Frequency Domain Channel State Information Compression

Abstract

Methods, systems, and circuit systems for reporting a precoding matrix to a base station are described. In one example, a user equipment (UE) includes one or more processors configured to identify a codebook specifying codebook parameters and a precoding matrix. Each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients defined for different sets of frequency resources. The processor is configured to: process a reference signal received from a base station to determine codebook parameters for the reference signal; calculate a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI identifies a selected linear combination of spatial beams defined in the precoding matrix for use in a downlink transmission from the base station to the UE; and report the PMI to the base station.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Provisional Patent Application No. 62 / 754,497, filed on November 1, 2018, entitled “METHOD FOR FREQUENCY DOMAIN CSICOMPRESSION,” and U.S. Provisional Patent Application No. 62 / 794,220, filed on January 18, 2019, entitled “FREQUENCY DOMAIN CHANNEL STATE INFORMATION (CSI) COMPRESSION,” which are incorporated herein by reference for all purposes. Technical Field

[0003] Various examples may generally relate to the field of wireless communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0004] Figure 1 An exemplary wireless communication network including a transmission / reception point (TRP) and a user equipment (UE) performing downlink communications is depicted according to some examples.

[0005] Figure 2A An exemplary representation of a precoding matrix is ​​depicted.

[0006] Figure 2B An exemplary representation of a precoding matrix is ​​depicted.

[0007] Figure 3 An exemplary representation of a precoding matrix is ​​depicted.

[0008] Figure 4 A functional block diagram of an exemplary UE wireless communication device according to some examples is shown.

[0009] Figure 5 A functional block diagram of an exemplary TRP / base station wireless communication device according to some examples is shown. Specific embodiments

[0010] The following detailed description refers to the accompanying drawings. The same reference numerals may be used in different drawings to identify the same or similar elements. In the following description, specific details such as specific structures, architectures, interfaces, technologies, etc. are described for the purpose of illustration rather than limitation, so as to provide a thorough understanding of various aspects of various examples. However, it will be apparent to those skilled in the art who benefit from the present disclosure that various aspects of various examples can be practiced in other examples that are separated from these specific details. In some cases, the description of known devices, circuits, and methods is omitted to avoid making the description of various examples difficult to understand with unnecessary details. For the purpose of this document, the phrase "A or B" means (A), (B), or (A and B).

[0011] Figure 1 A general overview of an exemplary downlink process for a wireless communication network including a base station 100 (e.g., eNB, gNB, TRP, etc.) and a user equipment (UE) 120 is shown. Figure 4 An exemplary UE 120 is shown in FIG. Figure 5 An exemplary base station 100 is shown in FIG. The base station 100 includes a baseband processor 110 that performs various functions for wireless communication. In the following description, if a base station is described as performing a certain function, it should be understood that the base station is the processor 110 that is performing the function. The UE 120 includes a baseband processor 130 that performs various functions for wireless communication. In the following description, if a UE is described as performing a certain function, it should be understood that the UE is the processor 130 that is performing the function.

[0012] As shown at A, to assist scheduling, link adaptation, precoding, and spatial multiplexing operations for downlink (DL) transmission, UE 120 monitors some predetermined channel state information (CSI) resources to receive CSI reference signals (CSI-RS). UE 120 calculates several reporting quantities based on the received CSI-RS. As shown at B, UE 120 sends CSI feedback (e.g., CSI report) including reporting quantities to base station 100 via a physical uplink control channel (PUCCH) or a physical uplink shared channel (PUSCH).

[0013] There are three main components of a CSI report: a channel quality indicator, a rank indicator, and a precoding matrix indicator. The channel quality indicator (CQI) contains information about the modulation and coding scheme recommended by the user equipment (UE) for downlink (DL) transmission. The rank indicator (RI) contains information about the number of spatial layers recommended by the UE for DL ​​transmission. The precoding matrix indicator (PMI) contains information about the precoding matrix recommended by the UE for DL ​​transmission. The PMI is a set of indices corresponding to specific precoding matrices from a specified finite set of precoding matrices called a "codebook". The RI determines the rank of the precoding matrix.

[0014] Return to Figure 1 , the base station 100 determines the PDSCH that should be used for downlink communication with the UE 120 based on the CSI report. As shown in C, the base station 100 sends downlink control information (DCI) to the UE 120 to describe the PDSCH to be used for downlink communication. The base station 100 then uses the PDSCH to send downlink data.

[0015] The 5G NR and LTE physical layers support codebooks with higher spatial resolution based on a linear combination of multiple mutually orthogonal digital Fourier transform (DFT) beams. Such codebooks include the 5G NR Type II codebook, the 5G NR Type II port selection codebook, and the Advanced LTE CSI codebook. The high spatial resolution of these codebooks is achieved by increasing the number of bits required for the precoding matrix indicator (PMI) report.

[0016] The embodiments described herein relate to a solution for reducing the number of bits required for PMI reporting for codebooks with higher spatial resolution based on linear combination of DFT beams.The solution presented in one or more embodiments presented herein is based on frequency domain compression exploiting the correlation of beam combining coefficients in the frequency domain.

[0017] Existing solutions based on linear combinations of multiple mutually orthogonal DFT beams to reduce the number of bits required to report PMI for codebooks with higher spatial resolution are based on singular value decomposition (SVD) of the spatial frequency matrix or linear matrix transformation of the spatial frequency matrix. Existing solutions have several disadvantages. One disadvantage is the lack of many details of frequency domain channel state information (CSI) compression, including the spatial frequency matrix definition of the linear transformation basis and the detailed definition of the quantization method of the compressed spatial frequency matrix.

[0018] Details of the CSI report

[0019] The examples presented herein describe the details of frequency domain CSI compression, including the definition of a spatial frequency matrix, the definition of a base matrix with more detailed CSI components for frequency domain CSI compression (including the definition of new CSI components), the details of a quantization scheme for the newly introduced CSI components, the details of CSI reporting for the newly introduced CSI components, and a method of CSI quantization (hybrid time-frequency quantization of spatial coefficients).

[0020] One or more embodiments described herein help reduce the overhead of PMI reporting for type II codebooks, which is beneficial to the performance of 5G NR cellular systems. The embodiments described herein may be part of the following features when adopted by 3GPP RAN1 WG: 5G NR type II codebook (3GPP TS 38.214, 3GPP TS 38.212), 5G NR type II port selection codebook (3GPP TS 38.214, 3GPP TS 38.212) and advanced LTE CSI codebook (3GPP TS36.213, 3GPP TS 36.212). The embodiments described herein may be specified in the following files when adopted by 3GPP RAN1 WG: 3GPP TS 38.214, 3GPP TS 38.212, 3GPP TS 36.213 and 3GPP TS 36.212.

[0021] DFT Spatial Beamform

[0022] For a uniform rectangular planar antenna array with cross-polarized antennas and based on the DFT spatial beamform v defined by l，m Optimized 5G NR and LTE codebooks:

[0023]

[0024]

[0025] Where N1 and N2 are the numbers of cross-polarized antenna elements in the first dimension and the second dimension, respectively. O1 and O2 are the oversampling factors in the first dimension and the second dimension, respectively. l = 0, 1, ..., (N1O1-1) is the index for determining the spatial beam direction in the first dimension, and m = 0, 1, ..., (N2O2-1) is the index for determining the spatial beam direction in the second dimension.

[0026] There are also 5G NR and LTE codebooks optimized for beamforming or precoded CSI reference signals (CSI-RS). In this case, the port selection vector b is used n Instead of the DFT spatial beam, where only the vector b nThe nth element of is equal to 1 and the other elements are equal to 0, n = 0, 1, ..., N p , N p is the number of CSI-RS ports with the same polarization.

[0027] 5G NR and LTE Codebooks

[0028] 5G NR and LTE codebooks can be divided into s groups: codebooks with normal spatial resolution based on the selection of DFT spatial beams and codebooks with high spatial resolution based on the linear combination of DFT spatial beams. Codebooks with high spatial resolution based on the linear combination of DFT spatial beams include the following 5G NR codebooks: type II codebooks, type II port selection codebooks. Codebooks with high spatial resolution based on the linear combination of DFT spatial beams include the following LTE codebooks: advanced CSI codebooks and codebooks with high spatial resolution based on beam linear combinations.

[0029] The precoding matrix of the codebook with high spatial resolution is constructed as a linear combination of L mutually orthogonal DFT spatial beams. The columns of the precoding matrix with beam combining structure are represented in (3) for rank 1 and in (4) for rank 2.

[0030]

[0031]

[0032]

[0033] The q1, q2, n1, and n2 indices determine the L DFT spatial beams used in beam combining. A set of, i = 0, 1, ..., L-1 is the index of the DFT spatial beam in the beam combination, l = 1, 2 is the index of the layer, is the broadband amplitude coefficient, is the subband amplitude coefficient, is the phase coefficient, k = 0, 1, ..., (2·L-1) is the index of the coefficient in the linear combination of the beams, and are the sets of indices that determine the broadband and subband amplitude coefficients, respectively, c l is a set of indices that determine the phase coefficients.

[0034] The number of beams in the linear combination L may be configured by higher layers and / or specified in the physical layer specification. The number of bits required for reporting and quantization of wideband and subband amplitude and phase coefficients may be fixedly configured by higher layers and / or specified in the physical layer specification. The subband amplitude and phase coefficients are not reported.

[0035] 5G NR Type II Codebook Configuration

[0036] The number of spatial beams used in the linear combination L is configured with the higher layer parameter numberOfBeams, where L = {2,3,4}. The number of bits and the quantization scheme used to report the phase coefficients are configured with the higher layer parameter phaseAlphabetSize, where the supported quantization schemes are QPSK and 8-PSK. The number of bits required to report the wideband amplitude coefficients is 3 bits. The number of bits required to report the sub-band amplitude coefficients is controlled by the higher layer parameter sub-bandAmplitude, which is set to TRUE (1 bit) or FALSE (0 bit).

[0037] Overhead for PMI reporting with beam combining based codebook

[0038] The number of bits for PMI reporting for the codebook based linear combination of DFT spatial beams can be calculated using (5).

[0039] N 位 =N 波束 +2L·R·N amplWB +2L·R·N SB ·N amplSB +2L·R·N SB ·N 相位 (5)

[0040] Where N 波束 is the number of bits required to report the indices of L mutually orthogonal beams, R is the rank value or number of layers, and N ampIWB is the number of bits required to report the wideband amplitude factor, N SB is the number of subbands configured for CSI reporting, N amp1WB is the number of bits required to report the subband amplitude coefficients, N 相位 is the number of bits required to report the phase coefficient.

[0041] Spatial Frequency Matrix

[0042] The equations for the precoding matrix (2, 3, 4) can be expressed in a simplified form with a two-level structure (6).

[0043] W(k)=W1·W2(k) (6)

[0044] Where W(k) is the precoding matrix for rank R and frequency resource k, with dimensions 2N1N2×R, W1 is the wideband channel information matrix, with dimensions 2N1N2×2L, W2(k) is the subband channel information matrix for frequency resource k, with dimensions 2L×R, k is the index of the subband, k=1, 2, ..., N. In one embodiment, the frequency resource is the subband configured for CSI reporting. For frequency domain compression, the precoding matrix can be represented in the alternative form (7).

[0045] Y(l)=W1·Y2(l) (7)

[0046] Wherein column k of Y(1) corresponds to layer 1 of the precoding matrix for frequency resource k, matrix Y(1) has dimensions 2N1N2×N, Y2(1) is the spatial frequency matrix for spatial layer 1, with dimensions 2L×N, 1=1, 2, ..., R is the index of the spatial layer. Equations (6) and (7) are schematically represented in Figure 2A and Figure 2B middle.

[0047] Compression of spatial-frequency matrix

[0048] Overhead reduction of PMI reporting can be achieved by frequency domain or time domain compression of the spatial frequency matrix Y2(1). Without compressing the spatial frequency matrix, the phase and amplitude of each coefficient of the spatial frequency matrix are quantized and reported by the UE.

[0049] In one embodiment, a linear transformation may be used to compress the spatial frequency matrix. The linear transformation corresponds to equation (8) and is schematically represented in Figure 3 middle.

[0050] Y2(l)=Z1(l)·Z2(l) (8)

[0051] Where Z1(l) is the matrix of coefficients of the linear transformation, with dimensions 2L×M, and Z2(l) is the basis matrix of the linear transformation, with dimensions M×N. M is the total number of vectors in the basis matrix, and N is the number of frequency resources.

[0052] In one embodiment, M=M1·O, where O is the oversampling factor. In one embodiment, the oversampling factor is configured by a higher layer. In one embodiment, M1 is the number of frequency resources. In one embodiment, the frequency resources are subbands configured for CSI reporting. In one embodiment, the frequency resources are subbands within the active bandwidth portion. In one embodiment, the frequency resources are physical resource blocks (PRBs) configured for CSI reporting. In one embodiment, the frequency resources are PRBs in the active bandwidth portion. To simplify further description, the linear transformation of the spatial frequency matrix Y2(l) is expressed by equation (9) as a linear combination of basis vectors.

[0053]

[0054] where z m is the row of the basis matrix Z2(r) with index m or basis vector m, m = 1, 2, ..., M, S is the number of basis vectors in the linear combination, g s,i,l , s = 0, 1, ..., S-1 is the index of the basis vector in the linear combination, a s,i,l are the coefficients of the linear combination, i = 1, 2, ..., 2L are the indices of the DFT beam and polarization, and l = 1, 2, ..., R are the indices of the spatial layers. In one embodiment, the rows of the basis matrix of the linear transformation Z2(r) are the DFT vectors z m (10).

[0055]

[0056] In one embodiment, the linear combination g s,i,l The indices of the basis vectors in are reported by the UE. In one embodiment, the linear combination g s,i,l The indices of the basis vectors in are different for different DFT beams and different polarizations. In one embodiment, the linear combination g s,i,l The indices of the basis vectors in g are the same for different DFT beams and different polarizations. s,i,l =g s,j,l , i = 1, 2, ..., 2L, j = 1, 2, ..., 2L. In one embodiment, the linear combination g s,i,l The indices of the basis vectors in g are the same for the DFT beams and different polarizations, s,i,l =g s,j,l , i = 1, 2, ..., L, j = i + L. In one embodiment, the linear combination g s,i,l The indices of the basis vectors in are different for different layers.

[0057] In one embodiment, the linear combination g s,i,l The indices of the basis vectors in g are the same for different layers.s,i,l =g s,i,j , l = 1, 2, ..., R, j = 1, 2, ... R. In one embodiment, the linear combination g s,i,l The indices of the basis vectors in are reported by the UE for s=0, 1, ..., S-1 respectively. In one embodiment, the linear combination g s,i,l The index of the basis vectors in is determined by the UE using the combined index G i,l (11) Reported jointly for s=0, 1, ..., S-1.

[0058]

[0059] where g s,i,l As s increases, C(x,y) is the combination coefficient (eg, Table 1).

[0060] Table 1: Combination coefficient C(x,y)

[0061]

[0062] In one embodiment, the number of basis vectors in the linear combination S is configured by a higher layer. In one embodiment, S is equal to M. In one embodiment, S is a function of M. In one embodiment, S is a function of N. In one embodiment, S is configured separately for different codebook rank values. In one embodiment, S is configured separately for different spatial layers.

[0063] Quantization of CSI components

[0064] In one embodiment, the linear combination a s,i,l The amplitude and phase of the coefficients of are quantized and reported by the UE. In one embodiment, the linear combination a s,i,l The phase of the coefficients of is quantized and reported by the UE. In one embodiment, a set of values ​​is used To quantify the linear combination a s,i,l The phase of the coefficients of m = 0, 1, ..., NPSK-1. In one embodiment, the linear combination a s,i,l The quantization scheme of the phase of the coefficients of is configured by a higher layer. In one embodiment, NPSK is configured by a higher layer. In one embodiment, the linear combination a s,i,l The amplitude of the coefficients of is quantized and reported by the UE. In one embodiment, a set of values ​​is used To quantify the linear combination a s,i,l The amplitude of the coefficients of n = 0, 1, ..., Na-2. In one embodiment, the set of values ​​is used To quantify the linear combination a s,i,l The amplitude of the coefficient, n=0,1,…,Na-2.

[0065] In one embodiment, the linear combination a s,i,l The quantization scheme of the phase of the coefficients of is configured by higher layers. In one embodiment, N a Configured by higher layers. In one embodiment, the linear combination A j,l The leading coefficient of the linear combination is reported by the UE. In one embodiment, the index of the leading coefficient is reported by the UE. In one embodiment, the ratio of the amplitude of the linear combination coefficient to the amplitude of the leading coefficient of the linear combination is |a s,i,l | / |A j,l |Reported by the UE. In one embodiment, a set of values ​​is used To quantify the ratio of the amplitude of the coefficients of the linear combination to the amplitude of the leading coefficient of the linear combination |a s,i,l | / |A j,l |,n=0,1,...,N a-2 In one embodiment, a set of values ​​is used To quantify the ratio of the amplitude of the coefficients of the linear combination to the amplitude of the leading coefficient of the linear combination |a s,i,l | / |A j,l |, n = 0, 1, ..., Na-2.

[0066] In one embodiment, the product a of the coefficient of the linear combination and the complex conjugate of the leading coefficient of the linear combination s,i,l ·A i,l The phase of * is reported by the UE. In one embodiment, the index of the leading coefficient of the linear combination is reported by the UE for each DFT beam and polarization and for each spatial layer. In one embodiment, the same index of the leading coefficient of the linear combination is reported by the UE for different DFT beams and polarizations.

[0067] CSI Report

[0068] 5G NR Type II codebook is reported via PUSCH. PUSCH-based CSI reporting consists of two parts: CSI Part 1 and CSI Part 2. The CSI parts are encoded and transmitted separately using mutually orthogonal resource elements. The payload size of CSI Part 1 is fixed for a given CSI configuration. The payload size of CSI Part 2 depends on the content of CSI Part 1.

[0069] In one embodiment, the linear combination g is reported in CSI Part 1 s,i,l In one embodiment, the linear combination g is reported in CSI Part 2 s,i,l In one embodiment, the linear combination g is reported in CSI part 1 for the first spatial layer (l=1).s,i,l The indices of the basis vectors in , and for the second spatial layer (l = 2) the linear combination g is reported in CSI Part 2 s,i,l The indices of the basis vectors in .

[0070] In one embodiment, the linear combination a is reported in CSI part 1 s,i,l In one embodiment, the linear combination a is reported in CSI Part 2 s,i,l In one embodiment, the linear combination a is reported in CSI part 1 for the first spatial layer (l=1). s,i,l The amplitude of the coefficients of , and for the second spatial layer (l = 2) the linear combination a is reported in CSI part 2 s,i,l The amplitude of the coefficient.

[0071] In one embodiment, the linear combination a with non-zero amplitude is reported in CSI part 1 s,i,l In one embodiment, the linear combination a with zero amplitude is reported in CSI part 1. s,i,l In one embodiment, the linear combination a with non-zero amplitude is reported in CSI part 1 for spatial layer l. s,i,l In one embodiment, the linear combination a with zero amplitude is reported in CSI part 1 for spatial layer l. s,i,l The number of coefficients.

[0072] In one embodiment, the linear combination A is reported in CSI part 1 i,l In one embodiment, the linear combination A is reported in CSI Part 1 i,l In one embodiment, the linear combination A is reported in CSI part 1 for the first spatial layer (l=1). i,l The leading coefficient of , and for the second spatial layer (l = 2) the linear combination A is reported in CSI Part 2 i,l The first coefficient of .

[0073] In one embodiment, the ratio of the amplitude of the coefficient of the linear combination to the amplitude of the leading coefficient of the linear combination is reported in CSI part 1. s,i,l | / |A i,l In one embodiment, the ratio of the amplitude of the coefficient of the linear combination to the amplitude of the leading coefficient of the linear combination is reported in CSI part 2. s,i,l | / |A i,l |.

[0074] In one embodiment, for the first spatial layer (l=1), the ratio of the amplitude of the coefficient of the linear combination to the amplitude of the leading coefficient of the linear combination is reported in CSI part 1: s,i,l | / |A i,l |, and for the second spatial layer (l=2) the ratio of the amplitude of the coefficient of the linear combination to the amplitude of the leading coefficient of the linear combination is reported in CSI part 2 |a s,i,l | / |A i,l |.

[0075] Hybrid time-frequency quantization of spatial coefficients

[0076] In one embodiment, the spatial frequency matrix Y2(l) is reported by the UE using hybrid time-frequency quantization. In one embodiment, s subsets of the rows of the spatial frequency matrix are quantized and reported as linear combinations of the basis vectors (9), and the other rows of the spatial frequency matrix The phase and / or amplitude of each element of this row is quantized and reported. In one embodiment, a subset of the rows of the spatial frequency matrix is ​​determined based on the average amplitude of the elements of the rows of the spatial frequency matrix. In one embodiment, the subset The number of rows in the spatial frequency matrix is ​​configured by higher layers.

[0077] Reporting of coefficients associated with the strongest beam / polarization

[0078] Since the SVD vector and the eigen vector are defined to be multiplied by at most the unit phase factor, if the precoder vector for the kth subband is V(k) or The performance of the MIMO system is the same, where is a complex exponential with arbitrary phase. This property can be used to achieve better performance frequency domain CSI compression and / or reduce reporting overhead.

[0079] Therefore, each column of the spatial frequency matrix Y2(l) can be multiplied by a complex number with arbitrary phase and unit amplitude. In one embodiment, the UE multiplies the kth column of the matrix Y2(l) by q(k)*, k=1,2,...,N. In one embodiment, q(k)=c(k) / |c(k)|, where c(k) is the row in the spatial frequency matrix Y2(l) associated with the strongest DFT beam / polarization (the DFT beam / polarization with the highest average or wideband power). After this operation, the frequency domain coefficient associated with the strongest DFT beam / polarization is a real number |c(k)|. The time domain coefficient C(m) associated with the strongest DFT beam / polarization is derived at the UE by DFT according to a certain oversampling factor of the frequency domain coefficient |c(k)| associated with the strongest DFT beam / polarization, m=1,2,...,M.

[0080] It can be assumed a priori that the frequency domain coefficients associated with the strongest DFT beam / polarization are real to reduce overhead or improve the performance of frequency domain compression. If the frequency domain coefficients are real, then the time domain coefficients (the coefficients after multiplication by the DFT matrix) have symmetric properties and the following equation is valid.

[0081] C(m)=C * ({(-m+1)mod M}+1) (12)

[0082] As can be seen from equation (12), some time domain coefficients can be derived from other time domain coefficients. In one embodiment, the time domain coefficients associated with the strongest DFT beam / polarization are divided into two sets C1 and C2. In one embodiment, C1 includes coefficients C(m) with index m≤(M / 2+1), and C2 includes the remaining coefficients C(m). In one embodiment, a subset of the coefficients from C1 is reported by the UE. In one embodiment, predefined equations are used to derive coefficients from C2 based on coefficients from C1. In one example, equation (12) is used to derive coefficients from C2 based on coefficients from C1. In one embodiment, the spatial frequency matrix Y2(l) is reconstructed using equation (9) considering the time domain coefficients from C2 derived based on the reported time domain coefficients from C1.

[0083] Figure 4 A user device 120 according to one aspect is shown (see also Figure 1 2). In some aspects, the user device 120 may be a mobile device or user equipment (UE). The device 120 is configured to send and receive RF signals and includes an application processor 405, a baseband processor 130 (also referred to as a baseband module), a radio front end module (RFEM) 415 (also referred to as a radio interface), a memory 420, a connection module 425, a near field communication (NFC) controller 430, an audio driver 435, a camera driver 440, a touch screen 445, a display driver 450, a sensor 455, a removable memory 460, a power management integrated circuit (PMIC) 465, and a smart battery 470.

[0084] In some aspects, the application processor 405 may include, for example, one or more CPU cores and one or more cache memories, a low dropout voltage regulator (LDO), an interrupt controller, a serial interface such as a serial peripheral interface (SPI), an inter-integrated circuit (I2C), or a general purpose programmable serial interface module, a real-time clock (RTC), a timer-counter including an interval and a watchdog timer, general purpose input output (IO), a memory card controller such as a secure digital / multimedia card (SD / MMC) or the like, a universal serial bus (USB) interface, a mobile industry processor interface (MIPI) interface, and a joint test access group (JTAG) test access port.

[0085] In some aspects, baseband module 130 may be implemented as, for example, a solder-in substrate including one or more integrated circuits, a single packaged integrated circuit soldered to a main circuit board, and / or a multi-chip module containing two or more integrated circuits.

[0086] Figure 5 An example base station or gNB / TRP / eNB 100 (see also Figure 1 2 ). The eNB 100 is configured to send and receive RF signals and may include one or more of the following: an application processor 505, a baseband module 110 (also referred to as a baseband processor), one or more radio front end modules 515 (also referred to as a radio interface), a memory 520, a power management circuitry 525, a power three-way interface circuitry 530, a network controller 535, a network interface connector 540, a satellite navigation receiver module 545, and a user interface 550.

[0087] In some aspects, the application processor 505 may include one or more CPU cores and one or more of the following: cache memory, a low dropout (LDO) voltage regulator, an interrupt controller, a serial interface such as SPI, I2C or a general programmable serial interface module, a real-time clock (RTC), a timer-counter including interval and watchdog timers, general purpose IO, a memory card controller such as SD / MMC or the like, a USB interface, a MIPI interface, and a Joint Test Access Group (JTAG) test access port.

[0088] In some aspects, baseband processor 110 may be implemented as, for example, a solder-in substrate including one or more integrated circuits, a single packaged integrated circuit soldered to a main circuit board, and / or a multi-chip module containing two or more integrated circuits.

[0089] In some aspects, the memory 520 may include one or more of the following: volatile memory including dynamic random access memory (DRAM) and / or synchronous dynamic random access memory (SDRAM), and non-volatile memory (NVM) including high-speed electrically erasable memory (commonly referred to as flash memory), phase change random access memory (PRAM), magnetoresistive random access memory (MRAM), and / or three-dimensional cross-point memory. The memory 520 may be implemented as one or more of a solder-in package integrated circuit, a socketed memory module, and a plug-in memory card.

[0090] In some aspects, the power management integrated circuit system 525 may include one or more of the following: a voltage regulator, a surge protector, a power alarm detection circuit system, and one or more backup power supplies such as a battery or capacitor. The power alarm detection circuit system may detect one or more of a brownout (undervoltage) and a surge (overvoltage) condition.

[0091] In some aspects, the power three-way interface circuitry 530 can provide power drawn from the network cable to provide both a power supply and a data connection to the base station radio head 100 using a single cable.

[0092] In some aspects, the network controller 535 can provide a connection to the network using a standard network interface protocol such as Ethernet. A physical connection can be used to provide a network connection, which is one of an electrical connection (commonly referred to as a copper interconnect), an optical connection, or a wireless connection.

[0093] In some aspects, the satellite navigation receiver module 545 may include circuitry for receiving and decoding signals transmitted by one or more navigation satellite constellations such as the Global Positioning System (GPS), the Global Navigation Satellite System (GLONASS), Galileo, and / or BeiDou. The receiver 545 may provide data to the application processor 505, which may include one or more of position data or time data. The application processor 505 may use the time data to synchronize operations with other radio base stations.

[0094] In some aspects, user interface 550 may include one or more of: a physical or virtual button, such as a reset button, one or more indicators, such as a light emitting diode (LED), and a display screen.

[0095] Although the present invention has been shown and described with respect to one or more embodiments, changes and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. In particular, with respect to the various functions performed by the above-described components or structures (assemblies, devices, circuits, circuit systems, systems, etc.), unless otherwise indicated, the terms used to describe such components (including references to "means") are intended to correspond to any component or structure that performs the specified function of the described component (e.g., which is functionally equivalent), even if not structurally equivalent to the disclosed structure that performs that function in the exemplary embodiments of the invention shown herein.

[0096] The various illustrative logics, logical blocks, modules, circuit systems, and circuits described in conjunction with the various aspects disclosed herein may be implemented or performed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, however, in an alternative, the processor may be any conventional processor, controller, microcontroller, or state machine.

[0097] The above description of the illustrated embodiments of the subject disclosure (including what is described in the Abstract) is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. Although specific embodiments and examples are described herein for illustrative purposes, various modifications considered within the scope of such embodiments and examples are possible, as those skilled in the relevant art may recognize.

[0098] In this regard, while the disclosed subject matter has been described in conjunction with various embodiments and corresponding figures, it should be understood that other similar embodiments may be used, or modifications and additions may be made to the described embodiments to perform the same, similar, alternative or substituted functions of the disclosed subject matter, without departing from the disclosed subject matter. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but rather should be interpreted in breadth and scope in accordance with the following appended claims.

[0099] Similar reference numerals are used throughout the disclosure to refer to similar elements, and the structures and devices shown therein are not necessarily drawn to scale. As used herein, the terms "module", "component", "system", "circuit", "circuitry", "element", "slice", etc. are intended to refer to computer-related entities, hardware, software (e.g., in execution) and / or firmware. For example, circuitry or similar terms can be a processor, a process running on a processor, a controller, an object, an executable program, a storage device, and / or a computer with a processing device. By way of illustration, applications and servers running on a server can also be circuitry. One or more circuitry systems may reside in a process, and the circuitry system may be located on a computer and / or distributed between two or more computers. A collection of elements or other circuitry systems may be described herein, where the term "collection" may be interpreted as "one or more".

[0100] As another example, a circuit system or similar terms may be a device having specific functionality provided by mechanical parts operated by an electrical or electronic circuit system, wherein the electrical or electronic circuit system may be operated by a software application or firmware application executed by one or more processors. The one or more processors may be internal or external to the device and may execute at least a portion of the software or firmware application. As yet another example, a circuit system may be a device that provides specific functionality through electronic components without mechanical parts; the electronic components may include field gates, logic components, hard-coded logic, register transfer logic, one or more processors to execute software and / or firmware that at least partially imparts the functionality to the electronic components.

[0101] It should be understood that when an element is referred to as being "electrically connected" or "electrically coupled" to another element, the element may be physically connected or coupled to the other element so that current and / or electromagnetic radiation may flow along a conductive path formed by the element. When elements are described as being electrically coupled or connected to each other, there may be an intermediate conductive, inductive or capacitive element between the element and the other element. Further, when electrically coupled or connected to each other, an element may be able to induce a voltage or current flow or propagation of an electromagnetic wave in another element without physical contact or intermediate components. Further, when a voltage, current or signal is referred to as being "applied" to an element, the voltage, current or signal may be conducted to the element by a physical connection or by capacitive, electromagnetic or inductive coupling that does not involve a physical connection.

[0102] The exemplary use of words is intended to present concepts in a specific manner. The terms used herein are only used for the purpose of describing specific examples and are not intended to limit examples. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "an" and "the" are also intended to include plural forms. It should be further understood that the terms "comprise", "comprising", "including" and / or "comprising" when used herein specify the presence of the described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or their groups.

[0103] For one or more examples, at least one of the components described in one or more of the previous figures may be configured to perform one or more operations, techniques, processes, and / or methods as described below in the Examples section. For example, the baseband circuitry as described above in conjunction with one or more of the previous figures may be configured to operate according to one or more of the examples described below. For another example, the circuitry associated with the UE, base station, network element, etc. as described above in conjunction with one or more of the previous figures may be configured to operate according to one or more of the examples described below in the Examples section.

[0104] Example

[0105] Example 1 is an apparatus for a user equipment (UE), comprising: a baseband circuit system having an RF interface configured to send and receive radio frequency (RF) signals; and one or more processors. The one or more processors are configured to: identify a codebook that specifies codebook parameters and a precoding matrix, wherein each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients defined for different frequency resource sets; process a reference signal received from a base station to determine the codebook parameters of the reference signal; calculate a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI identifies a selected linear combination of spatial beams defined in the precoding matrix for use in downlink transmission from the base station to the UE; and report the PMI to the base station.

[0106] Example 2 includes the subject matter of Example 1, including or omitting optional elements, wherein the frequency resource set comprises: a subband configured for CSI reporting, a subband in an active bandwidth portion, a physical resource block configured for CSI reporting, or a physical resource block within the active bandwidth portion.

[0107] Example 3 includes the subject matter of any of Examples 1-2, including or omitting optional elements, wherein the coefficients for each spatial beam and frequency resource set form a vector y that is a linear combination of a subset of basis vectors, where each basis vector is a column of a discrete Fourier transform matrix.

[0108] Example 4 includes the subject matter of Example 3, including or omitting the optional elements, wherein the total number of basis vectors is determined based on the number of frequency resources in the frequency resource set.

[0109] Example 5 includes the subject matter of Example 4, including or omitting optional elements, wherein the total number of basis vectors is determined based on the product of the number of frequency resources in the frequency resource set and an oversampling factor of the discrete Fourier transform.

[0110] Example 6 includes the subject matter of Example 3, including or omitting optional elements, wherein the total number of basis vectors or the number of basis vectors in the subset of basis vectors is configured by a higher layer.

[0111] Example 7 includes the subject matter of Example 3, including or omitting optional elements, wherein the number of basis vectors in the subset of basis vectors is configured by a higher layer for each spatial layer or for each rank.

[0112] Example 8 includes the subject matter of Example 3, including or omitting optional elements, wherein the number of basis vectors in the subset of basis vectors is equal to the total number of basis vectors or the number of frequency resources in the set of frequency resources.

[0113] Example 9 is an apparatus for a user equipment (UE), comprising: a baseband circuit system having a radio frequency (RF) interface configured to send and receive RF signals; and one or more processors. The one or more processors are configured to: identify a codebook that specifies codebook parameters and a precoding matrix, wherein each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients of the linear combination defined for different frequency resource sets, wherein the coefficients for each spatial beam and frequency resource set form a vector y that is a linear combination of a subset of basis vectors, further wherein each basis vector is a column of a discrete Fourier transform matrix and is identified by a unique value of a basis vector index; process a reference signal received from a base station to determine codebook parameters for the reference signal; calculate a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI includes the coefficients of the linear combination and corresponding basis vector indices for a selected subset of basis vectors, the selected subset of basis vectors defining a desired linear combination of spatial beams for use in a downlink transmission from the base station to the UE; and report the PMI to the base station.

[0114] Example 10 includes the subject matter of Example 9, including or omitting optional elements, wherein the basis vector indices for the selected subset of the basis vectors are different for different spatial layers and spatial beams.

[0115] Example 11 includes the subject matter of Example 9, including or omitting optional elements, wherein the basis vector indices for the selected subset of the basis vectors are the same for different spatial layers or different spatial beams.

[0116] Example 12 includes the subject matter of Example 9, including or omitting optional elements, wherein the one or more processors are configured to jointly report the basis vector indices in the selected subset of the basis vectors using combined indices.

[0117] Example 13 includes the subject matter of any of Examples 9-12, including or omitting optional elements, wherein the one or more processors are configured to: quantize coefficients of linear combinations of the basis vector indices in a selected subset of the basis vectors; and report the coefficients to the base station.

[0118] Example 14 includes the subject matter of Example 13, including or omitting optional elements, wherein the one or more processors are configured to: quantize the phase of the coefficients of the linear combination of the basis vector indices in the selected subset of the basis vectors; and report the phase of the coefficients to the base station.

[0119] Example 15 includes the subject matter of Example 14, including or omitting optional elements, wherein the one or more processors are configured to: quantize the amplitudes of coefficients of linear combinations of the basis vector indices in a selected subset of the basis vectors; and report the amplitudes of the coefficients to the base station.

[0120] Example 16 includes the subject matter of Example 13, including or omitting optional elements, wherein the one or more processors are configured to: quantize the leading coefficients of the linear combinations of the basis vector indices in a selected subset of the basis vectors; and report the preferred coefficients to the base station.

[0121] Example 17 includes the subject matter of Example 16, including or omitting optional elements, wherein the one or more processors are configured to report the index of the leading coefficient to the base station.

[0122] Example 18 includes the subject matter of Example 16, including or omitting optional elements, wherein the one or more processors are configured to: quantize the ratio of the amplitude of each coefficient of the linear combination to the amplitude of the leading coefficient of the linear combination; and report the ratio to the base station.

[0123] Example 19 includes the subject matter of Example 16, including or omitting optional elements, wherein the one or more processors are configured to: quantize the phase of the product of each coefficient of the linear combination and the complex conjugate of the leading coefficient of the linear combination; and report the phase to the base station.

[0124] Example 20 includes the subject matter of Example 9, including or omitting optional elements, wherein the one or more processors are configured to: identify the strongest spatial beam; and report to the base station a linear combination of a subset of basis vectors corresponding to the identified spatial beam.

[0125] Example 21 includes the subject matter of Example 9, including or omitting the optional elements, wherein the elements of vector y are real numbers.

[0126] Example 22 includes the subject matter of Example 21, including or omitting optional elements, wherein: the vector y is expressed as a vector c having elements partitioned into a set C1 and a set C2, wherein each element from C2 is the complex conjugate of the corresponding element of set C1; and the one or more processors are configured to report a subset of the elements from C1 to the base station.

[0127] Example 23 includes the subject matter of Example 22, including or omitting optional elements, wherein the one or more processors are configured to: derive a subset of elements of C2 based on the subset of elements of C1 reported to the base station; and report the subset of elements of C2 to the base station.

[0128] Example 24 is an apparatus for a user equipment (UE), comprising: a baseband circuit system having a radio frequency (RF) interface configured to send and receive RF signals; and one or more processors. The one or more processors are configured to: identify a codebook that specifies codebook parameters and a precoding matrix, wherein each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients of the linear combination defined for different frequency resource sets, wherein the coefficients for each spatial beam and frequency resource set form a vector y that is a linear combination of a subset of basis vectors, further wherein each basis vector is a column of a discrete Fourier transform matrix and is identified by a unique value of a basis vector index; process a reference signal received from a base station to determine codebook parameters for the reference signal; calculate a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI includes coefficients of the linear combination and corresponding basis vector indices for a selected subset of basis vectors, the selected subset of basis vectors defining a desired linear combination of spatial beams for use in a downlink transmission from the base station to the UE; and report the PMI to the base station in a CSI report having a first part and a second part.

[0129] Example 25 includes the subject matter of Example 24, including or omitting the optional elements, wherein the first portion includes a number of coefficients of linear combinations having non-zero amplitudes.

[0130] Example 26 includes the subject matter of Example 24, including or omitting optional elements, wherein the second part includes the phase of the coefficients of the linear combination, the amplitude of the coefficients of the linear combination, the amplitude of the leading coefficient of the linear combination, and the index of the basis vector in the subset of the basis vectors.

[0131] Unless explicitly stated otherwise, any of the above examples may be combined with any other example (or combination of examples). The foregoing description of one or more embodiments provides illustration and description, but is not intended to be exhaustive or to limit the scope of the examples to the precise form disclosed. Modifications and variations are possible in view of the above teachings or may be acquired from practice of the various examples.

Claims

1. An apparatus for a user equipment (UE) for reporting a precoding matrix indicator (PMI), the apparatus comprising a baseband circuit system and one or more processors, the baseband circuit system having an RF interface configured to send and receive radio frequency (RF) signals, the one or more processors configured to: Identifies the codebook that specifies the codebook parameters and precoding matrix, where Each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients defined for a different set of frequency resources; processing a reference signal received from a base station to determine a codebook parameter of the reference signal; calculating a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI identifies a selected linear combination of spatial beams defined in the precoding matrix for use in downlink transmissions from the base station to the UE; and reporting the PMI to the base station, wherein the coefficients for each spatial beam and frequency resource set form a vector y that is a linear combination of a subset of basis vectors, wherein each basis vector is a column of a discrete Fourier transform matrix, and wherein the total number of basis vectors is determined based on the product of the number of frequency resources in the frequency resource set and an oversampling factor of the discrete Fourier transform matrix.

2. The device according to claim 1, wherein: The frequency resource set includes: a subband configured for CSI reporting, a subband in an active bandwidth portion, a physical resource block configured for CSI reporting, or a physical resource block in the active bandwidth portion.

3. The device according to claim 1, wherein: The number of basis vectors in the subset of basis vectors is configured by higher layers.

4. The device according to claim 1, wherein: The number of basis vectors in the subset of basis vectors is configured by higher layers for each spatial layer or for each rank.

5. The device according to claim 1, wherein: The number of basis vectors in the subset of basis vectors is equal to the total number of basis vectors or the number of frequency resources in the frequency resource set.

6. An apparatus for a user equipment (UE) for reporting a precoding matrix indicator (PMI), the apparatus comprising a baseband circuit system and one or more processors, the baseband circuit system having an RF interface configured to send and receive RF signals, the one or more processors configured to: Identifies the codebook that specifies the codebook parameters and precoding matrix, where Each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients of a linear combination defined for a different set of frequency resources, wherein the coefficients for each spatial beam and set of frequency resources form a vector y, the vector y being a linear combination of a subset of basis vectors, further wherein each basis vector is a column of a discrete Fourier transform matrix and is identified by a unique value of a basis vector index; processing a reference signal received from a base station to determine a codebook parameter of the reference signal; calculating a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI comprises coefficients of the linear combination and corresponding basis vector indices for a selected subset of basis vectors that define a desired linear combination of spatial beams for use in downlink transmissions from the base station to the UE; Reporting the PMI to the base station; quantizing coefficients of linear combinations of the basis vector indices in the selected subset of the basis vectors; and reporting the coefficients to the base station, The total number of basis vectors is determined according to the product of the number of frequency resources in the frequency resource set and the oversampling factor of the discrete Fourier transform matrix.

7. The device according to claim 6, wherein: The basis vector indices for the selected subset of the basis vectors are different for different spatial layers and spatial beams.

8. The device according to claim 6, wherein: The basis vector indices for the selected subset of the basis vectors are the same for different spatial layers or different spatial beams.

9. The device according to claim 6, wherein: The one or more processors are configured to jointly report the basis vector indices in the selected subset of the basis vectors using a combined index.

10. The device according to claim 6, wherein: The one or more processors are configured to: quantizing the phases of coefficients of linear combinations of the basis vector indices in the selected subset of the basis vectors; and The phase of the coefficient is reported to the base station.

11. The device according to claim 10, wherein: The one or more processors are configured to: quantizing the amplitudes of coefficients of linear combinations of the basis vector indices in the selected subset of the basis vectors; and The amplitude of the coefficient is reported to the base station.

12. The device according to claim 6, wherein: The one or more processors are configured to: quantizing leading coefficients of linear combinations of the basis vector indices in the selected subset of the basis vectors; and The leading coefficient is reported to the base station.

13. The device according to claim 12, wherein: The one or more processors are configured to report an index of the leading coefficient to the base station.

14. The device according to claim 12, wherein: The one or more processors are configured to: quantizes the ratio of the amplitude of each coefficient of the linear combination to the amplitude of the leading coefficient of the linear combination; and The ratio is reported to the base station.

15. The device according to claim 12, wherein: The one or more processors are configured to: quantizing the phase of the product of each coefficient of the linear combination and the complex conjugate of the leading coefficient of the linear combination; and The phase is reported to the base station.

16. The device according to claim 6, wherein: The one or more processors are configured to: identifying the strongest spatial beam; and Linear combinations of a subset of basis vectors corresponding to the identified spatial beams are reported to the base station.

17. The device according to claim 6, wherein: The elements of vector y are real numbers.

18. The device according to claim 17, wherein: The vector y is expressed as a vector c having elements partitioned into a set C1 and a set C2, wherein each element from C2 is the complex conjugate of the corresponding element of the set C1; and The one or more processors are configured to report a subset of elements from C1 to the base station.

19. The device according to claim 18, wherein: The one or more processors are configured to: deriving a subset of elements of C2 based on the subset of elements of C1 reported to the base station; and A subset of the elements of C2 is reported to the base station.

20. An apparatus for a user equipment (UE) for reporting a precoding matrix indicator (PMI), the apparatus comprising baseband circuitry and one or more processors, the baseband circuitry having an RF interface configured to send and receive RF signals, the one or more processors configured to: Identifies the codebook that specifies the codebook parameters and precoding matrix, where Each column of the precoding matrix corresponds to a spatial layer and is constructed by a linear combination of spatial beams, wherein each spatial beam has coefficients of a linear combination defined for a different set of frequency resources, wherein the coefficients for each spatial beam and set of frequency resources form a vector y, the vector y being a linear combination of a subset of basis vectors, further wherein each basis vector is a column of a discrete Fourier transform matrix and is identified by a unique value of a basis vector index; processing a reference signal received from a base station to determine a codebook parameter of the reference signal; calculating a precoding matrix indicator (PMI) based on the codebook parameters, wherein the PMI comprises coefficients of the linear combination and corresponding basis vector indices for a selected subset of basis vectors, the selected subset of basis vectors defining a desired linear combination of spatial beams for use in downlink transmissions from the base station to the UE; and reporting the PMI to the base station in a CSI report having a first part and a second part, wherein the first part comprises the number of coefficients of linear combinations having non-zero amplitudes, The total number of basis vectors is determined according to the product of the number of frequency resources in the frequency resource set and the oversampling factor of the discrete Fourier transform matrix.

21. The device according to claim 20, wherein: The second part includes the phase of the coefficients of the linear combination, the amplitude of the coefficients of the linear combination, the amplitude of the leading coefficient of the linear combination, and the index of the basis vector in the subset of basis vectors.

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