment to the base station is available.

[0189] Example 17. An apparatus, comprising components for performing the following:

[0190] Measure an uplink channel for the user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information;

[0191] Infer downlink channel information for the user equipment based on uplink - downlink channel reciprocity and the determined uplink channel information;

[0192] Configure the reporting of the channel state information for the user equipment based on the inferred downlink channel information, and allocate one or more resources for the user equipment to report the channel state information;

[0193] Signal to the user equipment the configuration of the reporting indicating the channel state information and information on one or more allocated resources;

[0194] Send one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for the determination of the channel state information; and

[0195] Receive one or more reports of the channel state information from the user equipment on the one or more allocated resources.

[0196] Example 18. The apparatus according to Example 17, wherein inferring the downlink channel information further includes inferring one or more of the following downlink channel information:

[0197] Rank estimation;

[0198] The number parameter L of orthogonal beams;

[0199] The bit allocation parameter K, where the first K main coefficients will be reported at a higher resolution; quantization bit width; and

[0200] Wideband amplitude reporting or wideband and subband amplitude reporting.

[0201] Example 19. The apparatus according to Example 18, wherein inferring the rank estimation includes:

[0202] Calculating the spatial channel covariance matrix at the current subframe n by averaging over all used physical resource blocks;

[0203] Performing eigenvalue decomposition on the spatial channel covariance matrix;

[0204] Sorting the eigenvalues resulting from the eigenvalue decomposition in descending order; and

[0205] Performing one of the following:

[0206] Determining the rank as the maximum number of eigenvalues greater than a threshold; or

[0207] Measuring the difference between the two highest ranked eigenvalues, and if the difference is greater than the threshold, the rank is 1, otherwise the rank is 2.

[0208] Example 20. The apparatus according to any one of Examples 18 or 19, wherein inferring the number parameter L of orthogonal beams includes:

[0209] Calculating the spatial channel covariance matrix at the current subframe n by averaging over all used physical resource blocks;

[0210] Performing eigenvalue decomposition on the spatial channel covariance matrix;

[0211] Calculating the correlation between the principal eigenvector from the eigenvalue decomposition and the candidate orthogonal beams, comparing the correlation with a threshold, and if the correlation of a beam is higher than the threshold, considering the beam as the reported beam, where the parameter L is set to the number of reported beams.

[0212] Example 21. The apparatus according to Example 20, wherein in response to the main eigenvector being associated with a plurality of beams, but the parameter L is set to less than the number of reported beams of the plurality of beams, and wherein the component is further configured to perform enabling and setting of codebook subset restriction to prevent less preferred orthogonal beams from being reported, the less preferred orthogonal beams being among the plurality of beams but not among the number of reported beams.

[0213] Example 22. The apparatus according to Example 20, wherein configuring the reporting of the channel state information for the user equipment further includes configuring the reporting of the channel state information using a beamformed channel state information codebook, and wherein the parameter L is set to the number of reported beams and the beams conform to the beamformed channel state information codebook.

[0214] Example 23. The apparatus according to any one of Examples 18 to 22, wherein inferring the wideband amplitude report or the wideband and subband amplitude reports includes:

[0215] Measuring the channel frequency selectivity of the channel of the user equipment by at least performing the following:

[0216] Calculating the spatial channel covariance for each physical resource block among all used physical resource blocks;

[0217] Performing eigen-decomposition on the spatial channel covariance, and obtaining the main eigenvector for each physical resource block;

[0218] Measuring the average correlation between the main eigenvector for each physical resource block and the wideband main eigenvector for all used physical resource blocks;

[0219] Comparing the average correlation with a threshold, wherein an average correlation above the threshold indicates that the channel for the user equipment is not frequency selective, while an average correlation below the threshold indicates that the channel for the user equipment is frequency selective;

[0220] Using the result of the average correlation comparison to determine whether to use only the wideband amplitude report or both the wideband amplitude report and the subband amplitude reports.

[0221] Example 24. The apparatus according to Example 23, wherein inferring the quantization bit width further includes using the result of the average correlation comparison as an element to adjust the quantization bit width.

[0222] Example 25. The apparatus according to Example 24, wherein it is determined to use subband amplitude reporting, and wherein inferring the quantization bit width further includes determining whether more or fewer bits should be used for the subband amplitude reporting.

[0223] Example 26. The apparatus according to any one of Examples 23 to 25, wherein inferring the bit allocation parameter K further includes:

[0224] Adjusting the parameter K to adjust the overhead by allowing more bits for beams associated with higher value eigenvectors and fewer bits for beams associated with lower value eigenvectors.

[0225] Example 27. An apparatus comprising components for performing the following:

[0226] Transmitting one or more reference signals to a base station;

[0227] Receiving, from the base station, signaling that indicates a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report, based in part on the one or more transmitted reference signals;

[0228] Receiving one or more downlink reference signals from the base station;

[0229] Determining the channel state information using the configuration of the report of channel state information and the received one or more downlink reference signals;

[0230] Placing the determined channel state information into the one or more allocated resources; and

[0231] Transmitting, on the one or more allocated resources, one or more reports of the channel state information to the base station.

[0232] Example 28. The apparatus according to Example 12, wherein placing further includes placing the determined channel state information into the one or more allocated resources by omitting at least some of the determined channel state information according to one or more rules previously agreed upon between the user equipment and the base station.

[0233] Example 29. The apparatus according to any of the preceding apparatus examples, wherein the configuration includes one or more of the following:

[0234] Number parameter L of orthogonal beams;

[0235] Wideband amplitude reporting or wideband and subband amplitude reporting;

[0236] Coefficient phase reporting quantization; and

[0237] The bit allocation parameter K, where the first K main coefficients will be reported at a higher resolution.

[0238] Example 30. The apparatus according to any one of the preceding apparatus examples, wherein the configuration of the reporting of the channel state information is a configuration compliant with reporting based on a linear combination codebook.

[0239] Example 31. The apparatus according to any one of the preceding apparatus examples, applied to a frequency division duplex system.

[0240] Example 32. The apparatus according to any one of the preceding apparatus examples, wherein only a part of the uplink channel from the user equipment to the base station is available.

[0241] Example 33. The apparatus according to any one of the preceding examples, wherein the components include:

[0242] At least one processor; and

[0243] At least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the execution of the apparatus.

[0244] Example 34. A base station, including the apparatus according to any one of Examples 17 to 26 or Examples 29 to 33.

[0245] Example 35. A user equipment, including the apparatus according to any one of Examples 27 to 33.

[0246] Example 36. A wireless communication system, including the apparatus according to Example 34 and the apparatus according to Example 35.

[0247] Example 37. A computer program, including code for performing the method according to any one of Examples 1 to 16 when the computer program is run on a processor.

[0248] Example 38. The computer program according to Example 37, wherein the computer program is a computer program product including a computer-readable medium, the computer-readable medium carrying computer program code embodied therein for use with a computer.

[0249] Example 39. An apparatus, including:

[0250] One or more processors; and

[0251] One or more memories including computer program code,

[0252] The one or more memories and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform the following:

[0253] Measure an uplink channel for the user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information;

[0254] Infer downlink channel information for the user equipment based on uplink-downlink channel reciprocity and the determined uplink channel information;

[0255] Configure a report of channel state information for the user equipment based on the inferred downlink channel information, and allocate one or more resources for the user equipment to report the channel state information;

[0256] Signal to the user equipment the configuration of the report indicating the channel state information and information on the one or more allocated resources;

[0257] Send one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for the determination of the channel state information; and

[0258] Receive one or more reports of channel state information from the user equipment on the one or more allocated resources.

[0259] Example 40. The apparatus according to example 39, wherein the one or more memories and the computer program code are configured to, with the at least one processor, cause the apparatus to perform the method according to any one of examples 1 to 10 or examples 13 to 16.

[0260] Example 41. An apparatus, comprising:

[0261] One or more processors; and

[0262] One or more memories including computer program code,

[0263] The one or more memories and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform the following:

[0264] Send one or more reference signals to a base station;

[0265] Receive signaling from the base station, at least in part based on the one or more reference signals sent, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report;

[0266] Receive one or more downlink reference signals from the base station;

[0267] Use the configured report of the channel state information and the received one or more downlink reference signals to determine the channel state information;

[0268] Place the determined channel state information into the one or more allocated resources; and

[0269] Send one or more reports of the channel state information to the base station on the one or more allocated resources.

[0270] Example 42. The apparatus according to Example 41, wherein the one or more memories and the computer program code are configured to cause the apparatus, together with the at least one processor, to perform the method according to any one of Examples 11 to 16.

[0271] Without in any way limiting the scope, interpretation, or application of the claims that follow, the technical effects of one or more example embodiments disclosed herein are to predict and allocate signaling resources for type-II CSI reporting by exploring the channel reciprocity between UL and DL in an NR MIMO system. Another technical effect of one or more example embodiments disclosed herein is to avoid partial omission of CSI reporting or waste of signaling resources. Another technical effect of one or more example embodiments disclosed herein is to improve signaling overhead efficiency while ensuring type-II CSI reporting performance.

[0272] Embodiments herein may be implemented in software (executed by one or more processors), hardware (e.g., an application specific integrated circuit), or a combination of software and hardware. In an example embodiment, the software (e.g., application logic, instruction sets) is held on any of a variety of conventional computer-readable media. In the context of this document, "computer-readable media" may be any medium or device that can contain, store, communicate, propagate, or transport instructions for use by or in connection with an instruction execution system, apparatus, or device such as a computer, for example, as Figure 1 described and depicted in an example of a computer. Computer-readable media may include computer-readable storage media (e.g., memories 125, 155, 171, or other devices), which may be any medium or device that can contain, store, and / or transport instructions for use by or in connection with an instruction execution system, apparatus, or device such as a computer. Computer-readable storage media does not include propagated signals.

[0273] If desired, the different functions discussed herein may be performed in a different order and / or concurrently with each other. Additionally, if desired, one or more of the above functions may be optional or may be combined.

[0274] Although aspects of the present invention are set out in the independent claims, other aspects of the invention include other combinations of features from the described embodiments and / or dependent claims with the features of the independent claims, not only those combinations explicitly listed in the claims.

[0275] It should also be noted herein that although example embodiments of the present invention have been described above, these descriptions should not be taken in a limiting sense. Rather, various variations and modifications can be made without departing from the scope of the invention as defined in the appended claims.

[0276] The following abbreviations, which can be found in the specification and / or the drawings, are defined as follows:

[0277] 2D: Two-dimensional

[0278] 2G, 3G, 4G, 5G: Second, third, fourth, and fifth generation (G)

[0279] CBSR: Codebook subset restriction

[0280] CSI: Channel state information

[0281] DCI: Downlink control information

[0282] DFT: Discrete Fourier transform

[0283] DL: Downlink (from base station to UE)

[0284] eNB (or eNodeB): Evolved Node B (e.g., LTE base station)

[0285] FDD: Frequency division duplexing

[0286] FFS: Further to be studied

[0287] gNB 170: Base station for 5G / NR

[0288] HW: Hardware

[0289] I / F: Interface

[0290] IoT: Internet of Things

[0291] LCC: Linear combination codebook

[0292] LTE: Long Term Evolution

[0293] MAC: Media Access Control

[0294] MAC-CE: MAC Control Element

[0295] MIMO: Multiple-Input Multiple-Output

[0296] MME: Mobility Management Entity

[0297] MRC: Maximum Ratio Combining

[0298] NCE: Network Control Element

[0299] NLoS: Non-Line-of-Sight

[0300] NR: New Radio

[0301] N / W: Network

[0302] PMI: Precoding Matrix Indicator

[0303] PRB: Physical Resource Block

[0304] R15: Release 15

[0305] RAN: Radio Access Network

[0306] RRC: Radio Resource Control

[0307] RRH: Remote Radio Head

[0308] Rx: Receiver

[0309] SB: Sub-Band

[0310] SGW: Serving Gateway

[0311] SRS: Sounding Reference Signal

[0312] TDD: Time Division Duplex

[0313] Tx: Transmitter

[0314] UE: User Equipment (e.g., a wireless device, typically a mobile device)

[0315] UL: Uplink (from UE to base station)

[0316] WB: Wideband

Claims

1. A method for communication, comprising: Measuring an uplink channel for the user equipment based on one or more reference signals from the user equipment, wherein the measurement of the uplink channel determines uplink channel information; Inferring downlink channel information for the user equipment based on the determined uplink channel information, wherein the inference relies on uplink-downlink channel reciprocity of long-term broadband average spatial channel information; Configuring a report of channel state information for the user equipment based on the inferred downlink channel information, and allocating one or more resources for the user equipment to report the channel state information; Signaling to the user equipment the configuration of the report indicating the channel state information and information on one or more allocated resources; Sending one or more downlink reference signals to the user equipment, wherein the one or more downlink reference signals will be used by the user equipment for the determination of the channel state information; and Receiving one or more reports of channel state information from the user equipment on the one or more allocated resources.

2. The method according to claim 1, wherein inferring the downlink channel information further comprises inferring one or more of the following downlink channel information: Rank estimation; Number parameter L of orthogonal beams; Bit allocation parameter K, wherein the first K main coefficients will be reported with a higher resolution than other coefficients; Quantization bit width; and Broadband amplitude report or broadband and subband amplitude report.

3. The method according to claim 2, wherein inferring the rank estimation comprises: Calculating a spatial channel covariance matrix at the current subframe n by averaging channel covariance matrices over all used physical resource blocks; Performing eigenvalue decomposition on the spatial channel covariance matrix; Sorting the eigenvalues resulting from the eigenvalue decomposition in descending order; And Performing one of the following: Determining the rank as the maximum number of eigenvalues greater than a threshold; or Measuring the difference between the two highest ranked eigenvalues, and if the difference is greater than the threshold, the rank is 1, otherwise the rank is 2.

4. The method according to claim 2 or 3, wherein inferring the number parameter L of orthogonal beams comprises: Calculating a spatial channel covariance matrix at the current subframe n by averaging channel covariance matrices over all used physical resource blocks; Performing eigenvalue decomposition on the spatial channel covariance matrix; Calculating the correlation of the principal eigenvector from the eigenvalue decomposition with candidate orthogonal beams, comparing the correlation with a threshold, and if the correlation of a beam is higher than the threshold, considering the beam as a reported beam, wherein the parameter L is set to the number of reported beams.

5. The method according to claim 4, wherein configuring the reporting of the channel state information for the user equipment further comprises configuring the reporting of the channel state information using a beamformed channel state information codebook, and wherein the parameter L is set to the number of reported beams and the beams conform to the beamformed channel state information codebook.

6. The method according to claim 2 or 3, wherein inferring the wideband amplitude report or the wideband and sub-band amplitude reports comprises: measuring the channel frequency selectivity of the channel of the user equipment at least by performing the following: calculating the spatial channel covariance for each of all used physical resource blocks; performing eigen-decomposition on the spatial channel covariance and obtaining a principal eigenvector for each physical resource block; measuring the average correlation between the principal eigenvector for each physical resource block and the wideband principal eigenvector for all used physical resource blocks; comparing the average correlation with a threshold, wherein an average correlation above the threshold indicates that the channel for the user equipment is not frequency selective, while an average correlation below the threshold indicates that the channel for the user equipment is frequency selective; using the result of the average correlation comparison to determine whether to use only the wideband amplitude report or both the wideband amplitude report and the sub-band amplitude reports.

7. The method according to claim 6, wherein inferring the quantization bit width further comprises using the result of the average correlation comparison as an element to adjust the quantization bit width.

8. The method according to claim 7, wherein it is determined to use the sub-band amplitude report, and wherein inferring the quantization bit width further comprises determining whether a first number of bits or a second number of bits should be used for the sub-band amplitude report, the first number being greater than the second number.

9. The method according to claim 6, wherein inferring the bit allocation parameter K further comprises: adjusting the parameter K to adjust the overhead by allowing a first number of bits for a beam associated with a first eigenvector and a second number of bits for a beam associated with a second eigenvector, the first number being greater than the second number, and the value of the first eigenvector being higher than the value of the second eigenvector.

10. A method for communication, comprising: transmitting one or more reference signals to a base station, wherein, based on the one or more reference signals, the uplink channel for a user equipment is measured, and the measurement of the uplink channel determines uplink channel information; inferring the downlink channel information for the user equipment based on the determined uplink channel information, wherein the inference relies on the uplink-downlink channel reciprocity of long-term wideband average spatial channel information; configuring the reporting of the channel state information for the user equipment based on the inferred downlink channel information, and allocating one or more resources for the user equipment to report the channel state information; Receive signaling from the base station, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report; Receive one or more downlink reference signals from the base station; Determine the channel state information using the configuration of the report of the channel state information and the received one or more downlink reference signals; Place the determined channel state information into the one or more allocated resources; and Transmit one or more reports of the channel state information to the base station on the one or more allocated resources.

11. The method according to claim 10, wherein placing further comprises placing the determined channel state information into the one or more allocated resources by omitting at least some of the determined channel state information according to one or more rules previously agreed between the user equipment and the base station.

12. The method according to claim 10 or 11, wherein the configuration comprises one or more of the following: Number parameter L of orthogonal beams; Wideband amplitude report or wideband and subband amplitude reports; Coefficient phase report quantization; and Bit allocation parameter K, wherein the first K main coefficients will be reported with a higher resolution than other coefficients.

13. The method according to claim 10 or 11, wherein the configuration of the report of the channel state information conforms to a configuration of a report based on a linear combination codebook.

14. An apparatus for communication, comprising: One or more processors; And One or more memories comprising computer program code, The one or more memories and the computer program code being configured to, together with the one or more processors, cause the apparatus to at least perform the following: Measure an uplink channel for the user equipment based on one or more reference signals from the user equipment, the measurement of the uplink channel determining uplink channel information; Infer downlink channel information for the user equipment based on the determined uplink channel information, wherein the inference relies on uplink-downlink channel reciprocity of at least long-term wideband average spatial channel information; Configure a report of channel state information for the user equipment based on the inferred downlink channel information, and allocate one or more resources for the user equipment to report the channel state information; Signal to the user equipment information indicating the configuration of the report of the channel state information and the one or more allocated resources; Transmit one or more downlink reference signals to the user equipment, the one or more downlink reference signals to be used by the user equipment for the determination of the channel state information; and Receive one or more reports of channel state information from the user equipment on the one or more allocated resources.

15. An apparatus for communication, comprising: One or more processors; And One or more memories comprising computer program code, The one or more memories and the computer program code are configured to, with the one or more processors, cause the apparatus to at least perform the following: Transmit one or more reference signals to a base station, wherein, based on the one or more reference signals, an uplink channel for a user equipment is measured, and the measurement of the uplink channel determines uplink channel information; Infer downlink channel information for the user equipment based on the determined uplink channel information, wherein the inference relies on uplink-downlink channel reciprocity of long-term broadband average spatial channel information; Configure a report of channel state information for the user equipment based on the inferred downlink channel information, and allocate one or more resources for the user equipment to report the channel state information; Receive signaling from the base station, the signaling indicating a configuration of a report of channel state information to be used by a user equipment and one or more allocated resources to be used for the report; Receive one or more downlink reference signals from the base station; Determine the channel state information using the configuration of the report of channel state information and the received one or more downlink reference signals; Place the determined channel state information in the one or more allocated resources; and Transmit one or more reports of the channel state information to the base station on the one or more allocated resources.

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