METHOD AND APPARATUS FOR CSI REPORTING IN A WIRELESS COMMUNICATIONS NETWORK TECHNICAL FIELD The present disclosure relates to the field of wireless communications, and in particular to methods and apparatuses for CSI reporting in a wireless communications network such as advanced 5G or 6G networks. BACKGROUND The radio access technology (RAT) in fifth generation (5G) mobile communications system, also known as 5G new radio (NR), provides a higher level of performance and flexibility than the previous generations of mobile communications systems.5G mobile communications has been driven by the need to provide ubiquitous connectivity for applications as diverse automotive communications, remote control with feedback, video downloads, as well as data applications for Internet-of-Things (IoT) devices, machine type communication (MTC) devices, etc. 5G wireless technology brings several main benefits, such as faster speed, shorter delays and increased connectivity. 5G mobile communications supports massive multiple-input multiple-output antenna technologies from sub-6 GHz up to mmWave-frequencies, new beamforming management procedures to provide increased beamforming gain and link reliability, new waveforms, etc. The third-generation partnership project (3GPP) provides the complete system specification for the 5G network architecture, which includes at least a radio access network (RAN), core transport networks (CN) and service capabilities. Due to the amount of traffic that needs to be handled by the network is growing significantly, there exists a need to utilize the downlink resources efficiently. SUMMARY Until 3GPP NR phase 4 (Rel.18), only 32 antenna port based single-TRP transmission has been supported by the specification. However, for 3GPP NR phase 5 (Rel.19), it has been decided to specify support for single-TRP transmission for up to 128 antenna ports. To realize large number of antenna ports, the dimension of the antenna port layout in a first dimension, ^^, and a second dimension, ^^, need to be increased. In
one option, the first dimension may correspond to a column dimension and the second dimension may correspond to a row dimension of the antenna port layout. In another option, the first dimension may correspond to a row dimension and the second dimension may correspond to a column dimension of the antenna port layout. The antenna port layout may be associated with a number of rows and columns, wherein each entry (row index, column index) is associated with one antenna port or two antenna ports (e.g., in case of a dual-polarized antenna port layout). When the values of ^^ and ^^ (i.e., the number of antenna ports) are increased, the overhead associated with the Radio Resource Control (RRC) configuration information element n1-n2-codebookSubsetRestriction increases drastically. This becomes notable because a second bit sequence ^^ (used for the indication of the maximum allowed amplitude values or coefficients for the beam vectors associated with the precoder matrix) as a part of the information element n1-n2-codebookSubsetRestriction scales proportionally with increasing values of ^^ and ^^.This invention focuses on solutions related to the overhead reduction of the RRC signaling from the network node to the wireless device. It is an objective of the embodiments herein to provide methods and apparatuses for configuration overhead reduction in a wireless communications network such as advanced 5G networks. According to an aspect of some embodiments herein, there is provided a method performed by a wireless device (e.g., a UE) in a wireless communications network, the method comprising: ^ receiving from a network node a higher layer configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates maximum allowable amplitude values for a proper subset of beam vectors from a set of ^^^^ beam vectors for restricting an amplitude associated with a beam vector; ^ calculating a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors;
^ generating a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ reporting the CSI report to the network node. According to an aspect of some embodiments herein, there is provided a method performed by a wireless device (e.g., a UE) in a wireless communications network, the method comprising: ^ receiving from a network node a higher layer configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates a number of maximum allowable amplitude values, X, and a number of beam groups, Y, wherein a beam group comprises a set of beam vectors, and wherein a maximum allowable amplitude value is used for restricting an amplitude associated with a beam vector; ^ calculating a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; ^ generating a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ reporting the CSI report to the network node. According to another aspect of some embodiments herein, there is provided a method performed by a network node (e.g., a gNB), and the method comprising: ^ transmitting to a wireless device a configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates maximum allowable amplitude values for a proper subset of beam vectors from a set of ^^^^ beam vectors for restricting an amplitude associated with a beam vector; for enabling the wireless device to: o calculate a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors;
o generate a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ receiving from the wireless device a CSI report. According to another aspect of some embodiments herein, there is provided a method performed by a network node (e.g., a gNB), and the method comprising: ^ transmitting to a wireless device a configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates a number of maximum allowable amplitude values, X, and a number of beam groups, Y, wherein a beam group comprises a set of beam vectors, ^ and wherein a maximum allowable amplitude value is used for restricting an amplitude associated with a beam vector; for enabling the wireless device to: o calculate precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; o generate a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ receiving from the wireless device a CSI report. According to another aspect of embodiments herein, there is also provided a wireless device (e.g., a UE) comprising a processor and a memory containing instructions executable by the processor, whereby said wireless device is operative or configured to perform any one of the embodiments presented in the detailed description related to the actions performed by the wireless device. According to yet another aspect of embodiments herein, there is provided a network node comprising a processor and a memory containing instructions executable by the processor, whereby said network node is operative or configured to perform any one of the embodiments presented in the detailed description related to the actions performed by the network node.
There is also provided a computer program comprising instructions which when executed on at least one processor of the wireless device (e.g., a UE), cause the at least said one processor to carry out the actions or method steps presented herein. There is also provided a computer program comprising instructions which when executed on at least one processor of the network node, cause the at least said one processor to carry out the method steps presented herein. A carrier is also provided containing the computer program, wherein the carrier is one of a computer readable storage medium, an electronic signal, optical signal, or a radio signal. In this invention, several solutions related to the overhead reduction of the RRC configuration related to codebook subset restriction are proposed. Additional advantages of the embodiments herein are provided in the detailed description of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention are now described in further detail with reference to the accompanying drawings, in which: Fig. 1 shows a schematic representation of a wireless communications system; Fig. 2 shows a block-based model of a MIMO DL transmission using codebook- based-precoding in accordance with LTE Release 8; Fig. 3 illustrates a flowchart of a method performed by a wireless device (e.g., a UE) according to some embodiments herein; Fig. 4 illustrates a flowchart of a method performed by a wireless device (e.g., a UE) according to some embodiments herein; Fig. 5 illustrates a flowchart of a method performed by a network node (e.g., a gNB) according to some embodiments herein; Fig. 6 illustrates a flowchart of a method performed by a network node (e.g., a gNB) according to some embodiments herein;
Fig. 7 is a block diagram depicting a wireless device (e.g., a UE) according to exemplary embodiments herein; Fig. 8 is a block diagram depicting a network node (e.g., a gNB) according to exemplary embodiments herein. DETAILED DESCRIPTION In the following, a detailed description of the exemplary embodiments is described in conjunction with the drawings, in several scenarios to enable easier understanding of the solution(s) described herein. Figure 1 illustrates a simplified schematic view of an example of a wireless communications network 100 including a core network (CN) 110 and a radio access network (RAN) 120. The RAN 120 is shown including a plurality of network nodes or radio base stations, which in 5G are called gNBs. Three radio base stations are depicted gNB1, gNB2 and gNB3. Each gNB serves an area called a coverage area or a cell. Figure 1 illustrates 3 cells 121, 122 and 123, each served by its own gNB, gNB1, gNB2 and gNB3, respectively. It should be mentioned that the network 100 may include any number of cells and gNBs. The radio base stations, or network nodes serve users within a cell. In 4G or LTE, a radio base station is called an eNB, in 3G or UMTS, a radio base station is called an eNodeB, and BS in other radio access technologies. A user or a user equipment (UE) may be a wireless or a mobile terminal device or a stationary communication device. A mobile terminal device or a UE may also be an IoT device, an MTC device, etc. IoT devices may include wireless sensors, software, actuators, and computer devices. They can be imbedded into mobile devices, motor vehicle, industrial equipment, environmental sensors, medical devices, aerial vehicles and more, as well as network connectivity that enables these devices to collect and exchange data across an existing network infrastructure. Referring back to Figure 1, each cell is shown including UEs and IoT devices. gNB1 in cell 121 serves UE1121A, UE2121B and IoT device 121C. Similarly, gNB2 in cell 121 serves UE3122A, UE4122B and IoT device 122C, and gNB3 in cell 123 serves UE5 123A, UE6123B and IoT device 123C. The network 100 may include any number
of UEs and IoT devices or any other types of devices. The devices communicate with the serving gNB(s) in the uplink and the gNB(s) communicate with the devices in the downlink. The respective base station gNB1 to gNB3 may be connected to the CN 120, e.g., via the S1 interface, via respective backhaul links 111, 121D, 122D, 123D, which are schematically depicted in Fig. 1 by the arrows pointing to “core”. The core network 120 may be connected to one or more external networks, such as the Internet. The gNBs may be connected to each other via the S1 interface or the X2 interface or the XN interface in 5G, via respective interface links 121E, 122E and 123E, which is depicted in the figure by the arrows pointing to gNBs. For data transmission, a physical resource grid may be used. The physical resource grid may comprise a set of resource elements (REs) to which various physical channels and physical signals are mapped. For example, the physical channels may include the physical downlink, uplink and/or sidelink (SL) shared channels (PDSCH, PUSCH, PSSCH) carrying user specific data, also referred to as downlink, uplink or sidelink payload data, the physical broadcast channel (PBCH) carrying for example a master information block (MIB) and a system information block (SIB), the physical downlink, uplink and/or sidelink control channels (PDCCH, PUCCH, PSCCH) carrying for example the downlink control information (DCI), the uplink control information (UCI) or the sidelink control information (SCI). For the uplink, the physical channels may further include the physical random-access channel (PRACH or RACH) used by UEs for accessing the network once a UE is synchronized and obtains the MIB and SIB. The physical signals may comprise reference signals (RS), synchronization signals (SSs) and the like. The resource grid may comprise a frame or radio frame having a certain duration, like 10 milliseconds, in the time domain and having a given bandwidth in the frequency domain. The radio frame may have a certain number of subframes of a predefined length, e.g., 2 subframes with a length of 1 millisecond. Each subframe may include two slots of a number of OFDM symbols depending on the cyclic prefix (CP) length. IN 5G, each slot consists of 14 OFDM symbols or 12 OFDM symbols based on normal CP and extended CP respectively. A frame may also consist of a smaller number of OFDM symbols, e.g., when utilizing shortened transmission time intervals (TTIs) or a mini-slot/non-slot-based frame structure comprising just a few OFDM symbols. Slot aggregation is supported in 5G NR, and hence data transmission
can be scheduled to span over one or multiple slots. Slot format indication informs a wireless device or UE whether an OFDM symbol is downlink, uplink or flexible. In some examples, the wireless communication network system may be any single- tone or multicarrier system using frequency-division multiplexing, like the orthogonal frequency-division multiplexing (OFDM) system, the orthogonal frequency-division multiple access (OFDMA) system, or any other Discrete Fourier Transform (DFT) based signal with or without CP, e.g., DFT-spread OFDM (DFT-s-OFDM). Other waveforms, like non-orthogonal waveforms for multiple access, e.g., filter-bank multicarrier (FBMC), generalized frequency division multiplexing (GFDM) or universal filtered multi carrier (UFMC), may also be used. The wireless communication system may operate, e.g., in accordance with the LTE-Advanced Pro standard, the 5G or NR (New Radio) standard or any other standard using any of the aforementioned waveforms. The wireless communications network system depicted in Figure 1 may be a heterogeneous network having two distinct overlaid networks, a network of macro cells with each macro cell including a macro base station, like base station gNB1 to gNB3, and a network of small cell base stations (not shown in Figure 1), like femto- or pico- base stations. In addition to the above described wireless network also non-terrestrial wireless communication networks exist including spaceborne transceivers, like satellites, and/or airborne transceivers, like unmanned aircraft systems. The non- terrestrial wireless communication network or system may operate in a similar way as the terrestrial system described above with reference to Figure 1, for example in accordance with the LTE-advanced pro standard or the 5G or NR, standard. In the wireless communications network system such as the one depicted schematically in Figure 1, multi-antenna techniques may be used, e.g., in accordance with LTE, NR or any other communication system, to improve user data rates, link reliability, cell coverage and network capacity. To support multi-stream or multi-layer transmissions, linear precoding is used in the physical layer of the communication system. Linear precoding is performed by a precoder matrix which maps layers of data to antenna ports. The precoding may be seen as a generalization of beamforming, which is a technique to spatially direct or focus a data transmission towards an
intended receiver. The precoder matrix to be used at the gNB to map the data to the transmit antenna ports is decided using channel state information, CSI. In the wireless communications network system as described above, such as LTE or New Radio (5G), downlink signals convey data signals, control signals containing downlink, DL, control information (DCI), and a number of reference signals or symbols (RS) used for different purposes. A gNodeB (or gNB or base station) transmits data and downlink control information (DCI) through the so-called physical downlink shared channel (PDSCH) and physical downlink control channel (PDCCH) or enhanced PDCCH (ePDCCH), respectively. Moreover, the downlink signal(s) of the gNB may contain one or multiple types of reference signals (RSs) including a common RS (CRS) in LTE, a channel state information RS (CSI-RS), a demodulation RS (DM-RS), and a phase tracking RS (PT-RS). The CRS is transmitted over a DL system bandwidth part and used at the user equipment (UE) to obtain a channel estimate to demodulate the data or control information. The CSI-RS is transmitted with a reduced density in the time and frequency domain compared to CRS and used at the UE for channel estimation or for channel state information (CSI) acquisition. The DM-RS is transmitted only in a bandwidth part of the respective PDSCH and used by the UE for data demodulation. For signal precoding at the gNB, several CSI-RS reporting mechanisms are used such as non-precoded CSI-RS and beamformed CSI-RS reporting. For a non-precoded CSI-RS, a one-to-one mapping between a CSI-RS port and a transceiver unit, TXRU, of the antenna array at the gNB is utilized. Therefore, non- precoded CSI-RS provides a cell-wide coverage where the different CSI-RS ports have the same beam direction and beam width. For beamformed/precoded UE- specific or non-UE-specific CSI-RS, a beamforming operation is applied over a single antenna port or over multiple antenna ports to have several narrow beams with high gain in different directions and, therefore, no cell-wide coverage. In a wireless communications network system employing time division duplexing, TDD, due to channel reciprocity, the CSI is available at the base station (gNB). However, when employing frequency division duplexing, FDD, due to the absence of channel reciprocity, the channel is estimated at the UE and the estimate is fed back to the gNB.
Figure 2 shows a block-based model of a Multiple Input Multiple Output (MIMO) DL transmission using codebook-based-precoding in accordance with LTE release 8. Fig. 2 shows schematically the base station 200, gNB, the user equipment, UE, 202 and the channel 204, like a radio channel for a wireless data communication between the base station 200 and the user equipment 202. The base station includes an antenna array ANTT having a plurality of antennas or antenna elements, and a precoder 206 receiving a data vector 208 and a precoder matrix F from a codebook 210. The channel 204 may be described by the channel tensor/matrix 212. The user equipment 202 receives the data vector 214 via an antenna or an antenna array ANTR having a plurality of antennas or antenna elements. A feedback channel 216 between the user equipment 202 and the base station 200 is provided for transmitting feedback information. The previous releases of 3GPP up to Release 15 support the use of several downlink reference symbols (such as CSI-RS) for CSI estimation at the UE. In FDD systems (up to Rel.15), the estimated channel at the UE is reported to the gNB implicitly where the CSI report transmitted by the UE over the feedback channel includes the rank index (RI), the precoding matrix index (PMI) and the channel quality index (CQI) (and the CRI from Rel.13) allowing, at the gNB, to decide the precoding matrix, and the modulation order and coding scheme (MCS) of the symbols to be transmitted. The PMI and the RI are used to determine the precoding matrix from a predefined set of matrices Ω also referred to as codebook. The codebook, e.g., in accordance with LTE, may be a look-up table with matrices in each entry of the table, and the PMI and RI from the UE decide from which row and column of the table the precoder matrix to be used is obtained. The precoders and codebooks are designed up to Rel.15 for gNBs equipped with one-dimensional Uniform Linear Arrays (ULAs) having ^^ dual-polarized antennas (in total ^^ = 2^^ antennas or antenna ports), or with two-dimensional Uniform Planar Arrays (UPAs) having dual-polarized antennas at ^^^^ positions (in total ^^ = 2^^^^ antennas or antenna ports). The ULA allows controlling the radio wave in the horizontal (azimuth) direction only, so that azimuth- only beamforming at the gNB is possible, whereas the UPA supports transmit beamforming on both vertical (elevation) and horizontal (azimuth) directions, which is also referred to as full-dimension (FD) MIMO. The codebook, e.g., in the case of massive antenna arrays such as FD-MIMO, may be a set of beamforming weights that forms spatially separated electromagnetic transmit/receive beams using the array
response vectors of the array. The beamforming weights (also referred to as the array steering vectors) of the array are amplitude gains and phase adjustments that are applied to the signal fed to the antennas (or the signal received from the antennas) to transmit (or obtain) a radiation towards (or from) a particular direction. The components of the precoder matrix are obtained from the codebook, and the PMI and the RI are used to read the codebook and obtain the precoder. The array steering vectors may be described by the columns of a two-dimensional Discrete Fourier Transform (DFT) matrix when ULAs or UPAs are used for signal transmission. The precoder matrices used in the Type-I, Type-I multi-panel and Type-II CSI reporting schemes in 3GPP NR standards are defined by a dual-stage structure (i.e., two components codebook), ^ = ^^^^. The first component or the so-called first stage precoder or matrix, ^^, is used to select a number of beam vectors from a Discrete Fourier Transform-based (DFT-based) matrix, which is also called the spatial codebook. Moreover, the first stage precoder, ^^, corresponds to a wide-band matrix and contains a number of spatial beamforming vectors (the so-called spatial beams) selected from a DFT-based codebook matrix for the two polarizations of the antenna array. The second component or the so-called second stage precoder is used to combine the selected beam vectors. This means the second stage precoder or matrix, ^^, corresponds to a selection/combining/co-phasing matrix to select/combine/co- phase the beams defined in ^^. For rank-^ transmission, ^ contains ^ vectors, wherein ^ denotes the transmission rank, where the entries of each vector are chosen to combine single or multiple beams within each polarization. The selection of the matrices ^^ and ^^ is performed by the UE based on reference signals such as CSI- RS and the knowledge of the channel conditions. The selected matrices are indicated in a CSI report in the form of a RI (the RI is the rank indicator and denotes the rank of the precoding matrix) and a PMI and are used at the gNB to update the multi-user precoder for the next transmission time interval. The term ‘higher layer’ in the following, when used in isolation, denotes any communication layer above the physical layer in the protocol stack. When the term is used in connection with a specific layer, it denotes any communication in the protocol stack above said layer.
The term serving cell and carrier component (CC) may be used interchangeably in this disclosure as a serving cell configured for a UE and is usually a separate physical carrier centered around a particular carrier frequency. Depending on the frequency of a component carrier/serving cell, the size of the cell and the beamformed reference signals may vary. The term ‘PDxCH’ or ‘PDXCH’ may indicate either the physical downlink shared channel (PDSCH) or the physical downlink control channel (PDCCH), while ‘PUxCH’ or ‘PUXCH’ may indicate either the physical uplink shared channel (PUSCH) or the physical uplink control channel (PUCCH). The term ‘PxxCH’ or ‘PXXCH’ may denote a PDSCH, a PDCCH, a PUSCH, a PRACH, a PBCH, a PSSCH, or a PSCCH. The phrase ‘fixed/predetermined/provided in the specifications’ in this invention disclosure may mean the following: one or more rules and/or methods and/or particulars regarding certain parameter(s) are provided in the standard specifications that the UE and/or any network node is supposed to follow or implement. The term ‘configured’ may mean the following: one or more rules and/or methods and/or particulars regarding one or more parameters as provided in the standard specifications that the UE is supposed to follow or implement are provided to the UE by one or more network entities, e.g., via higher layer signaling, like radio resource control, RRC, signaling. In certain embodiments, the wireless device receives from a network node (e.g., gNB), a higher layer configuration indicating a number of antenna ports or CSI-RS ports, and a number of CSI-RS resources, wherein each CSI-RS resources comprises at least one antenna or CSI-RS port, and determines based on the higher layer configuration a precoder matrix for the number of antenna ports or CSI-RS ports of the CSI-RS resources. The wireless device generates a CSI report comprising a Precoder Matrix Indicator (PMI) and/or information related to the PMI, indicating the precoder matrix for the number of antenna or CSI-RS ports, and transmits over an uplink channel the generated CSI report to the network node. In certain embodiments, a method performed by a wireless device in a wireless communications network is proposed, the method comprising:
^ receiving from a network node a higher layer configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates maximum allowable amplitude values for a proper subset of beam vectors from a set of ^^^^ beam vectors for restricting an amplitude associated with a beam vector; ^ calculating a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; ^ generating a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ reporting the CSI report to the network node. In certain embodiments, a method performed by a wireless device in a wireless communications network is proposed, the method comprising: ^ receiving from a network node a higher layer configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates a number of maximum allowable amplitude values, X, and a number of beam groups, Y, wherein a beam group comprises a set of beam vectors, and wherein a maximum allowable amplitude value is used for restricting an amplitude associated with a beam vector; ^ calculating a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; ^ generating a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ reporting the CSI report to the network node. In the following, the phrase ‘maximum allowable amplitude coefficient value’, ‘maximum allowable amplitude value’ and ‘maximum allowable amplitude coefficient’ are used interchangeably and may have the same meaning. The phrase ‘beam vector’ and vector and ‘spatial vector’ are used interchangeably and may have the same
meaning. The phrase “precoding matrix” and “precoder matrix” are used interchangeably and may have the same meaning. The information element n1-n2-codebookSubsetRestriction is a RRC configured information element first introduced in the 3GPP New Radio Phase 1. The information element n1-n2-codebookSubsetRestriction forms the bit-sequence ^ = ^^^^, where bit sequences concatenated to form bit sequence B. The wireless device is configured with restrictions for ^ groups out of ^^^^ groups, wherein each group comprises ^^^^ orthogonal vectors. The remaining ^^^^ − ^ groups are not restricted. The ^ groups are ordered according to the equation ^(^) =
− 1} and ^^ ∈ {0, … , ^^ − 1} and wherein
is the group index and ^ = 0, … , ^ − 1 denotes the index of the ^ groups configured with restrictions and the indices are assigned such that ^(^) increases as ^ increases. The bit-sequence ^^ is a
indicator and indicates the ^ groups configured with restrictions. The second bit sequence ^ (^) ^ is the concatenation of bit sequences ^^ , ^ = 0,1, … , ^ − 1 given by ^ = ^ (^) (^) … ^(^^^) corresponding to the group indic (^) ^ ^ ^^ ^ es ^ , where ^ is the number of restricted oversampling groups. The ^ restricted oversampling groups are determined by the wireless device based on the bit-sequence ^^ which shall be configured to the wireless device by the network. The bit sequence ^(^) ^ is of length Bits ^(^,^^^^^^^) ^ … ^ (^,^) ^ . Bits amplitude coefficie ( ^ )
nt ^^,^ for the vector in group ^(^) indexed by ^^, ^^, where the maximum amplitude coefficients are given in the Table 1. The typical value of ^ is equal to 4. Table 1: Maximum allowed amplitude coefficients for restricted vectors Bits Maximum Amplitude (^,^(^ ) ^^,^(^^^^^^^)^ ^ ^ ^^ ^^) ^ ^ ^ ^ ^^ coefficient ^(^) ^,^ 00 0 01 √0.25 10 √0.5
11 1 Oversampling factors In certain embodiments, the values of ^^ and ^^ are configured via the higher layer information element n1-n2-CodebookSubsetRestriction. In certain embodiments, the oversampling factors ^^ and ^^ associated with ^^-th dimension and ^^-th dimension are determined by the wireless device or fixed in the specification. In some examples, the wireless determines the oversampling factors based on the configured values of ^^ and ^^. Here, ^^ and ^^ are the number of columns and rows of the antenna port layout at the network node, respectively. The oversampling factors ^^ and ^^ are associated with the column dimension and row dimension of the antenna port layout, respectively. In certain embodiments, the oversampling factors are dependent on the product of the value ^^ and value ^^, wherein the oversampling factors ^^ and ^^ for ^^^^ > ^ ^are smaller than the oversampling factors ^^ and ^^ for ^^^^ ≤ ^ ^, wherein ^^ is the threshold value, and wherein ^^ > 1 and ^^ > 1. For larger values of ^^ and ^^, the directivity of the spatial beam increases compared to smaller values of ^^ and ^^. Therefore, using large oversampling factors for the ^^-th dimension and the ^^-th dimension may not be needed. In one example, the threshold value ^^ is equal to 16. In another example, the threshold value ^^ is equal to 24. In a further example, the threshold value ^^ is equal to 32. In a further example, the threshold value ^^ is equal to 64. In one example, for ^^^^ > 16, the oversampling factors ^^ and ^^ are given by 2 and 2, respectively, whereas for ^^^^ ≤ 16, the oversampling factors ^^ and ^^ are given by 4 and 4, respectively. In certain embodiments, the oversampling factors ^^ and ^^ are dependent on the rank indicator RI. In some examples, for ^^ ≤ 2, ^^ and ^^ are given by 4 and 4, respectively, whereas for ^^ > 2, ^^ and ^^ are given by 2 and 2, respectively. In some examples, for ^^ ≤ 2, ^^ and ^^ are given by 2 and 2, respectively, whereas for ^^ > 2, ^^ and ^^ are given by 4 and 4, respectively.
Codebook Subset Restriction In certain embodiments, the wireless device is configured with restriction for one or more oversampling groups out of ^^^^ oversampling groups, wherein the one or more oversampling groups that are restricted comprise information bits associated with the maximum amplitude coefficients for less than ^^^^ beam vectors. In some examples, the number of oversampling groups configured for restriction is dependent on the values of ^^ and ^^. In some examples, the number of oversampling groups configured for restriction is dependent on the values of ^^ and ^^. In certain embodiments, when the product of ^^ and ^^ is greater than a threshold value i.e., ^^^^ > ^^, the number of oversampling groups configured for restriction is smaller than the number of oversampling groups configured for restriction when the product of ^^ and ^^ is smaller than or equal to a threshold value i.e., ^^^^ ≤ ^ ^, wherein ^^ is the threshold value and wherein ^^ > 1 and ^^ > 1. In some examples, ^^ ∈ {16,24,32,48,64}. In one example, for ^^^^ > 16, the number of oversampling groups configured for restriction is given by 2, whereas for ^^^^ ≤ 16, the number of oversampling groups configured for restriction is given by 4. In certain embodiments, when the product of ^^ and ^^ is greater than a threshold value i.e., ^ ^ ^^^ > ^ , the number of oversampling groups configured for restriction is greater than the number of oversampling groups configured for restriction when the product of ^^ and ^^ is smaller than or equal to a threshold value i.e., ^^^^ ≤ ^ ^, wherein ^^ is the threshold value, and wherein ^^ > 1 and ^^ > 1. In some examples, ^^ ∈ {16,24,32,48,64}. In one example, for ^^^^ > 16, the number of oversampling groups configured for restriction is given by 8, whereas for ^^^^ ≤ 16, the number of oversampling groups configured for restriction is given by 4. In certain embodiments, when the product of ^^ and ^^ is smaller than or equal to a threshold value i.e., ^^^^ ≤ ^^, the number of oversampling groups configured for restriction is smaller than the number of oversampling groups configured for restriction when the product of ^^ and ^^ is greater than a threshold value i.e., ^^^^ > ^ ^, wherein ^^ is the threshold value, and wherein ^^ > 1 and ^^ > 1. In some examples, ^^ ∈ {4,8,16}. In one example, for ^^^^ ≤ 4, the number of oversampling groups configured for restriction is given by 2, whereas for ^^^^ > 4, the number of oversampling groups configured for restriction is given by 4.
In certain embodiments, when the product of ^^ and ^^ is greater than a threshold value, ^’, the number of restricted oversampling groups is equal to the product of ^^ and ^^. In certain embodiments, when the product of ^^ and ^^ is greater than a threshold value, ^’, the number of oversampling groups configured for restriction is fixed to 4 for different values of ^^ and ^^ or different pairs of (^^, ^^) values. In some examples, the threshold value ^’ is equal to 16. In some examples, the threshold value ^’ is equal to 24. In some examples, the threshold value ^’ is equal to 32. In some examples, the threshold value ^’ is equal to 64. In certain embodiments, when the number of oversampling groups configured for restriction is equal to the total number of oversampling groups i.e., the product of ^^ and ^^, all oversampling groups are configured for restriction and the wireless device is not indicated with the oversampling groups configured for restriction as all oversampling groups are restricted. In this case, the bit-sequence ^^ is empty in the information element n1-n2-CodebookSubsetRestriction. In certain embodiments, the wireless device is configured with one or more sets of oversampling groups for restriction, wherein each set comprise one or more consecutive or non-consecutive oversampling groups. In some examples, for ^^ = 4 and ^^ = 2, there are eight oversampling groups and two sets of oversampling groups, wherein each set comprise four oversampling groups. In one example, the two sets of oversampling groups comprise consecutive oversampling groups {0,1,2,3} and {4,5,6,7}, respectively. In another example, the two sets of oversampling groups comprise non-consecutive oversampling groups {0,2,4,6} and {1,3,5,7}, respectively. In some other examples, for ^^ = 2 and ^^ = 2, there are four oversampling groups and two oversampling sets, wherein each set comprises two oversampling groups. In one example, the two sets of oversampling groups comprise consecutive oversampling groups {0,1} and {2,3}, respectively. In another example, the two sets of oversampling groups comprise non-consecutive oversampling groups {0,2} and {1,3}, respectively. In some examples, the number of oversampling groups in each set of oversampling groups may be identical or not identical. The wireless device may be configured with either one set or two or more sets of oversampling groups. In certain embodiments, when the number of sets of oversampling groups configured for restriction is equal to the total number of sets of oversampling groups i.e., when all
sets of oversampling groups are configured for restriction, the wireless device is not indicated with the sets of oversampling groups configured for restriction as all sets of oversampling groups are restricted. In this case, the bit-sequence ^^ is empty in the information element n1-n2-CodebookSubsetRestriction. In certain embodiments, when a set of oversampling groups configured for restriction comprises all oversampling groups i.e., the product of ^^ and ^^, all oversampling groups are configured for restriction and the wireless device is not indicated with the set of oversampling groups configured for restriction as all oversampling groups are restricted. In this case, the bit-sequence ^^ is empty in the information element n1-n2- CodebookSubsetRestriction. In certain embodiments, the oversampling groups are ordered according to the equation ^^^^ + ^^, where
= 0, … , ^^ − 1 and ^^ = 0, … , ^^ − 1. The first ^^ groups from left to right are associated with index ^^ = 0, the second ^^ groups from left to right are associated with index ^^ = 1 and so on and the last ^^ groups from left to right are associated with index ^^ = ^^ − 1. The ^^ groups associated with an index ^^ are ordered in an increasing order from left to right. In certain embodiments, the oversampling groups are ordered according to the equation ^^^^ + ^^, where
= ^^ − 1, … ,0 and ^^ = ^^ − 1, … , 0. The first ^^ groups from left to right are associated with index ^^ = ^^ − 1, the second ^^ groups from left to right are associated with index ^^ = ^^ − 2 and so on and the last ^^ groups from left to right are associated with index ^^ = 0. The ^^ groups associated with an index ^^ are ordered in a decreasing order from left to right. In certain embodiments, the oversampling groups are ordered according to the equation ^^^^ + ^^, where
− 1 and ^^ = 0, … , ^^ − 1. The first ^^ groups from left to right are associated with index
= 0, the second ^^ groups from left to right are associated with index
= 1 and so on and the last ^^ groups from left to right are associated with index
= ^^ − 1. The ^^ groups associated with an index ^^ are ordered in an increasing order from left to right. In certain embodiments, the oversampling groups are ordered according to the equation ^^^^ + ^^, where
= ^^ − 1, … ,0 and ^^ = ^^ − 1, … ,0. The first ^^ groups from left to right are associated with index = ^^ − 1, the second ^^ groups from left
to right are associated with index ^^ = ^^ − 2 and so on and the last ^^ groups from left to right are associated with index = 0. The ^^ groups associated with an index are ordered in a decreasing order from left to right. In some examples, each oversampling group comprises ^^ consecutive groups associated with index ^^, and ^^ consecutive groups associated with index ^^, where
some examples, ^^ < ^^ and ^^ < ^^. In some examples, ^^ < ^^ and ^^ = 1. In some examples, ^^ = 1 and ^^ < ^^. The oversampling groups in the first dimension may be configured to the wireless device via a ^^-length bitmap. The oversampling groups in the second dimension may be configured to the wireless device via a ^^-length bitmap. The oversampling groups in the first and second dimension may be configured to the wireless device via a ^^ + ^^-length bitmap. The oversampling groups or sets of oversampling groups configured for restriction may be indicated to the wireless device via a bit-sequence ^^. Each oversampling group may consist of ^^^^ beam vectors and each beam vector in an oversampling group may be associated with an index ^, where = 0,1, … ,
− 1. In certain embodiments, the ^^^^ beam vectors are ordered according to the equation ^^^^ + ^^, where ^^ = 0, … , ^^ − 1 and ^^ = 0, … , ^^ − 1. The first ^^ beam vectors from left to right are associated with index ^^ = 0, the second ^^ beam vectors from left to right are associated with index ^^ = 1 and so on and the last ^^ beam vectors from left to right are associated with index ^^ = ^^ − 1. The ^^ beam vectors associated with an index ^^ are ordered in an increasing order from left to right. In certain embodiments, the ^^^^ beam vectors are ordered according to the equation ^^^^ + ^^, where ^^ = ^^ − 1, … , 0 and ^^ = ^^ − 1, … , 0. The first ^^ beam vectors from left to right are associated with index ^^ = ^^ − 1, the second ^^ beam vectors from left to right are associated with index ^^ = ^^ − 2 and so on and the last ^^ beam vectors from left to right are associated with index ^^ = 0. The ^^ beam vectors associated with an index ^^ are ordered in a decreasing order from left to right. In certain embodiments, the ^^^^ beam vectors are ordered according to the equation ^^^^ + ^^, where ^^ = 0, … , ^^ − 1 and ^^ = 0, … , ^^ − 1. The first ^^ beam vectors
from left to right are associated with index ^^ = 0, the second ^^ beam vectors from left to right are associated with index ^^ = 1 and so on and the last ^^ beam vectors from left to right are associated with index ^^ = ^^ − 1. The ^^ beam vectors associated with an index ^^ are ordered in an increasing order from left to right. In certain embodiments, the ^^^^ beam vectors are ordered according to the equation ^^^^ + ^^, where ^^ = ^^ − 1, … , 0 and ^^ = ^^ − 1, … , 0. The first ^^ beam vectors from left to right are associated with index ^^ = ^^ − 1, the second ^^ beam vectors from left to right are associated with index ^^ = ^^ − 2 and so on and the last ^^ beam vectors from left to right are associated with index ^^ = 0. The ^^ beam vectors associated with an index ^^ are ordered in a decreasing order from left to right. In certain embodiments, the maximum allowable amplitude coefficient configured for a ^-th vector among the one or more oversampling groups associated with a set of oversampling groups configured for restriction is identical, wherein ^ = 0,1, … ,
− 1. In some examples, one set of oversampling groups comprising oversampling groups {1,2} is configured for restriction and the allowable amplitude coefficient for the first vector in oversampling group 1 and oversampling group 2 is given by 1 and the allowable amplitude coefficient for the second vector in the oversampling group 1 and oversampling group 2 is given by 0 and so on. In some examples, a set of oversampling groups comprises all or a proper subset of ^^^^ oversampling groups. Here, a proper subset comprises less than ^^^^ oversampling groups. In some examples, the one or more sets of oversampling groups configured for ^ restriction are indicated to the wireless device via a ^log^ ^ ^^ ^^-bit combinatorial indicator, where ^ is the total number of sets of oversampling groups
is the number of oversampling sets configured for restriction. Each set of oversampling groups comprise up to
^ consecutive or non-consecutive oversampling groups. In some examples, the one or more sets of oversampling groups configured for restriction are indicated to the wireless device via a bitmap of length ^ and comprise ones and ^ −
zeros, and wherein ^ is the total number of oversampling sets and
is the number of oversampling sets configured for restriction.
In certain embodiments, the wireless device is configured with restriction for one or more oversampling groups out of ^^^^ oversampling groups, wherein the one or more oversampling groups that are restricted comprise information bits associated with the maximum amplitude coefficients for less than ^^^^ vectors. In certain embodiments, for an oversampling group or for a set of oversampling groups configured for restriction, the wireless device is configured with a bit sequence indicating the maximum amplitude coefficient values. The number of indicated maximum coefficient values can be either ^^^^ or less than ^^^^. In certain embodiments, for an oversampling group or for a set of oversampling groups configured for restriction, the wireless device is configured with a bit sequence indicating the maximum amplitude coefficient values for a subset of ^^^^ beam vectors, wherein in the subset comprises less than ^^^^ vectors. In some examples, the subset comprises ^ beam vectors and are given by the consecutive indices ^ =
or ^ = ^ + 0, … , ^ + ^ − 1, and wherein ^ ∈ {0, … , ^^^^ − 1}. In some other examples, the subset comprises ^ beam vectors and are given by non- consecutive indices ^ = 0, ^, … , (^ − 1)^, or ^ = ^ + 0, ^ + ^ … , ^ + ^(^ − 1), and wherein ^ ∈ {0, … , ^^^^ − 1} and ^ is an integer. In the above examples, only ^ beam vectors are restricted and the remaining ^^^^ − ^ vectors are not restricted. In some examples, the value of ^ is fixed in the specification or determined by the wireless device from the values of ^^ and ^^ and/or configured to the wireless device. In some examples, the value of ^ is different for different values of ^^ and ^^ or different (^^, ^^) pairs. In certain embodiments, for an oversampling group or for a set of oversampling groups configured for restriction, the wireless device is configured with a bit sequence indicating the maximum amplitude coefficient values for ^^′ beam vectors out of ^^ beam vectors and ^^′ beam vectors out of ^^ beam vectors. In some examples, ^^ ^ < ^ ^ ^ and ^^ < ^^. In some examples, ^^ ^ < ^^ and ^^ ^ < ^^ and ^^ ^ = ^^. In some examples, ^^ ^ = ^^ and ^^ ^ < ^^. In some examples, ^^ ^ = 1 and ^^ ^ ≤ ^^. In some examples, ^^ ^ ≤ ^^ and ^^ ^ = 1. In certain embodiments, for an oversampling group or for a set of oversampling groups configured for restriction, the wireless device is configured with a bit sequence of
length (^^ ^ + ^^ ^)^, where R is a number of bits used to indicate the maximum allowed amplitude coefficient value for each beam vector. In certain embodiments, the set of oversampling groups comprise all or a proper subset of ^^^^ oversampling groups. Here, a proper subset comprises less than ^^^^ oversampling groups. For example, for ^^ = 8 and ^^ = 2, there are 16 beam vectors or spatial beams in each oversampling group, whereas for ^^ = 16 and ^^ = 2, there are 32 beam vectors or spatial beams in each oversampling group. As the value of ^^ and/or ^^ increase, the number of beam vectors or spatial beams increase for increasing values of ^^ and/or ^^. When (^^^^) = (8,2), X number of beam vectors or spatial beams cover a region of interest, whereas for (^^^^) = (16,2), 2X number of beam vectors or spatial beams cover the same region of interest. Therefore, one way to reduce the configuration overhead is to consider identical values of amplitude restriction for a set of consecutive beam vectors or spatial beams. Therefore, the size of the bitmap indicating the amplitude restriction or the maximum allowed amplitude coefficients or values may be reduced. In certain embodiments, for an oversampling group or for a set of oversampling groups configured for restriction, a single maximum amplitude coefficient value may be configured for a beam group comprising ^ beam vectors. In some examples, ^ ∈ {2,4,8}. In some examples, ^ > 1. In some examples, ^ = 1. In some examples, the beam group comprising S beam vectors has consecutive indices, e.g., {^, ^ + 1}. In another example, the beam group comprising ^ vectors has non-consecutive indices, e.g., {^, ^ + 2}. In some examples, ^ is derived from the values of ^^ and ^^ i.e., ^
. In some examples, the value of ^ is fixed in the specification or determined by the wireless device from the values of ^^ and ^^ and/or configured to the wireless device. In some examples, the value of ^ is different for different values of ^^ and ^^ or different (^^, ^^) pairs. In certain embodiments, a set of consecutive ^ bits indicating the maximum allowed amplitude coefficient value may be associated with a beam group comprising ^ beam vectors. In some examples, the group of vectors are associated with consecutive indices among ^^^^ indices. In one example, the group of vectors are associated with
non-consecutive indices among ^^^^ indices. In some examples, the number of beam . In some examples, the number of beam groups is equal to
In certain embodiments, the ^ beam vectors may be associated with ^^ ^ consecutive beam vectors out of ^^ beam vectors and ^^ ^ beam vectors out of ^^ beam vectors . In some examples ^ = ^ ^ ^ or ^ = ^^ + ^^. In som ^ ^ ^^^ ^ ^ e examples, ^^ = 1 and ^^ = ^^. In some examples, ^^ ^ = ^^ and ^^ ^ = 1. In some examples, ^^ ^ ^ = 1 and ^^ < ^^. In some examples, ^^ ^ < ^^ and ^^ ^ = 1. In some examples, ^^ ^ ^ < ^^ and ^^ < ^^. In some options, the number of maximum allowed amplitude coefficient values indicated via the bit-sequence ^^ associated with an oversampling group or a set of oversampling groups is given by ^^^^^/(^^ ^^^ ^). In some options, the number of maximum allowed amplitude coefficient values indicated via the bit-sequence ^^ associated with an oversampling group or a set of oversampling groups is given by (^ ^ ^ + ^^)^/(^^ + ^^ ^). In certain embodiments, the number of maximum allowed amplitude coefficient values indicated via bit-sequence ^^ associated with an oversampling group or a set of oversampling groups may not be dependent on the values of ^^ and ^^ but rather fixed for different values of ^^ and ^^ or different values of (^^, ^^) pairs. In some examples, the length of the bit-sequence for ^^ = 8 and ^^ = 3 is given by 12R or 24R. In some examples, the length of the bit-sequence for ^^ = 6 and ^^ = 4 is given by 12R or 24R. In some examples, the length of the bit-sequence for ^^ = 16 and ^^ = 2 is given by 16R or 24R or 32R. In some examples, the length of the bit- sequence for ^^ = 8 and ^^ = 4 is given by 16R or 24R or 32R. In some examples, the length of the bit-sequence for ^^ = 16 and ^^ = 4 is given by 16R or 24R or 32R or 48R or 64R. In some examples, the length of the bit-sequence for ^^ = 8 and ^^ = 8 is given by 16R or 24R or 32R or 48R or 64R. Here, R is the number of bits used to indicate the maximum allowed amplitude coefficient values. In certain embodiments, the length of the bit-sequence indicating the maximum allowed amplitude coefficient values for the ^ ^^^^^ ^^^ vectors is given by ^ , where R is the number of bits used to indicate the maximum allowed amplitude coefficient value
and ^ is the parameter to control the configuration overhead. In some examples, the value of ^ is greater than 1 such that the length of the bit-sequence associated with an oversampling group, or a set of oversampling groups configured for restriction has length less than ^^^^^. In certain embodiments, when single bit is used to indicate the maximum allowed amplitude coefficient or value, i.e., when ^ = 1, bit 0 indicates a maximum allowed amplitude coefficient value of 0 and bit 1 indicates a maximum allowed amplitude coefficient value of 1 or vice versa. In contrast to using ^ > 1, using ^ = 1, further reduces the configuration indication overhead as the length of the bit-sequence ^^ which is used to indicate the maximum allowable amplitude coefficient values for an oversampling group configured for restriction becomes independent of R. In certain embodiments, the parameter ^ is dependent on the values of ^^ and ^^ or pair. In certain embodiments, the values of the parameter ^ is fixed in the specification for different values of ^^ and ^^ or (^^, ^^) pair. In certain embodiments, the wireless device is configured to determine the values of ^^ and ^^ from the bit-sequence configured for amplitude restriction or codebook subset restriction. When the length of the second bit-sequence associated with each restricted oversampled group is less than ^^^^^ bits, the wireless device may not be able to determine the actual combination or (^^^^) values. Hence, the wireless device needs to be configured with other parameters to aid the wireless device to correctly determine the actual (^^^^) combination or exact values of ^^ and ^^. In some examples, the wireless device may be configured with a ⌈log^(64)⌉-length bitmap. Here, 64 is the maximum number of antenna ports supported per polarization. Using this indicator, the number of total antenna ports can be determined by the wireless device. In some examples, the wireless device may be configured with a ⌈log^(16)⌉-bit indicator to indicate the value of ^^. Here, 16 is the maximum number of antenna ports supported per polarization in the vertical dimension (columns) of the antenna port layout. In some examples, the wireless device may be configured with a ⌈log^(8)⌉-bit indicator to indicate the value of ^^. Here, 8 is the maximum number of antenna ports supported per polarization in the horizontal dimension (rows) of the antenna port
layout. In some examples, the wireless device may be configured with a 7-bit indicator to indicate the values of ^^ and ^^. The first 4 bits are used to indicate the value of ^^ and the remaining 3 bits are used to indicate the value of ^^. In certain embodiments, the precoder may be based on Rel.16 Type-II codebook, or Rel.18 Type-II codebook or Rel.19 Type-I codebook, where at least one beam vector is used to determine the precoder matrix. Referring to Figure 3, there is illustrated a method performed by a wireless device (700) according to some of the previously described embodiments. The method is performed by the wireless device (700) in a wireless communications network. The method comprises: ^ receiving (301) from a network node a higher layer configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates maximum allowable amplitude values for a proper subset of beam vectors from a set of ^^^^ beam vectors for restricting an amplitude associated with a beam vector; ^ calculating (302) a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; ^ generating (303) a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ reporting (304) the CSI report to the network node. Referring to Figure 4, there is illustrated a method performed by a wireless device (700) according to some of the previously described embodiments. The method is performed by the wireless device (700) in a wireless communications network. The method comprises: ^ receiving (401) from a network node a higher layer configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates a number of maximum allowable amplitude values, X, and a number of beam groups, Y, wherein a beam group comprises a set of beam vectors, and wherein a maximum allowable
amplitude value is used for restricting an amplitude associated with a beam vector; ^ calculating (402) a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; ^ generating (403) a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ reporting (404) the CSI report to the network node. In certain embodiments, the higher layer configuration comprises an indication of a set of oversampling groups, wherein the set of oversampling groups comprises all oversampling groups. In certain embodiments, the higher layer configuration comprises a bitmap ^, wherein the bitmap ^ comprises two bitmaps, a first bitmap ^^ and a second bitmap ^^, wherein ^ = ^^^^. In certain embodiments, a number of oversampling groups, ^, out of ^^^^ oversampling groups are indicated to the wireles device via the first bitmap ^^. In certain embodiments, each oversampling group comprises ^^^^ beam vectors. In certain embodiments, when the number of oversampling groups configured for restriction is equal to the total number of oversampling groups, the wireless device is not indicated with the number of oversampling groups configured for restriction and the first bitmap ^^ is empty. In certain embodiments, for each indicated oversampling group or for the indicated set of oversampling groups, the maximum allowable amplitude values are indicated to the wireless device via the second bitmap ^^. In certain embodiments, the second bitmap ^^ is the concatenation of bit sequences ^(^) ( ) ( ) ^ , ^ = 0,1, … , ^ − 1 given by ^^ = ^ (^) ^ ^ ^^ … ^ ^^^ ^ , wherein ^ is the number of indicated oversampling groups.
In certain embodiments, the maximum allowable amplitude value for a ^-th beam vector is identical in every indicated oversampling group, wherein ^ = 0,1, … , ^^^^ − 1 or ^ = 0,1, … , ^^ + ^^. In certain embodiments, the maximum allowable amplitude values are indicated to the wireless device via the second bitmap ^^, where ^^ comprise a single bit sequence of length
In certain embodiments, a number of sets of oversampling groups,
out of ^ sets of oversampling groups are indicated to the wireless device via the first bitmap ^^, where ^ is the total number of sets of oversampling groups and
is the number of oversampling sets configured for restriction. In certain embodiments, for each indicated set of oversampling groups, the maximum allowable amplitude values are indicated to the wireless device via the second bitmap ^^, wherein a set of oversampling groups comprise at least two consecutive or non- consecutive oversampling groups. In certain embodiments, the second bitmap ^^ is a concatenation of bit sequences ^(^) ^ , ^ = 0,1, … ,
− 1 given by ^^ = ^ (^) ^ ^(^) ^ … ^ (^ ^ ^^^), wherein
is the number of oversampling sets configured for restriction. In certain embodiments, the bit-sequence ^ (^) (^) ^ or ^^ indicates a maximum allowable amplitude value for a subset of the ^^^^ beam vectors comprising ^ beam vectors, wherein ^ < ^^^^. In certain embodiments, the ^ beam vectors are associated with consecutive or non- consecutive indices out of ^^^^ indices. In certain embodiments, the maximum allowable amplitude coefficient values are configured for a subset comprising ^ beam vectors. In certain embodiments, the maximum allowable amplitude coefficient values are not configured for the remaining ^^^^ − ^ beam vectors.
In certain embodiments, the length of the bit-sequence ^(^) ^ or is ^^, wherein ^ is the number of bits used to indicate the maximum allowable amplitude value for each beam vector. In certain embodiments, the subset comprises the first ^ beam vectors out of ^^^^ beam vectors out of the ^^^^ beam vectors. In certain embodiments, ^ = ^, and ^ =
and such that a single maximum allowable amplitude coefficient is associated with a beam group comprising ^ beam vectors out of ^^^^ beam vectors and wherein ^ > 1. In certain embodiments, the wireless device is configured with ^ beam groups, wherein a beam group comprises ^ beam vectors, wherein ^ > 1, and wherein all beam vectors in the beam group are associated with the same maximum allowable amplitude coefficient. In certain embodiments, the ^ beam vectors are associated with consecutive indices or non-consecutive indices out of ^^^^ indices. In certain embodiments, ^ = ^ such that a single allowable amplitude coefficient value is associated with a beam group comprising ^ beam vectors out of the set of ^^^^ beam vectors, and wherein ^ > 1. In certain embodiments,
In certain embodiments, the ^ beam vectors are associated with consecutive indices or non-consecutive indices out of ^^^^ indices or ^^+^^ indices. In certain embodiments, the S beam vectors are associated with ^^ ^ beam vectors out of ^^ beam vectors and ^^ ^ beam vectors out of ^^ beam vectors. In certain embodiments, ^^ ^ < ^^ and ^^ ^ ≤ ^^, or ^^ ^ ≤ ^^ and ^^ ^ < ^^, or ^^ ^ < ^^ and ^^ ^ < ^^. In certain embodiments, ^ = ^^ ^^^ ^ ^ or ^ = ^^ + ^^ ^.
In certain embodiments, the maximum allowable amplitude coefficient value configured for a ^-th vector among all oversampling groups associated with a set of oversampling groups configured for restriction is identical, wherein ^ = 0,1, … , ^^^^ − 1. In certain embodiments, the length of the bit-sequence ^(^) (^) ^ or ^^
and wherein R is the number of bits used to indicate the maximum allowable amplitude coefficient value for each beam group comprising ^ beam vectors. In certain embodiments, R = 1 or R = 2. In certain embodiments, R = 1, the maximum allowable amplitude values are given by 0 and 1. In certain embodiments, for R = 2, the maximum allowable amplitude values are given by 0, √0.25, √0.5 and 1. In certain embodiments, wherein for ^^^^ > 16, the number of indicated oversampling groups is given by ^ = ^^^^. In some examples, ^ < ^^^^. In order to perform the previously described process or method steps performed by the wireless device or UE, there is also provided a wireless device. Figure 7 illustrates a simplified block diagram depicting a wireless device 700. The wireless device 700 comprises a processor 710 or processing circuit or a processing module or a processor means 710; a receiver circuit or receiver module 740; a transmitter circuit or transmitter module 750; a memory module 720, a transceiver circuit or transceiver module 730 which may include the transmitter circuit 750 and the receiver circuit 740. The wireless device 700 further comprises an antenna system 760 which includes antenna circuitry for transmitting and receiving signals to/from at least the network node or other wireless device(s). The antenna system employs beamforming as previously described. The wireless device may be a UE or an IoT device. The wireless device 700 may belong to any radio access technology including 4G or LTE, LTE-A, 5G, advanced 5G
or a combination thereof that support beamforming technology. The wireless device comprising the processor and the memory contains instructions executable by the processor, whereby the wireless device 700 is operative or is configured to perform any one of the embodiments related to the wireless device as previously described. The processing module/circuit 710 includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like, and may be referred to as the “processor.” The processor 710 controls the operation of the wireless device and its components. Memory (circuit or module) 720 includes a random-access memory (RAM), a read only memory (ROM), and/or another type of memory to store data and instructions that may be used by processor 710. In general, it will be understood that the wireless device 700 in one or more embodiments includes fixed or programmed circuitry that is configured to carry out the operations in any of the embodiments disclosed herein. In at least one such example, the processor 710 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry that is configured to execute computer program instructions from a computer program stored in a non- transitory computer-readable medium that is in or is accessible to the processing circuitry. Here, “non-transitory” does not necessarily mean permanent or unchanging storage, and may include storage in working or volatile memory, but the term does connote storage of at least some persistence. The execution of the program instructions specially adapts or configures the processing circuitry to carry out the operations disclosed in this disclosure relating to the wireless device. Further, it will be appreciated that the wireless device 700 may comprise additional components. The wireless device 700 by means of processor 710 executes instructions contained in the memory 720 whereby the wireless device is operative to perform any one of the previously described embodiments related to the actions performed by the wireless device, some of which are presented in appended claims. There is also provided a computer program comprising instructions which when executed by the processor 710 of the wireless device cause the processor 710 to carry out the method according to any one of the previously described embodiments. Referring to Figure 5, there is illustrated a method performed by a network node (800)
according to some of the previously described embodiments. The method comprises: ^ transmitting (501) to a wireless device a configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates maximum allowable amplitude values for a proper subset of beam vectors from a set of ^^^^ beam vectors for restricting an amplitude associated with a beam vector; for enabling the wireless device to: o calculate a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; o generate a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ receiving (502) from the wireless device the CSI report. Referring to Figure 6, there is illustrated a method performed by a network node (800) according to some of the previously described embodiments. The method comprises: ^ transmitting (601) to a wireless device a configuration comprising an indication of a number of oversampling groups, wherein each indicated oversampling group indicates a number of maximum allowable amplitude values, X, associated with a number of beam vectors, Y, from a set of ^^^^ beam vectors and wherein a maximum allowable amplitude value is used for restricting an amplitude associated with a beam vector; for enabling the wireless device to: o calculate a precoding matrix, the precoding matrix being based on at least one beam vector from the set of ^^^^ beam vectors; o generate a CSI report comprising a Precoder Matrix Indicator, PMI, indicating the precoding matrix; and ^ receiving (602) from the wireless device the CSI report. To perform the previously described process or method steps performed by the network node there is also provided a network node. Figure 8 illustrates a block
diagram depicting a network node 800. The network node 800 comprises a processor 810 or processing circuit or a processing module or a processor means 810; a receiver circuit or receiver module 840; a transmitter circuit or transmitter module 850; a memory module 820, a transceiver circuit or transceiver module 830 which may include the transmitter circuit 850 and the receiver circuit 840. The network node 800 further comprises an antenna system 860 which includes antenna circuitry for transmitting and receiving signals to/from at least the wireless device. The antenna system employs beamforming as previously described. The network node 800 may belong to any radio access technology including 4G or LTE, LTE-A, 5G, advanced 5G or a combination thereof that support beamforming technology. The network node may be a gNB. The network device comprising the processor and the memory contains instructions executable by the processor, whereby the network node 800 is operative or is configured to perform any one of the embodiments related to the network node 800 as previously described. The processing module/circuit 810 includes a processor, microprocessor, an application specific integrated circuit (ASIC), field programmable gate array (FPGA), or the like, and may be referred to as the “processor.” The processor 810 controls the operation of the network node and its components. Memory (circuit or module) 820 includes a random-access memory (RAM), a read only memory (ROM), and/or another type of memory to store data and instructions that may be used by processor 810. In general, it will be understood that the network node in one or more embodiments includes fixed or programmed circuitry that is configured to carry out the operations in any of the embodiments disclosed herein. In at least one such example, the processor 810 includes a microprocessor, microcontroller, DSP, ASIC, FPGA, or other processing circuitry that is configured to execute computer program instructions from a computer program stored in a non- transitory computer-readable medium that is in or is accessible to the processing circuitry. Here, “non-transitory” does not necessarily mean permanent or unchanging storage, and may include storage in working or volatile memory, but the term does connote storage of at least some persistence. The execution of the program instructions specially adapts or configures the processing circuitry to carry out the
operations disclosed in this disclosure relating to the wireless device. Further, it will be appreciated that the wireless device 800 may comprise additional components. The network node 800 may also be viewed as a Transmitter and Receiver Point (TRP). The network node 800 by means of processor 810 executes instructions contained in the memory 820 whereby the network node 800 is operative to perform any one of the previously described embodiments related to the actions performed by the network node. There is also provided a computer program comprising instructions which when executed by the processor 810 of the network node cause the processor 810 to carry out the method according to some embodiments. Reference throughout this specification to “an example” or “exemplary” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present technology. Thus, appearances of the phrases “in an example” or the word “exemplary” in various places throughout this specification are not necessarily all referring to the same embodiment. Throughout this disclosure, the word "comprise" or “comprising” has been used in a non-limiting sense, i.e. meaning "consist at least of". Although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. The embodiments herein may be applied in any wireless systems including LTE or 4G, LTE-A (or LTE-Advanced), 5G, advanced 5G, WiMAX, WiFi, satellite communications, TV broadcasting etc.