Method and system for enhancing wireless data transmission using modified precoders

Abstract

The proposed invention relates to a method of enhancing wireless data transmission using modified precoders, and comprises determining of a subset of basis vectors by a second node based on selection of determined number of basis vectors from a down-sampled set of basis vectors The method also comprises determination of the subset of basis vectors based on a set of common basis vectors and a set of unique basis vectors. The method further comprises determining, by a first node, a precoder matrix where each column of the matrix is derived based on the subset of basis vectors and a subset of complex weights from the set of complex weights, and obtaining a signal based on precoding of a first signal with the precoder matrix.

Description

METHOD AND SYSTEM FOR ENHANCING WIRELESS DATA TRANSMISSION USING MODIFIED PRECODERS FIELD OF INVENTION

[0001] The present disclosure generally relates to wireless communication, and specifically relates to enhancing wireless data transmission based on modifying precoders to reduce signal overloading arising from higher number of CSI-RS ports. BACKGROUND

[0002] The subject matter discussed in the background section should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The subject matter in the background section merely represents different approaches, which in and of themselves may also correspond to implementations of the claimed technology.

[0003] In a wireless technology, the downlink channel state information is required at a BS (Base Station) to make an effective transmission to a UE. In 5G NR technology, a framework is adopted by the specification such that the DL channel state information is acquired by the BS (Base Station). Based on the received CSI report, the BS schedules a UE (User Equipment) appropriately. In 5G NR, the CSI consists of different kinds of information such as PMI (Precoding Matrix Indicator), RI (Rank Indicator), LI (Layer Indicator), CQI (Channel Quality Indicator) etc, where each field reports a different metric related to the channel.

[0004] The PMI field in the CSI report indicates to the BS an appropriate precoder matrix that could to be used for transmission of PDSCH, wherein the precoder matrix is used for controlling the amplitudes and phases of signals sent from one or more antennas in digital communication systems. Precoders are used for boosting signal strength of a signal transmitted from a transmitter node to a receiver node, and are also used to improve transmission rates, reduce interference and maximize received signals. The UE selects a precoder for reporting to the BS based on the estimated channel from CSI-RS such that the precoder enhances the channel gain. The precoder isselected by the UE from a codebook configured by the BS, where the codebook comprises a plurality of precoders, and the most suitable precoder for the channel is selected by the UE based on the channel estimation.

[0005] In NR, a codebook is defined as a set of precoder matrices. The precoder matrices in NR are derived based on oversampled DFT vectors. 3GPP has introduced multiple precoder structures in Release 15 i.e., Type-1 Single-panel codebook, Type-1 Multi-panel codebook, Type- 2 codebook and Type-2 Port selection codebook. Type-1 Single-panel codebook has a simpler structure and lower performance gain compared to Type-2 codebook which has more complex structure and gives higher performance gain. Type-2 CSI provides channel information with significantly higher granularity compared to Type-1 CSI. This higher granularity of the PMI feedback comes at the cost of significantly higher signalling overhead, since more information bits are required for feedback.

[0006] The current NR specification supports up to 32 CSI-RS ports. One of the challenges associated with extending a codebook for number of CSI ports higher than 32 is that the complexity at the UE for calculating the most appropriate precoder for a channel increases with the increase in number of ports. Additionally, if the number of ports increases, the signalling overhead also increases. Hence, there is a need for modifying the current CSI-RS reporting framework for using higher number of CSI-RS ports in the NR specification without causing signal overloading. OBJECT OF THE INVENTION

[0007] An objective of the present invention is to use higher number of CSI-RS ports in wireless data transmissions without increase in signal overloading.

[0008] Yet another objective of the present invention is to modify precoders used in the existing CSI-RS reporting framework to improve signal strength boosting without increasing complexity of computation of best precoder for a channel.

[0009] Yet another objective of the present invention is to report modified precoders if number of CSI-RS ports is greater than 32 based on reducing complexity of selecting beams from a beam grid. SUMMARY OF THE INVENTION

[0010] In accordance with an embodiment of the present disclosure, a method for enhancing wireless data transmission using modified precoders is provided. The method comprises signaling, by a first node, a configuration to configure at least one of a set of basis vectors to a second node,a pair of down-sampling factors (^^1, ^^2), a bitmap and a set of ^^ values to a second node. Themethod also comprises receiving, by the first node, at least one of an ^^ value from the configured set of ^^ values and a first subset of basis vectors from the second node, and receiving at least one of a rank (^^) of the precoder matrix and a set of complex weights for the precoder matrix from the second node, where the rank of the precoder matrix indicates the number of columns of the precoder matrix. The method further comprises determining, by the first node, a precoder matrix of rank ^^ where each column of the precoder matrix is derived based on the first subset of basis vectors and a subset of complex weights from the set of complex weights, and obtaining by the first node a second signal by precoding a first signal with the precoder matrix of rank. The method also comprises transmitting, by the first node, the second signal to the second node.

[0011] In one aspect, the signalling by the first node is performed using at least one of DCI, MAC-CE and RRC signalling. Further, the set of basis vectors are DFT based vectors.

[0012] In one aspect, the set of basis vectors is mapped using the bitmap, where the bit location in the bitmap is associated with a basis vector and the bit value indicates whether the associated basis vector is considered to form a second subset of basis vectors.

[0013] In another aspect, at least one of an ^^ value from the configured set of ^^ values and a first subset of basis vectors is received from the second node on at least one of uplink control channel and uplink data channel. Further, the at least one of a rank (^^) of the precoder matrix anda set of complex weights for the precoder matrix is received from the second node on at least one of uplink control channel and uplink data channel.

[0014] In another aspect, the column in the precoder matrix is obtained as a weighted sum of the received first subset of basis vectors, wherein the weights used in the weighted sum are derived from the received subset of complex weights. The column in the precoder matrix is obtained per polarization.

[0015] In accordance with another embodiment of the present disclosure, a method for enhancing wireless data transmission using modified precoders is provided. The method comprises receiving, by a second node, a configuration of at least one of a set of basis vectors to a secondnode, a pair of down-sampling factors (^^1, ^^2), a bitmap and a set of ^^ values from a first node,and determining, by the second node, at least one of an ^^ value from the received set of ^^ values and a second subset of basis vectors based on at least one of the received pair of down-samplingfactors (^^1, ^^2) and a bitmap from the first node. The method also comprises determining, by thesecond node, a first subset of basis vectors based on the determined ^^ value, where the first subset of basis vectors is a subset of the second subset of basis vectors and determining a rank (^^) of the precoder matrix, wherein the rank of the precoder matrix indicates the number of columns of the precoder matrix. The method further comprises determining, by the second node, a set of complex weights corresponding to each column of the precoder matrix. The method also comprises reporting, by the second node, at least one of the determined ^^ value and the determined first subset of basis vectors to the first node, and reporting the determined set of complex weights to the first node.

[0016] In one aspect, the receiving by the second node is performed using at least one of DCI, MAC-CE and RRC signalling. Further, the set of basis vectors are DFT based vectors.

[0017] In another aspect, each basis vector in the received set of basis vectors is associatedwith a pair of indices (^^1, ^^2) wherein ^^1 ∈ {0,1, .. , ^^1^^1 − 1} and ^^2 ∈ {0,1, .. , ^^2^^2 − 1}.The values of ^^1, ^^2, ^^1and ^^2are received by the second node from the first node using at least one of DCI, MAC-CE and RRC signalling. The second node determines the second subsetof basis vectors based on the received down-sampling factors (^^1, ^^2). A basis vector, from thereceived set of basis vectors, with the corresponding pair of indices (^^1, ^^2) is present in thesecond subset of basis vectors if ((^^^^^^(^^1, ^^1) − ^^1) = 0) and ((^^^^^^(^^2, ^^2) − ^^2) = 0),where ^^1and ^^2are received by the second node from the first node using at least one of DCI, MAC-CE and RRC signaling. Further, the second node determines the first subset of basis vectors based on the received bitmap, where the bit location in the bitmap is associated with a basis vector and a basis vector from the received set of basis vectors is present in the second subset of basis vectors if the bit in the bitmap corresponding to the basis vector is set to 0.

[0018] In another aspect, the second node reports at least one of the determined ^^ value, the determined rank (^^) of the precoder matrix, determined first subset of basis vectors and the determined set of complex weights to the first node using at least one of uplink control channel and uplink data channel.

[0019] In accordance with another embodiment of the present disclosure, a method for enhancing wireless data transmission using modified precoders is provided. The method comprises signaling, by a first node, a configuration to configure at least one of a set of basis vectors, ^^, ^^^^and ^^^^to the second node, where ^^ defines the total number of basis vectors corresponding to the precoding matrix, ^^^^defines the number of basis vectors that are common across all the columns of the precoder matrix and ^^^^defines the number of unique basis vectors corresponding to each column of the precoder matrix. The method further comprises receiving, by the first node, a first subset of basis vectors and a set of second subset of basis vectors, where each second subset of basis vectors is associated with a column in the precoder matrix, and receiving by the first node a set of complex weights from the second node. The method further comprises determining, by the first node, a precoder matrix of rank ^^, where each column of the precoder matrix is derived based on the first subset of basis vectors, the corresponding second subset of basis vectors and the corresponding complex weights. The method also comprises obtaining, by the first node, a second signal by precoding a first signal with the precoder matrix of rank ^^ and transmitting, by the first node, the second signal to the second node.

[0020] In one aspect, the signaling by the first node is performed using at least one of DCI, MAC-CE and RRC signalling. Further, the set of basis vectors are DFT based vectors.

[0021] In one aspect, the method further comprises signaling, by the first node, an association between a second subset and a column of the precoder matrix.

[0022] In another aspect, at least one of a rank (^^) of the precoder matrix and a set of complex weights for the precoder matrix is received from the second node on at least one of uplink control channel and uplink data channel. Further, the column in the precoder matrix is obtained as a weighted sum of the received first subset of basis vectors and an associated second set of basis vectors, wherein the weights used in the weighted sum are derived from the received set of complex weights. The column in the precoder matrix is obtained per polarization.

[0023] In accordance with another embodiment of the present disclosure, a method for enhancing wireless data transmission using modified precoders is provided. The method comprises receiving, by a second node, a configuration of at least one of a set of basis vectors, ^^, ^^^^and ^^^^from the first node, where ^^ defines the total number of basis vectors corresponding to the precoding matrix, ^^^^defines the number of basis vectors that are common across all the columns of the precoder matrix, and ^^^^defines the number of unique basis vectors corresponding to each column of the precoder matrix. The method further comprises determining, by the second node, a rank (^^) of the precoder matrix wherein the rank indicates the number of columns that are present in the precoder matrix and determining, by the second node, a first subset of basis vectors, wherein the number of basis vectors in the first subset are ^^^^. The method also comprises determining, by the second node, a set of second subsets of basis vectors, where the number of second subsets are ^^ and the number of basis vectors in each second subset is ^^^^and each second subset is associated with a column in the precoder matrix and determining, by the second node, a set of complex weights corresponding to each column of the precoder matrix. The method also comprises reporting, by the second node, at least one of the determined first subset of basis vectors, the determined set of second subset of basis vectors and the determined set of complex weights to the first node.

[0024] In one aspect, the receiving by the second node is performed using at least one of DCI, MAC-CE and RRC signalling. Further, the set of basis vectors are DFT based vectors.

[0025] In another aspect, each basis vector in the first set of basis vectors and the set of second subset of basis vectors are orthogonal with any other basis vector in the first set of basis vectors and the set of second subset of basis vectors.

[0026] In another aspect, the second node reports at least one of the determined rank (^^) of the precoder matrix, the determined first subset of basis vectors, the determined set of second subset of basis vectors and the determined set of complex weights.

[0027] In one aspect, the first node and the second node in the above-mentioned methods are a BS (Base Station) and a UE (User Equipment) respectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Having thus described the embodiments of the disclosure in general terms, reference now will be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:

[0029] Fig. 1 illustrates a timeline of selection of a precoder in existing methods of data transmission using precoders, in accordance with an embodiment of the present invention.

[0030] Fig. 2 illustrates an exemplary beam grid, in accordance with an embodiment of the present invention.

[0031] Fig.3 illustrates steps of the proposed method for enhancing existing precoder structure, in accordance with an embodiment of the present invention.

[0032] Fig. 4 illustrates an exemplary down-sampling of a beam set using down-sampling factors (2,2), in accordance with an embodiment of the present invention.

[0033] Fig. 5 illustrates a block diagram of a system used for implementing the proposed method, in accordance with an embodiment of the present inventionDESCRIPTION OF THE INVENTION

[0034] The description set forth below in connection with the appended drawings is intended as a description of various embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. Each embodiment described in this invention is provided merely as an example or illustration of the present invention, and should not necessarily be construed as preferred or advantageous over other embodiments. The description includes specific details for the purpose of providing a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details.

[0035] Some embodiments of the present disclosure now will be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all, embodiments of the disclosure are shown. Indeed, embodiments of the disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein, rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.

[0036] As used herein, the term “comprising” means including but not limited to and should be interpreted in the manner it is typically used in the patent context. Use of broader terms such as comprises, includes, and having should be understood to provide support for narrower terms such as consisting of, consisting essentially of, and comprised substantially of.

[0037] In a wireless technology, the downlink channel state information is required at a BS (Base Station) to make an effective transmission to a UE. In 5G NR technology, a framework is adopted such that the DL channel state information (CSI) is acquired by the BS. Based on the received CSI report, the BS schedules a UE (User Equipment) appropriately. In 5G NR, the CSI consists of different kinds of information such as PMI (Precoding Matrix Indicator), RI (Rank Indicator), LI (Layer Indicator), CQI (Channel Quality Indicator) etc, where each field reports a different metric related to the channel. The PMI field in the CSI report indicates to the BS an appropriate precoder matrix that could to be used for transmission of PDSCH, where the precodermatrix is selected by the UE from a codebook comprising a plurality of precoders. The codebook from which the appropriate precoder is selected is defined or configured by the BS.

[0038] Fig. 1 illustrates a timeline of selection of a precoder in existing methods of data transmission using precoders, in accordance with an embodiment of the present invention. Step S101 involves transmission of CSI-RS resources to the UE for performing channel estimation and CSI reporting. The transmission involves different parameters configured to the UE by the BS, which may be used for computing CSI parameters to be included in the CSI report. The parameters configured to the UE includes the number of beams to be selected from a beam grid for the selected precoder. Step S102 involves the performing of channel estimation by the UE. In addition to channel estimation, the UE also performs computations for determining the best precoder for the channel from a codebook configured to the UE by the BS. Step S103 involves sending of the CSI report to the BS by the UE, wherein the CSI report comprises several parameters including PMI for indicating the selected precoder. Step S104 involves using of the selected precoder by the BS for transmission of data, wherein the precoder is used for strengthening the signal used for data transmission.

[0039] In NR, a codebook is defined as a set of precoder matrices. The precoder matrices in NR are derived based on oversampled DFT vectors. 3GPP has introduced multiple precoder structures in Release 15 i.e., Type-1 Single-panel codebook, Type-1 Multi-panel codebook, Type- 2 codebook and Type-2 Port selection codebook. The different precoder structures have different complexities of structures, and different levels of performance gains. For instance, Type-1 Single- panel codebook has a simpler structure and lower performance gain compared to Type-2 codebook which has more complex structure and gives higher performance gain. Type-2 CSI provides channel information with significantly higher granularity compared to Type-1 CSI. This higher granularity of the PMI feedback comes at the cost of significantly higher signalling overhead. Existing methods of precoder construction

[0040] The construction of precoders used in Release 15 are based on different factors such as number of CSI-RS ports, number of beams selected, oversampling factors etc. All these parametersare configured to the UE by the BS via RRC (Radio Resource Control) signalling. For instance, in Release 15 Type-2 precoder, the number of CSI-RS ports is derived by the UE based on the formula 2^^1^^2, where BS configures ^^1and ^^2to the UE using the higher layer parameter n1- n2-codebookSubsetRestriction. UE obtains the over-sampling factors (^^1, ^^2) based on the configured ^^1 and ^^2 values, as indicated in Table 1. Table 1

[0041] Based on these ^^1, ^^2, ^^1and ^^2values, the UE forms a beam-grid that consists of ^^1*^^2*^^1*^^2beams. Each beam in the beam-grid is represented by an over-sampled 2D-DFT vector. An example beam-grid for (^^1, ^^2) = (2,2) and (^^1, ^^2) = (4,4) is illustrated in Fig.2. In the beam grid illustrated in Fig.2, the total number of beams present in the beam-grid is ^^1 ∗ ^^2 ∗ ^^1 ∗ ^^2. Each beam in the beam-grid is represented as ^^^^,^^, where ^^^^and ^^^^,^^is obtained based on Equation 1 and Equation 2 respectively.…… (Equation 1)……(Equation 2)

[0042] In the above equations, ^^ ∈ {0, .. , ^^1^^1 − 1} and ^^ ∈ {0, .. , ^^2^^2 − 1}. Two beams (^^1, ^^1) and (^^2, ^^2) are considered as a set of orthogonal beams if (^^2− ^^1) is an integer multiple of ^^1 & (^^2 − ^^1) is an integer multiple of ^^2. A beam set is defined as a set of beams in which each beam in the beam set is orthogonal to any other beam in the beam set. A beam-grid of ^^1^^2^^1^^2 beams comprises of ^^1^^2 beam-sets and each beam-set comprises of ^^1^^2 beams.

[0043] A R15 Type-2 precoder is constructed as a weighted linear combination of L number of orthogonal beams. L corresponds to the number of orthogonal beams selected from the beam-grid, and the value of L is configured to the UE by the BS with the higher layer parameter numberOfBeams, where ^^ = 2 when ^^^^^^^^−^^^^ = 4 and ^^ ∈ {2, 3, 4} when ^^^^^^^^−^^^^ > 4. The mathematical representation of the Type-2 precoder represented as a linear combination of L beams is represented by the Equation 3 below.……(Equation 3)

[0044] Where̅^̅^^̅^represents a beam (^^^^,^^) and ^^^^ represents a complex coefficient corresponding to beam̅^̅^^̅^. The R15 (Release 15) specification facilitates the UE to signal Type-2 precoder per each sub-band of the reporting bandwidth. This is achieved by reporting different complex coefficients for each sub-band in spite of using the same set of L beams for each sub- band. The R15 Type-2 precoder can be represented in matrix form as indicated by the Equation 4 below. ^^ = ^^1^^2……(Equation 4)

[0045] In Equation 4, ^^1 captures the long-term variations in the channel and ^^2 captures the short-term variations in the channel. ^^1 matrix contains the beams and ^^2 matrix contains the complex coefficients that are used for construction of the Type-2 precoder respectively. Hence,the R15 Type-2 precoder for N sub-bands and a layer l is represented in matrix form in Equation 5.…… (Equation 5)

[0046] Even though Type-2 CSI provides more channel information, this comes with a price of higher overhead since more information bits are required for feedback. Hence, in Release 16 of NR, enhancements has been made to the R15 Type-2 codebook to reduce CSI feedback overhead. This reduction in feedback overhead was achieved in R16 (Release 16) Type-2 CSI by applying frequency domain compression. The correlation among the coefficients in ^^2 can be exploited and used for compression. In R16 Type-2 CSI, DFT vectors are used for the compression of ^^2 coefficients. The UE compresses the elements in ^^2 matrix using M DFT vectors and reports back to the BS the vectors used for compression and the complex coefficients for each of the DFT vectors. The value of M is configured by the BS to the UE based on the channel conditions.

[0047] As per Equation 5, the Type-2 precoder is reported for N sub-bands and the precoder is constructed as a weighted linear combination of L beams, where the value of L is configured to the UE by the higher layer parameter paramCombination-r16 such that ^^ ∈ {2,4,6}. In this case, the number of coefficients in ^^2matrix are 2L*N. By exploiting the correlation among the coefficients across sub-bands, ^^2can be compressed and may be represented by Equation 6.……(Equation 6)

[0048] In the Equation 6, ^^^^ consists of M DFT vectors used for the compression of ^^2matrix and W2̃consists of the compressed complex coefficients. The M DFT vectors are selected from aN-Point DFT matrix, where N represents number of sub-bands for which the precoder is being reported for. Hence, the R16 Type 2 codebook may be represented by Equation 7.……(Equation 7) Existing mechanism of CSI reporting in Release 15 and Release 16

[0049] As per Release 15 specification, when ^^ ≤ 2, where ^^ is the associated RI value, each PMI corresponds to the codebook indices ^^1 and ^^2, where indices ^^1 and ^^2 are as represented in Equation 8 and Equation 9 respectively.……(Equation 9)

[0050] In Equation 8 and Equation 9, subbandAmplitude is configured by the BS to the UE via RRC signalling. The L vectors combined by the codebook are identified by the indices ^^1,1and ^^1,2. The strongest coefficient on layer l, l = 1,..,v is identified by ^^1,3,^^ ∈ {0,1, .. ,2^^ − 1}. The amplitude coefficients for layer l are identified by ^^1,4,^^ and ^^2,2,^^ whereas the phase coefficients for layer l are identified by ^^2,1,^^.

[0051] Further, as per Release 16 Specification, the PMI value corresponds to the codebook indices ^^1and ^^2, where indices ^^1and ^^2are as represented in Equation 10 and Equation 11 respectively.……(Equation 11)

[0052] The number of precoding matrices to be reported (^^3) is calculated based on higher layer parameter numberOfPMI-SubbandsPerCQI-Subband (^^), the number of configured sub- bands in csi-ReportingBand, and sub-band size configured by subbandSize. The number of DFTvectors used for compression (^^^^) is calculated as Mv = ⌈p^^3v^^ ⌉ , where ^^^^ is indicated by higher layer parameter paramCombination-r16.

[0053] The precoding matrices indicated by the PMI are determined from ^^ + ^^^^ vectors. Out of these ^^ +^^^^ vectors, ^^ vectors represent the 2D-DFT beams in the beam-grid and the remaining ^^^^ vectors are used for compressing the coefficients in ^^2matrix. The UE shall report the RI value ^^ according to the configured higher layer parameter typeII-RI-Restriction-r16. The L 2D- DFT beams are identified by the indices ^^1,1 and ^^1,2. ^^2,3,^^ indicates the wideband amplitudes for layer ^^ and two polarizations. The DFT vectors that are used for FD-compression are picked from a ^^3 point DFT matrix. The combination of ^^^^ DFT vectors out of the ^^3 DFT vectors is indicated by ^^1,6,^^ and ^^1,5 for layer ^^. ^^1,7,^^ indicates the locations of non-zero coefficients in W2̃matrix for layer ^^. and ^^2,5,^^ indicates the amplitudes and phases of all the non-zero coefficients in W2̃matrix. ^^1,8,^^indicates the strongest coefficient among all the non-zero coefficients in W2̃matrix for layer ^^.

[0054] The existing NR specification supports up to 32 CSI-RS ports. A challenge associated with extending codebooks such as R16 Type-2 codebook for higher than 32 ports is that the complexity at the UE for calculating the best Type-2 precoder increases with the increase in number of ports. For example, the ^^1,1 and ^^1,2 fields in R16 PMI reporting framework are used to indicate the L beams where ^^1,1 indicates one beam set out of ^^1^^2 beam sets and ^^1,2 indicates a combination of L beams within the indicated beam set. The number of L combinations within a beam-set of ^^1^^2 beams will increase with increase in number of CSI-RS ports, i.e., ^^1^^2. The increase in the number of combinations with increase in number of ports is as indicated in Table 2. Table 2

[0055] Due to the increase in the number of combinations, the complexity of selecting ^^ beams out of ^^1^^2beams will increase. Further, the signalling overhead will also increase. The present disclosure proposes a method of reducing the UE complexity for computing and reporting a precoder if number of CSI-RS ports are higher than 32.

[0056] The proposed method reduces the complexity of computation and reporting of the precoder for the UE based on the steps illustrates in Fig. 3. Step S301 involves dynamically changing L value to ensure that only necessary number of beams (alternatively referred to as basis vectors) are selected in accordance with channel conditions, as opposed to the existing method where value of L is configured to the UE by the BS via higher layer signalling. In an embodiment of the present invention, the set of basis vectors, hereafter referred to as beams, are DFT based vectors. Such configuration imposes certain rigidness at the UE side during the selection of Lbeams i.e., even if < L beams are sufficient for certain channel conditions, the UE still tries to select L beams which is unnecessary. Hence, step S301 involves enabling the ability to modify or change the L value dynamically.

[0057] In one embodiment, the L value may be changed dynamically by signalling L value to the UE via DCI (Downlink Control Information). In such a method a set of L values are configured to the UE by the BS via higher layer signalling. The BS signals one L value from the set of L values configured to the UE via the DCI that triggers an aperiodic / SP CSI-RS report and schedules a PUSCH to carry the corresponding aperiodic / SP CSI-RS report. In the existing specification, an aperiodic CSI-RS report can be triggered and scheduled using the DCI format 0_1. In the proposed embodiment, a new field will be introduced in the DCI format 0_1 that indicates the UE an L value among the configured set of L values. If the UE is not signalled any L value in the DCI, the UE follows a default configuration for L value.

[0058] In another embodiment, the L value may be changed dynamically based on selection of an optimal value of L by the UE from a set of L values configured to the UE by the BS. Herein, a set of L values are configured to the UE by the BS via higher layer signalling. The UE calculates an optimal value of L among the set of configured L values and reports to the BS in the CSI-RS report. The value of L reported by the UE will be signalled in part 1 of the CSIRS report if the CSI report consists of two parts. The BS decodes the other fields of the CSI report based on the L value signalled by the UE.

[0059] Step S302 involves reducing the beams in a beam set to reduce the computation complexity and signalling overhead. According to the current specification, all the L beams selected belongs to one beam set. A beam set comprises of ^^1^^2beams and the UE selects a combination of L beams out of the number of combinations, wherein the number of combinations depend on the values of ^^1and ^^2. If the number of ports increases, the number of possible combinations also increases thereby increasing the precoder computation complexity and signalling overhead. Hence, step S302 involves reducing the complexity and signalling overhead based on reducing the ^^1 and ^^2 values. The UE receives at least one set of beams from the BS,wherein each beam of received set of beams is associated with a pair of indices (^^1, ^^2) wherein^^1 ∈ {0,1, .. , ^^1^^1 − 1} and ^^2 ∈ {0,1, .. , ^^2^^2 − 1}. Further, the values of of ^^1, ^^2, ^^1 and ^^2are configured to the UE by the BS using at least one of DCI, MAC-CE and RRC signalling.

[0060] In one embodiment, the ^^1 and ^^2 values are reduced based on down-sampling using down-sampling factors. Herein, the UE selects the best beam-set based on the experienced channel. In order to pick the best L beams out of the ^^1^^2beams to form a Type-2 precoder, the UE first down-samples the selected beam-set by factors of (^^1, ^^2). The values of (^^1, ^^2) is signalled to the UE by the BS via higher layer signalling. Fig.4 illustrates an exemplary down-sampling of a beam set using down-sampling factors (2,2), in accordance with an embodiment of the present invention.

[0061] With respect to the exemplary down-sampling illustrated in Fig.4, the beam indices of the down-sampled beam set (^^’, ^^’) may be represented by Equation 12, where (^^1, ^^2) are the down-sampling factors and ^^^^ and ^^^^ defines the offset. In one aspect of the embodiment, (^^1, ^^2) and ^^^^, ^^^^ may be configured to the UE via higher layer signalling. In another aspect of the embodiment, (^^1, ^^2) are configured to the UE via higher layer signalling and the ^^^^, ^^^^ are reported to the BS by the UE.……(Equation 12)

[0062] In certain embodiments, the beams with the corresponding pair of indices (^^1, ^^2) ispresent in the down-sampled beam set if=0), wherein and ^^2are received by the second node from the first node using at least one of DCI, MAC-CE and RRC signaling.

[0063] In another embodiment, the ^^1and ^^2values are reduced based on down-sampling using a bitmap, where the bit location in the bitmap is associated with a beam (i.e., a basis vector). In the embodiment, a bitmap is configured to the UE by the BS via higher layer signalling. The size of the bitmap is equal to ^^1^^2 wherein each bit in the bitmap corresponds to a beam index in thebeam set. The UE forms a new beam set based on the configured bitmap by including in the new beam set all the beams corresponding to 1’s in the bitmap. Hence, the bit value of a bitmap indicate whether the corresponding beam is considered in forming of the reduced beam set. After down- sampling the beam-set, the UE chooses the best L beams among the down-sampled set and reports to the BS via the CSI report. The reduced beams set obtained after down-sampling by the down- sampling factors or the bitmap thereby constitute a subset of the beams.

[0064] Step S303 involves making enhancements to codebooks for enabling improved performance, based on use of different sets of L beams, wherein different sets of L beams are used for constructing the precoder for each layer. As per the current specification, the set of L beams used for construction of a Type-2 / e-Type-2 precoder are same for all the layers. Hence, in the current specification, the ideal precoder for each of the layer are uncorrelated with each other, as a result of which the best beams for each layer is not picked since the same beams are imposed across all the layers.

[0065] Thus, step S303 of the proposed method relates to improvement of the performance of existing precoder design and current codebook structure, based on utilization of different sets of L beams for constructing the precoder of each layer. The existing design of a precoder for a layer l is as represented by Equation 13, Where [^̅^0^^... ^̅^L^^−1] is the set of L beams corresponding to layer ^^ and ^^^^,^^ represents the beam coefficient of beam ^^ corresponding to the layer ^^ for a certain polarization.

[0066] In step S303, the enhancements made to existing structure of codebooks involve using different sets of L beams corresponding to each of the layer, where the L beams comprises of a set of common beams and a set of different beams. The common beams are the beams that are common across all the layers and the different beams are the beams that are different across all the layers. Herein, the UE reports to the BS a set of ^^^^ common beams and ^^ sets of ^^^^ different beams in the feedback report where ^^ is the rank of the precoder reported by the UE. The beam coefficients reported by the UE to the BS for each of the layer are independent of each other. The beam sets corresponding to each of the layer is selected independently.

[0067] The precoder structure obtained after the enhancement performed in step S303 is represented by Equation 13, where [^̅^0^^... ^̅^^^^^^^−1] are the set of common beams that are common for all the layers and [^̅^0^^... ^̅^^^^^^^−1] are the set of different beams corresponding to layer l. In one aspect of the embodiment, L is configured to the UE by the BS via higher layer signalling. ^^^^ and ^^^^ are reported to the BS by the UE explicitly or implicitly in the CSI report such that ^^^^ + ^^^^ = ^^.……(Equation 13)

[0068] Step S304 of the proposed method involves signalling of the L beams selected based on steps S301 to S303 to the BS. In certain embodiments of the present invention, the values of ^^c and ^^^^ are configured to the UE by the BS via higher layer signalling. In certain other embodiments, a set of beams, L, Lc, Ld are signalled to the UE by the BS using at least one of DCI, MAC-CE and RRC signalling. The UE reports the rank (r) of the precoder in the CSI report using a rank indicator. Further, the UE reports a set of ^^ beams to the BS using the ^^1,1 and ^^1,2 indices in the CSI report where, ^^ is calculated using Equation 14. ^^ = ^^^^ + ^^ ∗ ^^^^ ……(Equation 14)

[0069] If the set of ^^ beams are represented as {^^0, ^^1, .. , ^^^^−1}, the association between the beam indices with the common beams and dedicated beams for each layer is preconfigured to the UE by the BS. In one embodiment, the association between the beams and a corresponding layer may be preconfigured such that the common beams in the set of ^^ beams = {^^0, ^^1, .. , ^^^^^^−1}and dedicated beams in the set of ^^ beams for layer ^^ = {^^^^^^+^^∗^^^^ , ^^^^^^+^^∗^^^^+1, . . , ^^^^^^+(^^+1)∗^^^^−1}. For example, if the UE is configured with ^^^^ = 2 and ^^^^ = 2 and if the UE reports a Rank-2 precoder in the CSI report, then UE will report ^^ = 6 beams {^^0, ^^1, ^^2, ^^3, ^^4, ^^5} in the CSI report.

[0070] In the above example implemented for the embodiment, the UE is preconfigured such that out of the 6 beams, the first two beams {^^0, ^^1} are the common beams for both the layers and {^^2, ^^3} are the dedicated beams for layer 1 and {^^4, ^^5} are the dedicated beams for layer 2. Based on the L beams reported by the UE and based on the pre-configuration of UE, the beams for layer 1 may be determined as {^^0, ^^1, ^^2, ^^3} and beams for layer 2 may be determined as {^^0, ^^1, ^^4, ^^5}.

[0071] In another embodiment, signalling of step S304 is based on values of ^^, ^^^^ and ^^^^ configured to the UE by the BS via higher layer signalling. In such an embodiment, the UE reports the rank (r) of the precoder in the CSI report using rank indicator. The SD basis (i.e., set of beams for a given layer) {^^00, ^^10, .. , ^^^0^−1}corresponding to the first layer (^^ = 0) are signalled to the BS by using the ^^1,1and ^^1,2indices in the CSI report. The SD basis for the layer ^^ {^^0^^, ^^1^^, .. , ^^^^^^−1} is signalled on an offset basis in the CSI report where an offset of beam index ^^ in SD basis of layer ^^. For example, if {^^^0^, ^^^0^} represents a beam (^^^0^ ) in the SD basis of layer 0, then the beam index (^^^^^^) of layer l is calculated by Equation 15, where (^^^^^^,^^^^^^^^^^^^, ^^^^^^,^^^^^^^^^^^^) is reported to the BS by the UE in the CSI report. The set of possible values of ^^^^^^,^^^^^^^^^^^^and ^^^^^^,^^^^^^^^^^^^are preconfigured to the UE by the BS.……(Equation 15)

[0072] The value of L, set of complex weights for the precoder matrix, rank of the precoder matrix (i.e., number of columns of the precoder matrix) and the L beams selected by the UE may be transmitted to the BS, and may be used by the BS for determining the precoder matrix to be used for obtaining a signal to be transmitted, where the signal to be transmitted is obtained by precoding of a first signal with the precoder matrix of rank R. Herein, the column of the precoder matrix may be determined as a weighted sum of the L beams selected by the UE, wherein the weights used in the weighted sum are derived from the subset of complex weights, and is obtained as per polarization .

[0073] In an embodiment, the signalling by the BS to the UE of parameters such as the beams, down-sampling factors, bitmap, set of L values etc may be performed using DCI. In another embodiment, the signalling may be performed using MAC-CE. In yet another embodiment, the signalling may be performed using RRC signalling. Further, in certain embodiments, at least one of L value and the set of selected beams are transmitted by the UE to the BS on at least one of uplink control channel and uplink data channel. Further still, at least one of a rank of the precoder matrix and a set of complex weights for the precoder matrix is transmitted by the UE to the BS on at least one of uplink control channel and uplink data channel.

[0074] Fig. 5 illustrates a block diagram of a system used for implementing the proposed method, in accordance with an embodiment of the present invention. The system comprises a UE node 502, a BS node 504, and a T / R module 506 for enabling transmission and reception of signals, reports, and / or data between the UE node 502 and the BS node 504. The BS node 504 comprises a resource configuration module 508 and input processing module 510, where the resource configuration module may be used by the BS node 504 for configuring different resources and / or resource values to the UE for CSI-RS report generation and reporting. The resources configured to the UE may also include PMI (Precoding Matrix Indicator), L value, Lc, Ld, the set of possible values of ^^^^^^,^^^^^^^^^^^^and ^^^^^^,^^^^^^^^^^^^, down-sampling factors, bitmap for down-sampling etc. The input processing module 506 may be used by the BS node 504 for processing a CSI report received from the UE node 502, and may further be used for transmission of signals based on the received precoder and channel estimation.

[0075] The UE node 502 comprises a precoder construction and reporting module 512, a processor 514, and an I / O module 516, wherein the processor 514 may be used for managing the functioning of the precoder construction and reporting module 512 and the I / O module 516. The precoder and reporting module 512 comprises an L modification sub-module 518, a down- sampling sub-module 520, a precoder construction sub-module 522, and reporting sub-module 524. The L modification sub-module 518 is used for dynamically changing the L value to ensure that only necessary number of beams are selected in accordance with the channel conditions, wherein the L value is either signalled to the UE node 502 via DCI or is selected from a set of L values based on determined of its optimal value by the UE node 502.

[0076] The down-sampling sub-module 520 is used for reducing the beams in the beam set to reduce the computation complexity and signalling overhead. The complexity is reduced as reduction in size of the beam set results in a reduction in the number of ports used, thereby reducing the precoder computation complexity. The reduction of beams is performed by the down-sampling sub-module 520 based on the down-sampling of the beam grid based on either one of down- sampling factors or use of bitmap. The down-sampling factors and the bitmap is configured to the UE node 502 by the BS node 504.

[0077] The precoder construction sub-module 522 is used to construct the precoder based on the determined L value and the down-sampled beam set. The L beams are selected by the precoder construction sub-module 522 for each layer from the downs-sampled beam set different sets of L beams are used for constructing the precoder for each layer. Hence, the precoder construction sub- module 522 performs selection of the ideal precoder for each layer based on the selection of the best beams for each layer. The enhancements made to existing structure of codebooks by the precoder construction sub-module 522 involves using different sets of L beams corresponding to each of the layer, where the L beams comprises of a set of common beams and a set of different beams. The common beams are the beams that are common across all the layers and the different beams are the beams that are different across all the layers.

[0078] The precoder structure obtained after the selection of best beams for each layer by the precoder construction sub-module 522 is reported to the BS node 504 by the reporting sub-module 524, wherein the report sub-module 524 performs the reporting of the selected beams based on a pre-configuration by the BS node 504, or on an offset basis with respect to the beam index of layer 0.

[0079] The precoder structure obtained is reported to the BS node 504 by means of the CSI report, and the CSI report may be transmitted to the BS node 504 by the UE node 502 by means of the I / O module 516, and the CSI report along with the indicated precoder matrix may be used by the BS node 504 for transmission of signals.

[0080] In certain embodiments of the present invention, the proposed method may involve different combinations of steps S301 to S303. For example, in one embodiment, the method implemented for modifying and reporting precoders may only involve dynamically changing the L value. In another embodiment, in addition to dynamically changing the L value, different L beams may be selected for each layer. In another embodiment, the L value may not be changed, but a reduction of beam set may be performed. In yet another embodiment, different L beams may be selected for each layer from a reduced beam set, where the reduced beam set is obtained after down-sampling of an existing beam set. Further still, in certain embodiment, the different L beams and common beams for each layer may be selected from a beam set without dynamically changing value of L or performing down-sampling.

[0081] The various embodiments discussed above may be used for extending the existing CSI reporting frameworks relating to codebooks in Release 15 and Release 16 in cases where the number of CSI-RS ports exceed 32, without causing computation complexity and signalling overhead.

[0082] The figures of the disclosure are provided to illustrate some examples of the invention described. The figures are not to limit the scope of the depicted embodiments or the appended claims. Aspects of the disclosure are described herein with reference to the invention to example embodiments for illustration. It should be understood that specific details, relationships, and method are set forth to provide a full understanding of the example embodiments. One of ordinary skill in the art recognize the example embodiments can be practiced without one or more specific details and / or with other methods.

[0083] While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosures or of what may be claimed, but rather as descriptions of features specific to particular embodiments of particular disclosures. Certain features that are described herein in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more featuresfrom a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub combination or variation of a sub combination.

[0084] Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In certain implementations, multitasking and parallel processing may be advantageous.

[0085] It is to be understood that the disclosure is not to be limited to the specific embodiments disclosed, and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation, unless described otherwise.

Claims

CLAIMS:

1. A method of enhancing wireless data transmission using a precoder matrix, the method comprising: signaling, by a first node, a configuration to configure at least one of a set of basis vectorsto a second node, a pair of down-sampling factors (^^1, ^^2), a bitmap and a set of ^^ values to asecond node; receiving, by the first node, at least one of an ^^ value from the configured set of ^^ values and a first subset of basis vectors, from the second node; receiving, by the first node, at least one of a rank (^^) of the precoder matrix and a set of complex weights for the precoder matrix from the second node, wherein the rank of the precoder matrix indicates the number of columns of the precoder matrix; determining, by the first node, a precoder matrix of rank ^^ wherein each column of the precoder matrix is derived based on the first subset of basis vectors and a subset of complex weights from the set of complex weights; obtaining, by the first node, a second signal by precoding a first signal with the precoder matrix of rank ^^; and transmitting, by the first node, the second signal to the second node.

2. The method as claimed in claim 1, wherein the signaling by the first node is performed using at least one of DCI, MAC-CE and RRC signaling.

3. The method as claimed in claim 1, wherein the set of basis vectors are DFT based vectors.

4. The method as claimed in claim 1, wherein the set of basis vectors is mapped using the bitmap.

5. The method as claimed in claim 4, wherein the bit location in the bitmap is associated with a basis vector.

6. The method as claimed in claim 4, wherein the bit value indicates whether the associated basis vector is considered to form a second subset of basis vectors.

7. The method as claimed in claim 1, wherein at least one of an ^^ value from the configured set of ^^ values and a first subset of basis vectors is received from the second node on at least one of uplink control channel and uplink data channel.

8. The method as claimed in claim 1, wherein the at least one of a rank (^^) of the precoder matrix and a set of complex weights for the precoder matrix is received from the second node on at least one of uplink control channel and uplink data channel.

9. The method as claimed in claim 1, wherein the column in the precoder matrix is obtained as a weighted sum of the received first subset of basis vectors, wherein the weights used in the weighted sum are derived from the received set of complex weights.

10. The method as claimed in claim 9, wherein the column in the precoder matrix is obtained per polarization.

11. A method of enhancing wireless data transmission using a precoder matrix, the method comprising: receiving, by a second node, a configuration of at least one of a set of basis vectors, a pair ofdown-sampling factors^^2), a bitmap and a set of ^^ values from a first node;determining, by the second node, at least one of an ^^ value from the received set of ^^ values and a second subset of basis vectors based on at least one of the received pair of down-samplingfactors (^^1, ^^2) and a bitmap from the first node;determining, by the second node, a first subset of basis vectors based on the determined ^^ value, wherein the first subset of basis vectors is a subset of the second subset of basis vectors; determining, by the second node, a rank (^^) of the precoder matrix, wherein the rank of the precoder matrix indicates the number of columns of the precoder matrix;determining, by the second node, a set of complex weights corresponding to each column of the precoder matrix; reporting, by the second node, at least one of the determined ^^ value and the determined first subset of basis vectors to the first node; and reporting, by the second node, the determined set of complex weights to the first node.

12. The method as claimed in claim 11, wherein the receiving by the second node is performed using at least one of DCI, MAC-CE and RRC signaling.

13. The method as claimed in claim 11, wherein the set of basis vectors are DFT based vectors.

14. The method as claimed in claim 11, wherein each basis vector in the received set of basisvectors is associated with a pair of indices (^^1, ^^2) wherein− 1} and ^^2 ∈{0,1, .. , ^^2^^2 − 1}.

15. The method as claimed in claim 14, wherein the values of ^^1, ^^2, ^^1and ^^2are received by the second node from the first node using at least one of DCI, MAC-CE and RRC signaling.

16. The method as claimed in claim 14, wherein the second node determines the second subset ofbasis vectors based on the received down-sampling factors^^2).

17. The method as claimed in claim 16, wherein a basis vector, from the received set of basisvectors, with the corresponding pair of indices (^^1, ^^2) is present in the second subset of basisvectorswherein ^^1 and ^^2 arereceived by the second node from the first node using at least one of DCI, MAC-CE and RRC signaling.

18. The method as claimed in claim 14, wherein the second node determines the first subset of basis vectors based on the received bitmap.

19. The method as claimed in claim 18, wherein the bit location in the bitmap is associated with a basis vector.

20. The method as claimed in claim 18, wherein a basis vector from the received set of basis vectors is present in the second subset of basis vectors if the bit in the bitmap corresponding to the basis vector is set to 1.

21. The method as claimed in claim 19, wherein a basis vector from the received set of basis vectors is present in the second subset of basis vectors if the bit in the bitmap corresponding to the basis vector is set to 0.

22. The method as claimed in claim 11, wherein the second node reports at least one of the determined ^^ value, the determined rank (^^) of the precoder matrix, determined first subset of basis vectors and the determined set of complex weights to the first node using at least one of uplink control channel and uplink data channel.

23. A method of enhancing wireless data transmission using a precoder matrix, the method comprising: signaling, by a first node, a configuration to configure at least one of a set of basis vectors, ^^, ^^^^and ^^^^to the second node, wherein ^^ defines the total number of basis vectors corresponding to the precoding matrix, ^^^^defines the number of basis vectors that are common across all the columns of the precoder matrix and ^^^^defines the number of unique basis vectors corresponding to each column of the precoder matrix; receiving, by the first node, a first subset of basis vectors and a set of second subset of basis vectors, wherein each second subset of basis vectors is associated with a column in the precoder matrix; receiving, by the first node, a set of complex weights from the second node; determining, by the first node, a precoder matrix of rank ^^, wherein each column of the precoder matrix is derived based on the first subset of basis vectors, the corresponding second subset of basis vectors and the corresponding complex weights;obtaining, by the first node, a second signal by precoding a first signal with the precoder matrix of rank ^^; and transmitting, by the first node, the second signal to the second node.

24. The method as claimed in claim 23, wherein the signaling by a first node is performed using at least one of DCI, MAC-CE and RRC signaling.

25. The method as claimed in claim 23, wherein the set of basis vectors are DFT based vectors.

26. The method as claimed in claim 23, further comprising: signaling, by the first node, an association between a second subset of basis vectors and a column of the precoder matrix.

27. The method as claimed in claim 23, wherein at least one of a rank (^^) of the precoder matrix and a set of complex weights for the precoder matrix is received from the second node on at least one of uplink control channel and uplink data channel.

28. The method as claimed in claim 23, wherein the column in the precoder matrix is obtained as a weighted sum of the received first subset of basis vectors and an associated second set of basis vectors, wherein the weights used in the weighted sum are derived from the received set of complex weights.

29. The method as claimed in claim 28, wherein the column in the precoder matrix is obtained per polarization.

30. A method of enhancing wireless data transmission using a precoder matrix, the method comprising: receiving, by a second node, a configuration of at least one of a set of basis vectors, ^^, ^^^^and ^^^^from the first node, wherein ^^ defines the total number of unique basis vectors corresponding to the precoding matrix, ^^^^defines the number of unique basis vectors that are common acrossall the columns of the precoder matrix, and ^^^^defines the number of unique basis vectors corresponding to each column of the precoder matrix; determining, by the second node, a rank (^^) of the precoder matrix wherein the rank indicates the number of columns that are present in the precoder matrix; determining, by the second node, a first subset of basis vectors, wherein the number of basis vectors in the first subset are ^^^^; determining, by the second node, a set of second subsets of basis vectors, wherein the number of second subsets are ^^ and the number of basis vectors in each second subset is ^^^^and each second subset is associated with a column in the precoder matrix; determining, by the second node, a set of complex weights corresponding to each column of the precoder matrix; and reporting, by the second node, at least one of the determined first subset of basis vectors, the determined set of second subset of basis vectors and the determined set of complex weights to the first node.

31. The method as claimed in claim 30, wherein the receiving by the second node is performed using at least one of DCI, MAC-CE and RRC signaling.

32. The method as claimed in claim 30, wherein the set of basis vectors are DFT based vectors.

33. The method as claimed in claim 30, wherein each basis vector in the first set of basis vectors and the set of second subset of basis vectors are orthogonal with any other basis vector in the first set of basis vectors and the set of second subset of basis vectors.

34. The method as claimed in claim 30, wherein the second node reports at least one of the determined rank (^^) of the precoder matrix, the determined first subset of basis vectors, the determined set of second subset of basis vectors and the determined set of complex weights to the first node using at least one of uplink control channel and uplink data channel.

35. The method as claimed in claim 1, 11, 23, and 30, wherein the first node is a BS and the second node is a UE.

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