Method and apparatus for reducing feedback overhead - Patents.com

Abstract

Reduce feedback overhead. [Solution] The present invention relates to a method performed by a radio network node 700, a method performed by the radio network node 700, a method performed by a user equipment UE 500, and a UE 500. The method performed by the UE 500 includes at least the following: decomposing each entry corresponding to the (i,j)th combining coefficient of a precoder matrix into at least two coefficients (401); quantizing each of the at least two coefficients individually with at least one bit (402); and reporting information related to at least one phase value or at least one amplitude value, or at least one phase value and amplitude value, of the quantized coefficients (403).

Description

[Technical field]

[0001] The present disclosure relates to the field of wireless communications, and more particularly, to a method and apparatus for reducing feedback overhead (e.g., CSI feedback) by employing efficient amplitude and phase quantization and coefficient reporting in communication networks. [Background technology]

[0002] Beamforming is an important part of the 3rd Generation Partnership Project (3GPP) Release (Rel.) 15, which defines a New Radio (NR) access technology that enables radio base stations (gNBs) and user equipment (UE) to establish and adapt a communication link using spatially precoded pilot signals. The key information in 5G to improve the communication link and efficiently adapt the beamforming technology is the feedback reported by the gNB and / or UE on the channel state information, i.e. CSI feedback report.

[0003] The Rel-15 Type 2 CSI report assumes that dual-stage precoding is performed in the frequency domain on a per subband basis, i.e., a single precoder is computed for a group of adjacent physical resource blocks (PRBs), called a "subband". The Rel-15 Type 2 two-stage precoder consists of two components: The first stage precoder, called F1, is identical for all subbands and contains entries / beams selected from a discrete Fourier transform-based codebook (DFT-based codebook). The second stage precoder, called F2, contains subband-dependent beam-combining coefficients for all subbands.

[0004] The feedback overhead for reporting beam combining coefficients grows almost linearly with the number of subbands and becomes quite large when the number of subbands is large. To overcome the high feedback overhead of Release 15 type 2 CSI reporting, it was decided to consider a feedback compression scheme for the second stage precoder F2 in Non-Patent Document 1 of the 3GPP-Radio Access Network (RAN) standardization meeting 3GPP RAN#81. Non-Patent Documents 2-7 demonstrate that the number of beam combining coefficients of F2 can be significantly reduced when F2 is transformed to the delay domain using a small number of DFT or discrete cosine transform (DCT) basis vectors.

[0005] [Release 15 Dual Stage Precoding and CSI Reporting] Assuming a transmission of rank R in the gNB and a dual-polarized antenna array with configuration (N1, N2, 2), the Release 15 double-stage precoder disclosed in [8] for the sth subband and the rth transmission layer is given as follows:

[0006]

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[0007] According to Non-Patent Document 8, f^2 (r) (s) (^ is written just above f)A The reporting and quantization of the subband combination coefficients are as follows:

[0008] [Matrix F A Quantization and reporting of broadband amplitudes of The broadband amplitude corresponding to the strongest beam is not reported, with an amplitude value of 1. The broadband amplitude values ​​of the remaining 2L-1 beams are reported by quantizing each amplitude value with 3 bits.

[0009] Subband precoder f^2 (r) Regarding quantization and reporting of amplitude and phase values ​​of (s): The amplitude and phase values ​​of the coefficients associated with the first preceding beam are not reported (they are assumed to be equal to 1 and 0).

[0010] For each subband, the amplitude of the B coefficients associated with the first B−1 preceding beams (other than the first preceding beam) is 1 bit − [√0.5 1]. The amplitude values ​​of the remaining 2L-B beams are not reported (they are assumed to be equal to 1).

[0011] For each subband, the phase values ​​of the B-1 coefficients associated with the first B-1 preceding beams (other than the first preceding beam) are quantized with 3 bits. The phase values ​​of the remaining 2L-B beams are quantized with 2 bits.

[0012] The number of prior beams for which subband amplitudes are reported is given by B=4, 4, or 6 for the total number of constructed spatial beams L=2, 3, or 4, respectively. [Spatial Delay Precoder] The precoder F for all S subbands (r) (s) into the matrix F (r) These results are summarized in Non-Patent Document 2, Non-Patent Document 3, and Non-Patent Document 7.

[0013]

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[0014]

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[0015]

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[0017] The number of spatial beams and the index of the spatial beam may be different, the same, partially the same, or non-identical across the transmission layers. Furthermore, for spatial beams, the delays may be partially identical or non-identical across the beams. Due to the configuration of spatial beams that differ across layers, the delay configuration may vary across layers as well. Thus, multiple configurations of beam and delay configurations are possible. However, the spatial beam configuration and delay configuration of the spatial delay precoder must be matched with the physical structure of the wireless channel. The wireless channel is composed of multiple clusters of scatterings associated with respective delays (see 1st channel cluster #1, 1st delay #1, ..., 3rd channel cluster #3, 2nd delay #2 in Figure 1).

[0018] In the example of FIG. 1, each transmit spatial beam of the gNB (in this example, first beam #1, second beam #2, third beam #3, and fourth beam #4) is associated with a single or several channel clusters with corresponding delays. The first beam #1 is associated with the first cluster #1 and the first delay #1. The second beam #2 and the third beam #3 are associated with the direct line of sight (LOS) channel component and the third cluster #3 and the third delay #3. The fourth beam #4 is associated with the second cluster #2 and the second delay #2. As shown, the delays of the first cluster #1 and the second cluster #2 are different and longer than the delay of the third cluster #3 (closest to the UE).

[0019] To capture most of the energy of the radio channel at the UE, the spatial DFT / DCT beams of the first stage precoder need to point towards the channel clusters. In a typical channel setup, the clusters are uniformly distributed around the gNB, and each transmit spatial beam is associated with a single or a few adjacent clusters. Furthermore, due to the uniform distribution of channel clusters, each cluster is associated with a different delay. The number of clusters with which each spatial beam is associated mainly depends on the beamwidth (which is related to the aperture size of the antenna array at the gNB). The larger the beamwidth (i.e., the smaller the aperture size of the antenna array), the more channel clusters are associated with the spatial beam. Thus, the delay configuration of each spatial beam (number of delays per beam and the value of the delays) depends on the channel cluster(s) with which the spatial beam is associated.

[0020] In the transformed precoder, each spatial beam is associated with a single delay or a small set of delays. Thus, the transmit beam is "delayed" by a specific delay before transmission. The delays need to be selected such that all 2L beams are coherently combined at the UE. Note that each delay is represented by an entry in a DFT / DCT vector that models a linear phase increase over the subbands.

[0021] Therefore, the selection of delays for spatial beams is the same as the selection of DFT / DCT vectors. It should be understood that due to the delay distribution of the channel cluster, the delays associated with one spatial beam may be different from the delays associated with another spatial beam. Similarly, the delay configurations (number of delays and delay values) may be different for different beams. Different delay configurations are discussed in detail in the applicant's non-patent documents 2, 3 and 7. It should be noted that non-patent document 7 had not yet been published at the time of filing of this application, and therefore non-patent document 7 is not considered prior art for the subject matter of the claims and teachings of this application.

[0022] If different DFT / DCT vectors are used for each spatial beam, a matrix containing all selected DFT / DCT vectors of all constructed spatial beams may be used to form a common matrix for the transformation. The common transformation matrix contains all selected DFT / DCT vectors of all beams. When such a matrix is ​​used for the transformation, the combining coefficients associated with the beams contain a small number of non-zero coefficients only for the associated DFT / DCT vectors and are zero elsewhere. Thus, the matrix W2 in equation (3) (r) The complex coupling coefficients of may contain many values ​​close to zero. [Prior art documents] [Non-patent literature]

[0023] [Non-Patent Document 1] Samsung, "Revised WID: MIMO Enhancements for NR", RP-182067, 3GPP RAN#81, Gold Coast, Australia, September 10-13, 2018 [Non-Patent Document 2] Fraunhofer IIS, Fraunhofer HHI, "Enhancing the Type 2 CSI Reporting Scheme", R1-1806124, Busan, Korea, May 21-25, 2018 [Non-Patent Document 3] Fraunhofer IIS, Fraunhofer HHI, "Enhancing Type 2 CSI Reporting", R1-1811088, Chengdu, China, October 8-12, 2018 [Non-Patent Document 4] Fraunhofer IIS, Fraunhofer HHI, "Spatial Delay vs. Subband Precoding for mm-Wave Channels", R1-1800597, Vancouver, Canada, January 22-26, 2018 [Non-Patent Document 5] Ericsson, "Enhanced CSI for MU-MIMO Support", R1-1811193, Chengdu, China, October 8-12, 2018 [Non-Patent Document 6] Huawei, HiSilicon, "Discussion on CSI Enhancement for MU-MIMO", R1-1810103, Chengdu, China, October 8-12, 2018 [Non-Patent Document 7] Fraunhofer IIS, Fraunhofer HHI, "Enhancing the Type 2 CSI Reporting Scheme", R1-1813130, Spokane, USA, November 12-16, 2018 [Non-Patent Document 8] 3GPP TS 38.214 V15.3.0, "3GPP;TSG RAN;NR;Data Physical Layer Procedures (Release 15)," September 2018. [Non-Patent Document 9] Nokia, Nokia Shanghai Bell, "CSI Feedback Overhead Reduction for MU-MIMO Enhancement", R1-1813488, November 12-16, 2018 Summary of the Invention [Problem to be solved by the invention]

[0024] There is room for improved methods to reduce feedback overhead. [Means for solving the problem]

[0025] The objective of this specification is to provide a method and apparatus in the form of a user equipment (UE) and a radio base station or a network node or a gNB, respectively, for reducing (CSI) feedback overhead by employing efficient amplitude and phase quantization and reporting of coefficients in a communication network employing beamforming and / or MIMO operation. Furthermore, this embodiment addresses the problem of how to efficiently quantize and report the transformed combining coefficients.

[0026] According to an aspect of an embodiment herein, a method is provided that is performed by a UE for reducing CSI-related feedback overhead in a communication network employing MIMO operation.

[0027] Precoder matrix W2 (r) decomposing each entry corresponding to an (i,j)-th coupling coefficient of into at least two coefficients, where r denotes the r-th transmission layer, the (i,j)-th coupling coefficient being associated with the ith beam and the j-th delay, each coupling coefficient being associated with amplitude and phase information.

[0028] quantizing each of said at least two combination coefficients individually with at least one bit; and reporting information related to at least one phase value or at least one amplitude value of said quantized coefficients, or at least one phase value and amplitude value of said quantized coefficients.

[0029] According to another embodiment of the present specification, there is provided an apparatus in the form of a UE for reducing feedback overhead in a communication network, the UE comprising a processor and a memory, the memory containing instructions executable by the processor, whereby the UE is capable of performing any one of the subject methods of claims 1 to 29.

[0030] There is also provided a computer program comprising instructions which, when executed on at least one processor of a UE as claimed in claim 30, cause said at least one processor to operate to perform the method according to any of claims 1 to 29.

[0031] A carrier containing the computer program, the carrier being one of a computer readable storage medium, an electronic signal, an optical signal, or a radio signal.

[0032] There is also provided a method performed by a radio network node gNB for reducing feedback overhead related to channel state information (CSI) in a communication network employing multiple-input multiple-output (MIMO) operation, the method comprising the steps of: receiving a report from a UE comprising information related to at least one phase value or at least one amplitude value, or at least one phase value and amplitude value, of each quantized coefficient quantized with at least one bit by the UE;

[0033] Here, the precoder matrix W2 (r) Each entry corresponding to the (i,j)-th coupling coefficient is decomposed by the UE into at least two coefficients, where r represents the r-th transmission layer, the (i,j)-th coupling coefficient is associated with the i-th beam and the j-th delay, and each coupling coefficient is associated with amplitude information and phase information.

[0034] According to another embodiment of the present specification, there is also provided a radio network node or gNB for reducing feedback overhead in a communication network, the radio network node comprising a processor and a memory, the memory including instructions executable by the processor, whereby the radio network node is operable to perform the subject matter defined in any one of claims 31 to 39.

[0035] There is also provided a computer program comprising instructions which, when executed on at least one processor of a radio network node as claimed in claim 40, cause said at least one processor to carry out the method as claimed in any one of claims 31 to 39.

[0036] A carrier also provides a carrier containing the computer program, the carrier being either a computer readable storage medium, an electronic signal, an optical signal, or a radio signal.

[0037] Some advantages of the embodiments herein are presented in the detailed section of this disclosure. Examples and advantages of the embodiments herein are described in more detail with reference to the accompanying drawings. [Brief description of the drawings]

[0038] [Figure 1] 1 illustrates an exemplary network scenario in which embodiments herein may be employed. [Diagram 2] 1 shows the amplitude distribution of the coupling coefficients of the matrix W2(r). [Diagram 3] FIG. 13 illustrates the amplitude distribution of coefficients b i,j for a third scheme according to embodiments herein. [Figure 4] 4 is a flowchart of a method performed by a UE in accordance with certain example embodiments of the present disclosure. [Diagram 5] 1 is a block diagram depicting a UE in accordance with certain example embodiments of the present disclosure. [Figure 6] FIG. 2 is a block diagram depicting a radio network node in accordance with certain example embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] In the following, detailed descriptions of example embodiments are presented in conjunction with drawings in some scenarios to facilitate understanding of the solution(s) described herein. As mentioned above, in the 3GPP new wireless system, two types of codebooks, namely type 1 and type 2 codebooks, are standardized for CSI feedback in support of advanced MIMO operation.

[0040] In this embodiment, we address the problem of how to efficiently quantize and report the transformed combining coefficients in order to reduce the overhead of CSI feedback in a communication network employing beamforming.

[0041] [A. Matrix W2 (r) Quantization and reporting of complex coupling coefficients of W2, which is shown above in equation (3) and repeated below (r) is the overall precoder and can be written as

[0042]

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[0043] According to an exemplary embodiment, W2 (r) An approach to quantizing the amplitude and phase values ​​of the coefficients of is to directly quantize each amplitude and phase value with N1 and N2 bits, respectively.

[0044] For example, matrix W2 (r) Assuming that contains UD coefficients, W2 (r) To report the amplitude and phase information of the U beams to the gNB, UD(N1+N2) bits are required. However, as mentioned before, each of the U beams is typically associated with only a set of delays, and not with all D delays. Therefore, the matrix W2 (r) may be thought of as a sparse matrix with many coefficients close to zero.

[0045] In the following explanation, the matrix W2 in equation (3) (r) ∈C (U×D)(C, in white characters) may include complex coupling coefficients that are related to all (2L) spatial beams (i.e., U = 2L), or only to a subset of the spatial beams (e.g., U < 2L), and / or to all (V) delay / basis vectors (i.e., D = V), or only to a subset of the delay / basis vectors (e.g., D < V).

[0046] [1. Selection and Reporting of Non-Zero Coefficients Using a Bitmap] W2 (r) To save feedback overhead for reporting the quantized version of W2, an approach according to an exemplary embodiment is to feedback only the amplitude information and phase information of the non-zero coefficients of the matrix W2 (r) and indicate the indices of the reported coefficients with a bitmap. For example, the first bit of the bitmap is associated with the first coefficient, and the second bit may be associated with the first coefficient of the matrix W2 (r) . If the bit in the bitmap is set to "1", the corresponding coefficient (amplitude and / or phase) may be reported; otherwise, it is not reported. In this way, the overhead for reporting the coupling coefficients can be significantly reduced, but the number of feedback bits is not fixed and may vary for each instance to be reported. (How the number of feedback bits can be fixed will be described later).

[0047] [2. Selection and Reporting of the K Strongest Coefficients] To fix the number of feedback bits for reporting the coupling coefficients, the receiver may be configured to feedback the amplitude values and / or phase values of the K strongest coefficients of the matrix W2 (r) , where the value of the parameter K is configurable by the gNB. The K strongest coefficients may be represented by the K entries with the highest amplitude (or power) across the elements of W2 (r) . If the bit in the bitmap is set to "1", the user equipment (UE) may report the associated coefficient b i,jThe bitmap may therefore include no more than K "1"s.

[0048] To increase the flexibility of coefficient selection and improve system performance, the receiver (e.g., a UE or another gNB) may select the matrix W2 (r) K for each row / beam u may be configured to select the strongest coefficients, where the parameter K u may be configurable by the gNB (transmitter). u The value of the matrix W2 (r) Note that the parameter R may be the same for a set of rows / beams. In such a case, a single parameter R is used to calculate the multipole parameter K d may be configured as follows.

[0049] Similarly, the receiver has the matrix W (r) K for each column / delay d may be configured to select the strongest coefficients, where the parameter K d may be configured by the gNB. d The value of the matrix W2 (r) Note that the same can be true for a set of columns / delays of . In such a case, we use a single parameter O to represent multiple parameters K d Configure.

[0050] [3. F2 for reporting (r) Selection of submatrices of According to an exemplary embodiment, W2 (r) To reduce the overhead of reporting the coefficients of W2 (r) The W2 coefficients may be configured to report only amplitude and / or phase information for a subset of the coefficients of W2. (r) The subset of coefficients of W2 may include combining coefficients associated with the “strongest” beams and / or “strongest” delays. In such a case, W2 (r) The rows and / or columns of may be assumed to be ordered such that the coupling coefficients satisfy the following equation:

[0051]

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[0053] In another example, the receiver may be configured to report amplitude and / or phase information for coefficients associated with the D “strongest” delays. (r) ] i,j :j=1,...,D',∀i}.

[0054] In another example, the receiver may be configured to report amplitude and / or phase information for coefficients associated with the U′ “strongest” beams and the D “strongest” delays. (r) ] i,j ,U′,j=1,…,D′}.

[0055] W2 (r) To further significantly reduce the feedback overhead for reporting the quantized version of W2, (r) Three decomposition and quantization schemes for σ x , σ y , are described in accordance with certain embodiments herein.

[0056] [1. First scheme] The first scheme uses the matrix W2 associated with the i-th beam and the j-th delay. (r)The (i,j)-th coupling coefficient of i and b i,j Decompose into:

[0057] [W2 (r) ] i,j =a i b i,j It is. where b i,j is the complex-valued normalized coupling coefficient associated with the ith beam and the jth delay, and a i is a real-valued coefficient that represents the common amplitude of the coupling coefficients for all delays associated with the i-th beam. i Note that the computation of the value of is implementation specific.

[0058] [2. Second Scheme] The second scheme is the matrix W2 associated with the i-th beam and the j-th delay. (r) The (i,j)-th coupling coefficient of j and b i,j Decompose into:

[0059] [W2 (r) ] i,j =d j b i,j It is. where b i,j is the complex-valued normalized coupling coefficient associated with the ith beam and the jth delay, and d j is a real-valued coefficient that represents the common amplitude of the combination coefficients of all beams associated with the jth delay. d j Note that the computation of the value of is implementation specific.

[0060] [3. Third Scheme] The third scheme is the matrix W2 associated with the ith beam and the jth delay. (r) The (i,j)-th coupling coefficient of j and d j and b i,j Decompose into:

[0061] [W2 (r) ] i,j =a i dj b i,j It is. where b i,j is the complex-valued normalized coupling coefficient associated with the ith beam and the jth delay, d j is a real-valued coefficient that represents the common amplitude of the coupling coefficients of all beams associated with the jth delay, a i is a real-valued coefficient that represents the common amplitude of the coupling coefficients associated with all delays associated with the i-th beam. i and d j Note that the computation of the value of is implementation specific.

[0062] The receiver can select W2 by the first scheme, the second scheme, or the third scheme. (r) It should be noted that the proposed schemes may be combined to represent the coupling coefficients. For example, the receiver may be configured to represent only the coupling coefficients of W2 (r) Express the first set of coupling coefficients by the first scheme or the second scheme, and W2 (r) The second set of coupling coefficients may be configured to be expressed by a third scheme.

[0063] [4. Coefficient a i and b i,j and d j quantization of W2 (r) Each entry of coefficient a i and b i,j , or d j and b i,j , or a i ,d j and b i,j After decomposition into, according to one embodiment, the coefficients are quantized separately. The main advantage of the above decomposition scheme is that i,j The amplitude value of W2 (r) Therefore, when applying one of the proposed decomposition schemes, W2 (r) Advantageously, the feedback overhead for reporting the amplitude values ​​of the entries in is significantly reduced.

[0064] For example, the receiver may use a real-valued coefficient a i (and / or d j ) to N a (and / or N d ) bits. i,j are N for amplitude and phase, respectively. b,1 and N b,2 quantized in N bits b,1 is N b,2 It may be lower than that.

[0065] [Saving feedback overhead in the first scheme] In the first scheme, the matrix W2 (r) ∈C (U×D) Assuming that there are UD number of coupling coefficients included in (C is a white character), coefficient a i and coefficient b i,j To report the amplitude and phase information of a +UD(N b,1 +N b,2 ) bits are required. In contrast, matrix W2 (r) The entries of N per amplitude a Bits, N per phase a When quantizing directly in bits, W2 (r) To report the coefficient of a bits are required. i,j The phase value of is N b,2 =N a Assuming that the two are equally quantized in bits, the amount of feedback saved by the first scheme is U(D(N a -N b,1 )-N a ) bits. U=8, D=4, N a = 4, and N b,1 = 2, the number of beams (U), delay (D), and quantization bits (N a ) typical value of W2 (r) A total of 32 bits can be saved for reporting the amplitude and phase compared to directly quantizing the entries of .

[0066] [Saving feedback overhead in the second scheme] In the second scheme, the matrix W2 (r) ∈C (U×D) Assuming again that there are UD coupling coefficients in (C is an outline character), the coefficient d j and b i,j To report the amplitude and phase information of d +UD(N b,1 +N b,2 ) bits are required. i,j The phase value of is N b,2 =N d Assuming that the two are equally quantized in bits, the amount of feedback saved by the second scheme is D(U(N d -N b,1 )-N d ) bits. U=8, D=4, N d = 4, and N b,1 = 2, the number of beams (U), delay (D), and quantization bits (N d ) typical value of W2 (r) A total of 48 bits can be saved for reporting the amplitude and phase compared to directly quantizing the entries of .

[0067] [Saving feedback overhead in the third scheme] In the third scheme, the matrix W2 (r) ∈C (U×D) Assuming again that there are UD number of coupling coefficients included in (C is a white character), the coefficient a i ,d j ,b i,j To report the amplitude and phase information of a +DN d +UD(N b,1 +N b,2 ) bits are required. i and d j N a =N d quantized equally in bits, b i,j The phase value of is N b,2 =N aAssuming that the feedback is quantized with 128 bits, the amount of feedback saved in the third scheme is UD(N a -N b,1 )-(U+D)N a It is given in bits: U=8, D=4, N a = 4, and N b,1 = 1, the number of beams (U), delay (D), and quantization bits (N a ) typical value of W2 (r) A total of 48 bits may be saved for reporting the amplitude and phase information compared to directly quantizing the entries of .

[0068] [5. Non-zero coefficients using bitmap b i,j Selection and reporting W2 (r) To reduce the overhead of reporting the coefficients of , the UE reports the quantized non-zero coefficients b i,j The quantized non-zero coefficients b may be configured to report only the phase values, only the amplitude values, or both the amplitude and phase values ​​of i,j To indicate the index of b, the receiver may be configured to report a bitmap in addition to the amplitude and / or phase information, where each bit of the bitmap represents a coefficient b i,j For example, the first bit is associated with coefficient b 1,1 and the second bit is associated with coefficient b 1,2 If a bit in the bitmap is set to 1, the UE may associate the associated coefficient b i,j The bitmap may then report the phase and / or amplitude values ​​of b to the gNB. Thus, the bitmap may contain P "1's", where P is the non-zero coefficient b i,j corresponds to the number of

[0069] [6. The K strongest coefficients b i,j Selection and reporting W2 (r) In order to reduce the overhead of reporting the coefficients of and fix the number of feedback bits for CSI reporting, the UE calculates the matrix W2 (r)The gNB may be configured to report only phase values, only amplitude values, or amplitude and phase values ​​of the K strongest coefficients, where the value of the parameter K is configurable by the gNB.

[0070] The K strongest coefficients are W2 (r) In order to indicate the indices of the K strongest elements, the receiver may be configured to report a bitmap in addition to the K amplitude and / or phase information, where each bit in the bitmap represents a coefficient b i,j For example, the first bit is associated with coefficient b 1,1 and the second bit is associated with coefficient b 1,2 If a bit in the bitmap is set to 1, the UE may associate the associated coefficient b i,j The quantization matrix W2 may report phase and / or amplitude values ​​of the quantization matrix W2 to the gNB. The bitmap may therefore contain K "1"s. (r) If the number of non-zero amplitude values ​​of is less than K, the UE (r) For example, the bitmap may report only the amplitude and / or phase information for the non-zero coefficients of K. The bitmap may then contain fewer than K "1"s.

[0071] The amount of feedback required to report the amplitude and phase information is W2 (for the third scheme). (r) for amplitude and phase information of a +DN d +K(N b,1 +N b,2 ) bit and the UD bit for the bitmap. Thus, W2 (r) Compared to reporting the amplitude and phase information of all coefficients of (UD-K)(N b,1 +N b,2 )-UD bits may be saved.

[0072] To increase the flexibility of coefficient selection and improve system performance, the receiver uses matrix W2(r) K per row / beam u may be configured to select the strongest coefficients, where the parameter K u may be configurable by the gNB. u The value of the matrix W2 (r) Note that the θ may be identical for a set of rows / beams. In such cases, a single parameter R is used to calculate the multipole parameters K d may be configured as follows.

[0073] Similarly, the receiver has the matrix W (r) Of these, K are d may be configured to select the strongest coefficients, where the parameter K d may be configured by the gNB. d The value of the matrix W2 (r) Note that the same can be true for a set of columns / delays of . In such a case, we use a single parameter O to represent multiple parameters K d Configure.

[0074] [7. Reporting only phase information of matrix B without bitmap display and 1-bit amplitude quantization] 2 and 3 show the matrix W2 when applying the proposed third decomposition scheme according to the embodiment described above. (r) The amplitude distribution of the coupling coefficient in and the coefficient b i,j 4 shows the amplitude distribution of the

[0075] Thus, when applying the proposed third decomposition scheme, the matrix W2 (r) In contrast to the coupling coefficients in i,j can be efficiently represented with only two quantization levels. Therefore, the coefficient b i,j The amplitude information of can be quantized using only one bit for the amplitude value. Therefore, the receiver can b,1= 1, and each amplitude value is represented by two quantization levels "a" and "b", e.g. "a" and / or "b" may be given by "a = 0" and "b = 1". The bits in the bitmap are then assigned to coefficients b i,j corresponds directly to two quantization levels of the amplitude value of b i,j No additional reporting of the amplitude value of N is required. b,1 When the coefficient b = 1, the amount of feedback for reporting the phase value is significantly reduced because the phase value associated with the zero amplitude coefficient is not required to be reported. i,j The same quantization level may be used for the first and second schemes to quantize .

[0076] The above holds for the first and second schemes, i.e., the receiver has N b,1 = 1, and each amplitude value may be represented by two quantization levels "a" and "b", e.g., "a" and / or "b" may be given by "a=0" and "b=1".

[0077] [8.b i,j different quantization levels for phase values ​​of Coefficient b i,j To further reduce the overhead of reporting the phase information of i,j For example, the receiver may be configured to apply different quantization levels to the phase values ​​associated with the non-zero coefficients and the U strongest beams. b,2 We use N" bits to calculate the phase values ​​associated with the non-zero coefficients and the remaining beams. b,2 bits, where N′ b,2 >N″ b,2 It is.

[0078] [B. Reporting the indices associated with selected DFT / DCT vectors] Matrix W2 (r) In addition to reporting the quantized coefficients of the matrix KF (r) An approach is described for efficiently reporting the index of a DFT / DCT vector associated with the complex combination coefficients of D. The DFT / DCT vectors are selected from a predefined set of DFT / DCT basis vectors, with each DFT / DCT basis vector associated with an index. For example, if there are S DFT / DCT basis vectors, the first DFT / DCT basis vector is associated with a first index ("1"), the second DFT / DCT basis vector is associated with a second index ("1"), and the last DFT / DCT basis vector is associated with an index ("S"). When reporting the D selected DFT / DCT basis vectors,

[0079]

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[0080] Instead of directly reporting the indices of the DFT / DCT basis vectors, the receiver may be configured to report a bitmap, where each bit in the bitmap is associated with an index "d" from the set of basis vectors.

[0081] For example, the first bit may be associated with index 1, the second bit with index 2, etc. A "1" in the bitmap at position "d" then indicates selection of the DFT / DCT vector associated with index "d".

[0082] As an example, if the number of subbands is S=13 and D=6, the amount of feedback required to report the index of the selected DFT / DCT vector is

[0083]

number

[0084] According to an embodiment, if the reported bitmap consists of "1"s at positions "1", the amplitude and phase values ​​of the leading beam must be considered as follows: A "1" in position 1 of the bitmap indicates that the amplitude and phase of the combining coefficient of the preceding beam associated with index "1" are given by 1 and 0, respectively, and are not reported. The amplitude and phase values ​​of the combining coefficients of the remaining preceding beams associated with the other indices are given by 0 and 0, respectively, and are not reported. The amplitudes and phases associated with the preceding beams are known to the gNB.

[0085] As mentioned at the beginning, the proposed solution is suitable for the 3GPP Release 15 framework. In the following, according to some embodiments of the present specification, modifications (1) to (7) proposed by the present inventors to the Release 15 framework are presented.

[0086] (1)b i,j The number of preceding beams (B) whose amplitude values ​​have to be reported to the gNB is given by B = 2L or 2L-1 in the proposed CSI reporting using DFT / DCT transform, where L is the number of configured spatial beams, instead of B = 4, 4, and 6 for L = 2, 3, and 4 as in the current Release 15.

[0087] (2) b related to the first advance beam i,j All quantized amplitude and phase values ​​of are not reported to the gNB. (3)N a If = 3, a i The set of amplitudes to quantize is given by {1,√0.5,√0.25,√0.125,√0.0625,√0.0313,√0.0156,0}.

[0088] (4)N d When = 3, d j The set of amplitudes to quantize is given uniformly by {1, √0.5, √0.25, √0.125, √0.0625, √0.0313, √0.0156, 0}.

[0089] (5)N d When = 2, d j The set of amplitudes to quantize is given by {1,√0.5,√0.25,0}. (6)b i,j The set of amplitudes for quantizing x,y is given by {0,1}.

[0090] (7)b i,j The phase sets for quantizing are given by the 8PSK or 16PSK constellations. Unlike the above formula (3), in combination with the three decomposition / quantization schemes mentioned above, the U × S matrix F2 (r) It should be noted that a new transform / decomposition of F2 may be introduced below. Compared with equation (3), the following transform / decomposition further reduces the overhead for reporting the combining coefficients when combined with the three decomposition / quantization schemes mentioned above. The combining coefficient matrix F2 in the frequency domain (r) is decomposed into three matrices.

[0091]

number

[0092] F2 (r) (overlined just above F) is a complex-valued U × S matrix containing the US “subband” coupling coefficients between the U beams and the S subbands, and ·B (r) is a real-valued S × S diagonal matrix with S values ​​on the diagonal.

[0093] matrix A (r) is the matrix F2 (r) Contains the "average" amplitude values ​​of the rows / beams of the coupling coefficients of the matrix B (r) is the matrix F2 associated with the preceding beam (r)This is a normalization matrix that forces the S coupling coefficients in the rows of (written as an overline just above F) to be "1". The pre-beam is the matrix A (r) Note that the subband coefficient matrix F2 is associated with the highest "wideband" amplitude coefficient of (r) Considering the transformation of (written above F), the frequency domain coupling coefficient F2 (r) can be written as follows:

[0094]

number

[0095]

number

[0096]

number

[0097] W2 (r) The quantization and reporting of was previously described. B (r) For reporting, the receiver (i.e., UE, etc.) calculates the diagonal matrix B (r) S coefficients of N B In the case where the receiver is configured not to report the S coefficients, the transmitter (e.g., gNB) may use the matrix B (r) Assume that the identity matrix is ​​given by the matrix B (r)Note that the coefficients in may be represented with only two quantization levels "a" and "b", e.g., "a" and / or "b" are given by "a=√0.5" and "b=1".

[0098] It should be noted that all parameters and values ​​shown can take any suitable value, and some or all are design parameters that, when used, achieve the technical effects and advantages of the embodiments described in this disclosure.

[0099] Referring to FIG. 4, a flowchart of a method performed by a UE 500 for reducing CSI-related feedback overhead in a communication network employing MIMO operation (multiple-input multiple-output operation) is shown, the method comprising:

[0100] Precoder matrix W2 (r) a decomposition step (401) of decomposing each entry corresponding to an (i,j)-th coupling coefficient of the input signal into at least two coefficients, where r denotes an r-th transmission layer, the (i,j) coupling coefficient being associated with an ith beam and a j-th delay, and each coupling coefficient being associated with amplitude information and phase information.

[0101] quantizing (402) each of said at least two coefficients individually with at least one bit; and A step (403) of reporting information related to at least one phase value or at least one amplitude value of said quantized coefficients, or information related to at least one phase value and amplitude value of said quantized coefficients.

[0102] According to some embodiments of the present disclosure, a method performed by a UE is set forth in the subject matter of any one of claims 1 to 39. To perform the steps of the process or method described above for the UE, embodiments herein include a UE for reducing feedback overhead in a communication network. As shown in FIG. 5, the UE 500 is composed of a processor 510 or processing circuit or processing module or processor means, a receiver circuit 540 or receiver module, a transmitter circuit 550 or transmitter module, a memory module 520, and a transceiver circuit or transceiver module 530 that may include the transmitter circuit 550 and the receiver circuit 540. The UE 500 further comprises an antenna system 560 including at least an antenna circuit for transmitting and receiving signals to and from a radio network node or gNB. The antenna system may employ beamforming as previously described.

[0103] The UE 500 may operate with any radio access technology, including 2G, 3G, 4G or LTE, LTE-A, 5G, WLAN, WiMAX, etc., that supports beamforming technology.

[0104] The processing module / circuitry 510 may include a processor, microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc., and may be referred to as a "processor 510." The processor 510 controls the operation of the network node 500 and its components. The memory (circuitry or module) 520 includes random access memory (RAM), read only memory (ROM), and / or another type of memory for storing data and instructions that may be used by the processor 510. In general, it will be understood that the UE 500 in one or more embodiments includes fixed or programmed circuitry configured to perform the operations in any of the embodiments disclosed herein.

[0105] In at least one such example, the UE 500 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry configured to execute computer program instructions from a computer program stored in a non-transitory computer-readable medium within or accessible to the processing circuitry. Here, "non-transitory" does not necessarily mean permanent or unchanging storage, and may include storage within a working memory or a volatile memory, but the term refers to storage that has at least some persistence. Execution of the program instructions specially adapts or configures the processing circuitry to perform the operations disclosed herein, including any one of method claims 1-12. Additionally, it will be understood that the UE 500 may include additional components not shown in FIG. 5.

[0106] As previously presented, the UE 500 operates as follows: (r) into at least two coefficients, where r represents the rth transmission layer and the (i,j) combining coefficient is associated with the ith beam and the jth delay. Each combining coefficient is associated with amplitude and phase information. Each of the at least two combining coefficients is separately quantized with at least one bit. Report information related to at least one phase value or at least one amplitude value of the quantized coefficient, or information related to at least one phase value and amplitude value of the quantized coefficient.

[0107] The UE uses the first scheme to derive the matrix W2 associated with the i-th beam and the j-th delay. (r) The (i,j)-th coupling coefficient of i and b i,j It is constructed to decompose the signal into two coefficients:

[0108] [W2 (r) ] i,j =a i b i,j It is. where bi,j is the complex-valued normalized coupling coefficient associated with the ith beam and the jth delay, and a i is a real-valued coefficient representing the common amplitude of the combining coefficients for all delays associated with the i-th beam.

[0109] The UE (500) uses the second scheme to calculate the matrix W2 associated with the i-th beam and the j-th delay. (r) The (i,j)-th coupling coefficient of j and b i,j The device is configured to decompose into

[0110] [W2 (r) ] i,j =d j b i,j It is. where b i,j is the complex-valued normalized coupling coefficient associated with the ith beam and the jth delay, and d j is a real-valued coefficient representing the common amplitude of the combining coefficients for all beams associated with the jth delay.

[0111] The UE (500) uses the third scheme to calculate the matrix W2 associated with the i-th beam and the j-th delay. (r) The (i,j)-th coupling coefficient of j , d j and b i,j It is constructed to decompose the signal into three coefficients:

[0112] [W2 (r) ] i,j =a i d j b i,j It is. where b i,j is the complex-valued normalized coupling coefficient associated with the ith beam and the jth delay, and d j is a real-valued coefficient representing the common amplitude of the coupling coefficients for all beams associated with the jth delay, and a i is a real-valued coefficient representing the common amplitude of the combining coefficients for all delays associated with the i-th beam.

[0113] The UE (500) uses the first scheme, the second scheme, or the third scheme to determine only the coupling coefficient or the coupling coefficient set W2 (r) It is constructed to be expressed as: Additional details regarding the functions or acts performed by the UE have already been disclosed (see method steps performed by the UE).

[0114] There is also provided a computer program comprising instructions which, when executed on at least one processor 510 of a UE 500 as claimed in claim 30, cause the processor 510 to perform the method as claimed in any one of claims 1 to 29.

[0115] A method performed by a radio base station or radio network node or gNB700 is also provided in accordance with some demonstrative embodiments. A method for reducing CSI related feedback overhead in a communication network employing MIMO operation comprises:

[0116] Receive (601) from the UE 500 a report including information related to at least one phase value or at least one amplitude value, or at least one phase value and amplitude value, of each quantized coefficient quantized by the UE 500 with at least one bit, where the precoder matrix W2 (r) Each entry corresponding to the (i,j) combining coefficient of is decomposed by UE 500 into at least two coefficients, where r represents the r-th transmission layer. The (i,j) combining coefficient is associated with the ith beam and the j-th delay. Each combining coefficient is associated with amplitude and phase information.

[0117] The method further comprises the steps of: (r) The method includes configuring the UE to feed back amplitude and / or phase values ​​of the K strongest coefficients, where the value of K is configurable by the radio network node (700) or the gNB.

[0118] The method further comprises the steps of: (r) Of these, K are for each row / beam. u configuring the UE to select the strongest coefficients, where the parameter K u can be configured by a radio base station or a gNB.

[0119] The method is to use matrix W2 (r) Of these, K are d configuring the UE to select the strongest coefficients, where a parameter K d can be configured by a radio base station (700) or a gNB.

[0120] The method is W2 (r) The method includes configuring the UE to report amplitude and / or phase information of only a subset of the coefficients of the The method is according to the first scheme of claim 2, the second scheme of claim 3, or the third scheme of claim 4, (r) The method includes configuring the UE to represent only the coupling coefficient or set of coupling coefficients.

[0121] The method includes: i (and / or d j ) to N a (and / or N d ) bits, i is a real-valued coefficient representing the common amplitude of the combining coefficients for all delays associated with the i-th beam.

[0122] The method further comprises the steps of: i,j The method includes configuring the UE to report only phase values, only amplitude values, or amplitude and phase values ​​of the received signal. The method comprises configuring a UE to report a bitmap, where each bit in the bitmap is associated with an index "d" from a set of DFT / DCT basis vectors.

[0123] The additional functions performed by the radio network node 700 have already been disclosed and need not be repeated. To perform the process or method steps described above relating to a radio network node, certain embodiments herein include a radio network node 700 for reducing feedback overhead in a communications network.

[0124] As shown in Figure 6, the radio network node 700 comprises a processor 710 or processing circuit or processing module or processor means, a receiver circuit 740 or receiver module, a transmitter circuit 770 or transmitter module, a memory module 720, and a transceiver circuit or transceiver module 730 which may include the transmitter circuit 770 and the receiver circuit 740. The radio network node 700 further comprises an antenna system 760 including at least antenna circuitry for transmitting and receiving signals to and from the network node and other UEs etc. The antenna system employs beamforming as previously described.

[0125] The radio network node 700 may operate with any radio access technology including 2G, 3G, 4G or LTE, LTE-A, 5G, WLAN, WiMAX, etc. that supports beamforming technology.

[0126] The processing module / circuitry 710 may include a processor, microprocessor, application specific integrated circuit (ASIC), field programmable gate array (FPGA), etc., and may be referred to as a "processor 710." The processor 710 controls the operation of the UE 700 and its components. The memory (circuitry or module) 720 includes random access memory (RAM), read only memory (ROM), and / or another type of memory for storing data and instructions that may be used by the processor 710. In general, it will be understood that the radio network node 700 in one or more embodiments includes fixed or programmed circuitry configured to perform the operations in any of the embodiments disclosed herein.

[0127] In at least one such example, the radio network node 700 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry configured to execute computer program instructions from a computer program stored in a non-transitory computer-readable medium within or accessible to the processing circuitry. Here, "non-transitory" does not necessarily mean permanent or unchanging storage, and may include storage in working memory or volatile memory, but the term refers to storage that has at least some persistence. Execution of the program instructions specially adapts or configures the processing circuitry to perform the operations disclosed herein, including at least the features of the independent method claims. Furthermore, it will be understood that the radio network node 700 may comprise additional components not shown in FIG. 6.

[0128] To reduce feedback overhead associated with channel state information (CSI) in a communication network employing multiple-input multiple-output (MIMO) operation, a gNB is operative to perform the subject matter recited in any one of method claims 31 to 39.

[0129] The additional functions performed by the radio network node 700 have already been disclosed and need not be repeated again. There is also provided a computer program comprising instructions which, when executed on at least one processor 710 of a radio network node 700 as defined in claim 40, cause at least said at least one processor 710 to perform at least the method as defined in any one of claims 31 to 39.

[0130] Also provided is a carrier containing the computer program, where the carrier is one of a computer readable storage medium, an electronic signal, an optical signal, or a radio signal. As will be apparent from the above detailed description, several advantages are achieved by the disclosed embodiments.

[0131] Throughout this disclosure, the terms "configure" or "configuring" are used in a non-limiting sense, i.e., in the sense of "at least configure". Although specific terms may be employed herein, they are used in a general and descriptive sense only and not for purposes of limitation. The embodiments herein may be applied to any wireless system including GSM, 3G or WCDMA, LTE or 4G, LTE-A (or LTE-Advanced), 5G, WiMAX, WiFi, satellite communications, television broadcasting, etc., that may employ beamforming technology.

Claims

1. 1. A method performed by a user equipment (500) for reducing feedback overhead associated with channel state information (CSI) in a communication network employing multiple-input multiple-output (MIMO) operation, the method comprising: Precoder matrix W ２ （ｒ） a decomposition step (401) of decomposing each entry corresponding to an (i,j)-th combining coefficient of the precoder matrix W into at least two coefficients, where r denotes the r-th transmission layer, the (i,j) combining coefficient is associated with the i-th beam and the j-th delay, each combining coefficient being associated with information related to an amplitude value and information related to a phase value, ２ （ｒ） The decomposed (i, j) coupling coefficients are divided into two coefficients a ｉ and b ｉ，ｊ Due to [W ２ （ｒ） ] ｉ，ｊ =a ｉ b ｉ，ｊ is expressed as b ｉ，ｊ is the complex-valued normalized coupling coefficient corresponding to the i-th beam and the j-th delay, a ｉ is a real-valued coefficient representing a common amplitude value of the combining coefficients corresponding to all delays associated with the i-th beam; a quantization step (402) for individually quantizing each of said at least two coefficients with at least one bit; a reporting step (403) of reporting information related to at least one phase value or at least one amplitude value of the quantized coefficient, or information related to at least one phase value and amplitude value of the quantized coefficient; A method comprising:

2. 1. A method performed by a user equipment (500) for reducing feedback overhead associated with channel state information (CSI) in a communication network employing multiple-input multiple-output (MIMO) operation, the method comprising: Precoder matrix W ２ （ｒ） a decomposition step (401) of decomposing each entry corresponding to an (i,j)-th combining coefficient of the precoder matrix W into at least two coefficients, where r denotes the r-th transmission layer, the (i,j) combining coefficient is associated with the i-th beam and the j-th delay, each combining coefficient being associated with information related to an amplitude value and information related to a phase value, ２ （ｒ） The decomposed (i, j) coupling coefficients are divided into two coefficients d ｊ and b ｉ，ｊ By [W ２ （ｒ） ] ｉ，ｊ =d ｊ b ｉ，ｊ is expressed as b ｉ，ｊ is the complex-valued normalized coupling coefficient associated with the i-th beam and the j-th delay, d ｊ is a real-valued coefficient representing a common amplitude value of the combining coefficients of all beams associated with the jth delay; a quantization step (402) for individually quantizing each of said at least two coefficients with at least one bit; a reporting step (403) of reporting information related to at least one phase value or at least one amplitude value of the quantized coefficient, or information related to at least one phase value and amplitude value of the quantized coefficient; A method comprising:

3. 1. A method performed by a user equipment (500) for reducing feedback overhead associated with channel state information (CSI) in a communication network employing multiple-input multiple-output (MIMO) operation, the method comprising: Precoder matrix W ２ （ｒ） a decomposition step (401) of decomposing each entry corresponding to an (i,j)-th combining coefficient of the precoder matrix W into at least two coefficients, where r denotes the r-th transmission layer, the (i,j) combining coefficient is associated with the i-th beam and the j-th delay, each combining coefficient being associated with information related to an amplitude value and information related to a phase value, ２ （ｒ） The decomposed (i, j) coupling coefficients are divided into three coefficients a ｉ , d ｊ , b ｉ，ｊ By [W ２ （ｒ） ] ｉ，ｊ =a ｉ d ｊ b ｉ，ｊ is expressed as b ｉ，ｊ is the complex-valued normalized coupling coefficient associated with the i-th beam and the j-th delay, d ｊ is a real-valued coefficient representing the common amplitude value of the combining coefficients of all beams associated with the jth delay, a ｉ is a real-valued coefficient representing a common amplitude value of the combining coefficients for all delays associated with the i-th beam; a quantization step (402) for individually quantizing each of said at least two coefficients with at least one bit; a reporting step (403) of reporting information related to at least one phase value or at least one amplitude value of the quantized coefficient, or information related to at least one phase value and amplitude value of the quantized coefficient; A method comprising:

4. The method comprises: ２ （ｒ） expressing only the coupling coefficients or the set of coupling coefficients according to a first scheme, a second scheme, or a third scheme; The method according to any one of claims 1 to 3.

5. The method comprises: ２ （ｒ） The first set of coupling coefficients of W is represented by a first scheme or a second scheme, ２ （ｒ） expressing a second set of coupling coefficients by a third scheme; The method according to any one of claims 1 to 3.

6. The method further comprises the steps of: ｉ and / or d ｊ N ａ Bits and / or N ｄ quantizing (402) equally in bits; Each complex-valued coefficient b ｉ，ｊ are the amplitude and phase values, respectively. ｂ，１ Bit and N ｂ，２ It can be quantized in bits, N ｂ，１ is N ｂ，２ is lower than The method according to any one of claims 1 to 3.

7. The method includes: ａ N per bit and phase value ａ bits and the precoder matrix W ２ （ｒ） quantizing (402) the entries of The precoder matrix W ２ （ｒ） To report the coefficient of ａ A process using bits and UD is the precoder matrix W ２ （ｒ） is the number of coupling coefficients of The method of claim 1.

8. The quantization step (402) includes: N ｂ，２ = N ｄ Bit B ｉ，ｊ equally quantizing the phase values ​​of dj, Nd being the number of bits used to quantize the real-valued coefficients dj; Coefficient d ｊ and b ｉ，ｊ DN to report information related to the amplitude value and information related to the phase value of ｄ +UD(N ｂ，１ +N ｂ，２ ) bits, where N b,1 is the number of bits to quantize the amplitude values ​​of the complex-valued coefficients b i,j and N b,2 is the number of bits to quantize the phase values ​​of the complex-valued coefficients b i,j ; Equipped with D is the number of delays, UD is the precoder matrix W ２ （ｒ） is the number of coupling coefficients of The method of claim 2.

9. The quantization step (402) is a step of quantizing a real-valued coefficient a ｉ and d ｊ N ａ = N ｄ By bit, b ｉ，ｊ The phase value of N ｂ，２ = N ａ The amount of feedback that can be saved by the third scheme is UD(N ａ -N ｂ，１ )-(U+D)N ａ quantizing the complex-valued coefficients b i,j , b ,1 , b ,2 , b ,3 , and b ,4 , where N a is the number of bits used to quantize the real-valued coefficients a i , N d is the number of bits used to quantize the real-valued coefficients d j , N b,1 is the number of bits used to quantize the amplitude values ​​of the complex-valued coefficients b i,j , and N b,2 is the number of bits used to quantize the phase values ​​of the complex-valued coefficients b i,j ; Coefficient a ｉ , d ｊ and b ｉ，ｊ to report information related to the amplitude value and information related to the phase value of ａ +DN ｄ +UD(N ｂ，１ +N ｂ，２ ) a process using a bit; Equipped with D is the number of delays, U is the number of beams, UD is the precoder matrix W ２ （ｒ） is the number of coupling coefficients of The method according to claim 3.

10. The method further comprises the steps of: ２ （ｒ） reporting only phase values, only amplitude values, or amplitude and phase values ​​of the K strongest coefficients of The value of the parameter K is configurable by the network node or gNB. The method according to any one of claims 1 to 9.

11. The method uses the precoder matrix W ２ （ｒ） K for each row / beam ｕ selecting the strongest coefficients; Parameter K ｕ is configurable by a radio network node or a gNB; The method of claim 10.

12. The method uses the precoder matrix W ２ （ｒ） K for each column / delay ｄ selecting the strongest coefficients; Parameter K ｄ is configurable by a radio network node or a gNB; The method of claim 10.

13. The method further comprises: ｉ，ｊ using only two quantization levels; Coefficient b ｉ，ｊ quantizing information related to the amplitude value of N b,1 using only N b,1 =1 bit for the amplitude value, wherein the user equipment (500) is ｂ，１ = 1; representing each amplitude value by two quantization levels "a" and "b", at least one of "a" and "b" being given by "a=0" and "b=1"; The method of claim 3 comprising:

14. When using the first or second scheme, The user equipment (500) receives, from the radio base station, N ｂ，１ = 1, The method comprises the steps of representing each amplitude value by two quantization levels "a" and "b"; At least one of "a" and "b" is given by "a=0" and "b=1", The method according to claim 1 or 2.

15. The method further comprises: ｉ，ｊ applying different quantization levels to the phase values ​​of The method according to any one of claims 1 to 3.

16. The method provides N' for the phase values ​​associated with the non-zero coefficients and the U' strongest beams. ｂ，２ Using bits, N" for the phase values ​​associated with the non-zero coefficients and the remaining beams. ｂ，２ using a bit, N' ｂ，２ >N" ｂ，２ That is, The method of claim 15.

17. The method further comprises: Ｆ （ｒ） reporting an index of a discrete Fourier transform / discrete cosine transform (DFT / DCT) vector associated with the complex combination coefficients of The method according to any one of claims 1 to 16.

18. The method comprises the steps of selecting DFT / DCT vectors from a set of predefined DFT / DCT basis vectors; Each DFT / DCT basis vector is associated with an index, 20. The method of claim 17.

19. 1. A user equipment (UE) for reducing channel state information (CSI) related feedback overhead in a communication network employing multiple-input multiple-output (MIMO) operation, the UE comprising: Precoder matrix W ２ （ｒ） into at least two coefficients, where r denotes the r-th transmission layer, the (i,j) combining coefficients are associated with the i-th beam and the j-th delay, and each combining coefficient is associated with information related to an amplitude value and information related to a phase value, and the precoder matrix W ２ （ｒ） The decomposed (i, j) coupling coefficients are divided into two coefficients a ｉ and b ｉ，ｊ Due to [W ２ （ｒ） ] ｉ，ｊ =a ｉ b ｉ，ｊ is expressed as b ｉ，ｊ is the complex-valued normalized coupling coefficient corresponding to the i-th beam and the j-th delay, a ｉ is a real-valued coefficient representing a common amplitude value of combining coefficients corresponding to all delays associated with the i-th beam, and the UE further quantizing each of the at least two coefficients individually with at least one bit; The UE reports information related to at least one phase value or at least one amplitude value of a quantized coefficient, or information related to at least one phase value and amplitude value of a quantized coefficient.

20. 1. A user equipment (UE) for reducing channel state information (CSI) related feedback overhead in a communication network employing multiple-input multiple-output (MIMO) operation, the UE comprising: Precoder matrix W ２ （ｒ） into at least two coefficients, where r denotes the r-th transmission layer, the (i,j) combining coefficients are associated with the i-th beam and the j-th delay, and each combining coefficient is associated with information related to an amplitude value and information related to a phase value, and the precoder matrix W ２ （ｒ） The decomposed (i, j) coupling coefficients are divided into two coefficients d ｊ and b ｉ，ｊ Due to [W ２ （ｒ） ] ｉ，ｊ =d ｊ b ｉ，ｊ is expressed as b ｉ，ｊ is the complex-valued normalized coupling coefficient associated with the i-th beam and the j-th delay, d ｊ is a real-valued coefficient representing a common amplitude value of combining coefficients of all beams associated with the jth delay, and the UE further quantizing each of the at least two coefficients individually with at least one bit; The UE reports information related to at least one phase value or at least one amplitude value of a quantized coefficient, or information related to at least one phase value and amplitude value of a quantized coefficient.

21. 1. A user equipment (UE) for reducing channel state information (CSI) related feedback overhead in a communication network employing multiple-input multiple-output (MIMO) operation, the UE comprising: Precoder matrix W ２ （ｒ） into at least two coefficients, where r denotes the r-th transmission layer, the (i,j) combining coefficients are associated with the i-th beam and the j-th delay, and each combining coefficient is associated with information related to an amplitude value and information related to a phase value, and the precoder matrix W ２ （ｒ） The decomposed (i, j) coupling coefficients are divided into three coefficients a ｉ , d ｊ , b ｉ，ｊ By [W ２ （ｒ） ] ｉ，ｊ =a ｉ d ｊ b ｉ，ｊ is expressed as b ｉ，ｊ is the complex-valued normalized coupling coefficient associated with the i-th beam and the j-th delay, d ｊ is a real-valued coefficient representing the common amplitude value of the combining coefficients of all beams associated with the jth delay, a ｉ is a real-valued coefficient representing a common amplitude value of combining coefficients for all delays associated with the i-th beam, and the UE further quantizing each of the at least two coefficients individually with at least one bit; The UE reports information related to at least one phase value or at least one amplitude value of a quantized coefficient, or information related to at least one phase value and amplitude value of a quantized coefficient.

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