A method performed by a User Equipment, UE, the method comprising: - receiving from a network node, a radio signal via a Multiple Input Multiple Output, MIMO, channel, wherein the radio signal contains at least one DownLink, DL, reference signal according to a DL reference signal configuration; - estimating said MIMO channel based on said received at least one DL reference signal for configured resource blocks; - calculating a precoding matrix for a number of antenna ports of the network node and configured subbands; the precoding matrix being based on a first codebook and on a second codebook and a set of combining coefficients for complex scaling/combining one or more of vectors selected from the first codebook and the second codebook, wherein the first codebook contains one or more transmit-side spatial beam components/vectors of the precoding matrix and the second codebook contains one or more delay components/vectors of the precoding matrix; - quantizing the combining coefficients per beam of the precoding matrix, wherein each combining coefficient γ p, i, j l is a product of three coefficients a l,p,i, b l,p,i,j and d l,p,i,j, and is given by: γ p, i, j l = a l, p, i b l, p, i, j d l, p, i, j, where a l,p,i is a real-valued coefficient representing a common amplitude across all combining coefficients associated with a i -th beam, p -th polarization and l -th layer, b l,p,i,j is a real-valued normalized combining-coefficient representing the amplitude associated with the i -th beam, j -th delay vector, p-th polarization and l -th layer, and d l, p, i, j = exp j 2 πn 2 N; n ∈ {0,1,..., 2 N - 1}, N ∈ {1,2,3,4} is a coefficient to indicate the phase of γ p, i, j l; wherein the amplitudes a l,p,i are partitioned, per layer, into at least two disjoint subsets, and each subset is assigned a single and different value for said quantization, and wherein each subset contains the amplitudes a l,p,i with respect to a single polarization; and - reporting, to the network node, a Channel State Information, CSI, feedback and/or a Precoder matrix Indicator, PMI and/or a PMI/Rank Indicator, PMI/RI, used to indicate the precoding matrix for the configured antenna ports and subbands, wherein the report contains a bitmap for indicating at least selected delay vectors and spatial beam vectors associated with non-zero combining coefficients of said set of quantized combining coefficients included in the report transmitted to the network node. - receiving from a network node, a radio signal via a Multiple Input Multiple Output, MIMO, channel, wherein the radio signal contains at least one DownLink, DL, reference signal according to a DL reference signal configuration; - estimating said MIMO channel based on said received at least one DL reference signal for configured resource blocks; - calculating a precoding matrix for a number of antenna ports of the network node and configured subbands; the precoding matrix being based on a first codebook and on a second codebook and a set of combining coefficients for complex scaling/combining one or more of vectors selected from the first codebook and the second codebook, wherein the first codebook contains one or more transmit-side spatial beam components/vectors of the precoding matrix and the second codebook contains one or more delay components/vectors of the precoding matrix; - quantizing the combining coefficients per beam of the precoding matrix, wherein each combining coefficient γ p, i, j l is a product of three coefficients a l,p,i, b l,p,i,j and d l,p,i,j, and is given by: γ p, i, j l = a l, p, i b l, p, i, j d l, p, i, j, where a l,p,i is a real-valued coefficient representing a common amplitude across all combining coefficients associated with a i -th beam, p -th polarization and l -th layer, b l,p,i,j is a real-valued normalized combining-coefficient representing the amplitude associated with the i -th beam, j -th delay vector, p-th polarization and l -th layer, and d l, p, i, j = exp j 2 πn 2 N; n ∈ {0,1,..., 2 N - 1}, N ∈ {1,2,3,4} is a coefficient to indicate the phase of γ p, i, j l; wherein the amplitudes a l,p,i are partitioned, per layer, into at least two disjoint subsets, and each subset is assigned a single and different value for said quantization, and wherein each subset contains the amplitudes a l,p,i with respect to a single polarization; and - reporting, to the network node, a Channel State Information, CSI, feedback and/or a Precoder matrix Indicator, PMI and/or a PMI/Rank Indicator, PMI/RI, used to indicate the precoding matrix for the configured antenna ports and subbands, wherein the report contains a bitmap for indicating at least selected delay vectors and spatial beam vectors associated with non-zero combining coefficients of said set of quantized combining coefficients included in the report transmitted to the network node.