Patent Description:
To meet the demand for wireless data traffic having increased since deployment of <NUM>th generation (<NUM>) communication systems, efforts have been made to develop an improved <NUM>th generation (<NUM>) or pre-<NUM> communication system. Therefore, the <NUM> or pre-<NUM> communication system is also called a `Beyond <NUM> Network' or a 'Post LTE System'.

In the <NUM> system, Hybrid Frequency Shift Keying and Quadrature Amplitude Modulation (FQAM) and sliding window superposition coding (SWSC) as an advanced coding modulation (ACM), and filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as an advanced access technology have been developed.

Given the spatial multiplexing provided by FD-MIMO systems, understanding and correctly estimating the channel between a user equipment (UE) and an eNode B (eNB) is important for efficient and effective wireless communication. In order to correctly estimate the channel conditions, the UE will feedback information about channel measurement, e.g., channel state information (CSI), to the eNB. With this information about the channel, the eNB is able to select appropriate communication parameters to efficiently and effectively perform wireless data communication with the UE. However, with increase in the numbers of antennas and channel paths of wireless communication devices, so too has the amount of feedback increased that may be needed to ideally estimate the channel. This additionally-desired channel feedback may create additional overheads, thus reducing the efficiency of the wireless communication, for example, decrease the data rate. The efficient feedback scheme is required.

The document <NPL> discloses two alternatives for CSI reporting for rank <NUM> and rank <NUM> codebooks and symmetric antenna layouts.

Embodiments of the present disclosure provide a precoder codebook for advanced wireless communication systems.

The invention is defined in the appended independent claims.

The following documents and standards descriptions are considered: <NPL>); <NPL>); <NPL>); <NPL>); and <NPL>.

<FIG> below describe various embodiments implemented in wireless communications systems and with the use of OFDM or OFDMA communication techniques. The descriptions of <FIG> are not meant to imply physical or architectural limitations to the manner in which different embodiments may be implemented. Different embodiments of the present disclosure may be implemented in any suitably-arranged communications system.

<FIG> illustrates an example wireless network <NUM> according to embodiments of the present disclosure. The embodiment of the wireless network <NUM> shown in <FIG> is for illustration only.

As shown in <FIG>, the wireless network <NUM> includes an eNB <NUM>, an eNB <NUM>, and an eNB <NUM>. The eNB <NUM> communicates with the eNB <NUM> and the eNB <NUM>. The eNB <NUM> also communicates with at least one network <NUM>, such as the Internet, a proprietary Internet Protocol (IP) network, or other data network.

The eNB <NUM> provides wireless broadband access to the network <NUM> for a first plurality of user equipments (UEs) within a coverage area <NUM> of the eNB <NUM>. The first plurality of UEs includes a UE <NUM>, which may be located in a small business (SB); a UE <NUM>, which may be located in an enterprise (E); a UE <NUM>, which may be located in a WiFi hotspot (HS); a UE <NUM>, which may be located in a first residence (R); a UE <NUM>, which may be located in a second residence (R); and a UE <NUM>, which may be a mobile device (M), such as a cell phone, a wireless laptop, a wireless PDA, or the like. The eNB <NUM> provides wireless broadband access to the network <NUM> for a second plurality of UEs within a coverage area <NUM> of the eNB <NUM>. The second plurality of UEs includes the UE <NUM> and the UE <NUM>. In some embodiments, one or more of the eNBs <NUM>-<NUM> may communicate with each other and with the UEs <NUM>-<NUM> using <NUM>, LTE, LTE-A, WiMAX, WiFi, or other wireless communication techniques.

Depending on the network type, other well-known terms may be used instead of "eNodeB" or "eNB," such as "base station" or "access point. " For the sake of convenience, the terms "eNodeB" and "eNB" are used in this patent document to refer to network infrastructure components that provide wireless access to remote terminals. Also, depending on the network type, other well-known terms may be used instead of "user equipment" or "UE," such as "mobile station," "subscriber station," "remote terminal," "wireless terminal," or "user device. " For the sake of convenience, the terms "user equipment" and "UE" are used in this patent document to refer to remote wireless equipment that wirelessly accesses an eNB, whether the UE is a mobile device (such as a mobile telephone or smartphone) or is normally considered a stationary device (such as a desktop computer or vending machine).

It should be clearly understood that the coverage areas associated with eNBs, such as the coverage areas <NUM> and <NUM>, may have other shapes, including irregular shapes, depending upon the configuration of the eNBs and variations in the radio environment associated with natural and man-made obstructions.

As described in more detail below, one or more of the UEs <NUM>-<NUM> include circuitry, programing, or a combination thereof, for precoder codebook processing. In certain embodiments, and one or more of the eNBs <NUM>-<NUM> includes circuitry, programing, or a combination thereof, for processing of channel state information (CSI) received from the UEs <NUM>-<NUM> in accordance with a first number of antenna ports (N<NUM>) for a first dimension and a second number of antenna ports (N<NUM>) for a second dimension.

Although <FIG> illustrates one example of a wireless network <NUM>, various changes may be made to <FIG>. For example, the wireless network <NUM> could include any number of eNBs and any number of UEs in any suitable arrangement. Also, the eNB <NUM> could communicate directly with any number of UEs and provide those UEs with wireless broadband access to the network <NUM>. Similarly, each eNB <NUM>-<NUM> could communicate directly with the network <NUM> and provide UEs with direct wireless broadband access to the network <NUM>. Further, the eNBs <NUM>, <NUM>, and/or <NUM> could provide access to other or additional external networks, such as external telephone networks or other types of data networks.

<FIG> illustrates an example eNB <NUM> according to embodiments of the present disclosure. The embodiment of the eNB <NUM> illustrated in <FIG> is for illustration only, and the eNBs <NUM> and <NUM> of <FIG> could have the same or similar configuration. However, eNBs come in a wide variety of configurations, and <FIG> does not limit the scope of this disclosure to any particular implementation of an eNB.

As shown in <FIG>, the eNB <NUM> includes multiple antennas 205a-205n, multiple RF transceivers 210a-210n, transmit (TX) processing circuitry <NUM>, and receive (RX) processing circuitry <NUM>. The eNB <NUM> also includes a controller/processor <NUM>, a memory <NUM>, and a backhaul or network interface <NUM>.

The RF transceivers 210a-210n receive, from the antennas 205a-205n, incoming RF signals, such as signals transmitted by UEs in the wireless network <NUM>.

In some embodiments, the RF transceiver 210a-210n is also capable of transmitting downlink signals, to a user equipment (UE), including the single precoder codebook parameters, wherein a precoder matrix indicator (PMI) expression based on a codebook configuration in accordance with the single precoder codebook parameters is swapped at the UE. In some embodiment, the RF transceiver 210a-210n is also capable of receiving, from the UE, a reporting message including channel state information (CSI) based on the N<NUM> and N<NUM>.

In some embodiments, the RF transceiver 210a-210n is also capable of transmitting downlink signals, to the UE, including the single precoder codebook parameters, wherein the PMI expression based on the codebook configuration in accordance with the precoder codebook parameter is parameterized based on a pair of parameters comprising (d¡, d<NUM>) in accordance with the N<NUM> and N<NUM>.

The controller/processor <NUM> can include one or more processors or other processing devices that control the overall operation of the eNB <NUM>. For example, the controller/processor <NUM> could control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceivers 210a-210n, the RX processing circuitry <NUM>, and the TX processing circuitry <NUM> in accordance with well-known principles. The controller/processor <NUM> could support additional functions as well, such as more advanced wireless communication functions. For instance, the controller/processor <NUM> could support beam forming or directional routing operations in which outgoing signals from multiple antennas 205a-205n are weighted differently to effectively steer the outgoing signals in a desired direction. Any of a wide variety of other functions could be supported in the eNB <NUM> by the controller/processor <NUM>. In some embodiments, the controller/processor <NUM> includes at least one microprocessor or microcontroller. As described in more detail below, the eNB <NUM> may include circuitry, programing, or a combination thereof for processing of CSI received from the UE <NUM>-<NUM> in accordance with a first number of antenna ports (N<NUM>) for a first dimension and a second number of antenna ports (N<NUM>) for a second dimension. For example, controller/processor <NUM> can be configured to execute one or more instructions, stored in memory <NUM>, that are configured to cause the controller/processor to process CSI received from the UE <NUM>-<NUM> in accordance with a first number of antenna ports (N<NUM>) for a first dimension and a second number of antenna ports (N<NUM>) for a second dimension.

The backhaul or network interface <NUM> allows the eNB <NUM> to communicate with other devices or systems over a backhaul connection or over a network. For example, when the eNB <NUM> is implemented as part of a cellular communication system (such as one supporting <NUM>, LTE, or LTE-A), the interface <NUM> could allow the eNB <NUM> to communicate with other eNBs over a wired or wireless backhaul connection. When the eNB <NUM> is implemented as an access point, the interface <NUM> could allow the eNB <NUM> to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network (such as the Internet).

Although <FIG> illustrates one example of eNB <NUM>, various changes may be made to <FIG>. For example, the eNB <NUM> could include any number of each component shown in <FIG>. As another particular example, while shown as including a single instance of TX processing circuitry <NUM> and a single instance of RX processing circuitry <NUM>, the eNB <NUM> could include multiple instances of each (such as one per RF transceiver).

As shown in <FIG>, the UE <NUM> includes a plurality of antennas <NUM>, a radio frequency (RF) transceiver <NUM>, TX processing circuitry <NUM>, a microphone <NUM>, and receive (RX) processing circuitry <NUM>.

The RF transceiver <NUM> receives, from the plurality of antennas <NUM>, an incoming RF signal transmitted by an eNB of the wireless network <NUM>.

In some embodiments, the RF transceiver <NUM> is also capable of receiving, from an eNodeB (eNB), downlink signals indicating precoder codebook parameters that comprise a first number of antenna ports (N<NUM>) for a first dimension and a second number of antenna ports (N<NUM>) for a second dimension.

The RF transceiver <NUM> receives the outgoing processed baseband or IF signal from the TX processing circuitry <NUM> and up-converts the baseband or IF signal to an RF signal that is transmitted via the plurality of antennas <NUM>.

In 3GPP LTE system or LTE-A system, it is defined that the UE reports Channel State Information (CSI) to the eNB. The CSI indicates information associated with a quality of a wireless link or a wireless channel formed between the UE and the base station. The CSI may comprise a rank indicator (RI), a precoding matrix indicator (PMI), a channel quality indicator (CQI). The RI indicates information associated with a rank for channel, and represents the number of streams received by the UE through a resource. The PMI is a value reflected spatial characteristic for the channel, and indicates an index of precoder that the UE prefers. The CQI is a value indicating a strength of the channel. The CQI may be represent Signal-to-Interference plus Noise Ratio (SINR) of received signals when the eNB uses the PMI.

The processor <NUM> is also capable of executing other processes and programs resident in the memory <NUM>, such as processes for identifying a codebook configuration based on a single precoder codebook in accordance with the N<NUM> and N<NUM> and swapping precoder matrix indicator (PMI) expressions based on the identified codebook configuration, wherein the transceiver is further configured to transmit, to the eNB, a reporting message including channel state information (CSI) based on the N<NUM> and N<NUM>.

In some embodiments, the processor <NUM> is also capable of determine dummy variables based on a pair of parameters comprising (d¡, d<NUM>) in accordance with the N<NUM> and N<NUM>, the dummy variables being determined as i<NUM>,d1 = x and i<NUM>,d2=y. Wherein a rank-<NUM> codebook for a codebook configuration <NUM> is determined based on the dummy variables.

RI included in CSI may be a recommended value of a rank for transmission. Namely, the RI may indicate a number of layers to be used to downlink transmission. The rank may mean a maximum number of streams that can be sent as different information in a given channel.

PMI may indicate precoder matrix recommended to the eNB when the number of layers indicated by the RI is used. Thus, a number of rank associated with a codebook correspond to a number of layers for CSI reporting. For example, a rank-<NUM> codebook indicates a codebook for <NUM>-layer CSI reporting. Another example, a rank-<NUM> codebook indicates a codebook for <NUM>-layer CSI reporting. In other words, a rank-n codebook indicated a codebook for n-layer CSI reporting (i.e. n = <NUM>, <NUM>, <NUM>,.

In some embodiments, the processor <NUM> is also capable of identifying a pair of parameters comprising (d¡, d<NUM>) based on the N<NUM> and N<NUM> and parameterizing a codebook table based on the identified pair of parameters (d<NUM>, d<NUM>). Wherein the (d¡, d<NUM>) are defined as at least one of (d<NUM>, d<NUM>) = (<NUM>, <NUM>) when the N<NUM> is greater or equal to the N<NUM> or (d<NUM>, d<NUM>) = (<NUM>, <NUM>) when the N<NUM> is less than the N<NUM>. In one example, when the (d¡, d<NUM>) = (<NUM>, <NUM>), a master codebook for a <NUM> layer CSI reporting is determined. In another example, when the (d¡, d<NUM>) = (<NUM>, <NUM>), the master codebook for the <NUM> layer CSI reporting is determined.

In some embodiments, the processor <NUM> is also capable of determining a first discrete fourier transform (DFT) vector (vm) representing a vertical beam for the first dimension and a second DFT vector (un) representing a horizontal DFT beam for the second dimension; and swapping the PMI expressions in a rank <NUM> codebook and a rank <NUM> codebook for a codebook configuration <NUM> and a codebook configuration <NUM> based on the determined first and second DFT vectors. In such embodiments, the swapped PMI expressions comprise an order of (m<NUM>, m<NUM>) based on the N<NUM> and N<NUM>. In one example, when the N<NUM> is greater or equals to the N<NUM>, a rank <NUM> precoder based on the swapped PMI expressions is determined as <MAT>, where vm<NUM> ⊗ um<NUM> is wm<NUM>,m<NUM>. In another example, when the N<NUM> is less than the N<NUM>, the rank <NUM> precoder based on the swapped PMI expression is determined as <MAT> where vm2⊗ um1 is wm2,m1.

The processor <NUM> can move data into or out of the memory <NUM> as required by an executing process. In some embodiments, the processor <NUM> is configured to execute the applications <NUM> based on the OS <NUM> or in response to signals received from eNBs or an operator. The processor <NUM> is also coupled to the I/O interface <NUM>, which provides the UE <NUM> with the ability to connect to other devices, such as laptop computers and handheld computers.

The I/O interface <NUM> is the communication path between these accessories and the processor <NUM>.

<FIG> is a high-level diagram of transmit path circuitry <NUM>. For example, the transmit path circuitry <NUM> may be used for an orthogonal frequency division multiple access (OFDMA) communication. <FIG> is a high-level diagram of receive path circuitry <NUM>. For example, the receive path circuitry <NUM> may be used for an orthogonal frequency division multiple access (OFDMA) communication. In <FIG> and <FIG>, for downlink communication, the transmit path circuitry <NUM> may be implemented in a base station (eNB) <NUM> or a relay station, and the receive path circuitry <NUM> may be implemented in a user equipment (e.g. user equipment <NUM> of <FIG>). In other examples, for uplink communication, the receive path circuitry <NUM> may be implemented in a base station (e.g. eNB <NUM> of <FIG>) or a relay station, and the transmit path circuitry <NUM> may be implemented in a user equipment (e.g. user equipment <NUM> of <FIG>).

Transmit path circuitry <NUM> comprises channel coding and modulation block <NUM>, serial-to-parallel (S-to-P) block <NUM>, Size N Inverse Fast Fourier Transform (IFFT) block <NUM>, parallel-to-serial (P-to-S) block <NUM>, add cyclic prefix block <NUM>, and up-converter (UC) <NUM>. Receive path circuitry <NUM> comprises down-converter (DC) <NUM>, remove cyclic prefix block <NUM>, serial-to-parallel (S-to-P) block <NUM>, Size N Fast Fourier Transform (FFT) block <NUM>, parallel-to-serial (P-to-S) block <NUM>, and channel decoding and demodulation block <NUM>.

At least some of the components in <FIG> and <FIG> may be implemented in software, while other components may be implemented by configurable hardware or a mixture of software and configurable hardware. In particular, it is noted that the FFT blocks and the IFFT blocks described in this disclosure document may be implemented as configurable software algorithms, where the value of Size N may be modified according to the implementation.

Furthermore, although this disclosure is directed to an embodiment that implements the Fast Fourier Transform and the Inverse Fast Fourier Transform, this is by way of illustration only and should not be construed to limit the scope of the disclosure. It will be appreciated that in an alternate embodiment of the disclosure, the Fast Fourier Transform functions and the Inverse Fast Fourier Transform functions may easily be replaced by Discrete Fourier Transform (DFT) functions and Inverse Discrete Fourier Transform (IDFT) functions, respectively. It will be appreciated that for DFT and IDFT functions, the value of the N variable may be any integer number (i.e., <NUM>, <NUM>, <NUM>, <NUM>, etc.), while for FFT and IFFT functions, the value of the N variable may be any integer number that is a power of two (i.e., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, etc.).

In transmit path circuitry <NUM>, channel coding and modulation block <NUM> receives a set of information bits, applies coding (e.g., LDPC coding) and modulates (e.g., Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM)) the input bits to produce a sequence of frequency-domain modulation symbols. Serial-to-parallel block <NUM> converts (i.e., de-multiplexes) the serial modulated symbols to parallel data to produce N parallel symbol streams where N is the IFFT/FFT size used in BS <NUM> and UE <NUM>. Size N IFFT block <NUM> then performs an IFFT operation on the N parallel symbol streams to produce time-domain output signals. Parallel-to-serial block <NUM> converts (i.e., multiplexes) the parallel time-domain output symbols from Size N IFFT block <NUM> to produce a serial time-domain signal. Add cyclic prefix block <NUM> then inserts a cyclic prefix to the time-domain signal. Finally, up-converter <NUM> modulates (i.e., up-converts) the output of add cyclic prefix block <NUM> to RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before conversion to RF frequency.

The transmitted RF signal arrives at UE <NUM> after passing through the wireless channel, and reverse operations to those at eNB <NUM> are performed. Down-converter <NUM> down-converts the received signal to baseband frequency, and remove cyclic prefix block <NUM> removes the cyclic prefix to produce the serial time-domain baseband signal. Serial-to-parallel block <NUM> converts the time-domain baseband signal to parallel time-domain signals. Size N FFT block <NUM> then performs an FFT algorithm to produce N parallel frequency-domain signals. Parallel-to-serial block <NUM> converts the parallel frequency-domain signals to a sequence of modulated data symbols. Channel decoding and demodulation block <NUM> demodulates and then decodes the modulated symbols to recover the original input data stream.

Each of eNBs <NUM>-<NUM> may implement a transmit path that is analogous to transmitting in the downlink to user equipment <NUM>-<NUM> and may implement a receive path that is analogous to receiving in the uplink from user equipment <NUM>-<NUM>. Similarly, each one of user equipment <NUM>-<NUM> may implement a transmit path corresponding to the architecture for transmitting in the uplink to eNBs <NUM>-<NUM> and may implement a receive path corresponding to the architecture for receiving in the downlink from eNBs <NUM>-<NUM>.

<FIG> illustrates an example structure for a DL subframe <NUM> according to embodiments of the present disclosure. An embodiment of the DL subframe structure <NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. The downlink subframe (DL SF) <NUM> includes two slots <NUM> and a total of <MAT> symbols for transmitting of data information and downlink control information (DCI). The first <MAT> SF symbols are used to transmit PDCCHs and other control channels <NUM> (not shown in <FIG>). The remaining <MAT> SF symbols are primarily used to transmit physical downlink shared channels (PDSCHs) <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> or enhanced physical downlink control channels (EPDCCHs) <NUM>, <NUM>, <NUM>, and <NUM>. A transmission bandwidth (BW) comprises frequency resource units referred to as resource blocks (RBs). Each RB comprises either <MAT> sub-carriers or resource elements (REs) (such as <NUM> Res). A unit of one RB over one subframe is referred to as a physical RB (PRB). A UE is allocated to MPDSCH RBs for a total of <MAT> REs for a PDSCH transmission BW. An EPDCCH transmission is achieved in either one RB or multiple of RBs.

In the following description, it is assumed that a wireless environment for a Multiple-Input Multiple-Output (MIMO) system. For supporting a MIMO system, a user equipment (UE) and an eNB in the present disclosure may use a precoding scheme which divides uplink information and downlink information to each of antennas appropriately according to channel state.

The UE and the eNB may use a precoding scheme based on codebook information for precoding. In the precoding scheme based on codebook information, The UE and the eNB may determine beforehand a set of precoding matrices. The UE may determine a precoding matrix indicator (PMI) indicating a certain precoding matrix in the set of precoding matrices by using information associated with channel state between the eNB. The UE may transmit the PMI to the eNB. In this way, the eNB may share the certain precoding matrix with the UE. The UE has been described as a receiver, and the eNB has been described as a transmitter, but it is not limited to such description. So, the UE may be described as a transmitter, and the eNB may be described as a receiver.

Previously, a codebook for two, four, or eight antenna ports or a codebook for a one-dimensional layout. But, for increment of usage in a wireless channel and improvement in network speed, various codebook schemes are required. To meet this requirement, the UE and the base station in the present disclosure may share a codebook for eight, twelve, and sixteen antenna ports in full dimensional MIMO (FD-MIMO) with each other.

<FIG> illustrates an example antenna configurations and numbering <NUM> according to embodiments of the present disclosure. An embodiment of the antenna configurations and numbering <NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the antenna configurations and numbering <NUM> comprise a <NUM> port configuration A <NUM>, a <NUM> port configuration A <NUM>, a <NUM> port configuration B <NUM>, and a <NUM> port configuration B <NUM>.

As shown in <FIG>, in all of the four antenna configurations (e.g., <NUM> port configuration A and B, and <NUM> port configuration A and B), a cross pol (or X-pol) antenna array is considered, in which a pair of antenna elements in the same physical location is polarized in two distinct angles (e.g., +<NUM> degrees and -<NUM> degrees). More specifically, the <NUM> port configuration A <NUM> and the <NUM> port configuration B <NUM> are antenna configurations with <NUM> CSI-RS ports comprising <NUM> pairs of x-pol antenna elements placed in a 2D antenna panel. The <NUM> pairs can be placed in 2x4 (e.g., <NUM>) or <NUM>×<NUM> manner (e.g., <NUM>) on horizontal and vertical dimensions. In addition, the <NUM> port configuration <NUM> and the <NUM> port configuration B <NUM> are antenna configurations with <NUM> CSI-RS ports comprising <NUM> pairs of x-pol antenna elements placed in a 2D antenna panel. The <NUM> pairs can be placed in 2x3 (e.g., <NUM>) or 3x2 manner (e.g., <NUM>) on horizontal and vertical dimensions.

In some embodiments, antennas are indexed with integer numbers, <NUM>, <NUM>,. , <NUM> for <NUM>-port configurations (e.g., <NUM>, <NUM>), and <NUM>,. , <NUM> for <NUM>-port configurations (e.g., <NUM>, <NUM>). In fat arrays (such as <NUM>-port configuration <NUM> A and <NUM>-port configuration A <NUM>), antenna numbers are assigned such that consecutive numbers are assigned for all the antenna elements for a first polarization and proceed to a second polarization. For a given polarization, there may be some different numbering schemes. In one example (e.g., numbering scheme <NUM>), consecutive numbers are assigned for a first row with progressing one edge to another edge and proceed to a second row. In another example (e.g., numbering scheme <NUM>), consecutive numbers are assigned for a first column with progressing one edge to another edge and proceed to a second column.

For example, in the <NUM> port configuration A <NUM>, antenna numbers <NUM>-<NUM> are assigned for a first polarization and <NUM>-<NUM> are assigned for a second polarization, and antenna numbers <NUM>-<NUM> are assigned for a first row and <NUM>-<NUM> are assigned for a second row. Antenna numbers in tall arrays (such as the <NUM>-port configuration B <NUM> and the <NUM>-port configuration B <NUM>) are obtained by simply rotating the fat antenna arrays (such as the <NUM>-port configuration A <NUM> and <NUM>-port configuration A <NUM>) by <NUM> degrees.

In some embodiments, when a UE is configured with <NUM> or <NUM> port CSI-RS for a CSI-RS resource, the UE is configured to report a PMI feedback precoder according to the antenna numbers as shown <FIG>. A rank-<NUM> precoder, Wm,n,p, which is an NCSIRS x1 vector, to be reported by the UE is given by:<MAT>.

Where, N CSIRS = number of configured CSI-RS ports in the CSI-RS resource (e.g., <NUM>, <NUM>, etc.), un is a Nx1 oversampled DFT vector for a second dimension, whose oversampling factor is SN, vm is a Mx1 oversampled DFT vector for a first dimension, whose oversampling factor is SM , and ϕp is a co-phase (e.g., in a form of <MAT>, p = <NUM>,<NUM>,<NUM>,<NUM> ). An oversampling factor may be referred as an oversampling rate. The oversampling factor is an oversampling factor for DFT.

In the above equation for Wm,n,p Ⓧ may represent Kronecker product. The equation may be expressed by using Vm,n, instead of vmⓍun in the equation. The equation for Wm,n,p is expressed as following:
<MAT>, where ϕp represents ϕp = ejπ·p/<NUM>, as described above.

The dimension assignment can be done with N ≥ M according to the numbering scheme <NUM> as shown in <FIG>, with (N,M) e {(<NUM>,<NUM>),(<NUM>,<NUM>),(<NUM>,<NUM>)}; alternatively, the dimension assignment can be done with N ≤ M with swapping the role of columns and rows, with (N, M) e {(<NUM>,<NUM>), (<NUM>,<NUM>), (<NUM>,<NUM>)} according to the numbering scheme <NUM> as shown in <FIG>. In one example, a set of oversampling factors that can be configured for SN and SM are {<NUM>, <NUM>, <NUM>}; and m, m' ∈ {<NUM>, <NUM>,. , SM M}, and n, n' ∈ {<NUM>,<NUM>,. In a special case, m = m' and n = n'.

When any of <NUM>-port configuration A <NUM> and B <NUM> for numbering scheme <NUM> in <FIG> is used at an eNB with configuring NCSIRS =<NUM> to a UE, a submatrix vm Ⓧ un of Wm,n,p corresponds to a precoder applied on <NUM> co-pol elements, whose antenna numbers are <NUM> through <NUM>. Given the antenna configuration, M = <NUM> and N = <NUM> may be configured for vm and un.

If <NUM>-port configuration A <NUM> is used, un is a 4x1 vector representing a horizontal DFT beam and vm is a 2x1 vector representing a vertical DFT beam. If <NUM>-port configuration B <NUM> is used, un is a 4x1 vector representing a vertical DFT beam and vm is a 2x1 vector representing a horizontal DFT beam.

With <NUM> or <NUM>-port configurations, vm can be written as: <MAT>.

With <NUM>-port configurations, un can be written as: <MAT>.

<FIG> illustrates an example precoding weight application <NUM> to antenna configurations according to embodiments of the present disclosure. An embodiment of the precoding weight application <NUM> to antenna configurations shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the precoding weight application <NUM> comprises a <NUM> port configuration A <NUM> and a <NUM> port configuration B <NUM>.

Precoding weights to be applied to antenna port numbers <NUM> through <NUM> in the <NUM> port configuration A <NUM> and B <NUM> are un , and the precoding weights to be applied to antenna ports numbers <NUM> through <NUM> in the <NUM> port configuration A <NUM> and B <NUM> are <MAT> with an appropriate power normalization factor. Similarly, precoding weights to be applied to antenna port numbers <NUM> through <NUM> are un', and the precoding weights to be applied to antenna ports <NUM> through <NUM> arc <MAT> with an appropriate power normalization factor. The number ring scheme <NUM> and <NUM> in <FIG> may be applied to the precoding weight application <NUM> as shown in <FIG>.

<FIG> illustrates an example antenna element (or transmit resource unit (TXRU)) numbering <NUM> according to embodiments of the present disclosure. An embodiment of the antenna element (or transmit resource unit (TXRU)) numbering <NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure.

In some embodiments, an eNB is equipped with 2D rectangular antenna array (or TXRUs) comprising M rows and N columns with P=<NUM> polarized, wherein each element (or TXRU) is indexed with (m, n, p), and m = <NUM>,. , M-<NUM>, n = <NUM>,. , N-<NUM>, p = <NUM>,. , P-<NUM>, as shown in <FIG> with M=N=<NUM>. When <FIG> represents a TXRU array, the TXRU can be associated with multiple antenna elements. In one example (<NUM>-dimensional (1D) subarray partition), an antenna array comprising a column with a same polarization of a 2D rectangular array is partitioned into M groups of consecutive elements, and the M groups correspond to the M TXRUs in a column with a same polarization in the TXRU array as shown in <FIG>.

In some embodiments, a UE is configured with a CSI-RS resource comprising Q=MNP number of CSI-RS ports, wherein the CSI-RS resource is associated with MNP number of resource elements (REs) in a pair of PRBs in a subframe.

In some embodiments, a UE is configured with a CSI-RS configuration via higher layer, configuring Q antenna ports - antenna ports A(<NUM>) through A(Q). The UE is further configured with CSI reporting configuration via higher layer in association with the CSI-RS configuration. The CSI reporting configuration includes information element (IE) indicating the CSI-RS decomposition information (or component PMI port configuration). The information element may comprise at least two integers, say N<NUM> and N<NUM>, which respectively indicates a first number of antenna ports per pol for a first dimension, and a second number of antenna ports per pol for a second dimension, wherein Q = P · N<NUM> · N<NUM>.

In some embodiments, the first dimension may correspond to the horizontal direction or columns, and the second dimension may correspond to the vertical direction or rows, i.e., (N<NUM>, N<NUM>) = (N, M).

In some embodiments, the first dimension may correspond to the vertical direction or rows, and the second dimension may correspond to the horizontal direction or columns, i.e., (N<NUM>, N<NUM>) = (M, N).

In the rest of the disclosure, a notation (N<NUM>, N<NUM>) will be used in place of (M, N) or (N, M). Similarly, a notation (O<NUM>, O<NUM>) will be used for the oversampling factors in the two dimensions in place of (SN, SM ) or (SM ,SN).

A beam grouping scheme and a codebook can be defined in terms of two groups of parameters and one group per dimension. A group of parameters for dimension J comprises at least one of a number of antenna ports per pol Nd, an oversampling factor Od, a skip number (or beam group spacing) sd (e.g., for W1), a beam offset number fd, a beam spacing number pd (e.g., for W2), or a number of beams (in each beam group) Ld.

A beam group indicated by a first PMI i<NUM>,d of dimension d (corresponding to <MAT>) is determined based upon some parameters. For example, a total number of beams is Nd· od and the beams are indexed by an integer md, wherein beam ma, vmd , corresponds to a precoding vector <MAT>, md=<NUM>,. ,Nd· Od -<NUM>. The First PMI of the first dimension i<NUM>,d, i<NUM>,d = <NUM>,. , Nd·Od/ sd -<NUM>, can indicate any of Ld beams indexed by md = fd +sd ·i<NUM>,d, fd +sd ·i<NUM>,d+ pd,. ,fd +sd ·i<NUM>,d+(Ld-<NUM>) pd, wherein these Ld beams are referred to as a beam group.

Class A codebook in LTE specification may be configured with some RRC parameters, for example, N<NUM>, N<NUM> = {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>} where the valid candidates are (N<NUM>, N<NUM>) = (<NUM>, <NUM>), (<NUM>, <NUM>), (<NUM>, <NUM>), (<NUM>, <NUM>), (<NUM>, <NUM>), (<NUM>, <NUM>), and O<NUM>, O<NUM> = {<NUM>, <NUM>, <NUM>}, and Config = {<NUM>, <NUM>, <NUM>, <NUM>}. The Config is a parameter indicating a subset of a codebook entry, and is referred as a codebook configuration parameter. The N<NUM>, N<NUM>, O<NUM>, O<NUM>, and the codebook configuration parameter are parameters for configuring a codebook table, and are configured via higher layer signaling.

For dimension with one port, an oversampling factor and Config = {<NUM>, <NUM>} may not be applied to. In this example, for each (N<NUM>, N<NUM>), configurability of (O<NUM>, O<NUM>) is restricted to two possible fixed pairs as shown in Table <NUM>.

Given the set of values of N<NUM>, N<NUM>, O<NUM>, O<NUM>, W<NUM> matrices with (L'<NUM>,L'<NUM>) = (<NUM>,<NUM>), (<NUM>,<NUM>) are constructed for N<NUM>>=N<NUM> and N<NUM><N<NUM>, respectively. In this instance, W<NUM> = <MAT> where mi is the index for Xi and an associated codebook table is defined in terms of i'<NUM>, i<NUM> and i<NUM>.

Given the value of Config, a subset of codewords from the codebook table is selected as an active subset of values of i'<NUM>, associated with at least one of configurations, for example, Config =<NUM>: (L<NUM>, L<NUM>) = (<NUM>, <NUM>) for rank <NUM>-<NUM> , Config =<NUM>: (L<NUM>, L<NUM>) = (<NUM>, <NUM>) for rank <NUM>-<NUM> [square], Config =<NUM>: (L<NUM>, L<NUM>) = (<NUM>, <NUM>) for rank <NUM>-<NUM> [non-adjacent 2D beams/checkerboard], Config =<NUM>: (L<NUM>, L<NUM>) = (<NUM>, <NUM>), (<NUM>, <NUM>) for N<NUM>>=N<NUM> and N<NUM><N<NUM> respectively for rank <NUM>-<NUM>, or TBD rank <NUM>-<NUM>.

Table <NUM> shows a master codebook for <NUM> layer CSI reporting (with <NUM> CWs(codeword), (L'<NUM>, L'<NUM>) = (<NUM>, <NUM>)). A UE selects <NUM> or <NUM> CWs for the second PMI i<NUM> to be reported on PUSCH, based on Config from Table <NUM>, wherein the corresponding rank <NUM> precoder is given by: <MAT> , where <MAT>, and <MAT>.

Note that Table <NUM> is applicable to N<NUM>>=N<NUM>. For N<NUM><N<NUM>, (L'<NUM>, L'<NUM>) = (<NUM>, <NUM>) may be used. Accordingly, the codebook table needs to modified so that it can be used for N<NUM><N<NUM> configuration also.

Since the antenna port configurations (N<NUM>, N<NUM>) are symmetric in the sense that the antenna port layouts are transpose of one another. For example (N<NUM>, N<NUM>) = (<NUM>,<NUM>) and (<NUM>, <NUM>) for <NUM> port and (N<NUM>, N<NUM>) = (<NUM>, <NUM>) and (<NUM>, <NUM>) as shown in <FIG>. For such antenna port layouts, the same codebook table may be used for representing the different pre-coding vectors and matrices in the two layouts. In other words, a UE and an eNB according to various embodiments, by using a same codebook table, may determine a precoder for both (N<NUM>, N<NUM>) = (a, b) and (b, a).

In some embodiments, there is one (master) codebook table for both of symmetric antenna port configurations. The one codebook table is referred as a master codebook table. In this case, two symmetric port configurations may be defined for N<NUM> ≥ N<NUM> (configuration A) and N<NUM> < N<NUM> (configuration B) as shown <FIG>. However, depending on the configured antenna port configuration(i.e. a combination of (N<NUM>, N<NUM>)), the pre-coder may be derived differently.

In some embodiments, an order of (m<NUM>, m<NUM>) in <MAT> expression may be swapped dependent on a configuration. The m<NUM> is an index indicating a beam for the first dimension, and the m<NUM> is an index indicating a beam for the second dimension. For example, the m<NUM> is an index of a first discrete fourier transform (DFT) vector representing the beam for the first dimension and the m<NUM> is an index of a second discrete fourier transform (DFT) vector representing the beam for the second dimension.

In some embodiments, for the configuration in which N<NUM> ≥ N<NUM>, the order is (m<NUM>, m<NUM>), and the UE derives the rank-<NUM> pre-coder as <MAT>, and for the configuration in which N<NUM> < N<NUM>, the order is swapped as (m<NUM>, m<NUM>), and the UE derives the rank-<NUM> pre-coder as <MAT>. For example, assuming antenna port numbering <NUM> for a <NUM> port configuration, the configuration may be given by: <MAT> and <MAT> and <MAT>.

Similarly, for <NUM> port configuration, the configuration may be given by:
<MAT> and <MAT>.

Referring to the table <NUM>, if the codebook configuration parameter indicates the codebook configuration <NUM>, (s<NUM>,s<NUM>) = (<NUM>, <NUM>), the codebook table of the Table <NUM> may be represented according to a following Table <NUM>. <NUM> and m of the table <NUM> correspond to the m<NUM> and the m<NUM>, as described above, respectively.

Referring to the table <NUM>, if the codebook configuration parameter indicates the codebook configuration <NUM>, (s<NUM>,s<NUM>) = (<NUM>, <NUM>), the codebook table of the Table <NUM> may be represented according to a following Table <NUM>. l and m of the table <NUM> correspond to the m<NUM> and the m<NUM>, as described above, respectively.

According to various embodiments, the UE and the eNB may identify a precoder codebook for both a case of (N<NUM> ≥ N<NUM>) and a case of (N<NUM> < N<NUM>) from rank-<NUM> codebook table(namely, a codebook for <NUM> layer CSI reporting) by swapping an index associated with the first dimension (i.e. i<NUM>,<NUM> or l) and an index associated with the second dimension (i.e. i<NUM>,<NUM> orm).

Note that with the swapping operation, the dimensions of the two vectors to the left and to the right of Kronecker operator are swapped in the two expressions.

In some embodiments, vm<NUM> ⊗um<NUM> is presented as wm<NUM>,m<NUM>. In this case, the alternate expression for rank-<NUM> pre-coder is given by <MAT> for (N<NUM> ≥ N<NUM>) and <MAT> for (N<NUM> < N<NUM>).

In the Table <NUM> and Table <NUM>, as l and m is represented as m<NUM> and m<NUM>, Q may be represented as P. In the same way, wm1,m2 may be represented as wm1,m2 and ϕn may be represented as φn. As a result, the alternate expression for rank-<NUM> pre-coder may be given by <MAT> for (N<NUM> ≥ N<NUM>) and <MAT> for (N<NUM> < N<NUM>).

According to these alternatives, the expressions for rank <NUM>-<NUM> pre-coders are determined.

Table <NUM> shows four configurations for rank-<NUM> and Table 7A and 7B show a master codebook for <NUM> layers CSI reporting.

Referring to the table <NUM>, 7A and 7B, if the codebook configuration parameter indicates the codebook configuration <NUM>, (s<NUM>,s<NUM>) = (<NUM>, <NUM>), the rank-<NUM> codebook table may be represented according to a following Table <NUM>. <NUM> and m of the table <NUM> correspond to the m<NUM> and the m<NUM>, as described above, respectively.

Referring to the table <NUM>, 7A and 7B, if the codebook configuration parameter indicates the codebook configuration <NUM>, (s<NUM>,s<NUM>) = (<NUM>, <NUM>), the rank-<NUM> codebook table may be represented according to a following Table <NUM>. l and m of the table <NUM> correspond to the m<NUM> and the m<NUM>, as described above, respectively.

In some embodiments, the rank-<NUM> class A codebook is described in Table <NUM> and Table 7A and 7B, where i<NUM>,<NUM> = <NUM>,<NUM>,. , O<NUM>N<NUM>/s<NUM> - <NUM>, i<NUM>,<NUM> = <NUM>,<NUM>,. , O<NUM>N<NUM>/s<NUM> - <NUM>, and p<NUM> = <NUM> and p<NUM> = <NUM>, and the pre-coder expression are given by:
<MAT> <MAT> <MAT> <MAT>.

In the table <NUM> and <NUM>, as l and m is represented as m<NUM> and m<NUM>, Q may be represented as P. In the same way, wm1,m2 may be represented as wm1,m2 and ϕn may be represented as φn. As a result, the alternate expression for rank-<NUM> pre-coder may be given by <MAT> and<MAT>.

In some embodiments, a second alternative design for Configuration <NUM> (described in Table <NUM> and Table <NUM>) is also considered.

Table <NUM> shows a description of an alternative design for configuration <NUM> in rank-<NUM> codebook. Table <NUM> shows a codebook table for alternative design for configuration <NUM> in rank02 codebook.

<FIG> illustrates an example rank <NUM>-<NUM> orthogonal beam pair construction <NUM> according to embodiments of the present disclosure. An embodiment of the rank <NUM>-<NUM> orthogonal beam pair construction <NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the rank <NUM>-<NUM> orthogonal beam pair construction <NUM> comprises a leading beam group <NUM>, rank <NUM>-<NUM> orthogonal beams for 2D antenna <NUM>, and rank <NUM>-<NUM> orthogonal beams for 1D antenna <NUM>.

In some embodiments, for rank <NUM>-<NUM>, the codebook for a given rank value is characterized by four parameters such as {i<NUM>, i<NUM>, k, i<NUM>}. Different values of parameter k are used to construct different types of orthogonal beam groups for rank <NUM>-<NUM> codebook. An illustration of four orthogonal beam types, indexed by k = <NUM>, <NUM>, <NUM>, <NUM>, is shown in <FIG> and a single rank <NUM>-<NUM> codebooks tables are constructed for all orthogonal beam types.

Table <NUM> and Table <NUM> show the rank <NUM>-<NUM> codebook tables that can be used for any of Q = <NUM>, <NUM>, and <NUM> antenna port configurations, where i<NUM>,<NUM> = <NUM>,<NUM>,. , O<NUM>N<NUM>/s<NUM> - <NUM>; i<NUM>,<NUM> = <NUM>,<NUM>,. , O<NUM>N<NUM>/s<NUM> - <NUM>; and k = <NUM>, <NUM>, <NUM>,<NUM>; δ<NUM>, δ<NUM> are selected from Table <NUM> depending on the k value.

The corresponding rank <NUM> pre-coder expression is given by:
<MAT><MAT><MAT><MAT>.

The corresponding rank <NUM> pre-coder expression is given by:.

Table <NUM> shows orthogonal beam type to (δ<NUM>,δ<NUM> ) mapping and Table <NUM> shows an alternate orthogonal beam type to (δ<NUM>,δ<NUM> ) mapping.

Table <NUM> shows a codebook for <NUM> layers CSI reporting and Table <NUM> shows a codebook for <NUM> layers CSI reporting.

<FIG> illustrates an example orthogonal beam <NUM> for rank <NUM>-<NUM> according to embodiments of the present disclosure. An embodiment of the orthogonal beam <NUM> for rank <NUM>-<NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the orthogonal beam <NUM> for rank <NUM>-<NUM> comprises a configuration <NUM><NUM>, a configuration <NUM><NUM>, a configuration <NUM><NUM>, and a configuration <NUM><NUM>.

In some embodiments, a UE is configured with a beam group configuration from four configurations, namely the configuration <NUM><NUM>, the configuration <NUM><NUM>, the configuration <NUM><NUM>, and the configuration <NUM><NUM>, for codebook subset selection on mater rank <NUM>-<NUM> codebooks. For k = <NUM>, an illustration of the four configurations is shown <FIG>. Depending on the configuration, the UE selects <MAT> indices (in Table <NUM> and Table <NUM>) according to Table <NUM> and Table <NUM> for rank <NUM> and rank <NUM>, respectively, for PMI reporting. The parameters (s<NUM>,s<NUM>) and (p<NUM>,p<NUM>) for the four configurations are shown in Table <NUM> and Table <NUM>.

Table <NUM> shows selected <MAT> indices for rank-<NUM> CSI reporting and Table <NUM> shows selected <MAT> indices for rank-<NUM> CSI reporting.

Note that p<NUM> = s<NUM>/L<NUM> for the configurations <NUM>-<NUM>, where L<NUM> is the number of included beam indices along the first dimension of the master codebook. In other words, for the configurations <NUM>-<NUM>, the effective oversampling is kept fixed for rank <NUM>-<NUM>.

In some embodiments, a UE is configured with a second alternative design for a configuration <NUM> in rank <NUM>-<NUM> codebook, which is described in Table <NUM>. Table <NUM> shows a description of alternative design for the configuration <NUM> in rank <NUM>-<NUM> codebook.

In some embodiments, a UE feeds back k in PMI as part of W1 indication. In particular, k is jointly encoded with i<NUM> indication(s) or (i<NUM>,<NUM>, i<NUM>,<NUM>) indication. In some embodiments, a UE is configured with a k value. In some embodiments, there are two alternatives for the number of values of k. In one example, two values: k = <NUM>,<NUM> as shown in Table <NUM>. In another example, maximum eight values are determined if N<NUM> > <NUM> and N<NUM> > <NUM>: k = <NUM>,<NUM>,<NUM>. ,<NUM> as shown in Table <NUM>. In yet another example, maximum eight values are determined if N<NUM> = <NUM>: k = <NUM>, <NUM>, <NUM> as shown in Table <NUM>. In such example, a UE may be configured with at least one of examples.

In some embodiments, a UE is configured with rank <NUM>-<NUM> codebook tables as shown in Table <NUM> and Table <NUM> with (s<NUM>, s<NUM>) and (p<NUM>, p<NUM>) parameters according to Table <NUM>. In one example, Table <NUM> may be applicable to oversampling factors O<NUM>, O<NUM> = <NUM>, <NUM>, <NUM>, etc.. In another example, Table <NUM> may be applicable to a number of antenna ports Q = <NUM>, <NUM>, <NUM>, etc..

Note that Table <NUM> is for N<NUM> ≥ N<NUM> case. For N<NUM> < N<NUM>, the parameter table is obtained by swapping the dimension indices (<NUM>, <NUM>) with (<NUM>, <NUM>) in Table <NUM>.

The motivation behind this choice of parameters is to have the same effective oversampling factor for configuration = <NUM>, <NUM>, <NUM>. For instance, an effective oversampling factor for the parameters in Table <NUM> is (<NUM>, <NUM>), which is the same as the effective oversampling factor in LTE specification codebook. As an example, if O<NUM> = O<NUM> = <NUM>, then corresponding beam indices are <NUM>, <NUM>, <NUM>, <NUM>, etc. in the two dimensions. In one example for configuration <NUM>, in both dimensions, beams (<NUM>, <NUM>) form one beam group, beams (<NUM>, <NUM>) form the next beam group, and so on. In another example for configuration <NUM>, in 1st dimension, beams (<NUM>,<NUM>,<NUM>,<NUM>) form one beam group, beams (<NUM>, <NUM>, <NUM>, <NUM>) form the next beam group, and so on, and in 2nd dimension, beams (<NUM>, <NUM>) form one beam group, beams (<NUM>, <NUM>) form the next beam group, and so on. In yet another example for configuration <NUM>, in 1st dimension, beams (<NUM>, <NUM>, <NUM>, <NUM>) form one beam group, beams (<NUM>, <NUM>, <NUM>, <NUM>) form the next beam group, and so on, and in 2nd dimension, beam <NUM> forms one beam group, beam <NUM> forms the next beam group, and so on. Note that the effective oversampling factor is maintained at (O<NUM>, O<NUM>) for configuration <NUM>.

In some embodiments, a UE is configured with rank <NUM>-<NUM> codebook tables as shown in Table <NUM> and Table <NUM> with (s<NUM>, s<NUM>) and (p<NUM>,p<NUM>) parameters according to Table <NUM>, which corresponds to effective oversampling factors the same as the configured oversampling factors. Table <NUM> shows (s<NUM>,s<NUM>) and (p<NUM>,p<NUM>) parameters for rank <NUM>-<NUM> codebook for N<NUM> ≥ N<NUM>.

In some embodiments, a UE is configured with rank <NUM>-<NUM> codebook tables in Table <NUM> and <NUM> with (s<NUM>, s<NUM>) and (p<NUM>,p<NUM>) parameters the same as in the rank <NUM>-<NUM> codebook. In this case, the parameters are given by Table <NUM>. Table <NUM> shows (s<NUM>, s<NUM>) and (p<NUM>,p<NUM>) parameters for rank <NUM>-<NUM> codebook for N<NUM> ≥ N<NUM>.

In some embodiments, for rank <NUM>-<NUM>, the proposed codebooks are characterized by two parameters such as {i<NUM>,i<NUM>}. Consequently, only W1 feedback applies. For rank <NUM>, <NUM>, <NUM>, <NUM>, the precoding matrices are as in the following, where δ<NUM>,<NUM>, δ<NUM>,<NUM>, (δ<NUM>,<NUM> , δ<NUM>,<NUM> , δ<NUM>,<NUM>, δ<NUM>,<NUM> are determined by the RRC 'Config' parameter that can take values <NUM>,<NUM>,<NUM>,<NUM>. <MAT> where m<NUM> = vs<NUM>i<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>, m<NUM> = -vs<NUM>i<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>, m<NUM> = vs<NUM>i<NUM>,<NUM> +δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>, m<NUM> = -vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM> +δ<NUM>,<NUM>, and m<NUM> = vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>. <MAT> where m<NUM> = vs<NUM>i<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>, m<NUM> = -vs<NUM>i<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>, m<NUM> = vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>, m<NUM> = -vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>,i<NUM>,<NUM>+δ<NUM>,<NUM>, and m<NUM> = vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>. <MAT> where m<NUM> = -vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>. <MAT> <MAT> where m<NUM> = -vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM><MAT><MAT> where m<NUM> = vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>. <MAT>
where m<NUM> = -vs<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> ⊗ us<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>. <MAT> <MAT> n<NUM> = ws<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>,s<NUM>i<NUM>,<NUM>+δ<NUM><NUM>,<NUM>, n<NUM> = -ws<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>,s<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM> , and n<NUM> = ws<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>, s<NUM>,i<NUM>,<NUM>+δ<NUM>,<NUM>. <MAT> <MAT> <MAT> <MAT> <MAT><MAT> where n<NUM> = -ws<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>,s<NUM>i<NUM>,<NUM>+δ<NUM>,<NUM>.

<FIG> illustrates an example orthogonal beam grouping <NUM> for rank <NUM>-<NUM> according to embodiments of the present disclosure. An embodiment of the orthogonal beam grouping <NUM> for rank <NUM>-<NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the orthogonal beam grouping <NUM> comprises beams in the second dim <NUM> and beams in the first dim <NUM>.

In some embodiments, as shown in <FIG>, for <NUM> ports 2D case, there is only one orthogonal beam type which corresponds to Config = <NUM> for rank <NUM>-<NUM> codebook, and is parameterized by δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM> values given in Table <NUM>. In this case, the UE always maps the configuration parameter to configuration (e.g., config) = <NUM> as shown in <FIG>, regardless of the value of the "Config" parameter. Table <NUM> shoes delta values for <NUM>-port rank <NUM>-<NUM> codebooks.

<FIG> illustrates another example orthogonal beam grouping <NUM> for rank <NUM>-<NUM> according to embodiments of the present disclosure. An embodiment of the orthogonal beam grouping <NUM> for rank <NUM>-<NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the orthogonal beam grouping <NUM> comprises config=<NUM> and config=<NUM><NUM>, a config=<NUM><NUM>, and a config=<NUM><NUM>.

<FIG> illustrates yet another example orthogonal beam grouping <NUM> for rank <NUM>-<NUM> according to embodiments of the present disclosure. An embodiment of the orthogonal beam grouping <NUM> for rank <NUM>-<NUM> shown in <FIG> is for illustration only. Other embodiments may be used without departing from the scope of the present disclosure. As shown in <FIG>, the orthogonal beam grouping <NUM> comprises config=<NUM> and config=<NUM><NUM>, a config=<NUM><NUM>, and a config=<NUM><NUM>.

In some embodiments, as shown in <FIG>, <FIG>, <FIG>, and <FIG>, there are three orthogonal beam type configurations indexed by Config = <NUM>,<NUM>,<NUM>,<NUM> for rank <NUM>-<NUM> codebook, which are parameterized by δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM> values. Note that Config = <NUM> and Config = <NUM> corresponds to the same beam group. There are two alternatives for Config <NUM>, which are shown in <FIG> and <FIG> for <NUM> ports, and in <FIG>, and <FIG> for <NUM> ports. For <NUM> ports, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM>, δ<NUM>,<NUM> are defined in Table <NUM>, and for <NUM> ports they are defined in Table <NUM>. Table <NUM> shows delta values for <NUM>-port rank <NUM>-<NUM> codebooks.

Table <NUM> shows delta values for <NUM>-port rank <NUM>-<NUM> codebooks.

In some embodiments, (s<NUM>, s<NUM>) values for rank <NUM>-<NUM> codebook is given by Table <NUM> or Table <NUM>. For N<NUM> < N<NUM>, (s<NUM>,s<NUM>) parameters are swapped if Table <NUM> is used. Note that for N<NUM> = <NUM>, we have only Config <NUM>. Table <NUM> shows (s<NUM>,s<NUM>) parameters for rank <NUM>-<NUM> codebook for N<NUM> ≥ N<NUM>.

Table <NUM> shows (s<NUM>,s<NUM>) parameters for rank <NUM>-<NUM> codebook.

In some embodiments, a UE is configured with rank <NUM>-<NUM> codebook tables with the same effective oversampling factor, i.e., (<NUM>,<NUM>), for Config <NUM>-<NUM>, which is aligned with rank <NUM>-<NUM> codebook parameter in Table <NUM> and also with LTE specification codebook. Accordingly, for <NUM> antenna ports, (s<NUM>, s<NUM>) parameters for rank <NUM>-<NUM> codebook are given by Table <NUM>. There may be two alternatives for i<NUM>,<NUM>(or i<NUM>,<NUM>). In one example, i<NUM>,<NUM>(or i<NUM>,<NUM>) = <NUM>-<NUM>, in which redundant i<NUM>,<NUM> (or i<NUM>,<NUM> = <NUM>-<NUM> due to phase wrap around are not included. In another example, i<NUM>,<NUM> (or i<NUM>,<NUM>) = <NUM>-<NUM>, in which redundant i<NUM>,<NUM> (or i<NUM>,<NUM>) = <NUM>-<NUM> due to phase wrap around are included. The aforementioned examples may be used in future when N<NUM> (or N<NUM>) > <NUM>. Table <NUM> shows (s<NUM>, s<NUM>) parameters for rank <NUM>-<NUM> codebook for N<NUM> ≥ N<NUM>: <NUM> ports.

For <NUM> and <NUM> antenna ports, (s<NUM>, s<NUM>) parameters are given by Table <NUM>. Note that there may be two options for 1D case (N<NUM> =<NUM>). In one example, an effective oversampling is <NUM>. In another example, an effective oversampling is the configured oversampling factor O<NUM>. Similar to <NUM> port case, the aforementioned examples are allowed for i<NUM>,<NUM> in case of Config <NUM>-<NUM>. Table <NUM> shows (s<NUM>,s<NUM>) parameters for rank <NUM>-<NUM> codebook: N<NUM> ≥ N<NUM>: <NUM>,<NUM> ports.

In some embodiments, a UE is configured with rank <NUM>-<NUM> codebook tables with the same (s<NUM>, s<NUM>) parameters such that the effective oversampling factor is the same as configured oversampling factors, i.e., according to Table <NUM>. Again, two alternatives are allowed for i<NUM>,<NUM> in case of Config <NUM>-<NUM>. Table <NUM> shows (s<NUM>, s<NUM>) parameters for rank <NUM>-<NUM> codebook: N<NUM> ≥ N<NUM>: <NUM>, <NUM> ports.

In some embodiments, a UE is configured with rank <NUM>-<NUM> codebook tables with the (s<NUM>, s<NUM>) parameters such that the choice of parameter is constrained to use of the same number of (i<NUM>,<NUM>, i<NUM>,<NUM>) bits regardless of the Config parameter. For instance, if (i<NUM>,<NUM> and i<NUM>,<NUM> are constrained to be <NUM> bits each, then the rank <NUM>-<NUM> codebook parameters are given by Table <NUM> for both <NUM> and16 antenna ports. Note that there may be two options for Config <NUM>-<NUM> in Table <NUM>. In one example, a leading beam index of orthogonal beam groups is a multiple of O<NUM> for both <NUM> and <NUM> antenna ports (i.e., N<NUM> = <NUM> and <NUM>). In another example, a leading beam index of orthogonal beam groups depends on the value of N<NUM>, i.e., it is a multiple of N<NUM>. For instance, for <NUM> antenna ports, the leading beam index is a multiple of <NUM>, and for <NUM> antenna ports, the leading beam index is a multiple of <NUM>. Table <NUM> shows (s<NUM>, s<NUM>) parameters for rank <NUM>-<NUM> codebook for N<NUM> ≥ N<NUM>: <NUM>, <NUM> ports.

Note that the above (s<NUM>, s<NUM>) parameter tables is for N<NUM> ≥ N<NUM> case. For N<NUM> < N<NUM>, the parameter table is obtained by swapping the dimension subscripts (<NUM>, <NUM>) with (<NUM>, <NUM>). According to various embodiments, a UE and an eNB obtain a codebook parameter table for N<NUM> ≥ N<NUM> and a codebook parameter table for N<NUM> < N<NUM> by swapping a first index for the first dimension and a second index for the second dimension. For example, the UE and the eNB obtain a codebook parameter table for (N<NUM>, N<NUM>)=(<NUM>,<NUM>) and a codebook parameter table for (N<NUM>, N<NUM>)=(<NUM>,<NUM>).

In some embodiments, the KP expressions can be swapped for the two configurations, i.e., if <MAT> ; and if N<NUM> < N<NUM>, <MAT>. The aforementioned expressions may be applied various embodiments of the present disclosure for other ranks as well.

In some embodiments, the codebook table is parameterized with a parameter pair (d<NUM>, d<NUM>) which takes a value (d<NUM>, d<NUM>) = (<NUM>, <NUM>) if N<NUM> ≥ N<NUM> and a value (d<NUM>, d<NUM>) = (<NUM>, <NUM>) if N<NUM> < N<NUM>. In this case, the master rank-<NUM> codebook is given by Table 31A and 31B, where <MAT>, <MAT>, and <MAT>. Table 31A and 31B show a master codebook for <NUM> layer CSI reporting (e.g., parameterized).

For rank <NUM>-<NUM>, the parameterized master codebook can be constructed similarly.

In some embodiments, the order in which the Kronecker product is performed is dependent on the configuration. For instance, for the configuration in which N<NUM> ≥ N<NUM>, the UE derives the rank-<NUM> pre-coder as <MAT>, and for the configuration in which N<NUM> < N<NUM>, the UE derives the rank-<NUM> pre-coder as <MAT>. Note that the orders in which the Kronecker product is performed in the two expressions are opposite in order to ensure that the dimensions of the two vectors to the left and to the right of Kronecker operator are the same in the two expressions.

Also note that in some embodiments the KP expressions can be swapped for the two configurations, i.e., if <MAT> and if N<NUM> < N<NUM>, <MAT>. The aforementioned expression may be applied to various embodiments of the present disclosure for other ranks as well.

For example, assuming antenna port numbering <NUM> for a <NUM> port configuration, the two expressions are given by:
<MAT> and <MAT> and <MAT>.

Similarly, for <NUM> port configuration, the two expressions are given by:
<MAT> , and <MAT>.

The aforementioned embodiment is applicable to the antenna port numbering <NUM>, where (N<NUM>, N<NUM>) = (<NUM>, <NUM>) for config A and for (N<NUM>, N<NUM>) = (<NUM>, <NUM>) for config B. Note that even though <MAT>expression is different in two configurations, the master rank-<NUM> codebook table such as Table <NUM> can be used for both.

For rank-<NUM>, the pre-coding matrix is given by <MAT> for N<NUM> ≥ N<NUM> (config A) and <MAT> for N<NUM> < N<NUM> (config B).

The expressions for rank <NUM>-<NUM> for the two configurations can be expression similarly. Similar to rank-<NUM>, for rank <NUM>-<NUM> also, the master rank <NUM>-<NUM> codebooks in this case remain the same as aforementioned earlier in the present disclosure.

In addition, the beam grouping schemes or (L<NUM>, L<NUM>) configurations or codebook subset selection according to some embodiments of the present disclosure are applicable straightforwardly to this case once the master table for each of antenna port configurations is implemented.

In some embodiments, if the oversampling factor in the longer and shorter dimensions of the two symmetric port configurations is the same, then the pre-coder for one of the symmetric port configuration is derived from that for the other symmetric port configuration by applying a fixed mapping on the elements of the pre-coding vector.

In one embodiment, for the configuration in which N<NUM> ≥ N<NUM> (config A), the UE derives the rank-<NUM> pre-coder as <MAT>, and for the configuration in which N<NUM> < N<NUM> (config B), the UE derives the rank-<NUM> pre-coder as <MAT>, where the mapping function is defined as <MAT>.

Note that here the assumption is that O<NUM> and O<NUM> in case of N<NUM> ≥ N<NUM> is the same as O<NUM> and O<NUM> in case of N<NUM> < N<NUM>, respectively.

In one example, for (N<NUM>,N<NUM>) = (<NUM>, <NUM>) with (O<NUM>,O<NUM>) = (<NUM>, <NUM>), <MAT> and <MAT>, hence <MAT> ; and for (N<NUM>,N<NUM>) = (<NUM>,<NUM>) with (O<NUM>,O<NUM>) = (<NUM>,<NUM>), <MAT> and <MAT> , hence <MAT> , which can be obtained by applying the permutation σ({<NUM><NUM><NUM><NUM><NUM><NUM><NUM><NUM>})= {<NUM><NUM><NUM><NUM><NUM><NUM><NUM><NUM>} on the components of <MAT>.

In another embodiment, the pre-coder for N<NUM> ≥ N<NUM> can be derived by applying a similar fixed mapping on the pre-coder for N<NUM> < N<NUM> case. For rank <NUM>-<NUM>, the mapping can be constructed similarly.

Although the present disclosure has been described with an exemplary embodiment, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.

Claim 1:
A user equipment, UE, in a wireless communication system, the UE comprising:
a transceiver; and
at least one processor operable coupled to the transceiver, and configured to:
receive, from a base station, configuration information for indicating codebook parameters that include a first number of antenna ports, N<NUM>, for a first dimension, a second number of antenna ports, N<NUM>, for a second dimension, a first oversampling factor, O<NUM>, for the first dimension, a second oversampling factor, O<NUM>, for the second dimension, and a codebook configuration; and
determine a precoder codebook based on the codebook parameters;
determine at least one precoding matrix indicator, PMI, indicating a precoder of the precoder codebook, wherein the at least one PMI includes a first codebook index (i<NUM>,<NUM>), a second codebook index (i<NUM>,<NUM>), and a third codebook index (i<NUM>); and
transmit, to the base station, channel state information, CSI, including the at least one PMI, characterized in that
if the N<NUM> is greater than or equal to the N<NUM>, the precoder comprises a first matrix in which a first vector is determined in accordance with a first variable and a second vector is determined in accordance with a second variable, the first variable is associated with the first codebook index (i<NUM>,<NUM>) using a first function and the second variable is associated with the second codebook index (i<NUM>,<NUM>) using a second function, and
if the N<NUM> is smaller than the N<NUM>, the precoder comprises a second matrix in which the first vector is determined in accordance with the second variable and the second vector is determined in accordance with the first variable, the first variable is associated with the second codebook index (i<NUM>,<NUM>) using the first function and the second variable is associated with the first codebook index (i<NUM>,<NUM>) using the second function,
wherein the first vector is a discrete fourier transform, DFT, vector associated with a beam for the first dimension, the second vector is a DFT vector associated with a beam for the second dimension, and
wherein the first matrix and the second matrix include the Kronecker product of the first vector and the second vector.