Methods of CSI-rs beamforming in angle-delay domains for type ii port selection codebook

Abstract

To provide a terminal, a wireless communication method, and a system that appropriately report channel state information (CSI).SOLUTION: A terminal includes a control unit that determines a precoding matrix indicator (PMI) using a matrix which is associated with a spatial domain (SD) beam and which is an identity matrix without performing port selection, and a transmission unit that transmits a report of channel state information (CSI) including the PMI.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] One or more embodiments disclosed herein relate to an apparatus and method for beamforming in the angular delay domain. [Background technology]

[0002] In New Radio (NR), rank 1 and rank 2 Type II channel state information (CSI) feedback is supported (NR Release 15). In Type II CSI feedback, an amplitude scaling mode is configured.

[0003] In the amplitude scaling mode, a user equipment (UE) may be configured to report wideband (WB) amplitude along with subband (SB) amplitude and SB phase information. In conventional schemes, a significant percentage of the overall overhead may be accounted for by the overhead for reporting SB amplitude and phase. The following equation shows the SB precoder generation in Type-II CSI of Release 15 of NR for single layer transmission. W=W space W coeff (1)

[0004] Here, the matrix W(N t ×N SB ) has N SB The precoding vectors for N subbands are taken. t W represents the number of available TXRU ports. space (N t × 2L) consists of 2L broadband spatial 2D-Discrete Fourier Transform (DFT) beams. The matrix contains W coeffThe SB combination coefficients as expressed in (1) are captured by W coeff is captured by

[0005] Additionally, NR supports Type II CSI reporting for precoding downlink transmissions on the Physical Downlink Shared Channel (PDSCH). In this regard, Type II solutions focus on providing detailed CSI for Multi-User Multiple-Input Multiple-Output (MIMO) purposes. In NR Release 15, these solutions support up to two ranks, corresponding to up to two layers per UE (hereinafter also referred to as terminal or device). In NR Release 15, 2×2 MIMO provides two spatial streams for transmitting and receiving data over the air on the same channel or frequency. To achieve this, the maximum number of layers per cell is increased compared to previous releases, allowing multiple UEs to use 2×2 MIMO simultaneously while sharing a common resource block allocation. Type II reporting is based on the selection of a set of beams followed by the assignment of their relative amplitudes and phases to generate a weighted combination of beams for transmission at each layer. Therefore, the Type II Port Selection solution relies on the Base Station (BS) having some advance information to enable beamforming of the CSI Reference Signal (RS) transmissions. This advance information can be obtained from uplink measurements if channel reciprocity is available.Otherwise, it can be obtained from Beam Management reporting or wideband reporting based on different Precoding Matrix Indicator (PMI) reporting solutions can be used (i.e., a hybrid solution when a combination of PMI reporting solutions is used).

[0006] In NR, most of the parameters associated with PMI reporting are configured using the CodebookConfig parameter structure, which uses a combination of codebookType and subtype to identify one of the resolutions of the associated PMI report. Each PMI report resolution and corresponding associated parameter set is related to a Type II port selection resolution. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] 3GPP RP 193133, “New WID: Further enhancements on MIMO for NR”, December 2019 [Non-Patent Document 2] 3GPP TS 38.214, “NR; Physical layer procedures for data (Release 16)” Summary of the Invention

[0008] In general, in one aspect, embodiments disclosed herein relate to a terminal having a receiver for receiving beamforming information for one or more beamformed Channel State Information-Reference Signals (CSI-RS), the CSI-RS corresponding to one or more spatial domain (SD) or frequency domain (FD). The terminal also includes a controller for determining a type of the one or more CSI-RS and, if the type of the one or more CSI-RS is Type-II, for performing a Type-II port selection codebook with a beamformed one of the one or more CSI-RS in the SD and FD domains.

[0009] In general, in one aspect, embodiments disclosed herein relate to a terminal having a receiver for receiving beamforming information for one or more beamformed Channel State Information-Reference Signals (CSI-RS), the beamformed one or more CSI-RS corresponding to one or more spatial domains (SD) or frequency domains (FD), the beamforming information being obtained from higher layer signaling or downlink control information (DCI). The terminal also has a controller for determining a number of ports for an SD beam in the SD domain, determining a number of ports for an FD beam in the FD domain, and performing port selection using the SD beam and one beamformed CSI-RS of the one or more beamformed CSI-RS in the FD beam.

[0010] In general, in one aspect, embodiments disclosed herein relate to a terminal having a receiver for receiving beamforming information for one or more beamformed Channel State Information-Reference Signals (CSI-RS), the one or more CSI-RS corresponding to one or more spatial domains (SD) or frequency domains (FD). The terminal also has a controller for freely selecting a number of ports of an SD beam in the SD domain considered for beamforming from the beamformed one or more CSI-RS, freely selecting a number of ports of an FD beam in the FD domain considered for beamforming from the beamformed one or more CSI-RS, and performing port selection using the SD beam and a beamformed one CSI-RS of the one or more CSI-RS in the FD beam.

[0011] In general, in one aspect, embodiments disclosed herein relate to a terminal having a receiver for receiving beamforming information for one or more beamformed Channel State Information-Reference Signals (CSI-RS), the one or more beamformed CSI-RS corresponding to one or more spatial domains (SD) or frequency domains (FD). The terminal also has a controller for determining a number of ports for an SD beam in an SD domain of a first sampling size, determining a number of ports for an FD beam in an FD domain of a second sampling size, and performing port selection using the beamformed one CSI-RS of the one or more beamformed CSI-RS in the SD beam and the FD beam.

[0012] In general, in one aspect, embodiments disclosed herein relate to a method for beamforming in the angular delay domain, the method including obtaining beamforming information for one or more CSI-RS, where the CSI-RS beamforming corresponds to an SD domain and an FD domain, determining a type of the one or more CSI-RS, and if the type of the one or more CSI-RS is Type-II, performing a Type-II port selection codebook with the beamformed one CSI-RS in the SD domain and the FD domain.

[0013] In general, in one aspect, embodiments disclosed herein relate to a method for beamforming in the angular delay domain, the method including obtaining beamforming information for one or more CSI-RS, the CSI-RS corresponding to an SD domain and an FD domain, the beamforming information being obtained from higher layer signaling or DCI. The method includes determining a number of ports for an SD beam in the SD domain. The method includes determining a number of ports for an FD beam in the FD domain. The method includes performing port selection using a beamformed one of the one or more CSI-RS in the SD beam and the FD beam.

[0014] In general, in one aspect, embodiments disclosed herein relate to a method for beamforming in the angular delay domain, the method comprising: obtaining beamforming information for one or more CSI-RS, the CSI-RS corresponding to an SD domain and an FD domain; freely selecting a number of ports of an SD beam in the SD domain considered for beamforming a CSI-RS from the one or more CSI-RS; freely selecting a number of ports of an FD beam in the FD domain considered for beamforming a CSI-RS from the one or more CSI-RS; performing port selection using a beamformed one of the one or more CSI-RS in the SD beam and the FD beam.

[0015] In general, in one aspect, embodiments disclosed herein relate to a method for beamforming in the angular delay domain, the method including obtaining beamforming information for one or more CSI-RS, the CSI-RS corresponding to an SD domain and an FD domain, determining a number of ports for an SD beam in an SD domain of a first sampling size, determining a number of ports for an FD beam in an FD domain of a second sampling size, and performing port selection using a beamformed one of the one or more CSI-RS in the SD beam and the FD beam.

[0016] Advantageously, enhancements to CSI measurement and reporting are being discussed in the development of Release 17 of NR. One such enhancement includes the evaluation, and if necessary, specification, of CSI reporting for downlink (DL) multi-transmission reception point (TRP) and / or multi-panel transmissions to enable more dynamic channel / interference assumptions for non-coherent joint transmission (NCJT) covering both Frequency Range 1 (FR1) (i.e., 410 MHz to 7,125 MHz, sub-6 GHz) and Frequency Range 2 (FR2) (i.e., 24,250 MHz to 52,600 Mhz, mmWave). Another extension includes evaluation and, if necessary, specification of Type II port selection codebook extensions (based on Release 15 / 16 Type II port selection) where angle and delay related information is estimated at the gNB based on the Sounding Reference Signal (SRS) by utilizing DL / UL reciprocity of angles and delays. The remaining DL CSI is reported by the UE, mainly targeting Frequency Division Duplex (FDD) FR1, to achieve a better trade-off between UE complexity, performance and reporting overhead.

[0017] With respect to the above extensions, we now describe how Type-II port selection codebooks can be further extended by taking into account the inherent angular delay reciprocity of the propagation channel.

[0018] Other aspects of the present disclosure will become apparent from the following description and the appended claims. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a configuration of a wireless communication system in accordance with one or more embodiments of the present invention. [Diagram 2] 1 illustrates an example in accordance with one or more embodiments. [Figure 3A] 1 illustrates an example in accordance with one or more embodiments. [Figure 3B] 1 illustrates an example in accordance with one or more embodiments. [Figure 4] 1 illustrates an example in accordance with one or more embodiments. [Diagram 5] 1 illustrates an example of formula (4) according to one or more embodiments. [Figure 6] 1 illustrates an example of formula (5) according to one or more embodiments. [Figure 7] 1 illustrates an example of a frequency response graph according to one or more embodiments. [Figure 8] 1 illustrates an example of formula (6) according to one or more embodiments. [Figure 9] 1 illustrates an example of formula (7) according to one or more embodiments. [Figure 10] 1 illustrates an example of precoding selection according to one or more embodiments. [Figure 11] 1 illustrates an example of a set according to one or more embodiments. [Figure 12] 1 illustrates an example of a graph showing angles and delays according to one or more embodiments. [Figure 13] 1 illustrates an example set according to one or more embodiments. [Figure 14] FIG. 1 shows a block diagram of an apparatus according to one or more embodiments. [Figure 15] FIG. 1 shows a block diagram of an apparatus according to one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Specific embodiments of the present invention will now be described in detail with reference to the accompanying figures, in which like elements in different figures are designated with like reference numerals to maintain consistency.

[0021] In the following detailed description of the embodiments of the present invention, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without these specific details. In other instances, well-known features are not described in detail to avoid unnecessarily complicating the present disclosure.

[0022] Throughout the specification, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for an element (i.e., any noun in the specification). The use of ordinal numbers does not imply or result in a particular order of elements, nor does it limit the elements to a single element, unless expressly disclosed, for example, by the use of "preceding," "after," "single," and other such terms. Rather, the use of ordinal numbers is to distinguish elements. As an example, a first element is different from a second element, and a first element may encompass two or more elements and follow (or precede) a second element in the order of elements.

[0023] Referring now to FIG. 1, a wireless communication system 100 in accordance with one or more embodiments of the present invention is described.

[0024] 1, the wireless communication system 100 includes a user equipment (UE) 10, a base station (BS) 20, and a core network 30. The wireless communication system 100 may be a New Radio (NR) system or a Long Term Evolution (LTE) / LTE-Advanced (LTE-A) system.

[0025] The BS 20 communicates with the UE 10 via multiple antenna ports using a multiple-input and multiple-output (MIMO) technique. The BS 20 may be a gNodeB (gNB) or an Evolved NodeB (eNB). The BS 20 receives downlink packets from a network device, such as an upper node or a server, connected on the core network 30 via an access gateway device, and transmits the downlink packets to the UE 10 via multiple antenna ports. The BS 20 receives uplink packets from the UE 10, and transmits the uplink packets to the network device via multiple antenna ports.

[0026] The BS 20 includes an antenna for MIMO that transmits wireless signals to and from the UE 10, a communication interface (e.g., an X2 interface) for communicating with adjacent BSs 20, a communication interface (e.g., an S1 interface) for communicating with a core network, and a CPU (Central Processing Unit) such as a processor or circuit that processes signals transmitted to and received from the UE 10. The functions and processing of the BS 20 described below may be realized by a processor processing or executing data and programs stored in a memory. However, the BS 20 is not limited to the hardware configuration specified above, and may include any appropriate hardware configuration. In general, multiple BSs 20 may be deployed to cover a wider service area of ​​the wireless communication system 1.

[0027] The UE 10 communicates with the BS 20 using MIMO technology. The UE 10 transmits and receives wireless signals such as data signals and control signals between the BS 20 and the UE 10. The UE 10 may be an information processing device having a wireless communication function such as a mobile station, a smartphone, a mobile phone, a tablet, a wireless terminal, a mobile router, or a wearable device.

[0028] The UE 10 includes a CPU, e.g., a processor, a RAM (Random Access Memory), a flash memory, and a wireless communication device for transmitting and receiving wireless signals between the BS 20 and the UE 10. For example, the functions and processing of the UE 10 described below may be realized by the CPU processing or executing data and programs stored in the memory. However, the UE 10 is not limited to the hardware configuration specified above, and may be configured to include, for example, a circuit for realizing the processing described below.

[0029] The wireless communication system 100 supports Type II CSI feedback. As shown in FIG. 1, in step S1, the BS 20 transmits a CSI reference signal (RS). When the UE 10 receives the CSI-RS from the BS 20, the UE 10 measures the received CSI-RS. Then, in step S2, the UE 10 performs CSI reporting to notify the BS 20 of the CSI as CSI feedback. For example, the CSI includes at least one of a rank indicator (RI), a precoding matrix indicator (PMI), a channel quality information (CQI), a CSI-RS resource indicator (CRI), a wideband (WB) amplitude, and a subband (SB) amplitude. In one or more embodiments of the present invention, the CSI reporting to report the SB amplitude may be referred to as a SB amplitude reporting. For example, instead of reporting the SB amplitude every time a CSI report is performed, the period for reporting the SB amplitude may be dynamically adjusted using higher layer signaling from the BS 20. The SB amplitude may be reported for K leading coefficients. For example, if K is small, the number of coefficients for which the SB amplitude is reported is small.

[0030] The gain achievable by SB amplitude reporting may be small if the SB amplitude is significantly smaller than the amplitude of the strongest coefficient, which may occur, for example, when the user channel is very sparse in a very low scattering environment.

[0031] Furthermore, in one or more embodiments, the scheme may be modified to provide layer processing up to layers with RI of 1 and 2 for Type-II CSI feedback, but Type-II CSI feedback may be implemented at ranks greater than 2. That is, spectral efficiency may be further improved by extending the Type-II CSI feedback scheme to ranks greater than 2. Extending the Type-II CSI feedback scheme to ranks greater than 2 may reduce overhead typically associated with this scheme.

[0032] Here, and as mentioned above, Type-II CSI precoding vector generation for N precoding matrix indicator (PMI) subbands considering RI=v, layer l∈{1,2,...v} transmission may be evaluated. For example, W l (N t ×N3)=W 1,l W coeff,l (2)

[0033] In the above formula, W 1,l (N t × 2L) is a matrix of L SD 2D-DFT bases for layer l, where L is the beam number, and N t is the number of ports, and W coeff,l (2L×N3) is the SB complex combination coefficient matrix for layer l.

[0034] In the above formula, the subset of SD 2D-DFT basis is {b l,1 ,...b l,L}, where b l,i is the i-th (∈{1,...L}) 2D DFT basis vector corresponding to the l-th layer.

[0035] In one or more embodiments, the frequency domain compression is coeff,l It is necessary to consider the information in the , which can be compressed, i.e., the corresponding overhead can be further reduced. For example, the type-II CSI precoding vector of layer l for N SBs considering frequency domain (FD) compression is expressed as W coeff,l can be given by expanding

number

[0036] In the above formula, W freq,l (N3×M) is a matrix of M FD DFT basis vectors for layer l,

number

number

[0037] In one or more embodiments, it is important to properly identify the SD and FD bases across layers to achieve an appropriate balance between performance and overhead.

[0038] Referring now to FIG. 2, a wireless communication system 200 in accordance with one or more embodiments of the present invention is illustrated.

[0039] As shown in FIG. 2, a wireless communication system 200 includes a BS 20 that communicates with a UE 10 via multiple antenna ports using MIMO technology. The Type-II port selection codebook does not require the UE 10 to derive spatial domain (SD) beams by considering 2D-DFT bases as in the normal Type-II codebook. In this case, the BS 20 may be a gNB that transmits a number K of beamformed (BF) CSI-RS ports as a feasible set of SD beams. The UE 10 needs to identify the number L (≦K) of best CSI-RS ports (i.e., beams) and report their corresponding indexes in W1.

[0040] By further modifying (2) and (3) above, the generation of per-SB precoding vectors with NR Release 16 Type-II port selection codebook for layer l ∈ {1, 2, 3, 4} may be given as:

number

[0041] In this case, Q(N t ×K) may represent the number K of SD beams used for CSI-RS beamforming, W1(K×2L) may represent a block diagonal matrix,

number

[0042] Number of CSI-RS ports P CSI-RSmay contain the number K of BF CSI-RS ports that are configured by higher layer signaling. In this case, P CSI-RS ∈{4,8,12,16,24,32}. W1 consists of a column vector of the identity matrix. Thus, each such vector represents a selected beam, where the number of ports is selected, which may include a number L set by higher layer signaling. In this case, P CSI-RS >4, L∈{2,3,4}.

[0043] The selection of the SD beam in Q is transparent to the UE 10. Specifically, the SD beam may be determined based on the transmission of a sounding reference signal (SRS) or a UL demodulation reference signal (DMRS). In this case, even if the dominant sub-space of the UL is not the same as the dominant sub-space of the DL, the port selection in the DL allows the UE 10 to select a port that approximately covers the DL dominant sub-space.

[0044] 3A and 3B show reporting of W1 based on the selected beam. In some embodiments, a parameter d, which may be set by the BS 20, determines the sampling granularity of the two groups. In this case, CSI reporting in NR may be configured with two granularities (e.g., categories). In some embodiments, d may be set as d∈{1,2,3,4} and d≦L. In this case, the UE 10 uses i as part of the PMI to select L beams according to 1,1 Report:

number

[0045] For example, as shown in Figures 3A and 3B, (5) may be used to determine the port pairs available for selection from multiple beams for polarization. In Figure 3A, with K=8 and L=2, calculations show that in the first case with d=2, i 1,1 = {0, 1}. In this regard, the port pairs available for selection may be {B0, B1} and {B2, B3}. In FIG. 3B, with K=8 and L=2, the calculations show that in the second case with d=1, i 1,1 = {0,1,2,3}. In this regard, the port pairs available for selection may be {B0,B1}, {B1,B2}, {B2,B3}, and {B3,B0}.

[0046] In Figures 3A and 3B, W1 is set as follows:

number

number

number

[0047] In view of the above calculation, W in (4) f,l The Type-II port selection codebook can be further extended by considering port selection for both SD beams and frequency domain (FD) basis vectors in . Thus, in some embodiments, a general structure for per-SB precoder generation for a port selection codebook may be given as follows:

number

[0048] In this case, Q(N t×K) is the b i may denote the number K of beamformed CSI-RS ports for SD beam selection, with i∈{1,2,...K}, and S(N t ×K') is the f j may denote the number K' of beamformed CSI-RS ports for FD beam selection, with j∈{1,2,...K'}, and W1(K×2L) may denote a block diagonal matrix, with each matrix block consisting of L columns of a (K×K) identity matrix. f,l (K'×M) may represent a matrix consisting of columns of (K'×K') identity matrices,

number

[0049] In (2'), beamforming is performed in both SD and FD, and the FD basis for beamforming may be determined by considering delay reciprocity. BS20 transmits (K×K') beamformed CSI-RS ports. The selection of K SD beams and K' FD basis is transparent to UE10. In this case, the UE selects the number of SD beams, 2L, and the number of FD basis, M, and reports them to BS20 as part of the PMI. Here, W1 and W f,l may incorporate the selected SD and FD basis. Further, the UE 10 may calculate, together with the LC coefficients,

number

[0050] In some embodiments, each SD beam may be paired with a single FD basis, such that K=L, K'=M, and K=K'. Note that no port selection is performed, and thus the diagonal blocks in W1 of (2') are (K x K) identity matrices. Furthermore, W f,l is also a block diagonal matrix with two diagonal blocks of (K × K) identity matrices. This means that

number

number

[0051] For the above reasons, in UE10, 2K LC coefficients, which are the diagonal elements of the matrix, are used as part of the Precoding Matrix Indicator (PMI).

number

[0052] In some embodiments, each SD beam may be paired with a single FD basis such that K≧L, K′≧M, K=K′, and L=M. Here, UE 10 may select the number L of SD-FD pairs from the number K of beamformed CSI-RS ports. In this regard, the diagonal blocks in W1 of (2′) are (K×L) matrices, where each matrix block consists of L number of columns (corresponding to the selected ports) of a (K×K) identity matrix. Furthermore, since each SD beam is associated with a single FD basis, W1 in (2′) may be selected based on W1. f,l may be determined, where W f,l Each matrix block is a block diagonal matrix consisting of L columns, and

number

[0053] From the above, UE 10 identifies a number of ports L from the number K (beamformed CSI-RS ports) based on a predetermined criterion and reports it to BS 20 as part of the PMI. These L ports correspond to the L columns of W1,

number

[0054] In some embodiments, the general structure of the port selection codebook in equation (2'), which represents the final precoder generation on the NW side, may be further simplified and may be further simplified by the UE.

number

[0055] Let us rewrite formula (2'):

number

[0056] Each SD may be associated with a single FD, so when an SD beam is selected, the associated FD is also selected. Thus, W1 = W f,l It is.

[0057] As a result, the following is taken into consideration:

number

[0058] Here, the SD-FD pairs considered for beamforming are {b1,f1},{b2,f2},…{b K ,f K} and the indices of the selected SD and FD bases are assumed to be s(1), s(2) ... s(L).

[0059] Regarding common polarization port selection, consider the following:

number

number

[0060] Referring to FIG. 5, which shows an example of equation (4),

number

number

[0061] In equation (3),

number

[0062] 6, it is contemplated that the precoder from the UE's perspective may be given as shown by an example of equation (5) in FIG.

number

[0063] Now, with reference to Fig. 7, we consider why WB CSI reporting may be sufficient when SD-FD pair-based CSI-RS beamforming is considered. Consider the physical meaning of SD-FD pair-based CSI-RS beamforming. For example, consider a CSI-RS transmission of K ports. In this case, it is considered that the frequency response of the channel observed at the UE associated with the nth port is represented as shown by the graph in Fig. 7.

[0064] Consider the type II port selection codebook structure with reference to Figure 8. To further improve the performance, the UE may add an additional M ν FD basis. The precoder from the UE's perspective in that case may be given as shown by equation (6) in FIG.

[0065] In the formula (6),

number

number

[0066] Where:

number

[0067] Consider a type II port selection codebook structure with reference to Figure 9. It is considered that the selected DFT may be port specific. Therefore, equation (6) may be updated as shown by equation (7) in Figure 9. In equation (7),

number

number

[0068] Considering the type II port selection codebook structure with reference to Fig. 10. As described in some embodiments, considering that SB reporting (i.e., a precoder such as the precoder in Equation (6) or Equation (7)) or WB reporting (i.e., a precoder such as the precoder in Equation (5)) may be sufficient, it is considered that the UE may be configured to report additional DFT or not using higher layer signaling or DCI. For example, see the decision tree in Fig. 10, which illustrates the decision of additional DFT reporting. It is noted that such reporting may be signaled implicitly or explicitly.

[0069] In some embodiments, one or more of the following are possible for selecting the additional FD basis (DFT): In some embodiments, using higher layer signaling or DCI, the NW indicates / configures a "set of DFTs" and the UE selects M from the set. ν In some embodiments, the NW may explicitly indicate which DFT bases to consider for selecting additional FD bases, e.g., the NW may select multiple DFTs.

number

number

[0070] FIG. 11 illustrates an example of a set, according to one or more embodiments. In the example of FIG. 11, there may be multiple groups configured by higher layer signaling, and one group may be selected from them as shown using DCI or MAC-CE. Furthermore, in this case, the UE may select M from the configured DFT basis groups. ν In the case of =2,

number

number

[0071] In some embodiments, the UE ν The NW may freely select DFTs and report them. It should be noted that a difference from one or more embodiments is that in some embodiments, the "set of DFTs" is not configured by the NW for additional DFT selection.

[0072] Consider the importance of free choice of DFT. In case of FDD, since the effective antenna-spacing in the two bands may be different (i.e., different wavelengths even though the physical spacing is the same), the set of angles sampled in the UL will be different from the angles sampled in the DL when multiple angles are sampled by a phased array. An example may be given as shown in Figure 12.

[0073] In some embodiments, to report the selected DFT basis, the UE may:

number

number

number

number

[0074] In some embodiments, using higher layer signaling or DCI, the UE may ν That is, in some embodiments, there may be a set of values ​​configured using RRC signaling, and one value from them is indicated explicitly or implicitly using DCI. For example, a set of values ​​{1, 2, 3, 4} may be configured by RRC signaling, and one value from them may be indicated as M using two bits of DCI. ν Also, the DCI can be selected for M without using additional DCI bits. ν It is also possible to implicitly indicate to the UE the configured value of M. ν A set of values ​​for M is predefined in the specification(s) and one value is set from them using higher layer signaling or DCI. ν The value of is specified in one or more specifications, e.g., M ν = 2. ν Possible values ​​for are 1, 2 and 3. A person skilled in the art will understand that other values ​​are not excluded.

[0075] In some embodiments relating to higher rank transmissions, the selected additional M ν The FD basis may be common to all layers of the selected / specified rank. In some embodiments, additional M ν The FD bases are layer-specific and are therefore selected for each layer. In some embodiments, additional M ν This FD basis is common to a set of layers and is therefore selected for each layer group.

[0076] In some embodiments, each SD beam may be paired with multiple FD bases such that K≧L and K′≧M. Here, UE 10 may select the number L of SD beams and the number M of FD bases per SD beam. In this regard, each SD beam (out of the number K) is paired with all the number K′ of FD bases for the beamformed CSI-RS. Thus, the total number of CSI-RS ports may be KK′. The number M of bases selected may be “beam-common” or “beam-specific”. “Beam-common” is when the same set of number M of FD bases is selected for all SD beams. “Beam-specific” is when the number M of FD bases is SD-beam specific. The diagonal blocks in W1 of (6) are (K×L) matrices, where each matrix block consists of L columns (corresponding to the selected ports) of a (K×K) identity matrix.

[0077] In the "beam common" FD basis selection, W in (6) f,l is a (K'×M) matrix, and the number of columns M (corresponding to the chosen FD basis) comes from the (K'×K') identity matrix. Furthermore, in (6),

number

[0078] In the selection of the “beam-specific” FD basis, W in (6) f,l is a (K'×2LM) matrix, where the number of columns 2LM (corresponding to the chosen FD basis) comes from the (K'×K') identity matrix. Furthermore, W f,l is W f,l =[E1…E 2L ], where E i A (K'×M) matrix is ​​defined by i∈{1,2,…2L}, with columns derived from the (K'×K') identity matrix. Thus, E i The M selected FD bases of the i-th SD beam are taken into account. Furthermore,

number

number

[0079] From the above, UE 10 identifies a number of ports, L, from the number of SD beams, K, based on one or more criteria, and reports this to BS 20 as part of the PMI. These L ports correspond to the L columns of W1. In the "beam-common" FD basis selection, UE 10 identifies a number of ports, M, from the number of FD bases, K', that are common to all SD beams, based on some criteria, and reports this to BS 20 as part of the PMI. These M ports correspond to the L columns of W1. f,l In "beam-specific" FD basis selection, UE 10 separately identifies the number of ports M from the number of FD bases K' for each SD beam based on some criteria and reports it to BS 20 as part of the PMI. In this case, the M ports selected for the i-th SD beam are W f,l =[E1…E 2L ]E i In this case, W f,l is W f,l =[E1…E 2L ] for all E defined by i∈{1,2,…2L}. i In addition,

number

[0080] Thus, for example, in order for the UE 10 to operate with Release 17 of the 3GPP standard port selection codebook, the UE 10 may be configured with the higher layer parameter codebookType set to typeII-PortSelection-r17.

[0081] So, for example, the number of CSI-RS ports may be configured using the higher layer parameter nrofPorts, where the value may be, for example, one of 4, 8, 12, 16, 24, 32, 64. Other values ​​are not excluded.

[0082] From the above, for example, the number L of CSI-RS ports to be selected for an SD beam and the number M of ports to be selected for an FD basis are set using higher layer signaling or DCI.

[0083] The first possible values ​​for L are defined by the specification, and the NW uses x bits (one or more) of the higher layer signaling or DCI to select one of them. For example, let L ∈ {2, 4, 6, 8, 10, 12}, and the NW uses 3 bits of the DCI to select a value for the number L. The first possible values ​​for M are defined by the specification, and the NW uses x bits (one or more) of the higher layer signaling or DCI to select one of them. For example, let M ∈ {2, 4, 6, 8, 10, 12}, and the NW uses 3 bits of the DCI to select a value for the number M.

[0084] The second possible value is defined by using L=M and setting either L or M, where L or M may be set as described above.

[0085] The third possible value is defined using only SD-FD pairs if M is not set, which requires making a "joint" selection: it is sufficient to set L only.

[0086] In one or more embodiments, the UE 10 is free to select a set of SD beams from a number K and a set of FD bases from a number K′. In some embodiments, the UE 10 uses a bitmap to report the selected SD beam. In this example, to select the first, second, fourth and fifth beams from K=11 SD beams, the UE would use bitmap: 11011000000. In some embodiments, the UE 10 uses a bitmap to report the selected FD bases. In this example, to select the first, second and fifth FD bases from K′=8 FD bases, the UE 10 would use bitmap: 11001000. In some embodiments, the UE 10 uses a 2D bitmap to report the selected SD-FD pairs. As shown in Figure 4, the 2D bitmap may be considered to select, for example, the first, second, fourth and fifth beams from K = 10 SD beams and the associated FD bases, i.e., the second, third, fifth and sixth FD bases from K' = 8 FD bases. It is also possible to report multiple FDs for a given SD beam. The UE 10 may consider compression schemes, such as combined signaling or Huffman coding, to further reduce the size of the 2D bitmap.

[0087] In one or more embodiments, the UE 10 may report the selected SD beams in a bitmap. The associated FD basis may be reported directly without a bitmap. In this case, the NW may understand how the reported FDs are mapped to the appropriate SDs. For example, the UE 10 selects the first, second, fourth and fifth beams from K=11 SD beams and reports them in a bitmap: 11011000000. The associated FD basis is reported as f2, f3, f5, f6, and the NW knows that f2 is associated with the first SD beam, f3 with the second SD beam, f5 with the fourth SD beam and finally f6 with the sixth SD beam.

[0088] In one or more embodiments, the UE 10 determines the number of selected SD beams.

number

number

[0089] In one or more embodiments, the UE 10 determines the number of selected FD bases.

number

number

[0090] In one or more embodiments, the port selection sampling size d for SD beam selection and the port selection sampling size d' for FD basis selection are set using higher layer signaling or DCI. Possible values ​​for d are predefined, and the NW selects one from them using x bits (one or more) of the higher layer signaling or DCI. For example, d∈{2,4,6,8,10,12}, as defined by d≦L. In this case, the NW may select the d value using three bits of the DCI. Possible values ​​for d' are predefined, and the NW selects one from them using x bits (one or more) of the higher layer signaling or DCI. For example, d'∈{2,4,6,8,10,12}, as defined by d'≦M. In this case, the NW may select the d' value using three bits of the DCI.

[0091] In some embodiments described herein, only d needs to be set. Possible values ​​for d are defined in the specification, and the NW selects one from them using x bits (one or more bits) of higher layer signaling or DCI. For example, d∈{1,2,3,4,5,6}, as defined by d≦L, and the BS 20 may select the d value using 3 bits of DCI.

[0092] In one or more embodiments, the UE 10 may report a rank indicator (RI) value v according to the configured higher layer parameter typeII-PortSelectionRI-Restriction-r 17. The UE may not report v>4 at this stage.

[0093] A BS 20 according to one or more embodiments of the present invention will now be described with reference to FIG.

[0094] 14, the BS 20 may include a 3D MIMO antenna 201, an amplifier unit 202, a transmitter / receiver circuit 203 (hereinafter referred to as including a CSI-RS scheduler), a baseband signal processor 204 (hereinafter referred to as including a CS-RS generator), a call processor 205, and a transmission path interface 206. The transmitter / receiver unit 203 includes a transmitter and a receiver.

[0095] The antenna 201 may be a 2D antenna (flat antenna) or a multi-dimensional antenna including multiple antenna elements, such as a 3D antenna, such as a cylindrically arranged antenna or a cubic antenna. The antenna 201 includes antenna ports having one or more antenna elements. To perform 3D MIMO communication with the UE 10, the beams transmitted from each antenna port are controlled.

[0096] The number of antenna elements of the antenna 201 can be easily increased compared to a linear array antenna. Further improvement in system performance is expected by MIMO transmission using a large number of antenna elements. For example, with 3D beamforming, a high beamforming gain is expected as the number of antennas increases. Furthermore, MIMO transmission is advantageous from the viewpoint of reducing interference, for example, by controlling the null point of the beam, and effects such as removing interference between users of multi-user MIMO can also be expected.

[0097] The amplifier unit 202 generates an input signal to the antenna 201 and performs reception processing of an output signal from the antenna 201 .

[0098] A transmitter included in the transmitter / receiver circuit 203 transmits a data signal (e.g., a reference signal and a precoded data signal) to the UE 10 via the antenna 201. The transmitter transmits CSI-RS resource information (e.g., a subframe configuration ID and mapping information) indicating the state of the determined CSI-RS resource to the UE 20 by higher layer signaling or lower layer signaling. The transmitter transmits the CSI-RS allocated to the determined CSI-RS resource to the UE 10.

[0099] A receiver included in the transmitter / receiver circuit 203 receives a data signal (ie, a reference signal and CSI feedback information) from the UE 10 via the antenna 201.

[0100] The CSI-RS scheduler 203 determines the CSI-RS resources allocated to the CSI-RS. For example, the CSI-RS scheduler 203 determines the CSI-RS subframe that includes the CSI-RS in the subframe. The CSI-RS scheduler 203 at least determines the RE to which the CSI-RS is mapped.

[0101] The CSI-RS generating unit 204 generates a CSI-RS for estimating a downlink channel state. In addition to the CSI-RS, the CSI-RS generating unit 204 may generate reference signals defined by the LTE standard, a dedicated reference signal (DRS) and a cell-specific reference signal (CRS), synchronization signals such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), and newly defined signals.

[0102] The call processor 205 determines a precoder to be applied to the downlink data signal and the downlink reference signal. This precoder is called a precoding vector, or more generally, a precoding matrix. The call processor 205 determines a downlink precoding vector (precoding matrix) based on the CSI indicating the estimated downlink channel state and the input and decoded CSI feedback information.

[0103] The transmission path interface 206 multiplexes the CSI-RS into the RE based on the CSI-RS resources determined by the CSI-RS scheduler 203.

[0104] The reference signal to be transmitted may be cell-specific or UE-specific. For example, the reference signal may be multiplexed with a signal such as a PDSCH, or the reference signal may be precoded. Here, by notifying the UE 10 of the transmission rank of the reference signal, the estimation of the channel state can be realized with an appropriate rank according to the channel state.

[0105] In one or more embodiments, the BS 20 further includes hardware configured to reduce feedback overhead associated with bitmap reporting between user equipment and the base station. For example, the BS 20 may include the capabilities described above for reducing feedback overhead when communicating with the UE 10.

[0106] A UE 10 according to one or more embodiments of the present invention will now be described with reference to FIG.

[0107] 15, the UE 10 may include a UE antenna 101 used for communication with the BS 20, an amplifier unit 102, a transmitter / receiver circuit 103, and a controller 104, where the controller includes a CSI feedback controller, a codeword generator, and a CSI-RS controller. The transmitter / receiver circuit 103 includes a transmitter and a receiver 1031.

[0108] A transmitter included in the transmitter / receiver circuitry 103 transmits data signals (eg, reference signals and CSI feedback information) to the BS 20 via the UE antenna 101 .

[0109] A receiver included in the transmitter / receiver circuit 103 receives a data signal (eg, a reference signal such as a CSI-RS) from the BS 20 via the UE antenna 101.

[0110] The amplifier unit 102 separates the PDCCH signal from the signal received from the BS 20 .

[0111] The control unit 104 estimates the downlink channel state based on the CSI-RS transmitted from the BS 20, and outputs the estimated state to the CSI feedback control unit.

[0112] The CSI feedback control unit generates CSI feedback information based on a downlink channel state estimated using a reference signal for estimating the downlink channel state. The CSI feedback control unit outputs the generated CSI feedback information to a transmission unit, and the transmission unit transmits the CSI feedback information to the BS 20. The CSI feedback information may include at least one of a rank indicator (RI), a PMI, a CQI, a BI, and the like.

[0113] The CSI-RS control unit determines whether a specific user equipment is the user equipment itself based on the CSI-RS resource information when the CSI-RS is transmitted from the BS 20. If the CSI-RS control unit 16 determines that the specific user equipment is the user equipment itself, the transmission unit transmits CSI feedback based on the CSI-RS to the BS 20.

[0114] In one or more embodiments, the UE 10 further includes hardware configured to reduce feedback overhead associated with bitmap reporting between the user equipment and the base station. For example, the UE 10 may have the capabilities described above for reducing feedback overhead when communicating with the BS 20.

[0115] The above embodiments and modifications may be combined with each other, and the various features of the embodiments may be combined with each other in various combinations, and the invention is not limited to the specific combinations disclosed herein.

[0116] While the present disclosure has been described with respect to only a limited number of embodiments, it will be apparent to those skilled in the art, having the benefit of this disclosure, that various other embodiments may be devised without departing from the scope of the invention, which scope should therefore be limited only by the scope of the appended claims.

Claims

1. a controller for determining a precoding matrix indicator (PMI) without port selection using a matrix associated with a spatial domain (SD) beam, the matrix being an identity matrix; A terminal comprising: a transmitter that transmits a report of channel state information (CSI) including the PMI.

2. determining a precoding matrix indicator (PMI) without port selection using a matrix associated with a spatial domain (SD) beam, the matrix being an identity matrix; and transmitting a report of channel state information (CSI) including the PMI.

3. A system including a terminal and a base station, The terminal includes a control unit that determines a precoding matrix indicator (PMI) using a matrix associated with a spatial domain (SD) beam and that is an identity matrix without performing port selection; and A transmitter that transmits a report of channel state information (CSI) including the PMI, The base station, a receiver for receiving the CSI report.

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